[Federal Register Volume 75, Number 37 (Thursday, February 25, 2010)]
[Notices]
[Pages 8652-8671]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-3869]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XT57
Incidental Takes of Marine Mammals During Specified Activities;
Marine Geophysical Survey in the Commonwealth of the Northern Mariana
Islands, April to June 2010
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental take authorization; request for
comments.
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SUMMARY: NMFS has received an application from the Lamont-Doherty Earth
Observatory (L-DEO), a part of
[[Page 8653]]
Columbia University, for an Incidental Harassment Authorization (IHA)
to take small numbers of marine mammals, by harassment, incidental to
conducting a marine seismic survey in the Commonwealth of the Northern
Mariana Islands (CNMI) during April to June 2010. Pursuant to the
Marine Mammal Protection Act (MMPA), NMFS requests comments on its
proposal to authorize L-DEO to incidentally take, by Level B harassment
only, small numbers of marine mammals during the aforementioned
activity.
DATES: Comments and information must be received no later than March
29, 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 sent to addresses other than the one
provided here. Comments sent via e-mail, including all attachments,
must not exceed a 10-megabyte file size.
All comments received are a part of the public record and will
generally be posted to http://www.nmfs.noaa.gov/pr/permits/incidental.htm without change. All Personal Identifying Information
(for example, name, address, etc.) voluntarily submitted by the
commenter may be publicly accessible. Do not submit Confidential
Business Information or otherwise sensitive or protected information.
A copy of the application containing a list of the references used
in this document may be obtained by writing to the address specified
above, telephoning the contact listed below (see FOR FURTHER
INFORMATION CONTACT), or visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm. Documents cited in this
notice may be viewed, by appointment, during regular business hours, at
the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Howard Goldstein or Jolie Harrison,
Office of Protected Resources, NMFS, 301-713-2289.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.)
direct the Secretary of Commerce (Secretary) to allow, upon request,
the incidental, but not intentional, taking of marine mammals 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 either regulations are issued or, if the taking
is limited to harassment, a notice of a proposed authorization is
provided to the public for review.
An authorization for incidental 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), will not have an
unmitigable adverse impact on the availability of the species or
stock(s) for subsistence uses, and if the permissible methods of taking
and requirements pertaining to the mitigation, monitoring and reporting
of such takings are set forth. NMFS has defined ``negligible impact''
in 50 CFR 216.103 as ``* * * an impact resulting from the specified
activity that cannot be reasonably expected to, and is not reasonably
likely to, adversely affect the species or stock through effects on
annual rates of recruitment or survival.'' The authorization must also
set forth permissible methods of taking, other means of affecting the
least practicable adverse impact on the species or stock and its
habitat and requirements for monitoring and reporting such takings.
Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the United States can apply for an authorization
not to exceed one year to incidentally take small numbers of marine
mammals by 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''].
16 U.S.C. 1362(18)
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS'
review of an application followed by a 30-day public notice and comment
period for any proposed authorizations for the incidental harassment of
marine mammals. Within 45 days of the close of the comment period,
NMFS, on behalf of the Secretary, makes the findings set forth in
clause 101(a)(5)(D)(i) of the MMPA and must either issue the
authorization with appropriate conditions to meet the requirements of
clause 101(a)(5)(D)(ii) or deny it. NMFS will publish notice of
issuance or denial of the authorization within thirty days of issuance
or denial.
Summary of Request
On December 16, 2009, NMFS received an IHA application and an
Environmental Assessment (EA) from L-DEO for the taking, by Level B
harassment only, of small numbers of several species of marine mammals
incidental to conducting, with research funding from the National
Science Foundation (NSF), a marine seismic survey in the CNMI during
April to June, 2010. The CNMI is a commonwealth in a political union
with the U.S. The survey will take place in the Exclusive Economic Zone
(EEZ) of the U.S. in water depths greater than 2,000 m (6,561.7 ft).
The seismic study will use a towed array of 36 airguns with a total
discharge volume of approximately 6,600 in\3\.
Description of the Specified Activity
L-DEO plans to conduct a seismic survey in the CNMI. The survey
will occur in the area 16.5[deg] to 19[deg] North, 146.5[deg] to
150[deg] East within the EEZ (see Figure 1 of L-DEO's application). The
project is scheduled to occur from April 25 to June 6, 2010. Some minor
deviation of these dates is possible, depending on logistics and
weather (i.e., the cruise may depart earlier to be extended due to poor
weather; there could be extra days (up to three) of seismic operations
if collected data are of substandard quality.
L-DEO plans to conduct the seismic survey over the Mariana outer
forearc, the trench and the outer rise of the subducting and bending
Pacific plate. The objective is to understand the water cycle within
subduction-systems. Subduction systems are where the basic building
blocks of continental crust are made and where Earth's great
earthquakes occur. Little is known about either of these processes, but
water cycling through the system is thought to be the primary
controlling factor in both arc-crust generation and megathrust
seismicity.
An important new hypothesis has recently been suggested that, if
correct, will transform our understanding of the water budget of
subduction systems. This hypothesis holds that cracking attributable to
bending of the subducting plate enables water to penetrate through the
subducting crust into the mantle, where it hydrates the mantle by
forming the hydrous mineral phase serpentine. This phase is stable to
greater depths than the hydrous clay minerals of the crust, where most
of the subducting water was previously believed to be held. Thus, if
this
[[Page 8654]]
hypothesis is correct, it provides a mechanism for transporting water
far beneath the mantle wedge, where it promotes melting and crust
formation, and possibly even deeper into the mantle, providing a whole-
earth hydration mechanism that promotes the continued operation of
plate tectonics, without which our planet would likely be unable to
support life.
The scientists involved in this program will test this hypothesis
by measuring mantle seismic sounds speeds, which vary with degree of
serpentinization. By comparing these measurements from the Mariana
system, which is old and cold with the Costa Rica system, which is
young and warm and where similar measurements have recently been made,
we should be able to definitively determine whether or not substantial
water is taken up by the mantle of subducting plates near the outer
rise of seafloor trenches.
The planned survey will involve one source vessel, the R/V Marcus
G. Langseth (Langseth), which will occur in the CNMI. The Langseth will
deploy an array of 36 airguns (6,600 in\3\) as an energy source at a
tow depth of 9 m (30 ft). The receiving system will consist of a 6 km
(3.7 mi) hydrophone streamer and approximately 85 ocean bottom
seismometers (OBSs). As the airgun array is towed along the survey
lines, the hydrophone streamer will receive the returning acoustic
signals and transfer the data to the on-board processing system. The
OBSs record the returning acoustic signals internally for later
analysis. The OBSs to be used for the 2010 program will be deployed and
most (approximately 60) will be retrieved during the cruise, whereas 25
will be left in place for one year.
The planned seismic survey will consist of approximately 2,800 km
(1,739.8 mi) of transect lines within the CNMI (see Figure 1 of L-DEO's
application). The survey will take place in water depths greater than
2,000 m (6,561.7 ft). All planned geophysical data acquisition
activities will be conducted by L-DEO with onboard assistance by the
scientists who have proposed the study. The scientific team consists of
Dr. Doug Wiens (Washington University, St. Louis, MO) and Daniel
Lizarralde (Woods Hole Oceanographic Institution [WHOI], Woods Hole,
MA). The vessel will be self-contained, and the crew will live aboard
the vessel for the entire cruise.
In addition to the operations of the airgun array, a Kongsberg EM
multibeam echosounder (MBES) and a Knudsen 320B sub-bottom profiler
(SBP) will be operated from the Langseth continuously throughout the
CNMI cruise.
Vessel Specifications
The Langseth will be used as the source vessel. The Langseth will
tow the 36 airgun array along predetermined lines. The Langseth will
also tow the hydrophone streamer, retrieve OBSs, and may also deploy
OBSs. When the Langseth is towing the airgun array as well as the
hydrophone streamer, the turning rate of the vessel while the gear is
deployed is limited to five degrees per minute. Thus, the
maneuverability of the vessel is limited during operations with the
streamer.
The Langseth has a length of 71.5 m (234.6 ft), a beam of 17 m
(55.8 ft), and a maximum draft of 5.9 m (19.4 ft). The ship was
designed as a seismic research vessel, with a propulsion system
designed to be as quiet as possible to avoid interference with the
seismic signals. The ship is powered by two Bergen BRG-6 diesel
engines, each producing 3,550 horse-power (hp), that drive the two
propellers directly. Each propeller has four blades, and the shaft
typically rotates at 750 revolutions per minute (rpm). 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 (4 to 5 kt). When not towing seismic survey
gear, the Langseth can cruise at 20 to 24 km/hr (11 to 13 kt). The
Langseth has a range of 25,000 km (15,534 mi), which is the distance
the vessel can travel without refueling. The Langseth will also serve
as the platform from which vessel-based Protected Species Observers
(PSOs) will watch for marine animals before and during airgun
operations. NMFS believes that the realistic possibility of a ship-
strike of a marine mammal by the vessel during research operations and
in-transit during the proposed survey is discountable.
Acoustic Source Specifications--Seismic Airguns
During the proposed survey, the airgun array to be used will
consist of 36 airguns, with a total volume of approximately 6,600
in\3\. The airgun array will consist of a mixture of Bolt 1500LL and
1900LL airguns. The airguns array will be configured as four identical
linear arrays or ``strings'' (see Figure 2 in L-DEO's application).
