[Federal Register Volume 87, Number 154 (Thursday, August 11, 2022)]
[Proposed Rules]
[Pages 49656-49765]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-16509]



[[Page 49655]]

Vol. 87

Thursday,

No. 154

August 11, 2022

Part II





Department of Commerce





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National Oceanic and Atmospheric Administration





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50 CFR Part 218





Taking and Importing Marine Mammals; Taking Marine Mammals Incidental 
to the U.S. Navy Training Activities in the Gulf of Alaska Study Area; 
Proposed Rule

  Federal Register / Vol. 87 , No. 154 / Thursday, August 11, 2022 / 
Proposed Rules  

[[Page 49656]]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

[Docket No. 220726-0163]
RIN 0648-BK46


Taking and Importing Marine Mammals; Taking Marine Mammals 
Incidental to the U.S. Navy Training Activities in the Gulf of Alaska 
Study Area

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

ACTION: Proposed rule; request for comments and information.

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SUMMARY: NMFS has received a request from the U.S. Navy (Navy) to take 
marine mammals incidental to training activities conducted in the Gulf 
of Alaska (GOA) Study Area (hereafter referred to as the GOA Study 
Area). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is 
requesting comments on its proposal to issue regulations and a 
subsequent Letter of Authorization (LOA) to the Navy to incidentally 
take marine mammals during the specified activities. NMFS will consider 
public comments prior to issuing any final rule and making final 
decisions on the issuance of the requested LOA. Agency responses to 
public comments will be provided in the notice of the final decision. 
The Navy's activities qualify as military readiness activities pursuant 
to the MMPA, as amended by the National Defense Authorization Act for 
Fiscal Year 2004 (2004 NDAA).

DATES: Comments and information must be received no later than 
September 26, 2022.

ADDRESSES: Submit all electronic public comments via the Federal e-
Rulemaking Portal. Go to https://www.regulations.gov and enter NOAA-
NMFS-2022-0060 in the Search box. Click on the ``Comment'' icon, 
complete the required fields, and enter or attach your comments.
    Instructions: Comments sent by any other method, to any other 
address or individual, or received after the end of the comment period, 
may not be considered by NMFS. All comments received are a part of the 
public record and will generally be posted for public viewing on 
www.regulations.gov without change. All personal identifying 
information (e.g., name, address), confidential business information, 
or otherwise sensitive information submitted voluntarily by the sender 
will be publicly accessible. NMFS will accept anonymous comments (enter 
``N/A'' in the required fields if you wish to remain anonymous). 
Attachments to electronic comments will be accepted in Microsoft Word, 
Excel, or Adobe PDF file formats only.
    A copy of the Navy's application and other supporting documents and 
documents cited herein may be obtained online at: https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-navy-training-activities-gulf-alaska-temporary-maritime-0. In case of 
problems accessing these documents, please use the contact listed here 
(see FOR FURTHER INFORMATION CONTACT).

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

SUPPLEMENTARY INFORMATION:

Purpose of Regulatory Action

    These proposed regulations, issued under the authority of the MMPA 
(16 U.S.C. 1361 et seq.), would provide the framework for authorizing 
the take of marine mammals incidental to the Navy's training activities 
(which qualify as military readiness activities), including the use of 
sonar and other transducers, and in-air detonations at or near the 
surface (within 10 m above the water surface) in the GOA Study Area. 
The GOA Study Area is comprised of three areas: the Temporary Maritime 
Activities Area (TMAA), a warning area, and the Western Maneuver Area 
(WMA) (see Figure 1). The TMAA and WMA are temporary areas established 
within the GOA for ships, submarines, and aircraft to conduct training 
activities. The warning area overlaps and extends slightly beyond the 
northern corner of the TMAA. The WMA is located south and west of the 
TMAA and provides additional surface, sub-surface, and airspace in 
which to maneuver in support of activities occurring within the TMAA. 
The use of sonar and other transducers, and explosives would not occur 
within the WMA.
    NMFS received an application from the Navy requesting 7-year 
regulations and an authorization to incidentally take individuals of 
multiple species of marine mammals (``Navy's rulemaking/LOA 
application'' or ``Navy's application''). Take is anticipated to occur 
by Level A harassment and Level B harassment incidental to the Navy's 
training activities. No lethal take is anticipated or proposed for 
authorization.

Background

    The MMPA prohibits the ``take'' of marine mammals, with certain 
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA direct the 
Secretary of Commerce (as delegated to NMFS) to allow, upon request, 
the incidental, but not intentional, taking of small numbers of marine 
mammals by U.S. citizens who engage in a specified activity (other than 
commercial fishing) within a specified geographical region if certain 
findings are made and either regulations are proposed or, if the taking 
is limited to harassment, the public is provided with notice of the 
proposed incidental take authorization and provided the opportunity to 
review and submit comments.
    An authorization for incidental takings shall be granted if NMFS 
finds that the taking will have a negligible impact on the species or 
stocks and will not have an unmitigable adverse impact on the 
availability of the species or stocks for taking for subsistence uses 
(where relevant). Further, NMFS must prescribe the permissible methods 
of taking and other means of effecting the least practicable adverse 
impact on the affected species or stocks and their habitat, paying 
particular attention to rookeries, mating grounds, and areas of similar 
significance, and on the availability of such species or stocks for 
taking for certain subsistence uses (referred to in this rule as 
``mitigation measures''); and requirements pertaining to the monitoring 
and reporting of such takings. The MMPA defines ``take'' to mean to 
harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or 
kill any marine mammal. The Preliminary Analysis and Negligible Impact 
Determination section below discusses the definition of ``negligible 
impact.''
    The NDAA for Fiscal Year 2004 (2004 NDAA) (Pub. L. 108-136) amended 
section 101(a)(5) of the MMPA to remove the ``small numbers'' and 
``specified geographical region'' provisions indicated above and 
amended the definition of ``harassment'' as applied to a ``military 
readiness activity.'' The definition of harassment for military 
readiness activities (Section 3(18)(B) of the MMPA) is (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

[[Page 49657]]

point where such behavioral patterns are abandoned or significantly 
altered (Level B harassment). In addition, the 2004 NDAA amended the 
MMPA as it relates to military readiness activities such that the least 
practicable adverse impact analysis shall include consideration of 
personnel safety, practicality of implementation, and impact on the 
effectiveness of the military readiness activity.
    More recently, Section 316 of the NDAA for Fiscal Year 2019 (2019 
NDAA) (Pub. L. 115-232), signed on August 13, 2018, amended the MMPA to 
allow incidental take rules for military readiness activities under 
section 101(a)(5)(A) to be issued for up to 7 years. Prior to this 
amendment, all incidental take rules under section 101(a)(5)(A) were 
limited to 5 years.

Summary and Background of Request

    On October 9, 2020, NMFS received an adequate and complete 
application from the Navy requesting authorization for take of marine 
mammals, by Level A harassment and Level B harassment, incidental to 
training from the use of active sonar and other transducers and 
explosives (in-air, occurring at or above the water surface) in the 
TMAA over a 7-year period beginning when the current authorization 
expires. On March 12, 2021, the Navy submitted an updated application 
that provided revisions to the Northern fur seal take estimate and 
incorporated additional best available science. In August 2021, the 
Navy communicated to NMFS that it was considering an expansion of the 
GOA Study Area and an expansion of the Portlock Bank Mitigation Area 
proposed in its previous applications. On February 2, 2022, the Navy 
submitted a second updated application that described the addition of 
the WMA to the GOA Study Area (which previously just consisted of the 
TMAA) and the replacement of the Portlock Bank Mitigation Area with the 
Continental Shelf and Slope Mitigation Area. The Navy is not planning 
to conduct any testing activities.
    On January 8, 2021 (86 FR 1483), we published a notice of receipt 
(NOR) of application in the Federal Register, requesting comments and 
information related to the Navy's request for 30 days. We received one 
comment on the NOR that was non-substantive in nature.
    The following types of training, which are classified as military 
readiness activities pursuant to the MMPA, as amended by the 2004 NDAA, 
would be covered under the regulations and LOA (if issued): surface 
warfare (detonations at or above the water surface) and anti-submarine 
warfare (sonar and other transducers). The Navy is also conducting Air 
Warfare, Electronic Warfare, Naval Special Warfare, Strike Warfare, and 
Support Operations, but these activities do not involve sonar and other 
transducers, detonations at or above the water surface, or any other 
stressors that could result in the take of marine mammals. (See the 
2020 GOA Draft SEIS/OEIS for more detail on those activities). The 
activities would not include in-water explosives, pile driving/removal, 
or use of air guns.
    This would be the third time NMFS has promulgated incidental take 
regulations pursuant to the MMPA relating to similar military readiness 
activities in the GOA, following those effective beginning May 4, 2011 
(76 FR 25479; May 4, 2011) and April 26, 2017 (82 FR 19530; April 27, 
2017).
    The Navy's mission is to organize, train, equip, and maintain 
combat-ready naval forces capable of winning wars, deterring 
aggression, and maintaining freedom of the seas. This mission is 
mandated by Federal law (10 U.S.C. 8062), which requires the readiness 
of the naval forces of the United States. The Navy executes this 
responsibility by establishing and executing training programs, 
including at-sea training and exercises, and ensuring naval forces have 
access to the ranges, operating areas (OPAREA), and airspace needed to 
develop and maintain skills for conducting naval activities.
    The Navy has conducted training activities in the TMAA portion of 
the GOA Study Area since the 1990s. Since the 1990s, the Department of 
Defense has conducted a major joint training exercise in Alaska and off 
the Alaskan coast that involves the Departments of the Navy, Army, Air 
Force, and Coast Guard participants reporting to a unified or joint 
commander who coordinates the activities. These activities are planned 
to demonstrate and evaluate the ability of the services to engage in a 
conflict and successfully carry out plans in response to a threat to 
national security. The Navy's planned activities for the period of this 
proposed rule would be a continuation of the types and level of 
training activities that have been ongoing for more than a decade. 
While the specified activities have not changed, there are changes in 
the platforms and systems used in those activities, as well as changes 
in the bins (source classifications) used to analyze the activities. 
(For example, two new sonar bins were added (MF12 and ASW1) and another 
bin was eliminated (HF6). This was due to changes in platforms and 
systems.) Further, the Navy expanded the GOA Study Area to include the 
WMA, though the vast majority of the training activities would still 
occur only in the TMAA.
    The Navy's rulemaking/LOA application reflects the most up-to-date 
compilation of training activities deemed necessary by senior Navy 
leadership to accomplish military readiness requirements. The types and 
numbers of activities included in the proposed rule account for 
fluctuations in training in order to meet evolving or emergent military 
readiness requirements. These proposed regulations would become 
effective in December of 2022 and would cover training activities that 
would occur for a 7-year period following the expiration of the current 
MMPA authorization for the GOA, which expired on April 26, 2022.

Description of the Specified Activity

    The Navy requests authorization to take marine mammals incidental 
to conducting training activities. The Navy has determined that 
acoustic and explosives stressors are most likely to result in impacts 
on marine mammals that could rise to the level of harassment, and NMFS 
concurs with this determination. Detailed descriptions of these 
activities are provided in Chapter 2 of the 2020 GOA Draft Supplemental 
Environmental Impact Statement (SEIS)/Overseas EIS (OEIS) (2020 GOA 
DSEIS/OEIS) (https://www.goaeis.com/) and in the Navy's rulemaking/LOA 
application (https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-navy-training-activities-gulf-alaska-temporary-maritime-0) and are summarized here.

Dates and Duration

    Training activities would be conducted intermittently in the GOA 
Study Area over a maximum time period of up to 21 consecutive days 
annually from April to October to support a major joint training 
exercise in Alaska and off the Alaskan coast that involves the 
Departments of the Navy, Army, Air Force, and Coast Guard. The 
participants report to a unified or joint commander who coordinates the 
activities planned to demonstrate and evaluate the ability of the 
services to engage in a conflict and carry out plans in response to a 
threat to national security. The specified activities would occur over 
a maximum time period of up to 21 consecutive days each year during the 
7-year period of validity of the regulations. The proposed number of 
training activities are described in the Detailed Description of 
Proposed Activities section (Table 3) of this proposed rule.

[[Page 49658]]

Geographical Region

    The GOA Study Area (see Figure 1 below and Figure ES-1 of the 2022 
Supplement to the 2020 GOA DSEIS/OEIS) is entirely at sea and is 
comprised of the TMAA and a warning area in the Gulf of Alaska, and the 
WMA. The term ``at-sea'' refers to training activities in the Study 
Area (both the TMAA and WMA) that occur (1) on the ocean surface, (2) 
beneath the ocean surface, and (3) in the air above the ocean surface. 
Navy training activities occurring on or over the land outside the GOA 
Study Area are not included in this proposed rule, and are covered 
under separate environmental documentation prepared by the U.S. Air 
Force and the U.S. Army. As depicted in Figure 1 of this proposed rule, 
the TMAA is a polygon roughly resembling a rectangle oriented from 
northwest to southeast, approximately 300 nmi (556 km) in length by 150 
nmi (278 km) in width, located south of Montague Island and east of 
Kodiak Island. The GOA Study Area boundary was intentionally designed 
to avoid ESA-designated Steller sea lion critical habitat. The WMA is 
located south and west of the TMAA, and provides an additional 185,806 
nmi\2\ of surface, sub-surface, and airspace training to support 
activities occurring within the TMAA (Figure 1). The boundary of the 
WMA follows the bottom of the slope at the 4,000 m contour line, and 
was configured to avoid overlap and impacts to ESA-designated critical 
habitat, biologically important areas (BIAs), migration routes, and 
primary fishing grounds. The WMA provides additional airspace and sea 
space for aircraft and vessels to maneuver during training activities 
for increased training complexity. The TMAA and WMA are temporary areas 
established within the GOA for ships, submarines, and aircraft to 
conduct training activities.
    Additional detail can be found in Chapter 2 of the Navy's 
rulemaking/LOA application.
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Primary Mission Areas

    The Navy categorizes many of its training activities into 
functional warfare areas called primary mission areas. The Navy's 
planned activities for the GOA Study Area generally fall into the 
following six primary mission areas: Air Warfare; Surface Warfare; 
Anti-Submarine Warfare; Electronic Warfare; Naval Special Warfare; and 
Strike Warfare. Most activities conducted in the GOA are categorized 
under one of these primary mission areas; activities that do not fall 
within one of these areas are listed as ``support operations'' or 
``other training activities.'' Each warfare community (aviation, 
surface, and subsurface) may train in some or all of these primary 
mission areas. A description of the sonar, munitions, targets, systems, 
and other materials used during training activities within these 
primary mission areas is provided in Appendix A (Navy Activities 
Descriptions) of the 2020 GOA DSEIS/OEIS and section ES.2.2 (Proposed 
Activities in the Western Maneuver Area) of the 2022 Supplement to the 
2020 GOA DSEIS/OEIS.
    The Navy describes and analyzes the effects of its training 
activities within the 2020 GOA DSEIS/OEIS and 2022 Supplement to the 
2020 GOA DSEIS/OEIS. In its assessment, the Navy concluded that of the 
activities to be conducted within the GOA Study Area, sonar use and in-
air explosives occurring at or above the water surface were the 
stressors resulting in impacts on marine mammals that could rise to the 
level of harassment as defined under the MMPA. (The Navy is not 
proposing to conduct any activities that use in-water or underwater 
explosives.) Further, these activities are limited to the TMAA. No 
activities involving sonar use or explosives would occur in the WMA or 
the portion of the warning area that extends beyond the TMAA. 
Therefore, the Navy's rulemaking/LOA application provides the Navy's 
assessment of potential effects from sonar use and explosives occurring 
at or above the water surface in terms of the various warfare mission 
areas they are associated with. Those mission areas include the 
following:
     surface warfare (in-air detonations at or above the water 
surface); \1\ and
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    \1\ Defined herein as being within 10 meters of the ocean 
surface.
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     anti-submarine warfare (sonar and other transducers).
    The Navy's activities in Air Warfare, Electronic Warfare, Naval 
Special Warfare, Strike Warfare, Support Operations, and Other Training 
Activities do not involve sonar and other transducers, detonations at 
or near the surface, or any other stressors that could result in 
harassment, serious injury, or mortality of marine mammals. Therefore, 
the activities in these warfare areas are not discussed further in this 
proposed rule, but are analyzed fully in the 2020 GOA DSEIS/OEIS and 
2022 Supplement to the 2020 GOA DSEIS/OEIS. The specific acoustic 
sources analyzed in this proposed rule are contained in the 2020 GOA 
DSEIS/OEIS and are presented in the following sections based on the 
primary mission areas.
Surface Warfare
    The mission of surface warfare (named anti-surface warfare in the 
2011 GOA Final Environmental Impact Statement (FEIS)/Overseas 
Environmental Impact Statement (OEIS) and 2016 GOA Final Supplemental 
Environmental Impact Statement (FSEIS)/OEIS, but since changed by the 
Navy to ``Surface Warfare'') is to obtain control of sea space from 
which naval forces may operate, which entails offensive action against 
surface targets while also defending against enemy forces. In surface 
warfare, aircraft use guns, air-launched cruise missiles, or other 
precision-guided munitions; ships employ naval guns and surface-to-
surface missiles; and submarines attack surface ships using anti-ship 
cruise missiles.
Anti-Submarine Warfare
    The mission of anti-submarine warfare is to locate, neutralize, and 
defeat hostile submarine forces that threaten Navy surface forces. 
Anti-submarine warfare can involve various assets such as aircraft, 
ships, and submarines which all search for hostile submarines. These 
forces operate together or independently to gain early warning and 
detection, and to localize, track, target, and attack submarine 
threats.
    Anti-submarine warfare training addresses basic skills such as 
detecting and classifying submarines, as well as evaluating sounds to 
distinguish between enemy submarines and friendly submarines, ships, 
and marine life. These integrated anti-submarine warfare training 
exercises are conducted in coordinated, at-sea training events 
involving submarines, ships, and aircraft.

Overview of the Major Training Exercise Within the GOA Study Area

    The training activities in the GOA Study Area are considered to be 
a major training exercise (MTE). A MTE, for purposes of this 
rulemaking, is comprised of several unit-level activities conducted by 
several units operating together, commanded and controlled by a single 
Commander, and potentially generating more than 100 hours of active 
sonar. These exercises typically employ an exercise scenario developed 
to train and evaluate the exercise participants in tactical and 
operational tasks. In a MTE, most of the activities being directed and 
coordinated by the Commander in charge of the exercise are identical in 
nature to the activities conducted during individual, crew, and smaller 
unit-level training events. In a MTE, however, these disparate training 
tasks are conducted in concert, rather than in isolation. At most, only 
one MTE would occur in the GOA Study Area per year (over a maximum of 
21 days).

Description of Stressors

    The Navy uses a variety of sensors, platforms, weapons, and other 
devices, including ones used to ensure the safety of Sailors and 
Marines, to meet its mission. Training with these systems may introduce 
sound and energy into the environment. The proposed training activities 
were evaluated to identify specific components that could act as 
stressors by having direct or indirect impacts on the environment. This 
analysis included identification of the spatial variation of the 
identified stressors. The following subsections describe the acoustic 
and explosive stressors for marine mammals and their habitat (including 
prey species) within the GOA Study Area. Each description contains a 
list of activities that may generate the stressor. Stressor/resource 
interactions that were determined to have de minimis or no impacts 
(e.g., vessel noise, aircraft noise, weapons noise, and high-altitude 
(greater than 10 m above the water surface) explosions) were not 
carried forward for analysis in the Navy's rulemaking/LOA application. 
The Navy fully considered the possibility of vessel strike, conducted 
an analysis, and determined that requesting take of marine mammals by 
vessel strike was not warranted. Although the Navy did not request take 
for vessel strike, NMFS also fully analyzed the potential for vessel 
strike of marine mammals as part of this rulemaking. Therefore, this 
stressor is discussed in detail below. No Sinking Exercise (SINKEX) 
events are proposed in the GOA Study Area for this rulemaking, nor is 
establishment and use of a Portable Undersea Tracking Range (PUTR) 
proposed. NMFS reviewed the Navy's analysis and conclusions on de 
minimis and no-impact sources, included in Section 3.8.3 (Environmental 
Consequences) of

[[Page 49661]]

the 2020 GOA DSEIS/OEIS and finds them complete and supportable.

Acoustic Stressors

    Acoustic stressors include acoustic signals emitted into the water 
for a specific purpose, such as sonar, other transducers (devices that 
convert energy from one form to another--in this case, into sound 
waves), incidental sources of broadband sound produced as a byproduct 
of vessel movement, aircraft transits, and use of weapons or other 
deployed objects. Explosives also produce broadband sound but are 
characterized separately from other acoustic sources due to their 
unique hazardous characteristics. Characteristics of each of these 
sound sources are described in the following sections.
    In order to better organize and facilitate the analysis of 
approximately 300 sources of underwater sound used by the Navy, 
including sonar and other transducers and explosives, a series of 
source classifications, or source bins, were developed. The source 
classification bins do not include the broadband noise produced 
incidental to vessel movement, aircraft transits, and weapons firing. 
Noise produced from vessel movement, aircraft transits, and use of 
weapons or other deployed objects is not carried forward because those 
activities were found to have de minimis or no impacts, as described 
above.
    The use of source classification bins provides the following 
benefits:
     Provides the ability for new sensors or munitions to be 
covered under existing authorizations, as long as those sources fall 
within the parameters of a ``bin;''
     Improves efficiency of source utilization data collection 
and reporting requirements anticipated under the MMPA authorizations;
     Ensures a precautionary approach to all impact estimates, 
as all sources within a given class are modeled as the most impactful 
source (highest source level, longest duty cycle, or largest net 
explosive weight) within that bin;
     Allows analyses to be conducted in a more efficient 
manner, without any compromise of analytical results; and
     Provides a framework to support the reallocation of source 
usage (hours/explosives) between different source bins, as long as the 
total numbers of takes remain within the overall analyzed and 
authorized limits. This flexibility is required to support evolving 
Navy training and testing requirements, which are linked to real world 
events.
Sonar and Other Transducers
    Active sonar and other transducers emit non-impulsive sound waves 
into the water to detect objects, navigate safely, and communicate. 
Passive sonars differ from active sound sources in that they do not 
emit acoustic signals; rather, they only receive acoustic information 
about the environment, or listen. In this proposed rule, the terms 
sonar and other transducers will be used to indicate active sound 
sources unless otherwise specified.
    The Navy employs a variety of sonars and other transducers to 
obtain and transmit information about the undersea environment. Some 
examples are mid-frequency hull-mounted sonars used to find and track 
enemy submarines; high-frequency small object detection sonars used to 
detect mines; high-frequency underwater modems used to transfer data 
over short ranges; and extremely high-frequency (greater than 200 
kilohertz (kHz)) doppler sonars used for navigation, like those used on 
commercial and private vessels. The characteristics of these sonars and 
other transducers, such as source level, beam width, directivity, and 
frequency, depend on the purpose of the source. Higher frequencies can 
carry more information or provide more information about objects off 
which they reflect, but attenuate more rapidly. Lower frequencies 
attenuate less rapidly, so they may detect objects over a longer 
distance, but with less detail.
    Propagation of sound produced underwater is highly dependent on 
environmental characteristics such as bathymetry, bottom type, water 
depth, temperature, and salinity. The sound received at a particular 
location will be different than near the source due to the interaction 
of many factors, including propagation loss; how the sound is 
reflected, refracted, or scattered; the potential for reverberation; 
and interference due to multi-path propagation. In addition, absorption 
greatly affects the distance over which higher-frequency sounds 
propagate. The effects of these factors are explained in Appendix B 
(Acoustic and Explosive Concepts) of the 2020 GOA DSEIS/OEIS. Because 
of the complexity of analyzing sound propagation in the ocean 
environment, the Navy relies on acoustic models in its environmental 
analyses that consider sound source characteristics and varying ocean 
conditions across the TMAA. As noted above, the Navy does not propose 
to use sonar and other transducers within the WMA.
    The sound sources and platforms typically used in naval activities 
analyzed in the Navy's rulemaking/LOA application are described in 
Appendix A (Navy Activities Descriptions) of the 2020 GOA DSEIS/OEIS. 
Sonars and other transducers used to obtain and transmit information 
underwater during Navy training activities generally fall into several 
categories of use described below.

Anti-Submarine Warfare

    Sonar used during anti-submarine warfare would impart the greatest 
amount of acoustic energy of any category of sonar and other 
transducers analyzed in this proposed rule. Types of sonars used to 
detect potential enemy vessels include hull-mounted, towed, line array, 
sonobuoy, and helicopter dipping sonars. In addition, acoustic targets 
and decoys (countermeasures) may be deployed to emulate the sound 
signatures of vessels or repeat received signals.
    Most anti-submarine warfare sonars are mid-frequency (1-10 kHz) 
because mid-frequency sound balances sufficient resolution to identify 
targets with distance over which threats can be identified. However, 
some sources may use higher or lower frequencies. Duty cycles can vary 
widely, from rarely used to continuously active. For example, anti-
submarine warfare sonars can be wide angle in a search mode or highly 
directional in a track mode.
    Most anti-submarine warfare activities involving submarines or 
submarine targets would occur in waters greater than 600 feet (ft; 183 
m) deep due to safety concerns about running aground at shallower 
depths.

Navigation and Safety

    Similar to commercial and private vessels, Navy vessels employ 
navigational acoustic devices, including speed logs, Doppler sonars for 
ship positioning, and fathometers. These may be in use at any time for 
safe vessel operation. These sources are typically highly directional 
to obtain specific navigational data.

Communication

    Sound sources used to transmit data (such as underwater modems), 
provide location (pingers), or send a single brief release signal to 
bottom-mounted devices (acoustic release) may be used throughout the 
TMAA. These sources typically have low duty cycles and are usually only 
used when it is desirable to send a detectable acoustic message.

Classification of Sonar and Other Transducers

    Sonars and other transducers are grouped into classes that share an

[[Page 49662]]

attribute, such as frequency range or purpose. As detailed below, 
classes are further sorted by bins based on the frequency or bandwidth; 
source level; and, when warranted, the application for which the source 
would be used. Unless stated otherwise, a reference distance of 1 meter 
(m) is used for sonar and other transducers.
     Frequency of the non-impulsive acoustic source:
    [cir] Low-frequency sources operate below 1 kHz;
    [cir] Mid-frequency sources operate at and above 1 kHz, up to and 
including 10 kHz;
    [cir] High-frequency sources operate above 10 kHz, up to and 
including 100 kHz; and
    [cir] Very-high-frequency sources operate above 100 kHz but below 
200 kHz.
     Sound pressure level:
    [cir] Greater than 160 decibels (dB) referenced to 1 micropascal 
(re: 1 [micro]Pa), but less than 180 dB re: 1 [micro]Pa;
    [cir] Equal to 180 dB re: 1 [micro]Pa and up to and including 200 
dB re: 1 [micro]Pa; and
    [cir] Greater than 200 dB re: 1 [micro]Pa.
     Application for which the source would be used:
    [cir] Sources with similar functions that have similar 
characteristics, such as pulse length (duration of each pulse), beam 
pattern, and duty cycle.
    The bins used for classifying active sonars and transducers that 
are quantitatively analyzed in the TMAA are shown in Table 1. While 
general parameters or source characteristics are shown in the table, 
actual source parameters are classified.

                    Table 1--Sonar and Other Transducers Quantitatively Analyzed in the TMAA
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                                         For annual training activities
-----------------------------------------------------------------------------------------------------------------
    Source class category            Bin          Description         Units           Annual       7-Year total
----------------------------------------------------------------------------------------------------------------
Mid-Frequency (MF) Tactical               MF1   Hull-mounted                  H              271           1,897
 and non-tactical sources                        surface ship
 that produce signals from 1                     sonars (e.g.,
 to 10 kHz.                                      AN/SQS-53C and
                                                 AN/SQS-60).
                                          MF3   Hull-mounted                  H               25             175
                                                 submarine
                                                 sonars (e.g.,
                                                 AN/BQQ-10).
                                          MF4   Helicopter-                   H               27             189
                                                 deployed
                                                 dipping sonars
                                                 (e.g., AN/AQS-
                                                 22).
                                          MF5   Active acoustic               I              126             882
                                                 sonobuoys
                                                 (e.g., DICASS).
                                          MF6   Active                        I               14              98
                                                 underwater
                                                 sound signal
                                                 devices (e.g.,
                                                 MK 84).
                                         MF11   Hull-mounted                  H               42             294
                                                 surface ship
                                                 sonars with an
                                                 active duty
                                                 cycle greater
                                                 than 80%.
                                         MF12   Towed array                   H               14              98
                                                 surface ship
                                                 sonars with an
                                                 active duty
                                                 cycle greater
                                                 than 80%.
High-Frequency (HF) Tactical              HF1   Hull-mounted                  H               12              84
 and non-tactical sources                        submarine
 that produce signals greater                    sonars (e.g.,
 than 10 kHz but less than                       AN/BQQ-10).
 100 kHz.
Anti-Submarine Warfare (ASW)             ASW1   MF systems                    H               14              98
 Tactical sources used during                    operating
 ASW training activities.                        above 200 dB.
                                         ASW2   MF Multistatic                H               42             294
                                                 Active
                                                 Coherent
                                                 sonobuoy
                                                 (e.g., AN/SSQ-
                                                 125).
                                         ASW3   MF towed active               H              273           1,911
                                                 acoustic
                                                 countermeasure
                                                 systems (e.g.,
                                                 AN/SLQ-25).
                                         ASW4   MF expendable                 I                7              49
                                                 active
                                                 acoustic
                                                 device
                                                 countermeasure
                                                 s (e.g., MK3).
----------------------------------------------------------------------------------------------------------------
Notes: H = hours, I = count (e.g., number of individual pings or individual sonobuoys), DICASS = Directional
  Command Activated Sonobuoy System.

Explosive Stressors

    The near-instantaneous rise from ambient to an extremely high peak 
pressure is what makes an explosive shock wave potentially damaging. 
Farther from an explosive, the peak pressures decay and the explosive 
waves propagate as an impulsive, broadband sound. Several parameters 
influence the effect of an explosive: the weight of the explosive in 
the warhead, the type of explosive material, the boundaries and 
characteristics of the propagation medium, and the detonation depth in 
water. The net explosive weight, which is the explosive power of a 
charge expressed as the equivalent weight of trinitrotoluene (TNT), 
accounts for the first two parameters. The effects of these factors are 
explained in Appendix B (Acoustic and Explosive Concepts) of the 2020 
GOA DSEIS/OEIS.
Explosive Use
    Explosive detonations during training activities are from the use 
of explosive bombs, and naval gun shells; however, no in-water 
explosive detonations are included as part of the training activities. 
For purposes of the analysis in this proposed rule, detonations 
occurring in air at a height of 33 ft (10 m) or less above the water 
surface, and detonations occurring directly on the water surface, were 
modeled to detonate at a depth of 0.3 ft (0.1 m) below the water 
surface since there is currently no other identified methodology for 
modeling potential effects to marine

[[Page 49663]]

mammals that are underwater as a result of detonations occurring in-air 
at or above the surface of the ocean (within 10 m above the surface). 
This conservative approach over-estimates the potential underwater 
impacts due to low-altitude and surface explosives by assuming that all 
explosive energy is released and remains under the water surface.
    Explosive stressors resulting from the detonation of some 
munitions, such as missiles and gun rounds used in air-air and surface-
air scenarios, occur at high altitude. The resulting sound energy from 
those detonations in air would not impact marine mammals. The explosive 
energy released by detonations in air has been well studied, and basic 
methods are available to estimate the explosive energy exposure with 
distance from the detonation (e.g., U.S. Department of the Navy 
(1975)). In air, the propagation of impulsive noise from an explosion 
is highly influenced by atmospheric conditions, including temperature 
and wind. While basic estimation methods do not consider the unique 
environmental conditions that may be present on a given day, they do 
allow for approximation of explosive energy propagation under neutral 
atmospheric conditions. Explosions that occur during Air Warfare would 
typically be at a sufficient altitude that a large portion of the sound 
refracts upward due to cooling temperatures with increased altitude. 
Based on an understanding of the explosive energy released by 
detonations in air, detonations occurring in air at altitudes greater 
than 10 m above the surface of the ocean are not likely to result in 
acoustic impacts on marine mammals; therefore, these types of explosive 
activities will not be discussed further in this document. (Note that 
most of these in-air detonations would occur at altitudes substantially 
greater than 10 m above the surface of the ocean, as described in 
further detail in section 3.0.4.2.2 (Explosions in Air) of the 2020 GOA 
DSEIS/OEIS.) Activities such as air-surface bombing or surface-surface 
gunnery scenarios may involve the use of explosive munitions that 
detonate upon impact with targets at or above the water surface (within 
10 m above the surface). For these activities, acoustic effects 
modeling was undertaken as described below.
    In order to organize and facilitate the analysis of explosives, 
explosive classification bins were developed. The use of explosive 
classification bins provides the same benefits as described for 
acoustic source classification bins in the Acoustic Stressors section, 
above.
    The explosive bin types and the number of explosives detonating at 
or above the water surface in the TMAA are shown in Table 2.

   Table 2--Explosive Sources Quantitatively Analyzed That Detonate At or Above the Water Surface in the TMAA
----------------------------------------------------------------------------------------------------------------
                                                                                           Number of explosives
   Explosives  (source class and net explosive weight (NEW))      Number of explosives      with the specified
                            (lb.) *                                with the specified       activity  (7-year
                                                                  activity  (annually)            total)
----------------------------------------------------------------------------------------------------------------
E5 (>5-10 lb. NEW)............................................                       56                      392
E9 (>100-250 lb. NEW).........................................                       64                      448
E10 (>250-500 lb. NEW)........................................                        6                       42
E12 (>650-1,000 lb. NEW)......................................                        2                       14
----------------------------------------------------------------------------------------------------------------
* All of the E5, E9, E10, and E12 explosives would occur in-air, at or above the surface of the water, and would
  also occur offshore away from the continental shelf and slope beyond the 4,000-meter isobath.

    Propagation of explosive pressure waves in water is highly 
dependent on environmental characteristics such as bathymetry, bottom 
type, water depth, temperature, and salinity, which affect how the 
pressure waves are reflected, refracted, or scattered; the potential 
for reverberation; and interference due to multi-path propagation. In 
addition, absorption greatly affects the distance over which higher-
frequency components of explosive broadband noise can propagate. 
Appendix B (Acoustic and Explosive Concepts) of the 2020 GOA DSEIS/OEIS 
explains the characteristics of explosive detonations and how the above 
factors affect the propagation of explosive energy in the water. 
Because of the complexity of analyzing sound propagation in the ocean 
environment, the Navy relies on acoustic models in its environmental 
analyses that consider sound source characteristics and varying ocean 
conditions across the TMAA.
    For in-air explosives detonating at or above the water surface, the 
model estimating acoustic impacts assumes that all acoustic energy from 
the detonation is underwater with no loss of sound or energy into the 
air. Important considerations must be factored into the analysis of 
results with these modeling assumptions, given that the peak pressure 
and sound from a detonation in air significantly decreases across the 
air-water interface as it is partially reflected by the water's surface 
and partially transmitted underwater, as detailed in the following 
paragraphs.
    Detonation of an explosive in air creates a supersonic high 
pressure shock wave that expands outward from the point of detonation 
(Kinney and Graham, 1985; Swisdak, 1975). The near-instantaneous rise 
from ambient to an extremely high peak pressure is what makes the 
explosive shock wave potentially injurious to an animal experiencing 
the rapid pressure change (U.S. Department of the Navy, 2017a). As the 
shock wave-front travels away from the point of detonation, it slows 
and begins to behave as an acoustic wave-front travelling at the speed 
of sound. Whereas a shock wave from a detonation in-air has an abrupt 
peak pressure, that same pressure disturbance when transmitted through 
the water surface results in an underwater pressure wave that begins 
and ends more gradually compared with the in-air shock wave, and 
diminishes with increasing depth and distance from the source (Bolghasi 
et al., 2017; Chapman and Godin, 2004; Cheng and Edwards, 2003; Moody, 
2006; Richardson et al., 1995; Sawyers, 1968; Sohn et al., 2000; 
Swisdak, 1975; Waters and Glass, 1970; Woods et al., 2015). The 
propagation of the shock wave in-air and then transitioning underwater 
is very different from a detonation occurring deep underwater where 
there is little interaction with the surface. In the case of an 
underwater detonation occurring just below the surface, a portion of 
the energy from the detonation would be released into the air (referred 
to as surface blow off), and at greater depths a pulsating, air-filled 
cavitation bubble would form, collapse, and reform around the 
detonation point (Urick, 1983). The Navy's acoustic effects model for 
analyzing underwater impacts on marine species does not account for the 
loss of energy due to surface blow-

[[Page 49664]]

off or cavitation at depth. Both of these phenomena would diminish the 
magnitude of the acoustic energy received by an animal under real-world 
conditions (U.S. Department of the Navy, 2018b).
    To more completely analyze the results predicted by the Navy's 
acoustic effects model from detonations occurring in-air above the 
ocean surface, it is necessary to consider the transfer of energy 
across the air-water interface. Much of the scientific literature on 
the transferal of shock wave impulse across the air-water interface has 
focused on energy from sonic booms created by fast moving aircraft 
flying at low altitudes above the ocean (Chapman and Godin, 2004; Cheng 
and Edwards, 2003; Moody, 2006; Sawyers, 1968; Waters and Glass, 1970). 
The shock wave created by a sonic boom is similar to the propagation of 
a pressure wave generated by an explosion (although having a 
significantly slower rise in peak pressure) and investigations of sonic 
booms are somewhat informative. Waters and Glass (1970) were also 
investigating sonic booms, but their methodology involved actual in-air 
detonations. In those experiments, they detonated blasting caps 
elevated 30 ft (9 m) above the surface in a flooded quarry and measured 
the resulting pressure at and below the surface to determine the 
penetration of the shock wave across the air-water interface. 
Microphones above the water surface recorded the peak pressure in-air, 
and hydrophones at various shallow depths underwater recorded the 
unreflected remainder of the pressure wave after transition across the 
air-water interface. The peak pressure measurements were compared and 
the results supported the theoretical expectations for the penetration 
of a pressure wave from air into water, including the predicted 
exponential decay of energy with distance from the source underwater. 
In effect, the air-water interface acted as a low-pass filter 
eliminating the high-frequency components of the shock wave. At 
incident angles greater than 14 degrees perpendicular to the surface, 
most of the shock wave from the detonation was reflected off the water 
surface, which is consistent with results from similar research (Cheng 
and Edwards, 2003; Moody, 2006; Yagla and Stiegler, 2003). Given that 
marine mammals spend, on average, up to 90 percent of their time 
underwater (Costa, 1993; Costa and Block, 2009), and the shock wave 
from a detonation is only a few milliseconds in duration, marine 
mammals are unlikely to be exposed in-air when surfaced.

Vessel Strike

    NMFS also considered the chance that a vessel utilized in training 
activities could strike a marine mammal in the GOA Study Area, 
including both the TMAA and WMA portions of the Study Area. Vessel 
strikes have the potential to result in incidental take from serious 
injury and/or mortality. Vessel strikes are not specific to any 
particular training activity, but rather are a limited, sporadic, and 
incidental result of Navy vessel movement within a study area. Vessel 
strikes from commercial, recreational, and military vessels are known 
to seriously injure and occasionally kill cetaceans (Abramson et al., 
2011; Berman-Kowalewski et al., 2010; Calambokidis, 2012; Douglas et 
al., 2008; Laggner, 2009; Lammers et al., 2003; Van der Hoop et al., 
2012; Van der Hoop et al., 2013), although reviews of the literature on 
ship strikes mainly involve collisions between commercial vessels and 
whales (Jensen and Silber, 2003; Laist et al., 2001). Vessel speed, 
size, and mass are all important factors in determining both the 
potential likelihood and impacts of a vessel strike to marine mammals 
(Conn and Silber, 2013; Gende et al., 2011; Silber et al., 2010; 
Vanderlaan and Taggart, 2007; Wiley et al., 2016). For large vessels, 
speed and angle of approach can influence the severity of a strike.
    Navy vessels transit at speeds that are optimal for fuel 
conservation and to meet training requirements. Vessels used as part of 
the proposed specified activities include ships, submarines, unmanned 
vessels, and boats ranging in size from small, 22 ft (7 m) rigid hull 
inflatable boats to aircraft carriers with lengths up to 1,092 ft (333 
m). The average speed of large Navy ships ranges between 10 and 15 
knots (kn; 19-28 km/hr), and submarines generally operate at speeds in 
the range of 8 to 13 kn (15 to 24 km/hr), while a few specialized 
vessels can travel at faster speeds. Small craft (for purposes of this 
analysis, less than 18 m in length) have much more variable speeds (0 
to 50+ kn (0 to 93+ km/hr)), dependent on the activity), but generally 
range from 10 to 14 kn (19-26 km/hr). From unpublished Navy data, 
average median speed for large Navy ships in the other Navy ranges from 
2011-2015 varied from 5 to 10 kn (9 to 19 km/hr) with variations by 
ship class and location (i.e., slower speeds close to the coast). 
Similar patterns would occur in the GOA Study Area. A full description 
of Navy vessels that are used during training activities can be found 
in Section 1.2.1 and Section 2.4.2.1 of the 2011 GOA FEIS/OEIS.
    While these speeds are representative of most events, some vessels 
need to temporarily operate outside of these parameters for certain 
times or during certain activities. For example, to produce the 
required relative wind speed over the flight deck, an aircraft carrier 
engaged in flight operations must adjust its speed through the water 
accordingly. Also, there are other instances, such as launch and 
recovery of a small rigid hull inflatable boat; vessel boarding, 
search, and seizure training events; or retrieval of a target when 
vessels would be dead in the water or moving slowly ahead to maintain 
steerage.
    Large Navy vessels (greater than 18 m in length) within the 
offshore areas of range complexes operate differently from commercial 
vessels in ways that may reduce potential whale collisions. Surface 
ships operated by or for the Navy have multiple personnel assigned to 
stand watch at all times when a ship or surfaced submarine is moving 
through the water (underway). A primary duty of personnel standing 
watch on surface ships is to detect and report all objects and 
disturbances sighted in the water that may indicate a threat to the 
vessel and its crew, such as debris, a periscope, surfaced submarine, 
or surface disturbance. Per vessel safety requirements, personnel 
standing watch also report any marine mammals sighted in the path of 
the vessel as a standard collision avoidance procedure. All vessels 
proceed at a safe speed so they can take proper and effective action to 
avoid a collision with any sighted object or disturbance, and can be 
stopped within a distance appropriate to the prevailing circumstances 
and conditions.

Detailed Description of Proposed Activities

Proposed Training Activities

    The Navy proposes to conduct a single carrier strike group (CSG) 
exercise which would last for a maximum of 21 consecutive days in a 
year. The CSG exercise is comprised of several individual training 
activities. Table 3 lists and describes those individual activities 
that may result in takes of marine mammals. The events listed would 
occur intermittently during the 21 days and could be simultaneous and 
in the same general area within the TMAA or could be independent and 
spatially separate from other ongoing activities. The table is 
organized according to primary mission areas and includes the activity 
name, associated stressor(s), description and duration of the activity, 
sound source bin, the areas

[[Page 49665]]

where the activities are conducted in the GOA Study Area, the maximum 
number of events per year in the 21-day period, and the maximum number 
of events over 7 years. Not all sound sources are used with each 
activity. The ``Annual # of Events'' column indicates the maximum 
number of times that activity could occur during any single year. The 
``7-Year # of Events'' is the maximum number of times an activity would 
occur over the 7-year period of the proposed regulations if the 
training occurred each year and at the maximum levels requested. The 
events listed would occur intermittently during the exercise over a 
maximum of 21 days. The maximum number of activities may not occur in 
some years, and historically, training has occurred only every other 
year. However, to conduct a conservative analysis, NMFS analyzed the 
maximum times these activities could occur over one year and 7 years. 
The 2020 GOA DSEIS/OEIS includes more detailed activity descriptions. 
(Note the Navy proposes no low-frequency active sonar (LFAS) use for 
the activities in this rulemaking.)

           Table 3--Proposed Training Activities Analyzed for the 7-Year Period in the GOA Study Area
----------------------------------------------------------------------------------------------------------------
                                                                                    Annual # of     7-year # of
      Stressor  category           Activity       Description       Source bin        events          events
----------------------------------------------------------------------------------------------------------------
                                                 Surface Warfare
----------------------------------------------------------------------------------------------------------------
Explosive....................  Gunnery          Surface ship     E5.............               6              42
                                Exercise,        crews fire
                                Surface-to-      inert small-
                                Surface (GUNEX-  caliber, inert
                                S-S).            medium-
                                                 caliber, or
                                                 large-caliber
                                                 explosive
                                                 rounds at
                                                 surface
                                                 targets.
Explosive....................  Bombing          Fixed-wing       E9, E10, E12...              18             126
                                Exercise (Air-   aircraft
                                to-Surface)      conduct
                                (BOMBEX [A-S]).  bombing
                                                 exercises
                                                 against
                                                 stationary
                                                 floating
                                                 targets, towed
                                                 targets, or
                                                 maneuvering
                                                 targets.
----------------------------------------------------------------------------------------------------------------
                                          Anti-Submarine Warfare (ASW)
----------------------------------------------------------------------------------------------------------------
Acoustic.....................  Tracking         Helicopter       MF4, MF5, MF6..              22             154
                                Exercise--Heli   crews search
                                copter           for, track,
                                (TRACKEX--Helo   and detect
                                ).               submarines.
Acoustic.....................  Tracking         Maritime patrol  MF5, MF6, ASW2.              13              91
                                Exercise--Mari   aircraft crews
                                time Patrol      search for,
                                Aircraft         track, and
                                (TRACKEX--MPA).  detect
                                                 submarines.
Acoustic.....................  Tracking         Surface ship     ASW1, ASW3,                   2              14
                                Exercise--Ship   crews search     MF1, MF11,
                                (TRACKEX--Ship   for, track,      MF12.
                                ).               and detect
                                                 submarines.
Acoustic.....................  Tracking         Submarine crews  ASW4, HF1, MF3.               2              14
                                Exercise--Subm   search for,
                                arine            track, and
                                (TRACKEX--Sub).  detect
                                                 submarines.
----------------------------------------------------------------------------------------------------------------
Notes: S-S = Surface to Surface, A-S = Air to Surface.

Standard Operating Procedures

    For training to be effective, personnel must be able to safely use 
their sensors and weapon systems as they are intended to be used in 
military missions and combat operations and to their optimum 
capabilities. Standard operating procedures applicable to training have 
been developed through years of experience, and their primary purpose 
is to provide for safety (including public health and safety) and 
mission success. Because standard operating procedures are essential to 
safety and mission success, the Navy considers them to be part of the 
proposed specified activities, and has included them in the analysis. 
In many cases, there are benefits to natural and cultural resources 
resulting from standard operating procedures. Standard operating 
procedures that are recognized as having a potential benefit to marine 
mammals during training activities are noted below and discussed in 
more detail within the 2020 GOA DSEIS/OEIS.
     Vessel Safety;
     Weapons Firing Procedures;
     Target Deployment and Retrieval Safety; and
     Towed In-Water Device Procedures.
    Standard operating procedures (which are implemented regardless of 
their secondary benefits) are different from mitigation measures (which 
are designed entirely for the purpose of avoiding or reducing impacts). 
Information on mitigation measures is provided in the Proposed 
Mitigation Measures section below. Additional information on standard 
operating procedures is presented in Section 2.3.2 (Standard Operating 
Procedures) in the 2020 GOA DSEIS/OEIS.

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

    Marine mammal species and their associated stocks that have the 
potential to occur in the GOA Study Area are presented in Table 4 along 
with each stock's ESA and MMPA statuses, abundance estimate and 
associated coefficient of variation value, minimum abundance estimate, 
and expected occurrence in the GOA Study Area. The Navy requested 
authorization to take individuals of 16 marine mammal species by Level 
A harassment and Level B harassment, and NMFS has conservatively 
analyzed and proposes to authorize incidental take of two additional 
species. The Navy does not request authorization for any serious 
injuries or mortalities of marine mammals, and NMFS agrees that serious 
injury and mortality is unlikely to occur from the Navy's activities. 
NMFS recently designated critical habitat under the Endangered Species 
Act (ESA) for humpback whales in the TMAA portion of the GOA Study 
Area, and this designated critical habitat is considered below (86 FR 
21082; April 21, 2021). The WMA portion of the GOA Study Area does not 
overlap ESA-designated critical habitat for humpback whales or any 
other species.
    Information on the status, distribution, abundance, population 
trends, habitat, and ecology of marine mammals in the GOA Study Area 
may be found in Chapter 4 of the Navy's rulemaking/LOA application. 
NMFS has reviewed this information and found it

[[Page 49666]]

to be accurate and complete. Additional information on the general 
biology and ecology of marine mammals is included in the 2020 GOA 
DSEIS/OEIS. Table 4 incorporates the best available science, including 
data from the 2020 U.S. Pacific and the Alaska Marine Mammal Stock 
Assessment Reports (SARs; Carretta et al., 2021; Muto et al., 2021), 
2021 draft U.S. Pacific and Alaska Marine Mammal SARs, as well as 
monitoring data from the Navy's marine mammal research efforts.
    To better define marine mammal occurrence in the TMAA, the portion 
of the GOA Study Area where take of marine mammals is anticipated to 
occur, four regions within the TMAA were defined (and are depicted in 
Figure 3-1 of the Navy's rulemaking/LOA application), consistent with 
the survey strata used by Rone et al. (2017) during the most recent 
marine mammal surveys in the TMAA. The four regions are: inshore, 
slope, seamount, and offshore.

Species Not Included in the Analysis

    There has been no change in the species unlikely to be present in 
the GOA Study Area since the last MMPA rulemaking process (82 FR 19530; 
April 27, 2017). The species carried forward for analysis are those 
likely to be found in the GOA Study Area based on the most recent data 
available and do not include species that may have once inhabited or 
transited the area but have not been sighted in recent years (e.g., 
species which were extirpated from factors such as 19th and 20th 
century commercial exploitation). Several species and stocks that may 
be present in the northeast Pacific Ocean generally have an extremely 
low probability of presence in the GOA Study Area. These species and 
stocks are considered extralimital (may be sightings, acoustic 
detections, or stranding records, but the GOA Study Area is outside the 
species' range of normal occurrence) or rare (occur in the GOA Study 
Area sporadically, but sightings are rare). These species and stocks 
include the Eastern North Pacific Northern Resident and the West Coast 
Transient stocks of killer whale (Orcinus orca), beluga whale 
(Delphinapterus leucas), false killer whale (Pseudorca crassidens), 
short-finned pilot whale (Globicephala macrorhynchus), northern right 
whale dolphin (Lissodelphis borealis), and Risso's dolphin (Grampus 
griseus).
    The Eastern North Pacific Northern Resident and the West Coast 
Transient stocks of killer whale are considered extralimital in the GOA 
Study Area. Given the paucity of any beluga whale sightings in the GOA 
(Laidre et al. 2000), the occurrence of this species within the GOA 
Study Area is considered extralimital. The GOA Study Area is also 
outside of the normal range of the false killer whale's distribution in 
the Pacific Ocean, and despite rare stranding or sighting reports, the 
GOA Study Area is outside of the normal range of the short-finned pilot 
whale as well. There are two sighting records of northern right whale 
dolphins in the Gulf of Alaska, but these are considered extremely rare 
(U.S. Department of the Navy 2006; NOAA 2012) and extralimital in the 
GOA Study Area. There are a few records of Risso's dolphins near the 
GOA Study Area; however, their occurrence within the GOA Study Area is 
rare, and therefore Risso's dolphin is considered extralimital. NMFS 
agrees with the Navy's assessment that these species are unlikely to 
occur in the GOA Study Area and they are not discussed further.
    One species of marine mammal, the Northern sea otter, occurs in the 
Gulf of Alaska but is managed by the U.S. Fish and Wildlife Service and 
is not considered further in this document.

                                               Table 4--Marine Mammal Occurrence Within the GOA Study Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                              Stock abundance
                                                                             ESA  status,   (CV, Nmin, year of
           Common name              Scientific name           Stock          MMPA status,       most recent        PBR     Annual M/   Occurrence in GOA
                                                                            strategic  (Y/   abundance survey)               SI \3\     study area \4\
                                                                                N) \1\              \2\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Order Cetacea--Suborder Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Balaenidae (right
 whales):
    North Pacific right whale...  Eubalaena japonica.  Eastern North        E, D, Y         31 (0.226, 26,       \5\ 0.05          0  Rare.
                                                        Pacific.                             2008).
Family Balaenopteridae
 (rorquals):
    Humpback whale..............  Megaptera            Central North        -, -, Y         10,103 (0.3,               83         26  Seasonal; highest
                                   novaeangliae.        Pacific \6\.                         7,891, 2006).                             likelihood June
                                                                                                                                       to September.
                                                       California, Oregon,  -, -, Y         4,973 (0.05,             28.7     >=48.6  Seasonal; highest
                                                        and Washington \6\.                  4,776, 2018).                             likelihood June
                                                                                                                                       to September.
                                                       Western North        E, D, Y         1,107 (0.3, 865,            3        2.8  Seasonal; highest
                                                        Pacific.                             2006).                                    likelihood June
                                                                                                                                       to September.
    Blue whale..................  Balaenoptera         Eastern North        E, D, Y         1,898 (0.085,             4.1     >=19.4  Seasonal; highest
                                   musculus.            Pacific.                             1,767, 2018).                             likelihood June
                                                                                                                                       to December.
                                                       Central North        E, D, Y         133 (1.09, 63,            0.1          0  Seasonal; highest
                                                        Pacific.                             2010).                                    likelihood June
                                                                                                                                       to December.
    Fin whale...................  Balaenoptera         Northeast Pacific..  E, D, Y         3,168 (0.26,              5.1        0.6  Likely.
                                   physalus.                                                 2,554, 2013) \7\.
    Sei whale...................  Balaenoptera         Eastern North        E, D, Y         519 (0.4, 374,           0.75      >=0.2  Rare.
                                   borealis.            Pacific \8\.                         2014).
    Minke whale.................  Balaenoptera         Alaska.............  -, -, N         UNK...............        UND          0  Likely.
                                   acutorostrata.
Family Eschrichtiidae (gray
 whale):
    Gray whale..................  Eschrichtius         Eastern North        -, -, N         26,960 (0.05,             801        131  Likely: Highest
                                   robustus.            Pacific.                             25,849, 2016).                            numbers during
                                                                                                                                       seasonal
                                                                                                                                       migrations (fall,
                                                                                                                                       winter, spring).

[[Page 49667]]

 
                                                       Western North        E, D, Y         290 (N/A, 271,           0.12        UNK  Rare: Individuals
                                                        Pacific.                             2016).                                    migrate through
                                                                                                                                       GOA.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   Order Cetacea--Suborder Odontoceti (toothed whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Physeteridae (sperm
 whale):
    Sperm whale.................  Physeter             North Pacific......  E, D, Y         345 (0.43, 244,           UND        3.5  Likely; More
                                   macrocephalus.                                            2015) \9\.                                likely in waters
                                                                                                                                       >1,000 m depth,
                                                                                                                                       most often >2,000
                                                                                                                                       m.
Family Delphinidae (dolphins):
    Killer whale................  Orcinus orca.......  Eastern North        -, -, N         \10\ 2,347 (N/A,           24          1  Likely.
                                                        Pacific Alaska                       2,347, 2012).
                                                        Resident.
                                                       Eastern North        -, -, N         300 (0.1, 276,            2.8          0  Likely.
                                                        Pacific Offshore.                    2012).
                                                       AT1 Transient......  -, D, Y         \10\ 7 (N/A, 7,          0.01          0  Rare; more likely
                                                                                             2018).                                    inside Prince
                                                                                                                                       William Sound and
                                                                                                                                       Kenai Fjords.
                                                       Eastern North        -, -, N         \10\ 587 (N/A,           5.87        0.8  Likely.
                                                        Pacific GOA,                         587, 2012).
                                                        Aleutian Island,
                                                        and Bering Sea
                                                        Transient.
    Pacific white-sided dolphin.  Lagenorhynchus       North Pacific......  -, -, N         26,880 (N/A, N/A,         UND          0  Likely.
                                   obliquidens.                                              1990).
Family Phocoenidae (porpoises):
    Harbor porpoise.............  Phocoena phocoena..  GOA................  -, -, Y         31,046 (0.21, N/A,        UND         72  Rare; Inshore and
                                                                                             1998).                                    Slope Regions, if
                                                                                                                                       present.
                                                       Southeast Alaska...  -, -, Y         1,354 (0.12,               12         34  Rare.
                                                                                             1,224, 2012).
    Dall's porpoise.............  Phocoenoides dalli.  Alaska.............  -, -, N         83,400 (0.097,            UND         37  Likely.
                                                                                             3,110, 2015).
Family Ziphiidae (beaked
 whales):
    Cuvier's beaked whale.......  Ziphius cavirostris  Alaska.............  -, -, N         UNK...............        UND          0  Likely.
    Baird's beaked whale........  Berardius bairdii..  Alaska.............  -, -, N         UNK...............        UND          0  Likely.
    Stejneger's beaked whale....  Mesoplodon           Alaska.............  -, -, N         UNK...............        UND          0  Likely.
                                   stejnegeri.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        Order Carnivora--Suborder Pinnipedia \8\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otarieidae (fur seals and
 sea lions):
    Steller sea lion............  Eumetopias jubatus.  Eastern U.S........  -, -, N         \11\ 43,201 (N/A,       2,592        112  Rare.
                                                                                             43,201, 2017).
                                                       Western U.S........  E, D, Y         \11\ 52,932 (N/A,         318        254  Likely; Inshore
                                                                                             52,932, 2013).                            region.
    California sea lion.........  Zalophus             U.S................  -, -, N         257,606 (N/A,          14,011       >320  Rare (highest
                                   californianus.                                            233,515, 2014).                           likelihood April
                                                                                                                                       and May).
    Northern fur seal...........  Callorhinus ursinus  Eastern Pacific....  -, D, Y         626,618 (0.2,          11,403        373  Likely.
                                                                                             530,376, 2019).
                                                       California.........  -, D, N         14,050 (N/A,              451        1.8  Rare.
                                                                                             7,524, 2013).
Family Phocidae (true seals):
    Northern elephant seal......  Mirounga             California Breeding  -, -, N         187,386 (N/A,           5,122        5.3  Seasonal (highest
                                   angustirostris.                                           85,369, 2013).                            likelihood July-
                                                                                                                                       September).
    Harbor seal.................  Phoca vitulina.....  N Kodiak...........  -, -, N         8,677 (N/A, 7,609,        228         38  Likely; Inshore
                                                                                             2017).                                    region.
                                                       S Kodiak...........  -, -, N         26,448 (N/A,              939        127  Likely; Inshore
                                                                                             22,351, 2017).                            region.
                                                       Prince William       -, -, N         44,756 (N/A,            1,253        413  Likely; Inshore
                                                        Sound.                               41,776, 2015).                            region.
                                                       Cook Inlet/Shelikof  -, -, N         28,411 (N/A,              807        107  Likely; Inshore
                                                                                             26,907, 2018).                            region.
    Ribbon seal.................  Histriophoca         Unidentified.......  -, -, N         184,697 (N/A,           9,785        163  Rare.
                                   fasciata.                                                 163,086, 2013).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes: CV = coefficient of variation, ESA = Endangered Species Act, GOA = Gulf of Alaska, m = meter(s), MMPA = Marine Mammal Protection Act, N/A = not
  available, U.S. = United States, M/SI = mortality and serious injury, UNK = unknown, UND = undetermined.

[[Page 49668]]

 
\1\ 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 potential biological removal (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.
\2\ The stocks and stock abundance number are as provided in Carretta et al., 2021 and Muto et al., 2021. Nmin is the minimum estimate of stock
  abundance. In some cases, CV is not applicable. NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region.
\3\ These values, found in NMFS' SARs, represent annual levels of human-caused mortality and serious injury (M/SI) from all sources combined (e.g.,
  commercial fisheries, ship strike). Annual mortality and serious injury (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.
\4\ RARE: The distribution of the species is near enough to the GOA Study Area that the species could occur there, or there are a few confirmed
  sightings. LIKELY: Year-round sightings or acoustic detections of the species in the GOA Study Area, although there may be variation in local
  abundance over the year. SEASONAL: Species absence and presence as documented by surveys or acoustic monitoring. Regions within the GOA Study Area
  follow those presented in Rone et al. (2015); Rone et al. (2009); Rone et al. (2014); Rone et al. (2017): inshore, slope, seamount, and offshore.
\5\ See SAR for more details
\6\ Humpback whales in the Central North Pacific stock and the California, Oregon, and Washington stock are from three Distinct Population Segments
  based on animals identified in breeding areas in Hawaii, Mexico, and Central America (Carretta et al., 2021; Muto et al., 2021; National Marine
  Fisheries Service, 2016c).
\7\ The SAR reports this stock abundance assessment as provisional and notes that it is an underestimate for the entire stock because it is based on
  surveys which covered only a small portion of the stock's range.
\8\ This analysis assumes that these individuals are from the Eastern North Pacific stock; however, they are not discussed in the West Coast or the
  Alaska Stock Assessment Reports (Carretta et al., 2021; Muto et al., 2021).
\9\ The SAR reports that this is an underestimate for the entire stock because it is based on surveys of a small portion of the stock's extensive range
  and it does not account for animals missed on the trackline or for females and juveniles in tropical and subtropical waters.
\10\ Stock abundance is based on counts of individual animals identified from photo-identification catalogues. Surveys for abundance estimates of these
  stocks are conducted infrequently.
\11\ Stock abundance is the best estimate of pup and non-pup counts, which have not been corrected to account for animals at sea during abundance
  surveys.

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

Critical Habitat

    On April 21, 2021 (86 FR 21082), NMFS published a final rule 
designating critical habitat for the endangered Western North Pacific 
DPS, the endangered Central America DPS, and the threatened Mexico DPS 
of humpback whales, including specific marine areas located off the 
coasts of California, Oregon, Washington, and Alaska. Based on 
consideration of national security, economic impacts, and data 
deficiency in some areas, NMFS excluded certain areas from the 
designation for each DPS.
    NMFS identified prey species, primarily euphausiids and small 
pelagic schooling fishes (see the final rule for particular prey 
species identified for each DPS; 86 FR 21082; April 21, 2021) of 
sufficient quality, abundance, and accessibility within humpback whale 
feeding areas to support feeding and population growth, as an essential 
habitat feature. NMFS, through a critical habitat review team (CHRT), 
also considered inclusion of migratory corridors and passage features, 
as well as sound and the soundscape, as essential habitat features. 
However, NMFS did not include either, as the CHRT concluded that the 
best available science did not allow for identification of any 
consistently used migratory corridors or definition of any physical, 
essential migratory or passage conditions for whales transiting between 
or within habitats of the three DPSs. The best available science also 
currently does not enable NMFS to identify a sound-related habitat 
feature that is essential to the conservation of humpback whales.
    NMFS considered the co-occurrence of this designated humpback whale 
critical habitat and the GOA Study Area. Figure 4-1 of the Navy's 
rulemaking/LOA application shows the overlap of the humpback whale 
critical habitat with the TMAA. As shown in the Navy's rulemaking/LOA 
application, the TMAA overlaps with humpback whale critical habitat 
Unit 5 (destination for whales from the Hawaii, Mexico, and Western 
North Pacific DPSs; Calambokidis et al., 2008) and Unit 8 (destination 
for whales from the Hawaii and Mexico DPSs (Baker et al., 1986, 
Calambokidis et al., 2008); Western North Pacific DPS whales have not 
been photo-identified in this specific area, but presence has been 
inferred based on available data indicating that humpback whales from 
Western North Pacific wintering areas occur in the Gulf of Alaska (NMFS 
2020, Table C5)). Approximately 4 percent of the humpback whale 
critical habitat in the GOA region overlaps with the TMAA, and 
approximately 2 percent of critical habitat in both the GOA and U.S. 
west coast regions combined overlaps with the TMAA. The WMA portion of 
the GOA Study Area does not overlap ESA-designated critical habitat for 
humpback whales.
    As noted above in the Geographical Region section, the TMAA 
boundary was intentionally designed to avoid ESA-designated Western DPS 
(MMPA Western U.S. stock) Steller sea lion critical habitat.

Biologically Important Areas

    BIAs include areas of known importance for reproduction, feeding, 
or migration, or areas where small and resident populations are known 
to occur (Van Parijs, 2015). Unlike ESA critical habitat, these areas 
are not formally designated pursuant to any statute or law, but are a 
compilation of the best available science intended to inform impact and 
mitigation analyses. An interactive map of BIAs may be found here: 
https://cetsound.noaa.gov/biologically-important-area-map.
    The WMA does not overlap with any known BIAs. BIAs in the GOA that 
overlap portions of the TMAA include the following feeding and 
migration areas: North Pacific right whale feeding BIA (June-
September); Gray whale migratory corridor BIA (November-January, 
southbound; March-May, northbound) (Ferguson et al., 2015). Fin whale 
feeding areas (east, west, and southwest of Kodiak Island) occur to the 
west of the TMAA and gray whale feeding areas occur both east 
(Southeast Alaska) and west (Kodiak Island) of the TMAA; however, these 
feeding areas are located well outside of (> 20 nmi (37 km)) the TMAA 
and beyond the Navy's estimated range to effects for take by Level A 
harassment and Level B harassment.
    A portion of the North Pacific right whale feeding BIA overlaps 
with the western side of the TMAA by approximately 2,051 square 
kilometers (km\2\; approximately 1.4 percent of the TMAA, and 7 percent 
of the feeding BIA). A small portion of the gray whale migration 
corridor BIA also overlaps with the western side of the TMAA by 
approximately 1,582 km\2\ (approximately 1 percent of the TMAA, and 1 
percent of the migration corridor BIA). To mitigate impacts to marine 
mammals in these BIAs, the Navy would implement several procedural 
mitigation measures and mitigation areas (described in the Proposed 
Mitigation Measures section).

[[Page 49669]]

Unusual Mortality Events (UMEs)

    A UME is defined under Section 410(6) of the MMPA as a stranding 
that is unexpected; involves a significant die-off of any marine mammal 
population; and demands immediate response. There is one UME that is 
applicable to our evaluation of the Navy's activities in the GOA Study 
Area. The gray whale UME along the west coast of North America is 
active and involves ongoing investigations in the GOA that inform our 
analysis are discussed below.
Gray Whale UME
    Since January 1, 2019, elevated gray whale strandings have occurred 
along the west coast of North America, from Mexico to Canada. As of 
June 3, 2022, there have been a total of 578 strandings along the 
coasts of the United States, Canada, and Mexico, with 278 of those 
strandings occurring along the U.S. coast. Of the strandings on the 
U.S. coast, 118 have occurred in Alaska, 66 in Washington, 14 in 
Oregon, and 80 in California. Full or partial necropsy examinations 
were conducted on a subset of the whales. Preliminary findings in 
several of the whales have shown evidence of emaciation. These findings 
are not consistent across all of the whales examined, so more research 
is needed. As part of the UME investigation process, NOAA has assembled 
an independent team of scientists to coordinate with the Working Group 
on Marine Mammal Unusual Mortality Events to review the data collected, 
sample stranded whales, consider possible causal-linkages between the 
mortality event and recent ocean and ecosystem perturbations, and 
determine the next steps for the investigation. Please refer to: 
https://www.fisheries.noaa.gov/national/marine-life-distress/2019-2022-gray-whale-unusual-mortality-event-along-west-coast-and for more 
information on this UME.

Marine Mammal Hearing

    Hearing is the most important sensory modality for marine mammals 
underwater, and exposure to anthropogenic sound can have deleterious 
effects. To appropriately assess the potential effects of exposure to 
sound, it is necessary to understand the frequency ranges marine 
mammals are able to hear. Current data indicate that not all marine 
mammal species have equal hearing capabilities (e.g., Richardson et 
al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect 
this, Southall et al. (2007) recommended that marine mammals be divided 
into functional hearing groups based on directly measured or estimated 
hearing ranges on the basis of available behavioral response data, 
audiograms derived using auditory evoked potential techniques, 
anatomical modeling, and other data. Note that no direct measurements 
of hearing ability have been successfully completed for mysticetes 
(i.e., low-frequency cetaceans). Subsequently, NMFS (2018) described 
generalized hearing ranges for these marine mammal hearing groups. 
Generalized hearing ranges were chosen based on the approximately 65 dB 
threshold from the normalized composite audiograms, with the exception 
for lower limits for low-frequency cetaceans where the lower bound was 
deemed to be biologically implausible and the lower bound from Southall 
et al. (2007) retained. The functional groups and the associated 
frequencies are indicated below (note that these frequency ranges 
correspond to the range for the composite group, with the entire range 
not necessarily reflecting the capabilities of every species within 
that group):
     Low-frequency cetaceans (mysticetes): generalized hearing 
is estimated to occur between approximately 7 Hz and 35 kHz;
     Mid-frequency cetaceans (larger toothed whales, beaked 
whales, and most delphinids): generalized hearing is estimated to occur 
between approximately 150 Hz and 160 kHz;
     High-frequency cetaceans (porpoises, river dolphins, and 
members of the genera Kogia and Cephalorhynchus; including two members 
of the genus Lagenorhynchus, on the basis of recent echolocation data 
and genetic data): generalized hearing is estimated to occur between 
approximately 275 Hz and 160 kHz;
     Pinnipeds in water; Phocidae (true seals): generalized 
hearing is estimated to occur between approximately 50 Hz to 86 kHz; 
and
     Pinnipeds in water; Otariidae (eared seals): generalized 
hearing is estimated to occur between 60 Hz and 39 kHz.
    The pinniped functional hearing group was modified from Southall et 
al. (2007) on the basis of data indicating that phocid species have 
consistently demonstrated an extended frequency range of hearing 
compared to otariids, especially in the higher frequency range 
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth and Holt, 
2013).
    For more details concerning these groups and associated frequency 
ranges, please see NMFS (2018) for a review of the available 
information.

Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat

    This section includes a discussion of the ways that components of 
the specified activity may impact marine mammals and their habitat. The 
Estimated Take of Marine Mammals section later in this rule includes a 
quantitative analysis of the number of instances of take that could 
occur from these activities. The Preliminary Analysis and Negligible 
Impact Determination section considers the content of this section, the 
Estimated Take of Marine Mammals section, and the Proposed Mitigation 
Measures section to draw conclusions regarding the likely impacts of 
these activities on the reproductive success or survivorship of 
individuals and whether those impacts on individuals are likely to 
adversely affect the species through effects on annual rates of 
recruitment or survival.
    The Navy has requested authorization for the take of marine mammals 
that may occur incidental to training activities in the GOA Study Area. 
The Navy analyzed potential impacts to marine mammals in its 
rulemaking/LOA application. NMFS carefully reviewed the information 
provided by the Navy along with independently reviewing applicable 
scientific research and literature and other information to evaluate 
the potential effects of the Navy's activities on marine mammals, which 
are presented in this section. (As noted above, activities that would 
result in take of marine mammals would only occur in the TMAA portion 
of the GOA Study Area.)
    Other potential impacts to marine mammals from training activities 
in the GOA Study Area were analyzed in the Navy's rulemaking/LOA 
application as well as in the 2020 GOA DSEIS/OEIS and 2022 Supplement 
to the 2020 GOA DSEIS/OEIS, in consultation with NMFS as a cooperating 
agency, and determined to be unlikely to result in marine mammal take. 
These include incidental take from vessel strike and serious injury or 
mortality from explosives. Therefore, the Navy did not request 
authorization for incidental take of marine mammals by vessel strike or 
serious injury or mortality from explosives from its proposed specified 
activities. NMFS has carefully considered the information in the 2020 
GOA DSEIS/OEIS, the 2022 Supplement to the 2020 GOA DSEIS/OEIS, and all 
other pertinent information and agrees that incidental take is unlikely 
to occur from these sources. NMFS conducted a detailed analysis of the 
potential for vessel strike, and based on that analysis,

[[Page 49670]]

NMFS does not anticipate vessel strikes of large whales or smaller 
marine mammals in the GOA Study Area. In this proposed rule, NMFS 
analyzes the potential effects of the Navy's activities on marine 
mammals in the GOA Study Area, focusing primarily on the activity 
components that may cause the take of marine mammals: exposure to 
acoustic or explosive stressors including non-impulsive (sonar and 
other transducers) and impulsive (explosives) stressors.
    For the purpose of MMPA incidental take authorizations, NMFS' 
effects assessments serve four primary purposes: (1) to determine 
whether the specified activities would have a negligible impact on the 
affected species or stocks of marine mammals (based on whether it is 
likely that the activities would adversely affect the species or stocks 
through effects on annual rates of recruitment or survival); (2) to 
determine whether the specified activities would have an unmitigable 
adverse impact on the availability of the species or stocks for 
subsistence uses; (3) to prescribe the permissible methods of taking 
(i.e., Level B harassment (behavioral disturbance and temporary 
threshold shift (TTS)), Level A harassment (permanent threshold shift 
(PTS) and non-auditory injury), serious injury, or mortality), 
including identification of the number and types of take that could 
occur by harassment, serious injury, or mortality, and to prescribe 
means of effecting the least practicable adverse impact on the species 
or stocks and their habitat (i.e., mitigation measures); and (4) to 
prescribe requirements pertaining to monitoring and reporting.
    In this section, NMFS provides a description of the ways marine 
mammals potentially could be affected by these activities in the form 
of mortality, physical trauma, sensory impairment (permanent and 
temporary threshold shifts and acoustic masking), physiological 
responses (particularly stress responses), behavioral disturbance, or 
habitat effects. The Estimated Take of Marine Mammals section discusses 
how the potential effects on marine mammals from non-impulsive and 
impulsive sources relate to the MMPA definitions of Level A Harassment 
and Level B Harassment, and quantifies those effects that rise to the 
level of a take. The Preliminary Analysis and Negligible Impact 
Determination section assesses whether the proposed authorized take 
would have a negligible impact on the affected species and stocks.

