Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Military Readiness Activities in the Atlantic Fleet Training and Testing Study Area

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

[Docket No. 251030-0166]

RIN 0648-BN17

Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Military Readiness Activities in the Atlantic Fleet Training and Testing Study Area

AGENCY:

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

ACTION:

Final rule; notification of issuance of letters of authorization.

SUMMARY:

NMFS, upon 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; hereafter, Navy and Coast Guard are collectively referred to as Action Proponents), issues these regulations pursuant to the Marine Mammal Protection Act (MMPA) to govern the taking of marine mammals incidental to training and testing activities conducted in the Atlantic Fleet Training and Testing (AFTT) Study Area over the course of 7 years from November 2025 through November 2032. These regulations, which allow for the issuance of letters of authorization (LOAs) for the incidental take of marine mammals during specified activities and timeframes, prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on marine mammal species and their habitat, and establish requirements pertaining to the monitoring and reporting of such taking. 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:

Effective from November 14, 2025, through November 13, 2032.

ADDRESSES:

A copy of the Action Proponents' incidental take authorization (ITA) application and supporting documents, NMFS' proposed and final rules and subsequent LOAs for these regulations, 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:

Alyssa Clevenstine, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Purpose and Need for Regulatory Action

These regulations, issued under the authority of the MMPA (16 U.S.C. 1361

et seq.

), allow for the authorization of take of marine mammals incidental to the Action Proponents' training and testing activities (which qualify as military readiness activities) involving the use of active sonar and other transducers, air guns, and explosives (including in-water explosives and underwater detonations); pile driving and vibratory extraction; and vessel movement in the AFTT Study Area. The AFTT Study Area includes air and water space of the western Atlantic Ocean along the east coast of North America, the Gulf of America (formerly Gulf of Mexico), and portions of the Caribbean Sea, covering approximately 2.6 million square nautical miles (nmi

2

; 8.9 million square kilometers (km

2

)) of ocean area (see figure 1.1-1 of the application). Please see the Legal Authority for the Final Action section for relevant definitions.

Legal Authority for the Final Action

The MMPA prohibits the “take” of marine mammals, with certain exceptions. Section 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361

et seq.

) directs 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 (referred to in shorthand 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. The Analysis and Negligible 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 and amended the definition of “harassment” as applied to a “military readiness activity” to read as follows (section 3(18)(B) of the MMPA): (i) 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 (ii) 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). The 2004 NDAA also amended section 101(a)(5)(A)(iii) of the MMPA, establishing that “[f]or 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.” On August 13, 2018, the 2019 NDAA (Pub. L. 115-232) amended section 101(a)(5)(A)(ii) of the MMPA to allow incidental take regulations for military readiness activities to be issued for up to 7 years.

Summary of Major Provisions Within the Final Rule

The major provisions of this rule are:

• Take of marine mammals by Level A harassment and/or Level B harassment;

• Take of marine mammals by mortality or serious injury (M/SI);

• Use of defined powerdown and shutdown zones (based on activity);

• Measures to reduce the likelihood of vessel strikes;

• Activity limitations in certain areas and times that are biologically important (

i.e.,

for foraging, migration, reproduction) for marine mammals;

• Implementation of a Notification and Reporting Plan (for dead, live

stranded, or marine mammals struck by any vessel engaged in military readiness activities); and

• Implementation of a robust monitoring plan to improve our understanding of the environmental effects resulting from the Action Proponents' training and testing activities.

This 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 May 28, 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 and testing (characterized as military readiness activities) including the use of sonar and other transducers, explosives, air guns, and impact and vibratory pile driving and extraction conducted within the AFTT Study Area. In addition, the Action Proponents requested authorization to take, by serious injury or mortality, a limited number of several marine mammal species incidental to use of explosives, ship shock trials, and vessel movement during military readiness activities conducted within the AFTT Study Area over the 7-year period of the LOAs. In response to our comments and following information exchange, the Action Proponents submitted a final revised application on August 16, 2024, that we determined was adequate and complete on August 19, 2024. On September 20, 2024, we published a notice of receipt (NOR) of application in the

Federal Register

(89 FR 77106), requesting comments and information related to the Action Proponents' specified activities. During the 30-day public comment period, we did not receive any public comments. On October 8, 2024, the Action Proponents submitted an updated application to revise take estimates for a subset of Navy activities. On January 21, 2025, the Action Proponents submitted an updated application which removed ship shock trials and estimated take associated with that activity within the Virginia Capes (VACAPES) Range Complex. On February 13, 2025, the Action Proponents submitted an updated application containing minor revisions. On May 9, 2025, we published a proposed rule (90 FR 19858) and requested comments and information related to the Action Proponents' request for 30 days. All relevant comments received during the proposed rulemaking comment period were considered in this final rule. Comments received on the proposed rule are addressed in this final rule in the Comments and Responses section.

NMFS has previously promulgated incidental take regulations pursuant to the MMPA relating to similar military readiness activities in the AFTT Study Area. NMFS published the first rule effective from January 22, 2009 through January 22, 2014 (74 FR 4844, January 27, 2009), the second rule effective from November 14, 2013 through November 13, 2018 (78 FR 73009, December 4, 2013), and the third rule effective from November 14, 2018 through November 13, 2023 (83 FR 57076, November 14, 2018), which was subsequently amended, extending the effective date through November 13, 2025 (84 FR 70712, December 23, 2019) pursuant to the 2019 NDAA. For this rulemaking, the Action Proponents plan to conduct substantially similar training and testing activities within the AFTT Study Area that were conducted under previous rules.

The Action Proponents' application reflects the most up-to-date compilation of training and testing activities deemed necessary to accomplish military readiness requirements. The types and numbers of activities included in this rule account for interannual variability in training and testing to meet evolving or emergent military readiness requirements. These regulations cover military readiness activities in the AFTT Study Area that will occur for a 7-year period following the expiration of the pre-existing MMPA authorization after November 13, 2025.

Description of Specified Activity

The Action Proponents requested authorization to take marine mammals incidental to conducting military readiness activities. The Action Proponents have determined that acoustic and explosives stressors are most likely to result in take of marine mammals in the form of Level A and B harassment, and a limited number of takes by serious injury or mortality may result from vessel movement and explosive use including ship shock trials. NMFS concurs with these determinations. Detailed descriptions of these activities are provided in chapter 2 of the 2025 AFTT Supplemental Environmental Impact Statement (EIS)/Overseas EIS (OEIS) (2025 AFTT Supplemental EIS/OEIS) (

https://www.nepa.navy.mil/aftteis/

) and in the Action Proponents' application (

https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities

).

A detailed description of the specified activities was provided in our proposed rule (90 FR 19858, May 9, 2025). NMFS hereby refers to the information and analysis provided in the proposed rule which continue to apply to this final rule. Since that time, no changes have been made to the planned activities. Therefore, a detailed description is not provided here. Please refer to the proposed rulemaking for the complete description of the specified activity.

Foreign Navies

In furtherance of national security objectives, foreign militaries may participate in multinational training and testing events in the AFTT Study Area. Foreign military activities that are planned by and under the substantial control and responsibility of the Action Proponents are included in the specified activity. These participants could be in various training or testing events described in appendix A of the 2025 AFTT Supplemental EIS/OEIS, and their effects are analyzed in this final rule. However, when foreign military vessels and aircraft 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 a U.S. port, not all of which are at the request 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-led exercise or event, foreign military use of sonar and explosives, when combined with the Action Proponents' 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 final rule. Please see the Mitigation Measures section and Reporting section of this final rule for information about mitigation and reporting related to foreign navy activities in the AFTT Study Area.

Comments and Responses

We published the proposed rule in the

Federal Register

on May 9, 2025 (90 FR 19858) with a 30-day comment period. In that proposed rule, we requested public input on our analyses, our preliminary findings, and the proposed regulations, and requested that interested persons submit relevant information and comments. During the 30-day comment period, we received 1,216 comments. Of this total, one submission was from the Marine Mammal Commission (Commission), two were from non-governmental organizations Natural Resources Defense Council and Turtle Island Restoration Network, and the remaining comments were from private citizens. The majority of these comments were form letter submissions containing identical or nearly identical content expressing general opposition toward the Action Proponents' proposed training and testing activities and requesting that NMFS not issue the regulations and LOAs, but the commenters provided no specific recommendations or supporting information. These general comments have been noted, but because they did not include information pertinent to NMFS' decision, they are not addressed further.

NMFS has reviewed and considered all relevant public comments received on the proposed rule and issuance of the LOAs. All substantive, relevant comments and our responses are described below. We organize our comment responses by major categories.

Impact Analysis and Thresholds

Comment 1:

The Commission stated that a 5-minute accumulation time for an entire day of pile driving is insufficient, particularly because of the Commission's assertion that the Navy does not implement, and NMFS has not proposed to require, soft-start procedures during pile-driving training activities. The Commission also noted differences in pile driving between the proposed rule and another recent military readiness activity involving pile driving (90 FR 20283, May 13, 2025). The Commission recommended that NMFS revise: (1) the range to effects for pile driving for temporary threshold shift (TTS) and auditory injury (AUD INJ) based on the number of piles of each pile type and installation method that would be installed on a given day, the number of minutes or strikes needed to install each pile to depth, and the correct source levels, including for vibratory installation of 24-inch (0.61 meter (m)) sheet piles; (2) the range to effects for pile driving for behavioral response for vibratory installation of 24-inch (0.61 m) sheet piles based on a source level of 159 decibel referenced to 1 microPascal (dB re 1 μPa) at 11 m; and (3) the numbers of takes accordingly for the final rule.

Response:

NMFS disagrees with the Commission's assertion that the source levels used for vibratory installation of 24-inch (0.61 m) sheet piles are incorrect. As indicated in the proposed rule and 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, 2024b), hereafter referred to as the Acoustic Impacts Technical Report, a source level of 159 dB root-means-square (RMS) for vibratory driving of 24-inch (0.61 m) steel sheet piles measured at 10 m (32.8 feet (ft)) (NAVFAC, 2020) is a reasonable representation of likely sound levels.

The Navy assumed, and NMFS concurred, that most animals in the area of pile driving activities would avoid higher sound levels that could cause injury over periods of time shorter than 5 minutes. The Navy is required to shut down pile driving if a bottlenose dolphin occurs within 100 yards (yd) (91.4 m) of the pile driving site. Since pile driving occurs in relatively calm, shallow, coastal waters, and Lookouts are on stationary platforms (

e.g.,

elevated piers, bulkhead walls), there is a high likelihood that marine mammals would be sighted within or approaching the 100 yd (91.4 m) shutdown zone and mitigation would be implemented, therefore preventing potential TTS or AUD INJ, as all the predicted ranges for these effects are significantly smaller than 100 yd (91.4 m). As such, Level A harassment from pile driving activities is neither anticipated nor authorized, consistent with the proposed rule.

Navy considers soft-start procedures for impact pile driving to be part of its standard operating procedures. As such, neither the 2024 AFTT Draft Supplemental EIS/OEIS, application, nor the AFTT proposed rule (90 FR 19858, May 9, 2025) listed soft start as a mitigation measure. Navy states that its standard operating procedures are essential to safety and mission success and are implemented regardless of their secondary benefits, whereas its mitigation measures are designed entirely for the purpose of avoiding or reducing impacts on marine mammals. As such, the Action Proponents did not include a description of the soft-start procedure in the mitigation section of the application, and NMFS did not propose to include soft start as a mitigation measure in the proposed rule. However, NMFS agrees with the Commission that it is appropriate to require soft-start procedures as a mitigation measure, and this final rule clarifies that the Navy must implement soft start techniques for impact pile driving. Of note, Navy continues to consider soft-start procedures as part of their standard operating procedures, and as such, they are not listed as a mitigation measure in the 2025 AFTT Supplemental EIS/OEIS.

Comment 2:

The Commission recommended that NMFS work with the Navy to use an avoidance swim speed of no more than 2 meters per second (m/second) for harbor porpoises and 1 m/second for pinnipeds, and to revise the NAEMO modeling and take estimates appropriately for the final rule. The Commission further recommended that NMFS work with the Navy to incorporate moving animats (

i.e.,

a virtual animal) into NAEMO that can actively avoid sound sources based on species-specific dive profiles and swim speeds for Phase V activities (which would occur in AFTT from 2032 to 2039) and, if that is not feasible, incorporate species-specific swim speeds and the actual modeled sound propagation into NAEMO to simulate avoidance for a given event. The Commission stated that both creating an emulator and running simulation studies outside of NAEMO, as recommended by Simmons

et al.

(2025), should inform how best to deal with moving animats and implementing avoidance within NAEMO.

Response:

NMFS and the Navy acknowledge the importance of using appropriate swim speeds in the avoidance analysis in NAEMO, which assesses the potential for marine mammals to mitigate high-intensity sound exposures that could lead to auditory injury. While baseline swim speeds can be informative, the Navy prioritized data on swim behavior observed near and during anthropogenic disturbance because these data were considered more representative of how animals might respond to acoustic stimuli and potentially reduce injury risk. NMFS concurs with this approach.

The Commission referenced a study by Kastelein

et al.

(2018) as support for a lower harbor porpoise swim speed. However, the cited speed of 7.1 kilometers per hour (km/hr) represents the sustained average speed of a single captive harbor porpoise in a relatively small pool during a pile driving playback study at exposures below those causing auditory injury. This specific observation does not accurately reflect the full range of harbor porpoise swim capabilities. As documented in

table 8 of the appendix to the Acoustic Impacts Technical Report, data from free-swimming harbor porpoises indicate swim speeds up to and exceeding 3 m/second, supporting the Navy's chosen value for modeling avoidance.

For pinnipeds, the avoidance analysis used a reasonable swim speed of 2 m/second for a limited duration (10 minutes), acknowledging the lack of observed data on their swim behavior during acoustic exposures. This assumption balances the need for a realistic representation of potential avoidance behavior with the limited data availability, contributing to a conservative assessment of potential impacts.

The Navy's approach to modeling impacts is described in the Acoustic Impacts Technical Report. NMFS has reviewed the Acoustic Impacts Technical Report and concurs with Navy that the approach is based on the best available science. In early NAEMO development, the Navy compared the number of exposures (

i.e.,

>120 dB) using the Marine Mammal Movement and Behavior (3MB) model versus horizontally stationary animats and concluded that there was no significant difference in behavioral exposures between the two distribution methods. Thus, horizontally stationary animats were selected for computational efficiency.

NMFS and the Navy recognize the evolving nature of modeling techniques and acknowledge the Commission's desire for more dynamic and species-specific avoidance behaviors in future iterations of NAEMO. NMFS has encouraged the Navy to continue to explore NAEMO enhancements, and the Navy has indicated that it will consider species-specific swim speeds and potentially more complex movement models, as data availability and computational capabilities allow. Currently, however, detailed avoidance data for many species are limited, necessitating the use of surrogate data and generalized approaches, as is also the case with dive profiles.

The Navy states that it will continue to prioritize research and development efforts to enhance the accuracy of its impact modeling tools, ensuring the best available science informs its environmental assessments.

