[Federal Register Volume 85, Number 67 (Tuesday, April 7, 2020)]
[Notices]
[Pages 19580-19634]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-07289]
[[Page 19579]]
Vol. 85
Tuesday,
No. 67
April 7, 2020
Part II
Department of Commerce
-----------------------------------------------------------------------
National Oceanic and Atmospheric Administration
-----------------------------------------------------------------------
Takes of Marine Mammals Incidental to Specified Activities; Taking
Marine Mammals Incidental to a Marine Geophysical Survey in the
Northeast Pacific Ocean; Notice
Federal Register / Vol. 85, No. 67 / Tuesday, April 7, 2020 /
Notices
[[Page 19580]]
-----------------------------------------------------------------------
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XR074]
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to a Marine Geophysical Survey 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.
-----------------------------------------------------------------------
SUMMARY: NMFS has received a request from the Lamont-Doherty Earth
Observatory of Columbia University (L-DEO) for authorization to take
marine mammals incidental to a marine geophysical survey 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-year renewal that could be issued under
certain circumstances and if all requirements are met, as described in
Request for Public Comments at the end of this notice. NMFS will
consider public comments prior to making any final decision on the
issuance of the requested MMPA authorizations and agency responses will
be summarized in the final notice of our decision.
DATES: Comments and information must be received no later than May 7,
2020.
ADDRESSES: Comments should be addressed to Jolie Harrison, Chief,
Permits and Conservation Division, Office of Protected Resources,
National Marine Fisheries Service. Physical comments should be sent to
1315 East-West Highway, Silver Spring, MD 20910 and electronic comments
should be sent to [email protected].
Instructions: NMFS is not responsible for comments sent by any
other method, to any other address or individual, or received after the
end of the comment period. Comments received electronically, including
all attachments, must not exceed a 25-megabyte file size. Attachments
to electronic comments will be accepted in Microsoft Word or Excel or
Adobe PDF file formats only. All comments received are a part of the
public record and will generally be posted online at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act without change. All personal identifying
information (e.g., name, address) voluntarily submitted by the
commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.
FOR FURTHER INFORMATION CONTACT: Amy Fowler, Office of Protected
Resources, NMFS, (301) 427-8401. Electronic copies of the application
and supporting documents, as well as a list of the references cited in
this document, may be obtained online at: https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act. In case of problems accessing these
documents, please call the contact listed above.
SUPPLEMENTARY INFORMATION:
Background
The MMPA prohibits the ``take'' of marine mammals, with certain
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to
allow, upon request, the incidental, but not intentional, taking of
small numbers of marine mammals by U.S. citizens who engage in a
specified activity (other than commercial fishing) within a specified
geographical region if certain findings are made and either regulations
are issued or, if the taking is limited to harassment, a notice of a
proposed incidental take authorization may be provided to the public
for review.
Authorization for incidental takings shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s) and will not have an unmitigable adverse impact on the
availability of the species or stock(s) for taking for subsistence uses
(where relevant). Further, NMFS must prescribe the permissible methods
of taking and other ``means of effecting the least practicable adverse
impact'' on the affected species or stocks and their habitat, paying
particular attention to rookeries, mating grounds, and areas of similar
significance, and on the availability of 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.
National Environmental Policy Act
To comply with the National Environmental Policy Act of 1969 (NEPA;
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A,
NMFS must review our proposed action (i.e., the issuance of an
incidental harassment authorization) with respect to potential impacts
on the human environment.
Accordingly, NMFS plans to adopt the National Science Foundation's
(NSF's) Environmental Assessment (EA), as we have preliminarily
determined that it includes adequate information analyzing the effects
on the human environment of issuing the IHA. NSF's EA is available at
https://www.nsf.gov/geo/oce/envcomp/.
We will review all comments submitted in response to this notice
prior to concluding our NEPA process or making a final decision on the
IHA request.
Summary of Request
On November 8, 2019, NMFS received a request from L-DEO for an IHA
to take marine mammals incidental to a marine geophysical survey of the
Cascadia Subduction Zone off the coasts of Washington, Oregon, and
British Columbia, Canada. The application was deemed adequate and
complete on March 6, 2020. L-DEO's request is for take of small numbers
of 31 species of marine mammals by Level A and Level B harassment.
Neither L-DEO nor NMFS expects serious injury or mortality to result
from this activity and, therefore, an IHA is appropriate.
NMFS has previously issued IHAs to L-DEO for similar surveys in the
northeast Pacific (e.g., 84 FR 35073, July 22, 2019; 77 FR 41755, July
16, 2012). 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 L-DEO, Woods Hole Oceanographic Institution
(WHOI), and the University of Texas at Austin Institute of Geophysics
(UTIG), with funding from the NSF, and in collaboration with
researchers from Dalhousie University and Simon Fraser University (SFU)
propose to conduct a high-energy seismic survey from the Research
Vessel (R/V) Marcus G Langseth (Langseth) in the northeast Pacific
Ocean beginning in June 2020. The seismic survey would be conducted at
the Cascadia Subduction Zone off the coasts of Oregon, Washington, and
[[Page 19581]]
British Columbia, Canada. The proposed two-dimensional (2-D) seismic
survey would occur within the Exclusive Economic Zones (EEZs) of Canada
and the United States, including U.S. state waters and Canadian
territorial waters. The survey would use a 36-airgun towed array with a
total discharge volume of ~6,600 cubic inches (in\3\) as an acoustic
source, acquiring return signals using both a towed streamer as well
ocean bottom seismometers (OBSs) and ocean bottom nodes (OBNs).
The proposed study would use 2-D seismic surveying and OBSs and
OBNs to investigate the Cascadia Subduction Zone and provide data
necessary to illuminate the depth, geometry, and physical properties of
the seismogenic portion and updip extent of the megathrust zone between
the subducting Juan de Fuca plate and the overlying accretionary wedge/
North American plate. These data would provide essential constraints
for earthquake and tsunami hazard assessment in this heavily populated
region of the Pacific Northwest. The primary objectives of the survey
proposed by researchers from L-DEO, WHOI, and UTIG is to characterize:
(1) The deformation and topography of the incoming plate; (2) the
depth, topography, and reflectivity of the megathrust; (3) sediment
properties and amount of sediment subduction; and (4) the structure and
evolution of the accretionary wedge, including geometry and
reflectivity of fault networks, and how these properties vary along
strike, spanning the full length of the margin and down dip across what
may be the full width of the Cascadia Subduction Zone.
Dates and Duration
The proposed survey is expected to last for 40 days, with 37 days
of seismic operations, 2 days of equipment deployment, and 1 day of
transit. R/V Langseth would likely leave out of and return to port in
Astoria, Oregon, during June-July 2020.
Specific Geographic Region
The proposed survey would occur within ~42-51[deg] N, ~124-130[deg]
W. Representative survey tracklines are shown in Figure 1. Some
deviation in actual track lines, including the order of survey
operations, could be necessary for reasons such as science drivers,
poor data quality, inclement weather, or mechanical issues with the
research vessel and/or equipment. The survey is proposed to occur
within the EEZs of the United States and Canada, as well as in U.S.
state waters and Canadian territorial waters, ranging in depth 60-4400
meters (m). A maximum of 6,890 km of transect lines would be surveyed.
Most of the survey (63.2 percent) would occur in deep water (>1,000 m),
26.4 percent would occur in intermediate water (100-1,000 m deep), and
10.4 percent would take place in shallow water <100 m deep.
Approximately 4 percent of the transect lines (295 km) would be
undertaken in Canadian territorial waters (from 0-12 nautical miles
(22.2 km) from shore), with most effort in intermediate waters. NMFS
cannot authorize the incidental take of marine mammals in the
territorial seas of foreign nations, as the MMPA does not apply in
those waters. However, NMFS has still calculated the level of
incidental take in the entire activity area (including Canadian
territorial waters) as part of the analysis supporting our preliminary
determination under the MMPA that the activity will have a negligible
impact on the affected species.
[[Page 19582]]
[GRAPHIC] [TIFF OMITTED] TN07AP20.000
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 by NSF and operated on its behalf
by L-DEO. R/V Langseth would deploy an array of 36 airguns as an energy
source with a total volume of ~6,600 in\3\. The array consists of 20
Bolt 1500LL airguns with volumes of 180 to 360 in\3\ and 16 Bolt
1900LLX airguns with volumes of 40 to 120 in\3\. The airgun array
configuration is illustrated in Figure 2-11 of NSF and USGS's
Programmatic Environmental Impact Statement (PEIS; NSF-USGS, 2011). The
vessel speed during seismic operations would be approximately 4.2 knots
(~7.8 km/hour) during the survey and the airgun array would be towed at
a depth of 12 m. The receiving system would consist of one 15-kilometer
(km) long hydrophone streamer, OBSs, and OBNs. R/V Oceanus, which is
owned by NSF and operated by Oregon State University, would be used to
deploy the OBSs and OBNs. As the airguns are towed along the survey
lines, the hydrophone streamer would transfer the data to the on-board
processing system, and the OBSs and OBNs would receive and store the
returning acoustic signals internally for later analysis.
Long 15-km-offset multichannel seismic (MCS) data would be acquired
along numerous 2-D profiles oriented perpendicular to the margin and
located
[[Page 19583]]
to provide coverage in areas inferred to be rupture patches during past
earthquakes and their boundary zones. The survey would also include
several strike lines including one continuous line along the
continental shelf centered roughly over gravity-inferred fore-arc
basins to investigate possible segmentation near the down-dip limit of
the seismogenic zone. The margin normal lines would extend ~50 km
seaward of the deformation front to image the region of subduction bend
faulting in the incoming oceanic plate, and landward of the deformation
front to as close to the shoreline as can be safely maneuvered. It is
proposed that the southern transects off Oregon are acquired first,
followed by the profiles off Washington and Vancouver Island, British
Columbia.
The OBSs would consist of short-period multi-component OBSs from
the Ocean Bottom Seismometer Instrument Center (OBSIC) and a large-N
array of OBNs from a commercial provider to record shots along ~11 MCS
margin-perpendicular profiles. OBSs would be deployed at 10-km spacing
along ~11 profiles from Vancouver Island to Oregon, and OBNs would be
deployed at a 500-m spacing along a portion of two profiles off Oregon.
Two OBS deployments would occur with a total of 115 instrumented
locations. 60 OBSs would be deployed to instrument seven profiles off
Oregon, followed by a second deployment of 55 OBSs to instrument four
profiles off Washington and Vancouver Island. The first deployment off
Oregon would occur prior to the start of the proposed survey, after
which R/V Langseth would acquire data in the southern portion of the
study area. R/V Oceanus would start recovering the OBSs from deployment
1, and then re-deploy 55 OBSs off Washington and Vancouver Island, so
that R/V Langseth can acquire data in the northern portion of the
survey area. The OBSs have a height and diameter of ~1 m, and an ~80
kilogram (kg) anchor. To retrieve OBSs, an acoustic release transponder
(pinger) is used to interrogate the instrument at a frequency of 8-11
kHz, and a response is received at a frequency of 11.5-13 kHz. The
burn-wire release assembly is then activated, and the instrument is
released to float to the surface from the anchor, which is not
retrieved.
A total of 350 OBNs would be deployed: 229 nodes along one transect
off northern Oregon, and 121 nodes along a second transect off central
Oregon. The nodes are not connected to each other; each node is
independent from each other, and there are no cables attached to them.
Each node has internal batteries; all data is recorded and stored
internally. The nodes weigh 21 kg in air (9.5 kg in water). As the OBNs
are small (330 millimeters (mm) x 289 mm x 115 mm), compact, not
buoyant, and lack an anchor-release mechanism, they cannot be deployed
by free-fall as with the OBSs. The nodes would be deployed and
retrieved using a remotely operated vehicle (ROV); the ROV would be
deployed from R/V Oceanus. OBNs would be deployed 17 days prior to the
start of the R/V Langseth cruise. The ROV would be fitted with a skid
with capacity for 32 units, lowered to the seafloor, and towed at a
speed of 0.6 knots at 5-10 m above the seafloor between deployment
sites. After the 32 units are deployed, the ROV would be retrieved, the
skid would be reloaded with another 32 units, and sent back to the
seafloor for deployment, and so on. The ROV would recover the nodes 3
days after the completion of the R/V Langseth cruise. The nodes would
be recovered one by one by a suction mechanism. Take of marine mammals
is not expected to occur incidental to L-DEO's use of OBSs and OBNs.
In addition to the operations of the airgun array, a multibeam
echosounder (MBES), a sub-bottom profiler (SBP), and an Acoustic
Doppler Current Profiler (ADCP) would be operated from R/V Langseth
continuously during the seismic surveys, but not during transit to and
from the survey area. 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, or
ADCP because they will be operated only during seismic acquisition, and
it is assumed that, during simultaneous operations of the airgun array
and the other sources, any marine mammals close enough to be affected
by the MBES, SBP, and ADCP would already be affected by the airguns.
However, 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. Proposed
mitigation, monitoring, and reporting measures are described in detail
later in this document (please see Proposed Mitigation and Proposed
Monitoring and Reporting).
Description of Marine Mammals in the Area of Specified Activities
Sections 3 and 4 of the application summarize available information
regarding status and trends, distribution and habitat preferences, and
behavior and life history, of the potentially affected species.
Additional information regarding population trends and threats may be
found in NMFS's Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments) and more general information about these species
(e.g., physical and behavioral descriptions) may be found on NMFS's
website (https://www.fisheries.noaa.gov/find-species).
Table 1 lists all species with expected potential for occurrence in
the survey area and summarizes information related to the population or
stock, including regulatory status under the MMPA and ESA and potential
biological removal (PBR), where known. For taxonomy, we follow
Committee on Taxonomy (2019). 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's
SARs). While no 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
comprises 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 and Alaska SARs (Caretta et al., 2019; Muto et al.,
2019). All MMPA stock information presented in Table 1 is the most
recent available at the time of publication and is available in the
2018 SARs (Caretta et al., 2019; Muto et al., 2019) and draft 2019 SARs
(available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports). Where
available, abundance and status information is also presented
[[Page 19584]]
for marine mammals in Canadian waters in British Columbia.
Table 1--Marine Mammals That Could Occur in the Survey Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stock abundance
ESA/MMPA status; (CV, Nmin, most
Common name Scientific name Stock strategic (Y/N) recent abundance PBR Annual M/SI \3\
\1\ survey) \2\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Cetartiodactyla--Cetacea--Superfamily Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Eschrichtiidae:
Gray whale................. Eschrichtius Eastern North -/-; N 26,960 (0.05, 801................. 138.
robustus. Pacific. 25,849, 2016).
Family Balaenopteridae
(rorquals):
Humpback whale............. Megaptera California/Oregon/ -/-; Y 2,900 (0.05, 16.7................ >42.1.
novaeangliae. Washington. 2,784, 2014).
Central North -/-; Y 10,103 (0.30, 83.................. 25.
Pacific. 7,891, 2006).
Minke whale................ Balaenoptera California/Oregon/ -/-; N 636 (0.72, 369, 3.5................. >1.3.
acutorostrata. Washington. 2014).
Sei whale.................. Balaenoptera Eastern North E/D; Y 519 (0.4, 374, 0.75................ >0.2.
borealis. Pacific. 2014).
Fin whale.................. Balaenoptera California/Oregon/ E/D; Y 9,029 (0.12, 81.................. >2.0.
physalus. Washington. 8,127, 2014).
Northeast Pacific. E/D; Y 3,168 (0.26, 5.1................. 0.4.
2,554, 2013).
Blue whale................. Balaenoptera Eastern North E/D; Y 1,496 (0.44, 1.2................. >19.4.
musculus. Pacific. 1,050, 2014).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Physeteridae:
Sperm whale................ Physeter California/Oregon/ E/D; Y 1,997 (0.57, 2.5................. 0.4.
macrocephalus. Washington. 1,270, 2014).
Family Kogiidae:
Pygmy sperm whale.......... Kogia breviceps... California/Oregon/ -/-; N 4,111 (1.12, 19.................. 0.
Washington. 1,924, 2014).
Dwarf sperm whale.......... Kogia sima........ California/Oregon/ -/-; N Unknown (Unknown, Undetermined........ 0.
Washington. Unknown, 2014).
Family Ziphiidae (beaked
whales):
Cuvier's beaked whale...... Ziphius California/Oregon/ -/-; N 3,274 (0.67, 21.................. <0.1.
cavirostris. Washington. 2,059, 2014).
Baird's beaked whale....... Berardius bairdii. California/Oregon/ -/-; N 2,697 (0.6, 16.................. 0
Washington. 1,633, 2014).
Blainville's beaked whale.. Mesoplodon California/Oregon/ -/-; N 3,044 (0.54, 20.................. 0.1.
densirostris. Washington. 1,967, 2014).
Hubbs' beaked whale........ Mesoplodon
carlshubbi.
Stejneger's beaked whale... Mesoplodon
stejnegeri.
Family Delphinidae:
Bottlenose dolphin......... Tursiops truncatus California/Oregon/ -/-; N 1,924 (0.54, 11.................. >1.6.
Washington 1,255, 2014).
offshore.
Striped dolphin............ Stenella California/Oregon/ -/-; N 29,211 (0.2, 238................. >0.8.
coeruleoalba. Washington. 24,782, 2014).
Common dolphin............. Delphinus delphis. California/Oregon/ -/-; N 969,861 (0.17, 8,393............... >40.
Washington. 839,325, 2014).
Pacific white-sided dolphin Lagenorhynchus California/Oregon/ -/-; N 26,814 (0.28, 191................. 7.5.
obliquidens. Washington. 21,195, 2014).
British Columbia N/A 22,160 (unknown, Unknown............. Unknown.
\4\. 16,522, 2008).
Northern right whale Lissodelphis California/Oregon/ -/-; N 26,556 (0.44, 179................. 3.8.
dolphin. borealis. Washington. 18,608, 2014).
Risso's dolphin............ Grampus griseus... California/Oregon/ -/-; N 6,336 (0.32, 46.................. >3.7.
Washington. 4,817, 2014).
False killer whale......... Pseudorca N/A............... N/A N/A.............. N/A................. N/A.
crassidens.
Killer whale............... Orcinus orca...... Offshore.......... -/-; N 300 (0.1, 276, 2.8................. 0.
2012).
Southern Resident. E/D; Y 75 (N/A, 75, 0.13................ 0.
2018).
Northern Resident. -/-; N 302 (N/A, 302, 2.2................. 0.2.
2018).
West Coast -/-; N 243 (N/A, 243, 2.4................. 0.
Transient. 2009).
Short-finned pilot whale... Globicephala California/Oregon/ -/-; N 836 (0.79, 466, 4.5................. 1.2.
macrorhynchus. Washington. 2014).
Family Phocoenidae (porpoises):
Harbor porpoise............ Phocoena phocoena. Northern Oregon/ -/-; N 21,487 (0.44, 151................. >3.0.
Washington Coast. 15,123, 2011).
Northern -/-; N 35,769 (0.52, 475................. >0.6.
California/ 23,749, 2011).
Southern Oregon.
British Columbia N/A 8,091 (unknown, Unknown............. Unknown.
\4\. 4,885, 2008).
Dall's porpoise............ Phocoenoides dalli California/Oregon/ -/-; N 25,750 (0.45, 172................. 0.3.
Washington. 17,954, 2014).
British Columbia N/A 5,303 (unknown, Unknown............. Unknown.
\4\. 4,638, 2008).
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 19585]]
Order Carnivora--Superfamily Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otariidae (eared seals
and sea lions):.
Northern fur seal.......... Callorhinus Eastern Pacific... -/D; Y 620,660 (0.2, 11,295.............. 399.
ursinus. 525,333, 2016).
California........ -/D; N 14,050 (N/A, 451................. 1.8.
7,524, 2013).
California sea lion........ Zalophus U.S............... -/-; N 257,606 (N/A, 14,011.............. >321.
californianus. 233,515, 2014).
Steller sea lion........... Eumetopias jubatus Eastern U.S....... -/-; N 43,201 (see SAR, 2,592............... 113.
43,201, 2017).
British Columbia N/A 4,037 (unknown, Unknown............. Unknown.
\4\. 1,100, 2008).
Guadalupe fur seal......... Arctocephalus Mexico to T/D; Y 34,187 (N/A, 1,062............... >3.8.
philippii California. 31,019, 2013).
townsendi.
Family Phocidae (earless
seals):
Harbor seal................ Phoca vitulina.... Oregon/Washington -/-; N Unknown (Unknown, Undetermined........ 10.6.
Coastal. Unknown, 1999).
British Columbia N/A 24,916 (Unknown, Unknown............. Unknown.
\4\. 19,666, 2008).
Northern elephant seal..... Mirounga California -/-; N 179,000 (N/A, 4,882............... 8.8.
angustirostris. Breeding. 81,368, 2010).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\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: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments assessments. 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.
\4\ Best et al. (2015) total abundance estimates for animals in British Columbia based on surveys of the Strait of Georgia, Johnstone Strait, Queen
Charlotte Sound, Hecate Strait, and Dixon Entrance.
All species that could potentially occur in the proposed survey
areas are included in Table 1. However, additional species have been
recorded in the specified geographic region but are considered
sufficiently rare that take is not anticipated. The temporal and/or
spatial occurrence of North Pacific right whales (Eubalaena japonica)
is such that take is not expected to occur, and they are not discussed
further beyond the explanation provided here. Only 82 sightings of
right whales in the entire eastern North Pacific were reported from
1962 to 1999, with the majority of these occurring in the Bering Sea
and adjacent areas of the Aleutian Islands (Brownell et al., 2001).
Most sightings in the past 20 years have occurred in the southeastern
Bering Sea, with a few in the Gulf of Alaska (Wade et al., 2011).
Despite many miles of systematic aerial and ship-based surveys for
marine mammals off the coasts of Washington, Oregon and California over
several years, only seven documented sightings of right whales were
made from 1990 to 2000 (Waite et al., 2003), and NMFS is not aware of
any documented sightings in the area since then. 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.
In addition, the Northern sea otter (Enhydra lutris kenyoni) may be
found in coastal waters of the survey area. However, sea otters are
managed by the U.S. Fish and Wildlife Service and are not considered
further in this document.
Gray Whale
Two separate populations for gray whales have been recognized in
the North Pacific: The eastern North Pacific and the western North
Pacific (or Korean-Okhotsk) 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). Thus it is possible that whales
from either the ESA listed endangered Western North Pacific distinct
population segment (DPS) or the delisted Eastern North Pacific DPS
could occur in the survey area, although it is unlikely that a gray
whale from the Western North Pacific DPS would be encountered during
the time of the survey as they are expected to be in their feeding
grounds in the western North Pacific at the time of the proposed
survey. NMFS expects that any gray whales encountered by L-DEO during
the proposed survey would be from the Eastern North Pacific DPS only,
and is not proposing to authorize take of the endangered Western North
Pacific DPS; therefore, the Western North Pacific DPS will not be
discussed further in this document.
The eastern North Pacific gray whale breeds and winters in Baja
California, and migrates north to summer feeding grounds in the
northern Bering Sea, Chukchi Sea, and western Beaufort Sea (Rice and
Wolman 1971; Rice 1998; Jefferson et al., 2015). The northward
migration occurs from late February to June (Rice and Wolman 1971),
with a peak in the Gulf of Alaska during mid-April (Braham 1984).
Instead of migrating to arctic and sub-arctic waters, some individuals
spend the summer months scattered along the coast from California to
southeast Alaska (Rice and Wolman 1971; Nerini 1984; Darling et al.,
1998; Calambokidis and Quan 1999; Dunham and Duffus 2001, 2002;
Calambokidis et al., 2002, 2015, 2017). There is genetic evidence
indicating the existence of this Pacific Coast Feeding Group (PCFG) is
a
[[Page 19586]]
distinct local subpopulation (Frasier et al., 2011; Lang et al., 2014)
and the United States and Canada recognize it as such (COSEWIC 2017;
Caretta et al., 2019a). However, the status of the PCFG as a separate
stock is currently unresolved (Weller et al., 2013). For the purposes
of abundance estimates, the PCFG is defined as occurring between
41[deg] N to 52[deg] N from June 1 to November 30 (IWC 2012). The 2015
abundance estimate for the PCFG was 243 whales (Calambokidis et al.,
2017); approximately 100 of those may occur in British Columbia during
summer (Ford 2014). In British Columbia, most summer resident gray
whales are found in Clayoquot Sound, Barkley Sound, and along the
southwestern shore of Vancouver Island, and near Cape Caution on
mainland British Columbia (Ford 2014). During surveys in British
Columbia waters during summer, most sightings of gray whales were made
within 10 km of shore and in water shallower than 100 m (Ford et al.,
2010a). Two sightings of three gray whales were seen from R/V Northern
Light during a survey off southern Washington in July 2012 (RPS 2012a).
Biologically Important Areas (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 in Washington, Depoe Bay and Cape Blanco and Orford Reef in
Oregon, and Point St. George in California; most of these areas are of
importance from late spring through early fall (Calambokidis et al.,
2015). 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 surveys
would occur during the late spring/summer feeding season, when most
individuals from the eastern North Pacific stock occur farther north.
Nonetheless, individual gray whales, particularly those from the PCFG
could be encountered in nearshore waters of the proposed project area.
On May 30, 2019, NMFS declared an unusual mortality event (UME) for
gray whales after elevated numbers of strandings occurred along the
U.S. west coast. As of February 8, 2020, a total of 236 stranded gray
whales have been reported, including 124 in the United States (48 in
Alaska, 35 in Washington, 6 in Oregon, and 35 in California), 101 in
Mexico, and 11 in Canada. Full or partial necropsy examinations were
conducted on a subset of the whales. Preliminary findings in several of
the whales have shown evidence of emaciation. These findings are not
consistent across all of the whales examined, so more research is
needed. The UME is ongoing, and NMFS continues to investigate the
cause(s). Additional information about the UME is available at https://www.fisheries.noaa.gov/national/marine-life-distress/2019-2020-gray-whale-unusual-mortality-event-along-west-coast.
Humpback Whale
The humpback whale is found throughout all of the oceans of the
world (Clapham 2009). The worldwide population of humpbacks 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., Baker et al. 1993; Caballero et al. 2001).
Geographical overlap of these populations has been documented only off
Central America (Acevedo and Smultea 1995; Rasmussen et al. 2004,
2007). Although considered to be mainly a coastal species, humpback
whales often traverse deep pelagic areas while migrating (Clapham and
Mattila 1990; Norris et al. 1999; Calambokidis et al. 2001).
Humpback whales migrate between summer feeding grounds in high
latitudes and winter calving and breeding grounds in tropical waters
(Clapham and Mead 1999). North Pacific humpback whales summer in
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). Humpback 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, 2016) pursuant to the ESA. The DPSs that occur in U.S. waters do not
necessarily equate to the existing stocks designated under the MMPA and
shown in Table 1. Because MMPA stocks cannot be portioned, i.e., parts
managed as ESA-listed while other parts managed as not 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).
Within the proposed survey area, three current DPSs may occur: The
Hawaii DPS (not listed), Mexico DPS (threatened), and Central America
DPS (endangered). According to Wade et al. (2017), the probability that
whales encountered in Oregon and California waters are from a given DPS
are as follows: Mexico DPS, 32.7 percent; Central America DPS, 67.2
percent; Hawaii DPS, 0 percent. The probability that humpback whales
encountered in Washington and British Columbia waters are as follows:
Mexico DPS, 27.9 percent; Central America DPS, 8.7 percent; Hawaii DPS,
63.5 percent.
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). The highest
numbers have been reported off Oregon during May and June and off
Washington during July-September. Humpbacks occur primarily over the
continental shelf and slope during the summer, with few reported in
offshore pelagic waters (Green et al., 1992; Calambokidis et al., 2004,
2015; Becker et al., 2012; Barlow 2016). Six humpback whale sightings
(8 animals) were made off Washington/Oregon during the June-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 southern Washington (RPS 2012a), and 11 sightings (23 animals)
during the July 2012 L-DEO seismic survey off Oregon (RPS 2012c).
Humpback whales are common in the waters of British Columbia, where
they occur in inshore, outer coastal, and continental shelf waters, as
well as offshore (Ford 2014). Williams and Thomas (2007) estimated an
abundance of 1,310 humpback whales in inshore coastal waters of British
Columbia based on surveys conducted in 2004 and 2005. Best et al.
(2015) provided an estimate of 1,029 humpbacks in British Columbia
based on surveys during 2004-2008. In British Columbia, humpbacks are
typically seen within 20 km from the coast, in water less than 500 m
deep (Ford et al., 2010a). The greatest numbers of humpbacks are seen
in British Columbia between April and November, although humpbacks are
known to occur there throughout the
[[Page 19587]]
year (Ford et al., 2010a; Ford 2014). Humpback whales in British
Columbia are thought to belong to at least two distinct feeding stocks;
those identified off southern British Columbia show little interchange
with those seen off northern British Columbia (Calambokidis et al.,
2001, 2008). Humpback whales identified in southern British Columbia
show a low level of interchange with those seen off California/Oregon/
Washington (Calambokidis et al., 2001).
BIAs for feeding humpbacks along the coasts of Oregon and
Washington, which have been described from May to November, are all
within approximately 80 km from shore, and include the waters off
northern Washington, and Stonewall and Heceta Bank, Oregon
(Calambokidis et al., 2015). On October 9, 2019, NMFS issued a proposed
rule to designate critical habitat in nearshore waters of the North
Pacific Ocean for the endangered Central America DPS and the threatened
Mexico DPS of humpback whale (NMFS 2019b). Critical habitat for the
Central America DPS and Mexico DPS was proposed within the California
Current Ecosystem (CCE) off the coasts California, Oregon, and
Washington, representing areas of key foraging habitat. Off Washington
and northern Oregon, the critical habitat would extend from the 50-m
isobath out to the 1200-m isobath; off southern Oregon (south of
42[deg]10' N), it would extend out to the 2000-m isobath (NMFS 2019b).
Critical habitat for humpbacks has been designated in four
locations in British Columbia (DFO 2013), including in the waters of
the proposed survey area off southwestern Vancouver Island. The other
three locations are located north of the proposed survey area at Haida
Gwaii (Langara Island and Southeast Moresby Island) and at Gil Island
(DFO 2013). These areas show persistent aggregations of humpback whales
and have features such as prey availability, suitable acoustic
environment, water quality, and physical space that allow for feeding,
foraging, socializing, and resting (DFO 2013). Two of the proposed
transect lines intersect the critical habitat on Swiftsure and La
P[eacute]rouse Banks.
