Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to THwaites Offshore Research (THOR) Project in the Amundsen Sea, Antarctica, 69950-69978 [2019-27269]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 84, Number 244 (Thursday, December 19, 2019)]
[Notices]
[Pages 69950-69978]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-27269]



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Vol. 84

Thursday,

No. 244

December 19, 2019

Part IV





 Department of Commerce





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National Oceanic and Atmospheric Administration





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Takes of Marine Mammals Incidental to Specified Activities; Taking 
Marine Mammals Incidental to THwaites Offshore Research (THOR) Project 
in the Amundsen Sea, Antarctica; Notice

Federal Register / Vol. 84 , No. 244 / Thursday, December 19, 2019 / 
Notices

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XR069]


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to THwaites Offshore Research (THOR) 
Project in the Amundsen Sea, Antarctica

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

ACTION: Notice; proposed incidental harassment authorization; request 
for comments on proposed authorization and possible renewal.

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SUMMARY: NMFS has received a request from the National Science 
Foundation (NSF) Office of Polar Programs on behalf of the University 
of Houston for authorization to take marine mammals incidental to the 
THOR project in the Amundsen Sea, Antarctica. 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-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 authorizations and agency 
responses will be summarized in the final notice of our decision.

DATES: Comments and information must be received no later than January 
21, 2020.

ADDRESSES: Comments should be addressed to Jolie Harrison, Chief, 
Permits and Conservation Division, Office of Protected Resources, 
National Marine Fisheries Service. Physical comments should be sent to 
1315 East-West Highway, Silver Spring, MD 20910 and electronic comments 
should be sent 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 received electronically, 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/permit/incidental-take-authorizations-under-marine-mammal-protection-act 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: Bonnie DeJoseph, 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/permit/incidental-take-authorizations-under-marine-mammal-protection-act. 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 issued or, if the taking is limited to harassment, a notice of a 
proposed incidental take authorization may be 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 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 
incidental harassment authorization) with respect to potential impacts 
on the human environment.
    This action is consistent with categories of activities identified 
in Categorical Exclusion B4 (incidental harassment authorizations with 
no anticipated serious injury or mortality) of the Companion Manual for 
NOAA Administrative Order 216-6A, which do not individually or 
cumulatively have the potential for significant impacts on the quality 
of the human environment and for which we have not identified any 
extraordinary circumstances that would preclude this categorical 
exclusion. Accordingly, NMFS has preliminarily determined that the 
issuance of the proposed IHA qualifies to be categorically excluded 
from further NEPA review.
    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 July 24, 2019, NMFS received a request from NSF for an IHA to 
take marine mammals incidental to conducting a low-energy marine 
geophysical survey and icebreaking as necessary in the Amundsen Sea. 
The application was deemed adequate and complete on November 21, 2019. 
NSF's request is for take of a small number of 18 species of marine 
mammals, by harassment. Neither NSF nor NMFS expects serious injury or 
mortality to result from this activity and, therefore, an IHA is 
appropriate. The planned activity is not expected to exceed one year.

Description of Proposed Activity

Overview

    NSF plans to conduct low-energy marine seismic surveys in the 
Amundsen Sea during February 2019. The proposed activity will 
complement Thwaites Glacier and other Amundsen Sea oceanographic and 
geological/geophysical studies and provide reference data that can be 
used to initiate and evaluate the reliability of ocean models. Data 
obtained by the project would assist in establishing boundary 
conditions seaward of the Thwaites Glacier grounding line, obtaining 
records of external drivers of change, improving knowledge of processes 
leading to the collapse of Thwaites Glacier, and determining the

[[Page 69951]]

history of past change in grounding line migration and conditions at 
the glacier base.
    The seismic surveys would be conducted in approximately 8400 km\2\ 
between 75.25[deg]-73.5[deg] S and 101.0[deg]-108.5[deg]W of the 
Amundsen Sea in water depths ranging from approximately 100 to 1000 m 
plus. The surveys would involve one source vessel, the Research Vessel/
Icebreaker (RVIB) Nathaniel B. Palmer (Palmer). The Palmer would deploy 
up to two 45-in\3\ generator injector (GI) airguns at a depth of 2-4 m 
with a total maximum discharge volume for the largest, two-airgun array 
of 3441 cm\3\ maximum total volume (210 in\3\) along predetermined 
track lines. Because of the extent of sea ice in the Amundsen Sea that 
typically occurs between January and February annually, icebreaking 
activities are expected to be required during the cruise.

Dates and Duration

    The RVIB Palmer would likely depart from Punta Arenas, Chile, on or 
about January 25, 2020. Seismic surveys will begin on or about February 
6, 2020 for approximately eight days. An additional two contingency 
days are allotted for unforeseen events such as weather, logistical 
issues, or mechanical issues with the research vessel and/or equipment. 
Weather conditions permitting, it is anticipated that seismic surveying 
would not exceed 240 hours of operation.

Specific Geographic Region

    The proposed surveys would take place within the Amundsen Sea, 
between approximately between 75.25[deg]-73.5[deg] S and 101.0[deg]-
108.5[deg] W. Surveys will be contained in approximately 8400 km\2\ in 
the Amundsen Sea along representative track lines totaling 
approximately 1600 km, shown in Figure 1.
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Detailed Description of Specific Activity

Seismic Surveys and Other Acoustic Sources
    NSF proposes to conduct low-energy seismic surveys along a 1600-km 
track (Figure 1) using a one or two-generator injector airgun array, 
with a ``hot spare'', (Table 1) as a low-energy seismic source and 
returning acoustic signals would be collected via a hydrophone streamer 
(100-300 m in length). Other acoustic sources to be used include the 
following: acoustic doppler current profilers (ADCPs) and multi, 
single, and splitbeam echosounders. Data acquisition in the THOR survey 
area will occur in water depths that range between 100-1,000 m in 65 
percent of the survey area and depths greater than 1,000 m in 35 
percent of the study area (Figure 1).
    The procedures to be used for the seismic surveys would be similar 
to those used during previous seismic surveys by NSF and would use 
conventional seismic methodology. The surveys would involve one source 
vessel, RVIB Palmer, which is managed by Galliano Marine Service LLC. 
The airgun array would be deployed at a depth of approximately 2-4 m 
below the surface, spaced approximately 3 m apart for the two-gun 
array, and between 15-40 m astern. Each airgun would be configured in 
the true GI or harmonic mode, with varying displacement volumes (Table 
1). The total maximum discharge volume for the largest, two-airgun 
array would be 3441 cm3 (210 in\3\; Table 1). The receiving system 
would consist of one hydrophone streamer, 100-300 m in length, with the 
vessel traveling at 8.3 km/hr (4.5 knots) to achieve high-quality 
seismic reflection data. As the airguns are towed along the survey 
lines, the hydrophone streamer would receive the returning acoustic 
signals and transfer the data to the on-board processing system.

                       Table 1--Proposed Seismic Survey Activities in the Amundsen Sea \1\
----------------------------------------------------------------------------------------------------------------
                                                                           Frequency
                                         Airgun array total volume (GI      between
             Configuration                      configuration)           seismic shots       Streamer length
                                                                           (seconds)
----------------------------------------------------------------------------------------------------------------
Preferred.............................  2 x 45/105 in\3\ (300 in\3\                  5  100-300 m (328-984 ft).
                                         total) (true GI mode).
Alternate 1...........................  1 x 45/105 in\3\ (150 in\3\                  5
                                         total) (true GI mode).
Alternate 2 (used for take request)...  2 x 105/105 in\3\ (420 in\3\                 5
                                         total) (harmonic mode).
Alternate 3...........................  1 x 105/105 in\3\ (210 in\3\                 5
                                         total) (harmonic mode).
----------------------------------------------------------------------------------------------------------------
\1\ Seismic surveying operations are planned for 1600 km (994 mi) in length.

    The airguns would fire compressed air at an approximate firing 
pressure of 140 kg/cm\2\ (2000 psi). In harmonic mode, the injector 
volume is designed to destructively interfere with the reverberations 
of the generator (i.e., the

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source component). Firing the airguns in harmonic mode maximizes 
resolution in the data and minimizes excess noise in the water column 
or in the data, caused by the reverberations (i.e., bubble pulses). 
There would be approximately 720 shots per hour, and the relative 
linear distance between shots would be 12.5 m. The cumulative duration 
of airgun operation is anticipated to be no more than 240 hours, which 
includes equipment testing, ramp-up, line changes, and repeat coverage. 
If the preferred airgun configuration, the two-gun array in true GI 
mode, does not provide data to meet scientific objectives, alternate 
configurations would be utilized as shown in Table 1.
    There could be additional seismic operations in the project area 
associated with equipment testing, re-acquisition due to reasons such 
as but not limited to equipment malfunction, data degradation during 
poor weather, or interruption due to shut-down or track deviation in 
compliance with IHA requirements. To account for these additional 
seismic operations, 25 percent has been added in the form of 
operational days, which is equivalent to adding 25 percent to the 
proposed line km to be surveyed. There would be approximately 720 shots 
per hour, and the relative linear distance between shots would be 12.5 
m (41 ft). The cumulative duration of airgun operation is anticipated 
to be no more than 240 hours, which includes equipment testing, ramp-
up, line changes, and repeat coverage.
    In addition to the operations of the airgun array, a hull-mounted 
Single Beam Echo Sounder (Knudsen 3260 CHIRP), Multibeam Sonar 
(Kongsberg EM122), Acoustic Doppler Current Profiler (ADCP) (Teledyne 
RDI VM-150), and ADCP (Ocean Surveyor OS-38), as well as EK biological 
echo sounder (Simrad ES200-7C, ES38B, ES-120-7C) would also be operated 
from the Palmer continuously throughout the cruise. The vessel would be 
self-contained, and the crew would live aboard the vessel for the 
entire cruise.
    The Palmer has a length of 93.9 m, a beam of 18.3 m, and a design 
draft of 6.8 m. It is equipped with four Caterpillar Model 3608 diesel 
engines (each rated at 3300 brake horsepower [BHP] at 900 revolutions 
per minute [rpm]) and a water jet azimuthing bow thruster. Electrical 
power is provided by four Caterpillar 3512, 1050-kW diesel generators. 
When not towing seismic survey gear, the Palmer cruises at 
approximately 9.2 km/hr (5 knots), varying between 7.4-11.1 km/hr (4-6 
knots) when GI airguns are operating, and has the maximum speed of 26.8 
km/hr (14.5 knots). The Palmer would also serve as the platform from 
which vessel-based protected species visual observers (PSVO) would 
watch for marine mammals before and during airgun operations.
    Proposed mitigation, monitoring, and reporting measures are 
described in detail later in this document (please see Proposed 
Mitigation and Proposed Monitoring and Reporting).
Icebreaking
    The research activities and associated contingencies are designed 
to avoid areas of heavy sea ice condition since the Palmer is not 
suited to break multi-year sea ice. If the Palmer breaks ice during 
transit operations within the Amundsen Sea, seismic operations would 
not be conducted concurrently. It is noted that typical transit through 
areas of primarily open water and containing brash or pancake, ice are 
not considered icebreaking for the purposes of this activity.

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 about these species (e.g., physical and 
behavioral descriptions) may be found on NMFS's website (https://www.fisheries.noaa.gov/find-species).
    The populations of marine mammals considered in this document do 
not occur within the U.S. Exclusive Economic Zone (EEZ) and are 
therefore not assigned to stocks and are not assessed in NMFS' Stock 
Assessment Reports (SAR). As such, information on potential biological 
removal (PBR; 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) and on annual levels of serious injury and 
mortality from anthropogenic sources are not available for these marine 
mammal populations. Abundance estimates for marine mammals in the 
survey location are lacking; therefore estimates of abundance presented 
here are based on a variety of other sources including International 
Whaling Commission population estimates (IWC 2019), The International 
Union for Conservation of Nature's (IUCN) Red List of Threatened 
Species, and various literature estimates (see IHA application for 
further detail), as this is considered the best available information 
on potential abundance of marine mammals in the area.
    Table 2 lists all species with expected potential for occurrence in 
the Amundsen Sea, Antarctica, and summarizes information related to the 
population, including regulatory status under the MMPA and ESA. For 
taxonomy, we follow Committee on Taxonomy (2018).

 Table 2--Marine Mammal Species Potentially Present in the Project Area Expected To Be Affected by the Specified
                                                   Activities
----------------------------------------------------------------------------------------------------------------
                                                                           ESA/MMPA
                                                                            status;         Stock
          Common name            Scientific name         Stock \1\       strategic (Y/    abundance       PBR
                                                                            N) \2\
----------------------------------------------------------------------------------------------------------------
                      Order Cetartiodactyla--Cetacea--Superfamily Mysticeti (baleen whales)
----------------------------------------------------------------------------------------------------------------
Family Balaenopteridae
 (rorquals):
    Blue whale................  Balaenoptera       N/A.................  E/D;Y              \3\ 5,000  N/A
                                 musculus.
    Fin whale.................  Balaenoptera       N/A.................  E/D;Y             \4\ 38,200  N/A
                                 physalus.
    Humpback whale............  Megaptera          N/A.................  ............      \5\ 42,000  N/A
                                 novaeangliae.
    Minke whale \6\...........  Balaenoptera       N/A.................  -                \7\ 515,000  N/A
                                 acutorostrata.
    Sei whale.................  Balaenoptera       N/A.................  E                 \8\ 10,000  N/A
                                 borealis.
----------------------------------------------------------------------------------------------------------------
                        Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
----------------------------------------------------------------------------------------------------------------
Family Physeteridae:
    Sperm whale...............  Physeter           N/A.................  E                 \9\ 12,069  N/A
                                 macrocephalus.

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Family Ziphiidae (beaked
 whales):
    Arnoux's beaked whale.....  Berardius arnuxii  N/A.................  -               \10\ 599,300  N/A
    Gray's beaked whale.......  Mesoplodon grayi.  N/A.................  -               \10\ 599,300  N/A
    Southern bottlenose.......  Hyperoodon         N/A.................  -               \11\ 500,000  N/A
                                 planifrons.
Family Delphinidae:
    Killer whale..............  Orcinus orca.....  N/A.................  -                \12\ 25,000  N/A
    Long-finned whale.........  Globicephala       N/A.................  -               \13\ 200,000  N/A
                                 macrorhynchus.
Family Hyperoodontidae:
    Layard's beaked whales....  Mesoplodon         N/A.................  ............    \10\ 599,300  N/A
                                 layardii.
Family Phocidae (earless
 seals):
    Crabeater seal............  Lobodon            N/A.................  -             \14\ 5,000,000  N/A
                                 carcinophaga.
    Leopard seal..............  Hydrurga leptonyx  N/A.................  -               \15\ 222,000  N/A
    Southern elephant seal....  Mirounga leonina.  N/A.................  -               \16\ 750,000  N/A
    Ross seal.................  Ommatophoca        N/A.................  -               \17\ 250,000  N/A
                                 rossii.
    Weddell seal..............  Leptonychotes      N/A.................  -               \18\ 750,000  N/A
                                 weddellii.
----------------------------------------------------------------------------------------------------------------
N.A. = data not available.
\1\ The populations of marine mammals considered in this document do not occur within the U.S. EEZ and are
  therefore not assigned to stocks.
\2\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-)
  indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the
  MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is
  determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or
  stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\3\ Perrin et al 2009, IWC 2019.
\4\ Antarctic Range 5-8,000 (Cooke 2018).
\5\ Aguilar & Garc[iacute]a-Vernet 2018.
\6\ Partial coverage of Antarctic feeding grounds (IWC 2019).
\7\ Antarctic and Dwarf Minke whales information is combined.
\8\ Antarctic (Boyd 2002).
\9\ Cooke 2018.
\10\ Estimate for the Antarctic, south of 60[deg] S (Whitehead 2002).
\11\ All beaked whales south of the Antarctic Convergence; mostly southern bottlenose whales (Kasamatsu & Joyce
  1995).
\12\ Jefferson et al. 2008.
\13\ Branch & Butterworth 2001.
\14\ Antarctic (Boyd 2002).
\15\ Global population 5-10 million (Bengtson & Stewart 2018).
\16\ Global population is 222,000-440,000 (Rogers 2018).
\17\ Total world population (Hindell et al., 2016)
\18\ H[uuml]ckst[auml]dt 2015.

    All species that could potentially occur in the proposed survey 
areas are included in Table 2. As described below, all 18 species 
temporally and spatially co-occur with the activity to the degree that 
take is reasonably likely to occur, and we have proposed authorizing 
it.
    We have reviewed NSF's species descriptions, including life history 
information, distribution, regional distribution, diving behavior, and 
acoustics and hearing, for accuracy and completeness. We refer the 
reader to Section 4 of NSF's IHA application for a complete description 
of the species, and offer a brief introduction to the species here, as 
well as information regarding population trends and threats, and 
describe information regarding local occurrence.

