Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to U.S. Navy 2022 Ice Exercise Activities in the Arctic Ocean, 70451-70474 [2021-26762]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 86, Number 235 (Friday, December 10, 2021)]
[Notices]
[Pages 70451-70474]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-26762]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XB423]


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to U.S. Navy 2022 Ice Exercise 
Activities in the Arctic Ocean

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

ACTION: Notice; proposed incidental harassment authorization; request 
for

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comments on proposed authorization and possible renewal.

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SUMMARY: NMFS has received a request from the U.S. Navy (Navy) for 
authorization to take marine mammals incidental to Ice Exercise 2022 
(ICEX22) north of Prudhoe Bay, Alaska. Pursuant to the Marine Mammal 
Protection Act (MMPA), NMFS is requesting comments on its proposal to 
issue an incidental harassment authorization (IHA) to incidentally take 
marine mammals during the specified activities. NMFS is also requesting 
comments on a possible one-time, one-year renewal that could be issued 
under certain circumstances and if all requirements are met, as 
described in Request for Public Comments at the end of this notice. 
NMFS will consider public comments prior to making any final decision 
on the issuance of the requested MMPA authorization and agency 
responses will be summarized in the final notice of our decision. The 
Navy's activities are considered military readiness activities pursuant 
to the MMPA, as amended by the National Defense Authorization Act for 
Fiscal Year 2004 (2004 NDAA).

DATES: Comments and information must be received no later than January 
10, 2022.

ADDRESSES: Comments should be addressed to Jolie Harrison, Chief, 
Permits and Conservation Division, Office of Protected Resources, 
National Marine Fisheries Service, and should be submitted via email to 
[email protected].
    Instructions: NMFS is not responsible for comments sent by any 
other method, to any other address or individual, or received after the 
end of the comment period. Comments, including all attachments, must 
not exceed a 25-megabyte file size. All comments received are a part of 
the public record and will generally be posted online at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities without change. All 
personal identifying information (e.g., name, address) voluntarily 
submitted by the commenter may be publicly accessible. Do not submit 
confidential business information or otherwise sensitive or protected 
information.

FOR FURTHER INFORMATION CONTACT: Leah Davis, Office of Protected 
Resources, NMFS, (301) 427-8401. Electronic copies of the application 
and supporting documents, as well as a list of the references cited in 
this document, may be obtained online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities. In case of problems 
accessing these documents, please call the contact listed above.

SUPPLEMENTARY INFORMATION:

Background

    The MMPA prohibits the ``take'' of marine mammals, with certain 
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to 
allow, upon request, the incidental, but not intentional, taking of 
small numbers of marine mammals by U.S. citizens who engage in a 
specified activity (other than commercial fishing) within a specified 
geographical region if certain findings are made and either regulations 
are proposed or, if the taking is limited to harassment, a notice of a 
proposed incidental harassment authorization is provided to the public 
for review.
    Authorization for incidental takings shall be granted if NMFS finds 
that the taking will have a negligible impact on the species or 
stock(s) and will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for taking for subsistence uses 
(where relevant). Further, NMFS must prescribe the permissible methods 
of taking 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 the species or stocks for 
taking for certain subsistence uses (referred to in shorthand as 
``mitigation''); and requirements pertaining to the mitigation, 
monitoring, and reporting of the takings are set forth.
    The 2004 NDAA (Pub. L. 108-136) removed the ``small numbers'' and 
``specified geographical region'' limitations indicated above and 
amended the definition of ``harassment'' as applied to a ``military 
readiness activity.'' The activity for which incidental take of marine 
mammals is being requested addressed here qualifies as a military 
readiness activity. The definitions of all applicable MMPA statutory 
terms cited above are included in the relevant sections below.

National Environmental Policy Act

    To comply with the National Environmental Policy Act of 1969 (NEPA; 
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, 
NMFS must review our proposed action (i.e., the issuance of an IHA) 
with respect to potential impacts on the human environment. 
Accordingly, NMFS plans to adopt the Navy's Environmental Assessment 
(EA), provided our independent evaluation of the document finds that it 
includes adequate information analyzing the effects on the human 
environment of issuing the IHA. The Navy's EA was made available for 
public comment at https://www.nepa.navy.mil/icex/ for 30 days beginning 
November 24, 2021.
    We will review all comments submitted in response to this notice 
prior to concluding our NEPA process or making a final decision on the 
IHA request.

Summary of Request

    On August 26, 2021, NMFS received a request from the Navy for an 
IHA to take marine mammals incidental to submarine training and testing 
activities including establishment of a tracking range on an ice floe 
in the Arctic Ocean, north of Prudhoe Bay, Alaska. The application was 
deemed adequate and complete on November 4, 2021. The Navy's request is 
for take of a small number of ringed seals (Pusa hispida) by Level B 
harassment only. Neither the Navy nor NMFS expects serious injury or 
mortality to result from this activity and, therefore, an IHA is 
appropriate.
    NMFS previously issued IHAs to the Navy for similar activities (83 
FR 6522; February 14, 2018, 85 FR 6518; February 5, 2020). The Navy 
complied with all the requirements (e.g., mitigation, monitoring, and 
reporting) of the previous IHAs and information regarding their 
monitoring results may be found below, in the Estimated Take section.

Description of Proposed Activity

Overview

    The Navy proposes to conduct submarine training and testing 
activities, which includes the establishment of a tracking range and 
temporary ice camp, and research in the Arctic Ocean for six weeks 
beginning in February 2022. Submarine active acoustic transmissions may 
result in occurrence of Level B harassment, including temporary hearing 
impairment (temporary threshold shift (TTS)) and behavioral harassment, 
of ringed seals.

Dates and Duration

    The specified activities would occur over approximately a six-week 
period between February and April 2022, including deployment and 
demobilization of the ice camp. The submarine training and testing 
activities would occur over approximately four weeks during the six-
week period. The proposed IHA would be effective from

[[Page 70453]]

February 1, 2022 through April 30, 2022.

