[Federal Register Volume 75, Number 98 (Friday, May 21, 2010)]
[Notices]
[Pages 28568-28587]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-12296]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XU56
Takes of Marine Mammals Incidental to Specified Activities;
Marine Geophysical Survey in the Northwest Pacific Ocean, July Through
September 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 Lamont-Doherty Earth
Observatory (L-DEO), a part of Columbia University, for an Incidental
Harassment Authorization (IHA) to take marine mammals, by harassment,
incidental to conducting a marine geophysical survey at the Shatsky
Rise in the northwest Pacific Ocean, July
[[Page 28569]]
through September, 2010. Pursuant to the Marine Mammal Protection Act
(MMPA), NMFS is requesting comments on its proposal to issue an IHA to
L-DEO to incidentally harass, by Level B harassment only, 34 species of
marine mammals during the specified activity.
DATES: Comments and information must be received no later than June 21,
2010.
ADDRESSES: Comments on the application should be addressed to P.
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 send to addresses other than the one
provided here. Comments sent via e-mail, including all attachments,
must not exceed a 10-megabyte file size.
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#applications 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 above address,
telephoning the contact listed here (see FOR FURTHER INFORMATION
CONTACT) or visiting the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications. The following documents associated
with the application are also available at same internet address: the
National Science Foundation's (NSF) draft Environmental Assessment (EA)
and associated report (Report) prepared by LGL Limited Environmental
Research Associates (LGL) for NSF, titled, ``Environmental Assessment
of a Marine Geophysical Survey by the R/V Marcus G. Langseth on the
Shatsky Rise in the Northwest Pacific Ocean, July-September, 2010.''
Documents cited in this notice may be viewed, by appointment, during
regular business hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Jeannine Cody, Office of Protected
Resources, NMFS, (301) 713-2289, ext. 113 or Benjamin Laws, Office of
Protected Resources, NMFS, (301) 713-2289, ext. 159.
SUPPLEMENTARY INFORMATION:
Background
Section 101(a)(5)(D) of the MMPA (16 U.S.C. 1371 (a)(5)(D)) directs
the Secretary of Commerce to authorize, upon request, the incidental,
but not intentional, taking of small numbers of marine mammals of a
species or population stock, by United States citizens who engage in a
specified activity (other than commercial fishing) within a specified
geographical region if certain findings are made and, if the taking is
limited to harassment, a notice of a proposed authorization is provided
to the public for review.
Authorization for incidental taking of small numbers of marine
mammals shall be granted if NMFS finds that the taking will have a
negligible impact on the species or stock(s), and will not have an
unmitigable adverse impact on the availability of the species or
stock(s) for subsistence uses. The authorization must set forth the
permissible methods of taking, other means of effecting the least
practicable adverse impact on the species or stock and its habitat, and
monitoring and reporting of such takings. 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 United States can apply for an authorization
to incidentally take small numbers of marine mammals by harassment.
Section 101(a)(5)(D) of the MMPA 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 small numbers of marine mammals. Within 45 days of the
close of the public 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 February 2, 2010 from L-DEO for the
taking by harassment, of marine mammals, incidental to conducting a
marine geophysical survey in the northwest Pacific Ocean. L-DEO, with
research funding from the U.S. National Science Foundation (NSF), plans
to conduct a marine seismic survey in the northwest Pacific Ocean, from
July through September, 2010.
L-DEO plans to use one source vessel, the R/V Marcus G. Langseth
(Langseth), a seismic airgun array, and ocean bottom seismometers (OBS)
to conduct a geophysical survey at the Shatsky Rise, a large igneous
plateau in the northwest Pacific Ocean. The proposed survey will
provide data necessary to decipher the crustal structure of the Shatsky
Rise; may address major questions of Earth history, geodynamics, and
tectonics; could impact the understanding of terrestrial magmatism and
mantle convection; and may obtain data that could be used to improve
estimates of regional earthquake occurrence and distribution. In
addition to the proposed operations of the seismic airgun array, L-DEO
intends to operate a multibeam echosounder (MBES) and a sub-bottom
profiler (SBP) continuously throughout the survey.
Acoustic stimuli (i.e., increased underwater sound) generated
during the operation of the seismic airgun array, may have the
potential to cause marine mammals in the survey area to be behaviorally
disturbed in a manner that NMFS considers to be Level B harassment.
This is the principal means of marine mammal taking associated with
these activities and L-DEO has requested an authorization to take
several marine mammals by Level B harassment.
Description of the Specified Activity
L-DEO's proposed seismic survey on the Shatsky Rise is scheduled to
commence on July 24, 2010 and continue for approximately 17 days ending
on September 7, 2010. L-DEO will operate the Langseth to deploy an
airgun array, deploy and retrieve OBS, and tow a hydrophone streamer to
complete the survey.
The Langseth will depart from Apra Harbor, Guam on July 19, 2010
for a six-day transit to the Shatsky Rise, located at 30-37[deg] N,
154-161[deg] E in international waters offshore from Japan. Some minor
deviation from these dates is possible, depending on logistics, weather
conditions, and the need to repeat some lines if data quality is
substandard. Therefore, NMFS plans to issue an
[[Page 28570]]
authorization that extends to October 21, 2010.
Geophysical survey activities will involve conventional seismic
methodologies to decipher the crustal structure of the Shatsky Rise. To
obtain high-resolution, 3-D structures of the area's magmatic systems
and thermal structures, the Langseth will deploy a towed array of 36
airguns as an energy source and approximately 28 OBSs and a 6-kilometer
(km) long hydrophone streamer. As the airgun array is towed along the
survey lines, the hydrophone streamers will receive the returning
acoustic signals and transfer the data to the vessel's onboard
processing system. The OBSs record the returning acoustic signals
internally for later analysis.
The proposed Shatsky Rise study (e.g., equipment testing, startup,
line changes, repeat coverage of any areas, and equipment recovery)
will take place in international waters deeper than 1,000 meters (m)
(3,280 feet (ft)) and will require approximately 17 days (d) to
complete approximately 15 transects of variable lengths totaling 3,160
kilometers (km) of survey lines. Data acquisition will include
approximately 408 hours (hr) of airgun operation (17 d x 24 hr).
The scientific team consists of Drs. Jun Korenaga (Yale University,
New Haven, CT), William Sager (Texas A&M University, College Station,
TX), and John Diebold (L-DEO, Palisades, NY).
Vessel Specifications
The Langseth, owned by NSF, is a seismic research vessel with a
propulsion system designed to be as quiet as possible to avoid
interference with the seismic signals emanating from the airgun array.
The vessel, which has a length of 71.5 m (235 feet (ft); a beam of 17.0
m (56 ft); a maximum draft of 5.9 m (19 ft); and a gross tonnage of
3,834, can accommodate up to 55 people. The ship is powered by two
3,550 horsepower (hp) Bergen BRG-6 diesel engines which drive the two
propellers. Each propeller has four blades and the shaft typically
rotates at 750 revolutions per minute. The vessel also has an 800-hp
bowthruster, which is not used during seismic acquisition. The
operation speed during seismic acquisition is typically 7.4 to 9.3 km/
hr (3.9 to 5.0 knots (kn)) and the cruising speed of the Langseth
outside of seismic operations is 18.5 km/hr (9.9 kn).
The vessel also has an observation tower from which visual
observers will watch for marine mammals before and during the proposed
airgun operations. When stationed on the observation platform, the
observer's eye level will be approximately 18 m (58 ft) above sea level
providing an unobstructed view around the entire vessel.
Acoustic Source Specifications
Seismic Airguns
The full airgun array for the proposed survey consists of 36
airguns (a mixture of Bolt 1500LL and Bolt 1900LLX airguns ranging in
size from 40 to 360 cubic inches (in\3\)), with a total volume of
approximately 6,600 in\3\ and a firing pressure of 1,900 pounds per
square inch (psi). The dominant frequency components range from two to
188 Hertz (Hz).
The array configuration consists of four identical linear arrays or
strings, with 10 airguns on each string; the first and last airguns
will be spaced 16 m (52 ft) apart. For each operating array or string,
the Langseth crew will fire the nine airguns simultaneously. They will
keep the tenth airgun in reserve as a spare, which will be turned on in
case of failure of one of the other airguns. The crew will distribute
the four airgun strings across an area measuring approximately 24 by 16
m (79 by 52 ft) behind the Langseth and will be towed approximately 100
m (328 ft) behind the vessel at a tow depth of nine to 12 m (29.5 to
49.2 ft) depending on the transect. The airgun array will fire every 20
seconds (s) for the multi-channel seismic (MCS) surveying (13
transects) and will fire every 70 s when recording data on the OBS (2
transects). The tow depth of the array will be 9 m (29.5 ft) for the
MCS transects and 12 m (39.3 ft) for the OBS transects. During firing,
the airguns will emit a brief (approximately 0.1 s) pulse of sound. The
airguns will be silent during the intervening periods of operations.
Metrics Used in This Document
This section includes a brief explanation of the sound measurements
frequently used in the discussions of acoustic effects in this
document. Sound pressure is the sound force per unit area, and is
usually measured in micropascals ([mu]Pa), where 1 pascal (Pa) is the
pressure resulting from a force of one newton exerted over an area of
one square meter. Sound pressure level (SPL) is expressed as the ratio
of a measured sound pressure and a reference level. The commonly used
reference pressure level in underwater acoustics is 1 [mu]Pa, and the
units for SPLs are dB re: 1 [mu]Pa.
SPL (in decibels (dB)) = 20 log (pressure/reference pressure)
SPL is an instantaneous measurement and can be expressed as the
peak, the peak-peak (p-p), or the root mean square (rms). Root mean
square, which is the square root of the arithmetic average of the
squared instantaneous pressure values, is typically used in discussions
of the effects of sounds on vertebrates and all references to SPL in
this document refer to the root mean square unless otherwise noted. SPL
does not take the duration of a sound into account.
Characteristics of the Airgun Pulses
Airguns function by venting high-pressure air into the water which
creates an air bubble. The pressure signature of an individual airgun
consists of a sharp rise and then fall in pressure, followed by several
positive and negative pressure excursions caused by the oscillation of
the resulting air bubble. The oscillation of the air bubble transmits
sounds downward through the seafloor and sounds that travel
horizontally toward non-target areas.
The nominal source levels of the airgun arrays used by L-DEO on the
Langseth are 236 to 265 dB re: 1 [mu]Pa(p-p). The rms value
for a given airgun pulse is typically 16 dB re: 1 [mu]Pa lower than the
peak-to-peak value. Accordingly, L-DEO has predicted the received sound
levels in relation to distance and direction from the airguns, for the
36-airgun array and for a single 1900LL 40-in\3\ airgun, which will be
used during power downs. A detailed description of the modeling effort
is provided in Appendix A of LGL's Report. These are the nominal source
levels applicable to downward propagation. The effective source levels
for horizontal propagation are lower than those for downward
propagation when the source consists of numerous airguns spaced apart
from one another.
Appendix B of LGL's report and previous Federal Register notices
(see 69 FR 31792, June 7, 2004; 71 FR 58790, October 5, 2006; 72 FR
71625, December 18, 2007; 73 FR 52950, September 12, 2008, or 73 FR
71606, November 25, 2008, and 74 FR 42861, August 25, 2009) discuss the
characteristics of the airgun pulses in detail. NMFS refers the
reviewers to those documents for additional information.
