Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Marine Geophysical Survey in the Northeast Pacific Ocean, 19580-19634 [2020-07289]
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Federal Register / Vol. 85, No. 67 / Tuesday, April 7, 2020 / Notices
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
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.
AGENCY:
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 EastWest Highway, Silver Spring, MD 20910
and electronic comments should be sent
to ITP.Fowler@noaa.gov.
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 25megabyte 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
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SUMMARY:
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and will generally be posted online at
https://www.fisheries.noaa.gov/permit/
incidental-take-authorizations-undermarine-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-undermarine-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
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(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
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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 (in3) as
an acoustic source, acquiring return
signals using both a towed streamer as
well ocean bottom seismometers (OBSs)
and ocean bottom nodes (OBNs).
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.
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)
Dates and Duration
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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° N, ∼124–130° 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
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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.
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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 in3. The
array consists of 20 Bolt 1500LL airguns
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with volumes of 180 to 360 in3 and 16
Bolt 1900LLX airguns with volumes of
40 to 120 in3. 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
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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
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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 shortperiod 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 marginperpendicular 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
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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 onboard 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 downwarddirected 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).
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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/marinemammal-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/draftmarine-mammal-stock-assessmentreports). Where available, abundance
and status information is also presented
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for marine mammals in Canadian waters
in British Columbia.
TABLE 1—MARINE MAMMALS THAT COULD OCCUR IN THE SURVEY AREA
Common name
Scientific name
ESA/MMPA
status;
strategic
(Y/N) 1
Stock
Stock abundance
(CV, Nmin, most recent
abundance survey) 2
Annual
M/SI 3
PBR
Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)
Family Eschrichtiidae:
Gray whale ................
Eschrichtius robustus ......
Eastern North Pacific ......
-/-; N
26,960 (0.05, 25,849,
2016).
801 ....................
138.
Family Balaenopteridae
(rorquals):
Humpback whale ......
Megaptera novaeangliae
California/Oregon/Washington.
Central North Pacific .......
-/-; Y
2,900 (0.05, 2,784, 2014)
16.7 ...................
>42.1.
-/-; Y
83 ......................
25.
-/-; N
10,103 (0.30, 7,891,
2006).
636 (0.72, 369, 2014) .....
3.5 .....................
>1.3.
E/D; Y
E/D; Y
519 (0.4, 374, 2014) .......
9,029 (0.12, 8,127, 2014)
0.75 ...................
81 ......................
>0.2.
>2.0.
E/D; Y
E/D; Y
3,168 (0.26, 2,554, 2013)
1,496 (0.44, 1,050, 2014)
5.1 .....................
1.2 .....................
0.4.
>19.4.
Minke whale ..............
Sei whale ..................
Fin whale ...................
Balaenoptera
acutorostrata.
Balaenoptera borealis .....
Balaenoptera physalus ...
Blue whale ................
Balaenoptera musculus ..
California/Oregon/Washington.
Eastern North Pacific ......
California/Oregon/Washington.
Northeast Pacific .............
Eastern North Pacific ......
Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
Family Physeteridae:
Sperm whale .............
Physeter macrocephalus
California/Oregon/Washington.
E/D; Y
1,997 (0.57, 1,270, 2014)
2.5 .....................
0.4.
Family Kogiidae:
Pygmy sperm whale
Kogia breviceps ..............
California/Oregon/Washington.
California/Oregon/Washington.
-/-; N
4,111 (1.12, 1,924, 2014)
19 ......................
0.
-/-; N
Unknown (Unknown, Unknown, 2014).
Undetermined ....
0.
California/Oregon/Washington.
California/Oregon/Washington.
California/Oregon/Washington.
-/-; N
3,274 (0.67, 2,059, 2014)
21 ......................
<0.1.
-/-; N
2,697 (0.6, 1,633, 2014)
16 ......................
0
-/-; N
3,044 (0.54, 1,967, 2014)
20 ......................
0.1.
California/Oregon/Washington offshore.
California/Oregon/Washington.
California/Oregon/Washington.