Comment 3:

The Commission recommended that NMFS work with the Navy to use NAEMO to conduct modeling of both multi-day events and multiple single-day events to estimate the number of repeated exposures an individual is expected to incur and to better assess repeated exposures of individuals and population-level consequences, rather than rely on what it called a qualitative assessment. The Commission cited Simmons

et al.

(2025) recommendation of ways that NAEMO and results from NAEMO could be better used to estimate repeated takes and population-level impacts.

Response:

NMFS and the Navy have had ongoing discussions about how to better assess and characterize the number of repeated takes of individuals from training and testing activities, including whether NAEMO could be used to generate estimates of repeated takes of individuals. A credible assessment of the repeated takes due to the specified activities per the approach suggested in the comment would require treating animats as unique individuals over the course of a year's activity and across a large study area, while incorporating migration patterns and nomadic movement. Such an effort would be computationally intensive and Navy anticipates that it is likely infeasible given reasonable resources. In contrast, the action analyzed by Zeddies

et al.

(2017) and referenced by the Commission in supporting statements was less complex than the specified activities. Thus, Zeddies

et al.

(2017) could assess repeated takes within spatially and temporally limited areas with undirected animal ingress/egress. NMFS will continue to work with the Navy to better assess and characterize the number of repeated takes of individuals. Of note, Simmons

et al.

(2025), referenced by the Commission, was written after a joint workshop with the Navy and SMRU Consulting. Recommendations from the workshop and associated report are being considered for future modeling improvements.

While NMFS and the Action Proponents' analyses could be further refined, the information in NMFS' analysis is sufficient for assessing whether the authorized take would have a negligible impact on the species or stocks of marine mammals, and it is not necessary to have exact number of times that an animal is estimated to be repeatedly taken in order to make the determination. As described in the Preliminary Analysis and Negligible Impact Determination section of the proposed rule (90 FR 19858, May 9, 2025) and this final rule, generally speaking, the higher the number of takes as compared to the population abundance, the more repeated takes of individuals are likely, and the higher the actual percentage of individuals in the population that are likely taken at least once in a year. We look at this comparative metric (number of takes to population abundance) to give us a relative sense of where a larger portion of a species is being taken by the specified activities, where there is a likelihood that the same individuals are being taken across multiple days, and whether the number of days might be higher or more likely sequential. Where the number of instances of take is less than 100 percent of the abundance, and there is no information to specifically suggest that some subset of animals is known to congregate in an area in which activities are regularly occurring (

e.g.,

a small resident population, takes occurring in a known important area such as a Biologically Important Area (BIA), or a large portion of the takes occurring in a certain region and season), the overall likelihood and number of repeated takes is generally considered low, as it could, on one extreme, mean that every take represents a separate individual in the population being taken on 1 day (a minimal impact to an individual) or, more likely, that some smaller number of individuals are taken on 1 day annually and some are taken on a few, not likely sequential, days annually, and of course some are not taken at all.

In the ocean, the use of sonar and other active acoustic sources is often transient and is unlikely to repeatedly expose the same individual animals within a short period, for example, within one specific exercise. However, for some individuals of some species, repeated exposures across different activities could occur over the year, especially where events occur in generally the same area with more resident species. In short, for some species, we expect that the total anticipated takes represent exposures of a smaller number of individuals of which some would be exposed multiple times, but based on the nature of the specified activities and the movement patterns of marine mammals, it is unlikely that individuals from most stocks would be taken over more than a few days within a given year. This means that even where repeated takes of individuals are likely to occur, they are more likely to result from non-sequential exposures from different activities, and, even if sequential, individual animals are not predicted to be taken for more than several days in a row, at most. As described elsewhere, the nature of the majority of the exposures would be expected to be of a less severe nature, and based on the numbers, it is likely that any individual exposed multiple times is still taken on only a small percentage of the days of the year. The greater likelihood is that

not every individual is taken, or perhaps a smaller subset is taken with a slightly higher average and larger variability of highs and lows, but still with no reason to think that, for most species or stocks, any individuals would be taken a significant portion of the days of the year.

Of note, the Commission identified an error related to potential impacts to goose-beaked whales (Western North Atlantic stock) in the Preliminary Assessment and Negligible Impact Determination section of the proposed rule. This final rule includes a correction to that language to indicate that the impacts to the Western North Atlantic stock of goose-beaked whales could cause a limited number of females to forego reproduction for a year.

Comment 4:

The Commission recommended that NMFS work with the Navy to use its Range-Dependent Acoustic Model and the Navy's Standard Parabolic Equation (RAM/PE) model for non-impulsive sources to model all underwater detonations (

i.e.,

impulsive sources) for Phase IV activities for which modeling has not been completed and for all Phase V activities, until such time that Comprehensive Acoustic Simulation System/Gaussian Ray Bundle (CASS/GRAB) and the similitude equation have been validated for the range of detonation sizes and environmental parameters (

i.e.,

water depth and receiver range) in which it would be used. They supported this recommendation by stating that, given the comparability of the modeled zones from the Peregrine version of RAM/PE to the measured values and that RAM/PE is already used by the Navy for modeling non-impulsive sources that operate at less than 100 Hertz (Hz) and in shallow water, the Navy has the data to conduct a rigorous comparison of CASS/GRAB and the similitude equation and the in situ measurements of the USS Ford ship shock trial from Seger

et al.

(2023) to fulfill the project's intent and to inform future rulemakings.

Response:

Navy has indicated that it plans to conduct a verification of the impulsive propagation methods in NAEMO using the Seger

et al.

(2023) data, which was published by Madhusudhana

et al.

(2024).

The NAEMO impulsive modeling methods, as described in the Acoustic Impacts Technical Report, require arrival times, sound levels, and phases to be output from the propagation model. RAM/PE does not output the time information necessary for simulation and is thus not a suitable option for impulsive modeling in NAEMO. The limitations of the similitude equation are discussed in section 4.1.3.2 of the Acoustic Impacts Technical Report and comparisons between the peak pressure computed at various ranges against the theoretical value based on the similitude equation showed agreement, providing confidence that the similitude equation was appropriate for use in NAEMO.

The Navy states that it is committed to ensuring the accuracy of its impulsive propagation models and recognizes the importance of ongoing validation efforts. While the similitude equation has been evaluated and demonstrated good agreement with measured data, as detailed in section 4.1.3.2 of the Acoustic Impacts Technical Report, the Navy is open to exploring alternative approaches to meet NAEMO's requirements.

Comment 5:

The Commission highlighted multiple points regarding the behavioral response functions (BRF) following its review of the technical report “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase 4)” (U.S. Department of the Navy, 2024a), which was revised to include updates to the version published in September 2024 and is hereafter referred to as the revised Criteria and Thresholds Technical Report (U.S. Department of the Navy, 2025). These points generally relate to the upper bound of the BRFs, Southall

et al.

data, odontocete BRFs, sensitive species BRFs, harbor porpoise data, pinniped BRFs, response severity denotation, and inconsistencies in some tables and figures. Please see the Commission's letter for a detailed discussion of its recommendation.

The Commission recommended that NMFS require the Navy to revise their criteria and thresholds to clarify and address these points, as that document underpins the current and future Phase IV rulemakings. The Commission also states that to increase efficiency for all of the agencies involved and to ensure accurate information is being provided for public comment, the Commission would welcome the opportunity to informally review future versions of the Navy's criteria and threshold documents. The Commission further recommends that NMFS work with the Navy to use the dose-response functions that were developed from all of the raw data rather than those that were regenerated for only moderate and severe responses and to refrain from extrapolating beyond the bounds of the underlying data when revising the BRFs.

In a related comment, a commenter stated that NMFS has not incorporated recent behavioral response data on common dolphins (Southall

et al.,

2024), and other important studies highlighted by the Commission, into its biphasic risk functions. The commenter references a fuller description of its concern in a comment on the 2024 Hawaii-California Training and Testing (HCTT) Draft EIS/OEIS.

Response:

Regarding the upper bound of the BRFs, the Navy adjusted the upper bound of the BRFs in Phase IV to more accurately reflect observed behavioral data, particularly at higher received levels. For example, sonar received levels between 170 and 182 dB re 1 µPa for humpback whales during 3S2 study (the second phase of the Sea Mammals, Sonar, Safety (3S) project) and between 175 and 186 dB re 1 µPa for sperm whales during 3S3 study (the third phase of the 3S project) did not elicit observable responses. See section 3.1.6.1.2 of the Criteria and Thresholds Technical Report for discussion of the 3S and 3S2 study, and section and 3.1.6.1.3 for discussion of the 3S3 study. Please see table E-1 in the revised Criteria and Thresholds Technical Report for details of all individual responses documented during studies in conjunction with received levels of sonar and sonar like sources.

Extending the upper bound to 200 dB re 1 µPa allows the BRFs to account for this lack of response at higher received levels. This adjustment does not arbitrarily shift the entire curve to the right, as the Commission suggests. For groups like pinnipeds, where responses are consistently observed at lower received levels, the BRF approaches 100 percent response probability at 185 dB re 1 µPa. Therefore, the upper bound adjustment primarily impacts the odontocete and mysticete BRFs, reflecting the observed data at higher exposures. It is also important to note that the lower bound of the BRFs were extended to 90 dB re 1 µPa in Phase IV (compared to the 100 dB re 1 µPa lower limit used in Phase III), further demonstrating that the adjustments were not solely focused on increasing the upper bound.

The Commission's observation of a flat slope between 185 and 200 dB re 1 µPa for the Phase III BRFs shown in figure 42 (Department of the Navy, 2024a) was a result of anchoring the Phase III BRFs at 185 dB re 1 µPa and then extending them to 200 dB re 1 µPa for plotting purposes.

Finally, regarding the point that the upper level of the mysticete BRF exceeds the TTS onset, it is important to emphasize that auditory and behavioral criteria are not directly linked. The Navy recognizes the evolving nature of acoustic science and

will continue to refine its effects criteria as new data and understanding become available.

The descriptions of responses in appendix E (Behavioral Responses to Sonar and Sonar-Like Sources: All Individuals Included) of the revised Criteria and Thresholds Technical Report have been updated to include additional information on the observed responses.

Regarding data from Southall

et al.

(2024), the Navy develops its BRFs using the best available scientific data. While data from the Atlantic behavioral response study (BRS) cited by the Commission and Southall

et al.

(2024) cited by the commenter were collected during the timeframe referenced, these data were not available for use in the development of the BRFs for Phase IV. These functions are always developed in close consultation with scientists conducting BRS/controlled exposure experiment (CEE) studies, but when the data are not yet published, the researchers determine the appropriate time at which to share data with the Navy. In this case, Atlantic BRS behavioral response results and Southall

et al.

(2024) were not shared in time to be considered and/or included in the development of the Navy risk thresholds. The Navy did consider data from Southall

et al.

(2024) in appendix D of the 2025 AFTT Supplemental EIS/OEIS, indicating the potential responses observed in this study occurred at received levels and distances assessed for potentially significant behavioral responses in the analysis of Phase IV; however, the findings of this study do not change the conclusions made by the Navy nor NMFS' determination. The Navy remains committed to incorporating the best available scientific data into its impact assessments and will revisit its BRFs as new information, including the published results of the Atlantic BRS, becomes available.

Regarding the odontocete BRF, all the data from Houser

et al.

(2013a, 2013b) were included in the modified risk functions developed for subsampling in the Navy's BRFs. However, low-severity responses were classified as “non-responses” when deriving the BRFs (see also Southall

et al.

(2021) for a description of severity scoring). This approach, consistent with Phase III, reflects that low-severity behavioral responses are not typically considered “harassment” under the MMPA during military readiness activities. To balance field and captive study data, a subsampling method was used. This involved creating modified risk functions incorporating the new scoring values (classifying low-severity responses as non-responses) at different received levels. Thirty data points were then randomly selected from the bottlenose dolphin risk function generated using this method. This subsampling approach, similar to that used for beaked whale data in both Phase III and Phase IV, ensures each individual animal from the captive study receives equal weight, comparable to individuals from field studies. This allows for a more comprehensive consideration of exposures and responses for each species, unlike Phase III's selection of a single response level per individual. The Navy has clarified this methodology in the revised Criteria and Thresholds Technical Report. Further, the Navy's current odontocete BRF considers the potential for behavioral responses that may qualify as “harassment” under the MMPA for military readiness activities at the estimated received levels in Southall

et al.

(2024).

Regarding the sensitive species BRF, while the generalized additive model (GAM) published in Jacobson

et al.

(2022) only extended to 165 dB, the Navy requested that authors rerun their model to 200 dB to create a new curve that could be subsampled for the Navy Phase IV risk function; the same was done for the Moretti

et al.

(2014) data. Therefore, the two beaked whale range-based risk functions extended to the same bandwidth as the Navy BRF and the subsampling matched the rest of the data. The Navy has updated the Criteria and Thresholds Technical Report to reflect that the published GAMs were rerun with the broader bandwidth. Both Moretti

et al.

(2014) and Jacobson

et al.

(2022) were subsampled 10 times each.

To be included in the BRF, data sets needed to relate known or estimable received levels to observations of individual or group behavior. The data in Falcone

et al.

(2017) is not included in the development of the BRFs because it is not possible to reasonably estimate the received levels in this study; however, this data was considered in developing the distance conditions for the application of the sensitive species BRF.

The Navy is committed to ensuring scientific integrity in datasets used for BRF development. Using data that do not meet these criteria could result in unreliable or misleading risk assessments. A risk function has not yet been fit to Southern California Anti-Submarine Warfare Range (SOAR) data for beaked whales, nor has one been fit for minke whales at PMRF. The BRFs in Phase IV utilized only individual response-received level data outside of the four pre-existing risk functions that were subsampled. There were no individual response-received level data available for beaked whales at SOAR nor for minke whales at PMRF, therefore those data were not used in the Phase IV BRFs. As science continues to evolve, the Navy will continue to refine its effects criteria. The Navy remains committed to incorporating new data and analyses, including those from SOAR and PMRF, as they become available and meet the rigorous standards required for robust BRF development.

Regarding the Kastelein harbor porpoise data, when the same individuals were tested at multiple received levels for the same source within a single study, only the lowest received level eliciting a response was included in the data used for BRF development. However, in some studies, Kastelein tested the same sources using different parameters, such as an upsweep versus a downsweep signal (

e.g.,

Kastelein

et al.

(2014b), where both low frequency and mid frequency active sonar signals were tested as both a downsweep and upsweep), or as a continuous versus pulsed active sonar signal (

e.g.,

Kastelein

et al.,

2018). In that case, the response to both signal parameters would have been used in the BRF as those would be considered different signals. The citations for the relevant Kastelein studies, previously provided in tables 19 and 20, have been added to table E-1 in the revised Criteria and Thresholds Technical Report.

Regarding the pinniped BRFs, the Navy confirms that all data from the Houser

et al.

(2013a) California sea lion controlled exposure experiment were considered in developing the Phase IV BRFs. However, as with the odontocete BRF, low-severity responses were classified as “non-responses” when deriving the BRF. This decision aligns with the Navy's approach to assessing potential harassment under the MMPA during military readiness activities, where low-severity responses are not typically considered indicative of harassment. The original curves developed by Houser

et al.

