[Federal Register Volume 74, Number 116 (Thursday, June 18, 2009)]
[Notices]
[Pages 28890-28910]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E9-14380]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XO99
Incidental Takes of Marine Mammals During Specified Activities;
Low-Energy Marine Seismic Survey in the Northwest Atlantic Ocean,
August 2009
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental take authorization; request for
comments.
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SUMMARY: NMFS has received an application from Rice University (Rice),
for an Incidental Harassment Authorization (IHA) to take small numbers
of marine mammals, by harassment, incidental to conducting a marine
seismic survey in the Northwest Atlantic during August 2009. Pursuant
to the Marine Mammal Protection Act (MMPA), NMFS requests comments on
its proposal to authorize Rice to
[[Page 28891]]
incidentally take, by Level B harassment only, small numbers of marine
mammals during the aforementioned activity.
DATES: Comments and information must be received no later than July 20,
2009.
ADDRESSES: Comments on the application should be addressed to Michael
Payne, Chief, Permits, Conservation and Education Division, Office of
Protected Resources, National Marine Fisheries Service, 1315 East-West
Highway, Silver Spring, MD 20910-3225. The mailbox address for
providing e-mail comments is [email protected]. Comments sent via
e-mail, including all attachments, must not exceed a 10-megabyte file
size.
A copy of the application containing a list of the references used
in this document may be obtained by writing to the address specified
above, telephoning the contact listed below (see FOR FURTHER
INFORMATION CONTACT), or visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm.
Documents cited in this notice may be viewed, by appointment,
during regular business hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Howard Goldstein or Ken Hollingshead,
Office of Protected Resources, NMFS, 301-713-2289.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.)
direct the Secretary of Commerce to allow, upon request, the
incidental, but not intentional, taking of marine mammals by United
States citizens who engage in a specified activity (other than
commercial fishing) within a specified geographical region if certain
findings are made and either regulations are issued or, if the taking
is limited to harassment, a notice of a proposed authorization is
provided to the public for review.
Authorization for incidental taking shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s), will not have an unmitigable adverse impact on the
availability of the species or stock(s) for subsistence uses, and if
the permissible methods of taking and requirements pertaining to the
mitigation, monitoring and reporting of such takings are set forth.
NMFS has defined ``negligible impact'' in 50 CFR 216.103 as `` * * * an
impact resulting from the specified activity that cannot be reasonably
expected to, and is not reasonably likely to, adversely affect the
species or stock through effects on annual rates of recruitment or
survival.''
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.
Except with respect to certain activities not pertinent here, the MMPA
defines ``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [``Level A harassment'']; or (ii) has the potential to disturb
a marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[``Level B harassment''].
16 U.S.C. 1362(18).
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS'
review of an application followed by a 30-day public notice and comment
period on any proposed authorizations for the incidental harassment of
small numbers of marine mammals. Within 45 days of the close of the
comment period, NMFS must either issue or deny issuance of the
authorization.
Summary of Request
On April 21, 2009, NMFS received an application from Rice for the
taking, by Level B harassment only, of small numbers of marine mammals
incidental to conducting, under a cooperative agreement with the
National Science Foundation (NSF), a low-energy marine seismic survey
in the Northwest Atlantic Ocean. The funding for the survey is provided
by the NSF. The proposed survey will occur off New England within the
U.S Exclusive Economic Zone (EEZ). Seismic operations will occur over
the continental shelf southeast of the island of Martha's Vineyard,
Massachusetts, and likely also in Nantucket Sound (see Figure 1 of
Rice's application). The cruise is currently scheduled to occur from
August 12 to 25, 2009. The survey will use two Generator Injector (GI)
airguns with a discharge volume of 90 in\3\. Some minor deviation from
these dates is possible, depending on logistics and weather.
Description of the Specified Activity
Rice plans to conduct a low-energy marine seismic survey and
bathymetric program. The planned survey will involve one source vessel,
the R/V Endeavor (Endeavor), which will occur in the Northwest Atlantic
Ocean off of New England.
The proposed survey will examine stratigraphic controls on
freshwater beneath the continental shelf off the U.S. east coast. In
coastal settings worldwide, large freshwater volumes are sequestered in
permeable continental shelf sediments. Freshwater storage and discharge
have been documented off North and South America, Europe, and Asia. The
proposed survey will investigate the Atlantic continental shelf off New
England, where freshwater extends up to 100 km offshore. Using high-
resolution mathematical models and existing data, it is estimated that
approximately 1,300 km\3\ (312 mi\3\) of freshwater is sequestered in
the continental shelf from New York to Maine. However, the models
indicate that the amount of sequestered freshwater is highly dependent
on the thickness and distribution of aquifers and aquicludes. The
proposed survey will provide imaging of the subsurface and characterize
the distribution of aquifers and aquicludes off Martha's Vineyard.
The study will provide data integral to improved models to estimate
the abundance of sequestered freshwater and will provide site survey
data for an Integrated Ocean Drilling Program (IODP) proposal to drill
these freshwater resources for hydrogeochemical, biological, and
climate studies. Combined seismic and drilling data could help identify
undeveloped freshwater resources that may represent a resource to urban
coastal centers, if accurately characterized and managed. On a global
scale, vast quantities of freshwater have been sequestered in the
continental shelf and may represent an increasingly valuable resource
to humans. This survey will help constrain process-based mathematical
models for more precise estimations of the abundance and distribution
of freshwater wells on the continental shelf.
The source vessel, the Endeavor, will deploy two low-energy GI
airguns as an energy source (with a discharge volume of 90 in\3\) and a
600 m (1,969 ft) towed hydrophone streamer. The energy to the GI airgun
is compressed air supplied by compressors onboard the source vessel. As
the GI airgun is towed along the survey lines, the receiving systems
will receive the returning acoustic signals.
The planned seismic program will consist of approximately 1,757 km
(1,092 mi) of surveys lines and turns (see Figure 1 of Rice's
application). Most of the survey effort (approximately 1,638 km or
1,018 mi) will take place in water <100 m deep, and approximately 119
km (74 mi) will occur just past the
[[Page 28892]]
shelf edge, in water depths >100 m (328 ft). There may be additional
seismic operations associated with equipment testing, start-up, and
repeat coverage of any areas where initial data quality is sub-
standard.
All planned geophysical data acquisition activities will be
conducted with assistance by scientists who have proposed the study,
Dr. B. Dugan of Rice University, Dr. D. Lizarralde of Woods Hole
Oceanographic Institution, and Dr. M. Person of New Mexico Institute of
Mining and Technology. The vessel will be self-contained, and the crew
will live aboard the vessel for the entire cruise.
In addition to the seismic operations of the two GI airguns, a
Knudsen 3260 echosounder, and EdgeTech sub-bottom profiler, and a
``boomer'' system to image sub-bottom seafloor layers will be used at
times during the survey.
Vessel Specifications
The Endeavor has a length of 56.4 m (185 ft), a beam of 10.1 m
(33.1 ft), and a maximum draft of 5.6 m (18.4 ft). The Endeavor has
been operated by the University of Rhode Island's Graduate School of
Oceanography for over thirty years to conduct oceanographic research
throughout U.S. and world marine waters. The ship is powered by a
single GM/EMD diesel engine, producing 3,050 hp, which drives a single
propeller directly at a maximum of 900 revolutions per minute (rpm).
The vessel also has a 320 hp bowthruster, which is not used during
seismic acquisition. The optimal operation speed during seismic
acquisition will be approximately 7.4 km/hour. When not towing seismic
survey gear, the Endeavor can cruise at 18.5 km/hour. The Endeavor has
a range of 14,816 km (9,206 mi). The Endeavor will also serve as the
platform from which vessel-based Marine Mammal Visual Observers (MMVO)
will watch for animals before and during GI airgun operations.
Acoustic Source Specifications
Seismic Airguns
During the proposed survey, the Endeavor will tow two GI airguns,
with a volume of 90 in\3\, and a 600 m long streamer containing
hydrophones along predetermined lines. The two GI airguns will be towed
approximately 25 m (82 ft) behind the Endeavor at a depth of
approximately 3 m (10 ft). Seismic pulses will be emitted at intervals
of approximately 5 seconds. At a speed of 7.4 km/hour, the 5 second
spacing corresponds to a shot interval of approximately 10 m (33 ft).
The operating pressure will be 2,000 psi. A single GI airgun will be
used during turns.
The generator chamber of each GI airgun, the one responsible for
introducing the sound pulse into the ocean, has a volume of 45 in\3\.
The larger (105 in\3\) injector chamber injects air into the
previously-generated bubble to maintain its shape, and does not
introduce more sound into the water. Both GI airguns will be fired
simultaneously, for a total discharge volume of 90 in\3\. The GI
airguns are relatively small compared to most other airgun arrays used
for seismic arrays.
A single GI airgun, a single 15 in\3\ watergun, or a boomer system
may be used in shallow waters with sandy seafloors if the two GI
airguns do not provide accurate seafloor imaging. The watergun is a
marine seismic sound source that uses an implosive mechanism to provide
an acoustic signal. Waterguns provide a richer source spectra in high
frequencies (>200 Hz) than those of GI or airguns. The 15 in\3\
watergun potentially provides a cleaner signal for high-resolution
studies in shallow water, with a short-pulse (<30 ms) providing
resolution of approximately 10 m. The operating pressure will be 2,000
psi. Peak pressure of the single watergun and the boomer system is
estimated to be approximately 212 dB (0.4 bar-m). Thus, both sources
would have a considerably lower source level than the two GI airguns
and single GI airgun.
The root mean square (rms) received levels that are used as impact
criteria for marine mammals are not directly comparable to the peak (pk
or 0-pk) or peak-to-peak (pk-pk) values normally used to characterize
source levels of airgun arrays. The measurement units used to describe
airgun sources, peak or peak-to-peak decibels, are always higher than
the ``root mean square'' (rms) decibels referred to in biological
literature. A measured received level of 160 dB re 1 [mu]Pa (rms) in
the far field would typically correspond to a peak measurement of
approximately 170 to 172 dB, and to a peak-to-peak measurement of
approximately 176 to 178 dB, as measured for the same pulse received at
the same location (Greene, 1997; McCauley et al., 1998, 2000). The
precise difference between rms and peak or peak-to-peak values depends
on the frequency content and duration of the pulse, among other
factors. However, the rms level is always lower than the peak or peak-
to-peak level for an airgun-type source.
The sound pressure field of two 45 in\3\ GI airguns has not been
modeled, but those for two 45 in\3\ Nucleus G airguns and one 45 in\3\
GI airgun have been modeled by Lamont-Doherty Earth Observatory (L-DEO)
of Columbia University in relation to distance and direction from the
airguns (see Figure 2 and 3 of Rice's application). The GI airgun is
essentially two G airguns that are joined head to head. The G airgun
signal has more energy than the GI airgun signal, but the peak energy
levels are equivalent and appropriate for modeling purposes. The L-DEO
model does not allow for bottom interactions, and is most directly
applicable to deep water. Based on the modeling, estimates of the
maximum distances from GI airguns where sound levels of 190, 180, and
160 dB re 1 [mu]Pa (rms) are predicted to be received in deep (>1,000
m) water are shown in Table 1 of Rice's application. Because the model
results are for G airguns, which have more energy than GI airguns of
the same size, those distances are overestimates of the distances for
the 45 in\3\ GI airguns.
Echosounder
The Knudsen 3260 is a deep-water, dual-frequency echosounder with
operating frequencies of 3.5 and 12 kHz. The high frequency (12 kHz)
can be used to record water depth or to track pingers attached to
various instruments deployed over the side. The low frequency (3.5 kHz)
is used for sub-bottom profiling. Both frequencies will be used
simultaneously during the present study. It will be used with a hull-
mounted, downward-facing transducer. A pulse up to 24 ms in length is
emitted every several seconds with a nominal beam width of 80[deg].
Maximum output power at 3.5 kHz is 10 kW and at 12 kHz it is 2 kW. The
maximum source output (downward) for the 3260 is estimated to be 211 dB
re 1 [mu]Pam at 10 kW.
Sub-bottom Profiler (SBP)
The SBP is normally operated to provide information about
sedimentary features and bottom topography; it will provide a 10 cm
resolution of the sub-floor. During operations in deeper waters (>30-40
m), an EdgeTech 3200-XS SBP will be operated from the ship with a SB-
512i towfish that will be towed at a depth of 5 m. It will transmit and
record a 0.5-12 kHz swept pulse (or chirp), with a nominal beam width
of 16-32[deg]. The SBP will produce a 30 ms pulse repeated at 0.5 to 1
s intervals. Depending on seafloor conditions, it could penetrate up to
100 m.
Boomer
The `boomer' system will be an alternative source of sub-floor
imaging in shallower waters (<30 to 40 m or 98 to 131 ft). The Applied
Acoustics
[[Page 28893]]
AA200 `boomer' system, run by the National Oceanography Centre,
operates at frequencies of approximately 0.3 to 3 kHz. The system will
be surface-towed, and a 60 m (197 ft) hydrophone streamer will receive
its pulses. The streamer will be towed at 1 m depth and approximately
25 to 30 m (82 to 98 ft) behind the Endeavor. A 0.1 ms pulse will be
transmitted at 1 s intervals. The normal source output (downward) is
212 dB re 1 [mu]Pam.
Safety Radii
NMFS has determined that for acoustic effects, using acoustic
thresholds in combination with corresponding safety radii is the most
effective way to consistently apply measures to avoid or minimize the
impacts of an action, and to quantitatively estimate the effects of an
action. Thresholds are used in two ways: (1) To establish a mitigation
shut-down or power-down zone, i.e., if an animal enters an area
calculated to be ensonified above the level of an established
threshold, a sound source is powered down or shut down; and (2) to
calculate take, in that a model may be used to calculate the area
around the sound source that will be ensonified to that level or above,
then, based on the estimated density of animals and the distance that
the sound source moves, NMFS can estimate the number of marine mammals
that may be ``taken.''
