Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Geophysical Survey in the Ross Sea, Antarctica, 59204-59238 [2022-20928]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 87, Number 188 (Thursday, September 29, 2022)]
[Notices]
[Pages 59204-59238]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-20928]



[[Page 59203]]

Vol. 87

Thursday,

No. 188

September 29, 2022

Part III





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 a Geophysical Survey in the Ross Sea, 
Antarctica; Notice

Federal Register / Vol. 87 , No. 188 / Thursday, September 29, 2022 / 
Notices

[[Page 59204]]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XC218]


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to a Geophysical Survey in the Ross 
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 United States National 
Science Foundation (NSF) Office of Polar Programs for authorization to 
take marine mammals incidental to a geophysical survey in the Ross 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 October 
31, 2022.

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: Jenna Harlacher, 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.

Summary of Request

    On May 26, 2022, NMFS received a request from NSF for an IHA to 
take marine mammals incidental to conducting a low energy seismic 
survey and icebreaking in the Ross Sea. The application was deemed 
adequate and complete on July 22, 2022. NSF's request is for take of 
small numbers of 17 species of marine mammals by Level B harassment 
only. Neither NSF nor NMFS expects serious injury or mortality to 
result from this activity and, therefore, an IHA is appropriate.

Description of Proposed Activity

Overview

    Researchers from Louisiana State University, Texas A&M University, 
University of Texas at Austin, University of West Florida, and Dauphin 
Island Sea Lab, with funding from NSF, propose to conduct a two-part 
low-energy seismic survey from the Research Vessel/Icebreaker (RVIB) 
Nathaniel B. Palmer (NBP), in the Ross Sea during Austral Summer 2022-
2023. The two-part proposed survey would include the Ross Bank and the 
Drygalski Trough areas. The proposed seismic survey would take place in 
International waters of the Southern Ocean, in water depths ranging 
from ~150 to 1100 meters (m).
    The RVIB Palmer would deploy up to two 105-in\3\ generator injector 
(GI) airguns at a depth of 1-4 m with a total maximum discharge volume 
for the largest, two-airgun array of 210 in\3\ along predetermined 
track lines. During the Ross Bank survey, ~1920km of seismic data would 
be collected and

[[Page 59205]]

during the Drygalski Trough survey, ~1800 km of seismic acquisition 
would occur, for a total of 3720 line km.
    Although the proposed survey will occur in the Austral summer, some 
icebreaking activities are expected to be required during the cruise.
    The proposed Ross Bank portion of activity is to determine if, how, 
when, and why the Ross Ice Shelf unpinned from Ross Bank in the recent 
geologic past, to assess to what degree that event caused a re-
organization of ice sheet and ice shelf flow towards its current 
configuration. The Drygalski Trough activities are proposed to examine 
the gas hydrate contribution to the Ross Sea carbon budget. The 
Drygalski Trough activities would examine the warming and carbon 
cycling of the ephemeral reservoir of carbon at the extensive bottom 
ocean layer-sediment interface of the Ross Sea. This large carbon 
reserve appears to be sealed in the form of gas hydrate and is a 
thermogenic carbon source and carbon storage in deep sediment hydrates. 
The warming and ice melting coupled with high thermogenic gas hydrate 
loadings suggest the Ross Sea is an essential environment to determine 
contributions of current day and potential future methane, petroleum, 
and glacial carbon to shallow sediment and water column carbon cycles.

Dates and Duration

    The RVIB Palmer would likely depart from Lyttelton, New Zealand, on 
December 18, 2022, and would return to McMurdo Station, Antarctica, on 
January 18, 2023, after the program is completed. The cruise is 
expected to consist of 31 days at sea, including approximately 19 days 
of seismic operations (including 2 days of sea trials and/or 
contingency), 1 day of ocean bottom seismometer (OBS) deployment/
recovery, and approximately 11 days of transit. Some deviation in 
timing and ports of call could also result from unforeseen events such 
as weather or logistical issues.

Specific Geographic Region

    The proposed survey would take place in the Ross Sea, Antarctica 
(continental shelf between ~75[deg]-77.7[deg] S and 171[deg] E-173[deg] 
E and Drygalski Trough between ~74[deg]76.7[deg] S and 163.6[deg] E-
170[deg] E (Figure 1) in International waters of the Southern Ocean in 
water depths ranging from approximately 150 to 1100 m. Representative 
survey tracklines are shown in Figure 1; however, the actual survey 
effort could occur anywhere within the outlined study area as shown. 
The line locations for the survey area are preliminary and could be 
refined in light of information from data collected during the study 
and conditions within the survey area.
BILLING CODE 3510-22-P
[GRAPHIC] [TIFF OMITTED] TN29SE22.000

BILLING CODE 3510-22-C

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Detailed Description of Specific Activity

    The procedures to be used for the proposed survey would entail use 
of conventional seismic methodology. The survey would involve one 
source vessel, RVIB Palmer and the airgun array would be deployed at a 
depth of approximately 1-4 m below the surface, spaced approximately 
2.4 m apart for the two-gun array. Seismic acquisition is proposed to 
begin with a standard sea trial to determine which configuration and 
mode of GI airgun(s) provide the best reflection signals, which depends 
on sea-state and subsurface conditions. A maximum of two GI airguns 
would be used. Four GI configurations (each using one or two GI 
airguns) would be tested during the sea trial (Table 1). The largest 
volume airgun configuration (configuration 4) was carried forward in 
our analysis and used for estimating the take numbers proposed for 
authorization.
    The RVIB Palmer would deploy two 105 in\3\ GI airguns as an energy 
source with a total volume of ~210 in\3\. Seismic pulses would be 
emitted at intervals of 5 to 10 seconds from the GI airgun. The 
receiving system would consist of one hydrophone streamer, 75 m in 
length, with the vessel traveling at 8.3 km/hr (4.5 knots (kn)) 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. If sea-ice conditions permit, a multi-channel 
digital streamer would be used to improve signal-to-noise ratio by 
digital data processing; if ice is present, a single-channel digital 
steamer would be employed. When not towing seismic survey gear, the 
RVIB Palmer has a maximum speed of 26.9 km/h (14.5 kn), but cruises at 
an average speed of 18.7 km/h (10.1 kn). During the Ross Bank survey, 
~1920km of seismic data would be collected and during the Drygalski 
Trough survey, ~1800 km of seismic acquisition would occur, for a total 
of 3720 line km.
    During the Drygalski Trough survey, 2 deployments of 10 OBSs would 
occur along 2 different seismic refraction lines (see Fig. 1 for 
representative lines). Following refraction shooting of one line, OBSs 
on that line would be recovered, serviced, and redeployed on a 
subsequent refraction line. The spacing of OBSs on the initial 
refraction line would be 5 km apart, but OBSs could be deployed as 
close together as every 500 m on the subsequent refraction line. All 
OBSs would be recovered at the end of the survey. To retrieve the OBSs, 
the instrument is released via an acoustic release system to float to 
the surface from the wire and/or anchor, which are not retrieved.

     Table 1--Four GI Configurations (Each Using One or Two GI Airguns) Would Be Tested During the Sea Trial
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                                Airgun array total volume      Frequency  between
        Configuration              (GI configuration)            seismic shots             Streamer length
----------------------------------------------------------------------------------------------------------------
1...........................  50 in\3\ Harmonic Mode        5-10 seconds...........  75 m.
                               configured as 25 in\3\
                               Generator + 25 Injector
                               in\3\.
2...........................  90 in\3\ Harmonic Mode        5-10 seconds...........
                               configured as 45 in\3\
                               Generator + 45 Injector
                               in\3\.
3...........................  50 in\3\ True-GI Mode         5-10 seconds...........
                               configured as 45 in\3\
                               Generator + 105 Injector
                               in\3\.
4...........................  210 in\3\ Harmonic Mode       5-10 seconds...........
                               configured as 105 in\3\
                               Generator + 105 Injector
                               in\3\.
----------------------------------------------------------------------------------------------------------------

    There could be additional seismic operations in the study 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.
    Along with the airgun and OBS operations, additional acoustical 
data acquisition systems and other equipment may be operated during the 
seismic survey at any time to meet scientific objectives. The ocean 
floor would be mapped with a Multibeam Ecosounder (MBES), Sub-bottom 
Profiler (SBP), and/or Acoustic Doppler Current Profiler (ADCP). Data 
acquisition in the survey area will occur in water depths ranging from 
150 to 700 m. Take of marine mammals is not expected to occur 
incidental to use of these other sources, whether or not the airguns 
are operating simultaneously with the other sources. Given their 
characteristics (e.g., narrow downward-directed beam), marine mammals 
would experience no more than one or two brief ping exposures, if any 
exposure were to occur. NMFS does not expect that the use of these 
sources presents any reasonable potential to cause take of marine 
mammals.
    (1) Single Beam Echo Sounder (Knudsen 3260)--The hull-mounted 
compressed high-intensity radiated pulse (CHIRP) sonar is operated at 
12 kilohertz (kHz) for bottom-tracking purposes or at 3.5 kHz in the 
sub-bottom profiling mode. The sonar emits energy in a 30[deg] beam 
from the bottom of the ship and has a sound level of 224 dB re: 1 
[mu]Pa m (rms).
    (2) Multibeam Sonar (Kongsberg EM122)--The hull-mounted, multibeam 
sonar operates at a frequency of 12 kHz, has an estimated maximum 
source energy level of 242 dB re 1[mu]Pa (rms), and emits a very narrow 
(<2[deg]) beam fore to aft and 150[deg] in cross-track. The multibeam 
system emits a series of nine consecutive 15 millisecond (ms) pulses.
    (3) Acoustic Doppler Current Profiler (ADCP) (Teledyne RDI VM-
150)--The hull-mounted ADCP operates at a frequency of 150 kHz, with an 
estimated acoustic output level at the source of 223.6 dB re 1[mu]Pa 
(rms). Sound energy from the ADCP is emitted as a 30[deg], conically 
shaped beam.
    (4) ADCP (Ocean Surveyor OS-38)--The characteristics of this 
backup, hull-mounted ADCP unit are similar to the Teledyne VM-150. The 
ADCP operates at a frequency of 150 kHz with an estimated acoustic 
output level at the source of 223.6 dB re 1[mu]Pa (rms). Sound energy 
from the ADCP is emitted as a 30[deg] conically-shaped beam.
    (5) EK biological echo sounder (Simrad ES200-7C, ES38B, ES-120-
7C)--This echo sounder is a split-beam transducer with an estimated 
acoustic output level at the source of 183-185 dB

[[Page 59207]]

re 1[mu]Pa and emits a 7[deg] beam. It can operate at 38 kHz, 120 kHz 
and 200 kHz.
    (6) Acoustic Release--To retrieve OBSs, an acoustic release 
transponder (pinger) is used to interrogate the instrument at a 
frequency of 8-11 kHz, and a response is received at a frequency of 7-
15 kHz. The burn-wire release assembly is then activated, and the 
instrument is released to float to the surface from the wire and/or 
anchor which are not retrieved.
    (7) Oceanographic Sampling--during the Drygalski Trough study, the 
researchers would also conduct opportunistic oceanographic sampling as 
time and scheduling allows, including conductivity, temperature and 
depth (CTD) measurements, box cores, and/or multi-cores.
Icebreaking
    Icebreaking activities are expected to be limited during the 
proposed survey. The Ross Sea is generally clear of ice January through 
February, because of the large Ross Sea Polynya that occurs in front of 
the Ross Ice Shelf. Heavy ice conditions would hamper the proposed 
activities, as noise from icebreaking degrades the quality of the 
geophysical data to be acquired. If the RVIB Palmer would find itself 
in heavy ice conditions, it is unlikely that the airgun(s) and streamer 
could be towed, as this could damage the equipment and generate noise 
interference. The seismic survey could take place in low ice conditions 
if the RVIB Palmer were able to generate an open path behind the 
vessel. The RVIB Palmer is not rated for breaking multi-year ice and 
generally avoids transiting through ice two years or older and more 
than 1 m thick. If sea ice were to be encountered during the survey, 
the RVIB Palmer would likely proceed through one-year sea ice, and new, 
thin ice, but would follow leads wherever possible. Any time spent 
icebreaking would take away time from the proposed research activities, 
as the vessel would travel slower in ice-covered seas. Based on 
estimated transit to the survey area, it is estimated that the RVIB 
Palmer would break ice up to a distance of 500 km. Based on a ship 
speed of 5 kn under moderate ice conditions, this distance represents 
approximately 54 hours of icebreaking (or 2.2 days). Transit through 
areas of primarily open water containing brash ice or pancake ice is 
not considered icebreaking for the purposes of this assessment.
    Proposed mitigation, monitoring, and reporting measures are 
described in detail later in this document (please see Proposed 
Mitigation and Proposed Monitoring and Reporting).

Description of Marine Mammals in the Area of Specified Activities

    Sections 3 and 4 of the application summarize available information 
regarding status and trends, distribution and habitat preferences, and 
behavior and life history, of the potentially affected species. 
Additional information 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 (IWC) population estimates, 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.
    Seventeen species of marine mammals could occur in the Ross Sea, 
including 5 mysticetes (baleen whales), 7 odontocetes (toothed whales) 
and 5 pinniped species (Table 2). Another seven species occur in the 
Sub-Antarctic but are unlikely to be encountered in the proposed survey 
areas, as they generally occur farther to the north than the project 
area. These species are not discussed further here but include: the 
southern right whale (Eubalaena australis), common (dwarf) minke whale 
(Balaenoptera acutorostrata), Cuvier's beaked (Ziphius cavirostris), 
Gray's beaked (Mesoplodon grayi), Hector's beaked (Mesoplodon hectori), 
and spade-toothed beaked (Mesoplodon traversii) whales, southern right 
whale dolphin (Lissodelphis peronii), and spectacled porpoise (Phocoena 
dioptrica). Table 2 lists all species with expected potential for 
occurrence in the Ross Sea, Antarctica, and summarizes information 
related to the population, including regulatory status under the MMPA 
and ESA.

