Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Low-Energy Geophysical Survey in the South Atlantic Ocean, 51886-51928 [2019-21090]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 84, Number 189 (Monday, September 30, 2019)]
[Notices]
[Pages 51886-51928]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-21090]



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Vol. 84

Monday,

No. 189

September 30, 2019

Part IV





Department of Commerce





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National Oceanic and Atmospheric Administration





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Takes of Marine Mammals Incidental to Specified Activities; Taking 
Marine Mammals Incidental to a Low-Energy Geophysical Survey in the 
South Atlantic Ocean; Notice

Federal Register / Vol. 84 , No. 189 / Monday, September 30, 2019 / 
Notices

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XR056


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to a Low-Energy Geophysical Survey in 
the South Atlantic Ocean

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

ACTION: Notice; proposed incidental harassment authorization; request 
for comments on proposed authorization and possible renewal.

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SUMMARY: NMFS has received a request from the Scripps Institute of 
Oceanography (SIO) for authorization to take marine mammals incidental 
to a low-energy marine geophysical survey in the South Atlantic Ocean. 
Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting 
comments on its proposal to issue an incidental harassment 
authorization (IHA) to incidentally take marine mammals during the 
specified activities. NMFS is also requesting comments on a possible 
one-year Renewal that could be issued under certain circumstances and 
if all requirements are met, as described in Request for Public 
Comments at the end of this notice. NMFS will consider public comments 
prior to making any final decision on the issuance of the requested 
MMPA authorizations and agency responses will be summarized in the 
final notice of our decision.

DATES: Comments and information must be received no later than October 
30, 2019.

ADDRESSES: Comments should be addressed to Jolie Harrison, Chief, 
Permits and Conservation Division, Office of Protected Resources, 
National Marine Fisheries Service. Physical comments should be sent to 
1315 East-West Highway, Silver Spring, MD 20910 and electronic comments 
should be sent to [email protected].
    Instructions: NMFS is not responsible for comments sent by any 
other method, to any other address or individual, or received after the 
end of the comment period. Comments received electronically, including 
all attachments, must not exceed a 25-megabyte file size. Attachments 
to electronic comments will be accepted in Microsoft Word or Excel or 
Adobe PDF file formats only. All comments received are a part of the 
public record and will generally be posted online at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act without change. All personal identifying 
information (e.g., name, address) voluntarily submitted by the 
commenter may be publicly accessible. Do not submit confidential 
business information or otherwise sensitive or protected information.

FOR FURTHER INFORMATION CONTACT: Stephanie Egger, Office of Protected 
Resources, NMFS, (301) 427-8401. Electronic copies of the application 
and supporting documents, as well as a list of the references cited in 
this document, may be obtained online at: https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act. In case of problems accessing these 
documents, please call the contact listed above.

SUPPLEMENTARY INFORMATION:

Background

    The MMPA prohibits the ``take'' of marine mammals, with certain 
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to 
allow, upon request, the incidental, but not intentional, taking of 
small numbers of marine mammals by U.S. citizens who engage in a 
specified activity (other than commercial fishing) within a specified 
geographical region if certain findings are made and either regulations 
are issued or, if the taking is limited to harassment, a notice of a 
proposed incidental take authorization may be provided to the public 
for review.
    Authorization for incidental takings shall be granted if NMFS finds 
that the taking will have a negligible impact on the species or 
stock(s) and will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for taking for subsistence uses 
(where relevant). Further, NMFS must prescribe the permissible methods 
of taking and other ``means of effecting the least practicable adverse 
impact'' on the affected species or stocks and their habitat, paying 
particular attention to rookeries, mating grounds, and areas of similar 
significance, and on the availability of such species or stocks for 
taking for certain subsistence uses (referred to in shorthand as 
``mitigation''); and requirements pertaining to the mitigation, 
monitoring and reporting of such takings are set forth.

National Environmental Policy Act

    To comply with the National Environmental Policy Act of 1969 (NEPA; 
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, 
NMFS must review our proposed action (i.e., the issuance of an 
incidental harassment authorization) with respect to potential impacts 
on the human environment.
    This action is consistent with categories of activities identified 
in Categorical Exclusion B4 (incidental harassment authorizations with 
no anticipated serious injury or mortality) of the Companion Manual for 
NOAA Administrative Order 216-6A, which do not individually or 
cumulatively have the potential for significant impacts on the quality 
of the human environment and for which we have not identified any 
extraordinary circumstances that would preclude this categorical 
exclusion. Accordingly, NMFS has preliminarily determined that the 
issuance of the proposed IHA qualifies to be categorically excluded 
from further NEPA review.
    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 May 15, 2019, NMFS received a request from SIO for an IHA to 
take marine mammals incidental to conducting a low-energy marine 
geophysical survey in the Southeast Atlantic Ocean. The application was 
deemed adequate and complete on August 12, 2019. SIO's request is for 
take of a small number of 48 species of marine mammals by Level B 
harassment. Neither SIO nor NMFS expects serious injury or mortality to 
result from this activity and, therefore, an IHA is appropriate. The 
planned activity is not expected to exceed one year.

Description of Proposed Activity

Overview

    SIO plans to conduct low-energy marine seismic surveys in the 
Southeast Atlantic Ocean during November-December 2019. The seismic 
surveys would be conducted to understand the volcanic and tectonic 
development of Walvis Ridge and Rio Grande Rise in the South Atlantic 
Ocean. The seismic surveys would be conducted in International Waters 
with water depths ranging from approximately 500 to 5700 m. The surveys 
would involve one source vessel, R/V Thomas G. Thompson (Thompson). The 
Thompson would deploy up to two 45-in\3\ GI airguns at a depth of 2-4 m 
with a

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maximum total volume of ~90 in\3\ along predetermined tracklines.

Dates and Duration

    The R/V Thompson would likely depart from Montevideo, Uruguay, on 
or about November 3, 2019 and would arrive in Walvis Bay, Namibia, on 
or about 5 December 5, 2019. If the arrival port is Cape Town instead 
of Walvis Bay, an additional two days would be required for transit. 
Seismic operations would occur for approximately 14 days. Transit to 
and from the project area and between surveys would occur from 
approximately 16 days. Equipment deployment and recovery would take 
approximately 3 days. 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 majority of the survey would take place in the Southeast 
Atlantic Ocean between ~33.2[deg]-21[deg] S and 1[deg] W-8[deg] E (see 
Figure 1). A small survey area is proposed for the Southwest Atlantic 
Ocean between ~33.2[deg]-34.3[deg] S and 30.8[deg]-31.8[deg] W (see 
Figure 1). Seismic surveys would occur in five survey areas including 
Libra Massif in the Southwest Atlantic and Valdivia Bank, Gough, 
Tristan, and Central survey areas in the Southeast Atlantic; 
representative survey tracklines are shown in Figure 1.
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Detailed Description of Specific Activity

    SIO proposes to conduct low-energy seismic surveys in five areas in 
the South Atlantic Ocean. Reconnaissance Surveys are planned for three 
survey areas (Gough, Tristan, Central) and High Quality Surveys are 
planned to take place along the proposed seismic transect lines in the 
main survey area (Valdivia Bank) and Libra Massif survey area (Figure 
1). However, High-Quality Surveys may be replaced by Reconnaissance 
Surveys depending on weather conditions and timing (e.g., 10 percent of 
survey effort at Valdivia Bank is expected to consist of Reconnaissance 
Surveys). All data acquisition in the Tristan survey area would occur 
in water >1,000 m deep; all other survey areas have effort in 
intermediate (100-1,000 m) and deep (>1,000 m) water. Most of the 
survey effort (97 percent) would occur in water >1,000 m deep. The 
proposed surveys would be in support of a potential future 
International Ocean Discovery Program (IODP) project and to improve our 
understanding of volcanic and tectonic development of oceanic ridges 
and to enable the selection and analysis of potential future IODP drill 
sites. To achieve the program's goals, the Principal Investigators 
propose to collect low-energy, high-resolution multi-channel seismic 
(MCS) profiles. The proposed cruise would consist of digital 
bathymetric, echosounding, and MCS surveys.
    The procedures to be used for the seismic surveys would be similar 
to those used during previous seismic surveys by SIO and would use 
conventional seismic methodology. The surveys would involve one source 
vessel, R/V Thompson, which is managed by University of Washington 
(UW). The R/V Thompson would deploy up to two 45-in\3\ GI airguns as an 
energy source with a maximum total volume of ~90 in\3\. The receiving 
system would consist of one hydrophone streamer, 200 to 1,600 m in 
length, as described below. 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.
    The airgun array would be operated in one of two different types of 
array modes. The first would be highest-quality survey mode to collect 
the highest-quality seismic reflection data. The second mode would be a 
reconnaissance mode, which are quicker and less impacted by adverse 
weather. The reconnaissance mode also allows for operations to occur in 
poor weather where the use of streamer longer than 400-m may not be 
possible safely.
    The highest-quality mode is carried out using a pair of 45-in\3\ 
airguns, with airguns spaced 2 m apart at a depth of 2-4 m, with a 400, 
800, or 1,600 m hydrophone streamer and with the vessel traveling at to 
5 knots (5 kn) to achieve high-quality seismic reflection data. The 
reconnaissance mode is carried out using either one or two 45-in\3\ 
airguns, with airguns spaced 8 m apart (if 2 are being used) at a water 
depth of 2-4 m, with a 200 m hydrophone streamer and with the vessel 
traveling at 8 kn.
    Seismic data would be collected first as a single profile over the 
rift at Libra Massif, the most southeastern edifice of Rio Grande Rise. 
After crossing the Atlantic, data would be collected over three 
seamounts (Gough, Tristan, Central) in the ``Guyot Province'' of Walvis 
Ridge. Approximately 24 hr of seismic profiling is proposed at each 
location, before moving on to the Valdivia Bank survey area, where most 
survey effort (75 percent) would occur.
    There could be additional seismic operations in the project area 
associated with equipment testing, re-acquisition due to reasons such 
as but not limited to equipment malfunction, data degradation during 
poor weather, or interruption due to shut-down or track deviation in 
compliance with IHA requirements. 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 hull-mounted 
multibeam echosounder (MBES) and a sub-bottom profiler (SBP) would also 
be operated from the Thompson continuously throughout the seismic 
surveys, but not during transits to and from the project area. All 
planned data acquisition and sampling activities would be conducted by 
SIO and UW with on board assistance by the scientists who have proposed 
the project. The vessel would be self-contained, and the crew would 
live aboard the vessel for the entire cruise.
    The Thompson has a length of 83.5 m, a beam of 16 m, and a full 
load draft of 5.8 m. It is equipped with twin 360[deg]-azimuth stern 
thrusters each powered by 3,000-hp DC motors and a water-jet bow 
thruster powered by a 1,100-hp DC motor. An operation speed of ~9-15 
km/h (~5-8 kn) would be used during seismic acquisition. When not 
towing seismic survey gear, the Thompson cruises at 22 km/h (12 kn) and 
has a maximum speed of 26.9 km/h (14.5 kn). It has a normal operating 
range of ~24,400 km. The Thompson would also serve as the platform from 
which vessel-based protected species visual observers (PSVO) would 
watch for marine mammals and before and during airgun operations.
    During the survey, the Thompson would tow two 45-in\3\ GI airguns 
and a streamer containing hydrophones. The generator chamber of each GI 
gun, the one responsible for introducing the sound pulse into the 
ocean, is 45 in\3\. The larger (105 in\3\) injector chamber injects air 
into the previously generated bubble to maintain its shape and does not 
introduce more sound into the water. The 45-in\3\ GI airguns would be 
towed 21 m behind the Thompson, 2 m (during 5-kn high-quality surveys) 
or 8 m (8-kn reconnaissance surveys) apart, side by side, at a depth of 
2-4 m. High-quality surveys with the 2-m airgun separation 
configuration would use a streamer up to 1,600-m long, whereas the 
reconnaissance surveys with the 8-m airgun separation configuration 
would use a 200-m streamer. Seismic pulses would be emitted at 
intervals of 25 m for the 5-kn surveys using the 2-m GI airgun 
separation and at 50 m for the 8-kn surveys using the 8-m airgun 
separation.

        Table 1--Specifications of the R/V Thompson Airgun Array
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Number of airguns.........................  2.
Gun positions used........................  Two inline airguns 2- or 8-m
                                             apart.
Tow depth of energy source................  2-4 m.
Dominant frequency components.............  0-188 hertz (Hz).
Air discharge volume......................  Approximately 90 in\3\.
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    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 summarize available information 
regarding status and trends, distribution and habitat preferences, and 
behavior and life history, of the potentially affected species. 
Additional information about these species (e.g., physical and 
behavioral descriptions) may be found on NMFS's website (https://www.fisheries.noaa.gov/find-species).
    The populations of marine mammals considered in this document do 
not occur within the U.S. EEZ and are therefore not assigned to stocks 
and are not assessed in NMFS' Stock Assessment Reports (SAR). As such,

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information on potential biological removal (PBR; defined by the MMPA 
as the maximum number of animals, not including natural mortalities, 
that may be removed from a marine mammal stock while allowing that 
stock to reach or maintain its optimum sustainable population) and on 
annual levels of serious injury and mortality from anthropogenic 
sources are not available for these marine mammal populations. 
Abundance estimates for marine mammals in the survey location are 
lacking; therefore estimates of abundance presented here are based on a 
variety of proxy sources including International Whaling Commission 
population estimates (IWC 2019), the U.S. Atlantic SARs (Hayes et al., 
2018) for a few dolphin species, and various literature estimates (see 
IHA application for further detail), as this is considered the best 
available information on potential abundance of marine mammals in the 
area. However, as described above, the marine mammals encountered by 
the proposed survey are not assigned to stocks. All abundance estimate 
values presented in Table 2 are the most recent available at the time 
of publication and are available in the 2018 U.S. Atlantic SARs (e.g., 
Hayes et al. 2018) available online at: www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments, 
except where noted otherwise.
    Table 2 lists all species with expected potential for occurrence in 
the Argentine Basin, Southwest Atlantic Ocean, and summarizes 
information related to the population, including regulatory status 
under the MMPA and ESA. For taxonomy, we follow Committee on Taxonomy 
(2018).
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    All species that could potentially occur in the proposed survey 
areas are included in Table 2. As described below, all 48 species 
temporally and spatially co-occur with the activity to the degree that 
take is reasonably likely to occur, and we have proposed authorizing 
it.
    Though other marine mammal species are known to occur in the 
Southwest Atlantic Ocean, the temporal and/or spatial occurrence of 
several of these species is such that take of these species is not 
expected to occur, and they are therefore not discussed further beyond 
the explanation provided here. An additional 13 species of marine 
mammals are known to occur in the Southwest Atlantic Ocean; however, 
they are unlikely to occur within the proposed project area because 
they are coastally-distributed (e.g., Atlantic humpback dolphin, Sousa 
teuszii; Heaviside's dolphin, Cephalorhynchus heavisidii; Chilean 
dolphin, C. eutropia; long-beaked common dolphin, Delphinus capensis; 
Franciscana, Pontoporia blainvillei; Guiana dolphin, Sotalia 
guianensis; Burmeister's porpoise, Phocoena spinipinnis; West Indian 
manatee, Trichechus manatus; African manatee, T. senegalensis; South 
American fur seal, Arctocephalus australis); or (2) occur further south 
(spectacled porpoise, Phocoena dioptrica; Ross seal, Ommatophoca 
rossii; Weddell seal, Leptonychotes weddellii). Although a gray whale 
(Eschrichtius robustus) was sighted off Namibia in 2013 (Elwen and 
Gridley 2013), and the remains of a stranded Omura's whale 
(Balaenoptera omurai) were reported for Mauritania in western Africa 
(Jung et al. 2016), these species are not considered further as they 
typically do not occur in the Atlantic Ocean. None of these species are 
discussed further here.
    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 for a complete description 
of the species, and offer a brief introduction to the species here, as 
well as information regarding population trends and threats, and 
describe information regarding local occurrence.

Mysticetes

Southern Right Whale
    The southern right whale is circumpolar throughout the Southern 
Hemisphere between 20[deg] S and 55[deg] S (Jefferson et al. 2015), 
although it may occur further north where cold-water currents extend 
northwards (Best 2007). It migrates between summer foraging areas at 
high latitudes and winter breeding/calving areas in low latitudes 
(Jefferson et al. 2015). In the South Atlantic, known or historic 
breeding areas are located in the shallow coastal

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waters of South America, including Argentina and Brazil, as well as the 
Falkland Islands, Tristan de Cunha, Namibia, and South Africa (IWC 
2001). Rowntree et al. (2013) reported that during 2009, primary 
calving grounds included an estimated 3,864 southern right whales off 
South Africa.
    Although southern right whale calving/breeding areas are located in 
nearshore waters, feeding grounds in the Southern Ocean apparently are 
located mostly in highly-productive pelagic waters (Kenney 2018). 
Waters south of South Africa are believed to be a nursery area for 
southern right whales, as females and calves are seen there (Barendse 
and Best 2014). Right whales with calves are seen in nearshore waters 
of South Africa during July-November (Best 2007). Nearshore waters off 
western South Africa might be used as a year-round feeding area 
(Barendse and Best 2014). The highest sighting rates off western South 
Africa occur during early austral summer, and the lowest rates have 
been reported from autumn to mid-winter (Barendse and Best 2014). 
Although right whales were depleted in the early 19th century by 
whaling, they are now reappearing off Namibia; this likely indicates a 
range expansion of the stock from South Africa rather than a separate 
stock (Roux et al. 2001, 2015). Numerous sightings were made in the 
area from 1971 through 1999; most sightings were made from July through 
November, with one sighting during December (Roux et al. 2001). A total 
of 10 calves were born off Namibia between 1996 and 1999 (Roux et al. 
2001). However, Roux et al. (2015) postulated that Namibian waters 
currently serve as mating grounds rather than a calving area. Best 
(2007) reported a summer feeding concentration between 30[deg] and 
40[deg] S, including the Guyot Province of Walvis Ridge, where three 
proposed survey areas (Gough, Tristan, Central) are located.
Pygmy Right Whale
    The distribution of the pygmy right whale is circumpolar in the 
Southern Hemisphere between 30[deg] S and 55[deg] S in oceanic and 
coastal environments (Kemper 2018; Jefferson et al. 2015). The pygmy 
right whale appears to be non-migratory, although there may be some 
movement inshore in spring and summer (Kemper 2002; Jefferson et al. 
2015), possibly related to food availability (Kemper 2018). Foraging 
areas are not known, but it seems likely that pygmy right whales may 
feed at productive areas in higher latitudes, such as near the 
Subtropical Convergence (Best 2007). There may be hotspots of 
occurrence where mesozooplankton, such as Nyctiphanes australis and 
Calanus tonsus, are plentiful (Kemper et al. 2013).
    In the South Atlantic, pygmy right whale records exist for southern 
Africa, Argentina, Falkland Islands, and pelagic waters (Baker 1985). 
Leeney et al. (2013) reported 12 strandings and 8 records of skeletal 
remains for Namibia since 1978. Most of the records are for Walvis Bay; 
strandings have only been reported during austral summer (November-
March). The large number of juveniles suggests that the area may be a 
nursery ground (Leeney et al. 2013). Best (2007) reported records 
between 30[deg] S and 40[deg] S, including near the Central survey 
area. Bester and Ryan (2007) suggested that pygmy right whales occur in 
the Tristan da Cunha archipelago. One pygmy right whale was taken by 
whalers at 35[deg] S and 8[deg] W on 30 November 1970 (Budylenko et al. 
1973 in Best et al. 2009). There are no OBIS records of pygmy right 
whales for the offshore waters of the proposed survey area, but 10 
records exist off southwestern Africa (OBIS 2019). Pygmy right whales 
could be seen in any of the proposed project area at the time of the 
surveys, in particular in the Gough, Tristan, and Central survey areas.
Blue Whale
    The blue whale has a cosmopolitan distribution, but tends to be 
mostly pelagic, only occurring nearshore to feed and possibly breed 
(Jefferson et al. 2015). It is most often found in cool, productive 
waters where upwelling occurs (Reilly and Thayer 1990). The 
distribution of the species, at least during times of the year when 
feeding is a major activity, occurs in areas that provide large 
seasonal concentrations of euphausiids (Yochem and Leatherwood 1985). 
Seamounts and other deep ocean structures may be important habitat for 
blue whales (Lesage et al. 2016). Generally, blue whales are seasonal 
migrants between high latitudes in summer, where they feed, and low 
latitudes in winter, where they mate and give birth (Lockyer and Brown 
1981).
    An extensive data review and analysis by Branch et al. (2007a) 
showed that blue whales are essentially absent from the central regions 
of major ocean basins, including the South Atlantic. Blue whales were 
captured by the thousands off Angola, Namibia, and South Africa between 
1908 and 1967 (Branch et al. 2007a; Figueiredo and Weir 2014), 
including several catches near the proposed project area during 1958-
1973 (including in November and December) and a few sightings off South 
Africa. However, whales were nearly extirpated in this region, and 
sightings are now rare (Branch et al. 2007a). At least four records 
exist for Angola; all sightings were made in 2012, with at least one 
sighting in July, two in August, and one in October (Figueiredo and 
Weir 2014). Sightings were also made off Namibia in 2014 from seismic 
vessels (Brownell et al. 2016). Waters off Namibia may serve as a 
possible wintering and possible breeding ground for Antarctic blue 
whales (Best 1998, 2007; Thomisch et al. 2017). Antarctic blue whale 
calls were detected on acoustic recorders that were deployed northwest 
of Walvis Ridge (just to the north of the Valdivia Bank survey area) 
from November 2011 through May 2013 during all months except during 
September and October, indicating that not all whales migrate to higher 
latitudes during the summer (Thomisch et al. 2017). Most blue whales in 
southeastern Africa are expected to be Antarctic blue whales; however, 
~4 percent may be pygmy blue whales (Branch et al. 2007b, 2008). In 
fact, pygmy blue whale vocalizations were detected off northern Angola 
in October 2008; these calls were attributed to the Sri Lanka 
population (Cerchio et al. 2010). One offshore sighting of a blue whale 
was made at 13.4[deg] S, 26.8[deg] W and the other at 15.9[deg] S, 
4.6[deg] W (Branch et al. 2007a; OBIS 2019). The occurrence of blue 
whales in the Tristan da Cunha archipelago also seems likely (Bester 
and Ryan 2007). There are ~1845 blue whale records for the South 
Atlantic in the OBIS database; however, no records occur within the 
proposed project area (OBIS 2019). Blue whales could be encountered 
during the proposed surveys, in particular in the Valdivia Bank survey 
area.
Fin Whale
    The fin whale is widely distributed in all the world's oceans 
(Gambell 1985), although it is most abundant in temperate and cold 
waters (Aguilar and Garc[iacute]a-Vernet 2018). Nonetheless, its 
overall range and distribution is not well known (Jefferson et al. 
2015). Fin whales most commonly occur offshore, but can also be found 
in coastal areas (Jefferson et al. 2015). Most populations migrate 
seasonally between temperate waters where mating and calving occur in 
winter, and polar waters where feeding occurs in the summer; they are 
known to use the shelf edge as a migration route (Evans 1987). The 
northern and southern fin whale populations likely do not interact 
owing to their alternate seasonal migration; the resulting genetic 
isolation has led to the recognition of two subspecies, B. physalus 
quoyi and B. p. physalus in the