Potential Effects of Underwater Sound

    Anthropogenic sounds cover a broad range of frequencies and sound 
levels and can have a range of highly variable impacts on marine life, 
from none or minor to potentially severe responses, depending on 
received levels, duration of exposure, behavioral context, and various 
other factors. The potential effects of underwater sound from active 
acoustic sources can possibly result in one or more of the following: 
temporary or permanent hearing impairment, non-auditory physical or 
physiological effects, behavioral response, stress, and masking 
(Richardson et al., 1995; Gordon et al., 2004; Nowacek et al., 2007; 
Southall et al., 2007; G[ouml]tz et al., 2009, Southall et al., 2019a). 
The degree of effect is intrinsically related to the signal 
characteristics, received level, distance from the source, and duration 
of the sound exposure. In general, sudden, high level sounds can cause 
hearing loss, as can longer exposures to lower level sounds. Temporary 
or permanent loss of hearing can occur after exposure to noise, and 
occurs almost exclusively for noise within an animal's hearing range. 
Note that in the following discussion, we refer in many cases to a 
review article concerning studies of noise-induced hearing loss 
conducted from 1996-2015 (i.e., Finneran, 2015). For study-specific 
citations, please see that work. We first describe general 
manifestations of acoustic effects before providing discussion specific 
to the Navy's activities.
    Richardson et al. (1995) described zones of increasing intensity of 
effect that might be expected to occur, in relation to distance from a 
source and assuming that the signal is within an animal's hearing 
range. First is the area within which the acoustic signal would be 
audible (potentially perceived) to the animal, but not strong enough to 
elicit any overt behavioral or physiological response. The next zone 
corresponds with the area where the signal is audible to the animal and 
of sufficient intensity to elicit behavioral or physiological 
responsiveness. Third is a zone within which, for signals of high 
intensity, the received level is sufficient to potentially cause 
discomfort or tissue damage to auditory systems. Overlaying these zones 
to a certain extent is the area within which masking (i.e., when a 
sound interferes with or masks the ability of an animal to detect a 
signal of interest that is above the absolute hearing threshold) may 
occur; the masking zone may be highly variable in size.
    We also describe more severe potential effects (i.e., certain non-
auditory physical or physiological effects). Potential effects from 
impulsive sound sources can range in severity from effects such as 
behavioral disturbance or tactile perception to physical discomfort, 
slight injury of the internal organs and the auditory system, or 
mortality (Yelverton et al., 1973). Non-auditory physiological effects 
or injuries that theoretically might occur in marine mammals exposed to 
high level underwater sound or as a secondary effect of extreme 
behavioral reactions (e.g., change in dive profile as a result of an 
avoidance reaction) include neurological effects, bubble formation, 
resonance effects, and other types of organ or tissue damage (Cox et 
al., 2006; Southall et al., 2007; Zimmer and Tyack, 2007; Tal et al., 
2015).

Acoustic Sources

Direct Physiological Effects
    Non-impulsive sources of sound can cause direct physiological 
effects including noise-induced loss of hearing sensitivity (or 
``threshold shift''), nitrogen decompression, acoustically-induced 
bubble growth, and injury due to sound-induced acoustic resonance. Only 
noise-induced hearing loss is anticipated to occur due to the Navy's 
activities. Acoustically-induced (or mediated) bubble growth and other 
pressure-related physiological impacts are addressed below, but are not 
expected to result from the Navy's activities. Separately, an animal's 
behavioral reaction to an acoustic exposure might lead to physiological 
effects that might ultimately lead to injury or death, which is 
discussed later in the Stranding and Mortality subsection.

Hearing Loss--Threshold Shift

    Marine mammals exposed to high-intensity sound, or to lower-
intensity sound for prolonged periods, can experience hearing threshold 
shift, which is the loss of hearing sensitivity at certain frequency 
ranges after cessation of sound (Finneran, 2015). Threshold shift can 
be permanent (PTS), in which case the loss of hearing sensitivity is 
not fully recoverable, or temporary (TTS), in which case the animal's 
hearing threshold would recover over time (Southall et al., 2007). TTS 
can last from minutes or hours to days (i.e., there is recovery back to 
baseline/pre-exposure levels), can occur within a specific frequency 
range (i.e., an animal might only have a temporary loss of hearing 
sensitivity within a limited frequency band of its auditory

[[Page 49671]]

range), and can be of varying amounts (e.g., an animal's hearing 
sensitivity might be reduced by only 6 dB or reduced by 30 dB). While 
there is no simple functional relationship between TTS and PTS or other 
auditory injury (e.g., neural degeneration), as TTS increases, the 
likelihood that additional exposure sound pressure level (SPL) or 
duration will result in PTS or other injury also increases (see also 
the 2020 GOA DSEIS/OEIS for additional discussion). Exposure thresholds 
for the onset of PTS or other auditory injury are defined by the amount 
of sound energy that results in 40 dB of TTS. This value is informed by 
experimental data, and is used as a proxy for the onset of auditory 
injury; i.e., it is assumed that exposures beyond those capable of 
causing 40 dB of TTS have the potential to result in PTS or other 
auditory injury (e.g., loss of cochlear neuron synapses, even in the 
absence of PTS). In severe cases of PTS, there can be total or partial 
deafness, while in most cases the animal has an impaired ability to 
hear sounds in specific frequency ranges (Kryter, 1985).
    When PTS occurs, there is physical damage to the sound receptors in 
the ear (i.e., tissue damage), whereas TTS represents primarily tissue 
fatigue and is reversible (Southall et al., 2007). PTS is permanent 
(i.e., there is incomplete recovery back to baseline/pre-exposure 
levels), but also can occur in a specific frequency range and amount as 
mentioned above for TTS. In addition, other investigators have 
suggested that TTS is within the normal bounds of physiological 
variability and tolerance and does not represent physical injury (e.g., 
Ward, 1997). Therefore, NMFS does not consider TTS to constitute 
auditory injury.
    The following physiological mechanisms are thought to play a role 
in inducing auditory threshold shift: effects to sensory hair cells in 
the inner ear that reduce their sensitivity; modification of the 
chemical environment within the sensory cells; residual muscular 
activity in the middle ear; displacement of certain inner ear 
membranes; increased blood flow; and post-stimulatory reduction in both 
efferent and sensory neural output (Southall et al., 2007). The 
amplitude, duration, frequency, temporal pattern, and energy 
distribution of sound exposure all can affect the amount of associated 
threshold shift and the frequency range in which it occurs. Generally, 
the amount of threshold shift, and the time needed to recover from the 
effect, increase as amplitude and duration of sound exposure increases. 
Human non-impulsive noise exposure guidelines are based on the 
assumption that exposures of equal energy (the same sound exposure 
level (SEL)) produce equal amounts of hearing impairment regardless of 
how the sound energy is distributed in time (NIOSH, 1998). Previous 
marine mammal TTS studies have also generally supported this equal 
energy relationship (Southall et al., 2007). However, some more recent 
studies concluded that for all noise exposure situations the equal 
energy relationship may not be the best indicator to predict TTS onset 
levels (Mooney et al., 2009a and 2009b; Kastak et al., 2007). These 
studies highlight the inherent complexity of predicting TTS onset in 
marine mammals, as well as the importance of considering exposure 
duration when assessing potential impacts. Generally, with sound 
exposures of equal energy, those that were quieter (lower SPL) with 
longer duration were found to induce TTS onset at lower levels than 
those of louder (higher SPL) and shorter duration. Less threshold shift 
will occur from intermittent sounds than from a continuous exposure 
with the same energy (some recovery can occur between intermittent 
exposures) (Kryter et al., 1966; Ward, 1997; Mooney et al., 2009a, 
2009b; Finneran et al., 2010). For example, one short but loud (higher 
SPL) sound exposure may induce the same impairment as one longer but 
softer (lower SPL) sound, which in turn may cause more impairment than 
a series of several intermittent softer sounds with the same total 
energy (Ward, 1997). Additionally, though TTS is temporary, very 
prolonged or repeated exposure to sound strong enough to elicit TTS, or 
shorter-term exposure to sound levels well above the TTS threshold can 
cause PTS, at least in terrestrial mammals (Kryter, 1985; Lonsbury-
Martin et al., 1987).
    PTS is considered auditory injury (Southall et al., 2007). 
Irreparable damage to the inner or outer cochlear hair cells may cause 
PTS; however, other mechanisms are also involved, such as exceeding the 
elastic limits of certain tissues and membranes in the middle and inner 
ears and resultant changes in the chemical composition of the inner ear 
fluids (Southall et al., 2007).
    The NMFS Acoustic Technical Guidance (NMFS, 2018), which was used 
in the assessment of effects for this rule, compiled, interpreted, and 
synthesized the best available scientific information for noise-induced 
hearing effects for marine mammals to derive updated thresholds for 
assessing the impacts of noise on marine mammal hearing. More recently, 
Southall et al. (2019a) evaluated Southall et al. (2007) and used 
updated scientific information to propose revised noise exposure 
criteria to predict onset of auditory effects in marine mammals (i.e., 
PTS and TTS onset). Southall et al. (2019a) note that the quantitative 
processes described and the resulting exposure criteria (i.e., 
thresholds and auditory weighting functions) are largely identical to 
those in Finneran (2016) and NMFS (2018). They only differ in that the 
Southall et al. (2019a) exposure criteria are more broadly applicable 
as they include all marine mammal species (rather than only those under 
NMFS jurisdiction) for all noise exposures (both in air and underwater 
for amphibious species) and, while the hearing group compositions are 
identical, they renamed the hearing groups. Southall et al. (2021) 
updated the behavioral response severity criteria laid out in Southall 
et al. (2007) and included recommendations on how to present and score 
behavioral responses in future work.
    Many studies have examined noise-induced hearing loss in marine 
mammals (see Finneran (2015) and Southall et al. (2019a) for 
summaries), however for cetaceans, published data on the onset of TTS 
are limited to the captive bottlenose dolphin, beluga, harbor porpoise, 
and Yangtze finless porpoise, and for pinnipeds in water, measurements 
of TTS are limited to harbor seals, elephant seals, and California sea 
lions. These studies examine hearing thresholds measured in marine 
mammals before and after exposure to intense sounds. The difference 
between the pre-exposure and post-exposure thresholds can then be used 
to determine the amount of threshold shift at various post-exposure 
times. NMFS has reviewed the available studies, which are summarized 
below (see also the 2020 GOA DSEIS/OEIS which includes additional 
discussion on TTS studies related to sonar and other transducers).
     The method used to test hearing may affect the resulting 
amount of measured TTS, with neurophysiological measures producing 
larger amounts of TTS compared to psychophysical measures (Finneran et 
al., 2007; Finneran, 2015).
     The amount of TTS varies with the hearing test frequency. 
As the exposure SPL increases, the frequency at which the maximum TTS 
occurs also increases (Kastelein et al., 2014b). For high-level 
exposures, the maximum TTS typically occurs one-half to one octave 
above the exposure frequency (Finneran et al., 2007; Mooney et al., 
2009a; Nachtigall et al., 2004; Popov et al., 2011; Popov et al., 2013; 
Schlundt et al., 2000;

[[Page 49672]]

Kastelein et al., 2021b; Kastelien et al., 2022). The overall spread of 
TTS from tonal exposures can therefore extend over a large frequency 
range (i.e., narrowband exposures can produce broadband (greater than 
one octave) TTS).
     The amount of TTS increases with exposure SPL and duration 
and is correlated with SEL, especially if the range of exposure 
durations is relatively small (Kastak et al., 2007; Kastelein et al., 
2014b; Popov et al., 2014). As the exposure duration increases, 
however, the relationship between TTS and SEL begins to break down. 
Specifically, duration has a more significant effect on TTS than would 
be predicted on the basis of SEL alone (Finneran et al., 2010a; Kastak 
et al., 2005; Mooney et al., 2009a). This means if two exposures have 
the same SEL but different durations, the exposure with the longer 
duration (thus lower SPL) will tend to produce more TTS than the 
exposure with the higher SPL and shorter duration. In most acoustic 
impact assessments, the scenarios of interest involve shorter duration 
exposures than the marine mammal experimental data from which impact 
thresholds are derived; therefore, use of SEL tends to over-estimate 
the amount of TTS. Despite this, SEL continues to be used in many 
situations because it is relatively simple, more accurate than SPL 
alone, and lends itself easily to scenarios involving multiple 
exposures with different SPL.
     Gradual increases of TTS may not be directly observable 
with increasing exposure levels, before the onset of PTS (Reichmuth et 
al., 2019). Similarly, PTS can occur without measurable behavioral 
modifications (Reichmuth et al., 2019).
     The amount of TTS depends on the exposure frequency. 
Sounds at low frequencies, well below the region of best sensitivity, 
are less hazardous than those at higher frequencies, near the region of 
best sensitivity (Finneran and Schlundt, 2013). The onset of TTS--
defined as the exposure level necessary to produce 6 dB of TTS (i.e., 
clearly above the typical variation in threshold measurements)--also 
varies with exposure frequency. At low frequencies, onset-TTS exposure 
levels are higher compared to those in the region of best sensitivity. 
For example, for harbor porpoises exposed to one-sixth octave noise 
bands at 16 kHz (Kastelein et al., 2019f), 32 kHz (Kastelein et al., 
2019d), 63 kHz (Kastelein et al., 2020a), and 88.4 kHz (Kastelein et 
al., 2020b), less susceptibility to TTS was found as frequency 
increased, whereas exposure frequencies below ~6.5 kHz showed an 
increase in TTS susceptibility as frequency increased and approached 
the region of best sensitivity. Kastelein et al. (2020b) showed a much 
higher onset of TTS for a 88.5 kHz exposure as compared to lower 
exposure frequencies (i.e., 16 kHz (Kastelein et al., 2019) 1.5 kHz and 
6.5 kHz (Kastelein et al., 2020a)). For the 88.4 kHz test frequency, a 
185 dB re 1 micropascal squared per second ([micro]Pa\2\-s) exposure 
resulted in 3.6 dB of TTS, and a 191 dB re 1 [micro]Pa\2\-s exposure 
produced 5.2 dB of TTS at 100 kHz and 5.4 dB of TTS at 125 kHz. 
Together, these new studies demonstrate that the criteria for high-
frequency (HF) cetacean auditory impacts is likely to be conservative.
     TTS can accumulate across multiple exposures, but the 
resulting TTS will be less than the TTS from a single, continuous 
exposure with the same SEL (Finneran et al., 2010a; Kastelein et al., 
2014b; Kastelein et al., 2015b; Mooney et al., 2009b). This means that 
TTS predictions based on the total, cumulative SEL will overestimate 
the amount of TTS from intermittent exposures such as sonars and 
impulsive sources. The importance of duty cycle in predicting the 
likelihood of TTS is demonstrated further in Kastelein et al. (2021b). 
The authors found that reducing the duty cycle of a sound generally 
reduced the potential for TTS in California sea lions, and that, 
further, California sea lions are more susceptible to TTS than 
previously believed at the 2 and 4 kHz frequencies tested.
     The amount of observed TTS tends to decrease with 
increasing time following the exposure; however, the relationship is 
not monotonic (i.e., increasing exposure does not always increase TTS). 
The time required for complete recovery of hearing depends on the 
magnitude of the initial shift; for relatively small shifts recovery 
may be complete in a few minutes, while large shifts (e.g., 
approximately 40 dB) may require several days for recovery. Recovery 
times are consistent for similar-magnitude TTS, regardless of the type 
of fatiguing sound exposure (impulsive, continuous noise band, or 
sinusoidal wave; (Kastelein et al., 2019e)). Under many circumstances 
TTS recovers linearly with the logarithm of time (Finneran et al., 
2010a, 2010b; Finneran and Schlundt, 2013; Kastelein et al., 2012a; 
Kastelein et al., 2012b; Kastelein et al., 2013a; Kastelein et al., 
2014b; Kastelein et al., 2014c; Popov et al., 2011; Popov et al., 2013; 
Popov et al., 2014). This means that for each doubling of recovery 
time, the amount of TTS will decrease by the same amount (e.g., 6 dB 
recovery per doubling of time). Please see Section 3.8.3.1.1.2 of the 
2020 GOA DSEIS/OEIS for discussion of additional threshold shift 
literature.
    Nachtigall et al. (2018) and Finneran (2018) describe the 
measurements of hearing sensitivity of multiple odontocete species 
(bottlenose dolphin, harbor porpoise, beluga, and false killer whale) 
when a relatively loud sound was preceded by a warning sound. These 
captive animals were shown to reduce hearing sensitivity when warned of 
an impending intense sound. Based on these experimental observations of 
captive animals, the authors suggest that wild animals may dampen their 
hearing during prolonged exposures or if conditioned to anticipate 
intense sounds. Another study showed that echolocating animals 
(including odontocetes) might have anatomical specializations that 
might allow for conditioned hearing reduction and filtering of low-
frequency ambient noise, including increased stiffness and control of 
middle ear structures and placement of inner ear structures (Ketten et 
al., 2021). Finneran recommends further investigation of the mechanisms 
of hearing sensitivity reduction in order to understand the 
implications for interpretation of existing TTS data obtained from 
captive animals, notably for considering TTS due to short duration, 
unpredictable exposures.
    Marine mammal hearing plays a critical role in communication with 
conspecifics and in interpretation of environmental cues for purposes 
such as predator avoidance and prey capture. Depending on the degree 
(elevation of threshold in dB), duration (i.e., recovery time), and 
frequency range of TTS, and the context in which it is experienced, TTS 
can have effects on marine mammals ranging from discountable to 
serious, similar to those discussed in auditory masking below. For 
example, a marine mammal may be able to readily compensate for a brief, 
relatively small amount of TTS in a non-critical frequency range that 
takes place during a time where ambient noise is lower and there are 
not as many competing sounds present. Alternatively, a larger amount 
and longer duration of TTS sustained during a time when communication 
is critical for successful mother/calf interactions could have more 
serious impacts if it were in the same frequency band as the necessary 
vocalizations and of a severity that impeded communication. Animals 
exposed to high levels of sound that would be expected to result in 
this physiological response would also be expected to have behavioral 
responses of a

[[Page 49673]]

comparatively more severe or sustained nature, which is potentially 
more significant than simple existence of a TTS. However, it is 
important to note that TTS could occur due to longer exposures to sound 
at lower levels so that a behavioral response may not be elicited.
    Depending on the degree and frequency range, the effects of PTS on 
an animal could also range in severity, although it is considered 
generally more serious than TTS because it is a permanent condition. Of 
note, reduced hearing sensitivity as a simple function of aging has 
been observed in marine mammals, as well as humans and other taxa 
(Southall et al., 2007), so we can infer that strategies exist for 
coping with this condition to some degree, though likely not without 
some cost to the animal.

Acoustically-Induced Bubble Formation Due to Sonars and Other Pressure-
Related Impacts

    One theoretical cause of injury to marine mammals is rectified 
diffusion (Crum and Mao, 1996), the process of increasing the size of a 
bubble by exposing it to a sound field. This process could be 
facilitated if the environment in which the ensonified bubbles exist is 
supersaturated with gas. Repetitive diving by marine mammals can cause 
the blood and some tissues to accumulate gas to a greater degree than 
is supported by the surrounding environmental pressure (Ridgway and 
Howard, 1979). The deeper and longer dives of some marine mammals (for 
example, beaked whales) are theoretically predicted to induce greater 
supersaturation (Houser et al., 2001b). If rectified diffusion were 
possible in marine mammals exposed to high-level sound, conditions of 
tissue supersaturation could theoretically speed the rate and increase 
the size of bubble growth. Subsequent effects due to tissue trauma and 
emboli would presumably mirror those observed in humans suffering from 
decompression sickness.
    It is unlikely that the short duration (in combination with the 
source levels) of sonar pings would be long enough to drive bubble 
growth to any substantial size, if such a phenomenon occurs. However, 
an alternative but related hypothesis has also been suggested: stable 
bubbles could be destabilized by high-level sound exposures such that 
bubble growth then occurs through static diffusion of gas out of the 
tissues. In such a scenario the marine mammal would need to be in a 
gas-supersaturated state for a long enough period of time for bubbles 
to become of a problematic size. Recent research with ex vivo 
supersaturated bovine tissues suggested that, for a 37 kHz signal, a 
sound exposure of approximately 215 dB referenced to (re) 1 [mu]Pa 
would be required before microbubbles became destabilized and grew 
(Crum et al., 2005). Assuming spherical spreading loss and a nominal 
sonar source level of 235 dB re: 1 [mu]Pa at 1 m, a whale would need to 
be within 10 m (33 ft) of the sonar dome to be exposed to such sound 
levels. Furthermore, tissues in the study were supersaturated by 
exposing them to pressures of 400-700 kilopascals for periods of hours 
and then releasing them to ambient pressures. Assuming the 
equilibration of gases with the tissues occurred when the tissues were 
exposed to the high pressures, levels of supersaturation in the tissues 
could have been as high as 400-700 percent. These levels of tissue 
supersaturation are substantially higher than model predictions for 
marine mammals (Houser et al., 2001; Saunders et al., 2008). It is 
improbable that this mechanism is responsible for stranding events or 
traumas associated with beaked whale strandings because both the degree 
of supersaturation and exposure levels observed to cause microbubble 
destabilization are unlikely to occur, either alone or in concert.
    Yet another hypothesis (decompression sickness) has speculated that 
rapid ascent to the surface following exposure to a startling sound 
might produce tissue gas saturation sufficient for the evolution of 
nitrogen bubbles (Jepson et al., 2003; Fernandez et al., 2005; 
Fern[aacute]ndez et al., 2012). In this scenario, the rate of ascent 
would need to be sufficiently rapid to compromise behavioral or 
physiological protections against nitrogen bubble formation. 
Alternatively, Tyack et al. (2006) studied the deep diving behavior of 
beaked whales and concluded that: ``Using current models of breath-hold 
diving, we infer that their natural diving behavior is inconsistent 
with known problems of acute nitrogen supersaturation and embolism.'' 
Collectively, these hypotheses can be referred to as ``hypotheses of 
acoustically mediated bubble growth.''
    Although theoretical predictions suggest the possibility for 
acoustically mediated bubble growth, there is considerable disagreement 
among scientists as to its likelihood (Piantadosi and Thalmann, 2004; 
Evans and Miller, 2003; Cox et al., 2006; Rommel et al., 2006). Crum 
and Mao (1996) hypothesized that received levels would have to exceed 
190 dB in order for there to be the possibility of significant bubble 
growth due to supersaturation of gases in the blood (i.e., rectified 
diffusion). Work conducted by Crum et al. (2005) demonstrated the 
possibility of rectified diffusion for short duration signals, but at 
SELs and tissue saturation levels that are highly improbable to occur 
in diving marine mammals. To date, energy levels (ELs) predicted to 
cause in vivo bubble formation within diving cetaceans have not been 
evaluated (NOAA, 2002b). Jepson et al. (2003, 2005) and Fernandez et 
al. (2004, 2005, 2012) concluded that in vivo bubble formation, which 
may be exacerbated by deep, long-duration, repetitive dives may explain 
why beaked whales appear to be relatively vulnerable to MF/HF sonar 
exposures. It has also been argued that traumas from some beaked whale 
strandings are consistent with gas emboli and bubble-induced tissue 
separations (Jepson et al., 2003); however, there is no conclusive 
evidence of this (Rommel et al., 2006). Based on examination of sonar-
associated strandings, Bernaldo de Quiros et al. (2019) list diagnostic 
features, the presence of all of which suggest gas and fat embolic 
syndrome for beaked whales stranded in association with sonar exposure.
    As described in additional detail in the Nitrogen Decompression 
subsection of the 2020 GOA DSEIS/OEIS, marine mammals generally are 
thought to deal with nitrogen loads in their blood and other tissues, 
caused by gas exchange from the lungs under conditions of high ambient 
pressure during diving, through anatomical, behavioral, and 
physiological adaptations (Hooker et al., 2012). Although not a direct 
injury, variations in marine mammal diving behavior or avoidance 
responses have been hypothesized to result in nitrogen off-gassing in 
super-saturated tissues, possibly to the point of deleterious vascular 
and tissue bubble formation (Hooker et al., 2012; Jepson et al., 2003; 
Saunders et al., 2008) with resulting symptoms similar to decompression 
sickness, however the process is still not well understood.
    Fahlman et al. (2021) explained how stress can have a critical role 
in causing the gas emboli present in stranded cetaceans. The authors 
review decompression theory and the mechanisms dolphins have evolved to 
prevent high N2 levels and gas emboli in normal conditions, 
and describe how, in times of high stress, the selective gas exchange 
hypothesis states that this mechanism can break down. In addition, 
circulating microparticles may be a useful biomarker for decompression 
stress in cetaceans. Velazquez-Wallraf et al. (2021) found that 
individual variation also has an essential role in

[[Page 49674]]

this condition. To validate decompression sickness observations in 
certain stranded cetaceans found coincident with naval activities, the 
study used rabbits as an experimental pathological model and found that 
rabbit mortalities during or immediately following decompression showed 
systematically distributed gas bubbles (microscopic and macroscopic), 
as well as emphysema and hemorrhages in multiple organs, similar to 
observations in the stranded cetacean mortalities. Similar findings 
were not found in almost half the rabbits that survived at least one 
hour after decompression, revealing individual variation has an 
essential role in this condition.
    In 2009, Hooker et al. tested two mathematical models to predict 
blood and tissue tension N2 (PN2) using field 
data from three beaked whale species: northern bottlenose whales, 
Cuvier's beaked whales, and Blainville's beaked whales. The researchers 
aimed to determine if physiology (body mass, diving lung volume, and 
dive response) or dive behavior (dive depth and duration, changes in 
ascent rate, and diel behavior) would lead to differences in 
PN2 levels and thereby decompression sickness risk between 
species. In their study, they compared results for previously published 
time depth recorder data (Hooker and Baird, 1999; Baird et al., 2006, 
2008) from Cuvier's beaked whale, Blainville's beaked whale, and 
northern bottlenose whale. They reported that diving lung volume and 
extent of the dive response had a large effect on end-dive 
PN2. Also, results showed that dive profiles had a larger 
influence on end-dive PN2 than body mass differences between 
species. Despite diel changes (i.e., variation that occurs regularly 
every day or most days) in dive behavior, PN2 levels showed 
no consistent trend. Model output suggested that all three species live 
with tissue PN2 levels that would cause a significant 
proportion of decompression sickness cases in terrestrial mammals. The 
authors concluded that the dive behavior of Cuvier's beaked whale was 
different from both Blainville's beaked whale and northern bottlenose 
whale, and resulted in higher predicted tissue and blood N2 
levels (Hooker et al., 2009). They also suggested that the prevalence 
of Cuvier's beaked whales stranding after naval sonar exercises could 
be explained by either a higher abundance of this species in the 
affected areas or by possible species differences in behavior and/or 
physiology related to MF active sonar (Hooker et al., 2009).
    Bernaldo de Quiros et al. (2012) showed that, among stranded 
whales, deep diving species of whales had higher abundances of gas 
bubbles compared to shallow diving species. Kvadsheim et al. (2012) 
estimated blood and tissue PN2 levels in species 
representing shallow, intermediate, and deep diving cetaceans following 
behavioral responses to sonar and their comparisons found that deep 
diving species had higher end-dive blood and tissue N2 
levels, indicating a higher risk of developing gas bubble emboli 
compared with shallow diving species. Fahlmann et al. (2014) evaluated 
dive data recorded from sperm, killer, long-finned pilot, Blainville's 
beaked and Cuvier's beaked whales before and during exposure to low-
frequency (1-2 kHz), as defined by the authors, and mid-frequency (2-7 
kHz) active sonar in an attempt to determine if either differences in 
dive behavior or physiological responses to sonar are plausible risk 
factors for bubble formation. The authors suggested that CO2 
may initiate bubble formation and growth, while elevated levels of 
N2 may be important for continued bubble growth. The authors 
also suggest that if CO2 plays an important role in bubble 
formation, a cetacean escaping a sound source may experience increased 
metabolic rate, CO2 production, and alteration in cardiac 
output, which could increase risk of gas bubble emboli. However, as 
discussed in Kvadsheim et al. (2012), the actual observed behavioral 
responses to sonar from the species in their study (sperm, killer, 
long-finned pilot, Blainville's beaked, and Cuvier's beaked whales) did 
not imply any significantly increased risk of decompression sickness 
due to high levels of N2. Therefore, further information is 
needed to understand the relationship between exposure to stimuli, 
behavioral response (discussed in more detail below), elevated 
N2 levels, and gas bubble emboli in marine mammals. The 
hypotheses for gas bubble formation related to beaked whale strandings 
is that beaked whales potentially have strong avoidance responses to MF 
active sonars because they sound similar to their main predator, the 
killer whale (Cox et al., 2006; Southall et al., 2007; Zimmer and 
Tyack, 2007; Baird et al., 2008; Hooker et al., 2009). Further 
investigation is needed to assess the potential validity of these 
hypotheses.
    To summarize, while there are several hypotheses, there is little 
data directly connecting intense, anthropogenic underwater sounds with 
non-auditory physical effects in marine mammals. The available data do 
not support identification of a specific exposure level above which 
non-auditory effects can be expected (Southall et al., 2007) or any 
meaningful quantitative predictions of the numbers (if any) of marine 
mammals that might be affected in these ways. In addition, such 
effects, if they occur at all, would be expected to be limited to 
situations where marine mammals are exposed to high powered sounds at 
very close range over a prolonged period of time, which is not expected 
to occur based on the speed of the vessels operating sonar in 
combination with the speed and behavior of marine mammals in the 
vicinity of sonar.

Injury Due to Sonar-Induced Acoustic Resonance

    An object exposed to its resonant frequency will tend to amplify 
its vibration at that frequency, a phenomenon called acoustic 
resonance. Acoustic resonance has been proposed as a potential 
mechanism by which a sonar or sources with similar operating 
characteristics could damage tissues of marine mammals. In 2002, NMFS 
convened a panel of government and private scientists to investigate 
the potential for acoustic resonance to occur in marine mammals (NOAA, 
2002). They modeled and evaluated the likelihood that Navy mid-
frequency sonar (2-10 kHz) caused resonance effects in beaked whales 
that eventually led to their stranding. The workshop participants 
concluded that resonance in air-filled structures was not likely to 
have played a primary role in the Bahamas stranding in 2000. They 
listed several reasons supporting this finding including (among 
others): tissue displacements at resonance are estimated to be too 
small to cause tissue damage; tissue-lined air spaces most susceptible 
to resonance are too large in marine mammals to have resonant 
frequencies in the ranges used by mid-frequency or low-frequency sonar; 
lung resonant frequencies increase with depth, and tissue displacements 
decrease with depth so if resonance is more likely to be caused at 
depth it is also less likely to have an affect there; and lung tissue 
damage has not been observed in any mass, multi-species stranding of 
beaked whales. The frequency at which resonance was predicted to occur 
in the animals' lungs was 50 Hz, well below the frequencies used by the 
mid-frequency sonar systems associated with the Bahamas event. The 
workshop participants focused on the March 2000 stranding of beaked 
whales in the Bahamas as high-quality data were available, but the 
workshop report notes that the results apply to other sonar-related 
stranding events. For the reasons given by the

[[Page 49675]]

2002 workshop participants, we do not anticipate injury due to sonar-
induced acoustic resonance from the Navy's planned activities.
Physiological Stress
    There is growing interest in monitoring and assessing the impacts 
of stress responses to sound in marine animals. Classic stress 
responses begin when an animal's central nervous system perceives a 
potential threat to its homeostasis. That perception triggers stress 
responses regardless of whether a stimulus actually threatens the 
animal; the mere perception of a threat is sufficient to trigger a 
stress response (Moberg, 2000; Sapolsky et al., 2005; Seyle, 1950). 
Once an animal's central nervous system perceives a threat, it mounts a 
biological response or defense that consists of a combination of the 
four general biological defense responses: behavioral responses, 
autonomic nervous system responses, neuroendocrine responses, or immune 
responses.
    According to Moberg (2000), in the case of many stressors, an 
animal's first and sometimes most economical (in terms of biotic costs) 
response is behavioral avoidance of the potential stressor or avoidance 
of continued exposure to a stressor. An animal's second line of defense 
to stressors involves the sympathetic part of the autonomic nervous 
system and the classical ``fight or flight'' response which includes 
the cardiovascular system, the gastrointestinal system, the exocrine 
glands, and the adrenal medulla to produce changes in heart rate, blood 
pressure, and gastrointestinal activity that humans commonly associate 
with ``stress.'' These responses have a relatively short duration and 
may or may not have significant long-term effect on an animal's 
welfare.
    An animal's third line of defense to stressors involves its 
neuroendocrine systems or sympathetic nervous systems; the system that 
has received the most study has been the hypothalmus-pituitary-adrenal 
system (also known as the HPA axis in mammals or the hypothalamus-
pituitary-interrenal axis in fish and some reptiles). Unlike stress 
responses associated with the autonomic nervous system, virtually all 
neuro-endocrine functions that are affected by stress--including immune 
competence, reproduction, metabolism, and behavior--are regulated by 
pituitary hormones. Stress-induced changes in the secretion of 
pituitary hormones have been implicated in failed reproduction (Moberg, 
1987; Rivier and Rivest, 1991), altered metabolism (Elasser et al., 
2000), reduced immune competence (Blecha, 2000), and behavioral 
disturbance (Moberg, 1987; Blecha, 2000). Increases in the circulation 
of glucocorticosteroids (cortisol, corticosterone, and aldosterone in 
marine mammals; see Romano et al., 2004) have been equated with stress 
for many years.
    The primary distinction between stress (which is adaptive and does 
not normally place an animal at risk) and distress is the biotic cost 
of the response. During a stress response, an animal uses glycogen 
stores that can be quickly replenished once the stress is alleviated. 
In such circumstances, the cost of the stress response would not pose 
serious fitness consequences. However, when an animal does not have 
sufficient energy reserves to satisfy the energetic costs of a stress 
response, energy resources must be diverted from other biotic 
functions, which impairs those functions that experience the diversion. 
For example, when a stress response diverts energy away from growth in 
young animals, those animals may experience stunted growth. When a 
stress response diverts energy from a fetus, an animal's reproductive 
success and its fitness will suffer. In these cases, the animals will 
have entered a pre-pathological or pathological state which is called 
``distress'' (Seyle, 1950) or ``allostatic loading'' (McEwen and 
Wingfield, 2003). This pathological state of distress will last until 
the animal replenishes its energetic reserves sufficiently to restore 
normal function. Note that these examples involved a long-term (days or 
weeks) stress response exposure to stimuli.
    Relationships between these physiological mechanisms, animal 
behavior, and the costs of stress responses are well-studied through 
controlled experiments in both laboratory and free-ranging animals (for 
examples see, Holberton et al., 1996; Hood et al., 1998; Jessop et al., 
2003; Krausman et al., 2004; Lankford et al., 2005; Reneerkens et al., 
2002; Thompson and Hamer, 2000). However, it should be noted (and as is 
described in additional detail in the 2020 GOA DSEIS/OEIS) that our 
understanding of the functions of various stress hormones (for example, 
cortisol), is based largely upon observations of the stress response in 
terrestrial mammals. Atkinson et al., 2015 note that the endocrine 
response of marine mammals to stress may not be the same as that of 
terrestrial mammals because of the selective pressures marine mammals 
faced during their evolution in an ocean environment. For example, due 
to the necessity of breath-holding while diving and foraging at depth, 
the physiological role of epinephrine and norepinephrine (the 
catecholamines) in marine mammals might be different than in other 
mammals.
    Marine mammals naturally experience stressors within their 
environment and as part of their life histories. Changing weather and 
ocean conditions, exposure to disease and naturally occurring toxins, 
lack of prey availability, and interactions with predators all 
contribute to the stress a marine mammal experiences (Atkinson et al., 
2015). Breeding cycles, periods of fasting, and social interactions 
with members of the same species are also stressors, although they are 
natural components of an animal's life history. Anthropogenic 
activities have the potential to provide additional stressors beyond 
those that occur naturally (Fair et al., 2014; Meissner et al., 2015; 
Rolland et al., 2012). Anthropogenic stressors potentially include such 
things as fishery interactions, pollution, tourism, and ocean noise.
    Acoustically induced stress in marine mammals is not well 
understood. There are ongoing efforts to improve our understanding of 
how stressors impact marine mammal populations (e.g., King et al., 
2015; New et al., 2013a; New et al., 2013b; Pirotta et al., 2015a), 
however little data exist on the consequences of sound-induced stress 
response (acute or chronic). Factors potentially affecting a marine 
mammal's response to a stressor include the individual's life history 
stage, sex, age, reproductive status, overall physiological and 
behavioral plasticity, and whether they are na[iuml]ve or experienced 
with the sound (e.g., prior experience with a stressor may result in a 
reduced response due to habituation (Finneran and Branstetter, 2013; 
St. Aubin and Dierauf, 2001). Stress responses due to exposure to 
anthropogenic sounds or other stressors and their effects on marine 
mammals have been reviewed (Fair and Becker, 2000; Romano et al., 
2002b) and, more rarely, studied in wild populations (e.g., Romano et 
al., 2002a). For example, Rolland et al. (2012) found that noise 
reduction from reduced ship traffic in the Bay of Fundy was associated 
with decreased stress in North Atlantic right whales. These and other 
studies lead to a reasonable expectation that some marine mammals will 
experience physiological stress responses upon exposure to acoustic 
stressors and that it is possible that some of these would be 
classified as ``distress.'' In addition, any animal experiencing TTS 
would likely also experience stress responses (NRC, 2003).

[[Page 49676]]

    Other research has also investigated the impact from vessels (both 
whale-watching and general vessel traffic noise), and demonstrated 
impacts do occur (Bain, 2002; Erbe, 2002; Lusseau, 2006; Williams et 
al., 2006; Williams et al., 2009; Noren et al., 2009; Read et al., 
2014; Rolland et al., 2012; Skarke et al., 2014; Williams et al., 2013; 
Williams et al., 2014a; Williams et al., 2014b; Pirotta et al., 2015b). 
This body of research has generally investigated impacts associated 
with the presence of chronic stressors, which differ significantly from 
the proposed Navy training activities in the GOA Study Area. For 
example, in an analysis of energy costs to killer whales, Williams et 
al. (2009) suggested that whale-watching in Canada's Johnstone Strait 
resulted in lost feeding opportunities due to vessel disturbance, which 
could carry higher costs than other measures of behavioral change might 
suggest. Ayres et al. (2012) reported on research in the Salish Sea 
(Washington state) involving the measurement of southern resident 
killer whale fecal hormones to assess two potential threats to the 
species recovery: lack of prey (salmon) and impacts to behavior from 
vessel traffic. Ayres et al. (2012) suggested that the lack of prey 
overshadowed any population-level physiological impacts on southern 
resident killer whales from vessel traffic. In a conceptual model 
developed by the Population Consequences of Acoustic Disturbance (PCAD) 
working group, serum hormones were identified as possible indicators of 
behavioral effects that are translated into altered rates of 
reproduction and mortality (NRC, 2005). The Office of Naval Research 
hosted a workshop (Effects of Stress on Marine Mammals Exposed to 
Sound) in 2009 that focused on this topic (ONR, 2009). Ultimately, the 
PCAD working group issued a report (Cochrem, 2014) that summarized 
information compiled from 239 papers or book chapters relating to 
stress in marine mammals and concluded that stress responses can last 
from minutes to hours and, while we typically focus on adverse stress 
responses, stress response is part of a natural process to help animals 
adjust to changes in their environment and can also be either neutral 
or beneficial.
    Most sound-induced stress response studies in marine mammals have 
focused on acute responses to sound either by measuring catecholamines 
or by measuring heart rate as an assumed proxy for an acute stress 
response. Belugas demonstrated no catecholamine response to the 
playback of oil drilling sounds (Thomas et al., 1990) but showed a 
small but statistically significant increase in catecholamines 
following exposure to impulsive sounds produced from a seismic water 
gun (Romano et al., 2004). A bottlenose dolphin exposed to the same 
seismic water gun signals did not demonstrate a catecholamine response, 
but did demonstrate a statistically significant elevation in 
aldosterone (Romano et al., 2004), albeit the increase was within the 
normal daily variation observed in this species (St. Aubin et al., 
1996). Increases in heart rate were observed in bottlenose dolphins to 
which known calls of other dolphins were played, although no increase 
in heart rate was observed when background tank noise was played back 
(Miksis et al., 2001). Unfortunately, in this study, it cannot be 
determined whether the increase in heart rate was due to stress or an 
anticipation of being reunited with the dolphin to which the 
vocalization belonged. Similarly, a young beluga's heart rate was 
observed to increase during exposure to noise, with increases dependent 
upon the frequency band of noise and duration of exposure, and with a 
sharp decrease to normal or below normal levels upon cessation of the 
exposure (Lyamin et al., 2011). Spectral analysis of heart rate 
variability corroborated direct measures of heart rate (Bakhchina et 
al., 2017). This response might have been in part due to the conditions 
during testing, the young age of the animal, and the novelty of the 
exposure; a year later the exposure was repeated at a slightly higher 
received level and there was no heart rate response, indicating the 
beluga whale may have acclimated to the noise exposure. Kvadsheim et 
al. (2010) measured the heart rate of captive hooded seals during 
exposure to sonar signals and found an increase in the heart rate of 
the seals during exposure periods versus control periods when the 
animals were at the surface. When the animals dove, the normal dive-
related bradycardia (decrease in heart rate) was not impacted by the 
sonar exposure. Elmegaard et al. (2021) found that sonar sweeps did not 
elicit a startle response in captive harbor porpoises, but initial 
exposures induced bradycardia, whereas impulse exposures induced 
startle responses without a change in heart rate. The authors suggested 
that the parasympathetic cardiac dive response may override any 
transient sympathetic response, or that diving mammals may not have the 
cardiac startle response seen in terrestrial mammals in order to 
maintain volitional cardiovascular control at depth. Similarly, 
Thompson et al. (1998) observed a rapid but short-lived decrease in 
heart rates in harbor and grey seals exposed to seismic air guns (cited 
in Gordon et al., 2003). Williams et al. (2017) monitored the heart 
rates of narwhals released from capture and found that a profound dive 
bradycardia persisted, even though exercise effort increased 
dramatically as part of their escape response following release. Thus, 
although some limited evidence suggests that tachycardia might occur as 
part of the acute stress response of animals that are at the surface, 
the dive bradycardia persists during diving and might be enhanced in 
response to an acute stressor. Yang et al. (2021) measured cortisol 
concentrations in two bottlenose dolphins and found significantly 
higher concentrations after exposure to 140 dB re 1 [micro]Pa impulsive 
noise playbacks. Two out of six tested indicators of immune system 
function underwent acoustic dose-dependent changes, suggesting that 
repeated exposures or sustained stress response to impulsive sounds may 
increase an affected individual's susceptibility to pathogens. However, 
exposing dolphins to a different acoustic stressor yielded contrasting 
results. Houser et al. (2020) measured cortisol and epinephrine 
obtained from 30 bottlenose dolphins exposed to simulated U.S. Navy 
mid-frequency sonar and found no correlation between SPL and stress 
hormone levels. In the same experiment (Houser et al., 2013b), 
behavioral responses were shown to increase in severity with increasing 
received SPLs. These results suggest that behavioral reactions to sonar 
signals are not necessarily indicative of a hormonal stress response. 
Houser et al. (2020) notes that additional research is needed to 
determine the relationship between behavioral responses and 
physiological responses.
    Despite the limited amount of data available on sound-induced 
stress responses for marine mammals exposed to anthropogenic sounds, 
studies of other marine animals and terrestrial animals would also lead 
us to expect that some marine mammals experience physiological stress 
responses and, perhaps, physiological responses that would be 
classified as ``distress'' upon exposure to high-frequency, mid-
frequency, and low-frequency sounds. For example, Jansen (1998) 
reported on the relationship between acoustic exposures and 
physiological responses that are indicative of stress responses in 
humans (e.g., elevated respiration and increased heart rates). Jones 
(1998) reported on reductions in human performance when faced with 
acute,

[[Page 49677]]

repetitive exposures to acoustic disturbance. Trimper et al. (1998) 
reported on the physiological stress responses of osprey to low-level 
aircraft noise while Krausman et al. (2004) reported on the auditory 
and physiological stress responses of endangered Sonoran pronghorn to 
military overflights. However, take due to aircraft noise is not 
anticipated as a result of the Navy's activities. Smith et al. (2004a, 
2004b) identified noise-induced physiological transient stress 
responses in hearing-specialist fish (i.e., goldfish) that accompanied 
short- and long-term hearing losses. Welch and Welch (1970) reported 
physiological and behavioral stress responses that accompanied damage 
to the inner ears of fish and several mammals.
Auditory Masking
    Sound can disrupt behavior through masking, or interfering with, an 
animal's ability to detect, recognize, or discriminate between acoustic 
signals of interest (e.g., those used for intraspecific communication 
and social interactions, prey detection, predator avoidance, or 
navigation) (Richardson et al., 1995; Erbe and Farmer, 2000; Tyack, 
2000; Erbe et al., 2016). Masking occurs when the receipt of a sound is 
interfered with by another coincident sound at similar frequencies and 
at similar or higher intensity, and may occur whether the sound is 
natural (e.g., snapping shrimp, wind, waves, precipitation) or 
anthropogenic (e.g., shipping, sonar, seismic exploration) in origin. 
As described in detail in the 2020 GOA DSEIS/OEIS, the ability of a 
noise source to mask biologically important sounds depends on the 
characteristics of both the noise source and the signal of interest 
(e.g., signal-to-noise ratio, temporal variability, direction), in 
relation to each other and to an animal's hearing abilities (e.g., 
sensitivity, frequency range, critical ratios, frequency 
discrimination, directional discrimination, age, or TTS hearing loss), 
and existing ambient noise and propagation conditions. Masking these 
acoustic signals can disturb the behavior of individual animals, groups 
of animals, or entire populations. Masking can lead to behavioral 
changes including vocal changes (e.g., Lombard effect, increasing 
amplitude, or changing frequency), cessation of foraging, and leaving 
an area, to both signalers and receivers, in an attempt to compensate 
for noise levels (Erbe et al., 2016).
    In humans, significant masking of tonal signals occurs as a result 
of exposure to noise in a narrow band of similar frequencies. As the 
sound level increases, though, the detection of frequencies above those 
of the masking stimulus decreases also. This principle is expected to 
apply to marine mammals as well because of common biomechanical 
cochlear properties across taxa.
    Under certain circumstances, marine mammals experiencing 
significant masking could also be impaired from maximizing their 
performance fitness in survival and reproduction. Therefore, when the 
coincident (masking) sound is man-made, it may be considered harassment 
when disrupting natural behavioral patterns to the point where the 
behavior is abandoned or significantly altered. It is important to 
distinguish TTS and PTS, which persist after the sound exposure, from 
masking, which only occurs during the sound exposure. Because masking 
(without resulting in threshold shift) is not associated with abnormal 
physiological function, it is not considered a physiological effect, 
but rather a potential behavioral effect.
    Richardson et al. (1995b) argued that the maximum radius of 
influence of an industrial noise (including broadband low-frequency 
sound transmission) on a marine mammal is the distance from the source 
to the point at which the noise can barely be heard. This range is 
determined by either the hearing sensitivity (including critical 
ratios, or the lowest signal-to-noise ratio in which animals can detect 
a signal, Finneran and Branstetter, 2013; Johnson et al., 1989; 
Southall et al., 2000) of the animal or the background noise level 
present. Industrial masking is most likely to affect some species' 
ability to detect communication calls and natural sounds (i.e., surf 
noise, prey noise, etc.; Richardson et al., 1995).
    The frequency range of the potentially masking sound is important 
in determining any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation 
sounds produced by odontocetes but are more likely to affect detection 
of mysticete communication calls and other potentially important 
natural sounds such as those produced by surf and some prey species. 
The masking of communication signals by anthropogenic noise may be 
considered as a reduction in the communication space of animals (e.g., 
Clark et al., 2009; Matthews et al., 2016) and may result in energetic 
or other costs as animals change their vocalization behavior (e.g., 
Miller et al., 2000; Foote et al., 2004; Parks et al., 2007; Di Iorio 
and Clark, 2009; Holt et al., 2009). Masking can be reduced in 
situations where the signal and noise come from different directions 
(Richardson et al., 1995), through amplitude modulation of the signal, 
or through other compensatory behaviors (Houser and Moore, 2014). 
Masking can be tested directly in captive species (e.g., Erbe, 2008), 
but in wild populations it must be either modeled or inferred from 
evidence of masking compensation. There are few studies addressing 
real-world masking sounds likely to be experienced by marine mammals in 
the wild (e.g., Branstetter et al., 2013).
    The echolocation calls of toothed whales are subject to masking by 
high-frequency sound. Human data indicate low-frequency sound can mask 
high-frequency sounds (i.e., upward masking). Studies on captive 
odontocetes by Au et al. (1974, 1985, 1993) indicate that some species 
may use various processes to reduce masking effects (e.g., adjustments 
in echolocation call intensity or frequency as a function of background 
noise conditions). There is also evidence that the directional hearing 
abilities of odontocetes are useful in reducing masking at the high-
frequencies these cetaceans use to echolocate, but not at the low-to-
moderate frequencies they use to communicate (Zaitseva et al., 1980). A 
study by Nachtigall and Supin (2018) showed that false killer whales 
adjust their hearing to compensate for ambient sounds and the intensity 
of returning echolocation signals.
    Impacts on signal detection, measured by masked detection 
thresholds, are not the only important factors to address when 
considering the potential effects of masking. As marine mammals use 
sound to recognize conspecifics, prey, predators, or other biologically 
significant sources (Branstetter et al., 2016), it is also important to 
understand the impacts of masked recognition thresholds (often called 
``informational masking''). Branstetter et al., 2016 measured masked 
recognition thresholds for whistle-like sounds of bottlenose dolphins 
and observed that they are approximately 4 dB above detection 
thresholds (energetic masking) for the same signals. Reduced ability to 
recognize a conspecific call or the acoustic signature of a predator 
could have severe negative impacts. Branstetter et al., 2016 observed 
that if ``quality communication'' is set at 90 percent recognition the 
output of communication space models (which are based on 50 percent 
detection) would likely result in a significant decrease in 
communication range.
    As marine mammals use sound to recognize predators (Allen et al., 
2014; Cummings and Thompson, 1971; Cur[eacute]

[[Page 49678]]

et al., 2015; Fish and Vania, 1971), the presence of masking noise may 
also prevent marine mammals from responding to acoustic cues produced 
by their predators, particularly if it occurs in the same frequency 
band. For example, harbor seals that reside in the coastal waters off 
British Columbia are frequently targeted by mammal-eating killer 
whales. The seals acoustically discriminate between the calls of 
mammal-eating and fish-eating killer whales (Deecke et al., 2002), a 
capability that should increase survivorship while reducing the energy 
required to attend to all killer whale calls. Similarly, sperm whales 
(Cur[eacute] et al., 2016; Isojunno et al., 2016), long-finned pilot 
whales (Visser et al., 2016), and humpback whales (Cur[eacute] et al., 
2015) changed their behavior in response to killer whale vocalization 
playbacks; these findings indicate that some recognition of predator 
cues could be missed if the killer whale vocalizations were masked. The 
potential effects of masked predator acoustic cues depends on the 
duration of the masking noise and the likelihood of a marine mammal 
encountering a predator during the time that detection and recognition 
of predator cues are impeded.
    Redundancy and context can also facilitate detection of weak 
signals. These phenomena may help marine mammals detect weak sounds in 
the presence of natural or manmade noise. Most masking studies in 
marine mammals present the test signal and the masking noise from the 
same direction. The dominant background noise may be highly directional 
if it comes from a particular anthropogenic source such as a ship or 
industrial site. Directional hearing may significantly reduce the 
masking effects of these sounds by improving the effective signal-to-
noise ratio.
    Masking affects both senders and receivers of acoustic signals and 
can potentially have long-term chronic effects on marine mammals at the 
population level as well as at the individual level. Low-frequency 
ambient sound levels have increased by as much as 20 dB (more than 
three times in terms of SPL) in the world's ocean from pre-industrial 
periods, with most of the increase from distant commercial shipping 
(Hildebrand, 2009). All anthropogenic sound sources, but especially 
chronic and lower-frequency signals (e.g., from commercial vessel 
traffic), contribute to elevated ambient sound levels, thus 
intensifying masking.

Impaired Communication

    In addition to making it more difficult for animals to perceive and 
recognize acoustic cues in their environment, anthropogenic sound 
presents separate challenges for animals that are vocalizing. When they 
vocalize, animals are aware of environmental conditions that affect the 
``active space'' (or communication space) of their vocalizations, which 
is the maximum area within which their vocalizations can be detected 
before it drops to the level of ambient noise (Brenowitz, 2004; Brumm 
et al., 2004; Lohr et al., 2003). Animals are also aware of 
environmental conditions that affect whether listeners can discriminate 
and recognize their vocalizations from other sounds, which is more 
important than simply detecting that a vocalization is occurring 
(Brenowitz, 1982; Brumm et al., 2004; Dooling, 2004, Marten and Marler, 
1977; Patricelli et al., 2006). Anthropogenic sounds that reduce the 
signal-to-noise ratio of animal vocalizations, increase the masked 
auditory thresholds of animals listening for such vocalizations, or 
reduce the active space of an animal's vocalizations, impair 
communication between animals. Most species that vocalize have evolved 
with an ability to make adjustments to their vocalizations to increase 
the signal-to-noise ratio, active space, and recognizability/
distinguishability of their vocalizations in the face of temporary 
changes in background noise (Brumm et al., 2004; Patricelli et al., 
2006). Vocalizing animals can make adjustments to vocalization 
characteristics such as the frequency structure, amplitude, temporal 
structure, and temporal delivery (repetition rate), or may cease to 
vocalize.
    Many animals will combine several of these strategies to compensate 
for high levels of background noise. Although the fitness consequences 
of vocal adjustments are not directly known in all instances, like most 
other trade-offs animals must make, some of these strategies probably 
come at a cost (Patricelli et al., 2006). Shifting songs and calls to 
higher frequencies may also impose energetic costs (Lambrechts, 1996). 
For example, in birds, vocalizing more loudly in noisy environments may 
have energetic costs that decrease the net benefits of vocal adjustment 
and alter a bird's energy budget (Brumm, 2004; Wood and Yezerinac, 
2006).
    Marine mammals are also known to make vocal changes in response to 
anthropogenic noise. In cetaceans, vocalization changes have been 
reported from exposure to anthropogenic noise sources such as sonar, 
vessel noise, and seismic surveying (see the following for examples: 
Gordon et al., 2003; Di Iorio and Clark, 2010; Hatch et al., 2012; Holt 
et al., 2008; Holt et al., 2011; Lesage et al., 1999; McDonald et al., 
2009; Parks et al., 2007, Risch et al., 2012, Rolland et al., 2012), as 
well as changes in the natural acoustic environment (Caruso et al., 
2020; Dunlop et al., 2014; Helble et al., 2020). Vocal changes can be 
temporary, or can be persistent. For example, model simulation suggests 
that the increase in starting frequency for the North Atlantic right 
whale upcall over the last 50 years resulted in increased detection 
ranges between right whales. The frequency shift, coupled with an 
increase in call intensity by 20 dB, led to a call detectability range 
of less than 3 km to over 9 km (Tennessen and Parks, 2016). Holt et al. 
(2008) measured killer whale call source levels and background noise 
levels in the one to 40 kHz band and reported that the whales increased 
their call source levels by one dB SPL for every one dB SPL increase in 
background noise level. Similarly, another study on St. Lawrence River 
belugas reported a similar rate of increase in vocalization activity in 
response to passing vessels (Scheifele et al., 2005). Di Iorio and 
Clark (2010) showed that blue whale calling rates vary in association 
with seismic sparker survey activity, with whales calling more on days 
with surveys than on days without surveys. They suggested that the 
whales called more during seismic survey periods as a way to compensate 
for the elevated noise conditions.
    In some cases, these vocal changes may have fitness consequences, 
such as an increase in metabolic rates and oxygen consumption, as 
observed in bottlenose dolphins when increasing their call amplitude 
(Holt et al., 2015). A switch from vocal communication to physical, 
surface-generated sounds such as pectoral fin slapping or breaching was 
observed for humpback whales in the presence of increasing natural 
background noise levels, indicating that adaptations to masking may 
also move beyond vocal modifications (Dunlop et al., 2010).
    While these changes all represent possible tactics by the sound-
producing animal to reduce the impact of masking, the receiving animal 
can also reduce masking by using active listening strategies such as 
orienting to the sound source, moving to a quieter location, or 
reducing self-noise from hydrodynamic flow by remaining still. The 
temporal structure of noise (e.g., amplitude modulation) may also 
provide a considerable release from masking through comodulation 
masking release (a reduction of masking that occurs when broadband 
noise, with a frequency spectrum wider than an animal's auditory filter 
bandwidth at the

[[Page 49679]]

frequency of interest, is amplitude modulated) (Branstetter and 
Finneran, 2008; Branstetter et al., 2013). Signal type (e.g., whistles, 
burst-pulse, sonar clicks) and spectral characteristics (e.g., 
frequency modulated with harmonics) may further influence masked 
detection thresholds (Branstetter et al., 2016; Cunningham et al., 
2014).

Masking Due to Sonar and Other Transducers

    The functional hearing ranges of mysticetes, odontocetes, and 
pinnipeds underwater overlap the frequencies of the sonar sources used 
in the Navy's low-frequency active sonar (LFAS)/mid-frequency active 
sonar (MFAS)/high-frequency active sonar (HFAS) training exercises 
(though the Navy proposes no LFAS use for the activities in this 
rulemaking). Additionally, almost all affected species' vocal 
repertoires span across the frequencies of these sonar sources used by 
the Navy. The closer the characteristics of the masking signal to the 
signal of interest, the more likely masking is to occur. Masking by 
mid-frequency active sonar (MFAS) with relatively low-duty cycles is 
not anticipated (or would be of very short duration) for most cetaceans 
as sonar signals occur over a relatively short duration and narrow 
bandwidth (overlapping with only a small portion of the hearing range). 
While dolphin whistles and MFAS are similar in frequency, masking is 
not anticipated (or would be of very short duration) due to the low-
duty cycle of most sonars.
    As described in the 2020 GOA DSEIS/OEIS, newer high-duty cycle or 
continuous active sonars have more potential to mask vocalizations. 
These sonars transmit more frequently (greater than 80 percent duty 
cycle) than traditional sonars, but at a substantially lower source 
level. HFAS, such as pingers that operate at higher repetition rates 
(e.g., 2-10 kHz with harmonics up to 19 kHz, 76 to 77 pings per minute) 
(Culik et al., 2001), also operate at lower source levels and have 
faster attenuation rates due to the higher frequencies used. These 
lower source levels limit the range of impacts, however compared to 
traditional sonar systems, individuals close to the source are likely 
to experience masking at longer time scales. The frequency range at 
which high-duty cycle systems operate overlaps the vocalization 
frequency of many mid-frequency cetaceans. Continuous noise at the same 
frequency of communicative vocalizations may cause disruptions to 
communication, social interactions, acoustically mediated cooperative 
behaviors, and important environmental cues. There is also the 
potential for the mid-frequency sonar signals to mask important 
environmental cues (e.g., predator or conspecific acoustic cues), 
possibly affecting survivorship for targeted animals. Masking due to 
high duty cycle sonars is likely analogous to masking produced by other 
continuous sources (e.g., vessel noise and low-frequency cetaceans), 
and would likely have similar short-term consequences, though longer in 
duration due to the duration of the masking noise. A study by von 
Benda-Beckmann et al. (2021) modeled the effect of pulsed and 
continuous 1-2 kHz active sonar on sperm whale echolocation clicks, and 
found that the presence of upper harmonics in the sonar signal 
increased masking of clicks produced in the search phase of foraging 
compared to buzz clicks produced during prey capture. Different levels 
of sonar caused intermittent to continuous masking (120 to 160 dB re 1 
[mu]Pa2, respectively), but varied based on click level, whale 
orientation, and prey target strength. Continuous active sonar resulted 
in a greater percentage of time that echolocation clicks were masked 
compared to pulsed active sonar. Other short-term consequences may 
include changes to vocalization amplitude and frequency (Brumm and 
Slabbekoorn, 2005; Hotchkin and Parks, 2013) and behavioral impacts 
such as avoidance of the area and interruptions to foraging or other 
essential behaviors (Gordon et al., 2003; Isojunno et al., 2021). Long-
term consequences could include changes to vocal behavior and 
vocalization structure (Foote et al., 2004; Parks et al., 2007), 
abandonment of habitat if masking occurs frequently enough to 
significantly impair communication (Brumm and Slabbekoorn, 2005), a 
potential decrease in survivorship if predator vocalizations are masked 
(Brumm and Slabbekoorn, 2005), and a potential decrease in recruitment 
if masking interferes with reproductive activities or mother-calf 
communication (Gordon et al., 2003).

Masking Due to Vessel Noise

    Masking is more likely to occur in the presence of broadband, 
relatively continuous noise sources such as vessels. Several studies 
have shown decreases in marine mammal communication space and changes 
in behavior as a result of the presence of vessel noise. For example, 
right whales were observed to shift the frequency content of their 
calls upward while reducing the rate of calling in areas of increased 
anthropogenic noise (Parks et al., 2007) as well as increasing the 
amplitude (intensity) of their calls (Parks, 2009; Parks et al., 2011). 
Fournet et al. (2018) observed that humpback whales in Alaska responded 
to increasing ambient sound levels (natural and anthropogenic) by 
increasing the source levels of their calls (non-song vocalizations). 
Clark et al. (2009) also observed that right whales communication space 
decreased by up to 84 percent in the presence of vessels (Clark et al., 
2009). Cholewiak et al. (2018) also observed loss in communication 
space in Stellwagen National Marine Sanctuary for North Atlantic right 
whales, fin whales, and humpback whales with increased ambient noise 
and shipping noise. Gabriele et al. (2018) modeled the effects of 
vessel traffic sound on communication space in Glacier Bay National 
Park in Alaska and found that typical summer vessel traffic in the 
National Park causes losses of communication space to singing whales 
(reduced by 13-28 percent), calling whales (18-51 percent), and roaring 
seals (32-61 percent), particularly during daylight hours and even in 
the absence of cruise ships. Dunlop (2019) observed that an increase in 
vessel noise reduced modelled communication space and resulted in 
significant reduction in group social interactions in Australian 
humpback whales. However, communication signal masking did not fully 
explain this change in social behavior in the model, indicating there 
may also be an additional effect of the physical presence of the vessel 
on social behavior (Dunlop, 2019). Although humpback whales off 
Australia did not change the frequency or duration of their 
vocalizations in the presence of ship noise, their source levels were 
lower than expected based on source level changes to wind noise, 
potentially indicating some signal masking (Dunlop, 2016). Multiple 
delphinid species have also been shown to increase the minimum or 
maximum frequencies of their whistles in the presence of anthropogenic 
noise and reduced communication space (for examples see: Holt et al., 
2008; Holt et al., 2011; Gervaise et al., 2012; Williams et al., 2013; 
Hermannsen et al., 2014; Papale et al., 2015; Liu et al., 2017; Pine et 
al., 2021).

