Federal Register, Volume 91 Issue 143 (Tuesday, July 28, 2026)

[Federal Register Volume 91, Number 143 (Tuesday, July 28, 2026)]
[Rules and Regulations]
[Pages 47664-47711]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-15206]

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Vol. 91

Tuesday,

No. 143

July 28, 2026

Part III

Department of Commerce

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National Oceanic and Atmospheric Administration

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50 CFR Part 218

Takes of Marine Mammals Incidental to Specified Activities; Taking
Marine Mammals Incidental to U.S. Navy Operations of Surveillance Towed
Array Sensor System Low Frequency Active Sonar in the Western and
Central North Pacific Ocean and Eastern Indian Ocean; Final Rule

Federal Register / Vol. 91 , No. 143 / Tuesday, July 28, 2026 / Rules
and Regulations

[[Page 47664]]

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

[Docket No. 260723-0177]
RIN 0648-BN61

Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to U.S. Navy Operations of
Surveillance Towed Array Sensor System Low Frequency Active Sonar in
the Western and Central North Pacific Ocean and Eastern Indian Ocean

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

ACTION: Final rule; notification of issuance of Letter of
Authorization.

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SUMMARY: NMFS, upon request from the U.S. Department of the Navy
(Navy), issues these regulations pursuant to the Marine Mammal
Protection Act (MMPA) to govern the taking of marine mammals incidental
to training and testing activities using Surveillance Towed Array
Sensor System (SURTASS) Low Frequency Active (LFA) sonar systems in the
western and central North Pacific and eastern Indian oceans over the
course of 7 years from August 2026 through August 2033. These
regulations allow for the issuance of a letter of authorization (LOA)
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 Navy's 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 August 12, 2026, through August 11, 2033.

ADDRESSES: A copy of the Navy's Incidental Take Authorization (ITA)
application and supporting documents, as well as a list of the
references cited in this document, may be obtained online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities. In case of problems
accessing these documents, please call the contact listed below (see
FOR FURTHER INFORMATION CONTACT).

FOR FURTHER INFORMATION CONTACT: Alyssa Clevenstine, Office of
Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Purpose and Need for Regulatory Action

These regulations, issued under the authority of the MMPA (16
U.S.C. 1361 et seq.), allow for the authorization of take of marine
mammals incidental to the Navy's training and testing activities (which
qualify as military readiness activities) using SURTASS LFA sonar in
the western and central North Pacific Ocean and eastern Indian Ocean
(see figure 2-1 of this notice and LOA application (hereafter referred
to as the application)). Please see the Legal Authority for the Final
Action section for relevant definitions.

Legal Authority for the Final Action

The MMPA prohibits the ``take'' of marine mammals, with certain
exceptions. Section 101(a)(5)(A) 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 (16 U.S.C. 1362). 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 (16 U.S.C. 1371(a)(5)(F)), and amended the
definition of ``harassment'' in section 3(18)(B) of the MMPA as applied
to a ``military readiness activity'' to read as follows: ``(i) any act
that injures or has the significant potential to injure a marine mammal
or marine mammal stock in the wild [Level A Harassment]; or (ii) any
act that disturbs or is likely to disturb a marine mammal or marine
mammal stock in the wild by causing disruption of natural behavioral
patterns, including, but not limited to, migration, surfacing, nursing,
breeding, feeding, or sheltering, to a point where such behavioral
patterns are abandoned or significantly altered [Level B Harassment]''
(16 U.S.C. 1362(18)(B)). The 2004 NDAA also amended the MMPA to
establish in section 101(a)(5)(A)(iii) that ``[f]or a military
readiness activity . . . , a determination of `least practicable
adverse impact' . . . shall include consideration of personnel safety,
practicality of implementation, and impact on the effectiveness of the
military readiness activity'' (16 U.S.C. 1371(a)(5)(A)(iii)). On August
13, 2018, the 2019 NDAA (Pub. L. 115-232) amended the MMPA to allow
incidental take regulations (ITRs) for military readiness activities to
be issued for up to 7 years (16 U.S.C. 1371(a)(5)(A)(ii)).

Summary of Major Provisions Within the Final Rule

The major provisions of this final rule are:
Take of marine mammals by Level A harassment and Level B
harassment;
Use of visual, passive acoustic, and active acoustic
monitoring mitigation;
Implementation of geographic activity limitations
including within 22 kilometers (km) (12 nautical miles (nmi)) of any
emergent land and in certain offshore areas and times that are
biologically important (i.e., for foraging, migration, reproduction)
for marine mammals;
Implementation of a Notification and Reporting Plan (for
dead, live stranded, or marine mammals struck by any vessel engaged in
military readiness activities); and
Implementation of a robust monitoring plan to improve our
understanding of the environmental effects resulting from the Navy's
training and testing activities.
This rule includes an adaptive management component (i.e., the
authority to modify the LOA's mitigation, monitoring, and reporting

[[Page 47665]]

measures, consistent with the regulations).

Summary of Request

On April 6, 2025, NMFS received an application from the Navy
requesting authorization to take marine mammals, by Level A and Level B
harassment, incidental to training and testing activities
(characterized as military readiness activities) using SURTASS LFA
sonar in the western and central North Pacific Ocean and eastern Indian
Ocean. The Navy requested one 7-year LOA for training and testing
activities. In response to our comments and following an information
exchange, the Navy submitted a revised application, deemed adequate and
complete on July 1, 2025. On July 11, 2025, NMFS published a notice of
receipt (NOR) of application in the Federal Register (90 FR 30877),
requesting comments and information related to the Navy's request.
During the 30-day public comment period, NMFS received one public
comment from Turtle Island Restoration Network requesting that NMFS
deny the Navy's ITA request and consider alternatives that prioritize
avoiding critical habitats, reducing sonar intensity, or limiting
operational time frames. On March 10, 2026, NMFS published a proposed
rule (91 FR 11618) (hereafter proposed rule) and requested comments and
information related to the Navy's 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 using SURTASS LFA sonar. NMFS
published the first rule effective August 15, 2002, through August 15,
2007 (67 FR 46712, July 16, 2002); the second rule effective from
August 16, 2007, through August 15, 2012 (72 FR 46846, August 21,
2007); the third rule effective from August 15, 2012, through August
15, 2017 (77 FR 50290, August 20, 2012); and the fourth rule effective
from August 12, 2019, through August 11, 2026 (84 FR 40132, August 13,
2019). For the period August 16, 2017, through August 11, 2019, all
military readiness activities that use SURTASS LFA sonar were exempted
from compliance with the requirements of the MMPA under a National
Defense Exemption invoked by the Secretary of War \1\ under MMPA
section 101(a)(5)(f). For this rulemaking, the Navy plans to conduct
substantially similar training and testing activities using SURTASS LFA
sonar that were conducted under previous rules.
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\1\ Pursuant to Executive Order 14347, ``Restoring the United
States Department of War,'' (90 FR 43893), as of September 5, 2025,
the ``Secretary of Defense'' is authorized to use the additional
secondary title of ``Secretary of War.''
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The Navy's application reflects the most up-to-date compilation of
training and testing activities deemed necessary to accomplish military
readiness requirements. The types and numbers of activities included in
this rule account for interannual variability in training and testing
to meet evolving or emergent military readiness requirements. In this
rule, we have undertaken a comprehensive assessment of the impacts of
all SURTASS LFA sonar training and testing activities on marine mammals
likely to be present within the entire range of the Study Area.

Description of Specified Activity

The Navy requested authorization to take marine mammals incidental
to conducting military readiness activities. The Navy has determined
that acoustic stressors are likely to result in take of marine mammals
in the form of Level A and Level B harassment. Descriptions of these
activities are provided in the Navy's application (https://www.fisheries.noaa.gov/action/incidental-take-authorization-united-states-navys-surveillance-towed-array-sensor-system-low), with
additional detail provided in chapter 2 and appendix F of the 2026
SURTASS Supplemental Environmental Impact Statement/Overseas
Environmental Impact Statement (2026 SURTASS SEIS/OEIS) (https://www.nepa.navy.mil/surtass-lfa/).
The SURTASS LFA sonar transmission hours, which are classified as
military readiness activities pursuant to the section 315(f) of Public
Law 101-314 (16 U.S.C. 703), represent a distribution across three
activities that include:
Training (i.e., contractor crew proficiency training,
military crew proficiency training, active training);
Maintenance and upgrade (i.e., equipment maintenance
checks and performance evaluations, LFA/CLFA maintenance/performance
testing, and other maintenance/testing); and
Exercises (e.g., Valiant Shield, Rim of the Pacific
(RIMPAC)).
A detailed description of the specified activities was provided in
the proposed rule. NMFS hereby refers to the information and analysis
provided in the proposed rule which continue to apply to this final
rule. Since that time, no changes have been made to the planned
activities. Therefore, a detailed description is not provided here.
Please refer to the proposed rule for the complete description of the
specified activities.

Comments and Responses

We published a proposed rule in the Federal Register on March 10,
2026 (91 FR 11618), 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 seven comments. Of this total, one
submission was from Lincoln Land Community Partners, and the remaining
comments were from private citizens. NMFS has reviewed and considered
all relevant public comments received on the proposed rule and issuance
of the LOA. All substantive, relevant comments and our responses are
described below.
Comment 1: Lincoln Land Community Partners object to the rule under
three general categories: (1) absence of lawful authority; (2) risks of
harm to marine life; and (3) moral and ethical implications. As to the
first category, the commenter asserts that: (1) the rule violates
Article I Section 8 of the Constitution, which grants Congress to make
Rules for the Government and Regulation of the land and naval Forces,
because the rule impermissibly delegates that authority to the Navy to
regulate itself, or to a ``secondary agency'' (i.e., NMFS) to authorize
exceptions to the ``laws of nations''; (2) the rule violates Article I
Section 8, which grants Congress the power to ``define and punish [. .
.] Offences against the Law of Nations'' because SURTASS LFA sonar
activity inflicts auditory trauma and permanent injury on marine life,
a violation of the ``laws of nations'' and moral standards Congress is
sworn to uphold; (3) Navy and NMFS are attempting to bypass the ``Two-
Year Appropriation limit'' on raising and supporting Armies and the
duty to provide and maintain a Navy, which requires active governance
and frequent and direct congressional oversight of the Navy, through a
7-year authorization for SURTASS LFA sonar activities; (4) the rule
hides behind a department or agency, removing executive accountability
of the President as the Commander in Chief and insulating the President
from the moral and legal consequences of a direct command that harms
marine life; and (5) the Navy is instigating the very

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conflicts it seeks to prevent by conducting testing and readiness
activities in the backyards of other nations, and absent consent of the
people to use power to harm wildlife, Navy should instead protect
people, land, waters, and wildlife by demonstrating equality, respect,
and courtesy.
Regarding risk of harm to marine life category, the commenter
expresses concern over: (1) the ``massive'' geographic scope of the
rule in the western and central North Pacific Ocean and eastern Indian
Ocean, with mobile sources moving through migratory corridors and
feeding grounds; (2) the potential for physical and auditory damage
(Level A harassment) to affect animals that rely on echolocation and
cause physical trauma to ears; (3) the potential for Level B harassment
that can lead to separation of mothers and calves, cessation of
feeding, and strandings; (4) the vast distances that LFA sonar can
travel, reducing the ``quiet world these animals need to survive''; (5)
the 7-year duration of the activity, representing a sustained increase
in ``acoustic stress'' for marine populations on top of climate change,
vessel strikes, and plastic pollution; (6) the adaptive management
component as being reactive rather than proactive; and (7) the impacts
on endangered and threatened species.
In the third category, the commenter asserts there are moral and
ethical implications to the Navy's and NMFS' actions, stating that: (1)
governments have a heightened duty of stewardship to animals that
cannot consent to be governed; (2) the Navy is affecting the
``livelihoods and the liberty of citizens'' by bypassing their vote
through a closed bureaucratic loop that overlooks the impact on
national waters and all living things; (3) the LFA sonar testing and
training is an escalation rather than true military readiness, which
prevents and diffuses tension; and (4) the negligible impact standard
ignores the unintended unforeseen consequences of disrupting marine
consciousness.
Response: The comment from Lincoln Land Community Partners raises a
number of constitutional and legal assertions but does not provide
supporting authority and, in several respects, reflects a
misunderstanding of the provisions cited. We disagree with the
commenter's basic points as follows. We do not agree that our rule is
an improper delegation of Congress's authority. Through the MMPA,
Congress prohibited the take of marine mammals by any person, vessel,
or other conveyance subject to the jurisdiction of the United States,
including by government entities such as the Navy, except under certain
enumerated circumstances. Under section 101(a)(5)(A), Congress has
delegated to NMFS (through the Secretary of Commerce) authority to
allow the take of marine mammals incidental to a specified activity,
provided that we make certain findings and issue regulations after
notice and comment. Importantly, the statute lays out several
intelligible principles that guide and limit our exercise of discretion
(see FCC v. Consumers' Research, 606 U.S. 656, 673-675 (2025)
(discussing intelligible principle standard for delegation)). This
includes the requirement that we find the total taking for the period
in question will have a negligible impact on the affected species or
stocks of marine mammals, and that we must prescribe measures to effect
the least practicable adverse impact on the species or stocks and their
habitats as well as monitoring and reporting requirements. Likewise,
Congress through the MMPA exercised its judgment as to the appropriate
balance between the conduct of human activities, including military
readiness activities, in waters under the jurisdiction of the United
States and the impact of those activities on marine mammals. Further,
we do not agree that the Law of Nations or international law (see
Jesner v. Arab Bank, PLC, 584 U.S. 241 (2018) (discussing Law of
Nations as international law)) is implicated by our administration of
the MMPA. We disagree that the 7-year incidental take rule undermines
Congress's appropriations cycles for funding or oversight of the Navy
or removes any accountability by the Commander in Chief; in fact, the
rule demonstrates the Navy's compliance with applicable law. Finally,
we decline to address the comment regarding the wisdom of the Navy's
military readiness training and testing because it is outside the scope
of NMFS' statutory purview.
Regarding adaptive management, this final rule includes the
potential for proactive modifications, as appropriate. Regarding the
stated objection to the rulemaking based on risk of harm to marine
life, as stated in the Legal Authority for the Final Action section,
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). NMFS has made the required findings, and therefore,
has appropriately authorized take, by Level A and Level B harassment,
incidental to the Navy's SURTASS LFA sonar activities.
As stated by the commenter, the Navy's SURTASS LFA sonar activities
will occur over a broad geographic region, including in or near areas
that are known to be important for marine mammals; however, the
activity includes a limited maximum annual number of hours of sonar
spread across four vessels and a large geographic area, and the
training and testing occurs far from shore (>22 km) and outside of
known areas of concentration of LFA sonar-sensitive species (OBIAs).
Over the last 25 years, there has been no scientific evidence that
SURTASS LFA sonar has led to chronic stress or population-level impacts
to any species of marine mammals. The concentration of sound in the
same location would be limited, and the effects to specific regional
populations would be temporary and transitory. NMFS fully analyzed and
considered the potential effects from the Navy's specified activities
and has applied a reasoned and comprehensive approach to evaluating the
effects of these activities on marine mammal species and their habitat.
This analysis is detailed in the Preliminary Analysis and Negligible
Impact Determination section of the proposed rule and in the Analysis
and Negligible Impact Determination section herein. The commenter
offers no recommendations for NMFS to consider and no information that
would help inform NMFS' analysis of the Navy's activities and our
determination.
Finally, NMFS acknowledges the commenter's broad moral and ethical
concerns. However, the MMPA and other applicable laws reflect policy
judgments made through the legislative process regarding conservation
and protection of marine mammals and direct NMFS to evaluate specific
statutory factors, which do not include independent consideration of
generalized moral or ethical principles. Beyond that, the Navy's
actions are outside the scope of NMFS' purview.
Comment 2: A commenter recommended that NMFS take into
consideration the following four impacts to marine mammals: (1)
behavioral disruption; (2) physiological stress and distress on growing
mammals; (3) informational and auditory masking; and (4) risk of death
and stranding.
Response: NMFS concurs with the commenter's recommendation and took
all of the impacts raised by the commenter into consideration in
promulgation of its proposed rule and this final rule, as seemingly
referenced

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in the comment. The Potential Effects of Specified Activities on Marine
Mammals and Their Habitat section of the proposed rule described, in
detail, potential behavioral disruption, physiological stress and
distress (including on young, growing animals), informational and
auditory masking, as well as stranding and mortality.
Comment 3: A commenter recommended that NMFS require the Navy to
shut down activity upon a confirmed marine mammal detection within
2,000 yards (yd) (1.8 km) of the source. The commenter states that
resumption should occur only after 15 minutes without visual or
acoustic detections and after Passive Acoustic Monitoring (PAM) metrics
indicate detections are below the operational threshold and recommends
that NMFS include criteria in the regulatory text.
The commenter stated NMFS should require all protected species
observers (PSOs) and PAM operators to be independent, third-party
personnel and that PAM data should be accessible to NMFS in near-real-
time. The commenter stated that PAM should operate continuously during
transmissions, with minimum specifications identified explicitly in a
monitoring plan.
Response: The proposed rule and this final rule include a
mitigation and monitoring requirement consistent with that recommended
in the comment, including in the regulatory text. The rule requires the
Navy to begin PAM 30 minutes before the SURTASS LFA sonar begins to
transmit and continue until 15 minutes after SURTASS LFA sonar
transmissions cease. The rule further requires that if a marine mammal
is detected during visual or acoustic monitoring, within or about to
enter within 1.8 km of the SURTASS LFA source (i.e., the LFA mitigation
zone), the Navy must immediately delay or suspend SURTASS LFA sonar
transmissions. The Navy must not recommence SURTASS LFA sonar
transmissions until 15 minutes after all marine mammals have left the
area of the LFA sonar mitigation zone and there is no further detection
of any marine mammal within the 1.8 km LFA sonar mitigation zone as
determined by the visual, passive acoustic, and active acoustic high
frequency monitoring.
Regarding PSOs and PAM operators, the availability and deployment
feasibility of independent, third-party personnel is often limited by
factors such as cost, logistics, safety, security, and operational
constraints. As such, this rule requires the use of trained Lookouts to
conduct visual monitoring for marine mammals. A marine mammal biologist
qualified in conducting at-sea visual monitoring of marine mammals from
surface vessels will train and qualify designated personnel aboard the
Auxiliary General Ocean Surveillance (T-AGOS) vessels to conduct at-sea
visual monitoring for marine mammals and sea turtles. Training of the
civilian ship personnel will include effective and swift communication
within the observer's command structure to facilitate quick execution
of protective measures if marine mammals or other marine species are
observed at the sea surface. In addition, the Navy routinely conducts
training of the military crews stationed aboard T-AGOS vessels to
augment their sonar detection capabilities. Further, senior marine
acousticians and a senior marine biologist conduct passive acoustic
training of the military crews to increase their ability as sonar
operators to distinguish biological sounds from those of mission-
directed sounds.
Regarding the recommendation that PAM data be accessible to NMFS in
near-real-time, security and practicability concerns prevent such
accessibility. There are two sources of PAM data collected by the Navy.
One source is from detections from seafloor-mounted Navy hydrophones at
key locations in the Atlantic and Pacific oceans and the other is PAM
data collected by T-AGOS vessels. The Annual Pacific SURTASS LFA Study
Area Marine Species Monitoring Report provides detections and other
analysis from both ship-based SURTASS LFA sonar and seafloor-mounted
sensors. Given the sensitive nature of the material, it is controlled
unclassified information and may be reviewed by only Navy and NMFS. The
classified Annual Pacific SURTASS LFA Training and Testing Report
contains the quantity of usage from only ship-based SURTASS LFA sonar.
These data are highly classified because public release would
compromise national security by revealing sensor and other operational
capabilities. Further, while the commenter asserts that providing NMFS
with near-real-time access to PAM data would strengthen adaptive
management, the commenter did not recommend how NMFS would apply such
data. The real-time PAM data allows Navy personnel to respond promptly
to potential marine mammal presence and implement mitigation measures
when necessary. Finally, regarding the recommendation that minimum PAM
operating specifications be identified explicitly in a monitoring plan,
additional details on system performance and calibration are
classified.
Comment 4: A commenter stated PAM performance should be defined in
measurable terms, including detection probability by range and species,
false-positive/false-negative rates, and minimum signal-to-noise ratio
thresholds, and that routine calibration tests and quality assurance/
quality control (QA/QC) procedures should be included in monitoring
reports. In a related comment, a commenter stated that if the Navy's
request for an ITA is granted, it is imperative that the monitoring
systems used by the Navy for marine life are functional and up-to-date
on maintenance, adhering to specific ``PMCS'' procedures.
Response: As stated in response to Comment 3, additional details on
PAM system performance and calibration are classified. Therefore, Navy
cannot define PAM performance QA/QC procedures in monitoring reports,
as recommended by the commenter.
NMFS concurs with the commenter's recommendation that Navy's
monitoring systems should be functional and up-to-date. The commenter
does not define PMCS, but NMFS presumes the commenter is referring to
the common military term ``Preventative Maintenance Checks and
Services.'' Since 1963, all Navy assets, equipment, and sensors fall
under a Maintenance and Material Management (3M) System, which ensures
correct periodic maintenance is performed at the most appropriate
interval for each item. The 3M program would also apply to the SURTASS
equipment (cables, sensors, software, etc.). This program includes
daily through quarterly equipment maintenance procedures. In addition,
there are longer in-port maintenance periods for updates, major
repairs, and additional calibration. This is standard for the Navy for
all equipment.
Comment 5: A commenter stated that NMFS should require standardized
monitoring reports within 90 days of mission completion and raw PAM and
observer data archived to NOAA's designated repository within 6 months.
The commenter asserted that redactions should be limited to security
concerns and subject to NMFS review.
Response: In order to issue an ITA for an activity, section
101(a)(5)(A) of the MMPA states that NMFS must set forth requirements
pertaining to the monitoring and reporting of such taking. Effective
reporting is critical for both monitoring compliance as well as
ensuring that the most value is obtained from the required monitoring.
The proposed rule and this final rule include requirements to submit
Annual Study Area Marine Species Monitoring Reports and Annual SURTASS
LFA Training and Testing Reports, and to notify NMFS of injured, live
stranded,

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or dead marine mammals. Data collection for the Annual Study Area
Marine Species Monitoring Reports must adhere to methods that allow for
comparison to other range complexes and Study Areas in different
geographic regions, which appears consistent with the commenter's
recommendation that NMFS require ``standardized'' reports. While the
proposed rule did not explicitly state a due date for these reports,
the LOA requires that the annual report must be submitted to NMFS
annually within 3 months of the 1-year anniversary of the date of the
issuance of the LOA, as recommended by the commenter, and consistent
with the requirements for other Navy training and testing study areas.
The unclassified report will not include information that could pose a
security risk, though, if warranted, NMFS staff with the appropriate
security clearance may review such material.
NMFS is not requiring the Navy to submit raw PAM and observer data
to a designated NOAA repository within 6 months, and the commenter's
recommendation does not state why such a requirement is necessary. All
information and data under the SURTASS monitoring program are highly
classified and stored at secure Navy shore facilities or on-ship.
Public release of SURTASS data would compromise national security by
revealing sensor and other operational capabilities.
Comment 6: A commenter stated NMFS should specify corrective
actions for monitoring failures, and cites independent audits,
temporary suspension of transmissions, and LOA modification as
examples. The commenter states that these corrective actions would
ensure the LOA holder retains responsibility for mitigation and
monitoring and should include contract language ensuring subcontractors
adhere to all conditions.
Response: NMFS appreciates the commenter's concern for appropriate
implementation of mitigation and monitoring measures for this activity
and partially concurs with the recommendations. The Navy is responsible
for complying with the regulations and LOA. The regulations state that
the Navy is authorized to take marine mammals only if ``the activity is
in compliance with all terms, conditions, and requirements of [the
regulations] and the applicable LOA'' (50 CFR 218.232(a)). This
includes mitigation and monitoring requirements as well as reporting to
NMFS. Should the Navy subcontract any work conducted under the LOA, it
is responsible for ensuring that such contractors adhere to all
requirements. As such, NMFS declines to include contract language in
its regulations or LOA.
It is unclear what the commenter means by monitoring failures or
what the commenter recommends regarding independent audits and what
such audits would entail. However, the regulations include a provision
stating that under certain circumstances, at the request of the Navy or
NMFS' own initiative, NMFS may modify the mitigation, monitoring, or
reporting measures in an LOA, consistent with the measures in the
regulations.
In some cases, NMFS may advise the Navy of the need to implement
shutdown procedures for all permitted active acoustic sources within 50
km (27 nmi) of a stranding or near-shore atypical milling event, as
outlined in the Notification and Reporting Plan. Following this initial
shutdown, NMFS would communicate with the Navy to determine if
circumstances support any modification of the shutdown zone. The Navy
may decline to implement all or part of the shutdown if the holder of
the LOA, or his/her designee, determines that continuation of the
military readiness activities is necessary for national security.
However, these shutdowns are not tied to ``monitoring failures'' cited
by the commenter, and it is unclear from the comment what such
monitoring failures would entail.
Comment 7: A commenter recommended that NMFS include numeric
triggers for adaptive management, such as takes exceeding 10 percent of
modeled annual takes for any stock or three confirmed detections within
an Offshore Biologically Important Area (OBIA) during a closed season.
If a trigger is met, the commenter stated that transmissions should be
suspended, followed by a technical review within 30 days and public
reporting of required mitigation changes. According to the commenter, a
10 percent exceedance threshold would function as an early-warning
indicator that modeled assumptions may be diverging from observed
conditions. The commenter further asserted that multiple confirmed
detections in a closed OBIA indicate elevated risk and warrant
immediate review.
Response: NMFS disagrees with the recommended concept (i.e., that
there should be a ``trigger'' based on detections within an OBIA).
OBIAs by definition are areas known to have biological importance to
the relevant species for which they are identified. As such, three
detections of a given species would not indicate unanticipated impacts.
Moreover, the Navy did not propose to conduct, nor is NMFS requiring,
continuous monitoring for marine mammals in the OBIAs, such that marine
mammal detections independent of SURTASS LFA sonar would occur
(although PAM during SURTASS LFA sonar activities may detect marine
mammals within OBIAs during the effective period). Mitigation for OBIAs
requires that the received level of SURTASS LFA sonar transmissions not
exceed 180 decibels referenced to 1 microPascal (dB re 1 [mu]Pa) root-
mean-square (RMS) sound pressure level (SPL) at a distance of 1 km
seaward of the outer perimeter of any OBIA in the Study Area during the
effective period specified (table 11). Further, no more than 25 percent
of the sound source amount analyzed (i.e., no more than 275 hours in a
given year) of SURTASS LFA sonar for training and testing will be used
within 18.5 km of any single OBIA during any year, unless national
security presents such a requirement (see table 12). NMFS has not
adopted the quantitative triggers recommended by the commenter. Rather
than apply a single generic numeric trigger (e.g., 10 percent) as an
indication that modeled assumptions may be diverging from observed
conditions without regard to the species or stock, as suggested by the
commenter, NMFS will consider situation-specific circumstances in
determining whether an LOA needs to be modified.
Comment 8: A commenter recommended that NMFS disclose spatial
density inputs, model descriptions, and uncertainty metrics used in
take estimation to strengthen the administrative record supporting
negligible impact and small numbers determinations. If full public
release is prohibited for security reasons, the commenter recommends
that NMFS provide redacted spatial products and sensitivity analyses
including conservative upper-bound scenarios.
Response: NMFS provided a description of the model and density
inputs, including uncertainty, in the Navy Acoustics Effects Model
section and the Marine Mammal Density section, respectively, of the
proposed rule. These analyses are further described in the ``U.S. Navy
Marine Species Density Database for the Surveillance Towed Array Sensor
System (SURTASS) Low Frequency Active (LFA) Sonar Systems'' (U.S.
Department of the Navy, 2024a), hereafter referred to as the Density
Technical Report, and the ``Quantifying Acoustic Impacts on Marine
Mammals and Sea Turtles: Methods and Analytical Approach for Phase IV
Training and Testing'' (U.S. Department

