Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Low-Energy Geophysical Survey in the Southwest Atlantic Ocean, 39896-39927 [2019-17062]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 84, Number 155 (Monday, August 12, 2019)]
[Notices]
[Pages 39896-39927]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-17062]



[[Page 39895]]

Vol. 84

Monday,

No. 155

August 12, 2019

Part II





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 Low-Energy Geophysical Survey in the 
Southwest Atlantic Ocean; Notices

Federal Register / Vol. 84 , No. 155 / Monday, August 12, 2019 / 
Notices

[[Page 39896]]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XR007


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to a Low-Energy Geophysical Survey in 
the Southwest Atlantic Ocean

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 Scripps Institute of 
Oceanography (SIO) for authorization to take marine mammals incidental 
to a low-energy marine geophysical survey in the Southwest Atlantic 
Ocean. 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 
September 11, 2019.

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. Attachments 
to electronic comments will be accepted in Microsoft Word or Excel or 
Adobe PDF file formats only. 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: Amy Fowler, 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 such 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 such takings are set forth.

National Environmental Policy Act

    To comply with the National Environmental Policy Act of 1969 (NEPA; 
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, 
NMFS must review our proposed action (i.e., the issuance of an 
incidental harassment authorization) with respect to potential impacts 
on the human environment.
    This action is consistent with categories of activities identified 
in Categorical Exclusion B4 (incidental harassment authorizations with 
no anticipated serious injury or mortality) of the Companion Manual for 
NOAA Administrative Order 216-6A, which do not individually or 
cumulatively have the potential for significant impacts on the quality 
of the human environment and for which we have not identified any 
extraordinary circumstances that would preclude this categorical 
exclusion. Accordingly, NMFS has preliminarily determined that the 
issuance of the proposed IHA qualifies to be categorically excluded 
from further NEPA review.
    We will review all comments submitted in response to this notice 
prior to concluding our NEPA process or making a final decision on the 
IHA request.

Summary of Request

    On March 13, 2019, NMFS received a request from SIO for an IHA to 
take marine mammals incidental to conducting a low-energy marine 
geophysical survey in the Southwest Atlantic Ocean. The application was 
deemed adequate and complete on May 20, 2019. SIO's request is for take 
of a small number of 49 species of marine mammals by Level B 
harassment. Neither SIO nor NMFS expects serious injury or mortality to 
result from this activity and, therefore, an IHA is appropriate. The 
planned activity is not expected to exceed one year, hence, we do not 
expect subsequent MMPA incidental harassment authorizations would be 
issued for this particular activity.

Description of Proposed Activity

Overview

    SIO plans to conduct low-energy marine seismic surveys in the 
Southwest Atlantic Ocean during September-October 2019. The seismic 
surveys would be conducted in the Exclusive Economic Zone (EEZ) of the 
Falkland Islands and International Waters, with water depths ranging 
from ~50-5700 meters (m) (See Figure 1 in the IHA application). The 
surveys would involve one source vessel, R/V

[[Page 39897]]

Thomas G. Thompson (R/V Thompson). The Thompson would deploy up to two 
45-in\3\ GI airguns at a depth of 2-4 m with a maximum total volume of 
~90 in\3\ along predetermined tracklines associated with potential 
coring sites.

Dates and Duration

    The seismic survey would be carried out for approximately 28 days. 
The Thompson would likely depart from Montevideo, Uruguay, on or about 
September 12, 2019 and would return to Montevideo on or about October 
29, 2018. An additional 10 days are allotted to collecting cores and 
measuring water properties/collecting water samples and 5 contingency 
days have been allotted for adverse weather conditions. Transits from 
Montevideo to and from the project area would take approximately 2.5 
days each, for a total of 5 transit days. Some deviation in timing 
could result from unforeseen events such as weather, logistical issues, 
or mechanical issues with the research vessel and/or equipment. Seismic 
activities would occur 24 hours per day during the proposed survey.

Specific Geographic Region

    The proposed surveys would take place within the EEZ of the 
Falkland Islands and in International Waters of the Southwest Atlantic 
Ocean, between approximately 42.75[deg] and 49.5[deg] S, and 55.75[deg] 
and 61.1[deg] W. Work with occur over three survey areas, with these 
survey areas and representative tracklines shown in Figure 1 of the IHA 
application. The Thompson would depart from and return to Montevideo, 
Uruguay.

Detailed Description of Specific Activity

    SIO proposes to conduct low-energy seismic surveys low-energy 
seismic surveys in the Southwest Atlantic Ocean in the EEZ of the 
Falkland Islands and in International Waters between approximately 
42.75[deg] and 49.5[deg] S, and 55.75[deg] and 61.1[deg] W. Within this 
larger area, there are 3 separate survey areas with these survey areas 
and representative survey tracklines shown in Figure 1 in the IHA 
application. All data acquisition in Survey Areas 1 and 3 would occur 
in water >1,000 m deep. Area 2 ranges in depth from 50-5,700 m. The 
proposed surveys would be in support of a potential future 
International Ocean Discovery Program (IODP) project and would examine 
the histories of important deep ocean water masses that originate in 
the Southern Ocean and intersect the continental margin of Argentina. 
The proposed surveys would thus take place in an area that is of 
interest to the IODP. To achieve the program's goals, the Principal 
Investigators propose to collect low-energy, high-resolution multi-
channel seismic (MCS) profiles and sediment cores, and measure water 
properties.
    The procedures to be used for the seismic surveys would be similar 
to those used during previous seismic surveys by SIO and would use 
conventional seismic methodology. The surveys would involve one source 
vessel, R/V Thompson, which is managed by University of Washington 
(UW). The R/V Thompson would deploy up to two 45-in\3\ GI airguns as an 
energy source with a maximum total volume of ~90 in\3\. The receiving 
system would consist of one hydrophone streamer, 200-1,600 m in length, 
as described below. 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.
    The proposed cruise would consist of digital bathymetric, 
echosounding, and MCS surveys within three areas to collect data on 
ocean circulation and climate evolution and to enable the selection and 
analysis of potential future IODP drillsites (Survey Areas 1-3 in Fig. 
1). The airgun array would be operated in one of two different types of 
array modes. The first would be highest-quality survey mode to collect 
the highest-quality seismic reflection data at approximately 18 
potential IODP drill sites. The second mode would be a reconnaissance 
mode, which is quicker, and will occur at approximately 75 coring 
locations, primarily in Survey Area 2. The reconnaissance mode also 
allows for operations to occur in poor weather where the use of 
streamer longer than 200-m may not be possible safely.
    The reconnaissance mode is carried out using either one or two 45-
in\3\ airguns, with airguns spaced 8 m apart (if 2 are being used) at a 
water depth of 2-4 m, with a 200 m hydrophone streamer and with the 
vessel traveling at 8 knots (kn). The highest-quality mode is carried 
out using a pair of 45-in\3\ airguns, with airguns spaced 2 m apart at 
a depth of 2-4 m, with a 400, 800, or 1,600 m hydrophone streamer and 
with the vessel traveling at to 5 kn to achieve high-quality seismic 
reflection data.
    At the three proposed Survey Areas, ~7,500 km of seismic data would 
be collected. All data acquisition in Areas 1 and 3 would occur in 
water >1,000 m deep. Area 2 ranges in depth from 50-5,700 m; most of 
the survey effort (60 percent) would occur in water >1,000 m deep; less 
than one percent would occur in shallow water <100 m deep. There could 
be additional seismic operations in the project area associated with 
equipment testing, re-acquisition due to reasons such as but not 
limited to equipment malfunction, data degradation during poor weather, 
or interruption due to shutdown 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.
    In addition to the operations of the airgun array, a multibeam 
echosounder (MBES) and a sub-bottom profiler (SBP) would also be 
operated continuously throughout the survey, but not during transits to 
and from the project area. MBES and SBP data are essential for 
selecting core sites and for interpreting geological and oceanographic 
processes that affect the southern Argentine margin. A 12-kilohertz 
(kHz) pinger would be used during coring to track the depth. All 
planned geophysical data acquisition activities would be conducted by 
SIO and UW with on-board assistance by the scientists who have proposed 
the study. The vessel would be self-contained, and the crew would live 
aboard the vessel for the entire cruise.
    R/V Thompson has a length of 83.5 m, a beam of 16 m, and a full 
load draft of 5.8 m. It is equipped with twin 360[deg]-azimuth stern 
thrusters each powered by 3,000-hp DC motors and a water-jet bow 
thruster powered by a 1100-hp DC motor. An operation speed of ~9-15 km/
h (~5-8 kn) would be used during seismic acquisition. When not towing 
seismic survey gear, R/V Thompson cruises at 22 km/h (12 kn) and has a 
maximum speed of 26.9 km/h (14.5 kn). It has a normal operating range 
of ~24,400 km. R/V Thompson would also serve as the platform from which 
vessel-based protected species visual observers (PSVO) would watch for 
marine mammals and before and during airgun operations.
    During the survey, R/V Thompson would tow two 45-in\3\ GI airguns 
and a streamer containing hydrophones. The generator chamber of each GI 
gun, the one responsible for introducing the sound pulse into the 
ocean, is 45 in\3\. The larger (105 in\3\) injector chamber injects air 
into the previously generated bubble to maintain its shape and does not 
introduce more sound into the water. The 45-in\3\ GI airguns would be 
towed 21 m behind R/V Thompson, 2 m (during 5-kn high-quality surveys) 
or 8 m (8-kn reconnaissance surveys) apart, side by side, at a depth of 
2-4 m. High-

[[Page 39898]]

quality surveys with the 2-m airgun separation configuration would use 
a streamer up to 1,600-m long, whereas the reconnaissance surveys with 
the 8-m airgun separation configuration would use a 200-m streamer. 
Seismic pulses would be emitted at intervals of 25 m for the 5-kn 
surveys using the 2-m GI airgun separation and at 50 m for the 8-kn 
surveys using the 8-m airgun separation.

        Table 1--Specifications of the R/V Thompson Airgun Array
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Number of airguns.........................  2.
Gun positions used........................  Two inline airguns 2- or 8-m
                                             apart.
Tow depth of energy source................  2-4 m.
Dominant frequency components.............  0-188 hertz (Hz).
Air discharge volume......................  Approximately 90 in\3\.
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    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

    Section 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. 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 proxy sources including International Whaling Commission 
population estimates (IWC 2019), the U.S. Atlantic SARs (Hayes et al., 
2018), 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. However, as 
described above, the marine mammals encountered by the proposed survey 
are not assigned to stocks. All abundance estimate values presented in 
Table 2 are the most recent available at the time of publication and 
are available in the 2018 U.S. Atlantic SARs (e.g., Hayes et al. 2018) 
available online at: www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments, except where noted 
otherwise.
    Table 2 lists all species with expected potential for occurrence in 
the Argentine Basin, Southwest Atlantic Ocean, and summarizes 
information related to the population, including regulatory status 
under the MMPA and ESA. For taxonomy, we follow Committee on Taxonomy 
(2018).

               Table 2--Marine Mammal Species Potentially Present in the Project Area Expected To Be Affected by the Specified Activities
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                                                                             ESA/ MMPA
                                                                              status;                                           Relative  occurrence in
             Common name                  Scientific name     Stock \1\   strategic  (Y/N)         Abundance           PBR            project area
                                                                                \2\
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                                          Order Cetartiodactyla--Cetacea--Superfamily Mysticeti (baleen whales)
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Family Balaenidae:
    Southern right whale............  Eubalaena australis...        n/a  E/D;N              12,000 \3\............       N.A.  Uncommon.
                                                                                            3,300 \4\.............
Family Cetotheriidae:
    Pygmy right whale...............  Caperea marginata.....        n/a  .................  N.A...................       N.A.  Rare.
Family Balaenopteridae (rorquals):
    Blue whale......................  Balaenoptera musculus.        n/a  E/D;Y              2,300 true \3\........       N.A.  Rare.
                                                                                            1,500 pygmy \5\.......
    Fin whale.......................  Balaenoptera physalus.        n/a  E/D;Y              15,000 \5\............       N.A.  Uncommon.
    Sei whale.......................  Balaenoptera borealis.        n/a  E                  10,000 \5\............       N.A.  Uncommon.
    Common minke whale..............  Balaenoptera                  n/a  -                  515,000 3 6...........       N.A.  Common.
                                       acutorostrata.
    Antarctic minke whale...........  Balaenoptera                  n/a  -                  515,000 3 6...........       N.A.  Common.
                                       bonaerensis.
    Humpback whale..................  Megaptera novaeangliae        n/a  -                  42,000 \3\............       N.A.  Rare.
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                                            Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Physeteridae:
    Sperm whale.....................  Physeter macrocephalus        n/a  E                  12,069 \8\............       N.A.  Uncommon.
Family Kogiidae:
    Pygmy sperm whale...............  Kogia breviceps.......        n/a  -                  N.A...................       N.A.  Rare.
    Dwarf sperm whale...............  Kogia sima............        n/a  -                  N.A...................       N.A.  Rare.
Family Ziphiidae (beaked whales):
    Arnoux's beaked whale...........  Berardius arnuxii.....        n/a  -                  599,300 \9\...........       N.A.  Uncommon.
    Cuvier's beaked whale...........  Ziphius cavirostris...        n/a  -                  599,300 \9\...........       N.A.  Uncommon.
    Southern bottlenose whale.......  Hyperoodon planifrons.        n/a  -                  599,300 \9\...........       N.A.  Uncommon.
    Shepherd's beaked whale.........  Tasmacetus sheperdi...        n/a  -                  N.A...................       N.A.  Uncommon.
    Blainville's beaked whale.......  Mesoplodon                    n/a  -                  N.A...................       N.A.  Rare.
                                       densirostris.
    Gray's beaked whale.............  Mesoplodon grayi......        n/a  -                  599,300 \9\...........       N.A.  Uncommon.
    Hector's beaked whale...........  Mesoplodon hectori....        n/a  -                  N.A...................       N.A.  Rare.
    True's beaked whale.............  Mesoplodon mirus......        n/a  -                  N.A...................       N.A.  Rare.
    Strap-toothed beaked whale......  Mesoplodon layardii...        n/a  -                  599,300 \9\...........       N.A.  Uncommon.
    Andrews' beaked whale...........  Mesoplodon bowdoini...        n/a  -                  N.A...................       N.A.  Rare.
    Spade-toothed beaked whale......  Mesoplodon traversii..        n/a  -                  N.A...................       N.A.  Rare.
Family Delphinidae:
    Risso's dolphin.................  Grampus griseus.......        n/a  -                  18,250 \10\...........       N.A.  Uncommon.

[[Page 39899]]

 
    Rough-toothed dolphin...........  Steno bredanensis.....        n/a  -                  N.A...................       N.A.  Rare.
    Common bottlenose dolphin.......  Tursiops truncatus....        n/a  -                  77,532 \10\...........       N.A.  Uncommon.
    Pantropical spotted dolphin.....  Stenella attenuata....        n/a  -                  3,333 \10\............       N.A.  Rare.
    Atlantic spotted dolphin........  Stenella frontalis....        n/a  -                  44,715 \10\...........       N.A.  Rare.
    Spinner dolphin.................  Stenella longirostris.        n/a  -                  N.A...................       N.A.  Uncommon.
    Clymene dolphin.................  Stenella clymene......        n/a  -                  N.A...................       N.A.  Rare.
    Striped dolphin.................  Stenella coeruleoalba.        n/a  -                  54,807 \10\...........       N.A.  Uncommon.
    Short-beaked common dolphin.....  Delphinus delphis.....        n/a  -                  70,184 \10\...........       N.A.  Uncommon.
    Fraser's dolphin................  Lagenodelphis hosei...        n/a  -                  N.A...................       N.A.  Rare.
    Dusky dolphin...................  Lagenorhynchus                n/a  -                  7,252 \11\............       N.A.  Uncommon.
                                       obscurus.
    Hourglass dolphin...............  Lagenorhynchus                n/a  -                  150,000 \5\...........       N.A.  Common.
                                       cruciger.
    Peale's dolphin.................  Lagenorhynchus                n/a  -                  20,000 \12\...........       N.A.  Common.
                                       australis.
    Southern right whale dolphin....  Lissodelphis peronii..        n/a  -                  N.A...................       N.A.  Uncommon.
    Commerson's dolphin.............  Cephalorhynchus               n/a  -                  21,000 \13\...........       N.A.  Common.
                                       commersonii.
    Killer whale....................  Orcinus orca..........        n/a  -                  25,000 \14\...........       N.A.  Uncommon.
    Short-finned pilot whale........  Globicephala                  n/a  -                  200,000 \5\...........       N.A.  Rare.
                                       macrorhynchus.
    Long-finned pilot whale.........  Globicephala melas....        n/a  -                  200,000 \5\...........       N.A.  Common.
    False killer whale..............  Pseudorca crassidens..        n/a  -                  N.A...................       N.A.  Rare.
Family Phocoenidae (porpoises):
    Spectacled porpoise.............  Phocoena dioptrica....        n/a  -                  N.A...................       N.A.  Uncommon.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Order Carnivora--Superfamily Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otariidae (eared seals and
 sea lions):
    Antarctic fur seal..............  Arctocephalus gazella.        n/a  -                  4.5-6.2 million \15\..       N.A.  Rare.
    South American fur seal.........  Arctocephalus                 n/a  -                  99,000 \16\...........       N.A.  Common.
                                       australis.
    Subantarctic fur seal...........  Arctocephalus                 n/a  -                  400,000 \17\..........       N.A.  Uncommon.
                                       tropicalis.
    South American sea lion.........  Otaria flavescens.....        n/a  -                  445,000 \16\..........       N.A.  Common.
Family Phocidae (earless seals):
    Crabeater seal..................  Lobodon carcinophaga..        n/a  -                  5-10 million \18\.....       N.A.  Rare.
    Leopard seal....................  Hydrurga leptonyx.....        n/a  -                  222,000-440,000 \19\..       N.A.  Rare.
    Southern elephant seal..........  Mirounga leonina......        n/a  -                  750,000 \20\..........       N.A.  Uncommon.
--------------------------------------------------------------------------------------------------------------------------------------------------------
N.A. = data not available.
\1\ The populations of marine mammals considered in this document do not occur within the U.S. EEZ and are therefore not assigned to stocks.
\2\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed
  under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality
  exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
  under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\3\ Southern Hemisphere (IWC 2019).
\4\ Southwest Atlantic (IWC 2019).
\5\ Antarctic (Boyd 2002).
\6\ Dwarf and Antarctic minke whales combined.
\7\ There are 14 distinct population segments (DPSs) of humpback whales recognized under the ESA; the Brazil DPS is not listed (NOAA 2017).
\8\ Estimate for the Antarctic, south of 60[deg] S (Whitehead 2002).
\9\ All beaked whales south of the Antarctic Convergence; mostly southern bottlenose whales (Kasamatsu and Joyce 1995).
\10\ Estimate for the western North Atlantic (Hayes et al., 2018).
\11\ Estimate for Patagonian coast (Dans et al., 1997).
\12\ Estimate for Southern Patagonian waters, Argentina (Dellabianca et al., 2016).
\13\ Total world population (Dawson 2018).
\14\ Minimum estimate for Southern Ocean (Branch and Butterworth 2001).
\15\ South Georgia population (Dawson 2018).
\16\ Total population (C[aacute]rdenas-Alayza et al., 2016a).
\17\ Global population (Hofmeyr and Bester 2018).
\18\ Global population (Bengston and Stewart 2018).
\19\ Global population (Rogers 2018).
\20\ 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 49 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.
    Though other marine mammal species are known to occur in the 
Southwest Atlantic Ocean, the temporal and/or spatial occurrence of 
several of these species is such that take of these species is not 
expected to occur, and they are therefore not discussed further beyond 
the explanation provided here. An additional 11 species of marine 
mammals are known to occur in the Southwest Atlantic Ocean; however, 
they are unlikely to occur within the proposed project area because 
they are coastally-distributed (e.g., Franciscana, Pontoporia 
blainvillei; Guiana dolphin, Sotalia guianensis; Chilean dolphin, 
Cephalorhynchus eutropia; Burmeister's porpoise, Phocoena spinipinnis); 
or their distributional range is farther south (Ross seal, Ommatophoca 
rossii; Weddell seal, Leptonychotes weddellii) or north (Bryde's whale, 
Balaenoptera edeni; Gervais' beaked whale, Mesoplodon europaeus; melon-
headed whale, Peponocephala electra; pygmy killer whale, Feresa 
attenuata; long-beaked common dolphin, Delphinus capensis) of the 
proposed project area. None of these 11 species are discussed further 
here.
    We have reviewed SIO'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 SIO's IHA application for