Behavioral Response/Disturbance

    Behavioral responses to sound are highly variable and context-
specific. Many different variables can influence an animal's perception 
of and response to (nature and magnitude) an acoustic event. An 
animal's prior experience with a sound or sound source affects whether 
it is less likely (habituation) or more likely (sensitization) to 
respond to certain sounds in the future (animals

[[Page 49680]]

can also be innately predisposed to respond to certain sounds in 
certain ways) (Southall et al., 2007). Related to the sound itself, the 
perceived nearness of the sound, bearing of the sound (approaching vs. 
retreating), the similarity of a sound to biologically relevant sounds 
in the animal's environment (i.e., calls of predators, prey, or 
conspecifics), and familiarity of the sound may affect the way an 
animal responds to the sound (Southall et al., 2007; DeRuiter et al., 
2013). Individuals (of different age, gender, reproductive status, 
etc.) among most populations will have variable hearing capabilities, 
and differing behavioral sensitivities to sounds that will be affected 
by prior conditioning, experience, and current activities of those 
individuals. Often, specific acoustic features of the sound and 
contextual variables (i.e., proximity, duration, or recurrence of the 
sound, or the current behavior that the marine mammal is engaged in or 
its prior experience), as well as entirely separate factors such as the 
physical presence of a nearby vessel, may be more relevant to the 
animal's response than the received level alone. For example, Goldbogen 
et al. (2013) demonstrated that individual behavioral state was 
critically important in determining response of blue whales to sonar, 
noting that some individuals engaged in deep (>50 m) feeding behavior 
had greater dive responses than those in shallow feeding or non-feeding 
conditions. Some blue whales in the Goldbogen et al. (2013) study that 
were engaged in shallow feeding behavior demonstrated no clear changes 
in diving or movement even when received levels (RLs) were high (~160 
dB re: 1[micro]Pa) for exposures to 3-4 kHz sonar signals, while others 
showed a clear response at exposures at lower received levels of sonar 
and pseudorandom noise.
    Studies by DeRuiter et al. (2012) indicate that variability of 
responses to acoustic stimuli depends not only on the species receiving 
the sound and the sound source, but also on the social, behavioral, or 
environmental contexts of exposure. Another study by DeRuiter et al. 
(2013) examined behavioral responses of Cuvier's beaked whales to MF 
sonar and found that whales responded strongly at low received levels 
(RL of 89-127 dB re: 1[micro]Pa) by ceasing normal fluking and 
echolocation, swimming rapidly away, and extending both dive duration 
and subsequent non-foraging intervals when the sound source was 3.4-9.5 
km away. Importantly, this study also showed that whales exposed to a 
similar range of received levels (78-106 dB re: 1 [micro]Pa) from 
distant sonar exercises (118 km away) did not elicit such responses, 
suggesting that context may moderate reactions.
    Ellison et al. (2012) outlined an approach to assessing the effects 
of sound on marine mammals that incorporates contextual-based factors. 
The authors recommend considering not just the received level of sound, 
but also the activity the animal is engaged in at the time the sound is 
received, the nature and novelty of the sound (i.e., is this a new 
sound from the animal's perspective), and the distance between the 
sound source and the animal. They submit that this ``exposure 
context,'' as described, greatly influences the type of behavioral 
response exhibited by the animal. Forney et al. (2017) also point out 
that an apparent lack of response (e.g., no displacement or avoidance 
of a sound source) may not necessarily mean there is no cost to the 
individual or population, as some resources or habitats may be of such 
high value that animals may choose to stay, even when experiencing 
stress or hearing loss. Forney et al. (2017) recommend considering both 
the costs of remaining in an area of noise exposure such as TTS, PTS, 
or masking, which could lead to an increased risk of predation or other 
threats or a decreased capability to forage, and the costs of 
displacement, including potential increased risk of vessel strike, 
increased risks of predation or competition for resources, or decreased 
habitat suitable for foraging, resting, or socializing. This sort of 
contextual information is challenging to predict with accuracy for 
ongoing activities that occur over large spatial and temporal expanses. 
However, distance is one contextual factor for which data exist to 
quantitatively inform a take estimate, and the method for predicting 
Level B harassment in this rule does consider distance to the source. 
Other factors are often considered qualitatively in the analysis of the 
likely consequences of sound exposure, where supporting information is 
available.
    Friedlaender et al. (2016) provided the first integration of direct 
measures of prey distribution and density variables incorporated into 
across-individual analyses of behavior responses of blue whales to 
sonar, and demonstrated a five-fold increase in the ability to quantify 
variability in blue whale diving behavior. These results illustrate 
that responses evaluated without such measurements for foraging animals 
may be misleading, which again illustrates the context-dependent nature 
of the probability of response.
    Exposure of marine mammals to sound sources can result in, but is 
not limited to, no response or any of the following observable 
responses: increased alertness; orientation or attraction to a sound 
source; vocal modifications; cessation of feeding; cessation of social 
interaction; alteration of movement or diving behavior; habitat 
abandonment (temporary or permanent); and, in severe cases, panic, 
flight, stampede, or stranding, potentially resulting in death 
(Southall et al., 2007; Southall et al., 2021). A review of marine 
mammal responses to anthropogenic sound was first conducted by 
Richardson (1995). More recent reviews (Nowacek et al., 2007; DeRuiter 
et al., 2012 and 2013; Ellison et al., 2012; Gomez et al., 2016) 
address studies conducted since 1995 and focused on observations where 
the received sound level of the exposed marine mammal(s) was known or 
could be estimated. Gomez et al. (2016) conducted a review of the 
literature considering the contextual information of exposure in 
addition to received level and found that higher received levels were 
not always associated with more severe behavioral responses and vice 
versa. Southall et al. (2016) states that results demonstrate that some 
individuals of different species display clear yet varied responses, 
some of which have negative implications, while others appear to 
tolerate high levels, and that responses may not be fully predictable 
with simple acoustic exposure metrics (e.g., received sound level). 
Rather, the authors state that differences among species and 
individuals along with contextual aspects of exposure (e.g., behavioral 
state) appear to affect response probability.
    Sperm whales were exposed to pulsed active sonar (1-2 kHz) at 
moderate source levels and high source levels, as well as continuously 
active sonar at moderate levels for which the summed energy (SEL) 
equaled the summed energy of the high source level pulsed sonar 
(Isojunno et al., 2020). Foraging behavior did not change during 
exposures to moderate source level sonar, but non-foraging behavior 
increased during exposures to high source level sonar and to the 
continuous sonar, indicating that the energy of the sound (the SEL) was 
a better predictor of response than SPL. However, the time of day of 
the exposure was also an important covariate in determining the amount 
of non-foraging behavior, as were order effects (e.g. the SEL of the 
previous exposure). Isojunno et al. (2021) found that higher SELs 
reduced

[[Page 49681]]

sperm whale buzzing (i.e., foraging). Duration of continuous sonar 
activity also appears to impact sperm whale displacement and foraging 
activity (Stanistreet, 2022). During long bouts of sonar lasting up to 
13 consecutive hours, occurring repeatedly over an 8 day naval exercise 
(median and maximum SPL = 120 dB and 164 dB), sperm whales 
substantially reduced how often they produced clicks during sonar, 
indicating a decrease or cessation in foraging behavior. Few previous 
studies have shown sustained changes in sperm whales, but there was an 
absence of sperm whale clicks for 6 consecutive days of sonar activity. 
Cur[eacute] et al. (2021) also found that sperm whales exposed to 
continuous and pulsed active sonar were more likely to produce low or 
medium severity responses with higher cumulative SEL. Specifically, the 
probability of observing a low severity response increased to 0.5 at 
approximately 173 dB SEL and observing a medium severity response 
reached a probability of 0.35 at cumulative SELs between 179 and 189 
dB. These results again demonstrate that the behavioral state and 
environment of the animal mediates the likelihood of a behavioral 
response, as do the characteristics (e.g., frequency, energy level) of 
the sound source itself.
    The following subsections provide examples of behavioral responses 
that provide an idea of the variability in behavioral responses that 
would be expected given the differential sensitivities of marine mammal 
species to sound and the wide range of potential acoustic sources to 
which a marine mammal may be exposed. Behavioral responses that could 
occur for a given sound exposure should be determined from the 
literature that is available for each species, or extrapolated from 
closely related species when no information exists, along with 
contextual factors.
Flight Response
    A flight response is a dramatic change in normal movement to a 
directed and rapid movement away from the perceived location of a sound 
source. The flight response differs from other avoidance responses in 
the intensity of the response (e.g., directed movement, rate of 
travel). Relatively little information on flight responses of marine 
mammals to anthropogenic signals exist, although observations of flight 
responses to the presence of predators have occurred (Connor and 
Heithaus, 1996). The result of a flight response could range from 
brief, temporary exertion and displacement from the area where the 
signal provokes flight to, in extreme cases, being a component of 
marine mammal strandings associated with sonar activities (Evans and 
England, 2001). If marine mammals respond to Navy vessels that are 
transmitting active sonar in the same way that they might respond to a 
predator, their probability of flight responses should increase when 
they perceive that Navy vessels are approaching them directly, because 
a direct approach may convey detection and intent to capture (Burger 
and Gochfeld, 1981, 1990; Cooper, 1997, 1998). There are limited data 
on flight response for marine mammals in water; however, there are 
examples of this response in species on land. For instance, the 
probability of flight responses in Dall's sheep Ovis dalli dalli (Frid, 
2001), hauled-out ringed seals Phoca hispida (Born et al., 1999), 
Pacific brant (Branta bernicl nigricans), and Canada geese (B. 
canadensis) increased as a helicopter or fixed-wing aircraft more 
directly approached groups of these animals (Ward et al., 1999). Bald 
eagles (Haliaeetus leucocephalus) perched on trees alongside a river 
were also more likely to flee from a paddle raft when their perches 
were closer to the river or were closer to the ground (Steidl and 
Anthony, 1996).
Response to Predator
    As discussed earlier, evidence suggests that at least some marine 
mammals have the ability to acoustically identify potential predators. 
For example, harbor seals that reside in the coastal waters off British 
Columbia are frequently targeted by certain groups of killer whales, 
but not others. The seals discriminate between the calls of threatening 
and non-threatening killer whales (Deecke et al., 2002), a capability 
that should increase survivorship while reducing the energy required 
for attending to and responding to all killer whale calls. The 
occurrence of masking or hearing impairment provides a means by which 
marine mammals may be prevented from responding to the acoustic cues 
produced by their predators. Whether or not this is a possibility 
depends on the duration of the masking/hearing impairment and the 
likelihood of encountering a predator during the time that predator 
cues are impeded.
Alteration of Diving or Movement
    Changes in dive behavior can vary widely. They may consist of 
increased or decreased dive times and surface intervals as well as 
changes in the rates of ascent and descent during a dive (e.g., Frankel 
and Clark, 2000; Ng and Leung, 2003; Nowacek et al. 2004; Goldbogen et 
al., 2013a, 2013b). Variations in dive behavior may reflect 
interruptions in biologically significant activities (e.g., foraging) 
or they may be of little biological significance. Variations in dive 
behavior may also expose an animal to potentially harmful conditions 
(e.g., increasing the chance of ship-strike) or may serve as an 
avoidance response that enhances survivorship. The impact of a 
variation in diving resulting from an acoustic exposure depends on what 
the animal is doing at the time of the exposure and the type and 
magnitude of the response.
    Nowacek et al. (2004) reported disruptions of dive behaviors in 
foraging North Atlantic right whales when exposed to an alerting 
stimulus, an action, they noted, that could lead to an increased 
likelihood of ship strike. However, the whales did not respond to 
playbacks of either right whale social sounds or vessel noise, 
highlighting the importance of the sound characteristics in producing a 
behavioral reaction. Conversely, Indo-Pacific humpback dolphins have 
been observed to dive for longer periods of time in areas where vessels 
were present and/or approaching (Ng and Leung, 2003). In both of these 
studies, the influence of the sound exposure cannot be decoupled from 
the physical presence of a surface vessel, thus complicating 
interpretations of the relative contribution of each stimulus to the 
response. Indeed, the presence of surface vessels, their approach, and 
speed of approach, seemed to be significant factors in the response of 
the Indo-Pacific humpback dolphins (Ng and Leung, 2003). Arranz et al. 
(2021) attempted to distinguish effects of vessel noise from vessel 
presence by conducting a noise exposure experiment which compared 
behavioral reactions of resting short-finned pilot whale mother-calf 
pairs during controlled approaches by a tour boat with two electric 
(136-140 dB) or petrol engines (139-150 dB). Approach speed (<4 knots), 
distance of passes (60 m), and vessel features other than engine noise 
remained the same between the two experimental conditions. Behavioral 
data was collected via unmanned aerial vehicle and activity budgets 
were calculated from continuous focal follows. Mother pilot whales 
rested less and calves nursed less in response to both types of boat 
engines compared to control conditions (vessel >300 m, stationary in 
neutral). However, they found no significant impact on whale behaviors 
when the boat approached with the quieter electric engine, while 
resting

[[Page 49682]]

behavior decreased 29 percent and nursing decreased 81 percent when the 
louder petrol engine was installed in the same vessel. Low-frequency 
signals of the Acoustic Thermometry of Ocean Climate (ATOC) sound 
source were not found to affect dive times of humpback whales in 
Hawaiian waters (Frankel and Clark, 2000) or to overtly affect elephant 
seal dives (Costa et al., 2003). They did, however, produce subtle 
effects that varied in direction and degree among the individual seals, 
illustrating the equivocal nature of behavioral effects and consequent 
difficulty in defining and predicting them. Lastly, as noted 
previously, DeRuiter et al. (2013) noted that distance from a sound 
source may moderate marine mammal reactions in their study of Cuvier's 
beaked whales, which showed the whales swimming rapidly and silently 
away when a sonar signal was 3.4-9.5 km away while showing no such 
reaction to the same signal when the signal was 118 km away even though 
the received levels were similar.
Foraging
    Disruption of feeding behavior can be difficult to correlate with 
anthropogenic sound exposure, so it is usually inferred by observed 
displacement from known foraging areas, the appearance of secondary 
indicators (e.g., bubble nets or sediment plumes), or changes in dive 
behavior. As for other types of behavioral response, the frequency, 
duration, and temporal pattern of signal presentation, as well as 
differences in species sensitivity, are likely contributing factors to 
differences in response in any given circumstance (e.g., Croll et al., 
2001; Harris et al., 2017; Madsen et al., 2006a; Nowacek et al.; 2004; 
Yazvenko et al., 2007). A determination of whether foraging disruptions 
incur fitness consequences would require information on or estimates of 
the energetic requirements of the affected individuals and the 
relationship between prey availability, foraging effort and success, 
and the life history stage of the animal.
    Southall et al. (2019a) found that prey availability was higher in 
the western area of the Southern California Offshore Range where 
Cuvier's beaked whales preferentially occurred, while prey resources 
were lower in the eastern area and moderate in the area just north of 
the Range. This high prey availability may indicate that fewer foraging 
dives are needed to meet metabolic energy requirements than would be 
needed in another area with fewer resources. Benoit-Bird et al. (2020) 
demonstrated that differences in squid distribution could be a 
substantial factor for beaked whales' habitat preference. The 
researchers suggest that this be considered when comparing beaked whale 
habitat use both on and off Navy ranges.
    Noise from seismic surveys was not found to impact the feeding 
behavior in western grey whales off the coast of Russia (Yazvenko et 
al., 2007). Visual tracking, passive acoustic monitoring, and movement 
recording tags were used to quantify sperm whale behavior prior to, 
during, and following exposure to air gun arrays at received levels in 
the range of 140-160 dB at distances of 7-13 km, following a phase-in 
of sound intensity and full array exposures at 1-13 km (Madsen et al., 
2006a; Miller et al., 2009). Sperm whales did not exhibit horizontal 
avoidance behavior at the surface. However, foraging behavior may have 
been affected. The sperm whales exhibited 19 percent less vocal (buzz) 
rate during full exposure relative to post exposure, and the whale that 
was approached most closely had an extended resting period and did not 
resume foraging until the air guns had ceased firing. The remaining 
whales continued to execute foraging dives throughout exposure; 
however, swimming movements during foraging dives were six percent 
lower during exposure than control periods (Miller et al., 2009). These 
data raise concerns that air gun surveys may impact foraging behavior 
in sperm whales, although more data are required to understand whether 
the differences were due to exposure or natural variation in sperm 
whale behavior (Miller et al., 2009).
    Balaenopterid whales exposed to moderate low-frequency signals 
similar to the ATOC sound source demonstrated no variation in foraging 
activity (Croll et al., 2001), whereas five out of six North Atlantic 
right whales exposed to an acoustic alarm interrupted their foraging 
dives (Nowacek et al., 2004). Although the received SPLs were similar 
in the latter two studies, the frequency, duration, and temporal 
pattern of signal presentation were different. These factors, as well 
as differences in species sensitivity, are likely contributing factors 
to the differential response. Blue whales exposed to mid-frequency 
sonar in the Southern California Bight were less likely to produce low 
frequency calls usually associated with feeding behavior (Melc[oacute]n 
et al., 2012). However, Melc[oacute]n et al. (2012) were unable to 
determine if suppression of low frequency calls reflected a change in 
their feeding performance or abandonment of foraging behavior and 
indicated that implications of the documented responses are unknown. 
Further, it is not known whether the lower rates of calling actually 
indicated a reduction in feeding behavior or social contact since the 
study used data from remotely deployed, passive acoustic monitoring 
buoys. In contrast, blue whales increased their likelihood of calling 
when ship noise was present, and decreased their likelihood of calling 
in the presence of explosive noise, although this result was not 
statistically significant (Melc[oacute]n et al., 2012). Additionally, 
the likelihood of an animal calling decreased with the increased 
received level of mid-frequency sonar, beginning at a SPL of 
approximately 110-120 dB re: 1 [micro]Pa (Melc[oacute]n et al., 2012). 
Results from behavioral response studies in Southern California waters 
indicated that, in some cases and at low received levels, tagged blue 
whales responded to mid-frequency sonar but that those responses were 
generally brief, of low to moderate severity, and highly dependent on 
exposure context (Southall et al., 2011; Southall et al., 2012b; 
Southall et al., 2019b). Information on or estimates of the energetic 
requirements of the individuals and the relationship between prey 
availability, foraging effort and success, and the life history stage 
of the animal will help better inform a determination of whether 
foraging disruptions incur fitness consequences. Surface feeding blue 
whales did not show a change in behavior in response to mid-frequency 
simulated and real sonar sources with received levels between 90 and 
179 dB re: 1 [micro]Pa, but deep feeding and non-feeding whales showed 
temporary reactions including cessation of feeding, reduced initiation 
of deep foraging dives, generalized avoidance responses, and changes to 
dive behavior. The behavioral responses the researchers observed were 
generally brief, of low to moderate severity, and highly dependent on 
exposure context (behavioral state, source-to-whale horizontal range, 
and prey availability) (DeRuiter et al., 2017; Goldbogen et al., 2013b; 
Sivle et al., 2015). Goldbogen et al. (2013b) indicate that disruption 
of feeding and displacement could impact individual fitness and health. 
However, for this to be true, we would have to assume that an 
individual whale could not compensate for this lost feeding opportunity 
by either immediately feeding at another location, by feeding shortly 
after cessation of acoustic exposure, or by feeding at a later time. 
There is no indication this is the case, particularly since unconsumed 
prey would likely still be available in the environment in most cases 
following the cessation of acoustic exposure.

[[Page 49683]]

    Similarly, while the rates of foraging lunges decrease in humpback 
whales due to sonar exposure, there was variability in the response 
across individuals, with one animal ceasing to forage completely and 
another animal starting to forage during the exposure (Sivle et al., 
2016). In addition, almost half of the animals that exhibited avoidance 
behavior were foraging before the exposure but the others were not; the 
animals that exhibited avoidance behavior while not feeding responded 
at a slightly lower received level and greater distance than those that 
were feeding (Wensveen et al., 2017). These findings indicate that the 
behavioral state of the animal plays a role in the type and severity of 
a behavioral response. In fact, when the prey field was mapped and used 
as a covariate in similar models looking for a response in the same 
blue whales, the response in deep-feeding behavior by blue whales was 
even more apparent, reinforcing the need for contextual variables to be 
included when assessing behavioral responses (Friedlaender et al., 
2016).
Breathing
    Respiration naturally varies with different behaviors and 
variations in respiration rate as a function of acoustic exposure can 
be expected to co-occur with other behavioral reactions, such as a 
flight response or an alteration in diving. However, respiration rates 
in and of themselves may be representative of annoyance or an acute 
stress response. Mean exhalation rates of gray whales at rest and while 
diving were found to be unaffected by seismic surveys conducted 
adjacent to the whale feeding grounds (Gailey et al., 2007).
    Studies with captive harbor porpoises showed increased respiration 
rates upon introduction of acoustic alarms (Kastelein et al., 2001; 
Kastelein et al., 2006a) and emissions for underwater data transmission 
(Kastelein et al., 2005). Harbor porpoises did not respond to the low-
duty cycle mid-frequency tones at any received level, but one did 
respond to the high-duty cycle signal with more jumping and increased 
respiration rates (Kastelein et al., 2018b). Harbor porpoises responded 
to seal scarers with broadband signals up to 44 kHz with a slight 
respiration response at 117 dB re 1 [micro]Pa and an avoidance response 
at 139 dB re 1 [micro]Pa, but another scarer with a fundamental 
(strongest) frequency of 18 kHz did not have an avoidance response 
until 151 dB re 1 [micro]Pa (Kastelein et al., 2015e). However, 
exposure of the same acoustic alarm to a striped dolphin under the same 
conditions did not elicit a response (Kastelein et al., 2006a), again 
highlighting the importance in understanding species differences in the 
tolerance of underwater noise when determining the potential for 
impacts resulting from anthropogenic sound exposure. Lastly, Kastelein 
et al. (2019a) examined the potential masking effect of high sea state 
ambient noise on captive harbor porpoise perception of and response to 
high duty cycle playbacks of AN/SQS-53C sonar signals by observing 
their respiration rates. Results indicated that sonar signals were not 
masked by the high sea state noise, and received levels at which 
responses were observed were similar to those observed in prior studies 
of harbor porpoise behavior.
    Pilot whales exhibited reduced breathing rates relative to their 
diving behavior when the low frequency active sonar levels were high 
(reaching 180 dB re 1 [micro]Pa), but only on the first sonar exposure; 
on subsequent exposures their breathing rates increased (Isojunno et 
al., 2018), indicating a change in response tactic with additional 
exposures.
Social Relationships
    Social interactions between mammals can be affected by noise via 
the disruption of communication signals or by the displacement of 
individuals. Disruption of social relationships therefore depends on 
the disruption of other behaviors (e.g., avoidance, masking, etc.). 
Sperm whales responded to military sonar, apparently from a submarine, 
by dispersing from social aggregations, moving away from the sound 
source, remaining relatively silent, and becoming difficult to approach 
(Watkins et al., 1985). In contrast, sperm whales in the Mediterranean 
that were exposed to submarine sonar continued calling (J. Gordon pers. 
comm. cited in Richardson et al., 1995). Long-finned pilot whales 
exposed to three types of disturbance--playbacks of killer whale 
sounds, naval sonar exposure, and tagging--resulted in increased group 
sizes (Visser et al., 2016). In response to sonar, pilot whales also 
spent more time at the surface with other members of the group (Visser 
et al., 2016). However, social disruptions must be considered in 
context of the relationships that are affected. While some disruptions 
may not have deleterious effects, others, such as long-term or repeated 
disruptions of mother/calf pairs or interruption of mating behaviors, 
have the potential to affect the growth and survival or reproductive 
effort/success of individuals.
Vocalizations (Also see Auditory Masking Section)
    Vocal changes in response to anthropogenic noise can occur across 
the repertoire of sound production modes used by marine mammals, such 
as whistling, echolocation click production, calling, and singing. 
Changes in vocalization behavior that may result in response to 
anthropogenic noise can occur for any of these modes and may result 
from a need to compete with an increase in background noise or may 
reflect an increased vigilance or a startle response. For example, in 
the presence of potentially masking signals (low-frequency active 
sonar), humpback whales have been observed to increase the length of 
their songs (Miller et al., 2000; Fristrup et al., 2003). A similar 
compensatory effect for the presence of low-frequency vessel noise has 
been suggested for right whales; right whales have been observed to 
shift the frequency content of their calls upward while reducing the 
rate of calling in areas of increased anthropogenic noise (Parks et 
al., 2007; Rolland et al., 2012). Killer whales off the northwestern 
coast of the United States have been observed to increase the duration 
of primary calls once a threshold in observing vessel density (e.g., 
whale watching) was reached, which has been suggested as a response to 
increased masking noise produced by the vessels (Foote et al., 2004; 
NOAA, 2014). In contrast, both sperm and pilot whales potentially 
ceased sound production during the Heard Island feasibility test 
(Bowles et al., 1994), although it cannot be absolutely determined 
whether the inability to acoustically detect the animals was due to the 
cessation of sound production or the displacement of animals from the 
area.
    Cerchio et al. (2014) used passive acoustic monitoring to document 
the presence of singing humpback whales off the coast of northern 
Angola and to opportunistically test for the effect of seismic survey 
activity on the number of singing whales. Two recording units were 
deployed between March and December 2008 in the offshore environment; 
numbers of singers were counted every hour. Generalized Additive Mixed 
Models were used to assess the effect of survey day (seasonality), hour 
(diel variation), moon phase, and received levels of noise (measured 
from a single pulse during each ten-minute sampled period) on singer 
number. The number of singers significantly decreased with increasing 
received level of noise, suggesting that humpback whale

[[Page 49684]]

communication was disrupted to some extent by the survey activity.
    Castellote et al. (2012) reported acoustic and behavioral changes 
by fin whales in response to shipping and air gun noise. Acoustic 
features of fin whale song notes recorded in the Mediterranean Sea and 
northeast Atlantic Ocean were compared for areas with different 
shipping noise levels and traffic intensities and during an air gun 
survey. During the first 72 hours of the survey, a steady decrease in 
song received levels and bearings to singers indicated that whales 
moved away from the acoustic source and out of a Navy study area. This 
displacement persisted for a time period well beyond the 10-day 
duration of air gun activity, providing evidence that fin whales may 
avoid an area for an extended period in the presence of increased 
noise. The authors hypothesize that fin whale acoustic communication is 
modified to compensate for increased background noise and that a 
sensitization process may play a role in the observed temporary 
displacement.
    Seismic pulses at average received levels of 131 dB re 1 
[micro]Pa\2\-s caused blue whales to increase call production (Di Iorio 
and Clark, 2010). In contrast, McDonald et al. (1995) tracked a blue 
whale with seafloor seismometers and reported that it stopped 
vocalizing and changed its travel direction at a range of 10 km from 
the seismic vessel (estimated received level 143 dB re: 1 [micro]Pa 
peak-to-peak). Blackwell et al. (2013) found that bowhead whale call 
rates dropped significantly at onset of air gun use at sites with a 
median distance of 41-45 km from the survey. Blackwell et al. (2015) 
expanded this analysis to show that whales actually increased calling 
rates as soon as air gun signals were detectable before ultimately 
decreasing calling rates at higher received levels (i.e., 10-minute 
cumulative sound exposure level (cSEL) of ~127 dB). Overall, these 
results suggest that bowhead whales may adjust their vocal output in an 
effort to compensate for noise before ceasing vocalization effort and 
ultimately deflecting from the acoustic source (Blackwell et al., 2013, 
2015). Captive bottlenose dolphins sometimes vocalized after an 
exposure to impulse sound from a seismic water gun (Finneran et al., 
2010a). These studies demonstrate that even low levels of noise 
received far from the noise source can induce changes in vocalization 
and/or behavioral responses.
Avoidance
    Avoidance is the displacement of an individual from an area or 
migration path as a result of the presence of a sound or other 
stressors. Richardson et al. (1995) noted that avoidance reactions are 
the most obvious manifestations of disturbance in marine mammals. 
Avoidance is qualitatively different from the flight response, but also 
differs in the magnitude of the response (i.e., directed movement, rate 
of travel, etc.). Oftentimes avoidance is temporary, and animals return 
to the area once the noise has ceased. Acute avoidance responses have 
been observed in captive porpoises and pinnipeds exposed to a number of 
different sound sources (Kastelein et al., 2001; Finneran et al., 2003; 
Kastelein et al., 2006a; Kastelein et al., 2006b; Kastelein et al., 
2015d; Kastelein et al., 2015e; Kastelein et al., 2018b). Short-term 
avoidance of seismic surveys, low frequency emissions, and acoustic 
deterrents have also been noted in wild populations of odontocetes 
(Bowles et al., 1994; Goold, 1996; 1998; Stone et al., 2000; Morton and 
Symonds, 2002; Hiley et al., 2021) and to some extent in mysticetes 
(Gailey et al., 2007). Longer-term displacement is possible, however, 
which may lead to changes in abundance or distribution patterns of the 
affected species in the affected region if habituation to the presence 
of the sound does not occur (e.g., Blackwell et al., 2004; Bejder et 
al., 2006; Teilmann et al., 2006). Longer term or repetitive/chronic 
displacement for some dolphin groups and for manatees has been 
suggested to be due to the presence of chronic vessel noise (Haviland-
Howell et al., 2007; Miksis-Olds et al., 2007). Gray whales have been 
reported deflecting from customary migratory paths in order to avoid 
noise from air gun surveys (Malme et al., 1984). Humpback whales showed 
avoidance behavior in the presence of an active air gun array during 
observational studies and controlled exposure experiments in western 
Australia (McCauley et al., 2000a).
    As discussed earlier, Forney et al. (2017) detailed the potential 
effects of noise on marine mammal populations with high site fidelity, 
including displacement and auditory masking, noting that a lack of 
observed response does not imply absence of fitness costs and that 
apparent tolerance of disturbance may have population-level impacts 
that are less obvious and difficult to document. Avoidance of overlap 
between disturbing noise and areas and/or times of particular 
importance for sensitive species may be critical to avoiding 
population-level impacts because (particularly for animals with high 
site fidelity) there may be a strong motivation to remain in the area 
despite negative impacts. Forney et al. (2017) stated that, for these 
animals, remaining in a disturbed area may reflect a lack of 
alternatives rather than a lack of effects. The authors discuss several 
case studies, including western Pacific gray whales, which are a small 
population of mysticetes believed to be adversely affected by oil and 
gas development off Sakhalin Island, Russia (Weller et al., 2002; 
Reeves et al., 2005). Western gray whales display a high degree of 
interannual site fidelity to the area for foraging purposes, and 
observations in the area during air gun surveys have shown the 
potential for harm caused by displacement from such an important area 
(Weller et al., 2006; Johnson et al., 2007). Forney et al. (2017) also 
discuss beaked whales, noting that anthropogenic effects in areas where 
they are resident could cause severe biological consequences, in part 
because displacement may adversely affect foraging rates, reproduction, 
or health, while an overriding instinct to remain could lead to more 
severe acute effects.
    In 1998, the Navy conducted a Low Frequency Sonar Scientific 
Research Program (LFS SRP) specifically to study behavioral responses 
of several species of marine mammals to exposure to LF sound, including 
one phase that focused on the behavior of gray whales to low frequency 
sound signals. The objective of this phase of the LFS SRP was to 
determine whether migrating gray whales respond more strongly to 
received levels, sound gradient, or distance from the source, and to 
compare whale avoidance responses to a LF source in the center of the 
migration corridor versus in the offshore portion of the migration 
corridor. A single source was used to broadcast LFAS sounds at received 
levels of 170-178 dB re: 1 [micro]Pa. The Navy reported that the whales 
showed some avoidance responses when the source was moored one mile 
(1.8 km) offshore, and located within the migration path, but the 
whales returned to their migration path when they were a few kilometers 
beyond the source. When the source was moored two miles (3.7 km) 
offshore, responses were much less, even when the source level was 
increased to achieve the same received levels in the middle of the 
migration corridor as whales received when the source was located 
within the migration corridor (Clark et al., 1999). In addition, the 
researchers noted that the offshore whales did not seem to avoid the 
louder offshore source.
    Also during the LFS SRP, researchers sighted numerous odontocete 
and pinniped species in the vicinity of the

[[Page 49685]]

sound exposure tests with LFA sonar. The MF and HF hearing specialists 
present in California and Hawaii showed no immediately obvious 
responses or changes in sighting rates as a function of source 
conditions. Consequently, the researchers concluded that none of these 
species had any obvious behavioral reaction to LFA sonar signals at 
received levels similar to those that produced only minor short-term 
behavioral responses in the baleen whales (i.e., LF hearing 
specialists). Thus, for odontocetes, the chances of injury and/or 
significant behavioral responses to LFA sonar would be low given the 
MF/HF specialists' observed lack of response to LFA sounds during the 
LFS SRP and due to the MF/HF frequencies to which these animals are 
adapted to hear (Clark and Southall, 2009).
    Maybaum (1993) conducted sound playback experiments to assess the 
effects of MFAS on humpback whales in Hawaiian waters. Specifically, 
she exposed focal pods to sounds of a 3.3-kHz sonar pulse, a sonar 
frequency sweep from 3.1 to 3.6 kHz, and a control (blank) tape while 
monitoring behavior, movement, and underwater vocalizations. The two 
types of sonar signals differed in their effects on the humpback 
whales, but both resulted in avoidance behavior. The whales responded 
to the pulse by increasing their distance from the sound source and 
responded to the frequency sweep by increasing their swimming speeds 
and track linearity. In the Caribbean, sperm whales avoided exposure to 
mid-frequency submarine sonar pulses, in the range of 1000 Hz to 10,000 
Hz (IWC, 2005).
    Kvadsheim et al. (2007) conducted a controlled exposure experiment 
in which killer whales fitted with D-tags were exposed to mid-frequency 
active sonar (Source A: a 1.0 second upsweep 209 dB at 1-2 kHz every 10 
seconds for 10 minutes; Source B: with a 1.0 second upsweep 197 dB at 
6-7 kHz every 10 seconds for 10 minutes). When exposed to Source A, a 
tagged whale and the group it was traveling with did not appear to 
avoid the source. When exposed to Source B, the tagged whales along 
with other whales that had been carousel feeding, where killer whales 
cooperatively herd fish schools into a tight ball towards the surface 
and feed on the fish which have been stunned by tailslaps, and 
subsurface feeding (Simila, 1997) ceased feeding during the approach of 
the sonar and moved rapidly away from the source. When exposed to 
Source B, Kvadsheim et al. (2007) reported that a tagged killer whale 
seemed to try to avoid further exposure to the sound field by the 
following behaviors: immediately swimming away (horizontally) from the 
source of the sound; engaging in a series of erratic and frequently 
deep dives that seemed to take it below the sound field; or swimming 
away while engaged in a series of erratic and frequently deep dives. 
Although the sample sizes in this study are too small to support 
statistical analysis, the behavioral responses of the killer whales 
were consistent with the results of other studies.
    Southall et al. (2007) reviewed the available literature on marine 
mammal hearing and physiological and behavioral responses to human-made 
sound with the goal of proposing exposure criteria for certain effects. 
This peer-reviewed compilation of literature is very valuable, though 
Southall et al. (2007) note that not all data are equal and some have 
poor statistical power, insufficient controls, and/or limited 
information on received levels, background noise, and other potentially 
important contextual variables. Such data were reviewed and sometimes 
used for qualitative illustration, but no quantitative criteria were 
recommended for behavioral responses. All of the studies considered, 
however, contain an estimate of the received sound level when the 
animal exhibited the indicated response.
    In the Southall et al. (2007) publication, for the purposes of 
analyzing responses of marine mammals to anthropogenic sound and 
developing criteria, the authors differentiate between single pulse 
sounds, multiple pulse sounds, and non-pulse sounds. MFAS/HFAS are 
considered non-pulse sounds. Southall et al. (2007) summarize the 
studies associated with low-frequency, mid-frequency, and high-
frequency cetacean and pinniped responses to non-pulse sounds, based 
strictly on received level, in Appendix C of their article (referenced 
and summarized in the following paragraphs).
    The studies that address responses of low-frequency cetaceans to 
non-pulse sounds include data gathered in the field and related to 
several types of sound sources (of varying similarity to active sonar) 
including: vessel noise, drilling and machinery playback, low-frequency 
M-sequences (sine wave with multiple phase reversals) playback, 
tactical low-frequency active sonar playback, drill ships, ATOC source, 
and non-pulse playbacks. These studies generally indicate no (or very 
limited) responses to received levels in the 90 to 120 dB re: 1 
[micro]Pa range and an increasing likelihood of avoidance and other 
behavioral effects in the 120 to 160 dB re: 1 [micro]Pa range. As 
mentioned earlier, though, contextual variables play a very important 
role in the reported responses and the severity of effects are not 
linear when compared to received level. Also, few of the laboratory or 
field datasets had common conditions, behavioral contexts, or sound 
sources, so it is not surprising that responses differ.
    The studies that address responses of mid-frequency cetaceans to 
non-pulse sounds include data gathered both in the field and the 
laboratory and related to several different sound sources (of varying 
similarity to active sonar) including: pingers, drilling playbacks, 
ship and ice-breaking noise, vessel noise, Acoustic Harassment Devices 
(AHDs), Acoustic Deterrent Devices (ADDs), MFAS, and non-pulse bands 
and tones. Southall et al. (2007) were unable to come to a clear 
conclusion regarding the results of these studies. In some cases, 
animals in the field showed significant responses to received levels 
between 90 and 120 dB re: 1 [micro]Pa, while in other cases these 
responses were not seen in the 120 to 150 dB re: 1 [micro]Pa range. The 
disparity in results was likely due to contextual variation and the 
differences between the results in the field and laboratory data 
(animals typically responded at lower levels in the field).
    The studies that address responses of high-frequency cetaceans to 
non-pulse sounds include data gathered both in the field and the 
laboratory and related to several different sound sources (of varying 
similarity to active sonar) including: pingers, AHDs, and various 
laboratory non-pulse sounds. All of these data were collected from 
harbor porpoises. Southall et al. (2007) concluded that the existing 
data indicate that harbor porpoises are likely sensitive to a wide 
range of anthropogenic sounds at low received levels (~90 to 120 dB re: 
1 [micro]Pa), at least for initial exposures. All recorded exposures 
above 140 dB re: 1 [micro]Pa induced profound and sustained avoidance 
behavior in wild harbor porpoises (Southall et al., 2007). Rapid 
habituation was noted in some but not all studies. There are no data to 
indicate whether other high frequency cetaceans are as sensitive to 
anthropogenic sound as harbor porpoises.
    The studies that address the responses of pinnipeds in water to 
non-impulsive sounds include data gathered both in the field and the 
laboratory and related to several different sound sources including: 
AHDs, ATOC, various non-pulse sounds used in underwater data 
communication, underwater drilling, and construction noise. Few studies 
existed with enough information to

[[Page 49686]]

include them in the analysis. The limited data suggested that exposures 
to non-pulse sounds between 90 and 140 dB re: 1 [micro]Pa generally do 
not result in strong behavioral responses in pinnipeds in water, but no 
data exist at higher received levels.
    In 2007, the first in a series of behavioral response studies (BRS) 
on deep diving odontocetes conducted by NMFS, Navy, and other 
scientists showed one Blainville's beaked whale responding to an MFAS 
playback. Tyack et al. (2011) indicates that the playback began when 
the tagged beaked whale was vocalizing at depth (at the deepest part of 
a typical feeding dive), following a previous control with no sound 
exposure. The whale appeared to stop clicking significantly earlier 
than usual, when exposed to MF signals in the 130-140 dB (rms) received 
level range. After a few more minutes of the playback, when the 
received level reached a maximum of 140-150 dB, the whale ascended on 
the slow side of normal ascent rates with a longer than normal ascent, 
at which point the exposure was terminated. The results are from a 
single experiment and a greater sample size is needed before robust and 
definitive conclusions can be drawn. Tyack et al. (2011) also indicates 
that Blainville's beaked whales appear to be sensitive to noise at 
levels well below expected TTS (~160 dB re: 1[micro] Pa). This 
sensitivity was manifested by an adaptive movement away from a sound 
source. This response was observed irrespective of whether the signal 
transmitted was within the band width of MFAS, which suggests that 
beaked whales may not respond to the specific sound signatures. 
Instead, they may be sensitive to any pulsed sound from a point source 
in this frequency range of the MFAS transmission. The response to such 
stimuli appears to involve the beaked whale increasing the distance 
between it and the sound source. Overall the results from the 2007-2008 
study showed a change in diving behavior of the Blainville's beaked 
whale to playback of MFAS and predator sounds (Boyd et al., 2008; 
Southall et al., 2009; Tyack et al., 2011).
    Stimpert et al. (2014) tagged a Baird's beaked whale, which was 
subsequently exposed to simulated MFAS. Received levels of sonar on the 
tag increased to a maximum of 138 dB re: 1[mu]Pa, which occurred during 
the first exposure dive. Some sonar received levels could not be 
measured due to flow noise and surface noise on the tag.
    Reaction to mid-frequency sounds included premature cessation of 
clicking and termination of a foraging dive, and a slower ascent rate 
to the surface. Results from a similar behavioral response study in 
southern California waters were presented for the 2010-2011 field 
season (Southall et al., 2011; DeRuiter et al., 2013b). DeRuiter et al. 
(2013b) presented results from two Cuvier's beaked whales that were 
tagged and exposed to simulated MFAS during the 2010 and 2011 field 
seasons of the southern California behavioral response study. The 2011 
whale was also incidentally exposed to MFAS from a distant naval 
exercise. Received levels from the MFAS signals from the controlled and 
incidental exposures were calculated as 84-144 and 78-106 dB re: 1 
[micro]Pa rms, respectively. Both whales showed responses to the 
controlled exposures, ranging from initial orientation changes to 
avoidance responses characterized by energetic fluking and swimming 
away from the source. However, the authors did not detect similar 
responses to incidental exposure to distant naval sonar exercises at 
comparable received levels, indicating that context of the exposures 
(e.g., source proximity, controlled source ramp-up) may have been a 
significant factor. Specifically, this result suggests that caution is 
needed when using marine mammal response data collected from smaller, 
nearer sound sources to predict at what received levels animals may 
respond to larger sound sources that are significantly farther away--as 
the distance of the source appears to be an important contextual 
variable and animals may be less responsive to sources at notably 
greater distances. Cuvier's beaked whale responses suggested particular 
sensitivity to sound exposure as consistent with results for 
Blainville's beaked whale. Similarly, beaked whales exposed to sonar 
during British training exercises stopped foraging (DSTL, 2007), and 
preliminary results of controlled playback of sonar may indicate 
feeding/foraging disruption of killer whales and sperm whales (Miller 
et al., 2011).
    In the 2007-2008 Bahamas study, playback sounds of a potential 
predator--a killer whale--resulted in a similar but more pronounced 
reaction, which included longer inter-dive intervals and a sustained 
straight-line departure of more than 20 km from the area (Boyd et al., 
2008; Southall et al., 2009; Tyack et al., 2011). The authors noted, 
however, that the magnified reaction to the predator sounds could 
represent a cumulative effect of exposure to the two sound types since 
killer whale playback began approximately 2 hours after MF source 
playback. Pilot whales and killer whales off Norway also exhibited 
horizontal avoidance of a transducer with outputs in the mid-frequency 
range (signals in the 1-2 kHz and 6-7 kHz ranges) (Miller et al., 
2011). Additionally, separation of a calf from its group during 
exposure to MFAS playback was observed on one occasion (Miller et al., 
2011, 2012). Miller et al. (2012) noted that this single observed 
mother-calf separation was unusual for several reasons, including the 
fact that the experiment was conducted in an unusually narrow fjord 
roughly one km wide and that the sonar exposure was started unusually 
close to the pod including the calf. Both of these factors could have 
contributed to calf separation. In contrast, preliminary analyses 
suggest that none of the pilot whales or false killer whales in the 
Bahamas showed an avoidance response to controlled exposure playbacks 
(Southall et al., 2009).
    In the 2010 BRS study, researchers again used controlled exposure 
experiments to carefully measure behavioral responses of individual 
animals to sound exposures of MFAS and pseudo-random noise. For each 
sound type, some exposures were conducted when animals were in a 
surface feeding (approximately 164 ft (50 m) or less) and/or 
socializing behavioral state and others while animals were in a deep 
feeding (greater than 164 ft (50 m)) and/or traveling mode. The 
researchers conducted the largest number of controlled exposure 
experiments on blue whales (n=19) and of these, 11 controlled exposure 
experiments involved exposure to the MFAS sound type. For the majority 
of controlled exposure experiment transmissions of either sound type, 
they noted few obvious behavioral responses detected either by the 
visual observers or on initial inspection of the tag data. The 
researchers observed that throughout the controlled exposure experiment 
transmissions, up to the highest received sound level (absolute RMS 
value approximately 160 dB re: 1 [mu]Pa with signal-to-noise ratio 
values over 60 dB), two blue whales continued surface feeding behavior 
and remained at a range of around 3,820 ft (1,000 m) from the sound 
source (Southall et al., 2011). In contrast, another blue whale (later 
in the day and greater than 11.5 mi (18.5 km; 10 nmi) from the first 
controlled exposure experiment location) exposed to the same stimulus 
(MFA) while engaged in a deep feeding/travel state exhibited a 
different response. In that case, the blue whale responded almost 
immediately following the start of sound transmissions when received 
sounds

[[Page 49687]]

were just above ambient background levels (Southall et al., 2011). The 
authors note that this kind of temporary avoidance behavior was not 
evident in any of the nine controlled exposure experiments involving 
blue whales engaged in surface feeding or social behaviors, but was 
observed in three of the ten controlled exposure experiments for blue 
whales in deep feeding/travel behavioral modes (one involving MFA 
sonar; two involving pseudo-random noise) (Southall et al., 2011). The 
results of this study, as well as the results of the DeRuiter et al. 
(2013b) study of Cuvier's beaked whales discussed above, further 
illustrate the importance of behavioral context in understanding and 
predicting behavioral responses.
    Through analysis of the behavioral response studies, a preliminary 
overarching effect of greater sensitivity to all anthropogenic 
exposures was seen in beaked whales compared to the other odontocetes 
studied (Southall et al., 2009). Therefore, recent studies have focused 
specifically on beaked whale responses to active sonar transmissions or 
controlled exposure playback of simulated sonar on various military 
ranges (Defence Science and Technology Laboratory, 2007; Claridge and 
Durban, 2009; Moretti et al., 2009; McCarthy et al., 2011; Miller et 
al., 2012; Southall et al., 2011, 2012a, 2012b, 2013, 2014; Tyack et 
al., 2011). In the Bahamas, Blainville's beaked whales located on the 
instrumented range will move off-range during sonar use and return only 
after the sonar transmissions have stopped, sometimes taking several 
days to do so (Claridge and Durban 2009; Moretti et al., 2009; McCarthy 
et al., 2011; Tyack et al., 2011). Moretti et al. (2014) used 
recordings from seafloor-mounted hydrophones at the Atlantic Undersea 
Test and Evaluation Center (AUTEC) to analyze the probability of 
Blainsville's beaked whale dives before, during, and after Navy sonar 
exercises.
    Southall et al. (2016) indicates that results from Tyack et al. 
(2011), Miller et al. (2015), Stimpert et al. (2014), and DeRuiter et 
al. (2013b) beaked whale studies demonstrate clear, strong, and 
pronounced but varied behavioral changes including avoidance with 
associated energetic swimming and cessation of individual foraging 
dives at quite low received levels (~100 to 135 dB re: 1 [mu]Pa) for 
exposures to simulated or active MF military sonars (1-8 kHz) with 
sound sources approximately 2-5 km away. Similar responses by beaked 
whales to sonar have been documented by Stimpert et al. (2014), Falcone 
et al. (2017), DiMarzio et al. (2018), and Joyce et al. (2019). Jones-
Todd et al. (2021) developed a discrete-space, continuous-time analysis 
to estimate animal occurrence and unique movement probability into and 
out of an area over time, in response to sonar. They argue that 
existing models in the field are inappropriate for estimating a whale's 
exposure to sonar longitudinally and across multiple exercises; most 
models treat each day independently and don't consider repeated 
exposures over longer periods. This model also allows for individual 
variation in movement data. Using seven tagged Blainville's beaked 
whales' telemetry data, the model showed transition rates across an 
area's borders changing in response to sonar exposure, reflecting an 
avoidance response that lasted approximately 3 days after the end of 
the exposure. However, there are a number of variables influencing 
response or non-response including source distance (close vs. far), 
received sound levels, and other contextual variables such as other 
sound sources (e.g., vessels, etc.) (Manzano-Roth et al., 2016; Falcone 
et al., 2017; Harris et al., 2018). Wensveen et al. (2019) found 
northern bottlenose whales to avoid sonar out to distances of 28 km, 
but these distances are well in line with those observed on Navy ranges 
(Manzano-Roth et al., 2016; Joyce et al., 2019) where the animals 
return once the sonar has ceased. When exposed to especially long 
durations of naval sonar (up to 13 consecutive hours, repeatedly over 8 
days), Cuvier's beaked whale detection rates remained low even 7 days 
after the exercise. In addition, a Mesoplodont beaked whale species was 
entirely displaced from the area during and at least 7 days after the 
sonar activity (Stanistreet et al., 2022). Furthermore, beaked whales 
have also shown response to other non-sonar anthropogenic sounds such 
as commercial shipping and echosounders (Soto et al., 2006; Pirotta et 
al., 2012; Cholewiak et al., 2017). Pirotta et al. (2012) documented 
broadband ship noise causing a significant change in beaked whale 
behavior up to at least 5.2 km away from the vessel. Even though beaked 
whales appear to be sensitive to anthropogenic sounds, the level of 
response at the population level does not appear to be significant 
based on over a decade of research at two heavily used Navy training 
areas in the Pacific (Falcone et al., 2012; Schorr et al., 2014; 
DiMarzio et al., 2018; Schorr et al., 2019). With the exception of 
seasonal patterns, DiMarzio et al. (2018) did not detect any changes in 
annual Cuvier's beaked whale abundance estimates in Southern California 
derived from passive acoustic echolocation detections over 9 years 
(2010-2018). Similar results for Blainville's beaked whales abundance 
estimates over several years was documented in Hawaii (Henderson et 
al., 2016; DiMarzio et al., 2018). Visually, there have been documented 
repeated sightings in southern California of the same individual 
Cuvier's beaked whales over 10 years, sightings of mother-calf pairs, 
and sightings of the same mothers with their second calf (Falcone et 
al., 2012; Schorr et al., 2014; Schorr et al., 2019; Schorr, 
unpublished data).
    Baleen whales have shown a variety of responses to impulse sound 
sources, including avoidance, reduced surface intervals, altered 
swimming behavior, and changes in vocalization rates (Richardson et 
al., 1995; Gordon et al., 2003; Southall, 2007). While most bowhead 
whales did not show active avoidance until within 8 km of seismic 
vessels (Richardson et al., 1995), some whales avoided vessels by more 
than 20 km at received levels as low as 120 dB re: 1 [micro]Pa rms. 
Additionally, Malme et al. (1988) observed clear changes in diving and 
respiration patterns in bowheads at ranges up to 73 km from seismic 
vessels, with received levels as low as 125 dB re: 1 [micro]Pa.
    Gray whales migrating along the United States West Coast showed 
avoidance responses to seismic vessels by 10 percent of animals at 164 
dB re: 1 [micro]Pa, and by 90 percent of animals at 190 dB re: 1 
[micro]Pa, with similar results for whales in the Bering Sea (Malme, 
1986; 1988). In contrast, noise from seismic surveys was not found to 
impact feeding behavior or exhalation rates while resting or diving in 
western gray whales off the coast of Russia (Yazvenko et al., 2007; 
Gailey et al., 2007).
    Humpback whales showed avoidance behavior at ranges of 5-8 km from 
a seismic array during observational studies and controlled exposure 
experiments in western Australia (McCauley, 1998; Todd et al., 1996). 
Todd et al. (1996) found no clear short-term behavioral responses by 
foraging humpbacks to explosions associated with construction 
operations in Newfoundland, but did see a trend of increased rates of 
net entanglement and a shift to a higher incidence of net entanglement 
closer to the noise source.
    The strongest baleen whale response in any behavioral response 
study was observed in a minke whale in the 3S2 study, which responded 
at 146 dB re: 1 [micro]Pa by strongly avoiding the sound source 
(Kvadsheim et al., 2017; Sivle et al., 2015). Although the minke whale 
increased its swim speed, directional movement, and respiration rate, 
none of these were greater than rates observed in

[[Page 49688]]

baseline behavior, and its dive behavior remained similar to baseline 
dives. A minke whale tagged in the Southern California behavioral 
response study also responded by increasing its directional movement, 
but maintained its speed and dive patterns, and so did not demonstrate 
as strong of a response (Kvadsheim et al., 2017). In addition, the 3S2 
minke whale demonstrated some of the same avoidance behavior during the 
controlled ship approach with no sonar, indicating at least some of the 
response was to the vessel (Kvadsheim et al., 2017). Martin et al. 
(2015) found that the density of calling minke whales was reduced 
during periods of Navy training involving sonar relative to the periods 
before training, and increased again in the days after training was 
completed. The responses of individual whales could not be assessed, so 
in this case it is unknown whether the decrease in calling animals 
indicated that the animals left the range, or simply ceased calling. 
Similarly, minke whale detections made using Marine Acoustic Recording 
Instruments off Jacksonville, FL, were reduced or ceased altogether 
during periods of sonar use (Simeone et al., 2015; U.S. Department of 
the Navy, 2013b), especially with an increased ping rate (Charif et 
al., 2015). Harris et al. (2019b) utilized acoustically generated minke 
whale tracks at the U.S. Navy's Pacific Missile Range Facility to 
statistically demonstrate changes in the spatial distribution of minke 
whale acoustic presence before, during, and after surface ship mid-
frequency active sonar training. The spatial distribution of 
probability of acoustic presence was different in the ``During'' phase 
compared to the ``Before'' phase, and the probability of presence at 
the center of ship activity for the ``During'' phase was close to zero 
for both years. The ``After'' phases for both years retained lower 
probabilities of presence, suggesting the return to baseline conditions 
may take more than 5 days. While the results show a clear spatial 
redistribution of calling minke whales during surface ship mid-
frequency active sonar training, a limitation of passive acoustic 
monitoring is that one cannot conclude if the whales moved away, went 
silent, or a combination of the two.
Orientation
    A shift in an animal's resting state or an attentional change via 
an orienting response represent behaviors that would be considered mild 
disruptions if occurring alone. As previously mentioned, the responses 
may co-occur with other behaviors; for instance, an animal may 
initially orient toward a sound source, and then move away from it. 
Thus, any orienting response should be considered in context of other 
reactions that may occur.
Continued Pre-Disturbance Behavior and Habituation
    Under some circumstances, some of the individual marine mammals 
that are exposed to active sonar transmissions will continue their 
normal behavioral activities. In other circumstances, individual 
animals will respond to sonar transmissions at lower received levels 
and move to avoid additional exposure or exposures at higher received 
levels (Richardson et al., 1995).
    It is difficult to distinguish between animals that continue their 
pre-disturbance behavior without stress responses, animals that 
continue their behavior but experience stress responses (that is, 
animals that cope with disturbance), and animals that habituate to 
disturbance (that is, they may have experienced low-level stress 
responses initially, but those responses abated over time). Watkins 
(1986) reviewed data on the behavioral reactions of fin, humpback, 
right, and minke whales that were exposed to continuous, broadband low-
frequency shipping and industrial noise in Cape Cod Bay. He concluded 
that underwater sound was the primary cause of behavioral reactions in 
these species of whales and that the whales responded behaviorally to 
acoustic stimuli within their respective hearing ranges. Watkins also 
noted that whales showed the strongest behavioral reactions to sounds 
in the 15 Hz to 28 kHz range, although negative reactions (avoidance, 
interruptions in vocalizations, etc.) were generally associated with 
sounds that were either unexpected, too loud, suddenly louder or 
different, or perceived as being associated with a potential threat 
(such as an approaching ship on a collision course). In particular, 
whales seemed to react negatively when they were within 100 m of the 
source or when received levels increased suddenly in excess of 12 dB 
relative to ambient sounds. At other times, the whales ignored the 
source of the signal and all four species habituated to these sounds. 
Nevertheless, Watkins concluded that whales ignored most sounds in the 
background of ambient noise, including sounds from distant human 
activities even though these sounds may have had considerable energies 
at frequencies well within the whales' range of hearing. Further, he 
noted that of the whales observed, fin whales were the most sensitive 
of the four species, followed by humpback whales; right whales were the 
least likely to be disturbed and generally did not react to low-
amplitude engine noise. By the end of his period of study, Watkins 
(1986) concluded that fin and humpback whales had generally habituated 
to the continuous and broad-band noise of Cape Cod Bay while right 
whales did not appear to change their response. As mentioned above, 
animals that habituate to a particular disturbance may have experienced 
low-level stress responses initially, but those responses abated over 
time. In most cases, this likely means a lessened immediate potential 
effect from a disturbance. However, there is cause for concern where 
the habituation occurs in a potentially more harmful situation. For 
example, animals may become more vulnerable to vessel strikes once they 
habituate to vessel traffic (Swingle et al., 1993; Wiley et al., 1995).
    Aicken et al. (2005) monitored the behavioral responses of marine 
mammals to a new low-frequency active sonar system used by the British 
Navy (which would be considered mid-frequency active sonar under this 
rule as it operates at frequencies greater than 1,000 Hz). During those 
trials, fin whales, sperm whales, Sowerby's beaked whales, long-finned 
pilot whales, Atlantic white-sided dolphins, and common bottlenose 
dolphins were observed and their vocalizations were recorded. These 
monitoring studies detected no evidence of behavioral responses that 
the investigators could attribute to exposure to the low-frequency 
active sonar during these trials.

Explosive Sources

    Underwater explosive detonations send a shock wave and sound energy 
through the water and can release gaseous by-products, create an 
oscillating bubble, or cause a plume of water to shoot up from the 
water surface. The shock wave and accompanying noise are of most 
concern to marine animals. Depending on the intensity of the shock wave 
and size, location, and depth of the animal, an animal can be injured, 
killed, suffer non-lethal physical effects, experience hearing related 
effects with or without behavioral responses, or exhibit temporary 
behavioral responses or tolerance from hearing the blast sound. 
Generally, exposures to higher levels of impulse and pressure levels 
would result in greater impacts to an individual animal.
    Injuries resulting from a shock wave take place at boundaries 
between tissues of different densities. Different velocities are 
imparted to tissues of

[[Page 49689]]

different densities, and this can lead to their physical disruption. 
Blast effects are greatest at the gas-liquid interface (Landsberg, 
2000). Gas-containing organs, particularly the lungs and 
gastrointestinal tract, are especially susceptible (Goertner, 1982; 
Hill, 1978; Yelverton et al., 1973). Intestinal walls can bruise or 
rupture, with subsequent hemorrhage and escape of gut contents into the 
body cavity. Less severe gastrointestinal tract injuries include 
contusions, petechiae (small red or purple spots caused by bleeding in 
the skin), and slight hemorrhaging (Yelverton et al., 1973).
    Because the ears are the most sensitive to pressure, they are the 
organs most sensitive to injury (Ketten, 2000). Sound-related damage 
associated with sound energy from detonations can be theoretically 
distinct from injury from the shock wave, particularly farther from the 
explosion. If a noise is audible to an animal, it has the potential to 
damage the animal's hearing by causing decreased sensitivity (Ketten, 
1995). Lethal impacts are those that result in immediate death or 
serious debilitation in or near an intense source and are not, 
technically, pure acoustic trauma (Ketten, 1995). Sublethal impacts 
include hearing loss, which is caused by exposures to perceptible 
sounds. Severe damage (from the shock wave) to the ears includes 
tympanic membrane rupture, fracture of the ossicles, damage to the 
cochlea, hemorrhage, and cerebrospinal fluid leakage into the middle 
ear. Moderate injury implies partial hearing loss due to tympanic 
membrane rupture and blood in the middle ear. Permanent hearing loss 
also can occur when the hair cells are damaged by one very loud event, 
as well as by prolonged exposure to a loud noise or chronic exposure to 
noise (see the Hearing Loss--Threshold Shift section). The level of 
impact from blasts depends on both an animal's location and, at outer 
zones, on its sensitivity to the residual noise (Ketten, 1995).

Further Potential Effects of Behavioral Disturbance on Marine Mammal 
Fitness

    The different ways that marine mammals respond to sound are 
sometimes indicators of the ultimate effect that exposure to a given 
stimulus will have on the well-being (survival, reproduction, etc.) of 
an animal. There are few quantitative marine mammal data relating the 
exposure of marine mammals to sound to effects on reproduction or 
survival, though data exists for terrestrial species to which we can 
draw comparisons for marine mammals. Several authors have reported that 
disturbance stimuli may cause animals to abandon nesting and foraging 
sites (Sutherland and Crockford, 1993); may cause animals to increase 
their activity levels and suffer premature deaths or reduced 
reproductive success when their energy expenditures exceed their energy 
budgets (Daan et al., 1996; Feare, 1976; Mullner et al., 2004); or may 
cause animals to experience higher predation rates when they adopt 
risk-prone foraging or migratory strategies (Frid and Dill, 2002). Each 
of these studies addressed the consequences of animals shifting from 
one behavioral state (e.g., resting or foraging) to another behavioral 
state (e.g., avoidance or escape behavior) because of human disturbance 
or disturbance stimuli.
    One consequence of behavioral avoidance results in the altered 
energetic expenditure of marine mammals because energy is required to 
move and avoid surface vessels or the sound field associated with 
active sonar (Frid and Dill, 2002). Most animals can avoid that 
energetic cost by swimming away at slow speeds or speeds that minimize 
the cost of transport (Miksis-Olds, 2006), as has been demonstrated in 
Florida manatees (Miksis-Olds, 2006).
    Those energetic costs increase, however, when animals shift from a 
resting state, which is designed to conserve an animal's energy, to an 
active state that consumes energy the animal would have conserved had 
it not been disturbed. Marine mammals that have been disturbed by 
anthropogenic noise and vessel approaches are commonly reported to 
shift from resting to active behavioral states, which would imply that 
they incur an energy cost.
    Morete et al. (2007) reported that undisturbed humpback whale cows 
that were accompanied by their calves were frequently observed resting 
while their calves circled them (milling). When vessels approached, the 
amount of time cows and calves spent resting and milling, respectively, 
declined significantly. These results are similar to those reported by 
Scheidat et al. (2004) for the humpback whales they observed off the 
coast of Ecuador.
    Constantine and Brunton (2001) reported that bottlenose dolphins in 
the Bay of Islands, New Zealand, engaged in resting behavior just 5 
percent of the time when vessels were within 300 m, compared with 83 
percent of the time when vessels were not present. However, Heenehan et 
al. (2016) report that results of a study of the response of Hawaiian 
spinner dolphins to human disturbance suggest that the key factor is 
not the sheer presence or magnitude of human activities, but rather the 
directed interactions and dolphin-focused activities that elicit 
responses from dolphins at rest. This information again illustrates the 
importance of context in regard to whether an animal will respond to a 
stimulus. Miksis-Olds (2006) and Miksis-Olds et al. (2005) reported 
that Florida manatees in Sarasota Bay, Florida, reduced the amount of 
time they spent milling and increased the amount of time they spent 
feeding when background noise levels increased. Although the acute 
costs of these changes in behavior are not likely to exceed an animal's 
ability to compensate, the chronic costs of these behavioral shifts are 
uncertain.
    Attention is the cognitive process of selectively concentrating on 
one aspect of an animal's environment while ignoring other things 
(Posner, 1994). Because animals (including humans) have limited 
cognitive resources, there is a limit to how much sensory information 
they can process at any time. The phenomenon called ``attentional 
capture'' occurs when a stimulus (usually a stimulus that an animal is 
not concentrating on or attending to) ``captures'' an animal's 
attention. This shift in attention can occur consciously or 
subconsciously (for example, when an animal hears sounds that it 
associates with the approach of a predator) and the shift in attention 
can be sudden (Dukas, 2002; van Rij, 2007). Once a stimulus has 
captured an animal's attention, the animal can respond by ignoring the 
stimulus, assuming a ``watch and wait'' posture, or treat the stimulus 
as a disturbance and respond accordingly, which includes scanning for 
the source of the stimulus or ``vigilance'' (Cowlishaw et al., 2004).
    Vigilance is normally an adaptive behavior that helps animals 
determine the presence or absence of predators, assess their distance 
from conspecifics, or to attend cues from prey (Bednekoff and Lima, 
1998; Treves, 2000). Despite those benefits, however, vigilance has a 
cost of time; when animals focus their attention on specific 
environmental cues, they are not attending to other activities such as 
foraging or resting. These effects have generally not been demonstrated 
for marine mammals, but studies involving fish and terrestrial animals 
have shown that increased vigilance may substantially reduce feeding 
rates (Saino, 1994; Beauchamp and Livoreil, 1997; Fritz et al., 2002; 
Purser and Radford, 2011). Animals will spend more time being vigilant 
(which may translate to less time foraging or resting) when disturbance 
stimuli approach an animal more directly, remain at closer distances, 
have a greater group size (e.g., multiple surface

[[Page 49690]]

vessels), or co-occur with times that an animal perceives increased 
risk (e.g., when they are giving birth or accompanied by a calf). An 
example of this concept with terrestrial species involved bighorn sheep 
and Dall's sheep, which dedicated more time being vigilant, and less 
time resting or foraging, when aircraft made direct approaches over 
them (Frid, 2001; Stockwell et al., 1991). Vigilance has also been 
documented in pinnipeds at haul-out sites where resting may be 
disturbed when seals become alerted and/or flush into the water due to 
a variety of disturbances, which may be anthropogenic (noise and/or 
visual stimuli) or due to other natural causes such as other pinnipeds 
(Richardson et al., 1995; Southall et al., 2007; VanBlaricom, 2010; 
Lozano and Hente, 2014).
    Chronic disturbance can cause population declines through reduction 
of fitness (e.g., decline in body condition) and subsequent reduction 
in reproductive success, survival, or both (e.g., Harrington and 
Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). For example, 
Madsen (1994) reported that pink-footed geese (Anser brachyrhynchus) in 
undisturbed habitat gained body mass and had about a 46 percent 
reproductive success rate compared with geese in disturbed habitat 
(being consistently scared off the fields on which they were foraging) 
which did not gain mass and had a 17 percent reproductive success rate. 
Similar reductions in reproductive success have been reported for mule 
deer (Odocoileus hemionus) disturbed by all-terrain vehicles (Yarmoloy 
et al., 1988), caribou (Rangifer tarandus caribou) disturbed by seismic 
exploration blasts (Bradshaw et al., 1998), and caribou disturbed by 
low-elevation military jet fights (Luick et al., 1996; Harrington and 
Veitch, 1992). Similarly, a study of elk (Cervus elaphus) that were 
disturbed experimentally by pedestrians concluded that the ratio of 
young to mothers was inversely related to disturbance rate (Phillips 
and Alldredge, 2000). However, Ridgway et al. (2006) reported that 
increased vigilance in bottlenose dolphins exposed to sound over a 
five-day period in open-air, open-water enclosures in San Diego Bay did 
not cause any sleep deprivation or stress effects such as changes in 
cortisol or epinephrine levels.
    The primary mechanism by which increased vigilance and disturbance 
appear to affect the fitness of individual animals is by disrupting an 
animal's time budget and, as a result, reducing the time they might 
spend foraging and resting (which increases an animal's activity rate 
and energy demand while decreasing their caloric intake/energy). An 
example of this concept with terrestrial species involved a study of 
grizzly bears (Ursus horribilis) that reported that bears disturbed by 
hikers reduced their energy intake by an average of 12 kilocalories/min 
(50.2 x 103 kiloJoules/min), and spent energy fleeing or acting 
aggressively toward hikers (White et al., 1999). In a separate study, 
by integrating different sources of data (e.g., controlled exposure 
data, activity monitoring, telemetry tracking, and prey sampling) into 
a theoretical model to predict effects from sonar on a blue whale's 
daily energy intake, Pirotta et al. (2021) found that tagged blue 
whales' activity budgets, lunging rates, and ranging patterns caused 
variability in their predicted cost of disturbance.
    Lusseau and Bejder (2007) present data from three long-term studies 
illustrating the connections between disturbance from whale-watching 
boats and population-level effects in cetaceans. In Shark Bay, 
Australia, the abundance of bottlenose dolphins was compared within 
adjacent control and tourism sites over three consecutive 4.5-year 
periods of increasing tourism levels. Between the second and third time 
periods, in which tourism doubled, dolphin abundance decreased by 15 
percent in the tourism area and did not change significantly in the 
control area. In Fiordland, New Zealand, two populations (Milford and 
Doubtful Sounds) of bottlenose dolphins with tourism levels that 
differed by a factor of seven were observed and significant increases 
in travelling time and decreases in resting time were documented for 
both. Consistent short-term avoidance strategies were observed in 
response to tour boats until a threshold of disturbance was reached 
(average 68 minutes between interactions), after which the response 
switched to a longer-term habitat displacement strategy. For one 
population, tourism only occurred in a part of the home range. However, 
tourism occurred throughout the home range of the Doubtful Sound 
population and once boat traffic increased beyond the 68-minute 
threshold (resulting in abandonment of their home range/preferred 
habitat), reproductive success drastically decreased (increased 
stillbirths) and abundance decreased significantly (from 67 to 56 
individuals in a short period). Last, in a study of northern resident 
killer whales off Vancouver Island, exposure to boat traffic was shown 
to reduce foraging opportunities and increase traveling time. A simple 
bioenergetics model was applied to show that the reduced foraging 
opportunities equated to a decreased energy intake of 18 percent, while 
the increased traveling incurred an increased energy output of 3-4 
percent, which suggests that a management action based on avoiding 
interference with foraging might be particularly effective.
    On a related note, many animals perform vital functions, such as 
feeding, resting, traveling, and socializing, on a diel cycle (24-hour 
cycle). Behavioral reactions to noise exposure (such as disruption of 
critical life functions, displacement, or avoidance of important 
habitat) are more likely to be significant for fitness if they last 
more than one diel cycle or recur on subsequent days (Southall et al., 
2007). Consequently, a behavioral response lasting less than one day 
and not recurring on subsequent days is not considered particularly 
severe unless it could directly affect reproduction or survival 
(Southall et al., 2007). It is important to note the difference between 
behavioral reactions lasting or recurring over multiple days and 
anthropogenic activities lasting or recurring over multiple days. For 
example, just because at-sea exercises last for multiple days does not 
necessarily mean that individual animals will be either exposed to 
those activity-related stressors (i.e., sonar) for multiple days or 
further, exposed in a manner that would result in sustained multi-day 
substantive behavioral responses.
    Stone (2015a) reported data from at-sea observations during 1,196 
airgun surveys from 1994 to 2010. When large arrays of airguns 
(considered in this study to be 500 in\3\ or more) were firing, lateral 
displacement, more localized avoidance, or other changes in behavior 
were evident for most odontocetes. However, significant responses to 
large arrays were found only for the minke whale and fin whale. 
Behavioral responses observed included changes in swimming or surfacing 
behavior, with indications that cetaceans remained near the water 
surface at these times. Cetaceans were recorded as feeding less often 
when large arrays were active. Monitoring of gray whales during an air 
gun survey included recording whale movements and respirations pre-, 
during-, and post-seismic survey (Gailey et al., 2016). Behavioral 
state and water depth were the best ``natural'' predictors of whale 
movements and respiration and, after considering natural variation, 
none of the response variables were

[[Page 49691]]

significantly associated with survey or vessel sounds.
    In order to understand how the effects of activities may or may not 
impact species and stocks of marine mammals, it is necessary to 
understand not only what the likely disturbances are going to be, but 
how those disturbances may affect the reproductive success and 
survivorship of individuals, and then how those impacts to individuals 
translate to population-level effects. Following on the earlier work of 
a committee of the U.S. National Research Council (NRC, 2005), New et 
al. (2014), in an effort termed the Potential Consequences of 
Disturbance (PCoD), outline an updated conceptual model of the 
relationships linking disturbance to changes in behavior and 
physiology, health, vital rates, and population dynamics. In this 
framework, behavioral and physiological changes can have direct (acute) 
effects on vital rates, such as when changes in habitat use or 
increased stress levels raise the probability of mother-calf separation 
or predation; they can have indirect and long-term (chronic) effects on 
vital rates, such as when changes in time/energy budgets or increased 
disease susceptibility affect health, which then affects vital rates; 
or they can have no effect to vital rates (New et al., 2014). In 
addition to outlining this general framework and compiling the relevant 
literature that supports it, the authors chose four example species for 
which extensive long-term monitoring data exist (southern elephant 
seals, North Atlantic right whales, Ziphidae beaked whales, and 
bottlenose dolphins) and developed state-space energetic models that 
can be used to forecast longer-term, population-level impacts from 
behavioral changes. While these are very specific models with very 
specific data requirements that cannot yet be applied broadly to 
project-specific risk assessments for the majority of species, as well 
as requiring significant resources and time to conduct (more than is 
typically available to support regulatory compliance for one project), 
they are a critical first step towards being able to quantify the 
likelihood of a population level effect.
    Since New et al. (2014), several publications have described models 
developed to examine the long-term effects of environmental or 
anthropogenic disturbance of foraging on various life stages of 
selected species (sperm whale, Farmer et al. (2018); California sea 
lion, McHuron et al. (2018); blue whale, Pirotta et al. (2018a); pilot 
whales, Hin et al. (2021); gray whale, McHuron et al., 2021). These 
models continue to add to refinement of the approaches to the 
population consequences of disturbance (PCOD) framework. Such models 
also help identify what data inputs require further investigation. 
Pirotta et al. (2018b) provides a review of the PCOD framework with 
details on each step of the process and approaches to applying real 
data or simulations to achieve each step.
    New et al. (2020) found that closed populations of dolphins could 
not withstand a higher probability of disturbance, compared to open 
populations with no limitation on food. Two bottlenose dolphin 
populations in Australia were also modeled over 5 years against a 
number of disturbances (Reed et al., 2020), and results indicated that 
habitat/noise disturbance had little overall impact on population 
abundances in either location, even in the most extreme impact 
scenarios modeled. By integrating different sources of data (e.g., 
controlled exposure data, activity monitoring, telemetry tracking, and 
prey sampling) into a theoretical model to predict effects from sonar 
on a blue whale's daily energy intake, Pirotta et al. (2021) found that 
tagged blue whales' activity budgets, lunging rates, and ranging 
patterns caused variability in their predicted cost of disturbance. 
Dunlop et al. (2021) modeled migrating humpback whale mother-calf pairs 
in response to seismic surveys using both a forwards and backwards 
approach. While a typical forwards approach can determine if a stressor 
would have population-level consequences, authors demonstrated that 
working backwards through a PCoD model can be used to assess the 
``worst case'' scenario for an interaction of a target species and 
stressor. This method may be useful for future management goals when 
appropriate data becomes available to fully support the model. Harbor 
porpoise movement and foraging were modeled for baseline periods and 
then for periods with seismic surveys as well; the models demonstrated 
that the seasonality of the seismic activity was an important predictor 
of impact (Gallagher et al., 2021). Murray et al. (2021) conducted a 
cumulative effects assessment on Northern and Southern resident killer 
whales, which involved both a Pathways of Effects conceptual model and 
a Population Viability Analysis quantitative simulation model. Authors 
found that both populations were highly sensitive to prey abundance, 
and were also impacted by the interaction of low prey abundance with 
vessel strike, vessel noise, and polychlorinated biphenyls 
contaminants. However, more research is needed to validate the 
mechanisms of vessel disturbance and environmental containments. 
Czapanskiy et al. (2021) modeled energetic costs associated with 
behavioral response to mid-frequency active sonar using datasets from 
eleven cetaceans' feeding rates, prey characteristics, avoidance 
behavior, and metabolic rates. Authors found that the short-term 
energetic cost was influenced more by lost foraging opportunities than 
increased locomotor effort during avoidance. Additionally, the model 
found that mysticetes incurred more energetic cost that odontocetes, 
even during mild behavioral responses to sonar.

Stranding and Mortality

    The definition for a stranding under title IV of the MMPA is that 
(A) a marine mammal is dead and is (i) on a beach or shore of the 
United States; or (ii) in waters under the jurisdiction of the United 
States (including any navigable waters); or (B) a marine mammal is 
alive and is (i) on a beach or shore of the United States and is unable 
to return to the water; (ii) on a beach or shore of the United States 
and, although able to return to the water, is in need of apparent 
medical attention; or (iii) in the waters under the jurisdiction of the 
United States (including any navigable waters), but is unable to return 
to its natural habitat under its own power or without assistance (see 
MMPA section 410(3)). This definition is useful for considering 
stranding events even when they occur beyond lands and waters under the 
jurisdiction of the United States.
    Marine mammal strandings have been linked to a variety of causes, 
such as illness from exposure to infectious agents, biotoxins, or 
parasites; starvation; unusual oceanographic or weather events; or 
anthropogenic causes including fishery interaction, ship strike, 
entrainment, entrapment, sound exposure, or combinations of these 
stressors sustained concurrently or in series. Historically, the cause 
or causes of most strandings have remained unknown (Geraci et al., 
1976; Eaton, 1979; Odell et al., 1980; Best, 1982), but the development 
of trained, professional stranding response networks and improved 
analyses have led to a greater understanding of marine mammal stranding 
causes (Simeone and Moore 2017).
    Numerous studies suggest that the physiology, behavior, habitat, 
social relationships, age, or condition of cetaceans may cause them to 
strand or might predispose them to strand when exposed to another 
phenomenon. These

[[Page 49692]]

suggestions are consistent with the conclusions of numerous other 
studies that have demonstrated that combinations of dissimilar 
stressors commonly combine to kill an animal or dramatically reduce its 
fitness, even though one exposure without the other does not produce 
the same result (Bernaldo de Quiros et al., 2019; Chroussos, 2000; 
Creel, 2005; DeVries et al., 2003; Fair and Becker, 2000; Foley et al., 
2001; Moberg, 2000; Relyea, 2005a, 2005b; Romero, 2004; Sih et al., 
2004).
    Historically, stranding reporting and response efforts have been 
inconsistent, although significant improvements have occurred over the 
last 25 years. Reporting forms for basic (``Level A'') information, 
rehabilitation disposition, and human interaction have been 
standardized nationally (available at https://www.fisheries.noaa.gov/national/marine-mammal-protection/level-data-collection-marine-mammal-stranding-events). However, data collected beyond basic information 
varies by region (and may vary from case to case), and are not 
standardized across the United States. Logistical conditions such as 
weather, time, location, and decomposition state may also affect the 
ability of the stranding network to thoroughly examine a specimen 
(Carretta et al., 2016b; Moore et al., 2013). While the investigation 
of stranded animals provides insight into the types of threats marine 
mammal populations face, full investigations are only possible and 
conducted on a small fraction of the total number of strandings that 
occur, limiting our understanding of the causes of strandings (Carretta 
et al., 2016a). Additionally, and due to the variability in effort and 
data collected, the ability to interpret long-term trends in stranded 
marine mammals is complicated.
    Several mass strandings (strandings that involve two or more 
individuals of the same species, excluding a single mother-calf pair) 
that have occurred over the past two decades have been associated with 
anthropogenic activities that introduced sound into the marine 
environment such as naval operations and seismic surveys. An in-depth 
discussion of strandings is in the Navy's Technical Report on Marine 
Mammal Strandings Associated with U.S. Navy Sonar Activities (U.S. Navy 
Marine Mammal Program & Space and Naval Warfare Systems Command Center 
Pacific, 2017).
    Worldwide, there have been several efforts to identify 
relationships between cetacean mass stranding events and military 
active sonar (Cox et al., 2006; Hildebrand, 2004; IWC, 2005; Taylor et 
al., 2004). For example, based on a review of mass stranding events 
around the world consisting of two or more individuals of Cuvier's 
beaked whales, records from the International Whaling Commission (IWC) 
(2005) show that a quarter (9 of 41) were associated with concurrent 
naval patrol, explosion, maneuvers, or MFAS. D'Amico et al. (2009) 
reviewed beaked whale stranding data compiled primarily from the 
published literature (which provides an incomplete record of stranding 
events, as many are not written up for publication), along with 
unpublished information from some regions of the world.
    Most of the stranding events reviewed by the IWC involved beaked 
whales. A mass stranding of Cuvier's beaked whales in the eastern 
Mediterranean Sea occurred in 1996 (Frantzis, 1998), and mass stranding 
events involving Gervais' beaked whales, Blainville's beaked whales, 
and Cuvier's beaked whales occurred off the coast of the Canary Islands 
in the late 1980s (Simmonds and Lopez-Jurado, 1991). The stranding 
events that occurred in the Canary Islands and Kyparissiakos Gulf in 
the late 1990s and the Bahamas in 2000 have been the most intensively 
studied mass stranding events and have been associated with naval 
maneuvers involving the use of tactical sonar. Other cetacean species 
with naval sonar implicated in stranding events include harbor porpoise 
(Phocoena phocoena) (Norman et al., 2004; Wright et al., 2013) and 
common dolphin (Delphinus delphis) (Jepson and Deaville 2009). 
Strandings Associated with Impulsive Sound

Silver Strand

    During a Navy training event on March 4, 2011 at the Silver Strand 
Training Complex in San Diego, California, three or possibly four 
dolphins were killed in an explosion. During an underwater detonation 
training event, a pod of 100 to 150 long-beaked common dolphins were 
observed moving towards the 700-yd (640.1 m) exclusion zone around the 
explosive charge, monitored by personnel in a safety boat and 
participants in a dive boat. Approximately 5 minutes remained on a 
time-delay fuse connected to a single 8.76 lbs (3.97 kg) explosive 
charge (C-4 and detonation cord). Although the dive boat was placed 
between the pod and the explosive in an effort to guide the dolphins 
away from the area, that effort was unsuccessful and three long-beaked 
common dolphins near the explosion died. In addition to the three 
dolphins found dead on March 4, the remains of a fourth dolphin were 
discovered on March 7, 2011 near Oceanside, California (3 days later 
and approximately 68 km north of the detonation), which might also have 
been related to this event. Association of the fourth stranding with 
the training event is uncertain because dolphins strand on a regular 
basis in the San Diego area. Details such as the dolphins' depth and 
distance from the explosive at the time of the detonation could not be 
estimated from the 250 yd (228.6 m) standoff point of the observers in 
the dive boat or the safety boat.
    These dolphin mortalities are the only known occurrence of a U.S. 
Navy training or testing event involving impulsive energy (underwater 
detonation) that caused mortality or injury to a marine mammal. Despite 
this being a rare occurrence, NMFS and the Navy reviewed training 
requirements, safety procedures, and possible mitigation measures and 
implemented changes to reduce the potential for this to occur in the 
future--specifically increasing the size of the exclusion zone to 
better account for the time-delay fuse and the distance that marine 
mammals might travel during the time delay. Discussions of procedures 
associated with in-air explosives at or above the water surface during 
training are presented in the Proposed Mitigation Measures section.

