39276 Federal Register / Vol. 82, No. 158 / Thursday, August 17, 2017 / Notices 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

RIN 0648–XF329 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to a Low-Energy 

Geophysical Survey in the 

Northeastern 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 Scripps Institution of 

Oceanography (SIO) for authorization to 

take marine mammals incidental to a 

low-energy marine geophysical survey 

in the northeastern 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 September 18, 

2017. 

ADDRESSES: Comments should be 

addressed to Jolie Harrison, Chief, 

Permits and Conservation Division, 

Office of Protected Resources, National 

Marine Fisheries Service. Physical 

comments should be sent to 1315 EastWest Highway, Silver Spring, MD 20910 

and electronic comments should be sent 

to ITP.Carduner@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 

www.nmfs.noaa.gov/pr/permits/ 

incidental/research.htm 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: 

Jordan Carduner, 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: 

www.nmfs.noaa.gov/pr/permits/ 

incidental/research.htm. 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 is preparing an Environmental 

Assessment (EA) to consider the 

environmental impacts associated with 

the issuance of the proposed IHA. 

NMFS’ EA is available at 

www.nmfs.noaa.gov/pr/permits/ 

incidental/research.htm. 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 20, 2017, NMFS received a 

request from SIO for an IHA to take 

marine mammals incidental to 

conducting a low-energy marine 

geophysical survey in the northeastern 

Pacific Ocean. On July 5, 2017, we 

deemed SIO’s application for 

authorization to be adequate and 

complete. SIO’s request is for take of a 

small number of 27 species of marine 

mammals by Level B harassment and 

Level A harassment. Neither SIO nor 

NMFS expects mortality to result from 

this activity, 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 

SIO proposes to conduct a low-energy 

marine seismic survey offshore Oregon 

and Washington in the northeastern 

Pacific Ocean over the course of five 

days in September 2017. The proposed 

survey would occur off the Oregon 

continental margin out to 127.5° W. and 

between ∼43 and 46.5° N. (See Figure 1 

in IHA application). Water depths in the 

survey area are ∼130–2600 m. The 

proposed survey would involve one 

source vessel, the R/V Roger Revelle. 

The Revelle would tow a pair of 45 

cubic inch (in3) airguns with a total 

discharge volume of ∼90 in3 as an 

energy source along predetermined 

lines. 

Dates and Duration 

The seismic survey would be carried 

out for five days. The Revelle would 

likely depart from Newport, Oregon, on 


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or about September 22, 2017 and would 

return to Newport on or about 

September 29, 2017. Some deviation in 

timing could result from unforeseen 

events such as weather, logistical issues, 

or mechanical issues with the research 

vessel and/or equipment. Seismic 

activities would occur 24 hours per day 

during the proposed survey. 

Specific Geographic Region 

The survey would occur in the 

northeastern Pacific Ocean off the 

Oregon continental margin out to 127.5° 

W. and between ∼43 and 46.5° N. Two 

potential survey areas off the Oregon 

continental margin have been proposed 

(See Figure 1 in IHA application). One 

potential survey area, referred to by SIO 

as the Astoria Fan area, is located off 

northern Oregon off the mouth of the 

Columbia River and near the Astoria 

Canyon. The other potential survey area, 

referred to as the southern Oregon area, 

is located off the southern Oregon 

margin. Both the proposed Astoria Fan 

and Southern Oregon survey areas are 

located at least 23 kilometers (km) from 

the U.S. west coast over water depths 

∼130–2600 meters (m). SIO will 

ultimately select one of these two 

potential areas for the survey (i.e., both 

areas will not be surveyed). 

Representative survey track lines for 

both potential survey areas are shown in 

Figure 1 of the IHA application. The 

Revelle would depart from Newport, 

Oregon and return to Newport at the 

conclusion of the survey. 

Detailed Description of Specific Activity 

SIO plans to conduct a low-energy 

seismic survey off the coasts of Oregon 

and Washington. The proposed surveys 

involve an Early Career Seismic Chief 

Scientist Training Cruise which aims to 

train scientists on how to effectively 

plan seismic surveys, acquire data, and 

manage activities at sea. In addition, the 

survey would provide critical data to 

understand the sediment and crustal 

structure within the Cascadia 

continental margin. The proposed 

survey would take place on the active 

continental margin of the U.S. west 

coast where a variety of sedimentary 

and tectonic settings are available, 

providing many targets of geologic 

interest to a wide range of research 

cruise participants. 

The procedures to be used for the 

seismic survey would be similar to 

those used during previous seismic 

surveys by SIO and would use 

conventional seismic methodology. The 

survey would involve one source vessel, 

the R/V Roger Revelle. The Revelle 

would deploy a pair of 45-in3 GI airguns 

as an energy source with a total 

discharge volume of ∼90 in3. The 

receiving system would consist of one 

800-m hydrophone streamer. As the 

airguns are towed along the survey 

lines, the hydrophone streamer would 

receive the returning acoustic signals 

and transfer the data to the on-board 

processing system. 

Two potential sites off the Oregon 

continental margin, referred to by SIO as 

the Astoria Fan and southern Oregon 

sites, have been proposed for the survey 

(see Figure 1 in the IHA application). 

Only one of the two sites will be 

surveyed. Each of the proposed survey 

sites has several science targets. The 

southern Oregon survey includes the 

paleo objectives, a long plate transect 

that crosses Diebold Knoll, and a 

detailed survey of the megaslump 

segment of the Cascadia subduction 

zone, which has no previous seismic 

data. The Astoria Fan survey includes 

flexure, accretionary wedge mechanisms 

and gas hydrates as objectives; it covers 

a major seismic gap. The scientists on 

board would be responsible for 

modifying the survey to fit the allocated 

cruise length while meeting the project 

objectives, including choosing which 

survey or what portion of each survey 

to conduct. 

The total line km for the Southern 

Oregon survey would be 1013 km, ∼5 

percent of which would be in 

intermediate water (100–1000 m), with 

the remainder in water deeper than 

1000 m. The total length for the Astoria 

Fan survey would be 1057 km, with ∼23 

percent of line km in intermediate water 

and the remainder in water >1000 m. No 

effort during either survey would occur 

in shallow water <100 m deep. For 

purposes of this proposed IHA, the total 

track distance to be surveyed is 

estimated to be no greater than ∼1057 

km, which is the line km of the longer 

of the two potential surveys. There 

would be additional seismic operations 

in the survey area associated with 

airgun testing and repeat coverage of 

any areas where initial data quality is 

sub-standard. To account for these 

additional seismic operations, 25 

percent has been added in the form of 

operational days, which is equivalent to 

adding 25 percent to the proposed line 

km to be surveyed. 

In addition to the operations of the 

airgun array, a multibeam echosounder 

(MBES) and a sub-bottom profiler (SBP) 

would also be operated from the Revelle 

continuously throughout the seismic 

survey, but not during transits to and 

from the project area. All planned 

geophysical data acquisition activities 

would be conducted by SIO with onboard assistance by the scientists who 

have proposed the study. The vessel 

would be self-contained, and the crew 

would live aboard the vessel for the 

entire cruise. 

The Revelle has a length of 83 m, a 

beam of 16.0 m, and a maximum draft 

of 5.2 m. The ship is powered by two 

3,000 horsepower Propulsion General 

Electric motors and an 1180-hp 

azimuthing jet bow thruster. An 

operation speed of 9.3 km/h (5 knots 

(kt)) would be used during seismic 

acquisition. When not towing seismic 

survey gear, the Revelle cruises at 22.2– 

23.1 km/h (12–12.5 kt) and has a 

maximum speed of 27.8 km/h (15 kt). 

The Revelle would also serve as the 

platform from which vessel-based 

protected species observers (PSOs) 

would watch for marine mammals 

during airgun operations. 

During the survey, The Revelle would 

tow a pair of 45-in3 GI airguns and an 

800 m streamer containing hydrophones 

along predetermined lines. Seismic 

pulses would be emitted at intervals of 

∼8–10 seconds (s) (20–25 m). The 

generator chamber of each GI gun, the 

one responsible for introducing the 

sound pulse into the ocean, is 45 in3. 

The two 45-in3 GI guns would be towed 

21 m behind the Revelle, 2 m apart side 

by side, at a depth of 3 m. As the airguns 

are towed along the survey lines, the 

towed hydrophone array in the 800 m 

streamer would receive the reflected 

signals and transfer the data to the 

onboard processing system. 

TABLE 1—SPECIFICATIONS OF THE R/V 

REVELLE AIRGUN ARRAY

Number of airguns ................ 2. 

Tow depth of energy source 3 m. 

Dominant frequency components.0–188 Hz. 

Total volume .......................... ∼90 in3. 

Shot interval .......................... 7.8 seconds. 

Proposed mitigation, monitoring, and 

reporting measures are described in 

detail later in this document (please see 

‘‘Proposed Mitigation’’ and ‘‘Proposed 

Monitoring and Reporting’’). 

Description of Marine Mammals in the 

Area of Specified Activities 

Section 4 of the application 

summarizes available information 

regarding status and trends, distribution 

and habitat preferences, and behavior 

and life history, of the potentially 

affected species. Additional information 

regarding population trends and threats 

may be found in NMFS’ Stock 

Assessment Reports (SAR; 

www.nmfs.noaa.gov/pr/sars/), and more 

general information about these species 

(e.g., physical and behavioral 

descriptions) may be found on NMFS’ 


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Web site (www.nmfs.noaa.gov/pr/ 

species/mammals/). 

Table 2 lists all species with expected 

potential for occurrence in the 

northeastern Pacific Ocean and 

summarizes information related to the 

population or stock, including 

regulatory status under the MMPA and 

ESA and potential biological removal 

(PBR), where known. For taxonomy, we 

follow Committee on Taxonomy (2016). 

PBR is defined by the MMPA as the 

maximum number of animals, not 

including natural mortalities, that may 

be removed from a marine mammal 

stock while allowing that stock to reach 

or maintain its optimum sustainable 

population (as described in NMFS’ 

SARs). While no mortality is anticipated 

or authorized here, PBR and annual 

serious injury and mortality from 

anthropogenic sources are included here 

as gross indicators of the status of the 

species and other threats. 

Marine mammal abundance estimates 

presented in this document represent 

the total number of individuals that 

make up a given stock or the total 

number estimated within a particular 

study or survey area. NMFS’ stock 

abundance estimates for most species 

represent the total estimate of 

individuals within the geographic area, 

if known, that comprises that stock. For 

some species, this geographic area may 

extend beyond U.S. waters. All managed 

stocks in this region are assessed in 

NMFS’ U.S. Pacific SARs (e.g., Carretta 

et al. 2017). All values presented in 

Table 2 are the most recent available at 

the time of publication and are available 

in the 2017 SARs (Carretta et al. 2017), 

available online at: www.nmfs.noaa.gov/ 

pr/sars, except where noted otherwise. 

TABLE 2—MARINE MAMMALS THAT COULD OCCUR IN THE PROJECT AREA

Species Stock 

ESA/MMPA 

status; 

strategic 

(Y/N) 1

Stock abundance 2

(CV, Nmin, most 

recent abundance 

survey) 3

PBR 4 Relative occurrence in 

project area 

Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales) 

Family: Balaenopteridae 

North Pacific right whale 5

(Eubalaena japonica).

Eastern North Pacific ......... E/D; Y 31 ....................................... 0.1 Rare. 

Gray whale 5 (Eschrichtius 

robustus).

Eastern North Pacific ......... -/-; N 20,990 (0.05; 20,125; 

2011).

3.1 Common in nearshore 

areas, rare elsewhere. 

Humpback whale 6

(Megaptera 

novaeangliae).

California/Oregon/Washington.E/T/D; N 1,918 (0.03; 1,876; 2014) .. 11 Common in nearshore 

areas, rare elsewhere. 

Minke whale (Balaenoptera 

acutorostrata).

California/Oregon/Washington.-/-; N 636 (0.72; 369; 2014) ........ 3.5 Rare. 

Sei whale (Balaenoptera 

borealis).

Eastern N Pacific ............... E/D; Y 519 (0.4; 374; 2014) .......... 0.75 Rare. 

Fin whale (Balaenoptera 

physalus.

California/Oregon/Washington.E/D; Y 9,029 (0.12; 8,127; 2014) .. 81 Common. 

Blue whale (Balaenoptera 

musculus).

Eastern N Pacific ............... E/D; Y 1,647 (0.07; 1,551; 2011) .. 2.3 Rare. 

Order Cetartiodactyla—Cetacea—Superfamily Odontoceti (toothed whales, dolphins, and porpoises) 

Family: Physeteridae 

Sperm whale (Physeter 

macrocephalus).

California/Oregon/Washington.E/D; Y 2,106 (0.58; 1,332; 2014). 2.7 Common. 

Order Cetartiodactyla—Cetacea—Superfamily Odontoceti (toothed whales, dolphins, and porpoises) 

Family: Kogiidae 

Pygmy sperm whale (Kogia 

breviceps).

California/Oregon/Washington.-/-; N 4,111 (1.12; 1,924; 2014) .. 19 Rare. 

Dwarf sperm whale (Kogia 

sima).

California/Oregon/Washington.-/-; N unknown (unknown; unknown; 2014).Undet Rare. 

Order Cetartiodactyla—Cetacea—Superfamily Odontoceti (toothed whales, dolphins, and porpoises) 

Family delphinidae 

Killer whale (Orcinus orca) West coast transient .......... -/-; N 243 (n/a; 243; 2009) .......... 2.4 Rare. 

Eastern North Pacific offshore.-/-; N 240 (0.49; 162; 2014) ........ 1.6 Rare. 

False killer whale 7

(Pseudorca crassidens).

Hawaii Pelagic ................... -/-; N 1,540 (0.66; 928; 2010) ..... 9.3 Rare. 

Short-finned pilot whale 

(Globicephala 

macrorhynchus).

California/Oregon/Washington.-/-; N 836 (0.79; 466; 2014) ........ 4.5 Rare. 

Harbor porpoise (Phocoena 

phocoena).

Northern Oregon/Washington Coast.-/-; N 21,487 (0.44; 15,123; 

2011).

151 Abundant. 

Northern California/Southern Oregon.-/-; N 35,769 (0.52; 23,749; 

2011).

475 Abundant. 


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TABLE 2—MARINE MAMMALS THAT COULD OCCUR IN THE PROJECT AREA—Continued 

Species Stock 

ESA/MMPA 

status; 

strategic 

(Y/N) 1

Stock abundance 2

(CV, Nmin, most 

recent abundance 

survey) 3

PBR 4 Relative occurrence in 

project area 

Dall’s porpoise (Phocoena 

dalli).

California/Oregon/Washington.-/-; N 25,750 (0.45; 17,954; 

2014).

172 Abundant. 

Bottlenose dolphin 

(Tursiops truncatus).

California/Oregon/Washington Offshore.-/-; N 1,924 (0.54; 1,255; 2014) .. 11 Rare. 

Striped dolphin (Stenella 

coeruleoala).

California/Oregon/Washington.-/-; N 29,211 (0.2; 24,782; 2014) 238 Rare. 

Risso’s dolphin (Grampus 

griseus).

California/Oregon/Washington.-/-; N 6,336 (0.32; 4,817; 2014) .. 46 Common. 

Short-beaked common dolphin (Delphinus delphis).California/Oregon/Washington.-; N 969,861 (0.17; 839,325; 

2014).

8,393 Common. 

Pacific white-sided dolphin 

(Lagenorhynchus 

obliquidens).

California/Oregon/Washington.-; N 26,814 (0.28; 21,195; 

2014).

191 Abundant. 

Northern right whale dolphin (Lissodelphis borealis).California/Oregon/Washington.-; N 26,556 (0.44; 18,608; 

2014).

179 Common. 

Order Cetartiodactyla—Cetacea—Superfamily Odontoceti (toothed whales, dolphins, and porpoises) 

Family: Ziphiidae 

Cuvier’s beaked whale 

(Ziphius cavirostris).

California/Oregon/Washington.-/-; N 6,590 (0.55; 4,481; 2008) .. 45 Common. 

Baird’s beaked whale 

(Berardius bairdii).

California/Oregon/Washington.-; N 847 (0.81; 466; 2008) ........ 4.7 Common. 

Mesoplodont beaked 

whales 8.

California/Oregon/Washington.-/-; N 694 (0.65; 389; 2008) ........ 3.9 Rare. 

Order Carnivora—Superfamily Pinnipedia 

Family Otariidae (eared seals and sea lions) 

California sea lion 

(Zalophus californianus).

U.S. .................................... -; N 296,750 (n/a; 153,337; 

2011).

9,200 Rare. 

Steller sea lion (Eumetopias 

jubatus).

Eastern U.S. ...................... -; N 41,638 (n/a; 41,638; 2015) 2,498 Common in nearshore 

areas, rare elsewhere. 

Family Phocidae (earless seals) 

Harbor seal 9 (Phoca 

vitulina).

Oregon/Washington Coast -; N 24,732 (unk; unk; n/a) ....... Unknown Common in nearshore 

areas, rare elsewhere. 

Northern elephant seal 

(Mirounga angustirostris).

California breeding ............. -; N 179,000 (n/a; 81,368; 

2010).

4,882 Common in nearshore 

areas, rare elsewhere. 

Northern fur seal 

(Callorhinus ursinus).

California ............................ -; N 14,050 (n/a; 7,524; 2013) .. 451 Common in nearshore 

areas, rare elsewhere. 

1Endangered 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 (see footnote 3) 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. 2Abundance estimates from Carretta et al. (2017) unless otherwise noted. 3 CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable. For certain stocks, 

abundance estimates are actual counts of animals and there is no associated CV. The most recent abundance survey that is reflected in the 

abundance estimate is presented; there may be more recent surveys that have not yet been incorporated into the estimate. 4Potential 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 size (OSP). 5Values for gray whale and North Pacific right whale are from Muto et al. 2016. 6 Humpback whales in the survey area could originate from either the ESA threatened Mexico DPS or from the ESA endangered Central

America DPS. 7 NMFS does not have a defined stock for false killer whales off the West Coast of the U.S. as they are considered uncommon visitors to the 

area; any false killer whales observed off the West Coast of the U.S. would likely be part of the eastern North Pacific population. Of the stocks 

defined by NMFS, the Hawaii Pelagic stock is the most likely to include individuals in the eastern North Pacific population. 8 Includes the following species: Blainville’s beaked whale (M. densirostris), Perrin’s beaked whale (M. perrini), Lesser beaked whale (M. 

peruvianus), Stejneger’s beaked whale (M. stejnegeri), Gingko-toothed beaked whale (M. gingkodens), and Hubbs’ beaked whale (M. 

carlhubbsi). 9The most recent abundance estimate is from 1999. This is the best available information, but because this abundance estimate is >8 years 

old, there is no current estimate of abundance available for this stock. 

All species that could potentially 

occur in the proposed survey area are 

included in Table 2. However, as 

described below, the spatial occurrence 

of the North Pacific right whale and 

dwarf sperm whale are such that take is 


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not expected to occur for these species. 

The North Pacific right whale is one of 

the most endangered species of whale in 

the world (Carretta et al. 2017). Only 82 

sightings of right whales in the entire 

eastern North Pacific were reported 

from 1962 to 1999, with the majority of 

these occurring in the Bering Sea and 

adjacent areas of the Aleutian Islands 

(Brownell et al. 2001). Most sightings in 

the past 20 years have occurred in the 

southeastern Bering Sea, with a few in 

the Gulf of Alaska (Wade et al. 2011). 

Despite many miles of systematic aerial 

and ship-based surveys for marine 

mammals off the coasts of Washington, 

Oregon and California over several 

years, only seven documented sightings 

of right whales were made from 1990 to 

2000 (Waite et al. 2003). Because of the 

small population size and the fact that 

North Pacific right whales spend the 

summer feeding in high latitudes, the 

likelihood that the proposed survey 

would encounter a North Pacific right 

whale is discountable. Along the U.S. 

west coast, no at-sea sightings of dwarf 

sperm whales have ever been reported 

despite numerous vessel surveys of this 

region (Barlow 1995; Barlow and 

Gerrodette 1996; Barlow and Forney 

2007; Forney 2007; Barlow 2010, Barlow 

2016). Therefore, based on the best 

available information, we believe the 

likelihood of the survey encountering a 

dwarf sperm whale is discountable. SIO 

requested authorization for the 

incidental take of dwarf sperm whales 

(the request was for a combined two 

takes of pygmy and/or dwarf sperm 

whales). However as we have 

determined the likelihood of take of 

dwarf sperm whales is discountable, we 

do not propose to authorize take of 

dwarf sperm whales. Thus, the North 

Pacific right whale and dwarf sperm 

whale are not discussed further in this 

document. 

We have reviewed SIO’s species 

descriptions, including life history 

information, distribution, regional 

distribution, diving behavior, and 

acoustics and hearing, for accuracy and 

completeness. We refer the reader to 

Section 4 of SIO’s IHA application, 

rather than reprinting the information 

here. Below, for the 27 species that are 

likely to be taken by the activities 

described, we offer a brief introduction 

to the species and relevant stock(s) as 

well as available information regarding 

population trends and threats, and 

describe any information regarding local 

occurrence. 

Humpback Whale 

Humpback whales are found 

worldwide in all ocean basins. In 

winter, most humpback whales occur in 

the subtropical and tropical waters of 

the Northern and Southern Hemispheres 

(Muto et al., 2015). These wintering 

grounds are used for mating, giving 

birth, and nursing new calves. 

Humpback whales migrate nearly 3,000 

mi (4,830 km) from their winter 

breeding grounds to their summer 

foraging grounds in Alaska. The 

humpback whale is the most common 

species of large cetacean reported off the 

coasts of Oregon and Washington from 

May to November (Green et al. 1992; 

Calambokidis et al. 2004). 

There are five stocks of humpback 

whales, one of which occurs along the 

U.S. west coast: The California/Oregon/ 

Washington Stock, which includes 

animals that appear to be part of two 

separate feeding groups, a California 

and Oregon feeding group and a 

northern Washington and southern 

British Columbia feeding group 

(Calambokidis et al. 2008, Barlow et al. 

2011). Very few photographic matches 

between these feeding groups have been 

documented (Calambokidis et al. 2008). 