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Southern and Northern hemispheres, respectively (Anguilar and 
Garc[iacute]a-Vernet 2018).
    In the Southern Hemisphere, fin whales are typically distributed 
south of 50[deg] S in the austral summer, migrating northward to breed 
in the winter (Gambell 1985). Historical whaling data showed several 
catches for the Tristan da Cunha archipelago (Best et al. 2009), as 
well as off Namibia and southern Africa (Best 2007). Fin whales appear 
to be somewhat common in the Tristan da Cunha archipelago from October-
December (Bester and Ryan 2007). According to Edwards et al. (2015), 
sightings have been made south of South Africa from December-February; 
they did not report any sightings or acoustic detections near the 
proposed project area. Several fin whales sightings and strandings have 
been reported for Namibia in the last decade (NDP unpublished data in 
Pisces Environmental Services 2017). Fin whale calls were detected on 
acoustic recorders that were deployed northwest of Walvis Ridge from 
November 2011 through May 2013 during the months of November, January, 
and June through August, indicating that the waters off Namibia serve 
as wintering grounds (Thomisch et al. 2017). Similarly, Best (2007) 
also suggested that waters off Namibia may be wintering grounds.
Sei Whale
    The sei whale occurs in all ocean basins (Horwood 2018), 
predominantly inhabiting deep waters throughout their range (Acevedo et 
al. 2017a). It undertakes seasonal migrations to feed in sub-polar 
latitudes during summer, returning to lower latitudes during winter to 
calve (Horwood 2018). In the Southern Hemisphere, sei whales typically 
concentrate between the Subtropical and Antarctic convergences during 
the summer (Horwood 2018) between 40[deg] S and 50[deg] S, with larger, 
older whales typically travelling into the northern Antarctic zone 
while smaller, younger individuals remain in the lower latitudes 
(Acevedo et al. 2017a). Best (2007) showed summer concentrations 
between 30[deg] S and 50[deg] S, including near the three proposed 
survey areas (Central, Tristan, Gough) in the Guyot Province of Walvis 
Ridge. Waters off northern Namibia may serve as wintering grounds (Best 
2007).
    A sighting of a mother and calf were made off Namibia in March 
2012, and one stranding was reported in July 2013 (NDP unpublished data 
in Pisces Environmental Services 2017). One sighting was made during 
seismic surveys off the coast of northern Angola between 2004 and 2009 
(Weir 2011). A group of 2-4 sei whales was seen near St. Helena during 
April 2011 (Clingham et al. 2013). Although the occurrence of sei 
whales is likely in the Tristan da Cunha archipelago (Bester and Ryan 
2007), there have been no recent records of sei whales in the region; 
however, sei whale catches were made here in the 1960s (Best et al. 
2009). Sei whales were also taken off southern Africa during the 1960s, 
with some catches reported just to the southeast of the proposed survey 
area; catches were made during the May-July northward migration as well 
as during the August-October southward migration (Best and Lockyer 
2002). In the OBIS database, there are 40 sei whale records for the 
South Atlantic; the closest records were reported at 33.3[deg] S, 
8.0[deg] W and 35.1[deg] S, 6.4[deg] W (OBIS 2019). Sei whales could be 
encountered in any of the proposed survey areas at the time of the 
surveys, in particular in the Gough, Tristan, and Central survey areas.
Bryde's Whale
    Bryde's whale occurs in all tropical and warm temperate waters in 
the Pacific, Atlantic and Indian oceans, between 40[deg] N and 40[deg] 
S (Jefferson et al. 2015). It is one of the least known large baleen 
whales, and it remains uncertain how many species are represented in 
this complex (Kato and Perrin 2018). B. brydei is commonly used to 
refer to the larger form or ``true'' Bryde's whale and B. edeni to the 
smaller form; however, some authors apply the name B. edeni to both 
forms (Kato and Perrin 2018). Bryde's whale remains in warm (>16 
[deg]C) water year-round (Kato and Perrin 2018), but analyses have 
shown that it prefers water <20.6 [deg]C in the eastern tropical 
Atlantic (Weir et al. 2012). Seasonal movements have been recorded 
towards the Equator in winter and offshore in summer (Kato and Perrin 
2018). It is frequently observed in biologically productive areas such 
as continental shelf breaks (Davis et al. 2002) and regions subjected 
to coastal upwelling (Gallardo et al. 1983; Siciliano et al. 2004). 
Central oceanic waters of the South Atlantic, including the proposed 
project area, are considered part of its secondary range (Jefferson et 
al. 2015).
    In southern Africa, there are likely three populations of Bryde's 
whales--an inshore population, a pelagic population of the Southeast 
Atlantic stock, and the Southwest Indian Ocean stock (Best 2001). The 
Southeast Atlantic stock ranges from the equator to ~34[deg] S and 
migrates north in the fall and south during the spring, with most 
animals occurring off Namibia during the austral summer (Best 2001). 
Numerous sightings have been made off Gabon (Weir 2011), Angola (Weir 
2010, 2011), and South Africa (Findlay et al. 1992), including in deep 
slope waters. Strandings have also been reported along the Namibian 
coast (Pisces Environmental Services 2017). Bryde's whale was sighted 
in the offshore waters of the South Atlantic during a cruise from Spain 
to South Africa in November 2009, near 22[deg] S, 6[deg] W (Shirshov 
Institut n.d.). In the OBIS database, there are 12 records off the 
coast of South Africa (OBIS 2019). Bryde's whales are not expected to 
occur in the Libra Massif survey area. However, they could be 
encountered in the rest of the proposed project area, in particular the 
eastern portions of the Valdivia Bank survey area.
Common Minke Whale
    The common minke whale has a cosmopolitan distribution ranging from 
the tropics and subtropics to the ice edge in both hemispheres 
(Jefferson et al. 2015). A smaller form (unnamed subspecies) of the 
common minke whale, known as the dwarf minke whale, occurs in the 
Southern Hemisphere, where its distribution overlaps with that of the 
Antarctic minke whale (B. bonaerensis) during summer (Perrin et al. 
2018). The dwarf minke whale is generally found in shallower coastal 
waters and over the shelf in regions where it overlaps with B. 
bonaerensis (Perrin et al. 2018). The range of the dwarf minke whale is 
thought to extend as far south as 65[deg] S (Jefferson et al. 2015) and 
as far north as 2[deg] S in the Atlantic off South America, where it 
can be found nearly year-round (Perrin et al. 2018).
    It is known to occur off South Africa during autumn and winter 
(Perrin et al. 2018), but has not been reported for the waters off 
Angola or Namibia (Best 2007). It is likely to occur in the waters of 
the Tristan da Cunha archipelago (Bester and Ryan 2007). There are 36 
records for the South Atlantic in the OBIS database, including records 
off South America and along the coast of Namibia and South Africa; 
there are no records in the proposed project area (OBIS 2019). Dwarf 
minke whales could be encountered in the proposed project area at the 
time of the surveys.
Antarctic Minke Whale
    The Antarctic minke whale has a circumpolar distribution in coastal 
and offshore areas of the Southern Hemisphere from ~7[deg] S to the ice 
edge (Jefferson et al. 2015). It is found between 60[deg] S and the ice 
edge during the austral summer; in the austral winter, it is mainly 
found at mid-

[[Page 51896]]

latitude breeding grounds, including off western South Africa and 
northeastern Brazil, where it is primarily oceanic, occurring beyond 
the shelf break (Perrin et al. 2018). Antarctic minke whale densities 
are highest near pack ice edges, although they are also found amongst 
pack ice (Williams et al. 2014), where they feed almost entirely on 
krill (Tamura and Konishi 2009).
    In the Southeast Atlantic, Antarctic minke whales have been 
reported for the waters of South Africa, Namibia, and Angola (Best 
2007). Antarctic minke whale calls were detected on acoustic recorders 
that were deployed northwest of Walvis Ridge from November 2011 through 
May 2013 during the months of November, December, January, and June 
through August, indicating that not all whales migrate to higher 
latitudes during the summer (Thomisch et al. 2017). Sightings have also 
been made along the coast of Namibia, in particular during summer (NPD 
unpublished data in Pisces Environmental Services 2017). Antarctic 
minke whales are also likely to occur in the Tristan da Cunha 
archipelago (Bester and Ryan 2007). Two groups totaling seven whales 
were sighted at 36.4[deg] S, 8.5[deg] W on 7 October 1988 (Best et al. 
2009). A sighting of two whales was made off Brazil during an August-
September 2010 survey from Vit[oacute]ria, at ~20[deg] S, 40[deg] W, to 
Trindade and Martim Vaz islands; the whales were seen in association 
with a group of rough-toothed dolphins near 19.1[deg] S, 35.1[deg] W on 
21 August (Wedekin et al. 2014). There are five OBIS records for the 
South Atlantic, including along the coast of South America and South 
Africa; there are no records for the proposed project area (OBIS 2019). 
Antarctic minke whales could be encountered in the proposed project 
area at the time of the surveys.
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 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.
    In the Southern Hemisphere, humpback whales migrate annually from 
summer foraging areas in the Antarctic to breeding grounds in tropical 
seas (Clapham 2018). Two of the breeding grounds are in the South 
Atlantic, off Brazil and West Africa (Engel and Martin 2009). Bettridge 
et al. (2015) identified humpback whales at these breeding locations as 
the Brazil and Gabon/Southwest Africa DPSs. There may be two breeding 
substocks in Gabon/Southwest Africa, including individuals in the main 
breeding area in the Gulf of Guinea and those animals migrating past 
Namibia and South Africa (Rosenbaum et al. 2009; Barendse et al. 2010a; 
Branch 2011; Carvalho et al. 2011). Migration rates are relatively high 
between populations within the southeastern Atlantic (Rosenbaum et al. 
2009). However, Barendse et al. (2010a) reported no matches between 
individuals sighted in Namibia and South Africa based on a comparison 
of tail flukes. In addition, wintering humpbacks have also been 
reported on the continental shelf of northwest Africa, which may 
represent the northernmost humpback whales that are known to winter in 
the Gulf of Guinea (Van Waerebeek et al. 2013). Feeding areas for this 
stock include Bouvet Island (Rosenbaum et al. 2014) and waters of the 
Antarctic Peninsula (Barendse et al. 2010b).
    Humpbacks have been seen on breeding grounds around S[atilde]o 
Tom[eacute] in the Gulf of Guinea from August through November; off 
Gabon, whales occur from late June-December (Carvalho et al. 2011). The 
west coast of South Africa might not be a `typical' migration corridor, 
as humpbacks are also known to feed in the area; they are known to 
occur in the region during the northward migration (July-August), the 
southward migration (October-November), and into February (Barendse et 
al. 2010b; Carvalho et al. 2011; Seakamela et al. 2015). The highest 
sighting rates in the area occurred during mid-spring through summer 
(Barendse et al. 2010b). Off Namibia, the main peak of occurrence is 
during winter (July), with another peak during spring (September); 
however, this area is unlikely to be a breeding area (Elwen et al. 
2014). Elwen et al. (2014) suggested that humpbacks are migrating 
northward past Namibia during winter and migrate closer to shore during 
a southward migration during spring/summer. Humpback whale calls were 
detected on acoustic recorders that were deployed northwest of Walvis 
Ridge from November 2011 through May 2013 during the months of 
November, December, January, and May through August, indicating that 
not all whales migrate to higher latitudes during the summer (Thomisch 
et al. 2017). Based on whales that were satellite-tagged in Gabon in 
winter 2002, migration routes southward include offshore waters along 
Walvis Ridge (Rosenbaum et al. 2014). Hundreds of sightings have been 
made during seismic surveys off the coast of Angola between 2004 and 
2009, including in deep slope water; most sightings were reported 
during winter and spring (Weir 2011). Best et al. (1999) reported some 
sightings off the coast of Angola during November 1995. Humpback whale 
acoustic detections were made in the area from June through December 
2008 (Cerchio et al. 2014).
    Humpbacks occur occasionally around the Tristan da Cunha 
archipelago (Bester and Ryan 2007). Three records exist for Tristan 
waters, all south of 37[deg] S (Best et al. 2009). Humpback whales have 
also been sighted off St. Helena (MacLeod and Bennett 2007; Clingham et 
al. 2013). Numerous humpbacks were detected visually and acoustically 
during a survey off Brazil from Vit[oacute]ria at ~20[deg] S, 40[deg] 
W, to Trindade and Martim Vaz islands during August-September 2010 
(Wedekin et al. 2014). One adult humpback was seen on 31 August near 
Trindade Island, at 20.5[deg] S, 29.3[deg] W in a water depth of 150 m, 
but no acoustic detections were made east of 35[deg] W (Wedekin et al. 
2014). Numerous sightings were also made near Trindade Island during 
July-August 2007 and before that date (Siciliano et al. 2012). For the 
South Atlantic, the OBIS database shows over 700 records for the South 
Atlantic, including along the coast of South America and western 
Africa, and in offshore waters of the central Atlantic (OBIS 2019). The 
closest sightings to the proposed survey areas in the southeastern 
Atlantic occur near the Gough survey area at 33.8[deg] S, 2.1[deg] E 
and 32.5[deg] S, 3.8[deg] E (OBIS 2019). The waters of the proposed 
project area are considered part of the humpback's secondary range 
(Jefferson et al. 2015). However, humpback whales could be encountered 
at the time of the proposed surveys, in particular in the Valdivia Bank 
survey area.

Odontocetes

Sperm Whale
    The sperm whale is widely distributed, occurring from the edge of 
the polar pack ice to the Equator in both hemispheres, with the sexes 
occupying

[[Page 51897]]

different distributions (Whitehead 2018). In general, it is distributed 
over large temperate and tropical areas that have high secondary 
productivity and steep underwater topography, such as volcanic islands 
(Jaquet and Whitehead 1996). Its distribution and relative abundance 
can vary in response to prey availability, most notably squid (Jaquet 
and Gendron 2002). Females generally inhabit waters >1,000 m deep at 
latitudes <40[deg] where sea surface temperatures are <15[deg] C; adult 
males move to higher latitudes as they grow older and larger in size, 
returning to warm-water breeding grounds according to an unknown 
schedule (Whitehead 2018).
    Whaling data from the South Atlantic indicate that sperm whales may 
be migratory off South Africa, with peak abundances reported in the 
region during autumn and late winter/spring (Best 2007). The waters of 
northern Namibia and Angola were also historical whaling grounds (Best 
2007; Weir 2019). Sperm whales were the most frequently sighted 
cetacean during seismic surveys off the coast of northern Angola 
between 2004 and 2009; hundreds of sightings were made off Angola and a 
few sightings were reported off Gabon (Weir 2011). Sperm whales have 
also been sighted off South Africa during surveys of the Southern Ocean 
(Van Waerebeek et al. 2010). In addition, a sighting was made at 
30.1[deg] S, 14.3[deg] E (Clingham et al. 2013). Bester and Ryan (2007) 
reported that sperm whales might be common in the Tristan da Cunha 
archipelago. Catches of sperm whales in the 19th century were made in 
Tristan waters between October and January (Townsend 1935 in Best et 
al. 2009), and catches also occurred there in the 1960s (Best et al. 
2009). One group was seen at St. Helena during July 2009 (Clingham et 
al. 2013). There are ~3,080 records of sperm whales for the South 
Atlantic in the OBIS database, including nearshore waters of South 
American and Africa and offshore waters (OBIS 2019). Most (3,069) 
records are from historical catch data, which include captures within 
the proposed project area (OBIS 2019). Sperm whales could be 
encountered in the proposed project area at the time of the surveys.
Pygmy and Dwarf Sperm Whales
    Dwarf and pygmy sperm whales are distributed throughout tropical 
and temperate waters of the Atlantic, Pacific and Indian oceans, but 
their precise distributions are unknown because much of what we know of 
the species comes from strandings (McAlpine 2018). They are difficult 
to sight at sea, because of their dive behavior and perhaps because of 
their avoidance reactions to ships and behavior changes in relation to 
survey aircraft (W[uuml]rsig et al. 1998). The two species are often 
difficult to distinguish from one another when sighted (McAlpine 2018). 
It has been suggested that the pygmy sperm whale is more temperate and 
the dwarf sperm whale more tropical, based at least partially on live 
sightings at sea from a large database from the eastern tropical 
Pacific (Wade and Gerrodette 1993; McAlpine 2018). This idea is also 
supported by the distribution of strandings in South American waters 
(Mu[ntilde]oz-Hincapi[eacute] et al. 1998; Moura et al. 2016).
    Both species are known to occur in the South Atlantic, occurring as 
far south as northern Argentina in the west and South Africa in the 
east (Jefferson et al. 2015). There are 30 records of Kogia sp. for 
Namibia; most of these are strandings of pygmy sperm whales, but one 
live stranding of a dwarf sperm whale has also been reported (Elwen et 
al. 2013). Twenty-six sightings of dwarf sperm whales were made during 
seismic surveys off the coast Angola between 2004 and 2009 (Weir 2011). 
Findlay et al. (1992) reported numerous records of dwarf sperm whales 
for South Africa. Kogia sp. were sighted during surveys off St. Helena 
during August-October 2004 (Clingham et al. 2013). There are no records 
of Kogia sp. in the offshore waters of the proposed survey area (OBIS 
2019). The only records in the OBIS database for the South Atlantic are 
for Africa; there are 57 records of K. breviceps and 22 records of K. 
sima exist for southwestern Africa (OBIS 2019). Both pygmy and dwarf 
sperm whales could be encountered in the proposed project area at the 
time of the surveys.
Arnoux's Beaked Whale
    Arnoux's beaked whale is distributed in deep, cold, temperate, and 
subpolar waters of the Southern Hemisphere, occurring between 24[deg] S 
and Antarctica (Thewissen 2018). Most records exist for southeastern 
South America, Falkland Islands, Antarctic Peninsula, South Africa, New 
Zealand, and southern Australia (MacLeod et al. 2006; Jefferson et al. 
2015). One sighting was made south of Africa at ~40[deg] S during 
surveys of the Southern Ocean (Van Waerebeek et al. 2010). Arnoux's 
beaked whales likely occur in the Tristan da Cunha archipelago (Bester 
and Ryan 2007). There are three OBIS records for the Southeast Atlantic 
in South Africa and no records for the Southwest Atlantic (OBIS 2019). 
Based on information presented in Best (2007), it is more likely to be 
encountered in the southern Central, Gough, and Tristan survey areas 
than in the more northern survey area.
Cuvier's Beaked Whale
    Cuvier's beaked whale is probably the most widespread and common of 
the beaked whales, although it is not found in high-latitude polar 
waters (Heyning 1989; Baird 2018a). It is rarely observed at sea and is 
known mostly from strandings; it strands more commonly than any other 
beaked whale (Heyning 1989). Cuvier's beaked whale is found in deep 
water in the open-ocean and over and near the continental slope 
(Gannier and Epinat 2008; Baird 2018a).
    In the South Atlantic, there are stranding records for Brazil, 
Uruguay, Argentina, Falkland Islands, and South Africa (MacLeod et al. 
2006; Otley et al. 2012; Fisch and Port 2013; Bortolotto et al. 2016; 
Riccialdelli et al. 2017). Sighting records exist for nearshore Brazil, 
South Africa, and the central South Atlantic and Southern Ocean 
(Findlay et al. 1992; MacLeod et al. 2006; Prado et al. 2016), as well 
as for Gabon (Weir 2007) and Angola (Best 2007; Weir 2019). UNEP/CMS 
(2012) reported its presence in Namibia. Bester and Ryan (2007) 
suggested that Cuvier's beaked whales likely occur in the Tristan da 
Cunha archipelago. There are 11 OBIS records for the South Atlantic, 
including Brazil, Namibia, and South Africa; however, there are no 
records within or near the proposed project area (OBIS 2019). Cuvier's 
beaked whale could be encountered in the proposed project area at the 
time of the surveys.
Southern Bottlenose Whale
    The southern bottlenose whale is found throughout the Southern 
Hemisphere from 30[deg] S to the ice edge, with most sightings reported 
between ~57[deg] S and 70[deg] S (Jefferson et al. 2015; Moors-Murphy 
2018). It is apparently migratory, occurring in Antarctic waters during 
summer (Jefferson et al. 2015). Several sighting and stranding records 
exist for southeastern South America, Falkland Islands, South Georgia 
Island, southeastern Brazil, and Argentina, and numerous sightings have 
been reported for the Southern Ocean (MacLeod et al. 2006; de Oliveira 
Santos and e Figueiredo 2016; Riccialdelli et al. 2017). Southern 
bottlenose whales were sighted near 45[deg] S and south of there during 
surveys of the Southern Ocean (Van Waerebeek et al. 2010). There are 
eight records in the OBIS database for the South Atlantic, including 
one in the central South Atlantic at 37.1[deg] S, 12.3[deg] W, as well 
as Brazil, Namibia, and South Africa (OBIS 2019). Based on limited 
information on its distributional range (Best 2007; Jefferson et al. 
2015),