[[Page 39900]]

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

Southern Right Whale
    The southern right whale is circumpolar throughout the Southern 
Hemisphere between 20[deg] S and 55[deg] S (Jefferson et al. 2015), 
although it may occur further north where cold-water currents extend 
northwards (Best 2007). It migrates between summer foraging areas at 
high latitudes and winter breeding/calving areas in low latitudes 
(Jefferson et al. 2015). In the South Atlantic, known or historic 
breeding areas are located in the shallow coastal waters of South 
America, including Argentina and Brazil, as well as the Falkland 
Islands, Tristan de Cunha, Namibia, and South Africa (IWC 2001). 
Rowntree et al. (2013) reported that during 2009, primary calving 
grounds included an estimated 3,373 southern right whales off 
Argentina.
    In the western South Atlantic Ocean, Pen[iacute]nsula 
Vald[eacute]s, Argentina, is the main breeding and calving area 
(Zerbini et al. 2018). It is located just over 200 km from the 
northwestern portion of the proposed project area. Right whales 
occurring in breeding and nursing grounds off southern Brazil and 
Pen[iacute]nsula Vald[eacute]s, Argentina, may comprise two separate 
subpopulations that exploit different habitats. Feeding also occurs at 
these grounds, with breeding success likely influenced by climate-
induced variations in food (i.e., krill) availability, such as reduced 
krill abundance due to global warming (Vighi et al. 2014; Seyboth et 
al. 2016). Areas with potential foraging importance include the outer 
shelf of southern South America (including the northwest portion of the 
proposed project area), the South Atlantic Basin, Scotia Sea, and 
Weddell Sea (Zerbini et al. 2016, 2018).
Pygmy Right Whale
    The distribution of the pygmy right whale is circumpolar in the 
Southern Hemisphere between 30[deg] S and 55[deg] S in oceanic and 
coastal environments (Kemper 2018; Jefferson et al. 2015). The pygmy 
right whale appears to be non-migratory, although there may be some 
movement inshore in spring and summer (Kemper 2002; Jefferson et al. 
2015), possibly related to food availability (Kemper 2018). Foraging 
areas are not known, but it seems likely that pygmy right whales may 
feed at productive areas in higher latitudes, such as near the 
Subtropical Convergence (Best 2007). There may be hotspots of 
occurrence where mesozooplankton, such as Nyctiphanes australis and 
Calanus tonsus, are plentiful (Kemper et al. 2013).
    The project area is considered to be in the secondary 
distributional range for this species (Kemper 2018). In the South 
Atlantic, pygmy right whale records exist for southern Africa, 
Argentina, the Falkland Islands, and pelagic waters (Baker 1985). One 
stranding event of a single pygmy right whale occurred in the Falkland 
Islands during 1950 (Aug[eacute] et al. 2018). There are no OBIS 
records of pygmy right whales within or near the project area, but one 
record exists west of South Georgia and the South Sandwich Islands 
(53.6[deg] S, 40.6[deg] W) (OBIS 2019).
Blue Whale
    The blue whale has a cosmopolitan distribution, but tends to be 
mostly pelagic, only occurring nearshore to feed and possibly breed 
(Jefferson et al. 2015). It is most often found in cool, productive 
waters where upwelling occurs (Reilly and Thayer 1990). The 
distribution of the species, at least during times of the year when 
feeding is a major activity, occurs in areas that provide large 
seasonal concentrations of euphausiids (Yochem and Leatherwood 1985). 
Seamounts and other deep ocean structures may be important habitat for 
blue whales (Lesage et al. 2016). Generally, blue whales are seasonal 
migrants between high latitudes in summer, where they feed, and low 
latitudes in winter, where they mate and give birth (Lockyer and Brown 
1981).
    Brach et al. (2007) reported several catches near the proposed 
project area, particularly near the Falkland Islands, prior to 1974; 
however, most catches occurred in the waters of the Southern Ocean 
during January-March (Branch et al. 2007). There are two records in the 
OBIS database of blue whale sightings in the South Atlantic, including 
one off the Argentinian coast in 1993 and one northeast of Survey Area 
3 in 1913 (42.15[deg] S, 55.25[deg] W) (OBIS 2019). Blue whale songs 
and ~500 sightings have been reported near South Georgia (Southeast of 
proposed survey area) (Sirovic et al. 2016; OBIS 2019). Blue whales 
were also acoustically detected south of the Falkland Islands during a 
recent Antarctic Circumnavigation Expedition (Bell 2017). A rare 
sighting of a mother and calf was made off Brazil in July 2014 (Rocha 
et al. 2019). One blue whale stranding event was reported in southern 
Brazil during the 2000s (Prado et al. 2016). Three standings events of 
individual blue whales occurred in the Falkland Islands during 1940-
1962 (Aug[eacute] et al. 2018).
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).
    In the Southern Hemisphere, fin whales are typically distributed 
south of 50[deg] S in the austral summer, migrating northward to breed 
in the winter (Gambell 1985). According to Edwards et al. (2015), the 
greatest number of sightings near the Falkland Islands (including the 
proposed project area) have been reported during December and January; 
however, sightings have also been made in the area from June through 
November. There were 27 sightings of 57 fin whales made during surveys 
in Falkland Islands waters during February 1998 to January 2001, 
including two sightings within the project area and at least three 
sightings immediately west of the project area (White et al. 2002). 
Sightings predominantly occurred during November-January in water 
depths >200 m, but some sightings were also made during September 
(White et al. 2002). Otherwise, there are four records west/south of 
the Falkland Islands, three off southeastern Brazil, and ~500 near 
South Georgia (OBIS 2019).
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

[[Page 39901]]

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).
    There were 31 sightings of 45 sei whales during surveys in Falkland 
Islands waters from February 1998 to January 2001, with one sighting 
within and one immediately west of the project area; most sightings 
occurred during March and November and none occurred from August-
October (White et al. 2002). Twenty sightings of sei whales were made 
in the coastal waters of Argentina and in the Falkland Islands from 
2004-2008, with the majority of sightings during August-September 
(I[ntilde][iacute]guez et al. 2010). Sixty-five sightings of over 200 
sei whales were made in the Magellan Strait and adjacent waters during 
November-May, during 2004-2015; the majority of sightings occurred 
during December and January (Acevedo et al. 2017a). Aerial and 
photographic surveys indicated a minimum of 87 sei whales present in 
Berkeley Sound, Falkland Islands, during February-May 2017, mostly 
occurring singly or in pairs and otherwise in groups of up to seven 
whales (Weir 2017).
    There are no sei whale records within the proposed project area in 
the OBIS database; however, there are 32 records for the Southwest 
Atlantic, including eight sightings north of the project area during 
2001-2014, ten west of Survey Area 2 during 2009-2013, nine near the 
southern tip of South America during 2012 and 2014, and five between 
the Falkland Islands and South Georgia during 2000-2001 (OBIS 2019). 
Nine sightings of 25 individuals were made in the Beagle Channel off 
the southeastern tip of South America during January 2015 and February 
2016 (Reyes et al. 2016).
Common Minke Whale
    The common minke whale has a cosmopolitan distribution ranging from 
the tropics and subtropics to the ice edge in both hemispheres 
(Jefferson et al. 2015). A smaller form (unnamed subspecies) of the 
common minke whale, known as the dwarf minke whale, occurs in the 
Southern Hemisphere, where its distribution overlaps with that of the 
Antarctic minke whale (B. bonaerensis) during summer (Perrin et al. 
2018). The dwarf minke whale is generally found in shallower coastal 
waters and over the shelf in regions where it overlaps with B. 
bonaerensis (Perrin et al. 2018). The range of the dwarf minke whale is 
thought to extend as far south as 65[deg] S (Jefferson et al. 2015) and 
as far north as 2[deg] S in the Atlantic off South America, where it 
can be found nearly year-round (Perrin et al. 2018).
    The waters of the proposed project area are considered to be within 
the primary range of the common (dwarf) minke whale (Jefferson et al. 
2015). Sixty sightings of 68 minke whales were made during surveys in 
Falkland Islands waters from February 1998 to January 2001, including 
five sightings within the project area and ~20 sightings in the 
immediate vicinity; sightings occurred year-round (except during 
August), with most sightings during September-January (White et al. 
2002).
Antarctic Minke Whale
    The Antarctic minke whale has a circumpolar distribution in coastal 
and offshore areas of the Southern Hemisphere from ~7[deg] 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, 
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 (Williams et al. 2014), where they feed almost 
entirely on krill (Tamura and Konishi 2009).
    A sighting of two Antarctic minke whales was made off Brazil during 
an August-September 2010 survey from Vit[oacute]ria, at ~20[deg] S, 
40[deg] W, to Trindade and Martim Vaz islands; the whales were seen in 
association with a group of rough-toothed dolphins near 19.1[deg] S, 
35.1[deg] W on 21 August (Wedekin et al. 2014). There are no OBIS 
records of Antarctic minke whales within the project area, but two 
records exist for nearshore waters of Argentina west of Survey Area 2, 
and there are two records off southern South America (OBIS 2019). At 
least five strandings have been reported for southern Brazil, including 
two during the 1990s and three in the 2000s (Prado et al. 2016). One 
stranding of a single whale occurred in the Falkland Islands during May 
2016 (Aug[eacute] et al. 2018).
Humpback Whale
    Humpback whales are found worldwide in all ocean basins. In winter, 
most humpback whales occur in the subtropical and tropical waters of 
the Northern and Southern Hemispheres (Muto et al., 2015). These 
wintering grounds are used for mating, giving birth, and nursing new 
calves. Humpback whales were listed as endangered under the Endangered 
Species Conservation Act (ESCA) in June 1970. In 1973, the ESA replaced 
the ESCA, and humpbacks continued to be listed as endangered. NMFS 
recently evaluated the status of the species, and on September 8, 2016, 
NMFS divided the species into 14 distinct population segments (DPS), 
removed the current species-level listing, and in its place listed four 
DPSs as endangered and one DPS as threatened (81 FR 62259; September 8, 
2016). The remaining nine DPSs were not listed. The Brazil DPS, which 
is not listed under the ESA, is the only DPS of humpback whale that is 
expected to occur in the survey area.
    In the Southern Hemisphere, humpback whales migrate annually from 
summer foraging areas in the Antarctic to breeding grounds in tropical 
seas (Clapham 2018). Whales migrating southward from Brazil have been 
shown to traverse offshore, pelagic waters within a narrow migration 
corridor to the east of the proposed project area (Zerbini et al. 2006, 
2011) en route to feeding areas along the Scotia Sea, including the 
waters around Shag Rocks, South Georgia and the South Sandwich Islands 
(Stevick et al. 2006; Zerbini et al. 2006, 2011; Engel et al. 2008; 
Engel and Martin 2009).
    The waters of the proposed project area are considered part of the 
humpback's secondary range (Jefferson et al. 2015). Four humpback 
sightings totaling five individuals were made during surveys in 
Falkland Islands waters, between February 1999 and March 2000 (White et 
al. 2002). For the South Atlantic, the OBIS database shows numerous 
sightings along the coast of South America, including one record within 
Survey Area 2 during February 2000, one record near the Argentinian 
coast during January 2008, and six historical records north of the 
project area (OBIS 2019).

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

[[Page 39902]]

abundance can vary in response to prey availability, most notably squid 
(Jaquet and Gendron 2002). Females generally inhabit waters >1000 m 
deep at latitudes <40[deg] where sea surface temperatures are <15 
[deg]C; adult males move to higher latitudes as they grow older and 
larger in size, returning to warm-water breeding grounds according to 
an unknown schedule (Whitehead 2018).
    There were 21 sightings of 28 sperm whales during surveys in 
Falkland Islands waters from February 1998 to January 2001, with at 
least eight sightings within the proposed project area and one 
immediately west of the project area; sightings occurred year-round in 
water >200 m deep (White et al. 2002). Surveys conducted between 
January 2002 and May 2004 by observers on board longliners during 
hauling operations along the 1000-m isobath east and northeast of the 
Falkland Islands (including within the proposed project area) indicated 
that although sperm whales were present throughout the fishing areas, 
they were concentrated near the steepest depth gradients in north/east/
southeast Burdwood Bank and northeast of the Falkland Islands (Yates 
and Brickle 2007). Yates and Brickle (2007) sighted sperm whales 
throughout the year, and observed a higher abundance south of 53[deg] S 
during November-March and north of 50[deg] S during May-September. 
Sperm whales were detected acoustically in Falkland Island waters 
during all seasons during monitoring from July 2012 to July 2013 
(Premier Oil 2018).
    In the OBIS database, there is one record of sperm whales within 
Survey Area 1, 84 records within Survey Area 2, and two within Survey 
Area 3 (OBIS 2019). An additional 89 records are near the project area, 
and 10 records are near the Falkland Islands (OBIS 2019). Sperm whales 
were sighted and/or acoustically detected off southern South America 
during the 2014-2017 Argentine Southern Ocean Research Partnership 
cruise (Melcon et al. 2017). Sixteen strandings totaling 39 sperm 
whales occurred in the Falkland Islands from 1957-2011 (Aug[eacute] et 
al. 2018). There are ~30 stranding reports for southern Brazil from 
1983-2014 (Prado et al. 2016; Vianna et al. 2016).
Pygmy and Dwarf Sperm Whales
    Dwarf and pygmy sperm whales are distributed throughout tropical 
and temperate waters of the Atlantic, Pacific and Indian oceans, but 
their precise distributions are unknown because much of what we know of 
the species comes from strandings (McAlpine 2018). They are difficult 
to sight at sea, because of their dive behavior and perhaps because of 
their avoidance reactions to ships and behavior changes in relation to 
survey aircraft (W[uuml]rsig et al. 1998). The two species are often 
difficult to distinguish from one another when sighted (McAlpine 2018). 
It has been suggested that the pygmy sperm whale is more temperate and 
the dwarf sperm whale more tropical, based at least partially on live 
sightings at sea from a large database from the eastern tropical 
Pacific (Wade and Gerrodette 1993; McAlpine 2018). This idea is also 
supported by the distribution of strandings in South American waters 
(Mu[ntilde]oz-Hincapi[eacute] et al. 1998; Moura et al. 2016).
    The proposed project area is located along the southern edge of the 
presumed distributional range of Kogia spp. There are no records of 
Kogia spp. in proposed project area (OBIS 2019). The only records in 
the OBIS database for the South Atlantic are for Africa; 57 records of 
K. breviceps and 22 records of K. sima (OBIS 2019). Both species have 
been reported off southern Brazil (e.g., de Oliveira Santos et al. 
2010; Costa-Silva et al. 2016). Approximately 60 dwarf sperm whale 
strandings have been reported in Brazil between 1965 and 2014 (Moura et 
al. 2016; Prado et al. 2016). Approximately 50 pygmy sperm whale 
strandings occurred in Brazil during the same time period (Moura et al. 
2016; Prado et al. 2016; Vianna et al. 2016).
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). 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). There are no OBIS records for the Southwest Atlantic (OBIS 
2019). At least three stranding events have been reported in southern 
Brazil since the 2000s (Prado et al. 2016). Stranding records also 
exist for the coast of Tierra del Fuego, Argentina (Riccialdelli et al. 
2017).
Cuvier's Beaked Whale
    Cuvier's beaked whale is probably the most widespread and common of 
the beaked whales, although it is not found in high-latitude polar 
waters (Heyning 1989; Baird 2018a). It is rarely observed at sea and is 
known mostly from strandings; it strands more commonly than any other 
beaked whale (Heyning 1989). Cuvier's beaked whale is found in deep 
water in the open-ocean and over and near the continental slope 
(Gannier and Epinat 2008; Baird 2018a).
    In the South Atlantic, there are stranding records for Brazil, 
Uruguay, Argentina, Falkland Islands, and South Africa (MacLeod et al. 
2006; Otley et al. 2012; Fisch and Port 2013; Bortolotto et al. 2016; 
Riccialdelli et al. 2017). Sighting records exist for nearshore Brazil, 
South Africa, and the central South Atlantic and Southern Ocean 
(Findlay et al. 1992; MacLeod et al. 2006; Prado et al. 2016). There 
are no OBIS records within or near the proposed project area; the 
nearest sighting record occurred off southeastern Brazil during 2001 
(27.82[deg] S, 45.2[deg] W) (OBIS 2019).
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 ~57[deg] S and 70[deg] S (Jefferson et al. 2015; Moors-Murphy 
2018). It is apparently migratory, occurring in Antarctic waters during 
summer (Jefferson et al. 2015). Several sighting and stranding records 
exist for southeastern South America, Falkland Islands, South Georgia 
Island, southeastern Brazil, and Argentina, and numerous sightings have 
been reported for the Southern Ocean (MacLeod et al. 2006; de Oliveira 
Santos and e Figueiredo 2016; Riccialdelli et al. 2017). The Falkland 
Islands/Tierra del Fuego area is considered a beaked whale key area 
(MacLeod and Mitchell 2006). Southern bottlenose whales were regularly 
seen there (18 sightings of 34 individuals) during September-February 
1998-2001, including three sightings within the proposed project area 
(White et al. 2002). There are three records in the OBIS database of 
sightings in the Southwest Atlantic, one off eastern Brazil during 
November 2000 and two east of Survey Area 2 during November 2001 
(45.75[deg] S and 53.18[deg] W) (OBIS 2019).
Shepherd's Beaked Whale
    Based on known records, it is likely that Shepherd's beaked whale 
has a circumpolar distribution in the cold temperate waters of the 
Southern Hemisphere, between 33-50[deg] S (Mead 2018). It is primarily 
known from strandings, most of which have been recorded in New Zealand 
and the Tristan da Cunha archipelago (Pitman et al. 2006; Mead 2018). 
Additional records in the South Atlantic include a sighting in the 
Scotia Sea and several strandings in Argentina (Grandi et al. 2005; 
MacLeod et al. 2006; Pitman et al. 2006; Riccialdelli et al. 2017; Mead

[[Page 39903]]

