[Federal Register Volume 75, Number 171 (Friday, September 3, 2010)]
[Notices]
[Pages 54095-54114]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-22080]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XY12
Takes of Marine Mammals Incidental to Specified Activities; Low-
Energy Marine Seismic Survey in the Eastern Tropical Pacific Ocean Off
Central and South America, October-November 2010
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed Incidental Harassment Authorization; request
for comments.
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SUMMARY: NMFS has received an application from the Scripps Institution
of Oceanography (SIO) of the University of California for an Incidental
Harassment Authorization (IHA) to take marine mammals, by harassment,
incidental to conducting a low-energy marine seismic survey. Pursuant
to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments
on its proposal to issue an IHA to SIO to take, by Level B Harassment
only, 21 species of marine mammals during the specified activity.
DATES: Comments and information must be received no later than October
4, 2010.
ADDRESSES: Comments on the application should be addressed to Michael
Payne, Chief, Permits, Conservation and Education Division, Office of
Protected Resources, National Marine Fisheries Service, 1315 East-West
Highway, Silver Spring, MD 20910. The mailbox address for providing e-
mail comments is [email protected]. NMFS is not responsible for e-
mail comments sent to addresses other than the one provided here.
Comments sent via e-mail, including all attachments, must not exceed a
10-megabyte file size.
Instructions: All comments received are a part of the public record
and will generally be posted to http://www.nmfs.noaa.gov/pr/permits/incidental.htm without change. All Personal Identifying Information
(for example, name, address, etc.) voluntarily submitted by the
commenter may be publicly accessible. Do not submit Confidential
Business Information or otherwise sensitive or protected information.
A copy of the application containing a list of the references used
in this document may be obtained by writing to the address specified
above, telephoning the contact listed below (see FOR FURTHER
INFORMATION CONTACT), or visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm. The National Science
Foundation (NSF), which is providing funding for the proposed action,
has prepared a draft Environmental Assessment (EA) titled ``Marine
Geophysical Survey by the R/V Melville in the Pacific Ocean off Central
and South America, October-November 2010''. The NSF draft EA
incorporates an ``Environmental Assessment of a Marine Geophysical
Survey by the R/V Melville in the Pacific Ocean off Central and South
America, October-November 2010'', prepared by LGL Limited,
Environmental Research Associates, on behalf of NSF. These associated
documents, prepared in compliance with the National Environmental
Policy Act (NEPA), are also available at the same Internet address.
Documents cited in this notice may also be viewed, by appointment,
during regular business hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Ben Laws or Candace Nachman, Office of
Protected Resources, NMFS, (301) 713-2289.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.)
direct the Secretary of Commerce 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
[[Page 54096]]
authorization is provided to the public for review.
Authorization for incidental takings shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s), will not have an unmitigable adverse impact on the
availability of the species or stock(s) for subsistence uses (where
relevant), and if the permissible methods of taking and requirements
pertaining to the mitigation, monitoring and reporting of such takings
are set forth. NMFS has defined ``negligible impact'' in 50 CFR 216.103
as ``* * * an impact resulting from the specified activity that cannot
be reasonably expected to, and is not reasonably likely to, adversely
affect the species or stock through effects on annual rates of
recruitment or survival.''
Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the U.S. can apply for an authorization to
incidentally take small numbers of marine mammals by harassment.
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS review of
an application followed by a 30-day public notice and comment period on
any proposed authorizations for the incidental harassment of marine
mammals. Within 45 days of the close of the comment period, NMFS must
either issue or deny the authorization. Except with respect to certain
activities not pertinent here, the MMPA defines ``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
Summary of Request
NMFS received an application on May 28, 2010 from SIO for the
taking, by harassment, of marine mammals incidental to conducting, in
collaboration with Texas A&M University and with research funding
provided by the National Science Foundation, a low-energy marine
seismic survey. NMFS reviewed SIO's application and identified a number
of issues requiring further clarification. After addressing comments
from NMFS, SIO modified its application and submitted a revised
application on July 14, 2010. NMFS carefully evaluated SIO's
application, including their analyses, and determined that the
application is complete and provides sufficient data for NMFS to make
the necessary preliminary determinations pursuant to the MMPA. The July
14, 2010 application is the one available for public comment (see
ADDRESSES) and considered by NMFS for this proposed IHA.
The proposed survey will occur in the Eastern Tropical Pacific
Ocean (ETP), encompassing the area from approximately 8[deg] N-12[deg]
S and 80-91[deg] W, off the coasts of Costa Rica, Panama, Colombia,
Ecuador, and Peru, in International Waters and within the Exclusive
Economic Zones (EEZs) of Costa Rica, Panama, Colombia, and Ecuador, and
is scheduled to occur from October 19-November 14, 2010. Some minor
deviation from these dates is possible, depending on logistics and
weather. The survey will use a pair of Generator Injector (GI) airguns,
each with a discharge volume of 45 in\3\. Seismic airgun operations are
expected to result in the incidental take, by Level B harassment only,
of up to 21 species of marine mammals. These species include: Bryde's
whale; blue whale; sperm whale; humpback whale; Cuvier's beaked whale;
Blainville's beaked whale; pygmy beaked whale; gingko-toothed beaked
whale; rough-toothed dolphin; bottlenose dolphin; pantropical spotted
dolphin; spinner dolphin; striped dolphin; Fraser's dolphin; short-
beaked common dolphin; Risso's dolphin; melon-headed whale; pygmy
killer whale; false killer whale; killer whale; and short-finned pilot
whale.
Description of the Specified Activity
SIO plans to conduct a seismic survey as part of an integrated
geophysical and geochemical study. In addition to the GI airguns, a
multibeam echosounder (MBES) and a sub-bottom profiler (SBP) will be
utilized for research purposes. The planned survey will involve one
source vessel, the R/V Melville (Melville).
The purpose of this project is to better understand how marine
sediments record paleo-oceanographic information. The deposition of
sediments in the upper 500 m (1640.4 ft) of the sediment column will be
studied using known seismic horizons in the sediment column to estimate
rates of deposition downstream from potential sediment sources on the
topographic highs and to estimate loss from the ridges. The seismic
survey and associated coring and water sampling will allow comparisons
of geophysical estimates of the level of erosion from marine ridges and
highs with geochemical estimates of sediment focusing based upon the
distribution of Th-230, a particle-reactive isotope produced by the
decay of dissolved uranium in the water column. In addition, the study
will examine whether there are sediment sources for Th-230 in slowly-
accumulating sediments.
The Melville is expected to depart Puntarenas, Costa Rica, on
October 19, 2010, and spend approximately 15 days conducting seismic
surveys, 10 days collecting water and core samples, and approximately 2
days in transit, arriving at Arica, Chile, on November 14, 2010. At
each of four sites (see Figure 1 of SIO's application), seismic
operations will be conducted for approximately 2 days, and each water
sampling and coring station will be occupied for 1-2 days. Some minor
deviation from these dates is possible, depending on logistics and
weather.
The source vessel, the Melville, will deploy a pair of low-energy
GI airguns as an energy source at a depth of 2 m (each with a discharge
volume of 45 in\3\), plus either of two towed hydrophone streamers, one
725 m (2378.6 ft) long with 40 channels, and the other 350 m (1148.3
ft) long with 16 channels. Hydrophone streamers are towed at adjustable
depth to afford best reception of returning seismic signals, depending
upon surface conditions, but are typically towed in at approximately 10
m. The energy to the GI airgun is compressed air supplied by
compressors onboard the source vessel. As the GI airgun is towed along
the survey lines, the receiving systems will receive the returning
acoustic signals.
In addition to the GI airguns, an MBES and an SBP will be used
throughout the cruise, except while at water/core stations, to help
verify seafloor conditions at possible coring sites and to collect
additional seafloor bathymetric data. Passive geophysical sensors (a
gravimeter and a magnetometer) will also be operated continuously
throughout the entire cruise.
All potential incidental take, by harassment only, is expected to
result from the operation of the GI airguns. Take is not expected to
result from the use of the MBES or SBP, for reasons discussed below, or
from collision with the vessel because it is a single vessel, moving at
a relatively slow speed (operational speeds of approximately 11 km/hr
[6 knots] during seismic acquisition within the survey areas and 15-
18.5 km/hr [8-10 knots] between survey areas and stations), for a
relatively short period of time (approximately 30 days). It is likely
that any marine mammal would be able to avoid the vessel.
The seismic program will consist of approximately 5475 km (3402 mi)
of
[[Page 54097]]
survey lines, including turns (see Figure 1 of SIO's application).
Water depths at the seismic survey locations are approximately 1000-
4800 m (3280.8-15,748 ft). The GI airguns will be operated on a small
grid for approximately 45 hours at each of four sites (see Figure 1 of
SIO's application) where the 40-channel streamer will be used, and for
most of the time during transits between the sites, to the first site,
and after the last site, where the 12-channel streamer will be used.
There will be additional seismic operations associated with equipment
testing, startup, and possible line changes or repeat coverage of any
areas where initial data quality is sub-standard. Those additional
operations are allowed for in the estimated total line-kilometers given
above. The Melville is expected to depart Puntarenas, Costa Rica, on
October 19, 2010 and spend approximately 15 days conducting seismic
surveys, 10 days collecting water and core samples, and approximately 2
days in transit, arriving at Arica, Chile, on November 14, 2010.
All planned geophysical data acquisition activities will be
conducted by SIO with on-board assistance by the scientists who have
proposed the study. The Chief Scientist is Dr. Franco Marcantonio of
Texas A&M University. The vessel will be self-contained, and the crew
will live aboard the vessel for the entire cruise.
Vessel Specifications
The Melville has a length of 85 m (278.9 ft), a beam of 14 m (45.9
ft), and a maximum draft of 5 m (16.4 ft). The ship is powered by two
1385-hp diesel engines and a 900-hp retracting azimuthing bow thruster.
Operation speeds of approximately 11 km/hr (5.9 knots) and 15-18.5 km/
hr (8.1-10 knots) will be used during seismic acquisition within the
survey areas and between the areas and stations, respectively. When not
towing seismic survey gear, the Melville cruises at 21.7 km/hr (11.7
knots) and has a maximum speed of 25.9 km/hr (14 knots). The Melville
will also serve as the platform from which vessel-based protected
species observers (PSOs) will watch for animals before and during
airgun operations (discussed later in this document).
Acoustic Source Specifications
(1) Seismic Airguns
The Melville will tow a pair of 45-in\3\ Sercel GI airguns and a
streamer containing hydrophones along predetermined lines. Seismic
pulses will be emitted at intervals of 8-10 s. At speeds of
approximately 11-18.5 km/hr (5.9-10 knots), the 8-10 s spacing
corresponds to shot intervals of approximately 25-50 m (82-164 ft).
The generator chamber of each GI airgun, 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 two 45-in\3\ GI airguns will be towed 8 m (26.2 ft) apart
side by side, 21 m (68.9 ft) behind the Melville, at a depth of 2 m
(6.6 ft).
As the GI airgun is towed along the survey line, the towed
hydrophone array in the streamer receives the reflected signals and
transfers the data to the on-board processing system. Given the
relatively short streamer length behind the vessel, the turning rate of
the vessel while the gear is deployed is much higher than the limit of
five degrees per minute for a seismic vessel towing a streamer of more
typical length (greater than l km (0.6 mi)). Thus, the maneuverability
of the vessel is not limited much during operations.
The root mean square (rms) received levels that are used as impact
criteria for marine mammals are not directly comparable to the peak (pk
or 0-pk) or peak-to-peak (pk-pk) values normally used to characterize
source levels of airgun arrays. The measurement units used to describe
airgun sources, peak or peak-to-peak decibels, are always higher than
the rms decibels referred to in biological literature. A measured
received level of 160 dB re 1 [mu]Pa (rms) in the far field would
typically correspond to a peak measurement of approximately 170 dB and
to a peak-to-peak measurement of approximately 176-178 dB, as measured
for the same pulse received at the same location (Greene, 1997;
McCauley et al., 1998, 2000). The precise difference between rms and
peak or peak-to-peak values depends on the frequency content and
duration of the pulse, among other factors. However, the rms level is
always lower than the peak or peak-to-peak level for an airgun-type
source. The actual received level at any location in the water near the
GI airguns will not exceed the source level of the strongest individual
source. In this case, that will be about 224.6 dB re 1 [micro]Pa-m peak
or 229.8 dB re 1 [micro]Pa-m peak-to-peak. The dominant frequency
components of the GI airguns are 0-188 Hertz (Hz).
Received sound levels have been modeled by Lamont-Doherty Earth
Observatory (L-DEO) for a number of airgun configurations, including
two 45 in\3\ Nucleus G. Guns, in relation to distance and direction
from the airgun (see Figure 2 of SIO's application). The model does not
allow for bottom interactions and is most directly applicable to deep
water. Based on the modeling, estimates of the maximum distances from
the GI airguns where sound levels of 190, 180, and 160 dB re 1 [mu]Pa
(rms) are predicted to be received in deep (>1,000 m (3280.8 ft)) water
are shown in Table 1 below. Because the model results are for G. Guns,
which have more energy than GI airguns of the same size, the distances
in Table 1 overestimate the distances for the 45 in\3\ GI airguns.
(2) Multibeam Echosounder and Sub-Bottom Profiler
Along with the GI airgun operations, an MBES and a SBP will be
operated from the source vessel at certain times during the planned
study to help verify seafloor conditions at possible coring sites and
to collect additional seafloor bathymetric data.
The Kongsberg EM 122 MBES operates at 10.5-13 (usually 12)
kilohertz (kHz) and is hull-mounted on the Melville. The transmitting
beamwidth is 1[deg] fore-aft and 150[deg] athwartship. The maximum
source level is 242 dB re 1 [mu]Pa-m (rms). Each ``ping'' consists of
eight (in water >1000 m deep) or four (<1000 m deep) successive fan-
shaped transmissions, each ensonifying a sector that extends 1[deg]
fore-aft. Continuous-wave pulses increase from 2 to 15 ms long in water
depths up to 2600 m (8530.2 ft), and FM chirp pulses up to 100 ms long
are used in water >2600 m. The successive transmissions span an overall
cross-track angular extent of about 150[deg], with 2-ms gaps between
the pulses for successive sectors.
