Rule2025-23088
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Military Readiness Activities in the Hawaii-California Training and Testing Study Area
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
December 17, 2025
Effective
December 21, 2025
Issuing agencies
Commerce DepartmentNational Oceanic and Atmospheric Administration
Abstract
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) and U.S. Army (Army; hereafter, Navy, Coast Guard, and Army 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 and modernization and sustainment of ranges conducted in the Hawaii-California Training and Testing (HCTT) Study Area over the course of 7 years from December 2025 through December 2032. These regulations 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).
Full Text
<html>
<head>
<title>Federal Register, Volume 90 Issue 240 (Wednesday, December 17, 2025)</title>
</head>
<body><pre>
[Federal Register Volume 90, Number 240 (Wednesday, December 17, 2025)]
[Rules and Regulations]
[Pages 58810-59040]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-23088]
[[Page 58809]]
Vol. 90
Wednesday,
No. 240
December 17, 2025
Part II
Department of Commerce
-----------------------------------------------------------------------
National Oceanic and Atmospheric Administration
-----------------------------------------------------------------------
50 CFR Part 218
Takes of Marine Mammals Incidental to Specified Activities; Taking
Marine Mammals Incidental to Military Readiness Activities in the
Hawaii-California Training and Testing Study Area; Final Rule
Federal Register / Vol. 90 , No. 240 / Wednesday, December 17, 2025 /
Rules and Regulations
[[Page 58810]]
-----------------------------------------------------------------------
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Part 218
[Docket No. 251211-0182]
RIN 0648-BN44
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to Military Readiness Activities in
the Hawaii-California Training and Testing Study Area
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: 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) and U.S. Army (Army;
hereafter, Navy, Coast Guard, and Army 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 and modernization and
sustainment of ranges conducted in the Hawaii-California Training and
Testing (HCTT) Study Area over the course of 7 years from December 2025
through December 2032. These regulations 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 December 21, 2025, through December 20, 2032.
ADDRESSES: A copy of the Action Proponents' incidental take
authorization (ITA) application and supporting documents, as well as a
list of the references cited in this document, may be obtained online
at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities</a>. In case
of problems accessing these documents, please call the contact listed
below (see FOR FURTHER INFORMATION CONTACT).
FOR FURTHER INFORMATION CONTACT: Leah Davis, Office of Protected
Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Purpose and Need for Regulatory Action
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 and modernization and sustainment of ranges (that qualify as
military readiness activities) involving the use of active sonar and
other transducers, air guns, and explosives (also referred to as ``in-
water detonations''); pile driving and vibratory extraction; land-based
missile and target launches; and vessel movement in the HCTT Study
Area. The HCTT Study Area includes areas in the north-central Pacific
Ocean, from California west to Hawaii and the International Date Line,
and including the Hawaii Range Complex (HRC) and Temporary Operating
Area (TOA), Southern California (SOCAL) Range Complex, Point Mugu Sea
Range (PMSR), Silver Strand Training Complex (SSTC), areas along the
Southern California coastline from approximately Dana Point to Port
Hueneme, and the Northern California (NOCAL) Range Complex. Also
included in the HCTT Study Area are Navy pierside locations in Hawaii
and Southern California, Pearl Harbor, San Diego Bay, and the transit
corridor on the high seas where training and testing may occur (see
figure 1 of the proposed rulemaking and figure 1.1-1 of the
application). Please see the Legal Authority for the Proposed 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 (collectively referred to as
``mitigation''); and requirements pertaining to the monitoring and
reporting of the takings. The MMPA defines ``take'' to mean to harass,
hunt, capture, or kill, or attempt to harass, hunt, capture, or kill
any marine mammal. 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): (1) any act that injures or has the
significant potential to injure a marine mammal or marine mammal stock
in the wild (Level A Harassment); or (2) any act that disturbs or is
likely to disturb a marine mammal or marine mammal stock in the wild by
causing disruption of natural behavioral patterns, including, but not
limited to, migration, surfacing, nursing, breeding, feeding, or
sheltering, to a point where such behavioral patterns are abandoned or
significantly altered (Level B Harassment). 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 the section 101(a)(5)(A)(ii) of
the MMPA to allow incidental take regulations (ITRs) 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:
[[Page 58811]]
<bullet> Take of marine mammals by Level A harassment and/or Level
B harassment;
<bullet> Take of marine mammals by mortality or serious injury (M/
SI);
<bullet> Use of defined powerdown and shutdown zones (based on
activity);
<bullet> Measures to reduce the likelihood of vessel strikes;
<bullet> Activity limitations in certain areas and times that are
biologically important (i.e., for foraging, migration, reproduction)
for marine mammals;
<bullet> Implementation of a Notification and Reporting Plan (for
dead, live stranded, or marine mammals struck by any vessel engaged in
military readiness activities); and
<bullet> Implementation of a robust monitoring plan to improve our
understanding of the environmental effects resulting from the Action
Proponents' training and testing activities and modernization and
sustainment of ranges.
This rule includes an adaptive management component that allows for
timely modification of mitigation, monitoring, and/or reporting
measures based on new information, when appropriate.
Summary of Request
On September 16, 2024, NMFS received an application from the Action
Proponents requesting authorization to take marine mammals, by Level A
and B harassment, incidental to training, testing, and modernization
and sustainment of ranges (characterized as military readiness
activities) including the use of sonar and other transducers,
explosives, air guns, impact and vibratory pile driving and extraction,
and land-based missile and target launches conducted within the HCTT
Study Area. The Action Proponents also requested authorization to take,
by serious injury or mortality, a limited number of marine mammal
species incidental to the use of explosives and vessel movement during
military readiness activities conducted within the HCTT Study Area. The
Action Proponents requested multiple 7-year LOAs for Navy training
activities, Coast Guard training activities, Army training activities,
and Navy testing activities. In response to our comments and following
an information exchange, the Action Proponents submitted a revised
application, deemed adequate and complete on December 13, 2024. Also on
that same date (December 13, 2024), NMFS published a notice of receipt
of the application (NOR) in the Federal Register (89 FR 100982),
requesting comments and information related to the Action Proponents'
specified activities. During the 30-day public comment period, NMFS
received one public comment from the Center for Biological Diversity.
On July 16, 2025, NMFS published a proposed rule (90 FR 32118) and
requested comments and information related to the Action Proponents'
request for 30 days. All relevant comments received during the NOR and
the proposed rulemaking comment periods 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 previously promulgated ITRs pursuant to the MMPA relating to
similar military readiness activities in areas located within the HCTT
Study Area. NMFS published the first rule effective from January 5,
2009 through January 5, 2014, (74 FR 1456, January 12, 2009) for
incidental take relating to military readiness activities in the HRC
and January 14, 2009 through January 14, 2014 (74 FR 3882) for SOCAL.
The second rule, effective from December 24, 2013 through December 24,
2018 (78 FR 78106, December 24, 2013), combined the Hawaii and Southern
California range complexes, as well as the SSTC, pierside locations in
San Diego Bay and Pearl Harbor, and the transit corridor between SOCAL
and Hawaii, and throughout San Diego Bay. The third rule was effective
from December 21, 2018 through December 20, 2023 (83 FR 66846, December
27, 2018), which was subsequently amended, extending the effective date
from December 20, 2023 until December 20, 2025 (85 FR 41780, July 10,
2020) pursuant to the 2019 NDAA and NMFS later amended that rule to
increase the take of large whales by vessel strike and modify the
mitigation, monitoring, and reporting measures to reduce the occurrence
of vessel strikes involving large whales (90 FR 4944, January 16,
2025). For this rulemaking, the Action Proponents plan to conduct
substantially similar training and testing activities within the HCTT
Study Area that were conducted under previous rules (noting that the
Study Area has been expanded, as described in the Geographic Region
section of the proposed rulemaking).
The Action Proponents' application reflects the most up-to-date
compilation of training and testing activities, and modernization and
sustainment of ranges deemed necessary to accomplish military readiness
requirements. The types and numbers of activities included in this rule
account for interannual variability in training and testing to meet
evolving or emergent military readiness requirements. As explained
herein, these regulations also consolidate several actions conducted by
the Navy that were previously authorized by NMFS and include some new
military readiness activities carried out by the Action Proponents. In
particular, these regulations cover incidental take during military
readiness activities in the HCTT Study Area that will occur for a 7-
year period following the expiration of the pre-existing MMPA
authorization which expires on December 20, 2025 (85 FR 41780, as
amended by 90 FR 4944). In addition, this rule includes PMSR activities
for which incidental take was previously authorized under separate
authorizations and will supersede that recent PMSR regulations (87 FR
40888, July 8, 2022). This rule also includes areas along the Southern
California coastline from approximately Dana Point to Port Hueneme and
supersedes the incidental harassment authorization (IHA) allowing
incidental take of marine mammals during pile driving training
activities at Port Hueneme (90 FR 20283, May 13, 2025). In this rule,
we have undertaken a comprehensive assessment of the risks/impacts of
all military training and testing activities on marine mammals likely
to be present within the entire range of the Study Area.
Description of 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 likely to result in take of marine mammals in the form of
Level A and B harassment, and that a limited number of takes by serious
injury or mortality may result from vessel movement and use of
explosives (including ship shock trials). Detailed descriptions of
these activities are provided in chapter 2 and appendix A of the 2025
HCTT Environmental Impact Statement/Overseas Environmental Impact
Statement (2025 HCTT EIS/OEIS) (<a href="https://www.nepa.navy.mil/hctteis/">https://www.nepa.navy.mil/hctteis/</a>) and
in the Action Proponents' application (<a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities</a>). Of note, the U.S. Air Force (USAF) is a
joint lead agency for the 2025 HCTT EIS/OEIS; USAF activities consist
of air combat maneuvers and air-to-air gunnery (a gunnery exercise in
which fixed-wing aircraft fire medium caliber guns at air targets). The
Action Proponents determined that USAF activities would not result in
the taking
[[Page 58812]]
of marine mammals, and therefore these activities are not included in
the Action Proponents' application. NMFS concurs that these activities
are not anticipated to result in incidental take of marine mammals. As
such, no authorization for taking marine mammals incidental to USAF
activities is required and no LOA will be issued by NMFS for such USAF
activities.
A detailed description of the specified activities was provided in
our proposed rulemaking (90 FR 32118, July 16, 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, with the exception of a
reduction in the number of launch events at PMSR as described in the
Changes from the Proposed Rule to the Final Rule section. 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
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
HCTT 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, or foreign aircraft may enter U.S. airspace, 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 in associated
airspace.
The most significant joint training event is the Rim of the Pacific
(RIMPAC), a multi-national training exercise held biennially primarily
in the HRC. The participation level of foreign military vessels in U.S.
Navy-led training or testing events within the HRC and within SOCAL
differs greatly between RIMPAC and non-RIMPAC years. For example, in
2019 (a non-RIMPAC year), there were 0.1 foreign navy surface vessel
at-sea days (i.e., 1 day = 24 hours) within HRC and 20 foreign navy at-
sea days within SOCAL (U.S. Department of the Navy, 2021c). Out of 56
U.S.-led training events in 2019, 4 involved foreign navy vessels, with
an average time per event of 8.7 hours. During RIMPAC 2022, foreign
vessels operated and/or transited through the HRC for 576 hours (24
days). In 2023 (another non-RIMPAC year), there was no foreign vessel
participation within SOCAL. Even in a RIMPAC year, the days at sea for
foreign militaries engaged in a Navy-led training or testing activity
accounts for a small, but variable, percentage compared to the U.S.
Navy activities. For instance, the 2020 foreign military participation
(a RIMPAC-year) was 1.5 percent of the U.S. Navy's average days at sea
(32 days out of an estimated 2,056 days at sea). During RIMPAC 2024, 25
foreign surface vessels participated for a combined 5,000 hours in
U.S.-led training events. Therefore, foreign surface vessel activity is
estimated to conservatively account for up to 10 percent of the U.S.
Navy's annual at sea time in HCTT (205 days out of an estimated 2,056
days at sea). In RIMPAC 2024, 21 U.S. Navy maritime patrol aircraft
participated, as did 12 foreign maritime patrol aircraft.
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 HCTT Study
Area.
Comments and Responses
We published the proposed rule in the Federal Register on July 16,
2025 (90 FR 32118) 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 six comments. Of this total, one submission was
from the Marine Mammal Commission (Commission), and the remaining
comments were from non-governmental organizations (NGO) and private
citizens. The majority of the comments either opposed or recommended
revisions to the proposed rule.