(2013a) were not used because they included the low-severity responses as responses. The Navy has clarified this approach in the revised Criteria and Thresholds Technical Report.

Regarding the identified inconsistencies in some data, tables, and figures, NMFS and the Navy have carefully reviewed those identified in the Commission's comments and the Navy has made the necessary corrections to the revised Criteria and

Thresholds Technical Report. These revisions ensure consistency in the reported ranges of received levels, distances, and significant responses across the executive summary, tables, figures, and accompanying text. Specifically, the Navy updated table E-1 in the revised Criteria and Thresholds Technical Report to include data for Blainville's beaked whales from Tyack

et al.

(2011). The studies by Moretti

et al.

(2014) and Jacobson

et al.

(2022) involved aggregated and modeled data rather than individual animal responses and were therefore incorporated into the BRFs through a random subsampling process, as described in the Criteria and Thresholds Technical Report, rather than being presented directly in table E-1, which focuses on individual-level data. The Navy also addressed inconsistencies between Curé

et al.

(2025) and table E-1 of U.S. Department of the Navy (2025) identified by the Commission. The Navy updated the closest points of approach so that the onset closest point of approach is given for signals that elicited significant responses, while the closest point of approach of the overall exposure session is given for signals that did not elicit a significant response. These corrections only affect the way data was presented in table E-1 and do not change the BRFs.

Finally, the Navy has confirmed to NMFS that it used the data from Houser

et al.

(2013a) and Houser

et al.

(2013b) to develop the new risk functions. As noted previously, low-severity responses were scored as “non-responses” within these functions to align with the Navy's approach to assessing potential harassment under the MMPA. These new risk functions were then subsampled using the same method applied to the beaked whale range risk functions in both Phase III and Phase IV, ensuring consistency in the Navy's treatment of such data. This subsampling approach, described in detail within those reports, ensures appropriate weighting of individual responses and contributes to the robustness of the Navy's BRFs.

Regarding the Commissions' offer to informally review future versions of the criteria and threshold reports, NMFS recommends that the Commission coordinate directly with the Navy for any potential early reviews as the Navy is the primary author.

Comment 6:

The Commission recommended that NMFS work with the Navy in a concerted manner to incorporate data that support criteria and threshold development more often than on a decadal cycle and to revise NAEMO to implement the relevant criteria and thresholds at a true post-processing stage so that animat dosimeter data can be re-queried if thresholds change, rather than needing to remodel the animat-portion of NAEMO.

Response:

The criteria and thresholds are typically updated at the beginning of each at-sea phase. This is a significant effort that involves collecting published data, working with marine mammal researchers to collect and understand emergent data, developing methods to incorporate the data, writing and publishing the technical report, and seeking approvals from Navy leadership and NMFS. Nevertheless, emergent data is continuously assessed against the current criteria and thresholds to ascertain whether it would create significant changes to the Navy's analysis. If so, the analysis would be altered to reflect this emergent data.

The Navy is continuously reassessing and evolving its analysis methods including the need to more frequently update criteria and threshold and the feasibility for NAEMO to more rapidly incorporate such changes. For example, the Navy has undertaken efforts to investigate the feasibility of moving the weighting functions to the post-processor for impulsive modeling, which would allow added flexibility to the modeling process when new data emerges outside of the normal criteria and threshold timeline. NMFS supports such efforts.

Comment 7:

The Commission recommended that NMFS determine whether inclusion of data from Kastelein

et al.

(2024a, 2025a, 2025b) would alter the weighting functions and/or thresholds for the functional hearing groups and, if so, whether those modifications would be sufficient to warrant revision of the weighting functions and associated thresholds for non-impulsive sources as stipulated in their criteria and thresholds.

Response:

Whether and when to share data for ongoing research is at the discretion of the researchers and funding agencies. Because the specific data from Kastelein

et al.

(2024) were not shared with the Navy prior to peer review and publication, these data could not be incorporated into the development of the Phase IV Criteria and Thresholds. However, the Navy's current approach using the existing Phase IV criteria remains protective even when compared to the findings of Kastelein

et al.

(2024a). Specifically, incorporating the TTS onset value of 169 dB sound exposure level (SEL) reported by Kastelein

et al.

(2024a) would raise the very high frequency (VHF) non-impulse exposure function by 4 dB. The impact on other impulsive and non-impulsive exposure functions is negligible (1 dB or less).

NMFS has also reviewed the data from Kastelein

et al.

(2024b, 2025a, 2025b). Kastelein

et al.

(2025a) evaluated the effect of one-sixth octave band noise centered at 40 kilohertz (kHz) on TTS in two California sea lions (

Zalophus californianus

). Results indicate that TTS onset (6 dB threshold shift) occurred at approximately 169 dB cumulative SEL, which is lower than predicted by the current Phase IV TTS threshold and weighting function. Interestingly, this TTS onset level is lower than what was measured during exposure to 32 kHz in a previous study (179 dB cumulative SEL; Kastelein

et al.

(2024b)). So, despite hearing sensitivity decreasing at higher frequencies, Kastelein

et al.

(2025a) indicate that TTS onset occurs at a lower level than predicted, which contradicts typical trends in TTS onset previously measured in marine mammals. Thus, these data suggest a need to evaluate exposures at potentially higher frequencies to examine whether this disparate trend continues.

Kastelein

et al.

(2025b) examined TTS in two harbor seals (

Phoca vitulina

) exposed to one-sixth octave band noise centered at 8 kHz. In this study, TTS onset (6 dB threshold shift) occurred at approximately 181 dB cumulative SEL, which is higher than what is predicted with the current Navy Phase IV criteria.

In consideration of the information discussed above, NMFS and Navy have concluded that revisions to the Phase IV Criteria and Thresholds are not warranted at this time.

Comment 8:

The Commission recommended that NMFS determine whether the low-frequency (LF) cetacean weighting function has been shifted far enough to the higher frequencies to reflect that 32 kHz was the most sensitive frequency tested in minke whales, determine whether use of the phocid carnivore in water (PCW) composite audiogram, weighting function, and threshold parameters are more representative of very low-frequency (VLF) and LF cetaceans than medians and means of the five other functional hearing groups, and work with the Navy to revise the VLF and LF cetacean composite audiograms, weighting functions, and thresholds as needed for impulsive and non-impulsive sources for the final rule and 2025 AFTT Supplemental EIS/OEIS.

In a related comment, a commenter stated that NMFS has applied a patently unrealistic, non-conservative auditory weighting scheme for “low frequency cetaceans” and references a similar

comment on the 2024 HCTT Draft EIS/OEIS.

Response:

The lack of data on mysticete hearing, especially in terms of the impacts of noise on hearing, has made this a challenging group for which to develop acoustic criteria. The Navy has split the mysticetes into two hearing groups for its Phase IV analyses: VLF and LF cetaceans (see appendix B of the Criteria and Thresholds Technical Report). This decision is outlined in detail within the documentation and includes the best available science including the recommendations of Southall

et al.

(2019a) and the minke whale study by Houser

et al.

(2024). The Navy was given access to pre-published data on the 2023/2024 minke whale field season and was able to incorporate into their Phase IV criteria (noting, as the commenter did that the 2023 field season data was published in November 2024). In their Phase IV criteria, the Navy separated VLF cetaceans (

i.e.,

blue, fin, right, and bowhead whales) from LF cetaceans (all other mysticetes). Thus, they are acknowledging differences among mysticetes species.

NMFS and the Navy disagree that wholesale adoption of the PCW parameters or shifting the LF weighting function solely based on the 32 kHz sensitivity of minke whales is scientifically justified. There is no scientific evidence to support the exclusive use of the PCW composite audiogram and weighting function parameters for the LF and VLF groups. Adolescent minke whales were tested by Houser

et al.

(2024) specifically because of their small size compared to other baleen whales. Smaller head size generally facilitates hearing at higher frequencies, so a shift of the entire LF curve (intended to represent all species within the hearing group) to a center frequency of 32 kHz is not likely representative of most baleen whales, which are larger in size compared to adolescent minke whales.

Therefore, the Navy maintains, and NMFS concurs, that, based on the weight of the evidence, the existing LF weighting function and the use of medians and means from multiple functional hearing groups provide a more representative and protective approach for assessing acoustic impacts on VLF and LF cetaceans. This approach incorporates data from a broader range of species and avoids overreliance on data from a single species or functional hearing group. NMFS' approach has remained consistent throughout our technical guidance development (2016, 2018, 2024), and we have addressed comments on the LF cetacean weighting function in our previous

Federal Register

notices finalizing these documents (81 FR 51693, August 4, 2016; 89 FR 84872, October 24, 2024). NMFS' 2024 Technical Acoustic Guidance does not incorporate the recent data on minke whale hearing. However, NMFS has committed to incorporating this data into future versions, as indicated in our 2024 Updated Technical Guidance. NMFS is awaiting the publication from the 2024 field season to be published and made publicly available before re-evaluating our acoustic criteria for mysticetes.

Comment 9:

A commenter stated that NMFS has relied improperly on means and medians in establishing its thresholds for auditory impacts and references a similar comment on the 2024 HCTT Draft EIS/OEIS. In that comment, the commenter recommends implementation of a 6 dB reduction to its TTS and PTS thresholds in line with the suggestions by Tougaard

et al.

(2015). The commenter states that a 6 dB adjustment would accord with the minimum level of “non-trivial” TTS required to evaluate onset, effectively adjusting the exposure functions to more closely match the point where TTS begins.

Response:

The technical guidance appropriately uses measures of central tendency based on an onset level of 6 dB TTS. No reduction is necessary or supported by the scientific literature, especially considering numerous other conservative methods in the auditory criteria. For example, the Navy, and subsequently NMFS, assumes no recovery of hearing during time intervals between intermittent exposures. However, multiple studies from humans, terrestrial mammals, and marine mammals have demonstrated less TTS from intermittent exposures compared to continuous exposures with the same total energy because hearing is known to experience some recovery in between noise exposures. Therefore, the Navy's approach, as relied upon in NMFS' proposed and final rules, is known to overestimate the effects of intermittent noise sources such as tactical sonars. Further, marine mammal TTS data have shown that, for two exposures with equal energy, the longer duration exposure tends to produce a larger amount of TTS. Since most marine mammal TTS data have been obtained using exposure durations up to an hour, much longer than the durations of many tactical sources, the use of the existing marine mammal TTS data tends to over-estimate the effects of sonars with shorter duration signals.

Comment 10:

A commenter stated that NMFS wholly discounted gas-bubble pathology as a mechanism of harm to marine mammals due to the specified activities, and that the Action Proponents must assume that a number of beaked whales are subject to injury and mortality from gas-bubble formation.

Response:

The commenter's characterization of NMFS' analysis is incorrect. NMFS does not disregard the fact that it is possible for naval activities using hull-mounted tactical sonar to contribute to the death of marine mammals in certain circumstances (that are not present in the AFTT Study Area) via strandings resulting from behaviorally mediated physiological impacts or other gas-related injuries. In the Potential Effects of Specified Activities on Marine Mammals and Their Habitat section of the proposed rule, NMFS discusses these potential causes and outlines the few cases where active naval sonar (in the U.S. or, largely, elsewhere) has either potentially contributed to or, as with the Bahamas example, been more definitively causally linked with marine mammal strandings. As noted, there are a suite of factors that have been associated with these specific cases of strandings directly associated with sonar (steep bathymetry, multiple hull-mounted platforms using sonar simultaneously, constricted channels, strong surface ducts,

etc.

). These factors are not present together in the AFTT Study Area during the specified activities (and the Navy takes care across the world not to operate under these circumstances without additional monitoring). Further, there have never been any strandings associated with Navy sonar use in the AFTT Study Area. For these reasons, NMFS does not anticipate that the Action Proponents' training or testing activities will result in marine mammal strandings, and none are authorized. Furthermore, ongoing Navy funded beaked whale monitoring at a heavily used training and testing area in the SOCAL Range Complex has not documented mortality or habitat abandonment by beaked whales. Passive acoustic detections of beaked whales have not significantly changed over 10 years of monitoring (DiMarzio

et al.,

2018; DiMarzio

et al.,

2019; DiMarzio

et al.,

2020). From visual surveys in the area since 2006 there have been repeated sightings of the same individual beaked whales, beaked whale mother-calf pairs, and beaked whale mother-calf pairs with mothers on their second calf (Schorr

et al.,

2018; Schorr

et al.,

2020). Satellite tracking studies of beaked whales documented high site fidelity to this area even though the

study area is located in one of the most used Navy areas in the Pacific (Schorr

et al.,

2018; Schorr

et al.,

2020).

Comment 11:

A commenter stated that NMFS failed to present a meaningful analysis of the Navy's aggregate effects on marine mammal populations and refers to its comment on the 2024 HCTT Draft EIS/OEIS.

Response:

The commenter's supporting rationale for their comment is in reference to the 2024 HCTT Draft EIS/OEIS. While some of the information considered in the AFTT proposed rule and this final rule is generally similar, the commenter has not provided recommendations specific to how NMFS' analysis of the Action Proponents activities in the proposed rule fails to consider the Action Proponents' aggregate effects on marine mammal populations. NMFS fully analyzed and considered the potential for aggregate effects from all of the Action Proponents' specified activities, and has applied a reasoned and comprehensive approach to evaluating the effects of these activities on marine mammal species or stocks and their habitat. This analysis was detailed in the Preliminary Analysis and Negligible Impact Determination section of the proposed rule and is repeated here in the Analysis and Negligible Impact Determination section of the final rule.

Our analysis includes consideration of unusual mortality events (UMEs) and previous environmental impacts, where appropriate, to inform the baseline levels of both individual health and susceptibility to additional stressors, as well as stock status. Further, the species and stock-specific assessments in the Analysis and Negligible Impact Determination section (which have been updated and expanded since the previous AFTT rulemaking to consider additional species- and stock-specific factors) present and address the combined mortality, injury, behavioral harassment, and other effects of the aggregate activities, including impacts anticipated in important habitats such as Endangered Species Act (ESA)-designated critical habitat and known BIAs (and in consideration of applicable mitigation), as well as other information that supports our determinations that the Action Proponents' activities will not adversely affect any species or stocks via impacts on annual rates of recruitment or survival. We refer the reader to the Analysis and Negligible Impact Determination section for this analysis.

Further, widespread, extensive monitoring since 2006 on Navy ranges that have been used for training and testing for decades has demonstrated no evidence of population-level impacts (see

https://www.navymarinespeciesmonitoring.us/regions/pacific/current-projects/

for results,

e.g.,

“Cuvier's Beaked Whale and Fin Whale Population Dynamics and Impact Assessment at the Southern California Offshore Antisubmarine Warfare Range (SOAR)”). Based on the best available research from NMFS and Navy-funded marine mammal studies, there is no evidence that “population-level harm” to marine mammals, including beaked whales, is occurring in the AFTT Study Area.

