37560 Federal Register / Vol. 87, No. 120 / Thursday, June 23, 2022 / Notices 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XC041] 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to Marine 

Geophysical Surveys at the Cascadia 

Subduction Zone and Juan de Fuca 

Plate in the Northeast Pacific Ocean 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice; proposed incidental 

harassment authorization; request for 

comments on proposed authorization 

and possible renewal. 

SUMMARY: NMFS has received a request 

from Lamont-Doherty Earth Observatory 

(L–DEO) for authorization to take 

marine mammals incidental to 

geophysical surveys at the Cascadia 

Subduction Zone and Juan de Fuca 

Plate in the Northeast Pacific Ocean. 

Pursuant to the Marine Mammal 

Protection Act (MMPA), NMFS is 

requesting comments on its proposal to 

issue an incidental harassment 

authorization (IHA) to incidentally take 

marine mammals during the specified 

activities. NMFS is also requesting 

comments on a possible one-time, oneyear renewal that could be issued under 

certain circumstances and if all 

requirements are met, as described in 

Request for Public Comments at the end 

of this notice. NMFS will consider 

public comments prior to making any 

final decision on the issuance of the 

requested MMPA authorization and 

agency responses will be summarized in 

the final notice of our decision. 

DATES: Comments and information must 

be received no later than July 25, 2022. 

ADDRESSES: Comments should be 

addressed to Jolie Harrison, Chief, 

Permits and Conservation Division, 

Office of Protected Resources, National 

Marine Fisheries Service and should be 

submitted via email to ITP.Corcoran@

noaa.gov. 

Instructions: NMFS is not responsible 

for comments sent by any other method, 

to any other address or individual, or 

received after the end of the comment 

period. Comments, 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 

www.fisheries.noaa.gov/permit/ 

incidental-take-authorizations-undermarine-mammal-protection-act without 

change. All personal identifying 

information (e.g., name, address) 

voluntarily submitted by the commenter 

may be publicly accessible. Do not 

submit confidential business 

information or otherwise sensitive or 

protected information. 

FOR FURTHER INFORMATION CONTACT: Kim 

Corcoran, Office of Protected Resources, 

NMFS, (301) 427–8401. Electronic 

copies of the application and supporting 

documents, as well as a list of the 

references cited in this document, may 

be obtained online at: https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/incidentaltake-authorizations-research-and-otheractivities. In case of problems accessing 

these documents, please call the contact 

listed above. 

SUPPLEMENTARY INFORMATION: 

Background 

The MMPA prohibits the ‘‘take’’ of 

marine mammals, with certain 

exceptions. Sections 101(a)(5)(A) and 

(D) of the MMPA (16 U.S.C. 1361 et 

seq.) direct the Secretary of Commerce 

(as delegated to NMFS) to allow, upon 

request, the incidental, but not 

intentional, taking of small numbers of 

marine mammals by U.S. citizens who 

engage in a specified activity (other than 

commercial fishing) within a specified 

geographical region if certain findings 

are made and either regulations are 

proposed or, if the taking is limited to 

harassment, a notice of a proposed 

incidental harassment authorization is 

provided to the public for review. 

Authorization for incidental takings 

shall be granted if NMFS finds that the 

taking will have a negligible impact on 

the species or stock(s) and will not have 

an unmitigable adverse impact on the 

availability of the species or stock(s) for 

taking for subsistence uses (where 

relevant). Further, NMFS must prescribe 

the permissible methods of taking and 

other ‘‘means of effecting the least 

practicable adverse impact’’ on the 

affected species or stocks and their 

habitat, paying particular attention to 

rookeries, mating grounds, and areas of 

similar significance, and on the 

availability of the species or stocks for 

taking for certain subsistence uses 

(referred to in shorthand as 

‘‘mitigation’’); and requirements 

pertaining to the mitigation, monitoring 

and reporting of the takings are set forth. 

The definitions of all applicable 

MMPA statutory terms cited above are 

included in the relevant sections below. 

National Environmental Policy Act 

To comply with the National 

Environmental Policy Act of 1969 

(NEPA; 42 U.S.C. 4321 et seq.) and 

NOAA Administrative Order (NAO) 

216–6A, NMFS must review our 

proposed action (i.e., the issuance of an 

IHA) with respect to potential impacts 

on the human environment. 

This action is consistent with 

categories of activities identified in 

Categorical Exclusion B4 (IHAs with no 

anticipated serious injury or mortality) 

of the Companion Manual for NOAA 

Administrative Order 216–6A, which do 

not individually or cumulatively have 

the potential for significant impacts on 

the quality of the human environment 

and for which we have not identified 

any extraordinary circumstances that 

would preclude this categorical 

exclusion. Accordingly, NMFS has 

preliminarily determined that the 

issuance of the proposed IHA qualifies 

to be categorically excluded from 

further NEPA review. 

Summary of Request 

On December 14, 2021, NMFS 

received a request from L–DEO for an 

IHA to take marine mammals incidental 

to a marine geophysical survey off the 

coasts of Oregon and Washington in the 

northeast Pacific Ocean. The application 

was deemed adequate and complete on 

April 4, 2022. L–DEO request is for take 

of small numbers of 23 species of 

marine mammals by Level B harassment 

only. Neither L–DEO nor NMFS expects 

serious injury or mortality to result from 

this activity and, therefore, an IHA is 

appropriate. 

NMFS previously issued an IHA to L– 

DEO for larger surveys in a similar 

location in the Northeast Pacific (e.g., 86 

FR 29090; May 28, 2021; 84 FR 35073; 

July 22, 2019). These surveys, however, 

included survey areas much closer to 

the coast. L–DEO complied with all the 

requirements (e.g., mitigation, 

monitoring, and reporting) of the 

previous IHAs and information 

regarding their monitoring results may 

be found in the Description of Marine 

Mammals in the Area of Specified 

Activities section. 

Description of Proposed Activity 

Overview 

Researchers from New Mexico 

Institute of Mining and Technology 

(NMT) and Oregon State University 

(OSU), with funding from the U.S. 

National Science Foundation (NSF) 

propose to conduct low-energy seismic 

surveys from the Research Vessel (R/V) 

Marcus G. Langseth (Langseth), which is 

owned and operated by Lamont-Doherty 

Earth Observatory (L–DEO) of Columbia 

University, at the Cascadia subduction 

Zone and Juan de Fuca Plate in the 


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Federal Register / Vol. 87, No. 120 / Thursday, June 23, 2022 / Notices 37561 

Northeast Pacific Ocean during Summer 

2022. The proposed two-dimensional 

(2–D) seismic surveys would occur 

within the Exclusive Economic Zone 

(EEZ) of the United States, in waters 

deeper than 1600 meters (m). To 

complete this survey, the R/V Langseth 

would tow a Generator-Injector (GI)- 

airgun cluster consisting of two 45 cubic 

inch (in3) GI guns spaced 2.46 m apart, 

with a total discharge volume of 90 in3. 

The acoustic source would be towed at 

2 to 4 m deep along the survey lines, 

while the receiving system is towed in 

an 800–1400 m long hydrophone 

streamer. 

The proposed study would acquire 

high-resolution 2–D seismic reflection 

data in conjunction with densely-spaced 

heat flow measurements to better 

understand the thermal structure of the 

Juan de Fuca plate as it enters the 

Cascadia subduction zone. The seismic 

and heat flow data would be acquired 

across several distinct structures that 

have not been previously studied, 

including a pseudofault, complex 

buried seamounts, and small outcrops 

that represent the summit of much 

larger buried seamounts. 

Dates and Duration 

The proposed survey is expect to last 

for 23 days, with approximately six days 

of seismic operations, three days of 

transit and 14 days of heat flow 

measurements. R/V Langseth would 

likely leave out of and return to port in 

Newport, OR, during summer 2022. 

Specific Geographic Region 

The proposed survey would occur 

within ∼42–47°N, ∼125–127°W off the 

coast of Washington and Oregon in the 

Northeast Pacific ocean. Four regions 

where the surveys are proposed to occur 

are depicted in Figure 1; the tracklines 

could occur anywhere within the boxes 

shown in Figure 1. No representative 

survey tracklines are shown, as actual 

track lines and order of survey 

operations are dependent on science 

objectives and weather. The surveys are 

proposed to occur within the EEZ of the 

U.S., in waters >1600 m deep. 

BILLING CODE 3510–22–P 


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37562 Federal Register / Vol. 87, No. 120 / Thursday, June 23, 2022 / Notices 

BILLING CODE 3510–22–C 

Detailed Description of Specific Activity 

The procedures to be used for the 

proposed surveys would be similar to 

those used during previous seismic 

surveys by L–DEO and would use 

conventional seismic methodology. The 

surveys would involve one source 

vessel, R/V Langseth, which is owned 

and operated by L–DEO. R/V Langseth 

would deploy two 45/105 in3 GI airguns 

as an energy source with a total volume 

of ∼90 in3. The receiving system would 

consist of one 800–1400 m long 

hydrophone streamer. As the airguns are 

towed along the survey lines, the 

hydrophone streamer would transfer 

data to the on-board processing system. 

Approximately 1135 kilometers (km) of 

transect lines would be surveyed in four 

survey regions in the Northeast Pacific 

Ocean; 200 km, 95 km, 440 km, and 400 

km in the Coast, Nubbin, Pseudofault, 

and Oregon survey regions, respectively. 

All survey effort would occur in deep 

water >1600 m. In addition to the 

operations of the airgun array, the ocean 

floor would be mapped with the 

Kongsberg EM 122 multibeam 

echosounder (MBES), a Knudsen CHIRP 


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13 "W 1 ·w 12 ·w 

LEGEND 

Survey Regions and Seismic Line km: 

c:J Coast - 200 km 

Nubbin - 95 km 

Killer Whale 

Humpback Whale 

Steller Sea Lion 

Leatherback Sea Turtle 

Green Sturgeon 

- - 200 Nautical Miles 

·•·•· 12 Nautical Miles 

' -···-· 3 Nautical Miles 

.. ,, 

.. "!-

. 

f f 

... 

lsobath (m) 

\ 

I 

" l 

I 

<?.. l Pacific 

I Ocean 

. 

lo 

/ () I •"( 

J ') 

,,. {/';!:Q. 

I :,:t(. 

~ t 

\ 50 100 

'\ 

□ 
Federal Register / Vol. 87, No. 120 / Thursday, June 23, 2022 / Notices 37563 

3260 (SBP) and an Acoustic Doppler 

Current Profiler (ADCP) would be 

operated from the vessel continuously. 

All planned geophysical data 

acquisition activities would be 

conducted by L–DEO with on-board 

assistance by the scientists who have 

proposed the studies. The vessel would 

be self-contained, and the crew would 

live aboard the vessel. Take of marine 

mammals is not expected to occur 

incidental to use of the MBES, SBP and 

ADCP, whether or not the airguns are 

operating simultaneously with the other 

sources. Given their characteristics (e.g., 

narrow downward-directed beam), 

marine mammals would experience no 

more than one or two brief ping 

exposures, if any exposure were to 

occur. NMFS does not expect that the 

use of these sources presents any 

reasonable potential to cause take of 

marine mammals. 

Proposed mitigation, monitoring, and 

reporting measures are described in 

detail later in this document (please see 

Proposed Mitigation and Proposed 

Monitoring and Reporting). 

Description of Marine Mammals in the 

Area of Specified Activities 

Sections 3 and 4 of the application 

summarize available information 

regarding status and trends, distribution 

and habitat preferences, and behavior 

and life history of the potentially 

affected species. NMFS fully considered 

all of this information, and we refer the 

reader to these descriptions, 

incorporated here by reference, instead 

of reprinting the information. 

Additional information regarding 

population trends and threats may be 

found in NMFS’ Stock Assessment 

Reports (SARs; 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 action, and 

summarizes information related to the 

population or stock, including 

regulatory status under the MMPA and 

Endangered Species Act (ESA) and 

potential biological removal (PBR), 

where known. PBR is defined by the 

MMPA as the maximum number of 

animals, not including natural 

mortalities, that may be removed from a 

marine mammal stock while allowing 

that stock to reach or maintain its 

optimum sustainable population (as 

described in NMFS’ SARs). While no 

serious injury or mortality is anticipated 

or authorized here, PBR and annual 

serious injury and mortality from 

anthropogenic sources are included here 

as gross indicators of the status of the 

species and other threats. 

Marine mammal abundance estimates 

presented in this document represent 

the total number of individuals that 

make up a given stock or the total 

number estimated within a particular 

study or survey area. NMFS’s stock 

abundance estimates for most species 

represent the total estimate of 

individuals within the geographic area, 

if known, that comprise that stock. For 

some species, this geographic area may 

extend beyond U.S. waters. All managed 

stocks in this region are assessed in 

NMFS’s U.S. Pacific SARs (Carretta et 

al., 2021). All values presented in Table 

1 are the most recent available at the 

time of publication and are available in 

the 2020 SARs (Carretta et al., 2021) and 

draft 2021 SARs (available online at: 

https://www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

marine-mammal-stock-assessmentreports). 

TABLE 1—SPECIES LIKELY IMPACTED BY THE SPECIFIED ACTIVITIES

Common name Scientific name Stock 

ESA/ 

MMPA 

status; 

strategic 

(Y/N) 1

Stock abundance (CV, Nmin, most recent abundance survey) 2 PBR Annual 

M/SI 3

Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales) 

Family Balaenopteridae 

(rorquals): 

Humpback whale ... Megaptera 

novaeangliae.

California/Oregon/ 

Washington.

–,–,Y 4,973 (0.05, 4,776, 2018) 28.7 >48.6 

Minke whale .......... Balaenoptera 

acutorostrata.

California/Oregon/ 

Washington.

–,–,N 915 (0.792, 509, 2018) 4.1 >0.59 

Sei whale ............... Balaenoptera borealis .. Eastern North Pacific ... E, D, Y 519 (0.4, 374, 2014) 0.75 >0.2 

Fin whale ............... Balaenoptera physalus California/Oregon/ 

Washington.

E, D, Y 11,065 (0.405, 7,970, 2018) 80 >2.2 

Blue whale ............. Balaenoptera musculus Eastern North Pacific ... E, D, Y 1,898 (0.085, 1,767, 2018) 4.1 >19.4 

Superfamily Odontoceti (toothed whales, dolphins, and porpoises) 

Family Physeteridae: 

Sperm whale ......... Physeter 

macrocephalus.

California/Oregon/ 

Washington.

E, D, Y 1,997 (0.57, 1270, 2014) 2.5 0.6 

Family Kogiidae: 

Pygmy sperm 

whale.

Kogia breviceps ........... California/Oregon/ 

Washington.

–,–,N 4,111 (1.12, 1924, 2014) 19 0 

Dwarf sperm whale Kogia sima ................... California/Oregon/ 

Washington.

–,–,N UNK (UNK, UNK, 2014) UND 0 

Family Ziphiidae 

(beaked whales): 

Baird’s beaked 

whale.

Berardius Bairdii ........... California/Oregon/ 

Washington.

–,–,N 1,363 (0.53, 894, 2018) 8.9 >0.2 

Cuvier’s beaked 

whale.

Ziphius cavirostris ........ California/Oregon/ 

Washington.

–,–,N 3,274 (0.67, 2,059, 2014) 21 <0.1 

Mesoplodont 

Beaked Whales.

Mesoplodon spp. .......... California/Oregon/ 

Washington.

–,–,N 3,044 (0.54, 1,967, 2005) 20 0.1 

Family Delphinidae: 

Striped dolphin ...... Stenella coeruleoalba .. California/Oregon/ 

Washington.

–,–,N 29,988 (0.3, 23,448, 2018) 225 >4 

Short-beaked common dolphin.Delphinus delphis ......... California/Oregon/ 

Washington.

–,–,N 1,056,308 (0.21, 888,971, 2018) 8,889 >30.5 


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37564 Federal Register / Vol. 87, No. 120 / Thursday, June 23, 2022 / Notices 

TABLE 1—SPECIES LIKELY IMPACTED BY THE SPECIFIED ACTIVITIES—Continued 

Common name Scientific name Stock 

ESA/ 

MMPA 

status; 

strategic 

(Y/N) 1

Stock abundance (CV, Nmin, most recent abundance survey) 2 PBR Annual 

M/SI 3

Pacific white-sided 

dolphin.

Lagenorhynchus 

obliquidens.

California/Oregon/ 

Washington.

-,-,C 34,998 (0.222, 29,090, 2018) 279 7 

Northern right 

whale dolphin.

Lissodelphis borealis .... California/Oregon/ 

Washington.

–,–,N 29,285 (0.72, 17024, 2018) 163 >6.6 

Risso’s dolphin ...... Grampus griseus .......... California/Oregon/ 

Washington.

–,–,N 6,336 (0.32, 4,817, 2014) 46 >3.7 

Killer whale ............ Orcinus orca ................. West Coast Transient .. –,–,N 349 (N/A, 349, 2018) 3.5 0.4 

North Pacific Offshore .. –,–,N 300 (0.1, 276, 2012) 2.8 0 

Family Phocoenidae 

(porpoises): 

Dall’s porpoise ....... Phocoenoides dalli ....... California/Oregon/ 

Washington.

–,–,N 16,498 (0.61, 10,286, 2019) 99 >0.66 

Order Carnivora—Superfamily Pinnipedia 

Family Otariidae (eared 

seals and sea lions): 

Northern fur seal ... Callorhinus ursinus ...... Eastern Pacific ............. -,D,Y 626,618 (0.2, 530,376, 2020) 11,403 373 

California ...................... -,D,Y 14,050 (N/A, 7,524, 2013) 451 1.8 

Guadalupe fur seal Arctocephalus 

townsendi.

Mexico .......................... T, D, Y 34,187 (N/A, 31,019, 2013) 1,062 >3.8 

Steller sea lion ....... Eumetopias jubatus ..... Eastern ......................... –,–,N 43,201 (N/A, 43,201,2017) 2,592 112 

California sea lion .. Zalophus californianus United States ............... –,–,N 257,606 (N/A, 233,525, 2014) 14,011 >320 

Family Phocidae (earless seals): 

Northern elephant 

seal.

Mirounga angustirostris California Breeding ...... –,–,N 187,386 (N/A, 85,369, 2013) 5,122 5.3 

1—Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the 

ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or 

which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically 

designated under the MMPA as depleted and as a strategic stock. 2—NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable. 3—These values, found in NMFS’s SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated 

mortality due to commercial fisheries is presented in some cases. 

As indicated above, all 23 species 

(with 25 managed stocks) in Table 1 

temporally and spatially co-occur with 

the activity to the degree that take is 

reasonably likely to occur. While North 

Pacific right whales (Eubalaena 

japonica), bottlenose dolphins (Tursiops 

truncatus), short-finned pilot whales 

(Globicephala macrorhynchus), gray 

whales (Eschrichtius robustus), and 

false killer whales (Pseudorca 

crassidens) have been documented near 

the area, the temporal and/or spatial 

occurrence of these species is such that 

take is not expected to occur. Therefore, 

they are not discussed further beyond 

the explanation provided below. 

The North Pacific right whale is one 

of the rarest marine mammals in the 

world (Muto et al., 2021). The species 

comprises of an eastern and western 

population that are largely or wholly 

discrete. The summer range of the 

eastern stock includes the Gulf of 

Alaska and the Bergin Sea, while the 

western stock is believed to feed in the 

Okhotsk Sea and in pelagic waters of the 

northwestern North Pacific (Muto et al., 

2021). Whaling records from the 19th 

century and recent Soviet catch data 

have shown that right whales were 

broadly distributed across the eastern 

North Pacific (Scarff 1986, Brownell et 

al., 2001, Ivashchenko and Clapham 

2012). There are sporadic records from 

below 20 degrees north, but the bulk of 

the data show right whales concentrated 

north of 35 degrees north, including 

coastal and offshore waters ranging from 

Washington state and British Columbia 

through the Gulf of Alaska, Alaska 

Peninsula, Aleutian Islands, and the 

Bering Sea (Muto et al., 2021). 

The eastern North Pacific stock that 

occurs in the United States is estimated 

to contain 31 whales for the Bering sea 

and Aleutian Islands. A Biologically 

Important Area (BIA) for feeding for 

North Pacific right whales was 

designated east of the Kodiak 

Archipelago, which includes the Gulf of 

Alaska critical habitat and extends 

south of 56 degrees north and north of 

58 degrees north and beyond the shelf 

edge. South of 50 degrees north, only 29 

reliable sightings were recorded from 

1900–1994 (Scarff 1986, 1991; Carretta 

et al.,1994). Off the coast of California/ 

Oregon/Washington, only seven 

documented sightings of right whales 

were made from 1990 through 2000. 

Two North Pacific right whale calls 

were detected on a bottom-mounted 

hydrophone (located in water 1390 m 

deep) off the Washington coast on June 

29, 2013 (Sirovic et al., 2014). During L– 

DEO’s summer 2021 seismic survey in 

the Northeast Pacific, a sighting of two 

individuals was made northwest of the 

survey area in British Columbia, west of 

Haida Gwaii on July 27, 2021. Because 

of the small population size, and the 

fact that North Pacific right whales 

spend the summer feeding in high 

latitudes, the likelihood that the 

proposed survey would encounter a 

North Pacific right whale is 

discountable, and NMFS is not 

proposing to authorize take of this 

species. 

Bottlenose dolphins are distributed 

worldwide in tropical and warmtemperate waters. Bottlenose dolphins 

occur frequently off the coast of 

California, and sightings have been 

made as far north as 41 degrees north, 

but few records exist for Oregon and 

Washington (Carretta et al., 2021). In 

California, separate coastal and offshore 

populations are known (Walker 1981; 

Ross and Cockcroft 1999; Van 

Waerebeek et al., 1990; Lowther 2006). 

Three sightings and one stranding of 

bottlenose dolphins have been 

documented in Puget Sound since 2004 

(Cascadia Research 2011 in U.S.C. 


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2015). L–DEO requested authorization 

for the incidental take of bottlenose 

dolphins (the request was for a total of 

13 individuals). Although sightings of 

bottlenose dolphins in Puget Sound 

have increased considerably since 2016 

(Cascadia Research Collective, 2020), 

given the far north and offshore 

placement of the proposed survey and 

the species’ tendency to stay in coastal 

waters and in lower latitudes, we 

believe it is highly unlikely that 

bottlenose dolphins would be 

encountered in the proposed survey 

area, and NMFS is not proposing to 

authorize take of this species. 

Short-finned pilot whales are found in 

tropical and warm temperate waters 

(Olson 2018) and seen as far south as 40 

degrees south and as far north as 50 

degrees north (Jefferson et al., 2015). 

Pilot whales are generally nomadic, but 

may reside in certain locations, 

including California and Hawaii (Olson 

2018). The species were common off 

southern California (Dohl et al., 1980) 

until an El Nino event occurred in 

1982–1983 (Green et al., 1992; Carretta 

and Forney 1993; Barlow 1997). Few 

sightings were made off California/ 

Oregon/Washington in 1983–1984, but 

sightings remain rare (Barlow 1997; 

Buchanan et al., 2001; Barlow 2010). No 

short-finned pilot whales were seen 

during surveys off Oregon and 

Washington in 1989–1990, 1992, 1996, 

and 2001 (Barolow 2003). Only one 

sighting has occurred off Oregon from 

1991–2014 (Carretta et al., 2021). 

Although zero Level B harassment 

exposure estimates were calculated, L– 

DEO requested authorization for the 

incidental take of 29 short-finned pilot 

whales based on the average group size 

produced by Barlow (2016). However, 

considering the species’ historical 

occurrence in the proposed survey area, 

their preference for warmer tropical 

waters, and the best available 

information, the likelihood that L–DEO 

will encounter short-finned pilot whales 

in the proposed survey area is 

discountable, and NMFS is not 

proposing to authorize take of this 

species. 

Two separate populations of gray 

whales have been recognized in the 

North Pacific: the eastern North Pacific 

and western North Pacific stocks (LeDuc 

et al., 2002; Weller et al., 2013). 

However, the distinction between these 

two populations has been recently 

debated owing to evidence that whales 

from the western feeding area also travel 

to breeding areas in the eastern North 

Pacific (Weller et al., 2012, 2013; Mate 

et al., 2015). BIAs for feeding gray 

whales along the coasts of Washington, 

Oregon, and California have been 

identified, including northern Puget 

sound, Northwestern Washington, and 

Grays Harbor (WA); Depoe Bay and 

Cape Blanco and Orford Reef (OR), and 

Point St. George (CA); most of these 

areas are of importance from late spring 

through early fall (Calambokidis et al., 

2015); none occur within the proposed 

survey region. Resident gray whales 

have been observed foraging off the 

coast of Oregon from May through 

October and off Washington June 

through November (Newell and Cowles 

2006; Scordino et al., 2014). BIAs have 

also been identified for migrating gray 

whales along the entire coasts of 

Washington, Oregon, and California; 

although most whales travel within 10 

km from shore, the BIAs were extended 

out to 47 km from the coastline 

(Calambokidis et al., 2015); the 

proposed Oregon survey region is 

located adjacent to this BIA (see Figure 

1). Gray whales from the far north begin 

to migrate south to breeding grounds on 

the west coast of Baja California and the 

southeastern Gulf of California in 

October and November (Braham 1984; 

Rugh et al., 2001). Gray whales migrate 

closest to the Washington/Oregon 

coastline during spring (April–June), 

when most strandings are observed 

(Norman et al., 2004). The species’ stock 

range extends from as far south as 

Mexico all the way north to the Gulf of 

Alaska, primarily hugging the coastline 

(NMFS 2022). 

NOAA (2021b) declared an unusual 

mortality event (UME) for gray whales 

in 2019, as an elevated number of 

strandings have occurred along the coast 

of the Pacific Northwest since January 

2019. As of 1 October 2021, a total of 

212 dead gray whales have been 

reported, including 248 in the U.S. (55 

in Washington; 12 in Oregon), 225 in 

Mexico, and 19 in B.C.; some of the 

whales were emaciated. A UME for gray 

whales was also declared for 1999–2000 

(NOAA 2021c). 

The proposed survey is planned 

during the summer feeding season, 

when most individuals from the eastern 

North Pacific stock occur farther north. 

Although individuals, particularly from 

the Pacific Coast Feeding Group (PCFG), 

could be encountered in nearshore 

waters less than 10 km from shore, the 

likelihood that any gray whales will be 

encountered as far offshore as the 

proposed survey area is discountable. 

Gray whales have been observed to have 

a distinct ecological niche in nearshore 

and shallow waters (Darling et al., 1998) 

and L–DEO’s proposed activities to not 

overlap with this niche. L–DEO 

requested the incidental take of a 

singular gray whale, however NMFS 

does not propose to authorize any take 

of gray whales as it is temporally and 

spatially unlikely that they will be 

encountered. 

Lastly, the false killer whale is found 

worldwide in tropical and temperate 

waters, generally between 50 degrees 

north and 50 degrees south (Odell and 

McClune 1999). It is widely distributed, 

but not abundant anywhere (Carwardine 

1995). The false killer whale generally 

inhabits deep, offshore waters, but 

sometimes is found over the continental 

shelf and occasionally moves into very 

shallow water (Jefferson et al., 2015; 

Baird 2018b). In the eastern North 

Pacific, it has been reported only rarely 

north of Baja California (Leatherwood et 

al., 1982, 1987; Mangels and Gerrodete 

1994); however, the waters off the 

United States west coast all the way 

north to Alaska are considered part of 

its secondary range (Jefferson et al., 

2015). 

Its occurrence in Washington/Oregon 

is associated with warm-water 

incursions (Buchanan et al., 2001). 

However, no sightings of false killer 

whales were made along the U.S. west 

coast during surveys conducted from 

1986–2001 (Ferguson and Barlow 2001, 

2003; Barlow 2003) or in 2005 and 2008 

(Forney 2007; Barlow 2010). One pod of 

false killer whales occurred in Puget 

Sound for several months during the 

1990s (USN 2015). Two false killer 

whales were reported stranded along the 

Washington coast during 1930–2002, 

both in El Nin ̃ o years (Norman et al., 

2004). Based on the best available 

information, NMFS believes that the 

likelihood of the survey encountering a 

false killer whale is discountable and, 

although L–DEO requested incidental 

take of 5 whales based on their average 

group size (Mobley et al., 2000), NMFS 

does not propose authorizing any take of 

false killer whales. 

Humpback Whale 

The humpback whale is found 

throughout all of the oceans of the 

world (Clapham 2009). The worldwide 

population is divided into northern and 

southern ocean populations, but genetic 

analyses suggest some gene flow (either 

past or present) between the North and 

South Pacific (e.g., Jackson et al,. 2014; 

Bettriddge et al,. 2015). Although 

considered to be mainly a coastal 

species, humpback whales often 

traverse deep pelagic areas while 

migrating (Calambokidis et al., 2001; 

Garrigue et al., 2002; Zerbini et al., 

2011). Humpbacks migrate between 

summer feeding grounds in high 

latitudes and winter calving and 

breeding grounds in tropical waters 

(Clapham and Mead 1999). Northern 

Pacific humpback whales summer in 


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feeding grounds along the Pacific Rim 

and in the Bering and Okhotsk seas 

(Pike and MacAskie 1969; Rice 1978; 

Winn and Reichley 1985; Calambokidis 

et al., 2000, 2001, 2008; Bettridge et al., 

2015). Humpbacks in the north Pacific 

winter in four different breeding areas: 

(1) along the coast of Mexico; (2) along 

the coast of Central America; (3) around 

the main Hawaiian Islands; and (4) in 

the western Pacific, particularly around 

the Ogasawara and Ryukyu islands in 

southern Japan and the northern 

Philippines (Calambokidis et al., 2008; 

Bettridge et al., 2015). 