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 (ref 20, 21): 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 (in; 0.61 meters (m)) sheet piles; (2) the range to effects for
pile driving for behavioral response for vibratory installation of 24-
in (0.61 m) sheet piles based on a source level of 159 decibel
referenced to 1 microPascal (dB re 1 [mu]Pa) 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 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, 2024a), hereafter referred to
as the Acoustic Impacts Technical Report, a source level of 159 dB
root-mean-square (RMS) for vibratory driving of 24-inch (0.61 m) steel
sheet piles measured at 10 m (32.8 ft) (NAVFAC, 2020) is a reasonable
representation of likely sound levels.
[[Page 58813]]
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. Furthermore,
criteria for AUD INJ and TTS are conservative in that they do not
account for recovery of hearing effects during breaks in sound exposure
(e.g., silent periods as the hammer is repositioned, when pinnipeds
lift their heads out of the water or haul out).
The Navy considers soft-start procedures for impact pile driving to
be part of its standard operating procedures. As such, the 2025 HCTT
EIS/OEIS, 2024 HCTT Draft EIS/OEIS, application, and the HCTT proposed
rule (90 FR 32118, July 16, 2025) do not list soft start as a
mitigation measure. The 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 to 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.
Comment 2 (ref 12, 79): 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, 2025a). 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
Department of the Navy (2025a) to clarify and address these points, as
that document underpins the current and future Phase IV rulemakings.
The Commission also stated 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 recommended 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 [micro]Pa
for humpback whales during the 3S2 study (the second phase of the Sea
Mammals, Sonar, Safety (3S) project) and between 175 and 186 dB re 1
[micro]Pa for sperm whales during the 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 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.
The descriptions of responses in appendix E (Behavioral Responses
to Sonar and Sonar-Like Sources: All Individuals Included) of the
Criteria and Thresholds Technical Report were updated to include
additional information on the observed responses.
Extending the upper bound to 200 dB re 1 [micro]Pa 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 [micro]Pa. 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 [micro]Pa in Phase IV (compared to the 100 dB re 1 [micro]Pa
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 [micro]Pa for the Phase III BRFs shown in figure 42 (U.S.
Department of the Navy, 2024a) was a result of anchoring the Phase III
BRFs at 185 dB re 1 [micro]Pa and then extending them to 200 dB re 1
[micro]Pa 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.
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 were
collected during the timeframe referenced, these data are 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 have not been shared in time for the
development of the Navy risk thresholds. The Navy did consider data
from Southall et al. (2024) in appendix D of the 2025 HCTT 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-
[[Page 58814]]
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 clarified this methodology in
the 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. Navy 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 need to relate known or
estimable received levels to observations of individual or group
behavior. The data in Falcone et al. (2017) was 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 and NMFS are 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 Pacific Missile Range Facility (PMRF). The BRFs
in Phase IV utilized only individual response-RL data outside of the
four pre-existing risk functions that were subsampled. There were no
individual response-RL 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 and NMFS will
continue to refine the 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, were added to table E-1 in the 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 indicative of harassment. The
Navy clarified this approach in the 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 made the necessary corrections
to the 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
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
Cur[eacute] et al. (2025) and table E-1 of Criteria and Thresholds
Technical Report 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
[[Page 58815]]
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 3 (ref 13): 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 (i.e., a virtual animal)
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 analytical
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 4 (ref 10): 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 the
Criteria and Thresholds Technical Report.
Response: Whether and when to share data for ongoing research is at
the discretion of the researchers and funding agencies. Since the
specific data from Kastelein et al. (2024a) were not shared with the
Navy prior to peer review and publication, the 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 5 (ref 11, 78): 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 HCTT 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. (2019c) and the minke whale study by Houser et al.
(2024). 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
[[Page 58816]]
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 publication of results
from the 2024 field season before re-evaluating our acoustic criteria
for mysticetes.
Comment 6 (ref 14): 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 7 (ref 17, 18): The Commission recommended that NMFS work
with the Navy to use an avoidance swim speed of no more than 2 m 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 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 HCTT 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 the 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 8 (ref 19): 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 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
[[Page 58817]]
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 9 (ref 16): 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 sound pressure levels (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 HCTT EIS/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 HCTT 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 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 the 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 (<a href="https://exwc.navfac.navy.mil/Products-and-Services/Environmental-Security/LMR/">https://exwc.navfac.navy.mil/Products-and-Services/Environmental-Security/LMR/</a>). 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.
Comment 10 (ref 66): A commenter recommended that, in addition to
the designation of geographic mitigation areas identified above,
efforts should be undertaken in an iterative manner to identify
additional important habitat areas across the HCTT Study Area, using
the full range of data and information available (e.g., habitat-based
density models, NMFS-recognized Biologically Important Areas (BIAs),
Endangered Species Act (ESA) critical habitat designations, passive
acoustic monitoring data, other survey data, oceanographic and other
environmental data).
Response: NMFS and the Navy used the best available scientific
information (e.g., stock assessment reports (SARs) and numerous study
reports from Navy-funded monitoring and research in the specific
geographic region) in assessing
[[Page 58818]]
density, distribution, and other information regarding marine mammal
use of habitats in the HCTT Study Area. In addition, NMFS consulted
Calambokidis et al. (2024) and Kratofil et al. (2023), which provides a
specific, detailed assessment of known BIAs, which may be region-,
species-, and/or time-specific, include reproductive areas, feeding
areas, migratory corridors, and areas in which small and resident
populations are concentrated. While the science of marine mammal
occurrence, distribution, and density resides as a core NMFS mission,
the Navy does provide extensive support to the NMFS mission via ongoing
HCTT specific monitoring as detailed in this final rule. Also included
are direct Navy funding support to NMFS for programmatic marine mammal
surveys in Hawaii and the U.S. West Coast, and spatial habitat model
improvements.
Comment 11 (ref 68): A commenter stated that there is a need for
the Navy to compile more information regarding the number, nature, and
timing of testing and training events that take place within, or in
close proximity to, important habitat areas, and to refine its scale of
analysis of operations to match the scale of the habitat areas that are
considered to be important. The commenter states that while the 2024
HCTT Draft EIS/OEIS, in assessing environmental impacts on marine
mammals, breaks down estimated impacts by region, the resolution is
seldom greater than range complex or homeport and is not specifically
focused on areas of higher biological importance. Current and ongoing
efforts to identify important habitat areas for marine mammals should
be used by the Navy as a guide to the most appropriate scale(s) for the
analysis of operations.
Response: In their take request and effects analysis provided to
NMFS, the Action Proponents considered historic use (number and nature
of training and testing activities) and locational information of
training and testing activities when developing modeling boxes. The
timing of training cycles and testing needs varies based on deployment
requirements to meet current and emerging threats. Due to the
variability, the Action Proponents' description of the specified
activities is structured to provide flexibility in training and testing
locations, timing, and number. In addition, information regarding the
exact location of sonar usage is classified. Due to the variety of
factors, many of which influence locations that cannot be predicted in
advance (e.g., weather), the analysis is completed at a scale that is
necessary to allow for flexibility. The purpose of the Action
Proponents' quantitative acoustic analysis is to provide the best
estimate of impact/take to marine mammals and ESA-listed species for
the regulatory and ESA section 7 consultation analyses. Specifically,
the analysis must take into account multiple training and testing
activities over large areas of the ocean for multiple years; therefore,
analyzing activities in multiple locations over multiple seasons
produces the best estimate of impacts/take to inform the 2025 HCTT EIS/
OEIS and regulators. Also, the scale at which spatially explicit marine
mammal density models are structured is determined by the data
collection method and the environmental variables that are used to
build the model. Therefore, altogether, given the variables that
determine when and where the Action Proponents train and test, as well
as the resolution of the density data, the analysis of potential
impacts is scaled to the level that the data fidelity will support.
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 (e.g., in BIAs or
Sanctuaries, where possible).
The HCTT analysis in the Action Proponents' application (see
appendix A of the application) includes improved modeling since Phase
III to predict the number of expected takes, by effect type, within
important habitat areas such as identified BIAs and ESA-designated
critical habitat. NMFS is confident that the granularity of information
provided sufficiently allows for an accurate assessment of both the
impacts of the Action Proponents' activities on marine mammal
populations and the protective measures evaluated to mitigate those
impacts. NMFS and the Action Proponents will continue to consider how
to appropriately refine our future analyses.
Comment 12 (ref 77): 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 proposed and final rules assume 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, NMFS' approach in the 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 13 (ref 15, 80): 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
Melc[oacute]n et al. (2012). The commenter refers to a description of
their concern in a comment on the 2025 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
[[Page 58819]]
distances is provided in the 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 BRSs 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, Melc[oacute]n 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 Thresholds Technical Report: ``. . . Falcone et al.
(2017) modeled apparent responses to mid-powered sources out to 50 km
(27 nautical miles (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
minutes) 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 (MFAS) was present. The inter-deep dive interval duration
also increased for both mid- and high-powered MFAS sources starting at
100 km (54 nmi); however, the inter-deep dive interval duration only
exhibited the strongest increase 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 SPL). Although behavioral
responses are predicted beyond the cut-off conditions, these are not
expected to rise to the level of 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 (ref 81): 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 HCTT Study Area) via strandings resulting from behaviorally
mediated physiological impacts or other gas-related injuries. In the
Potential Effects of Specified
[[Page 58820]]
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 to 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 HCTT Study Area during
the specified activities. Further, there have never been any strandings
associated with Navy sonar use in the HCTT 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 15 (ref 82): 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: 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 included here in the Analysis and Negligible Impact
Determination section of this 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 HCTT 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 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 <a href="https://www.navymarinespeciesmonitoring.us/regions/pacific/current-projects/">https://www.navymarinespeciesmonitoring.us/regions/pacific/current-projects/</a>
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 HCTT Study Area.
Comment 16 (31): A commenter stated that the Eastern North Pacific
stock of gray whale has been declining for years since the recent UME,
and that NOAA estimates 13,000 Eastern North Pacific gray whales,
rather than 26,960 whales as reported in the proposed rule. The
commenter stated that this makes the other species estimates, impacts,
and information in the draft very questionable. The commenter further
states that there should be no harassment or takes of the Eastern North
Pacific gray whales, nor the Southern Resident killer whales, nor other
endangered or threatened species.
The commenter also stated that more research is needed on the
unknown impacts to multiple species of which the proposed rule proposed
to authorize take, particularly research on new technologies, impulsive
and continuous sonar broadcast, and uncrewed sea craft.
Response: The 2023 Pacific SAR indicates the Eastern North Pacific
stock of gray whales is increasing and has an abundance of 26,960
animals. However, recent (2024-2025) surveys conducted by NMFS'
Southwest Fisheries Science Center (SWFSC) indicated that the estimated
total abundance of gray whales during the 2024-2025 southbound
migration was 12,950 (Eguchi et al., 2025). NMFS has updated its
analysis to consider both abundance estimates, and has determined the
authorized take of the Eastern North Pacific stock of gray whale will
have a negligible impact on the stock, including in consideration of
the Eguchi et al. (2025) estimate. As described in the Analysis and
Negligible Impact Determination section, this stock is not listed under
the ESA and is not considered as depleted or strategic under the MMPA
and there are no UMEs or other for this stock. Any takes in the form of
TTS are 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 gray 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. For similar
reasons, while auditory injury impacts last longer, the low anticipated
levels of AUD INJ that could be reasonably expected to result from
these activities are unlikely to have any effect on fitness.
Regarding the likely severity of any single instance of take by
behavioral disturbance, as described above, the majority of the
predicted exposures are expected to be below 172 dB SPL and last from a
few minutes to a few hours, at most, with associated responses most
likely in the form of moving away from the source, foraging
interruptions, vocalization changes, or disruption of other social
behaviors, lasting from a few minutes to several hours. Gray whales are
large-bodied capital breeders with a slow pace of life and are
therefore generally less susceptible to impacts from shorter duration
foraging disruptions. Further, as described in the Group and Species-
Specific Analyses section and the Mitigation Measures section,
mitigation measures are expected to further reduce the potential
severity of impacts through real-time operational measures that
minimize higher level/longer duration exposures
[[Page 58821]]
and time/area measures that reduce impacts in high value habitat.
Given the number of takes by harassment as compared to the stock/
species abundance (see table 54), and the fact that a portion of the
takes of the Eastern North Pacific occur in BIAs, it is likely that
some portion of the individuals taken are taken repeatedly over a
limited number of days. However, given the variety of activity types
that contribute to take across separate exercises conducted at
different times and in different areas, and the fact that many result
from transient activities conducted at sea, it is unlikely that
repeated takes would occur either in numbers across sequential days in
a manner likely to impact foraging success and energetics or other
behaviors such that reproduction or survival of any individuals is
likely to be impacted.
Given the status of the stock and in consideration of other ongoing
anthropogenic mortality (fisheries interactions, vessel strike), the
authorized M/SI (three over the course of the 7-year rule, or 0.43
annually) will not, alone, nor in combination with the impacts of the
take by harassment discussed above (which is not expected to impact the
reproduction or survival of any individuals), be expected to adversely
affect rates of recruitment and survival for any of this stock.