 Table 2--Marine Mammal Species Potentially Present in the Project Area Expected To Be Affected by the Specified
                                                   Activities
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                                                                       ESA/MMPA
                                                                        status;
          Common name              Scientific name      Stock\1\     strategic (Y/         Stock abundance
                                                                        N) \2\
----------------------------------------------------------------------------------------------------------------
                      Order Cetartiodactyla--Cetacea--Superfamily Mysticeti (baleen whales)
----------------------------------------------------------------------------------------------------------------
Family Balaenopteridae (rorquals):
----------------------------------------------------------------------------------------------------------------
    Blue whale.................  Balaenoptera        N/A            E/D;Y           10,000-25,000.\5\
                                  musculus.                                         1,700.\7\
    Fin whale..................  Balaenoptera        N/A            E/D;Y           140,000.\5\
                                  physalus.                                         38,200.\ 6\
    Humpback whale.............  Megaptera           N/A            ..............  90,000.-100,000.\5\
                                  novaeangliae.                                     80,000.\10\
                                                                                    42,000.\11\
    Antarctic minke whale\6\...  Balaenoptera        N/A            ..............  Several 100,000 \5\
                                  bonaerensis.                                      515,000.\9\

[[Page 59208]]

 
    Sei whale..................  Balaenoptera        N/A            E               70,000.\8\
                                  borealis.
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                        Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
----------------------------------------------------------------------------------------------------------------
Family Physeteridae:
----------------------------------------------------------------------------------------------------------------
    Sperm whale................  Physeter            N/A            E               360,000.\12\
                                  macrocephalus.                                    12,069.\13\
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Family Ziphiidae (beaked whales):
----------------------------------------------------------------------------------------------------------------
    Arnoux's beaked whale......  Berardius arnuxii.  N/A            ..............  599,300.\14\
    Strap-toothed beaked whale.  Mesoplodon grayi..  N/A            ..............  599,300.\14\
    Southern bottlenose whale..  Hyperoodon          N/A            ..............  599,300.\14\
                                  planifrons.
----------------------------------------------------------------------------------------------------------------
Family Delphinidae:
----------------------------------------------------------------------------------------------------------------
    Killer whale...............  Orcinus orca......  N/A            ..............  50,000 \16\
                                                                                    25,000.\17\
    Long-finned pilot whale....  Globicephala        N/A            ..............  200,000.\15\
                                  macrorhynchus.
    Hourglass dolphin..........  Lagenorhynchus      NA             ..............  144,300.\15\
                                  cruciger.
----------------------------------------------------------------------------------------------------------------
Family Phocidae (earless seals):
----------------------------------------------------------------------------------------------------------------
    Crabeater seal.............  Lobodon             N/A            ..............  5-10 million \18\
                                  carcinophaga.                                     1.7 million.\19\
    Leopard seal...............  Hydrurga leptonyx.  N/A            ..............  222,000-440,00.\5\ \20\
    Southern elephant seal.....  Mirounga leonina..  N/A            ..............  750,000.\23\
    Ross seal..................  Ommatophoca rossii  N/A            ..............  250,000.\22\
    Weddell seal...............  Leptonychotes       N/A            ..............  1 million.\5\ \21\
                                  weddellii.
----------------------------------------------------------------------------------------------------------------
N.A. = data not available.
\1\ Occurrence in area at the time of the proposed activities; based on professional opinion and available data.
\2\ U.S. Endangered Species Act: EN = endangered, NL = not listed.
\5\ Worldwide (Jefferson et al., 2015).
\6\ Antarctic (Aguilar and Garc[iacute]a-Vernet 2018).
\7\ Antarctic (Branch et al., 2007).
\8\ Southern Hemisphere (Horwood 2018).
\9\ Southern Hemisphere (IWC 2020).
\10\ Southern Hemisphere (Clapham 2018).
\11\ Antarctic feeding area (IWC 2020).
\12\ Worldwide (Whitehead 2002).
\13\ Antarctic south of 60[deg] S (Whitehead 2002).
\14\ All beaked whales south of the Antarctic Convergence; mostly southern bottlenose whales (Kasamatsu and
  Joyce 1995).
\15\ Kasamatsu and Joyce (1995).
\16\ Worldwide (Forney and Wade 2006).
\17\ Minimum estimate for Southern Ocean (Branch and Butterworth 2001).
\18\ Worldwide (Bengtson and Stewart 2018).
\19\ Ross and Amundsen seas (Bengtson et al., 2011).
\20\ Rogers et al., 2018.
\21\ H[uuml]ckst[auml]dt 2018a.
\22\ Worldwide (Curtis et al., 2011 in H[uuml]ckst[auml]dt 2018b).
\23\ Total world population (Hindell et al., 2016).

    All species that could potentially occur in the proposed survey 
areas are included in Table 2. As described below, all 17 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).

[[Page 59209]]

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.
    The Antarctic blue whale is typically found south of 55[deg] S 
during summer, although some individuals do not migrate (Branch et al., 
2007a). The blue whale is considered to be rare in the Southern Ocean; 
up to 360,000 blue whales were harvested in the Southern Hemisphere in 
the early 20th century (Sears and Perrin 2018). Ainley (2010) noted 
that they were extirpated from the Ross Sea shelf break front in the 
1920s. Smith et al. (2012) estimated that 30 blue whales may occur in 
the Ross Sea. Several sighting records were reported for the northern 
Ross Sea between 1978 and 2005 (Kasamatsu et al., 1990; Nishiwaki et 
al., 1997; Matsuoka et al., 2006; Ainley et al., 2010) as well as 
during a 2008 survey (Baird and Mormede 2014). Acoustic detections were 
also made in the northeastern Ross Sea between 1996 to 2010 (Shabangu 
et al., 2018). Eight groups of 24 individuals were seen north of the 
Ross Sea during summer surveys in 2002-2003 (Ensor et al., 2003). No 
blue whales were seen during an NSF-funded seismic survey in the Ross 
Sea in January-February 2015 (RPS 2015a).
Fin Whale
    The fin whale 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 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 and 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.
    Based on Edwards et al. (2015), densities in the Southern Ocean 
south of 60[deg] S (including the northern part of the Ross Sea) are 
highest during December-February, with non-zero densities <0.003 
whales/km\2\. Pinkerton et al. (2010) assumed that ~200 fin whales use 
the Ross Sea during summer. Fin whale sightings have been reported for 
the Ross Sea by several authors (Nishiwaki et al., 1997; Matsuoka et 
al., 2006; Ainley et al., 2010; Baird and Mormede 2014; MacDiarmid and 
Stewart 2015). During an NSF-funded seismic survey in the Ross Sea in 
January through February 2015, 13 sightings totaling 34 fin whales were 
made, including within the proposed survey area (RPS 2015a). Ensor et 
al. (2003) reported sightings north of the Ross Sea during summer 
surveys in 2002-2003.
Humpback Whale
    The humpback whale is found in all ocean basins (Clapham 2018). 
Based on genetic data, there could be three subspecies, occurring in 
the North Pacific, North Atlantic, and Southern Hemisphere (Jackson et 
al., 2014). The humpback whale is highly migratory, undertaking one of 
the world's longest mammalian migrations by traveling between mid- to 
high-latitude waters where it feeds during spring to fall and low-
latitude wintering grounds over shallow banks, where it mates and 
calves (Winn and Reichley 1985; Bettridge et al., 2015). Although 
considered to be mainly a coastal species, it often traverses deep 
pelagic areas while migrating (Baker et al., 1998; Garrigue et al., 
2002; Zerbini et al., 2011).
    In the Southern Hemisphere, humpback whales migrate annually from 
summer foraging areas in the Antarctic to breeding grounds in tropical 
seas (Clapham 2018). The IWC recognizes seven breeding populations in 
the Southern Hemisphere that are linked to six foraging areas in the 
Antarctic (Bettridge et al., 2015; Clapham 2018). Humpbacks that occur 
in the western Ross Sea (west of 170[deg] W) are part of the Area V 
feeding stock (Schmitt et al., 2014); these individuals are from the 
Oceania DPS that breeds in French Polynesia, Cook Islands, and Tonga, 
and from the East Australia DPS (Schmitt et al., 2014; Bettridge et 
al., 2015).
    Humpback densities are high north of the Ross Sea (Branch 2011; 
Matsuoka and Hakamada 2020), but not within it (Ropert-Coudert et al., 
2014). Pinkerton et al. (2010) estimated that <5 percent (150 
individuals) of the Southern Ocean population occurs in the Ross Sea in 
the austral summer. Humpback whales were seen in the northern Ross Sea 
during surveys conducted between 1987 and 2009 (Baird and Mormede 2014; 
MacDiarmid and Stewart 2015). However, none were seen in the Ross Sea 
during the International Whaling Commission-Southern Ocean Whale and 
Ecosystem Research (IDCR/SOWER) surveys from 1978/79 to 2004/05 (Branch 
2011). During an NSF-funded seismic survey in the Ross Sea in January-
February 2015, two sightings totaling six individuals were made east of 
the proposed survey areas (RPS 2015a). Acoustic detections were also 
made in the northeastern Ross Sea between 1996 to 2010 (Shabangu et 
al., 2018). Ensor et al. (2003) reported numerous humpback sightings 
and acoustic detections north of the Ross Sea during summer surveys in 
2002-2003.
Antarctic Minke Whale
    The Antarctic minke whale has a circumpolar distribution in coastal 
and offshore areas of the Southern Hemisphere from ~7 degrees S to the 
ice edge (Jefferson et al., 2015). It is found between 60[deg] S and 
the ice edge during the austral summer; in the austral winter, it is 
mainly found at mid-latitude breeding grounds, including off western 
South Africa and northeastern Brazil, where it is primarily oceanic,

[[Page 59210]]

occurring beyond the shelf break (Perrin et al., 2018). Antarctic minke 
whale densities are highest near pack ice edges, although they are also 
found amongst pack ice (Ainley et al., 2012; Williams et al., 2014), 
where they feed almost entirely on krill (Tamura and Konishi 2009). 
Murase et al. (2006, 2007) found that minke whale distribution was 
related to krill density in the Ross Sea, with the greatest number of 
pods in areas with a krill density of 1 g/m\2\.
    Minke whales were harvested heavily in the Southern Ocean during 
the 1970s and 1980s, with >13,000 harvested in the early 1980s; but the 
hunt ceased in 1986 under an IWC moratorium (Ainley 2002). However, 
Japanese whaling continued under scientific permit taking hundreds of 
minke whales in the Ross Sea since the late 1980s (Ainley 2002). During 
Japanese sighting surveys from 1976-1988, high encounter rates occurred 
in the Ross Sea (Kasamatsu et al., 1996), where minke whales are known 
to form feeding aggregations (Kasamatsu et al., 1998). Saino and 
Guglielmo (2002) reported a mean density of 0.13 whales/km\2\ in the 
western Ross Sea. The minke whale is the most abundant species 
occupying the shelf waters in the Ross Sea (Waterhouse 2001; Smith et 
al., 2007). Approximately six percent of Antarctic minke whales occur 
in the Ross Sea (Ainley et a,l. 2010; Smith et al., 2012). The Ross Sea 
population was estimated at 14,300 by Ainley (2002) and 87,643 
individuals by Matsuoka et al., (2009).
    Ainley et al. (2017) reported that minke whales started to arrive 
in the southwestern Ross Sea in mid-November, with decreasing ice 
conditions. Ainley et al. (2010, 2012) and Ballard et al. (2012) 
reported sightings around the northwestern and northeastern periphery 
of the proposed Ross Bank survey area and within the Drygalski Trough 
survey area. Although minke whales have a high likelihood of occurrence 
in the Ross Sea (e.g., Ainley et al., 2012; Ropert-Coudert et al., 
2014), habitat suitability for the proposed survey area in summer was 
modeled as relatively low (Ballard et al., 2012). However, minke whales 
were seen in the Ross Sea during surveys conducted between 1978 and 
2009, including within the proposed survey area (Kasamatsu et al., 
1990; Baird and Mormede 2014; MacDiarmid and Stewart 2015). They were 
also detected acoustically in the Ross Sea in 2004 (Dolman et al., 
2005). Minke whales were seen feeding (presumable on fish) in the 
southwestern Ross Sea (Lauriano et al., 2007). During an NSF-funded 
seismic survey in the Ross Sea in January-February 2015, 224 sightings 
totaling 1023 minke whales were made, including within the proposed 
survey area and in McMurdo Sound (RPS 2015a). Ensor et al. (2003) 
reported numerous sightings north of the Ross Sea during summer surveys 
in 2002-2003.
Sei Whale
    The sei whale 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). Pinkerton et al. (2010) 
assumed that approximately 100 animals may occur in the Ross Sea. Ensor 
et al. (2003) reported no sightings south of 54[deg] S during a summer 
survey of the Southern Ocean in 2002-2003. No sei whales were seen 
during an NSF-funded seismic survey in the Ross Sea in January-February 
2015 (RPS 2015a).