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 farther south to within 2[deg] of the Equator (Perrin and
Brownell 2009).
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
coastal waters off the west coast of the United States (Dorsey et al.
1990).
Sightings of minke whales have been reported off Oregon and
Washington in shelf and deeper waters (Green et al., 1992; Adams et
al., 2014; Barlow 2016; Caretta et al., 2019a). There were no sightings
of minke whales off Washington/Oregon during the June-July 2012 L-DEO
Juan de Fuca plate seismic survey or during the July 2012 L-DEO seismic
survey off Oregon (RPS 2012b,c). One minke whale was seen during the
July 2012 L-DEO seismic survey off southern Washington (RPS 2012a).
Minke whales are sighted regularly in nearshore waters of British
Columbia, but they are not considered abundant (COSEWIC 2006). They are
most frequently sighted around the Gulf Islands and off northeastern
Vancouver Island (Ford 2014). They are also regularly seen off the east
coast of Moresby Island, and in Dixon Entrance, Hecate Strait, Queen
Charlotte Sound, and the west coast of Vancouver Island were they occur
in shallow and deeper water (Ford et al., 2010a; Ford 2014). Williams
and Thomas (2007) estimated minke whale abundance for inshore coastal
waters of British Columbia at 388 individuals based on surveys
conducted in 2004 and 2005 while Best et al. (2015) provided an
estimate of 522 minke whales based on surveys during 2004-2008.
Sei Whale
The distribution of the sei whale is not well known, but it is
found in all oceans and appears to prefer mid-latitude temperate waters
(Jefferson et al. 2015). The sei whale is pelagic and generally not
found in coastal waters (Jefferson et al. 2015). It is found 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. 1999a). 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 California, Oregon, and
Washington (Brueggeman et al., 1990; Green et al., 1992; Barlow 1994,
1997). Less than 20 confirmed sightings were reported in that region
during extensive surveys between 1991 and 2014 (Green et al., 1992,
1993; Hill and Barlow 1992; Caretta and Forney 1993; Mangels and
Gerrodette 1994; Von Saunder and Barlow 1999; Barlow 2003, 2010, 2014;
Forney 2007; Carretta et al., 2019a). 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 July 2012 L-DEO seismic surveys off Oregon and Washington
(RPS 2012a,c).
The patterns of seasonal abundance found in whaling records
suggested that the whales were caught as they migrated to summer
feeding grounds, with the peak of the migration in July and offshore
movement in summer, from ~25 km to ~100 km from shore (Gregr et al.,
2000). Historical whaling data show that sei whales used to be
distributed along the continental slope of British Columbia and over a
large area off the northwest coast of Vancouver Island (Gregr and
Trites 2001). Sei whales are now considered rare in Pacific waters of
the United States and Canada; in British Columbia there were no
sightings in the late 1900s after whaling ceased (Gregr et al., 2006).
Ford (2014) only reported two sightings for British Columbia, both of
those far offshore from Haida Gwaii. Possible sei whale vocalizations
were detected off the west coast of Vancouver Island during spring and
summer 2006 and 2007 (Ford et al., 2010b). Gregr and Trites (2001)
proposed that the area off northwestern Vancouver Island and the
continental slope may be critical habitat for sei whales because of
favorable feeding conditions.
[[Page 19588]]
Fin Whale
The fin whale is widely distributed in all the world's oceans
(Gambell 1985b), but typically occurs in temperate and polar regions
from 20-70[deg] north and south of the Equator (Perry et al. 1999b).
Northern and southern fin whale populations are distinct and are
recognized as different subspecies (Aguilar 2009). Fin whales occur in
coastal, shelf, and oceanic waters. Sergeant (1977) suggested that fin
whales tend to follow steep slope contours, either because they detect
them readily or because biological productivity is high along steep
contours because of tidal mixing and perhaps current mixing. Stafford
et al. (2009) noted that sea-surface temperature is a good predictor
variable for fin whale call detections in the North Pacific.
Fin whales appear to have complex seasonal movements and are
seasonal migrants; they mate and calve in temperate waters during the
winter and migrate to feed at northern latitudes during the summer
(Gambell 1985b). The North Pacific population summers from the Chukchi
Sea to California and winters from California southwards (Gambell
1985b). Aggregations of fin whales are found year-round off southern
and central California (Dohl et al. 1980, 1983; Forney et al. 1995;
Barlow 1997) and in the summer off Oregon (Green et al. 1992; Edwards
et al. 2015). Vocalizations from fin whales have also been detected
year-round off northern California, Oregon, and Washington (Moore et
al. 1998, 2006; Watkins et al. 2000a,b; Stafford et al. 2007, 2009;
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 2,369-3,940 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). Fin whales were also seen off southern Oregon
during July 2012 in water >2000 m deep during surveys by Adams et al.
(2014).
Whaling records indicate fin whale occurrence off the west coast of
British Columbia increased gradually from March to a peak in July, then
decreased rapidly in September and October (Gregr et al., 2000). Fin
whales occur throughout British Columbia waters near and past the
continental shelf break, as well as in inshore waters (Ford 2014). Fin
whales were the second most common cetacean sighted during DFO surveys
in 2002-2008 (Ford et al., 2010a). They appear to be more common in
northern British Columbia, but sightings have been made along the shelf
edge and in deep waters off western Vancouver Island (Ford et al.,
1994, 2010a; Calambokidis et al., 2003; Ford 2014). Acoustic detections
have been made throughout the year in pelagic waters west of Vancouver
Island (Edwards et al., 2015). Gregr and Trites (2001) proposed that
the area off northwestern Vancouver Island and the continental slope
may be critical habitat for fin whales because of favorable feeding
conditions.
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 whale 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., 2000a; Stafford
2003) suggests that there are two separate populations: One in the
eastern and one in the western North Pacific (Sears and Perrin 2009).
Broad-scale acoustic monitoring indicates 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 a major activity, 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-
November (Calambokidis et al., 1990; Mate et al., 1999). There are nine
BIAs for feeding blue whales off the coast of California (Calambokidis
et al., 2015), and core areas have also been identified there (Irvine
et al., 2014).
Blue whales are considered rare off Oregon, Washington, and British
Columbia (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).
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).
Sightings of blue whales in offshore waters of British Columbia are
rare (Ford 2014; DFO 2017) and there is no abundance estimate for
British Columbia waters (Nichol and Ford 2012). During surveys of
British Columbia from 2002-2013, 16 sightings of blue whales were made,
all of which occurred just to the south or west of Haida Gwaii during
June, July, and August (Ford 2014). There have also been sightings off
Vancouver Island during summer and fall (Calambokidis et al., 2004b;
Ford 2014), with the most recent one reported off southwestern Haida
Gwaii in July 2019 (CBC 2019).
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
juvenile animals of both sexes generally occur in tropical and
subtropical waters, whereas adult males are commonly found alone or in
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). Mature male sperm
whales migrate to warmer waters to breed when they are in their late
twenties (Best 1979).
Sperm whales generally are distributed over large areas that have
high secondary productivity and steep underwater topography, in waters
at least 1000 m deep (Jaquet and Whitehead 1996; Whitehead 2009). They
are often found far from shore, but can be found closer to oceanic
islands that rise steeply from deep ocean waters (Whitehead 2009).
Adult males can occur in water depths <100 m and as shallow as 40 m
(Whitehead et al., 1992; Scott and Sadove 1997). They can dive as deep
as ~2 km and possibly deeper on rare occasions for periods of over 1 h;
however, most of their foraging occurs at depths of ~300-800 m for 30-
45 min (Whitehead 2003).
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
[[Page 19589]]
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 SWFSC vessel survey (Barlow 2016). A
single sperm whale was sighted during a 2009 survey to the west of the
proposed survey area (Holst 2017).
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 were more common 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 the inshore site from June through January 2009, with an
absence of calls during February to May ([Scirc]irovi[cacute] et al.,
2012). In addition, sperm whales were sighted during surveys off
Washington in June 2011 and off Oregon in October 2011 (Adams et al.
2014).
Whaling records report large numbers of sperm whales taken in
April, with a peak in May. Analysis of data on catch locations, sex of
the catch, and fetus lengths indicated that males and females were both
50-80 km from shore while mating in April and May, and that by July and
August, adult females had moved to waters >100 km offshore to calve),
and adult males had moved to within ~25 km of shore (Gregr et al.,
2000). At least in the whaling era, females did not travel north of
Vancouver Island whereas males were observed in deep water off Haida
Gwaii (Gregr et al., 2000). After the whaling era, sperm whales have
been sighted and detected acoustically in British Columbia waters
throughout the year, with a peak during summer (Ford 2014). Acoustic
detections at La P[eacute]rouse Bank off southwestern Vancouver Island
have been recorded during spring and summer (Ford et al., 2010b).
Sightings west of Vancouver Island and Haida Gwaii indicate that this
species still occurs in British Columbia in small numbers (Ford et al.,
1994; Ford 2014). Based on whaling data, Gregr and Trites (2001)
proposed that the area off northwestern Vancouver Island and the
continental slope may be critical habitat for male sperm whales because
of favorable feeding conditions.
Pygmy and Dwarf Sperm Whales
The pygmy and dwarf sperm whales are distributed widely throughout
tropical and temperate seas, but their precise distributions are
unknown as most information on these species comes from strandings
(McAlpine 2009). They are difficult to sight at sea, 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
difficult to distinguish from one another when sighted (McAlpine 2009).
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). Several studies have suggested that pygmy
sperm whales live mostly beyond the continental shelf edge, whereas
dwarf sperm whales tend to occur closer to shore, often over the
continental shelf (Rice 1998; Wang et al. 2002; MacLeod et al. 2004).
Barros et al. (1998), on the other hand, suggested that dwarf sperm
whales could be more pelagic and dive deeper than pygmy sperm whales.
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). This idea is also supported by the
distribution of strandings in South American waters (Mu[ntilde]oz-
Hincapi[eacute] et al. 1998).
Pygmy and dwarf sperm whales are rarely sighted off Oregon and
Washington, with only one sighting of an unidentified Kogia spp. beyond
the U.S. EEZ, during the 1991-2014 NOAA vessel surveys (Carretta et
al., 2019a). 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. There are several unconfirmed
sighting reports of the pygmy sperm whale from the Canadian west coast
(Baird et al., 1996). There is a stranding record of a pygmy sperm
whale for northeastern Vancouver Island (Ford 2014), and there is a
single dwarf sperm whale stranding record for southwestern Vancouver
Island in September 1981 (Ford 2014). Willis and Baird (1998) state
that the dwarf sperm whale is likely found in British Columbia waters
more frequently than recognized, but Ford (2014) suggested that the
presence of Kogia spp. in British Columbia waters is extralimital.
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).
Baird's Beaked Whale
Baird's beaked whale has a fairly extensive range across the North
Pacific, with concentrations occurring in the Sea of Okhotsk and Bering
Sea (Rice 1998; Kasuya 2009). In the eastern Pacific, Baird's beaked
whale is reported to occur as far south as San Clemente Island,
California (Rice 1998; Kasuya 2009). Two forms of Baird's beaked whales
have been recognized, the common slate-gray form and a smaller, rare
black form (Morin et al., 2017). 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). Recent genetic studies suggest that the black
form could be a separate species (Morin et al., 2017). Baird's beaked
whales are 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 are occasionally seen close to shore, but
their primary habitat is in waters 1,000-3,000 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; Caretta et al., 2019a) from late spring to early fall (Green
et al., 1992). In the eastern North Pacific, Baird's beaked whales
apparently spend the winter and
[[Page 19590]]
spring far offshore, and in June move onto the continental slop, 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.
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 near the planned survey area in August 2016
during a SWFSC study using drifting acoustic recorders (Keating et al.
2018).
There are whaler's reports of Baird's beaked whales off the west
coast of Vancouver Island throughout the whaling season (May-
September), especially in July and August (Reeves and Mitchell 1993).
Twenty-four sightings have been made in British Columbia since the
whaling era, including off the west coast of Vancouver Island (Ford
2014). Three strandings have also been reported, including one on
northeastern Haida Gwaii and two on the west coast of Vancouver Island.
Blainville's Beaked Whale
Blainville's beaked whale is found in tropical and warm temperate
waters of all oceans (Pitman 2009). It has the widest distribution
throughout the world of all mesoplodont species and appears to be
relatively common (Pitman 2009). Like other beaked whales, Blainville's
beaked whale is generally found in waters 200-1400 m deep (Gannier
2000; Jefferson et al. 2015). Blainville's beaked whale 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
detection of Blainville's beaked whales recorded in Quinault Canyon off
Washington in waters 1,400 m deep during 2011 (Baumann-Pickering et
al., 2014).
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 U.S. West Coast (MacLeod et al. 2006). Most of
the records are from California, but it has been sighted as far north
as Prince Rupert, British Columbia (Mead 1989). Two strandings are
known from Washington/Oregon (Norman et al. 2004). There have been no
confirmed live sightings of Hubb's beaked whales in British Columbia.
Stejneger's Beaked Whale
Stejneger's beaked whale occurs in subarctic and cool temperate
waters of the North Pacific Ocean (Mead 1989). In the eastern North
Pacific Ocean, it is distributed from Alaska to southern California
(Mead et al. 1982; Mead 1989). Most stranding records are from Alaskan
waters, and the Aleutian Islands appear to be its center of
distribution (MacLeod et al. 2006). 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
off of Washington between January and June 2011, with an absence of
calls from mid-July through November 2011 ([Scirc]irovi[cacute] et al.,
2012b in Navy 2015). Analysis of these data suggest that this species
could be more than twice as prevalent in this area as Baird's beaked
whale (Baumann-Pickering et al., 2014). At least five stranding records
exist for British Columbia (Houston 1990b; Willis and Baird 1998; Ford
2014), including two strandings on the west coast of Haida Gwaii and
two strandings on the west coast of Vancouver Island (Ford 2014). A
possible sighting has been reported on the east coast of Vancouver
Island (Ford 2014).
Bottlenose Dolphin
The bottlenose dolphin is distributed worldwide in coastal and
shelf waters of tropical and temperate oceans (Jefferson et al. 2015).
There are two distinct bottlenose dolphin types: a shallow water type,
mainly found in coastal waters, and a deep water type, mainly found in
oceanic waters (Duffield et al. 1983; Hoelzel et al. 1998; Walker et
al. 1999). Coastal common bottlenose dolphins exhibit a range of
movement patterns including seasonal migration, year-round residency,
and a combination of long-range movements and repeated local residency
(Wells and Scott 2009).
Bottlenose dolphins occur frequently off the coast of California,
and sightings have been made as far north as 41[deg] N, but few records
exist for Oregon and Washington (Caretta et al., 2019a). Three
sightings and one stranding of bottlenose dolphins have been documented
in Puget Sound since 2004 (Cascadia Research 2011 in Navy 2015). During
surveys off the U.S. West Coast, offshore bottlenose dolphins were
generally found at distances greater than 1.86 miles (3 km) from the
coast and were most abundant off southern California (Barlow, 2010,
2016). Based on sighting data collected by SWFSC during systematic
surveys in the Northeast Pacific between 1986 and 2005, there were few
sightings of offshore bottlenose dolphins north of about 40[deg] N
(Hamilton et al., 2009). Bottlenose dolphins occur frequently off the
coast of California, and sightings have been made as far north as
41[deg] N, but few records exist for Oregon/Washington (Carretta et al.
2017). It is possible that bottlenose dolphins from the California/
Oregon/Washington Offshore stock may range as far north as the proposed
survey area during warm-water periods (Caretta et al., 2019a). Adams et
al. (2014) recorded one sighting off Washington in September 2012.
There are no confirmed records of bottlenose dolphins in British
Columbia, though an unconfirmed record exists for offshore waters
(Baird et al., 1993).
Striped Dolphin
The striped dolphin has a cosmopolitan distribution in tropical to
warm temperate waters (Perrin et al. 1994) and is generally seen south
of 43[deg] N (Archer 2009). However, in the eastern North Pacific, its
distribution extends as far north as Washington (Jefferson et al.,
2015). The striped dolphin is typically found in waters outside the
continental shelf and is often associated with convergence zones and
areas of upwelling (Archer 2009). However, it has also 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 nmi (Caretta et al., 2019a).
Striped dolphin encounters increase in deep, relatively warmer waters
off the U.S. West Coast, and their abundance decreases north of
[[Page 19591]]
about 42[deg]N (Barlow et al., 2009; Becker et al., 2012b; Becker et
al., 2016; Forney et al., 2012). However, few sightings have been made
off Oregon, and no sightings have been reported for Washington (Caretta
et al., 2019a) but strandings have occurred along the coasts of both
Washington and Oregon (Caretta et al., 2016). Striped dolphins are rare
and considered extralimital in British Columbia (Ford 2014). There are
a total of 14 confirmed records of stranded individuals or remains for
Vancouver Island (Ford 2014). A single confirmed sighting was made in
September 2019 in the Strait of Juan de Fuca (Pacific Whale Watch
Association 2019).
Common Dolphin
The common dolphin is found in tropical and warm temperate oceans
around the world (Perrin 2009). It ranges as far south as 40[deg] S in
the Pacific Ocean, is common in coastal waters 200-300 m deep and is
also associated with prominent underwater topography, such as seamounts
(Evans 1994). Common dolphins have been sighted as far as 550 km from
shore (Barlow et al. 1997).
The distribution of 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., 2017). 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.). However, their abundance decreases dramatically north
of about 40[deg] N (Barlow et al., 2009; Becker et al., 2012c; Becker
et al., 2016; Forney et al., 2012). Based on the absolute dynamic
topography of the region, 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 mouth during summer, with lower
densities off southern Oregon (Becker et al. 2014). There are three
stranding records of common dolphins in British Columbia, including one
from northwestern Vancouver Island, one from the Strait of Juan de
Fuca, and one from Hecate Strait (Ford 2014).
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, including waters off Oregon, 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) 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 percent) 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.
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). One group of 10 Pacific white-sided dolphins was sighted during
the 2009 ETOMO survey (Holst 2017).
Pacific white-sided dolphins are common throughout the waters of
British Columbia, including Dixon Entrance, Hecate Strait, Queen
Charlotte Sound, the west coast of Haida Gwaii, as well as western
Vancouver Island, and the mainland coast (Ford 2014). Stacey and Baird
(1991a) compiled 156 published and unpublished records to 1988 of the
Pacific white-sided dolphin within the Canadian 320-km extended EEZ.
These dolphins move inshore and offshore seasonally (Stacey and Baird
1991a). There were inshore records for all months except July, and
offshore records from all months except December. Offshore sightings
were much more common than inshore sightings, especially in June-
October; the mean water depth was ~1,100 m. Ford et al. (2011b)
reported that most sightings occur in water depths <500 m and within 20
km from shore.
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, including waters off
Oregon, 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[dash]offshore
and north[dash]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).
Survey data suggest that, at least in the eastern North Pacific,
seasonal inshore-offshore and north-south movements are related to prey
availability, with peak abundance in the Southern California Bight
during winter and distribution shifting northward into
[[Page 19592]]
Oregon and Washington as water temperatures increase during late spring
and summer (Barlow, 1995; Becker et al., 2014; Forney et al., 1995;
Forney & Barlow, 1998; Leatherwood & Walker, 1979). Seven northern
right whale 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 eight northern right whale dolphin
sightings (278 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).
There are 47 records of northern right whale dolphins from British
Columbia, mostly in deep water off the west coast of Vancouver Island;
however, sightings have also been reported in deep water off Haida
Gwaii (Ford 2014). Most sightings have occurred in water depths over
900 m (Baird and Stacey 1991a). One group of six northern right whale
dolphins was seen west of Vancouver Island in water deeper than 2,500 m
during a survey from Oregon to Alaska (Hauser and Holt 2009).
Risso's Dolphin
Risso's dolphin is distributed worldwide in temperate and tropical
oceans (Baird 2009), although it shows a preference for mid-temperate
waters of the shelf and slope between 30[deg] and 45[deg] N (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[ordm] N. Several sightings were made off southern Oregon during
surveys in 1991-2014 (Carretta et al., 2017). Sightings during ship
surveys in summer/fall 2008 were mostly between ~30 and 38[deg] N; none
were reported in Oregon/Washington (Barlow 2010).Two sightings of 38
individuals were recorded off Washington from August 2004 to September
2008 (Oleson et al. 2009). Risso's dolphins were sighted off Oregon, in
June and October 2011 (Adams et al. 2014). There were three Risso's
dolphin sightings (31 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), or off Washington/Oregon during the June-July 2012 L-DEO Juan
de Fuca plate seismic survey (RPS 2012b).
Risso's dolphin was once considered rare in British Columbia, but
there have been numerous sightings since the 1970s (Ford 2014). Most
sightings have been made in Gwaii Haanas National Park Reserve, Haida
Gwaii, but there have also been sightings in Dixon Entrance, off the
west coast of Haida Gwaii, Queen Charlotte Sound, and to the west of
Vancouver Island (Ford 2014).
False Killer Whale
The false killer whale is found in all tropical and warmer
temperate oceans, especially in deep, offshore waters (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 (Jefferson et al., 2015; Baird
2018b). It is gregarious and forms strong social bonds, as is evident
from its propensity to strand en masse (Baird 2018b). In the eastern
North Pacific, it has been reported only rarely north of Baja
California (Leatherwood et al., 1982, 1987; Mangels and Gerrodette
1994); however, the waters off the U.S. 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). One pod of false killer whales
occurred in Puget Sound for several months during the 1990s (USN 2015).
Two were reported stranded along the Washington coast between 1930-
2002, both in El Ni[ntilde]o years (Norman et al. 2004). One sighting
was made off southern California during 2014 (Barlow 2016).
Stacey and Baird (1991b) suggested that false killer whales are at
the limit of their distribution in Canada and have always been rare.
Sightings have been made along the northern and central mainland coast
of British Columbia, as well as in Queen Charlotte Strait, Strait of
Georgia, and along the west coast of Vancouver Island (Ford 2014).
Killer Whale
The killer whale is cosmopolitan and globally fairly abundant; it
has been observed in all oceans of the world (Ford 2009). 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
(Caretta 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 al., 2008).
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 BC through
parts of southeast Alaska; (3) Southern Residents, mainly in inland
waters of Washington State and southern BC; (4) Gulf of Alaska,
Aleutian Islands, and Bering Sea Transients, from Prince William Sound
(PWS) through to the Aleutians and Bering Sea; (5) AT1 Transients, from
PWS through the Kenai Fjords; (6) West Coast Transients, from
California through southeast Alaska; (7) Offshore, from California
through Alaska; and (8) Hawaiian (Carretta et al. 2018). Individuals
from the Southern Resident, Northern Resident, West Coast Transient,
and Offshore stocks could be encountered in the proposed project area.
All three pods (J, K, and L pods) of Southern Resident killer whales
may occur in the project area.
Southern Resident killer whales mainly feed on salmon, in
particular Chinook (Oncorhynchus tshawytscha), but also prey upon other
salmonids, such as chum (O. keta), coho (O. kitsutch), and steelhead
(O. mykiss), as well as rockfish (Sebastes spp.), Pacific
[[Page 19593]]
halibut (Hippoglossus stenolepis), Pacific herring (Clupea pallasi),
among others. Seasonal and spatial shifts in prey consumption have been
observed, with Chinook consumed in May through September, and chum
eaten in the fall. Chinook remain an important prey item while the
Southern Residents are in offshore coastal waters, where they also
consume a greater diversity of fish species (NMFS 2019).
Southern Resident killer whales occur for part of the year in the
inland waterways of the Salish Sea, including Puget Sound, the Strait
of Juan de Fuca, and the southern Strait of Georgia mostly during the
spring, summer, and fall. Their movement patterns appear related to the
seasonal availability of prey, especially Chinook salmon. They also
move to coastal waters, primarily off Washington and British Columbia,
in search of suitable prey, and have been observed as far as central
California and southeast Alaska (NMFS 2019). Although less is known
about the whales' movements in outer coastal waters than inland waters
of the Salish Sea, satellite tagging, opportunistic sighting, and
acoustic recording data suggest that Southern Residents spend nearly
all their time on the continental shelf, within 34 km of shore in water
less than 200 m deep (Hanson et al., 2017).
The Southern Resident DPS was listed as endangered under the ESA in
2005 after a nearly 20 percent decline in abundance between 1996 and
2001 (70 FR 69903; November 18, 2005). As compared to stable or growing
populations, the DPS reflects lower fecundity and has demonstrated
little to no growth in recent decades, and in fact has declined further
since the date of listing (NMFS 2019). The population abundance listed
in the draft 2019 SARs is 75, from the July 1, 2018 annual census
conducted by the Center for Whale Research (CWR) (Caretta et al.,
2019); since that date, four whales have died or are presumed dead, and
two calves were born in 2019, bringing the abundance to 73 whales (NMFS
2019). An additional adult male is considered missing as of January
2020 (CWR 2020). NMFS has identified three main causes of the
population decline: (1) Reduced quantity and quality of prey; (2)
persistent organic pollutants that could cause immune or reproductive
system dysfunction; and (3) noise and disturbance from increased
commercial and recreational vessel traffic (NMFS 2019).
The U.S. Southern Resident killer whale critical habitat designated
under the ESA currently includes inland waters of Washington relative
to a contiguous shoreline delimited by the line at a depth of 6.1 m
relative to extreme high water (71 FR 69054; November 29, 2006). On
September 19, 2019, NMFS published a proposed rule to revise designated
Southern Resident killer whale critical habitat to include 40,472.7
km\2\ of marine waters between the 6.1-m depth contour and the 200-m
depth contour from the U.S. international border with Canada south to
Point Sur, California (84 FR 49214; September 19, 2019). The proposed
survey tracklines overlap with NMFS' proposed expanded Southern
Resident critical habitat.
In Canada, Southern Resident killer whales are listed as Endangered
under the Species at Risk Act (SARA), and critical habitat has been
designated in the trans-boundary waters in southern British Columbia,
including the southern Strait of Georgia, Haro Strait, and Strait of
Juan de Fuca (SOR/2018-278, December 13, 2018; SOR/2009-68, February
19, 2009; DFO 2018). The continental shelf waters off southwestern
Vancouver Island, including Swiftsure and La P[eacute]rouse Banks have
also been designated as critical habitat (DFO 2018). Two of the
proposed survey tracklines intersect the Canadian Southern Resident
critical habitat on Swiftsure and La P[eacute]rouse Banks.
Northern Resident killer whales are not listed under the ESA, but
are listed as threatened under Canada's SARA (DFO 2018). In British
Columbia, Northern Resident killer whales inhabit the central and
northern Strait of Georgia, Johnstone Strait, Queen Charlotte Strait,
the west coast of Vancouver Island, and the entire central and north
coast of mainland British Columbia (Muto et al., 2019a,b). Northern
Resident killer whales are also regularly acoustically detected off the
coast of Washington (Hanson et al., 2017). Canada has designated
critical habitat for Northern Resident killer whales in Johnstone
Strait, southeastern Queen Charlotte Strait, western Dixon Entrance
along the north coast of Graham Island, Haida Gwaii, and Swiftsure and
La P[eacute]rouse Banks off southwestern Vancouver Island (SOR/2018-
278, December 13, 2018; SOR/2009-68, February 19, 2009; DFO 2018).
Critical habitat for both Northern and Southern Resident killer whales
has been established within the proposed survey area at Swiftsure and
La P[eacute]rouse Banks (SOR/2018-278, December 13, 2018).
The main diet of transient killer whales consists of marine
mammals, in particular porpoises and seals. West coast transient whales
(also known as Bigg's killer whales) range from Southeast Alaska to
California (Muto et al., 2019a). The seasonal movements of transients
are largely unpredictable, although there is a tendency to investigate
harbor seal haulouts off Vancouver Island more frequently during the
pupping season in August and September (Baird 1994; Ford 2014).
Transients have been sighted throughout British Columbia waters,
including the waters around Vancouver Island (Ford 2014).
Little is known about offshore killer whales, but they occur
primarily over shelf waters and feed on fish, especially sharks (Ford
2014). Dalheim et al. (2008) reported sightings in southeast Alaska
during spring and summer. Relatively few sightings of offshore killer
whales have been reported in British Columbia; there have been 103
records since 1988 (Ford 2014). The number of sightings are likely
influenced by the fact that these whales prefer deeper waters near the
continental slope, where little sighting effort has taken place (Ford
2014). Most sightings are from Haida Gwaii and 15 km or more off the
west coast of Vancouver Island near the continental slope (Ford et al.,
1994). Offshore killer whales are mainly seen off British Columbia
during summer, but they can occur in British Columbia year-round (Ford
2014).
Short-Finned Pilot Whale
The short-finned pilot whale is found in tropical, subtropical, and
warm temperate waters (Olson 2009); it is seen as far south as ~40[deg]
S and as far north as ~50[deg] N (Jefferson et al. 2015). Pilot whales
are generally nomadic, but may be resident in certain locations,
including California and Hawaii (Olson 2009). Short-finned pilot whales
were common off southern California (Dohl et al. 1980) until an El
Ni[ntilde]o event occurred in 1982-1983 (Carretta et al. 2017).
Few sightings were made off California/Oregon/Washington in 1984-
1992 (Green et al. 1992; Carretta and Forney 1993; Barlow 1997), and
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 (Barlow 2003). A few
sightings were made off California during surveys in 1991-2014 (Barlow
2010). Carretta et al. (2019a) reported one sighting off Oregon during
1991-2014. Several stranding events in Oregon/southern Washington have
been recorded over the past few decades, including in
[[Page 19594]]
March 1996, June 1998, and August 2002 (Norman et al. 2004).
Short-finned pilot whales are considered rare in British Columbia
waters (Baird and Stacey 1993; Ford 2014). There are 10 confirmed
records, including three bycatch records in offshore waters, six
sightings in offshore waters, and one stranding; the stranding occurred
in the Strait of Juan de Fuca (Ford 2014). There are also unconfirmed
records for nearshore waters of western Vancouver Island (Baird and
Stacey 1993; Ford 2014).
Harbor Porpoise
The harbor porpoise inhabits temperate, subarctic, and arctic
waters. It is typically found in shallow water (<100 m) nearshore but
is occasionally sighted in deeper offshore water (Jefferson et al.,
2015); abundance declines linearly as depth increases (Barlow 1988). In
the eastern north Pacific, its range extends from Point Barrow, Alaska
to Point Conception, California. Their seasonal movements appear to be
inshore-offshore, rather than north-south, as a response to the
abundance and distribution of food resources (Dohl et al., 1983; Barlow
1988). Genetic testing has also shown that harbor porpoises along the
west coast of North America are not migratory and occupy restricted
home ranges (Rosel et al., 1995).