Prior to 2016, humpback whales were 

listed under the ESA as an endangered 

species worldwide. Following a 2015 

global status review (Bettridge et al., 

2015), NMFS established 14 distinct 

population segments (DPS) with 

different listing statuses (81 FR 62259); 

September 8, 20216) pursuant to the 

ESA. The DPSs that occur in United 

States waters do not necessarily equate 

to the existing stocks designated under 

the MMPA and shown in Table 1. 

Because the MMPA stocks cannot be 

portioned (i.e,. parts managed as ESAlisted while other parts managed as nonESA listed), until such time as the 

MMPA stock delineations are reviewed 

in light of the DPS designations, NMFS 

considers the existing humpback whale 

stocks under the MMPA to be 

endangered and depleted for MMPA 

management purposes (e.g., selection of 

a recovery factor, stock status). 

NMFS has identified three DPSs of 

humpback whales that are found off the 

coasts of Washington, Oregon and 

California. These are: the Hawaii DPS 

(found predominately off Washington 

and southern British Columbia), which 

is not listed under the ESA; the Mexico 

DPS (found all along the west coast), 

which is listed as threatened under the 

ESA; and the Central America DPS 

(found all along the west coast, but most 

common off California and Oregon), 

which is listed as endangered under the 

ESA. According to Wade (2021), the 

probability that whales encountered in 

Oregon and California waters are from a 

given DPS are as follows: Central 

America DPS (42 percent); Mexico DPS 

(58 percent); Hawaii DPS (0 percent). 

The probability that humpback whales 

encountered in Washington and British 

Columbia waters are as follows: Central 

America DPS (6 percent); Mexico DPS 

(25 percent); Hawaii DPS (69 percent). 

Wade (2021) notes that the majority of 

humpback whales that may be found off 

of Washington are likely moving north 

of the United States border and feeding 

primarily off of southern British 

Columbia. 

Humpback whales are the most 

common species of large cetacean 

reported off the coasts of Oregon and 

Washington from May to November 

(Green et al., 1992; Calambokidis et al., 

2000, 2004). Humpbacks occur 

primarily over the continental shelf and 

slope during the summer, but a few 

individuals have been reported in 

offshore pelagic waters (Green et al., 

1992; Calambokidis et al., 2004, 2015; 

Becker et al., 2012; Barlow 2016; 

Carretta et al., 2021). Biologically 

Important Areas (BIAs) for feeding 

humpback whales along the coasts of 

Oregon and Washington, which have 

been designated from May through 

November, are all within approximately 

80 kilometers (km) from shore, and 

include the waters off northern 

Washington, and Stonewall and Heceta 

Bank, OR (Calambokidis et al., 2015). 

Six humpback whale sightings (eight 

animals) were made off Washington and 

Oregon during the June through July 

2012 L–DEO Juan de Fuca plate seismic 

survey. There were 98 humpback whale 

sightings (213 animals) made during the 

July 2012 L–DEO seismic survey off 

Oregon (RPS 2012a), and 11 sightings 

(23 animals) during the July 2012 L– 

DEO seismic survey off Oregon (RPS 

2012c). Numerous humpback whale 

sightings were made during L–DEO’s 

Cascadia summer survey off Oregon and 

Washington in 2021 (RPS). 

On April 21, 2021, NMFS designated 

critical habitat in nearshore waters of 

the North Pacific Ocean for the 

endangered Central America and 

Western North Pacific DPSs and the 

threatened Mexico DPS of humpback 

whales (NMFS 2021). Critical habitat for 

the Central America and Mexico DPSs 

include waters within the California 

Current Ecosystem (CCE) off the coasts 

of California, Oregon, and Washington 

(Figure 1). Off Washington, critical 

habitat includes waters from the 50 m 

to 1200 m isobaths, as well as the strait 

of Juan de Fuca eastward to Angeles 

Point; however, there is an exclusion 

area of 1461 nautical square miles 

(nmi2) around the Navy’s Quinault 

Range Site. Off Oregon, the critical 

habitat spans from the 50 m to 1200 m 

isobath until 42.17 degrees north where 

the critical habitat south of 42.17 

degrees north extends out to the 2000 m 

isobath (NMFS 2021). There is no 

critical habitat designated within the 

proposed survey regions, and ensonified 

areas would not extend into critical 

habitat. Humpback whales are expected 

to be uncommon in the proposed 

offshore survey areas. 

Blue Whale 

The blue whale has a cosmopolitan 

distribution and tends to be pelagic, 

only coming nearshore to feed and 

possibly to breed (Jefferson et al., 2015). 

Although it has been suggested that 

there are at least five subpopulations of 

blue whales in the North Pacific (NMFS 

1998), analysis of blue whales calls 

monitored from the U.S. Navy Sound 

surveillance system (SOSUS) and other 

offshore hydrophones (see Stafford et 

al., 1999, 2001, 2007; Watkins et al., 

2000; Stafford 2003) suggest that there 

are two separate populations: one in 

eastern and one in the western North 

Pacific (Sears and Perrin 2018). The 

status of these two populations could 

differ substantially, as little is known 

about the population size in the western 

North Pacific (Branch et al., 2016). 

Broad scale acoustic monitoring 

indicate that blue whales occurring in 

the northeast Pacific during summer 

and fall may winter in the eastern 

tropical Pacific (Stafford et al., 1999, 

2001). 

The distribution of the species, at 

least during times of the year when 

feeding is prevalent, occurs in areas that 

provide large seasonal concentrations of 

euphausiids (Yochem and Leatherwood 

1985). The eastern North Pacific stock 

feeds in California waters from June 

through November (Calambokidis et 

al.,1990; Mate et al., 2015), and core 

areas have also been identified. 

Blue whales are considered rare off 

Oregon, Washington, and B.C. 

(Buchanan et al. 2001; Gregr et al., 2006; 

Ford 2014), although satellite-tracked 

individuals have been reported off the 

coast (Bailey et al., 2009). Based on 

modeling of the dynamic topography of 

the region, blue whales could occur in 

relatively high densities off Oregon 

during summer and fall (Pardo et al. 

2015: Hazen et al. 2017). Recent 

phenology analysis of marine mammal 

sightings revealed a peak of blue whale 

density over the Oregon continental 

shelf in September, and their sighting 

rates in the region have increased over 

the past three decades as a response to 

environmental changes influencing prey 

availability shifting their range 

northward (Derville et al., 2022). 

Densities along the U.S. west coast, 

including Oregon, were predicted to be 

highest in shelf waters, with lower 

densities in deeper offshore areas 

(Becker et al., 2012; Calambokidis et al., 

2015). Blue whales have been detected 

acoustically off Oregon (McDonald et 

al., 1995; Stafford et al., 1998; Von 

Saunder and Barlow 1999). Blue whales 

could be encountered in the proposed 

survey areas. 


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Fin Whale 

The fin whale is widely distributed in 

all the World’s oceans (Gambell 1985b), 

although it is most abundant in 

temperate and cold waters (Aguilar and 

Garcı ́a-Vernet 2018). Nonetheless, its 

overall range and distribution are not 

well known (Jefferson et al., 2015). A 

review of fin whale distribution in the 

North Pacific noted the lack of sightings 

across pelagic waters between eastern 

and western winter areas (Mizroch et 

al., 2009). Fin whales most commonly 

occur offshore, but can also be found in 

coastal areas (Jefferson et al., 2015). 

Most populations migrate seasonally 

between temperate waters where mating 

and calving occur in winter, and polar 

waters where feeding occurs in summer 

(Aguilar and Garcı ́a-Vernet 2018). Some 

animals may remain at high latitudes in 

winter or low latitudes in summer 

(Edwards et al., 2015). The northern and 

southern fin whale populations likely 

do not interact owing to their alternate 

seasonal migration; the resulting genetic 

isolation has led to the recognition of 

two subspecies, B. physalus quoyi and 

B. p. physalus in the Southern and 

Northern hemispheres, respectively 

(Anguilar and Garcı ́a-Vernet 2018). The 

fin whale is known to use the shelf edge 

as a migration route (Evans 1987). 

Sergeant (1977) suggested that fin 

whales tend to follow steep slope 

contours, either because they detect 

them readily, or because the contours 

are areas of high biological productivity. 

However, fin whale movements have 

been reported to be complex (Jefferson 

et al., 2015). Stafford et al. (2009) noted 

that sea-surface temperature is a good 

predictor variable for fin whale call 

detections in the North Pacific. 

North Pacific fin whales summer from 

the Chukchi Sea to California and 

winter from California southwards 

(Gambell 1985b). Information about the 

seasonal distribution of fin whales in 

the North Pacific has been obtained 

from the detection of fin whale calls by 

bottom-mounted, offshore hydrophone 

arrays along the U.S. Pacific coast, in 

the central North Pacific, and in the 

western Aleutian Islands (Moore et al., 

1998, 2006; Watkins et al., 2000a,b; 

Stafford et al., 2007, 2009). Fin whale 

calls are recorded in the North Pacific 

year-round (e.g., Moore et al., 2006; 

Stafford et al., 2007, 2009; Edwards et 

al., 2015). In the central North Pacific, 

the Gulf of Alaska, and Aleutian Islands, 

call rates peak during fall and winter 

(Moore et al., 1998, 2006; Watkins et al., 

2000a,b; Stafford et al., 2009). 

Fin whales are routinely sighted 

during surveys off Oregon and 

Washington (Barlow and Forney 2007; 

Barlow 2010, 2016; Adams et al., 2014; 

Calambokidis et al., 2015; Edwards et 

al., 2015; Carretta et al., 2021), 

including in coastal as well as offshore 

waters. They have also been detected 

acoustically in those waters during 

June–August (Edwards et al., 2015). 

Eight fin whale sightings (19 animals) 

were made off Washington/Oregon 

during the June–July 2012 L–DEO Juan 

de Fuca plate seismic survey; sightings 

were made in waters 2369–3940 m deep 

(RPS 2012b). Fourteen fin whale 

sightings (28 animals) were made during 

the July 2012 L–DEO seismic surveys off 

southern Washington (RPS 2012a). No 

fin whales were sighted during the July 

2012 L–DEO seismic survey off Oregon 

(RPS 2012c). During L–DEO’s Cascadia 

survey during June–July 2021, five 

sightings of seven fin whales were made 

off Oregon (RPS 2021b). Fine whales 

were also seen off southern Oregon 

during July 2012 in water >2000 m deep 

during surveys by Adams et al., (2014). 

Fin whales are likely to be encountered 

in the proposed survey area. 

Sei Whale 

The sei whale occurs in all ocean 

basins (Horwood 2018), but appears to 

prefer mid-latitude temperate waters 

(Jefferson et al. 2015). It undertakes 

seasonal migrations to feed in subpolar 

latitudes during summer and returns to 

lower latitudes during winter to calve 

(Horwood 2018). The sei whale is 

pelagic and generally not found in 

coastal waters (Harwood and Wilson 

2001). It occurs in deeper waters 

characteristic of the continental shelf 

edge region (Hain et al., 1985) and in 

other regions of steep bathymetric relief 

such as seamounts and canyons 

(Kenney and Winn 1987; Gregr and 

Trites 2001). On feeding grounds, sei 

whales associate with oceanic frontal 

systems (Horwood 1987) such as the 

cold eastern currents in the North 

Pacific (Perry et al., 1999). Sei whales 

migrate from temperate zones occupied 

in winter to higher latitudes in the 

summer, where most feeding takes place 

(Gambell 1985a). During summer in the 

North Pacific, the sei whale can be 

found from the Bering Sea to the Gulf 

of Alaska and down to southern 

California, as well as in the western 

Pacific from Japan to Korea. Its winter 

distribution is concentrated at ∼20° N 

(Rice 1998). 

Sei whales are rare in the waters off 

Washington, Oregon, and California 

(Brueggeman et al., 1990; Green et al., 

1992; Barlow 1994, 1997). Less than 20 

confirmed sightings were reported in 

that region during extensive surveys 

during 1991–2014 (Green et al., 1992, 

1993; Hill and Barlow 1992; Carretta 

and Forney 1993; Mangels and 

Gerrodette 1994; Von Saunder and 

Barlow 1999; Barlow 2003, 2010, 2014; 

Forney 2007; Carretta et al., 2021). 

Based on surveys conducted in 1991– 

2008, the estimated abundance of sei 

whales off the coasts of Oregon and 

Washington was 52 (Barlow 2010); for 

2014, the abundance estimate was 468 

(Barlow 2016). Two sightings of four 

individuals were made during the June– 

July 2012 L–DEO Juan de Fuca plate 

seismic survey off Washington/Oregon 

(RPS 2012b). No sei whales were sighted 

during the summer 2012 or 2021 L–DEO 

seismic surveys off Oregon and 

Washington (RPS 2012a,c, 2021). Sei 

whales could be encountered during the 

proposed survey, although this species 

is considered rare in these waters. 

Minke Whale 

The minke whale has a cosmopolitan 

distribution that spans from tropical to 

polar regions in both hemispheres 

(Jefferson et al., 2015). In the Northern 

Hemisphere, the minke whale is usually 

seen in coastal areas, but can also be 

seen in pelagic waters during its 

northward migration in spring and 

summer and southward migration in 

autumn (Stewart and Leatherwood 

1985). In the North Pacific, the summer 

range of the minke whale extends to the 

Chukchi Sea; in the winter, the whales 

move south to within 2° of the Equator 

(Perrin et al., 2018). 

The International Whaling 

Commission (IWC) recognizes three 

stocks of minke whales in the North 

Pacific: the Sea of Japan/East China Sea, 

the rest of the western Pacific west of 

180° N, and the remainder of the Pacific 

(Donovan 1991). Minke whales are 

relatively common in the Bering and 

Chukchi seas and in the Gulf of Alaska 

but are not considered abundant in any 

other part of the eastern Pacific 

(Brueggeman et al., 1990). In the far 

north, minke whales are thought to be 

migratory, but they are believed to be 

year-round residents in nearshore 

waters off west coast of the U.S. (Dorsey 

et al., 1990). 

Sightings have been made off Oregon 

and Washington in shelf and deeper 

waters (Green et al., 1992; Adams et al., 

2014; Barlow 2016; Carretta et al., 2021). 

An estimated abundance of 211 minke 

whales was reported for the Oregon/ 

Washington region based on sightings 

data from 1991–2005 (Barlow and 

Forney 2007), whereas a 2008 survey 

did not record any minke whales while 

on survey effort (Barlow 2010). The 

abundance for Oregon/Washington for 

2014 was estimated at 507 minke 

whales (Barlow 2016). There were no 

sightings of minke whales off Oregon/ 


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Washington during L–DEO’s summer 

seismic surveys in 2012 or 2021 (RPS 

2012b,c, 2021). One minke whale was 

seen during the July 2012 L–DEO 

seismic survey off southern Washington 

(RPS 2012a). Minke whales are expected 

to be uncommon in the proposed survey 

areas. 

Sperm Whale 

The sperm whale is the largest of the 

toothed whales, with an extensive 

worldwide distribution (Rice 1989). 

Sperm whale distribution is linked to 

social structure: Mixed groups of adult 

females and juveniles animals of both 

sexes generally occur in tropical and 

subtropical waters, whereas adult makes 

are commonly found alone or in the 

same-sex aggregations, often occurring 

in higher latitudes outside the breeding 

season (Best 1979; Watkins and Moore 

1982; Arnbom and Whitehead 1989; 

Whitehead and Waters 1990). Males can 

migrate north in the summer to feed in 

the Gulf of Alaska, Bering Sea, and 

waters around the Aleutian Islands 

(Kasuya and Miyashita 1988). Females 

generally inhabit waters over 1000 m 

deep at latitudes under 40 degrees 

where sea surface temperatures are 

under 15 degrees Celsius; adult males 

move to higher latitudes as they grow 

older and larger in size, returning to 

warm-water breeding grounds according 

to an unknown schedule (Whitehead 

2018). 

Sperm whales are distributed widely 

across the North Pacific (Rice 1989). Off 

California, they occur year-round (Dohl 

et al., 1983: Barlow 1995; Forney et al., 

1995), with peak abundance from April 

to mid-June and from August to midNovember (Rice 1974). Off Oregon, 

sperm whales are seen in every season 

except winter (Green et al., 1992). 

Sperm whales were sighted during 

surveys off Oregon in October 2011 and 

off Washington in June 2011 (Adams et 

al., 2014). Sperm whale sightings were 

also made off Oregon and Washington 

during the 2014 Southwest Fisheries 

Science Center (SWFSC) vessel survey 

(Barlow 2016). Sperm whale were 

detected acoustically in waters off 

Oregon and Washington in August 2016 

during the SWFSC Passive Acoustics 

Survey of Cetacean Abundance Levels 

(PASCAL) study using drifting acoustic 

recorders (Keating et al., 2018). Oleson 

et al. (2009) noted a significant diel 

pattern in the occurrence of sperm 

whale clicks at offshore and inshore 

monitoring locations off Washington, 

whereby clicks were more commonly 

heard during the day at the offshore site 

and at night at the inshore location, 

suggesting possible diel movements up 

and down the slope in search of prey. 

Sperm whale acoustic detections were 

also reported at an inshore site from 

June through January 2009, with an 

absence of calls during February 

through May (Sirovic et al., 2012). 

Sperm whales are likely to be 

encountered in the proposed survey 

areas. 

Baird’s Beaked Whale 

Baird’s beaked whale has a fairly 

extensive range across the North Pacific 

north of 30° N, and strandings have 

occurred as far north as the Pribilof 

Islands (Rice 1986). Two forms of 

Baird’s beaked whales were previously 

recognized—the common slate-gray 

form and a smaller, rare black form 

(Morin et al., 2017), however the small 

body size of physically mature 

individuals in the latter form, as well as 

recent genetic studies (Morin et al., 

2017) have identified this form as a new 

species called Sato’s beaked whale 

(Berardius minimus) (Yamada et al., 

2019).The gray form is seen off Japan, in 

the Aleutians, and on the west coast of 

North America, whereas the black form 

has been reported for northern Japan 

and the Aleutians (Morin et al., 2017). 

Baird’s beaked whale is currently 

divided into three distinct stocks: Sea of 

Japan, Okhotsk Sea, and Bering Sea/ 

eastern North Pacific (Balcomb 1989; 

Reyes 1991). Baird’s beaked whales 

sometimes are seen close to shore, but 

their primary habitat is over or near the 

continental slope and oceanic 

seamounts in waters 1000–3000 m deep 

(Jefferson et al., 2015). 

Along the U.S. west coast, Baird’s 

beaked whales have been sighted 

primarily along the continental slope 

(Green et al., 1992; Becker et al., 2012; 

Carretta et al., 2021) from late spring to 

early fall (Green et al., 1992). The 

whales move out from those areas in 

winter (Reyes 1991). In the eastern 

North Pacific Ocean, Baird’s beaked 

whales apparently spend the winter and 

spring far offshore, and in June, they 

move onto the continental slope, where 

peak numbers occur during September 

and October. Green et al., (1992) noted 

that Baird’s beaked whales on the U.S. 

west coast were most abundant in the 

summer, and were not sighted in the fall 

or winter. MacLeod et al., (2006) 

reported numerous sightings and 

strandings of Berardius spp. off the U.S. 

west coast. 

Green et al., (1992) sighted five groups 

during 75,050 km of aerial survey effort 

in 1989–1990 off Washington/Oregon 

spanning coastal to offshore waters: two 

in slope waters and three in offshore 

waters. Two groups were sighted during 

summer/fall 2008 surveys off 

Washington/Oregon, in waters >2000 m 

deep (Barlow 2010). Acoustic 

monitoring offshore Washington 

detected Baird’s beaked whale pulses 

during January through November 2011, 

with peaks in February and July (Sˆirovic ́

et al., 2012b in USN 2015). Baird’s 

beaked whales were detected 

acoustically in the waters off Oregon 

and Washington in August 2016 during 

the SWFSC PASCAL study using 

drifting acoustic recorders (Keating et 

al., 2018). Baird’s beaked whales could 

be encountered in the proposed survey 

regions. 

Cuvier’s Beaked Whale 

Cuvier’s beaked whale is probably the 

most widespread of the beaked whales, 

although it is not found in polar waters 

(Heyning 1989). Cuvier’s beaked whale 

appears to prefer steep continental slope 

waters (Jefferson et al., 2015) and is 

most common in water depths >1000 m 

(Heyning 1989). It is mostly known from 

strandings and strands more commonly 

than any other beaked whale (Heyning 

1989). Its inconspicuous blows, deepdiving behavior, and tendency to avoid 

vessels all help to explain the infrequent 

sightings (Barlow and Gisiner 2006). 

The population in the California Current 

Large Marine Ecosystem seems to be 

declining (Moore and Barlow 2013). 

MacLeod et al., (2006) reported 

numerous sightings and strandings 

along the Pacific coast of the U.S. 

Cuvier’s beaked whale is the most 

common beaked whale off the U.S. West 

Coast (Barlow 2010), and it is the 

beaked whale species that has stranded 

most frequently on the coasts of Oregon 

and Washington. From 1942–2010, there 

were 23 reported Cuvier’s beaked whale 

strandings in Oregon and Washington 

(Moore and Barlow 2013). Most (75 

percent) Cuvier’s beaked whale 

strandings reported occurred in Oregon 

(Norman et al. 2004). Records of 

Cuvier’s beaked whale in British 

Columbia are scarce, although 20 

strandings, one incidental catch, and 

five sightings have been reported, 

including off western Vancouver Island 

(Ford 2014). Most strandings have been 

reported in summer (Ford 2014). 

Four beaked whale sightings were 

reported in water depths over 2000 m 

off Oregon/Washington during surveys 

in 2008 (Barlow 2010). None were seen 

in 1996 or 2001 (Barlow 2003), and 

several were recorded from 1991–1995 

(Barlow 1997). One Cuvier’s beaked 

whale sighting was made during surveys 

in 2014 (Barlow 2016). Acoustic 

monitoring in Washington offshore 

waters detected Cuvier’s beaked whale 

calls between January and November 

2011 (Sirovic et al., 2012b in USN 

2015). Cuvier’s beaked whales were 


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detected acoustically in waters off 

Oregon and Washington in August 2016 

during the SWFSC PASCAL study using 

drifting acoustic recorders (Keating et 

al., 2018). Curvier’s beaked whales 

could be encountered during the 

proposed surveys. 

Blainville’s Beaked Whale 

Blainville’s beaked whale is found in 

tropical and warm temperate waters of 

all oceans (Pitman 2018). It has the 

widest distribution throughout the 

world of all Mesoplodon species 

(Pitman 2018). Like other beaked 

whales, Blainville’s beaked whale is 

generally found in waters 200–1400 m 

deep (Gannier 2000; Jefferson et al., 

2015). Occasional occurrences in cooler, 

higher-latitude waters are presumably 

related to warm-water incursions 

(Reeves et al., 2002). MacLeod et al., 

(2006) reported stranding and sighting 

records in the eastern Pacific ranging 

from 37.3° N to 41.5° S. However, none 

of the 36 beaked whale stranding 

records in Oregon and Washington 

during 1930–2002 included Blainville’s 

beaked whale (Norman et al., 2004). 

One Blainville’s beaked whale was 

found stranded (dead) on the 

Washington coast in November 2016 

(COASST 2016). 

There was one acoustic encounter 

with Blainville’s beaked whales 

recorded in Quinault Canyon off 

Washington in waters 1400 m deep 

during 2011 (Baumann-Pickering et al., 

2014). Blainville’s beaked whales were 

not detected acoustically off 

Washington or Oregon during the 

August 2016 SWFSC PASCAL study 

using drifting acoustic recorders 

(Keating et al., 2018). Although 

Blainville’s beaked whales could be 

encountered during the proposed 

surveys, an encounter would be 

unlikely because the proposed survey 

regions are beyond the northern limits 

of this tropical species’ usual 

distribution. 

Hubbs’ Beaked Whale 

Hubbs’ beaked whale occurs in 

temperate waters of the North Pacific 

(Mead 1989). Its distribution appears to 

be correlated with the deep subarctic 

current (Mead et al., 1982). Numerous 

stranding records have been reported for 

the west coast of the U.S. (MacLeod et 

al., 2006). Most are from California, but 

at least seven strandings have been 

recorded along the B.C. coast as far 

north as Prince Rupert (Mead 1989; 

Houston 1990a; Willis and Baird 1998; 

Ford 2014). Several strandings are 

known from Washington/Oregon (e.g., 

Norman et al., 2004; Griffiths et al., 

2019). In addition, at least two sightings 

off Oregon/Washington, but outside the 

U.S. EEZ, were reported by Carretta et 

al. (2021), and one bycatch record off 

Oregon/Washington was reported by 

Griffiths et al. (2019). During the 2016 

SWFSC PASCAL study using drifting 

acoustic recorders, detections were 

made of beaked whale sounds presumed 

to be from Hubbs’ beaked whales off 

Washington and Oregon during August 

(Griffiths et al., 2019). This species 

seems to be less common in the region 

than some of the other beaked whales. 

Stejneger’s Beaked Whale 

Stejneger’s beaked whale occurs in 

subarctic and cool temperate waters of 

the North Pacific (Mead 1989). Most 

records are from Alaskan waters, and 

the Aleutian Islands appear to be its 

center of distribution (Mead 1989; Wade 

et al., 2003). After Cuvier’s beaked 

whale, Stejneger’s beaked whale was the 

second most commonly stranded beaked 

whale species in Oregon and 

Washington (Norman et al., 2004). 

Stejneger’s beaked whale calls were 

detected during acoustic monitoring 

offshore Washington between January 

and June 2011, with an absence of calls 

from mid-July–November 2011 (Sˆirovic ́

et al., 2012b in USN 2015). Analysis of 

these data suggest that this species 

could be more than twice as prevalent 

in this area than Baird’s beaked whale 

(Baumann-Pickering et al., 2014). 

Stejneger’s beaked whales were also 

detected acoustically in waters off 

Oregon and Washington in August 2016 

during the SWFSC PASCAL study using 

drifting acoustic recorders (Keating et 

al., 2018). 

Striped Dolphin 

The striped dolphin has a 

cosmopolitan distribution in tropical to 

warm temperate waters from ∼50° N to 

40° S (Perrin et al., 1994; Jefferson et al., 

2015). It occurs primarily in pelagic 

waters outside of the continental shelf, 

but has been observed approaching 

shore where there is deep water close to 

the coast (Jefferson et al., 2015). Striped 

dolphins regularly occur off California 

(Becker et al., 2012), including as far 

offshore as ∼300 n.mi. during NOAA 

Fisheries vessel surveys (Carretta et al., 

2021). However, few sightings have 

been made off Oregon, and no sightings 

have been reported for Washington 

(Carretta et al., 2021). However, 

strandings have occurred along the 

coasts of Oregon and Washington 

(Carretta et al., 2016). During surveys off 

the U.S. west coast in 2014, striped 

dolphins were seen as far north as 44° 

N; based on those sightings, Barlow 

(2016) calculated an abundance estimate 

of 13,171 striped dolphins for Oregon/ 

Washington. The abundance estimates 

for 2001, 2005, and 2008 were zero 

(Barlow 2016). It is possible, although 

unlikely, that striped dolphins could be 

encountered in the proposed survey 

area. 

Common Dolphin 

The common dolphin is found in 

tropical and warm temperate oceans 

around the world (Jefferson et al., 2015), 

ranging from ∼60° N to ∼50° S (Jefferson 

et al., 2015). It is the most abundant 

dolphin species in offshore areas of 

warm-temperate regions in the Atlantic 

and Pacific (Perrin 2018). It can be 

found in oceanic and coastal habitats; it 

is common in coastal waters 200–300 m 

deep and is also associated with 

prominent underwater topography, such 

as seamounts (Evans 1994). Shortbeaked common dolphins have been 

sighted as far as 550 km from shore 

(Barlow et al., 1997). 

The distribution of short-beaked 

common dolphins along the U.S. west 

coast is variable and likely related to 

oceanographic changes (Heyning and 

Perrin 1994; Forney and Barlow 1998). 

It is the most abundant cetacean off 

California; some sightings have been 

made off Oregon, in offshore waters 

(Carretta et al., 2021). During surveys off 

the west coast in 2014 and 2017, 

sightings were made as far north as 44° 

N (Barlow 2016; SIO n.d.). Based on the 

absolute dynamic topography of the 

region, short-beaked common dolphins 

could occur in relatively high densities 

off Oregon during July–December (Pardo 

et al., 2015). In contrast, habitat 

modeling predicted moderate densities 

of common dolphins off the Columbia 

River estuary during summer, with 

lower densities off southern Oregon 

(Becker et al., 2014). A group of six 

common dolphins was sighted during 

L–DEO’s Cascadia summer survey just 

south of the Columbia River off Oregon 

(RPS 2021b). Common dolphins could 

be encountered in the proposed survey 

regions. 

Pacific White-Sided Dolphin 

The Pacific white-sided dolphin is 

found in cool temperate waters of the 

North Pacific from the southern Gulf of 

California to Alaska. Across the North 

Pacific, it appears to have a relatively 

narrow distribution between 38° N and 

47° N (Brownell et al., 1999). In the 

eastern North Pacific Ocean, the Pacific 

white-sided dolphin is one of the most 

common cetacean species, occurring 

primarily in shelf and slope waters 

(Green et al., 1993; Barlow 2003, 2010). 

