[Federal Register Volume 76, Number 24 (Friday, February 4, 2011)]
[Notices]
[Pages 6430-6448]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-2538]
-----------------------------------------------------------------------
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XA124
Takes of Marine Mammals Incidental to Specified Activities;
Marine Geophysical Survey in the Pacific Ocean off Costa Rica, April
Through May, 2011
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental harassment authorization; request
for comments.
-----------------------------------------------------------------------
SUMMARY: NMFS has received an application from Lamont-Doherty Earth
Observatory (L-DEO), a part of Columbia University, for an Incidental
Harassment Authorization (IHA) to take marine mammals, by harassment,
incidental to conducting a marine geophysical survey in the eastern
tropical Pacific (ETP) Ocean off Costa Rica, April through May, 2011.
Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting
comments on its proposal to issue an IHA to L-DEO to incidentally
harass, by Level B harassment only, 19 species of marine mammals during
the specified activity.
DATES: Comments and information must be received no later than March 7,
2011.
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#applications without change. All Personal Identifying
Information (for example, name, address, etc.) voluntarily submitted by
the commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.
A copy of the application containing a list of the references used
in this document may be obtained by writing to the above address,
telephoning the
[[Page 6431]]
contact listed here (see FOR FURTHER INFORMATION CONTACT) or visiting
the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
The National Science Foundation (NSF), which is providing funding
for the proposed action, has prepared a draft Environmental Analysis
which incorporates an ``Environmental Assessment of a Marine
Geophysical Survey by the R/V Marcus G. Langseth in the Pacific Ocean
off Costa Rica, April-May, 2011'', prepared by LGL Limited, on behalf
of NSF is also available at the same internet address. Documents cited
in this notice may be viewed, by appointment, during regular business
hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Jeannine Cody, Office of Protected
Resources, NMFS, (301) 713-2289, ext. 113.
SUPPLEMENTARY INFORMATION:
Background
Section 101(a)(5)(D) of the MMPA (16 U.S.C. 1371(a)(5)(D)) directs
the Secretary of Commerce to authorize, upon request, the incidental,
but not intentional, taking of small numbers of marine mammals of a
species or population stock, by United States citizens who engage in a
specified activity (other than commercial fishing) within a specified
geographical region if certain findings are made and, if the taking is
limited to harassment, a notice of a proposed authorization is provided
to the public for review.
Authorization for the incidental taking of small numbers of marine
mammals shall be granted if NMFS finds that the taking will have a
negligible impact on the species or stock(s), and will not have an
unmitigable adverse impact on the availability of the species or
stock(s) for subsistence uses (where relevant). The authorization must
set forth the permissible methods of taking, other means of effecting
the least practicable adverse impact on the species or stock and its
habitat, and requirements pertaining to the mitigation, monitoring and
reporting of such takings. NMFS has defined ``negligible impact'' in 50
CFR 216.103 as ``* * * an impact resulting from the specified activity
that cannot be reasonably expected to, and is not reasonably likely to,
adversely affect the species or stock through effects on annual rates
of recruitment or survival.''
Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the United States can apply for an authorization
to incidentally take small numbers of marine mammals by harassment.
Section 101(a)(5)(D) of the MMPA establishes a 45-day time limit for
NMFS' review of an application followed by a 30-day public notice and
comment period on any proposed authorizations for the incidental
harassment of small numbers of marine mammals. Within 45 days of the
close of the public comment period, NMFS must either issue or deny the
authorization.
Except with respect to certain activities not pertinent here, the
MMPA defines ``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
Summary of Request
NMFS received an application on November 12, 2010, from L-DEO for
the taking by harassment, of marine mammals, incidental to conducting a
marine geophysical survey in the eastern tropical Pacific Ocean within
the Exclusive Economic Zone (EEZ) of Costa Rica. L-DEO, with research
funding from the U.S. National Science Foundation (NSF), plans to
conduct the proposed survey from April 7, 2011, through May 9, 2011.
Upon receipt of additional information, NMFS determined the application
complete and adequate on January 4, 2011.
L-DEO plans to use one source vessel, the R/V Marcus G. Langseth
(Langseth) and a seismic airgun array to image the structures along a
major plate-boundary fault off in the ETP off Costa Rica using three-
dimensional (3-D) seismic reflection techniques. L-DEO will use the 3-D
seismic reflection data to determine the fault structure and the
properties of the rocks that lie along the fault zone. In addition to
the proposed operations of the seismic airgun array, L-DEO intends to
operate a multibeam echosounder (MBES) and a sub-bottom profiler (SBP)
continuously throughout the survey.
Acoustic stimuli (i.e., increased underwater sound) generated
during the operation of the seismic airgun array, may have the
potential to cause a short-term behavioral disturbance for marine
mammals in the survey area. This is the principal means of marine
mammal taking associated with these activities and L-DEO has requested
an authorization to take 19 species marine mammals by Level B
harassment. Take is not expected to result from the use of the MBES or
SBP, for reasons discussed in this notice; nor is take expected to
result from collision with the vessel because it is a single vessel
moving at a relatively slow speed during seismic acquisition within the
survey, for a relatively short period of time (approximately 32 days).
It is likely that any marine mammal would be able to avoid the vessel.
Description of the Specified Activity
L-DEO's proposed seismic survey in the ETP off Costa Rica is
scheduled to commence on April 7, 2011 and continue for approximately
32 days ending on May 9, 2011. L-DEO will operate the Langseth to
deploy a seismic airgun array and hydrophone streamers to complete the
survey.
The Langseth will depart from Caldera, Costa Rica on April 7, 2011
and transit to the survey area offshore from Costa Rica. Some minor
deviation from these dates is possible, depending on logistics, weather
conditions, and the need to repeat some lines if data quality is
substandard. Therefore, NMFS plans to issue an authorization that
extends to June 6, 2011.
Geophysical survey activities will involve 3-D seismic
methodologies to determine the fault structure and the properties of
the rocks that lie along the fault zone and to assess the property
changes along the fault and determine where the large stress
accumulations that lead to large earthquakes occur along the fault
zone.
To obtain 3-D images of the fault zone which lies two to nine
kilometers (km) below the seafloor, the Langseth will deploy a two-
string subarray of nine airguns each as an energy source. The identical
subarrays will fire alternately, so that no more than 18 airguns will
fire at any time during the proposed survey. The receiving system will
consist of four 6-km-long hydrophone streamers. As the airgun subarrays
are towed along the survey lines, the hydrophone streamers will receive
the returning acoustic signals and transfer the data to the on-board
processing system. L-DEO also plans to use two or three small fishing
vessels around the Langseth to ensure that other vessels do not
entangle the streamers.
The proposed study (e.g., equipment testing, startup, line changes,
repeat coverage of any areas, and equipment recovery) will take place
in the EEZ of Costa Rica in water depths ranging from less than 100
meters (m) (328 feet (ft)) to greater than 2,500 m (1.55 miles (mi)).
The survey will require approximately 32 days (d) to complete
approximately 19 transects in a racetrack configuration
[[Page 6432]]
that will cover an area of approximately 57 x 12 km (35.4 x 7.5 mi). In
all, the proposed survey will complete approximately 2,145 km (1,333
mi) of survey lines with an additional 365 km (227 mi) of turns. Data
acquisition will include approximately 672 hours (hr) of airgun
operation (28 d x 24 hr).
The scientific team consists of Drs. Nathan Bangs, Kirk McIntosh
(Institute for Geophysics, University of Texas) and Eli Silver
(University of California at Santa Cruz).
Vessel Specifications
The Langseth, owned by NSF, is a seismic research vessel with a
propulsion system designed to be as quiet as possible to avoid
interference with the seismic signals emanating from the airgun array.
The vessel, which has a length of 71.5 m (235 ft); a beam of 17.0 m (56
ft); a maximum draft of 5.9 m (19 ft); and a gross tonnage of 3,834, is
powered by two 3,550 horsepower (hp) Bergen BRG-6 diesel engines which
drive two propellers. Each propeller has four blades and the shaft
typically rotates at 750 revolutions per minute. The vessel also has an
800-hp bowthruster, which is not used during seismic acquisition. The
Langseth's operation speed during seismic acquisition will be
approximately 8.5 km per hr (km/h) (5.3 mi per hr (mph) or 4.6 knots
(kts)) and the cruising speed of the vessel outside of seismic
operations is 18.5 km/h (11.5 mph or 10 kts).
The vessel also has an observation tower from which protected
species visual observers (PSVO) will watch for marine mammals before
and during the proposed airgun operations. When stationed on the
observation platform, the PSVO's eye level will be approximately 21.5 m
(71 ft) above sea level providing the PSVO an unobstructed view around
the entire vessel.
Acoustic Source Specifications
Seismic Airguns
The Langseth will deploy a 36-airgun array (two subarrays with 18
airguns each) at a tow depth of 7 meters (m) (23 feet (ft)). However,
the Langseth will fire one subarray at a time, so that no more than 18
airguns will fire at any time. The maximum discharge volume is 3,300
cubic inches (in\3\). The airguns are a mixture of Bolt 1500LL and Bolt
1900LLX airguns ranging in size from 40 to 360 in\3\, with a firing
pressure of 1,900 pounds per square inch. The dominant frequency
components range from zero to 188 Hertz (Hz).
The subarray configuration consists of two identical linear or
strings, with 10 airguns on each string; the first and last airguns
will be spaced 16 m (52 ft) apart. Of the 10 airguns, nine will fire
simultaneously while the tenth airgun will serve as a spare and will be
turned on in case of failure of one of the other airguns. Each airgun
subarray will emit a pulse at approximately 11-second (s) intervals
which corresponds to a shot interval of approximately 25 m (82 ft).
During firing, the airguns will emit a brief (approximately 0.1 s)
pulse of sound; during the intervening periods of operations, the
airguns will be silent.
L-DEO will tow each subarray approximately 140 m (459.3 ft) behind
the vessel and will distribute the subarrays across an area of
approximately 12 by 16 m (39.4 by 52.5 ft) behind the Langseth, offset
by 75 m (246 ft).
Metrics Used in This Document
This section includes a brief explanation of the sound measurements
frequently used in the discussions of acoustic effects in this
document. Sound pressure is the sound force per unit area, and is
usually measured in micropascals ([mu]Pa), where 1 pascal (Pa) is the
pressure resulting from a force of one newton exerted over an area of
one square meter. Sound pressure level (SPL) is expressed as the ratio
of a measured sound pressure and a reference level. The commonly used
reference pressure level in underwater acoustics is 1 [mu]Pa, and the
units for SPLs are dB re: 1 [mu]Pa.
SPL (in decibels (dB)) = 20 log (pressure/reference pressure)
SPL is an instantaneous measurement and can be expressed as the
peak, the peak-peak (p-p), or the root mean square (rms). Root mean
square, which is the square root of the arithmetic average of the
squared instantaneous pressure values, is typically used in discussions
of the effects of sounds on vertebrates and all references to SPL in
this document refer to the root mean square unless otherwise noted. SPL
does not take the duration of a sound into account.
Characteristics of the Airgun Pulses
Airguns function by venting high-pressure air into the water which
creates an air bubble. The pressure signature of an individual airgun
consists of a sharp rise and then fall in pressure, followed by several
positive and negative pressure excursions caused by the oscillation of
the resulting air bubble. The oscillation of the air bubble transmits
sounds downward through the seafloor and the amount of sound
transmitted in the near horizontal directions is reduced. However, the
airgun array also emits sounds that travel horizontally toward non-
target areas.
The nominal source levels of the airgun arrays used by L-DEO on the
Langseth are 236 to 265 dB re: 1 [mu]Pa(p-p) and the rms
value for a given airgun pulse is typically 16 dB re: 1 [mu]Pa lower
than the peak-to-peak value. However, the difference between rms and
peak or peak-to-peak values for a given pulse depends on the frequency
content and duration of the pulse, among other factors.
Accordingly, L-DEO has predicted the received sound levels in
relation to distance and direction from the 18-airgun subarray and the
single Bolt 1900LL 40-in\3\ airgun, which will be used during power
downs. A detailed description of L-DEO's modeling for marine seismic
source arrays for species mitigation is provided in Appendix A of L-
DEO's application. These are the nominal source levels applicable to
downward propagation. The effective source levels for horizontal
propagation are lower than those for downward propagation when the
source consists of numerous airguns spaced apart from one another.
Appendix B of L-DEO's environmental analysis discusses the
characteristics of the airgun pulses. NMFS refers the reviewers to the
application and environmental analysis documents for additional
information.
Predicted Sound Levels for the Airguns
Tolstoy et al., (2009) reported results for propagation
measurements of pulses from the Langseth's 36-airgun, 6,600 in\3\ array
in shallow-water (approximately 50 m (164 ft)) and deep-water depths
(approximately 1,600 m (5,249 ft)) in the Gulf of Mexico in 2007 and
2008. L-DEO has used these reported empirical values to determine
exclusion zones for the 18-airgun subarray and the single airgun; to
designate mitigation zones, and to estimate take (described in greater
detail in Section VII and Section IV of L-DEO's application and
environmental analysis, respectively) for marine mammals.