Based on genetic data and density discontinuities, six stocks have
been identified in California/Oregon/Washington: (1) Washington Inland
Waters, (2) Northern Oregon/Washington Coast, (3) Northern California/
Southern Oregon, (4) San Francisco-Russian River, (5) Monterey Bay, and
(6) Morro Bay (Caretta et al., 2019a). Harbor porpoises form the
Northern Oregon/Washington and the Northern California/Southern Oregon
stocks could occur in the proposed project area (Caretta et al.,
2019a).
Harbor porpoises inhabit coastal Oregon and Washington waters year-
round, although there appear to be distinct seasonal changes in
abundance there (Barlow 1988; Green et al., 1992). Green et al. (1992)
reported that encounter rates were similarly high during fall and
winter, intermediate during spring, and low during summer. Encounter
rates were highest along the Oregon/Washington coast in the area from
Cape Blanco (~43[deg] N) to California, from fall through spring.
During summer, the reported encounter rates decreased notably from
inner shelf to offshore waters. Green et al. (1992) reported that 96
percent of harbor porpoise sightings off Oregon/Washington occurred in
coastal waters <100 m deep, with a few sightings on the slope near the
200-m isobath. Similarly, predictive density distribution maps show the
highest in nearshore waters along the coasts of Oregon/Washington, with
very low densities beyond the 500-m isobath (Menza et al., 2016).
There were no harbor porpoise sightings made during the July 2012
L-DEO seismic surveys off southern Washington (RPS 2012a), the July
2012 L-DEO seismic survey off Oregon (RPS 2012c), or off Washington/
Oregon during the June-July 2012 L-DEO Juan de Fuca plate seismic
survey (RPS 2012b).
Harbor porpoises are found along the coast of British Columbia
year-round, primarily in coastal shallow waters, harbors, bays, and
river mouths (Osborne et al., 1988), but can also be found in deep
water over the continental shelf and over offshore banks that are no
deeper than 150 m (Ford 2014; COSEWIC 2016). Many sightings records
exist for nearshore waters of Vancouver Island, and occasional
sightings have also been made in shallow water of Swiftsure and La
P[eacute]rouse banks off southwestern Vancouver Island (Ford 2014).
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; Carretta et al. 2018). 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 from 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-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).
Dall's porpoise is found all along the coast of British Columbia
and is common inshore and offshore throughout the year (Jefferson 1990;
Ford 2014). It is most common over the continental shelf and slope, but
also occurs >2,400 km from the coast (Pike and MacAskie 1969 in
Jefferson 1990), and sightings have been made throughout the proposed
survey area (Ford 2014). During a survey from Oregon to Alaska, Dall's
porpoises were sighted west of Vancouver Island and Haida Gwaii in
early October during the southbound transit, but none were sighted in
mid-September during the northward transit; all sightings were made in
water deeper than 2000 m (Hauser and Holst 2009).
Guadalupe Fur Seal
Guadalupe fur seals were once plentiful on the California coast,
ranging from the Gulf of the Farallones near San Francisco, to the
Revillagigedo Islands, Mexico (Aurioles-Gamboa et al., 1999), but they
were over-harvested in the 19th century to near extinction. After being
protected, the population grew slowly; mature individuals of the
species were observed occasionally in the Southern California Bight
starting in the 1960s (Stewart et al., 1993), and, in 1997, a
[[Page 19595]]
female and pup were observed on San Miguel Island (Melin & DeLong,
1999). Since 2008, individual adult females, subadult males, and
between one and three pups have been observed annually on San Miguel
Island (Caretta et al., 2017).
During the summer breeding season, most adults occur at rookeries
in Mexico (Caretta et al., 2019a,b; Norris 2017 in Navy 2019a,b).
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 2,375 km (Ronald and Gots 2003).
Several rehabilitated Guadalupe fur seals that were satellite tagged
and released in central California traveled as far north as British
Columbia (Norris et al., 2015; Norris 2017 in Navy 2019a,b). Fur seals
younger than two years old are more likely to travel to more northerly,
offshore areas than older fur seals (Norris 2017 in Navy 2019a,b).
Stranding data also indicates that fur seals younger than two years old
are more likely to occur in the proposed survey area, as this age class
was most frequently reported (Lambourn et al., 2012 in Navy 2019a,b).
Guadalupe fur seals have not been observed in previous L-DEO surveys in
the northeast Pacific (RPS 2012a,b,c).
Increased strandings of Guadalupe fur seals have occurred along the
entire coast of California. Guadalupe fur seal strandings began in
January 2015 and were eight times higher than the historical average.
Strandings have continued since 2015 and have remained well above
average through 2019. Strandings are seasonal and generally peak in
April through June of each year. Strandings in Oregon and Washington
became elevated starting in 2019 and have continued to present.
Strandings in these two states in 2019 are five times higher than the
historical average. Guadalupe fur seals have stranded alive and dead.
Those stranding are mostly weaned pups and juveniles (1-2 years old).
The majority of stranded animals showed signs of malnutrition with
secondary bacterial and parasitic infections. NMFS has declared a UME
for Guadalupe fur seals along the entire U.S. West Coast; the UME is
ongoing and NMFS is continuing to investigate the cause(s). For
additional information on the UME, see https://www.fisheries.noaa.gov/national/marine-life-distress/2015-2020-guadalupe-fur-seal-unusual-mortality-event-california.
Northern Fur Seal
The northern fur seal is endemic to the North Pacific Ocean and
occurs from southern California to the Bering Sea, Sea of Okhotsk, and
Sea of Japan (Jefferson et al. 2015). The worldwide population of
northern fur seals has declined substantially from 1.8 million animals
in the 1950s (Muto et al. 2018). They were subjected to large-scale
harvests on the Pribilof Islands to supply a lucrative fur trade. Two
stocks are recognized in U.S. waters: The Eastern North Pacific and the
California stocks. The Eastern Pacific stock ranges from southern
California during winter to the Pribilof Islands and Bogoslof Island in
the Bering Sea during summer (Carretta et al. 2018; Muto et al. 2018).
Abundance of the Eastern Pacific Stock has been decreasing at the
Pribilof Islands since the 1940s and increasing on Bogoslof Island. The
California stock originated with immigrants from the Pribilof Islands
and Russian populations that recolonized San Miguel Island during the
late 1950s or early 1960s after northern fur seals were extirpated from
California in the 1700s and 1800s (DeLong 1982). The northern fur seal
population appears to be greatly affected by El Ni[ntilde]o events. In
the month of June, approximately 93.6 percent of the northern fur seals
in the survey area are expected to be from the Eastern Pacific stock
and 6.4 percent from the California stock (U.S. Navy 2019). Therefore,
although individuals from both the Eastern Pacific Stock and California
Stock may be present in the proposed survey area, the majority are
expected to be from the Eastern Pacific Stock.
Most northern fur seals are highly migratory. During the breeding
season, most of the world's population of northern fur seals occurs on
the Pribilof and Bogoslof islands (NMFS 2007). The main breeding season
is in July (Gentry 2009). Adult males usually occur onshore from May to
August, though some may be present until November; females are usually
found ashore from June to November (Muto et al. 2018). Nearly all fur
seals from the Pribilof Island rookeries are foraging at sea from fall
through late spring. In November, females and pups leave the Pribilof
Islands and migrate through the Gulf of Alaska to feeding areas
primarily off the coasts of BC, Washington, Oregon, and California
before migrating north again to the rookeries in spring (Ream et al.
2005; Pelland et al. 2014). Immature seals can remain in southern
foraging areas year-round until they are old enough to mate (NMFS
2007). Adult males migrate only as far south as the Gulf of Alaska or
to the west off the Kuril Islands (Kajimura 1984). Pups from the
California stock also migrate to Washington, Oregon, and northern
California after weaning (Lea et al. 2009). Although pups may be
present, there are no rookeries in Washington or Oregon.
The northern fur seals spends ~90 percent 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. While at sea, northern fur seals usually
occur singly or in pairs, although larger groups can form in waters
rich with prey (Antonelis and Fiscus 1980; Gentry 1981). Northern fur
seals dive to relatively shallow depths to feed: 100-200 m for females,
and <400 m for males (Gentry 2009). Tagged adult female fur seals were
shown to remain within 200 km of the shelf break (Pelland et al. 2014).
Bonnell et al. (1992) noted the presence of northern fur seals
year-round off Oregon/Washington, with the greatest numbers (87
percent) 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). Tagged adult fur
seals were tracked from the Pribilof Islands to the waters off
Washington/Oregon/California, with recorded movement throughout the
proposed survey area (Pelland et al. 2014).
Thirty-one northern fur seal sightings (63 animals) were made off
Washington/Oregon during the June-July 2012 L-DEO Juan de Fuca plate
seismic survey (RPS 2012b). There were six sightings (6 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).
Off British Columbia, females and subadult males are typically
found during the winter off the continental shelf (Bigg 1990). They
start arriving from Alaska during December and most will leave British
Columbia waters by July (Ford 2014). Ford (2014) also reported the
occurrence of northern fur seals throughout British Columbia, including
Dixon Entrance, Hecate Strait, Queen Charlotte Sound, and off the west
[[Page 19596]]
coasts of Haida Gwaii and Vancouver Island, with concentrations over
the shelf and slope, especially on La P[eacute]rouse Bank, southwestern
Vancouver Island. A few animals are seen in inshore waters in British
Columbia, and individuals occasionally come ashore, usually at sea lion
haulouts (e.g., Race Rocks, off southern Vancouver Island) during
winter and spring (Baird and Hanson 1997). Although fur seals sometimes
haul out in British Columbia, there are no breeding rookeries.
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 2019d).
There are two stocks and DPSs of Steller sea lions, the Western and
Eastern DPSs, which are divided at 144[deg] W longitude (Muto et al.,
2019b). The Western DPS is listed as endangered under the ESA and
includes animals that occur in Japan and Russia (Muto et al., 2019a,b);
the Eastern DPS is not listed. Only individuals from the Eastern DPS
are expected to occur in the proposed survey area.
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). The
eastern stock of Steller sea lions has historically bred on rookeries
located in Southeast Alaska, British Columbia, Oregon, and California.
However, within the last several years a new rookery has become
established on the outer Washington coast (at the Carroll Island and
Sea Lion Rock complex), with >100 pups born there in 2015 (Muto et al.,
2018). 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 2019e). 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).
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 percent) at-sea movements of juvenile Steller
sea lions were short (< 15 km) foraging trips. 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 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).
In British Columbia there are six main rookeries which are situated
at the Scott Islands off northwestern Vancouver Island, the Kerourd
Islands near Cape St. James at the southern end of Haida Gwaii, North
Danger Rocks in eastern Hecate Strait, Virgin Rocks in eastern Queen
Charlotte Sound, Garcin Rocks off southeastern Moresby Island in Haida
Gwaii, and Gosling Rocks on the central mainland coast (Ford 2014). The
Scott Islands and Cape St. James rookeries are the two largest breeding
sites with 4,000 and 850 pups born in 2010, respectively (Ford 2014).
Some adults and juveniles are also found on sites known as year-round
haulouts during the breeding season. Haulouts are located along the
coasts of Haida Gwaii, the central and northern mainland coast, the
west coast of Vancouver Island, and the Strait of Georgia; some are
year-round sites whereas others are only winter haulouts (Ford 2014).
Pitcher et al. (2007) reported 24 major haulout sites (>50 sea lions)
in British Columbia, but there are currently around 30 (Ford 2014). The
total pup and non-pup count of Steller sea lions in British Columbia in
2002 was 15,438; this represents a minimum population estimate (Pitcher
et al., 2007). The highest pup counts in British Columbia occur in July
(Bigg 1988).
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
British Columbia 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.
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 British Columbia (Lowry et al., 1992).
They remain there until spring (March-May), when they migrate back to
the breeding colonies (Lowry et al., 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). Peak numbers of California sea
lions off Oregon and Washington occur during the fall (Bonnell et al.,
1992). California sea lions have not been observed in previous L-DEO
surveys in the northeast Pacific (RPS 2012a,b,c).
California sea lions used to be rare in British Columbia, but their
numbers have increased substantially since the 1970s and 1980s (Ford
2014). Wintering California sea lion numbers have increased off
southern Vancouver Island since the 1970s, likely as a result of the
increasing California breeding population (Olesiuk and Bigg 1984).
Several thousand occur in the waters of British Columbia from fall to
spring (Ford 2014). Adult and subadult male California sea lions are
mainly seen in British Columbia during the winter (Olesiuk and Bigg
1984). They are mostly seen off the west coast of Vancouver Island and
in the Strait of Georgia, but they are also known to haul out along the
coasts of Haida Gwaii, including Dixon Entrance, and the mainland (Ford
2014).
Elevated strandings of California sea lion pups have occurred in
Southern California since January 2013 and NMFS has declared a UME. The
UME is confined to pup and yearling California sea lions, many of which
are emaciated, dehydrated, and underweight for their age. A change in
the availability of sea
[[Page 19597]]
lion prey, especially sardines, a high value food source for nursing
mothers, is a likely contributor to the large number of strandings.
Sardine spawning grounds shifted further offshore in 2012 and 2013, and
while other prey were available (market squid and rockfish), these may
not have provided adequate nutrition in the milk of sea lion mothers
supporting pups, or for newly-weaned pups foraging on their own.
Although the pups showed signs of some viruses and infections, findings
indicate that this event was not caused by disease, but rather by the
lack of high quality, close-by food sources for nursing mothers.
Current evidence does not indicate that this UME was caused by a single
infectious agent, though a variety of disease-causing bacteria and
viruses were found in samples from sea lion pups. Investigating and
identifying the cause of this UME is a true public-private effort with
many collaborators. The investigative team examined multiple potential
explanations for the high numbers of malnourished California sea lion
pups observed on the island rookeries and stranded on the mainland in
2013. The UME investigation is ongoing. For more information, see
https://www.fisheries.noaa.gov/national/marine-life-distress/2013-2017-california-sea-lion-unusual-mortality-event-california.
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). 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).
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 to March (Stewart and Huber
1993). Females arrive in late December or January and give birth within
~1 week of their arrival. Pups are weaned after just 27 days and are
abandoned by their mothers. Juvenile elephant seals typically leave the
rookeries in April or May and head north, traveling an average of 900-
1000 km. Hindell (2009) noted that traveling likely takes place at
depths >200 m. 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. 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.
Adult females and juveniles forage in the California current off
California to BC (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).
Off Washington, most elephant seal sightings at sea were made
during June, July, and September; off Oregon, sightings were recorded
from November through May (Bonnell et al. 1992). Several seals were
seen off Oregon during summer, fall, and winter surveys in 2011 and
2012 (Adams et al. 2014). Northern elephant seals were also taken as
bycatch off Oregon in the west coast groundfish fishery during 2002-
2009 (Jannot et al. 2011). Northern elephant seals were sighted five
times (5 animals) 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), or off
Washington/Oregon during the June-July 2012 L-DEO Juan de Fuca plate
seismic survey (RPS 2012b). One northern elephant seal was sighted
during the 2009 ETOMO survey off of British Columbia (Holst 2017).
Race Rocks Ecological Preserve, located off southern Vancouver
Island, is one of the few spots in British Columbia where elephant
seals regularly haul out. Based on their size and general appearance,
most animals using Race Rocks are adult females or subadults, although
a few males also haul out there. Use of Race Rocks by northern elephant
seals has increased substantially in recent years, most likely as a
result of the species' dramatic recovery from near extinction in the
early 20th century and its tendency to be highly migratory. A peak
number (22) of adults and subadults were observed in spring 2003
(Demarchi and Bentley 2004); pups have also been born there primarily
during December and January (Ford 2014). Haulouts can also be found on
the western and northeastern coasts of Haida Gwaii, and along the
coasts of Vancouver Island (Ford 2014).
Harbor Seal
Two subspecies of harbor seal occur in the Pacific: P.v. stejnegeri
in the northwest Pacific Ocean and P.v. richardii in the eastern
Pacific Ocean. P.v. richardii occurs in nearshore, coastal, and
estuarine areas ranging from Baja California, Mexico, north to the
Pribilof Islands in Alaska (Carretta et al., 2019a). Five stocks of
harbor seals are recognized along the U.S. West Coast: (1) Southern
Puget Sound, (2) Washington Northern Inland Waters Stock, (3) Hood
Canal, (4) Oregon/Washington Coast, and (5) California (Carretta et
al., 2019a). The Oregon/Washington Coast stock occurs in the proposed
survey area.
Harbor seals inhabit estuarine and coastal waters, hauling out on
rocks, reefs, beaches, and glacial ice flows. They are generally non-
migratory, but move locally with the tides, weather, season, food
availability, and reproduction (Scheffer and Slipp 1944; Fisher 1952;
Bigg 1969, 1981). Female harbor seals give birth to a single pup while
hauled out on shore or on glacial ice flows; pups are born from May to
mid-July. When molting, which occurs primarily in late August, seals
spend the majority of the time hauled out on shore, glacial ice, or
other substrates. Juvenile harbor seals can travel significant
distances (525 km) to forage or disperse (Lowry et al., 2001). The
smaller home range used by adults is suggestive of a strong site
fidelity (Pitcher and Calkins 1979; Pitcher and McAllister 1981; Lowry
et al., 2001).
Harbor seals haul out on rocks, reefs, and beaches along the U.S.
west coast (Carretta et al., 2019a). Jeffries et al. (2000) documented
several harbor seal rookeries and haulouts along the Washington
coastline. Bonnell et al. (1992) noted that most harbor seals sighted
off Oregon and Washington were within 20 km from shore, with the
farthest sighting 92 km from the coast. Menza et al. (2016) also showed
the highest predicted densities nearshore. During surveys off the
Oregon and Washington coasts, 88 percent of at-sea harbor seals
occurred over shelf waters <200 m deep, with a few sightings near the
2000-m contour, and only one sighting over deeper water (Bonnell et
[[Page 19598]]
al., 1992). Twelve sightings of harbor seals occurred in nearshore
waters from R/V Northern Light during a survey off southern Washington
during July 2012 (RPS 2012a).
Harbor seals occur along all coastal areas of British Columbia,
including the western coast of Vancouver Island, with the highest
concentration in the Strait of Georgia (13.1 seals per km of coast);
average densities elsewhere are 2.6 seals per km (Ford 2014). Almost
1,400 haulouts have been reported for British Columbia, many of them in
the Strait of Georgia (Ford 2014).
Marine Mammal Hearing
Hearing is the most important sensory modality for marine mammals
underwater, and exposure to anthropogenic sound can have deleterious
effects. To appropriately assess the potential effects of exposure to
sound, it is necessary to understand the frequency ranges marine
mammals are able to hear. Current data indicate that not all marine
mammal species have equal hearing capabilities (e.g., Richardson et
al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect
this, Southall et al. (2007) recommended that marine mammals be divided
into functional hearing groups based on directly measured or estimated
hearing ranges on the basis of available behavioral response data,
audiograms derived using auditory evoked potential techniques,
anatomical modeling, and other data. Note that no direct measurements
of hearing ability have been successfully completed for mysticetes
(i.e., low-frequency cetaceans). Subsequently, NMFS (2018) described
generalized hearing ranges for these marine mammal hearing groups.
Generalized hearing ranges were chosen based on the approximately 65
decibel (dB) threshold from the normalized composite audiograms, with
the exception for lower limits for low-frequency cetaceans where the
lower bound was deemed to be biologically implausible and the lower
bound from Southall et al. (2007) retained. Marine mammal hearing
groups and their associated hearing ranges are provided in Table 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 (dolphins, 150 Hz to 160 kHz.
toothed whales, beaked whales, bottlenose
whales).
High-frequency (HF) cetaceans (true 275 Hz to 160 kHz.
porpoises, Kogia, river dolphins,
cephalorhynchid, Lagenorhynchus cruciger &
L. australis).
Phocid pinnipeds (PW) (underwater) (true 50 Hz to 86 kHz.
seals).
Otariid pinnipeds (OW) (underwater) (sea 60 Hz to 39 kHz.
lions and fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
composite (i.e., all species within the group), where individual
species' hearing ranges are typically not as broad. Generalized
hearing range chosen based on ~65 dB threshold from normalized
composite audiogram, with the exception for lower limits for LF
cetaceans (Southall et al. 2007) and PW pinniped (approximation).
The pinniped functional hearing group was modified from Southall et
al. (2007) on the basis of data indicating that phocid species have
consistently demonstrated an extended frequency range of hearing
compared to otariids, especially in the higher frequency range
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth and Holt,
2013).
For more detail concerning these groups and associated frequency
ranges, please see NMFS (2018) for a review of available information.
31 marine mammal species (25 cetacean and six pinniped (four otariid
and two phocid) species) have the reasonable potential to co-occur with
the proposed survey activities. Please refer to Table 1. Of the
cetacean species that may be present, six are classified as low-
frequency cetaceans (i.e., all mysticete species), 15 are classified as
mid-frequency cetaceans (i.e., all delphinid and ziphiid species and
the sperm whale), and four are classified as high-frequency cetaceans
(i.e., porpoises and Kogia spp.).
Potential Effects of Specified Activities on Marine Mammals and Their
Habitat
This section includes a summary and discussion of the ways that
components of the specified activity may impact marine mammals and
their habitat. The Estimated Take by Incidental Harassment 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 by Incidental Harassment
section, and the Proposed Mitigation section, to draw conclusions
regarding the likely impacts of these activities on the reproductive
success or survivorship of individuals and how those impacts on
individuals are likely to impact marine mammal species or stocks.
Description of Active Acoustic Sound Sources
This section contains a brief technical background on sound, the
characteristics of certain sound types, and on metrics used in this
proposal inasmuch as the information is relevant to the specified
activity and to a discussion of the potential effects of the specified
activity on marine mammals found later in this document.
Sound travels in waves, the basic components of which are
frequency, wavelength, velocity, and amplitude. Frequency is the number
of pressure waves that pass by a reference point per unit of time and
is measured in hertz (Hz) or cycles per second. Wavelength is the
distance between two peaks or corresponding points of a sound wave
(length of one cycle). Higher frequency sounds have shorter wavelengths
than lower frequency sounds, and typically attenuate (decrease) more
rapidly, except in certain cases in shallower water. Amplitude is the
height of the sound pressure wave or the ``loudness'' of a sound and is
typically described using the relative unit of the dB. A sound pressure
level (SPL) in dB is described as the ratio between a measured pressure
and a reference pressure (for underwater sound, this is 1 microPascal
([mu]Pa)) and is a logarithmic unit that accounts for large variations
in amplitude; therefore, a relatively small change in dB corresponds to
large changes in sound pressure. The source level (SL) represents the
SPL referenced at a distance of 1 m from the source (referenced to 1
[mu]Pa) while the received level is the SPL at the listener's position
(referenced to 1 [mu]Pa).
Root mean square (rms) is the quadratic mean sound pressure over
the duration of an impulse. Root mean square is calculated by squaring
all of the sound amplitudes, averaging the squares, and then taking the
square root of the average (Urick, 1983). Root mean square accounts for
both positive and negative values; squaring the pressures
[[Page 19599]]
makes all values positive so that they may be accounted for in the
summation of pressure levels (Hastings and Popper, 2005). This
measurement is often used in the context of discussing behavioral
effects, in part because behavioral effects, which often result from
auditory cues, may be better expressed through averaged units than by
peak pressures.
Sound exposure level (SEL; represented as dB re 1 [mu]Pa\2\-s)
represents the total energy contained within a pulse and considers both
intensity and duration of exposure. Peak sound pressure (also referred
to as zero-to-peak sound pressure or 0-p) is the maximum instantaneous
sound pressure measurable in the water at a specified distance from the
source and is represented in the same units as the rms sound pressure.
Another common metric is peak-to-peak sound pressure (pk-pk), which is
the algebraic difference between the peak positive and peak negative
sound pressures. Peak-to-peak pressure is typically approximately 6 dB
higher than peak pressure (Southall et al., 2007).
When underwater objects vibrate or activity occurs, sound-pressure
waves are created. These waves alternately compress and decompress the
water as the sound wave travels. Underwater sound waves radiate in a
manner similar to ripples on the surface of a pond and may be either
directed in a beam or beams or may radiate in all directions
(omnidirectional sources), as is the case for pulses produced by the
airgun arrays considered here. The compressions and decompressions
associated with sound waves are detected as changes in pressure by
aquatic life and man-made sound receptors such as hydrophones.
Even in the absence of sound from the specified activity, the
underwater environment is typically loud due to ambient sound. Ambient
sound is defined as environmental background sound levels lacking a
single source or point (Richardson et al., 1995), and the sound level
of a region is defined by the total acoustical energy being generated
by known and unknown sources. These sources may include physical (e.g.,
wind and waves, earthquakes, ice, atmospheric sound), biological (e.g.,
sounds produced by marine mammals, fish, and invertebrates), and
anthropogenic (e.g., vessels, dredging, construction) sound. A number
of sources contribute to ambient sound, including the following
(Richardson et al., 1995):
Wind and waves: The complex interactions between wind and
water surface, including processes such as breaking waves and wave-
induced bubble oscillations and cavitation, are a main source of
naturally occurring ambient sound for frequencies between 200 Hz and 50
kHz (Mitson, 1995). In general, ambient sound levels tend to increase
with increasing wind speed and wave height. Surf sound becomes
important near shore, with measurements collected at a distance of 8.5
km from shore showing an increase of 10 dB in the 100 to 700 Hz band
during heavy surf conditions;
Precipitation: Sound from rain and hail impacting the
water surface can become an important component of total sound at
frequencies above 500 Hz, and possibly down to 100 Hz during quiet
times;
Biological: Marine mammals can contribute significantly to
ambient sound levels, as can some fish and snapping shrimp. The
frequency band for biological contributions is from approximately 12 Hz
to over 100 kHz; and
Anthropogenic: Sources of ambient sound related to human
activity include transportation (surface vessels), dredging and
construction, oil and gas drilling and production, seismic surveys,
sonar, explosions, and ocean acoustic studies. Vessel noise typically
dominates the total ambient sound for frequencies between 20 and 300
Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz
and, if higher frequency sound levels are created, they attenuate
rapidly. Sound from identifiable anthropogenic sources other than the
activity of interest (e.g., a passing vessel) is sometimes termed
background sound, as opposed to ambient sound.
The sum of the various natural and anthropogenic sound sources at
any given location and time--which comprise ``ambient'' or
``background'' sound--depends not only on the source levels (as
determined by current weather conditions and levels of biological and
human activity) but also on the ability of sound to propagate through
the environment. In turn, sound propagation is dependent on the
spatially and temporally varying properties of the water column and sea
floor, and is frequency-dependent. As a result of the dependence on a
large number of varying factors, ambient sound levels can be expected
to vary widely over both coarse and fine spatial and temporal scales.
Sound levels at a given frequency and location can vary by 10-20 dB
from day to day (Richardson et al., 1995). The result is that,
depending on the source type and its intensity, sound from a given
activity may be a negligible addition to the local environment or could
form a distinctive signal that may affect marine mammals. 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.
[[Page 19600]]
Acoustic Effects
Here, we discuss the effects of active acoustic sources on marine
mammals.
Potential Effects of Underwater Sound--Please refer to the
information given previously (``Description of Active Acoustic
Sources'') regarding sound, characteristics of sound types, and metrics
used in this document. Note that, in the following discussion, we refer
in many cases to a review article concerning studies of noise-induced
hearing loss conducted from 1996-2015 (i.e., Finneran, 2015). For
study-specific citations, please see that work. Anthropogenic sounds
cover a broad range of frequencies and sound levels and can have a
range of highly variable impacts on marine life, from none or minor to
potentially severe responses, depending on received levels, duration of
exposure, behavioral context, and various other factors. The potential
effects of underwater sound from active acoustic sources can
potentially result in one or more of the following: Temporary or
permanent hearing impairment, non-auditory physical or physiological
effects, behavioral disturbance, stress, and masking (Richardson et
al., 1995; Gordon et al., 2004; Nowacek et al., 2007; Southall et al.,
2007; G[ouml]tz et al., 2009). The degree of effect is intrinsically
related to the signal characteristics, received level, distance from
the source, and duration of the sound exposure. In general, sudden,
high level sounds can cause hearing loss, as can longer exposures to
lower level sounds. Temporary or permanent loss of hearing will occur
almost exclusively for noise within an animal's hearing range. We first
describe specific manifestations of acoustic effects before providing
discussion specific to the use of airgun arrays.
Richardson et al. (1995) described zones of increasing intensity of
effect that might be expected to occur, in relation to distance from a
source and assuming that the signal is within an animal's hearing
range. First is the area within which the acoustic signal would be
audible (potentially perceived) to the animal, but not strong enough to
elicit any overt behavioral or physiological response. The next zone
corresponds with the area where the signal is audible to the animal and
of sufficient intensity to elicit behavioral or physiological
responsiveness. Third is a zone within which, for signals of high
intensity, the received level is sufficient to potentially cause
discomfort or tissue damage to auditory or other systems. Overlaying
these zones to a certain extent is the area within which masking (i.e.,
when a sound interferes with or masks the ability of an animal to
detect a signal of interest that is above the absolute hearing
threshold) may occur; the masking zone may be highly variable in size.
We describe the more severe effects of certain non-auditory
physical or physiological effects only briefly as we do not expect that
use of airgun arrays are reasonably likely to result in such effects
(see below for further discussion). Potential effects from impulsive
sound sources can range in severity from effects such as behavioral
disturbance or tactile perception to physical discomfort, slight injury
of the internal organs and the auditory system, or mortality (Yelverton
et al., 1973). Non-auditory physiological effects or injuries that
theoretically might occur in marine mammals exposed to high level
underwater sound or as a secondary effect of extreme behavioral
reactions (e.g., change in dive profile as a result of an avoidance
reaction) caused by exposure to sound include neurological effects,
bubble formation, resonance effects, and other types of organ or tissue
damage (Cox et al., 2006; Southall et al., 2007; Zimmer and Tyack,
2007; Tal et al., 2015). The survey activities considered here do not
involve the use of devices such as explosives or mid-frequency tactical
sonar that are associated with these types of effects.