Comment 12:

The Commission recommended that NMFS work with the Navy to reprogram NAEMO to implement densities at a post-processing stage so that densities can be easily revised rather than needing to remodel the animat-portion of NAEMO when density estimates change. The Commission states that such an improvement was recommended by Simmons

et al.

(2025) to be addressed through modifications to animat seeding and investigating runs by hearing group within NAEMO.

Response:

NMFS concurs that it is appropriate to explore whether NAEMO can be reprogrammed to implement densities at a post-processing stage so that densities can be easily revised rather than needing to remodel the animat-portion of NAEMO when density estimates change. The Navy has undertaken work in Fiscal Year 2025 to explore standardization of animat distributions and statistical considerations of applying species' densities after the NAEMO post-processor to scale results. If the Navy, in coordination with NMFS, finds that this proves feasible and appropriate, the Navy hopes to implement this for Phase V.

Comment 13:

The Commission recommended that NMFS refrain from using cut-off distances in conjunction with the Bayesian BRFs and re-estimate the numbers of marine mammal takes based solely on the Bayesian BRFs for the final rule.

In a related comment, a commenter stated that NMFS reduces the Navy's modeled take estimates through the application of cut-off distances that do not make sense conceptually, that are based on little or no data from the behavioral response literature, and that contradict data that are available, including Falcone

et al.

(2017) and Melcón

et al.

(2012). The commenter refers to a description of their concern in a comment on the 2024 HCTT Draft EIS/OEIS, in which they state that they agree with the Commission's recommendation that the Navy refrain from using cut-off distances and rely instead on the take estimates produced through its response functions.

Response:

The consideration of proximity (cut-off distances) was part of the criteria developed in consultation between the Navy and NMFS, and is appropriate based on the best available science, which shows that marine mammal responses to sound vary based on both sound level and distance. Therefore, these cut-off distances were applied within NAEMO. The derivation of the BRFs and associated cut-off distances is provided in the revised Criteria and Thresholds Technical Report.

The Phase IV approach represents a refinement in assessing potential behavioral impacts. It employs a probability of response condition for high source level exposures, addressing previous concerns from the Commission about potentially cutting off responses when the probability remained above 50 percent. This approach, combined with the distance cut-off, provides a more nuanced and protective assessment compared to the Phase III methodology, which relied solely on distance cut-offs. Therefore, directly comparing Phase III and Phase IV cut-off distances is not appropriate.

NMFS and the Navy are confident that this combined distance and probability threshold approach is well-substantiated by available data and effectively avoids underestimating potential behavioral responses to acoustic sources.

To clarify, section 3.1.4 (Dose and Contextual Responses) of the Criteria and Thresholds Technical Report explains that at low received levels, distance to the sound source factors into the likelihood of a behavioral response. Although distance was investigated as a covariate in the Bayesian BRF model, most BRFs to date have used similar source levels making received level and source-receiver distance tightly correlated (see section 3.1.9 (Behavioral Cut-off Conditions) of the Criteria and Thresholds Technical Report). Therefore, including distance in the BRF model using the available response-received level data did not improve the BRFs. Still, NMFS and the Navy agree that distance is an important contextual factor. Since it was not possible to directly account for distance in the Bayesian model at this time, the Navy incorporated the behavioral cut-off conditions, beyond which significant behavioral reactions are assumed to be unlikely. As described in section 3.1.9 of the Criteria and Thresholds Technical Report, the distance cut-off conditions were conservatively estimated based on

observations from multiple cited studies. Applying the distance cut-off condition is appropriate to reasonably estimate significant impacts.

In addition, high source level exposures are addressed by also using a probability of response condition rather than the dual distance cut-off applied in Phase III. This method was devised in part to address public comments, including those from the Commission received in Phase III that were focused on cutting off behavioral responses, in some cases, where the probability of response was still above 50 percent. The probability of response cut-off condition in Phase IV allows for prediction of significant impacts beyond the distance cut-off.

Regarding the studies cited by a commenter, Melcón

et al.

(2012) found that the probability of recording blue whale “D calls” decreased with higher received levels at the high-frequency acoustic recording package (HARP) buoy averaged over many hours; however, this study does not provide any information about the distance between the sound source and any animals and cannot be used to derive cut-off distances. Falcone

et al.

(2017) was reviewed by the Navy and discussed in the Criteria and Threshold Technical Report: “. . . Falcone

et al.

(2017) modeled apparent responses to mid-powered sources out to 50 km (27 nmi) and responses to high-powered sources at distances as great as 100 km (54 nmi). However, the models were not developed to estimate distances to response, and care needs to be taken when interpreting the results in that context.” Responses at 100 km (54 nmi) were generally mild, such as a slight (

i.e.,

less than 2 minute) increase in the duration of shallow dives that was similar to the range of duration variability found in dives when no mid-frequency active sonar was present. The inter-deep dive interval duration also increased for both mid- and high-powered mid-frequency active sonar (MFAS) sources starting at 100 km (54 nmi); however, the inter-deep dive interval duration exhibited the strongest increase only within 20 km (10.8 nmi) of the source.

As described in section 3.1.9 of the Criteria and Thresholds Technical Report, the cut-off conditions are applied to predict significant behavioral responses. The data used to inform the BRFs includes observations beyond 10 km (5.4 nmi) and studies cited in section 3.1.9 of the Criteria and Thresholds Technical Report. This includes data on exposures to other sound sources which is informative when data on exposure to sonars is limited. All the identified significant behavioral responses that were used to develop the BRFs are within the cut-offs (either by distance or sound pressure level (SPL)). Although behavioral responses are predicted beyond the cut-off conditions, these are not expected to qualify as harassment under the MMPA as defined for military readiness activities.

NMFS and the Navy acknowledge the Commission's perspective but maintain that the combined use of cut-off distances and BRFs provides a more accurate and realistic assessment of potential behavioral impacts, particularly for military readiness activities. While Tyack and Thomas (2019) cautioned against using step functions anchored to the 50 percent response level of dose-response curves, the Navy's methodology does not employ such an approach. Instead, the cut-off distances, informed by the farthest observed distances of significant behavioral reactions in the available data (including those exceeding 10 km (5.4 nmi)), serve as a threshold for identifying responses reasonably likely to qualify as harassment under the MMPA. This approach prevents underestimating significant impacts while acknowledging that responses occurring beyond these distances, while possible, are less likely to reach this level of concern.

The Navy's Phase IV approach, incorporating both BRFs and scientifically informed cut-off distances, offers a more realistic assessment of potential behavioral impacts compared to relying solely on BRFs. This approach balances the statistical probabilities derived from the BRFs with empirical observations of behavioral responses in the field. NMFS and the Navy are confident that this combined approach, while still incorporating conservatism to account for uncertainty, does not underestimate potential take by Level B harassment under the MMPA during military readiness activities and provides a more accurate representation of potential impacts.

NMFS has independently assessed the thresholds used by the Navy to identify Level B harassment by behavioral disturbance and finds that they appropriately apply the best available science and it is not necessary to recalculate take estimates. As the science related to marine mammal behavior advances, NMFS and the Navy will continue to refine consideration of contextual factors, such as distance, in its assessment of behavioral responses.

Comment 14:

The Commission continues to maintain that NMFS has not provided adequate justification for dismissing the possibility that single underwater detonations can cause a behavioral response, and, therefore, again recommended that it estimate and authorize takes by Level B harassment of marine mammals during all explosive activities, including those that involve single detonations and gunnery exercises that have several detonations occurring within a few seconds. The Commission further recommends that NMFS encourage the Navy to invest resources in conducting BRSs on marine mammals' responses, including pinniped responses, to underwater detonations for the derivation of explosive BRFs, or at the very least a source-specific step-function threshold, noting that the Navy's Living Marine Resources program has provided funding for a few opportunistic studies involving behavioral response of cetaceans exposed to underwater detonations.

Response:

NMFS acknowledges the possibility that single underwater detonations (including some multiple explosive events, such as certain naval gunnery exercises, that may be treated as a single event because a few explosions occur closely spaced within a very short time (a few seconds)) can cause a behavioral response. The current take estimate framework allows for the consideration of animals exhibiting behavioral disturbance during single explosions as they are counted as “taken by Level B harassment” if they are exposed above the TTS threshold, which is 5 dB higher than the behavioral harassment threshold for multiple detonations. We acknowledge in our analysis that individuals exposed above the TTS threshold may also be harassed by behavioral disruption and those potential impacts are considered in the Analysis and Negligible Impact Determination section. Neither NMFS nor the Navy are aware of evidence to support the assertion that animals will have multiple significant behavioral responses (

i.e.,

those that would qualify as take) to temporally and spatially isolated explosions at received levels below the TTS threshold. However, if any such responses were to occur, they would be expected to be rare and since separated in space and time, would most likely result only in isolated startle responses (

i.e.,

additional behavioral responses would not be expected to add cumulatively or in severity). Furthermore, these rare responses would not be expected to occur at received levels below TTS onset. Thus, they would occur at received levels already bounded by the single

detonation criteria (

i.e.,

TTS is used as the Level B harassment criteria for single detonations) and would therefore already be accounted for in the current take estimates.

The derivation of the explosive injury criteria is provided in the Criteria and Thresholds Technical Report. There is limited information upon which to estimate behavioral response thresholds specific to explosives. Therefore, as described in the Criteria and Thresholds Technical Report, the behaviors exhibited by animals exposed to brief intense tones in the Schlundt

et al.

(2000) study continue to inform the behavioral response threshold for explosives. Some of the observed behaviors in that study would be considered moderate severity for captive animals with trained behaviors and thus may be potentially significant in the context of wild animals. Appropriate threshold metrics are applied for this criterion given the supporting data. Additionally, RMS SPLs are not a preferred metric for explosives due to the challenge of identifying the appropriate time window.

Most explosive activities, including all explosive gunnery activities, analyzed in the rule and the 2025 AFTT SEIS/OEIS include multiple detonations. For these activities, significant behavioral responses are assumed to occur if the cumulative SELs are greater than or equal to 5 dB less than the threshold for onset of TTS. For single detonations, the analysis in appendix E of the 2025 AFTT Supplemental EIS/OEIS assumes that any auditory impact (TTS or AUD INJ) may have a concurrent significant behavioral response. This assumption for single detonations has been clarified in the revised Criteria and Thresholds Technical Report.

BRSs on marine mammal responses to underwater detonations would support future analyses, and NMFS will consider such a recommendation to Navy relative to other new and ongoing research priorities. The Navy supports a wide range of research to inform the development of criteria. The Navy is supporting new research into marine mammal behavioral responses to detonations through its Living Marine Resources program (

https://exwc.navfac.navy.mil/Products-and-Services/Environmental-Security/LMR/

). The findings of this research will be incorporated into the behavioral response criteria when available. To clarify, the Navy has specifically monitored shock trial detonations since the 1990s. Madhusudhana

et al.

(2024) present data on pre- and post-detonation vocalizations at monitoring sites in the vicinity of the 2021 full ship shock trial. Most sites showed no significant changes in vocalization activity for the timeframes analyzed.

Mitigation and Monitoring

Comment 15:

The Commission strongly recommended that NMFS require the Navy to use passive acoustic monitoring (PAM) prior to and during activities involving ship shock trials in the final rule, consistent with explosive sonobuoys, explosive torpedoes, and sinking exercises. The Commission notes that since mission effectiveness would not be impacted, the measures are considered practicable, and their implementation would reduce the potential for the most lethal marine mammal impacts.

Response:

As detailed in table 38, the time and location of ship shock trials are chosen specifically to avoid impacts to large whales and, further, Naval Sea Systems Command (NAVSEA) will develop an extensive mitigation plan for NMFS review and concurrence prior to a ship shock trial. While use of sonobuoys would not affect the ship shock trial, PAM from a 2001 ship shock trial for the Churchill full ship shock trial indicated limited efficacy of the PAM (Clarke and Norman, 2005). As such, and given the significant expense associated with implementing PAM for ship shock trials, NMFS is not requiring the Navy to conduct PAM prior to and during ship shock trials.

Comment 16:

The Commission strongly recommended that NMFS require the Navy to use passive acoustic devices (

i.e.,

directional frequency analysis and recording (DIFAR) and other types of passive sonobuoys, operational hydrophones) prior to explosive bombing exercises and air-to-surface and surface-to-surface explosive missile and rocket exercises to detect marine mammals and implement the necessary mitigation measures in the final rule.

Response:

The Navy employs PAM to supplement visual monitoring when practicable to do so (

i.e.,

when assets that have PAM capabilities are already participating in the activity). For explosive events in which there are no platforms participating that have PAM capabilities, adding PAM capability for mitigation, either by adding a PAM device (

e.g.,

hydrophone) to a platform already participating in the activity or by adding a platform with integrated PAM capabilities to the activity (

e.g.,

a sonobuoy), is not practicable.

The type of aircraft that conduct these bombing, missile, and rocket exercises do not have the capability to deploy and employ sonobuoys. The Action Proponents state that diverting platforms that have PAM capabilities would impact their ability to meet their Title 10 requirements and reduce the service life of those systems. The Action Proponents additionally state that there are significant manpower and logistical constraints that make constructing and maintaining additional PAM systems or platforms for additional training and testing activities impracticable. Given the impracticality of such a measure, NMFS has found that this measure is not warranted, and it is not required in this final rule.

Comment 17:

The Commission recommended that NMFS prohibit detonation of explosive sonobuoys within 3 nmi (5.6 km) of the Southeast North Atlantic Right Whale Mitigation Area from 15 November through 15 April and the Rice's Whale Mitigation Area year-round in the final rule consistent with the Northeast North Atlantic Right Whale Mitigation Area.

Response:

NMFS concurs with the Commission's recommendation, and the Action Proponents have indicated that such a measure is practicable. Therefore, this final rule includes requirements that prohibit detonation of explosive sonobuoys within 3 nmi (5.6 km) of the Southeast North Atlantic Right Whale Mitigation Area from 15 November through 15 April and in the Rice's Whale Mitigation Area year-round.

Comment 18:

The Commission recommended that NMFS require the Navy to use its instrumented ranges and sonobuoys to localize marine mammals and implement the relevant mitigation measures during active acoustic events and to take a harder look at the technologies that the Canadian Department of National Defense (DND) uses during its at-sea activities and incorporate those technologies accordingly for other Phase IV LOA applications. The Commission cites the Lookout Effectiveness Study (Oedekoven and Thomas, 2022) in support of its recommendation. In a related comment, a commenter stated that to maximize the probability of detecting one or more North Atlantic right whales (NARWs) and further reduce risk to the species, the Action Proponents should use both visual observations and passive acoustic detections to inform mitigation decisions and raise the awareness of Lookouts.