Humpbacks from both groups have been 

photographically matched to breeding 

areas off Central America, mainland 

Mexico, and Baja California, but whales 

from the northern Washington and 

southern British Columbia feeding 

group also winter near the Hawaiian 

Islands and the Revillagigedo Islands off 

Mexico (Barlow et al. 2011). 

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. The Mexico DPS 

and the Central America DPS are the 

only DPSs that are expected to occur in 

the survey area. The Mexico DPS is 

listed as threatened and the Central 

America DPS is listed as endangered 

under the ESA (81 FR 62259; September 

8, 2016). The California/Oregon/ 

Washington stock is considered a 

depleted and strategic stock under the 

MMPA. 

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. 2008). 

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. 2000). North Pacific 

blue whales were once thought to 

belong to as many as five separate 

populations (Reeves et al. 1998), but 

acoustic evidence suggests only two 

populations, in the eastern and western 

North Pacific, respectively (Stafford et 

al. 2001, Stafford 2003, McDonald et al. 

2006, Monnahan et al. 2014). Only the 

Eastern North Pacific stock of blue 

whale occurs in the proposed survey 

area. 

Blue whale densities along the U.S. 

west coast including Oregon are 

believed to be highest in shelf waters, 

with lower densities in deeper offshore 

areas (Becker et al. 2012; Calambokidis 

et al. 2015). Based on the absolute 

dynamic topography of the region, blue 

whales could occur in relatively high 

densities off Oregon during July– 

December (Pardo et al. 2015). 

Five blue whale sightings were 

reported in the proposed project area off 

Oregon/Washington during 1991–2008; 

one sighting occurred within the 

nearshore portion of the proposed 

Astoria Fan survey area, and four 

sightings occurred nearshore, east of the 

Southern Oregon survey area (Carretta et 

al. 2017). Hazen et al. (2016) examined 

blue whale tag data from 182 

individuals along the western U.S. 

during 1993–2008; multiple tag data 

tracks were within the proposed project 

area, particularly between August and 

November. Blue whales are listed as 

endangered under the ESA, and the 

Eastern North Pacific stock of blue 

whales is considered a depleted and 

strategic stock under the MMPA. 

Fin Whale 

Fin whales are found throughout all 

oceans from tropical to polar latitudes. 

The species occurs most commonly 

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). 


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The North Pacific population 

summers from the Chukchi Sea to 

California and winters from California 

southwards (Gambell 1985). 

Aggregations of fin whales are found 

year-round off southern and central 

California (Dohl et al. 1980, 1983; 

Forney et al. 1995; Barlow 1997) and in 

the summer off Oregon (Green et al. 

1992; Edwards et al. 2015). 

Vocalizations from fin whales have also 

been detected year-round off northern 

California, Oregon, and Washington 

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

2000a; Stafford et al. 2007, 2009). Fin 

whales are listed as endangered under 

the ESA, and the California/Oregon/ 

Washington stock of fin whales is 

considered depleted and strategic under 

the MMPA. 

Sei Whale 

The sei whale occurs in all ocean 

basins (Horwood 2009) but appears to 

prefer mid-latitude temperate waters 

(Jefferson et al. 2008). 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). 

Sei whales are rare in the waters off 

California, Oregon, and Washington 

(Brueggeman et al. 1990; Green et al. 

1992; Barlow 1994, 1997). Only nine 

confirmed sightings were reported for 

California, Oregon, and Washington 

during extensive surveys from 1991– 

2008, including two within or near the 

westernmost portion of the Southern 

Oregon survey area (Green et al. 1992, 

1993; Hill and Barlow 1992; Carretta 

and Forney 1993; Mangels and 

Gerrodette 1994; Von Saunder and 

Barlow 1999; Barlow 2003; Forney 2007; 

Barlow 2010; Carretta et al. 2016a). Two 

sightings of four individuals were made 

from the Langseth seismic vessel off 

Washington/Oregon during June–July 

2012 (RPS 2012), including within the 

proposed project area. Sei whales are 

listed as endangered under the ESA, and 

the Eastern North Pacific stock of sei 

whales is considered a depleted and 

strategic stock under the MMPA. 

Minke Whale 

The minke whale has a cosmopolitan 

distribution ranging from the tropics 

and subtropics to the ice edge in both 

hemispheres (Jefferson et al. 2008). The 

California/Oregon/Washington stock of 

minke whale is the only stock that 

occurs in the proposed survey area. 

Minke whale sightings have been made 

off Oregon and Washington in shelf and 

deeper waters (Green et al. 1992; Adams 

et al. 2014; Carretta et al. 2017). A single 

minke whale was observed off the outer 

Washington coast (∼47° N.) during small 

boat surveys from August 2004 through 

September 2008, 14 km from shore with 

a bottom depth of 38 m (Oleson et al. 

2009). One sighting was made near the 

Astoria Fan survey area at the 200-m 

isopleth off the mouth of the Columbia 

River in July 2012 (Adams et al. 2014). 

Minke whales strandings have been 

reported in all seasons in Washington; 

most strandings (52 percent) occurred in 

spring (Norman et al. 2004). The minke 

whale is not listed as threatened or 

endangered under the ESA, and the 

California/Oregon/Washington stock is 

not listed as depleted or strategic under 

the MMPA. 

Gray Whale 

Gray whales occur along the eastern 

and western margins of the North 

Pacific. During summer and fall, most 

whales in the Eastern North Pacific 

stock feed in the Chukchi, Beaufort and 

northwestern Bering Seas, with the 

exception of a relatively small number 

of whales (approximately 200) that 

summer and feed along the Pacific coast 

between Kodiak Island, Alaska and 

northern California (Carretta et al. 

2017). Three primary wintering lagoons 

in Baja California, Mexico are utilized, 

and some females are known to make 

repeated returns to specific lagoons 

(Jones 1990). 

According to predictive density 

distribution maps, low densities of gray 

whales could be encountered 

throughout the Astoria Fan and 

Southern Oregon survey areas (Menza et 

al. 2016). During aerial surveys over the 

shelf and slope off Oregon and 

Washington, gray whales were seen 

during the months of January, June– 

July, and September; one sighting was 

made within the Astoria Fan survey area 

in water >200 m during June 2011 

(Adams et al. 2014). The proposed 

surveys would occur during the summer 

feeding season for gray whales in the 

Washington/Oregon region. Thus, gray 

whales could be encountered in the 

eastern portion of the proposed project 

area where the water is shallower. The 

Eastern North Pacific gray whale is not 

listed as threatened or endangered 

under the ESA nor is it classified as a 

depleted or strategic stock under the 

MMPA. 

Sperm Whale 

Sperm whales are widely distributed 

across the entire North Pacific and into 

the southern Bering Sea in summer, but 

the majority are thought to be south of 

40° N. in winter (Rice 1974, 1989; Gosho 

et al. 1984; Miyashita et al. 1995). They 

are generally distributed over large areas 

that have high secondary productivity 

and steep underwater topography, in 

waters at least 1000 m deep (Jaquet and 

Whitehead 1996; Whitehead 2009). 

Sperm whales are seen off Washington 

and Oregon in every season except 

winter (Green et al. 1992). Estimates of 

sperm whale abundance in California, 

Oregon, and Washington waters out to 

300 nautical miles ranged between 

2,000 and 3,000 animals for the 1991– 

2008 time series (Moore and Barlow 

2014). At least five sightings during 

these surveys were within or adjacent to 

the Southern Oregon survey area, and 

one sighting was within the Astoria Fan 

survey area (Carretta et al. 2017). Sperm 

whales are listed as endangered under 

the ESA, and the California/Oregon/ 

Washington stock is considered 

depleted and strategic under the MMPA. 

Pygmy Sperm Whale 

Pygmy sperm whales are found in 

tropical and warm-temperate waters 

throughout the world (Ross and 

Leatherwood 1994) and prefer deeper 

waters with observations of this species 

in greater than 4,000 m depth (Baird et 

al., 2013). Along the U.S. west coast, 

sightings of this species, and of animals 

identified only as Kogia spp., have been 

rare. However, this probably reflects 

their pelagic distribution, small body 

size and cryptic behavior, rather than a 

measure of rarity. Barlow (2010) used 

data collected in 1991–2008 to estimate 

an abundance of 229 Kogia spp. off 

Oregon and Washington. However, no 

Kogia spp. were sighted during surveys 

off Oregon and Washington in 2014 

(Barlow 2016). Pygmy sperm whales are 

not listed as endangered or threatened 

under the ESA, and the California/ 

Oregon/Washington stock is not 

considered strategic or designated as 

depleted under the MMPA. 

Killer Whale 

Killer whales have been observed in 

all oceans and seas of the world 

(Leatherwood and Dahlheim 1978). 

Although reported from tropical and 

offshore waters (Heyning and Dahlheim 

1988), killer whales prefer the colder 

waters of both hemispheres, with 

greatest abundances found within 800 

km of major continents (Mitchell 1975). 

Along the west coast of North America, 

killer whales occur along the entire 


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Alaskan coast, in British Columbia and 

Washington inland waterways, and 

along the outer coasts of Washington, 

Oregon and California (Carretta et al. 

2017). Based on aspects of morphology, 

ecology, genetics and behavior killer 

whale stocks off the U.S. west coast are 

classified as either resident, transient or 

offshore (Ford and Fisher 1982; Baird 

and Stacey 1988; Baird et al. 1992, 

Hoelzel et al. 1998). The offshore stocks 

apparently do not mix with the transient 

and resident killer whale stocks found 

in these regions (Ford et al. 1994, Black 

et al. 1997). 

Eight killer whale stocks are 

recognized within the Pacific U.S. 

Exclusive Economic Zone. Of these, two 

stocks occur in the proposed project 

area: the West Coast Transient stock 

which occurs from Alaska through 

California, and the Eastern North Pacific 

Offshore stock which occurs from 

Southeast Alaska through California. 

Killer whales are not listed as 

endangered or threatened under the 

ESA (with the exception of the 

endangered Southern Resident DPS 

which does not occur in the survey 

area), and the West Coast Transient 

stock and Eastern North Pacific Offshore 

stock are not designated as depleted or 

strategic under the MMPA. 

False Killer Whale 

False killer whales are found 

worldwide in tropical and warmtemperate waters (Stacey et al. 1994). In 

the North Pacific, this species occurs 

throughout the waters of southern 

Japan, Hawaii, and the eastern tropical 

Pacific. The species 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). 

False killer whales are typically only 

observed off the U.S. west coast during 

warm-water periods. Several sightings 

were made off California during 2014– 

2016 when waters were unusually warm 

(pers. comm. K. Forney, NMFS 

Southwest Fisheries Science Center, to 

J. Carduner, NMFS, July 27, 2017). False 

killer whales observed in the survey 

area would be expected to originate 

from the eastern North Pacific 

population that is primarily found south 

of U.S. waters (pers. comm. K. Forney, 

NMFS Southwest Fisheries Science 

Center, to J. Carduner, NMFS, July 27, 

2017). NMFS does not have a defined 

stock for false killer whales off the U.S. 

west coast as they are considered 

uncommon visitors to the area; any false 

killer whales observed off the U.S. west 

coast would likely be part of the broader 

eastern North Pacific population. Of the 

stocks defined by NMFS, the Hawaii 

Pelagic stock is the most likely to 

include individuals in the eastern North 

Pacific population. False killer whales 

are not listed as endangered or 

threatened under the ESA (with the 

exception of the endangered Main 

Hawaiian Islands insular DPS which 

does not occur in the survey area), and 

the Hawaii pelagic stock is not 

designated as depleted or strategic 

under the MMPA. 

Short-Finned Pilot Whale 

Short-finned pilot whales are found in 

all oceans, primarily in tropical and 

warm-temperate waters (Carretta et al., 

2016). The species prefers deeper 

waters, ranging from 324 m to 4,400 m, 

with most sightings between 500 m and 

3,000 m (Baird 2016). The California/ 

Oregon/Washington Stock of shortfinned pilot whales are largely confined 

to the California Current and eastern 

tropical Pacific. After a strong El Nin ̃ o 

event in 1982–83, short-finned pilot 

whales virtually disappeared from this 

region, and despite increased survey 

effort along the entire U.S. west coast, 

sightings and fishery takes are rare and 

have primarily occurred during warmwater years (Julian and Beeson 1998, 

Carretta et al. 2004, Barlow 2016). No 

short-finned pilot whales were seen 

during surveys off Oregon and 

Washington in 1989–1990, 1992, 1996, 

and 2001 (Barlow 2003). A few sightings 

were made off California during surveys 

in 1991–2008 (Barlow 2010). Carrettaet 

al. (2017) reported two sightings off 

Oregon during 1991–2008, both near the 

southern portion of the Astoria Fan 

survey area. Short-finned pilot whales 

are not listed as endangered or 

threatened under the ESA, and the 

California/Oregon/Washington stock is 

not considered a depleted or strategic 

stock under the MMPA. 

Harbor Porpoise 

In the eastern North Pacific Ocean, 

harbor porpoise are found in coastal and 

inland waters from Point Barrow, along 

the Alaskan coast, and down the west 

coast of North America to Point 

Conception, California (Gaskin 1984). 

Harbor porpoise are known to occur 

year-round in the inland transboundary 

waters of Washington and British 

Columbia, Canada (Osborne et al. 1988) 

and along the Oregon/Washington coast 

(Barlow 1988, Barlow et al. 1988, Green 

et al. 1992). Based on recent genetic 

evidence (Chivers et al. 2002, 2007) 

there are three separate stocks of North 

Pacific harbor porpoise that occur in 

Oregon/Washington waters: a Northern 

California/Southern Oregon stock (Point 

Arena, CA, to Lincoln City, OR), a 

Northern Oregon/Washington Coast 

stock (Lincoln City, OR, to Cape 

Flattery, WA), and the Washington 

Inland Waters stock (in waters east of 

Cape Flattery). Only the Northern 

California/Southern Oregon stock and 

Northern Oregon/Washington Coast 

stock occur in the proposed survey area. 

Harbor porpoises inhabit coastal 

Oregon and Washington waters yearround, although there appear to be 

distinct seasonal changes in abundance 

there (Barlow 1988; Green et al. 1992). 

Green et al. (1992) reported that 

encounter rates were high during fall 

and winter, intermediate during spring, 

and low during summer. Encounter 

rates were highest along the Oregon/ 

Washington coast in the area from Cape 

Blanco (∼43° N.), east of the proposed 

Southern Oregon survey area, to 

California, from fall through spring. 

During summer, the reported encounter 

rates decreased notably from inner shelf 

to offshore waters. Nearly 100 sightings 

were reported within or east of the 

proposed project area during aerial 

surveys in 2007–2012 (Forney et al. 

2014). Two sightings of nine individuals 

were made from the Langseth seismic 

vessel off the southern coast of 

Washington during July 2012 (RPS 

2012); all sightings occurred nearshore 

and to the east of the Astoria Fan survey 

area. The harbor porpoise is not listed 

as endangered or threatened under the 

ESA and the Northern California/ 

Southern Oregon stock and Northern 

Oregon/Washington Coast stock are not 

considered depleted or strategic stocks 

under the MMPA. 

Dall’s Porpoise 

The Dall’s porpoise is distributed 

throughout temperate to subantarctic 

waters of the North Pacific and adjacent 

seas (Jefferson et al. 2015). Off the U.S. 

west coast, they are generally found 

along shelf, slope and offshore waters 

(Morejohn 1979). Dall’s porpoise is 

likely the most abundant small cetacean 

in the North Pacific Ocean, and its 

abundance changes seasonally, likely in 

relation to water temperature (Becker 

2007). Becker et al. (2014) projected 

high densities off southern Oregon 

throughout the year, with moderate 

densities to the north. According to 

predictive density distribution maps, 

the highest densities off southern 

Washington and Oregon occur along the 

500 m isobath (Menza et al. 2016). Dall’s 

porpoise was the most abundant species 

sighted off Oregon/Washington during 

1996, 2001, 2005, and 2008 shipboard 

surveys up to ∼550 km from shore 

(Barlow 2003, 2010) with numerous 

other sightings within and near the 

Astoria Fan and Southern Oregon 

survey areas during the summer and fall 


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(Becker et al. 2014; Carretta et al. 

2016a). Dall’s porpoise is not listed as 

threatened or endangered under the 

ESA and the California/Oregon/ 

Washington stock is not classified as a 

depleted or strategic stock under the 

MMPA. 

Bottlenose Dolphin 

Bottlenose dolphins are widely 

distributed throughout the world in 

tropical and warm-temperate waters 

(Perrin et al. 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). Bottlenose dolphins 

occur frequently off the coast of 

California, and sightings have been 

made as far north as 41° N., but few 

records exist offshore Oregon and 

Washington (Carretta et al. 2017). 

Adams et al. (2014) made one sighting 

in Washington, to the north of the 

Astoria Fan survey area, during 

September 2012. Bottlenose dolphins 

are not listed as endangered or 

threatened under the ESA, and the 

California/Oregon/Washington pelagic 

stock is not considered a depleted or 

strategic stock under the MMPA. 

Striped Dolphin 

Striped dolphins are found in tropical 

to warm-temperate waters throughout 

the world (Carretta et al., 2016). 

However, in the eastern North Pacific, 

its distribution extends as far north as 

Washington (Jefferson et al. 2015). 

Striped dolphins are a deep water 

species, preferring depths greater than 

3,500 m (Baird 2016), but have been 

observed approaching shore where there 

is deep water close to the coast 

(Jefferson et al. 2008). The abundance of 

striped dolphins off the U.S. west coast 

appears to be variable among years and 

could be affected by oceanographic 

conditions (Carretta et al. 2016a). 

Striped dolphins regularly occur off 

California (Becker et al. 2012), where 

they are seen 185–556 km from the coast 

(Carretta et al. 2017), though very few 

sightings have been made off Oregon 

(Barlow 2016), and no sightings have 

been reported for Washington. However, 

strandings have occurred along the 

coasts of Oregon and Washington 

(Carretta et al. 2017). During surveys off 

the U.S. west coast in 2014, striped 

dolphins were seen as far north as 44ß 

N. Striped dolphins are not listed as 

endangered or threatened under the 

ESA, and the California/Oregon/ 

Washington stock is not considered a 

depleted or strategic stock under the 

MMPA. 

Short-Beaked Common Dolphin 

The short-beaked common dolphin is 

found in tropical and warm temperate 

oceans around the world (Perrin 2009). 

Short-beaked common dolphins are the 

most abundant cetacean off California, 

and are widely distributed between the 

coast and at least 300 nautical miles 

from shore. 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 sea 

mounts (Evans 1994). 

Few sightings of short-beaked 

common dolphins have been made off 

Oregon, and no sightings exist for 

Washington waters (Carretta et al. 2017). 

During surveys in 1991–2008, one 

sighting was made within the Astoria 

Fan survey area, and several records 

exist southwest of the Southern Oregon 

survey area (Carretta et al. 2017). During 

surveys off the west coast in 2014, 

sightings were made as far north as 44° 

N. (Barlow 2014). Short-beaked common 

dolphins are not listed as endangered or 

threatened under the ESA, and the 

California/Oregon/Washington stock is 

not considered a depleted or strategic 

stock under the MMPA. 

Pacific White-Sided Dolphin 

Pacific white-sided dolphins are 

endemic to temperate waters of the 

North Pacific Ocean, and common both 

on the high seas and along the 

continental margins (Brownell et al. 

1999). In the eastern North Pacific 

Ocean, including waters off Oregon, the 

Pacific white-sided dolphin is one of the 

most common cetacean species, 

occurring primarily in shelf and slope 

waters (Green et al. 1993; Barlow 2003, 

2010). It is known to occur close to 

shore in certain regions, including 

seasonally off southern California 

(Brownell et al. 1999). 

Based on year-round aerial surveys off 

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

cetacean species (Green et al. 1992, 

1993). Adams et al. (2014) also reported 

numerous offshore sightings off Oregon 

during summer, fall, and winter surveys 

in 2011 and 2012, including in the 

Southern Oregon survey area during 

September. Pacific white-sided dolphins 

are not listed as endangered or 

threatened under the ESA, and the 

California/Oregon/Washington stock is 

not considered a depleted or strategic 

stock under the MMPA. 

Northern Right Whale Dolphin 

Northern right-whale dolphins are 

endemic to temperate waters of the 

North Pacific Ocean. Off the U.S. west 

coast, they have been seen primarily in 

shelf and slope waters, with seasonal 

movements into the Southern California 

Bight (Leatherwood and Walker 1979; 

Dohl et al. 1980; 1983). Becker et al. 

(2014) predicted relatively high 

densities off southern Oregon, and 

moderate densities off northern Oregon 

and Washington. Barlow (2003, 2010) 

also found that the northern right whale 

dolphin was one of the most abundant 

marine mammal species off Oregon/ 

Washington during 1996, 2001, 2005, 

and 2008 shipboard surveys. Several 

sightings were within and near the 

Astoria Fan and Southern Oregon 

survey areas during the summer and fall 

during surveys off California, Oregon 

and Washington (Forney 2007; Barlow 

2010; Becker et al. 2012; Carretta et al. 

2017). Northern right-whale dolphins 

are not listed as endangered or 

threatened under the ESA, and the 

California/Oregon/Washington stock is 

not considered a depleted or strategic 

stock under the MMPA. 

Risso’s Dolphin 

Risso’s dolphins are found in tropical 

to warm-temperate waters (Carretta et 

al., 2016). The species occurs from 

coastal to deep water but is most often 

found in depths greater than 3,000 m 

with the highest sighting rate in depths 

greater than 4,500 m (Baird 2016). It 

primarily occurs between 60ßN and 60ßS 

where surface water temperatures are at 

least 10ßC (Kruse et al. 1999). The 

distribution and abundance of Risso’s 

dolphin is highly variable from 

California to Washington, presumably in 

response to changing oceanographic 

conditions on both annual and seasonal 

time scales (Forney and Barlow 1998; 

Buchanan et al. 2001). The highest 

densities were predicted along the 

coasts of Washington, Oregon, and 

central and southern California (Becker 

et al. 2012). Off Oregon and 

Washington, Risso’s dolphins are most 

abundant over continental slope and 

shelf waters during spring and summer, 

less so during fall, and rare during 

winter (Green et al. 1992, 1993). Risso’s 

dolphins were sighted off Oregon, 

including near the Astoria Fan and 

Southern Oregon survey areas, in June 

and October 2011 (Adams et al. 2014). 