Each string will have 10 airguns; the first and last airguns in the
strings are spaced 16 m (52.5 ft) apart. Nine airguns in each string
will be fired simultaneously, while the tenth is kept in reserve as a
spare, to be turned on in case of failure of another airgun. The four
airgun strings will be distributed across an approximate area of 24 x
16 m (78.7 x 52.5 ft) behind the Langseth and will be towed
approximately 140 m (459 ft) behind the vessel. The shot interval will
be 37.5 m (123.0 ft) or 150 m (492.1 ft) during the study. The shot
interval will be relatively short (approximately 37.5 m or
approximately 15 to 18 seconds [s]) for multi-channel seismic surveying
with the hydrophone streamer, and relatively long (approximately 150 m
or approximately 58 to 73 s) when recording data on the OBSs. The
firing pressure of the array is 1,900 pounds per square inch (psi).
During firing, a brief (approximately 0.1 s) pulse of sound is emitted.
The airguns will be silent during the intervening periods.
Because the actual source is a distributed source (36 airguns)
rather than a single point source, the highest sound levels measurable
at any location in the water will be less than the nominal source (265
dB re 1 [mu] Pa[middot]m, peak-to-peak [pk-pk]). In addition, the
effective source level for sound propagating in near-horizontal
directions will be substantially lower than the nominal source level
applicable to downward propagation because of the directional nature of
the sound from the airgun array.
Table 1--Distances To Which Sound Levels Greater Than or Equal to 190, 180, and 160 dB re 1 [mu]Pa (rms) Could
be Received in Deep (Greater Than 1,000 m) Water During the Proposed Survey in the CNMI, April 25 to June 6,
2010
----------------------------------------------------------------------------------------------------------------
Predicted RMS distances (m)
Source and volume Tow depth (m) Water depth -----------------------------------------------
190 dB 180 dB 160 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun (40 in3)... 9 Deep (>1,000 m). 12 40 385
4 strings, 36 airguns (6,600 9 Deep (>1,000 m). 400 940 3,850
in3).
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[[Page 8655]]
Acoustic Source Specifications--Multibeam Echosounder (MBES) and Sub-
bottom Profiler (SBP)
Along with the airgun operations, two additional acoustical data
acquisition systems will be operated during the survey. The ocean floor
will be mapped with Kongsberg EM 122 MBES and Knudsen 320 SBP. These
sound sources will be operated from the Langseth continuously
throughout the cruise.
The Kongsberg EM 122 MBES operates at 10.5 to 13 (usually 12) kHz
and is hull-mounted on the Langseth. The transmitting beamwidth is
1[deg] or 2[deg] fore-aft and 150[deg] athwartship. The maximum source
level is 242 dB re 1 [mu]Pam (rms). Each ``ping'' consists of eight (in
water greater than 1,000 m deep) or four (less than 1,000 m) successive
fan-shaped transmissions, each ensonifying a sector that extends 1[deg]
fore-aft. Continuous-wave (CW) pulses increase from two to 15 ms long
in water depths up to 2,600 m (8,530 ft), and FM chirp pulses up to 100
ms long are used in water greater than 2,600 m. The successive
transmissions span an overall cross-track angular extent of about
150[deg], with 2 ms gaps between pulses for successive sectors.
The Knudsen 320B SBP is normally operated to provide information
about the sedimentary features and the bottom topography that is being
mapped simultaneously by the MBES. The SBP beam is transmitted as a 27
degree cone, which is directed downward by a 3.5 kHz transducer in the
hull of the Langseth. The maximum output is 1,000 watts (204 dB), but
in practice, the output varies with water depth. The pulse interval is
1 s, but a common mode of operation is to broadcast five pulses at 1 s
intervals followed by a 5 s pause.
OBS Description and Deployment
Approximately 85 OBSs will be deployed by the Langseth before the
survey, in water depths 3,100 to 8,100 m (10,170.6 to 26,574.8 ft).
There are three types of OBS deployment:
(1) Approximately 20 broad-band OBSs located on the bottom in a
wide two-dimensional (2D) array with a spacing of no more than 100 km
(62.1 mi);
(2) Approximately five short-period OBSs tethered in the water
column above the trench areas deeper than 6 km; and
(3) Approximately 60 short-period OBSs located on the bottom in a
2D array with a spacing of about 75 km (46.6 mi).
The first two types will be left in place for one year for passive
recording, and the third type will be retrieved after the seismic
operations. OBSs deployed in water deeper than 5,500 m (18,044.6 ft)
will require a tether to keep the instruments at a depth of 5,500 to
6,000 m (18,044.6 to 19,685 ft), as the instruments are rated to a
maximum depth of 6,000 m. The lengths of the tethers will vary from 65
to 2,600 m (213.3 to 8,530.2 ft). The tether will fall to the seafloor
when the OBS is released.
Two different types of OBSs may be used during the 2010 program.
The WHOI ``D2'' OBS has a height of approximately 1 m (3.3 ft) and a
maximum diameter of 50 cm (19.7 in). The anchor is made of hot-rolled
steel and weighs 23 kg (50.7 lb). The anchor dimensions are
2.5x30.5x38.1 cm. The LC4x4 OBS from the Scripps Institution of
Oceanography (SIO) has a volume of approximately 1 m3, with
an anchor that consists of a large piece of steel grating
(approximately 1 m2). Once an OBS is ready to be retrieved,
an acoustic release transponder interrogates the OBS at a frequency of
9 to 11 kHz, and a response is received at a frequency of 9 to 13 kHz.
The burn-wire release assembly is then activated, and the instrument is
released from the anchor to float to the surface. The anchors will
remain on the sea floor.
Proposed Dates, Duration, and Specific Geographic Area
The survey will occur in the following specific geographic area:
16.5[deg] to 19[deg] North, 146.5[deg] to 150[deg] East within the EEZ
of the U.S. (see Figure 1 of L-DEO's application). Water depths in the
survey area range from greater than 2,000 m to greater than 8,000 m
(26,246.7 ft). The closest that the vessel will approach to any island
is approximately 50 km (31.1 mi) from Alamagan. The exact dates of the
activities depend on logistics and weather conditions. The Langseth
will depart from Guam on April 25, 2010 and return to Guam on June 6,
2010. Seismic operations will be carried out for 16 days, with the
balance of the cruise occupied in transit (approximately 2 days) and in
deployment and retrieval of OBSs and maintenance (25 days).
Description of Marine Mammals in the Proposed Activity Area
A total of 27 cetacean species, including 20 odontocete (dolphins
and small- and large-toothed whales) species and nine mysticetes
(baleen whales) are known to occur in the area affected by the
specified activities associated with the proposed CNMI marine
geophysical survey (see Table 2 of L-DEO's application). Cetaceans and
pinnipeds, which are the subject of this IHA application, are protected
by the MMPA and managed by NMFS in accordance with its requirements.
Information on the occurrence, distribution, population size, and
conservation status for each of the 27 marine mammal species that may
occur in the proposed project area is presented in the Table 2 of L-
DEO's application as well as here in the table below (Table 2). The
status of certain marine mammal species as threatened or endangered is
based on evaluation and listing procedures under the U.S. Endangered
Species Act (ESA), the International Union for Conservation of Nature
(IUCN) Red List of Threatened Species, and Convention on International
Trade in Endangered Species (CITES). Several marine mammal species that
may be affected by the proposed IHA are listed as Endangered under
Section 4 of the ESA, including the North Pacific right, sperm,
humpback, fin, sei, and blue whales.
There are no reported sightings of pinnipeds in the CNMI (e.g.,
DON, 2005). The dugong (Dugong dugon), also listed under the ESA as
Endangered, is distributed throughout most of the Indo-Pacific region
between approximately 27[deg] North and south of the equator (Marsh,
2002); it seems unlikely that dugongs have ever inhabited the Mariana
Islands (Nishiwaki et al., 1979). There have been some extralimital
sightings in Guam, including a single dugong in Cocos Lagoon in 1974
(Randall et al., 1975) and several sightings of an individual in 1985
along the southeastern coast (Eldredge, 2003).
Table 2 below outlines the cetacean species, their habitat and
abundance in the proposed project area, and the requested take levels.
Additional information regarding the distribution of these species
expected to be found in the project area and how the estimated
densities were calculated may be found in L-DEO's application.
[[Page 8656]]
Table 2--The Habitat, Regional Abundance, Conservation Status, and Best and Maximum Density Estimates of Marine
Mammals That Could Occur in or Near the Proposed Seismic Survey Area in the CNMI. See Tables 2 to 4 in L-DEO's
Application for Further Detail
----------------------------------------------------------------------------------------------------------------
Density/
Regional 1000 km2 Density/
Species Habitat population size \a\ ESA \b\ (best) 1000 km2
\c\ (max) \d\
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Mysticetes:
North Pacific right whale Pelagic and coastal. Few 100s........... EN.......... 0.01 0.01
(Eubalaena japonica).
Humpback whale (Megaptera Mainly nearshore 938-1107 \e\....... EN.......... 0.01 0.02
novaeangliae). waters and banks.
Minke whale (Balaenoptera Pelagic and coastal. 25,000 \f\......... NL.......... 0.01 0.02
acutorostrata).
Bryde's whale Balaenoptera Pelagic and coastal. 20,000-30,000...... NL.......... 0.41 0.62
brydei).
Sei whale (Balaenoptera Primarily offshore, 7,260-12,620 \g\... EN.......... 0.29 0.44
borealis). pelagic.
Fin whale (Balaenoptera Continental slope, 13.620-18.680 \h\.. EN.......... 0.01 0.02
physalus). mostly pelagic.
Blue whale (Balaenoptera Pelagic and coastal. N.A................ EN.......... 0.01 0.02
musculus).
Odontocetes:
Sperm whale (Physeter Usually pelagic and 29,674 \i\......... EN.......... 1.23 1.85
macrocephalus). deep seas.