Response:

The Action Proponents intend to continue to use PAM prior to activities involving explosive sonobuoys and explosive torpedoes, and during sinking exercises (SINKEX). During the use of active acoustics, Navy assets with

PAM capabilities (

e.g.,

sonobuoys) that are already participating in an activity will continue to monitor for marine mammals, as described in section 5.6 (Activity-based Mitigations) of the 2025 AFTT Supplemental EIS/OEIS. However, the fluidity and nature of military readiness activities (

e.g.,

fast-paced and mobile readiness evolutions), as well as the limitations of these monitoring capabilities, make it impractical for passive acoustic devices to be used as precise real-time indicators of marine mammal location for mitigation (

e.g.,

active sonar power downs or shutdowns, ceasing use of explosives) without an accompanying visual sighting. While we acknowledge that the Lookout Effectiveness Study suggests that detection of marine mammals is less certain than previously assumed at certain distances, we disagree with the assertion that the use of Lookouts has been shown to be wholly ineffective. Lookouts remain an important component of the Action Proponents' mitigation strategy, especially as it relates to minimizing exposure to the more harmful impacts that may occur within closer proximity to the source, where Lookouts are most effective. Further, this final rule requires that in the Northeast North Atlantic Right Whale Mitigation Area and the Dynamic North Atlantic Right Whale Mitigation Area, the Action Proponents must provide the WhaleMap web address (

https://whalemap.org

) and advise that risk of whale strike is increased: (1) after observing a NARW; (2) when operating within 5 nmi (9.3 km) of a known sighting reported within the past 24 hours; (3) within a NMFS-designated Seasonal Management Area, Dynamic Management Area, or Slow Zone; and (4) when transiting at night or during periods of reduced visibility. This final rule also requires that sightings data must be used when planning propulsion testing event details (

e.g.,

timing, location, duration) in the Dynamic North Atlantic Right Whale Mitigation Area to minimize impacts to NARW to the maximum extent practical, and during propulsion testing, to the maximum extent practical, Lookouts must be provided recent WhaleMap (

https://whalemap.org/

) sightings data to help inform visual observations. Last, in the Northeast North Atlantic Right Whale Mitigation Area, the Action Proponents must conduct a web query or email inquiry to the North Atlantic Right Whale Sighting Advisory System or WhaleMap (

https://whalemap.org/

) to obtain the latest NARW sightings data prior to transiting the mitigation area. The Action Proponents must provide the sightings data to Lookouts prior to them standing watch. Lookouts must use that data to help inform visual observations during vessel transits.

In the AFTT Study Area, a small subset of Navy training and testing takes place on the only instrumented range within the study area. The Navy's instrumented ranges do not have the capabilities to be used effectively for mitigation (see section 5.5.3 (Active and Passive Acoustic Monitoring Devices) of the 2018 AFTT EIS/OEIS). As such, NMFS disagrees with the Commission's assertion that real time localization of marine mammals using the Navy's instrumented ranges and sonobuoys is an appropriate requirement, beyond what the Action Proponents are currently doing.

The Action Proponents and NMFS have considered and will continue to study the Canadian DND project, including the technologies used during at-sea activities; however, NMFS disagrees that such a requirement is warranted in this final rule. As more information from the Canadian DND project becomes available, the Action Proponents and NMFS may reconsider whether additional requirements are needed.

Comment 19:

The Commission recommends that the NMFS final rule require the Action Proponents to follow established incident reporting procedures and halt any active acoustic, explosive, pile-driving, or air gun activity if a marine mammal is injured or killed during or immediately after the activity and require the Action Proponents to consult with NMFS to review or adapt the mitigation measures, as necessary.

Response:

The proposed rule and this final rule include a requirement for the Action Proponents to follow established incident reporting procedures if the specified activity is thought to have resulted in the mortality or serious injury of any marine mammals, as recommended by the Commission as outlined in the Notification and Reporting Plan. Note that the Notification and Reporting Plan also requires the Action Proponents to follow established incident reporting protocols for cetacean live strandings. Regarding the Commission's recommendation to require that the Action Proponents halt any active acoustic, explosive, pile driving, or air gun activity if a marine mammal is injured or killed during or immediately after the activity, and require the Action Proponents to consult with NMFS to review or adapt the mitigation measures, as necessary, NMFS agrees with the recommendation to suspend the use of explosives in an event if a marine mammal is injured or killed during or immediately after the activity. Neither NMFS nor the Action Proponents anticipate serious injury or mortality from any activity other than the use of explosives or vessel movement. For all activities involving explosives, the final rule expressly requires that, if a marine mammal is visibly injured or killed as a result of detonation, use of explosives in the event must be suspended immediately (see Mitigation Measures section). While similar language is not included for active acoustics, pile driving, and air gun activity, the proposed rule and this final rule require the Action Proponents to power down or shut down these sources if a marine mammal is observed within the applicable mitigation zone. The Action Proponents will also continue to follow incident reporting procedures (including for vessel strike, should it occur) and consult with NMFS to review or adapt the mitigation measures, as necessary, through the adaptive management process.

Comment 20:

The Commission recommended that NMFS—

• Clearly separate its application of the least practicable adverse impact requirement from its negligible impact determination;

• Adopt a clear decision-making framework that recognizes the species and stock component and the marine mammal habitat component of the least practicable adverse impact provision and always consider whether there are potentially adverse impacts on marine mammal habitat and whether it is practicable to minimize them;

• Rework its evaluation criteria for applying the least practicable adverse impact standard to separate the factors used to determine whether a potential impact on marine mammals or their habitat is adverse and whether possible mitigation measures would be effective;

• Address these concerns by adopting a simple, two-step analysis that more closely tracks the statutory provisions being implemented and, if NMFS is using some other legal standard to implement the least practicable adverse impact requirements, provide a clear and concise description of that standard and explain why it believes it to be “sufficient” to meet the statutory legal requirements; and

• Apply these basic steps and criteria consistently for least practicable adverse impact determinations across incidental take authorizations.

The Commission references previous letters in which it has included its

complete rationale for these recommendations.

Response:

NMFS has made clear in this and other rules that the agency separates its application of the least practicable adverse impact requirement in the Mitigation Measures section from its negligible impact analyses and determinations for each species or stock in the Analysis and Negligible Impact Determination section. Further, NMFS has made this separation clear in practice for years by requiring mitigation measures to reduce impacts to marine mammal species and stocks and their habitat for all projects, even those for which the anticipated take would clearly have a negligible impact, even in the absence of mitigation.

In the Mitigation Measures section of this rule, NMFS has explained in detail our interpretation of the least practicable adverse impact standard, the rationale for our interpretation, and how we implement the standard. The method the agency uses addresses all of the necessary components of the standard and produces effective mitigation measures that result in the least practicable adverse impact on both the species or stocks and their habitat. The commenter has failed to illustrate why NMFS' approach is inadequate or why the commenter's proposed approach would be better, and we therefore decline to accept the recommendation.

Also in the Mitigation Measures section, NMFS has explained in detail our application of the least practicable adverse impact standard. The commenter has recommended an alternate way of interpreting and implementing the least practicable adverse impact standard, in which NMFS would consider the effectiveness of a measure in our evaluation of its practicability. The commenter erroneously asserts that NMFS currently considers the effectiveness of a measure in a determination of whether the potential effects of an activity are adverse, but the commenter has misunderstood NMFS' application of the standard—rather, NMFS appropriately considers the effectiveness of a measure in the evaluation of the degree to which a measure will reduce adverse impacts on marine mammal species or stocks and their habitat, as a less effective measure will less successfully reduce these impacts on marine mammals. Further, the commenter has not provided information that shows that their proposed approach would more successfully evaluate mitigation under the least practicable adverse impact standard, and we decline to accept it.

Further, NMFS disagrees with the commenter's assertion that analysis of the rule's mitigation measures under the least practicable adverse impact standard remains unclear or that the suggested shortcomings exist. The commenter provides no rationale as to why the two-step process they describe is better than the process that NMFS uses to evaluate the least practicable adverse impact that is described in the rule, and therefore we decline to accept the recommendation.

Regarding the assertion that the standard shifts on a case-by-case basis, the commenter misunderstands NMFS' process. Neither the least practicable adverse impact standard nor NMFS' process for evaluating it shifts on a case-by-case basis. Rather, as the commenter suggests should be the case, the evaluation itself is case-specific to the proposed activity, the predicted impacts, and the mitigation under consideration.

Regarding the recommendation to apply the recommended steps and criteria for least practicable adverse impact determinations across incidental take authorizations, as outlined above, NMFS disagrees with these recommendations and therefore does not intend to apply them across incidental take authorizations.

Comment 21:

A commenter stated that to adequately protect NARW, the boundaries of the Southeast North Atlantic Right Whale Mitigation Area, and its requirements, should be extended north to Cape Fear, North Carolina. The commenter said this extension would limit the use of active sonar, prohibit in-water explosives and non-explosive ordnance, and impose several measures to reduce the risk of vessel strike in the entirety of the species' calving habitat from November 15 to April 15, reflecting the duration of the calving season.

Response:

Expansion of the Southeast North Atlantic Right Whale Mitigation Area northward to encompass all areas of potential occurrence would require training activities to move farther north or farther out to sea, which the Action Proponents indicate is impracticable due to implications for safety and sustainability, as detailed in section 5.4.3 (Mitigation Areas off the Mid-Atlantic and Southeastern United States) of the 2018 AFTT Final EIS/OEIS. Additionally, that section explains why further limitations on activities, including limitations on active sonar, in-water explosives and non-explosive ordnance, and imposition of additional measures to reduce the risk of vessel strike, within this area would be impracticable. NMFS reviewed and concurs with the Action Proponents' assessment of practicability, effects on mission effectiveness, and personnel safety, and as such, has not required expansion of the Southeast North Atlantic Right Whale Mitigation Area beyond that included in the proposed rule.

The best available density data for the AFTT Study Area shows that the Southeast North Atlantic Right Whale Mitigation Area encompasses the areas of highest density in the region (Roberts

et al.,

2023; U.S. Department of the Navy, 2025). Although NARW have been sighted on rare occasions east of the mitigation area, these animals were located outside of the higher use habitats that represent the primary occurrence of the population. Overall, most NARW sightings made during Navy and NMFS surveys have occurred in, or very close to, the Southeast North Atlantic Right Whale Mitigation Area, which further indicates that the mitigation area may have the highest seasonal abundance of NARW in waters off the mid-Atlantic and southeastern United States.

Though the spatial extent of the Southeast North Atlantic Right Whale Mitigation Area cannot be extended, this final rule includes additional mitigations in that area and in the Dynamic North Atlantic Right Whale Mitigation Area, which encompasses the U.S. Exclusive Economic Zone (EEZ) off the East Coast. In the Southeast North Atlantic Right Whale Mitigation Area, this final rule includes two new requirements. First, from November 15 to April 15, the Action Proponents must not detonate explosive sonobuoys within 3 nmi (5.6 km) of the Southeast North Atlantic Right Whale Mitigation Area. Second, during the same time period, the Action Proponents must not conduct vessel propulsion testing. In the Dynamic North Atlantic Right Whale Mitigation Area, in Protective Measures Assessment Protocol (PMAP)-generated reports, Action Proponents will provide the WhaleMap web address (

https://whalemap.org

); advise that risk of whale strike is increased after observing a NARW; when operating within 5 nmi (9.3 km) of a known sighting reported within the past 24 hours; within a NMFS-designated Seasonal Management Area, Dynamic Management Area, or Slow Zone; and when transiting at night or during periods of reduced visibility; and reinforce the requirement of the International Regulations for Preventing Collisions at Sea (COLREGS) for vessels to proceed at a safe speed, appropriate to the prevailing circumstances and conditions, to avoid a collision with any

sighted object or disturbance, including any marine mammal. Additionally, during propulsion testing in the mitigation area, to the maximum extent practical, Lookouts will be provided recent

https://www.whalemap.org

sightings data to help inform visual observations.

Further, this final rule requires that within the first year of AFTT Phase IV implementation, the Action Proponents must work collaboratively with the NMFS ESA Interagency Cooperation Division and the NMFS Permits and Conservation Division to: (1) analyze and discuss the application of new information from the NMFS North Atlantic Right Whale Persistence Modelling Efforts toward AFTT mitigation measures; (2) evaluate the practicability and conservation benefits of newly proposed mitigation measures and/or changes to existing measures based on information from the model; and (3) implement any new mitigation measures or changes to existing measures that meet the Action Proponents' Practicability Criteria and Sufficiently Beneficial requirements.

Comment 22:

The Commission stated that under the Gulf biological opinion (commonly referred to as BiOp) for oil and gas activities, the Bureau of Ocean Energy Management (BOEM) and the Bureau of Environmental Safety and Enforcement (BSEE) would be required to identify a near real-time platform (

e.g.,

WhaleAlert) to help oil- and gas-related vessels avoid strikes of Rice's whales. BOEM and BSEE, in collaboration with NMFS, also must work to ensure additional devices and near real-time detection data systems are integrated into the near real-time sightings platform to establish an integrated platform for all Rice's whale detections in the Gulf (

e.g.,

WhaleMap). The Commission recommends that NMFS require the Action Proponents to conduct a query of the aforementioned platform (

e.g.,

WhaleAlert, WhaleMap) that houses the Rice's whale sightings once it is established and prior to transiting the Rice's Whale Mitigation Area, provide those sightings data to the Lookouts prior to them standing watch, use the data to inform the Lookouts' visual observations during vessel transits, and implement speed reductions to 10 knots (kn) (18.5 km/hr) for surface ships transiting within 5 nmi (9.3 km) of a sighting reported in the platform within the previous 24 hours. Any modifications to the mitigation requirements for the Rice's Whale Mitigation Area can be addressed during the Navy's Annual Adaptive Management Meetings.

In a related comment, a commenter stated that protections must be afforded to Rice's whale throughout the entirety of their known habitat, and that NMFS and the Action Proponents should revise the boundaries of the Rice's Whale Mitigation Area westwards to include all U.S. waters between the 100-m and 400-m isobaths, to reflect best available scientific information on the species. The commenter also recommended that the requirements in the Rice's Whale Mitigation Area be expanded to include the following mitigation requirements that emulate a subset of those required for NARW in other proposed mitigation areas. The commenter stated that the recommendations account for the fact that an Early Warning System for Rice's whales does not yet exist. These include:

(1) Year-round within the mitigation area, surface ships must minimize transits and transit distances through Rice's whale habitat to the maximum extent practicable, and must implement speed reductions: (a) after they observe a Rice's whale, if they are within 5 nmi (9.3 km) of a sighting of a Rice's whale reported in the previous 12 hours, and (b) at minimum, at night and in restricted visibility; and

(2) The Action Proponents must provide Lookouts the sightings data prior to standing watch to help inform visual observations.