[[Page 51898]]

the southern bottlenose whale is more likely to occur in the southern 
survey areas than the Valdivia Bank survey area.
Shepherd's Beaked Whale
    Based on known records, it is likely that Shepherd's beaked whale 
has a circumpolar distribution in the cold temperate waters of the 
Southern Hemisphere, between 33-50[deg] S (Mead 2018). It is primarily 
known from strandings, most of which have been recorded in New Zealand 
and the Tristan da Cunha archipelago (Pitman et al. 2006; Mead 2018). 
The Tristan da Cunha archipelago has the second highest number of 
strandings (Mead 2018) and is thought to be a concentration area for 
Shepherd's beaked whales (Bester and Ryan 2007; Best et al. 2009). 
Pitman et al. (2006) and Best et al. (2009) reported six stranding 
records for Tristan da Cunha and possible sightings on the Tristan 
Plateau (2 sightings of 10 whales on 17 November 1985 near 37.3[deg] S, 
12.5[deg] W) and Gough Island (one sighting of 4-5 animals). Another 
stranding of two whales on Tristan da Cunha occurred on 13 January 2012 
(Best et al. 2014). Shepherd's beaked whales were sighted south of 
Africa during surveys of the Southern Ocean (Van Waerebeek et al. 
2010). There are three records for the South Atlantic in the OBIS 
database, all southwest of South Africa (OBIS 2019). Based on limited 
information on its distributional range (Best 2007; Jefferson et al. 
2015), Shepherd's beaked whale is more likely to occur in the southern 
survey areas than the Valdivia Bank survey area.
Blainville's Beaked Whale
    Blainville's beaked whale is found in tropical and warm temperate 
waters of all oceans (Pitman 2018). It has the widest distribution 
throughout the world of all Mesoplodon species (Pitman 2018). In the 
South Atlantic, strandings have been reported for southern Brazil and 
South Africa (Findlay et al. 1992; Secchi and Zarzur 1999; MacLeod et 
al. 2006; Prado et al. 2016). A sighting was made during a boat survey 
off St. Helena in November 2007 (Clingham et al. 2013). There are 20 
OBIS records for South Africa, but none for the offshore waters of the 
proposed project area (OBIS 2019). Based on limited information on its 
distributional range (Best 2007; Jefferson et al. 2015), Blainville's 
beaked whale could be encountered in the proposed project area.
Gray's Beaked Whale
    Gray's beaked whale is thought to have a circumpolar distribution 
in temperate waters of the Southern Hemisphere (Pitman 2018). It 
primarily occurs in deep waters beyond the edge of the continental 
shelf (Jefferson et al. 2015). Some sightings have been made in very 
shallow water, usually of sick animals coming in to strand (Gales et 
al. 2002; Dalebout et al. 2004). There are numerous sighting records 
from Antarctic and sub-Antarctic waters (MacLeod et al. 2006); in 
summer months, Gray's beaked whales appear near the Antarctic Peninsula 
and along the shores of the continent (sometimes in the sea ice).
    In the South Atlantic, several stranding records exist for Brazil, 
the southeast coast of South America, Falkland Islands, Namibia, and 
South Africa (Findlay et al. 1992; MacLeod et al. 2006; Otley 2012; 
Otley et al. 2012; Prado et al. 2016; Riccialdelli et al. 2017). 
Additionally, one sighting was reported off the southwestern tip of 
South Africa (MacLeod et al. 2006). A sighting was also made south of 
Arica near 45[deg] S during surveys of the Southern Ocean (Van 
Waerebeek et al. 2010). UNEP/CMS (2012) reported their presence in 
Namibia. Gray's beaked whales likely occur in the Tristan da Cunha 
archipelago (Bester and Ryan 2007). However, there are no OBIS records 
for the offshore waters of the proposed project area, but there are 
records for Argentina and South Africa (OBIS 2019). Based on limited 
information on its distributional range (Best 2007; Jefferson et al. 
2015). Gray's beaked whale is more likely to occur in the southern 
survey areas than the Valdivia Bank survey area.
Hector's Beaked Whale
    Hector's beaked whale is thought to have a circumpolar distribution 
in temperate waters of the Southern Hemisphere (Pitman 2018). Like 
other Mesoplodonts, Hector's beaked whale likely inhabits deep waters 
(200-2000 m) in the open ocean or continental slopes (Pitman 2018). To 
date, Hector's beaked whales have only been identified from strandings 
and have not been observed in the wild (Pitman 2018). Based on the 
number of stranding records for the species, it appears to be 
relatively rare. Nonetheless, in the South Atlantic, strandings have 
been reported for southern Brazil, Argentina, Falkland Islands, and 
South Africa (MacLeod et al. 2006; Otley et al. 2012; Prado et al. 
2016; Riccialdelli et al. 2017). However, there are no OBIS records for 
this species for the South Atlantic (OBIS 2019). Based on limited 
information on its distributional range (Best 2007; Jefferson et al. 
2015). Hector's beaked whale is more likely to occur in the southern 
survey areas than the Valdivia Bank survey area.
Gervais' Beaked Whale
    Although Gervais' beaked whale is generally considered to be a 
North Atlantic species, it likely occurs in deep waters of the 
temperate and tropical Atlantic Ocean in both the northern and southern 
hemispheres (Jefferson et al. 2015). Stranding records have been 
reported for Brazil and Ascension Island in the central South Atlantic 
(MacLeod et al. 2006). The southernmost stranding record was reported 
for S[atilde]o Paulo, Brazil, possibly expanding the known 
distributional range of this species southward (Santos et al. 2003). 
Although the distribution range of Gervais' beaked whale is not 
generally known to extend as far south as the proposed project area, 
this species might range as far south as Angola or northern Namibia in 
the South Atlantic (MacLeod et al. 2006; Best 2007; Jefferson et al. 
2015). In fact, one stranding has been reported for Namibia (Bachara 
and Norman 2014). There are no OBIS records for the South Atlantic 
(OBIS 2019). Gervais' beaked whale could be encountered in the proposed 
project area at the time of the surveys.
True's Beaked Whale
    True's beaked whale has a disjunct, antitropical distribution 
(Jefferson et al. 2015). In the Southern Hemisphere, it is known to 
occur in South Africa, South America, and Australia (Findlay et al. 
1992; Souza et al. 2005; MacLeod and Mitchell 2006; MacLeod et al. 
2006; Best et al. 2009). These areas may comprise three separate 
populations; the region of South Africa in the Indian Ocean is 
considered a key beaked whale area (MacLeod and Mitchell 2006). In the 
South Atlantic, True's beaked whale has stranded on Tristan da Cunha 
(Best et al. 2009). Based on stranding and sighting data, the proposed 
southern project area, including southern waters of Valdivia Bank 
survey area, is part of the possible range of True's beaked whale 
(MacLeod et al. 2006; Best 2007; Jefferson et al. 2015). There are 14 
OBIS records for the South Atlantic, all for the off South Africa (OBIS 
2019). True's beaked whale could be encountered in the proposed project 
area at the time of the surveys.

Strap-Toothed Beaked Whale

    The strap-toothed beaked whale is thought to have a circumpolar 
distribution in temperate and

[[Page 51899]]

subantarctic waters of the Southern Hemisphere, mostly between 32[deg] 
and 63[deg] S (MacLeod et al. 2006; Jefferson et al. 2015). It may 
undertake limited migration to warmer waters during the austral winter 
(Pitman 2018). Strap-toothed beaked whales are thought to migrate 
northward from Antarctic and subantarctic latitudes during April-
September (Sekiguchi et al. 1995).
    In the South Atlantic, stranding records have been reported for 
Brazil, Uruguay, Argentina, Falkland Islands, South Georgia, Namibia, 
and South Africa (Findlay et al. 1992; Pinedo et al. 2002; MacLeod et 
al. 2006; Otley et al. 2012; Prado et al. 2016; Riccialdelli et al. 
2017). In addition, sightings have been reported off the southern tip 
of Africa, near Bouvet Island, and in the Southern Ocean (Finlay et al. 
1992; MacLeod et al. 2006). One sighting was made south of Africa 
during surveys of the Southern Ocean (Van Waerebeek et al. 2010). 
Bester and Ryan (2007) suggested that strap-toothed beaked whales 
likely occur in the Tristan da Cunha archipelago (Bester and Ryan 
2007). There are 38 OBIS records for the South Atlantic, including for 
Argentina, Namibia, and South Africa; however, there are no records in 
the offshore waters of the proposed project area (OBIS 2019). Based on 
limited information on its distributional range (Best 2007; Jefferson 
et al. 2015), strap-toothed beaked whales are more likely to occur in 
the southern survey areas than the Valdivia Bank survey area.
Andrew's Beaked Whale
    Andrew's beaked whale has a circumpolar distribution in temperate 
waters of the Southern Hemisphere (Baker 2001; Pitman 2018). It is 
known only from stranding records between 32[deg] S and 55[deg] S, with 
more than half of the strandings occurring in New Zealand (Jefferson et 
al. 2015). In the South Atlantic, Andrew's beaked whales have also 
stranded in the Tristan da Cunha archipelago, Falkland Islands, 
Argentina, and Uruguay (Baker 2001; Laporta et al. 2005; MacLeod et al. 
2006; Best et al. 2009; Otley et al. 2012; Riccialdelli et al. 2017). 
There are no OBIS records for the South Atlantic (OBIS 2019). Based on 
limited information on its distributional range (Best 2007; Jefferson 
et al. 2015), Andrew's beaked whale is more likely to occur in the 
southern survey areas than the Valdivia Bank survey area.
Spade-Toothed Beaked Whale
    The spade-toothed beaked whale is the name proposed for the species 
formerly known as Bahamonde's beaked whale (M. bahamondi); genetic 
evidence has shown that it belongs to the species first identified by 
Gray in 1874 (Van Helden et al. 2002). The spade-toothed beaked whale 
is considered relatively rare and is known from only four records, 
three from New Zealand and one from Chile (Thompson et al. 2012). 
Although no records currently exist for the South Atlantic, the known 
records at similar latitudes suggest that the spade-toothed beaked 
whale could occur in the proposed project area.
Risso's Dolphin
    Risso's dolphin is distributed worldwide in mid-temperate and 
tropical oceans (Kruse et al. 1999), although it shows a preference for 
mid-temperate waters of the shelf and slope between 30[deg] and 45[deg] 
S (Jefferson et al. 2014). Although it occurs from coastal to deep 
water (~200-1000 m depth), it shows a strong preference for mid-
temperate waters of upper continental slopes and steep shelf-edge areas 
(Hartman 2018). In the southeastern Atlantic Ocean, there are records 
spanning from Gabon to South Africa (Jefferson et al. 2014). It appears 
to be relatively common off Angola; 75 sightings were made during 
seismic surveys off the coast of northern Angola between 2004 and 2009, 
including in deep slope waters (Weir 2011). Four sightings were also 
made off Gabon (Weir 2011). It was also sighted during surveys off 
southern Africa, and there are stranding records for Namibia (Findlay 
et al. 1992). There are 54 records for the South Atlantic in the OBIS 
database, including for Argentina, Namibia, and South Africa; however, 
there are no records in the proposed project area. Risso's dolphin 
could be encountered in the proposed survey areas at the time of the 
surveys.
Rough-Toothed Dolphin
    The rough-toothed dolphin is distributed worldwide in tropical and 
subtropical waters (Jefferson et al. 2015). It is generally seen in 
deep, oceanic water, although it is known to occur in coastal waters of 
Brazil (Jefferson et al. 2015; Cardoso et al. 2019). In the Southeast 
Atlantic, rough-toothed dolphins have been sighted off Namibia (Findlay 
et al. 1992), Gabon (de Boer 2010), and Angola (Weir 2007, 2010). 
Eighteen sightings were made during seismic surveys off the coast of 
northern Angola between 2004 and 2009, including in deep slope waters; 
one sighting was also made off Gabon (Weir 2011). Rough-toothed 
dolphins have also been sighted at St. Helena (MacLeod and Bennett 
2007; Clingham et al. 2013), near the Central survey area at 32.5[deg] 
S, 2.0[deg] W (Peters 1876 in Best et al. 2009), and near 37[deg] S, 
15[deg] E (Scheidat et al. 2011). One rough-toothed dolphin sighting 
was made during an August-September 2010 survey off Brazil from 
Vit[oacute]ria at ~20[deg] S, 40[deg] W to Trindade and Martim Vaz 
islands; the group of 30 individuals was seen in association with two 
minke whales at ~19.1[deg] S, 35.1[deg] W on 21 August (Wedekin et al. 
2014). For the South Atlantic, there are 42 records of rough-toothed 
dolphin in the OBIS database, including off Brazil, central West 
Africa, and South Africa (OBIS 2019). Rough-toothed dolphins could be 
encountered in the proposed project area during the surveys.
Common Bottlenose Dolphin
    The bottlenose dolphin occurs in tropical, subtropical, and 
temperate waters throughout the world (Wells and Scott 2018). Although 
it is more commonly found in coastal and shelf waters, it can also 
occur in deep offshore waters (Jefferson et al. 2015). Jefferson et al. 
(2015) reported central pelagic waters of the South Atlantic Ocean 
(within the proposed project area) as secondary range for the 
bottlenose dolphin. In the southeastern South Atlantic, common 
bottlenose dolphins occur off Gabon (de Boer 2010), Angola (Weir 2007, 
2010), Namibia (Findlay et al. 1992; Peddemors 1999), and South Africa 
(Findlay et al. 1992). Off Namibia, there is likely an inshore and an 
offshore ecotype (Peddemors 1999). Numerous sightings were made during 
seismic surveys off the coast of northern Angola between 2004 and 2009, 
including in deep slope waters; sightings were also made off Gabon 
(Weir 2011).
    Three sightings of common bottlenose dolphins were made at Trindade 
Island during December 2009-February 2010 surveys; two sightings of 15 
individuals were made during December and a single bottlenose dolphin 
was sighted on 23 February (Carvalho and Rossi-Santos 2011). 
Additionally, two sightings of common bottlenose dolphins were made 
during an August-September 2010 survey from Vit[oacute]ria at ~20[deg] 
S, 40[deg] W to Trindade and Martim Vaz islands; both groups were seen 
on 30 August at Trindade Island, near 20.5[deg] S, 29.3[deg] W (Wedekin 
et al. 2014). Common bottlenose dolphins have also been sighted near 
St. Helena (MacLeod and Bennett 2007; Clingham et al. 2013). There are 
132 OBIS records for the western and eastern South Atlantic; however, 
there are no records in the offshore waters of the proposed project 
area (OBIS 2019). Common bottlenose dolphins could be encountered in 
the

[[Page 51900]]

proposed project area during the surveys (Jefferson et al. 2015).
Pantropical Spotted Dolphin
    The pantropical spotted dolphin is distributed worldwide in 
tropical and some subtropical waters, between ~40[deg] N and 40[deg] S 
(Jefferson et al. 2015). It is one of the most abundant cetaceans and 
is found in coastal, shelf, slope, and deep waters (Perrin 2018a). In 
the South Atlantic, pantropical spotted dolphins have been sighted off 
Brazil (Moreno et al. 2005), Gabon (de Boer 2010), Angola (Weir 2007, 
2010), and St. Helena (MacLeod and Bennett 2007; Clingham et al. 2013). 
Four sightings were made during seismic surveys off the coast off 
northern Angola between 2004 and 2009, including in deep slope waters; 
and additional four sightings were made off Gabon (Weir 2011). Findlay 
et al (1992) reported sightings off the east coast of South Africa. In 
the OBIS database, there is one record for Brazil and one record for 
South Africa (OBIS 2019). Based on its distributional range (Best 2007; 
Jefferson et al. 2015), pantropical spotted dolphins could be 
encountered during the proposed surveys.
Atlantic Spotted Dolphin
    The Atlantic spotted dolphin is distributed in tropical and warm 
temperate waters of the North Atlantic from Brazil to New England and 
to the coast of Africa (Jefferson et al. 2015). Although its 
distributional range appears to be just to the north of the proposed 
project area (Best 2007; Jefferson et al. 2015), Culik (2004) reported 
its presence in Namibia. These dolphins were one of the most frequently 
sighted cetaceans during seismic surveys off the coast of northern 
Angola between 2004 and 2009, including in deep slope waters; about 100 
sightings were made off Angola and several sightings were also made off 
Gabon (Weir 2011). For the South Atlantic, there is one record for 
Brazil in the OBIS database (OBIS 2019). Atlantic spotted dolphins 
could be encountered in the proposed project area during the surveys.
Spinner Dolphin
    The spinner dolphin is pantropical in distribution, with a range 
nearly identical to that of the pantropical spotted dolphin, including 
oceanic tropical and sub-tropical waters between 40[deg] N and 40[deg] 
S (Jefferson et al. 2015). Spinner dolphins are extremely gregarious, 
and usually form large schools in the open sea and small ones in 
coastal waters (Perrin and Gilpatrick 1994).
    Its distributional range appears to be to the north of the proposed 
survey area in the South Atlantic (Best 2007; Jefferson et al. 2015). 
One group of three individuals was seen near the 1000-m isobath during 
seismic surveys off the coast of northern Angola between 2004 and 2009 
(Weir 2011). There are two OBIS records for the South Atlantic: One 
sighting north of the Falkland Islands at 47.4[deg] S, 54.2[deg] W and 
another off Brazil (OBIS 2019). Based on distributional information 
(Best 2007; Jefferson et al. 2015), spinner dolphins could be 
encountered during the proposed surveys, most likely in the northern 
parts of the Valdivia Bank survey area.
Clymene Dolphin
    The clymene dolphin only occurs in tropical and subtropical waters 
of the Atlantic Ocean (Jefferson et al. 2015). It inhabits areas where 
water depths are 700-4,500 m or deeper (Fertl et al. 2003). In the 
western Atlantic, it occurs from New Jersey to Florida, the Caribbean 
Sea, the Gulf of Mexico and south to Venezuela and Brazil (W[uuml]rsig 
et al. 2000; Fertl et al. 2003).
    In the eastern Atlantic, they have been sighted as far south as 
Angola (Weir 2006; Weir et al. 2014). One sighting was made during 
seismic surveys off the coast of northern Angola between 2004 and 2009 
(Weir 2011). Currently available information indicates that only the 
northern-most proposed project area might overlap with its 
distributional range (e.g., Fertl et al. 2003; Best 2007; Jefferson et 
al. 2015), although Weir et al. (2014) noted that it is unlikely that 
this species occurs farther south than Angola due to the cold Benguela 
Current there. There are no OBIS records for the South Atlantic (OBIS 
2019). Based on distributional information (Best 2007; Jefferson et al. 
2015), Clymene dolphins could be encountered in the northern parts of 
the Valdivia Bank survey area.
Striped Dolphin
    The striped dolphin has a cosmopolitan distribution in tropical to 
warm temperate waters from ~50[deg] N to 40[deg] S (Perrin et al. 1994; 
Jefferson et al. 2015). It occurs primarily in pelagic waters, but has 
been observed approaching shore where there is deep water close to the 
coast (Jefferson et al. 2015). In the South Atlantic, it is known to 
occur along the coast of South America, from Brazil to Argentina, and 
along the west coast of Africa (Jefferson et al. 2015).
    Sightings have been made on the west coast of South Africa (Findlay 
et al. 1992). Sixty-six sightings were made during seismic surveys off 
the coast of northern Angola between 2004 and 2009, including in deep 
slope waters (Weir 2011). There are approximately 60 OBIS records for 
the South Atlantic, including nearshore waters of Brazil, Uruguay, 
Argentina, Angola, and South Africa, and 19 records for offshore waters 
near 8.4[deg] S, 24.4[deg] W (OBIS 2019). Based on distributional 
information (Best 2007; Jefferson et al. 2015), striped dolphins could 
be encountered during the proposed surveys.
Short-Beaked Common Dolphin
    The short-beaked common dolphin is found in tropical and warm 
temperate oceans around the world (Jefferson et al. 2015), ranging from 
~60[deg] N to ~50[deg] S (Jefferson et al. 2015). It is the most 
abundant dolphin species in offshore areas of warm-temperate regions in 
the Atlantic and Pacific (Perrin 2018c).
    In the South Atlantic, the short-beaked common dolphin occurs along 
the coasts of South America and Africa (Perrin 2018c). Although 
according to Jefferson et al. (2015) and Perrin (2018c), its occurrence 
in central oceanic waters of the South Atlantic is uncertain, Best 
(2007) reported a few records between 30-41[deg] S, 15[deg] W-10[deg] 
E. Sightings have also been reported along the coast of Namibia (Best 
2007; NDP unpublished data in Pisces Environmental Services 2017). 
Sightings have been reported off the west coast of southern Africa 
during summer and winter, and there are stranding records for Namibia 
(Findlay et al. 1992). About 100 sightings of Delphinus sp. were made 
during seismic surveys off the coast of northern Angola between 2004 
and 2009, including in deep slope waters; sightings were also made off 
Gabon (Weir 2011). For the South Atlantic, there are 7 OBIS records for 
waters off Argentina and nearly 80 records for southwestern Africa, 
including Namibia and South Africa (OBIS 2019). Short-beaked common 
dolphins could be encountered in the proposed project area at the time 
of the surveys.
Fraser's Dolphin
    Fraser's dolphin is a tropical oceanic species generally 
distributed between 30[deg] N and 30[deg] S that generally inhabits 
deeper, offshore water (Dolar 2018). Strandings in more temperate 
waters, such as in Uruguay, are likely extralimital (Dolar 2018). Three 
sightings were made during seismic surveys off the coast of northern 
Angola between 2004 and 2009, all in water deeper than 1000 m; one 
sighting was made in the Gulf of Guinea (Weir et al. 2008; Weir 2011). 
Fraser's dolphin has