Mysticetes

Blue Whale
    The blue whale has a cosmopolitan distribution, but tends to be 
mostly pelagic, only occurring nearshore to feed and possibly breed 
(Jefferson et al. 2015). It is most often found in cool, productive 
waters where upwelling occurs (Reilly and Thayer 1990). The 
distribution of the species, at least during times of the year when 
feeding is a major activity, occurs in areas that provide large 
seasonal concentrations of euphausiids (Yochem and Leatherwood 1985). 
Seamounts and other deep ocean structures may be important habitat for 
blue whales (Lesage et al. 2016). Generally, blue whales are seasonal 
migrants between high latitudes in summer, where they feed, and low 
latitudes in winter, where they mate and give birth (Lockyer and Brown 
1981).
    Historically, blue whales were most abundant in the Southern Ocean. 
Although, the population structure of the Antarctic blue whale 
(Balaenoptera musculus intermedia) in the Southern Ocean is not well 
understood, there is evidence of discrete feeding stocks (Sears & 
Perrin 2018). Cooke (2018) explains that ``there are no complete 
estimates of recent or current abundance for the other regions, but 
plausible total numbers would be 1,000-3,000 in the North Atlantic, 
3,000-5,000 in the North Pacific, and possibly 1,000-3,000 in the 
eastern South Pacific. The number of Pygmy Blue whales is very 
uncertain but may be in the range 2,000-5,000. Taken together with a 
range of 5,000-8,000 in the Antarctic, the global population size in 
2018 is plausibly in the range 10,000-25,000 total or 5,000-15,000 
mature, compared with a 1926 global population of at least 140,000 
mature.'' Blue whales begin migrating north out of the Antarctic to 
winter breeding grounds earlier than fin and sei whales.
Fin Whale
    The fin whale (Balaenoptera physalus) is widely distributed in all 
the world's oceans (Gambell 1985), although it is most abundant in 
temperate and cold waters (Aguilar and Garc[iacute]a-Vernet 2018). 
Nonetheless, its overall range and distribution is not well known 
(Jefferson et al. 2015). Fin whales most commonly occur offshore, but 
can also be found in coastal areas (Jefferson et al. 2015). Most 
populations migrate seasonally between temperate waters where mating 
and calving occur in winter, and polar waters where feeding occurs in 
the summer; they are known to use the shelf edge as a migration route 
(Evans 1987). The northern and southern fin whale populations likely do 
not interact owing to their alternate seasonal migration; the

[[Page 69955]]

resulting genetic isolation has led to the recognition of two 
subspecies, B. physalus quoyi and B. p. physalus in the Southern and 
Northern hemispheres, respectively (Anguilar & Garc[iacute]a-Vernet 
2018).
    They likely migrate beyond 60[deg] S during the early to mid-
austral summer, arriving at southern feeding grounds after blue whales. 
Overall, fin whale density tends to be higher outside the continental 
slope than inside it. During the austral summer, the distribution of 
fin whales ranges from 40[deg] S-60[deg] S in the southern Indian and 
South Atlantic oceans and 50[deg] S-65[deg] S in the South Pacific. 
Aguilar and Garc[iacute]a-Vernet (2018) found abundance estimates 
resulted in 38,200 individuals in the Antarctic south of 307[deg] S. 
The RV Polarstern observed 33 fin whales in the Amundsen Sea during 
seismic survey transects (Gohl 2010). The New Zealand stock of fin 
whales spends summers from 170[deg] E-145[deg] W. Fin whales migrate 
north before the end of the austral summer toward breeding grounds in 
and around the Fiji Sea.
Humpback Whale
    Humpback whales (Megaptera novaeangliae) are found worldwide in all 
ocean basins. In winter, most humpback whales occur in the subtropical 
and tropical waters of the Northern and Southern Hemispheres (Muto et 
al., 2015). These wintering grounds are used for mating, giving birth, 
and nursing new calves. Humpback whales were listed as endangered under 
the Endangered Species Conservation Act (ESCA) in June 1970. In 1973, 
the ESA replaced the ESCA, and humpbacks continued to be listed as 
endangered. NMFS recently evaluated the status of the species, and on 
September 8, 2016, NMFS divided the species into 14 distinct population 
segments (DPS), removed the previousspecies-level listing, and in its 
place listed four DPSs as endangered and one DPS as threatened (81 FR 
62259; September 8, 2016). The remaining nine DPSs were not listed.
    In the Southern Hemisphere, humpback whales migrate annually from 
summer foraging areas in the Antarctic to breeding grounds in tropical 
seas (Clapham 2018). Whales migrating southward from Brazil have been 
shown to traverse offshore, pelagic waters (Zerbini et al. 2006, 2011) 
en route to feeding areas along the Scotia Sea, including the waters 
around Shag Rocks, South Georgia and the South Sandwich Islands 
(Stevick et al. 2006; Zerbini et al. 2006, 2011; Engel et al. 2008; 
Engel and Martin 2009). Southern Hemisphere humpback whales share 
feeding grounds in the Antarctic, near 60[deg] S and between 120[deg] E 
and 110[deg] W during the austral summer (December-March). The 
Polarstern observed 44 humpback whales in the Amundsen Sea during 
seismic survey transects (Gohl 2010). The IWC's (2019) best population 
estimate of humpback whales in the southern hemisphere (i.e., partial 
coverage of Antarctic feeding grounds) is 42,000.
Minke Whale
    The common minke whale has a cosmopolitan distribution ranging from 
the tropics and subtropics to the ice edge in both hemispheres 
(Jefferson et al. 2015). A smaller form of the common minke whale, 
known as the dwarf minke whale (Balaenoptera acutorostrata), occurs in 
the Southern Hemisphere, where its distribution overlaps with that of 
the Antarctic minke whale (B. bonaerensis) during summer (Perrin et al. 
2018). The dwarf minke whale is generally found in shallower coastal 
waters and over the shelf in regions where it overlaps with B. 
bonaerensis (Perrin et al. 2018). The range of the dwarf minke whale is 
thought to extend as far south as 65[deg] S (Jefferson et al. 2015) and 
as far north as 2[deg] S in the Atlantic off South America, where it 
can be found nearly year-round. In the far south, it is seasonally 
sympatric with the Antarctic minke whale on the feeding grounds during 
austral summer and transitions off South Africa during the fall and 
winter. Where the dwarf minke whale is sympatric with the Antarctic 
minke whale, it tends to occur in shallower, more coastal waters over 
the continental shelf (Perrin et al. 2018). Because the counts did not 
properly differentiate between the two species, IWC's (2019) best 
estimate for population abundance (515,000) will be divided evenly and 
assigned to each for our purposes.
Sei Whale
    The sei whale (Balaenoptera borealis) occurs in all ocean basins 
(Horwood 2018), predominantly inhabiting deep waters throughout their 
range (Acevedo et al. 2017a). It undertakes seasonal migrations to feed 
in sub-polar latitudes during summer, returning to lower latitudes 
during winter to calve (Horwood 2018). Recent observation records 
indicate that the sei whale may utilize the Vit[oacute]ria-Trindade 
Chain off Brazil as calving grounds (Heissler et al. 2016). In the 
Southern Hemisphere, sei whales typically concentrate between the 
Subtropical and Antarctic convergences during the summer (Horwood 2018) 
between 40[deg] S and 50[deg] S, with larger, older whales typically 
travelling into the northern Antarctic zone while smaller, younger 
individuals remain in the lower latitudes (Acevedo et al. 
2017a).Population estimates are not available for the Amundsen Sea 
region.

Odontocetes

Sperm Whale
    The sperm whale (Physeter macrocephalus) is widely distributed, 
occurring from the edge of the polar pack ice to the Equator in both 
hemispheres, with the sexes occupying different distributions 
(Whitehead 2018). In general, it is distributed over large temperate 
and tropical areas that have high secondary productivity and steep 
underwater topography, such as volcanic islands (Jaquet & Whitehead 
1996). Its distribution and relative abundance can vary in response to 
prey availability, most notably squid (Jaquet & Gendron 2002). Females 
generally inhabit waters >1000 m deep at latitudes <40 [deg] where sea 
surface temperatures are <15[deg] C; adult males move to higher 
latitudes as they grow older and larger in size, returning to warm-
water breeding grounds according to an unknown schedule (Whitehead 
2018).
    Ainley et al. (2007) observed 19 sperm whales during their 1994 
cetacean surveys (3,494 km) in the Amundsen and Bellingshausen seas.
Arnoux's Beaked Whale
    Arnoux's beaked whale (Berardius arnuxii) is distributed in deep, 
cold, temperate, and subpolar waters of the Southern Hemisphere, 
occurring between 24[deg] S and Antarctica (Thewissen 2018), as far 
south as the Ross Sea at approximately 78[deg] S (Perrin et al. 2009). 
Most records exist for southeastern South America, Falkland Islands, 
Antarctic Peninsula, South Africa, New Zealand, and southern Australia 
(MacLeod et al. 2006; Jefferson et al. 2015).
    Marine mammal observations conducted during seismic surveys in West 
Antarctica between January and April of 2010 counted 12 Arnoux's beaked 
whales (Gohl 2010).
Gray's Beaked Whale
    Gray's beaked whale (Mesoplodon grayi), also known as Haast's 
beaked whale, the scamperdown whale, or the southern beaked whale, 
typically lives in the Southern Hemisphere, between 30[deg] S-45[deg] 
S. Numerous strandings have occurred off New Zealand; others have 
occurred off South America and the Falkland Islands. This species has 
been sighted in groups in the Antarctic area.

[[Page 69956]]

Abundance estimates are not available for the Amundsen Sea.
Southern Bottlenose Whale
    The southern bottlenose whale (Hyperoodon planifrons) is found 
throughout the Southern Hemisphere from 30[deg] S to the ice edge, with 
most sightings reported between ~57[deg] S and 70[deg] S (Jefferson et 
al. 2015; Moors-Murphy 2018). It is migratory, occurring in Antarctic 
waters during summer (Jefferson et al. 2015).
Killer Whale
    Killer whales (Orcinus orca) have been observed in all oceans and 
seas of the world (Leatherwood and Dahlheim 1978). Based on sightings 
by whaling vessels between 1960 and 1979, killer whales are distributed 
throughout the South Atlantic (Budylenko 1981; Mikhalev et al. 1981). 
Although reported from tropical and offshore waters (Heyning and 
Dahlheim 1988), killer whales prefer the colder waters of both 
hemispheres, with greatest abundances found within 800 km of major 
continents (Mitchell 1975). Branch and Butterworth (2001) determined 
25,000 as the minimum estimate for the Southern Ocean.
Long-Finned Pilot Whales
    Three distinct populations or subspecies of long-finned pilot 
whales are recognized: Southern Hemisphere (Globicephala melas 
edwardii), North Atlantic (Globicephala melas melas), and an unnamed 
extinct form in the western North Pacific. In the Southern Hemisphere, 
their range extends from 19[deg]-60[deg] S, but they have been 
regularly sighted in the Antarctic Convergence Zone (47[deg]-62[deg] S) 
and in the Central and South Pacific as far south as 68[deg] S. Their 
distribution is considered circumpolar, and they have been documented 
near the Antarctic sea ice. They have been associated with the colder 
Benguela and Humboldt Currents, which may extend their normal range, as 
well as the Falklands. In the winter and spring, they are more likely 
to occur in offshore oceanic waters or on the continental slope. In the 
summer and autumn, long-finned pilot whales generally follow their 
favorite foods farther inshore and on to the continental shelf. In the 
Southern Hemisphere, there are an estimated 200,000 long-finned pilot 
whales in Antarctic waters (Jefferson et al. 2008, Reeves et al. 2002, 
Shirihai & Jarrett 2006).
Layard's Beaked Whales
    Layard's beaked whale (Mesoplodon layardii), also known as the 
strap-toothed whale due to its unusual tooth configuration, is 
distributed in cool temperate waters of the Southern Hemisphere between 
30[deg] S and the Antarctic Convergence. Strandings have been reported 
in New Zealand, Australia, southern Argentina, Tierra del Fuego, 
southern Chile, and the Falkland Islands. The world-wide population of 
all beaked whales south of the Antarctic Convergence is estimated at 
approximately 599,300 animals (Kasamatsu and Joyce 1995).
Crabeater Seal
    Crabeater seals (Lobodon carcinophaga) have a circumpolar 
distribution off Antarctica and generally spend the entire year in the 
advancing and retreating pack ice; occasionally they are seen in the 
far southern areas of South America though this is uncommon (Bengtson 
and Stewart 2018). Vagrants are occasionally found as far north as 
Brazil (Oliveira et al. 2006). Telemetry studies show that crabeater 
seals are generally confined to the pack ice, but spend ~14 percent of 
their time in open water outside of the breeding season (reviewed in 
Southwell et al. 2012). During the breeding season crabeater seals were 
most likely to be present within 5[deg] or less (~550 km) of the shelf 
break in the south, though non-breeding animals ranged further north. 
Pupping season peaks in mid- to late-October and adults are observed 
with their pubs as late as mid-December (Bengtson and Stewart 2018).
    Twenty-four hundred crabeater seals were counted during the 2010 
seismic surveys aboard the RV Polarstein in the Amundsen Sea (Gohl 
2010).
Leopard Seal
    The leopard seal (Hydrurga leptonyx) has a circumpolar distribution 
around the Antarctic continent where it is solitary and widely 
dispersed (Rogers 2018). Most leopard seals remain within the pack ice; 
however, members of this species regularly visit southern continents 
during the winter (Rogers 2018). Rogers (2018) estimates the global 
population to range from 222,000-440,000; however, densities are 
thought to be higher than previously thought from visual surveys alone 
(Southwell et al. 2008, Rogers et al. 2013).
    Leopard seals are top predators, consuming everything from krill 
and fish to penguins and other seals (e.g., Hall-Aspland & Rogers 2004; 
Hirukie et al. 1999). Pups are born during October to mid-November and 
weaned approximately one month later (Rogers 2018). Mating occurs in 
the water during December and January.
    Fifteen leopard seals were observed in the Amundsen Sea during 
transects conducted by Gohl (2010) and company from the RV Polarstern.
Southern Elephant Seal
    The southern elephant seal (Mirounga leonina) has a near 
circumpolar distribution in the Southern Hemisphere (Jefferson et al. 
2015), with breeding sites located on islands throughout the 
subantarctic (Hindell 2018). In the South Atlantic, southern elephant 
seals breed at Patagonia, South Georgia, and other islands of the 
Scotia Arc, Falkland Islands, Bouvet Island, and Tristan da Cunha 
archipelago (Bester & Ryan 2007). Pen[iacute]nsula Vald[eacute]s, 
Argentina, is the sole continental South American large breeding 
colony, where tens of thousands of southern elephant seals congregate 
(Lewis et al. 2006). Breeding colonies are otherwise island-based, with 
the occasional exception of the Antarctic mainland (Hindell 2018).
    When not breeding (September to October) or molting (November to 
April), southern elephant seals range throughout the Southern Ocean 
from areas north of the Antarctic Polar Front to the pack ice of the 
Antarctic, spending >80 percent of their time at sea each year, up to 
90 percent of which is spent submerged while hunting, travelling and 
resting in water depths >=200 m (Hindell 2018). Males generally feed in 
continental shelf waters, while females preferentially feed in ice-free 
Antarctic Polar Front waters or the marginal ice zone in accordance 
with winter ice expansion (Hindell 2018). Southern elephant seals 
tagged at South Georgia showed long-range movements from ~April through 
October into the open Southern Ocean and to the shelf of the Antarctic 
Peninsula (McConnell & Fedak 1996). One adult male that was sighted on 
Gough Island had previously been tagged at Marion Island in the Indian 
Ocean (Reisinger and Bester 2010). Vagrant southern elephant seals, 
mainly consisting of juvenile and subadult males, have been documented 
in Uruguay, Brazil, Argentina, Falkland Islands, and South Georgia 
(Lewis et al. 2006a; Oliveira et al. 2011; Mayorga et al. 2015).
Ross Seal
    Ross seals (Ommatophoca rossii) are considered the rarest of all 
Antarctic seals; they are the least documented because they are 
infrequently observed. Ross seals have a circumpolar Antarctic 
distribution. They are pelagic through most of the year. Satellite 
tracking data showed individuals traveled from East Antarctica and the 
Amundsen Sea north to forage in lower latitudes, spending the majority 
of their time south of the Antarctic polar front. They reach

[[Page 69957]]

distances of ~2000 km from the capture sites (Blix & Nord[oslash]y 
2007, Arcalis-Planas et al. 2015); yet, they return to areas with heavy 
pack ice for breeding (October to December) and again at the time of 
molting (January to March). Vagrants have been reported at several 
subantarctic islands, including South Georgia Island, Heard and 
McDonald Islands, Kerguelen Island, South Sandwich Islands, and 
Falklands/Malvinas Islands. Their behavior, habitat preference, and 
life cycle make it difficult to estimate population size. Genetic 
studies, estimating the effective population size of the species, are 
larger (~250,000 individuals) than traditional population size surveys 
(Curtis et al. 2011). There are no estimates available for Ross seal 
populations in the Amundsen Sea, but four individuals were observed 
during transects conducted aboard the RV Polarstern (Gohl 2010).
Weddell Seal
    The Weddell seal (Leptonychotes weddellii) has a circumpolar 
distribution around Antarctica, preferring land-fast ice habitats with 
access to open water. Their range is farther south than that of all 
other Antarctic seals. Occasionally, Weddell seals are seen at sub-
Antarctic islands (Perrin et al. 2009).
    Since they do not migrate north, adult Weddell seals live under the 
vast coating of sea ice during the coldest months and maintain 
breathing holes open by reaming them with their canine and incisor 
teeth, which are robust and project forward (Kooyman 1981b). They may 
suffer shortened lives due to damage sustained by their teeth and gums. 
They haul-out through cracks in the ice. Weddell seals give birth on 
fast ice, in late September to early November, while mating takes place 
in the water.
    Forty Weddell seals were observed in the Amundsen Sea during 
seismic survey transects conducted from the RV Polarstern (Gohl 2010).