Risso’s dolphins are not listed as 

endangered or threatened under the 

ESA, and the California/Oregon/ 

Washington stock is not considered a 

depleted or strategic stock under the 

MMPA. 


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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 found in 

deep water over and near the 

continental slope (Jefferson et al. 2008). 

Cuvier’s beaked whale abundance for 

waters off Oregon and Washington in 

2014 was estimated at 432 (Barlow 

2016). One Cuvier’s beaked whale 

sighting was made west of the proposed 

Southern Oregon survey area during the 

1991–2008 surveys (Carretta et al. 2017). 

One sighting of three individuals was 

recorded in June 2006 during surveys 

off Washington during August 2004 

through September 2008, north of the 

Astoria Fan survey area (Oleson et al. 

2009). Cuvier’s beaked whales are not 

listed as endangered or threatened 

under the ESA, and the California/ 

Oregon/Washington stock is not 

considered a depleted or strategic stock 

under the MMPA. 

Baird’s Beaked Whale 

Baird’s beaked whales are distributed 

throughout deep waters and along the 

continental slopes of the North Pacific 

Ocean (Balcomb 1989, Macleod et al. 

2006). It is sometimes seen close to 

shore where deep water approaches the 

coast, but its primary habitat is over or 

near the continental slope and oceanic 

seamounts (Jefferson et al. 2015). Along 

the U.S. west coast, Baird’s beaked 

whales have been sighted primarily 

along the continental slope (Green et al. 

1992; Becker et al. 2012; Carretta et al. 

2016a) from late spring to early fall 

(Green et al. 1992). During 1991–2008 

surveys, several sightings were reported 

to the south and west of the Southern 

Oregon survey area, to the west of the 

Astoria Fan survey area, and within the 

eastern portion of the Astoria Fan 

survey area (Carretta et al. 2016a). 

Predicted density modeling showed 

higher densities in slope waters off 

northern Oregon, near the Astoria Fan 

survey area, compared with southern 

Oregon (Becker et al. 2012). Baird’s 

beaked whales are not listed as 

endangered or threatened under the 

ESA, and the California/Oregon/ 

Washington stock is not considered a 

depleted or strategic stock under the 

MMPA. 

Mesoplodont Beaked Whales 

Mesoplodont beaked whales are 

distributed throughout deep waters and 

along the continental slopes of the 

North Pacific Ocean. The six species 

known to occur in this region are: 

Blainville’s beaked whale (M. 

densirostris), Perrin’s beaked whale (M. 

perrini), Lesser beaked whale (M. 

peruvianus), Stejneger’s beaked whale 

(M. stejnegeri), Gingko-toothed beaked 

whale (M. gingkodens), and Hubbs’ 

beaked whale (M. carlhubbsi) (Mead 

1989, Henshaw et al. 1997, Dalebout et 

al. 2002, MacLeod et al. 2006). Based on 

bycatch and stranding records in this 

region, it appears that Hubb’s beaked 

whale is most commonly encountered 

(Carretta et al. 2008, Moore and Barlow 

2013). Insufficient sighting records exist 

off the U.S. west coast to determine any 

possible spatial or seasonal patterns in 

the distribution of mesoplodont beaked 

whales. Until methods of distinguishing 

these six species at-sea are developed, 

the management unit must be defined to 

include all Mesoplodon stocks in this 

region. Although mesoplodont beaked 

whales have been sighted along the U.S. 

west coast on several line transect 

surveys utilizing both aerial and 

shipboard platforms, the rarity of 

sightings has historically precluded 

reliable population estimates. 

Mesoplodont beaked are not listed as 

endangered or threatened under the 

ESA, and the California, Oregon and 

Washington stock is not considered a 

depleted or strategic stock under the 

MMPA. 

California Sea Lion 

The primary range of the California 

sea lion includes the coastal areas and 

offshore islands of the eastern North 

Pacific Ocean from British Columbia, 

Canada, to central Mexico, including the 

Gulf of California (Jefferson et al. 2015). 

However, its distribution is expanding 

(Jefferson et al. 2015), and its secondary 

range extends into the Gulf of Alaska 

where it is occasionally recorded 

(Maniscalco et al. 2004) and southern 

Mexico (Gallo-Reynoso and Solo ́rzanoVelasco 1991). California sea lion 

breeding areas are on islands located in 

southern California, in western Baja 

California (Mexico), and the Gulf of 

California. During the breeding season, 

most California sea lions inhabit 

southern California and Mexico. In 

California and Baja California, births 

occur on land from mid-May to late 

June. 

California sea lions are coastal 

animals that often haul out on shore 

throughout the year. Off Oregon and 

Washington, peak numbers occur during 

the fall. During aerial surveys off the 

coasts of Oregon and Washington during 

1989–1990, California sea lions were 

sighted at sea during the fall and winter, 

but no sightings were made during 

June–August (Bonnell et al. 1992). 

Numbers off Oregon decrease during 

winter, as animals travel further north 

(Mate 1975 in Bonnell et al. 1992). 

California sea lions are not listed as 

threatened or endangered under the 

ESA, and the U.S. stock is not 

considered a depleted or strategic stock 

under the MMPA. 

Steller Sea Lion 

Steller sea lions range along the North 

Pacific Rim from northern Japan to 

California (Loughlin et al. 1984), with 

centers of abundance and distribution in 

the Gulf of Alaska and Aleutian Islands. 

They typically inhabit waters from the 

coast to the outer continental shelf and 

slope throughout their range and are not 

considered migratory, although foraging 

animals can travel long distances 

(Loughlin et al. 2003; Raum-Suryan et 

al. 2002). 

During surveys off the coasts of 

Oregon and Washington, Bonnell et al. 

(1992) noted that 89 percent of sea lions 

occurred over the shelf at a mean 

distance of 21 km from the coast and 

near or in waters <200 m deep; the 

farthest sighting occurred ∼40 km from 

shore, and the deepest sighting location 

was 1,611 m deep. Sightings were made 

along the 200 m depth contour within 

and near the proposed Astoria Fan and 

Southern Oregon survey sites 

throughout the year (Bonnell et al. 

1992). The Eastern DPS of Steller sea 

lions is not listed as endangered or 

threatened under the ESA and the 

Eastern U.S. stock is not considered a 

depleted or strategic stock under the 

MMPA. 

Harbor Seal 

Harbor seals inhabit coastal and 

estuarine waters off Baja California, 

north along the western coasts of the 

continental U.S., British Columbia, and 

Southeast Alaska, west through the Gulf 

of Alaska and Aleutian Islands, and in 

the Bering Sea north to Cape Newenham 

and the Pribilof Islands. They haul out 

on rocks, reefs, beaches, and drifting 

glacial ice and feed in marine, estuarine, 

and occasionally fresh waters. Harbor 

seals generally are non-migratory, with 

local movements associated with tides, 

weather, season, food availability, and 

reproduction (Scheffer and Slipp 1944; 

Fisher 1952; Bigg 1969, 1981). 

Jeffries et al. (2000) documented 

several harbor seal rookeries and 

haulouts along the Washington 

coastline; it is the only pinniped species 

that breeds in Washington. During 

surveys off the Oregon and Washington 

coasts, 88 percent of at-sea harbor seals 

occurred over shelf waters <200 m deep, 

with a few sightings near the 2000 m 

contour, and only one sighting over 

deeper water (Bonnell et al. 1992). Most 


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(68 percent) at-sea sightings were 

recorded in September and November 

(Bonnell et al. 1992). Harbor seals are 

not listed as endangered or threatened 

under the ESA and the Oregon/ 

Washington coast stock is not 

considered a depleted or strategic stock 

under the MMPA. 

Northern Elephant Seal 

Northern elephant seals gather at 

breeding areas, located primarily on 

offshore islands of Baja California and 

California, from approximately 

December to March before dispersing for 

feeding. Males feed near the eastern 

Aleutian Islands and in the Gulf of 

Alaska, while females feed at sea south 

of 45° N. (Stewart and Huber, 1993; Le 

Boeuf et al., 1993). Although movement 

and genetic exchange continues 

between rookeries, most elephant seals 

return to their natal rookeries when they 

start breeding (Huber et al., 1991). The 

California breeding population is now 

demographically isolated from the Baja 

California population and is considered 

to be a separate stock. Only the 

California breeding population is 

expected to occur in the proposed 

survey area. Off Washington, most 

elephant seal sightings at sea were 

during June, July, and September; off 

Oregon, sightings were recorded from 

November through May (Bonnell et al. 

1992). Several seals were seen off 

Oregon during summer, fall, and winter 

surveys in 2011 and 2012, including one 

near the Southern Oregon survey area 

during October 2011 (Adams et al. 

2014). Northern elephant seals are not 

listed as threatened or endangered 

under the ESA and the California 

breeding population is not considered a 

depleted or strategic stock under the 

MMPA. 

Northern Fur Seal 

Northern fur seals occur from 

southern California north to the Bering 

Sea and west to the Okhotsk Sea and 

Honshu Island, Japan. Two stocks of 

northern fur seals are recognized in U.S. 

waters: an eastern Pacific stock and a 

California stock (formerly referred to as 

the San Miguel Island stock). Only the 

California stock is expected to occur in 

the proposed survey area. Due to 

differing requirements during the 

annual reproductive season, adult males 

and females typically occur ashore at 

different, though overlapping, times. 

Adult males occur ashore and defend 

reproductive territories during a 3- 

month period from June through August 

while adult females are found ashore for 

as long as 6 months (June–November). 

The northern fur seals spends ∼90 

percent of its time at sea, typically in 

areas of upwelling along the continental 

slopes and over seamounts (Gentry 

1981). The remainder of its life is spent 

on or near rookery islands or haulouts. 

Bonnell et al. (1992) noted the 

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

greatest numbers (87 percent) occurring 

in January–May. Northern fur seals were 

seen as far out from the coast as 185 km, 

and numbers increased with distance 

from land; they were 5–6 times more 

abundant in offshore waters than over 

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

The highest densities were seen in the 

Columbia River plume (∼46° N.) and in 

deep offshore waters (≤2000 m) off 

central and southern Oregon (Bonnell et 

al. 1992). The waters off Washington are 

a known foraging area for adult females, 

and concentrations of fur seals were also 

reported to occur near Cape Blanco, 

Oregon, at ∼42.8° N. (Pelland et al. 

2014). Northern fur seals are not listed 

as threatened or endangered under the 

ESA listed and the California stock is 

not considered a depleted or strategic 

stock under the MMPA. 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

This section includes a summary and 

discussion of the ways that components 

of the specified activity may impact 

marine mammals and their habitat. The 

‘‘Estimated Take by Incidental 

Harassment’’ section later in this 

document includes a quantitative 

analysis of the number of individuals 

that are expected to be taken by this 

activity. The ‘‘Negligible Impact 

Analysis and Determination’’ section 

considers the content of this section, the 

‘‘Estimated Take by Incidental 

Harassment’’ section, and the ‘‘Proposed 

Mitigation’’ section, to draw 

conclusions regarding the likely impacts 

of these activities on the reproductive 

success or survivorship of individuals 

and how those impacts on individuals 

are likely to impact marine mammal 

species or stocks. 

Description of Active Acoustic Sound 

Sources 

This section contains a brief technical 

background on sound, the 

characteristics of certain sound types, 

and on metrics used in this proposal 

inasmuch as the information is relevant 

to the specified activity and to a 

discussion of the potential effects of the 

specified activity on marine mammals 

found later in this document. 

Sound travels in waves, the basic 

components of which are frequency, 

wavelength, velocity, and amplitude. 

Frequency is the number of pressure 

waves that pass by a reference point per 

unit of time and is measured in hertz 

(Hz) or cycles per second. Wavelength is 

the distance between two peaks or 

corresponding points of a sound wave 

(length of one cycle). Higher frequency 

sounds have shorter wavelengths than 

lower frequency sounds, and typically 

attenuate (decrease) more rapidly, 

except in certain cases in shallower 

water. Amplitude is the height of the 

sound pressure wave or the ‘‘loudness’’ 

of a sound and is typically described 

using the relative unit of the 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 (mPa)) and is a 

logarithmic unit that accounts for large 

variations in amplitude; therefore, a 

relatively small change in dB 

corresponds to large changes in sound 

pressure. The source level (SL) 

represents the SPL referenced at a 

distance of 1 m from the source 

(referenced to 1 mPa) while the received 

level is the SPL at the listener’s position 

(referenced to 1 mPa). 

Root mean square (rms) is the 

quadratic mean sound pressure over the 

duration of an impulse. Root mean 

square is calculated by squaring all of 

the sound amplitudes, averaging the 

squares, and then taking the square root 

of the average (Urick, 1983). Root mean 

square accounts for both positive and 

negative values; squaring the pressures 

makes all values positive so that they 

may be accounted for in the summation 

of pressure levels (Hastings and Popper, 

2005). This measurement is often used 

in the context of discussing behavioral 

effects, in part because behavioral 

effects, which often result from auditory 

cues, may be better expressed through 

averaged units than by peak pressures. 

Sound exposure level (SEL; 

represented as dB re 1 mPa2-s) represents 

the total energy contained within a 

pulse and considers both intensity and 

duration of exposure. Peak sound 

pressure (also referred to as 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 


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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 kilohertz (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 nonpulsed sounds can be transient signals 

of short duration but without the 

essential properties of pulses (e.g., rapid 

rise time). Examples of non-pulsed 

sounds include those produced by 

vessels, aircraft, machinery operations 

such as drilling or dredging, vibratory 

pile driving, and active sonar systems 

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

The duration of such sounds, as 

received at a distance, can be greatly 

extended in a highly reverberant 

environment. 

Airgun arrays produce pulsed signals 

with energy in a frequency range from 

about 10–2,000 Hz, with most energy 

radiated at frequencies below 200 Hz. 

The amplitude of the acoustic wave 

emitted from the source is equal in all 

directions (i.e., omnidirectional), but 

airgun arrays do possess some 

directionality due to different phase 

delays between guns in different 

directions. Airgun arrays are typically 

tuned to maximize functionality for data 

acquisition purposes, meaning that 

sound transmitted in horizontal 

directions and at higher frequencies is 

minimized to the extent possible. 

As described above, a MBES and a 

SBP would also be operated from the 

Revelle continuously throughout the 

survey, but not during transits to and 

from the project area. Due to the lower 

source level of the SBP relative to the 

Revelle’s airgun array, the sounds from 

the SBP are expected to be effectively 

subsumed by the sounds from the 

airgun array. Thus, any marine mammal 

that was exposed to sounds from the 

SBP would already have been exposed 

to sounds from the airgun array, which 

are expected to propagate further in the 

water. As such, the SBP is not expected 

to result in the take of any marine 

mammal that has not already been taken 

by the sounds from the airgun array, and 

therefore we do not consider noise from 

the SBP further in this analysis. Each 

ping emitted by the MBES consists of 

four 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 downwarddirected 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. Thus, we 

conclude that the likelihood of marine 

mammal take resulting from MBES 

exposure is discountable and therefore 


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we do not consider noise from the 

MBES further in this analysis 

Acoustic Effects 

Here, we first provide background 

information on marine mammal hearing 

before discussing the potential effects of 

the use of active acoustic sources on 

marine mammals. 

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 lowfrequency 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, with 

best hearing estimated to be from 100 

Hz to 8 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, 

with best hearing from 10 to less than 

100 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, with best hearing between 1– 

50 kHz; 

• Pinnipeds in water; Otariidae (eared 

seals): Generalized hearing is estimated 

to occur between 60 Hz and 39 kHz, 

with best hearing between 2–48 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 

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

2009; Reichmuth and Holt, 2013). 

TABLE 3—MARINE FUNCTIONAL MAMMAL HEARING GROUPS AND THEIR GENERALIZED HEARING RANGES

Hearing group Generalized hearing range* 

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

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

High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, cephalorhynchid, Lagenorhynchus 

cruciger and L. australis).

275 Hz to 160 kHz. 

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

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

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

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

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

For more detail concerning these 

groups and associated frequency ranges, 

please see NMFS (2016) for a review of 

available information. Twenty four 

marine mammal species (all cetaceans) 

have the reasonable potential to cooccur with the proposed survey 

activities. Please refer to Table 2. Of the 

cetacean species that may be present, 6 

are classified as low-frequency 

cetaceans (i.e., all mysticete species), 16 

are classified as mid-frequency 

cetaceans (i.e., all delphinid and ziphiid 

species and the sperm whale), and 2 are 

classified as high-frequency cetaceans 

(i.e., Kogia spp.). 

Potential Effects of Underwater 

Sound—Please refer to the information 

given previously (‘‘Description of Active 

Acoustic Sources’’) regarding sound, 

characteristics of sound types, and 

metrics used in this document. Note 

that, in the following discussion, we 

refer in many cases to a recent review 

article concerning studies of noiseinduced hearing loss conducted from 

1996–2015 (i.e., Finneran, 2015). For 

study-specific citations, please see that 

work. Anthropogenic sounds cover a 

broad range of frequencies and sound 

levels and can have a range of highly 

variable impacts on marine life, from 

none or minor to potentially severe 

responses, depending on received 

levels, duration of exposure, behavioral 

context, and various other factors. The 

potential effects of underwater sound 

from active acoustic sources can 

potentially result in one or more of the 

following: Temporary or permanent 

hearing impairment, non-auditory 

physical or physiological effects, 

behavioral disturbance, stress, and 

masking (Richardson et al., 1995; 

Gordon et al., 2004; Nowacek et al., 

2007; Southall et al., 2007; Go ̈tz et al., 

2009). The degree of effect is 

intrinsically related to the signal 

characteristics, received level, distance 

from the source, and duration of the 

sound exposure. In general, sudden, 

high level sounds can cause hearing 

loss, as can longer exposures to lower 

level sounds. Temporary or permanent 

loss of hearing will occur almost 

exclusively for noise within an animal’s 

hearing range. We first describe specific 

manifestations of acoustic effects before 

providing discussion specific to the use 

of airguns. 

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 


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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 

certain non-auditory physical or 

physiological effects only briefly as we 

do not expect that use of airgun arrays 

are reasonably likely to result in such 

effects (see below for further 

discussion). Potential effects from 

impulsive sound sources can range in 

severity from effects such as behavioral 

disturbance or tactile perception to 

physical discomfort, slight injury of the 

internal organs and the auditory system, 

or mortality (Yelverton et al., 1973). 

Non-auditory physiological effects or 

injuries that theoretically might occur in 

marine mammals exposed to high level 

underwater sound or as a secondary 

effect of extreme behavioral reactions 

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

of an avoidance reaction) caused by 

exposure to sound include neurological 

effects, bubble formation, resonance 

effects, and other types of organ or 

tissue damage (Cox et al., 2006; Southall 

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

Tal et al., 2015). The survey activities 

considered here do not involve the use 

of devices such as explosives or midfrequency tactical sonar that are 

associated with these types of effects. 

1. 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 peakpressure basis and PTS cumulative 

sound exposure level thresholds are 15 

to 20 dB higher than TTS cumulative 

sound exposure level thresholds 

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

level of sound or longer exposure 

duration necessary to cause PTS as 

compared with TTS, it is considerably 

less likely that PTS could occur. 

For mid-frequency cetaceans in 

particular, potential protective 

mechanisms may help limit onset of 

TTS or prevent onset of PTS. Such 

mechanisms include dampening of 

hearing, auditory adaptation, or 

behavioral amelioration (e.g., Nachtigall 

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

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

2016). 

TTS is the mildest form of hearing 

impairment that can occur during 

exposure to sound (Kryter, 1985). While 

experiencing TTS, the hearing threshold 

rises, and a sound must be at a higher 

level in order to be heard. In terrestrial 

and marine mammals, TTS can last from 

minutes or hours to days (in cases of 

strong TTS). In many cases, hearing 

sensitivity recovers rapidly after 

exposure to the sound ends. Few data 

on sound levels and durations necessary 

to elicit mild TTS have been obtained 

for marine mammals. 

Marine mammal hearing plays a 

critical role in communication with 

conspecifics, and interpretation of 

environmental cues for purposes such 

as predator avoidance and prey capture. 

Depending on the degree (elevation of 

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

time), and frequency range of TTS, and 

the context in which it is experienced, 

TTS can have effects on marine 

mammals ranging from discountable to 

serious. For example, a marine mammal 

may be able to readily compensate for 

a brief, relatively small amount of TTS 

in a non-critical frequency range that 

occurs during a time where ambient 

noise is lower and there are not as many 

competing sounds present. 

Alternatively, a larger amount and 

longer duration of TTS sustained during 

time when communication is critical for 

successful mother/calf interactions 

could have more serious impacts. 

Finneran et al. (2015) measured 

hearing thresholds in three captive 

bottlenose dolphins before and after 

exposure to ten pulses produced by a 

seismic airgun in order to study TTS 

induced after exposure to multiple 

pulses. Exposures began at relatively 

low levels and gradually increased over 

a period of several months, with the 

highest exposures at peak SPLs from 

196 to 210 dB and cumulative 

(unweighted) SELs from 193–195 dB. 

No substantial TTS was observed. In 

addition, behavioral reactions were 

observed that indicated that animals can 

learn behaviors that effectively mitigate 

noise exposures (although exposure 

patterns must be learned, which is less 

likely in wild animals than for the 

captive animals considered in this 

study). The authors note that the failure 

to induce more significant auditory 

effects 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 


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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). 

2. 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. 2013). 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 phasein of sound intensity and full array 

exposures at 1–13 km (Madsen et al., 

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

did not exhibit horizontal avoidance 

behavior at the surface. However, 

foraging behavior may have been 

affected. The sperm whales exhibited 19 

percent less vocal (buzz) rate during full 

exposure relative to post exposure, and 

the whale that was approached most 

closely had an extended resting period 

and did not resume foraging until the 

airguns had ceased firing. The 

remaining whales continued to execute 

foraging dives throughout exposure; 

however, swimming movements during 

foraging dives were six 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 


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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 hours 

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 mPa2-s caused blue 

whales to increase call production (Di 

Iorio and Clark, 2010). In contrast, 

McDonald et al. (1995) tracked a blue 

whale with seafloor seismometers and 

reported that it stopped vocalizing and 

changed its travel direction at a range of 

10 km from the acoustic source vessel 

(estimated received level 143 dB pk-pk). 

