Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Marine Geophysical Survey in the North Pacific Ocean

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XG144

Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Marine Geophysical Survey in the North Pacific Ocean

AGENCY:

National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.

ACTION:

Notice; proposed incidental harassment authorization; request for comments.

SUMMARY:

NMFS has received a request from the Lamont-Doherty Earth Observatory of Columbia University (L-DEO) for authorization to take marine mammals incidental to a marine geophysical survey in the North 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 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 30, 2018.

ADDRESSES:

Comments should be addressed to Jolie Harrison, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service. Physical comments should be sent to 1315 East-West Highway, Silver Spring, MD 20910 and electronic comments should be sent to

ITP.Pauline@noaa.gov.

Instructions:

NMFS is not responsible for comments sent by any other method, to any other address or individual, or received after the end of the comment period. Comments received electronically, including all attachments, must not exceed a 25-megabyte file size. Attachments to electronic comments will be accepted in Microsoft Word or Excel or Adobe PDF file formats only. All comments received are a part of the public record and will generally be posted online at

https://www.fisheries.noaa.gov/node/23111

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:

Rob Pauline, 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/node/23111.

In case of problems accessing these documents, please call the contact listed above.

SUPPLEMENTARY INFORMATION:

Background

Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361

et seq.

) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review.

An authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of such takings are set forth.

NMFS has defined “negligible impact” in 50 CFR 216.103 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.

The MMPA states that the term “take” means to harass, hunt, capture, kill or attempt to harass, hunt, capture, or kill any marine mammal.

Except with respect to certain activities not pertinent here, 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).

National Environmental Policy Act

To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321

et seq.

) and NOAA Administrative Order (NAO) 216-6A, NMFS must review our proposed action (

i.e.,

the issuance of an incidental harassment authorization) with respect to potential impacts on the human environment.

Accordingly, NMFS plans to adopt the National Science Foundation's EA, provided our independent evaluation of the document finds that it includes adequate information analyzing the effects on the human environment of issuing the IHA. We will review all comments submitted in response to this notice prior to concluding our NEPA process or making a final decision on the IHA request.

Summary of Request

On March 16, 2018, NMFS received a request from the L-DEO for an IHA to take marine mammals incidental to conducting a marine geophysical survey in the North Pacific Ocean. L-DEO submitted a revised application on June 11, 2018. On June 13, 2018 we deemed L-DEO's application for authorization to be adequate and complete. L-DEO's request is for take of small numbers of 39 species of marine mammals by Level A and Level B harassment. Underwater sound associated with airgun use may result in the behavioral harassment or auditory injury of marine mammals in the ensonified areas. Mortality is not an anticipated outcome of airgun surveys such as this, and, therefore, an IHA is appropriate. The planned activity is not expected to exceed one year, hence, we do not expect subsequent MMPA incidental harassment authorizations would be issued for this particular activity.

Description of Proposed Activity

Overview

The specified activity consists of two high-energy seismic surveys conducted at different locations in the North Pacific Ocean. Researchers from Lamont-Doherty Earth Observatory (L-DEO) and University of Hawaii, with funding from the U.S. National Science Foundation (NSF), in collaboration with researchers from United States Geological Survey (USGS), Oxford University, and GEOMAR Helmholtz Centre for Ocean Research Kiel (GEOMAR), propose to conduct the surveys from the Research Vessel (R/V)

Marcus G. Langseth

(

Langseth

) in the North Pacific Ocean. The NSF-owned

Langseth

is operated by Columbia University's L-DEO under an existing

Cooperative Agreement. The first proposed seismic survey would occur in the vicinity of the Main Hawaiian Islands, and a subsequent survey would take place at the Emperor Seamounts in 2019. The proposed timing for the Hawaii survey is summer/early fall 2018; the timing for the Emperor Seamounts survey would likely be spring/early summer 2019. Both surveys would use a 36-airgun towed array with a total discharge volume of ~6,600 in

3

.

The main goal of the surveys proposed by L-DEO and the University of Hawaii is to gain fundamental insight into the formation and evaluation of Hawaiian-Emperor Seamount chain, and inform a more comprehensive assessment of geohazards for the Hawaiian Islands region.

Dates and Duration

The Hawaii survey would be expected to last for 36 days, including ~19 days of seismic operations, 11 days of equipment deployment/retrieval, ~3 days of operational contingency time (

e.g.,

weather delays, etc.), and ~3 days of transit. The

Langseth

would leave out of and return to port in Honolulu during summer (likely mid-August) 2018. The Emperor Seamounts survey would be expected to last 42 days, including ~13 days of seismic operations, ~11 days of equipment deployment/retrieval, ~5.5 days of operational contingency time, and 12.5 days of transit. The

Langseth

would leave Honolulu and return to port likely in Adak or Dutch Harbor, Alaska. The dates for this cruise have not yet been determined, although late spring/early summer 2019 is most likely.

Specific Geographic Region

The specified activity consists of two seismic surveys in the North Pacific Ocean—one at the Main Hawaiian Islands (Fig. 1 in application) and the other at the Emperor Seamounts (Fig. 2 in application). The proposed Hawaii survey would occur within ~18-24° N, ~153-160° W, and the proposed Emperor Seamounts survey would occur within ~43-48° N, ~166-173° E. The Hawaiian-Emperor Seamount chain is a mostly undersea mountain range in the Pacific Ocean that reaches above sea level in Hawaii. It is composed of the Hawaiian ridge, consisting of the islands of the Hawaiian chain northwest to Kure Atoll, and the Emperor Seamounts: Together they form a vast underwater mountain region of islands and intervening seamounts, atolls, shallows, banks and reefs along a line trending southeast to northwest beneath the northern Pacific Ocean. The seamount chain, containing over 80 identified undersea volcanoes, stretches over 5,800 kilometers (km) or 3,600 miles (mi) from the Aleutian Trench in the far northwest Pacific to the Lo'ihi seamount, the youngest volcano in the chain, which lies about 35 km (22 mi) southeast of the Island of Hawaii. The Emperor Seamounts seismic survey location is located approximately 4,100 km (2,200 mi) northwest of the Hawaii seismic survey location.

Representative survey tracklines are shown in Figures 1 and 2 in the application. As described further in this document, however, some deviation in actual track lines, including order of survey operations, could be necessary for reasons such as science drivers, poor data quality, inclement weather, or mechanical issues with the research vessel and/or equipment. Thus, for the Emperor Seamounts survey, the tracklines could occur anywhere within the coordinates noted above and illustrated by the box in the inset map on Figure 2. The tracklines for the Hawaii survey could shift slightly, but would stay within the coordinates noted above and general vicinity of representative lines depicted in Figure 1. Water depths in the proposed Hawaii survey area range from ~700 to more than 5,000 m. The water depths in the Emperor Seamounts survey area range from 1,500-6,000 m. The proposed Hawaii seismic survey would be conducted within the U.S. exclusive economic zone (EEZ); the Emperor Seamounts survey would take place in International Waters.

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, the

Langseth,

which is owned by NSF and operated on its behalf by Columbia University's L-DEO. The

Langseth

would deploy an array of 36 airguns as an energy source with a total volume of ~6,600 in

3

. The receiving system would consist of OBSs and a single hydrophone streamer 15 km in length and OBSs. As the airgun arrays are towed along the survey lines, the hydrophone streamer would transfer the data to the on-board processing system, and the OBSs would receive and store the returning acoustic signals internally for later analysis.

The proposed study consists of two seismic surveys in the North Pacific Ocean. There would be a total of four seismic transects for the Hawaii survey—two North (N)-South (S) tracklines (Lines 1 and 2), and two East (E)-West (W) tracklines (Lines 3 and 4). An optional trackline (Line 5) could be acquired instead of Line 4 (Fig. 1). Lines 1 and 2 would be acquired twice—seismic refraction data would be acquired first, followed by multichannel seismic (MCS) reflection data. Only MCS reflection profiling would occur along Lines 3, 4, or 5. The location of the E-W tracklines (Lines 3, 4, or 5) could shift from what is currently depicted in Figure 1 depending on the science objectives; however, the E-W lines would remain in water >3,200 m deep.

The

Langseth

would first deploy 70 ocean bottom seismometers (OBS)s required for the refraction profiling—the vessel would transit from Honolulu to the north end of Line 2, deploy 35 OBSs along Line 2, ~15 km apart, and then transit to the south end of Line 1 to deploy 35 OBSs (~15 km apart) along Line 1. The streamer and airgun array would then be deployed. Refraction data would then be acquired from north to south on Line 1 followed by MCS profiling along the same line. If Lines 3 and 4 are to be surveyed (preferred option), MCS profiles would then be acquired along Line 3, followed by refraction data acquisition in a north-south direction along Line 2, followed by MCS profiles along Line 2 from south to north. The vessel would then acquire MCS profiles from the north end of Line 2 to the west end of Line 4, and along Line 4. After seismic acquisition ceases, the streamer, airgun source, and all OBSs would be recovered by the

Langseth.

There would be three seismic transects for the Emperor Seamounts survey (Fig. 2). Data would be acquired twice along the two OBS lines—once for seismic refraction data and once for MCS reflection profiling. Only MCS reflection profiling would occur along the third transect that connects the two OBS lines. The

Langseth

would first acquire MCS reflection data for all three lines—from north to south, then along the connecting transect, and from west to east. After recovering the streamer and airgun array, the

Langseth

would deploy 32 OBSs required for the refraction profiling from east to west along the first line. After seismic acquisition along the first OBS line from west to east, the OBSs would be recovered and re-deployed along the second OBS line, which would then be surveyed from north to south. The

Langseth

would then recover all OBSs, the streamer, and the airgun array.

In addition to the operations of the airgun array, a multibeam echosounder (MBES), a sub-bottom profiler (SBP), and an Acoustic Doppler Current

Profiler (ADCP) would be operated from the

Langseth

continuously during the seismic surveys, but not during transit to and from the survey areas. 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.

During the two surveys, the

Langseth

would tow the full array, consisting of four strings with 36 airguns (plus 4 spares) and a total volume of ~6,600 in

3

. The 4-string array would be towed at a depth of 12 m, and the shot intervals would range from 50 m for MCS acquisition and 150 m for OBS acquisition. To retrieve OBSs, an acoustic release transponder (pinger) is used to interrogate the instrument at a frequency of 8-11 kHz, and a response is received at a frequency of 11.5-13 kHz. The burn-wire release assembly is then activated, and the instrument is released to float to the surface from the anchor which is not retrieved.

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 the Specified Activity

Section 4 of the IHA application summarizes available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species. 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 with expected potential for occurrence in the North Pacific Ocean and summarizes information related to the population, including regulatory status under the MMPA and ESA. Some of the populations of marine mammals considered in this document occur within the U.S. EEZ and are therefore assigned to stocks and are assessed in NMFS' Stock Assessment Reports (

www.nmfs.noaa.gov/pr/sars/

). As such, information on potential biological removal (PBR; 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) and on annual levels of serious injury and mortality from anthropogenic sources are not available for these marine mammal populations.

Twenty-eight cetacean species, including 21 odontocetes (dolphins and small- and large-toothed whales) and seven mysticetes (baleen whales), and one pinniped species, could occur in the proposed Hawaii survey area (Table 4). In the Emperor Seamounts survey area, 27 marine mammal species could occur, including 15 odontocetes (dolphins and small- and large-toothed whales), eight mysticetes (baleen whales), and four pinniped species. Some species occur in both locations. In total, 39 species are expected to occur in the vicinity of the specified activity.

Baird

et al.

(2015) described numerous Biologically Important Areas (BIAs) for cetaceans for the Hawaii region. BIAs were identified for small resident populations of cetaceans based on sighting data, photo-identification, genetics, satellite tagging, and expert opinion, and one reproductive area for humpbacks was identified as a BIA; these are described in the following section for each marine mammal species. The BIAs range from ~700-23,500 km

2

in area (Baird

et al.

2015).

Marine mammal abundance estimates presented in this document represent the total number of individuals estimated within a particular study or survey area. All values presented in Table 1 are the most recent available at the time of publication.

Table 1—Marine Mammals That Could Occur in the Proposed Survey Areas

Common name

Scientific name

Stock

ESA/MMPA

status;

strategic

(Y/N)

1

Stock abundance

(CV, N

min

, most recent

abundance survey)

2

PBR

Annual

M/SI

3

Present at time of

survey (Y/N)

HI

Emperor

Seamounts

Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)

Family Eschrichtiidae:

Gray whale

Eschrichtius robustus

Western North Pacific

E/D; Y

140 (0.04, 135, 2011)

4

0.06

unk

N

Y

Family Balaenidae:

North Pacific right whale

Eubalaena japonica

Eastern North Pacific

E/D; Y

31 (0.226, 26, 2013)

6

N/A

0

N

Y

N/A

450

5

Family Balaenopteridae (rorquals):

Humpback whale

Megaptera novaeangliae

Central North Pacific

-/-; N

10,103 (0.03, 7,890, 2006)

6

83

25

Y

Y

Western North Pacific

E/D; Y

1,107 (0.30, 865,2006)

6

3

3.2

Minke whale

Balaenoptera acutorostrata

Hawaii

N/A

UNK

22,000

7

N

Y

Bryde's whale

(Balaenoptera edeni/brydei

Hawaii

Eastern Tropical Pacific

-/-; N

-/-; N—

1,751 (0.29, 1,378, 2010)

17

UNK

13.8

UND

0

Y

Y

Sei whale

Balaenoptera borealis

Hawaii

E/D; Y

178 (0.9, 93, 2010)

4

0.2

0.2

Y

Y

Fin whale

Balaenoptera physalus physalus

Hawaii

N/A

E/D; Y

154 (1.05, 75, 2010)

17

13,620-18,680

9

0.1

0

Y

Y

Blue whale

Balaenoptera musculus musculus)

Central North Pacific

E/D; Y

133 (1.09, 63, 2010)

17

0.1

0

Y

Y

Superfamily Odontoceti (toothed whales, dolphins, porpoises)

Family Physeteridae:

Sperm whale

Physeter macrocephalus

Hawaii

N/A

E/D; Y

N/A

4,559 (0.33, 3,478, 2010)

17

29,674

10

-26,300

11

13.9

0.7

Y

Y

Family Kogiidae:

Pygmy sperm whale

Kogia breviceps

Hawaii

-/-; N

7,138

4

UND

0

Y

Y

Dwarf sperm whale

Kogia sima

Hawaii

-/-; N

17,519

4

UND

0

Y

Y

Family Ziphiidae (beaked whales):

Cuvier's beaked whale

Ziphius cavirostris

Hawaii

-, -, N

723 (0.69, 428, 2010)

17

4.3

0

Y

Y

N/A

20,000

12

Longman's beaked whale

Indopacetus pacificus

Hawaii

-, -, N

7,619 (0.66, 4,592, 2010)

17

46

0

Y

N

Blainville's beaked whale

Mesoplodon densirostris

Hawaii

-, -, N

2,105 (1.13,1, 980, 2010)

17

10

0

Y

N

Stejneger's beaked whale

Mesoplodon stejnegeri

Alaska

N

UNK

UND

0

N

Y

Ginkgo-toothed beaked whale

Mesoplodon ginkgodens

N/A

25,300

12

Rare

Absent

Deraniyagala's beaked whale

Mesoplodon hotaula

N/A

25,300

12

Y

N

Hubb's beaked whale

Mesoplodon carlhubbsi

N/A

25,300

12

Y

N

Baird's beaked whale

Berardius bairdii

N/A

10,190

13

N

Y

Family Delphinidae:

Rough-toothed dolphin

Steno bredanensis

Hawaii

-, -, N

72,528 (0.39, 52,033, 2010)

17

46

UNK

Common

N

Common bottlenose dolphin

Tursiops truncatus

Hawaii Pelagic

-/-; N

21,815 (0.57, 13,957, 2010)

17

140

0.2

Common

N

Kaua'i and Ni'ihau

-/-; N

184 (0.11, 168, 2005)

4

1.7

unk

Common

N

O'ahu

-/-; N

743 (0.54, 485, 2006)