Response:

This rulemaking includes a Rice's Whale Mitigation Area that overlaps the Rice's whale small and resident population area identified by NMFS in its 2016 status review (Rosel

et al.,

2016) and most of the eastern portion of proposed critical habitat (88 FR 47453, July 24, 2023). Within this area, the Action Proponents must not use more than 200 hours of surface ship hull-mounted MFAS annually and must not detonate in-water explosives (including underwater explosives and explosives deployed against surface targets) except during mine warfare activities. Additionally, the Ship Shock Trial Mitigation Area would ensure that the northern Gulf of America ship shock trial box is situated outside of the Rice's whale core distribution area identified in 2019 (84 FR 15446, April 15, 2019). These restrictions will reduce the severity of impacts to Rice's whales by reducing their exposure to levels of sound from sonar or explosives that would have the potential to cause injury or mortality, thereby further supporting NMFS' determination that non-auditory injury and mortality are not expected to occur, reducing the likelihood of auditory injury, and, further, minimizing the severity of behavioral disturbance. Further, as described in the Changes from the Proposed Rule to the Final Rule section of this final rule, we have added three new measures in the Rice's Whale Mitigation Area since publication of the proposed rule. This final rule includes a requirement that the Action Proponents must not detonate explosive sonobuoys within 3 nmi (5.6 km) of the Rice's Whale Mitigation Area as well as two new measures to further reduce the risk of vessel strike of Rice's whale. The Action Proponents must avoid conducting vessel propulsion testing events in the Rice's Whale Mitigation Area to the maximum extent practical and the Action Proponents must issue an annual awareness message to Navy vessels that routinely train or test in the vicinity of the Rice's whale proposed critical habitat and Coast Guard vessels that routinely train anywhere in the Gulf of America.

While it is not practicable for the Action Proponents to issue speed restrictions (see section 5 (Mitigation Considered but Eliminated) of the 2025 AFTT SEIS/OEIS), as suggested by the commenter, this annual awareness message will advise that risk of whale strike is increased when transiting through Rice's whale proposed critical habitat (

i.e.,

within the 100 to 400 m isobaths), particularly at night or during periods of reduced visibility, and reinforce the requirement of the COLREGS (

https://www.imo.org/en/about/conventions/pages/colreg.aspx

) for vessels to proceed at a safe speed, appropriate for the prevailing circumstances and conditions, to avoid a collision with any sighted object or disturbance, including any marine mammal.

Regarding the recommendation for surface ships to minimize transits and transit distances through Rice's whale habitat to the maximum extent practicable, Navy asserts that it does not have many training events in the area, and vessel traffic in the area is already limited. As such, transits through this area are already minimized, as recommended by the commenter.

Regarding the commenter's recommendation to revise the boundaries of the Rice's Whale Mitigation Area westwards to include all U.S. waters between the 100-m and 400-m isobaths, the majority of the Navy's activities do not occur within the central/western portion of Rice's whale habitat. The potential for impacts in that area is very low due to infrequent use of Navy surface ship hull-mounted MFAS or explosives in the central/western portion of the habitat. The Coast Guard does train in this area but

their training activities do not include the use of sonar and other transducers or explosives (of note, the Coast Guard is not planning any testing activities as part of the specified activity in the AFTT Study Area). As such, the only applicable mitigation requirement for the waters west of the Rice's Whale Mitigation Area between the 100-m and 400-m isobaths is for the Action Proponents to issue an annual awareness message to Navy vessels that routinely train or test in the vicinity of the Rice's whale proposed critical habitat and for the Coast Guard to send the awareness messages required in the Rice's Whale Mitigation Area to all Coast Guard vessels that routinely train anywhere in the Gulf of America, and this final rule includes a requirement for the Action Proponents to do so.

Regarding the Commission's recommendation related to a future Rice's whale sightings platform (

e.g.,

WhaleAlert, WhaleMap), when such a platform is established, NMFS and the Action Proponents will evaluate its potential use for mitigating potential impacts to Rice's whale, including providing sightings data to the Lookouts prior to them standing watch, use of the data to inform the Lookouts' visual observations during vessel transits, and potential speed restrictions in a defined time and area relative to sightings. In the public comment related to the Commission's, the commenter stated that its recommendations account for the fact that an Early Warning System for Rice's whale does not yet exist, but it is unclear what the commenter is referring to regarding providing Lookouts the sightings data prior to standing watch to help inform visual observations absent a sighting platform such as WhaleMap, and as such, this final rule does not incorporate this recommendation.

Comment 23:

A commenter stated that while it provisionally supports aspects of the proposed rule, the least practicable adverse impact standard has not yet been met. The commenter provided specific mitigation recommendations in support of their assertion.

Response:

NMFS has described our well-reasoned process for identifying the measures needed to meet the least practicable adverse impact standard in the Mitigation Measures section in this rule, and we have followed the approach described there when analyzing potential mitigation for the Action Proponents' activities in the AFTT Study Area. Responses to specific recommendations for mitigation measures provided by the commenters are discussed separately.

Comment 24:

A commenter recommended that NMFS incorporate new scientific information into design of its mitigation areas, specifically referencing Houser

et al.

(2024) and Southall

et al.

(2024). The commenter recommended that NMFS use the data to inform which types of acoustic sources to limit in mitigation areas important to particular species, and the size of the stand-off distances to apply to those areas.

Response:

The mitigation measures in this rule are informed by multiple factors, including the sensitivity of certain hearing groups to certain sound sources (informed by the Phase IV criteria and thresholds) and vulnerability to other threats (

e.g.,

vessel strike). The Phase IV criteria and thresholds incorporate data from Houser

et al.

(2024), and as such, the mitigation areas in the proposed rule and final rule inherently consider those data. While the Phase IV criteria and thresholds do not incorporate data from Southall

et al.

(2024), they include delphinid response data from other studies, and the potential responses observed in Southall

et al.

(2024) occurred at received levels and distances assessed for potentially significant behavioral responses in the AFTT analysis. The commenter did not provide specific mitigation recommendations that may stem from the publications they reference. However, NMFS has responded to other mitigation recommendations from the commenter in separate responses herein and has explained that it has determined that the Action Proponents' planned mitigation measures would effect the least practicable adverse impact on the affected species and their habitat.

Comment 25:

A commenter stated that the proposed measure to minimize the use of helicopter dipping sonar to the maximum extent practicable in the Southeast North Atlantic Right Whale Mitigation Area is a step toward mitigation of impacts from dipping sonar. However, the commenter states that the available scientific evidence on the impacts of dipping sonar on deep-dive rates in beaked whales (family Ziphiidae), indicates that management of this acoustic source should be expanded, including to areas within the AFTT Study Area representing important habitat for beaked whale populations.

Response:

As stated in the Analysis and Negligible Impact Determination section of the proposed rule and this final rule, there are no known BIAs for beaked whales in the AFTT Study Area, though these stocks generally occur in higher densities year-round in deep waters over the Atlantic continental shelf margins. The Western North Atlantic stocks of goose-beaked whales and Blainville's beaked whales generally congregate over continental shelf margins from Canada to North Carolina, with goose-beaked whales reported as far south as the Caribbean and Blainville's beaked whales as far south as the Bahamas. The Western North Atlantic stock of Gervais' beaked whales generally congregate over continental shelf margins from New York to North Carolina. The Western North Atlantic stock of Sowerby's beaked whales is the most northerly distributed stock of deep-diving mesoplodonts, and they generally congregate over continental shelf margins from Labrador to Massachusetts. The Western North Atlantic stock of True's beaked whales generally congregate over continental shelf margins from Nova Scotia to Cape Hatteras, with northern occurrence likely relating to the Gulf Stream. The Western North Atlantic stock of northern bottlenose whales is uncommon in U.S. waters and generally congregates in areas of high relief, including shelf breaks and submarine canyons from the Davis Strait to New England, although strandings have occurred as far south as North Carolina.

The commenter provided a general recommendation for expansion of dipping sonar mitigation in important habitat for beaked whales but did not specify particular areas or beaked whale species to prioritize for such mitigation. As noted above, while beaked whales generally occur in higher densities year-round in deep waters over the Atlantic continental shelf margins, the latitudinal ranges vary depending on the species. If the entire shelf break were considered important habitat for beaked whales, that would limit the bathymetric scope of areas available for the training and testing of dipping sonar and would not be practical.

As the commenter notes, the proposed rule and this final rule include a Southeast North Atlantic Right Whale Mitigation Area in which the Action Proponents must minimize the use of helicopter dipping sonar to the maximum extent practical. This measure would benefit the Western North Atlantic stocks of goose-beaked whales and Blainville's beaked whales in the most southern portion of their range. The proposed rule and this final rule also include Major Training Exercise Planning Awareness Mitigation Areas across multiple areas along the Atlantic continental shelf break in which the Action Proponents must either limit major training exercises

(MTEs) or not conduct MTEs. These restrictions would benefit multiple beaked whale species, and would inherently limit or prohibit dipping sonar, as the majority of dipping sonar used during training activities in the mid-Atlantic is used during MTEs (unit-level training mostly occurs in the Jacksonville Operating Area (OPAREA)). Also of note, the Action Proponents already do not conduct much sonar in some beaked whale habitats, such as the Cape Hatteras area where goose-beaked whales are known to occur. This location was chosen for the Atlantic BRS on beaked whales specifically because those beaked whales are not frequently exposed to mid-frequency active sonar. Additional restrictions on the use of dipping sonar in the Atlantic is not practicable, and as such, is not required by this final rule.

Comment 26:

A commenter stated that, to reflect the best available scientific information and achieve the least practicable adverse impact to NARW, the boundaries of the Northeast North Atlantic Right Whale Mitigation Area should be extended to include the established foraging habitat south of Martha's Vineyard and Nantucket, Massachusetts.

Response:

NMFS concurs with the commenter that additional mitigation is warranted in the NARW feeding area south of Martha's Vineyard and Nantucket. As such, this final rule includes a new Martha's Vineyard North Atlantic Right Whale Mitigation Area in which the Action Proponents must avoid conducting vessel propulsion testing events to the maximum extent practical. In addition to the new Martha's Vineyard North Atlantic Right Whale Mitigation Area, this final rule includes multiple new mitigation measures for NARW, as described in response to

Comment 21,

including new measures in the Dynamic North Atlantic Right Whale Mitigation Area, which overlaps the new Martha's Vineyard North Atlantic Right Whale Mitigation Area. In this area, the Action Proponents will provide North Atlantic Right Whale Dynamic Management Area information (

e.g.,

location and dates) to applicable assets transiting and training or testing in the vicinity of the Dynamic Management Area. Further, in PMAP reports generated in the Dynamic North Atlantic Right Whale Mitigation Area, Action Proponents will provide the WhaleMap web address (

https://www.whalemap.org

), advise situations in which risk of vessel strike is increased, and reinforce the requirement for vessels to proceed at a safe speed. Additional details on the above can be found in the response to

Comment 21.

Additionally, in the Dynamic North Atlantic Right Whale Mitigation Area, during propulsion testing in the mitigation area, to the maximum extent practical, Lookouts will be provided recent

https://www.whalemap.org

sightings data to help inform visual observations. Further, the Action Proponents follow NARW sighting and avoidance measures regardless of location, including one or more Lookouts on manned underway surface vessels in accordance with the most recent navigation safety instruction and underway manned surface vessels maneuver themselves (which may include reducing speed) to maintain 500 yd (457.2 m) distance from whales, as mission and circumstances allow.

Within the northeast portion of the Study Area, the Northeast North Atlantic Right Whale Mitigation Area represents the largest area that is practical for the Navy to implement that full suite of mitigation. As such, this final rule does not require that the Action Proponents extend the boundary of the Northeast North Atlantic Right Whale Mitigation Area (and the mitigation required in that area) south of Martha's Vineyard and Nantucket for the reasons described below. Expanding the full suite of mitigation measures of the Northeast North Atlantic Right Whale Mitigation Area to the area south of Nantucket and Martha's Vineyard would encroach upon the primary water space where training and testing activities are planned to occur. Such modifications of training and testing activities would have a significant impact on safety, sustainability, and the Navy's ability to meet its mission requirements.

The Navy does not typically schedule MTEs in the Northeast Range Complexes, though MTEs originally planned for other locations may have to change during an exercise, or in exercise planning, based on an assessment of the performance of the units, or due to other conditions such as weather and mechanical issues. These contingency requirements preclude the Navy from completely eliminating MTEs from occurring in this area. For training and testing that does occur here, this area provides a wide range of bathymetric and topographic opportunities that support critical smaller scale training and testing necessary to meet mission requirements.

The area is important to the Navy's acoustic and oceanographic research. Specifically, having access to waterspace within 20 nmi (37 km) of Woods Hole Oceanographic Institute and in the vicinity of the New England Mud Patch is important to these research activities. Restricting the area would result in a reduced ability to conduct accurate oceanographic or acoustic research to meet research objectives, validate acoustic models, and conduct accurate engineering tests of acoustic sources, signal processing algorithms, and acoustic interactions.

Additionally, NAVSEA needs full access and flexibility to conduct testing in this area. Testing locations are typically located near systems command support facilities, which provide critical safety, platform, and infrastructure support and technical expertise necessary to conduct testing. Restricting the area would result in: (1) reduced ability to ensure the safety, functionality, and accuracy of systems, platforms, and components through maintenance, repairs, or testing prior to use at sea as needed or required by acquisition milestones, and (2) reduced ability to effectively test systems, platforms, and components before full-scale production or delivery in order to validate whether they perform as expected and determine whether they are operationally effective, suitable, survivable, and safe for their intended use by the fleet.

Comment 27:

A commenter recommended further research and exploration of the feasibility of signal modification, including converting upsweeps to downsweeps, reducing the level of the side bands, or lengthening the rise time. The 2024 AFTT Draft Supplemental EIS/OEIS considered, but rejected, modification of active sonar sources for training as part of a potential mitigation measure (“26. Reducing annual active sonar hours, replacing active sonar, with passive sonar or modifying active sonar sources for training”), deeming it impractical for achieving the mission. The commenter stated that the rationale provided in the 2024 AFTT Draft Supplemental EIS/OEIS does not clearly justify why signal modifications alone would be impractical. The commenter states that some of those modifications, such as converting up-sweeps to down-sweeps, would not alter the system's spectral output in any way. The commenter stated that it believes source modification requires greater validation across species and in more behavioral contexts before any decisions are made to alter signals—but, given the preliminary data, and given the potential of this measure to reduce the instances and severity of behavioral harassment, it urges NMFS to require or otherwise stimulate investigation of this potentially significant mitigation measure and provide a schedule for completion.

Another commenter stated that NMFS and Navy should prioritize identifying and implementing alternative training methods, technologies, and locations that do not place vulnerable marine life at such extreme risk, stating that this would not only fulfill legal obligations, but also demonstrate a commitment to sustainable stewardship of our ocean ecosystems.

Response:

Active sonar signals are designed explicitly to provide optimum performance at detecting underwater objects (

e.g.,

submarines) in a variety of acoustic environments. The Action Proponents train with various active sonar signals, including up-sweeps and down-sweeps, to accurately replicate operational scenarios. Reducing training realism by restricting the signal used would ultimately prevent units from deploying with the required level of readiness necessary to accomplish their missions and impede the Action Proponents' ability to certify forces to deploy to meet national security tasking. Likewise, testing program requirements include test parameters designed to accurately determine whether a system is meeting its operational and performance requirements. Reducing realism by restricting the signal used would impact the ability of researchers, program managers, and weapons system acquisition programs to effectively test systems and platforms (and components of these systems and platforms) before full-scale production or delivery to the fleet. For these reasons, the Navy has determined, and NMFS concurs, that modifying or limiting the sonar signal as mitigation is impractical to implement as it would result in degraded realism of training and testing.