NMFS did not propose to authorize take of southern resident killer
whale (90 FR 32118, July 16, 2025), and this final rule does not
authorize take of that stock. This rule does, however, authorize take
of certain species that are listed as threatened or endangered under
the ESA, as indicated in table 1. The MMPA provides for the
authorization of incidental take caused by specified activities at the
request of an applicant, provided certain findings are made. The law
directs NMFS to process adequate and complete applications for
incidental take authorization, and issue the authorization provided all
statutory findings and requirements, as well as all associated legal
requirements, are met. As described in the Analysis and Negligible
Impact Determination section, based on the analysis contained herein of
the likely effects of the specified activities on marine mammals and
their habitat, and taking into consideration the implementation of the
proposed monitoring and mitigation measures, NMFS finds that the total
marine mammal take from the specified activity will have a negligible
impact on all affected marine mammal species or stocks.
On September 16, 2024, NMFS received an application from the Action
Proponents requesting authorization to take marine mammals incidental
to training, testing, and modernization and sustainment of ranges
(characterized as military readiness activities) within the HCTT Study
Area. In response to our comments and following an information
exchange, the Action Proponents submitted a revised application, deemed
adequate and complete on December 13, 2024. NMFS, following its own
analysis and proposed rule, has determined it is appropriate to
promulgate a final rule and LOAs pursuant to 16 U.S.C. 1371(a)(5)(A)
and 50 CFR 216.105.
Regarding the commenter's assertion that more research is needed on
the unknown impacts to multiple species of which the proposed rule
proposed to authorize take, particularly research on new technologies,
impulsive and continuous sonar broadcast, and uncrewed sea craft, this
final rule requires the Action Proponents to conduct all monitoring and
reporting required under the LOAs, including abiding by the HCTT Study
Area monitoring program. Details on program goals, objectives, project
selection process, and current projects are available at <a href="https://www.navymarinespeciesmonitoring.us">https://www.navymarinespeciesmonitoring.us</a>.
The commenter appears to imply that NMFS should not authorize take
of marine mammals prior to completion of the research it states is
needed. However, as stated in the Legal Authority for the Final Action
section of this final rule, an authorization for incidental takings
shall be granted if NMFS finds that the taking will have a negligible
impact on the species or stocks and will not have an unmitigable
adverse impact on the availability of the species or stocks for taking
for subsistence uses (where relevant) (16 U.S.C. 1371(a)(5)(A)).
Further, NMFS must prescribe the permissible methods of taking and
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 such species or stocks for
taking for certain subsistence uses (referred to in this rule as
``mitigation measures''); and requirements pertaining to the monitoring
and reporting of such takings (16 U.S.C. 1371(a)(5)(A)). NMFS has made
the required findings, and therefore, it must issue the requested
incidental take authorization to the Navy.
Comment 17 (32-3): A commenter recommended that NMFS integrate
Indigenous and local ecological knowledge into baseline data collection
and cumulative impact assessments. In a related comment, the commenter
stated the proposed rule evaluates impacts primarily from the military
readiness activities themselves but does not meaningfully incorporate
the cumulative effects of commercial shipping, climate change-driven
habitat shifts, and prior authorization of incidental take in the same
region.
Response: It is unclear what the commenter is referring to
regarding baseline data collection, and the commenter has not
identified, with any degree of specificity, which Indigenous or local
ecological knowledge it recommends NMFS consider.
The MMPA requires that NMFS issue an incidental take authorization,
provided the necessary findings are made for the specified activity put
forth in the application and appropriate mitigation and monitoring
measures are set forth, as described in the Legal Authority for the
Final Action section of this rule. As described in the proposed rule
(90 FR 32118, July 16, 2025) and this final rule, the preamble for
NMFS' implementing regulations under section 101(a)(5) (54 FR 40338,
September 29, 1989) explains in response to comments that the impacts
from other past and ongoing anthropogenic activities are incorporated
into the negligible impact analysis via their impacts on the
environmental baseline. Consistent with that direction, NMFS has
factored into its negligible impact analyses the impacts of other past
and ongoing anthropogenic activities via their impacts on the baseline
(e.g., as reflected in the density/distribution and status of the
species, population size and growth rate, and other relevant stressors
(such as UMEs)). See the Analysis and Negligible Impact Determination
section of this rule.
Our 1989 final rule for the MMPA implementing regulations also
addressed how cumulative effects from unrelated activities would be
considered. There we stated that such effects are not separately
considered in making findings under section 101(a)(5) concerning
negligible impact, but that NMFS would consider cumulative effects that
are reasonably foreseeable when preparing a NEPA analysis and also that
reasonably foreseeable cumulative effects would be considered under
section 7 of the ESA for ESA-listed species.
The cumulative effects of the incremental impact of the proposed
action when added to other past, present, and reasonably foreseeable
future actions (as well as the effects of ocean pollution and ecosystem
[[Page 58822]]
alteration trends; see Table 4-2) were evaluated against the
appropriate resources and regulatory baselines in the 2025 HCTT EIS/
OEIS. The best available science and a comprehensive review of past,
present, and reasonably foreseeable actions (including commercial
shipping, ecosystem alteration trends, and other activities for which
incidental take of marine mammals may occur) was used to develop the
Cumulative Impacts analysis. This analysis is contained in chapter 4 of
the 2025 HCTT EIS/OEIS. As required under NEPA, the level and scope of
the analysis is commensurate with the scope of potential impacts of the
action and the extent and character of the potentially-impacted
resources (e.g., the geographic boundaries for cumulative impacts
analysis for some resources are expanded to include activities outside
the HCTT Study Area that might impact migratory or wide-ranging
animals), as reflected in the resource-specific discussions in chapter
3 (Affected Environment and Environmental Consequences) of the 2025
HCTT EIS/OEIS. The 2025 HCTT EIS/OEIS considered the proposed training
activities alongside other actions in the region whose impacts may be
additive to those of the proposed training. Past and present actions
are also included in the analytical process as part of the affected
environmental baseline conditions presented in chapter 3 of the 2025
HCTT EIS/OEIS.
Further, cumulative effects to listed species of the specified
activity in combination with other activities are analyzed in the ESA
biological opinion. This analysis is contained in section 7 (Cumulative
Effects). The opinion states that it assumes effects in the future
would be similar to those in the past and, therefore, are reflected in
the anticipated trends described in the Species and Designated Critical
Habitat that May be Affected and Environmental Baseline sections of the
biological opinion (sections 4 and 5, respectively).
Marine Mammal Densities
Comment 18 (ref 1): The Commission recommended that NMFS use an
abundance estimate of 72,631 rather than 48,780 for April-June and
63,850 rather than 43,360 for July-March, along with a 75 percent
assumption for the core area and 30 percent assumption for the
geographic area to revise the density estimates and resulting numbers
of takes of Guadalupe fur seals for the final rule.
Response: Ju[aacute]rez-Ruiz et al. (2022) revised abundance
estimate became available after the densities were derived for the
Navy's acoustic and explosive impact modeling. The Navy worked with one
of the co-authors on the paper by Ju[aacute]rez-Ruiz et al. (2022) to
develop the density estimates used in the analysis, which included
identifying the most appropriate abundance estimate for Guadalupe fur
seal.
During the process of calculating pinniped densities for the
pending Northwest Training and Testing Phase IV Supplemental EIS/OEIS
Study Area, The Marine Mammal Center reported to the Navy a revised
unpublished abundance for Guadalupe fur seals of 96,468. Considering
that this is a two-fold increase in the abundance estimate used to
derive densities, the Navy decided that the Guadalupe fur seal
densities should be revised and take estimates recalculated based on
the adjusted densities. Since there are only two uniform density strata
for Guadalupe fur seal, the Navy determined that remodeling to estimate
takes would not be necessary and that the increase in takes can be
estimated by calculating a multiplier equal to the ratio between the
initial and recalculated densities. Two multipliers were calculated and
used to revise take estimates: (1) a warm season multiplier of 2.07945;
and (2) a cold season multiplier of 2.05908. This was a reasonable
approach given that remodeling is not feasible at this point because
exposure estimates from previous analyses in at-sea study areas have
shown that changes in densities result in approximately proportional
changes in predicted exposures. The ``U.S. Navy Marine Species Density
Database Phase IV for the Hawaii-California Training and Testing Study
Area'' (U.S. Department of the Navy, 2024b), hereafter referred to as
the Density Technical Report, was amended with the revised densities in
September 2025 and is hereafter referred to as the revised Density
Technical Report (U.S. Department of the Navy, 2025b), and NMFS concurs
with that revision. The HCTT proposed rule and this final rule include
the resulting take numbers.
Comment 19 (ref 2): The Commission recommended that NMFS use the
monk seal abundance estimates from the 2022 SAR to derive its density
estimates and re-estimate the numbers of takes for the final rule.
Response: The abundance of 1,437 monk seals published in the 2021
SAR (Carretta et al., 2022) was the latest abundance estimate available
when the Navy calculated densities. The 2022 SAR (Carretta et al.,
2023b) was published in August 2023, over 1 year after densities were
finalized.
The Navy revised the density estimates for Hawaiian monk seal using
the latest abundance estimates reported in the 2024 draft SAR (Carretta
et al., in review) for each island where separate abundances were
reported. The total abundance reported by Carretta et al. (in review)
is 1,605 monk seals. In order to account for the increase in total
abundance, the Navy calculated multipliers for each island by taking
the ratio of the revised and initial densities. An analysis of the
acoustic effects modeling results showed that all predicted exposures
of Hawaiian monk seals occurred in the Main Hawaiian Islands (MHI) and
no exposures occurred in the Northwestern Hawaiian Islands. Therefore,
the Navy used the highest multiplier derived for the MHI of 1.2919 to
increase the estimated takes in waters both greater than and less than
200 m. NMFS concurs with this method.
Comment 20 (ref 3): The Commission recommended that NMFS: (1)
revise the elephant seal density estimates by increasing the (a) in-
water percentage of females from 0-25 percent for May and June, (b)
percentage of females off California from 80-100 percent for January,
February, and May, (c) in-water percentage of males from 0-25 percent
for August, and (d) percentage of females off California in September
and October from 5 percent and males off California in April, May,
June, and October from 0-10 percent to the percentage of the population
expected to be comprised of yearlings and juveniles and the sex-based
ratios provided in table 9-12 of the Density Technical Report; and (2)
re-estimate the numbers of takes accordingly for the final rule. The
Commission stated that these revisions are particularly important,
because NMFS relies on the Navy's density estimates for authorizing the
taking associated with many other activities off California and will do
so for at least the next 7 years until the Phase V densities are
available.
Response: The Navy used the kernel density distribution areas shown
in figure 4 in Robinson et al. (2012) to approximate the spatial strata
to use in density calculations. The Navy recognized that the data in
Figure 4 indicated a higher relative density of female elephant seals
off California in May and June; however, that is the time during which
females return to natal rookeries and are hauled out molting and
fasting and not expected to spend much, if any, time in the water. The
sex and age class haulout behavior of northern elephant seals is
complex and difficult to represent in this type of calculation where
some portion of seals of each age and sex class is hauled out at
different but overlapping time periods that span partial months. For 7
months (males) or 8 months (females) out of the
[[Page 58823]]
year, the Navy assumes 100 percent of seals are in the water, which is
undoubtedly an overestimate considering that seals are known to haulout
during foraging periods. While the Navy strives to improve density
estimates to accurately represent pinniped haulout behavior, the level
of precision is limited by both the available and sometimes conflicting
data on species' behavior and the large scale of the study area over
which behavior may vary. The assumptions made for the purposes of
calculating monthly densities at this scale were reasonable and
generally representative of the species behavior.
While the majority of tagged elephant seals reported by Robinson et
al. (2012) were from A[ntilde]o Nuevo Island, a few were tagged on
Islas San Benito, Mexico and followed similar migration patterns. Seals
from all other breeding and haulout sites are expected to follow
similar migration patterns (i.e., move north or northwest after
breeding and molting periods) and to follow similar annual breeding and
molting haulout cycles. For females, this means hauling out to molt in
May and June and spending little to no time in the water. Again, the
information in Robinson et al. (2012) was primarily used to define
strata for calculating densities. It's clear from Robinson et al.
(2012) figure 4 that 100 percent of females do not occur off CA in
January, February, and May; the Navy considers 80 percent to be a
reasonable estimate. It's not clear how the Commission determined that
10 percent instead of 5 percent of females would be off California in
September and October. While the density estimates do not distinguish
abundance by age class, the entire population abundance is used in the
calculations, which includes all age classes.