4

4.9

unk

Common

N

4 Islands Region

-/-; N

191 (0.24, 156, 2006)

unk

unk

Common

N

Hawaii Island

-/-; N

128 (0.13, 115, 2006)

4

1.6

unk

Common

N

Common dolphin

Delphinus delphis

N/A

2,963,000

14

N

Y

Pantropical spotted dolphin

Stenella attenuata

Hawaii Pelagic

-/-; N

55,795 (0.40, 40,338, 2010)

17

403

0

Y

N

O'ahu

-/-; N

unk

unk

unk

4 Island Region

-/-; N

unk

unk

unk

Hawaii Island

-/-; N

unk

unk

≥ 0.2

Spinner dolphin

Stenella longirostris

Hawaii Pelagic

-/-; N

unk

unk

unk

Y

N

Hawaii Island

-/-; N

631 (0.04, 585, 2013)

4

5.9

unk

Common

N

O'ahu/4-Islands

-/-; N

355 (0.09, 329, 2013)

4

3.3

unk

Y

N

Striped dolphin

Stenella coeruleoalba

Hawaii

-/-; N

61,021 (0.38, 44,922, 2010)

17

449

unk

Y

Y

N/A

964,362

15

Fraser's dolphin

Lagenodelphis hosei

Hawaii

-/-; N

51,491 (0.66, 31,034, 2010)

17

310

0

Y

N

Pacific white-sided dolphin

Lagenorhynchus obliquidens

Central North Pacific

988,333

16

N

Y

Northern right whale dolphin

Lissodelphis borealis

N/A

307,784

16

N

Y

Risso's dolphin

Grampus griseus

Hawaii

-/-; N

11,613 (0.39, 8,210, 2010)

17

82

0

Y

Y

N/A

110,457

15

Melon-headed whale

Peponocephala electra

Hawaii

Kohala Resident

-/-; N

-/-; N

8,666 (1.00, 4,299, 2010)

17

447 (0.12, 404, 2009)

4

43

4

0

0

Y

N

Pygmy killer whale

Feresa attenuata

Hawaii

-/-; N

10,640 (0.53, 6,998, 2010)

17

56

1.1

Y

N

False killer whale

Pseudorca crassidens

Hawaii Insular

E/D;Y

167 (0.14, 149, 2015)

17

0.3

0

Y

Y

Northwest Hawaiian Islands

-/-; N

617 (1.11, 290, 2010)

17

2.3

0.4

Hawaii Pelagic

-/-; N

1,540 (0.66, 928, 2010)

17

9.3

7.6

N/A

16,668

18

Killer whale

Orcinus orca

Hawaii

-/-; N

146 (0.96, 74, 2010)

0.7

0

Y

Y

N/A

8,500

19

Short-finned pilot whale

Globicephala macrorhynchus

Hawaii

N/A

-/-; N

19,503 (0.49, 13,197, 2010)

53,608

16

106

0.9

Y

Y

Family Phoenidae (porpoises):

Dall's porpoise

Phocoenoides dalli

N/A

1,186,000

20

N

Y

Order Carnivora—Superfamily Pinnipedia

Family Otariidae (eared seals and sea lions):

Steller sea lion

Eumetopias jubatus

Western DPS

E/D; Y

50,983 (-,50,983, 2015)

N

Y

Northern fur seal

Callorhinus ursinus

Eastern Pacific

-/D; Y

626,734 (0.2, 530,474, 2014)

11,405

437

N

Y

N/A

1,100,000

5

Family Phocidae (earless seals):

Hawaiian monk seal

Neomonachus schauinslandi

Hawaii

E/D; Y

1,324 (0.03, 1,261, 2015)

17

4.4

≥1.6

Y

N

Northern elephant seal

Mirounga angustirostris

210,000-239,000

21

N

Y

Ribbon seal

Histriophoca fasciata

Alaska

-/-; N

184,000 (0.12, 163,000, 2013)

9,785

3.8

N

Y

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:

www.nmfs.noaa.gov/pr/sars/.

CV is coefficient of variation; N

min

is the minimum estimate of stock abundance.

3

—These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (

e.g.,

commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial fisheries is presented in some cases.

4

—Carretta

et al.,

2017.

5

—Jefferson

et al.,

2015.

6

—Muto

et al.,

2017.

7

—IWC 2018.

8

—Central and Eastern North Pacific (Hakamada and Matsuoka 2015a).

9

—Ohsumi and Wada, 1974.

10

—Whitehead 2002.

11

—Barlow and Taylor 2005.

12

—Wade and Gerrodette 1993.

13

—Western Pacific Ocean (Okamura

et al.,

2012).

14

—ETP (Gerrodette and Forcada 2002 in Hammond

et al.,

2008b).

15

—Gerrodette

et al.,

2008.

16

—North Pacific (Miyashita 1993b).

17

—Carretta

et al.,

2018.

18

—Western North Pacific (Miyashita 1993a).

19

—Ford 2009.

20

—Buckland

et al.,

1993.

21

—Lowry

et al.,

2014.

Note

—Italicized species are not expected to be taken or proposed for authorization.

All species that could potentially occur in the proposed survey area are included in Table 1. With the exception of Steller sea lions, these species or stocks temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur. However, the temporal and/or spatial occurrence of Steller sea lions is such that take is not expected to occur, and they are not discussed further beyond the explanation provided here. The Steller sea lion occurs along the North Pacific Rim from northern Japan to California (Loughlin

et al.

1984). They are 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 (NMFS 2016c). There is little information available on at-sea occurrence of Steller sea lions in the northwestern Pacific Ocean. The Emperor Seamounts survey area is roughly 1,200 kilometers away from the Aleutian Islands in waters 2,000 to more than 5,000 meters deep. Steller sea lions are unlikely to occur in the proposed offshore survey area based on their known distributional range and habitat preference. Therefore, it is extremely unlikely that Steller sea lions would be exposed to the stressors associated with the proposed seismic activities and will not be discussed further.

We have reviewed L-DEO's species descriptions, including life history information, distribution, regional distribution, diving behavior, and acoustics and hearing, for accuracy and completeness. Below, for the 39 species that are likely to be taken by the activities described, we offer a brief introduction to the species and relevant stock as well as available information regarding population trends and threats, and describe any information regarding local occurrence.

Gray Whale

Two separate populations of gray whales have been recognized in the North Pacific (LeDuc

et al.

2002): The eastern North Pacific and western North Pacific (or Korean-Okhotsk) stocks. However, the distinction between these two populations has been recently debated owing to evidence that whales from the western feeding area also travel to breeding areas in the eastern North Pacific (Weller

et al.

2012, 2013; Mate

et al.

2015). Thus, it is possible that whales from both the

endangered

Western North Pacific and the delisted Eastern North Pacific DPS could occur in the proposed survey area in the Emperor Seamounts survey area.

The western population is known to feed in the Okhotsk Sea along the northeast coast of Sakhalin Island (Weller

et al.

1999, 2002a, 2008), eastern Kamchatka, and the northern Okhotsk Sea in the summer and autumn (Vladimirov

et al.

2008). Winter breeding grounds are not known; however, it has been postulated that wintering areas occur along the south coast of the Korean Peninsula, but it is more likely that they are located in the South China Sea, along the coast of Guangdong province and Hainan (Wang 1984 and Zhu 1998

in

Weller

et al.

2002a; Rice 1998). Winter records exist for Japan, North Korea, and South Korea (Weller

et al.

2002a,b). Migration into the Okhotsk Sea may occur through the Sea of Japan via the Tatar Strait and/or La Perouse Strait (see Reeves

et al.

2008). If migration timing is similar to that of the better-known eastern gray whale, southbound migration probably occurs mainly in December-January and northbound migration mainly in February-April, with northbound migration of newborn calves and their mothers probably concentrated at the end of that period. The eastern North Pacific gray whale breeds and winters in

Baja, California, and migrates north to summer feeding grounds in the northern Bering Sea, Chukchi Sea, and western Beaufort Sea (Rice and Wolman 1971; Jefferson

et al.

2015).

In the western North Pacific, gray whales migrate along the coast of Japan (Weller

et al.

2008), and records have been reported there from November through August, with the majority for March through May (Weller

et al.

2012). Although the offshore limit of this route is not well documented, gray whales are known to prefer nearshore coastal waters. However, some exchange between populations in the eastern and western North Pacific has been reported (Weller

et al.

2012, 2013; Mate

et al.

2015); thus, migration routes could include pelagic waters of the Pacific Ocean, including the proposed Emperor Seamounts survey area. Nonetheless, given their small population size and preference for nearshore waters, only very small numbers are likely to be encountered during the proposed Emperor Seamounts survey during any time of the year. Additionally, during summer, most gray whales would be feeding near Sakhalin Island. The gray whale does not occur in Hawaiian waters.

North Pacific Right Whale

North Pacific right whales summer in the northern North Pacific, primarily in the Okhotsk Sea (Brownell

et al.

2001) and in the Bering Sea (Shelden

et al.

2005; Wade

et al.

2006). The eastern North Pacific stock that occurs in U.S. waters numbers only ~31 individuals (Wade

et al.

2011), and critical habitat has been designated in the eastern Bering Sea and in the Gulf of Alaska, south of Kodiak Island (NMFS 2017b). Wintering and breeding areas are unknown, but have been suggested to include the Hawaiian Islands, Ryukyu Islands, and Sea of Japan (Allen 1942; Gilmore 1978; Reeves

et al.

1978; Herman

et al.

1980; Omura 1986). The Hawaiian Islands were not a major calving ground for right whales in the last 200 years, but mid-ocean whaling records of right whales during winter suggest that right whales may have wintered and calved far offshore in the Pacific Ocean (Scarff 1986, 1991; Clapham

et al.

2004). In April 1996, a right whale was sighted off Maui, the first documented sighting of a right whale in Hawaiian waters since 1979 (Salden and Mickelsen 1999).

Whaling records indicate that right whales once ranged across the entire North Pacific Ocean north of 35° N and occasionally occurred as far south as 20° N (

e.g.,

Scarff 1986, 1991). In the western Pacific, most sightings in the 1900s were reported from Japanese waters, followed by the Kuril Islands, and the Okhotsk Sea (Brownell

et al.

2001). Significant numbers of right whales have been seen in the Okhotsk Sea during the 1990s, suggesting that the adjacent Kuril Islands and Kamchatka coast are a major feeding ground (Brownell

et al.

2001). Right whales were also seen near Chichi-jima Island (Bonin Islands), Japan, in the 1990s (Mori

et al.

1998). During 1994-2014, right whale sightings were reported off northern Japan, the Kuril Islands, and Kamchatka during April through August, with highest densities in May and August (Matsuoka

et al.

2015). All sightings were north of 38° N, and in July-August, the main distribution was north of 42° N (Matsuoka

et al.

2015). Right whale sightings were made within the Emperor Seamounts survey area during August, and adjacent to the survey area during May and July (Matsuoka

et al.

2015). Ovsyanikova

et al.

(2015) also reported right whale sightings in the western Pacific Ocean during 1977-2014; although they also reported sightings off eastern Japan, the Kuril Islands, and southeast Kamchatka, including sightings to the west of the proposed Emperor Seamounts survey area, no sightings were reported within the proposed survey area. Sekiguchi

et al.

(2014) reported several sightings just to the north and west of the proposed survey area during June 2012.

Although there are a few historical records of North Pacific right whales in Hawaiian waters (Brownell

et al.

2001), they are very unlikely to occur in the Hawaiian survey area, especially during the summer. However, right whales could be encountered in the Emperor Seamounts survey area during spring and summer, and likely fall. Individuals that could occur there would likely be from a western North Pacific stock rather than the eastern North Pacific stock.

Humpback Whale

The humpback whale is found throughout all oceans of the World (Clapham 2009), with recent genetic evidence suggesting three separate subspecies: North Pacific, North Atlantic, and Southern Hemisphere (Jackson

et al.

2014). Nonetheless, genetic analyses suggest some gene flow (either past or present) between the North and South Pacific (

e.g.,

Jackson

et al.

2014; Bettridge

et al.

2015). Although considered to be mainly a coastal species, the humpback whale often traverses deep pelagic areas while migrating (

e.g.,

Mate

et al.

1999; Garrigue

et al.

2015).

North Pacific humpback whales migrate between summer feeding grounds along the Pacific Rim and the Bering and Okhotsk seas, and winter calving and breeding areas in subtropical and tropical waters (Pike and MacAskie 1969; Rice 1978; Winn and Reichley 1985; Calambokidis

et al.

2000, 2001, 2008). In the North Pacific, humpbacks 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; Fleming and Jackson 2011; Bettridge

et al.

2015).

Humpback whales were listed as endangered under the Endangered Species Conservation Act (ESCA) in June 1970. In 1973, the ESA replaced the ESCA, and humpbacks continued to be listed as endangered. NMFS recently evaluated the status of the species, and on September 8, 2016, NMFS divided the species into 14 distinct population segments (DPS), removed the current species-level listing, and in its place listed four DPSs as endangered and one DPS as threatened (81 FR 62259, September 8, 2016). The remaining nine DPSs were not listed. There are two DPSs that occur in the action area: The Hawaii DPS, which is not listed under the ESA (81 FR 62259) and the Western North Pacific DPS which is listed as

endangered.

The proposed seismic activity for the Emperor Seamount survey would take place in late spring or early summer 2019. Humpbacks were reported within the proposed action area in May, July, and August (Matsuoka

et al.

2015). Based on the timing of the action, it is likely that humpback whales from the Western North Pacific DPS would be migrating north through the action area to the feeding grounds, and thus be exposed to the action. Hawaii DPS and Mexico DPS humpbacks would also be migrating north at that time of year, but due to the location of the breeding areas of these DPSs, we do not expect their migratory path to take them through the action area.

There is potential for the mixing of the western and eastern North Pacific humpback populations, as several individuals have been seen in the wintering areas of Japan and Hawaii in separate years (Darling and Cerchio 1993; Salden

et al.

1999; Calambokidis

et al.

2001, 2008). Whales from these wintering areas have been shown to travel to summer feeding areas in British Columbia, Canada, and Kodiak Island, Alaska (Darling

et al.

1996;

Calambokidis

et al.

2001), but feeding areas in Russian waters may be most important (Calambokidis

et al.

2008). There appears to be a very low level of interchange between wintering and feeding areas in Asia and those in the eastern and central Pacific (Calambokidis

et al.

2008; Baker

et al.

2013).

Humpbacks use Hawaiian waters for breeding from December to April; peak abundance occurs from late-February to early-April (Mobley

et al.

2001). Most humpbacks have been sighted there in water depths <180 m (Fleming and Jackson 2011), but Frankel

et al.

(1995) detected singers up to 13 km from shore at depths up to 550 m. During vessel-based line-transect surveys in the Hawaiian Islands EEZ in July-December 2002, one humpback whale was sighted on 21 November at ~20.3° N, 154.9° W just north of the Island of Hawaii (Barlow

et al.

2004). Another sighting was made during summer-fall 2010 surveys, but the date and location of that sighting were not reported (Bradford

et al.

2017).

The Hawaiian Islands Humpback Whale National Marine Sanctuary (HIHWNMS) was established in 1992 by the U.S. Congress to protect humpback whales and their habitat in Hawaii (NOAA 2018a). The sanctuary provides essential breeding, calving, and nursing areas necessary for the long-term recovery of the North Pacific humpback whale population. The HIHWNMS provides protection to humpbacks in the shallow waters (from the shoreline to a depth of 100 fathoms or 183 m) around the four islands area of Maui, Penguin Bank; off the north shore of Kauai, the north and south shores of Oahu, and the north Kona and Koahal coast of the island of Hawaii (NOAA 2018a). These areas, as well as some of the waters surrounding them, are also considered breeding BIAs (Baird

et al.

2015). The proposed seismic lines are located at least 10 km from the HIHWNMS (Fig. 1). However, humpback whales are not expected to be encountered in the Hawaiian survey area during the summer.

