[Federal Register Volume 73, Number 168 (Thursday, August 28, 2008)]
[Notices]
[Pages 50760-50778]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-20014]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XJ24
Incidental Takes of Marine Mammals During Specified Activities;
Low-Energy Marine Seismic Surveys in the Santa Barbara Channel,
November 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 the Scripps Institute of
Oceanography (SIO) for an Incidental Harassment Authorization (IHA) to
take small numbers of marine mammals, by harassment, incidental to
conducting a seismic survey within the Santa Barbara Channel,
California. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS
requests comments on its proposal to authorize SIO to take, by Level B
harassment only, small numbers of marine mammals incidental to
conducting a marine seismic survey in November, 2008.
DATES: Comments and information must be received no later than
September 29, 2008.
ADDRESSES: Comments on the application should be addressed to Michael
Payne, Chief, Permits, Conservation and Education Division, Office of
Protected Resources, National Marine Fisheries Service, 1315 East-West
Highway, Silver Spring, MD 20910-3225. The mailbox address for
providing e-mail comments is [email protected]. Comments sent via
e-mail, including all attachments, must not exceed a 10-megabyte file
size.
A copy of the application containing a list of the references used
in this document may be obtained by writing to the address specified
above, telephoning the contact listed below (see FOR FURTHER
INFORMATION CONTACT), or visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm.
Documents cited in this notice may be viewed, by appointment,
during regular business hours, at the aforementioned address.
[[Page 50761]]
FOR FURTHER INFORMATION CONTACT: Jaclyn Daly or Howard Goldstein,
Office of Protected Resources, NMFS, (301) 713-2289.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.)
direct the Secretary of Commerce to allow, upon request, the
incidental, but not intentional, taking of marine mammals by United
States citizens who engage in a specified activity (other than
commercial fishing) within a specified geographical region if certain
findings are made and either regulations are issued or, if the taking
is limited to harassment, a notice of a proposed authorization is
provided to the public for review.
Authorization for incidental taking shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s), will not have an unmitigable adverse impact on the
availability of the species or stock(s) for subsistence uses, and if
the permissible methods of taking and requirements pertaining to the
mitigation, monitoring and reporting of such takings are set forth.
NMFS has defined ``negligible impact'' in 50 CFR 216.103 as ``. . . an
impact resulting from the specified activity that cannot be reasonably
expected to, and is not reasonably likely to, adversely affect the
species or stock through effects on annual rates of recruitment or
survival.''
Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the United States can apply for an authorization
to incidentally take small numbers of marine mammals by harassment.
Except with respect to certain activities not pertinent here, the MMPA
defines ``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [``Level A harassment'']; or (ii) has the potential to disturb
a marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[``Level B harassment'''].
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS'
review of an application followed by a 30-day public notice and comment
period on any proposed authorizations for the incidental harassment of
small numbers of marine mammals. Within 45 days of the close of the
comment period, NMFS must either issue or deny issuance of the
authorization.
Summary of Request
On June 27, 2008, NMFS received an application from SIO for the
taking, by Level B harassment only, of small numbers of 16 species of
marine mammals incidental to conducting a twelve-day, low-energy marine
seismic survey within the Santa Barbara Channel, CA, in November 2008.
The funding for this research survey is provided by the National
Science Foundation (NSF).
The purpose of the proposed study is to test the feasibility of
extending the paleoclimate record from Santa Barbara Basin established
in 1992 and 2005 from ~700,000 years ago back to ~1.2 million years
using detailed 3D modeling of the structure and outcrop stratigraphy of
the northern shelf, to locate optimal core sites, and high-resolution
multichannel seismic (MCS) reflection site surveys, test coring, and
core analyses in the northern shelf and mid-channel areas. The planned
seismic survey (including turns) will consist of approximately 600 km
of survey lines using a standard 45-in \3\ GI airgun and approximately
500 km of survey lines using a mini-sparker or boomer. The seismic
surveys will identify subsequent optimal and safe coring strategies
suitable for recovering a continuous paleoclimate record from the
shallow marine sediments in Santa Barbara Basin in the future as part
of the Integrated Ocean Drilling Program (IODP).
Description of the Specified Activity
The planned survey will involve one source vessel, the seismic ship
R/V Melville, owned by the U.S. Navy and operated by SIO. The Melville
is expected to depart San Diego and spend approximately 12 days
conducting the survey and piston coring activities in November 2008.