[[Page 47669]]

of the Navy, 2024b), hereafter referred to as the Acoustic Impacts
Technical Report.
As explained earlier in the Legal Authority for the Final Action
section, the 2004 NDAA (Pub. L. 108-136) amended section 101(a)(5) of
the MMPA to remove the ``small numbers'' provisions (16 U.S.C.
1371(a)(5)(F)). As such, this rule does not include a small numbers
determination.
Comment 9: A commenter stated that NMFS should clearly articulate
the biological basis for its negligible impact determinations for each
affected stock, including an explanation of how modeled take estimates
compare to stock abundance, potential biological removal (PBR), and the
uncertainty ranges reported in the most recent Stock Assessment Reports
(SARs). The commenter also stated that NMFS should describe how
uncertainty in density estimates, detection probabilities, and
behavioral response assumptions is incorporated into the negligible
impact analysis.
Response: The Preliminary Analysis and Negligible Impact
Determination section of the proposed rule and the Analysis and
Negligible Impact Determination section of this final rule describe our
analysis and determination for the affected species and stocks of
marine mammals. NMFS has relied on the best available scientific
information in its negligible impact analyses and determinations to
evaluate the impacts of the taking from the specified activity.
Although some amount of uncertainty is inherent, we believe the
information available is sufficient to enable us to make the required
findings.
Table 13 of this rule includes a column that indicates the maximum
annual instances of take as a percentage of stock abundance, where
available, consistent with the commenter's recommendation. Regarding
how modeled take estimates compare to PBR, no serious injury or
mortality is anticipated or authorized here. PBR and annual mortality
and serious injury (M/SI) from anthropogenic sources were included in
table 1 of the proposed rule and this final rule as gross indicators of
the status of the species or stocks and other threats.
The commenter appears to recommend that NMFS consider the
uncertainty associated with the SARs, presumably using the coefficient
of variation provided for abundance estimates in the SARs; however, the
commenter has not recommended how NMFS should utilize that information.
Similarly, the commenter did not provide specific recommendations for
how it suggests NMFS consider uncertainty in the density estimates and
behavioral response assumptions. NMFS acknowledges that there is
uncertainty associated with data in the SARs, density estimates, and
behavioral response functions. However, NMFS is required to use the
best available science in its analyses as it has done herein, which has
enabled us to make the required findings.
For additional information about the behavioral response functions
and underlying assumptions, please see the Navy's ``Criteria and
Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase
4)'' (U.S. Department of the Navy, 2025), hereafter referred to as the
Criteria and Thresholds Technical Report. The ``U.S. Navy Marine
Species Density Database for the Surveillance Towed Array Sensor System
(SURTASS) Low Frequency Active (LFA) Sonar Systems'' technical report
(U.S. Department of the Navy, 2024), hereafter referred to as the
Density Technical Report, includes additional information about the
marine mammal densities relied upon including associated uncertainty.
Regarding detection probabilities, NMFS' negligible impact
determination is based upon the anticipated impacts to marine mammals
from the specified activity. NMFS appropriately analyzed the model-
predicted take estimates, without any reductions due to activity-based
mitigation. As such, while NMFS qualitatively considers that activity-
based mitigation is expected to further reduce higher-level impacts
(for example, past results of the HF/M3 system tests provide
confirmation that the system has a demonstrated probability of single-
ping detection of 95 percent or greater for single marine mammals that
are 10 m in length or larger, and a probability approaching 100 percent
for multiple pings of any sized marine mammal (see chapter 4 of the
2026 SURTASS SEIS/OEIS)), the negligible impact determination is not
dependent upon a reduction of impacts from activity-based mitigation,
and detection probability does not affect the determination. While the
take estimation process does incorporate geographic mitigation, the
effectiveness of such mitigation does not rely on marine mammal
detection, as these measures will be implemented regardless of marine
mammal occurrence or detection. Therefore, detection probability is not
discussed in the negligible impact analysis.
Comment 10: A commenter indicated NMFS should describe the process
it uses to evaluate inputs that are considered classified by the Navy
and stated NMFS should ensure that the public administrative record
remains sufficient for meaningful review, including a summary of the
types of information withheld, the criteria NMFS applies when reviewing
classified material, and how NMFS ensures that key assumptions,
uncertainty ranges, and model outputs are adequately documented in the
public record.
Response: The exact sonar source levels, operational frequencies,
acoustic properties, and capabilities of SURTASS LFA sonar are
classified and cannot be shared with the public; however, the Navy uses
standardized unclassified nomenclature to assist with scientific review
and validation, to include analysis of assumptions, model outputs, and
uncertainties. Unclassified, general information about U.S. Navy sonar
is available at https://www.nepa.navy.mil/sots/at-sea/us-navy-sonar/.
Additionally, publicly releasable information on criteria development,
density derivation, and the Navy Acoustic Effects Model (NAEMO) is
available on the Navy's SURTASS LFA website at https://www.nepa.navy.mil/surtass-lfa/.
Comment 11: A commenter stated that NMFS should clearly describe
how cumulative effects were evaluated in the negligible impact
determination because SURTASS LFA sonar occurs alongside other Navy
training and testing activities, vessel traffic, and additional
incidental take authorizations.
Response: The MMPA requires that NMFS issue an ITA, provided the
necessary findings are made for the specified activity put forth in the
application and appropriate mitigation, monitoring, and reporting
measures are set forth, as described in the Legal Authority for the
Final Action section. As described in the proposed rule and this final
rule, the preamble for NMFS' implementing regulations under section
101(a)(5) (54 FR 40338, September 29, 1989) explains 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 unusual mortality events (UMEs)). See the Analysis and
Negligible Impact Determination section.
The cumulative effects of the incremental impact of the proposed
action when added to other past,

[[Page 47670]]

present, and reasonably foreseeable future actions (as well as the
effects of ocean pollution and ecosystem alteration trends) were
evaluated against the appropriate resources and regulatory baselines
under NEPA in the Navy's 2026 SURTASS SEIS/OEIS (see table 3-14). The
best available science and a comprehensive review of past, present, and
reasonably foreseeable actions (including maritime traffic, commercial
fishing, 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 3 of
the 2026 SURTASS SEIS/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 Study Area that might impact migratory or wide-ranging animals), as
reflected in the resource-specific discussions in chapter 3 (Affected
Environment, Environmental Consequences) of the 2026 SURTASS SEIS/OEIS.
The 2026 SURTASS SEIS/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 2026
SURTASS SEIS/OEIS.
Cumulative effects on ESA-listed species from 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 Status of the Species for
Further Analysis and Environmental Baseline sections of the biological
opinion (sections 4.2 and 5, respectively).

Changes From the Proposed Rule to the Final Rule

Relative to the proposed rule, this final rule includes new
geographic mitigation measures and modifications to existing geographic
measures added as a result of coordination between NMFS and the Navy.
The Navy has agreed that all of the following modifications and
additions to geographic mitigations are practicable:
OBIA #28 (Mariana Islands) is now effective from December
through May (previously February through April);
OBIA #33 (Southeast Kamchatka) is now effective year-round
(previously June through September) and has been spatially expanded
northward along the eastern side of the Kamchatka Peninsula to meet the
northern boundary of the Study Area;
OBIA #37 (Southern Bali) is now effective August through
November (previously October through November) and has been spatially
expanded to minimize impacts to pygmy blue whales participating in
reproductive and foraging activities in this area; and
OBIA #44 (Southeast Kamchatka Offshore) is a new OBIA for
North Pacific right whales (NPRW) offshore of Southeast Kamchatka,
effective from April through October;
Additionally, this final rule corrects errors in the effective
period of two OBIAs, making them consistent with the periods identified
in the 2026 SURTASS SEIS/OEIS: OBIA #42 (South of Java Island) is
effective from May through November and OBIA #43 (South of Lombok
Sumbawa Islands) is effective May through November (not October through
November as stated in the Geographic Mitigation section of the proposed
rule).
This final rule also includes revised language regarding adaptive
management to streamline the regulatory text and better reflect the
potential for modifications to the LOA. This final rule clarifies that,
at the request of the Navy or on NMFS' own initiative, NMFS may modify
the mitigation, monitoring, or reporting measures in an LOA, consistent
with the measures in the regulations, if: (1) the anticipated effects
of the modified measure are the same as those described and analyzed
for this subpart; (2) the modified measure has a reasonable likelihood
of effectiveness; (3) NMFS determines the modified measure does not
change the findings made for this subpart; and (4) Navy concurs with
the modified measure and that, where applicable, it meets the Navy's
practicability standards in the context of personnel safety,
practicality of implementation, and impacts on the effectiveness of the
Navy's military readiness activities.
Finally, this final rule does not include take of the Beringia
Distinct Population Segment (DPS) of bearded seals (Erignathus
barbatus) as a result of consultation with NMFS Endangered Species
Division. The proposed rule included take, by Level B harassment, of
one bearded seal annually and across the 7-year period of the LOA.
While the range of this DPS occurs primarily outside of the Study Area,
occasional sightings of vagrants within the Study Area have been
reported in nearshore areas around Kamchatka, the Sea of Japan, and
Tokyo Bay (Naito, 1979). Bearded seals inhabit shallow continental
shelf waters that are restricted to seasonal sea ice, and this species
is typically found in extremely low densities close to the shoreline;
therefore, any adverse effects from SURTASS LFA sonar are unlikely due
to the implementation of a Coastal Standoff Range (CSR) of 22 km from
any emergent land, including offshore islands. Based on the best
available information on this species' distribution and abundance, take
of bearded seals (Beringia DPS) is neither anticipated nor authorized
incidental to SURTASS LFA sonar activities in the Study Area.

Description of Marine Mammals and Their Habitat in the Area of
Specified Activities

Marine mammal species and their associated stocks that have the
potential to occur in the Study Area are presented in table 1 along
with each stock's ESA and MMPA status, abundance estimate and
associated coefficient of variation (CV) value, minimum abundance
estimate, PBR, annual M/SI, as applicable, and potential occurrence in
the Study Area. The Navy anticipates take of 43 species by Level B
harassment and, for a subset of those species (9 species), Level A
harassment, incidental to the use of SURTASS LFA sonar in the Study
Area. Of note, based on improvements to the Navy's density research
since the 2019 SURTASS LFA Final Rule (84 FR 40132, August 13, 2019),
seven additional species were modeled for this rulemaking. Of those
seven, the Navy's application includes estimated take of four species
from the proposed activity that were not included in the 2019 final
rule: (1) bearded seal; (2) ringed seal; (3) harbor seal; and (4)
Steller sea lion. Multiple stocks of some species are affected, and
independent assessments are conducted to make the necessary findings
and determinations for each of these.
There are 34 stocks under NMFS' jurisdiction with confirmed or
possible occurrence in the Study Area, of which 11 are listed as
endangered or threatened under the ESA (including bearded seal, of
which take is neither anticipated nor authorized, as discussed in the
Changes from the Proposed Rule to the Final Rule section) (16 U.S.C.
1531 et seq.). Currently, the false killer whale (Main Hawaiian Islands
Insular DPS) and Hawaiian monk seal have critical habitat designated
under the

[[Page 47671]]

ESA in the Study Area (see Critical Habitat section below). The
remaining species in the Central and Western Pacific and Eastern Indian
Oceans have no stock designation (NSD) under the MMPA.
The proposed rule included additional information about the species
in this final rule, marine mammal species for which take is not
authorized, marine mammal species which could occur in the area but are
not managed by NMFS, marine mammal hearing, and National Marine
Sanctuaries, all of which remains valid and applicable but has not been
reprinted in this final rule. NMFS hereby refers to the information and
analysis provided in the proposed rule, which continue to apply to this
final rule.
Further, as discussed in the Changes from the Proposed Rule to the
Final Rule section, this final rule does not include take of bearded
seals (Beringia DPS). The proposed rule included take, by Level B
harassment, of one bearded seal annually and across the 7-year period
of the LOA. While the range of this DPS occurs primarily outside of the
Study Area, occasional sightings of vagrants within the Study Area have
been reported in nearshore areas around Kamchatka, the Sea of Japan,
and Tokyo Bay (Naito, 1979). Bearded seals inhabit shallow continental
shelf waters that are restricted to seasonal sea ice, and this species
is typically found in extremely low densities close to the shoreline
and, therefore, any adverse effects from SURTASS LFA sonar are unlikely
due to the implementation of a CSR. Based on the best available
information on this species' distribution and abundance, take of
bearded seals (Beringia DPS) is neither anticipated nor authorized
incidental to SURTASS LFA sonar activities in the Study Area and, as
such, bearded seals are not discussed further.
Information on the status and trends, distribution and habitat
preferences, and behavior and life history of the potentially affected
species may be found in sections 3 and 4 and appendix A (Marine Mammal
Species Supplemental Information) of the application. NMFS reviewed
this information and found it to be accurate and complete. Additional
information on the general biology and ecology of marine mammals is
included in the 2026 SURTASS SEIS/OEIS. Table 1 incorporates the best
available science, including data from the 2024 Pacific and Alaska
Marine Mammal SARs (Carretta et al., 2026; Young et al., 2026) (see
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments) as well as monitoring data from the
Navy's marine mammal research efforts. NMFS has also reviewed new
scientific literature since publication of the proposed rule and
determined that none of these nor any other new information available
changes our determination of which species have the potential to be
affected by the Navy's activities or the information pertinent to
status, distribution, abundance, population trends, habitat, or ecology
of the species in this final rulemaking.

Table 1--Marine Mammal Occurrence Within the Pacific SURTASS LFA Sonar Study Area \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
ESA/MMPA Stock abundance
status; (CV, Nmin, most
Common name Scientific name Stock Strategic (Y/N) recent abundance PBR Annual M/SI \4\
\2\ survey) \3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Artiodactyla--Cetacea--Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Balaenidae:
North Pacific right whale... Eubalaena japonica. NSD................ E, N/A, N/A ................... UNK............... UNK.
Family Balaenopteridae
(rorquals):
Blue whale.................. Balaenoptera NSD................ E, N/A, N/A ................... UNK............... UNK.
musculus.
Blue whale.................. Balaenoptera Central North E, D, Y 133 (1.09, 63, 0.1............... 0.
musculus. Pacific. 2010).
Bryde's whale............... Balaenoptera edeni. NSD................ , N/A, N/A ................... UNK............... UNK.
Bryde's whale............... Balaenoptera edeni. Hawaii............. , -, N 791 (0.29, 623, 6.2............... 0.
2020).
Fin whale................... Balaenoptera NSD................ E, N/A, N/A ................... UNK............... UNK.
physalus.
Fin whale................... Balaenoptera Hawaii............. E, D, Y 203 (0.99, 101, 0.2............... 0.
physalus. 2017).
Humpback whale.............. Megaptera NSD................ \5\, N/A, N/A ................... UNK............... UNK.
novaeangliae.
Humpback whale.............. Megaptera Hawaii............. , -, N 11,278 (0.56, 127............... 27.09.
novaeangliae. 7,265, 2020).
Humpback whale.............. Megaptera Western North E, D, Y 1,084 (0.088, 3.4............... 5.82.
novaeangliae. Pacific. 1,007, 2006).
Antarctic minke whale....... Balaenoptera NSD................ , N/A, N/A ................... UNK............... UNK.
bonaerensis.
Minke whale................. Balaenoptera NSD................ , N/A, N/A ................... UNK............... UNK.
acutorostrata.
Minke whale................. Balaenoptera Hawaii............. , -, N 438 (1.05, 212, 2.1............... 0.
acutorostrata. 2017).
Omura's whale............... Balaenoptera omurai NSD................ , N/A, N/A ................... UNK............... UNK.
Sei whale................... Balaenoptera NSD................ E, N/A, N/A ................... UNK............... UNK.
borealis.
Sei whale................... Balaenoptera Hawaii............. E, D, Y 391 (0.9, 204, 0.4............... 0.2.
borealis. 2010).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Physeteridae:
Sperm whale................. Physeter NSD................ E, N/A, N/A ................... UNK............... UNK.
macrocephalus.
Sperm whale................. Physeter North Pacific...... E, D, Y UND (UND, UND, UND............... 3.5.
macrocephalus. 2015).
Sperm whale................. Physeter Hawaii............. E, D, Y 5,707 (0.23, 4,486, 18................ 0.
macrocephalus. 2017).
Family Kogiidae:
Dwarf sperm whale........... Kogia sima......... NSD................ , N/A, N/A ................... UNK............... UNK.
Dwarf sperm whale........... Kogia sima......... Hawaii............. , -, N UNK (UNK, UNK, UND............... 0.
2017).
Pygmy sperm whale........... Kogia breviceps.... NSD................ , N/A, N/A ................... UNK............... UNK.
Pygmy sperm whale........... Kogia breviceps.... Hawaii............. , -, N 42,083 (0.64, 257............... 0.
25,695, 2017).
Family Ziphiidae (beaked
whales):
Baird's beaked whale........ Berardius bairdii.. NSD................ , N/A, N/A ................... UNK............... UNK.

[[Page 47672]]

Blainville's beaked whale... Mesoplodon NSD................ , N/A, N/A ................... UNK............... UNK.
densirostris.
Blainville's beaked whale... Mesoplodon Hawaii............. , -, N 1,132 (0.99, 564, 5.6............... 0.
densirostris. 2017).
Deraniyagala's beaked whale. Mesoplodon hotaula. NSD................ , N/A, N/A ................... UNK............... UNK.
Ginkgo-toothed beaked whale. Mesoplodon NSD................ , N/A, N/A ................... UNK............... UNK.
ginkgodens.
Goose-beaked whale.......... Ziphius cavirostris NSD................ , N/A, N/A ................... UNK............... UNK.
Goose-beaked whale.......... Ziphius cavirostris Hawaii............. , -, N 4,431 (0.41, 3,180, 32................ 0.
2017).
Hubbs' beaked whale......... Mesoplodon NSD................ , N/A, N/A ................... UNK............... UNK.
carlshubbi.
Longman's beaked whale...... Indopacetus NSD................ , N/A, N/A ................... UNK............... UNK.
pacificus.
Longman's beaked whale...... Indopacetus Hawaii............. , -, N 2,550 (0.67, 1,527, 15................ 0.
pacificus. 2017).
Stejneger's beaked whale.... Mesoplodon NSD................ , N/A, N/A ................... UNK............... UNK.
stejnegeri.
Family Delphinidae:
False killer whale.......... Pseudorca NSD................ , N/A, N/A ................... UNK............... UNK.
crassidens.
False killer whale.......... Pseudorca Main Hawaiian E, D, Y 138 (0.08, 129, 0.26.............. 0.3.
crassidens. Islands Insular. 2015).
False killer whale.......... Pseudorca Hawaii Pelagic..... , -, Y 5,528 (0.35, 4,152, 33................ 47.
crassidens. 2017).
Killer whale................ Orcinus orca....... NSD................ , N/A, N/A ................... UNK............... UNK.
Killer whale................ Orcinus orca....... Hawaii............. , -, N 161 (1.06, 78, 0.8............... 0.
2017).
Melon-headed whale.......... Peponocephala NSD................ , N/A, N/A ................... UNK............... UNK.
electra.
Melon-headed whale.......... Peponocephala Hawaiian Islands... , -, N 40,647 (0.74, 233............... 0.
electra. 23,301 2017).
Pygmy killer whale.......... Feresa attenuata... NSD................ , N/A, N/A ................... UNK............... UNK.
Pygmy killer whale.......... Feresa attenuata... Hawaii............. , -, N 10,328 (0.75, 59................ 0.
5,885, 2017).
Short-finned pilot whale.... Globicephala NSD................ , N/A, N/A ................... UNK............... UNK.
macrorhynchus.
Short-finned pilot whale.... Globicephala Hawaii............. , -, N 19,242 (0.23, 159............... 0.2.
macrorhynchus. 15,894, 2020).
Bottlenose dolphin.......... Tursiops truncatus. NSD................ , N/A, N/A ................... UNK............... UNK.
Bottlenose dolphin.......... Tursiops truncatus. Hawaii Pelagic..... , -, N 24,669 (0.57, 158............... 0.
15,783, 2020).
Common dolphin.............. Delphinus delphis.. NSD................ , N/A, N/A ................... UNK............... UNK.
Fraser's dolphin............ Lagenodelphis hosei NSD................ , N/A, N/A ................... UNK............... UNK.
Fraser's dolphin............ Lagenodelphis hosei Hawaii............. , -, N 40,960 (0.7, 241............... 0.
24,068, 2017).
Northern right whale dolphin Lissodelphis NSD................ , N/A, N/A ................... UNK............... UNK.
borealis.
Pacific white-sided dolphin. Aethalodelphis North Pacific...... , -, N 26,880 (N/A, N/A, UND............... 0.
obliquidens. 1990).
Pantropical spotted dolphin. Stenella attenuata. NSD................ , N/A, N/A ................... UNK............... UNK.
Pantropical spotted dolphin. Stenella attenuata. Hawaii Pelagic..... , -, N 67,313 (0.27, 538............... 0.
53,839, 2020).
Risso's dolphin............. Grampus griseus.... NSD................ , N/A, N/A ................... UNK............... UNK.
Risso's dolphin............. Grampus griseus.... Hawaii............. , -, N 6,979 (0.29, 5,283, 53................ 0.
2020).
Rough-toothed dolphin....... Steno bredanensis.. NSD................ , N/A, N/A ................... UNK............... UNK.
Rough-toothed dolphin....... Steno bredanensis.. Hawaii............. , -, N 83,915 (0.49, 511............... 3.2.
56,782, 2017).
Spinner dolphin............. Stenella NSD................ , N/A, N/A ................... UNK............... UNK.
longirostris.
Spinner dolphin............. Stenella Hawaii Pelagic..... , -, N UNK (UNK, UNK, UND............... 0.
longirostris. 2010).
Striped dolphin............. Stenella NSD................ , N/A, N/A ................... UNK............... UNK.
coeruleoalba.
Striped dolphin............. Stenella Hawaii Pelagic..... , -, N 64,343 (0.28, 511............... 0.
coeruleoalba. 51,055, 2020).
Family Phocoenidae (porpoises):
Dall's porpoise............. Phocoenoides dalli. NSD................ , N/A, N/A ................... UNK............... UNK.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Carnivora--Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otariidae (eared seals
and sea lions):
Northern fur seal........... Callorhinus ursinus NSD................ , N/A, N/A ................... UNK............... UNK.
Steller sea lion............ Eumetopias jubatus. Western............ E, D, Y 49,837 (N/A, 299............... 267.
49,837, 2022).
Family Phocidae (earless seals):
Harbor seal................. Phoca vitulina..... California......... , -, N 30,968 (N/A, 1,641............. 43.
27,348, 2012).
Ribbon seal................. Histriophoca NSD................ , N/A, N/A ................... UNK............... UNK.
fasciata.
Hawaiian monk seal.......... Neomonachus Hawaii............. E, D, Y 1,605 (0.05, 1,508, 5.3............... >=4.8.
schauinslandi. 2022).
Ringed seal................. Pusa hispida....... NSD................ \5\, N/A, N/A ................... UNK............... UNK.
Spotted seal................ Phoca largha....... Bering............. , -, N 461,625 (N/A, 25,394............ 5,254.
423,237, 2013).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note: NSD = No Stock Designation, N/A = Not Applicable, UND = Undetermined, UNK = Unknown. A species or stock listed as `NSD' is not a designated stock
under the MMPA and, therefore, does not have a SAR or any SAR-specific information.
\1\ Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy
(https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/).

[[Page 47673]]

\2\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed
under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality
exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
under the ESA is automatically designated under the MMPA as depleted and as a strategic stock. MMPA status information is N/A to species for which no
stock is designated.
\3\ NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance.
\4\ These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g.,
commercial fisheries, vessel strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A
CV associated with estimated mortality due to commercial fisheries is presented in some cases.
\5\ Only designated DPSs are ESA-listed.

Below, we consider additional information about the marine mammals
in the area of the specified activities that informs our analysis, such
as identifying known areas of important habitat or behaviors, or where
UMEs have been designated.

Critical Habitat

Currently, the false killer whale (Main Hawaiian Islands Insular
DPS) and Hawaiian monk seal have ESA-designated critical habitat in the
Study Area.
False Killer Whale (Main Hawaiian Island Insular DPS)
Critical habitat for the ESA-listed Main Hawaiian Islands insular
false killer whale DPS was finalized in July 2018 (83 FR 35062, July
24, 2018) designating waters from the 45 m depth contour to the 3,200 m
depth contour around the main Hawaiian Islands from Ni[revaps]ihau east
to Hawaii. This designation does not include most bays, harbors, or
coastal in-water structures. NMFS excluded 14 areas. The total area
designated was approximately 45,504 square kilometers (km\2\) (13,267
square nautical miles (nmi\2\)) of marine habitat. Critical habitat for
the main Hawaiian Islands insular DPS of false killer whale overlaps
the Study Area.
Main Hawaiian Islands insular false killer whales are island-
associated whales that rely entirely on the productive submerged
habitat of the main Hawaiian Islands to support all of their life-
history stages. Island-associated marine habitat for Main Hawaiian
Islands insular false killer whale is the only essential feature of the
critical habitat. The following characteristics of this habitat support
insular false killer whales' ability to travel, forage, communicate,
and move freely around and among the waters surrounding the main
Hawaiian Islands: (1) adequate space for movement and use within shelf
and slope habitat; (2) prey species of sufficient quantity, quality,
and availability to support individual growth, reproduction, and
development, as well as overall population growth; (3) waters free of
pollutants of a type and amount harmful to Main Hawaiian Islands
insular false killer whales; and (4) sound levels that would not
significantly impair false killer whales' use or occupancy.
Hawaiian Monk Seal
Critical habitat for Hawaiian monk seals was designated in 1986 (51
FR 16047, April 30, 1986) and later revised in 1988 (53 FR 18988, May
26, 1988) and in 2015 (80 FR 50925, August 21, 2015). In the
Northwestern Hawaiian Islands Hawaiian monk seal critical habitat
includes all beach areas, sand spits, and islets, including all beach
crest vegetation, to its deepest extent inland as well as the seafloor
and marine habitat 10 m in height above the seafloor from the shoreline
out to the 200 m depth contour around Kure Atoll
(H[omacr]lanik[umacr]), Midway Atoll (Kuaihelani), Pearl and Hermes
Reef (Manawai), Lisianski Island (Kapou), Laysan Island (Kamole), Maro
Reef (Kamokuokamohoali`i), Gardner Pinnacles
([revaps][Omacr]n[umacr]nui), French Frigate Shoals (Lalo), Necker
Island (Mokumanamana) and Nihoa Island. In the main Hawaiian Islands,
Hawaiian monk seal critical habitat includes the seafloor and marine
habitat to 10 m above the seafloor from the 200 m depth contour through
the shoreline and extending into terrestrial habitat 5 m inland from
the shoreline between identified boundary points around Kaula Island
(includes marine habitat only), Ni[revaps]ihau (includes marine habitat
from 10 to 200 m in depth), Kaua[revaps]i, O[revaps]ahu, Maui Nui
(including Kaho[revaps]olawe, L[amacr]na[revaps]i, Maui, and
Moloka[revaps]i), and Hawaii Island. Critical habitat for the Hawaiian
monk seal overlaps the Study Area.
The essential features of Hawaiian monk seal critical habitat are:
(1) terrestrial areas and adjacent shallow, sheltered aquatic areas
with characteristics preferred by monk seals for pupping and nursing;
(2) marine areas from 0 to 200 m in depth that support adequate prey
quality and quantity for juvenile and adult monk seal foraging; and (3)
significant areas used by monk seals for hauling out, resting, or
molting.

Biologically Important Areas

Ferguson et al. (2015) identified BIAs within U.S. waters, which
represent areas and times in which cetaceans are known to concentrate
for reproduction, feeding, and migration, or areas where small and
resident populations are known to occur. Harrison et al. (2023)
identified a new scoring system, described below, and the BIAs in
Hawaiian waters were updated (Kratofil et al., 2023). Unlike ESA
critical habitat, BIAs are not formally designated pursuant to any
statute or law but are a compilation of the best available science
intended to inform impact and mitigation analyses. An interactive map
of the BIAs is available at: https://oceannoise.noaa.gov/biologically-important-areas. A summary of all of the BIAs in the Study Area is
included below.
Kratofil et al. (2023) delineates and scores BIAs for cetaceans in
the Hawaii region following standardized protocols. Experts identified
an overall Importance Score for each BIA that considers: (1)
``Intensity,'' meaning the intensity and characteristics underlying an
area's identification as a BIA; and (2) ``Data Support,'' meaning the
quantity, quality, and type of information, and associated
uncertainties, upon which the BIA delineation and scoring depend.
Importance Scores range from 1 to 3, with a higher score representing
an area of higher intensity and data support. Each BIA is also scored
for boundary uncertainty and spatiotemporal variability (dynamic,
ephemeral, or static). Additionally, hierarchical BIAs are identified
for some species and stocks where a higher intensity score is
appropriate for a smaller core area(s) (child BIA) within a larger BIA
unit (parent BIA).
The Study Area overlaps BIAs in Hawaii for small and resident
populations of the following species: spinner dolphin, short-finned
pilot whale, rough-toothed dolphin, pygmy killer whale, pantropical
spotted dolphin, melon-headed whale, false killer whale, dwarf sperm
whale, goose-beaked whale, common bottlenose dolphin, and Blainville's
beaked whale, and the updated BIAs for humpback whale reproduction
(Kratofil et al., 2023). Table 2 describes each BIA that overlaps the
Study Area and the scores for the above criteria. We note that the BIAs
for small and resident populations of spinner dolphin, melon-headed
whale, and dwarf sperm whale are all fully contained within OBIAs. The
BIAs for small and resident populations of short-finned pilot whale,
rough-toothed

[[Page 47674]]

dolphin, pygmy killer whale, goose-beaked whale, and common bottlenose
dolphin, and the reproductive BIA for humpback whale, are mostly
contained within the OBIAs. The BIAs for small and resident populations
of pantropical spotted dolphin, false killer whale, and Blainville's
beaked whale are partially contained within the OBIAs described in the
Geographic Mitigation section and required for implementation in this
rule.