As a matter of past practice and based on the best available
information at the time regarding the effects of marine sound compiled
over the past decade, NMFS has used conservative numerical estimates to
approximate where Level A harassment from acoustic sources begins: 180
re 1 [mu]Pa (rms) level for cetaceans and 190 dB re 1 [mu]Pa (rms) for
pinnipeds. A review of the available scientific data using an
application of science-based extrapolation procedures (Southall et al.,
2007) strongly suggests that Level A harassment (as well as TTS) from
single exposure impulse events may occur at much higher levels than the
levels previously estimated using very limited data. However, for
purposes of this proposed action, Rice's application sets forth, and
NMFS is using, the more conservative 180 and 190 dB re 1 [mu]Pa (rms)
criteria. NMFS considers 160 re 1 [mu]Pa (rms) as the criterion for
estimating the onset of Level B harassment from acoustic sources like
impulse sounds used in the seismic survey.
Emperical data concerning the 180 and 160 dB distances have been
acquired based on measurements during the acoustic verification study
conducted by L-DEO in the northern Gulf of Mexico from May 27 to June
3, 2003 (Tolstoy et al., 2004a,b). Although the results are limited the
data showed that radii around the airguns where the received level
would be 180 dB re 1 [mu]Pa (rms), the safety criterion applicable to
cetaceans (NMFS, 2000), vary with water depth. Similar depth-related
variation is likely in the 190 dB distances applicable to pinnipeds.
Correction factors were developed for water depths 100-1,000 m and <100
m; the proposed survey will occur in depths approximately 20 to 125 m.
The empirical data indicate that, for deep water (>1,000 m), the L-
DEO model tends to overestimate the received sound levels at a given
distance (Tolstoy et al., 2004a,b). However, to be precautionary
pending acquisition of additional empirical data, it is proposed that
safety radii during GI airgun operations in deep water will be values
predicted by L-DEO's model (see Table 1 below). Therefore, the assumed
180 and 190 dB radii are 40 m (131 ft) and 10 m (33 ft) respectively.
Empirical measurements were not conducted for intermediate depths
(100-1,000 m). On the expectation that results will be intermediate
between those from shallow and deep water, a 1.5x correction factor is
applied to the estimates provided by the model for deep water
situations. This is the same factor that was applied to the model
estimates during L-DEO cruises in 2003. The assumed 180 and 190 dB
radii in intermediate depth water are 60 m (197 ft) and 15 m (49 ft),
respectively (see Table 1 below).
Empirical measurements indicated that in shallow water (<100 m),
the L-DEO model underestimates actual levels. In previous L-DEO
projects, the exclusion zones were typically based on measured values
and ranged from 1.3 to 15x higher than the modeled values depending on
the size of the airgun array and the sound level measured (Tolstoy et
al., 2004a,b). During the proposed cruise, similar factors will be
applied to derive appropriate shallow water radii from the modeled deep
water radii (see Table 1 below). The assumed 180 and 190 dB radii in
shallow depth water are 296 m (971 ft) and 147 m (482 ft), respectively
(see Table 1 below).
Table 1
[Predicted distances to which sound levels >=190, 180, and 160 dB re 1 [mu]Pa might be received in shallow (<100
m; 328 ft), intermediate (100-1,000 m; 328-3,280 ft), and deep (>1,000 m; 3,280 ft) water from the two 45 in\3\
GI airguns used during the seismic surveys in the northwest Atlantic Ocean during August 2009, and one 45 in\3\
GI airgun that will be used during turns. Distances are based on model results provided by L-DEO.]
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Predicted RMS distances (m)
Source and volume Tow depth (m) Water depth -----------------------------------------------
190 dB 180 dB 160 dB
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One GI airgun 45 in\3\........ 3 Deep (>1,000 m). 8 23 220
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.............. Intermediate 12 35 330
(100-1,000 m).
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.............. Shallow (<100 m) 95 150 570
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Two GI airguns 45 in\3\....... 3 Deep (>1,000 m). 10 40 350
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.............. Intermediate 15 60 525
(100-1,000 m).
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.............. Shallow (<100 m) 147 296 1,029
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The GI airguns, watergun, or boomer will be shut-down immediately
when cetaceans are detected within or about to enter the 180 dB re 1
[mu]Pa (rms) radius for the two GI airguns, or when pinnipeds are
detected within or about to enter the 190 dB re 1 [mu]Pa (rms) radius
for the two GI airguns. The 180 and 190 dB shut down criteria are
consistent
[[Page 28894]]
with guidelines listed for cetaceans and pinnipeds, respectively, by
NMFS (2000) and other guidance by NMFS. Proposed Dates, Duration, and
Region of Activity
The Endeavor is expected to depart from Narragansett, Rhode Island,
on approximately August 12, 2009, for an approximately four hour
transit to the study area southeast of Martha's Vineyard (see Figure 1
of Rice's application). Seismic operations will commence upon arrival
at the study area, with highest priority given to the central NNW-SSE
line, followed by WSW-ENE lines, each of which cross the proposed IODP
sites; lowest priority will be given to the survey lines in Nantucket
Sound. The 14 day program will consist of approximately 11 days of
seismic operations, and three contingency days in case of inclement
weather. The Endeavor will return to Narragansett on approximately
August 25, 2009. The exact dates of the proposed activities depend on
logistics, weather conditions, and the need to repeat some lines if
data quality is substandard.
The proposed seismic survey will encompass the area 39.8[deg] to
41.5[deg] N, 69.8[deg] to 70.6[deg] W (see Figure 1 of Rice's
application). Water depths in the study area range from approximately
20 to 125 m (66 to 410 ft), but are typically <100 m. The proposed
survey will take place in Nantucket Sound and south of Nantucket and
Martha's Vineyard. The ship will approach the south shore of Martha's
Vineyard within 10 km (6.2 mi). The seismic survey will be conducted
within the Exclusive Economic Zone (EEZ) of the U.S.A.
Description of Marine Mammals in the Proposed Activity Area
A total of 34 marine mammal species (30 cetacean and 4 pinniped)
are known to or may occur in the proposed study area (see Table 2,
Waring et al., 2007). Several species are listed as Endangered under
the Endangered Species Act (ESA): the North Atlantic right, humpback,
sei, fin, blue, and sperm whales. The Western North Atlantic Coastal
Morphotype Stock of common bottlenose dolphins is listed as Depleted
under the MMPA.
Table 2 below outlines the marine mammal species, their habitat,
abundance, density, and conservation status in the proposed project
area. Additional information regarding the distribution of these
species expected to be found in the project area and how the estimated
densities were calculated may be found in Rice's application.
Table 2
[The occurrence, habitat, regional abundance, conservation status, best and maximum density estimates, number of marine mammals that could be exposed to
sound level at or above 160dB re 1[mu]Pa, best estimate of number of individuals exposed, and best estimate of number of exposures per marine mammal in
or near the proposed low-energy seismic survey area in the Northwest Atlantic Ocean. See Tables 2-4 in Rice's application for further detail.]
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Density/ Density/
Species Habitat Occurrence in study area Regional best abundance ESA\a\ 1000km \2\ 1000km \2\
est. (CV) \ 1\ (best) (max)
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Mysticetes
North Atlantic right whale (Eubalaena Coastal and shelf waters. Common................... 325 (0) \2\............. NL N.A. N.A.
glacialis).
Humpback whale (Megaptera Mainly nearshore waters Common................... 11,570 \3\.............. EN 0.56 19.68
novaeangliae). and banks.
Minke whale (Balaenoptera Pelagic and coastal...... Common................... 188,000 \4\............. NL 0.05 7.35
acutorostrata).
Bryde's whale (Balaenoptera brydei)... Primarily offshore, Rare..................... N.A..................... NL N.A. N.A.
pelagic.
Sei whale (Balaenoptera borealis)..... Primarily offshore, Uncommon................. 10,300 \5\.............. EN N.A. N.A.
pelagic.
Fin whale (Balaenoptera physalus)..... Continental slope, mostly Common................... 35,500 \6\.............. EN 3.86 26.09
pelagic.
Blue whale (Balaenoptera musculus).... Pelagic, shelf and Uncommon?................ 1,186 \7\............... EN N.A. N.A.
coastal.
Odontocetes
Sperm whale (Physeter macrocephalus).. Usually pelagic and deep Common?.................. 13,190 \8\.............. EN 0.38 26.88
seas.
Pygmy sperm whale (Kogia breviceps)... Deep waters off shelf.... Uncommon................. N.A..................... NL N.A. N.A.
Dwarf sperm whale (Kogia sima)........ Deep waters off the shelf Uncommon................. N.A..................... NL N.A. N.A.
Cuvier's beaked whale (Ziphius Pelagic.................. Uncommon................. N.A..................... NL N.A. N.A.
cavirostris).
Northern bottlenose whale (Hyperodon Pelagic.................. Rare..................... 40,000 \9\.............. NL N.A. N.A.
ampullatus).
True's beaked whale (Mesoplodon mirus) Pelagic.................. Rare..................... N.A..................... NL N.A. N.A.
Gervais' beaked whale (Mesoplodon Pelagic.................. Rare..................... N.A..................... NL N.A. N.A.
europaeus).
Sowerby's beaked whale (Mesoplodon Pelagic.................. Rare..................... N.A..................... NL N.A. N.A.
bidens).
Blainville's beaked whale (Mesoplodon Pelagic.................. Rare..................... N.A..................... NL N.A. N.A.
densirostris).
Unidentified beaked whale............. Pelagic.................. Rare..................... N.A..................... NL 0.01 0.82
Bottlenose dolphin (Tursiops Coastal, shelf and Common................... 81,588 (0.17) \10\...... NL 14.02 163.02
truncatus). offshore.
[[Page 28895]]
Pantropical spotted dolphin (Stenella Coastal and pelagic...... Rare..................... N.A..................... NL N.A. N.A.
attenuata).
Atlantic spotted dolphin (Stenella Mainly coastal waters.... Uncommon?................ 50,978 (0.42)........... NL N.A. N.A.
frontalis).
Spinner dolphins (Stenella Coastal and pelagic...... Rare..................... N.A..................... NL N.A. N.A.
longirostris).
Striped dolphin (Stenella Off continental shelf.... Common?.................. 94,462 (0.40)........... NL 0.11 73.61
coeruleoalba).
Short-beaked common dolphin (Delphinus Continental shelf and Common................... 120,743 (0.23).......... NL 128.88 1,108.71
delphis). pelagic.
White-beaked dolphin (Lagenorhynchus Continental shelf (<200 Uncommon?................ 10s to 100s of 1,000s NL N.A. N.A.
albirostris). m). \11\.
Atlantic white-sided dolphin Shelf and slope waters... Common................... 10s to 100s of 1,000s NL N.A. N.A.
(Lagenorhynchus acutus). \12\.
Risso's dolphin (Grampus griseus)..... Shelf, slope, seamounts Common................... 20,479 (0.59)........... NL 0.48 322.67
(waters 400-1,000 m).
False killer whale (Pseudorca Tropical, temperate, Extralimital............. N.A..................... NL N.A. N.A.
crassidens). pelagic.
Killer whale (Orcinus orca)........... Coastal, widely Rare..................... N.A..................... *NL N.A. N.A.
distributed.
Long-finned pilot whale (Globlicephala Mostly pelagic........... Common?.................. 810,000 \13\............ NL N.A. N.A.
melas).
Short-finned pilot whale (Globicephala Mostly pelagic, high- Common?.................. 810,000 \13\............ NL N.A. N.A.
macrorhynchus). relief topography.
Unidentified pilot whale (Globicephala Mostly pelagic........... Common?.................. 810,000 \13\............ NL 6.44 382.52
sp.).
Harbor porpoise (Phocoena phocoena)... Coastal and inland waters Common?.................. 500,000 \14\............ NL N.A. N.A.
Pinnipeds
Harbor seal (Phoca vitulina).......... Coastal.................. Common................... 99,340.................. NL N.A. N.A.
Gray seal (Halichoerus grypus)........ Coastal.................. Common................... 52,500 \15\............. NL N.A. N.A.
Harp seal (Pagophilius groenlandicus). Coastal.................. Uncommon................. 5,500,000 \16\.......... NL N.A. N.A.
Hooded seal (Cystophora cristata)..... Coastal.................. Uncommon................. 592,100 \17\............ NL N.A. N.A.
--------------------------------------------------------------------------------------------------------------------------------------------------------
N.A.--Data not available or species status was not assessed, ? indicated uncertainty
\a\ U.S. Endangered Species Act: EN = Endangered, T = Threatened, NL = Not listed
\1\ Abundance estimates are given from Waring et al. (2007), typically for U.S. Western North Atlantic stocks unless otherwise indicated; For species
whose distribution is primarily offshore or not known, the estimates for the U.S. EEZ in Waring et al. (2007) are not considered for the study area
and the regional population is given as N.A. unless it is available from another source.
\2\ Estimate updated in NMFS 2008 draft stock assessment report.
\3\ Estimate for the western North Atlantic (IWS, 2007a).
\4\ Estimate for the North Atlantic (IWC, 2007; Waring et al., 2007).
\5\ Estimate for the Northeast Atlantic (Cattanach et al., 1993).
\6\ Estimate for the North Atlantic (IWC, 2007a; Waring et al., 2007).
\7\ Estimate for the North Atlantic (NMFS, 1998).
\8\ Estimate for Northeast Atlantic (Whitehead, 2002).
\9\ Estimate for Northeast Atlantic (NAAMCO, 1995: 77).
\10\ Estimate for the Western North Atlantic and Offshore stock, and may include coastal forms. 43,951 animals estimated for all management units of the
Coastal morphotype (Waring et al., 2007).
\11\ Tens to low hundreds of thousands (Reeves et al., 1999a).
\12\ High tens to low hundreds of thousands (Reeves et al., 1999b).
\13\ Estimate may include both long- and short-finned pilot whales.
\14\ Estimate for the North Atlantic (Jefferson et al., 2008)
\15\ Estimate for the northwest Atlantic Ocean in the Gulf of St. Lawrence and along the Nova Scotia eastern shore (Hammill, 2005).