[[Page 51901]]

also been sighted off the east coast of South Africa (Findlay et al. 
1992). There are 24 OBIS records for the South Atlantic, all along the 
coast of South America (OBIS 2019). Based on its distribution 
(Jefferson et al. 2015), Fraser's dolphin could be encountered during 
the proposed surveys, but is more likely to be seen in the northern 
portions of the Valdivia Bank survey area than elsewhere.
Dusky Dolphin
    The dusky dolphin occurs throughout the Southern Hemisphere, 
primarily over continental shelves and slopes and sometimes over deep 
water close to continents or islands (Van Waerebeek and W[uuml]rsig 
2018). In the southeastern Atlantic, it occurs along the coast of 
Angola, Namibia, and South Africa, as well as Tristan da Cunha (Findlay 
et al. 1992; Culik 2004; Weir 2019). It appears to occur off the west 
coast of southern Africa year-round (Findlay et al. 1982). According to 
Jefferson et al. (2015), it is unlikely to occur in the deep waters of 
the proposed project area.
    It has been observed in groups of 10 to 20 individuals preying on 
Cape horse mackerel off Namibia (Bernasconi et al. 2011), and it has 
been seen in mixed groups with southern right whale dolphins there 
(Culik 2004). It was sighted during spring surveys off west coast of 
South Africa during 2014 (Seakamala et al. 2015). It has also been 
reported near Gough Island; animals there likely make up a disjunct 
oceanic population rather than suggesting movement of individuals 
between South America and southern Africa (Cassens et al. 2005). There 
are ~150 OBIS records for the South Atlantic, but none occur within the 
proposed project area. The dusky dolphin is unlikely to be encountered 
in the proposed survey areas in the southeastern Atlantic, and is not 
expected to occur in the Libra Massif survey area.
Hourglass Dolphin
    The hourglass dolphin occurs in all parts of the Southern Ocean, 
with most sightings between ~45[deg] S and 60[deg] S (Cipriano 2018a). 
However, some sightings have been made as far north as 33[deg] S 
(Jefferson et al. 2015). Although it is pelagic, it is also sighted 
near banks and islands (Cipriano 2018a). There are approximately 45 
records in the OBIS database for the Southwest Atlantic, but none 
within the Libra Massif survey area (OBIS 2019). Based on its known 
distributional range (Best 2007; Jefferson et al. 2015), it could occur 
in the southern-most portions of the proposed project area.
Southern Right Whale Dolphin
    The southern right whale dolphin is distributed between the 
Subtropical and Antarctic convergences in the Southern Hemisphere, 
generally between ~30[deg] S and 65[deg] S (Jefferson et al. 2015; 
Lipsky and Brownell 2018). It is sighted most often in cool, offshore 
waters, although it is sometimes seen near shore where coastal waters 
are deep (Jefferson et al. 2015). It is also known to occur off Namibia 
(Findlay et al. 1992; Culik 2004), where it has been seen out to the 
1000-m isobath (Rose and Payne 1991); it is thought to occur in the 
region year-round (Rose and Payne 1991). However, Best (2007) did not 
report any sightings in the Valdivia Bank survey area. There are no 
records for the South Atlantic in the OBIS database (OBIS 2019). Bester 
and Ryan (2007) suggested that southern right whale dolphins might be 
visitors to the southern waters of the Tristan da Cunha archipelago. 
One was captured near Tristan da Cunha on 10 December 1847 at 37.1[deg] 
S, 11.6[deg] W (Cruickshank and Brown 1981 in Best et al. 2009). There 
are no records for the South Atlantic in the OBIS database (OBIS 2019). 
According its distribution range (Best 2007; Jefferson et al. 2015), 
southern right whale dolphins could occur in the proposed project area, 
although they are more likely to be encountered in the more southerly 
survey areas.
Killer Whale
    Killer whales have been observed in all oceans and seas of the 
world (Leatherwood and Dahlheim 1978). Based on sightings by whaling 
vessels between 1960 and 1979, killer whales are distributed throughout 
the South Atlantic (Budylenko 1981; Mikhalev et al. 1981). 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). In the southeastern Atlantic, killer whales are known to occur 
off Gabon (de Boer 2010; Weir 2010), Angola (Weir 2007, 2010, 2011), as 
well as Namibia and South Africa (Findlay et al. 1992; Best 2007; Elwen 
and Leeney 2011). Sightings of killer whale pods of 1 to >100 
individuals have been made near the proposed survey areas during 
November and December (Budylenko 1981; Mikhalev et al. 1981). Eighteen 
sightings were made during seismic surveys off northern Angola between 
2004 and 2009, including in deep slope waters; one sighting was made 
off Gabon (Weir 2011). The number of sightings are thought to decrease 
north of Cape Town, South Africa, but sightings have been made year 
round, including in offshore waters (up to 600 km from shore), but not 
within the proposed project area (Rice and Saayman 1987). Killer whales 
are known to prey on longline catches in the waters off South Africa 
(Williams et al. 2009). Sightings of killer whale pods of 1 to >100 
individuals have been made near the Libra Massif survey area during 
November (Budylenko 1981; Mikhalev et al. 1981). A sighting was made 
south of the proposed survey areas at approximately 45[deg] S, 8[deg] W 
(Scheidat et al. 2011). There are about 55 records of killer whales for 
the South Atlantic in the OBIS database, including records for offshore 
and nearshore waters of South America, as well as South Africa (OBIS 
2019); however, there are no records near the proposed survey areas.
Short-Finned and Long-Finned Pilot Whale
    The short-finned pilot whale is found in tropical and warm 
temperate waters, and the long-finned pilot whale is distributed 
antitropically in cold temperate waters (Olson 2018). The ranges of the 
two species show little overlap (Olson 2018). Short-finned pilot whale 
distribution does not generally range south of 40[deg] S (Jefferson et 
al. 2008). Short-finned pilot whales were the most frequently sighted 
cetacean during seismic surveys off the coast of Angola between 2004 
and 2009; more than 100 sightings were off Angola including in deep 
slope waters and several sightings were also reported off Gabon (Weir 
2011). There are records of long-finned pilot whales for South Africa 
and Namibia (Findlay et al. 1992; Best 2007). Long-finned pilot whales 
are considered uncommon in Tristan waters (Bester and Ryan 2007); pilot 
whales have stranded on the islands of the Tristan da Cunha 
archipelago, although it is uncertain what species they were (Best et 
al. 2009). There is a single record of short-finned pilot whales in the 
Southwest Atlantic Ocean, but there are >100 long-finned pilot whale 
records for the waters off South America, Namibia, South Africa, and 
the central Atlantic Ocean (OBIS 2019). Based on their distributional 
ranges (Best 2007; Jefferson et al. 2015), short-finned pilot whales 
are more likely to occur in the Valdivia Bank survey area, whereas 
long-finned pilot whales are more likely to occur in the more southern 
survey areas.
False Killer Whale
    The false killer whale is found worldwide in tropical and temperate

[[Page 51902]]

waters, generally between 50[deg] N and 50[deg] S (Odell and McClune 
1999). It is widely distributed, but not abundant anywhere (Carwardine 
1995).
    The false killer whales occurs throughout the South Atlantic. In 
the southeast Atlantic Ocean, 13 sightings were made during seismic 
surveys off the coast of northern Angola between 2004 and 2009, all in 
water deeper than 1000 m (Weir 2011). Stranding records and sightings 
also exist for Namibia and South Africa (Findlay et al. 1992). They 
have also been recorded around St. Helena (Clingham et al. 2013). 
Predation events by killer whales or false killer whales in the 
Uruguayan longline fishery were recorded north of the Libra Massif 
survey area (Passadore et al. 2014, 2015). Although there are no OBIS 
records of false killer whales for the offshore waters of the proposed 
project area, there are 91 records for the South Atlantic, including 
offshore waters off South America and nearshore waters of Namibia and 
South Africa; however, there are no records near the proposed survey 
areas (OBIS 2019). Based on its distributional range (Best 2007; 
Jefferson et al. 2015), the false killer whale could be encountered in 
the proposed project areas.
Pygmy Killer Whale
    The pygmy killer whale has a worldwide distribution in tropical and 
subtropical waters, generally not ranging south of 35[deg] S (Jefferson 
et al. 2015). It is known to inhabit the warm waters of the Indian, 
Pacific, and Atlantic oceans (Jefferson et al. 2015). It can be found 
in nearshore areas where the water is deep and in offshore waters 
(Jefferson et al. 2015). In the southeast Atlantic, there are stranding 
records along the coast of southern Africa, including Namibia (Findlay 
et al. 1992). There is one stranding record for Brazil (Santos et al. 
2010). There are seven OBIS records for the Southeast Atlantic Ocean, 
but no records for the offshore waters of the proposed survey areas 
(OBIS 2019). Based on its distributional range (Best 2007; Jefferson et 
al. 2015), the pygmy killer whale could be encountered in the proposed 
survey areas.
Melon-Headed Whale
    The melon-headed whale is an oceanic species found worldwide in 
tropical and subtropical waters from ~40[deg] N to 35[deg] S (Jefferson 
et al. 2015). It occurs most often in deep offshore waters and 
occasionally in nearshore areas where the water is deep (Jefferson et 
al. 2015). Off the west coast of Africa, melon-headed whales have been 
recorded off Gabon (de Boer 2010; Weir 2011) and Angola (Weir 2007a, 
2010, 2011). Four sightings were made during seismic surveys off the 
coast of northern Angola between 2004 and 2009, all in water deeper 
than 1000 m (Weir 2011). Extralimital record exists for South Africa 
(Peddemors 1999; Jefferson et al. 2015). There is one OBIS record for 
South Africa (OBIS 2019). Based on its distributional range (Best 2007; 
Jefferson et al. 2015), melon-headed whale could be encountered in the 
northern portion of the Valdivia Bank survey area.

Pinnipeds

Subantarctic Fur Seal
    Subantarctic fur seals occur between 10[deg] W and 170[deg] E north 
of the Antarctic Polar Front in the Southern Ocean (Hofmeyr and Bester 
2018). Breeding occurs on several islands, with Gough Island in the 
central South Atlantic accounting for about two thirds of pup 
production (Hofmeyr and Bester 2018), but adults take long foraging 
journeys away from these colonies. Vagrant subantarctic fur seals have 
been reported in South Africa (Shaughnessy and Ross 1980). The at-sea 
distribution of subantarctic fur seals is poorly understood, although 
they are often seen in the waters between Tristan da Cunha and South 
Africa (Bester and Ryan 2007). There are 35 OBIS records for the South 
Atlantic, including in nearshore and offshore waters of South Africa, 
and 21 records at 40.3[deg] S, 9.9[deg] W; however, there are no 
records for the proposed project area (OBIS 2019).
Cape Fur Seal
    The Cape fur seal is endemic to the west coast of southern Africa, 
occurring from Algoa Bay, South Africa to Ilha dos Tigres, Angola 
(Kirkman et al. 2013). The population severely declined between the 
17th and 19th century, due to sealing and guano collection on many of 
the breeding islands (Kirkman et al. 2007). However, the population 
recovered when sealing limits were imposed in the early 20th century, 
and the population is now estimated to number ~2 million individuals 
(Kirkman et al. 2007). There have also been two mass die-offs of Cape 
fur seals in Namibia that were related to poor environmental conditions 
and reduced prey (Roux et al. 2002 in Kirkman et al. 2007).
    The Cape fur seal currently breeds at 40 colonies along the coast 
of South Africa, Namibia, and Angola, including on the mainland and 
nearshore islands (Kirkman et al. 2013). There have been several new 
breeding colonies established in recent years, as the population has 
shifted northward (Kirkman et al. 2013). More than half of the seal 
population occurs in Namibia (Wickens et al. 1991). High densities have 
been observed between 30 and 60 n.mi. from shore, with densities 
dropping farther offshore (Thomas and Sch[uuml]lein 1988). Cape fur 
seals typically forage over the shelf up to ~220 km offshore 
(Shaughnessy 1979), but they are known to travel distances up to 1970 
km along the coast of South America (Oosthuizen 1991). Breeding occurs 
during November and December (Warneke and Shaughnessy 1985 in Kirkman 
and Arnould 2018). There are over 2000 OBIS records along the coasts of 
Namibia and South Africa, but no records for the offshore survey areas. 
As Cape fur seals typically remain over the shelf to forage and are 
breeding during the time of the survey, they are unlikely to be 
encountered in the offshore project area.
Crabeater Seal
    Crabeater seals have a circumpolar distribution off Antarctica and 
generally spend the entire year in the advancing and retreating pack 
ice; occasionally they are seen in the far southern areas of South 
America though this is uncommon (Bengtson and Stewart 2018). Vagrants 
are occasionally found as far north as Brazil (Oliveira et al. 2006). 
Telemetry studies show that crabeater seals are generally confined to 
the pack ice, but spend ~14 percent of their time in open water outside 
of the breeding season (reviewed in Southwell et al. 2012). During the 
breeding season crabeater seals were most likely to be present within 
5[deg] or less (~550 km) of the shelf break in the south, though non-
breeding animals ranged further north. Pupping season peaks in mid- to 
late-October and adults are observed with their pubs as late as mid-
December (Bengtson and Stewart 2018). There are two records of 
crabeater seals for South Africa in the OBIS database (OBIS 2019).
Leopard Seal
    The leopard seal has a circumpolar distribution around the 
Antarctic continent where it is solitary and widely dispersed (Rogers 
2018). Leopard seals are top predators, consuming everything from krill 
and fish to penguins and other seals (e.g., Hall-Aspland and Rogers 
2004; Hirukie et al. 1999). Pups are born during October to mid-
November and weaned approximately one month later (Rogers 2018). Mating 
occurs in the water during December and January. There is one record 
for South Africa in the OBIS database (OBIS 2019).

[[Page 51903]]

Southern Elephant Seal
    The southern elephant seal has a near circumpolar distribution in 
the Southern Hemisphere (Jefferson et al. 2015), with breeding sites 
located on islands throughout the subantarctic (Hindell 2018). In the 
South Atlantic, southern elephant seals breed at Patagonia, South 
Georgia, and other islands of the Scotia Arc, Falkland Islands, Bouvet 
Island, and Tristan da Cunha archipelago (Bester and Ryan 2007). 
Pen[iacute]nsula Vald[eacute]s, Argentina is the sole continental South 
American large breeding colony, where tens of thousands of southern 
elephant seals congregate (Lewis et al. 2006). Breeding colonies are 
otherwise island-based, with the occasional exception of the Antarctic 
mainland (Hindell 2018).
    When not breeding (September-October) or molting (November-April), 
southern elephant seals range throughout the Southern Ocean from areas 
north of the Antarctic Polar Front to the pack ice of the Antarctic, 
spending >80 percent of their time at sea each year, up to 90 percent 
of which is spent submerged while hunting, travelling and resting in 
water depths >=200 m (Hindell 2018). Males generally feed in 
continental shelf waters, while females preferentially feed in ice-free 
Antarctic Polar Front waters or the marginal ice zone in accordance 
with winter ice expansion (Hindell 2018). Southern elephant seals 
tagged at South Georgia showed long-range movements from ~April through 
October into the open Southern Ocean and to the shelf of the Antarctic 
Peninsula (McConnell and Fedak 1996). One adult male that was sighted 
on Gough Island had previously been tagged at Marion Island in the 
Indian Ocean (Reisinger and Bester 2010). Vagrant southern elephant 
seals, mainly consisting of juvenile and subadult males, have been 
documented in Uruguay, Brazil, Argentina, Falkland Islands, and South 
Georgia (Lewis et al. 2006a; Oliveira et al. 2011; Mayorga et al. 
2015). For the South Atlantic, there are more than 2000 OBIS records 
for the nearshore and offshore waters of South America and along the 
coasts of Namibia and South Africa (OBIS 2019). Most of the records 
(1793) are for waters of the Patagonian Large Marine Ecosystem 
(Campagna et al. 2006), but none occur within the proposed project 
area.

Marine Mammal Hearing

    Hearing is the most important sensory modality for marine mammals 
underwater, and exposure to anthropogenic sound can have deleterious 
effects. To appropriately assess the potential effects of exposure to 
sound, it is necessary to understand the frequency ranges marine 
mammals are able to hear. Current data indicate that not all marine 
mammal species have equal hearing capabilities (e.g., Richardson et 
al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect 
this, Southall et al. (2007) recommended that marine mammals be divided 
into functional hearing groups based on directly measured or estimated 
hearing ranges on the basis of available behavioral response data, 
audiograms derived using auditory evoked potential techniques, 
anatomical modeling, and other data. Note that no direct measurements 
of hearing ability have been successfully completed for mysticetes 
(i.e., low-frequency cetaceans). Subsequently, NMFS (2018) described 
generalized hearing ranges for these marine mammal hearing groups. 
Generalized hearing ranges were chosen based on the approximately 65 
decibel (dB) threshold from the normalized composite audiograms, with 
the exception for lower limits for low-frequency cetaceans where the 
lower bound was deemed to be biologically implausible and the lower 
bound from Southall et al. (2007) retained. Marine mammal hearing 
groups and their associated hearing ranges are provided in Table 3.

                                      Table 3--Marine Mammal Hearing Groups
                                                  [NMFS, 2018]
----------------------------------------------------------------------------------------------------------------
                     Hearing group                                     Generalized hearing range *
----------------------------------------------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen whales)...........  7 Hz to 35 kHz.
Mid-frequency (MF) cetaceans (dolphins, toothed whales,  150 Hz to 160 kHz.
 beaked whales, bottlenose whales).
High-frequency (HF) cetaceans (true porpoises, Kogia,    275 Hz to 160 kHz.
 river dolphins, cephalorhynchid, Lagenorhynchus
 cruciger & L. australis).
Phocid pinnipeds (PW) (underwater) (true seals)........  50 Hz to 86 kHz.
Otariid pinnipeds (OW) (underwater) (sea lions and fur   60 Hz to 39 kHz.
 seals).
----------------------------------------------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a composite (i.e., all species within the
  group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen
  based on ~65 dB threshold from normalized composite audiogram, with the exception for lower limits for LF
  cetaceans (Southall et al. 2007) and PW pinniped (approximation).

    The pinniped functional hearing group was modified from Southall et 
al. (2007) on the basis of data indicating that phocid species have 
consistently demonstrated an extended frequency range of hearing 
compared to otariids, especially in the higher frequency range 
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth and Holt, 
2013).
    For more detail concerning these groups and associated frequency 
ranges, please see NMFS (2018) for a review of available information. 
Forty-eight marine mammal species (43 cetacean and 5 pinniped (2 
otariid and 3 phocid) species) have the reasonable potential to co-
occur with the proposed survey activities. Please refer to Table 2. Of 
the cetacean species that may be present, 9 are classified as low-
frequency cetaceans (i.e., all mysticete species), 31 are classified as 
mid-frequency cetaceans (i.e., most delphinid and ziphiid species and 
the sperm whale), and 3 are classified as high-frequency cetaceans 
(i.e., Kogia spp., hourglass dolphin).

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.

[[Page 51904]]

Description of Active Acoustic Sound Sources

    This section contains a brief technical background on sound, the 
characteristics of certain sound types, and on metrics used in this 
proposal inasmuch as the information is relevant to the specified 
activity and to a discussion of the potential effects of the specified 
activity on marine mammals found later in this document.
    Sound travels in waves, the basic components of which are 
frequency, wavelength, velocity, and amplitude. Frequency is the number 
of pressure waves that pass by a reference point per unit of time and 
is measured in hertz (Hz) or cycles per second. Wavelength is the 
distance between two peaks or corresponding points of a sound wave 
(length of one cycle). Higher frequency sounds have shorter wavelengths 
than lower frequency sounds, and typically attenuate (decrease) more 
rapidly, except in certain cases in shallower water. Amplitude is the 
height of the sound pressure wave or the ``loudness'' of a sound and is 
typically described using the relative unit of the dB. A sound pressure 
level (SPL) in dB is described as the ratio between a measured pressure 
and a reference pressure (for underwater sound, this is 1 microPascal 
([mu]Pa)) and is a logarithmic unit that accounts for large variations 
in amplitude; therefore, a relatively small change in dB corresponds to 
large changes in sound pressure. The source level (SL) represents the 
SPL referenced at a distance of 1 m from the source (referenced to 1 
[mu]Pa) while the received level is the SPL at the listener's position 
(referenced to 1 [mu]Pa).
    Root mean square (rms) is the quadratic mean sound pressure over 
the duration of an impulse. Root mean square is calculated by squaring 
all of the sound amplitudes, averaging the squares, and then taking the 
square root of the average (Urick, 1983). Root mean square accounts for 
both positive and negative values; squaring the pressures makes all 
values positive so that they may be accounted for in the summation of 
pressure levels (Hastings and Popper, 2005). This measurement is often 
used in the context of discussing behavioral effects, in part because 
behavioral effects, which often result from auditory cues, may be 
better expressed through averaged units than by peak pressures.
    Sound exposure level (SEL; represented as dB re 1 [mu]Pa\2\-s) 
represents the total energy contained within a pulse and considers both 
intensity and duration of exposure. Peak sound pressure (also referred 
to as zero-to-peak sound pressure or 0-p) is the maximum instantaneous 
sound pressure measurable in the water at a specified distance from the 
source and is represented in the same units as the rms sound pressure. 
Another common metric is peak-to-peak sound pressure (pk-pk), which is 
the algebraic difference between the peak positive and peak negative 
sound pressures. Peak-to-peak pressure is typically approximately 6 dB 
higher than peak pressure (Southall et al., 2007).
    When underwater objects vibrate or activity occurs, sound-pressure 
waves are created. These waves alternately compress and decompress the 
water as the sound wave travels. Underwater sound waves radiate in a 
manner similar to ripples on the surface of a pond and may be either 
directed in a beam or beams or may radiate in all directions 
(omnidirectional sources), as is the case for pulses produced by the 
airgun arrays considered here. The compressions and decompressions 
associated with sound waves are detected as changes in pressure by 
aquatic life and man-made sound receptors such as hydrophones.
    Even in the absence of sound from the specified activity, the 
underwater environment is typically loud due to ambient sound. Ambient 
sound is defined as environmental background sound levels lacking a 
single source or point (Richardson et al., 1995), and the sound level 
of a region is defined by the total acoustical energy being generated 
by known and unknown sources. These sources may include physical (e.g., 
wind and waves, earthquakes, ice, atmospheric sound), biological (e.g., 
sounds produced by marine mammals, fish, and invertebrates), and 
anthropogenic (e.g., vessels, dredging, construction) sound. A number 
of sources contribute to ambient sound, including the following 
(Richardson et al., 1995):
     Wind and waves: The complex interactions between wind and 
water surface, including processes such as breaking waves and wave-
induced bubble oscillations and cavitation, are a main source of 
naturally occurring ambient sound for frequencies between 200 Hz and 50 
kHz (Mitson, 1995). In general, ambient sound levels tend to increase 
with increasing wind speed and wave height. Surf sound becomes 
important near shore, with measurements collected at a distance of 8.5 
km from shore showing an increase of 10 dB in the 100 to 700 Hz band 
during heavy surf conditions;
     Precipitation: Sound from rain and hail impacting the 
water surface can become an important component of total sound at 
frequencies above 500 Hz, and possibly down to 100 Hz during quiet 
times;
     Biological: Marine mammals can contribute significantly to 
ambient sound levels, as can some fish and snapping shrimp. The 
frequency band for biological contributions is from approximately 12 Hz 
to over 100 kHz; and
     Anthropogenic: Sources of ambient sound related to human 
activity include transportation (surface vessels), dredging and 
construction, oil and gas drilling and production, seismic surveys, 
sonar, explosions, and ocean acoustic studies. Vessel noise typically 
dominates the total ambient sound for frequencies between 20 and 300 
Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz 
and, if higher frequency sound levels are created, they attenuate 
rapidly. Sound from identifiable anthropogenic sources other than the 
activity of interest (e.g., a passing vessel) is sometimes termed 
background sound, as opposed to ambient sound.
    The sum of the various natural and anthropogenic sound sources at 
any given location and time--which comprise ``ambient'' or 
``background'' sound--depends not only on the source levels (as 
determined by current weather conditions and levels of biological and 
human activity) but also on the ability of sound to propagate through 
the environment. In turn, sound propagation is dependent on the 
spatially and temporally varying properties of the water column and sea 
floor, and is frequency-dependent. As a result of the dependence on a 
large number of varying factors, ambient sound levels can be expected 
to vary widely over both coarse and fine spatial and temporal scales. 
Sound levels at a given frequency and location can vary by 10-20 dB 
from day to day (Richardson et al., 1995). The result is that, 
depending on the source type and its intensity, sound from a given 
activity may be a negligible addition to the local environment or could 
form a distinctive signal that may affect marine mammals. Details of 
source types are described in the following text.
    Sounds are often considered to fall into one of two general types: 
Pulsed and non-pulsed (defined in the following). The distinction 
between these two sound types is important because they have differing 
potential to cause physical effects, particularly with regard to 
hearing (e.g., Ward, 1997 in Southall et al., 2007). Please see 
Southall et al. (2007) for an in-depth discussion of these concepts.
    Pulsed sound sources (e.g., airguns, explosions, gunshots, sonic 
booms,