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 3.

                  Table 3--Marine Mammal Hearing Groups
                              [NMFS, 2018]
------------------------------------------------------------------------
                                                    Generalized hearing
                  Hearing group                           range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen whales)....  7 Hz to 35 kHz.
Mid-frequency (MF) cetaceans (dolphins, toothed   150 Hz to 160 kHz.
 whales, beaked whales, bottlenose whales).
High-frequency (HF) cetaceans (true porpoises,    275 Hz to 160 kHz.
 Kogia, river dolphins, cephalorhynchid,
 Lagenorhynchus cruciger & L. australis).
Phocid pinnipeds (PW) (underwater) (true seals).  50 Hz to 86 kHz.
Otariid pinnipeds (OW) (underwater) (sea lions    60 Hz to 39 kHz.
 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).

    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. 
Eighteen marine mammal species (13 cetacean and 5 pinniped (0 otariid 
and 5 phocid) species) have the reasonable potential to co-occur with 
the proposed survey activities. Please refer to Table 2. Of the 
cetacean species that may be present, six are classified as low-
frequency cetaceans (i.e., all mysticete species), seven are classified 
as mid-frequency cetaceans (i.e., all delphinid and ziphiid species and 
the sperm whale), and none are classified as high-frequency cetaceans 
(i.e., harbor porpoise and Kogia spp.).

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 Active Acoustic Sound Sources

    This section contains a brief technical background on sound, the 
characteristics of certain sound types, and on metrics used in this 
proposal inasmuch as the information is relevant to the specified 
activity and to a discussion of the potential effects of the specified 
activity on marine mammals found later in this document.

[[Page 69958]]

    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 hertz (Hz) or cycles per second. Wavelength is the 
distance between two peaks or corresponding points of a sound wave 
(length of one cycle). Higher frequency sounds have shorter wavelengths 
than lower frequency sounds, and typically attenuate (decrease) more 
rapidly, except in certain cases in shallower water. Amplitude is the 
height of the sound pressure wave or the ``loudness'' of a sound and is 
typically described using the relative unit of the dB. A sound pressure 
level (SPL) in dB is described as the ratio between a measured pressure 
and a reference pressure (for underwater sound, this is one microPascal 
([mu]Pa)) and is a logarithmic unit that accounts for large variations 
in amplitude; therefore, a relatively small change in dB corresponds to 
large changes in sound pressure. The source level (SL) represents the 
SPL referenced at a distance of one m from the source (referenced to 
one [mu]Pa) while the received level is the SPL at the listener's 
position (referenced to one [mu]Pa).
    Root mean square (rms) is the quadratic mean sound pressure over 
the duration of an impulse. Root mean square is calculated by squaring 
all of the sound amplitudes, averaging the squares, and then taking the 
square root of the average (Urick 1983). Root mean square 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.
    Sound exposure level (SEL; represented as dB re 1 [mu]Pa\2\-s) 
represents the total energy contained within a pulse and considers both 
intensity and duration of exposure. Peak sound pressure (also referred 
to as zero-to-peak sound pressure or 0-p) is the maximum instantaneous 
sound pressure measurable in the water at a specified distance from the 
source and is represented in the same units as the rms sound pressure. 
Another common metric is peak-to-peak sound pressure (pk-pk), which is 
the algebraic difference between the peak positive and peak negative 
sound pressures. Peak-to-peak pressure is typically approximately six 
dB higher than peak pressure (Southall et al., 2007).
    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 a 
manner similar to ripples on the surface of a pond and may be either 
directed in a beam or beams or may radiate in all directions 
(omnidirectional sources), as is the case for pulses produced by the 
airgun arrays considered here. 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., 
wind and waves, earthquakes, ice, atmospheric sound), biological (e.g., 
sounds produced by marine mammals, fish, and invertebrates), and 
anthropogenic (e.g., vessels, dredging, construction) sound. 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 sound for frequencies between 200 Hz and 50 
kHz (Mitson, 1995). In general, ambient sound levels tend to increase 
with increasing wind speed and wave height. Surf sound becomes 
important near shore, with measurements collected at a distance of 8.5 
km from shore showing an increase of 10 dB in the 100 to 700 Hz band 
during heavy surf conditions;
     Precipitation: Sound from rain and hail impacting the 
water surface can become an important component of total sound at 
frequencies above 500 Hz, and possibly down to 100 Hz during quiet 
times;
     Biological: Marine mammals can contribute significantly to 
ambient sound levels, as can some fish and snapping shrimp. The 
frequency band for biological contributions is from approximately 12 Hz 
to over 100 kHz; and
     Anthropogenic: Sources of ambient sound related to human 
activity include transportation (surface vessels), dredging and 
construction, oil and gas drilling and production, seismic surveys, 
sonar, explosions, and ocean acoustic studies. Vessel noise typically 
dominates the total ambient sound 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. 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.
    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 
human 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 (Richardson et al., 1995). The result is that, 
depending on the source type and its intensity, sound from a given 
activity may be a negligible addition to the local environment or could 
form a distinctive signal that may affect marine mammals. Details of 
source types are described in the following text.
    Sounds are often considered to fall into one of two general types: 
Pulsed and non-pulsed (defined in the following). 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.
    Pulsed sound sources (e.g., airguns, 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, 2005; Harris, 1998; NIOSH, 1998; ISO, 2003) and occur 
either as isolated events or repeated in some succession. Pulsed sounds 
are all characterized by a relatively rapid rise from ambient pressure 
to a maximal pressure value followed by a rapid decay period that

[[Page 69959]]

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.
    Non-pulsed 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-pulsed sounds can be transient signals 
of short duration but without the essential properties of pulses (e.g., 
rapid rise time). Examples of non-pulsed sounds include those produced 
by vessels, aircraft, machinery operations such as drilling or 
dredging, vibratory pile driving, and active sonar systems (such as 
those used by the U.S. Navy). The duration of such sounds, as received 
at a distance, can be greatly extended in a highly reverberant 
environment.
    Airgun arrays produce pulsed signals with energy in a frequency 
range from about 10-2,000 Hz, with most energy radiated at frequencies 
below 200 Hz. The amplitude of the acoustic wave emitted from the 
source is equal in all directions (i.e., omnidirectional), but airgun 
arrays do possess some directionality due to different phase delays 
between guns in different directions. Airgun arrays are typically tuned 
to maximize functionality for data acquisition purposes, meaning that 
sound transmitted in horizontal directions and at higher frequencies is 
minimized to the extent possible.
    As described above, a Kongsberg EM122 MBES and a Knudsen Chirp 3260 
SBP would be operated continuously during the proposed surveys, but not 
during transit to and from the survey areas. Additionally a 12-kHz 
pinger would be used during coring, when seismic airguns, are not in 
operation (more information on this pinger is available in NSF-USGS 
(2011). Each ping emitted by the MBES consists of eight (in water 
>1,000 m deep) or four (<1,000 m) successive fan-shaped transmissions, 
each ensonifying a sector that extends 1[deg] fore-aft. Given the 
movement and speed of the vessel, the intermittent and narrow downward-
directed nature of the sounds emitted by the MBES would result in no 
more than one or two brief ping exposures of any individual marine 
mammal, if any exposure were to occur.
    Due to the lower source levels of the Knudsen Chirp 3260 SBP 
relative to the Palmer's airgun array (maximum SL of 222 dB re 1 [mu]Pa 
[middot] m for the SBP, versus a minimum of 230.9 dB re 1 [mu]Pa 
[middot] m for the 2 airgun array (LGL, 2019)), sounds from the SBP are 
expected to be effectively subsumed by sounds from the airgun array. 
Thus, any marine mammal potentially exposed to sounds from the SBP 
would already have been exposed to sounds from the airgun array, which 
are expected to propagate further in the water.
    The use of pingers is also highly unlikely to affect marine mammals 
given their intermittent nature, short-term and transitory use from a 
moving vessel, relatively low source levels, and brief signal durations 
(NSF-USGS, 2011). As such, we conclude that the likelihood of marine 
mammal take resulting from exposure to sound from the MBES or SBP 
(beyond that which is already quantified as a result of exposure to the 
airguns) is discountable. Additionally the characteristics of sound 
generated by pingers means that take of marine mammals resulting from 
exposure to these pingers is discountable. Therefore we do not consider 
noise from the MBES, SBP, or pingers further in this analysis.

Acoustic Effects

    Here, we discuss the effects of active acoustic sources on marine 
mammals.
    Potential Effects of Underwater Sound--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 
potentially result in 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; G[ouml]tz 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. We first 
describe specific manifestations of acoustic effects before providing 
discussion specific to the use of airgun arrays.
    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 or other 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 describe the more severe effects of certain non-auditory 
physical or physiological effects only briefly as we do not expect that 
use of airgun arrays are reasonably likely to result in such effects 
(see below for further discussion). 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) caused by exposure to sound 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). The survey activities considered here do not 
involve the use of devices such as explosives or mid-frequency tactical 
sonar that are associated with these types of effects.
    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

[[Page 69960]]

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, and there is no PTS data for cetaceans but such 
relationships are assumed to be similar to those in humans and other 
terrestrial mammals. PTS typically occurs at exposure levels at least 
several dBs above (a 40-dB threshold shift approximates PTS onset; 
e.g., Kryter et al., 1966; Miller, 1974) that 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 airgun pulses as 
received close to the source) are at least 6 dB higher than the TTS 
threshold on a peak-pressure basis and PTS cumulative sound exposure 
level thresholds are 15 to 20 dB higher than TTS cumulative sound 
exposure level thresholds (Southall et al., 2007). Given the higher 
level of sound or longer exposure duration necessary to cause PTS as 
compared with TTS, it is considerably less likely that PTS could occur.
    For mid-frequency cetaceans in particular, potential protective 
mechanisms may help limit onset of TTS or prevent onset of PTS. Such 
mechanisms include dampening of hearing, auditory adaptation, or 
behavioral amelioration (e.g., Nachtigall and Supin, 2013; Miller et 
al., 2012; Finneran et al., 2015; Popov et al., 2016).
    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. Few data 
on sound levels and durations necessary to elicit mild TTS have been 
obtained for marine mammals.
    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 
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.
    Finneran et al. (2015) measured hearing thresholds in three captive 
bottlenose dolphins before and after exposure to ten pulses produced by 
a seismic airgun in order to study TTS induced after exposure to 
multiple pulses. Exposures began at relatively low levels and gradually 
increased over a period of several months, with the highest exposures 
at peak SPLs from 196 to 210 dB and cumulative (unweighted) SELs from 
193-195 dB. No substantial TTS was observed. In addition, behavioral 
reactions were observed that indicated that animals can learn behaviors 
that effectively mitigate noise exposures (although exposure patterns 
must be learned, which is less likely in wild animals than for the 
captive animals considered in this study). The authors note that the 
failure to induce more significant auditory effects likely due to the 
intermittent nature of exposure, the relatively low peak pressure 
produced by the acoustic source, and the low-frequency energy in airgun 
pulses as compared with the frequency range of best sensitivity for 
dolphins and other mid-frequency cetaceans.
    Currently, TTS data only exist for four species of cetaceans 
(bottlenose dolphin, beluga whale, harbor porpoise, and Yangtze finless 
porpoise) exposed to a limited number of sound sources (i.e., mostly 
tones and octave-band noise) in laboratory settings (Finneran, 2015). 
In general, harbor porpoises have a lower TTS onset than other measured 
cetacean species (Finneran, 2015). 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.
    Critical questions remain regarding the rate of TTS growth and 
recovery after exposure to intermittent noise and the effects of single 
and multiple pulses. Data at present are also insufficient to construct 
generalized models for recovery and determine the time necessary to 
treat subsequent exposures as independent events. More information is 
needed on the relationship between auditory evoked potential and 
behavioral measures of TTS for various stimuli. 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), Finneran (2015), and NMFS (2016a).
    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

[[Page 69961]]

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 showed pronounced 
behavioral reactions, including avoidance of loud sound sources 
(Ridgway et al., 1997). Observed responses of wild marine mammals to 
loud pulsed 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). 
However, many delphinids approach acoustic source vessels with no 
apparent discomfort or obvious behavioral change (e.g., Barkaszi et 
al., 2012).
    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, 
2005). 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; Ng and Leung, 2003; Nowacek et al., 2004; Goldbogen et 
al., 2013a, b). 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.
    Visual tracking, passive acoustic monitoring, and movement 
recording tags were used to quantify sperm whale behavior prior to, 
during, and following exposure to airgun arrays at received levels in 
the range 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., 
2006; 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 airguns 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 seismic 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).
    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 exposure (e.g., Kastelein et al., 2001, 2005, 2006; Gailey et 
al., 2007, 2016).
    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 sound 
production during production of aversive signals (Bowles et al., 1994).
    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 breeding 
activity 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 airgun 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 a seismic 
airgun survey. During the first 72 h of

[[Page 69962]]

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 the study area. This displacement persisted for a time period 
well beyond the 10-day duration of seismic airgun 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 [mu]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 acoustic 
source vessel (estimated received level 143 dB pk-pk). Blackwell et al. 
(2013) found that bowhead whale call rates dropped significantly at 
onset of airgun 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 airgun signals were 
detectable before ultimately decreasing calling rates at higher 
received levels (i.e., 10-minute SELcum 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). These studies demonstrate that even low 
levels of noise received far from the source can induce changes in 
vocalization and/or behavior for mysticetes.
    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, and is one of the most obvious manifestations of disturbance 
in marine mammals (Richardson et al., 1995). For example, gray whales 
are known to change direction--deflecting from customary migratory 
paths--in order to avoid noise from seismic surveys (Malme et al., 
1984). Humpback whales showed avoidance behavior in the presence of an 
active seismic array during observational studies and controlled 
exposure experiments in western Australia (McCauley et al., 2000). 
Avoidance may be short-term, with animals returning to the area once 
the noise has ceased (e.g., Bowles et al., 1994; Goold, 1996; Stone et 
al., 2000; Morton and Symonds, 2002; 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., Bejder et al., 2006; Teilmann et al., 2006).
    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, marine mammal strandings 
(Evans and England, 2001). However, it should be noted that response to 
a perceived predator does not necessarily invoke flight (Ford and 
Reeves, 2008), and whether individuals are solitary or in groups may 
influence the response.
    Behavioral disturbance can also impact marine mammals in more 
subtle ways. Increased vigilance may result in costs related to 
diversion of focus and attention (i.e., when a response consists of 
increased vigilance, it may come at the cost of decreased attention to 
other critical behaviors 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 (e.g., Beauchamp and 
Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). In 
addition, 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). However, 
Ridgway et al. (2006) reported that increased vigilance in bottlenose 
dolphins exposed to sound over a five-day period did not cause any 
sleep deprivation or stress effects.
    Many animals perform vital functions, such as feeding, resting, 
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption 
of such functions resulting from reactions to stressors such as sound 
exposure are more likely to be significant 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). Note that there is a difference between multi-day 
substantive behavioral reactions and multi-day anthropogenic 
activities. For example, just because an activity lasts for multiple 
days does not necessarily mean that individual animals are either 
exposed to activity-related stressors for multiple days or, further, 
exposed in a manner resulting in sustained multi-day substantive 
behavioral responses.
    Stone (2015) reported data from at-sea observations during 1,196 
seismic surveys from 1994 to 2010. When large arrays of airguns 
(considered 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. Behavioral observations of gray whales during a seismic 
survey monitored 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 significantly associated with seismic survey or 
vessel sounds.
    Stress Responses--An animal's perception of a threat may be 
sufficient to trigger stress responses consisting of some combination 
of behavioral responses, autonomic nervous system responses, 
neuroendocrine responses, or immune responses (e.g., Seyle, 1950; 
Moberg, 2000). In many cases, an animal's first and sometimes most 
economical (in terms of energetic costs) response is behavioral 
avoidance of the potential stressor. Autonomic nervous system responses 
to stress typically involve changes in heart rate, blood pressure, and 
gastrointestinal activity. These responses have a relatively short 
duration and may or may not have a significant long-term effect on an 
animal's fitness.
    Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that 
are