2018). Based on the known distributional range of Shepherd's beaked 
whale (MacLeod et al. 2006; Jefferson et al. 2015), the project area is 
within its possible range. There are no records for the Southwest 
Atlantic in the OBIS database (OBIS 2019).
Mesoplodont Beaked Whales (Including Blainville's, Gray's, Hector's, 
True's, Strapped-Toothed, Andrew's, and Spade-Toothed Beaked Whales)
    Mesoplodont beaked whales are distributed throughout deep waters 
along the continental slopes of the Southwest Atlantic and the open 
ocean. Blainville's beaked whale is primarily found in tropical and 
warn temperate waters of all oceans (Pittman 2018), and the proposed 
project area is located at the southernmost extend of this species' 
distributional range (Jefferson et al. 2015). Gray's beaked whale, 
Hector's beaked whale, and Andrew's beaked whale are all thought to 
have a circumpolar distribution in temperate waters of the Southern 
Hemisphere (Pitman 2018). True's beaked whale has a disjunct, 
antitropical distribution (Jefferson et al. 2015) and in the Southern 
Hemisphere, is known to occur in South Africa, South America, and 
Australia (Findlay et al. 1992; MacLeod and Mitchell 2006; MacLeod et 
al. 2006). 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 may undertake limited migration to 
warmer waters during the austral winter (Pitman 2018). The spade-
toothed beaked whale is considered relatively rare and is known from 
only four records, three from New Zealand and one from Chile (Thompson 
et al. 2012), but based on latitude, the species could occur in the 
proposed project area.
    Relatively few records exist of Mesoplodont beaked whale 
observations in the proposed survey area, with much of the evidence for 
Mesoplodont presence based on stranding records. Between February 1998 
and January 2001, there were 7 sightings of 15 unidentified beaked 
whales during surveys in the Falkland Islands, and one of these whales 
was likely a Gray's beaked whale (White et al. 2002).
Risso's Dolphin
    Risso's dolphin is distributed worldwide in mid-temperate and 
tropical oceans (Kruse et al. 1999), although it shows a preference for 
mid-temperate waters of the shelf and slope between 30[deg] and 45[deg] 
S (Jefferson et al. 2014). Although it occurs from coastal to deep 
water (~200-1000 m depth), it shows a strong preference for mid-
temperate waters of upper continental slopes and steep shelf-edge areas 
(Hartman 2018). The variations in Risso's dolphin distribution and 
seasonal movement patterns near Argentina may be influenced by that of 
its primary prey, squid (Riccialdelli et al. 2011).
    Sightings of Risso's dolphin have been reported on the Patagonian 
Shelf, Magellan Strait, and elsewhere around southern South America 
(Riccialdelli et al. 2011; Otley 2012; Jefferson et al. 2014). It has 
also been sighted during austral spring and fall surveys near 
southeastern Brazil from 2009 and 2014, in association with common 
bottlenose dolphins (Di Tullio et al. 2016). Retana and Lewis (2017) 
reported 11 records west of the project area. Although there are no 
records within the proposed project area in the OBIS database, 12 
records exist along the southeastern Argentinian coast (OBIS 2019). 
Several dozen stranding events have been reported in coastal waters of 
southern Argentina (Riccialdelli et al. 2011; Otley 2012). Few 
stranding records also exist for northern/northeastern Brazil (Toledo 
et al. 2015; S[aacute]nchez-Sarmiento et al. 2018).
Rough-Toothed Dolphin
    The rough-toothed dolphin is distributed worldwide in tropical and 
subtropical waters (Jefferson et al. 2015). It is generally seen in 
deep, oceanic water, although it is known to occur in coastal waters of 
Brazil (Jefferson et al. 2015; Cardoso et al. 2019). The proposed 
project area is located to the south of its primary distribution range 
(Jefferson et al. 2015); nonetheless, the rough-toothed dolphin could 
be encountered. Rough-toothed dolphins have been sighted in surveys off 
the coast of (Brazil Wedekin et al. 2014, de Oliveira Santos et al. 
2017) and were also acoustically detected off southeastern Brazil 
during passive acoustic monitoring surveys in February 2016 
(Bittencourt et al. 2018). There are no records of rough-toothed 
dolphin within the project area in the OBIS database; the nearest 
records occur of central-eastern Brazil (OBIS 2019). There have been 
~40 reported strandings in southern Brazil from 1983-2014 (Baptista et 
al. 2016; Prado et al. 2016; Vianna et al. 2016).
Common Bottlenose Dolphin
    The bottlenose dolphin occurs in tropical, subtropical, and 
temperate waters throughout the world (Wells and Scott 2018). In the 
South Atlantic, it occurs as far south Tierra del Fuego (Goodall et al. 
2011; Vermeulen et al. 2017; Wells and Scott 2018). Although no 
sightings have been reported in OBIS (2019) for the proposed project 
area or the Falkland Islands, several stranding records exist (Otley 
2012; Aug[eacute] et al. 2018). In the OBIS database, there are 100 
records within 700 km of the project area, including one nearshore 
southern Argentina and one near South Georgia (OBIS 2019).
Pantropical Spotted Dolphin
    The pantropical spotted dolphin is distributed worldwide in 
tropical and some subtropical waters, between ~40[deg] N and 40[deg] S 
(Jefferson et al. 2015). It is one of the most abundant cetaceans and 
is found in coastal, shelf, slope, and deep waters (Perrin 2018a). 
Based on distribution maps (e.g., Moreno et al. 2005; Jefferson et al. 
2015), the proposed project area is located just south of its regular 
range; nonetheless, it is possible that pantropical spotted dolphins 
could be encountered. For the South Atlantic, there is one record for 
Brazil, observed during 2013 (OBIS 2019) and one reported stranding 
event in southern Brazil during the 1990s (Prado et al. 2016).
Atlantic Spotted Dolphin
    The Atlantic spotted dolphin is distributed in tropical and warm 
temperate waters of the North Atlantic from Brazil to New England and 
to the coast of Africa (Jefferson et al. 2015). Based on distribution 
maps (e.g., Moreno et al. 2005; Jefferson et al. 2015), the proposed 
project area is located just south of its regular range; nonetheless, 
it is possible that Atlantic spotted dolphins could be encountered. 
Moreno et al. (2005) summarized records for Brazil. For the South 
Atlantic, there is one record for Brazil in the OBIS database (OBIS 
2019).
Spinner Dolphin
    The spinner dolphin is pantropical in distribution, with a range 
nearly identical to that of the pantropical spotted dolphin, including 
oceanic tropical and sub-tropical waters between 40[deg] N and 40[deg] 
S (Jefferson et al. 2015). Spinner dolphins are extremely gregarious, 
and usually form large schools in the open sea and small ones in 
coastal waters (Perrin and Gilpatrick 1994).
    Although its primary distributional range appears to be to the 
north of the proposed project area in the South Atlantic (Moreno et al. 
2005; Jefferson et al. 2015), one sighting record has been reported 
east of Survey Area 2 and another north of the Falkland Islands

[[Page 39904]]

(OBIS 2019). Sightings off Brazil have also been reported (Moreno et 
al. 2005; OBIS 2019).
Clymene Dolphin
    The clymene dolphin only occurs in tropical and subtropical waters 
of the Atlantic Ocean (Jefferson et al. 2015). It inhabits areas where 
water depths are 700-4500 m or deeper (Fertl et al. 2003). In the 
western Atlantic, it occurs from New Jersey to Florida, the Caribbean 
Sea, the Gulf of Mexico and south to Venezuela and Brazil (W[uuml]rsig 
et al. 2000; Fertl et al. 2003).
    Although currently available information indicates that the 
proposed project area likely does not overlap with its distributional 
range (Moreno et al. 2005; Jefferson et al. 2015), it is possible that 
clymene dolphins could be encountered. There are no OBIS records for 
the South Atlantic (OBIS 2019). Two stranding events of clymene 
dolphins were recorded in the Santa Catarina Coast of southern Brazil 
from 1983-2014 (Vianna et al. 2016).
Striped Dolphin
    The striped dolphin has a cosmopolitan distribution in tropical to 
warm temperate waters from ~50[deg] N to 40[deg] S (Perrin et al. 1994; 
Jefferson et al. 2015). It occurs primarily in pelagic waters, but has 
been observed approaching shore where there is deep water close to the 
coast (Jefferson et al. 2015). In the South Atlantic, it is known to 
occur along the coast of South America, from Brazil to Argentina, and 
along the west coast of Africa (Jefferson et al. 2015).
    The proposed project survey area is immediately south of its 
distributional range (Moreno et al. 2005; Jefferson et al. 2015). 
Sightings have been reported off the northern coast of Argentina 
(Moreno et al. 2005), with 10 records offshore Argentina north of the 
project area; the nearest record was located at 42.3[deg] S, 62[deg] W 
(OBIS 2019).
Short-Beaked Common Dolphin
    The short-beaked common dolphin is found in tropical and warm 
temperate oceans around the world (Jefferson et al. 2015), ranging from 
~60[deg] N to ~50[deg] S (Jefferson et al. 2015). It is the most 
abundant dolphin species in offshore areas of warm-temperate regions in 
the Atlantic and Pacific (Perrin 2018c).
    Short-beaked common dolphins were observed on the outer-continental 
shelf off southeastern Brazil during spring and fall surveys during 
2009-2014 (Di Tullio et al. 2016), and de Oliveira Santos et al. (2017) 
reported one sighting within the Parque Estadual Marinho da Laje de 
Santos MPA off Brazil's southeastern coast during boat-based cetacean 
surveys from 2013-2015. For the Southwest Atlantic, there are seven 
OBIS records for eastern South America, west and north of the proposed 
project area nearshore and offshore Argentina (OBIS 2019). There are at 
least 23 reported stranding events for short-beaked common dolphin in 
southern Brazil from 1983-2014 (Prado et al. 2016; Vianna et al. 2016). 
Strandings and incidental catches in fishing nets have been reported in 
Argentina (de Castro et al. 2016; Durante et al. 2016).
Fraser's Dolphin
    Fraser's dolphin is a tropical oceanic species generally 
distributed between 30[deg] N and 30[deg] S that generally inhabits 
deeper, offshore water (Dolar 2018). The proposed project area is 
located south of the presumed distribution range (Jefferson et al. 
2015), and strandings in more temperate waters, such as in Uruguay, are 
likely extralimital (Dolar 2018). However, there is one record in the 
OBIS database off central-eastern Argentina, west of the proposed 
project area (42.9[deg] S, 65[deg] W). Strandings and incidental 
captures in fishing nets have also been reported in Argentina (So et 
al. 2009; Durante et al. 2016).
Dusky Dolphin
    The dusky dolphin occurs throughout the Southern Hemisphere, 
primarily over continental shelves and slopes and sometimes over deep 
water close to continents or islands (Van Waerebeek and W[uuml]rsig 
2018). Along the east coast of South America, it is present from 
~36[deg] S to Southern Patagonia and the Falkland Islands (Otley 2012; 
Van Waerebeek and W[uuml]rsig 2018). It is the most common small 
cetacean near southeastern Argentina (Schiavini et al. 1999) and is 
incidentally captured in mid-water trawl fisheries in the region (Dans 
et al. 1997).
    Dusky dolphins have been sighted during aerial and boat-based 
surveys from the southeastern Argentinian coast to the edge of the EEZ; 
there are also a few records for the proposed project area (Crespo et 
al. 1997). During the past decade, the presence of dusky dolphin has 
increased in the Beagle Channel, southern Argentina, suggesting at 
least a seasonally-resident population during austral summer and fall 
(Dellabianca et al. 2018). There are seven records ranging from counts 
of one to 30 dusky dolphins within Survey Area 2 in the OBIS database, 
and an additional ~80 records within the Southwest Atlantic beyond the 
proposed project area, including five records west of Survey Area 1 
(OBIS 2019).
Hourglass Dolphin
    The hourglass dolphin occurs in all parts of the Southern Ocean, 
with most sightings between ~45[deg] S and 60[deg] S (Cipriano 2018a). 
However, some sightings have been made as far north as 33[deg] S 
(Jefferson et al. 2015). Although it is pelagic, it is also sighted 
near banks and islands (Cipriano 2018a). There were 177 sightings of 
886 hourglass dolphins made during surveys in Falkland Islands waters 
from February 1998 to January 2001, including within the proposed 
project area; sightings predominantly occurred from September-February 
in water deeper than 200 m (White et al. 2002). There are two records 
in the OBIS database near the Falkland Islands, 12 records east and 
southeast of the southern tip of Argentina, and 17 records between 
Falkland Islands and South Georgia (OBIS 2019).
Peale's Dolphin
    Peale's dolphin is endemic to southern South America and ranges 
from 38-59[deg] S (Cipriano 2018b). It is known to breed in the 
Falkland Islands (White et al. 2002). Peale's dolphin was the most 
frequent and numerous cetacean recorded during surveys in Falkland 
Island waters from February 1998 to January 2001, with 864 sightings 
totaling 2617 individuals (White et al. 2002). There were 134 schools 
(465 individuals) observed during eight scientific cruises in southern 
Patagonian waters during November-April between 2009 and 2015, 
including sightings within and/or near the project area (Dellabianca et 
al. 2016). In the OBIS database, there are two sightings within Survey 
Area 2 and ~130 records near the project area (OBIS 2019). There are 
also reports of strandings historically from Southern Brazil to the 
Falkland Islands (Prado et al. 2016, Aug[eacute] et al. 2018)
Southern Right Whale Dolphin
    The southern right whale dolphin is distributed between the 
Subtropical and Antarctic convergences in the Southern Hemisphere, 
generally between ~30[deg] S and 65[deg] S (Jefferson et al. 2015; 
Lipsky and Brownell 2018). It is sighted most often in cool, offshore 
waters, although it is sometimes seen near shore where coastal waters 
are deep (Jefferson et al. 2015).
    One sighting of 120 southern right whale dolphins was made in 
Survey Area 2 during September 1998; an additional two sightings of six 
and 20 individuals occurred southeast of the proposed project area 
during February and September 1999, respectively (White et al. 2002). 
Two strandings of

[[Page 39905]]

three southern right whale dolphins occurred in the Falkland Islands 
during February and September between 1945 and 2004 (Aug[eacute] et al. 
2018).
Commerson's Dolphin
    Commerson's dolphin principally occurs near Argentina and the 
Falkland Islands, Strait of Magellan, and the Kerguelen Islands in the 
Indian Ocean (Dawson 2018). In the Falkland Islands, Commerson's 
dolphin are distributed mainly coastally and are also known to breed 
there (White et al. 2002).
    Although these dolphins typically prefer water depths <100 m, there 
are two records within Survey Area 2 and over 500 records in the 
Southwest Atlantic in the OBIS database, with sightings particularly 
prevalent nearshore and offshore southeastern Argentina and the 
Falkland Islands (OBIS 2019). Commerson's dolphins have been observed 
year-round, except during May, with peak occurrence during April (White 
et al. 2002) in waters near the Falkland Islands, and in other surveys 
around Argentina.
Killer Whale
    Killer whales have been observed in all oceans and seas of the 
world (Leatherwood and Dahlheim 1978). Based on sightings by whaling 
vessels between 1960 and 1979, killer whales are distributed throughout 
the South Atlantic (Budylenko 1981; Mikhalev et al. 1981). Although 
reported from tropical and offshore waters (Heyning and Dahlheim 1988), 
killer whales prefer the colder waters of both hemispheres, with 
greatest abundances found within 800 km of major continents (Mitchell 
1975).
    There are 48 records of killer whales for the Southwest Atlantic 
near the project area in the OBIS database, including one record of 
three individuals within Survey Area 2, three records totaling ten 
whales east of Survey Area 2, and one record of six whales northeast of 
Survey Area 3 (OBIS 2019). In addition to these sightings, there are 
numerous recorded observations from surveys in the area.
Short-Finned and Long-Finned Pilot Whale
    The short-finned pilot whale is found in tropical and warm 
temperate waters, and the long-finned pilot whale is distributed 
antitropically in cold temperate waters (Olson 2018). The ranges of the 
two species show little overlap (Olson 2018). Short-finned pilot whale 
distribution does not generally range south of 40[deg] S (Jefferson et 
al. 2008). Long-finned pilot whales are one of the most regular sighted 
species in the Falkland Islands (White et al. 2002).
    There are eight records of long-finned pilot whales in Survey Area 
2 and one record in Survey Area 3 in the OBIS database, in addition to 
~100 records in the Southwest Atlantic beyond the project area; there 
is a single record of short-finned pilot whales off northeastern Brazil 
(OBIS 2019).
False Killer Whale
    The false killer whale is found worldwide in tropical and temperate 
waters, generally between 50[deg] N and 50[deg] S (Odell and McClune 
1999). It is widely distributed, but not abundant anywhere (Carwardine 
1995). The proposed project area is within the primary range of the 
false killer whale in the Southwest Atlantic Ocean (Baird 2018b). 
Within this portion of its range, false killer whales are known to prey 
on fishes caught in the Uruguayan pelagic longline fishery (Passadore 
et al. 2015). Although there are no OBIS records of false killer whales 
within the project area, there are two records northeast of there, one 
record also exists west of South Georgia, and 18 records are located 
offshore northeastern Brazil (OBIS 2019).
Spectacled Porpoise
    The spectacled porpoise is distributed in cool temperate, 
subantarctic, and Antarctic waters of the Southern Hemisphere (Goodall 
and Brownell 2018). In the Southwest Atlantic, it occurs from southern 
Brazil to Tierra del Fuego, Falkland Islands, and South Georgia, and 
its range extends southwards into the Drake Passage (Jefferson et al. 
2015).
    In the OBIS database, one record exists for the South Atlantic, 
west of Survey Area 2 at 47.5[deg] S, 62.7[deg] W during 2009 (OBIS 
2019) and the species is generally observed in group sizes of one to 
five individuals (Goodall and Brownell 2018). Strandings of spectacled 
porpoises have been recorded around the region including the Falkland 
Islands, southern Brazil, and strand most frequently on the beaches of 
Tierra del Fuego where it is the second-most frequently stranding 
cetacean (Costa and Rojas 2017; Aug[eacute] et al. 2018; Goodall and 
Brownell 2018).

Pinnipeds

Antarctic Fur Seal
    The Antarctic fur seal is the only fur seal that lives south of the 
Antarctic Convergence (Acevedo et al. 2011). It has a circumpolar 
distribution around Antarctica and ranges as far north as the Falkland 
Islands and Argentina during the non-breeding season (Forcada and 
Staniland 2018).
    Female Antarctic fur seals can disperse greater than 1,000 km onto 
the continental shelf of Patagonia once pups are weaned (Boyd et al. 
2002), with tagged animals showing focused foraging activity in waters 
of the South American continental shelf, including waters of the 
proposed project area. There are thousands of records of Antarctic fur 
seals in the OBIS database (OBIS 2019), including 108 records for the 
proposed project area for May through October.
South American Fur Seal
    The South American fur seal occurs along the Atlantic coast of 
South America from southern Brazil to the southernmost tip of 
Patagonia, extending out to include the Falkland Islands 
(C[aacute]rdenas-Alayza 2018a). There are no records of South American 
fur seals within the proposed offshore project area in the OBIS 
database (OBIS 2019). The closest record is ~270 km to the west and 
tagged individuals have undertaking foraging trips that bring them in 
waters near the project area (Baylis et al. 2018b), but with a tendency 
to be in waters less than 400 m deep.
Subantarctic Fur Seal
    Subantarctic fur seals occur between 10[deg] W and 170[deg] E north 
of the Antarctic Polar Front in the Southern Ocean (Hofmeyr and Bester 
2018). Breeding occurs on several islands, with Gough Island in the 
central South Atlantic accounting for about two thirds of pup 
production (Hofmeyr and Bester 2018), but adults take long foraging 
journeys away from these colonies. Subantarctic fur seals found in 
Brazil were most often seen there during the austral winter from July 
through October (de Moura and Siciliano 2007); most were males. There 
are no records of subantarctic fur seals within the proposed offshore 
project area in the OBIS database (OBIS 2019).
South American Sea Lion
    The South American sea lion is widely distributed along the South 
American coastline from Peru in the Pacific to southern Brazil in the 
Atlantic (C[aacute]rdenas-Alayza 2018b). On the Atlantic coast, it 
occurs from Brazil to Tierra del Fuego, including the Falkland Islands 
(C[aacute]rdenas-Alayza 2018b). The northernmost rookery is located on 
the coast of Uruguay; South American sea lions are also known to breed 
on the Falkland Islands (Thompson et al. 2005).

[[Page 39906]]

    There are 2,352 records for coastal and shelf waters of South 
America in the OBIS database; most records are for waters off Argentina 
(OBIS 2019). There are 80 records in the northwestern portion of the 
proposed project area and satellite tagged males have been recorded 
near Survey Area 2, but the animals tend to be found in waters 200 m 
deep or less.
Crabeater Seal
    Crabeater seals have a circumpolar distribution off Antarctica and 
generally spend the entire year in the advancing and retreating pack 
ice; occasionally they are seen in the far southern areas of South 
America though this is uncommon (Bengtson and Stewart 2018). Vagrants 
are occasionally found as far north as Brazil (de Oliveira et al. 
2006). There are no records of crabeater seals within the proposed 
offshore project area in the OBIS database (OBIS 2019). However, the 
species could possibly be present and Crabeater seals found on the 
coast of Brazil were most often observed during the austral summer and 
fall, but also in winter months (de Oliveira et al. 2006).
Leopard Seal
    The leopard seal has a circumpolar distribution around the 
Antarctic continent where it is solitary and widely dispersed (Rogers 
2018). Most leopard seals remain within the pack ice; however, members 
of this species regularly visit southern continents during the winter 
(Rogers 2018). On the Atlantic coast of South America, leopard seals 
have been reported in small groups on the Falkland Islands and as lone 
individuals in Brazil, Uruguay, Tierra del Fuego, Patagonia, and 
northern Argentina (summarized in Rodr[iacute]guez et al. 2003). There 
are no records of leopard seals within the proposed offshore survey 
area in the OBIS database (OBIS 2019).
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). In the 
South Atlantic, southern elephant seals breed at Patagonia, South 
Georgia, and other islands of the Scotia Arc, Falkland Islands, Bouvet 
Island, and Tristan da Cunha archipelago (Bester and Ryan 2007). 
Pen[iacute]nsula Vald[eacute]s, Argentina is the sole continental South 
American large breeding colony, where tens of thousands of southern 
elephant seals congregate (Lewis et al. 2006).
    Southern elephant seals are known to occur throughout the proposed 
project area (White et al. 2002; Campagna et al. 2008). All sightings 
north of 50[deg] S were made during January-May, and all records south 
of 50[deg] S were made during June, August, and November; most 
sightings were made near the 200-m isobath (White et al. 2002). For the 
South Atlantic, there are ~3,000 OBIS records for the nearshore and 
offshore waters of eastern South America (OBIS 2019); most of the 
records (2943) are for waters off Argentina and the Falkland Islands, 
including within and near the proposed project area, with the most 
records in survey Area 2.

