Notice2022-13328
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Marine Geophysical Surveys at the Cascadia Subduction Zone and Juan de Fuca Plate in the Northeast Pacific Ocean
Primary source
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Published
June 23, 2022
Issuing agencies
Commerce DepartmentNational Oceanic and Atmospheric Administration
Abstract
NMFS has received a request from Lamont-Doherty Earth Observatory (L-DEO) for authorization to take marine mammals incidental to geophysical surveys at the Cascadia Subduction Zone and Juan de Fuca Plate in the Northeast Pacific 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-time, one-year renewal that could be issued under certain circumstances and if all requirements are met, as described in Request for Public Comments at the end of this notice. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorization and agency responses will be summarized in the final notice of our decision.
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[Federal Register Volume 87, Number 120 (Thursday, June 23, 2022)]
[Notices]
[Pages 37560-37598]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2022-13328]
[[Page 37559]]
Vol. 87
Thursday,
No. 120
June 23, 2022
Part II
Department of Commerce
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National Oceanic and Atmospheric Administration
Takes of Marine Mammals Incidental to Specified Activities; Taking
Marine Mammals Incidental to Marine Geophysical Surveys at the Cascadia
Subduction Zone and Juan de Fuca Plate in the Northeast Pacific Ocean;
Notice
Federal Register / Vol. 87, No. 120 / Thursday, June 23, 2022 /
Notices
[[Page 37560]]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XC041]
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to Marine Geophysical Surveys at the
Cascadia Subduction Zone and Juan de Fuca Plate in the Northeast
Pacific 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 Lamont-Doherty Earth
Observatory (L-DEO) for authorization to take marine mammals incidental
to geophysical surveys at the Cascadia Subduction Zone and Juan de Fuca
Plate in the Northeast Pacific 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-time, one-year renewal that could be issued
under certain circumstances and if all requirements are met, as
described in Request for Public Comments at the end of this notice.
NMFS will consider public comments prior to making any final decision
on the issuance of the requested MMPA authorization and agency
responses will be summarized in the final notice of our decision.
DATES: Comments and information must be received no later than July 25,
2022.
ADDRESSES: Comments should be addressed to Jolie Harrison, Chief,
Permits and Conservation Division, Office of Protected Resources,
National Marine Fisheries Service and should be submitted via email to
<a href="/cdn-cgi/l/email-protection#632a37334d200c11000c11020d230d0c02024d040c15"><span class="__cf_email__" data-cfemail="a3eaf7f38de0ccd1c0ccd1c2cde3cdccc2c28dc4ccd5">[email protected]</span></a>.
Instructions: NMFS is not responsible for comments sent by any
other method, to any other address or individual, or received after the
end of the comment period. Comments, including all attachments, must
not exceed a 25-megabyte file size. All comments received are a part of
the public record and will generally be posted online at
<a href="http://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act">www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act</a> 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: Kim Corcoran, 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: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-research-and-other-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-research-and-other-activities</a>. In case of problems
accessing these documents, please call the contact listed above.
SUPPLEMENTARY INFORMATION:
Background
The MMPA prohibits the ``take'' of marine mammals, with certain
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to
allow, upon request, the incidental, but not intentional, taking of
small numbers of marine mammals by U.S. citizens who engage in a
specified activity (other than commercial fishing) within a specified
geographical region if certain findings are made and either regulations
are proposed or, if the taking is limited to harassment, a notice of a
proposed incidental harassment authorization is provided to the public
for review.
Authorization for incidental takings shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s) and will not have an unmitigable adverse impact on the
availability of the species or stock(s) for taking for subsistence uses
(where relevant). Further, NMFS must prescribe the permissible methods
of taking and other ``means of effecting the least practicable adverse
impact'' on the affected species or stocks and their habitat, paying
particular attention to rookeries, mating grounds, and areas of similar
significance, and on the availability of the species or stocks for
taking for certain subsistence uses (referred to in shorthand as
``mitigation''); and requirements pertaining to the mitigation,
monitoring and reporting of the takings are set forth.
The definitions of all applicable MMPA statutory terms cited above
are included in the relevant sections below.
National Environmental Policy Act
To comply with the National Environmental Policy Act of 1969 (NEPA;
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A,
NMFS must review our proposed action (i.e., the issuance of an IHA)
with respect to potential impacts on the human environment.
This action is consistent with categories of activities identified
in Categorical Exclusion B4 (IHAs with no anticipated serious injury or
mortality) of the Companion Manual for NOAA Administrative Order 216-
6A, which do not individually or cumulatively have the potential for
significant impacts on the quality of the human environment and for
which we have not identified any extraordinary circumstances that would
preclude this categorical exclusion. Accordingly, NMFS has
preliminarily determined that the issuance of the proposed IHA
qualifies to be categorically excluded from further NEPA review.
Summary of Request
On December 14, 2021, NMFS received a request from L-DEO for an IHA
to take marine mammals incidental to a marine geophysical survey off
the coasts of Oregon and Washington in the northeast Pacific Ocean. The
application was deemed adequate and complete on April 4, 2022. L-DEO
request is for take of small numbers of 23 species of marine mammals by
Level B harassment only. Neither L-DEO nor NMFS expects serious injury
or mortality to result from this activity and, therefore, an IHA is
appropriate.
NMFS previously issued an IHA to L-DEO for larger surveys in a
similar location in the Northeast Pacific (e.g., 86 FR 29090; May 28,
2021; 84 FR 35073; July 22, 2019). These surveys, however, included
survey areas much closer to the coast. L-DEO complied with all the
requirements (e.g., mitigation, monitoring, and reporting) of the
previous IHAs and information regarding their monitoring results may be
found in the Description of Marine Mammals in the Area of Specified
Activities section.
Description of Proposed Activity
Overview
Researchers from New Mexico Institute of Mining and Technology
(NMT) and Oregon State University (OSU), with funding from the U.S.
National Science Foundation (NSF) propose to conduct low-energy seismic
surveys from the Research Vessel (R/V) Marcus G. Langseth (Langseth),
which is owned and operated by Lamont-Doherty Earth Observatory (L-DEO)
of Columbia University, at the Cascadia subduction Zone and Juan de
Fuca Plate in the
[[Page 37561]]
Northeast Pacific Ocean during Summer 2022. The proposed two-
dimensional (2-D) seismic surveys would occur within the Exclusive
Economic Zone (EEZ) of the United States, in waters deeper than 1600
meters (m). To complete this survey, the R/V Langseth would tow a
Generator-Injector (GI)-airgun cluster consisting of two 45 cubic inch
(in\3\) GI guns spaced 2.46 m apart, with a total discharge volume of
90 in\3\. The acoustic source would be towed at 2 to 4 m deep along the
survey lines, while the receiving system is towed in an 800-1400 m long
hydrophone streamer.
The proposed study would acquire high-resolution 2-D seismic
reflection data in conjunction with densely-spaced heat flow
measurements to better understand the thermal structure of the Juan de
Fuca plate as it enters the Cascadia subduction zone. The seismic and
heat flow data would be acquired across several distinct structures
that have not been previously studied, including a pseudofault, complex
buried seamounts, and small outcrops that represent the summit of much
larger buried seamounts.
Dates and Duration
The proposed survey is expect to last for 23 days, with
approximately six days of seismic operations, three days of transit and
14 days of heat flow measurements. R/V Langseth would likely leave out
of and return to port in Newport, OR, during summer 2022.
Specific Geographic Region
The proposed survey would occur within ~42-47[deg]N, ~125-127[deg]W
off the coast of Washington and Oregon in the Northeast Pacific ocean.
Four regions where the surveys are proposed to occur are depicted in
Figure 1; the tracklines could occur anywhere within the boxes shown in
Figure 1. No representative survey tracklines are shown, as actual
track lines and order of survey operations are dependent on science
objectives and weather. The surveys are proposed to occur within the
EEZ of the U.S., in waters >1600 m deep.
BILLING CODE 3510-22-P
[[Page 37562]]
[GRAPHIC] [TIFF OMITTED] TN23JN22.000
BILLING CODE 3510-22-C
Detailed Description of Specific Activity
The procedures to be used for the proposed surveys would be similar
to those used during previous seismic surveys by L-DEO and would use
conventional seismic methodology. The surveys would involve one source
vessel, R/V Langseth, which is owned and operated by L-DEO. R/V
Langseth would deploy two 45/105 in\3\ GI airguns as an energy source
with a total volume of ~90 in\3\. The receiving system would consist of
one 800-1400 m long hydrophone streamer. As the airguns are towed along
the survey lines, the hydrophone streamer would transfer data to the
on-board processing system. Approximately 1135 kilometers (km) of
transect lines would be surveyed in four survey regions in the
Northeast Pacific Ocean; 200 km, 95 km, 440 km, and 400 km in the
Coast, Nubbin, Pseudofault, and Oregon survey regions, respectively.
All survey effort would occur in deep water >1600 m. In addition to the
operations of the airgun array, the ocean floor would be mapped with
the Kongsberg EM 122 multibeam echosounder (MBES), a Knudsen CHIRP
[[Page 37563]]
3260 (SBP) and an Acoustic Doppler Current Profiler (ADCP) would be
operated from the vessel continuously. All planned geophysical data
acquisition activities would be conducted by L-DEO with on-board
assistance by the scientists who have proposed the studies. The vessel
would be self-contained, and the crew would live aboard the vessel.
Take of marine mammals is not expected to occur incidental to use of
the MBES, SBP and ADCP, whether or not the airguns are operating
simultaneously with the other sources. Given their characteristics
(e.g., narrow downward-directed beam), marine mammals would experience
no more than one or two brief ping exposures, if any exposure were to
occur. NMFS does not expect that the use of these sources presents any
reasonable potential to cause take of marine mammals.
Proposed mitigation, monitoring, and reporting measures are
described in detail later in this document (please see Proposed
Mitigation and Proposed Monitoring and Reporting).
Description of Marine Mammals in the Area of Specified Activities
Sections 3 and 4 of the application summarize available information
regarding status and trends, distribution and habitat preferences, and
behavior and life history of the potentially affected species. NMFS
fully considered all of this information, and we refer the reader to
these descriptions, incorporated here by reference, instead of
reprinting the information. Additional information regarding population
trends and threats may be found in NMFS' Stock Assessment Reports
(SARs; <a href="http://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>) and more general information about these
species (e.g., physical and behavioral descriptions) may be found on
NMFS' website (<a href="https://www.fisheries.noaa.gov/find-species">https://www.fisheries.noaa.gov/find-species</a>).
Table 1 lists all species or stocks for which take is expected and
proposed to be authorized for this action, and summarizes information
related to the population or stock, including regulatory status under
the MMPA and Endangered Species Act (ESA) and potential biological
removal (PBR), where known. PBR is defined by the MMPA as the maximum
number of animals, not including natural mortalities, that may be
removed from a marine mammal stock while allowing that stock to reach
or maintain its optimum sustainable population (as described in NMFS'
SARs). While no serious injury or mortality is anticipated or
authorized here, PBR and annual serious injury and mortality from
anthropogenic sources are included here as gross indicators of the
status of the species and other threats.
Marine mammal abundance estimates presented in this document
represent the total number of individuals that make up a given stock or
the total number estimated within a particular study or survey area.
NMFS's stock abundance estimates for most species represent the total
estimate of individuals within the geographic area, if known, that
comprise that stock. For some species, this geographic area may extend
beyond U.S. waters. All managed stocks in this region are assessed in
NMFS's U.S. Pacific SARs (Carretta et al., 2021). All values presented
in Table 1 are the most recent available at the time of publication and
are available in the 2020 SARs (Carretta et al., 2021) and draft 2021
SARs (available online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports</a>).
Table 1--Species Likely Impacted by the Specified Activities
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ESA/MMPA
status; Stock abundance (CV, Nmin, most recent Annual M/
Common name Scientific name Stock strategic abundance survey) \2\ PBR SI \3\
(Y/N) \1\
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Order Cetartiodactyla--Cetacea--Superfamily Mysticeti (baleen whales)
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Family Balaenopteridae
(rorquals):
Humpback whale............. Megaptera California/Oregon/ -,-,Y 4,973 (0.05, 4,776, 2018) 28.7 >48.6
novaeangliae. Washington.
Minke whale................ Balaenoptera California/Oregon/ -,-,N 915 (0.792, 509, 2018) 4.1 >0.59
acutorostrata. Washington.
Sei whale.................. Balaenoptera Eastern North E, D, Y 519 (0.4, 374, 2014) 0.75 >0.2
borealis. Pacific.
Fin whale.................. Balaenoptera California/Oregon/ E, D, Y 11,065 (0.405, 7,970, 2018) 80 >2.2
physalus. Washington.
Blue whale................. Balaenoptera Eastern North E, D, Y 1,898 (0.085, 1,767, 2018) 4.1 >19.4
musculus. Pacific.
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Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
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Family Physeteridae:
Sperm whale................ Physeter California/Oregon/ E, D, Y 1,997 (0.57, 1270, 2014) 2.5 0.6
macrocephalus. Washington.
Family Kogiidae:
Pygmy sperm whale.......... Kogia breviceps.. California/Oregon/ -,-,N 4,111 (1.12, 1924, 2014) 19 0
Washington.
Dwarf sperm whale.......... Kogia sima....... California/Oregon/ -,-,N UNK (UNK, UNK, 2014) UND 0
Washington.
Family Ziphiidae (beaked
whales):
Baird's beaked whale....... Berardius Bairdii California/Oregon/ -,-,N 1,363 (0.53, 894, 2018) 8.9 >0.2
Washington.
Cuvier's beaked whale...... Ziphius California/Oregon/ -,-,N 3,274 (0.67, 2,059, 2014) 21 <0.1
cavirostris. Washington.
Mesoplodont Beaked Whales.. Mesoplodon spp... California/Oregon/ -,-,N 3,044 (0.54, 1,967, 2005) 20 0.1
Washington.
Family Delphinidae:
Striped dolphin............ Stenella California/Oregon/ -,-,N 29,988 (0.3, 23,448, 2018) 225 >4
coeruleoalba. Washington.
Short-beaked common dolphin Delphinus delphis California/Oregon/ -,-,N 1,056,308 (0.21, 888,971, 2018) 8,889 >30.5
Washington.
[[Page 37564]]
Pacific white-sided dolphin Lagenorhynchus California/Oregon/ -,-,C 34,998 (0.222, 29,090, 2018) 279 7
obliquidens. Washington.
Northern right whale Lissodelphis California/Oregon/ -,-,N 29,285 (0.72, 17024, 2018) 163 >6.6
dolphin. borealis. Washington.
Risso's dolphin............ Grampus griseus.. California/Oregon/ -,-,N 6,336 (0.32, 4,817, 2014) 46 >3.7
Washington.
Killer whale............... Orcinus orca..... West Coast -,-,N 349 (N/A, 349, 2018) 3.5 0.4
Transient.
North Pacific -,-,N 300 (0.1, 276, 2012) 2.8 0
Offshore.
Family Phocoenidae (porpoises):
Dall's porpoise............ Phocoenoides California/Oregon/ -,-,N 16,498 (0.61, 10,286, 2019) 99 >0.66
dalli. Washington.
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Order Carnivora--Superfamily Pinnipedia
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Family Otariidae (eared seals
and sea lions):
Northern fur seal.......... Callorhinus Eastern Pacific.. -,D,Y 626,618 (0.2, 530,376, 2020) 11,403 373
ursinus.
California....... -,D,Y 14,050 (N/A, 7,524, 2013) 451 1.8
Guadalupe fur seal......... Arctocephalus Mexico........... T, D, Y 34,187 (N/A, 31,019, 2013) 1,062 >3.8
townsendi.
Steller sea lion........... Eumetopias Eastern.......... -,-,N 43,201 (N/A, 43,201,2017) 2,592 112
jubatus.
California sea lion........ Zalophus United States.... -,-,N 257,606 (N/A, 233,525, 2014) 14,011 >320
californianus.
