2025-13258: Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Military Readiness Activities in the Hawaii-California Training and Testing Study Area

Federal Register, Volume 90 Issue 134 (Wednesday, July 16, 2025) [Federal Register Volume 90, Number 134 (Wednesday, July 16, 2025)] [Proposed Rules] [Pages 32118-32349] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 2025-13258] [[Page 32117]] Vol. 90 Wednesday, No. 134 July 16, 2025 Part II Department of Commerce ----------------------------------------------------------------------- National Oceanic and Atmospheric Administration ----------------------------------------------------------------------- 50 CFR Part 218 Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Military Readiness Activities in the Hawaii-California Training and Testing Study Area; Proposed Rule Federal Register / Vol. 90 , No. 134 / Wednesday, July 16, 2025 / Proposed Rules [[Page 32118]] ----------------------------------------------------------------------- DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 218 [Docket No. 250708-0120] RIN 0648-BN44 Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Military Readiness Activities in the Hawaii-California Training and Testing Study Area

Agency

National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.

Action

Proposed rule; proposed letters of authorization; request for comments. -----------------------------------------------------------------------

Summary

NMFS has received a request from the U.S. Department of the Navy (including the U.S. Navy and the U.S. Marine Corps) (Navy) and on behalf of the U.S. Coast Guard (Coast Guard) and U.S. Army (Army) (hereafter, Navy, Coast Guard, and Army are collectively referred to as the Action Proponents) for Incidental Take Regulations (ITR) and multiple associated Letters of Authorization (LOAs) pursuant to the Marine Mammal Protection Act (MMPA). The requested regulations would govern the authorization of take of marine mammals incidental to training and testing activities, and modernization and sustainment of ranges conducted in the Hawaii-California Training and Testing (HCTT) Study Area over the course of seven years from December 2025 through December 2032. NMFS requests comments on this proposed rule. NMFS will consider public comments prior to making any final decision on the promulgation of the requested ITR and issuance of the LOAs; agency responses to public comments will be summarized in the final rule, if issued. The Action Proponents' activities are considered military readiness activities pursuant to the MMPA, as amended by the National Defense Authorization Act for Fiscal Year 2004 (2004 NDAA) and the NDAA for Fiscal Year 2019 (2019 NDAA).

Dates

Comments and information must be received no later than August 15, 2025.

Addresses

A plain language summary of this proposed rule is available at: https://www.regulations.gov/docket/NOAA-NMFS-2025-0028. You may submit comments on this document, identified by NOAA-NMFS-2025-0028, by any of the following methods: Electronic Submission: Submit all electronic public comments via the Federal e-Rulemaking Portal. Visit https://www.regulations.gov and type NOAA-NMFS-2025-0028 in the Search box. Click on the ``Comment'' icon, complete the required fields, and enter or attach your comments. Mail: Submit written comments to Ben Laws, Incidental Take Program Supervisor, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910-3225. Fax: (301) 713-0376; Attn: Ben Laws. Instructions: Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing at: https://www.regulations.gov without change. All personal identifying information (e.g., name, address, etc.), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible. NMFS will accept anonymous comments (enter ``N/A'' in the required fields if you wish to remain anonymous). Attachments to electronic comments will be accepted in Microsoft Word, Excel, or Adobe PDF file formats only. A copy of the Action Proponents' Incidental Take Authorization (ITA) application and supporting documents, as well as a list of the references cited in this document, may be obtained online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities. In case of problems accessing these documents, please call the contact listed below (see FOR FURTHER INFORMATION CONTACT).

For Further Information Contact

Leah Davis, Office of Protected Resources, NMFS, (301) 427-8401.