California/Oregon/Washington.
British Columbia 4 ............
-/-; N
1,924 (0.54, 1,255, 2014)
11 ......................
>1.6.
-/-; N
238 ....................
>0.8.
8,393 .................
>40.
191 ....................
7.5.
Unknown ...........
Unknown.
179 ....................
3.8.
-/-; N
29,211 (0.2, 24,782,
2014).
969,861 (0.17, 839,325,
2014).
26,814 (0.28, 21,195,
2014).
22,160 (unknown,
16,522, 2008).
26,556 (0.44, 18,608,
2014).
6,336 (0.32, 4,817, 2014)
46 ......................
>3.7.
N/A
-/-; N
E/D; Y
-/-; N
-/-; N
-/-; N
N/A ..................................
300 (0.1, 276, 2012) .......
75 (N/A, 75, 2018) ..........
302 (N/A, 302, 2018) ......
243 (N/A, 243, 2009) ......
836 (0.79, 466, 2014) .....
N/A ....................
2.8 .....................
0.13 ...................
2.2 .....................
2.4 .....................
4.5 .....................
N/A.
0.
0.
0.2.
0.
1.2.
-/-; N
21,487 (0.44, 15,123,
2011).
35,769 (0.52, 23,749,
2011).
8,091 (unknown, 4,885,
2008).
25,750 (0.45, 17,954,
2014).
5,303 (unknown, 4,638,
2008).
151 ....................
>3.0.
475 ....................
>0.6.
Unknown ...........
Unknown.
172 ....................
0.3.
Unknown ...........
Unknown.
Dwarf sperm whale ...
Family Ziphiidae (beaked
whales):
Cuvier’s beaked
whale.
Baird’s beaked whale
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Blainville’s beaked
whale.
Hubbs’ beaked whale
Stejneger’s beaked
whale.
Family Delphinidae:
Bottlenose dolphin ....
Kogia sima ......................
Ziphius cavirostris ...........
Berardius bairdii ..............
Mesoplodon densirostris
Mesoplodon carlshubbi.
Mesoplodon stejnegeri.
Tursiops truncatus ..........
Striped dolphin ..........
Stenella coeruleoalba .....
Common dolphin .......
Delphinus delphis ............
Pacific white-sided
dolphin.
Lagenorhynchus
obliquidens.
Northern right whale
dolphin.
Risso’s dolphin ..........
Lissodelphis borealis .......
False killer whale ......
Killer whale ................
Pseudorca crassidens .....
Orcinus orca ....................
Short-finned pilot
whale.
Family Phocoenidae (porpoises):
Harbor porpoise ........
Dall’s porpoise ..........
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Grampus griseus .............
Globicephala
macrorhynchus.
Phocoena phocoena .......
Phocoenoides dalli ..........
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California/Oregon/Washington.
California/Oregon/Washington.
N/A ..................................
Offshore ..........................
Southern Resident ..........
Northern Resident ...........
West Coast Transient .....
California/Oregon/Washington.
Northern Oregon/Washington Coast.
Northern California/
Southern Oregon.
British Columbia 4 ............
California/Oregon/Washington.
British Columbia 4 ............
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-/-; N
-/-; N
N/A
-/-; N
-/-; N
N/A
-/-; N
N/A
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TABLE 1—MARINE MAMMALS THAT COULD OCCUR IN THE SURVEY AREA—Continued
Common name
Scientific name
ESA/MMPA
status;
strategic
(Y/N) 1
Stock
Stock abundance
(CV, Nmin, most recent
abundance survey) 2
Annual
M/SI 3
PBR
Order Carnivora—Superfamily Pinnipedia
Family Otariidae (eared
seals and sea lions):.
Northern fur seal .......
Callorhinus ursinus .........
Eastern Pacific ................
-/D; Y
California .........................
-/D; N
California sea lion .....
Zalophus californianus ....
U.S. .................................
-/-; N
Steller sea lion ..........
Eumetopias jubatus ........
Eastern U.S. ....................
-/-; N
British
Guadalupe fur seal ...