[[Page 51905]]

impact pile driving) produce signals that are brief (typically 
considered to be less than one second), broadband, atonal transients 
(ANSI, 1986, 2005; Harris, 1998; NIOSH, 1998; ISO, 2003) and occur 
either as isolated events or repeated in some succession. Pulsed sounds 
are all characterized by a relatively rapid rise from ambient pressure 
to a maximal pressure value followed by a rapid decay period that may 
include a period of diminishing, oscillating maximal and minimal 
pressures, and generally have an increased capacity to induce physical 
injury as compared with sounds that lack these features.
    Non-pulsed sounds can be tonal, narrowband, or broadband, brief or 
prolonged, and may be either continuous or non-continuous (ANSI, 1995; 
NIOSH, 1998). Some of these non-pulsed sounds can be transient signals 
of short duration but without the essential properties of pulses (e.g., 
rapid rise time). Examples of non-pulsed sounds include those produced 
by vessels, aircraft, machinery operations such as drilling or 
dredging, vibratory pile driving, and active sonar systems (such as 
those used by the U.S. Navy). The duration of such sounds, as received 
at a distance, can be greatly extended in a highly reverberant 
environment.
    Airgun arrays produce pulsed signals with energy in a frequency 
range from about 10-2,000 Hz, with most energy radiated at frequencies 
below 200 Hz. The amplitude of the acoustic wave emitted from the 
source is equal in all directions (i.e., omnidirectional), but airgun 
arrays do possess some directionality due to different phase delays 
between guns in different directions. Airgun arrays are typically tuned 
to maximize functionality for data acquisition purposes, meaning that 
sound transmitted in horizontal directions and at higher frequencies is 
minimized to the extent possible.
    As described above, a Kongsberg EM 300 MBES and a Knudsen Chirp 
3260 SBP would be operated continuously during the proposed surveys, 
but not during transit to and from the survey areas. Each ping emitted 
by the MBES consists of eight (in water >1,000 m deep) or four (<1,000 
m) successive fan-shaped transmissions, each ensonifying a sector that 
extends 1[deg] fore-aft. Given the movement and speed of the vessel, 
the intermittent and narrow downward-directed nature of the sounds 
emitted by the MBES would result in no more than one or two brief ping 
exposures of any individual marine mammal, if any exposure were to 
occur.
    Due to the lower source levels of the Knudsen Chirp 3260 SBP 
relative to the Thompson's airgun array (maximum SL of 222 dB re 1 
[mu]Pa [middot] m for the SBP, versus a minimum of 230.9 dB re 1 [mu]Pa 
[middot] m for the 2 airgun array (LGL, 2019)), sounds from the SBP are 
expected to be effectively subsumed by sounds from the airgun array. 
Thus, any marine mammal potentially 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, we conclude that the likelihood of marine mammal take 
resulting from exposure to sound from the MBES or SBP (beyond that 
which is already quantified as a result of exposure to the airguns) is 
discountable. Therefore, we do not consider noise from the MBES or SBP 
further in this analysis.

Acoustic Effects

    Here, we discuss the effects of active acoustic sources on marine 
mammals.
    Potential Effects of Underwater Sound--Please refer to the 
information given previously (Description of Active Acoustic Sound 
Sources section) regarding sound, characteristics of sound types, and 
metrics used in this document. Anthropogenic sounds cover a broad range 
of frequencies and sound levels and can have a range of highly variable 
impacts on marine life, from none or minor to potentially severe 
responses, depending on received levels, duration of exposure, 
behavioral context, and various other factors. The potential effects of 
underwater sound from active acoustic sources can potentially result in 
one or more of the following: Temporary or permanent hearing 
impairment, non-auditory physical or physiological effects, behavioral 
disturbance, stress, and masking (Richardson et al., 1995; Gordon et 
al., 2004; Nowacek et al., 2007; Southall et al., 2007; G[ouml]tz et 
al., 2009). The degree of effect is intrinsically related to the signal 
characteristics, received level, distance from the source, and duration 
of the sound exposure. In general, sudden, high level sounds can cause 
hearing loss, as can longer exposures to lower level sounds. Temporary 
or permanent loss of hearing will occur almost exclusively for noise 
within an animal's hearing range. We first describe specific 
manifestations of acoustic effects before providing discussion specific 
to the use of airgun arrays.
    Richardson et al. (1995) described zones of increasing intensity of 
effect that might be expected to occur, in relation to distance from a 
source and assuming that the signal is within an animal's hearing 
range. First is the area within which the acoustic signal would be 
audible (potentially perceived) to the animal, but not strong enough to 
elicit any overt behavioral or physiological response. The next zone 
corresponds with the area where the signal is audible to the animal and 
of sufficient intensity to elicit behavioral or physiological 
responsiveness. Third is a zone within which, for signals of high 
intensity, the received level is sufficient to potentially cause 
discomfort or tissue damage to auditory or other systems. Overlaying 
these zones to a certain extent is the area within which masking (i.e., 
when a sound interferes with or masks the ability of an animal to 
detect a signal of interest that is above the absolute hearing 
threshold) may occur; the masking zone may be highly variable in size.
    We describe the more severe effects of certain non-auditory 
physical or physiological effects only briefly as we do not expect that 
use of airgun arrays are reasonably likely to result in such effects 
(see below for further discussion). Potential effects from impulsive 
sound sources can range in severity from effects such as behavioral 
disturbance or tactile perception to physical discomfort, slight injury 
of the internal organs and the auditory system, or mortality (Yelverton 
et al., 1973). Non-auditory physiological effects or injuries that 
theoretically might occur in marine mammals exposed to high level 
underwater sound or as a secondary effect of extreme behavioral 
reactions (e.g., change in dive profile as a result of an avoidance 
reaction) caused by exposure to sound include neurological effects, 
bubble formation, resonance effects, and other types of organ or tissue 
damage (Cox et al., 2006; Southall et al., 2007; Zimmer and Tyack, 
2007; Tal et al., 2015). The survey activities considered here do not 
involve the use of devices such as explosives or mid-frequency tactical 
sonar that are associated with these types of effects.
    Threshold Shift--Marine mammals exposed to high-intensity sound, or 
to lower-intensity sound for prolonged periods, can experience hearing 
threshold shift (TS), which is the loss of hearing sensitivity at 
certain frequency ranges (Finneran, 2015). TS can be permanent (PTS), 
in which case the loss of hearing sensitivity is not fully recoverable, 
or temporary (TTS), in which case the animal's hearing threshold would 
recover over time (Southall et al., 2007). Repeated sound exposure that 
leads to TTS could cause PTS. In severe cases of PTS, there can be 
total or partial deafness, while in

[[Page 51906]]

most cases the animal has an impaired ability to hear sounds in 
specific frequency ranges (Kryter, 1985).
    When PTS occurs, there is physical damage to the sound receptors in 
the ear (i.e., tissue damage), whereas TTS represents primarily tissue 
fatigue and is reversible (Southall et al., 2007). In addition, other 
investigators have suggested that TTS is within the normal bounds of 
physiological variability and tolerance and does not represent physical 
injury (e.g., Ward, 1997). Therefore, NMFS does not consider TTS to 
constitute auditory injury.
    Relationships between TTS and PTS thresholds have not been studied 
in marine mammals, and there is no PTS data for cetaceans but such 
relationships are assumed to be similar to those in humans and other 
terrestrial mammals. PTS typically occurs at exposure levels at least 
several dBs above (a 40-dB threshold shift approximates PTS onset; 
e.g., Kryter et al., 1966; Miller, 1974) that inducing mild TTS (a 6-dB 
threshold shift approximates TTS onset; e.g., Southall et al. 2007). 
Based on data from terrestrial mammals, a precautionary assumption is 
that the PTS thresholds for impulse sounds (such as airgun pulses as 
received close to the source) are at least 6 dB higher than the TTS 
threshold on a peak-pressure basis and PTS cumulative sound exposure 
level thresholds are 15 to 20 dB higher than TTS cumulative sound 
exposure level thresholds (Southall et al., 2007). Given the higher 
level of sound or longer exposure duration necessary to cause PTS as 
compared with TTS, it is considerably less likely that PTS could occur.
    For mid-frequency cetaceans in particular, potential protective 
mechanisms may help limit onset of TTS or prevent onset of PTS. Such 
mechanisms include dampening of hearing, auditory adaptation, or 
behavioral amelioration (e.g., Nachtigall and Supin, 2013; Miller et 
al., 2012; Finneran et al., 2015; Popov et al., 2016).
    TTS is the mildest form of hearing impairment that can occur during 
exposure to sound (Kryter, 1985). While experiencing TTS, the hearing 
threshold rises, and a sound must be at a higher level in order to be 
heard. In terrestrial and marine mammals, TTS can last from minutes or 
hours to days (in cases of strong TTS). In many cases, hearing 
sensitivity recovers rapidly after exposure to the sound ends. Few data 
on sound levels and durations necessary to elicit mild TTS have been 
obtained for marine mammals.
    Marine mammal hearing plays a critical role in communication with 
conspecifics, and interpretation of environmental cues for purposes 
such as predator avoidance and prey capture. Depending on the degree 
(elevation of threshold in dB), duration (i.e., recovery time), and 
frequency range of TTS, and the context in which it is experienced, TTS 
can have effects on marine mammals ranging from discountable to 
serious. For example, a marine mammal may be able to readily compensate 
for a brief, relatively small amount of TTS in a non-critical frequency 
range that occurs during a time where ambient noise is lower and there 
are not as many competing sounds present. Alternatively, a larger 
amount and longer duration of TTS sustained during time when 
communication is critical for successful mother/calf interactions could 
have more serious impacts.
    Finneran et al. (2015) measured hearing thresholds in three captive 
bottlenose dolphins before and after exposure to ten pulses produced by 
a seismic airgun in order to study TTS induced after exposure to 
multiple pulses. Exposures began at relatively low levels and gradually 
increased over a period of several months, with the highest exposures 
at peak SPLs from 196 to 210 dB and cumulative (unweighted) SELs from 
193-195 dB. No substantial TTS was observed. In addition, behavioral 
reactions were observed that indicated that animals can learn behaviors 
that effectively mitigate noise exposures (although exposure patterns 
must be learned, which is less likely in wild animals than for the 
captive animals considered in this study). The authors note that the 
failure to induce more significant auditory effects likely due to the 
intermittent nature of exposure, the relatively low peak pressure 
produced by the acoustic source, and the low-frequency energy in airgun 
pulses as compared with the frequency range of best sensitivity for 
dolphins and other mid-frequency cetaceans.
    Currently, TTS data only exist for four species of cetaceans 
(bottlenose dolphin, beluga whale, harbor porpoise, and Yangtze finless 
porpoise) exposed to a limited number of sound sources (i.e., mostly 
tones and octave-band noise) in laboratory settings (Finneran, 2015). 
In general, harbor porpoises have a lower TTS onset than other measured 
cetacean species (Finneran, 2015). Additionally, the existing marine 
mammal TTS data come from a limited number of individuals within these 
species. There are no data available on noise-induced hearing loss for 
mysticetes.
    Critical questions remain regarding the rate of TTS growth and 
recovery after exposure to intermittent noise and the effects of single 
and multiple pulses. Data at present are also insufficient to construct 
generalized models for recovery and determine the time necessary to 
treat subsequent exposures as independent events. More information is 
needed on the relationship between auditory evoked potential and 
behavioral measures of TTS for various stimuli. For summaries of data 
on TTS in marine mammals or for further discussion of TTS onset 
thresholds, please see Southall et al. (2007), Finneran and Jenkins 
(2012), Finneran (2015), and NMFS (2018).
    Behavioral Effects--Behavioral disturbance may include a variety of 
effects, including subtle changes in behavior (e.g., minor or brief 
avoidance of an area or changes in vocalizations), more conspicuous 
changes in similar behavioral activities, and more sustained and/or 
potentially severe reactions, such as displacement from or abandonment 
of high-quality habitat. Behavioral responses to sound are highly 
variable and context-specific and any reactions depend on numerous 
intrinsic and extrinsic factors (e.g., species, state of maturity, 
experience, current activity, reproductive state, auditory sensitivity, 
time of day), as well as the interplay between factors (e.g., 
Richardson et al., 1995; Wartzok et al., 2003; Southall et al., 2007; 
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

[[Page 51907]]

avoidance, at a lower level of exposure. As noted, behavioral state may 
affect the type of response. For example, animals that are resting may 
show greater behavioral change in response to disturbing sound levels 
than animals that are highly motivated to remain in an area for feeding 
(Richardson et al., 1995; NRC, 2003; Wartzok et al., 2003). Controlled 
experiments with captive marine mammals have showed pronounced 
behavioral reactions, including avoidance of loud sound sources 
(Ridgway et al., 1997). Observed responses of wild marine mammals to 
loud pulsed sound sources (typically seismic airguns or acoustic 
harassment devices) have been varied but often consist of avoidance 
behavior or other behavioral changes suggesting discomfort (Morton and 
Symonds, 2002; see also Richardson et al., 1995; Nowacek et al., 2007). 
However, many delphinids approach acoustic source vessels with no 
apparent discomfort or obvious behavioral change (e.g., Barkaszi et 
al., 2012).
    Available studies show wide variation in response to underwater 
sound; therefore, it is difficult to predict specifically how any given 
sound in a particular instance might affect marine mammals perceiving 
the signal. If a marine mammal does react briefly to an underwater 
sound by changing its behavior or moving a small distance, the impacts 
of the change are unlikely to be significant to the individual, let 
alone the stock or population. However, if a sound source displaces 
marine mammals from an important feeding or breeding area for a 
prolonged period, impacts on individuals and populations could be 
significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007; NRC, 
2005). However, there are broad categories of potential response, which 
we describe in greater detail here, that include alteration of dive 
behavior, alteration of foraging behavior, effects to breathing, 
interference with or alteration of vocalization, avoidance, and flight.
    Changes in dive behavior can vary widely, and may consist of 
increased or decreased dive times and surface intervals as well as 
changes in the rates of ascent and descent during a dive (e.g., Frankel 
and Clark, 2000; Ng and Leung, 2003; Nowacek et al., 2004; Goldbogen et 
al., 2013a, b). Variations in dive behavior may reflect interruptions 
in biologically significant activities (e.g., foraging) or they may be 
of little biological significance. The impact of an alteration to dive 
behavior resulting from an acoustic exposure depends on what the animal 
is doing at the time of the exposure and the type and magnitude of the 
response.
    Disruption of feeding behavior can be difficult to correlate with 
anthropogenic sound exposure, so it is usually inferred by observed 
displacement from known foraging areas, the appearance of secondary 
indicators (e.g., bubble nets or sediment plumes), or changes in dive 
behavior. As for other types of behavioral response, the frequency, 
duration, and temporal pattern of signal presentation, as well as 
differences in species sensitivity, are likely contributing factors to 
differences in response in any given circumstance (e.g., Croll et al., 
2001; Nowacek et al.; 2004; Madsen et al., 2006; Yazvenko et al., 
2007). A determination of whether foraging disruptions incur fitness 
consequences would require information on or estimates of the energetic 
requirements of the affected individuals and the relationship between 
prey availability, foraging effort and success, and the life history 
stage of the animal.
    Visual tracking, passive acoustic monitoring, and movement 
recording tags were used to quantify sperm whale behavior prior to, 
during, and following exposure to airgun arrays at received levels in 
the range 140-160 dB at distances of 7-13 km, following a phase-in of 
sound intensity and full array exposures at 1-13 km (Madsen et al., 
2006; Miller et al., 2009). Sperm whales did not exhibit horizontal 
avoidance behavior at the surface. However, foraging behavior may have 
been affected. The sperm whales exhibited 19 percent less vocal (buzz) 
rate during full exposure relative to post exposure, and the whale that 
was approached most closely had an extended resting period and did not 
resume foraging until the airguns had ceased firing. The remaining 
whales continued to execute foraging dives throughout exposure; 
however, swimming movements during foraging dives were 6 percent lower 
during exposure than control periods (Miller et al., 2009). These data 
raise concerns that seismic surveys may impact foraging behavior in 
sperm whales, although more data are required to understand whether the 
differences were due to exposure or natural variation in sperm whale 
behavior (Miller et al., 2009).
    Variations in respiration naturally vary with different behaviors 
and alterations to breathing rate as a function of acoustic exposure 
can be expected to co-occur with other behavioral reactions, such as a 
flight response or an alteration in diving. However, respiration rates 
in and of themselves may be representative of annoyance or an acute 
stress response. Various studies have shown that respiration rates may 
either be unaffected or could increase, depending on the species and 
signal characteristics, again highlighting the importance in 
understanding species differences in the tolerance of underwater noise 
when determining the potential for impacts resulting from anthropogenic 
sound exposure (e.g., Kastelein et al., 2001, 2005, 2006; Gailey et 
al., 2007, 2016).
    Marine mammals vocalize for different purposes and across multiple 
modes, such as whistling, echolocation click production, calling, and 
singing. Changes in vocalization behavior in response to anthropogenic 
noise can occur for any of these modes and may result from a need to 
compete with an increase in background noise or may reflect increased 
vigilance or a startle response. For example, in the presence of 
potentially masking signals, humpback whales and killer whales have 
been observed to increase the length of their songs (Miller et al., 
2000; Fristrup et al., 2003; Foote et al., 2004), while right whales 
have been observed to shift the frequency content of their calls upward 
while reducing the rate of calling in areas of increased anthropogenic 
noise (Parks et al., 2007). In some cases, animals may cease sound 
production during production of aversive signals (Bowles et al., 1994).
    Cerchio et al. (2014) used passive acoustic monitoring to document 
the presence of singing humpback whales off the coast of northern 
Angola and to opportunistically test for the effect of seismic survey 
activity on the number of singing whales. Two recording units were 
deployed between March and December 2008 in the offshore environment; 
numbers of singers were counted every hour. Generalized Additive Mixed 
Models were used to assess the effect of survey day (seasonality), hour 
(diel variation), moon phase, and received levels of noise (measured 
from a single pulse during each ten minute sampled period) on singer 
number. The number of singers significantly decreased with increasing 
received level of noise, suggesting that humpback whale breeding 
activity was disrupted to some extent by the survey activity.
    Castellote et al. (2012) reported acoustic and behavioral changes 
by fin whales in response to shipping and airgun noise. Acoustic 
features of fin whale song notes recorded in the Mediterranean Sea and 
northeast Atlantic Ocean were compared for areas with different 
shipping noise levels and traffic intensities and during a seismic 
airgun survey. During the first 72 h of the survey, a steady decrease 
in song received levels and bearings to singers

[[Page 51908]]