Seismic operations will be conducted during daylight hours only for 1-2
days at each of five sites encompassing the small area approximately
34-34.5[deg] N, 119.5-120[deg] W, north and northwest of Santa Cruz
Island in the Santa Barbara Channel off southern California (see Figure
1 in SIO's application). The seismic program will consist of grids of
closely-spaced lines in each of 5 survey areas. Line spacing will be
100-400 m. There will be additional operations associated with
equipment testing, startup, line changes, and repeat coverage of any
areas where initial data quality is sub-standard. Water depths in the
survey area range from <50 m to ~580 m. The seismic survey will be
conducted in the territorial waters of the U.S., partly in California
state waters.
At three deeper-water sites outside state waters, a small 45-in\3\
GI airgun will be used, but will likely be reduced to 25- or 35-in\3\.
At two shallow-water sites that cross into California state waters, a
1.5-kJ electromechanical boomer or a 2-kJ electric sparker system will
be used, depending on water depth and seafloor conditions, and
depending on which source provides the highest resolution and best sub-
seafloor signal penetration. The two systems will not operate
concurrently and, in general, the boomer source likely will be
preferred. As the boomer, sparker, or GI airgun are towed along the
survey lines, a towed 72-channel, 450 m hydrophone streamer will
receive the returning acoustic signals and transfer the data to the on-
board processing system. Given the relatively short streamer length
behind the vessel, the turning rate of the vessel while the gear is
deployed is much higher than the limit of five degrees per minute for a
seismic vessel towing a streamer of more typical length (>1 km). Thus,
the maneuverability of the vessel is not limited much during
operations.
In addition to the GI airgun, sparker, and boomer, a towed chirp
system, a multibeam echosounder (MBES), and a sub-bottom profiler (SBP)
will be used at various times during the cruise. The chirp system will
be used in tandem with the seismic sources, or will be used separately
to locate optimal piston core sites, up to 4 hours at a time to a
maximum of 8-10 hours per day. A 3.5-kHz SBP will be used to help
verify seafloor conditions at possible coring sites, and will also be
used in tandem with a MBES during transit to and from the Santa Barbara
Channel area to collect additional seafloor bathymetric data.
Vessel Specifications
The Melville has a length of 85 m, a beam of 14.0 m, a maximum
draft of 5.0 m, and can accommodate 23 crew and 86 scientists. Its
gross tonnage is 2516 and is powered by two 1385-hp Propulsion General
Electric motors and a 900-hp retracting Azimuthing bow thruster. The
vessel will operate at a speed of ~7.4-8 km/h (4-4.3 knots) during
seismic acquisition. When not towing seismic survey gear, the Melville
cruises at 21.7 km/h (11.7 knots) and has a maximum speed of 25.9 km/h
(14 knots). It has a normal operating range of approximately 18,630 km.
The Melville will also serve as the platform from which vessel-based
marine mammal observers will watch for marine mammals and sea turtles
before and during airgun operations.
[[Page 50762]]
Acoustic Source Specifications
Seismic Airguns
The Melville will operate one small 45-in\3\ GI airgun but will
likely reduce the chamber size to 25-35-in\3\. However, in case that is
not possible, the specifications provided below are for a 45-in\3\ GI
airgun (Table 1). Seismic pulses will be emitted at intervals of 3
seconds. At a vessel speed of approximately 4 knots (7.4 km/h), the 3-s
spacing corresponds to a shot interval of approximately 6 m.
If possible, the generator chamber of the GI airgun, the one
responsible for introducing the sound pulse into the ocean, will be set
to 25 in\3\. The injector chamber also will be set to the same 25-in\3\
size and will inject air into the previously generated bubble to
maintain its shape. This does not introduce more sound into the water.
The airgun will be towed 21 m behind the Melville at a depth of 2 m.
The variation of the sound pressure field of that GI-gun set to its
original 45-in\3\ size and towed at a depth of 2.5 m has been modeled
by L-DEO in relation to distance and direction from the GI airgun. At
its reduced chamber size of 25 in\3\, these numbers will be further
reduced. For comparison, the peak source sound level of the 45-in\3\
gun is 225.3 dB re 1 [mu] Pa, whereas the peak source sound level of a
USGS GI airgun with chamber sizes reduced to 25 in\3\ is approximately
218 dB re 1 [mu]Pa[middot]m. More information on characteristics of
airgun sounds can be found in Appendix A in the SIO's EA.