Family Phocidae (earless
seals):
Harbor seal ...............
Northern elephant
seal.
Columbia 4
............
N/A
Arctocephalus philippii
townsendi.
Mexico to California ........
T/D; Y
Phoca vitulina ..................
Oregon/Washington
Coastal.
British Columbia 4 ............
-/-; N
N/A
California Breeding .........
-/-; N
Mirounga angustirostris ...
620,660 (0.2, 525,333,
2016).
14,050 (N/A, 7,524,
2013).
257,606 (N/A, 233,515,
2014).
43,201 (see SAR,
43,201, 2017).
4,037 (unknown, 1,100,
2008).
34,187 (N/A, 31,019,
2013).
Unknown (Unknown, Unknown, 1999).
24,916 (Unknown,
19,666, 2008).
179,000 (N/A, 81,368,
2010).
11,295 ...............
399.
451 ....................
1.8.
14,011 ...............
>321.
2,592 .................
113.
Unknown ...........
Unknown.
1,062 .................
>3.8.
Undetermined ....
10.6.
Unknown ...........
Unknown.
4,882 .................
8.8.
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1 Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the
ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or
which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically
designated under the MMPA as depleted and as a strategic stock.
2 NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-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
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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
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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 midApril (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
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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° N to 52° 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.
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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-graywhale-unusual-mortality-event-alongwest-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
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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
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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°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 Pe´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
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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° 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° 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 midlatitude 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
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19587
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° 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.
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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° 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
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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). Broadscale 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
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(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 samesex 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 midNovember (Rice 1974). Off Oregon,
sperm whales are seen in every season
except winter (Green et al., 1992).
Sperm whales were sighted during
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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 (Sˆirovic´ 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 Pe´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
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2009). They are difficult to sight at sea,
perhaps because of their avoidance
reactions to ships and behavior changes
in relation to survey aircraft (Wu¨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 (Mun˜oz-Hincapie´ 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
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strandings and strands more commonly
than any other beaked whale (Heyning
1989). Its inconspicuous blows, deepdiving 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
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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 (Sˆirovic´
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 warmwater incursions (Reeves et al. 2002).
MacLeod et al. (2006) reported
stranding and sighting records in the
eastern Pacific ranging from 37.3° N to
41.5° 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
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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 (Sˆirovic´ 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 (BaumannPickering 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
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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° 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° N (Hamilton et al., 2009).
Bottlenose dolphins occur frequently off
the coast of California, and sightings
have been made as far north as 41° 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 warmwater 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°
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
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about 42°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° 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° N (Barlow 2016; SIO
n.d.). However, their abundance
decreases dramatically north of about
40° 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
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narrow distribution between 38° N and
47° N (Brownell et al., 1999). In the
eastern North Pacific Ocean, including
waters off Oregon, the Pacific whitesided 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 whitesided 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).
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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° N to 50° 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-offshore and
north-south movements in the eastern
North Pacific Ocean between California
and Oregon/Washington; the
movements are believed to be related to
oceanographic influences, particularly
water temperature and presumably prey
distribution and availability (Green et
al., 1993; Forney and Barlow 1998;
Buchanan et al., 2001). Green et al.
(1992, 1993) found that northern right
whale dolphins were most abundant off
Oregon/Washington during fall, less
abundant during spring and summer,
and absent during winter, when this
species presumably moves south to
warmer California waters (Green et al.,
1992, 1993; Forney 1994; Forney et al.,
1995; Buchanan et al., 2001; Barlow
2003).
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
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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° and 45°
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
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et al. (1992, 1993) reported most Risso’s
dolphin groups off Oregon between ∼45
and 47ßN. 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° 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
Nin˜o years (Norman et al. 2004). One
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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
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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
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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 km2 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 Pe´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 Pe´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 Pe´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 Pe´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
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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° S and as far north
as ∼50° 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 Nin˜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
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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 yearround, 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° 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
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<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 Pe´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
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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
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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/2015-2020guadalupe-fur-seal-unusual-mortalityevent-california.