It is known to occur close to shore in 

certain regions, including (seasonally) 


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southern California (Brownell et al., 

1999). 

Results of aerial and shipboard 

surveys strongly suggest seasonal northsouth movements of the species 

between California and Oregon/ 

Washington; the movements apparently 

are related to oceanographic influences, 

particularly water temperature (Green et 

al., 1993; Forney and Barlow 1998; 

Buchanan et al., 2001). During winter, 

this species is most abundant in 

California slope and offshore areas; as 

northern waters begin to warm in the 

spring, it appears to move north to slope 

and offshore waters off Oregon/ 

Washington (Green et al., 1992, 1993; 

Forney 1994; Forney et al., 1995; 

Buchanan et al., 2001; Barlow 2003). 

The highest encounter rates off Oregon 

and Washington have been reported 

during March–May in slope and 

offshore waters (Green et al., 1992). 

Similarly, Becker et al., (2014) predicted 

relatively high densities off southern 

Oregon in shelf and slope waters. 

Based on year-round aerial surveys off 

Oregon/Washington, the Pacific whitesided dolphin was the most abundant 

cetacean species, with nearly all (97%) 

sightings occurring in May (Green et al., 

1992, 1993). Barlow (2003) also found 

that the Pacific white-sided dolphin was 

one of the most abundant marine 

mammal species off Oregon/Washington 

during 1996 and 2001 ship surveys, and 

it was the second most abundant species 

reported during 2008 surveys (Barlow 

2010). Adams et al., (2014) reported 

numerous offshore sightings off Oregon 

during summer, fall, and winter surveys 

in 2011 and 2012. Based on surveys 

conducted during 2014, the abundance 

was estimated at 20,711 for Oregon/ 

Washington (Barlow 2016). 

Fifteen Pacific white-sided dolphin 

sightings (231 animals) were made off 

Washington/Oregon during the June– 

July 2012 L–DEO Juan de Fuca plate 

seismic survey (RPS 2012b). There were 

fifteen Pacific white-sided dolphin 

sightings (462 animals) made during the 

July 2012 L–DEO seismic surveys off 

southern Washington (RPS 2012a). This 

species was not sighted during the July 

2012 L–DEO seismic survey off Oregon 

(RPS 2012c). Numerous Pacific whitesided dolphin sightings were made 

during L–DEO’s Cascadia summer 

survey off Oregon and Washington (RPS 

2021b). Pacific white-sided dolphins are 

likely to be common in the proposed 

survey regions. 

Northern Right-Whale Dolphin 

The northern right whale dolphin is 

found in cool temperate and sub-arctic 

waters of the North Pacific, from the 

Gulf of Alaska to near northern Baja 

California, ranging from 30° N to 50° N 

(Reeves et al., 2002). In the eastern 

North Pacific Ocean, the northern right 

whale dolphin is one of the most 

common marine mammal species, 

occurring primarily in shelf and slope 

waters ∼100 to >2000 m deep (Green et 

al., 1993; Barlow 2003). The northern 

right whale dolphin comes closer to 

shore where there is deep water, such as 

over submarine canyons (Reeves et al., 

2002). 

Aerial and shipboard surveys suggest 

seasonal inshore-offshore and northsouth movements in the eastern North 

Pacific Ocean between California and 

Oregon/Washington; the movements are 

believed to be related to oceanographic 

influences, particularly water 

temperature and presumably prey 

distribution and availability (Green et 

al., 1993; Forney and Barlow 1998; 

Buchanan et al., 2001). Green et al. 

(1992, 1993) found that northern right 

whale dolphins were most abundant off 

Oregon/Washington during fall, less 

abundant during spring and summer, 

and absent during winter, when this 

species presumably moves south to 

warmer California waters (Green et al., 

1992, 1993; Forney 1994; Forney et al., 

1995; Buchanan et al., 2001; Barlow 

2003). 

Becker et al. (2014) predicted 

relatively high densities off southern 

Oregon, and moderate densities off 

northern Oregon and Washington. Based 

on year-round aerial surveys off Oregon/ 

Washington, the northern right whale 

dolphin was the third most abundant 

cetacean species, concentrated in slope 

waters but also occurring in water out 

to ∼550 km offshore (Green et al., 1992, 

1993). Barlow (2003, 2010) also found 

that the northern right whale dolphin 

was one of the most abundant marine 

mammal species off Oregon/Washington 

during 1996, 2001, 2005, and 2008 ship 

surveys. Offshore sightings were made 

in the waters of Oregon during summer, 

fall, and winter surveys in 2011 and 

2012 (Adams et al., 2014). During L– 

DEO’s Cascadia survey during June–July 

2021, one sighting of 15 northern right 

whale dolphins was made off 

Washington, and another sighting of 12 

individuals was made off Oregon (RPS 

2021b). Northern right whale dolphins 

are likely to be encountered in the 

proposed survey regions. 

Risso’s Dolphin 

Risso’s dolphin is distributed 

worldwide in mid-temperate and 

tropical oceans (Kruse et al., 1999). 

Although it shows a preference for midtemperate waters of the shelf and slope 

between 30° and 45° (Jefferson et al., 

2014). Although it occurs from coastal 

to deep water (∼200–1000 m depth), it 

shows a strong preference for midtemperate waters of upper continental 

slopes and steep shelf-edge areas 

(Hartman 2018). 

Off the U.S. west coast, Risso’s 

dolphin is believed to make seasonal 

north-south movements related to water 

temperature, spending colder winter 

months off California and moving north 

to waters off Oregon/Washington during 

the spring and summer as northern 

waters begin to warm (Green et al., 

1992, 1993; Buchanan et al., 2001; 

Barlow 2003; Becker 2007). The 

distribution and abundance of Risso’s 

dolphins are highly variable from 

California to Washington, presumably in 

response to changing oceanographic 

conditions on both annual and seasonal 

time scales (Forney and Barlow 1998; 

Buchanan et al., 2001). The highest 

densities were predicted along the 

coasts of Washington, Oregon, and 

central and southern California (Becker 

et al., 2012). Off Oregon and 

Washington, Risso’s dolphins are most 

abundant over continental slope and 

shelf waters during spring and summer, 

less so during fall, and rare during 

winter (Green et al., 1992, 1993). Green 

et al., (1992, 1993) reported most Risso’s 

dolphin groups off Oregon between ∼45 

and 47° N. Several sightings were made 

off southern Oregon during surveys in 

1991–2014 (Barlow 2016; Carretta et al., 

2021). Sightings during ship surveys in 

summer/fall 2008 were mostly between 

∼30 and 38° N; none were reported in 

Oregon/Washington (Barlow 2010). 

Based on 2014 survey data, the 

abundance for Oregon/Washington was 

estimated at 430 (Barlow 2016). Risso’s 

dolphins could be encountered in the 

proposed survey regions. 

Killer Whale 

The killer whale is cosmopolitan and 

globally fairly abundant, being observed 

in all oceans of the world (Ford 2018). 

It is very common in temperate waters 

and also frequents tropical waters, at 

least seasonally (Heyning and Dahlheim 

1988). There are three distinct ecotypes, 

or forms, of killer whales recognized in 

the north Pacific: Resident, transient, 

and offshore. The three ecotypes differ 

morphologically, ecologically, 

behaviorally, and genetically. Resident 

killer whales exclusively prey upon 

fish, with a clear preference for salmon 

(Ford and Ellis 2006; Hanson et al., 

2010; Ford et al., 2016), while transient 

killer whales exclusively prey upon 

marine mammals (Carretta et al., 2019). 

Less is known about offshore killer 

whales, but they are believed to 

consume primarily fish, including 

several species of shark (Dahlheim et 


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al., 2008). Killer whales occur in 

inshore inlets, along the coast, over the 

continental shelf, and in offshore waters 

(Ford 2014). 

Currently, there are eight killer whale 

stocks recognized in the U.S. Pacific: (1) 

Alaska Residents, occurring from 

Southeast Alaska to the Aleutians and 

Bering Sea; (2) Northern Residents, from 

British Columbia through parts of the 

Southeast Alaska; (3) Southern 

Residents, mainly in inland waters of 

Washington State and southern British 

Columbia; (4) Gulf of Alaska, Aleutians, 

and Bering Sea Transients, from Prince 

William Sound through the Aleutians 

and Bering Sea; (5) AT1 Transients, 

from Prince William Sound through the 

Kenai Fjords; (6) West Coast Transients, 

from California through Southeast 

Alaska; (7) Offshore, from California 

through Alaska; and (8) Hawaiian (Muto 

et al., 2021; Carretta et al., 2021). 

Individuals from the West Coast 

Transient and Offshore stocks could be 

encountered in the proposed project 

areas. It is unlikely that individuals 

from the endangered Eastern North 

Pacific Southern Resident stock would 

be encountered in the offshore survey 

regions, as they are primarily found 

along the coasts and the proposed 

survey is located in waters deeper than 

1600 m and at least 46 km from the 

shoreline. 

The main diet of transient killer 

whales consists of marine mammals, in 

particular porpoises and seals. West 

coast transient killer whales (also 

known as Bigg’s killer whales) range 

from Southeast Alaska to California 

(Muto et al., 2021). The seasonal 

movements of transients are largely 

unpredictable (Baird 1994; Ford 2014). 

Green et al., (1992) noted that most 

groups seen during their surveys off 

Oregon and Washington were likely 

transients; during those surveys, killer 

whales were sighted only in shelf 

waters. Two of 17 killer whales that 

stranded in Oregon were confirmed as 

transient (Stevens et al., 1989 in 

Norman et al., 2004). 

Little is known about offshore killer 

whales, but they occur primarily over 

shelf waters and feed on fish, especially 

sharks (Ford 2014). Dahlheim et al., 

(2008) reported sightings in Southeast 

Alaska during spring and summer. 

Eleven sightings of approximately 536 

individuals were reported off Oregon/ 

Washington during the 2008 SWFSC 

vessel survey (Barlow 2010). Killer 

whales were sighted offshore 

Washington during surveys from August 

2004 to September 2008 (Oleson et al., 

2009). Keating et al., (2015) analyzed 

cetacean whistles from recordings made 

during 2000–2012; several killer whale 

acoustic detections were made offshore 

Washington. Killer whales were sighted 

off Washington in July and September 

2012 (Adams et al., 2014). 

During L–DEO’s Cascadia surveys 

during June through July 2021 in the 

Northeast Pacific Ocean, a sighting of 20 

killer whales was made near the shelf 

edge off northern Oregon (RPS 2021b). 

Killer whales could be encountered 

during the proposed survey, although it 

is unlikely the endangered Southern 

Resident Killer whales would occur as 

far offshore as the survey regions. 

Pygmy and Dwarf Sperm Whale 

Dwarf and pygmy sperm whales are 

distributed throughout tropical and 

temperate waters of the Atlantic, Pacific, 

and Indian oceans, but their precise 

distributions are unknown because 

much of what we know of the species 

comes from strandings (McAlpine 

2018). They are difficult to sight at sea, 

because of their dive behavior and 

perhaps because of their avoidance 

reactions to ships and behavior changes 

in relation to survey aircraft (Wu ̈rsig et 

al., 1998). The two species are often 

difficult to distinguish from one another 

when sighted (McAlpine 2018). 

Both Kogia species are sighted 

primarily along the continental shelf 

edge and slope and over deeper waters 

off the shelf (Hansen et al., 1994; Davis 

et al., 1998; Jefferson et al., 2015). 

Stomach content analyses from stranded 

whales further support this distribution 

(McAlpine 2018). Recent data indicate 

that both Kogia species feed in the water 

column and on/near the seabed, likely 

using echolocation to search for prey 

(McAlpine 2018). Several studies have 

suggested that pygmy sperm whales live 

and feed mostly beyond the continental 

shelf edge, whereas dwarf sperm whales 

tend to occur closer to shore, often over 

the continental shelf and slope (Rice 

1998; Wang et al., 2002; MacLeod et al., 

2004; McAlpine 2018). It has also been 

suggested that the pygmy sperm whale 

is more temperate and the dwarf sperm 

whale more tropical, based at least 

partially on live sightings at sea from a 

large database from the eastern tropical 

Pacific (Wade and Gerrodette 1993; 

McAlpine 2018). 

Pygmy and dwarf sperm whales are 

rarely sighted off Oregon and 

Washington, with only one sighting of 

an unidentified Kogia sp. beyond the 

U.S. EEZ, during the 1991–2014 NOAA 

vessel surveys (Carretta et al., 2021). 

Norman et al., (2004) reported eight 

confirmed stranding records of pygmy 

sperm whales for Oregon and 

Washington, five of which occurred 

during autumn and winter. Despite the 

limited number of sightings, it is 

possible that pygmy or dwarf sperm 

whales could be encountered within the 

proposed project areas. 

Dall’s Porpoise 

Dall’s porpoise is found in temperate 

to subarctic waters of the North Pacific 

and adjacent seas (Jefferson et al., 2015). 

It is widely distributed across the North 

Pacific over the continental shelf and 

slope waters, and over deep (>2500 m) 

oceanic waters (Hall 1979). It is 

probably the most abundant small 

cetacean in the North Pacific Ocean, and 

its abundance changes seasonally, likely 

in relation to water temperature (Becker 

2007). 

Off Oregon and Washington, Dall’s 

porpoise is widely distributed over shelf 

and slope waters, with concentrations 

near shelf edges, but is also commonly 

sighted in pelagic offshore waters 

(Morejohn 1979; Green et al., 1992; 

Becker et al., 2014; Fleming et al., 2018; 

Carretta et al., 2021). Combined results 

of various surveys out to ∼550 km 

offshore indicate that the distribution 

and abundance of Dall’s porpoise varies 

between seasons and years. North-south 

movements are believed to occur 

between Oregon/Washington and 

California in response to changing 

oceanographic conditions, particularly 

temperature and distribution and 

abundance of prey (Green et al., 1992, 

1993; Mangels and Gerrodette 1994; 

Barlow 1995; Forney and Barlow 1998; 

Buchanan et al., 2001). Becker et al., 

(2014) predicted high densities off 

southern Oregon throughout the year, 

with moderate densities to the north. 

According to predictive density 

distribution maps, the highest densities 

off southern Washington and Oregon 

occur along the 500-m isobath (Menza et 

al., 2016). 

Encounter rates reported by Green et 

al., (1992) during aerial surveys off 

Oregon/Washington were highest in fall, 

lowest during winter, and intermediate 

during spring and summer. Encounter 

rates during the summer were similarly 

high in slope and shelf waters, and 

somewhat lower in offshore waters 

(Green et al., 1992). Dall’s porpoise was 

the most abundant species sighted off 

Oregon/Washington during 1996, 2001, 

2005, and 2008 ship surveys up to ∼550 

km from shore (Barlow 2003, 2010). 

Oleson et al., (2009) reported 44 

sightings of 206 individuals off 

Washington during surveys form August 

2004 to September 2008. Dall’s porpoise 

were seen in the waters off Oregon 

during summer, fall, and winter surveys 

in 2011 and 2012 (Adams et al., 2014). 

Nineteen Dall’s porpoise sightings 

(144 animals) were made off 

Washington/Oregon during the June– 


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July 2012 L–DEO Juan de Fuca plate 

seismic survey (RPS 2012b). There were 

16 Dall’s porpoise sightings (54 animals) 

made during the July 2012 L–DEO 

seismic surveys off southern 

Washington (RPS 2012a). This species 

was not sighted during the July 2012 L– 

DEO seismic survey off Oregon (RPS 

2012c). During L–DEO’s Cascadia 

survey during June–July 2021, one 

sighting of four individuals was made 

near the shelf edge off the Columbia 

River (RPS 2021b). Dall’s porpoise is 

likely to be encountered during the 

proposed seismic surveys. 

Northern Fur Seal 

The northern fur seal is endemic to 

the North Pacific Ocean and occurs from 

southern California to the Bering Sea, 

Okhotsk Sea, and Honshu Island, Japan 

(Muto et al., 2021). During the breeding 

season, most of the worldwide 

population of northern fur seals inhabits 

the Pribilof Islands in the southern 

Bering Sea (NMFS 2007; Lee et al., 2014; 

Muto et al., 2021). The rest of the 

population occurs at rookeries on 

Bogoslof Island in the Bering Sea, in 

Russia (Commander Islands, Robben 

Island, Kuril Islands), on San Miguel 

Island in southern California (NMFS 

1993; Lee et al., 2014), and on the 

Farallon Islands off central California 

(Muto et al., 2021). In the U.S., two 

stocks are recognized—the Eastern 

Pacific and the California stocks (Muto 

et al., 2021). The Eastern Pacific stock 

ranges from the Pribilof Islands and 

Bogoslof Island in the Bering Sea during 

summer to California during winter 

(Muto et al., 2021). When not on rookery 

islands, northern fur seals are primarily 

pelagic but occasionally haul out on 

rocky shorelines (Muto et al., 2021). 

During the breeding season, adult 

males usually come ashore in May– 

August and may sometimes be present 

until November; adult females are found 

ashore from June–November (Carretta et 

al., 2021; Muto et al., 2021). After 

reproduction, northern fur seals spend 

the next 7–8 months feeding at sea 

(Roppel 1984). Immature seals can 

remain in southern foraging areas yearround until they are old enough to mate 

(NMFS 2007). In November, females and 

pups leave the Pribilof Islands and 

migrate through the Gulf of Alaska to 

feeding areas primarily off the coasts of 

B.C., Washington, Oregon, and 

California before migrating north again 

to the rookeries in spring (Ream et al., 

2005; Pelland et al., 2014). Males 

usually migrate only as far south as the 

Gulf of Alaska (Kajimura 1984). Ream et 

al. (2005) showed that migrating females 

moved over the continental shelf as they 

migrated southeasterly. Instead of 

following depth contours, their travel 

corresponded with movements of the 

Alaska Gyre and the North Pacific 

Current (Ream et al., 2005). Their 

foraging areas were associated with 

eddies, the subarctic-subtropical 

transition region, and coastal mixing 

(Ream et al., 2005; Alford et al., 2005). 

Some juveniles and non-pregnant 

females may remain in the Gulf of 

Alaska throughout the summer (Calkins 

1986). The northern fur seals spends 

∼90% of its time at sea, typically in 

areas of upwelling along the continental 

slopes and over seamounts (Gentry 

1981). The remainder of its life is spent 

on or near rookery islands or haulouts. 

Pups from the California stock also 

migrate to Washington, Oregon, and 

northern California after weaning (Lea et 

al., 2009). 

Northern fur seals were seen 

throughout the North Pacific during 

surveys conducted during 1987–1990, 

including off Washington and Oregon 

(Buckland et al., 1993). Tagged adult fur 

seals were tracked from the Pribilof 

Islands to the waters off Washington/ 

Oregon/California, with recorded 

movement throughout the region 

(Pelland et al., 2014). Tracked adult 

male fur seals that were tagged on St. 

Paul Island in the Bering Sea in October 

2009 wintered in the Bering Sea or 

northern North Pacific Ocean; females 

migrated to the Gulf of Alaska and the 

California Current (Sterling et al., 2014). 

Some individuals reach California by 

December, after which time numbers 

increase off the west coast of North 

America (Ford 2014). The peak density 

shifts over the course of the winter and 

spring, with peak densities occurring in 

California in February, April off Oregon 

and Washington, and May off B.C. and 

Southeast Alaska (Ford 2014). The use 

of continental shelf and slope waters of 

B.C. and the northwestern U.S. by adult 

females during winter is well 

documented from pelagic sealing data 

(Bigg 1990). 

Bonnell et al., (1992) noted the 

presence of northern fur seals yearround off Oregon/Washington, with the 

greatest numbers (87%) occurring in 

January–May. Northern fur seals were 

seen as far out from the coast as 185 km, 

and numbers increased with distance 

from land; they were 5–6 times more 

abundant in offshore waters than over 

the shelf or slope (Bonnell et al., 1992). 

The highest densities were seen in the 

Columbia River plume (∼46° N) and in 

deep offshore waters (>2000 m) off 

central and southern Oregon (Bonnell et 

al., 1992). The waters off Washington 

are a known foraging area for adult 

females, and concentrations of fur seals 

were also reported to occur near Cape 

Blanco, Oregon, at ∼42.8° N (Pelland et 

al., 2014). During L–DEO’s Cascadia 

survey during June–July 2021, one 

northern fur seal was sighted off 

Washington near the shelf edge (RPS 

2021b). 

Northern fur seals could be observed 

in the proposed survey regions, in 

particular females and juveniles. 

However, adult males are generally 

ashore during the reproductive season 

from May–August; adult females are 

generally ashore from June through 

November. 

Guadalupe Fur Seal 

Most breeding and births occur at Isla 

Guadalupe, Mexico; a secondary 

rookery exists at Isla Benito del Este 

(Maravilla-Chavez and Lowry 1999; 

Aurioles-Gamboa et al., 2010). A few 

Guadalupe fur seals are known to occur 

at California sea lion rookeries in the 

Channel Islands, primarily San Nicolas 

and San Miguel islands, and sightings 

have also been made at Santa Barbara 

and San Clemente islands (Stewart et 

al., 1987; Carretta et al., 2021). 

Guadalupe fur seals prefer rocky habitat 

for breeding and hauling out. They 

generally haul out at the base of 

towering cliffs on shores characterized 

by solid rock and large lava blocks 

(Peterson et al., 1968), although they 

can also inhabit caves and recesses 

(Belcher and Lee 2002). While at sea, 

this species usually is solitary but 

typically gathers in the hundreds to 

thousands at breeding sites. 

During the summer breeding season, 

most adults occur at rookeries in Mexico 

(Norris 2017 in USN 2019; Carretta et 

al., 2021). Following the breeding 

season, adult males tend to move 

northward to forage. Females have been 

observed feeding south of Guadalupe 

Island, making an average round trip of 

2375 km (Ronald and Gots 2003). 

Several rehabilitated Guadalupe fur 

seals that were satellite tagged and 

released in central California traveled as 

far north as B.C. (Norris et al., 2015; 

Norris 2017 in USN 2019). Fur seals 

younger than two years old are more 

likely to travel to more northerly, 

offshore areas than older fur seals 

(Norris 2017 in USN 2019). Stranding 

data also indicates that fur seals younger 

than 2 years are more likely to occur in 

the proposed survey area, as this age 

class was most frequently reported 

(Lambourn et al., 2012 in USN 2019). 

During 2015–2021, 724 Guadalupe fur 

seals stranded on the West Coast of the 

U.S., including 182 strandings along the 

coasts of Oregon and Washington during 

2019–2021; NMFS declared this an 

unusual mortality event (NOAA 2021d). 

Guadalupe fur seals could be 


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encountered during the proposed 

seismic surveys, but most animals are 

likely to occur at their breeding sites 

farther south at the time of the surveys. 

California Sea Lion 

The primary range of the California 

sea lion includes the coastal areas and 

offshore islands of the eastern North 

Pacific Ocean from B.C. to central 

Mexico, including the Gulf of California 

(Jefferson et al., 2015). However, its 

distribution is expanding (Jefferson et 

al., 2015), and its secondary range 

extends into the Gulf of Alaska 

(Maniscalco et al., 2004) and southern 

Mexico (Gallo-Reynoso and Solo ́rzanoVelasco 1991), where it is occasionally 

recorded. 

California sea lion rookeries are on 

islands located in southern California, 

western Baja California, and the Gulf of 

California (Carretta et al., 2021). Five 

genetically distinct geographic 

populations have been identified: (1) 

Pacific Temperate (includes rookeries in 

U.S. waters and the Coronados Islands 

to the south), (2) Pacific Subtropical, (3) 

Southern Gulf of California, (4) Central 

Gulf of California, and (5) Northern Gulf 

of California (Schramm et al., 2009). 

Animals from the Pacific Temperate 

population occur in the proposed 

project area. 

In California and Baja California, 

births occur on land from mid-May to 

late-June. During August and 

September, after the mating season, the 

adult males migrate northward to 

feeding areas as far north as Washington 

(Puget Sound) and B.C. (Lowry et al., 

1992). They remain there until spring 

(March–May), when they migrate back 

to the breeding colonies (Lowry et al., 

1992; Weise et al., 2006). The 

distribution of immature California sea 

lions is less well known but some make 

northward migrations that are shorter in 

length than the migrations of adult 

males (Huber 1991). However, most 

immature seals are presumed to remain 

near the rookeries for most of the year, 

as are females and pups (Lowry et al., 

1992). 

California sea lions are coastal 

animals that often haul out on shore 

throughout the year, but peak numbers 

off Oregon and Washington occur 

during the fall (Bonnell et al., 1992). 

During aerial surveys off the coasts of 

Oregon and Washington during 1989– 

1990, California sea lions were sighted 

at sea during the fall and winter, but no 

sightings were made during June– 

August (Bonnell et al., 1992). Numbers 

off Oregon decrease during winter, as 

animals travel further north (Mate 1975 

in Bonnell et al., 1992). King (1983) 

noted that sea lions are rarely found 

more than 16 km offshore. During fall 

and winter surveys off Oregon and 

Washington, mean distance from shore 

was ∼13 km and most were observed in 

water <200 m deep; however, sightings 

were made in water as deep as 356 m 

(Bonnell et al., 1992). Weise et al., 

(2006) reported that males normally 

forage almost exclusively over the 

continental shelf, but during anomalous 

climatic conditions they can forage 

farther out to sea (up to 450 km 

offshore). 

During aerial surveys over the shelf 

and slope off Oregon and Washington 

(Adams et al., 2014), California sea lions 

were seen during all survey months 

(January–February, June–July, 

September–October). Although most 

sightings occurred on the shelf, during 

February 2012, one sighting was made 

near the 2000-m depth contour, and 

during June 2011 and July 2012, 

sightings were made along the 200-m 

isobath off southern Oregon (Adams et 

al., 2014). During October 2011, 

sightings were made off the Columbia 

River estuary near the 200-m isopleth 

and on the southern Oregon shelf; 

during September 2012, sightings 

occurred in nearshore waters off 

Washington and in shelf waters along 

the coast of Oregon (Adams et al., 2014). 

Adams et al., (2014) reported sightings 

more than 60 km off the coast of Oregon. 

During L–DEO’s Cascadia survey during 

June–July 2021, four sightings of nine 

California sea lions were made in 

nearshore waters off Oregon (RPS 

2021b). California sea lions were also 

taken as bycatch off Washington and 

Oregon in the west coast groundfish 

fishery during 2002–2009 (Jannot et al., 

2011). California sea lions could be 

encountered in the proposed project 

regions. 

Steller Sea Lion 

The Steller sea lion occurs along the 

North Pacific Rim from northern Japan 

to California (Loughlin et al., 1984). It is 

distributed around the coasts to the 

outer shelf from northern Japan through 

the Kuril Islands and Okhotsk Sea, 

through the Aleutian Islands, central 

Bering Sea, southern Alaska, and south 

to California (NOAA 2021e). There are 

two stocks, or DPSs, of Steller sea 

lions—the Western and Eastern DPSs, 

which are divided at 144° W longitude 

(Muto et al., 2021). The Western DPS is 

listed as endangered and includes 

animals that occur in Japan and Russia 

(Muto et al., 2021); the Eastern DPS was 

delisted from threatened in 2013 (NMFS 

2013a). Only individuals from the 

Eastern DPS could occur in the 

proposed survey regions. 

Steller sea lions typically inhabit 

waters from the coast to the outer 

continental shelf and slope throughout 

their range; they are not considered 

migratory, although foraging animals 

can travel long distances (Loughlin et 

al., 2003; Raum-Suryan et al., 2002). 

Rookeries of Steller sea lions from the 

Eastern DPS are located in southeast 

Alaska, B.C., Oregon, and California; 

there are no rookeries in Washington 

(NMFS 2013a; Muto et al., 2021). 

Breeding adults occupy rookeries from 

late-May to early-July (NMFS 2008). 

Federally designated critical habitat for 

Steller sea lions in Oregon and 

California includes all rookeries (NMFS 

1993). Although the Eastern DPS was 

delisted from the ESA in 2013, the 

designated critical habitat remains valid 

(NOAA 2021e). The critical habitat in 

Oregon is located along the coast at 

Rogue Reef (Pyramid Rock) and Orford 

Reef (Long Brown Rock and Seal Rock). 

The critical habitat area includes 

aquatic zones that extend 0.9 km 

seaward and air zones extending 0.9 km 

above these terrestrial and aquatic zones 

(NMFS 1993). The nearest proposed 

seismic transect would be located 46 km 

from shore. 

Non-breeding adults use haulouts or 

occupy sites at the periphery of 

rookeries during the breeding season 

(NMFS 2008). Pupping occurs from 

mid-May to mid-July (Pitcher and 

Calkins 1981) and peaks in June (Pitcher 

et al., 2002). Territorial males fast and 

remain on land during the breeding 

season (NMFS 2008). Females with 

pups generally stay within 30 km of the 

rookeries in shallow (30–120 m) water 

when feeding (NMFS 2008). Tagged 

juvenile sea lions showed localized 

movements near shore (Briggs et al., 

2005). Loughlin et al., (2003) reported 

that most (88%) at-sea movements of 

juvenile Steller sea lions in the Aleutian 

Islands were short (<15 km) foraging 

trips. The mean distance of juvenile sea 

lion trips at sea was 16.6 km, and the 

maximum trip distance recorded was 

447 km. Long-range trips represented 

6% of all trips at sea, and trip distance 

and duration increase with age 

(Loughlin et al., 2003; Call et al., 2007). 