Predicted Sound Levels for the Airguns
Tolstoy et al., (2009) recently reported results for propagation
measurements of pulses from the Langseth's 36-airgun array in two water
depths, approximately 50 m and 1,600 m (164 and 5,249 ft), in the Gulf
of Mexico in 2007 and 2008. L-DEO has used these reported empirical
values to determine exclusion zones (EZ) for the airgun array,
designate mitigation zones, and estimate take (described in greater
detail
[[Page 28571]]
in Section VII of the application) for marine mammals.
L-DEO has summarized the modeled safety radii for the planned
airgun configuration in Table 1 which shows the measured and predicted
distances at which sound levels (160-, 180-, and 190-dB) are expected
to be received from the 36-airgun array and a single airgun operating
in water greater than 1,000 m (3,820 ft) in depth.
Table 1--Measured (Array) or Predicted (Single Airgun) Distances to Which Sound Levels >=190, 180, and 160 dB
re: 1 [mu]Pa Could Be Received in Deep (>1000 m; 3280 ft) Water From the 36-Airgun Array, as well as a Single
Airgun, During the Proposed Shatsky Rise Seismic Survey, July-September, 2010 (Based on L-DEO Models and Tolstoy
et al., 2009)
----------------------------------------------------------------------------------------------------------------
Predicted RMS distances (m)
Source and volume Tow depth (m) --------------------------------------
190 dB 180 dB 160 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun 40 in\3\.............................. 9-12 * 12 40 385
4 strings 36 airguns 6600 in\3\.......................... 9 400 940 3850
12 460 1100 4400
----------------------------------------------------------------------------------------------------------------
* The tow depth has minimal effect on the maximum near-field output and the shape of the frequency spectrum for
the single 40-in\3\ airgun; thus the predicted safety radii are essentially the same at each tow depth.
Results of the Gulf of Mexico calibration study (Tolstoy et al.,
2009) showed that radii around the airguns for various received levels
varied with water depth. The tow depth of the airgun array for the
proposed survey will range from 9 to 12 m (29.5 to 39.4 ft). However,
in the Gulf of Mexico calibration study, the Langseth towed the airgun
array at a depth of 6 m (19.6 ft) which is less than the tow depth
range (9 to 12 m (29.5 to 39.4 ft)) for this proposed seismic survey.
Accordingly, L-DEO has applied correction factors to the distances
reported by Tolstoy et al. (2009) for shallow and intermediate depth
water (i.e., they calculated the ratios between the 160-, 180-, and
190-dB distances at 6 m versus 9 m (19.6 ft versus 29.5 ft) and the
ratios between the 160-, 180-, and 190-dB distances at 6 m versus 12 m
(19.6 ft versus 39.4 ft) from the modeled results for the 6,600-in\3\
airgun array). Refer to Appendix A of LGL's Environmental Assessment
Report for additional information regarding how L-DEO calculated model
predictions in Table 1 and how the applicant used empirical
measurements to correct the modeled numbers.
Ocean Bottom Seismometer
The Langseth crew will deploy approximately 28 OBS on the Shatsky
Rise (see Figure 1 of L-DEO's application) over the course of
approximately three days. The Langseth crew will retrieve all OBSs
after seismic operations are completed. L-DEO expects the retrieval to
last approximately five days.
L-DEO proposes to use the Woods Hole Oceanographic Institution
(WHOI) ``D2'' OBS during the cruise. This type of OBS is approximately
one meter in height and has a maximum diameter of 50 centimeters (cm).
The anchor (2.5 x 30.5 x 38.1 cm) is made of hot-rolled steel and
weighs 23 kilograms (kg). The acoustic release transponder used to
communicate with the OBS uses frequencies of 9 to 13 kHz. The source
level of the release signal is 190 dB re: 1 [mu]Pa.
Multibeam Echosounder
The Langseth will operate a Kongsberg EM 122 MBES concurrently
during airgun operations to map characteristics of the ocean floor. The
hull-mounted MBES emits brief pulses of sound (also called a ping)
(10.5 to 13 kilohertz (kHz)) in a fan-shaped beam that extends downward
and to the sides of the ship. The transmitting beamwidth is one or two
degrees ([deg]) fore-aft and 150[deg] athwartship and the maximum
source level is 242 dB re: 1 [mu]Pa.
For deep-water operations, each ping consists of eight successive
fan-shaped transmissions, up to 15 milliseconds (ms) in duration and
each ensonifying a sector that extends 1[deg] fore-aft. The eight
successive transmissions span an overall cross-track angular extent of
about 150[deg], with 2 ms gaps between the pulses for successive
sectors.
Sub-Bottom Profiler
The Langseth will also operate a Knudsen 320B SBP continuously
throughout the cruise with the MBES. An SBP operates at mid to high
frequencies and is generally used simultaneously with an MBES to
provide information about the sedimentary features and bottom
topography. SBP pulses are directed downward at typical frequencies of
approximately three to 18 kHz. However, the dominant frequency
component of the SBP is 3.5 kHz which is directed downward in a 27[deg]
cone by a hull-mounted transducer on the vessel. The maximum output is
1,000 watts (204 dB re: 1 [mu]Pa), but in practice, the output varies
with water depth. The pulse interval is one second, but a common mode
of operation is to broadcast five pulses at 1-s intervals followed by a
5-second pause.
NMFS expects that acoustic stimuli resulting from the proposed
operation of the single airgun or the 36-airgun array has the potential
to harass marine mammals, incidental to the conduct of the proposed
seismic survey. NMFS does not expect that the movement of the Langseth,
during the conduct of the seismic survey, has the potential to harass
marine mammals because of the relatively slow operation speed of the
vessel (7.4 to 9.3 km/hr; 3.9 to 5.0 kn).
Description of the Marine Mammals in the Area of the Proposed Specified
Activity
Thirty-four marine mammal species may occur in the Shatsky Rise
survey area, including 26 odontocetes (toothed cetaceans), 7 mysticetes
(baleen whales) and one pinniped. Six of these species are listed as
endangered under the U.S. Endangered Species Act of 1973 (ESA; 16
U.S.C. 1531 et seq.), including the north Pacific right (Eubalena
japonica), humpback (Megaptera novaeangliae), sei (Balaenoptera
borealis), fin (Balaenoptera physalus), blue (Balaenoptera musculus),
and sperm (Physeter macrocephalus) whale.
The western North Pacific gray whale (Eschrichtius robustus) occurs
in the northwest Pacific Ocean and is listed as endangered under the
ESA and as critically endangered by the International Union for
Conservation of Nature (IUCN). L-DEO does not expect to encounter this
species within the proposed survey area as gray whales are known to
prefer nearshore coastal waters. Thus, L-DEO does not present analysis
for this species nor does the application request take for this
species.
[[Page 28572]]
Table 2 presents information on the abundance, distribution,
population status, and conservation status of marine mammals that may
occur in the proposed survey area.
Table 2--Habitat, Regional Population Size, and Conservation Status of Marine Mammals That May Occur in or Near
the Proposed Seismic Survey Area at the Shatsky Rise Area in the Northwest Pacific Ocean
----------------------------------------------------------------------------------------------------------------
Regional
Species Habitat population size U.S. ESA IUCN \c\ CITES \d\
\a\ \b\
----------------------------------------------------------------------------------------------------------------
Mysticetes
North Pacific right whale. Pelagic and coastal... few 100 \e\...... EN EN I
Humpback whale............ Mainly nearshore 938-1107 \f\..... EN LC I
waters and banks.
Minke whale............... Pelagic and coastal... 25,000 \g\....... NL LC I
Bryde's whale............. Pelagic and coastal... 20,501 \h\....... NL DD I
Sei whale................. Primarily offshore, 7260-12,620 \i\.. EN EN I
pelagic.
Fin whale................. Continental slope, 13,620-18,680 \j\ EN EN I
mostly pelagic.
Blue whale................ Pelagic and coastal... 3500 \k\......... EN EN I
Odontocetes
Sperm whale............... Usually pelagic and 29,674 \l\....... EN VU I
deep seas.
Pygmy sperm whale......... Deep waters off the N.A.............. NL DD II
shelf.
Dwarf sperm whale......... Deep waters off the 11,200 \m\....... NL DD II
shelf.
Cuvier's beaked whale..... Pelagic............... 20,000 \m\....... NL LC II
Baird's beaked whale...... Deep water............ N.A.............. NL DD II
Longman's beaked whale.... Deep water............ N.A.............. NL DD II
Hubb's beaked whale....... Deep water............ 25,300 \n\....... NL DD II
Ginkgo-toothed beaked Pelagic............... 25,300 \n\....... NL DD II
whale.
Blainville's beaked whale. Pelagic............... 25,300 \n\....... NL DD II
Stejneger's beaked whale.. Deep water............ 25,300 \n\....... NL DD II
Rough-toothed dolphin..... Deep water............ 145,900 \m\...... NL LC II
Common bottlenose dolphin. Coastal and oceanic, 168,000 \o\...... NL LC II
shelf break.
Pantropical spotted Coastal and pelagic... 438,000 \o\...... NL LC II
dolphin.
Spinner dolphin).......... Coastal and pelagic... 801,000 \p\...... NL DD II
Striped dolphin........... Off continental shelf. 570,000 \o\...... NL LC II
Fraser's dolphin.......... Waters >1000 m........ 289,300 \m\...... NL LC II
Short-beaked common Shelf and pelagic, 2,963,000 \q\.... NL LC II
dolphin. seamounts.
Pacific white-sided Continental slope and 988,000 \r\...... NL LC II
dolphin. pelagic.
Northern right whale Deep water............ 307,000 \r\...... NL LC II
dolphin.
Risso's dolphin........... Waters >1000 m, 838,000 \o\...... NL LC II
seamounts.
Melon-headed whale........ Oceanic............... 45,400 \m\....... NL LC II
Pygmy killer whale........ Deep, pantropical 38,900 \m\....... NL DD II
waters.
False killer whale........ Pelagic............... 16,000 \o\....... NL DD II
Killer whale.............. Widely distributed.... 8500 \m\......... NL DD II
Short-finned pilot whale.. Mostly pelagic, high- 53,000 \o\....... NL DD II
relief topography.
Dall's porpoise........... Deep water............ 1,337,224 \s\.... NL LC II
Pinnipeds
Northern fur seal......... Coastal and pelagic... 1.1 million \t\.. NL VU --
----------------------------------------------------------------------------------------------------------------
N.A.--Data not available or species status was not assessed.
\a\ Region for population size, in order of preference based on available data, is Western North Pacific, North
Pacific, or Eastern Tropical Pacific; see footnotes below.
\b\ U.S. Endangered Species Act; EN = Endangered, NL = Not listed.
\c\ Codes for IUCN (2009) classifications; EN = Endangered; VU = Vulnerable; LC = Least Concern; DD = Data
Deficient.
\d\ Convention on International Trade in Endangered Species of Wild Fauna and Flora (UNEP-WCMC 2009): Appendix I
= Threatened with extinction; Appendix II = not necessarily now threatened with extinction but may become so
unless trade is closely controlled.
\e\ North Pacific (Jefferson et al., 2008).
\f\ Western North Pacific (Calambokidis et al., 2008).
\g\ Northwest Pacific and Okhotsk Sea (Buckland et al., 1992; IWC 2009).