[[Page 47675]]

Table 2--BIAs Overlapping the Pacific SURTASS LFA Sonar Study Area
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Data
Species BIA type Parent/child non- BIA name Effective months BIA area Importance Intensity support Boundary Spatiotemporal Transboundary
hierarchical (km\2\) score score score certainty variability across
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Hawaii Study Area (Kratofil et al., 2023)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale............... Reproductive.... Parent.......... Main Hawaiian December through 23,041 2 2 2 2 Static.......... None.
Islands--Parent. May.
Humpback whale............... Reproductive.... Child........... Main Hawaiian December through 6,676 3 3 3 3 Static.......... None.
Islands--Child. May.
False killer whale........... Small and Parent.......... Main Hawaiian Year-round...... 94,217 1 1 3 3 Static.......... None.
Resident Islands Insular
Population. Stock--Parent.
False killer whale........... Small and Child........... Main Hawaiian Year-round...... 7,775 3 3 3 3 Static.......... None.
Resident Islands Insular
Population. Stock--Child.
False killer whale........... Small and Non-hierarchical Northwestern Year-round...... 138,001 1 1 2 2 Static.......... None.
Resident Hawaiian
Population. Islands Insular
Stock.
Dwarf sperm whale............ Small and Parent.......... Hawaii Island-- Year-round...... 1,341 3 3 2 2 Static.......... None.
Resident Parent.
Population.
Dwarf sperm whale............ Small and Child........... Hawaii Island-- Year-round...... 457 3 3 2 2 Static.......... None.
Resident Child.
Population.
Pygmy killer whale........... Small and Non-hierarchical O[revaps]ahu- Year-round...... 7,416 3 3 2 2 Static.......... None.
Resident Maui Nui.
Population.
Pygmy killer whale........... Small and Non-hierarchical Hawaii Island... Year-round...... 5,201 2 2 2 2 Static.......... None.
Resident
Population.
Short-finned pilot whale..... Small and Parent.......... Main Hawaiian Year-round...... 51,280 1 1 3 3 Static.......... None.
Resident Islands--Parent.
Population.
Short-finned pilot whale..... Small and Child........... Main Hawaiian Year-round...... 4,040 3 3 3 3 Static.......... None.
Resident Islands--Child
Population. (Western
Community Core
Range).
Short-finned pilot whale..... Small and Child........... Main Hawaiian Year-round...... 2,427 3 3 3 3 Static.......... None.
Resident Islands--Child
Population. (Central
Community Core
Range).
Short-finned pilot whale..... Small and Child........... Main Hawaiian Year-round...... 2,461 3 3 3 3 Static.......... None.
Resident Islands--Child
Population. (Eastern
Community Core
Range).
Common bottlenose dolphin.... Small and Parent.......... Kaua[revaps]i/ Year-round...... 36,634 1 1 3 2 Static.......... None.
Resident Ni[revaps]ihau-
Population. O[revaps]ahu-
Maui Nui.
Common bottlenose dolphin.... Small and Child........... Kaua[revaps]i/ Year-round...... 2,772 3 3 3 3 Static.......... None.
Resident Ni[revaps]ihau-
Population. O[revaps]ahu-
Maui Nui-
Kaua[revaps]i/
Ni[revaps]ihau).
Common bottlenose dolphin.... Small and Child........... Kaua[revaps]i/ Year-round...... 8,486 3 3 2 2 Static.......... None.
Resident Ni[revaps]ihau-
Population. O[revaps]ahu-
Maui Nui--
O[revaps]ahu.
Common bottlenose dolphin.... Small and Child........... Kaua[revaps]i/ Year-round...... 10,622 2 2 2 2 Static.......... None.
Resident Ni[revaps]ihau-
Population. O[revaps]ahu-
Maui Nui--Maui
Nui.
Common bottlenose dolphin.... Small and Non-hierarchical Hawaii Island... Year-round...... 8,299 2 2 3 3 Static.......... None.
Resident
Population.
Pantropical spotted dolphin.. Small and Parent.......... O[revaps]ahu- Year-round...... 57,711 1 1 2 2 Static.......... None.
Resident Maui Nui-Hawaii
Population. Island--Parent.
Pantropical spotted dolphin.. Small and Child........... O[revaps]ahu- Year-round...... 12,952 1 1 2 2 Static.......... None.
Resident Maui Nui-Hawaii
Population. Island--Child
(O[revaps]ahu).
Pantropical spotted dolphin.. Small and Child........... O[revaps]ahu- Year-round...... 6,743 1 1 2 2 Static.......... None.
Resident Maui Nui-Hawaii
Population. Island--Child
(Maui Nui).

[[Page 47676]]

Pantropical spotted dolphin.. Small and Child........... O[revaps]ahu- Year-round...... 10,768 1 1 2 2 Static.......... None.
Resident Maui Nui-Hawaii
Population. Island--Hawaii
Island- Child
(Hawaii Island).
Rough-toothed dolphin........ Small and Non-hierarchical Maui Nui-Hawaii Year-round...... 15,112 1 1 2 2 Static.......... None.
Resident Island.
Population.
Rough-toothed dolphin........ Small and Parent.......... Kaua[revaps]i/ Year-round...... 24,233 1 1 2 2 Static.......... None.
Resident Ni[revaps]ihau-
Population. O[revaps]ahu--P
arent.
Rough-toothed dolphin........ Small and Child........... Kaua[revaps]i/ Year-round...... 1,149 2 2 2 2 Static.......... None.
Resident Ni[revaps]ihau-
Population. O[revaps]ahu--C
hild
(Kaua[revaps]i/
Ni[revaps]ihau).
Melon-headed whale........... Small and Non-hierarchical Kohala Year-round...... 3,816 2 2 3 3 Static.......... None.
Resident Residents--Hawa
Population. ii Island.
Spinner dolphin.............. Small and Non-hierarchical Manawai (Pearl Year-round...... 2,094 1 2 1 2 Static.......... None.
Resident and Hermes
Population. Reef).
Spinner dolphin.............. Small and Non-hierarchical Kuaihelani/ Year-round...... 4,841 1 2 1 2 Static.......... None.
Resident H[omacr]lanik[u
Population. macr] (Midway/
Kure Atolls).
Spinner dolphin.............. Small and Non-hierarchical Kaua[revaps]i Year-round...... 7,233 1 1 2 3 Static.......... None.
Resident and
Population. Ni[revaps]ihau.
Spinner dolphin.............. Small and Non-hierarchical O[revaps]ahu and Year-round...... 14,651 1 1 2 3 Static.......... None.
Resident Maui Nui.
Population.
Spinner dolphin.............. Small and Non-hierarchical Hawaii Island... Year-round...... 9,477 1 1 3 3 Static.......... None.
Resident
Population.
Goose-beaked whale........... Small and Parent.......... Hawaii Island... Year-round...... 37,157 2 2 3 2 Static.......... None.
Resident
Population.
Goose-beaked whale........... Small and Child........... Hawaii Island... Year-round...... 5,400 3 3 3 3 Static.......... None.
Resident
Population.
Blainville's beaked whale.... Small and Parent.......... O[revaps]ahu- Year-round...... 78,714 1 1 3 2 Static.......... None.
Resident Maui Nui-Hawaii
Population. Island--Parent.
Blainville's beaked whale.... Small and Child........... O[revaps]ahu- Year-round...... 4,214 3 3 3 3 Static.......... None.
Resident Maui Nui-Hawaii
Population. Island--Child
(Hawaii Island).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 47677]]

Unusual Mortality Events

A UME is defined under section 410(9) of the MMPA as a stranding
that is unexpected; involves a significant die-off of any marine mammal
population; and demands immediate response (16 U.S.C. 1421h(9)). There
are no active UMEs in the Study Area.

Potential Effects of Specified Activities on Marine Mammals and Their
Habitat

We provided a detailed discussion of the potential effects of the
specified activities on marine mammals and their habitat in our
proposed rule. NMFS hereby refers to the information and analysis
provided in the proposed rule, which continues to apply to this final
rule. In the Potential Effects of Specified Activities on Marine
Mammals and Their Habitat section of the proposed rule, NMFS provided a
description of the ways marine mammals may be affected by these
activities in the form of, among other things, sensory impairment
(auditory injury, temporary threshold shift, and acoustic masking),
physiological responses, behavioral disturbance, or habitat effects.
All of this information remains valid and applicable. Therefore, we do
not reprint the information here and refer the reader to that document.
NMFS has also reviewed new relevant information from the scientific
literature since publication of the proposed rule. Summaries of the new
key scientific literature reviewed since publication of the proposed
rule are presented below.
Dunlop et al. (2026) used a behavioral observation audiometry (BOA)
in wild humpback whales to predict minimum response levels (MRLs),
which serves as a surrogate for determining the shape of this species'
masked audiogram (i.e., MRLs are not equivalent to an audiogram). These
data were compared to a hearing curve derived from anatomical models
and the authors found the BOAs to indicate the humpback whale hearing
range extends at least as low as approximately 80 Hz and at least as
high as approximately 22 kHz. These data predicted more sensitivity at
higher frequencies than the anatomically-based curve, indicating
humpback whale hearing may be more sensitive than previously thought.
Fournet and Schulze (2026) used underwater acoustic monitoring and
land-based visual surveys to evaluate the probability of humpback whale
breaching behavior with increasing low-frequency (50-1,500 Hz) ambient
noise levels in the foraging grounds of Glacier Bay National Park and
Preserve. Likelihood of breaching was found to increase with higher
ambient noise levels, with results correlated with total ambient levels
and not the proximity of vessels. The authors hypothesize that
breaching is a compensatory communication strategy when vocal signals
are masked. These results were consistent with other observations of
surface-active behaviors in humpback whales, but the authors found the
source of the noise (e.g., vessel, rain) associated with this study did
not affect the results (i.e., humpback whales respond to both
anthropogenic and natural sources equally).
Gao et al. (2026) compared ambient noise in the northern South
China Sea, focusing on differences in noise properties between the
continental slope and deep-water environments. The authors reported
continental slope spectrum levels (50 Hz-10 kHz) were consistently
higher than those measured in the deep-water environment. Below 4 kHz,
elevated ambient noise levels in the continental slope environment
result from shipping activity and other anthropogenic activities, while
above 4 kHz, wind-generated noise dominated in both environments. These
findings provide valuable insights for noise modeling in dynamic and
complex slope environments, as well as sonar performance simulation and
evaluation.
Houser et al. (2026) reviewed studies of baleen whale hearing
conducted over the past 30 years and generally compared the variety of
methods used to estimate hearing, including extrapolation from a
species' vocalization, behavioral methods, anatomically-based
predictions, and electrophysiological hearing tests. Notably, the
authors included a discussion of how auditory evoked potential (AEP)
tests on adolescent common minke whales (Kleivane et al., 2024; Houser
et al., 2024) support the notion that some baleen whales have a much
higher upper-frequency hearing limit than previously thought using the
other methods of estimating hearing. The Navy was given access to pre-
published data on the 2023-2024 minke whale field season and was able
to incorporate these data into their Phase IV acoustic criteria (noting
that the 2023 field season data was published in November 2024). In
their Phase IV criteria, the Navy separated very low-frequency (VLF)
cetaceans (i.e., blue, fin, right, and bowhead whales) from LF
cetaceans (all other mysticetes), thus acknowledging differences among
mysticetes species. Data from the 2024 field season are not yet
published.
Maciel et al. (2026) assessed the impacts of seismic surveys in
Brazil on vocal behavior of humpback whales and pantropical spotted
dolphins from 2020 to 2024. The authors reported that exposure to
seismic surveys reduced the call frequency and duration of humpback
whales but increased the call frequency and duration of pantropical
spotted dolphins. The authors hypothesized that the difference in vocal
responses of each species may be related to physiological limitations
in sound modulation.
Madrigal et al. (2026) tagged four false killer whales from the
Main Hawaiian Islands insular population to learn about their acoustic
communication. False killer whales are known for their complex group
behavior, and the small population of Main Hawaiian Islands insular
false killer whales consists of at least four social clusters that are
distinct genetically and use habitat variably. The authors used
biologgers with built-in hydrophones and found variable call rates
(call rates decreased with increasing swim speeds) and types across
dive state (probability of calling was greater when animals were closer
to the bottom compared to the surface) by individual, highlighting
vocal diversity even amongst this small population.
A review of laboratory-based studies by Reichmuth and Sills (2026)
described what is currently known about direct measures of hearing
sensitivity of marine mammals to low-frequency sounds below 100 Hz. The
authors describe low-frequency sensitivity increasing from the least
low-frequency-sensitive group studied, odontocetes, to sirenians, then
otariid carnivores, and finally phocid carnivores, which have the most
sensitive low-frequency hearing of any marine mammal studied to date.
This study does not provide new data.
Southall et al. (2026) describes a controlled exposure experiment
(CEE) in which blue whales (the predominant species in CEE) and fin
whales were exposed to simulated and operational marine vibrators (MV),
a low-frequency source (5-100 Hz) associated with seismic surveys. The
authors found that while simulated playbacks resulted in ``mild and
temporary avoidance responses'' by whales that were travelling or
feeding in low-density prey fields, whales feeding in concentrated prey
fields did not respond to the operational MV source.
Having considered the new information, along with information
provided in public comments on the proposed rule, we have determined
that there is no new information that substantively affects our
analysis of potential impacts on marine mammals and their habitat that
appeared in the proposed rule, all of which remains applicable and
valid for our assessment

[[Page 47678]]

of the effects of the Navy's activities during the 7-year period of
this rule.

Estimated Take of Marine Mammals

This section indicates the number of takes that NMFS is
authorizing, which is based on the amount of take that NMFS anticipates
is reasonably likely to occur. NMFS coordinated closely with the Navy
in the development of their incidental take application and agrees
that: (1) the methods the Navy has put forth described herein to
estimate take (including the model, thresholds, and density estimates);
and (2) the resulting take estimates are based on the best available
science and appropriate for authorization.
The 2026 SURTASS SEIS/OEIS considered all SURTASS LFA sonar
activities planned to occur in the Study Area that have the potential
to result in the take of marine mammals. The Navy determined that the
only stressors that could result in the incidental taking of marine
mammals are acoustic (i.e., sonars). NMFS has reviewed the Navy's data
and analysis and determined that it is complete and accurate and agrees
that acoustic stressors have the potential to result in take by
harassment of marine mammals from the specified activities. The
estimated take discussed herein would be in the form of harassment only
and would result primarily from marine mammal exposure to SURTASS LFA
sonar given the slower attenuation and long distance that the sound
would propagate in comparison to the active high-frequency marine
mammal monitoring (HF/M3) sonar that would operate simultaneously.
For this military readiness activity, the MMPA defines
``harassment'' as: (1) any act that injures or has the significant
potential to injure a marine mammal or marine mammal stock in the wild
(Level A harassment); or (2) any act that disturbs or is likely to
disturb a marine mammal or marine mammal stock in the wild by causing
disruption of natural behavioral patterns, including, but not limited
to, migration, surfacing, nursing, breeding, feeding, or sheltering, to
a point where the behavioral patterns are abandoned or significantly
altered (Level B harassment) (16 U.S.C. 1362(18)(B)).
Authorized takes are primarily in the form of Level B harassment,
as use of the acoustic sources is most likely to result in disruption
of natural behavioral patterns to a point where they are abandoned or
significantly altered (as defined specifically at the beginning of this
section, but referred to generally as behavioral disturbance) for
marine mammals, either via direct behavioral disturbance or temporary
threshold shift (TTS). There is also the potential for Level A
harassment, in the form of auditory injury to result from exposure to
SURTASS LFA sonar. Although we analyze the impacts of the potential
harassment takes that are authorized, the required mitigation and
monitoring measures are expected to minimize the severity of these
takes.
Generally speaking, NMFS estimates the amount and type of
harassment from acoustic sources by considering: (1) acoustic
thresholds above which NMFS believes the best available science
indicates marine mammals would experience behavioral disturbance or
incur some degree of temporary or permanent hearing impairment; (2) the
area or volume of water that would be ensonified above these levels in
a day or event; (3) the density or occurrence of marine mammals within
these ensonified areas; and (4) the number of days of activities.
It is important to note that for this SURTASS LFA sonar rule, the
Navy, in coordination with NMFS, elected to change both the acoustic
thresholds and the take estimation methodology used to better reflect
the best available science and also better align with the analytical
methods used in other Navy training and testing rules. Specifically,
all of the acoustic thresholds and take calculation methods used here
are referred to as ``Phase IV'' and described in the Criteria and
Thresholds Technical Report, mirroring those used in analyses
supporting the Phase IV AFTT (90 FR 50504, November 7, 2025) and HCTT
(90 FR 58810, December 17, 2025) training and testing ITRs (in the
previous SURTASS LFA sonar rule (84 FR 40132, August 13, 2019), Phase
III thresholds were used for acoustic injury prediction, a SURTASS-
specific threshold was used to predict behavioral disturbance, and
different SURTASS-specific methods and modeling were used in the
calculation of take).
We provided a detailed discussion of the acoustic thresholds,
acoustic effects modeling and estimation, range to effects, and marine
mammal density information in our proposed rule. NMFS hereby refers to
the information and analysis provided in the proposed rule, which
continue to apply to this final rule. In the Estimated Take of Marine
Mammals section of the proposed rule, we identified the subset of
potential effects that would be expected to rise to the level of takes
both annually and over the 7-year period covered by the rule, then
identified the maximum number of takes we believe are reasonably
expected to occur (by Level A and/or Level B harassment) based on the
methods described. All of this information remains valid and
applicable; therefore, we do not repeat the information here but refer
the reader to the proposed rule.

Estimated Take From Acoustic Stressors

The Navy is authorized to take marine mammals incidental to 1,100
hours of SURTASS LFA sonar training per year, which is an increase from
the 592 hours considered for the 2019 regulations; however, this
increase does not reflect new or additional training requirements.
Instead, it is the result of a change in how the Navy counts an
``hour'' of transmission. Previously, SURTASS LFA sonar hours were
calculated by adding the portions of time a sonar emits sound during
its ``duty cycle'' (ratio of time the signal is on compared to off).
Other Navy sonar systems, such as mid-frequency and high-frequency
active sonar, calculate hours based on total ``duration'' time (total
time the source is active, including silent periods between pings). To
bring SURTASS LFA sonar in line with these other sonar systems, the
Navy developed a conversion method that considers various factors
including LFA sonar pings, wave trains, and other classified
considerations. As a result, the 1,100 hours of annual SURTASS LFA
training requested are equivalent to the 592 hours considered under the
previous counting method.
The quantitative analysis process used for the 2026 SURTASS SEIS/
OEIS and the application to estimate potential exposures of marine
mammals resulting from acoustic stressors is detailed in the Acoustic
Impacts Technical Report.
Regarding how avoidance of loud sources is considered in the take
estimation, NAEMO does not simulate horizontal animat (i.e., a virtual
animal) movement during an event. However, NAEMO approximates marine
mammal avoidance of high sound levels due to exposure to sonars in a
one-dimensional calculation that scales how far an animat would be from
a sound source based on sensitivity to disturbance, swim speed, and
avoidance duration. This process reduces the SEL, defined as the
accumulation for a given animat, by reducing the received SPL of
individual exposures based on a spherical spreading calculation from
sources on each unique platform in an event. The onset of avoidance was
based on the behavioral response functions (BRFs). Avoidance speeds and
durations were informed by a review of available exposure and baseline
data. This method captures a more accurate representation of avoidance
by using the received sound levels, distance to

[[Page 47679]]

platform, and species-specific criteria to calculate potential
avoidance for each animat than the previous approach for SURTASS LFA
sonar modeling using the Acoustic Integration Model. However, this
method may underestimate avoidance of long-duration sources with lower
sound levels because it triggers avoidance calculations based on the
highest modeled SPL received level exceeding p(0.5) on the BRF, rather
than on cumulative exposure. This is because initiation of the
avoidance calculation is based on the highest modeled SPL received
level over p(0.5) on the BRF. Please see section 4.4.2.2 of the
Acoustic Impacts Technical Report.
The ability of marine mammals to reduce cumulative SEL through
avoidance depends on susceptibility to auditory effects, sensitivity to
behavioral disturbance, and characteristics of the sonar source
including duty cycle, source level, and frequency. Table 2-2 of
appendix B to the application shows the percentage reduction of
auditory injury (AUD INJ) across the modeled activities in this
analysis due to avoidance. The reduction in AUD INJ due to avoidance
differs across the planned action and between auditory and behavioral
groups. Groups that are relatively less sensitive to behavioral
disturbance compared to susceptibility to auditory effects are less
likely to avoid AUD INJ, which include the mysticete and odontocete
behavioral groups. Groups that are relatively more sensitive to
behavioral disturbance compared to susceptibility to auditory effects
are more likely to avoid AUD INJ, which include the Sensitive Species
and Pinniped behavioral groups. The reduction in AUD INJ for most
groups is less than assumed in prior analyses. Avoidance was able to be
applied only for pinnipeds. It is likely that no reduction of AUD INJ
could be applied to any other hearing group due to the high source
level and low frequency of the SURTASS LFA.
Regarding the consideration of mitigation effectiveness in the take
estimation, this quantitative analysis does not reduce model-estimated
impacts to account for activity-based mitigation. While the activity-
based mitigation is not quantitatively included in the take estimates
(which, of note, would result in a reduction in the number of takes),
section 2.3.2 of appendix B of the application indicates the percentage
of the instances of take where an animal's closest point of approach
was within a mitigation zone and, therefore, AUD INJ could potentially
be mitigated. Only mysticetes in the VLF and LF hearing groups have at
least one model-predicted AUD INJ. Five percent and 8 percent of the
modeled instances of AUD INJ for VLF and LF cetaceans occurred within
the mitigation zone, respectively, thus mitigation could potentially
avoid up to 5 or 8 percent of instances of AUD INJ. Note that these
percentages do not account for other factors, such as the sightability
of a given species or viewing conditions.
For additional information on the quantitative analysis process,
refer to the Acoustic Impacts Technical Report and appendices B and C
of the application.
As a general matter, NMFS does not prescribe the methods for
estimating take for any applicant, but we review and ensure that
applicants use the best available science and methodologies that are
logical and technically sound. Applicants may use different methods of
calculating take (especially when using models) and still get to a
result that is representative of the best available science and that
allows for a rigorous and accurate evaluation of the effects on marine
mammals. There are multiple pieces of the Navy's take estimation
methods (e.g., propagation models, animat movement models, and
behavioral thresholds). NMFS evaluates the acceptability of these
pieces as they evolve and are used in different rules and impact
analyses. Some of the pieces of the Navy's take estimation process have
been used in Navy incidental take rules since 2009 and have undergone
multiple public comment processes. All of them have undergone extensive
internal Navy review and comprehensive review by NMFS, which has
sometimes resulted in modifications to methods or models.
The Navy uses rigorous review processes (i.e., verification,
validation, and accreditation processes; peer and public review) to
ensure the data and methodology it uses represent the best available
science. For instance, NAEMO is the result of a NMFS-led Center for
Independent Experts review of the components used in earlier models.
The acoustic propagation component of NAEMO (titled CASS/GRAB) is
accredited by the Oceanographic and Atmospheric Master Library (OAML),
and many of the environmental variables used in NAEMO come from
approved OAML databases and are based on in-situ data collection. The
animal density components of NAEMO are base products of the NMSDD,
which include animal density components that have been validated and
reviewed by a variety of scientists from NMFS Science Centers and
academic institutions. Several components of the model, for example,
habitat-based density model results for species off Hawaii and
California, have been published in several peer-reviewed journals
(Becker et al., 2020; Becker et al., 2021; Becker et al., 2022a; Becker
et al., 2022b). Additionally, NAEMO simulation components underwent
quality assurance and quality control (QA/QC) review and validation for
model parts (scenario builder, acoustic builder, scenario simulator,
etc.) conducted by qualified statisticians and modelers to ensure
accuracy. Other models and methodologies have gone through similar
review processes.
In summary, we believe the Navy's methods, including the method for
incorporating avoidance, are the most appropriate methods for
predicting AUD INJ, non-auditory injury, TTS, and behavioral
disturbance. But even with the consideration of avoidance, given some
of the more conservative components of the methodology (e.g., the
thresholds do not consider ear recovery between pulses), we would
describe the application of these methods as identifying the maximum
number of instances in which marine mammals would be reasonably
expected to be taken through AUD INJ, non-auditory injury, TTS, or
behavioral disturbance.
The Navy does not expect physical or non-auditory injury or
mortality to any of the marine mammal species in the Study Area due to
the specified activities; therefore, those effects are not further
discussed. Additionally, masking effects from vessel noise during the
operation of T-AGOS vessels are not expected to qualify as take due to
the relative movement of the vessels in the Study Area (no more than
four vessels traversing an ocean basin at greater than 22 km from shore
(away from where marine mammal densities are higher)), resulting in a
very low likelihood of any meaningful masking resulting from the noise
of the vessels themselves.
Based on the methods discussed in the previous sections and NAEMO,
the Navy provided their take estimates and request for authorization of
takes incidental to the use of acoustic sources for military readiness
activities annually (based on the maximum number of activities that
could occur per 12-month period) and over the 7-year period. NMFS
agrees that the estimates for incidental takes by harassment from
SURTASS LFA sonar sources requested for authorization are the maximum
number of instances in which marine mammals are reasonably expected to
be taken.

[[Page 47680]]

Table 3 summarizes the maximum annual and 7-year total amount and
type of Level A harassment and Level B harassment that NMFS concurs is
reasonably expected to occur by species or stock for SURTASS training
and testing activities.

Table 3--Total Annual and 7-year Incidental Take Authorized by Species or Stock by Harassment Type
----------------------------------------------------------------------------------------------------------------
Maximum annual Maximum annual 7-year total 7-year total
Species Stock Level B Level A Level B Level A
harassment harassment harassment harassment
----------------------------------------------------------------------------------------------------------------
North Pacific right whale..... NSD............. 325 2 2,271 11
Blue whale.................... NSD............. 1,062 3 7,426 21
Blue whale.................... Central North 13 .............. 83 ..............
Pacific.
Bryde's whale................. NSD............. 816 1 5,708 5
Bryde's whale................. Hawaii.......... 7 .............. 41 ..............
Fin whale..................... NSD............. 5,738 32 40,165 218
Fin whale..................... Hawaii.......... 16 .............. 111 ..............
Humpback whale................ NSD............. 3 .............. 13 ..............
Humpback whale................ Hawaii.......... 13 .............. 79 ..............
Humpback whale................ Western North 1,133 4 7,926 24
Pacific.
Antarctic minke whale......... NSD............. 48 .............. 327 ..............
Minke whale................... NSD............. 3,020 6 21,135 42
Minke whale................... Hawaii.......... 3 .............. 15 ..............
Omura's whale................. NSD............. 217 1 1,513 3
Sei whale..................... NSD............. 2,021 9 14,140 58
Sei whale..................... Hawaii.......... 5 1 30 1
Sperm whale................... NSD............. 37 .............. 253 ..............
Sperm whale................... North Pacific... 225 .............. 1,569 ..............
Sperm whale................... Hawaii.......... 15 .............. 101 ..............
Dwarf sperm whale............. NSD............. 719 .............. 5,025 ..............
Dwarf sperm whale............. Hawaii.......... 151 .............. 1,056 ..............
Pygmy sperm whale............. NSD............. 864 .............. 6,039 ..............
Pygmy sperm whale............. Hawaii.......... 152 .............. 1,058 ..............
Baird's beaked whale.......... NSD............. 64,875 .............. 454,121 ..............
Blainville's beaked whale..... NSD............. 61,964 .............. 433,748 ..............
Blainville's beaked whale..... Hawaii.......... 2,073 .............. 14,511 ..............
Deraniyagala's beaked whale... NSD............. 9,448 .............. 66,130 ..............
Ginkgo-toothed beaked whale... NSD............. 30,342 .............. 212,384 ..............
Goose-beaked whale............ NSD............. 111,485 .............. 780,389 ..............
Goose-beaked whale............ Hawaii.......... 9,185 .............. 64,291 ..............
Hubbs' beaked whale........... NSD............. 25,289 .............. 177,021 ..............
Longman's beaked whale........ NSD............. 69,988 .............. 489,908 ..............
Longman's beaked whale........ Hawaii.......... 5,017 .............. 35,116 ..............
Stejneger's beaked whale...... NSD............. 37,258 .............. 260,803 ..............
False killer whale............ NSD............. 60 .............. 420 ..............
False killer whale............ Main Hawaiian 1 .............. 1 ..............
Islands Insular.
False killer whale............ Hawaii Pelagic.. 7 .............. 49 ..............
Killer whale.................. NSD............. 173 .............. 1,206 ..............
Killer whale.................. Hawaii.......... 1 .............. 4 ..............
Melon-headed whale............ NSD............. 537 .............. 3,749 ..............
Melon-headed whale............ Hawaiian Islands 107 .............. 749 ..............
Pygmy killer whale............ NSD............. 318 .............. 2,214 ..............
Pygmy killer whale............ Hawaii.......... 32 .............. 218 ..............
Short-finned pilot whale...... NSD............. 1,083 .............. 7,579 ..............
Short-finned pilot whale...... Hawaii.......... 76 .............. 528 ..............
Bottlenose dolphin............ NSD............. 1,901 .............. 13,299 ..............
Bottlenose dolphin............ Hawaii Pelagic.. 32 .............. 215 ..............
Common dolphin................ NSD............. 1,713 .............. 11,987 ..............
Fraser's dolphin.............. NSD............. 465 .............. 3,247 ..............
Fraser's dolphin.............. Hawaii.......... 152 .............. 1,056 ..............
Northern right whale dolphin.. NSD............. 10 .............. 67 ..............
Pacific white-sided dolphin... North Pacific... 49 .............. 342 ..............
Pantropical spotted dolphin... NSD............. 2,785 .............. 19,490 ..............
Pantropical spotted dolphin... Hawaii Pelagic.. 233 .............. 1,626 ..............
Risso's dolphin............... NSD............. 1,575 .............. 11,015 ..............
Risso's dolphin............... Hawaii.......... 38 .............. 262 ..............
Rough-toothed dolphin......... NSD............. 508 .............. 3,555 ..............
Rough-toothed dolphin......... Hawaii.......... 299 .............. 2,092 ..............
Spinner dolphin............... NSD............. 276 .............. 1,924 ..............
Spinner dolphin............... Hawaii Pelagic.. 15 .............. 98 ..............
Striped dolphin............... NSD............. 4,327 .............. 30,277 ..............
Striped dolphin............... Hawaii Pelagic.. 200 .............. 1,393 ..............
Dall's porpoise............... NSD............. 3,020 .............. 21,130 ..............
Northern fur seal............. NSD............. 1,296 .............. 9,067 ..............
Steller sea lion.............. Western......... 1 .............. 2 ..............