Family Phocidae (earless
seals):
Northern elephant seal..... Mirounga California -,-,N 187,386 (N/A, 85,369, 2013) 5,122 5.3
angustirostris. Breeding.
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\1\--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.
\2\--NMFS marine mammal stock assessment reports online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports</a>. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.
\3\--These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g.,
commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV
associated with estimated mortality due to commercial fisheries is presented in some cases.
As indicated above, all 23 species (with 25 managed stocks) in
Table 1 temporally and spatially co-occur with the activity to the
degree that take is reasonably likely to occur. While North Pacific
right whales (Eubalaena japonica), bottlenose dolphins (Tursiops
truncatus), short-finned pilot whales (Globicephala macrorhynchus),
gray whales (Eschrichtius robustus), and false killer whales (Pseudorca
crassidens) have been documented near the area, the temporal and/or
spatial occurrence of these species is such that take is not expected
to occur. Therefore, they are not discussed further beyond the
explanation provided below.
The North Pacific right whale is one of the rarest marine mammals
in the world (Muto et al., 2021). The species comprises of an eastern
and western population that are largely or wholly discrete. The summer
range of the eastern stock includes the Gulf of Alaska and the Bergin
Sea, while the western stock is believed to feed in the Okhotsk Sea and
in pelagic waters of the northwestern North Pacific (Muto et al.,
2021). Whaling records from the 19th century and recent Soviet catch
data have shown that right whales were broadly distributed across the
eastern North Pacific (Scarff 1986, Brownell et al., 2001, Ivashchenko
and Clapham 2012). There are sporadic records from below 20 degrees
north, but the bulk of the data show right whales concentrated north of
35 degrees north, including coastal and offshore waters ranging from
Washington state and British Columbia through the Gulf of Alaska,
Alaska Peninsula, Aleutian Islands, and the Bering Sea (Muto et al.,
2021).
The eastern North Pacific stock that occurs in the United States is
estimated to contain 31 whales for the Bering sea and Aleutian Islands.
A Biologically Important Area (BIA) for feeding for North Pacific right
whales was designated east of the Kodiak Archipelago, which includes
the Gulf of Alaska critical habitat and extends south of 56 degrees
north and north of 58 degrees north and beyond the shelf edge. South of
50 degrees north, only 29 reliable sightings were recorded from 1900-
1994 (Scarff 1986, 1991; Carretta et al.,1994). Off the coast of
California/Oregon/Washington, only seven documented sightings of right
whales were made from 1990 through 2000. Two North Pacific right whale
calls were detected on a bottom-mounted hydrophone (located in water
1390 m deep) off the Washington coast on June 29, 2013 (Sirovic et al.,
2014). During L-DEO's summer 2021 seismic survey in the Northeast
Pacific, a sighting of two individuals was made northwest of the survey
area in British Columbia, west of Haida Gwaii on July 27, 2021. Because
of the small population size, and the fact that North Pacific right
whales spend the summer feeding in high latitudes, the likelihood that
the proposed survey would encounter a North Pacific right whale is
discountable, and NMFS is not proposing to authorize take of this
species.
Bottlenose dolphins are distributed worldwide in tropical and warm-
temperate waters. Bottlenose dolphins occur frequently off the coast of
California, and sightings have been made as far north as 41 degrees
north, but few records exist for Oregon and Washington (Carretta et
al., 2021). In California, separate coastal and offshore populations
are known (Walker 1981; Ross and Cockcroft 1999; Van Waerebeek et al.,
1990; Lowther 2006). Three sightings and one stranding of bottlenose
dolphins have been documented in Puget Sound since 2004 (Cascadia
Research 2011 in U.S.C.
[[Page 37565]]
2015). L-DEO requested authorization for the incidental take of
bottlenose dolphins (the request was for a total of 13 individuals).
Although sightings of bottlenose dolphins in Puget Sound have increased
considerably since 2016 (Cascadia Research Collective, 2020), given the
far north and offshore placement of the proposed survey and the
species' tendency to stay in coastal waters and in lower latitudes, we
believe it is highly unlikely that bottlenose dolphins would be
encountered in the proposed survey area, and NMFS is not proposing to
authorize take of this species.
Short-finned pilot whales are found in tropical and warm temperate
waters (Olson 2018) and seen as far south as 40 degrees south and as
far north as 50 degrees north (Jefferson et al., 2015). Pilot whales
are generally nomadic, but may reside in certain locations, including
California and Hawaii (Olson 2018). The species were common off
southern California (Dohl et al., 1980) until an El Nino event occurred
in 1982-1983 (Green et al., 1992; Carretta and Forney 1993; Barlow
1997). Few sightings were made off California/Oregon/Washington in
1983-1984, but sightings remain rare (Barlow 1997; Buchanan et al.,
2001; Barlow 2010). No short-finned pilot whales were seen during
surveys off Oregon and Washington in 1989-1990, 1992, 1996, and 2001
(Barolow 2003). Only one sighting has occurred off Oregon from 1991-
2014 (Carretta et al., 2021). Although zero Level B harassment exposure
estimates were calculated, L-DEO requested authorization for the
incidental take of 29 short-finned pilot whales based on the average
group size produced by Barlow (2016). However, considering the species'
historical occurrence in the proposed survey area, their preference for
warmer tropical waters, and the best available information, the
likelihood that L-DEO will encounter short-finned pilot whales in the
proposed survey area is discountable, and NMFS is not proposing to
authorize take of this species.
Two separate populations of gray whales have been recognized in the
North Pacific: the eastern North Pacific and western North Pacific
stocks (LeDuc et al., 2002; Weller et al., 2013). However, the
distinction between these two populations has been recently debated
owing to evidence that whales from the western feeding area also travel
to breeding areas in the eastern North Pacific (Weller et al., 2012,
2013; Mate et al., 2015). BIAs for feeding gray whales along the coasts
of Washington, Oregon, and California have been identified, including
northern Puget sound, Northwestern Washington, and Grays Harbor (WA);
Depoe Bay and Cape Blanco and Orford Reef (OR), and Point St. George
(CA); most of these areas are of importance from late spring through
early fall (Calambokidis et al., 2015); none occur within the proposed
survey region. Resident gray whales have been observed foraging off the
coast of Oregon from May through October and off Washington June
through November (Newell and Cowles 2006; Scordino et al., 2014). BIAs
have also been identified for migrating gray whales along the entire
coasts of Washington, Oregon, and California; although most whales
travel within 10 km from shore, the BIAs were extended out to 47 km
from the coastline (Calambokidis et al., 2015); the proposed Oregon
survey region is located adjacent to this BIA (see Figure 1). Gray
whales from the far north begin to migrate south to breeding grounds on
the west coast of Baja California and the southeastern Gulf of
California in October and November (Braham 1984; Rugh et al., 2001).
Gray whales migrate closest to the Washington/Oregon coastline during
spring (April-June), when most strandings are observed (Norman et al.,
2004). The species' stock range extends from as far south as Mexico all
the way north to the Gulf of Alaska, primarily hugging the coastline
(NMFS 2022).
NOAA (2021b) declared an unusual mortality event (UME) for gray
whales in 2019, as an elevated number of strandings have occurred along
the coast of the Pacific Northwest since January 2019. As of 1 October
2021, a total of 212 dead gray whales have been reported, including 248
in the U.S. (55 in Washington; 12 in Oregon), 225 in Mexico, and 19 in
B.C.; some of the whales were emaciated. A UME for gray whales was also
declared for 1999-2000 (NOAA 2021c).
The proposed survey is planned during the summer feeding season,
when most individuals from the eastern North Pacific stock occur
farther north. Although individuals, particularly from the Pacific
Coast Feeding Group (PCFG), could be encountered in nearshore waters
less than 10 km from shore, the likelihood that any gray whales will be
encountered as far offshore as the proposed survey area is
discountable. Gray whales have been observed to have a distinct
ecological niche in nearshore and shallow waters (Darling et al., 1998)
and L-DEO's proposed activities to not overlap with this niche. L-DEO
requested the incidental take of a singular gray whale, however NMFS
does not propose to authorize any take of gray whales as it is
temporally and spatially unlikely that they will be encountered.
Lastly, the false killer whale is found worldwide in tropical and
temperate waters, generally between 50 degrees north and 50 degrees
south (Odell and McClune 1999). It is widely distributed, but not
abundant anywhere (Carwardine 1995). The false killer whale generally
inhabits deep, offshore waters, but sometimes is found over the
continental shelf and occasionally moves into very shallow water
(Jefferson et al., 2015; Baird 2018b). In the eastern North Pacific, it
has been reported only rarely north of Baja California (Leatherwood et
al., 1982, 1987; Mangels and Gerrodete 1994); however, the waters off
the United States west coast all the way north to Alaska are considered
part of its secondary range (Jefferson et al., 2015).
Its occurrence in Washington/Oregon is associated with warm-water
incursions (Buchanan et al., 2001). However, no sightings of false
killer whales were made along the U.S. west coast during surveys
conducted from 1986-2001 (Ferguson and Barlow 2001, 2003; Barlow 2003)
or in 2005 and 2008 (Forney 2007; Barlow 2010). One pod of false killer
whales occurred in Puget Sound for several months during the 1990s (USN
2015). Two false killer whales were reported stranded along the
Washington coast during 1930-2002, both in El Ni[ntilde]o years (Norman
et al., 2004). Based on the best available information, NMFS believes
that the likelihood of the survey encountering a false killer whale is
discountable and, although L-DEO requested incidental take of 5 whales
based on their average group size (Mobley et al., 2000), NMFS does not
propose authorizing any take of false killer whales.
Humpback Whale
The humpback whale is found throughout all of the oceans of the
world (Clapham 2009). The worldwide population is divided into northern
and southern ocean populations, but genetic analyses suggest some gene
flow (either past or present) between the North and South Pacific
(e.g., Jackson et al,. 2014; Bettriddge et al,. 2015). Although
considered to be mainly a coastal species, humpback whales often
traverse deep pelagic areas while migrating (Calambokidis et al., 2001;
Garrigue et al., 2002; Zerbini et al., 2011). Humpbacks migrate between
summer feeding grounds in high latitudes and winter calving and
breeding grounds in tropical waters (Clapham and Mead 1999). Northern
Pacific humpback whales summer in
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feeding grounds along the Pacific Rim and in the Bering and Okhotsk
seas (Pike and MacAskie 1969; Rice 1978; Winn and Reichley 1985;
Calambokidis et al., 2000, 2001, 2008; Bettridge et al., 2015).
Humpbacks in the north Pacific winter in four different breeding areas:
(1) along the coast of Mexico; (2) along the coast of Central America;
(3) around the main Hawaiian Islands; and (4) in the western Pacific,
particularly around the Ogasawara and Ryukyu islands in southern Japan
and the northern Philippines (Calambokidis et al., 2008; Bettridge et
al., 2015).
Prior to 2016, humpback whales were listed under the ESA as an
endangered species worldwide. Following a 2015 global status review
(Bettridge et al., 2015), NMFS established 14 distinct population
segments (DPS) with different listing statuses (81 FR 62259); September
8, 20216) pursuant to the ESA. The DPSs that occur in United States
waters do not necessarily equate to the existing stocks designated
under the MMPA and shown in Table 1. Because the MMPA stocks cannot be
portioned (i.e,. parts managed as ESA-listed while other parts managed
as non-ESA listed), until such time as the MMPA stock delineations are
reviewed in light of the DPS designations, NMFS considers the existing
humpback whale stocks under the MMPA to be endangered and depleted for
MMPA management purposes (e.g., selection of a recovery factor, stock
status).
NMFS has identified three DPSs of humpback whales that are found
off the coasts of Washington, Oregon and California. These are: the
Hawaii DPS (found predominately off Washington and southern British
Columbia), which is not listed under the ESA; the Mexico DPS (found all
along the west coast), which is listed as threatened under the ESA; and
the Central America DPS (found all along the west coast, but most
common off California and Oregon), which is listed as endangered under
the ESA. According to Wade (2021), the probability that whales
encountered in Oregon and California waters are from a given DPS are as
follows: Central America DPS (42 percent); Mexico DPS (58 percent);
Hawaii DPS (0 percent). The probability that humpback whales
encountered in Washington and British Columbia waters are as follows:
Central America DPS (6 percent); Mexico DPS (25 percent); Hawaii DPS
(69 percent). Wade (2021) notes that the majority of humpback whales
that may be found off of Washington are likely moving north of the
United States border and feeding primarily off of southern British
Columbia.
Humpback whales are the most common species of large cetacean
reported off the coasts of Oregon and Washington from May to November
(Green et al., 1992; Calambokidis et al., 2000, 2004). Humpbacks occur
primarily over the continental shelf and slope during the summer, but a
few individuals have been reported in offshore pelagic waters (Green et
al., 1992; Calambokidis et al., 2004, 2015; Becker et al., 2012; Barlow
2016; Carretta et al., 2021). Biologically Important Areas (BIAs) for
feeding humpback whales along the coasts of Oregon and Washington,
which have been designated from May through November, are all within
approximately 80 kilometers (km) from shore, and include the waters off
northern Washington, and Stonewall and Heceta Bank, OR (Calambokidis et
al., 2015). Six humpback whale sightings (eight animals) were made off
Washington and Oregon during the June through July 2012 L-DEO Juan de
Fuca plate seismic survey. There were 98 humpback whale sightings (213
animals) made during the July 2012 L-DEO seismic survey off Oregon (RPS
2012a), and 11 sightings (23 animals) during the July 2012 L-DEO
seismic survey off Oregon (RPS 2012c). Numerous humpback whale
sightings were made during L-DEO's Cascadia summer survey off Oregon
and Washington in 2021 (RPS).
On April 21, 2021, NMFS designated critical habitat in nearshore
waters of the North Pacific Ocean for the endangered Central America
and Western North Pacific DPSs and the threatened Mexico DPS of
humpback whales (NMFS 2021). Critical habitat for the Central America
and Mexico DPSs include waters within the California Current Ecosystem
(CCE) off the coasts of California, Oregon, and Washington (Figure 1).
Off Washington, critical habitat includes waters from the 50 m to 1200
m isobaths, as well as the strait of Juan de Fuca eastward to Angeles
Point; however, there is an exclusion area of 1461 nautical square
miles (nmi\2\) around the Navy's Quinault Range Site. Off Oregon, the
critical habitat spans from the 50 m to 1200 m isobath until 42.17
degrees north where the critical habitat south of 42.17 degrees north
extends out to the 2000 m isobath (NMFS 2021). There is no critical
habitat designated within the proposed survey regions, and ensonified
areas would not extend into critical habitat. Humpback whales are
expected to be uncommon in the proposed offshore survey areas.
Blue Whale
The blue whale has a cosmopolitan distribution and tends to be
pelagic, only coming nearshore to feed and possibly to breed (Jefferson
et al., 2015). Although it has been suggested that there are at least
five subpopulations of blue whales in the North Pacific (NMFS 1998),
analysis of blue whales calls monitored from the U.S. Navy Sound
surveillance system (SOSUS) and other offshore hydrophones (see
Stafford et al., 1999, 2001, 2007; Watkins et al., 2000; Stafford 2003)
suggest that there are two separate populations: one in eastern and one
in the western North Pacific (Sears and Perrin 2018). The status of
these two populations could differ substantially, as little is known
about the population size in the western North Pacific (Branch et al.,
2016). Broad scale acoustic monitoring indicate that blue whales
occurring in the northeast Pacific during summer and fall may winter in
the eastern tropical Pacific (Stafford et al., 1999, 2001).
The distribution of the species, at least during times of the year
when feeding is prevalent, occurs in areas that provide large seasonal
concentrations of euphausiids (Yochem and Leatherwood 1985). The
eastern North Pacific stock feeds in California waters from June
through November (Calambokidis et al.,1990; Mate et al., 2015), and
core areas have also been identified.