Furthermore, the analyzed abundance of elephant seals includes
22,000 seals from the Mexico breeding population (a likely overestimate
for that declining population as noted in the Density Technical Report
and revised Density Technical Report and exceeds the abundance of the
California breeding stock managed by NMFS. This conservative abundance
estimate puts more seals in the water during the majority of the year
and likely inflates predicted exposure estimates.
Lastly, the majority of sonar and explosive use occurs in the SOCAL
Range Complex located south of the elephant seal at-sea distribution
following both the post-breeding and post-molting migrations, which
extend north and northwest of the Channel Islands and into the North
Pacific.
As such, the Navy has not revised the density estimates as
recommended by the Commission. NMFS concurs, and has not revised the
number of estimated takes of this stock.
Comment 21 (ref 4, 5): The Commission recommended that NMFS: (1)
revise the harbor seal density estimates by using (a) the 2.86
correction factor from Harvey and Goley (2011) rather than 2.44 for the
Channel Islands and 1.15 for Point Mugu and La Jolla to estimate the
total abundances at the various locations in Table 9-21 of Density
Technical Report, (b) the 65 percent in-water percentage from Harvey
and Goley (2011) for Point Mugu, La Jolla, and all of the Channel
Islands except for San Nicolas and San Miguel Islands for the entire
year, and (c) 40 km from shore from Calambokidis (2004) and the 200-m
isobath based on Stewart and Yochem (1994) rather than 20 km from shore
and the 120-m isobath as stratum demarcations for areas where harbor
seals could occur; and (2) re-estimate the numbers of takes accordingly
for the final rule.
The Commission further recommended that NMFS: (1) contact the SWFSC
to obtain the maximum harbor seal abundance estimate from Santa
Catalina Island during which the relevant haul-out sites were surveyed
and use the 2.86 correction factor to estimate the total abundance at
Santa Catalina Island; (2) estimate the total abundance of harbor seals
from La Jolla to Point Mugu and from Point Mugu around past Pt.
Conception based on the number of harbor seals of the 30,968 abundance
estimate for the California stock from Harvey and Goley (2011) that
remains after subtracting the Channel Islands, Point Mugu, and La Jolla
abundance estimates; (3) use the 65 percent in-water percentage from
Harvey and Goley (2011), 40 km from shore from Calambokidis (2004), and
the 200-m isobath based on Stewart and Yochem (1994) to estimate the
harbor seal density for Santa Catalina Island, from La Jolla to Point
Mugu, and from Point Mugu around past Pt. Conception; and (4) re-
estimate the numbers of takes accordingly for the final rule.
Response: Regarding the Commission's recommendation to use the 2.86
correction factor from Harvey and Goley (2011), the correction factor
for San Nicolas Island from Stewart and Yochem (1983) of 59 percent in-
water is the most appropriate haulout factor (i.e., with one exception
it is the highest percentage of seals in the water) compared with other
available haulout factors. Harvey and Goley (2011) recommend a factor
of 1.54 (or 35 percent in water) for all of California. A factor of
2.86 (65 percent in-water) for southern California was also reported by
the authors, but was based only on one survey, so the authors
recommended using the mean of 1.54 (35 percent in-water) for California
over the 2.86 factor. Note that the authors describe the single survey
from southern California as ``a poor sample estimate of the proportion
ashore.'' The Navy used 2.44 (59 percent in-water), which is higher
than most other factors including all three of the mean haulout factors
derived by Harvey and Goley (2011) (see table 2 in the paper), which
would also have been reasonable alternatives.
Haulout factors were also chosen to be specific to season
(breeding/molting vs. non-breeding/molting) as well as location where
data were available. The survey data reported by Lowry et al. (2021)
that were used to estimate abundances and densities were conducted in
summer, so Navy used the most conservative haulout factor for summer
(59 percent in-water) from Stewart and Yochem (1983) for the in-water
abundance estimate, and NMFS concurs.
The 87 percent ashore estimate was a typo in the Navy's 2024 Marine
Species Density Database (NMSDD) which has been superseded by the
revised Density Technical Report. It should have been 83 percent ashore
equating to 17 percent in-water, as shown in table 9-20 in the revised
Density Technical Report. The factor of 1.2 or 17 percent in-water is
from table 1 in Huber et al. (2001) which cites the source as Hanan
(1996), a Ph.D. dissertation. The Navy corrected the typo in the
revised Density Technical Report. The Navy selected the 1.2 haulout
factor for the two mainland locations in Southern California because
several of the sites used in the research were located along the
mainland coast and the Navy sought out correction factors specific to
seals along the mainland, and NMFS concurs with this approach.
Below table 9-25 in the revised Density Technical Report, the
following text states which correction factor was used for the
September-February time period, ``For the September through February
time period, the in-water abundance was estimated as 86 percent of the
total abundance, based on data from San Miguel Island reported by
Yochem et al. (1987) and included in a summary by Huber et al.
(2001).'' Table 9-24 shows an in-water percentage range of 81-86
percent; the Navy selected 86 percent in-water as a more conservative
approach. NMFS concurs with this decision.
The Navy used the 59 percent in-water factor for March through
August
[[Page 58824]]
for all Channel Islands except for San Miguel Island, which used 23
percent based on a tagging study conducted with seals on the island,
and NMFS concurs.
As a conservative measure, the Navy used the highest counts from
2016 to 2019 by Lowry et al. (2021) to estimate in-water abundances
instead of using a multi-year average or counts from the most recent
year (i.e., 2019) (refer to table 9-25 in the revised Density Technical
Report). Both alternative options would have been reasonable to select,
but instead the Navy chose to use the maximum count over the 4 year
survey period. Note that the maximum counts for six of the eight
islands occurred in 2016 (the other two occurred in 2019), suggesting
that the overall harbor seal abundance in the Channel Islands may be
declining and that the Navy's density estimates may be high for
predicting takes beyond the year 2019. NMFS concurs with this approach.
Regarding the strata, harbor seals are well known for remaining
close to haulouts and foraging in relatively shallow waters, as
documented in the half dozen sources cited on page 237 of the revised
Density Technical Report. The sources also demonstrate that while
habitat use is generally similar in multiple regions, there is
variability in the depth and distance from shore characteristics of
harbor seal distribution in various studies. The Navy reviewed the
sources and attempted to define strata that captured the general and
expected distribution of the species. Expanding strata farther offshore
into deeper waters to capture extralimital and infrequent excursions by
individual seals (as recommended by the Commission) would have the
effect of reducing the density in the nearshore habitat where harbor
seals predominantly occur. Stewart and Yochem (1994) reported the 20 km
distance-from-shore metric used in the analysis. The 120 m depth
contour used to define strata encompassed the vast majority of reported
foraging depths without expanding the strata farther offshore (e.g., to
the 200 m depth contour representing the shelf break as the Commission
recommended) and reducing the densities. The density estimates are
intended to represent the predominant occurrence and distribution of
the population rather than capture all possible areas where wide-
ranging individuals have been sighted. The Channel Islands are part of
the Continental Borderland region in the Southern California Bight
which exhibits a complex bathymetry without a clearly distinct shelf
break. While the shelf break (often represented by the 200 m depth
contour) is a reasonable boundary to choose in more conventional
continental margins, it does not accurately demarcate the shelf break
in the Southern California Bight.
As noted above, the harbor seal abundances were based on counts
reported by Lowry et al. (2021), which reported eight harbor seals off
Santa Catalina island in 2019 only; no counts were reported in 2016
through 2018. Using a haulout factor of 59 percent results in a total
abundance of 20 seals associated with the island and in-water abundance
estimates of 12 seals (March-August) and 17 seals (September-February).
The area around Santa Catalina Island extending from shore to the 120 m
isobath is approximately 42,205 square kilometers (km\2\), which
results in densities of 0.0003 to 0.0004 seals/km\2\ for March-August
and September-February, respectively. The densities are about three
orders of magnitude lower than densities around the other islands where
the Navy conducts more activities (e.g., San Nicolas, San Miguel, San
Clemente). Based on these factors, the Navy has determined that adding
a density for Santa Catalina Island and remodeling would not contribute
substantively, if at all, to the current take estimates, and NMFS
concurs.
The Navy worked with scientists from the NMFS SWFSC to derive the
pinniped density estimates, including estimates for harbor seals. There
is a lack of survey data between La Jolla and Point Mugu along the
mainland coast, which is why densities are not provided along that part
of the coast. It is also noteworthy that the majority of training and
testing activities using sonar and other transducers or explosives
would occur beyond 12 nmi (22.2 km) from shore along the mainland
coast. The adjacent warning area (W-291) begins approximately 12 nmi
(22.2 km) from shore along the coast between La Jolla and Point Mugu.
Therefore, any harbor seals occurring along the coast in this area are
unlikely to be affected, and calculating the density using the method
suggested by the Commission is not warranted.
Calambokidis et al. (2004) reported harbor seal sightings off the
Washington coast from 1995 to 2002. While not as relevant to more
recently reported harbor seal behavior off California, the authors
reported a mean depth for the 15 sightings of 102 m and a mean distance
from shore of 15.5 km, which further supports the Navy's decision to
use the 120 m depth contour and a distance of 20 km from shore to
define the strata used in the Navy's HCTT density estimates rather than
greater depths and distances from shore recommended by the Commission.
Given that the densities remain unchanged, re-estimating the number
of takes for this final rule was not required.
Comment 22 (6, 7): The Commission recommended that NMFS work with
the Navy to derive harbor seal and bottlenose dolphin density estimates
for both within San Diego Bay and the SSTC area based on sightings data
from the numerous monitoring reports available, while also considering
the area beyond the Coronado Bridge in San Diego Bay.
Response: The Navy has derived densities for bottlenose dolphin for
the SSTC, located south of the entrance to San Diego Bay (see figure 6-
53 in the Density Technical Report). The Navy recognizes that in
addition to the regularly occurring California sea lion, other marine
mammal species, such as harbor seal and common bottlenose dolphin
occasionally enter San Diego Bay; however, those species tend to remain
near the mouth of the Bay, with only a few moving farther into the Bay.
The planned activities involving in-water sound sources within San
Diego Bay occur well into the Bay, typically south of the Coronado
Bridge, and do not include pile driving. The monitoring report for the
Naval Base Point Loma Pier 302 Replacement Project (available at
<a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-naval-base-point-loma-pier-302-replacement-project">https://www.fisheries.noaa.gov/action/incidental-take-authorization-naval-base-point-loma-pier-302-replacement-project</a>) cited by the
Commission reported observation of 1 bottlenose dolphin and 13 harbor
seals over 181 observer hours. It is not unusual for individuals of
both species that occur in nearshore waters to be sighted at the mouth
of San Diego Bay near Point Loma. The Naval Base San Diego (NBSD) Pier
6 Replacement Project monitoring report (available at <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-naval-base-san-diego-pier-6-replacement-project-san-diego">https://www.fisheries.noaa.gov/action/incidental-take-authorization-naval-base-san-diego-pier-6-replacement-project-san-diego</a>) recorded species during
two IHA periods over approximately 15 months (October 2021-January
2023). Only two harbor seals were observed over 450 monitoring days
under the first IHA and no harbor seals were observed over 88
monitoring days under the second IHA. These few observations are not
indicative of regular occurrence in the central or southern part of San
Diego Bay and do not support the need for a density estimate in San
Diego Bay.
The report also shows 86 bottlenose dolphin observations under the
first IHA and 0 bottlenose dolphin observations under the second IHA
[[Page 58825]]
(table 3-3). The report qualifies the total number of observations by
quantifying re-sightings in table 3-5 (i.e., sightings of the same
individual multiple times based on identifiable markings on dorsal fins
(e.g., cuts, scrapes, shape, etc.)). The data indicate approximately 72
percent of individuals observed were resights. Table 3-12 in the report
shows that bottlenose dolphins were only sighted in January, February,
and March of 2022 and were not sighted during any other month.
Monitoring also occurred in January 2023 with zero bottlenose dolphin
observations; however, no monitoring occurred in February or March of
2023. It is possible that the occurrence in San Diego Bay from January
to March of 2022 was an anomaly; the report noted that bottlenose
dolphins were not expected to occur in San Diego Bay at all. Observer
bias may have also contributed to the increased sightings, as noted in
section 3.2.2 of the report, which discussed a similar trend in
observations of California sea lions.
The Commission references 15 IHAs issued to the Navy in the last
decade, but aside from the two noted above, the Commission does not
clearly state which other projects are referenced. The non-systematic
observations reported in the monitoring reports mentioned previously do
not support robust density estimates for San Diego Bay. Additional data
would be required to better quantify abundance and seasonal occurrence
in the bay to support a density estimate.