[[Page 47681]]

Harbor seal................... California...... 1 .............. 1 ..............
Ribbon seal................... NSD............. 37,650 1 263,550 2
Hawaiian monk seal............ Hawaii.......... 1 .............. 7 ..............
Ringed seal................... NSD............. 25 .............. 165 ..............
Spotted seal.................. Bering.......... 71 .............. 487 ..............
----------------------------------------------------------------------------------------------------------------
Note: A stock or population listed as NSD is not a designated stock under the MMPA. Zero (0) impacts indicate
total less than 0.5 and a dash (-) is a true zero. In some cases where the estimated take within a cell is
equal to 1, that value has been rounded up from a value that is less than 0.5 to avoid underestimating
potential impacts to a species or stock based on the 7-year rounding rules discussed in section 2.4 of
appendix B (PAC SURTASS LFA Acoustic Analysis Report) of the application.

Table 4 provides estimated take by effect type from sonar (with
most take from LFA sonar), including the comparative amounts of TTS and
behavioral disturbance for each species or stock annually, noting that
if an animat was modeled as ``taken'' through exposure to both TTS and
behavioral disturbance in the model, it was recorded as a TTS because
predicted exposures above TTS thresholds, characterized as TTS takes,
could also include direct behavioral disturbance. Of note, a higher
proportion of the takes by Level B harassment of mysticetes include the
potential for TTS (as compared to other taxa and prior rules) due to a
combination of the fact that mysticetes are relatively less sensitive
to direct behavioral disturbance and the number of auditory impacts
from sonar (both TTS and AUD INJ) have increased for some species since
the previous analysis (84 FR 40132, August 13, 2019), largely due to
changes in both the acoustic criteria and the modeling approach. The
discussion of behavioral impacts in the Analysis and Negligible Impact
Determination section considers the total quantified TTS and direct
behavioral disturbance takes.
Additionally, the updated Phase IV HF cetacean criteria reflect
greater susceptibility to auditory effects at low and mid-frequencies
than previously analyzed for the 2019 SURTASS final rule. Consequently,
the predicted auditory effects due to sources under 10 kHz, including
SURTASS LFA sonar, are substantially greater for this auditory group
than in prior analyses of the same activities. Thus, some modeled
exposures that would previously have been categorized as significant
behavioral responses may now instead be counted as auditory effects
(TTS and AUD INJ). For VHF cetaceans, susceptibility to auditory
effects has not changed substantially since the prior analysis.

Table 4--Annual and 7-Year Estimated Take of Marine Mammal Species or Stock by Effect Type
--------------------------------------------------------------------------------------------------------------------------------------------------------
Maximum annual Maximum annual Maximum annual Maximum 7-year Maximum 7-year Maximum 7-year
Species Stock behavioral TTS AUD INJ behavioral TTS AUD INJ
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Pacific right whale......... NSD................. 0 325 2 0 2,271 11
Blue whale........................ NSD................. 1 1,061 3 4 7,422 21
Blue whale........................ Central North 1 12 .............. 1 82 ..............
Pacific.
Bryde's whale..................... NSD................. 17 799 1 115 5,593 5
Bryde's whale..................... Hawaii.............. 1 6 .............. 5 36 ..............
Fin whale......................... NSD................. 2 5,736 32 13 40,152 218
Fin whale......................... Hawaii.............. 0 16 .............. 0 111 ..............
Humpback whale.................... NSD................. 1 2 .............. 1 12 ..............
Humpback whale.................... Hawaii.............. 2 11 .............. 8 71 ..............
Humpback whale.................... Western North 5 1,128 4 34 7,892 24
Pacific.
Antarctic minke whale............. NSD................. 4 44 .............. 22 305 ..............
Minke whale....................... NSD................. 53 2,967 6 371 20,764 42
Minke whale....................... Hawaii.............. 1 2 .............. 3 12 ..............
Omura's whale..................... NSD................. 1 216 1 7 1,506 3
Sei whale......................... NSD................. 5 2,016 9 34 14,106 58
Sei whale......................... Hawaii.............. 1 4 1 2 28 1
Sperm whale....................... NSD................. 37 .............. .............. 253 .............. ..............
Sperm whale....................... North Pacific....... 224 1 .............. 1,568 1 ..............
Sperm whale....................... Hawaii.............. 15 .............. .............. 101 .............. ..............
Dwarf sperm whale................. NSD................. 718 1 .............. 5,024 1 ..............
Dwarf sperm whale................. Hawaii.............. 151 .............. .............. 1,056 .............. ..............
Pygmy sperm whale................. NSD................. 863 1 .............. 6,037 2 ..............
Pygmy sperm whale................. Hawaii.............. 151 1 .............. 1,057 1 ..............
Baird's beaked whale.............. NSD................. 64,875 0 .............. 454,121 0 ..............
Blainville's beaked whale......... NSD................. 61,964 .............. .............. 433,748 .............. ..............
Blainville's beaked whale......... Hawaii.............. 2,073 .............. .............. 14,511 .............. ..............

[[Page 47682]]

Deraniyagala's beaked whale....... NSD................. 9,448 .............. .............. 66,130 .............. ..............
Ginkgo-toothed beaked whale....... NSD................. 30,341 1 .............. 212,383 1 ..............
Goose-beaked whale................ NSD................. 111,484 1 .............. 780,388 1 ..............
Goose-beaked whale................ Hawaii.............. 9,185 .............. .............. 64,291 .............. ..............
Hubbs' beaked whale............... NSD................. 25,289 .............. .............. 177,021 .............. ..............
Longman's beaked whale............ NSD................. 69,987 1 .............. 489,906 2 ..............
Longman's beaked whale............ Hawaii.............. 5,017 .............. .............. 35,116 .............. ..............
Stejneger's beaked whale.......... NSD................. 37,258 .............. .............. 260,803 .............. ..............
False killer whale................ NSD................. 60 .............. .............. 420 .............. ..............
False killer whale................ Main Hawaiian 1 .............. .............. 1 .............. ..............
Islands Insular.
False killer whale................ Hawaii Pelagic...... 7 .............. .............. 49 .............. ..............
Killer whale...................... NSD................. 172 1 .............. 1,200 6 ..............
Killer whale...................... Hawaii.............. 1 .............. .............. 4 .............. ..............
Melon-headed whale................ NSD................. 536 1 .............. 3,747 2 ..............
Melon-headed whale................ Hawaiian Islands.... 107 .............. .............. 749 .............. ..............
Pygmy killer whale................ NSD................. 317 1 .............. 2,213 1 ..............
Pygmy killer whale................ Hawaii.............. 32 .............. .............. 218 .............. ..............
Short-finned pilot whale.......... NSD................. 1,081 2 .............. 7,567 12 ..............
Short-finned pilot whale.......... Hawaii.............. 76 .............. .............. 528 .............. ..............
Bottlenose dolphin................ NSD................. 1,897 4 .............. 13,276 23 ..............
Bottlenose dolphin................ Hawaii Pelagic...... 31 1 .............. 213 2 ..............
Common dolphin.................... NSD................. 1,712 1 .............. 11,984 3 ..............
Fraser's dolphin.................. NSD................. 464 1 .............. 3,244 3 ..............
Fraser's dolphin.................. Hawaii.............. 151 1 .............. 1,054 2 ..............
Northern right whale dolphin...... NSD................. 10 .............. .............. 67 .............. ..............
Pacific white-sided dolphin....... North Pacific....... 49 .............. .............. 342 .............. ..............
Pantropical spotted dolphin....... NSD................. 2,784 1 .............. 19,485 5 ..............
Pantropical spotted dolphin....... Hawaii Pelagic...... 233 .............. .............. 1,626 .............. ..............
Risso's dolphin................... NSD................. 1,574 1 .............. 11,013 2 ..............
Risso's dolphin................... Hawaii.............. 38 .............. .............. 262 .............. ..............
Rough-toothed dolphin............. NSD................. 508 .............. .............. 3,555 .............. ..............
Rough-toothed dolphin............. Hawaii.............. 299 .............. .............. 2,092 .............. ..............
Spinner dolphin................... NSD................. 275 1 .............. 1,923 1 ..............
Spinner dolphin................... Hawaii Pelagic...... 14 1 .............. 97 1 ..............
Striped dolphin................... NSD................. 4,325 2 .............. 30,269 8 ..............
Striped dolphin................... Hawaii Pelagic...... 199 1 .............. 1,391 2 ..............
Dall's porpoise................... NSD................. 3,019 1 .............. 21,128 2 ..............
Northern fur seal................. NSD................. 1,296 0 .............. 9,067 0 ..............
Steller sea lion.................. Western............. 1 .............. .............. 2 .............. ..............
Harbor seal....................... California.......... 1 .............. .............. 1 .............. ..............
Ribbon seal....................... NSD................. 3,376 34,274 1 23,632 239,918 2
Hawaiian monk seal................ Hawaii.............. 1 .............. .............. 7 .............. ..............
Ringed seal....................... NSD................. 24 1 .............. 164 1 ..............
Spotted seal...................... Bering.............. 70 1 .............. 486 1 ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note: A stock or population listed as NSD is not a designated stock under the MMPA. Zero (0) impacts indicate total less than 0.5 and a dash (-) is a
true zero. In some cases where the estimated take within a cell is equal to 1, that value has been rounded up from a value that is less than 0.5 to
avoid underestimating potential impacts to a species or stock based on the 7-year rounding rules discussed in section 2.4 of appendix B (PAC SURTASS
LFA Acoustic Analysis Report) of the application.

Mitigation Measures

Under section 101(a)(5)(A) of the MMPA, NMFS must set forth the
permissible methods of taking pursuant to the activity, and other means
of effecting the least practicable adverse impact on the 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 subsistence uses (``least
practicable adverse impact''). NMFS does not have a regulatory
definition for least

[[Page 47683]]

practicable adverse impact. The 2004 NDAA amended the MMPA as it
relates to military readiness activities and the ITA process such that
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. For
additional discussion of NMFS' interpretation of the least practicable
adverse impact standard, see the Mitigation Measures section of the
Gulf of Alaska Study Area final rule (88 FR 604, January 4, 2023).
NMFS' implementing regulations require applicants for incidental
take authorizations to include information about the availability and
feasibility (economic and technological) of equipment, methods, and
manner of conducting the activity or other means of effecting the least
practicable adverse impact on the affected species or stocks and their
habitat (50 CFR 216.104(a)(11). The measures described in the following
section were proposed by the Navy in their adequate and complete
application or are the result of subsequent coordination between NMFS
and the Navy. Pursuant to the 2004 NDAA, NMFS coordinated with the
Navy, and the Navy has agreed that all of the mitigation measures are
practicable. NMFS has fully reviewed the measures under the least
practicable adverse impact standard and has determined they are
appropriate. NMFS describes these below as mitigation requirements and
has included them in the final regulations.
As noted in the Changes from the Proposed Rule to the Final Rule
section, this final rule includes new geographic mitigation measures
and modifications to existing geographic measures added as a result of
coordination between NMFS and the Navy. The Navy has agreed that all of
the following modifications and additions to geographic mitigations are
practicable. These changes are described in detail in the sections
below. Besides these changes, the required measures remain the same as
those described in the proposed rule.

Implementation of Least Practicable Adverse Impact Standard

Here, we discuss how we determine whether a measure or set of
measures meets the ``least practicable adverse impact'' standard. Our
separate analysis of whether the take anticipated to result from the
Navy's activities meets the ``negligible impact'' standard appears in
the Analysis and Negligible Impact Determination section below.
Our evaluation of potential mitigation measures includes
consideration of two primary factors:
1. The manner in which, and the degree to which, implementation of
the potential measure(s) is expected to reduce adverse impacts to
marine mammal species or stocks, their habitat, or their availability
for subsistence uses (where relevant). This analysis considers such
things as the nature of the potential adverse impact (e.g., likelihood,
scope, and range), the likelihood that the measure will be effective if
implemented, and the likelihood of successful implementation.
2. The practicability of the measure(s) for applicant
implementation. Practicability of implementation may consider such
things as cost, impact on activities, and, in the case of a military
readiness activity, specifically considers personnel safety,
practicality of implementation, and impact on the effectiveness of the
military readiness activity.
While the language of the least practicable adverse impact standard
calls for minimizing impacts to affected species or stocks, we
recognize that the reduction of impacts to those species or stocks
accrues through the application of mitigation measures that limit
impacts to individual animals. Accordingly, NMFS' analysis focuses on
measures that are designed to avoid or minimize impacts on individual
marine mammals that are more likely to increase the probability or
severity of population-level effects.
While direct evidence of impacts to species or stocks from a
specified activity is rarely available, and additional study is still
needed to understand how specific disturbance events affect the fitness
of individuals of certain species, there have been improvements in
understanding the process by which disturbance effects are translated
to the population. With recent scientific advancements (both marine
mammal energetic research and the development of energetic frameworks),
the relative likelihood or degree of impacts on species or stocks may
often be inferred given a detailed understanding of the activity, the
environment, and the affected species or stocks--and the best available
science has been used here. This same information is used in the
development of mitigation measures and helps us understand how
mitigation measures contribute to lessening effects (or the risk
thereof) to species or stocks.
In the evaluation of specific measures, the details of the
specified activity will necessarily inform each of the two primary
factors discussed above (expected reduction of impacts and
practicability) and are carefully considered to determine the types of
mitigation that are appropriate under the least practicable adverse
impact standard. Analysis of how a potential mitigation measure may
reduce adverse impacts on a marine mammal stock or species,
consideration of personnel safety, practicality of implementation, and
consideration of the impact on effectiveness of military readiness
activities are not issues that can be meaningfully evaluated through a
yes/no lens. The manner in which, and the degree to which,
implementation of a measure is expected to reduce impacts, as well as
its practicability in terms of these considerations, can vary widely.
For example, a time/area restriction could be of very high value for
decreasing population-level impacts (e.g., avoiding disturbance of
feeding females in an area of established biological importance) or it
could be of lower value (e.g., decreased disturbance in an area of high
productivity but of less biological importance). Regarding
practicability, for example, a measure might involve restrictions in an
area or time that impede the Navy's ability to certify a ship (higher
impact on mission effectiveness), or it could mean delaying an event by
30 minutes to avoid exposure of a marine mammal to injurious levels of
sound (i.e., lower impact). A responsible evaluation of ``least
practicable adverse impact'' will consider the factors along these
realistic scales. Accordingly, the greater the likelihood that a
measure will contribute to reducing the probability or severity of
adverse impacts to the species or stock or its habitat, the greater the
weight that measure is given when considered in combination with
practicability to determine the appropriateness of the mitigation
measure, and vice versa. We discuss consideration of these factors in
greater detail below.
Reduction of Adverse Impacts to Marine Mammal Species or Stocks and
Their Habitat
The emphasis given to a measure's ability to reduce the impacts on
a species or stock considers the degree, likelihood, and context of the
anticipated reduction of impacts to individuals (and how many
individuals) as well as the status of the species or stock.
The ultimate impact on any individual from a disturbance event
(which informs the likelihood of adverse species- or stock-level
effects) is dependent on the circumstances and

[[Page 47684]]

associated contextual factors, such as duration of exposure to
stressors. Though any proposed mitigation needs to be evaluated in the
context of the specific activity and the species or stocks affected,
measures with the following types of effects have greater value in
reducing the likelihood or severity of adverse species- or stock-level
impacts: (1) avoiding or minimizing injury or mortality; (2) limiting
interruption of known feeding, breeding, mother/young, or resting
behaviors; (3) minimizing the abandonment of important habitat
(temporally and spatially); (4) minimizing the number of individuals
subjected to these types of disruptions; and (5) limiting degradation
of habitat. Mitigating these types of effects is intended to reduce the
likelihood that the activity will result in energetic or other types of
impacts that are more likely to result in reduced reproductive success
or survivorship. It is also important to consider the degree of impacts
expected in the absence of mitigation in order to assess the added
value of any potential measures. Finally, because the least practicable
adverse impact standard gives NMFS discretion to weigh a variety of
factors when determining appropriate mitigation measures and because
the focus of the standard is on reducing impacts at the species or
stock level, the least practicable adverse impact standard does not
compel mitigation for every kind of take, or for every individual
taken, if that mitigation is unlikely to meaningfully contribute to the
reduction of adverse impacts on the species or stock and its habitat,
even when practicable for implementation by the applicant.
The status of the species or stock is also relevant in evaluating
the appropriateness of potential mitigation measures in the context of
least practicable adverse impact. The following are examples of factors
that may, alone or in combination, result in greater emphasis on the
importance of a mitigation measure in reducing impacts on a species or
stock: (1) the stock is known to be decreasing or status is unknown,
but believed to be declining; (2) the known annual mortality (from any
source) is approaching or exceeding the PBR level (as defined in MMPA
section 3(20)); (3) the affected species or stock is a small, resident
population; or (4) the stock is involved in a UME or has other known
vulnerabilities (e.g., recovering from an oil spill).
Habitat mitigation, particularly as it relates to rookeries, mating
grounds, and areas of similar significance, is also relevant to
achieving the standard and can include measures such as reducing
impacts of the activity on known prey utilized in the activity area or
reducing impacts on physical habitat. As with species- or stock-related
mitigation, the emphasis given to a measure's ability to reduce impacts
on a species or stock's habitat considers the degree, likelihood, and
context of the anticipated reduction of impacts to habitat. Because
habitat value is informed by marine mammal presence and use, in some
cases there may be overlap in measures for the species or stock and for
use of habitat.
We consider available information indicating the likelihood of any
measure to accomplish its objective. If evidence shows that a measure
has not typically been effective nor successful, then either that
measure should be modified or the potential value of the measure to
reduce effects should be lowered.
Practicability
Factors considered may include cost, impact on activities, and, in
the case of a military readiness activity, will include personnel
safety, practicality of implementation, and impact on the effectiveness
of the military readiness activity (see 16 U.S.C. 1371(a)(5)(A)(iii)).

Assessment of Mitigation Measures for the Study Area

NMFS has fully reviewed the specified activities and the mitigation
measures included in the application and the 2026 SURTASS SEIS/OEIS to
determine if the mitigation measures would result in the least
practicable adverse impact on marine mammals and their habitat. NMFS
worked with the Navy in the development of their initially proposed
measures, which are informed by years of implementation and monitoring.
A complete discussion of the Navy's evaluation process used to develop,
assess, and select mitigation measures, which was informed by input
from NMFS, can be found in chapter 4 (Mitigation, Monitoring, and
Reporting) and appendix F (Marine Mammal Offshore Biologically
Important Area (OBIA) Analysis) of the 2026 SURTASS SEIS/OEIS. The
process described in these sections of the 2026 SURTASS SEIS/OEIS
supported NMFS' independent evaluation of whether the mitigation
measures would meet the least practicable adverse impact standard. The
Navy is required to implement the mitigation measures identified in
this final rule for the full 7 years to avoid or reduce potential
impacts from acoustic stressors on marine mammals.
As a general matter, where an applicant proposes measures that are
likely to reduce impacts to marine mammals, the fact that they are
included in the application indicates that the measures are
practicable, and it is not necessary for NMFS to conduct a detailed
analysis of the measures the applicant proposed (rather, they are
simply included). However, it is still necessary for NMFS to consider
whether there are additional practicable measures that would
meaningfully reduce the probability or severity of impacts that could
affect reproductive success or survivorship or habitat.
Since publication of the proposed rule, additional mitigation
requirements have been added that will further reduce the likelihood
and/or severity of adverse impacts on marine mammals and their habitat.
Pursuant to the 2004 NDAA, NMFS coordinated with the Navy, and the Navy
has agreed the additional mitigation measures are practicable for
implementation, as previously described in the Changes from the
Proposed Rule to the Final Rule section. Below we describe the measures
that the Navy must implement and explain the manner in which they are
expected to reduce the likelihood or severity of adverse impacts on
marine mammals and their habitats.
The Navy has agreed to mitigation measures that would reduce the
probability and/or severity of impacts expected to result from acute
exposure to acoustic sources and impacts to marine mammal habitat.
Specifically, the Navy must use a combination of delayed starts, sonar
ramp-ups, and shutdowns to minimize the likelihood or severity of AUD
INJ and reduce instances of TTS or more severe behavioral disturbance
typically caused by exposure to higher received sound levels from
acoustic sources. The Navy must implement the following primary
mitigation measures, which are described in more detail below:
Mitigation Monitoring: Use of a comprehensive suite of
mitigation monitoring methods to support activity-based mitigation,
including the use of visual monitoring, passive acoustic monitoring,
and active acoustic monitoring using the HF/M3 system described below.
Activity-Based Measures: Use of a combination of real-time
measures to minimize the likelihood or severity of AUD INJ and reduce
instances of TTS or more severe behavioral disturbance typically caused
by exposure to higher received sound levels from acoustic sources,
including delayed starts and shutdowns of the LFA sonar source, as well
as ramp-ups of the HF/M3 system.
Geographic Measures: Application of multiple time/area
restrictions, including a year-round, 22-km CSR and

[[Page 47685]]

avoiding identified OBIAs for marine mammals in areas or at times where
they are known to engage in important behaviors (e.g., calving), to
reduce impacts on reproduction or survival of individuals that could
lead to population-level impacts.
The Navy assessed the practicability of the proposed measures in
the context of personnel safety, practicality of implementation, and
their impacts on the Navy's ability to meet their congressionally
mandated requirements and found that the measures are supportable. As
described in more detail below, NMFS has independently evaluated the
measures the Navy proposed in the manner described earlier in this
section (i.e., in consideration of their ability to reduce adverse
impacts on marine mammal species and their habitat and their
practicability for implementation). We have determined that the
measures would significantly minimize impacts on the affected marine
mammal species and stocks and their habitat and, further, be
practicable for implementation by the Navy.
The Navy also evaluated numerous measures in the 2026 SURTASS SEIS/
OEIS that were not included in the application, and NMFS independently
reviewed and concurs with the Navy's analysis that their inclusion was
not appropriate under the least practicable adverse impact standard
based on our assessment. The Navy considered these additional potential
mitigation measures in the context of the potential benefits to marine
mammals and whether they are practical or impractical. This included
eight recommendations from NMFS, five of which the Navy concurred met
its Practicability Criteria and Sufficiently Beneficial requirements
and are included in this final rule. Three of the recommendations did
not meet these criteria as described below. The modifications and
additions deemed practicable by the Navy and included in this final
rule include: (1) extension of the effective period of OBIA #28 Mariana
Islands; (2) extension of the effective period of OBIA #33 Southeast
Kamchatka; (3) northward expansion of OBIA #33 Southeast Kamchatka; (4)
spatial and temporal expansion of OBIA #37 Southern Bali; and (5)
designation of a new OBIA for NPRW. The Navy determined that the
remaining three recommendations were not practicable: (1) the northward
expansion of OBIA #29 Ryukyu-Philippines; (2) designation of a new OBIA
for migratory humpback whales along the Izu-Ogasawara and Mariana
Trenches from November through May; and (3) designation of a new year-
round OBIA for migrating whales along the Emperor Seamount Chain and
Northern Hawaiian Ridge (North Pacific Transition Zone). The Navy
determined the acceptance of these three recommendations would
negatively impact SURTASS training and testing and rejected them based
on the need to train and test in each region due to specific
bathymetric and oceanographic conditions difficult to replicate
accurately elsewhere in the Study Area. All three areas are also
critical locations for several real-world military considerations that
might influence training and testing in each area. NMFS concurs with
the Navy's assessment that these OBIAs are impracticable, as described
in more detail below.
Regarding designation of a new Izu-Ogasawara and Mariana Trenches
OBIA, the Navy cited a lack of scientific evidence of Western North
Pacific DPS humpback whale migratory paths, whether along the Izu-
Ogasawara and Mariana Trenches or directly from breeding areas to
foraging grounds, bypassing the area recommended for OBIA designation.
Data from Mate et al. (2018) and Palacios et al. (2020) on the Central
Pacific DPS of humpback whales suggest the animals generally straight-
line migrate from Hawaiian breeding grounds to foraging grounds.
Regarding the Emperor Seamount Chain and Northern Hawaiian Ridge
(North Pacific Transition Zone), the Navy noted that Garrigue et al.
(2015) provided evidence that southern hemisphere humpback whales were
resident to specific seamounts for periods of a few days to a few
weeks, and not resident to every seamount for extended periods of time.
Regarding other large whale species, Konishi et al. (2024) tagged 55
sei whales with tag durations of 6-145 days (representing 2-40 percent
of their annual movements) and found only a few tagged animals passed
through the southern Emperor Seamount Chain. The Navy further stated
that, unlike breeding or foraging areas, training and testing impacts
on large whale movements are not expected to result in significant
behavioral responses to transiting whales such that they abandon their
migration. The limited number of T-AGOS vessels and relatively limited
time training and testing across the entire Study Area is not expected
to result in continued year-round usage near the seamount chain
recommended for inclusion as an OBIA.
Section 4.6 (Mitigation and Monitoring Measures Considered but
Eliminated) of chapter 4 of the 2026 SURTASS SEIS/OEIS includes an
analysis of an array of different types of mitigation that have been
recommended over the years by non-governmental organizations or the
public, through scoping or public comment on environmental compliance
documents. These recommendations generally fall into three categories,
discussed below: (1) reduction of activity; (2) activity-based
operational measures; and (3) time/area limitations.
As described in section 4.6 of the 2026 SURTASS SEIS/OEIS, the Navy
considered reducing the overall amount of training and testing
activities, longer suspension or delay period (clearance time),
restricting transmission to daylight hours, increased CSR, and expanded
geographic sound field operational constraints. Many of these
mitigation measures could potentially reduce the number of marine
mammals taken via direct reduction of the activities or amount of sound
energy put in the water. However, as described in chapter 4 of the 2026
SURTASS SEIS/OEIS, the Navy needs to train in the conditions in which
they fight. These types of modifications fundamentally change the
activity in a manner that would not support the purpose and need for
the training (i.e., are entirely impracticable) and therefore are not
considered further. NMFS finds the Navy's explanation of why adoption
of these recommendations would unacceptably undermine the purpose of
the training persuasive. After independent review, NMFS finds the
Navy's judgment on the impacts of these potential mitigation measures
to personnel safety, practicality of implementation, and the
effectiveness of training persuasive, and for these reasons, NMFS finds
that these measures do not meet the least practicable adverse impact
standard because they are not practicable.
Lastly, chapter 4 and appendix F of the 2026 SURTASS SEIS/OEIS also
describe a comprehensive analysis of potential geographic mitigation
that includes consideration of both a biological assessment of how the
potential time/area limitation would benefit the species and its
habitat (e.g., is a key area of biological importance or would result
in avoidance or reduction of impacts) in the context of the stressors
of concern in the specific area and an operational assessment of the
practicability of implementation (e.g., including an assessment of the
specific importance of an area for training, considering proximity to
training ranges and emergency landing fields and other issues). In some
cases, potential benefits to marine mammals were non-existent, while in
others the consequences on mission effectiveness were too great.