Blackwell et al. (2013) found that 

bowhead whale call rates dropped 

significantly at onset of airgun use at 

sites with a median distance of 41–45 

km from the survey. Blackwell et al. 

(2015) expanded this analysis to show 

that whales actually increased calling 

rates as soon as airgun signals were 

detectable before ultimately decreasing 

calling rates at higher received levels 

(i.e., 10-minute SELcum of ∼127 dB). 

Overall, these results suggest that 

bowhead whales may adjust their vocal 

output in an effort to compensate for 

noise before ceasing vocalization effort 

and ultimately deflecting from the 

acoustic source (Blackwell et al., 2013, 

2015). These studies demonstrate that 

even low levels of noise received far 

from the source can induce changes in 

vocalization and/or behavior for 

mysticetes. 

Avoidance is the displacement of an 

individual from an area or migration 

path as a result of the presence of a 

sound or other stressors, and is one of 

the most obvious manifestations of 

disturbance in marine mammals 

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

gray whales are known to change 

direction—deflecting from customary 

migratory paths—in order to avoid noise 

from seismic surveys (Malme et al., 

1984). Humpback whales showed 

avoidance behavior in the presence of 

an active seismic array during 

observational studies and controlled 

exposure experiments in western 

Australia (McCauley et al., 2000). 

Avoidance may be short-term, with 

animals returning to the area once the 

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

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

Morton and Symonds, 2002; Gailey et 

al., 2007). Longer-term displacement is 

possible, however, which may lead to 

changes in abundance or distribution 

patterns of the affected species in the 

affected region if habituation to the 

presence of the sound does not occur 

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

2006). 

A flight response is a dramatic change 

in normal movement to a directed and 

rapid movement away from the 

perceived location of a sound source. 

The flight response differs from other 

avoidance responses in the intensity of 

the response (e.g., directed movement, 

rate of travel). Relatively little 

information on flight responses of 

marine mammals to anthropogenic 

signals exist, although observations of 

flight responses to the presence of 

predators have occurred (Connor and 

Heithaus, 1996). The result of a flight 

response could range from brief, 

temporary exertion and displacement 

from the area where the signal provokes 

flight to, in extreme cases, marine 

mammal strandings (Evans and 

England, 2001). However, it should be 

noted that response to a perceived 

predator does not necessarily invoke 

flight (Ford and Reeves, 2008), and 

whether individuals are solitary or in 

groups may influence the response. 

Behavioral disturbance can also 

impact marine mammals in more subtle 

ways. Increased vigilance may result in 

costs related to diversion of focus and 

attention (i.e., when a response consists 

of increased vigilance, it may come at 

the cost of decreased attention to other 

critical behaviors such as foraging or 

resting). These effects have generally not 

been demonstrated for marine 

mammals, but studies involving fish 

and terrestrial animals have shown that 

increased vigilance may substantially 

reduce feeding rates (e.g., Beauchamp 

and Livoreil 1997; Fritz et al. 2002; 

Purser and Radford 2011). In addition, 

chronic disturbance can cause 

population declines through reduction 

of fitness (e.g., decline in body 

condition) and subsequent reduction in 

reproductive success, survival, or both 

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

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

However, Ridgway et al. (2006) reported 

that increased vigilance in bottlenose 

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

deprivation or stress effects. 

Many animals perform vital functions, 

such as feeding, resting, traveling, and 

socializing, on a diel cycle (24-hour 

cycle). Disruption of such functions 

resulting from reactions to stressors 

such as sound exposure are more likely 

to be significant if they last more than 

one diel cycle or recur on subsequent 


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days (Southall et al., 2007). 

Consequently, a behavioral response 

lasting less than one day and not 

recurring on subsequent days is not 

considered particularly severe unless it 

could directly affect reproduction or 

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

there is a difference between multi-day 

substantive behavioral reactions and 

multi-day anthropogenic activities. For 

example, just because an activity lasts 

for multiple days does not necessarily 

mean that individual animals are either 

exposed to activity-related stressors for 

multiple days or, further, exposed in a 

manner resulting in sustained multi-day 

substantive behavioral responses. 

Stone (2015) reported data from at-sea 

observations during 1,196 seismic 

surveys from 1994 to 2010. When large 

arrays of airguns (considered to be 500 

in3 or more) were firing, lateral 

displacement, more localized 

avoidance, or other changes in behavior 

were evident for most odontocetes. 

However, significant responses to large 

arrays were found only for the minke 

whale and fin whale. Behavioral 

responses observed included changes in 

swimming or surfacing behavior, with 

indications that cetaceans remained 

near the water surface at these times. 

Cetaceans were recorded as feeding less 

often when large arrays were active. 

Behavioral observations of gray whales 

during a seismic survey monitored 

whale movements and respirations 

pre-, during and post-seismic survey 

(Gailey et al., 2016). Behavioral state 

and water depth were the best ‘natural’ 

predictors of whale movements and 

respiration and, after considering 

natural variation, none of the response 

variables were significantly associated 

with seismic survey or vessel sounds. 

3. Stress Responses—An animal’s 

perception of a threat may be sufficient 

to trigger stress responses consisting of 

some combination of behavioral 

responses, autonomic nervous system 

responses, neuroendocrine responses, or 

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

Moberg 2000). In many cases, an 

animal’s first and sometimes most 

economical (in terms of energetic costs) 

response is behavioral avoidance of the 

potential stressor. Autonomic nervous 

system responses to stress typically 

involve changes in heart rate, blood 

pressure, and gastrointestinal activity. 

These responses have a relatively short 

duration and may or may not have a 

significant long-term effect on an 

animal’s fitness. 

Neuroendocrine stress responses often 

involve the hypothalamus-pituitaryadrenal system. Virtually all 

neuroendocrine functions that are 

affected by stress—including immune 

competence, reproduction, metabolism, 

and behavior—are regulated by pituitary 

hormones. Stress-induced changes in 

the secretion of pituitary hormones have 

been implicated in failed reproduction, 

altered metabolism, reduced immune 

competence, and behavioral disturbance 

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

Increases in the circulation of 

glucocorticoids are also equated with 

stress (Romano et al. 2004). 

The primary distinction between 

stress (which is adaptive and does not 

normally place an animal at risk) and 

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

During a stress response, an animal uses 

glycogen stores that can be quickly 

replenished once the stress is alleviated. 

In such circumstances, the cost of the 

stress response would not pose serious 

fitness consequences. However, when 

an animal does not have sufficient 

energy reserves to satisfy the energetic 

costs of a stress response, energy 

resources must be diverted from other 

functions. This state of distress will last 

until the animal replenishes its 

energetic reserves sufficiently to restore 

normal function. 

Relationships between these 

physiological mechanisms, animal 

behavior, and the costs of stress 

responses are well-studied through 

controlled experiments and for both 

laboratory and free-ranging animals 

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

1998; Jessop et al., 2003; Krausman et 

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

responses due to exposure to 

anthropogenic sounds or other stressors 

and their effects on marine mammals 

have also been reviewed (Fair and 

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

and, more rarely, studied in wild 

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

For example, Rolland et al. (2012) found 

that noise reduction from reduced ship 

traffic in the Bay of Fundy was 

associated with decreased stress in 

North Atlantic right whales. These and 

other studies lead to a reasonable 

expectation that some marine mammals 

will experience physiological stress 

responses upon exposure to acoustic 

stressors and that it is possible that 

some of these would be classified as 

‘‘distress.’’ In addition, any animal 

experiencing TTS would likely also 

experience stress responses (NRC, 

2003). 

4. Auditory Masking—Sound can 

disrupt behavior through masking, or 

interfering with, an animal’s ability to 

detect, recognize, or discriminate 

between acoustic signals of interest (e.g., 

those used for intraspecific 

communication and social interactions, 

prey detection, predator avoidance, 

navigation) (Richardson et al., 1995; 

Erbe et al., 2016). Masking occurs when 

the receipt of a sound is interfered with 

by another coincident sound at similar 

frequencies and at similar or higher 

intensity, and may occur whether the 

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

wind, waves, precipitation) or 

anthropogenic (e.g., shipping, sonar, 

seismic exploration) in origin. The 

ability of a noise source to mask 

biologically important sounds depends 

on the characteristics of both the noise 

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

signal-to-noise ratio, temporal 

variability, direction), in relation to each 

other and to an animal’s hearing 

abilities (e.g., sensitivity, frequency 

range, critical ratios, frequency 

discrimination, directional 

discrimination, age or TTS hearing loss), 

and existing ambient noise and 

propagation conditions. 

Under certain circumstances, marine 

mammals experiencing significant 

masking could also be impaired from 

maximizing their performance fitness in 

survival and reproduction. Therefore, 

when the coincident (masking) sound is 

man-made, it may be considered 

harassment when disrupting or altering 

critical behaviors. It is important to 

distinguish TTS and PTS, which persist 

after the sound exposure, from masking, 

which occurs during the sound 

exposure. Because masking (without 

resulting in TS) is not associated with 

abnormal physiological function, it is 

not considered a physiological effect, 

but rather a potential behavioral effect. 

The frequency range of the potentially 

masking sound is important in 

determining any potential behavioral 

impacts. For example, low-frequency 

signals may have less effect on highfrequency echolocation sounds 

produced by odontocetes but are more 

likely to affect detection of mysticete 

communication calls and other 

potentially important natural sounds 

such as those produced by surf and 

some prey species. The masking of 

communication signals by 

anthropogenic noise may be considered 

as a reduction in the communication 

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

and may result in energetic or other 

costs as animals change their 

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

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

2007; Di Iorio and Clark 2009; Holt et 

al. 2009). Masking can be reduced in 

situations where the signal and noise 

come from different directions 

(Richardson et al. 1995), through 

amplitude modulation of the signal, or 

through other compensatory behaviors 

(Houser and Moore 2014). Masking can 

be tested directly in captive species 

(e.g., Erbe 2008), but in wild 


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populations it must be either modeled 

or inferred from evidence of masking 

compensation. There are few studies 

addressing real-world masking sounds 

likely to be experienced by marine 

mammals in the wild (e.g., Branstetter et 

al. 2013). 

Masking affects both senders and 

receivers of acoustic signals and can 

potentially have long-term chronic 

effects on marine mammals at the 

population level as well as at the 

individual level. Low-frequency 

ambient sound levels have increased by 

as much as 20 dB (more than three times 

in terms of SPL) in the world’s ocean 

from pre-industrial periods, with most 

of the increase from distant commercial 

shipping (Hildebrand 2009). All 

anthropogenic sound sources, but 

especially chronic and lower-frequency 

signals (e.g., from vessel traffic), 

contribute to elevated ambient sound 

levels, thus intensifying masking. 

Ship Strike 

Vessel collisions with marine 

mammals, or ship strikes, can result in 

death or serious injury of the animal. 

Wounds resulting from ship strike may 

include massive trauma, hemorrhaging, 

broken bones, or propeller lacerations 

(Knowlton and Kraus 2001). An animal 

at the surface may be struck directly by 

a vessel, a surfacing animal may hit the 

bottom of a vessel, or an animal just 

below the surface may be cut by a 

vessel’s propeller. Superficial strikes 

may not kill or result in the death of the 

animal. These interactions are typically 

associated with large whales (e.g., fin 

whales), which are occasionally found 

draped across the bulbous bow of large 

commercial ships upon arrival in port. 

Although smaller cetaceans are more 

maneuverable in relation to large vessels 

than are large whales, they may also be 

susceptible to strike. The severity of 

injuries typically depends on the size 

and speed of the vessel, with the 

probability of death or serious injury 

increasing as vessel speed increases 

(Knowlton and Kraus 2001; Laist et al. 

2001; Vanderlaan and Taggart 2007; 

Conn and Silber 2013). Impact forces 

increase with speed, as does the 

probability of a strike at a given distance 

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

Pace and Silber (2005) also found that 

the probability of death or serious injury 

increased rapidly with increasing vessel 

speed. Specifically, the predicted 

probability of serious injury or death 

increased from 45 to 75 percent as 

vessel speed increased from 10 to 14 kn, 

and exceeded 90 percent at 17 kn. 

Higher speeds during collisions result in 

greater force of impact, but higher 

speeds also appear to increase the 

chance of severe injuries or death 

through increased likelihood of 

collision by pulling whales toward the 

vessel (Clyne, 1999; Knowlton et al. 

1995). In a separate study, Vanderlaan 

and Taggart (2007) analyzed the 

probability of lethal mortality of large 

whales at a given speed, showing that 

the greatest rate of change in the 

probability of a lethal injury to a large 

whale as a function of vessel speed 

occurs between 8.6 and 15 kt. The 

chances of a lethal injury decline from 

approximately 80 percent at 15 kt to 

approximately 20 percent at 8.6 kt. At 

speeds below 11.8 kt, the chances of 

lethal injury drop below 50 percent, 

while the probability asymptotically 

increases toward one hundred percent 

above 15 kt. 

The Revelle travels at a speed of ∼9.3 

km/hour (5 kt) while towing seismic 

survey gear (LGL 2017). At this speed, 

both the possibility of striking a marine 

mammal and the possibility of a strike 

resulting in serious injury or mortality 

are discountable. At average transit 

speed, the probability of serious injury 

or mortality resulting from a strike is 

less than 50 percent. However, the 

likelihood of a strike actually happening 

is again discountable. Ship strikes, as 

analyzed in the studies cited above, 

generally involve commercial shipping, 

which is much more common in both 

space and time than is geophysical 

survey activity. Jensen and Silber (2004) 

summarized ship strikes of large whales 

worldwide from 1975–2003 and found 

that most collisions occurred in the 

open ocean and involved large vessels 

(e.g., commercial shipping). Commercial 

fishing vessels were responsible for 

three percent of recorded collisions, 

while no such incidents were reported 

for geophysical survey vessels during 

that time period. 

It is possible for ship strikes to occur 

while traveling at slow speeds. For 

example, a hydrographic survey vessel 

traveling at low speed (5.5 kt) while 

conducting mapping surveys off the 

central California coast struck and killed 

a blue whale in 2009. The State of 

California determined that the whale 

had suddenly and unexpectedly 

surfaced beneath the hull, with the 

result that the propeller severed the 

whale’s vertebrae, and that this was an 

unavoidable event. This strike 

represents the only such incident in 

approximately 540,000 hours of similar 

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

95% CI = 0–5.5 × 10¥6; NMFS, 2013b). 

In addition, a research vessel reported a 

fatal strike in 2011 of a dolphin in the 

Atlantic, demonstrating that it is 

possible for strikes involving smaller 

cetaceans to occur. In that case, the 

incident report indicated that an animal 

apparently was struck by the vessel’s 

propeller as it was intentionally 

swimming near the vessel. While 

indicative of the type of unusual events 

that cannot be ruled out, neither of these 

instances represents a circumstance that 

would be considered reasonably 

foreseeable or that would be considered 

preventable. 

Although the likelihood of the vessel 

striking a marine mammal is low, we 

require a robust ship strike avoidance 

protocol (see ‘‘Proposed Mitigation’’), 

which we believe eliminates any 

foreseeable risk of ship strike. We 

anticipate that vessel collisions 

involving a seismic data acquisition 

vessel towing gear, while not 

impossible, represent unlikely, 

unpredictable events for which there are 

no preventive measures. Given the 

required mitigation measures, the 

relatively slow speed of the vessel 

towing gear, the presence of bridge crew 

watching for obstacles at all times 

(including marine mammals), the 

presence of marine mammal observers, 

and the short duration of the survey (5.5 

days), we believe that the possibility of 

ship strike is discountable and, further, 

that were a strike of a large whale to 

occur, it would be unlikely to result in 

serious injury or mortality. No 

incidental take resulting from ship 

strike is anticipated, and this potential 

effect of the specified activity will not 

be discussed further in the following 

analysis. 

Stranding—When a living or dead 

marine mammal swims or floats onto 

shore and becomes ‘‘beached’’ or 

incapable of returning to sea, the event 

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

Perrin and Geraci 2002; Geraci and 

Lounsbury 2005; NMFS, 2007). The 

legal definition for a stranding under the 

MMPA is (A) a marine mammal is dead 

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

United States; or (ii) in waters under the 

jurisdiction of the United States 

(including any navigable waters); or (B) 

a marine mammal is alive and is (i) on 

a beach or shore of the United States 

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

on a beach or shore of the United States 

and, although able to return to the 

water, is in need of apparent medical 

attention; or (iii) in the waters under the 

jurisdiction of the United States 

(including any navigable waters), but is 

unable to return to its natural habitat 

under its own power or without 

assistance. 

Marine mammals strand for a variety 

of reasons, such as infectious agents, 

biotoxicosis, starvation, fishery 

interaction, ship strike, unusual 

oceanographic or weather events, sound 


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exposure, or combinations of these 

stressors sustained concurrently or in 

series. However, the cause or causes of 

most strandings are unknown (Geraci et 

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

Best 1982). Numerous studies suggest 

that the physiology, behavior, habitat 

relationships, age, or condition of 

cetaceans may cause them to strand or 

might pre-dispose them to strand when 

exposed to another phenomenon. These 

suggestions are consistent with the 

conclusions of numerous other studies 

that have demonstrated that 

combinations of dissimilar stressors 

commonly combine to kill an animal or 

dramatically reduce its fitness, even 

though one exposure without the other 

does not produce the same result 

(Chroussos 2000; Creel 2005; DeVries et 

al. 2003; Fair and Becker 2000; Foley et 

al. 2001; Moberg, 2000; Relyea 2005; 

Romero 2004; Sih et al. 2004). 

Use of military tactical sonar has been 

implicated in a majority of investigated 

stranding events, although one 

stranding event was associated with the 

use of seismic airguns. This event 

occurred in the Gulf of California, 

coincident with seismic reflection 

profiling by the R/V Maurice Ewing 

operated by Lamont-Doherty Earth 

Observatory (LDEO) of Columbia 

University and involved two Cuvier’s 

beaked whales (Hildebrand 2004). The 

vessel had been firing an array of 20 

airguns with a total volume of 8,500 in3

(Hildebrand 2004; Taylor et al. 2004). 

Most known stranding events have 

involved beaked whales, though a small 

number have involved deep-diving 

delphinids or sperm whales (e.g., 

Mazzariol et al. 2010; Southall et al. 

2013). In general, long duration (∼1 

second) and high-intensity sounds (≤235 

dB SPL) have been implicated in 

stranding events (Hildebrand 2004). 

With regard to beaked whales, midfrequency sound is typically implicated 

(when causation can be determined) 

(Hildebrand 2004). Although seismic 

airguns create predominantly lowfrequency energy, the signal does 

include a mid-frequency component. 

We have considered the potential for the 

proposed survey to result in marine 

mammal stranding and have concluded 

that, based on the best available 

information, stranding is not expected 

to occur. 

Other Potential Impacts—Here, we 

briefly address the potential risks due to 

entanglement and contaminant spills. 

We are not aware of any records of 

marine mammal entanglement in towed 

arrays such as those considered here. 

The discharge of trash and debris is 

prohibited (33 CFR 151.51–77) unless it 

is passed through a machine that breaks 

up solids such that they can pass 

through a 25-mm mesh screen. All other 

trash and debris must be returned to 

shore for proper disposal with 

municipal and solid waste. Some 

personal items may be accidentally lost 

overboard. However, U.S. Coast Guard 

and Environmental Protection Act 

regulations require operators to become 

proactive in avoiding accidental loss of 

solid waste items by developing waste 

management plans, posting 

informational placards, manifesting 

trash sent to shore, and using special 

precautions such as covering outside 

trash bins to prevent accidental loss of 

solid waste. There are no meaningful 

entanglement risks posed by the 

described activity, and entanglement 

risks are not discussed further in this 

document. 

Marine mammals could be affected by 

accidentally spilled diesel fuel from a 

vessel associated with proposed survey 

activities. Quantities of diesel fuel on 

the sea surface may affect marine 

mammals through various pathways: 

surface contact of the fuel with skin and 

other mucous membranes, inhalation of 

concentrated petroleum vapors, or 

ingestion of the fuel (direct ingestion or 

by the ingestion of oiled prey) (e.g., 

Geraci and St. Aubin, 1980, 1985, 1990). 

However, the likelihood of a fuel spill 

during any particular geophysical 

survey is considered to be remote, and 

the potential for impacts to marine 

mammals would depend greatly on the 

size and location of a spill and 

meteorological conditions at the time of 

the spill. Spilled fuel would rapidly 

spread to a layer of varying thickness 

and break up into narrow bands or 

windrows parallel to the wind direction. 

The rate at which the fuel spreads 

would be determined by the prevailing 

conditions such as temperature, water 

currents, tidal streams, and wind 

speeds. Lighter, volatile components of 

the fuel would evaporate to the 

atmosphere almost completely in a few 

days. Evaporation rate may increase as 

the fuel spreads because of the 

increased surface area of the slick. 

Rougher seas, high wind speeds, and 

high temperatures also tend to increase 

the rate of evaporation and the 

proportion of fuel lost by this process 

(Scholz et al., 1999). We do not 

anticipate potentially meaningful effects 

to marine mammals as a result of any 

contaminant spill resulting from the 

proposed survey activities, and 

contaminant spills are not discussed 

further in this document. 

Anticipated Effects on Marine Mammal 

Habitat 

Effects to Prey—Marine mammal prey 

varies by species, season, and location 

and, for some, is not well documented. 

Fish react to sounds which are 

especially strong and/or intermittent 

low-frequency sounds. Short duration, 

sharp sounds can cause overt or subtle 

changes in fish behavior and local 

distribution. Hastings and Popper (2005) 

identified several studies that suggest 

fish may relocate to avoid certain areas 

of sound energy. Additional studies 

have documented effects of pulsed 

sound on fish, although several are 

based on studies in support of 

construction projects (e.g., Scholik and 

Yan 2001, 2002; Popper and Hastings 

2009). Sound pulses at received levels 

of 160 dB may cause subtle changes in 

fish behavior. SPLs of 180 dB may cause 

noticeable changes in behavior (Pearson 

et al. 1992; Skalski et al. 1992). SPLs of 

sufficient strength have been known to 

cause injury to fish and fish mortality. 