Supplementary Information

Purpose and Need for Regulatory Action This proposed rule, if promulgated, would provide a framework under the authority of the MMPA (16 U.S.C. 1361 et seq.) to allow for the authorization of take of marine mammals incidental to the Action Proponents' training and testing activities and modernization and sustainment of ranges (which qualify as military readiness activities) involving the use of active sonar and other transducers, air guns, and explosives (also referred to as ``in-water detonations''); pile driving and vibratory extraction; land-based missile and target launches; and vessel movement in the HCTT Study Area. The HCTT Study Area includes areas in the north-central Pacific Ocean, from California west to Hawaii and the International Date Line, and including the Hawaii Range Complex (HRC) and Temporary Operating Area (TOA), Southern California (SOCAL) Range Complex, Point Mugu Sea Range (PMSR), Silver Strand Training Complex, areas along the Southern California coastline from approximately Dana Point to Port Hueneme, and the Northern California (NOCAL) Range Complex (see figure 1.1-1 of the rulemaking and LOA application (hereafter referred to as the application)). Please see the Legal Authority for the Proposed Action section for relevant definitions. Legal Authority for the Proposed Action The MMPA prohibits the ``take'' of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are proposed or, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review and the opportunity to submit comment. Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking; other ``means of effecting the least practicable adverse impact'' on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stocks for taking for certain subsistence uses (collectively referred to as ``mitigation''); and requirements pertaining to the monitoring and reporting of the takings. The MMPA defines ``take'' to mean to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal (16 U.S.C. 1362). The Preliminary Analysis and Negligible [[Page 32119]] Impact Determination section discusses the definition of ``negligible impact.'' The 2004 NDAA (Pub. L. 108-136) amended section 101(a)(5) of the MMPA to remove the ``small numbers'' and ``specified geographical region'' provisions, 16 U.S.C. 1371(a)(5)(F), and amended the definition of ``harassment'' in section 3(18)(B) of the MMPA as applied to a ``military readiness activity'' to read as follows: (1) Any act that injures or has the significant potential to injure a marine mammal or marine mammal stock in the wild (Level A Harassment); or (2) Any act that disturbs or is likely to disturb a marine mammal or marine mammal stock in the wild by causing disruption of natural behavioral patterns, including, but not limited to, migration, surfacing, nursing, breeding, feeding, or sheltering, to a point where such behavioral patterns are abandoned or significantly altered (Level B Harassment). 16 U.S.C. 1362(18)(B). The 2004 NDAA also amended the MMPA to establish in section 101(a)(5)(A)(iii) that ``[f]or a military readiness activity . . . , a determination of `least practicable adverse impact' . . . shall include consideration of personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity.'' 16 U.S.C. 1371(a)(5)(A)(iii). On August 13, 2018, the 2019 NDAA (Pub. L. 115-232) amended the MMPA to allow ITRs for military readiness activities to be issued for up to 7 years. 16 U.S.C. 1371(a)(5)(A)(ii). Summary of Major Provisions Within the Proposed Rule The major provisions of this proposed rule are as follows: The proposed authorization of take of marine mammals by Level A harassment and/or Level B harassment; The proposed authorization of take of marine mammals by mortality or serious injury (M/SI); The proposed use of defined powerdown and shutdown zones (based on activity); Proposed measures to reduce the likelihood of vessel strikes; Proposed activity limitations in certain areas and times that are biologically important (i.e., for foraging, migration, reproduction) for marine mammals; The proposed implementation of a Notification and Reporting Plan (for dead, live stranded, or marine mammals struck by any vessel engaged in military readiness activities); and The proposed implementation of a robust monitoring plan to improve our understanding of the environmental effects resulting from the Action Proponents' training and testing activities and modernization and sustainment of ranges. This proposed rule includes an adaptive management component that allows for timely modification of mitigation, monitoring, and/or reporting measures based on new information, when appropriate. Summary of Request On September 16, 2024, NMFS received an application from the Action Proponents requesting authorization to take marine mammals, by Level A and Level B harassment, incidental to training, testing, and modernization and sustainment of ranges (characterized as military readiness activities) including the use of sonar and other transducers, explosives, air guns, impact and vibratory pile driving and extraction, and land-based missile and target launches conducted within the HCTT Study Area. The Action Proponents also request authorization to take, by serious injury or mortality, a limited number of marine mammal species incidental to the use of explosives and vessel movement during military readiness activities conducted within the HCTT Study Area. The Action Proponents are requesting multiple 7-year LOAs for Navy training activities, Coast Guard training activities, Army training activities, and Navy testing activities. In response to our comments and following an information exchange, the Action Proponents submitted a revised application, deemed adequate and complete on December 13, 2024. On that same date, we published a notice of receipt of application in the Federal Register (89 FR 100982), requesting comments and information related to the Action Proponents' request for 30 days. During the 30- day public comment period on the NOR, we received one public comment from the Center for Biological Diversity. NMFS reviewed and considered all submitted material during the drafting of this proposed rule. NMFS has previously promulgated ITRs pursuant to the MMPA relating to similar military readiness activities in areas located within the HCTT Study Area. NMFS published the first rule effective from January 5, 2009 through January 5, 2014, (74 FR 1456, January 12, 2009), the second rule effective from December 24, 2013 through December 24, 2018 (78 FR 78106, December 24, 2013), and the third rule effective from December 21, 2018 through December 20, 2023 (83 FR 66846, December 27, 2018), which was subsequently amended, extending the effective date until December 20, 2025 (85 FR 41780, July 10, 2020) pursuant to the 2019 NDAA and later further amended to increase the take of large whales by vessel strike and modify the mitigation, monitoring, and reporting measures to reduce vessel strikes (90 FR 4944, January 16, 2025). For this proposed rulemaking, the Action Proponents propose to conduct substantially similar training and testing activities within the HCTT Study Area that were conducted under previous rules (noting that the Study Area has been expanded, as described in the Geographic Region section). The Action Proponents' application reflects the most up-to-date compilation of training and testing activities, and modernization and sustainment of ranges deemed necessary to accomplish military readiness requirements. The types and numbers of activities included in the proposed rule account for interannual variability in training and testing to meet evolving or emergent military readiness requirements. As explained herein, these proposed regulations also consolidate several actions conducted by the Navy that were previously authorized by NMFS and include some new military readiness activities carried out by the Action Proponents. In particular, these proposed regulations would cover incidental take during military readiness activities in the HCTT Study Area that would occur for a 7-year period following the expiration of the existing MMPA authorization which expires on December 20, 2025 (85 FR 41780, as amended by 90 FR 4944). In addition, this proposed rule includes PMSR activities for which incidental take has previously been authorized under separate authorizations, and, if finalized, this rule would supersede the most recent PMSR regulations (87 FR 40888, July 8, 2022). This proposed rule also includes areas along the Southern California coastline from approximately Dana Point to Port Hueneme and would supersede the incidental harassment authorization (IHA) allowing incidental take of marine mammals during pile driving training activities at Port Hueneme (90 FR 20283, May 13, 2025). In this proposed rule, we have undertaken a comprehensive assessment of the risks/impacts of all military training and testing activities on marine mammals likely to be present within the entire range of the Study Area. Description of Proposed Activity Overview The Action Proponents request authorization to take marine mammals [[Page 32120]] incidental to conducting military readiness activities. The Action Proponents have determined that acoustic and explosives stressors are likely to result in take of marine mammals in the form of Level A and B harassment, and that a limited number of takes by serious injury or mortality may result from vessel movement and use of explosives (including ship shock trials). Detailed descriptions of these activities are provided in chapter 2 and appendix A of the 2024 HCTT Draft Environmental Impact Statement/Overseas Environmental Impact Statement (2024 HCTT Draft EIS/OEIS) (https://www.nepa.navy.mil/hctteis/) and in the Action Proponents' application (https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities), which are summarized here. Of note, the U.S. Air Force (USAF) is a joint lead agency for the 2024 HCTT Draft EIS/OEIS; USAF activities consist of air combat maneuvers and air-to-air gunnery (a gunnery exercise in which fixed-wing aircraft fire medium caliber guns at air targets). The Action Proponents determined that USAF activities would not result in the take of marine mammals, and therefore these activities are not included in the Action Proponents' application. NMFS concurs that these activities are not anticipated to result in incidental take of marine mammals. The Navy's statutory mission is to organize, train, equip, and maintain combat-ready naval forces for the peacetime promotion of the national security interests and prosperity of the United States, and for prompt and sustained combat incident to operations essential to the prosecution of a naval campaign. This mission is mandated by Federal law (10 U.S.C. 8062 and 10 U.S.C. 8063), which requires the readiness of the naval forces of the United States. The Navy executes this responsibility by establishing and executing at-sea training and testing, often in designated operating areas (OPAREAs) and testing and training ranges. The Navy must be able to access and utilize these areas and associated sea and air space to develop and maintain skills for conducting naval operations. The Navy's testing activities ensure naval forces are equipped with well-maintained systems that take advantage of the latest technological advances. The Navy's research and acquisition community conducts military readiness activities that involve testing. The Navy tests vessels, aircraft, weapons, combat systems, sensors, and related equipment, and conducts scientific research activities to achieve and maintain military readiness. The mission of the Coast Guard is to ensure the maritime safety, security, and stewardship of the United States. To advance this mission, the Coast Guard must ensure its personnel can qualify and train jointly with, and independently of, the Navy and other services in the effective and safe operational use of Coast Guard vessels, aircraft, and weapons under realistic conditions. These activities help ensure the Coast Guard can safely assist in the defense of the United States by protecting the United States' maritime safety, security, and natural resources in accordance with its national defense mission (14 U.S.C. 102). Coast Guard training, which accounts for a small portion of overall activities, is summarized below. The Army is increasingly required to support the naval mission, frequently training in concert with the Navy. Some of this training includes the use of explosives in the marine environment. Dates and Duration The specified activities would occur at any time during the 7-year period of validity of the regulations. The proposed number of military readiness activities are described in the Detailed Description of the Specified Activity section (table 2 through table 9). Geographic Region The HCTT Study Area includes areas in the north-central Pacific Ocean, from California west to Hawaii and the International Date Line, and including the HRC and TOA, SOCAL Range Complex, PMSR, Silver Strand Training Complex, and the NOCAL Range Complex. The HRC encompasses ocean areas around the Hawaiian Islands, extending from 16 degrees north latitude to 43 degrees north latitude and from 150 degrees west longitude to the International Date Line (figure 1). It also includes pierside locations and port transit channels, bays, harbors, inshore waterways, amphibious approach lanes, and civilian ports where military readiness activities occur as well as transits between homeports and the Hawaii and California Study Areas. The geographic extent of the HRC remains the same and has not changed since the last rulemaking. The SOCAL Range Complex is located between Dana Point, California and San Antonio, Mexico, and extends southwest into the Pacific Ocean. The PMSR is located adjacent to Los Angeles, Ventura, Santa Barbara, and San Luis Obispo Counties along the Pacific Coast of Southern California. The Silver Strand Training Complex is an integrated set of training areas located on and adjacent to the Silver Strand, a narrow, sandy isthmus separating the San Diego Bay from the Pacific Ocean. The NOCAL Range Complex consists of two separate areas located offshore of central and northern California, one northwest of San Francisco and the other southwest of Monterey Bay. The SOCAL Range Complex expansion, which is new, and incorporation of existing NOCAL Range Complex and the PMSR, are revisions for the HCTT Study Area (formerly HSTT (Hawaii-Southern California Training and Testing) Study Area) in this application (noting that take from activities at PMSR are currently authorized under a separate rule (87 FR 40888, July 8, 2022)). This proposed rule also incorporates areas along the Southern California coastline from approximately Dana Point to Port Hueneme and includes the new IHA allowing incidental take of marine mammals during pile driving training activities at Port Hueneme (90 FR 20283, May 13, 2025). Please refer to figure 1.1-1 of the application for a color map of the HCTT Study Area and figure 2-1 through figure 2-17 for additional maps of the range complexes, training and testing ranges, and other notable areas. A summary of the HCTT Study Area Training and Testing Ranges are provided in table 1. BILLING CODE 3510-22-P [[Page 32121]] [GRAPHIC] [TIFF OMITTED] TP16JY25.001 BILLING CODE 3510-22-C [[Page 32122]] Table 1--HCTT Study Area Training and Testing Ranges ------------------------------------------------------------------------ Spatial extent Name Basic location (air, sea, and undersea space) ------------------------------------------------------------------------ Hawaii Range Complex (HRC).... Ocean areas around 235,000 nmi\2\ main Hawaiian islands (80,602,744 from 16 degrees north ha). latitude to 43 degrees north latitude and from 150 degrees west longitude to the International Date Line. Temporary Operating Area (TOA) North and west from 2,000,000 nmi\2\ the island of (585,980,800 Kaua[revaps]i. ha). Southern California Range Off San Diego County 217,000 nmi\2\ Complex (SOCAL). out to approximately (74,428,916 550 nmi (1,109 km). ha). Silver Strand Training Complex Subset of areas within 16 nmi\2\ (5,488 San Diego Bay and ha). adjacent to ocean out to approximately 4 nmi. Point Mugu Sea Range (PMSR)... Off Los Angeles and 36,000 nmi\2\ Ventura Counties out (12,347,654 to approximately 400 ha). nmi. Northern California Range Two separate areas 16,000 nmi\2\ Complex (NOCAL). located offshore of (5,487,846 ha). central and northern California, one northwest of San Francisco and the other southwest of Monterey Bay. ------------------------------------------------------------------------ Note: nmi\2\ = square nautical miles, ha = hectares, nmi = nautical miles, km = kilometer. Ports included in HCTT: San Diego Bay, California; Port Hueneme, California; and Pearl Harbor, Hawaii. Detailed Description of the Specified Activity The Action Proponents propose to conduct military readiness activities within the HCTT Study Area and have been conducting military readiness activities in the Study Area since the 1940s. The tempo and types of military readiness activities have varied interannually due to the introduction of new technologies, the evolving nature of international events, advances in warfighting doctrine and procedures, and changes in force structure (organization of vessels, weapons, and personnel). Such developments influence the frequency, duration, intensity, and location of required military readiness activities. Primary Mission Areas The Navy categorizes their activities into functional warfare areas called primary mission areas, while the Coast Guard categorizes their activities as operational mission programs. For the Navy, these activities generally fall six primary mission areas (Coast Guard mission areas are discussed below). The Navy mission areas with activities that may result in take of marine mammals (and stressors associated with training and testing activities within those mission areas) include the following: Amphibious warfare (in-water detonations); Anti-submarine warfare (sonar and other transducers, in- water detonations); Expeditionary warfare (in-water detonations, pile driving and extraction); Mine warfare (sonar and other transducers, in-water detonations); Surface warfare (in-water detonations and those occurring at or near the surface); and Other (sonar and other transducers, air guns, vessel movement, airborne noise from missile and target launches from San Nicolas Island (SNI) and from shore-to-surface gunnery and missile and aerial target launches from the Pacific Missile Range Facility (PMRF), unmanned systems training, and maintenance of ship and submarine sonar at piers and at-sea). Most Navy activities conducted in HCTT are categorized under one of these primary mission areas; activities that do not fall within one of these areas are listed as ``other activities.'' In addition, ship shock (underwater detonations) trials, a specific Navy testing activity related to vessel evaluation, would be conducted. The testing community also categorizes most, but not all, of its testing activities under these primary mission areas. The testing community has three additional categories of activities: vessel evaluation (including ship shock trials), unmanned systems (i.e., unmanned surface vehicles (USVs), unmanned underwater vehicles (UUVs)), and acoustic and oceanographic science and technology. The Action Proponents describe and analyze the effects of their activities within the application (see the 2024 HCTT Draft EIS/OEIS for additional details). In their assessment, the Action Proponents concluded that sonar and other transducers, explosives (in-water detonations and those occurring at or near the surface), air guns, land-based missile and target launches, and pile driving/extraction were the stressors most likely to result in impacts on marine mammals that qualify as harassment (and serious injury or mortality by explosives or vessel strike) as defined under the MMPA. Therefore, the Action Proponents' application provides their assessment of potential effects from these stressors in terms of the primary warfare mission areas in which they would be conducted. The Coast Guard has four major national defense missions: Maritime intercept operations; Deployed port operations/security and defense; Peacetime engagement; and Environmental defense operations (including oil and hazardous substance response). The Coast Guard manages 6 major operational mission programs with 11 statutory missions, which includes defense readiness. As part of the Coast Guard's defense mission, 14 U.S.C. 1 states the Coast Guard is ``at all times an armed force of the United States.'' As part of the Joint Forces, the Coast Guard maintains its readiness to carry out military operations in support of the policies and objectives of the U.S. government. As an armed force, the Coast Guard trains and operates in the joint military arena at any time and functions as a specialized service under the Navy in time of war or when directed by the President. Coast Guard service members are trained to respond immediately to support military operations and national security. Federal law created the framework for the relationship between the Navy and the Coast Guard (10 U.S.C. 101; 14 U.S.C. 2 (7); 22 U.S.C. 2761; 50 U.S.C. 3004). To meet these statutory requirements and effectively carry out these missions, the Coast Guard's air and surface units train using realistic scenarios, including training with the Navy in their primary mission areas. Every Coast Guard unit is trained to support all statutory missions and, thus, trained to meet all mission requirements, which includes their defense mission requirements. Since all Coast Guard's missions generally entail the deployment of cutters or boats and either fixed-wing or rotary aircraft, the Coast Guard training requirements for one mission generally overlaps with the training requirements of other missions. Thus, when the Coast Guard is training [[Page 32123]] for its defense mission, the same skill sets are utilized for its other statutory missions. The Coast Guard's defense mission does not involve use of low- or mid-frequency active sonar (LFAS or MFAS), missiles, in-water detonations, pile driving and vibratory extraction, or air guns that would result in harassment of marine mammals. The Army's mission is mandated by Federal law (10 U.S.C. 7062), which requires an Army capable of, in conjunction with the other armed forces: Preserving the peace and security, and providing for the defense, of the United States, the Commonwealths and possessions, and any areas occupied by the United States; Supporting the national policies; Implementing the national objectives; and Overcoming any nations responsible for aggressive acts that imperil the peace and security of the United States. In general, the Army includes land combat and service forces, as well as aviation and water transport. It shall be organized, trained, and equipped primarily for prompt and sustained combat incident to operations on land. It is responsible for the preparation of land forces necessary for the effective prosecution of war except as otherwise assigned and, in accordance with integrated joint mobilization plans, for the expansion of the peacetime components of the Army to meet the needs of war. The Army is increasingly required to operate in the marine environment and with the Navy and, therefore, have an increased requirement to train in the maritime environment. The Army's activities include only the use of explosives, and do not include the use of sonars or other transducers, pile driving and vibratory extraction, or air guns that would result in harassment of marine mammals. Below, we provide additional detail for each of the applicable primary mission areas. Amphibious Warfare-- The mission of amphibious warfare is to project military power from the sea to the shore (i.e., attack a threat on land by a military force embarked on ships) through the use of naval firepower and expeditionary landing forces. Amphibious warfare operations include Army, Navy, and Marine Corps small unit reconnaissance or raid missions to large-scale amphibious exercises involving multiple ships and aircraft combined into a strike group. Amphibious warfare training ranges from individual, crew, and small unit events to large task force exercises. Individual and crew training includes amphibious vehicles and naval gunfire support training. Such training includes shore assaults, boat raids, airfield or port seizures, reconnaissance, and disaster relief. Large-scale amphibious exercises involve ship-to-shore maneuvers, naval fire support such as shore bombardment, air strikes, shore-based missile and artillery firing, and attacks on targets that are near friendly forces. Some amphibious activities include firing at ships from shore in defense of the amphibious objective. Testing of guns, munitions, aircraft, ships, and amphibious vessels and vehicles used in amphibious warfare are often integrated into training activities and, in most cases, the systems are used in the same manner in which they are used for training activities. Amphibious warfare tests, when integrated with training activities or conducted separately as full operational evaluations on existing amphibious vessels and vehicles following maintenance, repair, or modernization, may be conducted independently or in conjunction with other amphibious ship and aircraft activities. Testing is performed to ensure effective ship-to-shore coordination and transport of personnel, equipment, and supplies. Tests may also be conducted periodically on other systems, vessels, and aircraft intended for amphibious operations to assess operability and to investigate efficacy of new technologies. Anti-Submarine Warfare-- The mission of anti-submarine warfare is to locate, neutralize, and defeat hostile submarine forces that threaten Navy forces. Anti- submarine warfare is based on the principle that surveillance and attack aircraft, ships, and submarines all search for hostile submarines. These forces operate together or independently to gain early warning and detection and to localize, track, target, and attack submarine threats. Anti-submarine warfare training addresses basic skills such as detecting and classifying submarines, as well as evaluating sounds to distinguish between enemy submarines and friendly submarines, ships, and marine life. More advanced training integrates the full spectrum of anti-submarine warfare from detecting and tracking a submarine to attacking a target using either exercise torpedoes (i.e., torpedoes that do not contain a warhead) or simulated weapons. These integrated anti-submarine warfare training exercises are conducted in coordinated, at-sea training events involving submarines, ships, and aircraft. Testing of anti-submarine warfare systems is conducted to develop new technologies and assess weapon performance and operability with new systems and platforms, such as unmanned systems. Testing uses ships, submarines, and aircraft to demonstrate capabilities of torpedoes, missiles, countermeasure systems, and underwater surveillance and communications systems. Tests may be conducted as part of a large-scale fleet training event involving submarines, ships, fixed-wing aircraft, and helicopters. These integrated training events offer opportunities to conduct research and acquisition activities and to train aircrew in the use of new or newly enhanced systems during a large-scale, complex exercise. Expeditionary Warfare-- The mission of expeditionary warfare is to provide security and surveillance in the littoral (i.e., at the shoreline), riparian (i.e., along a river), or coastal environments. Expeditionary warfare is wide ranging and includes defense of harbors, operation of remotely operated vehicles, clearing obstacles, small boat attack, and boarding/seizure operations. Expeditionary warfare training activities conducted by the Action Proponents include underwater construction team training, diver propulsion device training and testing, parachute insertion, dive and salvage operations, and insertion/extraction via air, surface, and subsurface platforms, among others (see appendix A (Activity Descriptions) of the 2024 HCTT Draft EIS/OEIS for a full description of the expeditionary warfare activities). Mine Warfare-- The mission of mine warfare is to detect, classify, and avoid or neutralize (i.e., disable) mines to protect U.S. ships and submarines, and to maintain free access to ports and shipping lanes. Mine warfare training for the Navy falls into two primary categories: mine detection and classification, and mine countermeasure and neutralization. Mine warfare also includes offensive mine laying to gain control of or deny the enemy access to sea space. Naval mines can be laid by ships, submarines, UUVs, or aircraft. Mine warfare neutralization training includes exercises in which aircraft, ships, submarines, underwater vehicles, unmanned vehicles, or marine mammal detection systems search for mine shapes. Personnel train to destroy or disable mines by attaching underwater [[Page 32124]] explosives to or near the mine or using remotely operated vehicles to destroy the mine. Towed influence mine sweep systems mimic a particular ship's magnetic and acoustic signature, which would trigger a real mine causing it to explode. Testing and development of mine warfare systems is conducted to improve sonar, laser, and magnetic detectors intended to hunt, locate, and record the positions of mines for avoidance or subsequent neutralization. Mine detection and classification testing involves the use of air, surface, and subsurface vessels and uses sonar, including towed and side-scan sonar, and unmanned vehicles to locate and identify objects underwater. Mine detection and classification systems are sometimes used in conjunction with a mine neutralization system. Mine countermeasure and neutralization testing includes the use of air, surface, and subsurface units and uses tracking devices, countermeasure and neutralization systems, and general purpose bombs to evaluate the effectiveness of neutralizing mine threats. Most neutralization tests use mine shapes, or non-explosive practice mines, to accomplish the requirements of the activity. For example, during a mine neutralization test, a previously located mine is destroyed or rendered nonfunctional using a helicopter or manned surface vehicle/USV-based system that may involve the deployment of a towed neutralization system. A small percentage of mine warfare testing activities require the use of high-explosive mines to evaluate and confirm the ability of the system to neutralize a high-explosive mine under operational conditions. Only a subset of all mine warfare training areas are approved for underwater explosive use (see figures 2-5, 2-11, and 2-12 of the application). The majority of mine warfare systems are deployed by ships, helicopters, and unmanned vehicles. Tests may also be conducted in support of scientific research to support these new technologies (see appendix H (Description of Systems and Ranges) of the 2024 HCTT Draft EIS/OEIS for additional details). Surface Warfare-- The mission of surface warfare is to obtain control of sea space from which naval forces may operate and entails offensive action against surface and subsurface targets while also defending against enemy forces. In surface warfare, aircraft use guns, air-launched cruise missiles, or other precision-guided munitions; ships employ naval guns and surface-to-surface missiles; and submarines attack surface ships using torpedoes or submarine-launched, anti-ship cruise missiles. Surface warfare training includes Navy, Coast Guard, and Army surface-to-surface gunnery and missile exercises, air-to-surface gunnery, bombing, and missile exercises, submarine missile or torpedo launch events, other munitions against surface targets, and amphibious operations in a contested environment. Testing of weapons used in surface warfare is conducted to develop new technologies and to assess weapon performance and operability with new systems and platforms, such as unmanned systems. Tests include various air-to-surface guns and missiles, surface-to-surface guns and missiles, and bombing tests. Testing events may be integrated into training activities to test aircraft or aircraft systems in the delivery of ordnance on a surface target. In most cases the tested systems are used in the same manner in which they are used for training activities. Other Training Activities-- Other training activities are conducted in the HCTT Study Area that fall outside of the primary mission areas but support overall readiness. These activities include sonar and other transducers, vessel movement, missile and target launch noise from locations on SNI and PMRF, artillery firing noise from shore to surface gunnery at PMRF, unmanned systems training, and maintenance of ship and submarine sonar at piers and at-sea. Overview of Training Activities Within the Study Area The Action Proponents routinely train in the HCTT Study Area in preparation for national defense missions. Training activities and exercises covered in this proposed rule are briefly described below and in more detail within appendix A (Activity Descriptions) of the 2024 HCTT Draft EIS/OEIS. The description, annual number of activities, and location of each training activity are provided by stressor category in table 2 through table 5. Each training activity described meets a requirement that can be traced ultimately to requirements set forth by the National Command Authority. Within the Navy, a major training exercise (MTE) is comprised of multiple ``unit-level'' range exercises conducted by several units operating together while commanded and controlled by a single commander. These units are collectively referred to as carrier and expeditionary strike groups. These exercises typically employ an exercise scenario developed to train and evaluate the strike group in tactical naval tasks. In a MTE, most of the operations and activities being directed and coordinated by the strike group commander are identical in nature to the operations conducted during individual, crew, and smaller unit-level training events. However, in MTEs, these disparate training tasks are conducted in concert rather than in isolation. Some integrated or coordinated anti-submarine warfare exercises are similar in that they are composed of several unit-level exercises but are generally on a smaller scale than a MTE, are shorter in duration, use fewer assets, and use fewer hours of hull-mounted sonar per exercise. Coordinated training exercises involve multiple units working together to meet unit-level training requirements, whereas integrated training exercises involve multiple units working together in preparation for deployment. Coordinated exercises involving the use of sonar are presented under the category of anti-submarine warfare. The anti-submarine warfare portions of these exercises are considered together in coordinated activities for the sake of acoustic modeling. When other training objectives are being met, those activities are described via unit-level training in each of the relevant primary mission areas. With a smaller fleet of approximately 250 cutters, Coast Guard activities are not as extensive as Navy activities due to differing mission requirements. However, the Coast Guard does train with the Navy and conducts some of the same training as the Navy. The Coast Guard does not conduct any exercises similar in scale to Navy MTEs/integrated exercises, and the use of mid- or low-frequency sonar, missiles, and underwater detonations are examples of actions that are not a part of the Coast Guard's mission requirements. Coast Guard training generally occurs close to the vessel homeport or close to shore, on established Navy training and testing ranges, or in transit to a scheduled patrol/ mission. There are approximately 1,600 Coast Guard vessels (cutters up to 418 feet (ft); 127.4 meters (m) and boats less than 65 ft (19.8 m)), and the largest cutters would be underway for 3-4 months, whereas the smaller cutters would be underway from a few days to 4 weeks. Within California, there are approximately 20 cutters homeported. Cutters are defined as vessels larger than 65 ft (19.8 m). The service has about 1,680 boats nation-wide altogether. These craft include heavy weather response boats, special purpose craft, [[Page 32125]] aids-to-navigation (ATON) boats, and cutter-based boats. Sizes range from 64 ft (29.5 m) in length down to 12 ft (3.7 m). There are approximately 100 boats in California but the number of boats varies. Within Hawaii, the Coast Guard has eight cutters and an unspecified number of small boats homeported. The MTEs and integrated/coordinated training activities analyzed for this request are Navy-led exercises in which the Coast Guard may participate and described in table 2. For additional information on these activities see table 1-8 of the application and appendix A (Activity Descriptions) of the 2024 HCTT Draft EIS/OEIS. Table 3 describes the proposed Navy training activities analyzed within the HCTT Study Area while table 4 describes the proposed Coast Guard training activities analyzed within the HCTT Study Area and table 5 describes the Army training activities analyzed within the HCTT Study Area. In addition to participating in Navy-led exercises, Coast Guard and Army training activities include unit-level activities conducted independently of, and not in coordination with, the Navy. Table 2--MTEs and Integrated/Coordinated Training Activities Analyzed Within the HCTT Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Typical hull-mounted Training type Exercise group Description Scale Duration Location (range Exercise sonar per complex) examples event (hours) -------------------------------------------------------------------------------------------------------------------------------------------------------- Major Training Exercise....... Large Integrated Larger-scale, Greater than 6 Generally SOCAL, PMSR, HRC Strike Group >500 ASW. longer duration surface ASW greater than 10 COMPUTEX, integrated ASW units (up to 30 days. RIMPAC. exercises. with the largest exercises), 2 or more submarines, multiple ASW aircraft. Major Training Exercise....... Medium Medium-scale, Approximately 3- Generally 4-10 SOCAL, PMSR, HRC Task Force/ 100-500 Integrated ASW. medium duration 8 surface ASW days. Sustainment integrated ASW units, at least Exercise, Multi- exercises. 1 submarine, Warfare multiple ASW Exercise. aircraft. Integrated/Coordinated Small Integrated Small-scale, Approximately 3- Generally less SOCAL, HRC...... SWATT, NUWTAC... 50-100 Training. ASW. short duration 6 surface ASW than 5 days. integrated ASW units, 2 exercises. dedicated submarines, 2-6 ASW aircraft. Integrated/Coordinated Medium Medium-scale, Approximately 2- Generally 3-10 SOCAL, HRC...... SCC, Fleet <100 Training. Coordinated ASW. medium 4 surface ASW days. Battle Problem, duration, units, possibly TACDEVEX. coordinated ASW a submarine, 2- exercises. 5 ASW aircraft. Integrated/Coordinated Small Small-scale, Approximately 2- Generally 2-4 SOCAL, HRC...... ID CERTEX....... <50 Training. Coordinated ASW. short duration, 4 surface ASW days. coordinated ASW units, possibly exercises. a submarine, 1- 2 ASW aircraft. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: ASW = Anti-Submarine Warfare, HRC = Hawaii Range Complex, ID CERTEX = Independent Deployer Certification Exercise, NUWTAC = Naval Undersea Warfare Training Assessment Course, PMSR = Point Mugu Sea Range Overlap, RIMPAC = Rim of the Pacific, SCC = Submarine Commanders Course, SOCAL = Southern California Range Complex, SWATT = Surface Warfare Advanced Tactical Training, TACDEVEX = Tactical Development Exercise. Table 3--Proposed Navy Training Activities Analyzed Within the HCTT Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Number of Number of Stressor category Activity type Activity name Description Source bin activities activities Location 1-year 7-year -------------------------------------------------------------------------------------------------------------------------------------------------------- Acoustic...................... Major Training Composite Aircraft carrier LFH, MF to HF, 1-2 11 Hawaii, SOCAL, Exercise--Large Training Unit and carrier air MF1, MFH, MFM. PMSR, NOCAL. Integrated ASW. Exercise. wing integrates with surface and submarine units in a challenging multi-threat operational environment that certifies them ready to deploy. Duration: 21 days. Acoustic...................... Major Training Rim of the A biennial HFH, MF1, MFH, 0-1 4 Hawaii, SOCAL. Exercise--Large Pacific Exercise. multinational MFM. Integrated ASW. training exercise in which navies from around the world assemble in Pearl Harbor, Hawaii, to conduct training throughout the Hawaiian Islands in a number of warfare areas. Marine mammal systems may be used during a Rim of the Pacific exercise. Components of a Rim of the Pacific exercise, such as certain mine warfare and amphibious training, may be conducted in the Southern California Range Complex. Duration: 30 days. [[Page 32126]] Acoustic...................... Major Training Task Force/ Aircraft carrier LFH, MF to HF, 0-1 3 Hawaii. Exercise--Medium Sustainment and carrier air MF1, MFH, MFM. Integrated ASW. Exercise. wing integrates with surface and submarine units in a challenging multi-threat operational environment to maintain ability to deploy. Duration: 10 days. Acoustic...................... Major Training Task Force/ Aircraft carrier LFH, MF to HF, 0-1 3 SOCAL, PMSR, Exercise--Medium Sustainment and carrier air MF1, MFH, MFM. NOCAL. Integrated ASW. Exercise. wing integrates with surface and submarine units in a challenging multi-threat operational environment to maintain ability to deploy. Duration: 10 days. Acoustic...................... Integrated/ Composite Navy and USMC LFH, MF to HF, 1-2 10 Hawaii, SOCAL, Coordinated ASW. Training Unit forces conduct MF1, MFH, MFM. PMSR, NOCAL. Exercise--Amphib integration ious Ready Group/ training at sea Marine in preparation Expeditionary for deployment. Unit. Duration: 3 weeks. Acoustic...................... Integrated/ Independent Multiple ships, MF to HF, MF1, 8-19 89 SOCAL, PMSR, Coordinated ASW. Deployer aircraft, and MFH, MFM. NOCAL. Certification submarines Exercise/ conduct Tailored Surface integrated multi- Warfare Training. warfare training with a surface warfare emphasis. Serves as a ready-to- deploy certification for individual surface ships tasked with surface warfare missions. Duration: 2-3 days. Acoustic...................... Integrated/ Medium Multiple ships, MF to HF, MF1, 12-17 99 Hawaii. Coordinated ASW. Coordinated ASW. aircraft, and MFH, MFM. submarines integrate the use of their sensors, including sonobuoys and unmanned systems, to search, detect, and track threat submarines; event may include inert torpedo firings. Duration: 3-10 days. Acoustic...................... Integrated/ Medium Multiple ships, MF to HF, MF1, 5-13 59 SOCAL, PMSR, Coordinated ASW. Coordinated ASW. aircraft, and MFH, MFM. NOCAL. submarines integrate the use of their sensors, including sonobuoys and unmanned systems, to search, detect, and track threat submarines; event may include inert torpedo firings. Duration: 3-10 days. Acoustic...................... Integrated/ Small Joint Typically, a 5- LFH, MF to HF, 1 7 Hawaii. Coordinated ASW. Coordinated ASW. day exercise MF1, MFH, MFM. with multiple ships, aircraft and submarines integrating the use of their sensors, including sonobuoys, to search, detect, and track threat submarines. Duration: 5 days. Acoustic...................... Integrated/ Small Joint Typically, a 5- LFH, MF to HF, 4-9 43 SOCAL, PMSR, Coordinated ASW. Coordinated ASW. day exercise MF1, MFH, MFM. NOCAL. with multiple ships, aircraft and submarines integrating the use of their sensors, including sonobuoys, to search, detect, and track threat submarines. Duration: 5 days. Explosive..................... Integrated/ Large Amphibious The Large E9............... 0-1 2 Hawaii. Coordinated Exercise. Amphibious Training--Other. Exercise utilizes all elements of the Marine Air Ground Task Force (Amphibious) to secure the battlespace (air, land, and sea), maneuver to and seize the objective, and conduct self- sustaining operations ashore with logistic support of the Expeditionary Strike Group. This exercise could include manned and unmanned activities in multiple warfare areas to secure the battlespace (air, land, and sea) and maneuver and secure operations ashore. Duration: 1 week. [[Page 32127]] Explosive..................... Integrated/ Large Amphibious The Large E9............... 2-4 20 SOCAL, PMSR, Coordinated Exercise. Amphibious NOCAL. Training--Other. Exercise utilizes all elements of the Marine Air Ground Task Force (Amphibious) to secure the battlespace (air, land, and sea), maneuver to and seize the objective, and conduct self- sustaining operations ashore with logistic support of the Expeditionary Strike Group. This exercise could include manned and unmanned activities in multiple warfare areas to secure the battlespace (air, land, and sea) and maneuver and secure operations ashore. Duration: 1 week. Acoustic and Explosive........ Integrated/ Innovation and These exercises E5, HFH, LF to 0-1 4 Hawaii. Coordinated Demonstration are conducted to HF, LFH, MF to Training--Other. Exercise. demonstrate or HF, MF1, MFH, test new MFM. capabilities, tactics, techniques, and procedures; and generate standardized, actionable data for evaluation. Duration: 1 week. Acoustic and Explosive........ Integrated/ Innovation and These exercises E5, HFH, LF to 3 16 SOCAL. Coordinated Demonstration are conducted to HF, LFH, MF to Training--Other. Exercise. demonstrate or HF, MF1, MFH, test new MFM. capabilities, tactics, techniques, and procedures; and generate standardized, actionable data for evaluation. Duration: 1 week. Acoustic and Explosive........ Integrated/ Innovation and These exercises E5, HFH, LF to 1 7 Transit Corridor. Coordinated Demonstration are conducted to HF, LFH, MF to Training--Other. Exercise. demonstrate or HF, MF1, MFH, test new MFM. capabilities, tactics, techniques, and procedures; and generate standardized, actionable data for evaluation. Duration: 1 week. Acoustic and Explosive........ Integrated/ Multi-Warfare Live training E5, HFH, LF to 2 12 Hawaii. Coordinated Exercise. events which HF, LFH, MF to Training--Other. could involve HF, MF1, MFH, U.S., Joint, and MFM. coalition forces operating across all warfare areas (e.g., amphibious, electronic and cyber, air, surface, sub- surface, special warfare, and expeditionary) with manned and unmanned platforms. Events could be comprised of small units up to and including Carrier and Amphibious Strike Groups. Live-fire events could be ship-to- shore, shore-to- offshore target, and ship-to-ship utilizing live ordnance and laser systems. Duration: 1-5 days. Acoustic and Explosive........ Integrated/ Multi-Warfare Live training E5, HFH, LF to 6-7 43 SOCAL, PMSR. Coordinated Exercise. events which HF, LFH, MF to Training--Other. could involve HF, MF1, MFH, U.S., Joint, and MFM. coalition forces operating across all warfare areas (e.g., amphibious, electronic and cyber, air, surface, sub- surface, special warfare, and expeditionary) with manned and unmanned platforms. Events could be comprised of small units up to and including Carrier and Amphibious Strike Groups. Live-fire events could be ship-to- shore, shore-to- offshore target, and ship-to-ship utilizing live ordnance and laser systems. Duration: 1-5 days. [[Page 32128]] Explosive..................... Amphibious Amphibious Navy and Marine E2............... 15 105 Hawaii. Warfare. Operations in a Corps forces Contested conduct Environment. operations in coastal and offshore waterways against air, surface, and subsurface threats. Duration: 1-2 weeks. Explosive..................... Amphibious Amphibious Navy and Marine E2............... 10 70 SOCAL, SSTC. Warfare. Operations in a Corps forces Contested conduct Environment. operations in coastal and offshore waterways against air, surface, and subsurface threats. Duration: 1-2 weeks. Explosive..................... Amphibious Naval Surface Surface ship E5............... 20-25 155 Hawaii. Warfare. Fire Support crews fire large- Exercise-At Sea. caliber guns at a passive acoustic hydrophone scoring system. Duration: 1-2 hours of firing, 8 hours total. Explosive..................... Amphibious Shore-to-Surface Amphibious land- E6............... 1 7 PMRF. Warfare. Artillery based forces Exercise. fire artillery guns at surface targets. Duration: 1-2 hours of firing, 8 hours total. Explosive..................... Amphibious Shore-to-Surface Amphibious land- E6............... 12 84 SCI. Warfare. Artillery based forces Exercise. fire artillery guns at surface targets. Duration: 1-2 hours of firing, 8 hours total. Explosive..................... Amphibious Shore-to-Surface Amphibious land- E9............... 4 28 PMRF. Warfare. Missile Exercise. based forces fire anti- surface missiles, rockets, and loitering munitions at surface targets. Duration: 1-2 hours of firing, 8 hours total. Explosive..................... Amphibious Shore-to-Surface Amphibious land- E9............... 15 105 SCI. Warfare. Missile Exercise. based forces fire anti- surface missiles, rockets, and loitering munitions at surface targets. Duration: 1-2 hours of firing, 8 hours total. Acoustic...................... Anti-Submarine Anti-Submarine Helicopter crews HFH, MFH, MFM.... 3-5 27 BARSTUR. Warfare. Warfare Torpedo search for, Exercise--Helico track, and pter. detect submarines. Recoverable air launched torpedoes are employed against submarine targets. Duration: 2-5 hours. Acoustic...................... Anti-Submarine Anti-Submarine Helicopter crews HFH, MFH, MFM.... 3-5 27 SOAR. Warfare. Warfare Torpedo search for, Exercise--Helico track, and pter. detect submarines. Recoverable air launched torpedoes are employed against submarine targets. Duration: 2-5 hours. Acoustic...................... Anti-Submarine Anti-Submarine Maritime patrol HFH, MFM......... 20-80 320 BARSTUR. Warfare. Warfare Torpedo aircraft Exercise--Mariti aircrews search me Patrol for, track, and Aircraft. detect submarines. Recoverable air launched torpedoes are employed against submarine targets. Duration: 2-8 hours. Acoustic...................... Anti-Submarine Anti-Submarine Maritime patrol HFH, MFM......... 60-80 480 SOAR. Warfare. Warfare Torpedo aircraft Exercise--Mariti aircrews search me Patrol for, track, and Aircraft. detect submarines. Recoverable air launched torpedoes are employed against submarine targets. Duration: 2-8 hours. Acoustic...................... Anti-Submarine Anti-Submarine Surface ship HFH, MF to HF, 34 238 BARSTUR, BSUR. Warfare. Warfare Torpedo crews search MF1. Exercise--Ship. for, track, and detect submarines. Exercise torpedoes are used. Duration: 2-5 hours. Acoustic...................... Anti-Submarine Anti-Submarine Surface ship HFH, MF to HF, 104 728 SOAR. Warfare. Warfare Torpedo crews search MF1. Exercise--Ship. for, track, and detect submarines. Exercise torpedoes are used. Duration: 2-5 hours. Acoustic...................... Anti-Submarine Anti-Submarine Submarine crews HFH, LF to HF, 48 336 BARSTUR. Warfare. Warfare Torpedo search for, MFH. Exercise--Submar track, and ine. detect submarines. Exercise torpedoes are used. Duration: 8 hours. Acoustic...................... Anti-Submarine Anti-Submarine Submarine crews HFH, LF to HF, 26 182 SOAR. Warfare. Warfare Torpedo search for, MFH. Exercise--Submar track, and ine. detect submarines. Exercise torpedoes are used. Duration: 8 hours. [[Page 32129]] Acoustic...................... Anti-Submarine Anti-Submarine Helicopter crews MFH, MFM......... 125-130 890 Hawaii. Warfare. Warfare Tracking search for, Exercise--Helico track, and pter. detect submarines. Duration: 2-4 hours. Acoustic...................... Anti-Submarine Anti-Submarine Helicopter crews MFH, MFM......... 125-130 890 SOCAL, PMSR. Warfare. Warfare Tracking search for, Exercise--Helico track, and pter. detect submarines. Duration: 2-4 hours. Acoustic...................... Anti-Submarine Anti-Submarine Unmanned surface MFM.............. 5 35 Hawaii. Warfare. Warfare Tracking vessels search Exercise--Long- for, detect, and Range unmanned track a sub- Surface Vessel. surface target simulating a threat submarine with the goal of determining a firing solution that could be used to launch a torpedo. Duration: 1 day. Acoustic...................... Anti-Submarine Anti-Submarine Unmanned surface MFM.............. 2 14 SOCAL. Warfare. Warfare Tracking vessels search Exercise--Long- for, detect, and Range unmanned track a sub- Surface Vessel. surface target simulating a threat submarine with the goal of determining a firing solution that could be used to launch a torpedo. Duration: 1 day. Acoustic...................... Anti-Submarine Anti-Submarine Maritime patrol LFH, LFM, MFM.... 150-200 1,200 Hawaii. Warfare. Warfare Tracking aircraft Exercise--Mariti aircrews search me Patrol for, track, and Aircraft. detect submarines. Duration: 2-8 hours. Acoustic...................... Anti-Submarine Anti-Submarine Maritime patrol LFH, LFM, MFM.... 200 1,400 SOCAL, PMSR. Warfare. Warfare Tracking aircraft Exercise--Mariti aircrews search me Patrol for, track, and Aircraft. detect submarines. Duration: 2-8 hours. Acoustic...................... Anti-Submarine Anti-Submarine Surface ship MF to HF, MF1, 60-119 595 Hawaii. Warfare. Warfare Tracking crews search MFH. Exercise--Ship. for, track, and detect submarines. Duration: 2-4 hours. Acoustic...................... Anti-Submarine Anti-Submarine Surface ship MF to HF, MF1, 240-480 2,400 SOCAL, PMSR. Warfare. Warfare Tracking crews search MFH. Exercise--Ship. for, track, and detect submarines. Duration: 2-4 hours. Acoustic...................... Anti-Submarine Anti-Submarine Submarine crews HFH, MFH......... 200 1,400 Hawaii. Warfare. Warfare Tracking search for, Exercise--Submar track, and ine. detect submarines. Duration: 8 hours. Acoustic...................... Anti-Submarine Anti-Submarine Submarine crews HFH, MFH......... 60 420 SOCAL, PMSR, Warfare. Warfare Tracking search for, NOCAL. Exercise--Submar track, and ine. detect submarines. Duration: 8 hours. Acoustic...................... Anti-Submarine Anti-Submarine Submarine crews HFH, MFH......... 9 63 Transit Corridor. Warfare. Warfare Tracking search for, Exercise--Submar track, and ine. detect submarines. Duration: 8 hours. Acoustic and Explosive........ Anti-Submarine Training and End- A submarine E11, HFH, HFM, 2 14 BARSTUR. Warfare. to-End Mission launches MFH. Capability exercise and Verification--To explosive rpedo. torpedoes at a suspended target. Duration: 8 hours. Acoustic and Explosive........ Anti-Submarine Training and End- A submarine E11, HFH, HFM, 1 7 SOAR. Warfare. to-End Mission launches MFH. Capability exercise and Verification--To explosive rpedo. torpedoes at a suspended target. Duration: 8 hours. Acoustic...................... Expeditionary Port Damage Navy Pile Driving..... 12 84 Port Hueneme. Warfare. Repair. Expeditionary forces train to repair critical port facilities. Duration: 8 hours per day for 5 days. Explosive..................... Expeditionary Obstacle Trains forces to E2............... 40 280 FORACS. Warfare. Clearance. create cleared lanes in simulated enemy obstacle systems to allow friendly forces safe transit from sea to shore. Duration: 8 hours. Explosive..................... Expeditionary Obstacle Trains forces to E2............... 10 70 Lima Landing. Warfare. Clearance. create cleared lanes in simulated enemy obstacle systems to allow friendly forces safe transit from sea to shore. Duration: 8 hours. Explosive..................... Expeditionary Obstacle Trains forces to E2............... 10 70 Pearl Peninsula. Warfare. Clearance. create cleared lanes in simulated enemy obstacle systems to allow friendly forces safe transit from sea to shore. Duration: 8 hours. Explosive..................... Expeditionary Obstacle Trains forces to E6............... 10 70 Pu'uloa. Warfare. Clearance. create cleared lanes in simulated enemy obstacle systems to allow friendly forces safe transit from sea to shore. Duration: 8 hours. [[Page 32130]] Explosive..................... Expeditionary Obstacle Trains forces to E2............... 100-150 850 SOCAL. Warfare. Clearance. create cleared lanes in simulated enemy obstacle systems to allow friendly forces safe transit from sea to shore. Duration: 8 hours. Explosive..................... Expeditionary Obstacle Trains forces to E10.............. 6 42 SCI. Warfare. Clearance. create cleared lanes in simulated enemy obstacle systems to allow friendly forces safe transit from sea to shore. Duration: 8 hours. Explosive..................... Expeditionary Personnel Personnel are E1............... 8 56 FORACS. Warfare. Insertion/ inserted into a Extraction--Air. water objective via fixed-wing aircraft using parachutes or by helicopters via ropes or jumping into the water. Personnel are extracted by helicopters or small boats. Duration: 1 hour. Explosive..................... Expeditionary Personnel Personnel are E1............... 26 182 Pearl Peninsula. Warfare. Insertion/ inserted into a Extraction--Air. water objective via fixed-wing aircraft using parachutes or by helicopters via ropes or jumping into the water. Personnel are extracted by helicopters or small boats. Duration: 1 hour. Explosive..................... Expeditionary Personnel Personnel are E1............... 500 3,500 Hawaii. Warfare. Insertion/ inserted into a Extraction--Air. water objective via fixed-wing aircraft using parachutes or by helicopters via ropes or jumping into the water. Personnel are extracted by helicopters or small boats. Duration: 1 hour. Explosive..................... Expeditionary Personnel Personnel are E1............... 854-954 6,278 SOCAL. Warfare. Insertion/ inserted into a Extraction--Air. water objective via fixed-wing aircraft using parachutes or by helicopters via ropes or jumping into the water. Personnel are extracted by helicopters or small boats. Duration: 1 hour. Explosive..................... Expeditionary Personnel Personnel are E1............... 500-600 3,800 SSTC. Warfare. Insertion/ inserted into a Extraction--Air. water objective via fixed-wing aircraft using parachutes or by helicopters via ropes or jumping into the water. Personnel are extracted by helicopters or small boats. Duration: 1 hour. Explosive..................... Expeditionary Personnel Personnel are E1............... 270-336 2,088 Hawaii. Warfare. Insertion/ inserted into Extraction--Surf and extracted ace and from an subsurface. objective area by small boats or subsurface platforms. Duration: 2-4 hours. Explosive..................... Expeditionary Personnel Personnel are E1............... 1,049-1,149 7,643 SOCAL. Warfare. Insertion/ inserted into Extraction--Surf and extracted ace and from an subsurface. objective area by small boats or subsurface platforms. Duration: 2-4 hours. Explosive..................... Expeditionary Personnel Divers and E1............... 495 3,465 Hawaii Warfare. Insertion/ swimmers Extraction infiltrate Training--Swimme harbors, r/Diver. beaches, or moored vessels and conduct a variety of tasks. Duration: up to 12 hours. Explosive..................... Expeditionary Personnel Divers and E1............... 1,080-1,280 8,160 SOCAL. Warfare. Insertion/ swimmers Extraction infiltrate Training--Swimme harbors, r/Diver. beaches, or moored vessels and conduct a variety of tasks. Duration: up to 12 hours. Explosive..................... Mine Warfare..... Amphibious Amphibious forces E6............... 100 700 Hawaii. Breaching use explosive Operations. clearing systems to clear simulated mines on beaches, shallow water, and surf zones for potential landing of personnel and vehicles. Duration: 8 hours. [[Page 32131]] Explosive..................... Mine Warfare..... Amphibious Amphibious forces E6............... 275 1,925 SOCAL. Breaching use explosive Operations. clearing systems to clear simulated mines on beaches, shallow water, and surf zones for potential landing of personnel and vehicles. Duration: 8 hours. Explosive..................... Mine Warfare..... Amphibious Amphibious forces E6............... 315 2,205 SSTC. Breaching use explosive Operations. clearing systems to clear simulated mines on beaches, shallow water, and surf zones for potential landing of personnel and vehicles. Duration: 8 hours. Explosive..................... Mine Warfare..... Amphibious Amphibious forces E6............... 48-55 357 SWAT 2. Breaching use explosive Operations. clearing systems to clear simulated mines on beaches, shallow water, and surf zones for potential landing of personnel and vehicles. Duration: 8 hours. Acoustic and Explosive........ Mine Warfare..... Civilian Port Maritime security E4, HFH, HFM, MFH 1-2 10 Hawaii. Defense-Homeland personnel train Security Anti- to protect Terrorism/Force civilian ports Protection against enemy Exercise. efforts to interfere with access to those ports. Duration: multiple days. Acoustic and Explosive........ Mine Warfare..... Civilian Port Maritime security E4, HFH, HFM, MFH 1-2 11 SOCAL. Defense-Homeland personnel train Security Anti- to protect Terrorism/Force civilian ports Protection against enemy Exercise. efforts to interfere with access to those ports. Duration: multiple days. Acoustic and Explosive........ Mine Warfare..... Civilian Port Maritime security E4, HFH, HFM, MFH 1-2 9 PMSR. Defense-Homeland personnel train Security Anti- to protect Terrorism/Force civilian ports Protection against enemy Exercise. efforts to interfere with access to those ports. Duration: multiple days. Explosive..................... Mine Warfare..... Limpet Mine Navy Explosive E0, E3........... 6-8 48 Lima Landing. Neutralization Ordnance System. Disposal divers place a small charge on a simulated underwater mine. Duration: 2 hours. Explosive..................... Mine Warfare..... Limpet Mine Navy Explosive E0, E3........... 138-150 1,002 SOCAL. Neutralization Ordnance System. Disposal divers place a small charge on a simulated underwater mine. Duration: 2 hours. Explosive..................... Mine Warfare..... Limpet Mine Navy Explosive E0, E3........... 42-44 300 SSTC. Neutralization Ordnance System. Disposal divers place a small charge on a simulated underwater mine. Duration: 2 hours. Acoustic...................... Mine Warfare..... Mine Ship crews detect HFH, MF1K........ 30 210 Hawaii. Countermeasure and avoid mines Exercise--Ship while navigating Sonar. restricted areas or channels using active sonar. Duration: up to 15 hours. Acoustic...................... Mine Warfare..... Mine Ship crews detect HFH, MF1K........ 42 294 Pearl Harbor. Countermeasure and avoid mines Exercise--Ship while navigating Sonar. restricted areas or channels using active sonar. Duration: up to 15 hours. Acoustic...................... Mine Warfare..... Mine Ship crews detect HFH, MF1K........ 92 644 SOCAL. Countermeasure and avoid mines Exercise--Ship while navigating Sonar. restricted areas or channels using active sonar. Duration: up to 15 hours. Acoustic...................... Mine Warfare..... Mine Ship crews detect HFH, MF1K........ 164 1,148 San Diego Bay. Countermeasure and avoid mines Exercise--Ship while navigating Sonar. restricted areas or channels using active sonar. Duration: up to 15 hours. Acoustic and Explosive........ Mine Warfare..... Mine Ship, small boat, E4, HFM.......... 7-8 52 Hawaii MTRs. Countermeasures and helicopter Mine crews locate and Neutralization disable mines Remotely using remotely Operated Vehicle. operated underwater vehicles. Duration: 1-4 hours. Acoustic and Explosive........ Mine Warfare..... Mine Ship, small boat, E4, HFM.......... 11 74 SOCAL. Countermeasures and helicopter Mine crews locate and Neutralization disable mines Remotely using remotely Operated Vehicle. operated underwater vehicles. Duration: 1-4 hours. [[Page 32132]] Acoustic and Explosive........ Mine Warfare..... Mine Ship, small boat, E4, HFM.......... 6 42 SSTC. Countermeasures and helicopter Mine crews locate and Neutralization disable mines Remotely using remotely Operated Vehicle. operated underwater vehicles. Duration: 1-4 hours. Acoustic and Explosive........ Mine Warfare..... Mine Ship, small boat, E4, HFM.......... 3-6 30 TAR 2. Countermeasures and helicopter Mine crews locate and Neutralization disable mines Remotely using remotely Operated Vehicle. operated underwater vehicles. Duration: 1-4 hours. Acoustic and Explosive........ Mine Warfare..... Mine Ship, small boat, E4, HFM.......... 11 74 SCORE. Countermeasures and helicopter Mine crews locate and Neutralization disable mines Remotely using remotely Operated Vehicle. operated underwater vehicles. Duration: 1-4 hours. Explosive..................... Mine Warfare..... Mine Personnel disable E6............... 5-7 41 Hawaii. Neutralization threat mines Explosive using explosive Ordnance charges. Disposal. Duration: up to 4 hours. Explosive..................... Mine Warfare..... Mine Personnel disable E6............... 203-211 1,445 SOCAL. Neutralization threat mines Explosive using explosive Ordnance charges. Disposal. Duration: up to 4 hours. Explosive..................... Mine Warfare..... Mine Personnel disable E6............... 17-25 143 SSTC. Neutralization threat mines Explosive using explosive Ordnance charges. Disposal. Duration: up to 4 hours. Explosive..................... Mine Warfare..... Mine Personnel disable E6............... 0-1 5 SWAT 2. Neutralization threat mines Explosive using explosive Ordnance charges. Disposal. Duration: up to 4 hours. Acoustic...................... Mine Warfare..... Submarine Mine Submarine crews HFH, MF to HF, 80 560 Hawaii. Counter Measure use active sonar VHFH. Exercise. or UUVs, and shore-based personnel operate UUVs to detect and avoid training mine shapes or other underwater hazardous objects. Duration: 6 hours. Acoustic...................... Mine Warfare..... Submarine Mine Submarine crews HFH, MF to HF, 40 280 SOCAL. Counter Measure use active sonar VHFH. Exercise. or UUVs, and shore-based personnel operate UUVs to detect and avoid training mine shapes or other underwater hazardous objects. Duration: 6 hours. Acoustic...................... Mine Warfare..... Submarine Mobile Submarine crews HFL, HFM, MFM, 20 140 Hawaii. Mine and Mine and shore-based VHFL. Laying Exercise. personnel operating a UUV deploy exercise (inert) mobile mines or mines. Duration: 6 hours. Acoustic...................... Mine Warfare..... Submarine Mobile Submarine crews HFL, HFM, MFM, 30 210 SOCAL, PMSR. Mine and Mine and shore-based VHFL. Laying Exercise. personnel operating a UUV deploy exercise (inert) mobile mines or mines. Duration: 6 hours. Acoustic...................... Mine Warfare..... Surface Ship Ship crews detect MF1K............. 30 210 Hawaii. Object Detection. and avoid mines while navigating restricted areas or channels using active sonar. Duration: up to 15 hours. Acoustic...................... Mine Warfare..... Surface Ship Ship crews detect MF1K............. 42 294 Pearl Harbor. Object Detection. and avoid mines while navigating restricted areas or channels using active sonar. Duration: up to 15 hours. Acoustic...................... Mine Warfare..... Surface Ship Ship crews detect MF1K............. 92 644 SOCAL. Object Detection. and avoid mines while navigating restricted areas or channels using active sonar. Duration: up to 15 hours. Acoustic...................... Mine Warfare..... Surface Ship Ship crews detect MF1K............. 164 1,148 San Diego Bay. Object Detection. and avoid mines while navigating restricted areas or channels using active sonar. Duration: up to 15 hours. Explosive..................... Mine Warfare..... Underwater Navy divers E5, E6........... 5 35 Pu'uloa, Ewa Demolition conduct various Beach, Barbers Qualification levels of Point. and training and Certification. certification in placing underwater demolition charges. Duration: up to 8 hours. [[Page 32133]] Explosive..................... Mine Warfare..... Underwater Navy divers E5, E6........... 10-20 100 TAR 2. Demolition conduct various Qualification levels of and training and Certification. certification in placing underwater demolition charges. Duration: up to 8 hours. Explosive..................... Mine Warfare..... Underwater Navy divers E5, E6........... 24 168 SSTC. Demolition conduct various Qualification levels of and training and Certification. certification in placing underwater demolition charges. Duration: up to 8 hours. Explosive..................... Mine Warfare..... Underwater Units deploy E13.............. 6 42 TAR 2. Demolitions large explosive Multiple Charge-- systems from Large Area vessels or Clearance. vehicles to destroy barriers or obstacles over an area large enough to allow amphibious vehicles to access beach areas. Duration: 4 hours. Explosive..................... Surface Warfare.. Bombing Exercise Fixed-wing E9, E10, E12..... 194 1,358 Hawaii. Air-to-Surface. aircrews deliver bombs against surface targets. Duration: 1 hour. Explosive..................... Surface Warfare.. Bombing Exercise Fixed-wing E9, E10, E12..... 653 4,571 SOCAL. Air-to-Surface. aircrews deliver bombs against surface targets. Duration: 1 hour. Explosive..................... Surface Warfare.. Bombing Exercise Fixed-wing E9, E10, E12..... 10 70 NOCAL. Air-to-Surface. aircrews deliver bombs against surface targets. Duration: 1 hour. Explosive..................... Surface Warfare.. Gunnery Exercise Small boat crews E1............... 10 70 Hawaii. Surface-to- fire medium- Surface Boat caliber guns at Medium-Caliber. surface targets. Duration: 1 hour. Explosive..................... Surface Warfare.. Gunnery Exercise Small boat crews E1............... 14 98 SOCAL. Surface-to- fire medium- Surface Boat caliber guns at Medium-Caliber. surface targets. Duration: 1 hour. Explosive..................... Surface Warfare.. Gunnery Exercise Surface ship E3, E5........... 32 224 Hawaii. Surface-to- crews fire large- Surface Ship caliber guns at Large-Caliber. surface targets. Duration: up to 3 hours. Explosive..................... Surface Warfare.. Gunnery Exercise Surface ship E3, E5........... 125 875 SOCAL. Surface-to- crews fire large- Surface Ship caliber guns at Large-Caliber. surface targets. Duration: up to 3 hours. Explosive..................... Surface Warfare.. Gunnery Exercise Surface ship E3, E5........... 14 98 Transit Corridor. Surface-to- crews fire large- Surface Ship caliber guns at Large-Caliber. surface targets. Duration: up to 3 hours. Explosive..................... Surface Warfare.. Gunnery Exercise Surface ship E1............... 5-50 170 Hawaii. Surface-to- crews fire Surface Ship medium-caliber Medium-Caliber. guns at surface targets. Duration: 2-3 hours. Explosive..................... Surface Warfare.. Gunnery Exercise Surface ship E1............... 17-180 608 SOCAL. Surface-to- crews fire Surface Ship medium-caliber Medium-Caliber. guns at surface targets. Duration: 2-3 hours. Explosive..................... Surface Warfare.. Gunnery Exercise Surface ship E1............... 6-40 144 Transit Corridor. Surface-to- crews fire Surface Ship medium-caliber Medium-Caliber. guns at surface targets. Duration: 2-3 hours. Explosive..................... Surface Warfare.. Missile Exercise Fixed-wing and E6, E7, E8, E9... 17-22 134 Hawaii. Air-to-Surface. helicopter aircrews fire air-to-surface missiles at surface targets. Duration: 1 hour. Explosive..................... Surface Warfare.. Missile Exercise Fixed-wing and E6, E7, E8, E9... 4-9 43 SOCAL. Air-to-Surface. helicopter aircrews fire air-to-surface missiles at surface targets. Duration: 1 hour. Explosive..................... Surface Warfare.. Missile Exercise Fixed-wing and E6, E7, E8, E9... 90 630 PMSR. Air-to-Surface. helicopter aircrews fire air-to-surface missiles at surface targets. Duration: 1 hour. Explosive..................... Surface Warfare.. Missile Exercise Helicopter E3............... 109-129 823 Hawaii. Air-to-Surface aircrews fire Rocket. both precision- guided and unguided rockets at surface targets. Duration: 1 hour. Explosive..................... Surface Warfare.. Missile Exercise Helicopter E3............... 251-271 1,817 SOCAL. Air-to-Surface aircrews fire Rocket. both precision- guided and unguided rockets at surface targets. Duration: 1 hour. [[Page 32134]] Explosive..................... Surface Warfare.. Missile Exercise Surface ship E9............... 28-32 208 Hawaii. Surface-to- crews defend Surface. against surface threats (ships or small boats) and engage them with missiles. Duration: 2-5 hours. Explosive..................... Surface Warfare.. Missile Exercise Surface ship E9............... 10 70 SOCAL. Surface-to- crews defend Surface. against surface threats (ships or small boats) and engage them with missiles. Duration: 2-5 hours. Explosive..................... Surface Warfare.. Sinking Exercise. Aircraft, ship, E5, E8, E9, E11, 2-3 17 Hawaii. and submarine E12. crews deliberately sink a seaborne target, usually a decommissioned ship made environmentally safe for sinking according to U.S. Environmental Protection Agency standards, with a variety of ordnance. Duration: 4-8 hours. Explosive..................... Surface Warfare.. Sinking Exercise. Aircraft, ship, E5, E8, E9, E11, 0-1 3 SOCAL. and submarine E12. crews deliberately sink a seaborne target, usually a decommissioned ship made environmentally safe for sinking according to U.S. Environmental Protection Agency standards, with a variety of ordnance. Duration: 4-8 hours. Acoustic...................... Surface Warfare.. Surface Warfare Submarine crews HFH.............. 30 210 Hawaii. Torpedo search for, Exercise--Submar detect, and ine. track a surface ship simulating a threat surface ship with the goal of determining a firing solution that could be used to launch a torpedo with the intent to simulate destroying the targets. Duration: 8 hours. Acoustic...................... Surface Warfare.. Surface Warfare Submarine crews HFH.............. 10 70 SOCAL. Torpedo search for, Exercise--Submar detect, and ine. track a surface ship simulating a threat surface ship with the goal of determining a firing solution that could be used to launch a torpedo with the intent to simulate destroying the targets. Duration: 8 hours. Explosive..................... Surface Warfare.. Training and End- Submarine crews E9, E10.......... 2 14 Hawaii. to-End Mission launch Capability missile(s) which Verification--Su may have an bmarine Missile explosive Maritime. warhead at a maritime target simulating an adversary surface ship with the goal of destroying or disabling adversary surface ship. Duration: 8 hours. Explosive..................... Surface Warfare.. Training and End- Submarine crews E9, E10.......... 3 21 SOCAL. to-End Mission launch Capability missile(s) which Verification--Su may have an bmarine Missile explosive Maritime. warhead at a maritime target simulating an adversary surface ship with the goal of destroying or disabling adversary surface ship. Duration: 8 hours. Acoustic and Explosive........ Other Training Multi-Domain Multi-domain E5, E7, MF to HF, 50-100 500 Hawaii. Activities. Unmanned (surface, VHFH. Autonomous subsurface, and Systems. airborne) unmanned autonomous systems are launched from land, ships, and boats, in support of intelligence, surveillance, and reconnaissance operations; and deliver munitions or other non- munition systems to support mission and intelligence requirements. Duration: 4-8 hours. [[Page 32135]] Acoustic and Explosive........ Other Training Multi-Domain Multi-domain E5, E7, MF to HF, 55-105 535 Pyramid Cove, Activities. Unmanned (surface, VHFH. SWATs. Autonomous subsurface, and Systems. airborne) unmanned autonomous systems are launched from land, ships, and boats, in support of intelligence, surveillance, and reconnaissance operations; and deliver munitions or other non- munition systems to support mission and intelligence requirements. Duration: 4-8 hours. Acoustic and Explosive........ Other Training Multi-Domain Multi-domain E5, E7, MF to HF, 50-100 500 SOCAL. Activities. Unmanned (surface, VHFH. Autonomous subsurface, and Systems. airborne) unmanned autonomous systems are launched from land, ships, and boats, in support of intelligence, surveillance, and reconnaissance operations; and deliver munitions or other non- munition systems to support mission and intelligence requirements. Duration: 4-8 hours. Acoustic...................... Other Training Submarine Submarine crews HFH, MFH......... 220 1,540 Pearl Harbor. Activities. Navigation operate sonar Exercise. for navigation and object detection while transiting into and out of port during reduced visibility. Duration: 2 hours. Acoustic...................... Other Training Submarine Submarine crews HFH, MFH......... 80 560 San Diego Bay. Activities. Navigation operate sonar Exercise. for navigation and object detection while transiting into and out of port during reduced visibility. Duration: 2 hours. Acoustic...................... Other Training Submarine Sonar Maintenance of MFH.............. 260 1,820 Hawaii. Activities. Maintenance and submarine sonar Systems Checks. systems is conducted pierside or at sea. Duration: 1 hour. Acoustic...................... Other Training Submarine Sonar Maintenance of MFH.............. 260 1,820 Pearl Harbor. Activities. Maintenance and submarine sonar Systems Checks. systems is conducted pierside or at sea. Duration: 1 hour. Acoustic...................... Other Training Submarine Sonar Maintenance of MFH.............. 80 560 SOCAL. Activities. Maintenance and submarine sonar Systems Checks. systems is conducted pierside or at sea. Duration: 1 hour. Acoustic...................... Other Training Submarine Sonar Maintenance of MFH.............. 13 91 PMSR. Activities. Maintenance and submarine sonar Systems Checks. systems is conducted pierside or at sea. Duration: 1 hour. Acoustic...................... Other Training Submarine Sonar Maintenance of MFH.............. 92 644 San Diego Bay. Activities. Maintenance and submarine sonar Systems Checks. systems is conducted pierside or at sea. Duration: 1 hour. Acoustic...................... Other Training Submarine Sonar Maintenance of MFH.............. 10 70 Transit Corridor. Activities. Maintenance and submarine sonar Systems Checks. systems is conducted pierside or at sea. Duration: 1 hour. Acoustic...................... Other Training Submarine Under Submarine crews HFH.............. 12 84 Hawaii. Activities. Ice Training and train to operate Certification. under ice. Ice conditions are simulated during training and certification events. Duration: 5 days. Acoustic...................... Other Training Submarine Under Submarine crews HFH.............. 6 42 SOCAL. Activities. Ice Training and train to operate Certification. under ice. Ice conditions are simulated during training and certification events. Duration: 5 days. [[Page 32136]] Acoustic and Explosive........ Other Training Submarine and UUV Submarine crews E3, VHFH......... 20 140 Hawaii. Activities. Subsea and and shore-based Seabed Warfare operators train Exercise. to launch or recover and operate all classes of UUVs in the subsea and seabed environment in order to defend deep ocean and seabed infrastructure or take offensive action against a simulated adversary's subsea and seabed infrastructure. Duration: 1 day. Acoustic and Explosive........ Other Training Submarine and UUV Submarine crews E3, VHFH......... 10 70 SOCAL. Activities. Subsea and and shore-based Seabed Warfare operators train Exercise. to launch or recover and operate all classes of UUVs in the subsea and seabed environment in order to defend deep ocean and seabed infrastructure or take offensive action against a simulated adversary's subsea and seabed infrastructure. Duration: 1 day. Acoustic and Explosive........ Other Training Submarine and UUV Submarine crews E3, VHFH......... 5 35 PMSR. Activities. Subsea and and shore-based Seabed Warfare operators train Exercise. to launch or recover and operate all classes of UUVs in the subsea and seabed environment in order to defend deep ocean and seabed infrastructure or take offensive action against a simulated adversary's subsea and seabed infrastructure. Duration: 1 day. Acoustic and Explosive........ Other Training Submarine and UUV Submarine crews E3, VHFH......... 5 35 NOCAL. Activities. Subsea and and shore-based Seabed Warfare operators train Exercise. to launch or recover and operate all classes of UUVs in the subsea and seabed environment in order to defend deep ocean and seabed infrastructure or take offensive action against a simulated adversary's subsea and seabed infrastructure. Duration: 1 day. Acoustic...................... Other Training Surface Ship Maintenance of HFH, MF1, MF1K, 75 525 Hawaii. Activities. Sonar surface ship MFH. Maintenance and sonar systems is Systems Checks. conducted pierside or at sea. Duration: 4 hours. Acoustic...................... Other Training Surface Ship Maintenance of HFH, MF1, MF1K, 80 560 Pearl Harbor. Activities. Sonar surface ship MFH. Maintenance and sonar systems is Systems Checks. conducted pierside or at sea. Duration: 4 hours. Acoustic...................... Other Training Surface Ship Maintenance of HFH, MF1, MF1K, 250 1,750 SOCAL. Activities. Sonar surface ship MFH. Maintenance and sonar systems is Systems Checks. conducted pierside or at sea. Duration: 4 hours. Acoustic...................... Other Training Surface Ship Maintenance of HFH, MF1, MF1K, 250 1,750 San Diego Bay. Activities. Sonar surface ship MFH. Maintenance and sonar systems is Systems Checks. conducted pierside or at sea. Duration: 4 hours. Acoustic...................... Other Training Surface Ship Maintenance of HFH, MF1, MF1K, 8-12 68 Transit Corridor. Activities. Sonar surface ship MFH. Maintenance and sonar systems is Systems Checks. conducted pierside or at sea. Duration: 4 hours. Explosive..................... Other Training Training and End- Submarine crews E3............... 20 140 Hawaii. Activities. to-End Mission or shore-based Capability operators employ Verification--Su UUV with bsea and Seabed munitions or non- Warfare Kinetic munition systems Effectors. on the sea floor or in the water column. Duration: 8 hours. Explosive..................... Other Training Training and End- Submarine crews E3............... 10 70 SOCAL. Activities. to-End Mission or shore-based Capability operators employ Verification--Su UUV with bsea and Seabed munitions or non- Warfare Kinetic munition systems Effectors. on the sea floor or in the water column. Duration: 8 hours. [[Page 32137]] Explosive..................... Other Training Training and End- Submarine crews E3............... 5 35 PMSR. Activities. to-End Mission or shore-based Capability operators employ Verification--Su UUV with bsea and Seabed munitions or non- Warfare Kinetic munition systems Effectors. on the sea floor or in the water column. Duration: 8 hours. Explosive..................... Other Training Training and End- Submarine crews E3............... 5 35 NOCAL. Activities. to-End Mission or shore-based Capability operators employ Verification--Su UUV with bsea and Seabed munitions or non- Warfare Kinetic munition systems Effectors. on the sea floor or in the water column. Duration: 8 hours. Explosive..................... Other Training Training and End- Submarine crews E3............... 10 70 Hawaii. Activities. to-End Mission or shore-based Capability personnel Verification--Un controlling a manned Aerial UUV launch a Vehicle (UAV). capsule containing a UAV. The canister is deployed underwater and ascends to a programmed depth. The canister subsequently launches a UAV, and the canister sinks. Duration: 8 hours. Explosive..................... Other Training Training and End- Submarine crews E3............... 5 35 SOCAL. Activities. to-End Mission or shore-based Capability personnel Verification--Un controlling a manned Aerial UUV launch a Vehicle (UAV). capsule containing a UAV. The canister is deployed underwater and ascends to a programmed depth. The canister subsequently launches a UAV, and the canister sinks. Duration: 8 hours. Explosive..................... Other Training Training and End- Submarine crews E3............... 3 21 PMSR. Activities. to-End Mission or shore-based Capability personnel Verification--Un controlling a manned Aerial UUV launch a Vehicle (UAV). capsule containing a UAV. The canister is deployed underwater and ascends to a programmed depth. The canister subsequently launches a UAV, and the canister sinks. Duration: 8 hours. Explosive..................... Other Training Training and End- Submarine crews E3............... 2 14 NOCAL. Activities. to-End Mission or shore-based Capability personnel Verification--Un controlling a manned Aerial UUV launch a Vehicle (UAV). capsule containing a UAV. The canister is deployed underwater and ascends to a programmed depth. The canister subsequently launches a UAV, and the canister sinks. Duration: 8 hours. Acoustic...................... Other Training Unmanned Unmanned HFM, MF to HF, 82-178 862 Hawaii. Activities. Underwater underwater VHFH. Vehicle vehicle Training--Certif certification ication and involves Development training with Exercises. unmanned platforms to ensure submarine crew proficiency. Tactical development involves training with various payloads for multiple purposes to ensure that the systems can be employed effectively in an operational environment. Duration: up to 24 hours. Acoustic...................... Other Training Unmanned Unmanned HFM, MF to HF, 284-492 2,612 SOCAL. Activities. Underwater underwater VHFH. Vehicle vehicle Training--Certif certification ication and involves Development training with Exercises. unmanned platforms to ensure submarine crew proficiency. Tactical development involves training with various payloads for multiple purposes to ensure that the systems can be employed effectively in an operational environment. Duration: up to 24 hours. [[Page 32138]] Acoustic...................... Other Training Unmanned Unmanned HFM, MF to HF, 130-260 1,300 SSTC. Activities. Underwater underwater VHFH. Vehicle vehicle Training--Certif certification ication and involves Development training with Exercises. unmanned platforms to ensure submarine crew proficiency. Tactical development involves training with various payloads for multiple purposes to ensure that the systems can be employed effectively in an operational environment. Duration: up to 24 hours. Acoustic...................... Other Training Unmanned Unmanned HFM, MF to HF, 18-36 180 China Point. Activities. Underwater underwater VHFH. Vehicle vehicle Training--Certif certification ication and involves Development training with Exercises. unmanned platforms to ensure submarine crew proficiency. Tactical development involves training with various payloads for multiple purposes to ensure that the systems can be employed effectively in an operational environment. Duration: up to 24 hours. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: LF = low-frequency, MF = mid-frequency, HF = high-frequency, dB = decibels, L = low, M= medium, H = high (e.g., MFL = mid-frequency low source level), H = hours, C = count. BARSTUR = Barking Sands Tactical Underwater Range, FORACS = Fleet Operational Readiness Accuracy Check Site, Hawaii = the Hawaii Study Area, MTR = Mine Training Range, NOCAL = Northern California Range Complex, PMRF = Pacific Missile Range Facility, PMSR = Point Mugu Sea Range, SCI = San Clemente Island, SOAR = Southern California Offshore Anti-Submarine Warfare Range, SOCAL = Southern California Range Complex, SSTC = Silver Strand Training Complex, SWAT = Special Warfare Training Area, TAR = Training Area and Range. Table 4--Proposed Coast Guard Training Activities Analyzed Within the HCTT Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Number of Number of Stressor category Activity type Activity name Description Source bin activities activities Location 1-year 7-year -------------------------------------------------------------------------------------------------------------------------------------------------------- Explosive...................... Surface Warfare... Gunnery Exercise Surface ship E3............... 5 35 Hawaii. Surface-to- crews fire large- Surface Ship caliber guns at Large-caliber. surface targets. Duration: up to 3 hours. Explosive...................... Surface Warfare... Gunnery Exercise Surface ship E3............... 20 140 SOCAL. Surface-to- crews fire large- Surface Ship caliber guns at Large-caliber. surface targets. Duration: up to 3 hours. Explosive...................... Surface Warfare... Gunnery Exercise Surface ship E3............... 2 14 PMSR. Surface-to- crews fire large- Surface Ship caliber guns at Large-caliber. surface targets. Duration: up to 3 hours. Explosive...................... Surface Warfare... Gunnery Exercise Surface ship E3............... 2 14 NOCAL. Surface-to- crews fire large- Surface Ship caliber guns at Large-caliber. surface targets. Duration: up to 3 hours. Acoustic....................... Other Training.... Unmanned Unmanned HFM, MF to HF, 200 1,400 Hawaii. Underwater underwater VHFH. Vehicle Training-- vehicle Certification and certification Development involves Exercises. training with unmanned platforms to ensure submarine crew proficiency. Tactical development involves training with various payloads for multiple purposes to ensure that the systems can be employed effectively in an operational environment. Duration: up to 24 hours. Acoustic....................... Other Training.... Unmanned Unmanned HFM, MF to HF, 200 1,400 SOCAL. Underwater underwater VHFH. Vehicle Training-- vehicle Certification and certification Development involves Exercises. training with unmanned platforms to ensure submarine crew proficiency. Tactical development involves training with various payloads for multiple purposes to ensure that the systems can be employed effectively in an operational environment. Duration: up to 24 hours. Acoustic....................... Other Training.... Unmanned Unmanned HFM, MF to HF, 100 700 PMSR. Underwater underwater VHFH. Vehicle Training-- vehicle Certification and certification Development involves Exercises. training with unmanned platforms to ensure submarine crew proficiency. Tactical development involves training with various payloads for multiple purposes to ensure that the systems can be employed effectively in an operational environment. Duration: up to 24 hours. [[Page 32139]] Acoustic....................... Other Training.... Unmanned Unmanned HFM, MF to HF, 10 70 NOCAL. Underwater underwater VHFH. Vehicle Training-- vehicle Certification and certification Development involves Exercises. training with unmanned platforms to ensure submarine crew proficiency. Tactical development involves training with various payloads for multiple purposes to ensure that the systems can be employed effectively in an operational environment. Duration: up to 24 hours. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: LF = low-frequency, MF = mid-frequency, HF = high-frequency, dB = decibels, L = low, M = medium, H = high (e.g., MFL = mid-frequency low source level), H = hours, C = count. Hawaii = the Hawaii Study Area, NOCAL = Northern California Range Complex, PMSR = Point Mugu Sea Range, SOCAL = Southern California Range Complex. Table 5--Proposed Army Training Activities Analyzed Within the HCTT Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Number of Number of Stressor category Activity type Activity name Description Source bin activities activities Location 1-year 7-year -------------------------------------------------------------------------------------------------------------------------------------------------------- Explosive...................... Amphibious Warfare Shore-to-Surface Amphibious land- E6............... 