Geographic Region

    The ice camp would be established approximately 100-200 nautical 
miles (nmi) north of Prudhoe Bay, Alaska. The exact location of the 
camp cannot be identified ahead of time as required conditions (e.g., 
ice cover) cannot be forecasted until exercises are expected to 
commence. Prior to the establishment of the ice camp, reconnaissance 
flights would be conducted to locate suitable ice conditions. The 
reconnaissance flights would cover an area of approximately 70,374 
square kilometers (km\2\). The actual ice camp would be no more than 
1.6 kilometers (km) in diameter (approximately 2 km\2\ in area). The 
vast majority of submarine training and testing would occur near the 
ice camp, however some submarine training and testing may occur 
throughout the deep Arctic Ocean basin near the North Pole within the 
larger Navy Activity Study Area. Figure 1 shows the locations of the 
Navy Activity Study Area and Ice Camp Study Area, collectively referred 
to in this document as the ``ICEX22 Study Area''.
BILLING CODE 3510-22-P

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[GRAPHIC] [TIFF OMITTED] TN10DE21.018

BILLING CODE 3510-22-C

Detailed Description of Specific Activity

    The Navy proposes to conduct submarine training and testing 
activities, which includes the establishment of a tracking range and 
temporary ice camp, and research in the Arctic Ocean for six weeks 
beginning in February 2022. The activity proposed for 2022 and that is 
being evaluated for this proposed IHA-ICEX22-is part of a regular cycle 
of recurring training and testing activities that the Navy proposes to 
conduct in the Arctic. Under the Navy's proposed cycle, submarine and 
tracking range activities would be conducted biennially, but a 
temporary ice camp would be established annually, either in the ice 
camp study area (Figure 1) or on a frozen lake in Deadhorse, Alaska. 
Some of the

[[Page 70455]]

submarine training and testing may occur throughout the deep Arctic 
Ocean basin near the North Pole, within the Navy Activity Study Area 
(Figure 1). The temporary ice camps that would be constructed during 
years in which submarine training and testing is not conducted 
(referred to as ``beta camps'') would support testing and evaluation of 
Arctic equipment, but would involve fewer personnel and be shorter in 
duration than camps constructed during years in which submarine 
training and testing is conducted. Activities that the Navy proposes to 
conduct after ICEX22, including the construction of the beta camps, are 
outside of the scope of this proposed IHA, and therefore, are not 
discussed further in this document. Additional information about the 
Navy's proposed training and testing activities in the Arctic is 
available in the Navy's 2021 Draft Environmental Assessment/Overseas 
Environmental Assessment For the Ice Exercise Program, available at 
https://www.nepa.navy.mil/icex/. Only activities which may occur during 
ICEX22 are discussed in this section.
Ice Camp
    ICEX22 includes the deployment of a temporary camp situated on an 
ice floe. Reconnaissance flights to search for suitable ice conditions 
for the ice camp would depart from the public airport in Deadhorse, 
Alaska. The camp generally would consist of a command hut, dining hut, 
sleeping quarters, a powerhouse, runway, and helipad. The number of 
structures and tents would range from 15-20, and each tent is typically 
2 meters (m) by 6 m in size. The completed ice camp, including runway, 
would be approximately 1.6 km in diameter. Support equipment for the 
ice camp would include snowmobiles, gas-powered augers and saws (for 
boring holes through ice), and diesel generators. All ice camp 
materials, fuel, and food would be transported from Prudhoe Bay, 
Alaska, and delivered by air-drop from military transport aircraft 
(e.g., C-17 and C-130), or by landing at the ice camp runway (e.g., 
small twin-engine aircraft and military and commercial helicopters).
    A portable tracking range for submarine training and testing would 
be installed in the vicinity of the ice camp. Ten hydrophones, located 
on the ice and extending to 30 m below the ice, would be deployed by 
drilling or melting holes in the ice and lowering the cable down into 
the water column. Four hydrophones would be physically connected to the 
command hut via cables while the others would transmit data via radio 
frequencies. Additionally, tracking pingers would be configured aboard 
each submarine to continuously monitor the location of the submarines. 
Acoustic communications with the submarines would be used to coordinate 
the training and research schedule with the submarines. An underwater 
telephone would be used as a backup to the acoustic communications.
    Additional information about the ICEX22 ice camp is located in the 
2021 Draft Environmental Assessment/Overseas Environmental Assessment 
For the Ice Exercise Program. We have carefully reviewed this 
information and determined that activities associated with the ICEX22 
ice camp, including de minimis acoustic communications, would not 
result in incidental take of marine mammals.
Submarine Activities
    Submarine activities associated with ICEX22 generally would entail 
safety maneuvers, active sonar use, and exercise weapon use. The safety 
maneuvers and sonar use are similar to submarine activities conducted 
in other undersea environments and are being conducted in the Arctic to 
test their performance in a cold environment. The Navy anticipates the 
use of no more than 20 exercise weapons during ICEX22. The exercise 
weapons are inert (i.e., no explosives), and will be recovered by 
divers, who enter the water through melted holes, approximately 3-4 
feet wide. Submarine training and testing involves active acoustic 
transmissions, which have the potential to harass marine mammals. The 
Navy categorizes acoustic sources into ``bins'' based on frequency, 
source level, and mode of usage (U.S. Department of the Navy, 2013). 
The acoustic transmissions associated with submarine training fall 
within bins HF1 (hull-mounted submarine sonars that produce high-
frequency [greater than 10 kHz but less than 200 kHz] signals), M3 
(mid-frequency [1-10 kHz] acoustic modems greater than 190 dB re 1 
[micro]Pa), and TORP2 (heavyweight torpedo), as defined in the Navy's 
Phase III at-sea environmental documentation (see Section 3.0.3.3.1, 
Acoustic Stressors, of the 2018 AFTT Final Environmental Impact 
Statement/Overseas Environmental Impact Statement, available at https://www.nepa.navy.mil/AFTT-Phase-III/). The specifics of ICEX22 submarine 
acoustic sources are classified, including the parameters associated 
with the designated bins. Details of source use for submarine training 
are also classified. Any ICEX-specific acoustic sources not captured 
under one of the at-sea bins were modeled using source-specific 
parameters.
    Aspects of submarine training and testing activities other than 
active acoustic transmissions are fully analyzed within the 2021 Draft 
Environmental Assessment/Overseas Environmental Assessment for the Ice 
Exercise Program. We have carefully reviewed and discussed with the 
Navy these other aspects, such as vessel use and the firing of inert 
exercise weapons, and determined that aspects of submarine training and 
testing other than active acoustic transmissions would not result in 
take of marine mammals. These other aspects are therefore not discussed 
further, with the exception of potential vessel strike or exercise 
weapon strike, which are discussed in the Potential Effects of 
Specified Activities on Marine Mammals and Their Habitat section.
Research Activities
    Personnel and equipment proficiency testing and multiple research 
and development activities would be conducted as part of ICEX22. In-
water device data collection and unmanned underwater vehicle testing 
involve active acoustic transmissions, which have the potential to 
harass marine mammals; however, the acoustic transmissions that would 
be used in ICEX22 for research activities are de minimis. The Navy has 
defined de minimis sources as having the following parameters: Low 
source levels, narrow beams, downward directed transmission, short 
pulse lengths, frequencies above (outside) known marine mammal hearing 
ranges, or some combination of these factors (U.S. Department of the 
Navy, 2013). NMFS reviewed the Navy's analysis and conclusions on de 
minimis sources and finds them complete and supportable. Additional 
information about ICEX22 research activities is located in Table 2-1 of 
the 2021 Draft Environmental Assessment/Overseas Environmental 
Assessment For the Ice Exercise Program, and elsewhere in that 
document. We have carefully reviewed this information and determined 
that use of acoustic transmissions during research activities 
associated with ICEX22 would not result in incidental take of marine 
mammals. The possibility of vessel strikes caused by use of unmanned 
underwater vehicles during ICEX22 is discussed in the Potential Effects 
of Vessel Strike subsection within the Potential Effects of Specified 
Activities on Marine Mammals and Their Habitat section.
    Proposed mitigation, monitoring, and reporting measures are 
described in detail later in this document (please see