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 (baleen        7 Hz to 35 kHz.
 whales).
Mid-frequency (MF) cetaceans (dolphins,     150 Hz to 160 kHz.
 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) (true    50 Hz to 86 kHz.
 seals).
Otariid pinnipeds (OW) (underwater) (sea    60 Hz to 39 kHz.
 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 and Holt, 
2013).
    For more detail concerning these groups and associated frequency 
ranges, please see NMFS (2018) for a review of available information. 
Forty-nine marine mammal species (42 cetacean and 7 pinniped (4 otariid 
and 3 phocid) species) have the reasonable potential to co-occur with 
the proposed survey activities. Please refer to Table 2. Of the 
cetacean species that may be present, 8 are classified as low-frequency 
cetaceans (i.e., all mysticete species), 28 are classified as mid-
frequency cetaceans (i.e., most delphinid and ziphiid species and the 
sperm whale), and 6 are classified as high-frequency cetaceans (i.e., 
Kogia spp., hourglass dolphin, Peale's dolphin, Commerson's dolphin, 
spectacled porpoise).

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 by Incidental Harassment section 
later in this

[[Page 39907]]

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 by Incidental Harassment section, and the 
Proposed Mitigation section, to draw conclusions regarding the likely 
impacts of these activities on the reproductive success or survivorship 
of individuals and how those impacts on individuals are likely to 
impact marine mammal species or stocks.

Description of Active Acoustic Sound Sources

    This section contains a brief technical background on sound, the 
characteristics of certain sound types, and on metrics used in this 
proposal inasmuch as the information is relevant to the specified 
activity and to a discussion of the potential effects of the specified 
activity on marine mammals found later in this document.
    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 1 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 1 m from the source (referenced to 1 
[mu]Pa) while the received level is the SPL at the listener's position 
(referenced to 1 [mu]Pa).
    Root mean square (rms) is the quadratic mean sound pressure over 
the duration of an impulse. Root mean square is calculated by squaring 
all of the sound amplitudes, averaging the squares, and then taking the 
square root of the average (Urick, 1983). Root mean square accounts for 
both positive and negative values; squaring the pressures makes all 
values positive so that they may be accounted for in the summation of 
pressure levels (Hastings and Popper, 2005). This measurement is often 
used in the context of discussing behavioral effects, in part because 
behavioral effects, which often result from auditory cues, may be 
better expressed through averaged units than by peak pressures.
    Sound exposure level (SEL; represented as dB re 1 [mu]Pa\2\-s) 
represents the total energy contained within a pulse and considers both 
intensity and duration of exposure. Peak sound pressure (also referred 
to as zero-to-peak sound pressure or 0-p) is the maximum instantaneous 
sound pressure measurable in the water at a specified distance from the 
source and is represented in the same units as the rms sound pressure. 
Another common metric is peak-to-peak sound pressure (pk-pk), which is 
the algebraic difference between the peak positive and peak negative 
sound pressures. Peak-to-peak pressure is typically approximately 6 dB 
higher than peak pressure (Southall et al., 2007).
    When underwater objects vibrate or activity occurs, sound-pressure 
waves are created. These waves alternately compress and decompress the 
water as the sound wave travels. Underwater sound waves radiate in a 
manner similar to ripples on the surface of a pond and may be either 
directed in a beam or beams or may radiate in all directions 
(omnidirectional sources), as is the case for pulses produced by the 
airgun arrays considered here. The compressions and decompressions 
associated with sound waves are detected as changes in pressure by 
aquatic life and man-made sound receptors such as hydrophones.
    Even in the absence of sound from the specified activity, the 
underwater environment is typically loud due to ambient sound. Ambient 
sound is defined as environmental background sound levels lacking a 
single source or point (Richardson et al., 1995), and the sound level 
of a region is defined by the total acoustical energy being generated 
by known and unknown sources. These sources may include physical (e.g., 
wind and waves, earthquakes, ice, atmospheric sound), biological (e.g., 
sounds produced by marine mammals, fish, and invertebrates), and 
anthropogenic (e.g., vessels, dredging, construction) sound. A number 
of sources contribute to ambient sound, including the following 
(Richardson et al., 1995):
     Wind and waves: The complex interactions between wind and 
water surface, including processes such as breaking waves and wave-
induced bubble oscillations and cavitation, are a main source of 
naturally occurring ambient sound for frequencies between 200 Hz and 50 
kHz (Mitson, 1995). In general, ambient sound levels tend to increase 
with increasing wind speed and wave height. Surf sound becomes 
important near shore, with measurements collected at a distance of 8.5 
km from shore showing an increase of 10 dB in the 100 to 700 Hz band 
during heavy surf conditions;
     Precipitation: Sound from rain and hail impacting the 
water surface can become an important component of total sound at 
frequencies above 500 Hz, and possibly down to 100 Hz during quiet 
times;
     Biological: Marine mammals can contribute significantly to 
ambient sound levels, as can some fish and snapping shrimp. The 
frequency band for biological contributions is from approximately 12 Hz 
to over 100 kHz; and
     Anthropogenic: Sources of ambient sound related to human 
activity include transportation (surface vessels), dredging and 
construction, oil and gas drilling and production, seismic surveys, 
sonar, explosions, and ocean acoustic studies. Vessel noise typically 
dominates the total ambient sound for frequencies between 20 and 300 
Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz 
and, if higher frequency sound levels are created, they attenuate 
rapidly. Sound from identifiable anthropogenic sources other than the 
activity of interest (e.g., a passing vessel) is sometimes termed 
background sound, as opposed to ambient sound.
    The sum of the various natural and anthropogenic sound sources at 
any given location and time--which comprise ``ambient'' or 
``background'' sound--depends not only on the source levels (as 
determined by current weather conditions and levels of biological and 
human activity) but also on the ability of sound to propagate through 
the environment. In turn, sound propagation is dependent on the 
spatially and temporally varying properties of the water column and sea 
floor, and is frequency-dependent. As a result of the dependence on a 
large number of varying factors, ambient sound levels can be expected 
to vary widely over both coarse and fine spatial and temporal scales. 
Sound levels at a given frequency and location can vary by 10-20 dB 
from day to day (Richardson et al., 1995). The result is that, 
depending on the source type and its intensity, sound from a given 
activity may be a negligible addition to the local environment or could 
form a distinctive signal that may affect marine mammals.

[[Page 39908]]

Details of source types are described in the following text.
    Sounds are often considered to fall into one of two general types: 
Pulsed and non-pulsed (defined in the following). The distinction 
between these two sound types is important because they have differing 
potential to cause physical effects, particularly with regard to 
hearing (e.g., Ward, 1997 in Southall et al., 2007). Please see 
Southall et al. (2007) for an in-depth discussion of these concepts.
    Pulsed sound sources (e.g., airguns, explosions, gunshots, sonic 
booms, impact pile driving) produce signals that are brief (typically 
considered to be less than one second), broadband, atonal transients 
(ANSI, 1986, 2005; Harris, 1998; NIOSH, 1998; ISO, 2003) and occur 
either as isolated events or repeated in some succession. Pulsed sounds 
are all characterized by a relatively rapid rise from ambient pressure 
to a maximal pressure value followed by a rapid decay period that may 
include a period of diminishing, oscillating maximal and minimal 
pressures, and generally have an increased capacity to induce physical 
injury as compared with sounds that lack these features.
    Non-pulsed sounds can be tonal, narrowband, or broadband, brief or 
prolonged, and may be either continuous or non-continuous (ANSI, 1995; 
NIOSH, 1998). Some of these non-pulsed sounds can be transient signals 
of short duration but without the essential properties of pulses (e.g., 
rapid rise time). Examples of non-pulsed sounds include those produced 
by vessels, aircraft, machinery operations such as drilling or 
dredging, vibratory pile driving, and active sonar systems (such as 
those used by the U.S. Navy). The duration of such sounds, as received 
at a distance, can be greatly extended in a highly reverberant 
environment.
    Airgun arrays produce pulsed signals with energy in a frequency 
range from about 10-2,000 Hz, with most energy radiated at frequencies 
below 200 Hz. The amplitude of the acoustic wave emitted from the 
source is equal in all directions (i.e., omnidirectional), but airgun 
arrays do possess some directionality due to different phase delays 
between guns in different directions. Airgun arrays are typically tuned 
to maximize functionality for data acquisition purposes, meaning that 
sound transmitted in horizontal directions and at higher frequencies is 
minimized to the extent possible.
    As described above, a Kongsberg EM 300 MBES and a Knudsen Chirp 
3260 SBP would be operated continuously during the proposed surveys, 
but not during transit to and from the survey areas. Additionally a 12-
kHz pinger would be used during coring, when seismic airguns, are not 
in operation (more information on this pinger is available in NSF-USGS 
(2011). Each ping emitted by the MBES consists of eight (in water 
>1,000 m deep) or four (<1,000 m) successive fan-shaped transmissions, 
each ensonifying a sector that extends 1[deg] fore-aft. Given the 
movement and speed of the vessel, the intermittent and narrow downward-
directed nature of the sounds emitted by the MBES would result in no 
more than one or two brief ping exposures of any individual marine 
mammal, if any exposure were to occur.
    Due to the lower source levels of the Knudsen Chirp 3260 SBP 
relative to the Thompson's airgun array (maximum SL of 222 dB re 1 
[mu]Pa [middot] m for the SBP, versus a minimum of 230.9 dB re 1 [mu]Pa 
[middot] m for the 2 airgun array (LGL, 2019)), sounds from the SBP are 
expected to be effectively subsumed by sounds from the airgun array. 
Thus, any marine mammal potentially exposed to sounds from the SBP 
would already have been exposed to sounds from the airgun array, which 
are expected to propagate further in the water.
    The use of pingers is also highly unlikely to affect marine mammals 
given their intermittent nature, short-term and transitory use from a 
moving vessel, relatively low source levels, and brief signal durations 
(NSF-USGS, 2011). As such, we conclude that the likelihood of marine 
mammal take resulting from exposure to sound from the MBES or SBP 
(beyond that which is already quantified as a result of exposure to the 
airguns) is discountable. Additionally the characteristics of sound 
generated by pingers means that take of marine mammals resulting from 
exposure to these pingers is discountable. Therefore we do not consider 
noise from the MBES, SBP, or pingers further in this analysis.

Acoustic Effects

    Here, we discuss the effects of active acoustic sources on marine 
mammals.
    Potential Effects of Underwater Sound--Please refer to the 
information given previously (``Description of Active Acoustic 
Sources'') 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

[[Page 39909]]

(e.g., change in dive profile as a result of an avoidance reaction) 
caused by exposure to sound include neurological effects, bubble 
formation, resonance effects, and other types of organ or tissue damage 
(Cox et al., 2006; Southall et al., 2007; Zimmer and Tyack, 2007; Tal 
et al., 2015). The survey activities considered here do not involve the 
use of devices such as explosives or mid-frequency tactical sonar that 
are associated with these types of effects.
    Threshold Shift--Marine mammals exposed to high-intensity sound, or 
to lower-intensity sound for prolonged periods, can experience hearing 
threshold shift (TS), which is the loss of hearing sensitivity at 
certain frequency ranges (Finneran, 2015). TS can be permanent (PTS), 
in which case the loss of hearing sensitivity is not fully recoverable, 
or temporary (TTS), in which case the animal's hearing threshold would 
recover over time (Southall et al., 2007). Repeated sound exposure that 
leads to TTS could cause PTS. In severe cases of PTS, there can be 
total or partial deafness, while in most cases the animal has an 
impaired ability to hear sounds in specific frequency ranges (Kryter, 
1985).
    When PTS occurs, there is physical damage to the sound receptors in 
the ear (i.e., tissue damage), whereas TTS represents primarily tissue 
fatigue and is reversible (Southall et al., 2007). In addition, other 
investigators have suggested that TTS is within the normal bounds of 
physiological variability and tolerance and does not represent physical 
injury (e.g., Ward, 1997). Therefore, NMFS does not consider TTS to 
constitute auditory injury.
    Relationships between TTS and PTS thresholds have not been studied 
in marine mammals, and there is no PTS data for cetaceans but such 
relationships are assumed to be similar to those in humans and other 
terrestrial mammals. PTS typically occurs at exposure levels at least 
several dBs above (a 40-dB threshold shift approximates PTS onset; 
e.g., Kryter et al., 1966; Miller, 1974) that inducing mild TTS (a 6-dB 
threshold shift approximates TTS onset; e.g., Southall et al. 2007). 
Based on data from terrestrial mammals, a precautionary assumption is 
that the PTS thresholds for impulse sounds (such as airgun pulses as 
received close to the source) are at least 6 dB higher than the TTS 
threshold on a peak-pressure basis and PTS cumulative sound exposure 
level thresholds are 15 to 20 dB higher than TTS cumulative sound 
exposure level thresholds (Southall et al., 2007). Given the higher 
level of sound or longer exposure duration necessary to cause PTS as 
compared with TTS, it is considerably less likely that PTS could occur.
    For mid-frequency cetaceans in particular, potential protective 
mechanisms may help limit onset of TTS or prevent onset of PTS. Such 
mechanisms include dampening of hearing, auditory adaptation, or 
behavioral amelioration (e.g., Nachtigall and Supin, 2013; Miller et 
al., 2012; Finneran et al., 2015; Popov et al., 2016).
    TTS is the mildest form of hearing impairment that can occur during 
exposure to sound (Kryter, 1985). While experiencing TTS, the hearing 
threshold rises, and a sound must be at a higher level in order to be 
heard. In terrestrial and marine mammals, TTS can last from minutes or 
hours to days (in cases of strong TTS). In many cases, hearing 
sensitivity recovers rapidly after exposure to the sound ends. Few data 
on sound levels and durations necessary to elicit mild TTS have been 
obtained for marine mammals.
    Marine mammal hearing plays a critical role in communication with 
conspecifics, and interpretation of environmental cues for purposes 
such as predator avoidance and prey capture. Depending on the degree 
(elevation of threshold in dB), duration (i.e., recovery time), and 
frequency range of TTS, and the context in which it is experienced, TTS 
can have effects on marine mammals ranging from discountable to 
serious. For example, a marine mammal may be able to readily compensate 
for a brief, relatively small amount of TTS in a non-critical frequency 
range that occurs during a time where ambient noise is lower and there 
are not as many competing sounds present. Alternatively, a larger 
amount and longer duration of TTS sustained during time when 
communication is critical for successful mother/calf interactions could 
have more serious impacts.
    Finneran et al. (2015) measured hearing thresholds in three captive 
bottlenose dolphins before and after exposure to ten pulses produced by 
a seismic airgun in order to study TTS induced after exposure to 
multiple pulses. Exposures began at relatively low levels and gradually 
increased over a period of several months, with the highest exposures 
at peak SPLs from 196 to 210 dB and cumulative (unweighted) SELs from 
193-195 dB. No substantial TTS was observed. In addition, behavioral 
reactions were observed that indicated that animals can learn behaviors 
that effectively mitigate noise exposures (although exposure patterns 
must be learned, which is less likely in wild animals than for the 
captive animals considered in this study). The authors note that the 
failure to induce more significant auditory effects likely due to the 
intermittent nature of exposure, the relatively low peak pressure 
produced by the acoustic source, and the low-frequency energy in airgun 
pulses as compared with the frequency range of best sensitivity for 
dolphins and other mid-frequency cetaceans.
    Currently, TTS data only exist for four species of cetaceans 
(bottlenose dolphin, beluga whale, harbor porpoise, and Yangtze finless 
porpoise) exposed to a limited number of sound sources (i.e., mostly 
tones and octave-band noise) in laboratory settings (Finneran, 2015). 
In general, harbor porpoises have a lower TTS onset than other measured 
cetacean species (Finneran, 2015). Additionally, the existing marine 
mammal TTS data come from a limited number of individuals within these 
species. There are no data available on noise-induced hearing loss for 
mysticetes.
    Critical questions remain regarding the rate of TTS growth and 
recovery after exposure to intermittent noise and the effects of single 
and multiple pulses. Data at present are also insufficient to construct 
generalized models for recovery and determine the time necessary to 
treat subsequent exposures as independent events. More information is 
needed on the relationship between auditory evoked potential and 
behavioral measures of TTS for various stimuli. For summaries of data 
on TTS in marine mammals or for further discussion of TTS onset 
thresholds, please see Southall et al. (2007), Finneran and Jenkins 
(2012), Finneran (2015), and NMFS (2016a).
    Behavioral Effects--Behavioral disturbance may include a variety of 
effects, including subtle changes in behavior (e.g., minor or brief 
avoidance of an area or changes in vocalizations), more conspicuous 
changes in similar behavioral activities, and more sustained and/or 
potentially severe reactions, such as displacement from or abandonment 
of high-quality habitat. Behavioral responses to sound are highly 
variable and context-specific and any reactions depend on numerous 
intrinsic and extrinsic factors (e.g., species, state of maturity, 
experience, current activity, reproductive state, auditory sensitivity, 
time of day), as well as the interplay between factors (e.g., 
Richardson et al., 1995; Wartzok et al., 2003; Southall et al., 2007; 
Weilgart, 2007; Archer et al., 2010). Behavioral reactions can vary not 
only among individuals but also within an individual, depending on 
previous experience with a sound source,

[[Page 39910]]

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 showed pronounced behavioral reactions, 
including avoidance of loud sound sources (Ridgway et al., 1997). 
Observed responses of wild marine mammals to loud pulsed sound sources 
(typically seismic airguns or acoustic harassment devices) have been 
varied but often consist of avoidance behavior or other behavioral 
changes suggesting discomfort (Morton and Symonds, 2002; see also 
Richardson et al., 1995; Nowacek et al., 2007). However, many 
delphinids approach acoustic source vessels with no apparent discomfort 
or obvious behavioral change (e.g., Barkaszi et al., 2012).
    Available studies show wide variation in response to underwater 
sound; therefore, it is difficult to predict specifically how any given 
sound in a particular instance might affect marine mammals perceiving 
the signal. If a marine mammal does react briefly to an underwater 
sound by changing its behavior or moving a small distance, the impacts 
of the change are unlikely to be significant to the individual, let 
alone the stock or population. However, if a sound source displaces 
marine mammals from an important feeding or breeding area for a 
prolonged period, impacts on individuals and populations could be 
significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007; NRC, 
2005). However, there are broad categories of potential response, which 
we describe in greater detail here, that include alteration of dive 
behavior, alteration of foraging behavior, effects to breathing, 
interference with or alteration of vocalization, avoidance, and flight.
    Changes in dive behavior can vary widely, and may consist of 
increased or decreased dive times and surface intervals as well as 
changes in the rates of ascent and descent during a dive (e.g., Frankel 
and Clark, 2000; Ng and Leung, 2003; Nowacek et al., 2004; Goldbogen et 
al., 2013a, b). Variations in dive behavior may reflect interruptions 
in biologically significant activities (e.g., foraging) or they may be 
of little biological significance. The impact of an alteration to dive 
behavior resulting from an acoustic exposure depends on what the animal 
is doing at the time of the exposure and the type and magnitude of the 
response.
    Disruption of feeding behavior can be difficult to correlate with 
anthropogenic sound exposure, so it is usually inferred by observed 
displacement from known foraging areas, the appearance of secondary 
indicators (e.g., bubble nets or sediment plumes), or changes in dive 
behavior. As for other types of behavioral response, the frequency, 
duration, and temporal pattern of signal presentation, as well as 
differences in species sensitivity, are likely contributing factors to 
differences in response in any given circumstance (e.g., Croll et al., 
2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko et al., 
2007). A determination of whether foraging disruptions incur fitness 
consequences would require information on or estimates of the energetic 
requirements of the affected individuals and the relationship between 
prey availability, foraging effort and success, and the life history 
stage of the animal.
    Visual tracking, passive acoustic monitoring, and movement 
recording tags were used to quantify sperm whale behavior prior to, 
during, and following exposure to airgun arrays at received levels in 
the range 140-160 dB at distances of 7-13 km, following a phase-in of 
sound intensity and full array exposures at 1-13 km (Madsen et al., 
2006; Miller et al., 2009). Sperm whales did not exhibit horizontal 
avoidance behavior at the surface. However, foraging behavior may have 
been affected. The sperm whales exhibited 19 percent less vocal (buzz) 
rate during full exposure relative to post exposure, and the whale that 
was approached most closely had an extended resting period and did not 
resume foraging until the airguns had ceased firing. The remaining 
whales continued to execute foraging dives throughout exposure; 
however, swimming movements during foraging dives were 6 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