Therefore, given their occasional presence and the limitations of
the observational data, the Navy did not develop density estimates for
harbor seal and bottlenose dolphin specific to San Diego Bay for the
HCTT EIS/OEIS, and NMFS concurs such density estimates are not
necessary.
Comment 23 (ref 8): The Commission recommended that NMFS work with
the Navy to derive the California sea lion density estimates south of
the Coronado Bridge based on sightings data from the numerous
monitoring reports rather than Graham and Saunders (2015).
Response: While the observations of California sea lions during
pier replacement activities at NBSD confirm the presence of sea lions
south of the Coronado Bridge, the observations were not based on line
transect surveys unlike the data reported by Graham and Saunders
(2015). Naval Facilities Engineering Command Southwest (2024) reported
237 observations over 493 monitor days, or 0.48 animals per day, and
also acknowledged that the observations included repeat sightings
(approximately 26 percent of individuals), making the data less useful
for estimating densities. As with the bottlenose dolphin sightings, the
report noted that sightings of California sea lions increased
substantially in January, February, and March of 2022, and the increase
was likely due to the presence of additional observers. This suggests a
bias in the data that limits its usefulness for deriving densities
representative of species distribution and occurrence. These non-
systematic observations reported in both in the Naval Facilities
Engineering Command Southwest (2024) monitoring report do not support
robust density estimates for south and central San Diego Bay.
Additional data would be required to better quantify abundance and
seasonal occurrence in the bay to support a density estimate.
Furthermore, the proposed military readiness activities in San Diego
Bay do not include pile driving or other sound-producing activities
that would require a density for analysis.
Comment 24 (ref 9): The Commission noted the following points
related to the pinniped densities provided in the Density Technical
Report. The Commission recommended that NMFS work with the Navy to
revise the Density Technical Report to clarify and address these points
since the densities will inform the numbers of takes for the final rule
and other incidental take authorizations for activities conducted by
the Navy and other applicants.
<bullet> The Navy stated that, on average, post-partum female
northern fur seals spent 180 hours in the water for every 40 hours on
land, equating to 78 percent of time in the water, which equated to 78
percent of adult females being in the water from June through November.
The in-water percentage would be 82 rather than 78 percent.
<bullet> The Navy incorrectly identified the various in-water
percentages for California sea lions in Table 9-25 as haul-out
correction factors in the table heading and underlying text. The
heading and text should indicate that those are indeed in-water
percentages, similar to table 9-20 for harbor seals.
<bullet> The Navy did not include the California sea lion juveniles
and pups specified in table 9-25 in the non-breeding season abundance
estimate for the California breeding strata. Juveniles and pups should
be included in the abundance estimate as was done for the breeding
season density.
<bullet> The Navy specified that the in-water percentages for
Steller sea lions were correction factors for estimation of the in-
water abundances. The percentages should be specified as in-water
percentages rather than correction factors, similar to harbor seals.
Response: Regarding the Commission's first point, Antonelis et al.
(1990) states that the average foraging trip was 180.6 hours (standard
deviation (SD) = 37 hours) and the average time on land was 39.6 hours
(SD = 10 hours). The Navy interpreted that as a ratio of 40 hours on
land to 180 hours in water or 40:180 = 40/180 = 22 percent on land (78
percent in water). The Navy acknowledges a different interpretation of
the source is reasonable, but notes that any difference in the
resulting percentages (78 percent vs. 82 percent) is within the range
of the SD in both measurements. As such, the Navy has not adjusted the
percentage, and NMFS concurs no adjustment is warranted.
Regarding the Commission's second and fourth points, the Navy
changed the heading on table 9-25 in the Density Technical Report and
adjusted related text on correction factors in the sections on
California sea lions and Steller sea lions and in the revised Density
Technical Report. NMFS concurs with this change.
Regarding the Commission's third point, the abundance estimate used
to calculate densities for the non-breeding season was based on the
total stock abundance and therefore considered all lifestages, even
though they were not specifically called out in the calculation. The
in-water percentages reported in table 9-25 were based on data on
haulout behavior for each lifestage, but not all percentages were used
to calculate densities. For example, for the non-breeding season female
pups were effectively assigned the in-water percentage of 75 percent
characteristic of adult females, but used for all females, rather than
the 34 percent in-water percentage representing pup haulout behavior.
Using this approach helped to simplify the calculation somewhat but
also resulted in a more conservative density estimate. Also, the
abundance used was based on data reported by Hern[aacute]ndez-Camacho
et al. (2021) and exceeded the current abundance for the California
Stock reported in the SAR. As such, no change is warranted.
Mitigation
Comment 25 (ref 32-1): A commenter recommended that NMFS expand the
exclusion and shutdown zones to reflect what the author suggests is
``current science on behavioral harassment thresholds.''
Response: The comment is vague, and the commenter does not provide
citations or otherwise support the assertion that the proposed zones do
not adequately reflect current science. The mitigation zones and the
shutdown
[[Page 58826]]
requirements included in the proposed rule and this final rule
considered the current science regarding behavioral response, as well
as practicability for implementation. The practicability assessment
criteria are described in table 5-1 of the 2025 HCTT EIS/OEIS.
Comment 26 (ref 33): A commenter stated that for mitigation areas
to effectively protect marine mammals they must be properly sited, and
the management objectives for each mitigation area must be based on
best available scientific information. The commenter stated, when
uncertainty exists and options are proposed that risk overprotection or
underprotection, the MMPA requires the permitting agency to consider
``whether the precautionary approach would give more protection to
marine mammals, and then whether that protection would impede military
training to a degree making that mitigation not practicable.'' Natural
Resources Defense Council v. Pritzker, 828 F.3d 1125, 1138 (9th Cir.
2016). The commenter stated that the final rulemaking should reflect
that consideration to the extent that NMFS intends to adopt it for
purposes of MMPA authorization.
Response: NMFS concurs that for mitigation areas to effectively
protect marine mammals, they must be properly sited and management
objectives for each must be based on best available scientific
information. A full technical analysis of the mitigation areas is
provided in appendix K (Geographic Mitigation Assessment) of the 2025
HCTT EIS/OEIS. A complete discussion of the Action Proponents'
evaluation process used to develop, assess, and select mitigation
measures, can also be found in chapter 5 (Mitigation) of the 2025 HCTT
EIS/OEIS. NMFS has reviewed the information contained therein and finds
that it reflects the best available science. Supporting documents
include peer-reviewed articles; scientific committee reports; cruise
reports or transects; books, government reports, or non-governmental
organization (NGO) reports; and notes, abstracts, and conference
proceedings. NMFS independently analyzed the mitigation areas and found
these geographic mitigation areas are both practicable and will reduce
the likelihood, magnitude, or severity of adverse impacts to marine
mammals or their habitat in the manner described in the Action
Proponents' analysis and this rule.
We acknowledge that the Ninth Circuit opinion stated that NMFS
``should have considered whether `the precautionary approach' would
give more protection to marine mammals, and then whether that
protection would impede military training to a degree making that
mitigation not practicable.'' Pritzker, 828 F.3d at 1138. However,
taken in the context of the Court's full discussion, we read the Ninth
Circuit's use of the term ``the precautionary approach'' as
specifically referring to the recommendations in the White Paper for
designating Offshore Biologically Important Areas (OBIAs) in ``data-
poor'' regions of the ocean (described therein as a precautionary
approach for designating OBIAs), rather than a broader mandate to adopt
a ``precautionary approach'' in carrying out the requirements of the
MMPA. Accordingly, we disagree with the commenter's interpretation of
the MMPA and Pritzker case. As we explained in the preamble of our 2019
incidental take regulations for Surveillance Towed Array Sensor System
LFA training and testing in the North Pacific Ocean and Eastern Indian
Ocean (84 FR 40132, August 13, 2019), NMFS' interpretation of the Ninth
Circuit's opinion is based on the fact that neither the MMPA, 16 U.S.C.
1361 et seq., nor NMFS' implementing regulations, 50 CFR part 216,
subpart I, include express references to, or requirements for, the
precautionary approach, nor is there a clear, agreed-upon description
of what the precautionary approach is or would entail in the context of
the MMPA or any specific activity.
The MMPA by nature is inherently protective, including the
requirement to mitigate to the lowest level practicable (``least''
practicable adverse impacts, or ``LPAI,'' on species or stocks and
their habitat). To fulfill that requirement, NMFS considers all
measures that we are reasonably aware of (e.g., from recommendations or
review of data) that have the potential to reduce impacts on marine
mammal species or stocks, their habitat, or subsistence uses of those
stocks. The extent to which the mitigation areas reduce impacts on the
affected species is addressed in the Analysis and Negligible Impact
Determination section of this rule.
Comment 27 (ref 67): A commenter stated that the Navy does not
incorporate stand-off distances of any size within its requirements for
mitigation areas. Thus, activities that are otherwise restricted or
limited within a mitigation area could occur directly along the
boundary and ensonify the area at levels capable of causing injury or
increasing the risk or severity of behavioral disruption. The commenter
recommended that Navy consider establishing stand-off distances around
its mitigation areas to the greatest extent practicable, allowing for
variability in size given the location of the mitigation area, the type
of operation at issue, and the species of concern.
Response: The mitigation areas included in the final rule and
described in chapter 5 (Mitigation) of the 2025 HCTT EIS/OEIS represent
the maximum mitigation within mitigation areas and the maximum size of
mitigation areas that are practicable for the Action Proponents to
implement under their specified activity. The Action Proponents have
asserted, and NMFS concurs with the assessment, that implementing
additional mitigation (e.g., stand-off distances that would extend the
size of the mitigation areas) beyond what is included in the final rule
is impracticable due to implications for safety, sustainability, and
the Action Proponents' ability to continue meeting their mission
requirements.
When practicable, NMFS sometimes recommends the inclusion of
buffers around areas specifically delineated to contain certain
important habitat or high densities of certain species, to allow for
further reduced effects on specifically identified features/species.
However, buffers are not typically considered necessary or appropriate
in combination with more generalized and inclusive measures, such as
coastal offsets or other areas that are intended to broadly contain
important features for a multitude of species. In the case of this
rulemaking, NMFS and the Action Proponents have included an extensive
array of broad protective areas that will reduce impacts on numerous
species and habitats (including additions to what was described in the
proposed rule) and, as described above, limitations in additional areas
is not practicable.
Comment 28 (ref 34): A commenter stated that new scientific
information could be incorporated into the design of mitigation areas,
specifically referencing Houser et al. (2024) and Southall et al.
(2024). The commenter stated that they can 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
[[Page 58827]]
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 HCTT 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 29 (ref 73): A commenter recommended that NMFS should
consider requiring compensatory mitigation for the adverse impacts of
the permitted activity on marine mammals and their habitat that cannot
be prevented or mitigated.
Response: Compensatory mitigation is not required under the MMPA.
Instead, authorizations must include means of effecting the least
practicable adverse impact from the activities on the affected species
or stocks and their habitat, which this rule has done through the
required procedural and geographic area mitigation measures. Also, the
commenter did not recommend any specific measures, rendering it
impossible to consider its recommendation at a broader level.
Comment 30 (ref 69): A commenter recommended further research and
exploration of the feasibility of signal modification, including
converting up-sweeps to down-sweeps, reducing the level of the side
bands, or lengthening the rise time. The 2024 HCTT Draft 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 HCTT Draft 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
elevate that research with the Navy.
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 31 (70): 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
[[Page 58828]]
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 (RDT&E) 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.
Comment 32 (ref 24, 72): 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 the Navy has
substantial capability, at both SOAR and PMRF, to detect, identify,
localize, and track various cetacean species in real time, citing that
the capability has been used to support behavioral response studies in
both locations (e.g., Helble et al., 2015; Kates Varghese et al., 2020;
Jacobson et al., 2022). Yet, the Navy claims that using passive
acoustic range instrumentation for mitigation purposes is still in a
research and development stage ``not sufficiently beneficial'' (2024
HCTT Draft EIS/OEIS at 5-33, table 5-20). However, scientific studies
have used that instrumentation for exactly these types of purposes, and
the methodologies undertaken--while continually evolving--do not
require more research and development before they can be used to
support the mitigation of acoustic, explosive, and vessel-related
stressors. The commenter states that NMFS should require use of what is
plainly a viable form of mitigation.
Response: The Action Proponents intend to continue to use passive
acoustic monitoring (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 HCTT 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.
The Navy asserts that its instrumented ranges do not have the
capabilities to be used effectively for mitigation. The range
hydrophones cannot track animals with any granularity and can only
detect whether animals are present in a general area. Most notably,
there is not a real-time feed of hydrophone data to vessel and aircraft
operators. Further, animals are almost always present on the ranges,
therefore expending the resources to notify exercise participants is
not necessary. Given these practicability issues and expected
ineffectiveness, NMFS concludes that these suggested measures are not
practicable and is not requiring the Action Proponents to utilize its
passive acoustic range instrumentation for mitigating impacts to marine
mammals. Please see section 5.5.3 (Active and Passive Acoustic
Monitoring Devices) of the 2018 HSTT EIS/OEIS.