The Knudsen Engineering Model 320B/R SBP is a dual-frequency
transceiver designed to operate at 3.5 and/or 12 kHz. It is used in
conjunction with the MBES to provide data about the sedimentary
features that occur below the sea floor. The energy from the SBP is
directed downward via a 3.5-kHz transducer array mounted in the hull of
the Melville. The maximum power output of the 320B/R is 10 kilowatts
for the 3.5-kHz section and 2 kilowatts for the 12-kHz section. The
nominal beamwidth is 80[deg].
The pulse length for the 3.5-kHz section of the 320B/R is 0.8-24
ms, controlled by the system operator in regards to water depth and
reflectivity of the bottom sediments and will usually be 6, 12, or 24
ms at the water depths at the study sites and in transit from
Puntarenas and to Arica. The system produces one sound pulse and then
waits for its return before transmitting again. Thus, the pulse
[[Page 54098]]
interval is directly dependent upon water depth, and in this survey is
0.8-1.5 s. Using the Sonar Equations and assuming 100 percent
efficiency in the system (impractical in real world applications), the
source level for the 320B/R is calculated to be 211 dB re 1 [mu]Pa-m.
In practice, the system is rarely operated above 80 percent power
level.
(3) Safety Radii
NMFS has determined that for acoustic effects, using acoustic
thresholds in combination with corresponding safety radii is an
effective way to consistently apply measures to avoid or minimize the
impacts of an action, and to quantitatively estimate the effects of an
action. Thresholds are used in two ways: (1) To establish a mitigation
shut-down or power-down zone, i.e., if an animal enters an area
calculated to be ensonified above the level of an established
threshold, a sound source is powered down or shut down; and (2) to
calculate take, in that a model may be used to calculate the area
around the sound source that will be ensonified to that level or above,
then, based on the estimated density of animals and the distance that
the sound source moves, NMFS can estimate the number of marine mammals
that may be ``taken.''
As a matter of past practice and based on the best available
information at the time regarding the effects of marine sound, NMFS
estimates that Level A harassment from acoustic sources may occur when
animals are exposed to levels above 180 dB re 1 [mu]Pa (rms) level for
cetaceans and 190 dB re 1 [mu]Pa (rms) for pinnipeds. A review of the
available scientific data using an application of science-based
extrapolation procedures (Southall et al., 2007) strongly suggests that
Level A harassment (as well as temporary threshold shift (TTS)) from
single sound exposure impulse events may occur at much higher levels
than the levels previously estimated using very limited data. However,
for purposes of this proposed action, SIO's application sets forth, and
NMFS is using, the more conservative 180 and 190 dB re 1 [mu]Pa (rms)
criteria. NMFS also considers 160 dB re 1 [mu]Pa (rms) as the criterion
for estimating the onset of Level B harassment from acoustic sources
producing impulse sounds, as in this seismic survey.
Empirical data concerning the 180- and 160-dB distances have been
acquired based on measurements during the acoustic verification study
conducted by L-DEO in the northern Gulf of Mexico from May 27-June 3,
2003 (Tolstoy et al., 2004). Although the results are limited, the data
showed that radii around the airguns where the received level would be
180 dB re 1 [mu]Pa (rms), the safety criterion applicable to cetaceans
(NMFS 2000), vary with water depth. Similar depth-related variation is
likely in the 190 dB distances applicable to pinnipeds. Correction
factors were developed for water depths 100-1000 m and <100 m. The
proposed survey will occur in depths of approximately 1000-4800 m, so
the correction factors for shallow water are not relevant here. All of
the seismic operations will be in depths >1000 m.
The empirical data indicate that, for deep water (>1000 m), the L-
DEO model tends to overestimate the received sound levels at a given
distance (Tolstoy et al., 2004). However, to be precautionary pending
acquisition of additional empirical data, it is proposed that safety
radii during GI airgun operations in deep water will be values
predicted by L-DEO's model (see Table 1 in this document). Therefore,
the assumed 180- and 190-dB radii are 40 m (131.2 ft) and 10 m (32.8
ft), respectively.
Table 1--Predicted Distances To Which Sound Levels [gteqt]190, 180 and 160 dB re 1 [mu]Pa (rms) Might Be Received From Two 45 in\3\ GI Airguns That Will
Be Used During the Seismic Surveys in the Eastern Tropical Pacific Ocean During October-November 2010
[Distances are based on model results provided by L-DEO.]
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Estimated distances at received levels (m)
Source and volume Tow depth (m) Water depth --------------------------------------------------------
190 dB 180 dB 160 dB
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Two GI airguns, 45 in\3\ each............... 2 Deep (>1000 m)................ 10 40 400
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Description of Marine Mammals in the Area of the Specified Activity
Forty-three species of marine mammals, including 29 odontocetes, 7
mysticetes, 6 pinnipeds, and the marine sea otter (Enhydra lutris), are
known to occur in the ETP. Of these, 23 cetacean species are likely to
occur in the proposed survey areas in the ETP during October-November
(see Table 2 in this document), and are considered further here. Three
of these 23 cetacean species are listed under the Endangered Species
Act (ESA) as Endangered: The sperm (Physeter macrocephalus), humpback
(Megaptera novaeangliae), and blue (Balaenoptera musculus) whales.
Nine cetacean species, although present in the wider ETP, likely
would not be found in the proposed seismic survey areas because their
ranges do not extend that far south or north. Pacific white-sided
dolphins (Lagenorhynchus obliquidens) and Baird's beaked whales
(Berardius bairdii) are seen very occasionally in the northernmost
portions of the ETP (Ferguson and Barlow, 2001). Long-beaked common
dolphins (Delphinus capensis) are known to occur in the northernmost
areas of the ETP off Baja California, Mexico, and off the coast of Peru
(Heyning and Perrin, 1994). Southern right whales (Eubalaena australis)
are seen on rare occasions off the coasts of Peru and Chile (Aguayo et
al., 1992; Santillan et al., 2004). Gray's beaked whales (Mesoplodon
grayi) are distributed in the southernmost portions of the ETP and off
the coast of southern Peru (Culik, 2010). Dusky dolphins
(Lagenorhynchus obscurus), southern right whale dolphins (Lissodelphis
peronii), Burmeister's porpoises (Phocoena spinipinnis), and long-
finned pilot whales (Globicephala melas) also occur near the Peruvian
coast (Leatherwood et al., 1991; Van Waerebeek et al., 1991; Brownell
and Clapham, 1999; Olson and Reilly, 2002). These nine species are not
addressed in detail in SIO's application and are not considered further
in this Notice of Proposed IHA.
Sei (Balaenoptera borealis) and fin (B. physalus) whales, listed as
Endangered under the ESA, are known from the ETP but are considered
very rare in the proposed survey area. Sei whales may have been sighted
during surveys in the ETP (Wade and Gerrodette, 1993; Kinzey et al.,
1999, 2000, 2001); however, it is difficult to distinguish sei whales
from Bryde's whales (B. edeni) at sea. Because sei whales generally
have a more northerly and temperate distribution (Leatherwood et al.,
1988), Wade and Gerrodette (1993) classified
[[Page 54099]]
any tentative sei whale observations in the ETP as Bryde's whale
sightings. Sei whales may also have been sighted near the Galapagos
Islands (Clarke, 1962); although, Clarke and Aguayo (1965) suggested
that those sightings could have been Bryde's whales. Although the
occurrence of sei whales is documented off Costa Rica (Rodriguez-
Herrera et al., 2002), the reliability of the identification is
uncertain. Neither Ferguson and Barlow (2001) or Jackson et al. (2008)
positively identified sei whales in or near the proposed project area
during surveys conducted during July-December. Similarly, Rasmussen et
al. (2004) did not report sei whales in 8 years of surveys off Costa
Rica or Panama. No sei whales were detected during L-DEO seismic
surveys off Costa Rica or Nicaragua in November-December 2004 or
February-March 2008 (Holst et al., 2005b; Holst and Smultea, 2008), in
the Hess Deep approximately 1100 km (683.5 mi) west of the Galapagos
Islands in July 2003 (Smultea and Holst, 2003), or 1600-1950 km (994.2-
1211.7 mi) west of the proposed survey area in April-August 2008
(Hauser et al., 2008).
No confirmed fin whale sightings were made in the proposed study
area during 10 years of survey effort in July-December by Ferguson and
Barlow (2001) or by Jackson et al. (2008) during July-December surveys
in 2006. Despite >30 years of NMFS and other surveys, as well as
stranding records from the Pacific coast of Costa Rica, there have been
no confirmed records of fin whales (May-Collado et al., 2005). A
possible sighting of a fin whale in this region occurred off the Osa
Peninsula in 1997; however, the sighting was not confirmed (May-Collado
et al., 2005), although Rodriguez-Herrera et al. (2002) list the fin
whale as having been documented off Costa Rica. No fin whales were
detected during L-DEO seismic surveys off Costa Rica or Nicaragua in
November-December 2004 or February-March 2008 (Holst et al., 2005b;
Holst and Smultea, 2008), in the Hess Deep approximately 1100 km (683.5
mi) west of the Galapagos Islands in July 2003 (Smultea and Holst,
2003), or 1600-1950 km (994.2-1211.7 mi) west of the proposed survey
area in April-August 2008 (Hauser et al., 2008). Sei and fin whales are
not considered further in this document.
The general distribution of minke whales (Balaenoptera
acutorostrata) includes the offshore waters of the study area (Reeves
et al., 2002). However, minke whales are likely to be rare in the
survey area. This species has been found off the coast of Costa Rica on
occasion (Rodriguez-Herrera et al., 2002). No minke whales were found
in the proposed project region during July-December surveys during
1986-1996 by Ferguson and Barlow (2001) or in 2006 by Jackson et al.
(2008). Rasmussen et al. (2004) did not report seeing any minke whales
in 8 years of surveys (1996-2003) off Costa Rica or in 2001-2003 off
Panama. May-Collado et al. (2005) also did not report any minkes based
on compiled sightings off Costa Rica during 1979-2001, nor have minkes
been reported among compiled strandings off Costa Rica (Rodriguez-
Fonseca and Cubero-Pardo, 2001). Minke whales are unlikely to occur in
the planned survey areas and are not considered further in this
document.
Longman's beaked whale (Indopacetus pacificus), also known as the
tropical bottlenose whale, is considered rare in the ETP. Although
widespread throughout the tropical Pacific, the species is considered
rare because of a scarcity of sightings despite a great deal of survey
effort (Pitman et al., 1999). In the ETP, most tropical bottlenose
whale sightings have been made between 3-10[deg] N (Pitman et al.,
1999). Kinzey et al. (2001) reported one sighting of I. pacificus in
the ETP at about 135[deg] W. Jackson et al. (2008) also reported I.
pacificus in the ETP well to the west of the proposed study area. No
Longman's beaked whales were reported by May-Collado et al. (2005)
based on compiled sightings off Costa Rica from 1979-2001. The species
is very rare in the study area and is not considered further in this
document.
Dwarf (Kogia sima) and pygmy (K. breviceps) sperm whales may occur
in the proposed survey area, although dwarf sperm whales are likely to
be very rare and pygmy sperm whales are likely to be rare. No Kogia sp.
were detected during L-DEO seismic surveys off Costa Rica and Nicaragua
in November-December 2004 (Holst et al., 2005b) or in the Hess Deep
approximately 1100 km (683.5 mi) west of the Galapagos Islands in July
2003 (Smultea and Holst, 2003). One sighting of a dwarf sperm whale and
one sighting of two pygmy sperm whales were observed off the coast of
Costa Rica in waters approximately 2000 m (6561.7 ft) and 3500 m
(11482.9 ft) deep, respectively, during an L-DEO seismic survey off
Costa Rica and Nicaragua in February-March 2008 (Holst and Smultea,
2008), and one unidentified Kogia sp. was sighted during L-DEO seismic
surveys 1600-1950 km (994.2-1211.7 mi) west of the proposed survey area
in April-August 2008 (Hauser et al., 2008). Due to the rarity of these
species, no take has been requested and none will be authorized.
Six species of pinnipeds are known to occur in the ETP: The
Guadalupe fur seal (Arctocephalus townsendi), California sea lion
(Zalophus californianus), Galapagos sea lion (Z. wollebaeki), Galapagos
fur seal (A. galapagoensis), southern sea lion (Otaria flavescens), and
the South American fur seal (A. australis). Ranges of the first two are
substantially north of the proposed seismic survey areas, and the last
four species are not expected to occur in the offshore waters of the
study areas. The marine sea otter, which is managed by the U.S. Fish
and Wildlife Service, is a coastal species and does not occur in
offshore waters. Pinnipeds are highly unlikely to occur in the survey
area and are not considered in further detail here.
The ETP is a biologically productive area that supports a variety
of cetacean species (Au and Perryman, 1985). Several studies of marine
mammal distribution and abundance have been conducted in the wider ETP.
The most extensive regional distribution and abundance data that
encompass the study area come primarily from multi-year vessel surveys
conducted in the wider ETP by the NMFS Southwest Fisheries Science
Center (SWFSC). Information on the distribution of cetaceans inhabiting
the ETP has been summarized in several studies (Polacheck, 1987; Wade
and Gerrodette, 1993; Ferguson and Barlow, 2001; Gerrodette et al.,
2008). However, for some species, abundance in the proposed seismic
survey area could be quite different from that of the wider ETP,
depending on local oceanographic variability.
In addition, procedures used during the various surveys that are
cited have differed somewhat, and those differences could affect the
results. For example, Ferguson and Barlow (2001) calculated cetacean
densities in the ETP based on summer/fall research surveys in 1986-
1996. Their densities are corrected for both changes in detectability
of species with distance from the survey track line and for perception
and availability bias. Gerrodette et al. (2008) calculated dolphin
abundance in the ETP based on summer/fall research surveys in 1986-
1990, 1998-2000, 2003, and 2006. Their estimates are corrected for the
former but not the latter.