The most likely impact to fish from 

survey activities at the project area 

would be temporary avoidance of the 

area. The duration of fish avoidance of 

a given area after survey effort stops is 

unknown, but a rapid return to normal 

recruitment, distribution and behavior 

is anticipated. 

Information on seismic airgun 

impacts to zooplankton, which 

represent an important prey type for 

mysticetes, is limited. However, 

McCauley et al. (2017) reported that 

experimental exposure to a pulse from 

a 150 in3 airgun decreased zooplankton 

abundance when compared with 

controls, as measured by sonar and net 

tows, and caused a two- to threefold 

increase in dead adult and larval 

zooplankton. Although no adult krill 

were present, the study found that all 

larval krill were killed after air gun 

passage. Impacts were observed out to 

the maximum 1.2 km range sampled. 

In general, impacts to marine mammal 

prey are expected to be limited due to 

the relatively small temporal and spatial 

overlap between the proposed survey 

and any areas used by marine mammal 

prey species. The proposed survey 

would occur over a relatively short time 

period (5.5 days) and would occur over 

a very small area relative to the area 

available as marine mammal habitat in 

the northeast Pacific Ocean. We do not 

have any information to suggest the 

proposed survey area represents a 

significant feeding area for any marine 

mammal, and we believe any impacts to 

marine mammals due to adverse affects 

to their prey would be insignificant due 

to the limited spatial and temporal 


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impact of the proposed survey. 

However, adverse impacts may occur to 

a few species of fish and to zooplankton. 

Acoustic Habitat—Acoustic habitat is 

the soundscape—which encompasses 

all of the sound present in a particular 

location and time, as a whole—when 

considered from the perspective of the 

animals experiencing it. Animals 

produce sound for, or listen for sounds 

produced by, conspecifics 

(communication during feeding, mating, 

and other social activities), other 

animals (finding prey or avoiding 

predators), and the physical 

environment (finding suitable habitats, 

navigating). Together, sounds made by 

animals and the geophysical 

environment (e.g., produced by 

earthquakes, lightning, wind, rain, 

waves) make up the natural 

contributions to the total acoustics of a 

place. These acoustic conditions, 

termed acoustic habitat, are one 

attribute of an animal’s total habitat. 

Soundscapes are also defined by, and 

acoustic habitat influenced by, the total 

contribution of anthropogenic sound. 

This may include incidental emissions 

from sources such as vessel traffic, or 

may be intentionally introduced to the 

marine environment for data acquisition 

purposes (as in the use of airgun arrays). 

Anthropogenic noise varies widely in its 

frequency content, duration, and 

loudness and these characteristics 

greatly influence the potential habitatmediated effects to marine mammals 

(please see also the previous discussion 

on masking under ‘‘Acoustic Effects’’), 

which may range from local effects for 

brief periods of time to chronic effects 

over large areas and for long durations. 

Depending on the extent of effects to 

habitat, animals may alter their 

communications signals (thereby 

potentially expending additional 

energy) or miss acoustic cues (either 

conspecific or adventitious). For more 

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

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

Francis and Barber 2013; Lillis et al. 

2014. 

Problems arising from a failure to 

detect cues are more likely to occur 

when noise stimuli are chronic and 

overlap with biologically relevant cues 

used for communication, orientation, 

and predator/prey detection (Francis 

and Barber 2013). Although the signals 

emitted by seismic airgun arrays are 

generally low frequency, they would 

also likely be of short duration and 

transient in any given area due to the 

nature of these surveys. As described 

previously, exploratory surveys such as 

these cover a large area but would be 

transient rather than focused in a given 

location over time and therefore would 

not be considered chronic in any given 

location. 

In summary, activities associated with 

the proposed action are not likely to 

have a permanent, adverse effect on any 

fish habitat or populations of fish 

species or on the quality of acoustic 

habitat. Thus, any impacts to marine 

mammal habitat are not expected to 

cause significant or long-term 

consequences for individual marine 

mammals or their populations. 

Estimated Take 

This section provides an estimate of 

the number of incidental takes proposed 

for authorization through this IHA, 

which will inform both NMFS’ 

consideration of whether the number of 

takes is ‘‘small’’ and the negligible 

impact determination. 

Harassment is the only type of take 

expected to result from these activities. 

Except with respect to certain activities 

not pertinent here, section 3(18) of the 

MMPA defines ‘‘harassment’’ as: Any 

act of pursuit, torment, or annoyance 

which (i) has the potential to injure a 

marine mammal or marine mammal 

stock in the wild (Level A harassment); 

or (ii) has the potential to disturb a 

marine mammal or marine mammal 

stock in the wild by causing disruption 

of behavioral patterns, including, but 

not limited to, migration, breathing, 

nursing, breeding, feeding, or sheltering 

(Level B harassment). 

Authorized takes would primarily be 

by Level B harassment, as use of the 

seismic airguns have the potential to 

result in disruption of behavioral 

patterns for individual marine 

mammals. There is also some potential 

for auditory injury (Level A harassment) 

to result, primarily for high frequency 

cetaceans and phocid pinnipeds. 

Auditory injury is unlikely to occur for 

low- and mid-frequency species given 

very small modeled zones of injury for 

those species. The proposed mitigation 

and monitoring measures are expected 

to minimize the severity of such taking 

to the extent practicable. As described 

previously, no mortality is anticipated 

or proposed to be authorized for this 

activity. Below we describe how the 

take is estimated. 

Described in the most basic way, we 

estimate take by considering: (1) 

Acoustic thresholds above which NMFS 

believes the best available science 

indicates marine mammals will be 

behaviorally harassed or incur some 

degree of permanent hearing 

impairment; (2) the area or volume of 

water that will be ensonified above 

these levels in a day; (3) the density or 

occurrence of marine mammals within 

these ensonified areas; and (4) and the 

number of days of activities. Below, we 

describe these components in more 

detail and present the exposure estimate 

and associated numbers of take 

proposed for authorization. 

Acoustic Thresholds 

Using the best available science, 

NMFS has developed acoustic 

thresholds that identify the received 

level of underwater sound above which 

exposed marine mammals would be 

reasonably expected to be behaviorally 

harassed (equated to Level B 

harassment) or to incur PTS of some 

degree (equated to Level A harassment). 

Level B Harassment for non-explosive 

sources—Though significantly driven by 

received level, the onset of behavioral 

disturbance from anthropogenic noise 

exposure is also informed to varying 

degrees by other factors related to the 

source (e.g., frequency, predictability, 

duty cycle), the environment (e.g., 

bathymetry), and the receiving animals 

(hearing, motivation, experience, 

demography, behavioral context) and 

can be difficult to predict (Southall et 

al., 2007, Ellison et al. 2011). Based on 

the best available science and the 

practical need to use a threshold based 

on a factor that is both predictable and 

measurable for most activities, NMFS 

uses a generalized acoustic threshold 

based on received level to estimate the 

onset of behavioral harassment. NMFS 

predicts that marine mammals are likely 

to be behaviorally harassed in a manner 

we consider to fall under Level B 

harassment when exposed to 

underwater anthropogenic noise above 

received levels of 120 dB re 1 mPa (rms) 

for continuous (e.g. vibratory piledriving, drilling) and above 160 dB re 1 

mPa (rms) for non-explosive impulsive 

(e.g., seismic airguns) or intermittent 

(e.g., scientific sonar) sources. SIO’s 

proposed activity includes the use of 

impulsive seismic sources. Therefore, 

the 160 dB re 1 mPa (rms) criteria is 

applicable for analysis of level B 

harassment. 

Level A harassment for non-explosive 

sources—NMFS’ Technical Guidance 

for Assessing the Effects of 

Anthropogenic Sound on Marine 

Mammal Hearing (NMFS 2016) 

identifies dual criteria to assess auditory 

injury (Level A harassment) to five 

different marine mammal groups (based 

on hearing sensitivity) as a result of 

exposure to noise from two different 

types of sources (impulsive or nonimpulsive). The Technical Guidance 

identifies the received levels, or 

thresholds, above which individual 

marine mammals are predicted to 

experience changes in their hearing 

sensitivity for all underwater 


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anthropogenic sound sources, reflects 

the best available science, and better 

predicts the potential for auditory injury 

than does NMFS’ historical criteria. 

These thresholds were developed by 

compiling and synthesizing the best 

available science and soliciting input 

multiple times from both the public and 

peer reviewers to inform the final 

product, and are provided in Table 4 

below. The references, analysis, and 

methodology used in the development 

of the thresholds are described in NMFS 

2016 Technical Guidance, which may 

be accessed at: www.nmfs.noaa.gov/pr/ 

acoustics/guidelines.htm. As described 

above, SIO’s proposed activity includes 

the use of intermittent and impulsive 

seismic sources. 

TABLE 4—THRESHOLDS IDENTIFYING THE ONSET OF PERMANENT THRESHOLD SHIFT IN MARINE MAMMALS

Hearing group 

PTS onset thresholds 

Impulsive* Non-impulsive 

Low-Frequency (LF) Cetaceans ........................................................................................................ Lpk,flat: 219 dB ..........

LE,LF,24h: 183 dB ......

LE,LF,24h: 199 dB. 

Mid-Frequency (MF) Cetaceans ........................................................................................................ Lpk,flat: 230 dB ..........

LE,MF,24h: 185 dB ......

LE,MF,24h: 198 dB. 

High-Frequency (HF) Cetaceans ...................................................................................................... Lpk,flat: 202 dB ..........

LE,HF,24h: 155 dB ......

LE,HF,24h: 173 dB. 

Phocid Pinnipeds (PW) (Underwater) ............................................................................................... Lpk,flat: 218 dB ..........

LE,PW,24h: 185 dB .....

LE,PW,24h: 201 dB. 

Otariid Pinnipeds (OW) (Underwater) ............................................................................................... Lpk,flat: 232 dB ..........

LE,OW,24h: 203 dB .....

LE,OW,24h: 219 dB. 

Note: *Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a nonimpulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds 

should also be considered. 

Note: Peak sound pressure (Lpk) has a reference value of 1 μPa, and cumulative sound exposure level (LE) has a reference value of 1μPa2s. 

In this Table, thresholds are abbreviated to reflect American National Standards Institute standards (ANSI 2013). However, peak sound pressure 

is defined by ANSI as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript ‘‘flat’’ is being 

included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated 

with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF 

cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The cumulative sound exposure level 

thresholds could be exceeded in a multitude of ways (i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for 

action proponents to indicate the conditions under which these acoustic thresholds will be exceeded. 

Ensonified Area 

Here, we describe operational and 

environmental parameters of the activity 

that will feed into estimating the area 

ensonified above the acoustic 

thresholds. 

The proposed survey would entail the 

use of a 2-airgun array with a total 

discharge of 90 in3 at a tow depth of 3 

m. The distance to the predicted 

isopleth corresponding to the threshold 

for Level B harassment (160 dB re 1 mPa) 

was calculated based on results of 

modeling performed by LDEO. Received 

sound levels were predicted by LDEO’s 

model (Diebold et al. 2010) as a function 

of distance from the airgun array. The 

LDEO modeling approach uses ray 

tracing for the direct wave traveling 

from the array to the receiver and its 

associated source ghost (reflection at the 

air-water interface in the vicinity of the 

array), in a constant-velocity half-space 

(infinite homogeneous ocean layer 

unbounded by a seafloor). In addition, 

propagation measurements of pulses 

from a 36-airgun array at a tow depth of 

6 m have been reported in deep water 

(∼1,600 m), intermediate water depth on 

the slope (∼600–1100 m), and shallow 

water (∼50 m) in the Gulf of Mexico in 

2007–2008 (Tolstoy et al. 2009; Diebold 

et al. 2010). The estimated distances to 

the Level B harassment isopleth for the 

Revelle airgun array are shown in Table 

5. 

TABLE 5—PREDICTED RADIAL DISTANCES FROM R/V REVELLE 90 IN3

SEISMIC SOURCE TO ISOPLETH CORRESPONDING TO LEVEL B HARASSMENT THRESHOLD

Water depth 

Predicted 

distance to 

threshold 

(160 dB re 1 

μPa) 

> 1000 m .............................. 448 m 

100–1000 m .......................... 672 m 

For modeling of radial distances to 

predicted isopleths corresponding to 

harassment thresholds in deep water 

(>1,000 m), LDEO used the deep-water 

radii for various Sound Exposure Levels 

obtained from LDEO model results 

down to a maximum water depth of 

2,000 m (see Figure 2 in the IHA 

application). Radial distances to 

predicted isopleths corresponding to 

harassment thresholds in intermediate 

water depths (100–1,000 m) were 

derived by LDEO from the deep-water 

distances by applying a correction factor 

(multiplication) of 1.5, such that 

observed levels at very near offsets fall 

below the corrected mitigation curve 

(Fig. 16 in Appendix H of NSF–USGS 

2011). LDEO’s modeling methodology is 

described in greater detail in the IHA 

application (LGL 2017) and we refer to 

the reader to that document rather than 

repeating it here. 

Predicted distances to Level A 

harassment isopleths, which vary based 

on marine mammal functional hearing 

groups (Table 3), were calculated based 

on modeling performed by LDEO using 

the Nucleus software program and the 

NMFS User Spreadsheet, described 

below. The updated acoustic thresholds 

for impulsive sounds (such as airguns) 

contained in the Technical Guidance 

(NMFS 2016) were presented as dual 

metric acoustic thresholds using both 

SELcum and peak sound pressure level 

metrics. As dual metrics, NMFS 

considers onset of PTS (Level A 

harassment) to have occurred when 

either one of the two metrics is 

exceeded (i.e., metric resulting in the 

largest isopleth). The SELcum metric 

considers both level and duration of 

exposure, as well as auditory weighting 

functions by marine mammal hearing 

group. In recognition of the fact that the 

requirement to calculate Level A 

harassment ensonified areas could be 

more technically challenging to predict 

due to the duration component and the 

use of weighting functions in the new 

SELcum thresholds, NMFS developed an 

optional User Spreadsheet that includes 


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tools to help predict a simple isopleth 

that can be used in conjunction with 

marine mammal density or occurrence 

to facilitate the estimation of take 

numbers. 

The values for SELcum and peak SPL 

for the Revelle airgun array were 

derived from calculating the modified 

farfield signature (Table 6). The farfield 

signature is often used as a theoretical 

representation of the source level. To 

compute the farfield signature, the 

source level is estimated at a large 

distance below the array (e.g., 9 km), 

and this level is back projected 

mathematically to a notional distance of 

1 m from the array’s geometrical center. 

However, when the source is an array of 

multiple airguns separated in space, the 

source level from the theoretical farfield 

signature is not necessarily the best 

measurement of the source level that is 

physically achieved at the source 

(Tolstoy et al. 2009). Near the source (at 

short ranges, distances <1 km), the 

pulses of sound pressure from each 

individual airgun in the source array do 

not stack constructively, as they do for 

the theoretical farfield signature. The 

pulses from the different airguns spread 

out in time such that the source levels 

observed or modeled are the result of 

the summation of pulses from a few 

airguns, not the full array (Tolstoy et al. 

2009). At larger distances, away from 

the source array center, sound pressure 

of all the airguns in the array stack 

coherently, but not within one time 

sample, resulting in smaller source 

levels (a few dB) than the source level 

derived from the farfield signature. 

Because the farfield signature does not 

take into account the array effect near 

the source and is calculated as a point 

source, the modified farfield signature is 

a more appropriate measure of the 

sound source level for distributed sound 

sources, such as airgun arrays. Though 

the array effect is not expected to be as 

pronounced in the case of a 2-airgun 

array as it would be with a larger airgun 

array, the modified farfield method is 

considered more appropriate than use of 

the theoretical farfield signature. 

TABLE 6—MODELED SOURCE LEVELS USING MODIFIED FARFIELD METHOD FOR R/V REVELLE 90 IN3 AIRGUN ARRAY

Functional Hearing Group Peak SPLflat SELcum

Low frequency cetaceans (Lpk,flat: 219 dB; LE,LF,24h: 183 dB) .................................................................................... 232.805 dB .. 206.0165 dB. 

Mid frequency cetaceans (Lpk,flat: 230 dB; LE,MF,24h: 185 dB) .................................................................................... 229.89 dB ... 205.9638 dB. 

High frequency cetaceans (Lpk,flat: 202 dB; LE,HF,24h: 155 dB) ................................................................................... 232.867 dB .. 206.384 dB. 

Phocid Pinnipeds (Underwater) (Lpk,flat: 218 dB; LE,HF,24h: 185 dB) ........................................................................... 232.356 dB .. 205.9638 dB. 

Otariid Pinnipeds (Underwater) (Lpk,flat: 232 dB; LE,HF,24h: 203 dB) ........................................................................... 224.7897 dB 206.806 dB. 

In order to more realistically 

incorporate the Technical Guidance’s 

weighting functions over the seismic 

array’s full acoustic band, unweighted 

spectrum data for the Revelle’s airgun 

array (modeled in 1 Hz bands) was used 

to make adjustments (dB) to the 

unweighted spectrum levels, by 

frequency, according to the weighting 

functions for each relevant marine 

mammal hearing group. These adjusted/ 

weighted spectrum levels were then 

converted to pressures (mPa) in order to 

integrate them over the entire 

broadband spectrum, resulting in 

broadband weighted source levels by 

hearing group that could be directly 

incorporated within the User 

Spreadsheet (i.e., to override the 

Spreadsheet’s more simple weighting 

factor adjustment). Using the User 

Spreadsheet’s ‘‘safe distance’’ 

methodology for mobile sources 

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

hearing group-specific weighted source 

levels, and inputs assuming spherical 

spreading propagation, a source velocity 

of 2.57 meters/second, and shot interval 

of 7.78 seconds (LGL 2017), potential 

radial distances to auditory injury zones 

were then calculated for SELcum

thresholds. Inputs to the User 

Spreadsheet are shown in Table 6. 

Outputs from the User Spreadsheet in 

the form of estimated distances to Level 

A harassment isopleths are shown in 

Table 7. As described above, the larger 

distance of the dual criteria (SELcum or 

Peak SPLflat) is used for estimating takes 

by Level A harassment. The weighting 

functions used are shown in Table 3 of 

the IHA application. 

TABLE 7—MODELED RADIAL DISTANCES (M) FROM R/V REVELLE 90 IN3 AIRGUN ARRAY TO ISOPLETHS CORRESPONDING

TO LEVEL A HARASSMENT THRESHOLDS

Functional Hearing Group 

(Level A harassment thresholds) Peak SPLflat SELcum

Low frequency cetaceans (Lpk,flat: 219 dB; LE,LF,24h: 183 dB) ................................................................................ 4.9 7.9 

Mid frequency cetaceans (Lpk,flat: 230 dB; LE,MF,24h: 185 dB) ................................................................................ 0.9 0 

High frequency cetaceans (Lpk,flat: 202 dB; LE,HF,24h: 155 dB) .............................................................................. 34.9 0 

Phocid Pinnipeds (Underwater) (Lpk,flat: 218 dB; LE,HF,24h: 185 dB) ...................................................................... 5.2 0.1 

Otariid Pinnipeds (Underwater) (Lpk,flat: 232 dB; LE,HF,24h: 203 dB) ....................................................................... 0.4 0 

Note that because of some of the 

assumptions included in the methods 

used, isopleths produced may be 

overestimates to some degree, which 

will ultimately result in some degree of 

overestimate of Level A take. However, 

these tools offer the best way to predict 

appropriate isopleths when more 

sophisticated 3D modeling methods are 

not available, and NMFS continues to 

develop ways to quantitatively refine 

these tools and will qualitatively 

address the output where appropriate. 

For mobile sources, such as the 

proposed seismic survey, the User 

Spreadsheet predicts the closest 

distance at which a stationary animal 

would not incur PTS if the sound source 

traveled by the animal in a straight line 

at a constant speed. 

Marine Mammal Occurrence 

In this section we provide the 

information about the presence, density, 

or group dynamics of marine mammals 

that will inform the take calculations. 

The best available scientific 

information was considered in 

conducting marine mammal exposure 

estimates (the basis for estimating take). 

For most cetacean species, densities 

calculated by Barlow (2016) were used. 


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These represent the most 

comprehensive and recent density data 

available for cetacean species in slope 

and offshore waters of Oregon and 

Washington and are based on data 

collected via NMFS Southwest Fisheries 

Science Center (SWFSC) ship-based 

surveys in 1991, 1993, 1996, 2001, 2005, 

2008, and 2014. The surveys were 

conducted up to ∼556 km from shore 

from June or August to November or 

December. The densities from NMFS 

SWFSC vessel-based surveys were 

corrected by the authors for both 

trackline detection probability and 

availability bias. Trackline detection 

probability bias is associated with 

diminishing sightability with increasing 

lateral distance from the trackline and is 

measured by f(0). Availability bias refers 

to the fact that there is less than 100 

percent probability of sighting an 

animal that is present along the survey 

trackline, and it is measured by g(0). 

Abundance and density were not 

estimated for gray whales or harbor 

porpoises in the NMFS SWFSC surveys 

because their inshore habitats were 

inadequately covered in those studies. 

Gray whale density is derived from the 

abundance of gray whales that remain 

between Oregon and British Columbia 

in summer (updated based on 

abundance calculated by Calambokidis 

et al. 2014) and the area out to 43 km 

from shore, using the U.S. Navy (2010) 

method. Harbor porpoise densities are 

based on data from aerial line-transect 

surveys during 2007–2012 for the 

Northern Oregon/Washington Coast 

stock (Forney et al. 2014). 

Systematic, offshore, at-sea survey 

data for pinnipeds are more limited than 

those for cetaceans. Densities for the 

Steller sea lion, California sea lion, 

northern elephant seal, and northern fur 

seal were calculated using the methods 

in U.S. Navy (2010) with updated 

abundance estimates from Carretta et al. 