Northern Fur Seal
The northern fur seal is endemic to
the North Pacific Ocean and occurs from
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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 Nin˜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
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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 yearround 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° 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° 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
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coasts of Haida Gwaii and Vancouver
Island, with concentrations over the
shelf and slope, especially on La
Pe´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.
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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° 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 earlyJuly (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).
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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; RaumSuryan 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).
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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 Solo´rzanoVelasco 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
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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 publicprivate 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/2013-2017california-sea-lion-unusual-mortalityevent-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° 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)
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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° 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 shortlived. 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
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19597
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
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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 lowfrequency 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 whales) ................................................................................................
Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales) .....................
High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, cephalorhynchid, Lagenorhynchus
cruciger & L. australis).
Phocid pinnipeds (PW) (underwater) (true seals) .............................................................................................
Otariid pinnipeds (OW) (underwater) (sea lions and fur seals) .........................................................................
7 Hz to 35 kHz.
150 Hz to 160 kHz.
275 Hz to 160 kHz.
50 Hz to 86 kHz.
60 Hz to 39 kHz.
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* 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
(Hemila¨ 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
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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
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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 (mPa)) 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 mPa) while the received
level is the SPL at the listener’s position
(referenced to 1 mPa).
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
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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 mPa2¥s)
represents the total energy contained
within a pulse and considers both
intensity and duration of exposure. Peak
sound pressure (also referred to as zeroto-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
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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.
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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 nonpulsed 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.
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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; Go¨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
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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 midfrequency 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
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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 peakpressure 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
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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).
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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
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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.;
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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 phasein 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
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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.
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Seismic pulses at average received
levels of 131 dB re 1 mPa2-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
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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
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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 fiveday 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
in3 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
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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-pituitaryadrenal 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
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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
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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 highfrequency 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
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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; Bro¨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.
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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; Melco´n et al.
2012; Azzara et al. 2013; Tyack and
Janik 2013; Luı´s et al. 2014; Sairanen
2014; Papale et al. 2015; Bittencourt et
al. 2016; Dahlheim and Castellote 2016;
Gospic´ 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
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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
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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., Wu¨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
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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
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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 × 10¥6;
95% CI = 0–5.5 × 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
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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
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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 highfrequency 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 midfrequency 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
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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 midfrequency 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
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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 surfaceducting 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
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energy pulses—such as those produced
by airguns—have greater potential to
cause damage to auditory structures
(though this is unlikely for midfrequency 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 antipredator 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
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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–
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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 midfrequency 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,
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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.
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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 bottomassociated 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 bottomfeeding fishes could be temporarily
displaced from feeding areas. Overall,
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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).
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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
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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#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 fullscale 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
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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 freeswimming 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
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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,
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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 habitatmediated 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.
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.
Estimated Take
Acoustic Thresholds
This section provides an estimate of
the number of incidental takes proposed
for authorization through this IHA,
NMFS uses acoustic thresholds that
identify the received level of
underwater sound above which exposed
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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 mPa (rms) for continuous (e.g.,
vibratory pile-driving, drilling) and
above 160 dB re 1 mPa (rms) for nonexplosive 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 mPa (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 nonimpulsive). 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-technicalguidance.
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TABLE 3—THRESHOLDS IDENTIFYING THE ONSET OF PERMANENT THRESHOLD SHIFT
PTS onset acoustic thresholds *
(received level)
Hearing Group
Impulsive
Low-Frequency (LF) Cetaceans ......................................
Mid-Frequency (MF) Cetaceans ......................................
High-Frequency (HF) Cetaceans .....................................
Phocid Pinnipeds (PW) (Underwater) .............................
Otariid Pinnipeds (OW) (Underwater) .............................
Cell
Cell
Cell
Cell
Cell
1:
3:
5:
7:
9:
Lpk,flat:
Lpk,flat:
Lpk,flat:
Lpk,flat:
Lpk,flat:
219
230
202
218
232
dB;
dB;
dB;
dB;
dB;
Non-impulsive
LE,LF,24h: 183 dB .........................