Blue whales are considered rare off Oregon, Washington, and B.C.
(Buchanan et al. 2001; Gregr et al., 2006; Ford 2014), although
satellite-tracked individuals have been reported off the coast (Bailey
et al., 2009). Based on modeling of the dynamic topography of the
region, blue whales could occur in relatively high densities off Oregon
during summer and fall (Pardo et al. 2015: Hazen et al. 2017). Recent
phenology analysis of marine mammal sightings revealed a peak of blue
whale density over the Oregon continental shelf in September, and their
sighting rates in the region have increased over the past three decades
as a response to environmental changes influencing prey availability
shifting their range northward (Derville et al., 2022). Densities along
the U.S. west coast, including Oregon, were predicted to be highest in
shelf waters, with lower densities in deeper offshore areas (Becker et
al., 2012; Calambokidis et al., 2015). Blue whales have been detected
acoustically off Oregon (McDonald et al., 1995; Stafford et al., 1998;
Von Saunder and Barlow 1999). Blue whales could be encountered in the
proposed survey areas.
[[Page 37567]]
Fin Whale
The fin whale is widely distributed in all the World's oceans
(Gambell 1985b), although it is most abundant in temperate and cold
waters (Aguilar and Garc[iacute]a-Vernet 2018). Nonetheless, its
overall range and distribution are not well known (Jefferson et al.,
2015). A review of fin whale distribution in the North Pacific noted
the lack of sightings across pelagic waters between eastern and western
winter areas (Mizroch et al., 2009). 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 summer (Aguilar and Garc[iacute]a-Vernet 2018). Some animals
may remain at high latitudes in winter or low latitudes in summer
(Edwards et al., 2015). 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). The fin whale is known to use the shelf edge as a migration
route (Evans 1987). Sergeant (1977) suggested that fin whales tend to
follow steep slope contours, either because they detect them readily,
or because the contours are areas of high biological productivity.
However, fin whale movements have been reported to be complex
(Jefferson et al., 2015). Stafford et al. (2009) noted that sea-surface
temperature is a good predictor variable for fin whale call detections
in the North Pacific.
North Pacific fin whales summer from the Chukchi Sea to California
and winter from California southwards (Gambell 1985b). Information
about the seasonal distribution of fin whales in the North Pacific has
been obtained from the detection of fin whale calls by bottom-mounted,
offshore hydrophone arrays along the U.S. Pacific coast, in the central
North Pacific, and in the western Aleutian Islands (Moore et al., 1998,
2006; Watkins et al., 2000a,b; Stafford et al., 2007, 2009). Fin whale
calls are recorded in the North Pacific year-round (e.g., Moore et al.,
2006; Stafford et al., 2007, 2009; Edwards et al., 2015). In the
central North Pacific, the Gulf of Alaska, and Aleutian Islands, call
rates peak during fall and winter (Moore et al., 1998, 2006; Watkins et
al., 2000a,b; Stafford et al., 2009).
Fin whales are routinely sighted during surveys off Oregon and
Washington (Barlow and Forney 2007; Barlow 2010, 2016; Adams et al.,
2014; Calambokidis et al., 2015; Edwards et al., 2015; Carretta et al.,
2021), including in coastal as well as offshore waters. They have also
been detected acoustically in those waters during June-August (Edwards
et al., 2015). Eight fin whale sightings (19 animals) were made off
Washington/Oregon during the June-July 2012 L-DEO Juan de Fuca plate
seismic survey; sightings were made in waters 2369-3940 m deep (RPS
2012b). Fourteen fin whale sightings (28 animals) were made during the
July 2012 L-DEO seismic surveys off southern Washington (RPS 2012a). No
fin whales were sighted during the July 2012 L-DEO seismic survey off
Oregon (RPS 2012c). During L-DEO's Cascadia survey during June-July
2021, five sightings of seven fin whales were made off Oregon (RPS
2021b). Fine whales were also seen off southern Oregon during July 2012
in water >2000 m deep during surveys by Adams et al., (2014). Fin
whales are likely to be encountered in the proposed survey area.
Sei Whale
The sei whale occurs in all ocean basins (Horwood 2018), but
appears to prefer mid-latitude temperate waters (Jefferson et al.
2015). It undertakes seasonal migrations to feed in subpolar latitudes
during summer and returns to lower latitudes during winter to calve
(Horwood 2018). The sei whale is pelagic and generally not found in
coastal waters (Harwood and Wilson 2001). It occurs in deeper waters
characteristic of the continental shelf edge region (Hain et al., 1985)
and in other regions of steep bathymetric relief such as seamounts and
canyons (Kenney and Winn 1987; Gregr and Trites 2001). On feeding
grounds, sei whales associate with oceanic frontal systems (Horwood
1987) such as the cold eastern currents in the North Pacific (Perry et
al., 1999). Sei whales migrate from temperate zones occupied in winter
to higher latitudes in the summer, where most feeding takes place
(Gambell 1985a). During summer in the North Pacific, the sei whale can
be found from the Bering Sea to the Gulf of Alaska and down to southern
California, as well as in the western Pacific from Japan to Korea. Its
winter distribution is concentrated at ~20[deg] N (Rice 1998).
Sei whales are rare in the waters off Washington, Oregon, and
California (Brueggeman et al., 1990; Green et al., 1992; Barlow 1994,
1997). Less than 20 confirmed sightings were reported in that region
during extensive surveys during 1991-2014 (Green et al., 1992, 1993;
Hill and Barlow 1992; Carretta and Forney 1993; Mangels and Gerrodette
1994; Von Saunder and Barlow 1999; Barlow 2003, 2010, 2014; Forney
2007; Carretta et al., 2021). Based on surveys conducted in 1991-2008,
the estimated abundance of sei whales off the coasts of Oregon and
Washington was 52 (Barlow 2010); for 2014, the abundance estimate was
468 (Barlow 2016). Two sightings of four individuals were made during
the June-July 2012 L-DEO Juan de Fuca plate seismic survey off
Washington/Oregon (RPS 2012b). No sei whales were sighted during the
summer 2012 or 2021 L-DEO seismic surveys off Oregon and Washington
(RPS 2012a,c, 2021). Sei whales could be encountered during the
proposed survey, although this species is considered rare in these
waters.
Minke Whale
The minke whale has a cosmopolitan distribution that spans from
tropical to polar regions in both hemispheres (Jefferson et al., 2015).
In the Northern Hemisphere, the minke whale is usually seen in coastal
areas, but can also be seen in pelagic waters during its northward
migration in spring and summer and southward migration in autumn
(Stewart and Leatherwood 1985). In the North Pacific, the summer range
of the minke whale extends to the Chukchi Sea; in the winter, the
whales move south to within 2[deg] of the Equator (Perrin et al.,
2018).
The International Whaling Commission (IWC) recognizes three stocks
of minke whales in the North Pacific: the Sea of Japan/East China Sea,
the rest of the western Pacific west of 180[deg] N, and the remainder
of the Pacific (Donovan 1991). Minke whales are relatively common in
the Bering and Chukchi seas and in the Gulf of Alaska but are not
considered abundant in any other part of the eastern Pacific
(Brueggeman et al., 1990). In the far north, minke whales are thought
to be migratory, but they are believed to be year-round residents in
nearshore waters off west coast of the U.S. (Dorsey et al., 1990).
Sightings have been made off Oregon and Washington in shelf and
deeper waters (Green et al., 1992; Adams et al., 2014; Barlow 2016;
Carretta et al., 2021). An estimated abundance of 211 minke whales was
reported for the Oregon/Washington region based on sightings data from
1991-2005 (Barlow and Forney 2007), whereas a 2008 survey did not
record any minke whales while on survey effort (Barlow 2010). The
abundance for Oregon/Washington for 2014 was estimated at 507 minke
whales (Barlow 2016). There were no sightings of minke whales off
Oregon/
[[Page 37568]]
Washington during L-DEO's summer seismic surveys in 2012 or 2021 (RPS
2012b,c, 2021). One minke whale was seen during the July 2012 L-DEO
seismic survey off southern Washington (RPS 2012a). Minke whales are
expected to be uncommon in the proposed survey areas.
Sperm Whale
The sperm whale is the largest of the toothed whales, with an
extensive worldwide distribution (Rice 1989). Sperm whale distribution
is linked to social structure: Mixed groups of adult females and
juveniles animals of both sexes generally occur in tropical and
subtropical waters, whereas adult makes are commonly found alone or in
the same-sex aggregations, often occurring in higher latitudes outside
the breeding season (Best 1979; Watkins and Moore 1982; Arnbom and
Whitehead 1989; Whitehead and Waters 1990). Males can migrate north in
the summer to feed in the Gulf of Alaska, Bering Sea, and waters around
the Aleutian Islands (Kasuya and Miyashita 1988). Females generally
inhabit waters over 1000 m deep at latitudes under 40 degrees where sea
surface temperatures are under 15 degrees Celsius; 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).
Sperm whales are distributed widely across the North Pacific (Rice
1989). Off California, they occur year-round (Dohl et al., 1983: Barlow
1995; Forney et al., 1995), with peak abundance from April to mid-June
and from August to mid-November (Rice 1974). Off Oregon, sperm whales
are seen in every season except winter (Green et al., 1992). Sperm
whales were sighted during surveys off Oregon in October 2011 and off
Washington in June 2011 (Adams et al., 2014). Sperm whale sightings
were also made off Oregon and Washington during the 2014 Southwest
Fisheries Science Center (SWFSC) vessel survey (Barlow 2016). Sperm
whale were detected acoustically in waters off Oregon and Washington in
August 2016 during the SWFSC Passive Acoustics Survey of Cetacean
Abundance Levels (PASCAL) study using drifting acoustic recorders
(Keating et al., 2018). Oleson et al. (2009) noted a significant diel
pattern in the occurrence of sperm whale clicks at offshore and inshore
monitoring locations off Washington, whereby clicks were more commonly
heard during the day at the offshore site and at night at the inshore
location, suggesting possible diel movements up and down the slope in
search of prey. Sperm whale acoustic detections were also reported at
an inshore site from June through January 2009, with an absence of
calls during February through May (Sirovic et al., 2012). Sperm whales
are likely to be encountered in the proposed survey areas.
Baird's Beaked Whale
Baird's beaked whale has a fairly extensive range across the North
Pacific north of 30[deg] N, and strandings have occurred as far north
as the Pribilof Islands (Rice 1986). Two forms of Baird's beaked whales
were previously recognized--the common slate-gray form and a smaller,
rare black form (Morin et al., 2017), however the small body size of
physically mature individuals in the latter form, as well as recent
genetic studies (Morin et al., 2017) have identified this form as a new
species called Sato's beaked whale (Berardius minimus) (Yamada et al.,
2019).The gray form is seen off Japan, in the Aleutians, and on the
west coast of North America, whereas the black form has been reported
for northern Japan and the Aleutians (Morin et al., 2017). Baird's
beaked whale is currently divided into three distinct stocks: Sea of
Japan, Okhotsk Sea, and Bering Sea/eastern North Pacific (Balcomb 1989;
Reyes 1991). Baird's beaked whales sometimes are seen close to shore,
but their primary habitat is over or near the continental slope and
oceanic seamounts in waters 1000-3000 m deep (Jefferson et al., 2015).
Along the U.S. west coast, Baird's beaked whales have been sighted
primarily along the continental slope (Green et al., 1992; Becker et
al., 2012; Carretta et al., 2021) from late spring to early fall (Green
et al., 1992). The whales move out from those areas in winter (Reyes
1991). In the eastern North Pacific Ocean, Baird's beaked whales
apparently spend the winter and spring far offshore, and in June, they
move onto the continental slope, where peak numbers occur during
September and October. Green et al., (1992) noted that Baird's beaked
whales on the U.S. west coast were most abundant in the summer, and
were not sighted in the fall or winter. MacLeod et al., (2006) reported
numerous sightings and strandings of Berardius spp. off the U.S. west
coast.
Green et al., (1992) sighted five groups during 75,050 km of aerial
survey effort in 1989-1990 off Washington/Oregon spanning coastal to
offshore waters: two in slope waters and three in offshore waters. Two
groups were sighted during summer/fall 2008 surveys off Washington/
Oregon, in waters >2000 m deep (Barlow 2010). Acoustic monitoring
offshore Washington detected Baird's beaked whale pulses during January
through November 2011, with peaks in February and July
([Scirc]irovi[cacute] et al., 2012b in USN 2015). Baird's beaked whales
were detected acoustically in the waters off Oregon and Washington in
August 2016 during the SWFSC PASCAL study using drifting acoustic
recorders (Keating et al., 2018). Baird's beaked whales could be
encountered in the proposed survey regions.
Cuvier's Beaked Whale
Cuvier's beaked whale is probably the most widespread of the beaked
whales, although it is not found in polar waters (Heyning 1989).
Cuvier's beaked whale appears to prefer steep continental slope waters
(Jefferson et al., 2015) and is most common in water depths >1000 m
(Heyning 1989). It is mostly known from strandings and strands more
commonly than any other beaked whale (Heyning 1989). Its inconspicuous
blows, deep-diving behavior, and tendency to avoid vessels all help to
explain the infrequent sightings (Barlow and Gisiner 2006). The
population in the California Current Large Marine Ecosystem seems to be
declining (Moore and Barlow 2013).
MacLeod et al., (2006) reported numerous sightings and strandings
along the Pacific coast of the U.S. Cuvier's beaked whale is the most
common beaked whale off the U.S. West Coast (Barlow 2010), and it is
the beaked whale species that has stranded most frequently on the
coasts of Oregon and Washington. From 1942-2010, there were 23 reported
Cuvier's beaked whale strandings in Oregon and Washington (Moore and
Barlow 2013). Most (75 percent) Cuvier's beaked whale strandings
reported occurred in Oregon (Norman et al. 2004). Records of Cuvier's
beaked whale in British Columbia are scarce, although 20 strandings,
one incidental catch, and five sightings have been reported, including
off western Vancouver Island (Ford 2014). Most strandings have been
reported in summer (Ford 2014).
Four beaked whale sightings were reported in water depths over 2000
m off Oregon/Washington during surveys in 2008 (Barlow 2010). None were
seen in 1996 or 2001 (Barlow 2003), and several were recorded from
1991-1995 (Barlow 1997). One Cuvier's beaked whale sighting was made
during surveys in 2014 (Barlow 2016). Acoustic monitoring in Washington
offshore waters detected Cuvier's beaked whale calls between January
and November 2011 (Sirovic et al., 2012b in USN 2015). Cuvier's beaked
whales were
[[Page 37569]]
detected acoustically in waters off Oregon and Washington in August
2016 during the SWFSC PASCAL study using drifting acoustic recorders
(Keating et al., 2018). Curvier's beaked whales could be encountered
during the proposed surveys.
Blainville's Beaked Whale
Blainville's beaked whale is found in tropical and warm temperate
waters of all oceans (Pitman 2018). It has the widest distribution
throughout the world of all Mesoplodon species (Pitman 2018). Like
other beaked whales, Blainville's beaked whale is generally found in
waters 200-1400 m deep (Gannier 2000; Jefferson et al., 2015).
Occasional occurrences in cooler, higher-latitude waters are presumably
related to warm-water incursions (Reeves et al., 2002). MacLeod et al.,
(2006) reported stranding and sighting records in the eastern Pacific
ranging from 37.3[deg] N to 41.5[deg] S. However, none of the 36 beaked
whale stranding records in Oregon and Washington during 1930-2002
included Blainville's beaked whale (Norman et al., 2004). One
Blainville's beaked whale was found stranded (dead) on the Washington
coast in November 2016 (COASST 2016).
There was one acoustic encounter with Blainville's beaked whales
recorded in Quinault Canyon off Washington in waters 1400 m deep during
2011 (Baumann-Pickering et al., 2014). Blainville's beaked whales were
not detected acoustically off Washington or Oregon during the August
2016 SWFSC PASCAL study using drifting acoustic recorders (Keating et
al., 2018). Although Blainville's beaked whales could be encountered
during the proposed surveys, an encounter would be unlikely because the
proposed survey regions are beyond the northern limits of this tropical
species' usual distribution.
