[Federal Register Volume 90, Number 137 (Monday, July 21, 2025)]
[Notices]
[Pages 34212-34239]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-13687]
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Notices
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains documents other than rules
or proposed rules that are applicable to the public. Notices of hearings
and investigations, committee meetings, agency decisions and rulings,
delegations of authority, filing of petitions and applications and agency
statements of organization and functions are examples of documents
appearing in this section.
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Federal Register / Vol. 90 , No. 137 / Monday, July 21, 2025 /
Notices
[[Page 34212]]
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XE933]
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to a Marine Geophysical Surveys in the
Cascadia Subduction Zone 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 Scripps Institution of
Oceanography (SIO) for authorization to take marine mammals incidental
to a geophysical survey in the Cascadia Subduction Zone of the
Northeast Pacific Ocean. Pursuant to the Marine Mammal Protection Act
(MMPA), NMFS is requesting comments on its proposal to issue an
incidental harassment authorization (IHA) to incidentally take marine
mammals during the specified activities. NMFS is also requesting
comments on a possible one-time, 1-year renewal that could be issued
under certain circumstances and if all requirements are met, as
described in Request for Public Comments at the end of this notice.
NMFS will consider public comments prior to making any final decision
on the issuance of the requested MMPA authorization and agency
responses will be summarized in the final notice of our decision.
DATES: Comments and information must be received no later than August
20, 2025.
ADDRESSES: Comments should be addressed to Permits and Conservation
Division Office of Protected Resources, National Marine Fisheries
Service and should be submitted via email to [email protected].
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/national/marine-mammal-protection/incidental-take-authorizations-research-and-other-activities. In case of problems accessing these documents, please call
the contact listed below.
Instructions: NMFS is not responsible for comments sent by any
other method, to any other address or individual, or received after the
end of the comment period. Comments, including all attachments, must
not exceed a 25-megabyte file size. All comments received are a part of
the public record and will generally be posted online at 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: Kate Fleming, Office of Protected
Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Background
The MMPA prohibits the ``take'' of marine mammals, with certain
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to
allow, upon request, the incidental, but not intentional, taking of
small numbers of marine mammals by U.S. citizens who engage in a
specified activity (other than commercial fishing) within a specified
geographical region if certain findings are made and either regulations
are proposed or, if the taking is limited to harassment, a notice of a
proposed IHA is provided to the public for review.
Authorization for incidental takings shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s) and will not have an unmitigable adverse impact on the
availability of the species or stock(s) for taking for subsistence uses
(where relevant). Further, NMFS must prescribe the permissible methods
of taking and other ``means of effecting the least practicable adverse
impact'' on the affected species or stocks and their habitat, paying
particular attention to rookeries, mating grounds, and areas of similar
significance, and on the availability of the species or stocks for
taking for certain subsistence uses (referred to in shorthand as
``mitigation''); and requirements pertaining to the monitoring and
reporting of the takings. The definitions of all applicable MMPA
statutory terms used above are included in the relevant sections below
and can be found in section 3 of the MMPA (16 U.S.C. 1362) and NMFS
regulations at 50 CFR 216.103.
National Environmental Policy Act
To comply with the National Environmental Policy Act of 1969 (NEPA;
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A,
NMFS must review our proposed action (i.e., the issuance of an IHA)
with respect to potential impacts on the human environment.
This action is consistent with categories of activities identified
in Categorical Exclusion B4 (IHAs with no anticipated serious injury or
mortality) of the Companion Manual for NAO 216-6A, which do not
individually or cumulatively have the potential for significant impacts
on the quality of the human environment and for which we have not
identified any extraordinary circumstances that would preclude this
categorical exclusion. Accordingly, NMFS has preliminarily determined
that the issuance of the proposed IHA qualifies to be categorically
excluded from further NEPA review.
Summary of Request
On February 25, 2025, NMFS received a request from SIO for an IHA
to take marine mammals incidental to a geophysical survey in the
Cascadia Subduction Zone of the Northeast Pacific ocean. The
application was deemed adequate and complete on May 13, 2025. NMFS
proposes to authorize take of 24 species of marine mammals, by Level B
harassment only. Neither SIO nor NMFS expect serious injury or
mortality to result from this activity and, therefore, an IHA is
appropriate.
[[Page 34213]]
Description of Proposed Activity
Overview
Researchers from the New Mexico Institute of Mining and Technology
(New Mexico Tech) and Oregon State University, with funding from the
U.S. National Science Foundation (NSF), propose to conduct a low-energy
seismic survey, using airguns as the acoustic source, aboard the
Research Vessel (R/V) Sally Ride, which is owned by the U.S. Navy and
operated by the IHA applicant, SIO. The proposed survey would occur in
September 2025 within the Cascadia Subduction Zone of the Northeast
Pacific Ocean in the Exclusive Economic Zone (EEZ) of the United
States, in water depths ranging from 2000 to 3500 m. To complete this
2-dimensional (2-D) multi-channel seismic (MCS) reflection survey, the
R/V Sally Ride would tow a cluster of two 45 cubic inch (in\3\)
Generator-Injector (GI)-airguns spaced 2 m apart, with a total
discharge volume of 90 in\3\. The acoustic source would be towed at a
depth of 4 m along the survey lines, while the receiver is towed in a
1000 m long solid-state hydrophone streamer. The airguns would fire at
a shot interval of 12.5 to 15 m. Approximately 444 km of seismic data
acquisition is planned. Airguns would introduce underwater sound into
the marine environment and may result in incidental take of marine
mammals.
The proposed study would acquire high-resolution 2-D seismic data
to understand the thermal effects of fluid circulation in oceanic crust
entering the Cascadia Subduction Zone. The seismic data would be used
to define the basement topography and overlying sedimentary structure.
This information is needed to both plan the heat flow survey and
interpret the heat flow results. The survey builds upon research
conducted by Lamont-Doherty Earth Observatory (L-DEO) pursuant to a
2022 IHA (87 FR 47985), that was prematurely halted because of a ship
malfunction, and research conducted in 2024 in which heat flow data (no
seismic data acquisition) was collected. Information about the previous
survey is available at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-research-and-other-activities.
Dates and Duration
The proposed IHA would be valid for the statutory maximum of one
year from the date of effectiveness. It will become effective upon
written notification from the applicant to NMFS, but not beginning
later than one year from the date of issuance or extending beyond two
years from the date of issuance. The Sally Ride is proposed to depart
from Newport, Oregon on September 6, 2025 and return to Newport on
September 8, 2025. The cruise is expected to consist of 3 days at sea,
including 2 days of seismic operations and 1 day of transit. However,
unforeseen circumstances, such as inclemenet weather, equipment
maintenance and/or repair, transit to and from ports to survey
locations, could delay operations.
Specific Geographic Region
The proposed survey would occur within an area bounded by the
following approximate coordinates: 45[deg]N/127[deg]W, 47[deg]N/
127[deg]W, 47[deg]N/126[deg]W, and 45[deg]N/125.5[deg]W, off the coasts
of Oregon and Washington in the Northeast Pacific Ocean in the U.S.
EEZ, in water depths ranging from 2000 m to 3,500 m. The region where
the survey is proposed to occur is depicted in figure 1. Representative
survey tracklines are shown; however, some deviation in actual
tracklines, including the order of survey operations, could be
necessary for reasons such as science drivers, poor data quality,
inclement weather, or research vessel and/or equipment experiencing
mechanical issues. Therefore, for the proposed survey, the tracklines
could occur anywhere within the coordinates noted above and depicted
below in figure 1. The Sally Ride would likely leave from and return to
Newport, Oregon.
BILLING CODE 3510-22-P
[[Page 34214]]
[GRAPHIC] [TIFF OMITTED] TN21JY25.001
[[Page 34215]]
BILLING CODE 3510-22-C
Detailed Description of the Specified Activity
The procedures to be used for the proposed survey would be similar
to those used during previous seismic surveys and would use
conventional seismic methodology. The survey would involve one source
vessel, R/V Sally Ride, which is owned by the U.S. Navy and operated by
SIO. During the low-energy 2D MCS seismic reflection survey Sally Ride
would tow two GI airguns with a total discharge volume of 90 in\3\. The
two inline airguns would be spaced 2 m apart. The receiving system
would consist of a 1 km long solid-state hydrophone streamer. As the
airguns are towed along the survey lines, the hydrophone streamer would
transfer the data to the on-board processing system. Approximately 444
km of seismic data acquisition are planned. The survey would take place
in water depths ranging from approximately 2,000 m to 3,500 m.
In addition to the operations of the airguns, the ocean floor would
be mapped continuously with Kongsberg EM124 (12 kilohertz (kHz)) and
Kongsberg EM712 (40-100 kHz) multibeam echosounders, and a Kongsberg
BSP29 sub-bottom profiler (SBP). All planned geophysical data
acquisition would be conducted by SIO with on-board assistance by
scientists who have proposed the studies. The vessel would be self-
contained, and the crew would live aboard the vessel. A Teledyne RDI
Ocean Surveyor ADCP or Teledyne RDI 300 kHz Workhorse II Mariner
surveyor acoustic Doppler current profiler (ADCP) would be used to
measure water current velocities. Take of marine mammals is not
expected to occur incidental to the use of multibeam echosounder, SBP,
ADCP, operations whether or not the airguns are operating
simultaneously with the other sources. Given their characteristics
(e.g., narrow downward-directed beam), marine mammals would experience
no more than one or two brief ping exposures, if any exposure were to
occur. NMFS does not expect that the use of these sources is likely to
cause take of marine mammals.
Proposed mitigation, monitoring, and reporting measures are
described in detail later in this document (please see Proposed
Mitigation and Proposed Monitoring and Reporting).
Description of Marine Mammals in the Area of Specified Activities
Sections 3 and 4 of the application summarize available information
regarding status and trends, distribution and habitat preferences, and
behavior and life history of the potentially affected species. NMFS
fully considered all of this information, and we refer the reader to
these descriptions, instead of reprinting the information. Additional
information regarding population trends and threats may be found in
NMFS' 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' website (https://www.fisheries.noaa.gov/find-species).
Table 1 lists all species or stocks for which take is expected and
proposed to be authorized for this activity and summarizes information
related to the population or stock, including regulatory status under
the MMPA and Endangered Species Act (ESA) and potential biological
removal (PBR), where known. PBR is defined by the MMPA as the maximum
number of animals, not including natural mortalities, that may be
removed from a marine mammal stock while allowing that stock to reach
or maintain its optimum sustainable population (as described in NMFS'
SARs). While no serious injury or mortality is anticipated or proposed
to be authorized here, PBR and annual serious injury and mortality (M/
SI) from anthropogenic sources are included here as gross indicators of
the status of the species or stocks 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' 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' U.S. Pacific and Alaska SARs. All values presented in table 1 are
the most recent abundance estimates available at the time of
publication (including from the draft 2024 SARs) and are available
online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments.
Table 1--Species \1\ With Estimated Take From the Specified Activities
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ESA/MMPA status; Stock abundance (CV,
Common name Scientific name Stock Strategic (Y/N) Nmin, most recent PBR Annual M/
\2\ abundance survey) \3\ SI \4\
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Order Artiodactyla--Cetacea--Mysticeti (baleen whales)
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Family Balaenopteridae (rorquals):
Blue whale...................... Balaenoptera musculus.. Eastern N Pacific...... E, D, Y 1,898 (0.085, 1,767, 4.1 >=18.6
2018).
Fin whale....................... Balaenoptera physalus CA/OR/WA............... E, D, Y 11,065 (0.405, 7,970, 80 >=43.4
velifera. 2018).
Humpback whale.................. Megaptera novaeangliae. Central America/ E, D, Y 1,496 (0.171, 1,284, 3.5 14.9
Southern Mexico--CA/OR/ 2021).
WA.
Mainland Mexico--CA/OR/ T, D, Y 3,477 (0.101, 3,185, 43 22
WA. 2018).
Hawai[revaps]i......... -, -, N 11,278 (0.56, 7,265, 127 27.09
2020).
Minke whale..................... Balaenoptera CA/OR/WA............... -, -, N 915 (0.792, 509, 2018) 4.1 >=0.19
acutorostrata.
Sei whale....................... Balaenoptera borealis.. Eastern N Pacific...... E, D, Y 864 (0.40, 625, 2014). 1.25 UNK
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Odontoceti (toothed whales, dolphins, and porpoises)
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Family Physeteridae:
Sperm whale..................... Physeter macrocephalus. CA/OR/WA............... E, D, Y 2,606 (0.135, 2,011, 4 0.52
2018).
Family Kogiidae:
Dwarf sperm whale............... Kogia sima............. CA/OR/WA............... -, -, N UNK (UNK, UNK, 2014).. UND 0
Pygmy sperm whale............... Kogia breviceps........ CA/OR/WA............... -, -, N 4,111 (1.12, 1,924, 19.2 0
2014).
[[Page 34216]]
Family Ziphiidae (beaked whales):
Baird's beaked whale............ Berardius bairdii...... CA/OR/WA............... -, -, N 1,363 (0.53, 894, 8.9 >=0.2
2018).