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Proposed Mitigation and Proposed Monitoring and Reporting).

Description of Marine Mammals in the Area of Specified Activities

    Sections 3 and 4 of the application summarize available information 
regarding status and trends, distribution and habitat preferences, and 
behavior and life history of the potentially affected species. 
Additional information regarding population trends and threats may be 
found in NMFS's Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments) and more general information about these species 
(e.g., physical and behavioral descriptions) may be found on NMFS's 
website (https://www.fisheries.noaa.gov/find-species).
    Table 1 lists all species or stocks for which take is expected and 
proposed to be authorized, and summarizes information related to the 
population or stock, including regulatory status under the MMPA and the 
Endangered Species Act (ESA; 16 U.S.C. 1531 et seq.) and potential 
biological removal (PBR), where known. For taxonomy, we follow 
Committee on Taxonomy (2021). PBR is defined by the MMPA as the maximum 
number of animals, not including natural mortalities, that may be 
removed from a marine mammal stock while allowing that stock to reach 
or maintain its optimum sustainable population (as described in NMFS's 
SARs). While no serious injury or mortality is anticipated or 
authorized here, PBR and annual serious injury and mortality from 
anthropogenic sources are included in Table 1 as gross indicators of 
the status of the species and other threats.
    Marine mammal abundance estimates represent the total number of 
individuals that make up a given stock or the total number estimated 
within a particular study or survey area. NMFS's stock abundance 
estimates for most species represent the total estimate of individuals 
within the geographic area, if known, that comprises that stock. For 
some species, this geographic area may extend beyond U.S. waters. All 
managed stocks in this region are assessed in NMFS's U.S. Alaska SARs 
(Muto et al. 2021). All values presented in Table 1 are the most recent 
available at the time of publication and are available in the 2020 
Alaska SAR (Muto et al. 2021) and draft 2021 Alaska SAR (available 
online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports).

                    Table 1--Species That Spatially Co-Occur With the Activity to the Degree That Take Is Reasonably Likely To Occur
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                                                                                         ESA/MMPA status;    Stock abundance  (CV;
             Common name                  Scientific name               Stock             strategic (Y/N)      Nmin; most recent       PBR     Annual M/
                                                                                                \1\          abundance survey) \2\               SI \3\
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Family Phocidae (earless seals):
    Ringed seal.....................  Pusa hispida...........  Arctic.................  T/D; Y              171,418,\4\ \5\ (N/A,   \6\ 4,755  \7\ 6,459
                                                                                                             158,507;\4\ \5\ 2013).
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\1\ ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). Under the MMPA, a strategic stock is one for which the level of direct human-
  caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species
  or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\2\ NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments assessments. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.
\3\ This value, found in NMFS's SARs, represents annual levels of human-caused mortality (M) plus serious injury (SI) from all sources combined (e.g.,
  commercial fisheries, ship strike).
\4\ These estimates reflect the Bering Sea population only, as reliable abundance estimates for the Chukchi Sea and Beaufort Sea are not available.
\5\ This is expected to be an underestimate of ringed seals in the Bering Sea, as the estimate was not adjusted for seals in the water at the time of
  the surveys, nor does it include ringed seals in the shorefast ice zone.
\6\ The PBR value for this stock is based on a partial stock abundance estimate, and is therefore an underestimate for the full stock.
\7\ The majority of the M/SI for this stock (6,454 of 6,459 animals) is a result of the Alaska Native subsistence harvest. While M/SI appears to exceed
  PBR, given that the reported PBR is based on a partial stock abundance estimate, and is therefore, an underestimate for the full stock, M/SI likely
  does not exceed PBR.