[[Page 39911]]

were deployed between March and December 2008 in the offshore 
environment; numbers of singers were counted every hour. Generalized 
Additive Mixed Models were used to assess the effect of survey day 
(seasonality), hour (diel variation), moon phase, and received levels 
of noise (measured from a single pulse during each ten minute sampled 
period) on singer number. The number of singers significantly decreased 
with increasing received level of noise, suggesting that humpback whale 
breeding activity was disrupted to some extent by the survey activity.
    Castellote et al. (2012) reported acoustic and behavioral changes 
by fin whales in response to shipping and airgun noise. Acoustic 
features of fin whale song notes recorded in the Mediterranean Sea and 
northeast Atlantic Ocean were compared for areas with different 
shipping noise levels and traffic intensities and during a seismic 
airgun survey. During the first 72 h of 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 bowhead whale call rates dropped 
significantly at onset of airgun use at sites with a median distance of 
41-45 km from the survey. Blackwell et al. (2015) expanded this 
analysis to show that whales actually increased calling rates as soon 
as airgun signals were detectable before ultimately decreasing calling 
rates at higher received levels (i.e., 10-minute SELcum of 
~127 dB). Overall, these results suggest that bowhead whales may adjust 
their vocal output in an effort to compensate for noise before ceasing 
vocalization effort and ultimately deflecting from the acoustic source 
(Blackwell et al., 2013, 2015). These studies demonstrate that even low 
levels of noise received far from the source can induce changes in 
vocalization and/or behavior for mysticetes.
    Avoidance is the displacement of an individual from an area or 
migration path as a result of the presence of a sound or other 
stressors, and is one of the most obvious manifestations of disturbance 
in marine mammals (Richardson et al., 1995). For example, gray whales 
are known to change direction--deflecting from customary migratory 
paths--in order to avoid noise from seismic surveys (Malme et al., 
1984). Humpback whales showed avoidance behavior in the presence of an 
active seismic array during observational studies and controlled 
exposure experiments in western Australia (McCauley et al., 2000). 
Avoidance may be short-term, with animals returning to the area once 
the noise has ceased (e.g., Bowles et al., 1994; Goold, 1996; Stone et 
al., 2000; Morton and Symonds, 2002; Gailey et al., 2007). Longer-term 
displacement is possible, however, which may lead to changes in 
abundance or distribution patterns of the affected species in the 
affected region if habituation to the presence of the sound does not 
occur (e.g., Bejder et al., 2006; Teilmann et al., 2006).
    A flight response is a dramatic change in normal movement to a 
directed and rapid movement away from the perceived location of a sound 
source. The flight response differs from other avoidance responses in 
the intensity of the response (e.g., directed movement, rate of 
travel). Relatively little information on flight responses of marine 
mammals to anthropogenic signals exist, although observations of flight 
responses to the presence of predators have occurred (Connor and 
Heithaus, 1996). The result of a flight response could range from 
brief, temporary exertion and displacement from the area where the 
signal provokes flight to, in extreme cases, marine mammal strandings 
(Evans and England, 2001). However, it should be noted that response to 
a perceived predator does not necessarily invoke flight (Ford and 
Reeves, 2008), and whether individuals are solitary or in groups may 
influence the response.
    Behavioral disturbance can also impact marine mammals in more 
subtle ways. Increased vigilance may result in costs related to 
diversion of focus and attention (i.e., when a response consists of 
increased vigilance, it may come at the cost of decreased attention to 
other critical behaviors such as foraging or resting). These effects 
have generally not been demonstrated for marine mammals, but studies 
involving fish and terrestrial animals have shown that increased 
vigilance may substantially reduce feeding rates (e.g., Beauchamp and 
Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). In 
addition, chronic disturbance can cause population declines through 
reduction of fitness (e.g., decline in body condition) and subsequent 
reduction in reproductive success, survival, or both (e.g., Harrington 
and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). However, 
Ridgway et al. (2006) reported that increased vigilance in bottlenose 
dolphins exposed to sound over a five-day period did not cause any 
sleep deprivation or stress effects.
    Many animals perform vital functions, such as feeding, resting, 
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption 
of such functions resulting from reactions to stressors such as sound 
exposure are more likely to be significant if they last more than one 
diel cycle or recur on subsequent days (Southall et al., 2007). 
Consequently, a behavioral response lasting less than one day and not 
recurring on subsequent days is not considered particularly severe 
unless it could directly affect reproduction or survival (Southall et 
al., 2007). Note that there is a difference between multi-day 
substantive behavioral reactions and multi-day anthropogenic 
activities. For example, just because an activity lasts for multiple 
days does not necessarily mean that individual animals are either 
exposed to activity-related stressors for multiple days or, further, 
exposed in a manner resulting in sustained multi-day substantive 
behavioral responses.
    Stone (2015) reported data from at-sea observations during 1,196 
seismic surveys from 1994 to 2010. When large arrays of airguns 
(considered to be 500 in\3\ or more) were firing, lateral displacement, 
more localized avoidance, or other changes in behavior were evident for 
most odontocetes. However, significant responses to large arrays were 
found only for the minke whale and fin whale. Behavioral responses 
observed included changes in swimming or surfacing behavior, with 
indications that cetaceans remained near the water surface at these 
times. Cetaceans were recorded as feeding less often when large arrays 
were active. Behavioral observations of gray whales during a seismic 
survey monitored whale movements and respirations pre-, during and 
post-seismic survey (Gailey et al., 2016). Behavioral state and water 
depth were the best `natural' predictors of whale movements and 
respiration and, after considering

[[Page 39912]]

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 until the animal replenishes its energetic reserves 
sufficiently to restore normal function.
    Relationships between these physiological mechanisms, animal 
behavior, and the costs of stress responses are well-studied through 
controlled experiments and for both laboratory and free-ranging animals 
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; 
Krausman et al., 2004; Lankford et al., 2005). Stress responses due to 
exposure to anthropogenic sounds or other stressors and their effects 
on marine mammals have also been reviewed (Fair and Becker, 2000; 
Romano et al., 2002b) and, more rarely, studied in wild populations 
(e.g., Romano et al., 2002a). For example, Rolland et al. (2012) found 
that noise reduction from reduced ship traffic in the Bay of Fundy was 
associated with decreased stress in North Atlantic right whales. These 
and other studies lead to a reasonable expectation that some marine 
mammals will experience physiological stress responses upon exposure to 
acoustic stressors and that it is possible that some of these would be 
classified as ``distress.'' In addition, any animal experiencing TTS 
would likely also experience stress responses (NRC, 2003).
    Auditory Masking--Sound can disrupt behavior through masking, or 
interfering with, an animal's ability to detect, recognize, or 
discriminate between acoustic signals of interest (e.g., those used for 
intraspecific communication and social interactions, prey detection, 
predator avoidance, navigation) (Richardson et al., 1995; Erbe et al., 
2016). Masking occurs when the receipt of a sound is interfered with by 
another coincident sound at similar frequencies and at similar or 
higher intensity, and may occur whether the sound is natural (e.g., 
snapping shrimp, wind, waves, precipitation) or anthropogenic (e.g., 
shipping, sonar, seismic exploration) in origin. The ability of a noise 
source to mask biologically important sounds depends on the 
characteristics of both the noise source and the signal of interest 
(e.g., signal-to-noise ratio, temporal variability, direction), in 
relation to each other and to an animal's hearing abilities (e.g., 
sensitivity, frequency range, critical ratios, frequency 
discrimination, directional discrimination, age or TTS hearing loss), 
and existing ambient noise and propagation conditions.
    Under certain circumstances, marine mammals experiencing 
significant masking could also be impaired from maximizing their 
performance fitness in survival and reproduction. Therefore, when the 
coincident (masking) sound is man-made, it may be considered harassment 
when disrupting or altering critical behaviors. It is important to 
distinguish TTS and PTS, which persist after the sound exposure, from 
masking, which occurs during the sound exposure. Because masking 
(without resulting in TS) is not associated with abnormal physiological 
function, it is not considered a physiological effect, but rather a 
potential behavioral effect.
    The frequency range of the potentially masking sound is important 
in determining any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation 
sounds produced by odontocetes but are more likely to affect detection 
of mysticete communication calls and other potentially important 
natural sounds such as those produced by surf and some prey species. 
The masking of communication signals by anthropogenic noise may be 
considered as a reduction in the communication space of animals (e.g., 
Clark et al., 2009) and may result in energetic or other costs as 
animals change their vocalization behavior (e.g., Miller et al., 2000; 
Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2009; Holt 
et al., 2009). Masking can be reduced in situations where the signal 
and noise come from different directions (Richardson et al., 1995), 
through amplitude modulation of the signal, or through other 
compensatory behaviors (Houser and Moore, 2014). Masking can be tested 
directly in captive species (e.g., Erbe, 2008), but in wild populations 
it must be either modeled or inferred from evidence of masking 
compensation. There are few studies addressing real-world masking 
sounds likely to be experienced by marine mammals in the wild (e.g., 
Branstetter et al., 2013).
    Masking affects both senders and receivers of acoustic signals and 
can potentially have long-term chronic effects on marine mammals at the 
population level as well as at the individual level. Low-frequency 
ambient sound levels have increased by as much as 20 dB (more than 
three times in terms of SPL) in the world's ocean from pre-industrial 
periods, with most of the increase from distant commercial shipping 
(Hildebrand, 2009). All anthropogenic sound sources, but especially 
chronic and lower-frequency signals (e.g., from vessel traffic), 
contribute to elevated ambient sound levels, thus intensifying masking.
    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal calls and other natural sounds are expected 
to be limited, although there are few specific data on this. Because of 
the intermittent nature and low duty cycle of seismic pulses, animals 
can emit and receive sounds in the relatively quiet intervals between 
pulses. However, in exceptional situations, reverberation occurs for 
much or all of the interval between pulses (e.g., Simard et al. 2005; 
Clark and Gagnon 2006), which could mask calls. Situations with 
prolonged strong reverberation are infrequent. However, it is common 
for reverberation to cause some lesser degree of elevation of the

[[Page 39913]]

background level between airgun pulses (e.g., Gedamke 2011; Guerra et 
al. 2011, 2016; Klinck et al. 2012; Guan et al. 2015), and this weaker 
reverberation presumably reduces the detection range of calls and other 
natural sounds to some degree. Guerra et al. (2016) reported that 
ambient noise levels between seismic pulses were elevated as a result 
of reverberation at ranges of 50 km from the seismic source. Based on 
measurements in deep water of the Southern Ocean, Gedamke (2011) 
estimated that the slight elevation of background levels during 
intervals between pulses reduced blue and fin whale communication space 
by as much as 36-51 percent when a seismic survey was operating 450-
2,800 km away. Based on preliminary modeling, Wittekind et al. (2016) 
reported that airgun sounds could reduce the communication range of 
blue and fin whales 2000 km from the seismic source. Nieukirk et al. 
(2012) and Blackwell et al. (2013) noted the potential for masking 
effects from seismic surveys on large whales.
    Some baleen and toothed whales are known to continue calling in the 
presence of seismic pulses, and their calls usually can be heard 
between the pulses (e.g., Nieukirk et al. 2012; Thode et al. 2012; 
Br[ouml]ker et al. 2013; Sciacca et al. 2016). As noted above, Cerchio 
et al. (2014) suggested that the breeding display of humpback whales 
off Angola could be disrupted by seismic sounds, as singing activity 
declined with increasing received levels. In addition, some cetaceans 
are known to change their calling rates, shift their peak frequencies, 
or otherwise modify their vocal behavior in response to airgun sounds 
(e.g., Di Iorio and Clark 2010; Castellote et al. 2012; Blackwell et 
al. 2013, 2015). The hearing systems of baleen whales are undoubtedly 
more sensitive to low-frequency sounds than are the ears of the small 
odontocetes that have been studied directly (e.g., MacGillivray et al. 
2014). The sounds important to small odontocetes are predominantly at 
much higher frequencies than are the dominant components of airgun 
sounds, thus limiting the potential for masking. In general, masking 
effects of seismic pulses are expected to be minor, given the normally 
intermittent nature of seismic pulses.

Ship Noise

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

[[Page 39914]]

effects on individuals or at the population level. In addition, in all 
oceans of the world, large vessel traffic is currently so prevalent 
that it is commonly considered a usual source of ambient sound (NSF-
USGS 2011).

Ship Strike

    Vessel collisions with marine mammals, or ship strikes, can result 
in death or serious injury of the animal. Wounds resulting from ship 
strike may include massive trauma, hemorrhaging, broken bones, or 
propeller lacerations (Knowlton and Kraus, 2001). An animal at the 
surface may be struck directly by a vessel, a surfacing animal may hit 
the bottom of a vessel, or an animal just below the surface may be cut 
by a vessel's propeller. Superficial strikes may not kill or result in 
the death of the animal. These interactions are typically associated 
with large whales (e.g., fin whales), which are occasionally found 
draped across the bulbous bow of large 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 Thompson travels at a speed of either 5 (9.3 km/hour) or 8 kn 
(14.8 km/hour) while towing seismic survey gear (LGL 2019). At these 
speeds, both the possibility of striking a marine mammal and the 
possibility of a strike resulting in serious injury or mortality are 
discountable. At average transit speed, the probability of serious 
injury or mortality resulting from a strike is less than 50 percent. 
However, the likelihood of a strike actually happening is again 
discountable. Ship strikes, as analyzed in the studies cited above, 
generally involve commercial shipping, which is much more common in 
both space and time than is geophysical survey activity. Jensen and 
Silber (2004) summarized ship strikes of large whales worldwide from 
1975-2003 and found that most collisions occurred in the open ocean and 
involved large vessels (e.g., commercial shipping). No such incidents 
were reported for geophysical survey vessels during that time period.
    It is possible for ship strikes to occur while traveling at slow 
speeds. For example, a hydrographic survey vessel traveling at low 
speed (5.5 kn) while conducting mapping surveys off the central 
California coast struck and killed a blue whale in 2009. The State of 
California determined that the whale had suddenly and unexpectedly 
surfaced beneath the hull, with the result that the propeller severed 
the whale's vertebrae, and that this was an unavoidable event. This 
strike represents the only such incident in approximately 540,000 hours 
of similar coastal mapping activity (p = 1.9 x 10-6; 95 
percent CI = 0-5.5 x 10-6; NMFS, 2013b). In addition, a 
research vessel reported a fatal strike in 2011 of a dolphin in the 
Atlantic, demonstrating that it is possible for strikes involving 
smaller cetaceans to occur. In that case, the incident report indicated 
that an animal apparently was struck by the vessel's propeller as it 
was intentionally swimming near the vessel. While indicative of the 
type of unusual events that cannot be ruled out, neither of these 
instances represents a circumstance that would be considered reasonably 
foreseeable or that would be considered preventable.
    Although the likelihood of the vessel striking a marine mammal is 
low, we require a robust ship strike avoidance protocol (see Proposed 
Mitigation), which we believe eliminates any foreseeable risk of ship 
strike. We anticipate that vessel collisions involving a seismic data 
acquisition vessel towing gear, while not impossible, represent 
unlikely, unpredictable events for which there are no preventive 
measures. Given the required mitigation measures, the relatively slow 
speed of the vessel towing gear, the presence of bridge crew watching 
for obstacles at all times (including marine mammals), and the presence 
of marine mammal observers, we believe that the possibility of ship 
strike is discountable and, further, that were a strike of a large 
whale to occur, it would be unlikely to result in serious injury or 
mortality. No incidental take resulting from ship strike is 
anticipated, and this potential effect of the specified activity will 
not be discussed further in the following analysis.
    Stranding--When a living or dead marine mammal swims or floats onto 
shore and becomes ``beached'' or incapable of returning to sea, the 
event is a ``stranding'' (Geraci et al., 1999; Perrin and Geraci, 2002; 
Geraci and Lounsbury, 2005; NMFS, 2007). The legal definition for a 
stranding under the MMPA is that (A) a marine mammal is dead and is (i) 
on a beach or shore of the United States; or (ii) in waters under the 
jurisdiction of the United States (including any navigable waters); or 
(B) a marine mammal is alive and is (i) on a beach or shore of the 
United States and is unable to return to the water; (ii) on a beach or 
shore of the United States and, although able to return to the water, 
is in need of apparent medical attention; or (iii) in the waters under 
the jurisdiction of the United States (including any navigable waters), 
but is unable to return to its natural habitat under its own power or 
without assistance.
    Marine mammals strand for a variety of reasons, such as infectious 
agents, biotoxicosis, starvation, fishery interaction, ship strike, 
unusual oceanographic or weather events, sound exposure, or 
combinations of these stressors sustained concurrently or in series. 
However, the cause or causes of most strandings are unknown (Geraci et 
al., 1976; Eaton, 1979; Odell et al., 1980; Best, 1982). Numerous 
studies suggest that the physiology, behavior, habitat relationships, 
age, or condition of cetaceans may cause them to strand or might pre-
dispose them to strand when exposed to another phenomenon. These 
suggestions are consistent with the conclusions of numerous other 
studies that have demonstrated that combinations of dissimilar 
stressors commonly combine to kill an animal or dramatically reduce its 
fitness, even though one exposure without the other does not produce 
the same result (Chroussos, 2000; Creel, 2005; DeVries et al., 2003; 
Fair and Becker, 2000; Foley et al., 2001; Moberg, 2000; Relyea,

[[Page 39915]]

2005a; 2005b, Romero, 2004; Sih et al., 2004).
    Use of military tactical sonar has been implicated in a majority of 
investigated stranding events. Most known stranding events have 
involved beaked whales, though a small number have involved deep-diving 
delphinids or sperm whales (e.g., Mazzariol et al., 2010; Southall et 
al., 2013). In general, long duration (~1 second) and high-intensity 
sounds (>235 dB SPL) have been implicated in stranding events 
(Hildebrand, 2004). With regard to beaked whales, mid-frequency sound 
is typically implicated (when causation can be determined) (Hildebrand, 
2004). Although seismic airguns create predominantly low-frequency 
energy, the signal does include a mid-frequency component. We have 
considered the potential for the proposed surveys to result in marine 
mammal stranding and have concluded that, based on the best available 
information, stranding is not expected to occur.
    Effects to Prey--Marine mammal prey varies by species, season, and 
location and, for some, is not well documented. Fish react to sounds 
which are especially strong and/or intermittent low-frequency sounds. 
Short duration, sharp sounds can cause overt or subtle changes in fish 
behavior and local distribution. Hastings and Popper (2005) identified 
several studies that suggest fish may relocate to avoid certain areas 
of sound energy. Additional studies have documented effects of pulsed 
sound on fish, although several are based on studies in support of 
construction projects (e.g., Scholik and Yan, 2001, 2002; Popper and 
Hastings, 2009). Sound pulses at received levels of 160 dB may cause 
subtle changes in fish behavior. SPLs of 180 dB may cause noticeable 
changes in behavior (Pearson et al., 1992; Skalski et al., 1992). SPLs 
of sufficient strength have been known to cause injury to fish and fish 
mortality. The most likely impact to fish from survey activities at the 
project area would be temporary avoidance of the area. The duration of 
fish avoidance of a given area after survey effort stops is unknown, 
but a rapid return to normal recruitment, distribution and behavior is 
anticipated.
    Information on seismic airgun impacts to zooplankton, which 
represent an important prey type for mysticetes, is limited. However, 
McCauley et al. (2017) reported that experimental exposure to a pulse 
from a 150 inch\3\ airgun decreased zooplankton abundance when compared 
with controls, as measured by sonar and net tows, and caused a two- to 
threefold increase in dead adult and larval zooplankton. Although no 
adult krill were present, the study found that all larval krill were 
killed after air gun passage. Impacts were observed out to the maximum 
1.2 km range sampled.
    In general, impacts to marine mammal prey are expected to be 
limited due to the relatively small temporal and spatial overlap 
between the proposed survey and any areas used by marine mammal prey 
species. The proposed use of airguns as part of an active seismic array 
survey would occur over a relatively short time period (~28 days) and 
would occur over a very small area relative to the area available as 
marine mammal habitat in the Southwest Atlantic Ocean. We believe any 
impacts to marine mammals due to adverse effects to their prey would be 
insignificant due to the limited spatial and temporal impact of the 
proposed survey. However, adverse impacts may occur to a few species of 
fish and to zooplankton.
    Acoustic Habitat--Acoustic habitat is the soundscape--which 
encompasses all of the sound present in a particular location and time, 
as a whole--when considered from the perspective of the animals 
experiencing it. Animals produce sound for, or listen for sounds 
produced by, conspecifics (communication during feeding, mating, and 
other social activities), other animals (finding prey or avoiding 
predators), and the physical environment (finding suitable habitats, 
navigating). Together, sounds made by animals and the geophysical 
environment (e.g., produced by earthquakes, lightning, wind, rain, 
waves) make up the natural contributions to the total acoustics of a 
place. These acoustic conditions, termed acoustic habitat, are one 
attribute of an animal's total habitat.
    Soundscapes are also defined by, and acoustic habitat influenced 
by, the total contribution of anthropogenic sound. This may include 
incidental emissions from sources such as vessel traffic, or may be 
intentionally introduced to the marine environment for data acquisition 
purposes (as in the use of airgun arrays). Anthropogenic noise varies 
widely in its frequency content, duration, and loudness and these 
characteristics greatly influence the potential habitat-mediated 
effects to marine mammals (please see also the previous discussion on 
masking under ``Acoustic Effects''), which may range from local effects 
for brief periods of time to chronic effects over large areas and for 
long durations. Depending on the extent of effects to habitat, animals 
may alter their communications signals (thereby potentially expending 
additional energy) or miss acoustic cues (either conspecific or 
adventitious). For more detail on these concepts see, e.g., Barber et 
al., 2010; Pijanowski et al., 2011; Francis and Barber, 2013; Lillis et 
al., 2014.
    Problems arising from a failure to detect cues are more likely to 
occur when noise stimuli are chronic and overlap with biologically 
relevant cues used for communication, orientation, and predator/prey 
detection (Francis and Barber, 2013). Although the signals emitted by 
seismic airgun arrays are generally low frequency, they would also 
likely be of short duration and transient in any given area due to the 
nature of these surveys. As described previously, exploratory surveys 
such as this one cover a large area but would be transient rather than 
focused in a given location over time and therefore would not be 
considered chronic in any given location.
    In summary, activities associated with the proposed action are not 
likely to have a permanent, adverse effect on any fish habitat or 
populations of fish species or on the quality of acoustic habitat. 
Thus, any impacts to marine mammal habitat are not expected to cause 
significant or long-term consequences for individual marine mammals or 
their populations.