LE,MF,24h: 185 dB ........................
LE,HF,24h: 155 dB ........................
LE,PW,24h: 185 dB .......................
LE,OW,24h: 203 dB .......................
Cell
Cell
Cell
Cell
Cell
2: LE,LF,24h: 199 dB.
4: LE,MF,24h: 198 dB.
6: LE,HF,24h: 173 dB.
8: LE,PW,24h: 201 dB.
10: LE,OW,24h: 219 dB.
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* 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 μPa, and cumulative sound exposure level (LE) has a reference value of 1μPa2s.
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 in3 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
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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 seafloorreflected 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
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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-in3 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.
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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
Tow depth
(m)
Source and volume
36 airgun array, 6,600-in3 ............................................................................................................
a Distance
b Distance
12
Water depth
(m)
>1000
100–1000
<100
Level B
harassment
zone (m)
using L–DEO
model
a 6,733
b 9,468
b 12,650
based on L–DEO model results.
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-IN3 AIRGUN ARRAY
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Low frequency
cetaceans
(Lpk,flat: 219 dB;
LE,LF,24h: 183 dB)
Mid frequency
cetaceans
(Lpk,flat: 230 dB;
LE,MF,24h: 185 dB
High frequency
cetaceans
(Lpk,flat: 202 dB;
LE,HF,24h: 155 dB)
6,600 in3 airgun array (Peak
SPLflat) ......................................
6,600 in3 airgun array (SELcum) ...
252.06
232.98
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
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Phocid pinnipeds
(underwater)
(Lpk,flat: 218 dB;
LE,HF,24h: 185 dB)
253.24
233.10
252.25
232.84
Otariid pinnipeds
(underwater)
(Lpk,flat: 232 dB;
LE,HF,24h: 203 dB)
252.52
232.08
converted to pressures (mPa) 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
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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
SELcum .....................
Peak .........................
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
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MF cetaceans
426.9
38.9
HF cetaceans
0
13.6
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 nearfield 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:
with the condition that D >> l, and
where D is the distance, L is the longest
dimension of the array, and l is the
wavelength of the signal (Lurton, 2002).
Given that l can be defined by:
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:
and calculate D directly given a
particular frequency and known speed
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Phocids
1.3
268.3
Otariids
13.9
43.7
0
10.6
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/farfield 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 nearfield 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-in3 airgun array used in the
proposed survey has an approximate
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(6,600 in3).
Level A harassment zone (m)
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diagonal of 28.8 m, resulting in a nearfield 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 nearfield 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
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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
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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 markrecapture 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-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
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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 linetransect surveys conducted between
2007 and 2012. Separate density
estimates were provided for harbor
porpoises in Oregon south of 45° N and
Oregon/Washington north of 45° 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
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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 km2, so density within this
zone = 0.00015 whales/km2. 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 nonPCFG 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/km2 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;
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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/km2) 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
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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, shortfinned 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
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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
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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
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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)
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(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
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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 Nin˜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/
km2. 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
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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 hauledout 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 (#/km2)
khammond on DSKJM1Z7X2PROD with NOTICES2
Species
Shallow <100
m/category 1
LF Cetaceans:
Humpback whale .....................................
Blue whale ...............................................
Fin whale .................................................
Sei whale .................................................
Minke whale .............................................
Gray whale a ............................................
MF Cetaceans:
Sperm whale ............................................
Baird’s beaked whale ..............................
Small beaked whale ................................
Bottlenose dolphin ...................................
Striped dolphin .........................................
Short-beaked common dolphin ................
Pacific white-sided dolphin ......................
Northern right-whale dolphin ...................
Risso’s dolphin .........................................
False killer whale b ...................................
Killer whale (all stocks except Southern
Residents).
Short-finned pilot whale ...........................
HF Cetaceans:
Pygmy/dwarf sperm whale ......................
Dall’s porpoise .........................................
Harbor porpoise c .....................................
Otariids:
Northern fur seal d ....................................
Guadalupe fur seal e ................................