\16\ Estimate for the northwest Atlantic Ocean (DFO, 2007).
\17\ Estimate for the northwest Atlantic Ocean (ICES, 2006).
*Southern Resident killer whales in the eastern Pacific Ocean, near Washington state, are listed as endangered under the ESA, but not in the Atlantic
Ocean.
[caret]The Western North Atlantic Coastal Morphotype stock, ranging from NJ to FL, is listed as depleted under the MMPA.
Several Federal Marine Protected Areas (MPAs) or sanctuaries have
been established near the proposed study area, primarily with the
intention of preserving cetacean habitat (see Table 3 of Rice's
application; Hoyt, 2005; Cetacean Habitat, 2009; see also Figure 1 of
Rice's application). Cape Cod Bay is designated as Right Whale Critical
Habitat, as is the Great South Channel Northern Right Whale Critical
Habitat Area located to the east of Cape Cod.
[[Page 28896]]
The Gerry E. Studds Stellwagen Bank National Marine Sanctuary is
located north of the proposed study area in the Gulf of Maine. The
proposed survey is not located within any Federal MPAs or sanctuaries.
However, a sanctuary designated by the state of Massachusetts occurs
within the study area--the Cape & Islands Ocean Sanctuary. This
sanctuary includes nearshore waters of southern Cape Cod, Martha's
Vineyard, and Nantucket (see Table 3 of Rice's application). In
addition, there are four National Wildlife Refuges within the study
area (Monomoy, Nantucket, Mashpee, and Nomans Island) and a National
Estuarine Research Reserve (Waquoit Bay). Except for Nomans Island,
these refuges and reserves are located in Nantucket Sound. Three
Canadian protected areas also occur in the Northwest Atlantic for
cetacean habitat protection, including the Bay of Fundy and Roseway
Basin Right Whale Conservation Areas (see Figure 1 of Rice's
application), as well as the Gully Marine Protected Area off the
Scotian Shelf.
There are several areas that are closed to commercial fishing on a
seasonal basis to reduce the risk of entanglement or incidental
mortality to marine mammals. To protect large whales like right,
humpback, and fin whales, NMFS implemented seasonal area management
zones for lobster, several groundfish, and other marine invertebrate
trap/pot fisheries, prohibiting gear in the Great South Channel
Critical Habitat Area from April through June; additional dynamic area
management zones could be imposed for 15 day time periods if credible
fisheries observers identify concentrations of right whales in areas
north of 40[deg] N (NMFS 1999, 2008). To reduce fishery impacts on
harbor porpoises, additional time and area closures in the Gulf of
Maine include fall and winter along the mid-coastal area, winter and
spring in Massachusetts Bay and southern Cape Cod, winter and spring in
offshore areas, and February around Cashes Ledge (NMFS, 1998).
Fishermen are also required to use pingers, and New Jersey and mid-
Atlantic waters could close seasonally for fishermen failing to apply
specific gear modifications (NMFS, 1998).
Potential Effects on Marine Mammals
Potential Effects of Airguns
The effects of sounds from airguns might result in one or more of
the following: tolerance, masking of natural sounds, behavioral
disturbances, temporary or permanent hearing impairment, and non-
auditory physical or physiological effects (Richardson et al., 1995;
Gordon et al., 2004; Nowacek et al., 2007; Southall et al., 2007).
Permanent hearing impairment, in the unlikely event that it occurred,
would constitute injury, but temporary threshold shift (TTS) is not an
injury (Southall et al., 2007). Although the possibility cannot be
entirely excluded, it is unlikely that the project would result in any
cases of permanent hearing impairment, or any significant non-auditory
physical or physiological effects. Some behavioral disturbance is
expected, but this would be localized and short-term.
Tolerance
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
For a brief summary of the characteristics of airgun pulses, see
Appendix A of Rice's application. However, it should be noted that most
of the measurements of airgun sounds would be detectable considerably
farther away than the GI airguns planned for use in the proposed
project.
Several studies have shown that marine mammals at distances more
than a few kilometers from operating seismic vessels often show no
apparent response-see Appendix A of Rice's application. That is often
true even in cases when the pulsed sounds must be readily audible to
the animals based on measured received levels and the hearing
sensitivity of the mammal group. Although various baleen whales,
toothed whales, and (less frequently) pinnipeds have been shown to
react behaviorally to airgun pulses under some conditions, at other
times, mammals of all three types have shown no overt reactions. In
general, pinnipeds usually seem to be more tolerant of exposure to
airgun pulses than are cetaceans, with relative responsiveness of
baleen and toothed whales being variable. Given the relatively small
and low-energy GI airgun source planned for use in this project,
mammals are expected to tolerate being closer to this source more so
than would be the case for a larger airgun source typical of most
seismic surveys.
Masking
Obscuring of sounds of interest by interfering sounds, generally at
similar frequencies, is known as masking. Masking effects of pulsed
sounds (even from large arrays of airguns) on marine mammal calls and
other natural sounds are expected to be limited, although there are few
specific data of relevance. Because of the intermittent nature and low
duty cycle of seismic pulses, animals can emit and receive sounds in
the relatively quiet intervals between pulses. However in some
situations, multi-path arrivals and reverberation cause airgun sound to
arrive for much or all of the interval between pulses (Simard et al.,
2005; Clark and Gagnon, 2006), which could mask calls.
Some baleen and toothed whales are known to continue calling in the
presence of seismic pulses. The airgun sounds are pulsed, with quiet
periods between the pulses, and whale calls often can be heard between
the seismic pulses (Richardson et al., 1986; McDonald et al., 1995;
Greene et al., 1999; Nieukirk et al., 2004; Smultea et al., 2004; Holst
et al., 2005a,b, 2006). In the northeast Pacific Ocean, blue whale
calls have been recorded during a seismic survey off Oregon (McDonald
et al., 1995). Among odontocetes, there has been one report that sperm
whales cease calling when exposed to pulses from a very distant seismic
ship (Bowles et al., 1994). However, more recent studies found that
sperm whales continued calling in the presence of seismic pulses
(Madsen et al., 2002; Tyack et al., 2003; Smultea et al., 2004; Holst
et al., 2006; Jochens et al., 2006, 2008). Given the small source
planned for use during the proposed survey, there is even less
potential for masking of baleen or sperm whale calls during the present
study than in most seismic surveys. Masking effects of seismic pulses
are expected to be negligible in the case of the small odontocetes
given the intermittent nature of seismic pulses. Dolphins and porpoises
commonly are heard calling while airguns are operating (Gordon et al.,
2004; Smultea et al., 2004; Holst et al., 2005a,b; Potter et al.,
2007). Also, the sounds important to small odontocetes are
predominantly at much higher frequencies than the airgun sounds, thus
further limiting the potential for masking. In general, masking effects
of seismic pulses are expected to be minor, given the normally
intermittent nature of seismic pulses. Masking effects on marine
mammals are discussed further in Appendix A of Rice's application.
Disturbance Reactions
Disturbance includes a variety of effects, including subtle changes
in behavior, more conspicuous changes in activities, and displacement.
Reactions to sound, if any, depend on species, state of maturity,
experience, current activity, reproductive state, time of day, and many
other factors (Richardson et al., 1995; Wartzok et al., 2004; Southall
et al., 2007; Weilgart, 2007). If a marine mammal responds to an
underwater
[[Page 28897]]
sound by changing its behavior or moving a small distance, the response
may or may not rise to the level of ``harassment,'' or affect the stock
or the species as a whole. If a sound source displaces marine mammals
from an important feeding or breeding area for a prolonged period,
impacts on animals or on the stock or species could potentially be
significant (Lusseau and Bejder, 2007; Weilgart, 2007). Given the many
uncertainties in predicting the quantity and types of impacts of noise
on marine mammals, it is common practice to estimate how many mammals
are likely to be present within a particular distance of industrial
activities, or exposed to a particular level of industrial sound. In
most cases, this approach likely overestimates the numbers of marine
mammals that are affected in some biologically-important manner.
The sound exposure thresholds that are used to estimate how many
marine mammals might be disturbed to some biologically-important degree
by a seismic program are based on behavioral observations during
studies of several species. However, information is lacking for many
species. Detailed studies have been done on humpback, gray, bowhead,
and on ringed seals. Less detailed data are available for some other
species of baleen whales, sperm whales, small toothed whales, and sea
otters, but for many species there are no data on responses to marine
seismic surveys. Most of those studies have concerned reactions to much
larger airgun sources than planned for use in the proposed project.
Thus, effects are expected to be limited to considerably smaller
distances and shorter periods of exposure in the present project than
in most of the previous work concerning marine mammal reactions to
airguns.
Baleen Whales--Baleen whales generally tend to avoid operating
airguns, but avoidance radii are quite variable. Whales are often
reported to show no overt reactions to pulses from large arrays of
airguns at distances beyond a few kilometers, even though the airgun
pulses remain well above ambient noise levels out to much longer
distances. However, as reviewed in Appendix A of Rice's application,
baleen whales exposed to strong noise pulses from airguns often react
by deviating from their normal migration route and/or interrupting
their feeding activities and moving away from the sound source. In the
case of the migrating gray and bowhead whales, the observed changes in
behavior appeared to be of little or no biological consequence to the
animals. They simply avoided the sound source by displacing their
migration route to varying degrees, but within the natural boundaries
of the migration corridors.
Studies of gray, bowhead, and humpback whales have demonstrated
that received levels of pulses in the 160-170 dB re 1 [mu]Pa rms range
seem to cause obvious avoidance behavior in a substantial fraction of
the animals exposed. In many areas, seismic pulses from large arrays of
airguns diminish to those levels at distances ranging from 4.5-14.5 km
(2.8-9 mi) from the source. A substantial proportion of the baleen
whales within those distances may show avoidance or other strong
disturbance reactions to the airgun array. Subtle behavioral changes
sometimes become evident at somewhat lower received levels, and studies
summarized in Appendix A(5) of SIO's application have shown that some
species of baleen whales, notably bowhead and humpback whales, at times
show strong avoidance at received levels lower than 160-170 dB re 1
[mu]Pa (rms). Reaction distances would be considerably smaller during
the proposed project, for which the 160 dB radius is predicted to be
220 to 570 m (722 to 1,870 ft) (see Table 1 above), as compared with
several km when a large array of airguns is operating.
Responses of humpback whales to seismic surveys have been studied
during migration, on the summer feeding grounds, and on Angolan winter
breeding grounds; there has also been discussion of effects on the
Brazilian wintering grounds. McCauley et al. (1998, 2000a) studied the
responses of humpback whales off Western Australia to a full-scale
seismic survey with a 16-airgun, 2,678 in\3\ array, and to a single 20
in\3\ airgun with a source level of 227 dB re 1 [mu]Pa m peak-to-peak.
McCauley et al. (1998) documented that initial avoidance reactions
began at 5 to 8 km (3.1 to 5 mi) from the array, and that those
reactions kept most pods approximately 3 to 4 km (1.9 to 2.5 mi) from
the operating seismic boat. McCauley et al. (2000) noted localized
displacement during migration of 4 to 5 km (2.5 to 3.1 mi) by traveling
pods and 7 to12 km (4.3 to 7.5 mi) by cow-calf pairs. Avoidance
distances with respect to the single airgun were smaller (2 km (1.2
mi)) but consistent with the results from the full array in terms of
received sound levels. The mean received level for initial avoidance
reactions of an approaching airgun was a sound level of 140 dB re 1
[mu]Pa (rms) for humpback whale pods containing females. The standoff
range, i.e., the closest point of approach (CPA) of the whales to the
airgun, corresponded to a received level of 143 dB re 1 [mu]Pa (rms).
The initial avoidance response generally occurred at distances of 5 to
8 km (3.1 to 5 mi) from the airgun array and 2 km (1.2 mi) from the
single airgun. However, some individual humpback whales, especially
males, approached within distances of 100 to 400 m (328 to 1,312 ft),
where the maximum received level was 179 dB re 1 [mu]Pa (rms).
Humpback whales on their summer feeding grounds in southeast Alaska
did not exhibit persistent avoidance when exposed to seismic pulses
from a 1.64-L (100 in\3\) airgun (Malme et al., 1985). Some humpbacks
seemed ``startled'' at received levels of 150-169 dB re 1 [mu]Pa on an
approximate rms basis. Malme et al. (1985) concluded that there was no
clear evidence of avoidance, despite the possibility of subtle effects,
at received levels up to 172 re 1 [mu]Pa on an approximate rms basis.
Among wintering humpback whales off Angola (n = 52 useable groups),
there were no significant differences in encounter rates (sightings/hr)
when a 24 airgun array (3,147 in\3\ or 5,805 in\3\) was operating vs.
silent (Weir, 2008). There was also no significant difference in the
mean CPA distance of the humpback whale sightings when airguns were on
vs. off (3,050 m vs. 2,700 m or 10,007 vs. 8,858 ft, respectively).
It has been suggested that South Atlantic humpback whales wintering
off Brazil may be displaced or even strand upon exposure to seismic
surveys (Engel et al., 2004). The evidence for this was circumstantial
and subject to alternative explanations (IAGC, 2004). Also, the
evidence was not consistent with subsequent results from the same area
of Brazil (Parente et al., 2006), or with results from direct studies
of humpbacks exposed to seismic surveys in other areas and seasons.
After allowance for data from subsequent years, there was ``no
observable direct correlation'' between strandings and seismic surveys
(IWC, 2007b:236).
There are no data on reactions of right whales to seismic surveys,
but results from the closely-related bowhead whale show that their
responsiveness can be quite variable depending on the activity
(migrating vs. feeding). Bowhead whales migrating west across the
Alaskan Beaufort Sea in autumn, in particular, are unusually
responsive, with substantial avoidance occurring out to distances of
20-30 km (12.4-18.6 mi) from a medium-sized airgun source at received
sound levels of around 120-130 dB re 1 [mu]Pa (rms) (Miller et al.,
1999; Richardson et al., 1999; see Appendix A of Rice's EA). However,
more recent research on bowhead whales (Miller et al., 2005a; Harris et
al., 2007) corroborates earlier evidence that,
[[Page 28898]]
during the summer feeding season, bowheads are not as sensitive to
seismic sources. Nonetheless, subtle but statistically significant
changes in surfacing-respiration-dive cycles were evident upon
statistical analysis (Richardson et al., 1986). In summer, bowheads
typically begin to show avoidance reactions at a received level of
about 160-170 dB re 1 [mu]Pa (rms) (Richardson et al., 1986; Ljungblad
et al., 1988; Miller et al., 2005a).