During Japanese surveys in the western North Pacific from 1994-2014, humpbacks were seen off northern Japan, the Kuril Islands, and Kamchatka (Miyashita 2006; Matsuoka

et al.

2015). Sightings were reported for the months of April through September, with lowest densities in April and September (Matsuoka

et al.

2015). In May and June, sightings were concentrated east of northern Japan between 37° and 43° N; concentrations moved north of 45°N during July and August, off the Kuril Islands and Kamchatka (Mutsuoka

et al.

2015). Humpback whales were encountered within the proposed Emperor Seamount study area in May, July, and August (Matsuoka

et al.

2015).

Thus, humpbacks could be encountered in the Emperor Seamounts survey area during spring and summer, as individuals are migrating to northern feeding grounds at that time. They could also be encountered in the survey area during fall, on their southbound migration. Humpback whale occurrences in the Hawaii survey area during the time of the proposed survey would be rare.

Bryde's Whale

Bryde's whale occurs in all tropical and warm temperate waters in the Pacific, Atlantic, and Indian oceans, between 40° N and 40° S (Kato and Perrin 2009). It is one of the least known large baleen whales, and its taxonomy is still under debate (Kato and Perrin 2009).

B. brydei

is commonly used to refer to the larger form or “true” Bryde's whale and

B. edeni

to the smaller form; however, some authors apply the name

B. edeni

to both forms (Kato and Perrin 2009). Although there is a pattern of movement toward the Equator in the winter and the poles during the summer, Bryde's whale does not undergo long seasonal migrations, remaining in warm (≥16° C) water year-round (Kato and Perrin 2009). Bryde's whales are known to occur in both shallow coastal and deeper offshore waters (Jefferson

et al.

2015).

In the Pacific United States, a Hawaii and an Eastern Tropical Pacific stock are recognized (Carretta

et al.

2017). In Hawaii, Bryde's whales are typically seen offshore (

e.g.,

Barlow

et al.

2004; Barlow 2006), but Hopkins

et al.

(2009) reported a Bryde's whale within 70 km of the Main Hawaiian Islands. During summer-fall surveys of the Hawaiian Islands EEZ, 13 sightings were made in 2002 (Barlow 2006), and 32 sightings were reported during 2010 (Bradford

et al.

2017). Bryde's whales were primarily sighted in the western half of the Hawaiian Islands EEZ, with the majority of sightings associated with the Northwestern Hawaiian Islands; none was made in the proposed survey area (Barlow

et al.

2004; Barlow 2006; Bradford

et al.

2013; Forney

et al.

2015; Carretta

et al.

2017).

Bryde's whales have been regularly seen during Japanese summer sighting surveys in the western North Pacific, south of 43° S (Hakamada

et al.

2009, 2017), and individual movements have been tracked with satellite tags in offshore waters off Japan (Murase

et al.

2016). No recent sightings have been made in the proposed Emperor Seamounts survey area, but commercial catches have been reported there (IWC 2007a).

Limited numbers of Bryde's whale could occur in the Emperor Seamounts survey area, but its distributional range is generally to the south of this region. However, it could occur in the Hawaiian survey area at any time of the year.

Common Minke Whale

The common minke whale has a cosmopolitan distribution ranging from the tropics and subtropics to the ice edge in both hemispheres (Jefferson

et al.

2015). In the Northern Hemisphere, minke whales are usually seen in coastal areas, but can also be seen in pelagic waters during northward migrations in spring and summer, and southward migration in autumn (Stewart and Leatherwood 1985). In the North Pacific, the summer range extends to the Chukchi Sea; in the winter, minke whales move further south to within 2° of the Equator (Perrin and Brownell 2009). The International Whaling Commission (IWC) recognizes three stocks 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).

In U.S. Pacific waters, three stocks are recognized: Alaska, Hawaii, and California/Oregon/Washington stocks (Carretta

et al.

2017). In Hawaii, the minke whale is thought to occur seasonally from November through March (Rankin and Barlow 2005). It is generally believed to be uncommon in Hawaiian waters; however, several studies using acoustic detections suggest that minke whales may be more common than previously thought (Rankin

et al.

2007; Oswald

et al.

2011). Acoustic detections have been recorded around the Hawaiian Islands during fall-spring surveys in 1997 and 2000-2006 (Rankin and Barlow 2005; Barlow

et al.

2008; Rankin

et al.

2008), and from seafloor hydrophones positioned ~50 km from the coast of Kauai during February-April 2006. Similarly, passive acoustic detections of minke whales have been recorded at the ALOHA station (22.75° N, 158° W) from October-May for decades (Oswald

et al.

2011).

A lack of sightings is likely related to misidentification or low detection capability in poor sighting conditions (Rankin

et al.

2007). Two minke whale sightings were made west of 167° W, one in November 2002 and one in October 2010, during surveys of the Hawaiian Islands EEZ (Barlow

et al.

2004; Bradford

et al.

2013; Carretta

et al.

2017). Numerous additional sightings in

the EEZ were made by observers on Hawaii-based longline fishing vessels, including four near the proposed survey area to the north and south of the Main Hawaiian Islands (Carretta

et al.

2017).

Minke whales have been seen regularly during Japanese sighting surveys in the western North Pacific during summer (Miyashita 2006; Hakamada

et al.

2009), and one sighting was made in August 2010 in offshore waters off Japan during the Shatsky Rise cruise (Holst and Beland 2010). Minke whales were sighted within the Emperor Seamounts survey area in the greatest numbers in August, with the lowest numbers occurring during May and June (Hakamada

et al.

2009).

Thus, minke whales could be encountered in the Emperor Seamounts survey area during spring and summer, and likely fall, and could occur in limited numbers in the Hawaiian survey area during the summer.

Sei Whale

The sei whale occurs in all ocean basins (Horwood 2009), 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 2009). 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).

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. In the U.S. Pacific, an Eastern North Pacific and a Hawaii stock are recognized (Carretta

et al.

2017). In Hawaii, the occurrence of sei whales is considered rare (DoN 2005). However, six sightings were made during surveys in the Hawaiian Islands EEZ in July-December 2002 (Barlow 2006), including several along the north coasts of the Main Hawaiian Islands (Barlow

et al.

2004). All sightings occurred in November, with one sighting reported near proposed seismic Line 3 north of Hawaii Island (Barlow

et al.

2004). Bradford

et al.

(2017) reported two sightings in the northwestern portion of the Hawaiian Islands EEZ during summer-fall surveys in 2010. Hopkins

et al.

(2009) sighted one group of three subadult sei whales northeast of Oahu in November 2007. Sei whale vocalizations were also detected near Hawaii during November 2002 (Rankin and Barlow 2007). Breeding and calving areas for this species in the Pacific are unknown, but those sightings suggest that Hawaii may be an important reproductive area (Hopkins

et al.

2009).

Sei whales have been regularly seen during Japanese surveys during the summer in the western North Pacific (Miyashita 2006; Hakamada

et al.

2009; Sasaki

et al.

2013). Sei whales have been sighted in and near the Emperor Seamounts survey area, with the greatest numbers reported for July and August; few sightings were made during May and June (Hakamada

et al.

2009).

Thus, sei whales could be encountered in both the Emperor Seamounts and Hawaii survey areas during spring and summer.

Fin Whale

The fin whale is widely distributed in all the World's oceans (Gambell 1985), although it is most abundant in temperate and cold waters (Aguilar 2009). Nonetheless, its overall range and distribution are not well known (Jefferson

et al.

2015). A recent review of fin whale distribution in the North Pacific noted the lack of sightings across the pelagic waters between eastern and western winter areas (Mizroch

et al.

2009). The fin whale most commonly occurs offshore, but can also be found in coastal areas (Aguilar 2009). Most populations migrate seasonally between temperate waters where mating and calving occur in winter, and polar waters where feeding occurs in summer (Aguilar 2009). However, recent evidence suggests that some animals may remain at high latitudes in winter or low latitudes in summer (Edwards

et al.

2015).

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 1985). In the U.S., three stocks are recognized in the North Pacific: California/Oregon/Washington, Hawaii, and Alaska (Northeast Pacific) (Carretta

et al.

2017). 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, including near the Emperor Seamounts survey area (

e.g.,

Moore

et al.

2006; Stafford

et al.

2007, 2009; Edwards

et al.

2015). In the central North Pacific, call rates peak during fall and winter (Moore

et al.

1998, 2006; Watkins

et al.

2000a,b).

Sightings of fin whales have been made in Hawaiian waters during fall and winter (Edwards

et al.

2015), but fin whales are generally considered uncommon at that time (DoN 2005). During spring and summer, their occurrence in Hawaii is considered rare (DoN 2005; see Edwards

et al.

2015). There were five sightings of fin whales during summer-fall surveys in 2002, with sightings during every month except August (Barlow

et al.

2004). Most sightings were made to the northwest of the Main Hawaiian Islands; one sighting was made during October southeast of Oahu (Barlow

et al.

2004). Two sightings were made in the Northwestern Hawaiian Islands during summer-fall 2010 (Carretta

et al.

2017; Bradford

et al.

2017). Two additional sightings in the EEZ were made by observers on Hawaii-based longline fishing vessels, including one near proposed seismic Line 3 north of Maui (Carretta

et al.

2017). Fin whale vocalizations have also been detected in Hawaiian waters, mainly during winter (Oleson

et al.

2014, 2016).

In the western Pacific, fin whales are seen off northern Japan, the Kuril Islands, and Kamchatka during the summer (Miyashita 2006; Matsuoka

et al.

2015). During Japanese sightings surveys in the western North Pacific from 1994-2014, the fin whale was sighted more frequently than the blue, humpback, or right whale (Matsuoka

et al.

2015). During May-June, main distribution areas occurred from 35-40° N and moved north of 40° N during July and August; high densities were reported north of 45° N (Matsuoka

et al.

2015). During these surveys, fin whales were seen in the proposed Emperor Seamounts survey area from May through September, with most sightings during August (Matsuoka

et al.

2015). Summer sightings in the survey area during 1958-2000 were also reported by Mizroch

et al.

(2009) and during July-September 2005 (Miyashita 2006). Edwards

et al.

(2015) reported fin whale sightings within or near the Emperor

Seamounts survey area from spring through fall.

Thus, fin whales could be encountered in the Emperor Seamounts survey area from spring through fall, and could occur in the Hawaiian survey area during summer in limited numbers.

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). Blue whale migration is less well defined than for some other rorquals, and their movements tend to be more closely linked to areas of high primary productivity, and hence prey, to meet their high energetic demands (Branch

et al.

2007). Generally, blue whales are seasonal migrants between high latitudes in the summer, where they feed, and low latitudes in the winter, where they mate and give birth (Lockyer and Brown 1981). Some individuals may stay in low or high latitudes throughout the year (Reilly and Thayer 1990; Watkins

et al.

2000b).

In the North Pacific, blue whale calls are detected year-round (Stafford

et al.

2001, 2009; Moore

et al.

2002, 2006; Monnahan

et al.

2014). Stafford

et al.

(2009) reported that sea-surface temperature is a good predictor variable for blue whale call detections in the North Pacific. Although it has been suggested that there are at least five subpopulations in the North Pacific (Reeves

et al.

1998), analysis of calls monitored from the U.S. Navy Sound Surveillance System (SOSUS) and other offshore hydrophones (

e.g.,

Stafford

et al.

1999, 2001, 2007; Watkins

et al.

2000a; Stafford 2003) suggests that there are two separate populations: One in the eastern and one in the central North Pacific (Carretta

et al.

2017). The Eastern North Pacific Stock includes whales that feed primarily off California from June-November and winter off Central America (Calambokidis

et al.

1990; Mate

et al.

1999). The Central North Pacific Stock feeds off Kamchatka, south of the Aleutians and in the Gulf of Alaska during summer (Stafford 2003; Watkins

et al.

2000b), and migrates to the western and central Pacific (including Hawaii) to breed in winter (Stafford

et al.

2001; Carretta

et al.

2017). 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).

Blue whales are considered rare in Hawaii (DoN 2005). However, call types from both stocks have been recorded near Hawaii during August-April, although eastern calls were more prevalent; western calls were mainly detected during December-March, whereas eastern calls peaked during August and September and were rarely heard during October-March (Stafford

et al.

2001). No sightings were made in the Hawaiian Islands EEZ during surveys in July-December 2002 (Barlow

et al.

2004; Barlow 2006). One sighting was made in the Northwestern Hawaiian Islands during August-October 2010 (Bradford

et al.

2013). Three additional sightings in the EEZ were made by observers on Hawaii-based longline fishing vessels during 1994-2009, including one in offshore waters north of Maui (Carretta

et al.

2017).

In the western North Pacific, blue whale calls have been detected throughout the year, but are more prevalent from July-December (Stafford

et al.

2001). Numerous blue whale sightings have also been made in the western North Pacific during Japanese surveys during 1994-2014 (Miyashita 2006; Matsuoka

et al.

2015). A northward migration pattern was evident, with the main distribution occurring from 35-40° N during May and June, and north of 40° N during July and August (Matsuoka

et al.

2015). High densities were reported north of 45° N (Matsuoka

et al.

2015). Blue whales were seen in the proposed Emperor Seamounts survey area during August and September and adjacent to the area during May and July (Matsuoka

et al.

2015).

Thus, blue whales could be encountered in the Emperor Seamounts and Hawaii survey areas at any time of the year, but are more likely to occur in the Emperor Seamounts area during summer, and in the Hawaii survey area during winter.

Sperm Whale

The sperm whale is the largest of the toothed whales, with an extensive worldwide distribution from the edge of the polar pack ice to the Equator (Whitehead 2009). Sperm whale distribution is linked to its social structure: Mixed groups of adult females and juveniles of both sexes generally occur in tropical and subtropical waters at latitudes less than ~40° (Whitehead 2009). After leaving their female relatives, males gradually move to higher latitudes with the largest males occurring at the highest latitudes and only returning to tropical and subtropical regions to breed. Sperm whales generally are distributed over large areas that have high secondary productivity and steep underwater topography, in waters at least 1000 m deep (Jaquet and Whitehead 1996). They are often found far from shore, but can be found closer to oceanic islands that rise steeply from deep ocean waters (Whitehead 2009).

Sperm whale vocalizations have been recorded throughout the Central and Western Pacific Ocean (Merkens

et al.

2016). Sperm whales are widely distributed in Hawaiian waters throughout the year (Mobley

et al.

2000) and are considered a separate stock from the Oregon/Washington/California stock in U.S. waters (Carretta

et al.

2017). Higher densities occur in deep, offshore waters (Forney

et al.

2015). During summer-fall surveys of the Hawaiian Islands EEZ, 43 sightings were made in 2002 (Barlow 2006) and 41 were made in 2010 (Bradford

et al.

2013). Sightings were widely distributed across the EEZ during both surveys; numerous sightings occurred in and near the proposed survey area (Barlow

et al.

2004; Barlow 2006; Bradford

et al.

2017). All sightings during surveys of the Main Hawaiian Islands in 2000-2012 were made in water >1000 m in depth, with most sightings in areas >3000 m deep (Baird

et al.

2013). Sightings were made during surveys of the Island of Hawaii during all seasons, including near proposed seismic Line 1; no sightings were made off Oahu (Baird

et al.

2013). Sperm whales were also detected acoustically off the west coast of the Hawaii Island year-round (Klinck

et al.

2012; Giorli

et al.

2016).

Sperm whales have been regularly seen in the western North Pacific during Japanese surveys during summer (Miyashita 2006; Hakamada

et al.

2009), and sightings were also made in offshore waters east of Japan and on the Shatsky Rise during a summer survey in 2010 (Holst and Beland 2010). During winter, few sperm whales are observed off the east coast of Japan (Kato and Miyashita 1998). Sperm whales have been sighted in and near the Emperor Seamounts survey area from May through August, with the greatest numbers occurring there during June-August (Miyashita 2006; Hakamada

et al.

2009).

Thus, sperm whales could be encountered in the Emperor Seamounts and Hawaii survey areas at any time of the year.