Results of the Gulf of Mexico calibration study (Tolstoy et al.,
2009) showed that radii around the airguns for various received levels
varied with water depth. The empirical data for deep water (greater
than 1,000 m; 3,280 ft) indicated that the L-DEO model (as applied to
the Langseth's 36-airgun array) overestimated the received sound levels
at a given distance. However, to be conservative, L-DEO has applied the
modeled distances for the 36-airgun
[[Page 6433]]
array in deep water to the 18-airgun subarray when operating in deep-
water areas during the proposed study (Table 1). L-DEO set 2,000 m (1.2
mi) as the maximum relevant depth as very few, if any, mammals are
expected to occur below this depth.
The empirical data for shallow water (< 100 m; 328 ft) indicated
that the L-DEO model (as applied to the Langseth's 36-airgun array)
underestimated actual received levels. Accordingly, L-DEO has applied
correction factors to the distances reported by Tolstoy et al. (2009)
for shallow depth water. For the 36-airgun array, the distances
measured in shallow-water to the 160- to 190-dB isopleths ranged from
1.7 to 5.2 times higher than the distances in deep water (Tolstoy et
al. 2009). During the proposed cruise, the same factors will be applied
to derive appropriate shallow-water radii from the modeled deep-water
radii for the Langseth's 18-airgun subarray (Table 1).
For intermediate-depths (100-1,000 m; 328-3,280 ft), L-DEO has
applied a correction factor of 1.5 to the estimates provided by the
model for the 18-airgun subarray operating in deep-water situations to
predict safety radii for intermediate-depth sites. L-DEO applied the
same correction factor to model estimates for an L-DEO cruise in the
same area in 2003 and 2004.
Table 1 summarizes the predicted distances at which sound levels
(160- and 180-dB) are expected to be received from the 18-airgun
subarray and a single airgun operating in shallow, intermediate and
deep water depths.
Table 1--Predicted Distances To Which Sound Levels >= 190, 180, and 160 dB re: 1 [mu]Parms Could Be Received
During the Proposed Survey Using A 18-Airgun Subarray, as Well as a Single Airgun Towed at a Depth Of 7 M in the
Etp During April-May, 2011
[Distances are based on model results provided by L-DEO.]
----------------------------------------------------------------------------------------------------------------
Predicted RMS Distances (m)
Source and volume Water depth -------------------------------------
180 dB 160 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun (40 in\3\)..... Shallow < 100 m....................... 296 1,050
Intermediate.......................... 60 578
100-1,000 m...........................
Deep.................................. 40 385
> 1,000 m.............................
18-Airgun subarray (3,300 in\3\).. Shallow............................... 1,030 * 19,500
< 100 m...............................
Intermediate.......................... 675 5,700
100-1,000 m...........................
Deep.................................. 450 3,800
> 1,000 m.............................
----------------------------------------------------------------------------------------------------------------
* This is likely an overestimate, as the measured distance for the 36-airgun array operating in shallow waters
of the northern Gulf of Mexico was 17,500 m (17.5 km).
L-DEO conducted modeling for a 2008 survey off Costa Rica using
site specific data on sound velocity profiles in the water column and
bottom composition at a depth of 65 m (213.5 ft) in Drake Bay (at the
proposed survey area) and at a depth of 340 m (1,115 ft) in an area
approximately 100 km (62 mi) north of the survey area. The modeled
exclusion zones were smaller than the shallow- and intermediate-depth
ranges listed in Table 1, suggesting that L-DEO's estimates for the
proposed survey are overestimates and thus precautionary. Also, the
estimated 160-dB distance for the 18-airgun subarray in water depths
less than 100 m (328 ft) (Table 1) is higher than the measured distance
for the 36-airgun array (17.5 km; Tolstoy et al., 2009), again
suggesting that these estimates are precautionary. Refer to Appendix A
of L-DEO's environmental analysis for additional information on L-DEO's
calculations for the model.
Multibeam Echosounder
The Langseth will operate a Kongsberg EM 122 MBES concurrently
during airgun operations to map characteristics of the ocean floor. The
hull-mounted MBES emits brief pulses of sound (also called a ping)
(10.5 to 13 kilohertz (kHz)) in a fan-shaped beam that extends downward
and to the sides of the ship. The transmitting beamwidth is one or two
degrees ([deg]) fore-aft and 150[deg] athwartship and the maximum
source level is 242 dB re: 1 [mu]Pa.
For deep-water operations, each ping consists of eight (in water
greater than 1,000 m; 3,280 ft) or four (less than 1,000 m; 3,280 ft)
successive, fan-shaped transmissions, from two to 15 milliseconds (ms)
in duration and each ensonifying a sector that extends 1[deg] fore-aft.
The eight successive transmissions span an overall cross-track angular
extent of about 150[deg], with 2-ms gaps between the pulses for
successive sectors.
Sub-Bottom Profiler
The Langseth will also operate a Knudsen 320B SBP continuously
throughout the cruise with the MBES to provide information about the
sedimentary features and bottom topography. The dominant frequency
component of the SBP is 3.5 kHz which is directed downward in a 30[deg]
cone by a hull-mounted transducer on the vessel. The maximum output is
1,000 watts (204 dB re: 1 [mu]Pa), but in practice, the output varies
with water depth. The pulse interval is one second, but a common mode
of operation is to broadcast five pulses at 1-s intervals followed by a
5-s pause.
NMFS expects that acoustic stimuli resulting from the proposed
operation of the single airgun or the 18-airgun subarray has the
potential to harass marine mammals, incidental to the conduct of the
proposed seismic survey. NMFS expects these disturbances to be
temporary and result, at worst, in a temporary modification in behavior
and/or low-level physiological effects (Level B Harassment) of small
numbers of certain species of marine mammals. NMFS does not expect that
the movement of the Langseth, during the conduct of the seismic survey,
has the potential to harass marine mammals because of the relatively
slow operation speed of the vessel (4.6 kts; 8.5 km/h; 5.3 mph) during
seismic acquisition.
Description of the Specified Geographic Region
The survey will encompass the area bounded by 8.5-9[deg] N, 83.75-
84.25[deg] W
[[Page 6434]]
offshore from Costa Rica in the Pacific Ocean (see Figure 1 in L-DEO's
application). The closest that the Langseth will approach the coastline
is approximately 30 km.
Description of the Marine Mammals in the Area of the Proposed Specified
Activity
Twenty-eight marine mammal species may occur in the proposed survey
area, including 20 odontocetes (toothed cetaceans), 6 mysticetes
(baleen whales) and two pinnipeds. Of these, 19 cetacean species are
likely to occur in the proposed survey area in the ETP during April
through May. Five of these species are listed as endangered under the
U.S. Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531 et seq.),
including the humpback (Megaptera novaeangliae), sei (Balaenoptera
borealis), fin (Balaenoptera physalus), blue (Balaenoptera musculus),
and sperm (Physeter macrocephalus) whale.
The species of marine mammals expected to be most common in the
survey area (all delphinids) include the short-beaked common dolphin
(Delphinus delphis), spinner dolphin (Stenella longirostris),
pantropical spotted dolphin (Stenella attenuata), striped dolphin
(Stenella coeruleoalba), melon-headed whale (Peponocephala electra),
and bottlenose dolphin (Tursiops truncatus).
Two pinnipeds, the California sea lion (Zalophus californianus) and
the Gal[aacute]pagos sea lion (Zalophus wollebaeki), have the potential
to transit in the vicinity of the proposed seismic survey, although any
occurrence would be rare as they are vagrants to the area. Based on
available data and monitoring reports from previous seismic surveys in
the area, L-DEO does not expect to encounter these species within the
proposed survey area and does not present analysis for these species.
Accordingly, NMFS will not consider these pinniped species in greater
detail and the proposed IHA will only address requested take
authorizations for mysticetes and odontocetes.
Table 2 presents information on the abundance, distribution,
population status, and conservation status of the marine mammals that
may occur in the proposed survey area April through May, 2011.
Table 2--Habitat, Regional Abundance, and Conservation Status of Marine Mammals That May Occur in or Near the Proposed Seismic Survey Areas Off Costa
Rica in the Eastern Tropical Pacific Ocean
[See text and Tables 2-4 in L-DEO's application and environmental analysis for further details.]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Density
Species Occurrence in survey Habitat Abundance in the ETP \1\ ESA \2\ -------------------
area during April-May Best \3\ Max \4\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mysticetes
Humpback whale.................... Very rare............ Mainly nearshore NE Pacific 1392 \6\............. EN.............. 0.25 4.40
waters and banks. SE Pacific 2900 \7\.............
Bryde's whale..................... Uncommon............. Pelagic and coastal.. 13,000 \8\...................... NL.............. 0.96 2.52
Sei whale......................... Very rare............ Mostly pelagic....... N.A............................. EN.............. 0.01 0.01
Fin whale......................... Very rare............ Slope, mostly pelagic 2636 \6\........................ EN.............. 0.01 0.01
Blue whale........................ Rare................. Pelagic and coastal.. 1415 \9\........................ EN.............. 0.13 1.86
Common minke whale................ Very rare............ Coastal.............. N.A............................. NL.............. < 0.01 < 0.01
Odontocetes
Sperm whale....................... Uncommon............. Usually deep pelagic, 26,053 \10\..................... EN.............. 4.19 9.80
steep topography.
Pygmy sperm whale................. Very rare............ Deep waters off shelf N.A. \11\....................... NL.............. 0.03 0.05
Dwarf sperm whale................. Rare................. Deep waters off shelf 11,200 \12\..................... NL.............. 0.03 0.05
Cuvier's beaked whale............. Uncommon............. Slope and pelagic.... 20,000 \9\...................... NL.............. 2.47 3.70
Mesoplodon spp.................... Very rare or rare.... Pelagic.............. 25,300 \13\..................... NL.............. 0.36 1.00
Rough-toothed dolphin............. Common............... Mainly pelagic....... 107,633......................... NL.............. 4.19 11.19
Bottlenose dolphin................ Very common.......... Coastal, shelf, 335,834......................... NL.............. 17.06 90.91
pelagic.
Pantropical spotted dolphin....... Very common.......... Coastal and pelagic.. 1,575,247 \14\.................. NL.............. 76.96 236.66
Spinner dolphin................... Common............... Coastal and pelagic.. 1,797,716 \14\.................. NL.............. 58.43 364.26
Striped dolphin................... Uncommon............. Off continental shelf 964,362......................... NL.............. 67.75 154.21
Fraser's dolphin.................. Rare................. Pelagic.............. 289,300 \9\..................... NL.............. < 0.01 < 0.01
Short-beaked common dolphin....... Common............... Shelf, pelagic, high 3,127,203....................... NL.............. 110.89 763.50
relief.
Risso's dolphin................... Common............... Shelf, slope, 110,457......................... NL.............. 12.76 12.76
seamounts.
Melon-headed whale................ Rare................. Pelagic.............. 45,400 \9\...................... NL.............. 11.06 57.70
Pygmy killer whale................ Rare................. Pelagic.............. 38,900 \9\...................... NL.............. 1.25 2.30
False killer whale................ Uncommon............. Pelagic.............. 39,800 \9\...................... NL.............. 0.01 0.01
Killer whale...................... Rare................. Widely distributed... 8500 \15\....................... NL.............. 0.19 0.40
Short-finned pilot whale.......... Common............... Mostly pelagic, high- 589,315 \16\.................... NL.............. 11.88 28.22
relief.
--------------------------------------------------------------------------------------------------------------------------------------------------------
N.A. Not available or not assessed.
\1\ Abundance from Gerrodette et al. (2008) unless otherwise stated.
\2\ U.S. Endangered Species Act: EN = Endangered, T = Threatened, NL = Not listed.
\3\ Best density (/1000km\2\) estimate as listed in Table 3 of the application. Cetecean densities are based on NMFS SWFSC ship transect
surveys conducted in 1986-2006 from predictive modeling (Barlow et al. 2009; Read et al. 2009) or in 1986-1996 from Ferguson and Barlow (2003).
\4\ Maximum density (/1000km\2\) estimate as listed in Table 3 of the application.
\6\ U.S. west coast (Carretta et al., 2010).
\7\ Southeast Pacific; F[eacute]lix et al. (2005).
\8\ This estimate is mainly for Balaenoptera edeni but may include some B. borealis (Wade and Gerrodette, 1993).
\9\ ETP (Wade and Gerrodette, 1993).
\10\ Eastern temperate North Pacific (Whitehead, 2002).
\11\ California/Oregon/Washington (Carretta et al., 2010).
\12\ This abundance estimate is mostly for K. sima but may also include some K. breviceps (Wade and Gerrodette, 1993).
\13\ This estimate includes all species of the genus Mesoplodon in the ETP (Wade and Gerrodette, 1993).
\14\ For all stocks in ETP.
\15\ ETP (Ford, 2002).
[[Page 6435]]
\16\ This estimate is for G. macrorhynchus and G. melas in the ETP (Gerrodette and Forcada, 2002).
\17\ U.S. stock (Carretta et al., 2010).
\18\ Galapagos Islands (Alava and Salazar, 2006).
Refer to Section III of L-DEO's application for detailed
information regarding the abundance and distribution, population
status, and life history and behavior of these species and their
occurrence in the proposed project area. The application also presents
how L-DEO calculated the estimated densities for the marine mammals in
the proposed survey area. NMFS has reviewed these data and determined
them to be the best available scientific information for the purposes
of the proposed IHA.
Potential Effects on Marine Mammals
Acoustic stimuli generated by the operation of the airguns, which
introduce sound into the marine environment, may have the potential to
cause Level B harassment of marine mammals in the proposed survey area.