Estimated Take

    This section provides an estimate of the number of incidental takes 
proposed for authorization through this IHA, which will inform both 
NMFS' consideration of ``small numbers'' and the negligible impact 
determination.
    Harassment is the only type of take expected to result from these 
activities. Except with respect to certain activities not pertinent 
here, section 3(18) of the MMPA defines ``harassment'' as any act of 
pursuit, torment, or annoyance, which (i) has the potential to injure a 
marine mammal or marine mammal stock in the wild (Level A harassment); 
or (ii) has the potential to disturb a marine mammal or marine mammal 
stock in the wild by causing disruption of behavioral patterns, 
including, but not limited to, migration, breathing, nursing, breeding, 
feeding, or sheltering (Level B harassment).
    Authorized takes would be by Level B harassment only, as use of the 
acoustic sources (i.e., seismic airgun) has the potential to result in 
disruption of behavioral patterns for individual marine mammals. Based 
on the nature of the activity and the anticipated effectiveness of the 
mitigation measures (i.e., marine mammal exclusion zones) discussed in 
detail below in Proposed Mitigation section, Level A harassment is 
neither anticipated nor proposed to be

[[Page 39916]]

authorized. As described previously, no mortality is anticipated or 
proposed to be authorized for this activity. Below we describe how the 
take is estimated.
    Generally speaking, we estimate take by considering: (1) Acoustic 
thresholds above which NMFS believes the best available science 
indicates marine mammals will be behaviorally harassed or incur some 
degree of permanent hearing impairment; (2) the area or volume of water 
that will be ensonified above these levels in a day; (3) the density or 
occurrence of marine mammals within these ensonified areas; and, (4) 
and the number of days of activities. We note that while these basic 
factors can contribute to a basic calculation to provide an initial 
prediction of takes, additional information that can qualitatively 
inform take estimates is also sometimes available (e.g., previous 
monitoring results or average group size). Below, we describe the 
factors considered here in more detail and present the proposed take 
estimate.

Acoustic Thresholds

    Using the best available science, NMFS has developed acoustic 
thresholds that identify the received level of underwater sound above 
which exposed marine mammals would be reasonably expected to be 
behaviorally harassed (equated to Level B harassment) or to incur PTS 
of some degree (equated to Level A harassment).
    Level B Harassment for non-explosive sources--Though significantly 
driven by received level, the onset of behavioral disturbance from 
anthropogenic noise exposure is also informed to varying degrees by 
other factors related to the source (e.g., frequency, predictability, 
duty cycle), the environment (e.g., bathymetry), and the receiving 
animals (hearing, motivation, experience, demography, behavioral 
context) and can be difficult to predict (Southall et al., 2007, 
Ellison et al., 2012). Based on what the available science indicates, 
and the practical need to use a threshold based on a factor that is 
both predictable and measurable for most activities, NMFS uses a 
generalized acoustic threshold based on received level to estimate the 
onset of behavioral harassment. NMFS predicts that marine mammals are 
likely to be behaviorally harassed in a manner we consider Level B 
harassment when exposed to underwater anthropogenic noise above 
received levels of 120 dB re 1 [mu]Pa (rms) for continuous (e.g., 
vibratory pile-driving, drilling) and above 160 dB re 1 [mu]Pa (rms) 
for non-explosive impulsive (e.g., seismic airguns) or intermittent 
(e.g., scientific sonar) sources.
    SIO's proposed activity includes the use of impulsive seismic 
sources, and therefore the 160 dB re 1 [mu]Pa (rms) is applicable.
    Level A harassment for non-explosive sources--NMFS' Technical 
Guidance for Assessing the Effects of Anthropogenic Sound on Marine 
Mammal Hearing (Version 2.0) (Technical Guidance, 2018) identifies dual 
criteria to assess auditory injury (Level A harassment) to five 
different marine mammal groups (based on hearing sensitivity) as a 
result of exposure to noise from two different types of sources 
(impulsive or non-impulsive). SIO's proposed activity includes the use 
of impulsive seismic sources.
    These thresholds are provided in the table below. The references, 
analysis, and methodology used in the development of the thresholds are 
described in NMFS 2018 Technical Guidance, which may be accessed at 
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.

                     Table 4--Thresholds Identifying the Onset of Permanent Threshold Shift
----------------------------------------------------------------------------------------------------------------
                                                     PTS onset acoustic thresholds * (received level)
             Hearing group              ------------------------------------------------------------------------
                                                  Impulsive                         Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans...........  Cell 1: Lpk,flat: 219 dB;   Cell 2: LE,LF,24h: 199 dB.
                                          LE,LF,24h: 183 dB.
Mid-Frequency (MF) Cetaceans...........  Cell 3: Lpk,flat: 230 dB;   Cell 4: LE,MF,24h: 198 dB.
                                          LE,MF,24h: 185 dB.
High-Frequency (HF) Cetaceans..........  Cell 5: Lpk,flat: 202 dB;   Cell 6: LE,HF,24h: 173 dB.
                                          LE,HF,24h: 155 dB.
Phocid Pinnipeds (PW) (Underwater).....  Cell 7: Lpk,flat: 218 dB;   Cell 8: LE,PW,24h: 201 dB.
                                          LE,PW,24h: 185 dB.
Otariid Pinnipeds (OW) (Underwater)....  Cell 9: Lpk,flat: 232 dB;   Cell 10: LE,OW,24h: 219 dB.
                                          LE,OW,24h: 203 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for
  calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level
  thresholds associated with impulsive sounds, these thresholds should also be considered.
Note: Peak sound pressure (Lpk) has a reference value of 1 [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.
    The proposed survey would entail the use of a 2-airgun array with a 
total discharge of 90 in\3\ at a two depth of 2-4 m. Lamont-Doherty 
Earth Observatory (L-DEO) model results are used to determine the 160 
dBrms radius for the 2-airgun array in deep water (>1,000 m) 
down to a maximum water depth of 2,000 m. Received sound levels were 
predicted by L-DEO's model (Diebold et al., 2010) as a function of 
distance from the airguns, for the two 45 in\3\ airguns. This modeling 
approach uses ray tracing for the direct wave traveling from the array 
to the receiver and its associated source ghost (reflection at the air-
water interface in the vicinity of the array), in a constant-velocity 
half-space (infinite homogenous ocean layer, unbounded by a seafloor). 
In addition, propagation measurements of pulses from a 36-airgun array 
at a tow depth of 6 m have been reported in deep water (~1,600 m), 
intermediate water depth on the slope (~600-1,100 m), and shallow water 
(~50 m) in the Gulf of Mexico in 2007-2008 (Tolstoy et al., 2009; 
Diebold et al., 2010).
    For deep and intermediate water cases, the field measurements 
cannot be used readily to derive the Level A and

[[Page 39917]]

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, comparisons at short ranges 
between sound levels for direct arrivals recorded by the calibration 
hydrophone and model results for the same array tow depth are in good 
agreement (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. Aside from local topography effects, the region 
around the critical distance is where the observed levels rise closest 
to the model curve. However, the observed sound levels are found to 
fall almost entirely below the model curve. Thus, analysis of the Gulf 
of Mexico calibration measurements demonstrates that although simple, 
the L-DEO model is a robust tool for conservatively estimating 
isopleths.
    The proposed surveys would acquire data with two 45-in\3\ guns at a 
tow depth of 2-4 m. For deep water (>1000 m), we use the deep-water 
radii obtained from L-DEO model results down to a maximum water depth 
of 2000 m for the airgun array with 2-m and 8-m airgun separation. The 
radii for intermediate water depths (100-1000 m) are derived from the 
deep-water ones by applying a correction factor (multiplication) of 
1.5, such that observed levels at very near offsets fall below the 
corrected mitigation curve (see Figure 16 in Appendix H of NSF-USGS 
2011). The shallow-water radii are obtained by scaling the empirically 
derived measurements from the Gulf of Mexico calibration survey to 
account for the differences in source volume and tow depth between the 
calibration survey (6000 in\3\; 6-m tow depth) and the proposed survey 
(90 in\3\; 4-m tow depth); whereas the shallow water in the Gulf of 
Mexico may not exactly replicate the shallow water environment at the 
proposed survey sites, it has been shown to serve as a good and very 
conservative proxy (Crone et al., 2014). A simple scaling factor is 
calculated from the ratios of the isopleths determined by the deep-
water L-DEO model, which are essentially a measure of the energy 
radiated by the source array.
    L-DEO's modeling methodology is described in greater detail in 
SIO's IHA application. The estimated distances to the Level B 
harassment isopleths for the two proposed airgun configurations in each 
water depth category are shown in Table 5.

 Table 5--Predicted Radial Distances From R/V Thompson Seismic Source to
         Isopleths Corresponding to Level B Harassment Threshold
------------------------------------------------------------------------
                                                             Predicted
                                                           distances (m)
          Airgun configuration              Water depth      to 160 dB
                                                (m)       received south
                                                               level
------------------------------------------------------------------------
Two 45 in\3\ guns, 2-m separation.......          >1,000         \a\ 539
                                               100-1,000         \b\ 809
                                                    <100       \c\ 1,295
Two 45 in\3\ guns, 8-m separation.......          >1,000         \a\ 578
                                               100-1,000         \b\ 867
                                                    <100       \c\ 1,400
------------------------------------------------------------------------
\a\ Distance based on L-DEO model results.
\b\ Distance based on L-DEO model results with a 1.5 x correction factor
  between deep and intermediate water depths.
\c\ Distance based on empirically derived measurements in the Gulf of
  Mexico with scaling applied to account for differences in tow depth.

    Predicted distances to Level A harassment isopleths, which vary 
based on marine mammal hearing groups, were calculated based on 
modeling performed by L-DEO using the NUCLEUS software program and the 
NMFS User Spreadsheet, described below. The updated acoustic thresholds 
for impulsive sounds (e.g., airguns) contained in the Technical 
Guidance were presented as dual metric acoustic thresholds using both 
SELcum and peak sound pressure metrics (NMFS 2016a). As dual 
metrics, NMFS considers onset of PTS (Level A harassment) to have 
occurred when either one of the two metrics is exceeded (i.e., metric 
resulting in the largest isopleth). The SELcum metric 
considers both level and duration of exposure, as well as auditory 
weighting functions by marine mammal hearing group. In recognition of 
the fact that the requirement to calculate Level A harassment 
ensonified areas could be more technically challenging to predict due 
to the duration component and the use of weighting functions in the new 
SELcum thresholds, NMFS developed an optional User 
Spreadsheet that includes tools to help predict a simple isopleth that 
can be used in conjunction with marine mammal density or occurrence to 
facilitate the estimation of take numbers.
    The SELcum for the 2-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

[[Page 39918]]

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 we use this method for consistency 
across all array sizes.
    SIO used the same acoustic modeling as Level B harassment with a 
small grid step in both the inline and depth directions to estimate the 
SELcum and peak SPL. The propagation modeling takes into 
account all airgun interactions at short distances from the source 
including interactions between subarrays using the NUCLEUS software to 
estimate the notional signature and the MATLAB software to calculate 
the pressure signal at each mesh point of a grid. For a more complete 
explanation of this modeling approach, please see ``Appendix A: 
Determination of Mitigation Zones'' in SIO's IHA application.

                   Table 6--Modeled Source Levels (dB) for R/V Thompson 90 in\3\ Airgun Arrays
----------------------------------------------------------------------------------------------------------------
                                                    8-kt survey                     5-kt survey
                                                     with 8-m       8-kt survey      with 2-m       5-kt survey
                                                      airgun         with 8-m         airgun         with 2-m
            Functional hearing group                separation:       airgun        separation:       airgun
                                                   Peak SPLflat     separation:    Peak SPLflat     separation:
                                                                      SELcum                          SELcum
----------------------------------------------------------------------------------------------------------------
Low frequency cetaceans (Lpk,flat: 219 dB;                 228.8             207           232.8           206.7
 LE,LF,24h: 183 dB).............................
Mid frequency cetaceans (Lpk,flat: 230 dB;               N/A \1\           206.7           229.8           206.9
 LE,MF,24h: 185 dB).............................
High frequency cetaceans (Lpk,flat: 202 dB;                  233           207.6           232.9           207.2
 LE,HF,24h: 155 dB).............................
Phocid Pinnipeds (Underwater) (Lpk,flat: 218 dB;             230           206.7           232.8           206.9
 LE,HF,24h: 185 dB).............................
Otariid Pinnipeds (Underwater) (Lpk,flat: 232            N/A \1\             203           225.6           207.4
 dB; LE,HF,24h: 203 dB).........................
----------------------------------------------------------------------------------------------------------------
\1\ N/A indicates source level not applicable or not available.

    In order to more realistically incorporate the Technical Guidance's 
weighting functions over the seismic array's full acoustic band, 
unweighted spectrum data for the Thompson's airgun array (modeled in 1 
Hz bands) was used to make adjustments (dB) to the unweighted spectrum 
levels, by frequency, according to the weighting functions for each 
relevant marine mammal hearing group. These adjusted/weighted spectrum 
levels were then converted to pressures ([mu]Pa) in order to integrate 
them over the entire broadband spectrum, resulting in broadband 
weighted source levels by hearing group that could be directly 
incorporated within the User Spreadsheet (i.e., to override the 
Spreadsheet's more simple weighting factor adjustment). Using the User 
Spreadsheet's ``safe distance'' methodology for mobile sources 
(described by Sivle et al., 2014) with the hearing group-specific 
weighted source levels, and inputs assuming spherical spreading 
propagation and source velocities and shot intervals provided in SIO's 
IHA application, potential radial distances to auditory injury zones 
were calculated for SELcum thresholds, for both array 
configurations.
    Inputs to the User Spreadsheet in the form of estimated SLs are 
shown in Table 6. User Spreadsheets used by SIO to estimate distances 
to Level A harassment isopleths for the two potential airgun array 
configurations are shown in Tables A-4 and A-5 in Appendix A of SIO's 
IHA application. Outputs from the User Spreadsheet in the form of 
estimated distances to Level A harassment isopleths are shown in Table 
7. As described above, NMFS considers onset of PTS (Level A harassment) 
to have occurred when either one of the dual metrics (SELcum 
or Peak SPLflat) is exceeded (i.e., metric resulting in the 
largest isopleth).

          Table 7--Modeled Radial Distances to Isopleths Corresponding to Level A Harassment Thresholds
----------------------------------------------------------------------------------------------------------------
                                                    8-kt survey                     5-kt survey
                                                     with 8-m       8-kt survey      with 2-m       5-kt survey
  Functional hearing group (Level A harassment        airgun         with 8-m         airgun         with 2-m
                   thresholds)                      separation:       airgun        separation:       airgun
                                                   Peak SPLflat     separation:    Peak SPLflat     separation:
                                                                      SELcum                          SELcum
----------------------------------------------------------------------------------------------------------------
Low frequency cetaceans (Lpk,fla: 219 dB;                   3.08             2.4            4.89             6.5
 LE,LF,24h: 183 dB).............................
Mid frequency cetaceans (Lpk,flat: 230 dB;                     0               0            0.98               0
 LE,MF,24h: 185 dB).............................
High frequency cetaceans (Lpk,flat: 202 dB;                34.84               0           34.62               0
 LE,HF,24h: 155 dB).............................
Phocid Pinnipeds (Underwater) (Lpk,flat: 218 dB;            4.02               0            5.51             0.1
 LE,HF,24h: 185 dB).............................
Otariid Pinnipeds (Underwater) (Lpk,flat: 232                  0               0            0.48               0
 dB; LE,HF,24h: 203 dB).........................
----------------------------------------------------------------------------------------------------------------

    Note that because of some of the assumptions included in the 
methods used, isopleths produced may be overestimates to some degree, 
which will ultimately result in some degree of overestimate of Level A 
take. However, these tools offer the best way to predict appropriate 
isopleths when more sophisticated 3D modeling methods are not 
available, and NMFS continues to develop ways to quantitatively refine 
these tools and will qualitatively address the output where 
appropriate. For mobile sources, such as the proposed seismic survey, 
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.

[[Page 39919]]

Marine Mammal Occurrence

    In this section we provide the information about the presence, 
density, or group dynamics of marine mammals that will inform the take 
calculations.
    For the proposed survey area in the southwest Atlantic Ocean, SIO 
determined that the preferred source of density data for marine mammal 
species that might be encountered in the project area north of the 
Falklands was AECOM/NSF (2014). For certain species not included in the 
AECOM database, data from the NOAA Southwest Fisheries Science Center 
(SWFSC) Letter of Authorization (LOA) (2013, in AECOM/NSF 2014) was 
used. Better data on hourglass dolphins, southern bottlenose whales, 
and southern elephant seals were found in White et al., (2002). When 
density estimates were not available in the above named sources, 
densities were estimated using sightings and effort during aerial- and 
vessel-based surveys conducted in and adjacent to the proposed project 
area. The three other major sources of animal abundance included White 
et al. (2002), DeTullio et al. (2016) and Garaffo et al. (2011). Data 
sources and density calculations are described in detail in Appendix B 
of SIO's IHA application. For some species, the densities derived from 
past surveys may not be representative of the densities that would be 
encountered during the proposed seismic surveys. However, the approach 
used is based on the best available data. Estimated densities used to 
inform take estimates are presented in Table 8.