Pygmy and Dwarf Sperm Whales

The pygmy and dwarf sperm whales are distributed widely throughout tropical and temperate seas, but their precise distributions are unknown because much of what we know of the species comes from strandings (McAlpine 2009). It has 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 or ETP (Wade and Gerrodette 1993).

Kogia

spp. 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 (Würsig

et al.

1998). Although there are few useful estimates of abundance for pygmy or dwarf sperm whales anywhere in their range, they are thought to be fairly common in some areas.

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). However, several studies have suggested that pygmy sperm whales live mostly beyond the continental shelf edge, whereas dwarf sperm whales tend to occur closer to shore, often over the continental shelf (Rice 1998; Wang

et al.

2002; MacLeod

et al.

2004). On the other hand, McAlpine (2009) and Barros

et al.

(1998) suggested that dwarf sperm whales could be more pelagic and dive deeper than pygmy sperm whales.

Vocalizations of

Kogia

spp. have been recorded in the North Pacific Ocean (Merkens

et al.

2016). An insular resident population of dwarf sperm whales occurs within ~20 km from the Main Hawaiian Islands throughout the year (Baird

et al.

2013; Oleson

et al.

2013). During small-boat surveys in 2000-2012, dwarf sperm whales were sighted in all water depth categories up to 5000 m deep, but the highest sighting rates were in water 500-1,000 m deep (Baird

et al.

2013). Of a total of 74 sightings during those surveys, most sightings were made off the Island of Hawaii, including near proposed seismic Line 1 (Baird

et al.

2013). The area off the west coast of the Island of Hawaii is considered a BIA for dwarf sperm whales (Baird

et al.

2015). Only one sighting was made off Oahu (Baird

et al.

2013).

Only five sightings of pygmy sperm whales were made during the surveys, including several off the west coast of the Island of Hawaii; the majority of sightings were made in water >3,000 m deep (Baird

et al.

2013). The dwarf sperm whale was one of the most abundant species during a summer-fall survey of the Hawaiian EEZ in 2002 (Barlow 2006); during that survey, two sightings of pygmy sperm whales, five sightings of dwarf sperm whales, and one sighting of an unidentified

Kogia

sp. were made. All sightings were made in the western portion of the EEZ (Barlow

et al.

2004; Barlow 2006). During summer-fall surveys of the Hawaiian EEZ in 2010, one dwarf sperm whale and one unidentified

Kogia

sp. were sighted (Bradford

et al.

2017); no sightings were made in or near the proposed survey area (Carretta

et al.

2017).

Although

Kogia

spp. have been seen during Japanese sighting surveys in the western North Pacific in August-September (Kato

et al.

2005), to the best of our knowledge, there are no direct data available for the Emperor Seamounts survey area with respect to

Kogia

spp. It is possible that

Kogia

spp could occur at both survey locations is limited numbers.

Cuvier's Beaked Whale

Cuvier's beaked whale is the most widespread of the beaked whales, occurring in almost all temperate, subtropical, and tropical waters and even some sub-polar and polar waters (MacLeod

et al.

2006). It is likely the most abundant of all beaked whales (Heyning and Mead 2009). Cuvier's beaked whale is found in deep water over and near the continental slope (Jefferson

et al.

2015).

Cuvier's beaked whale has been sighted during surveys in Hawaii (Barlow 2006; Baird

et al.

2013; Bradford

et al.

2017). Resighting and telemetry data suggest that a resident insular population of Cuvier's beaked whale may exist in Hawaii, distinct from offshore, pelagic whales (

e.g.

McSweeney

et al.

2007; Baird

et al.

2013; Oleson

et al.

2013). During small-boat surveys around the Hawaiian Islands in 2000-2012, sightings were made in water depths of 500-4,000 m off the west coast of the Island of Hawaii during all seasons (Baird

et al.

2013). The waters around the Island of Hawaii are considered a BIA for Cuvier's beaked whale (Baird

et al.

2015); proposed seismic Line 1 would traverse this area.

During summer-fall surveys of the Hawaiian Islands EEZ, three sightings of Cuvier's beaked whale were made in the western portion of the EEZ in 2002 (Barlow 2006) and 23 were made in the EEZ in 2010 (Bradford

et al.

2013). It was one of the most abundant cetacean species sighted in 2002 (Barlow 2006). In 2010, most sightings were made in nearshore waters of the Northwestern Hawaiian Islands, but one was made on the west coast of the Island of Hawaii, and another was made far offshore and to the southwest of Kauai (Carretta

et al.

2017). Cuvier's beaked whales were also reported near proposed seismic line 1 during November 2009 (Klinck

et al.

2012). They have also been detected acoustically at hydrophones deployed near the Main Hawaiian Islands during spring and fall (Baumann-Pickering

et al.

2014, 2016), including off the west coast of the Island of Hawaii (Klinck

et al.

2012). Probable acoustic detections were also made at Cross Seamount, south of the Main Hawaiian Islands, at 18.72° N, 158.25° W (Johnston 2008).

Cuvier's beaked whale has been seen during Japanese sighting surveys in August-September in the western North Pacific (Kato

et al.

2005). It has also been detected acoustically in the Aleutian Islands (Baumann-Pickering

et al.

2014). There is very little information on this species for the Emperor Seamounts survey area, but what is known of its distribution and habitat preferences suggests that it could occur there. Therefore, Cuvier's beaked whales could occur at both survey locations.

Longman's Beaked Whale

Longman's beaked whale, also known Indo-Pacific beaked whale, used to be one of the least known cetacean species, but it is now one of the more frequently sighted beaked whales (Pitman 2009a). Longman's beaked whale occurs in tropical waters throughout the Indo-Pacific, with records from 30° S to 40° N (Pitman 2009a). Longman's beaked whale is most often sighted in waters with temperatures ≥26°C and depth >2,000 m, and sightings have also been reported along the continental slope (Anderson

et al.

2006; Pitman 2009a).

During small-boat surveys around the Hawaiian Islands in 2000-2012, a single sighting of Longman's beaked whale was made off the west coast of the Island of Hawaii during summer (Baird

et al.

2013). During summer-fall surveys of the Hawaiian Islands EEZ, one sighting was made in 2002 and three were made in 2010; one sighting was made in offshore waters southwest of Ohau, and another was made at the edge of the EEZ southwest of the Island of Hawaii (Barlow

et al.

2004; Barlow 2006; Bradford

et al.

2013). Acoustic detections have been made at the Palmyra Atoll and the Pearl and Hermes Reef (Baumann-Pickering

et al.

2014).

Longman's beaked whale has been seen during Japanese sighting surveys in August-September in the western North Pacific (Kato

et al.

2005). However, what is known about its distribution and habitat preferences suggests that it does not occur in the Emperor Seamounts survey area.

Blainville's Beaked Whale

Blainville's beaked whale is found in tropical and warm temperate waters of all oceans (Pitman 2009b). It has the widest distribution throughout the world of all mesoplodont species and appears to be common (Pitman 2009b).

It is commonly sighted in some areas of Hawaii (Jefferson

et al.

2015).

McSweeney

et al.

(2007), Schorr

et al.

(2009), Baird

et al.

(2013), and Oleson

et al.

(2013) have suggested the existence of separate insular and offshore Blainville's beaked whales in Hawaiian waters. During small-boat surveys around the Hawaiian Islands in 2000-2012, sightings were made in shelf as well as deep water, with the highest sighting rates in water 3500-4000 m deep, followed by water 500-1000 m deep (Baird

et al.

2013). Sightings were made during all seasons off the island of Hawaii, as well as off Oahu (Baird

et al.

2013). The area off the west coast of Hawaii Island is considered a BIA for Blainville's beaked whale (Baird

et al.

2015); proposed seismic Line 1 would traverse this BIA. During summer-fall shipboard surveys of the Hawaiian Islands EEZ, three sightings were made in 2002 and two were made in 2010, all in the western portion of the EEZ (Barlow

et al.

2004; Barlow 2006; Bradford

et al.

2013). In addition, there were four sightings of unidentified

Mesoplodon

there in 2002 (Barlow

et al.

2004; Barlow 2006) and 10 in 2010 (Bradford

et al.

2013).

Blainville's beaked whales have also been detected acoustically at hydrophones deployed near the Main Hawaiian Islands throughout the year (Baumann-Pickering

et al.

2014, 2016; Henderson

et al.

2016; Manzano-Roth

et al.

2016), including off the west coast of the Island of Hawaii, near proposed seismic Line 1, during October-November 2009 (Klinck

et al.

2012). Probable acoustic detections were also made at Cross Seamount, south of the Main Hawaiian Islands, at 18.72° N, 158.25° W (Johnston 2008). Blainville's beaked whale is expected to be absent from the Emperor Seamounts survey area.

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). In the western Pacific Ocean, Stejneger's beaked whale has been seen during Japanese sighting surveys during August-September (Kato

et al.

2005). Seasonal peaks in strandings along the western coast of Japan suggest that this species may migrate north in the summer from the Sea of Japan (Mead 1989). They have also been detected acoustically in the Aleutian Islands during summer, fall, and winter (Baumann-Pickering

et al.

2014).

Given its distributional range (see Jefferson

et al.

2015), Stejneger's beaked whale could occur in the Emperor Seamounts survey area. It does not occur in the Hawaiian survey area.

Ginkgo-Toothed Beaked Whale

Ginkgo-toothed beaked whale is only known from stranding and capture records (Mead 1989; Jefferson

et al.

2015). It is hypothesized to occupy tropical and warm temperate waters of the Indian and Pacific oceans (Pitman 2009b). Its distributional range in the North Pacific extends from Japan to the Galapagos Islands, and there are also records for the South Pacific as far south as Australia and New Zealand (Jefferson

et al.

2015). Although its distributional range is thought to be south of Hawaii (Jefferson

et al.

2015), vocalizations likely from this species have been detected acoustically at hydrophones deployed near the Main Hawaiian Islands and just to the south at Cross Seamount (18.72° N, 158.25° W), as well as at the Wake Atoll and Mariana Islands (Baumann-Pickering

et al.

2014, 2016). However, no sightings have been made in Hawaiian waters (Barlow 2006; Baird

et al.

2013; Bradford

et al.

2017).

The ginkgo-toothed beaked whale could occur in the southern parts of the Hawaiian survey area, but it is not expected to occur in the Emperor Seamounts survey area.

Deraniyagala's Beaked Whale

Deraniyagala's beaked whale is a newly recognized species of whale that recently has been described for the tropical Indo-Pacific, where it is thought to occur between ~15° N and ~10° S (Dalebout

et al.

2014). Strandings have been reported for the Maldives, Sri Lanka, the Seychelles, Kiribati, and Palmyra Atoll (Dalebout

et al.

2014), and acoustic detections have been made at Palmyra Atoll and Kingman Reef in the Line Islands (Baumann-Pickering

et al.

2014). It is closely related to ginkgo-toothed beaked whale, but DNA and morphological data have shown that the two are separate species (Dalebout

et al.

2014).

Although possible, Deraniyagala's beaked whale is unlikely to occur in the Hawaiian survey area, and its range does not include the Emperor Seamounts survey area.

Hubb's Beaked Whale

Hubb's beaked whale occurs in temperate waters of the North Pacific (Mead 1989). Most of the stranding records are from California (Willis and Baird 1998). Its distribution appears to be correlated with the deep subarctic current (Mead

et al.

1982). Its range is believed to be continuous across the North Pacific (Macleod

et al.

2006), although this has yet to be substantiated because very few direct at-sea observations exist.

Hubb's beaked whale was seen during Japanese sighting surveys in the western North Pacific during August-September (Kato

et al.

2005). However, there is very little information on this species for the Emperor Seamounts survey area, but what is known of its distribution suggests it would occur in limited numbers. The Hubb's beaked whale is unlikely to occur in the Hawaiian survey area.

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 have been recognized—the common slate-gray form and a smaller, rare black form (Morin

et al.

2017). The gray form is seen off Japan, in the Aleutians, and on the west coast of North America, whereas the black from has been reported for northern Japan and the Aleutians (Morin

et al.

2017). Recent genetic studies suggest that the black form could be a separate species (Morin

et al.

2017).

Baird's beaked whale is currently divided into three distinct stocks: Sea of Japan, Okhotsk Sea, and Bering Sea/eastern North Pacific (Balcomb 1989; Reyes 1991). The whales occur year-round in the Okhotsk Sea and Sea of Japan (Kasuya 2009). 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 1,000-3,000 m deep (Jefferson

et al.

1993; Kasuya and Ohsumi 1984; Kasuya 2009).

Off Japan's Pacific coast, Baird's beaked whales start to appear in May, numbers increase over the summer, and decrease toward October (Kasuya 2009). During this time, they are nearly absent in offshore waters (Kasuya 2009). Kato

et al.

(2005) also reported the presence of Baird's beaked whales in the western North Pacific in August-September. They have also been detected acoustically in the Aleutian Islands (Baumann-Pickering

et al.

2014).

Baird's beaked whale could be encountered at the Emperor Seamounts survey area, but its distribution does not include Hawaiian waters.

Rough-Toothed Dolphin

The rough-toothed dolphin is distributed worldwide in tropical to

warm temperate oceanic waters (Miyazaki and Perrin 1994; Jefferson 2009). In the Pacific, it occurs from central Japan and northern Australia to Baja California, Mexico, and southern Peru (Jefferson 2009). It generally occurs in deep, oceanic waters, but can be found in shallower coastal waters in some regions (Jefferson

et al.

2015).

The rough-toothed dolphin is expected to be one of the most abundant cetaceans in the Hawaiian survey area, based on previous surveys in the area (Barlow

et al.

2004; Barlow 2006; Baird

et al.

2013; Bradford

et al.

2017). Higher densities are expected to occur in deeper waters around the Hawaiian Islands than in far offshore waters of the Hawaiian EEZ (Forney

et al.

2015). During small-boat surveys around the Hawaiian Islands in 2000-2012, it was sighted in water as deep as 5,000 m, with the highest sighting rates in water >3500 m deep, throughout the year (Baird

et al.

2013). Sightings were made off the Island of Hawaii as well as Oahu (Baird

et al.

2013). The area west of the Island of Hawaii is considered BIA (Baird

et al.

2015); proposed seismic Line 1 would traverse this area. During summer-fall surveys of the Hawaiian Islands EEZ, rough-toothed dolphins were observed throughout the EEZ, including near the proposed survey area to the north and south of the Main Hawaiian Islands; in total, there were 18 sightings in 2002 and 24 sightings in 2010 (Barlow 2006; Barlow

et al.

2004; Bradford

et al.

2017). Acoustic detections have also been made in Hawaiian waters (Rankin

et al.

2015).

In the western North Pacific Ocean, rough-toothed dolphins have been seen during Japanese sighting surveys during August-September (Kato

et al.

2005). However, there is very little information on this species for the Emperor Seamounts survey area, but what is known of its distribution suggests that it is unlikely to occur there.

Common Bottlenose Dolphin

The bottlenose dolphin occurs in tropical, subtropical, and temperate waters throughout the World (Wells and Scott 2009). Generally, there are two distinct bottlenose dolphin ecotypes, one mainly found in coastal waters and one mainly found in oceanic waters (Duffield

et al.

1983; Hoelzel

et al.

1998; Walker

et al.

1999). As well as inhabiting different areas, these ecotypes differ in their diving abilities (Klatsky 2004) and prey types (Mead and Potter 1995).

The bottlenose dolphin is expected to be one of the most abundant cetaceans in the Hawaiian survey area, based on previous surveys in the region (Barlow 2006; Baird

et al.

2013; Bradford

et al.

2017). Higher densities are expected to occur around the Hawaiian Islands than in far offshore waters of the Hawaiian EEZ (Forney

et al.

2015). Photo-identification studies have shown that there are distinct resident populations at the four island groups in Hawaii (Kauai & Niihau, Oahu, the 4-island region, and the Island of Hawaii); the 1,000-m isobath serves as the boundary between these resident insular stocks and the Hawaii pelagic stock (Martien

et al.