Although Steller sea lions are not 

considered migratory, foraging animals 

can travel long distances outside of the 

breeding season (Loughlin et al., 2003; 

Raum-Suryan et al., 2002). During the 

summer, they mostly forage within 60 

km from the coast; during winter, they 

can range up to 200 km from shore 

(Ford 2014). 

During surveys off the coasts of 

Oregon and Washington, Bonnell et al., 

(1992) noted that 89% of sea lions 

occurred over the shelf at a mean 


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distance of 21 km from the coast and 

near or in waters <200 m deep; the 

farthest sighting occurred ∼40 km from 

shore, and the deepest sighting location 

was 1611 m deep. Sightings were made 

along the 200-m depth contour 

throughout the year (Bonnell et al., 

1992). During aerial surveys over the 

shelf and slope off Oregon and 

Washington, one Steller sea lion was 

seen on the Oregon shelf during January 

2011, and two sightings totaling eight 

individuals were made on September 

2012 off southern Oregon (Adams et al., 

2014). During a survey off Washington/ 

Oregon June–July 2012, two Steller sea 

lions were seen from R/V Langseth (RPS 

2012b) off southern Oregon. Eight 

sightings of 11 individuals were made 

from R//V Northern Light during a 

survey off southern Washington during 

July 2012 (RPS 2012a). No sightings 

were made during L–DEO’s Cascadia 

summer survey off Oregon and 

Washington (RPS 2021b). Steller sea 

lions were also taken as bycatch off 

southern Oregon in the west coast 

groundfish fishery during 2002–2009 

(Jannot et al., 2011). Steller sea lions 

could be encountered in the proposed 

project regions. 

Northern Elephant Seal 

The northern elephant seal breeds in 

California and Baja California, primarily 

on offshore islands, from Cedros off the 

west coast of Baja California, north to 

the Farallons in Central California 

(Stewart et al., 1994). Adult elephant 

seals engage in two long northward 

migrations per year, one following the 

breeding season, and another following 

the annual molt (Stewart and DeLong 

1995). Between the two foraging 

periods, they return to land to molt, 

with females returning earlier than 

males (March–April vs. July–August). 

After the molt, adults then return to 

their northern feeding areas until the 

next winter breeding season. Breeding 

occurs from December–March (Stewart 

and Huber 1993). Females arrive in late 

December or January and give birth 

within ∼1 week of their arrival. Juvenile 

elephant seals typically leave the 

rookeries in April or May and head 

north, traveling an average of 900–1000 

km. Most elephant seals return to their 

natal rookeries when they start breeding 

(Huber et al., 1991). 

When not at their breeding rookeries, 

adults feed at sea far from the rookeries. 

Adult females and juveniles forage in 

the California current off California to 

B.C. (Le Boeuf et al., 1986, 1993, 2000). 

Bonnell et al. (1992) reported that 

northern elephant seals were distributed 

equally in shelf, slope, and offshore 

waters during surveys conducted off 

Oregon and Washington, as far as 150 

km from shore, in waters >2000 m deep. 

Telemetry data indicate that they range 

much farther offshore than that (Stewart 

and DeLong 1995). Males may feed as 

far north as the eastern Aleutian Islands 

and the Gulf of Alaska, whereas females 

feed south of 45° N (Le Boeuf et al., 

1993; Stewart and Huber 1993). Adult 

male elephant seals migrate north via 

the California current to the Gulf of 

Alaska during foraging trips, and could 

potentially be passing through the area 

off Washington in May and August 

(migrating to and from molting periods) 

and November and February (migrating 

to and from breeding periods), but likely 

their presence there is transient and 

short-lived. Most elephant seal sightings 

at sea off Washington were made during 

June, July, and September; off Oregon, 

sightings were recorded from November 

through May (Bonnell et al., 1992). 

Northern elephant seal pups have been 

sighted at haulouts in the inland waters 

of Washington State (Jeffries et al., 

2000), and at least three were reported 

to have been born there (Hayward 2003). 

Pupping has also been observed at Shell 

Island (∼43.3° N) off southern Oregon, 

suggesting a range expansion (Bonnell et 

al., 1992; Hodder et al., 1998). Northern 

elephant seals could be encountered 

during the proposed seismic surveys. 

Marine Mammal Hearing 

Hearing is the most important sensory 

modality for marine mammals 

underwater, and exposure to 

anthropogenic sound can have 

deleterious effects. To appropriately 

assess the potential effects of exposure 

to sound, it is necessary to understand 

the frequency ranges marine mammals 

are able to hear. Not all marine mammal 

species have equal hearing capabilities 

(e.g., Richardson et al., 1995; Wartzok 

and Ketten, 1999; Au and Hastings, 

2008). To reflect this, Southall et al., 

(2007, 2019) recommended that marine 

mammals be divided into hearing 

groups based on directly measured 

(behavioral or auditory evoked potential 

techniques) or estimated hearing ranges 

(behavioral response data, anatomical 

modeling, etc.). Note that no direct 

measurements of hearing ability have 

been successfully completed for 

mysticetes (i.e., low-frequency 

cetaceans). Subsequently, NMFS (2018) 

described generalized hearing ranges for 

these marine mammal hearing groups. 

Generalized hearing ranges were chosen 

based on the approximately 65 decibel 

(dB) threshold from the normalized 

composite audiograms, with the 

exception for lower limits for lowfrequency cetaceans where the lower 

bound was deemed to be biologically 

implausible and the lower bound from 

Southall et al. (2007) retained. Marine 

mammal hearing groups and their 

associated hearing ranges are provided 

in Table 2. 

TABLE 2—MARINE MAMMAL HEARING GROUPS

[NMFS, 2018] 

Hearing group Generalized hearing 

range * 

Low-frequency (LF) cetaceans (baleen whales) ......................................................................................................................... 7 Hz to 35 kHz. 

Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales) .............................................. 150 Hz to 160 kHz. 

High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, Cephalorhynchid, Lagenorhynchus cruciger & L. 

australis).

275 Hz to 160 kHz. 

Phocid pinnipeds (PW) (underwater) (true seals) ....................................................................................................................... 50 Hz to 86 kHz. 

Otariid pinnipeds (OW) (underwater) (sea lions and fur seals) .................................................................................................. 60 Hz to 39 kHz. 

* Represents the generalized hearing range for the entire group as a composite (i.e., all species within the group), where individual species’ 

hearing ranges are typically not as broad. Generalized hearing range chosen based on ∼65 dB threshold from normalized composite audiogram, 

with the exception for lower limits for LF cetaceans (Southall et al. 2007) and PW pinniped (approximation). 

The pinniped functional hearing 

group was modified from Southall et al. 

(2007) on the basis of data indicating 

that phocid species have consistently 

demonstrated an extended frequency 

range of hearing compared to otariids, 

especially in the higher frequency range 

(Hemila ̈ et al., 2006; Kastelein et al., 

2009; Reichmuth and Holt, 2013). 


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For more detail concerning these 

groups and associated frequency ranges, 

please see NMFS (2018) for a review of 

available information. 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

This section includes a discussion of 

the ways that L–DEO’s specified activity 

may impact marine mammals and their 

habitat. The Estimated Take section 

later in this document includes a 

quantitative analysis of the number of 

individuals that are expected to be taken 

by this activity. The Negligible Impact 

Analysis and Determination section 

considers the content of this section, the 

Estimated Take section, and the 

Proposed Mitigation section, to draw 

conclusions regarding the likely impacts 

of these activities on the reproductive 

success or survivorship of individuals 

and how those impacts on individuals 

may or may not impact marine mammal 

species or stocks. 

Description of Active Acoustic Sound 

Sources 

This section contains a brief technical 

background on sound, the 

characteristics of certain sound types, 

and on metrics used in this proposal 

inasmuch as the information is relevant 

to the specified activity and to a 

discussion of the potential effects of the 

specified activity on a marine mammals 

found later in this document. 

Sound travels in waves, the basic 

components of which are frequency, 

wavelength, velocity, and amplitude. 

Frequency is the number of pressure 

waves that pass by a reference point per 

unit of time and is measured in hertz 

(Hz) or cycles per second. Wavelength is 

the distance between two peaks or 

corresponding points of a sound wave 

(length of one cycle). Higher frequency 

sounds have shorter wavelengths than 

lower frequency sounds, and typically 

attenuate (decrease) more rapidly, 

except in certain cases in shallower 

water. Amplitude is the height of the 

sound pressure wave or the ‘‘loudness’’ 

of a sound and is typically described 

using the relative unit of the dB. A 

sound pressure level (SPL) in dB is 

described as the ratio between a 

measured pressure and a reference 

pressure (for underwater sound, this is 

1 microPascal (mPa)) and is a 

logarithmic unit that accounts for large 

variations in amplitude; therefore, a 

relatively small change in dB 

corresponds to large changes in sound 

pressure. The source level (SL) 

represents the SPL referenced at a 

distance of 1 m from the source 

(referenced to 1 mPa) while the received 

level is the SPL at the listener’s position 

(referenced to 1 mPa). 

Root mean square (rms) is the 

quadratic mean sound pressure over the 

duration of an impulse. Root mean 

square is calculated by squaring all of 

the sound amplitudes, averaging the 

squares, and then taking the square root 

of the average (Urick, 1983). Root mean 

square accounts for both positive and 

negative values; squaring the pressures 

makes all values positive so that they 

may be accounted for in the summation 

of pressure levels (Hastings and Popper, 

2005). This measurement is often used 

in the context of discussing behavioral 

effects, in part because behavioral 

effects, which often result from auditory 

cues, may be better expressed through 

averaged units than by peak pressures. 

Sound exposure level (SEL; 

represented as dB re 1 mPa2¥s) 

represents the total energy contained 

within a pulse and considers both 

intensity and duration of exposure. Peak 

sound pressure (also referred to as zeroto-peak sound pressure or 0-p) is the 

maximum instantaneous sound pressure 

measurable in the water at a specified 

distance from the source and is 

represented in the same units as the rms 

sound pressure. Another common 

metric is peak-to-peak sound pressure 

(pk-pk), which is the algebraic 

difference between the peak positive 

and peak negative sound pressures. 

Peak-to-peak pressure is typically 

approximately 6 dB higher than peak 

pressure (Southall et al., 2007). 

When underwater objects vibrate or 

activity occurs, sound-pressure waves 

are created. These waves alternately 

compress and decompress the water as 

the sound wave travels. Underwater 

sound waves radiate in a manner similar 

to ripples on the surface of a pond and 

may be either directed in a beam or 

beams or may radiate in all directions 

(omnidirectional sources), as is the case 

for pulses produced by the airgun arrays 

considered here. The compressions and 

decompressions associated with sound 

waves are detected as changes in 

pressure by aquatic life and man-made 

sound receptors such as hydrophones. 

Even in the absence of sound from the 

specified activity, the underwater 

environment is typically loud due to 

ambient sound. Ambient sound is 

defined as environmental background 

sound levels lacking a single source or 

point (Richardson et al., 1995), and the 

sound level of a region is defined by the 

total acoustical energy being generated 

by known and unknown sources. These 

sources may include physical (e.g., 

wind and waves, earthquakes, ice, 

atmospheric sound), biological (e.g., 

sounds produced by marine mammals, 

fish, and invertebrates), and 

anthropogenic (e.g., vessels, dredging, 

construction) sound. A number of 

sources contribute to ambient sound, 

including the following (Richardson et 

al., 1995): 

• Wind and waves: The complex 

interactions between wind and water 

surface, including processes such as 

breaking waves and wave-induced 

bubble oscillations and cavitation, are a 

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 


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sound levels can be expected to vary 

widely over both coarse and fine spatial 

and temporal scales. Sound levels at a 

given frequency and location can vary 

by 10–20 dB from day to day 

(Richardson et al., 1995). The result is 

that, depending on the source type and 

its intensity, sound from a given activity 

may be a negligible addition to the local 

environment or could form a distinctive 

signal that may affect marine mammals. 

Details of source types are described in 

the following text. 

Sounds are often considered to fall 

into one of two general types: Pulsed 

and non-pulsed (defined in the 

following). The distinction between 

these two sound types is important 

because they have differing potential to 

cause physical effects, particularly with 

regard to hearing (e.g., Ward, 1997 in 

Southall et al., 2007). Please see 

Southall et al., (2007) for an in-depth 

discussion of these concepts. 

Pulsed sound sources (e.g., airguns, 

explosions, gunshots, sonic booms, 

impact pile driving) produce signals 

that are brief (typically considered to be 

less than one second), broadband, atonal 

transients (ANSI, 1986, 2005; Harris, 

1998; NIOSH, 1998; ISO, 2003) and 

occur either as isolated events or 

repeated in some succession. Pulsed 

sounds are all characterized by a 

relatively rapid rise from ambient 

pressure to a maximal pressure value 

followed by a rapid decay period that 

may include a period of diminishing, 

oscillating maximal and minimal 

pressures, and generally have an 

increased capacity to induce physical 

injury as compared with sounds that 

lack these features. 

Non-pulsed sounds can be tonal, 

narrowband, or broadband, brief or 

prolonged, and may be either 

continuous or non-continuous (ANSI, 

1995; NIOSH, 1998). Some of these nonpulsed sounds can be transient signals 

of short duration but without the 

essential properties of pulses (e.g., rapid 

rise time). Examples of non-pulsed 

sounds include those produced by 

vessels, aircraft, machinery operations 

such as drilling or dredging, vibratory 

pile driving, and active sonar systems 

(such as those used by the U.S. Navy). 

The duration of such sounds, as 

received at a distance, can be greatly 

extended in a highly reverberant 

environment. 

Airgun arrays produce pulsed signals 

with energy in a frequency range from 

about 10–2,000 Hz, with most energy 

radiated at frequencies below 200 Hz. 

The amplitude of the acoustic wave 

emitted from the source is equal in all 

directions (i.e., omnidirectional), but 

airgun arrays do possess some 

directionality due to different phase 

delays between guns in different 

directions. Airgun arrays are typically 

tuned to maximize functionality for data 

acquisition purposes, meaning that 

sound transmitted in horizontal 

directions and at higher frequencies is 

minimized to the extent possible. 

Acoustic Effects 

Here, we discuss the effects of active 

acoustic sources on marine mammals. 

Potential Effects of Underwater 

Sound—Please refer to the information 

given previously (‘‘Description of Active 

Acoustic Sound Sources’’) regarding 

sound, characteristics of sound types, 

and metrics used in this document. Note 

that, in the following discussion, we 

refer in many cases to Finneran (2015), 

a review article concerning studies of 

noise-induced hearing loss conducted 

from 1996–2015. For study-specific 

citations, please see Finneran (2015). 

Anthropogenic sounds cover a broad 

range of frequencies and sound levels 

and can have a range of highly variable 

impacts on marine life, from none or 

minor to potentially severe responses, 

depending on received levels, duration 

of exposure, behavioral context, and 

various other factors. The potential 

effects of underwater sound from active 

acoustic sources can potentially result 

in one or more of the following: 

Temporary or permanent hearing 

impairment, non-auditory physical or 

physiological effects, behavioral 

disturbance, stress, and masking 

(Richardson et al., 1995; Gordon et al., 

2004; Nowacek et al., 2007; Southall et 

al., 2007; Go ̈tz et al., 2009). The degree 

of effect is intrinsically related to the 

signal characteristics, received level, 

distance from the source, and duration 

of the sound exposure. In general, 

sudden, high level sounds can cause 

hearing loss, as can longer exposures to 

lower level sounds. Temporary or 

permanent loss of hearing, if it occurs at 

all, will occur almost exclusively in 

cases where a noise is within an 

animal’s hearing frequency range. We 

first describe specific manifestations of 

acoustic effects before providing 

discussion specific to the use of airgun 

arrays. 

Richardson et al., (1995) described 

zones of increasing intensity of effect 

that might be expected to occur, in 

relation to distance from a source and 

assuming that the signal is within an 

animal’s hearing range. First is the area 

within which the acoustic signal would 

be audible (potentially perceived) to the 

animal, but not strong enough to elicit 

any overt behavioral or physiological 

response. The next zone corresponds 

with the area where the signal is audible 

to the animal and of sufficient intensity 

to elicit behavioral or physiological 

response. Third is a zone within which, 

for signals of high intensity, the 

received level is sufficient to potentially 

cause discomfort or tissue damage to 

auditory or other systems. Overlaying 

these zones to a certain extent is the 

area within which masking (i.e., when a 

sound interferes with or masks the 

ability of an animal to detect a signal of 

interest that is above the absolute 

hearing threshold) may occur; the 

masking zone may be highly variable in 

size. 

We describe the more severe effects of 

certain non-auditory physical or 

physiological effects only briefly as we 

do not expect that use of airgun arrays 

are reasonably likely to result in such 

effects (see below for further 

discussion). Potential effects from 

impulsive sound sources can range in 

severity from effects such as behavioral 

disturbance or tactile perception to 

physical discomfort, slight injury of the 

internal organs and the auditory system, 

or mortality (Yelverton et al., 1973). 

Non-auditory physiological effects or 

injuries that theoretically might occur in 

marine mammals exposed to high level 

underwater sound or as a secondary 

effect of extreme behavioral reactions 

(e.g., change in dive profile as a result 

of an avoidance reaction) caused by 

exposure to sound include neurological 

effects, bubble formation, resonance 

effects, and other types of organ or 

tissue damage (Cox et al., 2006; Southall 

et al., 2007; Zimmer and Tyack, 2007; 

Tal et al., 2015). The survey activities 

considered here do not involve the use 

of devices such as explosives or midfrequency tactical sonar that are 

associated with these types of effects. 

Threshold Shift—Marine mammals 

exposed to high-intensity sound, or to 

lower-intensity sound for prolonged 

periods, can experience hearing 

threshold shift (TS), which is the loss of 

hearing sensitivity at certain frequency 

ranges (Finneran, 2015). TS can be 

permanent (PTS), in which case the loss 

of hearing sensitivity is not fully 

recoverable, or temporary (TTS), in 

which case the animal’s hearing 

threshold would recover over time 

(Southall et al., 2007). Repeated sound 

exposure that leads to TTS could cause 

PTS. In severe cases of PTS, there can 

be total or partial deafness, while in 

most cases the animal has an impaired 

ability to hear sounds in specific 

frequency ranges (Kryter, 1985). 

When PTS occurs, there is physical 

damage to the sound receptors in the ear 

(i.e., tissue damage), whereas TTS 

represents primarily tissue fatigue and 

is reversible (Southall et al., 2007). In 


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addition, other investigators have 

suggested that TTS is within the normal 

bounds of physiological variability and 

tolerance and does not represent 

physical injury (e.g., Ward, 1997). 

Therefore, NMFS does not typically 

consider TTS to constitute auditory 

injury. 

Relationships between TTS and PTS 

thresholds have not been studied in 

marine mammals, and there is no PTS 

data for cetaceans but such relationships 

are assumed to be similar to those in 

humans and other terrestrial mammals. 

PTS typically occurs at exposure levels 

at least several dBs above (a 40-dB 

threshold shift approximates PTS onset; 

e.g., Kryter et al., 1966; Miller, 1974) 

that inducing mild TTS (a 6-dB 

threshold shift approximates TTS onset; 

e.g., Southall et al., 2007). Based on data 

from terrestrial mammals, a 

precautionary assumption is that the 

PTS thresholds for impulse sounds 

(such as airgun pulses as received close 

to the source) are at least 6 dB higher 

than the TTS threshold on a peakpressure basis and PTS cumulative 

sound exposure level thresholds are 15 

to 20 dB higher than TTS cumulative 

sound exposure level thresholds 

(Southall et al., 2007). Given the higher 

level of sound or longer exposure 

duration necessary to cause PTS as 

compared with TTS, it is considerably 

less likely that PTS could occur. 

For mid-frequency cetaceans in 

particular, potential protective 

mechanisms may help limit onset of 

TTS or prevent onset of PTS. Such 

mechanisms include dampening of 

hearing, auditory adaptation, or 

behavioral amelioration (e.g., Nachtigall 

and Supin, 2013; Miller et al., 2012; 

Finneran et al., 2015; Popov et al., 

2016). 

TTS is the mildest form of hearing 

impairment that can occur during 

exposure to sound (Kryter, 1985). While 

experiencing TTS, the hearing threshold 

rises, and a sound must be at a higher 

level in order to be heard. In terrestrial 

and marine mammals, TTS can last from 

minutes or hours to days (in cases of 

strong TTS). In many cases, hearing 

sensitivity recovers rapidly after 

exposure to the sound ends. Few data 

on sound levels and durations necessary 

to elicit mild TTS have been obtained 

for marine mammals. 

Marine mammal hearing plays a 

critical role in communication with 

conspecifics, and interpretation of 

environmental cues for purposes such 

as predator avoidance and prey capture. 

Depending on the degree (elevation of 

threshold in dB), duration (i.e., recovery 

time), and frequency range of TTS, and 

the context in which it is experienced, 

TTS can have effects on marine 

mammals ranging from discountable to 

serious. For example, a marine mammal 

may be able to readily compensate for 

a brief, relatively small amount of TTS 

in a non-critical frequency range that 

occurs during a time where ambient 

noise is lower and there are not as many 

competing sounds present. 

Alternatively, a larger amount and 

longer duration of TTS sustained during 

time when communication is critical for 

successful mother/calf interactions 

could have more serious impacts. 

Finneran et al. (2015) measured 

hearing thresholds in three captive 

bottlenose dolphins before and after 

exposure to ten pulses produced by a 

seismic airgun in order to study TTS 

induced after exposure to multiple 

pulses. Exposures began at relatively 

low levels and gradually increased over 

a period of several months, with the 

highest exposures at peak SPLs from 

196 to 210 dB and cumulative 

(unweighted) SELs from 193–195 dB. 

No substantial TTS was observed. In 

addition, behavioral reactions were 

observed that indicated that animals can 

learn behaviors that effectively mitigate 

noise exposures (although exposure 

patterns must be learned, which is less 

likely in wild animals than for the 

captive animals considered in this 

study). The authors note that the failure 

to induce more significant auditory 

effects was likely due to the intermittent 

nature of exposure, the relatively low 

peak pressure produced by the acoustic 

source, and the low-frequency energy in 

airgun pulses as compared with the 

frequency range of best sensitivity for 

dolphins and other mid-frequency 

cetaceans. 

Currently, TTS data only exist for four 

species of cetaceans (bottlenose 

dolphin, beluga whale, harbor porpoise, 

and Yangtze finless porpoise) exposed 

to a limited number of sound sources 

(i.e., mostly tones and octave-band 

noise) in laboratory settings (Finneran, 

2015). In general, harbor porpoises have 

a lower TTS onset than other measured 

cetacean species (Finneran, 2015). 

Additionally, the existing marine 

mammal TTS data come from a limited 

number of individuals within these 

species. There are no direct data 

available on noise-induced hearing loss 

for mysticetes. 

Critical questions remain regarding 

the rate of TTS growth and recovery 

after exposure to intermittent noise and 

the effects of single and multiple pulses. 

Data at present are also insufficient to 

construct generalized models for 

recovery and determine the time 

necessary to treat subsequent exposures 

as independent events. More 

information is needed on the 

relationship between auditory evoked 

potential and behavioral measures of 

TTS for various stimuli. For summaries 

of data on TTS in marine mammals or 

for further discussion of TTS onset 

thresholds, please see Southall et al. 

(2007, 2019), Finneran and Jenkins 

(2012), Finneran (2015), and NMFS 

(2018). 

Behavioral Effects—Behavioral 

disturbance may include a variety of 

effects, including subtle changes in 

behavior (e.g., minor or brief avoidance 

of an area or changes in vocalizations), 

more conspicuous changes in similar 

behavioral activities, and more 

sustained and/or potentially severe 

reactions, such as displacement from or 

abandonment of high-quality habitat. 

Behavioral responses to sound are 

highly variable and context-specific, 

and any reactions depend on numerous 

intrinsic and extrinsic factors (e.g., 

species, state of maturity, experience, 

current activity, reproductive state, 

auditory sensitivity, time of day), as 

well as the interplay between factors 

(e.g., Richardson et al., 1995; Wartzok et 

al., 2003; Southall et al., 2007, 2019; 

Weilgart, 2007; Archer et al., 2010). 

Behavioral reactions can vary not only 

among individuals but also within an 

individual, depending on previous 

experience with a sound source, 

context, and numerous other factors 

(Ellison et al., 2012), and can vary 

depending on characteristics associated 

with the sound source (e.g., whether it 

is moving or stationary, number of 

sources, distance from the source). 

Please see Appendices B–C of Southall 

et al. (2007) for a review of studies 

involving marine mammal behavioral 

responses to sound. 

Habituation can occur when an 

animal’s response to a stimulus wanes 

with repeated exposure, usually in the 

absence of unpleasant associated events 

(Wartzok et al., 2003). Animals are most 

likely to habituate to sounds that are 

predictable and unvarying. It is 

important to note that habituation is 

appropriately considered as a 

‘‘progressive reduction in response to 

stimuli that are perceived as neither 

aversive nor beneficial,’’ rather than as, 

more generally, moderation in response 

to human disturbance (Bejder et al., 

2009). The opposite process is 

sensitization, when an unpleasant 

experience leads to subsequent 

responses, often in the form of 

avoidance, at a lower level of exposure. 

As noted, behavioral state may affect the 

type of response. For example, animals 

that are resting may show greater 

behavioral change in response to 

disturbing sound levels than animals 


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that are highly motivated to remain in 

an area for feeding (Richardson et al., 

1995; NRC, 2003; Wartzok et al., 2003). 

Controlled experiments with captive 

marine mammals have showed 

pronounced behavioral reactions, 

including avoidance of loud sound 

sources (Ridgway et al., 1997). Observed 

responses of wild marine mammals to 

loud pulsed sound sources (typically 

seismic airguns or acoustic harassment 

devices) have been varied but often 

consist of avoidance behavior or other 

behavioral changes suggesting 

discomfort (Morton and Symonds, 2002; 

see also Richardson et al., 1995; 

Nowacek et al., 2007). However, many 

delphinids approach acoustic source 

vessels with no apparent discomfort or 

obvious behavioral change (e.g., 

Barkaszi et al., 2012). 

Available studies show wide variation 

in response to underwater sound; 

therefore, it is difficult to predict 

specifically how any given sound in a 

particular instance might affect marine 

mammals perceiving the signal. If a 

marine mammal does react briefly to an 

underwater sound by changing its 

behavior or moving a small distance, the 

impacts of the change are unlikely to be 

significant to the individual, let alone 

the stock or population. However, if a 

sound source displaces marine 

mammals from an important feeding or 

breeding area for a prolonged period, 

impacts on individuals and populations 

could be significant (e.g., Lusseau and 

Bejder, 2007; Weilgart, 2007; NRC, 

2005). However, there are broad 

categories of potential response, which 

we describe in greater detail here, that 

include alteration of dive behavior, 

alteration of foraging behavior, effects to 

breathing, interference with or alteration 

of vocalization, avoidance, and flight. 

Changes in dive behavior can vary 

widely, and may consist of increased or 

decreased dive times and surface 

intervals as well as changes in the rates 

of ascent and descent during a dive (e.g., 

Frankel and Clark, 2000; Ng and Leung, 

2003; Nowacek et al., 2004; Goldbogen 

et al., 2013a, b). Variations in dive 

behavior may reflect disruptions in 

biologically significant activities (e.g., 

foraging) or they may be of little 

biological significance. The impact of an 

alteration to dive behavior resulting 

from an acoustic exposure depends on 

what the animal is doing at the time of 

the exposure and the type and 

magnitude of the response. 

Disruption of feeding behavior can be 

difficult to correlate with anthropogenic 

sound exposure, so it is usually inferred 

by observed displacement from known 

foraging areas, the appearance of 

secondary indicators (e.g., bubble nets 

or sediment plumes), or changes in dive 

behavior. As for other types of 

behavioral response, the frequency, 

duration, and temporal pattern of signal 

presentation, as well as differences in 

species sensitivity, are likely 

contributing factors to differences in 

response in any given circumstance 

(e.g., Croll et al., 2001; Nowacek et al.; 

2004; Madsen et al., 2006; Yazvenko et 

al., 2007). A determination of whether 

foraging disruptions incur fitness 

consequences would require 

information on or estimates of the 

energetic requirements of the affected 

individuals and the relationship 

between prey availability, foraging effort 

and success, and the life history stage of 

the animal. 

Visual tracking, passive acoustic 

monitoring, and movement recording 

tags were used to quantify sperm whale 

behavior prior to, during, and following 

exposure to airgun arrays at received 

levels in the range 140–160 dB at 

distances of 7–13 km, following a phasein of sound intensity and full array 

exposures at 1–13 km (Madsen et al., 

2006; Miller et al., 2009). Sperm whales 

did not exhibit horizontal avoidance 

behavior at the surface. However, 

foraging behavior may have been 

affected. The sperm whales exhibited 19 

percent less vocal (buzz) rate during full 

exposure relative to post exposure, and 

the whale that was approached most 

closely had an extended resting period 

and did not resume foraging until the 

airguns had ceased firing. The 

remaining whales continued to execute 

foraging dives throughout exposure; 

however, swimming movements during 

foraging dives were 6 percent lower 

during exposure than control periods 

(Miller et al., 2009). These data raise 

concerns that seismic surveys may 

impact foraging behavior in sperm 

whales, although more data are required 

to understand whether the differences 

were due to exposure or natural 

variation in sperm whale behavior 

(Miller et al., 2009). 