Threshold Shift--Marine mammals exposed to high-intensity sound, or
to lower-intensity sound for prolonged periods, can experience hearing
threshold shift (TS), which is the loss of hearing sensitivity at
certain frequency ranges (Finneran, 2015). TS can be permanent (PTS),
in which case the loss of hearing sensitivity is not fully recoverable,
or temporary (TTS), in which case the animal's hearing threshold would
recover over time (Southall et al., 2007). Repeated sound exposure that
leads to TTS could cause PTS. In severe cases of PTS, there can be
total or partial deafness, while in most cases the animal has an
impaired ability to hear sounds in specific frequency ranges (Kryter,
1985).
When PTS occurs, there is physical damage to the sound receptors in
the ear (i.e., tissue damage), whereas TTS represents primarily tissue
fatigue and is reversible (Southall et al., 2007). In addition, other
investigators have suggested that TTS is within the normal bounds of
physiological variability and tolerance and does not represent physical
injury (e.g., Ward, 1997). Therefore, NMFS does not consider TTS to
constitute auditory injury.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals, and there is no PTS data for cetaceans but such
relationships are assumed to be similar to those in humans and other
terrestrial mammals. PTS typically occurs at exposure levels at least
several dBs above (a 40-dB threshold shift approximates PTS onset;
e.g., Kryter et al., 1966; Miller, 1974) that inducing mild TTS (a 6-dB
threshold shift approximates TTS onset; e.g., Southall et al. 2007).
Based on data from terrestrial mammals, a precautionary assumption is
that the PTS thresholds for impulse sounds (such as airgun pulses as
received close to the source) are at least 6 dB higher than the TTS
threshold on a peak-pressure basis and PTS cumulative sound exposure
level thresholds are 15 to 20 dB higher than TTS cumulative sound
exposure level thresholds (Southall et al., 2007). Given the higher
level of sound or longer exposure duration necessary to cause PTS as
compared with TTS, it is considerably less likely that PTS could occur.
For mid-frequency cetaceans in particular, potential protective
mechanisms may help limit onset of TTS or prevent onset of PTS. Such
mechanisms include dampening of hearing, auditory adaptation, or
behavioral amelioration (e.g., Nachtigall and Supin, 2013; Miller et
al., 2012; Finneran et al., 2015; Popov et al., 2016).
TTS is the mildest form of hearing impairment that can occur during
exposure to sound (Kryter, 1985). While experiencing TTS, the hearing
threshold rises, and a sound must be at a higher level in order to be
heard. In terrestrial and marine mammals, TTS can last from minutes or
hours to days (in cases of strong TTS). In many cases, hearing
sensitivity recovers rapidly after exposure to the sound ends. Few data
on sound levels and durations necessary to elicit mild TTS have been
obtained for marine mammals.
Marine mammal hearing plays a critical role in communication with
conspecifics, and interpretation of environmental cues for purposes
such as predator avoidance and prey capture. Depending on the degree
(elevation of threshold in dB), duration (i.e., recovery time), and
frequency range of TTS, and the context in which it is experienced, TTS
can have effects on marine mammals ranging from discountable to
serious. For example, a marine mammal may be able to readily compensate
for a brief, relatively small amount of TTS in a non-critical frequency
range that occurs during a time where ambient noise is lower and there
are not as many competing sounds present. Alternatively, a larger
amount and longer duration of TTS sustained during
[[Page 19601]]
time when communication is critical for successful mother/calf
interactions could have more serious impacts.
Finneran et al. (2015) measured hearing thresholds in three captive
bottlenose dolphins before and after exposure to ten pulses produced by
a seismic airgun in order to study TTS induced after exposure to
multiple pulses. Exposures began at relatively low levels and gradually
increased over a period of several months, with the highest exposures
at peak SPLs from 196 to 210 dB and cumulative (unweighted) SELs from
193-195 dB. No substantial TTS was observed. In addition, behavioral
reactions were observed that indicated that animals can learn behaviors
that effectively mitigate noise exposures (although exposure patterns
must be learned, which is less likely in wild animals than for the
captive animals considered in this study). The authors note that the
failure to induce more significant auditory effects likely due to the
intermittent nature of exposure, the relatively low peak pressure
produced by the acoustic source, and the low-frequency energy in airgun
pulses as compared with the frequency range of best sensitivity for
dolphins and other mid-frequency cetaceans.
Currently, TTS data only exist for four species of cetaceans
(bottlenose dolphin, beluga whale, harbor porpoise, and Yangtze finless
porpoise) exposed to a limited number of sound sources (i.e., mostly
tones and octave-band noise) in laboratory settings (Finneran, 2015).
In general, harbor porpoises have a lower TTS onset than other measured
cetacean species (Finneran, 2015). Additionally, the existing marine
mammal TTS data come from a limited number of individuals within these
species. There are no data available on noise-induced hearing loss for
mysticetes.
Critical questions remain regarding the rate of TTS growth and
recovery after exposure to intermittent noise and the effects of single
and multiple pulses. Data at present are also insufficient to construct
generalized models for recovery and determine the time necessary to
treat subsequent exposures as independent events. More information is
needed on the relationship between auditory evoked potential and
behavioral measures of TTS for various stimuli. For summaries of data
on TTS in marine mammals or for further discussion of TTS onset
thresholds, please see Southall et al. (2007, 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 that are
highly motivated to remain in an area for feeding (Richardson et al.,
1995; NRC, 2003; Wartzok et al., 2003). Controlled experiments with
captive marine mammals have showed pronounced behavioral reactions,
including avoidance of loud sound sources (Ridgway et al., 1997).
Observed responses of wild marine mammals to loud pulsed sound sources
(typically seismic airguns or acoustic harassment devices) have been
varied but often consist of avoidance behavior or other behavioral
changes suggesting discomfort (Morton and Symonds, 2002; see also
Richardson et al., 1995; Nowacek et al., 2007). However, many
delphinids approach acoustic source vessels with no apparent discomfort
or obvious behavioral change (e.g., Barkaszi et al., 2012).
Available studies show wide variation in response to underwater
sound; therefore, it is difficult to predict specifically how any given
sound in a particular instance might affect marine mammals perceiving
the signal. If a marine mammal does react briefly to an underwater
sound by changing its behavior or moving a small distance, the impacts
of the change are unlikely to be significant to the individual, let
alone the stock or population. However, if a sound source displaces
marine mammals from an important feeding or breeding area for a
prolonged period, impacts on individuals and populations could be
significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007; NRC,
2005). However, there are broad categories of potential response, which
we describe in greater detail here, that include alteration of dive
behavior, alteration of foraging behavior, effects to breathing,
interference with or alteration of vocalization, avoidance, and flight.
Changes in dive behavior can vary widely, and may consist of
increased or decreased dive times and surface intervals as well as
changes in the rates of ascent and descent during a dive (e.g., Frankel
and Clark, 2000; Ng and Leung, 2003; Nowacek et al., 2004; Goldbogen et
al., 2013a, b). Variations in dive behavior may reflect interruptions
in biologically significant activities (e.g., foraging) or they may be
of little biological significance. The impact of an alteration to dive
behavior resulting from an acoustic exposure depends on what the animal
is doing at the time of the exposure and the type and magnitude of the
response.
Disruption of feeding behavior can be difficult to correlate with
anthropogenic sound exposure, so it is usually inferred by observed
displacement from known foraging areas, the appearance of secondary
indicators (e.g., bubble nets or sediment plumes), or changes in dive
behavior. As for other types of behavioral response, the frequency,
duration, and temporal pattern of signal presentation, as well as
differences in species sensitivity, are likely contributing factors to
differences in response in any given circumstance (e.g., Croll et al.,
2001; Nowacek et al.;
[[Page 19602]]
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, 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
[[Page 19603]]
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 large arrays of airguns
(considered to be 500 in\3\ or more) were firing, lateral displacement,
more localized avoidance, or other changes in behavior were evident for
most odontocetes. However, significant responses to large arrays were
found only for the minke whale and fin whale. Behavioral responses
observed included changes in swimming or surfacing behavior, with
indications that cetaceans remained near the water surface at these
times. Cetaceans were recorded as feeding less often when large arrays
were active. Behavioral observations of gray whales during a seismic
survey monitored whale movements and respirations pre-, during, and
post-seismic survey (Gailey et al., 2016). Behavioral state and water
depth were the best `natural' predictors of whale movements and
respiration and, after considering natural variation, none of the
response variables were significantly associated with seismic survey or
vessel sounds.
Stress Responses--An animal's perception of a threat may be
sufficient to trigger stress responses consisting of some combination
of behavioral responses, autonomic nervous system responses,
neuroendocrine responses, or immune responses (e.g., Seyle, 1950;
Moberg, 2000). In many cases, an animal's first and sometimes most
economical (in terms of energetic costs) response is behavioral
avoidance of the potential stressor. Autonomic nervous system responses
to stress typically involve changes in heart rate, blood pressure, and
gastrointestinal activity. These responses have a relatively short
duration and may or may not have a significant long-term effect on an
animal's fitness.
Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that
are affected by stress--including immune competence, reproduction,
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been
implicated in failed reproduction, altered metabolism, reduced immune
competence, and behavioral disturbance (e.g., Moberg, 1987; Blecha,
2000). Increases in the circulation of glucocorticoids are also equated
with stress (Romano et al., 2004).
The primary distinction between stress (which is adaptive and does
not normally place an animal at risk) and ``distress'' is the cost of
the response. During a stress response, an animal uses glycogen stores
that can be quickly replenished once the stress is alleviated. In such
circumstances, the cost of the stress response would not pose serious
fitness consequences. However, when an animal does not have sufficient
energy reserves to satisfy the energetic costs of a stress response,
energy resources must be diverted from other functions. This state of
distress will last 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
[[Page 19604]]
al., 2004; Lankford et al., 2005). Stress responses due to exposure to
anthropogenic sounds or other stressors and their effects on marine
mammals have also been reviewed (Fair and Becker, 2000; Romano et al.,
2002b) and, more rarely, studied in wild populations (e.g., Romano et
al., 2002a). For example, Rolland et al. (2012) found that noise
reduction from reduced ship traffic in the Bay of Fundy was associated
with decreased stress in North Atlantic right whales. These and other
studies lead to a reasonable expectation that some marine mammals will
experience physiological stress responses upon exposure to acoustic
stressors and that it is possible that some of these would be
classified as ``distress.'' In addition, any animal experiencing TTS
would likely also experience stress responses (NRC, 2003).
Auditory Masking--Sound can disrupt behavior through masking, or
interfering with, an animal's ability to detect, recognize, or
discriminate between acoustic signals of interest (e.g., those used for
intraspecific communication and social interactions, prey detection,
predator avoidance, navigation) (Richardson et al., 1995; Erbe et al.,
2016). Masking occurs when the receipt of a sound is interfered with by
another coincident sound at similar frequencies and at similar or
higher intensity, and may occur whether the sound is natural (e.g.,
snapping shrimp, wind, waves, precipitation) or anthropogenic (e.g.,
shipping, sonar, seismic exploration) in origin. The ability of a noise
source to mask biologically important sounds depends on the
characteristics of both the noise source and the signal of interest
(e.g., signal-to-noise ratio, temporal variability, direction), in
relation to each other and to an animal's hearing abilities (e.g.,
sensitivity, frequency range, critical ratios, frequency
discrimination, directional discrimination, age or TTS hearing loss),
and existing ambient noise and propagation conditions.
Under certain circumstances, marine mammals experiencing
significant masking could also be impaired from maximizing their
performance fitness in survival and reproduction. Therefore, when the
coincident (masking) sound is man-made, it may be considered harassment
when disrupting or altering critical behaviors. It is important to
distinguish TTS and PTS, which persist after the sound exposure, from
masking, which occurs during the sound exposure. Because masking
(without resulting in TS) is not associated with abnormal physiological
function, it is not considered a physiological effect, but rather a
potential behavioral effect.
The frequency range of the potentially masking sound is important
in determining any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation
sounds produced by odontocetes but are more likely to affect detection
of mysticete communication calls and other potentially important
natural sounds such as those produced by surf and some prey species.
The masking of communication signals by anthropogenic noise may be
considered as a reduction in the communication space of animals (e.g.,
Clark et al., 2009) and may result in energetic or other costs as
animals change their vocalization behavior (e.g., Miller et al., 2000;
Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2009; Holt
et al., 2009). Masking can be reduced in situations where the signal
and noise come from different directions (Richardson et al., 1995),
through amplitude modulation of the signal, or through other
compensatory behaviors (Houser and Moore, 2014). Masking can be tested
directly in captive species (e.g., Erbe, 2008), but in wild populations
it must be either modeled or inferred from evidence of masking
compensation. There are few studies addressing real-world masking
sounds likely to be experienced by marine mammals in the wild (e.g.,
Branstetter et al., 2013).
Masking affects both senders and receivers of acoustic signals and
can potentially have long-term chronic effects on marine mammals at the
population level as well as at the individual level. Low-frequency
ambient sound levels have increased by as much as 20 dB (more than
three times in terms of SPL) in the world's ocean from pre-industrial
periods, with most of the increase from distant commercial shipping
(Hildebrand, 2009). All anthropogenic sound sources, but especially
chronic and lower-frequency signals (e.g., from vessel traffic),
contribute to elevated ambient sound levels, thus intensifying masking.
Masking effects of pulsed sounds (even from large arrays of
airguns) on marine mammal calls and other natural sounds are expected
to be limited, although there are few specific data on this. Because of
the intermittent nature and low duty cycle of seismic pulses, animals
can emit and receive sounds in the relatively quiet intervals between
pulses. However, in exceptional situations, reverberation occurs for
much or all of the interval between pulses (e.g., Simard et al. 2005;
Clark and Gagnon 2006), which could mask calls. Situations with
prolonged strong reverberation are infrequent. However, it is common
for reverberation to cause some lesser degree of elevation of the
background level between airgun pulses (e.g., Gedamke 2011; Guerra et
al. 2011, 2016; Klinck et al. 2012; Guan et al. 2015), and this weaker
reverberation presumably reduces the detection range of calls and other
natural sounds to some degree. Guerra et al. (2016) reported that
ambient noise levels between seismic pulses were elevated as a result
of reverberation at ranges of 50 km from the seismic source. Based on
measurements in deep water of the Southern Ocean, Gedamke (2011)
estimated that the slight elevation of background levels during
intervals between pulses reduced blue and fin whale communication space
by as much as 36-51 percent when a seismic survey was operating 450-
2,800 km away. Based on preliminary modeling, Wittekind et al. (2016)
reported that airgun sounds could reduce the communication range of
blue and fin whales 2000 km from the seismic source. Nieukirk et al.
(2012) and Blackwell et al. (2013) noted the 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.
[[Page 19605]]
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., Parks et al. 2011, 2012, 2016a,b;
Castellote et al. 2012; Melc[oacute]n et al. 2012; Azzara et al. 2013;
Tyack and Janik 2013; Lu[iacute]s et al. 2014; Sairanen 2014; Papale et
al. 2015; Bittencourt et al. 2016; Dahlheim and Castellote 2016;
Gospi[cacute] and Picciulin 2016; Gridley et al. 2016; Heiler et al.
2016; Martins et al. 2016; O'Brien et al. 2016; Tenessen and Parks
2016). Harp seals did not increase their call frequencies in
environments with increased low-frequency sounds (Terhune and Bosker
2016). Holt et al. (2015) reported that changes in vocal modifications
can have increased energetic costs for individual marine mammals. A
negative correlation between the presence of some cetacean species and
the number of vessels in an area has been demonstrated by several
studies (e.g., Campana et al. 2015; Culloch et al. 2016).
Southern Resident killer whales often forage in the company of
whale watch boats in the waters around the San Juan Islands,
Washington. These observed behavioral changes have included faster
swimming speeds (Williams et al., 2002b), less directed swimming paths
(Williams et al., 2002b; Bain et al., 2006; Williams et al., 2009a),
and less time foraging (Bain et al., 2006; Williams et al., 2006;
Lusseau et al., 2009; Giles and Cendak 2010; Senigaglia et al., 2016).
Vessels in the path of the whales can also interfere with important
social behaviors such as prey sharing (Ford and Ellis 2006) or nursing
(Kriete 2007). Williams et al. (2006) found that with the disruption of
feeding behavior that has been observed in Northern Resident killer
whales, it is estimated that the presence of vessels could result in an
18 percent decrease in energy intake.
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.
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
[[Page 19606]]
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 4.2 kn (7.8 km/h) while
towing seismic survey gear (LGL 2018). 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 10-6; 95% CI
= 0-5.5 x 10-6; NMFS, 2013b). In addition, a research vessel
reported a fatal strike in 2011 of a dolphin in the Atlantic,
demonstrating that it is possible for strikes involving smaller
cetaceans to occur. In that case, the incident report indicated that an
animal apparently was struck by the vessel's propeller as it was
intentionally swimming near the vessel. While indicative of the type of
unusual events that cannot be ruled out, neither of these instances
represents a circumstance that would be considered reasonably
foreseeable or that would be considered preventable.
Although the likelihood of the vessel striking a marine mammal is
low, we require a robust ship strike avoidance protocol (see ``Proposed
Mitigation''), which we believe eliminates any foreseeable risk of ship
strike 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 required mitigation measures, the
relatively slow speed of the vessel towing gear, the presence of bridge
crew watching for obstacles at all times (including marine mammals),
and the presence of marine mammal observers, we believe that the
possibility of ship strike is discountable and, further, that were a
strike of a large whale to occur, it would be unlikely to result in
serious injury or mortality. No incidental take resulting from ship
strike is anticipated, and this potential effect of the specified
activity will not be discussed further in the following analysis.
Stranding--When a living or dead marine mammal swims or floats onto
shore and becomes ``beached'' or incapable of returning to sea, the
event is a ``stranding'' (Geraci et al., 1999; Perrin and Geraci, 2002;
Geraci and Lounsbury, 2005; NMFS, 2007). The legal definition for a
stranding under the MMPA is that ``(A) a marine mammal is dead and is
(i) on a beach or shore of the United States; or (ii) in waters under
the jurisdiction of the United States (including any navigable waters);
or (B) a marine mammal is alive and is (i) on a beach or shore of the
United States and is unable to return to the water; (ii) on a beach or
shore of the United States and, although able to return to the water,
is in need of apparent medical attention; or (iii) in the waters under
the jurisdiction of the United States (including any navigable waters),
but is unable to return to its natural habitat under its own power or
without assistance.''
Marine mammals strand for a variety of reasons, such as infectious
agents, biotoxicosis, starvation, fishery interaction, ship strike,
unusual oceanographic or weather events, sound exposure, or
combinations of these stressors sustained concurrently or in series.
However, the cause or causes of most strandings are unknown (Geraci et
al., 1976; Eaton, 1979; Odell et al., 1980; Best, 1982). Numerous
studies suggest that the physiology, behavior, habitat relationships,
age, or condition of cetaceans may cause them to strand or might pre-
dispose them to strand when exposed to another phenomenon. These
suggestions are consistent with the conclusions of numerous other
studies that have demonstrated that combinations of dissimilar
stressors commonly combine to kill an animal or dramatically reduce its
fitness, even though one exposure without the other does not produce
the same result (Chroussos, 2000; Creel, 2005; DeVries et al., 2003;
Fair and Becker, 2000; Foley et al., 2001; Moberg, 2000; Relyea, 2005a;
2005b, Romero, 2004; Sih et al., 2004).
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
[[Page 19607]]
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.
(2019a2019) suggested that certain species amongst the historical mid-
frequency hearing group (beaked whales, sperm whales, and killer
whales) are likely more sensitive to lower frequencies within the
group's generalized hearing range than are other species within the
group and state that the data for beaked whales suggest sensitivity to
approximately 5 kHz. However, this information is consistent with the
general conclusion that beaked whales (and other mid-frequency
cetaceans) are relatively insensitive to the frequencies where most
energy of an airgun signal is found. Military MFA sonar is typically
considered to operate in the frequency range of approximately 3-14 kHz
(D'Amico et al., 2009), i.e., outside the range of likely best hearing
for beaked whales but within or close to the lower bounds, whereas most
energy in an airgun signal is radiated at much lower frequencies, below
500 Hz (Dragoset, 1990).
It is important to distinguish between energy (loudness, measured
in dB) and frequency (pitch, measured in Hz). In considering the
potential impacts of mid-frequency components of airgun noise (1-10
kHz, where beaked whales can be expected to hear) on marine mammal
hearing, one needs to account for the energy associated with these
higher frequencies and determine what energy is truly ``significant.''
Although there is mid-frequency energy associated with airgun noise (as
expected from a broadband source), airgun sound is predominantly below
1 kHz (Breitzke et al., 2008; Tashmukhambetov et al., 2008; Tolstoy et
al., 2009). As stated by Richardson et al. (1995), ``[. . .] most
emitted [seismic airgun] energy is at 10-120 Hz, but the pulses contain
some energy up to 500-1,000 Hz.'' Tolstoy et al. (2009) conducted
empirical measurements, demonstrating that sound energy levels
associated with airguns were at least 20 decibels (dB) lower at 1 kHz
(considered ``mid-frequency'') compared to higher energy levels
associated with lower frequencies (below 300 Hz) (``all but a small
fraction of the total energy being concentrated in the 10-300 Hz
range'' [Tolstoy et al., 2009]), and at higher frequencies (e.g., 2.6-4
kHz), power might be less than 10 percent of the peak power at 10 Hz
(Yoder, 2002). Energy levels measured by Tolstoy et al. (2009) were
even lower at frequencies above 1 kHz. In addition, as sound propagates
away from the source, it tends to lose higher-frequency components
faster than low-frequency components (i.e., low-frequency sounds
typically propagate longer distances than high-frequency sounds)
(Diebold et al., 2010). Although higher-frequency components of airgun
signals have been recorded, it is typically in surface-ducting
conditions (e.g., DeRuiter et al., 2006; Madsen et al., 2006) or in
shallow water, where there are advantageous propagation conditions for
the higher frequency (but low-energy) components of the airgun signal
(Hermannsen et al., 2015). This should not be of concern because the
likely behavioral reactions of beaked whales that can result in acute
physical injury would result from noise exposure at depth (because of
the potentially greater consequences of severe behavioral reactions).
In summary, the frequency content of airgun signals is such that beaked
whales will not be able to hear the signals well (compared to MFA
sonar), especially at depth where we expect the consequences of noise
exposure could be more severe.
Aside from frequency content, there are other significant
differences between MFA sonar signals and the sounds produced by
airguns that minimize the risk of severe behavioral reactions that
could lead to strandings or deaths at sea, e.g., significantly longer
signal duration, horizontal sound direction, typical fast and
unpredictable source movement. All of these characteristics of MFA
sonar tend towards greater potential to cause severe behavioral or
physiological reactions in exposed beaked whales that may contribute to
stranding. Although both sources are powerful, MFA sonar contains
significantly greater energy in the mid-frequency range, where beaked
whales hear better. Short-duration, high
[[Page 19608]]
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 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,
[[Page 19609]]
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 nmi (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. Entanglement in OBSs and OBNs is also not expected to occur.
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 OBSs and OBNs, on 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 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
[[Page 19610]]
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, 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,
[[Page 19611]]
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
determination.
Harassment is the only type of take expected to result from these
activities. Except with respect to certain activities not pertinent
here, section 3(18) of the MMPA defines ``harassment'' as any act of
pursuit, torment, or annoyance, which (i) has the potential to injure a
marine mammal or marine mammal stock in the wild (Level A harassment);
or (ii) has the potential to disturb a marine mammal or marine mammal
stock in the wild by causing disruption of behavioral patterns,
including, but not limited to, migration, breathing, nursing, breeding,
feeding, or sheltering (Level B harassment).
Authorized takes would primarily be by Level B harassment, as use
of seismic airguns has the potential to result in disruption of
behavioral patterns for individual marine mammals. There is also some
potential for auditory injury (Level A harassment) for mysticetes and
high frequency cetaceans (i.e., porpoises, Kogia spp.). The proposed
mitigation and monitoring measures are expected to minimize the
severity of such taking to the extent practicable.
As described previously, no serious injury or mortality is
anticipated or proposed to be authorized for this activity. Below we
describe how the take is estimated.
Generally speaking, we estimate take by considering: (1) Acoustic
thresholds above which NMFS believes the best available science
indicates marine mammals will be behaviorally harassed or incur some
degree of permanent hearing impairment; (2) the area or volume of water
that will be ensonified above these levels in a day; (3) the density or
occurrence of marine mammals within these ensonified areas; and, (4)
and the number of days of activities. We note that while these basic
factors can contribute to a basic calculation to provide an initial
prediction of takes, additional information that can qualitatively
inform take estimates is also sometimes available (e.g., previous
monitoring results or average group size). Below, we describe the
factors considered here in more detail and present the proposed take
estimate.
Acoustic Thresholds
NMFS uses acoustic thresholds that identify the received level of
underwater sound above which exposed marine mammals would be reasonably
expected to be behaviorally harassed (equated to Level B harassment) or
to incur PTS of some degree (equated to Level A harassment).
Level B Harassment for non-explosive sources--Though significantly
driven by received level, the onset of behavioral disturbance from
anthropogenic noise exposure is also informed to varying degrees by
other factors related to the source (e.g., frequency, predictability,
duty cycle), the environment (e.g., bathymetry), and the receiving
animals (hearing, motivation, experience, demography, behavioral
context) and can be difficult to predict (Southall et al., 2007,
Ellison et al., 2012). NMFS uses a generalized acoustic threshold based
on received level to estimate the onset of behavioral harassment. NMFS
predicts that marine mammals are likely to be behaviorally harassed in
a manner we consider Level B harassment when exposed to underwater
anthropogenic noise above received levels of 120 dB re 1 [mu]Pa (rms)
for continuous (e.g., vibratory pile-driving, drilling) and above 160
dB re 1 [mu]Pa (rms) for non-explosive impulsive (e.g., seismic
airguns) or intermittent (e.g., scientific sonar) sources. L-DEO's
proposed activity includes the use of impulsive seismic sources.
Therefore, the 160 dB re 1 [mu]Pa (rms) criteria is applicable for
analysis of Level B harassment.
Level A harassment for non-explosive sources--NMFS' Technical
Guidance for Assessing the Effects of Anthropogenic Sound on Marine
Mammal Hearing (Version 2.0) (Technical Guidance, 2018) identifies dual
criteria to assess auditory injury (Level A harassment) to five
different marine mammal groups (based on hearing sensitivity) as a
result of exposure to noise from two different types of sources
(impulsive or non-impulsive). L-DEO's proposed seismic survey includes
the use of impulsive (seismic airguns) sources.
These thresholds are provided in the table below. The references,
analysis, and methodology used in the development of the thresholds are
described in NMFS 2018 Technical Guidance, which may be accessed at
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.
[[Page 19612]]
Table 3--Thresholds Identifying the Onset of Permanent Threshold Shift
----------------------------------------------------------------------------------------------------------------
PTS onset acoustic thresholds * (received level)
Hearing Group ------------------------------------------------------------------------
Impulsive Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans........... Cell 1: Lpk,flat: 219 dB; Cell 2: LE,LF,24h: 199 dB.
LE,LF,24h: 183 dB.
Mid-Frequency (MF) Cetaceans........... Cell 3: Lpk,flat: 230 dB; Cell 4: LE,MF,24h: 198 dB.
LE,MF,24h: 185 dB.
High-Frequency (HF) Cetaceans.......... Cell 5: Lpk,flat: 202 dB; Cell 6: LE,HF,24h: 173 dB.
LE,HF,24h: 155 dB.
Phocid Pinnipeds (PW) (Underwater)..... Cell 7: Lpk,flat: 218 dB; Cell 8: LE,PW,24h: 201 dB.
LE,PW,24h: 185 dB.
Otariid Pinnipeds (OW) (Underwater).... Cell 9: Lpk,flat: 232 dB; Cell 10: LE,OW,24h: 219 dB.
LE,OW,24h: 203 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for
calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level
thresholds associated with impulsive sounds, these thresholds should also be considered.
Note: Peak sound pressure (Lpk) has a reference value of 1 [micro]Pa, and cumulative sound exposure level (LE)
has a reference value of 1[micro]Pa\2\s. In this Table, thresholds are abbreviated to reflect American
National Standards Institute standards (ANSI 2013). However, peak sound pressure is defined by ANSI as
incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript
``flat'' is being included to indicate peak sound pressure should be flat weighted or unweighted within the
generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates
the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds)
and that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could
be exceeded in a multitude of ways (i.e., varying exposure levels and durations, duty cycle). When possible,
it is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be
exceeded.
Ensonified Area
Here, we describe operational and environmental parameters of the
activity that will feed into identifying the area ensonified above the
acoustic thresholds, which include source levels and acoustic
propagation modeling.
L-DEO's modeling methodology is described in greater detail in the
IHA application (LGL 2019). The proposed 2D survey would acquire data
using the 36-airgun array with a total discharge volume of 6,600 in\3\
at a maximum tow depth of 12 m. L-DEO model results are used to
determine the 160-dBrms radius for the 36-airgun array in deep water
(>1,000 m) down to a maximum water depth of 2,000 m. Water depths in
the project area may be up to 4,400 m, but marine mammals are generally
not anticipated to dive below 2,000 m (Costa and Williams 1999).
Received sound levels were predicted by L-DEO's model (Diebold et al.,
2010) which uses ray tracing for the direct wave traveling from the
array to the receiver and its associated source ghost (reflection at
the air-water interface in the vicinity of the array), in a constant-
velocity half-space (infinite homogeneous ocean layer, unbounded by a
seafloor). In addition, propagation measurements of pulses from the 36-
airgun array at a tow depth of 6 m have been reported in deep water
(approximately 1600 m), intermediate water depth on the slope
(approximately 600-1100 m), and shallow water (approximately 50 m) in
the Gulf of Mexico in 2007-2008 (Tolstoy et al. 2009; Diebold et al.
2010).
For deep and intermediate-water cases, the field measurements
cannot be used readily to derive Level A and Level B harassment
isopleths, as at those sites the calibration hydrophone was located at
a roughly constant depth of 350-500 m, which may not intersect all the
sound pressure level (SPL) isopleths at their widest point from the sea
surface down to the maximum relevant water depth for marine mammals of
~2,000 m. At short ranges, where the direct arrivals dominate and the
effects of seafloor interactions are minimal, the data recorded at the
deep and slope sites are suitable for comparison with modeled levels at
the depth of the calibration hydrophone. At longer ranges, the
comparison with the model--constructed from the maximum SPL through the
entire water column at varying distances from the airgun array--is the
most relevant.