Additional sighting records are available from recent surveys in
the ETP. Jackson et al. (2008) described cetacean sightings data
collected during a survey from July 28-December 7, 2006. The survey
area extended from 30[deg] N-18[deg] S from the coastline to 153[deg]
W, overlapping with the proposed
[[Page 54100]]
seismic survey area. Rasmussen et al. (2004) and Calambokidis et al.
(2010) described cetacean sightings resulting from humpback whale
surveys off Costa Rica and surrounding waters from January to March in
1996-2003 and 2010. Recent at-sea monitoring for L-DEO in the ETP also
provided sighting records for cetaceans during seismic programs.
Seismic monitoring programs took place at the Hess Deep in July 2003,
approximately 1100 km (683.5 mi) west of the Galapagos Islands (Smultea
and Holst, 2003); from Costa Rica to El Salvador in November-December
2004, mainly within approximately 100 km (62.1 mi) of the coast in
water depths extending to 5000 m (16,404.2 ft) (Holst et al., 2005b);
from Costa Rica to Nicaragua in March-April 2008, up to approximately
200 km (124.3 mi) from the coast in water depths extending to 5000 m
(Holst and Smultea, 2008); and approximately 1600-1900 km (994.2-
1,180.6 mi) west of the study area in April-August 2008 (Hauser et al.,
2008).
Information on the occurrence, distribution, population size, and
conservation status for each of the 23 cetacean species that may occur
in the proposed project area during October-November is presented in
Table 2 in this document. The five species of marine mammals expected
to be most common in the waters of the project area, all delphinids,
include the short beaked common dolphin (Delphinus delphis),
pantropical spotted dolphin (Stenella attenuata), bottlenose dolphin
(Tursiops truncatus), Risso's dolphin (Grampus griseus), and short-
finned pilot whale (Globicephala macrorhynchus). Additional information
regarding the abundance and distribution, population status, and life
history and behavior of these species expected to be found in the
project area and how the estimated densities were calculated may be
found in SIO's application. NMFS has reviewed these data and determined
them to be the best available scientific information for the purposes
of the proposed IHA. Please refer to the application for that
information (see ADDRESSES). Additional information can also be found
in the NMFS Stock Assessment Report (SAR). The Pacific 2009 SAR is
available at: http://www.nmfs.noaa.gov/pr/pdfs/sars/po2009.pdf.
Table 2--The Occurrence, Habitat, Regional Abundance, Conservation Status, and Best and Maximum Density
Estimates for Marine Mammals in or Near the Proposed Low-Energy Seismic Survey Area in the Eastern Tropical
Pacific Ocean. Cetacean Densities Are Based on NMFS SWFSC Ship Transect Surveys Conducted in 1986-2006 From
Predictive Modeling (Barlow et al. 2009; Read et al. 2009) or in 1986-1996 From Ferguson and Barlow (2003)
[See text and Tables 2-4 in SIO's application for further detail.]
----------------------------------------------------------------------------------------------------------------
Occurrence in Regional Density
Species survey area Habitat population size ESA \2\ (best) Density
during Oct-Nov \1\ \3\ (max) \4\
----------------------------------------------------------------------------------------------------------------
Mysticetes:
Bryde's Whale, Uncommon....... Pelagic and 13,000 \5\..... NL...... 0.53 1.15
(Balaenoptera edeni). coastal.
Blue whale, (Balaenoptera Uncommon....... Pelagic and 1415 \6\....... EN...... 0.13 0.23
musculus). coastal.
Humpback whale, Uncommon....... Mainly NE Pacific 1392 EN...... \15\ 0.1 \15\ 0.2
(Megaptera novaeangliae). nearshore \13\; SE
waters and Pacific 2900
banks. \14\.
Odontocetes:
Sperm whale, (Physeter Common......... Usually deep 26,053 \7\..... EN...... 3.95 15.20
macrocephalus). pelagic, steep
topography.
Pygmy sperm whale, (Kogia Rare........... Deep waters off NA \8\......... NL...... \16\ 0.01 \16\ 0.02
breviceps). shelf.
Dwarf sperm whale, (Kogia Very rare...... Deep waters off 11,200 \9\..... NL...... \16\ 0.01 \16\ 0.02
sima). shelf.
Cuvier's beaked whale, Common......... Slope and 20,000 \6\..... NL...... 1.83 3.70
(Ziphius cavirostris). pelagic.
Blainville's beaked Uncommon....... Pelagic........ 25,300 \10\.... NL...... \17\ 0.21 \17\ 0.37
whale, (Mesoplodon
densirostris).
Pygmy beaked whale, Uncommon....... Pelagic........ 25,300 \10\.... NL...... \17\ 0.21 \17\ 0.37
(Mesoplodon peruvianus).
Gingko-toothed beaked Very rare...... Pelagic........ 25,300 \10\.... NL...... \17\ 0.21 \17\ 0.37
whale, (Mesoplodon
stejnegeri).
Bottlenose dolphin, Very common.... Coastal, shelf, 335,834........ NL...... 15.14 23.09
(Tursiops truncatus). pelagic.
Rough-toothed dolphin, Common......... Mainly pelagic. 107,633........ NL...... 1.60 2.34
(Steno bredanensis).
Short-beaked common Very common.... Shelf, pelagic, 3,127,203...... NL...... 143.21 242.80
dolphin, (Delphinus high relief.
delphis).
Pantropical spotted Very common.... Coastal and 857,884........ NL...... 12.43 22.53
dolphin, (Stenella pelagic.
attenuata).
Risso's dolphin, (Grampus Very common.... Shelf, slope, 110,457........ NL...... 10.21 37.40
griseus). seamounts.
Spinner dolphin, Very common.... Coastal and 1,797,716...... NL...... 3.81 5.74
(Stenella longirostris). pelagic.
Striped dolphin, Very common.... Off continental 964,362........ NL...... 35.23 53.67
(Stenella coeruleoalba). shelf.
Fraser's dolphin, Common......... Pelagic........ 289,300 \6\.... NL...... 1.03 5.60
(Lagenodelphis hosei).
Melon-headed whale, Common......... Pelagic........ 45,400 \6\..... NL...... 2.80 9.30
(Peponocephala electra).
Pygmy killer whale, Uncommon....... Pelagic........ 38,900 \6\..... NL...... 0.60 1.80
(Feresa attenuata).
False killer whale, Uncommon....... Pelagic........ 39,800 \6\..... NL...... 0.39 2.10
(Pseudorca crassidens).
Killer whale, (Orcinus Uncommon....... Widely 8,500 \11\..... NL...... 0.85 4.00
orca). distributed.
[[Page 54101]]
Short-finned pilot whale, Common......... Mostly pelagic, 589,315 \12\... NL...... 6.29 11.74
(Globicephala high-relief.
macrorhynchus).
----------------------------------------------------------------------------------------------------------------
NA--Data not available or species status was not assessed. For density estimates, NA indicates that estimates
would be lower than the lowest estimate in this table.
\1\ Abundance from Gerrodette et al. (2008) unless otherwise stated.
\2\ U.S. Endangered Species Act: EN = Endangered, T = Threatened, NL = Not listed.
\3\ Best density (/1000km\2\) estimate as listed in Table 3 of the application. Cetecean densities are
based on NMFS SWFSC ship transect surveys conducted in 1986-2006 from predictive modeling (Barlow et al. 2009;
Read et al. 2009) or in 1986-1996 from Ferguson and Barlow (2003).
\4\ Maximum density (/1000km\2\) estimate as listed in Table 3 of the application.
\5\ This estimate is mainly for Balaenoptera edeni but may include some B. borealis.
\6\ ETP (Wade and Gerrodette 1993).
\7\ Eastern temperate North Pacific (Whitehead 2002).
\8\ California/Oregon/Washington (Carretta et al. 2010).
\9\ This abundance estimate is mostly for Kogia sima but may also include some K. breviceps. Density estimates
for Kogia spp. combined.
\10\ Estimates for population size and for density include all species of the genus Mesoplodon in the ETP
(Ferguson and Barlow 2001).
\11\ ETP (Ford 2002).
\12\ This estimate is for Globicephala macrorhynchus and G. melas in the ETP (Gerrodette and Forcada 2002).
\13\ U.S. west coast (Carretta et al. 2010).
\14\ Southeast Pacific; Felix et al. (2005).
\15\ Approximate estimates.
\16\ Density estimates are combined for pygmy and dwarf sperm whales.
\17\ Density estimates are combined for species of the genus Mesoplodon.
Marine Mammal Hearing
The primary effect on marine mammals anticipated from the specified
activities will result from exposure of animals to underwater sound.
Exposure to sound can affect marine mammal hearing. When considering
the influence of various kinds of sound on the marine environment, it
is necessary to understand that different kinds of marine life are
sensitive to different frequencies of sound. Based on available
behavioral data, audiograms derived using auditory evoked potential
techniques, anatomical modeling, and other data, Southall et al. (2007)
designate ``functional hearing groups'' for marine mammals and estimate
the lower and upper frequencies of functional hearing of the groups.
The functional groups and the associated frequencies are indicated
below (though animals are less sensitive to sounds at the outer edge of
their functional range and most sensitive to sounds of frequencies
within a smaller range somewhere in the middle of their functional
hearing range):
Low frequency cetaceans (13 species of mysticetes):
Functional hearing is estimated to occur between approximately 7 Hz and
22 kHz;
Mid-frequency cetaceans (32 species of dolphins, six
species of larger toothed whales, and 19 species of beaked and
bottlenose whales): Functional hearing is estimated to occur between
approximately 150 Hz and 160 kHz;
High frequency cetaceans (six species of true porpoises,
four species of river dolphins, two members of the genus Kogia, and
four dolphin species of the genus Cephalorhynchus): Functional hearing
is estimated to occur between approximately 200 Hz and 180 kHz; and
Pinnipeds in water: Functional hearing is estimated to
occur between approximately 75 Hz and 75 kHz, with the greatest
sensitivity between approximately 700 Hz and 20 kHz.
As mentioned previously in this document, 21 cetacean species are
likely to occur in the proposed survey area. Of the 21 species likely
to occur in SIO's project area, two are classified as low frequency
cetaceans (Bryde's, humpback, and blue whales) and 18 are classified as
mid-frequency cetaceans (sperm, Cuvier's beaked, Blainville's beaked,
pygmy beaked, gingko-toothed beaked, melon-headed, pygmy killer, false
killer, killer, and short-finned pilot whales and rough-toothed,
bottlenose, pantropical spotted, spinner, striped, Fraser's, short-
beaked common, and Risso's dolphins) (Southall et al., 2007).
Potential Effects of the Specified Activity on Marine Mammals
Potential Effects of Airguns
The effects of sounds from airguns might result in one or more of
the following: Tolerance, masking of natural sounds, behavioral
disturbances, temporary or permanent hearing impairment, and non-
auditory physical or physiological effects (Richardson et al., 1995;
Gordon et al., 2004; Nowacek et al., 2007; Southall et al., 2007).
Permanent hearing impairment, or PTS, in the unlikely event that it
occurred, would constitute injury, but temporary threshold shift (TTS)
is not an injury (Southall et al., 2007). It is unlikely that the
project would result in any cases of temporary or especially permanent
hearing impairment or any significant non-auditory physical or
physiological effects for reasons discussed later in this document.
Some behavioral disturbance is expected, but it is expected that this
would be localized and short-term because of the short amount of time
that would be spent at any particular site within the survey area
(approximately two days of seismic data acquisition at any one site).
(1) Tolerance
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at
[[Page 54102]]
distances of many kilometers. For a brief summary of the
characteristics of airgun pulses, see Appendix A(3) of the supporting
EA (see ADDRESSES). However, it should be noted that most of the
measurements are for airguns that would be detectable considerably
farther away than the GI airgun planned for use in the present project.
Several studies have shown that marine mammals at distances more
than a few kilometers from operating seismic vessels often show no
apparent response; see Appendix A(5) of the EA. That is often true even
in cases when the pulsed sounds must be readily audible to the animals
based on measured received levels and the hearing sensitivity of the
mammal group. Although various baleen whales, toothed whales, and (less
frequently) pinnipeds have been shown to react behaviorally to airgun
pulses under some conditions, at other times, mammals of all three
types have shown no overt reactions. In general, pinnipeds usually seem
to be more tolerant of exposure to airgun pulses than are cetaceans,
with the relative responsiveness of baleen and toothed whales being
variable. Given the relatively small and low-energy GI airgun source
planned for use in this project, mammals are expected to tolerate being
closer to this source than would be the case for a larger airgun source
typical of most seismic surveys.
(2) Masking
Obscuring of sounds of interest by interfering sounds, generally at
similar frequencies, is known as masking. Masking effects of pulsed
sounds (even from large arrays of airguns, much larger than that
proposed for use in this survey) on marine mammal calls and other
natural sounds are expected to be limited, although there are few
specific data of relevance. 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 some
situations, multi-path arrivals and reverberation cause airgun sound to
arrive for much or all of the interval between pulses (Simard et al.,
2005; Clark and Gagnon, 2006), which could mask calls. Whale calls
often can be heard between the seismic pulses (Richardson et al., 1986;
McDonald et al., 1995; Greene et al., 1999a,b; Nieukirk et al., 2004;
Smultea et al., 2004; Holst et al., 2005a,b, 2006; Dunn and Hernandez,
2009), and certain baleen and toothed whales are known to continue
calling in the presence of seismic pulses. However, Clark and Gagnon
(2006) reported that fin whales in the northeast Pacific Ocean went
silent for an extended period starting soon after the onset of a
seismic survey in the area. Similarly, there has been one report that
sperm whales ceased calling when exposed to pulses from a very distant
seismic ship (Bowles et al., 1994). However, more recent studies found
that sperm whales continued calling in the presence of seismic pulses
(Madsen et al., 2002; Tyack et al., 2003; Smultea et al., 2004; Holst
et al., 2006; Jochens et al., 2008). Given the small source planned for
use during the proposed survey, there is even less potential for
masking of baleen or sperm whale calls during the present study than in
most seismic surveys. Masking effects of seismic pulses are expected to
be negligible in the case of small odontocetes, given the intermittent
nature of seismic pulses. Dolphins and porpoises commonly are heard
calling while airguns are operating (Gordon et al., 2004; Smultea et
al., 2004; Holst et al., 2005a,b; Potter et al., 2007). 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. Masking effects on marine
mammals are discussed further in Appendix A(4) of the EA.