The effects of sounds from airgun operations might include one of the
following: tolerance, masking of natural sounds, behavioral
disturbance, temporary or permanent impairment, or non-auditory
physical or physiological effects (Richardson et al., 1995; Gordon et
al., 2004; Nowacek et al., 2007; Southall et al., 2007).
Permanent hearing impairment, in the unlikely event that it
occurred, would constitute injury, but temporary threshold shift (TTS)
is not an injury (Southall et al., 2007). Although the possibility
cannot be entirely excluded, it is unlikely that the proposed project
would result in any cases of temporary or permanent hearing impairment,
or any significant non-auditory physical or physiological effects.
Based on the available data and studies described here, some behavioral
disturbance is expected, but NMFS expects the disturbance to be
localized and short-term.
Tolerance to Sound
Studies on marine mammals' tolerance to sound in the natural
environment are relatively rare. Richardson et al. (1995) defines
tolerance as the occurrence of marine mammals in areas where they are
exposed to human activities or man-made noise. In many cases, tolerance
develops by the animal habituating to the stimulus (i.e., the gradual
waning of responses to a repeated or ongoing stimulus) (Richardson, et
al., 1995; Thorpe, 1963), but because of ecological or physiological
requirements, many marine animals may need to remain in areas where
they are exposed to chronic stimuli (Richardson, et al., 1995).
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
Malme et al., (1985) studied the responses of humpback whales on their
summer feeding grounds in southeast Alaska to seismic pulses from a
airgun with a total volume of 100-in\3\. They noted that the whales did
not exhibit persistent avoidance when exposed to the airgun and
concluded that there was no clear evidence of avoidance, despite the
possibility of subtle effects, at received levels up to 172 dB: re 1
[mu]Pa.
Weir (2008) observed marine mammal responses to seismic pulses from
a 24-airgun array firing a total volume of either 5,085 in\3\ or 3,147
in\3\ in Angolan waters between August 2004 and May 2005. She recorded
a total of 207 sightings of humpback whales (n = 66), sperm whales (n =
124), and Atlantic spotted dolphins (n = 17) and reported that there
were no significant differences in encounter rates (sightings/hr) for
humpback and sperm whales according to the airgun array's operational
status (i.e., active versus silent).
Masking of Natural Sounds
The term masking refers to the inability of a subject to recognize
the occurrence of an acoustic stimulus as a result of the interference
of another acoustic stimulus (Clark et al., 2009). Introduced
underwater sound may, through masking, reduce the effective
communication distance of a marine mammal species if the frequency of
the source is close to that used as a signal by the marine mammal, and
if the anthropogenic sound is present for a significant fraction of the
time (Richardson et al., 1995).
Masking effects of pulsed sounds (even from large arrays of
airguns) on marine mammal calls and other natural sounds are expected
to be limited. Because of the intermittent nature and low duty cycle of
seismic airgun pulses, animals can emit and receive sounds in the
relatively quiet intervals between pulses. However, in some situations,
reverberation occurs for much or the entire interval between pulses
(e.g., Simard et al., 2005; Clark and Gagnon, 2006) which could mask
calls. Some baleen and toothed whales are known to continue calling in
the presence of seismic pulses, and their calls can usually be heard
between the seismic pulses (e.g., Richardson et al., 1986; McDonald et
al., 1995; Greene et al., 1999; Nieukirk et al., 2004; Smultea et al.,
2004; Holst et al., 2005a,b, 2006; and Dunn and Hernandez, 2009).
However, Clark and Gagnon (2006) reported that fin whales in the
northeast Pacific Ocean went silent for an extended period starting
soon after the onset of a seismic survey in the area. Similarly, there
has been one report that sperm whales ceased calling when exposed to
pulses from a very distant seismic ship (Bowles et al., 1994). However,
more recent studies found that they continued calling in the presence
of seismic pulses (Madsen et al., 2002; Tyack et al., 2003; Smultea et
al., 2004; Holst et al., 2006; and Jochens et al., 2008). Dolphins and
porpoises commonly are heard calling while airguns are operating (e.g.,
Gordon et al., 2004; Smultea et al., 2004; Holst et al., 2005a, b; and
Potter et al., 2007). The sounds important to small odontocetes are
predominantly at much higher frequencies than are the dominant
components of airgun sounds, thus limiting the potential for masking.
In general, NMFS expects the masking effects of seismic pulses to
be minor, given the normally intermittent nature of seismic pulses.
Refer to Appendix B (4) of L-DEO's environmental analysis for a more
detailed discussion of masking effects on marine mammals.
Behavioral Disturbance
Disturbance includes a variety of effects, including subtle to
conspicuous changes in behavior, movement, and displacement. Reactions
to sound, if any, depend on species, state of maturity, experience,
current activity, reproductive state, time of day, and many other
factors (Richardson et al., 1995; Wartzok et al., 2004; Southall et
al., 2007; Weilgart, 2007). If a marine mammal does react briefly to an
underwater sound by changing its behavior or moving a small distance,
the impacts of the change are unlikely to be significant to the
individual, let alone the stock or population. However, if a sound
source displaces marine mammals from an important feeding or breeding
area for a prolonged period, impacts on individuals and populations
could be significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007).
Given the many uncertainties in predicting the quantity and types of
impacts of noise on marine mammals, it is common practice to estimate
how many mammals would be present within a
[[Page 6436]]
particular distance of industrial activities and/or exposed to a
particular level of industrial sound. In most cases, this approach
likely overestimates the numbers of marine mammals that would be
affected in some biologically-important manner.
The sound criteria used to estimate how many marine mammals might
be disturbed to some biologically-important degree by a seismic program
are based primarily on behavioral observations of a few species.
Scientists have conducted detailed studies on humpback, gray, bowhead
(Balaena mysticetus), and sperm whales. Less detailed data are
available for some other species of baleen whales, small toothed
whales, and sea otters (Enhydra lutris), but for many species there are
no data on responses to marine seismic surveys.
Baleen Whales--Baleen whales generally tend to avoid operating
airguns, but avoidance radii are quite variable (reviewed in
Richardson, et al., 1995). 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 L-DEO's environmental analysis, baleen whales exposed
to strong noise pulses from airguns often react by deviating from their
normal migration route and/or interrupting their feeding and moving
away. In the cases of migrating gray and bowhead whales, the observed
changes in behavior appeared to be of little or no biological
consequence to the animals (Richardson, et al., 1995). They simply
avoided the sound source by displacing their migration route to varying
degrees, but within the natural boundaries of the migration corridors.
Studies of gray, bowhead, and humpback whales have shown that
seismic pulses with received levels of 160 to 170 dB re: 1 [mu]Pa seem
to cause obvious avoidance behavior in a substantial fraction of the
animals exposed (Malme et al., 1986, 1988; Richardson et al., 1995). In
many areas, seismic pulses from large arrays of airguns diminish to
those levels at distances ranging from four to 15 km from the source. A
substantial proportion of the baleen whales within those distances may
show avoidance or other strong behavioral reactions to the airgun
array. Subtle behavioral changes sometimes become evident at somewhat
lower received levels, and studies summarized in Appendix B (5) of L-
DEO's environmental analysis have shown that some species of baleen
whales, notably bowhead and humpback whales, at times, show strong
avoidance at received levels lower than 160-170 dB re: 1 [mu]Pa.
McCauley et al. (1998, 2000) studied the responses of humpback
whales off western Australia to a full-scale seismic survey with a 16-
airgun array (2,678-in\3\) and to a single airgun (20-in\3\) with
source level of 227 dB re: 1 [mu]Pa(p-p). In the 1998 study,
they documented that avoidance reactions began at five to eight km from
the array, and that those reactions kept most pods approximately three
to four km from the operating seismic boat. In the 2000 study, they
noted localized displacement during migration of four to five km by
traveling pods and seven to 12 km by more sensitive resting pods of
cow-calf pairs. Avoidance distances with respect to the single airgun
were smaller but consistent with the results from the full array in
terms of the received sound levels. The mean received level for initial
avoidance of an approaching airgun was 140 dB re: 1 [mu]Pa for humpback
pods containing females, and at the mean closest point of approach
distance the received level was 143 dB re: 1 [mu]Pa. The initial
avoidance response generally occurred at distances of five to eight km
from the airgun array and two km from the single airgun. However, some
individual humpback whales, especially males, approached within
distances of 100 to 400 m (328 to 1,312 ft), where the maximum received
level was 179 dB re: 1 [mu]Pa.
Humpback whales on their summer feeding grounds in southeast Alaska
did not exhibit persistent avoidance when exposed to seismic pulses
from a 1.64-L (100-in\3\) airgun (Malme et al., 1985). Some humpbacks
seemed ``startled'' at received levels of 150 to 169 dB re: 1 [mu]Pa.
Malme et al. (1985) concluded that there was no clear evidence of
avoidance, despite the possibility of subtle effects, at received
levels up to 172 dB re: 1 [mu]Pa.
Studies have suggested that south Atlantic humpback whales
wintering off Brazil may be displaced or even strand upon exposure to
seismic surveys (Engel et al., 2004). The evidence for this was
circumstantial and subject to alternative explanations (IAGC, 2004).
Also, the evidence was not consistent with subsequent results from the
same area of Brazil (Parente et al., 2006), or with direct studies of
humpbacks exposed to seismic surveys in other areas and seasons. After
allowance for data from subsequent years, there was no observable
direct correlation between strandings and seismic surveys (IWC,
2007:236).
There are no data on reactions of right whales to seismic surveys,
but results from the closely-related bowhead whale show that their
responsiveness can be quite variable depending on their activity
(migrating versus feeding). Bowhead whales migrating west across the
Alaskan Beaufort Sea in autumn, in particular, are unusually
responsive, with substantial avoidance occurring out to distances of 20
to 30 km from a medium-sized airgun source at received sound levels of
around 120 to 130 dB re: 1 [mu]Pa (Miller et al., 1999; Richardson et
al., 1999; see Appendix B (5) of L-DEO's environmental analysis).
However, more recent research on bowhead whales (Miller et al., 2005;
Harris et al., 2007) corroborates earlier evidence that, during the
summer feeding season, bowheads are not as sensitive to seismic
sources. Nonetheless, subtle but statistically significant changes in
surfacing-respiration-dive cycles were evident upon statistical
analysis (Richardson et al., 1986). In the summer, bowheads typically
begin to show avoidance reactions at received levels of about 152 to
178 dB re: 1 [mu]Pa (Richardson et al., 1986, 1995; Ljungblad et al.,
1988; Miller et al., 2005).
Reactions of migrating and feeding (but not wintering) gray whales
to seismic surveys have been studied. Malme et al. (1986, 1988) studied
the responses of feeding eastern Pacific gray whales to pulses from a
single 100-in\3\ airgun off St. Lawrence Island in the northern Bering
Sea. They estimated, based on small sample sizes, that 50 percent of
feeding gray whales stopped feeding at an average received pressure
level of 173 dB re: 1 [mu]Pa on an (approximate) rms basis, and that 10
percent of feeding whales interrupted feeding at received levels of 163
dB re: 1 [mu]Pa. Those findings were generally consistent with the
results of experiments conducted on larger numbers of gray whales that
were migrating along the California coast (Malme et al., 1984; Malme
and Miles, 1985), and western Pacific gray whales feeding off Sakhalin
Island, Russia (Wursig et al., 1999; Gailey et al., 2007; Johnson et
al., 2007; Yazvenko et al., 2007a, b), along with data on gray whales
off British Columbia (Bain and Williams, 2006).
Various species of Balaenoptera (blue, sei, fin, and minke whales)
have occasionally been seen in areas ensonified by airgun pulses
(Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006), and
calls from blue and fin whales have been localized in areas with airgun
operations (e.g., McDonald et al., 1995; Dunn and
[[Page 6437]]
Hernandez, 2009). Sightings by observers on seismic vessels off the
United Kingdom from 1997 to 2000 suggest that, during times of good
sightability, sighting rates for mysticetes (mainly fin and sei whales)
were similar when large arrays of airguns were shooting vs. silent
(Stone, 2003; Stone and Tasker, 2006). However, these whales tended to
exhibit localized avoidance, remaining significantly further (on
average) from the airgun array during seismic operations compared with
non-seismic periods (Stone and Tasker, 2006). In a study off of Nova
Scotia, Moulton and Miller (2005) found little difference in sighting
rates (after accounting for water depth) and initial sighting distances
of balaenopterid whales when airguns were operating vs. silent.
However, there were indications that these whales were more likely to
be moving away when seen during airgun operations. Similarly, ship-
based monitoring studies of blue, fin, sei and minke whales offshore of
Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more than
small differences in sighting rates and swim directions during seismic
versus non-seismic periods (Moulton et al., 2005, 2006a,b).
Data on short-term reactions by cetaceans to impulsive noises are
not necessarily indicative of long-term or biologically significant
effects. It is not known whether impulsive sounds affect reproductive
rate or distribution and habitat use in subsequent days or years.
However, gray whales have continued to migrate annually along the west
coast of North America with substantial increases in the population
over recent years, despite intermittent seismic exploration (and much
ship traffic) in that area for decades (Appendix A in Malme et al.,
1984; Richardson et al., 1995; Allen and Angliss, 2010). The western
Pacific gray whale population did not seem affected by a seismic survey
in its feeding ground during a previous year (Johnson et al., 2007).