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.
[[Page 58829]]
Comment 33 (ref 25): The Commission strongly recommended that NMFS
require the Navy to use 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: Consistent with the proposed rule, this final rule
requires the Navy to use PAM prior to and during activities involving
explosive sonobuoys and explosive torpedoes, and during sinking
exercises when passive acoustic devices are already being used during
weapon firing. For ship shock trials, 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 was considered ineffective (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 34 (ref 26): 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 35 (ref 31, 32-2): A commenter recommended that NMFS
prohibit high-intensity acoustic and explosive activities in BIAs
during breeding, calving, or nursing seasons. Another commenter stated
that training places should also be limited and not take place in
marine protected areas or sensitive habitats.
Response: This final rule includes extensive mitigation measures in
BIAs, including reproductive BIAs that are important for breeding,
calving, and/or nursing. In Hawaii, mitigation in the Hawaii Island
Marine Mammal Mitigation Area and Hawaii 4-Islands Marine Mammal
Mitigation Area (including an expansion of this mitigation area since
publication of the proposed rule as described in the Changes from the
Proposed Rule to the Final Rule section), as well as the Hawaii
Humpback Whale Awareness Messages, are designed to protect marine
mammals in sensitive habitats, including reproductive habitat for
humpback whales, and to protect small and resident marine mammal
populations. In California, the Northern California Large Whale
Mitigation Area, Central California Large Whale Mitigation Area,
Southern California Blue Whale Mitigation Area, California Large Whale
Awareness Messages, California Large Whale Real-time Notification
Mitigation Area, and San Nicolas Island Pinniped Haulout Mitigation
Area are designed to protect marine mammals in sensitive habitats,
including foraging, migratory, and calving habitats for large whales,
and from more severe impacts (e.g., auditory injury, vessel strike).
Please see the Geographic Mitigation Areas section of this final rule
for additional detail about the restrictions within these mitigation
areas and the benefits they provide to marine mammals.
The Action Proponents have asserted, and NMFS concurs with the
assessment, that implementing additional mitigation (e.g., expanded
mitigation areas) beyond what is included in the final rule is
impracticable due to implications for safety, sustainability, and the
Action Proponents' ability to continue meeting their mission
requirements.
Comment 36 (ref 22a): The Commission recommended that NMFS include
the San Nicolas Island Mitigation Area in the final rule, limit the
number of sonar hours combined to no more than 300 hours of mid-
frequency (MF)1 hull-mounted surface ship sonar combined for this
mitigation area and the Southern California Blue Whale, the Central
California Large Whale, and Northern California Large Whale Mitigation
Areas from June 1 through November 30, and prohibit explosives (i.e.,
mine warfare, large-caliber gunnery rounds, torpedoes, bombs, and
missiles) from June 1 through November 30. The Commission states that
the current core feeding BIA for blue whales (figure K-19 in the 2024
HCTT Draft EIS/OEIS and figure 2 in Calambokidis et al. (2024))
overlaps the San Nicolas Island Mitigation Area that was part of the
litigation settlement agreement in 2015 for Conservation Council for
Hawaii v. National Marine Fisheries Service, as well as the Phase III
HSTT EIS/OEIS and associated rulemaking.
Response: The Action Proponents assert that, due to the inclusion
of Point Mugu Sea Range activities in the specified activities, it is
impractical to continue mitigation in the former San Nicolas Island
Mitigation Area and to extend the temporal restrictions beyond the 5
months already proposed. Doing so would modify military readiness
activities in a way that would prevent them from meeting mission
objectives and hinder Navy ability to realistically train and test in
furtherance of its statutory mandate. See table 5-1 of the HCTT EIS/
OEIS for examples. NMFS agrees that the suggested measures are not
practicable in light of the military readiness impacts, as explained
further below.
Of note, the portion of the blue whale core feeding BIA that
overlaps the recommended San Nicolas Island Mitigation Area would be
extremely small in comparison to the full BIA. Over 38 percent (38.41)
of the core blue whale feeding BIA overlaps the Northern California
Large Whale and Central California Large Whale Mitigation Areas, and
the mitigation in these areas will reduce impacts that could result in
lost feeding opportunities. Over 42 percent (42.35 percent) of the BIA
is outside of the HCTT Study Area.
Please see NMFS' response to Comment 37 and Comment 38 regarding
extension of the Southern California Blue Whale, Central California
Large Whale, and Northern California Large Whale Mitigation Areas
through November 30.
Comment 37 (ref 22b, 36, 37, 38): A commenter recommended that NMFS
extend the seasonality of the Southern
[[Page 58830]]
California Blue Whale Mitigation Area to April 1 to December 31, as
combined scientific evidence from sightings data and passive acoustic
detections show that blue whales are present off southern California
almost year-round and at relatively higher densities from April 1
through December 31. The commenter also recommended that NMFS limit all
sources of MFAS and require seasonal and/or dynamic vessel speed
restrictions within the mitigation area.
In a related comment, the Commission recommended that NMFS extend
the timing restrictions from October 31 to November 30 for the Southern
California Blue Whale, Central California Large Whale, and Northern
California Large Whale Mitigation Areas in the final rule.
Response: Regarding the recommendation to extend the seasonality of
the Southern California Blue Whale Mitigation Area to April 1 to
December 31 or November 30 as recommended by the commenter and the
Commission, respectively, the Action Proponents assert that extending
the temporal restrictions beyond the period of June 1 through October
31 included in the proposed rule would be impractical because it would
modify military readiness activities in a way that would prevent them
from meeting mission objectives and hinder Navy ability to
realistically train and test in furtherance of its statutory mandate.
See table 5-1 of the HCTT EIS/OEIS for examples. Further, the revised
blue whale core feeding area identified by Calambokidis et al. (2024)
is effective from June through November, and the Southern California
Blue Whale Mitigation Area is already effective from June 1 through
October 31 (i.e., all but 1 month that the BIA is in effect). Given the
practicality issues, NMFS is not requiring the Action Proponents to
extend the effective period of this mitigation area. Please see NMFS'
response to Comment 38 for a response to the Commission's
recommendation pertaining to the Central California Large Whale and
Northern California Large Whale Mitigation Areas.
Regarding the recommendation to limit all sources of MFAS within
the mitigation area, the Action Proponents assert that increasing the
active sonar restrictions beyond what is already proposed would be
impractical because it would modify military readiness activities in a
way that would prevent them from meeting mission objectives and hinder
Navy ability to realistically train and test in furtherance of its
statutory mandate. See table 5-1 of the HCTT EIS/OEIS for examples.
Other training and testing MFAS systems are likely to be used less
frequently in the vicinity of the Southern California Blue Whale
Mitigation Area than surface ship hull-mounted MFAS for which the
mitigation area contains restrictions. Given water depths, the Southern
California Blue Whale Mitigation Area is not conducive for large scale
anti-submarine warfare exercises, nor is it near areas where other
anti-submarine warfare training and testing occurs. However, due to the
presence of existing Navy subareas in the vicinity of the southern part
of the Southern California Blue Whale Mitigation Area, a limited amount
of helicopter dipping MFAS could occur. These designated range areas
are required for proximity to airfields in San Diego such as Naval Air
Station North Island and for airspace management. However, helicopters
only used these areas for a Kilo Dip. A Kilo Dip is a functional check
of approximately one to two pings of active sonar to confirm the system
is operational before the helicopter heads to more remote offshore
training areas. This ensures proper system operation and avoids loss of
limited training time, expenditure of fuel, and cumulative engine use
in the event of equipment malfunction. The potential effects of dipping
sonar have been accounted for in the Navy's analysis. Further, due to
lower power settings for dipping sonar, potential impact ranges of
dipping sonar are significantly lower than surface ship sonars, and
during a Kilo Dip or any other use of MFAS, the Action Proponents will
implement the activity-based mitigation measures.
Regarding the recommendation to require seasonal and/or dynamic
vessel speed restrictions within the mitigation area, the Action
Proponents assert that such restrictions are not practicable based on
safety, sustainability, and mission criteria. 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 row 16 of table 5-20 in
chapter 5 of the 2025 HCTT EIS/OEIS). Of note, in a review of Navy
unpublished data, the multi-year average of U.S. Navy surface ship
speeds on the continental shelf off California is between 10-15 knots
(kn) (18.5-27.8 km/hr). In addition to the practicality concerns, none
of the known vessel strikes by the Action Proponents in the HCTT Study
Area have occurred in the Southern California Blue Whale Mitigation
Area, suggesting that risk of vessel strike by the Action Proponents in
this area is relatively low in comparison to other parts of the Study
Area. As such, given the practicality concerns and the limited risk of
vessel strike within the mitigation area, this final rule does not
require speed restrictions in the Southern California Blue Whale
Mitigation Area. However, activity-based mitigation for manned surface
vessels requires maneuvering vessels to maintain a specified distance
from marine mammals, which may include reducing speed.
Comment 38 (refs 39, 40, 41, 42, 43, 44, 45): A commenter
recommended that NMFS extend the seasonality of the Central California
Large Whale Mitigation Area to April 1st to December 31st to reflect
that aggregations of humpback whales occur off central California
through December and that blue whales arrive in the region as early as
April. The commenter further recommended that NMFS prohibit use of
dipping sonar, restrict other sources of MFAS, prohibit use of low-
frequency active sonar (LFAS), prohibit the use of in-water explosives,
and require vessel speed restrictions. In a related comment, a
commenter recommended that NMFS enhance the mitigation measures in the
Northern California Large Whale Mitigation Area to align with those
proposed for the Central California Large Whale Mitigation Area.
Response: Regarding the commenter's recommendation to extend the
seasonality of the Central California Large Whale and Northern
California Large Whale Mitigation Areas to April 1st to December 31 or
November 30 as recommended by the commenter and the Commission,
respectively, the Action Proponents assert that extending the temporal
restrictions beyond the five months already proposed would be
impractical because it would modify military readiness activities in a
way that would prevent them from meeting mission objectives and hinder
the Action Proponents' abilities to realistically train and test in
furtherance of their statutory mandates. See table 5-1 of the 2025 HCTT
EIS/OEIS for examples.
Regarding active sonar sources, the Action Proponents anticipate
that use of dipping sonar in the Central California Large Whale and
Northern California Large Whale Mitigation Areas will be infrequent
relative to other portions of the California Study Area, given the
distance of the mitigation areas from airfields with helicopters that
would use dipping sonar. Further, other than hull-mounted MFAS, for
which this mitigation areas already include a restriction, and dipping
sonar, the Action Proponents anticipate that use of
[[Page 58831]]
MFAS in the Central California Large Whale and Northern California
Large Whale Mitigation Areas will be infrequent relative to other
portions of the California Study Area. Similarly, the Action Proponents
anticipate that use of LFAS and explosives in the Central California
Large Whale and Northern California Large Whale Mitigation Areas will
be infrequent relative to other portions of the California Study Area.
As such, restrictions on the already low use of these sources within
the mitigation areas would not provide sufficient benefits to marine
mammals, and are not required by this final rule. However, this rule
includes activity-based mitigation for all active sonar and explosive
activities.
Regarding the recommendation to require vessel speed restrictions
within the mitigation areas, the Navy asserts that such restrictions
are not practicable based on safety, sustainability, and mission
criteria. 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 row
16 of table 5-20 in chapter 5 of the 2025 HCTT EIS/OEIS). Of note, in a
review of Navy unpublished data, the multi-year average of U.S. Navy
surface ship speeds on the continental shelf off California is between
10-15 kn (18.5-27.8 km/hr). Given the practicality concerns, this final
rule does not require speed restrictions in the Central California
Large Whale and Northern California Large Whale Mitigation Areas.
However, activity-based mitigation for manned surface vessels requires
maneuvering vessels to maintain a specified distance from marine
mammals, which may include reducing speed.
Comment 39 (ref 47, 48): A commenter recommended that within the
California Large Whale Awareness Message Mitigation Area, NMFS should
require the Navy to issue awareness notifications for gray whales and
fin whales during the timeframes when they are most likely to occur in
the greatest densities, November through June, and June through
November respectively. The commenter also recommended that NMFS require
the Navy to use the dynamic species distribution models (SDMs)
developed by the SWFSC and the WhaleWatch model predictions to inform
their assets on where and when concentrations of whales are most likely
to be present based on recent oceanographic conditions.