\h\ Western North Pacific (Kitakado et al., 2008; IWC 2009).
\i\ North Pacific (Tillman, 1977).
\j\ North Pacific (Ohsumi and Wada, 1974).
\k\ North Pacific (NMFS, 1998).
\l\ Western North Pacific (Whitehead, 2002b).
\m\ Eastern Tropical Pacific (ETP) (Wade and Gerrodette, 1993).
\n\ ETP; all Mesoplodon spp. (Wade and Gerrodette, 1993).
\o\ Western North Pacific (Miyashita, 1993a).
\p\ Whitebelly spinner dolphin in the ETP in 2000 (Gerrodette et al., 2005 in Hammond et al., 2008a).
\q\ ETP (Gerrodette and Forcada 2002 in Hammond et al., 2008b).
\r\ North Pacific (Miyashita, 1993b).
\s\ North Pacific (Buckland et al., 1993).
\t\ North Pacific, 2004-2005 (Gelatt and Lowry, 2008).
[[Page 28573]]
Refer to Section IV of L-DEO's application for detailed information
regarding the status and distribution of these marine mammals and to
Section III of the application for additional information regarding how
L-DEO estimated the regional population size for the marine mammals in
Shatsky Rise area.
Potential Effects on Marine Mammals
Summary of Potential Effects of Airgun Sounds
Level B harassment of cetaceans and pinnipeds has the potential to
occur during the proposed seismic survey due to acoustic stimuli caused
by the firing of a single airgun or the 36-airgun array which
introduces sound into the marine environment. The effects of sounds
from airguns might include one or more of the following: Tolerance,
masking of natural sounds, behavioral disturbance, temporary or
permanent hearing impairment, or 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, in the
unlikely event that it occurred, would constitute injury, but temporary
threshold shift (TTS) is not an injury (Southall et al., 2007).
Although the possibility cannot be entirely excluded, it is unlikely
that the proposed project would result in any cases of temporary or
permanent hearing impairment, or any significant non-auditory physical
or physiological effects. Some behavioral disturbance is expected, but
NMFS expects the disturbance to be localized and short-term.
Tolerance
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
For a brief summary of the characteristics of airgun pulses, see
Appendix B of L-DEO's application.
Several studies have also shown that marine mammals at distances
more than a few kilometers from operating seismic vessels often show no
apparent response (tolerance) (see Appendix B (3) LGL's Report).
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 cetaceans, with the relative
responsiveness of baleen and toothed whales being variable (see
Appendix B (5) of LGL's Report).
Masking of Natural Sounds
The term masking refers to the inability of a subject to recognize
the occurrence of an acoustic stimulus as a result of the interference
of another acoustic stimulus (Clark et al., 2009). Introduced
underwater sound may, through masking, reduce the effective
communication distance of a marine mammal species if the frequency of
the source is close to that used as a signal by the marine mammal, and
if the anthropogenic sound is present for a significant fraction of the
time (Richardson et al., 1995).
Masking effects of pulsed sounds (even from large arrays of
airguns) on marine mammal calls and other natural sounds are expected
to be limited, although there are very few specific data on this.
Because of the intermittent nature and low duty cycle of seismic airgun
pulses, animals can emit and receive sounds in the relatively quiet
intervals between pulses. However, in some situations, reverberation
occurs for much or the entire interval between pulses (e.g., Simard et
al., 2005; Clark and Gagnon, 2006) which could mask calls. Some baleen
and toothed whales are known to continue calling in the presence of
seismic pulses, and their calls can usually be heard between the
seismic pulses (e.g., Richardson et al., 1986; McDonald et al., 1995;
Greene et al., 1999; Nieukirk et al., 2004; Smultea et al., 2004; Holst
et al., 2005a,b, 2006; and Dunn et al., 2009). 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 they continued calling in the presence of seismic pulses (Madsen
et al., 2002; Tyack et al., 2003; Smultea et al., 2004; Holst et al.,
2006; and Jochens et al., 2008). Dolphins and porpoises commonly are
heard calling while airguns are operating (e.g., Gordon et al., 2004;
Smultea et al., 2004; Holst et al., 2005a,b; and 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, NMFS expects the masking effects of seismic pulses to
be minor, given the normally intermittent nature of seismic pulses.
Masking effects on marine mammals are discussed further in Appendix
B(4) of LGL's Report.
Behavioral Disturbance
Disturbance includes a variety of effects, including subtle to
conspicuous changes in behavior, movement, 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 does react briefly to an
underwater sound by changing its behavior or moving a small distance,
the impacts of the change are unlikely to be significant to the
individual, let alone the stock or population. However, if a sound
source displaces marine mammals from an important feeding or breeding
area for a prolonged period, impacts on individuals and populations
could be significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007).
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 would be present within a particular distance of
industrial activities and/or exposed to a particular level of
industrial sound. In most cases, this approach likely overestimates the
numbers of marine mammals that would be affected in some biologically-
important manner.
The sound criteria used to estimate how many marine mammals might
be disturbed to some biologically-important degree by a seismic program
are based primarily on behavioral observations of a few species.
Scientists have conducted detailed studies on humpback, gray, bowhead
(Balaena mysticetus), and sperm whales. Less detailed data are
available for some other species of baleen whales, small toothed
whales, and sea otters (Enhydra lutris), but for many species there are
no data on responses to marine seismic surveys.
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 B (5) of the LGL report,
baleen whales exposed to strong noise pulses from airguns often react
by deviating from their normal migration route and/or interrupting
their feeding and moving away. In the cases of
[[Page 28574]]
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.
Studies of gray, bowhead, and humpback whales have shown that
seismic pulses with received levels of 160 to 170 dB re: 1 [mu]Pa 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 to 15 km from the source. A substantial
proportion of the baleen whales within those distances may show
avoidance or other strong behavioral reactions to the airgun array.
Subtle behavioral changes sometimes become evident at somewhat lower
received levels, and studies summarized in Appendix B (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.
Researchers have studied the responses of humpback whales to
seismic surveys during migration, feeding during the summer months,
breeding while offshore from Angola, and wintering offshore from
Brazil. McCauley et al. (1998, 2000a) studied the responses of humpback
whales off western Australia to a full-scale seismic survey with a 16-
airgun, 2,678-in\3\ array, and to a single 20-in\3\ airgun with source
level 227 dB re: 1 [mu]Pa(p-p). McCauley et al. (1998)
documented that avoidance reactions began at five to eight km from the
array, and that those reactions kept most pods approximately three to
four km from the operating seismic boat. McCauley et al. (2000a) noted
localized displacement during migration of four to five km by traveling
pods and seven to 12 km by more sensitive resting pods of 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
the received sound levels. The mean received level for initial
avoidance of an approaching airgun was 140 dB re: 1 [mu]Pa for humpback
pods containing females, and at the mean closest point of approach
(CPA) distance the received level was 143 dB re: 1 [mu]Pa. The initial
avoidance response generally occurred at distances of five to eight km
from the airgun array and two km from the single airgun. However, some
individual humpback whales, especially males, approached within
distances of 100 to 400 m, where the maximum received level was 179 dB
re: 1 [mu]Pa.
Humpback whales on their summer feeding grounds in southeast Alaska
did not exhibit persistent avoidance when exposed to seismic pulses
from a 1.64-L (100-in\3\) airgun (Malme et al., 1985). Some humpbacks
seemed ``startled'' at received levels of 150 to 169 dB re: 1 [mu]Pa.
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.
Studies have 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 direct studies of
humpbacks 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,
2007:236).
There are no data on reactions of right whales to seismic surveys,
but results from the closely-related bowhead whale show that their
responsiveness can be quite variable depending on their activity
(migrating versus 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
to 30 km from a medium-sized airgun source at received sound levels of
around 120 to 130 dB re: 1 [mu]Pa (Miller et al., 1999; Richardson et
al., 1999; see Appendix B (5) of LGL's report). 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 the summer, bowheads typically begin to show avoidance reactions at
received levels of about 152 to 178 dB re: 1 [mu]Pa (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 stopped 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. 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 western Pacific gray whales feeding off Sakhalin
Island, Russia (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).
Various species of Balaenoptera (blue, sei, fin, and minke whales)
have occasionally been seen 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 (e.g., McDonald et al., 1995; Dunn et al., 2009). Sightings
by observers on seismic vessels off the United Kingdom from 1997 to
2000 suggest that, during times of good sightability, sighting rates
for mysticetes (mainly fin and sei whales) were similar when large
arrays of airguns were shooting vs. silent (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 of 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 directions during seismic
versus non-seismic periods (Moulton et al., 2005, 2006a,b).
Data on short-term reactions by cetaceans to impulsive noises are
not necessarily indicative of long-term or biologically significant
effects. It is not known whether impulsive sounds affect reproductive
rate or distribution and habitat use in subsequent days or years.
[[Page 28575]]
However, gray whales have 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 (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 previous year (Johnson et al., 2007).
Similarly, bowhead whales have continued to travel to the eastern
Beaufort Sea each summer, and their numbers have increased notably,
despite seismic exploration in their summer and autumn range for many
years (Richardson et al., 1987; Angliss and Allen, 2009).
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 and (in
more detail) in Appendix B of the LGL report have been reported for
toothed whales. However, there are recent systematic studies on sperm
whales (e.g., Gordon et al., 2006; Madsen et al., 2006; Winsor and
Mate, 2006; Jochens et al., 2008; Miller et al., 2009). There is an
increasing amount of information about responses of various odontocetes
to seismic surveys based on monitoring studies (e.g., 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 marine mammal observers on seismic vessels
regularly see dolphins and other small toothed whales near operating
airgun arrays, but in general there is a tendency for most delphinids
to show some avoidance of operating seismic vessels (e.g., 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 arrays of airguns
are firing (e.g., Moulton and Miller, 2005). Nonetheless, small toothed
whales more often 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 (e.g., Stone and Tasker, 2006; Weir, 2008). In
most cases the avoidance radii for delphinids appear to be small, on
the order of one km 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 in the southeastern Beaufort Sea during summer
found that sighting rates of beluga whales were significantly lower at
distances 10 to 20 km compared with 20 to 30 km from an operating
airgun array, and observers on seismic boats in that area rarely see
belugas (Miller et al., 2005; Harris et al., 2007).
Captive bottlenose dolphins (Tursiops truncatus) 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). However, the animals tolerated
high received levels of sound before exhibiting aversive behaviors.
Results for porpoises depend on species. The limited available data
suggest that harbor porpoises (Phocoena phocoena) show stronger
avoidance of seismic operations than do Dall's porpoises (Phocoenoides
dalli) (Stone, 2003; MacLean and Koski, 2005; Bain and Williams, 2006;
Stone and Tasker, 2006). Dall's porpoises seem relatively tolerant of
airgun operations (MacLean and Koski, 2005; Bain and Williams, 2006),
although they too have been observed to avoid large arrays of operating
airguns (Calambokidis and Osmek, 1998; Bain and Williams, 2006). This
apparent difference in responsiveness of these two porpoise species is
consistent with their relative responsiveness to boat traffic and some
other acoustic sources (Richardson et al., 1995; Southall et al.,
2007).
Most studies of sperm whales exposed to airgun sounds indicate that
the sperm whale shows considerable tolerance of airgun pulses (e.g.,
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir,
2008). In most cases the whales do not show strong avoidance, and they
continue to call (see Appendix B of the LGL report for review).