2 14 PMRF. Artillery based forces Exercise. fire artillery guns at surface targets. Duration: 1-2 hours of firing, 8 hours total. Explosive...................... Amphibious Warfare Shore-to-Surface Amphibious land- E9............... 18 126 PMRF. Missile Exercise. based forces fire anti- surface missiles, rockets, and loitering munitions at surface targets. Duration: 1-2 hours of firing, 8 hours total. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: PMRF = Pacific Missile Range Facility. Overview of Testing Activities Within the Study Area While this proposed rule includes an evaluation of proposed training activities by the Navy, Coast Guard, and Army, all testing activities evaluated in this proposed rule would only be conducted by the Navy. The Navy's research and acquisition community engages in a broad spectrum of testing activities, some of which ultimately support all Action Proponents. These activities include, but are not limited to, basic and applied scientific research and technology development; testing, evaluation, and maintenance of systems (e.g., missiles, radar, and sonar) and platforms (e.g., surface ships, submarines, and aircraft); and acquisition of systems and platforms to support Navy missions and give a technological edge over adversaries. The individual commands within the research and acquisition community considered in the application are Naval Air Systems Command (NAVAIR), Naval Facilities Engineering and Expeditionary Warfare Center, Naval Sea Systems Command (NAVSEA), Office of Naval Research (ONR), and Naval Information Warfare Systems Command (NAVWAR). Although included in the testing community, proposed Expeditionary Warfare Center activities do not involve sonar and other transducers, underwater detonations, pile driving, airguns, or any other stressors that could result in harassment of marine mammals, and therefore, are not analyzed further in this proposed rule. The Action Proponents operate in an ever-changing strategic, tactical, financially-constrained, and time-constrained environment. Testing activities occur in response to emerging science or fleet operational needs. For example, future Navy studies to develop a better understanding of ocean currents may be designed based on advancements made by non-government researchers not yet published in the scientific literature. Similarly, future but yet unknown Navy, Coast Guard, and Army operations within a specific geographic area may require development of modified Navy assets to address local conditions. Such modifications must be tested in the field to ensure they meet fleet needs and requirements. Accordingly, generic descriptions of some of these activities are the best that can be articulated in a long-term, comprehensive document. Some testing activities are similar to training activities conducted by the fleet (e.g., both the fleet and the research and acquisition community fire torpedoes). While the firing of a torpedo might look identical to an observer, the difference is in the purpose of the firing. The fleet might fire the torpedo to practice the procedures for such a firing, whereas the research and acquisition community might be assessing a new torpedo guidance technology or testing it to ensure the torpedo meets performance specifications and operational requirements (see appendix A (Activity Descriptions) of the 2024 HCTT Draft EIS/OEIS for more detailed descriptions of the activities). NAVAIR testing activities generally fall in the primary mission areas used by the fleets and include the evaluation of new and in- service aircraft platforms and systems to deliver critical air warfare capabilities to the fleets. To accomplish its mission, NAVAIR conducts anti-submarine warfare tests using fixed-wing and rotary wing aircraft platforms, a suite of passive and active acoustic sonobuoys (to include Lot Acceptance Testing), and dipping sonar systems. The majority of testing activities conducted by NAVAIR are similar to fleet training activities, and many platforms and systems currently being tested are already being used by the fleet or will ultimately be integrated into fleet training activities. However, some testing activities may be conducted in different locations and in a different manner than similar fleet training activities, and, therefore, the analysis for those events and the potential environmental effects may differ. Table 6 summarizes the proposed testing [[Page 32140]] activities for NAVAIR analyzed within the HCTT Study Area. Table 6--Proposed NAVAIR Testing Activities Analyzed Within the HCTT Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Number of Number of Stressor category Activity type Activity name Description Source bin activities activities Location 1-year 7-year -------------------------------------------------------------------------------------------------------------------------------------------------------- Acoustic....................... Anti-Submarine ASW Torpedo Test-- This event is HFH, MFH, MFM.... 24-26 174 Hawaii. Warfare. Aircraft. similar to the training event torpedo exercise. Test evaluates anti- submarine warfare systems onboard rotary- wing and fixed- wing aircraft and the ability to search for, detect, classify, localize, track, and attack a submarine or similar target. Duration: 2-6 hours. Acoustic....................... Anti-Submarine ASW Torpedo Test-- This event is HFH, MFH, MFM.... 36-39 259 SOCAL. Warfare. Aircraft. similar to the training event torpedo exercise. Test evaluates anti- submarine warfare systems onboard rotary- wing and fixed- wing aircraft and the ability to search for, detect, classify, localize, track, and attack a submarine or similar target. Duration: 2-6 hours. Acoustic....................... Anti-Submarine ASW Torpedo Test-- This event is HFH, MFH, MFM.... 36-39 259 SCORE. Warfare. Aircraft. similar to the training event torpedo exercise. Test evaluates anti- submarine warfare systems onboard rotary- wing and fixed- wing aircraft and the ability to search for, detect, classify, localize, track, and attack a submarine or similar target. Duration: 2-6 hours. Acoustic....................... Anti-Submarine ASW Tracking Test-- The test HFM, LFH, LFM, 61-67 445 Hawaii. Warfare. Fixed-Wing. evaluates the MFM. sensors and systems used by maritime patrol aircraft to detect and track submarines and to ensure that aircraft systems used to deploy the tracking systems perform to specifications and meet operational requirements. Duration: 8 hours. Acoustic....................... Anti-Submarine ASW Tracking Test-- The test HFM, LFH, LFM, 68-75 497 SOCAL. Warfare. Fixed-Wing. evaluates the MFM. sensors and systems used by maritime patrol aircraft to detect and track submarines and to ensure that aircraft systems used to deploy the tracking systems perform to specifications and meet operational requirements. Duration: 8 hours. Acoustic....................... Anti-Submarine ASW Tracking Test-- The test MFH, MFM......... 66-73 483 Hawaii. Warfare. Rotary Wing. evaluates the sensors and systems used by helicopters to detect and track submarines and to ensure that aircraft systems used to deploy the tracking systems perform to specifications and meet operational requirements. Duration: 2 hours. Acoustic....................... Anti-Submarine ASW Tracking Test-- The test MFH, MFM......... 66-73 482 SOCAL. Warfare. Rotary Wing. evaluates the sensors and systems used by helicopters to detect and track submarines and to ensure that aircraft systems used to deploy the tracking systems perform to specifications and meet operational requirements. Duration: 2 hours. Acoustic....................... Anti-Submarine ASW Tracking Test-- The test MFH, MFM......... 66-73 482 SCORE. Warfare. Rotary Wing. evaluates the sensors and systems used by helicopters to detect and track submarines and to ensure that aircraft systems used to deploy the tracking systems perform to specifications and meet operational requirements. Duration: 2 hours. Acoustic....................... Anti-Submarine Kilo Dip Test..... Functional check MFH.............. 6-7 45 Hawaii. Warfare. of a helicopter- deployed dipping sonar system prior to conducting a testing or training event using the dipping sonar system. Duration: 1-2 hours. [[Page 32141]] Acoustic....................... Anti-Submarine Kilo Dip Test..... Functional check MFH.............. 6-7 45 SOCAL. Warfare. of a helicopter- deployed dipping sonar system prior to conducting a testing or training event using the dipping sonar system. Duration: 1-2 hours. Acoustic....................... Anti-Submarine Sonobuoy Lot Sonobuoys are HFM, LFH, LFM, 32-38 242 Hawaii. Warfare. Acceptance Test. deployed from MFM. surface vessels and aircraft to verify the integrity and performance of a lot or group of sonobuoys in advance of delivery to the fleet for operational use. Duration: 6 hours. Acoustic....................... Anti-Submarine Sonobuoy Lot Sonobuoys are HFM, LFH, LFM, 320-352 2,336 SOCAL. Warfare. Acceptance Test. deployed from MFM. surface vessels and aircraft to verify the integrity and performance of a lot or group of sonobuoys in advance of delivery to the fleet for operational use. Duration: 6 hours. Acoustic....................... Mine Warfare...... Airborne Dipping A mine-hunting HFH.............. 18-20 132 Hawaii. Sonar Minehunting dipping sonar Test. system that is deployed from a helicopter and uses high- frequency sonar for the detection and classification of bottom and moored mines. Duration: 2 hours. Acoustic....................... Mine Warfare...... Airborne Dipping A mine-hunting HFH.............. 18-20 132 SOCAL. Sonar Minehunting dipping sonar Test. system that is deployed from a helicopter and uses high- frequency sonar for the detection and classification of bottom and moored mines. Duration: 2 hours. Explosive...................... Mine Warfare...... Airborne Mine A test of the E4............... 36-39 261 Hawaii. Neutralization airborne mine System Test. neutralization system evaluates the system's ability to detect and destroy mines from an airborne mine countermeasures capable helicopter. The Airborne Mine Neutralization System uses up to four unmanned underwater vehicles equipped with high frequency sonar, video cameras, and explosive and non-explosive neutralizers. Duration: 2-3 hours. Explosive...................... Mine Warfare...... Airborne Mine A test of the E4............... 81-84 576 SOCAL. Neutralization airborne mine System Test. neutralization system evaluates the system's ability to detect and destroy mines from an airborne mine countermeasures capable helicopter. The Airborne Mine Neutralization System uses up to four unmanned underwater vehicles equipped with high frequency sonar, video cameras, and explosive and non-explosive neutralizers. Duration: 2-3 hours. Acoustic....................... Mine Warfare...... Airborne Sonobuoy A mine-hunting MFM.............. 9-10 66 Hawaii. Minehunting Test. system made up of sonobuoys deployed from a helicopter. A field of sonobuoys, using high-frequency sonar, is used to detect and classify bottom and moored mines. Duration: 2 hours. Acoustic....................... Mine Warfare...... Airborne Sonobuoy A mine-hunting MFM.............. 9-10 66 SOCAL. Minehunting Test. system made up of sonobuoys deployed from a helicopter. A field of sonobuoys, using high-frequency sonar, is used to detect and classify bottom and moored mines. Duration: 2 hours. [[Page 32142]] Explosive...................... Surface Warfare... Air-to-Surface This event is E7, E9........... 8-9 59 Hawaii. Bombing Test. similar to the training event bombing exercise air-to-surface. Fixed-wing aircraft test the delivery of bombs against surface maritime targets with the goal of evaluating the bomb, the bomb carry and delivery system, and any associated systems that may have been newly developed or enhanced. Duration: 2 hours. Explosive...................... Surface Warfare... Air-to-Surface This event is E7, E9........... 14-15 101 SOCAL. Bombing Test. similar to the training event bombing exercise air-to-surface. Fixed-wing aircraft test the delivery of bombs against surface maritime targets with the goal of evaluating the bomb, the bomb carry and delivery system, and any associated systems that may have been newly developed or enhanced. Duration: 2 hours. Explosive...................... Surface Warfare... Air-to-Surface This event is E7, E9........... 52 364 PMSR. Bombing Test. similar to the training event bombing exercise air-to-surface. Fixed-wing aircraft test the delivery of bombs against surface maritime targets with the goal of evaluating the bomb, the bomb carry and delivery system, and any associated systems that may have been newly developed or enhanced. Duration: 2 hours. Explosive...................... Surface Warfare... Air-to-Surface This event is E1............... 6-7 45 Hawaii. Gunnery Test. similar to the training event gunnery exercise (air to surface). Fixed- wing and rotary- wing aircrews evaluate new or enhanced aircraft guns against surface maritime targets to test that the gun, gun ammunition, or associated systems meet required specifications or to train aircrew in the operation of a new or enhanced weapon system. Duration: 2-3 hours. Explosive...................... Surface Warfare... Air-to-Surface This event is E1............... 60-66 438 SOCAL. Gunnery Test. similar to the training event gunnery exercise (air to surface). Fixed- wing and rotary- wing aircrews evaluate new or enhanced aircraft guns against surface maritime targets to test that the gun, gun ammunition, or associated systems meet required specifications or to train aircrew in the operation of a new or enhanced weapon system. Duration: 2-3 hours. Explosive...................... Surface Warfare... Air-to-Surface This event is E1............... 10 70 PMSR. Gunnery Test. similar to the training event gunnery exercise (air to surface). Fixed- wing and rotary- wing aircrews evaluate new or enhanced aircraft guns against surface maritime targets to test that the gun, gun ammunition, or associated systems meet required specifications or to train aircrew in the operation of a new or enhanced weapon system. Duration: 2-3 hours. Explosive...................... Surface Warfare... Air-to-Surface This event is E6, E7, E8, E9... 18-20 132 Hawaii. Missile Test. similar to the training event missile exercise air-to-surface. Test may involve both fixed-wing and rotary-wing aircraft launching missiles at surface maritime targets to evaluate the weapons system or as part of another system's integration test. Duration: 2-4 hours. [[Page 32143]] Explosive...................... Surface Warfare... Air-to-Surface This event is E6, E7, E8, E9... 8 56 SOCAL. Missile Test. similar to the training event missile exercise air-to-surface. Test may involve both fixed-wing and rotary-wing aircraft launching missiles at surface maritime targets to evaluate the weapons system or as part of another system's integration test. Duration: 2-4 hours. Explosive...................... Surface Warfare... Air-to-Surface This event is E6, E7, E8, E9... 180-186 1,275 PMSR. Missile Test. similar to the training event missile exercise air-to-surface. Test may involve both fixed-wing and rotary-wing aircraft launching missiles at surface maritime targets to evaluate the weapons system or as part of another system's integration test. Duration: 2-4 hours. Explosive...................... Surface Warfare... Rocket Test....... Rocket tests E3, E9........... 2 14 Hawaii. evaluate the integration, accuracy, performance, and safe separation of guided and unguided 2.75- inch (7 centimeter (cm)) rockets fired from a hovering or forward flying helicopter. Duration: 1-3 hours. Explosive...................... Surface Warfare... Rocket Test....... Rocket tests E3, E9........... 22-24 160 SOCAL. evaluate the integration, accuracy, performance, and safe separation of guided and unguided 2.75- inch (7 cm) rockets fired from a hovering or forward flying helicopter. Duration: 1-3 hours. Explosive...................... Surface Warfare... Rocket Test....... Rocket tests E3, E9........... 8 56 PMSR. evaluate the integration, accuracy, performance, and safe separation of guided and unguided 2.75- inch (7 cm) rockets fired from a hovering or forward flying helicopter. Duration: 1-3 hours. Explosive...................... Surface Warfare... Subsurface-to- Submarines launch E10.............. 4 28 PMSR. Surface Missile missiles at Test. surface maritime targets with the goal of destroying or disabling enemy ships or boats. Duration: 8 hours. Explosive...................... Surface Warfare... Surface-to-Surface Evaluates the E3, E5........... 10 70 PMSR. Gunnery Test-- performance and Large-Caliber. effectiveness of software and hardware modifications or upgrades of ship- based large- caliber gunnery systems against surface targets. 3 hours. Explosive...................... Surface Warfare... Surface-to-Surface Evaluates the E1, E3........... 26 182 PMSR. Gunnery Test-- performance and Medium-Caliber. effectiveness of software and hardware modifications or upgrades of ship- based medium- caliber gunnery systems against surface targets. Duration: 3 hours. Explosive...................... Surface Warfare... Surface-to-Surface Surface ships E9, E10.......... 44 308 PMSR. Missile Test. launch missiles at surface maritime targets. Duration: 2-5 hours. Acoustic....................... Other Testing..... Undersea Range Post installation MFM.............. 30-33 207 BARSTUR. System Test. node survey and test and periodic testing of range Node transmit functionality. Duration: varies. Acoustic....................... Other Testing..... Undersea Range Post installation MFM.............. 19-21 127 SOCAL. System Test. node survey and test and periodic testing of range Node transmit functionality. Duration: varies. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: LF = low-frequency, MF = mid-frequency, HF = high-frequency, dB = decibels, L = low, M = medium, H = high (e.g., MFL = mid-frequency low source level), H = hours, C = count. BARSTUR = Barking Sands Tactical Underwater Range, Hawaii = the Hawaii Study Area, PMSR = Point Mugu Sea Range, SCORE = Southern California Offshore Range, SOAR = Southern California Offshore Anti-Submarine Warfare Range, SOCAL = Southern California Range Complex. NAVSEA activities are generally aligned with the primary mission areas used by the fleets and include, but are not limited to, new ship construction, life cycle support, and other weapon system development and testing. Testing activities are conducted throughout the life of a Navy ship, from construction through deactivation from the fleet to verification of performance and mission capabilities. Activities include pierside and at-sea testing of ship systems, including sonar, acoustic countermeasures, radars, torpedoes, weapons, unmanned systems, and radio [[Page 32144]] equipment; tests to determine how the ship performs at sea (sea trials); development and operational test and evaluation programs for new technologies and systems, including ship shock trials to test the survivability of new ships; and testing on all ships and systems that have undergone overhaul or maintenance. Table 7 summarizes the proposed testing activities for NAVSEA analyzed within the HCTT Study Area. Table 7--Proposed NAVSEA Testing Activities Analyzed Within the HCTT Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Number of Number of Stressor category Activity type Activity name Description Source bin activities activities Location 1-year 7-year -------------------------------------------------------------------------------------------------------------------------------------------------------- Acoustic....................... Anti-Submarine ASW Mission Ships and their MF1, MFH......... 1 7 Hawaii. Warfare. Package Testing. supporting platforms (e.g., rotary-wing aircraft, unmanned aerial systems) detect, localize, and prosecute submarines. Duration: 1-2 weeks with 4-8 hours of active sonar use per day. Acoustic....................... Anti-Submarine ASW Mission Ships and their MF1, MFH......... 1 7 SOCAL. Warfare. Package Testing. supporting platforms (e.g., rotary-wing aircraft, unmanned aerial systems) detect, localize, and prosecute submarines. Duration: 1-2 weeks with 4-8 hours of active sonar use per day. Acoustic....................... Anti-Submarine At-Sea Sonar At-sea testing to HFH, HFL, HFM, LF 9-11 70 Hawaii. Warfare. Testing. ensure systems to HF, LF to MF, are fully LFH, LFM, MF to functional in an HF, MF1, MF1K, open ocean MFH, MFL, MFM. environment. Duration: 4 hours to 11 days. Acoustic....................... Anti-Submarine At-Sea Sonar At-sea testing to HFH, HFL, HFM, LF 16-22 128 SOCAL. Warfare. Testing. ensure systems to HF, LF to MF, are fully LFH, LFM, MF to functional in an HF, MF1, MF1K, open ocean MFH, MFL, MFM. environment. Duration: 4 hours to 11 days. Acoustic....................... Anti-Submarine At-Sea Sonar At-sea testing to HFH, HFL, HFM, LF 10-20 70 SOAR. Warfare. Testing. ensure systems to HF, LF to MF, are fully LFH, LFM, MF to functional in an HF, MF1, MF1K, open ocean MFH, MFL, MFM. environment. Duration: 4 hours to 11 days. Acoustic....................... Anti-Submarine At-Sea Sonar At-sea testing to HFH, HFL, HFM, LF 0-1 4 PMRF. Warfare. Testing. ensure systems to HF, LF to MF, are fully LFH, LFM, MF to functional in an HF, MF1, MF1K, open ocean MFH, MFL, MFM. environment. Duration: 4 hours to 11 days. Acoustic....................... Anti-Submarine Countermeasure Countermeasure HFH, LF to HF, MF 3-6 20 Hawaii, Maui Warfare. Testing. testing involves to HF, MFH, MFM, Basin, PMRF. the testing of VHFH. systems that detect, localize, and engage incoming weapons, including marine vessel targets and airborne missiles. Testing includes surface ship torpedo defense systems, marine vessel stopping payloads, and airborne decoys against targets. Duration: 4 hours to 6 days. Acoustic....................... Anti-Submarine Countermeasure Countermeasure HFH, LF to HF, MF 7-12 25 SOCAL, SCORE. Warfare. Testing. testing involves to HF, MFH, MFM, the testing of VHFH. systems that detect, localize, and engage incoming weapons, including marine vessel targets and airborne missiles. Testing includes surface ship torpedo defense systems, marine vessel stopping payloads, and airborne decoys against targets. Duration: 4 hours to 6 days. [[Page 32145]] Acoustic....................... Anti-Submarine Pierside Sonar Pierside testing HFH, HFM, MF to 13-25 171 Pearl Harbor. Warfare. Testing. to ensure HF, MFH, MFM. systems are fully functional in a controlled pierside environment prior to at-sea test activities and complete any troubleshooting. Duration: up to 3 weeks, with intermittent sonar use. Acoustic....................... Anti-Submarine Pierside Sonar Pierside testing HFH, HFM, MF to 44-55 383 San Diego Bay. Warfare. Testing. to ensure HF, MFH, MFM. systems are fully functional in a controlled pierside environment prior to at-sea test activities and complete any troubleshooting. Duration: up to 3 weeks, with intermittent sonar use. Acoustic....................... Anti-Submarine Pierside Sonar Pierside testing HFH, HFM, MF to 15-20 140 Port Hueneme. Warfare. Testing. to ensure HF, MFH, MFM. systems are fully functional in a controlled pierside environment prior to at-sea test activities and complete any troubleshooting. Duration: up to 3 weeks, with intermittent sonar use. Acoustic....................... Anti-Submarine Surface Ship Pierside and at- LFL, MF to HF, 3 7 Hawaii. Warfare. Sonar Testing/ sea testing of MF1, MF1K, MFM. Maintenance. ship systems occur periodically following major maintenance periods and for routine maintenance. Duration: up to 3 weeks, with intermittent sonar use. Acoustic....................... Anti-Submarine Surface Ship Pierside and at- LFL, MF to HF, 3 21 Pearl Harbor. Warfare. Sonar Testing/ sea testing of MF1, MF1K, MFM. Maintenance. ship systems occur periodically following major maintenance periods and for routine maintenance. Duration: up to 3 weeks, with intermittent sonar use. Acoustic....................... Anti-Submarine Surface Ship Pierside and at- LFL, MF to HF, 3 21 SOCAL. Warfare. Sonar Testing/ sea testing of MF1, MF1K, MFM. Maintenance. ship systems occur periodically following major maintenance periods and for routine maintenance. Duration: up to 3 weeks, with intermittent sonar use. Acoustic....................... Anti-Submarine Surface Ship Pierside and at- LFL, MF to HF, 3 21 San Diego Bay. Warfare. Sonar Testing/ sea testing of MF1, MF1K, MFM. Maintenance. ship systems occur periodically following major maintenance periods and for routine maintenance. Duration: up to 3 weeks, with intermittent sonar use. Acoustic and Explosive......... Anti-Submarine Torpedo Air, surface, or E8, E11, HFH, MF 1-5 17 Hawaii, SOCAL, Warfare. (Explosive) submarine crews to HF, MF1, MFH, PMSR. Testing. employ explosive MFM. and non- explosive torpedoes against artificial targets. Duration: 1-2 days, 8-12 hours per day. Acoustic....................... Anti-Submarine Torpedo (Non- Air, surface, or HFH, HFM, LF to 13-17 96 Hawaii, SOCAL, Warfare. Explosive) submarine crews HF, MF to HF, BARSTUR, PMSR. Testing. employ non- MF1, MFH, MFL, explosive MFM, VHFH. torpedoes against submarines, surface vessels, or artificial targets. Duration: up to 2 weeks. Explosive...................... Mine Warfare..... Mine Air, surface, and E4............... 18-45 315 SOCAL. Countermeasure subsurface and vessels Neutralization neutralize Testing. threat mines and mine-like objects. Duration: 1-10 days, with intermittent use of countermeasure systems. Acoustic and Explosive......... Mine Warfare..... Mine Vessels and E4, HFM, MFH..... 0-1 7 PMRF. Countermeasure associated Mission Package aircraft conduct Testing. mine countermeasure operations. Duration: 1-2 weeks, with intermittent use of countermeasure systems. Acoustic and Explosive......... Mine Warfare..... Mine Vessels and E4, HFM, MFH..... 16 109 Maui Basin. Countermeasure associated Mission Package aircraft conduct Testing. mine countermeasure operations. Duration: 1-2 weeks, with intermittent use of countermeasure systems. Acoustic and Explosive......... Mine Warfare..... Mine Vessels and E4, HFM, MFH..... 6 36 CPAAA. Countermeasure associated Mission Package aircraft conduct Testing. mine countermeasure operations. Duration: 1-2 weeks, with intermittent use of countermeasure systems. [[Page 32146]] Acoustic and Explosive......... Mine Warfare..... Mine Vessels and E4, HFM, MFH..... 6 36 SSTC. Countermeasure associated Mission Package aircraft conduct Testing. mine countermeasure operations. Duration: 1-2 weeks, with intermittent use of countermeasure systems. Acoustic and Explosive......... Mine Warfare..... Mine Vessels and E4, HFM, MFH..... 6 37 Tanner Bank. Countermeasure associated Mission Package aircraft conduct Testing. mine countermeasure operations. Duration: 1-2 weeks, with intermittent use of countermeasure systems. Acoustic and Explosive......... Mine Warfare..... Mine Vessels and E4, HFM, MFH..... 6 42 Imperial Beach Countermeasure associated Minefield. Mission Package aircraft conduct Testing. mine countermeasure operations. Duration: 1-2 weeks, with intermittent use of countermeasure systems. Acoustic and Explosive......... Mine Warfare..... Mine Vessels and E4, HFM, MFH..... 1 7 PMSR. Countermeasure associated Mission Package aircraft conduct Testing. mine countermeasure operations. Duration: 1-2 weeks, with intermittent use of countermeasure systems. Acoustic....................... Mine Warfare..... Mine Detection Air, surface, and HFH.............. 4-8 28 Hawaii. and subsurface Classification vessels and Testing. systems detect, classify, and avoid mines and mine-like objects. Vessels also assess their potential susceptibility to mines and mine-like objects. Duration: up to 24 days, 8-12 hours per day. Acoustic....................... Mine Warfare..... Mine Detection Air, surface, and HFH.............. 0-1 4 Imperial Beach and subsurface Minefield. Classification vessels and Testing. systems detect, classify, and avoid mines and mine-like objects. Vessels also assess their potential susceptibility to mines and mine-like objects. Duration: up to 24 days, 8-12 hours per day. Acoustic....................... Mine Warfare..... Mine Detection Air, surface, and HFH.............. 2 14 Maui Basin. and subsurface Classification vessels and Testing. systems detect, classify, and avoid mines and mine-like objects. Vessels also assess their potential susceptibility to mines and mine-like objects. Duration: up to 24 days, 8-12 hours per day. Acoustic....................... Mine Warfare..... Mine Detection Air, surface, and HFH.............. 2 14 Tanner Bank. and subsurface Classification vessels and Testing. systems detect, classify, and avoid mines and mine-like objects. Vessels also assess their potential susceptibility to mines and mine-like objects. Duration: up to 24 days, 8-12 hours per day. Acoustic....................... Mine Warfare..... Mine Detection Air, surface, and HFH.............. 4-8 28 PMSR. and subsurface Classification vessels and Testing. systems detect, classify, and avoid mines and mine-like objects. Vessels also assess their potential susceptibility to mines and mine-like objects. Duration: up to 24 days, 8-12 hours per day. Acoustic....................... Mine Warfare..... Mine Detection Air, surface, and HFH.............. 4-9 30 SOCAL. and subsurface Classification vessels and Testing. systems detect, classify, and avoid mines and mine-like objects. Vessels also assess their potential susceptibility to mines and mine-like objects. Duration: up to 24 days, 8-12 hours per day. Acoustic....................... Unmanned Systems. Unmanned Testing involves HFL, HFM, MF to 2 14 Pearl Harbor. Underwater the production HF, MFM, VHFH, Vehicle Testing. or upgrade of VHFL. unmanned underwater vehicles. This may include testing mine detection capabilities, evaluating the basic functions of individual platforms, or conducting complex events with multiple vehicles. Duration: up to 35 days, gliders could operate for multiple months. [[Page 32147]] Acoustic....................... Unmanned Systems. Unmanned Testing involves HFL, HFM, MF to 230 1,610 Port Hueneme. Underwater the production HF, MFM, VHFH, Vehicle Testing. or upgrade of VHFL. unmanned underwater vehicles. This may include testing mine detection capabilities, evaluating the basic functions of individual platforms, or conducting complex events with multiple vehicles. Duration: up to 35 days, gliders could operate for multiple months. Acoustic....................... Unmanned Systems. Unmanned Testing involves HFL, HFM, MF to 10-15 85 SOCAL. Underwater the production HF, MFM, VHFH, Vehicle Testing. or upgrade of VHFL. unmanned underwater vehicles. This may include testing mine detection capabilities, evaluating the basic functions of individual platforms, or conducting complex events with multiple vehicles. Duration: up to 35 days, gliders could operate for multiple months. Acoustic....................... Unmanned Systems. Unmanned Testing involves HFL, HFM, MF to 440 3,080 SOCAL nearshore. Underwater the production HF, MFM, VHFH, Vehicle Testing. or upgrade of VHFL. unmanned underwater vehicles. This may include testing mine detection capabilities, evaluating the basic functions of individual platforms, or conducting complex events with multiple vehicles. Duration: up to 35 days, gliders could operate for multiple months. Acoustic....................... Vessel Evaluation In-Port Each combat MF1.............. 5 30 Pearl Harbor. Maintenance system is tested Testing. to ensure they are functioning in a technically acceptable manner and are operationally ready to support at-sea testing. Duration: 3 weeks. Acoustic....................... Vessel Evaluation In-Port Each combat MF1.............. 5 30 San Diego Bay. Maintenance system is tested Testing. to ensure they are functioning in a technically acceptable manner and are operationally ready to support at-sea testing. Duration: 3 weeks. Acoustic....................... Vessel Evaluation In-Port Each combat MF1.............. 10 70 Port Hueneme. Maintenance system is tested Testing. to ensure they are functioning in a technically acceptable manner and are operationally ready to support at-sea testing. Duration: 3 weeks. Acoustic....................... Vessel Evaluation Signature Surface ship and HFM, MFM......... 2-4 14 Hawaii. Analysis submarine Operations. testing of electromagnetic, acoustic, optical, and radar signature measurements. Duration: 1-5 days. Acoustic....................... Vessel Evaluation Signature Surface ship and HFM, MFM......... 0-1 1 San Diego Bay. Analysis submarine Operations. testing of electromagnetic, acoustic, optical, and radar signature measurements. Duration: 1-5 days. Explosive...................... Vessel Evaluation Small Ship Shock Underwater E16.............. 0-1 1 SOCAL. Trial. detonations are used to test new ships or major upgrades. Duration: up to 3 weeks. Acoustic....................... Vessel Evaluation Submarine Sea Submarine weapons HFH, HFM, LF to 2-4 12 Hawaii. Trials--Weapons and sonar HF, MFH, MFL. System Testing. systems are tested at-sea to meet integrated combat system certification requirements. Duration: up to 7 days. Acoustic....................... Vessel Evaluation Submarine Sea Submarine weapons HFH, HFM, LF to 2-4 12 SOCAL. Trials--Weapons and sonar HF, MFH, MFL. System Testing. systems are tested at-sea to meet integrated combat system certification requirements. Duration: up to 7 days. [[Page 32148]] Acoustic and Explosive......... Vessel Evaluation Surface Warfare Tests capability E3, E5, E6, E7, 0-12 48 Hawaii. Testing. of shipboard E8, E9, HFH, MFM. sensors to detect, track, and engage surface targets. Testing may include ships defending against surface targets using explosive and non-explosive rounds, gun system structural test firing, and demonstration of the response to Call for Fire against land- based targets (simulated by sea-based locations). Duration: 7 days. Acoustic and Explosive......... Vessel Evaluation Surface Warfare Tests capability E3, E5, E6, E7, 4 35 PMRF. Testing. of shipboard E8, E9, HFH, MFM. sensors to detect, track, and engage surface targets. Testing may include ships defending against surface targets using explosive and non-explosive rounds, gun system structural test firing, and demonstration of the response to Call for Fire against land- based targets (simulated by sea-based locations). Duration: 7 days. Acoustic and Explosive......... Vessel Evaluation Surface Warfare Tests capability E3, E5, E6, E7, 3-15 39 SOCAL. Testing. of shipboard E8, E9, HFH, MFM. sensors to detect, track, and engage surface targets. Testing may include ships defending against surface targets using explosive and non-explosive rounds, gun system structural test firing, and demonstration of the response to Call for Fire against land- based targets (simulated by sea-based locations). Duration: 7 days. Acoustic and Explosive......... Vessel Evaluation Surface Warfare Tests capability E3, E5, E6, E7, 3-6 30 SOAR. Testing. of shipboard E8, E9, HFH, MFM. sensors to detect, track, and engage surface targets. Testing may include ships defending against surface targets using explosive and non-explosive rounds, gun system structural test firing, and demonstration of the response to Call for Fire against land- based targets (simulated by sea-based locations). Duration: 7 days. Acoustic and Explosive......... Vessel Evaluation Surface Warfare Tests capability E3, E5, E6, E7, 4-12 36 SCORE. Testing. of shipboard E8, E9, HFH, MFM. sensors to detect, track, and engage surface targets. Testing may include ships defending against surface targets using explosive and non-explosive rounds, gun system structural test firing, and demonstration of the response to Call for Fire against land- based targets (simulated by sea-based locations). Duration: 7 days. Acoustic and Explosive......... Vessel Evaluation Surface Warfare Tests capability E3, E5, E6, E7, 7-20 67 PMSR. Testing. of shipboard E8, E9, HFH, MFM. sensors to detect, track, and engage surface targets. Testing may include ships defending against surface targets using explosive and non-explosive rounds, gun system structural test firing, and demonstration of the response to Call for Fire against land- based targets (simulated by sea-based locations). Duration: 7 days. [[Page 32149]] Acoustic....................... Vessel Evaluation Undersea Warfare Ships demonstrate HFH, MF1, MFH, 1-7 26 Hawaii. Testing. capability of MFM. countermeasure systems and underwater surveillance, weapons engagement, and communications systems. This tests ships' ability to detect, track, and engage undersea targets. Duration: up to 10 days. Acoustic....................... Vessel Evaluation Undersea Warfare Ships demonstrate HFH, MF1, MFH, 2-3 16 PMRF. Testing. capability of MFM. countermeasure systems and underwater surveillance, weapons engagement, and communications systems. This tests ships' ability to detect, track, and engage undersea targets. Duration: up to 10 days. Acoustic....................... Vessel Evaluation Undersea Warfare Ships demonstrate HFH, MF1, MFH, 23-43 154 SOCAL. Testing. capability of MFM. countermeasure systems and underwater surveillance, weapons engagement, and communications systems. This tests ships' ability to detect, track, and engage undersea targets. Duration: up to 10 days. Acoustic....................... Vessel Evaluation Undersea Warfare Ships demonstrate HFH, MF1, MFH, 2-14 56 SCORE. Testing. capability of MFM. countermeasure systems and underwater surveillance, weapons engagement, and communications systems. This tests ships' ability to detect, track, and engage undersea targets. Duration: up to 10 days. Acoustic and Explosive......... Other Testing.... Acoustic and Research using E7, LFM.......... 1 7 Hawaii. Oceanographic active Research. transmissions from sources deployed from ships, aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Duration: up to 14 days. Acoustic and Explosive......... Other Testing.... Acoustic and Research using E7, LFM.......... 4-5 31 PMRF. Oceanographic active Research. transmissions from sources deployed from ships, aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Duration: up to 14 days. Acoustic and Explosive......... Other Testing.... Acoustic and Research using E7, LFM.......... 2 14 SOCAL. Oceanographic active Research. transmissions from sources deployed from ships, aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Duration: up to 14 days. Acoustic and Explosive......... Other Testing.... Acoustic and Research using E7, LFM.......... 0-1 3 PMSR. Oceanographic active Research. transmissions from sources deployed from ships, aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Duration: up to 14 days. Acoustic....................... Other Testing.... Insertion/ Testing of HFM, LF to MF, 2 14 Hawaii. Extraction. submersibles LFH. capable of inserting and extracting personnel and payloads into denied areas from strategic distances. Duration: up to 30 days. Acoustic....................... Other Testing.... Insertion/ Testing of HFM, LF to MF, 2 14 SOCAL. Extraction. submersibles LFH. capable of inserting and extracting personnel and payloads into denied areas from strategic distances. Duration: up to 30 days. Acoustic and Explosive......... Other Testing.... Semi-Stationary Semi-stationary E4, HFH.......... 4-8 40 Pearl Harbor. Equipment equipment (e.g., Testing. hydrophones) is deployed to determine functionality. Duration: up to 14 days. [[Page 32150]] Acoustic and Explosive......... Other Testing.... Semi-Stationary Semi-stationary E4, HFH.......... 4-8 40 San Diego Bay. Equipment equipment (e.g., Testing. hydrophones) is deployed to determine functionality. Duration: up to 14 days. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: LF = low-frequency, MF = mid-frequency, HF = high-frequency, dB = decibels, L = low, M = medium, H = high (e.g., MFL = mid-frequency low source level), H = hours, C = count. BARSTUR = Barking Sands Tactical Underwater Range, CPAAA = Camp Pendleton Amphibious Assault Area, Hawaii = the Hawaii Study Area, PMRF = Pacific Missile Range Facility, PMSR = Point Mugu Sea Range, SCORE = Southern California Offshore Range, SOAR = Southern California Offshore Anti-Submarine Range, SOCAL = Southern California Range Complex, SSTC = Silver Strand Training Complex. NAVWAR is the information warfare systems command for the Navy. The mission of NAVWAR is to identify, develop, deliver, and sustain information warfare capabilities and services that enable naval, joint, coalition, and other national missions operating in warfighting domains from seabed to space; and to perform such other functions and tasks as directed. NAVWAR Systems Center Pacific is the research and development part of NAVWAR focused on developing and transitioning technologies in the area of command, control, communications, computers, intelligence, surveillance, and reconnaissance. Table 8 summarizes the proposed testing activities for NAVWAR analyzed within the HCTT Study Area. Table 8--Proposed NAVWAR Testing Activities Analyzed Within the HCTT Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Number of Number of Stressor category Activity type Activity name Description Source bin activities activities Location 1-year 7-year -------------------------------------------------------------------------------------------------------------------------------------------------------- Acoustic....................... Acoustic and Acoustic, Testing includes HFM, LF to HF, 2 14 Pearl Harbor. Oceanographic Oceanographic, activities LFM, MF to HF, Science and and Energy utilizing the MFH, MFM. Technology. Research. marine environment for research, and test and evaluation. Tests may involve radar, environmental sensors, magnetic sensors, passive and active acoustic sensors, optical sensors, and lasers. Surface operations utilize a variety of vessels and vehicles for deployment, operation, and testing. Energy research and harvesting would include the development and testing of energy harvesting and storage technologies, maritime charging stations, remote communications, and associated infrastructure. This testing would also include bioacoustics research in support of marine mammal science. Duration: up to 14 days. Acoustic....................... Acoustic and Acoustic, Testing includes HFM, LF to HF, 10-16 88 SOCAL. Oceanographic Oceanographic, activities LFM, MF to HF, Science and and Energy utilizing the MFH, MFM. Technology. Research. marine environment for research, and test and evaluation. Tests may involve radar, environmental sensors, magnetic sensors, passive and active acoustic sensors, optical sensors, and lasers. Surface operations utilize a variety of vessels and vehicles for deployment, operation, and testing. Energy research and harvesting would include the development and testing of energy harvesting and storage technologies, maritime charging stations, remote communications, and associated infrastructure. This testing would also include bioacoustics research in support of marine mammal science. Duration: up to 14 days. [[Page 32151]] Acoustic....................... Acoustic and Acoustic, Testing includes HFM, LF to HF, 133-160 1,012 San Diego Bay. Oceanographic Oceanographic, activities LFM, MF to HF, Science and and Energy utilizing the MFH, MFM. Technology. Research. marine environment for research, and test and evaluation. Tests may involve radar, environmental sensors, magnetic sensors, passive and active acoustic sensors, optical sensors, and lasers. Surface operations utilize a variety of vessels and vehicles for deployment, operation, and testing. Energy research and harvesting would include the development and testing of energy harvesting and storage technologies, maritime charging stations, remote communications, and associated infrastructure. This testing would also include bioacoustics research in support of marine mammal science. Duration: up to 14 days. Acoustic....................... Acoustic and Acoustic, Testing includes HFM, LF to HF, 2-4 20 PMSR. Oceanographic Oceanographic, activities LFM, MF to HF, Science and and Energy utilizing the MFH, MFM. Technology. Research. marine environment for research, and test and evaluation. Tests may involve radar, environmental sensors, magnetic sensors, passive and active acoustic sensors, optical sensors, and lasers. Surface operations utilize a variety of vessels and vehicles for deployment, operation, and testing. Energy research and harvesting would include the development and testing of energy harvesting and storage technologies, maritime charging stations, remote communications, and associated infrastructure. This testing would also include bioacoustics research in support of marine mammal science. Duration: up to 14 days. Acoustic....................... Other Testing.... Communications... Testing of LF to MF......... 1 7 Hawaii. maritime communications, underwater network systems with fiber optics cables, laser communications, acoustic modem networks and launching of communication payloads and objects. Durations: typically 5 days for 6-8 hours per day. Acoustic....................... Other Testing.... Communications... Testing of LF to MF......... 4 28 SOCAL. maritime communications, underwater network systems with fiber optics cables, laser communications, acoustic modem networks and launching of communication payloads and objects. Durations: typically 5 days for 6-8 hours per day. Acoustic....................... Other Testing.... Intelligence, Testing Air gun, HFL, 15-17 108 Hawaii. Surveillance, deployable HFM, LF, LF to Reconnaissance. autonomous HF, LFH, MF to undersea HF, MFH, MFL, technologies MFM, VHFH. that may include mine detection and classification, detection and classification of targets of interest, sensors on the undersea systems testbed, expansion of the undersea systems testbed with fiber optic cables and nodes, sensor systems to detect mine shapes on ship hulls and pier structures, sensors for swimmer interdiction and other threats, and sensor systems that can detect explosive, radioactive, and other signatures of concern. Duration: up to 30 days. [[Page 32152]] Acoustic....................... Other Testing.... Intelligence, Testing Air gun, HFL, 2 14 Pearl Harbor. Surveillance, deployable HFM, LF, LF to Reconnaissance. autonomous HF, LFH, MF to undersea HF, MFH, MFL, technologies MFM, VHFH. that may include mine detection and classification, detection and classification of targets of interest, sensors on the undersea systems testbed, expansion of the undersea systems testbed with fiber optic cables and nodes, sensor systems to detect mine shapes on ship hulls and pier structures, sensors for swimmer interdiction and other threats, and sensor systems that can detect explosive, radioactive, and other signatures of concern. Duration: up to 30 days. Acoustic....................... Other Testing.... Intelligence, Testing Air gun, HFL, 83-123 700 SOCAL. Surveillance, deployable HFM, LF, LF to Reconnaissance. autonomous HF, LFH, MF to undersea HF, MFH, MFL, technologies MFM, VHFH. that may include mine detection and classification, detection and classification of targets of interest, sensors on the undersea systems testbed, expansion of the undersea systems testbed with fiber optic cables and nodes, sensor systems to detect mine shapes on ship hulls and pier structures, sensors for swimmer interdiction and other threats, and sensor systems that can detect explosive, radioactive, and other signatures of concern. Duration: up to 30 days. Acoustic....................... Other Testing.... Intelligence, Testing Air gun, HFL, 5-10 50 CPAAA. Surveillance, deployable HFM, LF, LF to Reconnaissance. autonomous HF, LFH, MF to undersea HF, MFH, MFL, technologies MFM, VHFH. that may include mine detection and classification, detection and classification of targets of interest, sensors on the undersea systems testbed, expansion of the undersea systems testbed with fiber optic cables and nodes, sensor systems to detect mine shapes on ship hulls and pier structures, sensors for swimmer interdiction and other threats, and sensor systems that can detect explosive, radioactive, and other signatures of concern. Duration: up to 30 days. Acoustic....................... Other Testing.... Intelligence, Testing Air gun, HFL, 8-10 62 San Diego Bay. Surveillance, deployable HFM, LF, LF to Reconnaissance. autonomous HF, LFH, MF to undersea HF, MFH, MFL, technologies MFM, VHFH. that may include mine detection and classification, detection and classification of targets of interest, sensors on the undersea systems testbed, expansion of the undersea systems testbed with fiber optic cables and nodes, sensor systems to detect mine shapes on ship hulls and pier structures, sensors for swimmer interdiction and other threats, and sensor systems that can detect explosive, radioactive, and other signatures of concern. Duration: up to 30 days. [[Page 32153]] Acoustic....................... Other Testing.... Intelligence, Testing Air gun, HFL, 11-19 101 SCIUR. Surveillance, deployable HFM, LF, LF to Reconnaissance. autonomous HF, LFH, MF to undersea HF, MFH, MFL, technologies MFM, VHFH. that may include mine detection and classification, detection and classification of targets of interest, sensors on the undersea systems testbed, expansion of the undersea systems testbed with fiber optic cables and nodes, sensor systems to detect mine shapes on ship hulls and pier structures, sensors for swimmer interdiction and other threats, and sensor systems that can detect explosive, radioactive, and other signatures of concern. Duration: up to 30 days. Acoustic....................... Other Testing.... Intelligence, Testing Air gun, HFL, 38-51 305 SCORE. Surveillance, deployable HFM, LF, LF to Reconnaissance. autonomous HF, LFH, MF to undersea HF, MFH, MFL, technologies MFM, VHFH. that may include mine detection and classification, detection and classification of targets of interest, sensors on the undersea systems testbed, expansion of the undersea systems testbed with fiber optic cables and nodes, sensor systems to detect mine shapes on ship hulls and pier structures, sensors for swimmer interdiction and other threats, and sensor systems that can detect explosive, radioactive, and other signatures of concern. Duration: up to 30 days. Acoustic....................... Other Testing.... Intelligence, Testing Air gun, HFL, 44-62 362 SSTC. Surveillance, deployable HFM, LF, LF to Reconnaissance. autonomous HF, LFH, MF to undersea HF, MFH, MFL, technologies MFM, VHFH. that may include mine detection and classification, detection and classification of targets of interest, sensors on the undersea systems testbed, expansion of the undersea systems testbed with fiber optic cables and nodes, sensor systems to detect mine shapes on ship hulls and pier structures, sensors for swimmer interdiction and other threats, and sensor systems that can detect explosive, radioactive, and other signatures of concern. Duration: up to 30 days. Acoustic....................... Other Testing.... Vehicle Testing.. Testing of HFL, HFM, LFH, 15-22 123 Hawaii. surface, MFH, MFL, VHFH. subsurface and airborne vehicles, sensor systems, payloads, communications, and navigation which may involve remotely operated vehicles, autonomous underwater vehicles, autonomous surface vehicles, and autonomous aerial vehicles. Testing may involve evaluating individual vehicles and payloads or conducting complex events with multiple vehicles. Durations: typically 5 days for 6-8 hours per day. Acoustic....................... Other Testing.... Vehicle Testing.. Testing of HFL, HFM, LFH, 32-39 245 SOCAL. surface, MFH, MFL, VHFH. subsurface and airborne vehicles, sensor systems, payloads, communications, and navigation which may involve remotely operated vehicles, autonomous underwater vehicles, autonomous surface vehicles, and autonomous aerial vehicles. Testing may involve evaluating individual vehicles and payloads or conducting complex events with multiple vehicles. Durations: typically 5 days for 6-8 hours per day. [[Page 32154]] Acoustic....................... Other Testing.... Vehicle Testing.. Testing of HFL, HFM, LFH, 10-12 76 SCORE. surface, MFH, MFL, VHFH. subsurface and airborne vehicles, sensor systems, payloads, communications, and navigation which may involve remotely operated vehicles, autonomous underwater vehicles, autonomous surface vehicles, and autonomous aerial vehicles. Testing may involve evaluating individual vehicles and payloads or conducting complex events with multiple vehicles. Durations: typically 5 days for 6-8 hours per day. Acoustic....................... Other Testing.... Vehicle Testing.. Testing of HFL, HFM, LFH, 4-8 40 Transit Corridor. surface, MFH, MFL, VHFH. subsurface and airborne vehicles, sensor systems, payloads, communications, and navigation which may involve remotely operated vehicles, autonomous underwater vehicles, autonomous surface vehicles, and autonomous aerial vehicles. Testing may involve evaluating individual vehicles and payloads or conducting complex events with multiple vehicles. Durations: typically 5 days for 6-8 hours per day. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: LF = low-frequency, MF = mid-frequency, HF = high-frequency, dB = decibels, L = low, M = medium, H = high (e.g., MFL = mid-frequency low source level), H = hours, C = count. CPAAA = Camp Pendleton Amphibious Assault Area, Hawaii = the Hawaii Study Area, PMRF = Pacific Missile Range Facility, PMSR = Point Mugu Sea Range, SCIUR = San Clemente Island Underwater Range, SCORE = Southern California Offshore Range, SOCAL = Southern California Range Complex, SSTC = Silver Strand Training Complex. ONR's mission is to plan, foster, and encourage scientific research in recognition of its paramount importance as related to the maintenance of future naval power, and the preservation of national security. ONR manages the Navy's basic, applied, and advanced research to foster transition from science and technology to higher levels of research, development, test, and evaluation. ONR is also a parent organization for the Naval Research Laboratory, which operates as the Navy's corporate research laboratory and conducts a broad multidisciplinary program of scientific research and advanced technological development. Table 9 summarizes the proposed testing activities for the ONR analyzed within the HCTT Study Area. Table 9--Proposed ONR Testing Activities Analyzed Within the HCTT Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Number of Number of Stressor category Activity type Activity name Description Source bin activities activities Location 1-year 7-year -------------------------------------------------------------------------------------------------------------------------------------------------------- Acoustic.......... Acoustic and Acoustic and Research using E1, E3, Air gun and 4-5 32 Hawaii. Oceanographic Oceanographic active non-explosive Science and Research. transmissions from impulses, HFH, Technology. sources deployed HFM, LFH, LFM, from ships, MFH, MFM, VHFM. aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Duration: up to 14 days. Acoustic.......... Acoustic and Acoustic and Research using E1, E3, Air gun and 4-5 32 SOCAL. Oceanographic Oceanographic active non-explosive Science and Research. transmissions from impulses, HFH, Technology. sources deployed HFM, LFH, LFM, from ships, MFH, MFM, VHFM. aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Duration: up to 14 days. Acoustic.......... Acoustic and Acoustic and Research using E1, E3, Air gun and 1-2 10 Acoustic Research Oceanographic Oceanographic active non-explosive Area. Science and Research. transmissions from impulses, HFH, Technology. sources deployed HFM, LFH, LFM, from ships, MFH, MFM, VHFM. aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Duration: up to 14 days. [[Page 32155]] Acoustic.......... Acoustic and Acoustic and Research using E1, E3, Air gun and 1-2 9 PMSR. Oceanographic Oceanographic active non-explosive Science and Research. transmissions from impulses, HFH, Technology. sources deployed HFM, LFH, LFM, from ships, MFH, MFM, VHFM. aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Duration: up to 14 days. Acoustic.......... Acoustic and Acoustic and Research using E1, E3, Air gun and 1-2 14 NOCAL. Oceanographic Oceanographic active non-explosive Science and Research. transmissions from impulses, HFH, Technology. sources deployed HFM, LFH, LFM, from ships, MFH, MFM, VHFM. aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Duration: up to 14 days. Acoustic.......... Acoustic and Long Range Acoustic Low-frequency bottom- LFM................ 1-2 11 Hawaii. Oceanographic Communications. mounted acoustic Science and source off of the Technology. Hawaiian Island of Kaua'i would transmit a variety of acoustic communications sequences. Duration: year- round; active transmissions 200 days a year. Acoustic.......... Acoustic and Mine Countermeasure Test involves the MFH................ 1-2 11 Hawaii. Oceanographic Technology Research. use of broadband Science and acoustic sources on Technology. unmanned underwater vehicles. Duration: up to 30 days. Acoustic.......... Acoustic and Mine Countermeasure Test involves the MFH................ 6-8 50 SOCAL. Oceanographic Technology Research. use of broadband Science and acoustic sources on Technology. unmanned underwater vehicles. Duration: up to 30 days. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: LF = low-frequency, MF = mid-frequency, HF = high-frequency, dB = decibels, L = low, M = medium, H = high (e.g., MFL = mid-frequency low source level), H = hours, C = count. Hawaii = the Hawaii Study Area, NOCAL = Northern California Range Complex, PMSR = Point Mugu Sea Range, SOCAL = Southern California Range Complex. Vessel Movement Vessels used as part of the proposed activities include both surface and sub-surface operations of both manned and unmanned vessels (USVs, UUVs). Vessels used as part of the Action Proponents' activities include ships, submarines, unmanned vessels, and boats ranging in size from small, 22 ft (6.7 m) rigid hull inflatable boats to aircraft carriers with lengths up to 1,092 ft (332.8 m). Unmanned systems may include vehicles ranging from 4-16 ft (1.2-4.9 m) but typical size of USVs is 36-328 ft (11-100 m) while UUVs are 33-98 ft (10-30 m) in length. The Marine Corps operates small boats from 10-50 ft (3-15.2 m) in length and include small unit riverine craft, rigid hull inflatable boats and amphibious combat vehicles. Coast Guard vessels range in size from small boats between 13 and 65 ft (3.9 to 19.8 m) to large cutters with lengths up to 418 ft (127.4 m). Large Navy ships greater than 350 ft (107 m) generally operate at speeds in the range of 10 to 15 knots (kn; 18.5 to 27.8 kilometers per hour (km/hr)) for fuel conservation. Submarines generally operate at lower speeds in transit and even lower speeds for certain tactical maneuvers. Small craft (considered in this proposed rule to be less than 60 ft (18 m) in length) have much more variable speeds (dependent on the mission). While these speeds for large Navy vessels are representative of most events, some of the Action Proponents' vessels may need to temporarily operate outside of these parameters. For example, to produce the required relative wind speed over the flight deck, an aircraft carrier vessel group engaged in flight operations must adjust its speed through the water accordingly. Additionally, there are specific events including high speed tests of newly constructed vessels. The Navy also anticipates testing large USVs, some of which would be at high speed. Conversely, there are other instances such as launch and recovery of a small rigid hull inflatable boat, vessel boarding, search and seizure training events, or retrieval of a target when vessels would be stopped or moving slowly ahead to maintain steerage. The Coast Guard currently operates approximately 250 cutters. Larger cutters (over 181 ft (55 m) in length) are controlled by Area Commands. The Pacific Area command is located in Alameda, CA. Smaller cutters come under control of district commands. There are four districts in the Pacific Area. Cutters usually carry a motor surf boat and/or a rigid-hulled inflatable boat. The Coast Guard operates approximately 1,600 boats, defined as any vessel less than 65 ft (20 m) in length. These boats generally operate near shore and on inland waterways. The most common is 25 ft (7.6 m) long, of which the Coast Guard has more than 350; the shortest is 13 ft (4.0 m). Boat training includes small boat crews engaging surface targets with small- and medium-caliber weapons. The number of vessels used in the HCTT Study Area varies based on military readiness requirements, deployment schedules, annual budgets, and other unpredictable factors. Most military readiness activities involve the use of vessels. These activities could be widely dispersed throughout the HCTT Study Area, but would typically be conducted near naval ports, piers, and range areas. Activities involving vessel movements occur intermittently and are variable in duration, ranging from a few hours to multiple weeks. Action Proponent vessel traffic would especially be concentrated near San Diego, California and Pearl Harbor, Hawaii. There is no seasonal differentiation in vessel use. Large vessel movement primarily occurs with the majority of the traffic flowing [[Page 32156]] between the installations and the OPAREAS. Support craft would be more concentrated in the coastal waters in the areas of naval installations, ports, and ranges. The number of testing activities that include the use of vessels is around 18 percent lower than the number of training activities, but testing activities are more likely to include the use of larger unmanned vessels (although these are expected to transition to training use during the effective period of the rule, if finalized). In addition, testing often occurs jointly with a training event so it is likely that the testing activity would be conducted from a vessel that was also conducting a training activity. Vessel movement in conjunction with testing activities could occur throughout the Study Area, but would typically be conducted near naval ports, piers, and range complexes. Additionally, a variety of smaller craft would be operated within the HCTT Study Area. Small craft types, sizes, and speeds vary. During military readiness activities, speeds generally range from 10 to 14 kn (18.5 to 25.9 km/hr); however, vessels can and will, on occasion, operate within the entire spectrum of their specific operational capabilities. During modernization and sustainment of ranges activities, vessels would operate more slowly, typically 3 kn (5.6 km/ hr) or less. In all cases, the vessels/craft will be operated in a safe manner consistent with the local conditions. Foreign Navies In furtherance of national security objectives, foreign militaries may participate in multinational training and testing events in the Study Area. Foreign military activities that are planned by and under the substantial control and responsibility of the Action Proponents are included in the proposed action. These participants could be in various training or testing events described in appendix A of the 2024 HCTT Draft EIS/OEIS, and their effects are analyzed in this proposed rule. However, when foreign military vessels operate independently within the Study Area as sovereign vessels outside the planning, control, and responsibility of the Action Proponents, those activities are not considered part of the specified activity. There are many reasons why foreign military vessels may traverse U.S. waters or come into U.S. port, not all of which are at the behest of any of the Action Proponents. Foreign military vessels and aircraft operate pursuant to their own national authorities and have independent rights under customary international law, embodied in the principle of sovereign immunity, to engage in various activities on the world's oceans and seas. When foreign militaries are participating in a U.S. Navy planned and substantially controlled exercise or event, foreign military use of sonar and explosives, when combined with the U.S. Navy's use of sonar and explosives, would not result in exceedance of the analyzed levels (within each Navy Acoustic Effects Model (NAEMO) modeled sonar and explosive bin) used for estimating predicted impacts, which formed the basis of our acoustic impacts effects analysis that was used to estimate take in this proposed rule. The most significant joint training event is the Rim of the Pacific (RIMPAC), a multi-national training exercise held every-other-year primarily in the HRC. The participation level of foreign military vessels in U.S. Navy-led training or testing events within the HRC and within SOCAL differs greatly between RIMPAC and non-RIMPAC years. For example, in 2019 (a non-RIMPAC year), there were 0.1 foreign navy surface vessel at-sea days (i.e., 1 day = 24 hours) within HRC and 20 foreign navy at-sea days within SOCAL (Navy 2021). Out of 56 U.S.-led training events in 2019, 4 involved foreign navy vessels, with an average time per event of 8.7 hours. During RIMPAC 2022, foreign vessels operated and/or transited through the HRC for 576 hours (24 days). In 2023 (another non-RIMPAC year), there was no foreign vessel participation within SOCAL. Even in a RIMPAC year, the days at sea for foreign militaries engaged in a Navy-led training or testing activity accounts for a small, but variable, percentage compared to the U.S. Navy activities. For instance, the 2020 foreign military participation (a RIMPAC-year) was 1.5 percent of the U.S. Navy's average days at sea (32 days out of an estimated 2,056 days at sea). During RIMPAC 2024, twenty-five foreign surface vessels participated for a combined 5,000 hours in U.S.-led training events. Therefore, foreign surface vessel activity is estimated to conservatively account for up to 10 percent of the U.S. Navy's annual at sea time in HCTT (205 days out of an estimated 2,056 days at sea). Please see the Proposed Mitigation Measures section and Proposed Reporting section of this proposed rule for information about mitigation and reporting related to foreign navy activities in the HCTT Study Area. When foreign militaries are participating in a U.S. Navy-led exercise or event, foreign military use of sonar and explosives, when combined with the U.S. Navy's use of sonar and explosives, would not result in exceedance of the analyzed levels (within each NAEMO modeled sonar and explosive bin) used for estimating predicted impacts, which formed the basis of our acoustic impacts effects analysis that was used to estimate take in this proposed rule. Please see the Proposed Mitigation Measures section and Proposed Reporting section of this proposed rule for information about mitigation and reporting related to foreign navy activities in the HCTT Study Area. Standard Operating Procedures For training and testing to be effective, Action Proponent personnel must be able to safely use their sensors, platforms, weapons, and other devices to their optimum capabilities and as intended for use in missions and combat operations. The Action Proponents have developed standard operating procedures through decades of experience to provide for safety and mission success. Because they are essential to safety and mission success, standard operating procedures are part of the Proposed Action and are considered in the environmental analysis for applicable resources (see chapter 3 (Affected Environment and Environmental Consequences) of the 2024 HCTT Draft EIS/OEIS). While standard operating procedures are designed for the safety of personnel and equipment and to ensure the success of training and testing activities, their implementation often yields additional benefits on environmental, socioeconomic, public health and safety, and cultural resources. Because standard operating procedures are essential to safety and mission success, the Action Proponents consider them to be part of the proposed activities and have included them in the environmental analysis. Standard operating procedures that are recognized as providing a potential secondary benefit on marine mammals during training and testing activities are noted below. Vessel safety; Weapons firing safety; Target deployment safety; Towed in-water device safety; Pile driving safety; and Coastal zones. Standard operating procedures (which are implemented regardless of their secondary benefits) are different from mitigation measures (which are designed entirely for the purpose of avoiding or reducing impacts). Information on mitigation measures is provided in the Proposed Mitigation Measures section. [[Page 32157]] Description of Stressors The Action Proponents use a variety of sensors, platforms, weapons, and other devices. Military readiness activities using these systems may introduce sound and energy into the environment. The proposed military readiness activities were evaluated to identify specific components that would act as stressors by having direct or indirect impacts on marine mammals and their habitat. This analysis included identification of the spatial variation of the identified stressors. The following subsections describe the acoustic and explosive stressors for marine mammals and their habitat within the HCTT Study Area. Each description contains a list of activities that may generate the stressor. Stressor/resource interactions that were determined to have impacts that do not qualify as take under the MMPA (i.e., vessel, aircraft, or weapons noise) were not carried forward for analysis in the application. NMFS reviewed the Action Proponents' analysis and conclusions on de minimis sources (i.e., those that are not likely to result in the take of marine mammals) and finds them complete and supportable (see section 3.7.4 of the technical report ``Quantifying Acoustic Impacts on Marine Mammals and Sea Turtles: Methods and Analytical Approach for Phase IV Training and Testing'' (U.S. Department of the Navy, 2024), hereafter referred to as the Acoustic Impacts Technical Report). Acoustic Stressors Acoustic stressors include acoustic signals emitted into the water for a specific purpose, such as sonar, other transducers (i.e., devices that convert energy from one form to another--in this case, into sound waves), and air guns, as well as incidental sources of broadband sound produced as a byproduct of vessel movement, aircraft transits, use of weapons or other deployed objects, vibratory pile extraction, and vibratory and impact pile driving. Explosives also produce broadband sound but are characterized separately from other acoustic sources due to their unique hazardous characteristics. Characteristics of each of these sound sources are described in the following sections. To better organize and facilitate the analysis of approximately 300 sources of underwater sound used for training and testing by the Action Proponents, including sonars and other transducers, air guns, and explosives, a series of source classifications, or source bins, were used. The acoustic source classification bins do not include the broadband noise produced incidental to pile driving, vessel and aircraft transits, weapons firing, and bow shocks. Noise produced from vessels and aircraft are not carried forward because those activities were found to have de minimis or no acoustic impacts, as stated above. Of note, the source bins used in this analysis have been revised from previous (Phase III) acoustic modeling to more efficiently group similar sources and use the parameters of the bin for propagation, making a comparison to previous bins impossible in most cases as some sources are modeled at different propagation parameters. For example, in previous analyses, non-impulsive narrowband sound sources were grouped into bins that were defined by their acoustic properties (i.e., frequency, source level, beam pattern, and duty cycle) or, in some cases, their purpose or application. In the current analysis, these sources are binned based only on their acoustic properties and not on their purpose or application. As such, sources that previously fell into a single ``purpose-based'' bin now, in many cases, fall into multiple bins while sources with similar acoustic parameters that were previously sorted into separate bins due to different purposes now share a bin. Therefore, the acoustic source bins used in the current analysis do not represent a one-for-one replacement with previous bins, making direct comparison not possible in most cases. The use of source classification bins provides the following benefits: Allows new sensors or munitions to be used under existing authorizations as long as those sources fall within the parameters of a ``bin''; Improves efficiency of source utilization data collection and reporting requirements anticipated under the MMPA authorizations; Ensures that impacts are not underestimated, as all sources within a given class are modeled as the most impactful source (highest source level, longest duty cycle, or largest net explosive weight (NEW)) within that bin; Allows analyses to be conducted in a more efficient manner, without any compromise of analytical results; and Provides a framework to support the reallocation of source usage (hours/explosives) between different source bins, as long as the total numbers of takes remain within the overall analyzed and authorized limits. This flexibility is required to support evolving training and testing requirements, which are linked to real world events. Sonar and Other Transducers-- Active sonar and other transducers emit non-impulsive sound waves into the water to detect objects, navigate safely, and communicate. Passive sonars differ from active sound sources in that they do not emit acoustic signals; rather, they only receive acoustic information about the environment (i.e., listen). In this proposed rule, the terms sonar and other transducers will be used to indicate active sound sources unless otherwise specified. The Action Proponents employ a variety of sonars and other transducers to obtain and transmit information about the undersea environment. Some examples are mid-frequency hull-mounted sonars used to find and track enemy submarines; high-frequency small object detection sonars used to detect mines; high-frequency underwater modems used to transfer data over short ranges; and extremely high-frequency (greater than 200 kilohertz (kHz)) Doppler sonars used for navigation, like those used on commercial and private vessels. The characteristics of these sonars and other transducers, such as source level (SL), beam width, directivity, and frequency, depend on the purpose of the source. Higher frequencies can carry more information or provide more information about objects off which they reflect, but attenuate more rapidly. Lower frequencies attenuate less rapidly, so they may detect objects over a longer distance, but with less detail. Propagation of sound produced underwater is highly dependent on environmental characteristics such as bathymetry, seafloor type, water depth, temperature, and salinity. The sound received at a particular location will be different than near the source due to the interaction of many factors, including propagation loss; how the sound is reflected, refracted, or scattered; the potential for reverberation; and interference due to multi-path propagation. In addition, absorption greatly affects the distance over which higher-frequency sounds propagate. The effects of these factors are explained in appendix D (Acoustic and Explosive Impacts Supporting Information) of the 2024 HCTT Draft EIS/OEIS. Because of the complexity of analyzing sound propagation in the ocean environment, the Action Proponents rely on acoustic models in their environmental analyses that consider sound source characteristics and varying ocean conditions across the HCTT Study Area. For additional information on how propagation is accounted for, see the Acoustic Impacts Technical Report. [[Page 32158]] The sound sources and platforms typically used in military readiness activities analyzed in the application are described in appendix A (Activity Descriptions) of the 2024 HCTT Draft EIS/OEIS. Sonars and other transducers used to obtain and transmit information underwater during military readiness activities generally fall into several categories of use described below. Anti-Submarine Warfare-- Sonar used during anti-submarine warfare training and testing would impart the greatest amount of acoustic energy of any category of sonar and other transducers analyzed in this proposed rule. Types of sonars used to detect potential enemy vessels include hull-mounted, towed, line array, sonobuoy, helicopter dipping, and torpedo sonars. In addition, acoustic targets and decoys (countermeasures) may be deployed to emulate the sound signatures of vessels or repeat received signals. Most anti-submarine warfare sonars are mid-frequency (1-10 kHz) because mid-frequency sound balances sufficient resolution to identify targets with distance over which threats can be identified. However, some sources may use higher or lower frequencies. Duty cycles can vary widely, from rarely used to continuously active. Anti-submarine warfare sonars can be wide-ranging in a search mode or highly directional in a track mode. Most anti-submarine warfare activities involving submarines or submarine targets would occur in waters greater than 600 ft (182.9 m) deep due to safety concerns about running aground at shallower depths. Sonars used for anti-submarine warfare activities would typically be used beyond 12 nmi (22.2 km) from shore. Exceptions include use of dipping sonar by helicopters, pierside testing and maintenance of systems while in port, and system checks while transiting to or from port. Mine Warfare, Small Object Detection, and Imaging-- Sonars used to locate mines and other small objects, as well as those used in imaging (e.g., for hull inspections or imaging of the seafloor), are typically high-frequency or very high-frequency. Higher frequencies allow for greater resolution and, due to their greater attenuation, are most effective over shorter distances. Mine detection sonar can be deployed (towed or vessel hull-mounted) at variable depths on moving platforms (ships, helicopters, or unmanned vehicles) to sweep a suspected mined area. Hull-mounted anti-submarine sonars can also be used in an object detection mode known as ``Kingfisher'' mode (MF1K) (e.g., used on vessels when transiting to and from port), where pulse length is shorter but pings are much closer together in both time and space, since the vessel goes slower when operating in this mode. Sonars used for imaging are usually used in close proximity to the area of interest, such as pointing downward near the seafloor. Mine detection sonar use would be concentrated in areas where practice mines are deployed, typically in water depths less than 200 ft (60.9 m), and at established training or testing minefields or temporary minefields close to strategic ports and harbors. Kingfisher mode on vessels is most likely to be used when transiting to and from port. Sound sources used for imaging would be used throughout the HCTT Study Area. Navigation and Safety-- Similar to commercial and private vessels, the Action Proponents' vessels employ navigational acoustic devices, including speed logs, Doppler sonars for ship positioning, and fathometers. These may be in use at any time for safe vessel operation. These sources are typically highly directional to obtain specific navigational data. Communication-- Sound sources used to transmit data (e.g., underwater modems), provide location (pingers), or send a single brief release signal to seafloor-mounted devices (acoustic release) may be used throughout the HCTT Study Area. These sources typically have low duty cycles and are usually only used when it is necessary to send a detectable acoustic message. Classification of Sonar and Other Transducers-- Sonars and other transducers are grouped into bins based on their acoustic properties. Sonars and other transducers are now grouped into bins based on the frequency or bandwidth, source level, duty-cycle, and three-dimensional beam coverage. Unless stated otherwise, a reference distance of 1 microPascal (re 1 [mu]Pa) at 1 m (3.3 ft) is used for sonar and other transducers. Frequency of the non-impulsive acoustic source: [cir] Low-frequency sources operate below 1 kHz; [cir] Mid-frequency sources operate at or above 1 kHz, up to and including 10 kHz; [cir] High-frequency sources operate above 10 kHz, up to and including 100 kHz; and [cir] Very high-frequency sources operate above 100 kHz but below 200 kHz; Sound pressure level (SPL): [cir] Greater than 160 decibels (dB) re 1 [mu]Pa, but less than 185 dB re 1 [mu]Pa; [cir] Equal to 185 dB re 1 [mu]Pa and up to 205 dB re 1 [mu]Pa; and [cir] Greater than 205 dB re 1 [mu]Pa. Active sonar and other transducer use that was quantitatively analyzed in the Study Area are shown in table 10. Table 10--Sonar and Other Transducers Quantitatively Analyzed in the HCTT Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Training 7- Testing 7- Source type Source category Description Unit Training annual year total Testing annual year total -------------------------------------------------------------------------------------------------------------------------------------------------------- Broadband.......................... LF.................... <205 dB............... H ............... ........... 430-570 3,430 Broadband.......................... LF to MF.............. <205 dB............... H ............... ........... 2,801-2,833 19,737 Broadband.......................... LF to HF.............. <205 dB............... C 806-818 5,678 686-859 4,413 Broadband.......................... LF to HF.............. <205 dB............... H ............... ........... 1,662-2,077 11,371 Broadband.......................... MF to HF.............. <205 dB............... H 8,097-11,585 67,142 1,451-1,779 10,483 Low-frequency acoustic............. LFL................... 160 dB to 185 dB...... H ............... ........... 12 70 Low-frequency acoustic............. LFM................... 185 dB to 205 dB...... C ............... ........... 1,160-1,384 8,792 Low-frequency acoustic............. LFM................... 185 dB to 205 dB...... H 468-536 3,480 7,531-8,984 56,955 Low-frequency acoustic............. LFH................... >205 dB............... C 1,498-2,120 12,372 6,046-6,704 44,296 Low-frequency acoustic............. LFH................... >205 dB............... H 14 98 4,050-6,050 34,350 Mid-frequency acoustic............. MFL................... 160 dB to 185 dB...... H ............... ........... 12,632-14,982 92,794 Mid-frequency acoustic............. MFM................... 185 dB to 205 dB...... C 4,908-6,552 39,400 15,080-16,928 110,737 Mid-frequency acoustic............. MFM................... 185 dB to 205 dB...... H 30 210 14,381-16,081 101,064 Mid-frequency acoustic............. MFH................... >205 dB............... H 1,951-3,003 17,010 8,115-10,424 63,221 High-frequency acoustic............ HFL................... 160 dB to 185 dB...... H 60 420 21,326-22,076 151,532 High-frequency acoustic............ HFM................... 185 dB to 205 dB...... C 9 63 1,800-2,346 14,238 [[Page 32159]] High-frequency acoustic............ HFM................... 185 dB to 205 dB...... H 3,907-5,290 31,498 12,409-13,259 89,322 High-frequency acoustic............ HFH................... >205 dB............... C 802-899 5,907 835-1,137 6,351 High-frequency acoustic............ HFH................... >205 dB............... H 2,419-2,498 17,170 1,367-1,920 10,735 Very high-frequency acoustic....... VHFL.................. 160 dB to 185 dB...... H 30 210 9,160 64,120 Very high-frequency acoustic....... VHFM.................. 185 dB to 205 dB...... H ............... ........... 96 672 Very high-frequency acoustic....... VHFH.................. >205 dB............... C ............... ........... 72-106 580 Very high-frequency acoustic....... VHFH.................. >205 dB............... H 5,458-7,862 45,418 12,544-16,824 100,648 Hull-mounted surface ship sonar.... MF1C.................. Hull-mounted surface H 796-1,406 7,404 45 314 ship sonar with duty cycle >80% (previously MF11). Hull-mounted surface ship sonar.... MF1K.................. Hull-mounted surface H 455 3,183 14 91 ship sonar in Kingfisher mode. Hull-mounted surface ship sonar.... MF1................... Hull-mounted surface H 5,096-8,758 46,828 413-917 4,275 ship sonar. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: LF = low frequency, MF = mid frequency, HF = high frequency, dB = decibels, L = low, M = medium, H = high (e.g., MFL = mid-frequency low source level), H = hours, C = count. Air Guns-- Air guns are essentially stainless steel tubes charged with high- pressure air via a compressor. An impulsive sound is generated when the air is almost instantaneously released into the surrounding water. Small air guns with capacities up to 60 cubic inches (in\3\; 983 cubic centimeters (cc)) would be used during testing activities in the offshore areas of the California Study Area and in the HRC. Generated impulses would have short durations, typically a few hundred milliseconds, with dominant frequencies below 1 kHz. The root- mean-square (RMS) SPL and peak pressure (SPL peak) at a distance 1 m (3.3 ft) from the air gun would be approximately 215 dB re 1 [mu]Pa and 227 dB re 1 [mu]Pa, respectively, if operated at the full capacity of 60 in\3\ (983 cc). The size of the air gun chamber can be adjusted, which would result in lower SPLs and sound exposure level (SEL) per shot. The air gun and non-explosive impulsive sources that were quantitatively analyzed in the HCTT Study Area are shown in table 11. Table 11--Training and Testing Air Gun Sources Quantitatively Analyzed in the Study Area -------------------------------------------------------------------------------------------------------------------------------------------------------- Training Training 7- Testing 7-year Source class category Description Bin Unit annual year total Testing annual total -------------------------------------------------------------------------------------------------------------------------------------------------------- Air Guns.................................. Small underwater air guns... AG C 0 0 30,432-36,780 232,068 -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: AG = air guns, C = count. Pile Driving-- Impact and vibratory pile driving and extraction would occur during Port Damage Repair training in Port Hueneme, CA. Pile driving would not occur at other locations within the HCTT Study Area. The pile driving method, pile type and size, and assumptions for acoustic impact analysis are presented in table 12. This training activity would occur up to 12 times per year. Each training event consists of up to 7 separate modules, each which could occur up to 3 iterations during a single event (for a maximum of 21 modules). Training events would last a total of 30 days, of which pile driving is only anticipated to occur for a maximum of 14 days. The training would involve the installation and extraction 12- to 20-inch (30.5- to 50.8-cm) steel, timber, or composite round piles, and 27.5- or 18-inch (69.9- or 45.7-cm) steel or FRP Z-shape piles using a vibratory hammer; extraction of 12- to 20- inch (30.5- to 50.8-cm) timber round piles and 12- to 20-inch (30.5- to 50.8 cm) steel H-piles using a vibratory hammer; and installation of 12- to 20-inch (30.5- to 50.8-cm) timber round piles, 12- to 20-inch (30.5- to 50.8-cm) steel H-piles, and 12- to 20-inch (30.5- to 50.8-cm) steel, timber, or composite round piles using an impact hammer table 12. Table 12--Port Damage Repair Training Piles Quantitatively Analyzed and Associated Underwater Sound Levels -------------------------------------------------------------------------------------------------------------------------------------------------------- SEL Number of Peak SPL (single RMS SPL Number of piles 7- (single strike; dB (single Unattenuated Method Pile size and type piles year strike; re 1 strike; SPL (RMS; dB Reference annual total dB re 1 [mu]Pa2 dB re 1 re 1 [mu]Pa) [mu]Pa) [middot]s) [mu]Pa) -------------------------------------------------------------------------------------------------------------------------------------------------------- Impact............................ 12- to 20-inch (30 to 360 2,520 180 160 170 .............. 14-inch (36 cm) round 51 cm) timber round. timber piles (Caltrans, 2020). Impact............................ 12- to 20-inch (30 to 144 1,008 195 170 180 .............. 14-inch (36 cm) steel 51 cm) steel H. H-beam piles (Caltrans, 2020). Impact............................ 12- to 20-inch (30 to 360 2,520 203 178 189 .............. 24-inch (61 cm) steel 51 cm) steel, pipe piles timber, or composite (Illingworth and round. Rodkin Inc., 2007). [[Page 32160]] Vibratory......................... 12- to 20-inch (30 to 360 2,520 ......... .......... ......... 166 24-inch (61 cm) steel 51 cm) timber round. piles (Washington State Department of Transportation, 2010). Vibratory......................... 12- to 20-inch (30 to 144 1,008 ......... .......... ......... 166 24-inch (61 cm) steel 51 cm) steel H. piles (Washington State Department of Transportation, 2010). Vibratory......................... 12- to 20-inch (30 to 1,440 10,080 ......... .......... ......... 166 24-inch (61 cm) steel 51 cm) steel, piles (Washington timber, or composite State Department of round. Transportation, 2010). Vibratory......................... 18- or 27.5-inch (46- 2,304 16,128 ......... .......... ......... 