[[Page 47686]]

NMFS has reviewed the Navy's analyses in the application and
chapter 4 and appendix F of the 2026 SURTASS SEIS/OEIS, which considers
the same factors that NMFS considers to satisfy the least practicable
adverse impact standard, and concurs with the analysis and conclusions.
Therefore, NMFS is not requiring any of the measures that the Navy
ruled out in the 2026 SURTASS SEIS/OEIS. Below are the mitigation
measures that NMFS has determined would ensure the least practicable
adverse impact on all affected species and their habitat, including the
specific considerations for military readiness activities.
The following sections describe the mitigation measures that must
be implemented in association with the activities analyzed in this
document. The mitigation measures are discussed in three sections: (1)
mitigation monitoring methods; (2) activity-based mitigation; (3) and
geographic mitigation. Table 5 describes the information designed to
aid Lookouts and other applicable personnel with their observation,
environmental compliance, and reporting responsibilities.

Table 5--Environmental Awareness and Education
------------------------------------------------------------------------
Stressor or activity: all training and testing activities, as applicable
-------------------------------------------------------------------------
Requirements: Navy personnel (including civilian personnel) involved in
mitigation and training or testing activity reporting under the
specified activities must complete one or more modules of the U.S. Navy
Afloat Environmental Compliance Training Series, as identified in their
career path training plan. Modules include:
Introduction to Afloat Environmental Compliance Training
Series. The introductory module provides information on
environmental laws (e.g., ESA, MMPA) and the corresponding
responsibilities that are relevant to military readiness
activities. The material explains why environmental compliance is
important in supporting the Navy's commitment to environmental
stewardship.
Marine Species Awareness Training. In 2021, the Navy
developed a new SURTASS-specific Marine Species Awareness Training
module. The module was developed by civilian marine biologists and
approved by NMFS. This video-based training provides information on
marine species sighting cues, visual observation tools and
techniques for SURTASS vessels, and sighting notification
procedures. It is designed as a complement to the U.S. Navy Lookout
Training Handbook adapted to SURTASS vessel training and testing.
The module is required for ship masters, bridge watchstanders, and
lookout personnel.
------------------------------------------------------------------------
Note: T-AGOS vessels have an onboard computer system that the Navy must
use to implement CSR and OBIA mitigation measures, including real-time
acoustic propagation prediction mapping. Similar mitigation is
implemented using Protective Measures Assessment Protocol (PMAP) and
Sonar Positional Reporting System (SPORTS) onboard vessels in other
Study Areas. The Navy intends for future T-AGOS vessels to use PMAP
and SPORTS; however, use of these specific programs is not proposed
herein to provide flexibility for existing T-AGOS vessels that may not
be able to operate those systems at this time.

Additionally, in the event of a live stranding (or near-shore
atypical milling) event within the Study Area or within 50 km of the
boundary of the Study Area, where the stranding network is engaged in
herding or other interventions to return animals to the water, NMFS OPR
will advise the Navy of the need to implement shutdown procedures for
SURTASS LFA sonar within 50 km of the stranding or near-shore atypical
milling event. Following this initial shutdown, NMFS will communicate
with the Navy to determine if circumstances support any modification of
the shutdown zone. The Navy may decline to implement all or part of the
shutdown if it determines that continuation of the military readiness
activities is necessary for national security. Shutdown procedures for
live stranding or milling cetaceans include the following:
If at any time, the marine mammal(s) die or are
euthanized, or if herding/intervention efforts are stopped, NMFS will
immediately advise that the shutdown around the animals' location is no
longer needed;
Otherwise, shutdown procedures will remain in effect until
NMFS determines and advises that all live animals involved have left
the area (either of their own volition or following an intervention);
and
If further observations of the marine mammals indicate the
potential for re-stranding, additional coordination will be required to
determine what measures are necessary to minimize that likelihood
(e.g., extending the shutdown or moving operations farther away) and to
implement those measures as appropriate.

Mitigation Monitoring

The Navy must use a comprehensive three-part monitoring program to
support the implementation of real-time, activity-based mitigation
measures described in the next section. The combined use of all three
types of monitoring (i.e., visual monitoring, passive acoustic
monitoring, and active acoustic monitoring) increases the likelihood of
marine mammal detection and, thereby, the effectiveness of the
mitigation measures. The mitigation monitoring measures are provided in
table 6.

Table 6--Mitigation Monitoring
------------------------------------------------------------------------
Monitoring method Requirements
------------------------------------------------------------------------
Visual Monitoring Visual observations must be conducted by
trained Lookouts on the vessel's bridge
using standard binoculars (7x) and the
naked eye. Pedestal-mounted `Big Eye'
(20 x 110 millimeter (mm)) binoculars
(if installed) must be used to assist in
the detection of marine mammals in the
vicinity of the vessel.
Lookouts must conduct visual monitoring
from the vessel's bridge during all
daylight hours (30 minutes before
sunrise until 30 minutes after sunset).
During training and testing activities
that employ SURTASS LFA sonar in the
active mode, Lookouts must conduct
visual monitoring beginning 30 minutes
before sunrise or 30 minutes before
SURTASS LFA sonar begins to transmit and
continue until 30 minutes after sunset
or until 15 minutes after the SURTASS
LFA sonar transmissions cease.
Lookouts must log all detections of
marine mammals during SURTASS LFA sonar
transmissions.
Lookouts must record the number,
identification, bearing, and range of
observed marine mammals and must
identify marine mammals to the lowest
taxonomic level possible.

[[Page 47687]]

Lookouts must continue visual
observations until 15 minutes have
passed since the last detection of the
marine mammal.
Passive Acoustic Monitoring.. Navy passive acoustic sonar technicians
must conduct passive acoustic monitoring
using the SURTASS towed horizontal line
array to detect vocalizing marine
mammals. Passive acoustic sonar
technicians are trained to identify
detected vocalizations to marine mammal
species whenever possible.
Passive acoustic monitoring must begin 30
minutes before the SURTASS LFA sonar
begins to transmit and continue until 15
minutes after SURTASS LFA sonar
transmissions cease.
If a detected sound is estimated to be
from a vocalizing marine mammal, the
sonar technician will notify the senior
military member-in-charge, who must
alert the HF/M3 sonar operator and
Lookouts (during daylight).
Active Acoustic (HF/M3) Active acoustic mitigation uses the HF/M3
Monitoring sonar to detect, locate, and track
marine mammals in relation to the
SURTASS LFA sonar array and the LFA
mitigation zone.
HF/M3 sonar monitoring must begin 30
minutes before the SURTASS LFA sonar
begins to transmit and continue until 15
minutes after SURTASS LFA sonar
transmissions cease.
If a marine mammal is detected during HF/
M3 monitoring within the SURTASS LFA
mitigation zone, the sonar operator must
notify the senior military member-in-
charge.
------------------------------------------------------------------------
Note: Effectiveness of the HF/M3 sonar system as a mitigation tool to
detect marine mammals has been described in the Navy's 2001 Final
Overseas Environmental Impact Statement/Environmental Impact Statement
(OEIS/EIS) (section 2 and section 4) for SURTASS LFA sonar (U.S.
Department of the Navy, 2001) in addition to the technical report by
Ellison and Stein (1999). To summarize the effectiveness of the HF/M3
sonar system, the Navy's testing and analysis of the HF/M3 sonar
system's capabilities indicated the system: (1) substantially
increased probability of detecting marine mammals within the LFA
mitigation zone; (2) provided a superior mitigation capability,
especially for medium- to large-sized marine mammals to a distance of
2-2.5 km from the system; (3) would result in detections of a marine
mammal before it even entered the LFA mitigation zone--based on the
scan rate of the HF/M3 sonar system, most animals would receive at
least eight pings from the sonar (i.e., eight sonar returns or
detections) before entering the LFA mitigation zone; (4) based on scan
rate, probability of any marine mammal being detected prior to
entering the LFA mitigation zone approached 100 percent (Ellison and
Stein, 1999); (5) the probability of HF/M3 sonar system detecting a
medium- to large-sized (approximately 10-30 m) marine mammal (humpback
to blue whale) swimming towards the system in the LFA mitigation zone
with only one HF/M3 ping would be near 100 percent (Ellison and Stein,
1999); (6) for small (approximately 2.5 m) marine mammals such as a
dolphin, detection probability is 55 percent from one HF/M3 ping when
the sonar is located at a distance of 800-930 m from the marine
mammal, while detection probability increased to 90 percent for four
HF/M3 pings; and (7) may result in higher detection probabilities in a
typical at-sea operating environment--during HF/M3 testing, analysts
noted that in expected at-sea conditions of reduced clutter
interference in the open ocean and small marine mammals traveling in
their typical group configurations (i.e., in pods), the detection rate
would be higher (Ellison and Stein, 1999). Also, we note that the
underwater conditions during which the HF/M3 data on detection
distances were collected were extremely challenging (i.e., poor sea
state and weather conditions).

Activity-Based Mitigation

The primary objective of activity-based mitigation is to reduce
overlap of marine mammals with stressors that have the potential to
cause mortality/serious injury, Level A harassment (AUD INJ and non-
auditory injury), or more severe Level B harassment (including TTS) in
real time. The Navy customizes mitigation for each applicable activity
category or stressor. Activity-based mitigation generally involves: (1)
the use of one or more trained Lookouts to diligently observe for
marine mammals within a mitigation zone; (2) requirements for Lookouts
to immediately communicate sightings of marine mammals to the
appropriate watch station for information dissemination; and (3)
requirements for the watch station to implement mitigation (e.g., halt
an activity) until certain recommencement conditions have been met.
For SURTASS LFA sonar, the Navy must implement the activity-based
mitigation measures described below (manned surface vessel mitigation
(table 7), ramp up of HF/M3 sonar (table 8), and the SURTASS LFA
mitigation zone and suspension/delay (table 9)), as appropriate, in
response to an applicable detection within, or entering into, the
relevant mitigation zone.

Table 7--Manned Surface Vessel Mitigation
------------------------------------------------------------------------
Mitigation requirements Mitigation benefits
------------------------------------------------------------------------
Manned surface vessel mitigation, which applies This mitigation is
to T-AGOS vessels underway, will be implemented intended to minimize
to the maximum extent practical based on the the already low
prevailing circumstances, including likelihood of vessel
consideration of safety of vessels, towing strike of a marine
platforms, and crews, as well as mammal.
maneuverability restrictions.
Immediately prior to getting underway and while
underway, the Lookouts will observe for marine
mammals. While underway Navy personnel must
maneuver the manned surface vessels (which may
include reducing speed) to maintain a distance
of at least 457.2 m around observed whales and
182.9 m around all other marine mammals (except
bow- or wake-riding dolphins), providing it is
safe to do so. No further action is necessary
if a dolphin continues to approach the vessel
after it has made one course and/or speed
change..
Pedestal-mounted `Big Eye' (20 x 110 mm)
binoculars (if installed) shall be used to
assist in the detection of marine mammals in
the vicinity of the vessel. If the presence of
marine mammals is detected acoustically,
Lookouts posted on the vessel shall increase
the vigilance of their visual observation.
Manned surface vessel mitigation will not be
implemented (1) when dolphins are determined to
be intentionally swimming at the bow, alongside
the vessel or vehicle, or directly behind the
vessel or vehicle (e.g., to bow-ride or wake-
ride), (2) when the vessel's safety is
threatened, or (3) when impractical based on
mission requirements (e.g., restricted ability
to maneuver during towing activities).
------------------------------------------------------------------------

[[Page 47688]]

Table 8--Ramp-Up of High Frequency Marine Mammal Monitoring (HF/M3)
Sonar
------------------------------------------------------------------------
Mitigation requirements Mitigation benefits
------------------------------------------------------------------------
Prior to full-power use, Navy personnel must A ramp-up procedure
ramp up the HF/M3 sonar power level beginning for the HF/M3 sonar
at a maximum SL of 180 dB re 1 [mu]Pa at 1 m system is intended to
RMS SPL in 10 dB increments to full operating prevent inadvertent
level (if required) over a period of no less exposures of marine
than 5 minutes. mammals to higher
Navy personnel must implement this ramp-up received levels more
procedure at least 30 minutes prior to any likely to result in
SURTASS LFA sonar transmissions and any time AUD INJ or more
after the HF/M3 sonar has been powered down for severe behavioral
more than 2 minutes.. responses if an
Navy personnel must not increase the HF/M3 animal were to occur
active sonar system's SPL once a marine mammal in close proximity to
is detected. The ramp-up may recommence once the HF/M3 sonar
marine mammals are no longer detected by all of system when it is
the monitoring methods.. turned on.
------------------------------------------------------------------------

Table 9--SURTASS LFA Mitigation Zone and Suspension/Delay
------------------------------------------------------------------------
Mitigation requirements Mitigation benefits
------------------------------------------------------------------------
The Navy has established a single, fixed This mitigation is
mitigation zone of 1.8 km for use with the designed to reduce
suspension and delay measures described below. exposure of marine
At 1.8 km, modeling shows that the sound field mammals to levels of
would be about 174.75 dB. Utilizing a single, sound that have the
fixed mitigation zone for SURTASS LFA sonar potential to cause
training and testing activities standardizes AUD INJ or more
and thus simplifies mitigation implementation severe behavioral
while continuing to ensure protection of marine impacts.
mammals in real time by limiting the potential
for marine mammals to be exposed to received
levels more likely to result in AUD INJ or more
severe behavioral responses.
If a marine mammal is detected during visual or
acoustic monitoring within the LFA mitigation
zone, the sonar operator must notify the senior
military member-in-charge, who must order the
immediate delay or suspension of LFA sonar
transmissions. During the delay/suspension,
active acoustic, visual, and passive acoustic
monitoring for marine mammals would continue..
If visual monitoring detects a marine mammal
outside the LFA mitigation zone, the bridge
officer will notify the senior military member-
in-charge of the estimated range and bearing of
the observed marine mammal. For possible visual
or acoustic marine mammal observations outside
of the zone, the sonar operator must verify (in
the case of a visual observation) or determine
(in the case of an acoustic detection) the
range and projected track of the marine mammal
and notify the senior military member-in-charge
that a detected animal is likely to pass within
the LFA mitigation zone. The senior military
member-in-charge must notify the bridge and
passive sonar operator of the potential
presence of a marine animal projected to enter
the mitigation zone. The senior military member-
in-charge must order the delay or suspension of
LFA sonar transmissions only when the marine
mammal enters the LFA mitigation zone.
Navy personnel must not commence or recommence
SURTASS LFA sonar transmissions earlier than 15
minutes after all marine mammals have left the
LFA mitigation zone and there is no further
detection of marine mammals within the LFA
mitigation zone by visual, active acoustic (HF/
M3 sonar), or passive acoustic mitigation.
------------------------------------------------------------------------

Geographic Mitigation

In addition to activity-based mitigation, the Navy must implement
geographic mitigation measures to avoid or minimize potential impacts
on marine mammals, including a CSR and activity limitations around
OBIAs. A full technical analysis of the geographic mitigation that the
Navy considered for marine mammals is provided in section 4.6 and
appendix F of the 2026 SURTASS SEIS/OEIS. The Navy took into account
public comments received on the 2025 SURTASS Draft SEIS/OEIS, 2019
SURTASS SEIS/OEIS, the best available science, and the practicability
of implementing additional mitigation measures and has enhanced its
mitigation areas and mitigation measures beyond those that were
included in the 2019-2026 regulations to further reduce impacts to
marine mammals.
NMFS conducted an independent analysis of the geographic mitigation
measures that the Navy proposed, which are described below, with a few
modifications resulting from coordination between NMFS and the Navy.
NMFS' analysis indicates that the measures in these 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 Navy's analysis and this rule. NMFS is heavily
reliant on the Navy's description of operational practicability, since
the Navy is best equipped to describe the degree to which a given
mitigation measure affects personnel safety or mission effectiveness,
and how practical it is to implement. The Navy considers the required
measures in this rule to be practicable, and NMFS concurs. We further
discuss the manner in which the geographic mitigations will reduce the
likelihood, magnitude, or severity of adverse impacts to marine mammal
species or their habitat in the Analysis and Negligible Impact
Determination section.
Table 10 details geographic mitigation related to the
implementation of a CSR.

[[Page 47689]]

Table 10--Coastal Standoff Range
------------------------------------------------------------------------
Mitigation requirements Mitigation benefits
------------------------------------------------------------------------
The received level of SURTASS LFA sonar Many areas of biological
transmissions will not exceed 180 dB importance to, and with higher
re 1 [mu]Pa RMS SPL within 22 km (12 density of, marine mammals
nmi) from any emergent land, including occur in coastal waters. The
offshore islands. CSR would lower the risk to
SURTASS LFA sonar activities will not many marine mammals which
occur within the territorial seas of aggregate in coastal waters.
foreign nations, which are areas from In a review of existing and
0 to 22 km (0-12 nmi) from shore.. proposed marine protected
areas, approximately 80
percent were found to be
located in the CSR. Coastal
waters are heavily used
seasonally for biologically
important behaviors such as
calving, foraging, and
migrating.
------------------------------------------------------------------------

Offshore Biologically Important Areas for SURTASS LFA Sonar
Given the unique transmission characteristics of SURTASS LFA sonar
and recognizing that certain areas of biological importance lie outside
of the CSR (i.e., more than 22 km from any emergent land), Navy and
NMFS developed the concept of marine mammal OBIAs for SURTASS LFA
sonar. OBIAs for SURTASS LFA sonar are not intended to apply to any
other Navy activities and were established solely as a mitigation
measure to reduce incidental harassment of marine mammals associated
with the use of SURTASS LFA sonar (77 FR 50290, August 20, 2012). OBIAs
pertain to only species considered more sensitive to SURTASS LFA sonar,
including marine mammals in the VLF and LF groups, as well as sperm
whales and elephant seals, since the potential for impacts to other
protected marine species from exposure to SURTASS LFA sonar
transmissions would be low to moderate, necessitating no additional
preventative measures for these taxa beyond those already established
for SURTASS LFA sonar. Table 11 lists the identified OBIAs (figure 1
herein) within the Study Area, and table 12 describes the mitigation
requirements within OBIAs.
Appendix F of the 2026 SURTASS SEIS/OEIS describes the selection
criteria and stepwise analysis Navy used to identify OBIAs. In summary,
the comprehensive assessment of marine areas as OBIA candidates
included a thorough review of the Important Marine Mammal Areas
(IMMAs), Ecologically or Biologically Significant Marine Areas (EBSAs),
areas listed in the World Database of Protected Areas (WDPA), Mission
Blue Hope Spots, Pew Bertarelli Ocean Legacy Sites, High Seas Alliance
Hot Spots, NOAA NMSs, NMFS ESA Critical Habitat, and areas previously
included on the OBIA Watch List or that otherwise previously received
full assessment for potential OBIA designation. The OBIA Watch List
includes potential marine areas already identified and reviewed by the
Navy and NMFS but for which documentation on the importance of the area
to marine mammals has not been established or is lacking in detail. A
total of 418 candidate marine areas in the Pacific and Indian Oceans
were identified and added to a database for recordkeeping and analysis.
While the BIAs identified by Kratofil et al. (2023) and discussed
in the Biologically Important Areas section of this rule were not
considered in the OBIA selection criteria, NMFS considered BIAs in this
rulemaking. Humpback whale is the only LF cetacean species for which
Kratofil et al. (2023) identified a BIA, and this BIA fully overlaps
identified OBIAs or the CSR, and therefore, mitigation will be
implemented within the BIA. All other BIAs identified in the Pacific
SURTASS LFA Study Area fully or partially overlap identified OBIAs or
the CSR, as described in the Biologically Important Areas section. NMFS
and the Navy also reviewed additional literature that led to the
recommended OBIA modifications and addition in this final rule, as
described below.
The process for selection of OBIAs for SURTASS LFA sonar, from the
candidate list, includes a stepwise analysis based on four criteria:
(1) geographic; (2) presence of LF-Hearing cetaceans; (3) biological
importance; and (4) Navy practicability:
Criterion 1: Geographic
A marine area must be located at least partly in the Study Area and
partly outside of the CSR (i.e., the area within 22 km of any emergent
land including islands or island systems) for OBIA consideration. The
CSR already receives the same protection as OBIAs, and therefore marine
areas entirely within the CSR are not considered for further OBIA
analysis.
Criterion 2: LF-Hearing Cetaceans
A marine area must have evidence of the presence of cetaceans that
specialize in LF-hearing, such as all baleen whales, or marine mammals
that have demonstrated sensitivity to LF sounds, such as sperm whales
and elephant seals. SURTASS LFA sonar transmissions are well below the
range of best hearing sensitivity for most other odontocetes and
pinnipeds based on the measured hearing thresholds (U.S. Department of
the Navy, 2025; Houser et al., 2008; Houser et al., 2024; Kastelein et
al., 2009; NMFS, 2024). The intent of OBIAs is to protect those marine
mammal species most likely to hear and be affected by SURTASS LFA sonar
transmissions and to provide the animal additional protections during
periods when they are conducting biologically significant activities.
Thus, the primary focus of the OBIA mitigation measures is on LF-
hearing sensitive species.
Criterion 3: Biological Importance
If a marine area meets Criteria 1 and 2, it must also have known
biological importance to the relevant species present. As such, the
marine area must meet at least one of the following biological sub-
criteria to be considered as an OBIA: (1) have a presence of small,
distinct populations with limited distributions; (2) have a presence of
particularly high densities; (3) be a known breeding/calving ground(s);
(4) be a known foraging ground(s); (5) be a known migration route(s);
or (6) be a Critical Habitat as designated under the ESA. When direct
data relevant to one of the biological subcriteria are limited, other
available data and information may be used if those data and
information, either alone or in combination with the limited direct
data, are sufficient to establish that the biological criteria are met.
Criterion 4: Navy Practicability
If an area meets the (1) geographic, (2) presence of LF-Hearing
cetaceans, and (3) biological importance criteria, it is considered a
candidate OBIA, and the Navy conducts a practicability assessment
(e.g., consideration of personnel safety, practicality of
implementation, and impacts on the effectiveness of SURTASS LFA sonar
training and testing activities). If the candidate area passes the
practicability assessment, then the marine area is considered to meet
all criteria for designation as a SURTASS LFA sonar

[[Page 47690]]

OBIA for marine mammals. If the Navy determines that it is not
practicable to designate the area as an OBIA, the Navy will identify
the concerns that lead to this conclusion and discuss with NMFS whether
modifications could be made to the proposed OBIA to alleviate the
Navy's practicability concerns.
Of the 38 marine areas assessed, the Navy and NMFS' analysis
resulted in the recommendation of 5 new OBIAs since publication of the
2019 SURTASS final rule (84 FR 40132, August 13, 2019), pending Navy
review for practicability. One OBIA is an expansion of an existing OBIA
(OBIA #35, Western Australia--Blue Whale), to include the entirety of
the Indian Ocean Blue Whale Migratory Route Important Marine Mammal
Area (a designation by the International Union for Conservation of
Nature). A second OBIA (OBIA #43, South of Lombok and Sumbawa Islands)
represents an area that connects an existing OBIA (OBIA #37, Southern
Bali) to the newly expanded OBIA #35, Western Australia-Blue Whale. The
remaining three OBIAs are standalone areas (OBIA #40, #41, #42),
disconnected from any existing OBIAs in the Study Area.
The five candidate OBIAs underwent Navy practicability review. The
Navy determined that the identification of the five candidate OBIAs in
the Study Area and the relevant seasonal effectiveness periods would
not impede the effectiveness of SURTASS LFA sonar training and testing
activities, would be practicable to implement as a geographic
mitigation measure, and would not impact personnel safety. As a result,
five new marine mammal OBIAs for SURTASS LFA sonar have been
identified: OBIA #35 (expansion), #40, #41, #42, and #43 (table 11).
Further, since publication of the proposed rule, NMFS and the Navy
identified a new OBIA and modifications to several OBIAs identified in
the proposed rule. The new OBIA #44 (Southeast Kamchatka Offshore) will
minimize impacts to Western NPRWs in an identified high use foraging
area offshore of Southeast Kamchatka. Ovsyanikova et al. (2015) found
NPRWs utilize deep, pelagic waters southeast of Kamchatka, an area that
could serve as a primary summer foraging grounds and Matsuoka et al.
(2021) described two main high-density areas, including one offshore
southeast of Kamchatka Peninsula, between latitudes 45 [deg]N and 51
[deg]N, and longitudes 158 [deg]E and 168 [deg]E, which is within the
Study Area. Additionally, this final rule includes the following
modifications to OBIAs identified in the proposed rule to further
minimize adverse impacts to marine mammal populations from SURTASS LFA
sonar:
OBIA #28 (Mariana Islands) is now effective from December
through May (previously February through April). This extension is
supported by information from Oleson et al. (2015), Hill et al. (2016),
Hill et al. (2020), and Deakos et al. (2021) showing humpback whales
have been regularly sighted in the Mariana Islands from January-March
and acoustic detections have been recorded from December-April with the
highest level of acoustic activity occurring in January in some areas
(Allen et al., 2021);
OBIA #33 (Southeast Kamchatka) is now effective year-round
(previously June through September) and has been spatially expanded
northward along the eastern side of the Kamchatka Peninsula to meet the
northern boundary of the Study Area. The temporal expansion is
supported by data from the NMSDD, which included the highest predicted
densities of NPRWs in the area of OBIA #33 Southeast Kamchatka (and
throughout the entire Study Area) are anticipated in the winter and
spring (December-May). The Southeast Kamchatka Coastal Waters Marine
EBSA, as determined by the Conference of the Parties to the Convention
on Biological Diversity, includes the migratory route for large whales
which, in addition to data on NPRW sightings off Cape Kozlova and the
western Aleutian Islands (Ovsyanikova et al., 2015), supports the
northward expansion of this OBIA; and
OBIA #37 (Southern Bali) is now effective August through
November (previously October through November) and has been spatially
expanded to minimize impacts to pygmy blue whales participating in
reproductive and foraging activities in this area. Sahri et al. (2022)
developed a pygmy blue whale habitat suitability model that predicted
this area as moderately suitable habitat. Further, a satellite tracking
study of pygmy blue whales by M[ouml]ller et al. (2020) confirmed the
use of the proposed expanded area south of Bali. In Indonesian waters,
whales mostly showed a high probability of being in area restricted
search behavior, which is possibly associated with breeding and/or
foraging (M[ouml]ller et al., 2020).
Additionally, this final rule corrects errors in the effective
period of two OBIAs: OBIA #42 South of Java Island is effective from
May through November and OBIA #43 South of Lombok Sumbawa Islands is
effective May through November.

Table 11--Identified OBIAs in the Study Area
----------------------------------------------------------------------------------------------------------------
Relevant marine
OBIA No. Name Location/water body mammal species Effective period
----------------------------------------------------------------------------------------------------------------
26....................... Main Hawaiian Central North Humpback whale...... November through
Islands. Pacific Ocean. April.
27....................... Northwestern Central North Humpback whale...... December through
Hawaiian Islands. Pacific Ocean. April.
28 **.................... Mariana Islands..... Western North Humpback whale...... December through
Pacific Ocean. May.
29....................... Ryukyu-Philippines.. Western North Humpback whale...... January through
Pacific Ocean. April.
30....................... Ogasawara--Sperm Western North Sperm whale......... June through
whale. Pacific Ocean. September.
31....................... Ogasawara-Kazin-- Western North Humpback whale...... December through
Humpback whale. Pacific Ocean. May.
32....................... Honshu.............. Western North Gray whale.......... January through
Pacific Ocean. May.
33 **.................... Southeast Kamchatka. Western North Fin, gray (Western Year-round.
Pacific Ocean. North Pacific
stock), humpback,
and North Pacific
right whale.
34....................... Gulf of Thailand.... Eastern Indian Ocean Bryde's whale....... April through
November.
35 *..................... Western Australia-- Eastern Indian Ocean Blue (pygmy) whale.. May through
Blue whale. November.
36....................... Western Australia-- Eastern Indian Ocean Humpback whale...... May through
Humpback whale. December.
37 **.................... Southern Bali....... Eastern Indian Ocean Blue (pygmy), August through
Bryde's, humpback, November.
Omura's, sei, and
sperm whale.
38....................... Swatch-of-No-Ground Northern Bay of Bryde's whale....... Year-round.
(SoNG). Bengal.
39....................... Sri Lanka........... Eastern Indian Ocean Blue (pygmy) and October through
sperm whale. April.
40 *..................... Maldives Archipelago Central Indian Ocean Blue (pygmy), October through
Bryde's, humpback, May.
and sperm whale.