    As indicated in Table 1, ringed seals (with one managed stock) 
temporally and spatially co-occur with the activity to the degree that 
take is reasonably likely to occur, and we have proposed authorizing 
it. While beluga whales (Delphinapterus leucas), gray whales 
(Eschrichtius robustus), bowhead whales (Balaena mysticetus), and 
spotted seals (Phoca largha), may occur in the ICEX22 Study Area, the 
temporal and/or spatial occurrence is such that take is not expected to 
occur, and they are not discussed further beyond the explanation 
provided here. Bowhead whales are unlikely to occur in the ICEX22 Study 
Area between February and April, as they spend winter (December to 
March) in the northern Bering Sea and southern Chukchi Sea, and migrate 
north through the Chukchi Sea and Beaufort Sea during April and May 
(Muto et al. 2021). On their spring migration, the earliest that 
bowhead whales reach Point Hope in the Chukchi Sea, well south of Point 
Barrow, is late March to mid-April (Braham et al. 1980). Although the 
ice camp location is not known with certainty, the distance between 
Point Barrow and the closest edge of the Ice Camp Study Area is over 
200 km. The distance between Point Barrow and the closest edge of the 
Navy Activity Study Area is over 50 km, and the distance between Point 
Barrow and Point Hope is an additional 525 km (straight line distance); 
accordingly, bowhead whales are unlikely to occur in the ICEX22 Study 
Area before ICEX22 activities conclude. Beluga whales follow a 
migration pattern similar to bowhead whales. They typically overwinter 
in the Bering Sea and migrate north during the spring to the eastern 
Beaufort Sea where they spend the summer and early fall months (Muto et 
al. 2021). Though the beluga whale migratory path crosses through the 
ICEX22 Study Area, they are unlikely to occur in the ICEX 22 Study Area 
between February and April. Gray whales feed primarily in the Beaufort 
Sea, Chukchi Sea, and Northwestern Bering Sea during the summer and 
fall, but migrate south to winter in Baja California lagoons (Muto et 
al. 2020). Typically, northward migrating gray whales do not reach the 
Bering Sea before May or June (Frost and Karpovich 2008), after the 
ICEX22 activities would occur, and several hundred kilometers south of 
the ICEX22 Study Area. Further, gray whales are primarily bottom 
feeders (Swartz et al. 2006) in water less than 60 m deep (Pike 1962). 
Therefore, on the rare occasion that a gray whale does overwinter in 
the Beaufort Sea (Stafford et al. 2007), we would expect an 
overwintering

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individual to remain in shallow water over the continental shelf where 
it could feed. Therefore, gray whales are not expected to occur in the 
ICEX22 Study Area during the ICEX22 activity period. Spotted seals may 
also occur in the ICEX22 Study Area during summer and fall, but they 
are not expected to occur in the ICEX22 Study Area during the ICEX22 
timeframe (Muto et al. 2020).
    Further, while the Navy requested take of bearded seals (Erignathus 
barbatus), which do occur in the ICEX22 Study Area during the project 
timeframe, NMFS does not expect that bearded seals would occur in the 
areas near the ice camp or where submarine activities involving active 
acoustics would occur, and therefore incidental take is not anticipated 
to occur and has not been proposed for authorization. Bearded seals are 
not discussed further beyond the explanation provided here. The Navy 
anticipates that the ice camp would be established 100-200 nmi (185-370 
km) north of Prudhoe Bay in water depths of 800 m or more, and also 
that submarine training and testing activities would occur in water 
depths of 800 m or more. Although bearded seals occur 20 to 100 nmi (37 
to 185 km) offshore during spring (Simpkins et al. 2003, Bengtson et 
al. 2005), they feed heavily on benthic organisms (Hamilton et al. 
2018; Hjelset et al. 1999; Fedoseev 1965), and during winter bearded 
seals are expected to select habitats where food is abundant and easily 
accessible to minimize the energy required to forage and maximize 
energy reserves in preparation for whelping, lactation, mating, and 
molting. Bearded seals are not known to dive as deep as 800 m to forage 
(Boveng and Cameron, 2013; Cameron and Boveng 2009; Cameron et al. 
2010; Gjertz et al. 2000; Kovacs 2002) and it is highly unlikely that 
they would occur near the ice camp or where the submarine activities 
would be conducted.
    In addition, the polar bear (Ursus maritimus) may be found in the 
ICEX22 Study Area. However, polar bears are managed by the U.S. Fish 
and Wildlife Service and are not considered further in this document.

Ringed Seal

    Ringed seals are the most common pinniped in the ICEX22 Study Area 
and have wide distribution in seasonally and permanently ice-covered 
waters of the Northern Hemisphere (North Atlantic Marine Mammal 
Commission 2004), though the status of the Arctic stock of ringed seals 
is unknown (Muto et al. 2020). Throughout their range, ringed seals 
have an affinity for ice-covered waters and are well adapted to 
occupying both shore-fast and pack ice (Kelly 1988c). Ringed seals can 
be found further offshore than other pinnipeds since they can maintain 
breathing holes in ice thickness greater than 2 m (Smith and Stirling 
1975). Breathing holes are maintained by ringed seals' sharp teeth and 
claws on their fore flippers. They remain in contact with ice most of 
the year and use it as a platform for molting in late spring to early 
summer, for pupping and nursing in late winter to early spring, and for 
resting at other times of the year (Muto et al. 2020).
    Ringed seals have at least two distinct types of subnivean lairs: 
Haul-out lairs and birthing lairs (Smith and Stirling 1975). Haul-out 
lairs are typically single-chambered and offer protection from 
predators and cold weather. Birthing lairs are larger, multi-chambered 
areas that are used for pupping in addition to protection from 
predators. Ringed seal populations pup on both land-fast ice as well as 
stable pack ice. Lentfer (1972) found that ringed seals north of 
Barrow, Alaska (which would be west of the ice camp), build their 
subnivean lairs on the pack ice near pressure ridges. They are also 
assumed to occur within the sea ice in the proposed ice camp area. 
Ringed seals excavate subnivean lairs in drifts over their breathing 
holes in the ice, in which they rest, give birth, and nurse their pups 
for 5-9 weeks during late winter and spring (Chapskii 1940; McLaren 
1958; Smith and Stirling 1975). Snow depths of at least 50-65 
centimeters (cm) are required for functional birth lairs (Kelly 1988b; 
Lydersen 1998; Lydersen and Gjertz 1986; Smith and Stirling 1975), and 
such depths typically occur only where 20-30 cm or more of snow has 
accumulated on flat ice and then drifted along pressure ridges or ice 
hummocks (Hammill 2008; Lydersen et al. 1990; Lydersen and Ryg 1991; 
Smith and Lydersen 1991). Ringed seal birthing season typically begins 
in March, but the majority of births occur in early April. About a 
month after parturition, mating begins in late April and early May.
    In Alaskan waters, during winter and early spring when sea ice is 
at its maximal extent, ringed seals are abundant in the northern Bering 
Sea, Norton and Kotzebue Sounds, and throughout the Chukchi and 
Beaufort Seas (Frost 1985; Kelly 1988c), including in the ICEX22 Study 
Area. Passive acoustic monitoring (PAM) of ringed seals from a high-
frequency recording package deployed at a depth of 240 m in the Chukchi 
Sea, 120 km north-northwest of Barrow, Alaska, detected ringed seals in 
the area between mid-December and late May over a four year study 
(Jones et al. 2014). With the onset of the fall freeze, ringed seal 
movements become increasingly restricted and seals will either move 
west and south with the advancing ice pack, with many seals dispersing 
throughout the Chukchi and Bering Seas, or remain in the Beaufort Sea 
(Crawford et al. 2012; Frost and Lowry 1984; Harwood et al. 2012). 
Kelly et al. (2010a) tracked home ranges for ringed seals in the 
subnivean period (using shorefast ice); the size of the home ranges 
varied from less than 1 km\2\ up to 27.9 km\2\ (median of 0.62 km\2\ 
for adult males and 0.65 km\2\ for adult females). Most (94 percent) of 
the home ranges were less than 3 km\2\ during the subnivean period 
(Kelly et al. 2010a). Near large polynyas, ringed seals maintain ranges 
up to 7,000 km\2\ during winter and 2,100 km\2\ during spring (Born et 
al. 2004). Some adult ringed seals return to the same small home ranges 
they occupied during the previous winter (Kelly et al. 2010a). The size 
of winter home ranges can vary by up to a factor of 10 depending on the 
amount of fast ice; seal movements were more restricted during winters 
with extensive fast ice, and were much less restricted where fast ice 
did not form at high levels (Harwood et al. 2015). Ringed seals may 
occur within the ICEX22 Study Area throughout the year and during the 
proposed specified activities.