Similarly, bowhead whales have continued to travel to the eastern
Beaufort Sea each summer, and their numbers have increased notably,
despite seismic exploration in their summer and autumn range for many
years (Richardson et al., 1987; Angliss and Allen, 2009).
Toothed Whales--Little systematic information is available about
reactions of toothed whales to noise pulses. Few studies similar to the
more extensive baleen whale/seismic pulse work summarized above and (in
more detail) in Appendix B of L-DEO's environmental analysis have been
reported for toothed whales. However, there are recent systematic
studies on sperm whales (e.g., Gordon et al., 2006; Madsen et al.,
2006; Winsor and Mate, 2006; Jochens et al., 2008; Miller et al.,
2009). There is an increasing amount of information about responses of
various odontocetes to seismic surveys based on monitoring studies
(e.g., Stone, 2003; Smultea et al., 2004; Moulton and Miller, 2005;
Bain and Williams, 2006; Holst et al., 2006; Stone and Tasker, 2006;
Potter et al., 2007; Hauser et al., 2008; Holst and Smultea, 2008;
Weir, 2008; Barkaszi et al., 2009; Richardson et al., 2009).
Seismic operators and marine mammal observers on seismic vessels
regularly see dolphins and other small toothed whales near operating
airgun arrays, but in general there is a tendency for most delphinids
to show some avoidance of operating seismic vessels (e.g., Goold,
1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and
Miller, 2005; Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008;
Richardson et al., 2009; see also Barkaszi et al., 2009). Some dolphins
seem to be attracted to the seismic vessel and floats, and some ride
the bow wave of the seismic vessel even when large arrays of airguns
are firing (e.g., Moulton and Miller, 2005). Nonetheless, small toothed
whales more often tend to head away, or to maintain a somewhat greater
distance from the vessel, when a large array of airguns is operating
than when it is silent (e.g., Stone and Tasker, 2006; Weir, 2008). In
most cases, the avoidance radii for delphinids appear to be small, on
the order of one km less, and some individuals show no apparent
avoidance. The beluga whale (Delphinapterus leucas) is a species that
(at least at times) shows long-distance avoidance of seismic vessels.
Aerial surveys conducted in the southeastern Beaufort Sea during summer
found that sighting rates of beluga whales were significantly lower at
distances 10 to 20 km compared with 20 to 30 km from an operating
airgun array, and observers on seismic boats in that area rarely see
belugas (Miller et al., 2005; Harris et al., 2007).
Captive bottlenose dolphins (Tursiops truncatus) and beluga whales
exhibited changes in behavior when exposed to strong pulsed sounds
similar in duration to those typically used in seismic surveys
(Finneran et al., 2000, 2002, 2005). However, the animals tolerated
high received levels of sound before exhibiting aversive behaviors.
Results for porpoises depend on species. The limited available data
suggest that harbor porpoises (Phocoena phocoena) show stronger
avoidance of seismic operations than do Dall's porpoises (Phocoenoides
dalli) (Stone, 2003; MacLean and Koski, 2005; Bain and Williams, 2006;
Stone and Tasker, 2006). Dall's porpoises seem relatively tolerant of
airgun operations (MacLean and Koski, 2005; Bain and Williams, 2006),
although they too have been observed to avoid large arrays of operating
airguns (Calambokidis and Osmek, 1998; Bain and Williams, 2006). This
apparent difference in responsiveness of these two porpoise species is
consistent with their relative responsiveness to boat traffic and some
other acoustic sources (Richardson et al., 1995; Southall et al.,
2007).
Most studies of sperm whales exposed to airgun sounds indicate that
the sperm whale shows considerable tolerance of airgun pulses (e.g.,
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir,
2008). In most cases the whales do not show strong avoidance, and they
continue to call (see Appendix B of L-DEO's environmental analysis for
review). However, controlled exposure experiments in the Gulf of Mexico
indicate that foraging behavior was altered upon exposure to airgun
sound (Jochens et al., 2008; Miller et al., 2009; Tyack, 2009).
There are almost no specific data on the behavioral reactions of
beaked whales to seismic surveys. However, some northern bottlenose
whales (Hyperoodon ampullatus) remained in the general area and
continued to produce high-frequency clicks when exposed to sound pulses
from distant seismic surveys (Gosselin and Lawson, 2004; Laurinolli and
Cochrane, 2005; Simard et al., 2005). Most beaked whales tend to avoid
approaching vessels of other types (e.g., Wursig et al., 1998). They
may also dive for an extended period when approached by a vessel (e.g.,
Kasuya, 1986), although it is uncertain how much longer such dives may
be as compared to dives by undisturbed beaked whales, which also are
often quite long (Baird et al., 2006; Tyack et al., 2006). Based on a
single observation, Aguilar-Soto et al. (2006) suggested that foraging
efficiency of Cuvier's beaked whales may be reduced by close approach
of vessels. In any event, it is likely that most beaked whales would
also show strong avoidance of an approaching seismic vessel, although
this has not been documented explicitly.
There are increasing indications that some beaked whales tend to
strand when naval exercises involving mid-frequency sonar operation are
ongoing nearby (e.g., Simmonds and Lopez-Jurado, 1991; Frantzis, 1998;
NOAA and
[[Page 6438]]
USN, 2001; Jepson et al., 2003; Hildebrand, 2005; Barlow and Gisiner,
2006; see also the Stranding and Mortality section in this notice).
These strandings are apparently a disturbance response, although
auditory or other injuries or other physiological effects may also be
involved. Whether beaked whales would ever react similarly to seismic
surveys is unknown. Seismic survey sounds are quite different from
those of the sonar in operation during the above-cited incidents.
Odontocete reactions to large arrays of airguns are variable and,
at least for delphinids and Dall's porpoises, seem to be confined to a
smaller radius than has been observed for the more responsive of the
mysticetes, belugas, and harbor porpoises (Appendix B of L-DEO's
environmental analysis).
Hearing Impairment and Other Physical Effects
Exposure to high intensity sound for a sufficient duration may
result in auditory effects such as a noise-induced threshold shift--an
increase in the auditory threshold after exposure to noise (Finneran,
Carder, Schlundt, and Ridgway, 2005). Factors that influence the amount
of threshold shift include the amplitude, duration, frequency content,
temporal pattern, and energy distribution of noise exposure. The
magnitude of hearing threshold shift normally decreases over time
following cessation of the noise exposure. The amount of threshold
shift just after exposure is called the initial threshold shift. If the
threshold shift eventually returns to zero (i.e., the threshold returns
to the pre-exposure value), it is called temporary threshold shift
(TTS) (Southall et al., 2007).
Researchers have studied TTS in certain captive odontocetes and
pinnipeds exposed to strong sounds (reviewed in Southall et al., 2007).
However, there has been no specific documentation of TTS let alone
permanent hearing damage, i.e., permanent threshold shift (PTS), in
free-ranging marine mammals exposed to sequences of airgun pulses
during realistic field conditions.
Temporary Threshold Shift--TTS is the mildest form of hearing
impairment that can occur during exposure to a strong sound (Kryter,
1985). While experiencing TTS, the hearing threshold rises and a sound
must be stronger in order to be heard. At least in terrestrial mammals,
TTS can last from minutes or hours to (in cases of strong TTS) days.
For sound exposures at or somewhat above the TTS threshold, hearing
sensitivity in both terrestrial and marine mammals recovers rapidly
after exposure to the noise ends. Few data on sound levels and
durations necessary to elicit mild TTS have been obtained for marine
mammals, and none of the published data concern TTS elicited by
exposure to multiple pulses of sound. Available data on TTS in marine
mammals are summarized in Southall et al. (2007). Table 1 presents the
distances from the Langseth's airguns at which the received energy
level (per pulse, flat-weighted) that would be expected to be greater
than or equal to 180 dB re: 1 [mu]Pa.
To avoid the potential for injury, NMFS (1995, 2000) concluded that
cetaceans should not be exposed to pulsed underwater noise at received
levels exceeding 180 dB re: 1 [mu]Pa. NMFS believes that to avoid the
potential for permanent physiological damage (Level A harassment),
cetaceans should not be exposed to pulsed underwater noise at received
levels exceeding 180 dB re: 1 [mu]Pa. The 180-dB level is a shutdown
criterion applicable to cetaceans, as specified by NMFS (2000); these
levels were used to establish the EZs. NMFS also assumes that cetaceans
exposed to levels exceeding 160 dB re: 1 [mu]Pa (rms) may experience
Level B harassment.
Researchers have derived TTS information for odontocetes from
studies on the bottlenose dolphin and beluga. For the one harbor
porpoise tested, the received level of airgun sound that elicited onset
of TTS was lower (Lucke et al., 2009). If these results from a single
animal are representative, it is inappropriate to assume that onset of
TTS occurs at similar received levels in all odontocetes (cf. Southall
et al., 2007). Some cetaceans apparently can incur TTS at considerably
lower sound exposures than are necessary to elicit TTS in the beluga or
bottlenose dolphin.
For baleen whales, there are no data, direct or indirect, on levels
or properties of sound that are required to induce TTS. The frequencies
to which baleen whales are most sensitive are assumed to be lower than
those to which odontocetes are most sensitive, and natural background
noise levels at those low frequencies tend to be higher. As a result,
auditory thresholds of baleen whales within their frequency band of
best hearing are believed to be higher (less sensitive) than are those
of odontocetes at their best frequencies (Clark and Ellison, 2004).
From this, it is suspected that received levels causing TTS onset may
also be higher in baleen whales (Southall et al., 2007). For this
proposed study, L--DEO expects no cases of TTS given: (1) The low
abundance of baleen whales in the planned study area at the time of the
survey; and (2) the strong likelihood that baleen whales would avoid
the approaching airguns (or vessel) before being exposed to levels high
enough for TTS to occur. Permanent Threshold Shift--When PTS occurs,
there is physical damage to the sound receptors in the ear. In severe
cases, there can be total or partial deafness, whereas in other cases,
the animal has an impaired ability to hear sounds in specific frequency
ranges (Kryter, 1985). There is no specific evidence that exposure to
pulses of airgun sound can cause PTS in any marine mammal, even with
large arrays of airguns. However, given the possibility that mammals
close to an airgun array might incur at least mild TTS, there has been
further speculation about the possibility that some individuals
occurring very close to airguns might incur PTS (e.g., Richardson et
al., 1995, p. 372ff; Gedamke et al., 2008). Single or occasional
occurrences of mild TTS are not indicative of permanent auditory
damage, but repeated or (in some cases) single exposures to a level
well above that causing TTS onset might elicit PTS.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals, but are assumed to be similar to those in humans and
other terrestrial mammals. PTS might occur at a received sound level at
least several decibels above that inducing mild TTS if the animal were
exposed to strong sound pulses with rapid rise time-see Appendix B (6)
of L-DEO's environmental analysis. Based on data from terrestrial
mammals, a precautionary assumption is that the PTS threshold for
impulse sounds (such as airgun pulses as received close to the source)
is at least 6 dB higher than the TTS threshold on a peak-pressure
basis, and probably greater than six dB (Southall et al., 2007).
Given the higher level of sound necessary to cause PTS as compared
with TTS, it is considerably less likely that PTS would occur. Baleen
whales generally avoid the immediate area around operating seismic
vessels, as do some other marine mammals.
Stranding and Mortality--Marine mammals close to underwater
detonations of high explosives can be killed or severely injured, and
the auditory organs are especially susceptible to injury (Ketten et
al., 1993; Ketten, 1995). However, explosives are no longer used for
marine waters for commercial seismic surveys or (with rare exceptions)
for seismic research; they have been replaced entirely by airguns or
related non-explosive pulse generators. Airgun pulses are less
energetic and have slower rise times,
[[Page 6439]]
and there is no specific evidence that they can cause serious injury,
death, or stranding even in the case of large airgun arrays. However,
the association of strandings of beaked whales with naval exercises
involving mid-frequency active sonar and, in one case, an L-DEO seismic
survey (Malakoff, 2002; Cox et al., 2006), has raised the possibility
that beaked whales exposed to strong ``pulsed'' sounds may be
especially susceptible to injury and/or behavioral reactions that can
lead to stranding (e.g., Hildebrand, 2005; Southall et al., 2007).
Appendix B (6) of L-DEO's environmental analysis provides additional
details.
Specific sound-related processes that lead to strandings and
mortality are not well documented, but may include:
(1) Swimming in avoidance of a sound into shallow water;
(2) a change in behavior (such as a change in diving behavior) that
might contribute to tissue damage, gas bubble formation, hypoxia,
cardiac arrhythmia, hypertensive hemorrhage or other forms of trauma;
(3) a physiological change such as a vestibular response leading to
a behavioral change or stress-induced hemorrhagic diathesis, leading in
turn to tissue damage; and
(4) tissue damage directly from sound exposure, such as through
acoustically-mediated bubble formation and growth or acoustic resonance
of tissues. Some of these mechanisms are unlikely to apply in the case
of impulse sounds. However, there are increasing indications that gas-
bubble disease (analogous to the bends), induced in supersaturated
tissue by a behavioral response to acoustic exposure, could be a
pathologic mechanism for the strandings and mortality of some deep-
diving cetaceans exposed to sonar. However, the evidence for this
remains circumstantial and associated with exposure to naval mid-
frequency sonar, not seismic surveys (Cox et al., 2006; Southall et
al., 2007).