[[Page 47691]]

41 *..................... Northeast Arabian Arabian Sea......... Blue, Bryde's, and Year-round.
Sea. humpback (Arabian
Sea stock) whale.
42 *..................... South of Java Island East Indian Ocean... Blue (pygmy) whale.. May through
November.
43 *..................... South of Lombok East Indian Ocean... Blue (pygmy) whale.. May through
Sumbawa Islands. November.
44 **.................... Southeast Kamchatka Western North North Pacific right April through
Offshore. Pacific Ocean. whale. October.
----------------------------------------------------------------------------------------------------------------
Note: This final rule corrects the effective period of OBIA #42 South of Java Island and OBIA #43 South of
Lombok Sumbawa Islands.
* New or expanded OBIAs since the 2019 SURTASS final rule (84 FR 40132, August 13, 2019).
** New or expanded OBIA since the proposed rule.

Table 12--OBIA Mitigation Requirements
------------------------------------------------------------------------
Mitigation requirements Mitigation benefits
------------------------------------------------------------------------
The received level of SURTASS LFA sonar OBIAs would protect species
transmissions will not exceed 180 dB considered more sensitive to
re 1 [mu]Pa RMS SPL at a distance of 1 SURTASS LFA sonar (including
km (0.5 nmi) seaward of the outer marine mammals in the VLF and
perimeter of any OBIA in the SURTASS LF groups, as well as sperm
LFA Study Area during the effective whales and elephant seals)
period \1\ specified. OBIAs and the from receiving injurious
related effective periods are listed effects (i.e., AUD INJ) and
in (table 11) or may be subsequently more severe behavioral impacts
identified through the adaptive from SURTASS LFA
management process.\2\ transmissions.
No more than 25 percent of the sound
source amount analyzed (i.e., no more
than 275 hours in a given year) of
SURTASS LFA sonar for training and
testing will be conducted within 18.5
km of any single OBIA during any
year.\3\
------------------------------------------------------------------------
\1\ OBIAs are active only during the specific time of year when
biologically significant activities are potentially occurring within
that area.
\2\ Although it is difficult to compare SPL and SEL based metrics since
SEL accumulates with increasing exposure time, auditory injury
thresholds are well above 180 dB, even without considering frequency
weighting of the received sound levels, except for VHF cetaceans.
However, VHF cetaceans do not hear well at the low frequencies
associated with SURTASS LFA, so it is expected that the received level
at these frequencies would be greatly reduced.
\3\ Should national security present a requirement to conduct more than
25 percent of the analyzed hours of SURTASS LFA sonar within 18.5 km
of any single OBIA during any year, personnel conducting the activity
would be required to obtain approval through the chain of command
prior to commencement of the activity. The Navy must provide NMFS with
notification as soon as is practicable and include the information
(e.g., sonar hours in exceedance of 25 percent) in its annual activity
reports submitted to NMFS.

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Mitigation Conclusions

NMFS has carefully evaluated the Navy's proposed mitigation
measures--many of which were developed with NMFS' input during the
previous phases of SURTASS LFA sonar activities--and considered a range
of other measures (i.e., the measures considered but eliminated in the
2026 SURTASS SEIS/OEIS, which reflect many of the comments that have
arisen from public input or through discussion with NMFS in past years)
in the context of ensuring that NMFS prescribes the means of effecting
the least practicable adverse impact on the affected marine

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mammal species and their habitat. Our evaluation of potential measures
included consideration of the following factors in relation to one
another: (1) the manner in which, and the degree to which, the
successful implementation of the mitigation measures is expected to
reduce the likelihood and/or magnitude of adverse impacts to marine
mammal species and their habitat; (2) the proven or likely efficacy of
the measures; and (3) the practicability of the measures for applicant
implementation, including consideration of personnel safety,
practicality of implementation, and impact on the effectiveness of the
military readiness activity.
Based on our evaluation of the Navy's proposed measures, as well as
other measures considered by the Navy and NMFS (see section 4.6 of the
2026 SURTASS SEIS/OEIS), NMFS has determined that these mitigation
measures are appropriate means of effecting the least practicable
adverse impact on marine mammal species and their habitat, paying
particular attention to rookeries, mating grounds, and areas of similar
significance, and considering specifically personnel safety,
practicality of implementation, and impact on the effectiveness of the
military readiness activity. Thus, NMFS concludes that the mitigation
measures outlined in this final rule satisfy the statutory standard.

Monitoring

Section 101(a)(5)(A) of the MMPA states that in order to authorize
incidental take for an activity, NMFS must set forth requirements
pertaining to the monitoring and reporting of such taking. The MMPA
implementing regulations at 50 CFR 216.104(a)(13) indicate that
requests for ITAs must include the suggested means of accomplishing the
necessary monitoring and reporting that will result in increased
knowledge of the species and of the level of taking or impacts on
populations of marine mammals that are expected to be present.
We provided a detailed discussion of monitoring in our proposed
rule. In the Proposed Monitoring section of the proposed rule, NMFS
provided a description of the Marine Mammal Monitoring Program and an
ongoing two-phase SURTASS LFA sonar BRS in the Study Area. All of this
information remains valid and applicable and is not repeated here.
Future monitoring efforts by the Navy in the Study Area are
anticipated to continue along the same objectives to inform: (1) our
understanding of the occurrence of marine mammals in the Study Area;
(2) the likely exposure of marine mammals to stressors in the Study
Area; (3) the response of marine mammals to exposures to stressors; (4)
the consequences of a particular marine mammal response to their
individual fitness and, ultimately, populations; and (5) the
effectiveness of implemented mitigation measures.

Reporting

In order to issue an ITA for an activity, section 101(a)(5)(A) of
the MMPA states that NMFS must set forth requirements pertaining to the
monitoring and reporting of such taking. Effective reporting is
critical both to compliance as well as ensuring that the most value is
obtained from the required monitoring.
We provided a detailed discussion of reporting in our proposed
rule. In the Proposed Reporting section of the proposed rule, NMFS
provided descriptions of: the Notification and Reporting Plan for
injured, live stranded, or dead marine mammals; annual Study Area
marine species monitoring report (Annual Pacific SURTASS LFA Study Area
Marine Species Monitoring Report); annual SURTASS LFA training and
testing report (Annual Pacific SURTASS LFA Training and Testing
Report); and other reporting and coordination. All of this information
remains valid and applicable and is not repeated here.

Analysis and Negligible Impact Determination

Introduction

NMFS has defined negligible impact as an impact resulting from the
specified activity that cannot be reasonably expected to, and is not
reasonably likely to, adversely affect the species or stock through
effects on annual rates of recruitment or survival (50 CFR 216.103). A
negligible impact finding is based on the lack of likely adverse
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough
information on which to base an impact determination. In addition to
considering estimates of the number of marine mammals that might be
taken by Level A harassment or Level B harassment (as presented in
table 3), NMFS considers other factors, such as the likely nature of
any responses (e.g., intensity, duration) and the context of any
responses (e.g., critical reproductive time or location, migration), as
well as effects on habitat and the likely effectiveness of the
mitigation. We also assess the number, intensity, and context of
estimated takes by evaluating this information relative to population
status. Consistent with the 1989 preamble for NMFS' implementing
regulations (54 FR 40338, September 29, 1989), the impacts from other
past and ongoing anthropogenic activities are incorporated into this
analysis via their impacts on the environmental baseline (e.g., as
reflected in the regulatory status of the species, population size and
growth rate where known, other ongoing sources of human-caused
mortality, and ambient noise levels).
In the Estimated Take of Marine Mammals section, we identified the
subset of potential effects that would be expected to qualify as take
under the MMPA both annually and over the 7-year period covered by this
rule and then identified the maximum number of takes we believe are
reasonably expected to occur (harassment) based on the methods
described. The impact that any given take will have is dependent on
many case-specific factors that need to be considered in the negligible
impact analysis (e.g., the context of behavioral exposures such as
duration or intensity of a disturbance, the health of impacted animals,
the status of a species that incurs fitness-level impacts on
individuals). For this rule we evaluated the likely impacts of the
enumerated maximum number of harassment takes that are authorized and
reasonably expected to occur, in the context of the specific
circumstances surrounding these predicted takes. Last, we collectively
evaluated this information, as well as mitigation measure
effectiveness, that supports our negligible impact conclusions for each
stock or species. To avoid repetition, the discussion of our analysis
applies to all the species listed in table 1, given that the
anticipated effects of this activity on these different marine mammal
species or stocks are expected to be similar. There is little
information about the nature or severity of the impacts, or the size,
status, or structure of any of these species or stocks that would lead
to a different analysis for this activity.

Analysis

In this section, we discuss multiple factors in the context of the
Navy's activity, including the calculation of take by harassment,
direct behavioral disturbance, the diel cycle, assessing the number of
individuals taken and the likelihood of repeated takes, physiological
stress responses, TTS, masking, AUD INJ, impacts on marine mammal
habitat, and the required mitigation measures, and how they are
considered in the negligible impact analysis.

[[Page 47694]]

Harassment

The specified activities reflect best estimates of the number of
hours the Navy will conduct SURTASS LFA training and testing
activities. The Description of the Specified Activity section describes
annual activities. There may be some flexibility in the exact number of
transmission hours from year to year, but it will not exceed the annual
total of 1,100 transmission hours for all vessels and take totals would
not exceed the maximum annual total and 7-year total indicated in table
3. We base our analysis and negligible impact determination on the
maximum number of takes that would be reasonably expected to occur
annually and are authorized, although, as stated before, the number of
takes is only one part of the analysis, which includes qualitative
consideration of other contextual factors that influence the degree of
impact of the takes on the affected individuals.
The Navy's harassment take request was calculated using a model
(NAEMO) for acoustic stressors, which NMFS reviewed and concurs does
appropriately estimate the maximum amount of harassment that is
reasonably likely to occur based on the maximum number of hours and
equal distribution of hours across the 15 geographic modeling areas. As
described in more detail in the Navy Acoustic Effects Model section of
the proposed rule, NAEMO calculates: (1) sound energy propagation from
SURTASS LFA sonar during military readiness activities; (2) the sound
received by animat dosimeters representing marine mammals distributed
in the area around the modeled activity; and (3) whether the sound
received by a marine mammal exceeds the thresholds for effects.
Assumptions in the Navy models intentionally err on the side of
overestimation when there are unknowns. The effects of the specified
activities are modeled as though they would occur regardless of
proximity to marine mammals, meaning that no activity-based mitigation
is considered (e.g., no power down or shut down). However, the modeling
does quantitatively consider the possibility that marine mammals would
avoid continued or repeated sound exposures to some degree, based on a
species' sensitivity to behavioral disturbance. NMFS provided input to,
independently reviewed, and concurred with the Navy on this process.
The Navy's analysis, which is described in detail in appendix B of the
application, was used to quantify harassment takes for this rule.
The Navy and NMFS anticipate more severe effects from takes
resulting from exposure to higher received levels and less severe
effects from takes resulting from exposure to lower received levels
(though this is in no way a strictly linear relationship for behavioral
effects throughout species, individuals, or circumstances). However,
there is also growing evidence of the importance of distance in
predicting marine mammal behavioral response to sound (i.e., sounds of
a similar level emanating from a more distant source have been shown to
be less likely to elicit a response of equal magnitude) (DeRuiter et
al., 2013b). The estimated number of takes by Level A harassment and
Level B harassment does not always equate to the number of individual
animals the Navy expects to harass (which is lower for some species),
but rather represents the instances of take (i.e., exposures above the
Level A harassment and Level B harassment threshold) that are
anticipated to occur over the 7-year period. These instances may
represent either brief exposures (i.e., seconds or minutes) or, in some
cases, longer durations of exposure within a day (though no more than 8
hours, which is the maximum amount Navy plans to transmit in 1 day). In
some cases, an animal that incurs a single take by AUD INJ or TTS may
also experience a direct behavioral harassment from the same exposure.
Direct Behavioral Disturbance
The estimates calculated using the BRF do not differentiate between
the different types of behavioral responses that qualify as Level B
harassment. As described in the application, the Navy identified, with
NMFS' input, that moderate behavioral responses, as characterized in
Southall et al. (2021), would be considered a take. The behavioral
responses predicted by the BRFs are assumed to be moderate severity
exposures (e.g., altered migration paths or dive profiles, interrupted
nursing, breeding or feeding, or avoidance) that may last for the
duration of an exposure. The Navy then compiled the available data
indicating received levels and distances at which those responses have
occurred and used the indicated literature to build biphasic behavioral
response curves and cut-off conditions that are used to predict how
many instances of Level B behavioral harassment occur in a day (see the
Criteria and Thresholds Technical Report). Take estimates alone do not
provide information regarding the potential fitness or other biological
consequences of the responses on the affected individuals. We therefore
consider the available activity-specific, environmental, and species-
specific information to determine the likely nature of the modeled
behavioral responses and the potential fitness consequences for
affected individuals.
The use of SURTASS LFA sonar in a given region would generally be
considered transient and temporary; however, we note the comparatively
large ensonified areas generated by the higher-power LF source. In the
range of potential behavioral effects that might be expected as part of
a response that qualifies as an instance of Level B harassment (which,
by nature of the way it is modeled/counted, occurs within 1 day), the
less severe end might include exposure to comparatively lower levels of
a sound, at a detectably greater distance from the animal, for a few or
several minutes to multiple hours within the day of the exposure
(though not more than 8 hours, which is the maximum transmission time
planned for any single day), which could result in a behavioral
response such as avoiding an area that an animal would otherwise have
chosen to move through or feed in for some amount of time or breaking
off one or a few feeding bouts. More severe effects could occur when
the animal is close enough to the SURTASS LFA sonar source to receive a
comparatively higher level or is exposed continuously to one source for
a longer time. Such effects might result in an animal having a more
severe flight response and leaving a larger area for a day or more or
potentially losing feeding opportunities for a day. However, such
severe behavioral effects are expected to occur infrequently. Of note,
monitoring reports indicate that there have been no apparent avoidance
responses observed since use of SURTASS LFA sonar training and testing
activities began in the Study Area in 2002.
To help assess this, for SURTASS LFA sonar used in the Study Area,
the Navy provided information estimating the instances of take by Level
B harassment by behavioral disturbance under each BRF that would occur
within 6-dB increments, and by distance in 5-km bins in section 2.3.3
of appendix A of the application. As mentioned above, all else being
equal, an animal's exposure to a higher received level is more likely
to result in a behavioral disturbance that could more likely accumulate
to impacts on reproductive success or survivorship of the animal, but
other contextual factors (e.g., distance, duration of exposure, and
behavioral state of the animals) are also important (Di Clemente et
al., 2018; Ellison et al., 2012; Moore and Barlow,

[[Page 47695]]

2013; Southall et al., 2019c; Wensveen et al., 2017, etc.). The
majority of takes by Level B harassment are expected to be
comparatively milder responses (i.e., lower-level exposures that still
qualify as take under the MMPA but would likely be less severe along
the continuum of responses that qualify as take). We anticipate more
severe effects from takes when animals are exposed to higher received
levels of sound or at closer proximity to the source, or for longer
durations. Specifically, given a range of behavioral responses that may
be classified as Level B harassment, to the degree that higher received
levels of sound are expected to result in more severe behavioral
responses, only a smaller percentage of the anticipated Level B
harassment from the specified activities might result in more severe
responses. As discussed in the Behavioral Responses section of the
proposed rule, behavioral response is likely variable across species
(especially considering the reduced sensitivity of HF and VHF species
to the SURTASS LFA sonar signal) and individuals within a species and
depending on the context of the exposure. Further, the mitigation
measures (described in detail in the Mitigation Measures section) are
anticipated to reduce the exposure of marine mammals to received levels
of SURTASS LFA sonar or HF/M3 sonar that would result in more severe
behavioral responses.
Diel Cycle
Many animals perform vital functions, such as feeding, resting,
traveling, and socializing on a diel cycle (24-hour cycle). Behavioral
responses to noise exposure, when taking place in a biologically
important context (e.g., disruption of critical life functions,
displacement, or avoidance of important habitat) are more likely to be
significant if they last more than one diel cycle or recur on
subsequent days (Southall et al., 2007). Henderson et al. (2016) found
that ongoing smaller scale MFAS events, for example, had little to no
impact on foraging dives for Blainville's beaked whale, while multi-day
training events may decrease foraging behavior for Blainville's beaked
whale (Manzano-Roth et al., 2016). Consequently, a behavioral response
lasting less than 1 day and not recurring on subsequent days is not
considered severe unless it could directly affect reproduction or
survival (Southall et al., 2007). Note that there is a difference
between multiple-day substantive behavioral responses and multiple-day
anthropogenic activities. SURTASS LFA sonar activities generally cover
large areas that are relatively far from shore (typically more than 22
km from shore) and in generally deep waters. Marine mammals are moving
as well, which would make it unlikely that the same animal could remain
in the immediate vicinity of the ship for the entire duration of the
activity. Further, as noted previously, SURTASS LFA sonar is not
planned to be used for more than 8 hours in a single day.
Assessing the Number of Individuals Taken and the Likelihood of
Repeated Takes
As described previously, Navy modeling uses the best available
science to predict the instances of exposure above certain acoustic
thresholds, which are equated, as appropriate, to harassment takes. As
further noted, for active acoustics it is typically challenging to
parse out the number of individuals taken by Level B harassment and the
number of times those individuals are taken from this larger number of
instances, though factors such as movement ecology (e.g., is the
species resident and more likely to remain in closer proximity to
ongoing activities, versus nomadic or migratory; Keen et al. (2021)) or
whether there are known areas where animals are known to congregate and
overlap with activities can help inform this. One method that NMFS uses
to help better understand the overall scope of the impacts is to
compare these total instances of take against the abundance of that
species (or stock if applicable). For example, if there are 100
harassment takes in a population of 100, the possibilities include
either that every individual was exposed above acoustic thresholds once
per year, or that some smaller number were exposed a few times per year
while a few were not exposed at all. Where the instances of take exceed
100 percent of the population, multiple takes of some individuals are
predicted and expected to occur within a year. Generally speaking, the
higher the number of takes as compared to the population abundance, the
more multiple takes of individuals are likely, and the higher the
actual percentage of individuals in the population that are likely
taken at least once in a year. We look at this comparative metric to
give us a relative sense of where larger portions of the species are
being taken by the Navy's SURTASS LFA sonar activities and where there
is a higher likelihood that the same individuals are being taken across
multiple days and where that number of days might be higher. It also
provides a relative picture of the scale of impacts on each species.
For SURTASS LFA sonar, given the limited maximum annual number of
hours of sonar spread across four vessels and a large geographic area,
the fact that the training and testing occurs far from shore (>22 km)
and outside of known areas of concentration of LFA sonar-sensitive
species (OBIAs), and considering the predicted take numbers as compared
to known stock abundances (with the exception of beaked whales and the
Western North Pacific stock of humpback whales (take as a percentage of
stock abundance ranges from 104-207 percent)), it is unlikely that the
individuals of most species or stocks are taken on multiple days (<1
percent for most, 1-10 percent for three stocks). Further, takes of
single stocks are expected across multiple regions. All beaked whale
stocks and species have comparatively higher numbers of takes and
percentages as compared to known abundances. These higher numbers are
driven by the BRF for sensitive species, which appropriately reflects
the known higher sensitivity of beaked whales to acoustic stressors.
However, we note that the BRFs used to predict takes from active
acoustic sources do not take into account how loud the animal may
perceive the sonar signal to be based on the frequency of the sonar
versus the animal's hearing range and, as noted previously, HF hearing
specialists (e.g., beaked whales) have significantly reduced hearing
sensitivity in the 100-500-Hz range of SURTASS LFA sonar (17-40-dB
reduced sensitivity), which means that the effects of these exposures
may be comparatively less severe than those from higher-frequency
active sonar. For these stocks, and for all beaked whale species, we
expect the total anticipated takes represent exposures of a smaller
number of individuals of which some could be exposed multiple times.
However, based on the nature of the Navy's SURTASS LFA sonar activities
and the movement patterns of marine mammals, it is highly unlikely that
any particular subset would be taken over more than several consecutive
days (with a few possible exceptions discussed in the Negligible Impact
Summary and Determinations section).
When calculating the proportion of a population taken (e.g., the
number of takes divided by population abundance), which can also be
helpful in estimating the number of days over which some individuals
may be taken, it is important to choose an appropriate population
estimate against which to make the comparison. Herein, NMFS considers
the abundance estimates from the SARs, where available and applicable.
The SARs, where available

[[Page 47696]]

and applicable, provide the official population estimate for a given
species or stock in U.S. waters in a given year. These estimates are
typically generated from the most recent shipboard and/or aerial
surveys conducted, and in some cases, the estimates show substantial
year-to-year variability. When the stock is known to range well outside
of U.S. Exclusive Economic Zone (EEZ) boundaries, population estimates
based on surveys conducted only within the U.S. EEZ are known to be
underestimates. The SAR abundance estimate is included in table 1 for
U.S. stocks. This rule authorizes take of populations of the following
species where there is no U.S. stock designated, as indicated in table
3: NPRW, blue whale, Bryde's whale, fin whale, humpback whale,
Antarctic minke whale, minke whale, Omura's whale, sei whale, sperm
whale, dwarf sperm whale, pygmy sperm whale, Baird's beaked whale,
Blainville's beaked whale, Deraniyagala's beaked whale, ginkgo-toothed
beaked whale, goose-beaked whale, Hubbs' beaked whale, Longman's beaked
whale, Stejneger's beaked whale, false killer whale, killer whale,
melon-headed whale, pygmy killer whale, short-finned pilot whale,
bottlenose dolphin, common dolphin, Fraser's dolphin, Northern right
whale dolphin, pantropical spotted dolphin, Risso's dolphin, rough-
toothed dolphin, spinner dolphin, striped dolphin, Dall's porpoise,
northern fur seal, ribbon seal, and ringed seal. For species for which
no stock is designated, and no abundance estimate is available, it is
not possible to calculate the proportion of the species taken. However,
there is no reason to expect that these percentages would be higher
than the U.S. stock percentages.
Physiological Stress Response
Some of the lower level physiological stress responses (e.g.,
orientation or startle response, change in respiration, change in heart
rate) discussed in the Potential Effects of Underwater Sound on Marine
Mammals section of the proposed rule, would likely co-occur with the
predicted harassments, although these responses are more difficult to
detect and fewer data exist relating these responses to specific
received levels of sound. Takes by Level B harassment, then, may have a
stress-related physiological component as well; however, given the
limited maximum number of total SURTASS LFA sonar hours in a year
(1,100) and the fact that they are shared across four vessels and
spread across an ocean basin, we would not expect SURTASS LFA sonar to
create conditions of long-term continuous noise leading to long-term
physiological stress responses in marine mammals that could affect
reproduction or survival.
Temporary Threshold Shift (TTS)
NMFS and the Navy have estimated that 29 species of marine mammals
may incur some level of TTS from SURTASS LFA sonar. As mentioned
previously, in general, TTS can last from a few minutes to days, be of
varying degree, and occur across various frequency bandwidths, all of
which determine the severity of the impacts on the affected individual,
which can range from minor to more severe. Table 4 indicates the number
of takes by TTS that may be incurred by different species from exposure
to active sonar. The TTS incurred by an animal is primarily
characterized by three characteristics:
1. Frequency. Available data suggest that most TTS occurs in the
frequency range of the source up to one octave higher than the source
(with the maximum TTS at one-half octave above) (Finneran, 2015;
Southall et al., 2019). TTS from SURTASS LFA sonar would occur below 2
kHz, which is in the range where many mysticetes communicate and also
where other auditory cues are located (e.g., waves, snapping shrimp,
fish prey), and out of the range of the majority of most odontocete
communication and all echolocation. Pinnipeds communicate across a
broad range, generally including low frequency grunts (in the tens of
Hz), but sometimes ranging to high frequency whistles (above 20 kHz),
depending on the species and context. Also of note, SURTASS LFA sonar
occupies a narrow frequency band (between 100 and 500 Hz), meaning that
the TTS incurred would also be across a narrower band (i.e., it would
not affect more than a small portion of any affected marine mammal's
hearing range).
2. Degree of the shift (i.e., by how many dB the sensitivity of
hearing is reduced). Generally, both the degree and the duration of TTS
will be greater if the marine mammal is exposed to a higher level of
energy (which would occur when the peak SPL is higher or the duration
is longer). The threshold for the onset of TTS was discussed in the
Hearing Loss and Auditory Injury section of the proposed rule. Animals
would have to approach closer to the source or remain in the vicinity
of the sound source appreciably longer to increase the received SEL,
which would be unlikely for most taxa considering the Lookouts and the
relative motion between the sonar vessel and the animal but, given the
large ensonified zone, could happen for some mysticetes, which is
reflected in their higher TTS numbers. In the TTS studies discussed in
the Potential Effects of Specified Activities on Marine Mammals and
Their Habitat section of the proposed rule (some using exposures of
almost an hour in duration or up to 217 SEL), most of the TTS induced
was 15 dB or less, though Finneran et al. (2007) induced 43 dB of TTS
in bottlenose dolphins with a 64-second exposure to a 20 kHz source
measured via auditory steady-state response (auditory evoked potential
measurement). In general, there is a higher potential for TTS
associated with sources with higher duty cycles, like continuous hull-
mounted sonars, compared to those sources that are intermittent or have
lower duty cycles (Kastelein et al., 2015a).
In short, given the anticipated duration and levels of sound
exposure, we do not expect marine mammals to incur more than low levels
of TTS in most cases for sonar exposure, with potentially occasional
moderate levels for some mysticete individuals. To add context to this
degree of TTS, individual marine mammals may regularly experience
variations of 6 dB differences in hearing sensitivity in their lifetime
(Finneran et al., 2000; Finneran et al., 2002; Schlundt et al., 2000).
3. Duration of TTS (recovery time). As discussed in the Potential
Effects of Specified Activities on Marine Mammals and Their Habitat
section of the proposed rule, in TTS laboratory studies using exposures
of up to an hour in duration or up to 217 dB SEL, most individuals
recovered within 1 day (or less, often in minutes) (Kastelein, 2020b).
One study resulted in a recovery that took 4 days (Finneran et al.,
2015; Southall et al., 2019). However, there is evidence that repeated
exposures resulting in TTS could potentially lead to residual threshold
shifts that persist for longer durations and can result in PTS
(Reichmuth et al., 2019).
Compared to laboratory studies, marine mammals are likely to
experience lower SELs from SURTASS LFA sonar in the Study Area due to
movement of the source and animals and the duty cycle of SURTASS LFA
sonar, though the larger ensonified area may result in longer exposures
than some other sonar sources. Also, for the same reasons discussed in
the Diel Cycle section of the Analysis and Negligible Impact
Determination section, and because of the short distance between the
source and animals needed to reach high SELs, it is unlikely that
marine mammals would be