However, controlled exposure experiments in the Gulf of Mexico indicate
that foraging behavior was 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 to seismic surveys. However, some northern bottlenose
whales (Hyperoodon ampullatus) remained in the general area and
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 (e.g., Wursig et al., 1998). They
may also dive for an extended period when approached by a vessel (e.g.,
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). Based on a
single observation, Aguilar-Soto et al. (2006) suggested that foraging
efficiency of Cuvier's beaked whales may be reduced by close approach
of vessels. 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.
There are increasing indications that some beaked whales tend to
strand when naval exercises involving mid-frequency sonar operation are
ongoing nearby (e.g., Simmonds and Lopez-Jurado, 1991; Frantzis, 1998;
NOAA and USN, 2001; Jepson et al., 2003; Hildebrand, 2005; Barlow and
Gisiner, 2006; see also the Strandings and Mortality subsection in this
notice). These strandings are apparently a disturbance response,
although auditory or other injuries or other physiological effects may
also be involved. Whether beaked whales would ever react similarly to
seismic surveys is unknown (see the Strandings and Mortality subsection
in this notice). Seismic survey sounds are quite different from those
of the sonar in operation during the above-cited incidents. 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, belugas, and harbor porpoises (Appendix B of the LGL
Report).
Hearing Impairment and Other Physical Effects
Temporary or permanent 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 TTS let alone permanent
hearing damage, i.e., permanent threshold shift (PTS), in free-ranging
marine mammals exposed to sequences of airgun pulses during realistic
field conditions.
L-DEO has included exclusion (i.e., shut-down) zones for the
proposed
[[Page 28576]]
seismic survey on the Shatsky Rise to minimize the exposure of marine
mammals to levels of sound associated with hearing impairment.
Several aspects of the planned monitoring and mitigation measures
for this project are designed to detect marine mammals occurring near
the airgun array, and to avoid exposing them to sound pulses that
might, at least in theory, cause hearing impairment (see below this
section). In addition, many cetaceans show some avoidance of the area
where received levels of airgun sound are high enough such 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 might (in theory) occur
in mammals close to a strong sound source include stress, neurological
effects, bubble formation, 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 transient sounds. However, as discussed below this section,
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
unlikely that any effects of these types would occur during the present
project given the brief duration of exposure of any given mammal, the
deep water in the study area, and the planned monitoring and mitigation
measures. The following subsections discuss in somewhat more detail the
possibilities of TTS, 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 Langseth'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 [micro]Pa are estimated in Table 1.
The above TTS information for odontocetes is derived from studies
on the bottlenose dolphin and beluga. For the one harbor porpoise
tested, the received level of airgun sound that elicited onset of TTS
was lower (Lucke et al., 2009). If these results from a single animal
are representative, it is inappropriate to assume that onset of TTS
occurs at similar received levels in all odontocetes (cf. Southall et
al., 2007). Some cetaceans apparently can incur TTS at considerably
lower sound exposures than are necessary to elicit TTS in the beluga or
bottlenose dolphin.
For baleen whales, there are no data, direct or indirect, on levels
or properties of sound that are required to induce TTS. The frequencies
to which baleen whales are most sensitive are assumed to be lower than
those to which odontocetes are most sensitive, and natural background
noise levels at those low frequencies tend to be higher. 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).
From this, it is suspected that received levels causing TTS onset may
also be higher in baleen whales (Southall et al., 2007). For this
proposed study, L-DEO expects no cases of TTS given three
considerations: (1) The low abundance of baleen whales in the planned
study area at the time of the survey; (2) the strong likelihood that
baleen whales would avoid the approaching airguns (or vessel) before
being exposed to levels high enough for TTS to occur; and (3) the
mitigation measures that are planned.
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, whereas 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 at least mild TTS, there has been further speculation
about the possibility that some individuals occurring very close to
airguns might incur PTS (e.g., Richardson et al., 1995, p. 372ff;
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 B(6)
of LGL's Report. 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
greater than six dB (Southall et al., 2007).
Given the higher level of sound necessary to cause PTS as compared
with TTS, it is considerably less likely that PTS would occur. Baleen
whales generally avoid the immediate area around operating seismic
vessels, as do some other marine mammals. The planned monitoring and
mitigation measures, including visual monitoring, passive acoustic
monitoring (PAM) to complement visual observations (if practicable),
power downs, and shut downs of the airguns when mammals are seen within
or approaching the ``exclusion zones,'' will further reduce the
probability of exposure of marine mammals to sounds strong enough to
induce PTS.
Stranding and Mortality--Marine mammals close to underwater
detonations of high explosives can be killed or severely injured, and
the auditory organs are especially susceptible to injury (Ketten et
al., 1993; Ketten, 1995). However, explosives are no longer used for
marine waters for commercial seismic surveys or (with rare exceptions)
for seismic research; they 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 serious injury, death, or stranding even in the
case of large airgun arrays. However, the association of strandings of
beaked whales with naval exercises involving mid-frequency active sonar
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 (e.g., Hildebrand,
2005; Southall et al., 2007).
[[Page 28577]]
Appendix B(6) of the LGL report 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. 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 supersaturated
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 signals 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 one kHz. Typical military mid-frequency sonar emits non-
impulse sounds at frequencies of two to 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 connection between the
effects of military sonar and seismic surveys on marine mammals.
However, evidence that sonar signals can, in special circumstances,
lead (at least indirectly) to physical damage and mortality (e.g.,
Balcomb and Claridge, 2001; NOAA and USN, 2001; Jepson et al., 2003;
Fern[aacute]ndez 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 (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 (8,490 in \3\) 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 in 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 any beaked whales nearby would avoid
the approaching vessel before being exposed to high sound levels,
(2) the proposed monitoring and mitigation measures, and
(3) differences between the sound sources operated by L-DEO and
those involved in the naval exercises associated with strandings.
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, and other types of organ or
tissue damage (Cox et al., 2006; Southall et al., 2007). Studies
examining such effects are limited. However, resonance effects (Gentry,
2002) and direct noise-induced bubble formations (Crum et al., 2005)
are implausible in the case of exposure to an impulsive broadband
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, very little is known about the potential for seismic
survey sounds (or other types of strong underwater sounds) to cause
non-auditory physical effects in marine mammals. Such effects, if they
occur at all, would presumably be limited to short distances 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
and some odontocetes, are especially unlikely to incur non-auditory
physical effects. Also, the planned mitigation measures (section XI of
L-DEO's application), including shut downs of the airguns will reduce
any such effects that might otherwise occur.
Potential Effects of Other Acoustic Devices
MBES
The Kongsberg EM 122 MBES will be operated from the source vessel
during the planned study. Sounds from the MBES are very short pulses,
occurring for two to 15 ms once every five to 20 s, depending on water
depth. Most of the energy in the sound pulses emitted by this MBES is
at frequencies near 12 kHz, and the maximum source level is 242 dB re:
1 [mu]Pa. The beam is narrow (1 to 2[deg]) in fore-aft extent and wide
(150[deg]) in the cross-track extent. Each ping consists of eight (in
water greater than 1,000 m deep) or four (less than 1,000 m deep)
successive fan-shaped transmissions (segments) at different cross-track
angles. Any given mammal at depth near the trackline would be in the
main beam for only one or two of the nine 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-to-15 ms pulse (or two pulses 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.
[[Page 28578]]
Navy sonars that have been linked to avoidance reactions and
stranding of cetaceans: (1) Generally have longer pulse duration than
the Kongsberg EM 122; and (2) are often directed close to horizontally
versus more downward for the MBES. The area of possible influence of
the MBES is much smaller--a narrow band below the source vessel. Also,
the duration of exposure for a given marine mammal can be much longer
for naval sonar. During L-DEO'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.
Masking--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 MBES
signals (12 kHz) do not overlap with the predominant frequencies in the
calls, which would avoid any significant masking.
Behavioral Responses--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 melas)
(Rendell and Gordon, 1999), and the previously-mentioned beachings by
beaked whales. During exposure to a 21 to 25 kHz ``whale-finding''
sonar with a source level of 215 dB re: 1 [micro]Pa, gray whales
reacted by orienting slightly away from the source and being deflected
from their course by approximately 200 m (Frankel, 2005). When a 38-kHz
echosounder and a 150-kHz acoustic Doppler current profiler were
transmitting during studies in the Eastern Tropical Pacific, baleen
whales showed no significant responses, while spotted and spinner
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 L DEO, 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.
Hearing Impairment and Other Physical Effects--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 L DEO is quite different than sonar used for navy
operations. Pulse duration of the MBES is very short relative to the
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 uses near-horizontally-directed sound. Those factors
would all reduce the sound energy received from the MBES rather
drastically relative to that from naval sonar.
NMFS believes that the brief exposure of marine mammals to one
pulse, or small numbers of signals, from the MBES is not likely to
result in the harassment of marine mammals.
SBP
Sounds from the SBP are very short pulses, occurring for one to
four ms once every second. Most of the energy in the sound pulses
emitted by the SBP is at 3.5 kHz, and the beam is directed downward.
The sub-bottom profiler on the Langseth has a maximum source level of
204 dB re: 1 [micro]Pa.
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--even for an SBP more powerful than that on the
Langseth--if the animal was in the area, it would have to pass the
transducer at close range and in order to be subjected to sound levels
that could cause TTS.
Masking--Marine mammal communications will not be masked
appreciably by the SBP signals given the directionality of the signal
and the brief period when an individual mammal is likely to be within
its beam. 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.
Behavioral Responses--Marine mammal behavioral reactions to other
pulsed sound sources are discussed above, 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 SBP are
considerably weaker than those from the MBES. Therefore, behavioral
responses are not expected unless marine mammals are very close to the
source.
Hearing Impairment and Other Physical Effects--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. In
the case of mammals that do not avoid the approaching vessel and its
various sound sources, mitigation measures that would be applied to
minimize effects of other sources would further reduce or eliminate any
minor effects of the SBP.
OBS
The acoustic release transponder used to communicate with the OBSs
uses frequencies of nine to 13 kHz. Once the OBS is ready to be
retrieved, the crew will use an acoustic release transponder to
interrogate (i.e., send a signal) to the OBS at a frequency of nine to
11 kHz (source level is 190 dB re: 1 [mu]Pa). The acoustic release
transponder will then receive a response at a frequency of nine to 13
kHz. The burn-wire release assembly activates and releases the OBS from
the anchor to float to the surface.
An animal would have to pass by the OBS at close range when the
signal is emitted in order to be exposed to any pulses at a source
level of 190 dB re: 1 [mu]Pa. The sound is expected to undergo a
spreading loss of approximately 40 dB in the first 100 m (328 ft).
Thus, any animals located 100 m (328 ft) or more from the signal will
be exposed to very weak signals (less than 150 dB) that are not
expected to have any effects. The signal is used only for short
intervals to interrogate and trigger the release of the OBS and
consists of pulses rather than a continuous sound. Given the short
duration use of this signal and rapid attenuation in seawater it is
unlikely that the acoustic release signals would significantly affect
marine mammals through masking, disturbance, or hearing impairment. L-
DEO states that any effects likely would be negligible given the brief
exposure at presumable low levels.