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 
[micro]Pa\2\-s caused blue whales to increase call production (Di Iorio 
and Clark, 2010). In contrast, McDonald et al. (1995) tracked a blue 
whale with seafloor seismometers and reported that it stopped 
vocalizing and changed its travel direction at a range of 10 km from 
the acoustic source vessel (estimated received level 143 dB pk-pk). 
Blackwell et al. (2013) found that bowhead whale call rates dropped 
significantly at onset of airgun use at sites with a median distance of 
41-45 km from the survey. Blackwell et al. (2015) expanded this 
analysis to show that whales actually increased calling rates as soon 
as airgun signals were detectable before ultimately decreasing calling 
rates at higher received levels (i.e., 10-minute SELcum of 
~127 dB). Overall, these results suggest that bowhead whales may adjust 
their vocal output in an effort to compensate for noise before ceasing 
vocalization effort and ultimately deflecting from the acoustic source 
(Blackwell et al., 2013, 2015). These studies demonstrate that even low 
levels of noise received far from the source can induce changes in 
vocalization and/or behavior for mysticetes.
    Avoidance is the displacement of an individual from an area or 
migration path as a result of the presence of a sound or other 
stressors, and is one of the most obvious manifestations of disturbance 
in marine mammals (Richardson et al., 1995). For example, gray whales 
are known to change direction--deflecting from customary migratory 
paths--in order to avoid noise from seismic surveys (Malme et al., 
1984). Humpback whales showed avoidance behavior in the presence of an 
active seismic array during observational studies and controlled 
exposure experiments in western Australia (McCauley et al., 2000). 
Avoidance may be short-term, with animals returning to the area once 
the noise has ceased (e.g., Bowles et al., 1994; Goold, 1996; Stone et 
al., 2000; Morton and Symonds, 2002; Gailey et al., 2007). Longer-term 
displacement is possible, however, which may lead to changes in 
abundance or distribution patterns of the affected species in the 
affected region if habituation to the presence of the sound does not 
occur (e.g., Bejder et al., 2006; Teilmann et al., 2006).
    A flight response is a dramatic change in normal movement to a 
directed and rapid movement away from the perceived location of a sound 
source. The flight response differs from other avoidance responses in 
the intensity of the response (e.g., directed movement, rate of 
travel). Relatively little information on flight responses of marine 
mammals to anthropogenic signals exist, although observations of flight 
responses to the presence of predators have occurred (Connor and 
Heithaus, 1996). The result of a flight response could range from 
brief, temporary exertion and displacement from the area where the 
signal provokes flight to, in extreme cases, marine mammal strandings 
(Evans and England, 2001). However, it should be noted that response to 
a perceived predator does not necessarily invoke flight (Ford and 
Reeves, 2008), and whether individuals are solitary or in groups may 
influence the response.
    Behavioral disturbance can also impact marine mammals in more 
subtle ways. Increased vigilance may result in costs related to 
diversion of focus and attention (i.e., when a response consists of 
increased vigilance, it may come at the cost of decreased attention to 
other critical behaviors such as foraging or resting). These effects 
have generally not been demonstrated for marine mammals, but studies 
involving fish and terrestrial animals have shown that increased 
vigilance may substantially reduce feeding rates (e.g., Beauchamp and 
Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). In 
addition, chronic disturbance can cause population declines through 
reduction of fitness (e.g., decline in body condition) and subsequent 
reduction in reproductive success, survival, or both (e.g., Harrington 
and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). However, 
Ridgway et al. (2006) reported that increased vigilance in bottlenose 
dolphins exposed to sound over a five-day period did not cause any 
sleep deprivation or stress effects.
    Many animals perform vital functions, such as feeding, resting, 
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption 
of such functions resulting from reactions to stressors such as sound 
exposure are more likely to be significant if they last more than one 
diel cycle or recur on subsequent days (Southall et al., 2007). 
Consequently, a behavioral response lasting less than one day and not 
recurring on subsequent days is not considered particularly severe 
unless it could directly affect reproduction or survival (Southall et 
al., 2007). Note that there is a difference between multi-day 
substantive behavioral reactions and multi-day anthropogenic 
activities. For example, just because an activity lasts for multiple 
days does not necessarily mean that individual animals are either 
exposed to activity-related stressors for multiple days or, further, 
exposed in a manner resulting in sustained multi-day substantive 
behavioral responses.
    Stone (2015) reported data from at-sea observations during 1,196 
seismic surveys from 1994 to 2010. When large arrays of airguns 
(considered to be 500 in\3\ or more) were firing, lateral displacement, 
more localized avoidance, or other changes in behavior were evident for 
most odontocetes. However, significant responses to large arrays were 
found only for the minke whale and fin whale. Behavioral responses 
observed included changes in swimming or surfacing behavior, with 
indications that cetaceans remained near the water surface at these 
times. Cetaceans were recorded as feeding less often when large arrays 
were active. Behavioral observations of gray whales during a seismic 
survey monitored whale movements and respirations pre-, during and 
post-seismic survey (Gailey et al., 2016). Behavioral state and water 
depth were the best `natural' predictors of whale movements and 
respiration and, after considering natural variation, none of the 
response variables were significantly associated with seismic survey or 
vessel sounds.
    Stress Responses--An animal's perception of a threat may be 
sufficient to trigger stress responses consisting of some combination 
of behavioral responses, autonomic nervous system responses, 
neuroendocrine responses, or immune responses (e.g., Seyle, 1950; 
Moberg, 2000). In many cases, an animal's first and sometimes most 
economical (in terms of energetic costs) response is behavioral 
avoidance of the potential stressor. Autonomic nervous system responses 
to stress typically involve changes in heart rate, blood pressure, and 
gastrointestinal activity. These responses have a relatively short 
duration and may or may not have a significant long-term effect on an 
animal's fitness.
    Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that 
are affected by stress--including immune competence, reproduction, 
metabolism,

[[Page 51909]]

and behavior--are regulated by pituitary hormones. Stress-induced 
changes in the secretion of pituitary hormones have been implicated in 
failed reproduction, altered metabolism, reduced immune competence, and 
behavioral disturbance (e.g., Moberg, 1987; Blecha, 2000). Increases in 
the circulation of glucocorticoids are also equated with stress (Romano 
et al., 2004).
    The primary distinction between stress (which is adaptive and does 
not normally place an animal at risk) and ``distress'' is the cost of 
the response. During a stress response, an animal uses glycogen stores 
that can be quickly replenished once the stress is alleviated. In such 
circumstances, the cost of the stress response would not pose serious 
fitness consequences. However, when an animal does not have sufficient 
energy reserves to satisfy the energetic costs of a stress response, 
energy resources must be diverted from other functions. This state of 
distress will last until the animal replenishes its energetic reserves 
sufficiently to restore normal function.
    Relationships between these physiological mechanisms, animal 
behavior, and the costs of stress responses are well-studied through 
controlled experiments and for both laboratory and free-ranging animals 
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; 
Krausman et al., 2004; Lankford et al., 2005). Stress responses due to 
exposure to anthropogenic sounds or other stressors and their effects 
on marine mammals have also been reviewed (Fair and Becker, 2000; 
Romano et al., 2002b) and, more rarely, studied in wild populations 
(e.g., Romano et al., 2002a). For example, Rolland et al. (2012) found 
that noise reduction from reduced ship traffic in the Bay of Fundy was 
associated with decreased stress in North Atlantic right whales. These 
and other studies lead to a reasonable expectation that some marine 
mammals will experience physiological stress responses upon exposure to 
acoustic stressors and that it is possible that some of these would be 
classified as ``distress.'' In addition, any animal experiencing TTS 
would likely also experience stress responses (NRC, 2003).
    Auditory Masking--Sound can disrupt behavior through masking, or 
interfering with, an animal's ability to detect, recognize, or 
discriminate between acoustic signals of interest (e.g., those used for 
intraspecific communication and social interactions, prey detection, 
predator avoidance, navigation) (Richardson et al., 1995; Erbe et al., 
2016). Masking occurs when the receipt of a sound is interfered with by 
another coincident sound at similar frequencies and at similar or 
higher intensity, and may occur whether the sound is natural (e.g., 
snapping shrimp, wind, waves, precipitation) or anthropogenic (e.g., 
shipping, sonar, seismic exploration) in origin. The ability of a noise 
source to mask biologically important sounds depends on the 
characteristics of both the noise source and the signal of interest 
(e.g., signal-to-noise ratio, temporal variability, direction), in 
relation to each other and to an animal's hearing abilities (e.g., 
sensitivity, frequency range, critical ratios, frequency 
discrimination, directional discrimination, age or TTS hearing loss), 
and existing ambient noise and propagation conditions.
    Under certain circumstances, marine mammals experiencing 
significant masking could also be impaired from maximizing their 
performance fitness in survival and reproduction. Therefore, when the 
coincident (masking) sound is man-made, it may be considered harassment 
when disrupting or altering critical behaviors. It is important to 
distinguish TTS and PTS, which persist after the sound exposure, from 
masking, which occurs during the sound exposure. Because masking 
(without resulting in TS) is not associated with abnormal physiological 
function, it is not considered a physiological effect, but rather a 
potential behavioral effect.
    The frequency range of the potentially masking sound is important 
in determining any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation 
sounds produced by odontocetes but are more likely to affect detection 
of mysticete communication calls and other potentially important 
natural sounds such as those produced by surf and some prey species. 
The masking of communication signals by anthropogenic noise may be 
considered as a reduction in the communication space of animals (e.g., 
Clark et al., 2009) and may result in energetic or other costs as 
animals change their vocalization behavior (e.g., Miller et al., 2000; 
Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2009; Holt 
et al., 2009). Masking can be reduced in situations where the signal 
and noise come from different directions (Richardson et al., 1995), 
through amplitude modulation of the signal, or through other 
compensatory behaviors (Houser and Moore, 2014). Masking can be tested 
directly in captive species (e.g., Erbe, 2008), but in wild populations 
it must be either modeled or inferred from evidence of masking 
compensation. There are few studies addressing real-world masking 
sounds likely to be experienced by marine mammals in the wild (e.g., 
Branstetter et al., 2013).
    Masking affects both senders and receivers of acoustic signals and 
can potentially have long-term chronic effects on marine mammals at the 
population level as well as at the individual level. Low-frequency 
ambient sound levels have increased by as much as 20 dB (more than 
three times in terms of SPL) in the world's ocean from pre-industrial 
periods, with most of the increase from distant commercial shipping 
(Hildebrand, 2009). All anthropogenic sound sources, but especially 
chronic and lower-frequency signals (e.g., from vessel traffic), 
contribute to elevated ambient sound levels, thus intensifying masking.
    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal calls and other natural sounds are expected 
to be limited, although there are few specific data on this. Because of 
the intermittent nature and low duty cycle of seismic pulses, animals 
can emit and receive sounds in the relatively quiet intervals between 
pulses. However, in exceptional situations, reverberation occurs for 
much or all of the interval between pulses (e.g., Simard et al. 2005; 
Clark and Gagnon 2006), which could mask calls. Situations with 
prolonged strong reverberation are infrequent. However, it is common 
for reverberation to cause some lesser degree of elevation of the 
background level between airgun pulses (e.g., Gedamke 2011; Guerra et 
al. 2011, 2016; Klinck et al. 2012; Guan et al. 2015), and this weaker 
reverberation presumably reduces the detection range of calls and other 
natural sounds to some degree. Guerra et al. (2016) reported that 
ambient noise levels between seismic pulses were elevated as a result 
of reverberation at ranges of 50 km from the seismic source. Based on 
measurements in deep water of the Southern Ocean, Gedamke (2011) 
estimated that the slight elevation of background levels during 
intervals between pulses reduced blue and fin whale communication space 
by as much as 36-51 percent when a seismic survey was operating 450-
2,800 km away. Based on preliminary modeling, Wittekind et al. (2016) 
reported that airgun sounds could reduce the communication range of 
blue and fin whales 2000 km from the seismic source. Nieukirk et al. 
(2012) and Blackwell et al. (2013) noted the potential for masking 
effects from seismic surveys on large whales.

[[Page 51910]]

    Some baleen and toothed whales are known to continue calling in the 
presence of seismic pulses, and their calls usually can be heard 
between the pulses (e.g., Nieukirk et al. 2012; Thode et al. 2012; 
Br[ouml]ker et al. 2013; Sciacca et al. 2016). As noted above, Cerchio 
et al. (2014) suggested that the breeding display of humpback whales 
off Angola could be disrupted by seismic sounds, as singing activity 
declined with increasing received levels. In addition, some cetaceans 
are known to change their calling rates, shift their peak frequencies, 
or otherwise modify their vocal behavior in response to airgun sounds 
(e.g., Di Iorio and Clark 2010; Castellote et al. 2012; Blackwell et 
al. 2013, 2015). The hearing systems of baleen whales are undoubtedly 
more sensitive to low-frequency sounds than are the ears of the small 
odontocetes that have been studied directly (e.g., MacGillivray et al. 
2014). The sounds important to small odontocetes are predominantly at 
much higher frequencies than are the dominant components of airgun 
sounds, thus limiting the potential for masking. In general, masking 
effects of seismic pulses are expected to be minor, given the normally 
intermittent nature of seismic pulses.

Ship Noise

    Vessel noise from the Thompson could affect marine animals in the 
proposed survey areas. Houghton et al. (2015) proposed that vessel 
speed is the most important predictor of received noise levels, and 
Putland et al. (2017) also reported reduced sound levels with decreased 
vessel speed. Sounds produced by large vessels generally dominate 
ambient noise at frequencies from 20 to 300 Hz (Richardson et al. 
1995). However, some energy is also produced at higher frequencies 
(Hermannsen et al. 2014); low levels of high-frequency sound from 
vessels has been shown to elicit responses in harbor porpoise (Dyndo et 
al. 2015). Increased levels of ship noise have been shown to affect 
foraging by porpoise (Teilmann et al. 2015; Wisniewska et al. 2018); 
Wisniewska et al. (2018) suggest that a decrease in foraging success 
could have long-term fitness consequences.
    Ship noise, through masking, can reduce the effective communication 
distance of a marine mammal if the frequency of the sound source is 
close to that used by the animal, and if the sound is present for a 
significant fraction of time (e.g., Richardson et al. 1995; Clark et 
al. 2009; Jensen et al. 2009; Gervaise et al. 2012; Hatch et al. 2012; 
Rice et al. 2014; Dunlop 2015; Erbe et al. 2015; Jones et al. 2017; 
Putland et al. 2017). In addition to the frequency and duration of the 
masking sound, the strength, temporal pattern, and location of the 
introduced sound also play a role in the extent of the masking 
(Branstetter et al. 2013, 2016; Finneran and Branstetter 2013; Sills et 
al. 2017). Branstetter et al. (2013) reported that time-domain metrics 
are also important in describing and predicting masking. In order to 
compensate for increased ambient noise, some cetaceans are known to 
increase the source levels of their calls in the presence of elevated 
noise levels from shipping, shift their peak frequencies, or otherwise 
change their vocal behavior (e.g., Parks et al. 2011, 2012, 2016a,b; 
Castellote et al. 2012; Melc[oacute]n et al. 2012; Azzara et al. 2013; 
Tyack and Janik 2013; Lu[iacute]s et al. 2014; Sairanen 2014; Papale et 
al. 2015; Bittencourt et al. 2016; Dahlheim and Castellote 2016; 
Gospi[cacute] and Picciulin 2016; Gridley et al. 2016; Heiler et al. 
2016; Martins et al. 2016; O'Brien et al. 2016; Tenessen and Parks 
2016). Harp seals did not increase their call frequencies in 
environments with increased low-frequency sounds (Terhune and Bosker 
2016). Holt et al. (2015) reported that changes in vocal modifications 
can have increased energetic costs for individual marine mammals. A 
negative correlation between the presence of some cetacean species and 
the number of vessels in an area has been demonstrated by several 
studies (e.g., Campana et al. 2015; Culloch et al. 2016).
    Baleen whales are thought to be more sensitive to sound at these 
low frequencies than are toothed whales (e.g., MacGillivray et al. 
2014), possibly causing localized avoidance of the proposed survey area 
during seismic operations. Reactions of gray and humpback whales to 
vessels have been studied, and there is limited information available 
about the reactions of right whales and rorquals (fin, blue, and minke 
whales). Reactions of humpback whales to boats are variable, ranging 
from approach to avoidance (Payne 1978; Salden 1993). Baker et al. 
(1982, 1983) and Baker and Herman (1989) found humpbacks often move 
away when vessels are within several kilometers. Humpbacks seem less 
likely to react overtly when actively feeding than when resting or 
engaged in other activities (Krieger and Wing 1984, 1986). Increased 
levels of ship noise have been shown to affect foraging by humpback 
whales (Blair et al. 2016). Fin whale sightings in the western 
Mediterranean were negatively correlated with the number of vessels in 
the area (Campana et al. 2015). Minke whales and gray seals have shown 
slight displacement in response to construction-related vessel traffic 
(Anderwald et al. 2013).
    Many odontocetes show considerable tolerance of vessel traffic, 
although they sometimes react at long distances if confined by ice or 
shallow water, if previously harassed by vessels, or have had little or 
no recent exposure to ships (Richardson et al. 1995). Dolphins of many 
species tolerate and sometimes approach vessels (e.g., Anderwald et al. 
2013). Some dolphin species approach moving vessels to ride the bow or 
stern waves (Williams et al. 1992). Pirotta et al. (2015) noted that 
the physical presence of vessels, not just ship noise, disturbed the 
foraging activity of bottlenose dolphins. Sightings of striped dolphin, 
Risso's dolphin, sperm whale, and Cuvier's beaked whale in the western 
Mediterranean were negatively correlated with the number of vessels in 
the area (Campana et al. 2015).
    There are few data on the behavioral reactions of beaked whales to 
vessel noise, though they seem to avoid approaching vessels (e.g., 
W[uuml]rsig et al. 1998) or dive for an extended period when approached 
by a vessel (e.g., Kasuya 1986). Based on a single observation, Aguilar 
Soto et al. (2006) suggest foraging efficiency of Cuvier's beaked 
whales may be reduced by close approach of vessels.
    In summary, project vessel sounds would not be at levels expected 
to cause anything more than possible localized and temporary behavioral 
changes in marine mammals, and would not be expected to result in 
significant negative effects on individuals or at the population level. 
In addition, in all oceans of the world, large vessel traffic is 
currently so prevalent that it is commonly considered a usual source of 
ambient sound (NSF-USGS 2011).

Ship Strike

    Vessel collisions with marine mammals, or ship strikes, can result 
in death or serious injury of the animal. Wounds resulting from ship 
strike may include massive trauma, hemorrhaging, broken bones, or 
propeller lacerations (Knowlton and Kraus, 2001). An animal at the 
surface may be struck directly by a vessel, a surfacing animal may hit 
the bottom of a vessel, or an animal just below the surface may be cut 
by a vessel's propeller. Superficial strikes may not kill or result in 
the death of the animal. These interactions are typically associated 
with large whales (e.g., fin whales), which are occasionally found 
draped across the bulbous bow of large commercial ships upon arrival in 
port. Although smaller cetaceans are more

[[Page 51911]]

maneuverable in relation to large vessels than are large whales, they 
may also be susceptible to strike. The severity of injuries typically 
depends on the size and speed of the vessel, with the probability of 
death or serious injury increasing as vessel speed increases (Knowlton 
and Kraus, 2001; Laist et al., 2001; Vanderlaan and Taggart, 2007; Conn 
and Silber, 2013). Impact forces increase with speed, as does the 
probability of a strike at a given distance (Silber et al., 2010; Gende 
et al., 2011).
    Pace and Silber (2005) also found that the probability of death or 
serious injury increased rapidly with increasing vessel speed. 
Specifically, the predicted probability of serious injury or death 
increased from 45 to 75 percent as vessel speed increased from 10 to 14 
kn, and exceeded 90 percent at 17 kn. Higher speeds during collisions 
result in greater force of impact, but higher speeds also appear to 
increase the chance of severe injuries or death through increased 
likelihood of collision by pulling whales toward the vessel (Clyne, 
1999; Knowlton et al., 1995). In a separate study, Vanderlaan and 
Taggart (2007) analyzed the probability of lethal mortality of large 
whales at a given speed, showing that the greatest rate of change in 
the probability of a lethal injury to a large whale as a function of 
vessel speed occurs between 8.6 and 15 kn. The chances of a lethal 
injury decline from approximately 80 percent at 15 kn to approximately 
20 percent at 8.6 kn. At speeds below 11.8 kn, the chances of lethal 
injury drop below 50 percent, while the probability asymptotically 
increases toward one hundred percent above 15 kn.
    The Thompson travels at a speed of either 5 (9.3 km/hour) or 8 kn 
(14.8 km/hour) while towing seismic survey gear (LGL 2019). At these 
speeds, both the possibility of striking a marine mammal and the 
possibility of a strike resulting in serious injury or mortality are 
discountable. At average transit speed, the probability of serious 
injury or mortality resulting from a strike is less than 50 percent. 
However, the likelihood of a strike actually happening is again 
discountable. Ship strikes, as analyzed in the studies cited above, 
generally involve commercial shipping, which is much more common in 
both space and time than is geophysical survey activity. Jensen and 
Silber (2004) summarized ship strikes of large whales worldwide from 
1975-2003 and found that most collisions occurred in the open ocean and 
involved large vessels (e.g., commercial shipping). No such incidents 
were reported for geophysical survey vessels during that time period.
    It is possible for ship strikes to occur while traveling at slow 
speeds. For example, a hydrographic survey vessel traveling at low 
speed (5.5 kn) while conducting mapping surveys off the central 
California coast struck and killed a blue whale in 2009. The State of 
California determined that the whale had suddenly and unexpectedly 
surfaced beneath the hull, with the result that the propeller severed 
the whale's vertebrae, and that this was an unavoidable event. This 
strike represents the only such incident in approximately 540,000 hours 
of similar coastal mapping activity (p = 1.9 x 10-6; 95 
percent CI = 0-5.5 x 10-6; NMFS, 2013b). In addition, a 
research vessel reported a fatal strike in 2011 of a dolphin in the 
Atlantic, demonstrating that it is possible for strikes involving 
smaller cetaceans to occur. In that case, the incident report indicated 
that an animal apparently was struck by the vessel's propeller as it 
was intentionally swimming near the vessel. While indicative of the 
type of unusual events that cannot be ruled out, neither of these 
instances represents a circumstance that would be considered reasonably 
foreseeable or that would be considered preventable.
    Although the likelihood of the vessel striking a marine mammal is 
low, we require a robust ship strike avoidance protocol (see Proposed 
Mitigation), which we believe eliminates any foreseeable risk of ship 
strike. We anticipate that vessel collisions involving a seismic data 
acquisition vessel towing gear, while not impossible, represent 
unlikely, unpredictable events for which there are no preventive 
measures. Given the required mitigation measures, the relatively slow 
speed of the vessel towing gear, the presence of bridge crew watching 
for obstacles at all times (including marine mammals), and the presence 
of marine mammal observers, we believe that the possibility of ship 
strike is discountable and, further, that were a strike of a large 
whale to occur, it would be unlikely to result in serious injury or 
mortality. No incidental take resulting from ship strike is 
anticipated, and this potential effect of the specified activity will 
not be discussed further in the following analysis.
    Stranding--When a living or dead marine mammal swims or floats onto 
shore and becomes ``beached'' or incapable of returning to sea, the 
event is a ``stranding'' (Geraci et al., 1999; Perrin and Geraci, 2002; 
Geraci and Lounsbury, 2005; NMFS, 2007). The legal definition for a 
stranding under the MMPA is that (A) a marine mammal is dead and is (i) 
on a beach or shore of the United States; or (ii) in waters under the 
jurisdiction of the United States (including any navigable waters); or 
(B) a marine mammal is alive and is (i) on a beach or shore of the 
United States and is unable to return to the water; (ii) on a beach or 
shore of the United States and, although able to return to the water, 
is in need of apparent medical attention; or (iii) in the waters under 
the jurisdiction of the United States (including any navigable waters), 
but is unable to return to its natural habitat under its own power or 
without assistance.
    Marine mammals strand for a variety of reasons, such as infectious 
agents, biotoxicosis, starvation, fishery interaction, ship strike, 
unusual oceanographic or weather events, sound exposure, or 
combinations of these stressors sustained concurrently or in series. 
However, the cause or causes of most strandings are unknown (Geraci et 
al., 1976; Eaton, 1979; Odell et al., 1980; Best, 1982). Numerous 
studies suggest that the physiology, behavior, habitat relationships, 
age, or condition of cetaceans may cause them to strand or might pre-
dispose them to strand when exposed to another phenomenon. These 
suggestions are consistent with the conclusions of numerous other 
studies that have demonstrated that combinations of dissimilar 
stressors commonly combine to kill an animal or dramatically reduce its 
fitness, even though one exposure without the other does not produce 
the same result (Chroussos, 2000; Creel, 2005; DeVries et al., 2003; 
Fair and Becker, 2000; Foley et al., 2001; Moberg, 2000; Relyea, 2005a; 
2005b, Romero, 2004; Sih et al., 2004).
    Use of military tactical sonar has been implicated in some 
investigated stranding events. 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, mid-frequency sound 
is typically implicated (when causation can be determined) (Hildebrand, 
2004). Although seismic airguns create predominantly low-frequency 
energy, the signal does include a mid-frequency component. We have 
considered the potential for the proposed surveys to result in marine 
mammal stranding and have concluded that, based on the best available 
information, stranding is not expected to occur.