(3) Disturbance Reactions
Disturbance includes a variety of effects, including subtle changes
in behavior, more conspicuous changes in activities, and displacement.
Reactions to sound, if any, depend on species, state of maturity,
experience, current activity, reproductive state, time of day, and many
other factors (Richardson et al., 1995; Wartzok et al., 2004; Southall
et al., 2007; Weilgart, 2007). If a marine mammal responds to an
underwater sound by changing its behavior or moving a small distance,
the response may or may not rise to the level of ``taking'', or affect
the stock or the species as a whole. However, if a sound source
displaces marine mammals from an important feeding or breeding area for
a prolonged period, impacts on animals or on the stock or species could
potentially be significant (Lusseau and Bejder, 2007; Weilgart, 2007).
Given the many uncertainties in predicting the quantity and types of
impacts of noise on marine mammals, it is common practice to estimate
how many mammals are likely to be present within a particular distance
of a given activity, or exposed to a particular level of sound. This
practice potentially overestimates the numbers of marine mammals that
are affected in some biologically-important manner.
The sound exposure thresholds that are used to estimate how many
marine mammals might be harassed by a seismic survey are based on
behavioral observations during studies of several species. However,
information is lacking for many species. Detailed studies have been
done on humpback, gray (Eschrichtius robustus), bowhead (Balaena
mysticetus), and sperm whales, and on ringed seals (Phoca hispida).
Less detailed data are available for some other species of baleen
whales, small toothed whales, and sea otters, but for many species
there are no data on responses to marine seismic surveys. Most of those
studies have concerned reactions to much larger airgun sources than
planned for use in the proposed SIO project. Thus, effects are expected
to be limited to considerably smaller distances and shorter periods of
exposure in the present project than in most of the previous work
concerning marine mammal reactions to airguns.
Baleen Whales--Baleen whales generally tend to avoid operating
airguns, but avoidance radii are quite variable. Whales are often
reported to show no overt reactions to pulses from large arrays of
airguns at distances beyond a few kilometers, even though the airgun
pulses remain well above ambient noise levels out to much longer
distances. However, as reviewed in Appendix A(5) of the EA, baleen
whales exposed to strong noise pulses from airguns often react by
deviating from their normal migration route (Richardson et al., 1999)
and/or interrupting their feeding activities and moving away from the
sound source. In the cases of migrating gray and bowhead whales, the
observed changes in behavior appeared to be of little or no biological
consequence to the animals. They simply avoided the sound source by
displacing their migration route to varying degrees, but within the
natural boundaries of the migration corridors (Schick and Urban, 2000;
Richardson et al., 1999; Malme et al., 1983).
Studies of gray, bowhead, and humpback whales have shown that
seismic pulses with received levels of pulses in the 160-170 dB re 1
[mu]Pa (rms) range seem to cause obvious avoidance behavior in a
substantial fraction of the animals exposed (Richardson et al., 1995).
In many areas, seismic pulses from large arrays of airguns diminish to
those levels at distances ranging from 4.5-14.5 km (2.8-9 mi) from the
source. A substantial proportion of the baleen whales within those
distances may show avoidance or other strong
[[Page 54103]]
disturbance reactions to the airgun array. Subtle behavioral changes
sometimes become evident at somewhat lower received levels, and studies
summarized in Appendix A(5) of the EA have shown that some species of
baleen whales, notably bowhead and humpback whales, at times show
strong avoidance at received levels lower than 160-170 dB re 1 [mu]Pa
(rms). Reaction distances would be considerably smaller during the
proposed project, for which the 160 dB radius is predicted to be 400 m
(1312.3 ft) (see Table 1 in this document), as compared with several
kilometers when a large array of airguns is operating.
Responses of humpback whales to seismic surveys have been studied
during migration, on summer feeding grounds, and on Angolan winter
breeding grounds; there has also been discussion of effects on the
Brazilian wintering grounds. McCauley et al. (1998, 2000a) studied the
responses of humpback whales off Western Australia to a full-scale
seismic survey with a 16-airgun, 2678-in \3\ array, and to a single 20-
in \3\ airgun with a source level of 227 dB re 1 [mu]Pa-m peak-to-peak.
McCauley et al. (1998) documented that initial avoidance reactions
began at 5-8 km (3.1-5 mi) from the array, and that those reactions
kept most pods approximately 3-4 km (1.9-2.5 mi) from the operating
seismic boat. McCauley et al. (2000a) noted localized displacement
during migration of 4-5 km (2.5-3.1 mi) by traveling pods and 7-12 km
(4.3-7.5 mi) by cow-calf pairs. Avoidance distances with respect to the
single airgun were smaller but consistent with the results from the
full array in terms of received sound levels. The mean received level
for initial avoidance reactions to an approaching airgun was 140 dB re
1 [mu]Pa (rms) for humpback whale pods containing females. The standoff
range, i.e., the mean closest point of approach of the whales to the
airgun, corresponded to a received level of 143 dB re 1 [mu]Pa (rms).
The initial avoidance response generally occurred at distances of 5-8
km (3.1-5.0 mi) from the airgun array and 2 km (1.2 mi) from the single
airgun. However, some individual humpback whales, especially males,
approached within distances of 100-400 m (328.1-1312.3 ft), where the
maximum received level was 179 dB re 1 [mu]Pa (rms).
Humpback whales on their summer feeding grounds in southeast Alaska
did not exhibit persistent avoidance when exposed to seismic pulses
from a 100-in \3\ airgun (Malme et al., 1985). Some humpbacks seemed
``startled'' at received levels of 150-169 dB re 1 [mu]Pa on an
(approximate) rms basis. Malme et al. (1985) concluded that there was
no clear evidence of avoidance, despite the possibility of subtle
effects, at received levels up to 172 re 1 [mu]Pa on an (approximate)
rms basis.
It has been suggested that South Atlantic humpback whales wintering
off Brazil may be displaced or even strand upon exposure to seismic
surveys (Engel et al., 2004). The evidence for this was circumstantial
and subject to alternative explanations (IAGC 2004). Also, the evidence
was not consistent with subsequent results from the same area of Brazil
(Parente et al., 2006), or with results from direct studies of humpback
whales exposed to seismic surveys in other areas and seasons. After
allowance for data from subsequent years, there was ``no observable
direct correlation'' between strandings and seismic surveys (IWC 2007).
Studies of bowhead whales show that their responsiveness can be
quite variable depending on the activity (e.g., migrating vs. feeding).
Bowhead whales migrating west across the Alaskan Beaufort Sea in
autumn, in particular, are unusually responsive, with substantial
avoidance occurring out to distances of 20-30 km (12.4-18.6 mi) from a
medium-sized airgun source at received sound levels of around 120-130
dB re 1 [mu]Pa (rms) (Miller et al., 1999; Richardson et al., 1999; see
also Appendix A (5) of the EA). However, more recent research on
bowhead whales (Miller et al., 2005; Harris et al., 2007) corroborates
earlier evidence that, during the summer feeding season, bowheads are
not as sensitive to seismic sources. Nonetheless, subtle but
statistically significant changes in surfacing-respiration-dive cycles
were evident upon statistical analysis (Richardson et al., 1986). In
summer, bowheads typically begin to show avoidance reactions at
received levels of about 152-178 dB re 1 [mu]Pa (rms) (Richardson et
al., 1986, 1995; Ljungblad et al., 1988; Miller et al., 2005).
Reactions of migrating and feeding (but not wintering) gray whales
to seismic surveys have been studied. Malme et al. (1986, 1988) studied
the responses of feeding Eastern Pacific gray whales to pulses from a
single 100-in\3\ airgun off St. Lawrence Island in the northern Bering
Sea. They estimated, based on small sample sizes, that 50 percent of
feeding gray whales ceased feeding at an average received pressure
level of 173 dB re 1 [mu]Pa on an (approximate) rms basis and that 10
percent of feeding whales interrupted feeding at received levels of 163
dB re 1 [mu]Pa (rms). Those findings were generally consistent with the
results of experiments conducted on larger numbers of gray whales that
were migrating along the California coast (Malme et al., 1984; Malme
and Miles, 1985) and with observations of Western Pacific gray whales
feeding off Sakhalin Island, Russia, when a seismic survey was underway
just offshore of their feeding area (Wursig et al., 1999; Gailey et
al., 2007; Johnson et al., 2007; Yazvenko et al., 2007a,b), along with
data on gray whales off British Columbia (Bain and Williams, 2006).
Gray whales typically show no conspicuous responses to airgun pulses
with received levels up to 150 to 160 dB re 1 [mu]Pa (rms), but are
increasingly likely to show avoidance as received levels increase above
that range. While neither bowhead nor gray whales are present in the
study area, these studies can be used to draw general inference about
the potential reactions of other baleen whales to underwater sound.
Various species of the genus Balaenoptera (e.g., blue, sei, fin,
Bryde's, and minke whales) have occasionally been reported in areas
ensonified by airgun pulses (Stone, 2003; MacLean and Haley, 2004;
Stone and Tasker, 2006), and calls from blue and fin whales have been
localized in areas with airgun operations (McDonald et al., 1995; Dunn
and Hernandez, 2009). Sightings by observers on seismic vessels off the
United Kingdom from 1997-2000 suggest that, at times of good
sightability, sighting rates for mysticetes (mainly fin and sei whales)
were similar when large arrays of airguns were shooting and not
shooting (Stone, 2003; Stone and Tasker, 2006). However, these whales
tended to exhibit localized avoidance, remaining significantly further
(on average) from the airgun array during seismic operations compared
with non-seismic periods (Stone and Tasker, 2006). In a study off Nova
Scotia, Moulton and Miller (2005) found little difference in sighting
rates (after accounting for water depth) and initial sighting distances
of balaenopterid whales when airguns were operating vs. silent.
However, there were indications that these whales were more likely to
be moving away when seen during airgun operations. Similarly, ship-
based monitoring studies of blue, fin, sei, and minke whales offshore
of Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more
than small differences in sighting rates and swim direction during
seismic vs. non-seismic periods (Moulton et al., 2005, 2006a,b).
Data on short-term reactions, or lack thereof, by cetaceans to
impulsive noises do not necessarily provide information about long-term
effects. It is
[[Page 54104]]
not known whether impulsive noises affect reproductive rate or
distribution and habitat use in subsequent days or years. However, gray
whales continued to migrate annually along the west coast of North
America with substantial increases in the population over recent years,
despite intermittent seismic exploration (and much ship traffic) in
that area for decades (see Appendix A in Malme et al., 1984; Richardson
et al., 1995; Angliss and Allen, 2009). The Western Pacific gray whale
population did not seem affected by a seismic survey in its feeding
ground during a prior year (Johnson et al., 2007). Bowhead whales have
continued to travel to the eastern Beaufort Sea each summer, and their
numbers have increased notably (3.4 percent annually for nearly a
decade), despite seismic exploration in their summer and autumn range
for many years (Richardson et al., 1987; Angliss and Allen 2009). In
any event, brief exposures to sound pulses from the proposed airgun
source are highly unlikely to result in prolonged effects.
Toothed Whales--Little systematic information is available about
reactions of toothed whales to noise pulses. Few studies similar to the
more extensive baleen whale/seismic pulse work summarized above have
been reported for toothed whales. However, systematic studies on sperm
whales have been done (Gordon et al., 2006; Madsen et al., 2006; Winsor
and Mate, 2006; Jochens et al., 2008; Miller et al., 2009), and there
is an increasing amount of information about responses of various
odontocetes to seismic surveys based on monitoring studies (Stone 2003;
Smultea et al., 2004; Moulton and Miller, 2005; Bain and Williams,
2006; Holst et al., 2006; Stone and Tasker, 2006; Potter et al., 2007;
Hauser et al., 2008; Holst and Smultea, 2008; Weir, 2008; Barkaszi et
al., 2009; Richardson et al., 2009).
Seismic operators and PSOs on seismic vessels regularly see
dolphins and other small toothed whales near operating airgun arrays,
but, in general, there seems to be a tendency for most delphinids to
show some avoidance of operating seismic vessels (Goold, 1996a,b,c;
Calambokidis and Osmek, 1998; Stone, 2003; Moulton and Miller, 2005;
Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008; Richardson et
al., 2009; see also Barkaszi et al., 2009). Some dolphins seem to be
attracted to the seismic vessel and floats, and some ride the bow wave
of the seismic vessel even when large airgun arrays are firing (Moulton
and Miller, 2005). Nonetheless, there have been indications that small
toothed whales sometimes tend to head away, or to maintain a somewhat
greater distance from the vessel, when a large array of airguns is
operating than when it is silent (Stone and Tasker, 2006; Weir, 2008).
In most cases, the avoidance radii for delphinids appear to be small,
on the order of 1 km (0.62 mi) or less, and some individuals show no
apparent avoidance. The beluga whale (Delphinapterus leucas) is a
species that (at least at times) shows long-distance avoidance of
seismic vessels. Aerial surveys conducted during seismic operations in
the southeastern Beaufort Sea during summer recorded much lower
sighting rates of beluga whales within 10-20 km (6.2-12.4 mi) compared
with 20-30 km (12.4-18.6 mi) from an operating airgun array, and
observers on seismic boats in that area rarely see beluga whales
(Miller et al., 2005; Harris et al., 2007). However, beluga whales are
not found in SIO's proposed project area.
Captive bottlenose dolphins and beluga whales exhibited changes in
behavior when exposed to strong pulsed sounds similar in duration to
those typically used in seismic surveys (Finneran et al., 2000, 2002,
2005). The animals tolerated high received levels of sound before
exhibiting aversive behaviors.
Most studies of sperm whales exposed to airgun sounds indicate that
this species shows considerable tolerance of airgun pulses (Stone,
2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 2008).
In most cases the whales do not show strong avoidance and continue to
call (see Appendix A of the EA for review). However, controlled
exposure experiments in the Gulf of Mexico indicate that foraging
effort is somewhat altered upon exposure to airgun sound (Jochens et
al., 2008; Miller et al., 2009; Tyack, 2009).