2012). Note that the Kauai/Niihau stock range does not occur near the proposed tracklines and will not be discussed further. Additionally, 98.5 percent of the Hawaii survey will take in deep (>1,000 m) water. The areas where the insular stocks are found are also considered BIAs (Baird

et al.

2015). Proposed seismic Lines 1 and 2 would traverse the BIAS to the west of Oahu and west of the Island of Hawaii.

During small-boat surveys around the Hawaiian Islands in 2000-2012, the bottlenose dolphin was sighted in water as deep as 4,500 m, but the highest sighting rates occurred in water <500 m deep (Baird

et al.

2013). Sightings were made during all seasons off the Island of Hawaii, including near proposed seismic Line 1, and off Oahu (Baird

et al.

2013). Common bottlenose dolphins were also observed during summer-fall surveys of the Hawaiian EEZ, mostly in nearshore waters but also in offshore waters, including in and near the proposed survey area among the Main Hawaiian Islands, and to the north and south of the islands (see map in Carretta

et al.

2017). Fifteen sightings were made in 2002 (Barlow 2006), and 19 sightings were made in 2010 (Bradford

et al.

2017).

In the western North Pacific Ocean, common bottlenose dolphins have been sighted off the east coast of Japan during summer surveys in 1983-1991 (Miyashita 1993a). Although only part of the proposed Emperor Seamounts survey area was surveyed during the month of August, no sightings were made within or near the survey area (Miyashita 1993a). Offshore sightings to the south of the proposed survey area were made during September (Miyashita 1993a), and there is also a record just to the southwest of the survey area during summer (Kanaji

et al.

2017). The distributional range of the common bottlenose dolphin does not appear to extend north to the Emperor Seamounts survey area; thus, it is not expected to be encountered during the survey.

Short-Beaked Common Dolphin

The common dolphin is found in tropical and warm temperate oceans around the World (Perrin 2009a). It ranges as far south as 40° S in the Pacific Ocean, is common in coastal waters 200-300 m deep, and is also associated with prominent underwater topography, such as seamounts (Evans 1994). There are two species of common dolphins: The short-beaked common dolphin (

D. delphis

) and the long-beaked common dolphin (

D. capensis

). The short-beaked common dolphin is mainly found in offshore waters, and the long-beaked common dolphin is more prominent in coastal areas.

During Japanese sighting surveys in the western North Pacific in August-September, both long- and short-beaked common dolphins have been seen (Kato

et al.

2005). Kanaji

et al.

(2017) reported one record to the southwest of the proposed survey area during summer. There are also bycatch records of short-beaked common dolphins near the Emperor Seamounts survey area during summer and winter (Hobbs and Jones 1993). Based on information regarding the distribution and habitat preferences, only the short-beaked common dolphin could occur in the region.

Both the the short-beaked and long-beaked common dolphin are not expected to occur in the Hawaiian survey area as no sightings have been made of either species during surveys of the Hawaii Islands (Barlow 2006; Baird

et al.

2013; Bradford

et al.

2017).

Pantropical Spotted Dolphin

The pantropical spotted dolphin is one of the most abundant cetaceans and is distributed worldwide in tropical and some subtropical waters (Perrin 2009b), between ~40° N and 40° S (Jefferson

et al.

2015). It is found primarily in deeper waters, but can also be found in coastal, shelf, and slope waters (Perrin 2009b). There are two forms of pantropical spotted dolphin: Coastal and offshore. The offshore form inhabits tropical, equatorial, and southern subtropical water masses; the pelagic individuals around the Hawaiian Islands belong to a stock distinct from those in the ETP (Dizon

et al.

1991; Perrin 2009b). Spotted dolphins are commonly seen together with spinner dolphins in mixed-species groups,

e.g.,

in the ETP (Au and Perryman 1985), off Hawaii (Psarakos

et al.

2003), and in the Marquesas Archipelago (Gannier 2002).

The pantropical spotted dolphin is expected to be one of the most abundant cetaceans in the proposed Hawaiian survey area based on previous surveys in the region (Baird

et al.

2013; Barlow 2006; Bradford

et al.

2017). Higher densities are expected to occur around the Main Hawaiian Islands than elsewhere in the Hawaiian EEZ (Forney

et al.

2015). Sightings rates peak in depths from 1,500 to 3,500 m (Baird

et al.

2013). The Main Hawaiian Islands insular spotted dolphin stock consists of two separate stocks at Oahu and 4-Islands (which extend 20 km seaward), and one stock off the Island of Hawaii, up to 65 km from shore (Carretta

et al.

2017). Spotted dolphins outside of these insular stocks are part of the Hawaii pelagic stock (Carretta

et al.

2017).

During small-boat surveys around the Hawaiian Islands in 2000-2012, the pantropical spotted dolphin was sighted in all water depth categories, with the lowest sighting rate in water <500 m (Baird

et al.

2013). It was observed during all seasons, including off of Hawaii Island and Oahu (Baird

et al.

2013). It was also seen during summer-fall surveys of the Hawaiian Islands EEZ including in the proposed survey area, with sightings to the north, south, and around the Main Hawaiian Islands (see map in Carretta

et al.

2017); 14 sightings were made in 2002 (Barlow 2006), and 12 sightings were made in 2010 (Bradford

et al.

2017). The areas off southwest Oahu, south of Lanai, and west of the Island of Hawaii are considered BIAs (Baird

et al.

2015); proposed seismic Line 1 traverses the BIA west of the Island of Hawaii. One sighting was made in July 2010 in the northwestern portion of the Hawaiian EEZ during the Shatsky Rise cruise (Holst and Beland 2010).

In the western Pacific, pantropical spotted dolphins occur from Japan south to Australia; they have been hunted in drive fisheries off Japan for decades (Kasuya 2007). A sighting of three individuals was made in offshore waters east of Japan in August 2010 during the Shatksy Rise cruise (Holst and Beland 2010). Pantropical spotted dolphins were also sighted off the east coast of Japan during summer surveys in 1983-1991, with the highest densities in offshore waters between 30° N and 37° N (Miyashita 1993a). Although only part of the proposed Emperor Seamounts survey area was surveyed during the month of August, no sightings were made within or near the survey area; offshore sightings to the south of the proposed survey area were made during August and September (Miyashita 1993a). The distributional range of the pantropical spotted dolphin does not appear to extend north to the Emperor Seamounts survey area; thus, it is not expected to be encountered during the survey.

Spinner Dolphin

The spinner dolphin is pantropical in distribution, including oceanic tropical and sub-tropical waters between 40° N and 40° S (Jefferson

et al.

2015). It is generally considered a pelagic species (Perrin 2009b), but can also be found in coastal waters and around oceanic islands (Rice 1998). In Hawaii, spinner dolphins belong to the offshore stock (

S.l. longirostris;

Gray's spinner) that is separate from animals in the ETP (Dizon

et al.

1991).

The spinner dolphin is expected to be one of the most abundant cetaceans in the Hawaiian survey area, based on previous surveys in the region (Barlow 2006; Baird

et al.

2013; Bradford

et al.

2017). Higher densities are expected to occur around in offshore waters south of the Hawaiian Islands (Forney

et al.

2015). There are six separate stocks managed within the Hawaiian EEZ—the Hawaii Island, Oahu/4-islands, Kauai/Niihau, Pearl & Hermes Reef, Midway Atoll/Kure, and Hawaiian pelagic stocks (Carretta

et al.

2017); individuals from three of these stocks (Hawaii pelagic, Hawaii Island, Oahu/4-Islands) are expected to overlap with the proposed survey area. The boundaries of these stocks are out to 10 n.mi. from shore; these regions are also considered BIAs (Baird

et al.

2015). Proposed seismic Line 1 traverses the BIA west of the Island of Hawaii.

During small-boat surveys around the Hawaiian Islands in 2000-2012, it was sighted in water as deep as 3,000 m, with the highest sighting rates in water <500 m deep (Baird

et al.

2013). It was seen during all months, including off the west coast of the Island of Hawaii and off Oahu (Baird

et al.

2013). Spinner dolphins were also sighted in the proposed survey area during summer-fall surveys of the Hawaiian Islands EEZ, including south of Ohau (see map in Carretta

et al.

2017); eight sightings were made in 2002 (Barlow 2006) and four were made in 2010 (Bradford

et al.

2013).

Kato

et al.

(2005) noted that spinner dolphins were seen during Japanese sighting surveys in the western North Pacific in August-September. To the best of our knowledge, there are no data on the occurrence of spinner dolphins near the Emperor Seamounts survey area. However, the survey area is located to the north of the known range of the spinner dolphins. Therefore, they are not anticipated to occur in the Emperor Seamounts area.

Striped Dolphin

The striped dolphin has a cosmopolitan distribution in tropical to warm temperate waters from ~50° N to 40° S (Perrin

et al.

1994a; Jefferson

et al.

2015). It is typically found in waters outside the continental shelf and is often associated with convergence zones and areas of upwelling (Archer 2009). It occurs primarily in pelagic waters, but has been observed approaching shore where there is deep water close to the coast (Jefferson

et al.

2015).

The striped dolphin is expected to be one of the most abundant cetaceans in the proposed Hawaiian survey area, based on previous surveys in the region (Barlow 2006; Baird

et al.

2013; Bradford

et al.

2017). Higher densities are expected to occur around in offshore waters of the Hawaiian EEZ (Forney

et al.

2015). During small-boat surveys around the Hawaiian Islands in 2000-2012, sightings were made in water depths of 1,000-5,000 m, with the highest sighting rates in water deeper than 3000 m (Baird

et al.

2013). Sightings were made during all seasons, including near proposed seismic Line 1 off the Island of Hawaii (Baird

et al.

2013). It was also sighted within the proposed survey area during summer-fall shipboard surveys of the Hawaii Islands EEZ, including north and south of the Main Hawaiian Islands (see map in Carretta

et al.

2017); 15 sightings were made in 2002 (Barlow 2006) and 25 sightings were made in 2010 (Bradford

et al.

2013).

In the western North Pacific, the striped dolphin was one of the most common dolphin species seen during Japanese summer sighting surveys (Miyashita 1993a). During these surveys, densities were highest in offshore areas between 35° N and 40° N, and in coastal waters of southeastern Japan (Miyashita 1993a). Although only part of the proposed Emperor Seamounts survey area was surveyed during the month of August, no sightings were made within the survey area; sightings near the proposed survey area, south of 41° N, were made during August (Miyashita 1993a). Kanaji

et al.

(2017) reported on another record during summer to the southwest of the survey area. One winter bycatch record was reported just to the south of the survey area for October 1990 to May 1991 (Hobbs and Jones 1993).

Based on its distributional range and habitat preferences, the striped dolphin could be encountered in both the Hawaii and Emperor Seamounts survey areas.

Fraser's Dolphin (Lagenodelphis hosei)

Fraser's dolphin is a tropical oceanic species distributed between 30° N and 30° S that generally inhabits deeper, offshore water (Dolar 2009). It occurs rarely in temperate regions and then only in relation to temporary oceanographic anomalies such as El Niño events (Perrin

et al.

1994b). In the eastern tropical pacific, it was sighted at

least 15 km from shore in waters 1,500-2,500 m deep (Dolar 2009).

Fraser's dolphin is one of the most abundant cetaceans in the offshore waters of the Hawaiian Islands EEZ (Barlow 2006; Bradford

et al.

2017). Summer-fall shipboard surveys of the EEZ resulted in two sightings of Fraser's dolphin in 2002 and four in 2010, all in the western portion of the EEZ (Barlow 2006; Bradford

et al.

2013; Carretta

et al.

2017). During small-boat surveys around the Hawaiian Islands in 2000-2012, only two sightings were made off the west coast of the Island of Hawaii, one during winter and one during spring in water deeper than 1000 m.

Fraser's dolphin was seen during Japanese sighting surveys in the western North Pacific during August-September (Kato

et al.

2005). However, its range does not extend as far north as the Emperor Seamounts survey area. Thus, Fraser's dolphin is not expected to occur in the Emperor Seamounts survey area, but it could be encountered in deep water of the Hawaii survey area.

Pacific White-Sided Dolphin

The Pacific white-sided dolphin is found throughout the temperate North Pacific, in a relatively narrow distribution between 38° N and 47° N (Brownell

et al.

1999). It is common both on the high seas and along the continental margins (Leatherwood

et al.

1984; Dahlheim and Towell 1994; Ferrero and Walker 1996). Pacific white-sided dolphins often associate with other species, including cetaceans (especially Risso's and northern right whale dolphins; Green

et al.

1993), pinnipeds, and seabirds.

Pacific white-sided dolphins were seen throughout the North Pacific during surveys conducted during 1983-1990 (Buckland

et al.

1993; Miyashita 1993b). Sightings were made in the western Pacific during the summer (Buckland

et al.

1993; Miyashita 1993b), as well as during spring and fall (Buckland

et al.

1993). Pacific white-sided dolphins were observed in the southern portion of the Emperor Seamounts survey area, south of 45° S, as well as at higher latitudes just to the east (Buckland

et al.

1993; Miyashita 1993b). Bycatch in the squid driftnet fishery has also been reported for the Emperor Seamounts survey area (Hobbs and Jones 1993; Yatsu

et al.

1993). Thus, Pacific white-sided dolphins could be encountered in the Emperor Seamounts survey area, but they are not known to occur as far south as Hawaii.

Northern Right Whale Dolphin

The northern right whale dolphin is found in cool temperate and sub-arctic waters of the North Pacific, ranging from 34-55° N (Lipsky 2009). It occurs from the Kuril Islands south to Japan and eastward to the Gulf of Alaska and southern California (Rice 1998). The northern right whale dolphin is one of the most common marine mammal species in the North Pacific, occurring primarily on the outer continental shelf, slope waters, and oceanic regions, where water depths are >100 m (see Green

et al.

1993; Barlow 2003; Carretta

et al.

2017). The northern right whale dolphin does, however, come closer to shore where there is deep water, such as over submarine canyons (Jefferson

et al.

2015).

Northern right whale dolphins were seen throughout the North Pacific during surveys conducted during 1983-1990, with sightings made in the western Pacific primarily during the summer (Buckland

et al.

1993; Miyashita 1993b). Northern right whale dolphins were observed in the southern portion of the Emperor Seamounts survey area, south of 45° S (Buckland

et al.

1993; Miyashita 1993b). Bycatch records for the Emperor Seamounts survey area have also been reported (Hobbs and Jones 1993; Yatsu

et al.

1993). One sighting was made just to the east of the survey area, at a more northerly latitude (Miyashita 1993b). Thus, northern right whale dolphins could be encountered in the Emperor Seamounts survey area, but their distribution does not range as far south as the Hawaiian Islands.

Risso's Dolphin

Risso's dolphin is primarily a tropical and mid-temperate species distributed worldwide (Kruse

et al.

1999). It occurs between 60° N and 60° S, where surface water temperatures are at least 10° C (Kruse

et al.

1999). Water temperature appears to be an important factor affecting its distribution (Kruse

et al.

1999). Although it occurs from coastal to deep water, it shows a strong preference for mid-temperate waters of the continental shelf and slope (Jefferson

et al.

2014).

During small-boat surveys around the Hawaiian Islands in 2000-2012, sighting rates were highest in water >3,000 m deep (Baird

et al.

2013). Sightings were made during all seasons off the west coast of the Island of Hawaii, including near proposed seismic Line 1; no sightings were made off Oahu (Baird

et al.

2013). During summer-fall surveys of the Hawaiian Islands EEZ, seven sightings were made in 2002 (Barlow 2006) and 10 were made in 2010 (Bradford

et al.

2017); several sightings occurred within the proposed survey area south of the Main Hawaiian Islands (see map in Carretta

et al.

2017).