[[Page 47697]]

exposed to the levels necessary to induce TTS in subsequent time
periods such that hearing recovery is impeded. Additionally, though the
frequency range of TTS that marine mammals might incur would overlap
with some of the frequency ranges of their vocalization types, the
frequency range of TTS from SURTASS LFA sonar does not span the entire
frequency range of one vocalization type, much less span all types of
vocalizations or other critical auditory cues.
As described above, we expect the majority of TTS takes to be in
the form of milder, relatively short-term (minutes to hours) TTS. This
means that for one to several times per year, for several minutes,
maybe a few hours, or at most in limited circumstances a few days, a
taken individual will have diminished hearing sensitivity (i.e., more
than natural variation, but nowhere near total deafness). Any such
exposure would occur within a narrower low-frequency band that may
overlap part (but not all) of the communication range of some
mysticetes or pinnipeds, a limited part of the odontocete communication
range, and no overlap with echolocation or predator sounds. It may
overlap some low frequency environmental sounds, such as those that
marine mammals use to navigate or find prey. The significance of TTS is
also related to the auditory cues that are germane within the time
period that the animal incurs the TTS. For example, if a mysticete has
TTS at frequencies that inhibits its detection of prey but incurs it at
night when it is resting and not feeding, it may not be as impactful.
In short, the expected results of any one of these limited number of
mild TTS occurrences could be that: (1) it does not overlap signals
that are pertinent to that animal in the given time period; (2) it
overlaps parts of signals that are important to the animal, but not in
a manner that impairs interpretation; or (3) it reduces detectability
of an important signal to a small degree for a short amount of time--in
which case the animal may be aware and able to compensate (but there
may be slight energetic cost), or the animal may have some reduced
opportunities (e.g., to detect prey) or reduced capabilities to react
with maximum effectiveness (e.g., to detect a predator or navigate
optimally). However, it is unlikely that individuals would experience
repeated or high degree TTS overlapping in frequency and time with
signals critical for behaviors in a manner that would impact overall
fitness.
Auditory Masking or Communication Impairment
The ultimate potential impacts of masking (i.e., when a sound
interferes with or masks the ability of an animal to detect a signal of
interest that is above the absolute hearing threshold) on an individual
(if it were to occur) are similar to those discussed for TTS, but an
important difference is that masking occurs only during the time of the
signal, versus TTS, which continues beyond the duration of the signal.
Inherent in the concept of masking is the fact that the potential for
the effect is present only during the times that the animal and the
source are in close enough proximity for the effect to occur (and
further, this time period would need to coincide with a time that the
animal was utilizing sounds at the masked frequency). As our analysis
has indicated, because of the relative movement of vessels and the
sound sources primarily involved in this rule, as well as the fact that
the Navy plans a maximum of 8 hours of SURTASS LFA sonar transmission
per day, we do not expect the exposures with the potential for masking
to be of a long duration.
Masking is fundamentally more of a concern with low-frequency
signals because they propagate significantly farther than higher
frequencies and are more likely to overlap both the narrower LF calls
of mysticetes and pinnipeds and many non-communication cues (e.g., fish
and invertebrate prey, and geologic sounds that inform navigation).
Masking is more of a concern from continuous sources where there is no
quiet time between pulses, making detection and interpretation of
auditory signals likely more challenging. While SURTASS LFA sonar has
comparatively long pings or wavetrains (6-100 seconds) and there are
opportunities for reflection and reverberation in the deep ocean, there
are also between 6- and 15-minute periods between each ping. Limiting
the hours of total annual LFA sonar transmission further reduces the
likelihood of long exposure for any given individual. For these
reasons, short-term exposure to the SURTASS LFA sonar is not expected
to result in a meaningful amount of masking, and it is not occurring in
amounts that would be expected to have the potential to affect
reproductive success or survival.
In conclusion, the bandwidth of a given SURTASS LFA sonar signal is
limited (100-500 Hz), the average pulse length is 60 seconds, the
signals do not remain at a single frequency for more than 10 seconds,
and the system is silent nominally 90-92.5 percent of the time during
at-sea training activities. With the nominal duty cycle of 7.5-10
percent, masking by SURTASS LFA sonar would occur only over a very
small temporal scale. Masking is more likely to occur in the presence
of broadband, relatively continuous noise sources such as from vessels;
however, masking effects from vessel noise during the operation of T-
AGOS vessels are not expected to rise to the level of take. The
duration of temporal and spatial overlap with any individual marine
mammal and the SURTASS LFA sonar would not be expected to result in
more than short-term, low impact masking that would not significantly
impact marine mammals or affect reproduction or survival.
Auditory Injury
Table 4 indicates the number of takes of each species by Level A
harassment in the form of auditory injury resulting from exposure to
active sonar that are estimated to occur, and table 3 indicates the
total number of takes across all SURTASS LFA sonar activities. The
number of takes estimated to result from auditory injury annually from
sonar for each species or stock ranges from 0 (for 35 species) to 32
(1-9 AUD INJ takes for 9 species or stocks, and 32 for fin whales with
no stock designation (NSD)). As described previously, the Navy's model
likely overestimates the number of injurious takes. Nonetheless, these
Level A harassment take numbers represent the maximum number of
instances in which marine mammals would be reasonably expected to incur
auditory injury, and we have analyzed them accordingly.
As discussed previously in relation to TTS, the likely consequences
to the health of an individual that incurs auditory injury can range
from mild to more serious and is dependent upon the degree of auditory
injury and the frequency band associated with auditory injury. The
majority of any auditory injury incurred as a result of exposure to
SURTASS LFA sonar would be expected to be in the 100-500 Hz range and
could overlap a small portion of the hearing and communication
frequency range of mysticetes and some pinnipeds. The SURTASS frequency
range is higher than the typical pelagic large whale main foraging and
communication range (e.g., blue, fin, sei whales are in the 20-40 Hz
range). SURTASS frequency range is also lower than the most sensitive
(i.e., ability to perceive without significant loudness) range of many
odontocetes and pinnipeds. Permanent loss of some degree of hearing is
a normal occurrence for older animals, and many animals are able to

[[Page 47698]]

compensate for the shift, both in old age or at younger ages as the
result of stressor exposure. While a small loss of hearing sensitivity
may include some degree of energetic costs for compensating or may mean
some small loss of opportunities or detection capabilities, at the
expected scale it would be unlikely to impact behaviors, opportunities,
or detection capabilities to a degree that would interfere with
reproductive success or survival.
The Navy implements mitigation measures (described in the
Mitigation Measures section) during SURTASS LFA sonar activities that
are expected to minimize the severity of any AUD INJ accrued. This
includes visual, active acoustic, and passive acoustic monitoring (the
combination of which has been shown to be over 98 percent effective at
detecting marine mammals) to support delaying initial sonar
transmissions and suspending ongoing transmission when a marine mammal
is observed in the shutdown zone (1.8 km around the LFA sonar array and
T-AGOS vessel). Monitoring for marine mammals during the SURTASS LFA
sonar activities must also include active (HF/M3) and passive acoustic
detection methods before the activity begins and continue until 15
minutes after LFA sonar transmissions are terminated, in order to cover
the mitigation zone. These mitigation measures are considered nearly
100 percent effective in avoiding exposures within the 1.8 km
mitigation zone and reduce the severity of any auditory injury
exposures (if incurred).
It is unlikely that any of the limited number of auditory injuries
accrued to any one species would result in reduced reproductive success
of any individuals, and auditory injury of the low severity anticipated
here is not expected to affect the survival of any individual marine
mammals.
Impacts to Marine Mammal Habitat
As described in the Marine Mammal Habitat section of the proposed
rule, the planned training and testing activities have the potential to
affect marine mammal habitat through impacts on the prey species of
marine mammals, as well as the acoustic habitat of marine mammals (see
masking discussion in the proposed rule). Impacts to habitat would be
expected to be localized around the T-AGOS vessel transmitting sonar,
and long-term consequences to fish or invertebrate populations would
not be expected based on the low level and short duration (at most 8
hours per day) of potential exposure to SURTASS LFA sonar. Most fish
species can hear low-frequency sounds and would be expected to be able
to hear the LF sonar associated with the planned activities. The most
likely effects on fishes exposed to low-frequency sounds are behavioral
responses. While there would be no probability for mortality or
physical injury from low-frequency sonar, there is the potential for
minor, temporary changes in behavior among fish, including increased
swimming rate, avoidance of the sound source, or changes in orientation
to the sound source. Marine invertebrate prey would be expected to
detect nearby low-frequency sounds in most cases, which could, in some
cases, cause behavioral effects. The most likely impacts for most prey
species in a given area would be temporary avoidance of the area and
long-term consequences to marine invertebrate populations would not be
expected as a result of exposure to sounds or vessels in the Study
Area.
Any anthropogenic noise attributed to SURTASS LFA sonar training
and testing activities in the Study Area would be temporary and the
ambient noise levels of the affected area would be expected to
immediately return to its original state when these activities cease.
The planned activities would add sound to the ambient ocean
environment, and water quality may potentially be affected should
pollutants be discharged from T-AGOS vessels into oceanic waters.
However, no impacts to the sediment or benthic environment would be
expected because all equipment would be deployed in the marine water
column.
The planned SURTASS LFA sonar activities would not affect the
physical characteristics of marine mammal habitats. Unless the sound
source is stationary and/or continuous over a long duration in one area
(noting the 8-hour daily maximum for SURTASS LFA sonar), the effects of
the introduction of sound into the environment are generally considered
to have a less severe impact on marine mammal habitat than actions
involving physical alteration of the habitat. Marine mammals may be
temporarily displaced from areas where SURTASS LFA training and testing
activities are occurring to avoid noise exposure (i.e., due to impacts
on acoustic habitat), but the habitat will not be physically altered
and will likely be available for use again after the activities have
ceased or moved out of the area. In addition, pings from SURTASS LFA
sonar are very sporadic and are not generally repeated in the exact
same area. SURTASS LFA training and testing activities would not result
in the deposition of materials, change bathymetry, strike or modify
features, or cause any physical alterations to marine mammal habitat.
NMFS does not expect any short- or long-term effects to marine
mammal food resources from SURTASS LFA sonar training and testing
activities. It is unlikely that the activities of the T-AGOS vessels
transmitting LFA sonar at any place in the Study Area over the course
of a year would implicate all of the areas for a given species or stock
in any year. It is anticipated that ample similar nearby habitat areas
are available for species/stocks in the event that portions of
preferred areas are ensonified. Further, in areas of known or likely
biological importance for marine mammal functions (feeding,
reproduction, etc.) effects are mitigated by the Coastal Standoff Range
(CSR) and OBIAs.
Mitigation
As described in the Mitigation Measures section, this final rule
includes mitigation measures that will reduce the probability and/or
severity of impacts expected to result from acute exposure to acoustic
sources and impacts to marine mammal habitat. Specifically, the Navy
will use a comprehensive suite of mitigation monitoring methods to
support activity-specific mitigation, including the use of visual
monitoring, passive acoustic monitoring, and active acoustic monitoring
using the HF/M3 system. Real-time activity specific measures will
include a combination of delayed starts, sonar ramp-ups, and shutdowns
to minimize the likelihood or severity of AUD INJ and reduce instances
of TTS or more severe behavioral disturbance caused by acoustic
sources. The Navy will also apply time/area restrictions, including a
22-km CSR and OBIAs for marine mammals. The CSR and OBIA geographic
restrictions on SURTASS LFA sonar training and testing activities are
expected to minimize the likelihood of disruption of marine mammals in
areas where important behavior patterns (e.g., migration, calving,
breeding, feeding, or sheltering) occur or in areas with small resident
populations or higher densities of marine mammals. As a result, the
takes that occur are less likely to result in energetic effects or
disturbances of other important behaviors that would reduce
reproductive success or survivorship.
In examining the results of the mitigation monitoring procedures
over the previous 22 years of SURTASS LFA sonar activities, NMFS has
concluded that the mitigation and monitoring measures for initiating
shutdowns of the LFA sonar system have been implemented properly and
have

[[Page 47699]]

successfully minimized the potential adverse effects of SURTASS LFA
sonar to marine mammals in the 1.8 km LFA sonar mitigation zone around
the vessel.

Negligible Impact Summary and Determinations

As described above and in detail in table 13, NMFS has estimated
and authorized the take, by Level B harassment, of 43 species of marine
mammals, including 33 stocks identified pursuant to the MMPA. A subset
of nine species could also be taken by Level A harassment over the
course of the 7-year period. For reasons stated previously, no
mortalities or serious injuries are anticipated to occur as a result of
the Navy's planned SURTASS LFA sonar training and testing activities,
and none are authorized by NMFS.

Table 13--Annual Estimated Take by Level B Harassment and Level A Harassment and Related Information for Marine Mammals in the Study Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
Maximum annual Maximum annual Maximum annual take as
SAR Level B Level A Maximum annual percentage of SAR
Marine mammal species Stock abundance harassment harassment take abundance (Level A and
(BEH + TTS) (AUD INJ) Level B only)
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Pacific right whale............. NSD...................... N/A 325 2 327 N/A
Blue whale............................ NSD...................... N/A 1,062 3 1,065 N/A
Blue whale............................ Central North Pacific.... 133 13 0 13 9.77
Bryde's whale......................... NSD...................... N/A 816 1 817 N/A
Bryde's whale......................... Hawaii................... 791 7 0 7 0.88
Fin whale............................. NSD...................... N/A 5,738 32 5,770 N/A
Fin whale............................. Hawaii................... 203 16 0 16 7.88
Humpback whale........................ NSD...................... N/A 3 0 3 N/A
Humpback whale........................ Hawaii................... 11,278 13 0 13 0.12
Humpback whale........................ Western North Pacific.... 1,084 1,133 4 1,137 104.89
Antarctic minke whale................. NSD...................... N/A 48 0 48 N/A
Minke whale........................... NSD...................... N/A 3,020 6 3,026 N/A
Minke whale........................... Hawaii................... 438 3 0 3 0.68
Omura's whale......................... NSD...................... N/A 217 1 218 N/A
Sei whale............................. NSD...................... N/A 2,021 9 2,030 N/A
Sei whale............................. Hawaii................... 391 5 1 6 1.53
Sperm whale........................... NSD...................... N/A 37 0 37 N/A
Sperm whale........................... North Pacific............ UNK 225 0 225 UND
Sperm whale........................... Hawaii................... 5,707 15 0 15 0.26
Dwarf sperm whale..................... NSD...................... N/A 719 0 719 N/A
Dwarf sperm whale..................... Hawaii................... UNK 151 0 151 N/A
Pygmy sperm whale..................... NSD...................... N/A 864 0 864 N/A
Pygmy sperm whale..................... Hawaii................... 42,083 152 0 152 0.36
Baird's beaked whale.................. NSD...................... N/A 64,875 0 64,875 N/A
Blainville's beaked whale............. NSD...................... N/A 61,964 0 61,964 N/A
Blainville's beaked whale............. Hawaii................... 1,132 2,073 0 2,073 183.13
Deraniyagala's beaked whale........... NSD...................... N/A 9,448 0 9,448 N/A
Ginkgo-toothed beaked whale........... NSD...................... N/A 30,342 0 30,342 N/A
Goose-beaked whale.................... NSD...................... N/A 111,485 0 111,485 N/A
Goose-beaked whale.................... Hawaii................... 4,431 9,185 0 9,185 207.29
Hubbs' beaked whale................... NSD...................... N/A 25,289 0 25,289 N/A
Longman's beaked whale................ NSD...................... N/A 69,988 0 69,988 N/A
Longman's beaked whale................ Hawaii................... 2,550 5,017 0 5,017 196.75
Stejneger's beaked whale.............. NSD...................... N/A 37,258 0 37,258 N/A
False killer whale.................... NSD...................... N/A 60 0 60 N/A
False killer whale.................... Main Hawaiian Islands 138 1 0 1 0.72
Insular.
False killer whale.................... Hawaii Pelagic........... 5,528 7 0 7 0.13
Killer whale.......................... NSD...................... N/A 173 0 173 N/A
Killer whale.......................... Hawaii................... 161 1 0 1 0.62
Melon-headed whale.................... NSD...................... N/A 537 0 537 N/A
Melon-headed whale.................... Hawaiian Islands......... 40,647 107 0 107 0.26
Pygmy killer whale.................... NSD...................... N/A 318 0 318 N/A
Pygmy killer whale.................... Hawaii................... 10,328 32 0 32 0.31
Short-finned pilot whale.............. NSD...................... N/A 1,083 0 1,083 N/A
Short-finned pilot whale.............. Hawaii................... 19,242 76 0 76 0.39
Bottlenose dolphin.................... NSD...................... N/A 1,901 0 1,901 N/A
Bottlenose dolphin.................... Hawaii Pelagic........... 24,669 32 0 32 0.13
Common dolphin........................ NSD...................... N/A 1,713 0 1,713 N/A
Fraser's dolphin...................... NSD...................... N/A 465 0 465 N/A
Fraser's dolphin...................... Hawaii................... 40,960 152 0 152 0.37
Northern right whale dolphin.......... NSD...................... N/A 10 0 10 N/A
Pacific white-sided dolphin........... North Pacific............ 26,880 49 0 49 0.18
Pantropical spotted dolphin........... NSD...................... N/A 2,785 0 2,785 N/A
Pantropical spotted dolphin........... Hawaii Pelagic........... 67,313 233 0 233 0.35
Risso's dolphin....................... NSD...................... N/A 1,575 0 1,575 N/A
Risso's dolphin....................... Hawaii................... 6,979 38 0 38 0.54
Rough-toothed dolphin................. NSD...................... N/A 508 0 508 N/A
Rough-toothed dolphin................. Hawaii................... 83,915 299 0 299 0.36
Spinner dolphin....................... NSD...................... N/A 276 0 276 N/A
Spinner dolphin....................... Hawaii Pelagic........... N/A 15 0 15 N/A

[[Page 47700]]

Striped dolphin....................... NSD...................... N/A 4,327 0 4,327 N/A
Striped dolphin....................... Hawaii Pelagic........... 64,343 200 0 200 0.31
Dall's porpoise....................... NSD...................... N/A 3,020 0 3,020 N/A
Northern fur seal..................... NSD...................... N/A 1,296 0 1,296 N/A
Steller sea lion...................... Western.................. 49,837 1 0 1 0.00
Harbor seal........................... California............... 30,968 1 0 1 0.00
Ribbon seal........................... NSD...................... N/A 37,650 1 37,651 N/A
Hawaiian monk seal.................... Hawaii................... 1,605 1 0 1 0.06
Ringed seal........................... NSD...................... N/A 25 0 25 N/A
Spotted seal.......................... Bering................... 461,625 71 0 71 0.02
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note: A stock or population listed as `NSD' is not a designated stock under the MMPA. N/A = Not Applicable, UND = Undetermined, UNK = Unknown.

For the following summarized reasons, based on the analysis and
information in this rule, as well as the referenced supporting
documentation, NMFS finds that the total take from SURTASS LFA sonar
training and testing activities will have a negligible impact on all
affected marine mammal species or stocks based on the following:
No mortality is anticipated or authorized, nor is any non-
auditory injury. Neither stranding nor vessel strikes are expected to
result from SURTASS LFA sonar training and testing. There is no
empirical evidence of strandings or vessel strikes of marine mammals
associated spatially or temporally with the use of SURTASS LFA sonar.
Moreover, the sonar system acoustic characteristics differ between LFA
sonar and MFA sonars that have been associated with strandings.
The maximum annual allowable instances of take under this
rule by Level A harassment (AUD INJ only) range from 0 to 32 (fin
whales with NSD).
Regarding authorized takes associated with auditory
impairment, as described in the Temporary Threshold Shift (TTS)
section, any takes in the form of TTS are expected to be lower-level
and of short duration. Any associated lost opportunities or
capabilities that 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, as discussed in
the Auditory Injury section, while auditory injury impacts last longer,
the low anticipated levels of AUD INJ that could be reasonably expected
to result from these activities, should they occur, are unlikely to
have any effect on fitness.
The operational characteristics of the specified
activities, including the limited maximum annual number of hours of
SURTASS LFA sonar (1,100) shared across multiple vessels (likely not in
close proximity to one another) and spread over the entire western and
central North Pacific Ocean and eastern Indian Ocean (including
multiple smaller and separated seas for some species), as well as the
8-hour maximum daily transmission, thus minimize the likelihood of
multi-day or long-duration exposures for any individual marine mammals.
Further, and as noted above, the context of exposures is important in
evaluating the ultimate impacts of Level B harassment on individuals,
and in the case of SURTASS LFA sonar, the approaching sound source
would be moving through the open ocean at low speeds, so concerns of
noise exposure are somewhat lessened in this context compared to
situations where animals may not be as able to avoid strong or rapidly
approaching sound sources.
Regarding the authorized takes associated with behavioral
disturbance, as described in the Potential Effects of Specified
Activities on Marine Mammals and Their Habitat section of the proposed
rule, behavioral disturbance from SURTASS LFA sonar activities in a
given region would generally be considered transient and temporary,
though the ensonified area generated by the LF source is comparatively
large. Behavioral disturbance is likely variable across species and
individuals within a species, and depends on the context of the
exposure, and responses are likely to range from less severe (e.g., an
animal avoiding an area that it would otherwise have chosen to move
through or feed in for some amount of time) to more severe (e.g., an
animal having a more severe flight response and leaving a larger area
for a day or more). Such severe behavioral effects are expected to
occur infrequently due to the implementation of the mitigation measures
(e.g., the SURTASS LFA mitigation zone, which is designed to ensure
that most marine mammal takes are limited to lower-level Level B
harassment, the CSR, and OBIAs).
Previous reports indicate that the HF/M3 active sonar
system has proven to be the most effective of the mitigation monitoring
measures to detect possible marine mammals in proximity to the
transmitting LFA sonar array, and the use of this system substantially
increases the probability of detecting marine mammals within the
mitigation zone. Because the HF/M3 system is able to monitor marine
mammals out to an effective range of 2-2.5 km from the vessel, it is
unlikely that the SURTASS LFA sonar operations would expose marine
mammals to an SPL greater than about 174 dB re 1 [mu]Pa. Past results
of the HF/M3 system tests provide confirmation that the system has a
demonstrated probability of single-ping detection of 95 percent or
greater for single marine mammals that are 10 m in length or larger,
and a probability approaching 100 percent for multiple pings of any
sized marine mammal (see chapter 4 of the 2026 SURTASS SEIS/OEIS).
In areas of known or likely biological importance for
functions such as feeding or reproduction, effects are mitigated by the
CSR and mitigation in the OBIAs for species sensitive to LF sound. The
sound field generated by SURTASS LFA sonar will not exceed 180 dB re 1
[mu]Pa RMS SPL within 22 km from any emergent land. Further, no

[[Page 47701]]

more than 25 percent (275 hours) of SURTASS LFA sonar will be used for
training activities within 18.5 km of any single OBIA during any year.
These measures are expected to minimize the likelihood of disruption of
marine mammals in areas where important behavior patterns (e.g.,
migration, calving, breeding, feeding, or sheltering) occur or in areas
with small resident populations or higher densities of marine mammals.
As a result, any takes that occur are less likely to result in
energetic effects or disturbances of other important behaviors that
would be more likely to reduce reproductive success or survivorship.
Based on the information in the Marine Mammal Habitat
section of the proposed rule, and the supporting information included
in the 2026 SURTASS SEIS/OEIS, NMFS has determined that the planned
training and testing activities will not have adverse or long-term
impacts on marine mammal habitat.
As noted above, there is a higher likelihood that some
number of individual beaked whales (of all species and stocks) and
humpback whales (Western North Pacific stock) may be taken on up to
several days within a year, considering annual take maxima and the
total across 7 years. However, as described, given the magnitude and
severity of the potential take (especially noting the reduced
sensitivity of beaked whales to SURTASS LFA sonar signal), and in
consideration of the required mitigation measures and other information
presented, the Navy's activities are not expected to result in impacts
on the reproduction or survival of any individuals, much less affect
annual rates of recruitment or survival at the species or stock level.

Determination

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 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.

Unmitigable Adverse Impact Analysis and Determination

The Navy will not operate SURTASS LFA sonar in Arctic waters nor in
the Gulf of Alaska, or off the Aleutian Island chain where subsistence
uses of marine mammals protected through sections 101(a)(5)(A) of the
MMPA occur. Therefore, there are no relevant subsistence uses of the
affected marine mammal stocks or species implicated by this action. As
such, there will be no impact on subsistence hunting, nor will SURTASS
LFA sonar cause abandonment of any harvest/hunting locations, displace
any subsistence users, or place physical barriers between marine
mammals and the hunters. NMFS has determined that the total taking of
affected species or stocks will not have an unmitigable adverse impact
on the availability of such species or stocks for taking for
subsistence purposes.

Adaptive Management and Modifications of Letters of Authorization

The regulations governing the take of marine mammals incidental to
military readiness activities in the Study Area contain an adaptive
management component (i.e., the authority to modify the LOA's
mitigation, monitoring, and reporting measures, consistent with the
regulations, based on either the Navy's request or NMFS' initiative in
light of new information). In order for NMFS to modify an LOA measure,
the modified measure must have the same anticipated effects as the
original measure, it must have a reasonable likelihood of
effectiveness, NMFS must determine it does not change the findings made
for promulgation of the regulations, and the Navy must concur with the
measure and affirm that it meets the Navy's practicability standards in
the context of personnel safety, practicality of implementation, and
impacts on the effectiveness of the Navy's military readiness activity.
The reporting requirements associated with this rule are designed
to provide NMFS with monitoring data from the previous year to allow it
to consider whether any changes to existing mitigation and monitoring
requirements are appropriate. The use of adaptive management allows
NMFS to consider new information from different sources to determine
(with input from the Navy regarding practicability) on an annual or
biennial basis if mitigation or monitoring measures should be modified.
Mitigation measures could be modified if new data suggests that such
modifications would have a reasonable likelihood of more effectively
accomplishing the goals of the mitigation and monitoring and if the
measures are practicable. If the modifications to the mitigation,
monitoring, or reporting measures are substantial, NMFS would publish a
notice in the Federal Register and solicit public comment.
The following are some of the possible sources of applicable data
to be considered through the adaptive management process: (1) results
from monitoring and exercise reports, as required by MMPA
authorizations; (2) compiled results of Navy-funded research and
development studies; (3) results from specific stranding
investigations; (4) results from general marine mammal and sound
research; and (5) any information which reveals that marine mammals may
have been taken in a manner, extent, or number not authorized under
these regulations and LOA.

Classification

Endangered Species Act (ESA)

There are 10 marine mammal species under NMFS jurisdiction that are
listed as endangered or threatened under the ESA with confirmed or
possible occurrence in the Study Area for which take is authorized: (1)
blue whale; (2) fin whale; (3) humpback whale (Western North Pacific
DPS); (4) NPRW; (5) sei whale; (6) sperm whale; (7) false killer whale
(Main Hawaiian Islands DPS); (8) Hawaiian monk seal; (9) Steller sea
lion (Western DPS); and (10) ringed seal (Okhotsk subspecies). The
humpback whale (86 FR 21082, April 21, 2021), false killer whale (83 FR
35062, July 24, 2018), and Hawaiian monk seal (51 FR 16047, April 30,
1986; revised in 1988 (53 FR 18988, May 26, 1988) and in 2015 (80 FR
50925, August 21, 2015)) have critical habitat designated under the ESA
in the Study Area.
The Navy consulted with NMFS pursuant to section 7 of the ESA for
the Study Area activities, and NMFS also consulted internally on the
promulgation of this rule and the issuance of an LOA under section
101(a)(5)(A) of the MMPA and the implementing regulations. NMFS issued
a biological and conference opinion concluding that the promulgation of
the rule and issuance of a subsequent LOA are not likely to jeopardize
the continued existence of threatened and endangered species under
NMFS' jurisdiction and are not likely to result in the destruction or
adverse modification of designated or proposed critical habitat in the
Study Area. The biological and conference opinion is available at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.

National Marine Sanctuaries Act

Under section 304(d) of the National Marine Sanctuaries Act (NMSA),
federal

[[Page 47702]]

agencies are required to consult with NOAA's Office of National Marine
Sanctuaries on activities that are likely to destroy, cause the loss
of, or injure any sanctuary resource, unless it is determined that
consultation is not required. Based on NMFS' assessment of its action
of authorizing incidental take through MMPA regulations and an LOA for
these activities, NMFS determined that consultation under the NMSA is
not required.

National Environmental Policy Act

To comply with the National Environmental Policy Act of 1969 (NEPA)
(42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A,
NMFS must review its proposed actions with respect to potential impacts
on the human environment. NMFS participated as a cooperating agency on
the 2026 SURTASS SEIS/OEIS, which was made available to the public on
May 8, 2026 (91 FR 25357), and is available at: https://www.nepa.navy.mil/surtass-lfa/. NMFS independently reviewed and
evaluated the 2026 SURTASS SEIS/OEIS and determined that it is adequate
and sufficient to meet our responsibilities under NEPA for the issuance
of this rule and associated LOA. NOAA, therefore, has relied on the
2026 SURTASS SEIS/OEIS. NMFS has prepared a separate Record of
Decision. NMFS' Record of Decision for reliance on the 2026 SURTASS
SEIS/OEIS and issuance of this final rule and subsequent LOA can be
found at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.

Regulatory Flexibility Act

Pursuant to the Regulatory Flexibility Act (RFA), the Chief Counsel
for Regulation of the Department of Commerce has certified to the Chief
Counsel for Advocacy of the Small Business Administration during the
proposed rule stage that this action would not have a significant
economic impact on a substantial number of small entities. The factual
basis for the certification was published in the proposed rule and is
not repeated here. No comments were received regarding this
certification. As a result, a final regulatory flexibility analysis was
not required and none was prepared.

Paperwork Reduction Act

This action does not contain any collection of information
requirements for purposes of the Paperwork Reduction Act of 1980 (44
U.S.C. 3501 et seq.).

Executive Order 12866

This final rule is not significant under Executive Order 12866.

Executive Order 14192

This final rule is considered an Executive Order 14192 deregulatory
action.