There are almost no specific data on the behavioral reactions of
beaked whales (Family Ziphiidae) to seismic surveys. However, northern
bottlenose whales (Hyperoodon ampullatus) continued to produce high-
frequency clicks when exposed to sound pulses from distant seismic
surveys (Gosselin and Lawson, 2004; Laurinolli and Cochrane, 2005;
Simard et al., 2005). Most beaked whales tend to avoid approaching
vessels of other types (Wursig et al., 1998). They may also dive for an
extended period when approached by a vessel (Kasuya, 1986), although it
is uncertain how much longer such dives may be as compared to dives by
undisturbed beaked whales, which also are often quite long (Baird et
al., 2006; Tyack et al., 2006). In any event, it is likely that most
beaked whales would also show strong avoidance of an approaching
seismic vessel, although this has not been documented explicitly.
Odontocete reactions to large arrays of airguns are variable and,
at least for delphinids and Dall's porpoises, seem to be confined to a
smaller radius than has been observed for the more responsive of the
mysticetes, beluga whales, and harbor porpoises (Appendix A of the EA).
Additional details on the behavioral reactions (or the lack
thereof) by all types of marine mammals to seismic vessels can be found
in Appendix A (5) of the EA.
(4) Hearing Impairment and Other Physical Effects
Temporary (TTS) or permanent (PTS) hearing impairment is a
possibility when marine mammals are exposed to very strong sounds. TTS
has been demonstrated and studied in certain captive odontocetes and
pinnipeds exposed to strong sounds (reviewed in Southall et al., 2007).
However, there has been no specific documentation of this for marine
mammals exposed to sequences of airgun pulses.
Several aspects of the planned monitoring and mitigation measures
for this project (see the ``Proposed Mitigation'' and ``Proposed
Monitoring and Reporting'' sections later in this document) are
designed to detect marine mammals occurring near the airguns to avoid
exposing them to sound pulses that might, at least in theory, cause
hearing impairment. In addition, many cetaceans are likely to show some
avoidance of the area where received levels of airgun sound are high
enough that hearing impairment could potentially occur. In those cases,
the avoidance responses of the animals themselves will reduce or (most
likely) avoid any possibility of hearing impairment.
Non-auditory physical effects may also occur in marine mammals
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that theoretically might
occur in mammals close to a strong sound source include stress,
neurological effects, bubble formation, resonance effects, and other
types of organ or tissue damage. It is possible that some marine mammal
species (i.e., beaked whales) may be especially susceptible to injury
and/or stranding when exposed to strong pulsed sounds. However, as
discussed later in this document, there is no definitive evidence that
any of these effects occur even for marine mammals in close proximity
to large arrays of airguns. It is especially unlikely that any
[[Page 54105]]
effects of these types would occur during the present project given the
brief duration of exposure for any given individual and the planned
monitoring and mitigation measures (see the ``Proposed Mitigation'' and
``Proposed Monitoring and Reporting'' sections later in this document).
The following subsections discuss in somewhat more detail the
possibilities of TTS, permanent threshold shift (PTS), and non-auditory
physical effects.
Temporary Threshold Shift--TTS is the mildest form of hearing
impairment that can occur during exposure to a strong sound (Kryter,
1985). While experiencing TTS, the hearing threshold rises, and a sound
must be stronger in order to be heard. At least in terrestrial mammals,
TTS can last from minutes or hours to (in cases of strong TTS) days.
For sound exposures at or somewhat above the TTS threshold, hearing
sensitivity in both terrestrial and marine mammals recovers rapidly
after exposure to the noise ends. Few data on sound levels and
durations necessary to elicit mild TTS have been obtained for marine
mammals, and none of the published data concern TTS elicited by
exposure to multiple pulses of sound. Available data on TTS in marine
mammals are summarized in Southall et al., (2007). The distances from
the Melville's airguns at which the received energy level (per pulse,
flat-weighted) that would be expected to be greater than or equal to
180 dB re 1 [mu]Pa are estimated in Table 1.
Given the available data, the received level of a single seismic
pulse (with no frequency weighting) might need to be approximately 186
dB re 1 [mu]Pa\2\-s (i.e., 186 dB sound exposure level (SEL) or
approximately 221-226 dB pk-pk) in order to produce brief, mild TTS.
Exposure to several strong seismic pulses that each have received
levels near 190 dB re 1 [mu]Pa (rms) (175-180 dB SEL) might result in
cumulative exposure of approximately 186 dB SEL and thus slight TTS in
a small odontocete, assuming the TTS threshold is (to a first
approximation) a function of the total received pulse energy. Levels
>=190 dB re 1 [mu]Pa (rms) are expected to be restricted to radii no
more than 15 m (49.2 ft) from the Melville's GI airguns. For an
odontocete closer to the surface, the maximum radius with >=190 dB re 1
[mu]Pa (rms) would be smaller.
The above TTS information for odontocetes is derived from studies
on the bottlenose dolphin and beluga whale. There is not published TTS
information for other species of cetaceans. However, preliminary
evidence from a harbor porpoise exposed to airgun sound suggests that
its TTS threshold may have been lower (Lucke et al., 2009).
For baleen whales, there are no data, direct or indirect, on levels
or properties for any sound source required to induce TTS. The
frequencies to which baleen whales are most sensitive are lower than
those for odontocetes, and natural background noise levels at those low
frequencies tend to be higher. Marine mammals can hear sounds at
varying frequency levels. However, sounds that are produced in the
frequency range at which an animal hears the best do not need to be as
loud as sounds in less functional frequencies to be detected by the
animal. As a result, auditory thresholds of baleen whales within their
frequency band of best hearing are believed to be higher (less
sensitive) than are those of odontocetes at their best frequencies
(Clark and Ellison, 2004), meaning that baleen whales require sounds to
be louder (i.e., higher dB levels) than odontocetes in the frequency
ranges at which each group hears the best. From this, it is suspected
that received levels causing TTS onset may also be higher in baleen
whales (Southall et al., 2007). Since current NMFS practice assumes the
same thresholds for the onset of hearing impairment in both odontocetes
and mysticetes, the threshold is likely conservative for mysticetes. In
any event, no cases of TTS are expected given two considerations: (1)
The small size of the GI airgun source (a total discharge volume of
approximately 90 in\3\ as opposed to arrays of much larger volumes up
to 6,600 in\3\); and (2) the strong likelihood that baleen whales would
avoid the approaching airguns (i.e., the vessel) before being exposed
to levels high enough for TTS to possibly occur (as discussed
previously in this document).
As noted above, most cetacean species tend to avoid operating
airguns, although not all individuals do so. In addition, ramping up
airgun arrays, which is standard operational protocol for large airgun
arrays and proposed for the much smaller airgun array for this action,
should allow cetaceans to move away from the seismic source and avoid
being exposed to the full acoustic output of the airgun array. Even
with a large airgun array, it is unlikely that the cetaceans would be
exposed to airgun pulses at a sufficiently high level for a
sufficiently long period to cause more than mild TTS, given the
relative movement of the vessel and the marine mammal. The potential
for TTS is much lower in this project because of the much smaller
airgun array proposed to be used. With a large array of airguns, TTS
would be most likely in any odontocetes that bow-ride or otherwise
linger near the airguns. While bow-riding, odontocetes would be at or
above the surface, and thus not exposed to strong pulses given the
pressure-release effect at the surface. However, bow-riding animals
generally dive below the surface intermittently. If they did so while
bow-riding near airguns, they would be exposed to strong sound pulses,
possibly repeatedly. If some cetaceans did incur TTS through exposure
to airgun sounds, this would very likely be mild, temporary, and
reversible.
To avoid the potential for injury, NMFS has determined that
cetaceans should not be exposed to pulsed underwater noise at received
levels exceeding 180 dB re 1 [mu]Pa (rms). As summarized above, data
that are now available imply that TTS is unlikely to occur unless
odontocetes (and probably mysticetes as well) are exposed to airgun
pulses stronger than 180 dB re 1 [mu]Pa (rms).
Permanent Threshold Shift--When PTS occurs, there is physical
damage to the sound receptors in the ear. In severe cases, there can be
total or partial deafness, while in other cases the animal has an
impaired ability to hear sounds in specific frequency ranges (Kryter,
1985).
There is no specific evidence that exposure to pulses of airgun
sound can cause PTS in any marine mammal, even with large arrays of
airguns. However, given the possibility that mammals close to an airgun
array might incur TTS, there has been further speculation about the
possibility that some individuals occurring very close to airguns might
incur PTS (Richardson et al., 1995, Gedamke et al., 2008). Single or
occasional occurrences of mild TTS are not indicative of permanent
auditory damage, but repeated or (in some cases) single exposures to a
level well above that causing TTS onset might elicit PTS.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals but are assumed to be similar to those in humans and
other terrestrial mammals. PTS might occur at a received sound level at
least several decibels above that inducing mild TTS if the animal were
exposed to strong sound pulses with rapid rise time (see Appendix A (6)
of the EA). Based on data from terrestrial mammals, a precautionary
assumption is that the PTS threshold for impulse sounds (such as airgun
pulses as received close to the source) is at least 6 dB higher than
the TTS threshold on a peak-pressure basis and probably > 6 dB
(Southall et al., 2007). On an SEL basis, Southall et al.,
[[Page 54106]]
(2007) estimated that received levels would need to exceed the TTS
threshold by at least 15 dB for there to be risk of PTS. Thus, for
cetaceans, Southall et al. estimate that the PTS threshold might be an
M-weighted SEL (for the sequence of received pulses) of approximately
198 dB re 1 [mu]Pa\2\-s (15 dB higher than the TTS threshold for an
impulse).
Southall et al. (2007) also note that, regardless of the SEL, there
is concern about the possibility of PTS if a cetacean or pinniped
receives one or more pulses with peak pressure exceeding 230 or 218 dB
re 1 [mu]Pa (peak), respectively. A peak pressure of 230 dB re 1 [mu]Pa
(3.2 bar -m, 0-pk) would only be found within a meter from a GI gun,
which has a peak pressure of 224.6 dB re 1[mu]Pa-m. A peak pressure of
218 dB re 1 [mu]Pa could be received somewhat farther away; to estimate
that specific distance, one would need to apply a model that accurately
calculates peak pressures in the near-field around an array of airguns.
However, no pinnipeds are expected in the proposed survey areas.
Given the higher level of sound necessary to cause PTS as compared
with TTS, it is considerably less likely that PTS could occur. Baleen
whales generally avoid the immediate area around operating seismic
vessels, as do some other marine mammals.
Non-auditory Physiological Effects--Non-auditory physiological
effects or injuries that theoretically might occur in marine mammals
exposed to strong underwater sound include stress, neurological
effects, bubble formation, resonance effects, and other types of organ
or tissue damage (Cox et al., 2006; Southall et al., 2007). Studies
examining such effects are limited. However, resonance (Gentry 2002)
and direct noise-induced bubble formation (Crum et al., 2005) are not
expected in the case of an impulsive source like an airgun array. If
seismic surveys disrupt diving patterns of deep diving species, this
might perhaps result in bubble formation and a form of ``the bends,''
as speculated to occur in beaked whales exposed to sonar. However,
there is no specific evidence of this upon exposure to airgun pulses.
In general, little is known about the potential for seismic survey
sounds to cause auditory impairment or other physical effects in marine
mammals. Available data suggest that such effects, if they occur at
all, would presumably be limited to short distances from the sound
source and to activities that extend over a prolonged period. The
available data do not allow identification of a specific exposure level
above which non-auditory effects can be expected (Southall et al.,
2007) or any meaningful quantitative predictions of the numbers (if
any) of marine mammals that might be affected in those ways. Marine
mammals that show behavioral avoidance of seismic vessels, including
most baleen whales, some odontocetes, and some pinnipeds, are
especially unlikely to incur auditory impairment or non-auditory
physical effects.
(5) Strandings and Mortality
Marine mammals close to underwater detonations of high explosives
can be killed or severely injured, and their auditory organs are
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995).
However, explosives are no longer used for marine seismic research or
commercial seismic surveys and have been replaced entirely by airguns
or related non-explosive pulse generators. Airgun pulses are less
energetic and have slower rise times, and there is no specific evidence
that they can cause injury, death, or stranding even in the case of
large airgun arrays. However, the association of mass strandings of
beaked whales with naval exercises and, in one case, an L-DEO seismic
survey (Malakoff, 2002; Cox et al., 2006) has raised the possibility
that beaked whales exposed to strong ``pulsed'' sounds may be
especially susceptible to injury and/or behavioral reactions that can
lead to stranding (Hildebrand, 2005; Southall et al., 2007). Appendix A
(6) of the EA provides additional details.
Specific sound-related processes that lead to strandings and
mortality are not well documented, but may include: (1) Swimming in
avoidance of a sound into shallow water; (2) a change in behavior (such
as a change in diving behavior) that might contribute to tissue damage,
gas bubble formation, hypoxia, cardiac arrhythmia, hypertensive
hemorrhage or other forms of trauma; (3) a physiological change such as
a vestibular response leading to a behavioral change or stress-induced
hemorrhagic diathesis, leading in turn to tissue damage; and (4) tissue
damage directly from sound exposure, such as through acoustically-
mediated bubble formation and growth or acoustic resonance of tissues.
As noted in SIO's application, some of these mechanisms are unlikely to
apply in the case of impulse sounds. However, there are increasing
indications that gas-bubble disease (analogous to ``the bends''),
induced in super-saturated tissue by a behavioral response to acoustic
exposure, could be a pathologic mechanism for the strandings and
mortality of some deep-diving cetaceans exposed to sonar. The evidence
for this remains circumstantial and associated with exposure to naval
mid-frequency sonar, not seismic surveys (Cox et al., 2006; Southall et
al., 2007).