Cuvier's Beaked Whale........... Ziphius cavirostris.... CA/OR/WA............... -, -, N 5,454 (0.27, 4,214, 42 <0.1
2016).
Mesoplodon beaked Whales........ Mesoplodon spp......... CA/OR/WA............... -, -, N 3,044 (0.54, 1,967, 20 0.1
2014).
Family Delphinidae:
Killer whale.................... Orcinus orca........... Eastern North Pacific -, -, N 300 (0.1, 276, 2012).. 2.8 0
Offshore.
West Coast Transient... -, -, N 349 (N/A, 349, 2018).. 3.5 0.4
Northern right whale dolphin.... Lissodelphis borealis.. CA/OR/WA............... -, -, N 29,285 (0.72, 17,024, 163 >=6.6
2018).
Pacific white-sided dolphin..... Lagenorhynchus CA/OR/WA............... -, -, N 34,999 (0.222, 29,090, 279 7
obliquidens. 2018).
Risso's dolphin................. Grampus griseus........ CA/OR/WA............... -, -, N 6,336 (0.32, 4,817, 46 >=3.7
2014).
Short beaked common dolphin..... Delphinus delphis...... CA/OR/WA............... -, -, N 1,056,308 (0.21, 8,889 >=30.5
888,971, 2018).
Family Phocoenidae (porpoises):
Dall's porpoise................. Phocoenoides dalli..... CA/OR/WA............... -, -, N 16,498 (0.61, 10,286, 99 >=0.66
2018).
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Order Carnivora--Pinnipedia
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Family Otariidae (eared seals and
sea lions):
California sea lion............. Zalophus californianus. U.S.................... -, -, N 257,606 (N/A, 233,515, 14,011 >321
2014).
Guadalupe fur seal.............. Arctocephalus townsendi Mexico................. T, D, Y 63,850 (N/A, 57,199, 1,959 >=10.0
2013).
Northern fur seal............... Callorhinus ursinus.... Eastern Pacific........ -, D, Y 626,618 (0.2, 530,376, 11,403 373
2019).
CA..................... -, -, N 19,634 (N/A, 8,788, 527 1.2
2022).
Steller sea lion................ Eumetopias jubatus..... Eastern................ -, -, N 36,308 (N/A, 36,308, 2,178 93.2
2022).
Family Phocidae (earless seals):
Northern elephant seal.......... Mirounga angustirostris California Breeding.... -, -, N 194,907 (N/A, 88,794, 5,328 11.2
2023).
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\1\ Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy
(https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/).
\2\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed
under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality
exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\3\ NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.
\4\ 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, vessel strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A
CV associated with estimated mortality due to commercial fisheries is presented in some cases.
As indicated above, all 24 species (with 26 managed stocks) in
table 1 temporally and spatially co-occur with the activity to the
degree that take is reasonably likely to occur. All species that could
potentially occur in the proposed survey areas are included in table 2
of the IHA application.
Some species could potentially occur in the proposed survey area
but are not likely to be encountered due to the rarity of their
occurrence in conjunction with the brief survey duration. These species
include North Pacific right whale (Eubalaena japonica), short-finned
pilot whale (Globicephala macrorhynchus), bottlenose dolphin (Tursiops
truncates), false killer whale (Pseudorca crassidens), and striped
dolphin (Stenella coeruleoalba). Therefore they are not discussed
further beyond the explanation provided below.
Based on the very low abundance of North Pacific right whale, its
rarity off the coasts of Washington and Oregon in recent decades, and
the likelihood that animals would be feeding in the Bering Sea and Gulf
of Alaska at the time of the survey, it is unlikely that a North
Pacific right whale would be encountered in the proposed survey area
during the period of operations.
Although zero estimated Level B harassment exposures were
calculated for short-finned pilot whales, bottlenose dolphins, false
killer whales, and striped dolphins, SIO requested authorization for
the incidental harassment of these species. However, all these species
have rare historical occurrence in the project area, and short-finned
pilot whales prefer warmer tropical waters, bottlenose dolphins tend to
stay in coastal waters in lower latitudes, and false killer whales are
rarely observed north of Baja, California. The likelihood that SIO
would encounter these species in the proposed survey area is
discountable and NMFS is not proposing to authorize take of these
species.
In addition to what is included in sections 3 and 4 of the IHA
application, and NMFS' website, further detail informing the regional
occurrence for select species of particular or unique vulnerability
(i.e., information regarding ESA listed or MMPA depleted species) is
provided below.
Blue Whale
Based on modeling of the dynamic topography of the region, blue
whales could occur in relatively high densities off Oregon during
summer and fall (Pardo et al., 2015: Hazen et al., 2017). Recent
phenology analysis of marine mammal sightings revealed a peak of blue
whale density over the Oregon continental shelf in September, and their
sighting rates in the region have increased over the past three decades
as a response to environmental changes influencing prey availability
shifting their range northward (Derville et al., 2022). Densities along
the U.S. west coast, including Oregon, were predicted
[[Page 34217]]
to be highest in shelf waters, with lower densities in deeper offshore
areas (Becker et al., 2012; Calambokidis et al., 2015). Blue whales
have been detected acoustically off Oregon (McDonald et al., 1995;
Stafford et al., 1998; Von Saunder and Barlow 1999).
Long-term passive acoustic monitoring of three shelf, slope, and
canyon sites off Washington found the highest number of call detections
on the slope and the lowest at the canyon site (Rice et al., 2021).
Call rates were highest during fall and winter, but vocalizations were
detected at all sites throughout the year (Rice et al., 2021).
One sighting (four animals) was made during the June-July 2021
Lamont-Doherty Earth Observatory (L-DEO) Cascadia survey (RPS 2022a),
but no sightings were made during L-DEO's August 2022 Cascadia survey
(RPS 2023), or LDEO's April 2022 Cascadia survey (RPS 2022b).
Although rare, blue whales could be encountered in the survey area.
Fin Whale
Information about the seasonal distribution of fin whales in the
North Pacific has been obtained from the detection of fin whale calls
by bottom-mounted, offshore hydrophone arrays along the U.S. Pacific
coast, in the central North Pacific, and in the western Aleutian
Islands (Moore et al., 1998, 2006; Watkins et al., 2000a,b; Stafford et
al., 2007, 2009). Fin whale calls are recorded in the North Pacific
year-round (e.g., Moore et al., 2006; Stafford et al., 2007, 2009;
Edwards et al., 2015). In the central North Pacific, the Gulf of
Alaska, and Aleutian Islands, call rates peak during fall and winter
(Moore et al., 1998, 2006; Watkins et al., 2000a,b; Stafford et al.,
2009).
Fin whales are routinely sighted during surveys off Oregon and
Washington (Barlow and Forney 2007; Barlow 2010, 2016; Adams et al.,
2014; Calambokidis et al., 2015; Edwards et al., 2015), including in
coastal as well as offshore waters. They have also been detected
acoustically in those waters during June-August (Edwards et al., 2015).
During long-term passive acoustic monitoring at three sites (shelf,
slope, canyon) off northwestern Washington during 2004-2013, the
highest number of call detections were recorded at the canyon site;
most detections were made during fall and winter, but calls were
detected throughout the year at all three sites (Rice et al., 2021).
Fin whales are likely to be encountered in the proposed survey area.
Four fin whale sightings (eight individuals) were made during the
August 2022 L-DEO Cascadia Survey (RPS 2023). Seventeen sightings (33
animals) were made during the June-July 2021 L-DEO Cascadia survey (RPS
2022a), and 1 sighting (3 animals) was made during the April 2022 L-DEO
survey off Oregon (RPS 2022b).
Fin whale could be encountered in the survey area.
Humpback Whale
The humpback whale is the most common species of large cetacean
reported off the coasts of Oregon and Washington from May-November
(Calambokidis et al., 2000, 2004; Henry et al., 2020). The highest
numbers have been reported off Oregon during May and June and off
Washington during July-September (Calambokidis et al., 2000;
Calambokidis and Barlow 2004). Based on data from 2016-2021, Derville
et al., (2022) reported that the peak in humpback occurrence on the
shelf of Oregon occurs during August. Humpbacks occur primarily over
the continental shelf and slope during the summer, with few reported in
offshore pelagic waters (Calambokidis and Barlow 2004, 2015; Becker et
al., 2012; Barlow 2016; Derville et al., 2022).
During long-term (2004-2013) passive acoustic monitoring at three
sites on the shelf, slope, and a canyon off northwestern Washington,
the highest number of call detections were recorded at the canyon site
and lowest at the slope site (Rice et al., 2021). Most detections
occurred during fall and winter, but calls were also detected at all
sites during August and September (Rice et al., 2021). Similarly,
monitoring with acoustic recorders deployed at different locations off
Washington during 2008-2013 showed that call rates were highest during
fall and winter (Emmons et al., 2020).
Seven sightings (11 individuals) were reported during the L-DEO
Cascadia survey in August 2022 (RPS 2023). Eighty-three sightings
totaling 210 humpbacks were made during the June-July 2021 L-DEO
Cascadia Subduction Zone seismic survey off the coast of the Pacific
Northwest (including Washington, Oregon, and southern British Columbia
(B.C)) (RPS 2022a), and 11 sightings of 24 animals were made during the
April 2022 L-DEO survey off Oregon (RPS 2022b).
Humpback whale could be encountered in the survey area.
The 2022 Alaska and Pacific SARs described a revised stock
structure for humpback whales, which modifies the previous stocks
designated under the MMPA to align more closely with the ESA-designated
distinct population segments (DPSs) (Caretta et al., 2023; Young et
al., 2023). Specifically, the three previous North Pacific humpback
whale stocks (the CA/OR/WA stock and the Central and Western North
Pacific stocks) were replaced by five stocks, largely corresponding
with the ESA-designated DPSs. These include Western North Pacific and
Hawaii stocks and a Central America/Southern Mexico-CA/OR/WA stock
(which corresponds with the Central America DPS). The remaining two
stocks, corresponding to the Mexico DPS, are the Mainland Mexico-CA/OR/
WA and Mexico-North Pacific stocks (Caretta et al.; Young et al.,
2023). The former stock is expected to occur along the west coast from
California to southern British Columbia, while the latter stock may
occur across the Pacific, from northern British Columbia through the
Gulf of Alaska and Aleutian Islands/Bering Sea region to Russia.
Within the project area, three humpback whale stocks may occur: The
Central America/Southern Mexico--CA-OR-WA stock, which corresponds with
the Central America DPS (found all along the west coast, but most
common off California and Oregon; the Central America DPS is listed as
endangered under the ESA); the Mainland Mexico--CA-OR-WA stock, which
corresponds with the Mexico DPS (found all along the west coast; the
Mexico DPS is listed as threatened under the ESA), and the Hawaii
stock, which corresponds with the Hawaii DPS (found predominately off
Washington and southern British Columbia; the Hawaii DPS is not listed
under the ESA). According to Wade (2021), the probability that whales
encountered in Oregon and California waters are from a given DPS are as
follows: Central America DPS (42 percent); Mexico DPS (58 percent);
Hawaii DPS (0 percent). The probability that humpback whales
encountered in Washington and British Columbia waters are as follows:
Central America DPS (6 percent); Mexico DPS (25 percent); Hawaii DPS
(69 percent). Wade (2021) notes that the majority of humpback whales
that may be found off of Washington are likely moving north of the
United States border and feeding primarily off of southern British
Columbia.
Sei Whale
Sei whales are rare in the waters off Oregon and Washington
(Brueggeman et al., 1990; Barlow 1994, 1997). Less than 20 confirmed
sightings were reported in that region during extensive surveys during
1991-2018 (Hill and Barlow 1992; Carretta and Forney 1993; Mangels and
Gerrodette 1994; Von Saunder and Barlow 1999; Barlow 2003,
[[Page 34218]]
2010, 2014; Forney 2007; Carretta et al., 2024).
A total of two sightings (four individuals) were reported during L-
DEO Cascadia Survey (RPS 2023). No sei whales were sighted during the
June-July 2021 L-DEO Cascadia survey (RPS 2022a), or the April 2022 L-
DEO survey off Oregon (RPS 2022b.
Sei whales could be encountered during the proposed survey,
although this species is considered rare in these waters.
Sperm Whale
Sperm whales are distributed widely across the North Pacific (Rice
1989). Sperm whales were sighted during surveys off Oregon in October
2011 and off Washington in June 2011 (Adams et al., 2014). Carretta et
al. (2024) also reported numerous sperm whale sightings off Oregon and
Washington during shipboard surveys. Sperm whales were detected
acoustically in waters off Oregon and Washington in August 2016 during
the NMFS Southwest Fisheries Science Center (SWFSC) Passive Acoustics
Survey of Cetacean Abundance Levels (PASCAL) study using drifting
acoustic recorders (Keating et al., 2018). Oleson et al. (2009) noted a
significant diel pattern in the occurrence of sperm whale clicks at
offshore and inshore monitoring locations off Washington, whereby
clicks were more commonly heard during the day at the offshore site and
at night at the inshore location, suggesting possible diel movements up
and down the slope in search of prey. During long-term passive acoustic
monitoring of three sites on the shelf, slope, and at a canyon off
Washington during 2004-2013, sperm whale clicks were detected year-
round with the highest number of call detections at the slope site
(Rice et al., 2021). Similarly, monitoring at acoustic recorders
deployed at different locations off Washington during 2008-2013 showed
clicks were detected year-round (Emmons et al., 2020).