Variations in respiration naturally 

vary with different behaviors and 

alterations to breathing rate as a 

function of acoustic exposure can be 

expected to co-occur with other 

behavioral reactions, such as a flight 

response or an alteration in diving. 

However, respiration rates in and of 

themselves may be representative of 

annoyance or an acute stress response. 

Various studies have shown that 

respiration rates may either be 

unaffected or could increase, depending 

on the species and signal characteristics, 

again highlighting the importance in 

understanding species differences in the 

tolerance of underwater noise when 

determining the potential for impacts 

resulting from anthropogenic sound 

exposure (e.g., Kastelein et al., 2001, 

2005, 2006; Gailey et al., 2007, 2016). 

Marine mammals vocalize for 

different purposes and across multiple 

modes, such as whistling, echolocation 

click production, calling, and singing. 

Changes in vocalization behavior in 

response to anthropogenic noise can 

occur for any of these modes and may 

result from a need to compete with an 

increase in background noise or may 

reflect increased vigilance or a startle 

response. For example, in the presence 

of potentially masking signals, 

humpback whales and killer whales 

have been observed to increase the 

length of their songs or amplitude of 

calls (Miller et al., 2000; Fristrup et al., 

2003; Foote et al., 2004; Holt et al., 

2012), while right whales have been 

observed to shift the frequency content 

of their calls upward while reducing the 

rate of calling in areas of increased 

anthropogenic noise (Parks et al., 2007). 

In some cases, animals may cease sound 

production during production of 

aversive signals (Bowles et al., 1994). 

Cerchio et al., (2014) used passive 

acoustic monitoring to document the 

presence of singing humpback whales 

off the coast of northern Angola and to 

opportunistically test for the effect of 

seismic survey activity on the number of 

singing whales. Two recording units 

were deployed between March and 

December 2008 in the offshore 

environment; numbers of singers were 

counted every hour. Generalized 

Additive Mixed Models were used to 

assess the effect of survey day 

(seasonality), hour (diel variation), 

moon phase, and received levels of 

noise (measured from a single pulse 

during each ten minute sampled period) 

on singer number. The number of 

singers significantly decreased with 

increasing received level of noise, 

suggesting that humpback whale 

breeding activity was disrupted to some 

extent by the survey activity. 

Castellote et al., (2012) reported 

acoustic and behavioral changes by fin 

whales in response to shipping and 

airgun noise. Acoustic features of fin 

whale song notes recorded in the 

Mediterranean Sea and northeast 

Atlantic Ocean were compared for areas 

with different shipping noise levels and 

traffic intensities and during a seismic 

airgun survey. During the first 72 h of 

the survey, a steady decrease in song 

received levels and bearings to singers 

indicated that whales moved away from 

the acoustic source and out of the study 

area. This displacement persisted for a 

time period well beyond the 10-day 

duration of seismic airgun activity, 


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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 mPa2-s caused blue 

whales to increase call production (Di 

Iorio and Clark, 2010). In contrast, 

McDonald et al., (1995) tracked a blue 

whale with seafloor seismometers and 

reported that it stopped vocalizing and 

changed its travel direction at a range of 

10 km from the acoustic source vessel 

(estimated received level 143 dB pk-pk). 

Blackwell et al., (2013) found that 

bowhead whale call rates dropped 

significantly at onset of airgun use at 

sites with a median distance of 41–45 

km from the survey. Blackwell et al. 

(2015) expanded this analysis to show 

that whales actually increased calling 

rates as soon as airgun signals were 

detectable before ultimately decreasing 

calling rates at higher received levels 

(i.e., 10-minute SELcum of ∼127 dB). 

Overall, these results suggest that 

bowhead whales may adjust their vocal 

output in an effort to compensate for 

noise before ceasing vocalization effort 

and ultimately deflecting from the 

acoustic source (Blackwell et al., 2013, 

2015). These studies demonstrate that 

even low levels of noise received far 

from the source can induce changes in 

vocalization and/or behavior for 

mysticetes. 

Avoidance is the displacement of an 

individual from an area or migration 

path as a result of the presence of a 

sound or other stressors, and is one of 

the most obvious manifestations of 

disturbance in marine mammals 

(Richardson et al., 1995). For example, 

gray whales are known to change 

direction—deflecting from customary 

migratory paths—in order to avoid noise 

from seismic surveys (Malme et al., 

1984). Humpback whales showed 

avoidance behavior in the presence of 

an active seismic array during 

observational studies and controlled 

exposure experiments in western 

Australia (McCauley et al., 2000). 

Avoidance may be short-term, with 

animals returning to the area once the 

noise has ceased (e.g., Bowles et al., 

1994; Goold, 1996; Stone et al., 2000; 

Morton and Symonds, 2002; Gailey et 

al., 2007). Longer-term displacement is 

possible, however, which may lead to 

changes in abundance or distribution 

patterns of the affected species in the 

affected region if habituation to the 

presence of the sound does not occur 

(e.g., Bejder et al., 2006; Teilmann et al., 

2006). 

Forney et al., (2017) detail the 

potential effects of noise on marine 

mammal populations with high site 

fidelity, including displacement and 

auditory masking, noting that a lack of 

observed response does not imply 

absence of fitness costs and that 

apparent tolerance of disturbance may 

have population-level impacts that are 

less obvious and difficult to document. 

As we discuss in describing our 

proposed mitigation later in this 

document, avoidance of overlap 

between disturbing noise and areas and/ 

or times of particular importance for 

sensitive species may be critical to 

avoiding population-level impacts 

because (particularly for animals with 

high site fidelity) there may be a strong 

motivation to remain in the area despite 

negative impacts. Forney et al., (2017) 

state that, for these animals, remaining 

in a disturbed area may reflect a lack of 

alternatives rather than a lack of effects. 

The authors discuss several case 

studies, including western Pacific gray 

whales, which are a small population of 

mysticetes believed to be adversely 

affected by oil and gas development off 

Sakhalin Island, Russia (Weller et al., 

2002; Reeves et al., 2005). Western gray 

whales display a high degree of 

interannual site fidelity to the area for 

foraging purposes, and observations in 

the area during airgun surveys has 

shown the potential for harm caused by 

displacement from such an important 

area (Weller et al., 2006; Johnson et al., 

2007). Forney et al., (2017) also discuss 

beaked whales, noting that 

anthropogenic effects in areas where 

they are resident could cause severe 

biological consequences, in part because 

displacement may adversely affect 

foraging rates, reproduction, or health, 

while an overriding instinct to remain 

could lead to more severe acute effects. 

A flight response is a dramatic change 

in normal movement to a directed and 

rapid movement away from the 

perceived location of a sound source. 

The flight response differs from other 

avoidance responses in the intensity of 

the response (e.g., directed movement, 

rate of travel). Relatively little 

information on flight responses of 

marine mammals to anthropogenic 

signals exist, although observations of 

flight responses to the presence of 

predators have occurred (Connor and 

Heithaus, 1996). The result of a flight 

response could range from brief, 

temporary exertion and displacement 

from the area where the signal provokes 

flight to, in extreme cases, marine 

mammal strandings (Evans and 

England, 2001). However, it should be 

noted that response to a perceived 

predator does not necessarily invoke 

flight (Ford and Reeves, 2008), and 

whether individuals are solitary or in 

groups may influence the response. 

Behavioral disturbance can also 

impact marine mammals in more subtle 

ways. Increased vigilance may result in 

costs related to diversion of focus and 

attention (i.e., when a response consists 

of increased vigilance, it may come at 

the cost of decreased attention to other 

critical behaviors such as foraging or 

resting). These effects have generally not 

been demonstrated for marine 

mammals, but studies involving fish 

and terrestrial animals have shown that 

increased vigilance may substantially 

reduce feeding rates (e.g., Beauchamp 

and Livoreil, 1997; Fritz et al., 2002; 

Purser and Radford, 2011). In addition, 

chronic disturbance can cause 

population declines through reduction 

of fitness (e.g., decline in body 

condition) and subsequent reduction in 

reproductive success, survival, or both 

(e.g., Harrington and Veitch, 1992; Daan 

et al., 1996; Bradshaw et al., 1998). 

However, Ridgway et al. (2006) reported 

that increased vigilance in bottlenose 

dolphins exposed to sound over a fiveday period did not cause any sleep 

deprivation or stress effects. 

Many animals perform vital functions, 

such as feeding, resting, traveling, and 

socializing, on a diel cycle (24-hour 

cycle). Disruption of such functions 

resulting from reactions to stressors 

such as sound exposure are more likely 

to be significant if they last more than 

one diel cycle or recur on subsequent 

days (Southall et al., 2007). 

Consequently, a behavioral response 

lasting less than one day and not 

recurring on subsequent days is not 

considered particularly severe unless it 

could directly affect reproduction or 

survival (Southall et al., 2007). Note that 

there is a difference between multi-day 

substantive behavioral reactions and 

multi-day anthropogenic activities. For 

example, just because an activity lasts 

for multiple days does not necessarily 

mean that individual animals are either 

exposed to activity-related stressors for 

multiple days or, further, exposed in a 

manner resulting in sustained multi-day 

substantive behavioral responses. 

Stone (2015) reported data from at-sea 

observations during 1,196 seismic 

surveys from 1994 to 2010. When arrays 

of large airguns (considered to be 500 

in3 or more) were firing, lateral 

displacement, more localized 

avoidance, or other changes in behavior 

were evident for most odontocetes. 

However, significant responses to large 

arrays were found only for the minke 

whale and fin whale. Behavioral 


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responses observed included changes in 

swimming or surfacing behavior, with 

indications that cetaceans remained 

near the water surface at these times. 

Cetaceans were recorded as feeding less 

often when large arrays were active. 

Behavioral observations of gray whales 

during a seismic survey monitored 

whale movements and respirations 

pre-, during, and post-seismic survey 

(Gailey et al., 2016). Behavioral state 

and water depth were the best ‘natural’ 

predictors of whale movements and 

respiration and, after considering 

natural variation, none of the response 

variables were significantly associated 

with seismic survey or vessel sounds. 

Stress Responses—An animal’s 

perception of a threat may be sufficient 

to trigger stress responses consisting of 

some combination of behavioral 

responses, autonomic nervous system 

responses, neuroendocrine responses, or 

immune responses (e.g., Seyle, 1950; 

Moberg, 2000). In many cases, an 

animal’s first and sometimes most 

economical (in terms of energetic costs) 

response is behavioral avoidance of the 

potential stressor. Autonomic nervous 

system responses to stress typically 

involve changes in heart rate, blood 

pressure, and gastrointestinal activity. 

These responses have a relatively short 

duration and may or may not have a 

significant long-term effect on an 

animal’s fitness. 

Neuroendocrine stress responses often 

involve the hypothalamus-pituitaryadrenal system. Virtually all 

neuroendocrine functions that are 

affected by stress—including immune 

competence, reproduction, metabolism, 

and behavior—are regulated by pituitary 

hormones. Stress-induced changes in 

the secretion of pituitary hormones have 

been implicated in failed reproduction, 

altered metabolism, reduced immune 

competence, and behavioral disturbance 

(e.g., Moberg, 1987; Blecha, 2000). 

Increases in the circulation of 

glucocorticoids are also equated with 

stress (Romano et al., 2004). 

The primary distinction between 

stress (which is adaptive and does not 

normally place an animal at risk) and 

‘‘distress’’ is the cost of the response. 

During a stress response, an animal uses 

glycogen stores that can be quickly 

replenished once the stress is alleviated. 

In such circumstances, the cost of the 

stress response would not pose serious 

fitness consequences. However, when 

an animal does not have sufficient 

energy reserves to satisfy the energetic 

costs of a stress response, energy 

resources must be diverted from other 

functions. This state of distress will last 

until the animal replenishes its 

energetic reserves sufficiently to restore 

normal function. 

Relationships between these 

physiological mechanisms, animal 

behavior, and the costs of stress 

responses are well-studied through 

controlled experiments and for both 

laboratory and free-ranging animals 

(e.g., Holberton et al., 1996; Hood et al., 

1998; Jessop et al., 2003; Krausman et 

al., 2004; Lankford et al., 2005). Stress 

responses due to exposure to 

anthropogenic sounds or other stressors 

and their effects on marine mammals 

have also been reviewed (Fair and 

Becker, 2000; Romano et al., 2002b) 

and, more rarely, studied in wild 

populations (e.g., Romano et al., 2002a). 

For example, Rolland et al., (2012) 

found that noise reduction from reduced 

ship traffic in the Bay of Fundy was 

associated with decreased stress in 

North Atlantic right whales. These and 

other studies lead to a reasonable 

expectation that some marine mammals 

will experience physiological stress 

responses upon exposure to acoustic 

stressors and that it is possible that 

some of these would be classified as 

‘‘distress.’’ In addition, any animal 

experiencing TTS would likely also 

experience stress responses (NRC, 

2003). 

Auditory Masking—Sound can 

disrupt behavior through masking, or 

interfering with, an animal’s ability to 

detect, recognize, or discriminate 

between acoustic signals of interest (e.g., 

those used for intraspecific 

communication and social interactions, 

prey detection, predator avoidance, 

navigation) (Richardson et al., 1995; 

Erbe et al., 2016). Masking occurs when 

the receipt of a sound is interfered with 

by another coincident sound at similar 

frequencies and at similar or higher 

intensity, and may occur whether the 

sound is natural (e.g., snapping shrimp, 

wind, waves, precipitation) or 

anthropogenic (e.g., shipping, sonar, 

seismic exploration) in origin. The 

ability of a noise source to mask 

biologically important sounds depends 

on the characteristics of both the noise 

source and the signal of interest (e.g., 

signal-to-noise ratio, temporal 

variability, direction), in relation to each 

other and to an animal’s hearing 

abilities (e.g., sensitivity, frequency 

range, critical ratios, frequency 

discrimination, directional 

discrimination, age or TTS hearing loss), 

and existing ambient noise and 

propagation conditions. 

Under certain circumstances, 

significant masking could disrupt 

behavioral patterns, which in turn could 

affect fitness for survival and 

reproduction. It is important to 

distinguish TTS and PTS, which persist 

after the sound exposure, from masking, 

which occurs during the sound 

exposure. Because masking (without 

resulting in TS) is not associated with 

abnormal physiological function, it is 

not considered a physiological effect, 

but rather a potential behavioral effect. 

The frequency range of the potentially 

masking sound is important in 

predicting any potential behavioral 

impacts. For example, low-frequency 

signals may have less effect on highfrequency echolocation sounds 

produced by odontocetes but are more 

likely to affect detection of mysticete 

communication calls and other 

potentially important natural sounds 

such as those produced by surf and 

some prey species. The masking of 

communication signals by 

anthropogenic noise may be considered 

as a reduction in the communication 

space of animals (e.g., Clark et al., 2009) 

and may result in energetic or other 

costs as animals change their 

vocalization behavior (e.g., Miller et al., 

2000; Foote et al., 2004; Parks et al., 

2007; Di Iorio and Clark, 2009; Holt et 

al., 2009). Masking 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, 


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animals can emit and receive sounds in 

the relatively quiet intervals between 

pulses. However, in exceptional 

situations, reverberation occurs for 

much or all of the interval between 

pulses (e.g., Simard et al., 2005; Clark 

and Gagnon 2006), which could mask 

calls. Situations with prolonged strong 

reverberation are infrequent. However, 

it is common for reverberation to cause 

some lesser degree of elevation of the 

background level between airgun pulses 

(e.g., Gedamke 2011; Guerra et al., 2011, 

2016; Klinck et al., 2012; Guan et al., 

2015), and this weaker reverberation 

presumably reduces the detection range 

of calls and other natural sounds to 

some degree. Guerra et al., (2016) 

reported that ambient noise levels 

between seismic pulses were elevated as 

a result of reverberation at ranges of 50 

km from the seismic source. Based on 

measurements in deep water of the 

Southern Ocean, Gedamke (2011) 

estimated that the slight elevation of 

background levels during intervals 

between pulses reduced blue and fin 

whale communication space by as much 

as 36–51 percent when a seismic survey 

was operating 450–2,800 km away. 

Based on preliminary modeling, 

Wittekind et al., (2016) reported that 

airgun sounds could reduce the 

communication range of blue and fin 

whales 2000 km from the seismic 

source. Nieukirk et al., (2012) and 

Blackwell et al., (2013) noted the 

potential for masking effects from 

seismic surveys on large whales. 

Some baleen and toothed whales are 

known to continue calling in the 

presence of seismic pulses, and their 

calls usually can be heard between the 

pulses (e.g., Nieukirk et al., 2012; Thode 

et al., 2012; Bro ̈ker et al., 2013; Sciacca 

et al., 2016). As noted above, Cerchio et 

al., (2014) suggested that the breeding 

display of humpback whales off Angola 

could be disrupted by seismic sounds, 

as singing activity declined with 

increasing received levels. In addition, 

some cetaceans are known to change 

their calling rates, shift their peak 

frequencies, or otherwise modify their 

vocal behavior in response to airgun 

sounds (e.g., Di Iorio and Clark 2010; 

Castellote et al., 2012; Blackwell et al., 

2013, 2015). The hearing systems of 

baleen whales are undoubtedly more 

sensitive to low-frequency sounds than 

are the ears of the small odontocetes 

that have been studied directly (e.g., 

MacGillivray et al., 2014). The sounds 

important to small odontocetes are 

predominantly at much higher 

frequencies than are the dominant 

components of airgun sounds, thus 

limiting the potential for masking. In 

general, masking effects of seismic 

pulses are expected to be minor, given 

the normally intermittent nature of 

seismic pulses. 

Ship Noise 

Vessel noise from the Langseth could 

affect marine animals in the proposed 

survey areas. Houghton et al., (2015) 

proposed that vessel speed is the most 

important predictor of received noise 

levels, and Putland et al., (2017) also 

reported reduced sound levels with 

decreased vessel speed. Sounds 

produced by large vessels generally 

dominate ambient noise at frequencies 

from 20 to 300 Hz (Richardson et al., 

1995). However, some energy is also 

produced at higher frequencies 

(Hermannsen et al., 2014); low levels of 

high-frequency sound from vessels has 

been shown to elicit responses in harbor 

porpoise (Dyndo et al., 2015). Increased 

levels of ship noise have been shown to 

affect foraging by porpoise (Teilmann et 

al., 2015; Wisniewska et al., 2018); 

Wisniewska et al., (2018) suggest that a 

decrease in foraging success could have 

long-term fitness consequences. 

Ship noise, through masking, can 

reduce the effective communication 

distance of a marine mammal if the 

frequency of the sound source is close 

to that used by the animal, and if the 

sound is present for a significant 

fraction of time (e.g., Richardson et al. 

1995; Clark et al., 2009; Jensen et al., 

2009; Gervaise et al., 2012; Hatch et al., 

2012; Rice et al., 2014; Dunlop 2015; 

Erbe et al., 2015; Jones et al., 2017; 

Putland et al., 2017). In addition to the 

frequency and duration of the masking 

sound, the strength, temporal pattern, 

and location of the introduced sound 

also play a role in the extent of the 

masking (Branstetter et al., 2013, 2016; 

Finneran and Branstetter 2013; Sills et 

al., 2017). Branstetter et al. (2013) 

reported that time-domain metrics are 

also important in describing and 

predicting masking. In order to 

compensate for increased ambient noise, 

some cetaceans are known to increase 

the source levels of their calls in the 

presence of elevated noise levels from 

shipping, shift their peak frequencies, or 

otherwise change their vocal behavior 

(e.g., Martins et al., 2016; O’Brien et al., 

2016; Tenessen and Parks 2016). Harp 

seals did not increase their call 

frequencies in environments with 

increased low-frequency sounds 

(Terhune and Bosker 2016). Holt et al. 

(2015) reported that changes in vocal 

modifications can have increased 

energetic costs for individual marine 

mammals. A negative correlation 

between the presence of some cetacean 

species and the number of vessels in an 

area has been demonstrated by several 

studies (e.g., Campana et al. 2015; 

Culloch et al., 2016). 

Baleen whales are thought to be more 

sensitive to sound at these low 

frequencies than are toothed whales 

(e.g., MacGillivray et al., 2014), possibly 

causing localized avoidance of the 

proposed survey area during seismic 

operations. Reactions of gray and 

humpback whales to vessels have been 

studied, and there is limited 

information available about the 

reactions of right whales and rorquals 

(fin, blue, and minke whales). Reactions 

of humpback whales to boats are 

variable, ranging from approach to 

avoidance (Payne 1978; Salden 1993). 

Baker et al., (1982, 1983) and Baker and 

Herman (1989) found humpbacks often 

move away when vessels are within 

several kilometers. Humpbacks seem 

less likely to react overtly when actively 

feeding than when resting or engaged in 

other activities (Krieger and Wing 1984, 

1986). Increased levels of ship noise 

have been shown to affect foraging by 

humpback whales (Blair et al., 2016). 

Fin whale sightings in the western 

Mediterranean were negatively 

correlated with the number of vessels in 

the area (Campana et al. 2015). Minke 

whales and gray seals have shown slight 

displacement in response to 

construction-related vessel traffic 

(Anderwald et al., 2013). 

Many odontocetes show considerable 

tolerance of vessel traffic, although they 

sometimes react at long distances if 

confined by ice or shallow water, if 

previously harassed by vessels, or have 

had little or no recent exposure to ships 

(Richardson et al. 1995). Dolphins of 

many species tolerate and sometimes 

approach vessels (e.g., Anderwald et al., 

2013). Some dolphin species approach 

moving vessels to ride the bow or stern 

waves (Williams et al., 1992). Pirotta et 

al., (2015) noted that the physical 

presence of vessels, not just ship noise, 

disturbed the foraging activity of 

bottlenose dolphins. Sightings of striped 

dolphin, Risso’s dolphin, sperm whale, 

and Cuvier’s beaked whale in the 

western Mediterranean were negatively 

correlated with the number of vessels in 

the area (Campana et al., 2015). 

There are few data on the behavioral 

reactions of beaked whales to vessel 

noise, though they seem to avoid 

approaching vessels (e.g., Wu ̈rsig et al., 

1998) or dive for an extended period 

when approached by a vessel (e.g., 

Kasuya 1986). Based on a single 

observation, Aguilar Soto et al., (2006) 

suggest foraging efficiency of Cuvier’s 

beaked whales may be reduced by close 

approach of vessels. 


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Sounds emitted by the Langseth are 

low frequency and continuous, but 

would be widely dispersed in both 

space and time. Vessel traffic associated 

with the proposed survey is of low 

density compared to traffic associated 

with commercial shipping, industry 

support vessels, or commercial fishing 

vessels, and would therefore be 

expected to represent an insignificant 

incremental increase in the total amount 

of anthropogenic sound input to the 

marine environment, and the effects of 

vessel noise described above are not 

expected to occur as a result of this 

survey. In summary, project vessel 

sounds would not be at levels expected 

to cause anything more than possible 

localized and temporary behavioral 

changes in marine mammals, and would 

not be expected to result in significant 

negative effects on individuals or at the 

population level. In addition, in all 

oceans of the world, large vessel traffic 

is currently so prevalent that it is 

commonly considered a usual source of 

ambient sound (NSF–USGS 2011). 

Ship Strike 

Vessel collisions with marine 

mammals, or ship strikes, can result in 

death or serious injury of the animal. 

Wounds resulting from ship strike may 

include massive trauma, hemorrhaging, 

broken bones, or propeller lacerations 

(Knowlton and Kraus, 2001). An animal 

at the surface may be struck directly by 

a vessel, a surfacing animal may hit the 

bottom of a vessel, or an animal just 

below the surface may be cut by a 

vessel’s propeller. Superficial strikes 

may not kill or result in the death of the 

animal. These interactions are typically 

associated with large whales (e.g., fin 

whales), which are occasionally found 

draped across the bulbous bow of large 

commercial ships upon arrival in port. 

Although smaller cetaceans are more 

maneuverable in relation to large vessels 

than are large whales, they may also be 

susceptible to strike. The severity of 

injuries typically depends on the size 

and speed of the vessel, with the 

probability of death or serious injury 

increasing as vessel speed increases 

(Knowlton and Kraus, 2001; Laist et al., 

2001; Vanderlaan and Taggart, 2007; 

Conn and Silber, 2013). Impact forces 

increase with speed, as does the 

probability of a strike at a given distance 

(Silber et al., 2010; Gende et al., 2011). 

Pace and Silber (2005) also found that 

the probability of death or serious injury 

increased rapidly with increasing vessel 

speed. Specifically, the predicted 

probability of serious injury or death 

increased from 45 to 75 percent as 

vessel speed increased from 10 to 14 kn, 

and exceeded 90 percent at 17 kn. 

Higher speeds during collisions result in 

greater force of impact, but higher 

speeds also appear to increase the 

chance of severe injuries or death 

through increased likelihood of 

collision by pulling whales toward the 

vessel (Clyne, 1999; Knowlton et al., 

1995). In a separate study, Vanderlaan 

and Taggart (2007) analyzed the 

probability of lethal mortality of large 

whales at a given speed, showing that 

the greatest rate of change in the 

probability of a lethal injury to a large 

whale as a function of vessel speed 

occurs between 8.6 and 15 kn. The 

chances of a lethal injury decline from 

approximately 80 percent at 15 kn to 

approximately 20 percent at 8.6 kn. At 

speeds below 11.8 kn, the chances of 

lethal injury drop below 50 percent, 

while the probability asymptotically 

increases toward one hundred percent 

above 15 kn. 

The Langseth will travel at a speed of 

4.6 kn (8.5 km/h) while towing seismic 

survey gear. At this speed, both the 

possibility of striking a marine mammal 

and the possibility of a strike resulting 

in serious injury or mortality are 

discountable. At average transit speed, 

the probability of serious injury or 

mortality resulting from a strike is less 

than 50 percent. However, the 

likelihood of a strike actually happening 

is again discountable. Ship strikes, as 

analyzed in the studies cited above, 

generally involve commercial shipping, 

which is much more common in both 

space and time than is geophysical 

survey activity. Jensen and Silber (2004) 

summarized ship strikes of large whales 

worldwide from 1975–2003 and found 

that most collisions occurred in the 

open ocean and involved large vessels 

(e.g., commercial shipping). No such 

incidents were reported for geophysical 

survey vessels during that time period. 

It is possible for ship strikes to occur 

while traveling at slow speeds. For 

example, a hydrographic survey vessel 

traveling at low speed (5.5 kn) while 

conducting mapping surveys off the 

central California coast struck and killed 

a blue whale in 2009. The State of 

California determined that the whale 

had suddenly and unexpectedly 

surfaced beneath the hull, with the 

result that the propeller severed the 

whale’s vertebrae, and that this was an 

unavoidable event. This strike 

represents the only such incident in 

approximately 540,000 hours of similar 

coastal mapping activity (p = 1.9 x 10¥6; 

95% CI = 0–5.5 x 10¥6; NMFS, 2013b). 

In addition, a research vessel reported a 

fatal strike in 2011 of a dolphin in the 

Atlantic, demonstrating that it is 

possible for strikes involving smaller 

cetaceans to occur. In that case, the 

incident report indicated that an animal 

apparently was struck by the vessel’s 

propeller as it was intentionally 

swimming near the vessel. While 

indicative of the type of unusual events 

that cannot be ruled out, neither of these 

instances represents a circumstance that 

would be considered reasonably 

foreseeable or that would be considered 

preventable. 

Although the likelihood of the vessel 

striking a marine mammal is low, we 

propose a robust ship strike avoidance 

protocol (see Proposed Mitigation), 

which we believe eliminates any 

foreseeable risk of ship strike during 

transit. We anticipate that vessel 

collisions involving a seismic data 

acquisition vessel towing gear, while 

not impossible, represent unlikely, 

unpredictable events for which there are 

no preventive measures. Given the 

proposed mitigation measures, the 

relatively slow speed of the vessel 

towing gear, the presence of bridge crew 

watching for obstacles at all times 

(including marine mammals), and the 

presence of marine mammal observers, 

the possibility of ship strike is 

discountable and, further, were a strike 

of a large whale to occur, it would be 

unlikely to result in serious injury or 

mortality. No incidental take resulting 

from ship strike is anticipated, and this 

potential effect of the specified activity 

will not be discussed further in the 

following analysis. 

Stranding—When a living or dead 

marine mammal swims or floats onto 

shore and becomes ‘‘beached’’ or 

incapable of returning to sea, the event 

is a ‘‘stranding’’ (Geraci et al., 1999; 

Perrin and Geraci, 2002; Geraci and 

Lounsbury, 2005; NMFS, 2007). The 

legal definition for a stranding under the 

MMPA is that ‘‘(A) a marine mammal is 

dead and is (i) on a beach or shore of 

the United States; or (ii) in waters under 

the jurisdiction of the United States 

(including any navigable waters); or (B) 

a marine mammal is alive and is (i) on 

a beach or shore of the United States 

and is unable to return to the water; (ii) 

on a beach or shore of the United States 

and, although able to return to the 

water, is in need of apparent medical 

attention; or (iii) in the waters under the 

jurisdiction of the United States 

(including any navigable waters), but is 

unable to return to its natural habitat 

under its own power or without 

assistance.’’ 