Response: The Action Proponents must broadcast awareness messages
to alert applicable assets (and their Lookouts) transiting and training
or testing off the U.S. West Coast to the possible presence of
concentrations of large whales, including gray whales, fin whales, and
mixed concentrations of blue, humpback, and fin whales that may occur
based on predicted oceanographic conditions for a given year (e.g.,
May-November, April-November) and are intended to be temporally
dynamic. The Navy currently releases two West Coast whale awareness
messages per year, a fall message for gray and fin whales and a spring
message for mixed concentrations of blue, humpback, and fin whales that
may occur based on predicted oceanographic conditions for a given year.
In this final rule and in response to comments relating to gray whales,
the effective end date of the fall message has been extended from May,
as included in the proposed rule, to June 30. The effective start date
of the spring message is based upon oceanographic conditions and
continues through November when the effective period of the BIAs
identified by Calambokidis et al. (2024) ends). While the commenter
suggests that the awareness messages align directly to the BIAs, for
the blue and fin whale message, NMFS and the Action Proponents agree
that it is more appropriate to base this message upon oceanographic
conditions, as fin whale or blue whale presence in the spring may vary
from year-to-year.
Dynamic SDMs and WhaleSafe information inform the details included
in the Navy's annual awareness messages. These models are not suitable
to the small scale range sub-areas Navy vessels must operate in due to
training and testing requirements, schedule deconfliction, and safety.
Nor are the models suitable or available to vessels at sea due to
satellite transmission bandwidth restrictions (i.e., limited internet
access).
Comment 40 (ref 49, 50, 51): A commenter recommended that within
the California Large Whale Real-Time Notification Mitigation Area, NMFS
require issuance of real-time notifications when one or more large
whales are observed within 1 nmi (1.8 km) of a Navy vessel, and extend
notifications to U.S. Coast Guard vessels performing or supporting
Navy-related activities. The commenter also recommended that within the
Mitigation Area, the Navy should be required to deploy unmanned
acoustic gliders or fixed hydrophones with real-time acoustic detection
capability, and to use both acoustic and visual detections to trigger
real-time notifications. Last, the commenter stated that upon receipt
of a real-time notification, Navy vessels and Coast Guard vessels
engaged in training and testing activities should reduce or maintain
vessel speeds at 10 kn (18.5 km/hr) until whales are no longer detected
in the area either visually or acoustically.
Response: This final rule includes a modification to the California
Large Whale Real-Time Notification Mitigation Area. Rather than
notifications being issued following observation of four or more large
whales within 1 nmi (1.8 km), this final rule requires notifications to
be issued following observation of three large whales within 1 nmi (1.8
km) of a Navy vessel. Individual large whale sightings within
California are particularly common. The Navy reviewed sighting data
from NMFS' SWFSC and Navy-funded researchers and determined that a
group of four large whales might be indicative of unusual foraging or
other life history events. However, following the additional strikes
that have occurred since the 2025 HCTT proposed rule (90 FR 32118, July
16, 2025), the Action Proponents are reducing this to three large
whales. Strike risk from U.S. Coast Guard vessels is different from
Navy vessels. Historic Coast Guard strikes were from smaller vessels
mostly outside of the HCTT Study Area with none associated with
combined Navy training. However, if Navy vessels are training in
coordination with U.S. Coast Guard vessels, bridge-to-bridge radio will
be used to disseminate these notifications. Of note, real-time PAM
would not detect whales that are not vocalizing, and passive acoustic
monitoring would only be indicative that whales are present but not of
their location relative to Navy or Coast Guard vessels.
Please see NMFS' response to Comment 32 regarding the
recommendation to use both visual and passive acoustic monitoring
platforms to detect whales and trigger awareness notification systems.
The dynamic vessel speed restrictions upon receipt of a real-time
notification within the mitigation area are not practicable for the
reasons discussed in response to Comment 50.
Comment 41 (ref 52): A commenter stated that NMFS should carefully
consider prohibiting major training exercises (MTE) or exercise
components involving hull-mounted MFAS within the Hawai[revaps]i Island
Marine Mammal Mitigation Area. The commenter states that if some major
exercises absolutely cannot be avoided, the Navy should consider
further reducing their number,
[[Page 58832]]
and, to the extent practicable, carry out each exercise in a different
portion of the Hawai[revaps]i Island Marine Mammal Mitigation Area
(i.e., one exercise in the north, one exercise in the south), to ensure
that marine mammal populations with highly discrete site fidelity, as
indicated by the designation of child small and resident BIAs, are not
exposed to multiple MTEs within a single year.
Response: An MTE, for purposes of this rulemaking, consists of
several unit-level activities conducted by several units operating
together, commanded and controlled by a single Commander, and typically
generating more than 100 hours of active sonar. The multiple units
involved in an MTE would often be spread across the Hawaii Range
Complex (HRC), and as such, there is rarely a concentration of sonar or
other stressors in one area. Further, the individual activities that
make up an MTE would not frequently occur within the Hawaii Island
Marine Mammal Mitigation Area. The main Hawaii-based MTE, Rim of the
Pacific (RIMPAC), occurs only every other year in the summer and
outside of humpback whale breeding season. While all areas of HRC could
be used for some sort of training during RIMPAC, the majority of sonar
and explosive use generally, but not exclusively, occurs outside of the
mitigation area. Mitigation within the Hawaii Island Marine Mammal
Mitigation Area requires that the Action Proponents must not use more
than 300 combined hours of MF1 and MF1C surface ship hull-mounted MFAS
or 20 hours of helicopter dipping sonar (an MFAS source) annually
within the mitigation area. This includes any combination of MTEs or
unit level training. Additionally, explosive use in the Hawaii Island
Marine Mammal Mitigation area is prohibited year-round.
Comment 42 (ref 23, 35, 53, 54, 55, 56, 57, 58): A commenter
recommended that NMFS extend the boundaries of the Hawaii 4-Islands
Marine Mammal Mitigation Area to encompass the child small and resident
BIAs for the endangered Main Hawaiian Islands Insular Distinct
Population Segment (DPS) of false killer whales, including the
northeast Kaiwi Channel. The commenter also recommended that NMFS
extend the prohibition on the use of MF1 surface ship hull-mounted MFAS
and LFAS in this area from December 1 through May 31 to align with the
effective period of the BIA for humpback whales identified by Kratofil
et al. (2023). Further, the commenter recommended that year-round, NMFS
prohibit the use of dipping sonar and limit all other sources of MFAS.
Last, the commenter recommended that NMFS require vessel speed
restrictions between December 1 and May 31. In a related comment, the
Commission recommended that NMFS include the core small and resident
BIA areas off Oahu, Lanai, and Molokai in the Hawaii 4-Islands
Mitigation Area, which prohibits use of MF1 hull-mounted surface ship
sonar from November 15 to April 15 and in-water explosives year-round.
In a related comment, a commenter stated that the HRC and Temporary
Operating Area overlap with essential calving and breeding habitats.
The commenter stated that to comply with MMPA intent, operations with
high acoustic or explosive output should be prohibited during known
sensitive periods for reproduction and nursing.
In a related comment, a commenter stated 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 representing
important habitat for beaked whale species.
Response: The Hawaii 4-Islands Marine Mammal Mitigation Area
contains portions of nine updated BIAs (Kratofil et al., 2023),
including part of the false killer whale core small and resident BIA.
This final rule includes an expansion of the Hawaii 4-Islands
Mitigation Area, as recommended by the Commission and the commenter.
The expanded area includes an additional portion (1,969 km\2\) of the
child small and resident BIA for the Main Hawaiian Islands Insular
stock of false killer whale, while avoiding restrictions in the Kaiwi
Channel between Oahu and Molokai, the Aloha Submarine Transit Lane, and
Penguin Bank which are important for Navy's training and testing
activities. This increases the portion of the child BIA overlapping the
mitigation area from approximately 40 percent of the BIA as included in
the proposed rule to 63 percent. Additionally, this final rule
clarifies that the MFAS mitigation in this area and in the Hawaii
Island Marine Mammal Mitigation Area includes both MF1 and MF1C surface
ship hull-mounted MFAS. MF1C was inadvertently left out of the Action
Proponents application and subsequently the proposed rule.
The Action Proponents assert that further expanding the Mitigation
Area would result in degraded training and testing realism. As stated
in section K.3.3.3 of the HCTT EIS/OEIS, as it relates to anti-
submarine warfare, the training value within the 4-Islands Region is
much higher compared to other near shore environments within the HRC
due to the challenging bathymetry. As such, NMFS is not requiring the
Action Proponents to expand the spatial extent of the mitigation area
to the full extent recommended by the commenter.
The Action Proponents assert that extending the restrictions on
active sonar or explosives, including limits or prohibition of MFAS and
LFAS sources, in the Hawaii 4-Islands Marine Mammal Mitigation Area
beyond that required by the proposed rule would be impractical because
it would modify military readiness activities in a way that would
prevent them from meeting mission objectives and inhibit their
abilities to meet statutory mandates. Further restrictions on dipping
sonar use would be impractical for the same reasons. However, the
current geographic extent of the Hawaii Island Marine Mammal Mitigation
Area wholly encompasses the most important portion (i.e., ``child''
portion of a hierarchical BIA) of the Blainville's beaked whale BIA,
the vast majority of the most important portion of the goose-beaked
whale BIA, and portions of both species' parent BIAs. Within this
mitigation area, the Action Proponents must not use more than 20 hours
of MF helicopter dipping sonar annually.
Regarding the recommendation to require vessel speed restrictions
within the mitigation area from December 1 through May 31, the Navy
asserts that such restrictions are not practicable based on safety,
sustainability, and mission criteria. 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 row 16 of table 5-20 in chapter 5 of the 2025
HCTT EIS/OEIS). Of note, in a review of Navy unpublished data, the
multi-year average of U.S. Navy surface ship speeds on the continental
shelf off California is between 10-15 kn (18.5-27.8 km/hr). Given the
practicality concerns, this final rule does not require speed
restrictions in the Southern California Blue Whale Mitigation Area.
However, activity-based mitigation for manned surface vessels requires
maneuvering vessels to maintain a specified distance from marine
mammals, which may include reducing speed.
Comment 43 (ref 62, 63): A commenter described what it
characterized as important beaked whale habitat in San Nicolas Basin,
Santa Catalina Basin, and the southernmost edge of the California
[[Page 58833]]
Current, west of Tanner and Cortez Banks. The commenter recommended
that the Navy and NMFS convene a group of experts to develop a suite of
mitigation measures ``that are feasible for the Navy but would still
reduce harm to individual beaked whales and the risk of population-
level impacts'' in the SOCAL Range Complex. The commenter recommended
that, until that time, NMFS should require maintenance of the San
Nicolas and Santa Barbara Mitigation Areas. The commenter also stated
that without meaningful additional mitigation, it does not see how
population-level harm would not occur or, ultimately, how a
``negligible impact'' finding under the MMPA could be reached with
respect to the goose-beaked whale population associated with San
Clemente Island.
The commenter also recommended considering source-based approaches
such as signal modification to mitigate impacts on goose-beaked whales
and other frequently exposed populations.
Response: NMFS and the Navy have fully considered potential
mitigation for all species of marine mammals throughout the HCTT Study
Area, including beaked whales, and NMFS has determined that the
mitigation included in this final rule will effect the least
practicable adverse impact on the affected species and stocks and their
habitat, as required by the MMPA.
Within San Nicolas Basin, there is a documented, recurring number
of goose-beaked whales (Falcone et al., 2009; Barlow et al., 2021a,
2021b; Curtis et al., 2021) strongly indicating that the Navy's
activities are not having a population-level impact to what may be a
resident population of this species. This is supported by repeated
visual re-sighting rates of individuals, sightings of calves and, more
importantly, reproductive females, and passive acoustic assessments of
steady vocalization rates and abundance over at least the most recent
7-year interval (Curtis et al., 2021; Schorr et al., 2024).
As described in response to Comment 36, the Action Proponents
assert that, due to the inclusion of Point Mugu Sea Range activities in
the specified activities, it is impractical to continue mitigation in
the former San Nicolas Island Mitigation Area. Doing so would modify
military readiness activities in a way that would prevent them from
meeting mission objectives and hinder Navy ability to realistically
train and test in furtherance of its statutory mandate. See table 5-1
of the HCTT EIS/OEIS for examples. NMFS agrees with this assessment and
is not requiring the Navy to continue the former San Nicolas Island
Mitigation Area, consistent with the proposed rule.