There were no sightings of sperm whale reported during L-DEO
Cascadia Survey conducted in August 2022 (RPS 2023), the L-DEO Cascadia
Survey conducted in June-July 2021 (RPS 2022a), or the L-DEO survey
conducted in April 2022 (RPS 2022b). However, sperm whales could be
encountered in the proposed survey area.
Guadalupe Fur Seal
While at sea, Guadalupe fur seal is solitary but typically gathers
in the hundreds to thousands at breeding sites. During the summer
breeding season, most adults occur at rookeries in Mexico (Norris 2020;
Carretta et al., 2021). Following the breeding season, adult males tend
to move northward to forage. Several rehabilitated Guadalupe fur seals
that were satellite tagged and released in central California traveled
as far north as B.C. (Norris 2020). Guadalupe fur seals could be
encountered during the proposed seismic surveys, but most animals are
likely to occur at their breeding sites farther south at the time of
the surveys.
There were no sightings of Guadalupe fur seal reported during L-DEO
Cascadia Survey conducted in August 2022 (RPS 2023), the L-DEO Cascadia
Survey conducted in June-July 2021 (RPS 2022a), or the L-DEO survey
conducted in April 2022 (RPS 2022b). Guadalupe fur seal could be
encountered in the survey area.
Northern Fur Seal
The northern fur seal breeding season spans from about May through
November, with adult males usually coming ashore in May-August (though
sometimes be present until November) and adult females coming ashore
from June-November (Young et al. 2024). When not on rookery islands in
the Bering seal, Russia, and southern and central California, northern
fur seals are primarily pelagic (Young et al., 2024), spending 7-8
months feeding at sea after reproduction (Roppel 1984), typically in
areas of upwelling along the continental slopes and over seamounts
(Gentry 1981).
Males usually migrate only as far south as the Gulf of Alaska
(Kajimura 1984). Ream et al. (2005) showed that migrating females moved
over the continental shelf as they migrated southeasterly. Instead of
following depth contours, their travel corresponded with movements of
the Alaska Gyre and the North Pacific Current (Ream et al. 2005). Pups
from the California stock also migrate to Washington, Oregon, and
northern California after weaning (Lea et al., 2009).
Tagged adult northern 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).
Tracked adult male fur seals that were tagged on St. Paul Island in the
Bering Sea in October 2009, wintered in the Bering Sea or northern
North Pacific Ocean; females migrated to the Gulf of Alaska and the
California Current, including off the west coasts of Haida Gwaii and
Vancouver Island (Sterling et al., 2014). Some individuals reach
California by December, after which time numbers increase off the west
coast of North America (Ford 2014). The peak density shift over the
course of the winter and spring, with peak densities occurring in
California in February, April off Oregon and Washington, and May off
B.C. and Southeast Alaska (Ford 2014).
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 (>2,000 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). While
zero northern fur seals were reported during L-DEO's Cascadia survey
conducted in August 2022 (RPS 2023), three northern fur seals were seen
during the 2021 L-DEO Cascadia survey (RPS 2022a), and five were seen
during the April 2022 L-DEO survey off Oregon (RPS 2022b). Northern fur
seals could be observed in the proposed survey area, in particular
females and juveniles. However, adult females are generally ashore from
June through November (during the planned survey period).
Marine Mammal Hearing
Hearing is the most important sensory modality for marine mammals
underwater, and exposure to anthropogenic sound can have deleterious
effects. To appropriately assess the potential effects of exposure to
sound, it is necessary to understand the frequency ranges marine
mammals are able to hear. Not all marine mammal species have equal
hearing capabilities (e.g., Richardson et al., 1995; Wartzok and
Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al.
(2007, 2019) recommended that marine mammals be divided into hearing
groups based on directly measured (behavioral or auditory evoked
potential techniques) or estimated hearing ranges (behavioral response
data, anatomical modeling, etc.). Generalized hearing ranges were
chosen based on the ~65 decibel (dB) threshold from composite
audiograms, previous analyses in NMFS (2018), and/or data from Southall
et al. (2007) and Southall et al. (2019). We note that the names of two
hearing groups and the generalized hearing ranges of all marine mammal
hearing
[[Page 34219]]
groups have been recently updated (NMFS 2024) as reflected below in
table 2.
Table 2--Marine Mammal Hearing Groups
[NMFS, 2024]
------------------------------------------------------------------------
Hearing group Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen 7 Hz to 36 kHz.
whales).
High-frequency (HF) cetaceans 150 Hz to 160 kHz.
(dolphins, toothed whales, beaked
whales, bottlenose whales).
Very High-frequency (VHF) cetaceans 200 Hz to 165 kHz.
(true porpoises, Kogia, river
dolphins, Cephalorhynchid,
Lagenorhynchus cruciger & L.
australis).
Phocid pinnipeds (PW) (underwater) 40 Hz to 90 kHz.
(true seals).
Otariid pinnipeds (OW) (underwater) 60 Hz to 68 kHz.
(sea lions and fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
composite (i.e., all species within the group), where individual
species' hearing ranges may not be as broad. Generalized hearing range
chosen based on ~65 dB threshold from composite audiogram, previous
analysis in NMFS 2018, and/or data from Southall et al. 2007; Southall
et al. 2019. Additionally, animals are able to detect very loud sounds
above and below that ``generalized'' hearing range.
For more detail concerning these groups and associated frequency
ranges, please see NMFS (2024) for a review of available information.
Potential Effects of Specified Activities on Marine Mammals and Their
Habitat
This section provides a discussion of the ways in which components
of the specified activity may impact marine mammals and their habitat.
The Estimated Take of Marine Mammals 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 of Marine Mammals 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 whether those impacts are reasonably expected to, or reasonably
likely to, adversely affect the species or stock through effects on
annual rates of recruitment or survival.
Description of Active Acoustic Sound Sources
This section contains a brief technical background on sound, the
characteristics of certain sound types, and on metrics used in this
proposal inasmuch as the information is relevant to the specified
activity and to a discussion of the potential effects of the specified
activity on marine mammals found later in this document.
Sound travels in waves, the basic components of which are
frequency, wavelength, velocity, and amplitude. Frequency is the number
of pressure waves that pass by a reference point per unit of time and
is measured in hertz (Hz) or cycles per second. Wavelength is the
distance between two peaks or corresponding points of a sound wave
(length of one cycle). Higher frequency sounds have shorter wavelengths
than lower frequency sounds, and typically attenuate (decrease) more
rapidly, except in certain cases in shallower water. Amplitude is the
height of the sound pressure wave or the ``loudness'' of a sound and is
typically described using the relative unit of the dB. A sound pressure
level (SPL) in dB is described as the ratio between a measured pressure
and a reference pressure (for underwater sound, this is 1 microPascal
([mu]Pa)) and is a logarithmic unit that accounts for large variations
in amplitude; therefore, a relatively small change in dB corresponds to
large changes in sound pressure. The source level (SL) represents the
SPL referenced at a distance of 1 m from the source (referenced to 1
[mu]Pa) while the received level is the SPL at the listener's position
(referenced to 1 [mu]Pa).
Root mean square (RMS) is the quadratic mean sound pressure over
the duration of an impulse. Root mean square is calculated by squaring
all of the sound amplitudes, averaging the squares, and then taking the
square root of the average (Urick, 1983). Root mean square accounts for
both positive and negative values; squaring the pressures makes all
values positive so that they may be accounted for in the summation of
pressure levels (Hastings and Popper, 2005). This measurement is often
used in the context of discussing behavioral effects, in part because
behavioral effects, which often result from auditory cues, may be
better expressed through averaged units than by peak pressures.
Sound exposure level (SEL; represented as dB re 1 [mu]Pa\2\-s)
represents the total energy contained within a pulse and considers both
intensity and duration of exposure. Peak sound pressure (also referred
to as zero-to-peak sound pressure or 0-p) is the maximum instantaneous
sound pressure measurable in the water at a specified distance from the
source and is represented in the same units as the RMS sound pressure.
Another common metric is peak-to-peak sound pressure (pk-pk), which is
the algebraic difference between the peak positive and peak negative
sound pressures. Peak-to-peak pressure is typically approximately 6 dB
higher than peak pressure (Southall et al., 2007).
When underwater objects vibrate or activity occurs, sound-pressure
waves are created. These waves alternately compress and decompress the
water as the sound wave travels. Underwater sound waves radiate in a
manner similar to ripples on the surface of a pond and may be either
directed in a beam or beams or may radiate in all directions
(omnidirectional sources), as is the case for pulses produced by the
airguns 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):
[[Page 34220]]
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 this 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. 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., NMFS, 2018; 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
(American National Standards Institute (ANSI), 1986, 2005; Harris,
1998; National Institute for Occupational Health and Safety (NIOSH),
1998; International Organization for Standardization (ISO), 2003) and
occur either as isolated events or repeated in some succession. Pulsed
sounds are all characterized by a relatively rapid rise from ambient
pressure to a maximal pressure value followed by a rapid decay period
that may include a period of diminishing, oscillating maximal and
minimal pressures, and generally have an increased capacity to induce
physical injury as compared with sounds that lack these features.
Non-pulsed sounds can be tonal, narrowband, or broadband, brief or
prolonged, and may be either continuous or non-continuous (ANSI, 1995;
NIOSH, 1998). Some of these non-pulsed sounds can be transient signals
of short duration but without the essential properties of pulses (e.g.,
rapid rise time). Examples of non-pulsed sounds include those produced
by vessels, aircraft, machinery operations such as drilling or
dredging, vibratory pile driving, and active sonar systems (such as
those used by the U.S. Navy). The duration of such sounds, as received
at a distance, can be greatly extended in a highly reverberant
environment.
Airgun arrays produce pulsed signals with energy in a frequency
range from about 10-2,000 Hz, with most energy radiated at frequencies
below 200 Hz. The amplitude of the acoustic wave emitted from the
source is equal in all directions (i.e., omnidirectional), but airgun
arrays do possess some directionality due to different phase delays
between guns in different directions. Airgun arrays are typically tuned
to maximize functionality for data acquisition purposes, meaning that
sound transmitted in horizontal directions and at higher frequencies is
minimized to the extent possible.
Acoustic Effects
Here, we discuss the effects of active acoustic sources on marine
mammals.
Potential Effects of Underwater Sound \1\--Anthropogenic sounds
cover a broad range of frequencies and sound levels and can have a
range of highly variable impacts on marine life, from none or minor to
potentially severe responses, depending on received levels, duration of
exposure, behavioral context, and various other factors. The potential
effects of underwater sound from active acoustic sources can
potentially result in one or more of the following: Temporary or
permanent hearing impairment; non-auditory physical or physiological
effects; behavioral disturbance; stress; and masking (Richardson et
al., 1995; Gordon et al., 2004; Nowacek et al., 2007; Southall et al.,
2007; G[ouml]tz et al., 2009). The degree of effect is intrinsically
related to the signal characteristics, received level, distance from
the source, and duration of the sound exposure. In general, sudden,
high level sounds can cause hearing loss, as can longer exposures to
lower level sounds. Temporary or permanent loss of hearing, if it
occurs at all, will occur almost exclusively in cases where a noise is
within an animal's hearing frequency range. We first describe specific
manifestations of acoustic effects before providing discussion specific
to the use of airgun arrays.
---------------------------------------------------------------------------
\1\ Please refer to the information given previously
(Description of Active Acoustic Sound Sources) regarding sound,
characteristics of sound types, and metrics used in this document.
---------------------------------------------------------------------------
Richardson et al. (1995) described zones of increasing intensity of
effect that might be expected to occur, in relation to distance from a
source and assuming that the signal is within an animal's hearing
range. First is the area within which the acoustic signal would be
audible (potentially perceived) to the animal, but not strong enough to
elicit any overt behavioral or physiological response. The next zone
corresponds with the area where the signal is audible to the animal and
of sufficient intensity to elicit behavioral or physiological response.
Third is a zone within which, for signals of high intensity, the
received level is sufficient to potentially cause discomfort or tissue
damage to auditory or other systems. Overlaying these zones to a
certain extent is the
[[Page 34221]]
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.
Marine mammals, like all mammals, develop increased hearing
thresholds over time due to age-related degeneration of auditory
pathways and sensory cells of the inner ear. This natural, age-related
hearing loss is contrasted by noise-induced hearing loss
(M[oslash]ller, 2012). Marine mammals exposed to high-intensity sound
or to lower-intensity sound for prolonged periods can experience a
noise-induced hearing threshold shift (TS), which NMFS defines as a
change, usually an increase, in the threshold of audibility at a
specified frequency or portion of an individual's hearing range above a
previously established reference level as a result of noise exposure
(NMFS, 2018, 2024). The amount of TS is customarily expressed in dB.