Odontocetes

Sperm Whale
    The sperm whale 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 and Whitehead 1996). Its distribution and 
relative abundance can vary in response to prey availability, most 
notably squid (Jaquet and Gendron 2002). Females generally inhabit 
waters greater than 1,000 m deep at latitudes less than 40[deg] where 
sea surface temperatures are less than 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).
    Few sperm whales are thought to occur in the Ross Sea (Smith et 
al., 2012), although Pinkerton et al. (2010) assumed that 800 sperm 
whales could be using the Ross Sea. Sperm whales generally do not occur 
south of approximately 73-74[deg] S in the Ross Sea (Matsuoka et al., 
1998; Ropert-Coudert et al., 2014). Nonetheless, sperm whales have been 
reported there by several authors (Kasamatsu et al., 1990; Baird and 
Mormede 2014). Ensor et al. (2003) reported numerous sightings and 
acoustic detections north of the Ross Sea during summer surveys in 
2002-2003. No sperm whales were seen during an NSF-funded seismic 
survey in the Ross Sea in January through February 2015 (RPS 2015a).
Arnoux's Beaked Whale
    Arnoux's beaked whale 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).
    Ainley et al. (2010) and Van Waerebeek et al. (2010), and Ropert-
Coudert et al. (2014) reported their occurrence in the Ross Sea. 
Lauriano et al. (2011) reported two sightings of single individuals in 
Terra Nova Bay, western Ross Sea, during summer 2004 surveys. There may 
be 50 (Pinkerton et al., 2010) to 150 (Smith et al., 2012) Arnoux's 
beaked whales in the Ross Sea. No Arnoux's beaked whales were seen 
during an NSF-funded seismic survey in the Ross Sea in January through 
February 2015 (RPS 2015a).
Southern Bottlenose Whale
    The southern bottlenose whale is found throughout the Southern 
Hemisphere from 30[deg] S to the ice edge, with most sightings reported 
between approximately 57[deg] S and 70[deg] S (Jefferson et al., 2015; 
Moors-Murphy 2018). Several sighting and stranding records exist for 
southeastern South America, Falkland Islands, South Georgia Island, 
southeastern Brazil, Argentina, South Africa, and numerous sightings 
have been reported for the Southern Ocean (Findlay et al., 1992; 
MacLeod et al. 2006; Riccialdelli et al., 2017). The population size of 
southern bottlenose whales in the Ross Sea was assumed to be 500 by 
Pinkerton et al. (2010). Ropert-Coudert et al. (2014) reported their 
occurrence in the Ross Sea, and Kasamatsu et al. (1990) reported 
sightings between 1978 and 1988. Southern bottlenose whales were also 
sighted in the northern Ross Sea and

[[Page 59211]]

north of there during surveys of the Southern Ocean by Van Waerebeek et 
al. (2010). Several unidentified beaked whales have also been reported 
in the Ross Sea, including in the Ross Bank survey area and near the 
Drygalski Trough survey area (Baird and Mormede 2014; MacDiarmid and 
Stewart 2015; Matsuoka and Hakamada 2020). Ensor et al. (2003) and 
Matsuoka and Hakamada (2020) reported numerous sightings of southern 
bottlenose whales north of the Ross Sea. No bottlenose whales were seen 
during an NSF-funded seismic survey in the Ross Sea in January-February 
2015 (RPS 2015a).
Strap-Toothed Beaked Whale
    The strap-toothed beaked whale is thought to have a circumpolar 
distribution in temperate and subantarctic waters of the Southern 
Hemisphere, mostly between 32[deg] and 63[deg] S (MacLeod et al., 2006; 
Jefferson et al., 2015). It is likely quite common in the Southern 
Ocean (Pitman 2018). It may undertake limited migration to warmer 
waters during the austral winter (Pitman 2018). Strap-toothed beaked 
whales are thought to migrate northward from Antarctic and subantarctic 
latitudes during April-September (Sekiguchi et al,. 1995). One group of 
three strap-toothed beaked whales was seen north of the Ross Sea, north 
of 65[deg] S, during a 2002 through 2003 summer survey (Ensor et al., 
2003). No strap-toothed beaked whales were seen during an NSF-funded 
seismic survey in the Ross Sea in January through February 2015 (RPS 
2015a).
Killer Whale
    The killer whale is cosmopolitan and globally abundant; it has been 
observed in all oceans of the world (Ford 2018). It is very common in 
temperate waters but also occurs in tropical waters (Heyning and 
Dahlheim 1988) and inhabits coastal and offshore regions (Budylenko 
1981). Mikhalev et al. (1981) noted that it appears to migrate from 
warmer waters during the winter to higher latitudes during the summer. 
In the Antarctic, it commonly occurs up to the pack ice edge but may 
also find its way into ice-covered water (Ford 2018).
    There are three ecotypes that occur in Antarctic waters: type A 
hunts marine mammals in open water, mainly seeking minke whales, type B 
hunt seals in loose pack ice, and type C feeds on fish in dense pack 
ice (Pitman and Ensor 2003); these types are likely different species 
(Morin et al., 2010; Pitman et al., 2017). Type D occurs in 
subantarctic waters and is also likely a separate species (Pitman et 
al., 2011). Type B travels widely to hunt its prey, whereas type C is 
more resident (Andrews et al., 2008). In fact, type Cs (Ross Sea killer 
whales) appear to have resident and transient groups in the Ross Sea 
(e.g., Ainley et al., 2017). In the Ross Sea, abundance has been 
estimated at 7500 individuals (Smith et al., 2007). Ainley et al. 
(2010) and Smith et al. (2012) estimated that approximately 50 percent 
of Ross Sea killer whales use the Ross Sea during summer foraging. 
Smith et al. (2012) reported 3350 type C killer whales and 70 type A/B 
killer whales in the Ross Sea. Pitman et al. (2017) reported only two 
ecotypes in the Ross Sea (types B and C), but Ainley et al. (2010) 
noted that type A could occur along the slope.
    Ainley et al. (2017) reported that type C and B killer whales start 
to arrive in the southwestern Ross Sea in mid-November, with decreasing 
ice conditions, with type Bs arriving earlier than type Cs. Type C 
killer whales have been seen feeding (presumable on fish) in the 
southwestern Ross Sea (Lauriano et al., 2007), and type B and C killer 
whales were reported during summer 2004 surveys in Terra Nova Bay, 
western Ross Sea (Lauriano et al., 2011). Eisert et al. (2014) reported 
Type C and B in McMurdo Sound. Type C killer whales have also been 
detected acoustically in McMurdo Sound (Wellard et al., 2020). During 
an NSF-funded seismic survey in the Ross Sea in January through 
February 2015, 14 sightings totaling 254 killer whales were made, 
including within the survey area and in McMurdo Sound (RPS 2015a). 
Saino and Guglielmo (2002) reported a mean density of 0.05 whales/km\2\ 
in the western Ross Sea. However, numbers of type C killer whales have 
apparently decreased in the southwestern Ross Sea, because of changes 
in prey distribution (Antarctic toothfish) likely brought on by fishing 
pressures (Ainley et al., 2009; Ainley and Ballard 2012). However, 
Pitman et al. (2018) suggested that the presence of a mega-iceberg at 
Ross Island may have also impeded killer whale movement, thereby 
affecting the population size; they estimated a population size of 470 
distinct individuals in McMurdo Sound. Type B killer whale numbers have 
not changed in the southern Ross Sea, where they hunt Weddell seals and 
emperor penguins (Ainley and Ballard 2012).
    Type C killer whale appears to favor the Ross Sea shelf and slope 
(Ballard et al., 2012). Sightings of type C killer whales within and 
west of the proposed study area have been reported during summer 
(Andrews et al., 2008; Ballard et al., 2012). The habitat suitability 
for the proposed survey area in summer for type C killer whales was 
modeled as relatively high, whereas it was lower for the Drygalski 
Trough survey area (Ballard et al., 2012). Andrew et al. (2008) 
documented movement of a tagged type B killer whale to the west of the 
proposed study area. Aubrey et al. (1982) reported sightings of killer 
whales in the Ross Sea off Cape Adare and over Pennell Banks, and noted 
that killer whales were abundant off Ross Island. Killer whales were 
also reported in the Ross Sea by several other authors (e.g., Kasamatsu 
et al., 1990; Van Dam and Kooyman 2004; Van Waerebeek et al., 2010; 
Baird and Mormede 2014; Ropert-Coudert et al., 2014). Acoustic 
detections were also made in the northeastern Ross Sea between 1996 to 
2010 (Shabangu et al., 2018). Ensor et al. (2003) reported numerous 
sightings and acoustic detections north of the Ross Sea during summer 
surveys in 2002-2003.
Long-Finned Pilot Whales
    The long-finned pilot whale is distributed antitropically in cold 
temperate waters, including the Southern Ocean, whereas the short-
finned pilot whale is found in tropical and warm temperate waters 
(Olson 2018). The ranges of the two species show little overlap (Olson 
2018). Long-finned pilot whales are geographically isolated and 
separated into two subspecies, G. melas melas and G. melas edwardii in 
the Northern and Southern hemispheres, respectively (Olson 2018). In 
the Southern Hemisphere, their range extends to the Antarctic 
Convergence and sometimes as far south as 68[deg] S (Jefferson et al., 
2015). Although generally not seen south of 68[deg] S, long-finned 
pilot whales were reported in the Ross Sea during observations from 
longliners between 1997 and 2009 (Baird and Mormede 2014). During 
summer surveys in 2002-2003, several sightings were made north of the 
Ross Sea (Ensor et al., 2003). They were also reported north of the 
Ross Sea during surveys by Van Waerebeek et al. (2010). No pilot whales 
were seen during an NSF-funded seismic survey in the Ross Sea in 
January-February 2015 (RPS 2015a).
Hourglass Dolphin
    The hourglass dolphin occurs in the Southern Ocean, with most 
sightings between approximately 45[deg] S and 60[deg] S (Cipriano 
2018). However, some sightings have been made as far north as 33[deg] S 
(Jefferson et al., 2015). Hourglass dolphins were sighted near 45[deg] 
S, north of the Ross Sea, during surveys of the Southern Ocean (Van 
Waerebeek et al.,

[[Page 59212]]

2010). Although it is pelagic, it is also sighted near banks and 
islands (Cipriano 2018). Ensor et al. (2003) reported numerous 
sightings of hourglass dolphins north of the Ross Sea, north of 65[deg] 
S, during a summer survey in 2002-2003. No hourglass dolphins were seen 
during an NSF-funded seismic survey in the Ross Sea in January through 
February 2015 (RPS 2015a).

Phocids

Crabeater Seal
    The crabeater seal has a circumpolar distribution off Antarctica 
and is the most abundant seal in the region, sometimes congregating in 
the hundreds (Bengtson and Stewart 2018). It generally spends the 
entire year in the advancing and retreating pack ice (Bengtson and 
Stewart 2018). However, outside of the breeding season, crabeater seals 
spend ~14 percent of their time in open water (reviewed in Southwell et 
al., 2012); they mainly forage on krill. During the breeding season, 
crabeater seals are most likely to be present within 5[deg] or less 
(~550 km) of the shelf break; non-breeding animals range farther north 
(Southwell et al., 2012). Pupping season peaks in mid- to late-October, 
and adults are observed with their pups as late as mid-December 
(Bengtson and Stewart 2018).
    Crabeater seals are most common in the pack ice of the northern 
Ross Sea (Waterhouse 2001). A population of approximately 204,000 has 
been estimated for the Ross Sea (Waterhouse 2001; Ainley 2002, 2010; 
Pinkerton and Bradford-Grieve 2010; Smith et al., 2012). Crabeater 
seals have been reported for the Ross Sea by several authors (Stirling 
1969; Van Dam and Kooyman 2004; Bester and Stewart 2006; Baird and 
Mormede 2014; Ropert-Coudert et al., 2014). Crabeater seals have been 
sighted within the proposed survey area (e.g., Saino and Guglielmo 
2000; Ainley et al., 2010; Ballard et al., 2012), with greater habitat 
suitability in summer in the Drygalski Trough survey area than in the 
Ross Bank survey area (Ballard et al., 2012). Similarly, Bengtson et 
al. (2011) reported relatively low densities in the Ross Bank area and 
higher densities in the Drygalski Trough area. Saino and Guglielmo 
(2002) showed increasing densities with increasing pack ice and 
distance from shore, with a mean density of 0.49 seals/km\2\, in the 
western Ross Sea. In contrast, Bengtson et al. (2011) reported the 
highest density (1.3 seals/km\2\) on the shelf at distances up to 200 
km from the ice edge during surveys of the Ross and Amundsen seas; 
densities in the proposed survey area were estimated to be low. During 
an NSF-funded seismic survey in the Ross Sea in January through 
February 2015, 9 sightings of 14 individuals were made (RPS 2015a).
Leopard Seal
    The leopard seal has a circumpolar distribution around the 
Antarctic continent where it is solitary and widely dispersed at low 
densities (Rogers 2018). It primarily occurs in pack ice, but when the 
sea ice extent is reduced, it can be found in coastal habitats (Meade 
et al., 2015). Leopard seals are top predators, consuming everything 
from krill and fish to penguins and other seals (e.g., Hall-Aspland and 
Rogers 2004). Pups are born during October to mid-November and weaned 
~one month later (Rogers 2018). Mating occurs in the water during 
December and January. A population of ~8000 is thought to occur in the 
Ross Sea (Waterhouse 2001; Ainley 2002, 2010; Pinkerton and Bradford-
Grieve 2010; Smith et al., 2012). Bengtson et al. (2011) reported an 
abundance of 15,000 leopard seals for the Ross and Amundsen seas. 
Densities were highest (0.024 seals/km\2\) in water <3000 m deep and 
<100 km from the ice edge; very low densities were estimated for the 
southern portion of the Ross Bank survey area, with low densities in 
the rest of the survey area and in the Drygalski Trough survey area 
(Bengtson et al., 2011). Leopard seals have been documented to take 
Ad[eacute]lie penguins at several colonies in the Ross Sea, including 
Cape Crozier (south of the proposed survey areas), and in McMurdo Sound 
(Ainley et al., 2005). Leopard seals have been reported within and near 
the Drygalski Trough survey area, no sightings have been reported 
within the Ross Bank survey area (Stirling 1969; Ackley et al., 2003; 
Van Dam and Kooyman 2004; Bester and Stewart 2006; Ainley et al., 2010; 
Baird and Mormede 2014; Ropert-Coudert et al., 2014). No leopard seals 
were sighted during an NSF-funded seismic survey in the Ross Sea in 
January-February 2015 (RPS 2015a).
Southern Elephant Seal
    The southern elephant seal has a near circumpolar distribution in 
the Southern Hemisphere (Jefferson et al., 2015), with breeding sites 
located on islands throughout the subantarctic (Hindell 2018). Breeding 
colonies are generally island-based, with the occasional exception of 
the Antarctic mainland (Hindell 2018).
    When not breeding (September-October) or molting (November-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 and Fedak 1996). Their occurrence in the Ross Sea 
is rare and only during the summer (Waterhouse 2001; Pinkerton and 
Bradford-Grieve 2010). The population size in the Ross Sea is estimated 
to number <100 individuals (Ainley 2010; Smith et al., 2012). Ropert-
Coudert et al. (2014) reported one record in the Ross Sea, in McMurdo 
Sound. No southern elephant seals were seen during an NSF-funded 
seismic survey in the Ross Sea in January-February 2015 (RPS 2015a)
Ross Seal
    Ross seals 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.
    The population in the Ross Sea may number 500 (Smith et al,. 2012) 
to 5000 individuals (Waterhouse 2001; Ainley 2010; Pinkerton and 
Bradford-Grieve 2010). According to surveys by Bester et al. (2006), 
Ross seals are relatively abundant in the Ross Sea. Based on surveys of 
the Ross and Amundsen seas, Bengtson et al. (2011) estimated an 
abundance of 22,600, with the highest density (0.032 seals/km\2\) in 
deep water (greater than 3000 m) within 200 km from the ice edge; low 
densities were estimated for the proposed survey area. Ross seals were 
seen in the western (Stirling 1969) and eastern Ross Sea during surveys 
(Stirling 1969; Ackley et al., 2003; Bester and Stewart 2006). During 
an NSF-funded seismic survey in the Ross Sea in January through 
February 2015, two sightings of single Ross seals were made to the east 
of the proposed survey area (RPS 2015a).
Weddell Seal
    The Weddell seal is the second most abundant species of Antarctic 
seal (H[uuml]ckst[auml]dt 2018a). It occurs in the fast