NMFS and the Navy will explore whether future studies on the efficacy and practicality of signal modification are appropriate in consideration of other ongoing research efforts, including some recommended by the commenter (

e.g.,

thermal detection). However, at this time, given the numerous other research priorities and established impracticality, NMFS is not requiring the Action Proponents to investigate the efficacy of signal modification.

Comment 28:

The Commission recommended that NMFS require Action Proponents' surface ships to maintain a speed of no more than 10 kn (18.5 km/hr) during transits when a NARW is observed, if the vessels are within 5 nmi (9.3 km) of a reported sighting, at night, and during periods of reduced visibility in the Northeast North Atlantic Right Whale Mitigation Area year-round and the Southeast North Atlantic Right Whale Mitigation Area from November 15 to April 15. The Commission also recommended that NMFS require Action Proponents' surface ships to maintain a speed of no more than 10 kn (18.5 km/hr) during transits when a Rice's whale is observed, at night, and during periods of reduced visibility in the Rice's Whale Mitigation Area year-round.

In a related comment, a commenter stated that according to the current vessel speed rule that was put into place to protect NARWs, military vessels are exempt from the speed restrictions. The commenter states that increasing naval vessel traffic in these same regions, especially when military vessels are exempt from civilian speed restrictions, will only heighten the risk of fatal interactions.

Response:

The proposed rule included multiple requirements to minimize the risk of vessel strike to NARW and Rice's whales, including a requirement within the Northeast North Atlantic Right Whale Mitigation Area requiring surface ships to implement speed reductions after observing a NARW, if transiting within 5 nmi (9.3 km) of a sighting reported to the North Atlantic Right Whale Sighting Advisory System within the past week, and when transiting at night or during periods of reduced visibility. It also included a requirement in the Southeast North Atlantic Right Whale Mitigation Area that from November 15 to April 15 requiring surface ships to minimize north-south transits to the maximum extent practical, and implement speed reductions after they observe a NARW, if they are within 5 nmi (9.3 km) of an Early Warning System sighting reported within the past 12 hours, and at night and in poor visibility. This final rule includes several additional measures to reduce the risk of vessel strike, as described below.

Within the Southeast North Atlantic Right Whale Mitigation Area, from November 15 to April 15, the Action Proponents must not conduct vessel propulsion testing. Further, this final rule includes a new Martha's Vineyard North Atlantic Right Whale Mitigation Area in which the Action Proponents must avoid conducting vessel propulsion testing events to the maximum extent practical. Additionally, in the Dynamic North Atlantic Right Whale Mitigation Area, the extent of which matches the boundary of the U.S. EEZ on the East Coast, the Action Proponents must provide North Atlantic Right Whale Dynamic Management Area information (

e.g.,

location and dates) to applicable assets transiting and training or testing in the vicinity of the Dynamic Management Area. The information must alert assets (and their Lookouts) to the possible presence of NARW in their vicinity. Lookouts must use the information to help inform visual observations during military readiness activities that involve vessel movements, active sonar, in-water explosives (including underwater explosives and explosives deployed against surface targets), or non-explosive ordnance deployed against surface targets in the mitigation area.

In PMAP reports generated in the Dynamic North Atlantic Right Whale Mitigation Area, this final rule requires that Action Proponents must provide the WhaleMap web address (

https://whalemap.org

) and advise that risk of whale strike is increased after: (1) observing a NARW; (2) when operating within 5 nmi (6.5 km) of a known sighting reported within the past 24 hours; (3) within a NMFS-designated Seasonal Management Area, Dynamic Management Area, or Slow Zone; and (4) when transiting at night or during periods of reduced visibility. The PMAP report must also reinforce the requirement of the COLREGS for vessels to proceed at a safe speed, appropriate for the prevailing circumstances and conditions, to avoid a collision with any sighted object or disturbance, including any marine mammal. Additionally, this final rule requires that during propulsion testing in the Dynamic North Atlantic Right Whale Mitigation Area, to the maximum extent practical, Lookouts must be provided recent

https://whalemap.org

sightings data to help inform visual observations.

This final rule also requires that within the first year of AFTT Phase IV implementation, the Action Proponents must work collaboratively with the NMFS ESA Interagency Cooperation Division and the NMFS Permits and Conservation Division to: (1) analyze and discuss the application of new information from the NMFS North Atlantic Right Whale Persistence Modelling Efforts toward AFTT mitigation measures; (2) evaluate the practicability and conservation benefits of newly proposed mitigation measures and/or changes to existing measures based on information from the model; and (3) implement any new mitigation measures or changes to existing measures that meet the Action Proponents' Practicability Criteria and Sufficiently Beneficial requirements.

This final rule also includes two new measures to reduce the risk of vessel strike of Rice's whale. The Action Proponents must avoid conducting vessel propulsion testing events in the Rice's Whale Mitigation Area, to the maximum extent practical. The Action

Proponents must also issue an annual awareness message to Navy and Coast Guard vessels that routinely train or test in the vicinity of the proposed Rice's whale proposed critical habitat. The message will advise that risk of whale strike is increased when transiting through proposed Rice's whale proposed critical habitat (

i.e.,

within the 100-400 m isobaths), particularly at night or during periods of reduced visibility, and reinforce the requirement of the COLREGS for vessels to proceed at a safe speed, appropriate for the prevailing circumstances and conditions, to avoid a collision with any sighted object or disturbance, including any marine mammal.

The Action Proponents require flexibility in use of variable ship speeds for training, testing, operational, safety, and engineering qualification requirements. Action Proponent vessels typically use the lowest speed practical given individual mission needs. NMFS has reviewed the analysis of these additional suggested restrictions and the impacts they would have on military readiness and concurs with the Navy's assessment that they are impracticable (see section 5.3.4.1 Vessel Movement and section 5.5 Measures Considered but Eliminated in the 2020 NWTT FSEIS/OEIS). Therefore, the Action Proponents are already planning to engage in the lowest practicable speed in biologically important habitats, including in designated critical habitat for NARW and proposed critical habitat for Rice's whales and other biologically important habitat for vulnerable species, as well as in all mitigation areas and other areas. As such, additional restrictions on vessel speed are not practicable and therefore, are not required.

The commenter did not provide a citation for the statement that naval vessel traffic is increasing in the AFTT Study Area. The Navy states that there has not been an increase in vessel traffic related to AFTT activities since the 2018 analysis. Rather, there has been a decrease in most areas and a decrease in the AFTT Study Area as a whole (see table 3.0-9 of the 2025 AFTT Supplemental EIS/OEIS).

Comment 29:

A commenter asserted that mitigation measures based on visual observation (

i.e.,

by Lookouts), such as safety zone maintenance, results in highly limited risk reduction for most species and under most conditions. The commenter stated that NMFS should require infrared and thermal detection technologies as alternative detection measures for mitigation and monitoring, stating that these technologies have achieved a readiness level that is capable of supporting monitoring and mitigation during Phase IV military readiness activities.

Response:

Lookouts remain an important component of the Action Proponents' mitigation strategy, especially as it relates to minimizing exposure to the more harmful impacts that may occur within closer proximity to the source, where Lookouts are most effective. As stated by the commenter, thermal detection technologies have advanced in recent years. However, significant limitations still exist, and the technology has not yet reached the level of performance needed for deployment during military readiness activities for mitigation uses. Current technologies are limited by: (1) low sensor resolution and a narrow field of view; (2) reduced performance in certain environmental conditions; and (3) high cost and uncertain long-term reliability.

Thermal detection systems are more useful for detecting marine mammals in some marine environments than others. Current technologies have limitations regarding water temperature and survey conditions (

e.g.,

rain, fog, sea state, glare, ambient brightness), for which further effectiveness studies are required. Thermal detection systems are generally thought to be most effective in cold environments, which have a large temperature differential between an animal's temperature and the environment. Current thermal detection systems have proven more effective at detecting large whale blows than the bodies of small animals, particularly at a distance. The effectiveness of current technologies has not been demonstrated for small marine mammals at-sea (noting that Richter

et al.

(2023) demonstrated efficacy in detecting killer whales in the Salish Sea using land-based thermal imaging systems). Thermal detection systems exhibit varying degrees of false positive detections (

i.e.,

incorrect notifications) due in part to their low sensor resolution and reduced performance in certain environmental conditions. False positive detections may incorrectly identify other features (

e.g.,

birds, waves, boats) as marine mammals (Boebel and Zitterbart, 2017; Zitterbart

et al.,

2020).

Thermal detection systems for military applications are deployed on various Department of Defense (DoD) platforms. These systems were initially developed for nighttime targeting and object detection such as a boat, vehicle, or people and are not optimized for marine mammal detections versus object detection, nor do these systems have the automated marine mammal detection algorithms the Navy is testing via its ongoing research program. The Action Proponents do not have available personnel to add Lookouts to use thermal detection systems in tandem with existing Lookouts who are using traditional observation techniques.

Existing specialized DoD infrared/thermal capabilities on Navy aircraft and surface ships are designed for fine-scale targeting. Viewing arcs of these thermal systems are narrow and focused on a target area. Furthermore, sensors are typically used only in select training events and have a limited lifespan before requiring expensive replacement. Some sensor elements can cost upward of $300,000 to $500,000 per device, so their use is predicated on a distinct military need.

The Office of Naval Research sponsored a project from 2019 to 2023 titled “Development of the Next Generation Automatic Surface Whale Detection System for Marine Mammal Mitigation and Distribution Estimation.” The aim of the project was to develop a system to be used by non-experts, with minimal installation requirements, applying algorithms to reliably detect, localize, and identify surfaced marine mammals from a vessel, while minimizing false detections. In 2024, the project transitioned to the Navy's Living Marine Resources Program, the applied research, development, test, and evaluation program that funds Navy driven research needs to support at-sea compliance and permitting. Thermal Imaging for Vessel Strike Mitigation on Autonomous Vessels (Project #LMR-68) will focus on adapting and testing two existing and proven thermal imaging-based whale detection systems to reduce the potential for vessel strike during navigation of unmanned Navy surface vessels.

When infrared and thermal mitigation technologies mature to the state where they are determined to be sufficiently effective at mitigating marine mammal impacts when considering the range of environmental conditions analogous to where the Action Proponents train and test and the species that could co-occur in space and time with the activities, then the Action Proponents will assess their compatibility with military readiness applications on both manned and unmanned vessels. This would include a practicality assessment of the budget and acquisition process (including costs associated with designing, building, installing, maintaining, and manning equipment), the logistical and physical considerations for retrofitting platforms with the appropriate equipment and their associated maintenance, repairs, or replacements (

e.g.,

conducting

engineering studies to ensure compatibility with existing shipboard systems), the resource considerations for training personnel to effectively operate the equipment, and the potential security and classification issues. New system integration on Action Proponents' assets can entail up to 5-10 years of effort to account for acquisition, engineering studies, and development and execution of systems training.

Given the assessment above, this final rule does not require the Action Proponents to utilize thermal detection for mitigating training and testing impacts on marine mammals. As thermal detection technology improves and practicability of applying the technology for training and testing activities is further assessed, NMFS will consider whether requirements to utilize thermal detection for mitigating impacts to marine mammals is appropriate.

Negligible Impact Determination

Comment 30:

A commenter stated that NMFS has not met the negligible impact standard based on current scientific understanding and population status of species like the Rice's whale and NARW. The commenter states that authorizing incidental takes in areas that are biologically sensitive, federally protected, and home to critically endangered species sets a dangerous precedent.

In a related comment, a commenter identified six points that they described as methodological problems that require addressing to ensure the negligible impact determinations are valid under the MMPA and Administrative Procedure Act (APA). The six points were: (1) improper reliance on means and medians in establishing thresholds for auditory impacts; (2) application of an unrealistic non-conservative auditory weighting scheme for low-frequency cetaceans; (3) lack of incorporation of recent behavioral response data into biphasic risk functions; (4) reduction of modeled take estimates through the application of cut-off distances; (5) discounting gas-bubble pathology as a mechanism of harm to marine mammals; and (6) failure to present a meaningful analysis of the aggregate effects on marine mammal populations.

Response:

NMFS disagrees with the commenter's assertion that the negligible impact standard has not been satisfied for each species or stock. The commenter has not provided sufficient information to support their assertion.

As described in the proposed rule and this final rule, serious injury or mortality of NARW and Rice's whale is neither anticipated nor authorized, nor is any non-auditory injury. The maximum allowable take is limited to Level A and B harassment in the form of AUD INJ (table 16). As described in the Auditory Injury from Sonar Acoustic Sources and Explosives and Non-Auditory Injury from Explosives section of the proposed rule, any take that occurs in the form of TTS is expected to be lower-level, of short duration (from minutes to, at most, several hours or less than a day), and mostly not in a frequency band that would be expected to interfere with NARW or Rice's whale communication or other important low-frequency cues. Any associated lost opportunities or capabilities individuals might experience as a result of TTS would not be at a level or duration that would be expected to impact reproductive success or survival.

NMFS carefully considered the population status and best scientific evidence available for Rice's whale, NARW, and all other marine mammal species and stocks in making its negligible impact determinations. NMFS has worked with the Navy over the years to increase the spatio-temporal specificity of the descriptions of activities planned in or near areas of biological importance, when possible (

i.e.,

in NARW ESA-designated critical habitat). NMFS' analysis includes explicit consideration of takes occurring in important areas, as included in appendix A of the application, and inclusion of mitigation measures in areas of biological importance, where appropriate. NMFS may still find that the impacts of a specified activity are negligible even where take occurs in BIAs, critical habitat, or other important areas, and even though impacts in these protected areas warrant additional consideration, including potential mitigation.

As described in the Analysis and Negligible Impact Determination section and the Mitigation Measures section of the proposed rule and this final rule, mitigation measures, several of which are designed specifically to reduce impacts to NARW and Rice's whale, are expected to further reduce the potential severity of impacts through real-time operational measures that minimize higher level/longer duration exposures and time/area measures that reduce impacts in high value habitat. Specifically, this rule includes several geographic mitigation areas for NARW: Northeast North Atlantic Right Whale Mitigation Area, Gulf of Maine Mitigation Area, Martha's Vineyard North Atlantic Right Whale Mitigation Area, Jacksonville Operating Area North Atlantic Right Whale Mitigation Area, Southeast North Atlantic Right Whale Mitigation Area, Dynamic North Atlantic Right Whale Mitigation Area, Major Training Exercise Planning Awareness Mitigation Areas in the northeast and mid-Atlantic, and ship shock trial mitigation areas. The Northeast North Atlantic Right Whale Mitigation Area and Southeast North Atlantic Right Whale Mitigation Area in particular would reduce exposures in times and areas where impacts would be more likely to affect feeding and energetics, or important cow/calf interactions that could lead to reduced reproductive success or survival, including those in areas known to be biologically important, and such impacts are not anticipated. For example, any impacts predicted in the NARW migratory corridor BIA along the East Coast are less likely to impact individuals during feeding or breeding behaviors.