California sea lion f ...................................
Steller sea lion g .......................................
Phocids:
Northern elephant seal ............................
Harbor seal h ............................................
Intermediate
100–1000 m/
category 2
Reference
Deep >1000
m/category 3
0.0052405
0.0020235
0.0002016
0.0004000
0.0013000
0.0155000
0.0040200
0.0010518
0.0009306
0.0004000
0.0013000
0.0010000
0.0004830
0.0003576
0.0013810
0.0004000
0.0013000
N.A.
Becker et al. (2016).
Becker et al. (2016).
Becker et al. (2016).
U.S. Navy (2019).
U.S. Navy (2019).
U.S. Navy (2019).
0.0000586
0.0001142
0.0007878
0.0000007
0.0000000
0.0005075
0.0515230
0.0101779
0.0306137
N.A.
0.0009200
0.0001560
0.0002998
0.0013562
0.0000011
0.0000025
0.0010287
0.0948355
0.0435350
0.0308426
N.A.
0.0009200
0.0013023
0.0014680
0.0039516
0.0000108
0.0001332
0.0016437
0.0700595
0.0621242
0.0158850
N.A.
0.0009200
Becker
Becker
Becker
Becker
Becker
Becker
Becker
Becker
Becker
U.S. Navy (2019).
0.0002500
0.0002500
0.0002500
U.S. Navy (2019).
0.0016300
0.1450767
0.6240000
0.0016300
0.1610605
0.4670000
0.0016300
0.1131827
N.A.
U.S. Navy (2019).
Becker et al. (2016).
Forney et al. (2014).
0.0113247
0.0234772
0.0288000
0.3088864
0.1346441
0.0262595
0.0037000
0.0022224
0.0103424
N.A.
0.0065000
N.A.
U.S.
U.S.
U.S.
U.S.
0.0345997
0.3424000
0.0345997
N.A.
0.0345997
N.A.
U.S. Navy (2019).
U.S. Navy (2019).
et
et
et
et
et
et
et
et
et
Navy
Navy
Navy
Navy
al.
al.
al.
al.
al.
al.
al.
al.
al.
(2016).
(2016).
(2016).
(2016).
(2016).
(2016).
(2016).
(2016).
(2016).
(2019).
(2019).
(2019).
(2019).
a Category
1 = 0–10 km offshore, Category 2 = 10–47 km offshore (U.S. Navy 2019).
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° N, Category 2 = North of 45° 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).
b No
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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 (KM2) ESTIMATED TO BE ENSONIFIED TO LEVEL A AND LEVEL B HARASSMENT THRESHOLDS
Criteria
Level B Harassment:
Shallow <100 m .....................................................
Intermediate 100–1000 m .....................................
Deep >1000 m .......................................................
160 dB ..........................................................................
160 dB ..........................................................................
160 dB ..........................................................................
Level A Harassment
All depth zones ......................................................
a Based
b Based
Total
ensonified
area
(km2)
Relevant
isopleth
(m)
Survey zone
LF Cetacean .................................................................
MF Cetacean ................................................................
HF Cetacean ................................................................
Otariid ...........................................................................
Phocid ...........................................................................
a 12,650
b 6,733
11,433.80
24,200.75
50,924.56
Overall
86,559.11
426.9
13.6
268.3
10.6
43.7
5,605.34
179.85
3,532.92
140.19
577.63
b 9,468
on L–DEO model results.
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/km2)
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Pod
K/L ................................................................................................................................................................
J ...................................................................................................................................................................
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0.000000
0.000001—0.002803
0.002804—0.005615
0.005616—0.009366
0.009367—0.015185
0.000000
0.000001—0.001991
0.001992—0.005010
07APN2
Ensonified
area
(km2)
5,883
17,875
2,817
1,200
320
7,260
8,648
1,128
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Federal Register / Vol. 85, No. 67 / Tuesday, April 7, 2020 / Notices
TABLE 9—SOUTHERN RESIDENT KILLER WHALE DENSITIES AND CORRESPONDING ENSONIFIED AREAS—Continued
Ensonified
area
(km2)
Density
(animals/km2)
Pod
0.005011—0.009602
0.009603—0.018822
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.