Reactions of migrating and feeding (but not wintering) gray whales
to seismic surveys have been studied. Malme et al. (1986, 1988) studied
the responses of feeding Eastern Pacific gray whales to pulses from a
single 100 in\3\ airgun off St. Lawrence Island in the northern Bering
Sea. Malme et al. (1986, 1988) estimated, based on small sample sizes,
that 50 percent of feeding gray whales ceased feeding at an average
received pressure level of 173 dB re 1 [mu]Pa on an (approximate) rms
basis, and that 10 percent of feeding whales interrupted feeding at
received levels of 163 dB. Those findings were generally consistent
with the results of experiments conducted on larger numbers of gray
whales that were migrating along the California coast (Malme et al.,
1984; Malme and Miles, 1985), and with observations of Western Pacific
gray whales feeding off Sakhalin Island, Russia, when a seismic survey
was underway just offshore of their feeding area (Gailey et al., 2007;
Johnson et al., 2007; Yazvenko et al., 2007a,b), along with data on
gray whales off British Columbia (Bain and Williams, 2006). Gray whales
typically show no conspicuous responses to airgun pulses with received
levels up to 150 to 160 dB re 1 [mu]Pa (rms), but are increasingly
likely to show avoidance as received levels increase above that range.
Various species of Balaenoptera (blue, sei, fin, Bryde's, and minke
whales) have occasionally been reported in areas ensonified by airgun
pulses (Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006).
Sightings by observers on seismic vessels off the United Kingdom from
1997 to 2000 suggest that, at times of good sightability, sighting
rates for mysticetes (mainly fin and sei whales) were similar when
large arrays of airguns were shooting and not shooting (Stone, 2003;
Stone and Tasker, 2006). However, these whales tended to exhibit
localized avoidance, remaining significantly (on average) from the
airgun array during seismic operations compared with non-seismic
periods (Stone and Tasker, 2006). In a study off Nova Scotia, Moulton
and Miller (2005) found little difference in sighting rates (after
accounting for water depth) and initial sighting distances of
balaenopterid whales when airguns were operating vs. silent. However,
there were indications that these whales were more likely to be moving
away when seen during airgun operations. Similarly, ship-based
monitoring studies of blue, fin, sei, and minke whales offshore of
Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more than
small differences in sighting rates and swim direction during seismic
vs. non-seismic periods (Moulton et al., 2005, 2006a,b).
Data on short-term reactions (or lack of reactions) of cetaceans to
impulsive noises do not necessarily provide information about long-term
effects. It is not known whether impulsive noises affect reproductive
rate or distribution and habitat use in subsequent days or years.
However, gray whales continued to migrate annually along the west coast
of North America with substantial increases in the population over
recent years, despite intermittent seismic exploration and much ship
traffic in that area for decades (see Appendix A in Malme et al., 1984;
Richardson et al., 1995; Angliss and Outlaw, 2008). The Western Pacific
gray whale population did not seem affected by a seismic survey in its
feeding ground during a prior year (Johnson et al., 2007). Bowhead
whales 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).
In any event, brief exposures to sound pulses from the proposed airgun
source are highly unlikely to result in prolonged effects.
Toothed Whales--Little systematic information is available about
reactions of toothed whales to noise pulses. Few studies similar to the
more extensive baleen whale/seismic pulse work summarized above have
been reported for toothed whales. However, systematic studies on sperm
whales have been done (Jochens and Biggs, 2003; Tyack et al., 2003;
Jochens et al., 2006; Miller et al., 2006), and there is an increasing
amount of information about responses of various odontocetes to seismic
surveys based on monitoring studies (Stone, 2003; Smultea et al., 2004;
Moulton and Miller, 2005; Bain and Williams, 2006; Holst et al., 2006;
Stone and Tasker, 2006; Potter et al., 2007; Weir, 2008).
Seismic operators and MMOs on seismic vessels regularly see
dolphins and other small toothed whales near operating airgun arrays,
but in general there seems to be a tendency for most delphinids to show
some avoidance of operating seismic vessels (Goold, 1996a,b,c;
Calambokidis and Osmek, 1998; Stone, 2003; Moulton and Miller, 2005;
Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008). Some dolphins
seem to be attracted to the seismic vessel and floats, and some ride
the bow wave of the seismic vessel even when large airgun arrays are
firing (Moulton and Miller, 2005). Nonetheless, there have been
indications that small toothed whales sometimes tend to head away or to
maintain a somewhat greater distance from the vessel when a large array
of airguns is operating than when it is silent (Stone and Tasker, 2006;
Weir, 2008). In most cases, the avoidance radii for delphinids appear
to be small, on the order of 1 km (0.62 mi) or less, and some
individuals show no apparent avoidance. Weir (2008b) noted that a group
of short-finned pilot whales initially showed an avoidance response to
ramp-up of a large airgun array, but that this response was limited in
time and space.
The beluga is a species that (at least at times) shows long-
distance avoidance of seismic vessels. Aerial surveys during seismic
operations in the southeastern Beaufort Sea during summer recorded much
lower sighting rates of beluga whales within 10-20 km (6.2-12.4 mi)
compared with 20-30 km (mi) from an operating airgun array, and
observers on seismic boats in that area rarely see belugas (Miller et
al., 2005a; Harris et al., 2007).
Captive bottlenose dolphins and beluga whales exhibited changes in
behavior when exposed to strong pulsed sounds similar in duration to
those typically used in seismic surveys (Finneran et al., 2000, 2002,
2005; Finneran and Schlundt, 2004). The animals tolerated high received
levels of sound (pk-pk level >200 dB re 1 [mu]Pa) before exhibiting
aversive behaviors. For pooled data at 3, 10, and 20 kHz, sound
exposure levels during sessions with 25, 50, and 75 percent altered
behavior were 180, 190, and 199 dB re 1 [mu]Pa\2\, respectively
(Finneran and Schlundt, 2004).
Results for porpoises depend on species. Dall's porpoises seem
relatively tolerant of airgun operations (MacLean and Koski, 2005) and,
during a survey with a large airgun array, tolerated higher noise
levels than did harbor porpoises and gray whales (Bain and Williams,
2006). However, Dall's porpoises do respond to the approach of large
airgun arrays by moving away (Calambokidis and Osmek, 1998; Bain and
Williams, 2006). The limited
[[Page 28899]]
available data suggest that harbor porpoises show stronger avoidance
(Stone, 2003; Bain and Williams, 2006; Stone and Tasker, 2006). This
apparent difference in responsiveness of these two porpoise species is
consistent with their relative responsiveness to boat traffic and some
other acoustic sources in general (Richardson et al., 1995; Southall et
al. 2007).
Most studies of sperm whales exposed to airgun sounds indicate that
this species shows considerable tolerance of airgun pulses (Stone,
2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 2008).
In most cases, the whales do not show strong avoidance and continue to
call (see Appendix A of Rice's EA for review). However, controlled
exposure experiments in the Gulf of Mexico indicate that foraging
effort is somewhat altered upon exposure to airgun sounds (Jochens et
al., 2006, 2008). In the SWSS study, D-tags (Johnson and Tyack, 2003)
were used to record the movement and acoustic exposure of eight
foraging sperm whales before, during, and after controlled sound
exposures of airgun arrays in the Gulf of Mexico (Jochens et al.,
2008). Whales were exposed to maximum received sound levels between 111
and 147 dB re 1 [mu]Pa (rms) (131 to 164 dB re 1 [mu]Pa pk-pk) at
ranges of approximately 1.4 to 12. 6 km (0.9 to 7.8 mi) from the sound
source. Although the tagged whales showed no horizontal avoidance, some
whales changed foraging behavior during full array exposure (Jochens et
al., 2008).
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 A of Rice's
application). Thus behavioral reactions of most odontocetes to the
small GI airgun source to be used during the proposed survey are
expected to be very localized.
Pinnipeds--In the event that any pinnipeds are encountered, they
are not likely to show a strong avoidance reaction to the airgun array.
Visual monitoring from seismic vessels has shown only slight (if any)
avoidance of airguns by pinnipeds, and only slight (if any) changes in
behavior (see Appendix A of Rice's application). In the Beaufort Sea,
some ringed seals avoided an area of 100 m (at most) to a few hundred
meters around seismic vessels, but many seals remained within 100 to
200 m of the trackline as the operating airgun array passed by (e.g.,
Harris et al., 2001; Moulton and Lawson, 2002; Miller et al., 2005a).
Ringed seal sightings averaged somewhat farther away from the seismic
vessel when the airguns were operating than when they were not, but the
difference was small (Moulton and Lawson, 2002). Similarly, in Puget
Sound, sighting distances for harbor seals and California sea lions
tended to be larger when airguns were operating (Calambokidis and
Osmek, 1998). Previous telemetry work suggests that avoidance and other
behavioral reactions may be stronger than evident to date from visual
studies (Thompson et al, 1998). Nonetheless, reactions are expected to
be confined to relatively small distances and durations, with no long-
term effects on pinniped individuals or populations.
Additional details on the behavioral reactions (or the lack
thereof) by all types of marine mammals to seismic vessels can be found
in Appendix A of Rice's EA.
Hearing Impairment and Other Physical Effects
Temporary or permanent hearing impairment is a possibility when
marine mammals are exposed to very strong sounds. Temporary threshold
shift (TTS) has been demonstrated and studied in certain captive
odontocetes (and pinnipeds) exposed to strong sounds (reviewed in
Southall et al., 2007). However, there has been no specific
documentation of TTS let alone permanent hearing damage, i.e.,
permanent threshold shift (PTS), in free-ranging marine mammals exposed
to sequences of airgun pulses during realistic field conditions.
NMFS will be developing new noise exposure criteria for marine
mammals that take account of the now-available scientific data on TTS,
the expected offset between the TTS and PTS thresholds, differences in
the acoustic frequencies to which different marine mammal groups are
sensitive, and other relevant factors. Detailed recommendations for new
science-based noise exposure criteria were published in late 2007
(Southall et al., 2007).
Because of the small GI airgun source in this proposed project,
along with the proposed monitoring and mitigation measures, there is
little likelihood that any marine mammals will be exposed to sounds
sufficiently strong enough to cause hearing impairment. Several aspects
of the proposed monitoring and mitigation measures for this project
(see below) are designed to detect marine mammals occurring near the
airguns (and other sound sources), and to avoid exposing them to sound
pulses that might, at least in theory, cause hearing impairment. In
addition, many cetaceans and (to a limited degree) pinnipeds are likely
to show some avoidance of the area where received levels of airgun
sound are high enough such that hearing impairment could potentially
occur. In those cases, the avoidance responses of the animals
themselves will reduce or (most likely) avoid any possibility of
hearing impairment.
Non-auditory physical effects may also occur in marine mammals
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that theoretically might
occur in mammals close to a strong sound source include stress,
neurological effects, bubble formation, resonance effects, and other
types of organ or tissue damage. It is possible that some marine mammal
species (i.e., beaked whales) may be especially susceptible to injury
and/or stranding when exposed to strong pulsed sounds. However, as
discussed below, there is no definitive evidence that any of these
effects occur even for marine mammals in close proximity to large
arrays of airguns. It is especially unlikely that any effects of these
types would occur during the proposed project given the small size of
the source, the brief duration of exposure of any given mammal, and the
proposed monitoring and mitigation measures (see below). The following
subsections discuss in somewhat more detail the possibilities of TTS,
PTS, and non-auditory physical effects.
Temporary Threshold Shift--TTS is the mildest form of hearing
impairment that can occur during exposure to a strong sound (Kryter,
1985). While experiencing TTS, the hearing threshold rises and a sound
must be stronger in order to be heard. At least in terrestrial mammals,
TTS can last from minutes or hours to (in cases of strong TTS) days.
For sound exposures at or somewhat above the TTS threshold, hearing
sensitivity in both terrestrial and marine mammals recovers rapidly
after exposure to the noise ends. Few data on sound levels and
durations necessary to elicit mild TTS have been obtained for 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).
For toothed whales exposed to single short pulses, the TTS
threshold appears to be, to a first approximation, a function of the
energy content of the pulse (Finneran et al., 2002, 2005). Given the
available data, the received level of a single seismic pulse (with no
frequency weighting) might need to be approximately 186 dB re 1
[mu]Pa\2\[middot]s (i.e.,
[[Page 28900]]
186 dB SEL or approximately 221-226 dB pk-pk) in order to produce
brief, mild TTS. Exposure to several strong seismic pulses that each
have received levels near 190 dB re 1 [mu]Pa (rms) (175-180 dB SEL)
might result in cumulative exposure of approximately 186 dB SEL and
thus slight TTS in a small odontocete, assuming the TTS threshold is
(to a first approximation) a function of the total received pulse
energy. The distances from the Endeavor's GI airguns at which the
received energy level (per pulse, flat-weighted) would be expected to
be >=175-180 dB SEL are the distances shown in the 190 dB re 1 [mu]Pa
(rms) column in Table 1 above (given that the rms level is
approximately 10 to 15 dB higher than the SEL value for the same
pulse). Seismic pulses with received levels >=175 to 180 dB SEL (190 dB
re 1 [mu]Pa (rms)) are expected to be restricted to radii no more than
150 m around the two GI airguns. The specific radius depends on the
depth of the water. For an odontocete closer to the surface, the
maximum radius with >= 190 dB 1 [mu]Pa (rms) would be smaller.
The above TTS information for odontocetes is derived from studies
on the bottlenose dolphin and beluga. There is no published TTS
information for other species of cetaceans. However, preliminary
evidence from harbor porpoise exposed to airgun sound suggests that its
TTS threshold may be lower (Lucke et al., 2007).