Pygmy sperm whale (Kogia Deep waters off N.A................ NL.......... 2.91 4.37
breviceps). shelf.
Dwarf sperm whale (Kogia Deep waters off the 11,200 \j\......... NL.......... 7.14 10.71
sima). shelf.
Cuvier's beaked whale Pelagic............. 20,000 \j\......... NL.......... 6.21 9.32
(Ziphius cavirostris).
Longman's beaked whale Deep water.......... N.A................ NL.......... 0.41 0.62
(Indopacetus pacificus).
Blainville's beaked whale Pelagic............. 25,300 \k\......... NL.......... 1.17 1.76
(Mesoplodon densirostris).
Ginkgo-toothed beaked whale Pelagic............. N.A................ NL.......... 0.01 0.02
(Mesoplodon ginkgodens).
Rough-toothed dolphin (Steno Deep water.......... 146,000 ETP \j\.... NL.......... 0.29 0.44
bredanensis).
Common bottlenose dolphin Coastal and oceanic, 243,500 ETP \j\.... NL.......... 0.21 0.32
(Tursiops truncatus). shelf break.
Pantropical spotted dolphin Coastal and pelagic. 800,000 ETP \j\.... NL.......... 22.60 33.90
(Stenella attenuata).
Spinner dolphin (Stenella Coastal and pelagic. 800,000 ETP \j\.... NL.......... 3.14 4.71
longirostris).
Striped dolphin (Stenella Off continental 1,000,000 ETP \j\.. NL.......... 6.16 9.24
coeruleoalba). shelf.
Fraser's dolphin Waters greater than 289,000 ETP \j\.... NL.......... 4.17 6.26
(Lagenodelphis hosei). 1,000 m.
Short-beaked common dolphin Shelf and pelagic, 3,000,000 ETP \j\.. NL.......... 0.01 0.01
(Delphinus delphis). seamounts.
Risso's dolphin (Grampus Waters greater than 175,000 ETP \j\.... NL.......... 0.97 1.46
griseus). 1,000 m, seamounts.
Melon-headed whale Oceanic............. 45,000 ETP \j\..... NL.......... 4.28 6.42
(Peponocephala electra).
Pygmy killer whale (Feresa Deep, pantropical 39,000 ETP \j\..... NL.......... 0.14 0.21
attenuata). waters.
False killer whale (Pseudorca Pelagic............. 40,000 \j\......... NL.......... 1.11 0.21
crassidens).
Killer whale (Orcinus orca).. Widely distributed.. 8,500 ETP \j\...... NL.......... 0.14 0.21
Short-finned pilot whale Mostly pelagic, high- 500,000 ETP \j\.... NL.......... 1.59 2.39
(Globicephala macrorhynchus). relief topography.
Sirenians: Dugong (Dugong dugon). Coastal............. N.A................ EN.......... N.A. N.A.
----------------------------------------------------------------------------------------------------------------
N.A.--Data not available or species status was not assessed,
\a\ North Pacific (Jefferson et al., 2008) unless otherwise indicated.
\b\ U.S. Endangered Species Act: EN = Endangered, NL = Not listed.
\c\ Best estimate as listed in Table 3 of the application.
\d\ Maximum estimate as listed in Table 3 of the application.
\e\ Western North Pacific (Calambokidis et al., 2008).
\f\ Northwest Pacific and Okhotsk Sea (IWC, 2007a).
\g\ North Pacific (Tillman, 1977).
\h\ North Pacific (Ohsumi and Wada, 1974).
\i\ Western North Pacific (Whitehead, 2002b).
\j\ Eastern Tropical Pacific = ETP (Wade and Gerrodette, 1993).
\k\ ETP; all Mesoplodon spp. (Wade and Gerodette, 1993).
Potential Effects on Marine Mammals
Potential Effects of Airgun Sounds
The effects of sounds from airguns might result in one or more of
the following: tolerance, masking of natural sounds, behavioral
disturbances, temporary or permanent hearing impairment, 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 project would result in any
cases of temporary or especially permanent hearing impairment, or any
significant non-auditory physical or physiological effects. Some
behavioral disturbance is expected, but this would be localized and
short-term. NMFS concurs with this determination.
The root mean square (rms) received levels that are used as impact
criteria for marine mammals are not directly comparable to the peak or
peak-to-peak values normally used to characterize source levels of
airgun arrays. The measurement units used to describe airgun sources,
peak or peak-to-peak decibels, are always higher than the rms decibels
referred to in biological literature. A measured received level of 160
dB rms in the far field would typically correspond to a peak
measurement of approximately 170 to 172 dB, and to a peak-to-peak
measurement of approximately 176 to 178 dB, as measured for the same
pulse received at the same location (Greene, 1997; McCauley et al.,
1998, 2000a). The precise difference between rms and peak or peak-to-
peak values depends on the frequency content and duration of the pulse,
among other factors. However, the rms level is always lower
[[Page 8657]]
than the peak or peak-to-peak level for an airgun-type source.
Tolerance
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
For a summary of the characteristics of airgun pulses, see Appendix B
(3) of the EA. Numerous studies have shown that marine mammals at
distances more than a few kilometers from operating seismic vessels
often show no apparent response--see Appendix B (5) of L-DEO's
application. That is often true even in cases when the pulsed sounds
must be readily audible to the animals based on measured received
levels and the hearing sensitivity of the mammal group. Although
various baleen whales, toothed whales, and (less frequently) pinnipeds
have been shown to react behaviorally to airgun pulses under some
conditions, at other times, mammals of all three types have shown no
overt reactions. In general, pinnipeds usually seem to be more tolerant
of exposure to airgun pulses than are cetaceans, with relative
responsiveness of baleen and toothed whales being variable.
Masking
Obscuring of sounds of interest by interfering sounds, generally at
similar frequencies, is known as masking. Masking effects of pulsed
sounds (even from large arrays of airguns) on marine mammal calls and
other natural sounds are expected to be limited, although there are few
specific data of relevance. Because of the intermittent nature and low
duty cycle of seismic pulses, animals can emit and receive sounds in
the relatively quiet intervals between pulses. However in exceptional
situations, reverberation occurs for much or all of the interval
between pulses (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. The airgun sounds are
pulsed, with quiet periods between the pulses, and whale calls often
can be heard between the seismic pulses (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; Dunn et al., 2009).
In the northeast Pacific Ocean, blue whale calls have been recorded
during a seismic survey off Oregon (McDonald et al., 1995). 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 the presence of seismic pulses (Madsen et
al., 2002; Tyack et al., 2003; Smultea et al., 2004; Holst et al.,
2006; Jochens et al., 2008). Dolphins and porpoises commonly are heard
calling while airguns are operating (Gordon et al., 2004; Smultea et
al., 2004; Holst et al., 2005a,b; Potter et al., 2007). The sounds
important to small odontocetes are predominantly at much higher
frequencies than the dominant components of airgun sounds, thus
limiting the potential for masking. In general, masking effects of
seismic pulses are expected to be minor, given the normally
intermittent nature of seismic pulses. Masking effects on marine
mammals are discussed further in Appendix B (4) of the L-DEO EA.
Disturbance Reactions
Disturbance includes a variety of effects, including subtle changes
in behavior, more conspicuous changes in activities, and displacement.
Reactions to sound, if any, depend on species, state of maturity,
experience, current activity, reproductive state, time of day, and many
other factors (Richardson et al., 1995; Wartzok et al., 2004; Southall
et al., 2007; Weilgart, 2007). If a marine mammal does react to an
underwater sound by changing its behavior or moving a small distance,
the response may or may not rise to the level of ``harassment'' to the
individual, or affect the stock or the species population as a whole.
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 are likely to be present within a
particular distance of industrial activities, and/or exposed to a
particular level of industrial sound. In most cases, this practice
potentially overestimates the numbers of marine mammals that would be
affected in some biologically-important manner.
The sound exposure 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
several species. However, information is lacking for many species.
Detailed studies have been done on humpback, gray, bowhead, and sperm
whales. Less detailed data are available for some other species of
baleen whales, small toothed whales, and sea otters, but for many
species there are no data on responses to marine seismic surveys.
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 L-DEO EA,
baleen whales exposed to strong noise pulses from airguns often react
by deviating from their normal migration route and/or interrupting
their feeding activities and moving away from the sound source. In the
case of the 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 demonstrated
that seismic pulses with received levels of 160 to 170 dB re 1 [mu]Pa
(rms) 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 (2.8 to 9 mi) 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 L-DEO 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 to 170 dB re 1 [mu]Pa (rms).
Responses of humpback whales to seismic surveys have been studied
during migration, on the summer feeding grounds, and on Angolan winter
breeding grounds; there has also been discussion of effects on the
Brazilian wintering grounds. McCauley et al. (1998, 2000a) studied the
responses of humpback whales off Western Australia to a full-scale
seismic survey with a 16 airgun, 2,678 in\3\ array, and to a single 20
in\3\ airgun with a source level of 227
[[Page 8658]]
dB re 1 [mu]Pam peak-to-peak. McCauley et al. (1998) documented that
initial avoidance reactions began at 5 to 8 km (3.1 to 5 mi) from the
array, and that those reactions kept most pods approximately 3 to 4 km
(1.9 to 2.5 mi) from the operating seismic boat. McCauley et al.