Risso's dolphins were regularly seen during Japanese summer sighting surveys in the western North Pacific (Miyashita 1993a), and one individual was seen in the offshore waters east of Japan on 18 August 2010 during the Shatksy Rise cruise (Holst and Beland 2010). Occurrence in the western North Pacific appears to be patchy, but high densities were observed in coastal waters, between 148° E-157° E, and east of 162° E (Miyashita 1993a). Although only part of the proposed Emperor Seamounts survey area was surveyed during the month of August, no sightings were made within the survey area; however, sightings were made south of 41° N (Miyashita 1993a). As its regular northern range extends to the southernmost portion of the Emperor Seamounts survey area, and one record has been reported outside of its range in the Aleutian Islands (Jefferson

et al.

2014). Therefore, the Risso's dolphin is expected to occur in the Emperor Seamounts survey area.

Melon-Headed Whale

The melon-headed whale is an oceanic species found worldwide in tropical and subtropical waters from ~40° N to 35° S (Jefferson

et al.

2015). It is commonly seen in mixed groups with other cetaceans (Jefferson and Barros 1997; Huggins

et al.

2005). It occurs most often in deep offshore waters and occasionally in nearshore areas where deep oceanic waters occur near the coast (Perryman 2009). In the North Pacific, it is distributed south of central Japan and southern California, as well as across the Pacific, including Hawaii.

Photo-identification and telemetry studies have revealed that there are two distinct populations of melon-headed whales in Hawaiian waters—the Hawaiian Islands stock and the Kohala resident stock associated with the west coast of the Island of Hawaii (Aschettino

et al.

2012; Oleson

et al.

2013; Carretta

et al.

2017). Individuals in the smaller Kohala resident stock have a limited range restricted to shallower waters of the Kohala shelf and west side of Hawaii Island. During small-boat surveys around the Hawaiian Islands in 2000-2012, sightings were made during all seasons in all water depths up to 5,000 m, including sightings off the west coasts of the Island of Hawaii and Oahu (Baird

et al.

2013). There are numerous records near the proposed seismic transect off the west coast of the Hawaiian Island (Carretta

et al.

2017); this area is considered a BIA (Baird

et al.

2015). During summer-fall surveys

of the Hawaiian Islands EEZ in 2002 and 2010, there was a single sighting each year; neither was located near the proposed survey area (Barlow

et al.

2004; Bradford

et al.

2017). Satellite telemetry data revealed distant pelagic movements, associated with feeding, nearly to the edge of the Hawaiian Islands EEZ (Oleson

et al.

2013).

Melon-headed whales have been seen during Japanese sighting surveys in the western North Pacific in August-September (Kato

et al.

2005). However, their distributional range does not extend to the Emperor Seamounts survey area. Thus, melon-headed whale is expected to occur in the proposed Hawaiian survey area, but not in the Emperor Seamounts survey area.

Pygmy Killer Whale

The pygmy killer whale has a worldwide distribution in tropical and subtropical waters (Donahue and Perryman 2009), generally not ranging south of 35° S (Jefferson

et al.

2015). In warmer water, it is usually seen close to the coast (Wade and Gerrodette 1993), but it is also found in deep waters. In the North Pacific, it occurs from Japan and Baja, California, southward and across the Pacific Ocean, including Hawaii.

A small resident population inhabits the waters around the Main Hawaiian Islands (Oleson

et al.

2013), where it generally occurs within ~20 km from shore (Baird

et al.

2011). During small-boat surveys around the Hawaiian Islands in 2000-2012, sightings were made during all seasons in water up to 3000 m deep, off the west coasts of Oahu and the Island of Hawaii (Baird

et al.

2013), including near proposed seismic Lines 1 and 2. The waters off the west and southeast coasts of the Island of Hawaii are considered a BIA (Baird

et al.

2015). Pygmy killer whales were also recorded during summer-fall surveys of the Hawaiian Islands EEZ: Three sightings in 2002 (Barlow

et al.

2004; Barlow 2006) and five in 2010 (Bradford

et al.

2017), including some within the study area to the north and south of the Main Hawaiian Islands (Carretta

et al.

2017).

Kato

et al.

(2005) reported the occurrence of this species during Japanese sighting surveys in the western North Pacific in August-September. However, its distributional range indicates that the pygmy killer whale is unlikely to occur in the Emperor Seamounts survey area.

False Killer Whale

The false killer whale is found worldwide in tropical and temperate waters, generally between 50° N and 50° S (Odell and McClune 1999). It is widely distributed, but generally uncommon throughout its range (Baird 2009). It is gregarious and forms strong social bonds, as is evident from its propensity to strand en masse (Baird 2009). 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.

2008; Baird 2009). In the North Pacific, it occurs from Japan and southern California, southward and across the Pacific, including Hawaii.

Telemetry, photo-identification, and genetic studies have identified three independent populations of false killer whales in Hawaiian waters: Main Hawaiian Islands Insular, Northwestern Hawaiian Islands, and Hawaii pelagic stocks (Chivers

et al.

2010; Baird

et al.

2010, 2013; Bradford

et al.

2014; Carretta

et al.

2017). The range of the Northwestern Hawaiian Islands stock is not the vicinity of the Hawaii survey tracklines and, therefore, will not be discussed further. The population inhabiting the Main Hawaiian Islands is thought to have declined dramatically since 1989; the reasons for this decline are still uncertain, although interactions with longline fisheries have been suggested (Reeves

et al.

2009; Bradford and Forney 2014). Higher densities likely occur in the western-most areas of the Hawaiian EEZ (Forney

et al.

2015).

During 2008-2012, 26 false killer whales were observed hooked or entangled by longline gear within the Hawaiian Islands EEZ or adjacent high-seas waters, and 22 of those were assessed as seriously injured; locations of false killer whale and unidentified blackfish takes observed included the proposed survey area (Bradford and Forney 2014). NMFS published a final rule to implement the False Killer Whale Take Reduction Plan on November 29, 2012, 77 FR 71260). The final rule includes gear requirements (“weak” circle hooks and strong branch lines) in the deep-set longline fishery, longline closure areas, training and certification for vessel owners and captains in marine mammal handling and release, captains' supervision of marine mammal handling and release, and posting of placards on longline vessels.

Critical habitat has been proposed for the endangered insular population of the false killer whale in Hawaii (82 FR 51186; November 3, 2017). In general, this includes waters between the 45- and 3,200-m isobaths in the Main Hawaiian Islands (NNMFS 2017c). Note that in the critical habitat proposal, NMFS invited the public to submit comments on whether it is appropriate to include anthropogenic noise as a feature essential to the conservation false killer whales in the final rule. The final rule is expected to be published ~1 July 2018 (NMFS 2017c).

High-use areas in Hawaii include the north half of the Island of Hawaii, the northern areas of Maui and Molokai, and southwest of Lanai (Baird

et al.

2012). These areas are considered BIAs (Baird

et al.

2015), and proposed seismic Line 1 to the west of the Island of Hawaii traverses the BIA. Individuals are found up to 122 km from shore (Baird

et al.

2012). Satellite-tagged false killer whales were also recorded using the areas off the western Island of Hawaii and west of Oahu during summer 2008 and fall 2009 (Baird

et al.

2012). During small-boat surveys around the Hawaiian Islands in 2000-2012, the highest sighting rates occurred in water >3,500 m deep (Baird

et al.

2013). Sightings were made during all seasons, including off the west coast of the Island of Hawaii and Oahu (Baird

et al.

2013). During summer-fall surveys of the Hawaiian Islands EEZ, two sightings were made in 2002 (Barlow

et al.

2004; Barlow 2006) and 14 were made in 2010 (Bradford

et al.

2017), including two within the study area, south of the Main Hawaiian Islands (see map in Carretta

et al.

2017). False killer whales were also detected acoustically off the west coast of the Hawaiian Island and off Kauai (Baumann-Pickering

et al.

2015).

False killer whales have been seen during Japanese summer sighting surveys in the western Pacific Ocean (Miyashita 1993a), and a sighting of four individuals was made in offshore waters east of Japan in August 2010 during the Shatksy Rise cruise (Holst and Beland 2010). The distribution in the western Pacific was patchy, with several high-density areas in offshore waters (Miyashita 1993a). Although only part of the proposed Emperor Seamounts survey area was surveyed during the month of August, no sightings were made within the survey area; however, one sighting was made just to the southeast of the survey area (Miyashita 1993a). Jefferson

et al.

(2015) did not show its distributional range to include the Emperor Seamounts region.

False killer whale is expected to occur in the proposed Hawaiian and Emperor Seamounts survey areas.

Killer Whale

The killer whale is cosmopolitan and globally fairly abundant; it has been observed in all oceans of the World (Ford 2009). It is very common in temperate waters and also frequents tropical waters, at least seasonally

(Heyning and Dahlheim 1988). High densities of the species occur in high latitudes, especially in areas where prey is abundant. Killer whale movements generally appear to follow the distribution of their prey, which includes marine mammals, fish, and squid.

Killer whales are rare in the Hawaii Islands EEZ. Baird

et al.

(2006) reported 21 sighting records in Hawaiian waters between 1994 and 2004. During small-boat surveys around Hawaii Island in 2000-2012, a single sighting was made during spring in water <2000 m deep off the west coast of Hawaii Island (Baird

et al.

2013). During summer—fall surveys of the Hawaiian Islands EEZ, two sightings were made in 2002 (Barlow

et al.

2004; Barlow 2006) and one was made in 2010 (Bradford

et al.

2017); none was made within the proposed survey area (Barlow

et al.

2004; Bradford

et al.

2017; Carretta

et al.

2017). Numerous additional sightings in and north of the EEZ have been made by observers on longliners, some at the edge of the EEZ north of the Main Hawaiian Islands (Carretta

et al.

2017).

Very little is known about killer whale abundance and distribution in the western Pacific Ocean outside of Kamchatka. However, they are common along the coast of Russia, Sea of Okhotsk, and Sea of Japan, Sakhalin Island, and Kuril Islands (Forney and Wade 2006). Kato

et al.

(2005) reported sightings of this species during Japanese sighting surveys in the western North Pacific in August-September. However, there is very little information on killer whales for the Emperor Seamounts survey area, but based on information regarding the distribution and habitat preferences, they are likely to occur there (see Forney and Wade 2006).

Killer whales are expected to occur in both the proposed Hawaiian and Emperor survey areas.

Short-Finned Pilot Whale

The short-finned pilot whale is found in tropical and warm temperate waters; it is seen as far south as ~40° S and as far north as 50° N (Jefferson

et al.

2015). It is generally nomadic, but may be resident in certain locations, including Hawaii. Pilot whales occur on the shelf break, over the slope, and in areas with prominent topographic features (Olson 2009). Based on genetic data, Van Cise

et al.

(2017) suggested that two types of short-finned pilot whales occur in the Pacific—one in the western and central Pacific, and one in the Eastern Pacific; they hypothesized that prey distribution rather than sea surface temperature determine their latitudinal ranges.

During surveys of the Main Hawaiian Islands during 2000-2012, short-finned pilot whales were the most frequently sighted cetacean (Baird

et al.

2013). Higher densities are expected to occur around the Hawaiian Islands rather than in far offshore waters of the Hawaiian EEZ (Forney

et al.

2015). Photo-identification and telemetry studies indicate that there may be insular and pelagic populations of short-finned pilot whales in Hawaii (Mahaffy 2012; Oleson

et al.

2013). Genetic research is also underway to assist in delimiting population stocks for management (Carretta

et al.

2017). During small-boat surveys around the Hawaiian Islands in 2000-2012, pilot whales were sighted in water as deep as 5,000 m, with the highest sighting rates in water depths of 500-2,500 m (Baird

et al.

2013). Sightings were made during all seasons, mainly off the west coasts of the Island of Hawaii and Ohau (Baird

et al.

2013). The waters off the west coast of the Island of Hawaii are considered a BIA (Baird

et al.

2015); proposed seismic tLine 1 traverses the BIA. During summer—fall surveys of the Hawaiian Islands EEZ, 25 sightings were made in 2002 (Barlow 2006) and 36 were made in 2010 (Bradford

et al.

2017), including within the proposed survey area, north, south, and between the Main Hawaiian Islands (see Carretta

et al.

2017). Short-finned pilot whales were also detected acoustically off the west coast of the Island of Hawaii and off Kauai (Baumann-Pickering

et al.

2015).

Stock structure of short-finned pilot whales has not been adequately studied in the North Pacific, except in Japanese waters, where two stocks have been identified based on pigmentation patterns and head shape differences of adult males (Kasuya

et al.

1988). The southern stock of short-finned pilot whales has been observed during Japanese summer sightings surveys (Miyashita 1993a) and is morphologically similar to pilot whales found in Hawaiian waters (Carretta

et al.

2017). Distribution of short-finned pilot whales in the western North Pacific appears to be patchy, but high densities were observed in coastal waters of central and southern Japan and in some areas offshore (Miyashita 1993a). A sighting of three individuals was made in offshore waters east of Japan in August 2010 during the Shatksy Rise cruise (Holst and Beland 2010). Although only part of the proposed Emperor Seamounts survey area was surveyed during the month of August, no sightings were made within or near the survey area; offshore sightings to the south of the proposed survey area were made during the month of September (Miyashita 1993a). Although Jefferson

et al.

(2015) did not include the Emperor Seamounts region in its distributional range, Olson (2009) did.

Short-finned pilot whales are expected to occur in both the proposed Hawaiian and Emperor Seamounts survey areas.

Dall's Porpoise

Dall's porpoise is only found in the North Pacific and adjacent seas. It is widely distributed across the North Pacific over the continental shelf and slope waters, and over deep (>2500 m) oceanic waters (Hall 1979), ranging from ~30-62° N (Jefferson

et al.

2015). In general, this species is common throughout its range (Buckland

et al.

1993). It is known to approach vessels to bowride (Jefferson 2009b).

In the western North Pacific, there are two different color morphs which are also considered sub-species: The

truei

-type (

P. d. truei

) and the

dalli

-type (

P. d. dalli

) (Jefferson

et al.

2015). They can be distinguished from each other by the extent of their white thoracic patches—the

truei

-type has a much broader patch, which extends nearly the length of the body. Both types could be encountered in the proposed Emperor Seamounts survey area.

Dall's porpoise was one of the most common cetaceans in the bycatch of the central and western North Pacific high-seas driftnet fisheries, but that source of mortality is not thought to have substantially depleted their abundance in the region (Hobbs and Jones 1993). Dall's porpoises were seen throughout the North Pacific during surveys conducted during 1987-1990 (Buckland

et al.

1993), including in the western Pacific during the summer (Buckland

et al.

1993; Kato

et al.

2005). The observed range included the entire Emperor Seamounts survey area (Buckland

et al.

1993). Records of both types within the Emperor Seamounts survey area, in particular for April-July, have also been reported by Kasuya (1982), and bycatch records in the proposed survey area have also been reported (Hobbs and Jones 1993; Yatsu

et al.

1993). Thus, Dall's porpoise could be encountered in the Emperor Seamounts survey area, but its distribution does not range as far south as the Hawaiian Islands.

Hawaiian Monk Seal

The Hawaiian monk seal only occurs in the Central North Pacific. It is distributed throughout the Hawaiian Island chain, with most of the population occurring in the Northwestern Hawaiian Islands (within the PMNM), and a small but increasing

number residing in the Main Hawaiian Islands (Baker

et al.

2011). Six main breeding subpopulations are located at the Kure Atoll, Midway Islands, Pearl and Hermes Reef, Lisianski Island, Laysan Island, and French Frigate Shoals (Baker

et al.

2011). Most births occur from February to August, with a peak in April to June, but births have been reported any time of the year (Gilmartin and Forcada 2009). Hawaiian monk seals show high site fidelity to natal islands (Gilmartin and Forcada 2009; Wilson

et al.

2017). They mainly occur within 50 km of atolls/islands (Parrish

et al.

2000; Stewart

et al.

2006; Wilson

et al.

2017) and within the 500-m isobath (

e.g.,

Parrish

et al.

2002; Wilson

et al.

2017). Secondary occurrence may occur in water as deep as 1000 m, but occurrence beyond the 1000-m isobath is rare (DoN 2005). Nonetheless, tagged monk seals have been tracked in water >1000 m deep (Wilson

et al.