Noise-induced hearing TS can be temporary (TTS) or permanent (PTS), and
higher-level sound exposures are more likely to cause PTS or other
auditory injury (AUD INJ). As described in NMFS (2018, 2024) there are
numerous factors to consider when examining the consequence of TS,
including, but not limited to, the signal temporal pattern (e.g.,
impulsive or non-impulsive), likelihood an individual would be exposed
for a long enough duration or to a high enough level to induce a TS,
the magnitude of the TS, time to recovery (seconds to minutes or hours
to days), the frequency range of the exposure (i.e., spectral content),
the hearing frequency range of the exposed species relative to the
signal's frequency spectrum (i.e., how animal uses sound within the
frequency band of the signal; e.g., Kastelein et al., 2014), and the
overlap between the animal and the source (e.g., spatial, temporal, and
spectral).
Auditory Injury (AUD INJ)
NMFS (2024) defines AUD INJ as damage to the inner ear that can
result in destruction of tissue, such as the loss of cochlear neuron
synapses or auditory neuropathy (Houser, 2021; Finneran, 2024). AUD INJ
may or may not result in a PTS. PTS is subsequently defined as a
permanent, irreversible increase in the threshold of audibility at a
specified frequency or portion of an individual's hearing range above a
previously established reference level (NMFS, 2024). PTS does not
generally affect more than a limited frequency range, and an animal
that has incurred PTS has some level of hearing loss at the relevant
frequencies; typically animals with PTS or other AUD INJ are not
functionally deaf (Au and Hastings, 2008; Finneran, 2016). For marine
mammals, AUD INJ is considered to be possible when sound exposures are
sufficient to produce 40 dB of TTS measured after exposure (Southall et
al. 2007, 1019). AUD INJ levels for marine mammals are estimates, as
with the exception of a single study unintentionally inducing PTS in a
harbor seal (Phoca vitulina) (Reichmuth et al. 2019), there are no
empirical data measuring AUD INJ in marine mammals largely due to the
fact that, for various ethical reasons, experiments involving
anthropogenic noise exposure at levels inducing AUD INJ are not
typically pursued or authorized (NMFS, 2024).
Temporary Threshold Shift (TTS)
TTS is a temporary, reversible increase in the threshold of
audibility at a specified frequency or portion of an individual's
hearing range above a previously established reference level (NMFS,
2024) that represents primarily tissue fatigue (Henderson et al.,
2008), and is not considered an AUD INJ. Based on data from marine
mammal TTS measurements (see Southall et al., 2007, 2019), a TTS of 6
dB is considered the minimum threshold shift clearly larger than any
day-to-day or session-to-session variation in a subject's normal
hearing ability (Finneran et al., 2000, 2002; Schlundt et al., 2000).
While experiencing TTS, the hearing threshold rises, and a sound must
be at a higher level in order to be heard (Finneran 2015).
In terrestrial and marine mammals, TTS can last from minutes or
hours to days (i.e., there is recovery back to baseline/pre-exposure
levels), can occur within a specific frequency range (i.e., an animal
might only have a temporary loss of hearing sensitivity within a
limited frequency band of its auditory range), and can be of varying
amounts (e.g., an animal's hearing sensitivity might be reduced by only
6 dB or reduced by 30 dB). In many cases, hearing sensitivity recovers
rapidly after exposure to the sound ends. While there are data on sound
levels and durations necessary to elicit mild TTS for marine mammals,
recovery is complicated to predict and dependent on multiple factors.
Depending on the degree (elevation of threshold in dB), duration (i.e.,
recovery time), and frequency range of TTS, and the context in which it
is experienced, TTS can have effects on marine mammals ranging from
discountable to serious. For example, a marine mammal may be able to
readily compensate for a brief, relatively small amount of TTS in a
non-critical frequency range that occurs during a time where ambient
noise is lower and there are not as many competing sounds present.
Alternatively, a larger amount and longer duration of TTS sustained
during time when communication is critical for successful mother/calf
interactions could have more serious impacts.
Finneran et al. (2015) measured hearing thresholds in 3 captive
bottlenose dolphins before and after exposure to 10 pulses produced by
a seismic airgun in order to study TTS induced after exposure to
multiple pulses. Exposures began at relatively low levels and gradually
increased over a period of several months, with the highest exposures
at peak SPLs from 196 to 210 dB and cumulative (unweighted) SELs from
193-195 dB. No substantial TTS was observed. In addition, behavioral
reactions were observed that indicated that animals can learn behaviors
that effectively mitigate noise exposures (although exposure patterns
must be learned, which is less likely in wild animals than for the
captive animals considered in this study). The authors note that the
failure to induce more significant auditory effects was likely due to
the intermittent nature of exposure, the relatively low peak pressure
produced by the acoustic source, and the low-frequency energy in airgun
pulses as compared with the frequency range of best sensitivity for
[[Page 34222]]
dolphins and other high-frequency cetaceans.
The amount and onset of TTS depends on the exposure frequency.
Sounds at low frequencies, well below the region of best sensitivity
for a species or hearing group, are less hazardous than those at higher
frequencies, near the region of best sensitivity (Finneran and
Schlundt, 2013). At low frequencies, onset-TTS exposure levels are
higher compared to those in the region of best sensitivity (i.e., a low
frequency noise would need to be louder to cause TTS onset when TTS
exposure level is higher), as shown for harbor porpoises and harbor
seals (Kastelein et al., 2019a, 2019c). Note that in general, harbor
seals and harbor porpoises have a lower TTS onset than other measured
pinniped or cetacean species (Finneran, 2015).
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.
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; National
Research Council (NRC), 2005). There are broad categories of potential
response, which we describe in greater detail here, that include
alteration of dive behavior, alteration of foraging behavior, effects
to breathing, interference with or alteration of vocalization,
avoidance, and flight.
Changes in dive behavior can vary widely, and may consist of
increased or decreased dive times and surface intervals as well as
changes in the rates of ascent and descent during a dive (e.g., Frankel
and Clark, 2000; Ng and Leung, 2003; Nowacek et al., 2004; Goldbogen et
al., 2013a,b). Variations in dive behavior may reflect disruptions in
biologically significant activities (e.g., foraging) or they may be of
little biological significance. The impact of an alteration to dive
behavior resulting from an acoustic exposure depends on what the animal
is doing at the time of the exposure and the type and magnitude of the
response.
Disruption of feeding behavior can be difficult to correlate with
anthropogenic sound exposure, so it is usually inferred by observed
displacement from known foraging areas, the appearance of secondary
indicators (e.g., bubble nets or sediment plumes), or changes in dive
behavior. As for other types of behavioral response, the frequency,
duration, and temporal pattern of signal presentation, as well as
differences in species sensitivity, are likely contributing factors to
differences in response in any given circumstance (e.g., Croll et al.,
2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko et al.,
2007a,b). A determination of whether foraging disruptions affect
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 (PAM), 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, or
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).
Changes 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
[[Page 34223]]
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) found that the number of humpback whales
singing off the coast of northern Angola decreased with increasing
received level of noise, suggesting that humpback whale communication
was disrupted to some extent by the survey activity. Castellote et al.
(2012) reported that fin whales moved away from the acoustic source and
out of the study area, and 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., (2015) suggested 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. These studies
demonstrate that even low levels of noise received far from the source
can induce changes in vocalization and/or behavior for mysticetes.
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 shown 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).
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 show 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). However, many
delphinids approach acoustic source vessels with no apparent discomfort
or obvious behavioral change (e.g., Barkaszi et al., 2012, Barkaszi and
Kelly, 2019).
Forney et al. (2017) detail the potential effects of noise on
marine mammal populations with high site fidelity, including
displacement and auditory masking, noting that a lack of observed
response does not imply absence of fitness costs and that apparent
tolerance of disturbance may have population-level impacts that are
less obvious and difficult to document. 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.
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 5-day period did not cause any sleep
deprivation or stress effects.
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;
[[Page 34224]]
Moberg, 2000). In many cases, an animal's first and sometimes most
economical (in terms of energetic costs) response is behavioral
avoidance of the potential stressor. Autonomic nervous system responses
to stress typically involve changes in heart rate, blood pressure, and
gastrointestinal activity. These responses have a relatively short
duration and may or may not have a significant long-term effect on an
animal's fitness.
Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that
are affected by stress--including immune competence, reproduction,
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been
implicated in failed reproduction, altered metabolism, reduced immune
competence, and behavioral disturbance (e.g., Moberg, 1987; Blecha,
2000). Increases in the circulation of glucocorticoids are also equated
with stress (Romano et al., 2004).
The primary distinction between stress (which is adaptive and does
not normally place an animal at risk) and distress is the cost of the
response. During a stress response, an animal uses glycogen stores that
can be quickly replenished once the stress is alleviated. In such
circumstances, the cost of the stress response would not pose serious
fitness consequences. However, when an animal does not have sufficient
energy reserves to satisfy the energetic costs of a stress response,
energy resources must be diverted from other functions. This state of
distress will last until the animal replenishes its energetic reserves
sufficiently to restore normal function.
Relationships between these physiological mechanisms, animal
behavior, and the costs of stress responses are well-studied through
controlled experiments and for both laboratory and free-ranging animals
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003;
Krausman et al., 2004; Lankford et al., 2005). Stress responses due to
exposure to anthropogenic sounds or other stressors and their effects
on marine mammals have also been reviewed (Fair and Becker, 2000;
Romano et al., 2002b) and, more rarely, studied in wild populations
(e.g., Romano et al., 2002a). For example, Rolland et al., (2012) found
that noise reduction from reduced ship traffic in the Bay of Fundy was
associated with decreased stress in North Atlantic right whales. These
and other studies lead to a reasonable expectation that some marine
mammals will experience physiological stress responses upon exposure to
acoustic stressors and that it is possible that some of these would be
classified as ``distress.'' In addition, any animal experiencing TTS
would likely also experience stress responses (NRC, 2003).
Auditory Masking--Sound can disrupt behavior through masking, or
interfering with, an animal's ability to detect, recognize, or
discriminate between acoustic signals of interest (e.g., those used for
intraspecific communication and social interactions, prey detection,
predator avoidance, navigation) (Richardson et al., 1995; Erbe et al.,
2016). Masking occurs when the receipt of a sound is interfered with by
another coincident sound at similar frequencies and at similar or
higher intensity, and may occur whether the sound is natural (e.g.,
snapping shrimp, wind, waves, precipitation) or anthropogenic (e.g.,
shipping, sonar, seismic exploration) in origin. The ability of a noise
source to mask biologically important sounds depends on the
characteristics of both the noise source and the signal of interest
(e.g., signal-to-noise ratio, temporal variability, direction), in
relation to each other and to an animal's hearing abilities (e.g.,
sensitivity, frequency range, critical ratios, frequency
discrimination, directional discrimination, age or TTS hearing loss),
and existing ambient noise and propagation conditions.
Under certain circumstances, significant masking could disrupt
behavioral patterns, which in turn could affect fitness for survival
and reproduction. It is important to distinguish TTS and PTS, which
persist after the sound exposure, from masking, which occurs during the
sound exposure. Because masking (without resulting in a TS) is not
associated with abnormal physiological function, it is not considered a
physiological effect, but rather a potential behavioral effect.
The frequency range of the potentially masking sound is important
in predicting any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation
sounds produced by odontocetes but are more likely to affect detection
of mysticete communication calls and other potentially important
natural sounds such as those produced by surf and some prey species.
The masking of communication signals by anthropogenic noise may be
considered as a reduction in the communication space of animals (e.g.,
Clark et al., 2009) and may result in energetic or other costs as
animals change their vocalization behavior (e.g., Miller et al., 2000;
Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2010; Holt
et al., 2009). Masking may be less in situations where the signal and
noise come from different directions (Richardson et al., 1995), through
amplitude modulation of the signal, or through other compensatory
behaviors (Houser and Moore, 2014). Masking can be tested directly in
captive species (e.g., Erbe, 2008), but in wild populations it must be
either modeled or inferred from evidence of masking compensation. There
are few studies addressing real-world masking sounds likely to be
experienced by marine mammals in the wild (e.g., Branstetter et al.,
2013).
Masking affects both senders and receivers of acoustic signals and
can potentially have long-term chronic effects on marine mammals at the
population level as well as at the individual level. Low-frequency
ambient sound levels have increased by as much as 20 dB (more than
three times in terms of SPL) in the world's ocean from pre-industrial
periods, with most of the increase from distant commercial shipping
(Hildebrand, 2009). All anthropogenic sound sources, but especially
chronic and lower-frequency signals (e.g., from vessel traffic),
contribute to elevated ambient sound levels, thus intensifying masking.
Masking effects of pulsed sounds (even from large arrays of
airguns) on marine mammal calls and other natural sounds are expected
to be limited, although there are few specific data on this. Because of
the intermittent nature and low duty cycle of seismic pulses, 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
[[Page 34225]]
background noise levels during intervals between seismic 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. Wittekind et al.
(2016) reported that airgun sounds could reduce the communication range
of blue and fin whales 2,000 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;
Sciacca et al. 2016). 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 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.
Vessel Noise
Vessel noise from the Sally Ride 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. 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).