[[Page 51912]]

    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. McCauley 
et al. (2017) reported that experimental exposure to a pulse from a 150 
inch\3\ 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.
    A modeling exercise was conducted as a follow-up to the McCauley et 
al. (2017) study (as recommended by McCauley et al.), in order to 
assess the potential for impacts on ocean ecosystem dynamics and 
zooplankton population dynamics (Richardson et al., 2017). Richardson 
et al. (2017) found that for copepods with a short life cycle in a 
high-energy environment, a full-scale airgun survey would impact 
copepod abundance up to three days following the end of the survey, 
suggesting that effects such as those found by McCauley et al. (2017) 
would not be expected to be detectable downstream of the survey areas, 
either spatially or temporally.
    Notably, a recently described study produced results inconsistent 
with those of McCauley et al. (2017). Researchers conducted a field and 
laboratory study to assess if exposure to airgun noise affects 
mortality, predator escape response, or gene expression of the copepod 
Calanus finmarchicus (Fields et al., 2019). Immediate mortality of 
copepods was significantly higher, relative to controls, at distances 
of 5 m or less from the airguns. Mortality one week after the airgun 
blast was significantly higher in the copepods placed 10 m from the 
airgun but was not significantly different from the controls at a 
distance of 20 m from the airgun. The increase in mortality, relative 
to controls, did not exceed 30 percent at any distance from the airgun. 
Moreover, the authors caution that even this higher mortality in the 
immediate vicinity of the airguns may be more pronounced than what 
would be observed in free-swimming animals due to increased flow speed 
of fluid inside bags containing the experimental animals. There were no 
sublethal effects on the escape performance or the sensory threshold 
needed to initiate an escape response at any of the distances from the 
airgun that were tested. Whereas McCauley et al. (2017) reported an SEL 
of 156 dB at a range of 509-658 m, with zooplankton mortality observed 
at that range, Fields et al. (2019) reported an SEL of 186 dB at a 
range of 25 m, with no reported mortality at that distance.
    Regardless, if we assume a worst-case likelihood of severe impacts 
to zooplankton within approximately 1 km of the acoustic source, the 
typically wide dispersal of survey vessels and brief time to 
regeneration of the potentially affected zooplankton populations does 
not lead us to expect any meaningful follow-on effects to the prey base 
for odontocete predators. Given the inconsistency of the McCauley et 
al. (2017) results with prior research on impacts to zooplankton as a 
result of exposure to airgun noise and with the research of Fields et 
al. (2019), further validation of those findings would be necessary to 
assume that these impacts are likely to occur. Moreover, a single study 
is not sufficient to evaluate the potential impacts, and further study 
in additional locations must be conducted.
    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 use of airguns as part of an active seismic array 
survey would occur over a relatively short time period (~28 days) and 
would occur over a very small area relative to the area available as 
marine mammal habitat in the Southwest Atlantic Ocean. We believe any 
impacts to marine mammals due to adverse effects to their prey would be 
insignificant due to the limited spatial and temporal 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 habitat-mediated 
effects to marine mammals (please see also the previous discussion on 
masking in the Acoustic Effects section), 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

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previously, exploratory surveys such as this one 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 ``small numbers'' and the negligible impact 
determination.
    Harassment is the only type of take expected to result from these 
activities. Except with respect to certain activities not pertinent 
here, section 3(18) of the MMPA defines ``harassment'' as any act of 
pursuit, torment, or annoyance, which (i) has the potential to injure a 
marine mammal or marine mammal stock in the wild (Level A harassment); 
or (ii) has the potential to disturb a marine mammal or marine mammal 
stock in the wild by causing disruption of behavioral patterns, 
including, but not limited to, migration, breathing, nursing, breeding, 
feeding, or sheltering (Level B harassment).
    Authorized takes would be by Level B harassment only, as use of the 
acoustic sources (i.e., seismic airgun) has the potential to result in 
disruption of behavioral patterns for individual marine mammals. Based 
on the nature of the activity and the anticipated effectiveness of the 
mitigation measures (i.e., marine mammal exclusion zones) discussed in 
detail below in Proposed Mitigation section, Level A harassment is 
neither anticipated nor proposed to be authorized. As described 
previously, no mortality is anticipated or proposed to be authorized 
for this activity. Below we describe how the take is estimated.
    Generally speaking, we estimate take by considering: (1) Acoustic 
thresholds above which NMFS believes the best available science 
indicates marine mammals will be behaviorally harassed or incur some 
degree of permanent hearing impairment; (2) the area or volume of water 
that will be ensonified above these levels in a day; (3) the density or 
occurrence of marine mammals within these ensonified areas; and, (4) 
and the number of days of activities. We note that while these basic 
factors can contribute to a basic calculation to provide an initial 
prediction of takes, additional information that can qualitatively 
inform take estimates is also sometimes available (e.g., previous 
monitoring results or average group size). Below, we describe the 
factors considered here in more detail and present the proposed take 
estimate.

Acoustic Thresholds

    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., 2012). Based on what the available science indicates, 
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 Level B 
harassment when exposed to underwater anthropogenic noise above 
received levels of 120 dB re 1 [mu]Pa (rms) for continuous (e.g., 
vibratory pile-driving, drilling) and above 160 dB re 1 [mu]Pa (rms) 
for non-explosive impulsive (e.g., seismic airguns) or intermittent 
(e.g., scientific sonar) sources.
    SIO's proposed activity includes the use of impulsive seismic 
sources, and therefore the 160 dB re 1 [mu]Pa (rms) is applicable.
    Level A harassment for non-explosive sources--NMFS' Technical 
Guidance for Assessing the Effects of Anthropogenic Sound on Marine 
Mammal Hearing (Version 2.0) (NMFS, 2018) identifies dual criteria to 
assess auditory injury (Level A harassment) to five different marine 
mammal groups (based on hearing sensitivity) as a result of exposure to 
noise from two different types of sources (impulsive or non-impulsive). 
SIO's proposed activity includes the use of impulsive seismic sources.
    These thresholds are provided in the table below. The references, 
analysis, and methodology used in the development of the thresholds are 
described in NMFS 2018 Technical Guidance, which may be accessed at 
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.
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Ensonified Area

    Here, we describe operational and environmental parameters of the 
activity that will feed into identifying the area ensonified above the 
acoustic thresholds, which include source levels and transmission loss 
coefficient.
    The proposed survey would entail the use of a 2-airgun array with a 
total discharge of 90 in\3\ at a two depth of 2-4 m. Lamont-Doherty 
Earth Observatory (L-DEO) model results are used to determine the 160 
dBrms radius for the 2-airgun array in deep water (> 1,000 
m) down to a maximum water depth of 2,000 m. Received sound levels were 
predicted by L-DEO's model (Diebold et al., 2010) as a function of 
distance from the airguns, for the two 45 in\3\ airguns. This modeling 
approach uses ray tracing for the direct wave traveling from the array 
to the receiver and its associated source ghost (reflection at the air-
water interface in the vicinity of the array), in a constant-velocity 
half-space (infinite homogenous 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 (~600-1,100 m), and shallow water 
(~50 m) in the Gulf of Mexico in 2007-2008 (Tolstoy et al., 2009; 
Diebold et al., 2010).
    For deep and intermediate water cases, the field measurements 
cannot be used readily to derive the Level A and Level B harassment 
isopleths, as at those sites the calibration hydrophone was located at 
a roughly constant depth of 350-550 m, which may not intersect all the 
SPL isopleths at their widest point from the sea surface down to the 
maximum relevant water depth (~2,000 m) for marine mammals. At short 
ranges, where the direct arrivals dominate and the effects of seafloor 
interactions are minimal, the data at the deep sites are suitable for 
comparison with modeled levels at the depth of the calibration 
hydrophone. At longer ranges, the comparison with the model--
constructed from the maximum SPL through the entire water column at 
varying distances from the airgun array--is the most relevant.

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    In deep and intermediate water depths, comparisons at short ranges 
between sound levels for direct arrivals recorded by the calibration 
hydrophone and model results for the same array tow depth are in good 
agreement (see Figures 12 and 14 in Appendix H of NSF-USGS 2011). 
Consequently, isopleths falling within this domain can be predicted 
reliably by the L-DEO model, although they may be imperfectly sampled 
by measurements recorded at a single depth. At greater distances, the 
calibration data show that seafloor-reflected and sub-seafloor-
refracted arrivals dominate, whereas the direct arrivals become weak 
and/or incoherent. Aside from local topography effects, the region 
around the critical distance is where the observed levels rise closest 
to the model curve. However, the observed sound levels are found to 
fall almost entirely below the model curve. Thus, analysis of the Gulf 
of Mexico calibration measurements demonstrates that although simple, 
the L-DEO model is a robust tool for conservatively estimating 
isopleths.
    The proposed surveys would acquire data with two 45-in\3\ guns at a 
tow depth of 2-4 m. For deep water (>1,000 m), we use the deep-water 
radii obtained from L-DEO model results down to a maximum water depth 
of 2,000 m for the airgun array with 2-m and 8-m airgun separation. The 
radii for intermediate water depths (100-1,000 m) are derived from the 
deep-water ones by applying a correction factor (multiplication) of 
1.5, such that observed levels at very near offsets fall below the 
corrected mitigation curve (see Figure 16 in Appendix H of NSF-USGS 
2011).
    L-DEO's modeling methodology is described in greater detail in 
SIO's IHA application. The estimated distances to the Level B 
harassment isopleths for the two proposed airgun configurations in each 
water depth category are shown in Table 5.

 Table 5--Predicted Radial Distances from R/V Thompson Seismic Source to
         Isopleths Corresponding to Level B Harassment Threshold
------------------------------------------------------------------------
                                                             Predicted
                                                           distances (m)
      Airgun configuration           Water depth (m)         to 160 dB
                                                          received sound
                                                               level
------------------------------------------------------------------------
Two 45 in\3\ guns, 2-m           >1,000 (deep)..........         \a\ 539
 separation.                     100-1,000                       \b\ 809
                                  (intermediate).
Two 45 in\3\ guns, 8-m           >1,000 (deep)..........         \a\ 578
 separation.                     100-1,000                       \b\ 867
                                  (intermediate).
------------------------------------------------------------------------
\a\ Distance based on L-DEO model results.
\b\ Distance based on L-DEO model results with a 1.5 x correction factor
  between deep and intermediate water depths.
\c\ Distance based on empirically derived measurements in the Gulf of
  Mexico with scaling applied to account for differences in tow depth.

    Predicted distances to Level A harassment isopleths, which vary 
based on marine mammal hearing groups, were calculated based on 
modeling performed by L-DEO using the NUCLEUS software program and the 
NMFS User Spreadsheet, described below. The updated acoustic thresholds 
for impulsive sounds (e.g., airguns) contained in the Technical 
Guidance were presented as dual metric acoustic thresholds using both 
SELcum and peak sound pressure metrics (NMFS 2018). As dual 
metrics, NMFS considers onset of PTS (Level A harassment) to have 
occurred when either one of the two metrics is exceeded (i.e., metric 
resulting in the largest isopleth). The SELcum metric 
considers both level and duration of exposure, as well as auditory 
weighting functions by marine mammal hearing group. In recognition of 
the fact that the requirement to calculate Level A harassment 
ensonified areas could be more technically challenging to predict due 
to the duration component and the use of weighting functions in the new 
SELcum thresholds, NMFS developed an optional User 
Spreadsheet that includes tools to help predict a simple isopleth that 
can be used in conjunction with marine mammal density or occurrence to 
facilitate the estimation of take numbers.
    The SELcum for the 2-GI airgun array is derived from 
calculating the modified farfield signature. The farfield signature is 
often used as a theoretical representation of the source level. To 
compute the farfield signature, the source level is estimated at a 
large distance (right) below the 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, it has been recognized that the 
source level from the theoretical farfield signature is never 
physically achieved at the source when the source is an array of 
multiple airguns separated in space (Tolstoy et al., 2009). Near the 
source (at short ranges, distances <1 km), the pulses of sound pressure 
from each individual airgun in the source array do not stack 
constructively as they do for the theoretical farfield signature. The 
pulses from the different airguns spread out in time such that the 
source levels observed or modeled are the result of the summation of 
pulses from a few airguns, not the full array (Tolstoy et al., 2009). 
At larger distances, away from the source 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 interactions of the two 
airguns that occur near the source center and is calculated as a point 
source (single airgun), the modified farfield signature is a more 
appropriate measure of the sound source level for large arrays. For 
this smaller array, the modified farfield changes will be 
correspondingly smaller as well, but we use this method for consistency 
across all array sizes.
    SIO used the same acoustic modeling as Level B harassment with a 
small grid step in both the inline and depth directions to estimate the 
SELcum and peak SPL. The propagation modeling takes into 
account all airgun interactions at short distances from the source 
including interactions between subarrays using the NUCLEUS software to 
estimate the notional signature and the MATLAB software to calculate 
the pressure signal at each mesh point of a grid. For a more complete 
explanation of this modeling approach, please see Appendix A: 
Determination of Mitigation Zones in SIO's IHA application.
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    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 Thompson's airgun array (modeled in 1 
Hz bands) was used to make adjustments (dB) to the unweighted spectrum 
levels, by frequency, according to the weighting functions for each 
relevant marine mammal hearing group. These adjusted/weighted spectrum 
levels were then converted to pressures ([mu]Pa) in order to integrate 
them over the entire broadband spectrum, resulting in broadband 
weighted source levels by hearing group that could be directly 
incorporated within the User Spreadsheet (i.e., to override the 
Spreadsheet's more simple weighting factor adjustment). Using the User 
Spreadsheet's ``safe distance'' methodology for mobile sources 
(described by Sivle et al., 2014) with the hearing group-specific 
weighted source levels, and inputs assuming spherical spreading 
propagation and source velocities and shot intervals provided in SIO's 
IHA application, potential radial distances to auditory injury zones 
were calculated for SELcum thresholds, for both array 
configurations.
    Inputs to the User Spreadsheet in the form of estimated SLs are 
shown in Table 6. User Spreadsheets used by SIO to estimate distances 
to Level A harassment isopleths for the two potential airgun array 
configurations are shown in Tables A-4 and A-5 in Appendix A of SIO's 
IHA application. Outputs from the User Spreadsheet in the form of 
estimated distances to Level A harassment isopleths are shown in Table 
7. As described above, NMFS considers onset of PTS (Level A harassment) 
to have occurred when either one of the dual metrics (SELcum 
or Peak SPLflat) is exceeded (i.e., metric resulting in the 
largest isopleth).

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    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 take by 
Level A harassment. 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.
    SIO determined that the preferred source of density data for marine 
mammal species that might be encountered in the proposed survey areas 
in the South Atlantic Ocean was Di Tullio et al. (2016). The rationale 
for using these data was that these surveys were conducted offshore 
along the continental slope at the same latitudes as the proposed 
seismic surveys and so come from a similar season, water depth 
category, and climatic region in the southern Atlantic Ocean. When data 
for species expected to occur in the proposed seismic survey areas were 
not available in Di Tullio et al. (2016), data from White et al. (2002) 
was used as calculated in LGL/NSF (2019) because they came from an area 
which was slightly south of the proposed project area but well north of 
the AECOM/NSF (2014) study area. An exception was made for the southern 
right whale, for which densities from AECOM/NSF (2014) were higher and 
thus more conservative. Next data came from AECOM/NSF (2014); although 
they come from an area south of the proposed project area, they were 
the next best data available for those species. For species not 
included in these sources stated above, data came from from de Boer 
(2010), Garaffo et al. (2011), NOAA-SWFSC LOA (2013 in AECOM/NSF 2014), 
Wedekin et al. (2014), Bradford et al. (2017), and Mannocci et al. 
(2017). When densities were not directly available from the above 
studies, they were estimated using sightings and effort reported in 
those sources. Densities calculated from de Boer (2010) come from LGL/
NSF (2016); densities from White et al. (2002), Garaffo et al. (2011), 
and Wedekin et al. (2014) are from LGL/NSF (2019). Data sources and 
density calculations are described in detail in Appendix B of SIO's IHA 
application. For some species, the densities derived from past surveys 
may not be representative of the densities that would be encountered 
during the proposed seismic surveys. However, the approach used is 
based on the best

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available data. Estimated densities used to inform take estimates are 
presented in Table 8.

      Table 8--Marine Mammal Densities in the Proposed Survey Area
------------------------------------------------------------------------
                                                              Estimated
                          Species                            density (#/
                                                              km\2\) \a\
------------------------------------------------------------------------
                              LF Cetaceans
------------------------------------------------------------------------
Southern right whale.......................................     0.007965
Pygmy right whale..........................................         N.A.
Blue whale.................................................     0.000051
Fin whale..................................................     0.000356
Sei whale..................................................     0.000086
Bryde's whale..............................................     0.000439
Common (dwarf) minke whale.................................     0.077896
Antarctic minke whale......................................     0.077896
Humpback whale.............................................     0.000310
------------------------------------------------------------------------
                              MF Cetaceans
------------------------------------------------------------------------
Sperm whale................................................     0.005975
Arnoux's beaked whale......................................     0.011379
Cuvier's beaked whale......................................     0.000548
Southern bottlenose whale..................................     0.007906
Shepherd's beaked whale....................................     0.009269
Blainville's beaked whale..................................     0.000053
Gray's beaked whale........................................     0.001885
Hector's beaked whale......................................     0.000212
Gervais' beaked whale......................................     0.001323
True's beaked whale........................................     0.000053
Strap-toothed beaked whale.................................     0.000582
Andrew's beaked whale......................................     0.000159
Spade-toothed beaked whale.................................     0.000053
Risso's dolphin............................................     0.010657
Rough-toothed dolphin......................................     0.005954
Common bottlenose dolphin..................................     0.040308
Pantropical spotted dolphin................................     0.003767
Atlantic spotted dolphin...................................     0.213721
Spinner dolphin............................................     0.040720
Clymene dolphin............................................     0.006800
Striped dolphin............................................     0.004089
Short-beaked common dolphin................................     0.717166
Fraser's dolphin...........................................     0.021040
Dusky dolphin..............................................     0.012867
Southern right whale dolphin...............................     0.006827
Killer whale...............................................     0.000266
Short-finned pilot whale...................................     0.002085
Long-finned pilot whale....................................     0.021379
False killer whale.........................................     0.000882
Pygmy killer whale.........................................     0.000321
Melon-headed whale.........................................     0.003540
------------------------------------------------------------------------
                              HF Cetaceans
------------------------------------------------------------------------
Pygmy sperm whale..........................................     0.003418
Dwarf sperm whale..........................................     0.002582
Hourglass dolphin..........................................     0.011122
------------------------------------------------------------------------
                                Otariids
------------------------------------------------------------------------
Subantarctic fur seal......................................      0.00274
Cape fur seal..............................................         N.A.
------------------------------------------------------------------------
                                 Phocids
------------------------------------------------------------------------
Crabeater seal.............................................      0.00649
Leopard seal...............................................      0.00162
Southern elephant seal.....................................      0.00155
------------------------------------------------------------------------
N.A. indicates density estimate is not available.
Species in italics are listed under the ESA as endangered.
\a\ See Appendix B in SIO's IHA application for density sources.

Take Calculation and Estimation

    Here we describe how the information provided above is brought 
together to produce a quantitative take estimate. In order to estimate 
the number of marine mammals predicted to be exposed to sound levels 
that would result in Level A harassment or Level B harassment, radial 
distances from the airgun array to predicted isopleths corresponding to 
the Level A harassment and Level B harassment thresholds are 
calculated, as described above. Those radial distances are then used to 
calculate the area(s) around the airgun array predicted to be 
ensonified to sound levels that exceed the Level A harassment and Level 
B harassment thresholds. The area estimated to be ensonified in a 
single day of the survey is then calculated (Table 9), based on the 
areas predicted to be ensonified around the array and the estimated 
trackline distance traveled per day. This number is then multiplied by 
the number of survey days. The product is then multiplied by 1.25 to 
account for the additional 25 percent contingency. This results in an 
estimate of the total area (km\2\) expected to be ensonified to the 
Level A and Level B harassment thresholds for each survey type (Table 
9).

                                  Table 9--Areas (km\2\) To Be Ensonified to Level A and Level B Harassment Thresholds
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                               Daily                                           Total
                Survey type                           Criteria               Relevant       ensonified     Total survey     25 percent      ensonified
                                                                           isopleth (m)    area (km\2\)        days          increase      area (km\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
5-kn survey...............................                                           Level B Harassment (160 dB)
                                           -------------------------------------------------------------------------------------------------------------
                                            Intermediate water..........             809           14.67              10            1.25          183.34
                                            Deep water..................             539          231.31              10            1.25         2891.42
                                           -------------------------------------------------------------------------------------------------------------
                                                                                         Level A Harassment
                                           -------------------------------------------------------------------------------------------------------------
                                            LF cetacean.................             6.5            2.89              10            1.25          36.125
                                            MF cetacean.................               1            0.44              10            1.25            5.55
                                            HF cetacean.................            34.6           15.37              10            1.25          192.13
                                            Phocids.....................             5.5            2.44              10            1.25           30.53
                                            Otariids....................             0.5            0.22              10            1.25            2.77
--------------------------------------------------------------------------------------------------------------------------------------------------------
8-kn survey...............................                                           Level B Harassment (160 dB)
                                           -------------------------------------------------------------------------------------------------------------
                                            Intermediate water..........             867           25.95               4            1.25          129.75
                                            Deep water..................             578          395.88               4            1.25         1979.38
                                           -------------------------------------------------------------------------------------------------------------
                                                                                         Level A Harassment
                                           -------------------------------------------------------------------------------------------------------------
                                            LF cetacean.................             3.1            2.21               4            1.25           11.04
                                            MF cetacean.................               0               0               4            1.25               0
                                            HF cetacean.................            34.8           24.78               4            1.25             124
                                            Phocids.....................               4            2.85               4            1.25           14.24
                                            Otariids....................               0               0               4            1.25               0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The total ensonified areas (km\2\) for each criteria presented in 
Table 9 were summed to determine the total ensonified area for all 
survey activities (Table 10).