2017).

Hawaiian monk seals are benthic foragers that feed on marine terraces of atolls and banks; most foraging occurs in water depths <100 m deep but occasionally to depths up to 500 m (Parrish

et al.

2002; Stewart

et al.

2006). Stewart

et al.

(2006) used satellite tracking to examine the foraging behavior of monk seals at the six main breeding colonies in the Northwestern Hawaiian Islands. Foraging trips varied by sex and by age and ranged from <1 km up to 322 km from haul-out sites. Wilson

et al.

(2017) reported foraging trips of up to 100 km. Satellite tracking of Hawaiian monk seals revealed that home ranges in Main Hawaiian Islands were much smaller than those in the Northwestern Hawaiian Islands (NMFS 2007, 2014); home ranges for most seals were <2000 km

2

(Wilson

et al.

2017).

Critical habitat has been designated based on preferred pupping and nursing areas, significant haul-out areas, and marine foraging areas out to a depth of 200 m (NMFS 2017b). In the Main Hawaiian Islands, critical habitat generally includes marine habitat from the seafloor to 10 m above the seafloor, from the 200-m isobath to the shoreline and 5 m inland, with some exceptions for specific areas (NMFS 2017b). For the Island of Hawaii of Hawaii, Maui, and Oahu (islands adjacent to the proposed transects), all marine habitat and inland habitat is included as critical habitat (NMFS 2017b). The seismic transects are located at least 10 km from monk seal critical habitat (Fig. 1).

Hawaiian monk seals have been reported throughout the Main Hawaiian Islands, including the west coast of Oahu, the east coast of Maui, and the north coast of the Island of Hawaii (Baker and Johanos 2004; DoN 2005). Tagged seals showed movements among the Main Hawaiian Islands, and were reported to occur near and crossing proposed seismic Lines 1 and 2 off the west coast of Oahu and the Island of Hawaii (Wilson

et al.

2017). However, the core area of occurrence around Oahu was reported to be off the south coast, not the west coast (Wilson

et al.

2017). Thus, monk seals could be encountered during the proposed survey, especially in nearshore portions (<1000 m deep), as well as areas near the islands where water depth is greater than >1000 m.

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.

2017). During the breeding season, most of the worldwide population of northern fur seals inhabits the Pribilof Islands in the southern Bering Sea (Lee

et al.

2014; Muto

et al.

2017). 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.

2017). In the United States, two stocks are recognized—the Eastern Pacific and the California stocks (Muto

et al.

2017). 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.

2017).

When not on rookery islands, northern fur seals are primarily pelagic but occasionally haul out on rocky shorelines (Muto

et al.

2017). 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.

2017; Muto

et al.

2017). After reproduction, northern fur seals spend the next 7-8 months feeding at sea (Roppel 1984). Once weaned, juveniles spend 2-3 years at sea before returning to rookeries. Animals may migrate to the Gulf of Alaska, off Japan, and the west coast of the United States (Muto

et al.

2017); in particular, adult males from the Pripilof Islands have been shown to migrate to the Kuril Islands in the western Pacific (Loughlin

et al.

1999). The southern extent of the migration is ~35 N.

Northern fur seals were seen throughout the North Pacific during surveys conducted during 1987-1990, including in the western Pacific during the summer (Buckland

et al.

1993). The observed range included the entire Emperor Seamounts survey area (Buckland

et al.

1993). They have also been reported as bycatch in squid and large-mesh fisheries during summer in the Emperor Seamounts survey area (Hobbs and Jones 1993; Yatsu

et al.

1993). 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, and approached near the eastern-most extent of the Emperor Seamounts survey area; females migrated to the Gulf of Alaska and the California Current (Sterling

et al.

2014). Tagged pups also approached the eastern portion of the Emperor Seamounts survey area during November (Lea

et al.

2009). Thus, northern fur seals could be encountered in the Emperor Seamounts survey area; only juveniles would be expected to occur there during the summer. Their distribution does not range as far south as the Hawaiian Islands.

Northern Elephant Seal

Northern elephant seals breed in California and Baja California, primarily on offshore islands (Stewart

et al.

1994), from December-March (Stewart and Huber 1993). Adult elephant seals engage in two long northward migrations per year, one following the breeding season, and another following the annual molt, with females returning earlier to molt (March-April) than males (July-August) (Stewart and DeLong 1995). Juvenile elephant seals typically leave the rookeries in April or May and head north, traveling an average of 900-1,000 km. Hindell (2009) noted that traveling likely takes place in water depths >200 m.

When not breeding, elephant seals feed at sea far from the rookeries, ranging as far north as 60° N, into the Gulf of Alaska and along the Aleutian Islands (Le Boeuf

et al.

2000). Some seals that were tracked via satellite-tags for no more than 224 days traveled distances in excess of 10,000 km during that time (Le Beouf

et al.

2000). Northern elephant seals that were satellite-tagged at a California rookery have been recorded traveling as far west as ~166.5-172.5° E, including the proposed Emperor Seamount survey area (Le Boeuf

et al.

2000; Robinson

et al.

2012; Robinson 2016

in

OBIS 2018; Costa 2017

in

OBIS 2018). Occurrence in the survey area was documented during August and September; during July and October, northern elephant seals were tracked just to the east of the survey area (Robinson

et al.

2012). Post-molting seals traveled longer and farther

than post-breeding seals (Robinson

et al.

2012).

Thus, northern elephant seals could be encountered in the Emperor Seamounts survey area during summer and fall. Although there are rare records of northern elephant seals in Hawaiian waters, they are unlikely to occur in the proposed survey area.

Ribbon Seal

Ribbon seals occur in the North Pacific and adjacent Arctic Ocean, ranging from the Okhotsk Sea, to the Aleutian Islands and the Bering, Chukchi, and western Beaufort seas. Ribbon seals inhabit the Bering Sea ice front from late-March to early-May and are abundant in the northern parts of the ice front in the central and western parts of the Bering Sea (Burns 1970; Burns 1981). In May to mid-July, when the ice recedes, some of the seals move farther north (Burns 1970; Burns 1981) to the Chukchi Sea (Kelly 1988c). However, most likely become pelagic and remain in the Bering Sea during the open-water season, and some occur on the Pacific Ocean side of the Aleutian Islands (Boveng

et al.

2008). Of 10 seals that were tagged along the cost of the Kamchatka Peninsula in 2005, most stayed in the central and eastern Bering Sea, but two were tracked along the south side of the Aleutian Islands; 8 of 26 seals that were tagged in the central Bering Sea in 2007 traveled to the Bering Strait, Chukchi Sea, and Arctic Basin (Boveng

et al.

2008). Although unlikely ribbon seals could be encountered in the proposed Emperor Seamounts survey area.

Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Current data indicate that not all marine mammal species have equal hearing capabilities (

e.g.,

Richardson

et al.,

1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall

et al.

(2007) recommended that marine mammals be divided into functional hearing groups based on directly measured or estimated hearing ranges on the basis of available behavioral response data, audiograms derived using auditory evoked potential techniques, anatomical modeling, and other data. Note that no direct measurements of hearing ability have been successfully completed for mysticetes (

i.e.,

low-frequency cetaceans). Subsequently, NMFS (2016) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65 dB threshold from the normalized composite audiograms, with the exception for lower limits for low-frequency cetaceans where the lower bound was deemed to be biologically implausible and the lower bound from Southall

et al.

(2007) retained. The functional groups and the associated frequencies are indicated below (note that these frequency ranges correspond to the range for the composite group, with the entire range not necessarily reflecting the capabilities of every species within that group):

• Low-frequency cetaceans (mysticetes): Generalized hearing is estimated to occur between approximately 7 Hz and 35 kHz;

• Mid-frequency cetaceans (larger toothed whales, beaked whales, and most delphinids): Generalized hearing is estimated to occur between approximately 150 Hz and 160 kHz;

• High-frequency cetaceans (porpoises, river dolphins, and members of the genera Kogia and Cephalorhynchus; including two members of the genus Lagenorhynchus, on the basis of recent echolocation data and genetic data): generalized hearing is estimated to occur between approximately 275 Hz and 160 kHz.

• Pinnipeds in water; Phocidae (true seals): Generalized hearing is estimated to occur between approximately 50 Hz to 86 kHz;

• Pinnipeds in water; Otariidae (eared seals): Generalized hearing is estimated to occur between 60 Hz and 39 kHz.

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 (Hemilä

et al.,

2006; Kastelein

et al.,

2009; Reichmuth and Holt, 2013).

For more detail concerning these groups and associated frequency ranges, please see NMFS (2016) for a review of available information. Forty marine mammal species (36 cetacean and 4 pinniped (1 otariid and 3 phocid) species) have the reasonable potential to co-occur with the proposed survey activities. Please refer to Table 1. Of the cetacean species that may be present, 8 are classified as low-frequency cetaceans (

i.e.,

all mysticete species), 25 are classified as mid-frequency cetaceans (

i.e.,

all delphinid and ziphiid species and the sperm whale), and 3 are classified as high-frequency cetaceans (

i.e.,

Dall's porpoise and Kogia spp.).

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

This section includes a summary and discussion of the ways that components of the specified activity may impact marine mammals and their habitat. The “Estimated Take by Incidental Harassment” section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The “Negligible Impact Analysis and Determination” section considers the content of this section, the “Estimated Take by Incidental Harassment” section, and the “Proposed Mitigation” section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and how those impacts on individuals are likely to impact marine mammal species or stocks.

Description of Active Acoustic Sound Sources

This section contains a brief technical background on sound, the characteristics of certain sound types, and on metrics used in this proposal inasmuch as the information is relevant to the specified activity and to a discussion of the potential effects of the specified activity on marine mammals found later in this document.

Sound travels in waves, the basic components of which are frequency, wavelength, velocity, and amplitude. Frequency is the number of pressure waves that pass by a reference point per unit of time and is measured in 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 decibel (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 (μPa)) 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 μPa) while the received level is the SPL at the listener's position (referenced to 1 μPa).

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 μPa

2

-s) represents the total energy contained within a puls and considers both intensity and duration of exposure. Peak sound pressure (also referred to as zero-to-peak sound pressure or 0-p) is the maximum instantaneous sound pressure measurable in the water at a specified distance from the source and is represented in the same units as the rms sound pressure. Another common metric is peak-to-peak sound pressure (pk-pk), which is the algebraic difference between the peak positive and peak negative sound pressures. Peak-to-peak pressure is typically approximately 6 dB higher than peak pressure (Southall

et al.,

2007).

When underwater objects vibrate or activity occurs, sound-pressure waves are created. These waves alternately compress and decompress the water as the sound wave travels. Underwater sound waves radiate in a manner similar to ripples on the surface of a pond and may be either directed in a beam or beams or may radiate in all directions (omnidirectional sources), as is the case for pulses produced by the airgun arrays considered here. The compressions and decompressions associated with sound waves are detected as changes in pressure by aquatic life and man-made sound receptors such as hydrophones.

Even in the absence of sound from the specified activity, the underwater environment is typically loud due to ambient sound. Ambient sound is defined as environmental background sound levels lacking a single source or point (Richardson

et al.,

1995), and the sound level of a region is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical (

e.g.,

wind and waves, earthquakes, ice, atmospheric sound), biological (

e.g.,

sounds produced by marine mammals, fish, and invertebrates), and anthropogenic (

e.g.,

vessels, dredging, construction) sound. A number of sources contribute to ambient sound, including the following (Richardson

et al.,

1995):

• Wind and waves: The complex interactions between wind and water surface, including processes such as breaking waves and wave-induced bubble oscillations and cavitation, are a main source of naturally occurring ambient sound for frequencies between 200 Hz and 50 kHz (Mitson, 1995). In general, ambient sound levels tend to increase with increasing wind speed and wave height. Surf sound becomes important near shore, with measurements collected at a distance of 8.5 km from shore showing an increase of 10 dB in the 100 to 700 Hz band during heavy surf conditions.

• Precipitation: Sound from rain and hail impacting the water surface can become an important component of total sound at frequencies above 500 Hz, and possibly down to 100 Hz during quiet times.

• Biological: Marine mammals can contribute significantly to ambient sound levels, as can some fish and snapping shrimp. The frequency band for biological contributions is from approximately 12 Hz to over 100 kHz.

• Anthropogenic: Sources of ambient sound related to human activity include transportation (surface vessels), dredging and construction, oil and gas drilling and production, seismic surveys, sonar, explosions, and ocean acoustic studies. Vessel noise typically dominates the total ambient sound for frequencies between 20 and 300 Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz and, if higher frequency sound levels are created, they attenuate rapidly. Sound from identifiable anthropogenic sources other than the activity of interest (

e.g.,

a passing vessel) is sometimes termed background sound, as opposed to ambient sound.

The sum of the various natural and anthropogenic sound sources at any given location and time—which comprise “ambient” or “background” sound—depends not only on the source levels (as determined by current weather conditions and levels of biological and human activity) but also on the ability of sound to propagate through the environment. In turn, sound propagation is dependent on the spatially and temporally varying properties of the water column and sea floor, and is frequency-dependent. As a result of the dependence on a large number of varying factors, ambient sound levels can be expected to vary widely over both coarse and fine spatial and temporal scales. Sound levels at a given frequency and location can vary by 10-20 dB from day to day (Richardson

et al.,

1995). The result is that, depending on the source type and its intensity, sound from a given activity may be a negligible addition to the local environment or could form a distinctive signal that may affect marine mammals. Details of source types are described in the following text.

Sounds are often considered to fall into one of two general types: Pulsed and non-pulsed (defined in the following). The distinction between these two sound types is important because they have differing potential to cause physical effects, particularly with regard to hearing (

e.g.,

Ward, 1997 in Southall

et al.,

2007). Please see Southall

et al.

(2007) for an in-depth discussion of these concepts.

Pulsed sound sources (

e.g.,

airguns, explosions, gunshots, sonic booms, impact pile driving) produce signals that are brief (typically considered to be less than one second), broadband, atonal transients (ANSI, 1986, 2005; Harris, 1998; NIOSH, 1998; ISO, 2003) and occur either as isolated events or repeated in some succession. Pulsed sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a rapid decay period that may include a period of diminishing, oscillating maximal and minimal pressures, and generally have an increased capacity to induce physical injury as compared with sounds that lack these features.

Non-pulsed sounds can be tonal, narrowband, or broadband, brief or prolonged, and may be either continuous or non-continuous (ANSI, 1995; NIOSH, 1998). Some of these non-pulsed sounds can be transient signals of short duration but without the essential properties of pulses (

e.g.,

rapid rise time). Examples of non-pulsed sounds include those produced by vessels, aircraft, machinery operations such as drilling or dredging, vibratory pile driving, and active sonar systems (such as those used by the U.S. Navy). The duration of such sounds, as received at a distance, can be greatly extended in a highly reverberant environment.

Airgun arrays produce pulsed signals with energy in a frequency range from about 10-2,000 Hz, with most energy radiated at frequencies below 200 Hz. The amplitude of the acoustic wave emitted from the source is equal in all directions (

i.e.,

omnidirectional), but airgun arrays do possess some

directionality due to different phase delays between guns in different directions. Airgun arrays are typically tuned to maximize functionality for data acquisition purposes, meaning that sound transmitted in horizontal directions and at higher frequencies is minimized to the extent possible.

As described above, a Kongsberg EM 122 MBES, a Knudsen Chirp 3260 SBP, and a Teledyne RDI 75 kHz Ocean Surveyor ADCP would be operated continuously during the proposed surveys, but not during transit to and from the survey areas. Due to the lower source level of the Kongsberg EM 122 MBES relative to the

Langseth's

airgun array (242 dB re 1 μPa · m for the MBES versus a minimum of 258 dB re 1 μPa · m (rms) for the 36 airgun array (NSF-USGS, 2011), sounds from the MBES are expected to be effectively subsumed by the sounds from the airgun array. Thus, any marine mammal potentially exposed to sounds from the MBES would already have been exposed to sounds from the airgun array, which are expected to propagate further in the water. Each ping emitted by the MBES consists of eight (in water >1,000 m deep) or four (<1,000 m) successive fan-shaped transmissions, each ensonifying a sector that extends 1° fore-aft. Given the movement and speed of the vessel, the intermittent and narrow downward-directed nature of the sounds emitted by the MBES would result in no more than one or two brief ping exposures of any individual marine mammal, if any exposure were to occur.