Hubbs' Beaked Whale
Hubbs' beaked whale occurs in temperate waters of the North Pacific
(Mead 1989). Its distribution appears to be correlated with the deep
subarctic current (Mead et al., 1982). Numerous stranding records have
been reported for the west coast of the U.S. (MacLeod et al., 2006).
Most are from California, but at least seven strandings have been
recorded along the B.C. coast as far north as Prince Rupert (Mead 1989;
Houston 1990a; Willis and Baird 1998; Ford 2014). Several strandings
are known from Washington/Oregon (e.g., Norman et al., 2004; Griffiths
et al., 2019). In addition, at least two sightings off Oregon/
Washington, but outside the U.S. EEZ, were reported by Carretta et al.
(2021), and one bycatch record off Oregon/Washington was reported by
Griffiths et al. (2019). During the 2016 SWFSC PASCAL study using
drifting acoustic recorders, detections were made of beaked whale
sounds presumed to be from Hubbs' beaked whales off Washington and
Oregon during August (Griffiths et al., 2019). This species seems to be
less common in the region than some of the other beaked whales.
Stejneger's Beaked Whale
Stejneger's beaked whale occurs in subarctic and cool temperate
waters of the North Pacific (Mead 1989). Most records are from Alaskan
waters, and the Aleutian Islands appear to be its center of
distribution (Mead 1989; Wade et al., 2003). After Cuvier's beaked
whale, Stejneger's beaked whale was the second most commonly stranded
beaked whale species in Oregon and Washington (Norman et al., 2004).
Stejneger's beaked whale calls were detected during acoustic monitoring
offshore Washington between January and June 2011, with an absence of
calls from mid-July-November 2011 ([Scirc]irovi[cacute] et al., 2012b
in USN 2015). Analysis of these data suggest that this species could be
more than twice as prevalent in this area than Baird's beaked whale
(Baumann-Pickering et al., 2014). Stejneger's beaked whales were also
detected acoustically in waters off Oregon and Washington in August
2016 during the SWFSC PASCAL study using drifting acoustic recorders
(Keating et al., 2018).
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
outside of the continental shelf, but has been observed approaching
shore where there is deep water close to the coast (Jefferson et al.,
2015). Striped dolphins regularly occur off California (Becker et al.,
2012), including as far offshore as ~300 n.mi. during NOAA Fisheries
vessel surveys (Carretta et al., 2021). However, few sightings have
been made off Oregon, and no sightings have been reported for
Washington (Carretta et al., 2021). However, strandings have occurred
along the coasts of Oregon and Washington (Carretta et al., 2016).
During surveys off the U.S. west coast in 2014, striped dolphins were
seen as far north as 44[deg] N; based on those sightings, Barlow (2016)
calculated an abundance estimate of 13,171 striped dolphins for Oregon/
Washington. The abundance estimates for 2001, 2005, and 2008 were zero
(Barlow 2016). It is possible, although unlikely, that striped dolphins
could be encountered in the proposed survey area.
Common Dolphin
The 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 2018). It can be found in oceanic and coastal habitats;
it is common in coastal waters 200-300 m deep and is also associated
with prominent underwater topography, such as seamounts (Evans 1994).
Short-beaked common dolphins have been sighted as far as 550 km from
shore (Barlow et al., 1997).
The distribution of short-beaked common dolphins along the U.S.
west coast is variable and likely related to oceanographic changes
(Heyning and Perrin 1994; Forney and Barlow 1998). It is the most
abundant cetacean off California; some sightings have been made off
Oregon, in offshore waters (Carretta et al., 2021). During surveys off
the west coast in 2014 and 2017, sightings were made as far north as
44[deg] N (Barlow 2016; SIO n.d.). Based on the absolute dynamic
topography of the region, short-beaked common dolphins could occur in
relatively high densities off Oregon during July-December (Pardo et
al., 2015). In contrast, habitat modeling predicted moderate densities
of common dolphins off the Columbia River estuary during summer, with
lower densities off southern Oregon (Becker et al., 2014). A group of
six common dolphins was sighted during L-DEO's Cascadia summer survey
just south of the Columbia River off Oregon (RPS 2021b). Common
dolphins could be encountered in the proposed survey regions.
Pacific White-Sided Dolphin
The Pacific white-sided dolphin is found in cool temperate waters
of the North Pacific from the southern Gulf of California to Alaska.
Across the North Pacific, it appears to have a relatively narrow
distribution between 38[deg] N and 47[deg] N (Brownell et al., 1999).
In the eastern North Pacific Ocean, the Pacific white-sided dolphin is
one of the most common cetacean species, occurring primarily in shelf
and slope waters (Green et al., 1993; Barlow 2003, 2010). It is known
to occur close to shore in certain regions, including (seasonally)
[[Page 37570]]
southern California (Brownell et al., 1999).
Results of aerial and shipboard surveys strongly suggest seasonal
north-south movements of the species between California and Oregon/
Washington; the movements apparently are related to oceanographic
influences, particularly water temperature (Green et al., 1993; Forney
and Barlow 1998; Buchanan et al., 2001). During winter, this species is
most abundant in California slope and offshore areas; as northern
waters begin to warm in the spring, it appears to move north to slope
and offshore waters off Oregon/Washington (Green et al., 1992, 1993;
Forney 1994; Forney et al., 1995; Buchanan et al., 2001; Barlow 2003).
The highest encounter rates off Oregon and Washington have been
reported during March-May in slope and offshore waters (Green et al.,
1992). Similarly, Becker et al., (2014) predicted relatively high
densities off southern Oregon in shelf and slope waters.
Based on year-round aerial surveys off Oregon/Washington, the
Pacific white-sided dolphin was the most abundant cetacean species,
with nearly all (97%) sightings occurring in May (Green et al., 1992,
1993). Barlow (2003) also found that the Pacific white-sided dolphin
was one of the most abundant marine mammal species off Oregon/
Washington during 1996 and 2001 ship surveys, and it was the second
most abundant species reported during 2008 surveys (Barlow 2010). Adams
et al., (2014) reported numerous offshore sightings off Oregon during
summer, fall, and winter surveys in 2011 and 2012. Based on surveys
conducted during 2014, the abundance was estimated at 20,711 for
Oregon/Washington (Barlow 2016).
Fifteen Pacific white-sided dolphin sightings (231 animals) were
made off Washington/Oregon during the June-July 2012 L-DEO Juan de Fuca
plate seismic survey (RPS 2012b). There were fifteen Pacific white-
sided dolphin sightings (462 animals) made during the July 2012 L-DEO
seismic surveys off southern Washington (RPS 2012a). This species was
not sighted during the July 2012 L-DEO seismic survey off Oregon (RPS
2012c). Numerous Pacific white-sided dolphin sightings were made during
L-DEO's Cascadia summer survey off Oregon and Washington (RPS 2021b).
Pacific white-sided dolphins are likely to be common in the proposed
survey regions.
Northern Right-Whale Dolphin
The northern right whale dolphin is found in cool temperate and
sub-arctic waters of the North Pacific, from the Gulf of Alaska to near
northern Baja California, ranging from 30[deg] N to 50[deg] N (Reeves
et al., 2002). In the eastern North Pacific Ocean, the northern right
whale dolphin is one of the most common marine mammal species,
occurring primarily in shelf and slope waters ~100 to >2000 m deep
(Green et al., 1993; Barlow 2003). The northern right whale dolphin
comes closer to shore where there is deep water, such as over submarine
canyons (Reeves et al., 2002).
Aerial and shipboard surveys suggest seasonal inshore-offshore and
north-south movements in the eastern North Pacific Ocean between
California and Oregon/Washington; the movements are believed to be
related to oceanographic influences, particularly water temperature and
presumably prey distribution and availability (Green et al., 1993;
Forney and Barlow 1998; Buchanan et al., 2001). Green et al. (1992,
1993) found that northern right whale dolphins were most abundant off
Oregon/Washington during fall, less abundant during spring and summer,
and absent during winter, when this species presumably moves south to
warmer California waters (Green et al., 1992, 1993; Forney 1994; Forney
et al., 1995; Buchanan et al., 2001; Barlow 2003).
Becker et al. (2014) predicted relatively high densities off
southern Oregon, and moderate densities off northern Oregon and
Washington. Based on year-round aerial surveys off Oregon/Washington,
the northern right whale dolphin was the third most abundant cetacean
species, concentrated in slope waters but also occurring in water out
to ~550 km offshore (Green et al., 1992, 1993). Barlow (2003, 2010)
also found that the northern right whale dolphin was one of the most
abundant marine mammal species off Oregon/Washington during 1996, 2001,
2005, and 2008 ship surveys. Offshore sightings were made in the waters
of Oregon during summer, fall, and winter surveys in 2011 and 2012
(Adams et al., 2014). During L-DEO's Cascadia survey during June-July
2021, one sighting of 15 northern right whale dolphins was made off
Washington, and another sighting of 12 individuals was made off Oregon
(RPS 2021b). Northern right whale dolphins are likely to be encountered
in the proposed survey regions.
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] (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).
Off the U.S. west coast, Risso's dolphin is believed to make
seasonal north-south movements related to water temperature, spending
colder winter months off California and moving north to waters off
Oregon/Washington during the spring and summer as northern waters begin
to warm (Green et al., 1992, 1993; Buchanan et al., 2001; Barlow 2003;
Becker 2007). The distribution and abundance of Risso's dolphins are
highly variable from California to Washington, presumably in response
to changing oceanographic conditions on both annual and seasonal time
scales (Forney and Barlow 1998; Buchanan et al., 2001). The highest
densities were predicted along the coasts of Washington, Oregon, and
central and southern California (Becker et al., 2012). Off Oregon and
Washington, Risso's dolphins are most abundant over continental slope
and shelf waters during spring and summer, less so during fall, and
rare during winter (Green et al., 1992, 1993). Green et al., (1992,
1993) reported most Risso's dolphin groups off Oregon between ~45 and
47[deg] N. Several sightings were made off southern Oregon during
surveys in 1991-2014 (Barlow 2016; Carretta et al., 2021). Sightings
during ship surveys in summer/fall 2008 were mostly between ~30 and
38[deg] N; none were reported in Oregon/Washington (Barlow 2010). Based
on 2014 survey data, the abundance for Oregon/Washington was estimated
at 430 (Barlow 2016). Risso's dolphins could be encountered in the
proposed survey regions.
Killer Whale
The killer whale is cosmopolitan and globally fairly abundant,
being observed in all oceans of the world (Ford 2018). It is very
common in temperate waters and also frequents tropical waters, at least
seasonally (Heyning and Dahlheim 1988). There are three distinct
ecotypes, or forms, of killer whales recognized in the north Pacific:
Resident, transient, and offshore. The three ecotypes differ
morphologically, ecologically, behaviorally, and genetically. Resident
killer whales exclusively prey upon fish, with a clear preference for
salmon (Ford and Ellis 2006; Hanson et al., 2010; Ford et al., 2016),
while transient killer whales exclusively prey upon marine mammals
(Carretta et al., 2019). Less is known about offshore killer whales,
but they are believed to consume primarily fish, including several
species of shark (Dahlheim et
[[Page 37571]]
al., 2008). Killer whales occur in inshore inlets, along the coast,
over the continental shelf, and in offshore waters (Ford 2014).
Currently, there are eight killer whale stocks recognized in the
U.S. Pacific: (1) Alaska Residents, occurring from Southeast Alaska to
the Aleutians and Bering Sea; (2) Northern Residents, from British
Columbia through parts of the Southeast Alaska; (3) Southern Residents,
mainly in inland waters of Washington State and southern British
Columbia; (4) Gulf of Alaska, Aleutians, and Bering Sea Transients,
from Prince William Sound through the Aleutians and Bering Sea; (5) AT1
Transients, from Prince William Sound through the Kenai Fjords; (6)
West Coast Transients, from California through Southeast Alaska; (7)
Offshore, from California through Alaska; and (8) Hawaiian (Muto et
al., 2021; Carretta et al., 2021). Individuals from the West Coast
Transient and Offshore stocks could be encountered in the proposed
project areas. It is unlikely that individuals from the endangered
Eastern North Pacific Southern Resident stock would be encountered in
the offshore survey regions, as they are primarily found along the
coasts and the proposed survey is located in waters deeper than 1600 m
and at least 46 km from the shoreline.
The main diet of transient killer whales consists of marine
mammals, in particular porpoises and seals. West coast transient killer
whales (also known as Bigg's killer whales) range from Southeast Alaska
to California (Muto et al., 2021). The seasonal movements of transients
are largely unpredictable (Baird 1994; Ford 2014). Green et al., (1992)
noted that most groups seen during their surveys off Oregon and
Washington were likely transients; during those surveys, killer whales
were sighted only in shelf waters. Two of 17 killer whales that
stranded in Oregon were confirmed as transient (Stevens et al., 1989 in
Norman et al., 2004).
Little is known about offshore killer whales, but they occur
primarily over shelf waters and feed on fish, especially sharks (Ford
2014). Dahlheim et al., (2008) reported sightings in Southeast Alaska
during spring and summer. Eleven sightings of approximately 536
individuals were reported off Oregon/Washington during the 2008 SWFSC
vessel survey (Barlow 2010). Killer whales were sighted offshore
Washington during surveys from August 2004 to September 2008 (Oleson et
al., 2009). Keating et al., (2015) analyzed cetacean whistles from
recordings made during 2000-2012; several killer whale acoustic
detections were made offshore Washington. Killer whales were sighted
off Washington in July and September 2012 (Adams et al., 2014).
During L-DEO's Cascadia surveys during June through July 2021 in
the Northeast Pacific Ocean, a sighting of 20 killer whales was made
near the shelf edge off northern Oregon (RPS 2021b). Killer whales
could be encountered during the proposed survey, although it is
unlikely the endangered Southern Resident Killer whales would occur as
far offshore as the survey regions.
Pygmy and Dwarf Sperm Whale
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).
Both Kogia species are sighted primarily along the continental
shelf edge and slope and over deeper waters off the shelf (Hansen et
al., 1994; Davis et al., 1998; Jefferson et al., 2015). Stomach content
analyses from stranded whales further support this distribution
(McAlpine 2018). Recent data indicate that both Kogia species feed in
the water column and on/near the seabed, likely using echolocation to
search for prey (McAlpine 2018). Several studies have suggested that
pygmy sperm whales live and feed mostly beyond the continental shelf
edge, whereas dwarf sperm whales tend to occur closer to shore, often
over the continental shelf and slope (Rice 1998; Wang et al., 2002;
MacLeod et al., 2004; McAlpine 2018). It has also 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).
Pygmy and dwarf sperm whales are rarely sighted off Oregon and
Washington, with only one sighting of an unidentified Kogia sp. beyond
the U.S. EEZ, during the 1991-2014 NOAA vessel surveys (Carretta et
al., 2021). Norman et al., (2004) reported eight confirmed stranding
records of pygmy sperm whales for Oregon and Washington, five of which
occurred during autumn and winter. Despite the limited number of
sightings, it is possible that pygmy or dwarf sperm whales could be
encountered within the proposed project areas.
Dall's Porpoise
Dall's porpoise is found in temperate to subarctic waters of the
North Pacific and adjacent seas (Jefferson et al., 2015). It is widely
distributed across the North Pacific over the continental shelf and
slope waters, and over deep (>2500 m) oceanic waters (Hall 1979). It is
probably the most abundant small cetacean in the North Pacific Ocean,
and its abundance changes seasonally, likely in relation to water
temperature (Becker 2007).