In deep and intermediate-water depths, comparisons at short ranges
between sound levels for direct arrivals recorded by the calibration
hydrophone and model results for the same array tow depth are in good
agreement (Fig. 12 and 14 in Appendix H of NSF-USGS, 2011).
Consequently, isopleths falling within this domain can be predicted
reliably by the L-DEO model, although they may be imperfectly sampled
by measurements recorded at a single depth. At greater distances, the
calibration data show that seafloor-reflected and sub-seafloor-
refracted arrivals dominate, whereas the direct arrivals become weak
and/or incoherent. Aside from local topography effects, the region
around the critical distance is where the observed levels rise closest
to the model curve. However, the observed sound levels are found to
fall almost entirely below the model curve. Thus, analysis of the Gulf
of Mexico calibration measurements demonstrates that although simple,
the L-DEO model is a robust tool for conservatively estimating
isopleths. For deep water (>1,000 m), L-DEO used the deep-water radii
obtained from model results down to a maximum water depth of 2,000 m.
A recent retrospective analysis of acoustic propagation from use of
the Langseth sources during a 2012 survey off Washington (i.e., in the
same location) suggests that predicted (modeled) radii (using the same
approach as that used here) were 2-3 times larger than the measured
radii in shallow water. (Crone et al., 2014). Therefore, because the
modeled shallow-water radii were specifically demonstrated to be overly
conservative for the region in which the current survey is planned, L-
DEO used the received levels from multichannel seismic data collected
by the Langseth during the 2012 survey to estimate Level B harassment
radii in shallow (<100 m) and intermediate (100-1,000 m) depths (Crone
et al., 2014). Streamer data in shallow water collected in 2012 have
the advantage of including the effects of local and complex subsurface
geology, seafloor topography, and water column properties, and thus
allow determination of radii more confidently than using data from
calibration experiments in the Gulf of Mexico.
The proposed survey would acquire data with a four-string 6,600-
in\3\ airgun array at a tow depth of 12 m while the data collected in
2012 were acquired with the same airgun array at a tow depth of 9 m. To
account for the differences in tow depth between the 2012 survey and
the proposed 2020 survey, L-DEO calculated a scaling factor using the
deep water modeling (see Appendix D in L-DEO's IHA application). A
scaling factor of 1.15 was applied to the measured radii from the
airgun array towed at 9 m.
[[Page 19613]]
The estimated distances to the Level B harassment isopleth for the
Langseth's 36-airgun array are shown in Table 4.
Table 4--Predicted Radial Distances to Isopleths Corresponding to Level B Harassment Threshold
----------------------------------------------------------------------------------------------------------------
Level B
harassment
Source and volume Tow depth (m) Water depth zone (m)
(m) using L-DEO
model
----------------------------------------------------------------------------------------------------------------
36 airgun array, 6,600-in\3\.................................... 12 >1000 \a\ 6,733
100-1000 \b\ 9,468
<100 \b\ 12,650
----------------------------------------------------------------------------------------------------------------
\a\ Distance based on L-DEO model results.
\b\ Distance based on data from Crone et al. (2014).
Predicted distances to Level A harassment isopleths, which vary
based on marine mammal hearing groups, were calculated based on
modeling performed by L-DEO using the NUCLEUS source modeling software
program and the NMFS User Spreadsheet, described below. The acoustic
thresholds for impulsive sounds (e.g., airguns) contained in the
Technical Guidance were presented as dual metric acoustic thresholds
using both SELcum and peak sound pressure metrics (NMFS
2018). As dual metrics, NMFS considers onset of PTS (Level A
harassment) to have occurred when either one of the two metrics is
exceeded (i.e., metric resulting in the largest isopleth). The
SELcum metric considers both level and duration of exposure,
as well as auditory weighting functions by marine mammal hearing group.
In recognition of the fact that the requirement to calculate Level A
harassment ensonified areas could be more technically challenging to
predict due to the duration component and the use of weighting
functions in the new SELcum thresholds, NMFS developed an
optional User Spreadsheet that includes tools to help predict a simple
isopleth that can be used in conjunction with marine mammal density or
occurrence to facilitate the estimation of take numbers.
The values for SELcum and peak SPL for the Langseth
airgun array were derived from calculating the modified far-field
signature (Table 5). The farfield signature is often used as a
theoretical representation of the source level. To compute the farfield
signature, the source level is estimated at a large distance below the
array (e.g., 9 km), and this level is back projected mathematically to
a notional distance of 1 m from the array's geometrical center.
However, when the source is an array of multiple airguns separated in
space, the source level from the theoretical farfield signature is not
necessarily the best measurement of the source level that is physically
achieved at the source (Tolstoy et al. 2009). Near the source (at short
ranges, distances <1 km), the pulses of sound pressure from each
individual airgun in the source array do not stack constructively, as
they do for the theoretical farfield signature. The pulses from the
different airguns spread out in time such that the source levels
observed or modeled are the result of the summation of pulses from a
few airguns, not the full array (Tolstoy et al. 2009). At larger
distances, away from the source array center, sound pressure of all the
airguns in the array stack coherently, but not within one time sample,
resulting in smaller source levels (a few dB) than the source level
derived from the farfield signature. Because the farfield signature
does not take into account the large array effect near the source and
is calculated as a point source, the modified farfield signature is a
more appropriate measure of the sound source level for distributed
sound sources, such as airgun arrays. L-DEO used the acoustic modeling
methodology as used for Level B harassment with a small grid step of 1
m in both the inline and depth directions. The propagation modeling
takes into account all airgun interactions at short distances from the
source, including interactions between subarrays, which are modeled
using the NUCLEUS software to estimate the notional signature and
MATLAB software to calculate the pressure signal at each mesh point of
a grid.
For a more complete explanation of this modeling approach, please
see ``Appendix A: Determination of Mitigation Zones'' in the IHA
application.
Table 5--Modeled Source Levels Based on Modified Farfield Signature for the 6,600-in\3\ Airgun Array
--------------------------------------------------------------------------------------------------------------------------------------------------------
Low frequency High frequency Phocid pinnipeds Otariid pinnipeds
cetaceans Mid frequency cetaceans (underwater) (underwater)
(Lpk,flat: 219 dB; cetaceans (Lpk,flat: 202 dB; (Lpk,flat: 218 dB; (Lpk,flat: 232 dB;
LE,LF,24h: 183 (Lpk,flat: 230 dB; LE,HF,24h: 155 LE,HF,24h: 185 LE,HF,24h: 203
dB) LE,MF,24h: 185 dB dB) dB) dB)
--------------------------------------------------------------------------------------------------------------------------------------------------------
6,600 in\3\ airgun array (Peak SPLflat)............. 252.06 252.65 253.24 252.25 252.52
6,600 in\3\ airgun array (SELcum)................... 232.98 232.84 233.10 232.84 232.08
--------------------------------------------------------------------------------------------------------------------------------------------------------
In order to more realistically incorporate the Technical Guidance's
weighting functions over the seismic array's full acoustic band,
unweighted spectrum data for the Langseth's airgun array (modeled in 1
Hz bands) was used to make adjustments (dB) to the unweighted spectrum
levels, by frequency, according to the weighting functions for each
relevant marine mammal hearing group. These adjusted/weighted spectrum
levels were then converted to pressures ([mu]Pa) in order to integrate
them over the entire broadband spectrum, resulting in broadband
weighted source levels by hearing group that could be directly
incorporated within the User
[[Page 19614]]
Spreadsheet (i.e., to override the Spreadsheet's more simple weighting
factor adjustment). Using the User Spreadsheet's ``safe distance''
methodology for mobile sources (described by Sivle et al., 2014) with
the hearing group-specific weighted source levels, and inputs assuming
spherical spreading propagation and source velocities (4.2 knots) and
shot intervals (37.5 m) specific to the planned survey, potential
radial distances to auditory injury zones were then calculated for
SELcum thresholds.
Inputs to the User Spreadsheets in the form of estimated SLs are
shown in Table 5. User Spreadsheets used by L-DEO to estimate distances
to Level A harassment isopleths for the 36-airgun array for the surveys
are shown in Table A-3 in Appendix A of the IHA application. Outputs
from the User Spreadsheets in the form of estimated distances to Level
A harassment isopleths for the survey are shown in Table 6. As
described above, NMFS considers onset of PTS (Level A harassment) to
have occurred when either one of the dual metrics (SELcum
and Peak SPLflat) is exceeded (i.e., metric resulting in the
largest isopleth).
Table 6--Modeled Radial Distances (m) to Isopleths Corresponding to Level A Harassment Thresholds
--------------------------------------------------------------------------------------------------------------------------------------------------------
Level A harassment zone (m)
Source (volume) Threshold -----------------------------------------------------------------------------------------
LF cetaceans MF cetaceans HF cetaceans Phocids Otariids
--------------------------------------------------------------------------------------------------------------------------------------------------------
36-airgun array (6,600 in\3\)........ SELcum................. 426.9 0 1.3 13.9 0
Peak................... 38.9 13.6 268.3 43.7 10.6
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note that because of some of the assumptions included in the
methods used (e.g., stationary receiver with no vertical or horizontal
movement in response to the acoustic source), isopleths produced may be
overestimates to some degree, which will ultimately result in some
degree of overestimation of Level A harassment. However, these tools
offer the best way to predict appropriate isopleths when more
sophisticated modeling methods are not available, and NMFS continues to
develop ways to quantitatively refine these tools and will
qualitatively address the output where appropriate. For mobile sources,
such as the proposed seismic survey, the User Spreadsheet predicts the
closest distance at which a stationary animal would not incur PTS if
the sound source traveled by the animal in a straight line at a
constant speed.
Auditory injury is unlikely to occur for mid-frequency cetaceans,
otariid pinnipeds, and phocid pinnipeds given very small modeled zones
of injury for those species (up to 43.7 m), in context of distributed
source dynamics. The source level of the array is a theoretical
definition assuming a point source and measurement in the far-field of
the source (MacGillivray, 2006). As described by Caldwell and Dragoset
(2000), an array is not a point source, but one that spans a small
area. In the far-field, individual elements in arrays will effectively
work as one source because individual pressure peaks will have
coalesced into one relatively broad pulse. The array can then be
considered a ``point source.'' For distances within the near-field,
i.e., approximately 2-3 times the array dimensions, pressure peaks from
individual elements do not arrive simultaneously because the
observation point is not equidistant from each element. The effect is
destructive interference of the outputs of each element, so that peak
pressures in the near-field will be significantly lower than the output
of the largest individual element. Here, the 230 dB peak isopleth
distances would in all cases be expected to be within the near-field of
the array where the definition of source level breaks down. Therefore,
actual locations within this distance of the array center where the
sound level exceeds 230 dB peak SPL would not necessarily exist. In
general, Caldwell and Dragoset (2000) suggest that the near-field for
airgun arrays is considered to extend out to approximately 250 m.
In order to provide quantitative support for this theoretical
argument, we calculated expected maximum distances at which the near-
field would transition to the far-field (Table 5). For a specific array
one can estimate the distance at which the near-field transitions to
the far-field by:
[GRAPHIC] [TIFF OMITTED] TN07AP20.001
with the condition that D >> [lambda], and where D is the distance, L
is the longest dimension of the array, and [lambda] is the wavelength
of the signal (Lurton, 2002). Given that [lambda] can be defined by:
[GRAPHIC] [TIFF OMITTED] TN07AP20.002
where f is the frequency of the sound signal and v is the speed of the
sound in the medium of interest, one can rewrite the equation for D as:
[GRAPHIC] [TIFF OMITTED] TN07AP20.003
and calculate D directly given a particular frequency and known speed
of sound (here assumed to be 1,500 meters per second in water, although
this varies with environmental conditions).
To determine the closest distance to the arrays at which the source
level predictions in Table 5 are valid (i.e., maximum extent of the
near-field), we calculated D based on an assumed frequency of 1 kHz. A
frequency of 1 kHz is commonly used in near-field/far-field
calculations for airgun arrays (Zykov and Carr, 2014; MacGillivray,
2006; NSF and USGS, 2011), and based on representative airgun spectrum
data and field measurements of an airgun array used on the Langseth,
nearly all (greater than 95 percent) of the energy from airgun arrays
is below 1 kHz (Tolstoy et al., 2009). Thus, using 1 kHz as the upper
cut-off for calculating the maximum extent of the near-field should
reasonably represent the near-field extent in field conditions.
If the largest distance to the peak sound pressure level threshold
was equal to or less than the longest dimension of the array (i.e.,
under the array), or within the near-field, then received levels that
meet or exceed the threshold in most cases are not expected to occur.
This is because within the near-field and within the dimensions of the
array, the source levels specified in Table 5 are overestimated and not
applicable. In fact, until one reaches a distance of approximately
three or four times the near-field distance the average intensity of
sound at any given distance from the array is still less than that
based on calculations that assume a directional point source (Lurton,
2002). The 6,600-in\3\ airgun array used in the proposed survey has an
approximate
[[Page 19615]]
diagonal of 28.8 m, resulting in a near-field distance of 138.7 m at 1
kHz (NSF and USGS, 2011). Field measurements of this array indicate
that the source behaves like multiple discrete sources, rather than a
directional point source, beginning at approximately 400 m (deep site)
to 1 km (shallow site) from the center of the array (Tolstoy et al.,
2009), distances that are actually greater than four times the
calculated 140-m near-field distance. Within these distances, the
recorded received levels were always lower than would be predicted
based on calculations that assume a directional point source, and
increasingly so as one moves closer towards the array (Tolstoy et al.,
2009). Given this, relying on the calculated distance (138.7 m) as the
distance at which we expect to be in the near-field is a conservative
approach since even beyond this distance the acoustic modeling still
overestimates the actual received level. Within the near-field, in
order to explicitly evaluate the likelihood of exceeding any particular
acoustic threshold, one would need to consider the exact position of
the animal, its relationship to individual array elements, and how the
individual acoustic sources propagate and their acoustic fields
interact. Given that within the near-field and dimensions of the array
source levels would be below those in Table 5, we believe exceedance of
the peak pressure threshold would only be possible under highly
unlikely circumstances.
In consideration of the received sound levels in the near-field as
described above, we expect the potential for Level A harassment of mid-
frequency cetaceans, otariid pinnipeds, and phocid pinnipeds to be de
minimis, even before the likely moderating effects of aversion and/or
other compensatory behaviors (e.g., Nachtigall et al., 2018) are
considered. We do not believe that Level A harassment is a likely
outcome for any mid-frequency cetacean, otariid pinniped, or phocid
pinniped and do not propose to authorize any Level A harassment for
these species.
Marine Mammal Occurrence
In this section we provide the information about the presence,
density, and group dynamics of marine mammals that will inform the take
calculations.
Extensive systematic aircraft- and ship-based surveys have been
conducted for marine mammals in offshore waters of Oregon and
Washington (e.g., Bonnell et al., 1992; Green et al., 1992, 1993;
Barlow 1997, 2003; Barlow and Taylor 2001; Calambokidis and Barlow
2004; Barlow and Forney 2007; Forney 2007; Barlow 2010). Ship surveys
for cetaceans in slope and offshore waters of Oregon and Washington
were conducted by NMFS' Southwest Fisheries Science Center (SWFSC) in
1991, 1993, 1996, 2001, 2005, 2008, and 2014 and synthesized by Barlow
(2016); these surveys were conducted from the coastline up to ~556 km
from shore from June or August to November or December. These data were
used by the SWFSC to develop spatial models of cetacean densities for
the California Current Ecosystem (CCE). Systematic, offshore, at-sea
survey data for pinnipeds are more limited (e.g., Bonnell et al., 1992;
Adams et al., 2014); In British Columbia, several systematic surveys
have been conducted in coastal waters (e.g., Williams and Thomas 2007;
Ford et al., 2010a; Best et al., 2015; Harvey et al., 2017). Surveys in
coastal as well as offshore waters were conducted by DFO during 2002 to
2008; however, little effort occurred off the west coast of Vancouver
Island during late spring/summer (Ford et al., 2010). Density estimates
for the proposed survey areas outside the U.S. EEZ, i.e., in the
Canadian EEZ, were not readily available, so density estimates for U.S.
waters were applied to the entire survey area.
The U.S. Navy primarily used SWFSC habitat-based cetacean density
models to develop a marine species density database (MSDD) for the
Northwest Training and Testing (NWTT) Study Area for NWTT Phase III
activities (U.S. Navy 2019a), which encompasses the U.S. portion of the
proposed survey area. For several cetacean species, the Navy updated
densities estimated by line-transect surveys or mark-recapture studies
(e.g., Barlow 2016). These methods usually produce a single value for
density that is an averaged estimate across very large geographical
areas, such as waters within the U.S. EEZ off California, Oregon, and
Washington (referred to as a ``uniform'' density estimate). This is the
general approach applied in estimating cetacean abundance in the NMFS
stock assessment reports. The disadvantage of these methods is that
they do not provide spatially- or temporally-explicit density
information. More recently, a newer method called spatial habitat
modeling has been used to estimate cetacean densities that address some
of these shortcomings (e.g., Barlow et al., 2009; Becker et al., 2010;
2012a; 2014; Becker et al., 2016; Ferguson et al., 2006; Forney et al.,
2012; 2015; Redfern et al., 2006). (Note that spatial habitat models
are also referred to as ``species distribution models'' or ``habitat-
based density models.'') These models estimate density as a continuous
function of habitat variables (e.g., sea surface temperature, seafloor
depth) and thus, within the study area that was modeled, densities can
be predicted at all locations where these habitat variables can be
measured or estimated. Spatial habitat models therefore allow estimates
of cetacean densities on finer scales (spatially and temporally) than
traditional line-transect or mark-recapture analyses.
The methods used to estimate pinniped at-sea densities are
typically different than those used for cetaceans, because pinnipeds
are not limited to the water and spend a significant amount of time on
land (e.g., at rookeries). Pinniped abundance is generally estimated
via shore counts of animals on land at known haulout sites or by
counting number of pups weaned at rookeries and applying a correction
factor to estimate the abundance of the population (for example Harvey
et al., 1990; Jeffries et al., 2003; Lowry, 2002; Sepulveda et al.,
2009). Estimating in[hyphen]water densities from land-based counts is
difficult given the variability in foraging ranges, migration, and
haulout behavior between species and within each species, and is driven
by factors such as age class, sex class, breeding cycles, and seasonal
variation. Data such as age class, sex class, and seasonal variation
are often used in conjunction with abundance estimates from known
haulout sites to assign an in-water abundance estimate for a given
area. The total abundance divided by the area of the region provides a
representative in-water density estimate for each species in a
different location. In addition to using shore counts to estimate
pinniped density, traditional line-transect derived estimates are also
used, particularly in open ocean areas.
The Navy's MSDD is currently the most comprehensive compendium for
density data available for the CCE. However, data products are
currently not publically available for the database; thus, in this
analysis the Navy's data products were used only for species for which
density data were not available from an alternative spatially-explicit
model (e.g., pinnipeds, Kogia spp., minke whales, sei whales, gray
whales, short-finned pilot whales, and Northern Resident, transient,
and offshore killer whales). For these species, GIS was used to
determine the areas expected to be ensonified in each density category
(i.e., distance from shore). For pinnipeds, the densities from the
Navy's MSDD were corrected by projecting the most recent population
growth and updated population estimates to 2020, when
[[Page 19616]]
available. Where available, the appropriate seasonal density estimate
from the MSDD was used in the estimation here (i.e., summer).
NMFS obtained data products from the Navy for densities of Southern
Resident killer whales in the NWTT Offshore Study Area. The modeled
density estimates were available on the scale of 1 km by 1 km grid
cells. The densities from grid cells overlapping the ensonified area in
each depth category were multiplied by the corresponding area to
estimate potential exposures (Table 9).
For most other species, (i.e., humpback, blue, fin, sperm, Baird's
beaked, and other small beaked whales; bottlenose, striped, common,
Pacific white-sided, Risso's and northern right whale dolphins; and
Dall's porpoise), habitat-based density models from Becker et al.
(2016) were used. Becker et al. (2016) used seven years of SWFSC
cetacean line-transect survey data collected between 1991 and 2009 to
develop predictive habitat-based models of cetacean densities in the
CCE. The modeled density estimates were available on the scale of 7 km
by 10 km grid cells. The densities from all grid cells overlapping the
ensonified areas within each water depth category were averaged to
calculate a zone-specific density for each species.
Becker et al. (2016) did not develop a density model for the harbor
porpoise, so densities from Forney et al. (2014) were used for that
species. Forney et al. (2014) presented estimates of harbor porpoise
abundance and density along the Pacific coast of California, Oregon,
and Washington based on aerial line-transect surveys conducted between
2007 and 2012. Separate density estimates were provided for harbor
porpoises in Oregon south of 45[deg] N and Oregon/Washington north of
45[deg] N (i.e., within the boundaries of the Northern California/
Southern Oregon and Northern Oregon/Washington Coast stocks), so stock-
specific take estimates were generated (Forney et al., 2014).
Background information on the density calculations for each
species/guild (if different from the general methods from the Navy's
MSDD, Becker et al. (2016), or Forney et al. (2014) described above)
are reported here. Density estimates for each species/guild (aside from
Southern Resident killer whales, which are discussed separately) are
found in Table 7.
Gray Whale
DeAngelis et al. (2011) developed a migration model that provides
monthly, spatially explicit predictions of gray whale abundance along
the U.S. West Coast from December through June. These monthly density
estimates apply to a ``main migration corridor'' that extends from the
coast to 10 km offshore. A zone from the main migration corridor out to
47 km offshore is designated as an area of ``potential presence''. To
derive a density estimate for this area the Navy assumed that 1 percent
of the population could be within the 47-km ``potential presence'' area
during migration. Given the 2014 stock assessment population estimate
of 20,990 animals (Carretta et al., 2017b), approximately 210 gray
whales may use this corridor. Assuming the migration wave lasts 30
days, then 7 whales on average on any one day could occur in the
``potential presence'' area. The area from the main migration route
offshore to 47 km within the NWTT study area = 45,722.06 km\2\, so
density within this zone = 0.00015 whales/km\2\. From July-November,
gray whale occurrence off the coast is expected to consist primarily of
whales belonging to the PCFG. Calambokidis et al. (2012) provided an
updated analysis of the abundance of the PCFG whales in the Pacific
Northwest and recognized that this group forms a distinct feeding
aggregation. For the purposes of establishing density, the Navy assumed
that from July 1 to November 30 all the 209 PCFG whales could be
present off the coast in the Northern California/Oregon/Washington
region (this accounts for the potential that some PCFG whales may be
outside of the area but that there also may be some non-PCFG whales in
the region as noted by Calambokidis et al.(2012)). Given that the PCFG
whales are found largely nearshore, it was assumed that all the whales
could be within 10 km of the coast. To capture the potential presence
of whales further offshore (e.g., Oleson et al., 2009), it was assumed
that a percentage of the whales could be present from 10 km out to 47
km off the coast; the 47 km outer limit is consistent with the
DeAngelis et al. (2011) migration model. Since 77 percent of the PCFG
sightings were within the nearshore BIAs (Calambokidis et al., 2015),
it was assumed that 23 percent (48 whales) could potentially be found
further offshore. Two strata were thus developed for the July-November
gray whale density layers: (1) From the coast to 10 km offshore, and
(2) from 10 km to 47 km offshore. The density was assumed to be 0
animals/km\2\ for areas offshore of 47 km.
Small Beaked Whale Guild
NMFS has developed habitat-based density models for a small beaked
whale guild in the CCE (Becker et al., 2012b; Forney et al., 2012). The
small beaked whale guild includes Cuvier's beaked whale and beaked
whales of the genus Mesoplodon, including Blainville's beaked whale,
Hubbs' beaked whale, and Stejneger's beaked whale. NMFS SWFSC developed
a CCE habitat-based density model for the small beaked whale guild
which provides spatially explicit density estimates off the U.S. West
Coast for summer and fall based on survey data collected between 1991
and 2009 (Becker et al., 2016).
False Killer Whale
False killer whales were not included in the Navy's MSDD, as they
are very rarely encountered in the northeast Pacific. Density estimates
for false killer whales were also not presented in Barlow (2016) or
Becker et al. (2016), as no sightings occurred during surveys conducted
between 1986 and 2008 (Ferguson and Barlow 2001, 2003; Forney 2007;
Barlow 2003, 2010). One sighting was made off of southern California
during 2014 (Barlow 2016). One pod of false killer whales occurred in
Puget Sound for several months during the 1990s (Navy 2015). Based on
the available information, NMFS does not believe false killer whales
are expected to be taken, but L-DEO has requested take of this species
so we are proposing to authorize take.
Killer Whale
A combination of movement data (from both visual observations and
satellite-linked tags) and detections from stationary acoustic
recorders have provided information on the offshore distribution of the
Southern Resident stock (Hanson et al., 2018). These data have been
used to develop state space movement models that provide estimates of
the probability of occurrence (or relative density) of Southern
Residents in the offshore study area in winter and spring (Hanson et
al., 2018). Since the total number of animals that comprise each pod is
known, the relative density estimates were used in association with the
total abundance estimates to derive absolute density estimates (i.e.,
number of animals/km\2\) within the offshore study area. Given that the
K and L pods were together during all but one of the satellite tag
deployments, Hanson et al. (2018) developed two separate state space
models, one for the combined K and L pods and one for the J pod. The
absolute density estimates were thus derived based on a total of 53
animals for the K and L pods (K pod = 18 animals, L pod = 35 animals)
and 22 animals for the J pod (Center for Whale Research, 2019). Of the
three pods, the
[[Page 19617]]
K and L pods appear to have a more extensive and seasonally variable
offshore coastal distribution, with rare sightings as far south as
Monterey Bay, California (Carretta et al., 2019; Ford et al., 2000;
Hanson et al., 2018). Two seasonal density maps were thus developed for
the K and L pods, one representing their distribution from January to
May (the duration of the tag deployments), and another representing
their distribution from June to December. Based on stationary acoustic
recording data, their excursions offshore from June to December are
more limited and typically do not extend south of the Columbia River
(Emmons 2019). To provide more conservative density estimates, the Navy
extended the June to December distribution to just south of the
Columbia River and redistributed the total K and L populations (53
animals) within the more limited range boundaries. A conservative
approach was also adopted for the J pod since the January to May
density estimates were assumed to represent annual occurrence patterns,
despite information that this pod typically spends more time in the
inland waters during the summer and fall (Carretta et al., 2019; Ford
et al., 2000; Hanson et al., 2018). Further, for all seasons the Navy
assumed that all members of the three pods of Southern Residents could
occur either offshore or in the inland waters, so the total number of
animals in the stock was used to derive density estimates for both
study areas.
Due to the difficulties associated with reliably distinguishing the
different stocks of killer whales from at sea sightings, and
anticipated equal likelihood of occurrence among the stocks, density
estimates for the rest of the stocks are presented as a whole (i.e.,
includes the Offshore, West Coast Transient, and Northern Resident
stocks). Barlow (2016) presents density values for killer whales in the
CCE, with separate densities for waters off Oregon/Washington (i.e.,
north of the California border) and Northern California for summer/
fall. Density data are not available for the NWTT Offshore area
northwest of the CCE study area, so data from the SWFSC Oregon/
Washington area were used as representative estimates. These values
were used to represent density year-round.
Short-Finned Pilot Whale
Along the U.S. West Coast, short-finned pilot whales were once
common south of Point Conception, California (Carretta et al., 2017b;
Reilly & Shane, 1986), but now sightings off the U.S. West Coast are
infrequent and typically occur during warm water years (Carretta et
al., 2017b). Stranding records for this species from Oregon and
Washington waters are considered to be beyond the normal range of this
species rather than an extension of its range (Norman et al., 2004).
Density values for short-finned pilot whales are available for the
SWFSC Oregon/Washington and Northern California strata for summer/fall
(Barlow, 2016). Density data are not available for the NWTT Offshore
area northwest of the SWFSC strata, so data from the SWFSC Oregon/
Washington stratum were used as representative estimates. These values
were used to represent density year-round.
Guadalupe Fur Seal
Adult male Guadalupe fur seals are expected to be ashore at
breeding areas over the summer, and are not expected to be present
during the planned geophysical survey (Caretta et al., 2017b; Norris
2017b). Additionally, breeding females are unlikely to be present
within the Offshore Study Area as they remain ashore to nurse their
pups through the fall and winter, making only short foraging trips from
rookeries (Gallo-Reynoso et al., 2008; Norris 2017b; Yochem et al.,
1987). To estimate the total abundance of Guadalupe fur seals, the Navy
adjusted the population reported in the 2016 SAR (Caretta et al.,
2017b) of 20,000 seals by applying the average annual growth rate of
7.64 percent over the seven years between 2010 and 2017. The resulting
2017 projected abundance was 33,485 fur seals. Using the reported
composition of the breeding population of Guadalupe fur seals (Gallo-
Reynoso 1994) and satellite telemetry data (Norris 2017b), the Navy
established seasonal and demographic abundances of Guadalupe fur seals
expected to occur within the Offshore Study Area.
The distribution of Guadalupe fur seals in the Offshore Study Area
was stratified by distance from shore (or water depth) to reflect their
preferred pelagic habitat (Norris, 2017a). Ten percent of fur seals in
the Study Area are expected to use waters over the continental shelf
(approximated as waters with depths between 10 and 200 m). A depth of
10 m is used as the shoreward extent of the shelf (rather than
extending to shore), because Guadalupe fur seals in the Offshore Study
Area are not expected to haul out and would not be likely to come close
to shore. All fur seals (i.e., 100 percent) would use waters off the
shelf (beyond the 200-m isobath) out to 300 km from shore, and 25 of
percent of fur seals would be expected to use waters between 300 and
700 km from shore (including the planned geophysical survey area). The
second stratum (200 m to 300 km from shore) is the preferred habitat
where Guadalupe fur seals are most likely to occur most of the time.
Individuals may spend a portion of their time over the continental
shelf or farther than 300 km from shore, necessitating a density
estimate for those areas, but all Guadalupe fur seals would be expected
to be in the central stratum most of the time, which is the reason 100
percent is used in the density estimate for the central stratum
(Norris, 2017a). Spatial areas for the three strata were estimated in a
GIS and used to calculate the densities.
The Navy's density estimate for Guadalupe fur seals projected the
abundance through 2017, while L-DEO's survey will occur in 2020.