For baleen whales, there are no data, direct or indirect, on levels
or properties of sound required to induce TTS. The frequencies to which
baleen whales are most sensitive are lower than those for odontocetes,
and natural background noise levels at those low frequencies tend to be
higher. As a result, auditory thresholds of baleen whales within their
frequency band of best hearing are believed to be higher (less
sensitive) than are those of odontocetes at their best frequencies
(Clark and Ellison, 2004). From this, it is suspected that received
levels causing TTS onset may also be higher in baleen whales (Southall
et al., 2007). In any event, no cases of TTS are expected given three
considerations:
(1) Small size of the GI airgun source (90 in\3\ total volume);
(2) The strong likelihood that baleen whales would avoid the
approaching airguns (or vessel) before being exposed to levels high
enough for TTS to possibly occur; and
(3) The proposed mitigation measures.
In pinnipeds, TTS thresholds associated with exposure to brief
pulses (single or multiple) of underwater sound have not been measured.
Initial evidence from prolonged (non-pulse) exposures suggested that
some pinnipeds may incur TTS at somewhat lower received levels than do
small odontocetes exposed for similar durations (Kastak et al., 1999,
2005; Ketten et al., 2001; Au et al., 2000). The TTS threshold for
pulsed sounds has been indirectly estimated as being an SEL of
approximately 171 dB re 1 [micro]Pa\2\[middot]s (Southall et al.,
2007), which would be equivalent to a single pulse with received level
approximately 181-186 re 1 [mu]Pa (rms), or a series of pulses for
which the highest rms values are a few dB lower. Corresponding values
for California sea lions and northern elephant seals are likely to be
higher (Kastak et al., 2005).
A marine mammal within a radius of less than 100 m (328 ft) around
a typical large array of operating airguns might be exposed to a few
seismic pulses with levels of greater than or equal to 205 dB, and
possibly more pulses if the mammal moved with the seismic vessel. (As
noted above, most cetacean species tend to avoid operating airguns,
although not all individuals do so.) In addition, ramping up airgun
arrays, which is standard operational protocol for large airgun arrays,
should allow cetaceans to move away form the seismic source and to
avoid being exposed to the full acoustic output of the airgun array.
Even with a large airgun array, it is unlikely that the cetaceans would
be exposed to airgun pulses at a sufficiently high level for a
sufficiently long period to cause more than mild TTS, given the
relative movement of the vessel and the marine mammal. The potential
for TTS is much lower in this project. With a large array of airguns,
TTS would be most likely in any odontocetes that bow-ride or otherwise
linger near the airguns. While bow-riding, odontocetes would be at or
above the surface, and thus not exposed to strong pulses given the
pressure-release effect at the surface. However, bow-riding animals
generally dive below the surface intermittently. If they did so while
bow-riding near airguns, they would be exposed to strong sound pulses,
possibly repeatedly. If some cetaceans did incur TTS through exposure
to airgun sounds, this would very likely be mild, temporary, and
reversible.
To avoid the potential for injury, NMFS has determined that
cetaceans and pinnipeds should not be exposed to pulsed underwater
noise at received levels exceeding, respectively, 180 and 190 dB re 1
[mu]Pa (rms). As summarized above, data that are now available imply
that TTS is unlikely to occur unless odontocetes (and probably
mysticetes as well) are exposed to airgun pulses stronger than 180 dB
re 1 [mu]Pa (rms).
Permanent Threshold Shift--When PTS occurs, there is physical
damage to the sound receptors in the ear. In severe cases, there can be
total or partial deafness, while in other cases the animal has an
impaired ability to hear sounds in specific frequency ranges (Kryter,
1985).
There is no specific evidence that exposure to pulses of airgun
sound can cause PTS in any marine mammal, even with large arrays of
airguns. However, given the possibility that mammals close to an airgun
array might incur TTS, there has been further speculation about the
possibility that some individuals occurring very close to airguns might
incur PTS (Richardson et al., 1995). Single or occasional occurrences
of mild TTS are not indicative of permanent auditory damage.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals, but are assumed to be similar to those in humans and
other terrestrial mammals. PTS might occur at a received sound level at
least several decibels above that inducing mild TTS if the animal were
exposed to strong sound pulses with rapid rise time (see Appendix A(5)
of SIO's application). Based on data from terrestrial mammals, a
precautionary assumption is that the PTS threshold for impulse sounds
(such as airgun pulses as received close to the source) is at least 6
dB higher than the TTS threshold on a peak-pressure basis, and probably
>6 dB (Southall et al., 2007). On an SEL basis, Southall et al. (2007)
estimated that received levels would need to exceed the TTS threshold
by at least 15 dB for there to be risk of PTS. Thus, for cetaceans they
estimate that the PTS threshold might be an M-weighted SEL (for the
sequence of received pulses) of approximately 198 dB re 1
[mu]Pa\2\[middot]s (15 dB higher than the TTS threshold for an
impulse). Additional assumptions had to be made to derive a
corresponding estimate for pinnipeds, as the only available data on TTS
thresholds in pinnipeds pertain to non-impulse sound. Southall et al.
(2007) estimate that the PTS threshold could be a cumulative
Mpw-weighted SEL of approximately 186 dB 1
[mu]Pa\2\[middot]s in the harbor seal to impulse sound. The PTS
threshold for the California sea lion and northern elephant seal the
PTS threshold would probably be higher, given the higher TTS thresholds
in those species.
Southall et al. (2007) also note that, regardless of the SEL, there
is concern about the possibility of PTS if a cetacean or pinniped
receives one or more pulses with peak pressure exceeding 230 or 218 dB
re 1 [mu]Pa (3.2 bar [middot] m, 0-pk),
[[Page 28901]]
which would only be found within a few meters of the largest (600-
in\3\) airguns in the planned airgun array (Caldwell and Dragoset,
2000). A peak pressure of 218 dB re 1 [mu]Pa could be received somewhat
farther away; to estimate that specific distance, one would need to
apply a model that accurately calculates peak pressures in the near-
field around an array of airguns.
In the proposed project employing two GI airguns, marine mammals
are unlikely to be exposed to received levels of seismic pulses strong
enough to cause TTS, as they would need to be quite close to the GI
airguns for that to occur. Given the higher level of sound necessary to
cause PTS as compared with TTS, it is considerably less likely that PTS
could occur. A mammal would not be exposed to more than one strong
pulse unless it swam immediately alongside the GI airguns for a period
longer than the inter-pulse interval. Baleen whales generally avoid the
immediate area around operating seismic vessels, as do some other
marine mammals. The planned monitoring and mitigation measures,
including visual monitoring and shut downs of the airguns when mammals
are seen about to enter or within the exclusion zone (EZ), will further
reduce the probability of exposure of marine mammals to sounds strong
enough to induce PTS.
Non-auditory Physiological Effects--Non-auditory physiological
effects or injuries that theoretically might occur in marine mammals
exposed to strong underwater sound include stress, neurological
effects, bubble formation, resonance effects, and other types of organ
or tissue damage (Cox et al., 2006; Southall et al., 2007). Studies
examining such effects are limited. However, resonance (Gentry, 2002)
and direct noise-induced bubble formation (Crum et al., 2005) are not
expected in the case of an impulsive source like an airgun array. If
seismic surveys disrupt diving patterns of deep diving species, this
might perhaps result in bubble formation and a form of ``the bends,''
as speculated to occur in beaked whales exposed to sonar. However,
there is no specific evidence of this upon exposure to airgun pulses.
In general, little is known about the potential for seismic survey
sounds to cause auditory impairment or other physical effects in marine
mammals. Available data suggest that such effects, if they occur at
all, would presumably be limited to short distances of the sound source
and to activities that extend over a prolonged period. The available
data do not allow identification of a specific exposure level above
which non-auditory effects can be expected (Southall et al., 2007), or
any meaningful quantitative predictions of the numbers (if any) of
marine mammals that might be affected in those ways. Marine mammals
that show behavioral avoidance of seismic vessels, including most
baleen whales, some odontocetes, and some pinnipeds, are especially
unlikely to incur auditory impairment or non-auditory physical effects.
Also, the planned mitigation measures, including shut downs of the
airgun, would reduce any such effects that might otherwise occur.
Strandings and Mortality
Marine mammals close to underwater detonations of high explosives
can be killed or severely injured, and their auditory organs are
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995).
However, explosives are no longer used for marine seismic research or
commercial seismic surveys, and have been replaced entirely by airguns
or related non-explosive pulse generators. Airgun pulses are less
energetic and have slower rise times, and there is no specific evidence
that they can cause injury, death, or stranding even in the case of
large airgun arrays. However, the association of mass strandings of
beaked whales with naval exercises and, in one case, an L-DEO seismic
survey (Malakoff, 2002; Cox et al., 2006), has raised the possibility
that beaked whales exposed to strong ``pulsed'' sounds may be
especially susceptible to injury and/or behavioral reactions that can
lead to stranding (Hildebrand 2005; Southall et al., 2007). Appendix A
of Rice's application 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 hemorrahage or other forms of trauma;
(3) A physiological change such as a vestibular response leading to
a behavioral change or stress-induced hemorrahagic diathesis, leading
in turn to tissue damage; and
(4) Tissue damage directly from sound exposure, such as through
acoustically mediated bubble formation and growth or acoustic resonance
of tissues.
As noted in Rice's application, some of these mechanisms are
unlikely to apply in the case of impulse sounds. However, there are
increasing indications that gas-bubble disease (analogous to ``the
bends''), induced in super-saturated tissue by a behavioral response to
acoustic exposure, could be a pathologic mechanism for the strandings
and mortality of some deep diving cetaceans exposed to sonar. The
evidence for this remains circumstantial and associated with exposure
to naval mid-frequency sonar, not seismic surveys (Cox et al., 2006;
Southall et al., 2007).
Seismic pulses and mid-frequency sonar pulses are quite different,
and some mechanisms by which sonar sounds have been hypothesized to
affect beaked whales are unlikely to apply to airgun pulses. Sounds
produced by airgun arrays are broadband with most of the energy below 1
kHz. Typical military mid-frequency sonars operate at frequencies of 2-
10 kHz, generally with a relatively narrow bandwidth at any one time. A
further difference between seismic surveys and naval exercises is that
naval exercises can involve sound sources on more than one vessel.
Thus, it is not appropriate to assume that there is a direct connection
between the effects of military sonar and seismic surveys on marine
mammals. However, evidence that sonar pulses can, in special
circumstances, lead (at least indirectly) to physical damage and
mortality (Balcomb and Claridge, 2001; NOAA and USN, 2001; Jepson et
al., 2003; Fern[aacute]ndez et al., 2004, 2005a,b; Hildebrand, 2005;
Cox et al., 2006) suggests that caution is warranted when dealing with
exposure of marine mammals to any high-intensity pulsed sound.
There is no conclusive evidence of cetacean strandings or deaths at
sea as a result of exposure to seismic surveys, but a few cases of
strandings in the general area where a seismic survey was ongoing have
led to speculation concerning a possible link between seismic surveys
and strandings. Suggestions that there was a link between seismic
surveys and strandings of humpback whales in Brazil (Engel et al.,
2004) were not well founded based on available data (IAGC, 2004; IWC,
2006). 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 (Ewing) was operating a 20 airgun,
8,490 in\3\ array in the general area. The link between the stranding
and the seismic survey was inconclusive and not based on any physical
evidence (Hogarth, 2002; Yoder, 2002). Nonetheless, the Gulf of
California incident plus the beaked whale strandings near naval
exercises involving use of mid-frequency sonar
[[Page 28902]]
suggests a need for caution when conducting seismic surveys in areas
occupied by beaked whales until more is known about effects of seismic
surveys on those species (Hildebrand, 2005).
No injuries of beaked whales are anticipated during the proposed
study because of (1) the high likelihood that any beaked whales nearby
would avoid the approaching vessel before being exposed to high sound
levels, (2) the proposed monitoring and mitigation measures, including
avoiding submarine canyons, where deep diving species (like beaked
whales and sperm whales) may congregate, and (3) differences between
the sound sources operated by Rice and those involved in the naval
exercises associated with strandings.
Potential Effects of Other Acoustic Devices
Echosounder Signals
The Knudsen echosounder will be operated from the source vessel
during most of the proposed study. Sounds from the echosounder are
short pulses, occurring for up to 24 ms once every few seconds. Most of
the energy in the sound pulses is at 3.5 and 12 kHz, and the beam is
directed downward. The source level of the echosounder is expected to
be relatively low compared to the GI airguns. Kremser et al. (2005)
noted that the probability of a cetacean swimming through the area of
exposure when an echosounder emits a pulse is small, and if the animal
was in the area, it would have to pass the transducer at close range in
order to be subjected to sound levels that could cause TTS.
Marine mammal communications will not be masked appreciably by the
echosounder signals given their directionality and the brief period
when an individual mammal is likely to be within its beam. Furthermore,
in the case of most baleen whales, the signals do not overlap with the
predominant frequencies in the calls, which would avoid significant
masking.
Behavioral reactions of free-ranging marine mammals to echosounders
and other sound sources appear to vary by species and circumstance.
Observed reactions have included silencing and dispersal by sperm
whales (Watkins et al., 1985), increased vocalizations and no dispersal
by pilot whales (Rendell and Gordon, 1999), and the previously
mentioned beaked whales. During exposure to a 21 to 25 kHz whale-
finding sonar with a source level of 215 dB re 1 [mu]Pam, gray whales
showed slight avoidance (approximately 200 m) behavior (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).
During a previous low-energy seismic survey from the R/V Thomas G.
Thompson, several echosounders were in operation most of the time, and
a fathometer was also used during part of the survey. Many cetaceans
and small numbers of fur seals were seen by the observers aboard the
ship, but no specific information about echosounder effects (if any) on
mammals were obtained (Ireland et al., 2005). These responses (if any)
could not be distinguished from responses to the GI airguns (when
operating) and to the ship itself.
Captive bottlenose dolphins and a beluga whale exhibited changes in
behavior when exposed to 1 s pulsed sounds at frequencies of
approximately 30 kHz and to shorter broadband pulsed signals.