(2016) and Muto et al. (2016), when 

appropriate. For the harbor seal, 

densities were calculated using the 

population estimate for the Oregon/ 

Washington Coastal stock and the range 

for that stock from Carretta et al. (2016). 

There is some uncertainty related to 

the estimated density data and the 

assumptions used in their calculations, 

as with all density data estimates. 

However, the approach used is based on 

the best available data. 

Take Calculation and Estimation 

Here we describe how the information 

provided above is brought together to 

produce a quantitative take estimate. In 

order to estimate the number of marine 

mammals predicted to be exposed to 

sound levels that would result in Level 

B harassment or Level A harassment, 

radial distances to predicted isopleths 

corresponding to the Level A 

harassment and Level B harassment 

thresholds are calculated, as described 

above. We then use those distances to 

calculate the area(s) around the airgun 

array predicted to be ensonified to 

sound levels that exceed the Level A 

and Level B harassment thresholds. The 

total ensonified area for the survey is 

then calculated, based on the areas 

predicted to be ensonified around the 

array and the trackline distance. In this 

case, 25 percent was added in the form 

of operational days, which is equivalent 

to adding 25 percent to the proposed 

line km to be surveyed, to account for 

potential additional seismic operations 

as described above. The marine 

mammals predicted to occur within the 

ensonified areas, based on estimated 

densities, are expected to be 

incidentally taken by the proposed 

survey. 

To summarize, the estimated density 

of each marine mammal species within 

an area (animals/km2) is multiplied by 

the total ensonified areas (km2) that 

correspond to the Level A and Level B 

harassment thresholds for the species. 

The product (rounded) is the estimated 

number of instances of take for each 

species . The number of instances of 

take for each species is then multiplied 

by 1.25 to account for the 25 percent 

contingency, as described above. The 

result is an estimate of the number of 

instances that marine mammals are 

predicted to be exposed to airgun 

sounds above the Level B harassment 

threshold and the Level A harassment 

threshold over the duration of the 

proposed survey. The total area 

estimated to be ensonified to the Level 

B harassment threshold for the proposed 

survey is 204.2 km2. Estimated takes for 

all marine mammal species are shown 

in Table 8. 

TABLE 8—NUMBERS OF POTENTIAL INCIDENTAL TAKE OF MARINE MAMMALS PROPOSED FOR AUTHORIZATION

Species Density 

(#/1,000 km2) 

Estimated and 

proposed 

Level A takes 

Estimated 

Level B takes 

Proposed 

Level B takes 

Total proposed 

Level A and 

Level B takes 

Total proposed 

Level A and 

Level B 

takes as a 

percentage of 

population 

Gray whale ............................................... 2.6 0 4 4 4 < 0.1 

Humpback whale ..................................... 2.1 0 3 3 3 0.2 

Minke whale ............................................. 1.3 0 2 2 2 0.3 

Sei whale 1 ............................................... 0.4 0 1 2 2 0.4 

Fin whale .................................................. 4.2 0 6 6 6 < 0.1 

Blue whale ............................................... 0.3 0 1 1 1 < 0.1 

Sperm whale 1 .......................................... 0.9 0 2 6 6 0.3 

Pygmy sperm whale ................................ 1.6 0 2 2 2 < 0.1 

Killer whale 1 ............................................ 0.9 0 2 8 8 

West coast transient stock ............... ........................ ........................ ........................ ........................ 3.3 

Eastern No. Pacific offshore stock ... ........................ ........................ ........................ ........................ ........................ 3.3 

False killer whale 1 ................................... 0 0 0 5 5 0.3 

Short-finned pilot whale 1 ......................... 0.2 0 0 1 18 2.2 

Harbor porpoise ....................................... 467.0 44 582 582 627 

No.California/So. Oregon stock ........ ........................ ........................ ........................ ........................ ........................ 1.8 

Northern Oregon/Washington coast 

stock .............................................. ........................ ........................ ........................ ........................ ........................ 2.9 

Dall’s porpoise ......................................... 54.4 5 68 68 73 0.3 

Bottlenose dolphin 1 ................................. 0 0 0 0 13 6.8 

Striped dolphin 1 ....................................... 7.7 0 10 109 109 3.7 

Risso’s dolphin 1 ....................................... 11.8 0 16 28 28 4.4 

Short-beaked common dolphin 1 .............. 69.2 0 89 286 286 < 0.1 

Pacific white sided dolphin 1 .................... 40.7 0 52 62 62 2.3 


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TABLE 8—NUMBERS OF POTENTIAL INCIDENTAL TAKE OF MARINE MAMMALS PROPOSED FOR AUTHORIZATION—Continued 

Species Density 

(#/1,000 km2) 

Estimated and 

proposed 

Level A takes 

Estimated 

Level B takes 

Proposed 

Level B takes 

Total proposed 

Level A and 

Level B takes 

Total proposed 

Level A and 

Level B 

takes as a 

percentage of 

population 

Northern right whale dolphin 1 ................. 46.4 0 60 63 63 2.5 

Cuvier’s beaked whale ............................. 2.8 0 4 4 4 < 0.1 

Baird’s beaked whale ............................... 10.7 0 14 14 14 1.7 

Mesoplodont beaked whales 2 ................. 1.2 0 2 2 2 2.9 

California sea lion .................................... 283.3 0 362 362 362 1.2 

Steller sea lion ......................................... 15.0 0 20 20 20 < 0.1 

Harbor seal .............................................. 292.3 4 367 367 371 1.5 

Northern elephant seal ............................ 83.1 1 105 105 106 < 0.1 

Northern fur seal ...................................... 83.4 0 107 107 107 0.8 

1The proposed number of authorized takes (Level B harassment only) for these species has been increased from the estimated take to mean 

group size (as reported in Barlow (2016)). 2 May be any of the following: Blainville’s beaked whale, Perrin’s beaked whale, Lesser beaked whale, Stejneger’s beaked whale, Gingkotoothed beaked whale, or Hubb’s beaked whale. 

Species With Take Estimates Less 

Than Mean Group Size: Using the 

approach described above to estimate 

take, the take estimates for the sei 

whale, sperm whale, killer whale, shortfinned pilot whale, false killer whale, 

bottlenose dolphin, short beaked 

common dolphin, striped dolphin, 

Pacific white sided dolphin, Risso’s 

dolphin and Northern right whale 

dolphin were less than the average 

group sizes estimated for these species 

(Table 8). However, information on the 

social structures and life histories of 

these species indicates it is common for 

these species to be encountered in 

groups. The results of take calculations 

support the likelihood that SIO’s survey 

is expected to encounter and to 

incidentally take these species, and we 

believe it is likely that these species 

may be encountered in groups, therefore 

it is reasonable to conservatively assume 

that one group of each of these species 

will be taken during the proposed 

survey. We therefore propose to 

authorize the take of the average (mean) 

group size for these species and stocks 

to account for the possibility that SIO’s 

survey encounters a group of any of 

these species or stocks (Table 8). 

No density data were available for the 

false killer whale or the bottlenose 

dolphin in the proposed survey area, as 

these species are not typically observed 

in the proposed survey area (Carretta et 

al. 2017). However, we believe it is 

possible that these species may be 

encountered by SIO during the 

proposed survey. Though false killer 

whales are a tropical species that is 

usually found in waters warmer than 

those typical of the proposed survey 

area, they have been observed off the 

U.S. west coast during warm-water 

periods. Several sightings were made off 

California during 2014–2016, when 

waters were unusually warm, and 

historically there are very rare records 

farther north (pers. comm. K. Forney, 

NMFS Southwest Fisheries Science 

Center, to J. Carduner, NMFS, July 27, 

2017). Bottlenose dolphins have not 

been observed off the coast of Oregon 

and Washington (Carretta et al. 2017). 

However, they occur frequently off the 

coast of California, and they may range 

into Oregon and Washington waters 

during warm-water periods. (Carretta et 

al. 2017). Though no density data are 

available, we believe it is reasonable to 

conservatively assume that SIO’s 

proposed survey may encounter and 

incidentally take false killer whales and 

bottlenose dolphins. We therefore 

propose to authorize the take of the 

average (mean) group size for both 

species (Table 8). 

It should be noted that the proposed 

take numbers shown in Table 8 are 

believed to be conservative for several 

reasons. First, in the calculations of 

estimated take, 25 percent has been 

added in the form of operational survey 

days (equivalent to adding 25 percent to 

the proposed line km to be surveyed) to 

account for the possibility of additional 

seismic operations associated with 

airgun testing, and repeat coverage of 

any areas where initial data quality is 

sub-standard. Additionally, marine 

mammals would be expected to move 

away from a sound source that 

represents an aversive stimulus. 

However, the extent to which marine 

mammals would move away from the 

sound source is difficult to quantify and 

is therefore not accounted for in take 

estimates shown in Table 8. 

For some marine mammal species, we 

propose to authorize a different number 

of incidental takes than the number of 

incidental takes requested by SIO (see 

Table 7 in the IHA application for 

requested take numbers). For instance, 

for several species, SIO increased the 

take request from the calculated take 

number to 1 percent of the estimated 

population size. However, we do not 

believe it is likely that 1 percent of the 

estimated population size of those 

species will be taken by SIO’s proposed 

survey, therefore we propose to 

authorize take numbers as shows in 

Table 8, which we believe are based on 

the best available information. 

To calculate distances to isopleths 

corresponding to Level A harassment 

thresholds using Peak SPLflat, LDEO first 

ran the modeling for a single shot and 

then applied a high pass filter for each 

hearing group based on the group’s 

generalized hearing range. A high pass 

filter is a type of band-pass filter, which 

pass frequencies within a defined range 

without reducing amplitude and 

attenuate frequencies outside that 

defined range (Yost 2007). LDEO ran the 

modeling both with and without the 

application of the high pass filter and 

SIO included information on isopleths 

corresponding to Level A harassment 

thresholds both with and without the 

high pass filter in their IHA application. 

The Technical Guidance referred to 

auditory weighting functions based on a 

generic band-pass filter (NMFS 2016). 

However, it is important to note that the 

two datasets relied upon to define peak 

sound pressure level thresholds, either 

directly or as a surrogate means to 

derive thresholds for groups where no 

data are available (i.e., a beluga exposed 

to seismic water gun and harbor 

porpoise exposed to a single airgun) did 

not use a filter of any kind (i.e., 

thresholds provided were flat across the 

entire spectrum of the sound source). 

Therefore, for the purposes of modeling 

isopleths corresponding to Level A 

harassment thresholds using Peak 


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SPLflat, NMFS believes that sound 

produced from the Revelle airgun array 

should be considered flat to result in no 

weighting/high pass filtering of any type 

at this time. Therefore, for the purposes 

of the take calculation, we rely on the 

distances to isopleths corresponding to 

Level A harassment thresholds using 

Peak SPLflat based on modeling 

performed by LDEO without the high 

pass filter applied. Thus, the proposed 

Level A take numbers shown in Table 

8 for harbor porpoise, Dall’s porpoise 

and harbor seal are higher than the 

Level A take numbers requested by SIO 

as they are the result of modeling of 

isopleths corresponding to Level A 

harassment thresholds using Peak 

SPLflat with no weighting/high pass 

filtering applied. Level A take numbers 

for other species are not affected. 

Proposed Mitigation 

In order to issue an IHA under 

Section 101(a)(5)(D) of the MMPA, 

NMFS must set forth the permissible 

methods of taking pursuant to such 

activity, ‘‘and other means of effecting 

the least practicable impact on such 

species or stock and its habitat, paying 

particular attention to rookeries, mating 

grounds, and areas of similar 

significance, and on the availability of 

such species or stock for taking’’ for 

certain subsistence uses (latter not 

applicable for this action). NMFS 

regulations require applicants for 

incidental take authorizations to include 

information about the availability and 

feasibility (economic and technological) 

of equipment, methods, and manner of 

conducting such activity or other means 

of effecting the least practicable adverse 

impact upon the affected species or 

stocks and their habitat (50 CFR 

216.104(a)(11)). 

In evaluating how mitigation may or 

may not be appropriate to ensure the 

least practicable adverse impact on 

species or stocks and their habitat, as 

well as subsistence uses where 

applicable, we carefully consider two 

primary factors: 

(1) The manner in which, and the 

degree to which, the successful 

implementation of the measure(s) is 

expected to reduce impacts to marine 

mammals, marine mammal species or 

stocks, and their habitat. This considers 

the nature of the potential adverse 

impact being mitigated (likelihood, 

scope, range). It further considers the 

likelihood that the measure will be 

effective if implemented (probability of 

accomplishing the mitigating result if 

implemented as planned) the likelihood 

of effective implementation (probability 

implemented as planned), and 

(2) the practicability of the measures 

for applicant implementation, which 

may consider such things as cost, 

impact on operations, and, in the case 

of a military readiness activity, 

personnel safety, practicality of 

implementation, and impact on the 

effectiveness of the military readiness 

activity. 

SIO has reviewed mitigation measures 

employed during seismic research 

surveys authorized by NMFS under 

previous incidental harassment 

authorizations, as well as recommended 

best practices in Richardson et al. 

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

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

Wright (2014), and Wright and 

Cosentino (2015), and has incorporated 

a suite of proposed mitigation measures 

into their project description based on 

the above sources. 

To reduce the potential for 

disturbance from acoustic stimuli 

associated with the activities, SIO has 

proposed to implement the following 

mitigation measures for marine 

mammals: 

(1) Vessel-based visual mitigation 

monitoring; 

(2) Establishment of an exclusion 

zone and buffer zone; 

(3) Shutdown procedures; 

(4) Ramp-up procedures; and 

(5) Ship strike avoidance measures. 

In addition to these measures, NMFS 

proposes the following additional 

mitigation measure: 

(1) Shutdown for killer whales 

observed at any distance. 

Vessel-Based Visual Mitigation 

Monitoring 

PSO observations would take place 

during all daytime airgun operations 

and nighttime start ups (if applicable) of 

the airguns. If airguns are operating 

throughout the night, observations 

would begin 30 minutes prior to 

sunrise. If airguns are operating after 

sunset, observations would continue 

until 30 minutes following sunset. 

Following a shutdown for any reason, 

observations would occur for at least 30 

minutes prior to the planned start of 

airgun operations. Observations would 

also occur for 30 minutes after airgun 

operations cease for any reason. 

Observations would also be made 

during daytime periods when the 

Revelle is underway without seismic 

operations, such as during transits, to 

allow for comparison of sighting rates 

and behavior with and without airgun 

operations and between acquisition 

periods. Airgun operations would be 

suspended when marine mammals are 

observed within, or about to enter, the 

designated Exclusion Zone (as described 

below). 

(i) During seismic operations, three 

visual PSOs would be based aboard the 

Revelle. PSOs would be appointed by 

SIO with NMFS approval. During the 

majority of seismic operations, two 

PSOs would monitor for marine 

mammals around the seismic vessel. A 

minimum of one PSO must be on duty 

at all times when the array is active. 

PSO(s) would be on duty in shifts of 

duration no longer than 4 hours. Other 

crew would also be instructed to assist 

in detecting marine mammals and in 

implementing mitigation requirements 

(if practical). Before the start of the 

seismic survey, the crew would be given 

additional instruction in detecting 

marine mammals and implementing 

mitigation requirements. 

The Revelle is a suitable platform 

from which PSOs would watch for 

marine mammals. The Revelle has been 

used for that purpose during the routine 

California Cooperative Oceanic 

Fisheries Investigations surveys. 

Observing stations are located at the 02 

level, with the observer eye level at 

∼10.4 m above the waterline. At a 

forward-centered position on the 02 

deck, the view is ∼240°; an aft-centered 

view includes the 100-m radius area 

around the GI airguns. The observer eye 

level on the bridge is ∼15 m above sea 

level. Standard equipment for marine 

mammal observers would be 7 × 50 

reticule binoculars and optical range 

finders. At night, night-vision 

equipment would be available. The 

observers would be in communication 

with ship’s officers on the bridge and 

scientists in the vessel’s operations 

laboratory, so they can advise promptly 

of the need for avoidance maneuvers or 

seismic source shutdown. 

The PSOs must have no tasks other 

than to conduct observational effort, 

record observational data, and 

communicate with and instruct relevant 

vessel crew with regard to the presence 

of marine mammals and mitigation 

requirements. PSO resumes would be 

provided to NMFS for approval. At least 

one PSO must have a minimum of 90 

days at-sea experience working as PSOs 

during a deep penetration seismic 

survey, with no more than eighteen 

months elapsed since the conclusion of 

the at-sea experience. One 

‘‘experienced’’ visual PSO would be 

designated as the lead for the entire 

protected species observation team. The 

lead would serve as primary point of 

contact for the vessel operator. 

The PSOs must have successfully 

completed relevant training, including 

completion of all required coursework 

and passing a written and/or oral 


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examination developed for the training 

program, and must have successfully 

attained a bachelor’s degree from an 

accredited college or university with a 

major in one of the natural sciences and 

a minimum of 30 semester hours or 

equivalent in the biological sciences and 

at least one undergraduate course in 

math or statistics. The educational 

requirements may be waived if the PSO 

has acquired the relevant skills through 

alternate training, including (1) 

secondary education and/or experience 

comparable to PSO duties; (2) previous 

work experience conducting academic, 

commercial, or government-sponsored 

marine mammal surveys; or (3) previous 

work experience as a PSO; the PSO 

should demonstrate good standing and 

consistently good performance of PSO 

duties. 

Exclusion Zone (EZ) and Buffer Zone 

An exclusion zone is a defined area 

within which occurrence of a marine 

mammal triggers mitigation action 

intended to reduce the potential for 

certain outcomes, e.g., auditory injury, 

disruption of critical behaviors. The 

PSOs would establish a minimum 

exclusion zone with a 100 m radius for 

the airgun array. The 100 m EZ would 

be based on radial distance from any 

element of the airgun array (rather than 

being based on the center of the array 

or around the vessel itself). With certain 

exceptions (described below), if a 

marine mammal appears within, enters, 

or appears on a course to enter this 

zone, the acoustic source would be shut 

down (see Shut Down Procedures 

below). 

The 100 m radial distance of the 

standard EZ is precautionary in the 

sense that it would be expected to 

contain sound exceeding peak pressure 

injury criteria for all marine mammal 

hearing groups (Table 7) while also 

providing a consistent, reasonably 

observable zone within which PSOs 

would typically be able to conduct 

effective observational effort. In this 

case, the 100 m radial distance would 

also be expected to contain sound that 

would exceed the Level A harassment 

threshold based on sound exposure 

level (SELcum) criteria for all marine 

mammal hearing groups (Table 7). In the 

2011 Programmatic Environmental 

Impact Statement for marine scientific 

research funded by NSF or the U.S. 

Geological Survey (NSF–USGS 2011), 

Alternative B (the Preferred Alternative) 

conservatively applied a 100 m EZ for 

all low-energy acoustic sources in water 

depths >100 m, with low-energy 

acoustic sources defined as any towed 

acoustic source with a single or a pair 

of clustered airguns with individual 

volumes of ≤250 in3. Thus the 100 m EZ 

proposed for this survey is consistent 

with the PEIS. 

Our intent in prescribing a standard 

exclusion zone distance is to (1) 

encompass zones within which auditory 

injury could occur on the basis of 

instantaneous exposure; (2) provide 

additional protection from the potential 

for more severe behavioral reactions 

(e.g., panic, antipredator response) for 

marine mammals at relatively close 

range to the acoustic source; (3) provide 

consistency for PSOs, who need to 

monitor and implement the EZ; and (4) 

define a distance within which 

detection probabilities are reasonably 

high for most species under typical 

conditions. 

PSOs would also establish and 

monitor a 200 m buffer zone. During use 

of the acoustic source, occurrence of 

marine mammals within the buffer zone 

(but outside the exclusion zone) would 

be communicated to the operator to 

prepare for potential shutdown of the 

acoustic source. The buffer zone is 

discussed further under Ramp Up 

Procedures below. 

Shutdown Procedures 

If a marine mammal is detected 

outside the EZ but is likely to enter the 

EZ, and if the vessel’s speed and/or 

course cannot be changed to avoid 

having the animal enter the EZ, the 

airguns would be shut down before the 

animal is within the EZ. Likewise, if a 

marine mammal is already within the 

EZ when first detected, the airguns 

would be shut down immediately. 

Following a shutdown, airgun activity 

would not resume until the marine 

mammal has cleared the 100 m EZ. The 

animal would be considered to have 

cleared the 100 m EZ if the following 

conditions have been met: 

• It is visually observed to have 

departed the 100 m EZ, or 

• it has not been seen within the 100 

m EZ for 15 min in the case of small 

odontocetes, or 

• it has not been seen within the 100 

m EZ for 30 min in the case of 

mysticetes and large odontocetes, 

including sperm, pygmy sperm, and 

beaked whales. 

This shutdown requirement would be 

in place for all marine mammals, with 

the exception of small delphinoids 

under certain circumstances. As defined 

here, the small delphinoid group is 

intended to encompass those members 

of the Family Delphinidae most likely to 

voluntarily approach the source vessel 

for purposes of interacting with the 

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

riding). This exception to the shutdown 

requirement would apply solely to 

specific genera of small dolphins — 

Tursiops, Stenella, Delphinus, 

Lagenorhynchus and Lissodelphis — 

and would only apply if the animals 

were traveling, including approaching 

the vessel. If, for example, an animal or 

group of animals is stationary for some 

reason (e.g., feeding) and the source 

vessel approaches the animals, the 

shutdown requirement applies. An 

animal with sufficient incentive to 

remain in an area rather than avoid an 

otherwise aversive stimulus could either 

incur auditory injury or disruption of 

important behavior. If there is 

uncertainty regarding identification (i.e., 

whether the observed animal(s) belongs 

to the group described above) or 

whether the animals are traveling, the 

shutdown would be implemented. 

We propose this small delphinoid 

exception because shutdown 

requirements for small delphinoids 

under all circumstances represent 

practicability concerns without likely 

commensurate benefits for the animals 

in question. Small delphinoids are 

generally the most commonly observed 

marine mammals in the specific 

geographic region and would typically 

be the only marine mammals likely to 

intentionally approach the vessel. As 

described below, auditory injury is 

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

as this group is relatively insensitive to 

sound produced at the predominant 

frequencies in an airgun pulse while 

also having a relatively high threshold 

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

permanent threshold shift). Please see 

‘‘Potential Effects of the Specified 

Activity on Marine Mammals’’ above for 

further discussion of sound metrics and 

thresholds and marine mammal hearing. 