      Table 8--Marine Mammal Densities in the Proposed Survey Area
------------------------------------------------------------------------
                                                             Estimated
                         Species                            density (#/
                                                            km\2\) \a\
------------------------------------------------------------------------
                              LF Cetaceans
------------------------------------------------------------------------
Southern right whale....................................         0.00080
Pygmy right whale.......................................            N.A.
Blue whale..............................................         0.00005
Fin whale...............................................         0.01820
Sei whale...............................................         0.00636
Common (dwarf) minke whale..............................         0.07790
Antarctic minke whale...................................         0.07790
Humpback whale..........................................         0.00066
------------------------------------------------------------------------
                              MF Cetaceans
------------------------------------------------------------------------
Sperm whale.............................................         0.00207
Arnoux's beaked whale...................................         0.01138
Cuvier's beaked whale...................................         0.00055
Southern bottlenose whale...............................         0.00791
Shepherd's beaked whale.................................         0.00627
Blainville's beaked whale...............................         0.00005
Gray's beaked whale.....................................         0.00189
Hector's beaked whale...................................         0.00021
True's beaked whale.....................................         0.00005
Strap-toothed beaked whale..............................         0.00058
Andrew's beaked whale...................................         0.00016
Spade-toothed beaked whale..............................         0.00005
Risso's dolphin.........................................         0.00436
Routh-toothed dolphin...................................         0.00595
Common bottlenose dolphin...............................         0.05091
Pantropical spotted dolphin.............................         0.00377
Atlantic spotted dolphin................................         0.22517
Spinner dolphin.........................................         0.01498
Clymene dolphin.........................................         0.01162
Striped dolphin.........................................         0.00719
Short-beaked common dolphin.............................         0.71717
Fraser's dolphin........................................            N.A.
Dusky dolphin...........................................     \b\ 0.12867
Southern right whale dolphin............................         0.00616
Killer whale............................................         0.01538
Short-finned pilot whale................................         0.00209
Long-finned pilot whale.................................         0.21456
False killer whale......................................            N.A.
------------------------------------------------------------------------
                              HF Cetaceans
------------------------------------------------------------------------
Pygmy sperm whale.......................................            N.A.
Dwarf sperm whale.......................................            N.A.
Hourglass dolphin.......................................         0.14871
Peale's dolphin.........................................         0.03014
Commerson's dolphin.....................................     \b\ 0.06763
Spectacled porpoise.....................................     \b\ 0.00150
------------------------------------------------------------------------
                                Otariids
------------------------------------------------------------------------
Antarctic fur seal......................................         0.00017
South American fur seal.................................         0.01642
Subantarctic fur seal...................................         0.00034
South American sea lion.................................         0.00249
------------------------------------------------------------------------
                                 Phocids
------------------------------------------------------------------------
Crabeater seal..........................................         0.00649
Leopard seal............................................         0.00162
Southern elephant seal..................................         0.00155
------------------------------------------------------------------------
N.A. indicates density estimate is not available.
\a\ See Appendix B in SIO's IHA application for density sources.
\b\ Density provided is for shallow water (<100 m depth). A correction
  factor for densities in deeper water was applied (see Appendix B in
  the IHA application).

Take Calculation and Estimation

    Here we describe how the information provided above is brought 
together to produce a quantitative take estimate. In order to estimate 
the number of marine mammals predicted to be exposed to sound levels 
that would result in Level A harassment or Level B harassment, radial 
distances from the airgun array to predicted isopleths corresponding to 
the Level A harassment and Level B harassment thresholds are 
calculated, as described above. Those radial distances are then used to 
calculate the area(s) around the airgun array predicted to be 
ensonified to sound levels that exceed the Level A harassment and Level 
B harassment thresholds. The area estimated to be ensonified in a 
single day of the survey is then calculated (Table 9), based on the 
areas predicted to be ensonified around the array and the estimated 
trackline distance traveled per day. This number is then multiplied by 
the number of survey days. The product is then multiplied by 1.25 to 
account for the additional 25 percent contingency. This results in an 
estimate of the total area (km\2\) expected to be ensonified to the 
Level A and Level B harassment thresholds for each survey type (Table 
9).

                                  Table 9--Areas (km\2\) To Be Ensonified to Level A and Level B Harassment Thresholds
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                               Daily                                           Total
                Survey type                           Criteria               Relevant       ensonified     Total survey     25 percent      ensonified
                                                                           isopleth (m)    area (km\2\)        days          increase      area (km\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                     Level B Harassment (160 dB)
                                           -------------------------------------------------------------------------------------------------------------
5-kt survey...............................  Shallow water...............             539            18.8              16            1.25             376
                                            Intermediate water..........             809          147.32              16            1.25          2946.4
                                            Deep water..................            1295          133.44              16            1.25          2668.8
                                           -------------------------------------------------------------------------------------------------------------
                                                                                         Level A Harassment
                                           -------------------------------------------------------------------------------------------------------------
                                            LF cetacean.................             6.5            2.89              16            1.25            57.8

[[Page 39920]]

 
                                            MF cetacean.................               1            0.44              16            1.25             8.8
                                            HF cetacean.................            34.6           15.37              16            1.25           307.4
                                            Phocids.....................             5.5            2.44              16            1.25            48.8
                                            Otariids....................             0.5            0.22              16            1.25             4.4
                                           -------------------------------------------------------------------------------------------------------------
                                                                                     Level B Harassment (160 dB)
                                           -------------------------------------------------------------------------------------------------------------
8-kt survey...............................  Shallow water...............             578           25.64              12            1.25           384.6
                                            Intermediate water..........             867          284.93              12            1.25         4273.95
                                            Deep water..................            1400          220.58              12            1.25          3308.7
                                           -------------------------------------------------------------------------------------------------------------
                                                                                         Level A Harassment
                                           -------------------------------------------------------------------------------------------------------------
                                            LF cetacean.................             3.1            2.22              12            1.25            33.3
                                            MF cetacean.................               0               0              12            1.25               0
                                            HF cetacean.................            34.8           24.93              12            1.25          373.95
                                            Phocids.....................               4            2.86              12            1.25            42.9
                                            Otariids....................               0               0              12            1.25               0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The total ensonified areas (km\2\) for each criteria presented in 
Table 9 were summed to determine the total ensonified area for all 
survey activities (Table 10).

        Table 10--Total Ensonified Areas (km\2\) for All Surveys
------------------------------------------------------------------------
                                                                Total
                                                              ensonified
                          Criteria                               area
                                                             (km\2\) for
                                                             all surveys
------------------------------------------------------------------------
160 dB Level B (all depths)................................    13,958.45
160 dB Level B (shallow water).............................       760.60
160 dB Level B (intermediate water)........................     7,220.35
160 dB Level B (deep water)................................     5,977.50
LF cetacean Level A........................................        91.10
MF cetacean Level A........................................         8.80
HF cetacean Level A........................................       681.35
Phocids Level A............................................        91.70
Otariids Level A...........................................         4.40
------------------------------------------------------------------------

    The marine mammals predicted to occur within these respective 
areas, based on estimated densities (Table 8), are assumed to be 
incidentally taken. While some takes by Level A harassment have been 
estimated, based on the nature of the activity and in consideration of 
the proposed mitigation measures (see Proposed Mitigation section 
below), Level A take is not expected to occur and has not been proposed 
to be authorized. Estimated exposures for the proposed survey are shown 
in Table 11.

                            Table 11--Calculated and Proposed Level A and Level B Exposures, and Percentage of Stock Exposed
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Calculated      Calculated    Proposed level  Proposed level                    Percent of
                         Species                              level B         level A            B               A          Total take      population
--------------------------------------------------------------------------------------------------------------------------------------------------------
LF Cetaceans:
    Southern right whale................................              11               0              11               0              11             0.3
    Pygmy right whale...................................  ..............  ..............           \a\ 2               0               2  ..............
    Blue whale..........................................               1               0           \a\ 3               0               3            <0.1
    Fin whale...........................................             252               2             254               0             254             1.7
    Sei whale...........................................              88               1              89               0              89             0.9
    Common (dwarf) minke whale..........................            1080               7            1087               0            1087             0.2
    Antarctic minke whale...............................            1080               7            1087               0            1087             0.2
    Humpback whale......................................               9               0               9               0               9            <0.1
MF Cetaceans:
    Sperm whale.........................................              29               0              29               0              29             0.2
    Arnoux's beaked whale...............................             159               0             159               0             159            <0.1
    Cuvier's beaked whale...............................               8               0               8               0               8            <0.1
    Southern bottlenose whale...........................             110               0             110               0             110            <0.1
    Shepherd's beaked whale.............................              88               0              88               0              88  ..............
    Blainville's beaked whale...........................               1               0           \a\ 1               0               1  ..............
    Gray's beaked whale.................................              26               0              26               0              26            <0.1
    Hector's beaked whale...............................               3               0               3               0               3  ..............
    True's beaked whale.................................               1               0           \a\ 2               0               2  ..............
    Strap-toothed beaked whale..........................               8               0               8               0               8            <0.1
    Andrew's beaked whale...............................               2               0           \a\ 2               0               2  ..............
    Spade-toothed beaked whale..........................               1               0  ..............               0               2  ..............
    Risso's dolphin.....................................              61               0              61               0              61             0.3
    Rough-toothed dolphin...............................              83               0              83               0              83  ..............
    Common bottlenose dolphin...........................             711               0             711               0             711             0.9
    Pantropical spotted dolphin.........................              53               0              53               0              53             1.6

[[Page 39921]]

 
    Atlantic spotted dolphin............................            3143               0            3143               0            3143             7.0
    Spinner dolphin.....................................             209               0             209               0             209  ..............
    Clymene dolphin.....................................             162               0             162               0             162  ..............
    Striped dolphin.....................................             100               0             100               0             100             0.2
    Short-beaked common dolphin.........................          10,004               6           10010               0           10010            14.3
    Fraser's dolphin....................................  ..............  ..............         \a\ 283               0             283  ..............
    Dusky dolphin.......................................            1034               1            1035               0            1035            14.3
    Southern right whale dolphin........................              86               0              86               0              86  ..............
    Killer whale........................................             215               0             215               0             215             0.9
    Short-finned pilot whale............................              29               0          \a\ 41               0              41            <0.1
    Long-finned pilot whale.............................            2993               2            2995               0            2995             1.5
    False killer whale..................................  ..............  ..............           \a\ 5               0               5  ..............
HF Cetaceans:
    Pygmy sperm whale...................................  ..............  ..............           \b\ 2               0               2  ..............
    Dwarf sperm whale...................................  ..............  ..............           \b\ 2               0               2  ..............
    Hourglass dolphin...................................            1975             101            2076               0            2076             1.4
    Peale's dolphin.....................................             400              21             421               0             421             2.1
    Commerson's dolphin.................................              94              46             140               0             140             0.7
    Spectacled porpoise.................................               2               1               3               0               3  ..............
Otariids:
    Antarctic fur seal..................................               2               0               2               0               2            <0.1
    South American fur seal.............................             229               0             229               0             229             0.2
    Subantarctic fur seal...............................               5               0               5               0               5            <0.1
    South American sea lion.............................              35               0              35               0              35            <0.1
Phocids:
    Crabeater seal......................................              90               1              91               0              91            <0.1
    Leopard seal........................................              23               0              23               0              23            <0.1
    Southern elephant seal..............................              22               0              22               0              22            <0.1
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Proposed take increased to mean group size from Bradford (2017) if available. Mean group sizes for pygmy right whale and false killer whale from
  Jefferson et al. (2015) and Mobley et al. (2000), respectively.
\b\ Proposed take increased to maximum group size from Barlow (2016).

    It should be noted that the proposed take numbers shown in Table 9 
are expected to be conservative for several reasons. First, in the 
calculations of estimated take, 25 percent has been added in the form 
of operational survey days to account for the possibility of additional 
seismic operations associated with airgun testing and repeat coverage 
of any areas where initial data quality is sub-standard, and in 
recognition of the uncertainties in the density estimates used to 
estimate take as described above. Additionally, marine mammals would be 
expected to move away from a loud sound source that represents an 
aversive stimulus, such as an airgun array, potentially reducing the 
likelihood of takes by Level A harassment. However, the extent to which 
marine mammals would move away from the sound source is difficult to 
quantify and is, therefore, not accounted for in the take estimates.

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 such 
activity, and other means of effecting the least practicable impact on 
such species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of such 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 such 
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.
    SIO has reviewed mitigation measures employed during seismic 
research surveys authorized by NMFS under previous incidental 
harassment authorizations, as well as recommended best practices in 
Richardson et al. (1995), Pierson et al. (1998), Weir and Dolman 
(2007), Nowacek et al. (2013), Wright (2014), and Wright and Cosentino 
(2015), and has incorporated a suite of proposed mitigation measures 
into their project description based on the above sources.
    To reduce the potential for disturbance from acoustic stimuli

[[Page 39922]]

associated with the activities, SIO has proposed to implement 
mitigation measures for marine mammals. Mitigation measures that would 
be adopted during the proposed surveys include (1) Vessel-based visual 
mitigation monitoring; (2) Establishment of a marine mammal exclusion 
zone (EZ) and buffer zone; (3) shutdown procedures; (4) ramp-up 
procedures; and (4) vessel strike avoidance measures.

Vessel-Based Visual Mitigation Monitoring

    Visual monitoring requires the use of trained observers (herein 
referred to as visual PSOs) to scan the ocean surface visually for the 
presence of marine mammals. PSO observations would take place during 
all daytime airgun operations and nighttime start ups (if applicable) 
of the airguns. If airguns are operating throughout the night, 
observations would begin 30 minutes prior to sunrise. If airguns are 
operating after sunset, observations would continue until 30 minutes 
following sunset. Following a shutdown for any reason, observations 
would occur for at least 30 minutes prior to the planned start of 
airgun operations. Observations would also occur for 30 minutes after 
airgun operations cease for any reason. Observations would also be made 
during daytime periods when the Thompson is underway without seismic 
operations, such as during transits, to allow for comparison of 
sighting rates and behavior with and without airgun operations and 
between acquisition periods. Airgun operations would be suspended when 
marine mammals are observed within, or about to enter, the designated 
EZ (as described below).
    During seismic operations, three visual PSOs would be based aboard 
the Thompson. PSOs would be appointed by SIO with NMFS approval. One 
dedicated PSO would monitor the EZ during all daytime seismic 
operations. PSO(s) would be on duty in shifts of duration no longer 
than 4 hours. Other vessel crew would also be instructed to assist in 
detecting marine mammals and in implementing mitigation requirements 
(if practical). Before the start of the seismic survey, the crew would 
be given additional instruction in detecting marine mammals and 
implementing mitigation requirements.
    The Thompson is a suitable platform from which PSOs would watch for 
marine mammals. Standard equipment for marine mammal observers would be 
7 x 50 reticule binoculars and optical range finders. At night, night-
vision equipment would be available. The observers would be in 
communication with ship's officers on the bridge and scientists in the 
vessel's operations laboratory, so they can advise promptly of the need 
for avoidance maneuvers or seismic source shutdown.
    The PSOs must have no tasks other than to conduct observational 
effort, record observational data, and communicate with and instruct 
relevant vessel crew with regard to the presence of marine mammals and 
mitigation requirements. PSO resumes shall be provided to NMFS for 
approval. At least one PSO must have a minimum of 90 days at-sea 
experience working as PSOs during a seismic survey. One ``experienced'' 
visual PSO will be designated as the lead for the entire protected 
species observation team. The lead will serve as primary point of 
contact for the vessel operator.

Exclusion Zone and Buffer Zone

    An EZ is a defined area within which occurrence of a marine mammal 
triggers mitigation action intended to reduce the potential for certain 
outcomes, e.g., auditory injury, disruption of critical behaviors. The 
PSOs would establish a minimum EZ with a 100 m radius for the airgun 
array. The 100-m EZ would be based on radial distance from any element 
of the airgun array (rather than being based on the center of the array 
or around the vessel itself). With certain exceptions (described 
below), if a marine mammal appears within, enters, or appears on a 
course to enter this zone, the acoustic source would be shut down (see 
Shutdown Procedures below).
    The 100-m radial distance of the standard EZ is precautionary in 
the sense that it would be expected to contain sound exceeding injury 
criteria for all marine mammal hearing groups (Table 7) while also 
providing a consistent, reasonably observable zone within which PSOs 
would typically be able to conduct effective observational effort. In 
this case, the 100-m radial distance would also be expected to contain 
sound that would exceed the Level A harassment threshold based on sound 
exposure level (SELcum) criteria for all marine mammal 
hearing groups (Table 7). In the 2011 Programmatic Environmental Impact 
Statement for marine scientific research funded by the National Science 
Foundation or the U.S. Geological Survey (NSF-USGS 2011), Alternative B 
(the Preferred Alternative) conservatively applied a 100-m EZ for all 
low-energy acoustic sources in water depths >100 m, with low-energy 
acoustic sources defined as any towed acoustic source with a single or 
a pair of clustered airguns with individual volumes of <=250 in\3\. 
Thus the 100-m EZ proposed for this survey is consistent with the PEIS.
    Our intent in prescribing a standard EZ distance is to (1) 
encompass zones within which auditory injury could occur on the basis 
of instantaneous exposure; (2) provide additional protection from the 
potential for more severe behavioral reactions (e.g., panic, 
antipredator response) for marine mammals at relatively close range to 
the acoustic source; (3) provide consistency for PSOs, who need to 
monitor and implement the EZ; and (4) define a distance within which 
detection probabilities are reasonably high for most species under 
typical conditions.
    PSOs will also establish and monitor a 200-m buffer zone. During 
use of the acoustic source, occurrence of marine mammals within the 
buffer zone (but outside the EZ) will be communicated to the operator 
to prepare for potential shutdown of the acoustic source. The buffer 
zone is discussed further under Ramp Up Procedures below.
    An extended EZ of 500 m would be enforced for all beaked whales, 
Kogia species, and Southern right whales. SIO would also enforce a 500-
m EZ for aggregations of six or more large whales (i.e., sperm whale or 
any baleen whale) that does not appear to be traveling (e.g., feeding, 
socializing, etc.) or a large whale with a calf (calf defined as an 
animal less than two-thirds the body size of an adult observed to be in 
close association with an adult).

Shutdown Procedures

    If a marine mammal is detected outside the EZ but is likely to 
enter the EZ, the airguns would be shut down before the animal is 
within the EZ. Likewise, if a marine mammal is already within the EZ 
when first detected, the airguns would be shut down immediately.
    Following a shutdown, airgun activity would not resume until the 
marine mammal has cleared the 100-m EZ. The animal would be considered 
to have cleared the 100-m EZ if the following conditions have been met:
     It is visually observed to have departed the 100-m EZ;
     it has not been seen within the 100-m EZ for 15 min in the 
case of small odontocetes and pinnipeds; or
     it has not been seen within the 100-m EZ for 30 min in the 
case of mysticetes and large odontocetes, including sperm, pygmy sperm, 
and beaked whales.
    This shutdown requirement would be in place for all marine mammals, 
with the exception of small delphinoids under certain circumstances. As 
defined here, the small delphinoid group is

[[Page 39923]]

intended to encompass those members of the Family Delphinidae most 
likely to voluntarily approach the source vessel for purposes of 
interacting with the vessel and/or airgun array (e.g., bow riding). 
This exception to the shutdown requirement would apply solely to 
specific genera of small dolphins--Delphinus, Lagenodelphis, 
Lagenorhynchus, Lissodelphis, Stenella, Steno, and Tursiops--and would 
only apply if the animals were traveling, including approaching the 
vessel. If, for example, an animal or group of animals is stationary 
for some reason (e.g., feeding) and the source vessel approaches the 
animals, the shutdown requirement applies. An animal with sufficient 
incentive to remain in an area rather than avoid an otherwise aversive 
stimulus could either incur auditory injury or disruption of important 
behavior. If there is uncertainty regarding identification (i.e., 
whether the observed animal(s) belongs to the group described above) or 
whether the animals are traveling, the shutdown would be implemented.
    We include this small delphinoid exception because shutdown 
requirements for small delphinoids under all circumstances represent 
practicability concerns without likely commensurate benefits for the 
animals in question. Small delphinoids are generally the most commonly 
observed marine mammals in the specific geographic region and would 
typically be the only marine mammals likely to intentionally approach 
the vessel. As described above, auditory injury is extremely unlikely 
to occur for mid-frequency cetaceans (e.g., delphinids), as this group 
is relatively insensitive to sound produced at the predominant 
frequencies in an airgun pulse while also having a relatively high 
threshold for the onset of auditory injury (i.e., permanent threshold 
shift).
    A large body of anecdotal evidence indicates that small delphinoids 
commonly approach vessels and/or towed arrays during active sound 
production for purposes of bow riding, with no apparent effect observed 
in those delphinoids (e.g., Barkaszi et al., 2012). The potential for 
increased shutdowns resulting from such a measure would require the 
Thompson to revisit the missed track line to reacquire data, resulting 
in an overall increase in the total sound energy input to the marine 
environment and an increase in the total duration over which the survey 
is active in a given area. Although other mid-frequency hearing 
specialists (e.g., large delphinoids) are no more likely to incur 
auditory injury than are small delphinoids, they are much less likely 
to approach vessels. Therefore, retaining a power-down/shutdown 
requirement for large delphinoids would not have similar impacts in 
terms of either practicability for the applicant or corollary increase 
in sound energy output and time on the water. We do anticipate some 
benefit for a shutdown requirement for large delphinoids in that it 
simplifies somewhat the total range of decision-making for PSOs and may 
preclude any potential for physiological effects other than to the 
auditory system as well as some more severe behavioral reactions for 
any such animals in close proximity to the source vessel.
    Shutdown of the acoustic source would also be required upon 
observation of a species for which authorization has not been granted, 
or a species for which authorization has been granted but the 
authorized number of takes are met, observed approaching or within the 
Level A or Level B harassment zones.