Seismic pulses and mid-frequency sonar pulses are quite different,
and some mechanisms by which sonar sounds have been hypothesized to
affect beaked whales are unlikely to apply to airgun pulses. Sounds
produced by airgun arrays are broadband impulses with most of the
energy below 1 kHz. Typical military mid-frequency sonars operate at
frequencies of 2-10 kHz, generally with a relatively narrow bandwidth
at any one time. A further difference between seismic surveys and naval
exercises is that naval exercises can involve sound sources on more
than one vessel. Thus, it is not appropriate to assume that there is a
direct correlation between the effects of military sonar and those of
seismic surveys on marine mammals. However, evidence that sonar pulses
can, in special circumstances, lead (at least indirectly) to physical
damage and mortality (Balcomb and Claridge, 2001; NOAA and USN, 2001;
Jepson et al., 2003; Fernandez et al., 2004, 2005; Hildebrand, 2005;
Cox et al., 2006) suggests that caution is warranted when dealing with
exposure of marine mammals to any high-intensity pulsed sound.
There is no conclusive evidence of cetacean strandings or deaths at
sea as a result of exposure to seismic surveys, but a few cases of
strandings in the general area where a seismic survey was ongoing have
led to speculation concerning a possible link between seismic surveys
and strandings. Suggestions that there was a link between seismic
surveys and strandings of humpback whales in Brazil (Engel et al.,
2004) were not well founded based on available data (IAGC, 2004; IWC,
2007). In September 2002, there was a stranding of two Cuvier's beaked
whales (Ziphius cavirostris) in the Gulf of California, Mexico, when
the L-DEO vessel R/V Maurice Ewing was operating a 20-airgun, 8490-
in\3\ array in the general area. The link between the stranding and the
seismic surveys was inconclusive and not based on any physical evidence
(Hogarth, 2002; Yoder, 2002). Nonetheless, the Gulf of California
incident plus the beaked whale strandings near naval exercises
involving use of mid-frequency sonar suggests a need for caution when
conducting seismic surveys in areas occupied by beaked whales until
more is known about effects of seismic surveys on those species
(Hildebrand, 2005). No injuries of beaked whales are anticipated during
the proposed study because of (1) the high likelihood that
[[Page 54107]]
any beaked whales nearby would avoid the approaching vessel before
being exposed to high sound levels, and (2) differences between the
sound sources operated by SIO and those involved in the naval exercises
associated with strandings.
Potential Effects of Other Acoustic Devices
(1) Multi-Beam Echosounder Signals
The Kongsberg EM 122 12-kHz MBES will be operated from the source
vessel at some times during the planned study. Information about this
equipment was provided earlier in this document. Any given mammal at
depth near the trackline would be in the main beam for only one or two
of the segments. Also, marine mammals that encounter the Kongsberg EM
122 are unlikely to be subjected to repeated pulses because of the
narrow fore-aft width of the beam and will receive only limited amounts
of pulse energy because of the short pulses. Animals close to the ship
(where the beam is narrowest) are especially unlikely to be ensonified
for more than one 2-15 ms pulse or 100-ms chirp (or two pulses or
chirps if in the overlap area). Similarly, Kremser et al. (2005) noted
that the probability of a cetacean swimming through the area of
exposure when an MBES emits a pulse is small. The animal would have to
pass the transducer at close range and be swimming at speeds similar to
the vessel in order to receive the multiple pulses that might result in
sufficient exposure to cause TTS.
Navy sonars that have been linked to avoidance reactions and
stranding of cetaceans generally have longer pulse durations than the
Kongsberg EM 122 and are often directed close to horizontally vs. more
downward for the MBES. The area of possible influence of the MBES is
much smaller--a narrow band below the source vessel. The duration of
exposure for a given marine mammal can be much longer for Navy sonar.
During SIO's operations, the individual pulses will be very short, and
a given mammal would not receive many of the downward-directed pulses
as the vessel passes by. Possible effects of an MBES on marine mammals
are outlined below.
Marine mammal communications will not be masked appreciably by the
MBES signals given the low duty cycle of the echosounder and the brief
period when an individual mammal is likely to be within its beam.
Furthermore, in the case of baleen whales, the echosounder signals (12
kHz) do not overlap with the predominant frequencies in the calls,
which would avoid any significant masking.
Behavioral reactions of free-ranging marine mammals to sonars,
echosounders, and other sound sources appear to vary by species and
circumstance. Observed reactions have included silencing and dispersal
by sperm whales (Watkins et al., 1985), increased vocalizations and no
dispersal by pilot whales (Globicephala spp.) (Rendell and Gordon,
1999), and the previously-mentioned beachings by beaked whales. During
exposure to a 21-25 kHz ``whale-finding'' sonar with a source level of
215 dB re 1 [mu]Pa-m, gray whales reacted by orienting slightly away
from the source and being deflected from their course by approximately
200 m (656.2 ft) (Frankel, 2005). When a 38-kHz echosounder and a 150-
kHz acoustic Doppler current profiler were transmitting during studies
in the ETP, baleen whales showed no significant responses, while
spotted (Stenella spp.) and spinner (Stenella longirostris) dolphins
were detected slightly more often and beaked whales less often during
visual surveys (Gerrodette and Pettis, 2005).
Captive bottlenose dolphins and a beluga whale exhibited changes in
behavior when exposed to 1-s tonal signals at frequencies similar to
those that will be emitted by the MBES used by SIO, and to shorter
broadband pulsed signals. Behavioral changes typically involved what
appeared to be deliberate attempts to avoid the sound exposure
(Schlundt et al., 2000; Finneran et al., 2002; Finneran and Schlundt,
2004). The relevance of those data to free-ranging odontocetes is
uncertain, and in any case, the test sounds were quite different in
duration as compared with those from an MBES.
Given recent stranding events that have been associated with the
operation of naval sonar, there is concern that mid-frequency sonar
sounds can cause serious impacts to marine mammals (see above).
However, the MBES proposed for use by SIO is quite different than sonar
used for Navy operations. Pulse duration of the MBES is very short
relative to naval sonar. Also, at any given location, an individual
marine mammal would be in the beam of the MBES for much less time given
the generally downward orientation of the beam and its narrow fore-aft
beamwidth; Navy sonar often use near-horizontally directed sound. Those
factors would all reduce the sound energy received from the MBES
relative to that from the sonar used by the Navy.
As noted earlier in this document, animals are unlikely to be
exposed to levels that would result in TTS or Level B harassment
because of the shape of the beam, the duration of the signal, and the
likelihood that they will be avoiding the vessel at greater horizontal
distance when airguns are operating.
(2) Sub-Bottom Profiler Signals
A SBP will be operated from the source vessel during the planned
study. Details about this equipment were provided earlier in this
document. The SBP on the Melville has a maximum source level of 211 dB
re 1 [mu]Pa-m. Kremser et al. (2005) noted that the probability of a
cetacean swimming through the area of exposure when a bottom profiler
emits a pulse is small, and--even for an SBP more powerful than those
on the Melville--if the animal was in the area, it would have to pass
the transducer at close range in order to be subjected to sound levels
that could cause TTS.
Marine mammal communications will not be masked appreciably by the
SBP signals given their directionality and the brief period when an
individual mammal is likely to be within their beams. Furthermore, in
the case of most baleen whales, the SBP signals do not overlap with the
predominant frequencies in the calls, which would avoid significant
masking.
Marine mammal behavioral reactions to other pulsed sound sources
were discussed previously, and responses to the SBP are likely to be
similar to those for other pulsed sources if received at the same
levels. However, the pulsed signals from the SBPs are considerably
weaker than those from the MBES. Therefore, behavioral responses are
not expected unless marine mammals are within 10 m of the source, which
is not expected to occur.
The source levels of the SBP are much lower than those of the
airguns. It is unlikely that the SBP produces pulse levels strong
enough to cause hearing impairment or other physical injuries even in
an animal that is (briefly) in a position near the source. The SBP is
usually operated simultaneously with other higher-power acoustic
sources. Many marine mammals will move away in response to the
approaching higher-power sources or the vessel itself before the
mammals would be close enough for there to be any possibility of
effects from the less intense sounds from the SBP. Because of the shape
of the beams of these sources and their power, NMFS believes it
unlikely that marine mammals will be exposed to either the MBES or the
SBP at levels at or above those likely to cause harassment. Further,
NMFS believes that the brief exposure of cetaceans to a few signals
from the multi-beam bathymetric sonar
[[Page 54108]]
system is not likely to result in the harassment of marine mammals.
As stated above, current NMFS practice assumes that the onset of
Level A harassment corresponds to 180 dB re 1 [mu]Pa (rms) for
cetaceans. The precautionary nature of these criteria is discussed in
Appendix A (5) of the supporting EA, including the fact that the
minimum sound level necessary to cause permanent hearing impairment is
higher, by a variable and generally unknown amount, than the level that
induces barely-detectable TTS, and the level associated with the onset
of TTS is often considered to be a level below which there is no danger
of permanent damage. NMFS also assumes that cetaceans or pinnipeds
exposed to levels exceeding 160 dB re 1 [mu]Pa (rms) may experience
Level B (behavioral) harassment.
Potential Effects on Marine Mammal Habitat
The proposed SIO seismic survey will not result in any permanent
impact to habitats used by marine mammals or to their food sources, and
there will be no physical damage to any habitat. While it is
anticipated that the specified activity may result in marine mammals
avoiding certain areas due to temporary ensonification, this impact to
habitat is temporary and reversible and was considered in further
detail earlier in this document, as behavioral modification. The main
impact issue associated with the proposed activity will be temporarily
elevated noise levels and the associated direct effects on marine
mammals, as described previously.
Effects on Fish and Invertebrates
The existing body of information on the impacts of seismic survey
sound on marine fish and invertebrates is very limited. Furthermore,
the available information on the impacts of seismic surveys on fish and
invertebrates is from studies of individuals or portions of a
population; there have been no studies at the population scale. Thus,
available information provides limited insight on possible real-world
effects at the ocean or population scale. This makes drawing
conclusions about impacts problematic because ultimately, the most
important aspect of potential impacts relates to how exposure to
seismic survey sound affects populations and their viability, including
their availability to fisheries. However, there is some unpublished and
very limited evidence of the potential for adverse effects on fish and
invertebrates, thereby justifying further discussion and analysis of
this issue. The three types of potential effects of exposure to seismic
surveys on fish and marine invertebrates are pathological,
physiological, and behavioral.
Pathological effects involve lethal and temporary or permanent
sublethal injury. Physiological effects involve temporary and permanent
primary and secondary stress responses, such as changes in levels of
enzymes and proteins. Behavioral effects refer to temporary and (if
they occur) permanent changes in exhibited behavior (e.g., startle and
avoidance behavior). The three categories are interrelated in complex
ways. For example, it is possible that certain physiological and
behavioral changes potentially could lead to an ultimate pathological
effect on individuals (i.e., mortality). The specific received sound
levels at which permanent adverse effects to fish potentially could
occur are little studied and largely unknown.
Based on the physical structure of their sensory organs, marine
invertebrates appear to be specialized to respond to particle
displacement components of an impinging sound field and not to the
pressure component (Popper et al., 2001; see also Appendix D of the
EA). More details concerning the effects of airguns on fish and
invertebrates are included in SIO's application and the associated EA.
In conclusion, NMFS has preliminarily determined that SIO's proposed
seismic survey operations are not expected to have any habitat-related
effects that could cause significant or long-term consequences for
individual marine mammals or on the food sources they utilize.
Proposed Mitigation
In order to issue an incidental take authorization (ITA) under
Sections 101(a)(5)(A) and (D) of the MMPA, NMFS must, where applicable,
set forth the permissible methods of taking pursuant to such activity,
and other means of effecting the least practicable adverse 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 (where relevant).
Mitigation and monitoring measures proposed to be implemented for
the proposed seismic survey have been developed and refined during
previous SIO seismic studies and associated EAs, IHA applications, and
IHAs. The mitigation and monitoring measures described herein represent
a combination of procedures required by past IHAs for other similar
projects and on best practices recommended in Richardson et al. (1995),
Pierson et al. (1998), and Weir and Dolman (2007). The measures are
described in detail below.
Mitigation measures proposed by SIO for adoption during the
proposed survey include (1) visual monitoring by protected species
observers (discussed later in this document), (2) establishment of an
exclusion zone (EZ), (3) speed or course alteration, provided that
doing so will not compromise operational safety requirements, (4) GI
airgun shut down procedures, and (5) ramp-up procedures. Although
power-down procedures are often standard operating practice for seismic
surveys, they will not be used here because powering down from two
airguns to one airgun would make only a small difference in the 180-dB
safety radius. The difference is not enough to allow continued one-
airgun operations if a mammal came within the safety radius for two
airguns.
Exclusion Zones--As discussed previously in this document, NMFS has
determined that for acoustic effects, using acoustic thresholds in
combination with corresponding safety radii is an effective way to
consistently apply measures to avoid or minimize the impacts of an
action. Thresholds are used to establish a mitigation shut-down, or
exclusion, zone, i.e., if an animal enters an area calculated to be
ensonified above the level of an established threshold, a sound source
is shut down.
As a matter of past practice and based on the best available
information at the time regarding the effects of marine sound, NMFS
estimates that Level A harassment from acoustic sources may occur when
cetaceans are exposed to levels above 180 dB re 1 [mu]Pa (rms) level.
NMFS also considers 160 dB re 1 [mu]Pa (rms) as the criterion for
estimating the onset of Level B harassment from acoustic sources
producing impulse sounds, as in this seismic survey.
Empirical data concerning the 180- and 160-dB distances have been
acquired based on measurements during the acoustic verification study
conducted by L-DEO in the northern Gulf of Mexico from May 27-June 3,
2003 (Tolstoy et al., 2004). The empirical data indicate that, for this
survey, the assumed 180- and 160-dB radii are 40 m (131.2 ft) and 400 m
(1312.3 ft), respectively (see Table 1 in this document).
Speed or Course Alteration--If a marine mammal is detected outside
the EZ but is likely to enter it based on relative movement of the
vessel and the animal, and if safety and scientific objectives allow,
the vessel speed and/
[[Page 54109]]
or course will be adjusted to minimize the likelihood of the animal
entering the EZ. In the event that safety and/or scientific objectives
do not allow for alteration of speed and/or course as a needed
mitigation measure, shut-down procedures will still be utilized (see
below). Major course and speed adjustments are often impractical when
towing long seismic streamers and large source arrays but are possible
in this case because only a small source and short streamers will be
used.