Off Oregon and Washington, Dall's porpoise is widely distributed
over shelf and slope waters, with concentrations near shelf edges, but
is also commonly sighted in pelagic offshore waters (Morejohn 1979;
Green et al., 1992; Becker et al., 2014; Fleming et al., 2018; Carretta
et al., 2021). Combined results of various surveys out to ~550 km
offshore indicate that the distribution and abundance of Dall's
porpoise varies between seasons and years. North-south movements are
believed to occur between Oregon/Washington and California in response
to changing oceanographic conditions, particularly temperature and
distribution and abundance of prey (Green et al., 1992, 1993; Mangels
and Gerrodette 1994; Barlow 1995; Forney and Barlow 1998; Buchanan et
al., 2001). Becker et al., (2014) predicted high densities off southern
Oregon throughout the year, with moderate densities to the north.
According to predictive density distribution maps, the highest
densities off southern Washington and Oregon occur along the 500-m
isobath (Menza et al., 2016).
Encounter rates reported by Green et al., (1992) during aerial
surveys off Oregon/Washington were highest in fall, lowest during
winter, and intermediate during spring and summer. Encounter rates
during the summer were similarly high in slope and shelf waters, and
somewhat lower in offshore waters (Green et al., 1992). Dall's porpoise
was the most abundant species sighted off Oregon/Washington during
1996, 2001, 2005, and 2008 ship surveys up to ~550 km from shore
(Barlow 2003, 2010). Oleson et al., (2009) reported 44 sightings of 206
individuals off Washington during surveys form August 2004 to September
2008. Dall's porpoise were seen in the waters off Oregon during summer,
fall, and winter surveys in 2011 and 2012 (Adams et al., 2014).
Nineteen Dall's porpoise sightings (144 animals) were made off
Washington/Oregon during the June-
[[Page 37572]]
July 2012 L-DEO Juan de Fuca plate seismic survey (RPS 2012b). There
were 16 Dall's porpoise sightings (54 animals) made during the July
2012 L-DEO seismic surveys off southern Washington (RPS 2012a). This
species was not sighted during the July 2012 L-DEO seismic survey off
Oregon (RPS 2012c). During L-DEO's Cascadia survey during June-July
2021, one sighting of four individuals was made near the shelf edge off
the Columbia River (RPS 2021b). Dall's porpoise is likely to be
encountered during the proposed seismic surveys.
Northern Fur Seal
The northern fur seal is endemic to the North Pacific Ocean and
occurs from southern California to the Bering Sea, Okhotsk Sea, and
Honshu Island, Japan (Muto et al., 2021). During the breeding season,
most of the worldwide population of northern fur seals inhabits the
Pribilof Islands in the southern Bering Sea (NMFS 2007; Lee et al.,
2014; Muto et al., 2021). The rest of the population occurs at
rookeries on Bogoslof Island in the Bering Sea, in Russia (Commander
Islands, Robben Island, Kuril Islands), on San Miguel Island in
southern California (NMFS 1993; Lee et al., 2014), and on the Farallon
Islands off central California (Muto et al., 2021). In the U.S., two
stocks are recognized--the Eastern Pacific and the California stocks
(Muto et al., 2021). The Eastern Pacific stock ranges from the Pribilof
Islands and Bogoslof Island in the Bering Sea during summer to
California during winter (Muto et al., 2021). When not on rookery
islands, northern fur seals are primarily pelagic but occasionally haul
out on rocky shorelines (Muto et al., 2021).
During the breeding season, adult males usually come ashore in May-
August and may sometimes be present until November; adult females are
found ashore from June-November (Carretta et al., 2021; Muto et al.,
2021). After reproduction, northern fur seals spend the next 7-8 months
feeding at sea (Roppel 1984). Immature seals can remain in southern
foraging areas year-round until they are old enough to mate (NMFS
2007). In November, females and pups leave the Pribilof Islands and
migrate through the Gulf of Alaska to feeding areas primarily off the
coasts of B.C., Washington, Oregon, and California before migrating
north again to the rookeries in spring (Ream et al., 2005; Pelland et
al., 2014). Males usually migrate only as far south as the Gulf of
Alaska (Kajimura 1984). Ream et al. (2005) showed that migrating
females moved over the continental shelf as they migrated
southeasterly. Instead of following depth contours, their travel
corresponded with movements of the Alaska Gyre and the North Pacific
Current (Ream et al., 2005). Their foraging areas were associated with
eddies, the subarctic-subtropical transition region, and coastal mixing
(Ream et al., 2005; Alford et al., 2005). Some juveniles and non-
pregnant females may remain in the Gulf of Alaska throughout the summer
(Calkins 1986). The northern fur seals spends ~90% of its time at sea,
typically in areas of upwelling along the continental slopes and over
seamounts (Gentry 1981). The remainder of its life is spent on or near
rookery islands or haulouts. Pups from the California stock also
migrate to Washington, Oregon, and northern California after weaning
(Lea et al., 2009).
Northern fur seals were seen throughout the North Pacific during
surveys conducted during 1987-1990, including off Washington and Oregon
(Buckland et al., 1993). Tagged adult fur seals were tracked from the
Pribilof Islands to the waters off Washington/Oregon/California, with
recorded movement throughout the region (Pelland et al., 2014). Tracked
adult male fur seals that were tagged on St. Paul Island in the Bering
Sea in October 2009 wintered in the Bering Sea or northern North
Pacific Ocean; females migrated to the Gulf of Alaska and the
California Current (Sterling et al., 2014). Some individuals reach
California by December, after which time numbers increase off the west
coast of North America (Ford 2014). The peak density shifts over the
course of the winter and spring, with peak densities occurring in
California in February, April off Oregon and Washington, and May off
B.C. and Southeast Alaska (Ford 2014). The use of continental shelf and
slope waters of B.C. and the northwestern U.S. by adult females during
winter is well documented from pelagic sealing data (Bigg 1990).
Bonnell et al., (1992) noted the presence of northern fur seals
year-round off Oregon/Washington, with the greatest numbers (87%)
occurring in January-May. Northern fur seals were seen as far out from
the coast as 185 km, and numbers increased with distance from land;
they were 5-6 times more abundant in offshore waters than over the
shelf or slope (Bonnell et al., 1992). The highest densities were seen
in the Columbia River plume (~46[deg] N) and in deep offshore waters
(>2000 m) off central and southern Oregon (Bonnell et al., 1992). The
waters off Washington are a known foraging area for adult females, and
concentrations of fur seals were also reported to occur near Cape
Blanco, Oregon, at ~42.8[deg] N (Pelland et al., 2014). During L-DEO's
Cascadia survey during June-July 2021, one northern fur seal was
sighted off Washington near the shelf edge (RPS 2021b).
Northern fur seals could be observed in the proposed survey
regions, in particular females and juveniles. However, adult males are
generally ashore during the reproductive season from May-August; adult
females are generally ashore from June through November.
Guadalupe Fur Seal
Most breeding and births occur at Isla Guadalupe, Mexico; a
secondary rookery exists at Isla Benito del Este (Maravilla-Chavez and
Lowry 1999; Aurioles-Gamboa et al., 2010). A few Guadalupe fur seals
are known to occur at California sea lion rookeries in the Channel
Islands, primarily San Nicolas and San Miguel islands, and sightings
have also been made at Santa Barbara and San Clemente islands (Stewart
et al., 1987; Carretta et al., 2021). Guadalupe fur seals prefer rocky
habitat for breeding and hauling out. They generally haul out at the
base of towering cliffs on shores characterized by solid rock and large
lava blocks (Peterson et al., 1968), although they can also inhabit
caves and recesses (Belcher and Lee 2002). While at sea, this species
usually is solitary but typically gathers in the hundreds to thousands
at breeding sites.
During the summer breeding season, most adults occur at rookeries
in Mexico (Norris 2017 in USN 2019; Carretta et al., 2021). Following
the breeding season, adult males tend to move northward to forage.
Females have been observed feeding south of Guadalupe Island, making an
average round trip of 2375 km (Ronald and Gots 2003). Several
rehabilitated Guadalupe fur seals that were satellite tagged and
released in central California traveled as far north as B.C. (Norris et
al., 2015; Norris 2017 in USN 2019). Fur seals younger than two years
old are more likely to travel to more northerly, offshore areas than
older fur seals (Norris 2017 in USN 2019). Stranding data also
indicates that fur seals younger than 2 years are more likely to occur
in the proposed survey area, as this age class was most frequently
reported (Lambourn et al., 2012 in USN 2019). During 2015-2021, 724
Guadalupe fur seals stranded on the West Coast of the U.S., including
182 strandings along the coasts of Oregon and Washington during 2019-
2021; NMFS declared this an unusual mortality event (NOAA 2021d).
Guadalupe fur seals could be
[[Page 37573]]
encountered during the proposed seismic surveys, but most animals are
likely to occur at their breeding sites farther south at the time of
the surveys.
California Sea Lion
The primary range of the California sea lion includes the coastal
areas and offshore islands of the eastern North Pacific Ocean from B.C.
to central Mexico, including the Gulf of California (Jefferson et al.,
2015). However, its distribution is expanding (Jefferson et al., 2015),
and its secondary range extends into the Gulf of Alaska (Maniscalco et
al., 2004) and southern Mexico (Gallo-Reynoso and Sol[oacute]rzano-
Velasco 1991), where it is occasionally recorded.
California sea lion rookeries are on islands located in southern
California, western Baja California, and the Gulf of California
(Carretta et al., 2021). Five genetically distinct geographic
populations have been identified: (1) Pacific Temperate (includes
rookeries in U.S. waters and the Coronados Islands to the south), (2)
Pacific Subtropical, (3) Southern Gulf of California, (4) Central Gulf
of California, and (5) Northern Gulf of California (Schramm et al.,
2009). Animals from the Pacific Temperate population occur in the
proposed project area.
In California and Baja California, births occur on land from mid-
May to late-June. During August and September, after the mating season,
the adult males migrate northward to feeding areas as far north as
Washington (Puget Sound) and B.C. (Lowry et al., 1992). They remain
there until spring (March-May), when they migrate back to the breeding
colonies (Lowry et al., 1992; Weise et al., 2006). The distribution of
immature California sea lions is less well known but some make
northward migrations that are shorter in length than the migrations of
adult males (Huber 1991). However, most immature seals are presumed to
remain near the rookeries for most of the year, as are females and pups
(Lowry et al., 1992).
California sea lions are coastal animals that often haul out on
shore throughout the year, but peak numbers off Oregon and Washington
occur during the fall (Bonnell et al., 1992). During aerial surveys off
the coasts of Oregon and Washington during 1989-1990, California sea
lions were sighted at sea during the fall and winter, but no sightings
were made during June-August (Bonnell et al., 1992). Numbers off Oregon
decrease during winter, as animals travel further north (Mate 1975 in
Bonnell et al., 1992). King (1983) noted that sea lions are rarely
found more than 16 km offshore. During fall and winter surveys off
Oregon and Washington, mean distance from shore was ~13 km and most
were observed in water <200 m deep; however, sightings were made in
water as deep as 356 m (Bonnell et al., 1992). Weise et al., (2006)
reported that males normally forage almost exclusively over the
continental shelf, but during anomalous climatic conditions they can
forage farther out to sea (up to 450 km offshore).
During aerial surveys over the shelf and slope off Oregon and
Washington (Adams et al., 2014), California sea lions were seen during
all survey months (January-February, June-July, September-October).
Although most sightings occurred on the shelf, during February 2012,
one sighting was made near the 2000-m depth contour, and during June
2011 and July 2012, sightings were made along the 200-m isobath off
southern Oregon (Adams et al., 2014). During October 2011, sightings
were made off the Columbia River estuary near the 200-m isopleth and on
the southern Oregon shelf; during September 2012, sightings occurred in
nearshore waters off Washington and in shelf waters along the coast of
Oregon (Adams et al., 2014). Adams et al., (2014) reported sightings
more than 60 km off the coast of Oregon. During L-DEO's Cascadia survey
during June-July 2021, four sightings of nine California sea lions were
made in nearshore waters off Oregon (RPS 2021b). California sea lions
were also taken as bycatch off Washington and Oregon in the west coast
groundfish fishery during 2002-2009 (Jannot et al., 2011). California
sea lions could be encountered in the proposed project regions.
Steller Sea Lion
The Steller sea lion occurs along the North Pacific Rim from
northern Japan to California (Loughlin et al., 1984). It is distributed
around the coasts to the outer shelf from northern Japan through the
Kuril Islands and Okhotsk Sea, through the Aleutian Islands, central
Bering Sea, southern Alaska, and south to California (NOAA 2021e).
There are two stocks, or DPSs, of Steller sea lions--the Western and
Eastern DPSs, which are divided at 144[deg] W longitude (Muto et al.,
2021). The Western DPS is listed as endangered and includes animals
that occur in Japan and Russia (Muto et al., 2021); the Eastern DPS was
delisted from threatened in 2013 (NMFS 2013a). Only individuals from
the Eastern DPS could occur in the proposed survey regions.
Steller sea lions typically inhabit waters from the coast to the
outer continental shelf and slope throughout their range; they are not
considered migratory, although foraging animals can travel long
distances (Loughlin et al., 2003; Raum-Suryan et al., 2002). Rookeries
of Steller sea lions from the Eastern DPS are located in southeast
Alaska, B.C., Oregon, and California; there are no rookeries in
Washington (NMFS 2013a; Muto et al., 2021). Breeding adults occupy
rookeries from late-May to early-July (NMFS 2008). Federally designated
critical habitat for Steller sea lions in Oregon and California
includes all rookeries (NMFS 1993). Although the Eastern DPS was
delisted from the ESA in 2013, the designated critical habitat remains
valid (NOAA 2021e). The critical habitat in Oregon is located along the
coast at Rogue Reef (Pyramid Rock) and Orford Reef (Long Brown Rock and
Seal Rock). The critical habitat area includes aquatic zones that
extend 0.9 km seaward and air zones extending 0.9 km above these
terrestrial and aquatic zones (NMFS 1993). The nearest proposed seismic
transect would be located 46 km from shore.
Non-breeding adults use haulouts or occupy sites at the periphery
of rookeries during the breeding season (NMFS 2008). Pupping occurs
from mid-May to mid-July (Pitcher and Calkins 1981) and peaks in June
(Pitcher et al., 2002). Territorial males fast and remain on land
during the breeding season (NMFS 2008). Females with pups generally
stay within 30 km of the rookeries in shallow (30-120 m) water when
feeding (NMFS 2008). Tagged juvenile sea lions showed localized
movements near shore (Briggs et al., 2005). Loughlin et al., (2003)
reported that most (88%) at-sea movements of juvenile Steller sea lions
in the Aleutian Islands were short (<15 km) foraging trips. The mean
distance of juvenile sea lion trips at sea was 16.6 km, and the maximum
trip distance recorded was 447 km. Long-range trips represented 6% of
all trips at sea, and trip distance and duration increase with age
(Loughlin et al., 2003; Call et al., 2007). Although Steller sea lions
are not considered migratory, foraging animals can travel long
distances outside of the breeding season (Loughlin et al., 2003; Raum-
Suryan et al., 2002). During the summer, they mostly forage within 60
km from the coast; during winter, they can range up to 200 km from
shore (Ford 2014).
During surveys off the coasts of Oregon and Washington, Bonnell et
al., (1992) noted that 89% of sea lions occurred over the shelf at a
mean
[[Page 37574]]
distance of 21 km from the coast and near or in waters <200 m deep; the
farthest sighting occurred ~40 km from shore, and the deepest sighting
location was 1611 m deep. Sightings were made along the 200-m depth
contour throughout the year (Bonnell et al., 1992). During aerial
surveys over the shelf and slope off Oregon and Washington, one Steller
sea lion was seen on the Oregon shelf during January 2011, and two
sightings totaling eight individuals were made on September 2012 off
southern Oregon (Adams et al., 2014). During a survey off Washington/
Oregon June-July 2012, two Steller sea lions were seen from R/V
Langseth (RPS 2012b) off southern Oregon. Eight sightings of 11
individuals were made from R//V Northern Light during a survey off
southern Washington during July 2012 (RPS 2012a). No sightings were
made during L-DEO's Cascadia summer survey off Oregon and Washington
(RPS 2021b). Steller sea lions were also taken as bycatch off southern
Oregon in the west coast groundfish fishery during 2002-2009 (Jannot et
al., 2011). Steller sea lions could be encountered in the proposed
project regions.