[[Page 28579]]
Anticipated Effects on Marine Mammal Habitat
The proposed seismic survey will not result in any permanent impact
on habitats used by marine mammals, including the food sources they
use. The main impact associated with the proposed activity will be
temporarily elevated noise levels and the associated direct effects on
marine mammals, previously discussed in this notice.
The Langseth will deploy 28 OBS on the Shatsky Rise and the 23-kg
OBS anchors will remain upon equipment recovery. Although OBS placement
may disrupt a very small area of seafloor habitat and may disturb
benthic invertebrates, the impacts are expected to be localized and
transitory. The Langseth will deploy the OBS in such a way that creates
the least disturbance to the area. Although OBS placement will disrupt
a very small area of seafloor habitat and could disturb benthic
invertebrates, L-DEO does not anticipate any significant impacts to the
habitats used by the 34 species of marine mammals in the Shatsky Rise
area.
Anticipated Effects on Fish
One reason for the adoption of airguns as the standard energy
source for marine seismic surveys is that, unlike explosives, they have
not been associated with large-scale fish kills. However, existing
information on the impacts of seismic surveys on marine fish
populations is limited (see Appendix D of the LGL Report). There are
three types of potential effects of exposure to seismic surveys: (1)
Pathological, (2) physiological, and (3) behavioral. Pathological
effects involve lethal and temporary or permanent sub-lethal 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 could potentially 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. Furthermore, the available information on the impacts of
seismic surveys on marine fish is from studies of individuals or
portions of a population; there have been no studies at the population
scale. The studies of individual fish have often been on caged fish
that were exposed to airgun pulses in situations not representative of
an actual seismic survey. Thus, available information provides limited
insight on possible real-world effects at the ocean or population
scale. This makes drawing conclusions about impacts on fish problematic
because, ultimately, the most important issues concern effects on
marine fish populations, their viability, and their availability to
fisheries.
The specific received sound levels at which permanent adverse
effects to fish potentially could occur are little studied and largely
unknown. Furthermore, the available information on the impacts of
seismic surveys on marine fish is from studies of individuals or
portions of a population; there have been no studies at the population
scale. The studies of individual fish have often been on caged fish
that were exposed to airgun pulses in situations not representative of
an actual seismic survey. Thus, available information provides limited
insight on possible real-world effects at the ocean or population
scale. This makes drawing conclusions about impacts on fish problematic
because, ultimately, the most important issues concern effects on
marine fish populations, their viability, and their availability to
fisheries.
Hastings and Popper (2005), Popper (2009), and Popper and Hastings
(2009a,b) provided recent critical reviews of the known effects of
sound on fish. The following sections provide a general synopsis of the
available information on the effects of exposure to seismic and other
anthropogenic sound as relevant to fish. The information comprises
results from scientific studies of varying degrees of rigor plus some
anecdotal information. Some of the data sources may have serious
shortcomings in methods, analysis, interpretation, and reproducibility
that must be considered when interpreting their results (see Hastings
and Popper, 2005). Potential adverse effects of the program's sound
sources on marine fish are then noted.
Pathological Effects--The potential for pathological damage to
hearing structures in fish depends on the energy level of the received
sound and the physiology and hearing capability of the species in
question (see Appendix D of the LGL Report). For a given sound to
result in hearing loss, the sound must exceed, by some substantial
amount, the hearing threshold of the fish for that sound (Popper,
2005). The consequences of temporary or permanent hearing loss in
individual fish on a fish population are unknown; however, they likely
depend on the number of individuals affected and whether critical
behaviors involving sound (e.g., predator avoidance, prey capture,
orientation and navigation, reproduction, etc.) are adversely affected.
Little is known about the mechanisms and characteristics of damage
to fish that may be inflicted by exposure to seismic survey sounds. Few
data have been presented in the peer-reviewed scientific literature. As
far as we know, there are only two papers with proper experimental
methods, controls, and careful pathological investigation implicating
sounds produced by actual seismic survey airguns in causing adverse
anatomical effects. One such study indicated anatomical damage, and the
second indicated TTS in fish hearing. The anatomical case is McCauley
et al. (2003), who found that exposure to airgun sound caused
observable anatomical damage to the auditory maculae of ``pink
snapper'' (Pagrus auratus). This damage in the ears had not been
repaired in fish sacrificed and examined almost two months after
exposure. On the other hand, Popper et al. (2005) documented only TTS
(as determined by auditory brainstem response) in two of three fish
species from the Mackenzie River Delta. This study found that broad
whitefish (Coregonus nasus) that received a sound exposure level of 177
dB re 1 [micro]Pa\2\ [middot] s showed no hearing loss. During both
studies, the repetitive exposure to sound was greater than would have
occurred during a typical seismic survey. However, the substantial low-
frequency energy produced by the airguns [less than 400 Hz in the study
by McCauley et al. (2003) and less than approximately 200 Hz in Popper
et al. (2005)] likely did not propagate to the fish because the water
in the study areas was very shallow (approximately 9 m in the former
case and less than two m in the latter). Water depth sets a lower limit
on the lowest sound frequency that will propagate (the ``cutoff
frequency'') at about one-quarter wavelength (Urick, 1983; Rogers and
Cox, 1988).
Wardle et al. (2001) suggested that in water, acute injury and
death of organisms exposed to seismic energy depends primarily on two
features of the sound source: (1) The received peak pressure and (2)
the time required for the pressure to rise and decay. Generally, as
received pressure increases, the period for the pressure to rise and
decay decreases, and the chance of acute pathological effects
increases. According to Buchanan et al. (2004), for the types of
seismic airguns and arrays involved with the proposed program, the
pathological (mortality)
[[Page 28580]]
zone for fish would be expected to be within a few meters of the
seismic source. Numerous other studies provide examples of no fish
mortality upon exposure to seismic sources (Falk and Lawrence, 1973;
Holliday et al., 1987; La Bella et al., 1996; Santulli et al., 1999;
McCauley et al., 2000a,b, 2003; Bjarti, 2002; Thomsen, 2002; Hassel et
al., 2003; Popper et al., 2005; Boeger et al., 2006).
Some studies have reported, some equivocally, that mortality of
fish, fish eggs, or larvae can occur close to seismic sources
(Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman et al., 1996;
Dalen et al., 1996). Some of the reports claimed seismic effects from
treatments quite different from actual seismic survey sounds or even
reasonable surrogates. However, Payne et al. (2009) reported no
statistical differences in mortality/morbidity between control and
exposed groups of capelin eggs or monkfish larvae. Saetre and Ona
(1996) applied a `worst-case scenario' mathematical model to
investigate the effects of seismic energy on fish eggs and larvae. They
concluded that mortality rates caused by exposure to seismic surveys
are so low, as compared to natural mortality rates, that the impact of
seismic surveying on recruitment to a fish stock must be regarded as
insignificant.
Physiological Effects--Physiological effects refer to cellular and/
or biochemical responses of fish to acoustic stress. Such stress
potentially could affect fish populations by increasing mortality or
reducing reproductive success. Primary and secondary stress responses
of fish after exposure to seismic survey sound appear to be temporary
in all studies done to date (Sverdrup et al., 1994; Santulli et al.,
1999; McCauley et al., 2000a,b). The periods necessary for the
biochemical changes to return to normal are variable and depend on
numerous aspects of the biology of the species and of the sound
stimulus (see Appendix D of the LGL Report).
Behavioral Effects--Behavioral effects include changes in the
distribution, migration, mating, and catchability of fish populations.
Studies investigating the possible effects of sound (including seismic
survey sound) on fish behavior have been conducted on both uncaged and
caged individuals (e.g., Chapman and Hawkins, 1969; Pearson et al.,
1992; Santulli et al., 1999; Wardle et al., 2001; Hassel et al., 2003).
Typically, in these studies fish exhibited a sharp ``startle'' response
at the onset of a sound followed by habituation and a return to normal
behavior after the sound ceased.
There is general concern about potential adverse effects of seismic
operations on fisheries, namely a potential reduction in the
``catchability'' of fish involved in fisheries. Although reduced catch
rates have been observed in some marine fisheries during seismic
testing, in a number of cases the findings are confounded by other
sources of disturbance (Dalen and Raknes, 1985; Dalen and Knutsen,
1986; L[oslash]kkeborg, 1991; Skalski et al., 1992; Eng[aring]s et al.,
1996). In other airgun experiments, there was no change in catch per
unit effort (CPUE) of fish when airgun pulses were emitted,
particularly in the immediate vicinity of the seismic survey (Pickett
et al., 1994; La Bella et al., 1996). For some species, reductions in
catch may have resulted from a change in behavior of the fish, e.g., a
change in vertical or horizontal distribution, as reported in Slotte et
al. (2004).
In general, any adverse effects on fish behavior or fisheries
attributable to seismic testing may depend on the species in question
and the nature of the fishery (season, duration, fishing method). They
may also depend on the age of the fish, its motivational state, its
size, and numerous other factors that are difficult, if not impossible,
to quantify at this point, given such limited data on effects of
airguns on fish, particularly under realistic at-sea conditions.
Anticipated Effects on Invertebrates
The existing body of information on the impacts of seismic survey
sound on marine invertebrates is very limited. However, there is some
unpublished and very limited evidence of the potential for adverse
effects on invertebrates, thereby justifying further discussion and
analysis of this issue. The three types of potential effects of
exposure to seismic surveys on marine invertebrates are pathological,
physiological, and behavioral. 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 E of the LGL Report).
The only information available on the impacts of seismic surveys on
marine invertebrates involves studies of individuals; there have been
no studies at the population scale. Thus, available information
provides limited insight on possible real-world effects at the regional
or ocean scale. The most important aspect of potential impacts concerns
how exposure to seismic survey sound ultimately affects invertebrate
populations and their viability, including availability to fisheries.
Literature reviews of the effects of seismic and other underwater
sound on invertebrates were provided by Moriyasu et al. (2004) and
Payne et al. (2008). The following sections provide a synopsis of
available information on the effects of exposure to seismic survey
sound on species of decapod crustaceans and cephalopods, the two
taxonomic groups of invertebrates on which most such studies have been
conducted. The available information is from studies with variable
degrees of scientific soundness and from anecdotal information. A more
detailed review of the literature on the effects of seismic survey
sound on invertebrates is provided in Appendix E of the LGL Report.
Pathological Effects--In water, lethal and sub-lethal injury to
organisms exposed to seismic survey sound appears to depend on at least
two features of the sound source: (1) The received peak pressure; and
(2) the time required for the pressure to rise and decay. Generally, as
received pressure increases, the period for the pressure to rise and
decay decreases, and the chance of acute pathological effects
increases. For the type of airgun array planned for the proposed
program, the pathological (mortality) zone for crustaceans and
cephalopods is expected to be within a few meters of the seismic
source, at most; however, very few specific data are available on
levels of seismic signals that might damage these animals. This premise
is based on the peak pressure and rise/decay time characteristics of
seismic airgun arrays currently in use around the world.
Some studies have suggested that seismic survey sound has a limited
pathological impact on early developmental stages of crustaceans
(Pearson et al., 1994; Christian et al., 2003; DFO, 2004). However, the
impacts appear to be either temporary or insignificant compared to what
occurs under natural conditions. Controlled field experiments on adult
crustaceans (Christian et al., 2003, 2004; DFO, 2004) and adult
cephalopods (McCauley et al., 2000a,b) exposed to seismic survey sound
have not resulted in any significant pathological impacts on the
animals. It has been suggested that exposure to commercial seismic
survey activities has injured giant squid (Guerra et al., 2004), but
the article provides little evidence to support this claim.