[[Page 69963]]

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, altered metabolism, reduced immune 
competence, and behavioral disturbance (e.g., Moberg, 1987; Blecha, 
2000). Increases in the circulation of glucocorticoids are also equated 
with stress (Romano et al., 2004).
    The primary distinction between stress (which is adaptive and does 
not normally place an animal at risk) and ``distress'' is the 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 functions. This state of 
distress will last until the animal replenishes its energetic reserves 
sufficiently to restore normal function.
    Relationships between these physiological mechanisms, animal 
behavior, and the costs of stress responses are well-studied through 
controlled experiments and for both laboratory and free-ranging animals 
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; 
Krausman et al., 2004; Lankford et al., 2005). Stress responses due to 
exposure to anthropogenic sounds or other stressors and their effects 
on marine mammals have also 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).
    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, navigation) (Richardson et al., 1995; 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. 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.
    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 or altering critical behaviors. It is important to 
distinguish TTS and PTS, which persist after the sound exposure, from 
masking, which occurs during the sound exposure. Because masking 
(without resulting in TS) is not associated with abnormal physiological 
function, it is not considered a physiological effect, but rather a 
potential behavioral effect.
    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) 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).
    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 vessel traffic), 
contribute to elevated ambient sound levels, thus intensifying masking.
    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal calls and other natural sounds are expected 
to be limited, although there are few specific data on this. Because of 
the intermittent nature and low duty cycle of seismic pulses, animals 
can emit and receive sounds in the relatively quiet intervals between 
pulses. However, in exceptional situations, reverberation occurs for 
much or all of the interval between pulses (e.g., Simard et al. 2005; 
Clark and Gagnon 2006), which could mask calls. Situations with 
prolonged strong reverberation are infrequent. However, it is common 
for reverberation to cause some lesser degree of elevation of the 
background level between airgun pulses (e.g., Gedamke 2011; Guerra et 
al. 2011, 2016; Klinck et al. 2012; Guan et al. 2015), and this weaker 
reverberation presumably reduces the detection range of calls and other 
natural sounds to some degree. Guerra et al. (2016) reported that 
ambient noise levels between seismic pulses were elevated as a result 
of reverberation at ranges of 50 km from the seismic source. Based on 
measurements in deep water of the Southern Ocean, Gedamke (2011) 
estimated that the slight elevation of background levels during 
intervals between pulses reduced blue and fin whale communication space 
by as much as 36-51 percent when a seismic survey was operating 450-
2,800 km away. Based on preliminary modeling, Wittekind et al. (2016) 
reported that airgun sounds could reduce the communication range of 
blue and fin whales 2000 km from the seismic source. Nieukirk et al. 
(2012) and Blackwell et al. (2013) noted the

[[Page 69964]]

potential for masking effects from seismic surveys on large whales.
    Some baleen and toothed whales are known to continue calling in the 
presence of seismic pulses, and their calls usually can be heard 
between the pulses (e.g., Nieukirk et al. 2012; Thode et al. 2012; 
Br[ouml]ker et al. 2013; Sciacca et al. 2016). As noted above, Cerchio 
et al. (2014) suggested that the breeding display of humpback whales 
off Angola could be disrupted by seismic sounds, as singing activity 
declined with increasing received levels. In addition, some cetaceans 
are known to change their calling rates, shift their peak frequencies, 
or otherwise modify their vocal behavior in response to airgun sounds 
(e.g., Di Iorio and Clark 2010; Castellote et al. 2012; Blackwell et 
al. 2013, 2015). The hearing systems of baleen whales are undoubtedly 
more sensitive to low-frequency sounds than are the ears of the small 
odontocetes that have been studied directly (e.g., MacGillivray et al. 
2014). The sounds important to small odontocetes are predominantly at 
much higher frequencies than are the dominant components of airgun 
sounds, thus limiting the potential for masking. In general, masking 
effects of seismic pulses are expected to be minor, given the normally 
intermittent nature of seismic pulses.

Ship Noise

    Vessel noise from the Palmer could affect marine animals in the 
proposed survey areas. Houghton et al. (2015) proposed that vessel 
speed is the most important predictor of received noise levels, and 
Putland et al. (2017) also reported reduced sound levels with decreased 
vessel speed. Sounds produced by large vessels generally dominate 
ambient noise at frequencies from 20 to 300 Hz (Richardson et al. 
1995). However, some energy is also produced at higher frequencies 
(Hermannsen et al. 2014); low levels of high-frequency sound from 
vessels has been shown to elicit responses in harbor porpoise (Dyndo et 
al. 2015). Increased levels of ship noise have been shown to affect 
foraging by porpoise (Teilmann et al. 2015; Wisniewska et al. 2018); 
Wisniewska et al. (2018) suggest that a decrease in foraging success 
could have long-term fitness consequences.
    Ship noise, through masking, can reduce the effective communication 
distance of a marine mammal if the frequency of the sound source is 
close to that used by the animal, and if the sound is present for a 
significant fraction of time (e.g., Richardson et al. 1995; Clark et 
al. 2009; Jensen et al. 2009; Gervaise et al. 2012; Hatch et al. 2012; 
Rice et al. 2014; Dunlop 2015; Erbe et al. 2015; Jones et al. 2017; 
Putland et al. 2017). In addition to the frequency and duration of the 
masking sound, the strength, temporal pattern, and location of the 
introduced sound also play a role in the extent of the masking 
(Branstetter et al. 2013, 2016; Finneran and Branstetter 2013; Sills et 
al. 2017). Branstetter et al. (2013) reported that time-domain metrics 
are also important in describing and predicting masking. In order to 
compensate for increased ambient noise, some cetaceans are known to 
increase the source levels of their calls in the presence of elevated 
noise levels from shipping, shift their peak frequencies, or otherwise 
change their vocal behavior (e.g., Parks et al. 2011, 2012, 2016a,b; 
Castellote et al. 2012; Melc[oacute]n et al. 2012; Azzara et al. 2013; 
Tyack and Janik 2013; Lu[iacute]s et al. 2014; Sairanen 2014; Papale et 
al. 2015; Bittencourt et al. 2016; Dahlheim and Castellote 2016; 
Gospi[cacute] and Picciulin 2016; Gridley et al. 2016; Heiler et al. 
2016; Martins et al. 2016; O'Brien et al. 2016; Tenessen and Parks 
2016). Harp seals did not increase their call frequencies in 
environments with increased low-frequency sounds (Terhune and Bosker 
2016). Holt et al. (2015) reported that changes in vocal modifications 
can have increased energetic costs for individual marine mammals. A 
negative correlation between the presence of some cetacean species and 
the number of vessels in an area has been demonstrated by several 
studies (e.g., Campana et al. 2015; Culloch et al. 2016).
    Baleen whales are thought to be more sensitive to sound at these 
low frequencies than are toothed whales (e.g., MacGillivray et al. 
2014), possibly causing localized avoidance of the proposed survey area 
during seismic operations. Reactions of gray and humpback whales to 
vessels have been studied, and there is limited information available 
about the reactions of right whales and rorquals (fin, blue, and minke 
whales). Reactions of humpback whales to boats are variable, ranging 
from approach to avoidance (Payne 1978; Salden 1993). Baker et al. 
(1982, 1983) and Baker and Herman (1989) found humpbacks often move 
away when vessels are within several kilometers. Humpbacks seem less 
likely to react overtly when actively feeding than when resting or 
engaged in other activities (Krieger and Wing 1984, 1986). Increased 
levels of ship noise have been shown to affect foraging by humpback 
whales (Blair et al. 2016). Fin whale sightings in the western 
Mediterranean were negatively correlated with the number of vessels in 
the area (Campana et al. 2015). Minke whales and gray seals have shown 
slight displacement in response to construction-related vessel traffic 
(Anderwald et al. 2013).
    Many odontocetes show considerable tolerance of vessel traffic, 
although they sometimes react at long distances if confined by ice or 
shallow water, if previously harassed by vessels, or have had little or 
no recent exposure to ships (Richardson et al. 1995). Dolphins of many 
species tolerate and sometimes approach vessels (e.g., Anderwald et al. 
2013). Some dolphin species approach moving vessels to ride the bow or 
stern waves (Williams et al. 1992). Pirotta et al. (2015) noted that 
the physical presence of vessels, not just ship noise, disturbed the 
foraging activity of bottlenose dolphins. Sightings of striped dolphin, 
Risso's dolphin, sperm whale, and Cuvier's beaked whale in the western 
Mediterranean were negatively correlated with the number of vessels in 
the area (Campana et al. 2015).
    There are few data on the behavioral reactions of beaked whales to 
vessel noise, though they seem to avoid approaching vessels (e.g., 
W[uuml]rsig et al. 1998) or dive for an extended period when approached 
by a vessel (e.g., Kasuya 1986). Based on a single observation, Aguilar 
Soto et al. (2006) suggest foraging efficiency of Cuvier's beaked 
whales may be reduced by close approach of vessels.
    In summary, project vessel sounds would not be at levels expected 
to cause anything more than possible localized and temporary behavioral 
changes in marine mammals, and would not be expected to result in 
significant negative effects on individuals or at the population level. 
In addition, in all oceans of the world, large vessel traffic is 
currently so prevalent that it is commonly considered a usual source of 
ambient sound (NSF-USGS 2011).

Ship Strike

    Vessel collisions with marine mammals, 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 may be struck directly by a vessel, a surfacing animal may hit 
the bottom of a vessel, or an animal just below the surface may be cut 
by a vessel's propeller. Superficial strikes may not kill or result in 
the death of the animal. These interactions are typically associated 
with large whales (e.g., fin whales), which are occasionally found 
draped across the bulbous bow of large

[[Page 69965]]

commercial ships upon arrival in port. Although smaller cetaceans are 
more maneuverable in relation to large vessels than are large whales, 
they may also be susceptible to strike. The severity of injuries 
typically depends on the size and speed of the vessel, with the 
probability of death or serious injury increasing as vessel speed 
increases (Knowlton and Kraus, 2001; Laist et al., 2001; 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).
    Pace and Silber (2005) also 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, but higher speeds also appear to 
increase the chance of severe injuries or death through increased 
likelihood of collision by pulling whales toward the vessel (Clyne, 
1999; Knowlton et al., 1995). 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 one hundred percent above 15 kn.
    The Palmer travels at a speed of either 5 kn (9.2 km/hour) or 4-6 
kn (7.4-11.1 km/hr). At these speeds, both the possibility of striking 
a marine mammal and the possibility of a strike resulting in serious 
injury or mortality are discountable. At average transit speed, the 
probability of serious injury or mortality resulting from a strike is 
less than 50 percent. However, the likelihood of a strike actually 
happening is again discountable. Ship strikes, as analyzed in the 
studies cited above, generally involve commercial shipping, which is 
much more common in both space and time than is geophysical survey 
activity. Jensen and Silber (2004) summarized ship strikes of large 
whales worldwide from 1975-2003 and found that most collisions occurred 
in the open ocean and involved large vessels (e.g., commercial 
shipping). No such incidents were reported for geophysical survey 
vessels during that time period.
    It is possible for ship strikes to occur while traveling at slow 
speeds. For example, a hydrographic survey vessel traveling at low 
speed (5.5 kn) while conducting mapping surveys off the central 
California coast struck and killed a blue whale in 2009. The State of 
California determined that the whale had suddenly and unexpectedly 
surfaced beneath the hull, with the result that the propeller severed 
the whale's vertebrae, and that this was an unavoidable event. This 
strike represents the only such incident in approximately 540,000 hours 
of similar coastal mapping activity (p = 1.9 x 10-\6\; 95 
percent CI = 0-5.5 x 10-\6\; NMFS, 2013b). In addition, a 
research vessel reported a fatal strike in 2011 of a dolphin in the 
Atlantic, demonstrating that it is possible for strikes involving 
smaller cetaceans to occur. In that case, the incident report indicated 
that an animal apparently was struck by the vessel's propeller as it 
was intentionally swimming near the vessel. While indicative of the 
type of unusual events that cannot be ruled out, neither of these 
instances represents a circumstance that would be considered reasonably 
foreseeable or that would be considered preventable.
    Although the likelihood of the vessel striking a marine mammal is 
low, we require a robust ship strike avoidance protocol (see Proposed 
Mitigation), which we believe eliminates any foreseeable risk of ship 
strike. We anticipate that vessel collisions involving a seismic data 
acquisition vessel towing gear, while not impossible, represent 
unlikely, unpredictable events for which there are no preventive 
measures. Given the required mitigation measures, the relatively slow 
speed of the vessel towing gear, the presence of bridge crew watching 
for obstacles at all times (including marine mammals), and the presence 
of marine mammal observers, we believe that the possibility of ship 
strike is discountable and, further, that were a strike of a large 
whale to occur, it would be unlikely to result in serious injury or 
mortality. No incidental take resulting from ship strike is 
anticipated, and this potential effect of the specified activity will 
not be discussed further in the following analysis.
    Stranding--When a living or dead marine mammal swims or floats onto 
shore and becomes ``beached'' or incapable of returning to sea, the 
event is a ``stranding'' (Geraci et al., 1999; Perrin and Geraci, 2002; 
Geraci and Lounsbury, 2005; NMFS, 2007). The legal definition for a 
stranding under 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.
    Marine mammals strand for a variety of reasons, such as infectious 
agents, biotoxicosis, starvation, fishery interaction, ship strike, 
unusual oceanographic or weather events, sound exposure, or 
combinations of these stressors sustained concurrently or in series. 
However, the cause or causes of most strandings are unknown (Geraci et 
al., 1976; Eaton, 1979; Odell et al., 1980; Best, 1982). Numerous 
studies suggest that the physiology, behavior, habitat relationships, 
age, or condition of cetaceans may cause them to strand or might pre-
dispose them to strand when exposed to another phenomenon. These 
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 (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).
    Use of military tactical sonar has been implicated in a majority of 
investigated stranding events. Most known stranding events have 
involved beaked whales, though a small number have involved deep-diving 
delphinids or sperm whales (e.g., Mazzariol et al., 2010; Southall et 
al., 2013). In general, long duration (~1 second) and high-intensity 
sounds (>235 dB SPL) have been implicated in stranding events 
(Hildebrand, 2004). With regard to beaked whales, mid-frequency sound 
is typically implicated (when causation can be determined) (Hildebrand, 
2004). Although seismic airguns create predominantly low-frequency 
energy, the signal does include a mid-frequency component. We have 
considered the potential for the proposed surveys to result in marine 
mammal stranding and have concluded that, based on the best available

[[Page 69966]]

information, stranding is not expected to occur.
    Effects to Prey--Marine mammal prey varies by species, season, and 
location and, for some, is not well documented. Fish react to sounds 
which are especially strong and/or intermittent low-frequency sounds. 
Short duration, sharp sounds can cause overt or subtle changes in fish 
behavior and local distribution. Hastings and Popper (2005) identified 
several studies that suggest fish may relocate to avoid certain areas 
of sound energy. Additional studies have documented effects of pulsed 
sound on fish, although several are based on studies in support of 
construction projects (e.g., Scholik and Yan, 2001, 2002; Popper and 
Hastings, 2009). Sound pulses at received levels of 160 dB may cause 
subtle changes in fish behavior. SPLs of 180 dB may cause noticeable 
changes in behavior (Pearson et al., 1992; Skalski et al., 1992). SPLs 
of sufficient strength have been known to cause injury to fish and fish 
mortality. The most likely impact to fish from survey activities at the 
project area would be temporary avoidance of the area. The duration of 
fish avoidance of a given area after survey effort stops is unknown, 
but a rapid return to normal recruitment, distribution and behavior is 
anticipated.
    Information on seismic airgun impacts to zooplankton, which 
represent an important prey type for mysticetes, is limited. However, 
McCauley et al. (2017) reported that experimental exposure to a pulse 
from a 150 inch\3\ airgun decreased zooplankton abundance when compared 
with controls, as measured by sonar and net tows, and caused a two- to 
threefold increase in dead adult and larval zooplankton. Although no 
adult krill were present, the study found that all larval krill were 
killed after air gun passage. Impacts were observed out to the maximum 
1.2 km range sampled.
    In general, impacts to marine mammal prey are expected to be 
limited due to the relatively small temporal and spatial overlap 
between the proposed survey and any areas used by marine mammal prey 
species. The proposed use of airguns as part of an active seismic array 
survey would occur over a relatively short time period (~28 days) and 
would occur over a very small area relative to the area available as 
marine mammal habitat in the Southwest Atlantic Ocean. We believe any 
impacts to marine mammals due to adverse effects to their prey would be 
insignificant due to the limited spatial and temporal impact of the 
proposed survey. However, adverse impacts may occur to a few species of 
fish and to zooplankton.
    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 airgun arrays). 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 see also the previous discussion on 
masking under Acoustic Effects), which may range from local effects for 
brief periods of time to chronic effects over large areas and for long 
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). For more detail on these concepts see, e.g., Barber et 
al., 2010; Pijanowski et al., 2011; Francis and Barber, 2013; Lillis et 
al., 2014.
    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). Although the signals emitted by 
seismic airgun arrays are generally low frequency, they would also 
likely be of short duration and transient in any given area due to the 
nature of these surveys. As described previously, exploratory surveys 
such as this one cover a large area but would be transient rather than 
focused in a given location over time and therefore would not be 
considered chronic in any given location.