[[Page 59213]]

and pack ice around all of Antarctica, as well as on land along the 
coast, but is rarely found in ice-free water (H[uuml]ckst[auml]dt 
2018a). It occurs on the Ross Sea shelf and slope (Ballard et al., 
21012). It is the most southerly breeding mammal in the world, 
occurring as far south as the RIS (H[uuml]ckst[auml]dt 2018a). Unlike 
other Antarctic ice seals, Weddell seals form colonies (Cameron et al., 
2007). There are numerous pupping locations throughout the western Ross 
Sea, including around Ross Island (Ainley et al., 2010). Juveniles tend 
to disperse widely, resulting in genetic diversity in the population 
(H[uuml]ckst[auml]dt 2018a). Seals outfitted with tags in the western 
Ross Sea were documented to disperse hundreds of kilometers, making 
their way into the proposed survey areas (Ainley et al., 2010; Goetz 
2015). However, some small colonies have been isolated from open water 
by ice sheets and therefore show inbreeding depression (Gelatt et al., 
2010). Weddell seals primarily feed on fish. Pups are born from October 
through November and are weaned after ~six to eight weeks 
(H[uuml]ckst[auml]dt 2018a). Paterson et al. (2015) suggested that the 
timing of reproduction by Weddell seals in Erebus Bay, McMurdo Sound, 
is coupled with periods of high productivity in Ross Bay. After the 
breeding season, the ice breaks down and seals disperse into the sea to 
forage for one to two months and return to ice or land to molt in 
January and February (H[uuml]ckst[auml]dt 2018a).
    Ainley et al. (2010) estimated that 50 to 72 percent of the South 
Pacific sector of Weddell seals occur in the Ross Sea. The population 
in the Ross Sea has been estimated between 32,000 and 50,000 
individuals (e.g., Ainley 2002, 2010; Pinkerton and Bradford-Grieve 
2010; Smith et al., 2012). Bengtson et al. (2011) estimated the 
population in the Ross and Amundsen seas at 330,000 seals. The highest 
densities (up to 0.173 seals/km\2\) were observed in water less than 
3000 m deep; densities in the proposed survey area were estimated to be 
lower (Bengtson et al., 2011). Populations at McMurdo Sound were 
permanently reduced by sealing in the 20th century (Ainley 2010). 
Sightings within the Ross Sea, including within and near the proposed 
survey area, have been reported by several sources (Stirling 1969; 
Saino and Guglielmo 2002; Ackley et al., 2003; Van Dam and Kooyman 
2004; Bester and Stewart 2006; Ainley et al., 2010; Ropert-Coudert et 
al., 2014; Baird and Mormede 2014). Ballard et al. (2012) relatively 
low habitat suitability for Weddell seals in the majority of the Ross 
Bank survey area, with higher suitability in the eastern portion of the 
Ross Bank survey area and within the Drygalski Trough survey area. 
During an NSF-funded seismic survey in the Ross Sea in January through 
February 2015, 17 sightings of Weddell seals were made, including 
within the proposed survey area (RPS 2015a).

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

    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 & Holt, 
2013).
    For more detail concerning these groups and associated frequency 
ranges, please see NMFS (2018) for a review of available information.

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.

[[Page 59214]]

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 in as much 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.
    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 & 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):
    (1) 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;
    (2) 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;
    (3) 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
    (4) 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 one 
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,

[[Page 59215]]

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 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, hull-mounted MBESs, SBP, and ADCPs would also 
be operated from vessel continuously throughout the seismic surveys. 
Given the higher frequencies and relatively narrow beampatterns 
associated with these sources, in context of the movement and speed of 
the vessel, exposures of marine mammals are considered unlikely and, 
therefore, we do not expect take of marine mammals to result from use 
of these sources and do not consider them 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 (Description of Active Acoustic Sound 
Sources section) 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 & 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 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;

[[Page 59216]]

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 is 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 (2018).
    Behavioral Effects--Behavioral disturbance may include a variety of 
effects, including subtle changes in behavior (e.g., minor or brief 
avoidance of an area or changes in vocalizations), more conspicuous 
changes in similar behavioral activities, and more sustained and/or 
potentially severe reactions, such as displacement from or abandonment 
of high-quality habitat. Behavioral responses to sound are highly 
variable and context-specific and any reactions depend on numerous 
intrinsic and extrinsic factors (e.g., species, state of maturity, 
experience, current activity, reproductive state, auditory sensitivity, 
time of day), as well as the interplay between factors (e.g., 
Richardson et al., 1995; Wartzok et al., 2003; Southall et al., 2007; 
Weilgart, 2007; Archer et al., 2010). Behavioral reactions can vary not 
only among individuals but also within an individual, depending on 
previous experience with a sound source, context, and numerous other 
factors (Ellison et al., 2012), and can vary depending on 
characteristics associated with the sound source (e.g., whether it is 
moving or stationary, number of sources, distance from the source). 
Please see Appendices B-C of Southall et al. (2007) for a review of 
studies involving marine mammal behavioral responses to sound.
    Habituation can occur when an animal's response to a stimulus wanes 
with repeated exposure, usually in the absence of unpleasant associated 
events (Wartzok et al., 2003). Animals are most likely to habituate to 
sounds that are predictable and unvarying. It is important to note that 
habituation is appropriately considered as a ``progressive reduction in 
response to stimuli that are perceived as neither aversive nor 
beneficial,'' rather than as, more generally, moderation in response to 
human disturbance (Bejder et al., 2009). The opposite process is 
sensitization, when an unpleasant experience leads to subsequent 
responses, often in the form of avoidance, at a lower level of 
exposure. As noted, behavioral state may affect the type of response. 
For example, animals that are resting may show greater behavioral 
change in response to disturbing sound levels than animals that are 
highly motivated to remain in an area for feeding (Richardson et al., 
1995; NRC, 2003; Wartzok et al., 2003). Controlled experiments with 
captive marine mammals have shown pronounced behavioral reactions, 
including avoidance of loud sound sources (Ridgway et al., 1997). 
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 & Symonds, 2002; see also 
Richardson et al., 1995; Nowacek et al., 2007). However, many 
delphinids approach acoustic source vessels with no apparent discomfort 
or

[[Page 59217]]

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 & 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 
& Clark, 2000; Ng & 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 10 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 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 
[micro]Pa\2\-s caused blue whales to increase call production (Di Iorio 
and Clark, 2010). In contrast, McDonald et al. (1995) tracked a blue 
whale with seafloor seismometers and reported that it stopped 
vocalizing and changed its travel direction at a range of 10 km from 
the acoustic source vessel (estimated received level 143 dB pk-pk). 
Blackwell et al. (2013) found that

[[Page 59218]]

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 & 
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 & England, 2001). However, it should be noted that response to a 
perceived predator does not necessarily invoke flight (Ford & 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 & 
Livoreil, 1997; Fritz et al., 2002; Purser & 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 
& 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 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

[[Page 59219]]

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 & 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 & 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. (2015) noted the 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

[[Page 59220]]

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.

Icebreaking

    Icebreakers produce more noise while breaking ice than ships of 
comparable size due, primarily, to the sounds of propeller cavitation 
(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 
ships (Cosens and 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 and Farmer, 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 and 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 haulout 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 haulout 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.

Ship Noise

    Vessel noise from the RVIB 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., 2016; 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)

[[Page 59221]]

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 & 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 if they 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.
    Sounds emitted by the Palmer are low frequency and continuous, but 
would be widely dispersed in both space and time. 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).
    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.

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 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 RVIB Palmer travels at a speed of 4.5 kn (8.3 km/hour) when 
towing seismic survey gear, or at an average speed of 18.7 km/h (10.1 
kn) while cruising. 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

[[Page 59222]]

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 an event in the wild in which (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 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 (16 U.S.C. 
1421h(3)).
    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 (Chrousos, 2000; Creel, 2005; DeVries et al., 2003; 
Fair & Becker, 2000; Foley et al., 2001; Moberg, 2000; Relyea, 2005a; 
2005b, Romero, 2004; Sih et al., 2004).
    There is no conclusive evidence that exposure to airgun noise 
results in behaviorally-mediated forms of injury. Behaviorally-mediated 
injury (i.e., mass stranding events) has been primarily associated with 
beaked whales exposed to mid-frequency active (MFA) naval sonar. 
Tactical sonar and the alerting stimulus used in Nowacek et al. (2004) 
are very different from the noise produced by airguns. One should 
therefore not expect the same reaction to airgun noise as to these 
other sources. As explained below, military MFA sonar is very different 
from airguns, and one should not assume that airguns will cause the 
same effects as MFA sonar (including strandings).
    To understand why Navy MFA sonar affects beaked whales differently 
than airguns do, it is important to note the distinction between 
behavioral sensitivity and susceptibility to auditory injury. To 
understand the potential for auditory injury in a particular marine 
mammal species in relation to a given acoustic signal, the frequency 
range the species is able to hear is critical, as well as the species' 
auditory sensitivity to frequencies within that range. Current data 
indicate that not all marine mammal species have equal hearing 
capabilities across all frequencies and, therefore, species are grouped 
into hearing groups with generalized hearing ranges assigned on the 
basis of available data (Southall et al., 2007, 2019). Hearing ranges 
as well as auditory sensitivity/susceptibility to frequencies within 
those ranges vary across the different groups. For example, in terms of 
hearing range, the high-frequency cetaceans (e.g., Kogia spp.) have a 
generalized hearing range of frequencies between 275 Hz and 160 kHz, 
while mid-frequency cetaceans--such as dolphins and beaked whales--have 
a generalized hearing range between 150 Hz to 160 kHz. Regarding 
auditory susceptibility within the hearing range, while mid-frequency 
cetaceans and high-frequency cetaceans have roughly similar hearing 
ranges, the high-frequency group is much more susceptible to noise-
induced hearing loss during sound exposure, i.e., these species have 
lower thresholds for these effects than other hearing groups (NMFS, 
2018). Referring to a species as behaviorally sensitive to noise simply 
means that an animal of that species is more likely to respond to lower 
received levels of sound than an animal of another species that is 
considered less behaviorally sensitive. So, while dolphin species and 
beaked whale species--both in the mid-frequency cetacean hearing 
group--are assumed to generally hear the same sounds equally well and 
be equally susceptible to noise-induced hearing loss (auditory injury), 
the best available information indicates that a beaked whale is more 
likely to behaviorally respond to that sound at a lower received level 
compared to an animal from other mid-frequency cetacean species that 
are less behaviorally sensitive. This distinction is important because, 
while beaked whales are more likely to respond behaviorally to sounds 
than are many other species (even at lower levels), they cannot hear 
the predominant, lower frequency sounds from seismic airguns as well as 
sounds that have more energy at frequencies that beaked whales can hear 
better (such as military MFA sonar).

[[Page 59223]]

    Navy MFA sonar affects beaked whales differently than airguns do 
because it produces energy at different frequencies than airguns. Mid-
frequency cetacean hearing is generically thought to be best between 
8.8 to 110 kHz, i.e., these cutoff values define the range above and 
below which a species in the group is assumed to have declining 
auditory sensitivity, until reaching frequencies that cannot be heard 
(NMFS, 2018). However, beaked whale hearing is likely best within a 
higher, narrower range (20-80 kHz, with best sensitivity around 40 
kHz), based on a few measurements of hearing in stranded beaked whales 
(Cook et al., 2006; Finneran et al., 2009; Pacini et al., 2011) and 
several studies of acoustic signals produced by beaked whales (e.g., 
Frantzis et al., 2002; Johnson et al., 2004, 2006; Zimmer et al., 
2005). While precaution requires that the full range of audibility be 
considered when assessing risks associated with noise exposure 
(Southall et al., 2007, 2019a, 2019), animals typically produce sound 
at frequencies where they hear best. More recently, Southall et al. 
(2019) suggested that certain species in the historical mid-frequency 
hearing group (beaked whales, sperm whales, and killer whales) are 
likely more sensitive to lower frequencies within the group's 
generalized hearing range than are other species within the group, and 
state that the data for beaked whales suggest sensitivity to 
approximately 5 kHz. However, this information is consistent with the 
general conclusion that beaked whales (and other mid-frequency 
cetaceans) are relatively insensitive to the frequencies where most 
energy of an airgun signal is found. Military MFA sonar is typically 
considered to operate in the frequency range of approximately 3-14 kHz 
(D'Amico et al., 2009), i.e., outside the range of likely best hearing 
for beaked whales but within or close to the lower bounds, whereas most 
energy in an airgun signal is radiated at much lower frequencies, below 
500 Hz (Dragoset, 1990).
    It is important to distinguish between energy (loudness, measured 
in dB) and frequency (pitch, measured in Hz). In considering the 
potential impacts of mid-frequency components of airgun noise (1-10 
kHz, where beaked whales can be expected to hear) on marine mammal 
hearing, one needs to account for the energy associated with these 
higher frequencies and determine what energy is truly ``significant.'' 
Although there is mid-frequency energy associated with airgun noise (as 
expected from a broadband source), airgun sound is predominantly below 
1 kHz (Breitzke et al., 2008; Tashmukhambetov et al., 2008; Tolstoy et 
al., 2009). As stated by Richardson et al. (1995), ``[. . .] most 
emitted [seismic airgun] energy is at 10-120 Hz, but the pulses contain 
some energy up to 500-1,000 Hz.'' Tolstoy et al. (2009) conducted 
empirical measurements, demonstrating that sound energy levels 
associated with airguns were at least 20 decibels (dB) lower at 1 kHz 
(considered ``mid-frequency'') compared to higher energy levels 
associated with lower frequencies (below 300 Hz) (``all but a small 
fraction of the total energy being concentrated in the 10-300 Hz 
range'' [Tolstoy et al., 2009]), and at higher frequencies (e.g., 2.6-4 
kHz), power might be less than 10 percent of the peak power at 10 Hz 
(Yoder, 2002). Energy levels measured by Tolstoy et al. (2009) were 
even lower at frequencies above 1 kHz. In addition, as sound propagates 
away from the source, it tends to lose higher-frequency components 
faster than low-frequency components (i.e., low-frequency sounds 
typically propagate longer distances than high-frequency sounds) 
(Diebold et al., 2010). Although higher-frequency components of airgun 
signals have been recorded, it is typically in surface-ducting 
conditions (e.g., DeRuiter et al., 2006; Madsen et al., 2006) or in 
shallow water, where there are advantageous propagation conditions for 
the higher frequency (but low-energy) components of the airgun signal 
(Hermannsen et al., 2015). This should not be of concern because the 
likely behavioral reactions of beaked whales that can result in acute 
physical injury would result from noise exposure at depth (because of 
the potentially greater consequences of severe behavioral reactions). 
In summary, the frequency content of airgun signals is such that beaked 
whales will not be able to hear the signals well (compared to MFA 
sonar), especially at depth where we expect the consequences of noise 
exposure could be more severe.
    Aside from frequency content, there are other significant 
differences between MFA sonar signals and the sounds produced by 
airguns that minimize the risk of severe behavioral reactions that 
could lead to strandings or deaths at sea, e.g., significantly longer 
signal duration, horizontal sound direction, typical fast and 
unpredictable source movement. All of these characteristics of MFA 
sonar tend towards greater potential to cause severe behavioral or 
physiological reactions in exposed beaked whales that may contribute to 
stranding. Although both sources are powerful, MFA sonar contains 
significantly greater energy in the mid-frequency range, where beaked 
whales hear better. Short-duration, high energy pulses--such as those 
produced by airguns--have greater potential to cause damage to auditory 
structures (though this is unlikely for mid-frequency cetaceans, as 
explained later in this document), but it is longer duration signals 
that have been implicated in the vast majority of beaked whale 
strandings. Faster, less predictable movements in combination with 
multiple source vessels are more likely to elicit a severe, potentially 
anti-predator response. Of additional interest in assessing the 
divergent characteristics of MFA sonar and airgun signals and their 
relative potential to cause stranding events or deaths at sea is the 
similarity between the MFA sonar signals and stereotyped calls of 
beaked whales' primary predator: the killer whale (Zimmer and Tyack, 
2007). Although generic disturbance stimuli--as airgun noise may be 
considered in this case for beaked whales--may also trigger 
antipredator responses, stronger responses should generally be expected 
when perceived risk is greater, as when the stimulus is confused for a 
known predator (Frid and Dill, 2002). In addition, because the source 
of the perceived predator (i.e., MFA sonar) will likely be closer to 
the whales (because attenuation limits the range of detection of mid-
frequencies) and moving faster (because it will be on faster-moving 
vessels), any antipredator response would be more likely to be severe 
(with greater perceived predation risk, an animal is more likely to 
disregard the cost of the response; Frid and Dill, 2002). Indeed, when 
analyzing movements of a beaked whale exposed to playback of killer 
whale predation calls, Allen et al. (2014) found that the whale engaged 
in a prolonged, directed avoidance response, suggesting a behavioral 
reaction that could pose a risk factor for stranding. Overall, these 
significant differences between sound from MFA sonar and the mid-
frequency sound component from airguns and the likelihood that MFA 
sonar signals will be interpreted in error as a predator are critical 
to understanding the likely risk of behaviorally-mediated injury due to 
seismic surveys.
    The available scientific literature also provides a useful contrast 
between airgun noise and MFA sonar regarding the likely risk of 
behaviorally-mediated injury. There is strong evidence for the 
association of beaked whale stranding events with MFA sonar use, and 
particularly detailed accounting of several events is available (e.g., 
a 2000 Bahamas stranding event for which