159 25-inch (64 cm) steel or 70-cm) steel or sheet piles (Naval FRP Z. Facilities Engineering Systems Command Southwest, 2020). -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: Impact method is for installation only. Only one hammer would be operated at any given point in time; there would not be any instances where multiple piles would be driven simultaneously. All piles and sheets would be extracted using the vibratory hammer. Impact pile driving would involve the use of an impact hammer with both it and the pile held in place by a crane. When the pile driving starts, the hammer part of the mechanism is raised up and allowed to fall, transferring energy to the top of the pile. The pile is thereby driven into the sediment by a repeated series of these hammer blows. Each blow results in an impulsive sound emanating from the length of the pile into the water column as well as from the bottom of the pile through the sediment. Broadband impulsive signals are produced by impact pile driving methods, with most of the acoustic energy concentrated below 1,000 hertz (Hz) (Hildebrand, 2009). For the purposes of this analysis, the Action Proponents assume the impact pile driver would generally operate on average 60 strikes per pile. Vibratory installation and extraction would involve the use of a vibratory hammer suspended from the crane and attached to the top of a pile. The pile is then vibrated by hydraulic motors rotating eccentric weights in the mechanism, causing a rapid up and down vibration in the pile, driving the pile into the sediment. During extraction, the vibration causes the sediment particles in contact with the pile to lose frictional grip on the pile. The crane slowly lifts the vibratory driver and pile until the pile is free of the sediment. In some cases, the crane may be able to lift the pile and vibratory driver without vibrations from the driver (i.e., dead pull), in which case no noise would be introduced into the water. Vibratory driving and extraction create broadband, continuous, non-impulsive noise at low source levels, for a short duration with most of the energy dominated by lower frequencies. Port Damage Repair training would occur in shallow water, and sound would be transmitted on direct paths through the water, be reflected at the water surface or bottom, or travel through seafloor substrate. Soft substrates such as sand would absorb or attenuate the sound more readily than hard substrates (e.g., rock), which may reflect the acoustic wave. The predicted sound levels produced by pile driving by method, pile size and type for Port Damage Repair training are presented in table 12. In addition to underwater noise, the installation and extraction of piles also results in airborne noise in the environment, denoted dBA; dBA is an A-weighted decibel level that represents the relative loudness of sounds as perceived by the human ear. A-weighting gives more value to frequencies in the middle of human hearing and less value to frequencies at the edges as compared to a flat or unweighted decibel level. Impact pile driving creates in-air impulsive sound about 100 dBA re 20 [mu]Pa at a range of 15 m for 24-inch (0.61 m) steel piles (Illingworth and Rodkin, 2016). During vibratory extraction, the three aspects that generate airborne noise are the crane, the power plant, and the vibratory extractor. The average sound level recorded in air during vibratory extraction was about 85 dBA re 20 [mu]Pa (94 dB re 20 [mu]Pa) within a range of 32.8-49.2 ft (10-15 m) (Illingworth and Rodkin, 2015). Explosive Stressors This section describes the characteristics of explosions during military readiness activities. The activities analyzed in the application that use explosives are described in appendix A (Activity Descriptions) of the 2024 HCTT Draft EIS/OEIS, and terminology and metrics used when describing explosives in the application are in appendix D (Acoustic and Explosive Impacts Supporting Information) of the 2024 HCTT Draft EIS/OEIS. The near-instantaneous rise from ambient to an extremely high peak pressure is what makes an explosive shock wave potentially damaging. Farther from an explosive, the peak pressures decay and the explosive waves propagate as an impulsive, broadband sound. Several parameters influence the effect of an explosive: the weight of the explosive warhead, the type of explosive material, the boundaries and characteristics of the propagation medium, and the detonation depth in water. The NEW, the explosive power of a charge expressed as the equivalent weight of trinitrotoluene (commonly referred to as TNT), accounts for the first two parameters. Explosions in Water-- Explosive detonations during military readiness activities are associated with high-explosive munitions, including, but not limited to bombs, missiles, [[Page 32161]] rockets, naval gun shells, torpedoes, mines, demolition charges, and explosive sonobuoys. Explosive detonations during military readiness activities involving the use of high-explosive munitions, including bombs, missiles, and naval gun shells, would occur in the air or near the water's surface. Explosive detonations associated with torpedoes and explosive sonobuoys would occur in the water column; mines and demolition charges would be detonated in the water column or on the ocean floor. The Coast Guard usage of explosives is limited to medium and large-caliber munitions used during gunnery exercises. Most detonations would occur in waters greater than 200 ft (60.9 m) in depth and greater than 3 nmi (5.6 km) from shore, although some mine warfare, demolition, and some testing detonations would occur in shallow water close to shore. The Army usage of explosives is limited to large- caliber projectiles used during shore-to-surface artillery and missile exercises, and all projectiles will impact beyond 3 nmi (5.6 km) from shore. To better organize and facilitate the analysis of explosives used by the Action Proponents during military readiness activities that would detonate in water or at the water surface, explosive classification bins were developed. The use of explosive classification bins provides the same benefits as described for acoustic source classification bins in the Sonar and Other Transducers section. Explosives detonated in water are binned by NEW. Table 13 shows explosives use that was quantitatively analyzed in the Study Area. A range of annual use indicates that occurrence is anticipated to vary annually, consistent with the variation in the number of annual activities described in chapter 2 (Description of Proposed Action and Alternatives) of the 2024 HCTT Draft EIS/OEIS. The 7-year total takes that variability into account. Table 13--Explosive Sources Quantitatively Analyzed Proposed for Use Underwater or at the Water Surface -------------------------------------------------------------------------------------------------------------------------------------------------------- Coast Coast Net explosive Example explosive Navy training Navy Guard Guard Army Army Navy testing Navy Bin weight (lb.) source annual training training training training training annual testing 7- 7-year annual 7-year annual 7-year year -------------------------------------------------------------------------------------------------------------------------------------------------------- E1.......... 0.1-0.25........... Medium-caliber 1,750-4,303 19,911 ......... ......... ......... ......... 7,305-7,430 51,510 projectile. E2.......... >0.25-0.5.......... Medium-caliber 2,950-3,000 20,800 ......... ......... ......... ......... .............. ......... projectile. E3.......... >0.5-2.5........... 2.75-inch (7 cm) 5,438-5,720 38,912 150 1,050 ......... ......... 4,744-6,568 36,704 rockets. E4.......... >2.5-5............. Mine neutralization 179-190 1,286 ......... ......... ......... ......... 1,324-2,624 18,352 charge. E5.......... >5-10.............. 5-inch (12.7 cm) 5,059-5,984 38,188 ......... ......... ......... ......... 2,024-2,676 16,732 projectile. E6.......... >10-20............. Hellfire missile... 1,693-1,757 12,043 ......... ......... 600 4,200 144-148 1,020 E7.......... >20-60............. Demo block/shaped 115-190 1,030 ......... ......... ......... ......... 549-622 2,322 charge. E8.......... >60-100............ Lightweight torpedo 3-5 27 ......... ......... ......... ......... 213-234 1,552 E9.......... >100-250........... 500 lb. (228 kg) 278-300 2,015 ......... ......... 108 756 111-115 789 bomb. E10......... >250-500........... Harpoon missile.... 89 620 ......... ......... ......... ......... 13 91 E11......... >500-675........... Heavyweight Torpedo 7-11 61 ......... ......... ......... ......... 1-2 8 E12......... >675-1,000......... 2,000 lb. (907.2 17-19 125 ......... ......... ......... ......... .............. ......... kg) bomb. E13......... >1,000-1,740....... Underwater 6 42 ......... ......... ......... ......... .............. ......... demolitions--large area clearance. E16......... 10,000............. Ship shock .............. ......... ......... ......... ......... ......... 0-3 3 detonation. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: > = greater than, in. = inch, lb. = pound, kg = kilogram. Propagation of explosive pressure waves in water is highly dependent on environmental characteristics such as bathymetry, seafloor type, water depth, temperature, and salinity, which affect how the pressure waves are reflected, refracted, or scattered; the potential for reverberation; and interference due to multi-path propagation. In addition, absorption greatly affects the distance over which higher- frequency components of explosive broadband noise can propagate. Appendix D (Acoustic and Explosive Impacts Supporting Information) of the 2024 HCTT Draft EIS/OEIS explains the characteristics of explosive detonations and how the above factors affect the propagation of explosive energy in the water. Because of the complexity of analyzing sound propagation in the ocean environment, the Action Proponents rely on acoustic models in their environmental analyses that consider sound source characteristics and varying ocean conditions across the Study Area. In-Air Acoustic Stressors The proposed military readiness activities would generate missile and aerial target launch noise from locations on SNI (California), noise from missile and aerial target launches at the PMRF (Kaua[revaps]i, Hawaii), and artillery firing noise from shore to surface gunnery at San Clemente Island and PMRF. Table 14 shows launch noise that was quantitatively analyzed in the HCTT Study Area. Noise from target and missile launches from land at SNI and PMRF may disturb hauled-out pinnipeds. At SNI, this disturbance has been documented over nearly two decades of monitoring and reporting of those activities (U.S. Department of the Navy, 2020, 2022, 2023). At PMRF, Hawaiian monk seals are known to haul out on a beach near the missile launch complex. If a seal is hauled out during a missile or aerial target launch, the seal may react to the noise and exhibit a behavioral response that may qualify as harassment (e.g., flushing into the water). (Though, of note, behavioral disturbance of monk seals (e.g., flushing or other disturbance) has not been observed due to these activities.) Currently, if a monk seal is hauled out on the beach (typically within approximately 1,000 ft (304.8 m) of the launch site) prior to a missile launch, the launch is halted or postponed until the seal has left the beach. [[Page 32162]] Table 14--Proposed Launches Analyzed Within the HCTT Study Area ---------------------------------------------------------------------------------------------------------------- Navy training Navy training Navy testing Navy testing 7- Launch type Location annual 7-year total annual year total ---------------------------------------------------------------------------------------------------------------- Missiles and Aerial Targets... SNI (PMSR)...... 0 0 40 280 Missiles and Aerial Targets... PMRF............ 22 154 13 91 Artillery..................... PMRF............ 900 6,300 0 0 ---------------------------------------------------------------------------------------------------------------- Note: SNI = San Nicolas Island, PMSR = Point Mugu Sea Range, PMRF = Pacific Missile Range Facility. Vessel Strike NMFS also considered the likelihood that vessel movement during military readiness activities could result in an incidental, but not intentional, strike of a marine mammal in the HCTT Study Area, which has the potential to result in serious injury or mortality. Vessel strikes are not specific to any specific military readiness activity but rather, a limited, sporadic, and incidental result of the Action Proponents' vessel movement during military readiness activities within the Study Area. Vessel strikes from commercial, recreational, and military vessels are known to seriously injure and occasionally kill cetaceans (Abramson et al., 2011; Berman-Kowalewski et al., 2010; Calambokidis, 2012; Crum et al., 2019; Douglas et al., 2008; Laggner 2009; Van der Hoop et al., 2012; Van der Hoop et al., 2013), although reviews of the literature on vessel strikes mainly involve collisions between commercial vessels and whales (Jensen and Silber, 2003, Laist et al., 2001). Vessel speed, size, and mass are all important factors in determining both the potential likelihood and impacts of a vessel strike to marine mammals (Blondin et al. 2025; Conn and Silber, 2013; Garrison et al. 2025; Gende et al., 2011; Redfern et al., 2019; Silber et al., 2010; Szesciorka et al., 2019; Vanderlaan and Taggart, 2007; Wiley et al., 2016). For large vessels, speed and angle of approach can influence the severity of a strike. The Action Proponents' vessels transit at speeds that are optimal for fuel conservation or to meet training and testing requirements. From unpublished Navy data, average speed for large (greater than 350 ft (107 m) Navy ships in Southern California and Hawaii from 2016-2023 varied from 10 to 15 kn (18.5 to 27.8 km/hr) in offshore waters greater than 12 nmi from land and from 5 to 10 kn (9.3 to 18.5 km/hr) closer to the coast (less than 12 nmi; Navy 2021, unpublished data). Small craft (for purposes of this analysis, less than 59 ft (18 m) in length) have much more variable speeds (0 to 50 kn (0 to 92.6 km/hr), dependent on the activity). Submarines generally operate at speeds in the range of 8 to 13 kn (14.8 to 24.1 km per hour). Similar patterns are anticipated in the HCTT Study Area. A full description of the Action Proponents' vessels proposed for use during military readiness activities can be found in Chapter 2 (Description of Proposed Action and Alternatives) of the 2024 HCTT Draft EIS/OEIS. While these speeds for large Navy vessels are representative of most events, some of the Action Proponents' vessels may need to temporarily operate outside of these parameters. For example, to produce the required relative wind speed over the flight deck, an aircraft carrier engaged in flight operations must adjust its speed through the water accordingly. There are specific events, including high speed tests of newly constructed vessels, where the Action Proponents' vessel would operate at higher speeds. By comparison, there are other instances when the Action Proponents vessel would be stopped or moving slowly ahead to maintain steerage, such as launch and recovery of a small rigid hull inflatable boat; vessel boarding, search, and seizure training events; or retrieval of a target. Large Navy vessels (>400 ft (121.9 m)) and Coast Guard vessels within the offshore areas of range complexes and testing ranges operate differently from commercial vessels, which may reduce potential vessel strikes of large whales. Surface ships operated by or for the Navy have multiple personnel assigned to stand watch at all times, when a ship or surfaced submarine is moving through the water (underway). A primary duty of personnel standing watch on surface ships is to detect and report all objects and disturbances sighted in the water that may indicate a threat to the vessel and its crew, such as debris, a periscope, surfaced submarine, or surface disturbance. Per vessel safety requirements, personnel standing watch also report any marine mammals sighted in the path of the vessel as a standard collision avoidance procedure. All vessels proceed at a safe speed so they can take proper and effective action to avoid a collision with any sighted object or disturbance, and can stop within a distance appropriate to the prevailing circumstances and conditions. As described in the Standard Operating Procedures section, the Action Proponents utilize Lookouts to avoid collisions, and Lookouts are trained to spot marine mammals so that vessels may change course or take other appropriate action to avoid collisions. Despite the precautions, should a vessel strike occur, NMFS anticipates it would likely result in incidental take in the form of serious injury and/or mortality, though it is possible that it could result in a non-serious injury (Level A harassment). Accordingly, for the purposes of the analysis, NMFS assumes that any vessel strike would result in serious injury or mortality. Proposed mitigation, monitoring, and reporting measures are described in detail later in this document (please see Proposed Mitigation Measures section, Proposed Monitoring section, and Proposed Reporting section). Description of Marine Mammals and Their Habitat in the Area of Specified Activities Marine mammal species and their associated stocks that have the potential to occur in the HCTT Study Area are presented in table 15 along with each stock's Endangered Species Act (ESA) and MMPA statuses, abundance estimate and associated coefficient of variation (CV) value, minimum abundance estimate, potential biological removal (PBR), annual M/SI, and potential occurrence in the HCTT Study Area. The Action Proponents request authorization to take individuals of 40 species (79 stocks) by Level A and Level B harassment incidental to military readiness activities from the use of sonar and other transducers, in- water detonations, air guns, missile and target launch noise, pile driving/extraction, and vessel movement in the HCTT Study Area. Currently, the humpback whale (Central America and Mexico Distinct Population Segments (DPSs)), killer whale (Eastern North Southern Resident DPS), false killer whale (Main Hawaiian Islands Insular DPS), and Hawaiian monk seal have critical habitat designated under the ESA in the HCTT Study Area (see Critical Habitat section below). [[Page 32163]] Sections 3 and 4 and appendix B (Marine Mammal Supplemental Information) of the application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species. NMFS fully considered all of this information, and we refer the reader to these descriptions, instead of reprinting the information. Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs) (https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments) and more general information about these species (e.g., physical and behavioral descriptions) may be found on NMFS' website at: https://www.fisheries.noaa.gov/find-species. Additional information on the general biology and ecology of marine mammals is included in the 2024 HCTT Draft EIS/OEIS. Table 15 incorporates the best available science, including data from the 2023 Pacific and Alaska Marine Mammal Stock Assessment Reports (Carretta et al., 2024; Young et al., 2024) (see https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments), and 2024 draft SARs, as well as monitoring data from the Navy's marine mammal research efforts. Table 15--Marine Mammal Occurrence Within the HCTT Study Area \1\ -------------------------------------------------------------------------------------------------------------------------------------------------------- ESA/MMPA status; Stock abundance (CV, Common name Scientific name Stock strategic (Y/N) Nmin, most recent PBR Annual M/ \2\ abundance survey) \3\ SI \4\ -------------------------------------------------------------------------------------------------------------------------------------------------------- Order Artiodactyla--Cetacea--Mysticeti (baleen whales) -------------------------------------------------------------------------------------------------------------------------------------------------------- Family Eschrichtiidae: Gray whale...................... Eschrichtius robustus.. Eastern North Pacific.. -, -, N 25,960 (0.05, 25,849, 801 131 2016). Gray whale...................... Eschrichtius robustus.. Western North Pacific.. E, D, Y 290 (N/A, 271, 2016).. 0.12 UNK Family Balaenopteridae (rorquals): Blue whale...................... Balaenoptera musculus.. Central North Pacific.. E, D, Y 133 (1.09, 63, 2010).. 0.1 0 Blue whale...................... Balaenoptera musculus.. Eastern North Pacific.. E, D, Y 1,898 (0.085, 1,767, 4.1 >=18.6 2018). Bryde's whale................... Balaenoptera edeni..... Eastern Tropical -, -, N UNK (UNK, UNK, N/A)... UND UNK Pacific. Bryde's whale................... Balaenoptera edeni..... Hawaii................. -, -, N 791 (0.29, 623, 2020). 6.2 0 Fin whale....................... Balaenoptera physalus.. Hawaii................. E, D, Y 203 (0.99, 101, 2017). 0.2 0 Fin whale....................... Balaenoptera physalus California/Oregon/ E, D, Y 11,065 (0.405, 7,970, 80 >=43.4 velifera. Washington. 2018). Humpback whale.................. Megaptera novaeangliae. Central America/ E, D, Y 1,496 (0.171, 1,284, 3.5 14.9 Southern Mexico- 2021). California-Oregon- Washington \5\. Humpback whale.................. Megaptera novaeangliae. Mainland Mexico- T, D, Y 3,477 (0.101, 3,185, 43 22 California-Oregon- 2018). Washington \5\. Humpback whale.................. Megaptera novaeangliae. Hawaii................. -, -, N 11,278 (0.56, 7,265, 127 27.09 2020). Minke whale..................... Balaenoptera Hawaii................. -, -, N 438 (1.05, 212, 2017). 2.1 0 acutorostrata. Minke whale..................... Balaenoptera California/Oregon/ -, -, N 915 (0.792, 509, 2018) 4.1 >=0.19 acutorostrata. Washington. Sei whale....................... Balaenoptera borealis.. Hawaii................. E, D, Y 391 (0.9, 204, 2010).. 0.4 0.2 Sei whale....................... Balaenoptera borealis.. Eastern North Pacific.. E, D, Y 864 (0.40, 625, 2014). 1.25 UNK -------------------------------------------------------------------------------------------------------------------------------------------------------- Odontoceti (toothed whales, dolphins, and porpoises) -------------------------------------------------------------------------------------------------------------------------------------------------------- Family Physeteridae: Sperm whale..................... Physeter macrocephalus. Hawaii................. E, D, Y 5,707 (0.23, 4,486, 18 0 2017). Sperm whale..................... Physeter macrocephalus. California/Oregon/ E, D, Y 2,606 (0.135, 2,011, 4 0.52 Washington. 2018). Family Kogiidae: Dwarf sperm whale............... Kogia sima............. Hawaii................. -, -, N UNK (UNK, UNK, 2017).. UND 0 Dwarf sperm whale............... Kogia sima............. California/Oregon/ -, -, N UNK (UNK, UNK, 2014).. UND 0 Washington. Pygmy sperm whale............... Kogia breviceps........ Hawaii................. -, -, N 42,083 (0.64, 25,695, 257 0 2017). Pygmy sperm whale............... Kogia breviceps........ California/Oregon/ -, -, N 4,111 (1.12, 1,924, 19.2 0 Washington. 2014). Family Ziphiidae (beaked whales): Baird's beaked whale............ Berardius bairdii...... California/Oregon/ -, -, N 1,363 (0.53, 894, 8.9 >=0.2 Washington. 2018). Blainville's beaked whale....... Mesoplodon densirostris Hawaii................. -, -, N 1,132 (0.99, 564, 5.6 0 2017). Goose-beaked whale.............. Ziphius cavirostris.... Hawaii................. -, -, N 4,431 (0.41, 3,180, 32 0 2017). Goose-beaked whale.............. Ziphius cavirostris.... California/Oregon/ -, -, N 5,454 (0.27, 4,214, 42 <0.1 Washington. 2016). Longman's beaked whale.......... Indopacetus pacificus.. Hawaii................. -, -, N 2,550 (0.67, 1,527, 15 0 2017). Mesoplodont beaked whale........ Mesoplodon spp. \6\.... California/Oregon/ -, -, N 3,044 (0.54, 1,967, 20 0.1 Washington. 2014). Family Delphinidae: False killer whale.............. Pseudorca crassidens... Main Hawaiian Islands E, D, Y 167 (0.14, 149, 2015). 0.3 0.1 Insular. False killer whale.............. Pseudorca crassidens... Northwest Hawaiian -, -, N 477 (1.71, 178, 2017). 1.43 0.16 Islands. False killer whale.............. Pseudorca crassidens... Hawaii Pelagic......... -, -, Y 5,528 (0.35, 4,152, 36 47 2017). False killer whale.............. Pseudorca crassidens... Baja California N/A 2.962 (0.71, N/A, N/A) N/A N/A Peninsula Mexico \7\. [[Page 32164]] Killer whale.................... Orcinus orca........... Hawaii................. -, -, N 161 (1.06, 78, 2017).. 0.8 0 Killer whale.................... Orcinus orca........... Eastern North Pacific -, -, N 300 (0.1, 276, 2012).. 2.8 0 Offshore. Killer whale.................... Orcinus orca........... Eastern North Pacific E, D, Y 75 (N/A, 75, 2023).... 0.13 0 Southern Resident. Killer whale.................... Orcinus orca........... West Coast Transient... -, -, N 349 (N/A, 349, 2018).. 3.5 0.4 Melon-headed whale.............. Peponocephala electra.. Hawaiian Islands....... -, -, N 40,647 (0.74, 23,301 233 0 \3\ 2017). Melon-headed whale.............. Peponocephala electra.. Kohala Resident -, -, N UNK (UNK, UNK, 2017).. UND 0 (Hawaii). Pygmy killer whale.............. Feresa attenuata....... Hawaii................. -, -, N 10,328 (0.75, 5,885, 59 0 2017). Pygmy killer whale.............. Feresa attenuata....... California-Baja N/A 229 (1.11, N/A, N/A).. N/A N/A California Peninsula Mexico \7\. Short-finned pilot whale........ Globicephala Hawaii................. -, -, N 19,242 (0.23, 15,894, 159 0.2 macrorhynchus. 2020). Short-finned pilot whale........ Globicephala California/Oregon/ -, -, N 836 (0.79, 466, 2014). 4.5 1.2 macrorhynchus. Washington. Bottlenose dolphin.............. Tursiops truncatus..... Maui Nui............... -, -, N 64 (0.15, 56, 2018)... 0.6 UNK Bottlenose dolphin.............. Tursiops truncatus..... Hawaii Island.......... -, -, N 136 (0.43, 96, 2018).. 1 >0.2 Bottlenose dolphin.............. Tursiops truncatus..... Hawaii Pelagic......... -, -, N 24,669 (0.57, 15,783, 158 0 2020). Bottlenose dolphin.............. Tursiops truncatus..... Kaua[revaps]i/ -, -, N 112 (0.24, 92, 2018).. 0.9 UNK Ni[revaps]ihau. Bottlenose dolphin.............. Tursiops truncatus..... O[revaps]ahu........... -, -, N 112 (0.17, 97, 2017).. 1 UNK Bottlenose dolphin.............. Tursiops truncatus..... California Coastal..... -, -, N 453 (0.06, 346, 2011). 2.7 >=2.0 Bottlenose dolphin.............. Tursiops truncatus..... California/Oregon/ -, -, N 3,477 (0.696, 2,048, 19.7 >=0.82 Washington Offshore. 2018). Fraser's dolphin................ Lagenodelphis hosei.... Hawaii................. -, -, N 40,960 (0.7, 24,068, 241 0 2017). Long-beaked common dolphin...... Delphinus delphis California............. -, -, N 83,379 (0.216, 69,636, 668 >=29.7 bairdii. 2018). Northern right whale dolphin.... Lissodelphis borealis.. California/Oregon/ -, -, N 29,285 (0.72, 17,024, 163 >=6.6 Washington. 2018). Pacific white-sided dolphin..... Lagenorhynchus California/Oregon/ -, -, N 34,999 (0.222, 29,090, 279 7 obliquidens. Washington. 2018). Pantropical spotted dolphin..... Stenella attenuata..... Maui Nui............... -, -, N UNK (UNK, UNK, N/A)... UND UNK Pantropical spotted dolphin..... Stenella attenuata..... Hawaii Island.......... -, -, N UNK (UNK, UNK, N/A)... UND UNK Pantropical spotted dolphin..... Stenella attenuata..... Hawaii Pelagic......... -, -, N 67,313 (0.27, 53,839, 538 0 2020). Pantropical spotted dolphin..... Stenella attenuata..... O[revaps]ahu........... -, -, N UNK (UNK, UNK, N/A)... UND UNK Pantropical spotted dolphin..... Stenella attenuata..... Baja California N/A 105,416 (0.46, N/A, N/ N/A N/A Peninsula Mexico \7\. A). Risso's dolphin................. Grampus griseus........ Hawaii................. -, -, N 6,979 (0.29, 5,283, 53 0 2020). Risso's dolphin................. Grampus griseus........ California/Oregon/ -, -, N 6,336 (0.32, 4,817, 46 >=3.7 Washington. 2014). Rough-toothed dolphin........... Steno bredanensis...... Hawaii................. -, -, N 83,915 (0.49, 56,782, 511 3.2 2017). Short-beaked common dolphin..... Delphinus delphis...... California/Oregon/ -, -, N 1,056,308 (0.21, 8,889 >=30.5 Washington. 888,971, 2018). Spinner dolphin................. Stenella longirostris.. Hawaii Pelagic......... -, -, N UNK (UNK, UNK, 2010).. UND 0 Spinner dolphin................. Stenella longirostris.. Hawaii Island.......... -, -, N 665 (0.09, 617, 2012). 6.2 >=1.0 Spinner dolphin................. Stenella longirostris.. Kaua[revaps]i/ -, -, N N/A (N/A, N/A, 2005).. UND UNK Ni[revaps]ihau. Spinner dolphin................. Stenella longirostris.. Midway Atoll/Kure...... -, -, N UNK (UNK, UNK, 2010).. UND UNK Spinner dolphin................. Stenella longirostris.. O[revaps]ahu/4 Islands -, -, N N/A (N/A, N/A, 2007).. UND >=0.4 Region. Spinner dolphin................. Stenella longirostris.. Pearl and Hermes....... -, -, N UNK (UNK, UNK, N/A)... UND UNK Spinner dolphin................. Stenella coeruleoalba.. Hawaii Pelagic......... -, -, N 64,343 (0.28, 51,055, 511 0 2020). Spinner dolphin................. Stenella coeruleoalba.. California/Oregon/ -, -, N 29,988 (0.3, 23,448, 225 >=4 Washington. 2018). Family Phocoenidae (porpoises): Dall's porpoise................. Phocoenoides dalli..... California/Oregon/ -, -, N 16,498 (0.61, 10,286, 99 >=0.66 Washington. 2018). Harbor porpoise................. Phocoena phocoena...... Monterey Bay........... -, -, N 3,760 (0.561, 2,421, 35 >=0.2 2013). Harbor porpoise................. Phocoena phocoena...... Morro Bay.............. -, -, N 4,191 (0.56, 2,698, 65 0 2012). Harbor porpoise................. Phocoena phocoena...... Northern California/ -, -, N 15,303 (0.575, 9,759, 195 0 Southern Oregon. 2022). Harbor porpoise................. Phocoena phocoena...... San Francisco/Russian -, -, N 7,777 (0.62, 4,811, 73 >=0.4 River. 2017). -------------------------------------------------------------------------------------------------------------------------------------------------------- Order Carnivora--Pinnipedia -------------------------------------------------------------------------------------------------------------------------------------------------------- Family Otariidae (eared seals and sea lions): California sea lion............. Zalophus californianus. U.S.................... -, -, N 257,606 (N/A, 233,515, 14,011 >321 2014). Guadalupe fur seal.............. Arctocephalus townsendi Mexico................. T, D, Y 68,850 (N/A, 57,199, 1,959 >=10.0 2013). Northern fur seal............... Callorhinus ursinus.... Eastern Pacific........ -, D, Y 612,765 (0.2, 518,651, 11,151 296 2022). [[Page 32165]] Northern fur seal............... Callorhinus ursinus.... California............. -, -, N 19,634 (N/A, 8,788, 527 >=1.2 2022). Steller sea lion................ Eumetopias jubatus..... Eastern................ -, -, N 36,308 (N/A, 36,308, 2,178 93 2022). Family Phocidae (earless seals): Harbor seal..................... Phoca vitulina......... California............. -, -, N 30,968 (N/A, 27,348, 1,641 43 2012). Hawaiian monk seal.............. Neomonachus Hawaii................. E, D, Y 1,605 (0.05, 1,508, 5 >=4.8 schauinslandi. 2022). Northern elephant seal.......... Mirounga angustirostris California Breeding.... -, -, N 194,907 (N/A, 88,794, 5,328 11 2023). -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: N/A = Not Applicable, UND = Undetermined, UNK = Unknown. Unless otherwise noted, abundance estimates are from the final 2022 Pacific stock assessment report (Carretta et al., 2024; Carretta et al., 2023b), the draft 2023 Pacific stock assessment report (Carretta et al., 2024), or the Alaska stock assessment reports (Young, 2024). \1\ Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy (https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/; Committee on Taxonomy (2022)). \2\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock. \3\ NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. \4\ These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial fisheries is presented in some cases. \5\ Humpback whales in the Central America/Southern Mexico-California-Oregon-Washington Stock make up the endangered Central America DPS, and humpback whales in the Mainland Mexico-California-Oregon-Washington Stock are part of the threatened Mexico DPS, along with whales from the Mexico-North Pacific Stock, which do not occur in the Study Area. \6\ Mesoplodont beaked whales are analyzed as a group due to insufficient data available to estimate species-specific densities. \7\ The Baja California Peninsula Mexico and California-Baja California Peninsula Mexico populations of false killer whale, pantropical spotted dolphin, and pygmy killer whales are not recognized stocks in NMFS Pacific stock assessment report (Carretta et al., 2024), but separate density estimates were derived to support the Navy's analysis. Species Not Included in the Analysis The species carried forward for analysis (and described in table 15) are those likely to be found in the HCTT Study Area based on the most recent data available, and do not include species that may have once inhabited or transited the area but have not been sighted in recent years (e.g., species which were extirpated from factors such as 19th and 20th century commercial exploitation). North Pacific right whale may be present in the northeast Pacific Ocean, but has an extremely low probability of presence in the HCTT Study Area. It is considered extralimital (i.e., not anticipated to occur in the Study Area) and was not included in the analysis. One species of marine mammal, the southern sea otter, occurs in the HCTT Study Area but is managed by the U.S. Fish and Wildlife Service (U.S. FWS) and thus are not considered further in this analysis. Below, we consider additional information about the marine mammals in the area of the specified activities that informs our analysis, such as identifying known areas of important habitat or behaviors, or where unusual mortality events have been designated. Critical Habitat Currently, the humpback whale (Central America and Mexico DPSs), killer whale (Eastern North Pacific Southern Resident DPS), false killer whale (Main Hawaiian Islands Insular DPS), and Hawaiian monk seal have ESA-designated critical habitat in the HCTT Study Area. Humpback Whale On April 21, 2021, NMFS designated critical habitat for the endangered Western North Pacific DPS, the endangered Central America DPS, and the threatened Mexico DPS of humpback whales (86 FR 21082). Areas proposed as critical habitat include specific marine areas located off the coasts of California, Oregon, Washington, and Alaska. Designated critical habitat for the Central America DPS overlaps the NOCAL Range Complex (Units 15, 16, and 17), as well as PMSR and the northern portion of the SOCAL Range Complex (Units 17 and 18). These areas are essential for humpback whale foraging and migration. One of the proposed critical habitat areas, critical habitat Unit 19, would have also overlapped with the SOCAL range in the HSTT Study Area but was excluded after consideration of potential national security and economic impacts of designation. NMFS, in the final rule designating critical habitat for humpback whales, identified prey species, primarily euphausiids and small pelagic schooling fishes of sufficient quality, abundance, and accessibility within humpback whale feeding areas to support feeding and population growth, as an essential habitat feature. NMFS, through a critical habitat review team (CHRT), also considered inclusion of migratory corridors and passage features, as well as sound and the soundscape, as essential habitat features. NMFS did not include either in the final critical habitat; however, as the CHRT concluded that the best available science did not allow for identification of any consistently used migratory corridors or definition of any physical, essential migratory or passage conditions for whales transiting between or within habitats of the three DPSs. Regardless of whether critical habitat is designated for a particular area, NMFS has considered all applicable information regarding marine mammals and their habitat in the analysis supporting these proposed regulations. Killer Whale NMFS designated critical habitat for the Southern Resident killer whale DPS on November 29, 2006 (71 FR 69054) in inland waters of Washington State, and on August 2, 2021, revised the designation by designating six additional coastal critical habitat areas along the U.S. West Coast (86 FR 41668). The HCTT Study Area overlaps two of the three continuous sections off the California coast: the North Central CA Coast Area and the Monterey Bay Area. Based on the natural history of the Southern Resident killer whales and their habitat needs, NMFS identified physical or biological features essential to the conservation of the Southern [[Page 32166]] Resident killer whale DPS: (1) water quality to support growth and development; (2) prey species of sufficient quantity, quality, and availability to support individual growth, reproduction, and development, as well as overall population growth; and (3) passage conditions to allow for migration, resting, and foraging. False Killer Whale (Main Hawaiian Island Insular DPS) Critical habitat for the ESA-listed Main Hawaiian Islands insular false killer whale DPS was finalized in July 2018 (83 FR 35062, July 24, 2018) designating waters from the 45 m depth contour to the 3,200 m depth contour around the main Hawaiian Islands from Ni[revaps]ihau east to Hawaii. This designation does not include most bays, harbors, or coastal in-water structures. NMFS excluded 14 areas. The total area designated was approximately 45,504 square kilometers (km\2\; 13,267 square nautical miles (nmi\2\)) of marine habitat. Critical habitat for the main Hawaiian Islands insular DPS of false killer whale entirely overlaps the HRC. Main Hawaiian Islands insular false killer whales are island- associated whales that rely entirely on the productive submerged habitat of the main Hawaiian Islands to support all of their life- history stages. Island-associated marine habitat for Main Hawaiian Islands insular false killer whale is the only essential feature of the critical habitat. The following characteristics of this habitat support insular false killer whales' ability to travel, forage, communicate, and move freely around and among the waters surrounding the main Hawaiian Islands: (1) adequate space for movement and use within shelf and slope habitat; (2) prey species of sufficient quantity, quality, and availability to support individual growth, reproduction, and development, as well as overall population growth; (3) waters free of pollutants of a type and amount harmful to Main Hawaiian Islands insular false killer whales; and (4) sound levels that would not significantly impair false killer whales' use or occupancy. Hawaiian Monk Seal Critical habitat for Hawaiian monk seals was designated in 1986 (51 FR 16047, April 30, 1986) and later revised in 1988 (53 FR 18988, May 26, 1988) and in 2015 (80 FR 50925, August 21, 2015). In the Northwestern Hawaiian Islands Hawaiian monk seal critical habitat includes all beach areas, sand spits and islets, including all beach crest vegetation to its deepest extent inland as well as the seafloor and marine habitat 10 m in height above the seafloor from the shoreline out to the 200 m depth contour around Kure Atoll (H[omacr]lanik[umacr]), Midway Atoll (Kuaihelani), Pearl and Hermes Reef (Manawai), Lisianski Island (Kapou), Laysan Island (Kamole), Maro Reef (Kamokuokamohoali[revaps]i), Gardner Pinnacles ([revaps][revaps][Omacr]n[umacr]nui), French Frigate Shoals (Lalo), Necker Island (Mokumanamana) and Nihoa Island. In the main Hawaiian Islands, Hawaiian monk seal critical habitat includes the seafloor and marine habitat to 10 m above the seafloor from the 200 m depth contour through the shoreline and extending into terrestrial habitat 5 m inland from the shoreline between identified boundary points around Kaula Island (includes marine habitat only), Ni[revaps]ihau (includes marine habitat from 10 m-200 m in depth), Kaua[revaps]i, O[revaps]ahu, Maui Nui (including Kaho[revaps]olawe, L[amacr]na[revaps]i, Maui, and Moloka[revaps]i), and Hawaii Island. A portion of the critical habitat overlaps the HRC. The essential features of Hawaiian monk seal critical habitat are: (1) terrestrial areas and adjacent shallow, sheltered aquatic areas with characteristics preferred by monk seals for pupping and nursing; (2) marine areas from 0 to 200 m in depth that support adequate prey quality and quantity for juvenile and adult monk seal foraging; and (3) significant areas used by monk seals for hauling out, resting or molting. Biologically Important Areas Ferguson et al. (2015) identified Biologically Important Areas (BIAs) within U.S. waters of the West Coast (Calambokidis et al. 2015) and in Hawaii (Baird et al. 2015), which represent areas and times in which cetaceans are known to concentrate in areas of known importance for activities related to reproduction, feeding, and migration, or areas where small and resident populations are known to occur. Unlike ESA critical habitat, these areas are not formally designated pursuant to any statute or law, but are a compilation of the best available science intended to inform impact and mitigation analyses. An interactive map of the BIAs is available at: https://oceannoise.noaa.gov/biologically-important-areas. In some cases, additional, or newer, information regarding known feeding, breeding, or migratory areas is available and has been used to update these BIAs (as cited below), and a summary of all of the BIAs is included below. The West Coast and Hawaii BIAs were updated in 2024 (Calambokidis et al.) and 2023 (Kratofil et al.), respectively (referred to as BIA II herein). Calambokidis et al. (2024) and Kratofil et al. (2023) use a new scoring system described here and in Harrison et al. (2023). Experts identified an overall Importance Score for each BIA that considers: (1) ``Intensity''--the intensity and characteristics underlying an area's identification as a BIA; and (2) ``Data Support''--the quantity, quality, and type of information, and associated uncertainties, upon which the BIA delineation and scoring depends. Importance Scores range from 1 to 3, with a higher score representing an area of higher intensity and data support. Each BIA identified in BIA II is also scored for boundary uncertainty and spatiotemporal variability (dynamic, ephemeral, or static). Additionally, BIA II includes hierarchical BIAs for some species and stocks where a higher intensity score is appropriate for a smaller core area(s) (child BIA) within a larger BIA unit (parent BIA). The Hawaii Study Area overlaps BIAs for small and resident populations of the following species: spinner dolphin, short-finned pilot whale, rough-toothed dolphin, pygmy killer whale, pantropical spotted dolphin, melon-headed whale, false killer whale, dwarf sperm whale, goose-beaked whale, common bottlenose dolphin, and Blainville's beaked whale. Further, the Hawaii Study Area overlaps updated BIAs for humpback whale reproduction (Kratofil et al. 2023). The California Study Area overlaps feeding BIAs for blue whale, fin whale, and humpback whale in SOCAL. Additionally, it overlaps a reproductive BIA as well as northbound and southbound migratory BIAs for gray whale (Calambokidis et al. 2024). Table 16 describes each BIA that overlaps the HCTT Study Area and the scores for the above criteria. [[Page 32167]] Table 16--BIAs Overlapping the HCTT Study Area ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Figure in action Data Species BIA type Parent/child/non- BIA name Effective months BIA area proponents' Importance Intensity support Boundary Spatiotemporal Transboundary across hierarchical (km\2\) LOA score score score certainty variability application ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Hawaii Study Area (Kratofil et al., 2023) ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Humpback whale.................. Reproductive....... Parent............. Main Hawaiian December through 23,041 B.1-11 2 2 2 2 Static.............. None. Islands--Parent. May. Humpback whale.................. Reproductive....... Child.............. Main Hawaiian December through 6,676 B.1-11 3 3 3 3 Static.............. None. Islands--Child. May. False killer whale.............. Small and Resident Parent............. Main Hawaiian Year-round........ 94,217 B.1-7 1 1 3 3 Static.............. None. Population. Islands Insular Stock--Parent. False killer whale.............. Small and Resident Child.............. Main Hawaiian Year-round........ 7,775 B.1-7 3 3 3 3 Static.............. None. Population. Islands Insular Stock--Child. False killer whale.............. Small and Resident Non-hierarchical... Northwestern Year-round........ 138,001 B.1-7 1 1 2 2 Static.............. None. Population. Hawaiian Islands Insular Stock. Dwarf sperm whale............... Small and Resident Parent............. Hawaii Island-- Year-round........ 1,341 B.1-14 3 3 2 2 Static.............. None. Population. Parent. Dwarf sperm whale............... Small and Resident Child.............. Hawaii Island-- Year-round........ 457 B.1-14 3 3 2 2 Static.............. None. Population. Child. Pygmy killer whale.............. Small and Resident Non-hierarchical... O[revaps]ahu-Maui Year-round........ 7,416 B.1-15 3 3 2 2 Static.............. None. Population. Nui. Pygmy killer whale.............. Small and Resident Non-hierarchical... Hawaii Island..... Year-round........ 5,201 B.1-15 2 2 2 2 Static.............. None. Population. Short-finned pilot whale........ Small and Resident Parent............. Main Hawaiian Year-round........ 51,280 B.1-16 1 1 3 3 Static.............. None. Population. Islands--Parent. Short-finned pilot whale........ Small and Resident Child.............. Main Hawaiian Year-round........ 4,040 B.1-16 3 3 3 3 Static.............. None. Population. Islands--Child (Western Community Core Range). Short-finned pilot whale........ Small and Resident Child.............. Main Hawaiian Year-round........ 2,427 B.1-16 3 3 3 3 Static.............. None. Population. Islands--Child (Central Community Core Range). Short-finned pilot whale........ Small and Resident Child.............. Main Hawaiian Year-round........ 2,461 B.1-16 3 3 3 3 Static.............. None. Population. Islands--Child (Eastern Community Core Range). Common bottlenose dolphin....... Small and Resident Parent............. Kaua[revaps]i/ Year-round........ 36,634 B.1-18 1 1 3 2 Static.............. None. Population. Ni[revaps]ihau- O[revaps]ahu-Maui Nui. Common bottlenose dolphin....... Small and Resident Child.............. Kaua[revaps]i/ Year-round........ 2,772 B.1-18 3 3 3 3 Static.............. None. Population. Ni[revaps]ihau- O[revaps]ahu-Maui Nui-Kaua[revaps]i/ Ni[revaps]ihau). Common bottlenose dolphin....... Small and Resident Child.............. Kaua[revaps]i/ Year-round........ 8,486 B.1-18 3 3 2 2 Static.............. None. Population. Ni[revaps]ihau- O[revaps]ahu-Maui Nui--O[revaps]ahu. Common bottlenose dolphin....... Small and Resident Child.............. Kaua[revaps]i/ Year-round........ 10,622 B.1-18 2 2 2 2 Static.............. None. Population. Ni[revaps]ihau- O[revaps]ahu-Maui Nui--Maui Nui. Common bottlenose dolphin....... Small and Resident Non-hierarchical... Hawaii Island..... Year-round........ 8,299 B.1-18 2 2 3 3 Static.............. None. Population. [[Page 32168]] Pantropical spotted dolphin..... Small and Resident Parent............. O[revaps]ahu-Maui Year-round........ 57,711 B.1-19 1 1 2 2 Static.............. None. Population. Nui-Hawaii Island--Parent. Pantropical spotted dolphin..... Small and Resident Child.............. O[revaps]ahu-Maui Year-round........ 12,952 B.1-19 1 1 2 2 Static.............. None. Population. Nui-Hawaii Island--Child (O[revaps]ahu). Pantropical spotted dolphin..... Small and Resident Child.............. O[revaps]ahu-Maui Year-round........ 6,743 B.1-19 1 1 2 2 Static.............. None. Population. Nui-Hawaii Island--Child (Maui Nui). Pantropical spotted dolphin..... Small and Resident Child.............. O[revaps]ahu-Maui Year-round........ 10,768 B.1-19 1 1 2 2 Static.............. None. Population. Nui-Hawaii Island--Hawaii Island--Child (Hawaii Island). Rough-toothed dolphin........... Small and Resident Non-hierarchical... Maui Nui-Hawaii Year-round........ 15,112 B.1-21 1 1 2 2 Static.............. None. Population. Island. Rough-toothed dolphin........... Small and Resident Parent............. Kaua[revaps]i/ Year-round........ 24,233 B.1-21 1 1 2 2 Static.............. None. Population. Ni[revaps]ihau- O[revaps]ahu--Par ent. Rough-toothed dolphin........... Small and Resident Child.............. Kaua[revaps]i/ Year-round........ 1,149 B.1-21 2 2 2 2 Static.............. None. Population. Ni[revaps]ihau- O[revaps]ahu--Chi ld (Kaua[revaps]i/ Ni[revaps]ihau). Melon-headed whale.............. Small and Resident Non-hierarchical... Kohala Residents-- Year-round........ 3,816 B.1-21 2 2 3 3 Static.............. None. Population. Hawaii Island. Spinner dolphin................. Small and Resident Non-hierarchical... Manawai (Pearl and Year-round........ 2,094 B.1-20 1 2 1 2 Static.............. None. Population. Hermes Reef). Spinner dolphin................. Small and Resident Non-hierarchical... Kuaihelani/ Year-round........ 4,841 B.1-20 1 2 1 2 Static.............. None. Population. H[omacr]lanik[uma cr] (Midway/Kure Atolls). Spinner dolphin................. Small and Resident Non-hierarchical... Kaua[revaps]i and Year-round........ 7,233 B.1-20 1 1 2 3 Static.............. None. Population. Ni[revaps]ihau. Spinner dolphin................. Small and Resident Non-hierarchical... O[revaps]ahu and Year-round........ 14,651 B.1-20 1 1 2 3 Static.............. None. Population. Maui Nui. Spinner dolphin................. Small and Resident Non-hierarchical... Hawaii Island..... Year-round........ 9,477 B.1-20 1 1 3 3 Static.............. None. Population. Goose-beaked whale.............. Small and Resident Parent............. Hawaii Island..... Year-round........ 37,157 B.1-23 2 2 3 2 Static.............. None. Population. Goose-beaked whale.............. Small and Resident Child.............. Hawaii Island..... Year-round........ 5,400 B.1-23 3 3 3 3 Static.............. None. Population. Blainville's beaked whale....... Small and Resident Parent............. O[revaps]ahu-Maui Year-round........ 78,714 B.1-24 1 1 3 2 Static.............. None. Population. Nui-Hawaii Island--Parent. Blainville's beaked whale....... Small and Resident Child.............. O[revaps]ahu-Maui Year-round........ 4,214 B.1-24 3 3 3 3 Static.............. None. Population. Nui-Hawaii Island--Child (Hawaii Island). ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- California Study Area (Calambokidis et al., 2024) ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Blue whale...................... Feeding............ Parent............. Blue whale West June through 173,433 B.1-1 2 2 3 3 Static.............. None. Coast--Parent. November. Blue whale...................... Feeding............ Child.............. Blue whale West June through 54,349 B.1-1 3 3 3 3 Static.............. None. Coast--Core. November. Fin whale....................... Feeding............ Parent............. Fin whale West June through 315,072 B.1-2 1 1 2 2 Static.............. None. Coast--Parent. November. [[Page 32169]] Fin whale....................... Feeding............ Child.............. Fin whale West June through 155,508 B.1-2 2 2 2 2 Static.............. None. Coast--Core. November. Humpback whale.................. Feeding............ Parent............. Humpback whale March through 140,303 B.1-5 2 2 3 3 Static.............. None. West Coast-- November. Parent. Humpback whale.................. Feeding............ Child.............. Humpback whale March through 38,052 B.1-5 3 3 3 3 Static.............. None. West Coast--Core. November. Gray whale...................... Migratory.......... Parent............. Gray Whale January through 167,066 B.1-13 1 1 2 2 Static.............. GOA. Migratory Route-- June, November Southbound and through December. Northbound. Gray whale...................... Migratory.......... Child.............. Southbound........ November-February. 70,110 B.1-13 2 2 3 3 Static.............. None. Gray whale...................... Migratory.......... Child.............. Northbound Phase A January-May....... 65,047 B.1-13 2 2 3 3 Static.............. None. Gray whale...................... Migratory.......... Child.............. Northbound Phase B March-May......... 51,947 B.1-13 3 3 3 3 Static.............. None. Gray whale...................... Reproductive....... Non-hierarchical... Gray whale--Cow March-May......... 51,947 B.1-13 3 3 3 3 Static.............. None. and Calf Migrants. Harbor porpoise................. Small and Resident Non-hierarchical... Monterey Bay...... Year-round........ 1,911 B.1-22 2 2 3 3 Static.............. None. Population. Harbor porpoise................. Small and Resident Non-hierarchical... Morro Bay......... Year-round........ 3,030 B.1-22 1 1 3 3 Static.............. None. Population. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- [[Page 32170]] National Marine Sanctuaries Under Title III of the Marine Protection, Research, and Sanctuaries Act of 1972 (also known as the National Marine Sanctuaries Act (NMSA)), NOAA can establish as national marine sanctuaries (NMS) areas of the marine environment with special conservation, recreational, ecological, historical, cultural, archaeological, scientific, educational, or aesthetic qualities. Sanctuary regulations prohibit destroying, causing the loss of, or injuring any sanctuary resource managed under the law or regulations for that sanctuary (15 CFR part 922). NMS are managed on a site-specific basis, and each sanctuary has site-specific regulations. Most, but not all sanctuaries have site-specific regulatory exemptions from the prohibitions for certain military activities. Separately, section 304(d) of the NMSA requires Federal agencies to consult with the Office of National Marine Sanctuaries (ONMS) whenever their Proposed Activities are likely to destroy, cause the loss of, or injure a sanctuary resource. There are seven designated NMSs and one proposed NMS within the HCTT Study Area (see section 6 of the 2024 HCTT Draft EIS/OEIS): Channel Islands NMS Chumash Heritage NMS; Cordell Bank NMS; Greater Farallones NMS; Monterey Bay NMS; Hawaiian Islands Humpback Whale NMS Pacific Remote Islands NMS (in designation); and Papah[amacr]naumoku[amacr]kea NMS. Channel Islands NMS is an ecosystem-based managed sanctuary consisting of an area of 1,109 nmi\2\ (3,803 km\2\) around Anacapa Island, Santa Cruz Island, Santa Rosa Island, San Miguel Island, and Santa Barbara Island to the south. It encompasses sensitive habitats (e.g., kelp forest habitat, deep benthic habitat) and includes various shipwrecks and maritime heritage artifacts. Channel Islands NMS waters and its remote, isolated position at the confluence of two major ocean currents support significant biodiversity of marine mammals, fish, and invertebrates. At least 33 species of cetaceans have been reported in the Channel Islands NMS region with common species, including: Long- beaked common dolphin, short-beaked common dolphin, Bottlenose dolphin, Pacific white-sided dolphin, Northern right whale dolphin, Risso's dolphin, California gray whale, Blue whale, and Humpback whale. The three species of pinnipeds that are commonly found throughout or in part of the Channel Islands NMS include: California sea lion, Northern elephant seal, and Pacific harbor seal. Chumash Heritage NMS encompasses 3,430 nmi\2\ (11,766 km\2\) of coastal and ocean waters offshore Central California stretching nearly 52 nmi (96.6 km) from shore and down to a maximum depth of 11,580 ft (3,530 m). The sanctuary protects and collaboratively manages natural and cultural resources, maritime historical resources, and Indigenous cultural history along 100 nmi (186.9 km) of coastline. Chumash Heritage NMS contains marine biodiversity, productive ecosystems, and sensitive species and habitats, with special geologic features like Rodriguez Seamount and Santa Lucia Bank, along with an important biogeographic transition zone and upwelling along the California Current, which drives biological productivity and creates ecological conditions in the area that supports a high abundance of marine mammals. Different types of ecological habitats found within the sanctuary include kelp forests, rocky reefs, deep-sea coral gardens, and sandy beaches. Cordell Bank NMS is an extremely productive marine area off the West Coast in northern California, just north of the Gulf of the Farallones. With its southern-most boundary located 36.5 nmi (67.6 km) north of San Francisco, the sanctuary is entirely offshore, with the eastern boundary 5.2 nmi (9.7 km) from shore and the western boundary 26.1 nmi (48.3 km) offshore. In total, the sanctuary protects an area of 971 nmi\2\ (3,330 km\2\). The centerpiece of the sanctuary is Cordell Bank, a 3.9 nmi by 8.3 nmi (7.2 km by 15.3 km) rocky undersea feature. The combination of ocean conditions and undersea topography creates a rich and diverse marine community in the sanctuary. The prevailing California Current flows southward along the coast, and the annual upwelling of nutrient-rich deep ocean water supports the sanctuary's rich biological community, including marine mammals. Greater Farallon NMS encompasses 2,488 nmi\2\ (8,534 km\2\) just north and west of San Francisco Bay, CA, within the California Current ecosystem. Due to a high degree of wind-driven upwelling, there is a ready supply of nutrients to surface waters and the California Current ecosystem is one of the most biologically productive regions in the world. Greater Farallones NMS provides breeding and feeding grounds for at least 25 endangered or threatened species; 36 marine mammal species, including blue, gray, and humpback whales, harbor seals, elephant seals, Pacific white-sided dolphins, and one of the southernmost U.S. populations of threatened Steller sea lion. Monterey Bay NMS is an ecosystem-based managed sanctuary consisting of an area of 4,601 nmi\2\ (15,781 km\2\) stretching from Marin to Cambria and extending an average of 26.1 nmi (48.3 km) from shore. Monterey Bay NMS contains extensive kelp forests and one of North America's largest underwater canyons and closest-to-shore deep ocean environments. Its diverse marine ecosystem also includes rugged rocky shores, wave-swept sandy beaches and tranquil estuaries. These habitats support a variety of marine life, including 36 species of marine mammals, more than 180 species of seabirds and shorebirds, at least 525 species of fishes, and an abundance of invertebrates and algae. Of the 36 species of marine mammals, six are pinnipeds with California sea lions being the most common, and the remainder are 26 species of cetaceans. Hawaiian Islands Humpback Whale NMS is a single-species managed sanctuary, composed of 1,035 nmi\2\ of the waters around Maui, L[amacr]na[revaps]i, and Moloka[revaps]i; and smaller areas off the north shore of Kaua[revaps]i, off Hawaii's west coast, and off the north and southeast coasts of O[revaps]ahu. Hawaiian Islands Humpback Whale NMS is entirely within the HRC of the HCTT Study Area and constitutes one of the world's most important Hawaii humpback whale DPS habitats (81 FR 62259, September 8, 2016), and is a primary region for humpback reproduction in the U.S. (National Marine Sanctuaries Program, 2002). Scientists estimate that more than 50 percent of the entire North Pacific humpback whale population migrates to Hawaiian waters each winter to mate, calve, and nurse their young. The North Pacific humpback whale population has been split into two DPSs. The Hawaii humpback whale DPS migrates to Hawaiian waters each winter and is not listed under the ESA. In addition to protection under the MMPA, the Hawaii humpback whale DPS is protected in sanctuary waters by the Hawaiian Islands Humpback Whale NMS. The sanctuary was created to protect humpback whales and shallow, protected waters important for calving and nursing (Office of National Marine Sanctuaries, 2010). Papah[amacr]naumoku[amacr]kea NMS, the largest NMS, consists of approximately 439,910 nmi\2\ (1,508,849 km\2\) of marine habitat. The sanctuary comprises several interconnected ecosystems, such as coral islands surrounded by shallow reefs, low-light mesophotic reefs with extensive algal beds, open ocean waters [[Page 32171]] connected to the greater North Pacific Ocean, deep-water habitats such as abyssal plains 16,400 ft (4,999 m) below sea level, and deep reef habitat characterized by seamounts, banks, and shoals. Hawaiian monk seals, one of the most endangered marine mammals in the world, live in Papah[amacr]naumoku[amacr]kea NMS. The Office of National Marine Sanctuaries is in the process of designating the Pacific Remote Islands NMS. The atolls, shoals, banks, reefs, seamounts, and open-ocean waters surrounding the Pacific Remote Islands are home to some of the most diverse tropical marine life on the planet. The region's diverse habitats and pristine reefs provide a haven for marine mammals and numerous threatened, endangered, and depleted species thrive in the area, including spinner dolphins and melon-headed whales. NMFS does not anticipate injury to Sanctuary resources in the proposed Pacific Remote Islands NMS, as the action proponents are not proposing to conduct activities within the vicinity of, or within, the proposed Pacific Islands Heritage NMS. Unusual Mortality Events An unusual mortality event (UME) is defined under Section 410(9) of the MMPA as a stranding that is unexpected; involves a significant die- off of any marine mammal population; and demands immediate response (16 U.S.C. 1421h(9)). From 1991 to the present, there have been 17 formally recognized UMEs affecting marine mammals in California and Hawaii and involving species under NMFS' jurisdiction; however, there are currently none that are active. Marine Mammal Hearing Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Not all marine mammal species have equal hearing capabilities (e.g., Richardson et al., 1995, Wartzok and Ketten, 1999, Au and Hastings, 2008). To reflect this, Southall et al. (2007), Southall et al. (2019c) recommended that marine mammals be divided into hearing groups based on directly measured (behavioral or auditory evoked potential techniques) or estimated hearing ranges (e.g., behavioral response data, anatomical modeling). NMFS (2024) generalized hearing ranges were chosen based on the approximately 65-dB threshold from the composite audiograms, previous analysis in NMFS (2018), and/or data from Southall et al. (2007) and Southall et al. (2019c). We note that the names of two hearing groups and the generalized hearing ranges of all marine mammal hearing groups have been recently updated (NMFS, 2024) as reflected below in table 16. Table 17--Marine Mammal Hearing Groups [NMFS, 2024] ------------------------------------------------------------------------ Hearing group Generalized hearing range * ------------------------------------------------------------------------ Low-frequency (LF) cetaceans (baleen 7 Hz to 36** kHz whales).. High-frequency (HF) cetaceans 150 Hz to 160 kHz. (dolphins, toothed whales, beaked whales, bottlenose whales). Very High-frequency (VHF) cetaceans 200 Hz to 165 kHz. (true porpoises, Kogia, river dolphins, Cephalorhynchid, Lagenorhynchus cruciger and L. australis). Phocid pinnipeds (PW) (underwater) 40 Hz to 90 kHz. (true seals). Otariid pinnipeds (OW) (underwater) 60 Hz to 68 kHz. (sea lions and fur seals). Phocid pinnipeds (PA) (in-air) (true 42 Hz to 52 kHz. seals). Otariid pinnipeds (OA) (in-air) (sea 90 Hz to 40 kHz. lions and fur seals). ------------------------------------------------------------------------ * Represents the generalized hearing range for the entire group as a composite (i.e., all species within the group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen based on the ~65-dB threshold from composite audiogram, previous analysis in NMFS (2018), and/or data from Southall et al. (2007) and Southall et al. (2019). Additionally, animals are able to detect very loud sounds above and below that ``generalized'' hearing range. ** The Action Proponents split the LF functional hearing group into LF and VLF based on Houser et al., (2024) while NMFS Updated Technical Guidance (NMFS, 2024) does not include these data. NMFS is aware these data and data collected during a final field season by Houser et al. (in prep) have implications for the generalized hearing range for low- frequency cetaceans and their weighting function, however, as described in the 2024 Updated Technical Guidance, it is premature for us to propose any changes to our current Updated Technical Guidance. Mysticete hearing data is identified as a special circumstance that could merit reevaluating the acoustic criteria for low-frequency cetaceans in the 2024 Updated Technical Guidance once the data from the final field season is published. Therefore, we anticipate that once the data are published, it will likely necessitate updating this document (i.e., likely after the data gathered in the summer 2024 field season and associated analysis are published). For more detail concerning these groups and associated frequency ranges, please see NMFS (2024) for a review of available information. The Navy adjusted these hearing groups using data from recent hearing measurements in minke whales (Houser et al., 2024). These data support separating mysticetes (the LF cetacean marine mammal hearing group in table 17) into two hearing groups, which the Navy designates as ``very low-frequency (VLF) cetaceans'' and ``low-frequency (LF) cetaceans,'' which follows the recommendations of Southall et al. (2019c). Within the Navy's adjusted hearing groups, the VLF cetacean group contains the larger mysticetes (i.e., blue, fin, right, and bowhead whales) and the LF cetacean group contains the mysticete species not included in the VLF group (e.g., minke, humpback, gray, pygmy right whales). Although there have been no direct measurements of hearing sensitivity in the larger mysticetes included in Navy's VLF hearing group, an audible frequency range of approximately 10 Hz to 30 kHz has been estimated from measured vocalization frequencies, observed responses to playback of sounds, and anatomical analyses of the auditory system. The upper frequency limit of hearing in Navy's LF hearing group has been estimated in a minke whale from direct measurements of auditory evoked potentials (Houser et al., 2024). Potential Effects of Specified Activities on Marine Mammals and Their Habitat This section provides a discussion of the ways in which components of the specified activity may impact marine mammals and their habitat. The Estimated Take of Marine Mammals section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken [[Page 32172]] by this activity. The Preliminary Analysis and Negligible Impact Determination section considers the content of this section, the Estimated Take of Marine Mammals section, and the Proposed Mitigation Measures section to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and whether those impacts on individuals are likely to adversely affect the species or stock through effects on annual rates of recruitment or survival. The Action Proponents have requested authorization for the take of marine mammals that may occur incidental to training and testing activities in the HCTT Study Area. The Action Proponents analyzed potential impacts to marine mammals from acoustic and explosive sources and from vessel use in the application. NMFS carefully reviewed the information provided by the Action Proponents and concurs with their synthesis of science, along with independently reviewing applicable scientific research and literature and other information to evaluate the potential effects of the Action Proponents' activities on marine mammals, which are presented in this section (see appendix D in the 2024 HCTT Draft EIS/OEIS for additional information). Other potential impacts to marine mammals from training and testing activities in the HCTT Study Area were analyzed in the 2024 HCTT Draft EIS/OEIS, in consultation with NMFS as a cooperating agency, and determined to be unlikely to result in marine mammal take. Therefore, the Action Proponents have not requested authorization for take of marine mammals incidental to other components of their proposed Specified Activities, and we agree that incidental take is unlikely to occur from those components. In this proposed rule, NMFS analyzes the potential effects on marine mammals from the activity components that may result in take of marine mammals: exposure to acoustic or explosive stressors including non-impulsive (i.e., sonar and other transducers, and vibratory pile driving) and impulsive (i.e., explosives, impact pile driving, launches, and air guns) stressors and vessel movement. For the purpose of MMPA incidental take authorizations, NMFS' effects assessments serve four primary purposes: (1) to determine whether the specified activities would have a negligible impact on the affected species or stocks of marine mammals (based on whether it is likely that the activities would adversely affect the species or stocks through effects on annual rates of recruitment or survival); (2) to determine whether the specified activities would have an unmitigable adverse impact on the availability of the species or stocks for subsistence uses; (3) to prescribe the permissible methods of taking (i.e., Level B harassment (behavioral harassment and temporary threshold shift (TTS)), Level A harassment (auditory injury (AUD INJ), non-auditory injury), serious injury, or mortality), including identification of the number and types of take that could occur by harassment, serious injury, or mortality, and to prescribe other means of effecting the least practicable adverse impact on the species or stocks and their habitat (i.e., mitigation measures); and (4) to prescribe requirements pertaining to monitoring and reporting. In this section, NMFS provides a description of the ways marine mammals may be generally affected by these activities in the form of mortality, physical injury, sensory impairment (permanent and temporary threshold shifts and acoustic masking), physiological responses (particular stress responses), behavioral disturbance, or habitat effects. Explosives and vessel strikes, which have the potential to result in incidental take by serious injury and/or mortality, will be discussed in more detail in the Estimated Take of Marine Mammals section. The Estimated Take of Marine Mammals section also discusses how the potential effects on marine mammals from non-impulsive and impulsive sources relate to the MMPA definitions of Level A Harassment and Level B Harassment, and quantifies those effects that do not qualify as a take under the MMPA. The Preliminary Analysis and Negligible Impact Determination section assesses whether the proposed authorized take would have a negligible impact on the affected species and stocks. Potential Effects of Underwater Sound on Marine Mammals The marine soundscape is composed of both ambient and anthropogenic sounds. Ambient sound is defined as the all-encompassing sound in a given place and is usually a composite of sound from many sources both near and far (American National Standards Institute, 1995). The sound level of an area is defined by the total acoustical energy being generated by known and unknown sources, which may include physical (e.g., waves, wind, precipitation, earthquakes, ice, atmospheric sound), biological (e.g., sounds produced by marine mammals, fish, and invertebrates), and anthropogenic sound (e.g., vessels, dredging, aircraft, construction). The sum of the various natural and anthropogenic sound sources at any given location and time--which comprise ``ambient'' or ``background'' sound--depends not only on the source levels (as determined by current weather conditions and levels of biological and shipping activity) but also on the ability of sound to propagate through the environment. In turn, sound propagation is dependent on the spatially and temporally varying properties of the water column and sea floor and is frequency-dependent. As a result of the dependence on a large number of varying factors, ambient sound levels can be expected to vary widely over both coarse and fine spatial and temporal scales. Sound levels at a given frequency and location can vary by 10-20 dB from day to day (Richardson et al., 1995). The result is that, depending on the source type and its intensity, sound from the specified activities may be a negligible addition to the local environment or could form a distinctive signal that may affect marine mammals. Anthropogenic sounds cover a broad range of frequencies and sound levels and can have a range of highly variable impacts on marine life, from none or minor to potentially severe responses, depending on received levels, duration of exposure, behavioral context, and various other factors. The potential effects of underwater sound from active acoustic sources can possibly result in one or more of the following: temporary or permanent hearing impairment, other auditory injury, non- auditory physical or physiological effects, behavioral disturbance, stress, and masking (Richardson et al., 1995; Gordon et al., 2003; Nowacek et al., 2007; Southall et al., 2007; G[ouml]tz et al., 2009, Southall et al., 2019a). The degree of effect is intrinsically related to the signal characteristics, received level, distance from the source, and duration of the sound exposure. In general, sudden, high- level sounds can cause auditory injury, as can longer exposures to lower level sounds. Temporary or permanent loss of hearing can occur after exposure to noise and occurs almost exclusively for noise within an animal's hearing range. Richardson et al. (1995) described zones of increasing intensity of effect that might be expected to occur, in relation to distance from a source and assuming that the signal is within an animal's hearing range. First is the area within which the acoustic signal would be audible (potentially perceived) to the animal, but not strong enough to elicit [[Page 32173]] any overt behavioral or physiological response. The next zone corresponds with the area where the signal is audible to the animal and of sufficient intensity to elicit behavioral or physiological responsiveness. Third is a zone within which, for signals of high intensity, the received level is sufficient to potentially cause discomfort or tissue damage to auditory systems. Overlaying these zones to a certain extent is the area within which masking (i.e., when a sound interferes with or masks the ability of an animal to detect a signal of interest that is above the absolute hearing threshold) may occur; the masking zone may be highly variable in size. We also describe more severe potential effects (i.e., certain non- auditory physical or physiological effects). Potential effects from impulsive sound sources can range in severity from effects such as behavioral disturbance or tactile perception to physical discomfort, slight injury of the internal organs and the auditory system, or, in the case of explosives, more severe injuries or mortality (Yelverton et al., 1973). Non-auditory physiological effects or injuries that theoretically might occur in marine mammals exposed to high levels of underwater sound or as a secondary effect of extreme behavioral responses (e.g., change in dive profile as a result of an avoidance response) caused by exposure to sound include neurological effects, bubble formation, resonance effects, and other types of organ or tissue damage (Cox et al., 2006; Southall et al., 2007; Zimmer and Tyack, 2007; Tal et al., 2015). Hearing Marine mammals have adapted hearing based on their biology and habitat: amphibious marine mammals (e.g., pinnipeds that spend time on land and underwater) have modified ears that allow them to hear both in-air and in-water, while fully aquatic marine mammals (e.g., cetaceans that are always underwater) have specialized ear adaptations for in-water hearing (Wartzok and Ketten, 1999). These adaptations explain the variation in hearing ability and sensitivity among marine mammals and have led to the characterization of marine mammal functional hearing groups based on those sensitivities: very low- frequency cetaceans (VLF group: blue, fin, right, and bowhead whales), low-frequency cetaceans (LF group: minke, sei, Bryde's, Rice's, humpback, gray, and pygmy right whales), high-frequency (HF) cetaceans (HF group: sperm whales, beaked whales, killer whale, melon-headed whale, false/pygmy killer whale, pilot whales, and some dolphin species), very high-frequency (VHF) cetaceans (VHF group: some dolphin species, porpoises, Amazon River dolphin, Kogia species, Baiji, and La Plata dolphin), sirenians (SI) (SI group: manatees, dugongs), otariids (OCW) and other non-phocid marine carnivores (OCA) in water and in air (OCW and OCA groups: sea lion, fur seal, walrus, otter), and phocids in water (PCW) and in air (PCA) (PCW and PCA groups: true seals) (Southall et al., 2019). In Phase III, VLF and LF cetaceans were part of one, combined LF cetacean hearing group. However, as described in the Navy's report ``Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase 4)'' (U.S. Department of the Navy, 2025), hereafter referred to as the Criteria and Thresholds Technical Report, Houser et al. (2024) recently reported obtaining hearing measurements for minke whales, the first direct measurements for a baleen whale species, using auditory evoked potential (AEP) methodology. The Action Proponents incorporated these measurements, as well as Southall et al. (2019), into their analysis. They determined that the data support dividing mysticetes into two separate hearing groups: VLF and LF cetaceans, and NMFS concurs, (as described further in the Estimated Take of Marine Mammals section), that this approach is appropriate for this action. The hearing sensitivity of marine mammals is also directional, meaning the angle between an animal's position and the location of a sound source impacts the animal's hearing threshold, thereby impacting an animal's ability to perceive the sound emanating from that source. This directionality is likely useful for determining the general location of a sound, whether for detection of prey, predators, or members of the same species, and can be dependent upon the frequency of the sound (Accomando et al., 2020; Au and Moore, 1984; Byl et al., 2016; Byl et al. 2019; Kastelein et al., 2005; Kastelein et al., 2019; Popov and Supin, 2009). Acoustic Signaling An acoustic signal refers to the sound waves used to communicate underwater, and marine mammals use a variety of acoustic signals for socially important functions, such as communicating, as well as biologically important functions, such as echolocating (Richardson et al., 1995; Wartzok and Ketten, 1999). Acoustic signals used for communication are lower frequency (i.e., 20 Hz to 30 kHz) than those signals used for echolocation, which are high-frequency (approximately 10-200 kHz peak frequency) signals used by odontocetes to sense their underwater environment. Lower frequency vocalizations used for communication may have a specific, prominent fundamental frequency (Brady et al., 2021) or have a wide frequency range, depending on the functional hearing group and whether the marine mammal is vocalizing in-water or in-air. Acoustic signals used for echolocation are high- frequency, high-energy sounds with patterns and peak frequencies that are often species-specific (Baumann-Pickering et al., 2013). Marine mammal species typically produce sounds at frequencies within their own hearing range, though auditory and vocal ranges do not perfectly align (e.g., odontocetes may only hear a portion of the frequencies of an echolocation click). Because determining a species vocal range is easier than determining a species' hearing range, vocal ranges are often used to infer a species' hearing range when species- specific hearing data are not available (e.g., large whale species). Hearing Loss and Auditory Injury Marine mammals, like all mammals, lose their ability to hear over time due to age-related degeneration of auditory pathways and sensory cells of the inner ear. This natural, age-related hearing loss is distinct from acute noise-induced hearing loss (M[oslash]ller, 2013). Noise-induced hearing loss can be temporary (i.e., TTS) or permanent (permanent threshold shift (PTS)), and higher-level sound exposures are more likely to cause PTS or other AUD INJ. For marine mammals, AUD INJ is considered to be possible when sound exposures are sufficient to produce 40 dB of TTS measured approximately 4 minutes after exposure (U.S. Department of the Navy, 2025). Numerous studies have directly examined noise-induced hearing loss in marine mammals by measuring an animal's hearing threshold before and after exposure to intense sounds. The difference between the post-exposure and pre-exposure hearing thresholds is then used to determine the amount of TTS (in dB) that was produced as a result of the sound exposure (see appendix D of the 2024 HCTT Draft EIS/OEIS for additional details). The Navy used these studies to generate exposure functions, which are predictions of the onset of TTS or PTS based on sound frequency, level, and type (continuous or impulsive), for each marine mammal functional hearing group (U.S. Department of the Navy, 2025). [[Page 32174]] TTS can last from minutes or hours to days (i.e., there is recovery back to baseline/pre-exposure hearing threshold), can occur within a specific frequency range (i.e., an animal might only have a temporary loss of hearing sensitivity within a limited frequency band of its auditory range), and can be of varying amounts (e.g., an animal's hearing sensitivity might be reduced by only 6 dB or reduced by 30 dB). While there is no simple functional relationship between TTS and PTS or other AUD INJ (e.g., neural degeneration), as TTS increases, the likelihood that additional exposure to increased SPL or duration will result in PTS or other injury also increases (see appendix D of the 2024 HCTT Draft EIS/OEIS for additional discussion). Exposure thresholds for the occurrence of AUD INJ, which include the potential for PTS, as well as situations when AUD INJ occurs without PTS, can therefore be defined based on a specific amount of TTS; that is, although an exposure has been shown to produce only TTS, we assume that any additional exposure may result in some AUD INJ. The specific upper limit of TTS is based on experimental data showing amounts of TTS that have not resulted in AUD INJ. In other words, we do not need to know the exact functional relationship between TTS and AUD INJ, we only need to know the upper limit for TTS before some AUD INJ is possible. In severe cases of AUD INJ, there can be total or partial deafness, while in most cases the animal has an impaired ability to hear sounds in specific frequency ranges (Kryter, 1985). The following physiological mechanisms are thought to play a role in inducing auditory threshold shift: effects to sensory hair cells in the inner ear that reduce their sensitivity; modification of the chemical environment within the sensory cells; residual muscular activity in the middle ear; displacement of certain inner ear membranes; increased blood flow; and post-stimulatory reduction in both efferent and sensory neural output (Southall et al., 2007). The amplitude, duration, frequency, temporal pattern, and energy distribution of sound exposure all can affect the amount of associated threshold shift and the frequency range in which it occurs. Generally, the amount of threshold shift, and the time needed to recover from the effect, increase as amplitude and duration of sound exposure increases. Human non-impulsive noise exposure guidelines are based on the assumption that exposures of equal energy (the same SEL) produce equal amounts of hearing impairment regardless of how the sound energy is distributed in time (NIOSH, 1998). Previous marine mammal TTS studies have also generally supported this equal energy relationship (Southall et al., 2007). SEL is used to predict TTS in marine mammals and is considered a good predictor of TTS for shorter duration exposures than longer duration exposures. The amount of TTS increases with exposure SPL and duration, and is correlated with SEL, but duration of the exposure has a more significant effect on TTS than would be predicted based on SEL alone (e.g., Finneran et al., 2010b; Kastak et al., 2007; Kastak et al., 2005; Kastelein et al., 2014a; Mooney et al., 2009a; Popov et al., 2014; Gransier and Kastelein, 2024). These studies highlight the inherent complexity of predicting TTS onset in marine mammals, as well as the importance of considering exposure duration when assessing potential impacts. Generally, TTS increases with SEL in a non-linear fashion, where lower SEL exposures will elicit a steady rate of TTS increase while higher SEL exposures will either increase TTS more rapidly or plateau (Finneran, 2015; U.S. Department of the Navy, 2025). Additionally, with sound exposures of equal energy, those that had lower SPL with longer duration were found to induce TTS onset at lower levels than those of higher SPL and shorter duration. Less threshold shift will occur from intermittent sounds than from a continuous exposure with the same energy (some recovery can occur between intermittent exposures) (Kryter et al., 1966; Ward, 1997; Mooney et al., 2009a, 2009b; Finneran et al., 2010; Kastelein et al., 2014; Kastelein et al., 2015). For example, one short, higher SPL sound exposure may induce the same impairment as one longer lower SPL sound, which in turn may cause more impairment than a series of several intermittent softer sounds with the same total energy (Ward, 1997). Additionally, though TTS is temporary, very prolonged or repeated exposure to sound strong enough to elicit TTS, or shorter-term exposure to sound levels well above the TTS threshold, can cause AUD INJ, at least in terrestrial mammals (Kryter, 1985; Lonsbury-Martin et al., 1987). Although TTS increases non-linearly in marine mammals, recovery from TTS typically occurs in a linear fashion with the logarithm of time (Finneran, 2015; Finneran et al., 2010a; Finneran et al., 2010b; Finneran and Schlundt, 2013; Kastelein et al., 2012a; Kastelein et al., 2012b; Kastelein et al., 2013a; Kastelein et al., 2014a; Kastelein et al., 2014b; Kastelein et al., 2014c; Popov et al., 2014; Popov et al., 2013; Popov et al., 2011; Muslow et al., 2023; Finneran et al., 2023). Considerable variation has been measured in individuals of the same species in both the amount of TTS incurred from similar SELs (Kastelein et al., 2012a; Popov et al., 2013) and the time-to-recovery from TTS (Finneran, 2015; Kastelein et al., 2019e). Many of these studies relied on continuous sound exposures, but intermittent, impulsive sound exposures have also been tested. The sound resulting from an explosive detonation is considered an impulsive sound, but no direct measurements of hearing loss from exposure to explosive sources have been made. Few studies (Finneran et al., 2002; Lucke et al., 2009; Sills et al., 2020; Muslow et al., 2023) using impulsive sounds have produced enough TTS to make predictions about hearing loss due to this source type (see U.S. Department of the Navy, 2025). In general, predictions of TTS based on SEL for this type of sound exposure are likely to overestimate TTS because some recovery from TTS may occur in the quiet periods between impulsive sounds--especially when the duty cycle is low. Peak SPL (unweighted) is also used to predict TTS due to impulsive sounds (Southall et al., 2007; Southall et al., 2019c; U.S. Department of the Navy, 2025). Specific to land-based missile and target launches (characterized by sudden onset of sound, moderate to high peak sound levels (depending on the type of missile and distance), and short sound duration) although it is possible that some pinnipeds may incur TTS during launches from SNI (TTS is not anticipated during launches from PMRF), hearing impairment has not been measured for pinniped species exposed to launch sounds. Auditory brainstem response (i.e., hearing assessment using measurements of electrical responses of the brain) was used to demonstrate that harbor seals did not exhibit loss in hearing sensitivity following launches of large rockets at Vandenberg Space Force Base (VSFB, formerly Vandenberg Air Force Base) (Thorson et al., 1999; Thorson et al., 1998). However, the hearing tests did not begin until at least 45 minutes after the launch; therefore, harbor seals may have incurred TTS which was undetectable by the time testing began. There was no sign of PTS in any of the harbor seals tested (Thorson et al., 1999; Thorson et al., 1998). Since 2001, no launch events at SNI have exposed pinnipeds to noise levels at or exceeding those where PTS could be incurred. Of note, the range to PTS and [[Page 32175]] TTS would not reach haulout locations for Hawaiian monk seals on beaches at PMRF (see section 6.3.2 of the application). Based on measurements of received sound levels during previous launches at SNI (Burke 2017; Holst et al., 2010; Holst et al., 2005a; Holst et al., 2008; Holst et al., 2011; Ugoretz 2016; Ugoretz and Greene Jr. 2012), the Navy expects that there is a very limited potential of TTS for a few of the pinnipeds present, particularly for phocids. Available evidence from launch monitoring at SNI in 2001-2017 suggests that only a limited number of launch events produced sound levels that could elicit TTS for some pinnipeds (Burke 2017; Holst et al., 2008; Holst et al., 2011; Ugoretz 2016; Ugoretz and Greene Jr. 2012). In general, if any TTS were to occur to pinnipeds, it is expected to be mild and reversible. It is possible that some launch sounds as measured close to the launchers may exceed the auditory injury criteria, but it is not expected that any pinnipeds would be close enough to the launchers to be exposed to sounds strong enough to cause auditory injury. Due to the expected sound levels of the activities proposed and the distance of the activity from marine mammal habitat, the effects of sounds from the proposed activities are unlikely to result in auditory injury. In some cases, intense noise exposures have caused AUD INJ (e.g., loss of cochlear neuron synapses), despite thresholds eventually returning to normal (i.e., it is possible to have AUD INJ without a resulting PTS (e.g., Kujawa and Liberman, 2006, 2009; Fernandez et al., 2015; Ryan et al., 2016; Houser, 2021)). In these situations, however, threshold shifts were 30-50 dB measured 24 hours after the exposure (i.e., there is no evidence that an exposure resulting in less than 40 dB TTS measured a few minutes after exposure can produce AUD INJ). Therefore, an exposure producing 40 dB of TTS, measured a few minutes after exposure, can also be used as an upper limit to prevent AUD INJ (i.e., it is assumed that exposures beyond those capable of causing 40 dB of TTS have the potential to result in INJ (which may or may not result in PTS)). Irreparable damage to the inner or outer cochlear hair cells may cause PTS; however, other mechanisms are also involved, such as exceeding the elastic limits of certain tissues and membranes in the middle and inner ears and resultant changes in the chemical composition of the inner ear fluids (Southall et al., 2007). When AUD INJ occurs, there is physical damage to the sound receptors in the ear, whereas TTS represents primarily tissue fatigue and is reversible (Southall et al., 2007). AUD INJ is permanent (i.e., there is incomplete recovery back to baseline/pre-exposure levels) but also can occur in a specific frequency range and amount as mentioned above for TTS. In addition, other investigators have suggested that TTS is within the normal bounds of physiological variability and tolerance and does not represent physical injury (e.g., Ward, 1997). Therefore, NMFS does not consider less than 40 dB of TTS to constitute AUD INJ. The NMFS Acoustic Updated Technical Guidance (NMFS, 2024), which was used in the assessment of effects for this proposed rule, compiled, interpreted, and synthesized the best available scientific information for noise-induced hearing effects for marine mammals to derive updated thresholds for assessing the impacts of noise on marine mammal hearing. While many studies have examined noise-induced hearing loss in marine mammals (see Finneran (2015) and Southall et al. (2019a) for summaries), published data on the onset of TTS for cetaceans are limited to the captive bottlenose dolphin, beluga, harbor porpoise, and Yangtze finless porpoise, and for pinnipeds in water, measurements of TTS are limited to harbor seals, elephant seals, California sea lions, and bearded seals. These studies examine hearing thresholds measured in marine mammals before and after exposure to intense sounds, which can then be used to determine the amount of threshold