(2000a) noted localized displacement during migration of 4 to 5 km (2.5
to 3.1 mi) by traveling pods and 7 to 12 km (4.3 to 7.5 mi) by cow-calf
pairs. Avoidance distances with respect to the single airgun were
smaller (2 km [1.2 mi]) but consistent with the results from the full
array in terms of received sound levels. The mean received level for
initial avoidance of an approaching airgun was 140 dB re 1 [mu]Pa (rms)
for humpback whale pods containing females, and at the mean closest
point of approach (CPA) distance the received level was 143 dB re 1
[mu]Pa (rms). The initial avoidance response generally occurred at
distances of 5 to 8 km (3.1 to 5 mi) from the airgun array and 2 km
(1.2 mi) from the single airgun. However, some individual humpback
whales, especially males, approached within distances of 100 to 400 m
(328 to 1,312 ft), where the maximum received level was 179 dB re 1
[mu]Pa (rms).
Humpback whales on their summer feeding grounds in southeast Alaska
did not exhibit persistent avoidance when exposed to seismic pulses
from a 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 on
an approximate rms basis. Malme et al. (1985) concluded that there was
no clear evidence of avoidance, despite the possibility of subtle
effects, at received levels up to 172 re 1 [mu]Pa on an approximate rms
basis.
It has been suggested that South Atlantic humpback whales wintering
off Brazil may be displaced or even strand upon exposure to seismic
surveys (Engel et al., 2004). The evidence for this was circumstantial
and subject to alternative explanations (IAGC, 2004). Also, the
evidence was not consistent with subsequent results from the same area
of Brazil (Parente et al., 2006), or with results from direct studies
of 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 the activity
(migrating vs. feeding). Bowhead whales migrating west across the
Alaskan Beaufort Sea in autumn, in particular, are unusually
responsive, with substantial avoidance occurring out to distances of 20
to 30 km (12.4 to 18.6 mi) from a medium-sized airgun source at
received sound levels of around 120 to 130 dB re 1 [mu]Pa (rms) (Miller
et al., 1999; Richardson et al., 1999; see Appendix B (5) of the EA).
However, more recent research on bowhead whales (Miller et al., 2005a;
Harris et al., 2007) corroborates earlier evidence that, during the
summer feeding season, bowheads are not as sensitive to seismic
sources. Nonetheless, subtle but statistically significant changes in
surfacing-respiration-dive cycles were evident upon statistical
analysis (Richardson et al., 1986). In summer, bowheads typically begin
to show avoidance reactions at a received level of about 152 to 178 dB
re 1 [mu]Pa (rms) (Richardson et al., 1986, 1995; Ljungblad et al.,
1988; Miller et al., 2005a).
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. Malme et al. (1986, 1988) estimated, based on small sample sizes,
that 50 percent of feeding gray whales ceased feeding at an average
received pressure level of 173 dB re 1 [mu]Pa on an (approximate) rms
basis, and that 10 percent of feeding whales interrupted feeding at
received levels of 163 dB dB re 1 [mu]Pa (rms). Those findings were
generally consistent with the results of experiments conducted on
larger numbers of gray whales that were migrating along the California
coast (Malme et al., 1984; Malme and Miles, 1985), and with
observations of Western Pacific gray whales feeding off Sakhalin
Island, Russia, when a seismic survey was underway just offshore of
their feeding area (Wursig et al., 1999; Gailey et al., 2007; Johnson
et al., 2007; Yazvenko et al. 2007a,b), along with data on gray whales
off British Columbia (Bain and Williams, 2006).
Various species of Balaenoptera (blue, sei, fin, Bryde's, and minke
whales) have occasionally been reported in areas ensonified by airgun
pulses (Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006),
and calls from blue and fin whales have been localized in areas with
airgun operations (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 and not shooting (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 Nova Scotia, Moulton
and Miller (2005) found little difference in sighting rates (after
accounting for water depth) and initial sighting distances of
balaenopterid whales when airguns were operating vs. silent. However,
there were indications that these whales were more likely to be moving
away when seen during airgun operations. Similarly, ship-based
monitoring studies of blue, fin, sei, and minke whales offshore of
Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more than
small differences in sighting rates and swim direction during seismic
vs. non-seismic periods (Moulton et al., 2005, 2006a,b).
Data on short-term reactions (or lack of reactions) of 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. However, gray whales continued to migrate
annually along the west coast of North America with substantial
increases in the population over recent years, despite intermittent
seismic exploration (and much ship traffic) in that area for decades
(see Appendix A in Malme et al., 1984; Richardson et al., 1995; Angliss
and Outlaw, 2008). The Western Pacific gray whale population did not
seem affected by a seismic survey in its feeding ground during a prior
year (Johnson et al., 2007). 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
Outlaw, 2008).
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 or the EA have been reported for toothed
whales. However, recent systematic studies on sperm whales have been
done (Gordon et al., 2006; Madsen et al., 2006; Winsor and Mate, 2006;
Jochens et al., 2008; Miller et al., 2009). There is an increasing
amount of information about responses
[[Page 8659]]
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 observers on seismic vessels regularly see
dolphins and other small toothed whales near operating airgun arrays,
but in general there seems to be a tendency for most delphinids to show
some avoidance of operating seismic vessels (Goold, 1996a,b,c;
Calambokidis and Osmek, 1998; Stone, 2003; Moulton and Miller, 2005;
Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008; Richardson et
al., 2009; Barkaszi et al., 2009). However, some dolphins seem to be
attracted to the seismic vessel and floats, and some ride the bow wave
of the seismic vessel even when large airgun arrays are firing (Moulton
and Miller, 2005). Nonetheless, there have been indications that small
toothed whales 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 (Stone and Tasker, 2006; Weir, 2008).
In most cases, the avoidance radii for delphinids appear to be small,
on the order of 1 km (0.62 mi) or less, and some individuals show no
apparent avoidance. The beluga is a species that (at least at times)
shows long-distance avoidance of seismic vessels. Aerial surveys during
seismic operations in the southeastern Beaufort Sea during summer found
that sighting rates of beluga whales were significantly lower at
distances 10 to 20 km (6.2 to 12.4 mi) compared with 20 to 30 km (mi)
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 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; Finneran and Schlundt, 2004). 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 show stronger avoidance of seismic
operations than do Dall's porpoises (Stone, 2003; 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 operations 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 in general (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 (Stone,
2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 2008).
In most cases, the whales do not show strong avoidance and continue to
call (see Appendix B in the L-DEO EA). However, controlled exposure
experiments in the Gulf of Mexico indicate that foraging behavior was
altered upon exposure to airgun sounds (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, northern bottlenose whales
(Hyperodon ampullatus) continued to produce high-frequency clicks when
exposed to sound pulses from distant seismic surveys (Laurinolli and
Cochrane, 2005; Simard et al., 2005). Most beaked whales tend to avoid
approaching vessels of other types (Wursig et al., 1998). They may also
dive for an extended period when approached by a vessel (Kasuya, 1986),
although it is uncertain how much longer such dives may be as compared
to dives by undisturbed beaked whales, which also are often quite long
(Baird et al., 2006; Tyack et al., 2006). It is likely that these
beaked whales would normally show strong avoidance of an approaching
seismic vessel, but this has not been documented explicitly.
Odontocete reactions to large arrays of airguns are variable and,
at least for delphinids and Dall's porpoises, seem to be confined to a
smaller radius than has been observed for the more responsive of the
mysticetes, belugas, and harbor porpoises (Appendix B of the L-DEO EA).
Hearing Impairment and Other Physical Effects
Temporary or permanent hearing impairment is a possibility when
marine mammals are exposed to very strong sounds, but there has been no
specific documentation of this for marine mammals exposed to sequences
of airgun pulses.
NMFS will be developing new noise exposure criteria for marine
mammals that take account of the now-available scientific data on
temporary threshold shift (TTS), the expected offset between the TTS
and permanent threshold shift (PTS) thresholds, differences in the
acoustic frequencies to which different marine mammal groups are
sensitive, and other relevant factors. Detailed recommendations for new
science-based noise exposure criteria were published in late 2007
(Southall et al., 2007).
Several aspects of the planned monitoring and mitigation measures
for this project (see below) are designed to detect marine mammals
occurring near the airguns to avoid exposing them to sound pulses that
might, at least in theory, cause hearing impairment. In addition, many
cetaceans are likely to show some avoidance of the area where received
levels of airgun sound are high enough 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 pulsed sounds. However, as discussed below, there is no
definitive evidence that any of these effects occur even for marine
mammals in close proximity to large arrays of airguns. It is especially
unlikely that any 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 proposed monitoring and
mitigation measures (see below). 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
[[Page 8660]]
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). Based on these data,
the received energy level of a single seismic pulse (with no frequency
weighting) might need to be approximately 186 dB re 1
[mu]Pa\2\[middot]s (i.e., 186 dB SEL or approximately 196 to 201 re 1
[mu]Pa [rms]) in order to produce brief, mild TTS. Exposure to several
strong seismic pulses that each have received levels near 190 re 1
[mu]Pa (rms) might result in cumulative exposure of approximately 186
dB SEL and thus slight TTS in a small odontocete, assuming the TTS
threshold is (to a first approximation) a function of the total
received pulse energy; however, this `equal energy' concept is an
oversimplification. The distance from the Langseth's airguns at which
the received energy level (per pulse, flat-weighted) would be expected
to be greater than or equal to 190 dB re 1 [mu]Pa (rms) are estimated
in Table 1 of L-DEO's application and above. Levels greater than or
equal to 190 dB re 1 [mu]Pa (rms) are expected to be restricted to
radii no more than 400 m. For an odontocete closer to the surface, the
maximum radius with greater than or equal to 190 dB re 1 [mu]Pa (rms)
would be smaller.