Seismic pulses and mid-frequency sonar signals are quite different,
and some mechanisms by which sonar sounds have been hypothesized to
affect beaked whales are unlikely to apply to airgun pulses. Sounds
produced by airgun arrays are broadband impulses with most of the
energy below one kHz. Typical military mid-frequency sonar emits non-
impulse sounds at frequencies of two to 10 kHz, generally with a
relatively narrow bandwidth at any one time. A further difference
between seismic surveys and naval exercises is that naval exercises can
involve sound sources on more than one vessel. Thus, it is not
appropriate to assume that there is a direct connection between the
effects of military sonar and seismic surveys on marine mammals.
However, evidence that sonar signals can, in special circumstances,
lead (at least indirectly) to physical damage and mortality (e.g.,
Balcomb and Claridge, 2001; NOAA and USN, 2001; Jepson et al., 2003;
Fern[aacute]ndez et al., 2004, 2005; Hildebrand 2005; Cox et al., 2006)
suggests that caution is warranted when dealing with exposure of marine
mammals to any high-intensity ``pulsed'' sound.
There is no conclusive evidence of cetacean strandings or deaths at
sea as a result of exposure to seismic surveys, but a few cases of
strandings in the general area where a seismic survey was ongoing have
led to speculation concerning a possible link between seismic surveys
and strandings. Suggestions that there was a link between seismic
surveys and strandings of humpback whales in Brazil (Engel et al.,
2004) were not well founded (IAGC, 2004; IWC, 2007). In September 2002,
there was a stranding of two Cuvier's beaked whales (Ziphius
cavirostris) in the Gulf of California, Mexico, when the L DEO vessel
R/V Maurice Ewing was operating a 20-airgun (8,490 in\3\) in the
general area. The link between the stranding and the seismic surveys
was inconclusive and not based on any physical evidence (Hogarth, 2002;
Yoder, 2002). Nonetheless, the Gulf of California incident plus the
beaked whale strandings near naval exercises involving use of mid-
frequency sonar suggests a need for caution in conducting seismic
surveys in areas occupied by beaked whales until more is known about
effects of seismic surveys on those species (Hildebrand, 2005). No
injuries of beaked whales are anticipated during the proposed study
because of:
(1) The high likelihood that any beaked whales nearby would avoid
the approaching vessel before being exposed to high sound levels,
(2) differences between the sound sources operated by L-DEO and
those involved in the naval exercises associated with strandings.
Non-auditory Physiological Effects-- Non-auditory physiological
effects or injuries that theoretically might occur in marine mammals
exposed to strong underwater sound include stress, neurological
effects, bubble formation, resonance, and other types of organ or
tissue damage (Cox et al., 2006; Southall et al., 2007). Studies
examining such effects are limited. However, resonance effects (Gentry,
2002) and direct noise-induced bubble formations (Crum et al., 2005)
are implausible in the case of exposure to an impulsive broadband
source like an airgun array. If seismic surveys disrupt diving patterns
of deep-diving species, this might perhaps result in bubble formation
and a form of the bends, as speculated to occur in beaked whales
exposed to sonar. However, there is no specific evidence of this upon
exposure to airgun pulses.
In general, very little is known about the potential for seismic
survey sounds (or other types of strong underwater sounds) to cause
non-auditory physical effects in marine mammals. Such effects, if they
occur at all, would presumably be limited to short distances and to
activities that extend over a prolonged period. The available data do
not allow identification of a specific exposure level above which non-
auditory effects can be expected (Southall et al., 2007), or any
meaningful quantitative predictions of the numbers (if any) of marine
mammals that might be affected in those ways. Marine mammals that show
behavioral avoidance of seismic vessels, including most baleen whales
and some odontocetes, are especially unlikely to incur non-auditory
physical effects.
Potential Effects of Other Acoustic Devices
MBES
L-DEO will operate the Kongsberg EM 122 MBES from the source vessel
during the planned study. Sounds from the MBES are very short pulses,
occurring for two to 15 ms once every five to 20 s, depending on water
depth. Most of the energy in the sound pulses emitted by this MBES is
at frequencies near 12 kHz, and the maximum source level is 242 dB re:
1 [mu]Pa. The beam is narrow (1 to 2[deg]) in fore-aft extent and wide
(150[deg]) in the cross-track extent. Each ping consists of eight (in
water greater than 1,000 m deep) or four (less than 1,000 m deep)
successive fan-shaped transmissions (segments) at different cross-track
angles. Any given mammal at depth near the trackline would be in the
main beam for only one or two of the nine segments. Also, marine
mammals that encounter the Kongsberg EM 122 are unlikely to be
subjected to repeated pulses because of the narrow fore-aft width of
the beam and will receive only limited amounts of pulse energy because
of the short pulses. Animals close to the ship (where the beam is
narrowest) are especially unlikely to be ensonified for more than one
2-to-15 ms pulse (or two pulses if in the overlap area). Similarly,
Kremser et al. (2005) noted that the probability of a cetacean swimming
through the area of exposure when an MBES emits
[[Page 6440]]
a pulse is small. The animal would have to pass the transducer at close
range and be swimming at speeds similar to the vessel in order to
receive the multiple pulses that might result in sufficient exposure to
cause TTS.
Navy sonars that have been linked to avoidance reactions and
stranding of cetaceans: (1) Generally have longer pulse duration than
the Kongsberg EM 122; and (2) are often directed close to horizontally
versus more downward for the MBES. The area of possible influence of
the MBES is much smaller--a narrow band below the source vessel. Also,
the duration of exposure for a given marine mammal can be much longer
for naval sonar. During L-DEO's operations, the individual pulses will
be very short, and a given mammal would not receive many of the
downward-directed pulses as the vessel passes by. Possible effects of
an MBES on marine mammals are outlined below.
Masking--Marine mammal communications will not be masked
appreciably by the MBES signals given the low duty cycle of the
echosounder and the brief period when an individual mammal is likely to
be within its beam. Furthermore, in the case of baleen whales, the MBES
signals (12 kHz) do not overlap with the predominant frequencies in the
calls, which would avoid any significant masking.
Behavioral Responses--Behavioral reactions of free-ranging marine
mammals to sonars, echosounders, and other sound sources appear to vary
by species and circumstance. Observed reactions have included silencing
and dispersal by sperm whales (Watkins et al., 1985), increased
vocalizations and no dispersal by pilot whales (Globicephala melas)
(Rendell and Gordon, 1999), and the previously-mentioned beachings by
beaked whales. During exposure to a 21 to 25 kHz ``whale-finding''
sonar with a source level of 215 dB re: 1 [mu]Pa, gray whales reacted
by orienting slightly away from the source and being deflected from
their course by approximately 200 m (Frankel, 2005). When a 38-kHz
echosounder and a 150-kHz acoustic Doppler current profiler were
transmitting during studies in the Eastern Tropical Pacific, baleen
whales showed no significant responses, while spotted and spinner
dolphins were detected slightly more often and beaked whales less often
during visual surveys (Gerrodette and Pettis, 2005).
Captive bottlenose dolphins and a beluga whale exhibited changes in
behavior when exposed to 1-s tonal signals at frequencies similar to
those that will be emitted by the MBES used by L DEO, and to shorter
broadband pulsed signals. Behavioral changes typically involved what
appeared to be deliberate attempts to avoid the sound exposure
(Schlundt et al., 2000; Finneran et al., 2002; Finneran and Schlundt,
2004). The relevance of those data to free-ranging odontocetes is
uncertain, and in any case, the test sounds were quite different in
duration as compared with those from an MBES.
Hearing Impairment and Other Physical Effects--Given recent
stranding events that have been associated with the operation of naval
sonar, there is concern that mid-frequency sonar sounds can cause
serious impacts to marine mammals (see above). However, the MBES
proposed for use by L DEO is quite different than sonar used for navy
operations. Pulse duration of the MBES is very short relative to the
naval sonar. Also, at any given location, an individual marine mammal
would be in the beam of the MBES for much less time given the generally
downward orientation of the beam and its narrow fore-aft beamwidth;
navy sonar often uses near-horizontally-directed sound. Those factors
would all reduce the sound energy received from the MBES rather
drastically relative to that from naval sonar.
NMFS believes that the brief exposure of marine mammals to one
pulse, or small numbers of signals, from the MBES is not likely to
result in the harassment of marine mammals.
SBP
L-DEO will also operate a SBP from the source vessel during the
proposed survey. Sounds from the SBP are very short pulses, occurring
for one to four ms once every second. Most of the energy in the sound
pulses emitted by the SBP is at 3.5 kHz, and the beam is directed
downward. The sub-bottom profiler on the Langseth has a maximum source
level of 204 dB re: 1 [mu]Pa.
Kremser et al. (2005) noted that the probability of a cetacean
swimming through the area of exposure when a bottom profiler emits a
pulse is small--even for an SBP more powerful than that on the
Langseth--if the animal was in the area, it would have to pass the
transducer at close range and in order to be subjected to sound levels
that could cause TTS.
Masking--Marine mammal communications will not be masked
appreciably by the SBP signals given the directionality of the signal
and the brief period when an individual mammal is likely to be within
its beam. Furthermore, in the case of most baleen whales, the SBP
signals do not overlap with the predominant frequencies in the calls,
which would avoid significant masking.
Behavioral Responses--Marine mammal behavioral reactions to other
pulsed sound sources are discussed above, and responses to the SBP are
likely to be similar to those for other pulsed sources if received at
the same levels. However, the pulsed signals from the SBP are
considerably weaker than those from the MBES. Therefore, behavioral
responses are not expected unless marine mammals are very close to the
source.
Hearing Impairment and Other Physical Effects--It is unlikely that
the SBP produces pulse levels strong enough to cause hearing impairment
or other physical injuries even in an animal that is (briefly) in a
position near the source. The SBP is usually operated simultaneously
with other higher-power acoustic sources. Many marine mammals will move
away in response to the approaching higher-power sources or the vessel
itself before the mammals would be close enough for there to be any
possibility of effects from the less intense sounds from the SBP.
The potential effects to marine mammals described in this section
of the document do not take into consideration the proposed monitoring
and mitigation measures described later in this document (see the
``Proposed Mitigation'' and ``Proposed Monitoring and Reporting''
sections) which, as noted are designed to effect the least practicable
adverse impact on affected marine mammal species and stocks.
Anticipated Effects on Marine Mammal Habitat
The proposed seismic survey will not result in any permanent impact
on habitats used by the marine mammals in the proposed survey area,
including the food sources they use (i.e. fish and invertebrates), and
there will be no physical damage to any habitat. While it is
anticipated that the specified activity may result in marine mammals
avoiding certain areas due to temporary ensonification, this impact to
habitat is temporary and reversible and was considered in further
detail earlier in this document, as behavioral modification. The main
impact associated with the proposed activity will be temporarily
elevated noise levels and the associated direct effects on marine
mammals, previously discussed in this notice.
Anticipated Effects on Fish
One reason for the adoption of airguns as the standard energy
source for marine seismic surveys is that, unlike
[[Page 6441]]
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 L-DEO's
environmental analysis). There are three types of potential effects of
exposure to seismic surveys: (1) Pathological, (2) physiological, and
(3) behavioral. Pathological effects involve lethal and temporary or
permanent sub-lethal injury. Physiological effects involve temporary
and permanent primary and secondary stress responses, such as changes
in levels of enzymes and proteins. Behavioral effects refer to
temporary and (if they occur) permanent changes in exhibited behavior
(e.g., startle and avoidance behavior). The three categories are
interrelated in complex ways. For example, it is possible that certain
physiological and behavioral changes could potentially lead to an
ultimate pathological effect on individuals (i.e., mortality).
The specific received sound levels at which permanent adverse
effects to fish potentially could occur are little studied and largely
unknown. Furthermore, the available information on the impacts of
seismic surveys on marine fish is from studies of individuals or
portions of a population; there have been no studies at the population
scale. The studies of individual fish have often been on caged fish
that were exposed to airgun pulses in situations not representative of
an actual seismic survey. Thus, available information provides limited
insight on possible real-world effects at the ocean or population
scale.
Hastings and Popper (2005), Popper (2009), and Popper and Hastings
(2009a,b) provided recent critical reviews of the known effects of
sound on fish. The following sections provide a general synopsis of the
available information on the effects of exposure to seismic and other
anthropogenic sound as relevant to fish. The information comprises
results from scientific studies of varying degrees of rigor plus some
anecdotal information. Some of the data sources may have serious
shortcomings in methods, analysis, interpretation, and reproducibility
that must be considered when interpreting their results (see Hastings
and Popper, 2005). Potential adverse effects of the program's sound
sources on marine fish are then noted.
Pathological Effects--The potential for pathological damage to
hearing structures in fish depends on the energy level of the received
sound and the physiology and hearing capability of the species in
question (see Appendix D L-DEO's environmental analysis). For a given
sound to result in hearing loss, the sound must exceed, by some
substantial amount, the hearing threshold of the fish for that sound
(Popper, 2005). The consequences of temporary or permanent hearing loss
in individual fish on a fish population are unknown; however, they
likely depend on the number of individuals affected and whether
critical behaviors involving sound (e.g., predator avoidance, prey
capture, orientation and navigation, reproduction, etc.) are adversely
affected.