shift at various post-exposure times. NMFS has reviewed the available studies, which are summarized below (see also the 2024 HCTT Draft EIS/OEIS which includes additional discussion on TTS studies related to sonar and other transducers). The method used to test hearing may affect the resulting amount of measured TTS, with neurophysiological measures producing larger amounts of TTS compared to psychophysical measures (Finneran et al., 2007; Finneran, 2015). The amount of TTS varies with the hearing test frequency. As the exposure SPL increases, the frequency at which the maximum TTS occurs also increases (Kastelein et al., 2014b). For high-level exposures, the maximum TTS typically occurs one-half to one octave above the exposure frequency (Finneran et al., 2007; Mooney et al., 2009a; Nachtigall et al., 2004; Popov et al., 2011; Popov et al., 2013; Schlundt et al., 2000). The overall spread of TTS from tonal exposures can therefore extend over a large frequency range (i.e., narrowband exposures can produce broadband (greater than one octave) TTS). The amount of TTS increases with exposure SPL and duration and is correlated with SEL, especially if the range of exposure durations is relatively small (Kastak et al., 2007; Kastelein et al., 2014b; Popov et al., 2014). As the exposure duration increases, however, the relationship between TTS and SEL begins to break down. Specifically, duration has a more significant effect on TTS than would be predicted on the basis of SEL alone (Finneran et al., 2010a; Kastak et al., 2005; Mooney et al., 2009a). This means if two exposures have the same SEL but different durations, the exposure with the longer duration (thus lower SPL) will tend to produce more TTS than the exposure with the higher SPL and shorter duration. In most acoustic impact assessments, the scenarios of interest involve shorter duration exposures than the marine mammal experimental data from which impact thresholds are derived; therefore, use of SEL tends to over-estimate the amount of TTS. Despite this, SEL continues to be used in many situations because it is relatively simple, more accurate than SPL alone, and lends itself easily to scenarios involving multiple exposures with different SPL (Finneran, 2015). Gradual increases of TTS may not be directly observable with increasing exposure levels, before the onset of PTS (Reichmuth et al., 2019). Similarly, PTS can occur without measurable behavioral modifications (Reichmuth et al., 2019). The amount of TTS depends on the exposure frequency. Sounds at low frequencies, well below the region of best sensitivity, are less hazardous than those at higher frequencies, near the region of best sensitivity (Finneran and Schlundt, 2013). The onset of TTS-- defined as the exposure level necessary to produce 6 dB of TTS (i.e., clearly above the typical variation in threshold measurements)--also varies with exposure frequency. At the low frequency end of a species' hearing curve, onset-TTS exposure levels are higher compared to those in the region of best sensitivity. TTS can accumulate across multiple exposures, but the resulting TTS will be less than the TTS from a single, continuous exposure with the same SEL (Finneran et al., 2010a; Kastelein et al., 2014b; Kastelein et al., 2015b; Mooney et al., 2009b). This means that TTS predictions based on the total, cumulative SEL will overestimate the amount of TTS from [[Page 32176]] intermittent exposures such as sonars and impulsive sources. The amount of observed TTS tends to decrease with increasing time following the exposure; however, the relationship is not monotonic (i.e., increasing exposure does not always increase TTS). The time required for complete recovery of hearing depends on the magnitude of the initial shift; for relatively small shifts recovery may be complete in a few minutes, while large shifts (e.g., approximately 40 dB) may require several days for recovery. Under many circumstances TTS recovers linearly with the logarithm of time (Finneran et al., 2010a, 2010b; Finneran and Schlundt, 2013; Kastelein et al., 2012a; Kastelein et al., 2012b; Kastelein et al., 2013a; Kastelein et al., 2014b; Kastelein et al., 2014c; Popov et al., 2011; Popov et al., 2013; Popov et al., 2014). This means that for each doubling of recovery time, the amount of TTS will decrease by the same amount (e.g., 6 dB recovery per doubling of time). Nachtigall et al. (2018) and Finneran (2018) describe the measurements of hearing sensitivity of multiple odontocete species (i.e., bottlenose dolphin, harbor porpoise, beluga, and false killer whale) when a relatively loud sound was preceded by a warning sound. These captive animals were shown to reduce hearing sensitivity when warned of an impending intense sound. Based on these experimental observations of captive animals, the authors suggest that wild animals may dampen their hearing during prolonged exposures or if conditioned to anticipate intense sounds. Finneran (2018) recommends further investigation of the mechanisms of hearing sensitivity reduction in order to understand the implications for interpretation of existing TTS data obtained from captive animals, notably for considering TTS due to short duration, unpredictable exposures. Marine mammal hearing plays a critical role in communication with conspecifics and in interpretation of environmental cues for purposes such as predator avoidance and prey capture. Depending on the degree (elevation of threshold in dB), duration (i.e., recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious similar to those discussed in auditory masking, below. For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that takes place during a time where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during a time when communication is critical for successful mother/calf interactions could have more serious impacts if it were in the same frequency band as the necessary vocalizations and of a severity that impeded communication. The fact that animals exposed to high levels of sound that would be expected to result in this physiological response would also be expected to have behavioral responses of a comparatively more severe or sustained nature is potentially more significant than the simple existence of a TTS. However, it is important to note that TTS could occur due to longer exposures to sound at lower levels so that a behavioral response may not be elicited. Depending on the degree and frequency range, the effects of AUD INJ on an animal could also range in severity, although it is considered generally more serious than TTS because it is a permanent condition (Reichmuth et al., 2019). Of note, reduced hearing sensitivity as a simple function of aging has been observed in marine mammals, as well as humans and other taxa (Southall et al., 2007), so we can infer that strategies exist for coping with this condition to some degree, though likely not without some cost to the animal. As the amount of research on hearing sensitivity has grown, so, too, has the understanding that marine mammals may be able to self- mitigate, or protect, against noise-induced hearing loss. An animal may learn to reduce or suppress their hearing sensitivity when warned of an impending intense sound exposure, or if the duty cycle of the sound source is predictable (Finneran, 2018; Finneran et al., 2024; Nachtigall and Supin, 2013, 2014, 2015; Nachtigall et al., 2016a, 2016b, 2016c, 2018). This has been shown with several species, including the false killer whale (Nachtigall and Supin, 2013), bottlenose dolphin (Finneran, 2018; Nachtigall and Supin, 2014, 2015; Nachtigall et al., 2016c), beluga whale (Nachtigall et al., 2016a), and harbor porpoise (Nachtigall et al., 2016b). Additionally, Finneran et al. (2023) and Finneran et al. (2024) found that odontocetes that had participated in TTS experiments in the past could have learned from that experience and subsequently protected their hearing during new sound exposure experiments. Behavioral Responses Behavioral responses to sound are highly variable and context- specific (Nowacek et al., 2007; Southall et al., 2007; Southall et al., 2019). Many different variables can influence an animal's perception of and response to (nature and magnitude) an acoustic event. An animal's prior experience with a sound or sound source affects whether it is less likely (habituation, self-mitigation) or more likely (sensitization) to respond to certain sounds in the future (animals can also be innately predisposed to respond to certain sounds in certain ways) (Southall et al., 2007; Southall et al., 2016; Finneran, 2018; Finneran et al., 2024; Nachtigall and Supin, 2013, 2014, 2015; Nachtigall et al., 2015; Nachtigall et al., 2016a, 2018; Nachtigall et al., 2016b). Related to the sound itself, the perceived proximity of the sound, bearing of the sound (approaching vs. retreating), the similarity of a sound to biologically relevant sounds in the animal's environment (i.e., calls of predators, prey, or conspecifics), familiarity of the sound, and navigational constraints may affect the way an animal responds to the sound (Ellison et al., 2012; Southall et al., 2007, DeRuiter et al., 2013a, Southall et al., 2021; Wartzok et al., 2003). Individuals (of different age, gender, reproductive status, etc.) among most populations will have variable hearing capabilities, and differing behavioral sensitivities to sounds that will be affected by prior conditioning, experience, and current activities of those individuals. Southall et al. (2007) and Southall et al. (2021) have developed and subsequently refined methods developed to categorize and assess the severity of acute behavioral responses, considering impacts to individuals that may consequently impact populations. Often, specific acoustic features of the sound and contextual variables (i.e., proximity, duration, or recurrence of the sound or the current behavior that the marine mammal is engaged in or its prior experience), as well as entirely separate factors such as the physical presence of a nearby vessel, may be more relevant to the animal's response than the received level alone. Studies by DeRuiter et al. (2013a) indicate that variability of responses to acoustic stimuli depends not only on the species receiving the sound and the sound source, but also on the social, behavioral, or environmental contexts of exposure. Another study by DeRuiter et al. (2013b) examined behavioral responses of goose-beaked whales to MF sonar and found that whales responded strongly at low received levels (89-127 dB re 1 [micro]Pa) by ceasing normal fluking [[Page 32177]] and echolocation, swimming rapidly away, and extending both dive duration and subsequent non-foraging intervals when the sound source was 2.1-5.9 mi (3.4-9.5 km) away. Importantly, this study also showed that whales exposed to a similar range of received levels (78-106 dB re: 1 [micro]Pa) from distant sonar exercises 73.3 mi (118 km away) did not elicit such responses, suggesting that context may moderate responses. Ellison et al. (2012) outlined an approach to assessing the effects of sound on marine mammals that incorporates contextual-based factors. The authors recommend considering not just the received level of sound, but also the activity the animal is engaged in at the time the sound is received, the nature and novelty of the sound (i.e., whether this a new sound from the animal's perspective), and the distance between the sound source and the animal. They submit that this ``exposure context,'' as described, greatly influences the type of behavioral response exhibited by the animal. Forney et al. (2017) also point out that an apparent lack of response (e.g., no displacement or avoidance of a sound source) may not necessarily mean there is no cost to the individual or population, as some resources or habitats may be of such high value that animals may choose to stay, even when experiencing stress or hearing loss. Forney et al. (2017) recommend considering both the costs of remaining in an area of noise exposure such as TTS, PTS, or masking, which could lead to an increased risk of predation or other threats or a decreased capability to forage, and the costs of displacement, including potential increased risk of vessel strike, increased risks of predation or competition for resources, or decreased habitat suitable for foraging, resting, or socializing. This sort of contextual information is challenging to predict with accuracy for ongoing activities that occur over large spatial and temporal expanses. However, distance is one contextual factor for which data exist to quantitatively inform a take estimate, and the method for predicting Level B harassment in this proposed rule does consider distance to the source. Other factors are often considered qualitatively in the analysis of the likely consequences of sound exposure, where supporting information is available. Friedlaender et al. (2016) provided the first integration of direct measures of prey distribution and density variables incorporated into across-individual analyses of behavior responses of blue whales to sonar, and demonstrated a five-fold increase in the ability to quantify variability in blue whale diving behavior. These results illustrate that responses evaluated without such measurements for foraging animals may be misleading, which again illustrates the context-dependent nature of the probability of response. Exposure of marine mammals to sound sources can result in, but is not limited to, no response or any of the following observable responses: increased alertness; orientation or attraction to a sound source; vocal modifications; cessation of feeding; cessation of social interaction; alteration of movement or diving behavior; habitat abandonment (temporary or permanent); and, in severe cases, panic, flight, stampede, or stranding, potentially resulting in death (Southall et al., 2007). A review of marine mammal responses to anthropogenic sound was first conducted by Richardson (1995). More recent reviews (Nowacek et al., 2007; DeRuiter et al., 2013a and 2013b; Ellison et al., 2012; Gomez et al., 2016) address studies conducted since 1995 and focused on observations where the received sound level of the exposed marine mammal(s) was known or could be estimated. Gomez et al. (2016) conducted a review of the literature considering the contextual information of exposure in addition to received level and found that higher received levels were not always associated with more severe behavioral responses and vice versa. Southall et al. (2016) states that results demonstrate that some individuals of different species display clear yet varied responses, some of which have negative implications, while others appear to tolerate high levels, and that responses may not be fully predictable with simple acoustic exposure metrics (e.g., received sound level). Rather, the authors state that differences among species and individuals along with contextual aspects of exposure (e.g., behavioral state) appear to affect response probability (Southall et al., 2019). The following parts provide examples of behavioral responses to stressors that provide an idea of the variability in responses that would be expected given the differential sensitivities of marine mammal species to sound and the wide range of potential acoustic sources to which a marine mammal may be exposed. Behavioral responses that could occur for a given sound exposure should be determined from the literature that is available for each species (see section D.4.5 (Behavioral Reactions) of the 2024 HCTT Draft EIS/OEIS for a comprehensive list of behavioral studies and species-specific findings) or extrapolated from closely related species when no information exists, along with contextual factors. Responses Due to Sonar and Other Transducers-- Mysticetes responses to sonar and other duty-cycled tonal sounds are dependent upon the characteristics of the signal, behavioral state of the animal, sensitivity and previous experience of an individual, and other contextual factors including distance of the source, movement of the source, physical presence of vessels, time of year, and geographic location (Goldbogen et al., 2013; Harris et al., 2019a; Harris et al., 2015; Martin et al., 2015; Sivle et al., 2015b). For example, a behavioral response study (BRS) in Southern California demonstrated that individual behavioral state was critically important in determining response of blue whales to Navy sonar. In this BRS, some blue whales engaged in deep (greater than 164 ft (50 m)) feeding behavior had greater dive responses than those in shallow feeding or non-feeding conditions, while some blue whales that were engaged in shallow feeding behavior demonstrated no clear changes in diving or movement even when received levels were high (approximately 160 dB re 1 [micro]Pa) from exposures to 3-4 kHz sonar signals, while others showed a clear response at exposures at lower received level of sonar and pseudorandom noise (Goldbogen et al., 2013). Generally, behavioral responses were brief and of low to moderate severity, and the whales returned to baseline behavior shortly after the end of the acoustic exposure (DeRuiter et al., 2017; Goldbogen et al., 2013; Southall et al., 2019c). To better understand the context of these behavioral responses, Friedlaender et al. (2016) mapped the prey field of the deep-diving blue whales and found that the response to sound was more apparent for individuals engaged in feeding than those that were not. The probability of a moderate behavioral response increased when the source was closer for these foraging blue whales, although there was a high degree of uncertainty in that relationship (Southall et al., 2019b). In the same BRS, none of the tagged fin whales demonstrated more than a brief or minor response regardless of their behavioral state (Harris et al., 2019a). The fin whales were exposed to both mid- frequency simulated sonar and pseudorandom noise of similar frequency, duration, and source level. They were less sensitive to disturbance than blue whales, with no significant differences [[Page 32178]] in response between behavioral states or signal types. The authors rated responses as low-to-moderate severity with no negative impact to foraging success (Southall et al., 2023). Similarly, while the rates of foraging lunges decrease in humpback whales due to sonar exposure, there was variability in the response across individuals, with one animal ceasing to forage completely and another animal starting to forage during the exposure (Sivle et al., 2016). In addition, almost half of the animals that exhibited avoidance behavior were foraging before the exposure, but the others were not; the animals that exhibited avoidance behavior while not feeding responded at a slightly lower received level and greater distance than those that were feeding (Wensveen et al., 2017). These findings indicate that the behavioral state of the animal plays a role in the type and severity of a behavioral response. Henderson et al. (2019) examined tagged humpback whale dive and movement behavior, including individuals incidentally exposed to Navy sonar during training activities, at the PMRF off Kaua[revaps]i, Hawaii. Tracking data showed that, regardless of exposure to sonar, individual humpbacks spent limited time, no more than a few days, in the vicinity of Kaua[revaps]i. Potential behavioral responses due to sonar exposure were limited and may have been influenced by breeding and social behaviors. Martin et al. (2015) found that the density of calling minke whales was reduced during periods of Navy training involving sonar relative to the periods before training began and increased again in the days following the completion of training activities. The responses of individual whales could not be assessed, so in this case it is unknown whether the decrease in calling animals indicated that the animals left the range or simply ceased calling. Harris et al. (2019b) utilized acoustically generated minke whale tracks to statistically demonstrate changes in the spatial distribution of minke whale acoustic presence before, during, and after surface ship MFAS training. The spatial distribution of probability of acoustic presence was different in the ``during'' phase compared to the ``before'' phase, and the probability of presence at the center of ship activity during MFAS training was close to zero for both years. The ``after'' phases for both years retained lower probabilities of presence suggesting the return to baseline conditions may take more than five days. The results show a clear spatial redistribution of calling minke whales during surface ship MFAS training, however a limitation of passive acoustic monitoring is that one cannot conclude if the whales moved away, went silent, or a combination of the two. Building on this work, Durbach et al. (2021) used the same data and determined that individual minke whales tended to be in either a fast or slow movement behavior state while on the missile range, where whales tended to be in the slow state in baseline or before periods but transitioned into the fast state with more directed movement during sonar exposures. They also moved away from the area of sonar activity on the range, either to the north or east depending on where the activity was located; this explains the spatial redistribution found by Harris et al. (2019b). Minke whales were also more likely to stop calling when in the fast state, regardless of sonar activity, or when in the slow state during sonar activity (Durbach et al., 2021). Similarly, minke whale detections were reduced or ceased altogether during periods of sonar use off Jacksonville, Florida, (Norris et al., 2012; Simeone et al., 2015; U.S. Department of the Navy, 2013), especially with an increased ping rate (Charif et al., 2015). Odontocetes have varied, context-dependent behavioral responses to sonar and other transducers. Much of the research on odontocetes has been focused on understanding the impacts of sonar and other transducers on beaked whales because they were hypothesized to be more susceptible to behavioral disturbance after several strandings of beaked whales in which military MFAS was identified as a contributing factor (see Stranding and Mortality section). Subsequent BRSs have shown that beaked whales are likely more sensitive to disturbance than most other cetaceans. Many species of odontocetes have been studied during BRSs, including Blainville's beaked whale, goose-beaked whale, Baird's beaked whale, northern bottlenose whale, harbor porpoise, pilot whale, killer whale, sperm whale, false killer whale, melon-headed whale, bottlenose dolphin, rough-toothed dolphin, Risso's dolphin, Pacific white-sided dolphin, and Commerson's dolphin. Observed responses by Blainville's beaked whales, goose-beaked whales, Baird's beaked whales, and northern bottlenose whales (the largest of the beaked whales), to mid-frequency sonar sounds include cessation of clicking, decline in group vocal periods, termination of foraging dives, changes in direction to avoid the sound source, slower ascent rates to the surface, longer deep and shallow dive durations, and other unusual dive behaviors (DeRuiter et al., 2013b; Hewitt et al., 2022; Jacobson et al., 2022; McCarthy et al., 2011; Miller et al., 2015; Moretti et al., 2014; Southall et al., 2011; Stimpert et al., 2014; Tyack et al., 2011). During a BRS in Southern California, a tagged Baird's beaked whale exposed to simulated MFA sonar within 3 km increased swim speed and modified its dive behavior (Stimpert et al., 2014). One goose-beaked whale was also incidentally exposed to real Navy sonar located over 62.1 mi (100 km) away in addition to the source used in the controlled exposure study, and the authors did not detect similar responses at comparable received levels. Received levels from the MFA sonar signals from the controlled (2.1 to 5.9 mi (3.4 to 9.5 km)) exposures were calculated as 84-144 dB re 1 [mu]Pa, and incidental (73.3 mi (118 km)) exposures were calculated as 78-106 dB re 1 [mu]Pa, indicating that context of the exposures (e.g., source proximity, controlled source ramp-up) may have been a significant factor in the responses to the simulated sonars (DeRuiter et al., 2013b). Long-term tagging work during the same BRS demonstrated that the longer duration dives considered a behavioral response by DeRuiter et al. (2013b) fell within the normal range of dive durations found for eight tagged goose-beaked whales on the Southern California Offshore Range (Schorr et al., 2014). However, the longer inter-deep dive intervals found by DeRuiter et al. (2013b), which were among the longest found by Schorr et al. (2014) and Falcone et al. (2017), may indicate a response to sonar. Williams et al. (2017) note that during normal deep dives or during fast swim speeds, beaked whales and other marine mammals use strategies to reduce their stroke rates (e.g., leaping, wave surfing when swimming, interspersing glides between bouts of stroking when diving). The authors determined that in the post- exposure dives by the tagged goose-beaked whales described in DeRuiter et al. (2013b), the whales ceased gliding and swam with almost continuous strokes. This change in swim behavior was calculated to increase metabolic costs by about 30.5 percent and increase the amount of energy expending on fast swim speeds from 27-59 percent of their overall energy budget. This repartitioning of energy was detected in the model up to 1.7 hours after the single sonar exposure. Therefore, while the overall post-exposure dive durations were similar, the metabolic energy calculated by Williams et al. (2017) was higher. However, Southall et al. (2019a) found that prey availability was higher [[Page 32179]] in the western area of the Southern California Offshore Range where goose-beaked whales preferentially occurred, while prey resources were lower in the eastern area and moderate in the area just north of the Range. This high prey availability may indicate that goose-beaked whales need fewer foraging dives to meet energy requirements than would be needed in another area with fewer resources. During a BRS in Norway, northern bottlenose whales avoided a sonar sound source over a wide range of distances (0.5 to 17.4 mi (0.8 to 28 km)) and estimated avoidance thresholds ranging from received SPLs of 117 to 126 dB re 1 [mu]Pa. The behavioral response characteristics and avoidance thresholds were comparable to those previously observed in beaked whale studies; however, researchers did not observe an effect of distance on behavioral response and found that onset and intensity of behavioral response were better predicted by received SPL. There was one instance where an individual northern bottlenose whale approached the vessel, circled the sound source (source level was only 122 dB re 1 [mu]Pa), and resumed foraging after the exposure. Conversely, one northern bottlenose whale exposed to a sonar source was documented performing the longest and deepest dive on record for the species, and continued swimming away from the source for more than 7 hours (Miller et al., 2015; Siegal et al., 2022; Wensveen et al., 2019). Research on Blainville's beaked whales at the Atlantic Undersea Test and Evaluation Center (AUTEC) range has shown that individuals move off-range during sonar use, only returning after the cessation of sonar transmission (Boyd et al., 2009; Henderson et al., 2015; Jones[hyphen]Todd et al., 2021; Manzano-Roth et al., 2022; Manzano-Roth et al., 2016; McCarthy et al., 2011; Tyack et al., 2011). Five Blainville's beaked whales estimated to be within 1.2 to 18 mi (2 to 29 km) of the AUTEC range at the onset of active sonar were displaced a maximum of 17.4 to 42.3 mi (28 to 68 km) after moving away from the range, although one individual did approach the range during active sonar use. Researchers found a decline in deep dives at the onset of the training and an increase in time spent on foraging dives as whales moved away from the range. Predicted received levels at which presumed responses were observed were comparable to those previously observed in beaked whale studies. Acoustic data indicated that vocal periods were detected on the range within 72 hours after training ended (Joyce et al., 2019). However, Blainville's beaked whales have been documented to remain on-range to forage throughout the year (Henderson et al., 2016), indicating the AUTEC range may be a preferred foraging habitat regardless of the effects of active sonar noise, or it could be that there are no long-term consequences of the sonar activity. In the SOCAL Range Complex, researchers conducting photo-identification studies have identified approximately 100 individual goose-beaked whales, with 40 percent having been seen in one or more prior years, with re-sightings up to 7 years apart, indicating a possible on-range resident population (Falcone and Schorr, 2014; Falcone et al., 2009). The probability of Blainville's beaked whale group vocal periods on the PMRF were modeled during periods of (1) no naval activity, (2) naval activity without hull-mounted MFA sonar, and (3) naval activity with hull-mounted MFA sonar (Jacobson et al., 2022). At a received level of 150 dB re 1 [mu]Pa RMS, the probability of detecting a group vocal period during MFA sonar use decreased by 77 percent compared to periods when general training activity was ongoing, and by 87 percent compared to baseline (no naval activity) conditions. Jacobsen et al (2022) found a greater reduction in probability of a group vocal period with MFA sonar than observed in a prior study of the same species at the AUTEC range (Moretti et al., 2014), which may be due to the baseline period in the AUTEC study including naval activity without MFA sonar, potentially lowering the baseline group vocal period activity in that study, or due to differences in the residency of the populations at each range. Stanistreet et al. (2022) used passive acoustic recordings during a multinational navy activity to assess marine mammal acoustic presence and behavioral response to especially long bouts of sonar lasting up to 13 consecutive hours, occurring repeatedly over 8 days (median and maximum SPL = 120 dB and 164 dB). Goose-beaked whales and sperm whales substantially reduced how often they produced clicks during sonar, indicating a decrease or cessation in foraging behavior. Few previous studies have shown sustained changes in foraging or displacement of sperm whales, but there was an absence of sperm whale clicks for 6 consecutive days of sonar activity. Sperm whales returned to baseline levels of clicks within days after the activity, but beaked whale detection rates remained low even 7 days after the exercise. In addition, there were no detections from a Mesoplodon beaked whale species within the area during, and at least 7 days after, the sonar activity. Clicks from northern bottlenose whales and Sowerby's beaked whales were also detected but were not frequent enough at the recording site used to compare clicks between baseline and sonar conditions. Goose-beaked whale behavioral responses (i.e., deep and shallow dive durations, surface interval durations, inter-deep dive intervals) on the Southern California Anti-Submarine Warfare Range were modeled against predictor values that included helicopter dipping sonar, mid- power MFA sonar and hull-mounted, high-power MFA sonar along with other non-MFA sonar predictors (Falcone et al., 2017). Falcone et al. (2017) found both shallow and deep dive durations increased as the proximity to both mid- and high-powered sources decreased and found that surface intervals and inter-deep dive intervals increased in the presence of both types of sonars (helicopter dipping and hull-mounted), although surface intervals shortened during periods without MFA sonar. Proximity of source and receiver were important considerations, as the responses to the mid-power MFA sonar at closer ranges were comparable to the responses to the higher source level vessel sonar, as was the context of the exposure. Helicopter dipping sonars are shorter duration and randomly located, therefore more difficult to predict or track by beaked whales and potentially more likely to elicit a response, especially at closer distances (3.7 to 15.5 mi (6 to 25 km)) (Falcone et al., 2017). Sea floor depths and quantity of light (i.e., lunar cycle) are also important variables to consider in BRSs, as goose-beaked whale foraging dive depth increased with sea floor depth (maximum 6,561.7 ft (2,000 m)) and the amount of time spent at foraging depths (and likely foraging) was greater at night (likely avoiding predation by staying deeper during periods of bright lunar illumination), although they spent more time near the surface during the night, as well, particularly on dark nights with little moonlight, (Barlow et al., 2020). Sonar occurred during 10 percent of the dives studied and had little effect on the resulting dive metrics. Watwood et al. (2017) found that the longer the duration of a sonar event, the greater reduction in detected goose-beaked whale group dives and, as helicopter dipping events occurred more frequently but with shorter durations than periods of hull-mounted sonar, when looking at the number of detected group dives there was a greater reduction during periods of hull- mounted sonar than during helicopter [[Page 32180]] dipping sonar. DiMarzio et al. (2019) also found that group vocal periods (i.e., clusters of foraging pulses), on average, decreased during sonar events on the Southern California Anti-Submarine Warfare Range, though the decline from before the event to during the event was significantly less for helicopter dipping events than hull-mounted events, and there was no difference in the magnitude of the decline between vessel-only events and events with both vessels and helicopters. Manzano-Roth et al. (2022) analyzed long-term passive acoustic monitoring data from the PMRF in Kaua[revaps]i, Hawaii, and found beaked whales reduced group vocal periods during submarine command course events and remained low for a minimum of 3 days after the MFA sonar activity. Harbor porpoise behavioral responses have been researched extensively using acoustic deterrent and acoustic harassment devices; however, BRSs using sonar are limited. Kastelein et al. (2018b) found harbor porpoises did not respond to low-duty cycle mid-frequency sonar tones (3.5-4.1 kHz at 2.7 percent duty cycle; e.g., one tone per minute) at any received level, but one individual did respond (i.e., increased jumping, increased respiration rates) to high-duty cycle sonar tones (3.5-4.1 kHz at 96 percent duty cycle; e.g., continuous tone for almost a minute). Behavioral responses by odontocetes (other than beaked whales and harbor porpoises) to sonar and other transducers include horizontal avoidance, reduced breathing rates, changes in behavioral state, changes in dive behavior (Antunes et al., 2014; Isojunno et al., 2018; Isojunno et al., 2017; Isojunno et al., 2020; Miller, 2012; Miller et al., 2011; Miller et al., 2014; Southall et al., 2024), and, in one study, separation of a killer whale calf from its group (Miller et al., 2011). Some species of dolphin (e.g., bottlenose, spotted, spinner, Clymene, Pacific white-sided, rough-toothed) are frequently documented bowriding with vessels and the drive to engage in bowriding, whether for pleasure or energetic savings (Fiori et al., 2024) may supersede the impact of associated sonar noise (W[uuml]rsig et al., 1998). In controlled exposure experiments on captive odontocetes, Houser et al. (2013a) recorded behavioral responses from bottlenose dolphins with 3 kHz sonar-like tones between 115-185 dB re 1 [mu]Pa, and individuals across 10 trials demonstrated a 50 percent probability of response at 172 dB re 1 [mu]Pa. Multiple studies have been conducted on bottlenose dolphins and beluga whales to measure TTS (Finneran et al., 2003a; Finneran et al., 2001; Finneran et al., 2005; Finneran and Schlundt, 2004; Schlundt et al., 2000). During these studies, when individuals were presented with 1-second tones up to 203 dB re 1 [mu]Pa, responses included changes in respiration rate, fluke slaps, and a refusal to participate or return to the location of the sound stimulus, including what appeared to be deliberate attempts by animals to avoid a sound exposure or to avoid the location of the exposure site during subsequent tests (Finneran et al., 2002; Schlundt et al., 2000). Bottlenose dolphins exposed to more intense 1-second tones exhibited short-term changes in behavior above received levels of 178-193 dB re 1 [mu]Pa, and beluga whales did so at received levels of 180-196 dB re 1 [mu]Pa and above. While several opportunistic observations of odontocete (other than beaked whales and harbor porpoises) responses have been recorded during previous Navy activities and BRSs that employed sonar and sonar-like sources, it is difficult to definitively attribute responses of non- focal species to sonar exposure. Responses range from no response to potential highlight-impactful responses, such as the separation of a killer whale calf from its group (Miller et al., 2011). This may be due, in part, to the variety of species and sensitivities of the odontocete taxonomic group, as well as the breadth of study types conducted and field observations, leading to the assessment of both contextually driven and dose-based responses. The available data indicate exposures to sonar in close proximity and with multiple vessels approaching an animal likely lead to higher-level responses by most odontocete species, regardless of received level or behavioral state. However, when sources are further away and moving in variable directions, behavioral responses are likely driven by behavioral state, individual experience, or species-level sensitivities, as well as exposure duration and received level, with the likelihood of response increasing with increased received levels. As such, it is expected odontocete behavioral responses to sonar and other transducers will vary by species, populations, and individuals, and long-term consequences or population-level effects are likely dependent upon the frequency and duration of the exposure and resulting behavioral response. Pinniped behavioral response to sonar and other transducers is context-dependent (e.g., Hastie et al., 2014; Southall et al., 2019). All studies on pinniped response to sonar thus far have been limited to captive animals, though, based on exposures of wild pinnipeds to vessel noise and impulsive sounds (see Responses Due to Vessel Noise section and Responses Due to Impulsive Noise section below), pinnipeds may only respond strongly to military sonar that is in close proximity or approaching an animal. Kvadsheim et al. (2010b) found that captive hooded seals exhibited avoidance response to sonar signals between 1-7 kHz (160 to 170 dB re 1 [mu]Pa RMS) by reducing diving activity, rapid surface swimming away from the source, and eventually moving to areas of least SPL. However, the authors noted a rapid adaptation in behavior (passive surface floating) during the second and subsequent exposures, indicating a level of habituation within a short amount of time. Kastelein et al. (2015c) exposed captive harbor seals to three different sonar signals at 25 kHz with variable waveform characteristics and duty cycles and found individuals responded to a frequency modulated signal at received levels over 137 dB re 1 [mu]Pa by hauling out more, swimming faster, and raising their heads or jumping out of the water. However, seals did not respond to a continuous wave or combination signals at any received level (up to 156 dB re 1 [mu]Pa). Houser et al. (2013a) conducted a study to determine behavioral responses of captive California sea lions to MFA sonar at various received levels (125 to 185 dB re 1 [mu]Pa). They found younger animals (less than 2 years old) were more likely to respond than older animals and responses included increased respiration rate, increased time spent submerged, refusal to participate in a repetitive task, and hauling out. Most responses below 155 dB re 1 [mu]Pa were changes in respiration, while more severe responses (i.e., refusing to participate, hauling out) began to occur over 170 dB re 1 [mu]Pa, and many of the most severe responses came from the young sea lions. Responses Due to Impulsive Noise-- Impulsive signals have a rapid rise time and higher instantaneous peak pressure than other signal types, particularly at close range, which means they are more likely to cause startle or avoidance responses. At long distances, however, the rise time increases as the signal duration lengthens (similar to a ``ringing'' sound), making the impulsive signal more similar to a non-impulsive signal (Hastie et al., 2019; Martin et al., 2020). Behavioral responses from explosive sounds are likely to be similar to responses studied for other impulsive noise, such as those produced by air [[Page 32181]] guns and impact pile driving. Data on behavioral responses to impulsive sound sources are limited across all marine mammal groups, with only a few studies available for mysticetes and odontocetes. Mysticetes have varied responses to impulsive sound sources, including avoidance, aggressive directed movement towards the source, reduced surface intervals, altered swimming behavior, and changes in vocalization rates (Gordon et al., 2003; McCauley et al., 2000a; Richardson et al., 1985; Southall et al., 2007). Studies have been conducted on many baleen whale species, including gray, humpback, blue, fin, and bowhead whales; it is assumed that these responses are representative of all baleen whale species. The behavioral state of the whale seems to be an integral part of whether the animal responds and how they respond, as does the location and movement of the sound source, more than the received level of the sound. If an individual is engaged in migratory behavior, it may be more likely to respond to impulsive noise, and some species may be more sensitive than others. Migrating gray whales showed avoidance responses to seismic vessels at received levels between 164 and 190 dB re 1 [mu]Pa (Malme et al., 1986, Malme et al., 1988). In one study, McCauley et al. (1998) found that migrating humpback whales in Australia showed avoidance behavior at ranges of 3.1-5 mi (5-8 km) from a seismic array during observational studies and controlled exposure experiments, and another study found humpback whales in Australia decreased their dive times and reduced their swimming speeds (Dunlop et al., 2015). However, when comparing received levels and behavioral responses between air gun ramp-up versus constant noise level of air guns, humpback whales did not change their dive behavior but did deviate from their predicted heading and decreased their swim speeds, deviating more during the constant noise source trials but reducing swim speeds more during ramp- up trials (Dunlop et al., 2016). In both cases, there was no dose- response relationship with the received level of the air gun noise, and similar responses were observed in control trials without air guns (vessel movement remained constant across trials), so some responses may have been due to vessel presence and not received level from the air guns. Social interactions between males and mother-calf pairs were reduced in the presence of vessels towing seismic air gun arrays, regardless of whether the air guns were active or not; which indicates that it was likely the presence of vessels (rather than the impulsive noise generated from active air guns) that affected humpback whale behavior (Dunlop et al., 2020). Proximity of the impulsive source is another important factor to consider when assessing the potential for behavioral responses in marine mammals. Dunlop et al. (2017) found that groups of humpback whales were more likely to avoid a smaller air gun array at closer proximity than a larger air gun array, despite the same received level, showing the difference in response between arrays has more to do with the combined effects of received level and source proximity. In this study, responses were varied and generally small, with short-term course deviations of about 1,640 ft (500 m). Studies on bowhead whales have shown they may be more sensitive than other species to impulsive noise, as individuals have shown clear changes in diving and breathing patterns up to 45.4 mi (73 km) from seismic vessels with received levels as low as 125 dB re 1 [mu]Pa (Malme et al. 1988). Richardson et al. (1995b) documented bowhead whales exhibiting avoidance behaviors at a distance of more than 12.4 mi (20 km) from seismic vessels when received levels were as low as 120 dB re 1 [mu]Pa, although most did not show active avoidance until 5 mi (8 km) from the source. Although bowhead whales may avoid the area around seismic surveys, from 3.7 to 5 mi (6 to 8 km) (Koski and Johnson 1987, as cited in Gordon et al., 2003) out to 12.4 or 18.6 mi (20 or 30 km) (Richardson et al., 1999), a study by Robertson et al. (2013) supports the idea that behavioral responses are contextually dependent, and that during seismic operations, bowhead whales may be less ``available'' for counting due to alterations in dive behavior but that they may not have completely vacated the area. In contrast, noise from seismic surveys was not found to impact feeding behavior or exhalation rates in western gray whales while resting or diving off the coast of Russia (Gailey et al., 2007; Yazvenko et al., 2007); however, the increase in vessel traffic associated with surveys and the proximity of the vessels to the whales did affect the orientation of the whales relative to the vessels and shortened their dive-surface intervals (Gailey et al., 2016). They also increased their speed and distance from the noise source and have been documented in one case study swimming towards shore to avoid an approaching seismic vessel (Gailey et al., 2022). Todd et al. (1996) found no clear short-term behavioral responses by foraging humpbacks to explosions associated with construction operations in Newfoundland but did see a trend of increased rates of net entanglement closer to the noise source, possibly indicating a reduction in net detection associated with the noise through masking or TTS. Distributions of fin and minke whales were modeled with multiple environmental variables and with the occurrence or absence of seismic surveys, and no evidence of a decrease in sighting rates relative to seismic activity was found for either species (Vilela et al., 2016). Their distributions were driven entirely by environmental variables, particularly those linked to prey, including warmer sea surface temperatures, higher chlorophyll-a values, and higher photosynthetically available radiation (a measure of primary productivity). Sighting rates based on over 8,000 hours of baleen and toothed whale survey data were compared on regular vessel surveys versus both active and passive periods of seismic surveys (Kavanagh et al., 2019). Models of sighting numbers were developed, and it was determined that baleen whale sightings were reduced by 88 percent during active and 87 percent during inactive phases of seismic surveys compared to regular surveys. These results seemed to occur regardless of geographic location of the survey; however, when only comparing active versus inactive periods of seismic surveys the geographic location did seem to affect the change in sighting rates. Mysticetes seem to be the most behaviorally sensitive taxonomic group of marine mammals to impulsive sound sources, with possible avoidance responses occurring out to 18.6 mi (30 km) and vocal changes occurring in response to sounds over 62.1 mi (100 km) away. However, they are also the most studied taxonomic group, yielding a larger sample size and greater chance of finding behavioral responses to impulsive noise. Also, their responses appear to be behavior-dependent, with most avoidance responses occurring during migration behavior and little observed response during feeding behavior. These response patterns are likely to hold true for impulsive sources used by the Action Proponents; however, their impulsive sources would largely be stationary (e.g., explosives fired at a fixed target, small air guns), and short term (hours rather than days or weeks) versus in the aforementioned studies, so responses would likely occur in closer proximity to animals or not at all. Odontocete responses to impulsive noise are not well studied and the majority of data have come from seismic [[Page 32182]] (i.e., air gun) surveys, pile driving, and construction activities, while only a few studies have been done to understand how explosive sounds impact odontocetes. What data are available show they may be less sensitive than mysticetes to impulsive sound and that responses occur at closer distances. This may be due to the predominance of low- frequency sound associated with impulsive sources that propagates across long distances and overlaps with the range of best hearing for mysticetes but is below that range for odontocetes. Even harbor porpoises--shown to be highly sensitive to most sound sources, avoiding both stationary (e.g., pile driving) and moving (e.g., seismic survey vessels) impulsive sound sources out to approximately 12.4 mi (20 km) (e.g., Haelters et al., 2014; Pirotta et al., 2014)--have short-term responses, returning to an area within hours upon cessation of the impulsive noise. Although odontocetes are generally considered less sensitive, impulsive noise does impact toothed whales in a variety of ways. In one study, dolphin detections were compared during 30 second periods before, during, and after underwater detonations near naval mine neutralization exercises in Virginia Capes Operating Area. Lammers et al. (2017) found that within 30 seconds after an explosion, the immediate response was an increase in whistles compared to the 30 seconds before an explosion, and that there was a reduction in dolphin acoustic activity during the day of and day after the exercise within 3.7 mi (6 km). This held true only during daytime, as nighttime activity did not appear different than before the exercise, and two days after the explosion there seemed to be an increase in daytime acoustic activity, indicating dolphins may have returned to the area or resumed vocalizations (Lammers et al., 2017). Weaver (2015) documented potential sex-based differences in behavioral responses to impulsive noise during construction (including blasting) of a bridge over a waterway commonly used by bottlenose dolphins, where females decreased area use and males continued using the area, perhaps indicating differential habitat uses. When exposed to multiple impulses from a seismic air gun, Finneran et al. (2015) noted some captive dolphins turned their heads away from the source just before the impulse, indicating they could anticipate the timing of the impulses and may be able to behaviorally mediate the exposure to reduce their received level. Kavanagh et al. (2019) found sightings of odontocete whales decreased by 53 percent during active phases of seismic air gun surveys and 29 percent during inactive phases compared to control surveys. Heide-Jorgensen et al. (2021) found that narwhals exposed to air gun noise in an Arctic fjord were sensitive to seismic vessels over 6.8 mi (11 km) away, even though the small air gun source reached ambient noise levels around 1.9 mi (3 km) (source level of 231 dB re 1 [mu]Pa at 1 m) and large air gun source reached ambient noise levels around 6.2 mi (10 km) (source level 241 dB re 1 [mu]Pa at 1 m). Behavioral responses included changes in swimming speed and swimming direction away from the impulsive sound source and towards the shoreline. Changes in narwhal swimming speed was context-dependent and usually increased in the presence of vessels but decreased (a ``freeze'' response) in response to closely approaching air gun pulses (Heide-Jorgensen et al., 2021). A cessation of feeding was also documented, when the impulsive noise was less than 6.2 mi (10 km) away, although received SELs were less than 130 dB re 1 [mu]Pa\2\s for either air gun at this distance. However, because of this study's research methods and criteria, the long-distance responses of narwhals may be conservatively estimating narwhals' range to behavioral response. Similarly, harbor porpoises seem to have an avoidance response to seismic surveys by leaving the area and decreasing foraging activity within 3.1-6.2 mi (5-10 km) of the survey, as evidenced by both a decrease in vocalizations near the survey and an increase in vocalizations at a distance (Pirotta et al., 2014; Thompson et al., 2013a). The response was short-term, as the porpoises returned to the area within 1 day upon cessation of the air gun operation. Sarnoci[nacute]ska et al. (2020) placed autonomous recording devices near oil and gas platforms and control sites to measure harbor porpoise acoustic activity during seismic air gun surveys. They noted a dose- response effect, with the lowest amount of porpoise activity closest to the seismic vessel (SELsingle shot = 155 dB re 1 [mu]Pa\2\s) and increasing porpoise activity out to 5 to 7.5 mi (8 to 12 km), and that distance to the seismic vessel, rather than sound level, was a better model predictor of porpoise activity. Overall porpoise activity in the seismic survey area was similar to the control sites (approximately 9.3 mi (15 km) apart), which may indicate the harbor porpoises were moving around the area to avoid the seismic vessel without leaving the area entirely. Pile driving, another activity that produces impulsive sound, elicited a similar response in harbor porpoises. Benhemma-Le Gall et al., 2021 examined changes in porpoise presence and foraging at two offshore windfarms between control (102-104 dB) and construction periods (155-161 dB), and found decreased presence (8-17 percent) and decreased foraging activity (41-62 percent) during construction periods. Porpoises were displaced up to 7.5 mi (12 km) away from pile driving and 2.5 mi (4 km) from construction vessels. Multiple studies have documented strong avoidance responses by harbor porpoises out to 12.4 mi (20 km) during pile driving activity, however, animals returned to the area after the activity stopped (Brandt et al., 2011; D[auml]hne et al., 2014; Haelters et al., 2014; Thompson et al., 2010; Tougaard et al., 2005; Tougaard et al., 2009). When bubble curtains were deployed around pile driving, the avoidance distance appeared to be reduced by half to 7.5 mi (12 km), and the animals returned to the area after approximately 5 hours rather than 1 day later (D[auml]hne et al., 2017). Further, Bergstr[ouml]m et al. (2014) found that although there was a high likelihood of acoustic disturbance during wind farm construction (including pile driving), the impact was short-term, and Graham et al. (2019) found that the distance at which behavioral responses of harbor porpoises were likely decreased over the course of a construction project, suggesting habituation to impulsive pile- driving noise. Kastelein et al. (2013b) exposed captive harbor porpoises to impact pile driving noise, and found that respiration rates increased above 136 dB re 1 [mu]Pa (zero-to-peak), and at higher sound levels individuals jumped more frequently. When a single harbor porpoise was exposed to playbacks of impact pile driving noise with different bandwidths, Kastelein et al. (2022) found the animal's behavioral response (i.e., swim speed, respiration rate, jumping) decreased with bandwidth. Overall, odontocete behavioral responses to impulsive sound sources are likely species- and context-dependent. Responses might be expected close to a noise source, under specific behavioral conditions such as females with offspring, or for sensitive species such as harbor porpoises, while many other species demonstrate little to no behavioral response. Pinnipeds seem to be the least sensitive marine mammal group to impulsive noise (Richardson et al., 1995b; Southall et al., 2007), and some may even experience hearing effects before exhibiting a behavioral response (Southall et al., 2007). Some species [[Page 32183]] may be more sensitive and are only likely to respond (e.g., startling, entering the water, ceasing foraging) to loud impulsive noises in close proximity, but only for brief periods of time before returning to their previous behavior. Demarchi et al. (2012) exposed Steller sea lions to in-air explosive blasts, which resulted in increased activity levels and often caused re-entry into the water from a hauled out state. These responses were brief (lasting only minutes) and the animals returned to haul outs and there were no documented lasting behavioral impacts in the days following the explosions. Ringed seals exhibited little or no response to pile driving noise with mean underwater levels of 157 dB re 1 [mu]Pa and in-air levels of 112 dB re 20 [mu]Pa (Blackwell et al., 2004) while harbor seals vacated the area surrounding an active pile driving site at estimated received levels between 166-178 dB re 1 [mu]Pa SPL (peak to peak), returning within 2 hours of the completion of piling activities (Russell et al., 2016). Wild-captured gray seals exposed to a startling treatment (sound with a rapid rise time and a 93 dB sensation level (the level above the animal's hearing threshold at that frequency)) avoided a known food source, whereas animals exposed to a non-startling treatment (sound with a slower rise time but peaking at the same level) did not react or habituated during the exposure period (G[ouml]tz and Janik, 2011). These results underscore the importance of the characteristics of an acoustic signal in predicting an animal's response of habituation. Hastie et al. (2021) studied how the number and severity of avoidance events may be an outcome of marine mammal cognition and risk assessment using captive grey seals. Five individuals were given the option to forage in a high- or low-density prey patch while continuously exposed to silence or an anthropogenic noise (pile driving or tidal turbine operation) playbacks (148 dB re 1 [mu]Pa at 1 m). For each trial, one prey patch was closer to the source, therefore having a higher received level in experimental exposures than the other prey patch. The authors found that foraging success was highest during silent periods and that the seals avoided both anthropogenic noises with higher received levels when the prey density was limited (low- density prey patch). The authors concluded that the seals made foraging decisions within the trials based on both the energetic value of the prey patch (low-density corresponding to low energetic value, high- density corresponding to high energetic value), and the nature and location of the acoustic signal relative to the prey patches of different value. Pinniped responses to Navy missile launches are limited to observations at SNI on the PMSR, and there are extensive observations from this site over more than two decades (Burke, 2017; Holst et al., 2011; Holst and Greene Jr., 2005; Holst and Greene Jr., 2008; Holst and Greene Jr., 2010; Navy, 2021a, 2021b, 2022; Ugoretz, 2014, 2015, 2016; Ugoretz and Greene Jr., 2012), including observations of northern elephant seals, California sea lions, and harbor seals) to every launch from SNI was required under these authorizations of launch activity. The results from these monitoring efforts (2001-2024) are summarized in this section. Over twenty years of observations of pinniped behavioral responses to land-based rocket and missile launches at VSFB are also available (Force, 2022).The observations at VSFB are consistent with those from SNI, but notable findings from VSFB are detailed below. Since launches were relatively infrequent, and of such brief duration, it is unlikely that pinnipeds near the SNI launch sites were habituated to launch sounds. The most common type of response to airborne noise from missile and target launches at SNI was a momentary ``alert'' response. When the animals heard or otherwise detected the launch, they were likely to become alert and interrupt prior activities to pay attention to the launch. For both northern elephant seals and California sea lions, the proportion of animals that moved was significantly related to the closest point of approach of the vehicle or the weighted SEL of the event (based on pinniped in-air M-weighting function from Southall et al. (2007). These relationships were not evident for harbor seals, despite this species being the most susceptible to disturbance (Holst et al., 2011). In cases where animals were displaced from normal activity, the displacement was typically short in duration (5-15 minutes, although some harbor seals left their haulout site until the following low tide when the haulout site was again accessible). Observations indicated that elephant seals rarely showed more than a momentary alert, even when exposed to noise levels or types that caused nearby harbor seals and California sea lions to react more. This was also the case for northern fur seals at VSFB. Most elephant seals raised their heads briefly upon hearing the launch sounds and then quickly returned to their previous activity pattern (usually sleeping). During some launches, a small proportion of northern elephant seals moved a short distance on the beach or into the water, away from their resting site, but settled within minutes. Because of this, elephant seals were not specifically targeted for launch monitoring after 2010 (75 FR 71672, November 24, 2010), although in subsequent years they were often in the field of view when monitoring other species. California sea lions (especially the young animals) exhibited more response than elephant seals, and responses varied by individual and age group. Some exhibited brief startle responses and increased vigilance for a short period after each launch. Others, particularly pups that were playing in groups along the margin of haulouts, appeared to react more vigorously. A greater proportion of hauled-out sea lions typically responded or entered the water when launch sounds were louder. Harbor seals tended to be the most sensitive of the three target species, and during the majority of launches at SNI, most harbor seals left their haulout sites on rocky ledges to enter the water. In some cases, harbor seals returned to their haulout after a short period of time, while in other cases they did not return during the duration of the video-recording period (which sometimes extended up to several hours after a launch). During the day following a launch, harbor seals usually hauled out again at these sites (Holst and Lawson, 2002). The height of the tide following a launch event may have played a significant role in when harbor seals were able to return to a haulout site. There were no observations of any sonic booms or stampedes at SNI and, specifically for the monitored launches at SNI from 2001 to 2024, there were no observed launch-related injuries or deaths (National Marine Fisheries Service, 2019b; Naval Air Warfare Center Weapons Division, 2018). On several occasions, harbor seals and California sea lion adults moved over pups (which can also happen without the presence of an anthropogenic noise) as the animals moved in response to the launches, but the pups did not appear to be injured. On one occasion, a stampede of California sea lions was observed in response to a sonic boom at VSFB. This was thought to have resulted from a particularly high amplitude sonic boom and is noted as an isolated incident. Responses Due to Vessel Noise-- Mysticetes have varied responses to vessel noise and presence, from having no response to approaching vessels to [[Page 32184]] exhibiting an avoidance response by both horizontal (swimming away) and vertical (increased diving) movement (Baker et al., 1983; Fiori et al., 2019; Gende et al., 2011; Watkins, 1981). Avoidance responses include changing swim patterns, speed, or direction (Jahoda et al., 2003), remaining submerged for longer periods of time (Au and Green, 2000), and performing shallower dives with more frequent surfacing. Behavioral responses to vessels range from smaller-scale changes, such as altered breathing patterns (e.g., Baker et al., 1983; Jahoda et al., 2003), to larger-scale changes such as a decrease in apparent presence (Anderwald et al., 2013). Other common behavioral responses include changes in vocalizations, surface time, feeding and social behaviors (Au and Green, 2000; Dunlop, 2019; Fournet et al., 2018; Machernis et al., 2018; Richter et al., 2003; Williams et al., 2002a). For example, North Atlantic right whales (NARWs) have been reported to increase the amplitude or frequency of their vocalizations or call at a lower rate in the presence of increased vessel noise (Parks et al., 2007; Parks et al., 2011) but generally demonstrate little to no response to vessels or sounds from approaching vessels and often continue to use habitats in high vessel traffic areas (Nowacek et al. 2004a). This lack of response may be due to habituation to the presence and associated noise of vessels in NARW habitat or may be due to propagation effects that may attenuate vessel noise near the surface (Nowacek et al., 2004a; Terhune and Verboom, 1999). Similarly, sei whales have been observed ignoring the presence of vessels entirely and even pass close to vessels (Reeves et al., 1998). Historically, fin whales tend to ignore vessels at a distance (Watkins, 1981) or habituate to vessels over time (Watkins, 1986) but still demonstrate vocal modifications (e.g., decreased frequency parameters of calls) during vessel traffic. Ramesh et al. (2021) found that fin whale calls in Ireland were less likely to be detected for every 1 dB re 1 [mu]Pa/minute increase in shipping noise levels. In the presence of tour boats in Chile, fin whales were changing their direction of movement more frequently, with less linear movement than occurred before the boats arrived; this behavior may represent evasion or avoidance of the boats (Santos-Carvallo et al., 2021). The increase in travel swim speeds after the vessels departed may be related to the rapid speeds at which the vessels traveled, sometimes in front of fin whales, leading to additional avoidance behavior post-exposure. Mysticete behavioral responses to vessels may also be affected by vessel behavior (Di Clemente et al., 2018; Fiori et al., 2019). Avoidance responses occurred most often after ``J'' type vessel approaches (i.e., traveling parallel to the whales' direction of travel, then overtaking the whales by turning in front of the group) compared to parallel or direct approaches. Mother humpbacks were particularly sensitive to direct and J type approaches and spent significantly more time diving in response (Fiori et al., 2019). The presence of a passing vessel did not change the behavior of resting humpback whale mother-calf pairs, but fast vessels with louder low- frequency weighted source levels (173 dB re 1 [mu]Pa, equating to weighted received levels of 133 dB re 1 [mu]Pa) at an average distance of 328 ft (100 m) resulted in a decreased resting behavior and increases in dives, swim speeds, and respiration rates (Sprogis et al., 2020). Humpback whale responses to vessel disturbance were dependent on their behavioral state. Di Clemente et al. (2018) found that when vessels passed within 1,640 ft (500 m) of humpback whales, individuals would continue to feed if already engaged in feeding behavior but were more likely to start swimming if they were surface active when approached. In response to an approaching large commercial vessel in an area of high ambient noise levels (125-130 dB re 1 [mu]Pa), a tagged female blue whale turned around mid-ascent and descended perpendicular to the vessel's path (Szesciorka et al., 2019). The whale did not respond until the vessel's closest point of approach (328 ft (100 m) distance, 135 dB re 1 [mu]Pa RMS), which was 10 dB above the ambient noise levels. After the vessel passed, the whale ascended to the surface again with a three-minute delay. Overall, mysticete responses to vessel noise and traffic are varied, and habituation or changes to vocalization are predominant long-term responses. When baleen whales do avoid vessels, they seem to do so by altering their swim and dive patterns to move away from the vessel. Although a lack of response in the presence of a vessel may minimize potential disturbance from passing vessels, it does increase the whales' vulnerability to vessel strike, which may be of greater concern for mysticetes than vessel noise. Odontocete responses due to vessel noise are varied and context- dependent, and it is difficult to separate the impacts of vessel noise from the impacts of vessel presence. Vessel presence has been shown to interrupt feeding behavior in delphinids in some studies (Meissner et al., 2015; Pirotta et al., 2015b) while a recent study by Mills et al. (2023) found that, in an important foraging area, bottlenose dolphins may continue to forage and socialize even while constantly exposed to high vessel traffic. Ng and Leung (2003) found that the type of vessel, approach, and speed of approach can all affect the probability of a negative behavioral response and, similarly, Guerra et al. (2014) documented varied responses in group structure and vocal behavior. While most odontocetes have documented neutral responses to vessels, avoidance (Bejder et al., 2006a; W[uuml]rsig et al., 1998) and attraction (Norris and Prescott, 1961; Ritter, 2002; Shane et al., 1986; Westdal et al., 2023; W[uuml]rsig et al., 1998) behaviors have also been observed (Hewitt, 1985). Archer et al. (2010) compared the responses of dolphin populations far offshore that were often targeted by tuna fisheries to populations closer (less than 100 nmi (185.2 km)) to shore and found the fisheries-associated populations (spotted, spinner, and common dolphins) showed evasive behavior when approached by vessels while those nearshore species not associated with offshore fisheries (coastal spotted and bottlenose dolphins) tended to be attracted to vessels. Arranz et al. (2021) used different engine types to determine whether behavioral responses of short-finned pilot whales were attributable to vessel noise, vessel presence, or both. Mother-calf pairs were approached by the same vessel outfitted with either ``quiet'' electric engines or ``noisy'' traditional combustion engines, controlling for approach speed and distance. Arranz et al. (2021) found mother pilot whales rested less and calves nursed less in response to both types of engines compared to control conditions, but only the ``noisy'' engine caused significant impacts (29 percent and 81 percent, respectively). Smaller vessels tend to generate more noise in higher frequency bands, are more likely to approach odontocetes directly, and spend more time near an animal. Carrera et al. (2008) found tour boat activity can cause short-term displacement of dolphins, and Haviland-Howell et al. (2007) documented longer term or repetitive displacement of dolphins due to chronic vessel noise. Delphinid behavioral states also change in the presence of small tour vessels that often approach animals: travel and resting increases, foraging and social behavior decreases, and animals move closer together (Cecchetti et al., 2017; Clarkson et al., [[Page 32185]] 2020; Kassamali-Fox et al., 2020; Meissner et al., 2015). Most studies on behavioral responses of bottlenose dolphins to vessel traffic show at least short-term changes in behavior, activities, or vocalization patterns when vessels are nearby (Acevedo, 1991; Arcangeli and Crosti, 2009; Berrow and Holmes, 1999; Fumagalli et al., 2018; Gregory and Rowden, 2001; Janik and Thompson, 1996; Lusseau, 2004; Marega et al., 2018; Mattson et al., 2005; Perez-Ortega et al., 2021; Puszka et al., 2021; Scarpaci et al., 2000). Information is limited on beaked whale responses to vessel noise, but W[uuml]rsig et al. (1998) noted that most beaked whales seem to exhibit avoidance behaviors when exposed to vessels and beaked whales may respond to all anthropogenic noise (i.e., sonar, vessel) at similar sound levels (Aguilar de Soto et al., 2006; Tyack et al., 2011; Tyack, 2009). The information available includes a disruption of foraging by a vocalizing goose-beaked whale in the presence of a passing vessel (Aguilar de Soto et al., 2006) and restriction of group movement, or possibly reduction in the number of individuals clicking within the group, after exposure to broadband (received level of 135 dB re 1 [mu]Pa) vessel noise up to at least 3.2 mi (5.2 km) away from the source, though no change in duration of Blainville's beaked whale foraging dives was observed (Pirotta et al., 2012). Porpoises and small delphinids are known to be sensitive to vessel noise, as well. Frankish et al. (2023) found harbor porpoises more likely to avoid large commercial vessels via horizontal movement during the day and vertical movement at night, which supports previous research that the species routinely avoids large, motorized vessels (Polacheck and Thorpe, 1990). Harbor porpoises have also been documented responding to vessels with increased changes in behavioral state and significantly decreased feeding (Akkaya Bas et al., 2017), fewer clicks (Sairanen, 2014), and fewer prey capture attempts and have disrupted foraging when vessels pass closely and noise levels are higher (Wisniewska et al., 2018). Habituation to vessel noise and presence was observed for a resident population of harbor porpoises that was in regular proximity to vessel traffic (32.8 ft to 0.6 mi (10 m to 1 km) away); the population had no response in 74 percent of interactions and an avoidance response in 26 percent of interactions. It should be noted that fewer responses in populations of odontocetes regularly subjected to high levels of vessel traffic could be a sign of habituation, or it could be that the more sensitive individuals in the population have abandoned that area of higher human activity. Most avoidance responses were the result of fast-moving or steady plane-hulling motorized vessels and the vessel type and speed were considered to be more relevant than vessel presence, as few responses were observed to non-motorized or stationary vessels (Oakley et al., 2017). Similarly, Akkaya Bas et al. (2017) found that when fast moving vessels were within 164 ft (50 m) of harbor porpoises, there was an 80 percent probability of change in swimming direction but only a 40 percent probability of change when vessels were beyond 1,312.3 ft (400 m). Frankish et al. (2023) found that harbor porpoises were most likely to avoid vessels less than 984.3 ft (300 m) away but, 5-10 percent of the time, they would also respond to vessels more than 1.2 mi (2 km) away, signifying that they were not just attuning to vessel presence, but to vessel noise as well. Although most vessel noise is constrained to frequencies below 1 kHz, at close ranges vessel noise can extend into mid- and high frequencies (into the tens of kHz) (Hermannsen et al., 2014; Li et al., 2015) and it is these frequencies that harbor porpoises are likely responding to; the mean M-weighted received SPL threshold for a response at these frequencies is 123 dB re 1 [mu]Pa (Dyndo et al., 2015). M-weighting functions are generalized frequency weightings for various groups of marine mammals that were defined by Southall et al. (2007) based on known or estimated auditory sensitivity at different frequencies and are used to characterize auditory effects of strong sounds. Hermannsen et al. (2019) estimated that noise in the 16 kHz frequency band resulting from small recreational vessels could cause behavioral directions in harbor porpoises and could be elevated up to 124 dB re 1 [mu]Pa and raise ambient noise levels by a maximum of 51 dB. The higher noise levels were associated with vessel speed and range, which exceeded the threshold levels found by Dyndo et al. (2015) and Wisniewska et al. (2018) by 49-85 percent of events with high levels of vessel noise. Lusseau and Bejder (2007) have reported some long-term consequences of vessel noise on odontocetes but, overall, there is little information on the long-term and cumulative impacts of vessel noise (National Academies of Sciences Engineering and Medicine, 2017; National Marine Fisheries Service, 2007). Many researchers speculate that long-term impacts may occur on odontocete populations that experience repeated interruption of foraging behaviors (Stockin et al., 2008), and Southall et al. (2021) indicates that, in many contexts, the localized and coastal home ranges typical of many species make them less resilient to this chronic stressor than mysticetes. Context and experience likely play a role in pinnipeds response to vessel noise, which vary from negative responses including increased vigilance and alerting to avoidance to reduced time spent doing biologically important activities (e.g., resting, feeding, and nursing) (Martin et al., 2023a; Martin et al., 2022; Mikkelsen et al., 2019; Richardson et al., 1995b) to attraction or lack of observable response (Richardson et al., 1995b). More severe responses, like flushing, could be more detrimental to individuals during biologically important activities and times, such as during pupping season. Blundell and Pendleton (2015) found that vessel presence reduces haul out time of Alaskan harbor seals during pupping season and larger vessels elicit stronger responses. Cates and Acevedo-Guti[eacute]rrez (2017) modeled harbor seal responses to passing vessels at haul out sites in less trafficked areas and found the model best predicting flushing behavior included number of boats, type of boats, and distance of seals to boats. The authors noted flushing occurred more in response to non- motorized vessels (e.g., kayaks), likely because they tended to pass closer (82 to 603.7 ft (25 to 184 m)) to haul out sites than motorized vessels (180.4 to 1,939 ft (55 to 591 m)) and tended to occur in groups rather than as a single vessel. Cape fur seals were also more responsive to vessel noise at sites with a large breeding colony than at sites with lower abundances of conspecifics (Martin et al., 2023a). A field study of harbor and gray seals showed that seal responses to vessels included interruption of resting and foraging during times when vessel noise was increasing or at its peak (Mikkelsen et al., 2019). And, although no behavioral differences were observed in hauled out wild cape fur seals exposed to low (60-64 dB re 20 [mu]Pa RMS SPL), medium (64-70 dB) and high-level (70-80 dB) vessel noise playbacks, mother-pup pairs spent less time nursing (15-31 percent) and more time awake (13-26 percent), vigilant (7-31 percent), and mobile (2-4 percent) during vessel noise conditions compared to control conditions (Martin et al., 2022). Masking Sound can disrupt behavior through masking, or interfering with, an animal's ability to detect, recognize, interpret, or [[Page 32186]] discriminate between acoustic signals of interest (e.g., those used for intraspecific communication and social interactions, prey detection, predator avoidance, or navigation) (Clark et al., 2009; Richardson et al., 1995; Erbe and Farmer, 2000; Tyack, 2000; Erbe et al., 2016; Branstetter and Sills, 2022). Masking occurs when the receipt of a sound is interfered with by another coincident sound at similar frequencies and at similar or higher intensity and may occur whether the coincident sound is natural (e.g., snapping shrimp, wind, waves, precipitation) or anthropogenic (e.g., shipping, sonar, seismic exploration) in origin. As described in detail in appendix D, section D.4.4 (Masking), of the 2024 HCTT Draft EIS/OEIS, the ability of a noise source to mask biologically important sounds depends on the characteristics of both the noise source and the signal of interest (e.g., signal-to-noise ratio, temporal variability, direction), in relation to each other and to an animal's hearing abilities (e.g., sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age, or TTS hearing loss), and existing ambient noise and propagation conditions. Masking these acoustic signals can disturb the behavior of individual animals, groups of animals, or entire populations. Masking can lead to behavioral changes including vocal changes (e.g., Lombard effect, increasing amplitude, or changing frequency), cessation of foraging, and leaving an area, to both signalers and receivers, in an attempt to compensate for noise levels (Erbe et al., 2016). Most research on auditory masking is focused on energetic masking, or the ability of the receiver (i.e., listener) to detect a signal in noise. However, from a fitness perspective, both signal detection and signal interpretation are necessary for success. This type of masking is called informational masking and occurs when a signal is detected by an animal but the meaning of that signal has been lost. Few data exist on informational masking in marine mammals but studies have shown that some recognition of predator cues might be missed by species that are preyed upon by killer whales if killer whale vocalizations are masked (Cur[eacute] et al., 2016; Cur[eacute] et al., 2015; Deecke et al., 2002; Isojunno et al., 2016; Visser et al., 2016). Von Benda-Beckman et al. (2021) modeled the effect of pulsed and continuous active sonars (CAS) on sperm whale echolocation and found that sonar sounds could reduce the ability of sperm whales to find prey under certain conditions. Under certain circumstances, marine mammals experiencing significant masking could also be impaired from maximizing their performance fitness in survival and reproduction. Therefore, when the coincident (i.e., masking) sound is man-made, it may be considered harassment when disrupting natural behavioral patterns to the point where the behavior is abandoned or significantly altered. It is important to distinguish TTS and PTS, which persist after the sound exposure, from masking, which only occurs during the sound exposure. Because masking (without resulting in threshold shift) is not associated with abnormal physiological function, it is not considered a physiological effect, but rather a potential behavioral effect. Richardson et al. (1995) argued that the maximum radius of influence of anthropogenic noise (including broadband low-frequency sound transmission) on a marine mammal is the distance from the source to the point at which the noise can barely be heard. This range is determined by either the hearing sensitivity (including critical ratios, or the lowest signal-to-noise ratio in which animals can detect a signal) of the animal (Finneran and Branstetter, 2013; Johnson et al., 1989; Southall et al., 2000) or the background noise level present. Masking is most likely to affect some species' ability to detect communication calls and natural sounds (i.e., surf noise, prey noise, etc.) (Richardson et al., 1995). The frequency range of the potentially masking sound is important in determining any potential behavioral impacts. For example, low- frequency signals may have less effect on high-frequency echolocation sounds produced by odontocetes but are more likely to affect detection of mysticete communication calls and other potentially important natural sounds such as those produced by surf and some prey species. The masking of communication signals by anthropogenic noise may be considered as a reduction in the communication space of animals (e.g., Clark et al., 2009; Matthews et al., 2016) and may result in energetic or other costs as animals change their vocalization behavior (e.g., Miller et al., 2000; Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2009; Holt et al., 2009). Masking can be reduced in situations where the signal and noise come from different directions (Richardson et al., 1995), through amplitude modulation of the signal, or through other compensatory behaviors (Houser and Moore, 2014). Masking can be tested directly in captive species, but in wild populations it must be either modeled or inferred from evidence of masking compensation. There are few studies addressing real-world masking sounds likely to be experienced by marine mammals in the wild (e.g., Cholewiak et al., 2018; Branstetter and Sills, 2022; Branstetter et al., 2024). High-frequency sounds may mask the echolocation calls of toothed whales. Human data indicate low-frequency sound can mask high-frequency sounds (i.e., upward masking). Studies on captive odontocetes by Au et al. (1974; 1985; 1993) indicate that some species may use various processes to reduce masking effects (e.g., adjustments in echolocation call intensity or frequency as a function of background noise conditions). Odontocete hearing is highly directional at high frequencies, facilitating echolocation in masked conditions (Au and Moore, 1984). A study by Nachtigall et al., (2018) showed that false killer whales adjust their hearing to compensate for ambient sounds and the intensity of returning echolocation signals. Impacts on signal detection, measured by masked detection thresholds, are not the only important factors to address when considering the potential effects of masking. As marine mammals use sound to recognize conspecifics, prey, predators, or other biologically significant sources (Branstetter et al., 2016), it is also important to understand the impacts of masked recognition thresholds (i.e., informational masking). Branstetter et al. (2016) measured masked recognition thresholds for whistle-like sounds of bottlenose dolphins and observed that they are approximately 4 dB above detection thresholds (energetic masking) for the same signals. Reduced ability to recognize a conspecific call or the acoustic signature of a predator could have severe negative impacts. Branstetter et al. (2016) observed that if ``quality communication'' is set at 90 percent recognition the output of communication space models (which are based on 50 percent detection) would likely result in a significant decrease in communication range. As marine mammals use sound to recognize predators (Allen et al., 2014; Cummings and Thompson, 1971; Cure et al., 2015; Fish and Vania, 1971), the presence of masking noise may also prevent marine mammals from responding to acoustic cues produced by their predators, particularly if it occurs in the same frequency band. For example, harbor seals that reside in the coastal waters of British Columbia are frequently targeted by mammal-eating killer whales. The seals acoustically [[Page 32187]] discriminate between the calls of mammal-eating and fish-eating killer whales (Deecke et al., 2002), a capability that should increase survivorship while reducing the energy required to identify all killer whale calls. Similarly, sperm whales (Cur[eacute] et al., 2016; Isojunno et al., 2016), long-finned pilot whales (Visser et al., 2016), and humpback whales (Cur[eacute] et al., 2015) changed their behavior in response to killer whale vocalization playbacks. The potential effects of masked predator acoustic cues depends on the duration of the masking noise and the likelihood of a marine mammal encountering a predator during the time that detection and recognition of predator cues are impeded. Redundancy and context can also facilitate detection of weak signals. These phenomena may help marine mammals detect weak sounds in the presence of natural or anthropogenic noise. Most masking studies in marine mammals present the test signal and the masking noise from the same direction. The dominant background noise may be highly directional if it comes from a particular anthropogenic source such as a vessel or industrial site. Directional hearing may significantly reduce the masking effects of these sounds by improving the effective signal-to- noise ratio. Masking affects both senders and receivers of acoustic signals and can potentially have long-term chronic effects on marine mammals at the population level as well as at the individual level. Low-frequency ambient sound levels have increased by as much as 20 dB (more than three times in terms of SPL) in the world's ocean from pre-industrial periods, with most of the increase from distant commercial shipping (Hildebrand, 2009; Cholewiak et al., 2018). All anthropogenic sound sources, but especially chronic and lower-frequency signals (e.g., from commercial vessel traffic), contribute to elevated ambient sound levels, thus intensifying masking for marine mammals. Masking Due to Sonar and Other Transducers-- The functional hearing ranges of mysticetes, odontocetes, and pinnipeds underwater overlap the frequencies of the sonar sources used in the Action Proponents' LFAS/MFAS/high-frequency active sonar (HFAS) training and the Navy's testing exercises. Additionally, almost all affected species' vocal repertoires span across the frequencies of these sonar sources used by the Action Proponents. Masking by LFAS or MFAS with relatively low-duty cycles is not anticipated (or would be of very short duration) for most cetaceans as sonar signals occur over a relatively short duration and narrow bandwidth (overlapping with only a small portion of the hearing range). LFAS could overlap in frequency with mysticete vocalizations, however LFAS does not overlap with vocalizations for most marine mammal species. For example, in the presence of LFAS, humpback whales were observed to increase the length of their songs (Fristrup et al., 2003; Miller et al., 2000), potentially due to the overlap in frequencies between the whale song and the LFAS. While dolphin whistles and MFAS are similar in frequency, masking is not anticipated (or would be of very short duration) due to the low-duty cycle and short durations of most sonars. As described in additional detail in the 2024 HCTT Draft EIS/OEIS, high duty-cycle or CAS have more potential to mask vocalizations. These sonars transmit more frequently (greater than 80 percent duty cycle) than traditional sonars, but typically at lower source levels. HFAS, such as pingers that operate at higher repetition rates, also operate at lower source levels and have faster attenuation rates due to the higher frequencies used. These lower source levels limit the range of impacts, however, compared to traditional sonar systems, individuals close to the source are likely to experience masking at longer time scales. The frequency range at which high-duty cycle systems operate overlaps the vocalization frequency of many odontocetes. Continuous noise at the same frequency of communicative vocalizations may cause disruptions to communication, social interactions, and acoustically mediated cooperative behaviors (S[oslash]rensen et al., 2023) such as foraging and mating. Similarly, because the high-duty cycle or CAS includes mid-frequency sources, there is also the potential for the mid-frequency sonar signals to mask important environmental cues (e.g., predator or conspecific acoustic cues), possibly affecting survivorship for targeted animals. Spatial release from masking may occur with higher duty cycle or CAS. While there are currently few studies of the impacts of high-duty cycle sonars on marine mammals, masking due to these systems is likely analogous to masking produced by other continuous sources (e.g., vessel noise and low-frequency cetaceans), and would likely have similar short-term consequences, though longer in duration due to the duration of the masking noise. These may include changes to vocalization amplitude and frequency (Brumm and Slabbekoorn, 2005; Hotchkin and Parks, 2013) and behavioral impacts such as avoidance of the area and interruptions to foraging or other essential behaviors (Gordon et al., 2003). Long-term consequences could include changes to vocal behavior and vocalization structure (Foote et al., 2004; Parks et al., 2007), abandonment of habitat if masking occurs frequently enough to significantly impair communication (Brumm and Slabbekoorn, 2005), a potential decrease in survivorship if predator vocalizations are masked (Brumm and Slabbekoorn, 2005), and a potential decrease in recruitment if masking interferes with reproductive activities or mother-calf communication (Gordon et al., 2003). Von Benda-Beckmann et al. (2021) modeled the effect of pulsed and continuous 1 to 2 kHz active sonar on sperm whale echolocation clicks and found that the presence of upper harmonics in the sonar signal increased masking of clicks produced in the search phase of foraging compared to buzz clicks produced during prey capture. Different levels of sonar caused intermittent to continuous masking (120 to 160 dB re 1 [mu]Pa\2\, respectively), but varied based on click level, whale orientation, and prey target strength. CAS resulted in a greater percentage of time that echolocation clicks were masked compared to pulsed active sonar. This means that sonar sounds could reduce the ability of sperm whales to find prey under certain conditions. However, echoes from prey are most likely spatially separated from the sonar source, and so spatial release from masking would be expected. Masking Due to Impulsive Noise-- Impulsive sound sources, including explosions, are intense and short in duration. Since impulsive noise is intermittent, the length of the gap between sounds (i.e., duty-cycle) and received level are relevant when considering the potential for masking. Impulsive sounds with lower duty cycles or lower received levels are less likely to result in masking than higher duty cycles or received levels. There are no direct observations of masking in marine mammals due to exposure to explosive sources. Potential masking from explosive sounds or weapon noise is likely similar to masking studied for other impulsive sounds, such as air guns. Masking of mysticete calls could occur due to the overlap between their low-frequency vocalizations and the dominant frequencies of impulsive sources (Castellote et al., 2012; Nieukirk [[Page 32188]] et al., 2012). For example, blue whale feeding/social calls increased when seismic exploration was underway (Di Lorio and Clark, 2010), indicative of a possible compensatory response to masking effects of the increased noise level. However, mysticetes that call at higher rates are less likely to be masked by impulsive noise with lower duty cycles (Clark et al., 2009) because of the decreased likelihood that the noise would overlap with the calls, and because of dip listening. Field observations of masking effects such as vocal modifications are difficult to interpret because when recordings indicate that call rates decline, this could be caused by (1) animals calling less frequently (i.e., actual noise-induced vocal modifications), (2) the calls being masked from the recording hydrophone due to the noise (e.g., animals are not calling less frequently but are being detected less frequently), or (3) the animals moving away from the noise, or any combination of these causes (Blackwell et al., 2013; Cerchio et al., 2014). Masking of pinniped communication sounds at 100 Hz center frequency is possible when vocalizations occur at the same time as an air gun pulse (Sills et al., 2017). This might result in some percentage of vocalizations being masked if an activity such as a seismic survey is being conducted in the vicinity, even when the sender and receiver are near one another. Release from masking due to ``dip listening'' is likely in this scenario. While a masking effect of impulsive noise can depend on the received level (Blackwell et al., 2015) and other characteristics of the noise, the vocal response of the affected animal to masking noise is an equally important consideration for inferring overall impacts to an animal. It is possible that the receiver would increase the rate and/or level of calls to compensate for masking; or, conversely, cease calling. In general, impulsive noise has the potential to mask sounds that are biologically important for marine mammals, reducing communication space or resulting in noise-induced vocal modifications that might impact marine mammals. Masking by close-range impulsive sound sources is most likely to impact marine mammal communication. Masking Due to Vessel Noise-- Masking is more likely to occur in the presence of broadband, relatively continuous noise sources such as vessels. Several studies have shown decreases in marine mammal communication space and changes in behavior as a result of the presence of vessel noise. For example, North Atlantic right whales were observed to shift the frequency content of their calls upward while reducing the rate of calling in areas of increased anthropogenic noise (Parks et al., 2007) as well as increasing the amplitude (intensity) of their calls (Parks, 2009; Parks et al., 2011). Fournet et al. (2018) observed that humpback whales in Alaska responded to increasing ambient sound levels (natural and anthropogenic) by increasing the source levels of their calls (non-song vocalizations). Clark et al. (2009) also observed that right whales communication space decreased by up to 84 percent in the presence of vessels (Clark et al., 2009). Cholewiak et al. (2018) also observed loss in communication space in Stellwagen National Marine Sanctuary for North Atlantic right whales, fin whales, and humpback whales with increased ambient noise and shipping noise. Gabriele et al. (2018) modeled the effects of vessel traffic sound on communication space in Glacier Bay National Park in Alaska and found that typical summer vessel traffic in Glacier Bay National Park causes losses of communication space to singing whales (reduced by 13-28 percent), calling whales (18-51 percent), and roaring seals (32-61 percent), particularly during daylight hours and even in the absence of cruise ships. Dunlop (2019) observed that an increase in vessel noise reduced modeled communication space and resulted in significant reduction in group social interactions in Australian humpback whales. However, communication signal masking did not fully explain this change in social behavior in the model, indicating there may also be an additional effect of the physical presence of the vessel on social behavior (Dunlop, 2019). Although humpback whales off Australia did not change the frequency or duration of their vocalizations in the presence of ship noise, their source levels were lower than expected based on source level changes to wind noise, potentially indicating some signal masking (Dunlop, 2016). Multiple delphinid species have also been shown to increase the minimum or maximum frequencies of their whistles in the presence of anthropogenic noise and reduced communication space (e.g., Holt et al., 2009; Holt et al., 2011; Gervaise et al., 2012; Williams et al., 2014; Hermannsen et al., 2014; Papale et al., 2015; Liu et al., 2017). Other Physiological Response Physiological stress is a natural and adaptive process that helps an animal survive changing conditions. When an animal perceives a potential threat, whether or not the stimulus actually poses a threat, a stress response is triggered (Selye, 1950; Moberg, 2000; Sapolsky, 2005). Once an animal's central nervous system perceives a threat, it mounts a biological response or defense that consists of a combination of behavioral responses, autonomic nervous system responses, neuroendocrine responses, or immune responses. The primary distinction between stress (which is adaptive and does not normally place an animal at risk) and distress is the biotic cost of the response. During a stress response, an animal uses glycogen stores that can be quickly replenished once the stress is alleviated. In such circumstances, the cost of the stress response would not pose serious fitness consequences. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other biotic functions. For example, when a stress response diverts energy away from growth in young animals, those animals may experience stunted growth. When a stress response diverts energy from a fetus, an animal's reproductive success and its fitness will suffer. In these cases, the animals will have entered a pre-pathological or pathological state which is called ``distress'' (Selye, 1950) or ``allostatic loading'' (McEwen and Wingfield, 2003). This pathological state of distress will last until the animal replenishes its energetic reserves sufficiently to restore normal function. According to Moberg (2000), in the case of many stressors, an animal's first and sometimes most economical (in terms of biotic costs) response is behavioral avoidance of the potential stressor or avoidance of continued exposure to a stressor. An animal's second line of defense to stressors involves the sympathetic part of the autonomic nervous system and the classical ``fight or flight'' response, which includes the cardiovascular system, the gastrointestinal system, the exocrine glands, and the adrenal medulla to produce changes in heart rate, blood pressure, and gastrointestinal activity that humans commonly associate with ``stress.'' These responses have a relatively short duration and may or may not have significant long-term effect on an animal's welfare. [[Page 32189]] An animal's third line of defense to stressors involves its neuroendocrine systems or sympathetic nervous systems; the system that has received the most study has been the hypothalamus-pituitary-adrenal (HPA) system (also known as the HPA axis in mammals or the hypothalamus-pituitary-interrenal axis in fish and some reptiles). Unlike stress responses associated with the autonomic nervous system, virtually all neuro-endocrine functions that are affected by stress, including immune competence, reproduction, metabolism, and behavior, are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction (Moberg, 1987; Rivier and Rivest, 1991), altered metabolism (Elasser et al., 2000), reduced immune competence (Blecha, 2000), and behavioral disturbance (Moberg, 1987; Blecha, 2000). Increases in the circulation of glucocorticosteroids (cortisol, corticosterone, and aldosterone in marine mammals; see Romano et al., 2004) have been equated with stress for many years. Marine mammals naturally experience stressors within their environment and as part of their life histories. Changing weather and ocean conditions, exposure to disease and naturally occurring toxins, lack of prey availability, and interactions with predators all contribute to the stress a marine mammal experiences (Atkinson et al., 2015). Breeding cycles, periods of fasting, social interactions with members of the same species, and molting (for pinnipeds) are also stressors, although they are natural components of an animal's life history. Anthropogenic activities have the potential to provide additional stressors beyond those that occur naturally (e.g., fishery interactions, pollution, tourism, ocean noise) (Fair et al., 2014; Meissner et al., 2015; Rolland et al., 2012). Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses are well-studied through controlled experiments for both laboratory and free-ranging animals (e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; Krausman et al., 2004; Lankford et al., 2005; Reneerkens et al., 2002; Thompson and Hamer, 2000). However, it should be noted (and as is described in additional detail in the 2024 HCTT Draft EIS/OEIS) that our understanding of the functions of various stress hormones (e.g., cortisol), is based largely upon observations of the stress response in terrestrial mammals. Atkinson et al., (2015) note that the endocrine response of marine mammals to stress may not be the same as that of terrestrial mammals because of the selective pressures marine mammals faced during their evolution in an ocean environment. For example, due to the necessity of breath-holding while diving and foraging at depth, the physiological role of epinephrine and norepinephrine (the catecholamines) in marine mammals might be different than in other mammals. Relatively little information exists on the linkage between anthropogenic sound exposure and stress in marine mammals, and even less information exists on the ultimate consequences of sound-induced stress responses (either acute or chronic). Most studies to date have focused on acute responses to sound either by measuring catecholamines, a neurohormone, or heart rate as a proxy for an acute stress response. The ability to make predictions from stress hormones about impacts on individuals and populations exposed to various forms of natural and anthropogenic stressors relies on understanding the linkages between changes in stress hormones and resulting physiological impacts. Currently, the sound characteristics that correlate with specific stress responses in marine mammals are poorly understood, as are the ultimate consequences of these changes. Several research efforts have improved the understanding of, and the ability to predict, how stressors ultimately affect marine mammal populations (e.g., King et al., 2015; New et al., 2013a; Pirotta et al., 2015a; Pirotta et al., 2022b). This includes determining how and to what degree various types of anthropogenic sound cause stress in marine mammals and understanding what factors may mitigate those physiological stress responses. Factors potentially affecting an animal's response to a stressor include life history, sex, age, reproductive status, overall physiological and behavioral adaptability, and whether they are na[iuml]ve or experienced with the sound (e.g., prior experience with a stressor may result in a reduced response due to habituation) (Finneran and Branstetter, 2013; St. Aubin and Dierauf, 2001). Because there are many unknowns regarding the occurrence of acoustically induced stress responses in marine mammals, any physiological response (e.g., hearing loss or injury) or significant behavioral response is assumed to be associated with a stress response. Non-impulsive sources of sound can cause direct physiological effects including noise-induced loss of hearing sensitivity (or ``threshold shift'') or other auditory injury, nitrogen decompression, acoustically-induced bubble growth, and injury due to sound-induced acoustic resonance. Separately, an animal's behavioral response to an acoustic exposure might lead to physiological effects that might ultimately lead to injury or death, which is discussed later in the Stranding and Mortality section. Heart Rate Response-- Several experimental studies have measured the heart rate response of a variety of marine mammals. For example, Miksis et al. (2001) observed increases in heart rates of captive bottlenose dolphins to which known calls of other dolphins were played, although no increase in heart rate was observed when background tank noise was played back. However, it cannot be determined whether the increase in heart rate was due to stress or social factors, such as expectation of an encounter with a known conspecific. Similarly, a young captive beluga's heart rate increased during exposure to noise, with increases dependent upon the frequency band of noise and duration of exposure, and with a sharp decrease to normal or below normal levels upon cessation of the exposure (Lyamin et al., 2011). Spectral analysis of heart rate variability corroborated direct measures of heart rate (Bakhchina et al., 2017). This response might have been in part due to the conditions during testing, the young age of the animal, and the novelty of the exposure; a year later the exposure was repeated at a slightly higher received level and there was no heart rate response, indicating the beluga whale had potentially habituated to the noise exposure. Kvadsheim et al. (2010a) measured the heart rate of captive hooded seals during exposure to sonar signals and found an increase in the heart rate of the seals during exposure periods versus control periods when the animals were at the surface. When the animals dove, the normal dive-related heart rate decrease was not impacted by the sonar exposure. Similarly, Thompson et al. (1998) observed a rapid, short- lived decrease in heart rates in wild harbor and grey seals exposed to seismic air guns (cited in Gordon et al., 2003). Two captive harbor porpoises showed significant bradycardia (reduced heart rate), below that which occurs with diving, when they were exposed to pinger-like sounds with frequencies between 100-140 kHz (Teilmann et al., 2006). The bradycardia was found only in the early noise exposures and the porpoises acclimated quickly across [[Page 32190]] successive noise exposures. Elmegaard et al. (2021) also found that initial exposures to sonar sweeps produced bradycardia but did not elicit a startle response in captive harbor porpoises. As with Teilmann et al. (2006), the cardiac response disappeared over several repeat exposures suggesting rapid acclimation to the noise. In the same animals, 40-kHz noise pulses induced startle responses but without a change in heart rate. Bakkeren et al. (2023) found no change in the heart rate of a harbor porpoise during exposure to masking noise (\1/3\ octave band noise, centered frequency of 125 kHz, maximum received level of 125 dB re 1 [mu]Pa) during an echolocation task but showed significant bradycardia while blindfolded for the same task. The authors attributed the change in heart rate to sensory deprivation, although no strong conclusions about acoustic masking could be made since the animal was still able to perform the echolocation task in the presence of the masking noise. Williams et al. (2022) observed periods of increased heart rate variability in narwhals during seismic air gun impulse exposure, but profound bradycardia was not noted. Conversely, Williams et al. (2017) found that a profound bradycardia persisted in narwhals, even though exercise effort increased dramatically as part of their escape response following release from capture and handling. Limited evidence across several different species suggests that increased heart rate might occur as part of the acute stress response of marine mammals that are at the surface. However, the decreased heart rate typical of diving marine mammals can be enhanced in response to an acute stressor, suggesting that the context of the exposure is critical to understanding the cardiac response. Furthermore, in instances where a cardiac response was noted, there appears to be rapid habituation when repeat exposures occur. Additional research is required to understand the interaction of dive bradycardia, noise-induced cardiac responses, and the role of habituation in marine mammals. Stress Hormone and Immune Response-- What is known about the function of the various stress hormones is based largely upon observations of the stress response in terrestrial mammals. The endocrine response of marine mammals to stress may not be the same as that of terrestrial mammals because of the selective pressures marine mammals faced during their evolution in an ocean environment (Atkinson et al., 2015). For example, due to the necessity of breath-holding while diving and foraging at depth, the physiological role of epinephrine and norepinephrine (the catecholamines) might be different in marine versus other mammals. Catecholamines increase during breath-hold diving in seals, co- occurring with a reduction in heart rate, peripheral vasoconstriction (i.e., constriction of blood vessels), and an increased reliance on anaerobic metabolism during extended dives (Hance et al., 1982; Hochachka et al., 1995; Hurford et al., 1996); the catecholamine increase is not associated with increased heart rate, glycemic release, and increased oxygen consumption typical of terrestrial mammals. Captive belugas demonstrated no catecholamine response to the playback of oil drilling sounds (Thomas et al., 1990b) but showed a small but statistically significant increase in catecholamines following exposure to impulsive sounds produced from a seismic water gun (Romano et al., 2004). A captive bottlenose dolphin exposed to the same sounds did not demonstrate a catecholamine response but did demonstrate a statistically significant elevation in aldosterone (Romano et al., 2004); however, the increase was within the normal daily variation observed in this species (St. Aubin et al., 1996) and was likely of little biological significance. Aldosterone has been speculated to not only contribute to electrolyte balance, but possibly also the maintenance of blood pressure during periods of vasoconstriction (Houser et al., 2011). In marine mammals, aldosterone is thought to play a role in mediating stress (St. Aubin and Dierauf, 2001; St. Aubin and Geraci, 1989). Yang et al. (2021) measured cortisol concentrations in two captive bottlenose dolphins and found significantly higher concentrations after exposure to 140 dB re 1 [mu]Pa impulsive noise playbacks. Two out of six tested indicators of immune system function underwent acoustic dose-dependent changes, suggesting that repeated exposures or sustained stress response to impulsive sounds may increase an affected individual's susceptibility to pathogens. Unfortunately, absolute values of cortisol were not provided, and it is not possible from the study to tell if cortisol rose to problematic levels (e.g., see normal variation and changes due to handling in Houser et al. (2021) and Champagne et al. (2018)). Exposing dolphins to a different acoustic stressor yielded contrasting results. Houser et al. (2020) measured cortisol and epinephrine obtained from 30 captive bottlenose dolphins exposed to simulated Navy MFAS and found no correlation between SPL and stress hormone levels, even though sound exposures were as high as 185 dB re 1 [mu]Pa. In the same experiment (Houser et al., 2013b), behavioral responses were shown to increase in severity with increasing received SPLs. These results suggest that behavioral responses to sonar signals are not necessarily indicative of a hormonal stress response. Whereas a limited amount of work has addressed the potential for acute sound exposures to produce a stress response, almost nothing is known about how chronic exposure to acoustic stressors affects stress hormones in marine mammals, particularly as it relates to survival or reproduction. In what is probably the only study of chronic noise exposure in marine mammals associating changes in a stress hormone with changes in anthropogenic noise, Rolland et al. (2012) compared the levels of cortisol metabolites in NARW feces collected before and after September 11, 2001. Following the events of September 11, 2001, shipping was significantly reduced in the region where fecal collections were made, and regional ocean background noise declined. Fecal cortisol metabolites significantly decreased during the period of reduced ship traffic and ocean noise (Rolland et al., 2012). Rolland et al. (2017) also compared acute (death by vessel strike) to chronic (entanglement or live stranding) stressors in NARW and found that whales subject to chronic stressors had higher levels of glucocorticoid stress hormones (cortisol and corticosterone) than either healthy whales or those killed by ships. It was presumed that whales subjected to acute stress may have died too quickly for increases in fecal glucocorticoids to be detected. Considerably more work has been conducted in an attempt to determine the potential effect of vessel disturbance on smaller cetaceans, particularly killer whales (Bain, 2002; Erbe, 2002; Lusseau, 2006; Noren et al., 2009; Pirotta et al., 2015b; Read et al., 2014; Rolland et al., 2012; Williams et al., 2009; Williams et al., 2014a; Williams et al., 2014b; Williams et al., 2006b). Most of these efforts focused primarily on estimates of metabolic costs associated with altered behavior or inferred consequences of boat presence and noise but did not directly measure stress hormones. However, Ayres et al. (2012) investigated Southern Resident killer whale fecal thyroid hormone and cortisol metabolites to assess two potential threats to the species' [[Page 32191]] recovery: lack of prey (salmon) and impacts from exposure to the physical presence of vessel traffic (but without measuring vessel traffic noise). Ayres et al. (2012) concluded from these stress hormone measures that the lack of prey overshadowed any population-level physiological impacts on Southern Resident killer whales due to vessel traffic. Lemos et al. (2022) investigated the potential for vessel traffic to affect gray whales. By assessing gray whale fecal cortisol metabolites across years in which vessel traffic was variable, Lemos et al. (2022) found a direct relationship between the presence/density of vessel traffic and fecal cortisol metabolite levels. Unfortunately, no direct noise exposure measurements were made on any individual making it impossible to tell if other natural and anthropogenic factors could also be related to the results. Collectively, these studies indicate the difficulty in determining which factors are primarily influence the secretion of stress hormones, including the separate and additive effects of vessel presence and vessel noise. While vessel presence could contribute to the variation in fecal cortisol metabolites in North Atlantic right whales and gray whales, there are other potential influences on fecal hormone metabolites, so it is difficult to establish a direct link between ocean noise and fecal hormone metabolites. Non-Auditory Injury Non-auditory injury, or direct injury, is considered less likely to occur in the context of the Action Proponents' activities than auditory injury and the primary anticipated source of non-auditory injury for these activities is exposure to the pressure generated by explosive detonations, which is discussed in the Potential Effects of Explosive Sources on Marine Mammals section below. Here, we discuss less direct non-auditory injury impacts, including acoustically induced bubble formation, injury from sonar-induced acoustic resonance, and behaviorally mediated injury. One theoretical cause of injury to marine mammals is rectified diffusion (Crum and Mao, 1996), the process of increasing the size of a bubble by exposing it to a sound field. This process could be facilitated if the environment in which the ensonified bubbles exist is supersaturated with gas. Repetitive diving by marine mammals can cause the blood and some tissues to accumulate gas to a greater degree than is supported by the surrounding environmental pressure (Ridgway and Howard, 1979). The deeper and longer dives of some marine mammals (for example, beaked whales) are theoretically predicted to induce greater supersaturation (Houser et al., 2001b). If rectified diffusion were possible in marine mammals exposed to high-level sound, conditions of tissue supersaturation could theoretically speed the rate and increase the size of bubble growth. Subsequent effects due to tissue trauma and emboli would presumably mirror those observed in humans suffering from decompression sickness. Acoustically-induced (or mediated) bubble growth and other pressure-related physiological impacts are addressed below but are not expected to result from the Action Proponents' proposed activities. It is unlikely that the short duration (in combination with the source levels) of sonar pings would be long enough to drive bubble growth to any substantial size, if such a phenomenon occurs. However, an alternative but related hypothesis has also been suggested: stable bubbles could be destabilized by high-level sound exposures such that bubble growth then occurs through static diffusion of gas out of the tissues. In such a scenario the marine mammal would need to be in a gas-supersaturated state for a long enough period of time for bubbles to become of a problematic size. Recent research with ex vivo supersaturated bovine tissues suggested that, for a 37 kHz signal, a sound exposure of approximately 215 dB re 1 [mu]Pa would be required before microbubbles became destabilized and grew (Crum et al., 2005). Assuming spherical spreading loss and a nominal sonar source level of 235 dB re 1 [mu]Pa at 1 m, a whale would need to be within 33 ft (10 m) of the sonar dome to be exposed to such sound levels. Furthermore, tissues in the study were supersaturated by exposing them to pressures of 400-700 kilopascals for periods of hours and then releasing them to ambient pressures. Assuming the equilibration of gases with the tissues occurred when the tissues were exposed to the high pressures, levels of supersaturation in the tissues could have been as high as 400-700 percent. These levels of tissue supersaturation are substantially higher than model predictions for marine mammals (Fahlman et al., 2009; Fahlman et al., 2014; Houser et al., 2001; Saunders et al., 2008). It is improbable that this mechanism is responsible for stranding events or traumas associated with beaked whale strandings because both the degree of supersaturation and exposure levels observed to cause microbubble destabilization are unlikely to occur, either alone or in concert. Yet another hypothesis has speculated that rapid ascent to the surface following exposure to a startling sound might produce tissue gas saturation sufficient for the evolution of nitrogen bubbles (i.e., decompression sickness) (Jepson et al., 2003; Fernandez et al., 2005). In this scenario, the rate of ascent would need to be sufficiently rapid to compromise behavioral or physiological protections against nitrogen bubble formation. Alternatively, Tyack et al. (2006) studied the deep diving behavior of beaked whales and concluded that: ``Using current models of breath-hold diving, we infer that their natural diving behavior is inconsistent with known problems of acute nitrogen supersaturation and embolism.'' Collectively, these hypotheses can be referred to as ``hypotheses of acoustically mediated bubble growth.'' Although theoretical predictions suggest the possibility for acoustically mediated bubble growth, there is considerable disagreement among scientists as to its likelihood (Piantadosi and Thalmann, 2004; Evans and Miller, 2003; Cox et al., 2006; Rommel et al., 2006). Crum and Mao (1996) hypothesized that received levels would have to exceed 190 dB in order for there to be the possibility of significant bubble growth due to supersaturation of gases in the blood (i.e., rectified diffusion). Work conducted by Crum et al. (2005) demonstrated the possibility of rectified diffusion for short duration signals, but at SELs and tissue saturation levels that are highly improbable to occur in diving marine mammals. To date, energy levels predicted to cause in vivo bubble formation within diving cetaceans have not been evaluated (NOAA, 2002b). Jepson et al. (2003, 2005) and Fernandez et al. (2004, 2005) concluded that in vivo bubble formation, which may be exacerbated by deep, long-duration, repetitive dives may explain why beaked whales appear to be relatively vulnerable to MFAS/HFAS exposures. It has also been argued that traumas from some beaked whale strandings are consistent with gas emboli and bubble-induced tissue separations (Jepson et al., 2003); however, there is no conclusive evidence of this (Rommel et al., 2006). Based on examination of sonar-associated strandings, Bernaldo de Quiros et al. (2019) list diagnostic features, the presence of all of which suggest gas and fat embolic syndrome for beaked whales stranded in association with sonar exposure. As described in additional detail in the Behaviorally Mediated Injury section of appendix D the 2024 HCTT Draft EIS/OEIS, marine mammals [[Page 32192]] generally are thought to deal with nitrogen loads in their blood and other tissues, caused by gas exchange from the lungs under conditions of high ambient pressure during diving, through anatomical, behavioral, and physiological adaptations (Hooker et al., 2012). Although not a direct injury, variations in marine mammal diving behavior or avoidance responses have been hypothesized to result in nitrogen off-gassing in super-saturated tissues, possibly to the point of deleterious vascular and tissue bubble formation (Hooker et al., 2012; Jepson et al., 2003; Saunders et al., 2008) with resulting symptoms similar to decompression sickness, however the process is still not well understood. In 2009, Hooker et al. tested two mathematical models to predict blood and tissue tension N2 (PN2) using field data from three beaked whale species: northern bottlenose whales, goose-beaked whales, and Blainville's beaked whales. The researchers aimed to determine if physiology (body mass, diving lung volume, and dive response) or dive behavior (dive depth and duration, changes in ascent rate, and diel behavior) would lead to differences in PN2 levels and thereby decompression sickness risk between species. In their study, they compared results for previously published time depth recorder data (Hooker and Baird, 1999; Baird et al., 2006, 2008) from goose-beaked whale, Blainville's beaked whale, and northern bottlenose whale. They reported that diving lung volume and extent of the dive response had a large effect on end-dive PN2. Also, results showed that dive profiles had a larger influence on end-dive PN2 than body mass differences between species. Despite diel changes (i.e., variation that occurs regularly every day or most days) in dive behavior, PN2 levels showed no consistent trend. Model output suggested that all three species live with tissue PN2 levels that would cause a significant proportion of decompression sickness cases in terrestrial mammals. The authors concluded that the dive behavior of goose-beaked whale was different from both Blainville's beaked whale and northern bottlenose whale and resulted in higher predicted tissue and blood N2 levels (Hooker et al., 2009). They also suggested that the prevalence of goose-beaked whales stranding after naval sonar exercises could be explained by either a higher abundance of this species in the affected areas or by possible species differences in behavior and/or physiology related to MF active sonar (Hooker et al., 2009). Bernaldo de Quiros et al. (2012) showed that, among stranded whales, deep diving species of whales had higher abundances of gas bubbles compared to shallow diving species. Kvadsheim et al. (2012) estimated blood and tissue PN2 levels in species representing shallow, intermediate, and deep diving cetaceans following behavioral responses to sonar and their comparisons found that deep diving species had higher end-dive blood and tissue N2 levels, indicating a higher risk of developing gas bubble emboli compared with shallow diving species. Fahlmann et al. (2014) evaluated dive data recorded from sperm, killer, long-finned pilot, Blainville's, and goose-beaked whales before and during exposure to low-frequency (1-2 kHz), as defined by the authors, and mid-frequency (2-7 kHz) active sonar in an attempt to determine if either differences in dive behavior or physiological responses to sonar are plausible risk factors for bubble formation. The authors suggested that CO2 may initiate bubble formation and growth, while elevated levels of N2 may be important for continued bubble growth. The authors also suggest that if CO2 plays an important role in bubble formation, a cetacean escaping a sound source may experience increased metabolic rate, CO2 production, and alteration in cardiac output, which could increase risk of gas bubble emboli. However, as discussed in Kvadsheim et al. (2012), the actual observed behavioral responses to sonar from the species in their study (sperm, killer, long-finned pilot, Blainville's beaked, and goose-beaked whales) did not imply any significantly increased risk of decompression sickness due to high levels of N2. Therefore, further information is needed to understand the relationship between exposure to stimuli, behavioral response (discussed in more detail below), elevated N2 levels, and gas bubble emboli in marine mammals. The hypotheses for gas bubble formation related to beaked whale strandings is that beaked whales potentially have strong avoidance responses to MFAS because they sound similar to their main predator, the killer whale (Cox et al., 2006; Southall et al., 2007; Zimmer and Tyack, 2007; Baird et al., 2008; Hooker et al., 2009). Further investigation is needed to assess the potential validity of these hypotheses. To summarize, while there are several hypotheses, there is little data directly connecting intense, anthropogenic underwater sounds with non-auditory physical effects in marine mammals. The available data do not support identification of a specific exposure level above which non-auditory effects can be expected (Southall et al., 2007) or any meaningful quantitative predictions of the numbers (if any) of marine mammals that might be affected in these ways. In addition, such effects, if they occur at all, would be expected to be limited to situations where marine mammals were exposed to high powered sounds at very close range over a prolonged period of time, which is not expected to occur based on the speed of the vessels operating sonar in combination with the speed and behavior of marine mammals in the vicinity of sonar. An object exposed to its resonant frequency will tend to amplify its vibration at that frequency, a phenomenon called acoustic resonance. Acoustic resonance has been proposed as a potential mechanism by which a sonar or sources with similar operating characteristics could damage tissues of marine mammals. In 2002, NMFS convened a panel of government and private scientists to investigate the potential for acoustic resonance to occur in marine mammals (NOAA, 2002). They modeled and evaluated the likelihood that Navy MFAS (2-10 kHz) caused resonance effects in beaked whales that eventually led to their stranding. The workshop participants concluded that resonance in air-filled structures was not likely to have played a primary role in the Bahamas stranding in 2000. They listed several reasons supporting this finding including (among others): tissue displacements at resonance are estimated to be too small to cause tissue damage; tissue- lined air spaces most susceptible to resonance are too large in marine mammals to have resonant frequencies in the ranges used by MFAS or LFAS; lung resonant frequencies increase with depth, and tissue displacements decrease with depth so if resonance is more likely to be caused at depth it is also less likely to have an affect there; and lung tissue damage has not been observed in any mass, multi-species stranding of beaked whales. The frequency at which resonance was predicted to occur in the animals' lungs was 50 Hz, well below the frequencies used by the MFAS systems associated with the Bahamas event. The workshop participants focused on the March 2000 stranding of beaked whales in the Bahamas as high-quality data were available, but the workshop report notes that the results apply to other sonar-related stranding events. For the reasons given by the 2002 workshop participants, we do not anticipate injury due to sonar-induced acoustic resonance from the Action Proponents' proposed activity. [[Page 32193]] Potential Effects of Explosive Sources on Marine Mammals Explosive detonations that occur in water send a shock wave and sound energy through the water and can release gaseous by-products, create an oscillating bubble, or cause a plume of water to shoot up from the water surface. The shock wave and accompanying noise are of most concern to marine animals and the potential effects of an explosive injury to marine mammals would consist of primary blast injury, which refers to injuries resulting from the compression of a body exposed to a blast wave. Blast effects are greatest at the gas- liquid interface (Landsberg, 2000) and are usually observed as barotrauma of gas-containing structures (e.g., lung, gastrointestinal tract) and structural damage to the auditory system (Goertner, 1982; Greaves et al., 1943; Hill, 1978; Office of the Surgeon General, 1991; Richmond et al., 1973; Yelverton et al., 1973). Depending on the intensity of the shock wave and size, location, and depth of the animal, an animal can be injured, killed, suffer non-lethal physical effects, experience hearing related effects with or without behavioral responses, or exhibit temporary behavioral responses or tolerance from hearing the blast sound. Generally, exposures to higher levels of impulse and pressure levels would result in greater impacts to an individual animal. The near instantaneous high magnitude pressure change near an explosion can injure an animal where tissue material properties significantly differ from the surrounding environment, such as around air-filled cavities in the lungs or gastrointestinal tract. Large pressure changes at tissue-air interfaces in the lungs and gastrointestinal tract may cause tissue rupture, resulting in a range of injuries depending on degree of exposure. The lungs are typically the first site to show any damage, while the solid organs (e.g., liver, spleen, and kidney) are more resistant to blast injury (Clark and Ward, 1943). Odontocetes can also incur hemorrhaging in the acoustic fats in the melon and jaw (Siebert et al., 2022). Recoverable injuries would include slight lung injury, such as capillary interstitial bleeding, and contusions to the gastrointestinal tract. More severe injuries, such as tissue lacerations, major hemorrhage, organ rupture, or air in the chest cavity (pneumothorax), would significantly reduce fitness and likely cause death in the wild. Rupture of the lung may also introduce air into the vascular system, producing air emboli that can cause a stroke or heart attack by restricting oxygen delivery to critical organs. Injuries resulting from a shock wave take place at boundaries between tissues of different densities. Different velocities are imparted to tissues of different densities, and this can lead to their physical disruption. Intestinal walls can bruise or rupture, with subsequent hemorrhage and escape of gut contents into the body cavity. Less severe gastrointestinal tract injuries include contusions, petechiae (i.e., small red or purple spots caused by bleeding in the skin), and slight hemorrhaging (Yelverton et al., 1973). Relatively little is known about auditory system trauma in marine mammals resulting from explosive exposure, although it is assumed that auditory structures would be vulnerable to blast injuries because the ears are the most sensitive to pressure and, therefore, they are the organs most sensitive to injury (Ketten, 2000). Sound-related damage associated with sound energy from detonations can be theoretically distinct from injury from the shock wave, particularly farther from the explosion. If a noise is audible to an animal, it has the potential to damage the animal's hearing by causing decreased sensitivity (Ketten, 1995). Lethal impacts are those that result in immediate death or serious debilitation in or near an intense source and are not, technically, pure acoustic trauma (Ketten, 1995). Sublethal impacts include hearing loss, which is caused by exposures to perceptible sounds. Severe damage (from the shock wave) to the ears includes tympanic membrane rupture, fracture of the ossicles, damage to the cochlea, hemorrhage, and cerebrospinal fluid leakage into the middle ear. Moderate injury implies partial hearing loss due to tympanic membrane rupture and blood in the middle ear. Permanent hearing loss also can occur when the hair cells are damaged by one very loud event, as well as by prolonged exposure to a loud noise or chronic exposure to noise. The level of impact from blasts depends on both an animal's location and, at outer zones, on its sensitivity to the residual noise (Ketten, 1995). Auditory trauma was found in 2 humpback whales that died after the detonation of an 11,023 lb (5,000 kg) explosive used off Newfoundland during demolition of an offshore oil rig platform (Ketten et al., 1993), but the proximity of the whales to the detonation was unknown. Eardrum rupture was examined in submerged terrestrial mammals exposed to underwater explosions (Richmond et al., 1973; Yelverton et al., 1973); however, results may not be applicable to the anatomical adaptations for underwater hearing in marine mammals given differences in impedance (Wartzok and Ketten 1999). In general, models predict that an animal would be less susceptible to injury near the water surface because the pressure wave reflected from the water surface would interfere with the direct path pressure wave, reducing positive pressure exposure (Goertner, 1982; Yelverton and Richmond, 1981). This is shown in the records of humans exposed to blast while in the water, which show that the gastrointestinal tract was more likely to be injured than the lungs, likely due to the shallower exposure geometry of the lungs (i.e., closer to the water surface) (Lance et al., 2015). Susceptibility would increase with depth, until normal lung collapse (due to increasing hydrostatic pressure) and increasing ambient pressures again reduce susceptibility (Goertner, 1982). The only known occurrence of mortality or injury to a marine mammal due to a Navy training event involving explosives occurred in March 2011 in nearshore waters off San Diego, California, at the Silver Strand Training Complex (see Strandings Associated with Explosive Use section below). Controlled tests with a variety of lab animals (i.e., mice, rats, dogs, pigs, sheep, and other species) are the best data sources on actual injury to mammals due to underwater exposure to explosions. In the early 1970s, the Lovelace Foundation for Medical Education and Research conducted a series of tests in an artificial pond at Kirtland Air Force Base, New Mexico, to determine the effects of underwater explosions on mammals, with the goal of determining safe ranges for human divers. The resulting data were summarized in two reports (Richmond et al., 1973; Yelverton et al., 1973). Specific physiological observations for each test animal are documented in Richmond et al. (1973). Gas-containing internal organs, such as lungs and intestines, were the principle damage sites in submerged terrestrial mammals; this is consistent with earlier studies of mammal exposures to underwater explosions in which lungs were consistently the first areas to show damage, with less consistent damage observed in the gastrointestinal tract (Clark and Ward, 1943; Greaves et al., 1943). In the Lovelace studies, the first positive acoustic impulse was found to be the metric most related to degree of injury, and size of an animal's gas-containing cavities was thought to play a role in blast injury susceptibility. For [[Page 32194]] these shallow exposures of small terrestrial mammals (masses ranging from 3.4 to 50 kg) to underwater detonations, Richmond et al. (1973) reported that no blast injuries were observed when exposures were less than 6 pounds per square inch per millisecond (psi-ms) (40 pascal seconds (Pa-s)), no instances of slight lung hemorrhage occurred below 20 psi-ms (140 Pa-s), and instances of no lung damage were observed in some exposures at higher levels up to 40 psi-ms (280 Pa-s). An impulse of 34 psi-ms (230 Pa-s) resulted in about 50 percent incidence of slight lung hemorrhage. About half of the animals had gastrointestinal tract contusions (with slight ulceration, i.e., some perforation of the mucosal layer) at exposures of 25-27 psi-ms (170-190 Pa-s). Lung injuries were found to be slightly more prevalent than gastrointestinal tract injuries for the same exposure. The anatomical differences between the terrestrial animals used in the Lovelace tests and marine mammals are summarized in Fetherston et al. (2019). Goertner (1982) examined how lung cavity size would affect susceptibility to blast injury by considering both marine mammal size and depth in a bubble oscillation model of the lung; however, the Goertner (1982) model did not consider how tissues surrounding the respiratory air spaces would reflect shock wave energy or constrain oscillation (Fetherston et al., 2019). Goertner (1982) suggested a peak overpressure gastrointestinal tract injury criterion because the size of gas bubbles in the gastrointestinal tract are variable, and their oscillation period could be short relative to primary blast wave exposure duration. The potential for gastrointestinal tract injury, therefore, may not be adequately modeled by the single oscillation bubble methodology used to estimate lung injury due to impulse. Like impulse, however, high instantaneous pressures may damage many parts of the body, but damage to the gastrointestinal tract is used as an indicator of any peak pressure-induced injury due to its vulnerability. Because gas-containing organs are more vulnerable to primary blast injury, adaptations for diving that allow for collapse of lung tissues with depth may make animals less vulnerable to lung injury with depth. Adaptations for diving include a flexible thoracic cavity, distensible veins that can fill space as air compresses, elastic lung tissue, and resilient tracheas with interlocking cartilaginous rings that provide strength and flexibility (Ridgway, 1972). Denk et al. (2020) found intra-species differences in the compliance of tracheobronchial structures of post-mortem cetaceans and pinnipeds under diving hydrostatic pressures, which would affect depth of alveolar collapse. Older literature suggested complete lung collapse depths at approximately 229.7 ft (70 m) for dolphins (Ridgway and Howard, 1979) and 65.6 to 164 ft (20 to 50 m) for phocid seals (Falke et al., 1985; Kooyman et al., 1972). Follow-on work by Kooyman and Sinnett (1982), in which pulmonary shunting was studied in harbor seals and sea lions, suggested that complete lung collapse for these species would be about 557.7 ft (170 m) and about 590.6 (180 m), respectively. Evidence in sea lions suggests that complete collapse might not occur until depths as great as 738.2 ft (225 m); although the depth of collapse and depth of the dive are related, sea lions can affect the depth of lung collapse by varying the amount of air inhaled on a dive (McDonald and Ponganis, 2012). This is an important consideration for all divers who can modulate lung volume and gas exchange prior to diving via the degree of inhalation and during diving via exhalation (Fahlman et al., 2009); indeed, there are noted differences in pre-dive respiratory behavior, with some marine mammals exhibiting pre-dive exhalation to reduce the lung volume (e.g., phocid seals) (Kooyman et al., 1973). Further Potential Effects of Behavioral Disturbance on Marine Mammal Fitness The different ways in which marine mammals respond to sound are sometimes indicators of the ultimate effect that exposure to a given stimulus will have on the well-being (survival, reproduction, etc.) of an animal. The long-term consequences of disturbance, hearing loss, chronic masking, and acute or chronic physiological stress are difficult to predict because of the different factors experienced by individual animals, such as context of stressor exposure, underlying health conditions, and other environmental or anthropogenic stressors. Linking these non-lethal effects on individuals to changes in population growth rates requires long-term data, which is lacking for many populations. We summarize several studies below, but there are few quantitative marine mammal data relating the exposure of marine mammals to sound to effects on reproduction or survival, though data exists for terrestrial species to which we can draw comparisons for marine mammals. Several authors have reported that disturbance stimuli may cause animals to abandon nesting and foraging sites (Sutherland and Crockford, 1993); may cause animals to increase their activity levels and suffer premature deaths or reduced reproductive success when their energy expenditures exceed their energy budgets (Daan et al., 1996; Feare, 1976; Mullner et al., 2004); or may cause animals to experience higher predation rates when they adopt risk-prone foraging or migratory strategies (Frid and Dill, 2002). Each of these studies addressed the consequences of animals shifting from one behavioral state (e.g., resting or foraging) to another behavioral state (e.g., avoidance or escape behavior) because of human disturbance or disturbance stimuli. Lusseau and Bejder (2007) present data from three long-term studies illustrating the connections between disturbance from whale-watching boats and population-level effects in cetaceans. In Shark Bay Australia, the abundance of bottlenose dolphins was compared within adjacent control and tourism sites over three consecutive 4.5-year periods of increasing tourism levels. Between the second and third time periods, in which tourism doubled, dolphin abundance decreased by 15 percent in the tourism area and did not change significantly in the control area. In Fiordland, New Zealand, two populations (Milford and Doubtful Sounds) of bottlenose dolphins with tourism levels that differed by a factor of seven were observed and significant increases in travelling time and decreases in resting time were documented for both. Consistent short-term avoidance strategies were observed in response to tour boats until a threshold of disturbance was reached (average 68 minutes between interactions), after which the response switched to a longer-term habitat displacement strategy. For one population, tourism only occurred in a part of the home range. However, tourism occurred throughout the home range of the Doubtful Sound population and once boat traffic increased beyond the 68-minute threshold (resulting in abandonment of their home range/preferred habitat), reproductive success drastically decreased (i.e., increased stillbirths) and abundance decreased significantly (from 67 to 56 individuals in a short period). Last, in a study of Northern Resident killer whales off Vancouver Island, exposure to boat traffic was shown to reduce foraging opportunities and increase traveling time. A simple bioenergetics model was applied to show that the reduced foraging opportunities equated to a decreased energy intake of 18 percent, while the increased traveling incurred [[Page 32195]] an increased energy output of 3-4 percent, which suggests that a management action based on avoiding interference with foraging might be particularly effective. An important variable to consider is duration of disturbance. Severity scales used to assess behavioral responses of marine mammals to acute sound exposures are not appropriate to apply to sustained or chronic exposures, which requires considering the health of a population over time rather than a focus on immediate impacts to individuals (Southall et al., 2021). For example, short-term costs experienced over the course of a week by an otherwise healthy individual may be recouped over time after exposure to the stressor ends. These short-term costs would be unlikely to result in long-term consequences to that individual or to that individual's population. Comparatively, long-term costs accumulated by otherwise healthy individuals over an entire season, year, or throughout a life stage (e.g., pup, juvenile, adult) would be less easily recouped and more likely to result in long-term consequences to that individual or population. Marine mammals exposed to frequent or intense anthropogenic activities may leave the area, habituate to the activity, or tolerate the disturbance and remain in the area (Wartzok et al., 2003). Highly resident or localized populations may also stay in an area of disturbance because the cost of displacement is higher than the cost of remaining in the area (Forney et al., 2017). As such, an apparent lack of response (e.g., no displacement or avoidance of a sound source) does not necessarily indicate there is no cost to the individual or population, as some resources or habitats may be of such high value that animals may choose to stay, even when experiencing the consequences of stress, masking, or hearing loss (Forney et al., 2017). Longer term displacement can lead to changes in abundance or distribution patterns of the species in the affected region (Bejder et al., 2006b; Blackwell et al., 2004; Teilmann et al., 2006). For example, gray whales in Baja California, Mexico, abandoned a historical breeding lagoon in the mid-1960s due to an increase in dredging and commercial shipping operations, and only repopulated the lagoon after shipping activities had ceased for several years (Bryant et al., 1984). Mysticetes in the northeast tended to adjust to vessel traffic over several years, trending towards more neutral behavioral responses to passing vessels (Watkins, 1986), indicating that some animals may habituate to high levels of human activity. A study on bottlenose dolphin responses to vessel approaches found that lesser responses in populations of dolphins regularly subjected to high levels of vessel traffic could be a sign of habituation, or it could be that the more sensitive animals in this population previously abandoned the area of higher human activity (Bejder et al., 2006a). Population characteristics (e.g., whether a population is open or closed to immigration and emigration) can influence sensitivity to disturbance as well; closed populations could not withstand a higher probability of disturbance compared to open populations with no limitation on food (New et al., 2020). Predicting population trends or long-term displacement patterns due to anthropogenic disturbance is challenging due to limited information and survey data for many species over sufficient spatiotemporal scales, as well as a full understanding of how other factors, such as oceanographic oscillations, affect marine mammal presence (Moore and Barlow, 2013; Barlow, 2016; Moore and Barlow, 2017). Population models are necessary to understand and link short-term effects to individuals from disturbance (anthropogenic impacts or environmental change) to long-term population consequences. Population models require inputs for the population size and changes in vital rates of the population (e.g., the mean values for survival age, lifetime reproductive success, recruitment of new individuals into the population), to predict changes in population dynamics (e.g., population growth rate). These efforts often rely on bioenergetic models, or energy budget models, which analyze energy intake from food and energy costs for life functions, such as maintenance, growth, and reproduction, either at the individual or population level (Pirotta, 2022), and model sensitivity analyses have identified the most consequential parameters, including prey characteristics, feeding processes, energy expenditure, body size, energy storage, and lactation capability (Pirotta, 2022). However, there is a high level of uncertainty around many parameters in these models (H[uuml]tt et al., 2023). The U.S. National Research Council (NRC) committee on Characterizing Biologically Significant Marine Mammal Behavior developed an initial conceptual model to link acoustic disturbance to population effects and inform data and research needs (NRC, 2005). This Population Consequences of Acoustic Disturbance, or PCAD, conceptual model linked the parameters of sound exposure, behavior change, life function immediately affected, vital rates, and population effects. In its report, the committee found that the relationships between vital rates and population effects were relatively well understood, but that the relationships between the other components of the model were not well-known or easily observed. Following the PCAD framework (NRC, 2005), an ONR working group developed the Potential Consequences of Disturbance (PCoD), outlining an updated conceptual model of the relationships linking disturbance to changes in behavior and physiology, health, vital rates, and population dynamics. The PCoD model considers all types of disturbance, not solely anthropogenic or acoustic, and incorporates physiological changes, such as stress or injury, along with behavioral changes as a direct result of disturbance (National Academies of Sciences Engineering and Medicine, 2017). In this framework, behavioral and physiological changes can have direct (acute) effects on vital rates, such as when changes in habitat use or increased stress levels raise the probability of mother-calf separation or predation; they can have indirect and long-term (chronic) effects on vital rates, such as when changes in time/energy budgets or increased disease susceptibility affect health, which then affects vital rates; or they can have no effect to vital rates (New et al., 2014; Pirotta et al., 2018a). In addition to outlining this general framework and compiling the relevant literature that supports it, the authors chose four example species for which extensive long-term monitoring data exist (southern elephant seals, North Atlantic right whale, Ziphiidae beaked whales, and bottlenose dolphins) and developed state-space energetic models that can be used to forecast longer-term, population-level impacts from behavioral changes. While these models cannot yet be applied broadly to project- specific risk assessments for the majority of species, as well as requiring significant resources and time to conduct (more than is typically available to support regulatory compliance for one project), they are a critical first step towards being able to quantify the likelihood of a population level effect. Since New et al. (2014), several publications have described models developed to examine the long-term effects of environmental or anthropogenic disturbance of foraging on various life stages of selected species [[Page 32196]] (sperm whale, Farmer et al. (2018); California sea lion, McHuron et al. (2018); and blue whale, Pirotta, et al. (2018a)). The PCoD model identifies the types of data that would be needed to assess population-level impacts. These data are lacking for many marine mammal species (Booth et al., 2020). Southall et al. (2021) states that future modeling and population simulation studies can help determine population-wide long-term consequences and impact analysis. However, the method to do so is still developing, as there are gaps in the literature, possible sampling biases, and results are rarely ground- truthed, with a few exceptions (Booth et al., 2022; Schwarz et al., 2022). Nowacek et al. (2016) reviewed technologies such as passive acoustic monitoring, tagging, and the use of unmanned aerial vehicles which can improve scientists' abilities to study these model inputs and link behavioral changes to individual life functions and ultimately population-level effects. Relevant data needed for improving analyses of population-level consequences resulting from disturbances will continue to be collected during the 7-year period of the LOAs through projects funded by the Navy's Marine Species Monitoring Program. Multiple case studies across marine mammal taxonomic groups have been conducted following the PCoD framework. From these studies, Keen et al. (2021) identified themes and contextual factors relevant to assessing impacts to populations due to disturbance, which have been considered in the context of the impacts of the Action Proponents' activities. A population's movement ecology determines the potential for spatiotemporal overlap with a disturbance. Resident populations or populations that rely on spatially limited habitats for critical life functions (i.e., foraging, breeding) would be at greater risk of repeated or chronic exposure to disturbances than populations that are wide-ranging relative to the footprint of a disturbance (Keen et al., 2021). Even for the same species, differences in habitat use between populations can result in different potential for repeated exposure to individuals for a similar stressor (Costa et al., 2016a). The location and radius of disturbance can impact how many animals are exposed and for how long (Costa et al., 2016b). While some models have shown the advantages of populations with larger ranges, namely the decreased chance of being exposed (Costa et al., 2016b), it's important to consider that for some species, the energetic cost of a longer migration could make a population more sensitive to energy lost through disturbance (Villegas-Amtmann et al., 2017). In addition to ranging patterns, a species' activity budgets and lunging rates can cause variability in their predicted cost of disturbance as well (Pirotta et al., 2021). Bioenergetics frameworks that examine the impact of foraging disruption on body reserves of individual whales found that rates of daily foraging disruption can predict the number of days to terminal starvation for various life stages (Farmer et al., 2018b). Similarly, when a population is displaced by a stressor, and only has access to areas of poor habitat quality (i.e., low prey abundance) for relocation, bioenergetic models may be more likely to predict starvation, longer recovery times, or extinction (Hin et al., 2023). There is some debate over the use of blubber thickness as a metric of cetacean energy stores and health, as marine mammals may not use their fat stores in a similar manner to terrestrial mammals (Derous et al., 2020). Resource limitation can impact marine mammal population growth rate regardless of additional anthropogenic disturbance. Stochastic Dynamic Programming models have been used to explore the impact declining prey species has on focal marine mammal predators (McHuron et al., 2023a; McHuron et al., 2023b). A Stochastic Dynamic Programming model determined that a decrease in walleye pollock (Gadus chalcogrammus) availability increased the time and distance northern fur seal mothers had to travel offshore, which negatively impacted pup growth rate and wean mass, despite attempts to compensate with longer recovery time on land (McHuron et al., 2023b). Prey is an important factor in long-term consequence models for many species of marine mammals. In disturbance models that predict habitat displacement or otherwise reduced foraging opportunities, populations are being deprived of energy dense prey or ``high quality'' areas which can lead to long-term impacts on fecundity and survival (Czapanskiy et al., 2021; Hin et al., 2019; McHuron et al., 2023a; New et al., 2013b). Prey density limits the energy available for growth, reproduction, and survival. Some disturbance models indicate that the immediate decrease in a portion of the population (e.g., young lactating mothers) is not necessarily detrimental to a population, since as a result, prey availability increases and the population's overall improved body condition reduces the age at first calf (Hin et al., 2021). The timing of a disturbance with seasonally available resources is also important; if a disturbance occurs during periods of low resource availability, the population- level consequences are greater and occur faster than if the disturbance occurs during periods when resource levels are high (Hin et al., 2019). Further, when resources are not evenly distributed, populations with cautious strategies and knowledge of resource variation have an advantage (Pirotta et al., 2020). Even when modeled alongside several anthropogenic sources of disturbance (e.g., vessel strike, vessel noise, chemical contaminants, sonar), several species of marine mammals are most influenced by lack of prey (Czapanskiy et al., 2021; Murray et al., 2021). Some species like killer whales are especially sensitive to prey abundance due to their limited diet (Murray et al., 2021). The short-term energetic cost of eleven species of cetaceans and mysticetes exposed to mid-frequency active sonar was influenced more by lost foraging opportunities than increased locomotor effort during avoidance (Czapanskiy et al., 2021). Additionally, the model found that mysticetes incurred more energetic cost than odontocetes, even during mild behavioral responses to sonar. These results may be useful in the development of future Population Consequences of Multiple Stressors and PCoD models since they should seek to qualify cetacean health in a more ecologically relevant manner. PCoD models have been used to assess the impacts of multiple and recurring stressors. A marine mammal population that is already subject to chronic stressors will likely be more vulnerable to acute disturbances. Models that have looked at populations of cetaceans who are exposed to multiple stressors over several years have found that even one major chronic stressor (e.g., epizootic disease, oil spill) has severe impacts on population size. A layer of one or more stressor (e.g., seismic surveys) in addition to a chronic stressor (e.g., an oil spill) can yield devastating impacts on a population. These results may vary based on species and location, as one population may be more impacted by chronic shipping noise, while another population may not. However, just because a population doesn't appear to be impacted by one chronic stressor (e.g., shipping noise), does not mean they aren't affected by others (e.g., disease) (Reed et al., 2020). Recurring or chronic stressors can impact population abundance even when instances of disturbance are short and have minimal behavioral impact on [[Page 32197]] an individual (Farmer et al., 2018a; McHuron et al., 2018b; Pirotta et al., 2019). Some changes to response variables like pup recruitment (survival to age one) are not noticeable for several years, as the impacts on pup survival does not affect the population until those pups are mature but impacts to young animals will ultimately lead to population-wide declines. The severity of the repeated disturbance can also impact a population's long-term reproductive success. Scenarios with severe repeated disturbance (e.g., 95 percent probability of exposure, with 95 percent reduction in feeding efficiency) can severely reduce fecundity and calf survival, while a weaker disturbance (25 percent probability of exposure, with 25 percent reduction in feeding efficiency) had no population-wide effect on vital rates (Pirotta et al., 2019). Farmer et al. (2018a) modeled how an oil spill led to chronic declines in a sperm whale population over 10 years, and if models included even one more stressor (i.e., behavioral responses to air guns), the population declined even further. However, the amount of additional population decline due to acoustic disturbance depended on the way the dose-response of the noise levels were modeled. A single step-function led to higher impacts than a function with multiple steps and frequency weighting. In addition, the amount of impact from both disturbances was mediated when the metric in the model that described animal resilience was changed to increase resilience to disturbance (e.g., able to make up reserves through increased foraging). Not all stressors have the same impact for all species and all locations. Another model analyzed the effect of a number of chronic disturbances on two bottlenose dolphin populations in Australia over 5 years (Reed et al., 2020). Results indicated that disturbance from fisheries interactions and shipping noise had little overall impact on population abundances in either location, even in the most extreme impact scenarios modeled. At least in this area, other factors (e.g., epizootic scenarios) had the largest impact on population size and fecundity. Recurring stressors can impact population abundance even when individual instances of disturbance are short and have minimal behavioral impact on an individual. A model on California sea lions introduced a generalized disturbance at different times throughout the breeding cycle, with their behavior response being an increase in the duration of a foraging trip by the female (McHuron et al., 2018b). Very short duration disturbances or responses led to little change, particularly if the disturbance was a single event, and changes in the timing of the event in the year had little effect. However, with even relatively short disturbances or mild responses, when a disturbance was modeled as recurring there were resulting reductions in population size and pup recruitment (survival to age one). Often, the effects weren't noticeable for several years, as the impacts on pup survival did not affect the population until those pups were mature. Stranding and Mortality The definition for a stranding under title IV of the MMPA is an event in the wild in which (A) a marine mammal is dead and is (i) on a beach or shore of the United States; or (ii) in waters under the jurisdiction of the United States (including any navigable waters); or (B) a marine mammal is alive and is (i) on a beach or shore of the United States and is unable to return to the water; (ii) on a beach or shore of the United States and, although able to return to the water, is in need of apparent medical attention; or (iii) in the waters under the jurisdiction of the United States (including any navigable waters), but is unable to return to its natural habitat under its own power or without assistance (see 16 U.S.C. 1421h(6)). This definition is useful for considering stranding events even when they occur beyond lands and waters under the jurisdiction of the United States. Marine mammal strandings have been linked to a variety of causes, such as illness from exposure to infectious agents, biotoxins, or parasites; starvation; unusual oceanographic or weather events; or anthropogenic causes including fishery interaction, vessel strike, entrainment, entrapment, sound exposure, or combinations of these stressors sustained concurrently or in series. Historically, the cause or causes of most strandings have remained unknown (e.g., Odell et al., 1980), but the development of trained, professional stranding response networks and improved analyses have led to a greater understanding of marine mammal stranding causes (Simeone and Moore 2018). Numerous studies suggest that the physiology, behavior, habitat, social relationships, age, or condition of cetaceans may cause them to strand or might predispose them to strand when exposed to another phenomenon. These suggestions are consistent with the conclusions of numerous other studies that have demonstrated that combinations of dissimilar stressors commonly combine to kill an animal or dramatically reduce its fitness, even though one exposure without the other does not produce the same result (Bernaldo de Quiros et al., 2019; Chroussos, 2000; Creel, 2005 Fair and Becker, 2000; Foley et al., 2001; Moberg, 2000; Relyea, 2005a; 2005b, Romero, 2004; Sih et al., 2004). Historically, stranding reporting and response efforts have been inconsistent, although significant improvements have occurred over the last 25 years. Reporting forms for basic (``Level A'') information, rehabilitation disposition, and human interaction have been standardized nationally are available at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/level-data-collection-marine-mammal-stranding-events. However, data collected beyond basic information varies by region (and may vary from case to case) and are not standardized across the United States. Logistical conditions such as weather, time, location, and decomposition state may also affect the ability of the stranding network to thoroughly examine a specimen (Carretta et al., 2023; Moore et al., 2013). While the investigation of stranded animals provides insight into the types of threats marine mammal populations face, full investigations are only possible and conducted on a small fraction of the total number of strandings that occur, limiting our understanding of the causes of strandings (Carretta et al., 2016a). Additionally, and due to the variability in effort and data collected, the ability to interpret long-term trends in stranded marine mammals is complicated. In the United States from 2006-2022, there were 27,781 cetacean strandings and 79,572 pinniped strandings (107,353 total) (P. Onens, NMFS, pers comm., 2024). Several mass strandings (strandings that involve two or more individuals of the same species, excluding a single mother-calf pair) that have occurred over the past two decades have been associated with anthropogenic activities that introduced sound into the marine environment such as naval operations and seismic surveys. An in-depth discussion of strandings can be found in appendix D of the 2024 HCTT Draft EIS/OEIS and in the Navy's Technical Report on Marine Mammal Strandings Associated with U.S. Navy Sonar Activities (U.S. Navy Marine Mammal Program and Space and Naval Warfare Systems Command Center Pacific, 2017b). Worldwide, there have been several efforts to identify relationships between cetacean mass stranding events and [[Page 32198]] military active sonar (Cox et al., 2006, Hildebrand, 2004; Taylor et al., 2004). D'Amico et al. (2009) reviewed beaked whale stranding data compiled primarily from the published literature, which provides an incomplete record of stranding events, as many are not written up for publication, along with unpublished information from some regions of the world. Most of the stranding events reviewed by the IWC involved beaked whales. A mass stranding of goose-beaked whales in the eastern Mediterranean Sea occurred in 1996 (Frantzis, 1998), and mass stranding events involving Gervais' beaked whales, Blainville's beaked whales, and goose-beaked whales occurred off the coast of the Canary Islands in the late 1980s (Simmonds and Lopez-Jurado, 1991). The stranding events that occurred in the Canary Islands and Kyparissiakos Gulf in the late 1990s and the Bahamas in 2000 have been the most intensively-studied mass stranding events and have been associated with naval maneuvers involving the use of tactical sonar. Other cetacean species with naval sonar implicated in stranding events include harbor porpoise (Norman et al., 2004, Wright et al., 2013) and common dolphin (Jepson et al., 2013). Strandings Associated With Active Sonar Over the past 21 years, there have been 5 stranding events coincident with naval MFAS use in which exposure to sonar is believed to have been a contributing factor: Greece (1996); the Bahamas (2000); Madeira (2000); Canary Islands (2002); and Spain (2006) (Cox et al., 2006; Fernandez, 2006; U.S. Navy Marine Mammal Program and Space and Naval Warfare Systems Command Center Pacific, 2017). These five mass strandings have resulted in about 40 known cetacean deaths consisting mostly of beaked whales and with close linkages to MFAS activity. In these circumstances, exposure to non-impulsive acoustic energy was considered a potential indirect cause of death of the marine mammals (Cox et al., 2006). Only one of these stranding events, the Bahamas (2000), was associated with exercises conducted by the U.S. Navy. Additionally, in 2004, during the RIMPAC exercises, between 150 and 200 usually pelagic melon-headed whales occupied the shallow waters of Hanalei Bay, Kaua[revaps]i, Hawaii for over 28 hours. NMFS determined that MFAS was a plausible, if not likely, contributing factor in what may have been a confluence of events that led to the Hanalei Bay stranding. A number of other stranding events coincident with the operation of MFAS, including the death of beaked whales or other species (i.e., minke whales, dwarf sperm whales, pilot whales), have been reported; however, the majority have not been investigated to the degree necessary to determine the cause of the stranding. Most recently, the Independent Scientific Review Panel investigating potential contributing factors to a 2008 mass stranding of melon-headed whales in Antsohihy, Madagascar released its final report suggesting that the stranding was likely initially triggered by an industry seismic survey (Southall et al., 2013). This report suggests that the operation of a commercial high-powered 12 kHz multibeam echosounder during an industry seismic survey was a plausible and likely initial trigger that caused a large group of melon-headed whales to leave their typical habitat and then ultimately strand as a result of secondary factors such as malnourishment and dehydration. The report indicates that the risk of this particular convergence of factors and ultimate outcome is likely very low but recommends that the potential be considered in environmental planning. Because of the association between tactical MFAS use and a limited number of marine mammal strandings, the Navy and NMFS have been considering and addressing the potential for strandings in association with Navy activities for years. In addition to the proposed mitigation measures intended to more broadly minimize impacts to marine mammals, the Navy will abide by the Notification and Reporting Plan, which sets out notification, reporting, and other requirements when dead, injured, or stranded marine mammals are detected in certain circumstances. Greece (1996)-- Twelve goose-beaked whales stranded atypically (in both time and space) along a 23.7 mi (38.2 km) strand of the Kyparissiakos Gulf coast on May 12 and 13, 1996 (Frantzis, 1998). From May 11 through May 15, the North Atlantic Treaty Organization (NATO) research vessel Alliance was conducting sonar tests with signals of 600 Hz and 3 kHz and source levels of 228 and 226 dB re 1 [mu]Pa, respectively (D'Amico and Verboom, 1998; D'Spain et al., 2006). The timing and location of the testing encompassed the time and location of the strandings (Frantzis, 1998). Necropsies of eight of the animals were performed but were limited to basic external examination and sampling of stomach contents, blood, and skin. No ears or organs were collected, and no histological samples were preserved. No significant apparent abnormalities or wounds were found, however examination of photos of the animals, taken soon after their death, revealed that the eyes of at least four of the individuals were bleeding (Frantzis, 2004). Stomach contents contained the flesh of cephalopods, indicating that feeding had recently taken place (Frantzis, 1998). All available information regarding the conditions associated with this stranding event was compiled, and many potential causes were examined including major pollution events, prominent tectonic activity, unusual physical or meteorological events, magnetic anomalies, epizootics, and conventional military activities (International Council for the Exploration of the Sea, 2005). However, none of these potential causes coincided in time or space with the mass stranding or could explain its characteristics (International Council for the Exploration of the Sea, 2005). The robust condition of the animals, plus the recent stomach contents, is inconsistent with pathogenic causes. In addition, environmental causes can be ruled out as there were no unusual environmental circumstances or events before or during this time period and within the general proximity (Frantzis, 2004). Because of the rarity of this mass stranding of goose-beaked whales in the Kyparissiakos Gulf (first one in historical records), the probability for the two events (the military exercises and the strandings) to coincide in time and location, while being independent of each other, was thought to be extremely low (Frantzis, 1998). However, because full necropsies had not been conducted, and no abnormalities were noted, the cause of the strandings could not be precisely determined (Cox et al., 2006). A Bioacoustics Panel convened by NATO concluded that the evidence available did not allow them to accept or reject sonar exposures as a causal agent in these stranding events. The analysis of this stranding event provided support for, but no clear evidence for, the cause-and-effect relationship of tactical sonar training activities and beaked whale strandings (Cox et al., 2006). Bahamas (2000)-- NMFS and the Navy prepared a joint report addressing the multi- species stranding in the Bahamas in 2000, which took place within 24 hours of U.S. Navy ships using MFAS as they passed through the Northeast and Northwest Providence Channels on March 15-16, 2000. The ships, which operated both AN/SQS-53C and AN/ [[Page 32199]] SQS-56 sonar, moved through the channel while emitting pings approximately every 24 seconds. Of the 17 cetaceans that stranded over a 36-hour period (goose-beaked whales, Blainville's beaked whales, minke whales, and a spotted dolphin), 7 animals died on the beach (5 goose-beaked whales, 1 Blainville's beaked whale, and 1 spotted dolphin), while the other 10 were returned to the water alive (though their ultimate fate is unknown). As discussed in the Bahamas report (DOC/DON, 2001), there is no likely association between the minke whale and spotted dolphin strandings and the operation of MFAS. Necropsies were performed on five of the stranded beaked whales. All five necropsied beaked whales were in good body condition, showing no signs of infection, disease, vessel strike, blunt trauma, or fishery related injuries, and three still had food remains in their stomachs. Auditory structural damage was discovered in four of the whales, specifically bloody effusions or hemorrhaging around the ears. Bilateral intracochlear and unilateral temporal region subarachnoid hemorrhage, with blood clots in the lateral ventricles, were found in two of the whales. Three of the whales had small hemorrhages in their acoustic fats (located along the jaw and in the melon). A comprehensive investigation was conducted and all possible causes of the stranding event were considered, whether they seemed likely at the outset or not. Based on the way in which the strandings coincided with ongoing naval activity involving tactical MFAS use, in terms of both time and geography, the nature of the physiological effects experienced by the dead animals, and the absence of any other acoustic sources, the investigation team concluded that MFAS aboard U.S. Navy ships that were in use during the active sonar exercise in question were the most plausible source of this acoustic or impulse trauma to beaked whales. This sound source was active in a complex environment that included the presence of a surface duct, unusual and steep bathymetry, a constricted channel with limited egress, intensive use of multiple, active sonar units over an extended period of time, and the presence of beaked whales that appear to be sensitive to the frequencies produced by these active sonars. The investigation team concluded that the cause of this stranding event was the confluence of the Navy MFAS and these contributory factors working together and further recommended that the Navy avoid operating MFAS in situations where these five factors would be likely to occur. This report does not conclude that all five of these factors must be present for a stranding to occur, nor that beaked whales are the only species that could potentially be affected by the confluence of the other factors. Based on this, NMFS believes that the operation of MFAS in situations where surface ducts exist, or in marine environments defined by steep bathymetry and/or constricted channels may increase the likelihood of producing a sound field with the potential to cause cetaceans (especially beaked whales) to strand, and therefore, suggests the need for increased vigilance while operating MFAS in these areas, especially when beaked whales (or potentially other deep divers) are likely present. Madeira, Portugal (2000)-- From May 10-14, 2000, three goose-beaked whales were found stranded on two islands in the Madeira Archipelago, Portugal (Cox et al., 2006). A fourth animal was reported floating in the Madeiran waters by fisherman but did not come ashore (Ketten, 2005). Joint NATO amphibious training peacekeeping exercises involving participants from 17 countries and 80 warships, took place in Portugal during May 2-15, 2000. The bodies of the three stranded whales were examined postmortem (Ketten, 2005), though only one of the stranded whales was fresh enough (24 hours after stranding) to be necropsied (Cox et al., 2006). Results from the necropsy revealed evidence of hemorrhage and congestion in the right lung and both kidneys (Cox et al., 2006). There was also evidence of intracochlear and intracranial hemorrhage similar to that which was observed in the whales that stranded in the Bahamas event (Cox et al., 2006). There were no signs of blunt trauma, and no major fractures, and the cranial sinuses and airways were found to be clear with little or no fluid deposition, which may indicate good preservation of tissues (Woods Hole Oceanographic Institution, 2005). Several observations on the Madeira stranded beaked whales, such as the pattern of injury to the auditory system, are the same as those observed in the Bahamas strandings. Blood in and around the eyes, kidney lesions, pleural hemorrhages, and congestion in the lungs are particularly consistent with the pathologies from the whales stranded in the Bahamas and are consistent with stress and pressure related trauma. The similarities in pathology and stranding patterns between these two events suggest that a similar pressure event may have precipitated or contributed to the strandings at both sites (Woods Hole Oceanographic Institution, 2005). Even though no definitive causal link can be made between the stranding event and naval exercises, certain conditions may have existed in the exercise area that, in their aggregate, may have contributed to the marine mammal strandings (Freitas, 2004): Exercises were conducted in areas of at least 547 fathoms (1,000 m) depth near a shoreline where there is a rapid change in bathymetry on the order of 547 to 3,281 fathoms (1,000 to 6,000 m) occurring across a relatively short horizontal distance (Freitas, 2004); multiple ships were operating around Madeira, though it is not known if MFAS was used, and the specifics of the sound sources used are unknown (Cox et al., 2006; Freitas, 2004); and exercises took place in an area surrounded by landmasses separated by less than 35 nmi (65 km) and at least 10 nmi (19 km) in length, or in an embayment. Exercises involving multiple ships employing MFAS near land may produce sound directed towards a channel or embayment that may cut off the lines of egress for marine mammals (Freitas, 2004). Canary Islands, Spain (2002)-- The southeastern area within the Canary Islands is well known for aggregations of beaked whales due to its ocean depths of greater than 547 fathoms (1,000 m) within a few hundred meters of the coastline (Fernandez et al., 2005). On September 24, 2002, 14 beaked whales were found stranded on Fuerteventura and Lanzarote Islands in the Canary Islands (International Council for Exploration of the Sea, 2005a). Seven whales died, while the remaining seven live whales were returned to deeper waters (Fernandez et al., 2005). Four beaked whales were found stranded dead over the next three days either on the coast or floating offshore. These strandings occurred within close proximity of an international naval exercise that utilized MFAS and involved numerous surface warships and several submarines. Strandings began about four hours after the onset of MFAS activity (International Council for Exploration of the Sea, 2005a; Fernandez et al., 2005). Eight goose-beaked whales, one Blainville's beaked whale, and one Gervais' beaked whale were necropsied, six of them within 12 hours of stranding (Fernandez et al., 2005). No pathogenic bacteria were isolated from the carcasses (Jepson et al., 2003). The animals displayed severe vascular congestion and hemorrhage especially around the [[Page 32200]] tissues in the jaw, ears, brain, and kidneys, displaying marked disseminated microvascular hemorrhages associated with widespread fat emboli (Jepson et al., 2003; International Council for Exploration of the Sea, 2005a). Several organs contained intravascular bubbles, although definitive evidence of gas embolism in vivo is difficult to determine after death (Jepson et al., 2003). The livers of the necropsied animals were the most consistently affected organ, which contained macroscopic gas-filled cavities and had variable degrees of fibrotic encapsulation. In some animals, cavitary lesions had extensively replaced the normal tissue (Jepson et al., 2003). Stomachs