[[Page 59224]]

investigators concluded that MFA sonar use was responsible; Evans and 
England, 2001). D'Amico et al. (2009) reviewed 126 beaked whale mass 
stranding events over the period from 1950 (i.e., from the development 
of modern MFA sonar systems) through 2004. Of these, there were two 
events where detailed information was available on both the timing and 
location of the stranding and the concurrent nearby naval activity, 
including verification of active MFA sonar usage, with no evidence for 
an alternative cause of stranding. An additional ten events were at 
minimum spatially and temporally coincident with naval activity likely 
to have included MFA sonar use and, despite incomplete knowledge of 
timing and location of the stranding or the naval activity in some 
cases, there was no evidence for an alternative cause of stranding. The 
U.S. Navy has publicly stated agreement that five such events since 
1996 were associated in time and space with MFA sonar use, either by 
the U.S. Navy alone or in joint training exercises with the North 
Atlantic Treaty Organization. The U.S. Navy additionally noted that, as 
of 2017, a 2014 beaked whale stranding event in Crete coincident with 
naval exercises was under review and had not yet been determined to be 
linked to sonar activities (U.S. Navy, 2017). Separately, the 
International Council for the Exploration of the Sea reported in 2005 
that, worldwide, there have been about 50 known strandings, consisting 
mostly of beaked whales, with a potential causal link to MFA sonar 
(ICES, 2005). In contrast, very few such associations have been made to 
seismic surveys, despite widespread use of airguns as a geophysical 
sound source in numerous locations around the world.
    A more recent review of possible stranding associations with 
seismic surveys (Castellote and Llorens, 2016) states plainly that, 
``[s]peculation concerning possible links between seismic survey noise 
and cetacean strandings is available for a dozen events but without 
convincing causal evidence.'' The authors' ``exhaustive'' search of 
available information found ten events worth further investigation via 
a ranking system representing a rough metric of the relative level of 
confidence offered by the data for inferences about the possible role 
of the seismic survey in a given stranding event. Only three of these 
events involved beaked whales. Whereas D'Amico et al. (2009) used a 1-5 
ranking system, in which ``1'' represented the most robust evidence 
connecting the event to MFA sonar use, Castellote and Llorens (2016) 
used a 1-6 ranking system, in which ``6'' represented the most robust 
evidence connecting the event to the seismic survey. As described 
above, D'Amico et al. (2009) found that two events were ranked ``1'' 
and ten events were ranked ``2'' (i.e., 12 beaked whale stranding 
events were found to be associated with MFA sonar use). In contrast, 
Castellote and Llorens (2016) found that none of the three beaked whale 
stranding events achieved their highest ranks of 5 or 6. Of the ten 
total events, none achieved the highest rank of 6. Two events were 
ranked as 5: one stranding in Peru involving dolphins and porpoises and 
a 2008 stranding in Madagascar. This latter ranking can only broadly be 
associated with the survey itself, as opposed to use of seismic 
airguns. An exhaustive investigation of this stranding event, which did 
not involve beaked whales, concluded that use of a high-frequency 
mapping system (12-kHz multibeam echosounder) was the most plausible 
and likely initial behavioral trigger of the event, which was likely 
exacerbated by several site- and situation-specific secondary factors. 
The review panel found that seismic airguns were used after the initial 
strandings and animals entering a lagoon system, that airgun use 
clearly had no role as an initial trigger, and that there was no 
evidence that airgun use dissuaded animals from leaving (Southall et 
al., 2013).
    However, one of these stranding events, involving two Cuvier's 
beaked whales, was contemporaneous with and reasonably associated 
spatially with a 2002 seismic survey in the Gulf of California 
conducted by Lamont-Doherty Earth Observatory (L-DEO), as was the case 
for the 2007 Gulf of Cadiz seismic survey discussed by Castellote and 
Llorens (also involving two Cuvier's beaked whales). However, neither 
event was considered a ``true atypical mass stranding'' (according to 
Frantzis [1998]) as used in the analysis of Castellote and Llorens 
(2016). While we agree with the authors that this lack of evidence 
should not be considered conclusive, it is clear that there is very 
little evidence that seismic surveys should be considered as posing a 
significant risk of acute harm to beaked whales or other mid-frequency 
cetaceans. We have considered the potential for the proposed survey to 
result in marine mammal stranding and have concluded that, based on the 
best available information, stranding is not expected to occur.
    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 (approximately 1 second) and 
high-intensity sounds (greater than 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 
survey to result in marine mammal stranding and have concluded that, 
based on the best available information, stranding is not expected to 
occur.
    Entanglement--Entanglements occur when marine mammals become 
wrapped around cables, lines, nets, or other objects suspended in the 
water column. During seismic operations, numerous cables, lines, and 
other objects primarily associated with the airgun array and hydrophone 
streamers will be towed behind the Palmer near the water`s surface. No 
incidents of entanglement of marine mammals with seismic survey gear 
have been documented in over 54,000 kt (100,000 km) of previous NSF-
funded seismic surveys when observers were aboard (e.g., Smultea and 
Holst 2003; Haley and Koski 2004; Holst 2004; Smultea et al., 2004; 
Holst et al., 2005a; Haley and Ireland 2006; SIO and NSF 2006b; Hauser 
et al., 2008; Holst and Smultea 2008). Although entanglement with the 
streamer is theoretically possible, it has not been documented during 
tens of thousands of miles of NSF-sponsored seismic cruises or, to our 
knowledge, during hundreds of thousands of miles of industrial seismic 
cruises. There are a relative few deployed devices, and no interaction 
between marine mammals and any such device has been recorded during 
prior NSF surveys using the devices. There are no meaningful 
entanglement risks posed by the proposed survey, and entanglement risks 
are not discussed further in this document.

Anticipated Effects on Marine Mammal Habitat

    Physical Disturbance--Sources of seafloor disturbance related to 
geophysical surveys that may impact marine mammal habitat include 
placement of anchors, nodes, cables, sensors, or other equipment on or 
in the seafloor for various activities. Equipment deployed on the 
seafloor has

[[Page 59225]]

the potential to cause direct physical damage and could affect bottom-
associated fish resources.
    Placement of equipment, such as the heat flow probe in the 
seafloor, could damage areas of hard bottom where direct contact with 
the seafloor occurs and could crush epifauna (organisms that live on 
the seafloor or surface of other organisms). Damage to unknown or 
unseen hard bottom could occur, but because of the small area covered 
by most bottom-founded equipment and the patchy distribution of hard 
bottom habitat, contact with unknown hard bottom is expected to be rare 
and impacts minor. Seafloor disturbance in areas of soft bottom can 
cause loss of small patches of epifauna and infauna due to burial or 
crushing, and bottom-feeding fishes could be temporarily displaced from 
feeding areas. Overall, any effects of physical damage to habitat are 
expected to be minor and temporary.
    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.
    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, and behavioral 
responses such as flight or avoidance are the most likely effects. 
However, the reaction of fish to airguns depends on the physiological 
state of the fish, past exposures, motivation (e.g., feeding, spawning, 
migration), and other environmental factors. Several studies have 
demonstrated that airgun sounds might affect the distribution and 
behavior of some fishes, potentially impacting foraging opportunities 
or increasing energetic costs (e.g., Fewtrell and McCauley, 2012; 
Pearson et al., 1992; Skalski et al., 1992; Santulli et al., 1999; 
Paxton et al., 2017), though the bulk of studies indicate no or slight 
reaction to noise (e.g., Miller and Cripps, 2013; Dalen and Knutsen, 
1987; Pena et al., 2013; Chapman and Hawkins, 1969; Wardle et al., 
2001; Sara et al., 2007; Jorgenson and Gyselman, 2009; Blaxter et al., 
1981; Cott et al., 2012; Boeger et al., 2006), and that, most commonly, 
while there are likely to be impacts to fish as a result of noise from 
nearby airguns, such effects will be temporary. For example, 
investigators reported significant, short-term declines in commercial 
fishing catch rate of gadid fishes during and for up to five days after 
seismic survey operations, but the catch rate subsequently returned to 
normal (Engas et al., 1996; Engas and Lokkeborg, 2002). Other studies 
have reported similar findings (Hassel et al., 2004). Skalski et al., 
(1992) also found a reduction in catch rates--for rockfish (Sebastes 
spp.) in response to controlled airgun exposure--but suggested that the 
mechanism underlying the decline was not dispersal but rather decreased 
responsiveness to baited hooks associated with an alarm behavioral 
response. A companion study showed that alarm and startle responses 
were not sustained following the removal of the sound source (Pearson 
et al., 1992). Therefore, Skalski et al. (1992) suggested that the 
effects on fish abundance may be transitory, primarily occurring during 
the sound exposure itself. In some cases, effects on catch rates are 
variable within a study, which may be more broadly representative of 
temporary displacement of fish in response to airgun noise (i.e., catch 
rates may increase in some locations and decrease in others) than any 
long-term damage to the fish themselves (Streever et al., 2016).
    SPLs of sufficient strength have been known to cause injury to fish 
and fish mortality and, in some studies, fish auditory systems have 
been damaged by airgun noise (McCauley et al., 2003; Popper et al., 
2005; Song et al., 2008). However, in most fish species, hair cells in 
the ear continuously regenerate and loss of auditory function likely is 
restored when damaged cells are replaced with new cells. Halvorsen et 
al. (2012b. (2012) showed that a TTS of 4-6 dB was recoverable within 
24 hours for one species. Impacts would be most severe when the 
individual fish is close to the source and when the duration of 
exposure is long--both of which are conditions unlikely to occur for 
this survey that is necessarily transient in any given location and 
likely result in brief, infrequent noise exposure to prey species in 
any given area. For this survey, the sound source is constantly moving, 
and most fish would likely avoid the sound source prior to receiving 
sound of sufficient intensity to cause physiological or anatomical 
damage. In addition, ramp-up may allow certain fish species the 
opportunity to move further away from the sound source.
    A recent comprehensive review (Carroll et al., 2017) found that 
results are mixed as to the effects of airgun noise on the prey of 
marine mammals. While some studies suggest a change in prey 
distribution and/or a reduction in prey abundance following the use of 
seismic airguns, others suggest no effects or even positive effects in 
prey abundance. As one specific example, Paxton et al. (2017), which 
describes findings related to the effects of a 2014 seismic survey on a 
reef off of North Carolina, showed a 78 percent decrease in observed 
nighttime abundance for certain species. It is important to note that 
the evening hours during which the decline in fish habitat use was 
recorded (via video recording) occurred on the same day that the 
seismic survey passed, and no subsequent data is presented to support 
an inference that the response was long-lasting. Additionally, given 
that the finding is based on video images, the lack of recorded fish 
presence does not support a conclusion that the fish actually moved 
away from the site or suffered any serious impairment. In summary, this 
particular study corroborates prior studies indicating that a startle 
response or short-term displacement should be expected.
    Available data suggest that cephalopods are capable of sensing the 
particle motion of sounds and detect low frequencies up to 1-1.5 kHz, 
depending on the species, and so are likely to detect airgun noise 
(Kaifu et al., 2008; Hu et al., 2009; Mooney et al., 2010; Samson et 
al., 2014). Auditory injuries (lesions occurring on the statocyst 
sensory hair cells) have been reported upon controlled exposure to low-
frequency sounds, suggesting that cephalopods are particularly 
sensitive to low-frequency sound (Andre et al., 2011; Sole et al., 
2013). Behavioral responses, such as inking and jetting, have also been 
reported upon exposure to low-frequency sound (McCauley et al., 2000b; 
Samson et al., 2014). Similar to fish, however, the transient nature of

