[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-
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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
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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
[[Page 51918]]
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
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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]
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