Kyle of Durness, Scotland

    On July 22, 2011 a mass stranding event involving long-finned pilot 
whales occurred at Kyle of Durness, Scotland. An investigation by 
Brownlow et al. (2015) considered unexploded ordnance detonation 
activities at a Ministry of Defense bombing range, conducted by the 
Royal Navy prior to and during the strandings, as a plausible 
contributing factor in the mass stranding event. While Brownlow et al. 
(2015) concluded that the serial detonations of underwater ordnance 
were an influential factor in the mass stranding event (along with the 
presence of a potentially compromised animal and navigational error in 
a topographically complex region), they also suggest that mitigation 
measures--which included observations from a zodiac only and by 
personnel not experienced in marine mammal observation, among other 
deficiencies--were likely insufficient to assess if cetaceans were in 
the vicinity of the detonations. The authors also cite information from 
the Ministry of Defense indicating ``an extraordinarily high level of 
activity'' (i.e., frequency and intensity of underwater explosions) on 
the range in the days leading up to the stranding.

[[Page 49693]]

Strandings Associated With Active Sonar
    Over the past 21 years, there have been five stranding events 
coincident with naval MF active sonar use in which exposure to sonar is 
believed to have been a contributing factor: Greece (1996); the Bahamas 
(2000); Madeira (2000); Canary Islands (2002); and Spain (2006) (Cox et 
al., 2006; Fernandez, 2006; U.S. Navy Marine Mammal Program & Space and 
Naval Warfare Systems Command Center Pacific, 2017). These five mass 
strandings have resulted in about 40 known cetacean deaths consisting 
mostly of beaked whales and with close linkages to mid-frequency active 
sonar activity. In these circumstances, exposure to non-impulsive 
acoustic energy was considered a potential indirect cause of death of 
the marine mammals (Cox et al., 2006). Only one of these stranding 
events, the Bahamas (2000), was associated with exercises conducted by 
the U.S. Navy. Additionally, in 2004, during the Rim of the Pacific 
(RIMPAC) exercises, between 150 and 200 usually pelagic melon-headed 
whales occupied the shallow waters of Hanalei Bay, Kauai, Hawaii for 
over 28 hours. NMFS determined that MFAS was a plausible, if not 
likely, contributing factor in what may have been a confluence of 
events that led to the Hanalei Bay stranding. A number of other 
stranding events coincident with the operation of MFAS, including the 
death of beaked whales or other species (minke whales, dwarf sperm 
whales, pilot whales), have been reported; however, the majority have 
not been investigated to the degree necessary to determine the cause of 
the stranding. Most recently, the Independent Scientific Review Panel 
investigating potential contributing factors to a 2008 mass stranding 
of melon-headed whales in Antsohihy, Madagascar released its final 
report suggesting that the stranding was likely initially triggered by 
an industry seismic survey (Southall et al., 2013). This report 
suggests that the operation of a commercial high-powered 12 kHz multi-
beam echosounder during an industry seismic survey was a plausible and 
likely initial trigger that caused a large group of melon-headed whales 
to leave their typical habitat and then ultimately strand as a result 
of secondary factors such as malnourishment and dehydration. The report 
indicates that the risk of this particular convergence of factors and 
ultimate outcome is likely very low, but recommends that the potential 
be considered in environmental planning. Because of the association 
between tactical mid-frequency active sonar use and a small number of 
marine mammal strandings, the Navy and NMFS have been considering and 
addressing the potential for strandings in association with Navy 
activities for years. In addition to the proposed mitigation measures 
intended to more broadly minimize impacts to marine mammals, the Navy 
would abide by the Notification and Reporting Plan, which sets out 
notification, reporting, and other requirements when dead, injured, or 
stranded marine mammals are detected in certain circumstances.

Greece (1996)

    Twelve Cuvier's beaked whales stranded atypically (in both time and 
space) along a 38.2-km strand of the Kyparissiakos Gulf coast on May 12 
and 13, 1996 (Frantzis, 1998). From May 11 through May 15, the North 
Atlantic Treaty Organization (NATO) research vessel Alliance was 
conducting sonar tests with signals of 600 Hz and 3 kHz and source 
levels of 228 and 226 dB re: 1[mu]Pa, respectively (D'Amico and 
Verboom, 1998; D'Spain et al., 2006). The timing and location of the 
testing encompassed the time and location of the strandings (Frantzis, 
1998).
    Necropsies of eight of the animals were performed but were limited 
to basic external examination and sampling of stomach contents, blood, 
and skin. No ears or organs were collected, and no histological samples 
were preserved. No significant apparent abnormalities or wounds were 
found, however examination of photos of the animals, taken soon after 
their death, revealed that the eyes of at least four of the individuals 
were bleeding (Frantzis, 2004). Stomach contents contained the flesh of 
cephalopods, indicating that feeding had recently taken place 
(Frantzis, 1998).
    All available information regarding the conditions associated with 
this stranding event was compiled, and many potential causes were 
examined including major pollution events, prominent tectonic activity, 
unusual physical or meteorological events, magnetic anomalies, 
epizootics, and conventional military activities (International Council 
for the Exploration of the Sea, 2005a). However, none of these 
potential causes coincided in time or space with the mass stranding, or 
could explain its characteristics (International Council for the 
Exploration of the Sea, 2005a). The robust condition of the animals, 
plus the recent stomach contents, is inconsistent with pathogenic 
causes. In addition, environmental causes can be ruled out as there 
were no unusual environmental circumstances or events before or during 
this time period and within the general proximity (Frantzis, 2004).
    Because of the rarity of this mass stranding of Cuvier's beaked 
whales in the Kyparissiakos Gulf (first one in historical records), the 
probability for the two events (the military exercises and the 
strandings) to coincide in time and location, while being independent 
of each other, was thought to be extremely low (Frantzis, 1998). 
However, because full necropsies had not been conducted, and no 
abnormalities were noted, the cause of the strandings could not be 
precisely determined (Cox et al., 2006). A Bioacoustics Panel convened 
by NATO concluded that the evidence available did not allow them to 
accept or reject sonar exposures as a causal agent in these stranding 
events. The analysis of this stranding event provided support for, but 
no clear evidence for, the cause-and-effect relationship of tactical 
sonar training activities and beaked whale strandings (Cox et al., 
2006).

Bahamas (2000)

    NMFS and the Navy prepared a joint report addressing the multi-
species stranding in the Bahamas in 2000, which took place within 24 
hours of U.S. Navy ships using MFAS as they passed through the 
Northeast and Northwest Providence Channels on March 15-16, 2000. The 
ships, which operated both AN/SQS-53C and AN/SQS-56, moved through the 
channel while emitting sonar pings approximately every 24 seconds. Of 
the 17 cetaceans that stranded over a 36-hour period (Cuvier's beaked 
whales, Blainville's beaked whales, minke whales, and a spotted 
dolphin), seven animals died on the beach (five Cuvier's beaked whales, 
one Blainville's beaked whale, and the spotted dolphin), while the 
other 10 were returned to the water alive (though their ultimate fate 
is unknown). As discussed in the Bahamas report (DOC/DON, 2001), there 
is no likely association between the minke whale and spotted dolphin 
strandings and the operation of MFAS.
    Necropsies were performed on five of the stranded beaked whales. 
All five necropsied beaked whales were in good body condition, showing 
no signs of infection, disease, ship strike, blunt trauma, or fishery 
related injuries, and three still had food remains in their stomachs. 
Auditory structural damage was discovered in four of the whales, 
specifically bloody effusions or hemorrhaging around the ears. 
Bilateral intracochlear and unilateral temporal region subarachnoid 
hemorrhage, with blood clots in the lateral ventricles,

[[Page 49694]]

were found in two of the whales. Three of the whales had small 
hemorrhages in their acoustic fats (located along the jaw and in the 
melon).
    A comprehensive investigation was conducted and all possible causes 
of the stranding event were considered, whether they seemed likely at 
the outset or not. Based on the way in which the strandings coincided 
with ongoing naval activity involving tactical MFAS use, in terms of 
both time and geography, the nature of the physiological effects 
experienced by the dead animals, and the absence of any other acoustic 
sources, the investigation team concluded that MFAS aboard U.S. Navy 
ships that were in use during the active sonar exercise in question 
were the most plausible source of this acoustic or impulse trauma to 
beaked whales. This sound source was active in a complex environment 
that included the presence of a surface duct, unusual and steep 
bathymetry, a constricted channel with limited egress, intensive use of 
multiple, active sonar units over an extended period of time, and the 
presence of beaked whales that appear to be sensitive to the 
frequencies produced by these active sonars. The investigation team 
concluded that the cause of this stranding event was the confluence of 
the Navy MFAS and these contributory factors working together, and 
further recommended that the Navy avoid operating MFAS in situations 
where these five factors would be likely to occur. This report does not 
conclude that all five of these factors must be present for a stranding 
to occur, nor that beaked whales are the only species that could 
potentially be affected by the confluence of the other factors. Based 
on this, NMFS believes that the operation of MFAS in situations where 
surface ducts exist, or in marine environments defined by steep 
bathymetry and/or constricted channels may increase the likelihood of 
producing a sound field with the potential to cause cetaceans 
(especially beaked whales) to strand, and therefore, suggests the need 
for increased vigilance while operating MFAS in these areas, especially 
when beaked whales (or potentially other deep divers) are likely 
present.

Madeira, Portugal (2000)

    From May 10-14, 2000, three Cuvier's beaked whales were found 
atypically stranded on two islands in the Madeira archipelago, Portugal 
(Cox et al., 2006). A fourth animal was reported floating in the 
Madeiran waters by a fisherman but did not come ashore (Woods Hole 
Oceanographic Institution, 2005). Joint NATO amphibious training 
peacekeeping exercises involving participants from 17 countries and 80 
warships, took place in Portugal during May 2-15, 2000.
    The bodies of the three stranded whales were examined post mortem 
(Woods Hole Oceanographic Institution, 2005), though only one of the 
stranded whales was fresh enough (24 hours after stranding) to be 
necropsied (Cox et al., 2006). Results from the necropsy revealed 
evidence of hemorrhage and congestion in the right lung and both 
kidneys (Cox et al., 2006). There was also evidence of intercochlear 
and intracranial hemorrhage similar to that which was observed in the 
whales that stranded in the Bahamas event (Cox et al., 2006). There 
were no signs of blunt trauma, and no major fractures (Woods Hole 
Oceanographic Institution, 2005). The cranial sinuses and airways were 
found to be clear with little or no fluid deposition, which may 
indicate good preservation of tissues (Woods Hole Oceanographic 
Institution, 2005).
    Several observations on the Madeira stranded beaked whales, such as 
the pattern of injury to the auditory system, are the same as those 
observed in the Bahamas strandings. Blood in and around the eyes, 
kidney lesions, pleural hemorrhages, and congestion in the lungs are 
particularly consistent with the pathologies from the whales stranded 
in the Bahamas, and are consistent with stress and pressure related 
trauma. The similarities in pathology and stranding patterns between 
these two events suggest that a similar pressure event may have 
precipitated or contributed to the strandings at both sites (Woods Hole 
Oceanographic Institution, 2005).
    Even though no definitive causal link can be made between the 
stranding event and naval exercises, certain conditions may have 
existed in the exercise area that, in their aggregate, may have 
contributed to the marine mammal strandings (Freitas, 2004): exercises 
were conducted in areas of at least 547 fathoms (1,000 m) depth near a 
shoreline where there is a rapid change in bathymetry on the order of 
547 to 3,281 fathoms (1,000 to 6,000 m) occurring across a relatively 
short horizontal distance (Freitas, 2004); multiple ships were 
operating around Madeira, though it is not known if MFAS was used, and 
the specifics of the sound sources used are unknown (Cox et al., 2006, 
Freitas, 2004); and exercises took place in an area surrounded by 
landmasses separated by less than 35 nmi (65 km) and at least 10 nmi 
(19 km) in length, or in an embayment. Exercises involving multiple 
ships employing MFAS near land may produce sound directed towards a 
channel or embayment that may cut off the lines of egress for marine 
mammals (Freitas, 2004).

Canary Islands, Spain (2002)

    The southeastern area within the Canary Islands is well known for 
aggregations of beaked whales due to its ocean depths of greater than 
547 fathoms (1,000 m) within a few hundred meters of the coastline 
(Fernandez et al., 2005). On September 24, 2002, 14 beaked whales were 
found stranded on Fuerteventura and Lanzarote Islands in the Canary 
Islands (International Council for Exploration of the Sea, 2005a). 
Seven whales died, while the remaining seven live whales were returned 
to deeper waters (Fernandez et al., 2005). Four beaked whales were 
found stranded dead over the next 3 days either on the coast or 
floating offshore. These strandings occurred within close proximity of 
an international naval exercise that utilized MFAS and involved 
numerous surface warships and several submarines. Strandings began 
about 4 hours after the onset of MFAS activity (International Council 
for Exploration of the Sea, 2005a; Fernandez et al., 2005).
    Eight Cuvier's beaked whales, one Blainville's beaked whale, and 
one Gervais' beaked whale were necropsied, 6 of them within 12 hours of 
stranding (Fernandez et al., 2005). No pathogenic bacteria were 
isolated from the carcasses (Jepson et al., 2003). The animals 
displayed severe vascular congestion and hemorrhage especially around 
the tissues in the jaw, ears, brain, and kidneys, displaying marked 
disseminated microvascular hemorrhages associated with widespread fat 
emboli (Jepson et al., 2003; International Council for Exploration of 
the Sea, 2005a). Several organs contained intravascular bubbles, 
although definitive evidence of gas embolism in vivo is difficult to 
determine after death (Jepson et al., 2003). The livers of the 
necropsied animals were the most consistently affected organ, which 
contained macroscopic gas-filled cavities and had variable degrees of 
fibrotic encapsulation. In some animals, cavitary lesions had 
extensively replaced the normal tissue (Jepson et al., 2003). Stomachs 
contained a large amount of fresh and undigested contents, suggesting a 
rapid onset of disease and death (Fernandez et al., 2005). Head and 
neck lymph nodes were enlarged and congested, and parasites were found 
in the kidneys of all animals (Fernandez et al., 2005).
    The association of NATO MFAS use close in space and time to the 
beaked

[[Page 49695]]

whale strandings, and the similarity between this stranding event and 
previous beaked whale mass strandings coincident with sonar use, 
suggests that a similar scenario and causative mechanism of stranding 
may be shared between the events. Beaked whales stranded in this event 
demonstrated brain and auditory system injuries, hemorrhages, and 
congestion in multiple organs, similar to the pathological findings of 
the Bahamas and Madeira stranding events. In addition, the necropsy 
results of the Canary Islands stranding event lead to the hypothesis 
that the presence of disseminated and widespread gas bubbles and fat 
emboli were indicative of nitrogen bubble formation, similar to what 
might be expected in decompression sickness (Jepson et al., 2003; 
Fern[aacute]ndez et al., 2005).

Hanalei Bay, Hawaii (2004)

    On July 3 and 4, 2004, approximately 150 to 200 melon-headed whales 
occupied the shallow waters of Hanalei Bay, Kauai, Hawaii for over 28 
hours. Attendees of a canoe blessing observed the animals entering the 
Bay in a single wave formation at 7 a.m. on July 3, 2004. The animals 
were observed moving back into the shore from the mouth of the Bay at 9 
a.m. The usually pelagic animals milled in the shallow bay and were 
returned to deeper water with human assistance beginning at 9:30 a.m. 
on July 4, 2004, and were out of sight by 10:30 a.m.
    Only one animal, a calf, was known to have died following this 
event. The animal was noted alive and alone in the Bay on the afternoon 
of July 4, 2004, and was found dead in the Bay the morning of July 5, 
2004. A full necropsy, magnetic resonance imaging, and computerized 
tomography examination were performed on the calf to determine the 
manner and cause of death. The combination of imaging, necropsy, and 
histological analyses found no evidence of infectious, internal 
traumatic, congenital, or toxic factors. Cause of death could not be 
definitively determined, but it is likely that maternal separation, 
poor nutritional condition, and dehydration contributed to the final 
demise of the animal. Although it is not known when the calf was 
separated from its mother, the animals' movement into the Bay and 
subsequent milling and re-grouping may have contributed to the 
separation or lack of nursing, especially if the maternal bond was weak 
or this was an inexperienced mother with her first calf.
    Environmental factors, abiotic and biotic, were analyzed for any 
anomalous occurrences that would have contributed to the animals 
entering and remaining in Hanalei Bay. The Bay's bathymetry is similar 
to many other sites within the Hawaiian Island chain and dissimilar to 
sites that have been associated with mass strandings in other parts of 
the United States. The weather conditions appeared to be normal for 
that time of year with no fronts or other significant features noted. 
There was no evidence of unusual distribution, occurrence of predator 
or prey species, or unusual harmful algal blooms, although Mobley et 
al. (2007) suggested that the full moon cycle that occurred at that 
time may have influenced a run of squid into the Bay. Weather patterns 
and bathymetry that have been associated with mass strandings elsewhere 
were not found to occur in this instance.
    The Hanalei event was spatially and temporally correlated with 
RIMPAC. Official sonar training and tracking exercises in the Pacific 
Missile Range Facility (PMRF) warning area did not commence until 
approximately 8 a.m. on July 3 and were thus ruled out as a possible 
trigger for the initial movement into the Bay. However, six naval 
surface vessels transiting to the operational area on July 2 
intermittently transmitted active sonar (for approximately 9 hours 
total from 1:15 p.m. to 12:30 a.m.) as they approached from the south. 
The potential for these transmissions to have triggered the whales' 
movement into Hanalei Bay was investigated. Analyses with the 
information available indicated that animals to the south and east of 
Kaua'i could have detected active sonar transmissions on July 2, and 
reached Hanalei Bay on or before 7 a.m. on July 3. However, data 
limitations regarding the position of the whales prior to their arrival 
in the Bay, the magnitude of sonar exposure, behavioral responses of 
melon-headed whales to acoustic stimuli, and other possible relevant 
factors preclude a conclusive finding regarding the role of sonar in 
triggering this event. Propagation modeling suggests that transmissions 
from sonar use during the July 3 exercise in the PMRF warning area may 
have been detectable at the mouth of the Bay. If the animals responded 
negatively to these signals, it may have contributed to their continued 
presence in the Bay. The U.S. Navy ceased all active sonar 
transmissions during exercises in this range on the afternoon of July 
3. Subsequent to the cessation of sonar use, the animals were herded 
out of the Bay.
    While causation of this stranding event may never be unequivocally 
determined, NMFS considers the active sonar transmissions of July 2-3, 
2004, a plausible, if not likely, contributing factor in what may have 
been a confluence of events. This conclusion is based on the following: 
(1) the evidently anomalous nature of the stranding; (2) its close 
spatiotemporal correlation with wide-scale, sustained use of sonar 
systems previously associated with stranding of deep-diving marine 
mammals; (3) the directed movement of two groups of transmitting 
vessels toward the southeast and southwest coast of Kauai; (4) the 
results of acoustic propagation modeling and an analysis of possible 
animal transit times to the Bay; and (5) the absence of any other 
compelling causative explanation. The initiation and persistence of 
this event may have resulted from an interaction of biological and 
physical factors. The biological factors may have included the presence 
of an apparently uncommon, deep-diving cetacean species (and possibly 
an offshore, non-resident group), social interactions among the animals 
before or after they entered the Bay, and/or unknown predator or prey 
conditions. The physical factors may have included the presence of 
nearby deep water, multiple vessels transiting in a directed manner 
while transmitting active sonar over a sustained period, the presence 
of surface sound ducting conditions, and/or intermittent and random 
human interactions while the animals were in the Bay.
    A separate event involving melon-headed whales and rough-toothed 
dolphins took place over the same period of time in the Northern 
Mariana Islands (Jefferson et al., 2006), which is several thousand 
miles from Hawaii. Some 500 to 700 melon-headed whales came into 
Sasanhaya Bay on July 4, 2004, near the island of Rota and then left of 
their own accord after 5.5 hours; no known active sonar transmissions 
occurred in the vicinity of that event. The Rota incident led to 
scientific debate regarding what, if any, relationship the event had to 
the simultaneous events in Hawaii and whether they might be related by 
some common factor (e.g., there was a full moon on July 2, 2004, as 
well as during other melon-headed whale strandings and nearshore 
aggregations (Brownell et al., 2009; Lignon et al., 2007; Mobley et 
al., 2007). Brownell et al. (2009) compared the two incidents, along 
with one other stranding incident at Nuka Hiva in French Polynesia and 
normal resting behaviors observed at Palmyra Island, in regard to 
physical features in the areas, melon-headed whale behavior, and lunar 
cycles. Brownell et al., (2009) concluded that the rapid entry of the 
whales into Hanalei Bay,

[[Page 49696]]

their movement into very shallow water far from the 100-m contour, 
their milling behavior (typical pre-stranding behavior), and their 
reluctance to leave the Bay constituted an unusual event that was not 
similar to the events that occurred at Rota, which appear to be similar 
to observations of melon-headed whales resting normally at Palmyra 
Island. Additionally, there was no correlation between lunar cycle and 
the types of behaviors observed in the Brownell et al. (2009) examples.

Spain (2006)

    The Spanish Cetacean Society reported an atypical mass stranding of 
four beaked whales that occurred January 26, 2006, on the southeast 
coast of Spain, near Moj[aacute]car (Gulf of Vera) in the Western 
Mediterranean Sea. According to the report, two of the whales were 
discovered the evening of January 26 and were found to be still alive. 
Two other whales were discovered during the day on January 27, but had 
already died. The first three animals were located near the town of 
Moj[aacute]car and the fourth animal was found dead, a few kilometers 
north of the first three animals. From January 25-26, 2006, Standing 
NATO Response Force Maritime Group Two (five of seven ships including 
one U.S. ship under NATO Operational Control) had conducted active 
sonar training against a Spanish submarine within 50 nmi (93 km) of the 
stranding site.
    Veterinary pathologists necropsied the two male and two female 
Cuvier's beaked whales. According to the pathologists, the most likely 
primary cause of this type of beaked whale mass stranding event was 
anthropogenic acoustic activities, most probably anti-submarine MFAS 
used during the military naval exercises. However, no positive acoustic 
link was established as a direct cause of the stranding. Even though no 
causal link can be made between the stranding event and naval 
exercises, certain conditions may have existed in the exercise area 
that, in their aggregate, may have contributed to the marine mammal 
strandings (Freitas, 2004). Exercises were conducted in areas of at 
least 547 fathoms (1,000 m) depth near a shoreline where there is a 
rapid change in bathymetry on the order of 547 to 3,281 fathoms (1,000 
to 6,000 m) occurring across a relatively short horizontal distance 
(Freitas, 2004). Multiple ships (in this instance, five) were operating 
MFAS in the same area over extended periods of time (in this case, 20 
hours) in close proximity; and exercises took place in an area 
surrounded by landmasses, or in an embayment. Exercises involving 
multiple ships employing MFAS near land may have produced sound 
directed towards a channel or embayment that may have cut off the lines 
of egress for the affected marine mammals (Freitas, 2004).
Behaviorally Mediated Responses to MFAS That May Lead to Stranding
    Although the confluence of Navy MFAS with the other contributory 
factors noted in the 2001 NMFS/Navy joint report was identified as the 
cause of the 2000 Bahamas stranding event, the specific mechanisms that 
led to that stranding (or the others) are not well understood, and 
there is uncertainty regarding the ordering of effects that led to the 
stranding. It is unclear whether beaked whales were directly injured by 
sound (e.g., acoustically mediated bubble growth, as addressed above) 
prior to stranding or whether a behavioral response to sound occurred 
that ultimately caused the beaked whales to be injured and strand.
    Although causal relationships between beaked whale stranding events 
and active sonar remain unknown, several authors have hypothesized that 
stranding events involving these species in the Bahamas and Canary 
Islands may have been triggered when the whales changed their dive 
behavior in a startled response to exposure to active sonar or to 
further avoid exposure (Cox et al., 2006; Rommel et al., 2006). These 
authors proposed three mechanisms by which the behavioral responses of 
beaked whales upon being exposed to active sonar might result in a 
stranding event. These include the following: gas bubble formation 
caused by excessively fast surfacing; remaining at the surface too long 
when tissues are supersaturated with nitrogen; or diving prematurely 
when extended time at the surface is necessary to eliminate excess 
nitrogen. More specifically, beaked whales that occur in deep waters 
that are in close proximity to shallow waters (for example, the 
``canyon areas'' that are cited in the Bahamas stranding event; see 
D'Spain and D'Amico, 2006), may respond to active sonar by swimming 
into shallow waters to avoid further exposures and strand if they were 
not able to swim back to deeper waters. Second, beaked whales exposed 
to active sonar might alter their dive behavior. Changes in their dive 
behavior might cause them to remain at the surface or at depth for 
extended periods of time which could lead to hypoxia directly by 
increasing their oxygen demands or indirectly by increasing their 
energy expenditures (to remain at depth) and increase their oxygen 
demands as a result. If beaked whales are at depth when they detect a 
ping from an active sonar transmission and change their dive profile, 
this could lead to the formation of significant gas bubbles, which 
could damage multiple organs or interfere with normal physiological 
function (Cox et al., 2006; Rommel et al., 2006; Zimmer and Tyack, 
2007). Baird et al. (2005) found that slow ascent rates from deep dives 
and long periods of time spent within 50 m of the surface were typical 
for both Cuvier's and Blainville's beaked whales, the two species 
involved in mass strandings related to naval sonar. These two 
behavioral mechanisms may be necessary to purge excessive dissolved 
nitrogen concentrated in their tissues during their frequent long dives 
(Baird et al., 2005). Baird et al. (2005) further suggests that 
abnormally rapid ascents or premature dives in response to high-
intensity sonar could indirectly result in physical harm to the beaked 
whales, through the mechanisms described above (gas bubble formation or 
non-elimination of excess nitrogen). In a review of the previously 
published data on the potential impacts of sonar on beaked whales, 
Bernaldo de Quir[oacute]s et al. (2019) suggested that the effect of 
mid-frequency active sonar on beaked whales varies among individuals or 
populations, and that predisposing conditions such as previous exposure 
to sonar and individual health risk factors may contribute to 
individual outcomes (such as decompression sickness).
    Because many species of marine mammals make repetitive and 
prolonged dives to great depths, it has long been assumed that marine 
mammals have evolved physiological mechanisms to protect against the 
effects of rapid and repeated decompressions. Although several 
investigators have identified physiological adaptations that may 
protect marine mammals against nitrogen gas supersaturation (alveolar 
collapse and elective circulation; Kooyman et al., 1972; Ridgway and 
Howard, 1979), Ridgway and Howard (1979) reported that bottlenose 
dolphins that were trained to dive repeatedly had muscle tissues that 
were substantially supersaturated with nitrogen gas. Houser et al. 
(2001b) used these data to model the accumulation of nitrogen gas 
within the muscle tissue of other marine mammal species and concluded 
that cetaceans that dive deep and have slow ascent or descent speeds 
would have tissues that are more supersaturated with nitrogen gas than 
other marine mammals. Based on these data, Cox et al. (2006) 
hypothesized that a critical dive sequence might make beaked

[[Page 49697]]

whales more prone to stranding in response to acoustic exposures. The 
sequence began with (1) very deep (to depths as deep as 2 km) and long 
(as long as 90 minutes) foraging dives; (2) relatively slow, controlled 
ascents; and (3) a series of ``bounce'' dives between 100 and 400 m in 
depth (see also Zimmer and Tyack, 2007). They concluded that acoustic 
exposures that disrupted any part of this dive sequence (for example, 
causing beaked whales to spend more time at surface without the bounce 
dives that are necessary to recover from the deep dive) could produce 
excessive levels of nitrogen supersaturation in their tissues, leading 
to gas bubble and emboli formation that produces pathologies similar to 
decompression sickness.
    Zimmer and Tyack (2007) modeled nitrogen tension and bubble growth 
in several tissue compartments for several hypothetical dive profiles 
and concluded that repetitive shallow dives (defined as a dive where 
depth does not exceed the depth of alveolar collapse, approximately 72 
m for Cuvier's beaked whale), perhaps as a consequence of an extended 
avoidance reaction to sonar sound, could pose a risk for decompression 
sickness and that this risk should increase with the duration of the 
response. Their models also suggested that unrealistically rapid rates 
of ascent from normal dive behaviors are unlikely to result in 
supersaturation to the extent that bubble formation would be expected. 
Tyack et al. (2006) suggested that emboli observed in animals exposed 
to mid-frequency range sonar (Jepson et al., 2003; Fernandez et al., 
2005; Fern[aacute]ndez et al., 2012) could stem from a behavioral 
response that involves repeated dives shallower than the depth at which 
lung collapse occurs. Given that nitrogen gas accumulation is a passive 
process (i.e., nitrogen is metabolically inert), a bottlenose dolphin 
was trained to repetitively dive a profile predicted to elevate 
nitrogen saturation to the point that nitrogen bubble formation was 
predicted to occur. However, inspection of the vascular system of the 
dolphin via ultrasound did not demonstrate the formation of 
asymptomatic nitrogen gas bubbles (Houser et al., 2007). Baird et al. 
(2008), in a beaked whale tagging study off Hawaii, showed that deep 
dives are equally common during day or night, but ``bounce dives'' are 
typically a daytime behavior, possibly associated with visual predator 
avoidance. This may indicate that ``bounce dives'' are associated with 
something other than behavioral regulation of dissolved nitrogen 
levels, which would be necessary day and night.
    If marine mammals respond to a Navy vessel that is transmitting 
active sonar in the same way that they might respond to a predator, 
their probability of flight responses could increase when they perceive 
that Navy vessels are approaching them directly, because a direct 
approach may convey detection and intent to capture (Burger and 
Gochfeld, 1981, 1990; Cooper, 1997, 1998). Please see the Flight 
Response section of this proposed rule for additional discussion.
    Despite the many theories involving bubble formation (both as a 
direct cause of injury, see Acoustically-Induced Bubble Formation Due 
to Sonars and Other Pressure-related Injury section and an indirect 
cause of stranding), Southall et al. (2007) summarizes that there is 
either scientific disagreement or a lack of information regarding each 
of the following important points: (1) received acoustical exposure 
conditions for animals involved in stranding events; (2) pathological 
interpretation of observed lesions in stranded marine mammals; (3) 
acoustic exposure conditions required to induce such physical trauma 
directly; (4) whether noise exposure may cause behavioral reactions 
(such as atypical diving behavior) that secondarily cause bubble 
formation and tissue damage; and (5) the extent the post mortem 
artifacts introduced by decomposition before sampling, handling, 
freezing, or necropsy procedures affect interpretation of observed 
lesions.
Strandings in the GOA Study Area
    Stranded marine mammals are reported along the entire western coast 
of the United States each year. Marine mammals strand due to natural or 
anthropogenic causes; the majority of reported type of occurrences in 
marine mammal strandings in the Pacific include fisheries interactions, 
entanglement, vessel strike, and predation (Carretta et al., 2019a; 
Carretta et al., 2019b; Carretta et al., 2017a; Helker et al., 2019; 
Helker et al., 2017; NOAA, 2018, 2019). Stranding events that are 
associated with active UMEs in Alaska (inclusive of the GOA Study Area) 
were previously discussed in the Description of Marine Mammals and 
Their Habitat in the Area of the Specified Activities section.
    In 2020, there were 65 confirmed strandings reported in the Gulf of 
Alaska (Savage, 2021). Of these strandings, 43 were cetaceans; 20 of 
the stranded cetaceans were gray whales, which as discussed in the 
Description of Marine Mammals and Their Habitat in the Area of the 
Specified Activities section of this proposed rule, are affected by a 
UME. Of the 2020 confirmed reports involving human interaction, most 
reports indicated an entanglement. Naval sonar has been identified as a 
contributing factor in a small number of strandings as discussed above; 
however, none of these have occurred in the GOA Study Area.

Potential Effects of Vessel Strike

    Vessel collisions with marine mammals, also referred to as vessel 
strikes or ship strikes, can result in death or serious injury of the 
animal. Wounds resulting from ship strike may include massive trauma, 
hemorrhaging, broken bones, or propeller lacerations (Knowlton and 
Kraus, 2001). An animal at the surface could be struck directly by a 
vessel, a surfacing animal could hit the bottom of a vessel, or an 
animal just below the surface could be cut by a vessel's propeller. 
Superficial strikes may not kill or result in the death of the animal. 
Lethal interactions are typically associated with large whales, which 
are occasionally found draped across the bulbous bow of large 
commercial ships upon arrival in port. Although smaller cetaceans are 
more maneuverable in relation to large vessels than are large whales, 
as a general matter they may also be susceptible to strike.
    The most vulnerable marine mammals are those that spend extended 
periods of time at the surface in order to restore oxygen levels within 
their tissues after deep dives (e.g., the sperm whale). In one recent 
case, an Australian naval vessel struck both a mother fin whale and 
calf off the coast of California. In addition, some baleen whales seem 
generally unresponsive to vessel sound, making them more susceptible to 
vessel collisions (Nowacek et al., 2004). These species are primarily 
large, slow moving whales. Marine mammal responses to vessels may 
include avoidance and changes in dive pattern (NRC, 2003).
    Some researchers have suggested the relative risk of a vessel 
strike can be assessed as a function of animal density and the 
magnitude of vessel traffic (e.g., Fonnesbeck et al., 2008; Vanderlaan 
et al., 2008). Differences among vessel types also influence the 
probability of a vessel strike. The ability of any ship to detect a 
marine mammal and avoid a collision depends on a variety of factors, 
including environmental conditions, ship design, size, speed, and 
ability and number of personnel observing, as well as the behavior of 
the animal.
    An examination of all known ship strikes from all shipping sources 
(civilian and military) indicates vessel speed is a principal factor in 
whether a

[[Page 49698]]

vessel strike occurs and, if so, whether it results in injury, serious 
injury, or mortality (Knowlton and Kraus, 2001; Laist et al., 2001; 
Jensen and Silber, 2003; Pace and Silber, 2005; Vanderlaan and Taggart, 
2007; Conn and Silber 2013). Impact forces increase with speed, as does 
the probability of a strike at a given distance (Silber et al., 2010; 
Gende et al., 2011). For large vessels, speed and angle of approach can 
influence the severity of a strike. In assessing records in which 
vessel speed was known, Laist et al. (2001) found a direct relationship 
between the occurrence of a whale strike and the speed of the vessel 
involved in the collision. The authors concluded that most deaths 
occurred when a vessel was traveling in excess of 13 kn.
    Jensen and Silber (2003) detailed 292 records of known or probable 
ship strikes of all large whale species from 1975 to 2002. Of these, 
vessel speed at the time of collision was reported for 58 cases. Of 
these 58 cases, 39 (or 67 percent) resulted in serious injury or death 
(19 of those resulted in serious injury as determined by blood in the 
water, propeller gashes or severed tailstock, and fractured skull, jaw, 
vertebrae, hemorrhaging, massive bruising or other injuries noted 
during necropsy and 20 resulted in death). Operating speeds of vessels 
that struck various species of large whales ranged from 2 to 51 kn. The 
majority (79 percent) of these strikes occurred at speeds of 13 kn or 
greater. The average speed that resulted in serious injury or death was 
18.6 kn. Pace and Silber (2005) found that the probability of death or 
serious injury increased rapidly with increasing vessel speed. 
Specifically, the predicted probability of serious injury or death 
increased from 45 to 75 percent as vessel speed increased from 10 to 14 
kn, and exceeded 90 percent at 17 kn. Higher speeds during collisions 
result in greater force of impact and also appear to increase the 
chance of severe injuries or death. While modeling studies have 
suggested that hydrodynamic forces pulling whales toward the vessel 
hull increase with increasing speed (Clyne, 1999; Knowlton et al., 
1995), this is inconsistent with Silber et al. (2010), which 
demonstrated that there is no such relationship (i.e., hydrodynamic 
forces are independent of speed).
    In a separate study, Vanderlaan and Taggart (2007) analyzed the 
probability of lethal mortality of large whales at a given speed, 
showing that the greatest rate of change in the probability of a lethal 
injury to a large whale as a function of vessel speed occurs between 
8.6 and 15 kn. The chances of a lethal injury decline from 
approximately 80 percent at 15 kn to approximately 20 percent at 8.6 
kn. At speeds below 11.8 kn, the chances of lethal injury drop below 50 
percent, while the probability asymptotically increases toward 100 
percent above 15 kn.
    Large whales also do not have to be at the water's surface to be 
struck. Silber et al. (2010) found when a whale is below the surface 
(about one to two times the vessel draft), there is likely to be a 
pronounced propeller suction effect. This suction effect may draw the 
whale into the hull of the ship, increasing the probability of 
propeller strikes.
    The Jensen and Silber (2003) report notes that the Large Whale Ship 
Strike Database represents a minimum number of collisions, because the 
vast majority probably goes undetected or unreported. In contrast, Navy 
personnel are more likely to detect any strike that does occur because 
of the required personnel training and Lookouts (as described in the 
Proposed Mitigation Measures section), and they are required to report 
all ship strikes involving marine mammals.
    There are some key differences between the operation of military 
and non-military vessels, which make the likelihood of a military 
vessel striking a whale lower than some other vessels (e.g., commercial 
merchant vessels), although as noted above strikes by naval vessels can 
occur. Key differences include:
     many military ships have their bridges positioned closer 
to the bow, offering better visibility ahead of the ship (compared to a 
commercial merchant vessel);
     there are often aircraft associated with the training 
activity (which can serve as Lookouts), which can more readily detect 
cetaceans in the vicinity of a vessel or ahead of a vessel's present 
course before crew on the vessel would be able to detect them;
     military ships are generally more maneuverable than 
commercial merchant vessels, and if cetaceans are spotted in the path 
of the ship, could be capable of changing course more quickly;
     the crew size on military vessels is generally larger than 
merchant ships, allowing for stationing more trained Lookouts on the 
bridge. At all times when vessels are underway, trained Lookouts and 
bridge navigation teams are used to detect objects on the surface of 
the water ahead of the ship, including cetaceans. Additional Lookouts, 
beyond those already stationed on the bridge and on navigation teams, 
are positioned as Lookouts during some training events; and
     when submerged, submarines are generally slow moving (to 
avoid detection) and therefore marine mammals at depth with a submarine 
are likely able to avoid collision with the submarine. When a submarine 
is transiting on the surface, there are Lookouts serving the same 
function as they do on surface ships.
    In the GOA Study Area, NMFS and the Navy have no documented vessel 
strikes of marine mammals by the Navy. Therefore, NMFS has not used the 
quantitative approach to assess the likelihood of vessel strikes used 
in the Phase III incidental take rulemakings for Navy activities in the 
Atlantic Fleet Training and Testing (AFTT) and Hawaii-Southern 
California Training and Testing (HSTT) Study Areas, which starts with 
the number of Navy strikes that have occurred in the study area in 
question. But based on this lack of strikes and other factors described 
below, which the Navy presented and NMFS agrees are appropriate factors 
to consider in assessing the likelihood of ship strike, the Navy does 
not anticipate vessel strikes and has not requested authorization to 
take marine mammals by serious injury or mortality within the GOA Study 
Area during training activities. Based on consideration of all 
pertinent information, including, as appropriate, information on ship 
strikes in other Navy study areas, NMFS agrees with the Navy's 
conclusion based on the analysis and other factors described below.
    Within Alaska waters, there were 28 reported marine mammal vessel 
strikes between 2013 and 2017 (none of which were from U.S. Navy 
vessels) (Delean et al., 2020), which is a primary consideration in the 
evaluation of the likelihood that a strike by U.S. Navy vessels would 
occur in the GOA Study Area in the next 7 years. Though not in the same 
region, and noting the larger scale and differences in types of 
activities that occur there, NMFS also considered the incidents of two 
accidental ship strikes of large whales by U.S. Navy vessels in the 
HSTT Study Area that occurred in June 2021 and July 2021 (the first 
U.S. Navy ship strikes in the HSTT Study Area since 2009). The two ship 
strikes were of large whales, but in both cases, the whale's species 
could not be determined. Appropriately, as indicated in the Navy's 2022 
application (87 FR 33113; June 1, 2022) to revise the 2020 HSTT 
regulations (50 CFR part 218, subpart H) and LOAs, and as has been the 
practice in NMFS analyses for all major Navy training and testing 
rules, those strikes

[[Page 49699]]

would be quantitatively incorporated into the prediction of future 
strikes in that region. However, due to differences across regions, 
both in the density and occurrence of marine mammals, the levels and 
types of activities, and other environmental factors--all of which 
contribute to differences in the historical strikes in a given region--
strikes that occur in the HSTT Study Area are not quantitatively 
considered in strike predictions for the GOA Study Area.
    More broadly regarding the likelihood of strikes from U.S. Navy 
vessels, large Navy vessels (greater than 18 m in length) within the 
offshore areas of range complexes operate differently from commercial 
vessels in ways that still likely reduce potential whale collisions. 
Surface ships operated by or for the Navy have multiple personnel 
assigned to stand watch at all times when a ship or surfaced submarine 
is moving through the water (underway). A primary duty of personnel 
standing watch on surface ships is to detect and report all objects and 
disturbances sighted in the water that may indicate a threat to the 
vessel and its crew, such as debris, a periscope, surfaced submarine, 
or surface disturbance. Per vessel safety requirements, personnel 
standing watch also report any marine mammals sighted in the path of 
the vessel as a standard collision avoidance procedure. All vessels 
proceed at a safe speed so they can take proper and effective action to 
avoid a collision with any sighted object or disturbance, and can be 
stopped within a distance appropriate to the prevailing circumstances 
and conditions.
    Between 2007 and 2009, the Navy developed and distributed 
additional training, mitigation, and reporting tools to Navy operators 
to improve marine mammal protection and to ensure compliance with LOA 
requirements. In 2009, the Navy implemented Marine Species Awareness 
Training designed to improve effectiveness of visual observation for 
marine resources, including marine mammals. Additionally, for over a 
decade, the Navy has implemented the Protective Measures Assessment 
Protocol software tool, which provides operators with notification of 
the required mitigation and a visual display of the planned training or 
testing activity location overlaid with relevant environmental data.
    Furthermore, specific to the Navy's proposed activities in the GOA 
Study Area, the training activities would occur over a maximum of 21 
days annually over a large area within the Gulf of Alaska, in 
comparison to Navy activities that occur 365 days-per-year in other 
Study Areas. The GOA Study Area activities would include one Carrier 
Strike Group, which the Navy indicates would include up to six surface 
vessels (though in some cases there could be more vessels, and in some 
cases there could be fewer). Therefore, the Navy's activities in the 
GOA Study Area would include an estimated 126 at-sea days (6 vessels x 
21 days) annually. This level of potential Navy vessel activity is far 
lower than vessel activity in other Study Areas. The estimated number 
of at-sea days for Navy training activities in the GOA Study Area is 
approximately 1/4th of that associated with Navy training and testing 
in the Mariana Islands Training and Testing (MITT) Study Area (where 
vessel strike is also not anticipated and has not occurred) over the 
same time period, and approximately 1/36th of that associated with Navy 
training and testing in the Hawaii-Southern California Training and 
Testing (HSTT) Study Area (where limited vessel strike is authorized) 
over the same time period. In addition to vessel strikes of large 
whales being unlikely to occur for the reasons explained, the Navy 
would implement certain additional mitigation measures that would 
reduce the chance of a vessel strike even further. See the Proposed 
Mitigation Measures section for more details.
    Based on all of these considerations, NMFS has preliminarily 
determined that the Navy's decision not to request incidental take 
authorization for vessel strike of large whales is reasonable and 
supported by multiple factors, including the lack of ship strike 
reports in recent (2013-2017) stranding records for Alaska waters 
(including no strikes by Navy vessels in the GOA Study Area; Delean et 
al., 2020), the relatively small numbers of Navy vessels across a large 
expanse of offshore waters in the GOA Study Area, the relatively short 
activity period in which Navy vessels would operate (maximum of 21 days 
per year), and the procedural mitigation measures that would be in 
place to further minimize the potential for vessel strike.
    In addition to the reasons listed above that make it unlikely that 
the Navy would hit a large whale (more maneuverable ships, larger crew, 
etc.), the following are additional reasons that vessel strike of 
dolphins, small whales, and pinnipeds is very unlikely. Dating back 
more than 20 years and for as long as it has kept records, the Navy has 
no records of any small whales or pinnipeds being struck by a vessel as 
a result of Navy activities. Over the same time period, NMFS and the 
Navy have only one record of a dolphin being struck by a vessel as a 
result of Navy activities. The dolphin was accidentally struck by a 
Navy small boat in fall 2021 in Saint Andrew's Pass, Florida. The 
smaller size and maneuverability of dolphins, small whales, and 
pinnipeds generally make such strikes very unlikely. Other than this 
one reported strike of a dolphin in 2021, NMFS has never received any 
reports from other LOA or Incidental Harassment Authorization holders 
indicating that these species have been struck by vessels. In addition, 
worldwide ship strike records show little evidence of strikes of these 
groups from the shipping sector and larger vessels, and the majority of 
the Navy's activities involving faster-moving vessels (that could be 
considered more likely to hit a marine mammal) are located in offshore 
areas where smaller delphinid densities are lower. The majority of the 
GOA Study Area is located offshore of the continental slope. While the 
Navy's specified activities in the GOA Study Area do involve the use of 
small boats also, use of small boats would occur on no more than 21 
days per year, the length of the Navy's proposed training exercise. 
Based on this information, NMFS concurs with the Navy's assessment that 
vessel strike is not likely to occur for either large whales or smaller 
marine mammals.

Marine Mammal Habitat

    The Navy's proposed training activities could potentially affect 
marine mammal habitat through the introduction of impacts to the prey 
species of marine mammals, acoustic habitat (sound in the water 
column), water quality, and biologically important habitat for marine 
mammals. Each of these potential effects was considered in the 2020 GOA 
DSEIS/OEIS and 2022 Supplement to the 2020 GOA DSEIS/OEIS, and based on 
the information below and the supporting information included in the 
2020 GOA DSEIS/OEIS, NMFS has preliminarily determined that the 
proposed training activities would not have adverse or long-term 
impacts on marine mammal habitat that would be expected to affect the 
reproduction or survival of any marine mammals.
Effects to Prey
    Sound may affect marine mammals through impacts on the abundance, 
behavior, or distribution of prey species (e.g., crustaceans, 
cephalopods, fish, zooplankton). Marine mammal prey varies by species, 
season, and location and, for some species, is not well documented. 
Here, we describe studies

[[Page 49700]]

regarding the effects of noise on known marine mammal prey.
    Fish utilize the soundscape and components of sound in their 
environment to perform important functions such as foraging, predator 
avoidance, mating, and spawning (e.g., Zelick et al., 1999; Fay, 2009). 
The most likely effects on fishes exposed to loud, intermittent, low-
frequency sounds are behavioral responses (i.e., flight or avoidance). 
Short duration, sharp sounds (such as pile driving or air guns) can 
cause overt or subtle changes in fish behavior and local distribution. 
The reaction of fish to acoustic sources depends on the physiological 
state of the fish, past exposures, motivation (e.g., feeding, spawning, 
migration), and other environmental factors. Key impacts to fishes may 
include behavioral responses, hearing damage, barotrauma (pressure-
related injuries), and mortality.
    Fishes, like other vertebrates, have a variety of different sensory 
systems to glean information from the ocean around them (Astrup and 
Mohl, 1993; Astrup, 1999; Braun and Grande, 2008; Carroll et al., 2017; 
Hawkins and Johnstone, 1978; Ladich and Popper, 2004; Ladich and 
Schulz-Mirbach, 2016; Mann, 2016; Nedwell et al., 2004; Popper et al., 
2003; Popper et al., 2005). Depending on their hearing anatomy and 
peripheral sensory structures, which vary among species, fishes hear 
sounds using pressure and particle motion sensitivity capabilities and 
detect the motion of surrounding water (Fay et al., 2008) (terrestrial 
vertebrates generally only detect pressure). Most marine fishes 
primarily detect particle motion using the inner ear and lateral line 
system, while some fishes possess additional morphological adaptations 
or specializations that can enhance their sensitivity to sound 
pressure, such as a gas-filled swim bladder (Braun and Grande, 2008; 
Popper and Fay, 2011).
    Hearing capabilities vary considerably between different fish 
species with data only available for just over 100 species out of the 
34,000 marine and freshwater fish species (Eschmeyer and Fong, 2016). 
In order to better understand acoustic impacts on fishes, fish hearing 
groups are defined by species that possess a similar continuum of 
anatomical features which result in varying degrees of hearing 
sensitivity (Popper and Hastings, 2009a). There are four hearing groups 
defined for all fish species (modified from Popper et al., 2014) within 
this analysis and they include: fishes without a swim bladder (e.g., 
flatfish, sharks, rays, etc.); fishes with a swim bladder not involved 
in hearing (e.g., salmon, cod, pollock, etc.); fishes with a swim 
bladder involved in hearing (e.g., sardines, anchovy, herring, etc.); 
and fishes with a swim bladder involved in hearing and high-frequency 
hearing (e.g., shad and menhaden).
    In terms of behavioral responses, Juanes et al. (2017) discuss the 
potential for negative impacts from anthropogenic soundscapes on fish, 
but the author's focus was on broader based sounds such as ship and 
boat noise sources. There are no detonations of explosives occurring 
underwater in the specified activity for this rulemaking, and 
occasional behavioral reactions to intermittent explosions occurring 
in-air at or above the water surface are unlikely to cause long-term 
consequences for individual fish or populations. Fish that experience 
hearing loss as a result of exposure to explosions may have a reduced 
ability to detect relevant sounds such as predators, prey, or social 
vocalizations. However, PTS has not been known to occur in fishes, and 
any hearing loss in fish may be as temporary as the timeframe required 
to repair or replace the sensory cells that were damaged or destroyed 
(Popper et al., 2014; Popper et al., 2005; Smith et al., 2006). It is 
not known if damage to auditory nerve fibers could occur and, if so, 
whether fibers would recover during this process. It is also possible 
for fish to be injured or killed by an explosion in the immediate 
vicinity of the surface from dropped or fired ordnance. Physical 
effects from pressure waves generated by in-air detonations at or above 
the water surface could potentially affect fish within proximity of 
training activities. The shock wave from an explosion occurring at or 
above the water surface may be lethal to fish at close range, causing 
massive organ and tissue damage and internal bleeding (Keevin and 
Hempen, 1997). At greater distance from the detonation point, the 
extent of mortality or injury depends on a number of factors, including 
fish size, body shape, orientation, and species (Keevin and Hempen, 
1997; Wright, 1982). At the same distance from the source, larger fish 
are generally less susceptible to death or injury, elongated forms that 
are round in cross-section are less at risk than deep-bodied forms, and 
fish oriented sideways to the blast suffer the greatest impact (Edds-
Walton and Finneran, 2006; O'Keeffe, 1984; O'Keeffe and Young, 1984; 
Wiley et al., 1981; Yelverton et al., 1975). Species with gas-filled 
organs have a higher potential for mortality than those without them 
(Gaspin, 1975; Gaspin et al., 1976; Goertner et al., 1994).
    Nonetheless, Navy activities involving in-air explosions at or 
above the water surface are dispersed in space and time; therefore, 
repeated exposure of individual fishes is unlikely. Mortality and 
injury effects to fishes from explosives would be localized around the 
area of a given explosion at or above the water surface, but only if 
individual fish and the explosive (and immediate pressure field) were 
co-located at the same time. Fishes deeper in the water column or on 
the bottom would not be affected by water surface explosions. Repeated 
exposure of individual fish to sound and energy from Navy events 
involving in-air detonations at or above the water surface is not 
likely given fish movement patterns, especially schooling prey species. 
Most acoustic effects, if any, are expected to be short term and 
localized. Long-term consequences for fish populations, including key 
prey species within the GOA Study Area, would not be expected.
    Vessels and surface targets do not normally collide with adult 
fish, most of which can detect and avoid them. Exposure of fishes to 
vessel strike stressors is limited to those fish groups that are large, 
slow moving, and may occur near the surface, such as basking sharks, 
which are not marine mammal prey species. Vessel strikes would not pose 
a risk to most of the other marine fish groups, because many fish can 
detect and avoid vessel movements, making strikes extremely unlikely 
and allowing the fish to return to their normal behavior after the ship 
or device passes. As a vessel approaches a fish, it could have a 
detectable behavioral or physiological response (e.g., swimming away 
and increased heart rate) as the passing vessel displaces it. However, 
such reactions are not expected to have effects on the survival, 
growth, recruitment, or reproduction of these marine fish groups at the 
population level.
    In addition to fish, prey sources such as marine invertebrates 
could potentially be impacted by sound stressors as a result of the 
planned activities. Data on response of invertebrates such as squid has 
been documented (de Soto, 2016; Sole et al., 2017). Sole et al. (2017) 
reported physiological injuries to cuttlefish in cages placed at sea 
when exposed during a controlled exposure experiment to low-frequency 
sources (315 Hz, 139-142 dB re 1 [mu]Pa\2\ and 400 Hz, 139-141 dB re 1 
[mu]Pa\2\). Fewtrell and McCauley (2012) reported squids maintained in 
cages displayed startle responses and behavioral changes when exposed 
to seismic air gun sonar (136-162 re 1 [mu]Pa\2\-s). However, the 
sources Sole et al. (2017) and Fewtrell and

[[Page 49701]]

McCauley (2012) used are not similar and are much lower frequency than 
typical Navy sources or those included in the Specified Activity within 
the GOA Study Area. Nor do the studies address the issue of individual 
displacement outside of a zone of impact when exposed to sound. Squids, 
like most fish species, are likely more sensitive to low-frequency 
sounds, and may not perceive mid- and high-frequency sonars such as 
Navy sonars. As with fish, cumulatively individual and population-level 
impacts from exposure to Navy sonar and explosives for squid are not 
anticipated, and explosive impacts would be short term, localized, and 
likely to be inconsequential to invertebrate populations.
    Explosions could kill or injure other nearby marine invertebrates. 
Vessels also have the potential to impact marine invertebrates by 
disturbing the water column or sediments, or directly striking 
organisms (Bishop, 2008). The propeller wash (water displaced by 
propellers used for propulsion) from vessel movement and water 
displaced from vessel hulls can potentially disturb marine 
invertebrates in the water column and is a likely cause of zooplankton 
mortality (Bickel et al., 2011). The localized and short-term exposure 
to explosions or vessels could displace, injure, or kill zooplankton, 
invertebrate eggs or larvae, and macro-invertebrates. However, 
mortality or long-term consequences for a few animals is unlikely to 
have measurable effects on overall stocks or populations. Long-term 
consequences to marine invertebrate populations would not be expected 
as a result of exposure to sounds or vessels in the GOA Study Area.
    Military expended materials resulting from training could 
potentially result in minor long term changes to benthic habitat. 
Military expended materials may be colonized over time by benthic 
organisms that prefer hard substrate and would provide structure that 
could attract some species of fish or invertebrates. Overall, the 
combined impacts of sound exposure, explosions, vessel strikes, and 
military expended materials resulting from the specified activity would 
not be expected to have measurable effects on populations of marine 
mammal prey species and marine mammal habitat.
Acoustic Habitat
    Acoustic habitat is the soundscape which encompasses all of the 
sound present in a particular location and time, as a whole when 
considered from the perspective of the animals experiencing it. Animals 
produce sound for, or listen for sounds produced by, conspecifics 
(communication during feeding, mating, and other social activities), 
other animals (finding prey or avoiding predators), and the physical 
environment (finding suitable habitats, navigating). Together, sounds 
made by animals and the geophysical environment (e.g., produced by 
earthquakes, lightning, wind, rain, waves) make up the natural 
contributions to the total acoustics of a place. These acoustic 
conditions, termed acoustic habitat, are one attribute of an animal's 
total habitat.
    Soundscapes are also defined by, and acoustic habitat influenced 
by, the total contribution of anthropogenic sound. This may include 
incidental emissions from sources such as vessel traffic or may be 
intentionally introduced to the marine environment for data acquisition 
purposes (as in the use of air gun arrays) or for Navy training 
purposes (as in the use of sonar and other acoustic sources). 
Anthropogenic noise varies widely in its frequency, content, duration, 
and loudness, and these characteristics greatly influence the potential 
habitat-mediated effects to marine mammals (please also see the 
previous discussion on ``Masking''), which may range from local effects 
for brief periods of time to chronic effects over large areas and for 
longer durations. Depending on the extent of effects to habitat, 
animals may alter their communications signals (thereby potentially 
expending additional energy) or miss acoustic cues (either conspecific 
or adventitious). Problems arising from a failure to detect cues are 
more likely to occur when noise stimuli are chronic and overlap with 
biologically relevant cues used for communication, orientation, and 
predator/prey detection (Francis and Barber, 2013). For more detail on 
these concepts see, e.g., Barber et al., 2009; Pijanowski et al., 2011; 
Francis and Barber, 2013; Lillis et al., 2014, Hatch et al., 2016; 
Duarte et al., 2021).
    The term ``listening area'' refers to the region of ocean over 
which sources of sound can be detected by an animal at the center of 
the space. Loss of communication space concerns the area over which a 
specific animal signal (used to communicate with conspecifics in 
biologically important contexts such as foraging or mating) can be 
heard, in noisier relative to quieter conditions (Clark et al., 2009). 
Lost listening area concerns the more generalized contraction of the 
range over which animals would be able to detect a variety of signals 
of biological importance, including eavesdropping on predators and prey 
(Barber et al., 2009). Such metrics do not, in and of themselves, 
document fitness consequences for the marine animals that live in 
chronically noisy environments. Long-term population-level consequences 
mediated through changes in the ultimate survival and reproductive 
success of individuals are difficult to study, and particularly so 
underwater. However, it is increasingly well documented that aquatic 
species rely on qualities of natural acoustic habitats, with 
researchers quantifying reduced detection of important ecological cues 
(e.g., Francis and Barber, 2013; Slabbekoorn et al., 2010) as well as 
survivorship consequences in several species (e.g., Simpson et al., 
2014; Nedelec et al., 2015).
    The sounds produced during Navy training activities can be widely 
dispersed or concentrated in small areas for varying periods. Sound 
produced from training activities in the GOA Study Area is temporary 
and limited to a 21 consecutive day period from April to October, 
unlike other Navy Study Areas where training occurs year-round. Any 
anthropogenic noise attributed to training activities in the GOA Study 
Area would be temporary and the affected area would be expected to 
immediately return to the original state when these activities cease.
Water Quality
    The 2011 GOA EIS/OEIS analyzed the potential effects on water 
quality from explosives, explosive byproducts, and military expended 
materials including their associated component metals and chemicals. 
This analysis remains accurate and complete, and is incorporated by 
reference in the 2016 GOA SEIS/OEIS and 2020 GOA DSEIS/OEIS. NMFS has 
reviewed this analysis and concurs that it reflects the best available 
science. High order explosions consume most of the explosive material, 
creating typical combustion products. For example, in the case of Royal 
Demolition Explosive, 98 percent of the products are common seawater 
constituents and the remainder is rapidly diluted below levels that 
would be expected to affect marine mammals. Explosion byproducts 
associated with high order detonations present no secondary stressors 
to marine mammals through sediment or water. However, low order 
detonations and unexploded ordnance present a potential for exposure, 
but only in the immediate vicinity of the ordnance. Degradation 
products of Royal Demolition Explosive are not toxic to marine 
organisms at realistic exposure levels (Carniel et al., 2019; Rosen and 
Lotufo, 2010) and any remnant undetonated components from

[[Page 49702]]

explosives such as TNT, royal demolition explosive, and high melting 
explosive experience rapid biological and photochemical degradation in 
marine systems (Carniel et al., 2019; Cruz-Uribe et al., 2007; Juhasz 
and Naidu, 2007; Pavlostathis and Jackson, 2002; Singh et al., 2009; 
Walker et al., 2006).
    The findings from multiple studies indicate the relatively low 
solubility of most explosives and their degradation products, metals, 
and chemicals meaning that concentrations of these contaminants in the 
marine environment, including those associated with either high-order 
or low-order detonations, are relatively low and readily diluted. A 
series of studies of a World War II dump site off Hawaii have 
demonstrated that only minimal concentrations of degradation products 
were detected in the adjacent sediments and that there was no 
detectable uptake in sampled organisms living on or in proximity to the 
site (Briggs et al., 2016; Carniel et al., 2019; Edwards et al., 2016; 
Hawaii Undersea Military Munitions Assessment, 2010; Kelley et al., 
2016; Koide et al., 2016). In the GOA Study Area, the concentration of 
unexploded ordnance, explosion byproducts, metals, and other chemicals 
would never exceed that of a World War II dump site. As another 
example, the Canadian Forces Maritime Experimental and Test Ranges near 
Nanoose, British Columbia, began operating in 1965 conducting test 
events for both U.S. and Canadian forces, which included some of the 
same activities proposed for the GOA Study Area. Environmental analyses 
of the impacts from military expended materials at Nanoose were 
documented in 1996 and 2005. The analyses concluded the Navy test 
activities ``. . . had limited and perhaps negligible effects on the 
natural environment'' (Environmental Science Advisory Committee, 2005). 
Based on these and other similar applicable findings from multiple Navy 
ranges, and based on the analysis in Section 3.3 (Water Resources) of 
the 2011 GOA Final SEIS/OEIS (incorporated by reference in the 2020 GOA 
Draft EIS/OEIS), indirect impacts on marine mammals from the training 
activities in the GOA Study Area would be negligible and would have no 
long-term effect on habitat.
    Equipment used by the Navy within the GOA Study Area, including 
ships and other marine vessels, aircraft, and other equipment, are also 
potential sources of by-products. All equipment is properly maintained 
in accordance with applicable Navy and legal requirements. All such 
operating equipment meets Federal water quality standards, where 
applicable.

Estimated Take of Marine Mammals

    This section indicates the number of takes that NMFS is proposing 
to authorize, which are based on the maximum 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 preliminarily agrees that the methods the Navy has put forth 
described herein to estimate take (including the model, thresholds, and 
density estimates), and the resulting numbers are based on the best 
available science and appropriate for authorization.
    Takes would be in the form of harassment only. For a military 
readiness activity, the MMPA defines ``harassment'' as (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).
    Proposed authorized takes would primarily be in the form of Level B 
harassment, as use of the acoustic and explosive sources (i.e., sonar 
and explosives) is most likely to result in the 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) or TTS 
for marine mammals. There is also the potential for Level A harassment, 
in the form of auditory injury that results from exposure to the sound 
sources utilized in training activities.
    Generally speaking, for acoustic impacts NMFS estimates the amount 
and type of harassment by considering: (1) acoustic thresholds above 
which NMFS believes the best available science indicates marine mammals 
would experience behavioral disturbance or incur some degree of 
temporary or permanent hearing impairment; (2) the area or volume of 
water that would be ensonified above these levels in a day or event; 
(3) the density or occurrence of marine mammals within these ensonified 
areas; and (4) the number of days of activities or events.

Acoustic Thresholds

    Using the best available science, NMFS, in coordination with the 
Navy, has established acoustic thresholds that identify the most 
appropriate received level of underwater sound above which marine 
mammals exposed to these sound sources could be reasonably expected to 
experience a disruption in behavior patterns to a point where they are 
abandoned or significantly altered (equated to onset of Level B 
harassment), or to incur TTS onset (equated to Level B harassment) or 
PTS onset (equated to Level A harassment). Thresholds have also been 
developed to identify the pressure and impulse levels above which 
animals may incur non-auditory injury or mortality from exposure to 
explosive detonations (although no non-auditory injury from explosives 
is anticipated as part of this rulemaking).
    Despite the rapidly evolving science, there are still challenges in 
quantifying expected behavioral responses that qualify as take by Level 
B harassment, especially where the goal is to use one or two 
predictable indicators (e.g., received level and distance) to predict 
responses that are also driven by additional factors that cannot be 
easily incorporated into the thresholds (e.g., context). So, while the 
thresholds that identify Level B harassment by behavioral disturbance 
(referred to as ``behavioral harassment thresholds'') have been refined 
to better consider the best available science (e.g., incorporating both 
received level and distance), they also still have some built-in 
conservative factors to address the challenge noted. For example, while 
duration of observed responses in the data are now considered in the 
thresholds, some of the responses that are informing take thresholds 
are of a very short duration, such that it is possible some of these 
responses might not always rise to the level of disrupting behavior 
patterns to a point where they are abandoned or significantly altered. 
We describe the application of this behavioral harassment threshold as 
identifying the maximum number of instances in which marine mammals 
could be reasonably expected to experience a disruption in behavior 
patterns to a point where they are abandoned or significantly altered. 
In summary, we believe these behavioral harassment thresholds are the 
most appropriate method for predicting Level B harassment by behavioral 
disturbance given the best available science and the associated 
uncertainty.

[[Page 49703]]

Hearing Impairment (TTS/PTS) and Non-Auditory Tissue Damage and 
Mortality
    NMFS' Acoustic Technical Guidance (NMFS, 2018) identifies dual 
criteria to assess auditory injury (Level A harassment) to five 
different marine mammal groups (based on hearing sensitivity) as a 
result of exposure to noise from two different types of sources 
(impulsive or non-impulsive). The Acoustic Technical Guidance also 
identifies criteria to predict TTS, which is not considered injury and 
falls into the Level B harassment category. The Navy's planned activity 
includes the use of non-impulsive (sonar) and impulsive (explosives) 
sources.
    These thresholds (Table 5 and Table 6) were developed by compiling 
and synthesizing the best available science and soliciting input 
multiple times from both the public and peer reviewers. The references, 
analysis, and methodology used in the development of the thresholds are 
described in Acoustic Technical Guidance, which may be accessed at: 
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.

  Table 5--Acoustic Thresholds Identifying the Onset of TTS and PTS for
        Non-Impulsive Sound Sources by Functional Hearing Groups
------------------------------------------------------------------------
                                                   Non-impulsive
                                         -------------------------------
        Functional hearing group           TTS threshold   PTS threshold
                                          SEL (weighted)  SEL (weighted)
------------------------------------------------------------------------
Low-Frequency Cetaceans.................             179             199
Mid-Frequency Cetaceans.................             178             198
High-Frequency Cetaceans................             153             173
Phocid Pinnipeds (Underwater)...........             181             201
Otarid Pinnipeds (Underwater)...........             199             219
------------------------------------------------------------------------
Note: SEL thresholds in dB re: 1 [mu]Pa\2\-s accumulated over a 24-hr
  period.

    Based on the best available science, the Navy (in coordination with 
NMFS) used the acoustic and pressure thresholds indicated in Table 6 to 
predict the onset of TTS, PTS, non-auditory tissue damage, and 
mortality for explosives (impulsive) and other impulsive sound sources.

                Table 6--Thresholds for TTS, PTS, Non-Auditory Tissue Damage, and Mortality Thresholds for Marine Mammals for Explosives
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        Weighted onset TTS                         Slight GI tract       Slight lung
    Functional hearing group            Species                \1\           Weighted onset PTS         injury             injury           Mortality
--------------------------------------------------------------------------------------------------------------------------------------------------------
Low-frequency cetaceans.........  All mysticetes.....  168 dB SEL or 213    183 dB SEL or 219    243 dB Peak SPL....  Equation 1.       Equation 2.
                                                        dB Peak SPL.         dB Peak SPL.
Mid-frequency cetaceans.........  Most delphinids,     170 dB SEL or 224    185 dB SEL or 230    243 dB Peak SPL....
                                   medium and large     dB Peak SPL.         dB Peak SPL.
                                   toothed whales.
High-frequency cetaceans........  Porpoises and Kogia  140 dB SEL or 196    155 dB SEL or 202    243 dB Peak SPL....
                                   spp.                 dB Peak SPL.         dB Peak SPL.
Phocidae........................  Harbor seal,         170 dB SEL or 212    185 dB SEL or 218    243 dB Peak SPL....
                                   Hawaiian monk        dB Peak SPL.         dB Peak SPL.
                                   seal, Northern
                                   elephant seal.
Otariidae.......................  California sea       188 dB SEL or 226    203 dB SEL or 232    243 dB Peak SPL....
                                   lion, Guadalupe      dB Peak SPL.         dB Peak SPL.
                                   fur seal, Northern
                                   fur seal.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
Equation 1: 47.5M1/3 (1+[DRm/10.1])1/6 Pa-sec.
Equation 2: 103M1/3 (1+[DRm/10.1])1/6 Pa-sec.
M = mass of the animals in kg.
DRm = depth of the receiver (animal) in meters.
SPL = sound pressure level.
Weighted SEL thresholds in dB re: 1 [mu]Pa\2\-s accumulated over a 24-h period.
\1\ Peak thresholds are unweighted.

    The criteria used to assess the onset of TTS and PTS due to 
exposure to sonars (non-impulsive, see Table 5 above) are discussed 
further in the Navy's rulemaking/LOA application (see Hearing Loss from 
Sonar and Other Transducers in Chapter 6, Section 6.4.2.1, Methods for 
Analyzing Impacts from Sonars and Other Transducers). Refer to the 
Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects 
Analysis (Phase III) report (U.S. Department of the Navy, 2017c) for 
detailed information on how the criteria and thresholds were derived, 
and to Section 3.8.3.1.1.2 of the 2020 GOA DSEIS/OEIS for a review of 
TTS research published following development of the criteria and 
thresholds applied in the Navy's analysis and in NMFS' Acoustic 
Technical Guidance. Further, since publication of the 2020 GOA DSEIS/
OEIS, several additional studies associated with TTS in harbor 
porpoises and seals have been published (e.g., Kastelein et al., 2020d; 
Kastelein et al., 2021a and 2021b; Sills et al., 2020). NMFS is aware 
of these recent papers and is currently working with the Navy to update 
NMFS' Technical Guidance for Assessing the Effects of Anthropogenic 
Sound on Marine Mammal Hearing Version 2.0 (Acoustic Technical 
Guidance; NMFS 2018) to reflect relevant papers that have been 
published since the 2018 update on our 3-5 year update schedule in the 
Acoustic Technical Guidance. First, we

[[Page 49704]]

note that the recent peer-reviewed updated marine mammal noise exposure 
criteria by Southall et al. (2019a) provide identical PTS and TTS 
thresholds and weighting functions to those provided in NMFS' Acoustic 
Technical Guidance.
    NMFS will continue to review and evaluate new relevant data as it 
becomes available and consider the impacts of those studies on the 
Acoustic Technical Guidance to determine what revisions/updates may be 
appropriate. However, any such revisions must undergo peer and public 
review before being adopted, as described in the Acoustic Guidance 
methodology. While some of the relevant data may potentially suggest 
changes to TTS/PTS thresholds for some species, any such changes would 
not be expected to change the predicted take estimates in a manner that 
would change the necessary determinations supporting the issuance of 
these regulations, and the data and values used in this rule reflect 
the best available science.
    Non-auditory injury (i.e., other than PTS) and mortality from sonar 
and other transducers is so unlikely as to be discountable under normal 
conditions for the reasons explained under the Potential Effects of 
Specified Activities on Marine Mammals and Their Habitat section--
Acoustically-Induced Bubble Formation Due to Sonars and Other Pressure-
related Impacts and is therefore not considered further in this 
analysis.
Level B Harassment by Behavioral Disturbance
    Though significantly driven by received level, the onset of Level B 
harassment by behavioral disturbance from anthropogenic noise exposure 
is also informed to varying degrees by other factors related to the 
source (e.g., frequency, predictability, duty cycle), the environment 
(e.g., bathymetry), and the receiving animals (hearing, motivation, 
experience, demography, behavioral context) and can be difficult to 
predict (Ellison et al., 2011; Southall et al., 2007). Based on what 
the available science indicates and the practical need to use 
thresholds based on a factor, or factors, that are both predictable and 
measurable for most activities, NMFS uses generalized acoustic 
thresholds based primarily on received level (and distance in some 
cases) to estimate the onset of Level B harassment by behavioral 
disturbance.