For Rice's whale, this rulemaking includes a Rice's Whale Mitigation Area that overlaps the Rice's whale small and resident population area identified by NMFS in its 2016 status review (Rosel

et al.,

2016) and most of the eastern portion of proposed critical habitat (88 FR 47453, July 24, 2023). Within this area, the Action Proponents must not use more than 200 hours of surface ship hull-mounted MFAS annually and must not detonate in-water explosives (including underwater explosives and explosives deployed against surface targets) except during mine warfare activities. Additionally, the Ship Shock Trial Mitigation Area would ensure the northern Gulf of America ship shock trial box is situated outside of the Rice's whale core distribution area identified in 2019 (84 FR 15446). These restrictions would reduce the severity of impacts to Rice's whales by reducing their exposure to levels of sound from sonar or explosives that would have the potential to cause injury or mortality, thereby reducing the likelihood of those effects and, further, minimizing the severity of behavioral disturbance.

Responses to the six “methodological problems” are included in NMFS response to

Comments 5, 8-11,

and

13.

Comment 31:

The Commission recommended that NMFS use the two-tiered approach from NMFS' 2020 Criteria for Determining Negligible Impact under MMPA Section 101(a)(5)(E) (NMFS, 2020), including using single negligible impact threshold (NIT

s

) instead of 10 percent of potential biological removal (PBR), for informing its negligible impact determinations that involve M/SI for the final rule and other incidental take authorizations involving M/SI. The Commission asserts that this

would provide consistency within NMFS' own policy directive.

Response:

As stated in the proposed rule (90 FR 19858, May 9, 2025), on June 17, 2020, NMFS finalized new Criteria for Determining Negligible Impact under MMPA section 101(a)(5)(E). The guidance explicitly notes the differences in the negligible impact determinations required under section 101(a)(5)(E), as compared to sections 101(a)(5)(A) and 101(a)(5)(D). As stated in the guidance, first, they differ in terms of the types of take being considered and consequently, the effects of the takes on population dynamics. In paragraphs (a)(5)(A) and (D) of section 101, NMFS must determine if the taking by harassment, injury, or mortality (or a combination of these) incidental to specified activities will have a negligible impact. In section 101(a)(5)(E), NMFS must determine if M/SI incidental to commercial fisheries will have a negligible impact. NMFS considers mortalities and serious injuries to be removals from the population that can be evaluated using well-documented models of population dynamics, whereas harassment and non-serious injury (sub-lethal taking) are not considered to be removals from the population. Second, they differ in whether they apply to all marine mammal stocks or only those stocks or species listed under the ESA: paragraphs (a)(5)(A) and (D) of section 101 apply to all marine mammal stocks (regardless of ESA listing status or MMPA depleted status), while paragraph (a)(5)(E) applies only to stocks designated as depleted because of their listing under the ESA. The guidance further specifies that the procedure in that document is limited to how the agency conducts negligible impact analyses for commercial fisheries under section 101(a)(5)(E) (

i.e.,

it is not intended to be a broad policy directive for M/SI analyses for all activities). As described in the Serious Injury and Mortality section of this final rule, when considering PBR during evaluation of effects of M/SI under section 101(a)(5)(A), we utilize a two-tiered analysis for each stock for which M/SI is proposed for authorization:

Tier 1:

Compare the total human-caused average annual M/SI estimate from all sources, including the M/SI proposed for authorization from the specific activity, to PBR. If the total M/SI estimate is less than or equal to PBR, then the specific activity is considered to have a negligible impact on that stock. If the total M/SI estimate (including from the specific activity) exceeds PBR, conduct the Tier 2 analysis.

Tier 2:

Evaluate the estimated M/SI from the specified activity relative to the stock's PBR. If the M/SI from the specified activity is less than or equal to 10 percent of PBR and other major sources of human-caused mortality have mitigation in place, then the individual specified activity is considered to have a negligible impact on that stock. If the estimate exceeds 10 percent of PBR, then, absent other mitigating factors, the specified activity could be considered likely to have a non-negligible impact on that stock.

In this final rule, NMFS has described its method for considering PBR to evaluate the effects of potential mortality in the negligible impact analysis. NMFS has reviewed the 2020 guidance and determined that our consideration of PBR in the evaluation of mortality, as described in the Serious Injury and Mortality section of the proposed rule and in this final rule, remains appropriate for use in the negligible impact analysis for the Action Proponents' activities under section 101(a)(5)(A). As such, NMFS disagrees with Commission's recommendation to use NMFS (2020) to inform its negligible impact determinations that involve M/SI.

Other Comments

Comment 32:

A commenter stated that the manuscripts for the East Coast and Gulf of America region BIAs have not yet been published; however, to the best of the commenter's knowledge, the scientific analysis has been completed and is available to NMFS for decision-making purposes. This scientific analysis represents the best available scientific information and should be incorporated into NMFS' impact analysis.

Response:

NMFS and the Action Proponents considered the best available science in developing the proposed rule and this final rule, including as it relates to BIAs for marine mammals. While the manuscripts for updated East Coast and Gulf of America region BIAs have not yet been published, NMFS and the Navy coordinated with the authors in development of the proposed rule to understand likely updates to the BIAs and consider the updated science they would rely upon.

Changes From the Proposed Rule to the Final Rule

Between publication of the proposed rule and development of the final rule, additional mitigation measures have been added in response to public comments and further proposals by the Action Proponents.

New mitigation measures were added in the following mitigation areas: (1) Southeast North Atlantic Right Whale Mitigation Area, (2) Dynamic North Atlantic Right Whale Mitigation Area, (3) Rice's Whale Mitigation Area, and (4) Major Training Exercise Planning Awareness Mitigation Areas.

In the Southeast North Atlantic Right Whale Mitigation Area, this final rule includes two new requirements. First, from November 15 to April 15, the Action Proponents must not detonate explosive sonobuoys within 3 nmi (5.6 km) of the Southeast North Atlantic Right Whale Mitigation Area. Second, during the same time period, the Action Proponents must not conduct vessel propulsion testing.

In PMAP reports generated in the Dynamic North Atlantic Right Whale Mitigation Area, this final rule requires that Action Proponents must provide the WhaleMap web address (

https://whalemap.org

) and advise that risk of whale strike is increased after: (1) observing a NARW; (2) when operating within 5 nmi (6.5 km) of a known sighting reported within the past 24 hours; (3) within a NMFS-designated Seasonal Management Area, Dynamic Management Area, or Slow Zone; and (4) when transiting at night or during periods of restricted visibility. The PMAP report must also reinforce the requirement of the COLREGS for vessels to proceed at a safe speed, appropriate for the prevailing circumstances and conditions, to avoid a collision with any sighted object or disturbance, including any marine mammal. Further, this final rule requires that sightings data must be used when planning propulsion testing event details (

e.g.,

timing, location, duration) to minimize impacts to NARW to the maximum extent practical. During propulsion testing in the Dynamic North Atlantic Right Whale Mitigation Area, to the maximum extent practical, Lookouts must be provided recent

https://whalemap.org

sightings data to help inform visual observations. Last, this final rule clarifies that the extent of the mitigation area matches the boundary of the U.S. EEZ on the East Coast (

i.e.,

the full extent of where NMFS could potentially establish Dynamic Management Areas).

In the Rice's Whale Mitigation Area, this final rule includes a requirement that the Action Proponents must not detonate explosive sonobuoys within 3 nmi (5.6 km) of the Rice's Whale Mitigation Area as well as two new measures to further reduce the risk of vessel strike of Rice's whale. The Action Proponents must avoid conducting vessel propulsion testing events in the Rice's Whale Mitigation Area, to the

maximum extent practical. The Action Proponents must also issue an annual awareness message to Navy vessels that routinely train or test in the vicinity of the Rice's Whale proposed critical habitat, and Coast Guard vessels that routinely train anywhere in the Gulf of America. The message will advise that risk of whale strike is increased when transiting through Rice's whale proposed critical habitat (

i.e.,

within the 100-400 m (328-1,312 ft) isobaths), particularly at night or during periods of restricted visibility, and reinforce the requirement of the COLREGS for vessels to proceed at a safe speed, appropriate for the prevailing circumstances and conditions, to avoid a collision with any sighted object or disturbance, including any marine mammal.

In the combined Major Training Exercise Planning Awareness Mitigation Areas located in the Gulf of America, this final rule includes a requirement that the Action Proponents must not conduct any MTEs in the mitigation area.

In the Dynamic North Atlantic Right Whale Mitigation Area, Northeast North Atlantic Right Whale Mitigation Area, Southeast North Atlantic Right Whale Mitigation Area, and Rice's Whale Mitigation Area, the term “reduced visibility” and “poor visibility” were updated to “restricted visibility” to align with the COLREGS used by the Action Proponents to train and test Lookouts.

In addition to the new measures within the existing mitigation areas, this final rule includes a new Martha's Vineyard North Atlantic Right Whale Mitigation Area in which the Action Proponents must avoid conducting vessel propulsion testing events to the maximum extent practical.

Regarding activity-based mitigation, this final rule clarifies that the Navy must implement soft start techniques for impact pile driving. Of note, Navy continues to consider soft-start procedures as part of their standard operating procedures, and as such, they are not listed as a mitigation measure in the 2025 AFTT Supplemental EIS/OEIS. Additionally, a new measure requires that for all activities involving explosives, if a marine mammal is visibly injured or killed as a result of detonation, explosives use in the event must be suspended immediately. This final rule also includes language that describes instances when activity-based mitigation for physical disturbance and strike stressors will not be implemented. These are listed in the Activity-Based Mitigation for Physical Disturbance and Strike Stressors section of this final rule.

Further, within the first year of AFTT Phase IV implementation, the Action Proponents must work collaboratively with the NMFS ESA Interagency Cooperation Division and the NMFS Permits and Conservation Division to: (1) analyze and discuss the application of new information from the NMFS North Atlantic Right Whale Persistence Modelling Efforts toward AFTT mitigation measures; (2) evaluate the practicability and conservation benefits of newly proposed mitigation measures and/or changes to existing measures based on information from the model; and (3) implement any new mitigation measures or changes to existing measures that meet the Action Proponents' Practicability Criteria and Sufficiently Beneficial requirements.

This final rule also includes a requirement for cetacean live-stranding or near-shore atypical milling events. These requirements have previously been included in the Notification and Reporting Plan only. In the event of a cetacean live stranding (or near-shore atypical milling) event within the AFTT Study Area or within 50 km (27 nmi) of the boundary of the AFTT Study Area, where the NMFS Stranding Network is engaged in herding or other interventions to return animals to the water, NMFS Office of Protected Resources (OPR) will advise the Action Proponents of the need to implement shutdown procedures for all active acoustic sources or explosive devices within 50 km of the stranding. Following this initial shutdown, NMFS will communicate with the Action Proponents to determine whether circumstances support modification of the shutdown zone. The Action Proponents may decline to implement all or part of the shutdown if the holder of the LOA, or his/her designee, determines that it is necessary for national security. Shutdown procedures for live stranding or milling cetaceans include the following:

• If at any time, the marine mammal(s) die or are euthanized, or if herding/intervention efforts are stopped, NMFS will immediately advise that the shutdown around the animals' location is no longer needed;

• Otherwise, shutdown procedures will remain in effect until NMFS determines and advises that all live animals involved have left the area (either of their own volition or following an intervention); and

• If further observations of the marine mammals indicate the potential for re-stranding, additional coordination will be required to determine what measures are necessary to minimize that likelihood (

e.g.,

extending the shutdown or moving operations farther away) and to implement those measures as appropriate.

Regarding reporting requirements, in addition to those included in the proposed rule, this final rule requires that in the Annual AFTT Training and Testing Reports, Navy personnel must confirm that foreign military use of sonar and explosives, when such militaries are participating in a U.S. Navy-led exercise or event, combined with the Action Proponents' use of sonar and explosives, would not cause exceedance of the analyzed levels within each NAEMO modeled sonar and explosive bin used for estimating predicted impacts.

NMFS also made several updates to its analysis in this final rule. Since publication of the proposed rule, the Society for Marine Mammalogy revised the taxonomy for Atlantic white-sided dolphin (

Lagenorhynchus acutus

) by reassigning the species to the genus

Leucopleurus

. The scientific name of the species is now

Leucopleurus acutus,

which has been updated in table 1. Further, in the

Group and Species-Specific Analyses

section, NMFS has updated the reproductive strategy of Bryde's-like whales (

i.e.,

Bryde's whales, Rice's whales) to “income” rather than capital, the movement ecology of Rice's whales to “resident” rather than nomadic, based on Constantine

et al.

(2018) and Izadi

et al.

(2018), as summarized in Garrison

et al.

(2024). Additionally, the Commission identified an error related to potential impacts to goose-beaked whales (Western North Atlantic stock) in the Preliminary Assessment and Negligible Impact Determination section of the proposed rule. This final rule includes a correction to that language to indicate that the impacts to the Western North Atlantic stock of goose-beaked whales could cause a limited number of females to forego reproduction for a year.

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 AFTT Study Area are presented in table 1 along with each stock's ESA and MMPA statuses, abundance estimate and associated coefficient of variation (CV) value, minimum abundance estimate (N

min

), PBR, annual M/SI, and potential occurrence in the AFTT Study Area. The Action Proponents anticipate take of individuals of 41 marine mammal species (81 stocks) by Level A and Level B harassment incidental to military readiness activities from the use of

sonar and other transducers, in-water explosives, air guns, pile driving/extraction, and vessel movement in the AFTT Study Area. The AFTT proposed rule included additional information about the species in this rule, marine mammal species for which take is not authorized, marine mammal species which could occur in the area but are not managed by NMFS, marine mammal hearing, National Marine Sanctuaries, and the 2010 Deepwater Horizon (DWH) oil spill, all of which remains valid and applicable but has not been reprinted in this final rule. NMFS hereby refers to the information and analysis provided in the proposed rule (90 FR 19858, May 9, 2025) which continue to apply to this final rule.

Information on the status, distribution, abundance, population trends, habitat, and ecology of marine mammals in the AFTT Study Area may be found in section 4 of the application. NMFS reviewed this information and found it to be accurate and complete. Additional information on the general biology and ecology of marine mammals is included in the 2025 AFTT Supplemental EIS/OEIS. Table 1 incorporates the best available science, including data from the U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessment Report (SAR; Hayes

et al.,

2024) (now referred to as the Gulf of America; see

https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments

), and 2024 draft SAR, as well as monitoring data from the Navy's marine mammal research efforts. NMFS has also reviewed scientific literature published since publication of the proposed rule and determined that none of this new information nor any other new information available changes our determination of which species have the potential to be affected by the Action Proponents' activities or the information pertinent to status, distribution, abundance, population trends, habitat, or ecology of the species in this final rulemaking, except as noted below.

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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 (UME) have been designated.

Critical Habitat

Currently, only the NARW has ESA-designated critical habitat in the AFTT Study Area. However, NMFS recently published a proposed rule proposing new ESA-designated critical habitat for the Rice's whale (88 FR 47453, July 24, 2023).

North Atlantic Right Whale

On February 26, 2016, NMFS issued a final rule (81 FR 4838) to replace the critical habitat for NARW with two new cr

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