Northern Elephant Seal
The northern elephant seal breeds in California and Baja
California, primarily on offshore islands, from Cedros off the west
coast of Baja California, north to the Farallons in Central California
(Stewart et al., 1994). Adult elephant seals engage in two long
northward migrations per year, one following the breeding season, and
another following the annual molt (Stewart and DeLong 1995). Between
the two foraging periods, they return to land to molt, with females
returning earlier than males (March-April vs. July-August). After the
molt, adults then return to their northern feeding areas until the next
winter breeding season. Breeding occurs from December-March (Stewart
and Huber 1993). Females arrive in late December or January and give
birth within ~1 week of their arrival. Juvenile elephant seals
typically leave the rookeries in April or May and head north, traveling
an average of 900-1000 km. Most elephant seals return to their natal
rookeries when they start breeding (Huber et al., 1991).
When not at their breeding rookeries, adults feed at sea far from
the rookeries. Adult females and juveniles forage in the California
current off California to B.C. (Le Boeuf et al., 1986, 1993, 2000).
Bonnell et al. (1992) reported that northern elephant seals were
distributed equally in shelf, slope, and offshore waters during surveys
conducted off Oregon and Washington, as far as 150 km from shore, in
waters >2000 m deep. Telemetry data indicate that they range much
farther offshore than that (Stewart and DeLong 1995). Males may feed as
far north as the eastern Aleutian Islands and the Gulf of Alaska,
whereas females feed south of 45[deg] N (Le Boeuf et al., 1993; Stewart
and Huber 1993). Adult male elephant seals migrate north via the
California current to the Gulf of Alaska during foraging trips, and
could potentially be passing through the area off Washington in May and
August (migrating to and from molting periods) and November and
February (migrating to and from breeding periods), but likely their
presence there is transient and short-lived. Most elephant seal
sightings at sea off Washington were made during June, July, and
September; off Oregon, sightings were recorded from November through
May (Bonnell et al., 1992). Northern elephant seal pups have been
sighted at haulouts in the inland waters of Washington State (Jeffries
et al., 2000), and at least three were reported to have been born there
(Hayward 2003). Pupping has also been observed at Shell Island
(~43.3[deg] N) off southern Oregon, suggesting a range expansion
(Bonnell et al., 1992; Hodder et al., 1998). Northern elephant seals
could be encountered during the proposed seismic surveys.
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. 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, 2019) recommended that marine mammals be divided into hearing
groups based on directly measured (behavioral or auditory evoked
potential techniques) or estimated hearing ranges (behavioral response
data, anatomical modeling, etc.). Note that no direct measurements of
hearing ability have been successfully completed for mysticetes (i.e.,
low-frequency cetaceans). Subsequently, NMFS (2018) described
generalized hearing ranges for these marine mammal hearing groups.
Generalized hearing ranges were chosen based on the approximately 65
decibel (dB) threshold from the normalized composite audiograms, with
the exception for lower limits for low-frequency cetaceans where the
lower bound was deemed to be biologically implausible and the lower
bound from Southall et al. (2007) retained. Marine mammal hearing
groups and their associated hearing ranges are provided in Table 2.
Table 2--Marine Mammal Hearing Groups
[NMFS, 2018]
------------------------------------------------------------------------
Hearing group Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen 7 Hz to 35 kHz.
whales).
Mid-frequency (MF) cetaceans 150 Hz to 160 kHz.
(dolphins, toothed whales, beaked
whales, bottlenose whales).
High-frequency (HF) cetaceans (true 275 Hz to 160 kHz.
porpoises, Kogia, river dolphins,
Cephalorhynchid, Lagenorhynchus
cruciger & L. australis).
Phocid pinnipeds (PW) (underwater) 50 Hz to 86 kHz.
(true seals).
Otariid pinnipeds (OW) (underwater) 60 Hz to 39 kHz.
(sea lions and fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
composite (i.e., all species within the group), where individual
species' hearing ranges are typically not as broad. Generalized
hearing range chosen based on ~65 dB threshold from normalized
composite audiogram, with the exception for lower limits for LF
cetaceans (Southall et al. 2007) and PW pinniped (approximation).
The pinniped functional hearing group was modified from Southall et
al. (2007) on the basis of data indicating that phocid species have
consistently demonstrated an extended frequency range of hearing
compared to otariids, especially in the higher frequency range
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth and Holt,
2013).
[[Page 37575]]
For more detail concerning these groups and associated frequency
ranges, please see NMFS (2018) for a review of available information.
Potential Effects of Specified Activities on Marine Mammals and Their
Habitat
This section includes a discussion of the ways that L-DEO's
specified activity may impact marine mammals and their habitat. The
Estimated Take section later in this document includes a quantitative
analysis of the number of individuals that are expected to be taken by
this activity. The Negligible Impact Analysis and Determination section
considers the content of this section, the Estimated Take section, and
the Proposed Mitigation section, to draw conclusions regarding the
likely impacts of these activities on the reproductive success or
survivorship of individuals and how those impacts on individuals may or
may not 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 a 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):
<bullet> 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;
<bullet> 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;
<bullet> 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
<bullet> 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 this dependence on a
large number of varying factors, ambient
[[Page 37576]]
sound levels can be expected to vary widely over both coarse and fine
spatial and temporal scales. Sound levels at a given frequency and
location can vary by 10-20 dB from day to day (Richardson et al.,
1995). The result is that, depending on the source type and its
intensity, sound from a given activity may be a negligible addition to
the local environment or could form a distinctive signal that may
affect marine mammals. Details of source types are described in the
following text.
Sounds are often considered to fall into one of two general types:
Pulsed and non-pulsed (defined in the following). The distinction
between these two sound types is important because they have differing
potential to cause physical effects, particularly with regard to
hearing (e.g., Ward, 1997 in Southall et al., 2007). Please see
Southall et al., (2007) for an in-depth discussion of these concepts.
Pulsed sound sources (e.g., airguns, explosions, gunshots, sonic
booms, impact pile driving) produce signals that are brief (typically
considered to be less than one second), broadband, atonal transients
(ANSI, 1986, 2005; Harris, 1998; NIOSH, 1998; ISO, 2003) and occur
either as isolated events or repeated in some succession. Pulsed sounds
are all characterized by a relatively rapid rise from ambient pressure
to a maximal pressure value followed by a rapid decay period that 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.
Acoustic Effects
Here, we discuss the effects of active acoustic sources on marine
mammals.
Potential Effects of Underwater Sound--Please refer to the
information given previously (``Description of Active Acoustic Sound
Sources'') regarding sound, characteristics of sound types, and metrics
used in this document. Note that, in the following discussion, we refer
in many cases to Finneran (2015), a review article concerning studies
of noise-induced hearing loss conducted from 1996-2015. For study-
specific citations, please see Finneran (2015). 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, if it
occurs at all, will occur almost exclusively in cases where a noise is
within an animal's hearing frequency 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 response.
Third is a zone within which, for signals of high intensity, the
received level is sufficient to potentially cause discomfort or tissue
damage to auditory or other systems. Overlaying these zones to a
certain extent is the area within which masking (i.e., when a sound
interferes with or masks the ability of an animal to detect a signal of
interest that is above the absolute hearing threshold) may occur; the
masking zone may be highly variable in size.
We describe the more severe effects of certain non-auditory
physical or physiological effects only briefly as we do not expect that
use of airgun arrays are reasonably likely to result in such effects
(see below for further discussion). Potential effects from impulsive
sound sources can range in severity from effects such as behavioral
disturbance or tactile perception to physical discomfort, slight injury
of the internal organs and the auditory system, or mortality (Yelverton
et al., 1973). Non-auditory physiological effects or injuries that
theoretically might occur in marine mammals exposed to high level
underwater sound or as a secondary effect of extreme behavioral
reactions (e.g., change in dive profile as a result of an avoidance
reaction) caused by exposure to sound include neurological effects,
bubble formation, resonance effects, and other types of organ or tissue
damage (Cox et al., 2006; Southall et al., 2007; Zimmer and Tyack,
2007; Tal et al., 2015). The survey activities considered here do not
involve the use of devices such as explosives or mid-frequency tactical
sonar that are associated with these types of effects.
Threshold Shift--Marine mammals exposed to high-intensity sound, or
to lower-intensity sound for prolonged periods, can experience hearing
threshold shift (TS), which is the loss of hearing sensitivity at
certain frequency ranges (Finneran, 2015). TS can be permanent (PTS),
in which case the loss of hearing sensitivity is not fully recoverable,
or temporary (TTS), in which case the animal's hearing threshold would
recover over time (Southall et al., 2007). Repeated sound exposure that
leads to TTS could cause PTS. In severe cases of PTS, there can 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
[[Page 37577]]
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
typically 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 was 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 direct 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, 2019), Finneran and
Jenkins (2012), Finneran (2015), and NMFS (2018).
Behavioral Effects--Behavioral disturbance may include a variety of
effects, including subtle changes in behavior (e.g., minor or brief
avoidance of an area or changes in vocalizations), more conspicuous
changes in similar behavioral activities, and more sustained and/or
potentially severe reactions, such as displacement from or abandonment
of high-quality habitat. Behavioral responses to sound are highly
variable and context-specific, and any reactions depend on numerous
intrinsic and extrinsic factors (e.g., species, state of maturity,
experience, current activity, reproductive state, auditory sensitivity,
time of day), as well as the interplay between factors (e.g.,
Richardson et al., 1995; Wartzok et al., 2003; Southall et al., 2007,
2019; Weilgart, 2007; Archer et al., 2010). Behavioral reactions can
vary not only among individuals but also within an individual,
depending on previous experience with a sound source, context, and
numerous other factors (Ellison et al., 2012), and can vary depending
on characteristics associated with the sound source (e.g., whether it
is moving or stationary, number of sources, distance from the source).
Please see Appendices B-C of Southall et al. (2007) for a review of
studies involving marine mammal behavioral responses to sound.
Habituation can occur when an animal's response to a stimulus wanes
with repeated exposure, usually in the absence of unpleasant associated
events (Wartzok et al., 2003). Animals are most likely to habituate to
sounds that are predictable and unvarying. It is important to note that
habituation is appropriately considered as a ``progressive reduction in
response to stimuli that are perceived as neither aversive nor
beneficial,'' rather than as, more generally, moderation in response to
human disturbance (Bejder et al., 2009). The opposite process is
sensitization, when an unpleasant experience leads to subsequent
responses, often in the form of avoidance, at a lower level of
exposure. As noted, behavioral state may affect the type of response.
For example, animals that are resting may show greater behavioral
change in response to disturbing sound levels than animals
[[Page 37578]]
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 disruptions 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 or amplitude of
calls (Miller et al., 2000; Fristrup et al., 2003; Foote et al., 2004;
Holt et al., 2012), while right whales have been observed to shift the
frequency content of their calls upward while reducing the rate of
calling in areas of increased anthropogenic noise (Parks et al., 2007).
In some cases, animals may cease sound production during production of
aversive signals (Bowles et al., 1994).
Cerchio et al., (2014) used passive acoustic monitoring to document
the presence of singing humpback whales off the coast of northern
Angola and to opportunistically test for the effect of seismic survey
activity on the number of singing whales. Two recording units were
deployed between March and December 2008 in the offshore environment;
numbers of singers were counted every hour. Generalized Additive Mixed
Models were used to assess the effect of survey day (seasonality), hour
(diel variation), moon phase, and received levels of noise (measured
from a single pulse during each ten minute sampled period) on singer
number. The number of singers significantly decreased with increasing
received level of noise, suggesting that humpback whale breeding
activity was disrupted to some extent by the survey activity.
Castellote et al., (2012) reported acoustic and behavioral changes
by fin whales in response to shipping and airgun noise. Acoustic
features of fin whale song notes recorded in the Mediterranean Sea and
northeast Atlantic Ocean were compared for areas with different
shipping noise levels and traffic intensities and during a seismic
airgun survey. During the first 72 h of 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,
[[Page 37579]]
providing evidence that fin whales may avoid an area for an extended
period in the presence of increased noise. The authors hypothesize that
fin whale acoustic communication is modified to compensate for
increased background noise and that a sensitization process may play a
role in the observed temporary displacement.
Seismic pulses at average received levels of 131 dB re 1 [mu]Pa\2\-
s caused blue whales to increase call production (Di Iorio and Clark,
2010). In contrast, McDonald et al., (1995) tracked a blue whale with
seafloor seismometers and reported that it stopped vocalizing and
changed its travel direction at a range of 10 km from the acoustic
source vessel (estimated received level 143 dB pk-pk). Blackwell et
al., (2013) found that bowhead whale call rates dropped significantly
at onset of airgun use at sites with a median distance of 41-45 km from
the survey. Blackwell et al. (2015) expanded this analysis to show that
whales actually increased calling rates as soon as airgun signals were
detectable before ultimately decreasing calling rates at higher
received levels (i.e., 10-minute SELcum of ~127 dB). Overall, these
results suggest that bowhead whales may adjust their vocal output in an
effort to compensate for noise before ceasing vocalization effort and
ultimately deflecting from the acoustic source (Blackwell et al., 2013,
2015). These studies demonstrate that even low levels of noise received
far from the source can induce changes in vocalization and/or behavior
for mysticetes.
Avoidance is the displacement of an individual from an area or
migration path as a result of the presence of a sound or other
stressors, and is one of the most obvious manifestations of disturbance
in marine mammals (Richardson et al., 1995). For example, gray whales
are known to change direction--deflecting from customary migratory
paths--in order to avoid noise from seismic surveys (Malme et al.,
1984). Humpback whales showed avoidance behavior in the presence of an
active seismic array during observational studies and controlled
exposure experiments in western Australia (McCauley et al., 2000).
Avoidance may be short-term, with animals returning to the area once
the noise has ceased (e.g., Bowles et al., 1994; Goold, 1996; Stone et
al., 2000; Morton and Symonds, 2002; Gailey et al., 2007). Longer-term
displacement is possible, however, which may lead to changes in
abundance or distribution patterns of the affected species in the
affected region if habituation to the presence of the sound does not
occur (e.g., Bejder et al., 2006; Teilmann et al., 2006).
Forney et al., (2017) detail the potential effects of noise on
marine mammal populations with high site fidelity, including
displacement and auditory masking, noting that a lack of observed
response does not imply absence of fitness costs and that apparent
tolerance of disturbance may have population-level impacts that are
less obvious and difficult to document. As we discuss in describing our
proposed mitigation later in this document, avoidance of overlap
between disturbing noise and areas and/or times of particular
importance for sensitive species may be critical to avoiding
population-level impacts because (particularly for animals with high
site fidelity) there may be a strong motivation to remain in the area
despite negative impacts. Forney et al., (2017) state that, for these
animals, remaining in a disturbed area may reflect a lack of
alternatives rather than a lack of effects. The authors discuss several
case studies, including western Pacific gray whales, which are a small
population of mysticetes believed to be adversely affected by oil and
gas development off Sakhalin Island, Russia (Weller et al., 2002;
Reeves et al., 2005). Western gray whales display a high degree of
interannual site fidelity to the area for foraging purposes, and
observations in the area during airgun surveys has shown the potential
for harm caused by displacement from such an important area (Weller et
al., 2006; Johnson et al., 2007). Forney et al., (2017) also discuss
beaked whales, noting that anthropogenic effects in areas where they
are resident could cause severe biological consequences, in part
because displacement may adversely affect foraging rates, reproduction,
or health, while an overriding instinct to remain could lead to more
severe acute effects.