Therefore, we have projected the abundance estimate in 2020 using the
abundance estimate (34,187 animals) and population growth rate (5.9
percent) presented in the 2019 draft SARs (Caretta et al., 2019). This
calculation yielded an increased density estimate of Guadalupe fur
seals than what was presented in the Navy's MSDD.
Northern Fur Seal
The Navy estimated the abundance of northern fur seals from the
Eastern Pacific stock and the California breeding stock that could
occur in the NWTT Offshore Study Area by determining the percentage of
time tagged animals spent within the Study Area and applying that
percentage to the population to calculate an abundance for adult
females, juveniles, and pups independently on a monthly basis. Adult
males are not expected to occur within the Offshore Study Area and the
planned survey area during the planned geophysical survey as they spend
the summer ashore at breeding areas in the Bering Sea and San Miguel
Island (Caretta et al., 2017b). Using the monthly abundances of fur
seals within the Offshore Study Area, the Navy created strata to
estimate the density of fur seals within three strata: 22 km to 70 km
from shore, 70 km to 130 km from shore, and 130 km to 463 km from shore
(the western Study Area boundary). L-DEO's planned survey is 423 km
from shore at the closest point. Based on satellite tag data and
historic sealing records (Olesiuk 2012; Kajimura 1984), the Navy
assumed 25 percent of the population present within the overall
Offshore Study Area may be within the 130 km to 463 km stratum.
The Navy's density estimates for northern fur seals did not include
the latest abundance data collected from Bogoslof Island or the
Pribilof Islands in 2015 and 2016. Incorporating the latest
[[Page 19618]]
pup counts yielded a slight decrease in the population abundance
estimate, which resulted in a slight decrease in the estimated
densities of northern fur seals in each depth stratum.
Steller Sea Lion
The Eastern stock of Steller sea lions has established rookeries
and breeding sites along the coasts of California, Oregon, British
Columbia, and southeast Alaska. A new rookery was recently discovered
along the coast of Washington at the Carroll Island and Sea Lion Rock
complete, where more than 100 pups were born in 2015 (Muto et al.,
2017; Wiles 2015). The 2017 SAR did not factor in pups born at sites
along the Washington coast (Muto et al., 2017). Considering that pups
have been observed at multiple breeding sites since 2013, specifically
at the Carroll Island and Sea Lion Rock complex (Wiles 2015), the 2017
SAR abundance of 1,407 Steller sea lions (non-pups only) for Washington
underestimates the total population. Wiles (2015) estimates that up to
2,500 Steller sea lions are present along the Washington coast, which
is the abundance estimate used by the Navy to calculate densities.
Approximately 30,000 Steller sea lions occur along the coast of British
Columbia, but these animals were not included in the Navy's
calculations. The Navy applied the annual growth rate for each regional
population (California, Oregon, Washington, and southeast Alaska),
reported in Muto et al. (2017), to each population to estimate the
stock abundance in 2017, and we further projected the population
estimate in 2020.
Sea lions from northern California and southern Oregon rookeries
migrate north in September following the breeding season and winter in
northern Oregon, Washington, and British Columbia waters. They disperse
widely following the breeding season, which extends from May through
July, likely in search of different types of prey, which may be
concentrated in areas where oceanic fronts and eddies persist (Fritz et
al., 2016; Jemison et al., 2013; Lander et al., 2010; Muto et al.,
2017; NMFS 2013; Raum-Suryan et al., 2004; Sigler et al., 2017). Adults
depart rookeries in August. Females with pups remain within 500 km of
their rookery during the non-breeding season and juveniles of both
sexes and adult males disperse more widely but remain primarily over
the continental shelf (Wiles 2015).
Based on 11 sightings along the Washington coast, Steller sea lions
were observed at an average distance of 13 km from shore and 35 km from
the shelf break (defined as the 200-m isobath) (Oleson et al., 2009).
The mean water depth in the area of occurrence was 42 m, and surveys
were conducted out to approximately 60 km from shore. Wiles (2015)
estimated that Steller sea lions off the Washington coast primarily
occurred within 60 km of shore, favoring habitats over the continental
shelf. However, a few individuals may travel several hundred km
offshore (Merrick & Loughlin 1997; Wiles 2015). Based on these
occurrence and distribution data, two strata were used to estimate
densities for Steller sea lions. The spatial area extending from shore
to the 200-m isobath (i.e., over the continental shelf) was defined as
one stratum, and the second stratum extended from the 200-m isobath to
300 km from shore to account for reports of Steller sea lions occurring
several hundred km offshore. Ninety-five percent of the population of
Steller sea lions occurring in the NWTT Study Area were distributed
over the continental shelf stratum and the remaining five percent were
assumed to occur between the 200-m isobath and 300 km from shore.
The percentage of time Steller sea lions spend hauled out varies by
season, life stage, and geographic location. To calculated densities in
the Study Area, the projected population abundance was adjusted to
account for time spent hauled out. In spring and winter, sea lions were
estimated to be in the water 64 percent of the time. In summer, when
sea lions are more likely to be in the water, the percent of animals
estimated to be in the water was increased to 76 percent, and in fall,
sea lions were anticipated to be in the water 53 percent of the time
(U.S. Navy 2019). Densities were calculated for each depth stratum off
Washington and off Oregon.
California Sea Lion
Seasonal at-sea abundance of California sea lions is estimated from
strip transect survey data collected offshore along the California
coastline (Lowry & Forney 2005). The survey area was divided into seven
strata, labeled A through G. Abundance estimates from the two
northernmost strata (A and B) were used to estimate the abundance of
California sea lions occurring in the NWTT Study Area. While the
northernmost stratum (A) only partially overlaps with the Study Area,
this approach conservatively assumes that all sea lions from the two
strata would continue north into the Study Area.
The majority of male sea lions would be expected in the NWTT Study
Area from August to mid-June (Wright et al., 2010). In summer, males
are expected to be at breeding sites off of Southern California. In-
water abundance estimates of adult and sub-adult males in strata A and
B were extrapolated to estimate seasonal densities in the Study Area.
Approximately 3,000 male California sea lions are known to pass through
the NWTT Study Area in August as they migrate northward to the
Washington coast and inland waters (DeLong 2018a; Wright et al., 2010).
Nearly all male sea lions are expected to be on or near breeding sites
off California in July (DeLong et al., 2017; Wright et al., 2010). An
estimate of 3,000 male sea lions is used for the month of August.
Projected 2017 seasonal abundance estimates were derived by applying an
annual growth rate of 5.4 percent (Caretta et al., 2017b) between 1999
and 2017 to the abundance estimates from Lowry & Forney (2005).
The strata used to calculated densities in the NWTT Study Area were
based on distribution data from Wright et al. (2010) and Lowry & Forney
(2005) indicating that approximately 90 percent of California sea lions
occurred within 40 km of shore and 100 percent of sea lions were within
70 km of shore. A third stratum was added that extends from shore to
450 km offshore to account for anomalous conditions, such as changes in
sea surface temperature and upwelling associated with El Ni[ntilde]o,
during which California sea lions have been encountered farther from
shore, presumably seeking prey (DeLong & Jeffries 2017; Weise et al.,
2010). The Navy calculated densities for each stratum (0 to 40 km, 40
to 70 km, and 0 to 450 km) for each season, spring, summer, fall, and
winter, but noted that the density of California sea lions in all
strata for June and July was 0 animals/km\2\. The Navy's calculated
densities for August were conservatively used here, as sightings of
California sea lions have been reported on the continental shelf in
June and July (Adams et al., 2014).
Northern Elephant Seal
The most recent surveys supporting the abundance estimate for
northern elephant seals were conducted in 2010 (Caretta et al., 2017b).
By applying the average growth rate of 3.8 percent per year for the
California breeding stock over the seven years from 2010 to 2017, the
Navy calculated a projected 2017 abundance estimate of 232,399 elephant
seals (Caretta et al., 2017b; Lowry et al., 2014). Male and female
distributions at sea differ both seasonally and spatially. Pup counts
reported by Lowry et al., (2014) and life tables compiled by Condit et
al., (2014) were used to determine the proportion of males and females
in the population, which was
[[Page 19619]]
estimated to be 56 percent female and 44 percent male. Females are
assumed to be at sea 100 percent of the time within their seasonal
distribution area in fall and summer (Robinson et al., 2012). Males are
at sea approximately 90 percent of the time in fall and spring, remain
ashore through the entire winter, and spend one month ashore to molt in
the summer (i.e., are at sea 66 percent of the summer). Monthly
distribution maps produced by Robinson et al. (2012) showing the extent
of foraging areas used by satellite tagged female elephant seals were
used to estimate the spatial areas to calculate densities. Although the
distributions were based on tagged female seals, Le Boeuf et al. (2000)
and Simmons et al. (2007) reported similar tracks by males over broad
spatial scales. The spatial areas representing each monthly
distribution were calculating using GIS and then averaged to produce
seasonally variable areas and resulting densities.
As with other pinniped species above, NMFS used the population
growth rate reported by Caretta et al. (2017b) to project the estimated
abundance in 2020. The resulting population estimate and estimated
densities increased from those presented in the Navy's MSDD (U.S. Navy
2019).
Harbor Seal
Only harbor seals from the Washington and Oregon Coast stock would
be expected to occur in the proposed survey area. The most recent
abundance estimate for the Washington and Oregon Coast stock is 24,732
harbor seals (Caretta et al., 2017b). Survey data supporting this
abundance estimate are from 1999, which exceeds the eight-year limit
beyond which NMFS will not confirm abundance in a SAR (Caretta et al.,
2017b). However, based on logistical growth curves for the Washington
and Oregon Coast stock that leveled off in the early 1990s (Caretta et
al., 2017b) and unpublished data from the Washington Department of Fish
and Wildlife (DeLong & Jeffries 2017), an annual growth rate of 0
percent (i.e., the population has remained stable) was applied such
that the 2017 abundance estimate used by the Navy, and 2020 estimate
used here, was still 24,732 harbor seals. A haulout factor of 33
percent was used to account for hauled-out seals (i.e., seals are
estimated to be in the water 33 percent of the time) (Huber et al.,
2001). A single stratum extending from shore to 30 km offshore was used
to define the spatial area used by the Navy for calculating densities
off Washington and Oregon (Bailey et al., 2014; Oleson et al., 2009).
Marine Mammal Densities
Densities for most species are presented by depth stratum (shallow,
intermediate, and deep water) in Table 7. For species where densities
are available based on other categories (gray whale, harbor porpoise,
northern fur seal, Guadalupe fur seal, California sea lion, Steller sea
lion), category definitions are provided in the footnotes of Table 7.
Table 7--Marine Mammal Density Values in the Survey Area
----------------------------------------------------------------------------------------------------------------
Estimated density (#/km\2\)
------------------------------------------------
Species Intermediate Reference
Shallow <100 m/ 100-1000 m/ Deep >1000 m/
category 1 category 2 category 3
----------------------------------------------------------------------------------------------------------------
LF Cetaceans:
Humpback whale.................... 0.0052405 0.0040200 0.0004830 Becker et al. (2016).
Blue whale........................ 0.0020235 0.0010518 0.0003576 Becker et al. (2016).
Fin whale......................... 0.0002016 0.0009306 0.0013810 Becker et al. (2016).
Sei whale......................... 0.0004000 0.0004000 0.0004000 U.S. Navy (2019).
Minke whale....................... 0.0013000 0.0013000 0.0013000 U.S. Navy (2019).
Gray whale \a\.................... 0.0155000 0.0010000 N.A. U.S. Navy (2019).
MF Cetaceans:
Sperm whale....................... 0.0000586 0.0001560 0.0013023 Becker et al. (2016).
Baird's beaked whale.............. 0.0001142 0.0002998 0.0014680 Becker et al. (2016).
Small beaked whale................ 0.0007878 0.0013562 0.0039516 Becker et al. (2016).
Bottlenose dolphin................ 0.0000007 0.0000011 0.0000108 Becker et al. (2016).
Striped dolphin................... 0.0000000 0.0000025 0.0001332 Becker et al. (2016).
Short-beaked common dolphin....... 0.0005075 0.0010287 0.0016437 Becker et al. (2016).
Pacific white-sided dolphin....... 0.0515230 0.0948355 0.0700595 Becker et al. (2016).
Northern right-whale dolphin...... 0.0101779 0.0435350 0.0621242 Becker et al. (2016).
Risso's dolphin................... 0.0306137 0.0308426 0.0158850 Becker et al. (2016).
False killer whale \b\............ N.A. N.A. N.A. ........................
Killer whale (all stocks except 0.0009200 0.0009200 0.0009200 U.S. Navy (2019).
Southern Residents).
Short-finned pilot whale.......... 0.0002500 0.0002500 0.0002500 U.S. Navy (2019).
HF Cetaceans:
Pygmy/dwarf sperm whale........... 0.0016300 0.0016300 0.0016300 U.S. Navy (2019).
Dall's porpoise................... 0.1450767 0.1610605 0.1131827 Becker et al. (2016).
Harbor porpoise \c\............... 0.6240000 0.4670000 N.A. Forney et al. (2014).
Otariids:
Northern fur seal \d\............. 0.0113247 0.1346441 0.0103424 U.S. Navy (2019).
Guadalupe fur seal \e\............ 0.0234772 0.0262595 N.A. U.S. Navy (2019).
California sea lion \f\........... 0.0288000 0.0037000 0.0065000 U.S. Navy (2019).
Steller sea lion \g\.............. 0.3088864 0.0022224 N.A. U.S. Navy (2019).
Phocids:
Northern elephant seal............ 0.0345997 0.0345997 0.0345997 U.S. Navy (2019).
Harbor seal \h\................... 0.3424000 N.A. N.A. U.S. Navy (2019).
----------------------------------------------------------------------------------------------------------------
\a\ Category 1 = 0-10 km offshore, Category 2 = 10-47 km offshore (U.S. Navy 2019).
\b\ No density estimates available for false killer whales in the survey area, take is based on mean group size
from Mobley et al. (2000).
\c\ Category 1 = South of 45[deg] N, Category 2 = North of 45[deg] N (Forney et al., 2014).
\d\ Category 1 = 22-70 km offshore, Category 2 = 70-130 km offshore, Category 3 = 130-463 km offshore (U.S. Navy
2019).
[[Page 19620]]
\e\ Category 1 = 10-200 m depth, Category 2 = 200 m depth-300 km offshore; No stock-specific densities are
available so these densities were applied to northern fur seals as a species (U.S. Navy 2019).
\f\ Category 1 = 0-40 km offshore, Category 2 = 40-70 km offshore, Category 3 = 0-450 km offshore (U.S. Navy
2019).
\g\ Category 1 = shore-200 m depth, Category 2 = 200 m depth-300 m offshore (U.S. Navy 2019).
\h\ Category 1 = 0-30 km offshore (U.S. Navy 2019).
Take Calculation and Estimation
Here we describe how the information provided above is brought
together to produce a quantitative take estimate. In order to estimate
the number of marine mammals predicted to be exposed to sound levels
that would result in Level A or Level B harassment, radial distances
from the airgun array to predicted isopleths corresponding to the Level
A harassment and Level B harassment thresholds are calculated, as
described above. Those radial distances are then used to calculate the
area(s) around the airgun array predicted to be ensonified to sound
levels that exceed the Level A and Level B harassment thresholds. The
distance for the 160-dB threshold (based on L-DEO model results) was
used to draw a buffer around every transect line in GIS to determine
the total ensonified area in each depth category (Table 8). The areas
presented in Table 8 do not include areas ensonified within Canadian
territorial waters (from 0-12 nmi (22.2 km) from shore). As discussed
above, NMFS cannot authorize the incidental take of marine mammals in
the territorial seas of foreign nations, as the MMPA does not apply in
those waters. However, NMFS has still calculated the level of
incidental take in the entire activity area (including Canadian
territorial waters) as part of the analysis supporting our preliminary
determination under the MMPA that the activity will have a negligible
impact on the affected species. The total estimated take in U.S. and
Canadian waters is presented in Table 11.
In past applications, to account for unanticipated delays in
operations, L-DEO has added 25 percent in the form of operational days,
which is equivalent to adding 25 percent to the proposed line km to be
surveyed. In this application, however, due to the strict operational
timelines and availability of the R/V Langseth, no additional time or
distance has been added to the survey calculations. 37 days is the
absolute maximum amount of time the R/V Langseth is available to
conduct seismic operations.
The ensonified areas in Table 8 were used to estimate take of
marine mammal species with densities available for the three depth
strata (shallow, intermediate, and deep waters). For other species
where densities are available based on other categories (i.e., gray
whale, harbor porpoise, northern fur seal, Guadalupe fur seal,
California sea lion, Steller sea lion; see Table 7), GIS was used to
determine the areas expected to be ensonified in each density category
(see Table B-2 in L-DEO's application for the ensonified areas in each
category).
Table 8--Areas (km\2\) Estimated to be Ensonified to Level A and Level B Harassment Thresholds
----------------------------------------------------------------------------------------------------------------
Total
Survey zone Criteria Relevant ensonified
isopleth (m) area (km\2\)
----------------------------------------------------------------------------------------------------------------
Level B Harassment:
Shallow <100 m............................ 160 dB.......................... \a\ 12,650 11,433.80
Intermediate 100-1000 m................... 160 dB.......................... \b\ 9,468 24,200.75
Deep >1000 m.............................. 160 dB.......................... \b\ 6,733 50,924.56
-----------------------------------------------------------------
Overall 86,559.11
Level A Harassment
All depth zones........................... LF Cetacean..................... 426.9 5,605.34
MF Cetacean..................... 13.6 179.85
HF Cetacean..................... 268.3 3,532.92
Otariid......................... 10.6 140.19
Phocid.......................... 43.7 577.63
----------------------------------------------------------------------------------------------------------------
\a\ Based on L-DEO model results.
\b\ Based on data from Crone et al. (2014).
Density estimates for Southern Resident killer whales from the U.S.
Navy's MSDD were overlaid with GIS layers of the Level B harassment
zones in each depth category to determine the areas expected to be
ensonified in each density category (Table 9).
Table 9--Southern Resident Killer Whale Densities and Corresponding
Ensonified Areas
------------------------------------------------------------------------
Density (animals/ Ensonified
Pod km\2\) area (km\2\)
------------------------------------------------------------------------
K/L............................... 0.000000 5,883
0.000001--0.002803 17,875
0.002804--0.005615 2,817
0.005616--0.009366 1,200
0.009367--0.015185 320
J................................. 0.000000 7,260
0.000001--0.001991 8,648
0.001992--0.005010 1,128
[[Page 19621]]
0.005011--0.009602 236
0.009603--0.018822 20
------------------------------------------------------------------------
The marine mammals predicted to occur within these respective
areas, based on estimated densities or other occurrence records, are
assumed to be incidentally taken. For species where NMFS expects take
by Level A harassment to potentially occur, the calculated Level A
harassment takes have been subtracted from the total within the Level B
harassment zone. Estimated exposures for the proposed survey outside of
Canadian territorial waters are shown in Table 10.
Table 10--Estimated Taking by Level A and Level B Harassment, and Percentage of Population
--------------------------------------------------------------------------------------------------------------------------------------------------------
Estimated take
Species MMPA stock \a\ Stock -------------------------------- Total Percent of
abundance Level B Level A proposed take MMPA stock
--------------------------------------------------------------------------------------------------------------------------------------------------------
LF Cetaceans:
Humpback whale........................ Central North Pacific....... 10,103 172 10 \b\ 182 1.80
California/Oregon/Washington 2,900 6.28
Blue whale............................ Eastern North Pacific....... 1,647 63 4 67 4.06
Fin whale............................. California/Oregon/Washington 9,029 89 6 95 1.06
Northeast Pacific........... 3,168 3.01
Sei whale............................. Eastern North Pacific....... 27,197 32 2 34 0.13
Minke whale........................... California/Oregon/Washington 25,000 105 7 112 0.45
Gray whale............................ Eastern North Pacific....... 26,960 90 2 92 0.34
MF Cetaceans:
Sperm whale........................... California/Oregon/Washington 26,300 71 0 71 0.27
Baird's beaked whale.................. California/Oregon/Washington 2,697 83 0 83 3.08
Small beaked whale.................... California/Oregon/Washington 6,318 244 0 \c\ 244 3.86
Bottlenose dolphin.................... California/Oregon/Washington 1,924 1 0 \d\ 13 0.68
(offshore).
Striped dolphin....................... California/Oregon/Washington 29,211 7 0 \d\ 46 0.16
Short-beaked common dolphin........... California/Oregon/Washington 969,861 114 0 \d\ 179 0.02
Pacific white-sided dolphin........... California/Oregon/Washington 26,814 6,452 0 6,452 24.06
Northern right-whale dolphin.......... California/Oregon/Washington 26,556 4,333 0 4,333 16.32
Risso's dolphin....................... California/Oregon/Washington 6,336 1,906 0 1,906 30.08
False killer whale.................... N.A......................... N.A. N.A. N.A. \e\ 5 N.A.
Killer whale.......................... Southern Resident........... 75 43 0 43 \g\ 57.33
Northern Resident........... 302 27 0 \f\ 27 8.94
West Coast Transient........ 243 26 \f\ 26 10.70
Offshore.................... 300 26 \f\ 26 8.67
Short-finned pilot whale.............. California/Oregon/Washington 836 24 0 \d\ 29 3.47
HF Cetaceans:
Pygmy/dwarf sperm whale............... California/Oregon/Washington 4,111 135 6 141 3.42
Dall's porpoise....................... California/Oregon/Washington 27,750 10,869 452 11,321 \g\ 40.80
Harbor porpoise....................... Northern Oregon/Washington 21,487 12,557 449 13,006 \g\ 60.53
Coast.
Northern California/Southern 35,769 \g\ 36.36
Oregon.
Otariid Seals:
Northern fur seal..................... Eastern Pacific............. 620,660 4,604 0 4,604 0.74
California.................. 14,050 32.77
Guadalupe fur seal.................... Mexico to California........ 34,187 2,387 0 2,387 6.98
California sea lion................... U.S......................... 257,606 1140 0 1,140 0.44
Steller sea lion...................... Eastern U.S................. 43,201 7281 0 7,281 16.85
[[Page 19622]]
Phocid Seals:
Northern elephant seal................ California Breeding......... 179,000 1995 0 1,995 1.11
Harbor seal........................... Oregon/Washington Coast..... \h\ 24,732 6537 0 6,537 26.43
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ In most cases, where multiple stocks are being affected, for the purposes of calculating the percentage of the stock impacted, the take is being
analyzed as if all proposed takes occurred within each stock.
\b\ Takes are allocated among the three DPSs in the area based on Wade et al. (2017) (Oregon: 32.7% Mexico DPS, 67.2% Central America DPS; Washington/
British Columbia: 27.9% Mexico DPS, 8.7% Central America DPS, 63.5% Hawaii DPS).
\c\ Total for small beaked whale guild. Requested take includes 7 Blainville's beaked whales, 86 Stejneger's beaked whales, 86 Cuvier's beaked whales,
and 74 Hubbs' beaked whales (see Appendix B of L-DEO's application for more information).
\d\ Proposed take increased to mean group size from Barlow (2016).
\e\ Proposed take increased to mean group size from Mobley et al. (2000).
\f\ Total estimated take is 86 killer whales. Approximately one-third of calculated takes were assigned to each stock due to expected equal likelihood
of occurrence in the survey area.
\g\ The percentage of these stocks expected to experience take is discussed further in the Small Numbers section later in the document.
\h\ As noted in Table 1, there is no current estimate of abundance available for the Oregon/Washington Coast stock of harbor seal. The abundance
estimate from 1999, included here, is the best available.
The proposed take numbers shown in Table 10 are expected to be
conservative. Marine mammals would be expected to move away from a loud
sound source that represents an aversive stimulus, such as an airgun
array, potentially reducing the number of takes by Level A harassment.
However, the extent to which marine mammals would move away from the
sound source is difficult to quantify and is therefore not accounted
for in the take estimates. Also, note that in consideration of the
near-field soundscape of the airgun array, we propose to authorize a
different number of takes of mid-frequency cetaceans and pinnipeds by
Level A harassment than the number proposed by L-DEO (see Appendix B in
L-DEO's IHA application).
Proposed Mitigation
In order to issue an IHA under Section 101(a)(5)(D) of the MMPA,
NMFS must set forth the permissible methods of taking pursuant to the
activity, and other means of effecting the least practicable impact on
the species or stock and its habitat, paying particular attention to
rookeries, mating grounds, and areas of similar significance, and on
the availability of the species or stock for taking for certain
subsistence uses (latter not applicable for this action). NMFS
regulations require applicants for incidental take authorizations to
include information about the availability and feasibility (economic
and technological) of equipment, methods, and manner of conducting the
activity or other means of effecting the least practicable adverse
impact upon the affected species or stocks and their habitat (50 CFR
216.104(a)(11)).
In evaluating how mitigation may or may not be appropriate to
ensure the least practicable adverse impact on species or stocks and
their habitat, as well as subsistence uses where applicable, we
carefully consider two primary factors:
(1) The manner in which, and the degree to which, the successful
implementation of the measure(s) is expected to reduce impacts to
marine mammals, marine mammal species or stocks, and their habitat.
This considers the nature of the potential adverse impact being
mitigated (likelihood, scope, range). It further considers the
likelihood that the measure will be effective if implemented
(probability of accomplishing the mitigating result if implemented as
planned), the likelihood of effective implementation (probability
implemented as planned); and
(2) the practicability of the measures for applicant
implementation, which may consider such things as cost, impact on
operations, and, in the case of a military readiness activity,
personnel safety, practicality of implementation, and impact on the
effectiveness of the military readiness activity.
L-DEO has reviewed mitigation measures employed during seismic
research surveys authorized by NMFS under previous incidental
harassment authorizations, as well as recommended best practices in
Richardson et al. (1995), Pierson et al. (1998), Weir and Dolman
(2007), Nowacek et al. (2013), Wright (2014), and Wright and Cosentino
(2015), and has incorporated a suite of proposed mitigation measures
into their project description based on the above sources.
To reduce the potential for disturbance from acoustic stimuli
associated with the activities, L-DEO has proposed to implement
mitigation measures for marine mammals. Mitigation measures that would
be adopted during the planned surveys include (1) Vessel-based visual
mitigation monitoring; (2) Vessel-based passive acoustic monitoring;
(3) Establishment of an exclusion zone; (4) Shutdown procedures; (5)
Ramp-up procedures; and (6) Vessel strike avoidance measures.
Vessel-Based Visual Mitigation Monitoring
Visual monitoring requires the use of trained observers (herein
referred to as visual PSOs) to scan the ocean surface visually for the
presence of marine mammals. The area to be scanned visually includes
primarily the exclusion zone, within which observation of certain
marine mammals requires shutdown of the acoustic source, but also the
buffer zone. The buffer zone means an area beyond the exclusion zone to
be monitored for the presence of marine mammals that may enter the
exclusion zone. During pre-clearance monitoring (i.e., before ramp-up
begins), the buffer zone also acts as an extension of the exclusion
zone in that observations of marine mammals within the buffer zone
would also prevent airgun operations from beginning (i.e. ramp-up). The
buffer zone encompasses the area at and below the sea surface from the
edge of the 0-500 m exclusion zone, out to a radius of 1,000 m from the
edges of the airgun array (500-1,000 m). Visual monitoring of the
exclusion zone and adjacent waters is intended to establish and, when
visual conditions allow, maintain zones around the sound source that
are clear of marine mammals, thereby reducing or eliminating the
potential for injury and minimizing the potential for more severe
behavioral reactions for animals occurring closer to the vessel.
[[Page 19623]]
Visual monitoring of the buffer zone is intended to (1) provide
additional protection to na[iuml]ve marine mammals that may be in the
area during pre-clearance, and (2) during airgun use, aid in
establishing and maintaining the exclusion zone by alerting the visual
observer and crew of marine mammals that are outside of, but may
approach and enter, the exclusion zone.
L-DEO must use dedicated, trained, NMFS-approved Protected Species
Observers (PSOs). The PSOs must have no tasks other than to conduct
observational effort, record observational data, and communicate with
and instruct relevant vessel crew with regard to the presence of marine
mammals and mitigation requirements. PSO resumes shall be provided to
NMFS for approval.
At least one of the visual and two of the acoustic PSOs (discussed
below) aboard the vessel must have a minimum of 90 days at-sea
experience working in those roles, respectively, during a deep
penetration (i.e., ``high energy'') seismic survey, with no more than
18 months elapsed since the conclusion of the at-sea experience. One
visual PSO with such experience shall be designated as the lead for the
entire protected species observation team. The lead PSO shall serve as
primary point of contact for the vessel operator and ensure all PSO
requirements per the IHA are met. To the maximum extent practicable,
the experienced PSOs should be scheduled to be on duty with those PSOs
with appropriate training but who have not yet gained relevant
experience.
During survey operations (e.g., any day on which use of the
acoustic source is planned to occur, and whenever the acoustic source
is in the water, whether activated or not), a minimum of two visual
PSOs must be on duty and conducting visual observations at all times
during daylight hours (i.e., from 30 minutes prior to sunrise through
30 minutes following sunset). Visual monitoring of the exclusion and
buffer zones must begin no less than 30 minutes prior to ramp-up and
must continue until one hour after use of the acoustic source ceases or
until 30 minutes past sunset. Visual PSOs shall coordinate to ensure
360[deg] visual coverage around the vessel from the most appropriate
observation posts, and shall conduct visual observations using
binoculars and the naked eye while free from distractions and in a
consistent, systematic, and diligent manner.
PSOs shall establish and monitor the exclusion and buffer zones.
These zones shall be based upon the radial distance from the edges of
the acoustic source (rather than being based on the center of the array
or around the vessel itself). During use of the acoustic source (i.e.,
anytime airguns are active, including ramp-up), detections of marine
mammals within the buffer zone (but outside the exclusion zone) shall
be communicated to the operator to prepare for the potential shutdown
of the acoustic source.
During use of the airgun (i.e., anytime the acoustic source is
active, including ramp-up), detections of marine mammals within the
buffer zone (but outside the exclusion zone) should be communicated to
the operator to prepare for the potential shutdown of the acoustic
source. Visual PSOs will immediately communicate all observations to
the on duty acoustic PSO(s), including any determination by the PSO
regarding species identification, distance, and bearing and the degree
of confidence in the determination. Any observations of marine mammals
by crew members shall be relayed to the PSO team. During good
conditions (e.g., daylight hours; Beaufort sea state (BSS) 3 or less),
visual PSOs shall conduct observations when the acoustic source is not
operating for comparison of sighting rates and behavior with and
without use of the acoustic source and between acquisition periods, to
the maximum extent practicable.