A large body of anecdotal evidence 

indicates that small delphinoids 

commonly approach vessels and/or 

towed arrays during active sound 

production for purposes of bow riding, 

with no apparent effect observed in 

those delphinoids (e.g., Barkaszi et al., 

2012). The potential for increased 

shutdowns resulting from such a 

measure would require the Revelle to 

revisit the missed track line to reacquire 

data, resulting in an overall increase in 

the total sound energy input to the 

marine environment and an increase in 

the total duration over which the survey 

is active in a given area. Although other 

mid-frequency hearing specialists (e.g., 

large delphinoids) are no more likely to 

incur auditory injury than are small 

delphinoids, they are much less likely 

to approach vessels. Therefore, retaining 

a shutdown requirement for large 

delphinoids would not have similar 

impacts in terms of either practicability 


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for the applicant or corollary increase in 

sound energy output and time on the 

water. We do anticipate some benefit for 

a shutdown requirement for large 

delphinoids in that it simplifies 

somewhat the total range of decisionmaking for PSOs and may preclude any 

potential for physiological effects other 

than to the auditory system as well as 

some more severe behavioral reactions 

for any such animals in close proximity 

to the source vessel. 

At any distance, shutdown of the 

acoustic source would also be required 

upon observation of any of the 

following: 

• A killer whale; 

• a large whale (i.e., sperm whale or 

any baleen whale) with a calf; or 

• an aggregation of large whales of 

any species (i.e., sperm whale or any 

baleen whale) that does not appear to be 

traveling (e.g., feeding, socializing, etc.). 

These would be the only three 

potential situations that would require 

shutdown of the array for marine 

mammals observed beyond the 100 m 

EZ. Southern Resident DPS killer 

whales are not expected to occur in the 

area of the proposed survey as the 

easternmost track lines of the proposed 

survey (those that approach nearest to 

shore) are further west than the 

migratory range of the Southern 

Resident stock off Oregon and southern 

Washington (pers. comm., B. Hanson, 

NMFS Northwest Fishery Science 

Center to J. Carduner, NMFS OPR, April 

12, 2017). As the Eastern North Pacific 

Southern Resident stock would be 

expected to occur closer to shore than 

the proposed survey area, the survey is 

not expected to encounter any 

individuals from this stock. However, as 

the known migratory range of the 

Southern Resident DPS occurs near the 

proposed survey area, and due to the 

precarious conservation status of the 

Southern Resident killer whale DPS, 

NMFS believes it is reasonable to 

implement measures that are 

conservative and also practicable in 

order to prevent the potential for a 

Southern Resident killer whale to be 

exposed to airgun sounds. Thus the 

requirement to shut down the array 

upon observation of a killer whale at 

any distance is designed to avoid any 

potential for harassment of any 

Southern Resident killer whales. 

Ramp-Up Procedures 

Ramp-up of an acoustic source is 

intended to provide a gradual increase 

in sound levels following a shutdown, 

enabling animals to move away from the 

source if the signal is sufficiently 

aversive prior to its reaching full 

intensity. Ramp-up would be required 

after the array is shut down for any 

reason. Ramp-up would begin with the 

activation of one 45 in3 airgun, with the 

second 45 in3 airgun activated after 5 

minutes. 

PSOs would be required to monitor 

during ramp-up. During ramp up, the 

PSOs would monitor the EZ, and if 

marine mammals were observed within 

or approaching the 100 m EZ, a 

shutdown would be implemented as 

though the full array were operational. 

If airguns have been shut down due to 

PSO detection of a marine mammal 

within or approaching the 100 m EZ, 

ramp-up would not be initiated until all 

marine mammals have cleared the EZ, 

during the day or night. Criteria for 

clearing the EZ would be as described 

above. 

Thirty minutes of pre-clearance 

observation are required prior to rampup for any shutdown of longer than 30 

minutes (i.e., if the array were shut 

down during transit from one line to 

another). This 30 minute pre-clearance 

period may occur during any vessel 

activity (i.e., transit). If a marine 

mammal were observed within or 

approaching the 100 m EZ during this 

pre-clearance period, ramp-up would 

not be initiated until all marine 

mammals cleared the EZ. Criteria for 

clearing the EZ would be as described 

above. If the airgun array has been shut 

down for reasons other than mitigation 

(e.g., mechanical difficulty) for a period 

of less than 30 minutes, it may be 

activated again without ramp-up if PSOs 

have maintained constant visual 

observation and no detections of any 

marine mammal have occurred within 

the EZ or buffer zone. Ramp-up would 

be planned to occur during periods of 

good visibility when possible. However, 

ramp-up would be allowed at night and 

during poor visibility if the 100 m EZ 

and 200 m buffer zone have been 

monitored by visual PSOs for 30 

minutes prior to ramp-up. 

The operator would be required to 

notify a designated PSO of the planned 

start of ramp-up as agreed-upon with 

the lead PSO; the notification time 

should not be less than 60 minutes prior 

to the planned ramp-up. A designated 

PSO must be notified again immediately 

prior to initiating ramp-up procedures 

and the operator must receive 

confirmation from the PSO to proceed. 

The operator must provide information 

to PSOs documenting that appropriate 

procedures were followed. Following 

deactivation of the array for reasons 

other than mitigation, the operator 

would be required to communicate the 

near-term operational plan to the lead 

PSO with justification for any planned 

nighttime ramp-up. 

Speed or Course Alteration 

If a marine mammal is detected 

outside the EZ, based on its position 

and the relative motion, is likely to 

enter the EZ, the vessel’s speed and/or 

direct course could be changed. This 

would be done if operationally 

practicable while minimizing the effect 

on the planned science objectives. The 

activities and movements of the marine 

mammal (relative to the seismic vessel) 

would then be closely monitored to 

determine whether the animal is 

approaching the EZ. If the animal 

appears likely to enter the EZ, a 

shutdown of the seismic source would 

cocur. Typically, during seismic 

operations, the source vessel is unable 

to change speed or course and one or 

more alternative mitigation measures (as 

described above) would need to be 

implemented. 

Based on our evaluation of the 

applicant’s proposed measures, NMFS 

has preliminarily determined that the 

proposed mitigation measures provide 

the means effecting the least practicable 

impact on the affected species or stocks 

and their habitat, paying particular 

attention to rookeries, mating grounds, 

and areas of similar significance. 

Proposed Monitoring and Reporting 

In order to issue an IHA for an 

activity, Section 101(a)(5)(D) of the 

MMPA states that NMFS must set forth, 

‘‘requirements pertaining to the 

monitoring and reporting of such 

taking.’’ The MMPA implementing 

regulations at 50 CFR 216.104 (a)(13) 

indicate that requests for authorizations 

must include the suggested means of 

accomplishing the necessary monitoring 

and reporting that will result in 

increased knowledge of the species and 

of the level of taking or impacts on 

populations of marine mammals that are 

expected to be present in the proposed 

action area. Effective reporting is critical 

both to compliance as well as ensuring 

that the most value is obtained from the 

required monitoring. 

Monitoring and reporting 

requirements prescribed by NMFS 

should contribute to improved 

understanding of one or more of the 

following: 

• Occurrence of marine mammal 

species or stocks in the area in which 

take is anticipated (e.g., presence, 

abundance, distribution, density). 

• Nature, scope, or context of likely 

marine mammal exposure to potential 

stressors/impacts (individual or 

cumulative, acute or chronic), through 

better understanding of: (1) Action or 

environment (e.g., source 

characterization, propagation, ambient 


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noise); (2) affected species (e.g., life 

history, dive patterns); (3) co-occurrence 

of marine mammal species with the 

action; or (4) biological or behavioral 

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

feeding areas). 

• Individual marine mammal 

responses (behavioral or physiological) 

to acoustic stressors (acute, chronic, or 

cumulative), other stressors, or 

cumulative impacts from multiple 

stressors. 

• How anticipated responses to 

stressors impact either: (1) Long-term 

fitness and survival of individual 

marine mammals; or (2) populations, 

species, or stocks. 

• Effects on marine mammal habitat 

(e.g., marine mammal prey species, 

acoustic habitat, or other important 

physical components of marine 

mammal habitat). 

• Mitigation and monitoring 

effectiveness. 

SIO submitted a marine mammal 

monitoring and reporting plan in 

section XIII of their IHA application. 

Monitoring that is designed specifically 

to facilitate mitigation measures, such as 

monitoring of the EZ to inform potential 

shutdowns of the airgun array, are 

described above and are not repeated 

here. 

SIO’s monitoring and reporting plan 

includes the following measures: 

Vessel-Based Visual Monitoring 

As described above, PSO observations 

would take place during daytime airgun 

operations and nighttime start ups (if 

applicable) of the airguns. During 

seismic operations, three visual PSOs 

would be based aboard the Revelle. 

PSOs would be appointed by SIO with 

NMFS approval. During the majority of 

seismic operations, one PSO would 

monitor for marine mammals around 

the seismic vessel. PSOs would be on 

duty in shifts of duration no longer than 

4 hours. Other crew would also be 

instructed to assist in detecting marine 

mammals and in implementing 

mitigation requirements (if practical). 

During daytime, PSOs would scan the 

area around the vessel systematically 

with reticle binoculars (e.g., 7 × 50 

Fujinon), Big-eye binoculars (25 × 150), 

and with the naked eye. 

PSOs would record data to estimate 

the numbers of marine mammals 

exposed to various received sound 

levels and to document apparent 

disturbance reactions or lack thereof. 

Data would be used to estimate numbers 

of animals potentially ‘taken’ by 

harassment (as defined in the MMPA). 

They would also provide information 

needed to order a shutdown of the 

airguns when a marine mammal is 

within or near the EZ. When a sighting 

is made, the following information 

about the sighting would be recorded: 

1. Species, group size, age/size/sex 

categories (if determinable), behavior 

when first sighted and after initial 

sighting, heading (if consistent), bearing 

and distance from seismic vessel, 

sighting cue, apparent reaction to the 

airguns or vessel (e.g., none, avoidance, 

approach, paralleling, etc.), and 

behavioral pace. 

2. Time, location, heading, speed, 

activity of the vessel, sea state, 

visibility, and sun glare. 

All observations and shutdowns 

would be recorded in a standardized 

format. Data would be entered into an 

electronic database. The accuracy of the 

data entry would be verified by 

computerized data validity checks as 

the data are entered and by subsequent 

manual checking of the database. These 

procedures would allow initial 

summaries of data to be prepared during 

and shortly after the field program and 

would facilitate transfer of the data to 

statistical, graphical, and other 

programs for further processing and 

archiving. The time, location, heading, 

speed, activity of the vessel, sea state, 

visibility, and sun glare would also be 

recorded at the start and end of each 

observation watch, and during a watch 

whenever there is a change in one or 

more of the variables. 

Results from the vessel-based 

observations would provide: 

1. The basis for real-time mitigation 

(airgun shutdown). 

2. Information needed to estimate the 

number of marine mammals potentially 

taken by harassment, which must be 

reported to NMFS. 

3. Data on the occurrence, 

distribution, and activities of marine 

mammals in the area where the seismic 

study is conducted. 

4. Information to compare the 

distance and distribution of marine 

mammals relative to the source vessel at 

times with and without seismic activity. 

5. Data on the behavior and 

movement patterns of marine mammals 

seen at times with and without seismic 

activity. 

Negligible Impact Analysis and 

Determination 

NMFS has defined negligible impact 

as an impact resulting from the 

specified activity that cannot be 

reasonably expected to, and is not 

reasonably likely to, adversely affect the 

species or stock through effects on 

annual rates of recruitment or survival 

(50 CFR 216.103). A negligible impact 

finding is based on the lack of likely 

adverse effects on annual rates of 

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

of takes alone is not enough information 

on which to base an impact 

determination. In addition to 

considering estimates of the number of 

marine mammals that might be ‘‘taken’’ 

through harassment, NMFS considers 

other factors, such as the likely nature 

of any responses (e.g., intensity, 

duration), the context of any responses 

(e.g., critical reproductive time or 

location, migration), as well as effects 

on habitat, and the likely effectiveness 

of the mitigation. We also assess the 

number, intensity, and context of 

estimated takes by evaluating this 

information relative to population 

status. Consistent with the 1989 

preamble for NMFS’ implementing 

regulations (54 FR 40338; September 29, 

1989), the impacts from other past and 

ongoing anthropogenic activities are 

incorporated into this analysis via their 

impacts on the environmental baseline 

(e.g., as reflected in the regulatory status 

of the species, population size and 

growth rate where known, ongoing 

sources of human-caused mortality, or 

ambient noise levels). 

To avoid repetition, our analysis 

applies to all the species listed in Table 

2, given that NMFS expects the 

anticipated effects of the proposed 

seismic survey to be similar in nature. 

Where there are meaningful differences 

between species or stocks, or groups of 

species, in anticipated individual 

responses to activities, impact of 

expected take on the population due to 

differences in population status, or 

impacts on habitat, NMFS has identified 

species-specific factors to inform the 

analysis. 

NMFS does not anticipate that serious 

injury or mortality would occur as a 

result of SIO’s proposed seismic survey, 

even in the absence of proposed 

mitigation. Thus the proposed 

authorization does not authorize any 

mortality. As discussed in the Potential 

Effects section, non-auditory physical 

effects, stranding, and vessel strike are 

not expected to occur. 

We propose to authorize a limited 

number of instances of Level A 

harassment (Table 8) for four species. 

However, we believe that any PTS 

incurred in marine mammals as a result 

of the proposed activity would be in the 

form of only a small degree of PTS and 

not total deafness that would not be 

likely to affect the fitness of any 

individuals, because of the constant 

movement of both the Revelle and of the 

marine mammals in the project area, as 

well as the fact that the vessel is not 

expected to remain in any one area in 

which individual marine mammals 


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would be expected to concentrate for an 

extended period of time (i.e., since the 

duration of exposure to loud sounds 

will be relatively short). Also, as 

described above, we expect that marine 

mammals would be likely to move away 

from a sound source that represents an 

aversive stimulus, especially at levels 

that would be expected to result in PTS, 

given sufficient notice of the Revelle’s 

approach due to the vessel’s relatively 

low speed when conducting seismic 

surveys. We expect that the majority of 

takes would be in the form of short-term 

Level B behavioral harassment in the 

form of temporary avoidance of the area 

or decreased foraging (if such activity 

were occurring), reactions that are 

considered to be of low severity and 

with no lasting biological consequences 

(e.g., Southall et al., 2007). 

Potential impacts to marine mammal 

habitat were discussed previously in 

this document (see Potential Effects of 

the Specified Activity on Marine 

Mammals and their Habitat). Marine 

mammal habitat may be impacted by 

elevated sound levels, but these impacts 

would be temporary. Feeding behavior 

is not likely to be significantly 

impacted, as marine mammals appear to 

be less likely to exhibit behavioral 

reactions or avoidance responses while 

engaged in feeding activities 

(Richardson et al., 1995). Prey species 

are mobile and are broadly distributed 

throughout the project area; therefore, 

marine mammals that may be 

temporarily displaced during survey 

activities are expected to be able to 

resume foraging once they have moved 

away from areas with disturbing levels 

of underwater noise. Because of the 

temporary nature of the disturbance, the 

availability of similar habitat and 

resources in the surrounding area, and 

the lack of important or unique marine 

mammal habitat, the impacts to marine 

mammals and the food sources that they 

utilize are not expected to cause 

significant or long-term consequences 

for individual marine mammals or their 

populations. In addition, there are no 

mating or calving areas known to be 

biologically important to marine 

mammals within the proposed project 

area. 

The activity is expected to impact a 

very small percentage of all marine 

mammal stocks that would be affected 

by SIO’s proposed survey (less than 7 

percent each for all marine mammal 

stocks). Additionally, the acoustic 

‘‘footprint’’ of the proposed survey 

would be very small relative to the 

ranges of all marine mammals that 

would potentially be affected. Sound 

levels would increase in the marine 

environment in a relatively small area 

surrounding the vessel compared to the 

range of the marine mammals within the 

proposed survey area. The seismic array 

would be active 24 hours per day 

throughout the duration of the proposed 

survey. However, the very brief overall 

duration of the proposed survey (five 

days) would further limit potential 

impacts that may occur as a result of the 

proposed activity. 

The proposed mitigation measures are 

expected to reduce the number and/or 

severity of takes by allowing for 

detection of marine mammals in the 

vicinity of the vessel by visual and 

acoustic observers, and by minimizing 

the severity of any potential exposures 

via shutdowns of the airgun array. 

Based on previous monitoring reports 

for substantially similar activities that 

have been previously authorized by 

NMFS, we expect that the proposed 

mitigation will be effective in 

preventing at least some extent of 

potential PTS in marine mammals that 

may otherwise occur in the absence of 

the proposed mitigation. 

Of the marine mammal species under 

our jurisdiction that are likely to occur 

in the project area, the following species 

are listed as endangered under the ESA: 

Humpback, blue, fin, sei, and sperm 

whales. Population estimates for 

humpback whales for the North Pacific 

have increased substantially from 1,200 

in 1966 to approximately 18,000–20,000 

whales in 2004 to 2006 (Calambokidis et 

al. 2008) indicating a growth rate of 6– 

7 percent (Carretta et al., 2017). There 

are currently insufficient data to 

determine population trends for blue, 

fin, sei, and sperm whales (Carretta et 

al., 2017); however, we are proposing to 

authorize very small numbers of takes 

for these species (Table 8), relative to 

their population sizes, therefore we do 

not expect population-level impacts to 

any of these species. The other marine 

mammal species that may be taken by 

harassment during SIO’s seismic survey 

are not listed as threatened or 

endangered under the ESA. There is no 

designated critical habitat for any ESAlisted marine mammals within the 

project area; and of the non-listed 

marine mammals for which we propose 

to authorize take, none are considered 

‘‘depleted’’ or ‘‘strategic’’ by NMFS 

under the MMPA. 

NMFS concludes that exposures to 

marine mammal species and stocks due 

to SIO’s proposed seismic survey would 

result in only short-term (temporary and 

short in duration) effects to individuals 

exposed, or some small degree of PTS to 

a very small number of individuals of 

four species.. Animals may temporarily 

avoid the immediate area, but are not 

expected to permanently abandon the 

area. Major shifts in habitat use, 

distribution, or foraging success are not 

expected. NMFS does not anticipate the 

proposed take estimates to impact 

annual rates of recruitment or survival. 

In summary and as described above, 

the following factors primarily support 

our preliminary determination that the 

impacts resulting from this activity are 

not expected to adversely affect the 

marine mammal species or stocks 

through effects on annual rates of 

recruitment or survival: 

• No mortality is anticipated or 

authorized; 

• The anticipated impacts of the 

proposed activity on marine mammals 

would primarily be temporary 

behavioral changes due to avoidance of 

the area around the survey vessel. The 

relatively short duration of the proposed 

survey (5 days) would further limit the 

potential impacts of any temporary 

behavioral changes that would occur; 

• The number of instances of PTS 

that may occur are expected to be very 

small in number (Table 8). Instances of 

PTS that are incurred in marine 

mammals would be of a low level, due 

to constant movement of the vessel and 

of the marine mammals in the area, and 

the nature of the survey design (not 

concentrated in areas of high marine 

mammal concentration); 

• The availability of alternate areas of 

similar habitat value for marine 

mammals to temporarily vacate the 

survey area during the proposed survey 

to avoid exposure to sounds from the 

activity; 

• The proposed project area does not 

contain areas of significance for feeding, 

mating or calving; 

• The potential adverse effects on fish 

or invertebrate species that serve as prey 

species for marine mammals from the 

proposed survey would be temporary 

and spatially limited; 

• The proposed mitigation measures, 

including visual and acoustic 

monitoring and shutdowns, are 

expected to minimize potential impacts 

to marine mammals. 

Based on the analysis contained 

herein of the likely effects of the 

specified activity on marine mammals 

and their habitat, and taking into 

consideration the implementation of the 

proposed monitoring and mitigation 

measures, NMFS preliminarily finds 

that the total marine mammal take from 

the proposed activity will have a 

negligible impact on all affected marine 

mammal species or stocks. 

Small Numbers 

As noted above, only small numbers 

of incidental take may be authorized 

under Section 101(a)(5)(D) of the MMPA 


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for specified activities other than 

military readiness activities. The MMPA 

does not define small numbers; so, in 

practice, where estimated numbers are 

available, NMFS compares the number 

of individuals taken to the most 

appropriate estimation of abundance of 

the relevant species or stock in our 

determination of whether an 

authorization is limited to small 

numbers of marine mammals. 

Additionally, other qualitative factors 

may be considered in the analysis, such 

as the temporal or spatial scale of the 

activities. Table 8 provides numbers of 

take by Level A harassment and Level 

B harassment proposed for 

authorization. These are the numbers 

we use for purposes of the small 

numbers analysis. 

The numbers of marine mammals that 

we propose for authorization to be 

taken, for all species and stocks, would 

be considered small relative to the 

relevant stocks or populations 

(approximately 6.8 percent for 

bottlenose dolphins, and less than 5 

percent for all other species and stocks). 

Based on the analysis contained herein 

of the proposed activity (including the 

proposed mitigation and monitoring 

measures) and the anticipated take of 

marine mammals, NMFS preliminarily 

finds that small numbers of marine 

mammals will be taken relative to the 

population size of the affected species 

or stocks. 

Unmitigable Adverse Impact Analysis 

and Determination 

There are no relevant subsistence uses 

of the affected marine mammal stocks or 

species implicated by this action. 

Therefore, NMFS has preliminarily 

determined that the total taking of 

affected species or stocks would not 

have an unmitigable adverse impact on 

the availability of such species or stocks 

for taking for subsistence purposes. 