The Santa Barbara Island Mitigation Area was previously created to
minimize impacts to blue whales and gray whales in identified BIAs
(Calambokidis et al., 2015), which have since been updated
(Calambokidis et al., 2024). Just a portion of the former Santa Barbara
Island Mitigation Area area meets the scientifically accepted minimum
depth criteria expected for beaked whale habitat, in Southern
California, usually greater than 800 m. The bathymetric area greater
than 800 m depth and within the Santa Barbara Island Mitigation Area is
approximately 24 square nmi (nmi\2\) (26 percent of the total
Mitigation Area spatial extent or only 0.02 percent of the total HSTT
SOCAL area, which would represent an even smaller percentage of the
California Study Area considered in this final rule). Beaked whale
monitoring at other locations within SOCAL have shown that even in
ocean basins thought to have a goose-beaked whale sub-population, there
is still quite a bit of variation in occurrence and movement of beaked
whales within a given basin (Schorr et al., 2017, 2018, 2020). The
small area around Santa Barbara Island is not known to have resident
marine mammals, formally identified BIAs (or watch areas formally
identified in Calambokidis et al. (2024), though the authors note that
some areas, including the San Nicolas Basin, appear to have higher
densities of beaked whales, and future consideration as a BIA may be
warranted), nor is it identified as a breeding or persistent foraging
location for cetaceans. Instead, the same marine mammals that range
throughout the offshore Southern California area could pass at some
point through the marine waters of Santa Barbara Island. In addition to
the limited benefit to beaked whales if this mitigation area were
required, restrictions beyond what is already proposed would be
impractical because it would modify military readiness activities in a
way that would prevent them from meeting mission objectives and hinder
Navy ability to realistically train and test in furtherance of its
statutory mandate. As such, NMFS is not requiring the Navy to continue
the former Santa Barbara Island Mitigation Area, consistent with the
proposed rule.
The water space areas mentioned in the comment as ``(SHOBA)'' off
the southern end of San Clemente Island are waters designated as
Federal Danger and Safety Zones via formal rule making (Danger Zone--33
CFR 334.950 and Safety Zone--33 CFR 165.1141) because they are adjacent
to the shore bombardment impact area that is on land at the southern
end of San Clemente Island. Waters designated as ``WILSON COVE'' on the
leeward norther side of San Clemente Island south of Safety Zone Area A
are associated with the Wilson Cove anchorages and moorings, where ship
calibration tests, sonobuoy lot testing, and special projects take
place, are designated as Federal Safety and Restricted Zones via formal
rule making (Safety Zone--33 CFR 165.1141 and Restricted Zone--33 CFR
334.920).
The commenter expressed concern that a population of goose-beaked
whale is, ``subject to regular acoustic disturbance due to the presence
of the Shore Bombardment Area,'' is not correct. The SHOBA is a naval
gun impact area located on land at the southern end of San Clemente
Island. This area is an instrumented land training range used for a
variety of bombardment training and testing activities. The in-water
administrative boundary for SHOBA does not delineate the locations
where a vessel firing at land targets must be located and does not
represent where gunfire rounds are targeted. The water area in Santa
Catalina Basin is a controlled safety zone in the very unlikely event a
round goes over the island and lands in the water. With the modern
advent of better precision munitions, computers, and advanced fire
control, that probability is very remote. Navy vessels use the waters
south of San Clemente Island (SHOBA West and SHOBA East) from which to
fire into land targets on southern San Clemente Island. Therefore,
there would not be any underwater acoustic disturbance to goose-beaked
whales located within the Santa Catalina Basin from in-water explosives
or ship firing. Goose-beaked whales are unlikely to occur in the
shallow waters of the Pyramid Cove Mine Training Range where these
stressors would occur.
The Navy has been funding goose-beaked whale research and
monitoring in SOCAL since 2004. This research includes information
related to overall beaked whale population health such as individual
re-sighting rates, passive acoustic detections on occurrence,
documentations of mother-calf pairs, satellite tracking, genetics, and
starting in 2025, body condition analysis using drone photographs. In
addition, numerous opportunistic exposure response studies are ongoing.
To date, no documentation of harm to individuals or populations has
been observed over 20 years of monitoring. Further, the Navy, in
consultation with NMFS, has already begun planning the
[[Page 58834]]
development of a Potential Consequence of Disturbance (PCOD) model for
SOCAL goose-beaked whales based on past and ongoing data collection
efforts. Rather than convening a mitigation-focused panel as
recommended by the commenter, NMFS and the Navy will consider the
outcome of this model and whether model results suggest that additional
mitigation measures for beaked whales may be warranted.
In Southern California, the goose-beaked whales that may be
impacted by the Action Proponents' training and testing are of the
California/Oregon/Washington stock, and NMFS has appropriately made its
negligible impact finding for this stock, as described in the Analysis
and Negligible Impact Determination section of this final rule.
Please see NMFS response to Comment 30 regarding signal
modification. Aside from signal modification, the commenter did not
recommend specific source-based mitigation approaches.
Comment 44 (ref 64): A commenter recommended that NMFS require a
year-round mitigation area to protect the Cross Seamount, given that it
represents important foraging habitat for a rare and potentially
evolutionary distinct species of beaked whale. The commenter stated
that such a designation would have secondary benefits for a variety of
other odontocete species foraging at Cross Seamount seasonally between
November and May. The commenter further recommended considering
habitat-based management measures for other nearby seamounts given the
scientific basis for the generalization of marine mammal-seamount
associations, and given evidence that a number of other seamounts
within the HCTT Study Area exhibit levels of productivity capable of
supporting commercial fisheries.
Response: Analysis and consideration of Cross Seamount and ``other
nearby seamounts'' for additional geographic mitigation was provided in
appendix K (Geographic Mitigation Assessment), section K.7.1 (Hawaii
Public Comment Mitigation Area Assessment), including sub-sections
K.7.1.1 (General Biological Assessment of Seamounts in the Hawaii
Portion of the Study Area) and K.7.1.2 (Cross Seamount) of the 2018
HSTT EIS/OEIS.
As discussed in appendix K (Geographic Mitigation Assessment),
section 4.7.1.3 (Mitigation Assessment) of the 2018 HSTT EIS/OEIS,
implementing new geographic mitigation measures in addition to ongoing
procedural mitigation within the vicinity of Cross Seamount would not
be effective at reducing adverse impacts on beaked whales or other
marine mammal populations. The Navy has been training and testing in
the broad ocean area around Cross Seamount with the same basic systems
for over 40 years, and there is no evidence of any adverse impacts to
marine species. Additionally, the suggested mitigation would not be
practicable to implement. The broad ocean area around Cross Seamount
and the seamounts to the north are unique in that there are no similar
broad ocean areas in the vicinity of the Hawaiian Islands that are not
otherwise encumbered by commercial vessel traffic and commercial air
traffic routes. In addition, beaked whales may be more widely
distributed than currently believed. Ongoing passive acoustic efforts
from NMFS and Navy within the Pacific have documented beaked whale
detections at many locations beyond slopes and seamounts to include
areas over abyssal plains (Klinck et al., 2015; Griffiths and Barlow,
2016; Rice et al., 2018).
Comment 45 (ref 65): A commenter stated that NMFS should further
consider implementing mitigation areas off Oahu, Kauai, and Niihau. The
commenter stated that providing mitigation measures for select
activities during even a limited season within some important habitat
areas could have value in reducing cumulative disturbance and stress in
resident populations.
Response: In the 2025 HCTT EIS/OEIS, the Action Proponents
considered the science, the military readiness requirements, and the
effectiveness of identified habitat areas off Oahu, Kauai, and Niihau
as presented in appendix K (Geographic Mitigation Assessment) section
K.3 (Biologically Important Areas within the Hawaii Study Area). This
includes the identified BIAs off Oahu (humpback whale, Blainville's
beaked whale, false killer whale, short-finned pilot whale, pygmy
killer whale, pantropical spotted dolphin, rough-toothed dolphin,
bottlenose dolphin, and spinner dolphin), BIAs off Kauai and Niihau
(humpback whale, short-finned pilot whale, false killer whale, rough-
toothed dolphin, spinner dolphin, and bottlenose dolphin), and BIAs off
Lanai and Molokai (humpback whale, Blainville's beaked whale, goose-
beaked whale, short-finned pilot whale, false killer whale, pygmy
killer whale, pantropical spotted dolphin, rough-toothed dolphin,
bottlenose dolphin and spinner dolphin).
There is no evidence to suggest there have been any population-
level effects in the waters around Oahu, Kauai, Niihau, Lanai, or
Molokai or in the HCTT Study Area resulting from the same training and
testing activities that have been ongoing for decades. In the waters
around Oahu, Kauai, and Niihau, documented long-term residency by
individuals and the existence of multiple small and resident
populations precisely where Navy training and testing have been
occurring for decades suggests a lack of significant impact to those
populations from the continuation of Navy training and testing.
Appendix K of the HCTT EIS/OEIS describes the importance of these areas
for Navy training and testing and why implementation of additional
mitigation areas would be impracticable. As such, NMFS is not requiring
the Action Proponents to implement an additional mitigation area in
this region. Of note, the Navy's monitoring program for Hawaii is
currently exclusively focused on monitoring whale and select dolphin
species off Kauai and Niihau since 2009. In 2025, the Navy will be
adding increased effort for rough-toothed dolphins due to the new BIA
designation (Kratofil et al., 2023).
Comment 46 (ref 59, 60): A commenter recommended that NMFS extend
the reporting period to December 1 through May 1 for the Hawaii
Humpback Whale Special Reporting Mitigation Area. The commenter also
recommended that NMFS require reporting of other sources of MFAS and
LFAS in the mitigation area.
Response: The proposed rule required that the Action Proponents
must report the total hours of MF1 and MF1C surface ship hull-mounted
MFAS used from November through May in the Hawaii Humpback Whale
Special Reporting Mitigation Area in their training and testing
activity reports submitted to NMFS. As such, the proposed time period
already includes that recommended by the commenter, and no change to
the time period is warranted in this final rule. Regarding the
reporting of other sources, MF1 surface ship hull-mounted MFAS was
chosen as the representative source to report because it is a well-
understood source in terms of its effects on marine mammals,
extensively used during training and testing activities, and has not
changed significantly since the initial Navy training and testing ITAs.
For consistency of reporting, retention of MF1 hours as the reporting
metric will allow for clear comparison to past documents. NMFS does not
find it necessary for the Action Proponents to report other forms of
MFAS and LFAS.
Comment 47 (ref 61): A commenter recommended that the Action
Proponents begin issuing awareness notification messages from November
1
[[Page 58835]]
through May 31, overlapping the effective period of the reproductive
BIA for humpback whales (December 1 through May 31), and beginning in
November 1 as initially proposed to support the detection of early
arriving humpback whales to the HRC.
Response: The Action Proponents have indicated that extending the
date range for the Hawaii Humpback Whale Awareness Messages from
November 1 through May 31 is practicable, and as such, NMFS has updated
the required date range for these messages in this final rule.
Comment 48 (ref 28): The Commission recommended that NMFS:
<bullet> Clearly separate its application of the least practicable
adverse impact requirement from its negligible impact determination;
<bullet> 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;
<bullet> 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;
<bullet> 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
<bullet> 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 explain why
NMFS' approach is inadequate or why the commenter's proposed approach
would be better. 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 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 49 (ref 86, 87, 88): A commenter stated that NMFS wholesale
endorses the Action Proponents' decision to reject additional
mitigation measures considered in the 2024 HCTT Draft EIS/OEIS and
provides no independent justification or analysis for its least
practicable adverse impact determination. The commenter stated that
without incorporating a broader suite of mitigation measures,
including, for example, mandatory reduced vessel speeds and updated
geographic mitigation areas based on updated science, the ITRs and LOAs
violate the MMPA's requirement to incorporate mitigation measures that
effectuate the least practicable adverse impact. The commenter further
stated that although NMFS acknowledges the existence of the updated
BIAs (Calambokidis et al., 2024; Harrison et al., 2023; Kratofil et
al., 2023) in its proposed rule, NMFS makes clear that it plans to
adopt the Action Proponents' proposed geographic mitigation areas
without any changes, claiming that it is ``heavily reliant on the
Action Proponents' description of operational practicability.''
The commenter additionally stated that NMFS failed to require the
following additional mitigation measures proposed in its Draft EIS/OEIS
comments:
<bullet> Imposing a 10-kn (18.5 km/hr) ship speed limit in whale
mitigation areas to reduce the risk of vessel strikes;
<bullet> Improving detection of marine mammals using alternative
detection methods including thermal and acoustic methods (Verfuss et
al., 2018);
<bullet> Restricting activities during times of low visibility;
<bullet> Capping the maximum level of activities each year;
<bullet> Avoiding testing and training exercises in key migration
corridors and prime feeding areas;
<bullet> Avoiding testing and training exercises during key feeding
times;
[[Page 58836]]
<bullet> Avoiding testing and training exercises in areas where the
whale presence in the area is ``High'' or ``Very High,'' per WhaleSafe;
[…truncated; see source link]Indexed from Federal Register on December 17, 2025.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.