Shut-down Procedures--If a marine mammal is detected by PSOs
outside the EZ but is likely to enter the EZ, and if the vessel's speed
and/or course cannot be changed to avoid having the animal enter the
EZ, the airgun array, MBES, and SBP will be shut down before the animal
is within the EZ. Likewise, if a marine mammal is already within the EZ
when first detected, the airgun array, MBES, and SBP will be shut down
immediately. Following a shut down, seismic activity will not resume
until the marine mammal has cleared the EZ. The animal will be
considered to have cleared the EZ if it (a) is visually observed to
have left the EZ, or (b) has not been seen within the EZ for 15 min in
the case of small odontocetes, or has not been seen within the EZ for
30 min in the case of mysticetes and large odontocetes, including sperm
and beaked whales.
Ramp-up Procedures--A ramp-up procedure will be followed when the
GI airguns begin operating after a specified period without GI airgun
operations. It is proposed that, for the present cruise, this period
would be approximately 1-2 min. This period is based on the 180-dB
radii for the GI airguns (see Table 1 in this document) in relation to
the planned speed of the Melville while shooting. Ramp-up will begin
with a single GI airgun (45 in\3\). The second GI airgun (45 in\3\)
will be added after 5 min. During ramp up, the PSOs will monitor the
exclusion zone, and, if marine mammals are sighted, a shut-down will be
implemented as though both GI airguns were operational.
If the complete EZ has not been visible for at least 30 min prior
to the start of operations in either daylight or nighttime, ramp-up
will not commence. If one GI airgun has operated, ramp-up to full power
will be permissible at night or in poor visibility on the assumption
that marine mammals will be alerted to the approaching seismic vessel
by the sounds from the single GI airgun and could move away if they
choose. A ramp-up from a shut-down may occur at night, but only when
the entire EZ is visible, and it has been determined from the pre-ramp
up watch that the EZ is clear of marine mammals. Ramp-up of the GI
airguns will not be initiated if a marine mammal is sighted within or
near the applicable EZ during day or night.
NMFS has carefully evaluated the applicant's proposed mitigation
measures and considered a range of other measures in the context of
ensuring that NMFS prescribes the means of effecting the least
practicable impact on the affected marine mammal species and stocks and
their habitat. Our evaluation of potential measures included
consideration of the following factors in relation to one another:
The manner in which, and the degree to which, the
successful implementation of the measure is expected to minimize
adverse impacts to marine mammals;
The proven or likely efficacy of the specific measure to
minimize adverse impacts as planned; and
The practicability of the measure for applicant
implementation.
Based on our evaluation of the applicant's proposed measures, as
well as other measures considered by NMFS, NMFS has preliminarily
determined that the proposed mitigation measures provide the means of
effecting the least practicable impact on marine mammal 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 ITA 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 ITAs
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.
SIO proposes to sponsor marine mammal monitoring during the present
project in order to implement the proposed mitigation measures that
require real-time monitoring and to satisfy the anticipated monitoring
requirements of the IHA. SIO's proposed Monitoring Plan is described
next. The monitoring work described here has been planned as a self-
contained project independent of any other related monitoring projects
that may be occurring simultaneously in the same regions. SIO is
prepared to discuss coordination of its monitoring program with any
related work that might be done by other groups insofar as this is
practical and desirable.
Vessel-based Visual Monitoring
Three protected species observers (PSOs) will be based aboard the
seismic source vessel for the duration of the cruise and will watch for
marine mammals near the vessel during daytime airgun operations and
during start-up of airguns at any time. Watches will be conducted by at
least one observer 100% of the time during seismic surveys in daylight
hours. Daylight observation by at least one observer will continue
during non-seismic periods, as long as weather conditions make
observations meaningful, for comparison of sighting rates and animal
behavior during periods with vs. without airgun operations. PSOs will
be appointed by SIO with NMFS concurrence after a review of their
qualifications.
The Melville is a suitable platform for marine mammal observations.
The observer platform is located one deck below and forward of the
bridge (12.46 meters (40.88 ft) above the waterline), affording a
relatively unobstructed 180-degree forward view. Aft views can be
obtained along the port and starboard decks. During daytime hours, the
observer(s) will scan the area systematically using reticulated 25x150
big-eye binoculars and 7x50 hand-held binoculars to determine bearing
and distance of sightings. A clinometer is used to determine distances
of animals in close proximity to the vessel. Hand-held fixed
rangefinders and distance marks on the ship's side rails are used to
measure the exact location of the safety zone. Laser rangefinders,
which have proven to be less reliable for open water sighting, are also
provided. During darkness, night-vision equipment will be available.
The PSOs will be in wireless 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 GI airgun
shut down.
Before commencing seismic operations during daylight hours, two
observers will maintain a 360-degree watch for all marine mammals for
at least 30 minutes prior to the start of seismic operations after an
extended shutdown of the airguns (1-2 minutes, depending on vessel
speed). If no marine mammals are observed within the EZ during this
time, the observers will notify the seismic personnel of an ``all
clear'' status. Watch periods are scheduled as a 2-hour rotation. The
[[Page 54110]]
observers continually scan the water from the horizon to the ship's
hull, and forward of 90 degrees from the port and starboard beams.
Based on PSO observations, the GI airgun will be shut down (as
described earlier in this document) when marine mammals are detected
within or about to enter a designated EZ that corresponds to the 180-dB
re 1 [micro]Pa (rms) isopleths. The PSOs will continue to maintain
watch to determine when the animal(s) are outside the EZ, and airgun
operations will not resume until the animal has left that EZ. The
predicted distance for the 180-dB EZ is listed in Table 1 earlier in
this document. Seismic operations will resume only after the animals
are seen to exit the safety radius or after no further visual detection
of the animal for 15 minutes (for small odontocetes and pinnipeds) or
30 minutes (for mysticetes and large odontocetes, including beaked
whales).
The bridge officers and other crew will be instructed to alert the
observer on watch of any suspected marine mammal sighting. If needed,
the bridge will be contacted in order to maneuver the ship to avoid
interception with approaching marine mammals.
PSO Data and Documentation
PSOs will record data to estimate the numbers of marine mammals
exposed to various received sound levels and to document reactions or
lack thereof. Data will be used to estimate numbers of animals
potentially `taken' by harassment (as defined in the MMPA). They will
also provide information needed to order a shutdown of the seismic
source when a marine mammal is within or near the EZ. When a sighting
is made, the following information about the sighting will be recorded:
Species, group size, and 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 seismic source or vessel (e.g.,
none, avoidance, approach, paralleling, etc.); and behavioral pace; and
Time, location, heading, speed, activity of the vessel,
sea state, visibility, cloud cover, and sun glare.
The data will 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.
All observations, as well as information regarding seismic source
shutdown, will be recorded in a standardized format. Data collection
procedures are adapted from the line-transect protocols developed by
the SWFSC for their marine mammal abundance research cruises. A laptop
computer is located on the observer platform for ease of data entry.
The computer is connected to the ship's Global Positioning System,
which allows a record of time and position to be made at 3-minute
intervals and for each event entered (such as sightings, weather
updates and effort changes). Data accuracy will be verified by the PSOs
at sea and preliminary reports will be prepared during the field
program and summaries forwarded to the SIO's shore facility and to NSF
weekly or more frequently. PSO observations will provide the following
information:
The basis for decisions about shutting down the airgun
arrays;
Information needed to estimate the number of marine
mammals potentially `taken by harassment', which will be reported to
NMFS;
Data on the occurrence, distribution, and activities of
marine mammals in the area where the seismic study is conducted; and
Data on the behavior and movement patterns of marine
mammals seen at times with and without seismic activity.
A report will be submitted to NMFS within 90 days after the end of
the cruise. The report will describe the operations that were conducted
and sightings of marine mammals near the operations. The report will be
submitted to NMFS, providing full documentation of methods, results,
and interpretation pertaining to all monitoring. The 90-day report will
summarize the dates and locations of seismic operations and all marine
mammal sightings (dates, times, locations, activities, associated
seismic survey activities). The report will also include estimates of
the amount and nature of potential ``take'' of marine mammals by
harassment or in other ways. All injured or dead marine mammals
(regardless of cause) will be reported to NMFS as soon as practicable.
The report should include species or description of animal, condition
of animal, location, time first found, observed behaviors (if alive),
and photo or video, if available.
Estimated Takes by Incidental Harassment
With respect to the activities described here, the MMPA defines
``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
All anticipated takes would be by Level B harassment, involving
temporary changes in behavior. The proposed mitigation and monitoring
measures are expected to minimize the possibility of injurious or
lethal takes such that take by Level A harassment, serious injury or
mortality is considered remote. However, as noted earlier, there is no
specific information demonstrating that injurious or lethal ``takes''
would occur even in the absence of the planned mitigation and
monitoring measures. The sections here describe methods to estimate
``take by Level B harassment'' and present estimates of the numbers of
marine mammals that might be affected during the proposed seismic
program. The estimates of ``take'' are based on data collected in the
ETP by NMFS SWFSC during 12 ship-based cetacean and ecosystem
assessment surveys conducted during July-December from 1986-2006.
It is assumed that, during simultaneous operations of the seismic
sources and the other sources, any marine mammals close enough to be
affected by the MBES or SBP would already be affected by the seismic
sources. However, whether or not the seismic sources are operating
simultaneously with the other sources, marine mammals are expected to
exhibit no more than short-term and inconsequential responses to the
MBES and SBP given their characteristics (e.g., narrow downward-
directed beam) and other considerations described above, such as the
unlikelihood of being exposed to the source at higher levels and the
fact that it would likely only be for one or two pulses. Such reactions
are not considered to constitute ``taking'' (NMFS, 2001). Therefore, no
additional allowance is included for animals that might be affected by
sound sources other than the seismic sources (i.e., air guns).
Extensive systematic ship-based surveys have been conducted by NMFS
SWFSC for marine mammals in the ETP. SWFSC has recently developed
habitat modeling as a method to estimate cetacean densities on a finer
spatial scale than traditional line-transect analyses by using a
continuous function of habitat variables, e.g., sea surface
temperature, depth, distance from shore, and prey density (Barlow et
al., 2009). The models have been incorporated into a Web-based
Geographic Information System (GIS) developed by Duke University's
Department of Defense Strategic Environmental Research and Development
Program (SERDP) team in close collaboration with the SWFSC SERDP team
(Read et al., 2009). The GIS was used to obtain densities for the 11
[[Page 54111]]
cetaceans in the model (Bryde's whale, blue whale, Kogia spp.,
Mesoplodon spp., rough-toothed, bottlenose, pantropical spotted,
spinner, striped, and short-beaked common dolphins, and short-finned
pilot whale) in each of eight areas: the four proposed survey areas
(see Figure 1 in SIO's application), and corridors 1[deg] wide and
centered on the tracklines between the survey areas and from the
southernmost survey area to the EEZ of Peru. For species sighted in
SWFSC surveys whose sample sizes were too small to model density (sperm
whale, humpback whale, Cuvier's beaked whale, Fraser's dolphin, Risso's
dolphin, melon-headed, pygmy killer, false killer, and killer whales),
SIO used densities from the surveys conducted during summer and fall
1986-1996, as summarized by Ferguson and Barlow (2001). Densities were
calculated from Ferguson and Barlow (2003) for 5[deg] x 5[deg] blocks
that include the proposed survey areas and corridors. Those blocks
included 27,275 km (16,947.9 mi) of survey effort in Beaufort sea
states 0-5 and 2564 km (1593.2 mi) of survey effort in Beaufort sea
states 0-2. Densities were obtained for an additional eight species
that were sighted in one or more of those blocks.
Oceanographic conditions, including occasional El Nino and La Nina
events, influence the distribution and numbers of marine mammals
present in the ETP, resulting in considerable year-to-year variation in
the distribution and abundance of many marine mammal species (Escorza-
Trevino, 2009). Thus, for some species, the densities derived from
recent surveys (see Table 2 of this document) may not be representative
of the densities that will be encountered during the proposed seismic
survey.
Table 3 in SIO's application gives the average (or ``best'') and
maximum densities for each species of cetacean likely to occur in the
study area, i.e., species for which densities were obtained or
assigned. These densities have been corrected for both detectability
and availability bias by the study authors. Detectability bias is
associated with diminishing sightability with increasing lateral
distance from the trackline. Availability bias refers to the fact that
there is less than 100 percent probability of sighting an animal that
is present along the survey trackline.
The estimated numbers of individuals potentially exposed are
presented next based on the 160-dB re 1 [mu]Pa (rms) Level B harassment
criterion for all cetaceans. It is assumed that marine mammals exposed
to airgun sounds at that level might change their behavior sufficiently
to be considered ``taken by harassment''.
It should be noted that the following estimates of ``takes by
harassment'' assume that the surveys will be undertaken and completed;
in fact, the planned number of line-kilometers has been increased to
accommodate lines that may need to be repeated, equipment testing, etc.
As is typical on offshore ship surveys, inclement weather and equipment
malfunctions are likely to cause delays and may limit the number of
useful line-kilometers of seismic operations that can be undertaken.
Furthermore, any marine mammal sightings within or near the designated
EZ will result in the shutdown of seismic operations as a mitigation
measure. Thus, the following estimates of the numbers of marine mammals
potentially exposed to 160-dB re 1 [mu]Pa (rms) sounds are
precautionary and probably overestimate the actual numbers of marine
mammals that might be taken. These estimates assume that there will be
no weather, equipment, or mitigation delays, which is highly unlikely.
There is some uncertainty about the representativeness of the data
and the assumptions used in the calculations presented here. However,
the approach used here is believed to be the best available approach.
Also, to provide some allowance for these uncertainties, ``maximum
estimates'' as well as ``best estimates'' of the densities present and
numbers potentially affected have been derived. Best estimates of
density are the mean densities weighted by effort in the eight survey
areas or corridors from Read et al. (2009) or the nine 5[deg] x 5[deg]
blocks from Ferguson and Barlow (2001, 2003), whereas maximum estimates
of density are the highest densities in any of those survey areas/
corridors or blocks.