Potential Effects of Icebreaking

    Icebreakers produce more noise while breaking ice than ships of 
comparable size due, primarily, to the sounds of propeller cavitating 
(Richardson et al., 1995). Icebreakers commonly back and ram into heavy 
ice until losing momentum to make way. The highest noise levels usually 
occur while backing full astern in preparation to ram forward through 
the ice. Overall the noise generated by an icebreaker pushing ice was 
10 to 15 dB greater than the noise produced by the ship underway in 
open water (Richardson et al., 1995). In general, the Antarctic and 
Southern Ocean is a noisy environment. Calving and grounding icebergs 
as well as the break-up of ice sheets, can produce a large amount of 
underwater noise. Little information is available about the increased 
sound levels due to icebreaking.
    Cetaceans--Few studies have been conducted to evaluate the 
potential interference of icebreaking noise with marine mammal 
vocalizations. Erbe and Farmer (1998) measured masked hearing 
thresholds of a captive beluga whale. They reported that the recording 
of a Canadian Coast Guard Ship (CCGS) Henry Larsen, ramming ice in the 
Beaufort Sea, masked recordings of beluga vocalizations at a noise to 
signal pressure ratio of 18 dB, when the noise pressure level was eight 
times as high as the call pressure. Erbe and Farmer (2000) also 
predicted when icebreaker noise would affect beluga whales through 
software that combined a sound propagation model and beluga whale 
impact threshold models. They again used the data from the recording of 
the Henry Larsen in the Beaufort Sea and predicted that masking of 
beluga whale vocalizations could extend between 40 and 71 km (21.6 and 
38.3 nmi) near the surface. Lesage et al. (1999) report that beluga 
whales changed their call type and call frequency when exposed to boat 
noise. It is possible that the whales adapt to the ambient noise levels 
and are able to communicate despite the sound. Given the documented 
reaction of belugas to ships and icebreakers it is highly unlikely that 
beluga whales would remain in the proximity of vessels where 
vocalizations would be masked.
    Beluga whales have been documented swimming rapidly away from ships 
and icebreakers in the Canadian high Arctic when a ship approaches to 
within 35 to 50 km (18.9 to 27 nmi), and they may travel up to 80 km 
(43.2 nmi) from the vessel's track (Richardson et al., 1995). It is 
expected that belugas avoid icebreakers as soon as they detect the

[[Page 69967]]

ships (Cosens & Dueck, 1993). However, the reactions of beluga whales 
to ships vary greatly and some animals may become habituated to high 
levels of ambient noise (Erbe & Darmber, 2000).
    There is little information about the effects of icebreaking ships 
on baleen whales. Migrating bowhead whales appeared to avoid an area 
around a drill site by greater than 25 km (13.5 mi) where an icebreaker 
was working in the Beaufort Sea. There was intensive icebreaking daily 
in support of the drilling activities (Brewer et al., 1993). Migrating 
bowheads also avoided a nearby drill site at the same time of year 
where little icebreaking was being conducted (LGL & Greeneridge, 1987). 
It is unclear as to whether the drilling activities, icebreaking 
operations, or the ice itself might have been the cause for the whale's 
diversion. Bowhead whales are not expected to occur in the proximity of 
the proposed action area.
    Pinnipeds--Brueggeman et al. (1992) reported on the reactions of 
seals to an icebreaker during activities at two prospects in the 
Chukchi Sea. Reactions of seals to the icebreakers varied between the 
two prospects. Most (67 percent) seals did not react to the icebreaker 
at either prospect. Reaction at one prospect was greatest during 
icebreaking activity (running/maneuvering/jogging) and was 0.23 km 
(0.12 nmi) of the vessel and lowest for animals beyond 0.93 km (0.5 
nmi). At the second prospect however, seal reaction was lowest during 
icebreaking activity with higher and similar levels of response during 
general (non-icebreaking) vessel operations and when the vessel was at 
anchor or drifting. The frequency of seal reaction generally declined 
with increasing distance from the vessel except during general vessel 
activity where it remained consistently high to about 0.46 km (0.25 
nmi) from the vessel before declining.
    Similarly, Kanik et al. (1980) found that ringed (Pusa hispida) and 
harp seals (Pagophilus groenlandicus) often dove into the water when an 
icebreaker was breaking ice within 1 km (0.5 nmi) of the animals. Most 
seals remained on the ice when the ship was breaking ice 1 to 2 km (0.5 
to 1.1 nmi) away.
    Sea ice is important for pinniped life functions such as resting, 
breeding, and molting. Icebreaking activities may damage seal breathing 
holes and would also reduce the haul-out area in the immediate vicinity 
of the ship's track. Icebreaking along a maximum of 500 km of 
tracklines would alter local ice conditions in the immediate vicinity 
of the vessel. This has the potential to temporarily lead to a 
reduction of suitable seal haul-out habitat. However, the dynamic sea-
ice environment requires that seals be able to adapt to changes in sea, 
ice, and snow conditions, and they therefore create new breathing holes 
and lairs throughout the winter and spring (Hammill and Smith, 1989). 
In addition, seals often use open leads and cracks in the ice to 
surface and breathe (Smith and Stirling, 1975). Disturbance of the ice 
would occur in a very small area relative to the Southern Ocean ice-
pack and no significant impact on marine mammals is anticipated by 
icebreaking during the proposed low-energy seismic survey.
    In summary, activities associated with the proposed action are not 
likely to have a permanent, adverse effect on any fish habitat or 
populations of fish species or on the quality of acoustic habitat. 
Thus, any impacts to marine mammal habitat are not expected to cause 
significant or long-term consequences for individual marine mammals or 
their populations.

Estimated Take

    This section provides an estimate of the number of incidental takes 
proposed for authorization through this IHA, which will inform both 
NMFS' consideration of ``small numbers'' and the negligible impact 
determination.
    Harassment is the only type of take expected to result from these 
activities. Except with respect to certain activities not pertinent 
here, section 3(18) of the MMPA defines ``harassment'' as any act of 
pursuit, torment, or annoyance, which (i) has the potential to injure a 
marine mammal or marine mammal stock in the wild (Level A harassment); 
or (ii) has the potential to disturb a marine mammal or marine mammal 
stock in the wild by causing disruption of behavioral patterns, 
including, but not limited to, migration, breathing, nursing, breeding, 
feeding, or sheltering (Level B harassment).
    Authorized takes would be by Level B harassment only, in the form 
of disruption of behavioral patterns for individual marine mammals 
resulting from exposure to the stressors of acoustic sources. Based on 
the nature of the activity (i.e., small Level A zones) and the 
anticipated effectiveness of the mitigation measures (i.e., visual 
mitigation monitoring; establishment of an exclusion zone; shutdown 
procedures; ramp-up procedures; and vessel strike avoidance measures)--
discussed in detail below in Proposed Mitigation section, Level A 
harassment is neither anticipated, nor proposed to be authorized.
    As described previously, no mortality is anticipated or proposed to 
be authorized for this activity. Below we describe how the take is 
estimated.
    Generally speaking, we estimate take by considering: (1) Acoustic 
thresholds above which NMFS believes the best available science 
indicates marine mammals will be behaviorally harassed or incur some 
degree of hearing impairment; (2) the area or volume of water that will 
be ensonified above these levels in a day; (3) the density or 
occurrence of marine mammals within these ensonified areas; and, (4) 
and the number of days of activities. We note that while these basic 
factors can contribute to a basic calculation to provide an initial 
prediction of takes, additional information that can qualitatively 
inform take estimates is also sometimes available (e.g., previous 
monitoring results or average group size). Below, we describe the 
factors considered here in more detail and present the proposed take 
estimate.

Acoustic Thresholds

    Using the best available science, NMFS has developed acoustic 
thresholds that identify the received level of underwater sound above 
which exposed marine mammals would be reasonably expected to be 
behaviorally harassed (equated to Level B harassment) or to incur PTS 
of some degree (equated to Level A harassment).
    Level B Harassment for non-explosive sources--Though significantly 
driven by received level, the onset of 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 (Southall et al., 2007, 
Ellison et al., 2012). Based on what the available science indicates 
and the practical need to use a threshold based on a factor that is 
both predictable and measurable for most activities, NMFS uses a 
generalized acoustic threshold based on received level to estimate the 
onset of behavioral harassment. NMFS predicts that marine mammals are 
likely to be behaviorally harassed in a manner we consider Level B 
harassment when exposed to underwater anthropogenic noise above 
received levels of 120 dB re 1 [mu]Pa (rms) for continuous (e.g., 
vibratory pile-driving, drilling) and above 160 dB re 1 [mu]Pa (rms) 
for non-explosive impulsive (e.g., seismic airguns) or intermittent 
(e.g., scientific sonar) sources.
    NSF includes the use of impulsive seismic sources and continuous

[[Page 69968]]

icebreaking, and therefore the 120 dB re 1 [mu]Pa (rms) is applicable.
    Level A harassment for non-explosive sources--NMFS' Technical 
Guidance for Assessing the Effects of Anthropogenic Sound on Marine 
Mammal Hearing (Version 2.0) (Technical Guidance, 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). NSF's proposed activity includes the use 
of impulsive seismic and icebreaking sources.
    These thresholds are provided in the table below. The references, 
analysis, and methodology used in the development of the thresholds are 
described in NMFS 2018 Technical Guidance, which may be accessed at 
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.

                     Table 4--Thresholds Identifying the Onset of Permanent Threshold Shift
----------------------------------------------------------------------------------------------------------------
                                                     PTS onset acoustic thresholds * (received level)
             Hearing group              ------------------------------------------------------------------------
                                                  Impulsive                         Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans...........  Cell 1: Lpk,flat: 219 dB;   Cell 2: LE,LF,24h: 199 dB.
                                          LE,LF,24h: 183 dB.
Mid-Frequency (MF) Cetaceans...........  Cell 3: Lpk,flat: 230 dB;   Cell 4: LE,MF,24h: 198 dB.
                                          LE,MF,24h: 185 dB.
High-Frequency (HF) Cetaceans..........  Cell 5: Lpk,flat: 202 dB;   Cell 6: LE,HF,24h: 173 dB.
                                          LE,HF,24h: 155 dB.
Phocid Pinnipeds (PW) (Underwater).....  Cell 7: Lpk,flat: 218 dB;   Cell 8: LE,PW,24h: 201 dB.
                                          LE,PW,24h: 185 dB.
Otariid Pinnipeds (OW) (Underwater)....  Cell 9: Lpk,flat: 232 dB;   Cell 10: LE,OW,24h: 219 dB.
                                          LE,OW,24h: 203 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for
  calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level
  thresholds associated with impulsive sounds, these thresholds should also be considered.
Note: Peak sound pressure (Lpk) has a reference value of 1 [mu]Pa, and cumulative sound exposure level (LE) has
  a reference value of 1[mu]Pa\2\s. In this Table, thresholds are abbreviated to reflect American National
  Standards Institute standards (ANSI 2013). However, peak sound pressure is defined by ANSI as incorporating
  frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript ``flat'' is
  being included to indicate peak sound pressure should be flat weighted or unweighted within the generalized
  hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the
  designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds) and
  that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could be
  exceeded in a multitude of ways (i.e., varying exposure levels and durations, duty cycle). When possible, it
  is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be
  exceeded.

Ensonified Area

    Here, we describe operational and environmental parameters of the 
activity that will feed into identifying the area ensonified above the 
acoustic thresholds, which include source levels and transmission loss 
coefficient.
    When the NMFS Technical Guidance (2016) was published, in 
recognition of the fact that ensonified area/volume could be more 
technically challenging to predict because of the duration component in 
the new thresholds, we developed a User Spreadsheet that includes tools 
to help predict a simple isopleth that can be used in conjunction with 
marine mammal density or occurrence to help predict takes. We note that 
because of some of the assumptions included in the methods used for 
these tools, we anticipate that isopleths produced are typically going 
to be overestimates of some degree, which may result in some degree of 
overestimate of Level A harassment take. However, these tools offer the 
best way to predict appropriate isopleths when more sophisticated 3D 
modeling methods are not available, and NMFS continues to develop ways 
to quantitatively refine these tools, and will qualitatively address 
the output where appropriate. For mobile sources such as seismic 
surveys and icebreaking, the User Spreadsheet predicts the closest 
distance at which a stationary animal would not incur PTS if the sound 
source traveled by the animal in a straight line at a constant speed. 
Inputs used in the User Spreadsheet, and the resulting isopleths are 
reported below in Tables 5 and 6.

                       Table 5--SELcum Methodology
------------------------------------------------------------------------
 
------------------------------------------------------------------------
Source Velocity (meters/second)...............................   * 2.315
1/Repetition rate[supcaret] (seconds).........................      ** 5
------------------------------------------------------------------------
Note:
[dagger] Methodology assumes propagation of 20 log R; Activity duration
  (time) independent.
[supcaret] Time between onset of successive pulses.
* 4.5 kts.
** shot interval will be assume to be 5 seconds.


 Table 6--Table Showing the Results for One Single SEL SL Modeling Without and With Applying Weighting Function
                                           to the Five Hearing Groups
----------------------------------------------------------------------------------------------------------------
 
----------------------------------------------------------------------------------------------------------------
SELcum Threshold................             183             185             155             185             203
Distance(m) (no weighting                19.8808        209.2295        209.5266        209.2295        210.1602
 function)......................
Modified Farfield SEL *.........        208.9687        209.2295        209.5266        209.2295        210.1602
Distance (m) (with weighting             10.1720             N/A             N/A             N/A             N/A
 function)......................
Adjustment (dB).................           -5.82             N/A             N/A             N/A             N/A
----------------------------------------------------------------------------------------------------------------
Note: The modified farfield signature is estimated using the distance from the source array geometrical center
  to where the SELcum threshold is the largest. Apropagation of 20 log10 (Radial distance) is used to estimate
  the modified farfield SEL.
* Propagation of 20 log R.