[[Page 59226]]

the survey leads to an expectation that effects will be largely limited 
to behavioral reactions and would occur as a result of brief, 
infrequent exposures.
    With regard to potential impacts on zooplankton, McCauley et al. 
(2017) found that exposure to airgun noise resulted in significant 
depletion for more than half the taxa present and that there were two 
to three times more dead zooplankton after airgun exposure compared 
with controls for all taxa, within 1 km of the airguns. However, the 
authors also stated that in order to have significant impacts on r-
selected species (i.e., those with high growth rates and that produce 
many offspring) such as plankton, the spatial or temporal scale of 
impact must be large in comparison with the ecosystem concerned, and it 
is possible that the findings reflect avoidance by zooplankton rather 
than mortality (McCauley et al., 2017). In addition, the results of 
this study are inconsistent with a large body of research that 
generally finds limited spatial and temporal impacts to zooplankton as 
a result of exposure to airgun noise (e.g., Dalen and Knutsen, 1987; 
Payne, 2004; Stanley et al., 2011). Most prior research on this topic, 
which has focused on relatively small spatial scales, has showed 
minimal effects (e.g., Kostyuchenko, 1973; Booman et al., 1996; 
S[aelig]tre and Ona, 1996; Pearson et al., 1994; Bolle et al., 2012).
    A modeling exercise was conducted as a follow-up to the McCauley et 
al. (2017) study (as recommended by McCauley et al.), in order to 
assess the potential for impacts on ocean ecosystem dynamics and 
zooplankton population dynamics (Richardson et al., 2017). Richardson 
et al. (2017) found that for copepods with a short life cycle in a 
high-energy environment, a full-scale airgun survey would impact 
copepod abundance up to three days following the end of the survey, 
suggesting that effects such as those found by McCauley et al. (2017) 
would not be expected to be detectable downstream of the survey areas, 
either spatially or temporally.
    Notably, a recently described study produced results inconsistent 
with those of McCauley et al. (2017). Researchers conducted a field and 
laboratory study to assess if exposure to airgun noise affects 
mortality, predator escape response, or gene expression of the copepod 
Calanus finmarchicus (Fields et al., 2019). Immediate mortality of 
copepods was significantly higher, relative to controls, at distances 
of 5 m or less from the airguns. Mortality one week after the airgun 
blast was significantly higher in the copepods placed 10 m from the 
airgun but was not significantly different from the controls at a 
distance of 20 m from the airgun. The increase in mortality, relative 
to controls, did not exceed 30 percent at any distance from the airgun. 
Moreover, the authors caution that even this higher mortality in the 
immediate vicinity of the airguns may be more pronounced than what 
would be observed in free-swimming animals due to increased flow speed 
of fluid inside bags containing the experimental animals. There were no 
sublethal effects on the escape performance or the sensory threshold 
needed to initiate an escape response at any of the distances from the 
airgun that were tested. Whereas McCauley et al. (2017) reported an SEL 
of 156 dB at a range of 509-658 m, with zooplankton mortality observed 
at that range, Fields et al. (2019) reported an SEL of 186 dB at a 
range of 25 m, with no reported mortality at that distance. Regardless, 
if we assume a worst-case likelihood of severe impacts to zooplankton 
within approximately 1 km of the acoustic source, the typically wide 
dispersal of survey vessels and brief time to regeneration of the 
potentially affected zooplankton populations does not lead us to expect 
any meaningful follow-on effects to the prey base for odontocete 
predators.
    A recent review article concluded that, while laboratory results 
provide scientific evidence for high-intensity and low-frequency sound-
induced physical trauma and other negative effects on some fish and 
invertebrates, the sound exposure scenarios in some cases are not 
realistic to those encountered by marine organisms during routine 
seismic operations (Carroll et al., 2017). The review finds that there 
has been no evidence of reduced catch or abundance following seismic 
activities for invertebrates, and that there is conflicting evidence 
for fish with catch observed to increase, decrease, or remain the same. 
Further, where there is evidence for decreased catch rates in response 
to airgun noise, these findings provide no information about the 
underlying biological cause of catch rate reduction (Carroll et al., 
2017).
    In summary, impacts of the specified activity on marine mammal prey 
species will likely be limited to behavioral responses, the majority of 
prey species will be capable of moving out of the area during the 
survey, a rapid return to normal recruitment, distribution, and 
behavior for prey species is anticipated, and, overall, impacts to prey 
species will be minor and temporary. Prey species exposed to sound 
might move away from the sound source, experience TTS, experience 
masking of biologically relevant sounds, or show no obvious direct 
effects. Mortality from decompression injuries is possible in close 
proximity to a sound, but only limited data on mortality in response to 
airgun noise exposure are available (Hawkins et al., 2014). The most 
likely impacts for most prey species in the survey area would be 
temporary avoidance of the area. The proposed survey would move through 
an area relatively quickly, limiting exposure to multiple impulsive 
sounds. In all cases, sound levels would return to ambient once the 
survey moves out of the area or ends and the noise source is shut down 
and, when exposure to sound ends, behavioral and/or physiological 
responses are expected to end relatively quickly (McCauley et al., 
2000b). 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. While the potential for 
disruption of spawning aggregations or schools of important prey 
species can be meaningful on a local scale, the mobile and temporary 
nature of this survey and the likelihood of temporary avoidance 
behavior suggest that impacts would be minor.
    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 (approximately 
25 days at sea) and would occur over a very small area relative to the 
area available as marine mammal habitat in the Ross Sea. 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,

[[Page 59227]]

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.
    Based on the information discussed herein, we conclude that impacts 
of the specified activity are not likely to have more than short-term 
adverse effects on any prey habitat or populations of prey species. 
Further, any impacts to marine mammal habitat are not expected to 
result in significant or long-term consequences for individual marine 
mammals, or to contribute to adverse impacts on 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).
    All proposed takes are by Level B harassment, involving temporary 
changes in behavior. No Level A harassment is expected or proposed for 
authorization. In the sections below, we describe methods to estimate 
the number of Level B harassment events. The main sources of 
distributional and numerical data used in deriving the estimates are 
summarized below.
    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) 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

    NMFS recommends the use of 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.
    The proposed activities include the use of continuous icebreaking 
and impulsive seismic sources and, and therefore the 120 and 160 dB re 
1 [mu]Pa (rms) are 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). The proposed activity includes the use of 
impulsive seismic and continuous non-impulsive 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.

[[Page 59228]]



                     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 [micro]Pa, and cumulative sound exposure level (LE)
  has a reference value of 1[micro]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 (e.g., 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.
    The proposed survey would entail the use of a 2-airgun array with a 
total discharge of 210 in\3\ at a tow depth of 1-4 m (with the worst-
case scenario of 4 m assumed for purposes of modeling). L-DEO model 
results are used to determine the 160 dBrms radius for the 
2-airgun array water depth ranging from 150-700 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 105 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, whereas the direct arrivals become weak and/or incoherent 
(see Figures 11, 12, and 16 in Appendix H of NSF-USGS 2011). 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 survey would acquire data with two 105-in\3\ guns at a 
tow depth of 1-4 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. 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).
    L-DEO's modeling methodology is described in greater detail in 
NSF's IHA application. The estimated distances to the Level B 
harassment isopleth for the

[[Page 59229]]

proposed airgun configuration are shown in Table 5.

 Table 5--Predicted Radial Distances From the RVIB Palmer Seismic Source
       to Isopleths Corresponding to Level B Harassment Threshold
------------------------------------------------------------------------
                                                             Predicted
                                                           distances (m)
          Airgun configuration              Water depth      to 160 dB
                                              (m) \a\     received sound
                                                               level
------------------------------------------------------------------------
Two 105-in\3\ GI guns...................          >1,000         726 \b\
                                               100-1,000       1,089 \c\
------------------------------------------------------------------------
\a\ No survey effort would occur in water >1000 m; the distance for this
  water depth is included for informational purposes only.
\b\ Distance is based on L-DEO model results.
\c\ Distance is based on L-DEO model results with a 1.5 x correction
  factor between deep and intermediate water depths.

    Table 6 presents the modeled PTS isopleths for each marine mammal 
hearing group based on the L-DEO modeling incorporated in the companion 
User Spreadsheet (NMFS 2018).

          Table 6--Modeled Radial Distances to Isopleths Corresponding to Level A Harassment Thresholds
----------------------------------------------------------------------------------------------------------------
                                                  SEL cumulative  SEL cumulative      Pk PTS          Pk PTS
                  Hearing group                    PTS threshold   PTS distance   threshold (dB)   distance (m)
                                                     (dB) \1\         (m) \1\           \1\             \1\
----------------------------------------------------------------------------------------------------------------
Low-frequency cetaceans.........................             183            25.4             219            6.69
Mid-frequency cetaceans.........................             185             0.0             230            1.50
High-frequency cetaceans........................             155             0.0             202           47.02
Phocid pinnipeds................................             185             0.3             218            7.53
Otariid pinnpeds................................             203             0.0             232            0.92
----------------------------------------------------------------------------------------------------------------
\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).

    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 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.
    The Level B harassment estimates are based on a consideration of 
the number of marine mammals that could be within the area around the 
operating airgun array where received levels of sound >=160 dB re 1 
[micro]Parms are predicted to occur (see Table 1). The estimated 
numbers are based on the densities (numbers per unit area) of marine 
mammals expected to occur in the area in the absence of seismic 
surveys. To the extent that marine mammals tend to move away from 
seismic sources before the sound level reaches the criterion level and 
tend not to approach an operating airgun array, these estimates likely 
overestimate the

[[Page 59230]]

numbers actually exposed to the specified level of sound.

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, NSF provided density data for marine 
mammal species that might be encountered in the project area. NMFS 
concurred that these data are the best available. Sightings data from 
the 2002-2003 (IWC-SOWER) Circumpolar Cruise, Area V (Ensor et al. 
2003) were used to estimate densities for four mysticete (i.e., 
humpback whale, Antarctic minke whale, fin whale, and blue whale) and 
six odontocete species (i.e., sperm whale, southern bottlenose whale, 
strap-toothed beaked whale, killer whale, long-finned pilot whale and 
hourglass dolphin). Densities for sei and Arnoux's beaked whales were 
based on those reported in the Naval Marine Species Density Database 
(NMSDD) (Department of Navy 2012). NMFS finds NMSDD a reasonable 
representation of the lower likelihood of encountering these species, 
as evidenced by previous monitoring reports from projects in the same 
or similar area (85 FR 5619; January 31, 2020 & 0648-XD705;January 29, 
2015) and primary literature on whale species density distribution in 
the Antarctic (Cetacean Population Studies Vol.2, 2020). Densities of 
pinnipeds were estimated using best available data (Waterhouse 2001; 
Pinkerton and Bradford-Grieve 2010) and dividing the estimated 
population of pinnipeds (number of animals) by the area of the Ross Sea 
(300,000 km\2\). Estimated densities used and Level B harassment 
ensonified areas to inform take estimates are presented in Table 7.

      Table 7--Marine Mammal Densities and Total Ensonified Area of Activities in the Proposed Survey Area
----------------------------------------------------------------------------------------------------------------
                                                                     Ross bank       Drygalski      Icebreaking
                                                     Estimated        level B      tough level B      level B
                     Species                        density (#/     ensonified      ensonified      ensonified
                                                      km\2\)       area (km\2\)    area (km\2\)    area (km\2\)
----------------------------------------------------------------------------------------------------------------
Fin whale.......................................       0.0306570  ..............  ..............  ..............
Blue whale......................................       0.0065132  ..............  ..............  ..............
Sei whale.......................................       0.0046340  ..............  ..............  ..............
Antarctic minke whale...........................       0.0845595  ..............  ..............  ..............
Humpback whale..................................       0.0321169  ..............  ..............  ..............
Sperm whale.....................................       0.0098821  ..............  ..............  ..............
Southern bottlenose whale.......................       0.0117912  ..............  ..............  ..............
Arnoux's beaked whale...........................       0.0134420  ..............  ..............  ..............
Strap-toothed beaked whale......................       0.0044919           5,272           4,942           8,278
Killer whale....................................       0.0208872  ..............  ..............  ..............
Long-finned pilot whale.........................       0.0399777  ..............  ..............  ..............
Hourglass dolphin...............................       0.0189782  ..............  ..............  ..............
Crabeater seal..................................       0.6800000  ..............  ..............  ..............
Leopard seal....................................       0.0266700  ..............  ..............  ..............
Ross seal.......................................       0.0166700  ..............  ..............  ..............
Weddell seal....................................       0.1066700  ..............  ..............  ..............
Southern elephant seal..........................       0.0001300  ..............  ..............  ..............
----------------------------------------------------------------------------------------------------------------

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 B harassment, the 
radial distance from the airgun array to the predicted isopleth 
corresponding to the Level B harassment threshold is calculated, as 
described above. The radial distance is then used to calculate the area 
around the airgun array predicted to be ensonified to the sound level 
that exceed the Level B harassment threshold. The area estimated to be 
ensonified in a single day of the survey is then calculated (Table 8), 
based on the area predicted to be ensonified around the array and the 
estimated trackline distance traveled per day. The daily ensonified 
area was then multiplied by the number of estimated seismic acquisition 
days -9.6 days for the Ross Bay survey and 9 days for the Drygalski 
Trough survey. The product is then multiplied by 1.25 to account for 
the additional 25 percent contingency, as described above. This results 
in an estimate of the total area (km\2\) expected to be ensonified to 
the Level B harassment threshold.

                                       Table 8--Area (km\2\) To Be Ensonified to the Level B Harassment Threshold
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                               Daily
                                                           Distance/day      Threshold      ensonified       Number of       Plus 25%          Total
                       Survey area                             (km)        distance (km)     area with      survey days    (contingency)    ensonified
                                                                                          endcap (km\2\)                                   area (km\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Ross Bank...............................................             200           1.089             439             9.6              12           5,272
Drygaiski Trough........................................             200           1.089             439               9           11.25           4,942
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Based on the small Level A harassment isopleths (as shown in Table 
6) and in consideration of the proposed mitigation measures (see 
Proposed Mitigation section below), take by Level A harassment is not 
expected to occur and is not proposed for authorization.

[[Page 59231]]

    The marine mammals predicted to occur within the respective areas, 
based on estimated densities (Table 7), are assumed to be incidentally 
taken. Estimated take, and percentages of the stocks estimated to be 
taken, for the proposed survey are shown in Table 10.
Icebreaking
    Applying the maximum estimated amount of icebreaking expected by 
NSF, i.e., 500 km, we calculate the total ensonified area of 
icebreaking (Table 9). Estimates of exposures assume that there would 
be approximately 2 days of icebreaking activities; the calculated takes 
have been increased by 25 percent (2.75 days).