While the R/V Langseth is surveying in water depths of 200 m or
less, a second vessel with additional PSOs would travel approximately 5
km ahead of the R/V Langseth. Two PSOs would be on watch on the second
vessel during all such survey operations and would alert PSOs on the R/
V Langseth of any marine mammal observations so that they may be
prepared to initiate shutdowns.
Visual PSOs on both vessels may be on watch for a maximum of four
consecutive hours followed by a break of at least one hour between
watches and may conduct a maximum of 12 hours of observation per 24-
hour period. Combined observational duties (visual and acoustic but not
at same time) may not exceed 12 hours per 24-hour period for any
individual PSO.
Passive Acoustic Monitoring
Acoustic monitoring means the use of trained personnel (sometimes
referred to as passive acoustic monitoring (PAM) operators, herein
referred to as acoustic PSOs) to operate PAM equipment to acoustically
detect the presence of marine mammals. Acoustic monitoring involves
acoustically detecting marine mammals regardless of distance from the
source, as localization of animals may not always be possible. Acoustic
monitoring is intended to further support visual monitoring (during
daylight hours) in maintaining an exclusion zone around the sound
source that is clear of marine mammals. In cases where visual
monitoring is not effective (e.g., due to weather, nighttime), acoustic
monitoring may be used to allow certain activities to occur, as further
detailed below.
Passive acoustic monitoring (PAM) would take place in addition to
the visual monitoring program. Visual monitoring typically is not
effective during periods of poor visibility or at night, and even with
good visibility, is unable to detect marine mammals when they are below
the surface or beyond visual range. Acoustical monitoring can be used
in addition to visual observations to improve detection,
identification, and localization of cetaceans. The acoustic monitoring
would serve to alert visual PSOs (if on duty) when vocalizing cetaceans
are detected. It is only useful when marine mammals call, but it can be
effective either by day or by night, and does not depend on good
visibility. It would be monitored in real time so that the visual
observers can be advised when cetaceans are detected.
The R/V Langseth will use a towed PAM system, which must be
monitored by at a minimum one on duty acoustic PSO beginning at least
30 minutes prior to ramp-up and at all times during use of the acoustic
source. Acoustic PSOs may be on watch for a maximum of four consecutive
hours followed by a break of at least one hour between watches and may
conduct a maximum of 12 hours of observation per 24-hour period.
Combined observational duties (acoustic and visual but not at same
time) may not exceed 12 hours per 24-hour period for any individual
PSO.
Survey activity may continue for 30 minutes when the PAM system
malfunctions or is damaged, while the PAM operator diagnoses the issue.
If the diagnosis indicates that the PAM system must be repaired to
solve the problem, operations may continue for an additional five hours
without acoustic monitoring during daylight hours only under the
following conditions:
Sea state is less than or equal to BSS 4;
No marine mammals (excluding delphinids, other than killer
whales) detected solely by PAM in the applicable exclusion zone in the
previous two hours;
NMFS is notified via email as soon as practicable with the
time and location in which operations began occurring without an active
PAM system; and
[[Page 19624]]
Operations with an active acoustic source, but without an
operating PAM system, do not exceed a cumulative total of five hours in
any 24-hour period.
Establishment of Exclusion and Buffer Zones
An exclusion zone (EZ) is a defined area within which occurrence of
a marine mammal triggers mitigation action intended to reduce the
potential for certain outcomes, e.g., auditory injury, disruption of
critical behaviors. The PSOs would establish a minimum EZ with a 500-m
radius. The 500-m EZ would be based on radial distance from the edge of
the airgun array (rather than being based on the center of the array or
around the vessel itself). With certain exceptions (described below),
if a marine mammal appears within or enters this zone, the acoustic
source would be shut down.
The 500-m EZ is intended to be precautionary in the sense that it
would be expected to contain sound exceeding the injury criteria for
all cetacean hearing groups, (based on the dual criteria of
SELcum and peak SPL), while also providing a consistent,
reasonably observable zone within which PSOs would typically be able to
conduct effective observational effort. Additionally, a 500-m EZ is
expected to minimize the likelihood that marine mammals will be exposed
to levels likely to result in more severe behavioral responses.
Although significantly greater distances may be observed from an
elevated platform under good conditions, we believe that 500 m is
likely regularly attainable for PSOs using the naked eye during typical
conditions.
An extended EZ of 1,500 m must be enforced for all beaked whales,
and dwarf and pygmy sperm whales. No buffer zone is required.
Pre-Clearance and Ramp-Up
Ramp-up (sometimes referred to as ``soft start'') means the gradual
and systematic increase of emitted sound levels from an airgun array.
Ramp-up begins by first activating a single airgun of the smallest
volume, followed by doubling the number of active elements in stages
until the full complement of an array's airguns are active. Each stage
should be approximately the same duration, and the total duration
should not be less than approximately 20 minutes. The intent of pre-
clearance observation (30 minutes) is to ensure no protected species
are observed within the buffer zone prior to the beginning of ramp-up.
During pre-clearance is the only time observations of protected species
in the buffer zone would prevent operations (i.e., the beginning of
ramp-up). The intent of ramp-up is to warn protected species of pending
seismic operations and to allow sufficient time for those animals to
leave the immediate vicinity. A ramp-up procedure, involving a step-
wise increase in the number of airguns firing and total array volume
until all operational airguns are activated and the full volume is
achieved, is required at all times as part of the activation of the
acoustic source. All operators must adhere to the following pre-
clearance and ramp-up requirements:
The operator must notify a designated PSO of the planned
start of ramp-up as agreed upon with the lead PSO; the notification
time should not be less than 60 minutes prior to the planned ramp-up in
order to allow the PSOs time to monitor the exclusion and buffer zones
for 30 minutes prior to the initiation of ramp-up (pre-clearance);
Ramp-ups shall be scheduled so as to minimize the time
spent with the source activated prior to reaching the designated run-
in;
One of the PSOs conducting pre-clearance observations must
be notified again immediately prior to initiating ramp-up procedures
and the operator must receive confirmation from the PSO to proceed;
Ramp-up may not be initiated if any marine mammal is
within the applicable exclusion or buffer zone. If a marine mammal is
observed within the applicable exclusion zone or the buffer zone during
the 30 minute pre-clearance period, ramp-up may not begin until the
animal(s) has been observed exiting the zones or until an additional
time period has elapsed with no further sightings (15 minutes for small
odontocetes and pinnipeds, and 30 minutes for all mysticetes and all
other odontocetes, including sperm whales, pygmy sperm whales, dwarf
sperm whales, beaked whales, pilot whales, false killer whales, and
Risso's dolphins);
Ramp-up shall begin by activating a single airgun of the
smallest volume in the array and shall continue in stages by doubling
the number of active elements at the commencement of each stage, with
each stage of approximately the same duration. Duration shall not be
less than 20 minutes. The operator must provide information to the PSO
documenting that appropriate procedures were followed;
PSOs must monitor the exclusion and buffer zones during
ramp-up, and ramp-up must cease and the source must be shut down upon
detection of a marine mammal within the applicable exclusion zone. Once
ramp-up has begun, detections of marine mammals within the buffer zone
do not require shutdown, but such observation shall be communicated to
the operator to prepare for the potential shutdown;
Ramp-up may occur at times of poor visibility, including
nighttime, if appropriate acoustic monitoring has occurred with no
detections in the 30 minutes prior to beginning ramp-up. Acoustic
source activation may only occur at times of poor visibility where
operational planning cannot reasonably avoid such circumstances;
If the acoustic source is shut down for brief periods
(i.e., less than 30 minutes) for reasons other than that described for
shutdown (e.g., mechanical difficulty), it may be activated again
without ramp-up if PSOs have maintained constant visual and/or acoustic
observation and no visual or acoustic detections of marine mammals have
occurred within the applicable exclusion zone. For any longer shutdown,
pre-clearance observation and ramp-up are required. For any shutdown at
night or in periods of poor visibility (e.g., BSS 4 or greater), ramp-
up is required, but if the shutdown period was brief and constant
observation was maintained, pre-clearance watch of 30 minutes is not
required; and
Testing of the acoustic source involving all elements
requires ramp-up. Testing limited to individual source elements or
strings does not require ramp-up but does require pre-clearance of 30
min.
Shutdown
The shutdown of an airgun array requires the immediate de-
activation of all individual airgun elements of the array. Any PSO on
duty will have the authority to delay the start of survey operations or
to call for shutdown of the acoustic source if a marine mammal is
detected within the applicable exclusion zone. The operator must also
establish and maintain clear lines of communication directly between
PSOs on duty and crew controlling the acoustic source to ensure that
shutdown commands are conveyed swiftly while allowing PSOs to maintain
watch. When both visual and acoustic PSOs are on duty, all detections
will be immediately communicated to the remainder of the on-duty PSO
team for potential verification of visual observations by the acoustic
PSO or of acoustic detections by visual PSOs. When the airgun array is
active (i.e., anytime one or more airguns is active, including during
ramp-up) and (1) a marine mammal appears within or enters the
applicable exclusion zone and/or (2) a marine mammal (other than
delphinids, see
[[Page 19625]]
below) is detected acoustically and localized within the applicable
exclusion zone, the acoustic source will be shut down. When shutdown is
called for by a PSO, the acoustic source will be immediately
deactivated and any dispute resolved only following deactivation.
Additionally, shutdown will occur whenever PAM alone (without visual
sighting), confirms presence of marine mammal(s) in the EZ. If the
acoustic PSO cannot confirm presence within the EZ, visual PSOs will be
notified but shutdown is not required. L-DEO must also implement
shutdown of the airgun array if killer whale vocalizations are
detected, regardless of localization.
Following a shutdown, airgun activity would not resume until the
marine mammal has cleared the 500-m EZ. The animal would be considered
to have cleared the 500-m EZ if it is visually observed to have
departed the 500-m EZ, or it has not been seen within the 500-m EZ for
15 min in the case of small odontocetes and pinnipeds, or 30 min in the
case of mysticetes and large odontocetes, including sperm whales, pygmy
sperm whales, dwarf sperm whales, pilot whales, beaked whales, false
killer whales, and Risso's dolphins.
The shutdown requirement can be waived for small dolphins if an
individual is visually detected within the exclusion zone. As defined
here, the small dolphin group is intended to encompass those members of
the Family Delphinidae most likely to voluntarily approach the source
vessel for purposes of interacting with the vessel and/or airgun array
(e.g., bow riding). This exception to the shutdown requirement applies
solely to specific genera of small dolphins--Tursiops, Delphinus,
Stenella, Lagenorhynchus, and Lissodelphis.
We include this small dolphin exception because shutdown
requirements for small dolphins under all circumstances represent
practicability concerns without likely commensurate benefits for the
animals in question. Small dolphins are generally the most commonly
observed marine mammals in the specific geographic region and would
typically be the only marine mammals likely to intentionally approach
the vessel. As described above, auditory injury is extremely unlikely
to occur for mid-frequency cetaceans (e.g., delphinids), as this group
is relatively insensitive to sound produced at the predominant
frequencies in an airgun pulse while also having a relatively high
threshold for the onset of auditory injury (i.e., permanent threshold
shift).
A large body of anecdotal evidence indicates that small dolphins
commonly approach vessels and/or towed arrays during active sound
production for purposes of bow riding, with no apparent effect observed
in those delphinoids (e.g., Barkaszi et al., 2012). The potential for
increased shutdowns resulting from such a measure would require the
Langseth to revisit the missed track line to reacquire data, resulting
in an overall increase in the total sound energy input to the marine
environment and an increase in the total duration over which the survey
is active in a given area. Although other mid-frequency hearing
specialists (e.g., large delphinoids) are no more likely to incur
auditory injury than are small dolphins, they are much less likely to
approach vessels. Therefore, retaining a shutdown requirement for large
delphinoids would not have similar impacts in terms of either
practicability for the applicant or corollary increase in sound energy
output and time on the water. We do anticipate some benefit for a
shutdown requirement for large delphinoids in that it simplifies
somewhat the total range of decision-making for PSOs and may preclude
any potential for physiological effects other than to the auditory
system as well as some more severe behavioral reactions for any such
animals in close proximity to the source vessel.
Visual PSOs shall use best professional judgment in making the
decision to call for a shutdown if there is uncertainty regarding
identification (i.e., whether the observed marine mammal(s) belongs to
one of the delphinid genera for which shutdown is waived or one of the
species with a larger exclusion zone).
Upon implementation of shutdown, the source may be reactivated
after the marine mammal(s) has been observed exiting the applicable
exclusion zone (i.e., animal is not required to fully exit the buffer
zone where applicable) or following 15 minutes for small odontocetes
and pinnipeds, and 30 minutes for mysticetes and all other odontocetes,
including sperm whales, pygmy sperm whales, dwarf sperm whales, beaked
whales, pilot whales, and Risso's dolphins, with no further observation
of the marine mammal(s).
L-DEO must implement shutdown if a marine mammal species for which
take was not authorized, or a species for which authorization was
granted but the takes have been met, approaches the Level A or Level B
harassment zones. L-DEO must also implement shutdown if any of the
following are observed at any distance:
Any large whale (defined as a sperm whale or any mysticete
species) with a calf (defined as an animal less than two-thirds the
body size of an adult observed to be in close association with an
adult;
An aggregation of six or more large whales;
A North Pacific right whale; and/or
A killer whale of any ecotype.
Vessel Strike Avoidance
These measures apply to all vessels associated with the planned
survey activity; however, we note that these requirements do not apply
in any case where compliance would create an imminent and serious
threat to a person or vessel or to the extent that a vessel is
restricted in its ability to maneuver and, because of the restriction,
cannot comply. These measures include the following:
1. Vessel operators and crews must maintain a vigilant watch for
all marine mammals and slow down, stop their vessel, or alter course,
as appropriate and regardless of vessel size, to avoid striking any
marine mammal. A single marine mammal at the surface may indicate the
presence of submerged animals in the vicinity of the vessel; therefore,
precautionary measures should be exercised when an animal is observed.
A visual observer aboard the vessel must monitor a vessel strike
avoidance zone around the vessel (specific distances detailed below),
to ensure the potential for strike is minimized. Visual observers
monitoring the vessel strike avoidance zone can be either third-party
observers or crew members, but crew members responsible for these
duties must be provided sufficient training to distinguish marine
mammals from other phenomena and broadly to identify a marine mammal to
broad taxonomic group (i.e., as a large whale or other marine mammal);
2. Vessel speeds must be reduced to 10 kn or less when mother/calf
pairs, pods, or large assemblages of any marine mammal are observed
near a vessel;
3. All vessels must maintain a minimum separation distance of 100 m
from large whales (i.e., sperm whales and all mysticetes);
4. All vessels must attempt to maintain a minimum separation
distance of 50 m from all other marine mammals, with an exception made
for those animals that approach the vessel; and
5. When marine mammals are sighted while a vessel is underway, the
vessel should take action as necessary to avoid violating the relevant
separation
[[Page 19626]]
distance (e.g., attempt to remain parallel to the animal's course,
avoid excessive speed or abrupt changes in direction until the animal
has left the area). If marine mammals are sighted within the relevant
separation distance, the vessel should reduce speed and shift the
engine to neutral, not engaging the engines until animals are clear of
the area. This recommendation does not apply to any vessel towing gear.
Operational Restrictions
While the R/V Langseth is surveying in waters 200 m deep or less,
survey operations will occur in daylight hours only (i.e., from 30
minutes prior to sunrise through 30 minutes following sunset) to ensure
the ability to use visual observation as a detection-based mitigation
tool and to implement shutdown procedures for species or situations
with additional shutdown requirements outlined above (e.g., killer
whale of any ecotype, aggregation of six or more large whales, large
whale with a calf).
Communication
Each day of survey operations, L-DEO will contact NMFS Northwest
Fisheries Science Center, NMFS West Coast Region, The Whale Museum,
Orca Network, Canada's DFO and/or other sources to obtain near real-
time reporting for the whereabouts of Southern Resident killer whales.
Mitigation Measures Considered But Eliminated
As stated above, in determining appropriate mitigation measures,
NMFS considers the practicability of the measures for applicant
implementation, which may include such things as cost or impact on
operations. NMFS has proposed expanding critical habitat for Southern
Resident killer whales to include marine waters between the 6.1-m depth
contour and the 200-m depth contour from the U.S. international border
with Canada south to Point Sur, California (84 FR 49214; September 19,
2019). Though the proposed expansion has not been finalized, due to the
habitat features of the area and the higher likelihood of occurrence
within the area, NMFS considered implementing a closure area and
prohibiting L-DEO from conducting survey operations between the 200-m
isobath and the coastline. However, this measure was eliminated from
consideration because the closure would not be practicable for L-DEO,
as the primary purpose of their proposed survey is to investigate the
geologic features that occur within that area. Therefore, NMFS is not
proposing to exclude L-DEO from waters within the 200-m isobath for
this survey.
We have carefully evaluated the suite of mitigation measures
described here and considered a range of other measures in the context
of ensuring that we prescribe the means of effecting the least
practicable adverse impact on the affected marine mammal species and
stocks and their habitat. Based on our evaluation of the proposed
measures, as well as other measures considered by NMFS described above,
NMFS has preliminarily determined that the mitigation measures provide
the means effecting the least practicable impact on the affected
species or stocks and their habitat, paying particular attention to
rookeries, mating grounds, and areas of similar significance.
Proposed Monitoring and Reporting
In order to issue an IHA for an activity, Section 101(a)(5)(D) of
the MMPA states that NMFS must set forth requirements pertaining to the
monitoring and reporting of such taking. The MMPA implementing
regulations at 50 CFR 216.104 (a)(13) indicate that requests for
authorizations must include the suggested means of accomplishing the
necessary monitoring and reporting that will result in increased
knowledge of the species and of the level of taking or impacts on
populations of marine mammals that are expected to be present in the
proposed action area. Effective reporting is critical both to
compliance as well as ensuring that the most value is obtained from the
required monitoring.
Monitoring and reporting requirements prescribed by NMFS should
contribute to improved understanding of one or more of the following:
Occurrence of marine mammal species or stocks in the area
in which take is anticipated (e.g., presence, abundance, distribution,
density);
Nature, scope, or context of likely marine mammal exposure
to potential stressors/impacts (individual or cumulative, acute or
chronic), through better understanding of: (1) Action or environment
(e.g., source characterization, propagation, ambient noise); (2)
affected species (e.g., life history, dive patterns); (3) co-occurrence
of marine mammal species with the action; or (4) biological or
behavioral context of exposure (e.g., age, calving or feeding areas);
Individual marine mammal responses (behavioral or
physiological) to acoustic stressors (acute, chronic, or cumulative),
other stressors, or cumulative impacts from multiple stressors;
How anticipated responses to stressors impact either: (1)
Long-term fitness and survival of individual marine mammals; or (2)
populations, species, or stocks;
Effects on marine mammal habitat (e.g., marine mammal prey
species, acoustic habitat, or other important physical components of
marine mammal habitat); and
Mitigation and monitoring effectiveness.
Vessel-Based Visual Monitoring
As described above, PSO observations would take place during
daytime airgun operations. During seismic operations, at least five
visual PSOs would be based aboard the Langseth. Two visual PSOs would
be on duty at all time during daytime hours, with an additional two
PSOs on duty aboard a second scout vessel at all times during daylight
hours when operating in waters shallower than 200 m. Monitoring shall
be conducted in accordance with the following requirements:
The operator shall provide PSOs with bigeye binoculars
(e.g., 25 x 150; 2.7 view angle; individual ocular focus; height
control) of appropriate quality (i.e., Fujinon or equivalent) solely
for PSO use. These shall be pedestal-mounted on the deck at the most
appropriate vantage point that provides for optimal sea surface
observation, PSO safety, and safe operation of the vessel; and
The operator will work with the selected third-party
observer provider to ensure PSOs have all equipment (including backup
equipment) needed to adequately perform necessary tasks, including
accurate determination of distance and bearing to observed marine
mammals.
PSOs must have the following requirements and qualifications:
PSOs shall be independent, dedicated, trained visual and
acoustic PSOs and must be employed by a third-party observer provider;
PSOs shall have no tasks other than to conduct
observational effort (visual or acoustic), collect data, and
communicate with and instruct relevant vessel crew with regard to the
presence of protected species and mitigation requirements (including
brief alerts regarding maritime hazards);
PSOs shall have successfully completed an approved PSO
training course appropriate for their designated task (visual or
acoustic). Acoustic PSOs are required to complete specialized training
for operating PAM systems and are encouraged to have familiarity with
the vessel with which they will be working;
[[Page 19627]]
PSOs can act as acoustic or visual observers (but not at
the same time) as long as they demonstrate that their training and
experience are sufficient to perform the task at hand;
NMFS must review and approve PSO resumes accompanied by a
relevant training course information packet that includes the name and
qualifications (i.e., experience, training completed, or educational
background) of the instructor(s), the course outline or syllabus, and
course reference material as well as a document stating successful
completion of the course;
NMFS shall have one week to approve PSOs from the time
that the necessary information is submitted, after which PSOs meeting
the minimum requirements shall automatically be considered approved;
PSOs must successfully complete relevant training,
including completion of all required coursework and passing (80 percent
or greater) a written and/or oral examination developed for the
training program;
PSOs must have successfully attained a bachelor's degree
from an accredited college or university with a major in one of the
natural sciences, a minimum of 30 semester hours or equivalent in the
biological sciences, and at least one undergraduate course in math or
statistics; and
The educational requirements may be waived if the PSO has
acquired the relevant skills through alternate experience. Requests for
such a waiver shall be submitted to NMFS and must include written
justification. Requests shall be granted or denied (with justification)
by NMFS within one week of receipt of submitted information. Alternate
experience that may be considered includes, but is not limited to (1)
secondary education and/or experience comparable to PSO duties; (2)
previous work experience conducting academic, commercial, or
government-sponsored protected species surveys; or (3) previous work
experience as a PSO; the PSO should demonstrate good standing and
consistently good performance of PSO duties.
For data collection purposes, PSOs shall use standardized data
collection forms, whether hard copy or electronic. PSOs shall record
detailed information about any implementation of mitigation
requirements, including the distance of animals to the acoustic source
and description of specific actions that ensued, the behavior of the
animal(s), any observed changes in behavior before and after
implementation of mitigation, and if shutdown was implemented, the
length of time before any subsequent ramp-up of the acoustic source. If
required mitigation was not implemented, PSOs should record a
description of the circumstances. At a minimum, the following
information must be recorded:
Vessel names (source vessel and other vessels associated
with survey) and call signs;
PSO names and affiliations;
Dates of departures and returns to port with port name;
Date and participants of PSO briefings;
Dates and times (Greenwich Mean Time) of survey effort and
times corresponding with PSO effort;
Vessel location (latitude/longitude) when survey effort
began and ended and vessel location at beginning and end of visual PSO
duty shifts;
Vessel heading and speed at beginning and end of visual
PSO duty shifts and upon any line change;
Environmental conditions while on visual survey (at
beginning and end of PSO shift and whenever conditions changed
significantly), including BSS and any other relevant weather conditions
including cloud cover, fog, sun glare, and overall visibility to the
horizon;
Factors that may have contributed to impaired observations
during each PSO shift change or as needed as environmental conditions
changed (e.g., vessel traffic, equipment malfunctions); and
Survey activity information, such as acoustic source power
output while in operation, number and volume of airguns operating in
the array, tow depth of the array, and any other notes of significance
(i.e., pre-clearance, ramp-up, shutdown, testing, shooting, ramp-up
completion, end of operations, streamers, etc.).
The following information should be recorded upon visual
observation of any protected species:
Watch status (sighting made by PSO on/off effort,
opportunistic, crew, alternate vessel/platform);
PSO who sighted the animal;
Time of sighting;
Vessel location at time of sighting;
Water depth;
Direction of vessel's travel (compass direction);
Direction of animal's travel relative to the vessel;
Pace of the animal;
Estimated distance to the animal and its heading relative
to vessel at initial sighting;
Identification of the animal (e.g., genus/species, lowest
possible taxonomic level, or unidentified) and the composition of the
group if there is a mix of species;
Estimated number of animals (high/low/best);
Estimated number of animals by cohort (adults, yearlings,
juveniles, calves, group composition, etc.);
Description (as many distinguishing features as possible
of each individual seen, including length, shape, color, pattern, scars
or markings, shape and size of dorsal fin, shape of head, and blow
characteristics);
Detailed behavior observations (e.g., number of blows/
breaths, number of surfaces, breaching, spyhopping, diving, feeding,
traveling; as explicit and detailed as possible; note any observed
changes in behavior);
Animal's closest point of approach (CPA) and/or closest
distance from any element of the acoustic source;
Platform activity at time of sighting (e.g., deploying,
recovering, testing, shooting, data acquisition, other); and
Description of any actions implemented in response to the
sighting (e.g., delays, shutdown, ramp-up) and time and location of the
action.
If a marine mammal is detected while using the PAM system, the
following information should be recorded:
An acoustic encounter identification number, and whether
the detection was linked with a visual sighting;
Date and time when first and last heard;
Types and nature of sounds heard (e.g., clicks, whistles,
creaks, burst pulses, continuous, sporadic, strength of signal); and
Any additional information recorded such as water depth of
the hydrophone array, bearing of the animal to the vessel (if
determinable), species or taxonomic group (if determinable),
spectrogram screenshot, and any other notable information.
Reporting
A report would be submitted to NMFS within 90 days after the end of
the cruise. The report would describe the operations that were
conducted and sightings of marine mammals near the operations. The
report would provide full documentation of methods, results, and
interpretation pertaining to all monitoring. The 90-day report would
summarize the dates and locations of seismic operations, and all marine
mammal sightings (dates, times, locations, activities, associated
seismic survey activities). The report would also include estimates of
the number and nature of exposures that occurred above the harassment
threshold based on PSO observations and including an estimate of those
that were not detected, in consideration of both the characteristics
[[Page 19628]]
and behaviors of the species of marine mammals that affect
detectability, as well as the environmental factors that affect
detectability.
The draft report shall also include geo-referenced time-stamped
vessel tracklines for all time periods during which airguns were
operating. Tracklines should include points recording any change in
airgun status (e.g., when the airguns began operating, when they were
turned off, or when they changed from full array to single gun or vice
versa). GIS files shall be provided in ESRI shapefile format and
include the UTC date and time, latitude in decimal degrees, and
longitude in decimal degrees. All coordinates shall be referenced to
the WGS84 geographic coordinate system. In addition to the report, all
raw observational data shall be made available to NMFS. The report must
summarize the information submitted in interim monthly reports as well
as additional data collected as described above and in the IHA. A final
report must be submitted within 30 days following resolution of any
comments on the draft report.
Reporting Injured or Dead Marine Mammals
Discovery of injured or dead marine mammals--In the event that
personnel involved in survey activities covered by the authorization
discover an injured or dead marine mammal, the L-DEO shall report the
incident to the Office of Protected Resources (OPR), NMFS and to the
NMFS West Coast Regional Stranding Coordinator as soon as feasible. The
report must include the following information:
Time, date, and location (latitude/longitude) of the first
discovery (and updated location information if known and applicable);
Species identification (if known) or description of the
animal(s) involved;
Condition of the animal(s) (including carcass condition if
the animal is dead);
Observed behaviors of the animal(s), if alive;
If available, photographs or video footage of the
animal(s); and
General circumstances under which the animal was
discovered.
Vessel strike--In the event of a ship strike of a marine mammal by
any vessel involved in the activities covered by the authorization, L-
DEO shall report the incident to OPR, NMFS and to the NMFS West Coast
Regional Stranding Coordinator as soon as feasible. The report must
include the following information:
Time, date, and location (latitude/longitude) of the
incident;
Vessel's speed during and leading up to the incident;
Vessel's course/heading and what operations were being
conducted (if applicable);
Status of all sound sources in use;
Description of avoidance measures/requirements that were
in place at the time of the strike and what additional measure were
taken, if any, to avoid strike;
Environmental conditions (e.g., wind speed and direction,
Beaufort sea state, cloud cover, visibility) immediately preceding the
strike;
Species identification (if known) or description of the
animal(s) involved;
Estimated size and length of the animal that was struck
Description of the behavior of the animal immediately
preceding and following the strike;
If available, description of the presence and behavior of
any other marine mammals present immediately preceding the strike;
Estimated fate of the animal (e.g., dead, injured but
alive, injured and moving, blood or tissue observed in the water,
status unknown, disappeared); and
To the extent practicable, photographs or video footage of
the animal(s).
Actions To Minimize Additional Harm to Live-stranded (or Milling)
Marine Mammals
In the event of a live stranding (or near-shore atypical milling)
event within 50 km of the survey operations, where the NMFS stranding
network is engaged in herding or other interventions to return animals
to the water, the Director of OPR, NMFS (or designee) will advise L-DEO
of the need to implement shutdown procedures for all active acoustic
sources operating within 50 km of the stranding. Shutdown procedures
for live stranding or milling marine mammals include the following: If
at any time, the marine mammal the marine mammal(s) die or are
euthanized, or if herding/intervention efforts are stopped, the
Director of OPR, NMFS (or designee) will advise the IHA-holder that the
shutdown around the animals' location is no longer needed. Otherwise,
shutdown procedures will remain in effect until the Director of OPR,
NMFS (or designee) determines and advises L-DEO that all live animals
involved have left the area (either of their own volition or following
an intervention).
If further observations of the marine mammals indicate the
potential for re-stranding, additional coordination with the IHA-holder
will be required to determine what measures are necessary to minimize
that likelihood (e.g., extending the shutdown or moving operations
farther away) and to implement those measures as appropriate.
Additional Information Requests--if NMFS determines that the
circumstances of any marine mammal stranding found in the vicinity of
the activity suggest investigation of the association with survey
activities is warranted, and an investigation into the stranding is
being pursued, NMFS will submit a written request to L-DEO indicating
that the following initial available information must be provided as
soon as possible, but no later than 7 business days after the request
for information:
Status of all sound source use in the 48 hours preceding
the estimated time of stranding and within 50 km of the discovery/
notification of the stranding by NMFS; and
If available, description of the behavior of any marine
mammal(s) observed preceding (i.e., within 48 hours and 50 km) and
immediately after the discovery of the stranding.