Behavioral changes typically involved what appeared to be deliberate
attempts to avoid the sound exposure (Schlundt et al., 2000; Finneran
et al., 2002; Finneran and Schlundt, 2004). The relevance of those data
to free-ranging odontocetes is uncertain, and in any case, the test
sounds were quite different in either duration or bandwidth as compared
with those from an echosounder.
Very few data are available on the reactions of pinnipeds to
echosounder sounds at frequencies similar to those used during seismic
operations. Hastie and Janik (2007) conducted a series of behavioral
response tests on two captive gray seals to determine their reactions
to the underwater operation of a 375 kHz multi-beam imaging sonar that
included significant signal components down to 6 kHz. Results indicated
that the two seals reacted to the sonar signal by significantly
increasing their dive durations. Based on observed pinniped responses
to other types of pulsed sounds, and the likely brevity of exposure to
the echosounder sounds, pinniped reactions are expected to be limited
to startle or otherwise brief responses of no lasting consequence to
the animals.
During the proposed 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. In the case of baleen whales,
the echosounder will operate at too high a frequency to have any
effect.
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 echosounder proposed for use is quite different than
sonars used for Navy operations. Pulse duration of the echosounder is
very short relative to naval sonars. Also, at any given location, an
individual marine mammal would be in the beam of the echosounder for
much less time given the generally downward orientation; Navy sonars
often use near-horizontally-directed sound.
Given the maximum source level of 211 dB re 1 [mu]Pam (rms), the
received energy level from a single pulse of duration 24 ms would be
approximately 195 dB re 1 [mu]Pa\2\[middot]s at 1 m, i.e., 211 dB + 10
log (0.024 s). As the TTS threshold for a cetacean receiving a single
non-impulse sound is 195 dB re 1 [mu]Pa\2\[middot]s and the anticipated
PTS threshold is 215 dB re 1 [mu]Pa\2\[middot]s (Southall et al.,
2007), it is very unlikely that an animal would ever come close enough
to the transducer to incur TTS (which would be fully recoverable), let
alone PTS. As noted by Burkhardt et al. (2007, 2008), cetaceans are
very unlikely to incur PTS from operation of scientific echosounders on
a ship that is underway.
For the harbor seal, the TTS threshold for non-impulse sounds is
approximately 183 dB re 1 [mu]Pa\2\[middot]s, as compared with
approximately 195 dB re 1 [mu]Pa\2\[middot]s in odontocetes (Kastak et
al., 2005; Southall et al., 2007). TTS onset occurs at higher received
energy levels in the California sea lion and northern elephant seal
than in the harbor seal. The received level for a harbor seal within
the echosounder beam 10 m below the ship would be approximately 191 dB
re 1 [mu]Pam (rms), assuming 40 dB of spreading loss over 100 m
(circular spreading). Given the narrow beam, only one pulse is likely
to be received by a given animal as the ship passes overhead. At 10 m,
the received energy level from a single pulse of duration 24 ms would
be approximately 175 dB re 1 [mu]Pa\2\[middot]s, i.e., 191 dB + 10 log
(0.024 s). Thus, a harbor seal would have to come very close to the
transducer in order to receive a single echosounder pulse with a
received energy level of >=183 dB re 1 [mu]Pa\2\[middot]s. Given the
intermittent nature of the signals and the narrow echosounder beam,
only a small fraction of the pinnipeds below (and close to) the ship
would receive a pulse as the ship passed overhead. Thus, it seems
unlikely that a pinniped would incur TTS, let alone PTS, is exposed to
a single pulse by the echosounder.
[[Page 28903]]
Sub-Bottom Profiler Signals
A SBP will be operated from the source vessel at all times during
the planned study. Sounds from the SBP are very short pulses, occurring
for 30 ms once every 0.5 to 1 s. The SBP will transmit a 0.5-12 kHz
swept pulse (or chirp). The source level of the SBP is expected to be
similar to or less than that of the Knudsen echosounder. Kremser et al.
(2005) noted that the probability of a cetacean swimming through the
area of exposure when a SBP emits a pulse is small--if the animal was
in the area, it would have to pass the transducer at close range in
order to be subjected to sound levels that could cause TTS.
Marine mammal communications will not be masked appreciably by the
SBP signals given their directionality and the brief period when an
individual mammal is likely to be within its beam.
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.
Therefore, behavioral responses are not expected unless marine mammals
are very close to the source.
It is unlikely that the SBP produces pulse levels strong enough to
cause hearing impairment or other physical injuries even in an animal
that is (briefly) in a position near the source. The SBP is usually
operated simultaneously with other higher-power acoustic sources. Many
marine mammals will move away in response to the approaching higher-
power sources or the vessel itself before the mammals would be close
enough for there to be any possibility of effects from the less intense
sounds from the SBP. In the case of mammals that do not avoid the
approaching vessel and its various sound sources, mitigation measures
that would be applied to minimize effects of other sources would
further reduce or eliminate any minor effects of the SBP.
Boomer Signals
The boomer will be operated from the source vessel at times during
the proposed study (see Acoustic Source Specifications above). Details
about this boomer are provided in Rice's IHA application, see above.
Sounds from the boomer are very short pulses, occurring for 0.1 ms once
every second. The boomer will transmit a 0.3 to 3 kHz pulse. The source
level of the boomer is similar to that of the Knudsen echosounder--212
dB re 1 [mu]Pam. If the animal was in the area, it would have to pass
the transducer at close range in order to be subjected to sound levels
that could cause TTS.
Marine mammal communications will not be masked appreciably by the
boomer signals given the directionality and brief period when an
individual mammal is likely to be within its beam.
Marine mammal behavioural reactions to other pulsed sound sources
are discussed above, and responses to the boomer are likely to be
similar to those for other pulsed sources if received at the same
levels. Behavioral responses are not expected unless marine mammals are
very close to the source.
It is unlikely that the boomer 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 boomer will
be operated simultaneously with the higher-power GI airguns. Many
marine mammals will move away in response to the approaching GI airguns
or the vessel itself before the mammals will move away in response to
the approaching GI airguns 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 boomer. In the case of mammals that do
not avoid the approaching vessel and its various sound sources,
mitigation measures that would be applied to minimize effects of other
sources would further reduce or eliminate any minor effects to the
boomer.
As stated above, NMFS is assuming that Level A harassment onset
corresponds to 180 and 190 dB re 1 [mu]Pa (rms) for cetaceans and
pinnipeds, respectively. The precautionary nature of these criteria is
discussed in Rice's application, including the fact that the minimum
sound level necessary to cause permanent hearing impairment is higher,
by a variable and generally unknown amount, than the level that induces
barely-detectable TTS and the level associated with the onset of TTS is
often considered to be a level below which there is no danger of
permanent damage. NMFS also assumes that cetaceans or pinnipeds exposed
to levels exceeding 160 re 1 [mu]Pa (rms) may experience Level B
harassment.
Estimated Take by Incidental Harassment
All anticipated takes would be ``takes by harassment,'' involving
temporary changes in behavior. The proposed monitoring and mitigation
measures are expected to minimize the possibility of injurious takes.
(However, as noted earlier and in Appendix A of Rice's application,
there is no specific information demonstrating that injurious ``takes''
would occur even in the absence of the planned monitoring and
mitigation measures.) The sections below describe methods to estimate
``take by harassment'', and present estimates of the numbers of marine
mammals that might be affected during the proposed seismic program in
the Northwest Atlantic Ocean. The estimates of ``take by harassment''
are based on (1) cetacean densities (numbers per unit area) obtained
during aerial surveys off New England during 2002 and 2004 by NMFS
Northeast Fisheries Science Center (NEFSC), and (2) estimates of the
size of the area where effects could potentially occur. Few, if any,
pinnipeds are expected to be encountered during the proposed survey in
the summer.
The following estimates are based on a consideration of the number
of marine mammals that might be disturbed appreciably by operations
with the GI airgun to be used during approximately 1,757 line km (1,092
mi) of surveys (including turns) off the New England coast. The
anticipated radii of influence of the other sound sources (i.e., SBP,
boomer system, and echosounder) are less than those for the GI airguns.
It is assumed that, during simultaneous operations of the GI airguns
and other sound sources, any marine mammals close enough to be affected
by the other sound sources would already be affected by the GI airguns.
However, whether or not the GI airguns are operating simultaneously
with the other sound sources, marine mammals are expected to exhibit no
more than short-term and inconsequential responses to the other sound
sources given their characteristics (e.g., narrow downward-directed
beam in the echosounder). Therefore, no additional allowance is
included for animals that could be affected by the other sound sources.
Extensive systematic aircraft and ship-based surveys have been
conducted for marine mammals offshore from New England (e.g., see
Palka, 2006). Those that were conducted in the proposed seismic survey
area were used for density estimates. Oceanographic conditions
influence the distribution and numbers of marine mammals present in the
study area, resulting in year-to-year variation in the distribution and
abundance of many marine mammal species. Thus, for some species the
densities derived from these surveys may not be representative of the
densities that will be encountered during the proposed seismic survey.
To provide some allowance for these uncertainties, ``maximum
estimates'' as
[[Page 28904]]
well as ``best estimates'' of the numbers potentially affected have
been derived. Best and maximum estimates are based on the average and
maximum estimates of densities calculated from the appropriate
densities reported by Palka (2006).
Table 4 of Rice's application gives the average and maximum
densities for each species of cetacean reported in the proposed survey
area off New England, corrected for effort, based on the densities as
described above. The densities from those studies had been corrected,
by the original authors, for both detectability bias and availability
bias. Detectability bias associated with diminishing sightability with
increasing lateral distance from the tracklines [[fnof](0)].
Availability bias refers to the fact that there is less-than-100-
percent probability of sighting an animal that is present along the
survey trackline, and it is measured by g(0).
It should be noted that the following estimates of ``takes by
harassment'' assume that the surveys will be undertaken and completed.
As is typical on offshore ship surveys, inclement weather, and
equipment malfunctions are likely to cause delays and may limit the
number of useful line kms of seismic operations that can be undertaken.
Furthermore, any marine mammal sightings within or near the designated
safety zones will result in the shut-down of seismic operations as a
mitigation measure. Thus, the following estimates of the numbers of
marine mammals potentially exposed to 160 dB sounds are precautionary,
and probably overestimate the actual numbers of marine mammals that
might be involved. These estimates assume that there will be no
weather, equipment, or mitigation delays, which is highly likely.
There is some uncertainty about the representativeness of the data
and the assumptions used in the calculations. However, the approach
used is believed to be the best available approach. Also, to provide
some allowance for these uncertainties ``maximum estimates'' as well as
``best estimates'' of the numbers potentially affected have been
derived. The estimated number of potential individuals exposed are
presented below based on the 160 dB re 1 [mu]Pa (rms) criterion for all
cetaceans and pinnipeds. It is assumed that a marine mammal exposed to
airgun at that received level might change their behavior sufficiently
to be considered ``taken by harassment.''
The number of different individuals that may be exposed to GI
airgun sounds with received levels =160 dB re 1 [mu]Pa (rms)
on one or more occasions was estimated by considering the total marine
area that would be within the 160-dB radius around the operating airgun
array on at least one occasion. The proposed seismic lines do not run
parallel to each other in close proximity, which minimizes the number
of times an individual mammal may be exposed during the survey. Table 5
of Rice's application shows the best and maximum estimates of the
number of marine mammals that could potentially be affected during the
seismic survey.
The number of different individuals potentially exposed to received
levels >=160 dB re 1 [micro]Pa (rms) was calculated by multiplying:
The expected species density, either ``mean'' (i.e., best
estimate) or ``maximum,'' times;
The anticipated area to be ensonified to that level during
GI airgun operations.
The area expected to be ensonified was determined by entering the
planned survey lines into a MapInfo Geographic Information System
(GIS), using the GIS to identify the relevant areas by ``drawing'' the
applicable 160 dB buffer around each seismic line (two GI airgun
buffer) and turns (one GI airgun buffer) (depending on water and tow
depth) and then calculating the total area within the buffers. Areas
where overlap occurred (because of intersecting lines) were included
only once to determine the area expected to be ensonified.
Applying the approach described above, approximately 2,877 km\2\
(1,111 mi\2\ ) would be within the 160 dB isopleth on one or more
occasions during the survey. This approach does not allow for
``turnover'' in the mammal populations in the study area during the
course of the studies. That might underestimate actual numbers of
individuals exposed, although the conservative distances used to
calculate the area may offset this. In addition, the approach assumes
that no cetaceans will move away or toward the trackline as the
Endeavor approaches in response to increasing sound levels prior to the
time the levels reach 160 dB. Another way of interpreting the estimates
that follow is that they represent the number of individuals that are
expected (in the absence of a seismic survey) to occur in the waters
that will be exposed to >=160 dB re 1 [mu]Pa (rms).
Table 3
[The estimates of the possible numbers of marine mammals exposed to sound levels greater than or equal to 160 dB
during Rice's proposed seismic survey off the coast of New England in August 2009. The proposed sound source is
two GI airguns. Received levels are expressed in dB re 1 [mu]Pa (rms) (averaged over pulse duration), consistent
with NMFS' practice. Not all marine mammals will change their behavior when exposed to these sound levels, but
some may alter their behavior when levels are lower (see text). See Tables 3-5 in Rice's application for further
detail.]