                                                   Table 9--Ensonified Area for Icebreaking Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                           Daily
                                                      Distance/day      Threshold     ensonified area     Number of         Plus 25%          Total
                     Criteria                             (km)        distance (km)     with endcap      survey days     (contingency)   ensonified area
                                                                                          (km\2\)                                            (km\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
120 dB............................................             223            6,456            3,010              2.2             2.75            8,278
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Estimated take from icebreaking for the proposed survey are shown 
in Table 10. As most cetaceans do not occur in pack ice, the estimates 
of the numbers of marine mammals potentially exposed to sounds greater 
than the Level B harassment threshold (120 dB re 1 [mu]Pa rms) are 
precautionary and probably overestimate the actual numbers of marine 
mammals that could be involved. No takes by Level A harassment are 
expected or proposed for authorization. The estimated number of takes 
for pinnipeds accounts for both seals that may be in the water and 
those hauled out on ice surfaces. Few cetaceans are expected to be seen 
during icebreaking activities, although some could occur along the ice 
margin.

              Table 10--Total Marine Mammal Take Estimated for the Proposed Survey in the Ross Sea
----------------------------------------------------------------------------------------------------------------
                                           Level B take             Total take
             Species             --------------------------------  proposed for     Population      Percent of
                                    All seismic     Icebreaking    authorization     abundance      population
----------------------------------------------------------------------------------------------------------------
Fin whale.......................             313             254             567          38,200            1.48
Blue whale......................              67              54             120           1,700            7.09
Sei whale.......................              47              38              86          10,000            0.86
Antarctic minke whale...........             864             700           1,564         515,000             0.3
Humpback whale..................             328             266             594          42,000            1.41
Sperm whale.....................             101              82             183          12,069            1.51
Southern bottlenose whale.......             120              98             218         599,300            0.04
Arnoux's beaked whale...........             137             111             249         599,300            0.04
Strap-toothed beaked whale......              46              37              83         599,300            0.01
Killer whale....................             213             173             386          25,000            1.55
Long-finned pilot whale.........             408             331             739         200,000            0.37
Hourglass dolphin...............             194             157             351         144,300            0.24
Crabeater seal..................           6,946           5,629          12,575       1,700,000               1
Leopard seal....................             272             221             493         220,000            0.22
Ross seal.......................             170             138             308         250,000            0.12
Weddell seal....................           1,090             883           1,973       1,000,000             0.2
Southern elephant seal..........               2               1               3         750,000           <0.01
----------------------------------------------------------------------------------------------------------------

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 measures that would be adopted during the planned survey 
include, but are not limited to: (1)

[[Page 59232]]

Vessel speed or course alteration, provided that doing so would not 
compromise operation safety requirements. (2) GI-airgun shut down 
within exclusion zones (EZ)s, and (3) ramp-up procedures.

Vessel-Visual Based 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. The area to 
be scanned visually includes primarily the exclusion zone, within which 
observation of certain marine mammals requires shutdown of the acoustic 
source, but also the buffer zone. The buffer zone means an area beyond 
the exclusion zone to be monitored for the presence of marine mammals 
that may enter the exclusion zone. During pre-start clearance (i.e., 
before ramp-up begins), the buffer zone also acts as an extension of 
the exclusion zone in that observations of marine mammals within the 
buffer zone would also prevent airgun operations from beginning (i.e., 
ramp-up). The buffer zone encompasses the area at and below the sea 
surface from the edge of the 100 m exclusion zone measured from the 
edges of the airgun array. Visual monitoring of the exclusion zone and 
adjacent waters is intended to establish and, when visual conditions 
allow, maintain zones around the sound source that are clear of marine 
mammals, thereby reducing or eliminating the potential for injury and 
minimizing the potential for more severe behavioral reactions for 
animals occurring closer to the vessel. Visual monitoring of the buffer 
zone is intended to (1) provide additional protection to na[iuml]ve 
marine mammals that may be in the area during pre-clearance, and (2) 
during airgun use, aid in establishing and maintaining the exclusion 
zone by altering the visual observer and crew of marine mammals that 
are outside of, but may approach and enter, the exclusion zone.
    NSF must use independent, dedicated, trained visual PSOs, meaning 
that the PSOs must be employed by a third-party observer provider, must 
not have tasks other than to conduct observational effort, collect 
data, and communicate with and instruct relevant vessel crew with 
regard to the presence of protected species and mitigation 
requirements, and must have successfully completed an approved PSO 
training course. PSO resumes shall be provided to NMFS for approval.
    At least one visual PSO must have a minimum of 90 days at-sea 
experience working in that role during a shallow penetration or low-
energy survey, with no more than 18 months elapsed since the conclusion 
of the at-sea experience. One PSO with such experience shall be 
designated as the lead for the entire protected species observation 
team. The lead PSO shall serve as primary point of contact for the 
vessel operator and ensure all PSO requirements per the IHA are met. To 
the maximum extent practicable, the experienced PSOs should be 
scheduled to be on duty with those PSOs with the appropriate training 
but who have not yet gained relevant experience.
    During survey operations (e.g., any day on which use of the 
acoustic source is planned to occur, and whenever the acoustic source 
is in the water, whether activated or not), a minimum of two PSOs must 
be on duty and conducting visual observations at all times during 
daylight hours (i.e., from 30 minutes prior to sunrise through 30 
minutes following sunset) and 30 minutes prior to and during ramp-up of 
the airgun array. Visual monitoring of the exclusion and buffer zones 
must begin no less than 30 minutes prior to ramp-up and must continue 
until one hour after use of the acoustic source ceases or until 30 
minutes past sunset. Visual PSOs must coordinate to ensure 360 degree 
visual coverage around the vessel from the most appropriate observation 
posts, and must conduct visual observations using binoculars and the 
naked eye while free from distractions and in a consistent, systematic, 
and diligent manner.
    PSOs shall establish and monitor the exclusion and buffer zones. 
These zones shall be based upon the radial distance from the edges of 
the acoustic source (rather than being based on the center of the array 
or around the vessel itself). During use of the acoustic source (i.e., 
anytime airguns are active, including ramp-up) shall be communicated to 
the operator to prepare for the potential shutdown of the acoustic 
source.
    During use of the airgun, detections of marine mammals within the 
buffer zone (but outside the exclusion zone) should be communicated to 
the operator to prepare for the potential shutdown of the acoustic 
source. Visual PSOs will immediately communicate all observations to 
the on duty acoustic PSO(s), including any determination by the PSO 
regarding species identification, distance, and bearing and the degree 
of confidence in the determination. Any observations of marine mammals 
by crew members shall be relayed to the PSO team. During good 
conditions (e.g., daylight hours; Beaufort sea state (BSS) 3 or less), 
visual PSOs shall conduct observations when the acoustic source is not 
operating for comparison of sightings rates and behavior with and 
without use of the acoustic source and between acquisition periods, to 
the maximum extent practicable.
    Visual PSOs may be on watch for a maximum of four consecutive hours 
followed by a break of at least one hour between watches and may 
conduct a maximum of 12 hours of observation per 24-hour period.

Exclusion Zone and Buffer Zone

    An exclusion zone (EZ) is a defined area within which occurrence of 
a marine mammal triggers mitigation action intended to reduce the 
potential for certain outcome, e.g., auditory injury, disruption of 
critical behaviors. The PSOs would establish a minimum EZ with a 100 m 
radius with an additional 100 m buffer zone (total of 200 m). The 200m 
zone would be based on radial distance from the edge 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 or enters this zone, the acoustic source would be 
shut down.
    The 100 m EZ, with additional 100 m buffer zone, is intended to be 
precautionary in the sense that it would be expected to contain sound 
exceeding the injury criteria for all cetacean hearing groups, (based 
on the dual criteria of SELcum and peak SPL), while also 
providing a consistent, reasonably observable zone within which PSOs 
would typically be able to conduct effective observational effort. 
Additionally, a 100 m EZ is expected to minimize the likelihood that 
marine mammals will be exposed to levels likely to result in more 
severe behavioral responses. Although significantly greater distances 
may be observed from an elevated platform under good conditions, we 
believe that 100 m is regularly attainable for PSOs using the naked eye 
during typical conditions.
    An extended 500 m exclusion zone must be established for beaked 
whales, large whales with a calf, and an aggregation of whales during 
all survey effort. No buffer zone is required.

Pre-Clearance and Ramp-Up

    Ramp-up (sometimes referred to as ``soft start'') is the gradual 
and systematic increase of emitted sound levels from an airgun array. 
Ramp-up would begin with one GI airgun 45 cu in first being activated, 
followed by the second after 5 minutes. The intent of pre-clearance 
observation (30 minutes)

[[Page 59233]]

is to ensure no marine mammals are observed within the buffer zone 
prior to the beginning of ramp-up. During pre-clearance is the only 
time observations of marine mammals in the buffer zone would prevent 
operations (i.e., the beginning of ramp-up). The intent of ramp-up is 
to warn protected species of pending seismic operations and to allow 
sufficient time for those animals to leave the immediate vicinity. A 
ramp-up procedure, involving a stepwise increase in the number of 
airguns are activated and the full volume is achieve, is required at 
all times as part of the activation of the acoustic source. All 
operators must adhere to the following pre-clearance and ramp-up 
requirements:
    (1) The operator must 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 in 
order to allow PSOs time to monitor the exclusion and buffer zones for 
30 minutes prior to the initiation of ramp-up (pre-clearance);
     Ramp-ups shall be scheduled so as to minimize the time 
spent with the source activated prior to reaching the designated run-
in;
     One of the PSOs conducting pre-clearance observations must 
be notified again immediately prior to initiating ramp-up procedures 
and the operator must receive confirmation from the PSO to proceed;
     Ramp-up may not be initiated if any marine mammal is 
within the applicable exclusion or buffer zone. If a marine mammal is 
observed within the applicable exclusion zone or the buffer zone during 
the 30 minutes pre-clearance period, ramp-up may not begin until the 
animal(s) has been observed exiting the zones or until an additional 
time period has elapsed with no further sightings (15 minutes for small 
odontocetes and pinnipeds, and 30 minutes for Mysticetes and all other 
odontocetes, including sperm whales and beaked whales);
     PSOs must monitor the exclusion and buffer zones during 
ramp-up, and ramp-up must cease and the source must be shut down upon 
detection of a marine mammal within the applicable exclusion zone. Once 
ramp-up has begun, detections of marine mammals within the buffer zone 
do not require shutdown, but such observation shall be communicated to 
the operator to prepare for the potential shutdown.
    (2) If the acoustic source is shut down for brief periods (i.e., 
less than 30 minutes) for reasons other than that described for 
shutdown (e.g., mechanical difficulty), it may be activated again 
without ramp-up if PSOs have maintained constant observation and no 
detections of marine mammals have occurred within the applicable 
exclusion zone. For any longer shutdown, pre-start clearance 
observation and ramp-up are required. For any shutdown at night or in 
periods of poor visibility (e.g., BSS 4 or greater), ramp-up is 
required, but if the shutdown period was brief and constant observation 
was maintained, pre-start clearance watch is not required.
     Testing of the acoustic source involving all elements 
requires ramp-up. Testing limited to individual source elements or 
strings does not require ramp-up but does require pre-start clearance 
watch.

Shutdown Procedures

    The shutdown of an airgun array requires the immediate de-
activation of all individual airgun elements of the array. Any PSO on 
duty will have the authority to delay the start of survey operations or 
to call for shutdown of the acoustic source if a marine mammal is 
detected within the applicable exclusion zone. The operator must also 
establish and maintain clear lines of communication directly between 
PSOs on duty and crew controlling the acoustic source to ensure that 
shutdown commands are conveyed swiftly while allowing PSOs to maintain 
watch. When both visual and acoustic PSOs are on duty, all detections 
will be immediately communicated to the remainder of the on-duty PSO 
team for potential verification of visual observations by the acoustic 
PSO or of acoustic detections by visual PSOs. When the airgun array is 
active (i.e., anytime one or more airguns is active, including during 
ramp-up) and (1) a marine mammal appears within or enters the 
applicable exclusion zone and/or (2) a marine mammal (other than 
delphinids, see below) is detected acoustically and localized within 
the applicable exclusion zone, the acoustic source will be shut down. 
When shutdown is called for by a PSO, the acoustic source will be 
immediately deactivated and any dispute resolved only following 
deactivation.
    Following a shutdown, airgun activity would not resume until the 
marine mammal has cleared the EZ. The animal would be considered to 
have cleared the EZ if it is visually observed to have departed the EZ, 
or it has not been seen within the EZ for 15 minutes in the case of 
small odontocetes and pinnipeds, and 30 minutes for Mysticetes and all 
other odontocetes, including sperm and beaked whales, with no further 
observation of the marine mammal(s).
    Upon implementation of shutdown, the source may be reactivated 
after the marine mammal(s) has been observed exiting the applicable 
exclusion zone (i.e., animal is not required to fully exit the buffer 
zone where applicable) or following a clearance period (15 minutes for 
small odontocetes and pinnipeds, and 30 minutes for mysticetes and all 
other odontocetes, including sperm whales, beaked whales, pilot whales, 
killer whales, and Risso's dolphin) with no further observation of the 
marine mammal(s).
    NSF must implement shutdown if a marine mammal species for which 
take was not authorized, or a species for which authorization was 
granted but the takes have been met, approaches the Level B harassment 
zones.