The above TTS information for odontocetes is derived from studies
on the bottlenose dolphin and beluga. 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 (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 required to induce TTS. The frequencies to which
baleen whales are most sensitive are lower than those to which
odontocetes are more 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). In any event, no
cases of TTS are expected given three considerations:
(1) The relatively low abundance of baleen whales expected in the
planned study areas;
(2) The strong likelihood that baleen whales would avoid the
approaching airguns (or vessel) before being exposed to levels high
enough for there to be any possibility of TTS; and
(3) The mitigation measures that are planned.
To avoid the potential for injury, NMFS (1995, 2000) concluded that
cetaceans and pinnipeds should not be exposed to pulsed underwater
noise at received levels exceeding 180 and 190 dB re 1 [mu]Pa (rms),
respectively. This sound level is not considered to be the level above
which TTS might occur. Rather, it was the received levels above which,
in the view of a panel of bioacoustics specialists convened by NMFS
before TTS measurements for marine mammals started to become available,
one could not be certain that there would be no injurious effects,
auditory or otherwise, to cetaceans. As summarized above and in
Southall et al. (2007), data that are now available imply that TTS is
unlikely to occur in most odontocetes (and probably mysticetes as well)
unless they are exposed to a sequence of several airgun pulses stronger
than 190 dB re 1 [mu]Pa (rms).
Permanent Threshold Shift--When PTS occurs, there is physical
damage to the sound receptors in the ear. In severe cases, there can be
total or partial deafness, 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 (Richardson et al., 1995; Gedamke et al.,
2008). Single or occasional occurrences of mild TTS are not indicative
of permanent auditory damage, but repeated or (in some cases) single
exposures to a level well above that causing TTS onset might elicit
PTS.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals, but are assumed to be similar to those in humans and
other terrestrial mammals. PTS might occur at a received sound level at
least several decibels above that inducing mild TTS if the animal were
exposed to strong sound pulses with rapid rise time (see Appendix B (6)
of the L-DEO EA). Based on data from terrestrial mammals, a
precautionary assumption is that the PTS threshold for impulse sounds
(such as airgun pulses as received close to the source) is at least 6
dB higher than the TTS threshold on a peak-pressure basis, and probably
greater than 6 dB (Southall et al., 2007). On an SEL basis, Southall et
al. (2007) estimated that received levels would need to exceed the TTS
threshold by at least 15 dB for there to be risk of PTS. Thus, for
cetaceans they estimate that the PTS threshold might be an M-weighted
SEL (for the sequence of received pulses) of approximately 198 dB re 1
[mu]Pa2[middot]s (15 dB higher than the Mmf -
weighted TTS threshold, in a beluga, for a watergun impulse), where the
SEL value is cumulated over the sequence of pulses.
Southall et al. (2007) also note that, regardless of the SEL, there
is concern about the possibility of PTS if a cetacean or pinniped
receives one or more pulses with peak pressure exceeding 230 or 218 dB
re 1 [mu]Pa (peak), respectively. Thus PTS might be expected upon
exposure of cetaceans to either SEL greater than or equal to 198 dB re
1 [mu]Pa2[middot]s or peak pressure greater than or equal to
230 dB re 1 [mu]Pa. Corresponding proposed dual criteria for pinnipeds
(at least harbor seals) are greater than or equal to 186 dB SEL and
greater than or equal to 218 dB peak pressure (Southall et al., 2007).
These estimates are all first approximations, given the limited
underlying data, assumptions, species differences, and evidence that
the ``equal energy'' model may not be entirely correct. A peak pressure
of 230 dB re 1 [mu]Pa (3.2 bar [middot] m, 0-pk), which would only be
found within a few meters of the largest (360 in3) airguns
in the planned airgun array (Caldwell and Dragoset, 2000). A peak
pressure of 218 dB re 1 [mu]Pa could be received somewhat farther away;
to estimate that specific distance, one would need to apply a model
that accurately calculates peak pressures in the near-field around an
array of airguns.
Given the higher level of sound necessary to cause PTS as compared
with TTS, it is considerably less likely that PTS could occur. Baleen
whales generally avoid the immediate area around operating seismic
vessels, as do some other marine mammals. 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 EZs will further reduce the probability of exposure
of marine mammals to sounds strong enough to induce PTS.
[[Page 8661]]
Strandings and Mortality--Marine mammals close to underwater
detonations of high explosives can be killed or severely injured, and
their auditory organs are especially susceptible to injury (Ketten et
al., 1993; Ketten, 1995). However, explosives are no longer used for
marine 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 proof that they
can cause serious injury, death, or stranding even in the case of large
airgun arrays. However, the association of mass strandings of beaked
whales with naval exercises and, in one case, an L-DEO seismic survey
(Malakoff, 2002; Cox et al., 2006), has raised the possibility that
beaked whales exposed to strong pulsed sounds may be especially
susceptible to injury and/or behavioral reactions that can lead to
stranding (Hildebrand, 2005; Southall et al., 2007). Appendix B(6) of
the L-DEO EA provides additional details.
Specific sound-related processes that lead to strandings and
mortality are not well documented, but may include:
(1) Swimming in avoidance of a sound into shallow water;
(2) A change in behavior (such as a change in diving behavior) that
might contribute to tissue damage, gas bubble formation, hypoxia,
cardiac arrhythmia, hypertensive hemorrhage or other forms of trauma;
(3) A physiological change such as a vetibular 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 1 kHz. Typical military mid-frequency sonars operate at
frequencies of 2 to 10 kHz, generally with a relatively narrow
bandwidth at any one time. 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 pulses
can, in special circumstances, lead (at least indirectly) to physical
damage and mortality (Balcomb and Claridge, 2001; NOAA and USN, 2001;
Jepson et al., 2003; Fern[aacute]ndez et al., 2004, 2005a; 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) was not well founded based on available data (IAGC, 2004; IWC,
2007b). In September 2002, there was a stranding of two Cuvier's beaked
whales in the Gulf of California, Mexico, when the L-DEO vessel R/V
Maurice Ewing (Ewing) was operating a 20 airgun, 8,490 in\3\ array in
the general area. The link between the stranding and the seismic survey
was inconclusive and not based on any physical evidence (Hogarth, 2002;
Yoder, 2002). Nonetheless, the Gulf of California incident plus the
beaked whale strandings near naval exercises involving use of mid-
frequency sonar suggests a need for caution when conducting seismic
surveys in areas occupied by beaked whales until more is known about
effects of seismic surveys on those species (Hildebrand, 2005). No
injuries of beaked whales are anticipated during the proposed study
because of:
(1) The high likelihood that 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 formation (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 monitoring and mitigation measures,
including shut-down of the airguns, will reduce any such effects that
might otherwise occur.
Potential Effects of Other Acoustic Devices--MBES Signals
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 2 to 15 ms once every 5 to 20 s, depending on water
depth. Most of the energy in the sound pulses emitted by the MBES is at
frequencies centered at 12 kHz, and the maximum source level is 242 dB
re 1 [micro]Pa (rms). 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 (greater
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 MBES are unlikely to
be subjected to
[[Page 8662]]
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 in order to receive the multiple pulses
that might result in sufficient exposure to cause TTS. Burkhardt et al.
(2007) concluded that immediate direct auditory injury was possible
only if a cetacean dived under the vessel into the immediate vicinity
of the transducer.
Navy sonars that have been linked to avoidance reactions and
stranding of cetaceans (1) generally have a longer pulse duration that
the Kongsberg EM 122, and (2) are often directed close to horizontally
vs. more downward for the MBES. The area of possible influence of the
MBES is much smaller--a narrow band below the source vessel. The
duration of exposure for a given marine mammal can be much longer for a
Navy sonar. During L-DEO's operations, the individual pulses will be
very short, and a given marine mammal would not receive many of the
downward-directed pulses as the vessel passes by.
Marine mammal communications will not be masked appreciably by the
MBES signals given its low duty cycle and the brief period when an
individual mammal is likely to be within its beam. Furthermore, in the
case of baleen whales, the signals (12 kHz) do not overlap with the
predominant frequencies in the calls, which would avoid significant
masking.
Behavioral reactions of free-ranging marine mammals to sonars,
echosounders, and other sound sources appear to vary by species and
circumstance. Observed reactions have included silencing and dispersal
by sperm whales (Watkins et al., 1985), increased vocalizations and no
dispersal by pilot whales (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
[mu]Pam, gray whales reacted by orienting slightly away from the source
and being deflected from their course by approximately 200 m (656 ft)
(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
either duration as compared with those from an MBES.
NMFS believes that the brief exposure of marine mammals to one
pulse, or small numbers of signals, from the MBES are not likely to
result in the harassment of marine mammals.
Potential Effects of Other Acoustic Devices--SBP Signals
A SBP will be operated from the source vessel during the planned
study. Sounds from the SBP are very short pulses, occurring for 1 to 4
ms once every second. Most of the energy in the sound pulses emitted by
the SBP is at 3.5 kHz, and the cone-shaped beam is directed downward.
The SBP on the Langseth has a maximum source level of 204 dB re 1
[micro]Pam. 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 in order to be subjected to sound levels that
could cause TTS.
Marine mammal communications will not be masked appreciably by the
SBP signals given their directionality 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.
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. The
pulsed signals from the SBP are somewhat weaker than those from the
MBES. Therefore, behavioral responses are not expected unless marine
mammals are very close to the source.
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 operated
simultaneously with other higher-power acoustic sources, including the
airguns. 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, monitoring and mitigation measures that would be applied to
minimize effects of other sources would further reduce or eliminate any
minor effects of the SBP.