contained a large amount of fresh and undigested contents, suggesting a rapid onset of disease and death (Fernandez et al., 2005). Head and neck lymph nodes were enlarged and congested, and parasites were found in the kidneys of all animals (Fernandez et al., 2005). The association of NATO MFAS use close in space and time to the beaked whale strandings, and the similarity between this stranding event and previous beaked whale mass strandings coincident with sonar use, suggests that a similar scenario and causative mechanism of stranding may be shared between the events. Beaked whales stranded in this event demonstrated brain and auditory system injuries, hemorrhages, and congestion in multiple organs, similar to the pathological findings of the Bahamas and Madeira stranding events. In addition, the necropsy results of the Canary Islands stranding event lead to the hypothesis that the presence of disseminated and widespread gas bubbles and fat emboli were indicative of nitrogen bubble formation, similar to what might be expected in decompression sickness (Jepson et al., 2003; Fern[aacute]ndez et al., 2005). Hanalei Bay (2004)-- On July 3 and 4, 2004, approximately 150 to 200 melon-headed whales occupied the shallow waters of Hanalei Bay, Kaua[revaps]i, Hawaii for over 28 hours. Attendees of a canoe blessing observed the animals entering Hanalei Bay in a single wave formation at 7 a.m. on July 3, 2004. The animals were observed moving back into the shore from the mouth of the Bay at 9 a.m. The usually pelagic animals milled in the shallow bay and were returned to deeper water with human assistance beginning at 9:30 a.m. on July 4, 2004, and were out of sight by 10:30 a.m. Only one animal, a calf, was known to have died following this event. The animal was noted alive and alone in Hanalei Bay on the afternoon of July 4, 2004, and was found dead in Hanalei Bay the morning of July 5, 2004. A full necropsy, magnetic resonance imaging, and computerized tomography examination were performed on the calf to determine the manner and cause of death. The combination of imaging, necropsy and histological analyses found no evidence of infectious, internal traumatic, congenital, or toxic factors. Cause of death could not be definitively determined, but it is likely that maternal separation, poor nutritional condition, and dehydration contributed to the final demise of the animal. Although it is not known when the calf was separated from its mother, the animals' movement into Hanalei Bay and subsequent milling and re-grouping may have contributed to the separation or lack of nursing, especially if the maternal bond was weak or this was an inexperienced mother with her first calf. Environmental factors, abiotic and biotic, were analyzed for any anomalous occurrences that would have contributed to the animals entering and remaining in Hanalei Bay. The Bay's bathymetry is similar to many other sites within the Hawaiian Island chain and dissimilar to sites that have been associated with mass strandings in other parts of the United States. The weather conditions appeared to be normal for that time of year with no fronts or other significant features noted. There was no evidence of unusual distribution, occurrence of predator or prey species, or unusual harmful algal blooms, although Mobley (2007) suggested that the full moon cycle that occurred at that time may have influenced a run of squid into the Bay. Weather patterns and bathymetry that have been associated with mass strandings elsewhere were not found to occur in this instance. The Hanalei Bay event was spatially and temporally correlated with RIMPAC. Official sonar training and tracking exercises in the PMRF warning area did not commence until approximately 8 a.m. on July 3 and were thus ruled out as a possible trigger for the initial movement into the bay. However, six naval surface vessels transiting to the operational area on July 2 intermittently transmitted active sonar (for approximately 9 hours total from 1:15 p.m. to 12:30 a.m.) as they approached from the south. The potential for these transmissions to have triggered the whales' movement into Hanalei Bay was investigated. Analyses with the information available indicated that animals to the south and east of Kaua[revaps]i could have detected active sonar transmissions on July 2 and reached Hanalei Bay on or before 7 a.m. on July 3. However, data limitations regarding the position of the whales prior to their arrival in Hanalei Bay, the magnitude of sonar exposure, behavioral responses of melon-headed whales to acoustic stimuli, and other possible relevant factors preclude a conclusive finding regarding the role of sonar in triggering this event. Propagation modeling suggests that transmissions from sonar use during the July 3 exercise in the PMRF warning area may have been detectable at the mouth of the Hanalei Bay. If the animals responded negatively to these signals, it may have contributed to their continued presence in Hanalei Bay. The U.S. Navy ceased all active sonar transmissions during exercises in this range on the afternoon of July 3. Subsequent to the cessation of sonar use, the animals were herded out of Hanalei Bay. While causation of this stranding event may never be unequivocally determined, NMFS considers the active sonar transmissions of July 2-3, 2004 a plausible, if not likely, contributing factor in what may have been a confluence of events. This conclusion is based on the following: (1) the evidently anomalous nature of the stranding; (2) its close spatiotemporal correlation with wide-scale, sustained use of sonar systems previously associated with stranding of deep-diving marine mammals; (3) the directed movement of two groups of transmitting vessels toward the southeast and southwest coast of Kaua[revaps]i; (4) the results of acoustic propagation modeling and an analysis of possible animal transit times to the bay; and (5) the absence of any other compelling causative explanation. The initiation and persistence of this event may have resulted from an interaction of biological and physical factors. The biological factors may have included the presence of an apparently uncommon, deep-diving cetacean species (and possibly an offshore, non-resident group), social interactions among the animals before or after they entered the Bay, and/or unknown predator or prey conditions. The physical factors may have included the presence of nearby deep water, multiple vessels transiting in a directed manner while transmitting active sonar over a sustained period, the presence of surface sound ducting conditions, and/or intermittent and random human interactions while the animals were in Hanalei Bay. A separate event involving melon-headed whales and rough-toothed dolphins took place over the same period of time in the Northern Mariana [[Page 32201]] Islands (Jefferson et al., 2006), which is several thousand miles from Hawaii. Some 500 to 700 melon-headed whales came into Sasanhaya Bay on July 4, 2004, near the island of Rota and then left of their own accord after 5.5 hours; no known active sonar transmissions occurred in the vicinity of that event. The Rota incident led to scientific debate regarding what, if any, relationship the event had to the simultaneous events in Hawaii and whether they might be related by some common factor (e.g., there was a full moon on July 2, 2004, as well as during other melon-headed whale strandings and nearshore aggregations (Brownell et al., 2009; Lignon et al., 2007; Mobley, 2007). Brownell et al. (2009) compared the two incidents, along with one other stranding incident at Nuka Hiva in French Polynesia and normal resting behaviors observed at Palmyra Island, in regard to physical features in the areas, melon-headed whale behavior, and lunar cycles. Brownell et al., (2009) concluded that the rapid entry of the whales into Hanalei Bay, their movement into very shallow water far from the 328-ft (100-m) contour, their milling behavior (typical pre-stranding behavior), and their reluctance to leave the bay constituted an unusual event that was not similar to the events that occurred at Rota, which appear to be similar to observations of melon-headed whales resting normally at Palmyra Island. Additionally, there was no correlation between lunar cycle and the types of behaviors observed in the Brownell et al. (2009) examples. Spain (2006)-- The Spanish Cetacean Society reported an atypical mass stranding of four beaked whales that occurred January 26, 2006, on the southeast coast of Spain, near Moj[aacute]car (Gulf of Vera) in the Western Mediterranean Sea. According to the report, two of the whales were discovered the evening of January 26 and were found to be still alive. Two other whales were discovered during the day on January 27 but had already died. The first three animals were located near the town of Moj[aacute]car and the fourth animal was found dead, a few kilometers north of the first three animals. From January 25-26, 2006, Standing NATO Response Force Maritime Group Two (five of seven ships including one U.S. ship under NATO Operational Control) had conducted active sonar training against a Spanish submarine within 50 nmi (93 km) of the stranding site. Veterinary pathologists necropsied the two male and two female goose-beaked whales. According to the pathologists, the most likely primary cause of this type of beaked whale mass stranding event was anthropogenic acoustic activities, most probably anti-submarine MFAS used during the military naval exercises. However, no positive acoustic link was established as a direct cause of the stranding. Even though no causal link can be made between the stranding event and naval exercises, certain conditions may have existed in the exercise area that, in their aggregate, may have contributed to the marine mammal strandings (Freitas, 2004). Exercises were conducted in areas of at least 547 fathoms (1,000 m) depth near a shoreline where there is a rapid change in bathymetry on the order of 547 to 3,281 fathoms (1,000 to 6,000 m) occurring across a relatively short horizontal distance (Freitas, 2004). Multiple ships (in this instance, five) were operating MFAS in the same area over extended periods of time (in this case, 20 hours) in close proximity; and exercises took place in an area surrounded by landmasses, or in an embayment. Exercises involving multiple ships employing MFAS near land may have produced sound directed towards a channel or embayment that may have cut off the lines of egress for the affected marine mammals (Freitas, 2004). Honaunau Bay (2022)-- On March 25, 2022, a beaked whale (species unknown) stranded in Honaunau Bay, Hawaii. The animal was observed swimming into shore and over rocks. Bystanders intervened to turn the animal off of the rocks, and it swam back out of Honaunau Bay on its own. Locals reported hearing a siren or alarm type of sound underwater on the same day, and a Navy vessel was observed from shore on the following day. The Navy confirmed it used CAS within 27 nmi (50 km) and 48 hours of the time of stranding, though the stranding has not been definitively linked to the Navy's CAS use, and there is no evidence to determine whether the animal had any further short- or long-term effects. Behaviorally Mediated Responses to MFAS That May Lead to Stranding Although the confluence of Navy MFAS with the other contributory factors noted in the 2001 NMFS/Navy joint report was identified as the cause of the 2000 Bahamas stranding event, the specific mechanisms that led to that stranding (or the others) are not well understood, and there is uncertainty regarding the ordering of effects that led to the stranding. It is unclear whether beaked whales were directly injured by sound (e.g., acoustically mediated bubble growth, as addressed above) prior to stranding or whether a behavioral response to sound occurred that ultimately caused the beaked whales to be injured and strand. Although causal relationships between beaked whale stranding events and active sonar remain unknown, several authors have hypothesized that stranding events involving these species in the Bahamas and Canary Islands may have been triggered when the whales changed their dive behavior in a startled response to exposure to active sonar or to further avoid exposure (Cox et al., 2006; Rommel et al., 2006). These authors proposed three mechanisms by which the behavioral responses of beaked whales upon being exposed to active sonar might result in a stranding event. These include the following: gas bubble formation caused by excessively fast surfacing; remaining at the surface too long when tissues are supersaturated with nitrogen; or diving prematurely when extended time at the surface is necessary to eliminate excess nitrogen. More specifically, beaked whales that occur in deep waters that are in close proximity to shallow waters (for example, the ``canyon areas'' that are cited in the Bahamas stranding event; see D'Spain and D'Amico, 2006), may respond to active sonar by swimming into shallow waters to avoid further exposures and strand if they were not able to swim back to deeper waters. Second, beaked whales exposed to active sonar might alter their dive behavior. Changes in their dive behavior might cause them to remain at the surface or at depth for extended periods of time which could lead to hypoxia directly by increasing their oxygen demands or indirectly by increasing their energy expenditures (to remain at depth) and increase their oxygen demands as a result. If beaked whales are at depth when they detect a ping from an active sonar transmission and change their dive profile, this could lead to the formation of significant gas bubbles, which could damage multiple organs or interfere with normal physiological function (Cox et al., 2006; Rommel et al., 2006; Zimmer and Tyack, 2007). Baird et al. (2006) found that slow ascent rates from deep dives and long periods of time spent within 164 ft (50 m) of the surface were typical for both goose-beaked and Blainville's beaked whales, the two species involved in mass strandings related to naval sonar. These two behavioral mechanisms may be necessary to purge excessive dissolved nitrogen concentrated in their tissues during [[Page 32202]] their frequent long dives (Baird et al., 2005). Baird et al. (2005) further suggests that abnormally rapid ascents or premature dives in response to high-intensity sonar could indirectly result in physical harm to the beaked whales, through the mechanisms described above (gas bubble formation or non-elimination of excess nitrogen). In a review of the previously published data on the potential impacts of sonar on beaked whales, Bernaldo de Quir[oacute]s et al. (2019) suggested that the effect of MFAS on beaked whales varies among individuals or populations, and that predisposing conditions such as previous exposure to sonar and individual health risk factors may contribute to individual outcomes (e.g., decompression sickness). Because many species of marine mammals make repetitive and prolonged dives to great depths, it has long been assumed that marine mammals have evolved physiological mechanisms to protect against the effects of rapid and repeated decompressions. Although several investigators have identified physiological adaptations that may protect marine mammals against nitrogen gas supersaturation (i.e., alveolar collapse and elective circulation; Kooyman et al., 1972; Ridgway and Howard, 1979), Ridgway and Howard (1979) reported that bottlenose dolphins that were trained to dive repeatedly had muscle tissues that were substantially supersaturated with nitrogen gas. Houser et al. (2001b) used these data to model the accumulation of nitrogen gas within the muscle tissue of other marine mammal species and concluded that cetaceans that dive deep and have slow ascent or descent speeds would have tissues that are more supersaturated with nitrogen gas than other marine mammals. Based on these data, Cox et al. (2006) hypothesized that a critical dive sequence might make beaked whales more prone to stranding in response to acoustic exposures. The sequence began with (1) very deep (to depths as deep as 1.2 mi (2 km)) and long (as long as 90 minutes) foraging dives; (2) relatively slow, controlled ascents; and (3) a series of ``bounce'' dives between 328 and 1,312 ft (100 and 400 m) in depth (see Zimmer and Tyack, 2007). They concluded that acoustic exposures that disrupted any part of this dive sequence (for example, causing beaked whales to spend more time at surface without the bounce dives that are necessary to recover from the deep dive) could produce excessive levels of nitrogen supersaturation in their tissues, leading to gas bubble and emboli formation that produces pathologies similar to decompression sickness. Zimmer and Tyack (2007) modeled nitrogen tension and bubble growth in several tissue compartments for several hypothetical dive profiles and concluded that repetitive shallow dives (defined as a dive where depth does not exceed the depth of alveolar collapse, approximately 236 ft (72 m) for goose-beaked whale), perhaps as a consequence of an extended avoidance response to sonar sound, could pose a risk for decompression sickness and that this risk should increase with the duration of the response. Their models also suggested that unrealistically rapid rates of ascent from normal dive behaviors are unlikely to result in supersaturation to the extent that bubble formation would be expected. Tyack et al. (2006) suggested that emboli observed in animals exposed to mid-frequency range sonar (Jepson et al., 2003; Fernandez et al., 2005) could stem from a behavioral response that involves repeated dives shallower than the depth of lung collapse. Given that nitrogen gas accumulation is a passive process (i.e., nitrogen is metabolically inert), a bottlenose dolphin was trained to repetitively dive a profile predicted to elevate nitrogen saturation to the point that nitrogen bubble formation was predicted to occur. However, inspection of the vascular system of the dolphin via ultrasound did not demonstrate the formation of asymptomatic nitrogen gas bubbles (Houser et al., 2010). Baird et al. (2008), in a beaked whale tagging study off Hawaii, showed that deep dives are equally common during day or night, but ``bounce dives'' are typically a daytime behavior, possibly associated with visual predator avoidance. This may indicate that ``bounce dives'' are associated with something other than behavioral regulation of dissolved nitrogen levels, which would be necessary day and night. Additional predictive modeling conducted to date has been performed with many unknowns about the respiratory physiology of deep-diving breath-hold animals. For example, Denk et al. (2020) found intra- species differences in the compliance of tracheobronchial structures of post-mortem cetaceans and pinnipeds under diving hydrostatic pressures, which would affect depth of alveolar collapse. Although, as hypothesized by Garcia Parraga et al. (2018) and reviewed in Fahlman et al., (2021), mechanisms may exist that allow marine mammals to create a pulmonary shunt without the need for hydrostatic pressure-induced lung collapse (i.e., by varying perfusion to the lung independent of lung collapse and degree of ventilation). If such a mechanism exists, then assumptions in prior gas models require reconsideration, the degree of nitrogen gas accumulation associated with dive profiles needs to be re- evaluated, and behavioral responses potentially leading to a destabilization of the relationship between pulmonary ventilation and perfusion should be considered. Costidis and Rommel (2016) suggested that gas exchange may continue to occur across the tissues of air- filled sinuses in deep diving odontocetes below the depth of lung collapse if hydrostatic pressures are high enough to drive gas exchange across into non-capillary veins. If marine mammals respond to an Action Proponent vessel that is transmitting active sonar in the same way that they might respond to a predator, their probability of flight responses could increase when they perceive that Action Proponent vessels are approaching them directly, because a direct approach may convey detection and intent to capture (Burger and Gochfeld, 1981, 1990; Cooper, 1997; Cooper, 1998). The probability of flight responses could also increase as received levels of active sonar increase (and the ship is, therefore, closer) and as ship speeds increase (that is, as approach speeds increase). For example, the probability of flight responses in ringed seals (Born et al., 1999), Pacific brant (Branta bernicla nigricans) and Canada geese (B. canadensis) increased as a helicopter or fixed-wing aircraft approached groups of these animals more directly (Ward et al., 1999). Bald eagles (Haliaeetus leucocephalus) perched on trees alongside a river were also more likely to flee from a paddle raft when their perches were closer to the river or were closer to the ground (Steidl and Anthony, 1996). Despite the many theories involving bubble formation (both as a direct cause of injury (see Non-Auditory Injury section) and an indirect cause of stranding), Southall et al. (2007) summarizes that there is either scientific disagreement or a lack of information regarding each of the following important points: (1) received acoustical exposure conditions for animals involved in stranding events; (2) pathological interpretation of observed lesions in stranded marine mammals; (3) acoustic exposure conditions required to induce such physical trauma directly; (4) whether noise exposure may cause behavioral responses (e.g., atypical diving behavior) that secondarily cause bubble formation and tissue damage; and (5) the extent the post mortem artifacts introduced by [[Page 32203]] decomposition before sampling, handling, freezing, or necropsy procedures affect interpretation of observed lesions. Strandings Associated With Explosive Use Silver Strand (2011)-- During a Navy training event on March 4, 2011, at the Silver Strand Training Complex in San Diego, California, three or possibly four dolphins were killed in an explosion. During an underwater detonation training event, a pod of 100 to 150 long-beaked common dolphins were observed moving towards the 700-yard (yd) (640.1-m) exclusion zone around the explosive charge, monitored by personnel in a safety boat and participants in a dive boat. Approximately 5 minutes remained on a time-delay fuse connected to a single 8.76 lb (3.97 kg) explosive charge (C-4 and detonation cord). Although the dive boat was placed between the pod and the explosive in an effort to guide the dolphins away from the area, that effort was unsuccessful and three long-beaked common dolphins near the explosion died. The Navy recovered those animals and transferred them to the local stranding network for necropsy. In addition to the three dolphins found dead on March 4, the remains of a fourth dolphin were discovered on March 7, 2011, near Oceanside, California (3 days later and approximately 42 mi (68 km) north of the detonation), which might also have been related to this event. Upon necropsy, all four animals were found to have sustained typical mammalian primary blast injuries (Danil and St. Leger, 2011). Association of the fourth stranding with the training event is uncertain because dolphins strand on a regular basis in the San Diego area. Details such as the dolphins' depth and distance from the explosive at the time of the detonation could not be estimated from the 250 yd (228.6 m) standoff point of the observers in the dive boat or the safety boat. These dolphin mortalities are the only known occurrence of a Navy training or testing event involving impulsive energy (underwater detonation) that caused mortality or injury to a marine mammal. Despite this being a rare occurrence, the Navy reviewed training requirements, safety procedures, and possible mitigation measures and implemented changes to reduce the potential for this to occur in the future. Discussions of procedures associated with underwater explosives training and other training events are presented in the Proposed Mitigation Measures section. Kyle of Durness, Scotland (2011)-- On July 22, 2011, a mass stranding event involving long-finned pilot whales occurred at Kyle of Durness, Scotland. An investigation by Brownlow et al. (2015) considered unexploded ordnance detonation activities at a Ministry of Defense bombing range, conducted by the Royal Navy prior to and during the strandings, as a plausible contributing factor in the mass stranding event. While Brownlow et al. (2015) concluded that the serial detonations of underwater ordnance were an influential factor in the mass stranding event (along with the presence of a potentially compromised animal and navigational error in a topographically complex region), they also suggest that mitigation measures--which included observations from a zodiac only and by personnel not experienced in marine mammal observation, among other deficiencies--were likely insufficient to assess if cetaceans were in the vicinity of the detonations. The authors also cite information from the Ministry of Defense indicating ``an extraordinarily high level of activity'' (i.e., frequency and intensity of underwater explosions) on the range in the days leading up to the stranding. Strandings on the Hawaii and California Coasts Stranded marine mammals are reported along the Hawaii and California coasts each year. Marine mammals strand due to natural or anthropogenic causes, and the majority of reported type of occurrences in marine mammal strandings in this region include fishery interactions, illness, predation, and vessel strikes (Carretta et al., 2024). Potential Effects of Vessel Strike Vessel strikes of marine mammals can result in death or serious injury of the animal. Wounds resulting from vessel strike may include massive trauma, hemorrhaging, broken bones, or propeller lacerations (Knowlton and Kraus, 2001). An animal at the surface could be struck directly by a vessel, a surfacing animal could hit the bottom of a vessel, or an animal just below the surface could be cut by a vessel's propeller. Superficial strikes may not kill or result in the death of the animal. Lethal interactions are typically associated with large whales, which are occasionally found draped across the bulbous bow of large commercial ships upon arrival in port. Although smaller cetaceans are more maneuverable in relation to large vessels than are large whales, they may also be susceptible to strike. The severity of injuries typically depends on the size and speed of the vessel (Knowlton and Kraus, 2001; Laist et al., 2001; Vanderlaan and Taggart, 2007; Conn and Silber, 2013). Impact forces increase with speed, as does the probability of a strike at a given distance (Silber et al., 2010; Gende et al., 2011). The most vulnerable marine mammals are those that spend extended periods of time at the surface in order to restore oxygen levels within their tissues after deep dives (e.g., the sperm whale; Jaquet and Whitehead, 1996; Watkins et al., 1999). In addition, some baleen whales seem generally unresponsive to vessel sound, making them more susceptible to vessel strikes (Nowacek et al., 2004). These species are primarily large, slow moving whales. Marine mammal responses to vessels may include avoidance and changes in dive pattern (NRC, 2003). Wounds resulting from vessel strike may include massive trauma, hemorrhaging, broken bones, or propeller lacerations (Knowlton and Kraus, 2001). An animal at the surface could be struck directly by a vessel, a surfacing animal could hit the bottom of a vessel, or an animal just below the surface could be cut by a vessel's propeller. Impact forces increase with speed as does the probability of a strike at a given distance (Silber et al., 2010; Gende et al., 2011). An examination of all known vessel strikes from all shipping sources (civilian and military) indicates vessel speed is a principal factor in whether a vessel strike results in death or serious injury (Knowlton and Kraus, 2001; Laist et al., 2001; Jensen and Silber, 2003; Pace and Silber, 2005; Vanderlaan and Taggart, 2007). In assessing records in which vessel speed was known, Laist et al. (2001) found a direct relationship between the occurrence of a whale strike and the speed of the vessel involved in the collision. The authors concluded that most deaths occurred when a vessel was traveling in excess of 13 kn (24 km/ hr). Jensen and Silber (2003) detailed 292 records of known or probable vessel strikes of all large whale species from 1975 to 2002. Of these, vessel speed at the time of collision was reported for 58 cases. Of these 58 cases, 39 (or 67 percent) resulted in serious injury or death (19 of those resulted in serious injury as determined by blood in the water, propeller gashes, or severed tailstock, and fractured skull, jaw, vertebrae, hemorrhaging, massive bruising or other injuries noted during necropsy, and 20 resulted in death). [[Page 32204]] Operating speeds of vessels that struck various species of large whales ranged from 2 to 51 kn (3.7 to 94.5 km/hr). The majority (79 percent) of these strikes occurred at speeds of 13 kn (24 km/hr) or greater. The average speed that resulted in serious injury or death was 18.6 kn (34.4 km/hr). Pace and Silber (2005) found that the probability of death or serious injury increased rapidly with increasing vessel speed. Specifically, the predicted probability of serious injury or death increased from 45 to 75 percent as vessel speed increased from 10 to 14 kn (18.5 to 25.9 km/hr) and exceeded 90 percent at 17 kn (31.5 km/hr). Higher speeds during strikes result in greater force of impact and also appear to increase the chance of severe injuries or death. While modeling studies have suggested that hydrodynamic forces pulling whales toward the vessel hull increase with increasing speed (Clyne, 1999; Knowlton et al., 1995), this is inconsistent with Silber et al. (2010), which demonstrated that there is no such relationship (i.e., hydrodynamic forces are independent of speed). In a separate study, Vanderlaan and Taggart (2007) analyzed the probability of lethal mortality of large whales at a given speed, showing that the greatest rate of change in the probability of a lethal injury to a large whale as a function of vessel speed occurs between 8.6 and 15 kn (15.9 and 27.8 km/hr). The chances of a lethal injury decline from approximately 80 percent at 15 kn to approximately 20 percent at 8.6 kn (15.9 km/hr). At speeds below 11.8 kn (21.9 km/hr), the chances of lethal injury drop below 50 percent, while the probability asymptotically increases toward 100 percent above 15 kn (27.8 km/hr). Garrison et al. (2025) reviewed and updated available data on whale-vessel interactions in U.S. waters to determine the effects of vessel speed and size on lethality of strikes of large whales and found vessel size class had a significant effect on the probability of lethality. Decreasing vessel speeds reduced the likelihood of a lethal outcome for all vessel size classes modeled, with the strongest effect for vessels less than 354 ft (108 m) long. Notably, the probability that a strike by a very large (i.e., in length) vessel will be lethal exceeded 0.80 at all speeds greater than 5 kn (9.26 km/hr) (Garrison et al., 2025). The Jensen and Silber (2003) report notes that the database represents a minimum number of strikes, because the vast majority probably goes undetected or unreported. In contrast, Action Proponent vessels are likely to detect any strike that does occur because of the required personnel training and Lookouts (as described in the Proposed Mitigation Measures section), and they are required to report all vessel strikes involving marine mammals. In the HCTT Study Area, commercial traffic is heaviest in the nearshore waters, near major ports and in the shipping lanes along the California coast and in Hawaii (specifically Honolulu), including a lane of high intensity farther off the California coast running northwest-southeast, which is a great circle route between the Panama Canal and Asia. Military vessel traffic is primarily concentrated in the waters off San Diego, CA, and the coasts of the Hawaiian islands, particularly south of O[revaps]ahu and east of Hawaii Island (Navy 2025, unpublished data). In the SOCAL portion of the Study Area, the U.S. Navy has struck a total of 19 marine mammals in the 32-year period from 1993 through 2025, an average of just under one per year. The species struck include gray whale, humpback whale, blue whale, and either fin or sei whale, though for some strikes, the species could not be determined. In the HRC portion of the Study Area, the Navy struck a total of five marine mammals in the 22-year period from 1993 through 2025, an average of zero to one strikes per year. The Coast Guard has had one known marine mammal strike in Hawaii, a humpback whale in 2020. Of the five Navy vessel strikes over the 22-year period in the HRC, all were reported as injuries. The vessel struck species include: one humpback whale in 1998, one unknown species and one humpback whale in 2003, one sperm whale in 2007, and an unknown species in 2008. No more than two whales were struck by Navy vessels in any given year in the HRC portion of the HSTT within the last 32 years. Between 2007 and 2009, the Navy developed and distributed additional training, mitigation, and reporting tools to Navy operators to improve marine mammal protection and to ensure compliance with permit requirements. In 2009, the Navy implemented Marine Species Awareness Training designed to improve effectiveness of visual observation for marine mammals and other marine resources. In subsequent years, the Navy issued refined policy guidance on vessel strikes in order to collect the most accurate and detailed data possible in response to a possible incident (also see the Notification and Reporting Plan for this proposed rule). For over a decade, the Navy has implemented the Protective Measures Assessment Protocol software tool, which provides operators with notification of the required mitigation and a visual display of the planned training or testing activity location overlaid with relevant environmental data. Marine Mammal Habitat The proposed training and testing activities could potentially affect marine mammal habitat through the introduction of impacts to the prey species of marine mammals, acoustic habitat (sound in the water column), water quality, and biologically important habitat for marine mammals. Each of these potential effects was considered in the 2024 HCTT Draft EIS/OEIS and was determined not to have adverse effects on marine mammal habitat. Based on the information below and the supporting information included in the 2024 HCTT Draft EIS/OEIS, NMFS has determined that the proposed training and testing activities would not have adverse or long-term impacts on marine mammal habitat. Effects to Prey Sound may affect marine mammals through impacts on the abundance, behavior, or distribution of prey species (e.g., crustaceans, cephalopods, fish, zooplankton). Marine mammal prey varies by species, season, and location and, for some species, is not well-documented. Here, we describe studies regarding the effects of noise on known marine mammal prey. Fish utilize the soundscape and components of sound in their environment to perform important functions such as foraging, predator avoidance, mating, and spawning (e.g., Zelick et al., 1999; Fay, 2009). The most likely effects on fishes exposed to loud, intermittent, low- frequency sounds are behavioral responses (i.e., flight or avoidance). Short duration, sharp sounds (such as pile driving or air guns) can cause overt or subtle changes in fish behavior and local distribution. The response of fish to acoustic sources depends on the physiological state of the fish, past exposures, motivation (e.g., feeding, spawning, migration), and other environmental factors. Key impacts to fishes may include behavioral responses, hearing damage, barotrauma (i.e., pressure-related injuries), and mortality. While it is clear that the behavioral responses of individual prey, such as displacement or other changes in distribution, can have direct impacts on the foraging success of marine mammals, the effects on marine mammals of individual prey that experience hearing damage, barotrauma, or mortality is less clear, [[Page 32205]] though obviously population scale impacts that meaningfully reduce the amount of prey available could have more serious impacts. Fishes, like other vertebrates, have a variety of different sensory systems to glean information from ocean around them (Astrup and Mohl, 1993; Astrup, 1999; Braun and Grande, 2008; Carroll et al., 2017; Hawkins and Johnstone, 1978; Ladich and Popper, 2004; Ladich and Schulz-Mirbach, 2016; Mann, 2016; Nedwell et al., 2004; Popper et al., 2003; Popper et al., 2005). Depending on their hearing anatomy and peripheral sensory structures, which vary among species, fishes hear sounds using pressure and particle motion sensitivity capabilities and detect the motion of surrounding water (Fay et al., 2008), while terrestrial vertebrates generally only detect pressure. Most marine fishes primarily detect particle motion using the inner ear and lateral line system, while some fishes possess additional morphological adaptations or specializations that can enhance their sensitivity to sound pressure, such as a gas-filled swim bladder (Braun and Grande, 2008; Popper and Fay, 2011). Hearing capabilities vary considerably between different fish species with data only available for just over 100 species out of the 34,000 marine and freshwater fish species (Eschmeyer and Fong, 2016). In order to better understand acoustic impacts on fishes, fish hearing groups are defined by species that possess a similar continuum of anatomical features which result in varying degrees of hearing sensitivity (Popper and Hastings, 2009a). There are four hearing groups defined for all fish species (modified from Popper et al., 2014) within this analysis and they include: fishes without a swim bladder (e.g., flatfish, sharks, rays, etc.); fishes with a swim bladder not involved in hearing (e.g., salmon, cod, pollock, etc.); fishes with a swim bladder involved in hearing (e.g., sardines, anchovy, herring, etc.); and fishes with a swim bladder involved in hearing and high-frequency hearing (e.g., shad and menhaden). Most marine mammal fish prey species would not be likely to perceive or hear mid- or high-frequency sonars. While hearing studies have not been done on sardines and northern anchovies, it would not be unexpected for them to possess hearing similarities to Pacific herring (up to 2-5 kHz) (Mann et al., 2005). Currently, less data are available to estimate the range of best sensitivity for fishes without a swim bladder. In terms of physiology, multiple scientific studies have documented a lack of mortality or physiological effects to fish from exposure to low- and mid-frequency sonar and other sounds (Cox et al., 2018; Halvorsen et al., 2012; J[oslash]rgensen et al., 2005; Kane et al., 2010; Kvadsheim and Sevaldsen, 2005; Popper et al., 2007; Popper et al., 2016; Watwood et al., 2016). Techer et al. (2017) exposed carp in floating cages for up to 30 days to low-power 23 and 46 kHz sources without any significant physiological response. Other studies have documented either a lack of TTS in species whose hearing range cannot perceive military sonar, or for those species that could perceive sonar-like signals, any TTS experienced would be recoverable (Halvorsen et al., 2012; Ladich and Fay, 2013; Popper and Hastings, 2009a, 2009b; Popper et al., 2014; Smith, 2016). Only fishes that have specializations that enable them to hear sounds above about 2,500 Hz (2.5 kHz) such as herring (Halvorsen et al., 2012; Mann et al., 2005; Mann, 2016; Popper et al., 2014) would have the potential to receive TTS or exhibit behavioral responses from exposure to mid-frequency sonar. In addition, any sonar induced TTS to fish whose hearing range could perceive sonar would only occur in the narrow spectrum of the source (e.g., 3.5 kHz) compared to the fish's total hearing range (e.g., 0.01 kHz to 5 kHz). Overall, military sonar sources are much narrower in terms of source frequency compared to a given fish species full hearing range (Halvorsen et al., 2012; J[oslash]rgensen et al., 2005; Juanes et al., 2017; Kane et al., 2010; Kvadsheim and Sevaldsen, 2005; Popper et al., 2007; Popper and Hawkins, 2016; Watwood et al., 2016). In terms of behavioral responses, Juanes et al. (2017) discuss the potential for negative impacts from anthropogenic soundscapes on fish, but the author's focus was on broader based sounds such as ship and boat noise sources. Watwood et al. (2016) also documented no behavioral responses by reef fish after exposure to MFAS. Doksaeter et al. (2009; 2012) reported no behavioral responses to mid-frequency naval sonar by Atlantic herring; specifically, no escape responses (vertically or horizontally) were observed in free swimming herring exposed to mid- frequency sonar transmissions. Based on these results (Doksaeter et al., 2009; Doksaeter et al., 2012; Sivle et al., 2012), Sivle et al. (2015) created a model in order to report on the possible population- level effects on Atlantic herring from active naval sonar. The authors concluded that the use of naval sonar poses little risk to populations of herring regardless of season, even when the herring populations are aggregated and directly exposed to sonar. Finally, Bruintjes et al. (2016) commented that fish exposed to any short-term noise within their hearing range might initially startle, but would quickly return to normal behavior. Occasional behavioral responses to intermittent explosions and impulsive sound sources are unlikely to cause long-term consequences for individual fish or populations. Fish that experience hearing loss as a result of exposure to explosions and impulsive sound sources may have a reduced ability to detect relevant sounds such as predators, prey, or social vocalizations. However, PTS has not been known to occur in fishes and any hearing loss in fish may be as temporary as the timeframe required to repair or replace the sensory cells that were damaged or destroyed (Popper et al., 2005; Popper et al., 2014; Smith et al., 2006). It is not known if damage to auditory nerve fibers could occur, and if so, whether fibers would recover during this process. It is also possible for fish to be injured or killed by an explosion in the immediate vicinity of the surface from dropped or fired ordnance, or near the bottom from shallow water bottom-placed underwater mine warfare detonations. Physical effects from pressure waves generated by underwater sounds (e.g., underwater explosions) could potentially affect fish within proximity of training or testing activities. SPLs of sufficient strength have been known to cause injury to fish and fish mortality (summarized in Popper et al., 2014). The shock wave from an underwater explosion is lethal to fish at close range, causing massive organ and tissue damage and internal bleeding (Keevin and Hempen, 1997). At greater distance from the detonation point, the extent of mortality or injury depends on a number of factors including fish size, body shape, orientation, and species (Keevin and Hempen, 1997; Wright, 1982). At the same distance from the source, larger fish are generally less susceptible to death or injury, elongated forms that are round in cross-section are less at risk than deep-bodied forms, and fish oriented sideways to the blast suffer the greatest impact (Edds-Walton and Finneran, 2006; O'Keeffe, 1984; O'Keeffe and Young, 1984; Wiley et al., 1981; Yelverton et al., 1975). Species with gas-filled organs are more susceptible to injury and mortality than those without them (Gaspin, 1975; Gaspin et al., 1976; Goertner et al., 1994). Barotrauma injuries have been documented during controlled exposure to impact pile driving (an impulsive noise source, as are explosives and air [[Page 32206]] guns) (Halvorsen et al., 2012b; Casper et al., 2013). Fish not killed or driven from a location by an explosion might change their behavior, feeding pattern, or distribution. Changes in behavior of fish have been observed as a result of sound produced by explosives, with effect intensified in areas of hard substrate (Wright, 1982). However, Navy explosive use avoids hard substrate to the best extent practical during underwater detonations, or deep-water surface detonations. Stunning from pressure waves could also temporarily immobilize fish, making them more susceptible to predation. The abundances of various fish (and invertebrates) near the detonation point for explosives could be altered for a few hours before animals from surrounding areas repopulate the area. However, these populations would likely be replenished as waters near the detonation point are mixed with adjacent waters. Repeated exposure of individual fish to sounds from underwater explosions is not likely and exposures are expected to be short-term and localized. Long-term consequences for fish populations would not be expected. Several studies have demonstrated that air gun sounds might affect the distribution and behavior of some fishes, potentially impacting foraging opportunities or increasing energetic costs (e.g., Fewtrell and McCauley, 2012; Pearson et al., 1992; Skalski et al., 1992; Santulli et al., 1999; Paxton et al., 2017). For fishes exposed to military sonar, there would be limited sonar use spread out in time and space across large offshore areas such that only small areas are actually ensonified (tens of miles) compared to the total life history distribution of fish prey species. There would be no probability for mortality or physical injury from sonar, and for most species, no or little potential for hearing or behavioral effects, except to a few select fishes with hearing specializations (e.g., herring) that could perceive mid-frequency sonar. Training and testing exercises involving explosions are dispersed in space and time; therefore, repeated exposure of individual fishes is unlikely. Mortality and injury effects to fishes from explosives would be localized around the area of a given in-water explosion, but only if individual fish and the explosive (and immediate pressure field) were co-located at the same time. Fishes deeper in the water column or on the bottom would not be affected by water surface explosions. Repeated exposure of individual fish to sound and energy from underwater explosions is not likely given fish movement patterns, especially schooling prey species. Most acoustic effects, if any, are expected to be short-term and localized. Long-term consequences for fish populations, including key prey species within the HCTT Study Area, would not be expected. Vessels and in-water devices do not normally collide with adult fish, particularly those that are common marine mammal prey, most of which can detect and avoid them. Exposure of fishes to vessel strike stressors is limited to those fish groups that are large, slow-moving, and may occur near the surface, such as ocean sunfish, whale sharks, basking sharks, and manta rays. These species are distributed widely in offshore portions of the HCTT Study Area. Any isolated cases of a military vessel striking an individual could injure that individual, impacting the fitness of an individual fish. Vessel strikes would not pose a risk to most of the other marine fish groups, because many fish can detect and avoid vessel movements, making strikes rare and allowing the fish to return to their normal behavior after the ship or device passes. As a vessel approaches a fish, they could have a detectable behavioral or physiological response (e.g., swimming away and increased heart rate) as the passing vessel displaces them. However, such responses are not expected to have lasting effects on the survival, growth, recruitment, or reproduction of these marine fish groups at the population level and therefore would not have an impact on marine mammal species as prey items. In addition to fish, prey sources such as marine invertebrates could potentially be impacted by sound stressors as a result of the proposed activities. However, most marine invertebrates' ability to sense sounds is very limited. In most cases, marine invertebrates would not respond to impulsive and non-impulsive sounds, although they may detect and briefly respond to nearby low-frequency sounds. These short- term responses would likely be inconsequential to invertebrate populations. Invertebrates appear to be able to detect sounds (Pumphrey, 1950; Frings and Frings, 1967) and are most sensitive to low-frequency sounds (Packard et al., 1990; Budelmann and Williamson, 1994; Lovell et al., 2005; Mooney et al., 2010). Data on response of invertebrates such as squid, another marine mammal prey species, to anthropogenic sound is more limited (de Soto, 2016; Sole et al., 2017). Data suggest that cephalopods are capable of sensing the particle motion of sounds and detect low frequencies up to 1-1.5 kHz, depending on the species, and so are likely to detect air gun noise (Kaifu et al., 2008; Hu et al., 2009; Mooney et al., 2010; Samson et al., 2014). Sole et al. (2017) reported physiological injuries to cuttlefish in cages placed at-sea when exposed during a controlled exposure experiment to low-frequency sources (315 Hz, 139 to 142 dB re: 1 [mu]Pa\2\ and 400 Hz, 139 to 141 dB re: 1 [mu]Pa\2\). Fewtrell and McCauley (2012) reported squids maintained in cages displayed startle responses and behavioral changes when exposed to seismic air gun sonar (136-162 re: 1 [mu]Pa\2\[middot]s). However, the sources Sole et al. (2017) and Fewtrell and McCauley (2012) used are not similar and were much lower than typical Navy sources within the HCTT Study Area. Nor do the studies address the issue of individual displacement outside of a zone of impact when exposed to sound. Jones et al. (2020) found that when squid (Doryteuthis (Amerigo) pealeii) were exposed to impulse pile driving noise, body pattern changes, inking, jetting, and startle responses were observed and nearly all squid exhibited at least one response. However, these responses occurred primarily during the first eight impulses and diminished quickly, indicating potential rapid, short-term habituation. Cephalopods have a specialized sensory organ inside the head called a statocyst that may help an animal determine its position in space (orientation) and maintain balance (Budelmann, 1992). Packard et al. (1990) showed that cephalopods were sensitive to particle motion, not sound pressure, and Mooney et al. (2010) demonstrated that squid statocysts act as an accelerometer through which particle motion of the sound field can be detected. Auditory injuries (lesions occurring on the statocyst sensory hair cells) have been reported upon controlled exposure to low-frequency sounds, suggesting that cephalopods are particularly sensitive to low-frequency sound (Andre et al., 2011; Sole et al., 2013). Behavioral responses, such as inking and jetting, have also been reported upon exposure to low-frequency sound (McCauley et al., 2000b; Samson et al., 2014). Squids, like most fish species, are likely more sensitive to low frequency sounds, and may not perceive mid- and high-frequency sonars such as Navy sonars. Cumulatively for squid as a prey species, individual and population impacts from exposure to Navy sonar and explosives, like fish, are not likely to be significant, and explosive impacts would be short-term and localized. [[Page 32207]] Explosions and pile driving would likely kill or injure nearby marine invertebrates. Vessels also have the potential to impact marine invertebrates by disturbing the water column or sediments, or directly striking organisms (Bishop, 2008). The propeller wash (water displaced by propellers used for propulsion) from vessel movement and water displaced from vessel hulls can potentially disturb marine invertebrates in the water column and is a likely cause of zooplankton mortality (Bickel et al., 2011). The localized and short-term exposure to explosions or vessels could displace, injure, or kill zooplankton, invertebrate eggs or larvae, and macro-invertebrates. However, mortality or long-term consequences for a few animals is unlikely to have measurable effects on overall populations. Long-term consequences to marine invertebrate populations would not be expected as a result of exposure to sounds of vessels in the HCTT Study Area. Impacts to benthic communities from impulsive sound generated by active acoustic sound sources are not well documented. (e.g., Andriguetto-Filho et al., 2005; Payne et al., 2007; 2008; Boudreau et al., 2009). There are no published data that indicate whether temporary or permanent threshold shifts, auditory masking, or behavioral effects occur in benthic invertebrates (Hawkins et al., 2014) and some studies showed no short-term or long-term effects of air gun exposure (e.g., Andriguetto-Filho et al., 2005; Payne et al., 2007; 2008; Boudreau et al., 2009). Exposure to air gun signals was found to significantly increase mortality in scallops, in addition to causing significant changes in behavioral patterns during exposure (Day et al., 2017). However, the authors state that the observed levels of mortality were not beyond naturally occurring rates. Explosions and pile driving could potentially kill or injure nearby marine invertebrates; however, mortality or long-term consequences for a few animals is unlikely to have measurable effects on overall populations. There is little information concerning potential impacts of noise on zooplankton populations. However, one study (McCauley et al., 2017) investigated zooplankton abundance, diversity, and mortality before and after exposure to air gun noise, finding that the mortality rate for zooplankton after air gun exposure was two to three times more compared with controls for all taxa. The majority of taxa present were copepods and cladocerans; for these taxa, the range within which effects on abundance were detected was up to approximately 0.75 mi (1.2 km). In order to have significant impacts on r-selected species (i.e., species that produce a large number of offspring and contribute few resources to each individual offspring) such as plankton, the spatial or temporal scale of impact must be large in comparison with the ecosystem concerned (McCauley et al., 2017). Notably, a recently described study produced results inconsistent with those of McCauley et al. (2017). Researchers conducted a field and laboratory study to assess if exposure to air gun noise affects mortality, predator escape response, or gene expression of the copepod Calanus finmarchicus (Fields et al., 2019). Immediate mortality of copepods was significantly higher, relative to controls, at distances of 16.4 ft (5 m) or less from the air guns. Mortality one week after the air gun blast was significantly higher in the copepods placed 32.8 ft (10 m) from the air gun but was not significantly different from the controls at a distance of 65.6 ft (20 m) from the air gun. The increase in mortality, relative to controls, did not exceed 30 percent at any distance from the air gun. Moreover, the authors caution that even this higher mortality in the immediate vicinity of the air guns may be more pronounced than what would be observed in free-swimming animals due to increased flow speed of fluid inside bags containing the experimental animals. There were no sublethal effects on the escape performance or the sensory threshold needed to initiate an escape response at any of the distances from the air gun that were tested. Whereas McCauley et al. (2017) reported an SEL of 156 dB at a range of 1,670-2,158.8 ft (509-658 m), with zooplankton mortality observed at that range, Fields et al. (2019) reported an SEL of 186 dB at a range of 82 ft (25 m), with no reported mortality at that distance. The large scale of effect observed here is of concern--particularly where repeated noise exposure is expected--and further study is warranted. Military expended materials resulting from training and testing activities could potentially result in minor long-term changes to benthic habitat; however, the impacts of small amount of expended materials are unlikely to have measurable effects on overall populations. Military expended materials may be colonized over time by benthic organisms that prefer hard substrate and would provide structure that could attract some species of fish or invertebrates. Overall, the combined impacts of sound exposure, explosions, vessel strikes, and military expended materials resulting from the proposed activities would not be expected to have measurable effects on populations of marine mammal prey species. Prey species exposed to sound might move away from the sound source, experience TTS, experience masking of biologically relevant sounds, or show no obvious direct effects. Mortality from decompression injuries is possible in close proximity to a sound, but only limited data on mortality in response to air gun noise exposure are available (Fields et al., 2019, Hawkins et al., 2014, McCauley et al., 2017). The most likely impacts for most prey species in a given area would be temporary avoidance of the area. Surveys using towed air gun arrays move through an area relatively quickly, limiting exposure to multiple impulsive sounds. In all cases, sound levels would return to ambient once a survey ends and the noise source is shut down and, when exposure to sound ends, behavioral and/or physiological responses are expected to end relatively quickly (McCauley et al., 2000b). The duration of fish avoidance of a given area after survey effort stops is unknown, but a rapid return to normal recruitment, distribution, and behavior is anticipated. While the potential for disruption of spawning aggregations or schools of important prey species can be meaningful on a local scale, the mobile and temporary nature of most surveys and the likelihood of temporary avoidance behavior suggest that impacts would be minor. Long-term consequences to marine invertebrate populations would not be expected as a result of exposure to sounds or vessels in the HCTT Study Area. Acoustic Habitat Acoustic habitat is the soundscape which encompasses all of the sound present in a particular location and time, as a whole when considered from the perspective of the animals experiencing it. Animals produce sound for, or listen for sounds produced by, conspecifics (e.g., communication during feeding, mating, and other social activities), other animals (e.g., finding prey or avoiding predators), and the physical environment (e.g., finding suitable habitats, navigating). Together, sounds made by animals and the geophysical environment (e.g., produced by earthquakes, lightning, wind, rain, waves) make up the natural contributions to the total acoustics of a place. These acoustic conditions, termed acoustic habitat, are one attribute of an animal's total habitat. Soundscapes are also defined by, and acoustic habitat influenced by, the total [[Page 32208]] contribution of anthropogenic sound. This may include incidental emissions from sources such as vessel traffic or may be intentionally introduced to the marine environment for data acquisition purposes (e.g., the use of air gun arrays) or for military training and testing purposes (e.g., the use of sonar and explosives and other acoustic sources). Anthropogenic noise varies widely in its frequency, content, duration, and SPL, and these characteristics greatly influence the potential habitat-mediated effects to marine mammals (please also see the previous discussion in the Masking section), which may range from local effects for brief periods of time to chronic effects over large areas and for long durations. Depending on the extent of effects to habitat, animals may alter their communications signals (thereby potentially expending additional energy) or miss acoustic cues (either conspecific or adventitious). Problems arising from a failure to detect cues are more likely to occur when noise stimuli are chronic and overlap with biologically relevant cues used for communication, orientation, and predator/prey detection (Francis and Barber, 2013). For more detail on these concepts see, e.g., Barber et al., 2009; Pijanowski et al., 2011; Lillis et al., 2014. The term ``listening area'' refers to the region of ocean over which sources of sound can be detected by an animal at the center of the space. Loss of communication space concerns the area over which a specific animal signal (used to communicate with conspecifics in biologically important contexts such as foraging or mating) can be heard, in noisier relative to quieter conditions (Clark et al., 2009). Lost listening area concerns the more generalized contraction of the range over which animals would be able to detect a variety of signals of biological importance, including eavesdropping on predators and prey (Barber et al., 2009). Such metrics do not, in and of themselves, document fitness consequences for the marine animals that live in chronically noisy environments. Long-term population-level consequences mediated through changes in the ultimate survival and reproductive success of individuals are difficult to study, and particularly so underwater. However, it is increasingly well documented that aquatic species rely on qualities of natural acoustic habitats, with researchers quantifying reduced detection of important ecological cues (e.g., Francis and Barber, 2013; Slabbekoorn et al., 2010) as well as survivorship consequences in several species (e.g., Simpson et al., 2015; Nedelec et al., 2015). The sounds produced during training and testing activities can be widely dispersed or concentrated in small areas for varying periods. Sound produced from training and testing activities in the HCTT Study Area is temporary and transitory. Any anthropogenic noise attributed to training and testing activities in the HCTT Study Area would be temporary and the affected area would be expected to immediately return to the original state when these activities cease. Water Quality Training and testing activities may introduce constituents into the water column. Based on the analysis of the 2024 HCTT Draft EIS/OEIS, military expended materials (e.g., undetonated explosive materials) would be released in quantities and at rates that would not result in a violation of any water quality standard or criteria. NMFS has reviewed this analysis and concurs that it reflects the best available science. High-order explosions consume most of the explosive material, creating typical combustion products. For example, in the case of Royal Demolition Explosive, 98 percent of the products are common seawater constituents and the remainder is rapidly diluted below threshold effect level. Explosion by-products associated with high order detonations present no secondary stressors to marine mammals through sediment or water. However, low order detonations and unexploded ordnance present elevated likelihood of impacts on marine mammals. Indirect effects of explosives and unexploded ordnance to marine mammals via sediment is possible in the immediate vicinity of the ordnance. Degradation products of Royal Demolition Explosive are not toxic to marine organisms at realistic exposure levels (Rosen and Lotufo, 2010). Relatively low solubility of most explosives and their degradation products means that concentrations of these contaminants in the marine environment are relatively low and readily diluted. Furthermore, while explosives and their degradation products were detectable in marine sediment approximately 6-12 inches (0.15-0.3 m) away from degrading ordnance, the concentrations of these compounds were not statistically distinguishable from background beyond 3-6 ft (1-2 m) from the degrading ordnance. Taken together, it is possible that marine mammals could be exposed to degrading explosives, but it would be within a very small radius of the explosive (1-6 ft (0.3-2 m)). Equipment used by the Action Proponents within the HCTT Study Area, including ships and other marine vessels, aircraft, and other equipment, are also potential sources of by-products. All equipment is properly maintained in accordance with applicable Navy, Coast Guard, Army, and legal requirements. All such operating equipment meets Federal water quality standards, where applicable. Estimated Take of Marine Mammals This section indicates the number of takes that NMFS is proposing to authorize, which is based on the amount of take that NMFS anticipates is reasonably likely to occur. NMFS coordinated closely with the Action Proponents in the development of their incidental take application, and preliminarily agrees that the methods the Action Proponents have put forth described herein to estimate take (including the model, thresholds, and density estimates), and the resulting numbers are based on the best available science and appropriate for authorization. Takes would be predominantly in the form of harassment, but a limited number of mortalities are also possible. For this military readiness activity, the MMPA defines ``harassment'' as (1) any act that injures or has the significant potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (2) any act that disturbs or is likely to disturb a marine mammal or marine mammal stock in the wild by causing disruption of natural behavioral patterns, including, but not limited to, migration, surfacing, nursing, breeding, feeding, or sheltering, to a point where the behavioral patterns are abandoned or significantly altered (Level B harassment) (16 U.S.C. 1362(18)(B)). Proposed authorized takes would primarily be in the form of Level B harassment, as use of the acoustic (e.g., active sonar, pile driving, and seismic air guns) and explosive sources and missile launches is most likely to result in disruption of natural behavioral patterns to a point where they are abandoned or significantly altered (as defined specifically at the beginning of this section, but referred to generally as behavioral disturbance) for marine mammals, either via direct behavioral disturbance or TTS. There is also the potential for Level A harassment, in the form of auditory injury to result from exposure to the sound sources utilized in military readiness activities. Lastly, no more than 7 serious injuries or mortalities total (over the 7-year period) [[Page 32209]] of large whales could potentially occur through vessel strikes, and 40 serious injuries or mortalities (over the 7-year period) from explosive use. Although we analyze the impacts of these potential serious injuries or mortalities that are proposed for authorization, the proposed mitigation and monitoring measures are expected to minimize the likelihood (i.e., further lower the already low probability) that vessel strike (and the associated serious injury or mortality) would occur, as well as the severity of other takes. Generally speaking, for acoustic impacts NMFS estimates the amount and type of harassment by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals would experience behavioral disturbance or incur some degree of temporary or permanent hearing impairment; (2) the area or volume of water that would be ensonified above these levels in a day or event; (3) the density or occurrence of marine mammals within these ensonified areas; and (4) the number of days of activities or events. Acoustic Thresholds Using the best available science, NMFS, in coordination with the Navy, has established acoustic thresholds that identify the most appropriate received level of underwater sound above which marine mammals exposed to these sound sources could be reasonably expected to directly incur a disruption in behavior patterns to a point where they are abandoned or significantly altered (equated to onset of Level B harassment), or to incur TTS onset (equated to Level B harassment via the indirect disruptions of behavioral patterns) or AUD INJ onset (equated to Level A harassment). Thresholds have also been developed to identify the pressure and impulse levels above which animals may incur non-auditory injury or mortality from exposure to explosive detonation. Hearing Impairment (TTS/AUD INJ), Non-Auditory Injury, and Mortality NMFS' 2024 Technical Guidance (NMFS, 2024) identifies dual criteria to assess AUD INJ (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). The Updated Technical Guidance also identifies criteria to predict TTS, which is not considered injury and falls into the Level B harassment category. The Action Proponents' specified activities include the use of non-impulsive (i.e., sonar, vibratory pile driving) and impulsive (i.e., explosives, air guns, impact pile driving) sources. For the consideration of impacts on hearing in Phase IV, marine mammals were divided into nine groups for analysis: VLF, LF, HF, VHF, SI, PCW and PCA, and OCW and OCA. For each group, a frequency-dependent weighting function and numeric thresholds for the onset of TTS and the onset of AUD INJ were estimated. The onset of TTS is defined as a TTS of 6 dB measured approximately 2-5 minutes after exposure. A TTS of 40 dB is used as a proxy for the onset of AUD INJ (i.e., it is assumed that exposures beyond those capable of causing 40 dB of TTS have the potential to result in PTS or other auditory injury (e.g., loss of cochlear neuron synapses)). Exposures just sufficient to cause TTS or AUD INJ are denoted as ``TTS onset'' or ``AUD INJ onset'' exposures. Onset levels are treated as step functions or ``all-or-nothing'' thresholds: exposures above the TTS or AUD INJ onset level are assumed to always result in TTS or AUD INJ, while exposures below the TTS or AUD INJ onset level are assumed to not cause TTS or AUD INJ. For non- impulsive exposures, onset levels are specified in frequency-weighted sound exposure level (SEL); for impulsive exposures, dual metrics of weighted SEL and unweighted peak sound pressure level (SPL) are used. To compare Phase IV weighting functions and TTS/AUD INJ SEL thresholds to those used in Phase III, both the weighting function shape and the weighted threshold values were considered; the weighted thresholds by themselves only indicate the TTS/AUD INJ threshold at the most susceptible frequency (based on the relevant weighting function). In contrast, the TTS/AUD INJ exposure functions incorporate both the shape of the weighting function and the weighted threshold value and provide the best means of comparing the frequency-dependent TTS/AUD INJ thresholds for Phase III and Phase IV. The most significant differences between the Phase III and Phase IV functions and thresholds include the following: Mysticetes were divided into two groups (VLF and LF), with the upper hearing limit for the LF group increased from Phase III to match recent hearing measurements in minke whales (Houser et al., 2024); Group names were changed from Phase III to be consistent with Southall et al. (2019). Specifically, the Phase III mid-frequency (MF) cetacean group is now designated as the high-frequency (HF) cetacean group, and the group previously designated as high-frequency (HF) cetaceans is now the very-high frequency (VHF) cetacean group; For the HF group, Phase IV onset TTS/AUD INJ thresholds are lower compared to Phase III at frequencies below approximately 10 kHz. This is a result of new TTS onset data for dolphins at low frequencies (Finneran et al., 2023); For the PCW group, new TTS data for harbor seals (Kastelein et al., 2020a; Kastelein et al., 2020b) resulted in slightly lower TTS/AUD INJ thresholds at high frequencies compared to Phase III; and For group OCW, new TTS data for California sea lions (Kastelein et al., 2021b; Kastelein et al., 2022a, 2022b) resulted in significantly lower TTS/AUD INJ thresholds compared to Phase III. Of note, the thresholds and weighting function for the LF cetacean hearing group in NMFS' 2024 Technical Guidance (NMFS, 2024) match the Navy's VLF cetacean hearing group. However, the weighting function for those hearing groups differs between the two documents (i.e., the Navy's LF cetacean group has a different weighting function from NMFS) due to the Houser et al. (2024) minke whale data incorporated into Navy 2024, but not NMFS (2024). While NMFS' 2024 Technical Guidance differs from the criteria that the Action Proponents used to assess AUD INJ and TTS for low-frequency cetaceans, NMFS concurs that the criteria the Action Proponents applied are appropriate for assessing the impacts of their proposed action. The criteria used by the Action Proponents are conservative in that those criteria show greater sensitivity at higher frequencies (i.e., application of those criteria result in a higher amount of estimated take by higher frequency sonars than would result from application of NMFS' 2024 Technical Guidance) which is where more of the take is expected. These thresholds (table 18 and table 19) were developed by compiling and synthesizing the best available science and soliciting input multiple times from both public and peer reviewers. The references, analysis, and methodology used in the development of the thresholds are described in Updated Technical Guidance, which may be accessed at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance. [[Page 32210]] Table 18--Acoustic Thresholds Identifying the Onset of TTS ---------------------------------------------------------------------------------------------------------------- TTS threshold SEL AUD INJ threshold SEL Group (weighted) (weighted) ---------------------------------------------------------------------------------------------------------------- Very low-frequency (VLF)....................................... 177 197 Low-frequency (LF)............................................. 177 197 High-frequency (HF)............................................ 181 201 Very high-frequency (VHF)...................................... 161 181 Phocid carnivores in water (PW)................................ 175 195 Otariid carnivores in water (OW)............................... 179 199 Phocid carnivores in air (PA).................................. 134 154 Otariid carnivores in air (OA)................................. 157 177 ---------------------------------------------------------------------------------------------------------------- Note: SEL thresholds in dB re 1 [mu]Pa\2\ s underwater and dB re 20 [mu]Pa\2\ s in air. Based on the best available science, the Action Proponents (in coordination with NMFS) used the acoustic and pressure thresholds indicated in table 18 to predict the onset of behavioral harassment, AUD INJ, TTS, tissue damage, and mortality due to explosive sources. For explosive activities using single detonations (i.e., no more than one detonation within a day), such as those described in the proposed activity, NMFS uses TTS onset thresholds to assess the likelihood of behavioral harassment, rather than the Level B harassment threshold for multiple detonations indicated in table 19. While marine mammals may also respond to single explosive detonations, these responses are expected to more typically be in the form of startle response, rather than a more meaningful disruption of a behavioral pattern. On the rare occasion that a single detonation might result in a behavioral response that qualifies as Level B harassment, it would be expected to be in response to a comparatively higher received level. Accordingly, NMFS considers the potential for these responses to be quantitatively accounted for through the application of the TTS criteria, which, as noted above, is 5 dB higher than the behavioral harassment threshold for multiple explosives. Table 19--Explosive Thresholds for Marine Mammals for AUD INJ, TTS, and Behavior [Multiple detonations] ---------------------------------------------------------------------------------------------------------------- AUD INJ impulsive TTS impulsive Behavioral threshold (multiple Hearing group threshold * threshold * detonations) ---------------------------------------------------------------------------------------------------------------- Low-Frequency (LF) Cetaceans... Cell 1: Lp,0- Cell 2: Lp,0- Cell 3: LE,LF,24h: 163 dB. pk,flat: 222 dB; pk,flat: 216 dB; LE,p,LF,24h: 183 LE,LF,24h: 168 dB. dB. High-Frequency (HF) Cetaceans.. Cell 4: Lp,0- Cell 5: Lp,0- Cell 6: LE,HF,24h: 173 dB. pk,flat: 230 dB; pk,flat: 224 dB; LE,p,HF,24h: 193 LE,HF,24h: 178 dB. dB. Very High-Frequency (VHF) Cell 7: Lp,0- Cell 8: Lp,0- Cell 9: LE,VHF,24h: 139 dB. Cetaceans. pk,flat: 202 dB; pk,flat: 196 dB; LE,p,VHF,24h: 159 LE,VHF,24h: 144 dB. dB. Phocid Pinnipeds (PW) Cell 10: Lp,0- Cell 11: Lp,0- Cell 12: LE,PW,24h: 163 dB. (Underwater). pk,flat: 223 dB; pk,flat: 217 dB; LE,p,PW,24h: 183 LE,PW,24h: 168 dB. dB. Otariid Pinnipeds (OW) Cell 13: Lp,0- Cell 14: Lp,0- Cell 15: LE,OW,24h: 165 dB. (Underwater). pk,flat: 230 dB; pk,flat: 224 dB; LE,p,OW,24h: 185 LE,OW,24h: 170 dB. dB. Phocid Pinnipeds (PA) (In-Air). Cell 16: Lp,0- Cell 17: Lp,0- Cell 18: N/A. pk,flat: 162 dB; pk,flat: 156 dB; LE,p,PA,24h: 140 LE,PA,24h: 125 dB. dB. Otariid Pinnipeds (OA) (In-Air) Cell 19: Lp,0- Cell 20: Lp,0- Cell 21: N/A. pk,flat : 177 dB; pk,flat: 171 dB; LE,p,OA,24h: 163 LE,OA,24h: 148 dB. dB. ---------------------------------------------------------------------------------------------------------------- Note: N/A = Not Applicable. Peak sound pressure level (Lp,0-pk) has a reference value of 1 [micro]Pa, and weighted cumulative sound exposure level (LE,p) has a reference value of 1 [micro]Pa\2\s. In this table, criteria are abbreviated to be more reflective of International Organization for Standardization standards (ISO, 2017; ISO, 2020). The subscript ``flat'' is being included to indicate peak sound pressure are flat weighted or unweighted within the generalized hearing range of marine mammals underwater (i.e., 7 Hz to 165 kHz) or in air (i.e., 42 Hz to 52 kHz). The subscript associated with cumulative sound exposure level criteria indicates the designated marine mammal auditory weighting function (LF, HF, and VHF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The weighted cumulative sound exposure level criteria could be exceeded in a multitude of ways (i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the conditions under which these criteria will be exceeded. * Dual metric criteria for impulsive sounds: Use whichever criteria results in the larger isopleth for calculating AUD INJ onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level criteria associated with impulsive sounds, the PK SPL criteria are recommended for consideration for non- impulsive sources. The criterion for mortality is based on severe lung injury observed in terrestrial mammals exposed to underwater explosions as recorded in Goertner (1982). The criteria for non-auditory injury are based on slight lung injury or gastrointestinal (commonly referred to as G.I.) tract injury observed in the same data set. Mortality and slight lung injury impacts to marine mammals are estimated using impulse thresholds based on both calf/pup/juvenile and adult masses (see the Criteria and Thresholds Technical Report). The peak pressure threshold applies to all species and age classes. Unlike the prior analysis (Phase III), this analysis relies on the onset rather than the mean estimated threshold for these effects. This revision results in a small increase in the predicted non-auditory injuries and mortalities for the same event versus prior analyses. Thresholds are provided in table 20 for use in non-auditory injury assessment for marine mammals exposed to underwater explosives. Of note, non-auditory injury and mortality from land-based missile and target launches are so unlikely as to [[Page 32211]] be discountable under normal conditions. Table 20--Non-Auditory Injury Thresholds for Underwater Explosives ---------------------------------------------------------------------------------------------------------------- Hearing group Mortality--impulse * Injury--impulse * Injury--peak pressure ---------------------------------------------------------------------------------------------------------------- All Marine Mammals.................. Cell 1: Modified Goertner Cell 2: Modified Cell 3: Lp0-pk,flat: model; Equation 1. Goertner model; 237 dB. Equation 2. ---------------------------------------------------------------------------------------------------------------- Note: Peak sound pressure (Lpk) has a reference value of 1 [micro]Pa. In this table, thresholds are abbreviated to reflect ANSI (2013). However, ANSI defines peak sound pressure as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript ``flat'' is being included to indicate peak sound pressure should be flat weighted or unweighted within the overall marine mammal generalized hearing range. * Lung injury (severe and slight) thresholds are dependent on animal mass (Recommendation: table C.9 from U.S. Department of the Navy (2017a) based on adult and/or calf/pup mass by species). Modified Goertner Equations for severe and slight lung injury (pascal-second) Equation 1: 103M\1/3\(1 + D/10.1)\1/6\ Pa-s Equation 2: 47.5M\1/3\(1 + D/10.1)\1/6\ Pa-s M animal (adult and/or calf/pup) mass (kg) (table C.9 in DoN 2017) D animal depth (meters). Level B Harassment by Behavioral Disturbance Though significantly driven by received level and distance, the onset of Level B harassment by behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors and can be difficult to predict (Southall et al., 2007; Ellison et al., 2012). As discussed in the Potential Effects of Specified Activities on Marine Mammals and Their Habitat section, marine mammal responses to sound (some of which are considered disturbances that qualify as take under the MMPA) are highly variable and context specific (i.e., they are affected by differences in acoustic conditions; differences between species and populations; differences in gender, age, reproductive status, or social behavior; and other prior experience of the individuals). This means there is support for considering alternative approaches for estimating Level B behavioral harassment. Despite the rapidly evolving science, there are still challenges in quantifying expected behavioral responses that qualify as take by Level B harassment, especially where the goal is to use one or two predictable indicators (e.g., received level and distance) to predict responses that are also driven by additional factors that cannot be easily incorporated into the thresholds (e.g., context). So, while the criteria that identify Level B harassment by behavioral disturbance (referred to as ``behavioral harassment thresholds'') have been refined to better consider the best available science (e.g., incorporating both received level and distance), they also still have some built-in factors to address the challenge noted. For example, while duration of observed responses in the data are now considered in the thresholds, some of the responses that are informing take thresholds are of a very short duration, such that it is possible some of these responses might not always rise to the level of disrupting behavior patterns to a point where they are abandoned or significantly altered. We describe the application of this behavioral harassment threshold as identifying the maximum number of instances in which marine mammals could be reasonably expected to experience a disruption in behavior patterns to a point where they are abandoned or significantly altered. In summary, we believe these behavioral harassment criteria are the most appropriate method for predicting Level B harassment by behavioral disturbance given the best available science and the associated uncertainty. Sonar-- In its analysis of impacts associated with sonar acoustic sources (which was coordinated with NMFS), the Action Proponents used an updated approach, as described below. Many of the behavioral responses identified using the Action Proponents' quantitative analysis are most likely to be of moderate severity as described in the Southall et al. (2021) behavioral response severity scale. These ``moderate'' severity responses were considered significant if they were sustained for the duration of the exposure or longer. Within the Action Proponents' quantitative analysis, many responses are predicted from exposure to sound that may exceed an animal's Level B behavioral harassment threshold for only a single exposure (lasting a few seconds) to several minutes, and it is likely that some of the resulting estimated behavioral responses that are counted as Level B harassment would not constitute ``significantly altering or abandoning natural behavioral patterns'' (i.e., the estimated number of takes by Level B harassment due to behavioral disturbance and response is likely somewhat of an overestimate). As noted above, the Action Proponents coordinated with NMFS to develop behavioral harassment thresholds specific to their military readiness activities utilizing active sonar that identify at what received level and distance Level B harassment by behavioral disturbance would be expected to result. These behavioral harassment thresholds consist of behavioral response functions (BRFs) and associated distance cut-off conditions, and are also referred to, together, as ``the criteria.'' These criteria are used to estimate the number of animals that may exhibit a behavioral response that qualifies as take under the MMPA when exposed to sonar and other transducers. The way the criteria were derived is discussed in detail in the Criteria and Thresholds Technical Report. Developing these behavioral harassment criteria involved multiple steps. All peer-reviewed published behavioral response studies conducted both in the field and on captive animals were examined in order to understand the breadth of behavioral responses of marine mammals to sonar and other transducers. Marine mammals were divided into four groups for analysis: mysticetes (all baleen whales); odontocetes (most toothed whales, dolphins, and porpoises); sensitive species (beaked whales and harbor porpoise); and pinnipeds and other marine carnivores (true seals, sea lions, walruses, sea otters, polar bears). These groups are like the groups used in the behavioral response analysis (Phase III), with the exception of combining beaked whales and harbor porpoise into a single curve. For each group, a biphasic BRF was developed using the best available data and Bayesian dose response models [[Page 32212]] developed at the University of St. Andrews. The BRF base probability of response on the highest SPL (RMS) received level. The analysis of BRFs differs from the previous phase (Phase III) due to the addition of new data and the separation of some species groups. Figure 10 in the Criteria and Thresholds Technical Report indicates the changes in BRFs from Phase III to Phase IV. The sensitive species BRF is more sensitive at lower received levels but less sensitive at higher received levels than the prior beaked whale and harbor porpoise functions. The odontocete BRF is less sensitive overall due to additional behavioral response research, which will result in a lower number of behavioral responses than in the prior analysis for the same event, but also reduces the avoidance of auditory effects. The pinnipeds (in-water) BRF is more sensitive due to the inclusion of additional captive pinniped data (only three behavioral studies using captive pinnipeds were available for the derivation of the BRF). Behavioral studies of captive animals can be difficult to extrapolate to wild animals due to several factors (e.g., use of trained subjects). This means the pinniped BRF likely overestimates effects compared to observed responses of wild pinnipeds to sound and anthropogenic activity. The mysticete BRF is less sensitive across most received levels due to including additional behavioral response research. This will result in a lower number of behavioral responses than in the prior analysis for the same event, but also reduces the avoidance of auditory effects. The BRFs only relate the highest received level of sound to the probability that an animal will have a behavioral response. The BRFs do not account for the duration or pattern of use of any individual sound source or of the activity as a whole, the number of sound sources that may be operating simultaneously, or how loud the animal may perceive the sonar signal to be based on the frequency of the sonar versus the animal's hearing range. Criteria for assessing marine mammal behavioral responses to sonars use the metric of highest received sound level (RMS) to evaluate the risk of immediate responses by exposed animals. Currently, there are limited data to develop criteria that include the context of an exposure, characteristics of individual animals, behavioral state, duration of an exposure, sound source duty cycle, and the number of individual sources in an activity (although these factors certainly influence the severity of a behavioral response) and, further, even where certain contextual factors may be predictive where known, it is difficult to reliably predict when such factors will be present. The BRFs also do not account for distance. At moderate to low received levels the correlation between probability of response and received level is very poor and it appears that other variables mediate behavioral responses (e.g., Ellison et al., 2012) such as the distance between the animal and the sound source. For this analysis, distance between the animal and the sound source (i.e., range) was initially included, however, range was too confounded with received level and therefore did not provide additional information about the possibility of response. Data suggest that beyond a certain distance, significant behavioral responses are unlikely. At shorter ranges (less than 10 km) some behavioral responses have been observed at received levels below 140 dB re 1 [mu]Pa. Thus, proximity may mediate behavioral responses at lower received levels. Since most data used to derive the BRFs are within 10 km of the source, probability of response at farther ranges is not well-represented. Therefore, the source-receiver range must be considered separately to estimate likely significant behavioral responses. This analysis applies behavioral cut-off conditions to responses predicted using the BRFs. Animals within a specified distance and above a minimum probability of response are assumed to have a significant behavioral response. The cut-off distance is based on the farthest source-animal distance across all known studies where animals exhibited a significant behavioral response. Animals beyond the cut-off distance but with received levels above the sound pressure level associated with a probability of response of 0.50 on the BRF are also assumed to have a significant behavioral response. The actual likelihood of significant behavioral responses occurring beyond the distance cut-off is unknown. Significant behavioral responses beyond 100 km are unlikely based on source-animal distance and attenuated received levels. The behavioral cut-off conditions and additional information on the derivation of the cut-off conditions can be found in table 2.2-3 of the Criteria and Thresholds Technical Report. The Action Proponents used cutoff distances beyond which the potential of significant behavioral responses (and therefore Level B harassment) is considered to be unlikely (see table 21). These distances were determined by examining all available published field observations of behavioral responses to sonar or sonar-like signals that included the distance between the sound source and the marine mammal. Behavioral effects calculations are based on the maximum SPL to which a modeled marine mammal is exposed. There is empirical evidence to suggest that animals are more likely to exhibit significant behavioral responses to moderate levels sounds that are closer and less likely to exhibit behavioral responses when exposed to moderate levels of sound from a source that is far away. To account for this, the Action Proponents have implemented behavioral cutoffs that consider both received sound level and distance from the source. These updated cutoffs conditions are unique to each behavioral hearing group and are outlined in table 21. Table 21--Behavioral Cut-Off Conditions for Each Behavioral Hearing Group ---------------------------------------------------------------------------------------------------------------- Received level associated with p(0.50) on the Cut-off range Behavioral group behavioral response function (dB RMS) (km) ---------------------------------------------------------------------------------------------------------------- Sensitive Species............................... 