Vessel Strike Avoidance Measures

    These measures apply to all vessels associated with the planned 
survey activity; however, we note that these 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. These measures include the following:
    (1) Vessel operators and crews must maintain a vigilant watch for 
all marine mammals and slow down, stop their vessel, or alter course, 
as appropriate and regardless of vessel size, to avoid striking any 
marine mammal. A single marine mammal at the surface may indicate the 
presence of submerged animals in the vicinity of the vessel; therefore, 
precautionary measures should be exercised when an animal is observed. 
A visual observer aboard the vessel must monitor a vessel strike 
avoidance zone around the vessel (specific distances detailed below), 
to ensure the potential for strike is minimized. Visual observers 
monitoring the vessel strike avoidance zone can be either third-party 
observers or crew members, but crew members responsible for these 
duties must be provided sufficient training to distinguish marine 
mammals from other phenomena and broadly to identify a marine mammal to 
broad taxonomic group (i.e., as a large whale or other marine mammal);
    (2) Vessel speeds must be reduced to 10 kn or less when mother/calf 
pairs, pods, or large assemblages of any marine mammal are observed 
near a vessel;
    (3) All vessels must maintain a minimum separation distance of 100 
m from large whales (i.e., sperm whales and all mysticetes);

[[Page 59234]]

    (4) All vessels must attempt to maintain a minimum separation 
distance of 50 m from all other marine mammals, with an exception made 
for those animals that approach the vessel; and
    (5) When marine mammals are sighted while a vessel is underway, the 
vessel should take action as necessary to avoid violating the relevant 
separation distance (e.g., attempt to remain parallel to the animal's 
course, avoid excessive speed or abrupt changes in direction until the 
animal has left the area). If marine mammals are sighted within the 
relevant separation distance, the vessel should reduce speed and shift 
the engine to neutral, not engaging the engines until animals are clear 
of the area. This recommendation does not apply to any vessel towing 
gear.
    Based on our evaluation of the applicant's proposed measures, NMFS 
has preliminarily determined that the proposed mitigation measures 
provide the means of 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:
    (1) Occurrence of marine mammal species or stocks in the area in 
which take is anticipated (e.g., presence, abundance, distribution, 
density).
    (2) 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).
    (3) Individual marine mammal responses (behavioral or 
physiological) to acoustic stressors (acute, chronic, or cumulative), 
other stressors, or cumulative impacts from multiple stressors.
    (4) How anticipated responses to stressors impact either: (1) long-
term fitness and survival of individual marine mammals; or (2) 
populations, species, or stocks.
    (5) Effects on marine mammal habitat (e.g., marine mammal prey 
species, acoustic habitat, or other important physical components of 
marine mammal habitat).
    (6) Mitigation and monitoring effectiveness.

Vessel-Based Visual Monitoring

    As described above, PSO observations would take place during 
daytime airgun operations. During seismic operations, at least three 
visual PSO would be based aboard the Palmer, with a minimum of one on 
duty at all times during daylight hours. NMFS' typical requirements for 
surveys of this type include a minimum of two PSOs on duty at all times 
during daylight hours. However, NSF stated in communications with NMFS 
that the requirement is not practicable in this circumstance due to the 
remote location of the proposed survey and associated logistical 
issues, including limited capacity to fly PSOs into and out of McMurdo 
Station in Antarctica and limited berth space on the Palmer, and 
requested an exception to the requirement. NMFS agrees that, in this 
circumstance, the requirement to have a minimum of two PSOs on duty 
during all daylight hours would be impracticable and, therefore, 
proposes that a minimum of one PSO be on duty. NSF must employ two PSOs 
on duty during all daylight hours to the maximum extent practicable. 
NSF Monitoring shall be conducted in accordance with the following 
requirements:
    (1) PSOs shall be independent, dedicated and trained and must be 
employed by a third-party observer provider;
    (2) PSOs shall have no tasks other than to conduct visual 
observational effort, collect data, and communicate with and instruct 
relevant vessel crew with regard to the presence of protected species 
and mitigation requirements (including brief alerts regarding maritime 
hazards);
    (3) PSOs shall have successfully completed an approved PSO training 
course appropriate for their designated task (visual or acoustic);
    (4) NMFS must review and approve PSO resumes accompanied by a 
relevant training course information packet that includes the name and 
qualifications (i.e., experience, training completed, or educational 
background) of the instructor(s), the course outline or syllabus, and 
course reference material as well as a document stating successful 
completion of the course;
    (5) NMFS shall have one week to approve PSOs from the time that the 
necessary information is submitted, after which PSOs meeting the 
minimum requirements shall automatically be considered approved;
    (6) PSOs must successfully complete relevant training, including 
completion of all required coursework and passing (80 percent or 
greater) a written and/or oral examination developed for the training 
program;
    (7) PSOs must have successfully attained a bachelor's degree from 
an accredited college or university with a major in one of the natural 
sciences, a minimum of 30 semester hours or equivalent in the 
biological sciences, and at least one undergraduate course in math or 
statistics; and
    (8) The educational requirements may be waived if the PSO has 
acquired the relevant skills through alternate experience. Requests for 
such a waiver shall be submitted to NMFS and must include written 
justification. Requests shall be granted or denied (with justification) 
by NMFS within one week of receipt of submitted information. Alternate 
experience that may be considered includes, but is not limited to
     secondary education and/or experience comparable to PSO 
duties;
     previous work experience conducting academic, commercial, 
or government-sponsored protected species surveys; or
     previous work experience as a PSO; the PSO should 
demonstrate good standing and consistently good performance of PSO 
duties.
    PSOs must use standardized data collection forms, whether hard copy 
or electronic. PSOs must record detailed information about any 
implementation of mitigation requirements, including the distance of 
animals to the acoustic source and description of specific actions that 
ensued, the behavior of the animal(s), any observed changes in behavior 
before and after implementation of mitigation, and if shutdown was 
implemented, the length of time before any subsequent ramp-up

[[Page 59235]]

of the acoustic source. If required mitigation was not implemented, 
PSOs should record a description of the circumstances. At a minimum, 
the following information must be recorded:
     Vessel name and call sign;
     PSO names and affiliations;
     Date and participants of PSO briefings (as discussed in 
General Requirement);
     Dates of departure and return to port with port name;
     Dates and times (Greenwich Mean Time) of survey effort and 
times corresponding with PSO effort;
     Vessel location (latitude/longitude) when survey effort 
began and ended and vessel location at beginning and end of visual PSO 
duty shifts;
     Vessel heading and speed at beginning and end of visual 
PSO duty shifts and upon any line change;
     Environmental conditions while on visual survey (at 
beginning and end of PSO shift and whenever conditions changed 
significantly), including BSS and any other relevant weather conditions 
including cloud cover, fog, sun glare, and overall visibility to the 
horizon;
     Factors that may have contributed to impaired observations 
during each PSO shift change or as needed as environmental conditions 
changed (e.g., vessel traffic, equipment malfunctions); and
     Survey activity information, such as acoustic source power 
output while in operation, number and volume of airguns operating in 
the array, tow depth of the array, and any other notes of significance 
(i.e., pre-start clearance, ramp-up, shutdown, testing, shooting, ramp-
up completion, end of operations, streamers, etc.).
    The following information should be recorded upon visual 
observation of any marine mammal:
     Watch status (sighting made by PSO on/off effort, 
opportunistic, crew, alternate vessel/platform);
     PSO who sighted the animal;
     Time of sighting;
     Vessel location at time of sighting;
     Water depth;
     Direction of vessel's travel (compass direction);
     Direction of animal's travel relative to the vessel;
     Pace of the animal;
     Estimated distance to the animal and its heading relative 
to vessel at initial sighting;
     Identification of the animal (e.g., genus/species, lowest 
possible taxonomic level, or unidentified) and the composition of the 
group if there is a mix of species;
     Estimated number of animals (high/low/best);
     Estimated number of animals by cohort (adults, yearlings, 
juveniles, calves, group composition, etc.);
     Description (as many distinguishing features as possible 
of each individual seen, including length, shape, color, pattern, scars 
or markings, shape and size of dorsal fin, shape of head, and blow 
characteristics);
     Detailed behavior observations (e.g., number of blows/
breaths, number of surfaces, breaching, spyhopping, diving, feeding, 
traveling; as explicit and detailed as possible; note any observed 
changes in behavior);
     Animal's closest point of approach (CPA) and/or closest 
distance from any element of the acoustic source;
     Platform activity at time of sighting (e.g., deploying, 
recovering, testing, shooting, data acquisition, other); and
     Description of any actions implemented in response to the 
sighting (e.g., delays, shutdown, ramp-up) and time and location of the 
action.

Reporting

    NSF must submit a draft comprehensive report to NMFS on all 
activities and monitoring results within 90 days of the completion of 
the survey or expiration of the IHA, whichever comes sooner. A final 
report must be submitted within 30 days following resolution of any 
comments on the draft report. 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. The 90-day 
report 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 and 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). Geographic Information System (GIS) files shall be provided in 
Environmental Systems Research Institute (ESRI) shapefile format and 
include the Coordinated Universal Time (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 report must summarize the information submitted 
in interim monthly reports as well as additional data collected as 
described above and in the IHA. A final report must be submitted within 
30 days following resolution of any comments on the draft report.

Reporting Injured or Dead Marine Mammals

    Discovery of injured or dead marine mammals--In the event that 
personnel involved in survey activities covered by the authorization 
discover an injured or dead marine mammal, the NSF shall report the 
incident to the Office of Protected Resources (OPR), NMFS as soon as 
feasible. The report must include the following information:
     Time, date, and location (latitude/longitude) of the first 
discovery (and updated location information if known and applicable);
     Species identification (if known) or description of the 
animal(s) involved;
     Condition of the animal(s) (including carcass condition if 
the animal is dead);
     Observed behaviors of the animal(s), if alive;
     If available, photographs or video footage of the 
animal(s); and
     General circumstances under which the animal was 
discovered.
    Vessel strike--In the event of a ship strike of a marine mammal by 
any vessel involved in the activities covered by the authorization, L-
DEO shall report the incident to Office of Protected Resources (OPR), 
NMFS and to the NMFS West Coast Regional Stranding Coordinator as soon 
as feasible. The report must include the following information:
     Time, date, and location (latitude/longitude) of the 
incident;
     Vessel's speed during and leading up to the incident;
     Vessel's course/heading and what operations were being 
conducted (if applicable);
     Status of all sound sources in use;
     Description of avoidance measures/requirements that were 
in place at the time of the strike and what additional measure were 
taken, if any, to avoid strike;
     Environmental conditions (e.g., wind speed and direction, 
Beaufort sea

[[Page 59236]]

state, cloud cover, visibility) immediately preceding the strike;
     Species identification (if known) or description of the 
animal(s) involved;
     Estimated size and length of the animal that was struck;
     Description of the behavior of the animal immediately 
preceding and following the strike;
     If available, description of the presence and behavior of 
any other marine mammals present immediately preceding the strike;
     Estimated fate of the animal (e.g., dead, injured but 
alive, injured and moving, blood or tissue observed in the water, 
status unknown, disappeared); and To the extent practicable, 
photographs or video footage of the animal(s).

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, the discussion of our analysis applies to all 
the species listed in Table 2 given that the anticipated effects of 
this activity on these different marine mammal stocks are expected to 
be similar, except where a species- or stock-specific discussion is 
warranted. NMFS does not anticipate that serious injury or mortality 
would occur as a result from low-energy survey, even in the absence of 
mitigation, and no serious injury or mortality is proposed to be 
authorized. As discussed in the Potential Effects of Specified 
Activities on Marine Mammals and their Habitat section, non-auditory 
physical effects and vessel strike are not expected to occur. NMFS 
expects that all potential take would be in the form of Level B 
behavioral harassment in the form of temporary avoidance of the area or 
decreased foraging (if such activity was occurring), responses that are 
considered to be of low severity, and with no lasting biological 
consequences (e.g., Southall et al., 2007, 2021). These low-level 
impacts of behavioral harassment are not likely to impact the overall 
fitness of any individual or lead to population level effects of any 
species. As described above, Level A harassment is not expected to 
occur given the estimated small size of the Level A harassment zones.
    In addition to being temporary, the maximum expected Level B 
harassment zone around the survey vessel is 1,089 m (and as much a 
6,456 m for icebreaking activities). Therefore, the ensonified area 
surrounding the vessel is relatively small compared to the overall 
distribution of animals in the area and their use of the habitat. 
Feeding behavior is not likely to be significantly impacted as prey 
species are mobile and are broadly distributed throughout the survey 
area; therefore, 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 short duration (19 days) and temporary 
nature of the disturbance and the availability of similar habitat and 
resources in the surrounding area, 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.
    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 serious injury or 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 EZ 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 RVIB 
Palmer's approach due to the vessel's relatively low speed when 
conducting seismic survey. 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, 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 Description of Marine Mammals in the Area 
of Specified Activities section, marine mammals in the survey area are 
not assigned to NMFS stocks. Therefore, we rely on the best available 
information on the abundance estimates for the species of marine 
mammals that could be taken.

[[Page 59237]]

The activity is expected to impact a very small percentage of all 
marine mammal populations that would be affected by NSF's proposed 
survey (approximately three percent or less 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 (19 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 observers, and by minimizing the 
severity of any potential exposures via ramp-ups and shutdowns of the 
airgun array.
    Of the marine mammal species that are likely to occur in the 
project area, the following species are listed as endangered under the 
ESA: blue, fin, sei, and sperm whales. We are proposing to authorize 
very small numbers of takes for these species (Table 9), 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.
    NMFS concludes that exposures of marine mammals due to NSF's 
proposed seismic survey would result in only short-term (temporary and 
short in duration) effects to individuals exposed. 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:
    (1) No mortality, serious injury or Level A harassment is 
anticipated or proposed to be authorized;
    (2) 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 
(19 days) would further limit the potential impacts of any temporary 
behavioral changes that would occur;
    (3) 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;
    (4) The potential adverse effects of the proposed survey on fish or 
invertebrate species that serve as prey species for marine mammals 
would be temporary and spatially limited; and
    (5) The proposed mitigation measures, including visual monitoring, 
ramp-ups, 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 would 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. When the predicted number of 
individuals to be taken is fewer than one-third of the species or stock 
abundance, the take is considered to be of small numbers. Additionally, 
other qualitative factors may be considered in the analysis, such as 
the temporal or spatial scale of the activities.
    The amount of take NMFS proposes to authorize is below one third of 
the estimated stock abundance for all species (in fact, take of 
individuals is less than ten percent of the abundance of the affected 
stocks, see Table 10). This is likely a conservative estimate because 
we assume all takes are of different individual animals, which is 
likely not the case. Some individuals may be encountered multiple times 
in a day, but PSOs would count them as separate individuals if they 
cannot be identified.
    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 species or stocks 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.

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 whenever we propose to authorize take for 
endangered or threatened species.
    We propose to authorize take of blue, fin, sei, and sperm whales, 
which are listed under the ESA, and have requested initiation of 
Section 7 consultation 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 survey and icebreaking in 
the Ross Sea, in January through February 2023, provided the previously 
mentioned mitigation, monitoring, and reporting

[[Page 59238]]

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 Ross 
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 Potential 
Effects of Specified Activities on Marine Mammals and their Habitat 
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:
    (1) A request for renewal is received no later than 60 days prior 
to expiration of the current IHA.
    (2) The request for renewal must include the following:
     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).
     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: September 22, 2022.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2022-20928 Filed 9-28-22; 8:45 am]
BILLING CODE 3510-22-P