Critical Habitat

    On January 8, 2021, NMFS published a revised proposed rule for the 
Designation of Critical Habitat for the Arctic Subspecies of the Ringed 
Seal (86 FR 1452). This proposed rule revises NMFS' December 9, 2014, 
proposed designation of critical habitat for the Arctic subspecies of 
the ringed seal under the ESA. NMFS identified the physical and 
biological features essential to the conservation of the species: (1) 
Snow-covered sea ice habitat suitable for the formation and maintenance 
of subnivean birth lairs used for sheltering pups during whelping and 
nursing, which is defined as areas of seasonal landfast (shorefast) ice 
and dense, stable pack ice, excluding any bottom-fast ice extending 
seaward from the coastline (typically in waters less than 2 m deep), 
that have undergone deformation and contain snowdrifts of sufficient 
depth, typically at least 54 cm deep; (2) Sea ice habitat suitable as a 
platform for basking and molting, which is defined as areas containing 
sea ice of 15 percent or more concentration, excluding any bottom-fast 
ice extending seaward from the

[[Page 70458]]

coastline (typically in waters less than 2 m deep); and (3) Primary 
prey resources to support Arctic ringed seals, which are defined to be 
Arctic cod, saffron cod, shrimps, and amphipods. The revised proposed 
critical habitat designation comprises a specific area of marine 
habitat in the Bering, Chukchi, and Beaufort seas, extending from mean 
lower low water to an offshore limit within the U.S. Exclusive Economic 
Zone, including a portion of the ICEX22 Study Area (86 FR 1452; January 
8, 2021). See the proposed ESA critical habitat rule for additional 
detail and a map of the proposed area.
    The proposed ice camp study area was excluded from the proposed 
ringed seal critical habitat because the benefits of exclusion due to 
national security impacts outweighed the benefits of inclusion of this 
area (86 FR 1452; March 9, 2021). However, as stated in NMFS' second 
revised proposed rule for the Designation of Critical Habitat for the 
Arctic Subspecies of the Ringed Seal (86 FR 1452; March 9, 2021), the 
area proposed for exclusion contains one or more of the essential 
features of the Arctic ringed seal's critical habitat, although data 
are limited to inform NMFS' assessment of the relative value of this 
area to the conservation of the species. As noted above, a portion of 
the proposed ringed seal critical habitat overlaps the larger proposed 
ICEX22 Study Area. This overlap includes the portion of the Navy 
Activity Study Area that overlaps the U.S. EEZ. However, as described 
later and in more detail in the Potential Effects of Specified 
Activities on Marine Mammals and Their Habitat section, we do not 
anticipate physical impacts to any marine mammal habitat as a result of 
the Navy's ICEX activities, including impacts to ringed seal sea ice 
habitat suitable as a platform for basking and molting and impacts on 
prey availability. Further, this proposed IHA includes mitigation 
measures, as described in the Proposed Mitigation section, that would 
minimize or prevent impacts to sea ice habitat suitable for the 
formation and maintenance of subnivean birth lairs.

Ice Seal Unusual Mortality Event

    Since June 1, 2018, elevated strandings of ringed seals, bearded 
seals, and spotted seals have occurred in the Bering and Chukchi Seas. 
This event has been declared an Unusual Mortality Event (UME). A UME is 
defined under the MMPA as a stranding that is unexpected; involves a 
significant die-off of any marine mammal population; and demands 
immediate response. From June 1, 2018 to November 17, 2021, there have 
been at least 368 dead seals reported; 106 bearded seals, 95 ringed 
seals, 62 spotted seals, and 105 unidentified seals. All age classes of 
seals have been reported stranded, and a subset of seals have been 
sampled for genetics and harmful algal bloom exposure, with a few 
having histopathology collected. Results are pending, and the cause of 
the UME remains unknown.
    There was a previous UME involving ice seals (which, in Alaska, 
includes bearded seals, ringed seals, ribbon seals, and spotted seals) 
from 2011 to 2016, which was most active in 2011-2012. A minimum of 657 
seals were affected. The UME investigation determined that some of the 
clinical signs were due to an abnormal molt, but a definitive cause of 
death for the UME was never determined. The number of stranded ice 
seals involved in this current UME, and their physical characteristics, 
is not at all similar to the 2011-2016 UME, as the seals in the current 
UME are not exhibiting hair loss or skin lesions, which were a primary 
finding in the 2011-2016 UME. The investigation into the cause of the 
current UME is ongoing.
    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 seals, and determine the next steps for the 
investigation. More detailed information is available at: https://www.fisheries.noaa.gov/alaska/marine-life-distress/2018-2021-ice-seal-unusual-mortality-event-alaska.