Vessel 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; 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.
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. 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 vessels (Richardson et al.
1995). Pirotta et al. (2015) noted that the physical presence of
vessels, not just ship noise, disturbed the foraging activity of
bottlenose dolphins. There is little 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).
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).
Vessel Strike
Vessel collisions with marine mammals, or vessel strikes, can
result in death or serious injury of the animal. Wounds resulting from
vessel strike may include massive trauma, hemorrhaging, broken bones,
or propeller lacerations (Knowlton and Kraus, 2001). An animal at the
surface may be struck directly by a vessel, a surfacing animal may hit
the bottom of a vessel, or an animal just below the surface may be cut
by a vessel's propeller. Superficial strikes may not kill or result in
the death of the animal. These interactions are typically associated
with large whales (e.g., fin whales), which are occasionally found
draped across the bulbous bow of large commercial vessels 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
knots (kn, 26 kilometer per hour (kph)), and exceeded 90 percent at 17
kn (31 kph). 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
(28 kph). The chances of a lethal injury decline from approximately 80
percent at 15 kn (28 kph) to approximately 20 percent at 8.6 kn (16
kph). At speeds below 11.8 kn (22 kph), the chances of lethal injury
drop below 50 percent, while the probability asymptotically increases
toward 100 percent above 15 kn (28 kph).
The Sally Ride will travel at a speed of 5 kn (9 kph) while towing
seismic survey gear. At this speed, both the possibility of striking a
marine mammal and the possibility of a strike resulting in serious
injury or mortality are discountable. At average transit speed, the
probability of serious injury or mortality resulting from a strike is
less than 50 percent. However, the likelihood of a strike actually
happening is again discountable. Vessel 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 vessel 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
[[Page 34226]]
geophysical survey vessels during that time period.
It is possible for vessel strikes to occur while traveling at slow
speeds. For example, a hydrographic survey vessel traveling at low
speed (5.5 kn (10 kph)) while conducting mapping surveys off the
central California coast struck and killed a blue whale in 2009. The
State of California determined that the whale had suddenly and
unexpectedly surfaced beneath the hull, with the result that the
propeller severed the whale's vertebrae, and that this was an
unavoidable event. This strike represents the only such incident in
approximately 540,000 hours of similar coastal mapping activity (p =
1.9 x 10-6; 95 percent confidence interval = 0-5.5 x
10-6; NMFS, 2013). In addition, a research vessel reported a
fatal strike in 2011 of a dolphin in the Atlantic, demonstrating that
it is possible for strikes involving smaller cetaceans to occur. In
that case, the incident report indicated that an animal apparently was
struck by the vessel's propeller as it was intentionally swimming near
the vessel. While indicative of the type of unusual events that cannot
be ruled out, neither of these instances represents a circumstance that
would be considered reasonably foreseeable or that would be considered
preventable.
Although the likelihood of the vessel striking a marine mammal is
low, we propose a robust vessel strike avoidance protocol (see Proposed
Mitigation), which we believe eliminates any foreseeable risk of vessel
strike during transit. We anticipate that vessel collisions involving a
seismic data acquisition vessel towing gear, while not impossible,
represent unlikely, unpredictable events for which there are no
preventive measures. Given the proposed mitigation measures, the
relatively slow speed of the vessel towing gear, the presence of bridge
crew watching for obstacles at all times (including marine mammals),
and the presence of marine mammal observers, the possibility of vessel
strike is discountable and, further, were a strike of a large whale to
occur, it would be unlikely to result in serious injury or mortality.
No incidental take resulting from vessel strike is anticipated, and
this potential effect of the specified activity will not be discussed
further in the following analysis.
Stranding--Marine mammals strand for a variety of reasons, such as
infectious agents, biotoxicosis, starvation, fishery interaction,
vessel strike, unusual oceanographic or weather events, sound exposure,
or combinations of these stressors sustained concurrently or in series,
though numerous studies suggest that the physiology, behavior, habitat
relationships, age, or condition of cetaceans may cause them to strand
or might predispose 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., 2003; 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) sonar. MFA sonar
operates at higher frequencies and emits longer pulses than airguns
(D'Amico et al., 2009, Dragoset, 1990).
One should therefore not expect the same reaction to airgun noise
as to these other sources, especially low-energy airgun noise. The
potential for stranding to occur as a result of this survey is so
unlikely as to be discountable.
Entanglement--Entanglements occur when marine mammals become
wrapped around cables, lines, nets, or other objects suspended in the
water column. During seismic operations, numerous cables, lines, and
other objects primarily associated with the airgun array and hydrophone
streamers will be towed behind the Sally Ride near the water's surface.
However, we are not aware of any cases of entanglement of marine
mammals in seismic survey equipment. Although entanglement with the
streamer is theoretically possible, it has not been documented during
tens of thousands of miles of NSF-sponsored seismic cruises or, to our
knowledge, during hundreds of thousands of miles of industrial seismic
cruises. There are relatively 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
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; Pe[ntilde]a et al., 2013; Chapman and Hawkins,
1969; Wardle et al., 2001; Jorgenson and Gyselman, 2009; 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 5 days after seismic survey
operations, but the catch rate subsequently returned to normal
(Eng[aring]s et al., 1996; Eng[aring]s 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;
[[Page 34227]]
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. (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 comprehensive review (Carroll et al., 2017) found that results
are mixed as to the effects of airgun noise on the prey of marine
mammals. While some studies suggest a change in prey distribution and/
or a reduction in prey abundance following the use of seismic airguns,
others suggest no effects or even positive effects in prey abundance.
As one specific example, Paxton et al. (2017), which describes findings
related to the effects of a 2014 seismic survey on a reef off of North
Carolina, showed a 78 percent decrease in observed nighttime abundance
for certain species. It is important to note that the evening hours
during which the decline in fish habitat use was recorded (via video
recording) occurred on the same day that the seismic survey passed, and
no subsequent data is presented to support an inference that the
response was long-lasting. Additionally, given that the finding is
based on video images, the lack of recorded fish presence does not
support a conclusion that the fish actually moved away from the site or
suffered any serious impairment. In summary, this particular study
corroborates prior studies indicating that a startle response or short-
term displacement should be expected.
Available data suggest that cephalopods are capable of sensing the
particle motion of sounds and detect low frequencies up to 1-1.5 kHz,
depending on the species, and so are likely to detect airgun noise
(Kaifu et al., 2008; Hu et al., 2009; Mooney et al., 2010; Samson et
al., 2014). Auditory injuries (lesions occurring on the statocyst
sensory hair cells) have been reported upon controlled exposure to low-
frequency sounds, suggesting that cephalopods are particularly
sensitive to low-frequency sound (Andr[eacute] et al., 2011;
Sol[eacute] 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 3 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 more 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 1 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 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 generally be limited to behavioral responses, the
majority of prey species will be capable of moving
[[Page 34228]]
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., 2015). 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., 2000). The duration of fish avoidance of a given area
after survey effort stops is unknown, but a rapid return to normal
recruitment, distribution, and behavior is anticipated. While the
potential for disruption of spawning aggregations or schools of
important prey species can be meaningful on a local scale, the mobile
and temporary nature of this survey and the likelihood of temporary
avoidance behavior suggest that impacts would be minor.
Acoustic Habitat--Acoustic habitat is the soundscape--which
encompasses all of the sound present in a particular location and time,
as a whole--when considered from the perspective of the animals
experiencing it. Animals produce sound for, or listen for sounds
produced by, conspecifics (communication during feeding, mating, and
other social activities), other animals (finding prey or avoiding
predators), and the physical environment (finding suitable habitats,
navigating). Together, sounds made by animals and the geophysical
environment (e.g., produced by earthquakes, lightning, wind, rain,
waves) make up the natural contributions to the total acoustics of a
place. These acoustic conditions, termed acoustic habitat, are one
attribute of an animal's total habitat.
Soundscapes are also defined by, and acoustic habitat influenced
by, the total contribution of anthropogenic sound. This may include
incidental emissions from sources such as vessel traffic, or may be
intentionally introduced to the marine environment for data acquisition
purposes (as in the use of airgun arrays). Anthropogenic noise varies
widely in its frequency content, duration, and loudness and these
characteristics greatly influence the potential habitat-mediated
effects to marine mammals (please see also the previous discussion on
masking under Acoustic Effects), which may range from local effects for
brief periods of time to chronic effects over large areas and for long
durations. Depending on the extent of effects to habitat, animals may
alter their communications signals (thereby potentially expending
additional energy) or miss acoustic cues (either conspecific or
adventitious). For more detail on these concepts see, e.g., 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 of Marine Mammals
This section provides an estimate of the number of incidental takes
proposed for authorization through the IHA, which will inform NMFS'
consideration of ``small numbers,'' the negligible impact
determinations, and impacts on subsistence uses.
Harassment is the only type of take expected to result from these
activities. Except with respect to certain activities not pertinent
here, section 3(18) of the MMPA defines ``harassment'' as any act of
pursuit, torment, or annoyance, which (i) has the potential to injure a
marine mammal or marine mammal stock in the wild (Level A harassment);
or (ii) has the potential to disturb a marine mammal or marine mammal
stock in the wild by causing disruption of behavioral patterns,
including, but not limited to, migration, breathing, nursing, breeding,
feeding, or sheltering (Level B harassment).
Authorized takes would be by Level B harassment only, in the form
of behavioral reactions and/or TTS for individual marine mammals
resulting from exposure to noise from the use of seismic airguns. Based
on the nature of the activity and the anticipated effectiveness of the
mitigation measures (i.e., shutdown) discussed in detail below in the
Proposed Mitigation section, Level A harassment is neither anticipated
nor proposed to be authorized.
As described previously, no serious injury or mortality is
anticipated or proposed to be authorized for this activity. Below we
describe how the proposed take numbers are estimated.
For acoustic impacts, generally speaking, we estimate take by
considering: (1) acoustic criteria above which NMFS believes the best
available science indicates marine mammals will likely be behaviorally
harassed or incur some degree of AUD INJ; (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) the number of days of activities. We note that while these
factors can contribute to a basic calculation to provide an initial
prediction of potential 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 estimates.
Acoustic Criteria
NMFS recommends the use of acoustic criteria 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 AUD INJ of some degree (equated to
Level A harassment). We note that the criteria for AUD INJ, as well as
the names of two hearing groups, have been recently updated (NMFS 2024)
as reflected below in the Level A harassment section.
Level B Harassment--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 or exposure context (e.g., frequency, predictability, duty
cycle, duration of the exposure,
[[Page 34229]]
signal-to-noise ratio, distance to the source), the environment (e.g.,
bathymetry, other noises in the area, predators in the area), and the
receiving animals (hearing, motivation, experience, demography, life
stage, depth) and can be difficult to predict (e.g., Southall et al.,
2007, 2021, Ellison et al., 2012). Based on what the available science
indicates and the practical need to use a threshold based on a metric
that is both predictable and measurable for most activities, NMFS
typically uses a generalized acoustic threshold based on received level
to estimate the onset of behavioral harassment. NMFS generally predicts
that marine mammals are likely to be behaviorally harassed in a manner
considered to be Level B harassment when exposed to underwater
anthropogenic noise above root-mean-squared pressure received levels
(RMS SPL) of 120 dB (referenced to 1 micropascal (re 1 [mu]Pa)) for
continuous (e.g., vibratory pile driving, drilling) and above RMS SPL
160 dB re 1 [mu]Pa for non-explosive impulsive (e.g., seismic airguns)
or intermittent (e.g., scientific sonar) sources. Generally speaking,
Level B harassment take estimates based on these behavioral harassment
thresholds are expected to include any likely takes by TTS as, in most
cases, the likelihood of TTS occurs at distances from the source less
than those at which behavioral harassment is likely. TTS of a
sufficient degree can manifest as behavioral harassment, as reduced
hearing sensitivity and the potential reduced opportunities to detect
important signals (conspecific communication, predators, prey) may
result in changes in behavior patterns that would not otherwise occur.
SIO's proposed activity includes the use of impulsive seismic
sources (i.e., airguns), and therefore the RMS SPL thresholds of 160 dB
re 1 [mu]Pa is applicable.
Level A harassment--NMFS' Updated Technical Guidance for Assessing
the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version
3.0) (Updated Technical Guidance, 2024) identifies dual criteria to
assess AUD INJ (Level A harassment) to five different underwater marine
mammal groups (based on hearing sensitivity) as a result of exposure to
noise from two different types of sources (impulsive or non-impulsive).
SIO's proposed activity includes the use of impulsive sources (i.e.,
airguns).
The 2024 Updated Technical Guidance criteria include both updated
thresholds and updated weighting functions for each hearing group. The
thresholds are provided in the table below. The references, analysis,
and methodology used in the development of the criteria are described
in NMFS' 2024 Updated Technical Guidance, which may be accessed at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools.
Table 3--Thresholds Identifying the Onset of Auditory Injury
----------------------------------------------------------------------------------------------------------------
AUD INJ onset acoustic thresholds * (received level)
Hearing group ------------------------------------------------------------------------
Impulsive Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans........... Cell 1: Lpk,flat: 222 dB; Cell 2: LE,LF,24h: 197 dB
LE,LF,24h: 183 dB.