133 40 Odontocetes..................................... 168 15 Mysticetes...................................... 185 10 Pinnipeds....................................... 156 5 ---------------------------------------------------------------------------------------------------------------- Note: Sensitive Species includes beaked whales and harbor porpoises. [[Page 32213]] The Action Proponents and NMFS have used the best available science to address the challenging differentiation between significant and non- significant behavioral responses (i.e., whether the behavior has been abandoned or significantly altered such that it qualifies as harassment), but have erred on the cautious side where uncertainty exists (e.g., counting these lower duration responses as take), which likely results in some degree of overestimation of Level B harassment by behavioral disturbance. We consider application of these behavioral harassment thresholds, therefore, as identifying the maximum number of instances in which marine mammals could be reasonably expected to experience a disruption in behavior patterns to a point where they are abandoned or significantly altered (i.e., Level B harassment). NMFS has carefully reviewed the criteria (i.e., BRFs and cutoff distances for the species), and agrees that it is the best available science and is the appropriate method to use at this time for determining impacts to marine mammals from military sonar and other transducers and for calculating take and to support the determinations made in this proposed rule. Because this is the most appropriate method for estimating Level B harassment given the best available science and uncertainty on the topic, it is these numbers of Level B harassment by behavioral disturbance that are analyzed in the Preliminary Analysis and Negligible Impact Determination section and would be authorized. Air Guns, Pile Driving, and Explosives-- Based on what the available science indicates and the practical need to use a threshold based on a factor that is both predictable and measurable for most activities, NMFS uses generalized acoustic thresholds based on received level to estimate the onset of behavioral harassment for sources other than active sonar. NMFS predicts that marine mammals are likely to be behaviorally harassed in a manner we consider Level B harassment when exposed to underwater anthropogenic noise above received levels of 120 dB re 1 [mu]Pa (RMS) for continuous (e.g., vibratory pile-driving, drilling) and above 160 dB re 1 [mu]Pa (RMS) for non-explosive impulsive (e.g., seismic air guns) or intermittent (e.g., scientific sonar) sources. For the Action Proponents' activities, to estimate behavioral effects from air guns, the threshold of 160 dB re 1 [micro]Pa (RMS) is used and the root mean square calculation for air guns is based on the duration defined by 90 percent of the cumulative energy in the impulse. The indicated thresholds were also applied to estimate behavioral effects from impact and vibratory pile driving (see table 22). These thresholds are the same as those applied in the prior analysis (Phase III) of these stressors in the Study Area, although the explosive behavioral threshold has shifted, corresponding to changes in the TTS thresholds. Table 22--Behavioral Response Thresholds for Air Guns, Pile Driving, and Explosives ------------------------------------------------------------------------ Sound source Behavioral threshold ------------------------------------------------------------------------ Air gun................................ 160 dB RMS re 1 [mu]Pa SPL. Impact pile driving.................... 160 dB RMS re 1 [mu]Pa SPL. Vibratory pile driving................. 120 dB RMS re 1 [mu]Pa SPL. Single explosion (underwater).......... TTS onset threshold (weighted SEL). Multiple explosions (underwater)....... 5 dB less than the TTS onset threshold (weighted SEL). Explosion in Air *..................... 100 dB 20 [mu]Pa (otariid and phocid). ------------------------------------------------------------------------ * Estimated takes from land-based missile and rocket launches are based on pinniped observations during prior activities rather than in-air thresholds. While the best available science for assessing behavioral responses of marine mammals to impulsive sounds relies on data from seismic and pile driving sources, it is likely that these predicted responses using a threshold based on seismic and pile driving represent a worst-case scenario compared to behavioral responses to explosives used in military readiness activities, which would typically consist of single impulses or a cluster of impulses rather than long-duration, repeated impulses (e.g., large-scale air gun arrays). For single explosions at received sound levels below hearing loss thresholds, the most likely behavioral response is a brief alerting or orienting response. Since no further sounds follow the initial brief impulses, significant behavioral responses would not be expected to occur. If a significant response were to occur, the Action Proponents' analysis assumes it would be as a result of an exposure at levels within the range of auditory impacts (TTS and AUD INJ). Because of this approach, the number of auditory impacts is higher than the number of behavioral impacts in the quantified results for some stocks. If more than one explosive event occurs within any given 24-hour period during a military readiness activity, behavioral disturbance is considered more likely to occur and specific criteria are applied to predict the number of animals that may have a behavioral response. For events with multiple explosions, the behavioral threshold used in this analysis is 5 dB less than the TTS onset threshold. This value is derived from observed onsets of behavioral response by test subjects (bottlenose dolphins) during non-impulse TTS testing (Schlundt et al., 2000). Navy Acoustic Effects Model The Navy Acoustic Effects Model (NAEMO) is their standard model for assessing acoustic effects on marine mammals. NAEMO calculates sound energy propagation from sonar and other transducers, air guns, and explosives during military readiness activities and the sound received by animat dosimeters. Animat dosimeters are virtual representations of marine mammals distributed in the area around the modeled activity and each dosimeter records its individual sound ``dose.'' The model bases the distribution of animats over the HCTT Study Area on the density values in the Navy Marine Species Density Database (NMSDD) and distributes animats in the water column proportional to the known time that species spend at varying depths. The model accounts for environmental variability of sound propagation in both distance and depth when computing the sound level received by the animats. The model conducts a statistical analysis based on multiple model runs to compute the estimated effects on animals. The number of animats that exceed the thresholds for effects is tallied to provide an estimate of the number of marine mammals that could be affected. [[Page 32214]] Assumptions in NAEMO intentionally err on the side of overestimation when there are unknowns. The specified activities are modeled as though they would occur regardless of proximity to marine mammals, meaning that the implementation of power downs or shutdowns are not modeled or, thereby, considered in the take estimates. For more information on this process, see the discussion in the Estimated Take from Acoustic Stressors section below. Many explosions from ordnance such as bombs and missiles actually occur upon impact with above-water targets. However, for this analysis, sources such as these were modeled as exploding underwater. This overestimates the amount of explosive and acoustic energy entering the water. The model estimates the acoustic impacts caused by sonars and other transducers, explosives, and air guns during individual military readiness activities. During any individual modeled event, impacts to individual animats are considered over 24-hour periods. The animats do not represent actual animals, but rather they represent a distribution of animals based on density and abundance data, which allows for a statistical analysis of the number of instances that marine mammals may be exposed to sound levels resulting in an effect. Therefore, the model estimates the number of instances in which an effect threshold was exceeded over the course of a year, but does not estimate the number of individual marine mammals that may be impacted over a year (i.e., some marine mammals could be impacted several times, while others would not experience any impact). A detailed explanation of NAEMO is provided in the Acoustic Impacts Technical Report. As NAEMO interrogates the simulation data in the Animat Processor, exposures that are both outside the distance cutoff and below the received level cutoff are omitted when determining the maximum SPL for each animat. This differs from Phase III, in which only distance cutoffs were applied, meaning that all exposures outside the distance cutoffs were omitted, with no consideration of received level. The presence of the two cutoff criteria in Phase IV provides a more accurate and conservative estimation of behavioral effects because louder exposures that would have been omitted previously, when only a distance cutoff was applied, are considered in Phase IV, while the estimation of behavioral effects still omits exposures at distances and received levels that would be unlikely to produce a significant behavioral response. NAEMO retains the capability of calculating behavioral effects without the cutoffs applied, depending on user preference. The impulsive behavioral criteria are not based on the probability of a behavioral response but rather on a single SPL metric. For consideration of impulsive behavioral effects, the cutoff conditions in table 21 are not applied. Pile Driving The Action Proponents performed a quantitative analysis without NAEMO to estimate the number of times marine mammals could be affected by pile driving and extraction used during port damage repair activities at Port Hueneme. The analysis considered details of the activity, sound exposure criteria, and the number and distribution of marine mammals. This information was then used in an ``area*density'' model in which the areas within each footprint (i.e., harassment zone) that encompassed a potential effect were calculated for a given day's activities. The effects analyzed included behavioral response, TTS, and AUD INJ for marine mammals. Then, these areas were multiplied by the density of each marine species within the Port Hueneme area (California sea lion and harbor seal) to estimate the number of effects. Uniform density values for species expected to be present in the nearshore areas where pile driving could occur were estimated using the NMSDD or available survey data specific to the activity location. More detail is provided in the 2024 HCTT Draft EIS/OEIS. Since the same animal can be ``taken'' every day (i.e., 24-hour reset time), the number of predicted effects from a given day were multiplied by the number of days for that activity. This generated a total estimated number of effects over the entire activity, which was then multiplied by the maximum number of times per year this activity could happen. The result was the estimated effects per species and stock in a year. Range to Effects This section provides range (distance) to effects for sonar and other active acoustic sources as well as explosives to specific acoustic thresholds determined using NAEMO. Ranges are determined by modeling the distance that noise from a source will need to propagate to reach exposure level thresholds specific to a hearing group that will cause behavioral response, TTS, AUD INJ, non-auditory injury, and mortality. Ranges to effects (table 23 through table 36) are utilized to help predict impacts from acoustic and explosive sources and assess the benefit of mitigation zones. Marine mammals exposed within these ranges for the shown duration are predicted to experience the associated effect. Range to effects is important information in not only predicting acoustic impacts, but also in verifying the accuracy of model results against real-world situations and determining adequate mitigation ranges to avoid higher level effects, especially physiological effects to marine mammals. Sonar Ranges to effects for sonar were determined by modeling the distance that sound would need to propagate to reach exposure level thresholds specific to a hearing group that would cause behavioral response, TTS, and AUD INJ, as described in the Criteria and Thresholds Technical Report. The ranges do not account for an animal avoiding a source nor for the movement of the platform, both of which would influence the actual range to onset of auditory effects during an actual exposure. Table 23 through table 28 below provide the ranges to TTS and AUD INJ for marine mammals from exposure durations of 1, 30, 60, and 120 seconds (s) for six sonar systems proposed for use (see also appendix A of the application). Due to the lower acoustic thresholds for TTS versus AUD INJ, ranges to TTS are larger. Successive pings can be expected to add together, further increasing the range to the onset of TTS and AUD INJ. Table 23--Very Low-Frequency Cetacean Ranges to Effects for Sonar ---------------------------------------------------------------------------------------------------------------- Duration Sonar type Depth (m) (s) Range to TTS (SD) Range to AUD INJ (SD) ---------------------------------------------------------------------------------------------------------------- Dipping sonar....................... <=200 1 160 m (30 m)........... 12 m (4 m). Dipping sonar....................... <=200 30 312 m (75 m)........... 21 m (6 m). Dipping sonar....................... <=200 60 423 m (97 m)........... 25 m (5 m). [[Page 32215]] Dipping sonar....................... <=200 120 628 m (135 m).......... 35 m (6 m). Dipping sonar....................... >200 1 140 m (20 m)........... 0 m (1 m). Dipping sonar....................... >200 30 260 m (49 m)........... 0 m (8 m). Dipping sonar....................... >200 60 340 m (70 m)........... 23 m (10 m). Dipping sonar....................... >200 120 500 m (112 m).......... 35 m (15 m). MF1 ship sonar...................... <=200 1 1,069 m (252 m)........ 90 m (17 m). MF1 ship sonar...................... <=200 30 1,069 m (252 m)........ 90 m (17 m). MF1 ship sonar...................... <=200 60 1,528 m (465 m)........ 140 m (24 m). MF1 ship sonar...................... <=200 120 1,792 m (636 m)........ 180 m (32 m). MF1 ship sonar...................... >200 1 1,000 m (85 m)......... 85 m (3 m). MF1 ship sonar...................... >200 30 1,000 m (85 m)......... 85 m (3 m). MF1 ship sonar...................... >200 60 1,500 m (252 m)........ 130 m (7 m). MF1 ship sonar...................... >200 120 1,944 m (484 m)........ 170 m (9 m). MF1C ship sonar..................... <=200 1 1,069 m (252 m)........ 90 m (17 m). MF1C ship sonar..................... <=200 30 1,792 m (636 m)........ 180 m (32 m). MF1C ship sonar..................... <=200 60 2,319 m (1,021 m)...... 260 m (56 m). MF1C ship sonar..................... <=200 120 2,845 m (1,479 m)...... 390 m (72 m). MF1C ship sonar..................... >200 1 1,000 m (85 m)......... 85 m (3 m). MF1C ship sonar..................... >200 30 1,944 m (484 m)........ 170 m (9 m). MF1C ship sonar..................... >200 60 2,792 m (1,103 m)...... 250 m (21 m). MF1C ship sonar..................... >200 120 4,000 m (1,599 m)...... 370 m (31 m). MF1K ship sonar..................... <=200 1 193 m (37 m)........... 12 m (4 m). MF1K ship sonar..................... <=200 30 355 m (73 m)........... 24 m (2 m). MF1K ship sonar..................... <=200 60 470 m (83 m)........... 30 m (3 m). MF1K ship sonar..................... <=200 120 668 m (126 m).......... 45 m (13 m). MF1K ship sonar..................... >200 1 190 m (15 m)........... 5 m (5 m). MF1K ship sonar..................... >200 30 340 m (34 m)........... 21 m (11 m). MF1K ship sonar..................... >200 60 440 m (52 m)........... 25 m (3 m). MF1K ship sonar..................... >200 120 625 m (66 m)........... 40 m (2 m). Mine-hunting sonar.................. <=200 1 3 m (1 m).............. 0 m (0 m). Mine-hunting sonar.................. <=200 30 6 m (1 m).............. 0 m (0 m). Mine-hunting sonar.................. <=200 60 9 m (1 m).............. 0 m (0 m). Mine-hunting sonar.................. <=200 120 13 m (2 m)............. 1 m (0 m). Mine-hunting sonar.................. >200 1 0 m (0 m).............. 0 m (0 m). Mine-hunting sonar.................. >200 30 5 m (2 m).............. 0 m (0 m). Mine-hunting sonar.................. >200 60 8 m (3 m).............. 0 m (0 m). Mine-hunting sonar.................. >200 120 12 m (0 m)............. 0 m (0 m). Sonobuoy sonar...................... <=200 1 13 m (6 m)............. 0 m (0 m). Sonobuoy sonar...................... <=200 30 25 m (6 m)............. 0 m (0 m). Sonobuoy sonar...................... <=200 60 35 m (7 m)............. 0 m (1 m). Sonobuoy sonar...................... <=200 120 50 m (4 m)............. 0 m (1 m). Sonobuoy sonar...................... >200 1 0 m (6 m).............. 0 m (0 m). Sonobuoy sonar...................... >200 30 23 m (10 m)............ 0 m (0 m). Sonobuoy sonar...................... >200 60 35 m (11 m)............ 0 m (0 m). Sonobuoy sonar...................... >200 120 50 m (3 m)............. 0 m (0 m). ---------------------------------------------------------------------------------------------------------------- Note: Median ranges are shown with standard deviation (SD) in parentheses. The Action Proponents split the LF functional hearing group into LF and VLF based on Houser et al., (2024). NMFS updated acoustic technical guidance (NMFS, 2024) does not include these data but we have included the VLF group here for reference. Table 24--Low-Frequency Cetacean Ranges to Effects for Sonar ---------------------------------------------------------------------------------------------------------------- Duration Sonar type Depth (m) (s) Range to TTS (SD) Range to AUD INJ (SD) ---------------------------------------------------------------------------------------------------------------- Dipping sonar....................... <=200 1 160 m (56 m)........... 12 m (4 m). Dipping sonar....................... <=200 30 311 m (100 m).......... 21 m (6 m). Dipping sonar....................... <=200 60 411 m (119 m).......... 25 m (7 m). Dipping sonar....................... <=200 120 581 m (137 m).......... 35 m (11 m). Dipping sonar....................... >200 1 150 m (82 m)........... 0 m (6 m). Dipping sonar....................... >200 30 240 m (123 m).......... 17 m (10 m). Dipping sonar....................... >200 60 287 m (160 m).......... 25 m (13 m). Dipping sonar....................... >200 120 409 m (133 m).......... 35 m (18 m). MF1 ship sonar...................... <=200 1 1,069 m (280 m)........ 95 m (19 m). MF1 ship sonar...................... <=200 30 1,069 m (280 m)........ 95 m (19 m). MF1 ship sonar...................... <=200 60 1,500 m (500 m)........ 140 m (24 m). MF1 ship sonar...................... <=200 120 1,736 m (668 m)........ 180 m (30 m). MF1 ship sonar...................... >200 1 1,000 m (185 m)........ 90 m (5 m). MF1 ship sonar...................... >200 30 1,000 m (185 m)........ 90 m (5 m). MF1 ship sonar...................... >200 60 1,569 m (415 m)........ 140 m (12 m). MF1 ship sonar...................... >200 120 2,153 m (734 m)........ 180 m (14 m). [[Page 32216]] MF1C ship sonar..................... <=200 1 1,069 m (280 m)........ 95 m (19 m). MF1C ship sonar..................... <=200 30 1,736 m (668 m)........ 180 m (30 m). MF1C ship sonar..................... <=200 60 2,194 m (1,062 m)...... 270 m (49 m). MF1C ship sonar..................... <=200 120 2,667 m (1,519 m)...... 399 m (68 m). MF1C ship sonar..................... >200 1 1,000 m (185 m)........ 90 m (5 m). MF1C ship sonar..................... >200 30 2,153 m (734 m)........ 180 m (14 m). MF1C ship sonar..................... >200 60 3,111 m (1,305 m)...... 260 m (21 m). MF1C ship sonar..................... >200 120 4,333 m (1,845 m)...... 380 m (29 m). MF1K ship sonar..................... <=200 1 200 m (34 m)........... 14 m (1 m). MF1K ship sonar..................... <=200 30 360 m (67 m)........... 25 m (1 m). MF1K ship sonar..................... <=200 60 480 m (84 m)........... 30 m (4 m). MF1K ship sonar..................... <=200 120 661 m (135 m).......... 45 m (14 m). MF1K ship sonar..................... >200 1 200 m (21 m)........... 12 m (1 m). MF1K ship sonar..................... >200 30 350 m (32 m)........... 24 m (0 m). MF1K ship sonar..................... >200 60 450 m (44 m)........... 30 m (0 m). MF1K ship sonar..................... >200 120 650 m (88 m)........... 45 m (0 m). Mine-hunting sonar.................. <=200 1 8 m (5 m).............. 0 m (0 m). Mine-hunting sonar.................. <=200 30 15 m (8 m)............. 1 m (0 m). Mine-hunting sonar.................. <=200 60 21 m (12 m)............ 2 m (1 m). Mine-hunting sonar.................. <=200 120 30 m (12 m)............ 3 m (2 m). Mine-hunting sonar.................. >200 1 8 m (5 m).............. 0 m (0 m). Mine-hunting sonar.................. >200 30 15 m (8 m)............. 0 m (0 m). Mine-hunting sonar.................. >200 60 21 m (12 m)............ 0 m (1 m). Mine-hunting sonar.................. >200 120 30 m (12 m)............ 0 m (1 m). Sonobuoy sonar...................... <=200 1 0 m (8 m).............. 0 m (0 m). Sonobuoy sonar...................... <=200 30 25 m (12 m)............ 0 m (0 m). Sonobuoy sonar...................... <=200 60 35 m (18 m)............ 0 m (0 m). Sonobuoy sonar...................... <=200 120 55 m (25 m)............ 0 m (1 m). Sonobuoy sonar...................... >200 1 0 m (7 m).............. 0 m (0 m). Sonobuoy sonar...................... >200 30 19 m (12 m)............ 0 m (0 m). Sonobuoy sonar...................... >200 60 35 m (19 m)............ 0 m (0 m). Sonobuoy sonar...................... >200 120 55 m (28 m)............ 0 m (1 m). ---------------------------------------------------------------------------------------------------------------- Note: Median ranges are shown with standard deviation (SD) in parentheses. The Action Proponents split the LF functional hearing group into LF and VLF based on Houser et al., (2024). NMFS updated acoustic technical guidance (NMFS, 2024) does not include these data but we have included the VLF group here for reference. Table 25--High-Frequency Cetacean Ranges to Effects for Sonar ---------------------------------------------------------------------------------------------------------------- Duration Sonar type Depth (m) (s) Range to TTS (SD) Range to AUD INJ (SD) ---------------------------------------------------------------------------------------------------------------- Dipping sonar....................... <=200 1 55 m (15 m)............ 5 m (2 m). Dipping sonar....................... <=200 30 120 m (34 m)........... 9 m (4 m). Dipping sonar....................... <=200 60 170 m (50 m)........... 12 m (5 m). Dipping sonar....................... <=200 120 250 m (85 m)........... 18 m (6 m). Dipping sonar....................... >200 1 50 m (28 m)............ 0 m (2 m). Dipping sonar....................... >200 30 100 m (54 m)........... 0 m (4 m). Dipping sonar....................... >200 60 130 m (74 m)........... 0 m (5 m). Dipping sonar....................... >200 120 200 m (105 m).......... 0 m (8 m). MF1 ship sonar...................... <=200 1 644 m (113 m).......... 45 m (7 m). MF1 ship sonar...................... <=200 30 644 m (113 m).......... 45 m (7 m). MF1 ship sonar...................... <=200 60 910 m (177 m).......... 65 m (12 m). MF1 ship sonar...................... <=200 120 1,011 m (243 m)........ 85 m (14 m). MF1 ship sonar...................... >200 1 600 m (52 m)........... 40 m (11 m). MF1 ship sonar...................... >200 30 600 m (52 m)........... 40 m (11 m). MF1 ship sonar...................... >200 60 875 m (93 m)........... 65 m (14 m). MF1 ship sonar...................... >200 120 1,000 m (126 m)........ 85 m (7 m). MF1C ship sonar..................... <=200 1 644 m (113 m).......... 45 m (7 m). MF1C ship sonar..................... <=200 30 1,011 m (243 m)........ 85 m (14 m). MF1C ship sonar..................... <=200 60 1,458 m (437 m)........ 130 m (23 m). MF1C ship sonar..................... <=200 120 1,903 m (730 m)........ 200 m (36 m). MF1C ship sonar..................... >200 1 600 m (52 m)........... 40 m (11 m). MF1C ship sonar..................... >200 30 1,000 m (126 m)........ 85 m (7 m). MF1C ship sonar..................... >200 60 1,500 m (309 m)........ 130 m (12 m). MF1C ship sonar..................... >200 120 2,142 m (786 m)........ 200 m (17 m). MF1K ship sonar..................... <=200 1 100 m (21 m)........... 7 m (3 m). MF1K ship sonar..................... <=200 30 190 m (34 m)........... 13 m (4 m). MF1K ship sonar..................... <=200 60 250 m (51 m)........... 17 m (5 m). MF1K ship sonar..................... <=200 120 363 m (72 m)........... 25 m (2 m). MF1K ship sonar..................... >200 1 100 m (19 m)........... 0 m (3 m). [[Page 32217]] MF1K ship sonar..................... >200 30 180 m (20 m)........... 11 m (6 m). MF1K ship sonar..................... >200 60 240 m (27 m)........... 16 m (8 m). MF1K ship sonar..................... >200 120 350 m (39 m)........... 24 m (11 m). Mine-hunting sonar.................. <=200 1 8 m (3 m).............. 0 m (0 m). Mine-hunting sonar.................. <=200 30 15 m (5 m)............. 1 m (0 m). Mine-hunting sonar.................. <=200 60 21 m (6 m)............. 1 m (1 m). Mine-hunting sonar.................. <=200 120 30 m (6 m)............. 2 m (1 m). Mine-hunting sonar.................. >200 1 7 m (3 m).............. 0 m (0 m). Mine-hunting sonar.................. >200 30 15 m (6 m)............. 0 m (0 m). Mine-hunting sonar.................. >200 60 21 m (7 m)............. 0 m (1 m). Mine-hunting sonar.................. >200 120 30 m (5 m)............. 0 m (1 m). Sonobuoy sonar...................... <=200 1 8 m (4 m).............. 0 m (0 m). Sonobuoy sonar...................... <=200 30 18 m (8 m)............. 0 m (0 m). Sonobuoy sonar...................... <=200 60 25 m (12 m)............ 0 m (0 m). Sonobuoy sonar...................... <=200 120 35 m (14 m)............ 0 m (1 m). Sonobuoy sonar...................... >200 1 0 m (4 m).............. 0 m (0 m). Sonobuoy sonar...................... >200 30 0 m (9 m).............. 0 m (0 m). Sonobuoy sonar...................... >200 60 0 m (12 m)............. 0 m (0 m). Sonobuoy sonar...................... >200 120 30 m (16 m)............ 0 m (1 m). ---------------------------------------------------------------------------------------------------------------- Note: Median ranges are shown with standard deviation (SD) in parentheses. Table 26--Very High-Frequency Cetacean Ranges to Effects for Sonar ---------------------------------------------------------------------------------------------------------------- Duration Sonar type Depth (m) (s) Range to TTS (SD) Range to AUD INJ (SD) ---------------------------------------------------------------------------------------------------------------- Dipping sonar....................... <=200 1 100 m (30 m)........... 8 m (2 m). Dipping sonar....................... <=200 30 202 m (77 m)........... 14 m (4 m). Dipping sonar....................... <=200 60 278 m (93 m)........... 19 m (5 m). Dipping sonar....................... <=200 120 420 m (100 m).......... 25 m (7 m). Dipping sonar....................... >200 1 95 m (50 m)............ 0 m (3 m). Dipping sonar....................... >200 30 180 m (101 m).......... 0 m (6 m). Dipping sonar....................... >200 60 240 m (123 m).......... 14 m (8 m). Dipping sonar....................... >200 120 330 m (85 m)........... 24 m (12 m). MF1 ship sonar...................... <=200 1 1,528 m (471 m)........ 150 m (25 m). MF1 ship sonar...................... <=200 30 1,528 m (471 m)........ 150 m (25 m). MF1 ship sonar...................... <=200 60 2,000 m (756 m)........ 220 m (39 m). MF1 ship sonar...................... <=200 120 2,250 m (974 m)........ 280 m (57 m). MF1 ship sonar...................... >200 1 1,569 m (357 m)........ 150 m (12 m). MF1 ship sonar...................... >200 30 1,569 m (357 m)........ 150 m (12 m). MF1 ship sonar...................... >200 60 2,403 m (885 m)........ 220 m (20 m). MF1 ship sonar...................... >200 120 2,944 m (1,143 m)...... 270 m (27 m). MF1C ship sonar..................... <=200 1 1,528 m (471 m)........ 150 m (25 m). MF1C ship sonar..................... <=200 30 2,250 m (974 m)........ 280 m (57 m). MF1C ship sonar..................... <=200 60 2,722 m (1,373 m)...... 417 m (68 m). MF1C ship sonar..................... <=200 120 3,330 m (1,819 m)...... 588 m (99 m). MF1C ship sonar..................... >200 1 1,569 m (357 m)........ 150 m (12 m). MF1C ship sonar..................... >200 30 2,944 m (1,143 m)...... 270 m (27 m). MF1C ship sonar..................... >200 60 4,097 m (1,620 m)...... 390 m (29 m). MF1C ship sonar..................... >200 120 5,972 m (2,314 m)...... 550 m (38 m). MF1K ship sonar..................... <=200 1 315 m (60 m)........... 20 m (2 m). MF1K ship sonar..................... <=200 30 550 m (103 m).......... 35 m (5 m). MF1K ship sonar..................... <=200 60 712 m (139 m).......... 50 m (12 m). MF1K ship sonar..................... <=200 120 958 m (214 m).......... 85 m (12 m). MF1K ship sonar..................... >200 1 300 m (37 m)........... 16 m (2 m). MF1K ship sonar..................... >200 30 525 m (43 m)........... 35 m (1 m). MF1K ship sonar..................... >200 60 675 m (66 m)........... 50 m (2 m). MF1K ship sonar..................... >200 120 975 m (116 m).......... 85 m (4 m). Mine-hunting sonar.................. <=200 1 90 m (26 m)............ 9 m (1 m). Mine-hunting sonar.................. <=200 30 190 m (85 m)........... 16 m (2 m). Mine-hunting sonar.................. <=200 60 329 m (128 m).......... 22 m (2 m). Mine-hunting sonar.................. <=200 120 521 m (166 m).......... 30 m (3 m). Mine-hunting sonar.................. >200 1 90 m (6 m)............. 7 m (1 m). Mine-hunting sonar.................. >200 30 150 m (30 m)........... 15 m (0 m). Mine-hunting sonar.................. >200 60 210 m (57 m)........... 22 m (0 m). Mine-hunting sonar.................. >200 120 300 m (79 m)........... 30 m (0 m). Sonobuoy sonar...................... <=200 1 65 m (20 m)............ 0 m (2 m). Sonobuoy sonar...................... <=200 30 126 m (39 m)........... 9 m (5 m). Sonobuoy sonar...................... <=200 60 191 m (79 m)........... 15 m (5 m). Sonobuoy sonar...................... <=200 120 314 m (120 m).......... 22 m (7 m). [[Page 32218]] Sonobuoy sonar...................... >200 1 65 m (31 m)............ 0 m (1 m). Sonobuoy sonar...................... >200 30 110 m (59 m)........... 0 m (4 m). Sonobuoy sonar...................... >200 60 180 m (75 m)........... 10 m (7 m). Sonobuoy sonar...................... >200 120 276 m (72 m)........... 21 m (10 m). ---------------------------------------------------------------------------------------------------------------- Note: Median ranges are shown with standard deviation (SD) in parentheses. Table 27--Phocid Carnivore in Water Ranges to Effects for Sonar ---------------------------------------------------------------------------------------------------------------- Duration Sonar type Depth (m) (s) Range to TTS (SD) Range to AUD INJ (SD) ---------------------------------------------------------------------------------------------------------------- Dipping sonar....................... <=200 1 200 m (52 m)........... 0 m (7 m). Dipping sonar....................... <=200 30 370 m (101 m).......... 21 m (12 m). Dipping sonar....................... <=200 60 496 m (134 m).......... 30 m (15 m). Dipping sonar....................... <=200 120 707 m (144 m).......... 45 m (12 m). Dipping sonar....................... >200 1 160 m (71 m)........... 0 m (4 m). Dipping sonar....................... >200 30 298 m (129 m).......... 0 m (8 m). Dipping sonar....................... >200 60 370 m (170 m).......... 0 m (10 m). Dipping sonar....................... >200 120 550 m (80 m)........... 0 m (19 m). MF1 ship sonar...................... <=200 1 1,250 m (384 m)........ 120 m (20 m). MF1 ship sonar...................... <=200 30 1,250 m (384 m)........ 120 m (20 m). MF1 ship sonar...................... <=200 60 1,625 m (632 m)........ 180 m (33 m). MF1 ship sonar...................... <=200 120 1,875 m (833 m)........ 230 m (45 m). MF1 ship sonar...................... >200 1 1,250 m (282 m)........ 120 m (53 m). MF1 ship sonar...................... >200 30 1,250 m (282 m)........ 120 m (53 m). MF1 ship sonar...................... >200 60 1,792 m (696 m)........ 180 m (21 m). MF1 ship sonar...................... >200 120 2,264 m (982 m)........ 230 m (23 m). MF1C ship sonar..................... <=200 1 1,250 m (384 m)........ 120 m (20 m). MF1C ship sonar..................... <=200 30 1,875 m (833 m)........ 230 m (45 m). MF1C ship sonar..................... <=200 60 2,333 m (1,223 m)...... 330 m (73 m). MF1C ship sonar..................... <=200 120 2,833 m (1,633 m)...... 481 m (97 m). MF1C ship sonar..................... >200 1 1,250 m (282 m)........ 120 m (53 m). MF1C ship sonar..................... >200 30 2,264 m (982 m)........ 230 m (23 m). MF1C ship sonar..................... >200 60 3,368 m (1,399 m)...... 330 m (31 m). MF1C ship sonar..................... >200 120 4,500 m (1,973 m)...... 462 m (46 m). MF1K ship sonar..................... <=200 1 248 m (58 m)........... 0 m (9 m). MF1K ship sonar..................... <=200 30 435 m (97 m)........... 25 m (8 m). MF1K ship sonar..................... <=200 60 550 m (133 m).......... 35 m (10 m). MF1K ship sonar..................... <=200 120 771 m (190 m).......... 65 m (14 m). MF1K ship sonar..................... >200 1 240 m (26 m)........... 0 m (8 m). MF1K ship sonar..................... >200 30 430 m (48 m)........... 24 m (13 m). MF1K ship sonar..................... >200 60 550 m (61 m)........... 35 m (16 m). MF1K ship sonar..................... >200 120 775 m (105 m).......... 65 m (28 m). Mine-hunting sonar.................. <=200 1 12 m (7 m)............. 0 m (0 m). Mine-hunting sonar.................. <=200 30 24 m (11 m)............ 0 m (1 m). Mine-hunting sonar.................. <=200 60 35 m (11 m)............ 0 m (1 m). Mine-hunting sonar.................. <=200 120 50 m (15 m)............ 0 m (2 m). Mine-hunting sonar.................. >200 1 0 m (5 m).............. 0 m (0 m). Mine-hunting sonar.................. >200 30 22 m (9 m)............. 0 m (0 m). Mine-hunting sonar.................. >200 60 30 m (4 m)............. 0 m (1 m). Mine-hunting sonar.................. >200 120 45 m (5 m)............. 0 m (1 m). Sonobuoy sonar...................... <=200 1 0 m (11 m)............. 0 m (0 m). Sonobuoy sonar...................... <=200 30 35 m (16 m)............ 0 m (1 m). Sonobuoy sonar...................... <=200 60 50 m (19 m)............ 0 m (1 m). Sonobuoy sonar...................... <=200 120 75 m (20 m)............ 0 m (3 m). Sonobuoy sonar...................... >200 1 0 m (7 m).............. 0 m (0 m). Sonobuoy sonar...................... >200 30 0 m (16 m)............. 0 m (0 m). Sonobuoy sonar...................... >200 60 45 m (23 m)............ 0 m (0 m). Sonobuoy sonar...................... >200 120 70 m (32 m)............ 0 m (1 m). ---------------------------------------------------------------------------------------------------------------- Note: Median ranges are shown with standard deviation (SD) in parentheses. Table 28--Otariid Carnivore in Water Ranges to Effects for Sonar ---------------------------------------------------------------------------------------------------------------- Duration Sonar type Depth (m) (s) Range to TTS (SD) Range to AUD INJ (SD) ---------------------------------------------------------------------------------------------------------------- Dipping sonar....................... <=200 1 60 m (16 m)............ 0 m (3 m). Dipping sonar....................... <=200 30 130 m (40 m)........... 0 m (5 m). Dipping sonar....................... <=200 60 180 m (58 m)........... 0 m (6 m). [[Page 32219]] Dipping sonar....................... <=200 120 274 m (88 m)........... 11 m (9 m). Dipping sonar....................... >200 1 55 m (30 m)............ 0 m (2 m). Dipping sonar....................... >200 30 120 m (66 m)........... 0 m (4 m). Dipping sonar....................... >200 60 160 m (90 m)........... 0 m (5 m). Dipping sonar....................... >200 120 210 m (116 m).......... 0 m (8 m). MF1 ship sonar...................... <=200 1 726 m (148 m).......... 50 m (10 m). MF1 ship sonar...................... <=200 30 726 m (148 m).......... 50 m (10 m). MF1 ship sonar...................... <=200 60 981 m (220 m).......... 80 m (12 m). MF1 ship sonar...................... <=200 120 1,139 m (296 m)........ 109 m (18 m). MF1 ship sonar...................... >200 1 725 m (93 m)........... 50 m (1 m). MF1 ship sonar...................... >200 30 725 m (93 m)........... 50 m (1 m). MF1 ship sonar...................... >200 60 1,000 m (157 m)........ 80 m (5 m). MF1 ship sonar...................... >200 120 1,250 m (251 m)........ 100 m (8 m). MF1C ship sonar..................... <=200 1 726 m (148 m).......... 50 m (10 m). MF1C ship sonar..................... <=200 30 1,139 m (296 m)........ 109 m (18 m). MF1C ship sonar..................... <=200 60 1,500 m (462 m)........ 160 m (23 m). MF1C ship sonar..................... <=200 120 1,861 m (690 m)........ 240 m (40 m). MF1C ship sonar..................... >200 1 725 m (93 m)........... 50 m (1 m). MF1C ship sonar..................... >200 30 1,250 m (251 m)........ 100 m (8 m). MF1C ship sonar..................... >200 60 1,750 m (549 m)........ 160 m (12 m). MF1C ship sonar..................... >200 120 2,250 m (1,071 m)...... 240 m (22 m). MF1K ship sonar..................... <=200 1 120 m (22 m)........... 8 m (4 m). MF1K ship sonar..................... <=200 30 230 m (40 m)........... 16 m (4 m). MF1K ship sonar..................... <=200 60 300 m (56 m)........... 20 m (3 m). MF1K ship sonar..................... <=200 120 426 m (77 m)........... 25 m (4 m). MF1K ship sonar..................... >200 1 120 m (12 m)........... 0 m (4 m). MF1K ship sonar..................... >200 30 220 m (30 m)........... 14 m (6 m). MF1K ship sonar..................... >200 60 290 m (38 m)........... 20 m (5 m). MF1K ship sonar..................... >200 120 420 m (58 m)........... 25 m (1 m). Mine-hunting sonar.................. <=200 1 6 m (3 m).............. 0 m (0 m). Mine-hunting sonar.................. <=200 30 11 m (6 m)............. 0 m (0 m). Mine-hunting sonar.................. <=200 60 18 m (8 m)............. 0 m (0 m). Mine-hunting sonar.................. <=200 120 25 m (10 m)............ 0 m (1 m). Mine-hunting sonar.................. >200 1 6 m (3 m).............. 0 m (0 m). Mine-hunting sonar.................. >200 30 11 m (5 m)............. 0 m (0 m). Mine-hunting sonar.................. >200 60 18 m (7 m)............. 0 m (0 m). Mine-hunting sonar.................. >200 120 25 m (10 m)............ 0 m (1 m). Sonobuoy sonar...................... <=200 1 0 m (6 m).............. 0 m (0 m). Sonobuoy sonar...................... <=200 30 18 m (11 m)............ 0 m (0 m). Sonobuoy sonar...................... <=200 60 30 m (13 m)............ 0 m (1 m). Sonobuoy sonar...................... <=200 120 45 m (20 m)............ 0 m (1 m). Sonobuoy sonar...................... >200 1 0 m (5 m).............. 0 m (0 m). Sonobuoy sonar...................... >200 30 0 m (11 m)............. 0 m (0 m). Sonobuoy sonar...................... >200 60 25 m (14 m)............ 0 m (0 m). Sonobuoy sonar...................... >200 120 40 m (22 m)............ 0 m (1 m). ---------------------------------------------------------------------------------------------------------------- Note: Median ranges are shown with standard deviation (SD) in parentheses. Air Guns Ranges to effects for air guns were determined by modeling the distance that sound would need to propagate to reach exposure level thresholds specific to a hearing group that would cause behavioral response, TTS, and AUD INJ, as described in the Criteria and Thresholds Technical Report. The air gun ranges to effects for TTS and AUD INJ in table 29 are based on the metric (i.e., SEL or SPL) that produced larger ranges. Table 29--Range to Effects for Air Guns ---------------------------------------------------------------------------------------------------------------- Behavioral Range to TTS Range to AUD INJ Functional hearing group Depth (m) Cluster size disturbance (SD) (SD) ---------------------------------------------------------------------------------------------------------------- VLF........................ <=200 1 N/A............... 5 m (0 m)........ 1 m (1 m). VLF........................ <=200 10 114 m (6 m)....... 81 m (1 m)....... 14 m (0 m). VLF........................ >200 1 N/A............... 5 m (0 m)........ 1 m (1 m). VLF........................ >200 10 115 m (7 m)....... 81 m (1 m)....... 14 m (0 m). LF......................... <=200 1 N/A............... 5 m (0 m)........ 2 m (0 m). LF......................... <=200 10 104 m (10 m)...... 36 m (1 m)....... 6 m (0 m). LF......................... >200 1 N/A............... 5 m (0 m)........ 2 m (0 m). LF......................... >200 10 107 m (11 m)...... 35 m (1 m)....... 6 m (0 m). HF......................... <=200 1 N/A............... 2 m (1 m)........ 0 m (0 m). HF......................... <=200 10 111 m (10 m)...... 2 m (1 m)........ 0 m (0 m). [[Page 32220]] HF......................... >200 1 N/A............... 2 m (1 m)........ 0 m (0 m). HF......................... >200 10 112 m (13 m)...... 2 m (1 m)........ 0 m (0 m). VHF........................ <=200 1 N/A............... 51 m (2 m)....... 25 m (0 m). VHF........................ <=200 10 111 m (13 m)...... 51 m (2 m)....... 25 m (0 m). VHF........................ >200 1 N/A............... 50 m (1 m)....... 25 m (0 m). VHF........................ >200 10 119 m (14 m)...... 50 m (1 m)....... 25 m (0 m). PCW........................ <=200 1 N/A............... 5 m (2 m)........ 2 m (1 m). PCW........................ <=200 10 110 m (11 m)...... 7 m (3 m)........ 2 m (1 m). PCW........................ >200 1 N/A............... 5 m (2 m)........ 2 m (1 m). PCW........................ >200 10 113 m (23 m)...... 7 m (3 m)........ 2 m (1 m). OCW........................ <=200 1 N/A............... 2 m (0 m)........ 1 m (0 m). OCW........................ <=200 10 112 m (18 m)...... 2 m (0 m)........ 1 m (0 m). OCW........................ >200 1 N/A............... 2 m (0 m)........ 1 m (0 m). OCW........................ >200 10 118 m (19 m)...... 2 m (0 m)........ 1 m (0 m). ---------------------------------------------------------------------------------------------------------------- Note: N/A = Not Applicable. The values listed for TTS and AUD INJ are the greater of the respective SPL and SEL ranges. Median ranges are shown with standard deviation (SD) in parentheses. The Action Proponents split the LF functional hearing group into LF and VLF based on Houser et al., (2024). NMFS updated acoustic technical guidance (NMFS, 2024) does not include these data but we have included the VLF group here for reference. Pile Driving Only California sea lions (U.S. stock) and harbor seals (California stock) are expected to be present in the waters of Port Hueneme, where impact and vibratory pile driving and extraction is proposed to occur up to 12 times per year. Table 30 shows the predicted ranges to AUD INJ, TTS, and behavioral response for the otariid carnivore in water and phocid carnivore in water hearing groups (the only functional hearing groups expected in the vicinity of pile driving and extraction activities) that were analyzed for their exposure to impact and vibratory pile driving. These ranges were estimated based on activity parameters described in the Acoustic Stressors section of the Explosive and Acoustic Analysis Report (see appendix A of the application) and using the calculations described in the Acoustic Impacts Technical Report. Table 30--Range to Effects for Pinnipeds from Pile Driving ---------------------------------------------------------------------------------------------------------------- Behavioral Range to Pile type Method Functional hearing response Range to AUD INJ group (m) TTS (m) (m) ---------------------------------------------------------------------------------------------------------------- 20-inch (51 cm) round timber/ Impact............. OCW............... 46 43 4 plastic. 20-inch (51 cm) H steel......... Impact............. OCW............... 215 201 20 20-inch (51 cm) round or H steel/ Impact............. OCW............... 858 685 69 timber/plastic. 27.5-inch (70 cm) sheet or Z Vibratory.......... OCW............... 3,981 12 1 steel. 20-inch (51 cm) round steel/ Vibratory.......... OCW............... 3,981 36 2 timber/plastic. 20-inch (51 cm) round timber/ Impact............. PCW............... 46 116 12 plastic. 20-inch (51 cm) H steel......... Impact............. PCW............... 215 538 54 20-inch (51 cm) round or H steel/ Impact............. PCW............... 858 1,839 184 timber/plastic. 27.5-inch (70 cm) sheet or Z Vibratory.......... PCW............... 11,659 35 2 steel. 20-inch (51 cm) round steel/ Vibratory.......... PCW............... 11,659 105 5 timber/plastic. ---------------------------------------------------------------------------------------------------------------- Note: cm = centimeter. Explosives This section provides the range (i.e., distance) over which specific physiological or behavioral effects are expected to occur based on the explosive criteria (see section 6.2.1 (Impacts from Explosives) of the application and the Criteria and Thresholds Technical Report and the explosive propagation calculations from NAEMO. The range to effects are shown for a range of explosive bins, from E1 (0.1-0.25 lb (0.045-0.113 kg) NEW) to E16 (greater than 7,250-14,500 lb (3,288-6,577 kg) NEW (ship shock trial only)) (table 31 through table 36). Ranges are determined by modeling the distance that noise from an explosion would need to propagate to reach exposure level thresholds specific to a hearing group that would cause behavioral response (to the degree of Level B behavioral harassment), TTS, and AUD INJ. NMFS has reviewed the range distance to effect data provided by the Action Proponents and concurs with the analysis. Range to effects is important information in not only predicting impacts from explosives, but also in verifying the accuracy of model results against real-world situations and determining appropriate mitigation ranges to avoid higher level effects, especially injury to marine mammals. For additional information on how ranges to impacts from explosions were estimated, see the Acoustic Impacts Technical Report. Table 31 through table 36 show the minimum, average, and maximum ranges to onset of auditory and likely behavioral effects that qualify as Level B harassment for all functional hearing groups based on the developed thresholds. Ranges are provided for a representative source depth and cluster size (i.e., the number of rounds fired, or buoys dropped, within a very short duration) for each bin. Ranges for behavioral response are only provided if more than one explosive cluster occurs. As noted previously, single explosions at received sound levels below TTS and AUD INJ thresholds are most likely to result in a brief alerting or orienting [[Page 32221]] response. For events with multiple explosions, sound from successive explosions can be expected to accumulate and increase the range to the onset of an impact based on SEL thresholds. Modeled ranges to TTS and AUD INJ based on peak pressure for a single explosion generally exceed the modeled ranges based on SEL even when accumulated for multiple explosions. Peak pressure-based ranges are estimated using the best available science; however, data on peak pressure at far distances from explosions are very limited. The explosive ranges to effects for TTS and AUD INJ that are in the tables are based on the metric (i.e., SEL or SPL) that produced larger ranges. Table 37 shows ranges to non-auditory injury and mortality as a function of animal mass and explosive bin. For non-auditory injury, the larger of the ranges to slight lung injury or gastrointestinal tract injury was used as a conservative estimate, and the boxplots in appendix A to the application present ranges for both metrics for comparison. For the non-auditory metric, ranges are only available for a cluster size of one. Animals within water volumes encompassing the estimated range to non-auditory injury would be expected to receive minor injuries at the outer ranges, increasing to more substantial injuries, and finally mortality as an animal approaches the detonation point. Table 31--Very Low-Frequency Cetacean Ranges to Effects for Explosives ---------------------------------------------------------------------------------------------------------------- Range to Bin Depth (m) Cluster size behavioral Range to TTS (SD) Range to AUD INJ disturbance (SD) (SD) ---------------------------------------------------------------------------------------------------------------- E1......................... <=200 1 N/A............... 206 m (73 m)..... 95 m (2 m). E1......................... <=200 5 618 m (230 m)..... 390 m (161 m).... 95 m (19 m). E1......................... <=200 25 1,246 m (444 m)... 785 m (267 m).... 182 m (61 m). E1......................... <=200 50 1,419 m (471 m)... 800 m (178 m).... 250 m (34 m). E1......................... >200 1 N/A............... 220 m (55 m)..... 95 m (3 m). E1......................... >200 5 600 m (61 m)...... 430 m (18 m)..... 95 m (2 m). E1......................... >200 25 950 m (155 m)..... 700 m (84 m)..... 190 m (5 m). E1......................... >200 50 1,000 m (290 m)... 850 m (98 m)..... 270 m (5 m). E2......................... <=200 1 N/A............... 362 m (42 m)..... 130 m (12 m). E2......................... >200 1 N/A............... 370 m (46 m)..... 130 m (13 m). E3......................... <=200 1 N/A............... 489 m (387 m).... 213 m (6 m). E3......................... <=200 5 1,531 m (615 m)... 909 m (370 m).... 213 m (6 m). E3......................... <=200 25 2,764 m (1,211 m). 1,722 m (685 m).. 414 m (178 m). E3......................... >200 1 N/A............... 825 m (304 m).... 214 m (7 m). E3......................... >200 5 1,000 m (346 m)... 751 m (154 m).... 220 m (5 m). E3......................... >200 25 1,750 m (971 m)... 1,000 m (369 m).. 420 m (26 m). E4......................... <=200 1 N/A............... 1,875 m (768 m).. 382 m (26 m). E4......................... >200 1 N/A............... 1,250 m (277 m).. 377 m (28 m). E5......................... <=200 1 N/A............... 815 m (851 m).... 358 m (27 m). E5......................... <=200 5 2,986 m (1,306 m). 1,586 m (714 m).. 358 m (27 m). E5......................... >200 1 N/A............... 650 m (152 m).... 343 m (25 m). E5......................... >200 5 2,146 m (956 m)... 1,056 m (452 m).. 350 m (54 m). E5......................... >200 20 3,889 m (975 m)... 2,625 m (600 m).. 575 m (178 m). E6......................... <=200 1 N/A............... 1,836 m (1,341 m) 534 m (382 m). E6......................... <=200 15 7,258 m (1,106 m). 5,397 m (814 m).. 2,029 m (104 m). E6......................... >200 1 N/A............... 1,347 m (762 m).. 516 m (48 m). E7......................... <=200 1 N/A............... 1,651 m (729 m).. 535 m (25 m). E7......................... >200 1 N/A............... 1,556 m (1,347 m) 537 m (24 m). E8......................... <=200 1 N/A............... 2,549 m (485 m).. 769 m (55 m). E8......................... >200 1 N/A............... 2,519 m (477 m).. 754 m (54 m). E9......................... <=200 1 N/A............... 3,417 m (1,563 m) 755 m (49 m). E9......................... >200 1 N/A............... 2,667 m (1,186 m) 754 m (49 m). E10........................ <=200 1 N/A............... 4,272 m (840 m).. 891 m (88 m). E10........................ >200 1 N/A............... 4,264 m (820 m).. 889 m (100 m). E11........................ <=200 1 N/A............... 14,182 m (3,939 1,778 m (60 m). m). E11........................ >200 1 N/A............... 14,814 m (4,258 1,833 m (116 m). m). E12........................ <=200 1 N/A............... 4,523 m (910 m).. 992 m (78 m). E12........................ >200 1 N/A............... 4,349 m (813 m).. 981 m (165 m). E13........................ <=200 1 N/A............... 7,208 m (5,750 m) 3,361 m (1,875 m). E16........................ >200 1 N/A............... 10,778 m (8,250 2,438 m (65 m). m). ---------------------------------------------------------------------------------------------------------------- Note: N/A = Not Applicable. Behavioral response criteria are applied to explosive clusters >1. The values listed for TTS and AUD INJ are the greater of the respective SPL and SEL ranges. Median ranges are shown with standard deviation (SD) in parentheses. The Action Proponents split the LF functional hearing group into LF and VLF based on Houser et al. (2024). NMFS updated acoustic technical guidance (NMFS, 2024) does not include these data but we have included the VLF group here for reference. E1 (0.1-0.25 lbs (0.045-0.113 kg)), E2 (>0.25-0.5 lbs (0.113-0.23 kg)), E3 (>0.5-2.5 lbs (0.23-1.13 kg)), E4 (>2.5-5 lbs (1.13-2.27 kg)), E5 (>5-10 lbs (2.27-4.54 kg)), E6 (>10-20 lbs (4.54-9.07 kg)), E7 (>20-60 lbs (9.07-27.2 kg)), E8 (>60-100 lbs (27.2- 45.4 kg)), E9 (>100-250 lbs (45.4-113 kg)), E10 (>250-500 lbs (113-227 kg)), E11 (>500-675 lbs (227-306 kg)), E12 (>675-1,000 lbs (306-454 kg)), E13 (>1,000-1,740 lbs (454-789 kg)), E16 (10,000 lbs (4,536 kg)). Table 32--Low-Frequency Cetacean Ranges to Effects for Explosives ---------------------------------------------------------------------------------------------------------------- Range to Bin Depth (m) Cluster size behavioral Range to TTS (SD) Range to AUD INJ disturbance (SD) (SD) ---------------------------------------------------------------------------------------------------------------- E1......................... <=200 1 N/A............... 214 m (76 m)..... 92 m (7 m). [[Page 32222]] E1......................... <=200 5 726 m (232 m)..... 428 m (164 m).... 100 m (22 m). E1......................... <=200 25 1,342 m (462 m)... 884 m (266 m).... 194 m (63 m). E1......................... <=200 50 1,457 m (602 m)... 846 m (296 m).... 240 m (47 m). E1......................... >200 1 N/A............... 250 m (60 m)..... 93 m (7 m). E1......................... >200 5 725 m (140 m)..... 480 m (87 m)..... 110 m (8 m). E1......................... >200 25 1,000 m (243 m)... 800 m (162 m).... 220 m (24 m). E1......................... >200 50 1,153 m (318 m)... 950 m (179 m).... 310 m (39 m). E2......................... <=200 1 N/A............... 375 m (57 m)..... 128 m (16 m). E2......................... >200 1 N/A............... 381 m (59 m)..... 129 m (17 m). E3......................... <=200 1 N/A............... 542 m (257 m).... 198 m (13 m). E3......................... <=200 5 1,482 m (563 m)... 946 m (328 m).... 205 m (86 m). E3......................... <=200 25 2,346 m (1,019 m). 1,664 m (605 m).. 435 m (159 m). E3......................... >200 1 N/A............... 775 m (206 m).... 199 m (14 m). E3......................... >200 5 1,000 m (364 m)... 861 m (191 m).... 240 m (33 m). E3......................... >200 25 1,500 m (916 m)... 1,000 m (405 m).. 361 m (110 m). E4......................... <=200 1 N/A............... 1,586 m (653 m).. 372 m (42 m). E4......................... >200 1 N/A............... 1,000 m (257 m).. 365 m (44 m). E5......................... <=200 1 N/A............... 854 m (753 m).... 305 m (39 m). E5......................... <=200 5 2,306 m (1,138 m). 1,433 m (604 m).. 319 m (83 m). E5......................... >200 1 N/A............... 725 m (184 m).... 297 m (38 m). E5......................... >200 5 1,861 m (965 m)... 1,000 m (415 m).. 380 m (70 m). E5......................... >200 20 3,944 m (1,014 m). 2,618 m (614 m).. 747 m (112 m). E6......................... <=200 1 N/A............... 1,597 m (1,167 m) 485 m (63 m). E6......................... <=200 15 4,916 m (981 m)... 3,605 m (763 m).. 1,433 m (181 m). E6......................... >200 1 N/A............... 1,250 m (836 m).. 488 m (61 m). E7......................... <=200 1 N/A............... 1,372 m (576 m).. 427 m (80 m). E7......................... >200 1 N/A............... 1,458 m (1,037 m) 429 m (82 m). E8......................... <=200 1 N/A............... 2,013 m (388 m).. 652 m (83 m). E8......................... >200 1 N/A............... 1,985 m (376 m).. 643 m (82 m). E9......................... <=200 1 N/A............... 2,528 m (1,170 m) 689 m (85 m). E9......................... >200 1 N/A............... 2,183 m (938 m).. 692 m (84 m). E10........................ <=200 1 N/A............... 3,220 m (660 m).. 841 m (112 m). E10........................ >200 1 N/A............... 3,203 m (664 m).. 836 m (122 m). E11........................ <=200 1 N/A............... 7,977 m (2,054 m) 1,468 m (173 m). E11........................ >200 1 N/A............... 7,750 m (3,163 m) 1,570 m (266 m). E12........................ <=200 1 N/A............... 3,844 m (1,097 m) 903 m (163 m). E12........................ >200 1 N/A............... 3,453 m (1,050 m) 979 m (170 m). E13........................ <=200 1 N/A............... 4,542 m (1,609 m) 2,757 m (1,128 m). E16........................ >200 1 N/A............... 5,194 m (1,347 m) 2,667 m (513 m). ---------------------------------------------------------------------------------------------------------------- Note: N/A = Not Applicable. Behavioral response criteria are applied to explosive clusters >1. The values listed for TTS and AUD INJ are the greater of the respective SPL and SEL ranges. Median ranges are shown with standard deviation (SD) in parentheses. The Action Proponents split the LF functional hearing group into LF and VLF based on Houser et al. (2024). NMFS updated acoustic technical guidance (NMFS, 2024) does not include these data but we have included the VLF group here for reference. E1 (0.1-0.25 lbs (0.045-0.113 kg)), E2 (>0.25-0.5 lbs (0.113-0.23 kg)), E3 (>0.5-2.5 lbs (0.23-1.13 kg)), E4 (>2.5-5 lbs (1.13-2.27 kg)), E5 (>5-10 lbs (2.27-4.54 kg)), E6 (>10-20 lbs (4.54-9.07 kg)), E7 (>20-60 lbs (9.07-27.2 kg)), E8 (>60-100 lbs (27.2- 45.4 kg)), E9 (>100-250 lbs (45.4-113 kg)), E10 (>250-500 lbs (113-227 kg)), E11 (>500-675 lbs (227-306 kg)), E12 (>675-1,000 lbs (306-454 kg)), E13 (>1,000-1,740 lbs (454-789 kg)), E16 (10,000 lbs (4,536 kg)). Table 33--High-Frequency Cetacean Ranges to Effects for Explosives ---------------------------------------------------------------------------------------------------------------- Range to Bin Depth (m) Cluster size behavioral Range to TTS (SD) Range to AUD INJ disturbance (SD) (SD) ---------------------------------------------------------------------------------------------------------------- E1......................... <=200 1 N/A............... 91 m (18 m)...... 42 m (2 m). E1......................... <=200 5 260 m (90 m)...... 180 m (49 m)..... 42 m (2 m). E1......................... <=200 25 479 m (201 m)..... 316 m (122 m).... 85 m (17 m). E1......................... <=200 50 497 m (182 m)..... 367 m (101 m).... 110 m (8 m). E1......................... >200 1 N/A............... 90 m (3 m)....... 42 m (2 m). E1......................... >200 5 280 m (29 m)...... 180 m (9 m)...... 42 m (2 m). E1......................... >200 25 490 m (109 m)..... 310 m (46 m)..... 85 m (3 m). E1......................... >200 50 800 m (176 m)..... 500 m (80 m)..... 110 m (4 m). E2......................... <=200 1 N/A............... 122 m (12 m)..... 57 m (6 m). E2......................... >200 1 N/A............... 122 m (12 m)..... 57 m (7 m). E3......................... <=200 1 N/A............... 181 m (48 m)..... 93 m (4 m). E3......................... <=200 5 491 m (183 m)..... 321 m (110 m).... 93 m (4 m). E3......................... <=200 25 847 m (281 m)..... 582 m (182 m).... 154 m (43 m). E3......................... >200 1 N/A............... 180 m (15 m)..... 93 m (5 m). E3......................... >200 5 538 m (106 m)..... 330 m (46 m)..... 93 m (5 m). E3......................... >200 25 986 m (258 m)..... 725 m (173 m).... 160 m (6 m). E4......................... <=200 1 N/A............... 356 m (106 m).... 135 m (34 m). [[Page 32223]] E4......................... >200 1 N/A............... 282 m (35 m)..... 132 m (19 m). E5......................... <=200 1 N/A............... 294 m (137 m).... 151 m (17 m). E5......................... <=200 5 812 m (233 m)..... 513 m (166 m).... 151 m (17 m). E5......................... >200 1 N/A............... 260 m (25 m)..... 149 m (14 m). E5......................... >200 5 794 m (213 m)..... 500 m (98 m)..... 149 m (14 m). E5......................... >200 20 1,250 m (299 m)... 875 m (178 m).... 220 m (17 m). E6......................... <=200 1 N/A............... 455 m (218 m).... 213 m (28 m). E6......................... <=200 15 1,624 m (167 m)... 1,223 m (117 m).. 427 m (47 m). E6......................... >200 1 N/A............... 403 m (50 m)..... 216 m (26 m). E7......................... <=200 1 N/A............... 422 m (93 m)..... 237 m (42 m). E7......................... >200 1 N/A............... 450 m (154 m).... 236 m (44 m). E8......................... <=200 1 N/A............... 621 m (71 m)..... 334 m (32 m). E8......................... >200 1 N/A............... 610 m (70 m)..... 332 m (32 m). E9......................... <=200 1 N/A............... 646 m (99 m)..... 378 m (48 m). E9......................... >200 1 N/A............... 701 m (160 m).... 381 m (46 m). E10........................ <=200 1 N/A............... 830 m (142 m).... 482 m (76 m). E10........................ >200 1 N/A............... 820 m (164 m).... 481 m (73 m). E11........................ <=200 1 N/A............... 1,271 m (157 m).. 699 m (70 m). E11........................ >200 1 N/A............... 1,325 m (194 m).. 738 m (88 m). E12........................ <=200 1 N/A............... 1,005 m (226 m).. 650 m (114 m). E12........................ >200 1 N/A............... 1,008 m (219 m).. 632 m (109 m). E13........................ <=200 1 N/A............... 5,569 m (4,190 m) 2,701 m (4,433 m). E16........................ >200 1 N/A............... 3,778 m (8,655 m) 1,882 m (7,911 m) ---------------------------------------------------------------------------------------------------------------- Note: N/A = Not Applicable. Behavioral response criteria are applied to explosive clusters >1. The values listed for TTS and AUD INJ are the greater of the respective SPL and SEL ranges. Median ranges are shown with standard deviation (SD) in parentheses. E1 (0.1-0.25 lbs (0.045-0.113 kg)), E2 (>0.25-0.5 lbs (0.113-0.23 kg)), E3 (>0.5-2.5 lbs (0.23-1.13 kg)), E4 (>2.5-5 lbs (1.13-2.27 kg)), E5 (>5-10 lbs (2.27-4.54 kg)), E6 (>10- 20 lbs (4.54-9.07 kg)), E7 (>20-60 lbs (9.07-27.2 kg)), E8 (>60-100 lbs (27.2-45.4 kg)), E9 (>100-250 lbs (45.4-113 kg)), E10 (>250-500 lbs (113-227 kg)), E11 (>500-675 lbs (227-306 kg)), E12 (>675-1,000 lbs (306-454 kg)), E13 (>1,000-1,740 lbs (454-789 kg)), E16 (10,000 lbs (4,536 kg)). Table 34--Very High-Frequency Cetacean Ranges to Effects for Explosives ---------------------------------------------------------------------------------------------------------------- Range to Bin Depth (m) Cluster size behavioral Range to TTS (SD) Range to AUD INJ disturbance (SD) (SD) ---------------------------------------------------------------------------------------------------------------- E1......................... <=200 1 N/A............... 1,034 m8 (156 m). 662 m (87 m). E1......................... <=200 5 1,778 m (1,398 m). 1,250 m (1,056 m) 662 m (87 m). E1......................... <=200 25 2,667 m (1,883 m). 1,965 m (1,556 m) 835 m (577 m). E1......................... <=200 50 4,056 m (2,398 m). 2,917 m (2,027 m) 924 m (695 m). E1......................... >200 1 N/A............... 1,500 m (413 m).. 646 m (85 m). E1......................... >200 5 2,500 m (1,219 m). 2,000 m (708 m).. 729 m (105 m). E1......................... >200 25 3,972 m (2,279 m). 2,861 m (1,520 m) 1,250 m (251 m). E1......................... >200 50 3,806 m (2,522 m). 3,035 m (1,737 m) 1,000 m (428 m). E2......................... <=200 1 N/A............... 1,397 m (241 m).. 798 m (107 m). E2......................... >200 1 N/A............... 1,431 m (235 m).. 799 m (104 m). E3......................... <=200 1 N/A............... 2,100 m (410 m).. 1,350 m (173 m). E3......................... <=200 5 2,708 m (1,843 m). 2,100 m (410 m).. 1,350 m (173 m). E3......................... <=200 25 3,171 m (2,026 m). 2,500 m (1,738 m) 1,350 m (173 m). E3......................... >200 1 N/A............... 2,250 m (913 m).. 1,352 m (167 m). E3......................... >200 5 3,708 m (2,026 m). 2,750 m (1,330 m) 1,352 m (167 m). E3......................... >200 25 3,000 m (2,086 m). 2,500 m (1,596 m) 1,471 m (526 m). E4......................... <=200 1 N/A............... 3,216 m (516 m).. 2,189 m (251 m). E4......................... >200 1 N/A............... 3,321 m (522 m).. 2,250 m (256 m). E5......................... <=200 1 N/A............... 2,229 m (447 m).. 1,472 m (260 m). E5......................... <=200 5 3,931 m (2,098 m). 3,322 m (1,800 m) 1,642 m (786 m). E5......................... >200 1 N/A............... 2,264 m (1,091 m) 1,415 m (254 m). E5......................... >200 5 4,924 m (3,027 m). 3,681 m (2,102 m) 1,750 m (457 m). E5......................... >200 20 11,958 m (2,934 m) 8,125 m (2,005 m) 2,250 m (555 m). E6......................... <=200 1 N/A............... 3,622 m (828 m).. 2,385 m (514 m). E6......................... <=200 15 4,411 m (761 m)... 3,945 m (631 m).. 2,633 m (362 m). E6......................... >200 1 N/A............... 3,667 m (779 m).. 2,423 m (488 m). E7......................... <=200 1 N/A............... 4,083 m (767 m).. 2,750 m (478 m). E7......................... >200 1 N/A............... 4,458 m (1,831 m) 2,838 m (465 m). E8......................... <=200 1 N/A............... 7,163 m (3,017 m) 3,215 m (825 m). E8......................... >200 1 N/A............... 6,023 m (2,763 m) 3,069 m (731 m). E9......................... <=200 1 N/A............... 5,469 m (992 m).. 3,194 m (633 m). E9......................... >200 1 N/A............... 5,319 m (1,041 m) 3,092 m (601 m). E10........................ <=200 1 N/A............... 7,028 m (1,433 m) 4,067 m (867 m). E10........................ >200 1 N/A............... 6,974 m (1,482 m) 4,000 m (825 m). [[Page 32224]] E11........................ <=200 1 N/A............... 27,993 m (6,335 16,304 m (5,256 m). m). E11........................ >200 1 N/A............... 26,087 m (6,856 15,150 m (6,163 m). m). E12........................ <=200 1 N/A............... 8,639 m (1,966 m) 4,514 m (1,389 m). E12........................ >200 1 N/A............... 8,882 m (2,905 m) 4,812 m (1,608 m). E13........................ <=200 1 N/A............... 11,222 m (3,196 4,931 m (1,169 m). m). E16........................ >200 1 N/A............... 6,639 m (6,673 m) 2,257 m (1,560 m). ---------------------------------------------------------------------------------------------------------------- Note: N/A = Not Applicable. Behavioral response criteria are applied to explosive clusters >1. The values listed for TTS and AUD INJ are the greater of the respective SPL and SEL ranges. Median ranges are shown with standard deviation (SD) in parentheses. E1 (0.1-0.25 lbs (0.045-0.113 kg)), E2 (>0.25-0.5 lbs (0.113-0.23 kg)), E3 (>0.5-2.5 lbs (0.23-1.13 kg)), E4 (>2.5-5 lbs (1.13-2.27 kg)), E5 (>5-10 lbs (2.27-4.54 kg)), E6 (>10- 20 lbs (4.54-9.07 kg)), E7 (>20-60 lbs (9.07-27.2 kg)), E8 (>60-100 lbs (27.2-45.4 kg)), E9 (>100-250 lbs (45.4-113 kg)), E10 (>250-500 lbs (113-227 kg)), E11 (>500-675 lbs (227-306 kg)), E12 (>675-1,000 lbs (306-454 kg)), E13 (>1,000-1,740 lbs (454-789 kg)), E16 (10,000 lbs (4,536 kg)). Table 35--Phocid Carnivore in Water Ranges to Effects for Explosives ---------------------------------------------------------------------------------------------------------------- Range to Bin Depth (m) Cluster size behavioral Range to TTS (SD) Range to AUD INJ disturbance (SD) (SD) ---------------------------------------------------------------------------------------------------------------- E1......................... <=200 1 N/A............... 227 m (67 m)..... 83 m (6 m). E1......................... <=200 5 673 m (210 m)..... 421 m (145 m).... 110 m (27 m). E1......................... <=200 25 1,138 m (420 m)... 822 m (242 m).... 199 m (61 m). E1......................... <=200 50 1,264 m (577 m)... 785 m (286 m).... 259 m (51 m). E1......................... >200 1 N/A............... 260 m (41 m)..... 84 m (6 m). E1......................... >200 5 675 m (179 m)..... 480 m (85 m)..... 110 m (4 m). E1......................... >200 25 975 m (360 m)..... 725 m (209 m).... 230 m (20 m). E1......................... >200 50 1,500 m (563 m)... 1,000 m (295 m).. 305 m (35 m). E2......................... <=200 1 N/A............... 347 m (52 m)..... 110 m (15 m). E2......................... >200 1 N/A............... 355 m (55 m)..... 112 m (16 m). E3......................... <=200 1 N/A............... 490 m (227 m).... 188 m (13 m). E3......................... <=200 5 1,221 m (433 m)... 837 m (245 m).... 209 m (59 m). E3......................... <=200 25 1,969 m (787 m)... 1,428 m (468 m).. 397 m (113 m). E3......................... >200 1 N/A............... 675 m (141 m).... 188 m (13 m). E3......................... >200 5 1,250 m (396 m)... 917 m (205 m).... 240 m (20 m). E3......................... >200 25 2,250 m (868 m)... 1,499 m (559 m).. 490 m (103 m). E4......................... <=200 1 N/A............... 1,124 m (441 m).. 295 m (114 m). E4......................... >200 1 N/A............... 900 m (114 m).... 283 m (59 m). E5......................... <=200 1 N/A............... 748 m (445 m).... 301 m (45 m). E5......................... <=200 5 1,917 m (829 m)... 1,258 m (431 m).. 311 m (85 m). E5......................... >200 1 N/A............... 768 m (184 m).... 294 m (42 m). E5......................... >200 5 1,611 m (814 m)... 1,000 m (379 m).. 370 m (60 m). E5......................... >200 20 3,674 m (1,149 m). 1,750 m (581 m).. 664 m (82 m). E6......................... <=200 1 N/A............... 1,108 m (704 m).. 431 m (79 m). E6......................... <=200 15 3,584 m (735 m)... 2,786 m (457 m).. 1,048 m (152 m). E6......................... >200 1 N/A............... 1,000 m (546 m).. 429 m (69 m). E7......................... <=200 1 N/A............... 1,080 m (368 m).. 472 m (95 m). E7......................... >200 1 N/A............... 1,250 m (545 m).. 471 m (96 m). E8......................... <=200 1 N/A............... 1,780 m (552 m).. 646 m (90 m). E8......................... >200 1 N/A............... 1,750 m (531 m).. 642 m (91 m). E9......................... <=200 1 N/A............... 1,708 m (690 m).. 721 m (138 m). E9......................... >200 1 N/A............... 1,604 m (628 m).. 711 m (128 m). E10........................ <=200 1 N/A............... 2,078 m (579 m).. 839 m (162 m). E10........................ >200 1 N/A............... 2,114 m (550 m).. 836 m (167 m). E11........................ <=200 1 N/A............... 4,881 m (1,625 m) 1,433 m (588 m). E11........................ >200 1 N/A............... 5,028 m (1,523 m) 1,556 m (568 m). E12........................ <=200 1 N/A............... 2,489 m (848 m).. 1,020 m (322 m). E12........................ >200 1 N/A............... 2,480 m (822 m).. 1,058 m (310 m). E13........................ <=200 1 N/A............... 4,139 m (776 m).. 2,146 m (522 m). E16........................ >200 1 N/A............... 2,389 m (840 m).. 1,361 m (528 m). ---------------------------------------------------------------------------------------------------------------- Note: N/A = Not Applicable. Behavioral response criteria are applied to explosive clusters >1. The values listed for TTS and AUD INJ are the greater of the respective SPL and SEL ranges. Median ranges are shown with standard deviation (SD) in parentheses. E1 (0.1-0.25 lbs (0.045-0.113 kg)), E2 (>0.25-0.5 lbs (0.113-0.23 kg)), E3 (>0.5-2.5 lbs (0.23-1.13 kg)), E4 (>2.5-5 lbs (1.13-2.27 kg)), E5 (>5-10 lbs (2.27-4.54 kg)), E6 (>10- 20 lbs (4.54-9.07 kg)), E7 (>20-60 lbs (9.07-27.2 kg)), E8 (>60-100 lbs (27.2-45.4 kg)), E9 (>100-250 lbs (45.4-113 kg)), E10 (>250-500 lbs (113-227 kg)), E11 (>500-675 lbs (227-306 kg)), E12 (>675-1,000 lbs (306-454 kg)), E13 (>1,000-1,740 lbs (454-789 kg)), E16 (10,000 lbs (4,536 kg)). [[Page 32225]] Table 36--Otariid Carnivore in Water Ranges to Effects for Explosives ---------------------------------------------------------------------------------------------------------------- Range to Bin Depth (m) Cluster size behavioral Range to TTS (SD) Range to AUD INJ disturbance (SD) (SD) ---------------------------------------------------------------------------------------------------------------- E1......................... <=200 1 N/A............... 156 m (48 m)..... 41 m (2 m). E1......................... <=200 5 424 m (170 m)..... 288 m (102 m).... 85 m (17 m). E1......................... <=200 25 779 m (306 m)..... 543 m (198 m).... 140 m (45 m). E1......................... <=200 50 835 m (454 m)..... 550 m (229 m).... 210 m (37 m). E1......................... >200 1 N/A............... 190 m (25 m)..... 41 m (2 m). E1......................... >200 5 450 m (78 m)...... 322 m (52 m)..... 85 m (4 m). E1......................... >200 25 600 m (135 m)..... 480 m (93 m)..... 170 m (19 m). E1......................... >200 50 769 m (133 m)..... 597 m (96 m)..... 230 m (30 m). E2......................... <=200 1 N/A............... 258 m (39 m)..... 60 m (8 m). E2......................... >200 1 N/A............... 261 m (41 m)..... 62 m (9 m). E3......................... <=200 1 N/A............... 321 m (126 m).... 90 m (8 m). E3......................... <=200 5 757 m (286 m)..... 532 m (185 m).... 140 m (42 m). E3......................... <=200 25 1,306 m (572 m)... 903 m (358 m).... 260 m (91 m). E3......................... >200 1 N/A............... 400 m (111 m).... 90 m (9 m). E3......................... >200 5 675 m (135 m)..... 525 m (89 m)..... 170 m (19 m). E3......................... >200 25 876 m (285 m)..... 674 m (158 m).... 300 m (52 m). E4......................... <=200 1 N/A............... 764 m (196 m).... 122 m (36 m). E4......................... >200 1 N/A............... 525 m (118 m).... 117 m (18 m). E5......................... <=200 1 N/A............... 525 m (253 m).... 147 m (22 m). E5......................... <=200 5 1,264 m (472 m)... 873 m (285 m).... 225 m (60 m). E5......................... >200 1 N/A............... 440 m (77 m)..... 141 m (19 m). E5......................... >200 5 758 m (197 m)..... 575 m (129 m).... 250 m (38 m). E6......................... <=200 1 N/A............... 808 m (379 m).... 208 m (34 m). E6......................... <=200 15 2,221 m (258 m)... 1,767 m (186 m).. 791 m (65 m). E6......................... >200 1 N/A............... 565 m (265 m).... 215 m (31 m). E7......................... <=200 1 N/A............... 694 m (244 m).... 200 m (46 m). E7......................... >200 1 N/A............... 650 m (210 m).... 180 m (100 m). E8......................... <=200 1 N/A............... 877 m (114 m).... 320 m (46 m). E8......................... >200 1 N/A............... 846 m (118 m).... 314 m (46 m). E9......................... <=200 1 N/A............... 929 m (361 m).... 317 m (40 m). E9......................... >200 1 N/A............... 729 m (158 m).... 331 m (44 m). E10........................ <=200 1 N/A............... 1,055 m (174 m).. 406 m (73 m). E10........................ >200 1 N/A............... 1,014 m (222 m).. 413 m (71 m). E11........................ <=200 1 N/A............... 1,764 m (212 m).. 717 m (86 m). E11........................ >200 1 N/A............... 1,694 m (280 m).. 750 m (108 m). E12........................ <=200 1 N/A............... 880 m (132 m).... 406 m (67 m). E12........................ >200 1 N/A............... 854 m (152 m).... 418 m (71 m). E13........................ <=200 1 N/A............... 4,514 m (1,620 m) 2,701 m (1,249 m). E16........................ >200 1 N/A............... 3,708 m (7,259 m) 2,181 m (822 m). ---------------------------------------------------------------------------------------------------------------- Note: N/A = Not Applicable. Behavioral response criteria are applied to explosive clusters >1. The values listed for TTS and AUD INJ are the greater of the respective SPL and SEL ranges. Median ranges are shown with standard deviation (SD) in parentheses. E1 (0.1-0.25 lbs (0.045-0.113 kg)), E2 (>0.25-0.5 lbs (0.113-0.23 kg)), E3 (>0.5-2.5 lbs (0.23-1.13 kg)), E4 (>2.5-5 lbs (1.13-2.27 kg)), E5 (>5-10 lbs (2.27-4.54 kg)), E6 (>10- 20 lbs (4.54-9.07 kg)), E7 (>20-60 lbs (9.07-27.2 kg)), E8 (>60-100 lbs (27.2-45.4 kg)), E9 (>100-250 lbs (45.4-113 kg)), E10 (>250-500 lbs (113-227 kg)), E11 (>500-675 lbs (227-306 kg)), E12 (>675-1,000 lbs (306-454 kg)), E13 (>1,000-1,740 lbs (454-789 kg)), E16 (10,000 lbs (4,536 kg)). Table 37--Explosive Ranges to Non-Auditory Injury and Mortality for All Marine Mammal Hearing Groups as a Function of Animal Mass -------------------------------------------------------------------------------------------------------------------------------------------------------- Bin Effect 10 kg (SD) 250 kg (SD) 1,000 kg (SD) 5,000 kg (SD) 25,000 kg (SD) 72,000 kg (SD) -------------------------------------------------------------------------------------------------------------------------------------------------------- E1.............. Non-auditory 22 m.............. 21 m.............. 19 m............. 21 m............. 22 m............. 21 m injury. (2 m)............. (2 m)............. (3 m)............ (2 m)............ (1 m)............ (1 m). E1.............. Mortality......... 3 m............... 1 m............... 0 m.............. 0 m.............. 0 m.............. 0 m (1 m)............. (1 m)............. (0 m)............ (0 m)............ (0 m)............ (0 m). E2.............. Non-auditory 27 m.............. 26 m.............. 26 m............. 25 m............. 26 m............. 26 m injury. (3 m)............. (3 m)............. (2 m)............ (2 m)............ (2 m)............ (1 m). E2.............. Mortality......... 6 m............... 2 m............... 1 m.............. 0 m.............. 0 m.............. 0 m (2 m)............. (2 m)............. (1 m)............ (0 m)............ (0 m)............ (0 m). E3.............. Non-auditory 37 m.............. 38 m.............. 41 m............. 43 m............. 38 m............. 45 m injury. (8 m)............. (8 m)............. (6 m)............ (3 m)............ (6 m)............ (1 m). E3.............. Mortality......... 6 m............... 3 m............... 0 m.............. 0 m.............. 0 m.............. 0 m (3 m)............. (2 m)............. (1 m)............ (0 m)............ (0 m)............ (0 m). E4.............. Non-auditory 55 m.............. 57 m.............. 60 m............. 61 m............. 60 m............. 60 m injury. (9 m)............. (9 m)............. (7 m)............ (7 m)............ (8 m)............ (6 m). E4.............. Mortality......... 19 m.............. 9 m............... 4 m.............. 1 m.............. 1 m.............. 0 m (6 m)............. (5 m)............. (1 m)............ (1 m)............ (0 m)............ (0 m). E5.............. Non-auditory 76 m.............. 76 m.............. 76 m............. 75 m............. 75 m............. 76 m injury. (4 m)............. (4 m)............. (4 m)............ (3 m)............ (4 m)............ (3 m). [[Page 32226]] E5.............. Mortality......... 16 m.............. 8 m............... 3 m.............. 2 m.............. 0 m.............. 0 m (4 m)............. (3 m)............. (1 m)............ (1 m)............ (0 m)............ (0 m). E6.............. Non-auditory 102 m............. 101 m............. 102 m............ 103 m............ 102 m............ 102 m injury. (11 m)............ (11 m)............ (11 m)........... (10 m)........... (11 m)........... (9 m). E6.............. Mortality......... 41 m.............. 19 m.............. 9 m.............. 6 m.............. 3 m.............. 2 m (14 m)............ (8 m)............. (2 m)............ (1 m)............ (1 m)............ (0 m). E7.............. Non-auditory 101 m............. 109 m............. 127 m............ 116 m............ 98 m............. 109 m injury. (17 m)............ (21 m)............ (21 m)........... (16 m)........... (22 m)........... (13 m). E7.............. Mortality......... 20 m.............. 10 m.............. 5 m.............. 3 m.............. 2 m.............. 1 m (7 m)............. (4 m)............. (1 m)............ (1 m)............ (1 m)............ (0 m). E8.............. Non-auditory 215 m............. 160 m............. 160 m............ 164 m............ 149 m............ 165 m injury. (41 m)............ (10 m)............ (11 m)........... (5 m)............ (12 m)........... (4 m). E8.............. Mortality......... 64 m.............. 30 m.............. 14 m............. 9 m.............. 4 m.............. 2 m (27 m)............ (13 m)............ (3 m)............ (2 m)............ (1 m)............ (1 m). E9.............. Non-auditory 345 m............. 192 m............. 194 m............ 204 m............ 180 m............ 211 m injury. (75 m)............ (19 m)............ (21 m)........... (13 m)........... (18 m)........... (10 m). E9.............. Mortality......... 156 m............. 22 m.............. 11 m............. 8 m.............. 4 m.............. 3 m (47 m)............ (30 m)............ (2 m)............ (2 m)............ (1 m)............ (1 m). E10............. Non-auditory 501 m............. 243 m............. 247 m............ 256 m............ 236 m............ 267 m injury. (131 m)........... (127 m)........... (34 m)........... (28 m)........... (31 m)........... (23 m). E10............. Mortality......... 258 m............. 67 m.............. 15 m............. 10 m............. 5 m.............. 4 m (69 m)............ (64 m)............ (5 m)............ (2 m)............ (1 m)............ (0 m). E11............. Non-auditory 652 m............. 367 m............. 374 m............ 361 m............ 363 m............ 371 m injury. (125 m)........... (50 m)............ (48 m)........... (26 m)........... (27 m)........... (26 m). E11............. Mortality......... 346 m............. 176 m............. 90 m............. 55 m............. 25 m............. 22 m (71 m)............ (55 m)............ (8 m)............ (7 m)............ (3 m)............ (3 m). E12............. Non-auditory 522 m............. 317 m............. 334 m............ 345 m............ 326 m............ 353 m injury. (181 m)........... (41 m)............ (36 m)........... (32 m)........... (50 m)........... (2 m). E12............. Mortality......... 309 m............. 136 m............. 19 m............. 12 m............. 7 m.............. 5 m (85 m)............ (92 m)............ (1 m)............ (3 m)............ (1 m)............ (0 m). E13............. Non-auditory 4,167 m........... 2,135 m........... 1,906 m.......... 2,073 m.......... 1,199 m.......... 953 m injury. (1,504 m)......... (1,522 m)......... (1,156 m)........ (1,404 m)........ (1,046 m)........ (182 m). E13............. Mortality......... 1,831 m........... 717 m............. 573 m............ 677 m............ 335 m............ 260 m (783 m)........... (759 m)........... (572 m).......... (658 m).......... (410 m).......... (202 m). E16............. Non-auditory 1,597 m........... 1,000 m........... 1,053 m.......... 1,069 m.......... 1,081 m.......... 975 m injury. (484 m)........... (628 m)........... (205 m).......... (341 m).......... (257 m).......... (4 m). E16............. Mortality......... 1,024 m........... 678 m............. 665 m............ 753 m............ 529 m............ 415 m (225 m)........... (284 m)........... (214 m).......... (263 m).......... (277 m).......... (233 m). -------------------------------------------------------------------------------------------------------------------------------------------------------- Note: Median ranges with standard deviation (SD) in parentheses. For non-auditory injury ranges, the greater of the respective ranges for 1 percent chance of gastro-intestinal tract injury and 1 percent chance of injury. E1 (0.1-0.25 lbs (0.045-0.113 kg)), E2 (>0.25-0.5 lbs (0.113-0.23 kg)), E3 (>0.5-2.5 lbs (0.23-1.13 kg)), E4 (>2.5-5 lbs (1.13-2.27 kg)), E5 (>5-10 lbs (2.27-4.54 kg)), E6 (>10-20 lbs (4.54-9.07 kg)), E7 (>20-60 lbs (9.07- 27.2 kg)), E8 (>60-100 lbs (27.2-45.4 kg)), E9 (>100-250 lbs (45.4-113 kg)), E10 (>250-500 lbs (113-227 kg)), E11 (>500-675 lbs (227-306 kg)), E12 (>675-1,000 lbs (306-454 kg)), E13 (>1,000-1,740 lbs (454-789 kg)), E16 (10,000 lbs (4,536 kg)). Marine Mammal Density A quantitative analysis of impacts on a species or stock requires data on their abundance and distribution that may be affected by anthropogenic activities in the potentially impacted area. The most appropriate metric for this type of analysis is density, which is the number of animals present per unit area. Marine species density estimation requires a significant amount of effort to both collect and analyze data to produce a reasonable estimate. Unlike surveys for terrestrial wildlife, many marine species spend much of their time submerged and are not easily observed. In order to collect enough sighting data to make reasonable density estimates, multiple observations are required, often in areas that are not easily accessible (e.g., far offshore). Ideally, marine mammal species sighting data would be collected for the specific area and time period (e.g., season) of interest and density estimates derived accordingly. However, in many places, poor weather conditions and high sea states prohibit the completion of comprehensive visual surveys. For most cetacean species, abundance is estimated using line- transect surveys or mark-recapture studies (e.g., Barlow, 2010; Barlow and Forney, 2007; Calambokidis et al., 2008). This is the general approach applied in estimating cetacean abundance in NMFS SARs. Although the single value provides a good average estimate of abundance (i.e., total number of individuals) for a specified area, it does not provide information on the species distribution or concentrations within that area, and it does not estimate density for other timeframes or seasons that were not surveyed. More recently, spatial habitat modeling has been used to estimate cetacean densities (e.g., Becker et al., 2022a, Becker et al., 2022b, Becker et al., 2021, Becker et al., 2020a; Becker et al., 2020b). These models estimate cetacean density as a continuous function of habitat variables (e.g., sea surface temperature, seafloor depth, etc.) and thus allow predictions of cetacean densities on finer spatial scales than traditional line- transect or mark recapture analyses, and for areas that have not been surveyed. Within the geographic area that was modeled, densities can be predicted wherever these habitat variables can be measured or estimated. Ideally, density data would be available for all species throughout the Study Area year-round, in order to best [[Page 32227]] estimate the impacts of specified activities on marine species. However, in many places, vessel availability, lack of funding, inclement weather conditions, and high sea states prevent the completion of comprehensive year-round surveys. Even with surveys that are completed, poor conditions may result in lower sighting rates for species that would typically be sighted with greater frequency under favorable conditions. Lower sighting rates preclude having an acceptably low uncertainty in the density estimates. A high level of uncertainty, indicating a low level of confidence in the density estimate, is typical for species that are rare or difficult to sight. In areas where survey data are limited or non-existent, known or inferred associations between marine habitat features and the likely presence of specific species are sometimes used to predict densities in the absence of actual animal sightings. Consequently, there is no single source of density data for every area, species, and season because of the fiscal costs, resources, and effort involved in providing enough survey coverage to sufficiently estimate density. To characterize the marine species density for large oceanic regions, the Action Proponents review, critically assess, and prioritize existing density estimates from multiple sources, requiring the development of a systematic method for selecting the most appropriate density estimate for each combination of species/stock, area, and season. The selection and compilation of the best available marine species density data resulted in the NMSDD, which includes seasonal density values for every marine mammal species and stock present within the HCTT Study Area. This database is described in the ``U.S. Navy Marine Species Density Database Phase IV for the Hawaii- California Training and Testing Study Area'' technical report (U.S. Department of the Navy, 2024), hereafter referred to as the Density Technical Report. NMFS reviewed all marine mammal densities provided by the Action Proponents prior to use in their acoustic analysis for the current rulemaking process. A variety of density data and density models are needed to develop a density database that encompasses the entirety of the HCTT Study Area. Because these data are collected using different methods with varying amounts of accuracy and uncertainty, the Action Proponents have developed a hierarchy to ensure the most accurate data are used when available. The Density Technical Report describes these models in detail and provides detailed explanations of the best available density estimate for each species. The list below describes possible sources of density data in order of preference: