[Federal Register Volume 73, Number 101 (Friday, May 23, 2008)]
[Notices]
[Pages 30076-30093]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-11546]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XG64
Small Takes of Marine Mammals Incidental to Specified Activities;
Low-Energy Marine Seismic Survey in the Northeast Pacific Ocean, June-
July 2008
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 University of Texas,
Institute of Geophysics (UTIG) for an Incidental Harassment
Authorization (IHA) to take marine mammals incidental to conducting a
low-energy marine seismic survey in the Northeast Pacific Ocean during
June-July, 2008. Pursuant to the Marine Mammal Protection Act (MMPA),
NMFS is requesting comments on its proposal to issue an IHA to UTIG to
incidentally take, by Level B harassment only, several species of
marine mammals during the aforementioned activity.
DATES: Comments and information must be received no later than June
23, 2008.
ADDRESSES: Comments on the application should be addressed to P.
Michael Payne, Chief, Permits, Conservation and Education Division,
Office of Protected Resources, National Marine Fisheries Service, 1315
East-West Highway, Silver Spring, MD 20910-3225. The mailbox address
for providing email comments is [email protected]. NMFS is not
responsible for e-mail comments sent to addresses other than the one
provided here. Comments sent via e-mail, including all attachments,
must not exceed a 10-megabyte file size.
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#applications.
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 U.S.
citizens who engage in a specified activity (other than commercial
fishing) within a specified geographical region if certain findings are
made and either regulations are issued or, if the taking is limited to
harassment, a notice of a proposed authorization is provided to the
public for review.
Authorization shall be granted if NMFS finds that the taking will
have a negligible impact on the species or stock(s), will not have an
unmitigable adverse impact on the availability of the species or
stock(s) for subsistence uses (where relevant), and if the permissible
methods of taking and requirements pertaining to the mitigation,
monitoring, and reporting of such takings are set forth. NMFS has
defined ``negligible impact'' in 50 CFR 216.103 as ''...an impact
resulting from the specified activity that cannot be reasonably
expected to, and is not reasonably likely to, adversely affect the
species or stock through effects on annual rates of recruitment or
survival.''
Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the U.S. can apply for an authorization to
incidentally take small numbers of marine mammals by harassment. 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].
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS
review of an application followed by a 30-day public notice and comment
period on any proposed authorizations for the incidental harassment of
marine mammals. Within 45 days of the close of the comment period, NMFS
must either approve or deny the authorization.
Summary of Request
On March 4, 2008, NMFS received an application from UTIG for the
taking, by Level B harassment only, of several
[[Page 30077]]
species of marine mammals incidental to conducting, with research
funding from the National Science Foundation (NSF), a bathymetric and
seismic survey program approximately 100 km (approximately 62 mi) off
the Oregon coast in the Northeast Pacific Ocean during June-July, 2008.
The purpose of the research program is to investigate the methane vent
systems that exist offshore Oregon. These systems release methane by
active venting at the seafloor. They can also form relatively high
concentrations of methane hydrate in the sub seafloor, up to 150 m (492
ft) below the sea bottom. The goal is to image these systems in detail
to understand how vent structure directs methane from the subsurface to
be vented into the oceans, or potentially stored in the subsurface as
methane hydrate. Methane is a significant greenhouse gas, and methane
release from vents or from hydrate has a significant potential to
affect the Earth's climate. Hydrates are also a potentially significant
source of energy. Also included in the research is the use of a
multibeam echosounder and sub-bottom profiler.
Description of the Proposed Activity
The seismic survey will involve one vessel, the R/V Thomas G.
Thompson (Thompson), which is scheduled to depart from Seattle,
Washington on June 30, 2008 and return on July 19, 2008. The exact
dates of the activities may vary by a few days because of weather
conditions, scheduling, repositioning, streamer operations and
adjustments, GI airguns deployment, or the need to repeat some lines if
data quality is substandard. The proposed ultra-high resolution 3-
dimensional (3-D) seismic surveys around the methane vent systems of
Hydrate Ridge, will take place off the Oregon coast in the northeastern
Pacific Ocean. The overall area within which the seismic surveys will
occur is located between approximately 44[deg] and 45[deg] N. and
124.5[deg] and 126[deg] W (Figure 1 in the application). The surveys
will occur approximately 100 km (approximately 62 mi) offshore from
Oregon in water depths between approximately 650 and 1,200 m (2,132 and
3,936 ft), entirely within the Exclusive Economic Zone (EEZ) of the
U.S.
The seismic survey will image the subsurface structures that
control venting. The vent systems control whether the methane is
directly released into the ocean and atmosphere or stored in methane
hydrate. Methane hydrate storage has the potential for rapid
dissociation and release into the ocean or atmosphere. The subsurface
structure that will be imaged will determine the mechanisms involved in
methane venting. The results will be applicable to the numerous vent
systems that exist on continental margins worldwide. The data will also
be used to design observatories that can monitor and assess the methane
fluxes and mechanisms of methane release that operate on Hydrate Ridge.
The Thompson will deploy two low-energy Generator-Injector (GI)
airguns (guns) as an energy source (with a discharge volume of 40-60
in\3\ for each gun or a total of 80-120 in\3\) , and a P-Cable system.
The 12 m (39.5 ft) long P-Cable system is supplied by Northampton
Oceanographic Center in the U.K. The towed system will consist of at
least 12 streamers (and possibly up to 24) spaced approximately 12.5 m
(41 ft) apart and each containing 11 hydrophones, all summed to a
single channel. The energy to the GI guns is compressed air supplied by
compressors on board the source vessel. As the GI guns are towed along
the survey lines, the P-Cable system will receive the returning
acoustic signals.
The seismic program will consist of three survey grids: two of the
surveys each cover a 15 km2 area and the third covers a 25 km\2\ (see
Figure 1 in UTIG's application). The line spacing within the three
survey grids will either be 75 m (246 ft) (if 12 streamers are used) or
150 m (492 ft) (if 24 streamers are used). The total line km to be
surveyed in the grids at the 75 m spacing is 975 km (605.8 mi),
including turns. Water depths at the seismic survey locations range
from 650 to 1,200 m (2132 to 3936 ft). Most (92 percent) of the survey
will take place over intermediate (100-1,000 m) water depths; the
remaining 8 percent will be in water deeper than 1,000 m. If time
permits, an additional 300 line km will be surveyed along the outside
edges of the three grids. The GI guns are expected to operate for a
total of approximately 150 hours during the cruise. There will be
additional seismic operations associated with equipment testing, start-
up, and repeat coverage of any areas where initial data quality is sub-
standard.
In addition to the operations of the two GI guns and P-cable
system, a Simrad EM300 30 kHz multibeam echosounder, and a Knudsen 12
kHz 320BR sub-bottom profiler will be used during the proposed cruise.
Vessel Specifications
The Thompson has a length of 83.5 m (274 ft), a beam of 16 m (52.5
ft), and a maximum draft of 5.8 m (19 ft). The ship is powered by twin
360[deg]-azimuth stern thrusters a single 3,000-hp DC motor and a
water-jet bow thruster powered by a 1,600-hp motor. The motors are
driven by up to three 1,500-kW and three 715-kW generators; normal
operations use two 1,500-kW and one 750-kW generator, but this changes
with ship speed, sea state, and other variables. An operation speed of
6.5 km/h (3.5 knots) will be used during seismic acquisition. When not
towing seismic survey gear, the Thompson cruises at 22.2 km/h (12
knots) and has a maximum speed of 26.9 km/h (14.5 knots). It has a
normal operating range of approximately 24,400 km (8,264 mi).
Acoustic Source Specifications
Seismic Airguns
The vessel Thompson will tow two GI guns and a P-Cable system of 12
to 24, 12 m long streamers containing hydrophones along predetermined
survey grids. Seismic pulses will be emitted at intervals of 3.5 s,
which corresponds to a shot interval of approximately 6.3 m (20.7 ft)
at a speed of 3.5 knots (6.5 km/h). The generator chamber of a GI gun,
the one responsible for introducing the sound pulse into the ocean, is
40-60 in3. The second injector chamber (40-60 in3) injects air into the
previously-generated bubble to maintain its shape and does not
introduce more sound into the water. The two 40-60 in3 GI guns will be
towed 29 m (95.1 ft) behind the Thompson, at a depth of 1.5-3 m (4.9-
9.8 ft). The dominant frequency components are 0-188 Hz.
The sound pressure field of two 105 in\3\ GI guns has been modeled
by the Lamont-Doherty Earth Observatory (L-DEO) of Columbia University
in relation to distance and direction from the GI guns. The model does
not allow for bottom interactions and is most directly applicable to
close distances and/or deep water. Because the L-DEO model is for a
pair of larger GI guns with a total discharge of up to 210 in\3\, the
values overestimate the distances for two GI guns with a discharge of
up to 120 in3, as planned for use during the proposed study. This
source, which is directed downward, was found to have an output (0-
peak) of 237 dB re 1 microPam.
The root mean square (rms) received levels that are used as impact
criteria for marine mammals are not directly comparable to the peak or
peak to peak values normally used to characterize source levels of
airgun arrays. The measurement units used to describe airgun sources,
peak or peak-to-peak decibels, are always higher than the rms decibels
referred to in biological literature. A measured received level of 160
dB rms in the far field would
[[Page 30078]]
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.
Sub-bottom Profiler
The Thompson will utilize a Simrad EM300 30-kHz Multibeam
Echosounder (MBES) as the primary bottom-mapping echosounder during the
cruise. The Simrad EM300 transducer is hull-mounted within a transducer
pod that is located midship. The system's normal operating frequency is
approximately 30 kHz. The transmit fan-beam is split into either three
or nine narrower beam sectors with independent active steering to
correct for vessel yaw. Angular coverage is 36 degrees (in Extra Deep
Mode, for use in water depths 3,000 to 6,000 m) or 150 degrees (in
shallower water). The total angular coverage of 36 or 150 degrees
consists of the 3 or 9 beams transmitted at slightly different
frequencies. The sectors are frequency coded between 30 and 34 kHz and
they are transmitted sequentially at each ping. Except in very deep
water where the total beam is 36 x 1, the composite fan beam will
overlap slightly if the vessel yaw is less than the fore-aft width of
the beam (1,2, or 4, respectively). Achievable swath width on a flat
bottom will normally be approximately 5x the water depth. The maximum
source level is 237 dB re 1 microPam (rms) (Hammerstand, 2005).
In deep water (500-3,000 m) a pulse length of 5 ms is normally used. At
intermediate depths (100-1,000 m), a pulse length of 2 ms is used, and
in shallow water (<300 m), a pulse length of 0.7 ms is used. The ping
rate is mainly limited by the round trip travel time in the water up to
a ping rate of 10 pings/s in shallow water.
The Thompson will also utilize the Knudsen Engineering Model 320BR
sub-bottom profiler, which is a dual-frequency echosounder designed to
operate at 3.5 and/or 12 kHz. It is used to provide data about the
sedimentary features that occur below the sea floor. The energy from
the sub-bottom profiler is directed downward (in an 80-degree cone) via
a 12 kHz transducer (EDO 323B) or a 3.5 kHz array of 16 ORE 137D
transducers in a 4 x 4 arrangement. The maximum power output of the
320BR is 10 kilowatts for the 3.5 kHz section and 2 kilowatts for the
12 kHz section.
The pulse length for the 3.5 kHz section of the 320BR is 0.8-24 ms,
controlled by the system operator in regards to water depth and
reflectivity of the bottom sediments, and will usually be 12 or 24 ms
in this survey. The system produces one sound pulse and then waits for
its return before transmitting again. Thus, the pulse interval is
directly dependent upon water depth, and in this survey the interval is
estimated to be every 4.5-8 sec. Using the Sonar Equations and assuming
100 percent efficiency in the system (impractical in real world
applications), the source level for the 320BR is calculated to be 211
dB re 1 microPa-m. In practice, the system is rarely operated above 80
percent power level.
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''. NMFS believes that to avoid permanent
physiological damage (Level A Harassment), cetaceans and pinnipeds
should not be exposed to pulsed underwater noise at received levels
exceeding, respectively, 180 and 190 dB re 1 microPa (rms). NMFS also
assumes that cetaceans or pinnipeds exposed to levels exceeding 160 dB
re 1 microPa (rms) may experience Level B Harassment.
Received sound levels have been modeled by L-DEO for a number of
airgun configurations, including one 45-in\3\ GI gun, in relation to
distance and direction from the airgun(s). The model does not allow for
bottom interactions and is most directly applicable to deep water.
Based on the modeling, estimates of the maximum distances from the GI
gun where sound levels of 190, 180, and 160 dB re 1 microPa (rms) are
predicted to be received in deep (>1000-m, 3280-ft) water are 8, 23,
and 220 m (26.2, 75.5, and 721.8 ft), respectively and 12, 35, and 330
m (39.4, 115, and 1,082.7 ft), respectively for intermediate water
depths (100-1000m, 328-3,280 ft). Because the model results are for a
2.5-m (8.2-ft) tow depth, the above distances slightly underestimate
the distances for the 45-in\3\ GI gun towed at 4-m (13-ft) depth.
Empirical data concerning the 180- and 160- dB distances have been
acquired based on measurements during the acoustic verification study
conducted by L-DEO in the northern Gulf of Mexico from 27 May to 3 June
2003 (Tolstoy et al. 2004). Although the results are limited, the data
showed that radii around the airguns where the received level would be
180 dB re 1 microPa (rms) 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 (328-
3,280 ft) and <100 m (328 ft). The proposed survey will occur in depths
650-1,200 m (2,132-3,936 ft), so the correction factors for the latter
are not relevant here.
The empirical data indicate that, for deep water (>1,000 m, 3,280
ft), the L-DEO model tends to overestimate the received sound levels at
a given distance (Tolstoy et al., 2004). However, to be precautionary
pending acquisition of additional empirical data, it is proposed that
safety radii during airgun operations in deep water will be the values
predicted by L-DEO's model (above). Therefore, the assumed 180- and
190-dB radii are 69 m and 20 m (226.3 and 65.6 ft), respectively.
Empirical measurements were not conducted for intermediate depths
(100-1,000 m, 328-3,280 ft). 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 104 m and 30 m (341.1 and 98.4
ft), respectively.
The GI guns will be shut down immediately when cetaceans or
pinnipeds are detected within or about to enter the measured 180-dB
(rms) or 190-dB (rms) radius, respectively.
Description of Marine Mammals in the Activity Area
Thirty-two marine mammal species, including 19 odontocete (dolphins
and small and large toothed whales) species, seven mysticete (baleen
whales) species, five pinniped species, and the sea otter,
[[Page 30079]]
may occur or have been documented to occur in the marine waters off
Oregon and Washington, excluding extralimital sightings or strandings
(Table 1 here). Six of the species that may occur in the project area
are listed under the U.S. Endangered Species Act (ESA) as endangered,
including sperm, humpback, blue, fin, sei, and North Pacific right
whales. In addition, the southern resident killer whale stock is also
listed as endangered, but is unlikely to be seen in offshore waters of
Oregon. The threatened Steller sea lion could also occur in the project
area. However, the threatened northern sea otter is only known to occur
in coastal waters and is not expected in the project area (the sea
otter is under the jurisdiction of the U.S. Fish and Wildlife Service.
Gray whales are also not expected in the project area because their
occurrence off Oregon is limited to very shallow, coastal waters. The
California sea lion, Steller sea lion, and harbor seal are also mainly
coastal and are not expected at the survey locations. Information on
habitat and abundance of the species that may occur in the study area
are given in Table 1 below. Vagrant ringed seals, hooded seals, and
ribbon seals have been sighted or stranded on the coast of California
(see Mead, 1981; Reeves et al., 2002) and presumably passed through
Oregon waters. A vagrant beluga was seen off the coast of Washington
(Reeves et al., 2002).
The six species of marine mammals expected to be most common in the
deep pelagic or slope waters of the project area, where most of the
survey sites are located, include the Pacific white-sided dolphin,
northern right whale dolphin, Risso's dolphin, short-beaked common
dolphin, Dall's porpoise, and northern fur seal (Green et al., 1992,
1993; Buchanan et al., 2001; Barlow, 2003; Carretta et al., 2006).
The sperm, pygmy sperm, mesoplodont species, Baird's beaked, and
Cuvier's beaked whales and the northern elephant seal are considered
pelagic species, but are generally uncommon in the waters near the
survey 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 UTIG's application.
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Species Habitat Abundance\1\ Rqstd Take
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Mysticetes ............................... .................... ..................
North Pacific right whale (Eubalaena Inshore, occasionally offshore N.A.\2\ 0
japonica) *
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Humpback whale (Megaptera Mainly nearshore waters and 1391 1
novaeangliae) * banks
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Minke whale (Balaenoptera Pelagic and coastal 1015 1
acutorostrata)
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Sei whale (Balaenoptera borealis) * Primarily offshore, pelagic 56 0
----------------------------------------------------------------------------------------------------------------
Fin whale (Balaenoptera physalus) * Continental slope, mostly 3279 1
pelagic
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Blue whale (Balaenoptera musculus) * Pelagic and coastal 1744 0
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Odontocetes ............................... .................... ..................
Sperm whale (Physeter macrocephalus) Usually pelagic and deep seas 1233 2
*
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Pygmy sperm whale (Kogia breviceps) Deep waters off the shelf 247 2
----------------------------------------------------------------------------------------------------------------
Dwarf sperm whale (Kogia sima) Deep waters off the shelf N.A. 0
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Cuvier's beaked whale (Ziphius Pelagic 1884 0
cavirostris)
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Baird's beaked whale (Berardius Pelagic 228 1
bairdii)
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Blainville's beaked whale (Mesoplodon Slope, offshore 1247 \3\ 0
densirostris)
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Hubb's beaked whale (Mesoplodon Slope, offshore 1247 \3\ 0
carlhubbsi)
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Stejneger's beaked whale (Mesoplodon Slope, offshore 1247 \3\ 0
stejnegeri)
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Mesoplodon sp. (Unidentified) Slope, offshore 1247 1
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Offshore bottlenose dolphin (Tursiops Offshore, slope 5,065 0
truncatus)
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Striped dolphin (Stenella Off continental shelf 13,934 0
coeruleoalba)
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Short-beaked common dolphin Shelf and pelagic, seamounts 449,846 7
(Delphinus delphis)
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Pacific white-sided dolphin Offshore, slope 59,274 6
(Lagenorhynchus obliquidens)
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Northern right whale dolphin Slope, offshore waters 20,362 5
(Lissodelphis borealis)
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Risso's dolphin (Grampus griseus) Shelf, slope, seamounts 16,066 3
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False killer whale (Pseudorca Pelagic, occasionally inshore N.A. 0
crassidens)
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Killer whale (Orcinus orca) Widely distributed 466 (Offshore) 1
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[[Page 30080]]
Short-finned pilot whale Mostly pelagic, high-relief 304 0
(Globicephala macrorhynchus) topography
----------------------------------------------------------------------------------------------------------------
Harbor porpoise (Phocoena phocoena) Coastal and inland waters 39,586 (OR/WA) 0
----------------------------------------------------------------------------------------------------------------
Dall's porpoise (Phocoenoides dalli) Shelf, slope, offshore 99,517 47
----------------------------------------------------------------------------------------------------------------
Pinnipeds ............................... .................... ..................
Northern fur seal (Callorhinus Pelagic, offshore 688,028 \2\ 19
ursinus)
----------------------------------------------------------------------------------------------------------------
California sea lion (Zalophus Coastal, shelf 237,000-244,000 NA
californianus californianus)
----------------------------------------------------------------------------------------------------------------
Northern elephant seal (Mirounga Coastal, pelagic when migrating 101,000 (CA) 2
angustirostris)
----------------------------------------------------------------------------------------------------------------
Table 1. Species expected to be encountered (and potentially harassed) during UTIG's NE Pacific Ocean cruise.
N.A. B Data not available or species status was not assessed.
* Species are listed as threatened or endangered under the Endangered Species Act.
\1\ Abundance given for U.S., Eastern North Pacific, or California/Oregon/Washington Stock, whichever is
included in the 2005 U.S. Pacific Marine Mammal Stock Assessments (Carretta et al. 2006), unless otherwise
stated.
\2\ Angliss and Outlaw (2005).
\3\ All mesoplodont whales
Potential Effects of Airguns
The effects of sounds from airguns might include one or more of the
following: tolerance, masking of natural sounds, behavioral
disturbance, and temporary or permanent hearing impairment or non-
auditory physical or physiological effects (Richardson et al., 1995;
Gordon et al., 2004). Given the small size of the GI guns planned for
the proposed project, effects are anticipated to be considerably less
than would be the case with a large array of airguns. It is very
unlikely that there would be any cases of temporary or, especially,
permanent hearing impairment or any significant non-auditory physical
or physiological effects. Also, behavioral disturbance is expected to
be limited to relatively short distances.
Tolerance
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
For a summary of the characteristics of airgun pulses, see Appendix A
of UTIG's application. However, it should be noted that most of the
measurements of airgun sounds that have been reported concerned sounds
from larger arrays of airguns, whose sounds would be detectable
considerably farther away than the two GI guns planned for use in the
proposed project.
Numerous other 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 (e) of UTIG's application). That is
often true even in cases when the pulsed sounds appear to be readily
audible to the animals based on measured received levels and the
hearing sensitivity of that 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 and small odontocetes seem to be more tolerant of
exposure to airgun pulses than are baleen whales. Given the relatively
small, low-energy airgun source planned for use in this project, NMFS
expects mammals to tolerate being closer to this source than for a
larger airgun source typical of most seismic surveys. Mysticetes,
odontocetes, pinnipeds and sea otters have all been seen commonly by
observers aboard vessels conducting small-source seismic surveys,
indicating some degree of tolerance of sounds from small airgun sources
(e.g., Calambokidis et al., 2002; Haley and Koski, 2004; Holst et al.,
2005a; Ireland et al., 2005; MacLean and Koski, 2005; see also ``site
survey'' portions of Stone, 2003 and Stone and Tasker, 2006).
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
very few specific data on this matter. Some whales are known to
continue calling in the presence of seismic pulses. Their calls can be
heard between the seismic pulses (e.g., Richardson et al., 1986;
McDonald et al., 1995; Greene et al., 1999; Nieukirk et al., 2004;
Smultea et al., 2004). Although there has been one report that sperm
whales cease calling when exposed to pulses from a very distant seismic
ship (Bowles et al., 1994), a recent study reports that sperm whales
off northern Norway continued calling in the presence of seismic pulses
(Madsen et al., 2002c). Similar reactions have also been shown during
recent work in the Gulf of Mexico (Tyack et al., 2003; Smultea et al.,
2004). Given the small source planned for use here, 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 smaller odontocete
cetaceans, given the intermittent nature of seismic pulses and the
relatively low source level of the airgun to be used here. Dolphins and
porpoises are commonly heard calling while airguns are operating
(Gordon et al., 2004; Smultea et al., 2004; Holst et al., 2005a,b).
Also, the sounds important to small odontocetes are predominantly at
much higher frequencies than are airgun sounds. Masking effects, in
general, are discussed further in Appendix A (d) of UTIG'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). If a marine mammal responds to an underwater sound by
changing its behavior or moving a small
[[Page 30081]]
distance, the response may or may not rise to the level of harassment,
let alone affect the stock or the species as a whole. Alternatively, if
a sound source displaces marine mammals from an important feeding or
breeding area, effects on the stock or species could potentially be
more than negligible. 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. This practice potentially
overestimates the numbers of marine mammals that are affected in some
biologically-important manner.
The sound criteria used to estimate how many marine mammals might
be disturbed to some biologically-important degree by a seismic program
are based on behavioral observations during studies of several species.
However, information is lacking for many species. Detailed studies have
been done on humpback, gray, and bowhead whales and ringed seals. Less
detailed data are available for some other species of baleen whales,
sperm whales, and small toothed whales. Most of those studies have
focused on the impacts resulting from the use of much larger airgun
sources than those planned for use in the present 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 (e) of UTIG'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 determined that
received levels of pulses in the 160-170 dB re 1 microPa (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 recent
studies, reviewed in Appendix A (e) of UTIG's application, have shown
that some species of baleen whales, notably bowheads and humpbacks, at
times show strong avoidance at received levels lower than 160-170 dB re
1 microPa (rms). Reaction distances would be considerably smaller
during the present project, in which the 160-dB radius is predicted to
be approximately 0.22 or 0.33 km (0.14 or 0.21 mi), as compared with
several kilometers when a large array of airguns is operating.
Responses of humpback whales to seismic surveys have been studied
during migration and on the summer feeding grounds, and there has also
been discussion of effects on the Brazilian wintering grounds. McCauley
et al. (1998, 2000) 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 microPa m. McCauley et al. (1998) documented that
avoidance reactions began at 5-8 km (3.1-5 mi) from the array, and that
those reactions kept most pods approximately 3-4 km (1.9-2.5 mi) from
the operating seismic boat. McCauley et al. (2000) noted localized
displacement during migration of 4-5 km (2.5-3.1 mi) by traveling pods
and 7-12 km (4.3-7.5 mi) by cow-calf pairs. Avoidance distances with
respect to the single airgun were smaller but consistent with the
results from the full array in terms of received sound levels. Mean
avoidance distance from the airgun corresponded to a received sound
level of 140 dB re 1 microPa (rms); that was the level at which
humpbacks started to show avoidance reactions to an approaching airgun.
The standoff range, i.e., the closest point of approach of the whales
to the airgun, corresponded to a received level of 143 dB re 1 microPa
(rms). The initial avoidance response generally occurred at distances
of 5-8 km (3.1-5 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 100-400 m (328-1,312 ft), where
the maximum received level was 179 dB re 1 microPa (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 microPa on an
approximate rms basis. Malme et al. (1985) conclude that there was no
clear evidence of avoidance, despite the possibility of subtle effects,
at received levels up to 172 re 1 microPa (approximately rms).
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,
subject to alternative explanations (IAGC 2004), and not consistent
with results from direct studies of humpbacks exposed to seismic
surveys in other areas and seasons. After allowance for data from
subsequent years, there was ``no observable direct correlation''
between strandings and seismic surveys (IWC 2007:236).
Results from bowhead whales show that responsiveness of baleen
whales to seismic surveys can be quite variable depending on the
activity (migrating vs. feeding) of the whales. 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, where received sound levels were on the order of
130 dB re 1 microPa (rms) (Miller et al., 1999; Richardson et al.,
1999). However, more recent research on bowhead whales (Miller et al.,
2005a) corroborates earlier evidence that, during the summer feeding
season, bowheads are not as sensitive to seismic sources. In summer,
bowheads typically begin to show avoidance reactions at a received
level of about 160-170 dB re 1 microPa (rms) (Richardson et al., 1986;
Ljungblad et al., 1988; Miller et al., 1999). There are no data on the
reactions of wintering bowhead whales to seismic surveys. See Appendix
A (e) of UTIG's application for more information regarding bowhead
whale reactions to airguns.
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
[[Page 30082]]
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 microPa 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 and on observations of Western Pacific gray whales feeding off
Sakhalin Island, Russia (Johnson et al., 2007).
Various species of Balaenoptera (blue, fin, sei, and minke whales)
have occasionally been reported in areas ensonified by airgun pulses.
Sightings by observers on seismic vessels off the U.K. from 1997 to
2000 suggest that, at times of good sightability, numbers of rorquals
seen are similar when airguns are shooting and not shooting (Stone,
2003). Although individual species did not show any significant
displacement in relation to seismic activity, all baleen whales
combined were found to remain significantly further from the airguns
during shooting compared with periods without shooting (Stone, 2003;
Stone and Tasker, 2006). In a study off Nova Scotia, Moulton and Miller
(2005) found little or no difference in sighting rates 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.
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 despite intermittent seismic exploration and much ship
traffic in that area for decades (Appendix A in Malme et al., 1984).
Bowhead whales continued to travel to the eastern Beaufort Sea each
summer despite seismic exploration in their summer and autumn range for
many years (Richardson et al., 1987). In any event, the brief exposures
to sound pulses from the present small 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, a systematic study on sperm
whales has been done (Jochens and Biggs, 2003; Tyack et al., 2003;
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; Bain and
Williams, 2006; Holst et al., 2006; Stone and Tasker, 2006; Moulton and
Miller, 2005).
Seismic operators and marine mammal observers sometimes 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 limited avoidance of seismic vessels operating large airgun
systems. However, some dolphins seem to be attracted to the seismic
vessel and floats, and some ride the bow wave of the seismic vessel
even when large arrays of airguns are firing. 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 (Goold,
1996; Calambokidis and Osmek, 1998; Stone, 2003). In most cases, the
avoidance radii for delphinids appear to be small, on the order of 1 km
(0.62 mi) or less.
The beluga may be a species that (at least at times) shows long-
distance avoidance of seismic vessels. Aerial surveys during seismic
operations in the southeastern Beaufort Sea recorded much lower
sighting rates of beluga whales within 10-20 km (6.2-12.4 mi) of an
active seismic vessel. These results were consistent with the low
number of beluga sightings reported by observers aboard the seismic
vessel, suggesting that some belugas might be avoiding the seismic
operations at distances of 10-20 km (6.2-12.4 mi) (Miller et al.,
2005a). Similarly, captive bottlenose dolphins and beluga whales
exhibit changes in behavior when exposed to strong pulsed sounds
similar in duration to those typically used in seismic surveys
(Finneran et al., 2000, 2002, 2005; Finneran and Schlundt, 2004).
However, the animals tolerated high received levels of sound (pk-pk
level >200 dB re 1 microPa) before exhibiting aversive behaviors.
Results for porpoises depend on species. Dall's porpoises seem
relatively tolerant of airgun operations (MacLean and Koski, 2005; Bain
and Williams, 2006), whereas the limited 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 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. In most
cases, the whales do not show strong avoidance, and they continue to
call (see Appendix A of UTIG's application for review). However,
controlled exposure experiments in the Gulf of Mexico indicate that
foraging effort is apparently somewhat reduced upon exposure to airgun
pulses from a seismic vessel operating in the area, and there may be a
delay in diving to foraging depth.
There are no specific data on the behavioral reactions of beaked
whales to seismic surveys. Most beaked whales tend to avoid approaching
vessels of other types (Wursig et al., 1998). They may also dive for an
extended period when approached by a vessel (Kasuya, 1986). It is
likely that these beaked whales would normally show strong avoidance of
an approaching seismic vessel, but this has not been documented
explicitly.Odontocete reactions to large arrays of airguns are variable
and, at least for delphinids and some porpoises, seem to be confined to
a smaller radius than has been observed for mysticetes (see Appendix A
of UTIG's application for more information). Behavioral reactions of
most odontocetes to the small GI gun source to be used here are
expected to be very localized.
Pinnipeds - Pinnipeds are not likely to show a strong avoidance
reaction to the two GI guns that will be used. Visual monitoring from
seismic vessels, usually employing larger sources, has shown only
slight (if any) avoidance of airguns by pinnipeds, and only slight (if
any) changes in behavior (see Appendix A (e) of UTIG's application).
Ringed seals frequently do not avoid the area within a few hundred
meters of operating airgun arrays (Harris et al., 2001; Moulton and
Lawson, 2002; Miller et al., 2005a). However, initial telemetry work
suggests that avoidance and other behavioral reactions by two other
species of seals to small airgun sources may at times be stronger than
evident to date from visual studies of pinniped reactions to airguns
(Thompson et al., 1998). Even if reactions of any pinnipeds that might
be encountered in the present study area are as strong as those evident
in the telemetry study, reactions are expected to be confined to
relatively small distances and durations, with no long-
[[Page 30083]]
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 (e) of UTIG's application.
Hearing Impairment and Other Physical Effects
Temporary or permanent hearing impairment is a possibility when
marine mammals are exposed to very strong sounds, but there has been no
specific documentation of this for marine mammals exposed to sequences
of airgun pulses. Current NMFS policy regarding exposure of marine
mammals to high-level sounds is that cetaceans and pinnipeds should not
be exposed to impulsive sounds of 180 and 190 dB re 1 microPa (rms),
respectively (NMFS, 2000). Those criteria have been used in defining
the safety (shut-down) radii planned for the proposed seismic survey.
The precautionary nature of these criteria is discussed in Appendix A
(f) of UTIG'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 temporary threshold shift (TTS) (which NMFS' criteria
are based on) 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 is presently 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 permanent threshold
shift (PTS) thresholds, differences in the acoustic frequencies to
which different marine mammal groups are sensitive, and other relevant
factors.
Because of the small size of the airgun source in this project (two
40-60 in\3\ GI gun), alongwith the planned monitoring and mitigation
measures, there is little likelihood that any marine mammals will be
exposed to sounds sufficiently strong to cause hearing impairment.
Several aspects of the planned monitoring and mitigation measures for
this project are designed to detect marine mammals occurring near the
GI guns (and multibeam echosounder and sub-bottom profiler), and to
avoid exposing them to sound pulses that might, at least in theory,
cause hearing impairment. In addition, many cetaceans are likely to
show some avoidance of the area with high received levels of airgun
sound (see above). 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 present project given the small size of
the source, the brief duration of exposure of any given mammal, and the
planned 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) - 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. 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 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.
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
microPa\2\s (i.e., 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 175-180 dB SEL might
result in 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 Thompson's GI guns at which the received
energy level (per pulse) would be expected to be [gteqt]175-180 dB SEL
are the distances shown in the 190 dB re 1 microPa (rms) column in
Table 1 of UTIG's application (given that the rms level is
approximately 10-15 dB higher than the SEL value for the same pulse).
Seismic pulses with received energy levels [gteqt]175-180 dB SEL (190
dB re 1 microPa (rms)) are expected to be restricted to radii no more
than 69-104 m (226.3-341.1 ft) around the two GI guns. The specific
radius depends on the depth of the water. For an odontocete closer to
the surface, the maximum radius with [gteqt]175-180 dB SEL or
[gteqt]190 dB re 1 microPa (rms) would be smaller. Such levels would be
limited to distances within tens of meters of the small GI guns source
to be used in this project.
For baleen whales, direct or indirect data do not exist on levels
or properties of sound thatare required to induce TTS. The frequencies
to which baleen whales are most sensitive are lower than those to which
odontocetes are most sensitive, and natural background noise levels at
those low frequencies tend to be higher. As a result, auditory
thresholds of baleen whales within their frequency band of best hearing
are believed to be higher (less sensitive) than are those of
odontocetes at their best frequencies (Clark and Ellison, 2004). From
this, it is suspected that received levels causing TTS onset may also
be higher in baleen whales. In any event, no cases of TTS are expected
given three considerations: (1) the low abundance of baleen whales
expected in the planned study areas; (2) the strong likelihood that
baleen whales would avoid the approaching airguns (or vessel) before
being exposed to levels high enough for there to be any possibility of
TTS; and (3) the mitigation measures that are proposed to be
implemented.
In pinnipeds, TTS thresholds associated with exposure to brief
pulses (single or multiple) of underwater sound have not been measured.
Initial evidence from prolonged exposures suggests 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; cf. Au et al., 2000). The TTS threshold for pulsed
sounds has been indirectly estimated as being an SEL of about 171 dB re
microPa\2\s (Southall et al., 2007), which would be equivalent
to about 181-186 dB re 1 microPa (rms). Corresponding values for
California sea lions and northern elephant seals are likely to be
higher (Kastak et al., 2005).
To avoid injury, NMFS has determined that cetaceans and pinnipeds
should not be exposed to
[[Page 30084]]
pulsed underwater noise at received levels exceeding, respectively, 180
and 190 dB re 1 microPa (rms). Those sound levels were not considered
to be the levels above which TTS might occur. Rather, they were the
received levels above which, in the view of a panel of bioacoustics
specialists convened by NMFS before TTS measurements for marine mammals
started to become available, one could not be certain that there would
be no injurious effects, auditory or otherwise, to marine mammals. 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 microPa (rms).
Permanent Threshold Shift (PTS) - When PTS occurs, there is
physical damage to the sound receptors in the ear. In some 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.
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. Single or occasional occurrences of mild TTS are not
indicative of permanent auditory damage in terrestrial mammals.
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 (f)
of UTIG's application). The specific difference between the PTS and TTS
thresholds has not been measured for marine mammals exposed to any
sound type. However, 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
more than 6 dB.
On an SEL basis, Southall et al. (2007) estimate 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 SEL of about 198 dB re 1 microPa\2\.s. Additional
assumptions had to be made to derive a corresponding estimate for
pinnipeds. Southall et al. (2007) estimate that the PTS threshold could
be an SEL of about 186 dB re 1 microPa\2\s in the harbor seal;
for the California sea lion and northern elephant seal the PTS
threshold would probably be higher. Southall et al. (2007) also not
that, regardless of the SEL, there is concern about the possibility of
PTS if a cetacean or pinniped received one or more pulses with peak
pressure exceeding 230 or 218 dB 1 microPa (peak).
In the proposed project employing two 40 to 60-in\3\ GI guns,
marine mammals are highly unlikely to be exposed to received levels of
seismic pulses strong enough to cause TTS, as they would probably need
to be within a few tens of meters of the GI guns for that to occur.
Given the higher level of sound necessary to cause PTS, it is even less
likely that PTS could occur. In fact, even the levels immediately
adjacent to the GI guns may not be sufficient to induce PTS, especially
since a mammal would not be exposed to more than one strong pulse
unless it swam immediately alongside the GI guns 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 and sea turtles. The planned monitoring and mitigation
measures, including visual monitoring and shut downs of the GI guns
when mammals are seen within or about to enter the ``safety radii'' or
exclusion zone (EZ), will minimize the already-minimal 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. However, studies examining such effects are limited.
If any such effects do occur, they would probably be limited to unusual
situations when animals might be exposed at close range for unusually
long periods, when the sound is strongly channeled with less-than-
normal propagation loss, or when dispersal of the animals is
constrained by shorelines, shallows, etc. Airgun pulses, because of
their brevity and intermittence, are less likely to trigger resonance
or bubble formation than are more prolonged sounds. It is doubtful that
any single marine mammal would be exposed to strong seismic sounds for
time periods long enough to induce physiological stress.
Until recently, it was assumed that diving marine mammals are not
subject to the bends or air embolism. This possibility was first
explored at a workshop (Gentry [ed.], 2002) held to discuss whether the
stranding of beaked whales in the Bahamas in 2000 (Balcomb and
Claridge, 2001; NOAA and USN, 2001) might have been related to bubble
formation in tissues caused by exposure to noise from naval sonar.
However, this link could not be confirmed. Jepson et al. (2003) first
suggested a possible link between mid-frequency sonar activity and
acute chronic tissue damage that results from the formation in vivo of
gas bubbles, based on the beaked whale stranding in the Canary Islands
in 2002 during naval exercises. Fernandez et al. (2005a) showed those
beaked whales did indeed have gas bubble-associated lesions, as well as
fat embolisms. Fernandez et al. (2005b) also found evidence of fat
embolism in three beaked whales that stranded 100 km (62 mi) north of
the Canaries in 2004 during naval exercises. Examinations of several
other stranded species have also revealed evidence of gas and fat
embolisms (Arbelo et al., 2005; Jepson et al., 2005a; Mendez et al.,
2005). Most of the afflicted species were deep divers. There is
speculation that gas and fat embolisms may occur if cetaceans ascend
unusually quickly when exposed to aversive sounds, or if sound in the
environment causes the destablization of existing bubble nuclei
(Potter, 2004; Arbelo et al., 2005; Fernandez et al., 2005a; Jepson et
al., 2005b; Cox et al., 2006). Even if gas and fat embolisms can occur
during exposure to mid-frequency sonar, there is no evidence that that
type of effect occurs in response to airgun sounds.
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 be limited to short distances and probably to projects
involving large arrays of airguns. However, the available data do not
allow for 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 other physical effects. Also,
the planned mitigation measures, including shut downs of the GI guns,
will reduce any such effects that might otherwise occur.
[[Page 30085]]
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).
Airgun pulses are less energetic and have slower rise times, and there
is no proof that they can cause serious injury, death, or stranding
even in the case of large airgun arrays. However, the association of
mass strandings of beaked whales with naval exercises and, in one case,
an L-DEO seismic survey, 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. Appendix A of
UTIG's application provides additional details.
Seismic pulses and mid-frequency sonar pulses are quite different.
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. 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 to physical damage and mortality (Balcomb
and Claridge, 2001; NOAA and USN, 2001; Jepson et al., 2003; Fernandez
et al., 2004, 2005a; Cox et al., 2006), even if only indirectly,
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 as a result
of exposure to seismic surveys. Speculation concerning a possible link
between seismic surveys and strandings of humpback whales in Brazil
(Engel et al., 2004) was not well founded based on available data
(IAGC, 2004; IWC, 2006). In September 2002, there was a stranding of
two Cuvier's beaked whales in the Gulf of California, Mexico, when the
L-DEO research vessel Maurice Ewing was operating a 20-gun, 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 preceding example plus
the incidents involving beaked whale strandings near naval exercises
suggests a need for caution in conducting seismic surveys in areas
occupied by beaked whales. No injuries of beaked whales are anticipated
during the proposed study because of the proposed monitoring and
mitigation measures.
The proposed project will involve a much smaller sound source than
used in typical seismic surveys. That, along with the monitoring and
mitigation measures that are planned, are expected to minimize any
possibility for strandings and mortality.
Potential Effects of Other Acoustic Devices
Multibeam Echosounder Signals
A Simrad EM300 30-kHz MBES will be operated from the source vessel
during approximately two days of the proposed study. Sounds from the
MBES are very short pulses occurring for 2-5 ms, at a ping rate of up
to 10 pings/s depending on depth. Given the minimum water depth in the
study area (650 m; 2-way travel time [gteqt]0.9 s), the pulse
repetition rate is not likely to exceed 1 ping/s. Most of the energy in
the sound pulses emitted by the MBES is at freqencies near 30 kHz
within the audible range for odontocetes and at least some pinnipeds,
but probably not for baleen whales (Southall et al., 2007). The beam is
narrow (1-4[deg]) in fore-aft extent and wide (150[deg]) in the cross-
track extent. Each ping consists of nine beams transmitted at slightly
different frequencies. Any given mammal at depth near the trackline
would be in the main beam for only one or two of the nine segments.
Also, marine mammals that encounter the Simrad EM300 are unlikely to be
subjected to repeated pulses because of the narrow fore-aft width of
the beam and will receive only limited amounts of pulse energy because
of the short pulses. Animals close to the ship (where the beam is
narrowest) are especially unlikely to be ensonified for more than one 5
ms pulse (or two pulses if in the overlap area). Similarly, Kremser et
al. (2005) noted that the probability of a cetacean swimming through
the area of exposure when MBES emits a pulse is small due to the narrow
beam being emitted. The animal would have to pass the transducer at
close range and be swimming at speeds similar to the vessel in order to
be subjected to sound levels that could cause TTS. Burkhardt et al.
(2007) concluded that immediate direct injury was possible only if a
cetacean dived under the vessel into the immediate vicinity of the
transducer.
Navy sonars that have been linked to avoidance reactions and
stranding of cetaceans (1) generally have a longer pulse duration than
the Simrad EM300, and (2) are often directed close to horizontally vs.
more downward for the MBES. The area of possible influence of the MBES
is much smaller a narrow band below the source vessel. The duration of
exposure for a given marine mammal can be much longer for a navy sonar.
Possible effects of an MBES on marine mammals are outlined below.
Marine mammal communications will not be masked appreciably by the
MBES signals given its low duty cycle and the brief period when an
individual mammal is likely to be within its beam. Furthermore, in the
case of baleen whales, the signals (30 kHz) do not overlap with the
frequencies in the calls or with the functional hearing range, which
would avoid any possibility of 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 beachings by beaked whales. During exposure to a 21-25 kHz
whale-finding sonar with a source level of 215 dB re 1 microPam, gray
whales showed slight avoidance (~200 m or 656 ft) behavior (Frankel,
2005). However, all of those observations are of limited relevance to
the present situation. Pulse durations from those sonars were much
longer than those of the MBES, and a given mammal would have received
many pulses from the naval sonars. During UTIG's operations, the
individual pulses will be very short, and a given mammal would not
receive many of the downward-directed pulses as the vessel passes by.
In the case of baleen whales, the MBES will operate at too high a
frequency to have any effect.
Captive bottlenose dolphins and a beluga whale exhibited changes in
behavior when exposed to 1 s pulsed sounds at frequencies similar to
those that will be emitted by the MBES used by UTIG, 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 MBES.
During a previous low-energy seismic survey from the Thompson, the
EM300 MBES was in operation most of the time. Many cetaceans and small
numbers of fur seals were seen by marine mammal visual observers
(MMVOs) aboard the ship, but no
[[Page 30086]]
specific information about MBES effects (if any) on mammals was
obtained (Ireland et al., 2005). These responses (if any) could not be
distinguished from responses to the airgun (when operating) and to the
ship itself.
Given recent stranding events that have been associated with the
operations of naval sonar, there is concern that mid-frequency sonar
sounds can cause serious impacts to marine mammals (see above).
However, the MBES proposed for use by UTIG is quite different than
sonars used for navy operations. Pulse duration of the MBES is very
short relative to naval sonars. Also, at any given location, an
individual marine mammals would be in the beam of the MBES for much
less time given the generally downward orientation of the beam and its
narrow fore-aft beamwidth; navy sonars often use near horizontally
directed sound. Those factors would all reduce the sound energy
received from the MBES rather drastically relative to that from the
sonars used by the navy.
Although the source level of the Simrad EM300 is not available, the
maximum source level of a relatively powerful MBES (Simrad EM120) is
242 dB re 1 microParms. At that source level, the received
level for an animals within the MBES beam 100 m below the ship would be
~202 dB re 1 microPa (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. The received energy from a single
pulse of duration 5 ms would be about 179 dB 1 microPas, i.e.,
202 dB+10 log (0.005 s). That would be below the TTS thresholds for an
odontocete or pinniped exposed to a single non-impulsive sonar
transmission (195 and [gteqt]183 dB re 1 microPas,
respectively) and even further below the anticipated PTS threshold (215
and [gteqt]203 dB re 1 microPas, respectively) (Southall et
al., 2007). In contrast, an animal that was only 10 m below the MBES
when a ping is emitted would be expected to receive a level 20 dB
higher, i.e., 199 dB re 1 Pa s in the case of the EM120. That animal
might incur some TTS (which would be fully recoverable), but the
exposure would still be below the anticipated PTS threshold for both
cetaceans and pinnipeds.
Chirp Echosounder Signals
A chirp echosounder or sub-bottom profiler will be operated from
the source vessel at all times during the proposed study. Sounds from
the sub-bottom profiler are very short pulses, occurring for up to 24
ms once every few seconds. Most of the energy in the sound pulses
emitted by this sub-bottom profiler is at 12 kHz, and the beam is
directed downward. The source level of the chirp is expected to be
lower than that of the MBES. Kremser et al. (2005) noted that the
probability of a cetacean swimming through the area 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
sub-bottom profiler 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 odontocetes, the sonar signals do not
overlap with the predominant frequencies in the calls, which would
avoid significant masking.
Marine mammal behavioral reactions to other pulsed sound sources
are discussed above, and responses to the sub-bottom profiler are
likely to be similar to those for other pulsed sources if received at
the same levels. However, the pulsed signals from the chirp are
somewhat weaker than those from the MBES. Therefore, behavioral
responses are not expected unless marine mammals are very close to the
source.
Source levels of the chirp are much lower than those of the airguns
and the MBES, which are discussed above. Thus, it is unlikely that the
chirp 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 chirp is often 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 chirp. In
the case of mammals that do not avoid the approaching vessel and its
various sound sources, mitigation measures that would be applied to
minimized effects of the higher-power sources would further reduce or
eliminate any minor effects of the chirp.
Estimated Take by Incidental Harassment
All anticipated takes would be ``takes by harassment'', involving
temporary changes in behavior. The proposed mitigation measures are
expected to minimize the possibility of injurious takes. (However, as
noted earlier, there is no specific information demonstrating that
injurious ``takes'' would occur even in the absence of the planned
mitigation measures.) In the sections below, we describe methods to
estimate ``take by harassment'', and present estimates of the numbers
of marine mammals that might be affected during the proposed seismic
survey in the northeast Pacific Ocean. The estimates are based on data
concerning marine mammal densities (numbers per unit area) obtained
during surveys off Oregon and Washington during 1996 and 2001 by NMFS
Southwest Fisheries Science Center (SWFSC) and estimates of the size of
the area where effects potentially could occur.
The following estimates are based on a consideration of the number
of marine mammals that might be disturbed appreciably by operations
with the two GI guns to be used during approximately 1275 line-km of
surveys off the coast of Oregon in the northeastern Pacific Ocean. The
anticipated radii of influence of the echosounders are less than those
for the GI guns. It is assumed that, during simultaneous operations of
the GI guns and echosounders, any marine mammals close enough to be
affected by the echosounders would already be affected by the airgun.
However, whether or not the GI guns are operating simultaneously with
the echosounders, marine mammals are expected to exhibit no more than
short-term and inconsequential responses to the echosounders, given
their characteristics (e.g., narrow downward-directed beam) and other
considerations described previously. Therefore, no additional allowance
is included for animals that might be affected by the echosounders.
Extensive systematic aircraft- and ship-based surveys have been
conducted for marine mammals offshore of Oregon and Washington (Bonnell
et al., 1992; Green et al., 1992, 1993; Barlow, 1997, 2003; Barlow and
Taylor, 2001; Calambokidis and Barlow, 2004; Barlow and Forney, 2007).
The most comprehensive and recent density data available for cetacean
species off slope and offshore waters of Oregon are from the 1996 and
2001 NMFS/SWFSC ``ORCAWALE'' or ``CSCAPE'' ship surveys as synthesized
by Barlow and Forney (2007). The surveys were conducted up to
approximately 550 km (342 mi) offshore from June or July to early
November or December. Systematic, offshore, at-sea survey data for
pinnipeds are more limited. The most comprehensive studies are reported
by Bonnell et al. (1992) and Green et al. (1993) based on systematic
aerial surveys conducted in 1989 1990 and 1992, primarily from coastal
to
[[Page 30087]]
slope waters with some offshore effort as well.
Oceanographic conditions, including occasional El Nino and La Nina
events, influence the distribution and numbers of marine mammals
present in the northeastern Pacific Ocean, including Oregon, resulting
in considerable year-to-year variation in the distribution and
abundance of many marine mammal species (Forney and Barlow, 1998;
Buchanan et al., 2001; Escorza-Trevino, 2002; Ferrero et al., 2002;
Philbrick et al., 2003). Thus, for some species the densities derived
from recent surveys may not be representative of the densities that
will be encountered during the proposed seismic survey.
Table 3 in UTIG's application gives the average and maximum
densities for each species or species group of marine mammals reported
off Oregon and Washington (and used to calculate the take estimates in
Table 1 here), corrected for effort, based on the densities reported
for the 1996, 2001, and 2005 surveys (Barlow, 2003). The densities from
these studies had been corrected, by the original authors, for both
detectability bias and availability bias. Detectability bias is
associated with diminishing sightability with increasing lateral
distance from the trackline [f(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). Table 3 also includes mean density information for three of
the five pinnipeds species that occur off Oregon and Washington and
mean and maximum densities for one of those species, from Bonnell et
al. (1992). Densities were not calculated for the other two species
because of the small number of sightings on systematic transect
surveys.
It should be noted that the following estimates of ``takes by
harassment'' assume that the seismic surveys will be undertaken and
completed; in fact, the planned number of line-kms has been increased
by 25 percent to accommodate lines that may need to be repeated,
equipment testing, etc. As is typical on offshore ship surveys,
inclement weather, and equipment malfunctions may 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 unlikely.
There is some uncertainty about the representativeness of the data
and the assumptions used in the take calculations. However, the
approach used here is believed to be the best available approach. Also,
to provide some allowance for the uncertainties, ``maximum estimates''
as 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 reported by Barlow and Forney (2007) and
Bonnel et al. (1992) described above. The estimated numbers of
potential individuals exposed are based on the 160-dB re 1 microPa rms
criterion for all cetaceans and pinnipeds, and also based on the 170-dB
criterion for delphinids and pinnipeds only. It is assumed that marine
mammals exposed to airgun sounds this strong might change their
behavior sufficiently to be considered ``take by harassment''. UTIG has
requested authorization for the take of the maximum estimates and NMFS
has analyzed the maximum estimate for it's effect on the species or
stock.
The number of different individuals that may be exposed to GI-gun
sounds with received levels [gteqt]160 dB re 1 microPa (rms) on one or
more occasions can be estimated by considering the total marine area
that would be within the 160 dB radius around the operating GI guns 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. However, it is
unlikely that a particular animal would stay in the area during the
entire survey. The best estimates in this section are based on the
average of the densities from the 1996, 2001, and 2005 NMFS surveys,
and maximum estimates are based on the higher estimate. Table 4 in
UTIG's application (and used to calculate the take estimates in Table 1
here) 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 [gteqt]160 dB re 1 microPa (rms) was calculated by multiplying:
The expected species density, either ``mean'' (i.e., best
estimate) or ``maximum, `` times
The anticipated minimum area to be ensonified to that
level during the GI guns operations including overlap (exposures), or
The anticipated minimum area to be ensonified to that
level during GI gun operations excluding overlap (individuals).
The area expected to be ensonified was determined by entering the
planned survey lines into a MapInfo Geographic Information System
(GIS), using the GIS to identify the relevant areas by ``drawing'' the
applicable 160 dB or 170 dB buffer around each seismic line and then
calculating the total area within the buffers. Areas where overlap
occurred (because of intersecting lines) were included only once to
determine the minimum area expected to be ensonified.
Applying the approach described above, approximately 189 km\2\
would be within the 160 dB isopleth on one or more occasions during the
survey, whereas approximately 1,391 km\2\ is the area ensonified when
overlap is included. Because this approach does not allow for turnover
in the mammal populations in the study area during the course of the
survey, the actual number of individuals exposed may be underestimated.
However, this will be offset to some degree by the fact that the 160 dB
(and other) distances assumed here actually apply to a pair of slightly
larger GI guns to be used in the project. In addition, the approach
assumes that no cetaceans will move away or toward the trackline as the
Thompson 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 program) to occur in the waters
that will be exposed to [gteqt]160 dB re 1 microPa (rms).
The ``best estimate'' of the number of individual cetaceans that
might be exposed to seismic sounds with received levels [gteqt]160 dB
re 1 microPa (rms) during the surveys is 42 (Table 4 in UTIG's
application). The total does not include any endangered or beaked
whales. Dall's porpoise is estimated to be the most common species
exposed; the best estimates for those species are 28 (Table 4 in UTIG
application). The best estimate of the number of exposures of cetaceans
to seismic sounds with received levels [gteqt]160 dB re 1 microPa (rms)
during the survey is 536, including 1 humpback whale, 1 fin whale, and
2 sperm whales. Dall's porpoise was exposed most frequently, with a
best estimate of 209 exposures.
The ``maximum estimate'' column in Table 4 of UTIG's application
shows an estimated total of 85 cetaceans that
[[Page 30088]]
might be exposed to seismic sounds [gteqt]160 dB during the surveys. In
most cases, those estimates are based on survey data, as described
above. For endangered species, the 'maximum estimate' is the mean group
size (from Barlow and Forney, in press) in cases where the calculated
maximum number of individuals exposed was between 0.05 and the mean
group size (humpback, fin, blue, and sperm whales). The numbers for
which take authorization is requested, given in the far right column of
Table 4 in UTIG's application are the maximum estimates. Based on the
abundance numbers given in UTIG's application and Table 1 here for non-
listed cetacean species, NMFS believes that the estimated take numbers
are small relative to the stock sizes for these species (i.e., no more
than 0.4 percent of any species).
The best and maximum estimates of the numbers of exposures to
[gteqt]170 dB for all delphinids during the surveys are 9 and 13,
respectively. Corresponding estimates for Dall's porpoise are 17 and
29. The estimates are based on the predicted 170 dB radii around the GI
guns to be used during the study and are considered to be more
realistic estimates of the number of individual delphinids and Dall's
porpoises that may be affected.
Only two of the five pinniped species discussed in Section III of
UTIG's application the northern fur seal and the northern elephant seal
are likely to occur in the offshore and slope waters; the other three
species of pinnipeds known to occur regularly off Oregon and Washington
the California sea lion, Steller sea lion, and harbor seal are
infrequent there. This conclusion is based on results of extensive
aerial surveys conducted from the coast to offshore waters of Oregon
and Washington (Bonnell et al., 1992; Green et al., 1993; Buchanan et
al., 2001; Carretta et al., 2007). However, the available density data
are probably not truly representative of densities that could be
encountered during surveys, as the data were averaged over a number of
months and over coastal, shelf, slope, and offshore waters. These
factors strongly influence the densities of these pinnipeds at sea, as
all pinnipeds off Oregon and Washington exhibit seasonal and/or inshore
offshore movements largely related to breeding and feeding (Bonnell et
al., 1992; Buchanan et al., 2001; Carretta et al., 2007).
Most pinnipeds, like delphinids, seem to be less sensitive to
airgun sounds than are mysticetes. Thus, the numbers of pinnipeds
likely to be exposed to received levels [gteqt]170 dB re 1 microPa
(rms) were also calculated, based on the estimated 170-dB radii in
Table 1 of UTIG's application. For operations in deep water, the
estimated 160 and 170 dB radii are very likely over-estimates of the
actual 160- and 170-dB distances (Tolstoy et al., 2004a,b). Thus, the
resulting estimates of the numbers of pinnipeds exposed to such levels
may be overestimated.
The methods described previously for cetaceans were also used to
calculate exposure numbers for the one pinniped species likely to be in
the survey area and whose densities were estimated by Bonnell et al.
(1992). Based on the ``best'' densities, two northern fur seals are
considered likely to be exposed to GI gun sounds [gteqt]160 dB re 1
microPa (rms). The ``Maxim Estimate'' column in Table 4 of UTIG's
application shows an estimated 19 northern fur seals that could be
exposed to GI airgun sounds [gteqt]160-dB or [gteqt]170dB re 1 microPa
(rms), respectively, during the survey. Also included are low maximum
estimates for the northern elephant seals, a species that likely would
be present but whose density was not calculated because of the small
number of sightings on systematic transect surveys. The numbers of
which ``take authorization'' is requested, given in the far right
column of Table 4 of UTIG's application, are based on the maximum 160
dB estimates.
The proposed UTIG seismic survey in the northeastern Pacific Ocean
involves towing two GI guns that introduce pulsed sounds into the
ocean, as well as echosounder operations. A towed P-Cable system will
be deployed to receive and record the returning signals. Routine vessel
operations, other than the proposed GI gun operations, are
conventionally assumed not to affect marine mammals sufficiently to
constitute ``taking.'' No ``taking'' of marine mammals is expected in
association with operations of the echosounders given the
considerations discussed in section IV(1)(b) of UTIGS's application,
i.e., sounds are beamed downward, the beam is narrow, and the pulses
are extremely short.
Strong avoidance reactions by several species of mysticetes to
seismic vessels have been observed at ranges up to 6-8 km (3.7-5 mi)
and occasionally as far as 20-30 km (12.4-18.6 mi) from the source
vessel when much larger airgun arrays have been used. However,
reactions at the longer distances appear to be atypical of most species
and situations and in any case apply to larger airgun systems than will
be used in this project. If mysticetes are encountered, the numbers
estimated to occur within the 160 dB isopleth in the survey area are
expected to be very low. In addition, the estimated numbers presented
in Table 4 of UTIG's application are considered overestimates of actual
numbers because the estimated 160 and 170 dB radii used here are
probably overestimates of the actual 160 and 170 dB radii at deep-water
locations such as the present study areas (Tolstoy et al., 2004a,b). In
addition, the radii were based on a larger airgun source than the one
proposed for use during the present survey.
Odontocete reactions to seismic pulses, or at least the reactions
of delphinids and Dall's porpoises are expected to extend to lesser
distances than are those of mysticetes. Odontocete low-frequency
hearing is less sensitive than that of mysticetes, and delphinids and
Dall's porpoises are often seen from seismic vessels. In fact, there
are documented instances of dolphins and Dall's porpoises approaching
active seismic vessels. However, delphinids and porpoises (along with
other cetaceans) sometimes show avoidance responses and/or other
changes in behavior when near operating seismic vessels.
Taking into account the mitigation measures that are proposed in
UTIG's application, effects on cetaceans are generally expected to be
limited to avoidance of the area around the seismic operation and
short-term changes in behavior, falling within the MMPA definition of
``Level B harassment.'' Furthermore, the estimated numbers of animals
potentially exposed to sound levels sufficient to cause appreciable
disturbance are very low percentages of the regional population sizes.
The best estimates of the numbers of individual cetaceans (33 for all
species combined) that would be exposed to sounds [gteqt]160 dB re 1
microPa (rms) during the proposed survey represent, on a species-by-
species basis, no more than 0.11 pertcent of the regional populations
(see Table 4 of UTIG's application). Dall's porpoise is the cetacean
species with the highest estimated number of individuals exposed to
[gteqt]160 dB.
Varying estimates of the numbers of marine mammals that might be
exposed to the GI guns sounds during the proposed summer 2008 seismic
survey in the northeastern Pacific Ocean have been presented, depending
on the specific exposure criterion ([gteqt]160 or [gteqt]170 dB) and
density criterion used (best or maximum). The request ``take
authorization'' for each species is based on the estimated maximum
number of individuals that might be exposed to [gteqt]160 re 1 microPa
(rms). That figure likely
[[Page 30089]]
overestimates (in most cases by a large margin) the actual number of
animals that will be exposed to and will react to the seismic sounds.
The reasons for that conclusion are outlined above. The relatively
short-term exposures are unlikely to result in any long-term negative
consequences for the individuals or their populations.
The many cases of apparent tolerance by cetaceans of seismic
exploration, vessel traffic, and some other human activities show that
co-existence is possible. Mitigation measures such as controlled speed,
course alteration, look outs, non-pursuit, and shut downs when marine
mammals are seen within defined ranges should further reduce short-term
reactions, and minimize any effects on hearing sensitivity. In all
cases, the effects are expected to be short-term, with no lasting
biological consequence.
Only two of the five pinniped species discussed in Section III of
UTIG's application, the northern fur seal and northern elephant seal,
are likely to occur in the offshore and slope waters of the study area.
A best estimate of a single northern fur seal could be exposed to
airgun sounds with received levels [gteqt]160 dB re 1 microPa (rms).
The numbers for which ``take authorization'' is requested are given in
the far right column of Table 4 of UTIG's application. As for
cetaceans, the estimated numbers of pinnipeds that may be exposed to
received levels [gteqt]160 dB are probably overestimates of the actual
numbers that will be affected, and are very small proportions of the
respective population sizes.
Potential Effects on Habitat
The proposed seismic surveys 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 discussed above.
One of the reasons for the adoption of airguns as the standard
energy source for marine seismic surveys was that, unlike explosives,
they have not been associated with any appreciable fish kills. However,
the existing body of information relating to the impacts of seismic
surveys on marine fish (see Appendix B of UTIG's application) and
invertebrate species is very limited. The various types of potential
effects of exposure to seismic on fish and invertebrates can be
considered in three categories: (1) pathological, (2) physiological,
and (3) behavioral. Pathological effects include lethal and temporary
or permanent sub-lethal damage to the animals, physiological effects
include temporary and permanent primary and secondary stress responses,
such as changes in levels of enzymes and proteins. Behavioral effects
refer to temporary and categories are interrelated in complex ways. For
example, it is possible that certain physiological and behavioral
changes could potentially lead to the ultimate pathological effect on
individual animals (i.e., mortality).
The specific received levels at which permanent adverse effects to
fish potentially could occur are little studies and largely unknown.
Furthermore, available information on the impacts of seismic surveys on
marine fish and invertebrates is from studies of individuals or
portions of a population; there have been no studies at the population
scale. Thus, available information provides limited insight on possible
real world effects at the ocean or population scale. This makes drawing
conclusions about impacts 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 an general overview of the available
information that exists on the effects of exposure to seismic surveys
and other anthropogenic sound as relevant to fish and invertebrates.
The information comprises results from scientific studies of varying
degrees of soundness and some anecdotal information.
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 B of UTIG'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.
There are 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. McCauley et al. (2003) 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 fishes
from the Mackenzie River Delta. This study found that broad whitefish
(Coreogonus nasus) that received a sound exposure level of 177 dB re 1
microPa\2\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, 29.5
ft, in the former case and <2 m, 6.6 ft, 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).
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 (Hubbs and Rechnitzer, 1952; Wardle et al., 2001).
Generally, the higher the received pressure and the less time it takes
for the pressure to rise and decay, the greater the chance of acute
pathological effects. Considering the peak pressure and rise/decay time
characteristics of seismic airgun arrays used today, the pathological
zone for fish and invertebrates would be expected to be within a few
meters of the seismic source (Buchanan et al., 2004). For the proposed
survey, any injurious effects on fish would be limited to very short
distances, especially considering the small source planned for use in
this project (two 40-60-in\3\ GI guns). Numerous other studies provide
examples of no fish mortality upon exposure to seismic sources (Falk
and
[[Page 30090]]
Lawrence, 1973; Holliday et al., 1987; La Bella et al., 1996; Santulli
et al., 1999; McCauley et al., 2000a, 2000b, 2003; Bjarti, 2002; Hassel
et al., 2003; Popper et al., 2005).
Except for these two studies, at least with airgun-generated sound
treatments, most contributions rely on rather subjective assays such as
fish ``alarm'' or ``startle response'' or changes in catch rates by
fishers. These observations are important in that they attempt to use
the levels of exposures that are likely to be encountered by most free-
ranging fish in actual survey areas. However, the associated sound
stimuli are often poorly described, and the biological assays are
varied (Hastings and Popper, 2005).
Some studies have reported 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 and
concluded that mortality rates caused by exposure to seismic are so low
compared to natural mortality that the impact of seismic surveying on
recruitment to a fish stock must be regarded as insignificant.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
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 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 B of
UTIG's application for more information on the effects of airgun sounds
on marine fish). Such stress could potentially affect animal
populations by reducing reproductive capacity and adult abundance and
increasing mortality.
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
sound) on fish behavior have been conducted on both uncaged and caged
individuals (e.g., Chapman and Hawkings, 1969; Pearson et al., 1992;
Santulli et al., 1999, Wardle et al., 2001, Hassel et al., 2003).
Typically, in these studies fish exhibited sharp ``startle'' response
at the onset of a sound followed by habituation and a return to normal
behavior after the sound ceased.
There is general concern about potential adverse effects of seismic
operations on fisheries, namely a reduction in the ``catchability'' of
fish involved in fisheries. Although reduced catch rates have been
observed in some marine fisheries during seismic testing, in a number
of cases the findings are confounded by other sources of disturbance
(Dalen and Raknes, 1985; Dalen and Knutsen, 1986; L kkeborg, 1991;
Skalski et al., 1992; Engas et al., 1996). In other airgun experiments,
there was no change in CPUE of fish when airgun pulses were emitted,
particularly in the immediate vicinity of the seismic survey (Pickett
et al., 1994; La Bella et al., 1996). For some species, reductions in
catch may have resulted from a change in behavior of the fish, e.g., a
change in vertical or horizontal distribution, as reported in the
Slotte et al. (2004).
Summary of Physical (Pathological and Physiological) Effects - As
indicated in the preceding general discussion, 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. Again, this study will employ a sound source that
will generate low 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 2008 is predicted to have
negligible to low physical effects on the various life stages of fish
and invertebrates for its relatively short duration (approximately 150
total hours at each of the three sites off the coast of Oregon) and
approximately 975 km (606 mi) extent. Therefore, physical effects of
the proposed program on the fish and invertebrates would be not
significant.
Behavioral Effects - Because of the apparent lack of serious
pathological and physiological effects of seismic energy on marine fish
and invertebrates, most concern now centers on the possible effects of
exposure to seismic surveys on the distribution, migration patterns,
mating, and catchability of fish. There is a need for more information
on exactly what effects such sound sources might have on the detailed
behavior patterns of fish and invertebrates at different ranges.
Studies investigating the possible effects of seismic energy on
fish and invertebrate behavior have been conducted on both uncaged and
caged animals (Chapman and Hawkins, 1969; Pearson et al., 1992;
Santulli et al., 1999; Wardle et al., 2001; Hassel et al., 2003).
Typically, in these studies fish exhibited a sharp ``startle'' response
at the onset of a sound followed by habituation and a return to normal
behavior after the sound ceased.
There is general concern about potential adverse effects of seismic
operations on fisheries, namely a potential reduction in the
``catchability'' of fish involved in fisheries. Although reduced catch
rates have been observed in some marine fisheries during seismic
testing, in a number of cases the findings are confounded by other
sources of disturbance (Dalen and Raknes, 1985; Dalen and Knutsen,
1986; L kkeborg, 1991; Skalski et al., 1992; Engas et al., 1996). In
other airgun experiments, there was no change in
[[Page 30091]]
catch per unit effort of fish when airgun pulses were emitted,
particularly in the immediate vicinity of the seismic survey (Pickett
et al., 1994; La Bella et al., 1996). For some species, reductions in
catch may have resulted from a change in behavior of the fish (e.g., a
change in vertical or horizontal distribution) as reported in Slotte et
al. (2004).
In general, any adverse effects on fish behavior or fisheries
attributable to seismic testing may depend on the species in question
and the nature of the fishery (season, duration, fishing method). They
may also depend on the age of the fish, its motivational state, its
size, and numerous other factors that are difficult, if not impossible,
to quantify at this point, given such limited data on effects of
airguns on fish, particularly under realistic at-sea conditions.
In general, any adverse effects on fish behavior or fisheries
attributable to seismic testing may depend on the species in question
and the nature of the fishery (season, duration, fishing method). They
may also depend on the age of the fish, its motivational state, its
size, and numerous other factors that are difficult, if not impossible,
to quantify at this point, given such limited data on effects of
airguns on fish, particularly under realistic at-sea conditions.
Effects on Invertebrates
The existing body of information on the impacts of seismic survey
sound on marine invertebrates is very limited. However, there is some
unpublished and very limited evidence of the potential for adverse
effects on invertebrates, thereby justifying further discussion and
analysis of this issue. Th three types of potential effects of exposure
to seismic surveys on marine invertebrates are pathological,
physiological, and behavioral. Based on the physical structure of their
sensory organs, marine invertebrates appear to be specialized to
respond to particle displacement components of an impinging sound field
and not to the pressure component (Popper et al. 2001; see also
Appendix C of UTIG'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.
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 two GI guns planned for the proposed program, the
pathological (mortality) zone for crustaceans and cephalopods is
expected to be within a few metes 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 stage 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 animals.
It has been suggested that exposure to commercial seismic survey
activities has injured giant squid (Guerra et al., 2003), 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 cold 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 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. Changes in behavior could potentially affect such aspects as
reproductive success, distribution, susceptibility to predation, and
catchability by fisheries. Studies investigating the possible
behavioral effects of exposure to seismic survey sound on crustaceans
and cephalopods have been conducted on both uncaged and caged animals.
In some cases, invertebrates exhibited startle responses (e.g., squid
in McCauley et al., 2000a,b). In other cases, no behavioral impacts
were noted (e.g., crustaceans in Christian et al., 2003, 2004; DFO,
2004). Ther have been anecdotal reports of reduced catch rates of
shrimp shortly after exposure to seismic survey; however, other studies
have not observed any significant changes in shrimp catch rate
(Andriguetto-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).
During the proposed study, only a small fraction of the available
habitat would be ensonified at any given time, and fish and
invertebrate species would return to their pre-disturbance behavior
once the seismic activity ceased. The proposed seismic program is
predicted to have negligible to low behavioral effects on the various
life stages of the fish and invertebrates during its duration (total of
approximately 150 hours) and 975 km (606 mi) extent.
Because of the reasons noted above and the nature of the proposed
activities (small airgun and limited duration), the proposed operations
are not expected to have any habitat-related effects that could cause
significant or long-term consequences for individual marine mammals or
their populations or stocks. Similarly, any effects to food sources are
expected to be negligible.
The effects of the proposed activity on marine mammal habitats and
food resources are expected to be negligible, as described above. A
small minority of the marine mammals that are present near the proposed
activity may be temporarily displaced as much as a few kilometers by
the planned activity. During the proposed survey, marine mammals will
be distributed according to their habitat preferences, in shelf, slope,
and pelagic waters.
[[Page 30092]]
Concentrations of marine mammals and/or marine mammal prey species are
not expected to occur in or near the proposed study area, and that area
does not appear to constitute an area of localized or critical feeding,
breeding, or migration for any marine mammal species. The proposed
activity is not expected to have any habitat-related effects that could
cause significant or long-term consequences for individual marine
mammals or their populations, because operations at the various sites
will be limited in duration.
Proposed Monitoring
Vessel-based marine mammal visual observers (MMVOs) will be aboard
the seismic source vessel and will watch for marine mammals near the
vessel during all daytime GI gun operations and during start-ups of the
gun at night. MMVOs will also watch for marine mammals near the seismic
vessel for at least 30 minutes prior to the start of GI gun operations
after an extended shut down. When feasible, MMVOs will also make
observations during daytime periods when the seismic system is not
operating for comparison of sighting rates and behavior with vs.
without GI guns operations. Based on MMVO observations, the GI guns
will be shut down when marine mammals are observed within or about to
enter a designated exclusion zone (EZ; safety radius). The EZ is a
region in which a possibility exists of adverse effects on animal
hearing or other physical effects.
MMVOs will be appointed by the academic institution conducting the
research cruise, with NMFS Office of Protected Resources concurrence. A
total of three MMVOs are planned to be aboard the source vessel. At
least one MMVO will monitor the EZ during daytime GI guns operations
and any night-time startups. MMVOs will normally work in daytime shifts
of 4 hours duration or less. The vessel crew will also be instructed to
assist in detecting marine mammals.
The Thompson will serve as the platform from which MMVOs will watch
for marine mammals before and during the GI guns operations. Two
locations are likely as observation stations onboard the Thompson. At
one station on the bridge, the eye level will be approximately 13.8 m
(45.3 ft) above sea level and the location will offer a good view
around the vessel (approximately 310 degrees for one observer and a
full 360 degrees when two observers are stationed at different vantage
points). A second observation station is the 03 deck where the
observer's eye level will be approximately 10.8 m (35.4 ft) above sea
level. The 03 deck offers a view of 330[deg] for two observers.
Standard equipment for MMVOs will be 7 x 50 reticle binoculars and
optical range finders. At night, night-vision devices (NVDs) will be
available. Vessel lights and/or NVDs are useful in sighting some marine
mammals at the surface within a short distance from the ship (within
the EZ for the two GI guns). The observers 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 guns shut down.
MMVOs will record data to estimate the numbers of marine mammals
exposed to various received sound levels and to document any apparent
disturbance reactions. Data will be used to estimate the numbers of
mammals potentially ``taken'' by harassment (as defined in the MMPA).
They will also provide the information needed to order a shutdown of
the two GI guns when a marine mammal is within or near the EZ. When a
mammal sighting is made, the following information about the sighting
will be recorded:
(1) Species, group size, age/size/sex categories (if determinable),
behavior when first sighted and after initial sighting, heading (if
consistent), bearing and distance from seismic vessel, sighting cue,
apparent reaction to the GI gun or seismic vessel (e.g., none,
avoidance, approach, paralleling, etc.), and behavioral pace.
(2) Time, location, heading, speed, activity of the vessel
(shooting or not), sea state, visibility, and sun glare.
The data listed under (2) will also be recorded at the start and
end of each observation watch and during a watch, whenever there is a
change in one or more of the variables.
All marine mammal observations and information regarding airgun
operations 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 field program and summaries forwarded to the
operating institution'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 the GI guns.
(2) Information needed to estimate the number of marine mammals
potentially ``taken by harassment.'' These data will be reported to
NMFS and/or USFWS per terms of MMPA authorizations..
(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.
Mitigation
Mitigation and monitoring measures proposed to be implemented for
the proposed seismic survey have been developed and refined during
previous SIO and L-DEO seismic studies and associated EAs, IHA
applications, and IHAs. The mitigation and monitoring measures
described herein represent a combination of the procedures required by
past IHAs for other SIO and L-DEO projects. The measures are described
in detail below.
Mitigation measures that are proposed to be implemented include (1)
vessel speed or course alteration, provided that doing so will not
compromise operational safety requirements, (2) GI guns ramp up and
shut down, and (3) minimizing approach to slopes and submarine canyons,
if possible, because of sensitivity of beaked whales. Two other
standard mitigation measures airgun array power down are not possible
because only two, low-volume GI guns will be used for the surveys.
Speed or Course Alteration - If a marine mammal is detected outside
the EZ but is likely to enter it based on relative movement of the
vessel and the animal, then if safety requirements allow, the vessel
speed and/or direct course will be adjusted to minimize the likelihood
of the animal entering the EZ. 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 guns and a
short P-Cable system with streamers will be used. If the animal appears
likely to enter the EZ, further mitigative actions will be taken, i.e.
either further course alterations or shut down of the airgun.
Ramp-up Procedures - A ``ramp-up'' procedure will be followed when
the airguns begin operating after a period without airgun operations.
The two GI guns will be added in sequence 5 minutes apart. During ramp-
up procedures, the safety radius for the two GI guns will be
maintained.
Shut-down Procedures - If a marine mammal is within or about to
enter the EZ for the two GI guns, it will be shut down immediately.
Following a shut down, the GI guns activity will not resume until the
marine mammal is outside the EZ for the full array. The animal will be
considered to have cleared the EZ if it: (1) is visually observed to
have left the EZ; (2) has not
[[Page 30093]]
been seen within the EZ for 10 minutes in the case of small odontocetes
and pinnipeds; or (3) has not been seen within the EZ for 15 minutes in
the case of mysticetes and large odontocetes, including sperm, pygmy
sperm, dwarf sperm, and beaked whales.
The 10- and 15-min periods specified in (2) and (3), 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 guns. GI gun operations will
be able to resume following a shut-down during either the day or night,
as the relatively small exclusion zone(s) will normally be visible even
at night (see section VIII of UTIG's application).
Minimize Approach to Slopes and Submarine Canyons - Although
sensitivity of beaked whales to airguns is not specifically known, they
appear to be sensitive to other sound sources (e.g., mid-frequency
sonar; see section IV of UTIG's application). Beaked whales tend to
concentrate in continental slope areas, and in areas where there are
submarine canyons. Avoidance of airgun operations over or near
submarine canyons where practicable has become a standard mitigation
measure, but there are no submarine canyons within or near the study
area. Also, airgun operations are not planned over slope sites during
the proposed survey.
Reporting
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 the marine mammals that were detected 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, all marine mammal and turtle 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.
ESA
Under section 7 of the ESA, the NSF has begun informal consultation
on this proposed seismic survey. NMFS will also consult informally 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 prepared an Environmental Assessment (EA) of a Planned Low-
Energy Marine Seismic Survey by the Scripps Institution of Oceanography
in the Northeast Pacific Ocean, September 2007. NMFS adopted NSF's 2007
EA and will conducted a separate NEPA analysis and prepare a
Supplemental EA, prior to making a determination on the issuance of the
IHA.
Preliminary Determinations
NMFS has preliminarily determined that the impact of conducting the
seismic survey in the northeast Pacific Ocean may result, at worst, in
a temporary modification in behavior (Level B Harassment) of small
numbers of ten species 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 adverse impact on the availability of the affected species
or stock for subsistence uses does not apply to this proposed action as
there are no subsistence users within the geographic area of the
proposed project.
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 marine mammals would have to
be closer than either 104 m (341.1 ft) in intermediate depths or 69 m
(226.3 ft) in deep water from the vessel to be exposed to levels of
sound (180 dB) believed to have even a minimal chance of causing TTS;
and (3) the likelihood that marine mammal detection ability by trained
observers is high at that short distance from the vessel. As a result,
no take by injury 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 potential incidental harassment takes 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 UTIG for conducting a low-energy seismic survey in the
northeastern Pacific Ocean during June-July, 2008, provided the
previously mentioned mitigation, monitoring, and reporting requirements
are incorporated.
Dated: May 16, 2008.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. E8-11546 Filed 5-22-08; 8:45 am]
BILLING CODE 3510-22-S