NMFS believes that to avoid the potential for permanent
physiological damage (Level A harassment), cetaceans and pinnipeds
should not be exposed to pulsed underwater noise at received levels
exceeding, respectively, 180 and 190 dB re 1 [mu]Pa (rms). The
precautionary nature of these criteria is discussed in the L-DEO EA,
including the fact that the minimum sound level necessary to cause
permanent hearing impairment is higher, by a variable and generally
unknown amount, than the level that induces barely-detectable TTS and
the level associated with the onset of TTS is often considered to be a
level below which there is no danger of permanent damage. NMFS also
assumes that cetaceans or pinnipeds exposed to levels exceeding 160 dB
re 1 [mu]Pa (rms) may experience Level B harassment.
Possible Effects of Acoustic Release Signals
The acoustic release transponder used to communicate with the OBSs
uses frequencies of 9 to 13 kHz. These signals will be used very
intermittently. It is unlikely that the acoustic release signals would
have significant effects on marine mammals through masking,
disturbance, or hearing impairment. Any effects likely would be
negligible given the brief exposure at presumable low levels.
Estimated Take of Marine Mammals by Incidental Harassment
All anticipated takes would be ``takes by Level B harassment,''
involving temporary changes in behavior. The proposed monitoring and
mitigation measures are expected to minimize the possibility of
injurious takes or mortality. However, as noted earlier, there is no
specific information
[[Page 8663]]
demonstrating that injurious ``takes'' or mortality would occur even in
the absence of the planned mitigation measures. NMFS believes,
therefore, that injurious take or mortality to the affected species
marine mammals is extremely unlikely to occur as a result of the
specified activities within the specified geographic area for which L-
DEO seeks the IHA. The sections below describe methods to estimate
``take by harassment'', and present estimates of the numbers of marine
mammals that could be affected during the proposed seismic program. The
estimates of ``take by harassment'' are based on consideration of the
number of marine mammals that might be disturbed appreciably by
operations with the 36 airgun array to be used during approximately
2,800 km of seismic surveys in the CNMI study area. The sources of
distributional and numerical data used in deriving the estimates are
described below.
It is assumed 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. Such reactions are not considered to constitute
``taking'' (NMFS, 2001). Therefore, no additional allowance is included
for animals that could be affected by sound sources other than airguns.
The only systematic marine mammal survey conducted in the CNMI was
a ship-based survey conducted by the U.S. Navy during January to April,
2007 in four legs: January 16 to February 2, February 6 to 25, March 1
to 20, and March 24 to April 12 (SRS--Parsons et al., 2007). The cruise
area was defined by the boundaries 10[deg] to 18[deg] North, 142[deg]
to 148[deg] East, encompassing an area approximately 585,000 km\2\
including the islands of Guam and the southern CNMI almost as far north
as Pagan. The systematic line-transect survey effort was conducted from
the flying bridge (10.5 m or 34.5 ft above sea level) of the 56 m
(183.7 ft) long M/V Kahana using standard line-transect protocols
developed by NMFS Southwest Fisheries Science Center (SWFSC). Observers
visually surveyed 11,033 km (6,855.6 mi) of tracklines, mostly in high
sea states (88 percent of the time in Beaufort Sea states 4 to 6).
L-DEO used the densities calculated in SRS--Parsons et al. (2007)
for the 12 species sighted in that survey. For eight species not
sighted in that survey, but expected to occur in the CNMI, relevant
densities are available for the ``outer EEZ stratum'' of Hawaiian
waters, based on a 13,500 km (mi) survey conducted by NMFS SWFSC in
August to November, 2002 (Barlow, 2006). Another potential source of
relevant densities is the SWFSC surveys conducted in the ETP during
summer/fall 1986 to 1996 (Ferguson and Barlow, 2001). However, for five
of the remaining seven species that could occur in the survey area,
there were no sightings in offshore tropical strata during those
surveys, and for another (the humpback whale), there was only one
sighting in more than 50 offshore tropical (less than 20[deg] latitude)
5[deg] x 5[deg] strata. For those six species, an arbitrary low density
was assigned. The short-beaked common dolphin was sighted in a number
of offshore tropical strata, so its density was calculated as the mean
of densities in the 17 offshore 5[deg] x 5[deg] strata between 10[deg]
North and 20[deg] North.
The densities mentioned above had been corrected, by the original
authors, for detectability bias, and in two of the three areas, for
availability bias. Detectability bias is associated with diminishing
sightability with increasing lateral distance from the track line
[[fnof](0)]. Availability bias refers to the fact that there is less
than 100 percent probability of sighting an animal that is present
along the survey track line, and it is measured by g(0). SRS--Parsons
et al. (2007) did not correct the Marianas densities for g(0), which
for all but large (greater than 20) groups of dolphins [where g(0) =
1], resulted in underestimates of density.
There is some uncertainty about the representativeness of the
density data and the assumptions used in the calculations. For example,
the timing of the surveys was either before (Marianas) or after (Hawaii
and ETP) the proposed surveys. Also, most of the Marianas survey was in
high sea states that would have prevented detection of many marine
mammals, especially cryptic species such as beaked whales and Kogia
spp. However, the approach used here is believed to be the best
available approach. To provide some allowance for these uncertainties,
particularly underestimates of densities present and numbers of marine
mammals potentially affected have been derived; maximum estimates are
1.5x the best estimates. Densities calculated or estimated as described
above are given in Table 3 of L-DEO's application.
The estimated numbers of individuals potentially exposed are based
on the 160 dB re 1 Pa (rms) Level B harassment exposure threshold for
all cetaceans, see Table 4 of L-DEO's application. It is assumed that
the species of marine mammals affected by the proposed survey, if
exposed to airgun sounds at these levels, might change their behavior
sufficiently to be considered ``take by Level B harassment.''
It should be noted that the following estimates of exposures to
various sound levels and related incidental takes by Level B harassment
assume that the proposed marine geophysical 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-km of seismic operations that can be undertaken.
Furthermore, any marine mammals sightings within or near the designated
EZs 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 160 dB re 1 [mu]Pam (rms) sounds
are precautionary and probably overestimate the actual numbers of
marine mammals that might be involved. These estimates 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 >=160 dB re 1 [mu]Pa (rms) on one or more
occasions was estimated by considering the total marine area that would
be within the 160 dB radius around the operating airgun array on at
least one occasion. 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
[[Page 8664]]
individual mammal would most likely not be exposed numerous times
during the survey; the area including overlap is only 1.4x 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 >=160 dB re 1 [micro]Pa (rms) was calculated by multiplying:
The expected species density, either ``mean'' (i.e., best
estimate) or ``maximum,'' times,
The anticipated minimum area to be ensonified to that
level during airgun operations excluding overlap (exposures), or
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 of L-DEO's application) around
each seismic line, and then calculating the total area within the
buffers. Areas where overlap were included only once when estimating
the number of individuals exposed.
Applying the approach described above, approximately 15,685 km\2\
(6,056 mi\2\) would be within the 160 dB isopleth on one or more
occasions during the survey, where as 21,415 km\2\ (8,268.4 mi\2\) is
the area ensonified to greater than or equal to 160 dB when overlap is
included. 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 3--The Estimates of the Possible Numbers of Marine Mammals Exposed to Sound Levels Greater Than or Equal
to 160 dB During L-DEO's Proposed Seismic Survey in the CNMI in April to June, 2010*
----------------------------------------------------------------------------------------------------------------
No. of No. of Approx. percent
individuals individuals of regional
Species exposed (best) exposed (max) popu lation
\1\ \1\ (best) \2\
----------------------------------------------------------------------------------------------------------------
Mysticetes:
0 1 0
North Pacific right whale................................
(Eubalaena japonica).....................................
Humpback whale........................................... 0 2 0
(Megaptera novaeangliae).................................
Minke whale.............................................. 0 0 0
(Balaenoptera acutorostrata).............................
Bryde's whale............................................ 6 10 0.03
(Balaenoptera brydei)....................................
Sei whale................................................ 5 7 0.05
(Balaenoptera borealis)..................................
Fin whale................................................ 0 2 0
(Balaenoptera physalus)..................................
Blue whale............................................... 0 2 0
(Balaenoptera musculus)..................................
Odontocetes:
19 29 0.07
Sperm whale..............................................
(Physeter macrocephalus).................................
Pygmy sperm whale........................................ 46 68 N.A.
(Kogia breviceps)........................................
Dwarf sperm whale........................................ 112 168 <0.01
(Kogia sima).............................................
Cuvier's beaked whale.................................... 97 146 0.49
(Ziphius cavirostris)....................................
Longman's beaked whale................................... 9 13 N.A.
(Indopacetus pacificus)..................................
Blainville's beaked whale................................ 18 28 0.07
(Mesoplodon densirostris)................................
Ginkgo-toothed beaked whale.............................. 0 0 N.A.
(Mesoplodon ginkgodens)..................................
Rough-toothed dolphin.................................... 5 7 <0.01
(Steno bredanensis)......................................
Bottlenose dolphin....................................... 3 5 <0.01
(Tursiops truncatus).....................................
Pantropical spotted dolphin.............................. 355 532 0.04
(Stenella attenuata).....................................
Spinner dolphin.......................................... 49 74 <0.01
(Stenella longirostris)..................................
Striped dolphin.......................................... 97 145 0.01
(Stenella coeruleoalba)..................................
Fraser's dolphin......................................... 65 98 0.02
(Lagenodelphis hosei)....................................
Short-beaked common dolphin.............................. 0 0 0
(Delphinus delphis)......................................
[[Page 8665]]
Risso's dolphin.......................................... 15 23 0.01
(Grampus griseus)........................................
Melon-headed whale....................................... 67 101 0.15
(Peponocephala electra)..................................
Pygmy killer whale....................................... 2 3 <0.01
(Feresa attenuata).......................................
False killer whale....................................... 17 26 <0.01
(Pseudorca crassidens)...................................