[[Page 69969]]

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    The proposed survey would entail the use of a 2-airgun array with a 
total discharge of 300 in\3\ at a two depth of 2-4 m. Lamont-Doherty 
Earth Observatory (L-DEO) model results are used to determine the 160 
dBrms radius for the 2-airgun array in deep water (<1,000 m) 
down to a maximum water depth of 2,000 m. Received sound levels were 
predicted by L-DEO's model (Diebold et al., 2010) as a function of 
distance from the airguns, for the two 45 in\3\ airguns. This modeling 
approach uses ray tracing for the direct wave traveling from the array 
to the receiver and its associated source ghost (reflection at the air-
water interface in the vicinity of the array), in a constant-velocity 
half-space (infinite homogenous ocean layer, unbounded by a seafloor). 
In addition, propagation measurements of pulses from a 36-airgun array 
at a tow depth of 6 m have been reported in deep water (~1,600 m), 
intermediate water depth on the slope (~600-1,100 m), and shallow water 
(~50 m) in the Gulf of Mexico in 2007-2008 (Tolstoy et al., 2009; 
Diebold et al., 2010).
    For deep and intermediate water cases, the field measurements 
cannot be used readily to derive the Level A and Level B harassment 
isopleths, as at those sites the calibration hydrophone was located at 
a roughly constant depth of 350-550 m, which may not intersect all the 
SPL isopleths at their widest point from the sea surface down to the 
maximum relevant water depth (~2,000 m) for marine mammals. At short 
ranges, where the direct arrivals dominate and the effects of seafloor 
interactions are minimal, the data at the deep sites are suitable for 
comparison with modeled levels at the depth of the calibration 
hydrophone. At longer ranges, the comparison with the model--
constructed from the maximum SPL through the entire water column at 
varying distances from the airgun array--is the most relevant.
    In deep and intermediate water depths at short ranges, sound levels 
for direct arrivals recorded by the calibration hydrophone and L-DEO 
model results for the same array tow depth are in good alignment (see 
Figures 12 and 14 in Appendix H of NSF-USGS 2011). Consequently, 
isopleths falling within this domain can be predicted reliably by the 
L-DEO model, although they may be imperfectly sampled by measurements 
recorded at a single depth. At greater distances, the calibration data 
show that seafloor-reflected and sub-seafloor-refracted arrivals 
dominate. Although the direct arrivals become weak and/or incoherent. 
Aside from local topography effects, the region around the critical 
distance is where the observed levels rise closest to the model curve. 
However, the observed sound levels are found to fall almost entirely 
below the model curve. Thus, analysis of the Gulf of Mexico calibration 
measurements demonstrates that although simple, the L-DEO model is a 
robust tool for conservatively estimating isopleths.
    The proposed surveys would acquire data with two 45-in\3\ guns at a 
tow depth of 2-4 m. For deep water (>1000 m), we use the deep-water 
radii obtained from L-DEO model results down to a maximum water depth 
of 2,000 m for the airgun array with 2-m and 8-m airgun separation. The 
radii for intermediate water depths (100-1,000 m) are derived from the 
deep-water ones by applying a correction factor (multiplication) of 
1.5, such that observed levels at very near offsets fall below the 
corrected mitigation curve (see Figure 16 in Appendix H of NSF-USGS 
2011). The shallow-water radii are obtained by scaling the empirically 
derived measurements from the Gulf of Mexico calibration survey to 
account for the differences in source volume and tow depth between the 
calibration survey (6,000 in\3\; 6-m tow depth) and the proposed survey 
(90 in\3\; 4-m tow depth); whereas the shallow water in the Gulf of 
Mexico may not exactly replicate the shallow water environment at the 
proposed survey sites, it has been shown to serve as a good and very 
conservative proxy (Crone et al., 2014). A simple scaling factor is 
calculated from the ratios of the isopleths determined by the deep-
water L-DEO model, which are essentially a measure of the energy 
radiated by the source array.
    L-DEO's modeling methodology is described in greater detail in 
NSF's IHA application. The estimated distances to the Level B 
harassment isopleths for the two proposed airgun configurations in each 
water depth category are shown in Table 7.

[[Page 69970]]



                         Table 7--Level B--Predicted Distances to the Level B Threshold
                                          [160 re 1[mu]Parms isopleths]
----------------------------------------------------------------------------------------------------------------
                                                                                                   Predicted 160
                                                                                                   re 1[mu]Parms
                  Source and volume  (cm3)[in3]                      Tow depth      Water depth       (m)[ft]
                                                                      (m)[ft]        (m)[ft] 1      isopleth 2
 
----------------------------------------------------------------------------------------------------------------
2 x 45/105 in3 (300 in3) GI guns................................         3 [9.8]  100-1000 [328-      979 [3211]
                                                                                           3280]
                                                                  ..............   >1000 [>3280]      653 [2142]
1 x 45/105 in3 (150 in3) GI guns................................         3 [9.8]  100-1000 [328-      503 [1650]
                                                                                           3280]
                                                                  ..............   >1000 [>3280]      335 [1099]
2 x 105/105 in3 (420 in3) GI guns...............................         3 [9.8]  100-1000 [328-     1044 [3425]
                                                                                           3280]
                                                                  ..............   >1000 [>3280]      696 [2283]
1 x 105/105 in3 (210 in3) GI guns...............................         3 [9.8]  100-1000 [328-      531 [1742]
                                                                                           3280]
                                                                  ..............   >1000 [>3280]      354 [1161]
----------------------------------------------------------------------------------------------------------------
\1\ No seismic operations would be conducted in shallow depths (0-100 m [0-328 ft]).
\2\ RMS radii is based on LDEO modeling and empirical measurements. Radii for 100-1000 m (328-3280 ft) depth
  values = deep water values * 1.5 correction factor.

    Table 8 presents the proposed exclusion zone (EZ) for each marine 
mammal hearing group, which are based on LDEO modeling incorporated 
into the companion user spreadsheet (NMFS 2018).

                    Table 8--Predicted Distances to the Level A Threshold for Marine Mammals
----------------------------------------------------------------------------------------------------------------
                                                  SEL cumulative  SEL cumulative     Peak PTS        Peak PTS
                  Hearing group                    PTS threshold   PTS distance      threshold       distance
                                                      (dB) 1         (m)[ft] 1        (dB) 1         (m)[ft] 1
----------------------------------------------------------------------------------------------------------------
Low-frequency cetaceans.........................             183      31.1 [102]             219     7.55 [24.8]
Mid-frequency cetaceans.........................             185             0.0             230      1.58 [5.2]
Phocid pinnipeds................................             185      0.3 [0.98]             218     8.47 [27.8]
----------------------------------------------------------------------------------------------------------------
\1\ Cumulative sound exposure level for PTS (SELcumPTS) or Peak (SPLflat) resulting in Level A harassment (i.e.,
  injury). Based on 2018 NMFS Acoustic Technical Guidance (NMFS 2018).
\2\ Per NMFS Acoustic Technical Guidance (NMFS 2018), the larger of the dual criteria results are used for the
  EZ.

    Predicted distances to Level A harassment isopleths, which vary 
based on marine mammal hearing groups, were calculated based on 
modeling performed by L-DEO using the NUCLEUS software program and the 
NMFS User Spreadsheet, described below. The updated acoustic thresholds 
for impulsive sounds (e.g., airguns) contained in the Technical 
Guidance were presented as dual metric acoustic thresholds using both 
SELcum and peak sound pressure metrics (NMFS 2016a). As dual 
metrics, NMFS considers onset of PTS (Level A harassment) to have 
occurred when either one of the two metrics is exceeded (i.e., metric 
resulting in the largest isopleth). The SELcum metric 
considers both level and duration of exposure, as well as auditory 
weighting functions by marine mammal hearing group. In recognition of 
the fact that the requirement to calculate Level A harassment 
ensonified areas could be more technically challenging to predict due 
to the duration component and the use of weighting functions in the new 
SELcum thresholds, NMFS developed an optional User 
Spreadsheet that includes tools to help predict a simple isopleth that 
can be used in conjunction with marine mammal density or occurrence to 
facilitate the estimation of take numbers.
    The SELcum for the two-GI airgun array is derived from 
calculating the modified farfield signature. The farfield signature is 
often used as a theoretical representation of the source level. To 
compute the farfield signature, the source level is estimated at a 
large distance (right) below the array (e.g., 9 km), and this level is 
back projected mathematically to a notional distance of 1 m from the 
array's geometrical center. However, it has been recognized that the 
source level from the theoretical farfield signature is never 
physically achieved at the source when the source is an array of 
multiple airguns separated in space (Tolstoy et al., 2009). Near the 
source (at short ranges, distances <1 km), the pulses of sound pressure 
from each individual airgun in the source array do not stack 
constructively as they do for the theoretical farfield signature. The 
pulses from the different airguns spread out in time such that the 
source levels observed or modeled are the result of the summation of 
pulses from a few airguns, not the full array (Tolstoy et al., 2009). 
At larger distances, away from the source array center, sound pressure 
of all the airguns in the array stack coherently, but not within one 
time sample, resulting in smaller source levels (a few dB) than the 
source level derived from the farfield signature. Because the farfield 
signature does not take into account the interactions of the two 
airguns that occur near the source center and is calculated as a point 
source (single airgun), the modified farfield signature is a more 
appropriate measure of the sound source level for large arrays. For 
this smaller array, the modified farfield changes will be 
correspondingly smaller as well, but this method is used for 
consistency across all array sizes.
    NSF used the same acoustic modeling as Level B harassment with a 
small grid step in both the inline and depth directions to estimate the 
SELcum and peak SPL. The propagation modeling takes into 
account all airgun

[[Page 69971]]

interactions at short distances from the source including interactions 
between subarrays using the NUCLEUS software to estimate the notional 
signature and the MATLAB software to calculate the pressure signal at 
each mesh point of a grid. For a more complete explanation of this 
modeling approach, please see ``Attachment A: Modeling Data'' in NSF's 
IHA application.

Marine Mammal Occurrence

    In this section we provide the information about the presence, 
density, or group dynamics of marine mammals that will inform the take 
calculations.
    For the proposed survey area in west Antarctica, NSF provided 
density data for marine mammal species that might be encountered in the 
project area. NMFS concurred with these data and additionally included 
information regarding the Southern elephant seal Densities were 
estimated using sightings and effort during aerial- and vessel-based 
surveys conducted in and adjacent to the proposed project area (see NSF 
IHA application). The three other major sources of animal abundance 
included the Navy Marine Species Density Database (NMSDD) 2012, Ainley 
et al. 2007, and Gohl 2010. Data sources and density calculations are 
described in detail in Attachment B of NSF's IHA application. For some 
species, the densities derived from past surveys may not be 
representative of the densities that would be encountered during the 
proposed seismic surveys. However, the approach used is based on the 
best available data. Estimated densities used to inform take estimates 
are presented in Table 9.

      Table 9--Marine Mammal Densities in the Proposed Survey Area
------------------------------------------------------------------------
                                                             Estimated
                         Species                           density  (#/
                                                               km2)
------------------------------------------------------------------------
Low-frequency Cetaceans:
    Blue whale..........................................       0.0000510
    Fin whale...........................................       0.0072200
    Humpback whale......................................       0.0001000
    Minke whale.........................................       0.0930166
    Sei whale...........................................       0.0002550
Mid-frequency Cetaceans:
    Arnoux's beaked whale...............................       0.0062410
    Killer whale........................................       0.0014110
    Southern bottlenose whale...........................       0.0067570
    Sperm whale.........................................       0.0169934
Phocids:
    Crabeater...........................................         0.00762
    Leopard.............................................         0.00005
    Ross................................................         0.00001
    Weddell.............................................     0.000126984
    Southern Elephant...................................        \a\ 1.03
------------------------------------------------------------------------
Note: See Attachment B in NSF's IHA application for density sources.
\a\ Hofmeyr 2015.

Take Calculation and Estimation

    Here we describe how the information provided above is brought 
together to produce a quantitative take estimate.

Seismic Surveys

    In order to estimate the number of marine mammals predicted to be 
exposed to sound levels that would result in Level A harassment or 
Level B harassment, radial distances from the airgun array to predicted 
isopleths corresponding to the Level A harassment and Level B 
harassment thresholds are calculated, as described above. Those radial 
distances are then used to calculate the area(s) around the airgun 
array predicted to be ensonified to sound levels that exceed the Level 
A harassment and Level B harassment thresholds. The area estimated to 
be ensonified in a single day of the survey is then calculated (Table 
10), based on the areas predicted to be ensonified around the array and 
the estimated trackline distance traveled per day. This number is then 
multiplied by the number of survey days. The product is then multiplied 
by 1.25 to account for the additional 25 percent contingency. This 
results in an estimate of the total area (km\2\) expected to be 
ensonified to the Level A and Level B harassment thresholds for each 
survey type (Table 11).

                                                       Table 10--Areas (km2) To Be Ensonified to Level A and Level B Harassment Thresholds
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                   Distance/day
                                                                                                                                   * 2r + [pi]r2
                                                                                                  Distance/day *   [pi]r2 (km) =     =  daily                                          Total
                       % Distance at depth                         Distance/day      Radius to     2r  [length *   [endcaps-both    ensonified    Number days of     Plus 25%       ensonified
                                                                  (km)  [length]   Level B  (km)   width = area]       ends]         area(km2)        survey       buffer (days)   area (km\2\)
                                                                                                                                   [Adding of 2
                                                                                                                                     endcaps]
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Level A Area:
    Low-frequency...............................................          160.00            0.03            9.95            0.00            9.96            8.00           10.00           99.55
    Mid-frequency...............................................          160.00            0.00            0.51            0.00            0.51            8.00           10.00            5.06
    Phocids.....................................................          160.00            0.01            2.71            0.00            2.71            8.00           10.00           27.11
Level B Area:
    65% = 100-1000 m............................................          104.00            1.04          217.15            3.42          220.57            8.00           10.00        2,205.74
    35% = >1000 m...............................................           56.00            0.70           77.95            1.52           79.47            8.00           10.00          794.73
                                                                 -------------------------------------------------------------------------------------------------------------------------------
        All Depths..............................................  ..............  ..............  ..............  ..............  ..............  ..............  ..............        3,000.47
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    The marine mammals predicted to occur within these respective 
areas, based on estimated densities (Table 9), are assumed to be 
incidentally taken. Based on the small anticipated Level A harassment 
isopleths and in consideration of the proposed mitigation measures (see 
Proposed Mitigation section below), take by Level A harassment is not 
expected to occur and has not been proposed to be authorized. Estimated 
exposures for the proposed survey are shown in Table 11.

              Table 11--Calculated and Proposed Level B Exposures, and Percentage of Stock Exposed
----------------------------------------------------------------------------------------------------------------
                                                                                       Stock
                                                    Calculated       Proposed        abundance      Percent of
                     Species                      total  Level B      Level B       regional or     population
                                                                                     worldwide
----------------------------------------------------------------------------------------------------------------
Low-frequency cetaceans:
    Blue whale..................................            0.15              <1           5,000             0.0
    Fin whale...................................           21.66              24          38,200             0.1

[[Page 69972]]

 
    Humpback whale..............................            0.30              <1          42,000             0.0
    Minke whale.................................          279.09             311         515,000             0.1
        Antarctic minke whale...................          139.55  ..............         257,500             0.1
        Common (dwarf) minke whale..............          139.55  ..............         257,500             0.1
    Sei whale...................................            0.77               1          10,000             0.0
Mid-frequency cetaceans:
    Arnoux's beaked whale.......................           18.73              21         599,300             0.0
    Killer whale................................            4.23               5          25,000             0.0
    Layard's beaked whale.......................            1.91  ..............         599,300             0.0
    Long-finned pilot whale.....................           23.58  ..............         200,000             0.0
    Southern bottlenose whale...................           20.27              23         500,000             0.0
    Sperm whale.................................           50.99              57          12,069             0.4
    Gray's beaked whale.........................            0.84  ..............         599,300             0.0
Phocids:
    Crabeater seal..............................           22.86              25       5,000,000             0.0
    Leopard seal................................            0.14              <1         222,000             0.0
    Ross seal...................................            0.04              <1         250,000             0.0
    Southern Elephant Seal......................        3,095.73  ..............         325,000             1.0
    Weddell seal................................            0.38              <1         413,671             0.0
----------------------------------------------------------------------------------------------------------------

    It should be noted that the proposed take numbers shown in Table 10 
are expected to be conservative because in the calculations of 
estimated take, 25 percent has been added in the form of operational 
survey days. This is to account for the possibility of additional 
seismic operations associated with airgun testing and repeat coverage 
of any areas where initial data quality is sub-standard, and in 
recognition of the uncertainties in the density estimates used to 
estimate take as described above. However, the extent to which marine 
mammals would move away from the sound source is difficult to quantify 
and is, therefore, not accounted for in the take estimates.

Icebreaking

    As the vessel passes through the ice, the ship causes the ice to 
part and travel alongside the hull. This ice typically returns to fill 
the wake as the ship passes. The effects are transitory, hours at most, 
and localized, constrained to a relatively narrow swath to each side of 
the vessel. Applying the maximum estimated amount of icebreaking 
expected by NSF, i.e., 500 km, we calculate the ensonified area of 
icebreaking, including endcaps (Table 12).