Due to the lower source levels of both the Knudsen Chirp 3260 SBP and the Teledyne RDI 75 kHz Ocean Surveyor ADCP relative to the

Langseth's

airgun array (maximum SL of 222 dB re 1 μPa · m for the SBP and maximum SL of 224 dB re 1 μPa · m for the ADCP, versus a minimum of 258 dB re 1 μPa · m for the 36 airgun array (NSF-USGS, 2011), sounds from the SBP and ADCP are expected to be effectively subsumed by sounds from the airgun array. Thus, any marine mammal potentially exposed to sounds from the SBP and/or the ADCP would already have been exposed to sounds from the airgun array, which are expected to propagate further in the water. As such, we conclude that the likelihood of marine mammal take resulting from exposure to sound from the MBES, SBP or ADCP is discountable and therefore we do not consider noise from the MBES, SBP or ADCP further in this analysis.

Acoustic Effects

Here, we discuss the effects of active acoustic sources on marine mammals.

Potential Effects of Underwater Sound

—Please refer to the information given previously (“Description of Active Acoustic Sources”) regarding sound, characteristics of sound types, and metrics used in this document. 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; Götz

et al.,

2009). The degree of effect is intrinsically related to the signal characteristics, received level, distance from the source, and duration of the sound exposure. In general, sudden, high level sounds can cause hearing loss, as can longer exposures to lower level sounds. Temporary or permanent loss of hearing will occur almost exclusively for noise within an animal's hearing range. We first describe specific manifestations of acoustic effects before providing discussion specific to the use of airgun arrays.

Richardson

et al.

(1995) described zones of increasing intensity of effect that might be expected to occur, in relation to distance from a source and assuming that the signal is within an animal's hearing range. First is the area within which the acoustic signal would be audible (potentially perceived) to the animal, but not strong enough to elicit any overt behavioral or physiological response. The next zone corresponds with the area where the signal is audible to the animal and of sufficient intensity to elicit behavioral or physiological responsiveness. Third is a zone within which, for signals of high intensity, the received level is sufficient to potentially cause discomfort or tissue damage to auditory or other systems. Overlaying these zones to a certain extent is the area within which masking (

i.e.,

when a sound interferes with or masks the ability of an animal to detect a signal of interest that is above the absolute hearing threshold) may occur; the masking zone may be highly variable in size.

We describe the more severe effects of certain non-auditory physical or physiological effects only briefly as we do not expect that use of airgun arrays are reasonably likely to result in such effects (see below for further discussion). Potential effects from impulsive sound sources can range in severity from effects such as behavioral disturbance or tactile perception to physical discomfort, slight injury of the internal organs and the auditory system, or mortality (Yelverton

et al.,

1973). Non-auditory physiological effects or injuries that theoretically might occur in marine mammals exposed to high level underwater sound or as a secondary effect of extreme behavioral reactions (

e.g.,

change in dive profile as a result of an avoidance reaction) caused by exposure to sound include neurological effects, bubble formation, resonance effects, and other types of organ or tissue damage (Cox

et al.,

2006; Southall

et al.,

2007; Zimmer and Tyack, 2007; Tal

et al.,

2015). The survey activities considered here do not involve the use of devices such as explosives or mid-frequency tactical sonar that are associated with these types of effects.

Threshold Shift

—Marine mammals exposed to high-intensity sound, or to lower-intensity sound for prolonged periods, can experience hearing threshold shift (TS), which is the loss of hearing sensitivity at certain frequency ranges (Finneran, 2015). TS can be permanent (PTS), in which case the loss of hearing sensitivity is not fully recoverable, or temporary (TTS), in which case the animal's hearing threshold would recover over time (Southall

et al.,

2007). Repeated sound exposure that leads to TTS could cause PTS. In severe cases of PTS, there can be total or partial deafness, while in most cases the animal has an impaired ability to hear sounds in specific frequency ranges (Kryter, 1985).

When PTS occurs, there is physical damage to the sound receptors in the ear (

i.e.,

tissue damage), whereas TTS represents primarily tissue fatigue and is reversible (Southall

et al.,

2007). In addition, other investigators have suggested that TTS is within the normal bounds of physiological variability and tolerance and does not represent physical injury (

e.g.,

Ward, 1997). Therefore, NMFS does not consider TTS to constitute auditory injury.

Relationships between TTS and PTS thresholds have not been studied in marine mammals, and there is no PTS data for cetaceans but such relationships are assumed to be similar to those in humans and other terrestrial mammals. PTS typically occurs at exposure levels at least several decibels above (a 40-dB threshold shift approximates PTS onset;

e.g.,

Kryter

et al.,

1966; Miller, 1974) that inducing mild TTS (a 6-dB threshold shift approximates TTS onset;

e.g.,

Southall

et al.

2007). Based on data

from terrestrial mammals, a precautionary assumption is that the PTS thresholds for impulse sounds (such as airgun pulses as received close to the source) are at least 6 dB higher than the TTS threshold on a peak-pressure basis and PTS cumulative sound exposure level thresholds are 15 to 20 dB higher than TTS cumulative sound exposure level thresholds (Southall

et al.,

2007). Given the higher level of sound or longer exposure duration necessary to cause PTS as compared with TTS, it is considerably less likely that PTS could occur.

For mid-frequency cetaceans in particular, potential protective mechanisms may help limit onset of TTS or prevent onset of PTS. Such mechanisms include dampening of hearing, auditory adaptation, or behavioral amelioration (

e.g.,

Nachtigall and Supin, 2013; Miller

et al.,

2012; Finneran

et al.,

2015; Popov

et al.,

2016).

TTS is the mildest form of hearing impairment that can occur during exposure to sound (Kryter, 1985). While experiencing TTS, the hearing threshold rises, and a sound must be at a higher level in order to be heard. In terrestrial and marine mammals, TTS can last from minutes or hours to days (in cases of strong TTS). In many cases, hearing sensitivity recovers rapidly after exposure to the sound ends. Few data on sound levels and durations necessary to elicit mild TTS have been obtained for marine mammals.

Marine mammal hearing plays a critical role in communication with conspecifics, and interpretation of environmental cues for purposes such as predator avoidance and prey capture. Depending on the degree (elevation of threshold in dB), duration (

i.e.,

recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious. For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that occurs during a time where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical for successful mother/calf interactions could have more serious impacts.

Finneran

et al.

(2015) measured hearing thresholds in three captive bottlenose dolphins before and after exposure to ten pulses produced by a seismic airgun in order to study TTS induced after exposure to multiple pulses. Exposures began at relatively low levels and gradually increased over a period of several months, with the highest exposures at peak SPLs from 196 to 210 dB and cumulative (unweighted) SELs from 193-195 dB. No substantial TTS was observed. In addition, behavioral reactions were observed that indicated that animals can learn behaviors that effectively mitigate noise exposures (although exposure patterns must be learned, which is less likely in wild animals than for the captive animals considered in this study). The authors note that the failure to induce more significant auditory effects likely due to the intermittent nature of exposure, the relatively low peak pressure produced by the acoustic source, and the low-frequency energy in airgun pulses as compared with the frequency range of best sensitivity for dolphins and other mid-frequency cetaceans.

Currently, TTS data only exist for four species of cetaceans (bottlenose dolphin, beluga whale, harbor porpoise, and Yangtze finless porpoise) exposed to a limited number of sound sources (

i.e.,

mostly tones and octave-band noise) in laboratory settings (Finneran, 2015). In general, harbor porpoises have a lower TTS onset than other measured cetacean species (Finneran, 2015). Additionally, the existing marine mammal TTS data come from a limited number of individuals within these species. There are no data available on noise-induced hearing loss for mysticetes.

Critical questions remain regarding the rate of TTS growth and recovery after exposure to intermittent noise and the effects of single and multiple pulses. Data at present are also insufficient to construct generalized models for recovery and determine the time necessary to treat subsequent exposures as independent events. More information is needed on the relationship between auditory evoked potential and behavioral measures of TTS for various stimuli. For summaries of data on TTS in marine mammals or for further discussion of TTS onset thresholds, please see Southall

et al.

(2007), Finneran and Jenkins (2012), Finneran (2015), and NMFS (2016).

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; Weilgart, 2007; Archer

et al.,

2010). Behavioral reactions can vary not only among individuals but also within an individual, depending on previous experience with a sound source, context, and numerous other factors (Ellison

et al.,

2012), and can vary depending on characteristics associated with the sound source (

e.g.,

whether it is moving or stationary, number of sources, distance from the source). Please see Appendices B-C of Southall

et al.

(2007) for a review of studies involving marine mammal behavioral responses to sound.

Habituation can occur when an animal's response to a stimulus wanes with repeated exposure, usually in the absence of unpleasant associated events (Wartzok

et al.,

2003). Animals are most likely to habituate to sounds that are predictable and unvarying. It is important to note that habituation is appropriately considered as a “progressive reduction in response to stimuli that are perceived as neither aversive nor beneficial,” rather than as, more generally, moderation in response to human disturbance (Bejder

et al.,

2009). The opposite process is sensitization, when an unpleasant experience leads to subsequent responses, often in the form of avoidance, at a lower level of exposure. As noted, behavioral state may affect the type of response. For example, animals that are resting may show greater behavioral change in response to disturbing sound levels than animals that are highly motivated to remain in an area for feeding (Richardson

et al.,

1995; NRC, 2003; Wartzok

et al.,

2003). Controlled experiments with captive marine mammals have showed pronounced behavioral reactions, including avoidance of loud sound sources (Ridgway

et al.,

1997). Observed responses of wild marine mammals to loud pulsed sound sources (typically seismic airguns or acoustic harassment devices) have been varied but often consist of avoidance behavior or other behavioral changes suggesting discomfort (Morton and Symonds, 2002; see also Richardson

et al.,

1995; Nowacek

et al.,

2007). However, many delphinids approach acoustic source vessels with no apparent discomfort or obvious behavioral change (

e.g.,

Barkaszi

et al.,

2012).

Available studies show wide variation in response to underwater sound; therefore, it is difficult to predict specifically how any given sound in a particular instance might affect marine mammals perceiving the signal. If a marine mammal does react briefly to an underwater sound by changing its behavior or moving a small distance, the impacts of the change are unlikely to be significant to the individual, let alone the stock or population. However, if a sound source displaces marine mammals from an important feeding or breeding area for a prolonged period, impacts on individuals and populations could be significant (

e.g.,

Lusseau and Bejder, 2007; Weilgart, 2007; NRC, 2005). However, there are broad categories of potential response, which we describe in greater detail here, that include alteration of dive behavior, alteration of foraging behavior, effects to breathing, interference with or alteration of vocalization, avoidance, and flight.

Changes in dive behavior can vary widely, and may consist of increased or decreased dive times and surface intervals as well as changes in the rates of ascent and descent during a dive (

e.g.,

Frankel and Clark, 2000; Ng and Leung, 2003; Nowacek

et al.;

2004; Goldbogen

et al.,

2013a, b). Variations in dive behavior may reflect interruptions in biologically significant activities (

e.g.,

foraging) or they may be of little biological significance. The impact of an alteration to dive behavior resulting from an acoustic exposure depends on what the animal is doing at the time of the exposure and the type and magnitude of the response.

Disruption of feeding behavior can be difficult to correlate with anthropogenic sound exposure, so it is usually inferred by observed displacement from known foraging areas, the appearance of secondary indicators (

e.g.,

bubble nets or sediment plumes), or changes in dive behavior. As for other types of behavioral response, the frequency, duration, and temporal pattern of signal presentation, as well as differences in species sensitivity, are likely contributing factors to differences in response in any given circumstance (

e.g.,

Croll

et al.,

2001; Nowacek

et al.;

2004; Madsen

et al.,

2006; Yazvenko

et al.,

2007). A determination of whether foraging disruptions incur fitness consequences would require information on or estimates of the energetic requirements of the affected individuals and the relationship between prey availability, foraging effort and success, and the life history stage of the animal.

Visual tracking, passive acoustic monitoring, and movement recording tags were used to quantify sperm whale behavior prior to, during, and following exposure to airgun arrays at received levels in the range 140-160 dB at distances of 7-13 km, following a phase-in of sound intensity and full array exposures at 1-13 km (Madsen

et al.,

2006; Miller

et al.,

2009). Sperm whales did not exhibit horizontal avoidance behavior at the surface. However, foraging behavior may have been affected. The sperm whales exhibited 19 percent less vocal (buzz) rate during full exposure relative to post exposure, and the whale that was approached most closely had an extended resting period and did not resume foraging until the airguns had ceased firing. The remaining whales continued to execute foraging dives throughout exposure; however, swimming movements during foraging dives were 6 percent lower during exposure than control periods (Miller

et al.,

2009). These data raise concerns that seismic surveys may impact foraging behavior in sperm whales, although more data are required to understand whether the differences were due to exposure or natural variation in sperm whale behavior (Miller

et al.,

2009).

Variations in respiration naturally vary with different behaviors and alterations to breathing rate as a function of acoustic exposure can be expected to co-occur with other behavioral reactions, such as a flight response or an alteration in diving. However, respiration rates in and of themselves may be representative of annoyance or an acute stress response. Various studies have shown that respiration rates may either be unaffected or could increase, depending on the species and signal characteristics, again highlighting the importance in understanding species differences in the tolerance of underwater noise when determining the potential for impacts resulting from anthropogenic sound exposure (

e.g.,

Kastelein

et al.,

2001, 2005, 2006; Gailey

et al.,

2007; Gailey

et al.,

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 (Miller

et al.,

2000; Fristrup

et al.,

2003; Foote

et al.,

2004), while right whales have been observed to shift the frequency content of their calls upward while reducing the rate of calling in areas of increased anthropogenic noise (Parks

et al.,

2007). In some cases, animals may cease sound production during production of aversive signals (Bowles

et al.,

1994).

Cerchio

et al.

(2014) used passive acoustic monitoring to document the presence of singing humpback whales off the coast of northern Angola and to opportunistically test for the effect of seismic survey activity on the number of singing whales. Two recording units were deployed between March and December 2008 in the offshore environment; numbers of singers were counted every hour. Generalized Additive Mixed Models were used to assess the effect of survey day (seasonality), hour (diel variation), moon phase, and received levels of noise (measured from a single pulse during each ten minute sampled period) on singer number. The number of singers significantly decreased with increasing received level of noise, suggesting that humpback whale breeding activity was disrupted to some extent by the survey activity.

Castellote

et al.

(2012) reported acoustic and behavioral changes by fin whales in response to shipping and airgun noise. Acoustic features of fin whale song notes recorded in the Mediterranean Sea and northeast Atlantic Ocean were compared for areas with different shipping noise levels and traffic intensities and during a seismic airgun survey. During the first 72 h of the survey, a steady decrease in song received levels and bearings to singers indicated that whales moved away from the acoustic source and out of the study area. This displacement persisted for a time period well beyond the 10-day duration of seismic airgun activity, providing evidence that fin whales may avoid an area for an extended period in the presence of increased noise. The authors hypothesize that fin whale acoustic communication is modified to compensate for increased background noise and that a sensitization process may play a role in the observed temporary displacement.

Seismic pulses at average received levels of 131 dB re 1 µPa

2

-s caused blue whales to increase call production (Di Iorio and Clark, 2010). In contrast, McDonald

et al.

(1995) tracked a blue whale with seafloor seismometers and reported that it stopped vocalizing and changed its travel direction at a range of 10 km from the acoustic source vessel (estimated received level 143 dB pk-pk). Blackwell

et al.

(2013) found that bowhead whale call rates dropped

significantly at onset of airgun use at sites with a median distance of 41-45 km from the survey. Blackwell

et al.

(

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