Killer whale............................................. 2 3 0.04
(Orcinus orca)...........................................
Short-finned pilot whale................................. 25 37 <0.01
(Globicephala macrorhynchus).............................
Sirenians: Dugong............................................ 0 0 N.A.
(Dugong dugon)...............................................
----------------------------------------------------------------------------------------------------------------
* The proposed sound source consists of a 36 airgun, 6,600 in\3\ array. Received levels are expressed in dB re 1
[mu]Pa (rms) (averaged over pulse duration), consistent with NMFS' practice. Not all marine mammals will
change their behavior when exposed to these sound levels, but some may alter their behavior when levels are
lower (see text). See Tables 2 to 4 in L-DEO's application for further detail.
N.A.--Data not available or species status was not assessed
\1\ Best estimate and maximum density estimates are from Table 3 of L-DEO's application.
\2\ Regional population size estimates are from Table 2.
Table 4 of L-DEO's application shows the best and maximum estimates
of the number of exposures and the number of different individual
marine mammals that potentially could be exposed to greater than or
equal to 160 dB re 1 [mu]Pa (rms) during the seismic survey if no
animals moved away from the survey vessel. For ESA listed species, the
maximum estimate and Requested Take Authorization have been increased
to the mean group size for the particular species in cases where the
calculated maximum number of individuals exposed was between 0.05 and
the mean group size (i.e., for North Pacific, right, humpback, fin, and
blue whales).
The ``best estimate'' of the total number of individual marine
mammals that could be exposed to seismic sounds with received levels
greater than or equal to 160 dB re 1 [micro]Pa (rms) during the survey
is 1,011 animals and is shown in Table 4 of L-DEO's application and
Table 3 (shown above). These estimates were derived from the best
density estimates calculated for these species in the area. That total
includes 11 baleen whales, five of which are ESA-listed sei whales, or
0.05 percent of the regional population. In addition, 19 ESA-listed
sperm whales or 0.07 percent of the regional population could be
exposed during the survey, and 121 beaked whales including Cuvier's,
Longman's, and Blainville's beaked whales. Most (69.4 percent) of the
cetaceans exposed are delphinids; pantropical spotted, striped, and
Fraser's dolphins and melon-headed whales are estimated to be the most
common species in the area, with best estimates of 355 (0.04 percent of
the regional population), 97 (0.01 percent), 65 (0.02 percent), and 67
(0.15 percent) exposed to greater or equal to 160 dB re 1 [mu]Pa (rms)
respectively.
Potential Effects on Marine Mammal Habitat
The proposed L-DEO seismic survey will not result in any permanent
impact on habitats used by marine mammals, including the food sources
they use. The main impact issue associated with the proposed activity
will be temporarily elevated noise levels and the associated direct
effects on marine mammals, as described above. The following sections
briefly review effects of airguns on fish and invertebrates, and more
details are included in Appendices C and D of the L-DEO EA,
respectively.
Potential 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 EA). There are three
types of potential effects on fish and invertebrates from 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 potentially could lead to an ultimate pathological
effect on individuals (i.e., mortality).
The specific received sound levels at which permanent adverse
effects to fish potentially could occur are little studied and largely
unknown. 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 aspect of potential impacts
relates to how exposure to seismic survey sound affects marine fish
populations and their viability, including their availability to
fisheries.
[[Page 8666]]
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
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 L-DEO EA). 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.
There are only two known valid papers with proper experimental methods,
controls, and careful pathological investigation implicating sounds
produced by actual seismic survey airguns with 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
(Coreogonus 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 airgun arrays [less than approximately 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 2 m in the latter). Water depth sets a lower
limit on the lowest sound frequency that will propagate (the ``cut-off
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) zone for fish and invertebrates 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 morality/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; McCauley et al.,
2000a, 2000b). 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
EA).
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 (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; Engas 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
[[Page 8667]]
effects of airguns on fish, particularly under realistic at-sea
conditions.
Potential 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 Appendix E
of the L-DEO EA).
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 L-DEO EA.
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
there is no evidence to support such claims.
Physiological Effects--Physiological effects refer mainly to
biochemical 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 effect 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).
During the proposed study, only a small fraction of the available
habitat would be ensonified at any given time, and fish species would
return to their pre-disturbance behavior once the seismic activity
ceased. The proposed seismic program is predicted to have negligible to
low behavioral effects on the various life stages of the fish and
invertebrates during its relatively short duration and extent.
Because of the reasons noted above and the nature of the proposed
activities, the proposed operations are not expected to have any
habitat-related effects that could cause significant or long-term
consequences for individual marine mammals or their populations or
stocks. Similarly, any effects to food sources are expected to be
negligible.
Proposed Mitigation
In order to issue an Incidental Take Authorization (ITA) for small
numbers of marine mammals 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 on the availability of such species or stock for
taking for certain subsistence uses. As noted, NMFS has determined that
the proposed IHA would not impact marine mammals for purposes of their
use for subsistence.
Mitigation and monitoring measures and procedures described herein
to be implemented for the proposed seismic survey have been developed
and refined during previous L-DEO seismic research cruises as approved
by NMFS, and associated environmental assessments (EAs), IHA
applications, and IHAs, and on recommended best practices in Richardson
et al. (1995), Pierson et al. (1998), and Weir and Dolman (2007). The
following information provides more detailed
[[Page 8668]]
information about the mitigation measures that would be an integral
part of the planned activities designed to affect the least practicable
impact on stocks and species of affected marine mammals and their
habitat. The measures are described in detail below.
Planning Phase
In designing the proposed seismic survey, L-DEO and NSF have
considered potential environmental impacts including seasonal,
biological, and weather factors; ship schedules; and equipment
availability during a preliminary assessment carried out when ship
schedules were still flexible. Part of the considerations was whether
the research objectives could be met with a smaller source or with a
different survey design that involves less prolonged seismic
operations.
Proposed Exclusion Zones (EZ)
Received sound levels have been predicted by L-DEO, 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. Results were recently reported for propagation measurements of
pulses from the 36 airgun array in two water depths (approximately
1,600 m and 50 m) in the Gulf of Mexico in 2007 to 2008 (Tolstoy et
al., 2009). It would be prudent to use the empirical values that
resulted to determine EZs for the airgun array. Measurements were not
reported for the mitigation airgun, so model results will not be used.
Results of the propagation measurements (Tolstoy et al., 2009)
showed that radii around the airguns for various received levels varied
with water depth. During the proposed study, all survey effort will
take place in deep (greater than 1,000 m) water, so propagation in
shallow water is not relevant here. However, the depth of the array was
different in the Gulf of Mexico calibration study (6 m or 20 ft) than
in the proposed survey (9 m or 30 ft). Because propagation varies with
array depth, correction factors have been applied to the distances
reported by Tolstoy et al. (2009). The correction factors used were the
ratios of the 160, 180, and 190 dB distances from the modeled results
for the 6,600 in\3\ airgun array towed at 6 m and 9 m depths; these
distances were used for the L-DEO seismic survey in the Northeast
Pacific Ocean (see Table 1 in LGL Ltd., 2009). The factors are 1.34 to
1.38 for the 180 to 190 dB distances, and 1.29 for the 160 dB distance.
Using the corrected measurements (array) or model (mitigation gun),
Table 1 shows the distances at which four rms sound levels 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); these levels were
used to establish the EZs. If the PSVO detects marine mammal(s) within
or about to enter the appropriate EZ, the airguns will be powered-down
(or shut-down if necessary) immediately (see below).
Detailed recommendations for new science-based noise exposure
criteria were published in early 2008 (Southall et al., 2007). L-DEO
will be prepared to revise its procedures for estimating numbers of
mammals ``taken,'' EZs, etc., as may be required by any new guidelines
that result. As yet, NMFS has not specified a new procedure for
determining EZs. Such procedures, if applicable would be implemented
through a modification to the IHA if issued.
Mitigation measures that will be adopted during the proposed CNMI
survey include:
(1) Power-down procedures;
(2) Shut-down procedures; and
(3) Ramp-up procedures;
Power-down Procedures--A power-down involves reducing the number of
airguns in use such that the radius of the 180 dB (or 190 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, one airgun will be operated. 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 all airgun activity is suspended.
If a marine mammal (other than right whales [immediate shut-down,
see end of section]) is detected outside the EZ but is likely to enter
the EZ, the airguns will be powered-down to a single airgun before the
animal is within the EZ. Likewise, if a mammal is already within the EZ
when first detected, the airguns will be powered-down immediately.
During a power-down of the airgun array, the 40 in\3\ airgun will be
operated. If a marine mammal is detected within or near the smaller EZ
around that single airgun (see Table 1 of L-DEO's application and Table
1 above), all airguns will be shut down (see next subsection).
Following a power-down, airgun activity will not resume until the
marine mammal is outside the EZ for the full array. The animal will be
considered to have cleared the EZ if it:
(1) Is visually observed to have left the EZ, or
(2) Has not been seen within the EZ for 15 minutes in the case for
species with shorter dive durations (e.g., small odontocetes); or
(3) Has not been seen within the EZ for 30 minutes in the case for
species with longer dive durations (e.g., mysticetes and large
odontocetes, including sperm, pygmy sperm, dwarf sperm, killer, and
beaked whales).
During airgun operations following a power-down (or shut-down)
whose duration has exceeded the limits specified above and subsequent
animal departures, the airgun array will be ramped-up gradually. Ramp-
up procedures are described below.
Shut-down Procedures--The operating airguns(s) will be shut-down if
a marine mammal is detected within or approaching the EZ for a single
airgun source. Shut-downs will be implemented (1) if an animal enters
the EZ of the single airgun after a power-down has been initiated, or
(2) if an animal is initially seen within the EZ of a single airgun
when more than one airgun (typically the full array) is operating.