Physiological Effects--Physiological effects refer mainly to
biochemical
[[Page 28581]]
responses by marine invertebrates to acoustic stress. Such stress
potentially could affect invertebrate populations by increasing
mortality or reducing reproductive success. Primary and secondary
stress responses (i.e., changes in haemolymph levels of enzymes,
proteins, etc.) of crustaceans have been noted several days or months
after exposure to seismic survey sounds (Payne et al., 2007). The
periods necessary for these biochemical changes to return to normal are
variable and depend on numerous aspects of the biology of the species
and of the sound stimulus.
Behavioral Effects--There is increasing interest in assessing the
possible direct and indirect effects of seismic and other sounds on
invertebrate behavior, particularly in relation to the consequences for
fisheries. Changes in behavior could potentially affect such aspects as
reproductive success, distribution, susceptibility to predation, and
catchability by fisheries. Studies investigating the possible
behavioral effects of exposure to seismic survey sound on crustaceans
and cephalopods have been conducted on both uncaged and caged animals.
In some cases, invertebrates exhibited startle responses (e.g., squid
in McCauley et al., 2000a,b). In other cases, no behavioral impacts
were noted (e.g., crustaceans in Christian et al., 2003, 2004; DFO
2004). There have been anecdotal reports of reduced catch rates of
shrimp shortly after exposure to seismic surveys; however, other
studies have not observed any significant changes in shrimp catch rate
(Andriguetto-Filho et al., 2005). Similarly, Parry and Gason (2006) did
not find any evidence that lobster catch rates were affected by seismic
surveys. Any adverse effects on crustacean and cephalopod behavior or
fisheries attributable to seismic survey sound depend on the species in
question and the nature of the fishery (season, duration, fishing
method).
Proposed Mitigation
In order to issue an incidental take authorization (ITA) under
Section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible
methods of taking pursuant to such activity, and other means of
effecting the least practicable adverse impact on such species or stock
and its habitat, paying particular attention to rookeries, mating
grounds, and areas of similar significance, and the availability of
such species or stock for taking for certain subsistence uses.
L-DEO has based the mitigation measures described herein, to be
implemented for the proposed seismic survey, on the following:
(1) Protocols used during previous L-DEO seismic research cruises
as approved by NMFS;
(2) previous IHA applications and IHAs approved and authorized by
NMFS; and
(3) recommended best practices in Richardson et al. (1995), Pierson
et al. (1998), and Weir and Dolman, (2007).
To reduce the potential for disturbance from acoustic stimuli
associated with the activities, L-DEO and/or its designees has proposed
to implement the following mitigation measures for marine mammals:
(1) Proposed exclusion zones;
(2) power-down procedures;
(3) shutdown procedures, including procedures for species of
concern such as emergency shut-down procedures for North Pacific right
whales; and
(4) ramp-up procedures.
Proposed Exclusion Zones--During the proposed study, all proposed
survey effort will take place in deep (greater than 1,000 m) water. L-
DEO uses safety radii to designate exclusion zones and to estimate take
(described in greater detail in Section VII of the application) for
marine mammals. Table 1 shows the distances at which three sound levels
(160-, 180-, and 190-dB) are expected to be received from the 36-airgun
array and a single airgun. The 180- and 190-dB levels are shut-down
criteria applicable to cetaceans and pinnipeds, respectively, as
specified by NMFS (2000); and L-DEO used these levels to establish the
EZs. If the protected species visual observer (PSVO) detects marine
mammal(s) within or about to enter the appropriate EZ, the Langseth
crew will immediately power down the airguns, or perform a shut down if
necessary (see Shut-down Procedures).
Power-down Procedures--A power down involves decreasing the number
of airguns in use such that the radius of the 180-dB zone is decreased
to the extent that marine mammals are no longer in or about to enter
the EZ. A power down of the airgun array can also occur when the vessel
is moving from one seismic line to another. During a power down for
mitigation, L-DEO will operate one airgun. The continued operation of
one airgun is intended to alert marine mammals to the presence of the
seismic vessel in the area. In contrast, a shut down occurs when the
Langseth suspends all airgun activity.
If the PSVO detects a marine mammal (other than a north Pacific
right whale--see Shut-down Procedures) outside the EZ, but it is likely
to enter the EZ, L-DEO will power down the airguns before the animal is
within the EZ. Likewise, if a mammal is already within the EZ, when
first detected, L-DEO will power down the airguns immediately. During a
power down of the airgun array, L-DEO will also operate the 40-in\3\
airgun. If a marine mammal is detected within or near the smaller EZ
around that single airgun (Table 1), L-DEO will shut down the airgun
(see next Section).
Following a power down, L-DEO will not resume airgun activity until
the marine mammal has cleared the safety zone. L-DEO will consider the
animal to have cleared the EZ if
A PSVO has visually observed the animal leave the EZ, or
A PSVO has not sighted the animal within the EZ for 15 min
for small odontocetes (or pinnipeds), or 30 min for mysticetes and
large odontocetes, including sperm, pygmy sperm, dwarf sperm, and
beaked whales.
During airgun operations following a power down (or shut down)
whose duration has exceeded the time limits specified previously, L-DEO
will ramp-up the airgun array gradually (see Shut-down Procedures).
Shut-down Procedures--L-DEO will shut down the operating airgun(s)
if a marine mammal is seen within or approaching the EZ for the single
airgun. L-DEO will implement a shut down:
(1) If an animal enters the EZ of the single airgun after L-DEO has
initiated a power down, or (2) if a an animal is initially seen within
the EZ of the single airgun when more than one airgun (typically the
full airgun array) is operating.
L-DEO will not resume airgun activity until the marine mammal has
cleared the EZ, or until the PSVO is confident that the animal has left
the vicinity of the vessel. Criteria for judging that the animal has
cleared the EZ will be as described in the preceding section.
Considering the conservation status for North Pacific right whales,
L-DEO will shut down the airgun(s) immediately in the unlikely event
that this species is observed, regardless of the distance from the
Langseth. L-DEO will only begin a ramp-up if the right whale has not
been seen for 30 min.
Ramp-up Procedures--L-DEO will follow a ramp-up procedure when the
airgun array begins operating after a specified period without airgun
operations or when a power down has exceeded that period. L-DEO
proposes that, for the present cruise, this period would be
approximately eight min. This period is based on the 180-dB radius (940
m, 3,084 ft) for the 36-airgun array towed at a depth of nine m in
relation
[[Page 28582]]
to the minimum planned speed of the Langseth while shooting (7.4 km/h,
4.6 mi/hr). Similar periods (approximately eight to ten min) were used
during previous L-DEO surveys.
Ramp-up will begin with the smallest airgun in the array (40-
in\3\). Airguns will be added in a sequence such that the source level
of the array will increase in steps not exceeding six dB per five-
minute period over a total duration of approximately 35 min. During
ramp-up, the PSVOs will monitor the EZ, and if marine mammals are
sighted, L-DEO will implement a power down or shut down as though the
full airgun array 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, L-DEO will
not commence the ramp-up unless at least one airgun (40-in\3\ or
similar) has been operating during the interruption of seismic survey
operations. Given these provisions, it is likely that the airgun array
will not be ramped up from a complete shut down at night or in thick
fog, because the outer part of the safety zone for that array will not
be visible during those conditions. If one airgun has operated during a
power-down period, 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
airgun and could move away. L-DEO will not initiate a ramp-up of the
airguns if a marine mammal is sighted within or near the applicable EZs
during the day or close to the vessel at night.
NMFS has carefully evaluated the applicant's proposed mitigation
measures and has considered a range of other measures in the context of
ensuring that NMFS prescribes the means of effecting the least
practicable adverse 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: (1)
The manner in which, and the degree to which, the successful
implementation of the measure is expected to minimize adverse impacts
to marine mammals; (2) the proven or likely efficacy of the specific
measure to minimize adverse impacts as planned; and (3) 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 or recommended by the public,
NMFS has determined that the required mitigation measures provide the
means of effecting the least practicable adverse impacts on marine
mammals 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 IHAs
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 action area.
L-DEO 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. L-DEO's proposed Monitoring Plan is
described below this section. L-DEO understands that this monitoring
plan will be subject to review by NMFS, and that refinements may be
required. 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. L-
DEO 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
PSVOs will be based aboard the seismic source vessel and will watch
for marine mammals near the vessel during daytime airgun operations and
during any start-ups at night. PSVOs will also watch for marine mammals
near the seismic vessel for at least 30 min prior to the start of
airgun operations after an extended shut down. When feasible, PSVOs
will also observe during daytime periods when the seismic system is not
operating for comparison of sighting rates and behavior with vs.
without airgun operations. Based on PSVO observations, the airguns will
be powered down or shut down when marine mammals are observed within or
about to enter a designated EZ. The EZ is a region in which a
possibility exists of adverse effects on animal hearing or other
physical effects.
During seismic operations at the Shatsky Rise, five PSVOs will be
based aboard the Langseth. L-DEO will appoint the PSVOs with NMFS'
concurrence. At least one PSVO and when practical, two PSVOs will
monitor marine mammals near the seismic vessel during ongoing daytime
operations and nighttime start ups of the airguns. Use of two
simultaneous observers will increase the effectiveness of detecting
animals near the source vessel. PSVOs will be on duty in shifts of
duration no longer than four hours. L-DEO will also instruct other crew
to assist in detecting marine mammals and implementing mitigation
requirements (if practical). Before the start of the seismic survey, L-
DEO will give the crew additional instruction regarding how to
accomplish this task.
The Langseth is a suitable platform for marine mammal and turtle
observations. When stationed on the observation platform, the eye level
will be approximately 21.5 m (70.5 ft) above sea level, and the
observer will have a good view around the entire vessel. During
daytime, the PSVOs will scan the area around the vessel systematically
with reticle binoculars (e.g., 7 x 50 Fujinon), Big-eye binoculars (25
x 150), and with the naked eye. During darkness, night vision devices
(NVDs) will be available (ITT F500 Series Generation 3 binocular-image
intensifier or equivalent), when required. Laser range-finding
binoculars (Leica LRF 1200 laser rangefinder or equivalent) will be
available to assist with distance estimation. Those are useful in
training observers to estimate distances visually, but are generally
not useful in measuring distances to animals directly; that is done
primarily with the reticles in the binoculars.
Passive Acoustic Monitoring
Passive Acoustic Monitoring (PAM) will complement the visual
monitoring program, when practicable. Visual monitoring typically is
not effective during periods of poor visibility or at night, and even
with good visibility, is unable to detect marine mammals when they are
below the surface or beyond visual range. L-DEO can use acoustical
monitoring in addition to visual observations to improve detection,
identification, and localization of cetaceans. The acoustic monitoring
will serve to alert visual observers (if on duty) when vocalizing
cetaceans are detected. It is only useful when marine mammals call, but
it can be effective either by day or by night, and does not depend on
good visibility. It will be monitored in real time so that the visual
observers can be advised when
[[Page 28583]]
cetaceans are detected. When bearings (primary and mirror-image) to
calling cetacean(s) are determined, the bearings will be relayed to the
visual observer to help him/her sight the calling animal(s).