Marine mammals strand for a variety 

of reasons, such as infectious agents, 

biotoxicosis, starvation, fishery 

interaction, ship strike, unusual 

oceanographic or weather events, sound 

exposure, or combinations of these 

stressors sustained concurrently or in 


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series. However, the cause or causes of 

most strandings are unknown (Geraci et 

al., 1976; Eaton, 1979; Odell et al., 1980; 

Best, 1982). Numerous studies suggest 

that the physiology, behavior, habitat 

relationships, age, or condition of 

cetaceans may cause them to strand or 

might pre-dispose them to strand when 

exposed to another phenomenon. These 

suggestions are consistent with the 

conclusions of numerous other studies 

that have demonstrated that 

combinations of dissimilar stressors 

commonly combine to kill an animal or 

dramatically reduce its fitness, even 

though one exposure without the other 

does not produce the same result 

(Chroussos, 2000; Creel, 2005; DeVries 

et al., 2003; Fair and Becker, 2000; Foley 

et al., 2001; Moberg, 2000; Relyea, 

2005a; 2005b, Romero, 2004; Sih et al., 

2004). 

There is no conclusive evidence that 

exposure to airgun noise results in 

behaviorally-mediated forms of injury. 

Behaviorally-mediated injury (i.e., mass 

stranding events) has been primarily 

associated with beaked whales exposed 

to mid-frequency active (MFA) naval 

sonar. Tactical sonar and the alerting 

stimulus used in Nowacek et al., (2004) 

are very different from the noise 

produced by airguns. One should 

therefore not expect the same reaction to 

airgun noise as to these other sources. 

As explained below, military MFA 

sonar is very different from airguns, and 

one should not assume that airguns will 

cause the same effects as MFA sonar 

(including strandings). 

To understand why Navy MFA sonar 

affects beaked whales differently than 

airguns do, it is important to note the 

distinction between behavioral 

sensitivity and susceptibility to auditory 

injury. To understand the potential for 

auditory injury in a particular marine 

mammal species in relation to a given 

acoustic signal, the frequency range the 

species is able to hear is critical, as well 

as the species’ auditory sensitivity to 

frequencies within that range. Current 

data indicate that not all marine 

mammal species have equal hearing 

capabilities across all frequencies and, 

therefore, species are grouped into 

hearing groups with generalized hearing 

ranges assigned on the basis of available 

data (Southall et al., 2007, 2019). 

Hearing ranges as well as auditory 

sensitivity/susceptibility to frequencies 

within those ranges vary across the 

different groups. For example, in terms 

of hearing range, the high-frequency 

cetaceans (e.g., Kogia spp.) have a 

generalized hearing range of frequencies 

between 275 Hz and 160 kHz, while 

mid-frequency cetaceans—such as 

dolphins and beaked whales—have a 

generalized hearing range between 150 

Hz to 160 kHz. Regarding auditory 

susceptibility within the hearing range, 

while mid-frequency cetaceans and 

high-frequency cetaceans have roughly 

similar hearing ranges, the highfrequency group is much more 

susceptible to noise-induced hearing 

loss during sound exposure, i.e., these 

species have lower thresholds for these 

effects than other hearing groups 

(NMFS, 2018). Referring to a species as 

behaviorally sensitive to noise simply 

means that an animal of that species is 

more likely to respond to lower received 

levels of sound than an animal of 

another species that is considered less 

behaviorally sensitive. So, while 

dolphin species and beaked whale 

species—both in the mid-frequency 

cetacean hearing group—are assumed to 

generally hear the same sounds equally 

well and be equally susceptible to noiseinduced hearing loss (auditory injury), 

the best available information indicates 

that a beaked whale is more likely to 

behaviorally respond to that sound at a 

lower received level compared to an 

animal from other mid-frequency 

cetacean species that are less 

behaviorally sensitive. This distinction 

is important because, while beaked 

whales are more likely to respond 

behaviorally to sounds than are many 

other species (even at lower levels), they 

cannot hear the predominant, lower 

frequency sounds from seismic airguns 

as well as sounds that have more energy 

at frequencies that beaked whales can 

hear better (such as military MFA 

sonar). 

Navy MFA sonar affects beaked 

whales differently than airguns do 

because it produces energy at different 

frequencies than airguns. Mid-frequency 

cetacean hearing is generically thought 

to be best between 8.8 to 110 kHz, i.e., 

these cutoff values define the range 

above and below which a species in the 

group is assumed to have declining 

auditory sensitivity, until reaching 

frequencies that cannot be heard 

(NMFS, 2018). However, beaked whale 

hearing is likely best within a higher, 

narrower range (20–80 kHz, with best 

sensitivity around 40 kHz), based on a 

few measurements of hearing in 

stranded beaked whales (Cook et al., 

2006; Finneran et al., 2009; Pacini et al., 

2011) and several studies of acoustic 

signals produced by beaked whales (e.g., 

Frantzis et al., 2002; Johnson et al., 

2004, 2006; Zimmer et al., 2005). While 

precaution requires that the full range of 

audibility be considered when assessing 

risks associated with noise exposure 

(Southall et al., 2007, 2019a2019), 

animals typically produce sound at 

frequencies where they hear best. More 

recently, Southall et al., (2019) 

suggested that certain species in the 

historical mid-frequency hearing group 

(beaked whales, sperm whales, and 

killer whales) are likely more sensitive 

to lower frequencies within the group’s 

generalized hearing range than are other 

species within the group, and state that 

the data for beaked whales suggest 

sensitivity to approximately 5 kHz. 

However, this information is consistent 

with the general conclusion that beaked 

whales (and other mid-frequency 

cetaceans) are relatively insensitive to 

the frequencies where most energy of an 

airgun signal is found. Military MFA 

sonar is typically considered to operate 

in the frequency range of approximately 

3–14 kHz (D’Amico et al., 2009), i.e., 

outside the range of likely best hearing 

for beaked whales but within or close to 

the lower bounds, whereas most energy 

in an airgun signal is radiated at much 

lower frequencies, below 500 Hz 

(Dragoset, 1990). 

It is important to distinguish between 

energy (loudness, measured in dB) and 

frequency (pitch, measured in Hz). In 

considering the potential impacts of 

mid-frequency components of airgun 

noise (1–10 kHz, where beaked whales 

can be expected to hear) on marine 

mammal hearing, one needs to account 

for the energy associated with these 

higher frequencies and determine what 

energy is truly ‘‘significant.’’ Although 

there is mid-frequency energy 

associated with airgun noise (as 

expected from a broadband source), 

airgun sound is predominantly below 1 

kHz (Breitzke et al., 2008; 

Tashmukhambetov et al., 2008; Tolstoy 

et al., 2009). As stated by Richardson et 

al. (1995), ‘‘[. . .] most emitted [seismic 

airgun] energy is at 10–120 Hz, but the 

pulses contain some energy up to 500– 

1,000 Hz.’’ Tolstoy et al., (2009) 

conducted empirical measurements, 

demonstrating that sound energy levels 

associated with airguns were at least 20 

decibels (dB) lower at 1 kHz (considered 

‘‘mid-frequency’’) compared to higher 

energy levels associated with lower 

frequencies (below 300 Hz) (‘‘all but a 

small fraction of the total energy being 

concentrated in the 10–300 Hz range’’ 

[Tolstoy et al., 2009]), and at higher 

frequencies (e.g., 2.6–4 kHz), power 

might be less than 10 percent of the 

peak power at 10 Hz (Yoder, 2002). 

Energy levels measured by Tolstoy et 

al., (2009) were even lower at 

frequencies above 1 kHz. In addition, as 

sound propagates away from the source, 

it tends to lose higher-frequency 

components faster than low-frequency 

components (i.e., low-frequency sounds 


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typically propagate longer distances 

than high-frequency sounds) (Diebold et 

al., 2010). Although higher-frequency 

components of airgun signals have been 

recorded, it is typically in surfaceducting conditions (e.g., DeRuiter et al., 

2006; Madsen et al., 2006) or in shallow 

water, where there are advantageous 

propagation conditions for the higher 

frequency (but low-energy) components 

of the airgun signal (Hermannsen et al., 

2015). This should not be of concern 

because the likely behavioral reactions 

of beaked whales that can result in acute 

physical injury would result from noise 

exposure at depth (because of the 

potentially greater consequences of 

severe behavioral reactions). In 

summary, the frequency content of 

airgun signals is such that beaked 

whales will not be able to hear the 

signals well (compared to MFA sonar), 

especially at depth where we expect the 

consequences of noise exposure could 

be more severe. 

Aside from frequency content, there 

are other significant differences between 

MFA sonar signals and the sounds 

produced by airguns that minimize the 

risk of severe behavioral reactions that 

could lead to strandings or deaths at sea, 

e.g., significantly longer signal duration, 

horizontal sound direction, typical fast 

and unpredictable source movement. 

All of these characteristics of MFA 

sonar tend towards greater potential to 

cause severe behavioral or physiological 

reactions in exposed beaked whales that 

may contribute to stranding. Although 

both sources are powerful, MFA sonar 

contains significantly greater energy in 

the mid-frequency range, where beaked 

whales hear better. Short-duration, high 

energy pulses—such as those produced 

by airguns—have greater potential to 

cause damage to auditory structures 

(though this is unlikely for midfrequency cetaceans, as explained later 

in this document), but it is longer 

duration signals that have been 

implicated in the vast majority of 

beaked whale strandings. Faster, less 

predictable movements in combination 

with multiple source vessels are more 

likely to elicit a severe, potentially antipredator response. Of additional interest 

in assessing the divergent characteristics 

of MFA sonar and airgun signals and 

their relative potential to cause 

stranding events or deaths at sea is the 

similarity between the MFA sonar 

signals and stereotyped calls of beaked 

whales’ primary predator: the killer 

whale (Zimmer and Tyack, 2007). 

Although generic disturbance stimuli— 

as airgun noise may be considered in 

this case for beaked whales—may also 

trigger antipredator responses, stronger 

responses should generally be expected 

when perceived risk is greater, as when 

the stimulus is confused for a known 

predator (Frid and Dill, 2002). In 

addition, because the source of the 

perceived predator (i.e., MFA sonar) 

will likely be closer to the whales 

(because attenuation limits the range of 

detection of mid-frequencies) and 

moving faster (because it will be on 

faster-moving vessels), any antipredator 

response would be more likely to be 

severe (with greater perceived predation 

risk, an animal is more likely to 

disregard the cost of the response; Frid 

and Dill, 2002). Indeed, when analyzing 

movements of a beaked whale exposed 

to playback of killer whale predation 

calls, Allen et al., (2014) found that the 

whale engaged in a prolonged, directed 

avoidance response, suggesting a 

behavioral reaction that could pose a 

risk factor for stranding. Overall, these 

significant differences between sound 

from MFA sonar and the mid-frequency 

sound component from airguns and the 

likelihood that MFA sonar signals will 

be interpreted in error as a predator are 

critical to understanding the likely risk 

of behaviorally-mediated injury due to 

seismic surveys. 

The available scientific literature also 

provides a useful contrast between 

airgun noise and MFA sonar regarding 

the likely risk of behaviorally-mediated 

injury. There is strong evidence for the 

association of beaked whale stranding 

events with MFA sonar use, and 

particularly detailed accounting of 

several events is available (e.g., a 2000 

Bahamas stranding event for which 

investigators concluded that MFA sonar 

use was responsible; Evans and 

England, 2001). D’Amico et al., (2009) 

reviewed 126 beaked whale mass 

stranding events over the period from 

1950 (i.e., from the development of 

modern MFA sonar systems) through 

2004. Of these, there were two events 

where detailed information was 

available on both the timing and 

location of the stranding and the 

concurrent nearby naval activity, 

including verification of active MFA 

sonar usage, with no evidence for an 

alternative cause of stranding. An 

additional ten events were at minimum 

spatially and temporally coincident 

with naval activity likely to have 

included MFA sonar use and, despite 

incomplete knowledge of timing and 

location of the stranding or the naval 

activity in some cases, there was no 

evidence for an alternative cause of 

stranding. The U.S. Navy has publicly 

stated agreement that five such events 

since 1996 were associated in time and 

space with MFA sonar use, either by the 

U.S. Navy alone or in joint training 

exercises with the North Atlantic Treaty 

Organization. The U.S. Navy 

additionally noted that, as of 2017, a 

2014 beaked whale stranding event in 

Crete coincident with naval exercises 

was under review and had not yet been 

determined to be linked to sonar 

activities (U.S. Navy, 2017). Separately, 

the International Council for the 

Exploration of the Sea reported in 2005 

that, worldwide, there have been about 

50 known strandings, consisting mostly 

of beaked whales, with a potential 

causal link to MFA sonar (ICES, 2005). 

In contrast, very few such associations 

have been made to seismic surveys, 

despite widespread use of airguns as a 

geophysical sound source in numerous 

locations around the world. 

A more recent review of possible 

stranding associations with seismic 

surveys (Castellote and Llorens, 2016) 

states plainly that, ‘‘[s]peculation 

concerning possible links between 

seismic survey noise and cetacean 

strandings is available for a dozen 

events but without convincing causal 

evidence.’’ The authors’ ‘‘exhaustive’’ 

search of available information found 

ten events worth further investigation 

via a ranking system representing a 

rough metric of the relative level of 

confidence offered by the data for 

inferences about the possible role of the 

seismic survey in a given stranding 

event. Only three of these events 

involved beaked whales. Whereas 

D’Amico et al., (2009) used a 1–5 

ranking system, in which ‘‘1’’ 

represented the most robust evidence 

connecting the event to MFA sonar use, 

Castellote and Llorens (2016) used a 1– 

6 ranking system, in which ‘‘6’’ 

represented the most robust evidence 

connecting the event to the seismic 

survey. As described above, D’Amico et 

al. (2009) found that two events were 

ranked ‘‘1’’ and ten events were ranked 

‘‘2’’ (i.e., 12 beaked whale stranding 

events were found to be associated with 

MFA sonar use). In contrast, Castellote 

and Llorens (2016) found that none of 

the three beaked whale stranding events 

achieved their highest ranks of 5 or 6. 

Of the ten total events, none achieved 

the highest rank of 6. Two events were 

ranked as 5: one stranding in Peru 

involving dolphins and porpoises and a 

2008 stranding in Madagascar. This 

latter ranking can only broadly be 

associated with the survey itself, as 

opposed to use of seismic airguns. An 

exhaustive investigation of this 

stranding event, which did not involve 

beaked whales, concluded that use of a 

high-frequency mapping system (12-kHz 

multibeam echosounder) was the most 


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plausible and likely initial behavioral 

trigger of the event, which was likely 

exacerbated by several site- and 

situation-specific secondary factors. The 

review panel found that seismic airguns 

were used after the initial strandings 

and animals entering a lagoon system, 

that airgun use clearly had no role as an 

initial trigger, and that there was no 

evidence that airgun use dissuaded 

animals from leaving (Southall et al., 

2013). 

However, one of these stranding 

events, involving two Cuvier’s beaked 

whales, was contemporaneous with and 

reasonably associated spatially with a 

2002 seismic survey in the Gulf of 

California conducted by L–DEO, as was 

the case for the 2007 Gulf of Cadiz 

seismic survey discussed by Castellote 

and Llorens (also involving two Cuvier’s 

beaked whales). However, neither event 

was considered a ‘‘true atypical mass 

stranding’’ (according to Frantzis [1998]) 

as used in the analysis of Castellote and 

Llorens (2016). While we agree with the 

authors that this lack of evidence should 

not be considered conclusive, it is clear 

that there is very little evidence that 

seismic surveys should be considered as 

posing a significant risk of acute harm 

to beaked whales or other midfrequency cetaceans. We have 

considered the potential for the 

proposed surveys to result in marine 

mammal stranding and have concluded 

that, based on the best available 

information, stranding is not expected 

to occur. 

Entanglement—Entanglements occur 

when marine mammals become 

wrapped around cables, lines, nets, or 

other objects suspended in the water 

column. During seismic operations, 

numerous cables, lines, and other 

objects primarily associated with the 

airgun array and hydrophone streamers 

will be towed behind the Langseth near 

the water‘s surface. However, we are not 

aware of any cases of entanglement of 

mysticetes in seismic survey equipment. 

No incidents of entanglement of marine 

mammals with seismic survey gear have 

been documented in over 54,000 kt 

(100,000 km) of previous NSF-funded 

seismic surveys when observers were 

aboard (e.g., Smultea and Holst 2003; 

Haley and Koski 2004; Holst 2004; 

Smultea et al., 2004; Holst et al., 2005a; 

Haley and Ireland 2006; SIO and NSF 

2006b; Hauser et al., 2008; Holst and 

Smultea 2008). Although entanglement 

with the streamer is theoretically 

possible, it has not been documented 

during tens of thousands of miles of 

NSF-sponsored seismic cruises or, to 

our knowledge, during hundreds of 

thousands of miles of industrial seismic 

cruises. There are a relative few 

deployed devices, and no interaction 

between marine mammals and any such 

device has been recorded during prior 

NSF surveys using the devices. There 

are no meaningful entanglement risks 

posed by the proposed survey, and 

entanglement risks are not discussed 

further in this document. 

Anticipated Effects on Marine Mammal 

Habitat 

Physical Disturbance—Sources of 

seafloor disturbance related to 

geophysical surveys that may impact 

marine mammal habitat include 

placement of anchors, nodes, cables, 

sensors, or other equipment on or in the 

seafloor for various activities. 

Equipment deployed on the seafloor has 

the potential to cause direct physical 

damage and could affect bottomassociated fish resources. 

Placement of equipment, such as the 

heat flow probe in the seafloor, could 

damage areas of hard bottom where 

direct contact with the seafloor occurs 

and could crush epifauna (organisms 

that live on the seafloor or surface of 

other organisms). Damage to unknown 

or unseen hard bottom could occur, but 

because of the small area covered by 

most bottom-founded equipment and 

the patchy distribution of hard bottom 

habitat, contact with unknown hard 

bottom is expected to be rare and 

impacts minor. Seafloor disturbance in 

areas of soft bottom can cause loss of 

small patches of epifauna and infauna 

due to burial or crushing, and bottomfeeding fishes could be temporarily 

displaced from feeding areas. Overall, 

any effects of physical damage to habitat 

are expected to be minor and temporary. 

Effects to Prey—Marine mammal prey 

varies by species, season, and location 

and, for some, is not well documented. 

Fish react to sounds which are 

especially strong and/or intermittent 

low-frequency sounds, and behavioral 

responses such as flight or avoidance 

are the most likely effects. However, the 

reaction of fish to airguns depends on 

the physiological state of the fish, past 

exposures, motivation (e.g., feeding, 

spawning, migration), and other 

environmental factors. Several studies 

have demonstrated that airgun sounds 

might affect the distribution and 

behavior of some fishes, potentially 

impacting foraging opportunities or 

increasing energetic costs (e.g., Fewtrell 

and McCauley, 2012; Pearson et al., 

1992; Skalski et al., 1992; Santulli et al., 

1999; Paxton et al., 2017), though the 

bulk of studies indicate no or slight 

reaction to noise (e.g., Miller and 

Cripps, 2013; Dalen and Knutsen, 1987; 

Pena et al., 2013; Chapman and 

Hawkins, 1969; Wardle et al., 2001; Sara 

et al., 2007; Jorgenson and Gyselman, 

2009; Blaxter et al., 1981; Cott et al., 

2012; Boeger et al., 2006), and that, most 

commonly, while there are likely to be 

impacts to fish as a result of noise from 

nearby airguns, such effects will be 

temporary. For example, investigators 

reported significant, short-term declines 

in commercial fishing catch rate of 

gadid fishes during and for up to five 

days after seismic survey operations, but 

the catch rate subsequently returned to 

normal (Engas et al., 1996; Engas and 

Lokkeborg, 2002). Other studies have 

reported similar findings (Hassel et al., 

2004). Skalski et al., (1992) also found 

a reduction in catch rates—for rockfish 

(Sebastes spp.) in response to controlled 

airgun exposure—but suggested that the 

mechanism underlying the decline was 

not dispersal but rather decreased 

responsiveness to baited hooks 

associated with an alarm behavioral 

response. A companion study showed 

that alarm and startle responses were 

not sustained following the removal of 

the sound source (Pearson et al., 1992). 

Therefore, Skalski et al., (1992) 

suggested that the effects on fish 

abundance may be transitory, primarily 

occurring during the sound exposure 

itself. In some cases, effects on catch 

rates are variable within a study, which 

may be more broadly representative of 

temporary displacement of fish in 

response to airgun noise (i.e., catch rates 

may increase in some locations and 

decrease in others) than any long-term 

damage to the fish themselves (Streever 

et al., 2016). 

SPLs of sufficient strength have been 

known to cause injury to fish and fish 

mortality and, in some studies, fish 

auditory systems have been damaged by 

airgun noise (McCauley et al., 2003; 

Popper et al., 2005; Song et al., 2008). 

However, in most fish species, hair cells 

in the ear continuously regenerate and 

loss of auditory function likely is 

restored when damaged cells are 

replaced with new cells. Halvorsen et al. 

(2012b. (2012) showed that a TTS of 4– 

6 dB was recoverable within 24 hours 

for one species. Impacts would be most 

severe when the individual fish is close 

to the source and when the duration of 

exposure is long—both of which are 

conditions unlikely to occur for this 

survey that is necessarily transient in 

any given location and likely result in 

brief, infrequent noise exposure to prey 

species in any given area. For this 

survey, the sound source is constantly 

moving, and most fish would likely 

avoid the sound source prior to 

receiving sound of sufficient intensity to 

cause physiological or anatomical 

damage. In addition, ramp-up may 


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allow certain fish species the 

opportunity to move further away from 

the sound source. 

A recent comprehensive review 

(Carroll et al., 2017) found that results 

are mixed as to the effects of airgun 

noise on the prey of marine mammals. 

While some studies suggest a change in 

prey distribution and/or a reduction in 

prey abundance following the use of 

seismic airguns, others suggest no 

effects or even positive effects in prey 

abundance. As one specific example, 

Paxton et al., (2017), which describes 

findings related to the effects of a 2014 

seismic survey on a reef off of North 

Carolina, showed a 78 percent decrease 

in observed nighttime abundance for 

certain species. It is important to note 

that the evening hours during which the 

decline in fish habitat use was recorded 

(via video recording) occurred on the 

same day that the seismic survey 

passed, and no subsequent data is 

presented to support an inference that 

the response was long-lasting. 

Additionally, given that the finding is 

based on video images, the lack of 

recorded fish presence does not support 

a conclusion that the fish actually 

moved away from the site or suffered 

any serious impairment. In summary, 

this particular study corroborates prior 

studies indicating that a startle response 

or short-term displacement should be 

expected. 

Available data suggest that 

cephalopods are capable of sensing the 

particle motion of sounds and detect 

low frequencies up to 1–1.5 kHz, 

depending on the species, and so are 

likely to detect airgun noise (Kaifu et al., 

2008; Hu et al., 2009; Mooney et al., 

2010; Samson et al., 2014). Auditory 

injuries (lesions occurring on the 

statocyst sensory hair cells) have been 

reported upon controlled exposure to 

low-frequency sounds, suggesting that 

cephalopods are particularly sensitive to 

low-frequency sound (Andre et al., 

2011; Sole et al., 2013). Behavioral 

responses, such as inking and jetting, 

have also been reported upon exposure 

to low-frequency sound (McCauley et 

al., 2000b; Samson et al., 2014). Similar 

to fish, however, the transient nature of 

the survey leads to an expectation that 

effects will be largely limited to 

behavioral reactions and would occur as 

a result of brief, infrequent exposures. 

With regard to potential impacts on 

zooplankton, McCauley et al., (2017) 

found that exposure to airgun noise 

resulted in significant depletion for 

more than half the taxa present and that 

there were two to three times more dead 

zooplankton after airgun exposure 

compared with controls for all taxa, 

within 1 km of the airguns. However, 

the authors also stated that in order to 

have significant impacts on r-selected 

species (i.e., those with high growth 

rates and that produce many offspring) 

such as plankton, the spatial or 

temporal scale of impact must be large 

in comparison with the ecosystem 

concerned, and it is possible that the 

findings reflect avoidance by 

zooplankton rather than mortality 

(McCauley et al., 2017). In addition, the 

results of this study are inconsistent 

with a large body of research that 

generally finds limited spatial and 

temporal impacts to zooplankton as a 

result of exposure to airgun noise (e.g., 

Dalen and Knutsen, 1987; Payne, 2004; 

Stanley et al., 2011). Most prior research 

on this topic, which has focused on 

relatively small spatial scales, has 

showed minimal effects (e.g., 

Kostyuchenko, 1973; Booman et al., 

1996; S#tre and Ona, 1996; Pearson et 

al., 1994; Bolle et al., 2012). 

A modeling exercise was conducted 

as a follow-up to the McCauley et al. 

(2017) study (as recommended by 

McCauley et al.,), in order to assess the 

potential for impacts on ocean 

ecosystem dynamics and zooplankton 

population dynamics (Richardson et al., 

2017). Richardson et al., (2017) found 

that for copepods with a short life cycle 

in a high-energy environment, a fullscale airgun survey would impact 

copepod abundance up to three days 

following the end of the survey, 

suggesting that effects such as those 

found by McCauley et al., (2017) would 

not be expected to be detectable 

downstream of the survey areas, either 

spatially or temporally. 

Notably, a recently described study 

produced results inconsistent with 

those of McCauley et al., (2017). 

Researchers conducted a field and 

laboratory study to assess if exposure to 

airgun noise affects mortality, predator 

escape response, or gene expression of 

the copepod Calanus finmarchicus 

(Fields et al., 2019). Immediate 

mortality of copepods was significantly 

higher, relative to controls, at distances 

of 5 m or less from the airguns. 

Mortality one week after the airgun blast 

was significantly higher in the copepods 

placed 10 m from the airgun but was not 

significantly different from the controls 

at a distance of 20 m from the airgun. 

The increase in mortality, relative to 

controls, did not exceed 30 percent at 

any distance from the airgun. Moreover, 

the authors caution that even this higher 

mortality in the immediate vicinity of 

the airguns may be more pronounced 

than what would be observed in freeswimming animals due to increased 

flow speed of fluid inside bags 

containing the experimental animals. 

There were no sublethal effects on the 

escape performance or the sensory 

threshold needed to initiate an escape 

response at any of the distances from 

the airgun that were tested. Whereas 

McCauley et al. (2017) reported an SEL 

of 156 dB at a range of 509–658 m, with 

zooplankton mortality observed at that 

range, Fields et al. (2019) reported an 

SEL of 186 dB at a range of 25 m, with 

no reported mortality at that distance. 

Regardless, if we assume a worst-case 

likelihood of severe impacts to 

zooplankton within approximately 1 km 

of the acoustic source, the brief time to 

regeneration of the potentially affected 

zooplankton populations does not lead 

us to expect any meaningful follow-on 

effects to the prey base for marine 

mammals. 

A recent review article concluded 

that, while laboratory results provide 

scientific evidence for high-intensity 

and low-frequency sound-induced 

physical trauma and other negative 

effects on some fish and invertebrates, 

the sound exposure scenarios in some 

cases are not realistic to those 

encountered by marine organisms 

during routine seismic operations 

(Carroll et al., 2017). The review finds 

that there has been no evidence of 

reduced catch or abundance following 

seismic activities for invertebrates, and 

that there is conflicting evidence for fish 

with catch observed to increase, 

decrease, or remain the same. Further, 

where there is evidence for decreased 

catch rates in response to airgun noise, 

these findings provide no information 

about the underlying biological cause of 

catch rate reduction (Carroll et al., 

2017). 

In summary, impacts of the specified 

activity on marine mammal prey species 

will likely be limited to behavioral 

responses, the majority of prey species 

will be capable of moving out of the area 

during the survey, a rapid return to 

normal recruitment, distribution, and 

behavior for prey species is anticipated, 

and, overall, impacts to prey species 

will be minor and temporary. Prey 

species exposed to sound might move 

away from the sound source, experience 

TTS, experience masking of biologically 

relevant sounds, or show no obvious 

direct effects. Mortality from 

decompression injuries is possible in 

close proximity to a sound, but only 

limited data on mortality in response to 

airgun noise exposure are available 

(Hawkins et al., 2014). The most likely 

impacts for most prey species in the 

survey area would be temporary 

avoidance of the area. The proposed 

survey would move through an area 

relatively quickly, limiting exposure to 

multiple impulsive sounds. In all cases, 


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sound levels would return to ambient 

once the survey moves out of the area 

or ends and the noise source is shut 

down and, when exposure to sound 

ends, behavioral and/or physiological 

responses are expected to end relatively 

quickly (McCauley et al., 2000b). The 

duration of fish avoidance of a given 

area after survey effort stops is 

unknown, but a rapid return to normal 

recruitment, distribution, and behavior 

is anticipated. While the potential for 

disruption of spawning aggregations or 

schools of important prey species can be 

meaningful on a local scale, the mobile 

and temporary nature of this survey and 

the likelihood of temporary avoidance 

behavior suggest that impacts would be 

minor. 

Acoustic Habitat—Acoustic habitat is 

the soundscape—which encompasses 

all of the sound present in a particular 

location and time, as a whole—when 

considered from the perspective of the 

animals experiencing it. Animals 

produce sound for, or listen for sounds 

produced by, conspecifics 

(communication during feeding, mating, 

and other social activities), other 

animals (finding prey or avoiding 

predators), and the physical 

environment (finding suitable habitats, 

navigating). Together, sounds made by 

animals and the geophysical 

environment (e.g., produced by 

earthquakes, lightning, wind, rain, 

waves) make up the natural 

contributions to the total acoustics of a 

place. These acoustic conditions, 

termed acoustic habitat, are one 

attribute of an animal’s total habitat. 