Airgun activity will not resume until the marine mammal has cleared the
EZ, or until the PSVO is confident that the animal has left the
vicinity of the vessel (or the PSVO not observing the animal(s) within
the EZ for 15 or 30 min depending upon the species). Criteria for
judging that the animal has cleared the EZ will be as described in the
preceding subsection.
Ramp-up Procedures--A ramp-up procedure will be followed when the
airgun array begins operating after a specified period without airgun
operations or when a power-down has exceeded that period. It is
proposed that, for the present cruise, this period would be
approximately 8 minutes. This period is based on the largest modeled
180 dB radius for the 36 airgun array (940 m or 3,084 ft) in relation
to the minimum planned speed of the Langseth while shooting (7.4 km/hr
or 4.6 mi/hr). Similar periods (approximately 8 to 10 minutes) 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 6 dB per 5 min period
over a total duration of approximately 35 minutes. During ramp-up, the
PSVOs will monitor the EZ, and if marine mammals are sighted, a power-
down or shut-down will be
[[Page 8669]]
implemented as though the full 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, ramp up
will not commence 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 EZ 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 if they choose. Ramp-up of the airguns will not be
initiated if a marine mammal is sighted within or near the applicable
EZ during the day or close to the vessel at night.
Procedures for Species of Particular Concern--One species of
particular concern could occur in the study area.
Considering the conservation status for North Pacific right whales,
the airgun(s) will be shut-down immediately in the unlikely event that
this species is observed, regardless of the distance from the Langseth.
Ramp-up will only begin if the right whale has not been seen for 30
minutes.
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) require 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.
L-DEO proposes to sponsor marine mammal monitoring during the
proposed 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 as well as in their IHA application.
L-DEO understands that this Monitoring Plan will be subject to review
by NMFS, and that refinements may be required as part of the MMPA
consultation process.
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
Protected Species Visual Observers (PSVOs) will be based aboard the
seismic source vessel and will watch for marine mammals and other
protected species near the vessel during daytime airgun operations and
during start-ups of airguns at night. PSVOs will also watch for marine
mammals near the seismic vessel for at least 30 minutes prior to the
start of airgun operations and after an extended shut-down of the
airguns. When feasible, PSVOs will also observe during daytime periods
when the seismic system is not operating for comparison of sighting
rates and animal behavior with vs. without airgun operations. Based on
PSVO observations, the airguns will be powered-down or shut-down (see
below) when marine mammals are detected within or about to enter a
designated EZ, and in the case of the North Pacific right whale
immediately when any individuals of that species is spotted at any
distance. The PSVOs will continue to maintain watch to determine when
the animal(s) are outside the EZ in accordance with the criteria
established above in the mitigation section, and airgun operations will
not resume until the animal has left that EZ. The predicted distances
for the safety radius are listed according to the sound source, water
depth, and received isopleths in Table 1. The EZ is a region in which a
possibility exists of adverse effects on animal hearing or other
physical effects.
During seismic operations in CNMI, five PSOs will be based aboard
the Langseth. PSOs will be appointed by L-DEO with NMFS concurrence. At
least one PSVO, and when practical two PSVOs, will monitor for marine
mammals and other specified protected species near the seismic vessel
during ongoing daytime operations and nighttime start-ups of the
airguns. Use of two simultaneous PSVOs will increase the effectiveness
of detecting animals near the sound source. PSVO(s) will be on duty in
shift of duration no longer than 4 hours. The vessel crew will also be
instructed to assist in detecting marine mammals and other specified
protected species, and implementing mitigation measures (if practical).
Before the start of the seismic survey the crew will be given
additional instruction regarding how to do so.
The Langseth is a suitable platform for observations for marine
mammals and other protected species. 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 the daytime, the PSVO(s) will scan the area around the
vessel systematically with reticle binoculars (e.g., 7x50 Fujinon),
Big-eye binoculars (25x150), 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 rangefinding binoculars (Leica LRF 1200 laser rangefinder or
equivalent) will be available to assist with distance estimation. Those
are useful in training PSVOs 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' lenses.
Passive Acoustic Monitoring (PAM)
PAM will take place to complement the visual monitoring program,
when practicable. Visual monitoring typically is not effective during
periods of poor visibility (e.g., bad weather) or at night, and even
with good visibility, is unable to detect marine mammals when they are
below the surface or beyond visual range. Acoustical monitoring can be
used 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 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 low-noise, towed
hydrophone array that is connected to the vessel by a ``hairy'' faired
cable. The array will be deployed from a winch located on the back
deck. A deck cable will connect from the winch to the main computer lab
where the acoustic station and signal condition and processing system
will be located. The lead-in from the hydrophone array
[[Page 8670]]
is approximately 400 m (1,312 ft) long, and the active part of the
hydrophone is approximately 56 m (184 ft) long. The hydrophone array is
typically towed at depths less than 20 m (65.6 ft).
The towed hydrophone array will be monitored 24 hours per day while
at the survey area during airgun operations, and during most periods
when the Langseth is underway while the airguns are not operating. One
Protected Species Observer 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. PSOs monitoring the
acoustical data will be on a shift for one to six hours. Besides the
visual PSOs, an additional PSO with primary responsibility for PAM will
also be aboard. All PSOs 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 PSO will contact the PSVO immediately to alert
him/her to the presence of the cetacean(s) (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 vocalization 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.
L-DEO will coordinate the planned protected species monitoring
program associated with the CNMI seismic survey with other parties that
may have interest in the area and/or be conducting marine mammal
studies in the same region during the proposed seismic survey. L-DEO
and NSF will coordinate with applicable U.S. agencies (e.g., NMFS), and
will comply with their requirements.
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 seismic source when a marine mammal is within or
near the EZ.
When a sighting is made, the following information about the
sighting will be recorded:
(1) Species, group size, and age/size/sex categories (if
determinable); behavior when first sighted and after initial sighting;
heading (if consistent), bearing, and distance from seismic vessel;
sighting cue; apparent reaction to the seismic source or vessel (e.g.,
none, avoidance, approach, paralleling, etc.); and behavioral pace.
(2) Time, location, heading, speed, activity of the vessel, sea
state, visibility, and sun glare.
The data listed under (2) above will also be recorded at the start
and end of each observation watch, and during a watch whenever there is
a change in one or more of the variables.
All observations, as well as information regarding seismic source
power-downs and shut-downs, will be recorded in a standardized format.
The accuracy of 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 for 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 per
terms of MMPA authorizations or regulations.
(3) Data on the occurrence, distribution, and activities of marine
mammals in the area where the seismic study is conducted.
(4) Information to compare the distance and distribution of marine
mammals relative to the source vessel at times with and without seismic
activity.
(5) Data on the behavior and movement patterns of marine mammals
seen at times with and without seismic activity.
A report will be submitted 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 near the operations. The
report will be providing full documentation of methods, results, and
interpretation pertaining to all monitoring. The 90-day report will
summarize the dates and locations of seismic operations, and all marine
mammal sightings (dates, times, locations, activities, associated
seismic survey activities). The report will also include estimates of
the amount and nature of potential ``take'' of marine mammals by
harassment or in other ways.
All injured or dead marine mammals (regardless of cause) will be
reported to NMFS as soon as practicable. Report should include species
or description of animal, condition of animal, location, time first
found, observed behaviors (if alive) and photo or video, if available.
Negligible Impact and Small Numbers of Marine Mammals Analysis and
Determination
The Secretary, in accordance with paragraph 101(a)(5)(D) of the
MMPA, shall authorize the take of small numbers of marine mammals
incidental to specified activities other than commercial fishing within
a specific geographic region if, among other things, he determines that
the authorized incidental take will have a ``negligible impact'' on
species or stocks affected by the authorization. NMFS implementing
regulations codified at 50 CFR 216.103 states that a ``negligible
impact is 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.''
Based on the analysis contained herein, of the likely effects of
the specified activity on marine mammals and their habitat within the
specific area of study for the CNMI marine geophysical survey, and
taking into consideration the implementation of the mitigation and
monitoring measures, NMFS, on behalf the Secretary, preliminarily finds
that L-DEO's proposed activities would result in the incidental take of
small numbers of marine mammals, by Level B harassment only, and that
the total taking from the proposed seismic survey would have a
negligible impact on the affected species or stocks of marine mammals.
Impact on Availability of Affected Species for Taking for Subsistence
Uses
There is no subsistence hunting for marine mammals in the waters
off of the coast of the CNMI that implicates MMPA Section 101(a)(5)(D).
[[Page 8671]]
Endangered Species Act (ESA)
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)
With its complete application, L-DEO provided NMFS an EA analyzing
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 EA, prepared by LGL
Environmental Research Associated (LGL) on behalf of NSF and L-DEO is
entitled Environmental Assessment of a Marine Geophysical Survey by the
R/V Marcus G. Langseth in the Commonwealth of the Northern Mariana
Islands, April-June 2010 (L-DEO EA). Prior to making a final decision
on the IHA application, NMFS will either prepare an independent EA, or,
after review and evaluation of the L-DEO EA 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 L-DEO 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 within the U.S. EEZ within
the CNMI 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 (180 dB)
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) is estimated
to be small, less than a few 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. Also, there are no known important reproduction or feeding
areas in the proposed action area.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
issue an IHA to L-DEO for conducting a marine geophysical survey in the
CNMI from April to June, 2010, 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: February 19, 2010.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2010-3869 Filed 2-24-10; 8:45 am]
BILLING CODE 3510-22-P