Sonar

    As noted above, the Navy coordinated with NMFS to develop, and 
propose for use in this rule, thresholds specific to their military 
readiness activities utilizing active sonar that identify at what 
received level and distance Level B harassment by behavioral 
disturbance would be expected to result. These thresholds are referred 
to as ``behavioral harassment thresholds'' throughout the rest of the 
rule. These behavioral harassment thresholds consist of behavioral 
response functions (BRFs) and associated cutoff distances, and are also 
referred to, together, as ``the criteria.'' These criteria are used to 
estimate the number of animals that may exhibit a behavioral response 
that rises to the level of a take when exposed to sonar and other 
transducers. The way the criteria were derived is discussed in detail 
in the Criteria and Thresholds for U.S. Navy Acoustic and Explosive 
Effects Analysis (Phase III) report (U.S. Department of the Navy, 
2017c). Developing these behavioral harassment criteria involved 
multiple steps. All peer-reviewed published behavioral response studies 
conducted both in the field and on captive animals were examined in 
order to understand the breadth of behavioral responses of marine 
mammals to tactical sonar and other transducers. NMFS has carefully 
reviewed the Navy's criteria, i.e., BRFs and cutoff distances for the 
species, and agrees that it is the best available science and is the 
appropriate method to use at this time for determining impacts to 
marine mammals from military sonar and other transducers and for 
calculating take and to support the determinations made in this 
proposed rule.
    As discussed above, marine mammal responses to sound (some of which 
are considered disturbances that rise to the level of a take) are 
highly variable and context specific, i.e., they are affected by 
differences in acoustic conditions; differences between species and 
populations; differences in gender, age, reproductive status, or social 
behavior; and other prior experience of the individuals. This means 
that there is support for considering alternative approaches for 
estimating Level B harassment by behavioral disturbance. Although the 
statutory definition of Level B harassment for military readiness 
activities means that a natural behavior pattern of a marine mammal is 
significantly altered or abandoned, the current state of science for 
determining those thresholds is somewhat unsettled.
    In its analysis of impacts associated with sonar acoustic sources 
(which was coordinated with NMFS), the Navy used an updated 
conservative approach that likely overestimates the number of takes by 
Level B harassment due to behavioral disturbance and response. Many of 
the behavioral responses identified using the Navy's quantitative 
analysis are most likely to be of moderate severity as described in the 
Southall et al. (2007) behavioral response severity scale. These 
``moderate'' severity responses were considered significant if they 
were sustained for the duration of the exposure or longer. Within the 
Navy's quantitative analysis, many reactions are predicted from 
exposure to sound that may exceed an animal's threshold for Level B 
harassment by behavioral disturbance for only a single exposure (a few 
seconds) to several minutes, and it is likely that some of the 
resulting estimated behavioral responses that are counted as Level B 
harassment would not constitute ``significantly altering or abandoning 
natural behavioral patterns.'' The Navy and NMFS have used the best 
available science to address the challenging differentiation between 
significant and non-significant behavioral reactions (i.e., whether the 
behavior has been abandoned or significantly altered such that it 
qualifies as harassment), but have erred on the cautious side where 
uncertainty exists (e.g., counting these lower duration reactions as 
take), which likely results in some degree of overestimation of Level B 
harassment by behavioral disturbance. We consider application of these 
behavioral harassment thresholds, therefore, as identifying the maximum 
number of instances in which marine mammals could be reasonably 
expected to experience a disruption in behavior patterns to a point 
where they are abandoned or significantly altered (i.e., Level B 
harassment). Because this is the most appropriate method for estimating 
Level B harassment given the best available science and uncertainty on 
the topic, it is these numbers of Level B harassment by behavioral 
disturbance that are analyzed in the Preliminary Analysis and 
Negligible Impact Determination section and would be authorized.
    In the Navy's acoustic impact analyses during Phase II (the 
previous phase of Navy testing and training, 2017-2022, see also Navy's 
Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects 
Analysis Technical Report, 2012), the likelihood of Level B harassment 
by behavioral disturbance in response to sonar and other transducers 
was based on a probabilistic function (termed a BRF), that related the 
likelihood (i.e., probability) of a behavioral response (at the level 
of a Level B harassment) to the received SPL. The BRF was used to 
estimate the percentage of an exposed population that is likely to 
exhibit Level B

[[Page 49705]]

harassment due to altered behaviors or behavioral disturbance at a 
given received SPL. This BRF relied on the assumption that sound poses 
a negligible risk to marine mammals if they are exposed to SPL below a 
certain ``basement'' value. Above the basement exposure SPL, the 
probability of a response increased with increasing SPL. Two BRFs were 
used in Navy acoustic impact analyses: BRF1 for mysticetes and BRF2 for 
other species. BRFs were not used for beaked whales during Phase II 
analyses. Instead, a step function at an SPL of 140 dB re: 1 [mu]Pa was 
used for beaked whales as the threshold to predict Level B harassment 
by behavioral disturbance. Similarly, a 120 dB re: 1 [mu]P step 
function was used during Phase II for harbor porpoises.
    Developing the behavioral harassment criteria for Phase III (the 
current phase of Navy training and testing activities) involved 
multiple steps: all available behavioral response studies conducted 
both in the field and on captive animals were examined to understand 
the breadth of behavioral responses of marine mammals to sonar and 
other transducers (see also Navy's Criteria and Thresholds for U.S. 
Navy Acoustic and Explosive Effects Analysis (Phase III) Technical 
Report, 2017). Six behavioral response field studies with observations 
of 14 different marine mammal species reactions to sonar or sonar-like 
signals and 6 captive animal behavioral studies with observations of 8 
different species reactions to sonar or sonar-like signals were used to 
provide a robust data set for the derivation of the Navy's Phase III 
marine mammal behavioral response criteria. The current criteria have 
been rigorously vetted within the Navy community, among scientists 
during expert elicitation, and then reviewed by the public before being 
applied. All behavioral response research that has been published since 
the derivation of the Navy's Phase III criteria (December 2016) has 
been considered and is consistent with the current BRFs. While it is 
unreasonable to revise and update the criteria and risk functions every 
time a new study is published, these new studies provide additional 
information, and NMFS and the Navy are considering them for updates to 
the criteria in the future, when the next round of updated criteria 
will be developed. The Navy and NMFS continue to evaluate the 
information as new science becomes available.
    Marine mammal species were placed into behavioral criteria groups 
based on their known or suspected behavioral sensitivities to sound. In 
most cases these divisions were driven by taxonomic classifications 
(e.g., mysticetes, pinnipeds). The data from the behavioral studies 
were analyzed by looking for significant responses, or lack thereof, 
for each experimental session.
    The Navy used cutoff distances beyond which the potential of 
significant behavioral responses (and therefore Level B harassment) is 
considered to be unlikely (see Table 7 below). These distances were 
determined by examining all available published field observations of 
behavioral reactions to sonar or sonar-like signals that included the 
distance between the sound source and the marine mammal. The longest 
distance, rounded up to the nearest 5-km increment, was chosen as the 
cutoff distance for each behavioral criteria group (i.e., odontocetes, 
pinnipeds, mysticetes, beaked whales, and harbor porpoise). For animals 
within the cutoff distance, BRFs for each behavioral criteria group 
based on a received SPL as presented in Chapter 6, Section 6.4.2.1 
(Methods for Analyzing Impacts from Sonars and other Transducers) of 
the Navy's rulemaking/LOA application were used to predict the 
probability of a potential significant behavioral response. For 
training activities that contain multiple platforms or tactical sonar 
sources that exceed 215 dB re: 1 [mu]Pa at 1 m, this cutoff distance is 
substantially increased (i.e., doubled) from values derived from the 
literature. The use of multiple platforms and intense sound sources are 
factors that probably increase responsiveness in marine mammals overall 
(however, we note that helicopter dipping sonars were considered in the 
intense sound source group, despite lower source levels, because of 
data indicating that marine mammals are sometimes more responsive to 
the less predictable employment of this source). There are currently 
few behavioral observations under these circumstances; therefore, the 
Navy conservatively predicted significant behavioral responses that 
would rise to Level B harassment at farther ranges than shown in Table 
7, versus less intense events.

  Table 7--Cutoff Distances for Moderate Source Level, Single Platform Training Events and for All Other Events
        With Multiple Platforms or Sonar With Source Levels at or Exceeding 215 dB re: 1 [micro]Pa at 1 m
----------------------------------------------------------------------------------------------------------------
                                                                Moderate SL/single
                      Criteria group                         platform cutoff distance    High SL/multi-platform
                                                                       (km)               cutoff distance (km)
----------------------------------------------------------------------------------------------------------------
Odontocetes...............................................                         10                         20
Pinnipeds.................................................                          5                         10
Mysticetes................................................                         10                         20
Beaked Whales.............................................                         25                         50
Harbor Porpoise...........................................                         20                         40
----------------------------------------------------------------------------------------------------------------
Notes: dB re: 1 [micro]Pa at 1 m = decibels referenced to 1 micropascal at 1 meter, km = kilometer, SL = source
  level.

    The range to received sound levels in 6-dB steps from three 
representative sonar bins and the percentage of animals that may be 
taken by Level B harassment under each BRF are shown in Tables 8 
through 10. Cells are shaded if the mean range value for the specified 
received level exceeds the distance cutoff distance for a particular 
group and therefore are not included in the estimated take. See Chapter 
6, Section 6.4.2.1 (Methods for Analyzing Impacts from Sonars and Other 
Transducers) of the Navy's rulemaking/LOA application for further 
details on the derivation and use of the BRFs, thresholds, and the 
cutoff distances to identify takes by Level B harassment, which were 
coordinated with NMFS. As noted previously, NMFS carefully reviewed, 
and contributed to, the Navy's proposed behavioral harassment 
thresholds (i.e., the BRFs and the cutoff distances) for the species, 
and agrees that these methods represent the best available science at 
this time for determining impacts to marine mammals from sonar and 
other transducers.
    Tables 8 through 10 identify the maximum likely percentage of 
exposed individuals taken at the indicated received level and 
associated range (in which marine mammals would be

[[Page 49706]]

reasonably expected to experience a disruption in behavior patterns to 
a point where they are abandoned or significantly altered) for mid-
frequency active sonar (MFAS).
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[[Page 49707]]


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[[Page 49708]]


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BILLING CODE 3510-22-C

Explosives

    Phase III explosive criteria for behavioral harassment thresholds 
for marine mammals is the functional hearing groups' TTS onset 
threshold (in SEL) minus 5 dB (see Table 11 below and Table 6 for the 
TTS thresholds for explosives) for events that contain multiple 
impulses from explosives underwater. This is the same approach as taken 
in Phase II for explosive analysis. See the Criteria and Thresholds for 
U.S. Navy Acoustic and Explosive Effects Analysis (Phase III) report 
(U.S. Department of the Navy, 2017c) for detailed information on how 
the criteria and thresholds were derived. NMFS continues to concur that 
this approach represents the best available science for determining 
impacts to marine mammals from explosives. As noted previously, 
detonations occurring in air at a height of 33 ft (10 m) or less above 
the water surface, and detonations occurring directly on the water 
surface were modeled to detonate at a depth of 0.3 ft (0.1 m) below the 
water surface. There are no detonations of explosives occurring 
underwater as part of the planned activities.

  Table 11--Thresholds for Level B Harassment by Behavioral Disturbance
                    for Explosives for Marine Mammals
------------------------------------------------------------------------
                                     Functional hearing
              Medium                        group         SEL (weighted)
------------------------------------------------------------------------
Underwater........................  Low-frequency                    163
                                     cetaceans.
Underwater........................  Mid-frequency                    165
                                     cetaceans.
Underwater........................  High-frequency                   135
                                     cetaceans.
Underwater........................  Phocids.............             165
Underwater........................  Otariids............             183
------------------------------------------------------------------------
Note: Weighted SEL thresholds in dB re: 1 [mu]Pa\2\s underwater


[[Page 49709]]

Navy's Acoustic Effects Model

    The Navy's Acoustic Effects Model calculates sound energy 
propagation from sonar and other transducers and explosives during 
naval activities and the sound received by animat dosimeters. Animat 
dosimeters are virtual representations of marine mammals distributed in 
the area around the modeled naval activity and each dosimeter records 
its individual sound ``dose.'' The model bases the distribution of 
animats over the TMAA, the portion of the GOA Study Area where sonar 
and other transducers and explosives are proposed for use, on the 
density values in the Navy Marine Species Density Database and 
distributes animats in the water column proportional to the known time 
that species spend at varying depths.
    The model accounts for environmental variability of sound 
propagation in both distance and depth when computing the sound level 
received by the animats. The model conducts a statistical analysis 
based on multiple model runs to compute the estimated effects on 
animals. The number of animats that exceed the thresholds for effects 
is tallied to provide an estimate of the number of marine mammals that 
could be affected.
    Assumptions in the Navy model intentionally err on the side of 
overestimation when there are unknowns. Naval activities are modeled as 
though they would occur regardless of proximity to marine mammals, 
meaning that no mitigation is considered (i.e., no power down or shut 
down modeled) and without any avoidance of the activity by the animal. 
The final step of the quantitative analysis of acoustic effects is to 
consider the implementation of mitigation and the possibility that 
marine mammals would avoid continued or repeated sound exposures. For 
more information on this process, see the discussion in the Take 
Request subsection below. All explosives used in the TMAA would 
detonate in the air at or above the water surface. However, for this 
analysis, detonations occurring in air at a height of 33 ft. (10 m) or 
less above the water surface, and detonations occurring directly on the 
water surface were modeled to detonate at a depth of 0.3 ft. (0.1 m) 
below the water surface since there is currently no other identified 
methodology for modeling potential effects to marine mammals that are 
underwater as a result of detonations occurring at or above the surface 
of the ocean. This overestimates the amount of explosive and acoustic 
energy entering the water.
    The model estimates the impacts caused by individual training 
exercises. During any individual modeled event, impacts to individual 
animats are considered over 24-hour periods. The animats do not 
represent actual animals, but rather they represent a distribution of 
animals based on density and abundance data, which allows for a 
statistical analysis of the number of instances that marine mammals may 
be exposed to sound levels resulting in an effect. Therefore, the model 
estimates the number of instances in which an effect threshold was 
exceeded over the course of a year, but does not estimate the number of 
individual marine mammals that may be impacted over a year (i.e., some 
marine mammals could be impacted several times, while others would not 
experience any impact). A detailed explanation of the Navy's Acoustic 
Effects Model is provided in the technical report Quantifying Acoustic 
Impacts on Marine Mammals and Sea Turtles: Methods and Analytical 
Approach for Phase III Training and Testing (U.S. Department of the 
Navy, 2018).

Range to Effects

    This section provides range to effects for sonar and other active 
acoustic sources as well as explosives to specific acoustic thresholds 
determined using the Navy Acoustic Effects Model. Marine mammals 
exposed within these ranges for the shown duration are predicted to 
experience the associated effect. Range to effects is important 
information in not only predicting acoustic impacts, but also in 
verifying the accuracy of model results against real-world situations 
and determining adequate mitigation ranges to avoid higher level 
effects, especially physiological effects to marine mammals.
Sonar
    The ranges to received sound levels in 6-dB steps from three 
representative sonar bins and the percentage of the total number of 
animals that may be disturbed (and therefore Level B harassment) under 
each BRF are shown in Table 8 though Table 10 above. See Chapter 6, 
Section 6.4.2.1 (Methods for Analyzing Impacts from Sonars and Other 
Transducers) of the Navy's rulemaking/LOA application for additional 
details on the derivation and use of the BRFs, thresholds, and the 
cutoff distances that are used to identify Level B harassment by 
behavioral disturbance. NMFS has reviewed the range distance to effect 
data provided by the Navy and concurs with the analysis.
    The ranges to PTS for three representative sonar systems for an 
exposure of 30 seconds is shown in Table 12 relative to the marine 
mammal's functional hearing group. This period (30 seconds) was chosen 
based on examining the maximum amount of time a marine mammal would 
realistically be exposed to levels that could cause the onset of PTS 
based on platform (e.g., ship) speed and a nominal animal swim speed of 
approximately 1.5 m per second. The ranges provided in the table 
include the average range to PTS, as well as the range from the minimum 
to the maximum distance at which PTS is possible for each hearing 
group.

          Table 12--Ranges to Permanent Threshold Shift (Meters) for Three Representative Sonar Systems
----------------------------------------------------------------------------------------------------------------
                                            Approximate range in meters for PTS from 30 second exposure \1\
            Hearing group             --------------------------------------------------------------------------
                                            Sonar bin MF1            Sonar bin MF4            Sonar bin MF5
----------------------------------------------------------------------------------------------------------------
High-frequency cetaceans.............            180 (180-180)               31 (30-35)                 9 (8-10)
Low-frequency cetaceans..............               65 (65-65)                13 (0-15)                  0 (0-0)
Mid-frequency cetaceans..............               16 (16-16)                  3 (3-3)                  0 (0-0)
Otariids \2\.........................                  6 (6-6)                  0 (0-0)                  0 (0-0)
Phocids \2\..........................               45 (45-45)               11 (11-11)                  0 (0-0)
----------------------------------------------------------------------------------------------------------------
\1\ PTS ranges extend from the sonar or other transducer sound source to the indicated distance. The average
  range to PTS is provided as well as the range from the estimated minimum to the maximum range to PTS in
  parenthesis.
\2\ Otariids and phocids are separated because true seals (phocids) generally dive much deeper than sea lions
  and fur seals (otariids).
Notes: MF = mid-frequency, PTS = permanent threshold shift.


[[Page 49710]]

    The tables below illustrate the range to TTS for 1, 30, 60, and 120 
seconds from three representative sonar systems (see Table 13 through 
Table 15).

          Table 13--Ranges to Temporary Threshold Shift (Meters) for Sonar Bin MF1 Over a Representative Range of Environments Within the TMAA
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                      Approximate TTS ranges (meters) \1\
                                                     ---------------------------------------------------------------------------------------------------
                    Hearing group                                                                Sonar bin MF1
                                                     ---------------------------------------------------------------------------------------------------
                                                              1 second                30 seconds               60 seconds              120 seconds
--------------------------------------------------------------------------------------------------------------------------------------------------------
High-frequency cetaceans............................      3,554 (1,525-6,775)      3,554 (1,525-6,775)      5,325 (2,275-9,525)     7,066 (2,525-13,025)
Low-frequency cetaceans.............................          920 (850-1,025)          920 (850-1,025)      1,415 (1,025-2,025)      2,394 (1,275-4,025)
Mid-frequency cetaceans.............................            209 (200-210)            209 (200-210)            301 (300-310)            376 (370-390)
Otariids............................................               65 (65-65)               65 (65-65)            100 (100-110)            132 (130-140)
Phocids.............................................            673 (650-725)            673 (650-725)          988 (900-1,025)      1,206 (1,025-1,525)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Ranges to TTS represent the model predictions in different areas and seasons within the TMAA. The zone in which animals are expected to incur TTS
  extends from onset-PTS to the distance indicated. The average range to TTS is provided as well as the range from the estimated minimum to the maximum
  range to TTS in parenthesis.
Notes: MF = mid-frequency, TTS = temporary threshold shift.


          Table 14--Ranges to Temporary Threshold Shift (Meters) for Sonar Bin MF4 Over a Representative Range of Environments Within the TMAA
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                      Approximate TTS ranges (meters) \1\
                                                     ---------------------------------------------------------------------------------------------------
                    Hearing group                                                                Sonar bin MF4
                                                     ---------------------------------------------------------------------------------------------------
                                                              1 second                30 seconds               60 seconds              120 seconds
--------------------------------------------------------------------------------------------------------------------------------------------------------
High-frequency cetaceans............................            318 (220-550)          686 (430-1,275)          867 (575-1,525)        1,225 (825-2,025)
Low-frequency cetaceans.............................               77 (0-100)            175 (130-340)            299 (190-550)          497 (280-1,000)
Mid-frequency cetaceans.............................               22 (22-22)               35 (35-35)               50 (50-50)               71 (70-75)
Otariids............................................                  8 (8-8)               15 (15-15)               19 (19-19)               25 (25-25)
Phocids.............................................               67 (65-70)            123 (110-150)            172 (150-210)            357 (240-675)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Ranges to TTS represent the model predictions in different areas and seasons within the TMAA. The zone in which animals are expected to incur TTS
  extends from onset-PTS to the distance indicated. The average range to TTS is provided as well as the range from the estimated minimum to the maximum
  range to TTS in parenthesis.
Notes: MF = mid-frequency, TTS = temporary threshold shift.


          Table 15--Ranges to Temporary Threshold Shift (Meters) for Sonar Bin MF5 Over a Representative Range of Environments Within the TMAA
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                      Approximate TTS ranges (meters) \1\
                                                     ---------------------------------------------------------------------------------------------------
                    Hearing group                                                                Sonar bin MF5
                                                     ---------------------------------------------------------------------------------------------------
                                                              1 second                30 seconds               60 seconds              120 seconds
--------------------------------------------------------------------------------------------------------------------------------------------------------
High-frequency cetaceans............................            117 (110-140)            117 (110-140)            176 (150-320)            306 (210-800)
Low-frequency cetaceans.............................                 9 (0-12)                 9 (0-12)                13 (0-17)                19 (0-24)
Mid-frequency cetaceans.............................                  5 (0-9)                  5 (0-9)               12 (11-13)               18 (17-18)
Otariids............................................                  0 (0-0)                  0 (0-0)                  0 (0-0)                  0 (0-0)
Phocids.............................................                 9 (8-10)                 9 (8-10)               14 (14-15)               21 (21-22)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Ranges to TTS represent the model predictions in different areas and seasons within the TMAA. The zone in which animals are expected to incur TTS
  extends from onset-PTS to the distance indicated. The average range to TTS is provided as well as the range from the estimated minimum to the maximum
  range to TTS in parenthesis.
Notes: MF = mid-frequency, TTS = temporary threshold shift.

Explosives
    The following section provides the range (distance) over which 
specific physiological or behavioral effects are expected to occur 
based on the explosive criteria (see Chapter 6, Section 6.5.2 (Impacts 
from Explosives) of the Navy's rulemaking/LOA application and the 
Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects 
Analysis (Phase III) report (U.S. Department of the Navy, 2017c)) and 
the explosive propagation calculations from the Navy Acoustic Effects 
Model (see Chapter 6, Section 6.5.2.2 (Impact Ranges for Explosives) of 
the Navy's rulemaking/LOA application). The range to effects are shown 
for a range of explosive bins, from E5 (greater than 5-10 lbs net 
explosive weight) to E12 (greater than 650 lbs to 1,000 lbs net 
explosive weight) (Tables 16 through 29). Ranges are determined by 
modeling the distance that noise from an explosion would need to 
propagate to reach exposure level thresholds specific to a hearing 
group that would cause behavioral response (to the degree of Level B 
harassment), TTS, PTS, and non-auditory injury. NMFS has reviewed the 
range distance to effect data provided by the Navy and concurs with the 
analysis. Range to effects is important information in not only 
predicting impacts from explosives, but

[[Page 49711]]

also in verifying the accuracy of model results against real-world 
situations and determining adequate mitigation ranges to avoid higher 
level effects, especially physiological effects to marine mammals. For 
additional information on how ranges to impacts from explosions were 
estimated, see the technical report Quantifying Acoustic Impacts on 
Marine Mammals and Sea Turtles: Methods and Analytical Approach for 
Phase III Training and Testing (U.S. Navy, 2018).
    Tables 16 through 27 show the minimum, average, and maximum ranges 
to onset of auditory and likely behavioral effects that rise to the 
level of Level B harassment based on the developed thresholds. Ranges 
are provided for a representative source depth and cluster size (the 
number of rounds fired, or buoys dropped, within a very short duration) 
for each bin. For events with multiple explosions, sound from 
successive explosions can be expected to accumulate and increase the 
range to the onset of an impact based on SEL thresholds. Ranges to non-
auditory injury and mortality are shown in Table 28 and Table 29, 
respectively.
    No underwater detonations are planned as part of the Navy's 
activities, but marine mammals could be exposed to in-air detonations 
at or above the water surface. The Navy Acoustic Effects Model cannot 
account for the highly non-linear effects of cavitation and surface 
blow off for shallow underwater explosions, nor can it estimate the 
explosive energy entering the water from a low-altitude detonation. 
Thus, for this analysis, sources detonating in-air at or above (within 
10 m above) the water surface are modeled as if detonating completely 
underwater at a depth of 0.1 m, with all energy reflected into the 
water rather than released into the air. Therefore, the amount of 
explosive and acoustic energy entering the water, and consequently the 
estimated ranges to effects, are likely to be overestimated.
    Table 16 shows the minimum, average, and maximum ranges to onset of 
auditory and likely behavioral effects that rise to the level of Level 
B harassment for high-frequency cetaceans based on the developed 
thresholds.

                 Table 16--SEL-Based Ranges to Onset PTS, Onset TTS, and Behavioral Disturbance (in Meters) for High-Frequency Cetaceans
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                              Range to effects for explosives: high-frequency cetaceans \1\
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                Source depth
                    Bin\2\                           (m)        Cluster size             PTS                      TTS                   Behavioral
--------------------------------------------------------------------------------------------------------------------------------------------------------
E5...........................................             0.1               1            910 (850-975)      1,761 (1,275-2,275)      2,449 (1,775-3,275)
                                                                            7      1,275 (1,025-1,525)      3,095 (2,025-4,525)      4,664 (2,275-7,775)
E9...........................................             0.1               1      1,348 (1,025-1,775)      3,615 (2,025-5,775)      5,365 (2,525-8,525)
E10..........................................             0.1               1      1,546 (1,025-2,025)      4,352 (2,275-7,275)      5,949 (2,525-9,275)
E12..........................................             0.1               1      1,713 (1,275-2,025)      5,115 (2,275-7,775)     6,831 (2,775-10,275)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Average distance (meters) to PTS, TTS, and behavioral thresholds are depicted above the minimum and maximum distances which are in parentheses.
  Values depict the range produced by SEL hearing threshold criteria levels. No underwater explosions are planned. The model assumes that all explosive
  energy from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating ranges to effect. PTS = permanent
  threshold shift, SEL = sound exposure level, TTS = temporary threshold shift.
\2\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 17 shows the minimum, average, and maximum ranges to onset of 
auditory effects for high-frequency cetaceans based on the developed 
thresholds.

    Table 17--Peak Pressure-Based Ranges to Onset PTS and Onset TTS (in Meters) for High Frequency Cetaceans
----------------------------------------------------------------------------------------------------------------
                         Range to effects for explosives: high-frequency cetaceans[sup1]
-----------------------------------------------------------------------------------------------------------------
                                 Source depth
            Bin \2\                   (m)        Cluster size             PTS                      TTS
----------------------------------------------------------------------------------------------------------------
E5............................             0.1               1      1,161 (1,000-1,525)      1,789 (1,025-2,275)
                                                             7      1,161 (1,000-1,525)      1,789 (1,025-2,275)
E9............................             0.1               1      2,331 (1,525-2,775)      5,053 (2,025-9,275)
E10...........................             0.1               1      2,994 (1,775-4,525)     7,227 (2,025-14,775)
E12...........................             0.1               1      4,327 (2,025-7,275)    10,060 (2,025-22,275)
----------------------------------------------------------------------------------------------------------------
\1\ Average distance (meters) is shown with the minimum and maximum distances due to varying propagation
  environments in parentheses. No underwater explosions are planned. The model assumes that all explosive energy
  from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating
  ranges to effect. PTS = permanent threshold shift, TTS = temporary threshold shift.
\2\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 18 shows the minimum, average, and maximum ranges to onset of 
auditory and likely behavioral effects that rise to the level of Level 
B harassment for low-frequency cetaceans based on the developed 
thresholds.

[[Page 49712]]



                 Table 18--SEL-Based Ranges to Onset PTS, Onset TTS, and Behavioral Disturbance (in Meters) for Low-Frequency Cetaceans
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                              Range to effects for explosives: low-frequency cetaceans \1\
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   Source depth
                     Bin \2\                            (m)        Cluster size            PTS                    TTS                   Behavioral
--------------------------------------------------------------------------------------------------------------------------------------------------------
E5..............................................             0.1               1         171 (100-190)            633 (230-825)          934 (310-1,525)
                                                                               7         382 (170-450)        1,552 (380-5,775)       3,712 (600-13,025)
E9..............................................             0.1               1         453 (180-550)        3,119 (550-9,025)     6,462 (1,275-19,275)
E10.............................................             0.1               1         554 (210-700)       4,213 (600-13,025)     9,472 (1,775-27,275)
E12.............................................             0.1               1         643 (230-825)     6,402 (1,275-19,775)    13,562 (2,025-34,775)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Average distance (meters) to PTS, TTS, and behavioral thresholds are depicted above the minimum and maximum distances which are in parentheses.
  Values depict the range produced by SEL hearing threshold criteria levels. No underwater explosions are planned. The model assumes that all explosive
  energy from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating ranges to effect. PTS = permanent
  threshold shift, SEL = sound exposure level, TTS = temporary threshold shift.
\2\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 19 shows the minimum, average, and maximum ranges to onset of 
auditory effects for low-frequency cetaceans based on the developed 
thresholds.

     Table 19--Peak Pressure-Based Ranges to Onset PTS and Onset TTS (in Meters) for Low Frequency Cetaceans
----------------------------------------------------------------------------------------------------------------
                          Range to effects for explosives: low-frequency cetaceans \1\
-----------------------------------------------------------------------------------------------------------------
                                 Source depth
            Bin \2\                   (m)        Cluster size             PTS                      TTS
----------------------------------------------------------------------------------------------------------------
E5............................             0.1               1            419 (170-500)            690 (210-875)
                                                             7            419 (170-500)            690 (210-875)
E9............................             0.1               1          855 (270-1,275)        1,269 (400-1,775)
E10...........................             0.1               1          953 (300-1,525)        1,500 (450-2,525)
E12...........................             0.1               1        1,135 (360-1,525)        1,928 (525-4,775)
----------------------------------------------------------------------------------------------------------------
\1\ Average distance (meters) is shown with the minimum and maximum distances due to varying propagation
  environments in parentheses. No underwater explosions are planned. The model assumes that all explosive energy
  from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating
  ranges to effect. PTS = permanent threshold shift, TTS = temporary threshold shift.
\2\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 20 shows the minimum, average, and maximum ranges to onset of 
auditory and likely behavioral effects that rise to the level of Level 
B harassment for mid-frequency cetaceans based on the developed 
thresholds.

                 Table 20--SEL-Based Ranges to Onset PTS, Onset TTS, and Behavioral Disturbance (in Meters) for Mid-Frequency Cetaceans
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                              Range to effects for explosives: mid-frequency cetaceans \1\
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                Source depth
                   Bin \2\                           (m)        Cluster size             PTS                      TTS                   Behavioral
--------------------------------------------------------------------------------------------------------------------------------------------------------
E5...........................................             0.1               1               79 (75-80)            363 (360-370)            581 (550-600)
                                                                            7            185 (180-190)            777 (650-825)        1,157 (800-1,275)
E9...........................................             0.1               1            215 (210-220)            890 (700-950)        1,190 (825-1,525)
E10..........................................             0.1               1            275 (270-280)          974 (750-1,025)        1,455 (875-1,775)
E12..........................................             0.1               1            340 (340-340)        1,164 (825-1,275)        1,746 (925-2,025)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Average distance (meters) to PTS, TTS, and behavioral thresholds are depicted above the minimum and maximum distances which are in parentheses.
  Values depict the range produced by SEL hearing threshold criteria levels. No underwater explosions are planned. The model assumes that all explosive
  energy from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating ranges to effect. PTS = permanent
  threshold shift, SEL = sound exposure level, TTS = temporary threshold shift.
\2\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 21 shows the minimum, average, and maximum ranges to onset of 
auditory effects for mid-frequency cetaceans based on the developed 
thresholds.

[[Page 49713]]



     Table 21--Peak Pressure-Based Ranges to Onset PTS and Onset TTS (in Meters) for Mid-Frequency Cetaceans
----------------------------------------------------------------------------------------------------------------
                         Range to effects for explosives: mid-frequency cetaceans[sup1]
-----------------------------------------------------------------------------------------------------------------
                                 Source depth
            Bin \2\                   (m)        Cluster size             PTS                      TTS
----------------------------------------------------------------------------------------------------------------
E5............................             0.1               1            158 (150-160)            295 (290-300)
                                                             7            158 (150-160)            295 (290-300)
E9............................             0.1               1            463 (430-470)            771 (575-850)
E10...........................             0.1               1            558 (490-575)          919 (625-1,025)
E12...........................             0.1               1            679 (550-725)        1,110 (675-1,275)
----------------------------------------------------------------------------------------------------------------
\1\ Average distance (meters) is shown with the minimum and maximum distances due to varying propagation
  environments in parentheses. No underwater explosions are planned. The model assumes that all explosive energy
  from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating
  ranges to effect. PTS = permanent threshold shift, TTS = temporary threshold shift.
\2\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 22 shows the minimum, average, and maximum ranges to onset of 
auditory and likely behavioral effects that rise to the level of Level 
B harassment for otariid pinnipeds based on the developed thresholds.

                         Table 22--SEL-Based Ranges to Onset PTS, Onset TTS, and Behavioral Disturbance (in Meters) for Otariids
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                      Range to effects for explosives: otariids \1\
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                Source depth
                   Bin \2\                           (m)        Cluster size             PTS                      TTS                   Behavioral
--------------------------------------------------------------------------------------------------------------------------------------------------------
E5...........................................             0.1               1               25 (24-25)            110 (110-110)            185 (180-190)
                                                                            7               58 (55-60)            265 (260-270)            443 (430-450)
E9...........................................             0.1               1               68 (65-70)            320 (310-330)            512 (490-525)
E10..........................................             0.1               1               88 (85-90)            400 (390-410)            619 (575-675)
E12..........................................             0.1               1            105 (100-110)            490 (470-500)            733 (650-825)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Average distance (meters) to PTS, TTS, and behavioral thresholds are depicted above the minimum and maximum distances which are in parentheses.
  Values depict the range produced by SEL hearing threshold criteria levels. No underwater explosions are planned. The model assumes that all explosive
  energy from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating ranges to effect. PTS = permanent
  threshold shift, SEL = sound exposure level, TTS = temporary threshold shift.
\2\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 23 shows the minimum, average, and maximum ranges to onset of 
auditory effects for otariid pinnipeds based on the developed 
thresholds.

            Table 23--Peak Pressure-Based Ranges to Onset PTS and Onset TTS (in Meters) for Otariids
----------------------------------------------------------------------------------------------------------------
                                  Range to effects for explosives: otariids \1\
-----------------------------------------------------------------------------------------------------------------
                                       Source depth
               Bin \2\                      (m)        Cluster Size            PTS                   TTS
----------------------------------------------------------------------------------------------------------------
E5..................................             0.1               1         128 (120-130)         243 (240-250)
                                                                   7         128 (120-130)         243 (240-250)
E9..................................             0.1               1         383 (380-390)         656 (600-700)
E10.................................             0.1               1         478 (470-480)         775 (675-850)
E12.................................             0.1               1         583 (550-600)       896 (750-1,025)
----------------------------------------------------------------------------------------------------------------
\1\ Average distance (meters) is shown with the minimum and maximum distances due to varying propagation
  environments in parentheses. No underwater explosions are planned. The model assumes that all explosive energy
  from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating
  ranges to effect. PTS = permanent threshold shift, TTS = temporary threshold shift.
\2\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 24 shows the minimum, average, and maximum ranges to onset of 
auditory and likely behavioral effects that rise to the level of Level 
B harassment for phocid pinnipeds, excluding elephant seals, based on 
the developed thresholds.

[[Page 49714]]



            Table 24--SEL-Based Ranges to Onset PTS, Onset TTS, and Behavioral Disturbance (in Meters) for Phocids, Excluding Elephant Seals
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                      Range to effects for explosives: phocids \1\
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   Source depth
                     Bin \2\                            (m)        Cluster size            PTS                    TTS                   Behavioral
--------------------------------------------------------------------------------------------------------------------------------------------------------
E5..............................................             0.1               1         150 (150-150)            681 (675-700)        1,009 (975-1,025)
                                                                               7         360 (350-370)      1,306 (1,025-1,525)      1,779 (1,275-2,275)
E9..............................................             0.1               1         425 (420-430)      1,369 (1,025-1,525)      2,084 (1,525-2,775)
E10.............................................             0.1               1         525 (525-525)      1,716 (1,275-2,275)      2,723 (1,525-4,025)
E12.............................................             0.1               1         653 (650-675)      1,935 (1,275-2,775)      3,379 (1,775-5,775)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Excluding elephant seals.
\2\ Average distance (meters) is shown with the minimum and maximum distances due to varying propagation environments in parentheses. No underwater
  explosions are planned. The model assumes that all explosive energy from detonations at or above (within 10 m) the water surface is released
  underwater, likely over-estimating ranges to effect. PTS = permanent threshold shift, TTS = temporary threshold shift.
\3\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 25 shows the minimum, average, and maximum ranges to onset of 
auditory effects for phocids pinnipeds, excluding elephant seals, based 
on the developed thresholds.

   Table 25--Peak Pressure-Based Ranges to Onset PTS and Onset TTS (in Meters) for Phocids, Excluding Elephant
                                                      Seals
----------------------------------------------------------------------------------------------------------------
                                  Range to effects for explosives: phocids \1\
-----------------------------------------------------------------------------------------------------------------
                                 Source depth
            Bin \2\                   (m)        Cluster size             PTS                      TTS
----------------------------------------------------------------------------------------------------------------
E5............................             0.1               1            537 (525-550)            931 (875-975)
                                                             7            537 (525-550)            931 (875-975)
E9............................             0.1               1      1,150 (1,025-1,275)      1,845 (1,275-2,525)
E10...........................             0.1               1      1,400 (1,025-1,775)      2,067 (1,275-2,525)
E12...........................             0.1               1      1,713 (1,275-2,025)      2,306 (1,525-2,775)
----------------------------------------------------------------------------------------------------------------
\1\ Excluding elephant seals.
\2\ Average distance (meters) is shown with the minimum and maximum distances due to varying propagation
  environments in parentheses. No underwater explosions are planned. The model assumes that all explosive energy
  from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating
  ranges to effect. PTS = permanent threshold shift, TTS = temporary threshold shift.
\3\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 26 shows the minimum, average, and maximum ranges to onset of 
auditory and likely behavioral effects that rise to the level of Level 
B harassment for elephant seals based on the developed thresholds.

                    Table 26--SEL-Based Ranges to Onset PTS, Onset TTS, and Behavioral Disturbance (in Meters) for Elephant Seals \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                              Range to effects for explosives: phocids (elephant seals) \2\
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   Source depth
                     Bin \3\                            (m)        Cluster size            PTS                    TTS                   Behavioral
--------------------------------------------------------------------------------------------------------------------------------------------------------
E5..............................................             0.1               1         150 (150-150)            688 (675-700)      1,025 (1,025-1,025)
                                                                               7         360 (350-370)      1,525 (1,525-1,525)      2,345 (2,275-2,525)
E9..............................................             0.1               1         425 (420-430)      1,775 (1,775-1,775)      2,858 (2,775-3,275)
E10.............................................             0.1               1         525 (525-525)      2,150 (2,025-2,525)      3,421 (3,025-4,025)
E12.............................................             0.1               1         656 (650-675)      2,609 (2,525-3,025)      4,178 (3,525-5,775)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Elephant seals are separated from other phocids due to their dive behavior, which far exceeds the dive depths of the other phocids analyzed.
\2\ Average distance (meters) to PTS, TTS, and behavioral thresholds are depicted above the minimum and maximum distances which are in parentheses.
  Values depict the range produced by SEL hearing threshold criteria levels. No underwater explosions are planned. The model assumes that all explosive
  energy from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating ranges to effect. PTS = permanent
  threshold shift, SEL = sound exposure level, TTS = temporary threshold shift.
\3\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 27 shows the minimum, average, and maximum ranges to onset of 
auditory effects for elephant seals, based on the developed thresholds.

[[Page 49715]]



       Table 27--Peak Pressure-Based Ranges to Onset PTS and Onset TTS (in Meters) for Elephant Seals \1\
----------------------------------------------------------------------------------------------------------------
                          Range to effects for explosives: phocids (elephant seals) \2\
-----------------------------------------------------------------------------------------------------------------
                                 Source depth
            Bin \3\                   (m)        Cluster size             PTS                      TTS
----------------------------------------------------------------------------------------------------------------
E5............................             0.1               1            537 (525-550)            963 (950-975)
                                                             7            537 (525-550)            963 (950-975)
E9............................             0.1               1      1,275 (1,275-1,275)      2,525 (2,525-2,525)
E10...........................             0.1               1      1,775 (1,775-1,775)      3,046 (3,025-3,275)
E12...........................             0.1               1      2,025 (2,025-2,025)      3,539 (3,525-3,775)
----------------------------------------------------------------------------------------------------------------
\1\ Elephant seals are separated from other phocids due to their dive behavior, which far exceeds the dive
  depths of the other phocids analyzed.
\2\ Average distance (meters) is shown with the minimum and maximum distances due to varying propagation
  environments in parentheses. No underwater explosions are planned. The model assumes that all explosive energy
  from detonations at or above (within 10 m) the water surface is released underwater, likely over-estimating
  ranges to effect. PTS = permanent threshold shift, TTS = temporary threshold shift.
\3\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).

    Table 28 shows the minimum, average, and maximum ranges due to 
varying propagation conditions to non-auditory injury as a function of 
animal mass and explosive bin (i.e., net explosive weight). Ranges to 
gastrointestinal tract injury typically exceed ranges to slight lung 
injury; therefore, the maximum range to effect is not mass-dependent. 
Animals within these water volumes would be expected to receive minor 
injuries at the outer ranges, increasing to more substantial injuries, 
and finally mortality as an animal approaches the detonation point.

Table 28--Ranges to 50 Percent Non-Auditory Injury for All Marine Mammal
                             Hearing Groups
------------------------------------------------------------------------
                                                        Range to non-
                      Bin \1\                          auditory injury
                                                        (meters) \2\
------------------------------------------------------------------------
E5................................................            40 (40-40)
E9................................................          121 (90-130)
E10...............................................         152 (100-160)
E12...............................................         190 (110-200)
------------------------------------------------------------------------
\1\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10
  (>250-500), E12 (>650-1,000).
\2\ Average distance (m) is shown with the minimum and maximum distances
  due to varying propagation environments in parentheses.
Notes: All ranges to non-auditory injury within this table are driven by
  gastrointestinal tract injury thresholds regardless of animal mass.

    Ranges to mortality, based on animal mass, are shown in Table 29 
below.

                     Table 29--Ranges to 50 Percent Mortality Risk for All Marine Mammal Hearing Groups as a Function of Animal Mass
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                 Animal mass intervals (kg) \2\
                Bin \1\                -----------------------------------------------------------------------------------------------------------------
                                                10                250               1,000              5,000              25,000             72,000
--------------------------------------------------------------------------------------------------------------------------------------------------------
E5....................................         13 (12-14)           7 (4-11)            3 (3-4)            2 (1-3)            1 (1-1)            1 (0-1)
E9....................................         35 (30-40)         20 (13-30)          10 (9-13)            7 (6-9)            4 (3-4)            3 (2-3)
E10...................................         43 (40-50)         25 (16-40)         13 (11-16)           9 (7-11)            5 (4-5)            4 (3-4)
E12...................................         55 (50-60)         30 (20-50)         17 (14-20)          11 (9-14)            6 (5-7)            5 (4-6)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Bin (net explosive weight, lb.): E5 (>5-10), E9 (>100-250), E10 (>250-500), E12 (>650-1,000).
\2\ Average distance (m) to mortality is depicted above the minimum and maximum distances, which are in parentheses for each animal mass interval.

Marine Mammal Density

    A quantitative analysis of impacts on a species or stock requires 
data on their abundance and distribution that may be affected by 
anthropogenic activities in the potentially impacted area. The most 
appropriate metric for this type of analysis is density, which is the 
number of animals present per unit area. Marine species density 
estimation requires a significant amount of effort to both collect and 
analyze data to produce a reasonable estimate. Unlike surveys for 
terrestrial wildlife, many marine species spend much of their time 
submerged, and are not easily observed. In order to collect enough 
sighting data to make reasonable density estimates, multiple 
observations are required, often in areas that are not easily 
accessible (e.g., far offshore). Ideally, marine mammal species 
sighting data would be collected for the specific area and time period 
(e.g., season) of interest and density estimates derived accordingly. 
However, in many places, poor weather conditions and high sea states 
prohibit the completion of comprehensive visual surveys.
    For most cetacean species, abundance is estimated using line-
transect surveys or mark-recapture studies (e.g., Barlow, 2010; Barlow 
and Forney, 2007; Calambokidis et al., 2008). The result provides one 
single density estimate value for each species across broad geographic 
areas. This is the general approach applied in estimating cetacean 
abundance in NMFS' Stock Assessment Reports (SARs). Although the single 
value provides a good average estimate of abundance (total number of 
individuals) for a specified area, it does not provide information on 
the species distribution or concentrations within that area, and it 
does not estimate density for other timeframes or seasons that were not 
surveyed. More recently, spatial habitat modeling developed by NMFS' 
Southwest Fisheries Science Center has been used to estimate cetacean 
densities (Barlow et al., 2009; Becker et al., 2010, 2012a, 2012b, 
2012c, 2014, 2016; Ferguson et al., 2006a; Forney et al., 2012, 2015; 
Redfern et al., 2006). These models estimate cetacean density as a 
continuous function of habitat variables (e.g., sea surface 
temperature, seafloor depth, etc.) and thus allow predictions of 
cetacean

[[Page 49716]]

densities on finer spatial scales than traditional line-transect or 
mark recapture analyses and for areas that have not been surveyed. 
Within the geographic area that was modeled, densities can be predicted 
wherever these habitat variables can be measured or estimated.
    Ideally, density data would be available for all species throughout 
the study area year-round, in order to best estimate the impacts of 
Navy activities on marine species. However, in many places ship 
availability, lack of funding, inclement weather conditions, and high 
sea states prevent the completion of comprehensive year-round surveys. 
Even with surveys that are completed, poor conditions may result in 
lower sighting rates for species that would typically be sighted with 
greater frequency under favorable conditions. Lower sighting rates 
preclude having an acceptably low uncertainty in the density estimates. 
A high level of uncertainty, indicating a low level of confidence in 
the density estimate, is typical for species that are rare or difficult 
to sight. In areas where survey data are limited or non-existent, known 
or inferred associations between marine habitat features and the likely 
presence of specific species are sometimes used to predict densities in 
the absence of actual animal sightings. Consequently, there is no 
single source of density data for every area, species, and season 
because of the fiscal costs, resources, and effort involved in 
providing enough survey coverage to sufficiently estimate density.
    To characterize marine species density for large oceanic regions, 
the Navy reviews, critically assesses, and prioritizes existing density 
estimates from multiple sources, requiring the development of a 
systematic method for selecting the most appropriate density estimate 
for each combination of species/stock, area, and season. The selection 
and compilation of the best available marine species density data 
resulted in the Navy Marine Species Density Database (NMSDD), which 
includes seasonal density values for every marine mammal species and 
stock present within the TMAA. This database is described in the 
technical report titled U.S. Navy Marine Species Density Database Phase 
III for the Gulf of Alaska Temporary Maritime Activities Area (U.S. 
Department of the Navy, 2021), hereafter referred to as the Density 
Technical Report. NMFS vetted all cetacean densities by the Navy prior 
to use in the Navy's acoustic analysis for the current rulemaking 
process.
    A variety of density data and density models are needed in order to 
develop a density database that encompasses the entirety of the TMAA 
(densities beyond the TMAA were not considered because sonar and other 
transducers and explosives would not be used in the GOA Study Area 
beyond the TMAA). Because this data is collected using different 
methods with varying amounts of accuracy and uncertainty, the Navy has 
developed a hierarchy to ensure the most accurate data is used when 
available. The Density Technical Report describes these models in 
detail and provides detailed explanations of the models applied to each 
species density estimate. The below list describes models in order of 
preference.
    1. Spatial density models are preferred and used when available 
because they provide an estimate with the least amount of uncertainty 
by deriving estimates for divided segments of the sampling area. These 
models (see Becker et al., 2016; Forney et al., 2015) predict spatial 
variability of animal presence as a function of habitat variables 
(e.g., sea surface temperature, seafloor depth, etc.). This model is 
developed for areas, species, and, when available, specific timeframes 
(months or seasons) with sufficient survey data; therefore, this model 
cannot be used for species with low numbers of sightings.
    2. Stratified design-based density estimates use line-transect 
survey data with the sampling area divided (stratified) into sub-
regions, and a density is predicted for each sub-region (see Barlow, 
2016; Becker et al., 2016; Bradford et al., 2017; Campbell et al., 
2014; Jefferson et al., 2014). While geographically stratified density 
estimates provide a better indication of a species' distribution within 
the study area, the uncertainty is typically high because each sub-
region estimate is based on a smaller stratified segment of the overall 
survey effort.
    3. Design-based density estimations use line-transect survey data 
from vessel and aerial surveys designed to cover a specific geographic 
area (see Carretta et al., 2015). These estimates use the same survey 
data as stratified design-based estimates, but are not segmented into 
sub-regions and instead provide one estimate for a large surveyed area.
    Relative environmental suitability (RES) models provide estimates 
for areas of the oceans that have not been surveyed using information 
on species occurrence and inferred habitat associations and have been 
used in past density databases, however, these models were not used in 
the current quantitative analysis.
    The Navy describes some of the challenges of interpreting the 
results of the quantitative analysis summarized above and described in 
the Density Technical Report: ``It is important to consider that even 
the best estimate of marine species density is really a model 
representation of the values of concentration where these animals might 
occur. Each model is limited to the variables and assumptions 
considered by the original data source provider. No mathematical model 
representation of any biological population is perfect, and with 
regards to marine mammal biodiversity, any single model method will not 
completely explain the actual distribution and abundance of marine 
mammal species. It is expected that there would be anomalies in the 
results that need to be evaluated, with independent information for 
each case, to support if we might accept or reject a model or portions 
of the model'' (U.S. Department of the Navy, 2017a).
    The Navy's estimate of abundance (based on the density estimates 
used) in the TMAA may differ from population abundances estimated in 
NMFS' SARs in some cases for a variety of reasons. Models may predict 
different population abundances for many reasons. The models may be 
based on different data sets or different temporal predictions may be 
made. The SARs are often based on single years of NMFS surveys, whereas 
the models used by the Navy generally include multiple years of survey 
data from NMFS, the Navy, and other sources. To present a single, best 
estimate, the SARs often use a single season survey where they have the 
best spatial coverage (generally summer). Navy models often use 
predictions for multiple seasons, where appropriate for the species, 
even when survey coverage in non-summer seasons is limited, to 
characterize impacts over multiple seasons as Navy activities may occur 
outside of the summer months. Predictions may be made for different 
spatial extents. Many different, but equally valid, habitat and density 
modeling techniques exist and these can also be the cause of 
differences in population predictions. Differences in population 
estimates may be caused by a combination of these factors. Even similar 
estimates should be interpreted with caution and differences in models 
fully understood before drawing conclusions.
    In particular, the global population structure of humpback whales, 
with 14 DPSs all associated with multiple feeding areas at which 
individuals from multiple DPSs convene, is another reason that SAR 
abundance estimates can differ from other estimates and be somewhat 
confusing--the same individuals are addressed in multiple

[[Page 49717]]

SARs. For some species, the stock assessment for a given species may 
exceed the Navy's density prediction because those species' home range 
extends beyond the GOA Study Area or TMAA boundaries. The primary 
source of density estimates are geographically specific survey data and 
either peer-reviewed line-transect estimates or habitat-based density 
models that have been extensively validated to provide the most 
accurate estimates possible.
    These factors and others described in the Density Technical Report 
should be considered when examining the estimated impact numbers in 
comparison to current population abundance information for any given 
species or stock. For a detailed description of the density and 
assumptions made for each species, see the Density Technical Report.
    NMFS coordinated with the Navy in the development of its take 
estimates and concurs that the Navy's approach for density 
appropriately utilizes the best available science. Later, in the 
Preliminary Analysis and Negligible Impact Determination section, we 
assess how the estimated take numbers compare to stock abundance in 
order to better understand the potential number of individuals 
impacted, and the rationale for which abundance estimate is used is 
included there.

Take Request

    The 2020 GOA DSEIS/OEIS considered all training activities proposed 
to occur in the TMAA, and the 2022 Supplement to the 2020 GOA DSEIS/
OEIS considered all training activities proposed to occur in the WMA, 
together for which they covered all activities proposed for the GOA 
Study Area. The Navy's rulemaking/LOA application described the 
activities that are reasonably likely to result in the MMPA-defined 
take of marine mammals, all of which would occur in the TMAA portion of 
the GOA Study Area. The Navy determined that the two stressors below 
could result in the incidental taking of marine mammals. NMFS has 
reviewed the Navy's data and analysis for the entire Study Area and 
determined that it is complete and accurate, and agrees that the 
following stressors have the potential to result in takes by harassment 
of marine mammals from the Navy's planned activities.
     Acoustics (sonar and other transducers); and
     Explosives (explosive shock wave and sound, assumed to 
encompass the risk due to fragmentation).
    The quantitative analysis process used to estimate potential 
exposures to marine mammals resulting from acoustic and explosive 
stressors for the Navy's take request in the rulemaking/LOA application 
and the 2020 GOA DSEIS/OEIS is detailed in the technical report titled 
Quantifying Acoustic Impacts on Marine Mammals and Sea Turtles: Methods 
and Analytical Approach for Phase III Training and Testing (U.S. 
Department of the Navy, 2018). The Navy Acoustic Effects Model 
estimates acoustic and explosive effects without taking mitigation into 
account; therefore, the model overestimates predicted impacts on marine 
mammals within mitigation zones.
    To account for mitigation for marine species in the take estimates, 
the Navy conducts a quantitative assessment of mitigation. The Navy 
conservatively quantifies the manner in which procedural mitigation is 
expected to reduce the risk for model-estimated PTS for exposures to 
sonars and for model-estimated mortality for exposures to explosives, 
based on species sightability, observation area, visibility, and the 
ability to exercise positive control over the sound source. Where the 
analysis indicates mitigation would effectively reduce risk, the model-
estimated PTS are considered reduced to TTS and the model-estimated 
mortalities are considered reduced to injury, though, for training 
activities in the GOA Study Area, no mortality or non-auditory injury 
is anticipated, even without consideration of planned mitigation 
measures. For a complete explanation of the process for assessing the 
effects of mitigation, see the Navy's rulemaking/LOA application 
(Section 6: Take Estimates for Marine Mammals, and Section 11: 
Mitigation Measures) and the technical report titled Quantifying 
Acoustic Impacts on Marine Mammals and Sea Turtles: Methods and 
Analytical Approach for Phase III Training and Testing (U.S. Department 
of the Navy, 2018). The extent to which the mitigation areas reduce 
impacts on the affected species is addressed separately in the 
Preliminary Analysis and Negligible Impact Determination section.
    The Navy assesses the effectiveness of its procedural mitigation 
measures on a per-scenario basis for four factors: (1) species 
sightability, (2) a Lookout's ability to observe the range to PTS (for 
sonar and other transducers) and range to mortality (for explosives, 
although for this rule the Navy's modeling indicated that no mortality 
would occur), (3) the portion of time when mitigation could potentially 
be conducted during periods of reduced daytime visibility (to include 
inclement weather and high sea-state) and the portion of time when 
mitigation could potentially be conducted at night, and (4) the ability 
for sound sources to be positively controlled (e.g., powered down).
    During training activities, there is typically at least one, if not 
numerous, support personnel involved in the activity (e.g., range 
support personnel aboard a torpedo retrieval boat or support aircraft). 
In addition to the Lookout posted for the purpose of mitigation, these 
additional personnel observe and disseminate marine species sighting 
information amongst the units participating in the activity whenever 
possible as they conduct their primary mission responsibilities. 
However, as a conservative approach to assigning mitigation 
effectiveness factors, the Navy elected to only account for the minimum 
number of required Lookouts used for each activity; therefore, the 
mitigation effectiveness factors may underestimate the likelihood that 
some marine mammals may be detected during activities that are 
supported by additional personnel who may also be observing the 
mitigation zone.
    For a rulemaking where NMFS and the Navy determine that the planned 
activities, such as use of explosives, could cause mortality, the Navy 
would use the equations in the below sections to calculate the 
reduction in model-estimated mortality impacts due to implementing 
procedural mitigation.
    Equation 1:

Mitigation Effectiveness = Species Sightability x Visibility x 
Observation Area x Positive Control

    Species Sightability is the ability to detect marine mammals and is 
dependent on the animal's presence at the surface and the 
characteristics of the animal that influence its sightability. The Navy 
considered applicable data from the best available science to 
numerically approximate the sightability of marine mammals and 
determined the standard ``detection probability'' referred to as g(0) 
is most appropriate. Also, Visibility = 1- sum of individual visibility 
reduction factors; Observation Area = portion of impact range that can 
be continuously observed during an event; and Positive Control = 
positive control factor of all sound sources involving mitigation. For 
further details on these mitigation effectiveness factors please refer 
to the technical report titled Quantifying Acoustic Impacts on Marine 
Mammals and Sea Turtles: Methods and Analytical Approach for Phase III 
Training and Testing (U.S. Department of the Navy, 2018).
    To quantify the number of marine mammals predicted to be sighted by 
Lookouts in the injury zone during

[[Page 49718]]

implementation of procedural mitigation for sonar and other 
transducers, the species sightability is multiplied by the mitigation 
effectiveness scores and number of model-estimated PTS impacts, as 
shown in the equation below:
    Equation 2:

Number of Animals Sighted by Lookouts = Mitigation Effectiveness x 
Model - Estimated Impacts

    The marine mammals sighted by Lookouts in the injury zone during 
implementation of mitigation, as calculated by the equation above, 
would not be exposed to these higher level impacts. To quantify the 
number of marine mammals predicted to be sighted by Lookouts in the 
mortality zone during implementation of procedural mitigation during 
events using explosives (if any mortality were anticipated to occur), 
the species sightability is multiplied by the mitigation effectiveness 
scores and number of model-estimated mortality impacts, as shown in 
equation 1 above. The marine mammals predicted to be sighted in the 
mortality zone by Lookouts during implementation of procedural 
mitigation, as calculated by the above equation 2, are not predicted to 
be exposed in these ranges. The Navy corrects the category of predicted 
impact for the number of animals sighted within the mitigation zone, 
but does not modify the total number of animals predicted to experience 
impacts from the scenario. For example, the number of animals sighted 
(i.e., number of animals that will avoid mortality) is first subtracted 
from the model-predicted mortality impacts, and then added to the 
model-predicted injurious impacts.
    The NAEMO model overestimates the number of marine mammals that 
would be exposed to sound sources that could cause PTS because the 
model does not consider horizontal movement of animats, including 
avoidance of high intensity sound exposures. Therefore, the potential 
for animal avoidance is considered separately. At close ranges and high 
sound levels, avoidance of the area immediately around the sound source 
is one of the assumed behavioral responses for marine mammals. Animal 
avoidance refers to the movement out of the immediate injury zone for 
subsequent exposures, not wide-scale area avoidance. Various 
researchers have demonstrated that cetaceans can perceive the location 
and movement of a sound source (e.g., vessel, seismic source, etc.) 
relative to their own location and react with responsive movement away 
from the source, often at distances of 1 km or more (Au and Perryman, 
1982; Jansen et al., 2010; Richardson et al., 1995; Tyack et al., 2011; 
Watkins, 1986; W[uuml]rsig et al., 1998). A marine mammal's ability to 
avoid a sound source and reduce its cumulative sound energy exposure 
would reduce risk of both PTS and TTS. However, the quantitative 
analysis conservatively only considers the potential to reduce some 
instances of PTS by accounting for marine mammals swimming away to 
avoid repeated high-level sound exposures. All reductions in PTS 
impacts from likely avoidance behaviors are instead considered TTS 
impacts.
    NMFS coordinated with the Navy in the development of this 
quantitative method to address the effects of procedural mitigation on 
acoustic and explosive exposures and takes, and NMFS independently 
reviewed and concurs with the Navy that it is appropriate to 
incorporate the quantitative assessment of mitigation into the take 
estimates based on the best available science. We reiterate, however, 
that no mortality was modeled for the GOA TMAA activities, and as 
stated above, the Navy does not propose the use of sonar and other 
transducers and explosives in the WMA. Therefore, this method was not 
applied here, as it relates to modeled mortality. This method was 
applied to potential takes by PTS resulting from sonar and other 
transducers in the TMAA, but not for the use of explosives. For 
additional information on the quantitative analysis process and 
mitigation measures, refer to the technical report titled Quantifying 
Acoustic Impacts on Marine Mammals and Sea Turtles: Methods and 
Analytical Approach for Phase III Training and Testing (U.S. Department 
of the Navy, 2018) and Chapter 6 (Take Estimates for Marine Mammals) 
and Chapter 11 (Mitigation Measures) of the Navy's rulemaking/LOA 
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 the 
affected populations. There are multiple pieces of the Navy take 
estimation methods--propagation models, animat movement models, and 
behavioral thresholds, for example. 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 all of them have undergone comprehensive 
review by NMFS, which has sometimes resulted in modifications to 
methods or models.
    The Navy uses rigorous review processes (verification, validation, 
and accreditation processes; peer and public review) to ensure the data 
and methodology it uses represent the best available science. For 
instance, the NAEMO model is the result of a NMFS-led Center for 
Independent Experts (CIE) review of the components used in earlier 
models. The acoustic propagation component of the NAEMO model (CASS/
GRAB) is accredited by the Oceanographic and Atmospheric Master Library 
(OAML), and many of the environmental variables used in the NAEMO model 
come from approved OAML databases and are based on in-situ data 
collection. The animal density components of the NAEMO model are base 
products of the NMSDD, which includes 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 the Duke University habitat-based density models, 
have been published in peer reviewed literature. Others like the 
Atlantic Marine Assessment Program for Protected Species, which was 
conducted by NMFS Science Centers, have undergone quality assurance and 
quality control (QA/QC) processes. Finally, the NAEMO model simulation 
components underwent QA/QC review and validation for model parts such 
as the 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 underlying 
NAEMO modeling and the method for incorporating mitigation and 
avoidance, are the most appropriate methods for predicting non-auditory 
injury, PTS, TTS, and behavioral disturbance. But even with the 
consideration of mitigation and 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

[[Page 49719]]

instances in which marine mammals would be reasonably expected to be 
taken through non-auditory injury, PTS, TTS, or behavioral disturbance.
Summary of Requested Take From Training Activities
    Based on the methods discussed in the previous sections and the 
Navy's model and quantitative assessment of mitigation, the Navy 
provided its take estimate and request for authorization of takes 
incidental to the use of acoustic and explosive sources for training 
activities both annually (based on the maximum number of activities 
that could occur per 12-month period) and over the 7-year period 
covered by the Navy's rulemaking/LOA application. The following 
species/stocks present in the TMAA were modeled by the Navy and 
estimated to have 0 takes of any type from any activity source: Western 
North Pacific stock of humpback whale; Eastern North Pacific and 
Western North Pacific stocks of gray whales; Eastern North Pacific 
Alaska Resident and AT1 Transient stocks of killer whales; Gulf of 
Alaska and Southeast Alaska stocks of harbor porpoises; U.S. stock of 
California sea lion; Eastern U.S. and Western U.S. stock of Steller sea 
lion; Cook Inlet/Shelikof Strait, North Kodiak, Prince William Sound, 
and South Kodiak stocks of harbor seals, and Alaska stock of Ribbon 
seals.
    The Phase II rule (82 FR 19530; April 26, 2017), valid from April 
2017 to April 2022, authorized Level B harassment take of the Eastern 
North Pacific Alaska Resident stock of killer whales, Gulf of Alaska 
and Southeast Alaska stocks of harbor porpoise, California sea lion, 
Eastern U.S. and Western U.S. stock of Steller sea lion, and South 
Kodiak and Prince William Sound stocks of harbor seal. Takes of these 
stocks in Phase II were all expected to occur as a result of exposure 
to sonar activity, rather than explosive use. Inclusion of new density/
distribution information and updated BRFs and corresponding cut-offs 
resulted in 0 estimated takes for these species and stocks in this 
rulemaking for Phase III.
    NMFS has reviewed the Navy's data, methodology, and analysis for 
the current phase of rulemaking (Phase III) and determined that it is 
complete and accurate. However, NMFS has conservatively proposed to 
include incidental take of the Western North Pacific stock of humpback 
whale and Eastern North Pacific stock of gray whale, for the following 
reasons. For the Western North Pacific stock of humpback whale, in 
calculating takes by Level B harassment from sonar in Phase III, the 
application of the Phase III BRFs with corresponding cut-offs (20 km 
for mysticetes), in addition to the stock guild breakout which assigns 
0.05 percent of the take of humpback whales to the Western North 
Pacific stock, generated a near-zero result, which the Navy rounded to 
zero in its rulemaking/LOA application. However, NMFS authorized take 
of one Western North Pacific humpback whale in the Phase II LOA, and, 
given that they do occur in the area, NMFS is conservatively proposing 
to authorize take by Level B harassment of one group (3 animals) 
annually in this Phase III rulemaking. The annual take estimate of 3 
animals reflects the average group size of on and off-effort survey 
sightings of humpback whales reported in Rone et al. (2017). For the 
Eastern North Pacific stock of gray whales, application of the Phase 
III BRFs with corresponding cut-offs (20 km for mysticetes) resulted in 
true zero takes by Level B harassment for Phase III. However, Palacios 
et al. (2021) reported locations of three tagged gray whales within the 
TMAA as well as tracks of two additional gray whales that crossed the 
TMAA, and as noted previously, the TMAA overlaps with the gray whale 
migratory corridor BIA (November-January, southbound; March-May, 
northbound). As such, NMFS is conservatively proposing to authorize 
take by Level B harassment of one group (4 animals) of Eastern North 
Pacific gray whales annually in this Phase III rulemaking. The annual 
take estimate of 4 animals reflects the average group sizes of on and 
off-effort survey sightings of gray whales (excluding an outlier of an 
estimated 25 gray whales in one group) reported in Rone et al. (2017).
    For all other species and stocks, NMFS agrees that the estimates 
for incidental takes by harassment from all sources requested for 
authorization are the maximum number of instances in which marine 
mammals are reasonably expected to be taken. NMFS also agrees that no 
mortality or serious injury is anticipated to occur, and no lethal take 
is proposed to be authorized.
Estimated Harassment Take From Training Activities
    For the Navy's training activities, Table 30 summarizes the Navy's 
take estimate and request and the maximum annual and 7-year total 
amount and type of Level A harassment and Level B harassment for the 7-
year period that NMFS anticipates is reasonably likely to occur 
(including the incidental take of Western North Pacific stock of 
humpback whale and Eastern North Pacific stock of gray whale, discussed 
above) by species and stock. Note that take by Level B harassment 
includes both behavioral disruption and TTS. Tables 6-10 through 6-24 
(sonar and other transducers) and 6-41 through 6-49 (explosives) in 
Section 6 of the Navy's rulemaking/LOA application provide the 
comparative amounts of TTS and behavioral disruption for each species 
and stock annually, noting that if a modeled marine mammal was 
``taken'' through exposure to both TTS and behavioral disruption in the 
model, it was recorded as a TTS.

 Table 30--Annual and 7-Year Total Species/Stock-Specific Take Estimates Proposed for Authorization From Acoustic and Explosive Sound Source Effects for
                                                           All Training Activities in the TMAA
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                      Annual                       7-year total
                    Species                                       Stock                  ---------------------------------------------------------------
                                                                                              Level B         Level A         Level B         Level A
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Order Cetacea
                                                           Suborder Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Balaenidae (right whales):
    North Pacific right whale *................  Eastern North Pacific..................               3               0              21               0
Family Balaenopteridae (rorquals):
    Humpback whale.............................  California, Oregon, & Washington *.....              10               0              70               0
                                                 Central North Pacific *................              79               0             553               0
                                                 Western North Pacific *................           \a\ 3               0          \a\ 21               0
    Blue whale *...............................  Central North Pacific..................               3               0              21               0
                                                 Eastern North Pacific..................              36               0             252               0
    Fin whale *................................  Northeast Pacific......................           1,242               2           8,694              14

[[Page 49720]]

 
    Sei whale *................................  Eastern North Pacific..................              37               0             259               0
    Minke whale................................  Alaska.................................              50               0             350               0
Family Eschrichtiidae (gray whale):
    Gray whale.................................  Eastern North Pacific..................           \a\ 4               0          \a\ 28               0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Suborder Odontoceti (toothed whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Delphinidae (dolphins):
    Killer whale...............................  Eastern North Pacific, Offshore........              81               0             567               0
                                                 Gulf of Alaska, Aleutian Island, &                  143               0           1,001               0
                                                  Bering Sea Transient.
    Pacific white-sided dolphin................  North Pacific..........................           1,574               0          11,018               0
Family Phocoenidae (porpoises):
    Dall's porpoise............................  Alaska.................................           9,287              64          65,009             448
Family Physeteridae (sperm whale):
    Sperm whale *..............................  North Pacific..........................             112               0             784               0
Family Ziphiidae (beaked whales):
    Baird's beaked whale.......................  Alaska.................................             106               0             742               0
    Cuvier's beaked whale......................  Alaska.................................             433               0           3,031               0
    Stejneger's beaked whale...................  Alaska.................................             482               0           3,374               0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                     Order Carnivora
                                                                   Suborder Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otarridae:
    Northern fur seal..........................  Eastern Pacific........................           3,003               0          21,021               0
                                                 California.............................              61               0             427               0
Family Phocidae (true seals):
    Northern elephant seal.....................  California.............................           2,547               8          17,829              56
--------------------------------------------------------------------------------------------------------------------------------------------------------
* ESA-listed species and stocks within the GOA Study Area.
\a\ The Navy's Acoustic Effects Model estimated zero takes for each of these stocks. However, NMFS conservatively proposes to authorize take by Level B
  harassment of one group of Western North Pacific humpback whale and one group of Eastern North Pacific gray whale. The annual take estimates reflect
  the average group sizes of on and off-effort survey sightings of humpback whale and gray whale (excluding an outlier of an estimated 25 gray whales in
  one group) reported in Rone et al. (2017).