The PAM system consists of hardware (i.e., hydrophones) and
software. The ``wet end'' of the system consists of a towed four-
hydrophone array, two of which are monitored simultaneously; the active
section of the array is approximately 30 m (98 ft) long. The array is
attached to the vessel by a 250-m (820 ft) electromechanical lead-in
cable and a 50-m (164 ft) long deck lead-in cable. However, not the
entire length of lead-in cable is used; thus, the hydrophones are
typically located 120 m (394 ft) behind the stern of the ship. The deck
cable is connected from the array to a computer in the laboratory where
signal conditioning and processing takes place. The digitized signal is
then sent to the main laboratory, where the acoustic PSVO monitors the
system. The hydrophone array is typically towed at depths less than 20
m (66 ft).
The towed hydrophones will ideally be monitored 24 hr/d while at
the seismic survey area during airgun operations, and during most
periods when the Langseth is underway while the airguns are not
operating. One PSVO will monitor the acoustic detection system at any
one time, by listening to the signals from two channels via headphones
and/or speakers and watching the real-time spectrographic display for
frequency ranges produced by cetaceans. PSVOs monitoring the acoustical
data will be on shift for one to six hours at a time. Besides the
visual PSVO, an additional PSVO with primary responsibility for PAM
will also be aboard. All PSVOs are expected to rotate through the PAM
position, although the most experienced with acoustics will be on PAM
duty more frequently.
When a vocalization is detected while visual observations are in
progress, the acoustic PSVO will contact the visual PSVO immediately,
to alert him/her to the presence of cetaceans (if they have not already
been seen), and to allow a power down or shut down to be initiated, if
required. The information regarding the call will be entered into a
database. The data to be entered include an acoustic encounter
identification number, whether it was linked with a visual sighting,
date, time when first and last heard and whenever any additional
information was recorded, position and water depth when first detected,
bearing if determinable, species or species group (e.g., unidentified
dolphin, sperm whale), types and nature of sounds heard (e.g., clicks,
continuous, sporadic, whistles, creaks, burst pulses, strength of
signal, etc.), and any other notable information. The acoustic
detection can also be recorded for further analysis.
PSVO Data and Documentation
PSVOs will record data to estimate the numbers of marine mammals
exposed to various received sound levels and to document apparent
disturbance reactions or lack thereof. Data 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 power down
or shut down of the airguns when a marine mammal is within or near the
EZ.
When a sighting is made, the following information about the
sighting will be recorded:
1. Species, group size, age/size/sex categories (if determinable),
behavior when first sighted and after initial sighting, heading (if
consistent), bearing and distance from seismic vessel, sighting cue,
apparent reaction to the airguns or vessel (e.g., none, avoidance,
approach, paralleling, etc.), and behavioral pace.
2. Time, location, heading, speed, activity of the vessel, sea
state, visibility, and sun glare.
The data listed under (2) 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 and power downs or shut downs will be recorded in
a standardized format. Data will be entered into an electronic
database. The accuracy of the data entry will be verified by
computerized data validity checks as the data are entered and by
subsequent manual checking of the database. These procedures will allow
initial summaries of data to be prepared during and shortly after the
field program, and will facilitate transfer of the data to statistical,
graphical, and other programs for further processing and archiving.
Results from the vessel-based observations will provide:
1. The basis for real-time mitigation (airgun power down or shut
down).
2. Information needed to estimate the number of marine mammals
potentially taken by harassment, which must be reported to NMFS.
3. Data on the occurrence, distribution, and activities of marine
mammals and turtles in the area where the seismic study is conducted.
4. Information to compare the distance and distribution of marine
mammals and turtles relative to the source vessel at times with and
without seismic activity.
5. Data on the behavior and movement patterns of marine mammals and
turtles seen at times with and without seismic activity.
L-DEO will submit a report to NMFS and NSF within 90 days after the
end of the cruise. The report will describe the operations that were
conducted and sightings of marine mammals and turtles near the
operations. The report will provide 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 number and nature of exposures that could result in
``takes'' of marine mammals by harassment or in other ways.
L-DEO will report all injured or dead marine mammals (regardless of
cause) to NMFS as soon as practicable. The report should include the
species or description of the animal, the condition of the animal,
location, time first found, observed behaviors (if alive) and photo or
video, if available.
Estimated Take by Incidental Harassment
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].
Only take by Level B harassment is anticipated and authorized as a
result of the proposed marine geophysical survey at the Shatsky Rise.
Acoustic stimuli (i.e., increased underwater sound) generated during
the operation of the seismic airgun array, may have the potential to
cause marine mammals in the survey area to be exposed to sounds at or
greater than 160 decibels (dB) or cause temporary, short-term changes
in behavior. There is no evidence that the planned activities could
result in injury or mortality within the specified geographic area for
which L-DEO seeks the IHA. The required mitigation and monitoring
measures will minimize any potential risk for injury or mortality.
The following sections describe L-DEO's methods to estimate take by
[[Page 28584]]
incidental harassment and present the applicant's estimates of the
numbers of marine mammals that could be affected during the proposed
geophysical survey. The estimates are based on a consideration of the
number of marine mammals that could be disturbed appreciably by
operations with the 36-airgun array to be used during approximately
3,160 km of seismic surveys at the Shatsky Rise.
L-DEO assumes that, during simultaneous operations of the airgun
array and the other sources, any marine mammals close enough to be
affected by the MBES and SBP would already be affected by the airguns.
However, whether or not the airguns 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 previously. Such reactions are not considered
to constitute ``taking'' (NMFS, 2001). Therefore, L-DEO provides no
additional allowance for animals that could be affected by sound
sources other than airguns.
Density data on 18 marine mammal species in the Shatsky Rise area
are available from two sources using conventional line transect
methods: Japanese sighting surveys conducted since the early 1980s, and
fisheries observers in the high-seas driftnet fisheries during 1987-
1990 (see Table 3 in L-DEO's application). For the 16 other marine
mammal species that could be encountered in the proposed survey area,
data from the western North Pacific right whale are not available (see
Table 3 in L-DEO's application Table 3). L-DEO is not aware of any
density estimates for three of those species--Hubb's (Mesoplodon
carlhubbsi), Stejneger's (Mesoplodon stejnegeri), and gingko-toothed
beaked whales (Mesoplodon ginkgodens). For the remaining 13 species
(see Table 3 in L-DEO's application), density estimates are available
from other areas of the Pacific: 11 species from the offshore stratum
of the 2002 Hawaiian Islands survey (Barlow, 2006) and two species from
surveys of the California Current ecosystem off the U.S. west coast
between 1991 and 2005 (Barlow and Forney, 2007). Those estimates are
based on standard line-transect protocols developed by NMFS' Southwest
Fisheries Science Center (SWFSC).
Densities for 14 species are available from Japanese sighting
surveys in the Shatsky Rise survey area. Miyashita (1993a) provided
estimates for six dolphin species in this area that have been taken in
the Japanese drive fisheries. The densities used here are Miyashita's
(1993a) estimates for the `Eastern offshore' survey area (30-42[deg] N,
145[deg]-180[deg] E). Kato and Miyashita (1998) provided estimates for
sperm whale densities from Japanese sightings data during 1982 to 1996
in the western North Pacific (20-50[deg] N, 130[deg]-180[deg] E), and
Hakamada et al. (2004) provided density estimates for sei whales during
August through September in the JARPN II sub-areas 8 and 9 (35-50[deg]
N, 150-170[deg] E excluding waters in the Exclusive Economic Zone of
Russia) during 2002 and 2003. L-DEO used density estimates during 1994
through 2007 for minke whales at 35-40[deg] N, 157-170[deg] E from
Hakamada et al. (2009), density estimates during 1998 through 2002 for
Bryde's whales at 31-43[deg] N, 145-165[deg] E from Kitakado et al.
(2008), and density estimates during 1994-2007 for blue, fin, humpback,
and North Pacific right whales at 31-51[deg] N, 140-170[deg] E from
Matsuoka et al. (2009).
For four species (northern fur seal, Dall's porpoise, Pacific
white-sided dolphin (Lagenorhynchus obliquidens), northern right-whale
dolphin (Lissodelphis borealis)), estimates of densities in the Shatsky
Rise area are available from sightings data collected by observers in
the high-seas driftnet fisheries during 1987 through 1990 (Buckland et
al., 1993). Those data were analyzed for 5[deg] x 5[deg] blocks, and
the densities used here are from blocks for which available data
overlap the proposed survey area. In general, those data represent the
average annual density in the northern half of the Shatsky Rise survey
area (35-40[deg] N).
The densities mentioned above had been corrected by the original
authors for detectability bias and, with the exception of Kitakado et
al. (2008) and Hakamada et al. (2009), for availability bias.
Detectability bias is associated with diminishing sightability with
increasing lateral distance from the track line [f(0)]. Availability
bias refers to the fact that there is less than a 100 percent
probability of sighting an animal that is present along the survey
track line, and it is measured by g(0).
There is some uncertainty about the accuracy of the density data
from the the Japanese Whale Research Program under Special Permit
(JARPN/JARPN II). For example, densities in Miyashita (1993a) and
Buckland et al. (1993) are from the 1980s and represent the best
available information for the Shatsky Rise area at this time. To
provide some allowance for these uncertainties, particularly
underestimates of densities present and numbers of marine mammals
potentially affected have been derived; L-DEO `s maximum estimates
(precautionary estimates) are 1.5 times greater than the best
estimates.
The estimated numbers of individuals potentially exposed are based
on the 160-dB re 1 [mu]Pa [middot] mrms criterion for all
cetaceans (see Table 3 in this notice). It is assumed that marine
mammals exposed to airgun sounds that strong might change their
behavior sufficiently to be considered ``taken by harassment.''
L-DEO estimates of exposures to various sound levels assume that
the proposed surveys will be completed. As is typical during 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 exclusion zones will
result in the power down or shut down of seismic operations as a
mitigation measure. Thus, the following estimates of the numbers of
marine mammals potentially exposed to sound levels of 160 re 1 [mu]Pa
[middot] mrms are precautionary and probably overestimate
the actual numbers of marine mammals that might be involved. These
estimates also assume that there will be no weather, equipment, or
mitigation delays, which is highly unlikely.
Table 4 of L-DEO's application shows the best and maximum estimated
number of exposures and the number of different individuals potentially
exposed during the seismic survey if no animals moved away from the
survey vessel. The requested take authorization, given in the far right
column of Table 4 of L-DEO's application, is based on the maximum
estimates rather than the best estimates of the numbers of individuals
exposed, because of uncertainties associated with applying density data
from one area to another.
The number of different individuals that may be exposed to airgun
sounds with received levels greater than or equal to 160 dB re 1 [mu]Pa
[middot] mrms 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. The
number of possible exposures (including repeated exposures of the same
individuals) can be estimated by considering the total marine area that
would be within the 160-dB radius around the operating airguns,
including areas of overlap. In the proposed survey, the seismic lines
are widely spaced in the proposed survey area, so an individual mammal
would most likely not be exposed
[[Page 28585]]
numerous times during the survey; the area including overlap is only
1.4 times the area excluding overlap. Moreover, it is unlikely that a
particular animal would stay in the area during the entire survey. The
number of different individuals potentially exposed to received levels
greater than or equal to 160 re 1 [mu]Pa [middot] mrms was
calculated by multiplying:
(1) The expected species density, either ``mean'' (i.e., best
estimate) or ``maximum'', times;
(2) The anticipated minimum area to be ensonified to that level
during airgun operations including overlap (exposures); or
(3) The anticipated area to be ensonified to that level during
airgun operations excluding overlap (individuals).