236
20
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
Species
LF Cetaceans:
Humpback whale .........
Blue whale ...................
Fin whale .....................
Sei whale .....................
Minke whale .................
Gray whale ...................
MF Cetaceans:
Sperm whale ................
Baird’s beaked whale ..
Small beaked whale ....
Bottlenose dolphin .......
Striped dolphin .............
Short-beaked common
dolphin.
Pacific white-sided dolphin.
Northern right-whale
dolphin.
Risso’s dolphin .............
False killer whale .........
Killer whale ..................
Short-finned pilot whale
khammond on DSKJM1Z7X2PROD with NOTICES2
HF Cetaceans:
Pygmy/dwarf sperm
whale.
Dall’s porpoise .............
Harbor porpoise ...........
Otariid Seals:
Northern fur seal ..........
Guadalupe fur seal ......
California sea lion ........
Steller sea lion .............
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Stock
abundance
MMPA stock a
Central North Pacific ..........
California/Oregon/Washington.
Eastern North Pacific .........
California/Oregon/Washington.
Northeast Pacific ................
Eastern North Pacific .........
California/Oregon/Washington.
Eastern North Pacific .........
California/Oregon/Washington.
California/Oregon/Washington.
California/Oregon/Washington.
California/Oregon/Washington (offshore).
California/Oregon/Washington.
California/Oregon/Washington.
California/Oregon/Washington.
California/Oregon/Washington.
California/Oregon/Washington.
N.A. ....................................
Southern Resident .............
Northern Resident ..............
West Coast Transient .........
Offshore ..............................
California/Oregon/Washington.
California/Oregon/Washington.
California/Oregon/Washington.
Northern Oregon/Washington Coast.
Northern California/Southern Oregon.
Eastern Pacific ...................
California ............................
Mexico to California ...........
U.S. ....................................
Eastern U.S. .......................
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Estimated take
Level B
Total
proposed
take
Level A
Percent of
MMPA stock
10,103
2,900
172
10
b 182
1.80
6.28
1,647
9,029
63
89
4
6
67
95
4.06
1.06
3,168
27,197
25,000
32
105
2
7
34
112
3.01
0.13
0.45
26,960
90
2
92
0.34
26,300
71
0
71
0.27
2,697
83
0
83
3.08
6,318
244
0
c 244
3.86
1,924
1
0
d 13
0.68
29,211
7
0
d 46
0.16
969,861
114
0
d 179
0.02
26,814
6,452
0
6,452
24.06
26,556
4,333
0
4,333
16.32
6,336
1,906
0
1,906
30.08
N.A.
75
302
243
300
836
N.A.
43
27
26
26
24
N.A.
0
0
e5
N.A.
g 57.33
0
43
f 27
f 26
f 26
d 29
4,111
135
6
141
3.42
27,750
10,869
452
11,321
g 40.80
21,487
12,557
449
13,006
g 60.53
g 36.36
35,769
620,660
14,050
34,187
257,606
43,201
Fmt 4701
Sfmt 4703
8.94
10.70
8.67
3.47
4,604
0
4,604
2,387
1140
7281
0
0
0
2,387
1,140
7,281
E:\FR\FM\07APN2.SGM
07APN2
0.74
32.77
6.98
0.44
16.85
19622
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TABLE 10—ESTIMATED TAKING BY LEVEL A AND LEVEL B HARASSMENT, AND PERCENTAGE OF POPULATION—Continued
Species
Phocid Seals:
Northern elephant seal
Harbor seal ..................
Stock
abundance
MMPA stock a
California Breeding .............
Oregon/Washington Coast
Estimated take
Level B
179,000
h 24,732
Total
proposed
take
Level A
1995
6537
0
0
Percent of
MMPA stock
1,995
6,537
1.11
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 midfrequency cetaceans and pinnipeds by
Level A harassment than the number
proposed by L–DEO (see Appendix B in
L–DEO’s IHA application).
khammond on DSKJM1Z7X2PROD with NOTICES2
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
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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.