Proposed 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 practicable adverse impact. The 2004 NDAA amended 
the MMPA as it relates to military readiness activities and the 
incidental take authorization 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.
    In Conservation Council for Hawaii v. National Marine Fisheries 
Service, 97 F. Supp. 3d 1210, 1229 (D. Haw. 2015), the Court stated 
that NMFS ``appear[s] to think [it] satisf[ies] the statutory `least 
practicable adverse impact' requirement with a `negligible impact' 
finding.'' In 2016, expressing similar concerns in a challenge to a 
U.S. Navy Surveillance Towed Array Sensor System Low Frequency Active 
Sonar (SURTASS LFA) incidental take rule (77 FR 50290), the Ninth 
Circuit Court of Appeals in Natural Resources Defense Council (NRDC) v. 
Pritzker, 828 F.3d 1125, 1134 (9th Cir. 2016), stated ``[c]ompliance 
with the `negligible impact' requirement does not mean there [is] 
compliance with the `least practicable adverse impact' standard.'' As 
the Ninth Circuit noted in its opinion, however, the Court was 
interpreting the statute without the benefit of NMFS' formal 
interpretation. We state here explicitly that NMFS is in full agreement 
that the ``negligible impact'' and ``least practicable adverse impact'' 
requirements are distinct, even though both statutory standards refer 
to species and stocks. With that in mind, we provide further 
explanation of our interpretation of least practicable adverse impact, 
and explain what distinguishes it from the negligible impact standard. 
This discussion is consistent with previous rules we have published, 
such as the Navy's HSTT rule (83 FR 66846; December 27, 2018), AFTT 
rule (84 FR 70712; December 23, 2019), Mariana Islands Training and 
Testing (MITT) rule (85 FR 46302; July 31, 2020), and the Northwest 
Training and Testing (NWTT) rule (85 FR 72312; November 12, 2020).
    Before NMFS can issue incidental take regulations under section 
101(a)(5)(A) of the MMPA, it must make a finding that the total taking 
will have a ``negligible impact'' on the affected ``species or stocks'' 
of marine mammals. NMFS' and U.S. Fish and Wildlife Service's 
implementing regulations for section 101(a)(5) both define ``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 and 50 CFR 18.27(c)). 
Recruitment (i.e., reproduction) and survival rates are used to 
determine

[[Page 49721]]

population growth rates \2\ and, therefore are considered in evaluating 
population level impacts.
---------------------------------------------------------------------------

    \2\ A growth rate can be positive, negative, or flat.
---------------------------------------------------------------------------

    As stated in the preamble to the proposed rule for the MMPA 
incidental take implementing regulations (53 FR 8473; March 15, 1988), 
not every population-level impact violates the negligible impact 
requirement. The negligible impact standard does not require a finding 
that the anticipated take will have ``no effect'' on population numbers 
or growth rates: the statutory standard does not require that the same 
recovery rate be maintained, rather it requires that no significant 
effect on annual rates of recruitment or survival occurs. The key 
factor is the significance of the level of impact on rates of 
recruitment or survival. (54 FR 40338, 40341-42; September 29, 1989).
    While some level of impact on population numbers or growth rates of 
a species or stock may occur and still satisfy the negligible impact 
requirement--even without consideration of mitigation--the least 
practicable adverse impact provision separately requires NMFS to 
prescribe means of effecting the least practicable adverse impact on 
the species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance (50 CFR 
216.102(b)), which are typically identified as the subject of 
mitigation measures.\3\
---------------------------------------------------------------------------

    \3\ Separately, NMFS also must prescribe means of effecting the 
least practicable adverse impact on the availability of the species 
or stocks for subsistence uses, when applicable. See the Subsistence 
Harvest of Marine Mammals section for separate discussion of the 
effects of the specified activities on Alaska Native subsistence 
use.
---------------------------------------------------------------------------

    The negligible impact and least practicable adverse impact 
standards in the MMPA both call for evaluation at the level of the 
``species or stock.'' The MMPA does not define the term ``species.'' 
However, Merriam-Webster Dictionary defines ``species'' to include 
``related organisms or populations potentially capable of 
interbreeding.'' See www.merriam-webster.com/dictionary/species 
(emphasis added). Section 3(11) of the MMPA defines ``stock'' as a 
group of marine mammals of the same species or smaller taxa in a common 
spatial arrangement that interbreed when mature. The definition of 
``population'' is a group of interbreeding organisms that represents 
the level of organization at which speciation begins. www.merriam-webster.com/dictionary/population. The definition of ``population'' is 
strikingly similar to the MMPA's definition of ``stock,'' with both 
involving groups of individuals that belong to the same species and are 
located in a manner that allows for interbreeding. In fact, under MMPA 
section 3(11), the statutory term ``stock'' in the MMPA is 
interchangeable with the statutory term ``population stock.'' Both the 
negligible impact standard and the least practicable adverse impact 
standard call for evaluation at the level of the species or stock, and 
the terms ``species'' and ``stock'' both relate to populations; 
therefore, it is appropriate to view both the negligible impact 
standard and the least practicable adverse impact standard as having a 
population-level focus.
    This interpretation is consistent with Congress' statutory findings 
for enacting the MMPA, nearly all of which are most applicable at the 
species or stock (i.e., population) level. See MMPA section 2 (finding 
that it is species and population stocks that are or may be in danger 
of extinction or depletion; that it is species and population stocks 
that should not diminish beyond being significant functioning elements 
of their ecosystems; and that it is species and population stocks that 
should not be permitted to diminish below their optimum sustainable 
population level). Annual rates of recruitment (i.e., reproduction) and 
survival are the key biological metrics used in the evaluation of 
population-level impacts, and accordingly these same metrics are also 
used in the evaluation of population level impacts for the least 
practicable adverse impact standard.
    Recognizing this common focus of the least practicable adverse 
impact and negligible impact provisions on the ``species or stock'' 
does not mean we conflate the two standards; despite some common 
statutory language, we recognize the two provisions are different and 
have different functions. First, a negligible impact finding is 
required before NMFS can issue an incidental take authorization. 
Although it is acceptable to use the mitigation measures to reach a 
negligible impact finding (see 50 CFR 216.104(c)), no amount of 
mitigation can enable NMFS to issue an incidental take authorization 
for an activity that still would not meet the negligible impact 
standard. Moreover, even where NMFS can reach a negligible impact 
finding--which we emphasize does allow for the possibility of some 
``negligible'' population-level impact--the agency must still prescribe 
measures that will affect the least practicable amount of adverse 
impact upon the affected species or stock.
    Section 101(a)(5)(A)(i)(II) requires NMFS to issue, in conjunction 
with its authorization, binding--and enforceable--restrictions (in the 
form of regulations) setting forth how the activity must be conducted, 
thus ensuring the activity has the ``least practicable adverse impact'' 
on the affected species or stocks. In situations where mitigation is 
specifically needed to reach a negligible impact determination, section 
101(a)(5)(A)(i)(II) also provides a mechanism for ensuring compliance 
with the ``negligible impact'' requirement. Finally, the least 
practicable adverse impact standard also requires consideration of 
measures for marine mammal habitat, with particular attention to 
rookeries, mating grounds, and other areas of similar significance, and 
for subsistence impacts, whereas the negligible impact standard is 
concerned solely with conclusions about the impact of an activity on 
annual rates of recruitment and survival.\4\ In NRDC v. Pritzker, the 
Court stated, ``[t]he statute is properly read to mean that even if 
population levels are not threatened significantly, still the agency 
must adopt mitigation measures aimed at protecting marine mammals to 
the greatest extent practicable in light of military readiness needs.'' 
Pritzker at 1134 (emphases added). This statement is consistent with 
our understanding stated above that even when the effects of an action 
satisfy the negligible impact standard (i.e., in the Court's words, 
``population levels are not threatened significantly''), still the 
agency must prescribe mitigation under the least practicable adverse 
impact standard. However, as the statute indicates, the focus of both 
standards is ultimately the impact on the affected ``species or 
stock,'' and not solely focused on or directed at the impact on 
individual marine mammals.
---------------------------------------------------------------------------

    \4\ Outside of the military readiness context, mitigation may 
also be appropriate to ensure compliance with the ``small numbers'' 
language in MMPA sections 101(a)(5)(A) and (D).
---------------------------------------------------------------------------

    We have carefully reviewed and considered the Ninth Circuit's 
opinion in NRDC v. Pritzker in its entirety. While the Court's 
reference to ``marine mammals'' rather than ``marine mammal species or 
stocks'' in the italicized language above might be construed as holding 
that the least practicable adverse impact standard applies at the 
individual ``marine mammal'' level, i.e., that NMFS must require 
mitigation to minimize impacts to each individual marine mammal unless 
impracticable, we believe such an interpretation reflects an incomplete 
appreciation of the Court's holding. In our view, the opinion as a 
whole turned on the Court's determination that NMFS had not given 
separate and independent

[[Page 49722]]

meaning to the least practicable adverse impact standard apart from the 
negligible impact standard, and further, that the Court's use of the 
term ``marine mammals'' was not addressing the question of whether the 
standard applies to individual animals as opposed to the species or 
stock as a whole. We recognize that, while consideration of mitigation 
can play a role in a negligible impact determination, consideration of 
mitigation measures extends beyond that analysis. In evaluating what 
mitigation measures are appropriate, NMFS considers the potential 
impacts of the specified activities, the availability of measures to 
minimize those potential impacts, and the practicability of 
implementing those measures, as we describe below.

Implementation of Least Practicable Adverse Impact Standard

    Given the NRDC v. Pritzker decision, we discuss here 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 Navy's activities meets the 
``negligible impact'' standard appears in the Preliminary 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 (such as 
likelihood, scope, and range), the likelihood that the measure will be 
effective if implemented, and the likelihood of successful 
implementation; and
    (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 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. We also acknowledge that there is always 
the potential that new information, or a new recommendation, could 
become available in the future and necessitate reevaluation of 
mitigation measures (which may be addressed through adaptive 
management) to see if further reductions of population impacts are 
possible and practicable.
    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, a measure might involve restrictions in an area or time 
that impede the Navy's ability to certify a strike group (higher impact 
on mission effectiveness), or it could mean delaying a small in-port 
training event by 30 minutes to avoid exposure of a marine mammal to 
injurious levels of sound (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.
    1. 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 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: 
avoiding or minimizing injury or mortality; limiting interruption of 
known feeding, breeding, mother/young, or resting behaviors; minimizing 
the abandonment of important habitat (temporally and spatially); 
minimizing the number of individuals subjected to these types of 
disruptions; and 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 that are expected in the 
absence of mitigation in order to assess the added value of any 
potential

[[Page 49723]]

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 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 (either alone, or in combination) result in greater emphasis 
on the importance of a mitigation measure in reducing impacts on a 
species or stock: the stock is known to be decreasing or status is 
unknown, but believed to be declining; the known annual mortality (from 
any source) is approaching or exceeding the potential biological 
removal (PBR) level (as defined in MMPA section 3(20)); the affected 
species or stock is a small, resident population; or the stock is 
involved in a UME or has other known vulnerabilities, such as 
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.
    2. 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 MMPA section 
101(a)(5)(A)(ii)).

Assessment of Mitigation Measures for the GOA Study Area

    NMFS has fully reviewed the specified activities and the mitigation 
measures included in the Navy's rulemaking/LOA application, the 2020 
GOA DSEIS/OEIS, and the 2022 Supplement to the 2020 GOA DSEIS/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 the Navy's 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 5 (Mitigation) of the 2020 
GOA DSEIS/OEIS. The process described in Chapter 5 (Mitigation) of the 
2020 GOA DSEIS/OEIS robustly supported NMFS' independent evaluation of 
whether the mitigation measures would meet the least practicable 
adverse impact standard, including the addition of the Continental 
Shelf and Slope Mitigation Area presented in the February 2022 second 
updated application and analyzed in the 2022 Supplement to the 2020 GOA 
DSEIS/OEIS. The Navy would be required to implement the mitigation 
measures identified in this rule for the full 7 years to avoid or 
reduce potential impacts from acoustic and explosive stressors.
    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.
    Overall the Navy has agreed to procedural mitigation measures that 
would reduce the probability and/or severity of impacts expected to 
result from acute exposure to acoustic sources or explosives, ship 
strike, and impacts to marine mammal habitat. Specifically, the Navy 
would use a combination of delayed starts, powerdowns, and shutdowns to 
avoid mortality or serious injury, minimize the likelihood or severity 
of PTS or other injury, and reduce instances of TTS or more severe 
behavioral disruption caused by acoustic sources or explosives. The 
Navy would also implement multiple time/area restrictions that would 
reduce take of marine mammals in areas or at times where they are known 
to engage in important behaviors, such as foraging, where the 
disruption of those behaviors would have a higher probability of 
resulting in 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 Title 10 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 and adequately reduce impacts on the affected marine 
mammal species and stocks and their habitat and, further, be 
practicable for Navy implementation. Therefore, the mitigation measures 
assure that the Navy's activities would have the least practicable 
adverse impact on the species or stocks and their habitat.
    The Navy also evaluated numerous measures in the 2020 GOA DSEIS/
OEIS that were not included in the Navy's rulemaking/LOA application, 
and NMFS independently reviewed and preliminarily 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 two 
groups. First, Chapter 5 (Mitigation) of the 2020 GOA DSEIS/OEIS, in 
the Measures Considered but Eliminated section, 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. As 
described in Chapter 5 (Mitigation) of the 2020 GOA DSEIS/OEIS, the 
Navy considered reducing its overall amount of training, reducing 
explosive use, modifying its sound sources, completely replacing live 
training with computer simulation, and including time of day

[[Page 49724]]

restrictions. 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 5 (Mitigation) of the 2020 GOA DSEIS/OEIS, the 
Navy needs to train in the conditions in which it fights--and 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 for 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 for implementation in either the TMAA or the GOA Study 
Area overall.
    Second, in Chapter 5 (Mitigation) of the 2020 GOA DSEIS/OEIS, the 
Navy evaluated additional potential procedural mitigation measures, 
including increased mitigation zones, ramp-up measures, additional 
passive acoustic and visual monitoring, and decreased vessel speeds. 
Some of these measures have the potential to incrementally reduce take 
to some degree in certain circumstances, though the degree to which 
this would occur is typically low or uncertain. However, as described 
in the Navy's analysis, the measures would have significant direct 
negative effects on mission effectiveness and are considered 
impracticable (see Chapter 5, Mitigation, of 2020 GOA DSEIS/OEIS). NMFS 
independently reviewed the Navy's evaluation and concurs with this 
assessment, which supports NMFS' preliminary findings that the 
impracticability of this additional mitigation would greatly outweigh 
any potential minor reduction in marine mammal impacts that might 
result; therefore, these additional mitigation measures are not 
warranted.
    Last, Chapter 5 (Mitigation) of the 2020 GOA DSEIS/OEIS, also 
describes 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 its 
second updated application and the 2022 Supplement to the 2020 GOA 
DSEIS/OEIS, the Navy included an expansion to the mitigation area 
previously referred to as the Portlock Bank Mitigation Area, now 
referred to as the Continental Shelf and Slope Mitigation Area. The 
Navy has found that geographic mitigation beyond what is included in 
the 2020 GOA DSEIS/OEIS and 2022 Supplement to the 2020 GOA DSEIS/OEIS 
is not warranted because the anticipated reduction of adverse impacts 
on marine mammal species and their habitat is not sufficient to offset 
the impracticability of implementation. In some cases potential 
benefits to marine mammals were non-existent, while in others the 
consequences on mission effectiveness were too great.
    NMFS has reviewed the Navy's analysis in Chapter 5 (Mitigation) of 
the 2020 GOA DSEIS/OEIS and Chapter 5 (Standard Operating Procedures, 
Mitigation, and Monitoring) of the 2022 Supplement to the 2020 GOA 
DSEIS/OEIS, which consider 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 proposing to 
include any of the measures that the Navy ruled out in the 2020 GOA 
DSEIS/OEIS. Below are the mitigation measures that NMFS has 
preliminarily 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 would be 
implemented in association with the training activities analyzed in 
this document. The mitigation measures are organized into two 
categories: procedural mitigation and mitigation areas.

Procedural Mitigation

    Procedural mitigation is mitigation that the Navy would implement 
whenever and wherever an applicable training activity takes place 
within the GOA Study Area. The Navy customizes procedural mitigation 
for each applicable activity category or stressor. Procedural 
mitigation generally involves: (1) the use of one or more trained 
Lookouts to diligently observe for specific biological resources 
(including marine mammals) within a mitigation zone, (2) requirements 
for Lookouts to immediately communicate sightings of specific 
biological resources 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. The first procedural mitigation (Table 31) is 
designed to aid Lookouts and other applicable Navy personnel with their 
observation, environmental compliance, and reporting responsibilities. 
The remainder of the procedural mitigation measures (Table 32 through 
Table 39) are organized by stressor type and activity category and 
include acoustic stressors (i.e., active sonar, weapons firing noise), 
explosive stressors (i.e., large-caliber projectiles, bombs), and 
physical disturbance and strike stressors (i.e., vessel movement, towed 
in-water devices, small-, medium-, and large-caliber non-explosive 
practice munitions, non-explosive bombs).

     Table 31--Procedural Mitigation for Environmental Awareness and
                                Education
------------------------------------------------------------------------
                    Procedural mitigation description
-------------------------------------------------------------------------
Stressor or Activity:
     All training activities, as applicable.
Mitigation Requirements:
     Appropriate Navy personnel (including civilian personnel)
     involved in mitigation and training activity reporting under the
     specified activities will 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:

[[Page 49725]]

 
        --Introduction to the U.S. Navy Afloat Environmental Compliance
         Training Series. The introductory module provides information
         on environmental laws (e.g., Endangered Species Act, Marine
         Mammal Protection Act) and the corresponding responsibilities
         that are relevant to Navy training activities. The material
         explains why environmental compliance is important in
         supporting the Navy's commitment to environmental stewardship.
        --Marine Species Awareness Training. All bridge watch personnel,
         Commanding Officers, Executive Officers, maritime patrol
         aircraft aircrews, anti[hyphen]submarine warfare aircrews,
         Lookouts, and equivalent civilian personnel must successfully
         complete the Marine Species Awareness Training prior to
         standing watch or serving as a Lookout. The Marine Species
         Awareness Training provides information on sighting cues,
         visual observation tools and techniques, and sighting
         notification procedures. Navy biologists developed Marine
         Species Awareness Training to improve the effectiveness of
         visual observations for biological resources, focusing on
         marine mammals and sea turtles, and including floating
         vegetation, jellyfish aggregations, and flocks of seabirds.
        --U.S. Navy Protective Measures Assessment Protocol. This module
         provides the necessary instruction for accessing mitigation
         requirements during the event planning phase using the
         Protective Measures Assessment Protocol software tool.
        --U.S. Navy Sonar Positional Reporting System and Marine Mammal
         Incident Reporting. This module provides instruction on the
         procedures and activity reporting requirements for the Sonar
         Positional Reporting System and marine mammal incident
         reporting.
------------------------------------------------------------------------

Procedural Mitigation for Acoustic Stressors
    Mitigation measures for acoustic stressors are provided in Table 32 
and Table 33.

            Table 32--Procedural Mitigation for Active Sonar
------------------------------------------------------------------------
                    Procedural mitigation description
-------------------------------------------------------------------------
Stressor or Activity:
     Mid-frequency active sonar and high-frequency active sonar:
        --For vessel-based active sonar activities, mitigation applies
         only to sources that are positively controlled and deployed
         from manned surface vessels (e.g., sonar sources towed from
         manned surface platforms).
        --For aircraft-based active sonar activities, mitigation applies
         only to sources that are positively controlled and deployed
         from manned aircraft that do not operate at high altitudes
         (e.g., rotary-wing aircraft). Mitigation does not apply to
         active sonar sources deployed from unmanned aircraft or
         aircraft operating at high altitudes (e.g., maritime patrol
         aircraft).
Number of Lookouts and Observation Platform:
     Hull-mounted sources:
        --1 Lookout: Platforms with space or manning restrictions while
         underway (at the forward part of a small boat or ship) and
         platforms using active sonar while moored or at anchor.
        --2 Lookouts: Platforms without space or manning restrictions
         while underway (at the forward part of the ship).
     Sources that are not hull-mounted:
        --1 Lookout on the ship or aircraft conducting the activity.
Mitigation Requirements:
     Mitigation zones:
        --1,000 yd (914.4 m) power down, 500 yd (457.2 m) power down,
         and 200 yd (182.9 m) shut down for hull-mounted mid-frequency
         active sonar (see During the activity below).
        --200 yd (182.9 m) shut down for mid-frequency active sonar
         sources that are not hull-mounted, and high-frequency active
         sonar (see During the activity below).
     Prior to the initial start of the activity (e.g., when
     maneuvering on station):
        --Navy personnel will observe the mitigation zone for floating
         vegetation and marine mammals; if floating vegetation or a
         marine mammal is observed, Navy personnel will relocate or
         delay the start of active sonar transmission until the
         mitigation zone is clear of floating vegetation or the
         Commencement/recommencement conditions in this table are met
         for marine mammals.
     During the activity:
        --Hull-mounted mid-frequency active sonar: Navy personnel will
         observe the mitigation zone for marine mammals; Navy personnel
         will power down active sonar transmission by 6 dB if a marine
         mammal is observed within 1,000 yd (914.4 m) of the sonar
         source; Navy personnel will power down active sonar
         transmission an additional 4 dB (10 dB total) if a marine
         mammal is observed within 500 yd (457.2 m) of the sonar source;
         Navy personnel will cease transmission if a marine mammal is
         observed within 200 yd (182.9 m) of the sonar source.
        --Mid-frequency active sonar sources that are not hull-mounted,
         and high-frequency active sonar: Navy personnel will observe
         the mitigation zone for marine mammals; Navy personnel will
         cease transmission if a marine mammal is observed within 200 yd
         (182.9 m) of the sonar source.
     Commencement/recommencement conditions after a marine
     mammal sighting before or during the activity:
        --Navy personnel will allow a sighted marine mammal to leave the
         mitigation zone prior to the initial start of the activity (by
         delaying the start) or during the activity (by not recommencing
         or powering up active sonar transmission) until one of the
         following conditions has been met: (1) the animal is observed
         exiting the mitigation zone; (2) the animal is thought to have
         exited the mitigation zone based on a determination of its
         course, speed, and movement relative to the sonar source; (3)
         the mitigation zone has been clear from any additional
         sightings for 10 minutes for aircraft-deployed sonar sources or
         30 minutes for vessel-deployed sonar sources; (4) for mobile
         activities, the active sonar source has transited a distance
         equal to double that of the mitigation zone size beyond the
         location of the last sighting; or (5) for activities using hull-
         mounted sonar, the Lookout concludes that dolphins are
         deliberately closing in on the ship to ride the ship's bow
         wave, and are therefore out of the main transmission axis of
         the sonar (and there are no other marine mammal sightings
         within the mitigation zone).
------------------------------------------------------------------------


[[Page 49726]]


        Table 33--Procedural Mitigation for Weapons Firing Noise
------------------------------------------------------------------------
                    Procedural mitigation description
-------------------------------------------------------------------------
Stressor or Activity:
     Weapon firing noise associated with large-caliber gunnery
     activities.
Number of Lookouts and Observation Platform:
     1 Lookout positioned on the ship conducting the firing
        --Depending on the activity, the Lookout could be the same one
         described in Procedural Mitigation for Explosive Large-Caliber
         Projectiles (Table 34) or Procedural Mitigation for Small-,
         Medium-, and Large-Caliber Non-Explosive Practice Munitions
         (Table 38).
Mitigation Requirements:
     Mitigation zone:
        --30[deg] on either side of the firing line out to 70 yd (64 m)
         from the muzzle of the weapon being fired.
     Prior to the initial start of the activity:
        --Navy personnel will observe the mitigation zone for floating
         vegetation and marine mammals; if floating vegetation or a
         marine mammal is observed, Navy personnel will relocate or
         delay the start of weapon firing until the mitigation zone is
         clear of floating vegetation or the Commencement/recommencement
         conditions in this table are met for marine mammals.
     During the activity:
        --Navy personnel will observe the mitigation zone for marine
         mammals; if a marine mammal is observed, Navy personnel will
         cease weapon firing.
     Commencement/recommencement conditions after a marine
     mammal sighting before or during the activity:
        --Navy personnel will allow a sighted marine mammal to leave the
         mitigation zone prior to the initial start of the activity (by
         delaying the start) or during the activity (by not recommencing
         weapon firing) until one of the following conditions has been
         met: (1) the animal is observed exiting the mitigation zone;
         (2) the animal is thought to have exited the mitigation zone
         based on a determination of its course, speed, and movement
         relative to the firing ship; (3) the mitigation zone has been
         clear from any additional sightings for 30 minutes; or (4) for
         mobile activities, the firing ship has transited a distance
         equal to double that of the mitigation zone size beyond the
         location of the last sighting.
------------------------------------------------------------------------

Procedural Mitigation for Explosive Stressors
    Mitigation measures for explosive stressors are provided in Table 
34 and Table 35.

 Table 34--Procedural Mitigation for Explosive Large-Caliber Projectiles
------------------------------------------------------------------------
                    Procedural mitigation description
-------------------------------------------------------------------------
Stressor or Activity:
     Gunnery activities using explosive large-caliber
     projectiles.
        --Mitigation applies to activities using a surface target.
Number of Lookouts and Observation Platform:
     1 Lookout on the vessel or aircraft conducting the
     activity.
        --Depending on the activity, the Lookout could be the same as
         the one described for Procedural Mitigation for Weapons Firing
         Noise in Table 33.
     If additional platforms are participating in the activity,
     Navy personnel positioned in those assets (e.g., safety observers,
     evaluators) will support observing the mitigation zone for marine
     mammals while performing their regular duties.
Mitigation Requirements:
     Mitigation zones:
        --1,000 yd (914.4 m) around the intended impact location.
     Prior to the initial start of the activity (e.g., when
     maneuvering on station):
        --Navy personnel will observe the mitigation zone for floating
         vegetation and marine mammals; if floating vegetation or a
         marine mammal is observed, Navy personnel will relocate or
         delay the start of firing until the mitigation zone is clear of
         floating vegetation or the Commencement/recommencement
         conditions in this table are met for marine mammals.
     During the activity:
        --Navy personnel will observe the mitigation zone for marine
         mammals; if a marine mammal is observed, Navy personnel will
         cease firing.
     Commencement/recommencement conditions after a marine
     mammal sighting before or during the activity:
        --Navy personnel will allow a sighted marine mammal to leave the
         mitigation zone prior to the initial start of the activity (by
         delaying the start) or during the activity (by not recommencing
         firing) until one of the following conditions has been met: (1)
         the animal is observed exiting the mitigation zone; (2) the
         animal is thought to have exited the mitigation zone based on a
         determination of its course, speed, and movement relative to
         the intended impact location; (3) the mitigation zone has been
         clear from any additional sightings for 30 minutes; or (4) for
         activities using mobile targets, the intended impact location
         has transited a distance equal to double that of the mitigation
         zone size beyond the location of the last sighting.
     After completion of the activity (e.g., prior to
     maneuvering off station):
        --Navy personnel will, when practical (e.g., when platforms are
         not constrained by fuel restrictions or mission-essential
         follow-on commitments), observe the vicinity of where
         detonations occurred; if any injured or dead marine mammals are
         observed, Navy personnel will follow established incident
         reporting procedures.
        --If additional platforms are supporting this activity (e.g.,
         providing range clearance), Navy personnel positioned on these
         assets will assist in the visual observation of the area where
         detonations occurred.
------------------------------------------------------------------------


[[Page 49727]]


           Table 35--Procedural Mitigation for Explosive Bombs
------------------------------------------------------------------------
                    Procedural mitigation description
-------------------------------------------------------------------------
Stressor or Activity:
     Explosive bombs.
Number of Lookouts and Observation Platform:
     1 Lookout positioned in the aircraft conducting the
     activity.
     If additional platforms are participating in the activity,
     Navy personnel positioned in those assets (e.g., safety observers,
     evaluators) will support observing the mitigation zone for marine
     mammals while performing their regular duties.
Mitigation Requirements:
     Mitigation zone:
        --2,500 yd (2,286 m) around the intended target.
     Prior to the initial start of the activity (e.g., when
     arriving on station):
        --Navy personnel will observe the mitigation zone for floating
         vegetation and marine mammals; if floating vegetation or a
         marine mammal is observed, Navy personnel will relocate or
         delay the start of bomb deployment until the mitigation zone is
         clear of floating vegetation or the Commencement/recommencement
         conditions in this table are met for marine mammals.
     During the activity (e.g., during target approach):
        --Navy personnel will observe the mitigation zone for marine
         mammals; if a marine mammal is observed, Navy personnel will
         cease bomb deployment.
     Commencement/recommencement conditions after a marine
     mammal sighting before or during the activity:
        --Navy personnel will allow a sighted marine mammal to leave the
         mitigation zone prior to the initial start of the activity (by
         delaying the start) or during the activity (by not recommencing
         bomb deployment) until one of the following conditions has been
         met: (1) the animal is observed exiting the mitigation zone;
         (2) the animal is thought to have exited the mitigation zone
         based on a determination of its course, speed, and movement
         relative to the intended target; (3) the mitigation zone has
         been clear from any additional sightings for 10 minutes; or (4)
         for activities using mobile targets, the intended target has
         transited a distance equal to double that of the mitigation
         zone size beyond the location of the last sighting.
     After completion of the activity (e.g., prior to
     maneuvering off station):
        --Navy personnel will, when practical (e.g., when platforms are
         not constrained by fuel restrictions or mission-essential
         follow-on commitments), observe for marine mammals in the
         vicinity of where detonations occurred; if any injured or dead
         marine mammals are observed, Navy personnel will follow
         established incident reporting procedures.
        --If additional platforms are supporting this activity (e.g.,
         providing range clearance), Navy personnel positioned on these
         assets will assist in the visual observation of the area where
         detonations occurred.
------------------------------------------------------------------------

Procedural Mitigation for Physical Disturbance and Strike Stressors
    Mitigation measures for physical disturbance and strike stressors 
are provided in Table 36 through Table 39.

           Table 36--Procedural Mitigation for Vessel Movement
------------------------------------------------------------------------
                    Procedural Mitigation Description
-------------------------------------------------------------------------
Stressor or Activity:
     Vessel movement
        --The mitigation will not be applied if (1) the vessel's safety
         is threatened, (2) the vessel is restricted in its ability to
         maneuver (e.g., during launching and recovery of aircraft or
         landing craft, during towing activities, when mooring), (3) the
         vessel is submerged or operated autonomously, or (4) when
         impractical based on mission requirements (e.g., during Vessel
         Visit, Board, Search, and Seizure activities as military
         personnel from ships or aircraft board suspect vessels).
Number of Lookouts and Observation Platform:
     1 or more Lookouts on the underway vessel
     If additional watch personnel are positioned on underway
     vessels, those personnel (e.g., persons assisting with navigation
     or safety) will support observing for marine mammals while
     performing their regular duties.
Mitigation Requirements:
     Mitigation zones:
        --500 yd (457.2 m) around the vessel for whales.
        --200 yd (182.9 m) around the vessel for marine mammals other
         than whales (except those intentionally swimming alongside or
         closing in to swim alongside vessels, such as bow-riding or
         wake-riding dolphins).
     When Underway:
        --Navy personnel will observe the direct path of the vessel and
         waters surrounding the vessel for marine mammals.
        --If a marine mammal is observed in the direct path of the
         vessel, Navy personnel will maneuver the vessel as necessary to
         maintain the appropriate mitigation zone distance.
        --If a marine mammal is observed within waters surrounding the
         vessel, Navy personnel will maintain situational awareness of
         that animal's position. Based on the animal's course and speed
         relative to the vessel's path, Navy personnel will maneuver the
         vessel as necessary to ensure that the appropriate mitigation
         zone distance from the animal continues to be maintained.
     Additional requirements:
        --If a marine mammal vessel strike occurs, Navy personnel will
         follow established incident reporting procedures.
------------------------------------------------------------------------


[[Page 49728]]


       Table 37--Procedural Mitigation for Towed In-Water Devices
------------------------------------------------------------------------
                    Procedural mitigation description
-------------------------------------------------------------------------
Stressor or Activity:
     Towed in-water devices
        --Mitigation applies to devices that are towed from a manned
         surface platform or manned aircraft, or when a manned support
         craft is already participating in an activity involving in-
         water devices being towed by unmanned platforms.
        --The mitigation will not be applied if the safety of the towing
         platform or in-water device is threatened.
Number of Lookouts and Observation Platform:
     1 Lookout positioned on the towing platform or support
     craft.
Mitigation Requirements:
     Mitigation zones:
        --250 yd (228.6 m) around the towed in-water device for marine
         mammals (except those intentionally swimming alongside or
         choosing to swim alongside towing vessels, such as bow-riding
         or wake-riding dolphins)
     During the activity (i.e., when towing an in-water device)
        --Navy personnel will observe the mitigation zone for marine
         mammals; if a marine mammal is observed, Navy personnel will
         maneuver to maintain distance.
------------------------------------------------------------------------


 Table 38--Procedural Mitigation for Small-, Medium-, and Large-Caliber
                    Non-Explosive Practice Munitions
------------------------------------------------------------------------
                    Procedural mitigation description
-------------------------------------------------------------------------
Stressor or Activity:
     Gunnery activities using small-, medium-, and large-caliber
     non-explosive practice munitions
        --Mitigation applies to activities using a surface target.
Number of Lookouts and Observation Platform:
     1 Lookout positioned on the platform conducting the
     activity.
        --Depending on the activity, the Lookout could be the same as
         the one described in Procedural Mitigation for Weapons Firing
         Noise (Table 33).
Mitigation Requirements:
     Mitigation zone:
        --200 yd (182.9 m) around the intended impact location
     Prior to the initial start of the activity (e.g., when
     maneuvering on station):
        --Navy personnel will observe the mitigation zone for floating
         vegetation and marine mammals; if floating vegetation or a
         marine mammal is observed, Navy personnel will relocate or
         delay the start of firing until the mitigation zone is clear of
         floating vegetation or the Commencement/recommencement
         conditions in this table are met for marine mammals.
     During the activity:
        --Navy personnel will observe the mitigation zone for marine
         mammals; if a marine mammal is observed, Navy personnel will
         cease firing.
     Commencement/recommencement conditions after a marine
     mammal, sighting before or during the activity:
        --Navy personnel will allow a sighted marine mammal to leave the
         mitigation zone prior to the initial start of the activity (by
         delaying the start) or during the activity (by not recommencing
         firing) until one of the following conditions has been met: (1)
         the animal is observed exiting the mitigation zone; (2) the
         animal is thought to have exited the mitigation zone based on a
         determination of its course, speed, and movement relative to
         the intended impact location; (3) the mitigation zone has been
         clear from any additional sightings for 10 minutes for aircraft-
         based firing or 30 minutes for vessel-based firing; or (4) for
         activities using a mobile target, the intended impact location
         has transited a distance equal to double that of the mitigation
         zone size beyond the location of the last sighting.
------------------------------------------------------------------------


         Table 39--Procedural Mitigation for Non-Explosive Bombs
------------------------------------------------------------------------
                    Procedural mitigation description
-------------------------------------------------------------------------
Stressor or Activity:
     Non-explosive bombs.
Number of Lookouts and Observation Platform:
     1 Lookout positioned in an aircraft.
Mitigation Requirements:
     Mitigation zone:
        --1,000 yd (914.4 m) around the intended target.
     Prior to the initial start of the activity (e.g., when
     arriving on station):
        --Navy personnel will observe the mitigation zone for floating
         vegetation and marine mammals; if floating vegetation or a
         marine mammal is observed, Navy personnel will relocate or
         delay the start of bomb deployment until the mitigation zone is
         clear of floating vegetation or the Commencement/recommencement
         conditions in this table are met for marine mammals.
     During the activity (e.g., during approach of the target):
        --Navy personnel will observe the mitigation zone for marine
         mammals; if a marine mammal is observed, Navy personnel will
         cease bomb deployment.
     Commencement/recommencement conditions after a marine
     mammal sighting prior to or during the activity:
        --Navy personnel will allow a sighted marine mammal to leave the
         mitigation zone prior to the initial start of the activity (by
         delaying the start) or during the activity (by not recommencing
         bomb deployment) until one of the following conditions has been
         met: (1) the animal is observed exiting the mitigation zone;
         (2) the animal is thought to have exited the mitigation zone
         based on a determination of its course, speed, and movement
         relative to the intended target; (3) the mitigation zone has
         been clear from any additional sightings for 10 minutes; or (4)
         for activities using mobile targets, the intended target has
         transited a distance equal to double that of the mitigation
         zone size beyond the location of the last sighting.
------------------------------------------------------------------------


[[Page 49729]]

Mitigation Areas

    In addition to procedural mitigation, the Navy would implement 
mitigation measures within mitigation areas to avoid or minimize 
potential impacts on marine mammals. The Navy took into account the 
best available science and the practicability of implementing 
additional mitigation measures, and has enhanced its mitigation 
measures beyond those that were included in the 2017-2022 regulations 
to further reduce impacts to marine mammals.
    Information on the mitigation measures that the Navy would 
implement within mitigation areas is provided in Table 40 (see below).
    NMFS conducted an independent analysis of the mitigation areas that 
the Navy proposed, which are described below. NMFS preliminarily 
concurs with the Navy's analysis, which indicates that the measures in 
these mitigation areas are both practicable and would reduce the 
likelihood or severity of adverse impacts to marine mammal species 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 is practical to implement. The Navy considers the 
measures in this proposed rule to be practicable, and NMFS concurs. We 
further discuss the manner in which the Geographic Mitigation Areas in 
the proposed rule would reduce the likelihood or severity of adverse 
impacts to marine mammal species or their habitat in the Preliminary 
Analysis and Negligible Impact Determination section.

   Table 40--Geographic Mitigation Areas for Marine Mammals in the GOA
                               Study Area
------------------------------------------------------------------------
                       Mitigation area description
-------------------------------------------------------------------------
Stressor or Activity:
     Sonar.
     Explosives.
     Physical disturbance and strikes.
Mitigation Requirements: \1\
     North Pacific Right Whale Mitigation Area.
        --From June 1-September 30 within the North Pacific Right Whale
         Mitigation Area, Navy personnel will not use surface ship hull-
         mounted MF1 mid-frequency active sonar during training.
     Continental Shelf and Slope Mitigation Area.
        --Navy personnel will not detonate explosives below 10,000 ft.
         altitude (including at the water surface) in the Continental
         Shelf and Slope Mitigation Area during training.
     Pre-event Awareness Notifications in the Temporary Maritime
     Activities Area.
        --The Navy will issue pre-event awareness messages to alert
         vessels and aircraft participating in training activities
         within the TMAA to the possible presence of concentrations of
         large whales on the continental shelf and slope. Occurrences of
         large whales may be higher over the continental shelf and slope
         relative to other areas of the TMAA. Large whale species in the
         TMAA include, but are not limited to, fin whale, blue whale,
         humpback whale, gray whale, North Pacific right whale, sei
         whale, and sperm whale. To maintain safety of navigation and to
         avoid interactions with marine mammals, the Navy will instruct
         personnel to remain vigilant to the presence of large whales
         that may be vulnerable to vessel strikes or potential impacts
         from training activities. Additionally, Navy personnel will use
         the information from the awareness notification messages to
         assist their visual observation of applicable mitigation zones
         during training activities and to aid in the implementation of
         procedural mitigation.
------------------------------------------------------------------------
\1\ Should national security present a requirement to conduct training
  prohibited by the mitigation requirements specified in this table,
  naval units will obtain permission from the designated Command, U.S.
  Third Fleet Command Authority, prior to commencement of the activity.
  The Navy will provide NMFS with advance notification and include
  relevant information about the event (e.g., sonar hours, use of
  explosives detonated below 10,000 ft altitude (including at the water
  surface) in its annual activity reports to NMFS.

BILLING CODE 3510-22-P

[[Page 49730]]

[GRAPHIC] [TIFF OMITTED] TP11AU22.004

BILLING CODE 3510-22-C

North Pacific Right Whale Mitigation Area

    Mitigation within the North Pacific Right Whale Mitigation Area is 
primarily designed to avoid or further reduce potential impacts to 
North Pacific right whales within important feeding habitat. The 
mitigation area fully encompasses the portion of the BIA identified by 
Ferguson et al. (2015) for North Pacific right whale feeding that 
overlaps the GOA Study Area (overlap between the GOA Study Area and the 
BIA occurs in the TMAA only) (Figure 2). North Pacific right whales are 
thought to occur in the highest densities in the BIA from June to 
September. The Navy would not use surface ship hull-mounted MF1 mid-
frequency active sonar in the mitigation area from June 1 to September 
30, as was also required in the Phase II (2017-2022) rule. The North 
Pacific Right Whale Mitigation Area is fully within the boundary of the 
Continental Shelf and Slope Mitigation Area, discussed below. 
Therefore, the mitigation requirements in that area also apply to the 
North Pacific Right Whale

[[Page 49731]]

Mitigation Area. While the potential occurrence of North Pacific right 
whales in the GOA Study Area is expected to be rare due to the species' 
extremely low population, these mitigation requirements would help 
further avoid or further reduce the potential for impacts to occur 
within North Pacific right whale feeding habitat, thus likely reducing 
the number of takes of North Pacific right whales, as well as the 
severity of any disturbances by reducing the likelihood that feeding is 
interrupted, delayed, or precluded for some limited amount of time.
    Additionally, the North Pacific Right Whale Mitigation Area 
overlaps with a small portion of the humpback whale critical habitat 
Unit 5, in the southwest corner of the TMAA. While the overlap of the 
two areas is limited, mitigation in the North Pacific Right Whale 
Mitigation Area may reduce the number and/or severity of takes of 
humpback whales in this important area.
    The mitigation in this area would also help avoid or reduce 
potential impacts on fish and invertebrates that inhabit the mitigation 
area and which marine mammals prey upon. As described in Section 
5.4.1.5 (Fisheries Habitats) of the 2020 GOA DSEIS/OEIS, the productive 
waters off Kodiak Island support a strong trophic system from plankton, 
invertebrates, small fish, and higher-level predators, including large 
fish and marine mammals.

Continental Shelf and Slope Mitigation Area

    The Continental Shelf and Slope Mitigation Area encompasses the 
portion of the continental shelf and slope that overlaps the TMAA (the 
entire continental shelf and slope out to the 4,000 m depth contour; 
Figure 2). The Navy would not detonate explosives below 10,000 ft. 
altitude (including at the water surface) in the Continental Shelf and 
Slope Mitigation Area during training. (As stated previously, the Navy 
does not plan to use in-water explosives anywhere in the GOA Study 
Area.) Mitigation in the Continental Shelf and Slope Mitigation Area 
was initially designed to avoid or reduce potential impacts on fishery 
resources for Alaska Natives. However, the area includes highly 
productive waters where marine mammals, including humpback whales 
(Lagerquist et al. 2008) and North Pacific right whales, feed, and 
overlaps with a small portion of the North Pacific right whale feeding 
BIA off of Kodiak Island. Additionally, the Continental Shelf and Slope 
Mitigation Area overlaps with a very small portion of the humpback 
whale critical habitat Unit 5, on the western side of the TMAA, and a 
small portion of humpback whale critical habitat Unit 8 on the north 
side of the TMAA. The Continental Shelf and Slope mitigation area also 
overlaps with a very small portion of the gray whale migration BIA. The 
remainder of the designated critical habitat and BIAs are located 
beyond the boundaries of the GOA Study Area. While the overlap of the 
mitigation area with critical habitat and feeding and migratory BIAs is 
limited, mitigation in the Continental Shelf and Slope Mitigation Area 
may reduce the probability, number, and/or severity of takes of 
humpback whales, North Pacific right whales, and gray whales in this 
important area (noting that no takes are predicted for gray whales). 
Additionally, mitigation in this area will likely reduce the number and 
severity of potential impacts to marine mammals in general, by reducing 
the likelihood that feeding is interrupted, delayed, or precluded for 
some limited amount of time.

Pre-Event Awareness Notifications in the Temporary Maritime Activities 
Area

    The Navy will issue awareness messages prior to the start of TMAA 
training activities to alert vessels and aircraft operating within the 
TMAA to the possible presence of concentrations of large whales, 
including but not limited to, fin whale, blue whale, humpback whale, 
gray whales, North Pacific right whale, sei whale, minke whale, and 
sperm whale, especially when traversing on the continental shelf and 
slope where densities of these species may be higher. To maintain 
safety of navigation and to avoid interactions with marine mammals, the 
Navy will instruct vessels to remain vigilant to the presence of large 
whales that may be vulnerable to vessel strikes or potential impacts 
from training activities. Navy personnel will use the information from 
the awareness notification messages to assist their visual observation 
of applicable mitigation zones during training activities and to aid in 
the implementation of procedural mitigation.
    This mitigation would help avoid or further reduce any potential 
impacts from vessel strikes and training activities on large whales 
within the TMAA.

Availability for Subsistence Uses

    The nature of subsistence activities by Alaska Natives in the GOA 
Study Area are discussed below, in the Subsistence Harvest of Marine 
Mammals section of this proposed rule.

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 Navy training authorizations but several of which 
are new since implementation of the 2017 to 2022 regulations--and 
considered a broad range of other measures (i.e., the measures 
considered but eliminated in the 2020 GOA DSEIS/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 mammal species and their habitat. Our 
evaluation of potential measures included consideration of the 
following factors in relation to one another: 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; the proven 
or likely efficacy of the measures; and 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, NMFS has preliminarily 
determined that these proposed 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. Additionally, an adaptive management component 
helps further ensure that mitigation is regularly assessed and provides 
a mechanism to improve the mitigation, based on the factors above, 
through modification as appropriate.
    The proposed rule comment period provides the public an opportunity 
to submit recommendations, views, and/or concerns regarding the Navy's 
activities and the proposed mitigation measures. While NMFS has 
preliminarily determined that the Navy's proposed mitigation measures 
would effect the least practicable adverse impact on the affected 
species and their habitat, NMFS

[[Page 49732]]

will consider all public comments to help inform our final 
determination. Consequently, the proposed mitigation measures may be 
refined, modified, removed, or added to prior to the issuance of the 
final rule based on public comments received and, as appropriate, 
analysis of additional potential mitigation measures.

Proposed 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 incidental take authorizations 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.
    Although the Navy has been conducting research and monitoring for 
over 20 years in areas where it has been training, it developed a 
formal marine species monitoring program in support of the GOA Study 
Area MMPA and ESA processes in 2009. Across all Navy training and 
testing study areas, the robust marine species monitoring program has 
resulted in hundreds of technical reports and publications on marine 
mammals that have informed Navy and NMFS analyses in environmental 
planning documents, rules, and Biological Opinions. The reports are 
made available to the public on the Navy's marine species monitoring 
website (www.navymarinespeciesmonitoring.us) and the data on the Ocean 
Biogeographic Information System Spatial Ecological Analysis of 
Megavertebrate Populations (OBIS-SEAMAP) (https://seamap.env.duke.edu/
).
    The Navy would continue collecting monitoring data to inform our 
understanding of the occurrence of marine mammals in the GOA Study 
Area; the likely exposure of marine mammals to stressors of concern in 
the GOA Study Area; the response of marine mammals to exposures to 
stressors; the consequences of a particular marine mammal response to 
their individual fitness and, ultimately, populations; and the 
effectiveness of implemented mitigation measures. Taken together, 
mitigation and monitoring comprise the Navy's integrated approach for 
reducing environmental impacts from the specified activities. The 
Navy's overall monitoring approach seeks to leverage and build on 
existing research efforts whenever possible.
    As agreed upon between the Navy and NMFS, the monitoring measures 
presented here, as well as the mitigation measures described above, 
focus on the protection and management of potentially affected marine 
mammals. A well-designed monitoring program can provide important 
feedback for validating assumptions made in analyses and allow for 
adaptive management of marine resources. Monitoring is required under 
the MMPA, and details of the monitoring program for the specified 
activities have been developed through coordination between NMFS and 
the Navy through the regulatory process for previous Navy at-sea 
training and testing activities.

Integrated Comprehensive Monitoring Program

    The Navy's Integrated Comprehensive Monitoring Program (ICMP) is 
intended to coordinate marine species monitoring efforts across all 
regions and to allocate the most appropriate level and type of effort 
for each range complex based on a set of standardized objectives, and 
in acknowledgement of regional expertise and resource availability. The 
ICMP is designed to be flexible, scalable, and adaptable through the 
adaptive management and strategic planning processes to periodically 
assess progress and reevaluate objectives. This process includes 
conducting an annual adaptive management review meeting, at which the 
Navy and NMFS jointly consider the prior-year goals, monitoring 
results, and related scientific advances to determine if monitoring 
plan modifications are warranted to more effectively address program 
goals. Although the ICMP does not specify actual monitoring field work 
or individual projects, it does establish a matrix of goals and 
objectives that have been developed in coordination with NMFS. As the 
ICMP is implemented through the Strategic Planning Process, detailed 
and specific studies will be developed which support the Navy's and 
NMFS top-level monitoring goals. In essence, the ICMP directs that 
monitoring activities relating to the effects of Navy training and 
testing activities on marine species should be designed to contribute 
towards or accomplish one or more of the following top-level goals:
     An increase in the understanding of the likely occurrence 
of marine mammals and ESA-listed marine species in the vicinity of the 
action (i.e., presence, abundance, distribution, and density of 
species);
     An increase in the understanding of the nature, scope, or 
context of the likely exposure of marine mammals and ESA-listed species 
to any of the potential stressors associated with the action (e.g., 
sound, explosive detonation, or expended materials), through better 
understanding of one or more of the following: (1) the nature of the 
action and its surrounding environment (e.g., sound-source 
characterization, propagation, and ambient noise levels), (2) the 
affected species (e.g., life history or dive patterns), (3) the likely 
co-occurrence of marine mammals and ESA-listed marine species with the 
action (in whole or part), and (4) the likely biological or behavioral 
context of exposure to the stressor for the marine mammal and ESA-
listed marine species (e.g., age class of exposed animals or known 
pupping, calving, or feeding areas);
     An increase in the understanding of how individual marine 
mammals or ESA-listed marine species respond (behaviorally or 
physiologically) to the specific stressors associated with the action 
(in specific contexts, where possible, e.g., at what distance or 
received level);
     An increase in the understanding of how anticipated 
individual responses, to individual stressors or anticipated 
combinations of stressors, may impact either (1) the long-term fitness 
and survival of an individual; or (2) the population, species, or stock 
(e.g., through impacts on annual rates of recruitment or survival);
     An increase in the understanding of the effectiveness of 
mitigation and monitoring measures;
     A better understanding and record of the manner in which 
the Navy complies with the incidental take regulations and LOAs and the 
ESA Incidental Take Statement;
     An increase in the probability of detecting marine mammals 
(through improved technology or methods), both specifically within the 
mitigation zone (thus allowing for more effective implementation of the 
mitigation) and in general, to better achieve the above goals; and
     Ensuring that adverse impacts of activities remain at the 
least practicable level.

Strategic Planning Process for Marine Species Monitoring

    The Navy also developed the Strategic Planning Process for Marine 
Species Monitoring, which serves to guide the investment of resources 
to most efficiently address ICMP objectives and intermediate scientific 
objectives developed through this process. The

[[Page 49733]]

Strategic Planning Process establishes the guidelines and processes 
necessary to develop, evaluate, and fund individual projects based on 
objective scientific study questions. The process uses an underlying 
framework designed around intermediate scientific objectives and a 
conceptual framework incorporating a progression of knowledge spanning 
occurrence, exposure, response, and consequence. The Strategic Planning 
Process for Marine Species Monitoring is used to set overarching 
intermediate scientific objectives; develop individual monitoring 
project concepts; evaluate, prioritize, and select specific monitoring 
projects to fund or continue supporting for a given fiscal year; 
execute and manage selected monitoring projects; and report and 
evaluate progress and results. This process addresses relative 
investments to different range complexes based on goals across all 
range complexes, and monitoring would leverage multiple techniques for 
data acquisition and analysis whenever possible. More information on 
the Strategic Planning Process for Marine Species Monitoring including 
results, reports, and publications, is also available online (https://www.navymarinespeciesmonitoring.us/).

Past and Current Monitoring in the GOA Study Area

    The monitoring program has undergone significant changes since the 
first rule was issued for the TMAA in 2011, which highlights the 
monitoring program's evolution through the process of adaptive 
management. The monitoring program developed for the first cycle of 
environmental compliance documents (e.g., U.S. Department of the Navy, 
2008a, 2008b) utilized effort-based compliance metrics that were 
somewhat limiting. Through adaptive management discussions, the Navy 
designed and conducted monitoring studies according to scientific 
objectives and eliminated specific effort requirements.
    Progress has also been made on the conceptual framework categories 
from the Scientific Advisory Group for Navy Marine Species Monitoring 
(U.S. Department of the Navy, 2011), ranging from occurrence of 
animals, to their exposure, response, and population consequences. The 
Navy continues to manage the Atlantic and Pacific program as a whole, 
including what is now the GOA Study Area, with monitoring in each range 
complex taking a slightly different but complementary approach. The 
Navy has continued to use the approach of layering multiple 
simultaneous components in many of the range complexes to leverage an 
increase in return of the progress toward answering scientific 
monitoring questions. This includes in the TMAA, for example (a) 
Passive Acoustic Monitoring for Marine Mammals in the Gulf of Alaska 
Temporary Maritime Activities Area May to September 2015 and April to 
September 2017 (Rice et al., 2018b); (b) analysis of existing passive 
acoustic monitoring datasets; and (c) Passive Acoustic Monitoring of 
Marine Mammals Using Gliders (Klinck et al., 2016).
    Numerous publications, dissertations, and conference presentations 
have resulted from research conducted under the marine species 
monitoring program, including research conducted in what is now the GOA 
Study Area (https://www.navymarinespeciesmonitoring.us/reading-room/publications/), leading to a significant contribution to the body of 
marine mammal science. Publications on occurrence, distribution, and 
density have fed the modeling input, and publications on exposure and 
response have informed Navy and NMFS analysis of behavioral response 
and consideration of mitigation measures.
    Furthermore, collaboration between the monitoring program and the 
Navy's research and development (e.g., the Office of Naval Research) 
and demonstration-validation (e.g., Living Marine Resources) programs 
has been strengthened, leading to research tools and products that have 
already transitioned to the monitoring program. These include Marine 
Mammal Monitoring on Ranges, controlled exposure experiment behavioral 
response studies, acoustic sea glider surveys, and global positioning 
system-enabled satellite tags. Recent progress has been made with 
better integration with monitoring across all Navy at-sea study areas, 
including the AFTT Study Area in the Atlantic Ocean, and various other 
ranges. Publications from the Living Marine Resources and Office of 
Naval Research programs have also resulted in significant contributions 
to hearing, acoustic criteria used in effects modeling, exposure, and 
response, as well as in developing tools to assess biological 
significance (e.g., consequences).
    NMFS and the Navy also consider data collected during procedural 
mitigations as monitoring. Data are collected by shipboard personnel on 
hours spent training, hours of observation, hours of sonar, and marine 
mammals observed within the mitigation zones when mitigations are 
implemented. These data are provided to NMFS in both classified and 
unclassified annual training reports, which would continue under this 
proposed rule.
    NMFS has received multiple years' worth of annual training and 
monitoring reports addressing active sonar use and explosive 
detonations within the TMAA and other Navy range complexes. The data 
and information contained in these reports have been considered in 
developing mitigation and monitoring measures for the proposed training 
activities within the GOA Study Area. The Navy's annual training and 
monitoring reports may be viewed at: https://www.navymarinespeciesmonitoring.us/reporting/.
    The Navy's marine species monitoring program supports monitoring 
projects in the GOA Study Area. Additional details on the scientific 
objectives for each project can be found at https://www.navymarinespeciesmonitoring.us/regions/pacific/current-projects/. 
Projects can be either major multi-year efforts, or one to 2-year 
special studies. The emphasis on monitoring in the GOA Study Area is 
directed towards collecting and analyzing passive acoustic monitoring 
and telemetry data for marine mammals and salmonids.
    Specific monitoring under the previous regulations (which covered 
only the TMAA) included:
     The continuation of the Navy's collaboration with NOAA on 
the Pacific Marine Assessment Program for Protected Species (PacMAPPS) 
survey. A systematic line transect survey in the Gulf of Alaska was 
completed in 2021. A second PacMAPPS survey is planned for the Gulf of 
Alaska in 2023. These surveys will increase knowledge of marine mammal 
occurrence, density, and population identity in the TMAA.
     A Characterizing the Distribution of ESA-Listed Salmonids 
in Washington and Alaska study. The goal of this study is to use a 
combination of acoustic and pop-up satellite tagging technology to 
provide critical information on spatial and temporal distribution of 
salmonids to inform salmon management, U.S. Navy training activities, 
and Southern Resident killer whale conservation. The study seeks to (1) 
determine the occurrence and timing of salmonids within the Navy 
training ranges; (2) describe the influence of environmental covariates 
on salmonid occurrence; and (3) describe the occurrence of salmonids in 
relation to Southern Resident killer whale distribution. Methods 
include acoustic telemetry (pinger tags) and pop-up satellite tagging.
     A Telemetry and Genetic Identity of Chinook Salmon in 
Alaska study. The goal of this study is to provide critical

[[Page 49734]]

information on the spatial and temporal distribution of Chinook salmon 
and to utilize genetic analysis techniques to inform salmon management. 
Tagging is occurring at several sites within the Gulf of Alaska.
     A North Pacific Humpback Whale Tagging study. This project 
combines tagging, biopsy sampling, and photo-identification efforts 
along the United States west coast and Hawaii to examine movement 
patterns and whale use of Navy training and testing areas and NMFS-
identified BIAs, examine migration routes, and analyze dive behavior 
and ecological relationships between whale locations and oceanographic 
conditions (Mate et al., 2017; Irvine et al., 2020).
    Future monitoring efforts in the GOA Study Area are anticipated to 
continue along the same objectives: determining the species and 
populations of marine mammals present and potentially exposed to Navy 
training activities in the GOA Study Area, through tagging, passive 
acoustic monitoring, refined modeling, photo identification, biopsies, 
and visual monitoring, as well as characterizing spatial and temporal 
distribution of salmonids, including Chinook salmon.

Adaptive Management

    The proposed regulations governing the take of marine mammals 
incidental to Navy training activities in the GOA Study Area contain an 
adaptive management component. Our understanding of the effects of Navy 
training activities (e.g., acoustic and explosive stressors) on marine 
mammals continues to evolve, which makes the inclusion of an adaptive 
management component both valuable and necessary within the context of 
7-year regulations.
    The reporting requirements associated with this rule are designed 
to provide NMFS with monitoring data from the previous year to allow 
NMFS 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 (including additions or deletions). 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 of the planned LOA 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 by these 
regulations or subsequent LOA. The results from monitoring reports and 
other studies may be viewed at https://www.navymarinespeciesmonitoring.us.

Proposed Reporting

    In order to issue incidental take authorization 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. Reports 
from individual monitoring events, results of analyses, publications, 
and periodic progress reports for specific monitoring projects would be 
posted to the Navy's Marine Species Monitoring web portal: https://www.navymarinespeciesmonitoring.us.
    There are several different reporting requirements pursuant to the 
2017-2022 regulations. All of these reporting requirements would be 
continued under this proposed rule for the 7-year period; however, the 
reporting schedule for the GOA Annual Training Report would be slightly 
changed to align the reporting schedule with the activity period (see 
the GOA Annual Training Report section, below).

Notification of Injured, Live Stranded, or Dead Marine Mammals

    The Navy would consult the Notification and Reporting Plan, which 
sets out notification, reporting, and other requirements when injured, 
live stranded, or dead marine mammals are detected. The Notification 
and Reporting Plan is available for review at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.

Annual GOA Marine Species Monitoring Report

    The Navy would submit an annual report to NMFS of the GOA Study 
Area monitoring, which would be included in a Pacific-wide monitoring 
report and include results specific to the GOA Study Area, describing 
the implementation and results of monitoring from the previous calendar 
year. Data collection methods would be standardized across Pacific 
Range Complexes including the MITT, HSTT, NWTT, and GOA Study Areas to 
the best extent practicable, to allow for comparison among different 
geographic locations. The report would be submitted to the Director, 
Office of Protected Resources, NMFS, either within 3 months after the 
end of the calendar year, or within 3 months after the conclusion of 
the monitoring year, to be determined by the Adaptive Management 
process. NMFS would submit comments or questions on the draft 
monitoring report, if any, within 3 months of receipt. The report would 
be considered final after the Navy has addressed NMFS' comments, or 3 
months after submittal if NMFS does not provide comments on the report. 
The report would describe progress of knowledge made with respect to 
monitoring study questions across multiple Navy ranges associated with 
the ICMP. Similar study questions would be treated together so that 
progress on each topic is summarized across all Navy ranges. The report 
need not include analyses and content that does not provide direct 
assessment of cumulative progress on the monitoring plan study 
questions. This would allow the Navy to provide a cohesive monitoring 
report covering multiple ranges (as per ICMP goals), rather than 
entirely separate reports for the MITT, HSTT, NWTT, and GOA Study 
Areas.

GOA Annual Training Report

    Each year in which training activities are conducted in the GOA 
Study Area, the Navy would submit one preliminary report (Quick Look 
Report) to NMFS detailing the status of applicable sound sources within 
21 days after the completion of the training activities in the GOA 
Study Area. Each year in which activities are conducted, the Navy would 
also submit a detailed report (GOA Annual Training Report) to NMFS 
within 3 months after completion of the training activities. The Phase 
II rule required the Navy to submit the GOA Annual Training Report 
within 3 months after the anniversary of the date of issuance of the 
LOA. NMFS would submit comments or questions on the

[[Page 49735]]

report, if any, within one month of receipt. The report would be 
considered final after the Navy has addressed NMFS' comments, or one 
month after submittal if NMFS does not provide comments on the report. 
The annual reports would contain information about the MTE, (exercise 
designator, date that the exercise began and ended, location, number 
and types of active and passive sonar sources used in the exercise, 
number and types of vessels and aircraft that participated in the 
exercise, etc.), individual marine mammal sighting information for each 
sighting in each exercise where mitigation was implemented, a 
mitigation effectiveness evaluation, and a summary of all sound sources 
used (total hours or quantity of each bin of sonar or other non-
impulsive source; total annual number of each type of explosive(s); and 
total annual expended/detonated rounds (bombs and large-caliber 
projectiles) for each explosive bin).
    The annual report (which, as stated above, would only be required 
during years in which activities are conducted) would also contain 
cumulative sonar and explosive use quantity from previous years' 
reports through the current year. Additionally, if there were any 
changes to the sound source allowance in the reporting year, or 
cumulatively, the report would include a discussion of why the change 
was made and include analysis to support how the change did or did not 
affect the analysis in the GOA SEIS/OEIS and MMPA final rule. The 
analysis in the detailed report would be based on the accumulation of 
data from the current year's report and data collected from previous 
annual reports. The final annual/close-out report at the conclusion of 
the authorization period (year seven) would also serve as the 
comprehensive close-out report and include both the final year annual 
use compared to annual authorization as well as a cumulative 7-year 
annual use compared to 7-year authorization. This report would also 
note any years in which training did not occur. NMFS must submit 
comments on the draft close-out report, if any, within 3 months of 
receipt. The report would be considered final after the Navy has 
addressed NMFS' comments, or 3 months after the submittal of the draft 
if NMFS does not provide comments. Information included in the annual 
reports may be used to inform future adaptive management of activities 
within the GOA Study Area. See the regulations below for more detail on 
the content of the annual report.

Other Reporting and Coordination

    The Navy would continue to report and coordinate with NMFS for the 
following:
     Annual marine species monitoring technical review meetings 
that also include researchers and the Marine Mammal Commission; and
     Annual Adaptive Management meetings that also include the 
Marine Mammal Commission (and occur in conjunction with the annual 
marine species monitoring technical review meetings).

Preliminary Analysis and Negligible Impact Determination

General Negligible Impact Analysis

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. For Level A 
harassment or Level B harassment (as presented in Table 30), in 
addition to considering estimates of the number of marine mammals that 
might be taken 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 rise to the level 
of takes both annually and over the 7-year period covered by this 
proposed rule, and then identified the maximum number of harassment 
takes that are reasonably expected to occur based on the methods 
described. The impact that any given take would 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 to 
individuals, etc.). For this proposed rule we evaluated the likely 
impacts of the enumerated maximum number of harassment takes that are 
proposed for authorization 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 
other more taxa-specific information and mitigation measure 
effectiveness, in group-specific assessments that support our 
negligible impact conclusions for each stock or species. Because all of 
the Navy's specified activities would occur within the ranges of the 
marine mammal stocks identified in the rule, all negligible impact 
analyses and determinations are at the stock level (i.e., additional 
species-level determinations are not needed).
    As explained in the Estimated Take of Marine Mammals section, no 
take by serious injury or mortality is authorized or anticipated to 
occur. There have been no recorded Navy vessel strikes of any marine 
mammals during training in the GOA Study Area to date, nor were 
incidental takes by injury or mortality resulting from vessel strike 
predicted in the Navy's analysis. For these and the other reasons 
described in the Potential Effects of Vessel Strike section, NMFS 
concurs that vessel strike is not likely to occur during the 21-day GOA 
Study Area training activities, and therefore is not proposing 
authorization in this rule.
    The specified activities reflect representative levels of training 
activities. The Description of the Specified Activity section describes 
annual activities. There may be some flexibility in the exact number of 
hours, items, or detonations that may vary from year to year, but take 
totals would not exceed the maximum annual totals and 7-year totals 
indicated in Table 30. (Further, as noted previously, the GOA Study 
Area training activities would not occur continuously throughout the 
year, but rather, for a maximum of 21 days once annually between April 
and October.) We base our analysis and negligible impact determination 
on the maximum number of takes that would be reasonably expected to 
occur annually and are proposed to be authorized, although, as stated 
before,

[[Page 49736]]

the number of takes is only a part of the analysis, which includes 
extensive qualitative consideration of other contextual factors that 
influence the degree of impact of the takes on the affected 
individuals. To avoid repetition, we provide some general analysis 
immediately below that applies to all the species listed in Table 30, 
given that some of the anticipated effects of the Navy's training 
activities on marine mammals are expected to be relatively similar in 
nature. However, below that, we break our analysis into species (and/or 
stocks), or groups of species (and the associated stocks) where 
relevant similarities exist, to provide more specific information 
related to the anticipated effects on individuals of a specific stock 
or where there is information about the status or structure of any 
species or stock that would lead to a differing assessment of the 
effects on the species or stock. Organizing our analysis by grouping 
species or stocks that share common traits or that would respond 
similarly to effects of the Navy's activities and then providing 
species- or stock-specific information allows us to avoid duplication 
while assuring that we have analyzed the effects of the specified 
activities on each affected species or stock.
Harassment
    The Navy's harassment take request is based on a model and 
quantitative assessment of mitigation, which NMFS reviewed and concurs 
appropriately predicts the maximum amount of harassment that is 
reasonably likely to occur, with the exception of the Eastern North 
Pacific stock of gray whale, and the Western North Pacific stock of 
humpback whale, for which NMFS has proposed authorizing 4 and 3 Level B 
harassment takes annually, respectively, as described in the Estimated 
Take of Marine Mammals section. The model calculates sound energy 
propagation from sonar, other active acoustic sources, and explosives 
during naval activities; the sound or impulse received by animat 
dosimeters representing marine mammals distributed in the area around 
the modeled activity; and whether the sound or impulse energy received 
by a marine mammal exceeds the thresholds for effects. Assumptions in 
the Navy model intentionally err on the side of overestimation when 
there are unknowns. Naval activities are modeled as though they would 
occur regardless of proximity to marine mammals, meaning that no 
mitigation is considered (e.g., no power down or shut down) and without 
any avoidance of the activity by the animal. As described above in the 
Estimated Take of Marine Mammals section, no mortality was modeled for 
any species for the TMAA activities, and therefore the quantitative 
post-modeling analysis that allows for the consideration of mitigation 
to prevent mortality, which has been applied in other Navy rules, was 
appropriately not applied here. (Though, as noted in the Estimated Take 
of Marine Mammals section, where the analysis indicates mitigation 
would effectively reduce risk, the model-estimated PTS are considered 
reduced to TTS.) NMFS provided input to, independently reviewed, and 
concurs with the Navy on this process and the Navy's analysis, which is 
described in detail in Section 6 of the Navy's rulemaking/LOA 
application, that was used to quantify harassment takes for this rule.
    Generally speaking, the Navy and NMFS anticipate more severe 
effects from takes resulting from exposure to higher received levels 
(though this is in no way a strictly linear relationship for behavioral 
effects throughout species, individuals, or circumstances) and less 
severe effects from takes resulting from exposure to lower received 
levels. 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 evoke a response of equal 
magnitude (DeRuiter 2012, Falcone et al. 2017). The estimated number of 
takes by Level A harassment and Level B harassment does not equate to 
the number of individual animals the Navy expects to harass (which is 
lower), but rather to the instances of take (i.e., exposures above the 
Level A harassment and Level B harassment threshold) that are 
anticipated to occur annually and over the 7-year period. These 
instances may represent either brief exposures (seconds or minutes) or, 
in some cases, longer durations of exposure within a day. Some 
individuals may experience multiple instances of take (meaning over 
multiple days) over the course of the 21 day exercise, which means that 
the number of individuals taken is smaller than the total estimated 
takes. Generally speaking, the higher the number of takes as compared 
to the population abundance, the more repeated takes of individuals are 
likely, and the higher the actual percentage of individuals in the 
population that are likely taken at least once in a year. We look at 
this comparative metric to give us a relative sense of where a larger 
portion of a species is being taken by Navy activities, 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 or more 
likely sequential. Where the number of instances of take is less than 
100 percent of the abundance and there is no information to 
specifically suggest that a small subset of animals is being repeatedly 
taken over a high number of sequential days, the overall magnitude is 
generally considered low, as it could on one extreme mean that every 
take represents a separate individual in the population being taken on 
one day (a very minimal impact) or, more likely, that some smaller 
number of individuals are taken on one day annually and some are taken 
on a few not likely sequential days annually, while some are not taken 
at all.
    In the ocean, the use of sonar and other active acoustic sources is 
often transient and is unlikely to repeatedly expose the same 
individual animals within a short period, for example within one 
specific exercise. However, for some individuals of some species 
repeated exposures across different activities could occur across the 
21-day period. In short, for some species we expect that the total 
anticipated takes represent exposures of a smaller number of 
individuals of which some would be exposed multiple times, but based on 
the nature of the Navy activities and the movement patterns of marine 
mammals, it is unlikely that individuals from most stocks would be 
taken over more than a few non-sequential days. This means that even 
where repeated takes of individuals may occur, they are more likely to 
result from non-sequential exposures from different activities, and, 
even if a few individuals were taken on sequential days, they are not 
predicted to be taken for more than a few days in a row, at most. As 
described elsewhere, the nature of the majority of the exposures would 
be expected to be of a less severe nature and based on the numbers and 
duration of the activity (no more than 21 days) any individual exposed 
multiple times is still only taken on a small percentage of the days of 
the year.
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 earlier 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 A harassment or Level B harassment, then, may 
have a

[[Page 49737]]

stress-related physiological component as well; however, we would not 
expect the Navy's generally short-term, intermittent, and (typically in 
the case of sonar) transitory activities to create conditions of long-
term continuous noise leading to long-term physiological stress 
responses in marine mammals that could affect reproduction or survival.
Behavioral Response
    The estimates calculated using the BRF do not differentiate between 
the different types of behavioral responses that rise to the level of 
take by Level B harassment. As described in the Navy's application, the 
Navy identified (with NMFS' input) the types of behaviors that would be 
considered a take: Moderate behavioral responses as characterized in 
Southall et al. (2007) (e.g., altered migration paths or dive profiles, 
interrupted nursing, breeding or feeding, or avoidance) that also would 
be expected to continue for the duration of an exposure. The Navy then 
compiled the available data indicating at what received levels and 
distances those responses have occurred, and used the indicated 
literature to build biphasic behavioral response curves that are used 
to predict how many instances of Level B harassment by behavioral 
disturbance occur in a day. Take estimates alone do not provide 
information regarding the potential fitness or other biological 
consequences of the reactions 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.
    Use of sonar and other transducers would typically be transient and 
temporary. The majority of acoustic effects to individual animals from 
sonar and other active sound sources during training activities would 
be primarily from ASW events. It is important to note that although ASW 
is one of the warfare areas of focus during Navy training, there are 
significant periods when active ASW sonars are not in use. Behavioral 
reactions are assumed more likely to be significant during MTEs than 
during other ASW activities due to the use of high-powered ASW sources 
as well as the duration (i.e., multiple days) and scale (i.e., multiple 
sonar platforms) of the MTEs.
    On the less severe end, exposure to comparatively lower levels of 
sound at a detectably greater distance from the animal, for a few or 
several minutes, could result in a behavioral response such as avoiding 
an area that an animal would otherwise have moved through or fed in, or 
breaking off one or a few feeding bouts. More severe effects could 
occur when the animal gets close enough to the source to receive a 
comparatively higher level of sound, is exposed continuously to one 
source for a longer time, or is exposed intermittently to different 
sources throughout a day. 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.
    To help assess this, for sonar (MFAS/HFAS) used in the TMAA, the 
Navy provided information estimating the percentage of animals that may 
be taken by Level B harassment under each BRF that would occur within 
6-dB increments (percentages discussed below in the Group and Species-
Specific Analyses section). As mentioned above, all else being equal, 
an animal's exposure to a higher received level is more likely to 
result in a behavioral response that is more likely to lead to adverse 
effects, which could more likely accumulate to impacts on reproductive 
success or survivorship of the animal, but other contextual factors 
(such as distance) are also important. The majority of takes by Level B 
harassment are expected to be in the form of milder responses (i.e., 
lower-level exposures that still rise to the level of take, but would 
likely be less severe in the range of responses that qualify as take) 
of a generally shorter duration. We anticipate more severe effects from 
takes when animals are exposed to higher received levels of sound or at 
closer proximity to the source. Because species belonging to taxa that 
share common characteristics are likely to respond and be affected in 
similar ways, these discussions are presented within each species group 
below in the Group and Species-Specific Analyses section. As noted 
previously in this proposed rule, behavioral responses vary 
considerably between species, between individuals within a species, and 
across contexts of different exposures. 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 Navy activities might necessarily 
be expected to potentially result in more severe responses (see the 
Group and Species-Specific Analyses section below for more detailed 
information). To fully understand the likely impacts of the predicted/
proposed authorized take on an individual (i.e., what is the likelihood 
or degree of fitness impacts), one must look closely at the available 
contextual information, such as the duration of likely exposures and 
the likely severity of the exposures (e.g., whether they would occur 
for a longer duration over sequential days or the comparative sound 
level that would be received). Ellison et al. (2012) and Moore and 
Barlow (2013), among others, emphasize the importance of context (e.g., 
behavioral state of the animals, distance from the sound source, etc.) 
in evaluating behavioral responses of marine mammals to acoustic 
sources.
Diel Cycle
    Many animals perform vital functions, such as feeding, resting, 
traveling, and socializing on a diel cycle (24-hour cycle). Behavioral 
reactions to noise exposure, when taking place in a biologically 
important context, such as 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 events 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 one 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 reactions and multiple-day 
anthropogenic activities. For example, just because an at-sea exercise 
lasts for multiple days does not necessarily mean that individual 
animals are either exposed to those exercises for multiple days or, 
further, exposed in a manner resulting in a sustained multiple day 
substantive behavioral response. Large multi-day Navy exercises such as 
ASW activities, typically include vessels that are continuously moving 
at speeds typically 10-15 kn (19-28 km/hr), or higher, and likely cover 
large areas that are relatively far from shore (typically more than 3 
nmi (6 km) from shore) and in waters greater than 600 ft (183 m) deep. 
Additionally 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