Little is known about the mechanisms and characteristics of damage
to fish that may be inflicted by exposure to seismic survey sounds. Few
data have been presented in the peer-reviewed scientific literature. As
far as we know, there are only two papers with proper experimental
methods, controls, and careful pathological investigation implicating
sounds produced by actual seismic survey airguns in causing adverse
anatomical effects. One such study indicated anatomical damage, and the
second indicated TTS in fish hearing. The anatomical case is McCauley
et al. (2003), who found that exposure to airgun sound caused
observable anatomical damage to the auditory maculae of pink snapper
(Pagrus auratus). This damage in the ears had not been repaired in fish
sacrificed and examined almost two months after exposure. On the other
hand, Popper et al. (2005) documented only TTS (as determined by
auditory brainstem response) in two of three fish species from the
Mackenzie River Delta. This study found that broad whitefish (Coregonus
nasus) that exposed to five airgun shots were not significantly
different from those of controls. During both studies, the repetitive
exposure to sound was greater than would have occurred during a typical
seismic survey. However, the substantial low-frequency energy produced
by the airguns [less than 400 Hz in the study by McCauley et al. (2003)
and less than approximately 200 Hz in Popper et al. (2005)] likely did
not propagate to the fish because the water in the study areas was very
shallow (approximately 9 m in the former case and less than two m in
the latter). Water depth sets a lower limit on the lowest sound
frequency that will propagate (the ``cutoff frequency'') at about one-
quarter wavelength (Urick, 1983; Rogers and Cox, 1988).
Wardle et al. (2001) suggested that in water, acute injury and
death of organisms exposed to seismic energy depends primarily on two
features of the sound source: (1) The received peak pressure and (2)
the time required for the pressure to rise and decay. Generally, as
received pressure increases, the period for the pressure to rise and
decay decreases, and the chance of acute pathological effects
increases. According to Buchanan et al. (2004), for the types of
seismic airguns and arrays involved with the proposed program, the
pathological (mortality) zone for fish would be expected to be within a
few meters of the seismic source. Numerous other studies provide
examples of no fish mortality upon exposure to seismic sources (Falk
and Lawrence, 1973; Holliday et al., 1987; La Bella et al., 1996;
Santulli et al., 1999; McCauley et al., 2000a,b, 2003; Bjarti, 2002;
Thomsen, 2002; Hassel et al., 2003; Popper et al., 2005; Boeger et al.,
2006).
Some studies have reported, some equivocally, that mortality of
fish, fish eggs, or larvae can occur close to seismic sources
(Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman et al., 1996;
Dalen et al., 1996). Some of the reports claimed seismic effects from
treatments quite different from actual seismic survey sounds or even
reasonable surrogates. However, Payne et al. (2009) reported no
statistical differences in mortality/morbidity between control and
exposed groups of capelin eggs or monkfish larvae. Saetre and Ona
(1996) applied a `worst-case scenario' mathematical model to
investigate the effects of seismic energy on fish eggs and larvae. They
concluded that mortality rates caused by exposure to seismic surveys
are so low, as compared to natural mortality rates, that the impact of
seismic surveying on recruitment to a fish stock must be regarded as
insignificant.
Physiological Effects--Physiological effects refer to cellular and/
or biochemical responses of fish to acoustic stress. Such stress
potentially could affect fish populations by increasing mortality or
reducing reproductive success. Primary and secondary stress responses
of fish after exposure to seismic survey sound appear to be temporary
in all studies done to date (Sverdrup et al., 1994; Santulli et al.,
1999; McCauley et al., 2000a,b). The periods necessary for the
biochemical changes to return to normal are variable and depend on
numerous aspects of the biology of the species and of the sound
stimulus (see Appendix D of L-DEO's environmental analysis).
Behavioral Effects--Behavioral effects include changes in the
distribution, migration, mating, and catchability of fish populations.
Studies investigating the possible effects of sound (including seismic
survey sound) on fish behavior have been conducted on both uncaged and
caged individuals (e.g., Chapman and Hawkins, 1969; Pearson et al.,
1992;
[[Page 6442]]
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; Lokkeborg, 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 effects of
airguns on fish, particularly under realistic at-sea conditions.
Anticipated Effects on Invertebrates
The existing body of information on the impacts of seismic survey
sound on marine invertebrates is very limited. However, there is some
unpublished and very limited evidence of the potential for adverse
effects on invertebrates, thereby justifying further discussion and
analysis of this issue. The three types of potential effects of
exposure to seismic surveys on marine invertebrates are pathological,
physiological, and behavioral. Based on the physical structure of their
sensory organs, marine invertebrates appear to be specialized to
respond to particle displacement components of an impinging sound field
and not to the pressure component (Popper et al., 2001; see also
Appendix E of L-DEO's environmental analysis).
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 L-DEO's
environmental analysis.
Pathological Effects--In water, lethal and sub-lethal injury to
organisms exposed to seismic survey sound appears to depend on at least
two features of the sound source: (1) The received peak pressure; and
(2) the time required for the pressure to rise and decay. Generally, as
received pressure increases, the period for the pressure to rise and
decay decreases, and the chance of acute pathological effects
increases. For the type of airgun array planned for the proposed
program, the pathological (mortality) zone for crustaceans and
cephalopods is expected to be within a few meters of the seismic
source, at most; however, very few specific data are available on
levels of seismic signals that might damage these animals. This premise
is based on the peak pressure and rise/decay time characteristics of
seismic airgun arrays currently in use around the world.
Some studies have suggested that seismic survey sound has a limited
pathological impact on early developmental stages of crustaceans
(Pearson et al., 1994; Christian et al., 2003; DFO, 2004). However, the
impacts appear to be either temporary or insignificant compared to what
occurs under natural conditions. Controlled field experiments on adult
crustaceans (Christian et al., 2003, 2004; DFO, 2004) and adult
cephalopods (McCauley et al., 2000a,b) exposed to seismic survey sound
have not resulted in any significant pathological impacts on the
animals. It has been suggested that exposure to commercial seismic
survey activities has injured giant squid (Guerra et al., 2004), but
the article provides little evidence to support this claim.
Physiological Effects--Physiological effects refer mainly to
biochemical responses by marine invertebrates to acoustic stress. Such
stress potentially could affect invertebrate populations by increasing
mortality or reducing reproductive success. Primary and secondary
stress responses (i.e., changes in haemolymph levels of enzymes,
proteins, etc.) of crustaceans have been noted several days or months
after exposure to seismic survey sounds (Payne et al., 2007). The
periods necessary for these biochemical changes to return to normal are
variable and depend on numerous aspects of the biology of the species
and of the sound stimulus.
Behavioral Effects--There is increasing interest in assessing the
possible direct and indirect effects of seismic and other sounds on
invertebrate behavior, particularly in relation to the consequences for
fisheries. Changes in behavior could potentially affect such aspects as
reproductive success, distribution, susceptibility to predation, and
catchability by fisheries. Studies investigating the possible
behavioral effects of exposure to seismic survey sound on crustaceans
and cephalopods have been conducted on both uncaged and caged animals.
In some cases, invertebrates exhibited startle responses (e.g., squid
in McCauley et al., 2000a,b). In other cases, no behavioral impacts
were noted (e.g., crustaceans in Christian et al., 2003, 2004; DFO
2004). There have been anecdotal reports of reduced catch rates of
shrimp shortly after exposure to seismic surveys; however, other
studies have not observed any significant changes in shrimp catch rate
(Andriguetto-Filho et al., 2005). Similarly, Parry and Gason (2006) did
not find any evidence that lobster catch rates were affected by seismic
surveys. Any adverse effects on crustacean and cephalopod behavior or
fisheries attributable to seismic survey sound depend on the species in
question and the nature of the fishery (season, duration, fishing
method).
Proposed Mitigation
In order to issue an incidental take authorization (ITA) under
Section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible
methods of taking pursuant to such activity, and other means of
effecting the least practicable adverse impact on such species or stock
and its habitat, paying particular attention to rookeries, mating
[[Page 6443]]
grounds, and areas of similar significance, and the availability of
such species or stock for taking for certain subsistence uses.
L-DEO has based the mitigation measures described herein, to be
implemented for the proposed seismic survey, on the following:
(1) Protocols used during previous L-DEO seismic research cruises
as approved by NMFS;
(2) previous IHA applications and IHAs approved and authorized by
NMFS; and
(3) recommended best practices in Richardson et al. (1995), Pierson
et al. (1998), and Weir and Dolman (2007).
To reduce the potential for disturbance from acoustic stimuli
associated with the activities, L-DEO and/or its designees has proposed
to implement the following mitigation measures for marine mammals:
(1) Proposed exclusion zones;
(2) power-down procedures;
(3) shutdown procedures; and
(4) ramp-up procedures.
Proposed Exclusion Zones-L-DEO uses safety radii to designate
exclusion zones and to estimate take (described in greater detail in
Section IV and Appendix A of L-DEO's environmental analysis) for marine
mammals. Table 1 shows the distances at which two sound levels (160-
and 180-dB) are expected to be received from the 18-airgun subarray and
a single airgun. The 180-dB level shut-down criterion is applicable to
cetaceans, as specified by NMFS (2000); and L-DEO used these levels to
establish the EZs. If the protected species visual observer (PSVO)
detects marine mammal(s) within or about to enter the appropriate EZ,
the Langseth crew will immediately power down the airgun subarrays, or
perform a shut down if necessary (see Shut-down Procedures).
Power-down Procedures-A power-down involves decreasing the number
of airguns in use such that the radius of the 180-dB zone is decreased
to the extent that marine mammals are no longer in or about to enter
the EZ. A power down of the airgun subarray can also occur when the
vessel is moving from one seismic line to another. During a power-down
for mitigation, L-DEO will operate one airgun. The continued operation
of one airgun is intended to alert marine mammals to the presence of
the seismic vessel in the area. In contrast, a shut down occurs when
the Langseth suspends all airgun activity.
If the PSVO detects a marine mammal outside the EZ, but it is
likely to enter the EZ, L-DEO will power down the airguns before the
animal is within the EZ. Likewise, if a mammal is already within the
EZ, when first detected L-DEO will power down the airguns immediately.
During a power down of the airgun array, L-DEO will also operate the
40-in\3\ airgun. If a marine mammal is detected within or near the
smaller EZ around that single airgun (Table 1), L-DEO will shut down
the airgun (see next section).
Following a power-down, L-DEO will not resume airgun activity until
the marine mammal has cleared the safety zone. L-DEO will consider the
animal to have cleared the EZ if
a PSVO has visually observed the animal leave the EZ, or
a PSVO has not sighted the animal within the EZ for 15 min
for small odontocetes, or 30 min for mysticetes and large odontocetes,
including sperm, pygmy sperm, dwarf sperm, and beaked whales.
During airgun operations following a power-down (or shut-down)
whose duration has exceeded the time limits specified previously, L-DEO
will ramp-up the airgun array gradually (see Shut-down Procedures).
Shut-down Procedures--L-DEO will shut down the operating airgun(s)
if a marine mammal is seen within or approaching the EZ for the single
airgun. L-DEO will implement a shut-down:
(1) if an animal enters the EZ of the single airgun after L-DEO has
initiated a power down, or
(2) if an animal is initially seen within the EZ of the single
airgun when more than one airgun (typically the full airgun array) is
operating.
L-DEO will not resume airgun activity until the marine mammal has
cleared the EZ, or until the PSVO is confident that the animal has left
the vicinity of the vessel. Criteria for judging that the animal has
cleared the EZ will be as described in the preceding section.
Ramp-up Procedures--L-DEO will follow a ramp-up procedure when the
airgun subarrays begin operating after a specified period without
airgun operations or when a power down has exceeded that period. L-DEO
proposes that, for the present cruise, this period would be
approximately eight min. This period is based on the 180-dB radius for
the 18-airgun subarray towed at a depth of seven m (23 ft) in relation
to the minimum planned speed of the Langseth while shooting (8.5 km/h;
5.3 mph; 4.6 kts). L-DEO has used similar periods (8-10 min) during
previous L-DEO surveys.
Ramp-up will begin with the smallest airgun in the array (40-
in\3\). Airguns will be added in a sequence such that the source level
of the array will increase in steps not exceeding six dB per five-
minute period over a total duration of approximately 30 min. During
ramp-up, the PSVOs will monitor the EZ, and if marine mammals are
sighted, L-DEO will implement a power down or shut down as though the
full airgun array were operational.
If the complete EZ has not been visible for at least 30 min prior
to the start of operations in either daylight or nighttime, L-DEO will
not commence the ramp-up unless at least one airgun (40-in\3\ or
similar) has been operating during the interruption of seismic survey
operations. Given these provisions, it is likely that the airgun array
will not be ramped up from a complete shut down at night or in thick
fog, because the outer part of the safety zone for that array will not
be visible during those conditions. If one airgun has operated during a
power-down period, ramp-up to full power will be permissible at night
or in poor visibility, on the assumption that marine mammals will be
alerted to the approaching seismic vessel by the sounds from the single
airgun and could move away. L-DEO will not initiate a ramp-up of the
airguns if a marine mammal is sighted within or near the applicable EZs
during the day or close to the vessel at night.