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         Table 10--Total Ensonified Areas (km2) for All Surveys
------------------------------------------------------------------------
                                                                Total
                                                              ensonified
                          Criteria                               area
                                                             (km\2\) for
                                                             all surveys
------------------------------------------------------------------------
160 dB Level B (all depths)................................      5183.89
160 dB Level B (intermediate water)........................       313.09
160 dB Level B (deep water)................................      4870.80
LF cetacean Level A........................................        47.11
MF cetacean Level A........................................         5.55
HF cetacean Level A........................................       316.04
Phocids Level A............................................        44.77
Otariids Level A...........................................         2.77
------------------------------------------------------------------------

    The marine mammals predicted to occur within these respective 
areas, based on estimated densities (Table 8), are assumed to be 
incidentally taken. While some takes by Level A harassment have been 
estimated, based on the nature of the activity and in consideration of 
the proposed mitigation measures (see Proposed Mitigation section 
below), Level A take is not expected to occur and has not been proposed 
to be authorized. Estimated exposures for the proposed survey are shown 
in Table 11.
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    It should be noted that the proposed take numbers shown in Table 11 
are expected 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 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, and in 
recognition of the uncertainties in the density estimates used to 
estimate take as described above. Additionally, marine mammals would be 
expected to move away from a loud sound source that represents an 
aversive stimulus, such as an airgun array, potentially reducing the 
likelihood of takes by Level A harassment. However, the extent to which 
marine mammals would move away from the sound source is difficult to 
quantify and is, therefore, not accounted for in the take estimates.

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 
mitigation measures for marine mammals. Mitigation measures that would 
be adopted during the proposed surveys include (1) Vessel-based visual 
mitigation monitoring; (2) Establishment of a marine mammal exclusion 
zone (EZ) and buffer zone; (3) shutdown procedures; (4) ramp-up 
procedures;

[[Page 51922]]

and (4) vessel strike avoidance measures.

Vessel-Based Visual Mitigation Monitoring

    Visual monitoring requires the use of trained observers (herein 
referred to as visual PSOs) to scan the ocean surface visually for the 
presence of marine mammals. 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 Thompson 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 
EZ (as described below).
    During seismic operations, three visual PSOs would be based aboard 
the Thompson. PSOs would be appointed by SIO with NMFS approval. One 
dedicated PSO would monitor the EZ during all daytime seismic 
operations. PSO(s) would be on duty in shifts of duration no longer 
than 4 hours. Other vessel 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 Thompson is a suitable platform from which PSOs would watch for 
marine mammals. Standard equipment for marine mammal observers would be 
7 x 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 shall 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 seismic survey. One ``experienced'' 
visual PSO will be designated as the lead for the entire protected 
species observation team. The lead will serve as primary point of 
contact for the vessel operator.

Exclusion Zone and Buffer Zone

    An EZ is a defined area within which occurrence of a marine mammal 
triggers mitigation action intended to reduce the potential for certain 
outcomes, e.g., auditory injury, disruption of critical behaviors. The 
PSOs would establish a minimum EZ with a 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 
Shutdown 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 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 the National Science 
Foundation 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 in\3\. 
Thus the 100-m EZ proposed for this survey is consistent with the PEIS.
    Our intent in prescribing a standard EZ 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 will 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 EZ) will 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.
    An extended EZ of 500 m would be enforced for all beaked whales, 
Kogia species, and Southern right whales. SIO would also enforce a 500-
m EZ for aggregations of six or more large whales (i.e., sperm whale or 
any baleen whale) that does not appear to be traveling (e.g., feeding, 
socializing, etc.) or a large whale with a calf (calf defined as an 
animal less than two-thirds the body size of an adult observed to be in 
close association with an adult).

Shutdown Procedures

    If a marine mammal is detected outside the EZ but is likely to 
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;
     it has not been seen within the 100-m EZ for 15 min in the 
case of small odontocetes and pinnipeds; or
     it has not been seen within the 100-m EZ for 30 min in the 
case of mysticetes and large odontocetes (including sperm whale beaked 
whales), and also pygmy sperm, dwarf 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--
Delphinus, Lagenodelphis,

[[Page 51923]]

Lagenorhynchus, Lissodelphis, Stenella, Steno, and Tursiops--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 include 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 above, auditory injury is extremely unlikely 
to occur for mid-frequency cetaceans (e.g., delphinids), as this group 
is relatively insensitive to sound produced at the predominant 
frequencies in an airgun pulse while also having a relatively high 
threshold for the onset of auditory injury (i.e., permanent threshold 
shift).
    A large body of anecdotal evidence indicates that small 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 
Thompson 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 power-down/shutdown 
requirement for large delphinoids would not have similar impacts in 
terms of either practicability for the applicant or corollary increase 
in sound energy output and time on the water. We do anticipate some 
benefit for a shutdown requirement for large delphinoids in that it 
simplifies somewhat the total range of decision-making for PSOs and may 
preclude any potential for physiological effects other than to the 
auditory system as well as some more severe behavioral reactions for 
any such animals in close proximity to the source vessel.
    Shutdown of the acoustic source would also be required upon 
observation of a species for which authorization has not been granted, 
or a species for which authorization has been granted but the 
authorized number of takes are met, observed approaching or within the 
Level A or Level B harassment zones.

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 for longer than 15 minutes. Ramp-up would 
begin with the activation of one 45 in\3\ airgun, with the second 45 
in\3\ airgun activated after 5 minutes.
    Two 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 the EZ or buffer zone, 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 
ramp-up 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.

Vessel Strike Avoidance Measures

    Vessel strike avoidance measures are intended to minimize the 
potential for collisions with marine mammals. These requirements do not 
apply in any case where compliance would create an imminent and serious 
threat to a person or vessel or to the extent that a vessel is 
restricted in its ability to maneuver and, because of the restriction, 
cannot comply.
    The proposed measures include the following: Vessel operator and 
crew would maintain a vigilant watch for all marine mammals and slow 
down or stop the vessel or alter course to avoid striking any marine 
mammal. A visual observer aboard the vessel would monitor a vessel 
strike avoidance zone around the vessel according to the parameters 
stated below. Visual observers monitoring the vessel strike avoidance 
zone would be either third-party observers or crew members, but crew 
members responsible for these duties would be provided sufficient 
training to distinguish marine mammals from other phenomena. Vessel 
strike avoidance measures would be followed during surveys and while in 
transit.
    The vessel would maintain a minimum separation distance of 100 m 
from large whales (i.e., baleen whales and sperm whales). If a large 
whale is within 100 m of the vessel, the vessel would reduce speed and 
shift the engine to neutral, and would not engage the engines until the 
whale has moved outside of the vessel's path and the minimum separation 
distance has been

[[Page 51924]]

established. If the vessel is stationary, the vessel would not engage 
engines until the whale(s) has moved out of the vessel's path and 
beyond 100 m. The vessel would maintain a minimum separation distance 
of 50 m from all other marine mammals (with the exception of delphinids 
of the genera Delphinus, Lagenodelphis, Lagenorhynchus, Lissodelphis, 
Stenella, Steno, and Tursiops that approach the vessel, as described 
above). If an animal is encountered during transit, the vessel would 
attempt to remain parallel to the animal's course, avoiding excessive 
speed or abrupt changes in course. Vessel speeds would be reduced to 10 
kn or less when mother/calf pairs, pods, or large assemblages of 
cetaceans are observed near the vessel.
    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 noise); (2) 
affected species (e.g., life history, dive patterns); (3) co-occurrence 
of marine mammal species with the action; or (4) biological or 
behavioral context of exposure (e.g., age, calving or feeding areas);
     Individual marine mammal responses (behavioral or 
physiological) to acoustic stressors (acute, chronic, or cumulative), 
other stressors, or cumulative impacts from multiple stressors;
     How anticipated responses to stressors impact either: (1) 
Long-term fitness and survival of individual marine mammals; or (2) 
populations, species, or stocks;
     Effects on marine mammal habitat (e.g., marine mammal prey 
species, acoustic habitat, or other important physical components of 
marine mammal habitat); and
     Mitigation and monitoring effectiveness.
    SIO described marine mammal monitoring and reporting plan within 
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 Thompson. PSOs would be appointed by SIO with NMFS 
approval. The 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, 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.
    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., 7x50 Fujinon) and with the naked eye. At night, PSOs would be 
equipped with night-vision equipment.
    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; and
    (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 (e.g., 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

[[Page 51925]]

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; and
    (5) Data on the behavior and movement patterns of marine mammals 
seen at times with and without seismic activity.

Reporting

    A draft report would be submitted to NMFS within 90 days after the 
end of the survey. The report would describe the operations that were 
conducted and sightings of marine mammals near the operations. The 
report would provide full documentation of methods, results, and 
interpretation pertaining to all monitoring and would summarize the 
dates and locations of seismic operations, and all marine mammal 
sightings (dates, times, locations, activities, associated seismic 
survey activities). The report would also include estimates of the 
number and nature of exposures that occurred above the harassment 
threshold based on PSO observations, including an estimate of those 
that were not detected in consideration of both the characteristics and 
behaviors of the species of marine mammals that affect detectability, 
as well as the environmental factors that affect detectability.
    The draft report shall also include geo-referenced time-stamped 
vessel tracklines for all time periods during which airguns were 
operating. Tracklines should include points recording any change in 
airgun status (e.g., when the airguns began operating, when they were 
turned off, or when they changed from full array to single gun or vice 
versa). GIS files shall be provided in ESRI shapefile format and 
include the UTC date and time, latitude in decimal degrees, and 
longitude in decimal degrees. All coordinates shall be referenced to 
the WGS84 geographic coordinate system. In addition to the report, all 
raw observational data shall be made available to NMFS. The 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 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 on the draft report.

Negligible Impact Analysis and Determination

    NMFS has defined negligible impact as an impact resulting from the 
specified activity that cannot be reasonably expected to, and is not 
reasonably likely to, adversely affect the species or stock through 
effects on annual rates of recruitment or survival (50 CFR 216.103). A 
negligible impact finding is based on the lack of likely adverse 
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough 
information on which to base an impact determination. In addition to 
considering estimates of the number of marine mammals that might be 
``taken'' through harassment, NMFS considers other factors, such as the 
likely nature of any responses (e.g., intensity, duration), the context 
of any responses (e.g., critical reproductive time or location, 
migration), as well as effects on habitat, and the likely effectiveness 
of the mitigation. We also assess the number, intensity, and context of 
estimated takes by evaluating this information relative to population 
status. Consistent with the 1989 preamble for NMFS's implementing 
regulations (54 FR 40338; September 29, 1989), the impacts from other 
past and ongoing anthropogenic activities are incorporated into this 
analysis via their impacts on the environmental baseline (e.g., as 
reflected in the regulatory status of the species, population size and 
growth rate where known, ongoing sources of human-caused mortality, or 
ambient noise levels).
    To avoid repetition, our analysis applies to all 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, 
neither stranding nor vessel strike are expected to occur.
    No takes by Level A harassment are proposed to be authorized. The 
100-m exclusion zone encompasses the Level A harassment isopleths for 
all marine mammal hearing groups, and is expected to prevent animals 
from being exposed to sound levels that would cause PTS. 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 Thompson's approach due to the vessel's 
relatively low speed when conducting seismic surveys. We expect that 
any instances of take would be in the form of short-term Level B 
behavioral harassment in the form of temporary avoidance of the area or 
short-term 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). 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).
    Potential impacts to marine mammal habitat were discussed 
previously in this document (see Potential Effects of the Specified 
Activity on Marine Mammals and their Habitat). Marine mammal habitat 
may be impacted by elevated sound levels, but these impacts would be 
temporary. Prey species are mobile and are broadly distributed 
throughout the project 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 feeding, 
mating or calving areas known to be biologically important to marine 
mammals within the proposed project area.
    As described above, marine mammals in the survey area are not 
assigned to NMFS stocks. For purposes of the small numbers analysis we 
rely on the best available information on the abundance estimates for 
the species of marine mammals that could be taken. The activity is 
expected to impact a very small percentage of all marine mammal 
populations, most cases 0.1 percent or

[[Page 51926]]

less that would be affected by SIO's proposed survey (less than 5.3 
percent each for all marine mammal populations where abundance 
estimates exist). 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 (14 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: Fin, sei, blue, sperm, and southern right 
whales. We are proposing to authorize very small numbers of takes for 
these species (Table 11), relative to their population sizes (again, 
for species where population abundance estimates exist), 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 ESA-listed 
marine mammals within the project area; 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 due to SIO's 
proposed seismic survey would result in only short-term (temporary and 
short in duration) effects of Level B harassment to individuals 
exposed. Marine mammals may temporarily avoid the immediate area, but 
are not expected to permanently abandon the area. Major shifts in 
habitat use, distribution, or foraging success are not expected. NMFS 
does not anticipate the proposed take estimates to impact annual rates 
of recruitment or survival.
    In summary and as described above, the following factors primarily 
support our preliminary determination that the impacts resulting from 
this activity are not expected to adversely affect the species or stock 
through effects on annual rates of recruitment or survival:
     No mortality is anticipated or authorized;
     No take by Level A harassment 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 (14 days) would further limit the 
potential impacts of any temporary behavioral changes that would occur;
     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; and
     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 Sections 101(a)(5)(A) and (D) of the MMPA for 
specified activities other than military readiness activities. The MMPA 
does not define small numbers and so, in practice, where estimated 
numbers are available, NMFS compares the number of individuals taken to 
the most appropriate estimation of abundance of the relevant species or 
stock in our determination of whether an authorization is limited to 
small numbers of marine mammals. Additionally, other qualitative 
factors may be considered in the analysis, such as the temporal or 
spatial scale of the activities.
    The numbers of marine mammals that we authorize to be taken would 
be considered small relative to the relevant populations (less than 5.3 
percent for all species) for the species for which abundance estimates 
are available. No known current worldwide or regional population 
estimates are available for 16 species under NMFS jurisdiction that 
could be incidentally taken as a result of the proposed survey: The 
pygmy right whale, pygmy sperm whale, dwarf sperm whale, Shepherd's 
beaked whale, Blainville's beaked whale, Hector's beaked whale, 
Gervais' beaked whale, True's beaked whale, Andrew's beaked whale, 
spade-toothed beaked whale, rough-toothed dolphin, spinner dolphin, 
Clymene dolphin, Fraser's dolphin, southern right whale dolphin, false 
killer whale, pygmy killer whale, and Melon-headed whale and Cape fur 
seal.
    NMFS has reviewed the geographic distributions and habitat 
preferences of these species in determining whether the numbers of 
takes authorized herein are likely to represent small numbers. Pygmy 
right whales have a circumglobal distribution and occur throughout 
coastal and oceanic waters in the Southern Hemisphere (between 30 to 
55[deg] S) (Jefferson et al. 2015; Kemper 2018). Pygmy and dwarf sperm 
whales occur in deep waters on the outer continental shelf and slope in 
tropical to temperate waters of the Atlantic, Indian, and Pacific 
Oceans, but their precise distributions are unknown because much of 
what we know of the species comes from strandings (McAlpine 2018). 
Based on stranding records and the known habitat preferences of beaked 
whales in general, Shepherd's beaked whales are assumed to have a 
circumpolar distribution in deep, cold temperate waters of the Southern 
Ocean (Pitman et al., 2006; Mead 2018). Blainville's beaked whale is 
the most widely distributed beaked Mesoplodon species with sightings 
and stranding records throughout the North and South Atlantic Ocean 
(MacLeod et al., 2006; Pitman 2018). Hector's beaked whales are found 
in cold temperate waters throughout the southern hemisphere between 
35[deg] S and 55[deg] S (Zerbini and Secchi 2001; Pitman 2018). True's 
beaked whale has a disjunct, antitropical distribution (Jefferson et 
al. 2015). In the Southern Hemisphere, it is known to occur in South 
Africa, South

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America, and Australia (Findlay et al. 1992; Souza et al. 2005; MacLeod 
and Mitchell 2006; MacLeod et al. 2006; Best et al. 2009). Andrew's 
beaked whales have a circumpolar distribution north of the Antarctic 
Convergence to 32[deg] S (MacLeod et al., 2006; Pitman 2018). Andrew's 
beaked whale is known only from stranding records between 32[deg] S and 
55[deg] S, with more than half of the strandings occurring in New 
Zealand (Jefferson et al. 2015). Gervais' beaked whale is generally 
considered to be a North Atlantic species, it likely occurs in deep 
waters of the temperate and tropical Atlantic Ocean in both the 
northern and southern hemispheres (Jefferson et al. 2015). The 
southernmost stranding record was reported for S[atilde]o Paulo, 
Brazil, possibly expanding the known distributional range of this 
species southward (Santos et al. 2003), but the distribution range of 
Gervais' beaked whale is not generally known to extend as far south as 
the proposed project area. The spade-toothed beaked whale is considered 
relatively rare and is known from only four records, three from New 
Zealand and one from Chile (Thompson et al. 2012). The rough-toothed 
dolphin is distributed worldwide in tropical and subtropical waters 
(Jefferson et al. 2015). Rough-toothed dolphins are generally seen in 
deep, oceanic water, although it is known to occur in coastal waters of 
Brazil (Jefferson et al., 2015; Cardoso et al., 2019). The Clymene 
dolphin only occurs in tropical and subtropical waters of the Atlantic 
Ocean (Jefferson et al., 2015). Clymeme dolphins inhabits areas where 
water depths are 700-4500 m or deeper (Fertl et al., 2003). Fraser's 
dolphins are distributed in tropical oceanic waters worldwide, between 
30[deg] N and 30[deg] S and generally inhabits deeper, offshore water 
(Moreno et al., 2003, Dolar 2018). The southern right whale dolphin is 
distributed between the Subtropical and Antarctic convergences in the 
Southern Hemisphere, generally between ~30[deg] S and 65[deg] S 
(Jefferson et al., 2015; Lipsky and Brownell 2018). The false killer 
whale is found worldwide in tropical and temperate waters, generally 
between 50[deg] N and 50[deg] S (Odell and McClune 1999). It is widely 
distributed, but not abundant anywhere (Carwardine 1995). The false 
killer whale generally inhabits deep, offshore waters, but sometimes is 
found over the continental shelf and occasionally moves into very 
shallow water (Jefferson et al. 2015; Baird 2018b). The pygmy killer 
whale has a worldwide distribution in tropical and subtropical waters, 
generally not ranging south of 35[deg] S (Jefferson et al. 2015). The 
melon-headed whale is an oceanic species found worldwide in tropical 
and subtropical waters from ~40[deg] N to 35[deg] S (Jefferson et al. 
2015). The Cape fur seal currently breeds at 40 colonies along the 
coast of South Africa, Namibia, and Angola, including on the mainland 
and nearshore islands (Kirkman et al. 2013). There have been several 
new breeding colonies established in recent years, as the population 
has shifted northward (Kirkman et al. 2013). More than half of the seal 
population occurs in Namibia (Wickens et al. 1991). High densities have 
been observed between 30 and 60 nm from shore, with densities dropping 
farther offshore (Thomas and Sch[uuml]lein 1988).
    Based on the broad spatial distributions and habitat preferences of 
these species relative to the areas where SIO's proposed survey will 
occur, NMFS preliminarily concludes that the proposed take of these 
species likely represent small numbers relative to the affected 
species' overall population sizes, though we are unable to quantify the 
take numbers as a percentage of population.
    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 Endangered Species Act of 1973 (ESA: 16 
U.S.C. 1531 et seq.) requires that each Federal agency insure that any 
action it authorizes, funds, or carries out is not likely to jeopardize 
the continued existence of any endangered or threatened species or 
result in the destruction or adverse modification of designated 
critical habitat. To ensure ESA compliance for the issuance of IHAs, 
NMFS consults internally, in this case with the ESA Interagency 
Cooperation Division, whenever we propose to authorize take for 
endangered or threatened species.
    NMFS is proposing to authorize take of fin, sei, blue, sperm, and 
southern right whales which are listed under the ESA. The Permit and 
Conservation Division has requested initiation of Section 7 
consultation with the Interagency Cooperation Division for the issuance 
of this IHA. NMFS will conclude the ESA consultation prior to reaching 
a determination regarding the proposed issuance of the authorization.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to SIO for conducting a marine geophysical survey in the 
southwest Atlantic Ocean in November and December 2019, provided the 
previously mentioned mitigation, monitoring, and reporting requirements 
are incorporated. A draft of the proposed IHA can be found at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act.

Request for Public Comments

    We request comment on our analyses, the proposed authorization, and 
any other aspect of this Notice of Proposed IHA for the proposed 
survey. We also request comment on the potential for renewal of this 
proposed IHA as described in the paragraph below. Please include with 
your comments any supporting data or literature citations to help 
inform our final decision on the request for MMPA authorization.
    On a case-by-case basis, NMFS may issue a one-year IHA renewal with 
an additional 15 days for public comments when (1) another year of 
identical or nearly identical activities as described in the Specified 
Activities section of this notice is planned or (2) the activities as 
described in the Specified Activities section of this notice would not 
be completed by the time the IHA expires and a Renewal would allow for 
completion of the activities beyond that described in the Dates and 
Duration section of this notice, provided all of the following 
conditions are met:
     A request for renewal is received no later than 60 days 
prior to expiration of the current IHA;
     The request for renewal must include the following:
    (1) An explanation that the activities to be conducted under the 
requested Renewal are identical to the activities analyzed under the 
initial IHA, are a subset of the activities, or include changes so 
minor (e.g., reduction in pile size) that the changes do not affect the 
previous analyses, mitigation and monitoring requirements, or take 
estimates (with the exception of

[[Page 51928]]

reducing the type or amount of take because only a subset of the 
initially analyzed activities remain to be completed under the 
Renewal); and
    (2) A preliminary monitoring report showing the results of the 
required monitoring to date and an explanation showing that the 
monitoring results do not indicate impacts of a scale or nature not 
previously analyzed or authorized;
    Upon review of the request for Renewal, the status of the affected 
species or stocks, and any other pertinent information, NMFS determines 
that there are no more than minor changes in the activities, the 
mitigation and monitoring measures will remain the same and 
appropriate, and the findings in the initial IHA remain valid.

    Dated: September 24, 2019.
Donna S. Wieting,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2019-21090 Filed 9-27-19; 8:45 am]
BILLING CODE 3510-22-P