[[Page 49738]]

exercise. Further, the Navy does not necessarily operate active sonar 
the entire time during an exercise. While it is certainly possible that 
these sorts of exercises could overlap with individual marine mammals 
multiple days in a row at levels above those anticipated to result in a 
take, because of the factors mentioned above, it is considered unlikely 
for the majority of takes. However, it is also worth noting that the 
Navy conducts many different types of noise-producing activities over 
the course of the 21-day exercise, and it is likely that some marine 
mammals will be exposed to more than one activity and taken on multiple 
days, even if they are not sequential.
    Durations of Navy activities utilizing tactical sonar sources and 
explosives vary and are fully described in Appendix A (Navy Activity 
Descriptions) of the 2020 GOA DSEIS/OEIS. Sonar used during ASW would 
impart the greatest amount of acoustic energy of any category of sonar 
and other transducers analyzed in the Navy's rulemaking/LOA application 
and include hull-mounted, towed array, sonobuoy, and helicopter dipping 
sonars. Most ASW sonars are MFAS (1-10 kHz); however, some sources may 
use higher frequencies. ASW training activities using hull mounted 
sonar proposed for the TMAA generally last for only a few hours (see 
Appendix A (Navy Activity Descriptions) of the 2020 GOA DSEIS/OEIS). 
Some ASW training activities typically last about 8 hours. Because of 
the need to train in a large variety of situations, the Navy does not 
typically conduct successive ASW exercises in the same locations. Given 
the average length of ASW exercises (times of sonar use) and typical 
vessel speed, combined with the fact that the majority of the cetaceans 
would not likely remain in proximity to the sound source, it is 
unlikely that an animal would be exposed to MFAS/HFAS at levels or 
durations likely to result in a substantive response that would then be 
carried on for more than 1 day or on successive days (and as noted 
previously, no LFAS use is planned by the Navy).
    Most planned explosive events are scheduled to occur over a short 
duration (1-3 hours); however, the explosive component of these 
activities only lasts for minutes. Although explosive exercises may 
sometimes be conducted in the same general areas repeatedly, because of 
their short duration and the fact that they are in the open ocean and 
animals can easily move away, it is similarly unlikely that animals 
would be exposed for long, continuous amounts of time, or demonstrate 
sustained behavioral responses. All of these factors make it unlikely 
that individuals would be exposed to the exercise for extended periods 
or on consecutive days, though some individuals may be exposed on 
multiple days.
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 (and 
further corrected to account for mitigation and avoidance). As further 
noted, for active acoustics it is more 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. 
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, one can assume 
either that every individual was exposed above acoustic thresholds in 
no more than one day, or that some smaller number were exposed in one 
day but a few of those individuals were exposed multiple days within a 
year and 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 or stock are being taken by Navy 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 to 
each species or stock.
    In the ocean, unlike a modeling simulation with static animals, the 
use of sonar and other active acoustic sources is often transient, and 
is unlikely to repeatedly expose the same individual animals within a 
short period, for example within one specific exercise. However, some 
repeated exposures across different activities could occur over the 
year with more resident species. Nonetheless, the episodic nature of 
activities in the TMAA (21 days per year) would mean less frequent 
exposures as compared to some other ranges. In short, we expect that 
for some stocks, the total anticipated takes represent exposures of a 
smaller number of individuals of which some could be exposed multiple 
times, but based on the nature of the Navy's activities and the 
movement patterns of marine mammals, it is unlikely that individuals of 
most species or stocks would be taken over more than a few non-
sequential days within a year.
    When calculating the proportion of a population affected by takes 
(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. The SARs, 
where available, provide the official population estimate for a given 
species or stock in U.S. waters in a given year (and are typically 
based solely on the most recent survey data). 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 information used to estimate 
take includes the best available survey abundance data to model density 
layers. Accordingly, in calculating the percentage of takes versus 
abundance for each species or stock in order to assist in understanding 
both the percentage of the species or stock affected, as well as how 
many days across a year individuals could be taken, we use the data 
most appropriate for the situation. For the GOA Study Area, for all 
species and stocks except for beaked whales for which SAR data are 
unavailable, the most recent NMFS SARs are used to calculate the 
proportion of a population affected by takes.
    The estimates found in NMFS' SARs remain the official estimates of 
stock abundance where they are current. These estimates are typically 
generated from the most recent shipboard and/or aerial surveys 
conducted. In some cases, NMFS' abundance estimates show substantial 
year-to-year variability. However, for highly migratory species (e.g., 
large whales) or those whose geographic distribution extends well 
beyond the boundaries of the GOA Study Area (e.g., populations with 
distribution along the entire eastern Pacific Ocean rather than just 
the GOA Study Area), comparisons to the SAR

[[Page 49739]]

are appropriate. Many of the stocks present in the GOA Study Area have 
ranges significantly larger than the GOA Study Area and that abundance 
is captured by the SAR. A good descriptive example is migrating large 
whales, which occur seasonally in the GOA. Therefore, at any one time 
there may be a stable number of animals, but over the course of the 
potential activity period (April to October), the entire population 
could occur in the GOA Study Area. Therefore, comparing the estimated 
takes to an abundance, in this case the SAR abundance, which represents 
the total population, may be more appropriate than modeled abundances 
for only the GOA Study Area.
Temporary Threshold Shift
    NMFS and the Navy have estimated that most species or stocks of 
marine mammals in the TMAA may sustain some level of TTS from active 
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 41 to Table 46 indicate the number of takes by TTS that 
may be incurred by different species and stocks from exposure to active 
sonar and explosives. The TTS sustained by an animal is primarily 
classified by three characteristics:
    1. Frequency--Available data (of mid-frequency hearing specialists 
exposed to mid- or high-frequency sounds; Southall et al., 2007) 
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 \1/2\ octave 
above). The Navy's MF sources, which are the highest power and most 
numerous sources and the ones that cause the most take, utilize the 1-
10 kHz frequency band, which suggests that if TTS were to be induced by 
any of these MF sources it would be in a frequency band somewhere 
between approximately 2 and 20 kHz, which is in the range of 
communication calls for many odontocetes, but below the range of the 
echolocation signals used for foraging. There are fewer hours of HF 
source use and the sounds would attenuate more quickly, plus they have 
lower source levels, but if an animal were to incur TTS from these 
sources, it would cover a higher frequency range (sources are between 
10 and 100 kHz, which means that TTS could range up to 200 kHz), which 
could overlap with the range in which some odontocetes communicate or 
echolocate. However, HF systems are typically used less frequently and 
for shorter time periods than surface ship and aircraft MF systems, so 
TTS from these sources is unlikely. As noted previously, the Navy 
proposes no LFAS use for the activities in this rulemaking. The 
frequency provides information about the cues to which a marine mammal 
may be temporarily less sensitive, but not the degree or duration of 
sensitivity loss. The majority of sonar sources from which TTS may be 
incurred occupy a narrow frequency band, which means that the TTS 
incurred would also be across a narrower band (i.e., not affecting the 
majority of an animal's hearing range). TTS from explosives would be 
broadband.
    2. Degree of the shift (i.e., by how many dB the sensitivity of the 
hearing is reduced)--Generally, both the degree of TTS 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 dB level is higher or 
the duration is longer). The threshold for the onset of TTS was 
discussed previously in this rule. An animal 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 
difficult considering the Lookouts and the nominal speed of an active 
sonar vessel (10-15 kn; 19-28 km/hr) and the relative motion between 
the sonar vessel and the animal. In the TTS studies discussed in the 
Potential Effects of Specified Activities on Marine Mammals and their 
Habitat section, 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 with a 64-second exposure 
to a 20 kHz source. However, since any hull-mounted sonar such as the 
SQS-53 (MFAS), emits a ping typically every 50 seconds, incurring those 
levels of TTS is highly unlikely. Since any hull-mounted sonar, such as 
the SQS-53, engaged in anti-submarine warfare training would be moving 
at between 10 and 15 kn (19-28 km/hr) and nominally pinging every 50 
seconds, the vessel would have traveled a minimum distance of 
approximately 257 m during the time between those pings. A scenario 
could occur where an animal does not leave the vicinity of a ship or 
travels a course parallel to the ship, however, the close distances 
required make TTS exposure unlikely. For a Navy vessel moving at a 
nominal 10 kn (19 km/hr), it is unlikely a marine mammal could maintain 
speed parallel to the ship and receive adequate energy over successive 
pings to suffer TTS.
    In short, given the anticipated duration and levels of sound 
exposure, we would not expect marine mammals to incur more than 
relatively low levels of TTS (i.e., single digits of sensitivity loss). 
To add context to this degree of TTS, individual marine mammals may 
regularly experience variations of 6 dB differences in hearing 
sensitivity across time (Finneran et al., 2000, 2002; Schlundt et al., 
2000).
    3. Duration of TTS (recovery time)--In the TTS laboratory studies 
(as discussed in the Potential Effects of Specified Activities on 
Marine Mammals and their Habitat section), some using exposures of 
almost an hour in duration or up to 217 SEL, almost all individuals 
recovered within 1 day (or less, often in minutes), although in one 
study (Finneran et al., 2007), recovery took 4 days.
    Based on the range of degree and duration of TTS reportedly induced 
by exposures to non-pulse sounds of energy higher than that to which 
free-swimming marine mammals in the field are likely to be exposed 
during MFAS/HFAS training exercises in the TMAA, it is unlikely that 
marine mammals would ever sustain a TTS from MFAS that alters their 
sensitivity by more than 20 dB for more than a few hours--and any 
incident of TTS would likely be far less severe due to the short 
duration of the majority of the events during the 21 days and the speed 
of a typical vessel, especially given the fact that the higher power 
sources resulting in TTS are predominantly intermittent, which have 
been shown to result in shorter durations of TTS. Also, for the same 
reasons discussed in the Preliminary Analysis and Negligible Impact 
Determination--Diel Cycle section, and because of the short distance 
within which animals would need to approach the sound source, it is 
unlikely that animals would be exposed to the levels necessary to 
induce TTS in subsequent time periods such that their recovery is 
impeded. Additionally, though the frequency range of TTS that marine 
mammals might sustain would overlap with some of the frequency ranges 
of their vocalization types, the frequency range of TTS from MFAS would 
not usually span the entire frequency range of one vocalization type, 
much less span all types of vocalizations or other critical auditory 
cues.
    Tables 41 to 46 indicate the number of incidental takes by TTS for 
each species or stock that are likely to result from the Navy's 
activities. As a general point, the majority of these TTS takes are the 
result of exposure to hull-

[[Page 49740]]

mounted MFAS (MF narrower band sources), with fewer from explosives 
(broad-band lower frequency sources), and even fewer from HFAS sources 
(narrower band). As described above, we expect the majority of these 
takes to be in the form of mild (single-digit), short-term (minutes to 
hours), narrower band (only affecting a portion of the animal's hearing 
range) TTS. This means that for one to several times within the 21 
days, for several minutes to maybe a few hours at most each, a taken 
individual will have slightly diminished hearing sensitivity (slightly 
more than natural variation, but nowhere near total deafness). More 
often than not, such an exposure would occur within a narrower mid- to 
higher frequency band that may overlap part (but not all) of a 
communication, echolocation, or predator range, but sometimes across a 
lower or broader bandwidth. 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 an odontocete has TTS at 
echolocation frequencies, but incurs it at night when it is resting and 
not feeding, it is not 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 be 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, given the small number of 
times that any individual might incur TTS, the low degree of TTS and 
the short anticipated duration, and the low likelihood that one of 
these instances would occur in a time period in which the specific TTS 
overlapped the entirety of a critical signal, it is unlikely that TTS 
of the nature expected to result from the Navy activities would result 
in behavioral changes or other impacts that would impact any 
individual's (of any hearing sensitivity) reproduction or survival.
Auditory Masking or Communication Impairment
    The ultimate potential impacts of masking on an individual (if it 
were to occur) are similar to those discussed for TTS, but an important 
difference is that masking only occurs during the time of the signal, 
versus TTS, which continues beyond the duration of the signal. 
Fundamentally, masking is referred to as a chronic effect because one 
of the key harmful components of masking is its duration--the fact that 
an animal would have reduced ability to hear or interpret critical cues 
becomes much more likely to cause a problem the longer it is occurring. 
Also inherent in the concept of masking is the fact that the potential 
for the effect is only present 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 
species involved in this rule, we do not expect the exposures with the 
potential for masking to be of a long duration. In addition, masking is 
fundamentally more of a concern at lower frequencies, because low 
frequency signals propagate significantly further than higher 
frequencies and because they are more likely to overlap both the 
narrower LF calls of mysticetes, as well as many non-communication cues 
such as fish and invertebrate prey, and geologic sounds that inform 
navigation (although the Navy proposes no LFAS use for the activities 
in this rulemaking). Masking is also more of a concern from continuous 
sources (versus intermittent sonar signals) where there is no quiet 
time between pulses within which auditory signals can be detected and 
interpreted. For these reasons, dense aggregations of, and long 
exposure to, continuous LF activity are much more of a concern for 
masking, whereas comparatively short-term exposure to the predominantly 
intermittent pulses of often narrow frequency range MFAS or HFAS, or 
explosions are not expected to result in a meaningful amount of 
masking. While the Navy occasionally uses LF and more continuous 
sources (although, as noted above, the Navy proposes no LFAS use for 
the activities in this rulemaking), it is not in the contemporaneous 
aggregate amounts that would accrue to a masking concern. Specifically, 
the nature of the activities and sound sources used by the Navy do not 
support the likelihood of a level of masking accruing that would have 
the potential to affect reproductive success or survival. Additional 
detail is provided below.
    Standard hull-mounted MFAS typically pings every 50 seconds. Some 
hull-mounted anti-submarine sonars can also be used in an object 
detection mode known as ``Kingfisher'' mode (e.g., used on vessels when 
transiting to and from port) where pulse length is shorter but pings 
are much closer together in both time and space since the vessel goes 
slower when operating in this mode (note also that the duty cycle for 
MF11 and MF12 sources is greater than 80 percent). For the majority of 
other sources, the pulse length is significantly shorter than hull-
mounted active sonar, on the order of several microseconds to tens of 
milliseconds. Some of the vocalizations that many marine mammals make 
are less than one second long, so, for example with hull-mounted sonar, 
there would be a 1 in 50 chance (only if the source was in close enough 
proximity for the sound to exceed the signal that is being detected) 
that a single vocalization might be masked by a ping. However, when 
vocalizations (or series of vocalizations) are longer than one second, 
masking would not occur. Additionally, when the pulses are only several 
microseconds long, the majority of most animals' vocalizations would 
not be masked.
    Most ASW sonars and countermeasures use MF frequencies and a few 
use HF frequencies. Most of these sonar signals are limited in the 
temporal, frequency, and spatial domains. The duration of most 
individual sounds is short, lasting up to a few seconds each. A few 
systems operate with higher duty cycles or nearly continuously, but 
they typically use lower power, which means that an animal would have 
to be closer, or in the vicinity for a longer time, to be masked to the 
same degree as by a higher level source. Nevertheless, masking could 
occasionally occur at closer ranges to these high-duty cycle and 
continuous active sonar systems, but as described previously, it would 
be expected to be of a short duration when the source and animal are in 
close proximity. While data are limited on behavioral responses of 
marine mammals to continuously active sonars (Isojunno et al., 2020), 
mysticete species are known to be able to habituate to novel and 
continuous sounds (Nowacek et al., 2004), suggesting that they are 
likely to have similar responses to high-duty cycle sonars. 
Furthermore, most of these systems are hull-mounted on surface ships 
with the ships moving at least 10 kn (19 km/hr), and it is unlikely 
that the ship and the marine mammal would continue to move in the same 
direction and the marine mammal subjected to the same exposure due to 
that movement. Most ASW activities are

[[Page 49741]]

geographically dispersed and last for only a few hours, often with 
intermittent sonar use even within this period. Most ASW sonars also 
have a narrow frequency band (typically less than one-third octave). 
These factors reduce the likelihood of sources causing significant 
masking. HF signals (above 10 kHz) attenuate more rapidly in the water 
due to absorption than do lower frequency signals, thus producing only 
a very small zone of potential masking. If masking or communication 
impairment were to occur briefly, it would more likely be in the 
frequency range of MFAS (the more powerful source), which overlaps with 
some odontocete vocalizations (but few mysticete vocalizations); 
however, it would likely not mask the entirety of any particular 
vocalization, communication series, or other critical auditory cue, 
because the signal length, frequency, and duty cycle of the MFAS/HFAS 
signal does not perfectly resemble the characteristics of any single 
marine mammal species' vocalizations.
    Other sources used in Navy training that are not explicitly 
addressed above, many of either higher frequencies (meaning that the 
sounds generated attenuate even closer to the source) or lower amounts 
of operation, are similarly not expected to result in masking. For the 
reasons described here, any limited masking that could potentially 
occur would be minor and short-term.
    In conclusion, masking is more likely to occur in the presence of 
broadband, relatively continuous noise sources such as from vessels, 
however, the duration of temporal and spatial overlap with any 
individual animal and the spatially separated sources that the Navy 
uses would not be expected to result in more than short-term, low 
impact masking that would not affect reproduction or survival.
PTS From Sonar Acoustic Sources and Explosives and Non-Auditory Tissue 
Damage From Explosives
    Tables 41 to 46 indicate the number of individuals of each species 
or stock for which Level A harassment in the form of PTS resulting from 
exposure to active sonar and/or explosives is estimated to occur. The 
Northeast Pacific stock of fin whale, Alaska stock of Dall's porpoise, 
and California stock of Northern elephant seal are the only stocks 
which may incur PTS (from sonar and explosives). For all other species/
stocks only take by Level B harassment (behavioral disturbance and/or 
TTS) is anticipated. No species/stocks have the potential to incur non-
auditory tissue damage from training activities.
    Data suggest that many marine mammals would deliberately avoid 
exposing themselves to the received levels of active sonar necessary to 
induce injury by moving away from or at least modifying their path to 
avoid a close approach. Additionally, in the unlikely event that an 
animal approaches the sonar-emitting vessel at a close distance, NMFS 
has determined that the mitigation measures (i.e., shutdown/powerdown 
zones for active sonar) would typically ensure that animals would not 
be exposed to injurious levels of sound. As discussed previously, the 
Navy utilizes both aerial (when available) and passive acoustic 
monitoring (during ASW exercises, passive acoustic detections are used 
as a cue for Lookouts' visual observations when passive acoustic assets 
are already participating in an activity) in addition to Lookouts on 
vessels to detect marine mammals for mitigation implementation. As 
discussed previously, the Navy utilized a post-modeling quantitative 
assessment to adjust the take estimates based on avoidance and the 
likely success of some portion of the mitigation measures. As is 
typical in predicting biological responses, it is challenging to 
predict exactly how avoidance and mitigation would affect the take of 
marine mammals. Therefore, in conducting the post-modeling quantitative 
assessment, the Navy erred on the side of caution in choosing a method 
that would more likely still overestimate the take by PTS to some 
degree. Nonetheless, these Level A harassment take numbers represent 
the maximum number of instances in which marine mammals would be 
reasonably expected to incur PTS, and we have analyzed them 
accordingly.
    If a marine mammal is able to approach a surface vessel within the 
distance necessary to incur PTS in spite of the mitigation measures, 
the likely speed of the vessel (nominally 10-15 kn (19-28 km/hr)) and 
relative motion of the vessel would make it very difficult for the 
animal to remain in range long enough to accumulate enough energy to 
result in more than a mild case of PTS. As discussed previously in 
relation to TTS, the likely consequences to the health of an individual 
that incurs PTS can range from mild to more serious dependent upon the 
degree of PTS and the frequency band it is in. The majority of any PTS 
incurred as a result of exposure to Navy sources would be expected to 
be in a narrow band in the 2-20 kHz range (resulting from the most 
powerful hull-mounted sonar) and could overlap a small portion of the 
communication frequency range of many odontocetes, whereas other marine 
mammal groups have communication calls at lower frequencies. Regardless 
of the frequency band, the more important point in this case is that 
any PTS accrued as a result of exposure to Navy activities would be 
expected to be of a small amount (single digits of dB hearing loss). 
Permanent loss of some degree of hearing is a normal occurrence for 
older animals, and many animals are able to 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 Proposed 
Mitigation Measures section) during explosive activities, including 
delaying detonations when a marine mammal is observed in the mitigation 
zone. Nearly all explosive events would occur during daylight hours to 
improve the sightability of marine mammals and thereby improve 
mitigation effectiveness. Observing for marine mammals during the 
explosive activities would include visual and passive acoustic 
detection methods (when they are available and part of the activity) 
before the activity begins, in order to cover the mitigation zones that 
can range from 200 yd (182.9 m) to 2,500 yd (2,286 m) depending on the 
source (e.g., explosive bombs; see Table 34 and Table 35). For all of 
these reasons, the proposed mitigation measures associated with 
explosives are expected to further ensure that no non-auditory tissue 
damage occurs to any potentially affected species, and no species are 
anticipated to incur non-auditory tissue damage during the period of 
the proposed rule.

Group and Species-Specific Analyses

    The maximum amount and type of incidental take of marine mammals 
reasonably likely to occur and therefore proposed to be authorized from 
exposures to sonar and other active acoustic sources and in-air 
explosions at or above the water surface during the 7-year training 
period are shown in Table 30. The vast majority of predicted exposures 
(greater than 99 percent) are expected to be non-injurious Level B 
harassment (TTS and behavioral disturbance) from acoustic and

[[Page 49742]]

explosive sources during training activities at relatively low received 
levels. A small number of takes by Level A harassment (PTS only) are 
predicted for three species (Dall's porpoise, fin whales, and Northern 
elephant seals).
    In the discussions below, the estimated takes by Level B harassment 
represent instances of take, not the number of individuals taken (the 
less frequent Level A harassment takes are far more likely to be 
associated with separate individuals), and in some cases individuals 
may be taken more than one time. Below, we compare the total take 
numbers (including PTS, TTS, and behavioral disturbance) for species or 
stocks to their associated abundance estimates to evaluate the 
magnitude of impacts across the species and to individuals. Generally, 
when an abundance percentage comparison is below 100, it means that 
that percentage or less of the individuals would be affected (i.e., 
some individuals would not be taken at all), that the average for those 
taken is one day per year, and that we would not expect any individuals 
to be taken more than a few times during the 21 days per year. When it 
is more than 100 percent, it means there would definitely be some 
number of repeated takes of individuals. For example, if the percentage 
is 300, the average would be each individual is taken on 3 days in a 
year if all were taken, but it is more likely that some number of 
individuals would be taken more than three times and some number of 
individuals fewer or not at all. While it is not possible to know the 
maximum number of days across which individuals of a stock might be 
taken, in acknowledgement of the fact that it is more than the average, 
for the purposes of this analysis, we assume a number approaching twice 
the average. For example, if the percentage of take compared to the 
abundance is 800, we estimate that some individuals might be taken as 
many as 16 times. Those comparisons are included in the sections below.
    To assist in understanding what this analysis means, we clarify a 
few issues related to estimated takes and the analysis here. An 
individual that incurs a PTS or TTS take may sometimes, for example, 
also be subject to behavioral disturbance at the same time. As 
described above in this section, the degree of PTS, and the degree and 
duration of TTS, expected to be incurred from the Navy's activities are 
not expected to impact marine mammals such that their reproduction or 
survival could be affected. Similarly, data do not suggest that a 
single instance in which an animal accrues PTS or TTS and is also 
subjected to behavioral disturbance would result in impacts to 
reproduction or survival. Alternately, we recognize that if an 
individual is subjected to behavioral disturbance repeatedly for a 
longer duration and on consecutive days, effects could accrue to the 
point that reproductive success is jeopardized, although those sorts of 
impacts are not expected to result from these activities. Accordingly, 
in analyzing the number of takes and the likelihood of repeated and 
sequential takes, we consider the total takes, not just the takes by 
Level B harassment by behavioral disturbance, so that individuals 
potentially exposed to both threshold shift and behavioral disturbance 
are appropriately considered. The number of Level A harassment takes by 
PTS are so low (and zero in most cases) compared to abundance numbers 
that it is considered highly unlikely that any individual would be 
taken at those levels more than once.
    Occasional, milder behavioral reactions are unlikely to cause long-
term consequences for individual animals or populations, and even if 
some smaller subset of the takes are in the form of a longer (several 
hours or a day) and more severe response, if they are not expected to 
be repeated over sequential days, impacts to individual fitness are not 
anticipated. Nearly all studies and experts agree that infrequent 
exposures of a single day or less are unlikely to impact an 
individual's overall energy budget (Farmer et al., 2018; Harris et al., 
2017; King et al., 2015; NAS 2017; New et al., 2014; Southall et al., 
2007; Villegas-Amtmann et al., 2015).
    If impacts to individuals are of a magnitude or severity such that 
either repeated and sequential higher severity impacts occur (the 
probability of this goes up for an individual the higher total number 
of takes it has) or the total number of moderate to more severe impacts 
increases substantially, especially if occurring across sequential 
days, then it becomes more likely that the aggregate effects could 
potentially interfere with feeding enough to reduce energy budgets in a 
manner that could impact reproductive success via longer cow-calf 
intervals, terminated pregnancies, or calf mortality. It is important 
to note that these impacts would only accrue to females, which only 
comprise a portion of the population (typically approximately 50 
percent). Based on energetic models, it takes energetic impacts of a 
significantly greater magnitude to cause the death of an adult marine 
mammal, and females will always terminate a pregnancy or stop lactating 
before allowing their health to deteriorate. Also, the death of an 
adult female has significantly more impact on population growth rates 
than reductions in reproductive success, while the death of an adult 
male has very little effect on population growth rates. However, as 
will be explained further in the sections below, the severity and 
magnitude of takes expected to result from Navy activities in the TMAA 
are such that energetic impacts of a scale that might affect 
reproductive success are not expected to occur at all.
    The analyses below in some cases address species collectively if 
they occupy the same functional hearing group (i.e., low, mid, and 
high-frequency cetaceans), share similar life history strategies, and/
or are known to behaviorally respond similarly to acoustic stressors. 
Because some of these groups or species share characteristics that 
inform the impact analysis similarly, it would be duplicative to repeat 
the same analysis for each species. In addition, similar species 
typically have the same hearing capabilities and behaviorally respond 
in the same manner.
    Thus, our analysis below considers the effects of the Navy's 
activities on each affected species or stock even where discussion is 
organized by functional hearing group and/or information is evaluated 
at the group level. Where there are meaningful differences between a 
species or stock that would further differentiate the analysis, they 
are either described within the section or the discussion for those 
species or stocks is included as a separate subsection. Specifically 
below, we first provide broad discussion of the expected effects on the 
mysticete, odontocete, and pinniped groups generally, and then 
differentiate into further groups as appropriate.
Mysticetes
    This section builds on the broader discussion above and brings 
together the discussion of the different types and amounts of take that 
different species and stocks would likely incur, the applicable 
mitigation, and the status of the species and stocks to support the 
preliminary negligible impact determinations for each species or stock. 
We have described (earlier in this section) the unlikelihood of any 
masking having effects that would impact the reproduction or survival 
of any of the individual marine mammals affected by the Navy's 
activities. We have also described above in the Potential Effects of 
Specified Activities on Marine Mammals and their Habitat section the 
unlikelihood of any habitat impacts having effects that would

[[Page 49743]]

impact the reproduction or survival of any of the individual marine 
mammals affected by the Navy's activities. For mysticetes, there is no 
predicted non-auditory tissue damage from explosives for any species, 
and only two fin whales could be taken by PTS by exposure to in-air 
explosions at or above the water surface. Much of the discussion below 
focuses on the behavioral effects and the mitigation measures that 
reduce the probability or severity of effects. Because there are 
species-specific and stock-specific considerations, at the end of the 
section we break out our findings on a species-specific and, for one 
species, stock-specific basis.
    In Table 41 below for mysticetes, we indicate for each species and 
stock the total annual numbers of take by Level A harassment and Level 
B harassment, and a number indicating the instances of total take as a 
percentage of abundance.

   Table 41--Annual Estimated Takes by Level B Harassment and Level A Harassment for Mysticetes and Number Indicating the Instances of Total Take as a
                                                          Percentage of Species/Stock Abundance
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Instances of indicated types of incidental
                                                                             take \1\
                                                         ------------------------------------------------                                  Instances of
                                                                Level B harassment            Level A                        Abundance     total take as
              Species                       Stock        --------------------------------   harassment      Total takes     (NMFS SARs)    percentage of
                                                                           TTS (may also ----------------                       \2\          abundance
                                                            Behavioral        include
                                                            disturbance    disturbance)         PTS
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Pacific right whale.........  Eastern North                      1               2               0               3              31             9.7
                                     Pacific.
Humpback whale....................  California, Oregon,                2               8               0              10           4,973              <1
                                     & Washington.
                                    Central North                     11              68               0              79          10,103              <1
                                     Pacific.
                                    Western North                  \3\ 3               0               0           \3\ 3           1,107              <1
                                     Pacific.
Blue whale........................  Central North                      0               3               0               3             133             2.3
                                     Pacific.
                                    Eastern North                      4              32               0              36           1,898             1.9
                                     Pacific.
Fin whale.........................  Northeast Pacific...             115           1,127               2           1,244       \4\ 3,168            39.3
Sei whale.........................  Eastern North                      3              34               0              37             519             7.1
                                     Pacific.
Minke whale.......................  Alaska..............               6              44               0              50         \5\ 389            12.9
Gray whale........................  Eastern North                  \3\ 4               0               0           \3\ 4          26,960              <1
                                     Pacific.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Estimated impacts are based on the maximum number of activities in a given year under the specified activity. Not all takes represent separate
  individuals, especially for behavioral disturbance.
\2\ Presented in the 2021 draft SARs or most recent SAR.
\3\ The Navy's Acoustic Effects Model estimated zero takes for each of these stocks. However, NMFS conservatively proposes to authorize take by Level B
  harassment of one group of Western North Pacific humpback whale and one group of Eastern North Pacific gray whale. The annual take estimates reflect
  the average group sizes of on- and off-effort survey sightings of humpback whale and gray whale (excluding an outlier of an estimated 25 gray whales
  in one group) reported in Rone et al. (2017).
\4\ The SAR reports this stock abundance assessment as provisional and notes that it is an underestimate for the entire stock because it is based on
  surveys which covered only a small portion of the stock's range.
\5\ The 2018 final SAR (most recent SAR) for the Alaska stock of minke whales reports the stock abundance as unknown because only a portion of the
  stock's range has been surveyed. To be conservative, for this stock we report the smallest estimated abundance produced during recent surveys.

    The majority of takes by harassment of mysticetes in the TMAA would 
be caused by anti-submarine warfare (ASW) activities. Anti-submarine 
activities include sources from the MFAS bin (which includes hull-
mounted sonar). They are high level, narrowband sources in the 1-10 kHz 
range, which intersect what is estimated to be the most sensitive area 
of hearing for mysticetes. They also are used in a large portion of 
exercises (see Table 1 and Table 3). Most of the takes (88 percent) 
from the MF1 bin in the TMAA would result from received levels between 
166 and 178 dB SPL, while another 11 percent would result from exposure 
between 160 and 166 dB SPL. For the remaining active sonar bin types, 
the percentages are as follows: MF4 = 97 percent between 142 and 154 dB 
SPL and MF5 = 97 percent between 118 and 142 dB SPL. For mysticetes, 
exposure to explosives would result in comparatively smaller numbers of 
takes by Level B harassment by behavioral disturbance (0-11 per stock) 
and TTS takes (0-2 per stock). Based on this information, the majority 
of the takes by Level B harassment by behavioral disturbance would be 
expected to be of low to sometimes moderate severity and of a 
relatively shorter duration. Exposure to explosives would also result 
in two takes by Level A harassment by PTS of the Northeast Pacific 
stock of fin whale. No mortality or serious injury and no Level A 
harassment from non-auditory tissue damage from training activities is 
anticipated or proposed for authorization for any species or stock.
    Research and observations show that if mysticetes are exposed to 
sonar or other active acoustic sources they may react in a number of 
ways depending on the characteristics of the sound source, their 
experience with the sound source, and whether they are migrating or on 
seasonal feeding or breeding grounds. Behavioral reactions may include 
alerting, breaking off feeding dives and surfacing, diving or swimming 
away, or no response at all (DOD, 2017; Nowacek, 2007; Richardson, 
1995; Southall et al., 2007). Overall, mysticetes have been observed to 
be more reactive to acoustic disturbance when a noise source is located 
directly on their migration route. Mysticetes disturbed while migrating 
could pause their migration or route around the disturbance, while 
males en route to breeding grounds have been shown to be less 
responsive to disturbances. Although some may pause temporarily, they 
would resume migration shortly after the exposure ends. Animals 
disturbed while engaged in other activities such as feeding or 
reproductive behaviors may be more likely to ignore or tolerate the 
disturbance and continue their natural behavior patterns. Alternately, 
adult females with calves may be more responsive to stressors.
    As noted in the Potential Effects of Specified Activities on Marine 
Mammals and Their Habitat section, while there are multiple examples 
from behavioral response studies of odontocetes ceasing their feeding 
dives when exposed to sonar pulses at certain levels, blue whales were 
less likely to show a visible response to sonar exposures at certain 
levels when feeding than when traveling. However, Goldbogen et al. 
(2013) indicated some horizontal displacement of deep foraging blue 
whales in response to

[[Page 49744]]

simulated MFAS. Southall et al. (2019b) observed that after exposure to 
simulated and operational mid-frequency active sonar, more than 50 
percent of blue whales in deep-diving states responded to the sonar, 
while no behavioral response was observed in shallow-feeding blue 
whales. Southall et al. (2019b) noted that the behavioral responses 
they observed were generally brief, of low to moderate severity, and 
highly dependent on exposure context (behavioral state, source-to-whale 
horizontal range, and prey availability).
    Richardson et al. (1995) noted that avoidance (temporary 
displacement of an individual from an area) reactions are the most 
obvious manifestations of disturbance in marine mammals. Avoidance is 
qualitatively different from the startle or flight response, but also 
differs in the magnitude of the response (i.e., directed movement, rate 
of travel, etc.). Oftentimes avoidance is temporary, and animals return 
to the area once the noise has ceased. Some mysticetes may avoid larger 
activities as they move through an area, although the Navy's activities 
do not typically use the same training locations day-after-day during 
multi-day activities, except periodically in instrumented ranges, which 
are not present in the GOA Study Area. Therefore, displaced animals 
could return quickly after even a large activity or MTE is completed.
    At most, only one MTE would occur per year (over a maximum of 21 
days), and additionally, MF1 mid-frequency active sonar would be 
prohibited from June 1 to September 30 within the North Pacific Right 
Whale Mitigation Area. Explosives detonated below 10,000 ft. altitude 
(including at the water surface) would be prohibited in the Continental 
Shelf and Slope Mitigation Area, including in the portion that overlaps 
the North Pacific Right Whale Mitigation Area. In the open waters of 
the Gulf of Alaska, the use of Navy sonar and other active acoustic 
sources is transient and would be unlikely to expose the same 
population of animals repeatedly over a short period of time, 
especially given the broader-scale movements of mysticetes and the 21-
day duration of the activities.
    The implementation of procedural mitigation and the sightability of 
mysticetes (due to their large size) would further reduce the potential 
for a significant behavioral reaction or a threshold shift to occur 
(i.e., shutdowns are expected to be successfully implemented), which is 
reflected in the amount and type of incidental take that would be 
anticipated to occur and is proposed for authorization. Level B 
harassment by behavioral disturbance of mysticetes resulting from the 
TMAA activities would likely be short-term and of low to sometimes 
moderate severity, with no anticipated effect on reproduction or 
survival of any individuals.
    As noted previously, when an animal incurs a threshold shift, it 
occurs in the frequency from that of the source up to one octave above. 
This means that the vast majority of threshold shifts caused by Navy 
sonar sources would typically occur in the range of 2-20 kHz (from the 
1-10 kHz MF bin, though in a specific narrow band within this range as 
the sources are narrowband), and if resulting from hull-mounted sonar, 
would be in the range of 3.5-7 kHz. The majority of mysticete 
vocalizations occur in frequencies below 1 kHz, which means that TTS 
incurred by mysticetes would not interfere with conspecific 
communication. Additionally, many of the other critical sounds that 
serve as cues for navigation and prey (e.g., waves, fish, 
invertebrates) occur below a few kHz, which means that detection of 
these signals would not be inhibited by most threshold shift either. 
When we look in ocean areas where the Navy has been intensively 
training and testing with sonar and other active acoustic sources for 
decades, there is no data suggesting any long-term consequences to 
reproduction or survival rates of mysticetes from exposure to sonar and 
other active acoustic sources.
    All the mysticete species discussed in this section would benefit 
from the procedural mitigation measures described earlier in the 
Proposed Mitigation Measures section. Additionally, the Navy would 
issue awareness messages prior to the start of TMAA training activities 
to alert vessels and aircraft operating within the TMAA to the possible 
presence of concentrations of large whales, including mysticetes, 
especially when traversing on the continental shelf and slope where 
densities of these species may be higher. To maintain safety of 
navigation and to avoid interactions with marine mammals, the Navy 
would instruct vessels to remain vigilant to the presence of large 
whales that may be vulnerable to vessel strikes or potential impacts 
from training activities. Further, the Navy would limit activities and 
employ other measures in mitigation areas that would avoid or reduce 
impacts to mysticetes. Where these mitigation areas are expected to 
mitigate impacts to particular species or stocks (North Pacific right 
whale, humpback whale, gray whale), they are discussed in detail below. 
Below we compile and summarize the information that supports our 
preliminary determinations that the Navy's activities would not 
adversely affect any mysticete species or stock through effects on 
annual rates of recruitment or survival.

North Pacific Right Whale (Eastern North Pacific Stock)

    North Pacific right whales are listed as endangered under the ESA, 
and this species is currently one of the most endangered whales in the 
world (Clapham, 2016; NMFS, 2013, 2017; Wade et al., 2010). The current 
population trend is unknown. ESA-designated critical habitat for the 
North Pacific right whale is located in the western Gulf of Alaska off 
Kodiak Island and in the southeastern Bering Sea/Bristol Bay area (Muto 
et al., 2017; Muto et al., 2018b; Muto et al., 2020a); there is no 
designated critical habitat for this species within the GOA Study Area. 
North Pacific right whales are anticipated to be present in the GOA 
Study Area year round, but are considered rare, with a potentially 
higher density between June and September. A BIA for feeding (June 
through September; Ferguson et al., 2015b) overlaps with the TMAA 
portion of the GOA Study Area by approximately 2,051 km\2\ 
(approximately 7 percent of the feeding BIA and 1.4 percent of the 
TMAA). This BIA does not overlap with any portion of the WMA. This 
proposed rule includes a North Pacific Right Whale Mitigation Area and 
Continental Shelf and Slope Mitigation Area, which both overlap with 
the portion of the North Pacific right whale feeding BIA that overlaps 
with the TMAA. From June 1 to September 30, Navy personnel will not use 
surface ship hull-mounted MF1 mid-frequency active sonar during 
training activities within the North Pacific Right Whale Mitigation 
Area. Further, Navy personnel will not detonate explosives below 10,000 
ft altitude (including at the water surface) during training at all 
times in the Continental Shelf and Slope Mitigation Area (including in 
the portion that overlaps the North Pacific Right Whale Mitigation 
Area). These restrictions would reduce the severity of impacts to North 
Pacific right whales by reducing interference in feeding that could 
result in lost feeding opportunities or necessitate additional energy 
expenditure to find other good foraging opportunities.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), only 3 instances of take by level B harassment 
(2 TTS, and 1 behavioral disturbance) are estimated,

[[Page 49745]]

which equate to about 10 percent of the very small estimated abundance. 
Given this very small estimate, repeated exposures of individuals are 
not anticipated. Regarding the severity of individual takes by Level B 
harassment by behavioral disturbance, we have explained that the 
duration of any exposure is expected to be between minutes and hours 
(i.e., relatively short) and the received sound levels largely below 
172 dB with a small portion up to 184 dB (i.e., of a moderate or 
sometimes lower level). Regarding the severity of TTS takes, they are 
expected to be low-level, of short duration, and mostly not in a 
frequency band that would be expected to interfere with North Pacific 
right whale communication or other important low-frequency cues. 
Therefore, the associated lost opportunities and capabilities are not 
at a level that would impact reproduction or survival.
    Altogether, North Pacific right whales are listed as endangered 
under the ESA, and the current population trend is unknown. Only three 
instances of take are estimated to occur (a small portion of the 
stock), and any individual North Pacific right whale is likely to be 
disturbed at a low-moderate level. This low magnitude and severity of 
harassment effects is not expected to result in impacts on the 
reproduction or survival of any individuals, let alone have impacts on 
annual rates of recruitment or survival of this stock. No mortality or 
Level A harassment is anticipated or proposed to be authorized. For 
these reasons, we have preliminarily determined, in consideration of 
all of the effects of the Navy's activities combined, that the proposed 
authorized take would have a negligible impact on the Eastern North 
Pacific stock of North Pacific right whales.

Humpback Whale (California/Oregon/Washington Stock)

    The California/Oregon/Washington (CA/OR/WA) stock of humpback 
whales includes individuals from three ESA DPSs: Central America 
(endangered), Mexico (threatened), and Hawaii (not listed). A small 
portion of ESA-designated critical habitat overlaps with the TMAA 
portion of the GOA Study Area (see Figure 4-1 of the Navy's rulemaking/
LOA application). The ESA-designated critical habitat does not overlap 
with any portion of the WMA. No other BIAs are identified for this 
species in the GOA Study Area. The SAR identifies this stock as stable 
(having shown a long-term increase from 1990 and then leveling off 
between 2008 and 2014). Navy personnel will not use surface ship hull-
mounted MF1 mid-frequency active sonar from June 1 to September 30 
within the North Pacific Right Whale Mitigation Area, which overlaps 18 
percent of the humpback whale critical habitat in the TMAA. Further, 
Navy personnel will not detonate explosives below 10,000 ft altitude 
(including at the water surface) during training at all times in the 
Continental Shelf and Slope Mitigation Area (including in the portion 
that overlaps the North Pacific Right Whale Mitigation Area), which 
fully overlaps the portion of the humpback whale critical habitat in 
the TMAA. These measures would reduce the severity of impacts to 
humpback whales by reducing interference in feeding that could result 
in lost feeding opportunities or necessitate additional energy 
expenditure to find other good opportunities.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated total instances of 
take is 10 (8 TTS and 2 behavioral disturbance), which is less than 1 
percent of the abundance. Given the very low number of anticipated 
instances of take, only a very small portion of individuals in the 
stock are likely impacted and repeated exposures of individuals are not 
anticipated. Regarding the severity of those individual takes by Level 
B harassment by behavioral disturbance, we have explained that the 
duration of any exposure is expected to be between minutes and hours 
(i.e., relatively short) and the received sound levels largely below 
172 dB with a small portion up to 184 dB (i.e., of a moderate or 
sometimes lower level). Regarding the severity of TTS takes, they are 
expected to be low-level, of short duration, and mostly not in a 
frequency band that would be expected to interfere with humpback whale 
communication or other important low-frequency cues. Therefore, the 
associated lost opportunities and capabilities are not at a level that 
would impact reproduction or survival.
    Altogether, this population is stable (even though two of the three 
associated DPSs are listed as endangered or threatened under the ESA), 
only a very small portion of the stock is anticipated to be impacted, 
and any individual humpback whale is likely to be disturbed at a low-
moderate level. No mortality or serious injury and no Level A 
harassment is anticipated or proposed to be authorized. This low 
magnitude and severity of harassment effects is not expected to result 
in impacts on the reproduction or survival of any individuals, let 
alone have impacts on annual rates of recruitment or survival of this 
stock. For these reasons, we have preliminarily determined, in 
consideration of all of the effects of the Navy's activities combined, 
that the proposed authorized take would have a negligible impact on the 
CA/OR/WA stock of humpback whales.

Humpback Whale (Central North Pacific Stock)

    The Central North Pacific stock of humpback whales consists of 
winter/spring humpback whale populations of the Hawaiian Islands which 
migrate primarily to foraging habitat in northern British Columbia/
Southeast Alaska, the Gulf of Alaska, and the Bering Sea/Aleutian 
Islands. The population is increasing (Muto et al. 2020), the Hawaii 
DPS is not ESA-listed, and no BIAs have been identified for this 
species in the GOA Study Area. Navy personnel will not use surface ship 
hull-mounted MF1 mid-frequency active sonar from June 1 to September 30 
within the North Pacific Right Whale Mitigation Area, which overlaps 18 
percent of the humpback whale critical habitat within the TMAA. As 
noted above, the Hawaii DPS is not ESA-listed; however, this ESA-
designated critical habitat still indicates the likely value of habitat 
in this area to non-listed humpback whales. Further, Navy personnel 
will not detonate explosives below 10,000 ft altitude (including at the 
water surface) during training at all times in the Continental Shelf 
and Slope Mitigation Area (including in the portion that overlaps the 
North Pacific Right Whale Mitigation Area), which fully overlaps the 
portion of the humpback whale critical habitat in the TMAA. These 
measures would reduce the severity of impacts to humpback whales by 
reducing interference in feeding that could result in lost feeding 
opportunities or necessitate additional energy expenditure to find 
other good opportunities.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated instances of take 
compared to the abundance is less than 1 percent. This information and 
the complicated far-ranging nature of the stock structure indicates 
that only a very small portion of the stock is likely impacted. While 
no BIAs have been identified in the GOA Study Area, highest densities 
in the nearby Kodiak Island feeding BIA (July to September) and Prince 
William Sound feeding BIA (September to December) overlap with much of 
the potential window for the Navy's exercise in the GOA Study Area 
(April to October). Given that some whales

[[Page 49746]]

may remain in the area surrounding these BIAs for some time to feed 
during the Navy's exercise, there may be a few repeated exposures of a 
few individuals, most likely on non-sequential days. Regarding the 
severity of those individual takes by Level B harassment by behavioral 
disturbance, we have explained that the duration of any exposure is 
expected to be between minutes and hours (i.e., relatively short) and 
the received sound levels largely below 172 dB with a small portion up 
to 184 dB (i.e., of a moderate or sometimes lower level). Regarding the 
severity of TTS takes, they are expected to be low-level, of short 
duration, and mostly not in a frequency band that would be expected to 
interfere with humpback whale communication or other important low-
frequency cues. Therefore, the associated lost opportunities and 
capabilities are not at a level that would impact reproduction or 
survival.
    Altogether, this population is increasing and the associated DPS is 
not listed as endangered or threatened under the ESA. Only a very small 
portion of the stock is anticipated to be impacted and any individual 
humpback whale is likely to be disturbed at a low-moderate level. This 
low magnitude and severity of harassment effects is not expected to 
result in impacts on individual reproduction or survival, let alone 
have impacts on annual rates of recruitment or survival of this stock. 
No mortality or Level A harassment is anticipated or proposed to be 
authorized. For these reasons, we have preliminarily determined, in 
consideration of all of the effects of the Navy's activities combined, 
that the proposed authorized take would have a negligible impact on the 
Central North Pacific stock of humpback whales.

Humpback Whale (Western North Pacific Stock)

    The Western North Pacific stock of humpback whales includes 
individuals from the Western North Pacific DPS, which is ESA-listed as 
endangered. A relatively small portion of ESA-designated critical 
habitat overlaps with the TMAA (2,708 km\2\ (1,046 mi\2\) of critical 
habitat Unit 5, 5,991 km\2\ (2,313 mi\2\) of critical habitat Unit 8; 
see Figure 4-1 of the Navy's rulemaking/LOA application). The ESA-
designated critical habitat does not overlap with any portion of the 
WMA. No other BIAs are identified for this species in the GOA Study 
Area. The current population trend for this stock is unknown. Navy 
personnel will not use surface ship hull-mounted MF1 mid-frequency 
active sonar from June 1 to September 30 within the North Pacific Right 
Whale Mitigation Area, which overlaps 18 percent of the humpback whale 
critical habitat within the TMAA. Further, Navy personnel will not 
detonate explosives below 10,000 ft altitude (including at the water 
surface) during training at all times in the Continental Shelf and 
Slope Mitigation Area (including in the portion that overlaps the North 
Pacific Right Whale Mitigation Area), which fully overlaps the portion 
of the humpback whale critical habitat in the TMAA. These measures 
would reduce the severity of impacts to humpback whales by reducing 
interference in feeding that could result in lost feeding opportunities 
or necessitate additional energy expenditure to find other good 
opportunities.
    Regarding the magnitude of takes by Level B harassment (behavioral 
disturbance only), the number of estimated total instances of take is 
three, which is less than 1 percent of the abundance. Given the very 
low number of anticipated instances of take, only a very small portion 
of individuals in the stock are likely impacted and repeated exposures 
of individuals are not anticipated. Regarding the severity of those 
individual takes by Level B harassment by behavioral disturbance, we 
have explained that the duration of any exposure is expected to be 
between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB with a small portion up to 184 dB 
(i.e., of a moderate or sometimes lower level).
    Altogether, the status of this stock is unknown, only a very small 
portion of the stock is anticipated to be impacted (3 individuals), and 
any individual humpback whale is likely to be disturbed at a low-
moderate level. No mortality, serious injury, Level A harassment, or 
TTS is anticipated or proposed to be authorized. This low magnitude and 
severity of harassment effects is not expected to result in impacts on 
the reproduction or survival of any individuals, let alone have impacts 
on annual rates of recruitment or survival of this stock. For these 
reasons, we have preliminarily determined, in consideration of all of 
the effects of the Navy's activities combined, that the proposed 
authorized take would have a negligible impact on the Western North 
Pacific stock of humpback whales.

Blue Whale (Central North Pacific Stock and Eastern North Pacific 
Stock)

    Blue whales are listed as endangered under the ESA throughout their 
range, but there is no ESA designated critical habitat and no BIAs have 
been identified for this species in the GOA Study Area. The current 
population trend for the Central North Pacific stock is unknown, and 
the Eastern North Pacific stock is stable.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance is 2 percent for both the Central North 
Pacific stock, and the Eastern North Pacific stock. For the Central 
North Pacific stock, only 3 instances of take (TTS) are anticipated.
    Given the range of both blue whale stocks, the absence of any known 
feeding or aggregation areas, and the very low number of anticipated 
instances of take of the Central North Pacific stock, this information 
indicates that only a small portion of individuals in the stock are 
likely impacted and repeated exposures of individuals are not 
anticipated. Regarding the severity of those individual takes by Level 
B harassment by behavioral disturbance, we have explained that the 
duration of any exposure is expected to be between minutes and hours 
(i.e., relatively short) and the received sound levels largely below 
172 dB with a small portion up to 184 dB (i.e., of a moderate or 
sometimes lower level). Regarding the severity of TTS takes, we have 
explained that they are expected to be low-level, of short duration, 
and mostly not in a frequency band that would be expected to interfere 
with blue whale communication or other important low-frequency cues. 
Therefore, the associated lost opportunities and capabilities are not 
at a level that would impact reproduction or survival.
    Altogether, blue whales are listed as endangered under the ESA 
throughout their range, the current population trend for the Central 
North Pacific stock is unknown, and the Eastern North Pacific stock is 
stable. Only a small portion of the stocks are anticipated to be 
impacted, and any individual blue whale is likely to be disturbed at a 
low-moderate level. The low magnitude and severity of harassment 
effects is not expected to result in impacts on the reproduction or 
survival of any individuals, let alone have impacts on annual rates of 
recruitment or survival of this stock. No mortality and no Level A 
harassment is anticipated or proposed for authorization. For these 
reasons, we have preliminarily determined, in consideration of all of 
the effects of the Navy's activities combined, that the proposed 
authorized take would have a negligible impact on the Central North 
Pacific stock and the Eastern North Pacific stock of blue whales.

[[Page 49747]]

Fin Whale (Northeast Pacific Stock)

    Fin whales are listed as endangered under the ESA throughout their 
range, but there is no ESA designated critical habitat and no BIAs have 
been identified for this species in the GOA Study Area. The SAR 
identifies this stock as increasing.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance is 39 percent (though, as noted in Table 
41, the SAR reports the stock abundance assessment as provisional and 
notes that it is an underestimate for the entire stock because it is 
based on surveys which covered only a small portion of the stock's 
range, and therefore 39 percent is likely an overestimate). Given the 
large range of the stock and short duration of the Navy's activities in 
the GOA Study Area, this information suggests that notably fewer than 
half of the individuals of the stock would likely be impacted, and that 
most affected individuals would likely be disturbed on a few days 
within the 21-day exercise, with the days most likely being non-
sequential. Regarding the severity of those individual takes by Level B 
harassment by behavioral disturbance, we have explained that the 
duration of any exposure is expected to be between minutes and hours 
(i.e., relatively short) and the received sound levels largely below 
172 dB with a small portion up to 184 dB (i.e., of a moderate or 
sometimes lower level). Regarding the severity of TTS takes, they are 
expected to be low-level, of short duration, and mostly not in a 
frequency band that would be expected to interfere with fin whale 
communication or other important low-frequency cues. Therefore, the 
associated lost opportunities and capabilities are not at a level that 
would impact reproduction or survival.
    For these same reasons (low level and frequency band), while a 
small permanent loss of hearing sensitivity (PTS) may include some 
degree of energetic costs for compensating or may mean some small loss 
of opportunities or detection capabilities, at the expected scale the 
estimated two takes by Level A harassment by PTS would be unlikely to 
impact behaviors, opportunities, or detection capabilities to a degree 
that would interfere with reproductive success or survival of those 
individuals. Thus, the two takes by Level A harassment by PTS would be 
unlikely to affect rates of recruitment and survival for the stock.
    Altogether, fin whales are listed as endangered under the ESA, 
though this population is increasing. Only a small portion of the stock 
is anticipated to be impacted, and any individual fin whale is likely 
to be disturbed at a low-moderate level. This low magnitude and 
severity of harassment effects is not expected to result in impacts on 
reproduction or survival of any individuals, let alone have impacts on 
annual rates of recruitment or survival of this stock. No mortality or 
serious injury and no Level A harassment from non-auditory tissue 
damage is anticipated or proposed for authorization. For these reasons, 
we have preliminarily determined, in consideration of all of the 
effects of the Navy's activities combined, that the proposed authorized 
take would have a negligible impact on the Northeast Pacific stock of 
fin whales.

Sei Whale (Eastern North Pacific Stock)

    The population trend of this stock is unknown, however sei whales 
are listed as endangered under the ESA throughout their range. There is 
no ESA designated critical habitat and no BIAs have been identified for 
this species in the GOA Study Area.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance is 7 percent. This information and the 
rare occurrence of sei whales in the TMAA suggests that only a small 
portion of individuals in the stock would likely be impacted and 
repeated exposures of individuals would not be anticipated. Regarding 
the severity of those individual takes by Level B harassment by 
behavioral disturbance, we have explained that the duration of any 
exposure is expected to be between minutes and hours (i.e., relatively 
short) and the received sound levels largely below 172 dB with a small 
portion up to 184 dB (i.e., of a moderate or sometimes lower level). 
Regarding the severity of TTS takes, they are expected to be low-level, 
of short duration, and mostly not in a frequency band that would be 
expected to interfere with sei whale communication or other important 
low-frequency cues. Therefore, the associated lost opportunities and 
capabilities are not at a level that would impact reproduction or 
survival.
    Altogether, the status of the stock is unknown and the species is 
listed as endangered, only a small portion of the stock is anticipated 
to be impacted, and any individual sei whale is likely to be disturbed 
at a low-moderate level. This low magnitude and severity of harassment 
effects is not expected to result in impacts on individual reproduction 
or survival, much less annual rates of recruitment or survival. No 
mortality and no Level A harassment is anticipated or proposed for 
authorization. For these reasons, we have preliminarily determined, in 
consideration of all of the effects of the Navy's activities combined, 
that the proposed authorized take would have a negligible impact on the 
Eastern North Pacific stock of sei whales.

Minke Whale (Alaska Stock)

    The status of this stock is unknown and the species is not listed 
under the ESA. No BIAs have been identified for this species in the GOA 
Study Area.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance is 13 percent for the Alaska stock 
(based on, to be conservative, the smallest available provisional 
estimate in the SAR, which is derived from surveys that cover only a 
portion of the stock's range). Given the range of the Alaska stock of 
minke whales, this information indicates that only a small portion of 
individuals in this stock are likely to be impacted and repeated 
exposures of individuals are not anticipated. Regarding the severity of 
those individual takes by Level B harassment by behavioral disturbance, 
we have explained that the duration of any exposure is expected to be 
between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB with a small portion up to 184 dB 
(i.e., of a moderate or sometimes lower level). Regarding the severity 
of TTS takes, they are expected to be low-level, of short duration, and 
mostly not in a frequency band that would be expected to interfere with 
minke whale communication or other important low-frequency cues. 
Therefore, the associated lost opportunities and capabilities are not 
at a level that would impact reproduction or survival.
    Altogether, although the status of the stock is unknown, the 
species is not listed under the ESA as endangered or threatened, only a 
small portion of the stock is anticipated to be impacted, and any 
individual minke whale is likely to be disturbed at a low-moderate 
level. This low magnitude and severity of harassment effects is not 
expected to result in impacts on individual reproduction or survival, 
let alone have impacts on annual rates of recruitment or survival of 
this stock. No mortality, serious injury, or Level A harassment is 
anticipated or proposed to be

[[Page 49748]]

authorized. For these reasons, we have preliminarily determined, in 
consideration of all of the effects of the Navy's activities combined, 
that the proposed authorized take would have a negligible impact on the 
Alaska stock of minke whales.

Gray Whale (Eastern North Pacific Stock)

    The Eastern North Pacific stock of gray whale is not ESA-listed, 
and the SAR indicates that the stock is increasing. The TMAA portion of 
the GOA Study Area overlaps with a gray whale migration corridor that 
has been identified as a BIA (November-January (outside of the 
potential training window), southbound; March-May, northbound; Ferguson 
et al., 2015). The WMA portion of the GOA Study Area does not overlap 
with any known important areas for gray whales.
    Regarding the magnitude of takes by Level B harassment (behavioral 
disturbance only), the number of estimated total instances of take is 
four, which is less than 1 percent of the abundance. Given the very low 
number of anticipated instances of take, only a very small portion of 
individuals in the stock are likely impacted and repeated exposures of 
individuals are not anticipated. Regarding the severity of those 
individual takes by Level B harassment by behavioral disturbance, we 
have explained that the duration of any exposure is expected to be 
between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB with a small portion up to 184 dB 
(i.e., of a moderate or sometimes lower level).
    Altogether, while we have considered the impacts of the gray whale 
UME, this population of gray whales is not endangered or threatened 
under the ESA, and the stock is increasing. No mortality, Level A 
harassment, or TTS is anticipated or proposed to be authorized. Only a 
very small portion of the stock is anticipated to be impacted, and any 
individual gray whale is likely to be disturbed at a low-moderate 
level. This low magnitude and severity of harassment effects is not 
expected to result in impacts on the reproduction or survival of any 
individuals, let alone have impacts on annual rates of recruitment or 
survival of this stock. For these reasons, we have preliminarily 
determined, in consideration of all of the effects of the Navy's 
activities combined, that the proposed authorized take would have a 
negligible impact on the Eastern North Pacific stock of gray whales.
Odontocetes
    This section builds on the broader discussion above and brings 
together the discussion of the different types and amounts of take that 
different species and stocks would likely incur, the applicable 
mitigation, and the status of the species and stocks to support the 
negligible impact determinations for each species or stock. We have 
described (earlier in this section) the unlikelihood of any masking 
having effects that would impact the reproduction or survival of any of 
the individual marine mammals affected by the Navy's activities. We 
have also described above in the Potential Effects of Specified 
Activities on Marine Mammals and their Habitat section the unlikelihood 
of any habitat impacts having effects that would impact the 
reproduction or survival of any of the individual marine mammals 
affected by the Navy's activities. There is no predicted PTS from sonar 
or explosives for most odontocetes, with the exception of Dall's 
porpoise, which is discussed below. There is no anticipated M/SI or 
non-auditory tissue damage from sonar or explosives for any species. 
Here, we include information that applies to all of the odontocete 
species, which are then further divided and discussed in more detail in 
the following subsections: sperm whales; beaked whales; dolphins and 
small whales; and porpoises. These subsections include more specific 
information about the groups, as well as conclusions for each species 
or stock represented.
    The majority of takes by harassment of odontocetes in the TMAA are 
caused by sources from the MFAS bin (which includes hull-mounted sonar) 
because they are high level, typically narrowband sources at a 
frequency (in the 1-10 kHz range) that overlaps a more sensitive 
portion (though not the most sensitive) of the MF hearing range and 
they are used in a large portion of exercises (see Table 1 and Table 
3). For odontocetes other than beaked whales (for which these 
percentages are indicated separately in that section), most of the 
takes (95 percent) from the MF1 bin in the TMAA would result from 
received levels between 160 and 172 dB SPL. For the remaining active 
sonar bin types, the percentages are as follows: MF4 = 98 percent 
between 142 and 160 dB SPL and MF5 = 94 percent between 118 and 142 dB 
SPL. Based on this information, the majority of the takes by Level B 
harassment by behavioral disturbance are expected to be low to 
sometimes moderate in nature, but still of a generally shorter 
duration.
    For all odontocetes, takes from explosives (Level B harassment by 
behavioral disturbance, TTS, or PTS) comprise a very small fraction 
(and low number) of those caused by exposure to active sonar. For the 
following odontocetes, zero takes from explosives are expected to 
occur: sperm whale, killer whale, Pacific white-sided dolphin, Baird's 
beaked whale, and Stejneger's beaked whale. For Level B harassment by 
behavioral disturbance from explosives, one take is anticipated for 
Cuvier's beaked whale and 38 takes are anticipated for Dall's porpoise. 
No TTS or PTS is expected to occur from explosives for any stocks 
except Dall's porpoise. Because of the lower TTS and PTS thresholds for 
HF odontocetes, the Alaska stock of Dall's porpoise is expected to have 
229 takes by TTS and 45 takes by PTS from explosives.
    Because the majority of harassment takes of odontocetes result from 
the sources in the MFAS bin, the vast majority of threshold shift would 
occur at a single frequency within the 1-10 kHz range and, therefore, 
the vast majority of threshold shift caused by Navy sonar sources would 
be at a single frequency within the range of 2-20 kHz. The frequency 
range within which any of the anticipated narrowband threshold shift 
would occur would fall directly within the range of most odontocete 
vocalizations (2-20 kHz) (though phocoenids generally communicate at 
higher frequencies (Soerensen et al., 2018; Clausen et al. 2010), which 
would not be impacted by this threshold shift). For example, the most 
commonly used hull-mounted sonar has a frequency around 3.5 kHz, and 
any associated threshold shift would be expected to be at around 7 kHz. 
However, odontocete vocalizations typically span a much wider range 
than this, and alternately, threshold shift from active sonar will 
often be in a narrower band (reflecting the narrower band source that 
caused it), which means that TTS incurred by odontocetes would 
typically only interfere with communication within a portion of their 
hearing range (if it occurred during a time when communication with 
conspecifics was occurring) and, as discussed earlier, it would only be 
expected to be of a short duration and relatively small degree. 
Odontocete echolocation occurs predominantly at frequencies 
significantly higher than 20 kHz (though there may be some small 
overlap at the lower part of their echolocating range for some 
species), which means that there is little likelihood that threshold 
shift, either temporary or permanent, would interfere with feeding 
behaviors.

[[Page 49749]]

Many of the other critical sounds that serve as cues for navigation and 
prey (e.g., waves, fish, invertebrates) occur below a few kHz, which 
means that detection of these signals will not be inhibited by most 
threshold shift either. The low number of takes by threshold shift that 
might be incurred by individuals exposed to explosives would likely be 
lower frequency (5 kHz or less) and spanning a wider frequency range, 
which could slightly lower an individual's sensitivity to navigational 
or prey cues, or a small portion of communication calls, for several 
minutes to hours (if temporary) or permanently. There is no reason to 
think that the vast majority of the individual odontocetes taken by TTS 
would incur TTS on more than one day, although a small number could 
incur TTS on a few days at most. Therefore, odontocetes are unlikely to 
incur impacts on reproduction or survival as a result of TTS. PTS takes 
from these sources are very low (0 for all species other than Dall's 
porpoise), and while spanning a wider frequency band, are still 
expected to be of a low degree (i.e., low amount of hearing sensitivity 
loss) and unlikely to affect reproduction or survival.
    The range of potential behavioral effects of sound exposure on 
marine mammals generally, and odontocetes specifically, has been 
discussed in detail previously. There are behavioral patterns that 
differentiate the likely impacts on odontocetes as compared to 
mysticetes however. First, odontocetes echolocate to find prey, which 
means that they actively send out sounds to detect their prey. While 
there are many strategies for hunting, one common pattern, especially 
for deeper diving species, is many repeated deep dives within a bout, 
and multiple bouts within a day, to find and catch prey. As discussed 
above, studies demonstrate that odontocetes may cease their foraging 
dives in response to sound exposure. If enough foraging interruptions 
occur over multiple sequential days, and the individual either does not 
take in the necessary food, or must exert significant effort to find 
necessary food elsewhere, energy budget deficits can occur that could 
potentially result in impacts to reproductive success, such as 
increased cow/calf intervals (the time between successive calving). 
However, the relatively low impact of the Navy's activities on 
odontocetes in the TMAA indicate this is not likely to occur. Second, 
while many mysticetes rely on seasonal migratory patterns that position 
them in a geographic location at a specific time of the year to take 
advantage of ephemeral large abundances of prey (i.e., invertebrates or 
small fish, which they eat by the thousands), odontocetes forage more 
homogeneously on one fish or squid at a time. Therefore, if odontocetes 
are interrupted while feeding, it is often possible to find more prey 
relatively nearby.
    All the odontocete species and stocks discussed in this section 
would benefit from the procedural mitigation measures described earlier 
in the Proposed Mitigation Measures section.

Sperm Whale (North Pacific Stock)

    This section builds on the broader odontocete discussion above and 
brings together the discussion of the different types and amounts of 
take that sperm whales would likely incur, the applicable mitigation, 
and the status of the species/stock to support the preliminary 
negligible impact determination for the stock.
    Sperm whales are listed as endangered under the ESA. No critical 
habitat has been designated for sperm whales under the ESA and no BIAs 
for sperm whales have been identified in the GOA Study Area. The 
stock's current population trend is unknown. The Navy would issue 
awareness messages prior to the start of TMAA training activities to 
alert Navy ships and aircraft operating within the TMAA to the possible 
presence of increased concentrations of large whales, including sperm 
whales. This measure would further reduce any possibility of ship 
strike of sperm whales.
    In Table 42 below for sperm whales, we indicate the total annual 
numbers of take by Level A harassment and Level B harassment, and a 
number indicating the instances of total take as a percentage of 
abundance.

 Table 42--Annual Estimated Takes by Level B Harassment and Level A Harassment for Sperm Whales in the TMAA and Number Indicating the Instances of Total
                                                     Take as a Percentage of Species/Stock Abundance
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        Instances of indicated types of incidental
                                                                         take\1\
                                                   ---------------------------------------------------                                     Instances of
                                                           Level B harassment             Level A                       Abundance (NMFS   total take as
            Species                    Stock       ----------------------------------    harassment      Total takes        SARs)\2\      percentage of
                                                                      TTS (may also  -----------------                                      abundance
                                                       Behavioral        include
                                                      disturbance      disturbance)         PTS
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sperm whale....................  North Pacific....             107                5                0              112          \3\ 345             32.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Estimated impacts are based on the maximum number of activities in a given year under the specified activity. Not all takes represent separate
  individuals, especially for disturbance.
\2\ Presented in the 2021 draft SARs or most recent SAR.
\3\ The SAR reports that this is an underestimate for the entire stock because it is based on surveys of a small portion of the stock's extensive range
  and it does not account for animals missed on the trackline or for females and juveniles in tropical and subtropical waters.

    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance is 33 percent. Given the range of this 
stock, this information indicates that fewer than half of the 
individuals in the stock are likely to be impacted, with those 
individuals disturbed on likely one, but not more than a few non-
sequential days within the 21 days per year. Additionally, while 
interrupted feeding bouts are a known response and concern for 
odontocetes, we also know that there are often viable alternative 
habitat options in the relative vicinity. Regarding the severity of 
those individual takes by Level B harassment by behavioral disturbance, 
we have explained that the duration of any exposure is expected to be 
between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB (i.e., of a lower, to occasionally 
moderate, level and less likely to evoke a severe response). As 
discussed earlier in the Preliminary Analysis and Negligible Impact 
Determination section, we anticipate more severe effects from takes 
when animals are exposed to higher received levels or for longer 
durations. Occasional milder Level B harassment

[[Page 49750]]

by behavioral disturbance, as is expected here, is unlikely to cause 
long-term consequences for either individual animals or populations, 
even if some smaller subset of the takes are in the form of a longer 
(several hours or a day) and more moderate response. Regarding the 
severity of TTS takes, they are expected to be low-level, of short 
duration, and mostly not in a frequency band that would be expected to 
interfere with sperm whale communication or other important low-
frequency cues. Therefore, the associated lost opportunities and 
capabilities are not at a level that would impact reproduction or 
survival.
    Altogether, sperm whales are listed as endangered under the ESA, 
and the current population trend is unknown. Fewer than half of the 
individuals of the stock are anticipated to be impacted, and any 
individual sperm whale is likely to be disturbed at a low-moderate 
level. This low magnitude and severity of harassment effects is not 
expected to result in impacts on reproduction or survival for any 
individuals, let alone have impacts on annual rates of recruitment or 
survival of this stock. No mortality, serious injury, or Level A 
harassment is anticipated or proposed to be authorized. For these 
reasons, we have preliminarily determined, in consideration of all of 
the effects of the Navy's activities combined, that the proposed 
authorized take would have a negligible impact on the North Pacific 
stock of sperm whales.

Beaked Whales

    This section builds on the broader odontocete discussion above and 
brings together the discussion of the different types and amounts of 
take that different beaked whale species and stocks would likely incur, 
the applicable mitigation, and the status of the species and stocks to 
support the preliminary negligible impact determinations for each 
species or stock. For beaked whales, no mortality or Level A harassment 
is anticipated or proposed for authorization.
    In Table 43 below for beaked whales, we indicate the total annual 
numbers of take by Level A harassment and Level B harassment, and a 
number indicating the instances of total take as a percentage of 
abundance.

Table 43--Annual Estimated Takes by Level B Harassment and Level A Harassment for Beaked Whales in the TMAA and Number Indicating the Instances of Total
                                                     Take as a Percentage of Species/Stock Abundance
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Instances of indicated types of incidental
                                                                              take\1\
                                                         ------------------------------------------------                                  Instances of
                                                                Level B harassment            Level A                        Abundance     total take as
              Species                       Stock        --------------------------------   harassment      Total takes   (NMFS SARs)\2\   percentage of
                                                                           TTS (may also ----------------                                    abundance
                                                            Behavioral        include
                                                            disturbance    disturbance)         PTS
--------------------------------------------------------------------------------------------------------------------------------------------------------
Baird's beaked whale..............  Alaska..............             106               0               0             106              NA              NA
Cuvier's beaked whale.............  Alaska..............             430               3               0             433              NA              NA
Stejneger's beaked whale..........  Alaska..............             467              15               0             482              NA              NA
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Estimated impacts are based on the maximum number of activities in a given year under the specified activity. Not all takes represent separate
  individuals, especially for disturbance.
\2\ Reliable estimates of abundance for these stocks are currently unavailable.