NMFS has carefully evaluated the applicant's proposed mitigation
measures and has considered a range of other measures in the context of
ensuring that NMFS prescribes the means of effecting the least
practicable adverse impact on the affected marine mammal species and
stocks and their habitat. Our evaluation of potential measures included
consideration of the following factors in relation to one another: (1)
The manner in which, and the degree to which, the successful
implementation of the measure is expected to minimize adverse impacts
to marine mammals; (2) the proven or likely efficacy of the specific
measure to minimize adverse impacts as planned; and (3) the
practicability of the measure for applicant implementation.
Based on our evaluation of the applicant's proposed measures, as
well as other measures considered by NMFS or recommended by the public,
NMFS has preliminarily determined that the proposed mitigation measures
provide the means of effecting the least practicable adverse impacts on
marine mammals species or stocks and their habitat, paying particular
attention to rookeries, mating grounds, and areas of similar
significance.
[[Page 6444]]
Proposed Monitoring and Reporting
In order to issue an ITA for an activity, section 101(a)(5)(D) of
the MMPA states that NMFS must set forth ``requirements pertaining to
the monitoring and reporting of such taking.'' The MMPA implementing
regulations at 50 CFR 216.104(a)(13) indicate that requests for IHAs
must include the suggested means of accomplishing the necessary
monitoring and reporting that will result in increased knowledge of the
species and of the level of taking or impacts on populations of marine
mammals that are expected to be present in the action area.
Monitoring
L-DEO proposes to sponsor marine mammal monitoring during the
present project, in order to implement the proposed mitigation measures
that require real-time monitoring, and to satisfy the anticipated
monitoring requirements of the IHA. L-DEO's proposed Monitoring Plan is
described below this section. L-DEO understands that this monitoring
plan will be subject to review by NMFS, and that refinements may be
required. The monitoring work described here has been planned as a
self-contained project independent of any other related monitoring
projects that may be occurring simultaneously in the same regions. L-
DEO is prepared to discuss coordination of its monitoring program with
any related work that might be done by other groups insofar as this is
practical and desirable.
Vessel-based Visual Monitoring
PSVOs will be based aboard the seismic source vessel and will watch
for marine mammals near the vessel during daytime airgun operations and
during any start-ups at night. PSVOs will also watch for marine mammals
near the seismic vessel for at least 30 min prior to the start of
airgun operations after an extended shut down.
PSVOs will conduct observations during daytime periods when the
seismic system is not operating for comparison of sighting rates and
behavior with and without airgun operations and between acquisition
periods. Based on PSVO observations, the airguns will be powered down
or shut down when marine mammals are observed within or about to enter
a designated EZ. The EZ is a region in which a possibility exists of
adverse effects on animal hearing or other physical effects.
During seismic operations off Costa Rica, at least three PSVOs will
be based aboard the Langseth. L-DEO will appoint the PSVOs with NMFS'
concurrence. During all daytime periods, two PSVOs will be on duty from
the observation tower to monitor and PSVOs will be on duty in shifts of
duration no longer than four hours.
During mealtimes it is sometimes difficult to have two PSVOs on
effort, but at least one PSVO will be on watch during bathroom breaks
and mealtimes. Use of two simultaneous observers increases the
effectiveness of detecting animals near the source vessel. However,
during meal times, only one PSVO may be on duty.
Two PSVOs will also be on visual watch during all nighttime start-
ups of the seismic airguns. A third PSVO will monitor the PAM equipment
24 hours a day to detect vocalizing marine mammals present in the
action area. In summary, a typical daytime cruise would have scheduled
two PSVOs on duty from the observation tower, and a third PSVO on PAM.
L-DEO will also instruct other crew to assist in detecting marine
mammals and implementing mitigation requirements (if practical). Before
the start of the seismic survey, L-DEO will give the crew additional
instruction regarding how to accomplish this task.
The Langseth is a suitable platform for marine mammal observations.
When stationed on the observation platform, the eye level will be
approximately 21.5 m (70.5 ft) above sea level, and the observer will
have a good view around the entire vessel. During daytime, the PSVOs
will scan the area around the vessel systematically with reticle
binoculars (e.g., 7 x 50 Fujinon), Big-eye binoculars (25 x 150), and
with the naked eye. During darkness, night vision devices (NVDs) will
be available (ITT F500 Series Generation 3 binocular-image intensifier
or equivalent), when required. Laser range-finding binoculars (Leica
LRF 1200 laser rangefinder or equivalent) will be available to assist
with distance estimation. Those are useful in training observers to
estimate distances visually, but are generally not useful in measuring
distances to animals directly; that is done primarily with the reticles
in the binoculars.
Passive Acoustic Monitoring
Passive Acoustic Monitoring (PAM) will complement the visual
monitoring program, when practicable. Visual monitoring typically is
not effective during periods of poor visibility or at night, and even
with good visibility, is unable to detect marine mammals when they are
below the surface or beyond visual range.
Besides the three PSVOs, an additional acoustic Protected Species
Observer (PSO) with primary responsibility for PAM will also be aboard
the vessel. L-DEO can use acoustical monitoring in addition to visual
observations to improve detection, identification, and localization of
cetaceans. The acoustic monitoring will serve to alert visual observers
(if on duty) when vocalizing cetaceans are detected. It is only useful
when marine mammals call, but it can be effective either by day or by
night, and does not depend on good visibility. It will be monitored in
real time so that the visual observers can be advised when cetaceans
are detected. When bearings (primary and mirror-image) to calling
cetacean(s) are determined, the bearings will be relayed to the visual
observer to help him/her sight the calling animal(s).
The PAM system consists of hardware (i.e., hydrophones) and
software. The ``wet end'' of the system consists of a towed hydrophone
array that is connected to the vessel by a cable. The lead in from the
hydrophone array is approximately 400 m (1,312 ft) long, the active
section of the array is approximately 56 m (184 ft) long, and the
hydrophone array is typically towed at depths of less than 20 m (66
ft).
The deck cable is connected from the array to a computer in the
laboratory where signal conditioning and processing takes place. The
digitized signal is then sent to the main laboratory, where the
acoustic PSO monitors the system.
Ideally, the acoustic PSO will monitor the towed hydrophones 24 h
per day during airgun operations and during most periods when the
Langseth is underway while the airguns are not operating. However, PAM
may not be possible if damage occurs to both the primary and back-up
hydrophone the arrays during operations. The primary PAM streamer on
the Langseth is a digital hydrophone streamer. Should the digital
streamer fail, back-up systems should include an analog spare streamer
and a hull-mounted hydrophone. Every effort would be made to have a
working PAM system during the cruise. In the unlikely event that all
three of these systems were to fail, L-DEO would continue science
acquisition with the visual-based observer program. The PAM system is a
supplementary enhancement to the visual monitoring program. If weather
conditions were to prevent the use of PAM then conditions would also
likely prevent the use of the airgun array.
One acoustic PSO will monitor the acoustic detection system at any
one
[[Page 6445]]
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. Acoustic PSOs monitoring the
acoustical data will be on shift for one to six hours at a time.
Besides the PSVO, an additional acoustic PSO with primary
responsibility for PAM will also be aboard the source vessel. All PSVOs
are expected to rotate through the PAM position, although the most
experienced with acoustics will be on PAM duty more frequently.
When a vocalization is detected while visual observations are in
progress, the acoustic PSO will contact the visual PSVO immediately, to
alert him/her to the presence of cetaceans (if they have not already
been seen), and to allow a power down or shut down to be initiated, if
required. The information regarding the call will be entered into a
database. Data entry will include an acoustic encounter identification
number, whether it was linked with a visual sighting, date, time when
first and last heard and whenever any additional information was
recorded, position and water depth when first detected, bearing if
determinable, species or species group (e.g., unidentified dolphin,
sperm whale), types and nature of sounds heard (e.g., clicks,
continuous, sporadic, whistles, creaks, burst pulses, strength of
signal, etc.), and any other notable information. The acoustic
detection can also be recorded for further analysis.
PSVO Data and Documentation
PSVOs will record data to estimate the numbers of marine mammals
exposed to various received sound levels and to document apparent
disturbance reactions or lack thereof. Data will be used to estimate
numbers of animals potentially `taken' by harassment (as defined in the
MMPA). They will also provide information needed to order a power down
or shut down of the airguns when a marine mammal is within or near the
EZ.
When a sighting is made, the following information about the
sighting will be recorded:
1. Species, group size, age/size/sex categories (if determinable),
behavior when first sighted and after initial sighting, heading (if
consistent), bearing and distance from seismic vessel, sighting cue,
apparent reaction to the airguns or vessel (e.g., none, avoidance,
approach, paralleling, etc.), and behavioral pace.
2. Time, location, heading, speed, activity of the vessel, sea
state, visibility, and sun glare.
The data listed under (2) will also be recorded at the start and
end of each observation watch, and during a watch whenever there is a
change in one or more of the variables.
All observations and power downs or shut downs will be recorded in
a standardized format. Data will be entered into an electronic
database. The accuracy of the data entry will be verified by
computerized data validity checks as the data are entered and by
subsequent manual checking of the database. These procedures will allow
initial summaries of data to be prepared during and shortly after the
field program, and will facilitate transfer of the data to statistical,
graphical, and other programs for further processing and archiving.
Results from the vessel-based observations will provide:
1. The basis for real-time mitigation (airgun power down or shut
down).
2. Information needed to estimate the number of marine mammals
potentially taken by harassment, which must be reported to NMFS.
3. Data on the occurrence, distribution, and activities of marine
mammals and turtles in the area where the seismic study is conducted.
4. Information to compare the distance and distribution of marine
mammals and turtles relative to the source vessel at times with and
without seismic activity.
5. Data on the behavior and movement patterns of marine mammals
seen at times with and without seismic activity.
L-DEO will submit a report to NMFS and NSF within 90 days after the
end of the cruise. The report will describe the operations that were
conducted and sightings of marine mammals and turtles near the
operations. The report will provide full documentation of methods,
results, and interpretation pertaining to all monitoring. The 90-day
report will summarize the dates and locations of seismic operations,
and all marine mammal sightings (dates, times, locations, activities,
associated seismic survey activities). The report will also include
estimates of the number and nature of exposures that could result in
``takes'' of marine mammals by harassment or in other ways.
L-DEO will report all injured or dead marine mammals (regardless of
cause) to NMFS as soon as practicable. The report should include the
species or description of the animal, the condition of the animal,
location, time first found, observed behaviors (if alive) and photo or
video, if available.
Estimated Take by Incidental Harassment
Except with respect to certain activities not pertinent here, the
MMPA defines ``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
Only take by Level B harassment is anticipated and authorized as a
result of the proposed marine geophysical survey off Costa Rica.
Acoustic stimuli (i.e., increased underwater sound) generated during
the operation of the seismic airgun array, may have the potential to
cause marine mammals in the survey area to be exposed to sounds at or
greater than 160 decibels (dB) or cause temporary, short-term changes
in behavior. There is no evidence that the planned activities could
result in injury, serious injury or mortality within the specified
geographic area for which L-DEO seeks the IHA. The required mitigation
and monitoring measures will minimize any potential risk for injury or
mortality.
The following sections describe L-DEO's methods to estimate take by
incidental harassment and present the applicant's estimates of the
numbers of marine mammals that could be affected during the proposed
geophysical survey. The estimates are based on a consideration of the
number of marine mammals that could be disturbed appreciably by
operations with the 18-airgun subarray to be used during approximately
2,145 km (1,333 mi) of survey lines with an additional 365 km (227 mi)
of turns.
L-DEO assumes that, during simultaneous operations of the airgun
array and the other sources, any marine mammals close enough to be
affected by the MBES and SBP would already be affected by the airguns.
However, whether or not the airguns are operating simultaneously with
the other sources, marine mammals are expected to exhibit no more than
short-term and inconsequential responses to the MBES and SBP given
their characteristics (e.g., narrow downward-directed beam) and other
considerations described previously. Such reactions are not considered
to constitute ``taking'' (NMFS, 2001). Therefore, L-DEO provides no
additional allowance for animals that could be affected by sound
sources other than airguns.
[[Page 6446]]
Density data on the marine mammal species in the proposed survey
area are available from extensive ship-based surveys for marine mammals
in the ETP conducted by NMFS' Southwest Fisheries Science Center
(SWFSC). L-DEO used densities from two sources: (1) The SWFSC's habitat
models that predict density for 15 cetacean species in the ETP; and (2)
densities from the surveys conducted during summer and fall 1986-1996,
as summarized by Ferguson and Barlow (2001, 2003) for species sighted
in SWFSC surveys whose sample sizes were too small to model density.
For the predictive models, the SWFSC developed habitat modeling as
a method to estimate cetacean densities on a finer spatial scale
compared to traditional line-transect analyses by using a continuous
function of habitat variables, e.g., sea surface temperature, depth,
distance from shore, and prey density (Barlow et al. 2009). The SWFSC
incorporated the models into a web-based Geographic Information System
(GIS) developed by Duke University's Department of Defense Strategic
Environmental Research and Development Program (SERDP) team and L-DEO
used the GIS to obtain mean and maximum densities for 11 cetacean
species in the model in the proposed survey area.