In the event that the investigation is still inconclusive, the
investigation of the association of the survey activities is still
warranted, and the investigation is still being pursued, NMFS may
provide additional information requests, in writing, regarding the
nature and location of survey operations prior to the time period
above.
Reporting Species of Concern
To support NMFS's goal of improving our understanding of occurrence
of marine mammal species or stocks in the area (e.g., presence,
abundance, distribution, density), L-DEO will immediately report
observations of Southern Resident killer whales and North Pacific right
whales to OPR, NMFS .
Negligible Impact Analysis and Determination
NMFS has defined negligible impact as an impact resulting from the
specified activity that cannot be reasonably expected to, and is not
reasonably likely to, adversely affect the species or stock through
effects on annual rates of recruitment or survival (50 CFR 216.103). A
negligible impact finding is based on the lack of likely adverse
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough
information on which to base an impact determination. In addition to
considering estimates of the number of
[[Page 19629]]
marine mammals that might be ``taken'' through harassment, NMFS
considers other factors, such as the likely nature of any responses
(e.g., intensity, duration), the context of any responses (e.g.,
critical reproductive time or location, migration), as well as effects
on habitat, and the likely effectiveness of the mitigation. We also
assess the number, intensity, and context of estimated takes by
evaluating this information relative to population status. Consistent
with the 1989 preamble for NMFS's implementing regulations (54 FR
40338; September 29, 1989), the impacts from other past and ongoing
anthropogenic activities are incorporated into this analysis via their
impacts on the environmental baseline (e.g., as reflected in the
regulatory status of the species, population size and growth rate where
known, ongoing sources of human-caused mortality, or ambient noise
levels).
To avoid repetition, our analysis applies to all species listed in
Tables 10 and 11, given that NMFS expects the anticipated effects of
the planned geophysical survey to be similar in nature. Where there are
meaningful differences between species or stocks, or groups of species,
in anticipated individual responses to activities, impact of expected
take on the population due to differences in population status, or
impacts on habitat, NMFS has identified species-specific factors to
inform the analysis. As described above, we proposed to authorize only
the takes estimated to occur outside of Canadian territorial waters
(Table 10); however, for the purposes of our negligible impact analysis
and determination, we consider the total number of takes that are
anticipated to occur as a result of the entire proposed survey
(including the portion of the survey that would occur within the
Canadian territorial waters (approximately four percent of the survey)
(Table 11).
Table 11--Total Estimated Take Including Canadian Territorial Waters
--------------------------------------------------------------------------------------------------------------------------------------------------------
Estimated take (excluding Estimated take (Canadian Total estimated take
Canadian territorial waters) territorial waters) -------------------------------
Species ----------------------------------------------------------------
Level A Level B Level A Level B Level B Level A
--------------------------------------------------------------------------------------------------------------------------------------------------------
LF Cetaceans:
Humpback whale...................................... 172 10 23 1 195 11
Blue whale.......................................... 63 4 8 0 71 4
Fin whale........................................... 89 6 2 0 91 6
Sei whale........................................... 32 2 2 0 34 2
Minke whale......................................... 105 7 6 0 111 7
Gray whale.......................................... 90 2 24 1 114 3
MF Cetaceans:
Sperm whale......................................... 71 0 1 0 72 0
Baird's beaked whale................................ 83 0 1 0 84 0
Small beaked whale.................................. 244 0 5 0 249 0
Bottlenose dolphin.................................. 13 0 0 0 13 0
Striped dolphin..................................... 7 0 0 0 7 0
Short-beaked common dolphin......................... 179 0 4 0 183 0
Pacific white-sided dolphin......................... 6,452 0 354 0 6,806 0
Northern right-whale dolphin........................ 4,333 0 123 0 4,457 0
Risso's dolphin..................................... 1,906 0 155 0 2,062 0
False killer whale.................................. 5 0 5 0 10 0
Killer whale (Southern Resident).................... 43 0 2 0 45 0
Killer whale (Northern Resident).................... 27 0 2 0 29 0
Killer whale (West Coast Transient)................. 26 0 2 0 28 0
Killer whale (Offshore)............................. 26 0 2 0 28 0
Short-finned pilot whale............................ 29 0 1 0 30 0
HF Cetaceans:
Pygmy/dwarf sperm whale............................. 135 6 8 0 143 6
Dall's porpoise..................................... 10,869 452 746 24 11,615 476
Harbor porpoise..................................... 12,557 449 2,622 86 15,179 535
Otariid Seals:
Northern fur seal................................... 4,604 0 58 0 4,662 0
Guadalupe fur seal.................................. 2,387 0 122 0 2,509 0
California sea lion................................. 1,140 0 147 0 1,287 0
Steller sea lion.................................... 7,281 0 1,342 0 8,623 0
Phocid Seals:
Northern elephant seal.............................. 1,995 0 176 0 2,171 0
Harbor seal......................................... 6,537 0 1,744 0 8,281 0
--------------------------------------------------------------------------------------------------------------------------------------------------------
NMFS does not anticipate that serious injury or mortality would
occur as a result of L-DEO's planned survey, even in the absence of
mitigation, and none would be authorized. As discussed in the Potential
Effects section, non-auditory physical effects, stranding, and vessel
strike are not expected to occur.
We are proposing to authorize a limited number of instances of
Level A harassment of nine species (low- and high-frequency cetacean
hearing groups only) and Level B harassment of 31 marine mammal
species. However, we believe that any PTS incurred in marine mammals as
a result of the planned activity would be in the form of only a small
degree of PTS, not total deafness, because of the constant movement of
relative to each other of both the R/V Langseth and of the marine
mammals in the project areas, as well as the fact that the vessel is
not expected to remain in any one area in which individual marine
mammals would be expected to concentrate for an extended period of
[[Page 19630]]
time (i.e., since the duration of exposure to loud sounds will be
relatively short) and, further, would be unlikely to affect the fitness
of any individuals. Also, as described above, we expect that marine
mammals would be likely to move away from a sound source that
represents an aversive stimulus, especially at levels that would be
expected to result in PTS, given sufficient notice of the R/V
Langseth's approach due to the vessel's relatively low speed when
conducting seismic surveys. We expect that the majority of takes would
be in the form of short-term Level B behavioral harassment in the form
of temporary avoidance of the area or decreased foraging (if such
activity were occurring), reactions that are considered to be of low
severity and with no lasting biological consequences (e.g., Southall et
al., 2007, Ellison et al., 2012).
Potential impacts to marine mammal habitat were discussed
previously in this document (see Potential Effects of the Specified
Activity on Marine Mammals and their Habitat). Marine mammal habitat
may be impacted by elevated sound levels, but these impacts would be
temporary. Prey species are mobile and are broadly distributed
throughout the project areas; therefore, marine mammals that may be
temporarily displaced during survey activities are expected to be able
to resume foraging once they have moved away from areas with disturbing
levels of underwater noise. Because of the relatively short duration
(37 days) and temporary nature of the disturbance, the availability of
similar habitat and resources in the surrounding area, the impacts to
marine mammals and the food sources that they utilize are not expected
to cause significant or long-term consequences for individual marine
mammals or their populations.
The tracklines of this survey either traverse or are proximal to
BIAs for humpback and gray whales (Ferguson et al., 2015). The entire
U.S. West Coast within 47 km of the coast is a BIA for migrating gray
whale potential presence from January to July and October to December.
The BIA for northbound gray whale migration is broken into two phases,
Phase A (within 8 km of shore) and Phase B (within 5 km of shore),
which are active from January to July and March to July, respectively.
The BIA for southbound migration includes waters within 10 km of shore
and is active from October to March. There are four gray whale feeding
BIAs within the proposed survey area: the Grays Harbor gray whale
feeding BIA is used between April and November; the Northwest
Washington gray whale feeding BIA is used between May and November; and
the Depoe Bay and Cape Blanco and Orford Reef gray whale feeding BIAs
off Oregon are each used between June and November. There are also two
humpback whale feeding BIAs within the survey area: the Stonewall and
Heceta Bank humpback whale feeding BIA off central Oregon and the
northern Washington BIA off the Washington Olympic Peninsula are each
used between May and November.
For the humpback whale feeding and gray whale feeding and
northbound migration BIAs, L-DEO's proposed survey beginning in June
2020 could overlap with a period where BIAs represent an important
habitat. However, only a portion of seismic survey days would actually
occur in or near these BIAs, and all survey efforts would be completed
by mid-July, still in the early window of primary use for these BIAs.
Gray whales are most commonly seen migrating northward between March
and May and southward between November and January. As proposed, there
is no possibility that L-DEO's survey impacts the southern migration,
and presence of northern migrating individuals should be below peak
during survey operations beginning in June 2020.
Although migrating gray whales may slightly alter their course in
response to the survey, the exposure would not substantially impact
their migratory behavior (Malme et al., 1984; Malme and Miles 1985;
Richardson et al., 1995), and Yazvenko et al. (2007b) reported no
apparent changes in the frequency of feeding activity in Western gray
whales exposed to airgun sounds in their feeding grounds near Sakhalin
Island. Goldbogen et al. (2013) found blue whales feeding on highly
concentrated prey in shallow depths (such as the conditions expected
within humpback feeding BIAs) were less likely to respond and cease
foraging than whales feeding on deep, dispersed prey when exposed to
simulated sonar sources, suggesting that the benefits of feeding for
humpbacks foraging on high-density prey may outweigh perceived harm
from the acoustic stimulus, such as the seismic survey (Southall et
al., 2016). Additionally, L-DEO will shut down the airgun array upon
observation of an aggregation of six or more large whales, which would
reduce impacts to cooperatively foraging animals. For all habitats, no
physical impacts to BIA habitat are anticipated from seismic
activities. While SPLs of sufficient strength have been known to cause
injury to fish and fish and invertebrate mortality, in feeding
habitats, the most likely impact to prey species from survey activities
would be temporary avoidance of the affected area and any injury or
mortality of prey species would be localized around the survey and not
of a degree that would adversely impact marine mammal foraging. 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 expected. Given the short operational seismic time near or
traversing BIAs, as well as the ability of cetaceans and prey species
to move away from acoustic sources, NMFS expects that there would be,
at worst, minimal impacts to animals and habitat within the designated
BIAs.
Critical habitat has been established on the U.S. West Coast for
the eastern DPS of Steller sea lions (58 FR 45269; August 27, 1993) and
in inland waters of Washington for Southern Resident killer whales (71
FR 69054; November 29, 2006). Critical habitat for the Mexico and
Central America DPSs of humpback whales has been proposed along the
U.S. West Coast (84 FR 54354; October 9, 2019), and NMFS has proposed
expanding Southern Resident killer whale critical habitat to include
coastal waters of Washington, Oregon, and California (84 FR 49214;
September 19, 2019). Only a portion of L-DEO's proposed seismic survey
will occur in or near these critical habitats.
Critical habitat for Steller sea lions has been established at two
rookeries on the Oregon 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 rookeries (NMFS 1993). Steller sea lions
occupy rookeries and pup from late-May through early-July (NMFS 2008),
which coincides with L-DEO's proposed survey. The Orford Reef and Rogue
Reef critical habitats are located 7 km and 9 km from the nearest
proposed seismic transect line, respectively. Impacts to Steller sea
lions within these areas, and throughout the survey area, are expected
to be limited to short-term behavioral disturbance, with no lasting
biological consequences.
Critical habitat for the threatened Mexico DPS and endangered
Central America DPS humpback whales has been proposed along the U.S.
West Coast (84 FR 54354; October 9, 2019). The proposed critical
habitat encompasses the humpback whale feeding BIAs described above and
generally includes waters between the 50-m isobath and the 1,200-m
isobath, though some areas of the proposed critical habitat extend
further offshore. NMFS determined that prey within humpback whale
feeding areas are
[[Page 19631]]
essential to the conservation of each of the three DPSs of humpback
whales for which critical habitat was proposed (Mexico, Central
America, and Western North Pacific DPSs). Critical habitat was
therefore proposed in consideration of importance that the whales not
only have reliable access to prey within their feeding areas, but that
prey are of a sufficient density to support feeding and the build-up of
energy reserves. Although humpback whales are generalist predators and
prey availability can very seasonally and spatially, substantial data
indicate that the humpback whales' diet is consistently dominated by
euphausiid species (of genus Euphausia, Thysanoessa, Nyctiphanes, and
Nematoscelis) and small pelagic fishes, such as northern anchovy
(Engraulis mordax), Pacific herring (Clupea pallasii), Pacific sardine
(Sardinops sagax), and capelin (Mallotus villosus) (Nemoto 1957, 1959;
Klumov 1963; Rice Krieger and Wing 1984; Baker 1985; Kieckhefer 1992;
Clapham et al., 1997; Neilson et al., 2015). While there are possible
impacts of seismic activity on plankton and fish species (e.g.,
McCauley et al., 2017; Hastings and Popper 2005), the areas expected to
be affected by L-DEO's activities are small relative to the greater
habitat areas available.
Additionally, humpback whales feeding on high-density prey may be
less likely to cease foraging when the benefit of energy intake
outweighs the perceived harm from acoustic stimulus (Southall et al.,
2016). Therefore, this seismic activity is not expected to have a
lasting physical impact on humpback whale proposed critical habitat,
prey within it, or overall humpback whale fitness. Any impact would be
a temporary increase in sound levels when the survey is occurring in or
near the critical habitat and resulting temporary avoidance of prey or
marine mammals themselves due these elevated sound levels. As stated
above, L-DEO will shut down the airgun array upon observation of an
aggregation of six or more large whales, which would reduce direct
impacts to groups of humpback whales that may be cooperatively feeding
in the area.
Southern Resident Killer Whales
In acknowledgment of our concern regarding the status of Southern
Resident killer whales, including low abundance and decreasing trend,
we address impacts to this stock separately in this section.
L-DEO's proposed tracklines do not overlap with existing Southern
Resident killer whale habitat, but NMFS has proposed expanding Southern
Resident critical habitat to include waters between the 6.1-m and 200-m
depth contours from the U.S. international border with Canada south to
Point Sur, California (84 FR 49214; September 19, 2019). The proposed
expanded critical habitat areas were identified in consideration of
physical and biological features essential to conservation of Southern
Resident killer whales (essential features): (1) Water quality to
support growth and development; (2) Prey species of sufficient
quantity, quality, and availability to support individual growth,
reproduction, and development, as well as overall population growth;
and (3) Passage conditions to allow for migration, resting, and
foraging. NMFS did not identify in-water sound levels as a separate
essential feature of existing or proposed expanded critical habitat
areas, though anthropogenic sound is recognized as one of the primary
threats to Southern Resident killer whales (NMFS 2019). Exposure to
vessel noise and presence of whale watching boats can significantly
affect the foraging behavior of Southern Resident killer whales
(Williams et al., 2006; Lusseau et al., 2009; Giles and Cendak 2010;
Senigaglia et al., 2016). Nutritional stress has also been identified
as a primary cause of Southern Resident killer whale decline (Ayres et
al., 2012; Wasser et al., 2017), suggesting that reduced foraging
effort may have a greater impact than behavioral disturbance alone.
However, these studies have primarily focused on effects of whale watch
vessels operating in close proximity to Southern Resident killer
whales, and commercial shipping traffic in the Salish Sea (i.e., the
inland waters of Washington and British Columbia). Commercial whale
watch and private recreational vessels operating in the waters around
the San Juan Islands in summer months number in the dozens (Erbe 2002),
and at least 400 piloted vessels (commercial vessels over 350 gross
tons and pleasure craft over 500 gross tons that are required to be
guided in and out of the Port of Vancouver by British Columbia Coast
Pilots) transit through Haro Strait each month (Joy et al., 2002).
Concentration of vessel traffic on the outer coast, where the proposed
survey area occurs, is much lower than in the inland waters (Cominelli
et al., 2018), suggesting that effects from vessel noise may be lower
than in inland waters. Increased noise levels from the proposed survey
in any specific area would be short-term due to the mobile nature of
the survey, unlike the near-constant vessel presence in inland waters.
Approximately 23 percent of L-DEO's total tracklines occur within
the 200-m isobath along Washington and Oregon. L-DEO would be required
to shut down seismic airguns immediately upon visual observation or
acoustic detection of killer whales of any ecotype at any distance to
minimize potential exposures of Southern Resident killer whales, and
will operate within the 200-m isobath in daylight hours only, to
increase the ability to visually detect killer whales and implement
shutdowns. Southern Resident killer whales exposed to elevated sound
levels from the R/V Langseth and the airgun array may reduce foraging
time, but the amount of tracklines that overlap with the areas of
highest estimated densities of Southern Resident killer whales (see
Figures 7-9 and 7-11 in the U.S. Navy's MSDD (U.S. Navy 2019)) is low
relative to the total survey effort. Approximately 360 km of survey
tracklines occur within the areas of highest Southern Resident killer
whale density (the three highest density ranges for each pod), which
represents approximately 5 percent of the total survey tracklines, or
just under two days of survey operations. If Southern Resident killer
whales are encountered during the survey in these areas and reduce
foraging effort in response, the relatively small amount of time of
altered behavior would not likely affect their overall foraging
ability. While Southern Resident killer whales may be encountered
outside of these areas of highest density, the likelihood is
significantly decreased and thus the likelihood of impacts to foraging
is decreased. Short-term impacts to foraging ability are not likely to
result in significant or lasting consequences for individual Southern
Resident killer whales or the population as a whole (Ayres et al.,
2012). Due to the mobile nature of the survey, animals would not be
exposed to elevated sounds for an extended period, and the proposed
critical habitat contains a large area of suitable habitat that would
allow Southern Resident killer whales to forage away from the survey.
Noren et al. (2016) reported that although resident killer whales
increase energy expenditure in response to vessel presence, the
increase is considered to be negligible.
No permanent hearing impairment (Level A harassment) is anticipated
or proposed to be authorized. Authorized takes of Southern Resident
killer whales would be limited to Level B harassment in the form of
behavioral disturbance. We anticipate 45 instances of Level B
[[Page 19632]]
harassment of Southern Resident killer whales, which we expect would
likely occur to a smaller subset of the population on only a few days.
Limited, short term behavioral disturbance of the nature expected here
would not be expected to result in fitness-level effects to individual
Southern Resident killer whales or the population as a whole.
Negligible Impact Conclusions
The proposed survey would be of short duration (37 days of seismic
operations), and the acoustic ``footprint'' of the proposed survey
would be small relative to the ranges of the marine mammals that would
potentially be affected. Sound levels would increase in the marine
environment in a relatively small area surrounding the vessel compared
to the range of the marine mammals within the proposed survey area.
Short term exposures to survey operations are not likely to
significantly disrupt marine mammal behavior, and the potential for
longer-term avoidance of important areas is limited.
The proposed mitigation measures are expected to reduce the number
and/or severity of takes by allowing for detection of marine mammals in
the vicinity of the vessel by visual and acoustic observers, and by
minimizing the severity of any potential exposures via shutdowns of the
airgun array. Based on previous monitoring reports for substantially
similar activities that have been previously authorized by NMFS, we
expect that the proposed mitigation will be effective in preventing, at
least to some extent, potential PTS in marine mammals that may
otherwise occur in the absence of the proposed mitigation (although all
authorized PTS has been accounted for in this analysis). Further, for
Southern Resident Killer Whales (as described above), additional
mitigation (e.g., second monitoring vessel, daylight only surveys) is
expected to increase the ability of PSOs to detect killer whales and
shut down the airgun array to reduce the instances and severity of
behavioral disturbance.
NMFS concludes that exposures to marine mammal species and stocks
due to L-DEO's proposed survey would result in only short-term
(temporary and short in duration) effects to individuals exposed, over
relatively small areas of the affected animals' ranges. Animals may
temporarily avoid the immediate area, but are not expected to
permanently abandon the area. Major shifts in habitat use,
distribution, or foraging success are not expected. NMFS does not
anticipate the proposed take estimates to impact annual rates of
recruitment or survival.
In summary and as described above, the following factors primarily
support our preliminary determination that the impacts resulting from
this activity are not expected to adversely affect the species or stock
through effects on annual rates of recruitment or survival:
No serious injury or mortality is anticipated or proposed
to be authorized;
The proposed activity is temporary and of relatively short
duration (37 days);
The anticipated impacts of the proposed activity on marine
mammals would primarily be temporary behavioral changes due to
avoidance of the area around the survey vessel;
The number of instances of potential PTS that may occur
are expected to be very small in number. Instances of potential PTS
that are incurred in marine mammals are expected to be of a low level,
due to constant movement of the vessel and of the marine mammals in the
area, and the nature of the survey design (not concentrated in areas of
high marine mammal concentration);
The availability of alternate areas of similar habitat
value for marine mammals to temporarily vacate the survey area during
the proposed survey to avoid exposure to sounds from the activity;
The potential adverse effects on fish or invertebrate
species that serve as prey species for marine mammals from the proposed
survey would be temporary and spatially limited, and impacts to marine
mammal foraging would be minimal; and
The proposed mitigation measures, including visual and
acoustic monitoring, shutdowns, and enhanced measures for areas of
biological importance (e.g., additional monitoring vessel, daylight
operations only) are expected to minimize potential impacts to marine
mammals (both amount and severity).
Additionally as described above for Southern Resident
killer whales specifically, anticipated impacts are limited to few days
of behavioral disturbance for any one individual and additional
mitigation (e.g., additional monitoring vessel, survey timing,
shutdowns) are expected to ensure that both the numbers and severity of
impacts to this stock are minimized, and, therefore the proposed
authorization of Southern Resident killer whale take is not expected
impact the fitness of any individuals, much less rates of recruitment
or survival.
Based on the analysis contained herein of the likely effects of the
specified activity on marine mammals and their habitat, and taking into
consideration the implementation of the proposed mitigation and
monitoring measures, NMFS preliminarily finds that the total marine
mammal take from the proposed activity will have a negligible impact on
all affected marine mammal species or stocks.
Small Numbers
As noted above, only small numbers of incidental take may be
authorized under Sections 101(a)(5)(A) and (D) of the MMPA for
specified activities other than military readiness activities. The MMPA
does not define small numbers and so, in practice, where estimated
numbers are available, NMFS compares the number of individuals taken to
the most appropriate estimation of abundance of the relevant species or
stock in our determination of whether an authorization is limited to
small numbers of marine mammals. Additionally, other qualitative
factors may be considered in the analysis, such as the temporal or
spatial scale of the activities.
There are several stocks for which the estimated instances of take
appear high when compared to the stock abundance (Table 10), including
the Southern Resident killer whale stock, the California/Oregon/
Washington Dall's porpoise stock, and the Northern California/Southern
Oregon and Northern Oregon/Washington Coast harbor porpoise stocks.
However, when other qualitative factors are used to inform an
assessment of the likely number of individual marine mammals taken, the
resulting numbers are appropriately considered small. We discuss these
in further detail below.
For all other stocks (aside from the four referenced above and
described below), the proposed take is less than one-third of the best
available stock abundance (recognizing that some of those takes may be
repeats of the same individual, thus rendering the actual percentage
even lower).
The expected take of Southern Resident killer whales, as a
proportion of the population abundance, is 57.33 percent, if all takes
are assumed to occur for unique individuals. In their NWTT Phase III
MSDD, the U.S. Navy created density estimates of Southern Resident
killer whales in their Offshore Study Area (U.S. Navy 2019). These
density estimates were developed with the assumption that all members
of the Southern Resident population were within the Study Area (i.e.,
no Southern Resident killer whales were assumed to be in the inland
waters of the Salish Sea). In reality, Southern Resident killer whales
have historically spent much of
[[Page 19633]]
their time in the Salish Sea from spring through fall to forage on
Fraser River Chinook salmon (Shields et al., 2017) and it is likely
that some or all of the population may be in inland waters during the
proposed survey. Therefore, we expect that there will be multiple takes
of a smaller number of individuals within the action area, such that
the number of individuals taken will be less than one-third of the
population.
The expected take of the California/Oregon/Washington stock of
Dall's porpoises, as a proportion of the population abundance, is 40.8
percent, if all takes are assumed to occur for unique individuals. In
reality, it is unlikely that all takes would occur to different
individuals. L-DEO's proposed survey area represents a small portion of
the stock's overall range (Caretta et al., 2017), and it is more likely
that there will be multiple takes of a smaller number of individuals
within the action area. In addition, Best et al. (2015) estimated the
population of Dall's porpoise in British Columbia to be 5,303 porpoises
based on systematic line-transect surveys of the Strait of Georgia,
Johnstone Strait, Queen Charlotte Sound, Hecate Strait, and Dixon
Entrance between 2004 and 2007. In consideration of the greater
abundance estimate combining the U.S. stock and animals in British
Columbia, and the likelihood of repeated takes of individuals, it is
unlikely that more than one-third of the stock would be exposed to the
seismic survey.
When assuming all takes of harbor porpoise would occur to either
the Northern Oregon/Washington Coast or Northern California/Southern
Oregon stocks, the take appears high relative to stock abundance (60.53
and 36.36 percent, respectively). In reality, takes will occur to both
stocks, and therefore, the number of takes of each stock will be much
lower. NMFS has no commonly used method to estimate the relative
proportion of each stock that would experience take, but here we
propose to apportion the takes between the two stocks based on the
stock boundary (Lincoln City, Oregon) and the approximate proportion of
the survey area that will occur on either side of the stock boundary.
North of Lincoln City, Oregon, harbor porpoises belong to the Northern
Oregon/Washington Coast stock, and south of Lincoln City, harbor
porpoises belong to the Northern California/Southern Oregon stock.
Approximately one-third of the proposed survey occurs south of Lincoln
City, therefore one-third of the total estimated takes are assumed to
be from the Northern California/Southern Oregon stock. The remaining
two-thirds of the estimated takes are assumed to be from the Northern
Oregon/Washington Coast stock. The estimated one-third of total takes
assigned to the Northern California/Southern Oregon stock (4,335 total
Level A and Level B takes) represent 12.12 percent of the stock
abundance, which NMFS considers to be small relative to the stock
abundance. In addition, the proposed survey area represents a small
portion of the stock's range, and it is likely that there will be
multiple takes of a small portion of individuals, further reducing the
number of individuals exposed. The estimated two-thirds of total takes
assigned to the Northern Oregon/Washington Coast stock (8,671 takes)
represent 40.35 percent of the stock abundance, which is still
considered high relative to stock abundance. However, the Northern
Oregon/Washington Coast stock abundance estimate does not include
animals in Canadian waters (Caretta et al., 2017). Best et al. (2015)
estimated a population abundance of 8,091 harbor porpoises in British
Columbia. The estimated takes of animals in the northern portion of the
survey area (north of Lincoln City) represent 29.32 percent of the
combined British Columbia and Northern Oregon/Washington Coast
abundance estimates, which NMFS considers to be small relative to
estimated abundance.
Based on the analysis contained herein of the proposed activity
(including the proposed mitigation and monitoring measures) and the
anticipated take of marine mammals, NMFS preliminarily finds that small
numbers of marine mammals will be taken relative to the population size
of the affected species or stocks.
Unmitigable Adverse Impact Analysis and Determination
There are no relevant subsistence uses of the affected marine
mammal stocks or species implicated by this action. Therefore, NMFS has
determined that the total taking of affected species or stocks would
not have an unmitigable adverse impact on the availability of such
species or stocks for taking for subsistence purposes.
Endangered Species Act (ESA)
Section 7(a)(2) of the Endangered Species Act of 1973 (ESA: 16
U.S.C. 1531 et seq.) requires that each Federal agency insure that any
action it authorizes, funds, or carries out is not likely to jeopardize
the continued existence of any endangered or threatened species or
result in the destruction or adverse modification of designated
critical habitat. To ensure ESA compliance for the issuance of IHAs,
NMFS consults internally whenever we propose to authorize take for
endangered or threatened species.
NMFS is proposing to authorize take of blue whales, fin whales, sei
whales, sperm whales, Central America DPS humpback whales, Mexico DPS
humpback whales, Southern Resident killer whale DPS, and Guadalupe fur
seal, which are listed under the ESA. The NMFS Office of Protected
Resources (OPR) Permits and Conservation Division has requested
initiation of Section 7 consultation with the NMFS OPR ESA Interagency
Cooperation Division for the issuance of this IHA. NMFS will conclude
the ESA consultation prior to reaching a determination regarding the
proposed issuance of the authorization.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
issue an IHA to L-DEO for conducting a marine geophysical survey in the
northeast Pacific Ocean beginning in June 2020, provided the previously
mentioned mitigation, monitoring, and reporting requirements are
incorporated. A draft of the proposed IHA can be found at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act.
Request for Public Comments
We request comment on our analyses, the proposed authorization, and
any other aspect of this Notice of Proposed IHA for the proposed
geophysical survey. We also request at this time comment on the
potential Renewal of this proposed IHA as described in the paragraph
below. Please include with your comments any supporting data or
literature citations to help inform decisions on the request for this
IHA or a subsequent Renewal IHA.
On a case-by-case basis, NMFS may issue a one-year Renewal IHA
following notice to the public providing an additional 15 days for
public comments when (1) up to another year of identical, or nearly
identical, activities as described in the Specified Activities section
of this notice is planned or (2) the activities as described in the
Specified Activities section of this notice would not be completed by
the time the IHA expires and a Renewal would allow for completion of
the activities beyond that described in the Dates and Duration section
of this notice, provided all of the following conditions are met:
A request for renewal is received no later than 60 days
prior to the needed Renewal IHA effective date (recognizing
[[Page 19634]]
that the Renewal IHA expiration date cannot extend beyond one year from
expiration of the initial IHA);
The request for renewal must include the following:
(1) An explanation that the activities to be conducted under the
requested Renewal IHA are identical to the activities analyzed under
the initial IHA, are a subset of the activities, or include changes so
minor (e.g., reduction in pile size) that the changes do not affect the
previous analyses, mitigation and monitoring requirements, or take
estimates (with the exception of reducing the type or amount of take);
and
(2) A preliminary monitoring report showing the results of the
required monitoring to date and an explanation showing that the
monitoring results do not indicate impacts of a scale or nature not
previously analyzed or authorized.
Upon review of the request for Renewal, the status of the
affected species or stocks, and any other pertinent information, NMFS
determines that there are no more than minor changes in the activities,
the mitigation and monitoring measures will remain the same and
appropriate, and the findings in the initial IHA remain valid.
Dated: April 1, 2020.
Donna S. Wieting,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2020-07289 Filed 4-6-20; 8:45 am]
BILLING CODE 3510-22-P