The number of different individuals that may be exposed to GI
airgun sounds with received levels >=160 dB re 1 [mu]Pa (rms) on one or
more occasions was estimated by considering the total marine area that
would be within the 160-dB radius around the operating airgun array on
at least one occasion, along with the expected density of animals in
the area. The proposed seismic lines do not run parallel to each other
in close proximity, which minimizes the number of times an individual
mammal may be exposed during the survey; in this case, an individual
could be exposed 1.01 times on average. The numbers of different
individuals potentially exposed to >=160 dB re 1 [mu]Pa (rms) were
calculated by multiplying the expected species density, either ``mean''
(i.e., best estimate) or ``maximum'', times the anticipated area to be
ensonified to that level during GI airgun operations.
The area expected to be ensonified was determined by entering the
planned survey lines into a MapInfo GIS, using the GIS to identify the
relevant areas by ``drawing'' the applicable 160-dB buffer (see Table 1
in this document) around each seismic line, and then calculating the
total area within the buffers. Areas where overlap occurred (because of
intersecting lines) were included only once when estimating the number
of individuals exposed.
Applying the approach described here, approximately 4340 km\2\
(1675.7 mi\2\) would be within the 160-dB isopleth on one or more
occasions during the surveys. This approach does not allow for turnover
in the mammal populations in the study area during the course of the
survey. That might underestimate actual numbers of individuals exposed,
although the conservative distances used to calculate the area may
offset this. In addition, the approach assumes that no cetaceans will
move away or toward the trackline as the Melville approaches in
response to increasing sound levels prior to the time the levels reach
160 dB. Another way of interpreting the estimates that follow (Table 3
in this document) is that they represent the number of individuals that
are expected (in the absence of a seismic program) to occur in the
waters that will be exposed to >=160 dB re 1 [mu]Pa (rms). The take
estimates presented here do not take the proposed mitigation measures
into consideration and thus are likely to be overestimates.
[[Page 54112]]
Table 3--The Estimates of the Possible Numbers of Marine Mammals Exposed to Sound Levels Greater Than or Equal
to 160 dB During SIO's Proposed Seismic Survey in the Eastern Tropical Pacific Ocean in Oct-Nov 2010. The
Proposed Sound Source Is a Pair of GI Airguns. Received Levels Are Expressed in dB re 1 [mu]Pa (rms) (Averaged
Over Pulse Duration), Consistent With NMFS' Practice. Not All Marine Mammals Will Change Their Behavior When
Exposed to These Sound Levels, But Some May Alter Their Behavior When Levels Are Lower (See Text)
[See Tables 2-4 in SIO's Application for Further Detail]
----------------------------------------------------------------------------------------------------------------
Number of Number of Approx. %
individuals individuals regional Requested take
Species exposed (best) exposed (max) population authorization
\1\ \1\ (best) \2\
----------------------------------------------------------------------------------------------------------------
Mysticetes:
Bryde's whale, (Balaenoptera edeni). 3 6 0.02 3
Blue whale, (Balaenoptera musculus). 1 1 0.05 * 2
Humpback whale, (Megaptera 1 1 \3\ NA * 2
novaeangliae)......................
Odontocetes:
Sperm whale, (Physeter 23 82 0.09 23
macrocephalus).....................
Cuvier's beaked whale, (Ziphius 10 20 0.05 10
cavirostris).......................
Mesoplodon sp. (unidentified)....... 1 2 <0.01 1
Rough-toothed dolphin, (Steno 9 13 0.01 * 15
bredanensis).......................
Pantropical spotted dolphin, 67 122 0.01 * 131
(Stenella attenuata)...............
Spinner dolphin, (Stenella 21 31 <0.01 * 109
longirostris)......................
Bottlenose dolphin, (Tursiops 82 125 0.02 82
truncatus).........................
Striped dolphin, (Stenella 6 291 <0.01 6
coeruleoalba)......................
Fraser's dolphin, (Lagenodelphis 6 30 <0.01 * 440
hosei).............................
Short-beaked common dolphin, 777 1317 0.02 777
(Delphinus delphis)................
Pygmy killer whale, (Feresa 3 10 0.01 * 30
attenuata).........................
Melon-headed whale, (Peponocephala 15 50 0.03 * 258
electra)...........................
Risso's dolphin, (Grampus griseus).. 55 203 0.05 55
False killer whale, (Pseudorca 2 11 0.01 * 11
crassidens)........................
Killer whale, (Orcinus orca)........ 5 22 0.05 5
Short-finned pilot whale, 34 64 0.01 34
(Globicephala macrorhynchus).......
----------------------------------------------------------------------------------------------------------------
* Requested take authorization increased from `best' exposure estimate to mean group size as reported in
Ferguson et al. (2006).
\1\ Best estimate and maximum estimate density are from Table 3 of SIO's application; therefore, takes are not
anticipated for sei, fin, humpback, minke, Longman's beaked whales, pygmy sperm whales, and dwarf sperm
whales. Humpback whale estimates calculated independently using methodology described previously.
\2\ Regional population size estimates are from Table 2 in this document.
\3\ Southern Hemisphere population sizes are poorly understood. However, the number of individuals potentially
exposed is low relative to regional population.
Table 4 in SIO's application shows the best and maximum estimates
of the number of exposures and the number of individual marine mammals
that potentially could be exposed to >=160 dB re 1 [mu]Pa (rms) during
the seismic survey if no animals moved away from the survey vessel.
Proposed take authorizations are based on best estimates, calculated
according to the methodology described previously. The best estimate of
the number of individual cetaceans that could be exposed to seismic
sounds with received levels >=160 dB re 1 [mu]Pa (rms) (but below Level
A harassment thresholds) during the survey is shown in Table 4 of SIO's
application and Table 3 here. That total includes 25 endangered whales:
1 blue whale (0.05% of the regional population), 1 humpback whale, and
23 sperm whales (0.09%). Percentage of regional population for humpback
whale is not listed because Southern Hemisphere population numbers are
poorly understood; however, the authorized take is low compared to
regional population. It should be noted that the applicant did not
initially request take authorization for humpback whales, believing
that migrating individuals would depart the proposed study area prior
to the activity dates. In subsequent discussions between NMFS and the
applicant, it was agreed that there was some reasonable chance that
late-migrant Southern Hemisphere individuals could be present in one or
more of the study areas. The proposed take authorization for humpback
whales reflects this decision. Most (96.8%) of the cetaceans
potentially exposed are delphinids; short-beaked common, pantropical
spotted, bottlenose, and Risso's dolphins and short-finned pilot whales
are estimated to be the most common species in the area, with best
estimates of 777 (0.02% of the regional population), 67 (0.01%), 82
(0.02%), 55 (0.05%), and 34 (0.01%) exposed to >=160 dB re 1 [mu]Pa
(rms), respectively. For certain species where the calculated number of
individuals exposed was between 1 and the mean group size, the
requested take authorization has been increased to the mean group size
as observed in the ETP (Ferguson et al., 2006).
Negligible Impact and Small Numbers Analysis and Preliminary
Determination
NMFS has defined ``negligible impact'' in 50 CFR 216.103 as ``* * *
an impact resulting from the specified activity that cannot be
reasonably expected to, and is not reasonably likely to, adversely
affect the species or stock through effects on annual rates of
recruitment or survival.'' In making a negligible impact determination,
NMFS considers a variety of factors, including but not limited to: (1)
The number of anticipated mortalities; (2) the number and nature of
anticipated injuries; (3) the number, nature, intensity, and duration
of Level B harassment; and (4) the context in which the take occurs.
NMFS has preliminarily determined that the impact of conducting the
low-energy marine seismic survey in the ETP may result, at worst, in a
temporary modification in behavior (Level B harassment) of small
numbers of marine mammals. No mortality or injuries are
[[Page 54113]]
anticipated as a result of the specified activity, and none are
proposed to be authorized. Additionally, animals in the area are not
expected to incur hearing impairment (i.e., TTS or PTS) or non-auditory
physiological effects. Due to the nature, degree, and context of
behavioral harassment anticipated, the activity is not expected to
impact rates of recruitment or survival. This activity is expected to
result in a negligible impact on the affected species or stocks.
Many animals perform vital functions, such as feeding, resting,
traveling, and socializing, on a diel cycle (24-hr cycle). Behavioral
reactions to noise exposure (such as disruption of critical life
functions, displacement, or avoidance of important habitat) 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). Seismic operations
are only scheduled to occur at each site for approximately 2 days.
Additionally, the source vessel will be constantly moving and will not
remain in any one spot for a prolonged period of time. Survey
operations will be conducted solely in deep-water areas of no
specifically-known (e.g., breeding) importance for the species
described.
Several species for which take authorization is requested are
either ESA-listed and/or are considered ``Depleted'' under the MMPA.
Blue, sperm, and humpback whales are listed as Endangered under the ESA
(as well as MMPA-Depleted). Along the California coast blue whale
abundance has been increasing during the past two decades (Calambokidis
et al., 1990; Barlow, 1994; Calambokidis, 1995). Though the magnitude
of this apparent increase is too large to be accounted for by
population growth alone and, therefore, is assumed to partly result
from a shift in distribution, there is an apparent increasing trend.
Some individuals from this stock may be present year-round on the Costa
Rica Dome (Reilly and Thayer, 1990). Although the population in the
North Pacific is expected to have grown since being given protected
status in 1966, there is no evidence showing that the eastern North
Pacific stock is currently growing, and no information exists on the
rate of growth of blue whale populations in the Pacific (Best, 1993).
Slightly more information is available for sperm whales, and it has
been suggested that ETP animals of this species may form a distinct
stock (Dufault and Whitehead 1995; Jaquet et al., 2003). However,
little is known about population trends and growth rates in the survey
area. Again, populations are assumed to have increased since the
species gained protection. Humpback whales potentially seen in the
survey area would likely be late migrant individuals belonging to
Southern Hemisphere stocks, where the International Whaling Commission
has designated seven major breeding stocks linked to seven major
feeding areas. In most areas for which there are good data, humpback
whales have shown evidence of strong recovery towards their unexploited
size, with annual increase rates of about 10% being recorded in a
number of areas including off South America. The total Southern
Hemisphere abundance is probably at least 60,000, although little data
on which to base this number exists. The eastern spinner dolphin (S. l.
orientalis), considered an offshore species and common in the survey
area, is considered a Depleted stock under the MMPA. The long-term
trend is flat for this stock. For all of these species, the levels of
requested take are small relative to the regional population (see Table
3 in this document).
For reasons stated previously in this document, the negligible
impact determination is also supported by the likelihood that, given
sufficient ``notice'' through relatively slow ship speed, marine
mammals are expected to move away from a noise source that is annoying
prior to its becoming potentially injurious; the fact that cetaceans
would have to be closer than 40 m (131.2 ft) in deep water when the GI
airgun is in use from the vessel to be exposed to levels of sound (180
dB) believed to have even a minimal chance of causing PTS; and the
likelihood that marine mammal detection ability by trained observers is
high at that short distance from the vessel, enabling the
implementation of shut-downs to avoid injury, serious injury, or
mortality. As a result, no take by injury or death is anticipated, and
the potential for temporary or permanent hearing impairment is very low
and will be avoided through the incorporation of the proposed
mitigation measures.
While the number of marine mammals potentially incidentally
harassed will depend on the distribution and abundance of marine
mammals in the vicinity of the survey activity, the number of potential
harassment takings is estimated to be small, less than one percent of
any of the estimated population sizes, and has been mitigated to the
lowest level practicable through incorporation of the proposed
mitigation and monitoring measures mentioned previously in this
document.
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 mitigation and monitoring
measures, NMFS preliminarily finds that the proposed SIO seismic survey
will result in the incidental take of small numbers of marine mammal,
by Level B harassment only, and that the total taking from the seismic
survey will have a negligible impact on the affected species or stocks.
Impact on Availability of Affected Species or Stock for Taking for
Subsistence Uses
Subsistence whaling of several species of small cetaceans,
including the bottlenose dolphin, takes place in territorial coastal
waters of Peru (Read et al., 1998). This hunt is mainly for human
consumption and uses gill nets, purse seines, and harpoons. Read et al.
(1998) estimated that approximately 10,000 dolphins and porpoises were
landed in Peru in 1985. Because the seismic surveys are in offshore
waters, the proposed activities will not have any impact on the
availability of the species or stocks for subsistence users. However,
there are no relevant subsistence uses of marine mammals implicated by
this action.
Endangered Species Act (ESA)
There are six marine mammal species that are listed as endangered
under the ESA with confirmed or possible occurrence in the study area:
The humpback whale, South Pacific right whale, sei whale, fin whale,
blue whale, and sperm whale. Under section 7 of the ESA, SIO has begun
consultation with NMFS on the proposed seismic survey. NMFS will also
consult internally on the issuance of an IHA under section 101(a)(5)(D)
of the MMPA for this activity. As discussed previously in this
document, take is requested only for species likely to occur in the
survey area during the project timeframe (blue, humpback, and sperm
whales), and consultation will consider these three species.
Consultation will be concluded prior to a determination on the issuance
of an IHA.
National Environmental Policy Act (NEPA)
On behalf of NSF, LGL Limited, Environmental Research Associates,
prepared an EA titled ``Environmental Assessment of a Marine
Geophysical Survey by the R/V Melville in the Pacific
[[Page 54114]]
Ocean off Central and South America, October-November 2010''. NMFS,
after independently reviewing and evaluating the document for
sufficiency and compliance with the Council on Environmental Quality
regulations and NOAA Administrative Order 216-6, will either adopt
NSF's EA or conduct a separate NEPA analysis, as necessary, prior to
making a determination on the issuance of the IHA.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
issue an IHA for Level B harassment, at levels specified in Table 3 of
this document, to SIO incidental to conducting a low-energy marine
seismic survey in the ETP during the period October-November 2010,
provided the previously mentioned mitigation, monitoring, and reporting
requirements are incorporated.
Dated: August 30, 2010.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2010-22080 Filed 9-2-10; 8:45 am]
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