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 
decibel (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. Marine mammal hearing 
groups and their associated hearing ranges are provided in Table 2.

                  Table 2--Marine Mammal Hearing Groups
                              [NMFS, 2018]
------------------------------------------------------------------------
            Hearing group                 Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen  7 Hz to 35 kHz.
 whales).
Mid-frequency (MF) cetaceans          150 Hz to 160 kHz.
 (dolphins, toothed whales, beaked
 whales, bottlenose whales).
High-frequency (HF) cetaceans (true   275 Hz to 160 kHz.
 porpoises, Kogia, river dolphins,
 cephalorhynchid, Lagenorhynchus
 cruciger and L. australis).
Phocid pinnipeds (PW) (underwater)    50 Hz to 86 kHz.
 (true seals).
Otariid pinnipeds (OW) (underwater)   60 Hz to 39 kHz.
 (sea lions and fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
  composite (i.e., all species within the group), where individual
  species' hearing ranges are typically not as broad. Generalized
  hearing range chosen based on ~65 dB threshold from normalized
  composite audiogram, with the exception for lower limits for LF
  cetaceans (Southall et al. 2007) and PW pinniped (approximation).


[[Page 70459]]

    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 detail concerning these groups and associated frequency 
ranges, please see NMFS (2018) for a review of available information. 
Only ringed seals (a phocid pinniped species) have the reasonable 
potential to co-occur with the proposed ICEX22 activities.

Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat

    This section includes a summary and discussion of the ways that 
components of the specified activity may impact marine mammals and 
their habitat. The Estimated Take section later in this document 
includes a quantitative analysis of the number of individuals that are 
expected to be taken by this activity. The Negligible Impact Analysis 
and Determination section considers the content of this section, the 
Estimated Take section, and the Proposed Mitigation section, to draw 
conclusions regarding the likely impacts of these activities on the 
reproductive success or survivorship of individuals and how those 
impacts on individuals are likely to impact marine mammal species or 
stocks.

Description of Sound Sources

    Here, we first provide background information on marine mammal 
hearing before discussing the potential effects of the use of active 
acoustic sources on marine mammals.
    Sound travels in waves, the basic components of which are 
frequency, wavelength, velocity, and amplitude. Frequency is the number 
of pressure waves that pass by a reference point per unit of time and 
is measured in Hz or cycles per second. Wavelength is the distance 
between two peaks of a sound wave; lower frequency sounds have longer 
wavelengths than higher frequency sounds and attenuate (decrease) more 
rapidly in shallower water. Amplitude is the height of the sound 
pressure wave or the `loudness' of a sound and is typically measured 
using the dB scale. A dB is the ratio between a measured pressure (with 
sound) and a reference pressure (sound at a constant pressure, 
established by scientific standards). It is a logarithmic unit that 
accounts for large variations in amplitude; therefore, relatively small 
changes in dB ratings correspond to large changes in sound pressure. 
When referring to sound pressure levels (SPLs; the sound force per unit 
area), sound is referenced in the context of underwater sound pressure 
to 1 microPascal ([mu]Pa). One pascal is the pressure resulting from a 
force of one newton exerted over an area of one square meter. The 
source level (SL) represents the sound level at a distance of 1 m from 
the source (referenced to 1 [mu]Pa). The received level is the sound 
level at the listener's position. Note that all underwater sound levels 
in this document are referenced to a pressure of 1 [micro]Pa.
    Root mean square (RMS) is the quadratic mean sound pressure over 
the duration of an impulse. RMS is calculated by squaring all of the 
sound amplitudes, averaging the squares, and then taking the square 
root of the average (Urick 1983). RMS accounts for both positive and 
negative values; squaring the pressures makes all values positive so 
that they may be accounted for in the summation of pressure levels 
(Hastings and Popper 2005). This measurement is often used in the 
context of discussing behavioral effects, in part because behavioral 
effects, which often result from auditory cues, may be better expressed 
through averaged units than by peak pressures.
    When underwater objects vibrate or activity occurs, sound-pressure 
waves are created. These waves alternately compress and decompress the 
water as the sound wave travels. Underwater sound waves radiate in all 
directions away from the source (similar to ripples on the surface of a 
pond), except in cases where the source is directional. The 
compressions and decompressions associated with sound waves are 
detected as changes in pressure by aquatic life and man-made sound 
receptors such as hydrophones.
    Even in the absence of sound from the specified activity, the 
underwater environment is typically loud due to ambient sound. Ambient 
sound is defined as environmental background sound levels lacking a 
single source or point (Richardson et al. 1995), and the sound level of 
a region is defined by the total acoustical energy being generated by 
known and unknown sources. These sources may include physical (e.g., 
waves, earthquakes, ice, atmospheric sound), biological (e.g., sounds 
produced by marine mammals, fish, and invertebrates), and anthropogenic 
sound (e.g., vessels, dredging, aircraft, construction). A number of 
sources contribute to ambient sound, including the following 
(Richardson et al. 1995):
     Wind and waves: The complex interactions between wind and 
water surface, including processes such as breaking waves and wave-
induced bubble oscillations and cavitation, are a main source of 
naturally occurring ambient noise for frequencies between 200 Hz and 50 
kHz (Mitson, 1995). Under sea ice, noise generated by ice deformation 
and ice fracturing may be caused by thermal, wind, drift, and current 
stresses (Roth et al. 2012);
     Precipitation: Sound from rain and hail impacting the 
water surface can become an important component of total noise at 
frequencies above 500 Hz, and possibly down to 100 Hz during quiet 
times. In the ice-covered ICEX22 Study Area, precipitation is unlikely 
to impact ambient sound;
     Biological: Marine mammals can contribute significantly to 
ambient noise levels, as can some fish and shrimp. The frequency band 
for biological contributions is from approximately 12 Hz to over 100 
kHz; and
     Anthropogenic: Sources of ambient noise related to human 
activity include transportation (surface vessels and aircraft), 
dredging and construction, oil and gas drilling and production, seismic 
surveys, sonar, explosions, and ocean acoustic studies. Shipping noise 
typically dominates the total ambient noise for frequencies between 20 
and 300 Hz. In general, the frequencies of anthropogenic sounds are 
below 1 kHz and, if higher frequency sound levels are created, they 
attenuate rapidly (Richardson et al. 1995). Sound from identifiable 
anthropogenic sources other than the activity of interest (e.g., a 
passing vessel) is sometimes termed background sound, as opposed to 
ambient sound. Anthropogenic sources are unlikely to significantly 
contribute to ambient underwater noise during the late winter and early 
spring in the ICEX22 Study Area as most anthropogenic activities would 
not be active due to ice cover (e.g. seismic surveys, shipping; Roth et 
al. 2012).
    The sum of the various natural and anthropogenic sound sources at 
any given location and time--which comprise ``ambient'' or 
``background'' sound--depends not only on the source levels (as 
determined by current weather conditions and levels of biological and 
shipping activity) but also on the ability of sound to propagate 
through the environment. In turn, sound propagation is dependent on the 
spatially and temporally varying properties of the water column and sea 
floor, and is frequency-dependent. As a result of the dependence on a 
large number of varying factors, ambient sound levels can be expected 
to vary widely over both coarse and fine spatial and temporal scales. 
Sound levels at a given frequency and location can vary by 10-20 dB 
from day to day