Ramp-Up Procedures

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

Vessel Strike Avoidance Measures

    Vessel strike avoidance measures are intended to minimize the 
potential for collisions with marine mammals. These requirements do not 
apply in any case where compliance would create an imminent and serious 
threat to a person or vessel or to the extent that a vessel is 
restricted in its ability to maneuver and, because of the restriction, 
cannot comply.
    The proposed measures include the following: Vessel operator and 
crew would maintain a vigilant watch for all marine mammals and slow 
down or stop the vessel or alter course to avoid striking any marine 
mammal. A visual observer aboard the vessel would monitor a vessel 
strike avoidance zone around the vessel according to the parameters 
stated below. Visual observers monitoring the vessel strike avoidance 
zone would be either third-party observers or crew members, but crew 
members responsible for these duties would be provided sufficient 
training to distinguish marine mammals from other phenomena. Vessel 
strike avoidance measures would be followed during surveys and while in 
transit.

[[Page 39924]]

    The vessel would maintain a minimum separation distance of 100 m 
from large whales (i.e., baleen whales and sperm whales). If a large 
whale is within 100 m of the vessel, the vessel would reduce speed and 
shift the engine to neutral, and would not engage the engines until the 
whale has moved outside of the vessel's path and the minimum separation 
distance has been established. If the vessel is stationary, the vessel 
would not engage engines until the whale(s) has moved out of the 
vessel's path and beyond 100 m. The vessel would maintain a minimum 
separation distance of 50 m from all other marine mammals (with the 
exception of delphinids of the genera Delphinus, Lagenodelphis, 
Lagenorhynchus, Lissodelphis, Stenella, Steno, and Tursiops that 
approach the vessel, as described above). If an animal is encountered 
during transit, the vessel would attempt to remain parallel to the 
animal's course, avoiding excessive speed or abrupt changes in course. 
Vessel speeds would be reduced to 10 kt or less when mother/calf pairs, 
pods, or large assemblages of cetaceans are observed near the vessel.
    Based on our evaluation of the applicant's proposed measures, NMFS 
has preliminarily determined that the proposed mitigation measures 
provide the means effecting the least practicable impact on the 
affected species or stocks and their habitat, paying particular 
attention to rookeries, mating grounds, and areas of similar 
significance.

Proposed Monitoring and Reporting

    In order to issue an IHA for an activity, Section 101(a)(5)(D) of 
the MMPA states that NMFS must set forth requirements pertaining to the 
monitoring and reporting of such taking. The MMPA implementing 
regulations at 50 CFR 216.104 (a)(13) indicate that requests for 
authorizations must include the suggested means of accomplishing the 
necessary monitoring and reporting that will result in increased 
knowledge of the species and of the level of taking or impacts on 
populations of marine mammals that are expected to be present in the 
proposed action area. Effective reporting is critical both to 
compliance as well as ensuring that the most value is obtained from the 
required monitoring.
    Monitoring and reporting requirements prescribed by NMFS should 
contribute to improved understanding of one or more of the following:
     Occurrence of marine mammal species or stocks in the area 
in which take is anticipated (e.g., presence, abundance, distribution, 
density).
     Nature, scope, or context of likely marine mammal exposure 
to potential stressors/impacts (individual or cumulative, acute or 
chronic), through better understanding of: (1) Action or environment 
(e.g., source characterization, propagation, ambient noise); (2) 
affected species (e.g., life history, dive patterns); (3) co-occurrence 
of marine mammal species with the action; or (4) biological or 
behavioral context of exposure (e.g., age, calving or feeding areas).
     Individual marine mammal responses (behavioral or 
physiological) to acoustic stressors (acute, chronic, or cumulative), 
other stressors, or cumulative impacts from multiple stressors.
     How anticipated responses to stressors impact either: (1) 
Long-term fitness and survival of individual marine mammals; or (2) 
populations, species, or stocks.
     Effects on marine mammal habitat (e.g., marine mammal prey 
species, acoustic habitat, or other important physical components of 
marine mammal habitat).
     Mitigation and monitoring effectiveness.
    SIO submitted a marine mammal monitoring and reporting plan in 
their IHA application. Monitoring that is designed specifically to 
facilitate mitigation measures, such as monitoring of the EZ to inform 
potential shutdowns of the airgun array, are described above and are 
not repeated here. SIO's monitoring and reporting plan includes the 
following measures:

Vessel-Based Visual Monitoring

    As described above, PSO observations would take place during 
daytime airgun operations and nighttime start-ups (if applicable) of 
the airguns. During seismic operations, three visual PSOs would be 
based aboard the Thompson. PSOs would be appointed by SIO with NMFS 
approval. The PSOs must have successfully completed relevant training, 
including completion of all required coursework and passing a written 
and/or oral examination developed for the training program, and must 
have successfully attained a bachelor's degree from an accredited 
college or university with a major in one of the natural sciences and a 
minimum of 30 semester hours or equivalent in the biological sciences 
and at least one undergraduate course in math or statistics. The 
educational requirements may be waived if the PSO has acquired the 
relevant skills through alternate training, including (1) secondary 
education and/or experience comparable to PSO duties; (2) previous work 
experience conducting academic, commercial, or government-sponsored 
marine mammal surveys; or (3) previous work experience as a PSO; the 
PSO should demonstrate good standing and consistently good performance 
of PSO duties.
    During the majority of seismic operations, one PSO would monitor 
for marine mammals around the seismic vessel. PSOs would be on duty in 
shifts of duration no longer than 4 hours. Other crew would also be 
instructed to assist in detecting marine mammals and in implementing 
mitigation requirements (if practical). During daytime, PSOs would scan 
the area around the vessel systematically with reticle binoculars 
(e.g., 7x50 Fujinon) and with the naked eye. At night, PSOs would be 
equipped with night-vision equipment.
    PSOs would record data to estimate the numbers of marine mammals 
exposed to various received sound levels and to document apparent 
disturbance reactions or lack thereof. Data would be used to estimate 
numbers of animals potentially `taken' by harassment (as defined in the 
MMPA). They would also provide information needed to order a shutdown 
of the airguns when a marine mammal is within or near the EZ. When a 
sighting is made, the following information about the sighting would be 
recorded:
    (1) Species, group size, age/size/sex categories (if determinable), 
behavior when first sighted and after initial sighting, heading (if 
consistent), bearing and distance from seismic vessel, sighting cue, 
apparent reaction to the airguns or vessel (e.g., none, avoidance, 
approach, paralleling, etc.), and behavioral pace; and
    (2) Time, location, heading, speed, activity of the vessel, sea 
state, visibility, and sun glare.
    All observations and shutdowns would be recorded in a standardized 
format. Data would be entered into an electronic database. The accuracy 
of the data entry would be verified by computerized data validity 
checks as the data are entered and by subsequent manual checking of the 
database. These procedures would allow initial summaries of data to be 
prepared during and shortly after the field program and would 
facilitate transfer of the data to statistical, graphical, and other 
programs for further processing and archiving. The time, location, 
heading, speed, activity of the vessel, sea state, visibility, and sun 
glare would also be recorded at the start and end of each observation 
watch, and during a watch whenever there is a change in one or more of 
the variables.

[[Page 39925]]

    Results from the vessel-based observations would provide:
    (1) The basis for real-time mitigation (e.g., airgun shutdown);
    (2) Information needed to estimate the number of marine mammals 
potentially taken by harassment, which must be reported to NMFS;
    (3) Data on the occurrence, distribution, and activities of marine 
mammals in the area where the seismic study is conducted;
    (4) Information to compare the distance and distribution of marine 
mammals relative to the source vessel at times with and without seismic 
activity; and
    (5) Data on the behavior and movement patterns of marine mammals 
seen at times with and without seismic activity.

Reporting

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

Negligible Impact Analysis and Determination

    NMFS has defined negligible impact as an impact resulting from the 
specified activity that cannot be reasonably expected to, and is not 
reasonably likely to, adversely affect the species or stock through 
effects on annual rates of recruitment or survival (50 CFR 216.103). A 
negligible impact finding is based on the lack of likely adverse 
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough 
information on which to base an impact determination. In addition to 
considering estimates of the number of marine mammals that might be 
``taken'' through harassment, NMFS considers other factors, such as the 
likely nature of any responses (e.g., intensity, duration), the context 
of any responses (e.g., critical reproductive time or location, 
migration), as well as effects on habitat, and the likely effectiveness 
of the mitigation. We also assess the number, intensity, and context of 
estimated takes by evaluating this information relative to population 
status. Consistent with the 1989 preamble for NMFS's implementing 
regulations (54 FR 40338; September 29, 1989), the impacts from other 
past and ongoing anthropogenic activities are incorporated into this 
analysis via their impacts on the environmental baseline (e.g., as 
reflected in the regulatory status of the species, population size and 
growth rate where known, ongoing sources of human-caused mortality, or 
ambient noise levels).
    To avoid repetition, our analysis applies to all the species listed 
in Table 2, given that NMFS expects the anticipated effects of the 
proposed seismic survey to be similar in nature. Where there are 
meaningful differences between species or stocks, or groups of species, 
in anticipated individual responses to activities, impact of expected 
take on the population due to differences in population status, or 
impacts on habitat, NMFS has identified species-specific factors to 
inform the analysis.
    NMFS does not anticipate that serious injury or mortality would 
occur as a result of SIO's proposed seismic survey, even in the absence 
of proposed mitigation. Thus the proposed authorization does not 
authorize any mortality. As discussed in the Potential Effects section, 
non-auditory physical effects, stranding, and vessel strike are not 
expected to occur.
    No takes by Level A harassment are proposed to be authorized. The 
100-m exclusion zone encompasses the Level A harassment isopleths for 
all marine mammal hearing groups, and is expected to prevent animals 
from being exposed to sound levels that would cause PTS. Also, as 
described above, we expect that marine mammals would be likely to move 
away from a sound source that represents an aversive stimulus, 
especially at levels that would be expected to result in PTS, given 
sufficient notice of the Thompson's approach due to the vessel's 
relatively low speed when conducting seismic surveys. We expect that 
any instances of take would be in the form of short-term Level B 
behavioral harassment in the form of temporary avoidance of the area or 
decreased foraging (if such activity were occurring), reactions that 
are considered to be of low severity and with no lasting biological 
consequences (e.g., Southall et al., 2007).
    Potential impacts to marine mammal habitat were discussed 
previously in this document (see Potential Effects of the Specified 
Activity 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 described above, marine mammals in the survey area are not 
assigned to NMFS stocks. For purposes of the small numbers analysis we 
rely on the best

[[Page 39926]]

available information on the abundance estimates for the species of 
marine mammals that could be taken. The activity is expected to impact 
a very small percentage of all marine mammal populations that would be 
affected by SIO's proposed survey (less than 15 percent each for all 
marine mammal populations where abundance estimates exist). 
Additionally, the acoustic ``footprint'' of the proposed survey would 
be very small relative to the ranges of all marine mammals 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 (28 days) would further limit potential impacts that 
may occur as a result of the proposed activity.
    The proposed mitigation measures are expected to reduce the number 
and/or severity of takes by allowing for detection of marine mammals in 
the vicinity of the vessel by visual and acoustic observers, and by 
minimizing the severity of any potential exposures via shutdowns of the 
airgun array. Based on previous monitoring reports for substantially 
similar activities that have been previously authorized by NMFS, we 
expect that the proposed mitigation will be effective in preventing at 
least some extent of potential PTS in marine mammals that may otherwise 
occur in the absence of the proposed mitigation.
    Of the marine mammal species under our jurisdiction that are likely 
to occur in the project area, the following species are listed as 
endangered under the ESA: Fin, sei, blue, sperm, and southern right 
whales. We are proposing to authorize very small numbers of takes for 
these species (Table 11), relative to their population sizes (again, 
for species where population abundance estimates exist), therefore we 
do not expect population-level impacts to any of these species. The 
other marine mammal species that may be taken by harassment during 
SIO's seismic survey are not listed as threatened or endangered under 
the ESA. There is no designated critical habitat for any ESA-listed 
marine mammals within the project area; of the non-listed marine 
mammals for which we propose to authorize take, none are considered 
``depleted'' or ``strategic'' by NMFS under the MMPA.
    NMFS concludes that exposures to marine mammal species due to SIO's 
proposed seismic survey would result in only short-term (temporary and 
short in duration) effects to individuals exposed, or some small degree 
of PTS to a very small number of individuals of four species. Marine 
mammals may temporarily avoid the immediate area, but are not expected 
to permanently abandon the area. Major shifts in habitat use, 
distribution, or foraging success are not expected. NMFS does not 
anticipate the proposed take estimates to impact annual rates of 
recruitment or survival.
    In summary and as described above, the following factors primarily 
support our preliminary determination that the impacts resulting from 
this activity are not expected to adversely affect the species or stock 
through effects on annual rates of recruitment or survival:
     No mortality is anticipated or authorized;
     The anticipated impacts of the proposed activity on marine 
mammals would primarily be temporary behavioral changes due to 
avoidance of the area around the survey vessel. The relatively short 
duration of the proposed survey (28 days) would further limit the 
potential impacts of any temporary behavioral changes that would occur;
     The number of instances of PTS that may occur are expected 
to be very small in number (Table 11). Instances of PTS that are 
incurred in marine mammals would be of a low level, due to constant 
movement of the vessel and of the marine mammals in the area, and the 
nature of the survey design (not concentrated in areas of high marine 
mammal concentration);
     The availability of alternate areas of similar habitat 
value for marine mammals to temporarily vacate the survey area during 
the proposed survey to avoid exposure to sounds from the activity;
     The proposed project area does not contain areas of 
significance for feeding, mating or calving;
     The potential adverse effects on fish or invertebrate 
species that serve as prey species for marine mammals from the proposed 
survey would be temporary and spatially limited; and
     The proposed mitigation measures, including visual and 
acoustic monitoring and shutdowns, are expected to minimize potential 
impacts to marine mammals.
    Based on the analysis contained herein of the likely effects of the 
specified activity on marine mammals and their habitat, and taking into 
consideration the implementation of the proposed monitoring and 
mitigation measures, NMFS preliminarily finds that the total marine 
mammal take from the proposed activity will have a negligible impact on 
all affected marine mammal species or stocks.

Small Numbers

    As noted above, only small numbers of incidental take may be 
authorized under Sections 101(a)(5)(A) and (D) of the MMPA for 
specified activities other than military readiness activities. The MMPA 
does not define small numbers and so, in practice, where estimated 
numbers are available, NMFS compares the number of individuals taken to 
the most appropriate estimation of abundance of the relevant species or 
stock in our determination of whether an authorization is limited to 
small numbers of marine mammals. Additionally, other qualitative 
factors may be considered in the analysis, such as the temporal or 
spatial scale of the activities.
    The numbers of marine mammals that we authorize to be taken would 
be considered small relative to the relevant populations (less than 15 
percent for all species) for the species for which abundance estimates 
are available. No known current worldwide or regional population 
estimates are available for 16 species under NMFS jurisdiction that 
could be incidentally taken as a result of the proposed survey: The 
pygmy right whale, pygmy sperm whale, dwarf sperm whale, Shepherd's 
beaked whale, Blainville's beaked whale, Hector's beaked whale, True's 
beaked whale, Andrew's beaked whale, spade-toothed beaked whale, rough-
toothed dolphin, spinner dolphin, Clymene dolphin, Fraser's dolphin, 
southern right whale dolphin, false killer whale, and spectacled 
porpoise.
    NMFS has reviewed the geographic distributions and habitat 
preferences of these species in determining whether the numbers of 
takes authorized herein are likely to represent small numbers. Pygmy 
right whales have a circumglobal distribution and occur throughout 
coastal and oceanic waters in the Southern Hemisphere (between 30 to 
55[deg] S) (Jefferson et al., 2008). Pygmy and dwarf sperm whales occur 
in deep waters on the outer continental shelf and slope in tropical to 
temperate waters of the Atlantic, Indian, and Pacific Oceans. Based on 
stranding records and the known habitat preferences of beaked whales in 
general, Shepherd's beaked whales are assumed to have a circumpolar 
distribution in deep, cold temperate waters of the Southern Ocean 
(Pitman et al., 2006). Blainville's beaked whale is the most widely 
distributed beaked Mesoplodon species with sightings and stranding 
records throughout the North and South Atlantic Ocean (MacLeod et al., 
2006).

[[Page 39927]]

Hector's beaked whales are found in cold temperate waters throughout 
the southern hemisphere between 35[deg] S and 55[deg] S (Zerbini and 
Secchi 2001). True's beaked whales occur in the Southern hemisphere 
from the western Atlantic Ocean to the Indian Ocean to the waters of 
southern Australia and possibly New Zealand (Jefferson et al., 2008). 
Andrew's beaked whales have a circumpolar distribution north of the 
Antarctic Convergence to 32[deg] S (MacLeod et al., 2006). Stranding 
records of spade-toothed beaked whales suggest a Southern hemisphere 
distribution in temperate waters between 33[deg] and 44[deg] S in the 
South Pacific, with potential occurrence in the southern Atlantic Ocean 
(MacLeod et al., 2006). Rough-toothed dolphins occur in tropical and 
warm temperate seas around the world, preferring deep offshore waters 
(Lodi 1992). Spinner dolphins are found in tropical, subtropical, and, 
less frequently, warm temperate waters throughout the world (Secchi and 
Siciliano 1995). The Clymene dolphin is found in tropical and warm 
temperate waters of both the North and South Atlantic Oceans (Fertl et 
al., 2003). Fraser's dolphins are distributed in tropical oceanic 
waters worldwide, between 30[deg] N and 30[deg] S (Moreno et al., 
2003). Southern right whale dolphins have a circumpolar distribution 
and generally occur in deep temperate to sub-Antarctic waters in the 
Southern hemisphere (between 30 to 65[deg] S) (Jefferson et al.,2008). 
Short-finned pilot whales are found in warm temperate to tropical 
waters throughout the world, generally in deep offshore areas (Olson 
and Reilly, 2002). Spectacled porpoises occur in oceanic cool temperate 
to Antarctic waters and are circumpolar in high latitude Southern 
hemisphere distribution (Natalie et al., 2018).
    Based on the broad spatial distributions and habitat preferences of 
these species relative to the areas where SIO's proposed survey will 
occur, NMFS preliminarily concludes that the proposed take of these 
species likely represent small numbers relative to the affected 
species' overall population sizes, though we are unable to quantify the 
take numbers as a percentage of population.
    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 size 
of the affected species or stocks.

Unmitigable Adverse Impact Analysis and Determination

    There are no relevant subsistence uses of the affected marine 
mammal stocks or species implicated by this action. Therefore, NMFS has 
preliminarily 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, in this case with the ESA Interagency 
Cooperation Division, whenever we propose to authorize take for 
endangered or threatened species.
    NMFS is proposing to authorize take of fin, sei, blue, sperm, and 
southern right whales which are listed under the ESA. The Permit and 
Conservation Division has requested initiation of Section 7 
consultation with the Interagency Cooperation Division for the issuance 
of this IHA. NMFS will conclude the ESA consultation prior to reaching 
a determination regarding the proposed issuance of the authorization.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to SIO for conducting a marine geophysical survey in the 
southwest Atlantic Ocean in September-October 2019, provided the 
previously mentioned mitigation, monitoring, and reporting requirements 
are incorporated. A draft of the proposed IHA can be found at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act.

Request for Public Comments

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

Donna S. Wieting,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2019-17062 Filed 8-9-19; 8:45 am]
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