For the second source, L-DEO used the densities calculated from
Ferguson and Barlow (2003) for 5[deg] x 5[deg] blocks that include the
proposed survey area (Block 138) and blocks adjacent to 138 that
include coastal waters: Blocks 119, 137, 138, 139, 158, and 159. Those
blocks included 18,385 km (11,423 mi) of survey effort in Beaufort sea
states 0-5, and 3,899 square kilometers (km\2\) (1,505 square miles
(mi\2\)) of survey effort in Beaufort sea states 0-2. L-DEO also
obtained densities for an additional seven species that were sighted in
one or more of those blocks.
For two endangered species for which there are only unconfirmed
sightings in the region, the sei and fin whales, L-DEO assigned low
density values (equal to the density of the species with the lowest
calculated density). The false killer whale has been sighted near the
survey area but not in the seven blocks of Ferguson and Barlow (2003),
so it was also assigned the same low density value.
Oceanographic conditions, including occasional El Ni[ntilde]o and
La Ni[ntilde]a events, influence the distribution and numbers of marine
mammals present in the ETP, resulting in considerable year-to-year
variation in the distribution and abundance of many marine mammal
species (e.g., Escorza-Trevi[ntilde]o, 2009). Thus, for some species
the densities derived from recent surveys may not be representative of
the densities that will be encountered during the proposed seismic
survey. Table 2 includes L-DEO's estimates of the ``best'' and
``maximum'' densities of marine mammals in the ETP near the proposed
survey area. For the modeled species, best estimates and maximum
estimates of density in the survey area are the mean and maximum
densities given in Read et al. (2009). For the other species, best
estimates of density are the effort-weighted mean densities in the
seven 5[deg] x 5[deg] blocks from Ferguson and Barlow (2001, 2003), and
maximum estimates of density are the highest densities in any of the
blocks.
L-DEO's estimates of exposures to various sound levels assume that
the proposed surveys will be completed. As is typical during offshore
ship surveys, inclement weather and equipment malfunctions are likely
to cause delays and may limit the number of useful line-kilometers of
seismic operations that can be undertaken. L-DEO has included an
additional 25% of line transects to account for mission uncertainty and
follow a precautionary approach. Furthermore, any marine mammal
sightings within or near the designated exclusion zones will result in
the power down or shut down of seismic operations as a mitigation
measure. Thus, the following estimates of the numbers of marine mammals
potentially exposed to sound levels of 160 dB re: 1 [micro]Pa are
precautionary and probably overestimate the actual numbers of marine
mammals that might be involved. These estimates also assume that there
will be no weather, equipment, or mitigation delays, which is highly
unlikely.
L-DEO estimated the number of different individuals that may be
exposed to airgun sounds with received levels greater than or equal to
160 dB re: 1 [micro]Pa on one or more occasions by considering the
total marine area that would be within the 160-dB radius around the
operating airgun array on at least one occasion and the expected
density of marine mammals. 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 parallel and in close proximity;
thus individuals could be exposed on two or more occasions. The area
including overlap is 31.9 times the area excluding overlap. Thus a
marine mammal that stayed in the survey area during the entire survey
could be exposed 32 times (14 times), on average. Given the pattern of
the seismic lines, the interval between exposures of a stationary
animal would be approximately 18 hr. Moreover, it is unlikely that a
particular animal would stay in the area during the entire survey. The
number of different individuals potentially exposed to received levels
greater than or equal to 160 re: 1 [micro]Pa was calculated by
multiplying:
(1) The expected species density, either ``mean'' (i.e., best
estimate) or ``maximum'', times
(2) the anticipated area to be ensonified to that level during
airgun operations excluding overlap, which is approximately 3,225 km\2\
(2,003 mi\2\).
The area expected to be ensonified was determined by entering the
planned survey lines into a MapInfo GIS, using the GIS to identify the
relevant areas by ``drawing'' the applicable 160-dB buffer (see Table
1) around each seismic line, and then calculating the total area within
the buffers. Areas of overlap were included only once when estimating
the number of individuals exposed. Applying this approach,
approximately 3,225 km\2\ (1,245 mi\2\) would be within the 160-dB
isopleth on one or more occasions during the survey. Because this
approach does not allow for turnover in the mammal populations in the
study area during the course of the survey, the actual number of
individuals exposed could be underestimated. However, the approach
assumes that no cetaceans will move away from or toward the trackline
as the Langseth approaches in response to increasing sound levels prior
to the time the levels reach 160 dB, which will result in overestimates
for those species known to avoid seismic vessels.
Table 3 shows the best and maximum estimates of the number
individual cetaceans that potentially could be exposed to greater than
or equal to 160 dB re: 1 [mu]Pa during the seismic survey if no animals
moved away from the survey vessel. The requested take authorization,
given in the far right column of Table 3, 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 total `maximum estimate' of the number of individual cetaceans
that could be exposed to seismic sounds with received levels greater
than or equal to 160 dB re: 1 [mu]Pa during the proposed survey is
7,078 (see Table 3 below this section). That total includes 38 baleen
whales, four of which are endangered: 18 humpback whales or 1.2
[[Page 6447]]
percent of the regional population; one sei whale, one fin whale (less
than 0.01 percent); and eight blue whales (0.6 percent). In addition,
40 sperm whales (also listed as endangered under the ESA) or 0.15
percent of the regional population could be exposed during the survey,
and 19 beaked whales. Most (97 percent) of the cetaceans that could be
potentially exposed are delphinids (e.g., short-beaked common, striped,
pantropical spotted, striped and spinner dolphins) with maximum
estimates ranging from two to 3,077 exposed to levels greater than or
equal to 160 dB re: 1 [mu]Pa.
Table 3--Estimates of the Possible Numbers of Marine Mammals Exposed to Different Sound Levels During L-DEO's
Proposed Seismic Survey in the ETP During April-May, 2011.
----------------------------------------------------------------------------------------------------------------
Estimated number Estimated number
of individuals of individuals Approximate
exposed to sound exposed to sound Requested take percent of
Species levels >= 160 dB levels >= 160 dB authorization regional
re: 1 [mu]Pa re: 1 [mu]Pa population \2\
(Best \1\) (Maximum \1\) (Max)
----------------------------------------------------------------------------------------------------------------
Humpback whale.......................... 1 18 18 1.29
Bryde's whale........................... 4 10 10 0.08
Sei whale............................... 0 0 \3\ 1 NA
Fin whale............................... 0 0 \3\ 1 0.04
Blue whale.............................. 1 8 8 0.57
Sperm whale............................. 17 40 40 0.15
Pygmy/Dwarf sperm whale................. 0 0 0 0.00
Cuvier's beaked whale................... 10 15 15 0.08
Mesoplodon spp.......................... 1 4 4 0.01
Rough-toothed dolphin................... 17 45 45 0.04
Bottlenose dolphin...................... 69 366 366 0.11
Pantropical spotted dolphin............. 310 954 954 0.06
Spinner dolphin......................... 236 1,468 1468 0.08
Striped dolphin......................... 273 622 622 0.06
Short-beaked common dolphin............. 447 3,077 3077 0.10
Risso's dolphin......................... 51 91 91 0.08
Melon-headed whale...................... 45 233 \3\ 258 0.57
Pygmy killer whale...................... 5 9 \3\ 30 0.08
False killer whale...................... 0 0 0 0.00
Killer whale............................ 1 2 \3\ 5 0.06
Short-finned pilot whale................ 48 114 114 0.02
----------------------------------------------------------------------------------------------------------------
\1\ Best and maximum estimates are based on densities from Table 3 and ensonified areas (including 25%
contingency) of 4030.63 for 160 dB and 1605.71 km\2\ for 170 dB (identified in parentheses). Takes are not
anticipated for the minke whale and Fraser's dolphin.
\2\ Regional population size estimates are from Table 2; NA means not available.
\3\ Requested Take Authorization increased to mean group size in the ETP for baleen whales (Jackson et al. 2008)
and delphinids (Ferguson et al. 2006).
Negligible Impact and Small Numbers Analysis and Determination
NMFS has defined ``negligible impact'' in 50 CFR 216.103 as ``* * *
an impact resulting from the specified activity that cannot be
reasonably expected to, and is not reasonably likely to, adversely
affect the species or stock through effects on annual rates of
recruitment or survival.''
In making a negligible impact determination, NMFS considers:
(1) The number of anticipated mortalities;
(2) the number and nature of anticipated injuries;
(3) the number, nature, and intensity, and duration of Level B
harassment; and
(4) the context in which the takes occur.
As mentioned previously, NMFS estimates that 19 species of marine
mammals could be potentially affected by Level B harassment over the
course of the IHA. For each species, these numbers are small (each,
less than two percent) relative to the population size.
No injuries, serious injuries or mortalities are anticipated to
occur as a result of the L-DEO's planned marine geophysical survey, and
none are authorized. Only short-term behavioral disturbance is
anticipated to occur due to the brief and sporadic duration of the
survey activities. No mortality or injury is expected to occur, and due
to the nature, degree, and context of behavioral harassment
anticipated, the activity is not expected to impact rates of
recruitment or survival.
NMFS has preliminarily determined, provided that the aforementioned
mitigation and monitoring measures are implemented, that the impact of
conducting a marine geophysical survey in the ETP off Costa Rica, April
through May, 2011, may result, at worst, in a temporary modification in
behavior and/or low-level physiological effects (Level B harassment) of
small numbers of certain species of marine mammals.
While behavioral modifications, including temporarily vacating the
area during the operation of the airgun(s), may be made by these
species to avoid the resultant acoustic disturbance, the availability
of alternate areas within these areas and the short and sporadic
duration of the research activities, have led NMFS to preliminary
determine that this action will have a negligible impact on the species
in the specified geographic region.
Based on the analysis contained herein of the likely effects of the
specified activity on marine mammals and their habitat, and taking into
consideration the implementation of the mitigation and monitoring
measures, NMFS preliminarily finds that L-DEO's planned research
activities, will result in the incidental take of small numbers of
marine mammals, by Level B harassment only, and that the total taking
from the marine geophysical survey will have a negligible impact on the
affected species or stocks.
[[Page 6448]]
Impact on Availability of Affected Species or Stock for Taking for
Subsistence Uses
There are no relevant subsistence uses of marine mammals implicated
by this action.
Endangered Species Act
Of the species of marine mammals that may occur in the proposed
survey area, five are listed as endangered under the ESA, including the
humpback, sei, fin, blue, and sperm whales. Under Section 7 of the ESA,
NSF has initiated formal consultation with the NMFS, Office of
Protected Resources, Endangered Species Division, on this proposed
seismic survey. NMFS' Office of Protected Resources, Permits,
Conservation and Education Division, has initiated formal consultation
under section 7 of the ESA with NMFS' Office of Protected Resources,
Endangered Species Division, to obtain a Biological Opinion evaluating
the effects of issuing the IHA on threatened and endangered marine
mammals and, if appropriate, authorizing incidental take. NMFS will
conclude formal section 7 consultation prior to making a determination
on whether or not to issue the IHA. If the IHA is issued, L-DEO, in
addition to the mitigation and monitoring requirements included in the
IHA, 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)
To meet NMFS' National Environmental Policy Act (NEPA; 42 U.S.C.
4321 et seq.) requirements for the issuance of an IHA to L-DEO, NMFS
will prepare an Environmental Assessment (EA) titled ``Issuance of an
Incidental Harassment Authorization to the Lamont-Doherty Earth
Observatory to Take Marine Mammals by Harassment Incidental to a Marine
Geophysical Survey in the Pacific Ocean off Costa Rica, April-May,
2011.'' This EA will incorporate the NSF's Environmental Analysis
Pursuant To Executive Order 12114 (NSF, 2010) and an associated report
(Report) prepared by LGL Limited Environmental Research Associates
(LGL) for NSF, titled, ``Environmental Assessment of a Marine
Geophysical Survey by the R/V Marcus G. Langseth in the Pacific Ocean
off Costa Rica (LGL, 2010) (draft),'' by reference pursuant to 40 CFR
1502.21 and NOAA Administrative Order (NAO) 216-6 Sec. 5.09(d). Prior
to making a final decision on the IHA application, NMFS will 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 ETP off Costa Rica
may result, at worst, in a temporary modification in behavior (Level B
harassment) of small numbers of marine mammals. Further, NMFS has
preliminarily determined that 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 450 m
(1,476 ft) in deep water when the 18-airgun subarray is in use at a 7 m
(23 ft) tow depth from the vessel to be exposed to levels of sound
believed to have even a minimal chance of causing PTS;
(3) The fact that marine mammals would have to be closer than 3,800
m (2.4 mi) in deep water when the full array is in use at a 7 m (23 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
presently anticipated nor would it be authorized were NMFS to issue a
final IHA, and the potential for temporary or permanent hearing
impairment is very low and would likely be avoided through the
incorporation of the proposed monitoring and mitigation measures.
While the number of marine mammals potentially incidentally
harassed would depend on the distribution and abundance of marine
mammals in the vicinity of the survey activity, the number of potential
Level B incidental harassment takings (see Table 3 above this section)
should a final IHA be issued is estimated to be small, less than two
percent of any of the estimated population sizes based on the data
disclosed in Table 2 of this notice. NMFS has preliminarily determined
that impacts to affected species or stocks of marine mammals have been
mitigated to the lowest level practicable through incorporation of the
monitoring and mitigation measures mentioned previously in this
document.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
issue an IHA to L-DEO for conducting a marine geophysical survey in the
ETP off Costa Rica, 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: January 31, 2011.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2011-2538 Filed 2-3-11; 8:45 am]
BILLING CODE 3510-22-P