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 arrays of large 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
[[Page 37580]]
responses observed included changes in swimming or surfacing behavior,
with indications that cetaceans remained near the water surface at
these times. Cetaceans were recorded as feeding less often when large
arrays were active. Behavioral observations of gray whales during a
seismic survey monitored whale movements and respirations pre-, during,
and post-seismic survey (Gailey et al., 2016). Behavioral state and
water depth were the best `natural' predictors of whale movements and
respiration and, after considering natural variation, none of the
response variables were significantly associated with seismic survey or
vessel sounds.
Stress Responses--An animal's perception of a threat may be
sufficient to trigger stress responses consisting of some combination
of behavioral responses, autonomic nervous system responses,
neuroendocrine responses, or immune responses (e.g., Seyle, 1950;
Moberg, 2000). In many cases, an animal's first and sometimes most
economical (in terms of energetic costs) response is behavioral
avoidance of the potential stressor. Autonomic nervous system responses
to stress typically involve changes in heart rate, blood pressure, and
gastrointestinal activity. These responses have a relatively short
duration and may or may not have a significant long-term effect on an
animal's fitness.
Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that
are affected by stress--including immune competence, reproduction,
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been
implicated in failed reproduction, altered metabolism, reduced immune
competence, and behavioral disturbance (e.g., Moberg, 1987; Blecha,
2000). Increases in the circulation of glucocorticoids are also equated
with stress (Romano et al., 2004).
The primary distinction between stress (which is adaptive and does
not normally place an animal at risk) and ``distress'' is the cost of
the response. During a stress response, an animal uses glycogen stores
that can be quickly replenished once the stress is alleviated. In such
circumstances, the cost of the stress response would not pose serious
fitness consequences. However, when an animal does not have sufficient
energy reserves to satisfy the energetic costs of a stress response,
energy resources must be diverted from other functions. This state of
distress will last 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, significant masking could disrupt
behavioral patterns, which in turn could affect fitness for survival
and reproduction. 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 predicting 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 may be less 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,
[[Page 37581]]
animals can emit and receive sounds in the relatively quiet intervals
between pulses. However, in exceptional situations, reverberation
occurs for much or all of the interval between pulses (e.g., Simard et
al., 2005; Clark and Gagnon 2006), which could mask calls. Situations
with prolonged strong reverberation are infrequent. However, it is
common for reverberation to cause some lesser degree of elevation of
the background level between airgun pulses (e.g., Gedamke 2011; Guerra
et al., 2011, 2016; Klinck et al., 2012; Guan et al., 2015), and this
weaker reverberation presumably reduces the detection range of calls
and other natural sounds to some degree. Guerra et al., (2016) reported
that ambient noise levels between seismic pulses were elevated as a
result of reverberation at ranges of 50 km from the seismic source.
Based on measurements in deep water of the Southern Ocean, Gedamke
(2011) estimated that the slight elevation of background levels during
intervals between pulses reduced blue and fin whale communication space
by as much as 36-51 percent when a seismic survey was operating 450-
2,800 km away. Based on preliminary modeling, Wittekind et al., (2016)
reported that airgun sounds could reduce the communication range of
blue and fin whales 2000 km from the seismic source. Nieukirk et al.,
(2012) and Blackwell et al., (2013) noted the 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 Langseth 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., 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.
[[Page 37582]]
Sounds emitted by the Langseth are low frequency and continuous,
but would be widely dispersed in both space and time. Vessel traffic
associated with the proposed survey is of low density compared to
traffic associated with commercial shipping, industry support vessels,
or commercial fishing vessels, and would therefore be expected to
represent an insignificant incremental increase in the total amount of
anthropogenic sound input to the marine environment, and the effects of
vessel noise described above are not expected to occur as a result of
this survey. In summary, project vessel sounds would not be at levels
expected to cause anything more than possible localized and temporary
behavioral changes in marine mammals, and would not be expected to
result in significant negative effects on individuals or at the
population level. In addition, in all oceans of the world, large vessel
traffic is currently so prevalent that it is commonly considered a
usual source of ambient sound (NSF-USGS 2011).
Ship Strike
Vessel collisions with marine mammals, or ship strikes, can result
in death or serious injury of the animal. Wounds resulting from ship
strike may include massive trauma, hemorrhaging, broken bones, or
propeller lacerations (Knowlton and Kraus, 2001). An animal at the
surface may be struck directly by a vessel, a surfacing animal may hit
the bottom of a vessel, or an animal just below the surface may be cut
by a vessel's propeller. Superficial strikes may not kill or result in
the death of the animal. These interactions are typically associated
with large whales (e.g., fin whales), which are occasionally found
draped across the bulbous bow of large 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 Langseth will travel at a speed of 4.6 kn (8.5 km/h) while
towing seismic survey gear. At this speed, 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<SUP>-6</SUP>; 95% CI
= 0-5.5 x 10<SUP>-6</SUP>; 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 propose a robust ship strike avoidance protocol (see Proposed
Mitigation), which we believe eliminates any foreseeable risk of ship
strike during transit. 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 proposed 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, the possibility of ship
strike is discountable and, further, 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
[[Page 37583]]
series. However, the cause or causes of most strandings are unknown
(Geraci et al., 1976; Eaton, 1979; Odell et al., 1980; Best, 1982).
Numerous studies suggest that the physiology, behavior, habitat
relationships, age, or condition of cetaceans may cause them to strand
or might pre-dispose them to strand when exposed to another phenomenon.
These suggestions are consistent with the conclusions of numerous other
studies that have demonstrated that combinations of dissimilar
stressors commonly combine to kill an animal or dramatically reduce its
fitness, even though one exposure without the other does not produce
the same result (Chroussos, 2000; Creel, 2005; DeVries et al., 2003;
Fair and Becker, 2000; Foley et al., 2001; Moberg, 2000; Relyea, 2005a;
2005b, Romero, 2004; Sih et al., 2004).
There is no conclusive evidence that exposure to airgun noise
results in behaviorally-mediated forms of injury. Behaviorally-mediated
injury (i.e., mass stranding events) has been primarily associated with
beaked whales exposed to mid-frequency active (MFA) naval sonar.
Tactical sonar and the alerting stimulus used in Nowacek et al., (2004)
are very different from the noise produced by airguns. One should
therefore not expect the same reaction to airgun noise as to these
other sources. As explained below, military MFA sonar is very different
from airguns, and one should not assume that airguns will cause the
same effects as MFA sonar (including strandings).
To understand why Navy MFA sonar affects beaked whales differently
than airguns do, it is important to note the distinction between
behavioral sensitivity and susceptibility to auditory injury. To
understand the potential for auditory injury in a particular marine
mammal species in relation to a given acoustic signal, the frequency
range the species is able to hear is critical, as well as the species'
auditory sensitivity to frequencies within that range. Current data
indicate that not all marine mammal species have equal hearing
capabilities across all frequencies and, therefore, species are grouped
into hearing groups with generalized hearing ranges assigned on the
basis of available data (Southall et al., 2007, 2019). Hearing ranges
as well as auditory sensitivity/susceptibility to frequencies within
those ranges vary across the different groups. For example, in terms of
hearing range, the high-frequency cetaceans (e.g., Kogia spp.) have a
generalized hearing range of frequencies between 275 Hz and 160 kHz,
while mid-frequency cetaceans--such as dolphins and beaked whales--have
a generalized hearing range between 150 Hz to 160 kHz. Regarding
auditory susceptibility within the hearing range, while mid-frequency
cetaceans and high-frequency cetaceans have roughly similar hearing
ranges, the high-frequency group is much more susceptible to noise-
induced hearing loss during sound exposure, i.e., these species have
lower thresholds for these effects than other hearing groups (NMFS,
2018). Referring to a species as behaviorally sensitive to noise simply
means that an animal of that species is more likely to respond to lower
received levels of sound than an animal of another species that is
considered less behaviorally sensitive. So, while dolphin species and
beaked whale species--both in the mid-frequency cetacean hearing
group--are assumed to generally hear the same sounds equally well and
be equally susceptible to noise-induced hearing loss (auditory injury),
the best available information indicates that a beaked whale is more
likely to behaviorally respond to that sound at a lower received level
compared to an animal from other mid-frequency cetacean species that
are less behaviorally sensitive. This distinction is important because,
while beaked whales are more likely to respond behaviorally to sounds
than are many other species (even at lower levels), they cannot hear
the predominant, lower frequency sounds from seismic airguns as well as
sounds that have more energy at frequencies that beaked whales can hear
better (such as military MFA sonar).
Navy MFA sonar affects beaked whales differently than airguns do
because it produces energy at different frequencies than airguns. Mid-
frequency cetacean hearing is generically thought to be best between
8.8 to 110 kHz, i.e., these cutoff values define the range above and
below which a species in the group is assumed to have declining
auditory sensitivity, until reaching frequencies that cannot be heard
(NMFS, 2018). However, beaked whale hearing is likely best within a
higher, narrower range (20-80 kHz, with best sensitivity around 40
kHz), based on a few measurements of hearing in stranded beaked whales
(Cook et al., 2006; Finneran et al., 2009; Pacini et al., 2011) and
several studies of acoustic signals produced by beaked whales (e.g.,
Frantzis et al., 2002; Johnson et al., 2004, 2006; Zimmer et al.,
2005). While precaution requires that the full range of audibility be
considered when assessing risks associated with noise exposure
(Southall et al., 2007, 2019a2019), animals typically produce sound at
frequencies where they hear best. More recently, Southall et al.,
(2019) suggested that certain species in the historical mid-frequency
hearing group (beaked whales, sperm whales, and killer whales) are
likely more sensitive to lower frequencies within the group's
generalized hearing range than are other species within the group, and
state that the data for beaked whales suggest sensitivity to
approximately 5 kHz. However, this information is consistent with the
general conclusion that beaked whales (and other mid-frequency
cetaceans) are relatively insensitive to the frequencies where most
energy of an airgun signal is found. Military MFA sonar is typically
considered to operate in the frequency range of approximately 3-14 kHz
(D'Amico et al., 2009), i.e., outside the range of likely best hearing
for beaked whales but within or close to the lower bounds, whereas most
energy in an airgun signal is radiated at much lower frequencies, below
500 Hz (Dragoset, 1990).
It is important to distinguish between energy (loudness, measured
in dB) and frequency (pitch, measured in Hz). In considering the
potential impacts of mid-frequency components of airgun noise (1-10
kHz, where beaked whales can be expected to hear) on marine mammal
hearing, one needs to account for the energy associated with these
higher frequencies and determine what energy is truly ``significant.''
Although there is mid-frequency energy associated with airgun noise (as
expected from a broadband source), airgun sound is predominantly below
1 kHz (Breitzke et al., 2008; Tashmukhambetov et al., 2008; Tolstoy et
al., 2009). As stated by Richardson et al. (1995), ``[. . .] most
emitted [seismic airgun] energy is at 10-120 Hz, but the pulses contain
some energy up to 500-1,000 Hz.'' Tolstoy et al., (2009) conducted
empirical measurements, demonstrating that sound energy levels
associated with airguns were at least 20 decibels (dB) lower at 1 kHz
(considered ``mid-frequency'') compared to higher energy levels
associated with lower frequencies (below 300 Hz) (``all but a small
fraction of the total energy being concentrated in the 10-300 Hz
range'' [Tolstoy et al., 2009]), and at higher frequencies (e.g., 2.6-4
kHz), power might be less than 10 percent of the peak power at 10 Hz
(Yoder, 2002). Energy levels measured by Tolstoy et al., (2009) were
even lower at frequencies above 1 kHz. In addition, as sound propagates
away from the source, it tends to lose higher-frequency components
faster than low-frequency components (i.e., low-frequency sounds
[[Page 37584]]
typically propagate longer distances than high-frequency sounds)
(Diebold et al., 2010). Although higher-frequency components of airgun
signals have been recorded, it is typically in surface-ducting
conditions (e.g., DeRuiter et al., 2006; Madsen et al., 2006) or in
shallow water, where there are advantageous propagation conditions for
the higher frequency (but low-energy) components of the airgun signal
(Hermannsen et al., 2015). This should not be of concern because the
likely behavioral reactions of beaked whales that can result in acute
physical injury would result from noise exposure at depth (because of
the potentially greater consequences of severe behavioral reactions).
In summary, the frequency content of airgun signals is such that beaked
whales will not be able to hear the signals well (compared to MFA
sonar), especially at depth where we expect the consequences of noise
exposure could be more severe.
Aside from frequency content, there are other significant
differences between MFA sonar signals and the sounds produced by
airguns that minimize the risk of severe behavioral reactions that
could lead to strandings or deaths at sea, e.g., significantly longer
signal duration, horizontal sound direction, typical fast and
unpredictable source movement. All of these characteristics of MFA
sonar tend towards greater potential to cause severe behavioral or
physiological reactions in exposed beaked whales that may contribute to
stranding. Although both sources are powerful, MFA sonar contains
significantly greater energy in the mid-frequency range, where beaked
whales hear better. Short-duration, high energy pulses--such as those
produced by airguns--have greater potential to cause damage to auditory
structures (though this is unlikely for mid-frequency cetaceans, as
explained later in this document), but it is longer duration signals
that have been implicated in the vast majority of beaked whale
strandings. Faster, less predictable movements in combination with
multiple source vessels are more likely to elicit a severe, potentially
anti-predator response. Of additional interest in assessing the
divergent characteristics of MFA sonar and airgun signals and their
relative potential to cause stranding events or deaths at sea is the
similarity between the MFA sonar signals and stereotyped calls of
beaked whales' primary predator: the killer whale (Zimmer and Tyack,
2007). Although generic disturbance stimuli--as airgun noise may be
considered in this case for beaked whales--may also trigger
antipredator responses, stronger responses should generally be expected
when perceived risk is greater, as when the stimulus is confused for a
known predator (Frid and Dill, 2002). In addition, because the source
of the perceived predator (i.e., MFA sonar) will likely be closer to
the whales (because attenuation limits the range of detection of mid-
frequencies) and moving faster (because it will be on faster-moving
vessels), any antipredator response would be more likely to be severe
(with greater perceived predation risk, an animal is more likely to
disregard the cost of the response; Frid and Dill, 2002). Indeed, when
analyzing movements of a beaked whale exposed to playback of killer
whale predation calls, Allen et al., (2014) found that the whale
engaged in a prolonged, directed avoidance response, suggesting a
behavioral reaction that could pose a risk factor for stranding.
Overall, these significant differences between sound from MFA sonar and
the mid-frequency sound component from airguns and the likelihood that
MFA sonar signals will be interpreted in error as a predator are
critical to understanding the likely risk of behaviorally-mediated
injury due to seismic surveys.
The available scientific literature also provides a useful contrast
between airgun noise and MFA sonar regarding the likely risk of
behaviorally-mediated injury. There is strong evidence for the
association of beaked whale stranding events with MFA sonar use, and
particularly detailed accounting of several events is available (e.g.,
a 2000 Bahamas stranding event for which investigators concluded that
MFA sonar use was responsible; Evans and England, 2001). D'Amico et
al., (2009) reviewed 126 beaked whale mass stranding events over the
period from 1950 (i.e., from the development of modern MFA sonar
systems) through 2004. Of these, there were two events where detailed
information was available on both the timing and location of the
stranding and the concurrent nearby naval activity, including
verification of active MFA sonar usage, with no evidence for an
alternative cause of stranding. An additional ten events were at
minimum spatially and temporally coincident with naval activity likely
to have included MFA sonar use and, despite incomplete knowledge of
timing and location of the stranding or the naval activity in some
cases, there was no evidence for an alternative cause of stranding. The
U.S. Navy has publicly stated agreement that five such events since
1996 were associated in time and space with MFA sonar use, either by
the U.S. Navy alone or in joint training exercises with the North
Atlantic Treaty Organization. The U.S. Navy additionally noted that, as
of 2017, a 2014 beaked whale stranding event in Crete coincident with
naval exercises was under review and had not yet been determined to be
linked to sonar activities (U.S. Navy, 2017). Separately, the
International Council for the Exploration of the Sea reported in 2005
that, worldwide, there have been about 50 known strandings, consisting
mostly of beaked whales, with a potential causal link to MFA sonar
(ICES, 2005). In contrast, very few such associations have been made to
seismic surveys, despite widespread use of airguns as a geophysical
sound source in numerous locations around the world.