High-Frequency (HF) Cetaceans.......... Cell 3: Lpk,flat: 230 dB; Cell 4: LE,HF,24h: 201 dB
LE,HF,24h: 193 dB.
Very High-Frequency (VHF) Cetaceans.... Cell 5: Lpk,flat: 202 dB; Cell 6: LE,VHF,24h: 181 dB
LE,VHF,24h: 159 dB.
Phocid Pinnipeds (PW) (Underwater)..... Cell 7: Lpk,flat: 223 dB; Cell 8: LE,PW,24h: 195 dB
LE,PW,24h: 183 dB.
Otariid Pinnipeds (OW) (Underwater).... Cell 9: Lpk,flat: 230 dB; Cell 10: LE,OW,24h: 199 dB
LE,OW,24h: 185 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric criteria for impulsive sounds: Use whichever criteria results in the larger isopleth for
calculating AUD INJ onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure
level criteria associated with impulsive sounds, the PK SPL criteria are recommended for consideration for non-
impulsive sources.
Note: Peak sound pressure level (Lp,0-pk) has a reference value of 1 [mu]Pa, and weighted cumulative sound
exposure level (LE,p) has a reference value of 1 [mu]Pa\2\s. In this table, criteria are abbreviated to be
more reflective of International Organization for Standardization standards (ISO 2017). The subscript ``flat''
is being included to indicate peak sound pressure are flat weighted or unweighted within the generalized
hearing range of marine mammals underwater (i.e., 7 Hz to 165 kHz). The subscript associated with cumulative
sound exposure level criteria indicates the designated marine mammal auditory weighting function (LF, HF, and
VHF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The weighted
cumulative sound exposure level criteria 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 criteria will be exceeded.
Ensonified Area
Here, we describe operational and environmental parameters of the
activity that are used in estimating the area ensonified above the
acoustic thresholds, including source levels and transmission loss
coefficient.
The ensonified area associated with Level A harassment is more
technically challenging to predict due to the need to account for a
duration component. Therefore, NMFS developed an optional User
Spreadsheet tool to accompany the 2024 Updated Technical Guidance that
can be used to relatively simply predict an isopleth distance for use
in conjunction with marine mammal density or occurrence to help predict
potential takes. We note that because of some of the assumptions
included in the methods underlying this optional tool, we anticipate
that the resulting isopleth estimates are typically going to be
overestimates of some degree, which may result in an overestimate of
potential take by Level A harassment. However, this optional tool
offers the best way to estimate isopleth distances when more
sophisticated modeling methods are not available or practical.
The proposed survey would entail the use of a cluster of two GI
airguns with a total discharge volume of 90 in\3\ (1,475 cc) at a tow
depth of 4 m. L-DEO model results are used to determine the 160 dB RMS
radius for the airgun source down to a maximum depth of 2,000 m.
Received sound levels have been predicted by L-DEO's model (Diebold et
al. 2010) as a function of distance from the airguns. This modeling
approach uses ray tracing for the direct wave traveling from the
airguns to the receiver and its associated source ghost (reflection at
the air-water interface in the vicinity of the airguns), 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
(~1,600 m), intermediate water depth on the slope (~600-1,100 m), and
shallow water (~50 m) in the Gulf of America (previously Gulf of
Mexico) (Tolstoy et al. 2009; Diebold et al. 2010).
[[Page 34230]]
For deep and intermediate water cases, the field measurements
cannot be used readily to derive the harassment isopleths, as at those
sites the calibration hydrophone was located at a roughly constant
depth of 350-550 m, which may not intersect all the SPL isopleths at
their widest point from the sea surface down to the assumed maximum
relevant water depth (~2000 m) for marine mammals. At short ranges,
where the direct arrivals dominate and the effects of seafloor
interactions are minimal, the data at the deep sites are suitable for
comparison with modeled levels at the depth of the calibration
hydrophone. At longer ranges, the comparison with the model--
constructed from the maximum SPL through the entire water column at
varying distances from the airgun array--is the most relevant.
In deep and intermediate water depths at short ranges, sound levels
for direct arrivals recorded by the calibration hydrophone and L-DEO
model results for the same array tow depth are in good alignment (see
figures 12 and 14 in Diebold et al. 2010). 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
(see figures 11, 12, and 16 in Diebold et al. 2010). 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 America calibration measurements
demonstrates that although simple, the L-DEO model is a robust tool for
conservatively estimating isopleths.
The proposed low-energy survey would acquire data with two GI
airguns at a tow depth of 4 m. For deep water (>1,000 m), we use the
deep-water radii obtained from the L-DEO model results down to a
maximum water depth of 2,000 m for the airguns.
L-DEO's modeling methodology is described in greater detail in
SIO's application. The estimated distances to the Level B harassment
isopleth for the proposed airgun configuration are shown in table 4.
Table 4--Predicted Radial Distances from the Sally Ride Seismic Source to Isopleth Corresponding to Level B
Harassment Threshold
----------------------------------------------------------------------------------------------------------------
Predicted
distances (in
Water depth m) to the
Airgun configuration Tow depth (m) Separation (m) (m) Level B
harassment
threshold
----------------------------------------------------------------------------------------------------------------
Two 45 in\3\ airguns............................ 4 2 >1,000 505
----------------------------------------------------------------------------------------------------------------
Table 5--Modeled Radial Distance to Isopleths Corresponding to Level A Harassment Thresholds
----------------------------------------------------------------------------------------------------------------
Very high
Low frequency High frequency frequency Phocid Otariid
cetaceans cetaceans cetaceans pinnipeds pinnipeds
----------------------------------------------------------------------------------------------------------------
PTS SELcum...................... 4 1.3 37.5 3.5 1.3
PTS Peak........................ 18.0 0 0 0.3 0
----------------------------------------------------------------------------------------------------------------
The largest distance (in bold) of the dual criteria (SELcum or Peak) was used to estimate threshold distances
and potential takes by Level A harassment.
Table 5 presents the modeled Level A harassment isopleths for each
marine mammal hearing group based on L-DEO modeling incorporated in the
companion user spreadsheet, for the low-energy surveys with the
shortest shot interval (i.e. greatest potential to cause injury based
on accumulated sound energy) (NMFS 2018, 2024).
Predicted distances to Level A harassment isopleths, which vary
based on marine mammal hearing groups, were calculated based on
modeling performed by L-DEO using the Nucleus software program and the
NMFS user spreadsheet, described below. The acoustic thresholds for
impulsive sounds contained in the NMFS Technical Guidance were
presented as dual metric acoustic thresholds using both
SELcum and peak sound pressure metrics (NMFS, 2016). 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.
The SELcum for the two GI airguns is derived from
calculating the modified farfield signature. The farfield signature is
often used as a theoretical representation of the source level. To
compute the farfield signature, the source level is estimated at a
large distance (right) below the airguns (e.g., 9 km), and this level
is back projected mathematically to a notional distance of 1 m from the
geometrical center of the two airguns. However, it has been recognized
that the source level from the theoretical farfield signature is never
physically achieved at the source when the source is an array of
multiple airguns separated in space (Tolstoy et al., 2009). Near the
source (at short ranges, distances <1 km), the pulses of sound pressure
from each individual airgun in the source array do not stack
constructively as they do for the theoretical farfield signature. The
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, sound pressure of the two
airguns 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 farfield signature is not an appropriate measure of
the sound source level for large arrays. See SIO's
[[Page 34231]]
application for further detail on acoustic modeling.
In consideration of the received sound levels in the near-field as
described above, we expect the potential for Level A harassment of any
species 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 anticipate that auditory injury or
Level A harassment is a likely outcome for any species and do not
propose to authorize any take by Level A harassment for any species,
given the very small modeled zones of injury for those species
(estimated zones are less than 38 m for all species), in context of
distributed source dynamics.
The Level B harassment estimates are based on a consideration of
the number of marine mammals that could be within the area around the
operating airguns where received levels of sound >=160 dB re 1 [mu]Pa
RMS are predicted to occur. The estimated numbers are based on the
densities (numbers per unit area) of marine mammals expected to occur
in the area in the absence of seismic surveys. To the extent that
marine mammals tend to move away from seismic sources before the sound
level reaches the criterion level and tend not to approach an operating
airgun array, these estimates likely overestimate the numbers actually
exposed to the specified level of sound.
Marine Mammal Occurrence
In this section we provide information about the occurrence of
marine mammals, including density or other relevant information which
will inform the take calculations.
Ship surveys for cetaceans in slope and offshore waters of Oregon
and Washington were conducted by NMFS/SWFSC in 1991, 1993, 1996, 2001,
2005, 2008, 2014, and 2018 and synthesized by Becker et al. (2020).
These surveys were conducted up to ~556 km from shore typically from
July to November, but included the months of June and December in 2018
(Becker et al. 2020). These data were used by SWFSC to develop spatial
models of cetacean densities for the California Current Ecosystem
(CCE). Although Becker et al. (2020) did not include updated densities
for sperm or small beaked whales, these models were provided to SIO by
Elizabeth Becker via pers. comm. in January 2025 (see application). The
density models for cetaceans in the CCE were available in the form 10 x
10 km grid cells in Geographic Information System layers. There were
215 grid cells that overlapped with the survey area and an ``all
touched'' method, in which any cell that overlapped any amount of the
survey area was included in the calculations. The densities in the grid
cells that overlap the proposed survey area were averaged to calculate
densities for each species.
For species for which densities were not available from Becker et
al. (2020), SIO used annual densities developed from the U.S. Navy
Northwest Training and Testing Study Area (DON 2019).
Except California sea lion, SIO initially used the highest
densities for spring, summer, or fall from DON (2019). Following
discussion with NMFS, SIO updated the abundance estimates informing the
density values by projecting the population growth based on information
in the SARs, and then updated the density values accordingly. However,
since the draft 2024 SAR includes up-to-date revisions to population
estimates for Guadalupe fur seal, northern elephant seal, and northern
fur seal (California stock), those population estimates did not require
population growth corrections.
Table 6--Modeled Marine Mammal Density Values and Daily Ensonified Area for SIO's Proposed Survey
----------------------------------------------------------------------------------------------------------------
Daily
Species Density (#/ ensonified Number of Source
km\2\) area (km\2\) seismic days
----------------------------------------------------------------------------------------------------------------
Blue whale............................ 0.000025 221 2 Becker 2020.
Fin whale............................. 0.004482 221 2 Becker 2020.
Humpback whale........................ 0.000480 221 2 Becker 2020.
Minke whale........................... 0.000869 221 2 Becker 2020.
Sei whale............................. 0.000400 221 2 DON 2019, MSEL 2021.
Sperm whale........................... 0.002731 221 2 Becker personal
communication, 2025.
Baird's beaked whale.................. 0.000051 221 2 Becker 2020.
Mesoplodont and Cuviers beaked whale.. 0.002320 221 2 Becker personal
communication, 2025.
Killer whale.......................... 0.000920 221 2 DON 2019, MSEL 2021.
Northern right whale dolphin.......... 0.116618 221 2 Becker 2020.
Pacific white-sided dolphin........... 0.069054 221 2 Becker 2020.
Risso's dolphin....................... 0.014357 221 2 Becker 2020.
Short beaked common dolphin........... 0.001305 221 2 Becker 2020.
Dwarf and pygmy sperm whale........... 0.001630 221 2 DON 2019, MSEL 2021.
Dall's porpoise....................... 0.047357 221 2 Becker 2020.
California sea lion................... 0.71400 221 2 DON 2019, MSEL 2021; 70-
450 km from shore'
distance band.
Guadalupe fur seal.................... 0.032833 221 2 Based on DON 2019,
summer/fall; 200 m
isobaths to 300 km from
shore distance band.
Northern fur seal..................... 0.011340 221 2 Based on DON 2019,
summer/fall; (>130 km
to 463 km from shore
distance band.
Steller sea lion...................... 0.002771 221 2 Based on DON 2019,
summer; 200 m isobaths
to 300 km from shore
distance band.
Northern elephant seal................ 0.030137 221 2 Based on DON 2019, fall.
----------------------------------------------------------------------------------------------------------------
Take Estimation
Here we describe how the information provided above is synthesized
to produce a quantitative estimate of the take that is reasonably
likely to occur and proposed for authorization.
In order to estimate the number of marine mammals predicted to be
exposed to sound levels that would result in Level B harassment, radial
distances from the airguns to the predicted isopleth corresponding to
the
[[Page 34232]]
Level A and Level B harassment thresholds are calculated, as described
above. Those radial distances are then used to calculate the area(s)
around the airguns predicted to be ensonified to sound levels that
exceed the harassment thresholds. The distance for the 160-dB Level B
harassment threshold (based on SIO model results) was used to draw a
buffer around the area expected to be ensonified (i.e., the survey
area). The ensonified areas were then increased by 25 percent to
account for potential delays, which is the equivalent to adding 25
percent to the proposed line km to be surveyed. The density for each
species in table 6 were then multiplied by the daily ensonified areas
expected to be ensonified (increased as described above), and then
multiplied by the number of survey days (2) to estimate the potential
takes (see appendix B of SIO's application).