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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 preclearance monitoring (i.e., before rampup 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.
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07APN2
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Federal Register / Vol. 85, No. 67 / Tuesday, April 7, 2020 / Notices
Visual monitoring of the buffer zone is
intended to (1) provide additional
protection to naı¨ve marine mammals
that may be in the area during preclearance, 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 atsea 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° 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
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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
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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
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• 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.
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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
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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 preclearance 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
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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), rampup is required, but if the shutdown
period was brief and constant
observation was maintained, preclearance watch of 30 minutes is not
required; and
• Testing of the acoustic source
involving all elements requires rampup. 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
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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 midfrequency 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).
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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 midfrequency 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:
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• 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
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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).
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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 6.1m 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
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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;
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• 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 pedestalmounted 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 thirdparty 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;
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• 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
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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, rampup, shutdown, testing, shooting, rampup 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;
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19627
• 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
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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;
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• 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 restranding, additional coordination with
the IHA-holder will be required to
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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., populationlevel 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
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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 Canadian
territorial waters)
Species
Estimated take
(Canadian
territorial waters)
Total estimated take
Level B
Level A
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LF Cetaceans:
Humpback whale ..............................
Blue whale ........................................
Fin whale ..........................................
Sei whale ..........................................
Minke whale ......................................
Gray whale ........................................
MF Cetaceans:
Sperm whale .....................................
Baird’s beaked whale .......................
Small beaked whale .........................
Bottlenose dolphin ............................
Striped dolphin ..................................
Short-beaked common dolphin .........
Pacific white-sided dolphin ...............
Northern right-whale dolphin ............
Risso’s dolphin ..................................
False killer whale ..............................
Killer whale (Southern Resident) ......
Killer whale (Northern Resident) ......
Killer whale (West Coast Transient)
Killer whale (Offshore) ......................
Short-finned pilot whale ....................
HF Cetaceans:
Pygmy/dwarf sperm whale ...............
Dall’s porpoise ..................................
Harbor porpoise ................................
Otariid Seals:
Northern fur seal ...............................
Guadalupe fur seal ...........................
California sea lion .............................
Steller sea lion ..................................
Phocid Seals:
Northern elephant seal .....................
Harbor seal .......................................
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, nonauditory physical effects, stranding, and
vessel strike are not expected to occur.
VerDate Sep<11>2014
18:28 Apr 06, 2020
Jkt 250001
Level B
Level A
172
63
89
32
105
90
10
4
6
2
7
2
23
8
2
2
6
24
1
0
0
0
0
1
195
71
91
34
111
114
11
4
6
2
7
3
71
83
244
13
7
179
6,452
4,333
1,906
5
43
27
26
26
29
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
5
0
0
4
354
123
155
5
2
2
2
2
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
72
84
249
13
7
183
6,806
4,457
2,062
10
45
29
28
28
30
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
135
10,869
12,557
6
452
449
8
746
2,622
0
24
86
143
11,615
15,179
6
476
535
4,604
2,387
1,140
7,281
0
0
0
0
58
122
147
1,342
0
0
0
0
4,662
2,509
1,287
8,623
0
0
0
0
1,995
6,537
0
0
176
1,744
0
0
2,171
8,281
0
0
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
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Level B
Frm 00051
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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
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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 longterm 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
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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 highdensity 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
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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
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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
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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
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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 200m 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
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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.
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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
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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
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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 linetransect 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
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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
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19633
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-undermarine-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
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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,
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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
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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
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]]>Agencies
[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
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National Oceanic and Atmospheric Administration
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Takes of Marine Mammals Incidental to Specified Activities; Taking
Marine Mammals Incidental to a Marine Geophysical Survey in the
Northeast Pacific Ocean; Notice
Federal Register / Vol. 85, No. 67 / Tuesday, April 7, 2020 /
Notices
[[Page 19580]]
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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.
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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.
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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