The area expected to be ensonified was determined by entering the
planned survey lines into a MapInfo Geographic Information System
(GIS), using the GIS to identify the relevant areas by ``drawing'' the
applicable 160-dB buffer (see Table 1) around each seismic line, and
then calculating the total area within the buffers. Areas of overlap
were included only once when estimating the number of individuals
exposed.
Applying the approach described above, approximately 20,831 square
kilometers (km\2\) would be within the 160-dB isopleth on one or more
occasions during the survey, whereas 22,614 km\2\ is the area
ensonified to greater than or equal to 160 dB when overlap is included.
Thus, an average individual marine mammal would be exposed only once
during the survey. Because this approach does not allow for turnover in
the mammal populations in the study area during the course of the
survey, the actual number of individuals exposed could be
underestimated. However, the approach assumes that no cetaceans will
move away from or toward the trackline as the Langseth approaches in
response to increasing sound levels prior to the time the levels reach
160 dB, which will result in overestimates for those species known to
avoid seismic vessels.
Table 4 of L-DEO's application shows the best and maximum estimates
of the number of exposures and the number of different individual
cetaceans that potentially could be exposed to greater than or equal to
160 dB re: 1 [mu]Pa during the seismic survey if no animals moved away
from the survey vessel.
The `best estimate' of the number of individual cetaceans that
could be exposed to seismic sounds with received levels greater than or
equal to 160 dB re: 1 [mu]Pa during the proposed survey is 13,299 (see
Table 3 below this section). That total includes 155 baleen whales, 87
of which are endangered: one North Pacific right whale or 0.6% of the
regional population; 15 humpback whales (1.4%), 37 sei whales (0.4%),
22 fin whales (0.1%), and 12 blue whales (0.4%). In addition, 22 sperm
whales (also listed as endangered under the ESA) or less than 0.1% of
the regional population could be exposed during the survey, and 198
beaked whales including Cuvier's, Longman's, Baird's, Blainville's, and
possibly ginkgo-toothed, Stejneger's, or Hubb's beaked whales. Most
(96%) of the cetaceans potentially exposed are delphinids; short-beaked
common, striped, pantropical spotted, and Pacific white-sided dolphins
and melon-headed whales are estimated to be the most common species in
the area, with best estimates of 6,444 (0.2% of the regional
population), 2,480 (0.4%), 1,467 (0.3%), and 758 (0.1%) exposed to
levels greater than or equal to 160 dB re: 1 [mu]Pa, respectively.
Table 3--Estimates of the Possible Numbers of Marine Mammals Exposed to Different Sound Levels During L-DEO's
Proposed Seismic Survey at Shatsky Rise During July-September, 2010
----------------------------------------------------------------------------------------------------------------
Estimated number Estimated number
of individuals of individuals Approximate
exposed to sound exposed to sound percent of
Species levels >=160 dB levels >=160 dB regional
re: 1 [mu]Pa re: 1 [mu]Pa population (best)
(Best) (Maximum)
----------------------------------------------------------------------------------------------------------------
North Pacific right whale.............................. 1 2 0.60
Humpback whale......................................... 15 22 1.43
Minke whale............................................ 57 85 0.23
Bryde's whale.......................................... 11 16 0.05
Sei whale.............................................. 37 56 0.37
Fin whale.............................................. 22 34 0.14
Blue whale............................................. 12 18 0.35
Sperm whale............................................ 22 32 0.07
Pygmy sperm whale...................................... 66 100 <0.01
Dwarf sperm whale...................................... 163 244 <0.01
Cuvier's beaked whale.................................. 142 212 0.71
Baird's beaked whale................................... 18 27 N.A.
Longman's beaked whale................................. 9 14 N.A.
Blainville's beaked whale.............................. 27 40 0.11
Mesoplodon spp......................................... 2 3 0.01
Rough-toothed dolphin.................................. 65 97 0.04
Bottlenose dolphin..................................... 500 750 0.21
Pantropical spotted dolphin............................ 1,467 2,200 0.33
Spinner dolphin........................................ 17 26 <0.01
Striped dolphin........................................ 2,480 3,721 0.44
Fraser's dolphin....................................... 95 143 0.03
Short-beaked common dolphin............................ 6,444 9,666 0.22
Pacific white-sided dolphin............................ 758 1,137 0.08
Northern right whale dolphin........................... 9 13 <0.01
Risso's dolphin........................................ 225 337 0.03
Melon-headed whale..................................... 27 41 0.06
Pygmy killer whale..................................... 0 0 0.00
False killer whale..................................... 43 64 0.27
Killer whale........................................... 3 5 0.04
[[Page 28586]]
Short-finned pilot whale............................... 104 156 0.20
Dall's porpoise........................................ 457 686 0.03
Northern fur seal...................................... 37 56 <0.01
----------------------------------------------------------------------------------------------------------------
Best and maximum estimates and regional population size estimates are based on Table 3 in L-DEO's application.
N.A. means not available.
Mesoplodon spp. could include ginkgo-toothed, Stejneger's, or Hubb's beaked whales; density (not available) is
an arbitrary low value.
Negligible Impact and Small Numbers Analysis and 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:
(1) The number of anticipated mortalities;
(2) the number and nature of anticipated injuries;
(3) the number, nature, and intensity, and duration of Level B
harassment; and
(4) the context in which the takes occur.
As mentioned previously, NMFS estimates that 34 species of marine
mammals could be potentially affected by Level B harassment over the
course of the IHA. For each species, these numbers are small (each,
less than two percent) relative to the population size.
No injuries or mortalities are anticipated to occur as a result of
the L-DEO's planned marine geophysical survey, and none are authorized.
Only short-term behavioral disturbance is anticipated to occur due to
the brief and sporadic duration of the survey activities. No mortality
or injury is expected to occur, and due to the nature, degree, and
context of behavioral harassment anticipated, the activity is not
expected to impact rates of recruitment or survival.
NMFS has preliminarily determined, provided that the aforementioned
mitigation and monitoring measures are implemented, that the impact of
conducting a marine geophysical survey at the Shatsky Rise in the
northwest Pacific Ocean, July through September 2010, may result, at
worst, in a temporary modification in behavior and/or low-level
physiological effects (Level B harassment) of small numbers of certain
species of marine mammals.
While behavioral modifications, including temporarily vacating the
area during the operation of the airgun(s), may be made by these
species to avoid the resultant acoustic disturbance, the availability
of alternate areas within these areas and the short and sporadic
duration of the research activities, have led NMFS to preliminarily
determine that this action will have a negligible impact on the species
in the specified geographic region.
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 L-DEO's planned research
activities, will result in the incidental take of small numbers of
marine mammals, by Level B harassment only, and that the total taking
from the marine geophysical 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
There are no relevant subsistence uses of marine mammals implicated
by this action.
Endangered Species Act
Of the 34 species of marine mammals that may occur in the proposed
survey area, six are listed as endangered under the ESA, including the
north Pacific right, humpback, sei, fin, blue, and sperm whales. Under
Section 7 of the ESA, NSF has initiated formal consultation with the
NMFS, Office of Protected Resources, Endangered Species Division, on
this proposed seismic survey. NMFS' Office of Protected Resources,
Permits, Conservation and Education Division, has initiated formal
consultation under Section 7 of the ESA with NMFS' Office of Protected
Resources, Endangered Species Division, to obtain a Biological Opinion
evaluating the effects of issuing the IHA on threatened and endangered
marine mammals and, if appropriate, authorizing incidental take. NMFS
will conclude formal Section 7 consultation prior to making a
determination on whether or not to issue the IHA. If the IHA is issued,
L-DEO will be required to comply with the Terms and Conditions of the
Incidental Take Statement corresponding to NMFS' Biological Opinion
issued to both NSF and NMFS' Office of Protected Resources.
National Environmental Policy Act (NEPA)
L-DEO has prepared an EA, and an associated environmental report
that analyzes the direct, indirect and cumulative environmental impacts
of the proposed specified activities on marine mammals including those
listed as threatened or endangered under the ESA. The associated
report, prepared by LGL on behalf of NSF and L-DEO is entitled,
``Environmental Assessment of a Marine Geophysical Survey by the R/V
Marcus G. Langseth on the Shatsky Rise in the Northwest Pacific Ocean,
July-September, 2010.'' Prior to making a final decision on the IHA
application, NMFS will either prepare an independent EA, or, after
review and evaluation of NSF's EA and associated Report, for
consistency with the regulations published by the Council of
Environmental Quality (CEQ) and NOAA Administrative Order 216-6,
Environmental Review Procedures for Implementing the National
Environmental Policy Act, adopt the NSF EA and make a decision of
whether or not to issue a Finding of No Significant Impact (FONSI).
Preliminary Determinations
NMFS has preliminarily determined that the impact of conducting the
specific seismic survey activities described in this notice and the IHA
request in the specific geographic region
[[Page 28587]]
within the Shatsky Rise area in the northwest Pacific Ocean may result,
at worst, in a temporary modification in behavior (Level B harassment)
of small numbers of marine mammals. Further, this activity is expected
to result in a negligible impact on the affected species or stocks of
marine mammals. The provision requiring that the activity not have an
unmitigable impact on the availability of the affected species or stock
of marine mammals for subsistence uses is not implicated for this
proposed action.
For reasons stated previously in this document, the specified
activities associated with the proposed survey are not likely to cause
TTS, PTS or other non-auditory injury, serious injury, or death to
affected marine mammals because:
(1) 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;
(2) The fact that cetaceans would have to be closer than 940 m (0.6
mi) in deep water when the full array is in use at a 9 m (29.5 ft) tow
depth from the vessel to be exposed to levels of sound believed to have
even a minimal chance of causing PTS;
(3) The fact that marine mammals would have to be closer than 3,850
m (2.4 mi) in deep water when the full array is in use at a 9 m (29.5
ft) tow depth from the vessel to be exposed to levels of sound (160 dB)
believed to have even a minimal chance at causing TTS; and
(4) The likelihood that marine mammal detection ability by trained
observers is high at that short distance from the vessel.
As a result, no take by injury, serious injury, or death is
anticipated or authorized, and the potential for temporary or permanent
hearing impairment is very low and will be avoided through the
incorporation of the proposed monitoring and 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
Level B incidental harassment takings (see Table 3 above this section)
is estimated to be small, less than two percent of any of the estimated
population sizes based on the data disclosed in Table 2 of this notice,
and has been mitigated to the lowest level practicable through
incorporation of the monitoring and mitigation measures mentioned
previously in this document.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
issue an IHA to L-DEO for conducting a marine geophysical survey at the
Shatsky Rise area in the northwest Pacific Ocean, provided the
previously mentioned mitigation, monitoring, and reporting requirements
are incorporated. The duration of the IHA would not exceed one year
from the date of its issuance.
Information Solicited
NMFS requests interested persons to submit comments and information
concerning this proposed project and NMFS' preliminary determination of
issuing an IHA (see ADDRESSES). Concurrent with the publication of this
notice in the Federal Register, NMFS is forwarding copies of this
application to the Marine Mammal Commission and its Committee of
Scientific Advisors.
Dated: May 17, 2010.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2010-12296 Filed 5-20-10; 8:45 am]
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