SIO assumed that their estimates of marine mammal exposures above
harassment thresholds equate to take and requested authorization of
those takes. Those estimates in turn form the basis for our proposed
take authorization numbers. Estimated exposures and proposed take
numbers for authorization are shown in table 7.
Table 7--Estimated Take Proposed for Authorization
--------------------------------------------------------------------------------------------------------------------------------------------------------
Estimated takes Proposed takes by
Species Stock by Level B Level B Population Percent of
harassment harassment abundance population
--------------------------------------------------------------------------------------------------------------------------------------------------------
Blue whale.................................. Eastern N. Pacific............ \2\ 0.01 \3\ 2 1,898 <1
Fin whale................................... CA/OR/WA...................... 2.48 2 11,065 <1
Humpback whale.............................. Central America/Southern \2\ 0.27 3 4 2 1,496 <1
Mexico--CA/OR/WA.
Mainland Mexico--CA/OR/WA..... 3,477 <1
Hawai'i....................... 11,278 <1
Minke whale................................. CA/OR/WA...................... \2\ 0.48 1 915 <1
Sei whale................................... Eastern N Pacific............. \2\ 0.22 \6\ 2 864 <1
Sperm whale................................. CA/OR/WA...................... 1.51 \5\ 7 2,606 <1
Baird's beaked whale........................ CA/OR/WA...................... \2\ 0.03 \5\ 7 1,363 <1
Mesoplodont \1\ and goose-beaked whales..... CA/OR/WA...................... 1.28 \5\ 2 3,044 <1
Killer whale................................ Eastern N Pacific Offshore.... 0.51 \6\ 7 300 2.3
West Coast Transient.......... 349 2.0
Northern right whale dolphin................ CA/OR/WA...................... 64.43 64 29,285 <1
Pacific white-sided dolphin................. CA/OR/WA...................... 38.15 \5\ 55 34,999 <1
Risso's dolphin............................. CA/OR/WA...................... 7.93 \5\ 19 6,336 <1
Short beaked common dolphin................. CA/OR/WA...................... 0.72 \5\ 156 1,056,308 <1
Dwarf sperm whale........................... CA/OR/WA...................... 0.90 1 UNK (\6\)
Pygmy sperm whale........................... CA/OR/WA...................... 4,111 <1
Dall's porpoise............................. CA/OR/WA...................... 26.17 26 16,498 <1
California sea lion......................... U.S........................... 39.45 39 257,606 <1
Guadalupe fur seal.......................... Mexico........................ 18.14 18 63,850 <1
Northern fur seal........................... Eastern Pacific............... 6.27 6 626,618 <1
California.................... 19,634 <1
Steller sea lion............................ Eastern....................... 1.53 2 36,308 <1
Northern elephant seal...................... California breeding........... 16.65 17 194,907 <1
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Includes: Stejneger's, Hubbs' and Blainsville's beaked whales.
\2\ Although estimated take results in less than 1, NMFS proposes to authorize one group given observations reported during previous surveys in the
project area in 2021 and 2022 (RPS 2022a, RPS 2022b, RPS 2023).
\3\ Proposed take has been increased to mean group size from Becker et al. 2020.
\4\ We assume that these takes may come from any stock.
\5\ Proposed take has been increased to mean group size from Barlow 2016.
\6\ No information is available to provide a reliable population estimate for this stock.
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, NMFS
considers 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;
[[Page 34233]]
(2) The practicability of the measures for applicant
implementation, which may consider such things as cost, and impact on
operations.
The mitigation requirements described in the following were
proposed by SIO in its adequate and complete application or are the
result of subsequent coordination between NMFS and SIO. SIO has agreed
that all of the mitigation measures are practicable. NMFS has fully
reviewed the specified activities and the mitigation measures included
in the application to determine if the mitigation measures would result
in the least practicable adverse impact on marine mammals and their
habitat, as required by the MMPA, and has determined the proposed
measures are appropriate. NMFS describes these below as proposed
mitigation requirements, and has included them in the proposed IHA.
Vessel-Based Visual Mitigation Monitoring
Visual monitoring requires the use of trained observers (herein
referred to as visual protected species observers (PSOs)) to scan the
ocean surface for the presence of marine mammals. The area to be
scanned visually includes primarily the shutdown zone (SZ), within
which observation of certain marine mammals requires shutdown of the
acoustic source, a buffer zone, and to the extent possible depending on
conditions, the surrounding waters. The buffer zone means an area
beyond the SZ to be monitored for the presence of marine mammals that
may enter the SZ. During pre-start clearance monitoring (i.e., before
ramp-up begins), the buffer zone also acts as an extension of the SZ 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 0-100 m SZ, out to a radius of 200 m from the edges of the airguns
(100-200 m). This 200-m zone (SZ plus buffer zone) represents the pre-
start clearance zone. Visual monitoring of the SZ and adjacent waters
(buffer plus surrounding 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. Visual
monitoring of the buffer zone is intended to (1) provide additional
protection to marine mammals that may be in the vicinity of the vessel
during pre-start clearance, and (2) during airgun use, aid in
establishing and maintaining the SZ by alerting the visual observer and
crew of marine mammals that are outside of, but may approach and enter,
the SZ.
During survey operations (e.g., any day on which use of the airguns
are planned to occur and whenever the airguns are 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). SIO also plans to employ two PSOs to conduct visual monitoring
30 minutes before and during ramp-ups. Visual monitoring of the pre-
start clearance zone (i.e., the shutdown zone and the buffer zone) must
begin no less than 30 minutes prior to ramp-up and monitoring must
continue until 1 hour after use of the airguns 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 SZ and buffer zone. These
zones shall be based upon the radial distance from the edges of the
airguns (rather than being based on the center of the array or around
the vessel itself). During use of the airguns (i.e., anytime airguns
are active, including ramp-up), detections of marine mammals within the
buffer zone (but outside the SZ) shall be communicated to the operator
to prepare for the potential shutdown of the airguns. 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 airguns are
not operating for comparison of sighting rates and behavior with and
without use of the airguns and between acquisition periods, to the
maximum extent practicable.
Visual PSOs may be on watch for a maximum of 4 consecutive hours
followed by a break of at least 1 hour between watches and may conduct
a maximum of 12 hours of observation per 24-hour period.
Establishment of Shutdown and Pre-Start Clearance Zones
A SZ 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 SZ with a 100-m radius. The 100-m SZ
would be based on radial distance from the edge of the airguns (rather
than being based on the center of the airguns or around the vessel
itself). With certain exceptions (described below), if a marine mammal
appears within or enters this zone, the airguns would be shut down.
The pre-start clearance zone is defined as the area that must be
clear of marine mammals prior to beginning ramp-up of the airguns and
includes the SZ plus the buffer zone. Detections of marine mammals
within the pre-start clearance zone would prevent airgun operations
from beginning (i.e., ramp-up).
The 100-m SZ 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 100-m SZ 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 expect that 100 m is likely
regularly attainable for PSOs using the naked eye during typical
conditions. The pre-start clearance zone simply represents the addition
of a buffer to the SZ, doubling the SZ size during pre-clearance.
An extended SZ of 500 m must be implemented for all beaked whales,
a large whale with a calf, and groups of six or more large whales. No
buffer of this extended SZ is required, as NMFS concludes that this
extended SZ is sufficiently protective to mitigate harassment to these
groups.
Pre-Start 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.
The intent of pre-start clearance observation (30 minutes) is to ensure
no marine mammals are observed within the pre-start clearance zone (or
extended SZ, for beaked whales, a large whale with a calf, and groups
of six or more large whales) prior to the beginning of ramp-up. During
the pre-start clearance period is the only time observations of marine
mammals in the buffer zone would prevent operations (i.e., the
beginning of
[[Page 34234]]
ramp-up). The intent of the ramp-up is to warn marine mammals of
pending seismic survey operations and to allow sufficient time for
those animals to leave the immediate vicinity prior to the sound source
reaching full intensity. A ramp-up procedure, involving a stepwise
increase in the number of airguns firing and total 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 airguns. All
operators must adhere to the following pre-start 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 pre-start clearance zone
(and extended SZ) for 30 minutes prior to the initiation of ramp-up
(pre-start 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-start 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 shutdown or buffer zone. If a marine mammal is
observed within the pre-start clearance zone (or extended SZ, for
beaked whales, a large whale with a calf, and groups of six or more
large whales) during the 30 minute pre-start 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, kogia, beaked whales, and large delphinids, such as Risso's
dolphins);
Ramp-up must begin by activating one GI airgun followed by
the second, with each stage lasting no less than 5 minutes. The
operator must provide information to the PSO documenting that
appropriate procedures were followed;
PSOs must monitor the pre-start clearance zone and
extended SZ during ramp-up, and ramp-up must cease and the source must
be shut down upon detection of a marine mammal within the applicable
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 if
appropriate monitoring has occurred with no observations in the 30
minutes prior to beginning ramp-up. No monitoring is required as a
prerequisite to nighttime ramp-up.
If the airguns are shut down for brief periods (i.e., less
than 30 minutes) for reasons other than implementation of prescribed
mitigation (e.g., mechanical difficulty), it may be activated again
without ramp-up if PSOs have maintained constant visual observation and
no visual observations of marine mammals have occurred within the pre-
start clearance zone (or extended SZ, where applicable). For any longer
shutdown, pre-start clearance observation and ramp-up are required; and
Testing of the airguns involving all elements requires
ramp-up. Testing limited to individual source elements or strings does
not require ramp-up but does require pre-start clearance of 30 minutes.
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 call for shutdown of the airgun array
if a marine mammal is detected within the applicable SZ. The operator
must also establish and maintain clear lines of communication directly
between PSOs on duty and crew controlling the airguns to ensure that
shutdown commands are conveyed swiftly while allowing PSOs to maintain
watch. When the airguns are active (i.e., anytime one or more airguns
is active, including during ramp-up) and a marine mammal appears within
or enters the applicable SZ the airguns will be shut down. When
shutdown is called for by a PSO, the airguns will be immediately
deactivated and any dispute resolved only following deactivation.
Following a shutdown, airgun activity would not resume until the
marine mammal has cleared the SZ. The animal would be considered to
have cleared the SZ if it is visually observed to have departed the SZ
(i.e., animal is not required to fully exit the buffer zone where
applicable), or it has not been seen within the SZ for 15 minutes for
small odontocetes and pinnipeds or 30 minutes for all mysticetes and
all other odontocetes, including sperm whales, kogia, beaked whales,
and large delphinids, such as Risso's dolphin.
The shutdown requirement is waived for specific genera of small
dolphins if an individual is detected within the SZ. 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 airguns (e.g., bow riding). This
exception to the shutdown requirement applies solely to the specific
genera of small dolphins (Lagenorhynchus, Lissodelphis, and Delphinus).
We include this small dolphin exception because shutdown
requirements for these species 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 high-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
(e.g., Barkaszi et al., 2012; Barkaszi and Kelly, 2019). The potential
for increased shutdowns resulting from such a measure would require the
Sally Ride 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 high-frequency hearing
specialists (e.g., large delphinids) 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
delphinids 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 delphinids 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 Sally Ride.
Visual PSOs shall use best professional judgment in making the
decision to call for a shutdown if there
[[Page 34235]]
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 SZ).
SIO must implement shutdown if a marine mammal species for which
take was not authorized or a species for which authorization was
granted but the authorized takes have been met approaches the Level B
harassment zones. SIO must also implement shutdown if any large whale
(defined as a sperm whale or any baleen whale 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) and/or an
aggregation of six or more large whales are observed at any distance.
Vessel Strike Avoidance Mitigation Measures
Vessel personnel should use an appropriate reference guide that
includes identifying information on all marine mammals that may be
encountered. Vessel operators must comply with the below measures
except under extraordinary circumstances when the safety of the vessel
or crew is in doubt or the safety of life at sea is in question. 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.
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 always be exercised. A visual observer
aboard the vessel must monitor a vessel strike avoidance zone around
the vessel (separation distances stated below). Visual observers
monitoring the vessel strike avoidance zone may be third-party
observers (i.e., PSOs) or crew members, but crew members responsible
for these duties must be provided sufficient training to (1)
distinguish marine mammals from other phenomena and (2) broadly to
identify a marine mammal as a large whale (defined in this context as
sperm whales or baleen whales), or other marine mammals.
Vessel speeds must be reduced to 10 kn (18.5 kph) or less when
mother/calf pairs, pods, or large assemblages of cetaceans are observed
near a vessel. All vessels must maintain a minimum separation distance
of 100 m from sperm whales and all mystecites. All vessels must, to the
maximum extent practicable, attempt to maintain a minimum separation
distance of 50 m from all other marine mammals, with an understanding
that at times this may not be possible (e.g., for animals that approach
the vessel).
When marine mammals are sighted while a vessel is underway, the
vessel shall take action as necessary to avoid violating the relevant
separation 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 must reduce speed and shift
the engine to neutral, not engaging the engines until animals are clear
of the area. This does not apply to any vessel towing gear or any
vessel that is navigationally constrained.