Table 1--Specifications of GI-Airgun Proposed To Be Used During the SIO
Seismic Survey, November 2008
------------------------------------------------------------------------
GI-airgun specifications
-------------------------------------------------------------------------
GI airgun of 45 in\3\ or GI
Energy source airgun of 25 in\3\
------------------------------------------------------------------------
Source output (downward) (45 in\3\).... 0-pk is 1.8 bar-m (225.3 dB re
1 [mu]Pa[middot]mp); pk-pk is
3.4 bar-m (230.7 dB re 1
[mu]Pa[middot]mp-p).
Source output (downward) (25 in\3\).... approx. 218 dB re 1
[mu]Pa[middot]mp.
Towing depth of energy source.......... 2 meters.
Air discharge volume................... approx. 45 in\3\ or 25 in\3\.
Dominant frequency components.......... 0-188 Hz (45 in\3\) or <500 Hz
(25 in\3\).
------------------------------------------------------------------------
Electric Sparker
The Melville will use a minisparker system similar to the SQUID
2000\TM\ sparker system manufactured by Applied Acoustic Engineering,
Inc. This minisparker includes electrodes mounted on a small pontoon
sled that simultaneously discharge electric current through the
seawater to an electrical ground, creating an electrical arc that
momentarily vaporizes water between positive and negative leads. The
collapsing bubbles produce an omnidirectional pulse. The pontoon sled
that supports the minisparker is towed on the sea surface,
approximately 5 m behind the ship.
Source characteristics of the SQUID 2000\TM\ provided by the
manufacturer show a source level of 209 dB re 1 [mu]Parms. This is at
the full power level of 2 kJ. The power level of this source may be
reduced to provide more consistent, reliable output signals if
necessary. The amplitude spectrum of this pulse indicates that most of
the sound energy lies between 150 Hz and 1700 Hz, and the peak
amplitude is at 900 Hz. The output sound pulse of the minisparker has a
duration of about 0.8 ms. When operated at sea for the proposed MCS-
reflection survey, the minisparker will be discharged every 0.5-3
seconds.
Electromechanical Boomer
A boomer is a broad-band sound source operating in the 100-2500 Hz
range. By sending electrical energy from the power supply through wire
coils, spring-loaded plates in the boomer transducer are electrically
charged causing the plates to repel, thus generating an acoustic pulse.
The boomer planned for this cruise has three plates with a power input
of 500 J per plate. The source level 219 dB re 1 [mu] Papeak; 209 dB re
1 [mu]Parms and the boomer will be towed on the surface. When operated
at sea for the proposed MCS-reflection survey, the boomer will be
discharged every 0.5-2 seconds.
Multibeam Echosounders and Sub-Bottom Profilers
Along with the seismic operations, two additional acoustical data
acquisition systems will be operated during part of the R/V Melville's
cruise but only in transit, not during airgun use. The ocean floor will
be mapped with the 12-kHz Simrad EM120 multi-beam echosounder (MBES) in
transit to the survey area, and a 3.5-kHz sub-bottom profiler (SBP)
will also be operated along with the MBES and also to help verify sea
floor conditions at possible coring sites.
The Melville will operate a Kongsberg-Simrad EM120 Multi Beam Echo
Sounder (MBES). The Kongsberg-Simrad EM120 operates at 11.25-12.6 kHz,
and is mounted in the hull of the Melville. It operates in several
modes, depending on water depth. In the proposed survey, it will be
used in automatic mode, changing from ``Shallow'' to ``Medium'' mode at
450 m and from ``Medium'' to ``Deep'' mode at 1000 m. In ``Shallow''
mode, the beamwidth is 2[deg] fore-aft and the estimated maximum source
level is 232 dB re 1 [mu]Parms. Each ``ping'' consists of three
successive fan-shaped transmissions, each 2 ms in duration with a delay
of 3 ms between pulses for successive sectors. In ``Medium'' mode, the
beamwidth is 1[deg] or 2[deg] fore-aft and the estimated maximum source
levels are 232 or 226 dB re 1 [mu]Parms. Each ``ping'' consists of
three successive fan-shaped transmissions, each 5 ms in duration with a
delay of 6 ms between pulses for successive sectors. In ``Deep'' mode,
the beamwidth is 1[deg] or 2[deg] fore-aft and the estimated maximum
source levels are 239 or 233 dB re 1 [mu]Parms. Each ``ping'' consists
of nine successive fan-shaped transmissions, each 15 ms in duration
with a delay of 16 ms between pulses for successive sectors. The MBES
will be used during transit to and from the Santa Barbara Channel area
to collect additional sea floor bathymetric data.