A more recent review of possible stranding associations with
seismic surveys (Castellote and Llorens, 2016) states plainly that,
``[s]peculation concerning possible links between seismic survey noise
and cetacean strandings is available for a dozen events but without
convincing causal evidence.'' The authors' ``exhaustive'' search of
available information found ten events worth further investigation via
a ranking system representing a rough metric of the relative level of
confidence offered by the data for inferences about the possible role
of the seismic survey in a given stranding event. Only three of these
events involved beaked whales. Whereas D'Amico et al., (2009) used a 1-
5 ranking system, in which ``1'' represented the most robust evidence
connecting the event to MFA sonar use, Castellote and Llorens (2016)
used a 1-6 ranking system, in which ``6'' represented the most robust
evidence connecting the event to the seismic survey. As described
above, D'Amico et al. (2009) found that two events were ranked ``1''
and ten events were ranked ``2'' (i.e., 12 beaked whale stranding
events were found to be associated with MFA sonar use). In contrast,
Castellote and Llorens (2016) found that none of the three beaked whale
stranding events achieved their highest ranks of 5 or 6. Of the ten
total events, none achieved the highest rank of 6. Two events were
ranked as 5: one stranding in Peru involving dolphins and porpoises and
a 2008 stranding in Madagascar. This latter ranking can only broadly be
associated with the survey itself, as opposed to use of seismic
airguns. An exhaustive investigation of this stranding event, which did
not involve beaked whales, concluded that use of a high-frequency
mapping system (12-kHz multibeam echosounder) was the most
[[Page 37585]]
plausible and likely initial behavioral trigger of the event, which was
likely exacerbated by several site- and situation-specific secondary
factors. The review panel found that seismic airguns were used after
the initial strandings and animals entering a lagoon system, that
airgun use clearly had no role as an initial trigger, and that there
was no evidence that airgun use dissuaded animals from leaving
(Southall et al., 2013).
However, one of these stranding events, involving two Cuvier's
beaked whales, was contemporaneous with and reasonably associated
spatially with a 2002 seismic survey in the Gulf of California
conducted by L-DEO, as was the case for the 2007 Gulf of Cadiz seismic
survey discussed by Castellote and Llorens (also involving two Cuvier's
beaked whales). However, neither event was considered a ``true atypical
mass stranding'' (according to Frantzis [1998]) as used in the analysis
of Castellote and Llorens (2016). While we agree with the authors that
this lack of evidence should not be considered conclusive, it is clear
that there is very little evidence that seismic surveys should be
considered as posing a significant risk of acute harm to beaked whales
or other mid-frequency cetaceans. We have considered the potential for
the proposed surveys to result in marine mammal stranding and have
concluded that, based on the best available information, stranding is
not expected to occur.
Entanglement--Entanglements occur when marine mammals become
wrapped around cables, lines, nets, or other objects suspended in the
water column. During seismic operations, numerous cables, lines, and
other objects primarily associated with the airgun array and hydrophone
streamers will be towed behind the Langseth near the water`s surface.
However, we are not aware of any cases of entanglement of mysticetes in
seismic survey equipment. No incidents of entanglement of marine
mammals with seismic survey gear have been documented in over 54,000 kt
(100,000 km) of previous NSF-funded seismic surveys when observers were
aboard (e.g., Smultea and Holst 2003; Haley and Koski 2004; Holst 2004;
Smultea et al., 2004; Holst et al., 2005a; Haley and Ireland 2006; SIO
and NSF 2006b; Hauser et al., 2008; Holst and Smultea 2008). Although
entanglement with the streamer is theoretically possible, it has not
been documented during tens of thousands of miles of NSF-sponsored
seismic cruises or, to our knowledge, during hundreds of thousands of
miles of industrial seismic cruises. There are a relative few deployed
devices, and no interaction between marine mammals and any such device
has been recorded during prior NSF surveys using the devices. There are
no meaningful entanglement risks posed by the proposed survey, and
entanglement risks are not discussed further in this document.
Anticipated Effects on Marine Mammal Habitat
Physical Disturbance--Sources of seafloor disturbance related to
geophysical surveys that may impact marine mammal habitat include
placement of anchors, nodes, cables, sensors, or other equipment on or
in the seafloor for various activities. Equipment deployed on the
seafloor has the potential to cause direct physical damage and could
affect bottom-associated fish resources.
Placement of equipment, such as the heat flow probe in the
seafloor, could damage areas of hard bottom where direct contact with
the seafloor occurs and could crush epifauna (organisms that live on
the seafloor or surface of other organisms). Damage to unknown or
unseen hard bottom could occur, but because of the small area covered
by most bottom-founded equipment and the patchy distribution of hard
bottom habitat, contact with unknown hard bottom is expected to be rare
and impacts minor. Seafloor disturbance in areas of soft bottom can
cause loss of small patches of epifauna and infauna due to burial or
crushing, and bottom-feeding fishes could be temporarily displaced from
feeding areas. Overall, any effects of physical damage to habitat are
expected to be minor and temporary.
Effects to Prey--Marine mammal prey varies by species, season, and
location and, for some, is not well documented. Fish react to sounds
which are especially strong and/or intermittent low-frequency sounds,
and behavioral responses such as flight or avoidance are the most
likely effects. However, the reaction of fish to airguns depends on the
physiological state of the fish, past exposures, motivation (e.g.,
feeding, spawning, migration), and other environmental factors. Several
studies have demonstrated that airgun sounds might affect the
distribution and behavior of some fishes, potentially impacting
foraging opportunities or increasing energetic costs (e.g., Fewtrell
and McCauley, 2012; Pearson et al., 1992; Skalski et al., 1992;
Santulli et al., 1999; Paxton et al., 2017), though the bulk of studies
indicate no or slight reaction to noise (e.g., Miller and Cripps, 2013;
Dalen and Knutsen, 1987; Pena et al., 2013; Chapman and Hawkins, 1969;
Wardle et al., 2001; Sara et al., 2007; Jorgenson and Gyselman, 2009;
Blaxter et al., 1981; Cott et al., 2012; Boeger et al., 2006), and
that, most commonly, while there are likely to be impacts to fish as a
result of noise from nearby airguns, such effects will be temporary.
For example, investigators reported significant, short-term declines in
commercial fishing catch rate of gadid fishes during and for up to five
days after seismic survey operations, but the catch rate subsequently
returned to normal (Engas et al., 1996; Engas and Lokkeborg, 2002).
Other studies have reported similar findings (Hassel et al., 2004).
Skalski et al., (1992) also found a reduction in catch rates--for
rockfish (Sebastes spp.) in response to controlled airgun exposure--but
suggested that the mechanism underlying the decline was not dispersal
but rather decreased responsiveness to baited hooks associated with an
alarm behavioral response. A companion study showed that alarm and
startle responses were not sustained following the removal of the sound
source (Pearson et al., 1992). Therefore, Skalski et al., (1992)
suggested that the effects on fish abundance may be transitory,
primarily occurring during the sound exposure itself. In some cases,
effects on catch rates are variable within a study, which may be more
broadly representative of temporary displacement of fish in response to
airgun noise (i.e., catch rates may increase in some locations and
decrease in others) than any long-term damage to the fish themselves
(Streever et al., 2016).
SPLs of sufficient strength have been known to cause injury to fish
and fish mortality and, in some studies, fish auditory systems have
been damaged by airgun noise (McCauley et al., 2003; Popper et al.,
2005; Song et al., 2008). However, in most fish species, hair cells in
the ear continuously regenerate and loss of auditory function likely is
restored when damaged cells are replaced with new cells. Halvorsen et
al. (2012b. (2012) showed that a TTS of 4-6 dB was recoverable within
24 hours for one species. Impacts would be most severe when the
individual fish is close to the source and when the duration of
exposure is long--both of which are conditions unlikely to occur for
this survey that is necessarily transient in any given location and
likely result in brief, infrequent noise exposure to prey species in
any given area. For this survey, the sound source is constantly moving,
and most fish would likely avoid the sound source prior to receiving
sound of sufficient intensity to cause physiological or anatomical
damage. In addition, ramp-up may
[[Page 37586]]
allow certain fish species the opportunity to move further away from
the sound source.
A recent comprehensive review (Carroll et al., 2017) found that
results are mixed as to the effects of airgun noise on the prey of
marine mammals. While some studies suggest a change in prey
distribution and/or a reduction in prey abundance following the use of
seismic airguns, others suggest no effects or even positive effects in
prey abundance. As one specific example, Paxton et al., (2017), which
describes findings related to the effects of a 2014 seismic survey on a
reef off of North Carolina, showed a 78 percent decrease in observed
nighttime abundance for certain species. It is important to note that
the evening hours during which the decline in fish habitat use was
recorded (via video recording) occurred on the same day that the
seismic survey passed, and no subsequent data is presented to support
an inference that the response was long-lasting. Additionally, given
that the finding is based on video images, the lack of recorded fish
presence does not support a conclusion that the fish actually moved
away from the site or suffered any serious impairment. In summary, this
particular study corroborates prior studies indicating that a startle
response or short-term displacement should be expected.
Available data suggest that cephalopods are capable of sensing the
particle motion of sounds and detect low frequencies up to 1-1.5 kHz,
depending on the species, and so are likely to detect airgun noise
(Kaifu et al., 2008; Hu et al., 2009; Mooney et al., 2010; Samson et
al., 2014). Auditory injuries (lesions occurring on the statocyst
sensory hair cells) have been reported upon controlled exposure to low-
frequency sounds, suggesting that cephalopods are particularly
sensitive to low-frequency sound (Andre et al., 2011; Sole et al.,
2013). Behavioral responses, such as inking and jetting, have also been
reported upon exposure to low-frequency sound (McCauley et al., 2000b;
Samson et al., 2014). Similar to fish, however, the transient nature of
the survey leads to an expectation that effects will be largely limited
to behavioral reactions and would occur as a result of brief,
infrequent exposures.
With regard to potential impacts on zooplankton, McCauley et al.,
(2017) found that exposure to airgun noise resulted in significant
depletion for more than half the taxa present and that there were two
to three times more dead zooplankton after airgun exposure compared
with controls for all taxa, within 1 km of the airguns. However, the
authors also stated that in order to have significant impacts on r-
selected species (i.e., those with high growth rates and that produce
many offspring) such as plankton, the spatial or temporal scale of
impact must be large in comparison with the ecosystem concerned, and it
is possible that the findings reflect avoidance by zooplankton rather
than mortality (McCauley et al., 2017). In addition, the results of
this study are inconsistent with a large body of research that
generally finds limited spatial and temporal impacts to zooplankton as
a result of exposure to airgun noise (e.g., Dalen and Knutsen, 1987;
Payne, 2004; Stanley et al., 2011). Most prior research on this topic,
which has focused on relatively small spatial scales, has showed
minimal effects (e.g., Kostyuchenko, 1973; Booman et al., 1996;
S[aelig]tre and Ona, 1996; Pearson et al., 1994; Bolle et al., 2012).
A modeling exercise was conducted as a follow-up to the McCauley et
al. (2017) study (as recommended by McCauley et al.,), in order to
assess the potential for impacts on ocean ecosystem dynamics and
zooplankton population dynamics (Richardson et al., 2017). Richardson
et al., (2017) found that for copepods with a short life cycle in a
high-energy environment, a full-scale airgun survey would impact
copepod abundance up to three days following the end of the survey,
suggesting that effects such as those found by McCauley et al., (2017)
would not be expected to be detectable downstream of the survey areas,
either spatially or temporally.
Notably, a recently described study produced results inconsistent
with those of McCauley et al., (2017). Researchers conducted a field
and laboratory study to assess if exposure to airgun noise affects
mortality, predator escape response, or gene expression of the copepod
Calanus finmarchicus (Fields et al., 2019). Immediate mortality of
copepods was significantly higher, relative to controls, at distances
of 5 m or less from the airguns. Mortality one week after the airgun
blast was significantly higher in the copepods placed 10 m from the
airgun but was not significantly different from the controls at a
distance of 20 m from the airgun. The increase in mortality, relative
to controls, did not exceed 30 percent at any distance from the airgun.
Moreover, the authors caution that even this higher mortality in the
immediate vicinity of the airguns may be more pronounced than what
would be observed in free-swimming animals due to increased flow speed
of fluid inside bags containing the experimental animals. There were no
sublethal effects on the escape performance or the sensory threshold
needed to initiate an escape response at any of the distances from the
airgun that were tested. Whereas McCauley et al. (2017) reported an SEL
of 156 dB at a range of 509-658 m, with zooplankton mortality observed
at that range, Fields et al. (2019) reported an SEL of 186 dB at a
range of 25 m, with no reported mortality at that distance. Regardless,
if we assume a worst-case likelihood of severe impacts to zooplankton
within approximately 1 km of the acoustic source, the brief time to
regeneration of the potentially affected zooplankton populations does
not lead us to expect any meaningful follow-on effects to the prey base
for marine mammals.
A recent review article concluded that, while laboratory results
provide scientific evidence for high-intensity and low-frequency sound-
induced physical trauma and other negative effects on some fish and
invertebrates, the sound exposure scenarios in some cases are not
realistic to those encountered by marine organisms during routine
seismic operations (Carroll et al., 2017). The review finds that there
has been no evidence of reduced catch or abundance following seismic
activities for invertebrates, and that there is conflicting evidence
for fish with catch observed to increase, decrease, or remain the same.
Further, where there is evidence for decreased catch rates in response
to airgun noise, these findings provide no information about the
underlying biological cause of catch rate reduction (Carroll et al.,
2017).
In summary, impacts of the specified activity on marine mammal prey
species will likely be limited to behavioral responses, the majority of
prey species will be capable of moving out of the area during the
survey, a rapid return to normal recruitment, distribution, and
behavior for prey species is anticipated, and, overall, impacts to prey
species will be minor and temporary. Prey species exposed to sound
might move away from the sound source, experience TTS, experience
masking of biologically relevant sounds, or show no obvious direct
effects. Mortality from decompression injuries is possible in close
proximity to a sound, but only limited data on mortality in response to
airgun noise exposure are available (Hawkins et al., 2014). The most
likely impacts for most prey species in the survey area would be
temporary avoidance of the area. The proposed survey would move through
an area relatively quickly, limiting exposure to multiple impulsive
sounds. In all cases,
[[Page 37587]]
sound levels would return to ambient once the survey moves out of the
area or ends and the noise source is shut down and, when exposure to
sound ends, behavioral and/or physiological responses are expected to
end relatively quickly (McCauley et al., 2000b). The duration of fish
avoidance of a given area after survey effort stops is unknown, but a
rapid return to normal recruitment, distribution, and behavior is
anticipated. While the potential for disruption of spawning
aggregations or schools of important prey species can be meaningful on
a local scale, the mobile and temporary nature of this survey and the
likelihood of temporary avoidance behavior suggest that impacts would
be minor.
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 these cover a large area but would be transient rather than
focused in a given location over time and therefore would not be
considered chronic in any given location.
Based on the information discussed herein, we conclude that impacts
of the specified activity are not likely to have more than short-term
adverse effects on any prey habitat or populations of prey species.
Further, any impacts to marine mammal habitat are not expected to
result in significant or long-term consequences for individual marine
mammals, or to contribute to adverse impacts on their populations.
Estimated Take
This section provides an estimate of the number of incidental takes
proposed for authorization through this IHA, which will inform both
NMFS' consideration of ``small numbers'' and the negligible impact
determinations.
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
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