                                                        Table 12--Ensonified Area for Icebreaking
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               Distance/day  *
                                                                                2r + [pi]r2 =
                                         Distance/ day *     [pi]r2 (km) =     daily ensonified   Number  days of    Plus 25%  buffer  Total  ensonified
Distance/day  (km)     Radius  (km)       2r  [length *        [endcaps]          area(km2)            survey             (days)          area  (km\2\)
                                          width = area]                          [adding of 2
                                                                                   endcaps]
--------------------------------------------------------------------------------------------------------------------------------------------------------
           62.50               6.456             807.00             130.87             937.87               8.00              10.00           9,378.75
--------------------------------------------------------------------------------------------------------------------------------------------------------


                                                         Table 13--Level B Take for Icebreaking
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                               Stock
                                                            Density (#/        Daily        Calculated    Proposed Level     abundance      Percent of
                         Species                              km\2\)        ensonified        Level B            B          regional or     population
                                                                           area (km\2\)                                      worldwide
--------------------------------------------------------------------------------------------------------------------------------------------------------
Low-frequency cetaceans:
    Blue whale..........................................        0.000051          937.87            0.05              <1           5,000             0.0
    Fin whale...........................................         0.00722          937.87            6.77               4          38,200           0.018
    Humpback whale......................................          0.0001          937.87            0.09              <1          42,000             0.0
    Minke whale.........................................       0.0930166          937.87           87.24              53         515,000             0.0
        Antarctic minke whale...........................        0.046508          937.87           43.62  ..............         257,500             0.0
        Common (dwarf) minke whale......................       0.0465083          937.87           43.62  ..............         257,500             0.0
    Sei whale...........................................        0.000255          937.87            0.24              <1          10,000             0.0
Mid-frequency cetaceans:
    Arnoux's beaked whale...............................        0.006241          937.87            5.85               4         599,300             0.0
    Killer whale........................................        0.001411          937.87            1.32              <1          25,000             0.0
    Layard's beaked whale...............................        0.000638          937.87            0.60  ..............         599,300             0.0
    Long-finned pilot whale.............................        0.007859          937.87            7.37  ..............         200,000             0.0
    Southern bottlenose whale...........................        0.006757          937.87            6.34               4         500,000             0.0
    Sperm whale.........................................       0.0169934          937.87           15.94              10          12,069             0.1
    Gray's beaked whale.................................        0.000281          937.87            0.26  ..............         599,300             0.0

[[Page 69973]]

 
Phocids:
    Crabeater seal......................................        0.007619          937.87            7.15               4       5,000,000             0.0
    Leopard seal........................................       0.0000476          937.87            0.04              <1         222,000             0.0
    Ross seal...........................................       0.0000127          937.87            0.01              <1         250,000             0.0
    Southern Elephant Seal..............................            1.03          937.87          967.65  ..............         325,000             0.3
    Weddell seal........................................        0.000127          937.87            0.12              <1         413,671             0.0
--------------------------------------------------------------------------------------------------------------------------------------------------------

Proposed Mitigation

    In order to issue an IHA under Section 101(a)(5)(D) of the MMPA, 
NMFS must set forth the permissible methods of taking pursuant to the 
activity, and other means of effecting the least practicable impact on 
the species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of the species or stock for taking for certain 
subsistence uses (latter not applicable for this action). NMFS 
regulations require applicants for incidental take authorizations to 
include information about the availability and feasibility (economic 
and technological) of equipment, methods, and manner of conducting the 
activity or other means of effecting the least practicable adverse 
impact upon the affected species or stocks and their habitat (50 CFR 
216.104(a)(11)).
    In evaluating how mitigation may or may not be appropriate to 
ensure the least practicable adverse impact on species or stocks and 
their habitat, as well as subsistence uses where applicable, we 
carefully consider two primary factors:
    (1) The manner in which, and the degree to which, the successful 
implementation of the measure(s) is expected to reduce impacts to 
marine mammals, marine mammal species or stocks, and their habitat. 
This considers the nature of the potential adverse impact being 
mitigated (likelihood, scope, range). It further considers the 
likelihood that the measure will be effective if implemented 
(probability of accomplishing the mitigating result if implemented as 
planned), the likelihood of effective implementation (probability 
implemented as planned), and;
    (2) the practicability of the measures for applicant 
implementation, which may consider such things as cost, impact on 
operations, and, in the case of a military readiness activity, 
personnel safety, practicality of implementation, and impact on the 
effectiveness of the military readiness activity.

Mitigation for Marine Mammals and Their Habitat

    NSF has reviewed mitigation measures employed during seismic 
research surveys authorized by NMFS under previous incidental 
harassment authorizations, as well as recommended best practices in 
Richardson et al. (1995), Pierson et al. (1998), Weir and Dolman 
(2007), Nowacek et al. (2013), Wright (2014), and Wright and Cosentino 
(2015), and has incorporated a suite of proposed mitigation measures 
into their project description based on the above sources.
    To reduce the potential for disturbance from acoustic stimuli 
associated with the activities, NSF has proposed to implement 
mitigation measures for marine mammals. Mitigation measures that would 
be adopted during the proposed surveys include (1) Vessel-based visual 
mitigation monitoring; (2) Establishment of a marine mammal EZ and 
buffer zone; (3) shutdown procedures; (4) ramp-up procedures; and (4) 
vessel strike avoidance measures.

Vessel-Based Visual Mitigation Monitoring

    Visual monitoring requires the use of trained observers (herein 
referred to as visual Protected Species Observers (PSOs)) to scan the 
ocean surface visually for the presence of marine mammals. PSO 
observations would take place during all daytime airgun operations and 
nighttime start ups (if applicable) of the airguns. If airguns are 
operating throughout the night, observations would begin 30 minutes 
prior to sunrise. If airguns are operating after sunset, observations 
would continue until 30 minutes following sunset. Following a shutdown 
for any reason, observations would occur for at least 30 minutes prior 
to the planned start of airgun operations. Observations would also 
occur for 30 minutes after airgun operations cease for any reason. 
Observations would also be made during daytime periods when the Palmer 
is underway without seismic operations, such as during transits, to 
allow for comparison of sighting rates and behavior with and without 
airgun operations and between acquisition periods. Airgun operations 
would be suspended when marine mammals are observed within, or about to 
enter, the designated EZ (as described below).
    During seismic operations, three visual PSOs would be based aboard 
the Palmer. PSOs would be appointed by NSF with NMFS approval. One 
dedicated PSO would monitor the EZ during all daytime seismic 
operations. PSO(s) would be on duty in shifts of duration no longer 
than four hours. Other vessel crew would also be instructed to assist 
in detecting marine mammals and in implementing mitigation requirements 
(if practical). Before the start of the seismic survey, the crew would 
be given additional instruction in detecting marine mammals and 
implementing mitigation requirements.
    The Palmer is a suitable platform from which PSOs would watch for 
marine mammals. Standard equipment for marine mammal observers would be 
7 x 50 reticule binoculars and optical range finders. At night, night-
vision equipment would be available. The observers would be in 
communication with ship's officers on the bridge and scientists in the 
vessel's operations laboratory, so they can advise promptly of the need 
for avoidance maneuvers or seismic source shutdown.
    The PSOs must have no tasks other than to conduct observational 
effort, record observational data, and communicate with and instruct 
relevant vessel crew with regard to the presence of marine mammals and 
mitigation requirements. PSO resumes shall be provided to NMFS for 
approval. At least one PSO must have a minimum of 90 days at-sea 
experience working as a PSO during a seismic survey. One 
``experienced'' visual PSO will be designated as the lead for the 
entire protected species observation team. The

[[Page 69974]]

lead will serve as primary point of contact for the vessel operator.

Exclusion Zone and Buffer Zone

    An EZ is a defined area within which occurrence of a marine mammal 
triggers mitigation action intended to reduce the potential for certain 
outcomes, e.g., auditory injury, disruption of critical behaviors. The 
PSOs would establish a minimum EZ with a 100 m radius for the airgun 
array. The 100-m EZ would be based on radial distance from any element 
of the airgun array (rather than being based on the center of the array 
or around the vessel itself). With certain exceptions (described 
below), if a marine mammal appears within, enters, or appears on a 
course to enter this zone, the acoustic source would be shut down (see 
Shutdown Procedures below).
    The 100-m radial distance of the standard EZ is precautionary in 
the sense that it would be expected to contain sound exceeding injury 
criteria for all marine mammal hearing groups (Table 5) while also 
providing a consistent, reasonably observable zone within which PSOs 
would typically be able to conduct effective observational effort. In 
this case, the 100-m radial distance would also be expected to contain 
sound that would exceed the Level A harassment threshold based on sound 
exposure level (SELcum) criteria for all marine mammal 
hearing groups (Table 5). In the 2011 Programmatic Environmental Impact 
Statement for marine scientific research funded by the National Science 
Foundation or the U.S. Geological Survey (NSF-USGS 2011), Alternative B 
(the Preferred Alternative) conservatively applied a 100-m EZ for all 
low-energy acoustic sources in water depths >100 m, with low-energy 
acoustic sources defined as any towed acoustic source with a single or 
a pair of clustered airguns with individual volumes of <=250 in\3\. 
Thus the 100-m EZ proposed for this survey is consistent with the PEIS.
    Our intent in prescribing a standard EZ distance is to (1) 
encompass zones within which auditory injury could occur on the basis 
of instantaneous exposure; (2) provide additional protection from the 
potential for more severe behavioral reactions (e.g., panic, 
antipredator response) for marine mammals at relatively close range to 
the acoustic source; (3) provide consistency for PSOs, who need to 
monitor and implement the EZ; and (4) define a distance within which 
detection probabilities are reasonably high for most species under 
typical conditions.
    PSOs will also establish and monitor a 200-m buffer zone. During 
use of the acoustic source, occurrence of marine mammals within the 
buffer zone (but outside the EZ) will be communicated to the operator 
to prepare for potential shutdown of the acoustic source. The buffer 
zone is discussed further under Ramp-up Procedures below.
    An extended EZ of 500 m would be enforced for all beaked whales and 
Southern right whales. This is a precautionary measure as right whales 
are not expected in the survey area. NSF would also enforce a 500-m EZ 
for aggregations of six or more large whales (i.e., sperm whale or any 
baleen whale) or a large whale with a calf (calf defined as an animal 
less than two-thirds the body size of an adult observed to be in close 
association with an adult).

Shutdown Procedures

    If a marine mammal is detected outside the EZ but is likely to 
enter the EZ, the airguns would be shut down before the animal is 
within the EZ. Likewise, if a marine mammal is already within the EZ 
when first detected, the airguns would be shut down immediately.
    Following a shutdown, airgun activity would not resume until the 
marine mammal has cleared the 100-m EZ. The animal would be considered 
to have cleared the 100-m EZ if the following conditions have been met:
     It is visually observed to have departed the 100-m EZ;
     it has not been seen within the 100-m EZ for 15 minutes in 
the case of small odontocetes and pinnipeds; or
     it has not been seen within the 100-m EZ for 30 minutes in 
the case of mysticetes and large odontocetes, including sperm, pygmy 
sperm, and beaked whales.
    Shutdown of the acoustic source would also be required upon 
observation of a species for which authorization has not been granted, 
or a species for which authorization has been granted but the 
authorized number of takes are met, observed approaching or within the 
Level A or Level B harassment zones.

Ramp-Up Procedures

    Ramp-up of an acoustic source is intended to provide a gradual 
increase in sound levels following a shutdown, enabling animals to move 
away from the source if the signal is sufficiently aversive prior to 
its reaching full intensity. Ramp-up would be required after the array 
is shut down for any reason for longer than 15 minutes. Ramp-up would 
begin with the activation of one 45 in\3\ airgun, with the second 45 
in\3\ airgun activated after 5 minutes.
    Two PSOs would be required to monitor during ramp-up. During ramp 
up, the PSOs would monitor the EZ, and if marine mammals were observed 
within the EZ or buffer zone, a shutdown would be implemented as though 
the full array were operational. If airguns have been shut down due to 
PSO detection of a marine mammal within or approaching the 100 m EZ, 
ramp-up would not be initiated until all marine mammals have cleared 
the EZ, during the day or night. Criteria for clearing the EZ would be 
as described above.
    Thirty minutes of pre-clearance observation are required prior to 
ramp-up for any shutdown of longer than 30 minutes (i.e., if the array 
were shut down during transit from one line to another). This 30-minute 
pre-clearance period may occur during any vessel activity (i.e., 
transit). If a marine mammal were observed within or approaching the 
100 m EZ during this pre-clearance period, ramp-up would not be 
initiated until all marine mammals cleared the EZ. Criteria for 
clearing the EZ would be as described above. If the airgun array has 
been shut down for reasons other than mitigation (e.g., mechanical 
difficulty) for a period of less than 30 minutes, it may be activated 
again without ramp-up if PSOs have maintained constant visual 
observation and no detections of any marine mammal have occurred within 
the EZ or buffer zone. Ramp-up would be planned to occur during periods 
of good visibility when possible. However, ramp-up would be allowed at 
night and during poor visibility if the 100 m EZ and 200 m buffer zone 
have been monitored by visual PSOs for 30 minutes prior to ramp-up.
    The operator would be required to notify a designated PSO of the 
planned start of ramp-up as agreed-upon with the lead PSO; the 
notification time should not be less than 60 minutes prior to the 
planned ramp-up. A designated PSO must be notified again immediately 
prior to initiating ramp-up procedures and the operator must receive 
confirmation from the PSO to proceed. The operator must provide 
information to PSOs documenting that appropriate procedures were 
followed. Following deactivation of the array for reasons other than 
mitigation, the operator would be required to communicate the near-term 
operational plan to the lead PSO with justification for any planned 
nighttime ramp-up.

Vessel Strike Avoidance Measures

    Vessel strike avoidance measures are intended to minimize the 
potential for collisions with marine mammals. These

[[Page 69975]]

requirements do not apply in any case where compliance would create an 
imminent and serious threat to a person or vessel or to the extent that 
a vessel is restricted in its ability to maneuver and, because of the 
restriction, cannot comply.
    The proposed measures include the following: Vessel operator and 
crew would maintain a vigilant watch for all marine mammals and slow 
down or stop the vessel or alter course to avoid striking any marine 
mammal. A visual observer aboard the vessel would monitor a vessel 
strike avoidance zone around the vessel according to the parameters 
stated below. Visual observers monitoring the vessel strike avoidance 
zone would be either third-party observers or crew members, but crew 
members responsible for these duties would be provided sufficient 
training to distinguish marine mammals from other phenomena. Vessel 
strike avoidance measures would be followed during surveys and while in 
transit.
    The vessel would maintain a minimum separation distance of 100 m 
from large whales (i.e., baleen whales and sperm whales). If a large 
whale is within 100 m of the vessel, the vessel would reduce speed and 
shift the engine to neutral, and would not engage the engines until the 
whale has moved outside of the vessel's path and the minimum separation 
distance has been established. If the vessel is stationary, the vessel 
would not engage engines until the whale(s) has moved out of the 
vessel's path and beyond 100 m. If an animal is encountered during 
transit, the vessel would attempt to remain parallel to the animal's 
course, avoiding excessive speed or abrupt changes in course. Vessel 
speeds would be reduced to 10 kts or less when mother/calf pairs, pods, 
or large assemblages of cetaceans are observed near the vessel.
    Based on our evaluation of the applicant's proposed measures, as 
well as other measures considered by NMFS, NMFS has preliminarily 
determined that the proposed mitigation measures provide the means 
effecting the least practicable impact on the affected species or 
stocks and their habitat, paying particular attention to rookeries, 
mating grounds, and areas of similar significance.