In addition, an Edgetech 512i Chirp sub-bottom profiler (SBP) will
also be a high resolution system that provides full-spectrum
(``chirp'') imaging. The system is towed either at the water surface or
slightly submerged, depending on the application and water depth. The
512i has a source level of 198 dB re 1 [mu]Parms. It has a frequency
range of 500 Hz-12 kHz with pulse widths from 5 ms to 50 ms depending
on the application. The chirp system will be used in tandem with the
seismic sources, or will be used separately to locate optimal piston
core sites, up to 4 hours at a time to a maximum of 8-10 hours per day.
[[Page 50763]]
Safety Radii
To aid in estimating the number of marine mammals that are likely
to be taken, pursuant to the MMPA, and in developing effective
mitigation measures, NMFS applies certain acoustic thresholds that
indicate the received level at which Level A or Level B harassment
would occur in marine mammals where exposed.
The distance from the sound source at which an animal would be
exposed to these different received sound levels may be estimated and
is typically referred to as safety radii. These safety radii are
specifically used to help NMFS estimate the number of marine mammals
likely to be harassed by the proposed activity and in deciding how
close a marine mammal may approach an operating sound source before the
applicant will be required to power-down or shut down the sound source.
GI-Airguns
NMFS has established a 160 dB re 1 [mu]Parms behavioral harassment
(Level B) threshold for both cetaceans and pinnipeds and a 190 dB and
180 dB re 1 [mu]Parms threshold for the potential onset of injury
(Level A) for pinnipeds and cetaceans, respectively. Received sound
levels have been modeled by Lamont-Doherty Earth Observatory of
Columbia University (L-DEO) for a number of airgun configurations,
including one 45-in\3\ GI airgun, in relation to distance and direction
from the GI airgun. 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 airgun where sound
levels of 190, 180, 160 dB re 1 [mu]Parms are predicted to be received
in deep (>1000-m) water are shown in Table 2. Because the model results
are for a 2.5-m tow depth, which is deeper than the proposed 2-m tow
depth, the distances in Table 2 slightly overestimate safety and
harassment isopleth distances.
Empirical data concerning the 180- and 160-dB distances were
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 show that radii around the airguns where the received level would
be 180 dB re 1 [mu]Parms, the safety thresholds applicable to cetaceans
(NMFS 2000), vary with water depth. Similar depth-related variation is
likely in the 190-dB distances applicable to pinnipeds. Correction
factors were developed for water depths 100-1000 m and <100 m. The
empirical data indicate that, for deep water (>1000 m), 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 GI airgun operations in deep water will be the values
predicted by L-DEO's model. Therefore, the assumed 190- and 180 dB re 1
[mu] Pa radii are 8 m and 23 m, respectively, and the 160 dB radius for
this depth is 330 m (Table 2).
Empirical measurements were not conducted for intermediate depths
(100-1000m). 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 190 and 180 dB re 1
[mu] Pa radii in intermediate-depth water are 12m and 35m,
respectively, and the 160 dB radius for this depth is 220m (Table 2).
Additional information regarding how the safety radii were calculated
and how the empirical measurements were used to correct the modeled
numbers may be found in the SIO application and EA. The proposed survey
using the GI airgun will occur only in depths approximately 150-580m;
therefore the 12m, 35m, and 330m radii are applicable.
Table 2--Distances To Which Sound Levels >=190, 180, and 160 dB re 1
[mu]Parms Could Be Received From the 45-in\3\ GI Airgun That Will Be
Used During the Seismic Surveys in the Santa Barbara Channel in November
2008. Distances are Based on Model Results Provided by L-DEO
------------------------------------------------------------------------
Estimated distances (m) at received
levels
Water depth --------------------------------------
190 dB 180 dB 160 dB
------------------------------------------------------------------------
>1000m........................... 8 23 220
100-1000m........................ 12 35 330
------------------------------------------------------------------------
Boomer/Sparker
Either the boomer or the mini sparker will be used in State waters.
The boomer likely will be used and its source level is higher than that
of the mini sparker; therefore, the propagation distances for the
boomer will be used. Received sound levels from the boomer proposed for
use in shallow water have not been modeled or measured. However,
Burgess and Lawson (2001) measured received sound levels from a boomer
with a source level of 203 dB re 1 [mu]Parms in water depths 12-14m,
and Greene (2006) measured received sound levels from a boomer with a
source level of 188.8 dB re 1 [mu]Parms in water depths 37-48m, both in
the Alaskan Beaufort Sea. The distances at which sound levels 190-,
180-, and 160-dB re 1 [mu]Parms were received are given in Table 3
together with the distances predicted using a spherical spreading
model. In each case, more so for the larger source level, the modeled
distance exceeded the measured distance. As a conservative (i.e.,
precautionary) measure, the modeled distances will be used to
calculation take estimates. The source level of the boomer is p,
corresponding roughly to 209 dB re 1 [mu]Pa[middot]mrms. Based on the
spherical spreading model, distances to which sound levels >=190, 180,
170, and 160 dB re 1 [mu]Parms could be received from the boomer are 9,
28, 90, and 280, respectively (Table 3).
[[Page 50764]]
Table 3--Distances To Which Received Sound Levels >=190, 180, and 160 dB
re 1 [mu]Parms Were Measured for Two Boomers in the Alaskan Beaufort
Sea, and Distances Predicted by a Spherical Spreading Model for Those
Sources and for the Boomer To Be Used in the Proposed Surveys
------------------------------------------------------------------------
Estimated distances (m) at received
Boomer source level (dB re 1 levels
[mu]Pa[middot]mrms) and -----------------------------------------
distance 190 dB 180 dB 160 dB
------------------------------------------------------------------------
203, measured................. <1 2 22
203, modeled.................. 4.5 16 140
188.8, measured............... 0.9 2.3 14.6
188.8, modeled................ 1 2.7 27.5
209 (this study), modeled..... 9 28 280
------------------------------------------------------------------------
Description of Marine Mammals in the Activity Area
Thirty-two species of marine mammals, including 17 odontocetes, 8
mysticetes, 6 pinnipeds, and the southern sea otter (Enhydra lutris)
could occur in the Santa Barbara Channel (SBC). In the U.S., sea otters
are managed by the U.S. Fish and Wildlife Service (USFWS). The SIO is
in the process of requesting consultation from the USFWS for impacts on
sea otters; therefore, they will not be discussed further in this
document. Of the 32 species, 20 are considered residents or regular
visitors to the Channel Islands (CINMS), 14 of which are at least
seasonally common to abundant in the SBC. The other 12 species are rare
to extremely rare. Table 4 indicated relative abundance, density,
habitat, status, and requested take for each species. Seven of the
marine mammal species which could in the action area are endangered or
threatened under the U.S. Endangered Species Act (ESA), including the
North Pacific right whale (Eubalaena japonica), humpback whale
(Megaptera novaeangliae), sei whale (Balaenoptera borealis), fin whale
(Balaenoptera physalus), blue whale (Balenoptera musculus), sperm whale
(Physeter macrocephalus), and southern resident killer whales (Orcinus
orca). However, not all these species are expected to be harassed from
the proposed seismic survey due to rarity in the area and the small
harassment isopleth distances. Table 4 below outlines the species by
the requested number of takes by both instances and individuals. Number
of exposed individuals and number of exposures are listed with respect
to the 160dB re 1 [mu]Pa threshold. Cetaceans and pinnipeds would not
be exposed to sound levels at or above 180 and 190 dB, respectively,
due to implementation of mitigation measures (see Proposed Mitigation
section). For more information on the status, distribution, and
seasonal distribution of species or stocks of marine mammals which
could be in the action area, please refer to SIO's application, section
IV.
Table 4--The Occurrence, Habitat, Regional Abundance, Conservation Status, Best and Maximum Density Estimates, Number of Marine Mammals That Could be
Exposed to Sound Level at or Above 160dB re 1[mu]Pa, Best Estimate of Number of Individuals Exposed, and Best Estimate of Number of Exposures per Marine
Mammal in or Near the Proposed Seismic Survey Area in the Santa Barbara Channel (SBC). See Tables 3-5 in SIO's Application for Further Detail
--------------------------------------------------------------------------------------------------------------------------------------------------------
Density/ Density/ Number of
Species Occurrence in SBC Habitat Abundance ESA \1\ 1000km\2\ 1000km\2\ individuals Number of
(best) (max) exposed exposures
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Pacific right whale...... Extremely rare; Offshore, 100-200 EN 0 0 0 0
winter-spring occasionally
vagrant. inshore.
Gray whale..................... Common when Coastal except 18,813 NL 0 0 0 0
migrating; rare near Channel
Oct-Nov. Islands.
Humpback whale................. All year, common Mainly nearshore >6000 EN 0.22 0.33 0 0
May-Jun, Sep-Dec. waters and banks.
Minke whale.................... All year, common Pelagic and 9000 NL 0.36 0.54 0 0
spring-fall. coastal.
Bryde's whale.................. Rare.............. Pelagic and 13,000 NL 0 0 0 0
coastal.
Sei whale...................... Very rare......... Mostly pelagic.... 7260-12,620 EN 0 0 0 0
Fin whale...................... Uncommon all year. Slope, mostly 13,620-18,6 EN 0.55 0.82 0 0
pelagic. 80
Blue whale..................... All year, common Pelagic and 1186 EN 5.45 8.15 2 4
Jun--ct. coastal.
Sperm whale.................... Uncommon all year. Usually deep 24,000 EN 0.31 0.47 0 0
pelagic.
Pygmy sperm whale.............. Uncommon all year. Deep waters off N.A. NL 21.78 32.68 6 15
shelf.
Dwarf sperm whale.............. Very rare......... Deep waters off 11,200 NL 0 0 0 0
shelf.
Cuvier's beaked whale.......... Rare all year..... Slope and pelagic. 20,000 NL 1.44 2.16 1 1
[[Page 50765]]
Baird's beaked whale........... Rare all year..... Slope and pelagic. 6000 NL 0 0 0 0
Mesoplodon spp. beaked whale... Rare all year..... Slope and pelagic. 1024 NL 0 0 0 0
Offshore bottlenose dolphin.... Common all year... Offshore, slope, 3257 NL 6.12 9.18 2 4
shelf.
Coastal bottlenose dolphin..... Common all year... Within 1 km of 323 NL 6.12 9.18 2 2
shore.
Striped dolphin................ Rare.............. Off continental 1,824,000 NL 3.37 5.05 1 2
shelf.
Short-beaked common dolphin.... Common all year... Shelf, pelagic, 487,622 NL 1364.41 2046.61 394 942
high relief.
Long-beaked common dolphin..... Common all year... Coastal, high 1893 NL 174.69 262.04 50 121
relief.
Pacific white-sided dolphin.... All year, common Offshore, slope... 931,000 NL 33 49.5 10 23
fall-winter.
Northern right whale dolphin... Common only Slope, offshore 15,305 NL 16.8 25.2 5 12
winter, spring. waters.
Risso's dolphin................ Common all year... Shelf, slope, 12,093 NL 18.35 27.53 5 13
seamounts.
Killer whale................... Uncommon all year. Widely distributed 8500 NL 0 0 0 0
Short-finned pilot whale....... Rare all year..... Mostly pelagic, 160,200 NL 0 0 0 0
high-relief.
Dall's porpoise................ Uncommon all year. Shelf, slope, 57,549 NL 9.17 13.76 3 0
offshore.
Harbor porpoise................ Rare.............. Coastal........... 202,988 NL 0 0 0 0
Guadalupe fur seal............. Extremely rare.... Coastal........... 7408 T N/A N/A 0 0
Northern fur seal.............. Uncommon all year. Pelagic, offshore. 721,935 NL N/A N/A 0 0
California sea lion............ Common all year... Coastal, shelf.... 238,000 NL 100 300 29 69
Steller sea lion............... Rare all year..... Coastal, shelf.... 44,584 T N/A N/A 0 0
Harbor seal.................... Common all year... Coastal........... 34,233 NL N/A N/A 0 0
Northern elephant seal......... All year, common Coastal, pelagic 124,000 NL N/A N/A 0 0
Dec-Mar peak. when migrating.
--------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------------------------------
Number of
Species Occurrence in SBC Habitat Abundance ESA \1\ Number of individuals Requested take
exposures \2\ exposed \3\ \4\
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Pacific right whale........ Extremely rare; Offshore, 100-200 EN 0 0 0
winter-spring occasionally
vagrant. inshore.
Gray whale....................... Common when Coastal except near 18,813 NL 0 0 0
migrating; rare Oct- Channel Islands.
Nov.
Humpback whale................... All year, common May- Mainly nearshore >6000 EN 0 0 2
Jun, Sep-Dec. waters and banks.
Minke whale...................... All year, common Pelagic and coastal 9000 NL 0 0 0
spring-fall.