[[Page 70460]]

(Richardson et al. 1995). The result is that, depending on the source 
type and its intensity, sound from the specified activity may be a 
negligible addition to the local environment or could form a 
distinctive signal that may affect marine mammals.
    Underwater sounds fall into one of two general sound types: 
Impulsive and non-impulsive (defined in the following paragraphs). The 
distinction between these two sound types is important because they 
have differing potential to cause physical effects, particularly with 
regard to hearing (e.g., Ward, 1997 in Southall et al. 2007). Please 
see Southall et al. (2007) for an in-depth discussion of these 
concepts.
    Impulsive sound sources (e.g., explosions, gunshots, sonic booms, 
impact pile driving) produce signals that are brief (typically 
considered to be less than one second), broadband, atonal transients 
(ANSI 1986; Harris 1998; NIOSH 1998; ISO 2016; ANSI 2005) and occur 
either as isolated events or repeated in some succession. Impulsive 
sounds are all characterized by a relatively rapid rise from ambient 
pressure to a maximal pressure value followed by a rapid decay period 
that may include a period of diminishing, oscillating maximal and 
minimal pressures, and generally have an increased capacity to induce 
physical injury as compared with sounds that lack these features. There 
are no pulsed sound sources associated with any planned ICEX22 
activities.
    Non-impulsive sounds can be tonal, narrowband, or broadband, brief 
or prolonged, and may be either continuous or non-continuous (ANSI 
1995; NIOSH 1998). Some of these non-impulsive sounds can be transient 
signals of short duration but without the essential properties of 
pulses (e.g., rapid rise time). Examples of non-impulsive sounds 
include those produced by vessels, aircraft, machinery operations such 
as drilling or dredging, vibratory pile driving, and active sonar 
sources (such as those planned for use by the Navy as part of the 
proposed ICEX22 activities) that intentionally direct a sound signal at 
a target that is reflected back in order to discern physical details 
about the target.
    Modern sonar technology includes a variety of sonar sensor and 
processing systems. In concept, the simplest active sonar emits sound 
waves, or ``pings,'' sent out in multiple directions, and the sound 
waves then reflect off of the target object in multiple directions. The 
sonar source calculates the time it takes for the reflected sound waves 
to return; this calculation determines the distance to the target 
object. More sophisticated active sonar systems emit a ping and then 
rapidly scan or listen to the sound waves in a specific area. This 
provides both distance to the target and directional information. Even 
more advanced sonar systems use multiple receivers to listen to echoes 
from several directions simultaneously and provide efficient detection 
of both direction and distance. In general, when sonar is in use, the 
sonar `pings' occur at intervals, referred to as a duty cycle, and the 
signals themselves are very short in duration. For example, sonar that 
emits a 1-second ping every 10 seconds has a 10 percent duty cycle. The 
Navy's most powerful hull-mounted mid-frequency sonar source used in 
ICEX activities typically emits a 1-second ping every 50 seconds 
representing a 2 percent duty cycle. The Navy utilizes sonar systems 
and other acoustic sensors in support of a variety of mission 
requirements.

Acoustic Impacts

    Please refer to the information given previously regarding sound, 
characteristics of sound types, and metrics used in this document. 
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 include one or more of the following: Temporary or 
permanent hearing impairment, non-auditory physical or physiological 
effects, behavioral disturbance, stress, and masking (Richardson et al. 
1995; Gordon et al. 2004; Nowacek et al. 2007; Southall et al. 2007; 
Gotz et al. 2009). 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 will occur almost exclusively 
for noise within an animal's hearing range. In this section, we first 
describe specific manifestations of acoustic effects before providing 
discussion specific to the proposed activities in the next section.
    Permanent Threshold Shift--Marine mammals exposed to high-intensity 
sound, or to lower-intensity sound for prolonged periods, can 
experience hearing threshold shift (TS), which is the loss of hearing 
sensitivity at certain frequency ranges (Finneran 2015). TS 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). 
Repeated sound exposure that leads to TTS could cause 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). 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.
    Relationships between TTS and PTS thresholds have not been studied 
in marine mammals--PTS data exists only for a single harbor seal 
(Kastak et al. 2008)--but are assumed to be similar to those in humans 
and other terrestrial mammals. PTS typically occurs at exposure levels 
at least several dB above (a 40-dB threshold shift approximates PTS 
onset; e.g., Kryter et al. 1966; Miller, 1974) those inducing mild TTS 
(a 6-dB threshold shift approximates TTS onset; e.g., Southall et al. 
2007). Based on data from terrestrial mammals, a precautionary 
assumption is that the PTS thresholds for impulse sounds (such as 
impact pile driving pulses as received close to the source) are at 
least six dB higher than the TTS threshold on a peak-pressure basis and 
PTS cumulative sound exposure level (SEL) thresholds are 15 to 20 dB 
higher than TTS cumulative SEL thresholds (Southall et al. 2007).
    Temporary Threshold Shift--TTS is the mildest form of hearing 
impairment that can occur during exposure to sound (Kryter, 1985). 
While experiencing TTS, the hearing threshold rises, and a sound must 
be at a higher level in order to be heard. In terrestrial and marine 
mammals, TTS can last from minutes or hours to days (in cases of strong 
TTS). In many cases, hearing sensitivity recovers rapidly after 
exposure to the sound ends.
    Marine mammal hearing plays a critical role in communication with 
conspecifics, and 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