Soundscapes are also defined by, and 

acoustic habitat influenced by, the total 

contribution of anthropogenic sound. 

This may include incidental emissions 

from sources such as vessel traffic, or 

may be intentionally introduced to the 

marine environment for data acquisition 

purposes (as in the use of airgun arrays). 

Anthropogenic noise varies widely in its 

frequency content, duration, and 

loudness and these characteristics 

greatly influence the potential habitatmediated effects to marine mammals 

(please see also the previous discussion 

on masking under ‘‘Acoustic Effects’’), 

which may range from local effects for 

brief periods of time to chronic effects 

over large areas and for long durations. 

Depending on the extent of effects to 

habitat, animals may alter their 

communications signals (thereby 

potentially expending additional 

energy) or miss acoustic cues (either 

conspecific or adventitious). For more 

detail on these concepts see, e.g., Barber 

et al., 2010; Pijanowski et al., 2011; 

Francis and Barber, 2013; Lillis et al., 

2014. 

Problems arising from a failure to 

detect cues are more likely to occur 

when noise stimuli are chronic and 

overlap with biologically relevant cues 

used for communication, orientation, 

and predator/prey detection (Francis 

and Barber, 2013). Although the signals 

emitted by seismic airgun arrays are 

generally low frequency, they would 

also likely be of short duration and 

transient in any given area due to the 

nature of these surveys. As described 

previously, exploratory surveys such as 

these cover a large area but would be 

transient rather than focused in a given 

location over time and therefore would 

not be considered chronic in any given 

location. 

Based on the information discussed 

herein, we conclude that impacts of the 

specified activity are not likely to have 

more than short-term adverse effects on 

any prey habitat or populations of prey 

species. Further, any impacts to marine 

mammal habitat are not expected to 

result in significant or long-term 

consequences for individual marine 

mammals, or to contribute to adverse 

impacts on their populations. 

Estimated Take 

This section provides an estimate of 

the number of incidental takes proposed 

for authorization through this IHA, 

which will inform both NMFS’ 

consideration of ‘‘small numbers’’ and 

the negligible impact determinations. 

Harassment is the only type of take 

expected to result from these activities. 

Except with respect to certain activities 

not pertinent here, section 3(18) of the 

MMPA defines ‘‘harassment’’ as any act 

of pursuit, torment, or annoyance, 

which (i) has the potential to injure a 

marine mammal or marine mammal 

stock in the wild (Level A harassment); 

or (ii) has the potential to disturb a 

marine 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, primarily in the form 

of behavioral disruption and including 

through Temporary Threshold Shift 

(TTS) for low frequency cetaceans 

resulting from exposure to sound from 

seismic airguns. TTS is not expected for 

all other hearing groups and is 

considered to be unlikely for low 

frequency cetaceans. Given the small 

size of the Level A harassment isopleths 

(28.6 m for LF cetaceans and less than 

one meter for all other species) and the 

anticipated effectiveness of the 

mitigation measures (i.e., shutdown, 

ramp-up, etc.) discussed in detail below 

in 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. 

Generally speaking, we estimate take 

by considering: (1) Acoustic thresholds 

above which NMFS believes the best 

available science indicates marine 

mammals will be behaviorally harassed 

or incur some degree of permanent 

hearing impairment; (2) the area or 

volume of water that will be ensonified 

above these levels in a day; (3) the 

density or occurrence of marine 

mammals within these ensonified areas; 

and (4) and the number of days of 

activities. We note that while these 

basic factors can contribute to a basic 

calculation to provide an initial 

prediction of takes, additional 

information that can qualitatively 

inform take estimates is also sometimes 

available (e.g., previous monitoring 

results or average group size). Below, we 

describe the factors considered here in 

more detail and present the proposed 

take estimate. 

Acoustic Thresholds 

NMFS recommends the use of 

acoustic thresholds that identify the 

received level of underwater sound 

above which exposed marine mammals 

would be reasonably expected to be 

behaviorally harassed (equated to Level 

B harassment) or to incur PTS of some 

degree (equated to Level A harassment). 

Level B Harassment—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, 

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 


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when exposed to underwater 

anthropogenic noise above root-meansquared pressure received levels (RMS 

SPL) of 120 dB (referenced to 1 

micropascal (re 1 mPa)) for continuous 

(e.g., vibratory pile-driving, drilling) and 

above RMS SPL 160 dB re 1 mPa (rms) 

for non-explosive impulsive (e.g., 

seismic airguns) or intermittent (e.g., 

scientific sonar) sources. 

L–DEO’s proposed survey includes 

the use of impulsive seismic sources 

(e.g., GI-airgun) and therefore the 160 

dB re 1 mPa (rms) criteria is applicable 

for analysis of Level B harassment. 

Level A harassment—NMFS’ 

Technical Guidance for Assessing the 

Effects of Anthropogenic Sound on 

Marine Mammal Hearing (Version 2.0) 

(Technical Guidance, 2018) identifies 

dual criteria to assess auditory injury 

(Level A harassment) to five different 

marine mammal groups (based on 

hearing sensitivity) as a result of 

exposure to noise from two different 

types of sources (impulsive or nonimpulsive). L–DEO’s proposed survey 

includes the use of impulsive and 

intermittent sources. 

For more information, see NMFS’ 

2018 Technical Guidance, which may 

be accessed at: www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

marine-mammal-acoustic-technicalguidance. 

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 proposed 2D survey would 

acquire data using a 2 GI-airgun cluster 

with a total discharge volume of 90 in3

at a maximum tow depth of 2–4 m. L– 

DEO model results are used to 

determine the 160 dB rms radius for the 

2–GI airgun array in deep water (>1000 

m) down to a maximum depth of 2000 

m, as animals are generally not 

anticipated to dive below 2000 m (Costa 

and Williams, 1999). Received sound 

levels for the two 45 in3 GI airguns 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 array 

to the receiver and its associated source 

ghost (reflection at the air-water 

interface in the vicinity of the array), in 

a constant-velocity half-space (infinite 

homogeneous ocean layer, unbounded 

by a seafloor). In addition, propagation 

measurements of pulses from a 36- 

airgun array at a tow depth of 6 m have 

been reported in deep water (∼1600 m), 

intermediate water depth on the slope 

(∼600–1100 m), and shallow water (∼50) 

in the Gulf of Mexico in 2007–2008 

(Tolstoy et al., 2009; Diebold et al., 

2010). 

For deep and intermediate-water 

cases, the field measurements cannot be 

used readily to derive mitigation radii, 

as at those sites the calibration 

hydrophone was located at a roughly 

constant depth of 350–500 m, which 

may not intersect all the sound pressure 

level (SPL) isopleths at their widest 

point from the sea surface down to the 

maximum relevant water depth (∼2000 

m) for marine mammals. At short 

ranges, where the direct arrivals 

dominate and the effects of seafloor 

interactions are minimal, the data 

recorded 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 mitigation model—constructed from 

the maximum SPL through the entire 

water column at varying distances from 

the airgun array—is the most relevant. 

In deep and intermediate-water 

depths, comparisons at short ranges 

between sound levels for direct arrivals 

recorded by the calibration hydrophone 

and model results for the same array 

tow depth are in good agreement (Fig. 

12 and 14 in Appendix H of L–DEO’s 

PEIS). Consequently, isopleths falling 

within this domain can be predicted 

reliably by the L–DEO model, although 

they may be imperfectly sampled by 

measurements recorded at a single 

depth. At greater distances, the 

calibration data show that seafloorreflected and sub-seafloor-refracted 

arrivals dominate, whereas the direct 

arrivals become weak and/or 

incoherent. Aside from local topography 

effects, the region around the critical 

distance is where the observed levels 

rise closest to the mitigation model 

curve. However, the observed sound 

levels are found to fall almost entirely 

below the mitigation model curve. Thus, 

analysis of the Gulf of Mexico 

calibration measurements demonstrate 

that although simple, the L–DEO model 

is a robust tool for conservatively 

estimating isopleths and the deep water 

radii obtained from model results down 

to a maximum water depth of 2000 m. 

A recent retrospective analysis of 

acoustic propagation of R/V Langseth 

sources in a coastal/shelf environment 

from the Cascadia Margin off 

Washington suggests that predicted 

(modeled) radii (using a similar 

approach) for R/V Langseth sources 

were 2–3 times larger than measured in 

shallow water (Crone et al., 2014). 

Similarly, data collected by Crone et al. 

(2017) during a survey off New Jersey in 

2014 and 2015 confirmed that in situ 

measurements and estimates of the 160- 

and 180-dB distances collected by R/V 

Langseth hydrophone streamer were 2– 

3 times smaller than the predicted 

operational mitigation radii. Five 

separate comparisons conducted of the 

L–DEO model with in situ received 

level have confirmed that the L–DEO 

model generated conservative mitigation 

zones, resulting in significantly larger 

zones. 

The proposed surveys would acquire 

data with two 45 in3 GI funs at a tow 

depth of 2–4 m. As the entire survey 

occurs in deep water (>1000 m), L–DEO 

used the deep-water radii obtained from 

the model results explained above down 

to a maximum warter depth of 2000 m 

(see Figure A–1 in L–DEO’s 

application). The estimated distances to 

the Level B harassment isopleth for the 

proposed survey are shown in Table 3. 

The acoustic propagation modeling 

methodologies are described in greater 

detail in L–DEO’s IHA application. 

TABLE 3—PREDICTED RADIAL DISTANCES TO ISOPLETHS CORRESPONDING TO THE LEVEL B HARASSMENT THRESHOLD

[160 dB re 1μPa (rms)] 

Airgun configuration Water depth 

(m) 

Predicted 

distances (m) to 

a received sound 

level 

of 160 dB re 1 μParms

Two 45-in3 GI guns ................................................................................................................................. >1,000 553 


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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 PGS 

Nucleus source modeling software 

program and the NMFS User 

Spreadsheet, described below. The 

acoustic thresholds for impulsive 

sounds (e.g., airguns) contained in the 

Technical Guidance were presented as 

dual metric acoustic thresholds using 

both SELcum and peak sound pressure 

metrics (NMFS 2018). As dual metrics, 

NMFS considers onset of PTS (Level A 

harassment) to have occurred when 

either one of the two metrics is 

exceeded (i.e., metric resulting in the 

largest isopleth). The SELcum metric 

considers both level and duration of 

exposure, as well as auditory weighting 

functions by marine mammal hearing 

group. In recognition of the fact that the 

requirement to calculate Level A 

harassment ensonified areas could be 

more technically challenging to predict 

due to the duration component and the 

use of weighting functions in the new 

SELcum thresholds, NMFS developed an 

optional User Spreadsheet that includes 

tools to help predict a simple isopleth 

that can be used in conjunction with 

marine mammal density or occurrence 

to facilitate the estimation of take 

numbers. 

In order to more realistically 

incorporate the Technical Guidance’s 

weighting functions over the seismic 

array’s full acoustic band, unweighted 

spectrum data for the Langseth’s airgun 

array (modeled in 1 Hz bands) was used 

to make adjustments (dB) to the 

unweighted spectrum levels, by 

frequency, according to the weighting 

functions for each relevant marine 

mammal hearing group. These adjusted/ 

weighted spectrum levels were then 

converted to pressures (mPa) in order to 

integrate them over the entire 

broadband spectrum, resulting in 

broadband weight source levels by 

hearing group that could be directly 

incorporated within the User 

Spreadsheet (i.e., to override the 

Spreadsheet’s more simple weighting 

factor adjustment). Using the User 

Spreadsheet’s ‘‘safe distance’’ 

methodology for mobile sources 

(described by Sivle et al., 2014) with the 

hearing group-specific weighted source 

levels, and inputs assuming spherical 

spreading propagation and source 

velocities (2.32 m/s) and shot intervals 

(every 2.69 s) specific to the planned 

survey, potential radial distances to 

auditory injury zones were then 

calculated for SELcum thresholds. 

Outputs from the User Spreadsheet in 

the form of estimated distance to Level 

A harassment isopleths for the survey 

are shown in Table 4. NMFS considers 

onset of PTS (Level A harassment) to 

have occurred when either one of the 

dual metrics (SELcum and Peakflat) is 

exceeded (i.e., metric resulting in the 

largest isopleth). 

TABLE 4—MODELED RADIAL DISTANCES (m) TO ISOPLETHS CORRESPONDING TO LEVEL A HARASSMENT THRESHOLDS

Source 

(volume) 

Level A harassment zones (m) 

LF MF HF Phocid Otariid 

Two 45 cu in GI guns .......................................................... 28.6 0 0.1 0.3 0 

Note that because of some of the 

assumptions included in the methods 

used (e.g., stationary receiver with no 

vertical or horizontal movement in 

response to the acoustic source), 

isopleths produced may be 

overestimates to some degree, which 

will ultimately result in some degree of 

overestimation of Level A harassment. 

However, these tools offer the best way 

to predict appropriate isopleths when 

more sophisticated modeling methods 

are not available. NMFS continues to 

develop ways to quantitatively refine 

these tools and will qualitatively 

address the output where appropriate. 

For mobile sources, such as the 

proposed seismic survey, the User 

Spreadsheet predicts the closest 

distance at which a stationary animal 

would not incur PTS if the sound source 

traveled by the animal in a straight line 

at a constant speed. 

Auditory injury for all species is 

unlikely to occur given the small 

modeled zones of injury (estimated zone 

less than 30 m for low-frequency 

cetaceans and near zero for all other 

species). Additionally, animals are 

expected to have aversive/compensatory 

behavior in response to the activity 

(Nachtigall et al., 2018) further limiting 

the likelihood of auditory injury for all 

species. L–DEO did not request 

authorization of take by Level A 

harassment, and no take by Level A 

harassment is proposed for 

authorization by NMFS. 

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. 

The U.S. Navy (USN) primarily use 

the Southwest Fishery Science Center 

(SWFSC) habitat-based cetacean density 

models to develop a marine species 

density database for the Northwest 

Training and Testing Study Area, which 

encompasses the proposed survey area 

(USN 2019). For species where density 

spatial modeling was unavailable, other 

data sources were used. The USN 

marine species density database is 

currently the most comprehensive 

density data set available for the 

California Current Ecosystem (CCE) 

which encompasses waters off the coast 

of California, Oregon, and Washington. 

However, GIS data layers are currently 

unavailable for this database; thus, in 

this analysis the USN data were only 

used for species for which density data 

were not available from an alternative 

spatially-explicit model (i.e., minke, sei, 

and killer whales, Kogia spp., and 

pinnipeds). 

For most pinnipeds, L–DEO used the 

highest densities for spring, summer, or 

fall from USN (2019), but corrected the 

estimates by projecting the most recent 

population growth/updated population 

estimates to 2022, when available. This 

same approach was used by NMFS for 

previous L–DEO surveys (e.g,. Northeast 

Pacific Ocean Survey (85 FR 19580; 

April 7, 2020)) in the region in 2021. For 

California sea lions, spring densities 

from USN (2019) were used directly, the 

density for the ‘40–70 km from shore’ 

distance band was used for the Oregon 

survey region, and the density for the 

‘70–450 km from shore’ distance band 

was used for other survey regions. For 

the northern fur seal, the density for the 

spring for the ‘up to 70 km from shore’ 

distance band was used for the Oregon 

survey region, and the spring density for 

the ‘>130 km from shore’ distance band 

was used for the other survey regions. 

For the Guadalupe fur seal and Steller 

sea lion, summer densities for the ‘200 

m isobath to 300 km from shore’ were 

used. For the gray whale, the summer/ 

fall density for the ‘10–47 km from 

shore’ distance band (USN 2019) was 

used for the Oregon survey region and 


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a density of zero was used for all other 

survey regions. For killer whales, the 

annual density for all stocks occurring 

offshore was used from USN (2019). 

Spatially-explicit density data from 

summer/fall from the NOAA CetSound 

website (NOAA 2022) were used for 

most other species (i.e., humpback, 

blue, fin, sperm, Baird’s, beaked, and 

other small beaked whales; striped, 

short-beaked common, Pacific whitesided, Risso’s, and northern right whale 

dolphins; and Dall’s porpoise. CetMap 

(https://cetsound.noaa.gov/cda) 

provides output of summer/fall habitatbased density models for cetaceans in 

the CCE (Becker et al., 2020) in the form 

of GIS layers; these were used to 

calculate takes in the survey area. The 

density estimates were available in the 

form of a GIS grid with each cell in the 

grid measuring ∼7 km east-west by 10 

km north-south. This grid was 

intersected with a GIS layer of the area 

expected to be ensonified to >160 dB 

SPL from the survey area. North, west, 

and south boundaries are based on 

overlap/intersection with geographic 

extents of all four combined survey 

regions; eastern grid coverage limit was 

defined by inclusion of cells that 

contained >25 percent overlap with the 

angled boundary of the survey area 

polygon. The densities from all grid 

cells overlapping the ensonified areas 

were averaged to calculate an average 

species-specific density for each species 

(Table 5). 

TABLE 5—MODELED MARINE MAMMAL DENSITY VALUES AND DAILY ENSONIFIED AREA FOR L–DEO’S PROPOSED

SURVEY * 

Species Density 

(#/km2) 

Daily 

ensonified 

area 

(km2) 

Number of 

seismic days Source 

LF Cetaceans: 

Humpback whale ..................................................... 0.000464 221 6 Becker et al. (2020). 

Blue whale ............................................................... 0.000226 221 6 Becker et al. (2020). 

Fin whale ................................................................. 0.00241 221 6 Becker et al. (2020). 

Sei whale ................................................................. 0.0004 221 6 USN (2019). 

Minke whale ............................................................. 0.0013 221 6 USN (2019). 

MF Cetaceans: 

Sperm whale ............................................................ 0.002859 221 6 Becker et al. (2020). 

Baird’s beaked whale .............................................. 0.000407 221 6 Becker et al. (2020). 

Small beaked whale ................................................ 0.002446 221 6 Becker et al. (2020). 

Striped dolphin ......................................................... 0.002095 221 6 Becker et al. (2020). 

Short-beaked common dolphin ................................ 0.004845 221 6 Becker et al. (2020). 

Pacific white-sided dolphin ...................................... 0.059902 221 6 Becker et al. (2020). 

Northern right-whale dolphin ................................... 0.049535 221 6 Becker et al. (2020). 

Risso’s dolphin ......................................................... 0.009917 221 6 Becker et al. (2020). 

Killer whale .............................................................. 0.00092 221 6 USN (2019). 

HF Cetaceans: 

Pygmy/dwarf sperm whale ...................................... 0.00163 221 6 USN (2019). 

Dall’s porpoise ......................................................... 0.093613 221 6 Becker et al. (2020). 

Otariid Seals: 

Northern fur seal ...................................................... * 0.036115/0.032983 221 6 USN (2019). 

Guadalupe fur seal .................................................. 0.02945 221 6 USN (2019). 

California sea lion .................................................... * 1.2951/0.0714 221 6 USN (2019). 

Steller sea lion ......................................................... 0.002573 221 6 USN (2019). 

Phocid Seal: 

Northern elephant seal ............................................ 0.043301 221 6 USN (2019). 

* Species in this table differ slightly from those included in L–DEO’s application as NMFS has determined that their occurrence in the survey 

area is rare and unlikely to be encountered. For more information, please see the Description of Marine Mammals in the Area of Specified Activity section of this notice. 

** Two different densities were used depending on water depth/distance from shore. 

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 

airgun array to the predicted isopleth 

corresponding to the Level B 

harassment thresholds are calculated, as 

described above. Those radial distances 

are then used to calculate the area(s) 

around the airgun array predicted to be 

ensonified to sound levels that exceed 

the Level B harassment threshold. The 

distance for the 160-dB threshold (based 

on L–DEO 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 5 were then 

multiplied by the daily ensonified areas 

expected to be ensonified, increased by 

25 percent, and then multiplied by the 

number of survey days (6) to estimate 

the Level B takes. 

The marine mammals predicted to 

occur within these respective areas, 

based on the estimated densities, are 

assumed to be incidentally taken. 

Estimated exposures for the proposed 

survey are shown in Table 6. 


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TABLE 6—ESTIMATED TAKE BY LEVEL B HARASSMENT, AND PERCENTAGE OF MARINE MAMMAL STOCK POPULATION

Species MMPA stock 

Estimated take 

by Level B 

harassment 

Take by level B 

harassment 

proposed for 

authorization 

Stock 

abundance 

Percent of 

MMPA stock 

Humpback whale a ......................... California/Oregon Washington ...... 1 d 2 4,973 0.04 

Blue whale ..................................... Eastern North Pacific ..................... 0 d 2 1,898 0.11 

Fin whale ....................................... California/Oregon Washington ...... 4 4 11,065 0.04 

Sei whale ....................................... Eastern North Pacific ..................... 1 d 2 519 0.39 

Minke whale ................................... California/Oregon Washington ...... 2 2 915 0.22 

Sperm whale .................................. California/Oregon Washington ...... 5 d 7 1,997 0.35 

Baird’s beaked whale .................... California/Oregon Washington ...... 1 d 9 1,363 0.66 

Small beaked whale b .................... California/Oregon Washington ...... 4 4 3,044 0.13 

Striped dolphin ............................... California/Oregon Washington ...... 3 d 46 29,988 0.15 

Common dolphin ............................ California/Oregon Washington ...... 8 d 179 1,056,308 0.02 

Pacific white-sided dolphin ............ California/Oregon Washington ...... 99 99 34,998 0.28 

Northern right-whale dolphin ......... California/Oregon Washington ...... 82 82 29,285 0.28 

Risso’s dolphin ............................... California/Oregon Washington ...... 16 d 22 6,336 0.35 

Killer whale .................................... West Coast Transient .................... 2 d 7 349 0.00 

North Pacific Offshore ................... 300 0.00 

Pygmy/dwarf sperm whale ............ California/Oregon Washington ...... 3 3 4,111 0.07 

Dall’s porpoise ............................... California/Oregon Washington ...... 155 155 16,498 0.94 

Northern fur seal c .......................... Eastern Pacific ............................... 17 17 626,618 0.00 

California ........................................ 530,376 0.00 

Guadalupe fur seal ........................ Mexico ........................................... 49 49 34,187 0.14 

California sea lion .......................... United States ................................. 9 9 257,606 0.00 

Steller sea lion ............................... Eastern .......................................... 4 4 43,201 0.01 

Northern elephant seal .................. California Breeding ........................ 62 62 5,122 1.21 

aTakes are allocated among the three DPSs in the area based on Wade 2021 (Oregon: 42 percent Central America DPS, 58 percent Mexico 

DPS; Washington: 6 percent Central America DPS, 25 percent Mexico DPS, 69 percent Hawaii DPS). bProposed takes include one each of Blainville’s beaked whale, Stejneger’s beaked whale, Cuvier’s beaked whale, and Hubbs’ beaked whale 

(see Appendix B of L–DEO’s application for more information). c In cases where multiple stocks are being affected, for the purposes of calculating the percentage of the stock impacted, the take is being 

analyzed as if all proposed takes occurred within each stock. dProposed take increased to mean group size from Barlow (2016). 

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; 

(2) The practicability of the measures 

for applicant implementation, which 

may consider such things as cost, 

impact on operations. 

L–DEO reviewed mitigation measures 

employed during seismic research 

surveys authorized by NMFS under 

previous incidental harassment 

authorizations, as well as recommended 

best practices in Richardson et al. 

(1995), Pierson et al. (1998), Weir and 

Dolman (2007), Nowacek et al. (2013), 

Wright (2014), and Wright and 

Cosentino (2015), and has proposed 

mitigation measures based on the above 

sources. 

To reduce the potential for 

disturbance from acoustic stimuli 

associated with the activities, L–DEO 

proposed to implement mitigation 

measures for marine mammals. 

Mitigation measures that would be 

adopted during the planned survey 

include, but are not limited to: (1) 

Vessel speed or course alteration, 

provided that doing so would not 

compromise operation safety 

requirements. (2) GI-airgun shut down 

within EZs, and (3) ramp-up 

procedures. 

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 

visually for the presence of marine 

mammals. The area to be scanned 

visually includes primarily the 

exclusion zone, within which 

observation of certain marine mammals 

requires shutdown of the acoustic 

source, but also the buffer zone. The 

buffer zone means an area beyond the 

exclusion zone to be monitored for the 

presence of marine mammals that may 

enter the exclusion zone. During prestart clearance (i.e., before ramp-up 

begins), the buffer zone also acts as an 

extension of the exclusion zone in that 

observations of marine mammals within 

the buffer zone would also prevent 


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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 100 m exclusion 

zone measured from the edges of the 

airgun array. Visual monitoring of the 

exclusion zone and adjacent waters is 

intended to establish and, when visual 

conditions allow, maintain zones 

around the sound source that are clear 

of marine mammals, thereby reducing or 

eliminating the potential for injury and 

minimizing the potential for more 

severe behavioral reactions for animals 

occurring closer to the vessel. Visual 

monitoring of the buffer zone is 

intended to (1) provide additional 

protection to naı ̈ve marine mammals 

that may be in the area during preclearance, and (2) during airgun use, aid 

in establishing and maintaining the 

exclusion zone by altering the visual 

observer and crew of marine mammals 

that are outside of, but may approach 

and enter, the exclusion zone. 

L–DEO must use independent, 

dedicated, trained visual PSOs, meaning 

that the PSOs must be employed by a 

third-party observer provider, must not 

have tasks other than to conduct 

observational effort, collect data, and 

communicate with and instruct relevant 

vessel crew with regard to the presence 

of protected species and mitigation 

requirements, and must have 

successfully completed an approved 

PSO training course. PSO resumes shall 

be provided to NMFS for approval. 

At least one visual PSO must have a 

minimum of 90 days at-sea experience 

working in that role during a shallow 

penetration or low-energy survey, with 

no more than 18 months elapsed since 

the conclusion of the at-sea experience. 

One PSO with such experience shall be 

designated as the lead for the entire 

protected species observation team. The 

lead PSO shall serve as primary point of 

contact for the vessel operator and 

ensure all PSO requirements per the 

IHA are met. To the maximum extent 

practicable, the experienced PSOs 

should be scheduled to be on duty with 

those PSOs with the appropriate 

training but who have not yet gained 

relevant experience. 

During survey operations (e.g., any 

day on which use of the acoustic source 

is planned to occur, and whenever the 

acoustic source is in the water, whether 

activated or not), a minimum of two 

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) and 30 minutes prior 

to and during ramp-up of the airgun 

array. Visual monitoring of the 

exclusion and buffer zones must begin 

no less than 30 minutes prior to rampup and must continue until one hour 

after use of the acoustic source ceases or 

until 30 minutes past sunset. Visual 

PSOs must coordinate to ensure 360 

degree visual coverage around the vessel 

from the most appropriate observation 

posts, and must conduct visual 

observations using binoculars and the 

naked eye while free from distractions 

and in a consistent, systematic, and 

diligent manner. 

PSOs shall establish and monitor the 

exclusion and buffer zones. These zones 

shall be based upon the radial distance 

from the edges of the acoustic source 

(rather than being based on the center of 

the array or around the vessel itself). 

During use of the acoustic source (i.e., 

anytime airguns are active, including 

ramp-up) shall be communicated to the 

operator to prepare for the potential 

shutdown of the acoustic source. 

During use of the airgun, detections of 

marine mammals within the buffer zone 

(but outside the exclusion zone) should 

be communicated to the operator to 

prepare for the potential shutdown of 

the acoustic source. Visual PSOs will 

immediately communicate all 

observations to the on duty acoustic 

PSO(s), including any determination by 

the PSO regarding species 

identification, distance, and bearing and 

the degree of confidence in the 

determination. Any observations of 

marine mammals by crew members 

shall be relayed to the PSO team. During 

good conditions (e.g., daylight hours; 

Beaufort sea state (BSS) 3 or less), visual 

PSOs shall conduct observations when 

the acoustic source is not operating for 

comparison of sightings rates and 

behavior with and without use of the 

acoustic source and between acquisition 

periods, to the maximum extent 

practicable. 

Visual PSOs may be on watch for a 

maximum of four consecutive hours 

followed by a break of at least one hour 

between watches and may conduct a 

maximum of 12 hours of observation per 

24-hour period. 

Establishment of Exclusion and Buffer 

Zones 

An exclusion zone (EZ) is a defined 

area within which occurrence of a 

marine mammal triggers mitigation 

action intended to reduce the potential 

for certain outcome, e.g., auditory 

injury, disruption of critical behaviors. 

The PSOs would establish a minimum 

EZ with a 100 m radius with an 

additional 100 m buffer zone (total of 

200 m). The 200m zone would be based 

on radial distance from the edge of the 

airgun array (rather than being based on 

the center of the array or around the 

vessel itself). With certain exceptions 

(described below), if a marine mammal 

appears within or enters this zone, the 

acoustic source would be shut down. 

The 100 m EZ, with additional 100 m 

buffer zone, 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 EZ is expected to 

minimize the likelihood that marine 

mammals will be exposed to levels 

likely to result in more severe 

behavioral responses. Although 

significantly greater distances may be 

observed from an elevated platform 

under good conditions, we believe that 

100 m is regularly attainable for PSOs 

using the naked eye during typical 

conditions. 