NMFS conducted an independent evaluation of the applicant's
proposed measures, and has preliminarily determined that the proposed
mitigation measures provide the means of 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 while
conducting the activities. 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 activity; 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.
The monitoring and reporting requirements described in the
following were proposed by SIO in its adequate and complete application
or are the result of subsequent coordination between NMFS and SIO. SIO
has agreed that all of the monitoring and reporting measures are
practicable. NMFS describes those below as proposed requirements, and
has included them in the proposed IHA.
Vessel-Based Visual Monitoring
As described above, PSO observations would take place during
daytime airgun operations. Two visual PSOs would be on duty at all
times during daytime hours. 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. SIO must use dedicated, trained, and NMFS-
approved PSOs. At least one visual PSO aboard the vessel must have a
minimum of 90 days at-sea experience working in those roles,
respectively, 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
[[Page 34236]]
should be scheduled to be on duty with those PSOs with appropriate
training but who have not yet gained relevant experience. 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.
Monitoring shall be conducted in accordance with the following
requirements:
PSOs shall be independent, dedicated, trained visual PSOs
and must be employed by a third-party observer provider;
PSOs shall have no tasks other than to conduct visual
observational effort, 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); and
PSOs shall have successfully completed an approved PSO
training course appropriate for their designated task (visual).
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;
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
with a major in one of the natural sciences; 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 1 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
electronic data collection forms. PSOs shall record detailed
information about any implementation of mitigation requirements,
including the distance of animals to the airguns 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 airgun array. If required mitigation was
not implemented, PSOs should record a description of the circumstances.
At a minimum, the following information must be recorded:
[cir] Vessel name, vessel size and type, maximum speed capability
of vessel;
[cir] Dates (MM/DD/YYYY) of departures and returns to port with
port name;
[cir] PSO names and affiliations, PSO ID (initials or other
identifier);
[cir] Date (MM/DD/YYYY) and participants of PSO briefings;
[cir] Visual monitoring equipment used (description);
[cir] PSO location on vessel and height (meters) of observation
location above water surface;
[cir] Watch status (description);
[cir] Dates (MM/DD/YYYY) and times (Greenwich Mean Time (GMC)/
Coordinated Universal Time (UTC)) of survey on/off effort and times
(GMC/UTC) corresponding with PSO on/off effort;
[cir] Vessel location (decimal degrees) when survey effort began
and ended and vessel location at beginning and end of visual PSO duty
shifts;
[cir] Vessel location (decimal degrees) at 30-second intervals if
obtainable from data collection software, otherwise at practical
regular interval;
[cir] Vessel heading (compass heading) and speed (knots) at
beginning and end of visual PSO duty shifts and upon any change;
[cir] Water depth (meters) (if obtainable from data collection
software);
[cir] 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;
[cir] Factors that may have contributed to impaired observations
during each PSO shift change or as needed as environmental conditions
changed (description) (e.g., vessel traffic, equipment malfunctions);
and
[cir] Vessel/Survey activity information (and changes thereof)
(description), such as airgun power output while in operation, number
and volume of airguns operating, tow depth of the airguns, and any
other notes of significance (i.e., pre-start clearance, ramp-up,
shutdown, testing, shooting, ramp-up completion, end of operations,
streamers, etc.).
Upon visual observation of any marine mammals, the
following information must be recorded:
[cir] Sighting ID (numeric);
[cir] Watch status (sighting made by PSO on/off effort,
opportunistic, crew, alternate vessel/platform);
[cir] Location of PSO/observer (description);
[cir] Vessel activity at the time of the sighting (e.g., deploying,
recovering, testing, shooting, data acquisition, other);
[cir] PSO who sighted the animal/ID;
[cir] Time/date of sighting (GMT/UTC, MM/DD/YYYY);
[cir] Initial detection method (description);
[cir] Sighting cue (description);
[cir] Vessel location at time of sighting (decimal degrees);
[cir] Water depth (meters);
[cir] Direction of vessel's travel (compass direction);
[cir] Speed (knots) of the vessel from which the observation was
made;
[cir] Direction of animal's travel relative to the vessel
(description, compass heading);
[cir] Bearing to sighting (degrees);
[cir] 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;
[cir] Species reliability (an indicator of confidence in
identification) (1 = unsure/possible, 2 = probable, 3 = definite/sure,
9 = unknown/not recorded);
[cir] Estimated distance to the animal (meters) and method of
estimating distance;
[cir] Estimated number of animals (high/low/best) (numeric);
[cir] Estimated number of animals by cohort (adults, yearlings,
juveniles, calves, group composition, etc.);
[cir] 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);
[cir] 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);
[[Page 34237]]
[cir] Animal's closest point of approach (meters) and/or closest
distance from any of the airguns;
[cir] Description of any actions implemented in response to the
sighting (e.g., delays, shutdown, ramp-up) and time and location of the
action.
[cir] Photos (Yes/No);
[cir] Photo Frame Numbers (List of numbers); and
[cir] Conditions at time of sighting (Visibility; Beaufort Sea
State).
Reporting
SIO shall submit a draft comprehensive report on all activities and
monitoring results within 90 days of the completion of the survey or
expiration of the IHA, whichever comes sooner. The report must describe
all activities conducted and sightings of marine mammals, must provide
full documentation of methods, results, and interpretation pertaining
to all monitoring, and must summarize the dates and locations of survey
operations and all marine mammal sightings (dates, times, locations,
activities, associated survey activities). 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 sources
began operating, when they were turned off, or when they changed
operational status such as from two airguns to single gun or vice
versa). Geographic Information System files shall be provided in
Environmental Systems Research Institute 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. The report must summarize
data collected as described above in Proposed Monitoring and Reporting.
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 the survey activities discover an injured or dead
marine mammal, SIO shall report the incident to the Office of Protected
Resources (OPR) 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 strike of a marine mammal by any
vessel involved in the activities covered by the authorization, SIO
shall report the incident to OPR 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,
BSS, 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 marine mammal
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).
Negligible Impact Analysis and Determination
NMFS has defined negligible impact as an impact resulting from the
specified activity that cannot be reasonably expected to, and is not
reasonably likely to, adversely affect the species or stock through
effects on annual rates of recruitment or survival (50 CFR 216.103). A
negligible impact finding is based on the lack of likely adverse
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough
information on which to base an impact determination. In addition to
considering estimates of the number of marine mammals that might be
``taken'' through harassment, NMFS considers other factors, such as the
likely nature of any impacts or responses (e.g., intensity, duration),
the context of any impacts or responses (e.g., critical reproductive
time or location, foraging impacts affecting energetics), 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' 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 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, the discussion of our analysis applies to all
species listed in table 1, given that the anticipated effects of this
activity on these different marine mammal stocks are expected to be
similar. There is little information about the nature or severity of
the impacts, or the size, status, or structure of any of these species
or stocks that would lead to a different analysis for this activity.
NMFS does not anticipate that serious injury or mortality would
occur as a result of SIO's planned survey, even in the absence of
mitigation, and no serious injury or mortality is proposed to be
authorized. As discussed in the Potential Effects of Specified
Activities on Marine Mammals and their Habitat section above, non-
auditory physical effects and vessel strike are not expected to occur.
NMFS expects that all potential take would be in the form of Level B
behavioral harassment in the form of temporary avoidance of the area or
decreased foraging (if such activity was occurring), responses that are
considered to be of low severity, and with no lasting biological
consequences (e.g., Southall et al., 2007, 2021). These low-level
impacts of behavioral harassment are not likely to impact the overall
fitness of any individual or lead to population level effects of any
species. As described above, Level A harassment is not expected to
occur given the estimated small size of the Level A harassment zones.
[[Page 34238]]
In addition, the maximum expected Level B harassment zone around
the survey vessel is 505 m. Therefore, the ensonified area surrounding
the vessel is relatively small compared to the overall distribution of
animals in the area and their use of the habitat. Feeding behavior is
not likely to be significantly impacted as prey species are mobile and
are broadly distributed throughout the survey area; therefore, marine
mammals that may be temporarily displaced during survey activities are
expected to be able to resume foraging once they have moved away from
areas with disturbing levels of underwater noise. Because of the short
duration (two survey days) and temporary nature of the disturbance and
the availability of similar habitat and resources in the surrounding
area, the impacts to marine mammals and marine mammal prey species are
not expected to cause significant or long-term fitness consequences for
individual marine mammals or their populations.
Additionally, the acoustic ``footprint'' of the proposed survey
would be very small relative to the ranges of all marine mammals that
would potentially be affected. Sound levels would increase in the
marine environment in a relatively small area surrounding the vessel
compared to the range of the marine mammals within the proposed survey
area. The seismic airguns would be active 24 hours per day throughout
the duration of the proposed survey. However, the very brief overall
duration of the proposed survey (2 survey days) would further limit
potential impacts that may occur as a result of the proposed activity.
Of the marine mammal species that are likely to occur in the survey
area, the following species are listed as endangered or threatened
under the ESA: humpback whale (Central America and Mexico Distinct
Population Segments), sei whale, fin whale, blue whale, sperm whale,
and Guadalupe fur seal. The take numbers proposed for authorization for
these species (table 7) are minimal relative to their modeled
population sizes; therefore, we do not expect population-level impacts
to any of these species. Moreover, the actual range of the populations
extends past the area covered by the model, so modeled population sizes
are likely smaller than their actual population size. Lastly, as
previously described, meaningful impacts from the seismic survey are
even less likely to occur for high-frequency cetaceans (e.g.,
delphinids), as this group is relatively insensitive to sound produced
at the predominant frequencies in an airgun pulse. The other marine
mammal species that may be taken by harassment during SIO's seismic
survey are not listed as threatened or endangered under the ESA or
depleted under the MMPA. There is no designated critical habitat for
any ESA-listed marine mammals within the survey area.
There are no rookeries, mating, or calving grounds known to be
biologically important to marine mammals within the survey area, and
there are no feeding areas known to be biologically important to marine
mammals within the survey area.
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 any of the species
or stocks through effects on annual rates of recruitment or survival:
No Level A harassment, serious injury, or mortality is
anticipated or authorized;
The proposed activity is temporary and of very short
duration (3 days total with 3 days of planned survey activity);
The anticipated impacts of the proposed activity on marine
mammals would be temporary behavioral changes due to avoidance of the
ensonified area, which is relatively small (see tables 4 and 5);
The availability of alternative 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 is
readily abundant;
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 are expected to reduce
the number and severity of takes, to the extent practicable, by
visually and/or acoustically detecting marine mammals within the
established zones and implementing corresponding mitigation measures
(e.g., delay; shutdown).
Based on the analysis contained herein of the likely effects of the
specified activity on marine mammals and their habitat, and taking into
consideration the implementation of the proposed monitoring and
mitigation measures, NMFS preliminarily finds that the total marine
mammal take from the proposed activity will have a negligible impact on
all affected marine mammal species or stocks.
Small Numbers
As noted previously, only take of small numbers of marine mammals
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. When the predicted number of
individuals to be taken is fewer than one-third of the species or stock
abundance, the take is considered to be of small numbers (see 86 FR
5322, January 19, 2021). Additionally, other qualitative factors may be
considered in the analysis, such as the temporal or spatial scale of
the activities.
The number of takes NMFS proposes to authorize is below one-third
of the modeled abundance for all relevant populations (specifically,
take of individuals is equal or less than 2 percent of the modeled
abundance of each affected population, see table 7). This is
conservative because the modeled abundance represents a population of
the species and we assume all takes are of different individual marine
mammals, which is likely not the case. Some individuals may be
encountered multiple times in a day, but PSOs would count them as
separate individuals if they cannot be identified.
There is no abundance information available for the CA/WA/OR stock
of dwarf sperm whale. However, the take numbers proposed for
authorization are sufficiently small (one take by Level B harassment)
that we can safely assume that they are small relative to any
reasonable assumption of likely population abundance for this stock.
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 would 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.
[[Page 34239]]
Endangered Species Act
Section 7(a)(2) of the ESA of 1973 (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 humpback whale (Central
America and Mexico Distinct Population Segments), sei whale, fin whale,
blue whale, sperm whale, and Guadalupe fur seal which are listed under
the ESA.
The Permits and Conservation Division has requested initiation of
section 7 consultation with the Interagency Cooperation Division for
the issuance of this IHA. NMFS will conclude the ESA consultation prior
to reaching a determination regarding the proposed issuance of the
authorization.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
issue an IHA to SIO for conducting a marine geophysical survey in the
Cascadia Subduction Zone in the Northeast Pacific Ocean, 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/national/marine-mammal-protection/incidental-take-authorizations-research-and-other-activities.
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 marine
geophysical survey. We also request 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-time, 1-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 Description of Proposed
Activity section of this notice is planned or (2) the activities as
described in the Description of Proposed Activity 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 that the
renewal IHA expiration date cannot extend beyond 1 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).
(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: July 17, 2025.
Shannon Bettridge,
Acting Director, Office of Protected Resources, National Marine
Fisheries Service.
[FR Doc. 2025-13687 Filed 7-18-25; 8:45 am]
BILLING CODE 3510-22-P