[[Page 70461]]

serious. 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 occurs 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 time when 
communication is critical for successful mother/calf interactions could 
have more serious impacts.
    Currently, TTS data only exist for four species of cetaceans 
(bottlenose dolphin (Tursiops truncatus), beluga whale, harbor porpoise 
(Phocoena phocoena), and Yangtze finless porpoise (Neophocoena 
asiaeorientalis)) and three species of pinnipeds (northern elephant 
seal (Mirounga angustirostris), harbor seal (Phoca vitulina), and 
California sea lion (Zalophus californianus)) exposed to a limited 
number of sound sources (i.e., mostly tones and octave-band noise) in 
laboratory settings (Finneran 2015). TTS was not observed in trained 
spotted and ringed seals exposed to impulsive noise at levels matching 
previous predictions of TTS onset (Reichmuth et al. 2016). In general, 
harbor seals and harbor porpoises have a lower TTS onset than other 
measured pinniped or cetacean species. Additionally, the existing 
marine mammal TTS data come from a limited number of individuals within 
these species. There are no data available on noise-induced hearing 
loss for mysticetes. For summaries of data on TTS in marine mammals or 
for further discussion of TTS onset thresholds, please see Southall et 
al. (2007), Finneran and Jenkins (2012), and Finneran (2015).
    Behavioral effects--Behavioral disturbance may include a variety of 
effects, including subtle changes in behavior (e.g., minor or brief 
avoidance of an area or changes in vocalizations), more conspicuous 
changes in similar behavioral activities, and more sustained and/or 
potentially severe reactions, such as displacement from or abandonment 
of high-quality habitat. Behavioral responses to sound are highly 
variable and context-specific and any reactions depend on numerous 
intrinsic and extrinsic factors (e.g., species, state of maturity, 
experience, current activity, reproductive state, auditory sensitivity, 
time of day), as well as the interplay between factors (e.g., 
Richardson et al. 1995; Wartzok et al. 2003; Southall et al. 2007; 
Weilgart, 2007; Archer et al. 2010). Behavioral reactions can vary not 
only among individuals but also within an individual, depending on 
previous experience with a sound source, context, and numerous other 
factors (Ellison et al. 2012), and can vary depending on 
characteristics associated with the sound source (e.g., whether it is 
moving or stationary, number of sources, distance from the source). 
Please see Appendices B-C of Southall et al. (2007) for a review of 
studies involving marine mammal behavioral responses to sound.
    Habituation can occur when an animal's response to a stimulus wanes 
with repeated exposure, usually in the absence of unpleasant associated 
events (Wartzok et al. 2003). Animals are most likely to habituate to 
sounds that are predictable and unvarying. It is important to note that 
habituation is appropriately considered as a ``progressive reduction in 
response to stimuli that are perceived as neither aversive nor 
beneficial,'' rather than as, more generally, moderation in response to 
human disturbance (Bejder et al. 2009). The opposite process is 
sensitization, when an unpleasant experience leads to subsequent 
responses, often in the form of avoidance, at a lower level of 
exposure. As noted, behavioral state may affect the type of response. 
For example, animals that are resting may show greater behavioral 
change in response to disturbing sound levels than animals that are 
highly motivated to remain in an area for feeding (Richardson et al. 
1995; NRC 2003; Wartzok et al. 2003). Controlled experiments with 
captive marine mammals have shown pronounced behavioral reactions, 
including avoidance of loud sound sources (Ridgway et al. 1997; 
Finneran et al. 2003). Observed responses of wild marine mammals to 
loud impulsive sound sources (typically seismic airguns or acoustic 
harassment devices) have been varied but often consist of avoidance 
behavior or other behavioral changes suggesting discomfort (Morton and 
Symonds 2002; see also Richardson et al. 1995; Nowacek et al. 2007).
    Available studies show wide variation in response to underwater 
sound; therefore, it is difficult to predict specifically how any given 
sound in a particular instance might affect marine mammals perceiving 
the signal. If a marine mammal does react briefly to an underwater 
sound by changing its behavior or moving a small distance, the impacts 
of the change are unlikely to be significant to the individual, let 
alone the stock or population. However, if a sound source displaces 
marine mammals from an important feeding or breeding area for a 
prolonged period, impacts on individuals and populations could be 
significant (e.g., Lusseau and Bejder 2007; Weilgart 2007; NRC 2003). 
However, there are broad categories of potential response, which we 
describe in greater detail here, that include alteration of dive 
behavior, alteration of foraging behavior, effects to breathing, 
interference with or alteration of vocalization, avoidance, and flight.
    Changes in dive behavior can vary widely, and 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; Costa et al. 2003; Ng and Leung, 2003; Nowacek et al. 
2004; Goldbogen et al. 2013). Variations in dive behavior may reflect 
interruptions in biologically significant activities (e.g., foraging) 
or they may be of little biological significance. The impact of an 
alteration to dive behavior 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.
    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; Nowacek et al. 2004; Madsen et al. 2006; 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.
    Variations in respiration naturally vary with different behaviors 
and alterations to breathing 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. Various studies have shown that respiration rates may 
either be unaffected or could increase, depending on the species and 
signal characteristics, again highlighting the importance in 
understanding species differences in the tolerance of underwater noise 
when determining the potential for impacts resulting from anthropogenic 
sound

[[Page 70462]]

exposure (e.g., Kastelein et al. 2001, 2005b, 2006; Gailey et al. 
2007).
    Marine mammals vocalize for different purposes and across multiple 
modes, such as whistling, echolocation click production, calling, and 
singing. Changes in vocalization behavior 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 increased 
vigilance or a startle response. For example, in the presence of 
potentially masking signals, humpback whales and killer whales have 
been observed to increase the length of their songs (Miller et al. 
2000; Fristrup et al. 2003; Foote et al. 2004), while 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). In some cases, animals may cease so