Waiver of Delay in Effective Date

The Assistant Administrator for Fisheries has determined that he
Administrative Procedure Act's (APA) 30-day delay in the effective date
requirement does not apply to this final rule because it relieves a
restriction and because there is good cause for the rule to take effect
on August 12, 2026. Section 553 of the APA provides that the required
publication or service of a substantive rule shall be made not less
than 30 days before its effective date with certain exceptions,
including (1) for a substantive rule that relieves a restriction or (2)
when the agency finds and provides good cause for foregoing delayed
effectiveness (5 U.S.C. 553(d)(1) and (d)(3)).
This final rule is a substantive action that relieves the statutory
prohibition on the taking of marine mammals, specifically, the
incidental taking of marine mammals associated with the Navy's
specified activities. Without this rule in place, the Navy would not
have incidental take coverage for the specified activities in this rule
absent a national security exemption under section 101(f) of the MMPA.
The Assistant Administrator has also determined that there is good
cause under the APA to waive the 30-day delay in the effective date of
this final rule. No individual or entity, other than the Navy, is
affected by the provisions of these regulations, and the Navy does not
require 30 days to prepare for implementation of the regulations. The
Navy has been conducting SURTASS LFA sonar training and testing in the
Study Area for over 20 years and take of marine mammals from these
activities was most recently authorized under an LOA that is effective
from August 12, 2019, through August 11, 2026, with similar
requirements to those promulgated herein (https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-navys-surveillance-towed-array-sensor-system-low-frequency). The Navy has
requested that this final rule take effect on or before August 12,
2026, to accommodate issuance of an LOA to be in effect when the Navy's
existing LOA expires on August 11, 2026, so as to not cause a
disruption in training and testing activities. The final rule taking
effect on August 12, 2026, will ensure that the MMPA final rule and LOA
are in place by the time the previous authorization expires. Any delay
in effectiveness of the final rule would result in either: (1) a
suspension of planned naval training and testing, which would disrupt
vital training and testing essential to national security; or (2) the
Navy's non-compliance with the MMPA (should the Navy conduct training
and testing without an LOA), thereby resulting in the potential for
unauthorized takes of marine mammals. Moreover, the Navy is ready to
implement the regulations immediately. For these reasons, NMFS finds
that the 30-day delay requirement does not apply to this final rule.

List of Subjects in 50 CFR Part 218

Administrative practice and procedure, Endangered and threatened
species, Fish, Fisheries, Marine mammals, Penalties, Reporting and
recordkeeping requirements, Transportation, Wildlife.

Dated: July 23, 2026.
Samuel D. Rauch III,
Deputy Assistant Administrator for Regulatory Programs, National Marine
Fisheries Service.

For the reasons set forth in the preamble, NMFS amends 50 CFR part
218 as follows:

PART 218--REGULATIONS GOVERNING THE TAKING AND IMPORTING OF MARINE
MAMMALS

0
1. The authority citation for part 218 continues to read as follows:

Authority: 16 U.S.C. 1361 et seq.

0
2. Revise subpart X to read as follows:

Subpart X--Taking and Importing Marine Mammals; U.S. Navy
Surveillance Towed Array Sensor System Low Frequency Active
(SURTASS LFA) Sonar Training and Testing in the Central and Western
North Pacific and Eastern Indian Oceans

Sec.
218.230 Specified activity and geographical region.
218.231 Effective dates.
218.232 Permissible methods of taking.
218.233 Prohibitions.
218.234 Mitigation requirements.
218.235 Requirements for monitoring and reporting.
218.236 Letter of Authorization.
218.237 Modifications of Letter of Authorization.
218.238-218.239 [Reserved]

[[Page 47703]]

Sec. 218.230 Specified activity and geographical region.

(a) Regulations in this subpart apply only to the U.S. Navy (Navy)
for the taking of marine mammals that occurs in the area described in
paragraph (b) of this section and that occurs incidental to the
activities listed in paragraph (c) of this section. Requirements
imposed on the Navy must be implemented by those persons they authorize
or fund to conduct activities on their behalf.
(b) The taking of marine mammals by the Navy under this subpart may
be authorized in a letter of authorization (LOA) only if it occurs
within the Pacific Surveillance Towed Array Sensor System Low Frequency
Active (SURTASS LFA) Sonar Study Area. The Pacific SURTASS LFA Sonar
Study Area is delineated in Figure 1 to this paragraph (b) and includes
the western and central North Pacific Ocean and eastern Indian Ocean,
not including the western Indian Ocean or Sea of Okhotsk.
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(c) The taking of marine mammals by the Navy is authorized only if
it occurs incidental to the Navy conducting military readiness
activities, including those in the following categories:
(1) Training;
(2) Maintenance and upgrades; and
(3) Exercises.

Sec. 218.231 Effective dates.

Regulations in this subpart are effective from August 12, 2026,
through August 11, 2033.

Sec. 218.232 Permissible methods of taking.

(a) Under LOAs issued pursuant to Sec. 216.106 of this chapter and
this subpart, the Navy may incidentally, but not intentionally, take
marine mammals within the area described in

[[Page 47705]]

Sec. 218.230(b) by Level A harassment and Level B harassment
associated with the use of SURTASS LFA sonar during activities listed
in Sec. 218.230(c), provided the activity is in compliance with all
terms, conditions, and requirements of this subpart and the applicable
LOA.
(b) The incidental take of marine mammals by the activities listed
in Sec. 218.230(c) is limited to the following species:

Table 1 to Paragraph (b)
------------------------------------------------------------------------
Species Stock
------------------------------------------------------------------------
North Pacific right whale.............. No stock designation (NSD).
Blue whale............................. NSD.
Blue whale............................. Central North Pacific.
Bryde's whale.......................... NSD.
Bryde's whale.......................... Hawaii.
Fin whale.............................. NSD.
Fin whale.............................. Hawaii.
Humpback whale......................... NSD.
Humpback whale......................... Hawaii.
Humpback whale......................... Western North Pacific.
Antarctic minke whale.................. NSD.
Minke whale............................ NSD.
Minke whale............................ Hawaii.
Omura's whale.......................... NSD.
Sei whale.............................. NSD.
Sei whale.............................. Hawaii.
Sperm whale............................ NSD.
Sperm whale............................ North Pacific.
Sperm whale............................ Hawaii.
Dwarf sperm whale...................... NSD.
Dwarf sperm whale...................... Hawaii.
Pygmy sperm whale...................... NSD.
Pygmy sperm whale...................... Hawaii.
Baird's beaked whale................... NSD.
Blainville's beaked whale.............. NSD.
Blainville's beaked whale.............. Hawaii.
Deraniyagala's beaked whale............ NSD.
Ginkgo-toothed beaked whale............ NSD.
Goose-beaked whale..................... NSD.
Goose-beaked whale..................... Hawaii.
Hubbs' beaked whale.................... NSD.
Longman's beaked whale................. NSD.
Longman's beaked whale................. Hawaii.
Stejneger's beaked whale............... NSD.
False killer whale..................... NSD.
False killer whale..................... Main Hawaiian Islands Insular.
False killer whale..................... Hawaii Pelagic.
Killer whale........................... NSD.
Killer whale........................... Hawaii.
Melon-headed whale..................... NSD.
Melon-headed whale..................... Hawaiian Islands.
Pygmy killer whale..................... NSD.
Pygmy killer whale..................... Hawaii.
Short-finned pilot whale............... NSD.
Short-finned pilot whale............... Hawaii.
Bottlenose dolphin..................... NSD.
Bottlenose dolphin..................... Hawaii Pelagic.
Common dolphin......................... NSD.
Fraser's dolphin....................... NSD.
Fraser's dolphin....................... Hawaii.
Northern right whale dolphin........... NSD.
Pacific white-sided dolphin............ North Pacific.
Pantropical spotted dolphin............ NSD.
Pantropical spotted dolphin............ Hawaii Pelagic.
Risso's dolphin........................ NSD.
Risso's dolphin........................ Hawaii.
Rough-toothed dolphin.................. NSD.
Rough-toothed dolphin.................. Hawaii.
Spinner dolphin........................ NSD.
Spinner dolphin........................ Hawaii Pelagic.
Striped dolphin........................ NSD.
Striped dolphin........................ Hawaii Pelagic.
Dall's porpoise........................ NSD.
Northern fur seal...................... NSD.
Steller sea lion....................... Western.
Harbor seal............................ California.
Ribbon seal............................ NSD.

[[Page 47706]]

Hawaiian monk seal..................... Hawaii.
Ringed seal............................ NSD.
Spotted seal........................... Bering.
------------------------------------------------------------------------

Sec. 218.233 Prohibitions.

Except incidental take described in Sec. 218.232 and authorized by
an LOA issued under Sec. 216.106 of this chapter and this subpart, it
shall be unlawful for any person to do the following in connection with
the activities described in this subpart:
(a) Violate, or fail to comply with, the terms, conditions, and
requirements of this subpart or an LOA issued under Sec. 216.106 of
this chapter and this subpart;
(b) Take any marine mammal not specified in Sec. 218.232(b);
(c) Take any marine mammal specified in Sec. 218.232(b) in any
manner other than as specified in the LOA;
(d) Take a marine mammal specified in Sec. 218.232(b) after NMFS
determines such taking results in more than a negligible impact on the
species or stock of such marine mammal; or
(e) Take a marine mammal specified in Sec. 218.232(b) after NMFS
determines such taking is having, or may have, an unmitigable adverse
impact on the availability of the species or stock for taking for
subsistence uses.

Sec. 218.234 Mitigation requirements.

When conducting the activities identified in Sec. 218.230(c), the
mitigation measures contained in this section and any LOA issued under
Sec. 216.106 of this chapter and this subpart must be implemented by
Navy personnel or contractors who are trained according to the
requirements in the LOA. If Navy contractors are serving on behalf of
Navy personnel, Navy contractors must follow the mitigation applicable
to Navy personnel. These mitigation measures include, but are not
limited to:
(a) General operating procedures. Prior to SURTASS LFA sonar
activities, the Navy must promulgate executive guidance for the
administration and execution of and compliance with the regulations in
this subpart and LOA.
(b) Manned surface vessel mitigation. Manned surface vessel
mitigation applies to Auxiliary General Ocean Surveillance (T-AGOS)
vessels underway and must be implemented to the maximum extent
practical based on the prevailing circumstances, including
consideration of safety of vessels, towing platforms, and crews, as
well as maneuverability restrictions, consistent with the following:
(1) Immediately prior to getting underway and while underway,
Lookouts will observe for marine mammals;
(2) While underway, Navy personnel must maneuver the manned surface
vessels (which may include reducing speed) to maintain a distance of at
least 457.2 meters (m) (500 yards (yd)) around observed whales and
182.9 m (200 yd) around all other marine mammals (except bow- or wake-
riding dolphins), providing it is safe to do so. No further action is
necessary if a dolphin continues to approach the vessel after the
vessel has made one course and/or speed change.
(3) Pedestal-mounted `Big Eye' (20 x 110 millimeter (mm))
binoculars (if installed) shall be used to assist in the detection of
marine mammals in the vicinity of the vessel. If the presence of marine
mammals is detected acoustically, Lookouts posted on the vessel shall
increase the vigilance of their visual observation.
(4) Manned surface vessel mitigation will not be implemented if one
or more of the following conditions applies:
(i) Dolphins are determined to be intentionally swimming at the
bow, alongside the vessel or vehicle, or directly behind the vessel or
vehicle (e.g., to bow-ride or wake-ride);
(ii) The vessel's safety is threatened; or
(iii) Doing so is impractical based on mission requirements (e.g.,
restricted ability to maneuver during towing activities).
(c) SURTASS LFA sonar mitigation zone; suspension and delay. If a
marine mammal is detected, through monitoring required under Sec.
218.235, within or about to enter within 2,000 yd (1.8 kilometers (km))
of the SURTASS LFA source (i.e., the LFA mitigation zone), Navy
personnel must immediately delay or suspend SURTASS LFA sonar
transmissions.
(d) Recommencement of SURTASS LFA sonar transmissions. The
following requirements for commencement or recommencement of SURTASS
LFA sonar transmissions apply:
(1) Navy personnel must not commence or recommence SURTASS LFA
sonar transmissions earlier than 15 minutes after:
(i) All marine mammals have left the area of the 2,000-yd (1.8 km)
LFA sonar mitigation zone; and
(ii) There is no further detection of any marine mammal within the
2,000-yd (1.8 km) LFA sonar mitigation zone as determined by the
visual, passive acoustic, and active acoustic high frequency monitoring
described in Sec. 218.235.
(2) [Reserved]
(e) Ramp-up of the high-frequency/marine mammal monitoring (HF/M3)
active sonar. The following requirements for ramp-up procedures for the
HF/M3 active sonar apply:
(1) Prior to full-power use, Navy personnel must ramp up the HF/M3
active sonar power level beginning at a maximum source sound pressure
level of 180 decibels referenced to 1 microPascal (dB re 1 [mu]Pa)
root-mean-square (RMS) sound pressure level (SPL) in 10-dB increments
to full operating levels over a period of no less than 5 minutes. Navy
personnel must implement this ramp-up procedure:
(i) At least 30 minutes prior to any SURTASS LFA sonar
transmissions; and
(ii) Any time after the HF/M3 source has been powered down for more
than 2 minutes.
(2) Navy personnel must not increase the HF/M3 SPL once a marine
mammal is detected; and
(3) Ramp-up may recommence once marine mammals are no longer
detected by all of the monitoring methods.
(f) Geographic mitigation. The Navy must implement the geographic
mitigation requirements described in paragraphs (f)(1) through (f)(3)
of this section.
(1) The activities specified in Sec. 218.230(c) must be conducted
such that:
(i) The received level of SURTASS LFA sonar transmissions will not
exceed 180 dB re 1 [mu]Pa RMS SPL within 22 km (12 nautical miles
(nmi)) from any emergent land, including offshore islands;
(ii) The received level of SURTASS LFA sonar transmissions will not
exceed 180 dB re 1 [mu]Pa RMS SPL at a distance of 1 km (0.5 nmi)
seaward of the outer perimeter of any Offshore Biologically Important
Area (OBIA) in

[[Page 47707]]

the SURTASS LFA Study Area during the effective period specified. OBIAs
and the related effective periods are listed in paragraph (f)(2) of
this section or may be subsequently identified through the adaptive
management process specified in Sec. 218.237(c)(1). The boundaries and
effective periods of the OBIAs will be kept on file in NMFS' Office of
Protected Resources (OPR) and on its website.
(iii) No more than 25 percent of the sound source amount analyzed
(no more than 275 hours in a given year) of SURTASS LFA sonar for
training and testing will be conducted within 18.5 km (10 nmi) of any
single OBIA during any year; and
(iv) SURTASS LFA sonar activities will not occur within territorial
seas of foreign nations, which are areas from 0-22 km (0-12 nmi) from
shore.
(2) Figure 1 to this paragraph (f)(1) shows the location of the
OBIAs. Table 1 to paragraph (f)(1) shows the specified timeframes when
the requirements from paragraph (f)(1) apply.
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[[Page 47709]]

Table 1 to Paragraph (f)(1)--OBIAs for Marine Mammals in the Pacific SURTASS LFA Sonar Study Area
----------------------------------------------------------------------------------------------------------------
Relevant marine
OBIA No. Name Location/water body mammal species Effective period
----------------------------------------------------------------------------------------------------------------
26....................... Main Hawaiian Central North Humpback whale...... November through
Islands. Pacific Ocean. April.
27....................... Northwestern Central North Humpback whale...... December through
Hawaiian Islands. Pacific Ocean. April.
28....................... Mariana Islands..... Western North Humpback whale...... December through
Pacific Ocean. May.
29....................... Ryukyu-Philippines.. Western North Humpback whale...... January through
Pacific Ocean. April.
30....................... Ogasawara--Sperm Western North Sperm whale......... June through
whale. Pacific Ocean. September.
31....................... Ogasawara-Kazin-- Western North Humpback whale...... December through
Humpback whale. Pacific Ocean. May.
32....................... Honshu.............. Western North Gray whale.......... January through
Pacific Ocean. May.
33....................... Southeast Kamchatka. Western North Fin, gray (Western Year-round.
Pacific Ocean. North Pacific
stock), humpback,
and North Pacific
right whale.
34....................... Gulf of Thailand.... Eastern Indian Ocean Bryde's whale....... April through
November.
35....................... Western Australia-- Eastern Indian Ocean Blue (pygmy) whale.. May through
Blue whale. November.
36....................... Western Australia-- Eastern Indian Ocean Humpback whale...... May through
Humpback whale. December.
37....................... Southern Bali....... Eastern Indian Ocean Blue (pygmy), August through
Bryde's, humpback, November.
Omura's, sei, and
sperm whale.
38....................... Swatch-of-No-Ground Northern Bay of Bryde's whale....... Year-round.
(SoNG). Bengal.
39....................... Sri Lanka........... Eastern Indian Ocean Blue (pygmy) and October through
sperm whale. April.
40....................... Maldives Archipelago Central Indian Ocean Blue (pygmy), October through
Bryde's, humpback, May.
and sperm whale.
41....................... Northeast Arabian Arabian Sea......... Blue, Bryde's, and Year-round.
Sea. humpback (Arabian
Sea stock) whale.
42....................... South of Java Island East Indian Ocean... Blue (pygmy) whale.. May through
November.
43....................... South of Lombok East Indian Ocean... Blue (pygmy) whale.. May through
Sumbawa Islands. November.
44....................... Southeast Kamchatka Western North North Pacific right April through
Offshore. Pacific Ocean. whale. October.
----------------------------------------------------------------------------------------------------------------

(3) Should national security require the Navy to exceed a
requirement in paragraph (f)(1)(iii) of this section, personnel
conducting the activity are required to obtain approval through the
chain of command prior to commencement of the activity. The Navy must
provide NMFS with notification as soon as is practicable and include
the information (e.g., sonar hours in exceedance of 25 percent) in its
annual activity reports submitted to NMFS.
(g) Cetacean live stranding. In the event of a cetacean live
stranding (or near-shore atypical milling) event within the Study Area
or within 50 km (27 nmi) of the boundary of the Study Area, where the
NMFS Marine Mammal Stranding Network is engaged in herding or other
interventions to return animals to the water, NMFS OPR will advise the
Navy of the need to implement shutdown procedures for all active
acoustic sources within 50 km of the stranding. Following this initial
shutdown, NMFS will communicate with the Navy to determine whether
circumstances support modification of the shutdown zone. The Navy may
decline to implement all or part of the shutdown if the holder of the
LOA, or his/her designee, determines that it is necessary for national
security. Shutdown procedures for live stranding or milling cetaceans
include the following:
(1) Shutdown no longer needed. If at any time, the marine mammal(s)
die or are euthanized, or if herding/intervention efforts are stopped,
NMFS will immediately advise that the shutdown around the animals'
location is no longer needed;
(2) Shutdown procedures remain in effect. Otherwise, shutdown
procedures must remain in effect until NMFS determines and advises that
all live animals involved have left the area (either of their own
volition or following an intervention); and
(3) Further observations. If further observations of the marine
mammals indicate the potential for re-stranding, additional
coordination with NMFS will be required to determine what measures are
necessary to minimize that likelihood (e.g., extending the shutdown or
moving operations farther away) and to implement those measures as
appropriate.

Sec. 218.235 Requirements for monitoring and reporting.

The Navy must implement the following monitoring and reporting
requirements when conducting the specified activities:
(a) Notification of take. If the Navy reasonably believes that the
specified activity identified in Sec. 218.230 resulted in the
mortality or serious injury of any marine mammals, or in any Level A
harassment or Level B harassment of marine mammals not identified in
this subpart, then the Navy must notify NMFS immediately or as soon as
operational security considerations allow.
(b) Monitoring and reporting under the LOA. The Navy must conduct
all monitoring and reporting required under the LOA.
(c) Notification of injured, live stranded, or dead marine mammals.
Navy personnel must abide by the Notification and Reporting Plan, which
sets out notification, reporting, and other requirements when dead,
injured, or live stranded marine mammals are detected. The Notification
and Reporting Plan is available at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.
(d) Mitigation monitoring. The Navy must conduct all monitoring
required under the LOA, including:
(1) Visual Observations. Visual observations must be conducted by
trained Lookouts on the vessel's bridge using standard binoculars (7x)
and the naked eye. Pedestal-mounted `Big Eye' (20 x 110 mm) binoculars
(if installed) must be used to assist in the detection of marine
mammals in the vicinity of the vessel.
(i) Lookouts must conduct visual monitoring from the vessel's
bridge during all daylight hours (30 minutes before sunrise until 30
minutes after sunset);
(ii) During training and testing activities that employ SURTASS LFA
sonar in the active mode, Lookouts must

[[Page 47710]]

conduct visual monitoring beginning 30 minutes before sunrise or 30
minutes before SURTASS LFA sonar begins to transmit and continue until
30 minutes after sunset or until 15 minutes after the SURTASS LFA sonar
transmissions cease;
(iii) Lookouts must log all detections of marine mammals during
SURTASS LFA sonar transmissions during training and testing activities;
(iv) Lookouts must record the number, identification, bearing, and
range of observed marine mammals during training and testing
activities, and must identify marine mammals to the lowest taxonomic
level possible; and
(v) Lookouts must continue visual observations until 15 minutes
have passed since the last detection of the marine mammal.
(2) Passive Acoustic Monitoring. During activities specified in
Sec. 218.230(c) that employ SURTASS LFA sonar in the active mode, Navy
personnel must conduct passive acoustic monitoring using the SURTASS
towed horizontal line array to detect vocalizing marine mammals.
(i) Passive acoustic monitoring must begin 30 minutes before the
SURTASS LFA sonar begins to transmit and continue until 15 minutes
after SURTASS LFA sonar transmissions cease; and
(ii) If a detected sound is estimated to be from a vocalizing
marine mammal, the sonar technician must notify the senior military
member-in-charge, who must alert the HF/M3 sonar operator and Lookouts
(during daylight).
(3) Active Acoustic (HF/M3) Monitoring. During activities specified
in Sec. 218.230(c) that employ SURTASS LFA sonar in the active mode,
Navy personnel must use the HF/M3 sonar to detect, locate, and track
marine mammals in relation to the SURTASS LFA sonar array and the LFA
mitigation zone, subject to the ramp-up requirements in Sec.
218.234(e).
(i) HF/M3 sonar monitoring must begin 30 minutes before the SURTASS
LFA sonar begins to transmit and continue until 15 minutes after
SURTASS LFA sonar transmissions cease; and
(ii) If a marine mammal is detected during HF/M3 monitoring within
the SURTASS LFA mitigation zone, the sonar operator must notify the
senior military member-in-charge.
(4) Cessation of Monitoring. Navy personnel must continue
monitoring either for at least 15 minutes after completion of the
SURTASS LFA sonar training and testing transmission or, if marine
mammals are exhibiting unusual changes in behavioral patterns, until
behavior patterns return to normal or conditions prevent continued
observations.
(e) Designation of qualified individuals. The Navy must designate
qualified on-site individuals to conduct the mitigation, monitoring,
and reporting activities specified in these regulations and LOA issued
under Sec. Sec. 216.106 of this chapter and 218.236.
(f) Marine Mammal Monitoring Program. The Navy must continue to
assess data from the Marine Mammal Monitoring Program and work toward
making some portion of that data, after appropriate security reviews,
available to scientists with appropriate clearances. Any portions of
the analyses conducted by these scientists based on these data that are
determined to be unclassified after appropriate security reviews will
be made publicly available.
(g) Annual Pacific SURTASS LFA Study Area marine species monitoring
report. The Navy must submit an unclassified annual report (Annual
Pacific SURTASS LFA Study Area Marine Species Monitoring Report) of the
Study Area marine species monitoring describing the implementation and
results from the previous calendar year. Data collection methods will
be standardized across range complexes and the Study Area to allow for
comparison in different geographic locations. The draft report must be
submitted annually to the Director, Office of Protected Resources,
NMFS. NMFS will submit any comments or questions on the report within 3
months of receipt. The report will be considered final after the Navy
has addressed NMFS' comments, or 3 months after submittal of the draft
if NMFS does not provide comments on the draft report. The report must
describe progress of knowledge made with respect to new or continuing
scientific knowledge of marine mammals.
(h) Quick look reports. In the event that the sound source amount
analyzed in the preambles of the Marine Mammal Protection Act (MMPA)
proposed rule (91 FR 11618, March 10, 2026) and this final rule are
exceeded within a given reporting year, the Navy must submit a
preliminary report detailing the exceedance within 21 days after the
anniversary date of issuance of the LOA.
(i) Annual Pacific SURTASS LFA training and testing report. The
Navy must submit a classified and unclassified report (Annual Pacific
SURTASS LFA Training and Testing Report) to the Director, Office of
Protected Resources, NMFS, annually within 3 months of the 1-year
anniversary of the date of the issuance of the LOA. For the final
reporting year, the Navy must submit a final/close-out (year 7) Annual
Pacific SURTASS LFA Training and Testing Report. NMFS will submit any
comments or questions on the report within 1 month of receipt. The
report will be considered final after the Navy has addressed NMFS'
comments, or 1 month after submittal of the drafts if NMFS does not
provide comments on the draft report.
(1) Annual Reports. The Annual Pacific SURTASS LFA Training and
Testing Report must include elements listed below. The analysis in the
report must be based on the data from the current year's report and
data collected from previous annual reports.
(i) Dates, times, and locations of each vessel during each training
and testing activity;
(ii) Information on sonar transmissions during each training and
testing activity, including:
(A) Total annual hours or quantity of each bin of sonar used in all
training and testing events,
(B) Cumulative sonar use quantity from previous years' reports
through the current year, and
(C) Records of any sonar delays or suspensions due to the presence
of marine mammals.
(iii) Marine mammal detection information during specified
activities where mitigation was implemented:
(A) Date, time, and location of sighting;
(B) Species (if not possible, indication of whale/dolphin/
pinniped);
(C) Number of individuals;
(D) Initial Detection Sensor (e.g., visual, passive acoustic, HF/M3
sonar);
(E) Indication of specific type of platform observation was made
from (including, for example, what type of surface vessel or testing
platform);
(F) Length of time observers maintained visual contact with marine
mammal;
(G) Sea state;
(H) Visibility;
(I) Sound source in use at the time of sighting;
(J) Indication of whether animal was less than 200 yd (182.9 m),
200 to 500 yd (182.9 to 457.2 m), 500 to 1,000 yd (457.2 to 914.4 m),
1,000 to 2,000 yd (914.4 m to 1.8 km), or greater than 2,000 yd (1.8
km) from sonar source;
(K) Whether operation of sonar sensor was delayed, or sonar was
powered or shut down, and the length of delay;
(L) Bearing and range from the vessel; and
(M) For visual observations, Lookouts must report the observed
behavior of the animal(s) in plain language and without trying to
categorize in any way (such as

[[Page 47711]]

animal closing to bow ride, paralleling course/speed, floating on
surface and not swimming, etc.) and if any calves were present.
(iv) Delays or suspensions of LFA sonar transmissions due to
mitigation monitoring protocol. Information on marine mammal detections
would include marine mammal type (i.e., whales, dolphins) and/or
species identifications, number of marine mammals detected, time of
detections, type of detection (visual, passive acoustic, HF/M3 sonar),
bearing and range from the vessel, abnormal behavior (if any), and
remarks or narrative as necessary.
(v) An evaluation (based on data gathered during the reporting
year) of the effectiveness of mitigation measures designed to minimize
the received level to which marine mammals may be exposed. This
evaluation must identify the specific observations that support any
conclusions the Navy reaches about the effectiveness of the mitigation.
(2) Final/close-out report. The final/close-out report at the
conclusion of the authorization period (year 7) will also serve as the
comprehensive close-out report and provide the annual totals for each
sound source bin with a comparison to the annual amount analyzed and
the 7-year total for each sound source bin with a comparison to the 7-
year amount analyzed.
(j) National security requirement. If the Navy invokes the national
security requirement described in Sec. 218.234(f)(3), Navy personnel
must include information about the event in its Annual Pacific SURTASS
LFA Training and Testing Report.

Sec. 218.236 Letter of Authorization.

(a) To incidentally take marine mammals pursuant to this subpart,
the Navy must apply for and obtain an LOA.
(b) An LOA, unless suspended or revoked, may be effective for a
period of time not to exceed the expiration date of this subpart.
(c) The LOA will set forth:
(1) Permissible methods of incidental taking;
(2) Geographic areas for incidental taking;
(3) Means of effecting the least practicable adverse impact (i.e.,
mitigation) on the species and stocks of marine mammals and their
habitat; and
(4) Requirements for monitoring and reporting.
(d) Issuance of the LOA must be based on a determination that the
level of taking is consistent with the findings made for the total
taking allowable under the regulations of this subpart.
(e) Notice of issuance, modification, or denial of the LOA will be
published in the Federal Register within 30 days of a determination.
(f) In the event of projected changes to mitigation, monitoring, or
reporting measures required by an LOA, the Navy must apply for and
obtain a modification of the LOA under Sec. 218.237.

Sec. 218.237 Modifications of Letters of Authorization.

(a) NMFS may modify the mitigation, monitoring, or reporting
measures in a LOA issued under Sec. Sec. 216.106 of this chapter and
218.236 of this subpart at the request of the Navy or NMFS' own
initiative if:
(1) The anticipated effects of the modified measure are the same as
those described and analyzed for this subpart;
(2) The modified measure has a reasonable likelihood of
effectiveness;
(3) NMFS determines the modified measure does not change the
findings made for this subpart; and
(4) Navy concurs with the modified measure and that, where
applicable, it is practicable for the Navy in the context of personnel
safety, practicality of implementation, and impacts on the
effectiveness of the military readiness activity.
(b) If modifications to the mitigation, monitoring, or reporting
measures are substantial NMFS will publish a notice of the proposed LOA
modification in the Federal Register and solicit public comment.

Sec. Sec. 218.238-218.239 [Reserved]

[FR Doc. 2026-15206 Filed 7-27-26; 8:45 am]
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