An extended 500 m exclusion zone 

must be established for all beaked 

whales, dwarf and pygmy sperm 

whales, killer whales, a large whale 

with a calf, and groups of six or more 

large whales during all survey effort. No 

buffer zone is required. 

Pre-Clearance and Ramp-Up 

Ramp-up (sometimes referred to as 

‘‘soft start’’) is the gradual and 

systematic increase of emitted sound 

levels from an airgun array. Ramp-up 

would begin with one GI airgun 45 cu 

in first being activated, followed by the 

second after 5 minutes. The intent of 

pre-clearance observation (30 minutes) 

is to ensure no marine mammals are 

observed within the buffer zone prior to 

the beginning of ramp-up. During preclearance is the only time observations 

of marine mammals in the buffer zone 

would prevent operations (i.e., the 

beginning of ramp-up). The intent of 

ramp-up is to warn protected species of 

pending seismic operations and to allow 

sufficient time for those animals to leave 

the immediate vicinity. A ramp-up 

procedure, involving a step-wise 

increase in the number of airguns are 

activated and the full volume is achieve, 

is required at all times as part of the 

activation of the acoustic source. All 

operators must adhere to the following 

pre-clearance and ramp-up 

requirements: 

• The operator must notify a 

designated PSO of the planned start of 

ramp-up as agreed upon with the lead 

PSO; the notification time should not be 

less than 60 minutes prior to the 

planned ramp-up in order to allow PSOs 

time to monitor the exclusion and buffer 


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zones for 30 minutes prior to the 

initiation of ramp-up (pre-clearance); 

• Ramp-ups shall be scheduled so as 

to minimize the time spent with the 

source activated prior to reaching the 

designated run-in; 

• One of the PSOs conducting preclearance observations must be notified 

again immediately prior to initiating 

ramp-up procedures and the operator 

must receive confirmation from the PSO 

to proceed; 

• Ramp-up may not be initiated if any 

marine mammal is within the applicable 

exclusion or buffer zone. If a marine 

mammal is observed within the 

applicable exclusion zone or the buffer 

zone during the 30 minutes preclearance 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 Mysticetes and all other 

odontocetes, including sperm whales, 

pygmy sperm whales, dwarf sperm 

whales, beaked whales, pilot whales, 

killer whales, Risso’s dolphin); 

• PSOs must monitor the exclusion 

and buffer zones during ramp-up, and 

ramp-up must cease and the source 

must be shut down upon detection of a 

marine mammal within the applicable 

exclusion zone. Once ramp-up has 

begun, detections of marine mammals 

within the buffer zone do not require 

shutdown, but such observation shall be 

communicated to the operator to 

prepare for the potential shutdown. 

• If the acoustic source is shut down 

for brief periods (i.e., less than 30 

minutes) for reasons other than that 

described for shutdown (e.g., 

mechanical difficulty), it may be 

activated again without ramp-up if PSOs 

have maintained constant observation 

and no detections of marine mammals 

have occurred within the applicable 

exclusion zone. For any longer 

shutdown, pre-start clearance 

observation and ramp-up are required. 

For any shutdown at night or in periods 

of poor visibility (e.g., BSS 4 or greater), 

ramp-up is required, but if the 

shutdown period was brief and constant 

observation was maintained, pre-start 

clearance watch is not required. 

• Testing of the acoustic source 

involving all elements requires rampup. Testing limited to individual source 

elements or strings does not require 

ramp-up but does require pre-start 

clearance watch. 

Shutdown 

The shutdown of an airgun array 

requires the immediate de-activation of 

all individual airgun elements of the 

array. Any PSO on duty will have the 

authority to delay the start of survey 

operations or to call for shutdown of the 

acoustic source if a marine mammal is 

detected within the applicable 

exclusion zone. The operator must also 

establish and maintain clear lines of 

communication directly between PSOs 

on duty and crew controlling the 

acoustic source to ensure that shutdown 

commands are conveyed swiftly while 

allowing PSOs to maintain watch. When 

both visual and acoustic PSOs are on 

duty, all detections will be immediately 

communicated to the remainder of the 

on-duty PSO team for potential 

verification of visual observations by the 

acoustic PSO or of acoustic detections 

by visual PSOs. When the airgun array 

is active (i.e., anytime one or more 

airguns is active, including during 

ramp-up) and (1) a marine mammal 

appears within or enters the applicable 

exclusion zone and/or (2) a marine 

mammal (other than delphinids, see 

below) is detected acoustically and 

localized within the applicable 

exclusion zone, the acoustic source will 

be shut down. When shutdown is called 

for by a PSO, the acoustic source will 

be immediately deactivated and any 

dispute resolved only following 

deactivation. 

Following a shutdown, airgun activity 

would not resume until the marine 

mammal has clear the EZ. The animal 

would be considered to have cleared the 

EZ if it is visually observed to have 

departed the EZ, or it has not been seen 

within the EZ for 15 minutes in the case 

of small odontocetes and pinnipeds, and 

30 minutes for Mysticetes and all other 

odontocetes, including sperm whales, 

beaked whales, pilot whales, killer 

whales, and Risso’s dolphin) with no 

further observation of the marine 

mammal(s). 

The shutdown requirement can be 

waived for small dolphins if an 

individual is visually detected and 

localized within an exclusion zone. As 

defined here, the small dolphin group is 

intended to encompass those members 

of the Family Delphinidae most likely to 

voluntarily approach the source vessel 

for purposes of interacting with the 

vessel and/or airgun array (e.g., bow 

riding). This exception to the shutdown 

requirement applies solely to specific 

genera of small dolphins-Delphinus, 

Stenella, and Lissodelphis. 

We propose this small dolphin 

exception because shutdown 

requirements for small dolphins under 

all circumstances represent 

practicability concerns without likely 

commensurate benefits for the animals 

in question. Small dolphins are 

generally the most commonly observed 

marine mammals in the specific 

geographic region and would typically 

be the only marine mammals likely to 

intentionally approach the vessel. As 

described above, auditory injury is 

extremely unlikely to occur for midfrequency cetaceans (e.g., delphinids), 

as this group is relatively insensitive to 

sound produced at the predominant 

frequencies in an airgun pulse while 

also having a relatively high threshold 

for the onset of auditory injury (i.e., 

permanent threshold shift). 

A large body of anecdotal evidence 

indicates that small dolphins commonly 

approach vessels and/or towed arrays 

during active sound production for 

purposes of bow riding, with no 

apparent effect observed in those 

delphinids (e.g., Barkaszi et al., 2012). 

The potential for increased shutdowns 

resulting from such a measure would 

require the Langseth to revisit the 

missed track line to reacquire data, 

resulting in an overall increase in the 

total sound energy input to the marine 

environment and an increase in the total 

duration over which the survey is active 

in a given area. Although other midfrequency hearing specialists (e.g., large 

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 source vessel. Visual 

PSOs shall use best professional 

judgment in making the decision to call 

for a shutdown if there is uncertainty 

regarding identification (i.e., whether 

the observed marine mammal(s) belongs 

to one of the delphinid genera for which 

shutdown is waived or one of the 

species with a larger exclusion zone). 

Upon implementation of shutdown, 

the source may be reactivated after the 

marine mammal(s) has been observed 

exiting the applicable exclusion zone 

(i.e., animal is not required to fully exit 

the buffer zone where applicable) or 

following a clearance period (15 

minutes for small odontocetes and 

pinnipeds, and 30 minutes for 

mysticetes and all other odontocetes, 

including sperm whales, beaked whales, 

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dolphin) with no further observation of 

the marine mammal(s). 

L–DEO must implement shutdown if 

a marine mammal species for which 

take was not authorized, or a species for 

which authorization was granted but the 

takes have been met, approaches the 

Level B harassment zones. 

Vessel Strike Avoidance 

These measures apply to all vessels 

associated with the planned survey 

activity; however, we note that these 

requirements do not apply in any case 

where compliance would create an 

imminent and serious threat to a person 

or vessel or to the extent that a vessel 

is restricted in its ability to maneuver 

and, because of the restriction, cannot 

comply. These measures include the 

following: 

1. Vessel operators and crews must 

maintain a vigilant watch for all marine 

mammals and slow down, stop their 

vessel, or alter course, as appropriate 

and regardless of vessel size, to avoid 

striking any marine mammal. A single 

marine mammal at the surface may 

indicate the presence of submerged 

animals in the vicinity of the vessel; 

therefore, precautionary measures 

should be exercised when an animal is 

observed. A visual observer aboard the 

vessel must monitor a vessel strike 

avoidance zone around the vessel 

(specific distances detailed below), to 

ensure the potential for strike is 

minimized. Visual observers monitoring 

the vessel strike avoidance zone can be 

either third-party observers or crew 

members, but crew members 

responsible for these duties must be 

provided sufficient training to 

distinguish marine mammals from other 

phenomena and broadly to identify a 

marine mammal to broad taxonomic 

group (i.e., as a large whale or other 

marine mammal); 

2. Vessel speeds must be reduced to 

10 kn or less when mother/calf pairs, 

pods, or large assemblages of any 

marine mammal are observed near a 

vessel; 

3. All vessels must maintain a 

minimum separation distance of 100 m 

from large whales (i.e., sperm whales 

and all mysticetes); 

4. All vessels must attempt to 

maintain a minimum separation 

distance of 50 m from all other marine 

mammals, with an exception made for 

those animals that approach the vessel; 

and 

5. When marine mammals are sighted 

while a vessel is underway, the vessel 

should take action as necessary to avoid 

violating the relevant separation 

distance (e.g., attempt to remain parallel 

to the animal’s course, avoid excessive 

speed or abrupt changes in direction 

until the animal has left the area). If 

marine mammals are sighted within the 

relevant separation distance, the vessel 

should reduce speed and shift the 

engine to neutral, not engaging the 

engines until animals are clear of the 

area. This recommendation does not 

apply to any vessel towing gear. 

Based on our evaluation of the 

applicant’s proposed measures, NMFS 

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 

action; or (4) biological or behavioral 

context of exposure (e.g., age, calving or 

feeding areas); 

• Individual marine mammal 

responses (behavioral or physiological) 

to acoustic stressors (acute, chronic, or 

cumulative), other stressors, or 

cumulative impacts from multiple 

stressors; 

• How anticipated responses to 

stressors impact either: (1) long-term 

fitness and survival of individual 

marine mammals; or (2) populations, 

species, or stocks; 

• Effects on marine mammal habitat 

(e.g., marine mammal prey species, 

acoustic habitat, or other important 

physical components of marine 

mammal habitat); and, 

• Mitigation and monitoring 

effectiveness. 

Vessel-Based Visual Monitoring 

As described above, PSO observations 

would take place during daytime airgun 

operations. During seismic operations, 

at least three visual PSO would be based 

aboard the Langseth. Two visual PSOs 

would be on duty at all time during 

daytime hours. Monitoring shall be 

conducted in accordance with the 

following requirements: 

• PSOs shall be independent, 

dedicated and trained 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); 

• PSOs shall have successfully 

completed an approved PSO training 

course appropriate for their designated 

task (visual or acoustic); 

• NMFS must review and approve 

PSO resumes accompanied by a relevant 

training course information packet that 

includes the name and qualifications 

(i.e., experience, training completed, or 

educational background) of the 

instructor(s), the course outline or 

syllabus, and course reference material 

as well as a document stating successful 

completion of the course; 

• NMFS shall have one week to 

approve PSOs from the time that the 

necessary information is submitted, 

after which PSOs meeting the minimum 

requirements shall automatically be 

considered approved; 

• PSOs must successfully complete 

relevant training, including completion 

of all required coursework and passing 

(80 percent or greater) a written and/or 

oral examination developed for the 

training program; 

• PSOs must have successfully 

attained a bachelor’s degree from an 

accredited college or university with a 

major in one of the natural sciences, a 

minimum of 30 semester hours or 

equivalent in the biological sciences, 

and at least one undergraduate course in 

math or statistics; and 


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• The educational requirements may 

be waived if the PSO has acquired the 

relevant skills through alternate 

experience. Requests for such a waiver 

shall be submitted to NMFS and must 

include written justification. Requests 

shall be granted or denied (with 

justification) by NMFS within one week 

of receipt of submitted information. 

Alternate experience that may be 

considered includes, but is not limited 

to (1) secondary education and/or 

experience comparable to PSO duties; 

(2) previous work experience 

conducting academic, commercial, or 

government-sponsored protected 

species surveys; or (3) previous work 

experience as a PSO; the PSO should 

demonstrate good standing and 

consistently good performance of PSO 

duties. 

PSOs must use standardized data 

collection forms, whether hard copy or 

electronic. PSOs must record detailed 

information about any implementation 

of mitigation requirements, including 

the distance of animals to the acoustic 

source and description of specific 

actions that ensued, the behavior of the 

animal(s), any observed changes in 

behavior before and after 

implementation of mitigation, and if 

shutdown was implemented, the length 

of time before any subsequent ramp-up 

of the acoustic source. If required 

mitigation was not implemented, PSOs 

should record a description of the 

circumstances. At a minimum, the 

following information must be recorded: 

• Vessel name and call sign; 

• PSO names and affiliations; 

• Date and participants of PSO 

briefings (as discussed in General 

Requirement); 

• Dates of departure and return to 

port with port name; 

• Dates and times (Greenwich Mean 

Time) of survey effort and times 

corresponding with PSO effort; 

• Vessel location (latitude/longitude) 

when survey effort began and ended and 

vessel location at beginning and end of 

visual PSO duty shifts; 

• Vessel heading and speed at 

beginning and end of visual PSO duty 

shifts and upon any line change; 

• Environmental conditions while on 

visual survey (at beginning and end of 

PSO shift and whenever conditions 

changed significantly), including BSS 

and any other relevant weather 

conditions including cloud cover, fog, 

sun glare, and overall visibility to the 

horizon; 

• Factors that may have contributed 

to impaired observations during each 

PSO shift change or as needed as 

environmental conditions changed (e.g., 

vessel traffic, equipment malfunctions); 

and 

• Survey activity information, such as 

acoustic source power output while in 

operation, number and volume of 

airguns operating in the array, tow 

depth of the array, and any other notes 

of significance (i.e., pre-start clearance, 

ramp-up, shutdown, testing, shooting, 

ramp-up completion, end of operations, 

streamers, etc.). 

The following information should be 

recorded upon visual observation of any 

marine mammal: 

• Watch status (sighting made by PSO 

on/off effort, opportunistic, crew, 

alternate vessel/platform); 

• PSO who sighted the animal; 

• Time of sighting; 

• Vessel location at time of sighting; 

• Water depth; 

• Direction of vessel’s travel (compass 

direction); 

• Direction of animal’s travel relative 

to the vessel; 

• Pace of the animal; 

• Estimated distance to the animal 

and its heading relative to vessel at 

initial sighting; 

• Identification of the animal (e.g., 

genus/species, lowest possible 

taxonomic level, or unidentified) and 

the composition of the group if there is 

a mix of species; 

• Estimated number of animals (high/ 

low/best); 

• Estimated number of animals by 

cohort (adults, yearlings, juveniles, 

calves, group composition, etc.); 

• Description (as many distinguishing 

features as possible of each individual 

seen, including length, shape, color, 

pattern, scars or markings, shape and 

size of dorsal fin, shape of head, and 

blow characteristics); 

• Detailed behavior observations (e.g., 

number of blows/breaths, number of 

surfaces, breaching, spyhopping, diving, 

feeding, traveling; as explicit and 

detailed as possible; note any observed 

changes in behavior); 

• Animal’s closest point of approach 

(CPA) and/or closest distance from any 

element of the acoustic source; 

• Platform activity at time of sighting 

(e.g., deploying, recovering, testing, 

shooting, data acquisition, other); and 

• Description of any actions 

implemented in response to the sighting 

(e.g., delays, shutdown, ramp-up) and 

time and location of the action. 

Reporting 

L–DEO must submit a draft 

comprehensive report to NMFS on all 

activities and monitoring results within 

90 days of the completion of the survey 

or expiration of the IHA, whichever 

comes sooner. A final report must be 

submitted within 30 days following 

resolution of any comments on the draft 

report. The report would describe the 

operations that were conducted and 

sightings of marine mammals near the 

operations. The report would provide 

full documentation of methods, results, 

and interpretation pertaining to all 

monitoring. The 90-day report would 

summarize the dates and locations of 

seismic operations, and all marine 

mammal sightings (dates, times, 

locations, activities, associated seismic 

survey activities). The report would also 

include estimates of the number and 

nature of exposures that occurred above 

the harassment threshold based on PSO 

observations and including an estimate 

of those that were not detected, in 

consideration of both the characteristics 

and behaviors of the species of marine 

mammals that affect detectability, as 

well as the environmental factors that 

affect detectability. 

The draft report shall also include 

geo-referenced time-stamped vessel 

tracklines for all time periods during 

which airguns were operating. 

Tracklines should include points 

recording any change in airgun status 

(e.g., when the airguns began operating, 

when they were turned off, or when 

they changed from full array to single 

gun or vice versa). GIS files shall be 

provided in ESRI shapefile format and 

include the UTC date and time, latitude 

in decimal degrees, and longitude in 

decimal degrees. All coordinates shall 

be referenced to the WGS84 geographic 

coordinate system. In addition to the 

report, all raw observational data shall 

be made available to NMFS. The report 

must summarize the information 

submitted in interim monthly reports as 

well as additional data collected as 

described above and in the IHA. A final 

report must be submitted within 30 days 

following resolution of any comments 

on the draft report. 

Reporting Injured or Dead Marine 

Mammals 

Discovery of injured or dead marine 

mammals—In the event that personnel 

involved in survey activities covered by 

the authorization discover an injured or 

dead marine mammal, the L–DEO shall 

report the incident to the Office of 

Protected Resources (OPR), NMFS and 

to the NMFS West Coast Regional 

Stranding Coordinator as soon as 

feasible. The report must include the 

following information: 

• Time, date, and location (latitude/ 

longitude) of the first discovery (and 

updated location information if known 

and applicable); 

• Species identification (if known) or 

description of the animal(s) involved; 


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• Condition of the animal(s) 

(including carcass condition if the 

animal is dead); 

• Observed behaviors of the 

animal(s), if alive; 

• If available, photographs or video 

footage of the animal(s); and 

• General circumstances under which 

the animal was discovered. 

Vessel strike—In the event of a ship 

strike of a marine mammal by any vessel 

involved in the activities covered by the 

authorization, L–DEO shall report the 

incident to OPR, NMFS and to the 

NMFS West Coast Regional Stranding 

Coordinator as soon as feasible. The 

report must include the following 

information: 

• Time, date, and location (latitude/ 

longitude) of the incident; 

• Vessel’s speed during and leading 

up to the incident; 

• Vessel’s course/heading and what 

operations were being conducted (if 

applicable); 

• Status of all sound sources in use; 

• Description of avoidance measures/ 

requirements that were in place at the 

time of the strike and what additional 

measure were taken, if any, to avoid 

strike; 

• Environmental conditions (e.g., 

wind speed and direction, Beaufort sea 

state, cloud cover, visibility) 

immediately preceding the strike; 

• Species identification (if known) or 

description of the animal(s) involved; 

• Estimated size and length of the 

animal that was struck; 

• Description of the behavior of the 

animal immediately preceding and 

following the strike; 

• If available, description of the 

presence and behavior of any other 

marine mammals present immediately 

preceding the strike; 

• Estimated fate of the animal (e.g., 

dead, injured but alive, injured and 

moving, blood or tissue observed in the 

water, status unknown, disappeared); 

and 

• To the extent practicable, 

photographs or video footage of the 

animal(s). 

Actions To Minimize Additional Harm 

to Live-Stranded (or Milling) Marine 

Mammals 

In the event of a live stranding (or 

near-shore atypical milling) event 

within 50 km of the survey operations, 

where the NMFS stranding network is 

engaged in herding or other 

interventions to return animals to the 

water, the Director of OPR, NMFS (or 

designee) will advise L–DEO of the need 

to implement shutdown procedures for 

all active acoustic sources operating 

within 50 km of the stranding. 

Shutdown procedures for live stranding 

or milling marine mammals include the 

following: If at any time, the marine 

mammal the marine mammal(s) die or 

are euthanized, or if herding/ 

intervention efforts are stopped, the 

Director of OPR, NMFS (or designee) 

will advise the IHA-holder that the 

shutdown around the animals’ location 

is no longer needed. Otherwise, 

shutdown procedures will remain in 

effect until the Director of OPR, NMFS 

(or designee) determines and advises L– 

DEO that all live animals involved have 

left the area (either of their own volition 

or following an intervention). 

If further observations of the marine 

mammals indicate the potential for restranding, additional coordination with 

the IHA-holder will be required to 

determine what measures are necessary 

to minimize that likelihood (e.g., 

extending the shutdown or moving 

operations farther away) and to 

implement those measures as 

appropriate. 

Additional Information Requests—if 

NMFS determines that the 

circumstances of any marine mammal 

stranding found in the vicinity of the 

activity suggest investigation of the 

association with survey activities is 

warranted, and an investigation into the 

stranding is being pursued, NMFS will 

submit a written request to L–DEO 

indicating that the following initial 

available information must be provided 

as soon as possible, but no later than 7 

business days after the request for 

information: 

• Status of all sound source use in the 

48 hours preceding the estimated time 

of stranding and within 50 km of the 

discovery/notification of the stranding 

by NMFS; and 

• If available, description of the 

behavior of any marine mammal(s) 

observed preceding (i.e., within 48 

hours and 50 km) and immediately after 

the discovery of the stranding. 

In the event that the investigation is 

still inconclusive, the investigation of 

the association of the survey activities is 

still warranted, and the investigation is 

still being pursued, NMFS may provide 

additional information requests, in 

writing, regarding the nature and 

location of survey operations prior to 

the time period above. 

Reporting Species of Concern 

To support NMFS’s goal of improving 

our understanding of occurrence of 

marine mammal species or stocks in the 

area (e.g., presence, abundance, 

distribution, density), L–DEO will 

immediately report observations of 

Southern Resident killer whales or 

North Pacific right whales to OPR, 

NMFS. Although, the likelihood of 

encountering either species is 

considered to be rare and unexpected. 

Negligible Impact Analysis and 

Determination 

NMFS has defined negligible impact 

as an impact resulting from the 

specified activity that cannot be 

reasonably expected to, and is not 

reasonably likely to, adversely affect the 

species or stock through effects on 

annual rates of recruitment or survival 

(50 CFR 216.103). A negligible impact 

finding is based on the lack of likely 

adverse effects on annual rates of 

recruitment or survival (i.e., populationlevel effects). An estimate of the number 

of takes alone is not enough information 

on which to base an impact 

determination. In addition to 

considering estimates of the number of 

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 the species 

listed in Table 6, given that the 

anticipated effects of this activity on 

these different marine mammal stocks 

are expected to be similar, except where 

a species- or stock-specific discussion is 

warranted. NMFS does not anticipate 

that serious injury or mortality would 

occur as a result from low-energy 

surveys, 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, 

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 


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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). TTS is not expect for 

most hearing groups (HF, MF, otariids 

and phocids) and is considered to be 

highly unlikely for LF cetaceans. Even 

repeated Level B harassment of some 

small subset of an overall stock is 

unlikely to result in any significant 

realized decrease in viability for the 

affected individuals, and thus would 

not result in any adverse impact to the 

stock as a whole. As described above, 

Level A harassment is not expected to 

occur given the estimated small size of 

the Level A harassment zones. 

In addition to being temporary, the 

maximum expected Level B harassment 

zone around the survey vessel is 553 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 (6 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 the 

food sources that they utilize are not 

expected to cause significant or longterm consequences for individual 

marine mammals or their populations. 

The entire U.S. West Coast within 47 

km of the coast is a BIA for migrating 

gray whale potential presence January to 

July and October to December. The BIA 

for northbound gray whale migration is 

broken into two phases, Phase A (within 

8 km of shore) and Phase B (within 5 km 

of shore), which are active from January 

to July and March to July, respectively. 

The BIA for southbound migration 

includes waters within 10 km of shore 

and is active from October to March. All 

planned survey areas are outside of all 

gray whale BIAs and no takes of gray 

whales are proposed for authorization. 

There are also two humpback whale 

feeding BIAs (Stonewall and Heceta 

Bank) adjacent to the survey area, 

however no overlap occurs between the 

survey area and the BIAs. There are no 

rookeries, mating or calving grounds 

known to be biologically important to 

marine mammals within the proposed 

survey area. 

Critical habitat for the Mexico and 

Central America DPSs of humpback 

whales has been established along the 

U.S. West Coast (86 FR 21082; May 5, 

2021), and NMFS has expanded the 

Southern Resident killer whale critical 

habitat to include coastal waters of 

Washington, Oregon, and California (86 

FR 41668; August 2, 2021). No part of 

L–DEO’s proposed seismic survey will 

occur in or near these critical habitats. 

No permanent hearing impairment 

(Level A harassment) is anticipated or 

proposed to be authorized. Authorized 

takes of killer whales is expected to 

comprise almost entirely of the West 

Coast Transient and/or North Pacific 

Offshore stocks as Southern Resident 

killer whales are typically confined to 

coastal and inland waters. Therefore 

take of Southern Resident killer whales 

is unlikely given the far offshore 

location of the proposed survey, and no 

take of Southern Resident killer whales 

is proposed for authorization. 

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 serious injury or mortality is 

anticipated or authorized; 

• The proposed activity is temporary 

and of relatively short duration (6 days); 

• The anticipated impacts of the 

proposed activity on marine mammals 

would be temporary behavioral changes 

due to avoidance of the area around the 

vessel; 

• No take by Level A harassment is 

proposed for authorization; 

• 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, 

including visual, shutdowns, and 

enhanced measures for areas of 

biological importance (e.g., additional 

monitoring vessel, daylight operations 

only) are expected to minimize potential 

impacts to marine mammals (both 

amount and severity). 

Based on the analysis contained 

herein of the likely effects of the 

specified activity on marine mammals 

and their habitat, and taking into 

consideration the implementation of the 

proposed monitoring and mitigation 

measures, NMFS preliminarily finds 

that the total marine mammal take from 

the proposed activity will have a 

negligible impact on all affected marine 

mammal species or stocks. 

Small Numbers 

As noted above, only small numbers 

of incidental take may be authorized 

under sections 101(a)(5)(A) and (D) of 

the MMPA for specified activities other 

than military readiness activities. The 

MMPA does not define small numbers 

and so, in practice, where estimated 

numbers are available, NMFS compares 

the number of individuals taken to the 

most appropriate estimation of 

abundance of the relevant species or 

stock in our determination of whether 

an authorization is limited to small 

numbers of marine mammals. 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. 

Additionally, other qualitative factors 

may be considered in the analysis, such 

as the temporal or spatial scale of the 

activities. 

The amount of take NMFS proposes to 

authorize is below one third of the 

estimated stock abundance for all 

species (in fact, take of individuals is 

less than ten percent of the abundance 

of the affected stocks, see Table 6). This 

is likely a conservative estimate because 

we assume all takes are of different 

individual animals, 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. 

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. 

Endangered Species Act 

Section 7(a)(2) of the Endangered 

Species Act of 1973 (ESA: 16 U.S.C. 

1531 et seq.) requires that each Federal 


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37598 Federal Register / Vol. 87, No. 120 / Thursday, June 23, 2022 / Notices 

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, in 

this case with the ESA Interagency 

Cooperation Division within NMFS’ 

Office of Protected Resources (OPR). 

NMFS is proposing to authorize take 

of blue whales, fin whales, sei whales, 

sperm whales, Central America DPS 

humpback whales, Mexico DPS 

humpback whales, and Guadalupe fur 

seal, which are listed under the ESA. 

The NMFS OPR Permits and 

Conservation Division has requested 

initiation of Section 7 consultation with 

the NMFS OPR ESA Interagency 

Cooperation Division for the issuance of 

this IHA. NMFS will conclude the ESA 

consultation prior to reaching a 

determination regarding the proposed 

issuance of the authorization. 

Proposed Authorization 

As a result of these preliminary 

determinations, NMFS proposes to issue 

an IHA to L–DEO for conducting 

geophysical surveys in the Northeast 

Pacific Ocean during Summer 2022, 

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-researchand-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 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, one-year renewal IHA 

following notice to the public providing 

an additional 15 days for public 

comments when (1) up to another year 

of identical or nearly identical activities 

as described in the Description of 

Proposed Activities section of this 

notice is planned or (2) the activities as 

described in the Description of 

Proposed Activities section of this 

notice would not be completed by the 

time the IHA expires and a renewal 

would allow for completion of the 

activities beyond that described in the 

Dates and Duration section of this 

notice, provided all of the following 

conditions are met: 

• A request for renewal is received no 

later than 60 days prior to the needed 

renewal IHA effective date (recognizing 

that the renewal IHA expiration date 

cannot extend beyond one year from 

expiration of the initial IHA). 

• The request for renewal must 

include the following: 

(1) An explanation that the activities 

to be conducted under the requested 

renewal IHA are identical to the 

activities analyzed under the initial 

IHA, are a subset of the activities, or 

include changes so minor (e.g., 

reduction in pile size) that the changes 

do not affect the previous analyses, 

mitigation and monitoring 

requirements, or take estimates (with 

the exception of reducing the type or 

amount of take). 

(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: June 16, 2022. 

Kimberly Damon-Randall, 

Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2022–13328 Filed 6–22–22; 8:45 am] 

BILLING CODE 3510–22–P 


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