[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)
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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.
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Order Carnivora--Superfamily Pinnipedia
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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.
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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]
BILLING CODE 3510-22-P