----------------------------------------------------------------------------------------------------------------
Number of Number of Approx. %
individuals individuals regional
Species exposed (best) exposed (max) population (best)
\1\ \1\ \2\
----------------------------------------------------------------------------------------------------------------
Mysticetes
North Atlantic right whale \3\ (Eubalaena glacialis)..... 1 1 0.31
Humpback whale (Megaptera novaeangliae).................. 2 57 0.02
Minke whale (Balaenoptera acutorostrata)................. 0 21 <0.01
Bryde's whale (Balaenoptera brydei)...................... 0 0 0
Sei whale (Balaenoptera borealis)........................ 0 0 0
Fin whale (Balaenoptera physalus)........................ 11 75 0.02
Blue whale (Balaenoptera musculus)....................... 0 0 0
Odontocetes
Sperm whale (Physeter macrocephalus)..................... 2 77 0.02
Pygmy sperm whale (Kogia breviceps)...................... 0 0 0
Dwarf sperm whale (Kogia sima)........................... 0 0 0
Cuvier's beaked whale (Ziphius cavirostris).............. 0 0 0
Northern bottlenose whale (Hyperodon ampullatus)......... 0 0 0
True's beaked whale (Mesoplodon mirus)................... 0 0 0
[[Page 28905]]
Gervais' beaked whale (Mesopldon europaeus).............. 0 0 0
Sowerby's beaked whale (Mesoplodon bidens)............... 0 0 0
Blainville's beaked whale (Mesoplodon densirostris)...... 0 0 0
Unidentified beaked whale................................ 0 2 N.A.
Bottlenose dolphin \3\ (Tursiops truncatus).............. 39 4,700 0.05
Pantropical spotted dolphin (Stenella attenuata)......... 0 0 0
Atlantic spotted dolphin (Stenella frontalis)............ 0 0 0
Spinner dolphins (Stenella longirostris)................. 0 0 0
Striped dolphin (Stenella coeruleoalba).................. 0 212 <0.01
Common dolphin\5\ (Delphinus sp.)........................ 349 3,189 0.17
White-beaked dolphin (Lagenorhynchus albirostris)........ 0 0 0
Atlantic white-sided dolphin\3\ (Lagenorhynchus acutus).. 0 0 0
Risso's dolphin (Grampus griseus)........................ 2 929 0.01
False killer whale (Pseudorca crassidens)................ 0 0 0
Killer whale (Orcinus orca).............................. 0 0 0
Long-finned pilot whale (Globicephala melas)............. N.A. N.A. <0.01
Short-finned pilot whale (Globicephala macrorhynchus).... N.A. N.A. <0.01
Unidentified pilot whale (Globicephala sp.).............. 10 1,101 <0.01
Harbor porpoise (Phocoena phocoena)...................... 0 0 0
Pinnipeds
Harbor seal \4\ (Phoca vitulina)......................... 10 N.A. 0.01
Gray seal (Halichoerus grypus)........................... 5 N.A. <0.01
Harp seal \4\ (Pagophilius groenlandicus)................ 0 0 0
Hooded seal (Cystophora cristata)........................ 0 0 0
----------------------------------------------------------------------------------------------------------------
N.A.--Data not available or species status was not assessed.
\1\ Best estimate and maximum estimates of exposure are from Table 5 of Rice's application. Best and maximum
density estimates are from Table 4 of Rice's application.
\2\ Regional population size estimates are from Table 2 (above) and Table 2 of Rice's application.
\3\ Species not sighted in the surveys used for density estimates, but that could occur in low densities in the
proposed survey area.
\4\ Species for which summer densities in the study area are unavailable, but could occur there in low numbers.
\5\ Not identified to species level.
Table 5 of Rice's application shows the best and maximum estimates
of the number of exposures and the number of individual marine mammals
that potentially could be exposed to greater than or equal to 160 dB re
1 [mu]Pa (rms) during the different legs of the seismic survey if no
animals moved away from the survey vessel.
The ``best estimate'' of the number of individual marine mammals
that could be exposed to seismic sounds with received levels greater
than or equal to 160 dB re 1 [micro]Pa (rms) (but below
Level A harassment thresholds) during the survey is shown in Table 5 of
Rice's application and Table 3 (shown above). That includes 1 North
Atlantic right (0.31 percent of the regional population), 2 humpback
(0.02 percent of the regional population), 11 fin (0.03 percent of the
regional population), and 2 sperm whales (0.02 percent of the regional
population), and no beaked whales. Based on the best estimates, most
(93 percent) of the marine mammals potentially exposed are dolphins.
The common dolphin and bottlenose dolphin are estimated to be the most
common species exposed to 160 dB re [mu]Pa (rms); the best take
estimates for those species are 349 (0.17 percent of the regional
population) and 39 (0.05 percent of the regional population),
respectively. Estimates for the other dolphin species that could be
exposed are lower (see Table 5 of Rice's application). In addition, it
is estimated that 10 harbor seals (0.01 percent) and 5 gray seals
(<0.01 percent) may be exposed to sound levels greater than or equal to
160 dB re 1 [mu]Pa (rms).
The ``maximum estimate'' column of Table 5 of Rice's application
shows an estimated total of 9,479 cetaceans exposed to seismic sounds
>=160 dB during the surveys. Those estimates are based on the highest
calculated density in any survey stratum; in this case, the stratum
with the highest density invariably was one of the areas where very
little of the proposed seismic survey will take place, i.e., Georges
Central or Shelf Central. In other words, densities observed in the
2002 and 2004 aerial surveys were lowest in the Georges West operation
area, where most of the proposed seismic surveys will take place.
Therefore, the numbers for which ``take authorization'' is requested,
given in the far right column of Table 5 of Rice's application, are the
best estimates. For three endangered species, the best estimates were
set at the species' mean group size. The North Atlantic right whale,
which was not sighted during the aerial surveys, could occur in the
survey area, and is usually seen individually (feeding aggregations are
not expected to occur in the study area). The humpback and sperm
whales, each of whose calculated best estimate was one, have a mean
group size of two.
Potential Effects on Marine Mammal Habitat
The proposed Rice seismic survey will not result in any permanent
impact on habitats used by marine mammals, or to the food sources they
use. The main impact issue associated with the proposed activity will
be temporarily elevated noise levels and the associated direct effects
on marine mammals, as
[[Page 28906]]
described above. The following sections briefly review effects of
airguns on fish and invertebrates, and more details are included in
Rice's application and associated EA.
Potential Effects on Fish and Invertebrates
One reason for the adoption of airguns as the standard energy
source for marine seismic surveys is that, unlike explosives, they have
not been associated with large-scale fish kills. However, existing
information on the impacts of seismic surveys on marine fish
populations is very limited (see Appendix C of Rice's application).
There are three types of potential effects on fish and invertebrates
from exposure to seismic surveys: (1) Pathological, (2) physiological,
and (3) behavioral. Pathological effects involve lethal and temporary
or permanent sub-lethal injury. Physiological effects involve temporary
and permanent primary and secondary stress responses, such as changes
in levels of enzymes and proteins. Behavioral effects refer to
temporary and (if they occur) permanent changes in exhibited behavior
(e.g., startle and avoidance behavior). The three categories are
interrelated in complex ways. For example, it is possible that certain
physiological and behavioral changes potentially could lead to an
ultimate pathological effect on individuals (i.e., mortality).
The specific received sound levels at which permanent adverse
effects to fish potentially could occur are little studied and largely
unknown. Furthermore, the available information on the impacts of
seismic surveys on marine fish is from studies of individuals or
portions of a population; there have been no studies at the population
scale. Thus, available information provides limited insight on possible
real-world effects at the ocean or population scale. This makes drawing
conclusions about impacts on fish problematic because ultimately, the
most important aspect of potential impacts relates to how exposure to
seismic survey sound affects marine fish populations and their
viability, including their availability to fisheries.
The following sections provide a general synopsis of available
information on the effects of exposure to seismic and other
anthropogenic sound as relevant to fish. The information comprises
results from scientific studies of varying degrees of rigor plus some
anecdotal information. Some of the data sources may have serious
shortcomings in methods, analysis, interpretation, and reproducibility
that must be considered when interpreting their results (see Hastings
and Popper, 2005). Potential adverse effects of the program's sound
sources on marine fish are then noted.
Pathological Effects--The potential for pathological damage to
hearing structures in fish depends on the energy level of the received
sound and the physiology and hearing capability of the species in
question (see Appendix C of Rice's application). For a given sound to
result in hearing loss, the sound must exceed, by some specific 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 is unknown; however, it likely depends 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 valid papers with proper
experimental methods, controls, and careful pathological investigation
implicating sounds produced by actual seismic survey airguns with
adverse anatomical effects. One such study indicated anatomical damage
and the second indicated TTS in fish hearing. The anatomical case is
McCauley et al. (2003), who found that exposure to airgun sound caused
observable anatomical damage to the auditory maculae of pink snapper
(Pagrus auratus). This damage in the ears had not been repaired in fish
sacrificed and examined almost two months after exposure. On the other
hand, Popper et al. (2005) documented only TTS (as determined by
auditory brainstem response) in two of three fish species from the
Mackenzie River Delta. This study found that broad whitefish
(Coreogonus nasus) that received a sound exposure level of 177 dB re 1
[micro]Pa\2\[middot]s showed no hearing loss. During both studies, the
repetitive exposure to sound was greater than would have occurred
during a typical seismic survey. However, the substantial low-frequency
energy produced by the airgun arrays [less than approximately 400 Hz in
the study by McCauley et al. (2003) and less than approximately 200 Hz
in Popper et al. (2005)] likely did not propagate to the fish because
the water in the study areas was very shallow (approximately 9 m in the
former case and less than 2 m in the latter). Water depth sets a lower
limit on the lowest sound frequency that will propagate (the ``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 and invertebrates would be
expected to be within a few meters of the seismic source. Numerous
other studies provide examples of no fish mortality upon exposure to
seismic sources (Falk and Lawrence, 1973; Holliday et al., 1987; La
Bella et al., 1996; Santulli et al., 1999; McCauley et al., 2000a,b,
2003; Bjarti, 2002; Hassel et al., 2003; Popper et al., 2005).
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. Saetre and Ona (1996) applied a `worst-case
scenario' mathematical model to investigate the effects of seismic
energy on fish eggs and larvae. They concluded that mortality rates
caused by exposure to seismic surveys are so low, as compared to
natural mortality rates, that the impact of seismic surveying on
recruitment to a fish stock must be regarded as insignificant.
Physiological Effects--Physiological effects refer to cellular and/
or biochemical responses of fish to acoustic stress. Such stress
potentially could affect fish populations by increasing mortality or
reducing reproductive success. Primary and secondary stress responses
of fish after exposure to seismic survey sound appear to be temporary
in all studies done to date (Sverdrup et al., 1994; McCauley et al.,
2000a, 2000b). The periods necessary for the biochemical changes to
return to normal are variable, and depend on numerous aspects of the
biology of the species and of the sound stimulus (see Appendix C of
Rice's application).
Summary of Physical (Pathological and Physiological) Effects--As
indicated in the preceding general discussion,
[[Page 28907]]
there is a relative lack of knowledge about the potential physical
(pathological and physiological) effects of seismic energy on marine
fish and invertebrates. Available data suggest that there may be
physical impacts on egg, larval, juvenile, and adult stages at very
close range. Considering typical source levels associated with
commercial seismic arrays, close proximity to the source would result
in exposure to very high energy levels. Whereas egg and larval stages
are not able to escape such exposures, juveniles and adults most likely
would avoid it. In the case of eggs and larvae, it is likely that the
numbers adversely affected by such exposure would not be that different
from those succumbing to natural mortality. Limited data regarding
physiological impacts on fish and invertebrates indicate that these
impacts are short term and are most apparent after exposure at close
range.
The proposed seismic program for 2009 is predicted to have
negligible to low physical effects on the various stags of fish and
invertebrates for its relatively short duration (approximately 15 days)
and unique survey lines extent. Therefore, physical effects of the
proposed program on fish and invertebrates would not be significant.
Behavioral Effects--Behavioral effects include changes in the
distribution, migration, mating, and catchability of fish populations.
Studies investigating the possible effects of sound (including seismic
survey sound) on fish behavior have been conducted on both uncaged and
caged individuals (Chapman and Hawkins, 1969; Pearson et al., 1992;
Santulli et al., 1999; Wardle et al., 2001; Hassel et al., 2003).
Typically, in these studies fish exhibited a sharp ``startle'' response
at the onset of a sound followed by habituation and a return to normal
behavior after the sound ceased.
The existing body of information on the impacts of seismic survey
sound on marine invertebrates is very limited. However, there is some
unpublished and very limited evidence of the potential for adverse
effects on invertebrates, thereby justifying further discussion and
analysis of this issue. The three types of potential effects of
exposure to seismic surveys on marine invertebrates are pathological,
physiological, and behavioral. Based on the physical structure of their
sensory organs, marine invertebrates appear to be specialized to
respond to particle displacement components of an impinging sound field
and not to the pressure component (Popper et al., 2001; see Appendix D
of Rice's application).
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.
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 D of Rice's application.
Pathological Effects--In water, lethal and sub-lethal injury to
organisms exposed to seismic survey sound could 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 single GI gun 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; however, very
few specific data are available on levels of seismic signals that might
damage these animals. This premise is based on the peak pressure and
rise/decay time characteristics of seismic airgun arrays currently in
use around the world.
Some studies have suggested that seismic survey sound has a limited
pathological impact on early developmental stages of crustaceans
(Pearson et al., 1994; Christian et al., 2003; DFO, 2004). However, the
impacts appear to be either temporary or insignificant compared to what
occurs under natural conditions. Controlled field experiments on adult
crustaceans (Christian et al., 2003, 2004; DFO, 2004) and adult
cephalopods (McCauley et al., 2000a,b) exposed to seismic survey sound
have not resulted in any significant pathological impacts on the
animals. It has been suggested that exposure to commercial seismic
survey activities has injured giant squid (Guerra et al., 2004), but
there is no evidence to support such claims.
Physiological Effects--Physiological effects refer mainly to
biochemical responses by marine invertebrates to acoustic stress. Such
stress potentially could affect invertebrate populations by increasing
mortality or reducing reproductive success. Any primary and secondary
stress responses (i.e., changes in haemolymph levels of enzymes,
proteins, etc.) of crustaceans after exposure to seismic survey sounds
appear to be temporary (hours to days) in studies done to date (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. Change in behavior could potentially affect such aspects as
reproductive success, distribution, susceptibility to predation, and
catchability by fisheries. Studies investigating the possible
behavioral effect of exposure to seismic survey sound on crustaceans
and cephalopods have been conducted on both uncaged and caged animals.