Endangered Species Act (ESA) 

Section 7(a)(2) of the ESA of 1973 (16 

U.S.C. 1531 et seq.) requires that each 

Federal agency insure that any action it 

authorizes, funds, or carries out is not 

likely to jeopardize the continued 

existence of any endangered or 

threatened species or result in the 

destruction or adverse modification of 

designated critical habitat. To ensure 

ESA compliance for the issuance of 

IHAs, NMFS consults internally, in this 

case with the ESA Interagency 

Cooperation Division, whenever we 

propose to authorize take for 

endangered or threatened species. 

The NMFS Permits and Conservation 

Division is proposing to authorize the 

incidental take of 5 species of marine 

mammals which are listed under the 

ESA: The humpback whale (Mexico 

DPS), sei whale, fin whale, blue whale 

and sperm whale. We have requested 

initiation of Section 7 consultation with 

the Interagency Cooperation Division for 

the issuance of this IHA. NMFS will 

conclude the ESA section 7 consultation 

prior to reaching a determination 

regarding the proposed issuance of the 

authorization. 

Proposed Authorization 

As a result of these preliminary 

determinations, NMFS proposes to issue 

an IHA to SIO for conducting a seismic 

survey in the northeast Pacific Ocean in 

September, 2017, provided the 

previously mentioned mitigation, 

monitoring, and reporting requirements 

are incorporated. This section contains 

a draft of the IHA itself. The wording 

contained in this section is proposed for 

inclusion in the IHA (if issued). 

1. This IHA is valid for a period of 

one year from the date of issuance. 

2. This IHA is valid only for marine 

geophysical survey activity, as specified 

in the SIO IHA application and using an 

airgun array aboard the R/V Revelle 

with characteristics specified in the 

application, in the northeast Pacific 

Ocean. 

3. General Conditions. 

(a) A copy of this IHA must be in the 

possession of SIO, the vessel operator 

and other relevant personnel, the lead 

PSO, and any other relevant designees 

of SIO operating under the authority of 

this IHA. 

(b) The species authorized for taking 

are listed in Table 8. The taking, by 

Level A and Level B harassment only, 

is limited to the species and numbers 

listed in Table 8. Any taking exceeding 

the authorized amounts listed in Table 

8 is prohibited and may result in the 

modification, suspension, or revocation 

of this IHA. 

(c) The taking by serious injury or 

death of any species of marine mammal 

is prohibited and may result in the 

modification, suspension, or revocation 

of this IHA. 

(d) During use of the airgun(s), if 

marine mammal species other than 

those listed in Table 8 are detected by 

PSOs, the acoustic source must be shut 

down to avoid unauthorized take. 

(e) SIO shall ensure that the vessel 

operator and other relevant vessel 

personnel are briefed on all 

responsibilities, communication 

procedures, marine mammal monitoring 

protocol, operational procedures, and 

IHA requirements prior to the start of 

survey activity, and when relevant new 

personnel join the survey operations. 

4. Mitigation Requirements. 

The holder of this Authorization is 

required to implement the following 

mitigation measures: 

(b) SIO must use at least three (3) 

dedicated, trained, NMFS-approved 

PSO. The PSOs must have no tasks 

other than to conduct observational 

effort, record observational data, and 

communicate with and instruct relevant 

vessel crew with regard to the presence 

of marine mammals and mitigation 

requirements. PSO resumes shall be 

provided to NMFS for approval. 

(c) At least one PSO must have a 

minimum of 90 days at-sea experience 

working as a PSO during a deep 

penetration seismic survey, with no 

more than eighteen months elapsed 

since the conclusion of the at-sea 

experience. One ‘‘experienced’’ visual 

PSO shall be designated as the lead for 

the entire protected species observation 

team. The lead PSO shall serve as 

primary point of contact for the vessel 

operator. 

(d) Visual Observation. 

(i) During survey operations (e.g., any 

day on which use of the acoustic source 

is planned to occur; whenever the 

acoustic source is in the water, whether 

activated or not), typically two, and 

minimally one, PSO(s) must be on duty 

and conducting visual observations at 

all times during daylight hours (i.e., 

from 30 minutes prior to sunrise 

through 30 minutes following sunset). 

(ii) Visual monitoring must begin not 

less than 30 minutes prior to ramp-up, 

including for nighttime ramp-ups of the 

airgun array, and must continue until 

one hour after use of the acoustic source 

ceases or until 30 minutes past sunset. 

(iii) PSOs shall coordinate to ensure 

360° visual coverage around the vessel 

from the most appropriate observation 

posts and shall conduct visual 

observations using binoculars and the 

naked eye while free from distractions 

and in a consistent, systematic, and 

diligent manner. 

(iv) PSOs may be on watch for a 

maximum of four consecutive hours 

followed by a break of at least one hour 

between watches and may conduct a 

maximum of 12 hours observation per 

24 hour period. 

(v) During good conditions (e.g., 

daylight hours; Beaufort sea state 3 or 

less), visual PSOs shall conduct 

observations when the acoustic source 

is not operating for comparison of 

sighting rates and behavior with and 

without use of the acoustic source and 

between acquisition periods, to the 

maximum extent practicable. 

(e) Exclusion Zone and buffer zone— 

PSOs shall establish and monitor a 100 

m EZ and 200 m buffer zone. The zones 

shall be based upon radial distance from 


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any element of the airgun array (rather 

than being based on the center of the 

array or around the vessel itself). During 

use of the acoustic source, occurrence of 

marine mammals outside the EZ but 

within 200 m from any element of the 

airgun array shall be communicated to 

the operator to prepare for potential 

further mitigation measures as described 

below. During use of the acoustic 

source, occurrence of marine mammals 

within the EZ, or on a course to enter 

the EZ, shall trigger further mitigation 

measures as described below. 

(i) Ramp-up—A ramp-up procedure, 

is required at all times as part of the 

activation of the acoustic source. Rampup would begin with one 45 in3 airgun, 

and the second 45 in3 airgun would be 

added after 5 minutes. 

(ii) If the airgun array has been shut 

down due to a marine mammal 

detection, ramp-up shall not occur until 

all marine mammals have cleared the 

EZ. A marine mammal is considered to 

have cleared the EZ if: 

(A) It has been visually observed to 

have left the EZ; or 

(B) It has not been observed within 

the EZ, for 15 minutes (in the case of 

small odontocetes) or for 30 minutes (in 

the case of mysticetes and large 

odontocetes including sperm, pygmy 

sperm, and beaked whales). 

(iii) Thirty minutes of pre-clearance 

observation of the 100 m EZ and 200 m 

buffer zone are required prior to rampup for any shutdown of longer than 30 

minutes. This pre-clearance period may 

occur during any vessel activity. If any 

marine mammal (including delphinids) 

is observed within or approaching the 

100 m EZ during the 30 minute preclearance period, ramp-up may not 

begin until the animal(s) has been 

observed exiting the EZ or until an 

additional time period has elapsed with 

no further sightings (i.e., 15 minutes for 

small odontocetes and 30 minutes for all 

other species). 

(iv) During ramp-up, PSOs shall 

monitor the 100 m EZ and 200 m buffer 

zone. Ramp-up may not be initiated if 

any marine mammal (including 

delphinids) is observed within or 

approaching the 100 m EZ. If a marine 

mammal is observed within or 

approaching the 100 m EZ during rampup, a shutdown shall be implemented as 

though the full array were operational. 

Ramp-up may not begin again until the 

animal(s) has been observed exiting the 

100 m EZ or until an additional time 

period has elapsed with no further 

sightings (i.e., 15 minutes for small 

odontocetes and 30 minutes for 

mysticetes and large odontocetes 

including sperm, pygmy sperm, and 

beaked whales). 

(v) If the airgun array has been shut 

down for reasons other than mitigation 

(e.g., mechanical difficulty) for a period 

of less than 30 minutes, it may be 

activated again without ramp-up if PSOs 

have maintained constant visual 

observation and no visual detections of 

any marine mammal have occurred 

within the buffer zone. 

(vi) Ramp-up at night and at times of 

poor visibility shall only occur where 

operational planning cannot reasonably 

avoid such circumstances. Ramp-up 

may occur at night and during poor 

visibility if the 100 m EZ and 200 m 

buffer zone have been continually 

monitored by visual PSOs for 30 

minutes prior to ramp-up with no 

marine mammal detections. 

(vii) The vessel operator must notify 

a designated PSO of the planned start of 

ramp-upA designated PSO must be 

notified again immediately prior to 

initiating ramp-up procedures and the 

operator must receive confirmation from 

the PSO to proceed. 

(f) Shutdown requirements—An 

exclusion zone of 100 m shall be 

established and monitored by PSOs. If a 

marine mammal is observed within, 

entering, or approaching the 100 m 

exclusion zone all airguns shall be shut 

down. 

(i) Any PSO on duty has the authority 

to call for shutdown of the airgun array. 

When there is certainty regarding the 

need for mitigation action on the basis 

of visual detection, the relevant PSO(s) 

must call for such action immediately. 

(ii) The operator must establish and 

maintain clear lines of communication 

directly between PSOs on duty and 

crew controlling the airgun array to 

ensure that shutdown commands are 

conveyed swiftly while allowing PSOs 

to maintain watch. 

(iii) When a shutdown is called for by 

a PSO, the shutdown must occur and 

any dispute resolved only following 

shutdown. 

(iv) The shutdown requirement is 

waived for dolphins of the following 

genera: Tursiops, Stenella, Delphinus, 

Lagenorhynchus and Lissodelphis. The 

shutdown waiver only applies if 

animals are traveling, including 

approaching the vessel. If animals are 

stationary and the vessel approaches the 

animals, the shutdown requirement 

applies. If there is uncertainty regarding 

identification (i.e., whether the observed 

animal(s) belongs to the group described 

above) or whether the animals are 

traveling, shutdown must be 

implemented. 

(v) Upon implementation of a 

shutdown, the source may be 

reactivated under the conditions 

described at 4(e)(vi). Where there is no 

relevant zone (e.g., shutdown due to 

observation of a calf), a 30-minute 

clearance period must be observed 

following the last observation of the 

animal(s). 

(vi) Shutdown of the array is required 

upon observation of a whale (i.e., sperm 

whale or any baleen whale) with calf, 

with ‘‘calf’’ defined as an animal less 

than two-thirds the body size of an adult 

observed to be in close association with 

an adult, at any distance. 

(vii) Shutdown of the array is required 

upon observation of an aggregation (i.e., 

six or more animals) of large whales of 

any species (i.e., sperm whale or any 

baleen whale) that does not appear to be 

traveling (e.g., feeding, socializing, etc.) 

at any distance. 

(viii) Shutdown of the array is 

required upon observation of a killer 

whale at any distance. 

(g) Vessel Strike Avoidance—Vessel 

operator and crew must maintain a 

vigilant watch for all marine mammals 

and slow down or stop the vessel or 

alter course, as appropriate, to avoid 

striking any marine mammal, unless 

such action represents a human safety 

concern. A visual observer aboard the 

vessel must monitor a vessel strike 

avoidance zone around the vessel 

according to the parameters stated 

below. Visual observers monitoring the 

vessel strike avoidance zone can be 

either third-party observers or crew 

members, but crew members 

responsible for these duties must be 

provided sufficient training to 

distinguish marine mammals from other 

phenomena. 

(i) The vessel must maintain a 

minimum separation distance of 100 m 

from large whales, unless such action 

represents a human safety concern. The 

following avoidance measures must be 

taken if a large whale is within 100 m 

of the vessel: 

(A) The vessel must reduce speed and 

shift the engine to neutral, when 

feasible, and must not engage the 

engines until the whale has moved 

outside of the vessel’s path and the 

minimum separation distance has been 

established unless such action 

represents a human safety concern. 

(B) If the vessel is stationary, the 

vessel must not engage engines until the 

whale(s) has moved out of the vessel’s 

path and beyond 100 m unless such 

action represents a human safety 

concern. 

(ii) The vessel must maintain a 

minimum separation distance of 50 m 

from all other marine mammals, with an 

exception made for animals described in 

4(e)(iv) that approach the vessel. If an 

animal is encountered during transit, 

the vessel shall attempt to remain 


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parallel to the animal’s course, avoiding 

excessive speed or abrupt changes in 

course unless such action represents a 

human safety concern. 

(iii) Vessel speeds must be reduced to 

10 knots or less when mother/calf pairs, 

pods, or large assemblages of cetaceans 

are observed near the vessel unless such 

action represents a human safety 

concern. 

(h) Miscellaneous Protocols. 

(i) The airgun array must be 

deactivated when not acquiring data or 

preparing to acquire data, except as 

necessary for testing. Unnecessary use 

of the acoustic source shall be avoided. 

Operational capacity of 90 in3 (not 

including redundant backup airguns) 

must not be exceeded during the survey, 

except where unavoidable for source 

testing and calibration purposes. All 

occasions where activated source 

volume exceeds notified operational 

capacity must be noticed to the PSO(s) 

on duty and fully documented. The lead 

PSO must be granted access to relevant 

instrumentation documenting acoustic 

source power and/or operational 

volume. 

(ii) Testing of the acoustic source 

involving all elements requires normal 

mitigation protocols (e.g., ramp-up). 

Testing limited to individual source 

elements or strings does not require 

ramp-up but does require pre-clearance. 

5. Monitoring Requirements. 

The holder of this Authorization is 

required to conduct marine mammal 

monitoring during survey activity. 

Monitoring shall be conducted in 

accordance with the following 

requirements: 

(a) The operator must provide a nightvision device suited for the marine 

environment for use during nighttime 

ramp-up pre-clearance, at the discretion 

of the PSOs. At minimum, the device 

should feature automatic brightness and 

gain control, bright light protection, 

infrared illumination, and optics suited 

for low-light situations. 

(b) PSOs must also be equipped with 

reticle binoculars (e.g., 7 × 50) of 

appropriate quality (i.e., Fujinon or 

equivalent), GPS, digital single-lens 

reflex camera of appropriate quality 

(i.e., Canon or equivalent), compass, and 

any other tools necessary to adequately 

perform necessary tasks, including 

accurate determination of distance and 

bearing to observed marine mammals. 

(c) PSO Qualifications 

(i) PSOs must have successfully 

completed relevant training, including 

completion of all required coursework 

and passing a written and/or oral 

examination developed for the training 

program. 

(ii) PSOs must have successfully 

attained a bachelor’s degree from an 

accredited college or university with a 

major in one of the natural sciences and 

a minimum of 30 semester hours or 

equivalent in the biological sciences and 

at least one undergraduate course in 

math or statistics. The educational 

requirements may be waived if the PSO 

has acquired the relevant skills through 

alternate experience. Requests for such 

a waiver must include written 

justification. Alternate experience that 

may be considered includes, but is not 

limited to (1) secondary education and/ 

or experience comparable to PSO duties; 

(2) previous work experience 

conducting academic, commercial, or 

government-sponsored marine mammal 

surveys; or (3) previous work experience 

as a PSO; the PSO should demonstrate 

good standing and consistently good 

performance of PSO duties. 

(d) Data Collection—PSOs must use 

standardized data forms, whether hard 

copy or electronic. PSOs shall record 

detailed information about any 

implementation of mitigation 

requirements, including the distance of 

animals to the acoustic source and 

description of specific actions that 

ensued, the behavior of the animal(s), 

any observed changes in behavior before 

and after implementation of mitigation, 

and if shutdown was implemented, the 

length of time before any subsequent 

ramp-up of the acoustic source to 

resume survey. If required mitigation 

was not implemented, PSOs should 

submit a description of the 

circumstances. We require that, at a 

minimum, the following information be 

reported: 

(i) PSO names and affiliations. 

(ii) Dates of departures and returns to 

port with port name. 

(iii) Dates and times (Greenwich Mean 

Time) of survey effort and times 

corresponding with PSO effort. 

(iv) Vessel location (latitude/ 

longitude) when survey effort begins 

and ends; vessel location at beginning 

and end of visual PSO duty shifts. 

(v) Vessel heading and speed at 

beginning and end of visual PSO duty 

shifts and upon any line change. 

(vi) Environmental conditions while 

on visual survey (at beginning and end 

of PSO shift and whenever conditions 

change significantly), including wind 

speed and direction, Beaufort sea state, 

Beaufort wind force, swell height, 

weather conditions, cloud cover, sun 

glare, and overall visibility to the 

horizon. 

(vii) Factors that may be contributing 

to impaired observations during each 

PSO shift change or as needed as 

environmental conditions change (e.g., 

vessel traffic, equipment malfunctions). 

(viii) Survey activity information, 

such as acoustic source power output 

while in operation, number and volume 

of airguns operating in the array, tow 

depth of the array, and any other notes 

of significance (i.e., pre-ramp-up survey, 

ramp-up, shutdown, testing, shooting, 

ramp-up completion, end of operations, 

streamers, etc.). 

(ix) If a marine mammal is sighted, 

the following information should be 

recorded: 

(A) Watch status (sighting made by 

PSO on/off effort, opportunistic, crew, 

alternate vessel/platform); 

(B) PSO who sighted the animal; 

(C) Time of sighting; 

(D) Vessel location at time of sighting; 

(E) Water depth; 

(F) Direction of vessel’s travel 

(compass direction); 

(G) Direction of animal’s travel 

relative to the vessel; 

(H) Pace of the animal; 

(I) Estimated distance to the animal 

and its heading relative to vessel at 

initial sighting; 

(J) Identification of the animal (e.g., 

genus/species, lowest possible 

taxonomic level, or unidentified); also 

note the composition of the group if 

there is a mix of species; 

(K) Estimated number of animals 

(high/low/best); 

(L) Estimated number of animals by 

cohort (adults, yearlings, juveniles, 

calves, group composition, etc.); 

(M) Description (as many 

distinguishing features as possible of 

each individual seen, including length, 

shape, color, pattern, scars or markings, 

shape and size of dorsal fin, shape of 

head, and blow characteristics); 

(N) Detailed behavior observations 

(e.g., number of blows, number of 

surfaces, breaching, spyhopping, diving, 

feeding, traveling; as explicit and 

detailed as possible; note any observed 

changes in behavior); 

(O) Animal’s closest point of 

approach (CPA) and/or closest distance 

from the center point of the acoustic 

source; 

(P) Platform activity at time of 

sighting (e.g., deploying, recovering, 

testing, shooting, data acquisition, 

other); and 

(Q) Description of any actions 

implemented in response to the sighting 

(e.g., delays, shutdown, ramp-up, speed 

or course alteration, etc.) and time and 

location of the action. 

6. Reporting. 

(a) SIO shall submit a draft 

comprehensive report on all activities 

and monitoring results within 90 days 

of the completion of the survey or 


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expiration of the IHA, whichever comes 

sooner. The report must describe all 

activities conducted and sightings of 

marine mammals near the activities, 

must provide full documentation of 

methods, results, and interpretation 

pertaining to all monitoring, and must 

summarize the dates and locations of 

survey operations and all marine 

mammal sightings (dates, times, 

locations, activities, associated survey 

activities). Geospatial data regarding 

locations where the acoustic source was 

used must be provided as an ESRI 

shapefile with all necessary files and 

appropriate metadata. In addition to the 

report, all raw observational data shall 

be made available to NMFS. The report 

must summarize the data collected as 

required under condition 5(d) of this 

IHA. The draft report must be 

accompanied by a certification from the 

lead PSO as to the accuracy of the 

report, and the lead PSO may submit 

directly to NMFS a statement 

concerning implementation and 

effectiveness of the required mitigation 

and monitoring. A final report must be 

submitted within 30 days following 

resolution of any comments from NMFS 

on the draft report. 

(b) Reporting injured or dead marine 

mammals: 

(i) In the event that the specified 

activity clearly causes the take of a 

marine mammal in a manner not 

prohibited by this IHA (if issued), such 

as serious injury or mortality, SIO shall 

immediately cease the specified 

activities and immediately report the 

incident to NMFS. The report must 

include the following information: 

(A) Time, date, and location (latitude/ 

longitude) of the incident; 

(B) Vessel’s speed during and leading 

up to the incident; 

(C) Description of the incident; 

(D) Status of all sound source use in 

the 24 hours preceding the incident; 

(E) Water depth; 

(F) Environmental conditions (e.g., 

wind speed and direction, Beaufort sea 

state, cloud cover, and visibility); 

(G) Description of all marine mammal 

observations in the 24 hours preceding 

the incident; 

(H) Species identification or 

description of the animal(s) involved; 

(I) Fate of the animal(s); and 

(J) Photographs or video footage of the 

animal(s). 

Activities shall not resume until 

NMFS is able to review the 

circumstances of the prohibited take. 

NMFS will work with SIO to determine 

what measures are necessary to 

minimize the likelihood of further 

prohibited take and ensure MMPA 

compliance. SIO may not resume their 

activities until notified by NMFS. 

(ii) In the event that SIO discovers an 

injured or dead marine mammal, and 

the lead observer determines that the 

cause of the injury or death is unknown 

and the death is relatively recent (e.g., 

in less than a moderate state of 

decomposition), SIO shall immediately 

report the incident to NMFS. The report 

must include the same information 

identified in condition 6(b)(i) of this 

IHA. Activities may continue while 

NMFS reviews the circumstances of the 

incident. NMFS will work with SIO to 

determine whether additional 

mitigation measures or modifications to 

the activities are appropriate. 

(iii) In the event that SIO discovers an 

injured or dead marine mammal, and 

the lead observer determines that the 

injury or death is not associated with or 

related to the specified activities (e.g., 

previously wounded animal, carcass 

with moderate to advanced 

decomposition, or scavenger damage), 

SIO shall report the incident to NMFS 

within 24 hours of the discovery. SIO 

shall provide photographs or video 

footage or other documentation of the 

sighting to NMFS. 

7. This Authorization may be 

modified, suspended or withdrawn if 

the holder fails to abide by the 

conditions prescribed herein, or if 

NMFS determines the authorized taking 

is having more than a negligible impact 

on the species or stock of affected 

marine mammals. 

Request for Public Comments 

We request comment on our analyses, 

the draft authorization, and any other 

aspect of this Notice of Proposed IHA 

for the proposed seismic survey by SIO. 

Please include with your comments any 

supporting data or literature citations to 

help inform our final decision on the 

request for MMPA authorization. 

Dated: August 11, 2017. 

Donna Wieting, 

Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2017–17378 Filed 8–16–17; 8:45 am] 

BILLING CODE 3510–22–P 


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