    This first paragraph provides specific information that is in lieu 
of the parallel information provided for odontocetes as a whole. The 
majority of takes by harassment of beaked whales in the TMAA would be 
caused by sources from the MFAS bin (which includes hull-mounted sonar) 
because they are high level narrowband sources that fall within the 1-
10 kHz range, which overlap a more sensitive portion (though not the 
most sensitive) of the MF hearing range. Also, of the sources expected 
to result in take, they are used in a large portion of exercises (see 
Table 1 and Table 3). Most of the takes (98 percent) from the MF1 bin 
in the TMAA would result from received levels between 148 and 166 dB 
SPL. For the remaining active sonar bin types, the percentages are as 
follows: MF4 = 97 percent between 130 and 148 dB SPL and MF5 = 99 
percent between 100 and 148 dB SPL. Given the levels they are exposed 
to and beaked whale sensitivity, some responses would be of a lower 
severity, but many would likely be considered moderate, but still of 
generally short duration.
    Research has shown that beaked whales are especially sensitive to 
the presence of human activity (Pirotta et al., 2012; Tyack et al., 
2011) and therefore have been assigned a lower harassment threshold, 
with lower received levels resulting in a higher percentage of 
individuals being harassed and a more distant distance cutoff (50 km 
for high source level, 25 km for moderate source level).
    Beaked whales have been documented to exhibit avoidance of human 
activity or respond to vessel presence (Pirotta et al., 2012). Beaked 
whales were observed to react negatively to survey vessels or low 
altitude aircraft by quick diving and other avoidance maneuvers, and 
none were observed to approach vessels (Wursig et al., 1998). Available 
information suggests that beaked whales likely have enhanced 
sensitivity to sonar sound, given documented incidents of stranding in 
conjunction with specific circumstances of MFAS use, although few 
definitive causal relationships between MFAS use and strandings have 
been documented (see Potential Effects of Specified Activities on 
Marine Mammals and their Habitat section). NMFS neither anticipates nor 
proposes to authorize the mortality of beaked whales (or any other 
species or stocks) resulting from exposure to active sonar.
    Research and observations show that if beaked whales are exposed to 
sonar or other active acoustic sources, they may startle, break off 
feeding dives, and avoid the area of the sound source to levels of 157 
dB re: 1 [micro]Pa, or below (McCarthy et al., 2011). For example, 
after being exposed to 1-2 kHz upsweep naval sonar signals at a 
received SPL of 107 dB re 1 [mu]Pa, Northern bottlenose whales began 
moving in an unusually straight course, made a near 180[deg] turn away 
from the source, and performed the longest and deepest dive (94 min, 
2339 m) recorded for this species (Miller et al., 2015). Wensveen et 
al. (2019) also documented avoidance behaviors in Northern bottlenose 
whales exposed to 1-2 kHz tonal sonar signals with SPLs ranging between 
117-126 dB re: 1 [micro]Pa, including interrupted diving behaviors, 
elevated swim speeds, directed movements away from the sound source, 
and cessation of acoustic signals throughout exposure periods. Acoustic 
monitoring during actual sonar exercises revealed some beaked whales 
continuing to forage at levels up to 157

[[Page 49751]]

dB re: 1 [micro]Pa (Tyack et al., 2011). Stimpert et al. (2014) tagged 
a Baird's beaked whale, which was subsequently exposed to simulated 
MFAS. Changes in the animal's dive behavior and locomotion were 
observed when received level reached 127 dB re: 1 [mu]Pa. However, 
Manzano-Roth et al. (2013) found that for beaked whale dives that 
continued to occur during MFAS activity, differences from normal dive 
profiles and click rates were not detected with estimated received 
levels up to 137 dB re: 1 [micro]Pa while the animals were at depth 
during their dives. In research done at the Navy's fixed tracking range 
in the Bahamas, animals were observed to leave the immediate area of 
the anti-submarine warfare training exercise (avoiding the sonar 
acoustic footprint at a distance where the received level was ``around 
140 dB SPL,'' according to Tyack et al. (2011)), but return within a 
few days after the event ended (Claridge and Durban, 2009; McCarthy et 
al., 2011; Moretti et al., 2009, 2010; Tyack et al., 2010, 2011). Joyce 
et al. (2019) found that Blainville's beaked whales moved up to 68 km 
away from an Atlantic Undersea Test and Evaluation Center site and 
reduced time spent on deep dives after the onset of mid-frequency 
active sonar exposure; whales did not return to the site until 2-4 days 
after the exercises ended. Changes in acoustic activity have also been 
documented. For example, Blainville's beaked whales showed decreased 
group vocal periods after biannual multi-day Navy training activities 
(Henderson et al., 2016). Tyack et al. (2011) reported that, in 
reaction to sonar playbacks, most beaked whales stopped echolocating, 
made long slow ascent to the surface, and moved away from the sound. A 
similar behavioral response study conducted in Southern California 
waters during the 2010-2011 field season found that Cuvier's beaked 
whales exposed to MFAS displayed behavior ranging from initial 
orientation changes to avoidance responses characterized by energetic 
fluking and swimming away from the source (DeRuiter et al., 2013b). 
However, the authors did not detect similar responses to incidental 
exposure to distant naval sonar exercises at comparable received 
levels, indicating that context of the exposures (e.g., source 
proximity, controlled source ramp-up) may have been a significant 
factor. The study itself found the results inconclusive and meriting 
further investigation. Falcone et al. (2017) however, documented that 
Cuvier's beaked whales had longer dives and surface durations after 
exposure to mid-frequency active sonar, with the longer surface 
intervals contributing to a longer interval between deep dives, a proxy 
for foraging disruption in this species. Cuvier's beaked whale 
responses suggested particular sensitivity to sound exposure consistent 
with results for Blainville's beaked whale.
    Populations of beaked whales and other odontocetes on the Bahamas 
and other Navy fixed ranges that have been operating for decades appear 
to be stable. Behavioral reactions (avoidance of the area of Navy 
activity) seem most likely in cases where beaked whales are exposed to 
anti-submarine sonar within a few tens of kilometers, especially for 
prolonged periods (a few hours or more) since this is one of the most 
sensitive marine mammal groups to anthropogenic sound of any species or 
group studied to date and research indicates beaked whales will leave 
an area where anthropogenic sound is present (De Ruiter et al., 2013; 
Manzano-Roth et al., 2013; Moretti et al., 2014; Tyack et al., 2011). 
Research involving tagged Cuvier's beaked whales in the SOCAL Range 
Complex reported on by Falcone and Schorr (2012, 2014) indicates year-
round prolonged use of the Navy's training and testing area by these 
beaked whales and has documented movements in excess of hundreds of 
kilometers by some of those animals. Given that some of these animals 
may routinely move hundreds of kilometers as part of their normal 
pattern, leaving an area where sonar or other anthropogenic sound is 
present may have little, if any, cost to such an animal. Photo 
identification studies in the SOCAL Range Complex, a Navy range that is 
utilized for training and testing, have identified approximately 100 
Cuvier's beaked whale individuals with 40 percent having been seen in 
one or more prior years, with re-sightings up to 7 years apart (Falcone 
and Schorr, 2014). These results indicate long-term residency by 
individuals in an intensively used Navy training and testing area, 
which may also suggest a lack of long-term consequences as a result of 
exposure to Navy training and testing activities. More than 8 years of 
passive acoustic monitoring on the Navy's instrumented range west of 
San Clemente Island documented no significant changes in annual and 
monthly beaked whale echolocation clicks, with the exception of 
repeated fall declines likely driven by natural beaked whale life 
history functions (DiMarzio et al., 2018). Finally, results from 
passive acoustic monitoring estimated that regional Cuvier's beaked 
whale densities were higher than indicated by NMFS' broad scale visual 
surveys for the United States West Coast (Hildebrand and McDonald, 
2009).
    Below we compile and summarize the information that supports our 
preliminary determinations that the Navy's activities would not 
adversely affect any of the beaked whale stocks through effects on 
annual rates of recruitment or survival. Baird's, Cuvier's, and 
Stejneger's beaked whales (Alaska stocks)
    Baird's beaked whale, Cuvier's beaked whale, and Stejneger's beaked 
whale are not listed as endangered or threatened species under the ESA, 
and the 2019 Alaska SARs indicate that trend information is not 
available for any of the Alaska stocks. No BIAs for beaked whales have 
been identified in the GOA Study Area.
    As indicated in Table 43, no abundance estimates are available for 
any of the stocks. However, the ranges of all three stocks are large 
compared to the GOA Study Area (Cuvier's is the smallest, occupying all 
of the Gulf of Alaska, south of the Canadian border and west along the 
Aleutian Islands. Baird's range even farther south and Baird's and 
Stejneger's also cross north over the Aleutian Islands).
    Regarding abundance and distribution of these species in the 
vicinity of the TMAA, passive acoustic data indicate spatial overlap of 
all three beaked whales; however, detections are spatially offset, 
suggesting some level of habitat portioning in the Gulf of Alaska (Rice 
et al., 2021). Peaks in detections by Rice et al. (2021) were also 
temporally offset, with detections of Baird's beaked whale clicks 
peaking in winter at the slope and in spring at the seamounts. Rice et 
al. (2021) indicates Baird's beaked whales were highest in number at 
Quinn seamount, which overlaps with the southern edge of the TMAA, and 
therefore, a portion of this habitat is outside of the TMAA. Baumann 
Pickering et al. (2012b) did not acoustically detect Baird's beaked 
whales from July-October in the northern Gulf of Alaska (overlapping 
with the majority of the Navy's potential training period), while 
acoustic detections from November-January suggest that Baird's beaked 
whales may winter in this area. Rice et al. (2021) reported the highest 
detections of Baird's beaked whales within the TMAA during the spring 
in the portion of the TMAA that is farther offshore, with lowest 
detections in the summer and an increase in detections on the 
continental slope in the winter, indicating that the whales are either 
not producing clicks in the summer or they

[[Page 49752]]

are migrating farther north or south to feed or mate during this time.
    Data from a satellite-tagged Baird's beaked whale off Southern 
California recently documented movement north along the shelf-edge for 
more than 400 nmi over a six-and-a-half-day period (Schorr et. al., 
Unpublished). If that example is reflective of more general behavior, 
Baird's beaked whales present in the TMAA may have much larger home 
ranges than the waters bounded by the TMAA, reducing the potential for 
repeated takes of individuals.
    Regarding Stejneger's beaked whale, passive acoustic monitoring 
detected the whales most commonly at the slope and offshore in the TMAA 
(Rice et al., 2021; Rice et al., 2018b; Rice et al., 2020b). At the 
slope, Stejneger's beaked whale detections peaked in fall (Rice et al., 
2021). Rice et al. (2021) notes that to date, there have been no 
documented sightings of Stejneger's beaked whales that were 
simultaneous with recording of vocalizations, which is necessary to 
confirm the vocalizations were produced by the species, and therefore, 
detections should be interpreted with caution. Baumann-Pickering et al. 
(2012b) recorded acoustic signals believed to be produced by 
Stejneger's beaked whales (based on frequency characteristics, 
interpulse interval, and geographic location; Baumann-Pickering et al., 
2012a) almost weekly from July 2011 to February 2012 in the northern 
Gulf of Alaska.
    Regarding Cuvier's beaked whale, passive acoustic monitoring at 
five sites in the TMAA (Rice et al., 2021; Rice et al., 2015; Rice et 
al., 2018b; Rice et al., 2020a) has intermittently detected Cuvier's 
beaked whale vocalizations in low numbers in every month except April, 
although there are generally multiple months in any given year where no 
detections are made.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the anticipated takes would occur within a 
small portion of the stocks' ranges (including that none of the stocks 
are expected to occur in the far western edge of the TMAA; U.S. 
Department of the Navy, 2021) and would occur within the 21-day window 
of the annual activities. In consideration of these factors and the 
passive acoustic monitoring data described in this section, which 
indicates relatively low beaked whale presence in the TMAA during the 
Navy's potential training period, it is likely that a portion of the 
stocks would be taken, and a subset of them may be taken on a few days, 
with no indication that these days would be sequential.
    Regarding the severity of those individual takes by Level B 
harassment by behavioral disturbance, we have explained that the 
duration of any exposure is expected to be between minutes and hours 
(i.e., relatively short) and the received sound levels largely below 
166 dB, though with beaked whales, which are considered somewhat more 
sensitive, this could mean that some individuals would leave preferred 
habitat for a day (i.e., moderate level takes). However, while 
interrupted feeding bouts are a known response and concern for 
odontocetes, we also know that there are often viable alternative 
habitat options nearby. Regarding the severity of TTS takes 
(anticipated for Cuvier's and Stejneger's beaked whales only), they are 
expected to be low-level, of short duration, and mostly not in a 
frequency band that would be expected to interfere with beaked whale 
communication or other important low-frequency cues. Therefore, the 
associated lost opportunities and capabilities are not at a level that 
would impact reproduction or survival. As mentioned earlier in the 
odontocete overview, we anticipate more severe effects from takes when 
animals are exposed to higher received levels or sequential days of 
impacts.
    Altogether, none of these species are ESA-listed, only a portion of 
the stocks are anticipated to be impacted, and any individual beaked 
whale is likely to be disturbed at a moderate or sometimes low level. 
This low magnitude and moderate to lower severity of harassment effects 
is not expected to result in impacts on individual reproduction or 
survival, let alone have impacts on annual rates of recruitment or 
survival of this stock. No mortality, serious injury, or Level A 
harassment is anticipated or proposed for authorization. For these 
reasons, we have preliminarily determined, in consideration of all of 
the effects of the Navy's activities combined, that the proposed 
authorized take would have a negligible impact on the Alaska stocks of 
beaked whales.

Dolphins and Small Whales

    This section builds on the broader odontocete discussion above and 
brings together the discussion of the different types and amounts of 
take that different dolphin and small whale species and stocks would 
likely incur, the applicable mitigation, and the status of the species 
and stocks to support the preliminary negligible impact determinations 
for each species or stock. For all dolphin and small whale stocks 
discussed here, no mortality or Level A harassment is anticipated or 
proposed for authorization.
    In Table 44 below for dolphins and small whales, we indicate the 
total annual numbers of take by Level A harassment and Level B 
harassment, and a number indicating the instances of total take as a 
percentage of abundance.

    Table 44--Annual Estimated Takes by Level B Harassment and Level A Harassment for Dolphins and Small Whales in the TMAA and Number Indicating the
                                           Instances of Total Take as a Percentage of Species/Stock Abundance
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Instances of indicated types of incidental
                                                                             take \1\
                                                         ------------------------------------------------                                  Instances of
                                                                Level B harassment            Level A                        Abundance     total take as
              Species                       Stock        --------------------------------   harassment      Total takes     (NMFS SARs)    percentage of
                                                                           TTS (may also ----------------                       \2\          abundance
                                                            Behavioral        include
                                                            disturbance    disturbance)         PTS
--------------------------------------------------------------------------------------------------------------------------------------------------------
Killer whale......................  Eastern North                     64              17               0              81             300            27.0
                                     Pacific Offshore.
                                    Eastern North                    119              24               0             143             587            24.4
                                     Pacific Gulf of
                                     Alaska, Aleutian
                                     Islands, and Bering
                                     Sea Transient.
Pacific white-sided dolphins......  North Pacific.......           1,102             472               0           1,574          26,880             5.9
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Estimated impacts are based on the maximum number of activities in a given year under the specified activity. Not all takes represent separate
  individuals, especially for disturbance.
\2\ Presented in the 2021 draft SARs or most recent SAR.


[[Page 49753]]

    As described above, the large majority of Level B harassment by 
behavioral disturbance to odontocetes, and thereby dolphins and small 
whales, from hull-mounted sonar (MFAS) in the TMAA would result from 
received levels between 160 and 172 dB SPL. Therefore, the majority of 
takes by Level B harassment are expected to be in the form of low to 
occasionally moderate responses of a generally shorter duration. As 
mentioned earlier in this section, we anticipate more severe effects 
from takes when animals are exposed to higher received levels or for 
longer durations. Occasional milder occurrences of Level B harassment 
by behavioral disturbance are unlikely to cause long-term consequences 
for individual animals, much less have any effect on annual rates of 
recruitment or survival. No mortality, serious injury, or Level A 
harassment is expected or proposed for authorization.
    Research and observations show that if delphinids are exposed to 
sonar or other active acoustic sources they may react in a number of 
ways depending on their experience with the sound source and what 
activity they are engaged in at the time of the acoustic exposure. 
Delphinids may not react at all until the sound source is approaching 
within a few hundred meters to within a few kilometers depending on the 
environmental conditions and species. Some dolphin species (the more 
surface-dwelling taxa--typically those with ``dolphin'' in the common 
name, such as bottlenose dolphins, spotted dolphins, spinner dolphins, 
rough-toothed dolphins, etc., but not Risso's dolphin), especially 
those residing in more industrialized or busy areas, have demonstrated 
more tolerance for disturbance and loud sounds and many of these 
species are known to approach vessels to bow-ride. These species are 
often considered generally less sensitive to disturbance. Dolphins and 
small whales that reside in deeper waters and generally have fewer 
interactions with human activities are more likely to demonstrate more 
typical avoidance reactions and foraging interruptions as described 
above in the odontocete overview.
    Below we compile and summarize the information that supports our 
preliminary determinations that the Navy's activities would not 
adversely affect any of the dolphins and small whales through effects 
on annual rates of recruitment or survival.
Killer Whales (Eastern North Pacific Offshore; Eastern North Pacific 
Gulf of Alaska, Aleutian Islands, and Bering Sea Transient)
    No killer whale stocks in the TMAA are listed as DPSs under the 
ESA, and no BIAs for killer whales have been identified in the GOA 
Study Area. The Eastern North Pacific Offshore stock is reported as 
``stable,'' and the population trend of the Eastern North Pacific Gulf 
of Alaska, Aleutian Islands, and Bering Sea Transient stock is unknown.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance is 27 percent for the Eastern North 
Pacific Offshore stock and 24 percent for the Eastern North Pacific 
Gulf of Alaska, Aleutian Islands, and Bering Sea Transient stock. This 
information indicates that only a portion of each stock is likely 
impacted, with those individuals disturbed on likely one, but not more 
than a few non-sequential days within the 21 days per year. Regarding 
the severity of those individual takes by Level B harassment by 
behavioral disturbance, we have explained that the duration of any 
exposure is expected to be between minutes and hours (i.e., relatively 
short) and the received sound levels largely below 172 dB (i.e., of a 
lower, to occasionally moderate, level and less likely to evoke a 
severe response). Regarding the severity of TTS takes, they are 
expected to be low-level, of short duration, and mostly not in a 
frequency band that would be expected to interfere with killer whale 
communication or other important low-frequency cues. Therefore, the 
associated lost opportunities and capabilities are not at a level that 
would impact reproduction or survival.
    Altogether, these killer whale stocks are not listed under the ESA. 
The Eastern North Pacific Offshore stock is reported as ``stable,'' and 
the population trend of the Eastern North Pacific Gulf of Alaska, 
Aleutian Islands, and Bering Sea Transient stock is unknown. Only a 
portion of these killer whale stocks is anticipated to be impacted, and 
any individual is likely to be disturbed at a low-moderate level, with 
the taken individuals likely exposed on one day but not more than a few 
non-sequential days within a year. This low magnitude and severity of 
harassment effects is unlikely to result in impacts on individual 
reproduction or survival, let alone have impacts on annual rates of 
recruitment or survival of either of the stocks. No mortality or Level 
A harassment is anticipated or proposed for authorization for either of 
the stocks. For these reasons, we have preliminarily determined, in 
consideration of all of the effects of the Navy's activities combined, 
that the proposed authorized take would have a negligible impact on 
these killer whale stocks.
Pacific White-Sided Dolphins (North Pacific Stock)
    Pacific white-sided dolphins are not listed under the ESA and the 
current population trend of the North Pacific stock is unknown. No BIAs 
for this stock have been identified in the GOA Study Area.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance is 6 percent. Given the number of takes, 
only a small portion of the stock is likely impacted, and individuals 
are likely disturbed between one and a few days, most likely non-
sequential, within a year. Regarding the severity of those individual 
takes by Level B harassment by behavioral disturbance, we have 
explained that the duration of any exposure is expected to be between 
minutes and hours (i.e., relatively short) and the received sound 
levels largely below 172 dB (i.e., of a lower, to occasionally 
moderate, level and less likely to evoke a severe response). However, 
while interrupted feeding bouts are a known response and concern for 
odontocetes, we also know that there are often viable alternative 
habitat options nearby. Regarding the severity of TTS takes, they are 
expected to be low-level, of short duration, and mostly not in a 
frequency band that would be expected to interfere with dolphin 
communication or other important low-frequency cues. Therefore, the 
associated lost opportunities and capabilities are not at a level that 
would impact reproduction or survival.
    Altogether, though the status of this stock is unknown, this stock 
is not listed under the ESA. Any individual is likely to be disturbed 
at a low-moderate level, and those individuals likely disturbed on one 
to a few non-sequential days within a year. This low magnitude and 
severity of harassment effects is not expected to result in impacts on 
individual reproduction or survival, let alone have impacts on annual 
rates of recruitment or survival of this stock. No mortality, serious 
injury, or Level A harassment is anticipated or proposed for 
authorization. For these reasons, we have preliminarily determined, in 
consideration of all of the effects of the Navy's activities combined, 
that the

[[Page 49754]]

proposed authorized take would have a negligible impact on the North 
Pacific stock of Pacific white-sided dolphins.

Dall's Porpoise (Alaska Stock)

    This section builds on the broader odontocete discussion above and 
brings together the discussion of the different types and amounts of 
take that this porpoise stock would likely incur, the applicable 
mitigation, and the status of the stock to support the negligible 
impact determination.
    In Table 45 below for Dall's porpoise, we indicate the total annual 
numbers of take by Level A harassment and Level B harassment, and a 
number indicating the instances of total take as a percentage of 
abundance.

  Table 45--Annual Estimated Takes by Level B Harassment and Level A Harassment for Dall's Porpoise in the TMAA and Number Indicating the Instances of
                                                  Total Take as a Percentage of Species/Stock Abundance
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Instances of indicated types of incidental take
                                                                           \1\
                                                   ---------------------------------------------------                                     Instances of
                                                           Level B harassment             Level A                       Abundance (NMFS   total take as
            Species                    Stock       ----------------------------------    harassment      Total takes       SARs) \2\      percentage of
                                                                      TTS (may also  -----------------                                      abundance
                                                       Behavioral        include
                                                      disturbance      disturbance)         PTS
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dall's porpoise................  Alaska...........             348            8,939               64            9,351           83,400             11.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Estimated impacts are based on the maximum number of activities in a given year under the Specified Activity. Not all takes represent separate
  individuals, especially for disturbance.
\2\ Presented in the 2021 draft SARs or most recent SAR.

    Dall's porpoise is not listed under the ESA and the current 
population trend for the Alaska stock is unknown. No BIAs for Dall's 
porpoise have been identified in the GOA Study Area.
    While harbor porpoises have been observed to be especially 
sensitive to human activity, the same types of responses have not been 
observed in Dall's porpoises. Dall's porpoises are typically notably 
longer than, and weigh more than twice as much as, harbor porpoises, 
making them generally less likely to be preyed upon and likely 
differentiating their behavioral repertoire somewhat from harbor 
porpoises. Further, they are typically seen in large groups and feeding 
aggregations, or exhibiting bow-riding behaviors, which is very 
different from the group dynamics observed in the more typically 
solitary, cryptic harbor porpoises, which are not often seen bow-
riding. For these reasons, Dall's porpoises are not treated as an 
especially sensitive species (versus harbor porpoises which have a 
lower behavioral harassment threshold and more distant cutoff) but, 
rather, are analyzed similarly to other odontocetes (with takes from 
the sonar bin in the TMAA resulting from the same received levels 
reported in the Odontocete section above). Therefore, the majority of 
Level B harassment by behavioral disturbance is expected to be in the 
form of milder responses compared to higher level exposures. As 
mentioned earlier in this section, we anticipate more severe effects 
from takes when animals are exposed to higher received levels.
    We note that Dall's porpoise, as a HF-sensitive species, has a 
lower PTS threshold than other groups and therefore is generally more 
likely to experience TTS and PTS, and potentially occasionally to a 
greater degree, and NMFS accordingly has evaluated and authorized 
higher numbers. Also, however, regarding PTS from sonar exposure, 
porpoises are still likely to avoid sound levels that would cause 
higher levels of TTS (greater than 20 dB) or PTS. Therefore, even 
though the number of TTS takes are higher than for other odontocetes, 
any PTS is expected to be at a lower to occasionally moderate level and 
for all of the reasons described above, TTS and PTS takes are not 
expected to impact reproduction or survival of any individual.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance is 11 percent. This indicates that only 
a small portion of this stock is likely to be impacted, and a subset of 
those individuals would likely be taken on no more than a few non-
sequential days within a year. Regarding the severity of those 
individual takes by Level B harassment by behavioral disturbance, we 
have explained that the duration of any exposure is expected to be 
between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB (i.e., of a lower, to occasionally 
moderate, level and less likely to evoke a severe response). Regarding 
the severity of TTS takes, they are expected to be low-level, of short 
duration, and mostly not in a frequency band that would be expected to 
interfere with communication or other important low-frequency cues. 
Therefore, the associated lost opportunities and capabilities are not 
at a level that would impact reproduction or survival.
    For the same reasons explained above for TTS (low to occasionally 
moderate level and the likely frequency band), while a small permanent 
loss of hearing sensitivity may include some degree of energetic costs 
for compensating or may mean some small loss of opportunities or 
detection capabilities, the estimated annual takes by Level A 
harassment by PTS for this stock (64 takes) would be unlikely to impact 
behaviors, opportunities, or detection capabilities to a degree that 
would interfere with reproductive success or survival of any 
individuals.
    Altogether, the status of the Alaska stock of Dall's porpoise is 
unknown, however Dall's porpoise are not listed as endangered or 
threatened under the ESA. Only a small portion of this stock is likely 
to be impacted, any individual is likely to be disturbed at a low-
moderate level, and a subset of taken individuals would likely be taken 
on a few non-sequential days within a year. This low magnitude and 
severity of Level B harassment effects is not expected to result in 
impacts on individual reproduction or survival, much less annual rates 
of recruitment or survival. Some individuals (64 annually) could be 
taken by PTS of likely low to occasionally moderate severity. A small 
permanent loss of hearing sensitivity (PTS) may include some degree of 
energetic costs for compensating or may mean some small loss of 
opportunities or detection capabilities, but at the expected scale the 
estimated takes by Level A harassment by PTS for this stock would be 
unlikely, alone or in combination with the Level B harassment take by 
behavioral disturbance and TTS, to impact behaviors, opportunities, or 
detection capabilities to a degree that

[[Page 49755]]

would interfere with reproductive success or survival of any 
individuals, let alone have impacts on annual rates of recruitment or 
survival of this stock. No mortality or serious injury and no Level A 
harassment from non-auditory tissue damage is anticipated or proposed 
for authorization. For these reasons, we have preliminarily determined, 
in consideration of all of the effects of the Navy's activities 
combined, that the proposed authorized take would have a negligible 
impact on the Alaska stock of Dall's porpoise.
Pinnipeds
    This section builds on the broader discussion above and brings 
together the discussion of the different types and amounts of take that 
different species and stocks would likely incur, the applicable 
mitigation, and the status of the species and stocks to support the 
negligible impact determinations for each species or stock. We have 
described (earlier in this section) the unlikelihood of any masking 
having effects that would impact the reproduction or survival of any of 
the individual marine mammals affected by the Navy's activities. We 
have also described above in the Potential Effects of Specified 
Activities on Marine Mammals and their Habitat section the unlikelihood 
of any habitat impacts having effects that would impact the 
reproduction or survival of any of the individual marine mammals 
affected by the Navy's activities. For pinnipeds, there is no mortality 
or serious injury and no Level A harassment from non-auditory tissue 
damage from sonar or explosives anticipated or proposed to be 
authorized for any species.
    Regarding behavioral disturbance, research and observations show 
that pinnipeds in the water may be tolerant of anthropogenic noise and 
activity (a review of behavioral reactions by pinnipeds to impulsive 
and non-impulsive noise can be found in Richardson et al. (1995) and 
Southall et al. (2007)). Available data, though limited, suggest that 
exposures between approximately 90 and 140 dB SPL do not appear to 
induce strong behavioral responses in pinnipeds exposed to non-pulse 
sounds in water (Costa et al., 2003; Jacobs and Terhune, 2002; 
Kastelein et al., 2006c). Based on the limited data on pinnipeds in the 
water exposed to multiple pulses (small explosives, impact pile 
driving, and seismic sources), exposures in the approximately 150 to 
180 dB SPL range generally have limited potential to induce avoidance 
behavior in pinnipeds (Blackwell et al., 2004; Harris et al., 2001; 
Miller et al., 2004). If pinnipeds are exposed to sonar or other active 
acoustic sources they may react in a number of ways depending on their 
experience with the sound source and what activity they are engaged in 
at the time of the acoustic exposure. Pinnipeds may not react at all 
until the sound source is approaching within a few hundred meters and 
then may alert, ignore the stimulus, change their behaviors, or avoid 
the immediate area by swimming away or diving. Effects on pinnipeds 
that are taken by Level B harassment in the TMAA, on the basis of 
reports in the literature as well as Navy monitoring from past 
activities, would likely be limited to reactions such as increased 
swimming speeds, increased surfacing time, or decreased foraging (if 
such activity were occurring). Most likely, individuals would simply 
move away from the sound source and be temporarily displaced from those 
areas, or not respond at all, which would have no effect on 
reproduction or survival. While some animals may not return to an area, 
or may begin using an area differently due to training activities, most 
animals are expected to return to their usual locations and behavior. 
Given their documented tolerance of anthropogenic sound (Richardson et 
al., 1995 and Southall et al., 2007), repeated exposures of individuals 
of any of these species to levels of sound that may cause Level B 
harassment are unlikely to result in hearing impairment or to 
significantly disrupt foraging behavior. Thus, even repeated Level B 
harassment of some small subset of individuals of an overall stock is 
unlikely to result in any significant realized decrease in fitness to 
those individuals that would result in any adverse impact on rates of 
recruitment or survival for the stock as a whole.
    While no take of Steller sea lion is anticipated or proposed to be 
authorized, we note that the GOA Study Area boundary was intentionally 
designed to avoid ESA-designated Steller sea lion critical habitat.
    All the pinniped species discussed in this section would benefit 
from the procedural mitigation measures described earlier in the 
Proposed Mitigation Measures section.
    In Table 46 below for pinnipeds, we indicate the total annual 
numbers of take by Level A harassment and Level B harassment, and a 
number indicating the instances of total take as a percentage of 
abundance.

  Table 46--Annual Estimated Takes by Level B Harassment and Level A Harassment for Pinnipeds in the TMAA and Number Indicating the Instances of Total
                                                     Take as a Percentage of Species/Stock Abundance
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Instances of indicated types of incidental
                                                                             take \1\
                                                         ------------------------------------------------                                  Instances of
                                                                Level B harassment            Level A                        Abundance     total take as
              Species                       Stock        --------------------------------   harassment      Total Takes     (NMFS SARs)    percentage of
                                                                           TTS (may also ----------------                       \2\          abundance
                                                            Behavioral        include
                                                            disturbance    disturbance)         PTS
--------------------------------------------------------------------------------------------------------------------------------------------------------
Northern fur seal.................  Eastern Pacific.....           2,972              31               0           3,003         626,618              <1
Northern fur seal.................  California..........              60               1               0              61          14,050              <1
Northern elephant seal............  California..........             904           1,643               8           2,555         187,386             1.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Estimated impacts are based on the maximum number of activities in a given year under the specified activity. Not all takes represent separate
  individuals, especially for disturbance.
\2\ Presented in the 2021 draft SARs or most recent SAR.

    The majority of takes by harassment of pinnipeds in the TMAA are 
caused by sources from the MFAS bin (which includes hull-mounted sonar) 
because they are high level sources at a frequency (1-10 kHz) which 
overlaps the most sensitive portion of the pinniped hearing range, and 
of the sources expected to result in take, they are used in a large 
portion of exercises (see Table 1 and Table 3). Most of the takes (>99 
percent) from the MF1 bin in the TMAA would result from received levels 
between 166 and 178 dB SPL. For the remaining active sonar bin types, 
the percentages are as follows: MF4 = 97 percent between 148 and 172 dB 
SPL and MF5 = 99 percent between 130 and

[[Page 49756]]

160 dB SPL. Given the levels they are exposed to and pinniped 
sensitivity, most responses would be of a lower severity, with only 
occasional responses likely to be considered moderate, but still of 
generally short duration.
    As mentioned earlier in this section, we anticipate more severe 
effects from takes when animals are exposed to higher received levels. 
Occasional milder takes by Level B harassment by behavioral disturbance 
are unlikely to cause long-term consequences for individual animals or 
populations, especially when they are not expected to be repeated over 
sequential multiple days. For all pinnipeds except Northern elephant 
seals, no take is expected to occur from explosives. For Northern 
elephant seals, harassment takes from explosives (behavioral 
disturbance, TTS, and PTS) comprise a very small fraction of those 
caused by exposure to active sonar.
    Because the majority of harassment takes of pinnipeds result from 
narrowband sources in the range of 1-10 kHz, the vast majority of 
threshold shift caused by Navy sonar sources would typically occur in 
the range of 2-20 kHz. This frequency range falls within the range of 
pinniped hearing, however, pinniped vocalizations typically span a 
somewhat lower range than this (<0.2 to 10 kHz) and threshold shift 
from active sonar would often be in a narrower band (reflecting the 
narrower band source that caused it), which means that TTS incurred by 
pinnipeds would typically only interfere with communication within a 
portion of a pinniped's range (if it occurred during a time when 
communication with conspecifics was occurring). As discussed earlier, 
it would only be expected to be of a short duration and relatively 
small degree. Many of the other critical sounds that serve as cues for 
navigation and prey (e.g., waves, fish, invertebrates) occur below a 
few kHz, which means that detection of these signals would not be 
inhibited by most threshold shifts either. The very low number of takes 
by threshold shifts that might be incurred by individuals exposed to 
explosives would likely be lower frequency (5 kHz or less) and spanning 
a wider frequency range, which could slightly lower an individual's 
sensitivity to navigational or prey cues, or a small portion of 
communication calls, for several minutes to hours (if temporary) or 
permanently.
    Neither of these species are ESA-listed and the SAR indicates that 
the status of the Eastern Pacific stock of Northern fur seal is stable, 
the California stock of Northern fur seal is increasing, and the 
California stock of Northern elephant seal is increasing. BIAs have not 
been identified for pinnipeds.
    Regarding the magnitude of takes by Level B harassment (TTS and 
behavioral disturbance) for the Eastern Pacific and California stocks 
of Northern fur seals, the estimated instances of takes as compared to 
the stock abundance is <1 percent for each stock. For the California 
stock of Northern elephant seal, the number of estimated total 
instances of take compared to the abundance is 1 percent. This 
information indicates that only a very small portion of individuals in 
these stocks are likely impacted, particularly given the large ranges 
of the stocks. Impacted individuals would be disturbed on likely one, 
but not more than a few non-sequential days within a year.
    Regarding the severity of those individual takes by Level B 
harassment by behavioral disturbance for all pinniped stocks, we have 
explained that the duration of any exposure is expected to be between 
minutes and hours (i.e., relatively short) and the received sound 
levels largely below 178 dB, which is considered a relatively low to 
occasionally moderate level for pinnipeds.
    Regarding the severity of TTS takes, they are expected to be low-
level, of short duration, and mostly not in a frequency band that would 
be expected to interfere with pinniped communication or other important 
low-frequency cues. Therefore, the associated lost opportunities and 
capabilities are not at a level that would impact reproduction or 
survival. For these same reasons (low level and frequency band), while 
a small permanent loss of hearing sensitivity may include some degree 
of energetic costs for compensating or may mean some small loss of 
opportunities or detection capabilities, the 8 estimated Level A 
harassment takes by PTS for the California stock of Northern elephant 
seal would be unlikely to impact behaviors, opportunities, or detection 
capabilities to a degree that would interfere with reproductive success 
or survival of any individuals.
    Altogether, none of these species are listed under the ESA, and the 
SARs indicate that the status of the Eastern Pacific stock of Northern 
fur seal is stable, the California stock of Northern fur seal is 
increasing, and the California stock of Northern elephant seal is 
increasing. No mortality or serious injury and no Level A harassment 
from non-auditory tissue damage for pinnipeds is anticipated or 
proposed for authorization. Level A harassment by PTS is only 
anticipated for the California stock of Northern elephant seal (8 takes 
by Level A harassment). For all three pinniped stocks, only a small 
portion of the stocks are anticipated to be impacted and any individual 
is likely to be disturbed at a low-moderate level. This low magnitude 
and severity of harassment effects is not expected to result in impacts 
on individual reproduction or survival, let alone have impacts on 
annual rates of recruitment or survival of these stocks. For these 
reasons, in consideration of all of the effects of the Navy's 
activities combined, we have preliminarily determined that the proposed 
authorized take would have a negligible impact on all three stocks of 
pinnipeds.

Preliminary Determination

    Based on the analysis contained herein of the likely effects of the 
specified activity on marine mammals and their habitat, and taking into 
consideration the implementation of the proposed monitoring and 
mitigation measures, NMFS preliminarily finds that the total marine 
mammal take from the specified activities will have a negligible impact 
on all affected marine mammal species or stocks.

Subsistence Harvest of Marine Mammals

    In order to issue an incidental take authorization, NMFS must find 
that the specified activity will not have an ``unmitigable adverse 
impact'' on the subsistence uses of the affected marine mammal species 
or stocks by Alaska Natives. NMFS has defined ``unmitigable adverse 
impact'' in 50 CFR 216.103 as an impact resulting from the specified 
activity: (1) That is likely to reduce the availability of the species 
to a level insufficient for a harvest to meet subsistence needs by: (i) 
Causing the marine mammals to abandon or avoid hunting areas; (ii) 
Directly displacing subsistence users; or (iii) Placing physical 
barriers between the marine mammals and the subsistence hunters; and 
(2) That cannot be sufficiently mitigated by other measures to increase 
the availability of marine mammals to allow subsistence needs to be 
met.
    When applicable, NMFS must prescribe means of effecting the least 
practicable adverse impact on the availability of the species or stocks 
for subsistence uses. As discussed in the Proposed Mitigation Measures 
section, 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

[[Page 49757]]

adverse impacts on the availability of species or stocks for 
subsistence uses, and (2) the practicability of the measure(s) for 
applicant implementation.
    The Navy has met with and will continue to engage in meaningful 
consultation and communication with several federally recognized Alaska 
Native tribes that have traditional marine mammal harvest areas in the 
GOA (though, as noted below, these areas do not overlap directly with 
the GOA Study Area). Further, the Navy will continue to keep the Tribes 
informed of the timeframes of future joint training exercises.
    To our knowledge, subsistence hunting of marine mammals does not 
occur in the GOA Study Area where training activities would occur. The 
GOA Study Area is located over 12 nmi from shore with the nearest 
inhabited land being the Kenai Peninsula (24 nmi from the GOA Study 
Area). Information provided by Tribes in previous conversations with 
the Navy, and according to Alaska Department of Fish and Game (1995), 
indicates that harvest of pinnipeds occurs nearshore, and the Tribes do 
not use the GOA Study Area for subsistence hunting of marine mammals. 
The TMAA portion of the GOA Study Area is the closest to the area of 
nearshore subsistence harvest conducted by the Sun'aq Tribe of Kodiak, 
the Native Village of Eyak, and the Yakutat Tlingit Tribe (Alaska 
Department of Fish and Game, 1995). The WMA is offshore of subsistence 
harvest areas that occur in Unalaska, Akutan, False Pass, Sand Point, 
and King Cove (Alaska Department of Fish and Game, 1997). The Tribes 
listed here harvest harbor seals and sea lions (Alaska Department of 
Fish and Game, 1995, 1997).
    In addition to the distance between subsistence hunting areas and 
the GOA Study Area, which would ensure that the Navy's activities do 
not displace subsistence users or place physical barriers between the 
marine mammals and the subsistence hunters, there is no reason to 
believe that any behavioral disturbance or limited TTS or PTS of 
pinnipeds that occurs offshore in the GOA Study Area would affect their 
subsequent behavior in a manner that would interfere with subsistence 
uses should those pinnipeds later interact with hunters, particularly 
given that neither harbor seals, Steller sea lions, or California sea 
lions are expected to be taken by the Navy's training activities. The 
specified activity would be a continuation of the types of training 
activities that have been ongoing for more than a decade, and as 
discussed in the 2011 GOA FEIS/OEIS and 2016 GOA FSEIS/OEIS, no impacts 
on traditional subsistence practices or resources are predicted to 
result from the specified activity.
    Based on the information above, NMFS has preliminarily determined 
that the total taking of affected species or stocks would not have an 
unmitigable adverse impact on the availability of the species or stocks 
for taking for subsistence purposes. However, we have limited 
information on marine mammal subsistence use in the GOA Study Area and 
seek additional information pertinent to making the final 
determination.

Classification

Endangered Species Act

    There are eight marine mammal species under NMFS jurisdiction that 
are listed as endangered or threatened under the ESA with confirmed or 
possible occurrence in the GOA Study Area: North Pacific right whale, 
humpback whale (Mexico, Western North Pacific, and Central America 
DPSs), blue whale, fin whale, sei whale, gray whale (Western North 
Pacific stock), sperm whale, and Steller sea lion (Western DPS). The 
humpback whale has critical habitat recently designated under the ESA 
in the TMAA portion of the GOA Study Area (86 FR 21082; April 21, 
2021). As discussed previously, the GOA Study Area boundaries were 
intentionally designed to avoid ESA-designated critical habitat for 
Steller sea lions.
    The Navy will consult with NMFS pursuant to section 7 of the ESA 
for GOA Study Area activities. NMFS will also consult internally on the 
issuance of the regulations and an LOA under section 101(a)(5)(A) of 
the MMPA.

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 evaluate our proposed actions and alternatives with respect 
to potential impacts on the human environment. Accordingly, NMFS plans 
to adopt the GOA SEIS/OEIS for the GOA Study Area provided our 
independent evaluation of the document finds that it includes adequate 
information analyzing the effects on the human environment of issuing 
regulations and an LOA under the MMPA. NMFS is a cooperating agency on 
the 2020 GOA DSEIS/OEIS and 2022 Supplement to the 2020 GOA DSEIS/OEIS 
and has worked extensively with the Navy in developing the documents. 
The 2020 GOA DSEIS/OEIS and 2022 Supplement to the 2020 GOA DSEIS/OEIS 
were made available for public comment in February 2020 and March 2022, 
respectively, at https://www.goaeis.com/, which also provides 
additional information about the NEPA process. We will review all 
comments prior to concluding our NEPA process and making a final 
decision on the MMPA rulemaking and request for a LOA.

Regulatory Flexibility Act

    The Office of Management and Budget has determined that this 
proposed rule is not significant for purposes of Executive Order 12866.
    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 that this 
proposed rule, if adopted, would not have a significant economic impact 
on a substantial number of small entities. The RFA requires Federal 
agencies to prepare an analysis of a rule's impact on small entities 
whenever the agency is required to publish a notice of proposed 
rulemaking. However, a Federal agency may certify, pursuant to 5 U.S.C. 
605(b), that the action will not have a significant economic impact on 
a substantial number of small entities. The Navy is the sole entity 
that would be affected by this rulemaking, and the Navy is not a small 
governmental jurisdiction, small organization, or small business, as 
defined by the RFA. Any requirements imposed by an LOA issued pursuant 
to these regulations, and any monitoring or reporting requirements 
imposed by these regulations, would be applicable only to the Navy. 
NMFS does not expect the issuance of these regulations or the 
associated LOA to result in any impacts to small entities pursuant to 
the RFA. Because this action, if adopted, would directly affect the 
Navy and not a small entity, NMFS concludes that the action would not 
result in a significant economic impact on a substantial number of 
small entities.

List of Subjects in 50 CFR Part 218

    Exports, Fish, Imports, Incidental take, Indians, Labeling, Marine 
mammals, Navy, Penalties, Reporting and recordkeeping requirements, 
Seafood, Sonar, Transportation.


[[Page 49758]]


    Dated: July 28, 2022.
Samuel D. Rauch, III,
Deputy Assistant Administrator for Regulatory Programs, National Marine 
Fisheries Service.

    For reasons set forth in the preamble, 50 CFR part 218 is proposed 
to be amended 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., unless otherwise noted.

0
2. Revise subpart P to read as follows:

Subpart P--Taking and Importing Marine Mammals; U.S. Navy Training 
Activities in the Gulf of Alaska Study Area

Sec.
218.150 Specified activity and geographical region.
218.151 Effective dates.
218.152 Permissible methods of taking.
218.153 Prohibitions.
218.154 Mitigation requirements.
218.155 Requirements for monitoring and reporting.
218.156 Letters of Authorization.
218.157 Renewals and modifications of Letter of Authorization.
218.158 [Reserved]


Sec.  218.150   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.
    (b) The GOA Study Area is entirely at sea and is comprised of three 
areas: a Temporary Maritime Activities Area (TMAA) a warning area, and 
the Western Maneuver Area (WMA) located south and west of the TMAA. The 
TMAA and WMA are temporary areas established within the GOA for ships, 
submarines, and aircraft to conduct training activities. The TMAA is a 
polygon roughly resembling a rectangle oriented from northwest to 
southeast, approximately 300 nautical miles (nmi; 556 km) in length by 
150 nmi (278 km) in width, located south of Montague Island and east of 
Kodiak Island. The warning area overlaps and extends slightly beyond 
the northern corner of the TMAA. The WMA provides an additional 185,806 
nmi\2\ of surface, sub-surface, and airspace training area to support 
activities occurring within the TMAA. The boundary of the WMA follows 
the bottom of the slope at the 4,000 m contour line.
    (c) The taking of marine mammals by the Navy is only authorized if 
it occurs incidental to the Navy conducting training activities, 
including:
    (1) Anti-submarine warfare; and
    (2) Surface warfare.


Sec.  218.151   Effective dates.

    Regulations in this subpart are effective from December 15, 2022 
through December 14, 2029.


Sec.  218.152   Permissible methods of taking.

    (a) Under a Letter of Authorization (LOA) issued pursuant to Sec.  
216.106 of this chapter and Sec.  218.156, the Holder of the LOA 
(hereinafter ``Navy'') may incidentally, but not intentionally, take 
marine mammals within the TMAA only, as described in Sec.  218.150(b), 
by Level A harassment and Level B harassment associated with the use of 
active sonar and other acoustic sources and explosives, 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.  218.150(c) is limited to the following species:

                      Table 1 to Sec.   218.152(b)
------------------------------------------------------------------------
           Species                               Stock
------------------------------------------------------------------------
Blue whale...................  Central North Pacific.
Blue whale...................  Eastern North Pacific.
Fin whale....................  Northeast Pacific.
Humpback whale...............  Western North Pacific.
Humpback whale...............  Central North Pacific.
Humpback whale...............  California/Oregon/Washington.
Minke whale..................  Alaska.
North Pacific right whale....  Eastern North Pacific.
Sei whale....................  Eastern North Pacific.
Gray whale...................  Eastern North Pacific.
Killer whale.................  Eastern North Pacific Offshore.
Killer whale.................  Eastern North Pacific Gulf of Alaska,
                                Aleutian Islands, and Bering Sea
                                Transient.
Pacific white-sided dolphin..  North Pacific.
Dall's porpoise..............  Alaska.
Sperm whale..................  North Pacific.
Baird's beaked whale.........  Alaska.
Cuvier's beaked whale........  Alaska.
Stejneger's beaked whale.....  Alaska.
Northern fur seal............  Eastern Pacific.
Northern fur seal............  California.
Northern elephant seal.......  California.
------------------------------------------------------------------------

Sec.  218.153   Prohibitions.

    (a) Except for incidental takings contemplated in Sec.  218.152(a) 
and authorized by an LOA issued under Sec. Sec.  216.106 of this 
chapter and 218.156, it shall be unlawful for any person to do any of 
the following in connection with the activities listed in Sec.  
218.150(c):
    (1) Violate, or fail to comply with, the terms, conditions, and 
requirements of this subpart or an LOA issued under Sec. Sec.  216.106 
of this chapter and 218.156;
    (2) Take any marine mammal not specified in Sec.  218.152(b);
    (3) Take any marine mammal specified in Sec.  218.152(b) in any 
manner other than as specified in the LOA; or
    (4) Take a marine mammal specified in Sec.  218.152(b) if NMFS 
determines such taking results in more than a negligible impact on the 
species or stocks of such marine mammal.

[[Page 49759]]

    (b) [Reserved]


Sec.  218.154   Mitigation requirements.

    (a) When conducting the activities identified in Sec.  218.150(c), 
the mitigation measures contained in any LOA issued under Sec. Sec.  
216.106 of this chapter and 218.156 must be implemented. These 
mitigation measures include, but are not limited to:
    (1) Procedural mitigation. Procedural mitigation is mitigation that 
the Navy must implement whenever and wherever an applicable training 
activity takes place within the GOA Study Area for acoustic stressors 
(i.e., active sonar, weapons firing noise), explosive stressors (i.e., 
large-caliber projectiles, bombs), and physical disturbance and strike 
stressors (i.e., vessel movement, towed in-water devices, small-, 
medium-, and large-caliber non-explosive practice munitions, non-
explosive bombs).
    (i) Environmental awareness and education. Appropriate Navy 
personnel (including civilian personnel) involved in mitigation and 
training activity reporting under the specified activities will 
complete the environmental compliance training modules identified in 
their career path training plan, as specified in the LOA.
    (ii) Active sonar. Active sonar includes mid-frequency active 
sonar, and high-frequency active sonar. For vessel-based active sonar 
activities, mitigation applies only to sources that are positively 
controlled and deployed from manned surface vessels (e.g., sonar 
sources towed from manned surface platforms). For aircraft-based active 
sonar activities, mitigation applies only to sources that are 
positively controlled and deployed from manned aircraft that do not 
operate at high altitudes (e.g., rotary-wing aircraft). Mitigation does 
not apply to active sonar sources deployed from unmanned aircraft or 
aircraft operating at high altitudes (e.g., maritime patrol aircraft).
    (A) Number of Lookouts and observation platform for hull-mounted 
sources. For hull-mounted sources, the Navy must have one Lookout for 
platforms with space or manning restrictions while underway (at the 
forward part of a small boat or ship) and platforms using active sonar 
while moored or at anchor; and two Lookouts for platforms without space 
or manning restrictions while underway (at the forward part of the 
ship).
    (B) Number of Lookouts and observation platform for sources not 
hull-mounted. For sources that are not hull-mounted, the Navy must have 
one Lookout on the ship or aircraft conducting the activity.
    (C) Prior to activity. Prior to the initial start of the activity 
(e.g., when maneuvering on station), Navy personnel must observe the 
mitigation zone for floating vegetation and marine mammals; if floating 
vegetation or a marine mammal is observed, Navy personnel must relocate 
or delay the start of active sonar transmission until the mitigation 
zone is clear of floating vegetation or until the conditions in 
paragraph (a)(1)(ii)(F) of this section are met for marine mammals.
    (D) During the activity for hull-mounted mid-frequency active 
sonar. During the activity, for hull-mounted mid-frequency active 
sonar, Navy personnel must observe the following mitigation zones for 
marine mammals.
    (1) Powerdowns for marine mammals. Navy personnel must power down 
active sonar transmission by 6 dB if a marine mammal is observed within 
1,000 yd (914.4 m) of the sonar source; Navy personnel must power down 
active sonar transmission an additional 4 dB (10 dB total) if a marine 
mammal is observed within 500 yd (457.2 m) of the sonar source.
    (2) Shutdowns for marine mammals. Navy personnel must cease 
transmission if a marine mammal is observed within 200 yd (182.9 m) of 
the sonar source.
    (E) During the activity, for mid-frequency active sonar sources 
that are not hull-mounted, and high-frequency active sonar. During the 
activity, for mid-frequency active sonar sources that are not hull-
mounted and high-frequency active sonar, Navy personnel must observe 
the mitigation zone for marine mammals. Navy personnel must cease 
transmission if a marine mammal is observed within 200 yd (182.9 m) of 
the sonar source.
    (F) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing or powering up active sonar transmission) until 
one of the following conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the sonar source;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 minutes (min) for aircraft-
deployed sonar sources or 30 minutes for vessel-deployed sonar sources;
    (4) Sonar source transit. For mobile activities, the active sonar 
source has transited a distance equal to double that of the mitigation 
zone size beyond the location of the last sighting; or
    (5) Bow-riding dolphins. For activities using hull-mounted sonar, 
the Lookout concludes that dolphins are deliberately closing in on the 
ship to ride the ship's bow wave, and are therefore out of the main 
transmission axis of the sonar (and there are no other marine mammal 
sightings within the mitigation zone).
    (iii) Weapons firing noise. Weapons firing noise associated with 
large-caliber gunnery activities.
    (A) Number of Lookouts and observation platform. One Lookout must 
be positioned on the ship conducting the firing. Depending on the 
activity, the Lookout could be the same as the one provided for under 
``Explosive large-caliber projectiles'' or under ``Small-, medium-, and 
large-caliber non-explosive practice munitions'' in paragraphs 
(a)(1)(iv)(A) and (a)(1)(viii)(A) of this section.
    (B) Mitigation zone. Thirty degrees on either side of the firing 
line out to 70 yd (64 m) from the muzzle of the weapon being fired.
    (C) Prior to activity. Prior to the initial start of the activity, 
Navy personnel must observe the mitigation zone for floating vegetation 
and marine mammals; if floating vegetation or a marine mammal is 
observed, Navy personnel must relocate or delay the start of weapons 
firing until the mitigation zone is clear of floating vegetation or 
until the conditions in paragraph (a)(1)(iii)(E) of this section are 
met for marine mammals.
    (D) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if a marine mammal is 
observed, Navy personnel must cease weapons firing.
    (E) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing weapons firing) until one of the following 
conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the firing ship;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 30 min; or

[[Page 49760]]

    (4) Firing ship transit. For mobile activities, the firing ship has 
transited a distance equal to double that of the mitigation zone size 
beyond the location of the last sighting.
    (iv) Explosive large-caliber projectiles. Gunnery activities using 
explosive large-caliber projectiles. Mitigation applies to activities 
using a surface target.
    (A) Number of Lookouts and observation platform. One Lookout must 
be on the vessel or aircraft conducting the activity. Depending on the 
activity, the Lookout could be the same as the one described in 
``Weapons firing noise'' in paragraph (a)(1)(iii)(A) of this section. 
If additional platforms are participating in the activity, Navy 
personnel positioned in those assets (e.g., safety observers, 
evaluators) must support observing the mitigation zone for marine 
mammals while performing their regular duties.
    (B) Mitigation zones. 1,000 yd (914.4 m) around the intended impact 
location.
    (C) Prior to activity. Prior to the initial start of the activity 
(e.g., when maneuvering on station), Navy personnel must observe the 
mitigation zone for floating vegetation and marine mammals; if floating 
vegetation or a marine mammal is observed, Navy personnel must relocate 
or delay the start of firing until the mitigation zone is clear of 
floating vegetation or until the conditions in paragraph (a)(1)(iv)(E) 
of this section are met for marine mammals.
    (D) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if a marine mammal is 
observed, Navy personnel must cease firing.
    (E) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing firing) until one of the following conditions has 
been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended impact location;
    (3) Clear of additional sightings. The mitigation zone has been 
clear from any additional sightings for 30 minutes; or,
    (4) Impact location transit. For activities using mobile targets, 
the intended impact location has transited a distance equal to double 
that of the mitigation zone size beyond the location of the last 
sighting.
    (F) After activity. After completion of the activity (e.g., prior 
to maneuvering off station), Navy personnel must, when practical (e.g., 
when platforms are not constrained by fuel restrictions or mission-
essential follow-on commitments), observe for marine mammals in the 
vicinity of where detonations occurred; if any injured or dead marine 
mammals are observed, Navy personnel must follow established incident 
reporting procedures. If additional platforms are supporting this 
activity (e.g., providing range clearance), Navy personnel positioned 
on these Navy assets must assist in the visual observation of the area 
where detonations occurred.
    (v) Explosive bombs.
    (A) Number of Lookouts and observation platform. One Lookout must 
be positioned in an aircraft conducting the activity. If additional 
platforms are participating in the activity, Navy personnel positioned 
in those assets (e.g., safety observers, evaluators) must support 
observing the mitigation zone for marine mammals while performing their 
regular duties.
    (B) Mitigation zone. 2,500 yd (2,286 m) around the intended target.
    (C) Prior to activity. Prior to the initial start of the activity 
(e.g., when arriving on station), Navy personnel must observe the 
mitigation zone for floating vegetation and marine mammals; if floating 
vegetation or a marine mammal is observed, Navy personnel must relocate 
or delay the start of bomb deployment until the mitigation zone is 
clear of floating vegetation or until the conditions in paragraph 
(a)(1)(v)(E) of this section are met for marine mammals.
    (D) During activity. During the activity (e.g., during target 
approach), Navy personnel must observe the mitigation zone for marine 
mammals; if a marine mammal is observed, Navy personnel must cease bomb 
deployment.
    (E) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing bomb deployment) until one of the following 
conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended target;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min; or
    (4) Intended target transit. For activities using mobile targets, 
the intended target has transited a distance equal to double that of 
the mitigation zone size beyond the location of the last sighting.
    (F) After activity. After completion of the activity (e.g., prior 
to maneuvering off station), Navy personnel must, when practical (e.g., 
when platforms are not constrained by fuel restrictions or mission-
essential follow-on commitments), observe for marine mammals in the 
vicinity of where detonations occurred; if any injured or dead marine 
mammals are observed, Navy personnel must follow established incident 
reporting procedures. If additional platforms are supporting this 
activity (e.g., providing range clearance), Navy personnel positioned 
on these Navy assets must assist in the visual observation of the area 
where detonations occurred.
    (vi) Vessel movement. The mitigation will not be applied if: the 
vessel's safety is threatened; the vessel is restricted in its ability 
to maneuver (e.g., during launching and recovery of aircraft or landing 
craft, during towing activities, when mooring); the vessel is submerged 
or operated autonomously; or when impractical based on mission 
requirements (e.g., during Vessel Visit, Board, Search, and Seizure 
activities as military personnel from ships or aircraft board suspect 
vessels).
    (A) Number of Lookouts and observation platform. One or more 
Lookouts must be on the underway vessel. If additional watch personnel 
are positioned on the underway vessel, those personnel (e.g., persons 
assisting with navigation or safety) must support observing for marine 
mammals while performing their regular duties.
    (B) Mitigation zone.
    (1) Whales. 500 yd (457.2 m) around the vessel for whales.
    (2) Marine mammals other than whales. 200 yd (182.9 m) around the 
vessel for all marine mammals other than whales (except those 
intentionally swimming alongside or closing in to swim alongside 
vessels, such as bow-riding or wake-riding dolphins).
    (C) When underway. Navy personnel will observe the direct path of 
the vessel and waters surrounding the vessel for marine mammals. If a 
marine mammal is observed in the direct path of the vessel, Navy 
personnel will maneuver the vessel as necessary to maintain the 
appropriate mitigation zone distance. If

[[Page 49761]]

a marine mammal is observed within waters surrounding the vessel, Navy 
personnel will maintain situational awareness of that animal's 
position. Based on the animal's course and speed relative to the 
vessel's path, Navy personnel will maneuver the vessel as necessary to 
ensure that the appropriate mitigation zone distance from the animal 
continues to be maintained.
    (D) Incident reporting procedures. If a marine mammal vessel strike 
occurs, Navy personnel must follow the established incident reporting 
procedures.
    (vii) Towed in-water devices. Mitigation applies to devices that 
are towed from a manned surface platform or manned aircraft, or when a 
manned support craft is already participating in an activity involving 
in-water devices being towed by unmanned platforms. The mitigation will 
not be applied if the safety of the towing platform or in-water device 
is threatened.
    (A) Number of Lookouts and observation platform. One Lookout must 
be positioned on a manned towing platform or support craft.
    (B) Mitigation zone. 250 yd (228.6 m) around the towed in-water 
device for marine mammals (except those intentionally swimming 
alongside or choosing to swim alongside towing vessels, such as bow-
riding or wake-riding dolphins).
    (C) During activity. During the activity (i.e., when towing an in-
water device), Navy personnel must observe the mitigation zone for 
marine mammals; if a marine mammal is observed, Navy personnel must 
maneuver to maintain distance.
    (viii) Small-, medium-, and large-caliber non-explosive practice 
munitions. Gunnery activities using small-, medium-, and large-caliber 
non-explosive practice munitions. Mitigation applies to activities 
using a surface target.
    (A) Number of Lookouts and observation platform. One Lookout must 
be positioned on the platform conducting the activity. Depending on the 
activity, the Lookout could be the same as the one described for 
``Weapons firing noise'' in paragraph (a)(1)(iii)(A) of this section.
    (B) Mitigation zone. 200 yd (182.9 m) around the intended impact 
location.
    (C) Prior to activity. Prior to the initial start of the activity 
(e.g., when maneuvering on station), Navy personnel must observe the 
mitigation zone for floating vegetation and marine mammals; if floating 
vegetation or a marine mammal is observed, Navy personnel must relocate 
or delay the start of firing until the mitigation zone is clear of 
floating vegetation or until the conditions in paragraph 
(a)(1)(viii)(E) of this section are met for marine mammals.
    (D) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if a marine mammal is 
observed, Navy personnel must cease firing.
    (E) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing firing) until one of the following conditions has 
been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended impact location;
    (3) Clear of additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 minutes for aircraft-based 
firing or 30 minutes for vessel-based firing; or
    (4) Impact location transit. For activities using a mobile target, 
the intended impact location has transited a distance equal to double 
that of the mitigation zone size beyond the location of the last 
sighting.
    (ix) Non-explosive bombs. Non-explosive bombs.
    (A) Number of Lookouts and observation platform. One Lookout must 
be positioned in an aircraft.
    (B) Mitigation zone. 1,000 yd (914.4 m) around the intended target.
    (C) Prior to activity. Prior to the initial start of the activity 
(e.g., when arriving on station), Navy personnel must observe the 
mitigation zone for floating vegetation and marine mammals; if floating 
vegetation or a marine mammal is observed, Navy personnel must relocate 
or delay the start of bomb deployment until the mitigation zone is 
clear of floating vegetation or until the conditions in paragraph 
(a)(1)(ix)(E) of this section are met for marine mammals.
    (D) During activity. During the activity (e.g., during approach of 
the target), Navy personnel must observe the mitigation zone for marine 
mammals and, if a marine mammal is observed, Navy personnel must cease 
bomb deployment.
    (E) Commencement/recommencement conditions after a marine mammal 
sighting prior to or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing bomb deployment) until one of the following 
conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended target;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min; or
    (4) Intended target transit. For activities using mobile targets, 
the intended target has transited a distance equal to double that of 
the mitigation zone size beyond the location of the last sighting.
    (2) Mitigation areas. In addition to procedural mitigation, Navy 
personnel must implement mitigation measures within mitigation areas to 
avoid or reduce potential impacts on marine mammals.
    (i) North Pacific Right Whale Mitigation Area. Figure 1 shows the 
location of the mitigation area.
    (A) Surface ship hull-mounted MF1 mid-frequency active sonar. From 
June 1-September 30 within the North Pacific Right Whale Mitigation 
Area, Navy personnel must not use surface ship hull-mounted MF1 mid-
frequency active sonar during training.
    (B) National security exception. Should national security require 
that the Navy cannot comply with the restrictions in paragraph 
(a)(2)(i)(A) of this section, Navy personnel must obtain permission 
from the designated Command, U.S. Third Fleet Command Authority, prior 
to commencement of the activity. Navy personnel must provide NMFS with 
advance notification and include information about the event in its 
annual activity reports to NMFS.
    (ii) Continental Shelf and Slope Mitigation Area. Figure 1 shows 
the location of the mitigation area.
    (A) Explosives. Navy personnel must not detonate explosives below 
10,000 ft. altitude (including at the water surface) in the Continental 
Shelf and Slope Mitigation Area during training.
    (B) National security exception. Should national security require 
that the Navy cannot comply with the restrictions in paragraph 
(a)(2)(ii)(A) of this section, Navy personnel must obtain permission 
from the designated Command, U.S. Third Fleet Command Authority, prior 
to commencement of

[[Page 49762]]

the activity. Navy personnel must provide NMFS with advance 
notification and include information about the event in its annual 
activity reports to NMFS.
    (iii) Pre-event Awareness Notifications in the Temporary Maritime 
Activities Area. The Navy must issue pre-event awareness messages to 
alert vessels and aircraft participating in training activities within 
the TMAA to the possible presence of concentrations of large whales on 
the continental shelf and slope. Occurrences of large whales may be 
higher over the continental shelf and slope relative to other areas of 
the TMAA. Large whale species in the TMAA include, but are not limited 
to, fin whale, blue whale, humpback whale, gray whale, North Pacific 
right whale, sei whale, and sperm whale. To maintain safety of 
navigation and to avoid interactions with marine mammals, the Navy must 
instruct personnel to remain vigilant to the presence of large whales 
that may be vulnerable to vessel strikes or potential impacts from 
training activities. Additionally, Navy personnel must use the 
information from the awareness notification messages to assist their 
visual observation of applicable mitigation zones during training 
activities and to aid in the implementation of procedural mitigation.
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[GRAPHIC] [TIFF OMITTED] TP11AU22.005

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    (b) [Reserved]


Sec.  218.155   Requirements for monitoring and reporting.

    (a) Unauthorized take. Navy personnel must notify NMFS immediately 
(or as soon as operational security considerations allow) if the 
specified activity identified in Sec.  218.150 is thought to have 
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 
authorized under this subpart.
    (b) Monitoring and reporting under the LOA. The Navy must conduct 
all monitoring and reporting required under the LOA, including abiding 
by the U.S. Navy's Marine Species Monitoring Program. Details on 
program goals, objectives, project selection process, and current 
projects are available at www.navymarinespeciesmonitoring.us.
    (c) Notification of injured, live stranded, or dead marine mammals. 
Navy personnel must consult the Notification and Reporting Plan, which 
sets out notification, reporting, and

[[Page 49764]]

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) Annual GOA Marine Species Monitoring Report. The Navy must 
submit an annual report of the GOA Study Area monitoring, which will be 
included in a Pacific-wide monitoring report and include results 
specific to the GOA Study Area, describing the implementation and 
results from the previous calendar year. Data collection methods must 
be standardized across Pacific Range Complexes including the Mariana 
Islands Training and Testing (MITT), Hawaii-Southern California 
Training and Testing (HSTT), Northwest Training and Testing (NWTT), and 
Gulf of Alaska (GOA) Study Areas to allow for comparison among 
different geographic locations. The report must be submitted to the 
Director, Office of Protected Resources, NMFS, either within 3 months 
after the end of the calendar year, or within 3 months after the 
conclusion of the monitoring year, to be determined by the adaptive 
management process. NMFS will submit comments or questions on the 
report, if any, within 3 months of receipt. The report will be 
considered final after the Navy has addressed NMFS' comments, or 3 
months after submittal if NMFS does not provide comments on the report. 
This report will describe progress of knowledge made with respect to 
intermediate scientific objectives within the GOA Study Area associated 
with the Integrated Comprehensive Monitoring Program (ICMP). Similar 
study questions must be treated together so that progress on each topic 
can be summarized across all Navy ranges. The report need not include 
analyses and content that does not provide direct assessment of 
cumulative progress on the monitoring plan study questions. This will 
continue to allow the Navy to provide a cohesive monitoring report 
covering multiple ranges (as per ICMP goals), rather than entirely 
separate reports for the GOA, NWTT, HSTT, and MITT Study Areas.
    (e) GOA Annual Training Report. Each year in which training 
activities are conducted in the GOA Study Area, the Navy must submit 
one preliminary report (Quick Look Report) to NMFS detailing the status 
of applicable sound sources within 21 days after the completion of the 
training activities in the GOA Study Area. Each year in which 
activities are conducted, the Navy must also submit a detailed report 
(GOA Annual Training Report) to the Director, Office of Protected 
Resources, NMFS, within 3 months after completion of the training 
activities. NMFS must submit comments or questions on the report, if 
any, within one month of receipt. The report will be considered final 
after the Navy has addressed NMFS' comments, or one month after 
submittal if NMFS does not provide comments on the report. The annual 
reports must contain information about the Major Training Exercise 
(MTE), including the information listed in paragraphs (e)(1) and (2) of 
this section. The annual report, which is only required during years in 
which activities are conducted, must also contain cumulative sonar and 
explosive use quantity from previous years' reports through the current 
year. Additionally, if there were any changes to the sound source 
allowance in the reporting year, or cumulatively, the report must 
include a discussion of why the change was made and include analysis to 
support how the change did or did not affect the analysis in the GOA 
SEIS/OEIS and MMPA final rule. The analysis in the detailed report must 
be based on the accumulation of data from the current year's report and 
data collected from previous annual reports. The final annual/close-out 
report at the conclusion of the authorization period (year seven) will 
also serve as the comprehensive close-out report and include both the 
final year annual use compared to annual authorization as well as a 
cumulative 7-year annual use compared to 7-year authorization. This 
report must also note any years in which training did not occur. NMFS 
must submit comments on the draft close-out report, if any, within 3 
months of receipt. The report will be considered final after the Navy 
has addressed NMFS' comments, or 3 months after the submittal if NMFS 
does not provide comments. Information included in the annual reports 
may be used to inform future adaptive management of activities within 
the GOA Study Area. In addition to the information discussed above, the 
GOA Annual Training Report must include the following information.
    (1) MFAS/HFAS. The Navy must submit the following information for 
the MTE conducted in the GOA Study Area.
    (i) Exercise Information (for each MTE):
    (A) Exercise designator.
    (B) Date that exercise began and ended.
    (C) Location.
    (D) Number and types of active sources used in the exercise.
    (E) Number and types of passive acoustic sources used in exercise.
    (F) Number and types of vessels, aircraft, etc., participating in 
exercise.
    (G) Total hours of observation by Lookouts.
    (H) Total hours of all active sonar source operation.
    (I) Total hours of each active sonar source bin.
    (J) Wave height (high, low, and average during exercise).
    (ii) Individual marine mammal sighting information for each 
sighting in each exercise where mitigation was implemented:
    (A) Date/Time/Location of sighting.
    (B) Species (if not possible, indication of whale/dolphin/
pinniped).
    (C) Number of individuals.
    (D) Initial Detection Sensor (e.g., sonar or Lookout).
    (E) Indication of specific type of platform observation 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 to 1,828.8 m), or greater than 2,000 yd 
(1,828.8 m) from sonar source.
    (K) Sonar mitigation implementation. Whether operation of sonar 
sensor was delayed, or sonar was powered or shut down, and how long the 
delay was.
    (L) Bearing, direction, and motion. If source in use is hull-
mounted, true bearing of animal from ship, true direction of ship's 
travel, and estimation of animal's motion relative to ship (opening, 
closing, parallel).
    (M) Observed behavior. Lookouts shall report, in plain language and 
without trying to categorize in any way, the observed behavior of the 
animals (such as animal closing to bow ride, paralleling course/speed, 
floating on surface and not swimming, etc.) and if any calves present.
    (iii) Mitigation effectiveness evaluation. An evaluation (based on 
data gathered during all of the MTEs) of the effectiveness of 
mitigation measures designed to minimize the received level to which 
marine mammals may be exposed. This evaluation shall identify the 
specific observations that support any conclusions the Navy reaches 
about the effectiveness of the mitigation.
    (2) Summary of sources used. (i) This section shall include the 
following information summarized from the authorized sound sources used 
in all training events:

[[Page 49765]]

    (A) Total hours. Total annual hours or quantity (per the LOA) of 
each bin of sonar or other non-impulsive source; and
    (B) Number of explosives. Total annual number of each type of 
explosive exercises and total annual expended/detonated rounds (bombs, 
large-caliber projectiles) for each explosive bin.


Sec.  218.156   Letters of Authorization.

    (a) To incidentally take marine mammals pursuant to this subpart, 
the Navy must apply for and obtain an LOA in accordance with Sec.  
216.106 of this chapter.
    (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) If an LOA expires prior to the expiration date of this subpart, 
the Navy may apply for and obtain a renewal of the LOA.
    (d) In the event of projected changes to the activity or to 
mitigation, monitoring, or reporting (excluding changes made pursuant 
to the adaptive management provision of Sec.  218.157(c)(1)) required 
by an LOA issued under this subpart, the Navy must apply for and obtain 
a modification of the LOA as described in Sec.  218.157.
    (e) Each 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.
    (f) Issuance of the LOA will be based on a determination that the 
level of taking is consistent with the findings made for the total 
taking allowable under this subpart.
    (g) Notice of issuance or denial of the LOA will be published in 
the Federal Register within 30 days of a determination.


Sec.  218.157   Renewals and modifications of Letters of Authorization.

    (a) An LOA issued under Sec. Sec.  216.106 of this chapter and 
218.156 for the activity identified in Sec.  218.150(c) may be renewed 
or modified upon request by the applicant, provided that:
    (1) The planned specified activity and mitigation, monitoring, and 
reporting measures, as well as the anticipated impacts, are the same as 
those described and analyzed for this subpart (excluding changes made 
pursuant to the adaptive management provision in paragraph (c)(1) of 
this section); and
    (2) NMFS determines that the mitigation, monitoring, and reporting 
measures required by the previous LOA were implemented.
    (b) For LOA modification or renewal requests by the applicant that 
include changes to the activity or to the mitigation, monitoring, or 
reporting measures (excluding changes made pursuant to the adaptive 
management provision in paragraph (c)(1) of this section) that do not 
change the findings made for this subpart or result in no more than a 
minor change in the total estimated number of takes (or distribution by 
species or stock or years), NMFS may publish a notice of planned LOA in 
the Federal Register, including the associated analysis of the change, 
and solicit public comment before issuing the LOA.
    (c) An LOA issued under Sec. Sec.  216.106 of this chapter and 
218.156 may be modified by NMFS under the following circumstances:
    (1) After consulting with the Navy regarding the practicability of 
the modifications, NMFS may modify (including adding or removing 
measures) the existing mitigation, monitoring, or reporting measures if 
doing so creates a reasonable likelihood of more effectively 
accomplishing the goals of the mitigation and monitoring.
    (i) Possible sources of data that could contribute to the decision 
to modify the mitigation, monitoring, or reporting measures in an LOA 
include:
    (A) Results from the Navy's monitoring from the previous year(s);
    (B) Results from other marine mammal and/or sound research or 
studies; or
    (C) Any information that reveals marine mammals may have been taken 
in a manner, extent, or number not authorized by this subpart or a 
subsequent LOA.
    (ii) If, through adaptive management, the modifications to the 
mitigation, monitoring, or reporting measures are substantial, NMFS 
will publish a notice of planned LOA in the Federal Register and 
solicit public comment.
    (2) If NMFS determines that an emergency exists that poses a 
significant risk to the well-being of the species or stocks of marine 
mammals specified in LOAs issued pursuant to Sec. Sec.  216.106 of this 
chapter and 218.156, an LOA may be modified without prior notice or 
opportunity for public comment. Notice would be published in the 
Federal Register within 30 days of the action.


Sec.  218.158   [Reserved]

[FR Doc. 2022-16509 Filed 8-10-22; 8:45 am]
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