In some cases, invertebrates exhibiting 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 and catch
rate (Andriguietto-Filho et al., 2005). 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).
Because of the reasons noted above and the nature of the proposed
activities, the proposed operations are not expected to cause
significant impacts on habitats that could cause significant or long-
term consequences for individual marine mammals or their populations or
stocks. Similarly, any effects to food sources are expected to be
negligible.
Subsistence Activities
There is no subsistence hunting for marine mammals in the waters
off of the
[[Page 28908]]
coast of New England that implicates MMPA Section 101(a)(5)(D).
Proposed Mitigation and Monitoring
Mitigation and monitoring measures proposed to be implemented for
the proposed seismic survey have been developed and refined during
previous NSF-funded seismic studies and associated environmental
assessments (EAs), IHA applications, and IHAs. The mitigation and
monitoring measures described herein represent a combination of
procedures required by past IHAs for other similar projects and on
recommended best practices in Richardson et al. (1995), Pierson et al.
(1998), and Weir and Dolman (2007). The measures are described in
detail below.
Mitigation measures proposed for the survey include:
(1) Speed or course alteration, provided that doing so will not
compromise operational safety requirements;
(2) GI airgun shut-down procedures;
(3) GI airgun power-downs procedures (including turns);
(4) GI airgun ramp-up procedures;
(5) Procedures for species of particular concern, e.g., emergency
shut-down procedures if a North Atlantic right whale is sighted at any
distance, and concentrations of humpback, fin, sperm, blue, and/or sei
whales will be avoided.
The thresholds for estimating take are also used in connection with
proposed mitigation. The radii in Table 2 (above) will be used as shut-
down criteria for the other sound sources (single GI airgun, watergun,
and boomer), all of which have lower source levels than the two GI
airguns.
Vessel-Based Visual Monitoring
Marine Mammal Visual Observers (MMVOs) will be based aboard the
seismic source vessel and will watch for marine mammals near the vessel
during daytime GI airgun operations and during start-ups of airguns at
night. MMVOs will also watch for marine mammals near the seismic vessel
for at least 30 minutes prior to the start of airgun operations and
after an extended shut-down of the airguns. When feasible MMVOs will
also make observations during daytime periods when the seismic system
is not operating for comparison of sighting rates and animal behavior
with vs. without GI airgun operations. Based on MMVO observations, the
GI airgun will be shut-down (see below) when marine mammals are
detected within or about to enter a designated EZ. The EZ is an area in
which a possibility exists of adverse effects on animal hearing or
other physical effects (see Table 1 above for the isopleths as they
correspond to the relevant EZs). The MMVOs will continue to maintain
watch to determine when the animal(s) are outside the safety radius,
and airgun operations will not resume until the animal has left that
zone. The predicted distances for the safety radius are listed
according to the sound source, water depth, and received isopleths in
Table 1.
MMVOs will be appointed by the academic institution conducting the
research cruise, with NMFS Office of Protected Resources concurrence.
During seismic operations off the coast of New England, a total of
three MMVOs are planned to be aboard the Endeavor. At least one MMVO
will monitor the EZ during daytime GI airgun operations and any
nighttime startups of the airguns. MMVOs will normally work in daytime
shifts of 4 hour duration or less. The vessel crew will also be
instructed to assist in detecting marine mammals and implementing
mitigation measures (if practical). Before the start of the seismic
survey the crew will be given additional instruction regarding how to
do so.
The Endeavor is a suitable platform from which MMVOs will conduct
marine mammal observations. Two locations are likely as observation
stations onboard the Endeavor; observations may take place from the
flying bridge approximately 11 m (36 ft) above sea level or the bridge
(8.2 m or 27 ft).
During the daytime, the MMVO(s) will scan the area around the
vessel systematically with standard equipment such as reticle
binoculars (e.g., 7x50), optical range finders, and with the naked eye.
During darkness, night vision devices (NVDs) will be available, when
required. Vessel lights and/or NVDs are useful in sightings some marine
mammals at the surface within a short distance from the ship (within
the EZ for the two GI airguns). The MMVOs will be in wireless
communication with ship's officers on the bridge and scientists in the
vessel's operations laboratory, so they can advise promptly of the need
for avoidance maneuvers or GI airgun shut-down.
Speed or Course Alteration--If a marine mammal is detected outside
the EZ, but is likely to enter based on its position and the relative
movement of the vessel and animal, then if safety and scientific
objectives allow, the vessel speed and/or course may be adjusted to
minimize the likelihood of the animal entering the EZ. Typically,
during seismic operations, major course and speed adjustments are often
impractical when towing long seismic streamers and large source arrays,
but are possible in this case because only two GI airguns and a
relatively short streamer will be used.
Shut-down Procedures--The operating airgun(s) will be shut-down if
a marine mammal is detected within or approaching the EZ for the GI
airgun source. Following a shut-down, GI airgun activity will not
resume until the marine mammal is outside the EZ for the two GI
airguns. The animal will be considered to have cleared the EZ if it:
Is visually observed to have left the EZ;
Has not been seen within the EZ for 10 min in the case of
species with shorter dive durations--small odontocetes and pinnipeds;
and
Has not been seen within the EZ for 15 min in the case of
species with longer dive durations--mysticetes and large odontocetes,
including sperm, pygmy sperm, dwarf sperm, killer, and beaked whales;
The 10 and 15 min periods specified above are shorter than would be
used in a large-source project given the small 180 and 190 dB (rms)
radii for the two GI airguns.
Power-down Procedures--A power-down involves decreasing the number
of GI airguns in use from two to one. During turns between successive
survey lines, a single GI airgun will be operated. The continued
operation of one airgun is intended to alert marine mammals to the
presence of the survey vessel in the area.
Ramp-up Procedures--A ramp-up procedure will be followed when the
GI airguns begin operating after a specified period without GI airgun
operations. It is proposed that, for the present cruise, this period
would be approximately five minutes. This period is based on the 180 dB
radii for the GI airguns (see Table 1 above) in relation to the planned
speed of the Endeavor while shooting.
Ramp-up will begin with a single GI airgun (45 in\3\). The second
GI airgun (45 in\3\) will be added after five min. During ramp-up, the
MMVOs will monitor the EZ, and if marine mammals are sighted, a shut-
down will be implemented as though both GI airguns were operational.
If the complete EZ has not been visible for at least 30 min prior
to the start of operations in either daylight or nighttime, ramp-up
will not commence. If one GI airgun has been operating, 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
[[Page 28909]]
approaching seismic vessel by the sounds from the single GI airgun and
have an opportunity to move away if they choose. A ramp-up from a shut-
down may occur at night, but only in intermediate-water depths, where
the safety radius is small enough to be visible. Ramp-up of the GI
airguns will not be initiated if a marine mammal is sighted within or
near the applicable EZs during the day or close to the vessel at night.
Procedures for Species of Particular Concern--Several species of
concern could occur in the study area. Special mitigation procedures
will be used for these species as follows:
(1) The GI airguns will be shut-down if a North Atlantic right
whale is sighted at any distance from the vessel;
(2) Concentrations or groups of humpback, fin, sperm, blue, and/or
sei whales will be avoided.
A typical ``concentration or group'' of whales for this survey
consists of three or more individuals visually sighted. If a
concentration or group of the whale species listed above is sighted and
does not appear to be traveling (i.e. feeding, socializing), then Rice
will avoid them by implementing a power-down or shut-down, delay
seismic operations, or move to another area for seismic data
acquisition. If the concentration or group of whales appears to be
traveling, then Rice will power-down or shut-down seismic operations
and wait for approximately 30 min for the individuals to move out of
the study area before re-initiating seismic operations. Rice and NSF
will coordinate their planned marine mammal monitoring program
associated with the seismic survey off the coast of New England with
applicable U.S. agencies (e.g., NMFS), and will comply with their
requirements.
Proposed Reporting
MMVO Data and Documentation
MMVOs 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. They will also
provide information needed to order a shut-down of the seismic source
when a marine mammal is within or near the EZ.
When a sighting is made, the following information about the
sighting will be recorded:
(1) Species, group size, and age/size/sex categories (if
determinable); behavior when first sighted and after initial sighting;
heading (if consistent), bearing, and distance from seismic vessel;
sighting cue; apparent reaction to the seismic source or vessel (e.g.,
none, avoidance, approach, paralleling, etc.); and behavioral pace.
(2) Time, location, heading, speed, activity of the vessel, sea
state, visibility, and sun glare.
The data listed (time, location, etc.) will also be recorded at the
start and end of each observation watch, and during a watch whenever
there is a change in one or more of the variables.
All observations, as well as information regarding seismic source
shut-down, will be recorded in a standardized format. Data accuracy
will be verified by the MMVOs at sea, and preliminary reports will be
prepared during the survey and summaries forwarded to the Rice's shore
facility and to NSF weekly or more frequently. MMVO observations will
provide the following information:
(1) The basis for decisions about shutting-down airgun arrays.
(2) Information needed to estimate the number of marine mammals
potentially ``taken by harassment.''
(3) Data on the occurrence, distribution, and activities of marine
mammals in the area where the seismic study is conducted.
(4) Data on the behavior and movement patterns of marine mammals
seen at times with and without seismic activity.
A report will be submitted to NMFS within 90 days after the end of
the cruise. The report will describe the operations that were conducted
and sightings of marine mammals near the operations. The report will be
submitted to NMFS, providing full documentation of methods, results,
and interpretation pertaining to all monitoring. The 90-day report will
summarize the dates and locations of seismic operations, and all marine
mammal sightings (dates, times, locations, activities, associated
seismic survey activities). The report will also include estimates of
the amount and nature of potential ``take'' of marine mammals by
harassment or in other ways.
All injured or dead marine mammals (regardless of cause) will be
reported to NMFS as soon as practicable. The report should include
species or description of animal, condition of animal, location, time
first found, observed behaviors (if alive) and photo or video, if
available.
Endangered Species Act (ESA)
Under Section 7 of the ESA, NSF has begun consultation with the
NMFS, Office of Protected Resources, Endangered Species Division on
this proposed seismic survey. NMFS will also consult on the issuance of
an IHA under section 101(a)(5)(D) of the MMPA for this activity.
Consultation will be concluded prior to a determination on the issuance
of the IHA.
National Environmental Policy Act (NEPA)
NSF has prepared a draft EA titled ``Marine Seismic Survey in the
Northwest Atlantic Ocean, August 2009.'' NSF's draft EA incorporates an
``Environmental Assessment (EA) of a Marine Geophysical Survey by the
R/V Endeavor in the Northwest Atlantic Ocean, August 2009,'' prepared
on behalf of NSF and Rice by LGL Limited, Environmental Research
Associates. NMFS will either adopt NSF's EA or conduct a separate NEPA
analysis, as necessary, prior to making a determination on the issuance
of the IHA.
Preliminary Determinations
NMFS has preliminarily determined that the impact of conducting the
low-energy marine seismic survey in the Northwest Atlantic Ocean may
result, at worst, in a temporary modification in behavior (Level B
harassment) of small numbers of marine mammals. Further, this activity
is expected to result in a negligible impact on the affected species or
stocks. The provision requiring that the activity not have an
unmitigable impact on the availability of the affected species or stock
for subsistence uses is not implicated for this proposed action.
For reasons stated previously in this document, this determination
is supported by:
(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 40 m (131
ft) in deep water, 60 m (197 ft) in intermediate depths, and 296 m (971
ft) in shallow water when the two GI airguns are in use from the vessel
to be exposed to levels of sound (180 dB) believed to have even a
minimal chance of causing PTS;
(3) The fact that pinnipeds would have to closer than 10 m (33 ft)
in deep water, 15 m (49 ft) in intermediate depths, and 147 m (482 ft)
in shallow water when the two GI airguns are in use from the vessel to
be exposed to levels of sound (190 dB) believed to have even a minimal
chance of causing PTS;
(4) The fact that cetaceans would have to be closer than 23 m (76
ft) in deep
[[Page 28910]]
water, 35 m (115 ft) in intermediate depths, and 150 m (492 ft) in
shallow water when the single GI airgun is in use from the vessel to be
exposed to levels (180 dB) believed to have even a minimal chance of
causing PTS;
(5) The fact that pinnipeds would have closer than 8 m (26 ft) in
deep water, 12 m (39 ft) in intermediate depths, and 95 m (312 ft) in
shallow water when the single GI airgun is in use from the vessel to be
exposed to levels (190 dB) believed to have even a minimal chance of
causing PTS.
(6) The fact that marine mammals would have to be closer than 350 m
(1,148 ft) in deep water, 525 m (1,722 ft) at intermediate depths, and
1,029 m (3,376 ft) in shallow water when the two GI airguns are in use
from the vessel to be exposed to levels of sound (160 dB) believed to
have even a minimal chance at causing TTS;
(7) The fact that marine mammals would have to be closer than 220 m
(721 ft) in deep water, 330 m (1,083 ft) at intermediate depths, and
570 m (1,870 ft) in shallow water when the single GI airgun is in use
from the vessel to be exposed to levels of sound (160 dB) believed to
have even a minimal chance at causing TTS; and
(8) The likelihood that marine mammal detection ability by trained
observers is high at those short distances from the vessel and will
trigger shut-downs to prevent injury, and due to the implementation of
the other mitigation measures such as ramp-ups. As a result, no take by
injury or death is anticipated, and the potential for temporary or
permanent hearing impairment is very low and will be avoided through
the incorporation of the proposed mitigation measures.
While the number of marine mammals potentially incidentally
harassed will depend on the distribution and abundance of marine
mammals in the vicinity of the survey activity, the number of potential
harassment takings is estimated to be small, less than a few percent of
any of the estimated population sizes, and has been mitigated to the
lowest level practicable through incorporation of the measures
mentioned previously in this document.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
issue an IHA to Rice for conducting a low-energy marine seismic survey
in the Northwest Atlantic Ocean in August, 2009, provided the
previously mentioned mitigation, monitoring, and reporting requirements
are incorporated.
Dated: June 12, 2009.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. E9-14380 Filed 6-17-09; 8:45 am]
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