Proposed Monitoring and Reporting

    In order to issue an IHA for an activity, Section 101(a)(5)(D) of 
the MMPA states that 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 
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 in the 
proposed action area. Effective reporting is critical both to 
compliance as well as ensuring that the most value is obtained from the 
required monitoring.
    Monitoring and reporting requirements prescribed by NMFS should 
contribute to improved understanding of one or more of the following:
     Occurrence of marine mammal species or stocks in the area 
in which take is anticipated (e.g., presence, abundance, distribution, 
density).
     Nature, scope, or context of likely marine mammal exposure 
to potential stressors/impacts (individual or cumulative, acute or 
chronic), through better understanding of: (1) Action or environment 
(e.g., source characterization, propagation, ambient noise); (2) 
affected species (e.g., life history, dive patterns); (3) co-occurrence 
of marine mammal species with the action; or (4) biological or 
behavioral context of exposure (e.g., age, calving or feeding areas).
     Individual marine mammal responses (behavioral or 
physiological) to acoustic stressors (acute, chronic, or cumulative), 
other stressors, or cumulative impacts from multiple stressors.
     How anticipated responses to stressors impact either: (1) 
Long-term fitness and survival of individual marine mammals; or (2) 
populations, species, or stocks.
     Effects on marine mammal habitat (e.g., marine mammal prey 
species, acoustic habitat, or other important physical components of 
marine mammal habitat).
     Mitigation and monitoring effectiveness.
    NSF described marine mammal monitoring and reporting plan within 
their IHA application. Monitoring that is designed specifically to 
facilitate mitigation measures, such as monitoring of the EZ to inform 
potential shutdowns of the airgun array, are described above and are 
not repeated here. NSF's monitoring and reporting plan includes the 
following measures:

Vessel-Based Visual Monitoring

    As described above, PSO observations would take place during 
daytime airgun operations and nighttime start-ups (if applicable) of 
the airguns. During seismic operations, three visual PSOs would be 
based aboard the Palmer. PSOs would be appointed by NSF with NMFS 
approval. The PSOs must have successfully completed relevant training, 
including completion of all required coursework and passing a written 
and/or oral examination developed for the training program, and must 
have successfully attained a bachelor's degree from an accredited 
college or university with a major in one of the natural sciences and a 
minimum of 30 semester hours or equivalent in the biological sciences 
and at least one undergraduate course in math or statistics. The 
educational requirements may be waived if the PSO has acquired the 
relevant skills through alternate training, including (1) secondary 
education and/or experience comparable to PSO duties; (2) previous work 
experience conducting academic, commercial, or government-sponsored 
marine mammal surveys; or (3) previous work experience as a PSO; the 
PSO should demonstrate good standing and consistently good performance 
of PSO duties.
    During the majority of seismic operations, one PSO would monitor 
for marine mammals around the seismic vessel. PSOs would be on duty in 
shifts of duration no longer than four hours. Other crew would also be 
instructed to assist in detecting marine mammals and in implementing 
mitigation requirements (if practical). During daytime, PSOs would scan 
the area around the vessel systematically with reticle binoculars 
(e.g., 7x50 Fujinon) and with the naked eye. At night, PSOs would be 
equipped with night-vision equipment.
    PSOs would record data to estimate the numbers of marine mammals 
exposed to various received sound levels and to document apparent 
disturbance reactions or lack thereof. Data would be used to estimate 
numbers of animals potentially `taken' by harassment (as defined in the 
MMPA). They would also provide information needed to order a shutdown 
of the airguns when a marine mammal is within or near the EZ. When a 
sighting is made, the following information about the sighting would be 
recorded:
    (1) Species, group size, age/size/sex categories (if determinable), 
behavior when first sighted and after initial sighting, heading (if 
consistent), bearing and distance from seismic vessel, sighting cue, 
apparent reaction to the airguns or vessel (e.g., none, avoidance, 
approach, paralleling, etc.), and behavioral pace; and
    (2) Time, location, heading, speed, activity of the vessel, sea 
state, visibility, and sun glare.

[[Page 69976]]

    All observations and shutdowns would be recorded in a standardized 
format. Data would be entered into an electronic database. The accuracy 
of the data entry would be verified by computerized data validity 
checks as the data are entered and by subsequent manual checking of the 
database. These procedures would allow initial summaries of data to be 
prepared during and shortly after the field program and would 
facilitate transfer of the data to statistical, graphical, and other 
programs for further processing and archiving. The time, location, 
heading, speed, activity of the vessel, sea state, visibility, and sun 
glare would also be recorded at the start and end of each observation 
watch, and during a watch whenever there is a change in one or more of 
the variables.
    Results from the vessel-based observations would provide:
    (1) The basis for real-time mitigation (e.g., airgun shutdown);
    (2) Information needed to estimate the number of marine mammals 
potentially taken by harassment, which must be reported to NMFS;
    (3) Data on the occurrence, distribution, and activities of marine 
mammals in the area where the seismic study is conducted;
    (4) Information to compare the distance and distribution of marine 
mammals relative to the source vessel at times with and without seismic 
activity; and
    (5) Data on the behavior and movement patterns of marine mammals 
seen at times with and without seismic activity.

Reporting

    A draft report would be submitted to NMFS within 90 days after the 
end of the survey. The report would describe the operations that were 
conducted and sightings of marine mammals near the operations. The 
report would provide full documentation of methods, results, and 
interpretation pertaining to all monitoring and would summarize the 
dates and locations of seismic operations, and all marine mammal 
sightings (dates, times, locations, activities, associated seismic 
survey activities). The report would also include estimates of the 
number and nature of exposures that occurred above the harassment 
threshold based on PSO observations, including an estimate of those 
that were not detected in consideration of both the characteristics and 
behaviors of the species of marine mammals that affect detectability, 
as well as the environmental factors that affect detectability.
    The draft report shall also include geo-referenced time-stamped 
vessel tracklines for all time periods during which airguns were 
operating. Tracklines should include points recording any change in 
airgun status (e.g., when the airguns began operating, when they were 
turned off, or when they changed from full array to single gun or vice 
versa). GIS files shall be provided in ESRI shapefile format and 
include the UTC date and time, latitude in decimal degrees, and 
longitude in decimal degrees. All coordinates shall be referenced to 
the WGS84 geographic coordinate system. In addition to the report, all 
raw observational data shall be made available to NMFS. The draft 
report must be accompanied by a certification from the lead PSO as to 
the accuracy of the report, and the lead PSO may submit directly NMFS a 
statement concerning implementation and effectiveness of the required 
mitigation and monitoring. A final report must be submitted within 30 
days following resolution of any comments on the draft report.

Negligible Impact Analysis and Determination

    NMFS has defined negligible impact as an impact resulting from the 
specified activity that cannot be reasonably expected to, and is not 
reasonably likely to, adversely affect the species or stock through 
effects on annual rates of recruitment or survival (50 CFR 216.103). A 
negligible impact finding is based on the lack of likely adverse 
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough 
information on which to base an impact determination. In addition to 
considering estimates of the number of marine mammals that might be 
``taken'' through harassment, NMFS considers other factors, such as the 
likely nature of any responses (e.g., intensity, duration), 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's 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, ongoing sources of human-caused mortality, or 
ambient noise levels).
    To avoid repetition, our analysis applies to all the species listed 
in Table 2, given that NMFS expects the anticipated effects of the 
proposed seismic survey to be similar in nature. Where there are 
meaningful differences between species or stocks, or groups of species, 
in anticipated individual responses to activities, impact of expected 
take on the population due to differences in population status, or 
impacts on habitat, NMFS has identified species-specific factors to 
inform the analysis.
    NMFS does not anticipate that serious injury or mortality would 
occur as a result of NSF's proposed seismic survey, even in the absence 
of proposed mitigation. Thus, the proposed authorization does not 
authorize any mortality. As discussed in the Potential Effects of 
Specified Activities on Marine Mammals and their Habitat section, non-
auditory physical effects, stranding, and vessel strike are not 
expected to occur.
    No takes by Level A harassment are proposed to be authorized. The 
100-m exclusion zone encompasses the Level A harassment isopleths for 
all marine mammal hearing groups, and is expected to prevent animals 
from being exposed to sound levels that would cause PTS. Also, as 
described above, we expect that marine mammals would be likely to move 
away from a sound source that represents an aversive stimulus, 
especially at levels that would be expected to result in PTS, given 
sufficient notice of the Palmer's approach due to the vessel's 
relatively low speed when conducting seismic surveys. We expect that 
any instances of take would be in the form of short-term Level B 
behavioral harassment in the form of temporary avoidance of the area or 
decreased foraging (if such activity were occurring), reactions that 
are considered to be of low severity and with no lasting biological 
consequences (e.g., Southall et al., 2007).
    Potential impacts to marine mammal habitat were discussed 
previously in this document (see Potential Effects of Specified 
Activities on Marine Mammals and their Habitat). Marine mammal habitat 
may be impacted by elevated sound levels, but these impacts would be 
temporary. Feeding behavior is not likely to be significantly impacted, 
as marine mammals appear to be less likely to exhibit behavioral 
reactions or avoidance responses while engaged in feeding activities 
(Richardson et al., 1995). Prey species are mobile and are broadly 
distributed throughout the project area; therefore,

[[Page 69977]]

marine mammals that may be temporarily displaced during survey 
activities are expected to be able to resume foraging once they have 
moved away from areas with disturbing levels of underwater noise. 
Because of the temporary nature of the disturbance, the availability of 
similar habitat and resources in the surrounding area, and the lack of 
important or unique marine mammal habitat, the impacts to marine 
mammals and the food sources that they utilize are not expected to 
cause significant or long-term consequences for individual marine 
mammals or their populations. In addition, there are no feeding, mating 
or calving areas known to be biologically important to marine mammals 
within the proposed project area.
    As explained above in the Marine Mammal section, marine mammals in 
the survey area are not assigned to NMFS stocks. For purposes of the 
small numbers analysis (discussed in the next section), we rely on the 
best available information on the abundance estimates for the species 
of marine mammals that could be taken. The activity is expected to 
impact a very small percentage of all marine mammal populations that 
would be affected by NSF's proposed survey (less than two percent each 
for all marine mammal populations where abundance estimates exist). 
Additionally, the acoustic ``footprint'' of the proposed survey would 
be very small relative to the ranges of all marine mammal species that 
would potentially be affected. Sound levels would increase in the 
marine environment in a relatively small area surrounding the vessel 
compared to the range of the marine mammals within the proposed survey 
area. The seismic array would be active 24 hours per day throughout the 
duration of the proposed survey. However, the very brief overall 
duration of the proposed survey (eight days) would further limit 
potential impacts that may occur as a result of the proposed activity.
    The proposed mitigation measures are expected to reduce the number 
and/or severity of takes by allowing for detection of marine mammals in 
the vicinity of the vessel by visual and acoustic observers, and by 
minimizing the severity of any potential exposures via shutdowns of the 
airgun array. Based on previous monitoring reports for substantially 
similar activities that have been previously authorized by NMFS, we 
expect that the proposed mitigation will be effective in preventing at 
least some extent of potential PTS in marine mammals that may otherwise 
occur in the absence of the proposed mitigation.
    Of the marine mammal species under our jurisdiction that are likely 
to occur in the project area, the following species are listed as 
endangered under the ESA: Blue, fin, humpback, sei, and sperm whales. 
We are proposing to authorize very small numbers of takes for these 
species (Table 11), relative to their population sizes (again, for 
species where population abundance estimates exist), therefore we do 
not expect population-level impacts to any of these species. The other 
marine mammal species that may be taken by harassment during NSF's 
seismic survey are not listed as threatened or endangered under the 
ESA. There is no designated critical habitat for any ESA-listed marine 
mammals within the project area; of the non-listed marine mammals for 
which we propose to authorize take, none are considered ``depleted'' or 
``strategic'' by NMFS under the MMPA.
    NMFS concludes that exposures to marine mammal species due to NSF's 
proposed seismic survey would result in only short-term (temporary and 
short in duration) effects to individuals exposed, or some small degree 
of PTS to a very small number of individuals. Marine mammals may 
temporarily avoid the immediate area, but are not expected to 
permanently abandon the area. Major shifts in habitat use, 
distribution, or foraging success are not expected. NMFS does not 
anticipate the proposed take estimates to impact annual rates of 
recruitment or survival.
    In summary and as described above, the following factors primarily 
support our preliminary determination that the impacts resulting from 
this activity are not expected to adversely affect the species or stock 
through effects on annual rates of recruitment or survival:
     No mortality, serious injury and Level A harassment is 
anticipated or authorized;
     The anticipated impacts of the proposed activity on marine 
mammals would primarily be temporary behavioral changes of small 
percentages of the affected species due to avoidance of the area around 
the survey vessel. The relatively short duration of the proposed survey 
(eight days) would further limit the potential impacts of any temporary 
behavioral changes that would occur;
     The availability of alternate areas of similar habitat 
value for marine mammals to temporarily vacate the survey area during 
the proposed survey to avoid exposure to sounds from the activity;
     The proposed project area does not contain areas of 
significance for feeding, mating or calving;
     The potential adverse effects on fish or invertebrate 
species that serve as prey species for marine mammals from the proposed 
survey would be temporary and spatially limited; and
     The proposed mitigation measures, including visual and 
acoustic monitoring and shutdowns, are expected to minimize potential 
impacts to marine mammals.
    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 proposed activity will have a negligible impact on 
all affected marine mammal species or stocks.

Small Numbers

    As noted above, only small numbers of incidental take may be 
authorized under Sections 101(a)(5)(A) and (D) of the MMPA for 
specified activities other than military readiness activities. The MMPA 
does not define small numbers and so, in practice, where estimated 
numbers are available, NMFS compares the number of individuals taken to 
the most appropriate estimation of abundance of the relevant species or 
stock in our determination of whether an authorization is limited to 
small numbers of marine mammals. Additionally, other qualitative 
factors may be considered in the analysis, such as the temporal or 
spatial scale of the activities.
    The numbers of marine mammals that we authorize to be taken would 
be considered small relative to the relevant populations (less than two 
percent for all species) for the species for which abundance estimates 
are available.
    Based on the analysis contained herein of the proposed activity 
(including the proposed mitigation and monitoring measures) and the 
anticipated take of marine mammals, NMFS preliminarily finds that small 
numbers of marine mammals will be taken relative to the population 
sizes of the affected species.

Unmitigable Adverse Impact Analysis and Determination

    There are no relevant subsistence uses of the affected marine 
mammal stocks or species implicated by this action. Therefore, NMFS has 
determined that the total taking of affected species or stocks would 
not have an unmitigable adverse impact on the availability of such 
species or stocks for taking for subsistence purposes.

[[Page 69978]]

Endangered Species Act (ESA)

    Section 7(a)(2) of the Endangered Species Act of 1973 (ESA: 16 
U.S.C. 1531 et seq.) requires that each Federal agency insure that any 
action it authorizes, funds, or carries out is not likely to jeopardize 
the continued existence of any endangered or threatened species or 
result in the destruction or adverse modification of designated 
critical habitat. To ensure ESA compliance for the issuance of IHAs, 
NMFS consults internally, in this case with the ESA Interagency 
Cooperation Division, whenever we propose to authorize take for 
endangered or threatened species.
    NMFS is proposing to authorize take of blue, fin, humpback, sei, 
and sperm whales, which are listed under the ESA. The Permit and 
Conservation Division has requested initiation of Section 7 
consultation with the Interagency Cooperation Division for the issuance 
of this IHA. NMFS will conclude the ESA consultation prior to reaching 
a determination regarding the proposed issuance of the authorization.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to NSF for conducting seismic surveys, other acoustic 
sources, and icebreaking in the Amundsen Sea from on or about February 
6-14, 2020, provided the previously mentioned mitigation, monitoring, 
and reporting requirements are incorporated. A draft of the proposed 
IHA can be found at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act.

Request for Public Comments

    We request comment on our analyses, the proposed authorization, and 
any other aspect of this Notice of Proposed IHA for the proposed low-
energy marine geophysical survey and icebreaking activity in the 
Amundsen Sea. We also request at this time comment on the potential 
renewal of this proposed IHA as described in the paragraph below. 
Please include with your comments any supporting data or literature 
citations to help inform decisions on the request for this IHA or a 
subsequent Renewal.
    On a case-by-case basis, NMFS may issue a one-year IHA renewal with 
an additional 15 days for public comments when (1) another year of 
identical or nearly identical activities as described in the Specified 
Activities section of this notice is planned or (2) the activities as 
described in the Specified Activities section of this notice would not 
be completed by the time the IHA expires and a Renewal would allow for 
completion of the activities beyond that described in the Dates and 
Duration section of this notice, provided all of the following 
conditions are met:
     A request for renewal is received no later than 60 days 
prior to expiration of the current IHA.
     The request for renewal must include the following:
    (1) An explanation that the activities to be conducted under the 
requested Renewal are identical to the activities analyzed under the 
initial IHA, are a subset of the activities, or include changes so 
minor (e.g., reduction in pile size) that the changes do not affect the 
previous analyses, mitigation and monitoring requirements, or take 
estimates (with the exception of reducing the type or amount of take 
because only a subset of the initially analyzed activities remain to be 
completed under the Renewal).
    (2) A preliminary monitoring report showing the results of the 
required monitoring to date and an explanation showing that the 
monitoring results do not indicate impacts of a scale or nature not 
previously analyzed or authorized.
     Upon review of the request for Renewal, the status of the 
affected species or stocks, and any other pertinent information, NMFS 
determines that there are no more than minor changes in the activities, 
the mitigation and monitoring measures will remain the same and 
appropriate, and the findings in the initial IHA remain valid.

    Dated: December 13, 2019.
Donna S. Wieting,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2019-27269 Filed 12-18-19; 8:45 am]
 BILLING CODE 3510-22-P