Bryde's whale.................... Rare................ Pelagic and coastal 13,000 NL 0 0 0
Sei whale........................ Very rare........... Mostly pelagic..... 7260-12,620 EN 0 0 0
Fin whale........................ Uncommon all year... Slope, mostly 13,620-18,680 EN 0 0 2
pelagic.
Blue whale....................... All year, common Jun- Pelagic and coastal 1186 EN 4 2 2
Oct.
Sperm whale...................... Uncommon all year... Usually deep 24,000 EN 0 0 8
pelagic.
Pygmy sperm whale................ Uncommon all year... Deep waters off N.A. NL 15 6 9
shelf.
[[Page 50766]]
Dwarf sperm whale................ Very rare........... Deep waters off 11,200 NL 0 0 0
shelf.
Cuvier's beaked whale............ Rare all year....... Slope and pelagic.. 20,000 NL 1 1 1
Baird's beaked whale............. Rare all year....... Slope and pelagic.. 6000 NL 0 0 0
Mesoplodont beaked whale......... Rare all year....... Slope and pelagic.. 1024 NL 0 0 0
Offshore bottlenose dolphin...... Common all year..... Offshore, slope, 3257 NL 4 2 3
shelf.
Coastal bottlenose dolphin....... Common all year..... Within 1 km of 323 NL 4 2 3
shore.
Striped dolphin.................. Rare................ Off continental 1,824,000 NL 2 1 1
shelf.
Short-beaked common dolphin...... Common all year..... Shelf, pelagic, 487,622 NL 942 394 591
high relief.
Long-beaked common dolphin....... Common all year..... Coastal, high 1893 NL 121 50 76
relief.
Pacific white-sided dolphin...... All year, common Offshore, slope.... 931,000 NL 23 10 14
fall-winter.
Northern right whale dolphin..... Common only winter, Slope, offshore 15,305 NL 12 5 7
spring. waters.
Risso's dolphin.................. Common all year..... Shelf, slope, 12,093 NL 13 5 8
seamounts.
Killer whale..................... Uncommon all year... Widely distributed. 8500 NL 0 0 0
Short-finned pilot whale......... Rare all year....... Mostly pelagic, 160,200 NL 0 0 0
high-relief.
Dall's porpoise.................. Uncommon all year... Shelf, slope, 57,549 NL 0 3 4
offshore.
Harbor porpoise.................. Rare................ Coastal............ 202,988 NL 0 0 0
Guadalupe fur seal............... Extremely rare...... Coastal............ 7408 T 0 0 0
Northern fur seal................ Uncommon all year... Pelagic, offshore.. 721,935 NL 0 0 0
California sea lion.............. Common all year..... Coastal, shelf..... 238,000 NL 69 29 87
Steller sea lion................. Rare all year....... Coastal, shelf..... 44,584 T 0 0 0
Harbor seal...................... Common all year..... Coastal............ 34,233 NL 0 0 20
Northern elephant seal........... All year, common Dec- Coastal, pelagic 124,000 NL 0 0 0
Mar peak. when migrating.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ U.S. Endangered Species Act: EN = Endangered, T = Threatened, NL = Not listed
\2\ Best estimate as listed in Table 5 of the application
\3\ Best estimate as listed in Table 5 of the application
\4\ Requested number of takes as listed in Table 5 of application
Potential Effects of the Proposed Activity on Marine Mammals
Potential Effects of Airgun Sounds on Marine Mammals
The effects of sounds from airguns might include one or more of the
following: tolerance, masking of natural sounds, behavioral
disturbance, temporary or permanent hearing impairment, or non-auditory
physical or physiological effects (Richardson et al., 1995; Gordon et
al., 2004; Nowacek et al., 2007; Southall et al., 2007). Given the
small size of the GI gun planned for the present 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. Permanent hearing impairment, in the unlikely event that it
occurred, would constitute injury, but temporary threshold shift (TTS)
is not an injury (Southall et al., 2007). With the possible exception
of some cases of temporary threshold shift in harbor seals and perhaps
some other seals, it is unlikely that the project would result in any
cases of temporary or especially permanent hearing impairment, or any
significant non-auditory physical or physiological effects. Some
behavioral disturbance is expected, but is expected to be localized and
short-term.
Tolerance
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
A summary of the characteristics of airgun pulses, is provided in
Appendix A of NSF's EA prepared for this survey. Several studies have
also shown that marine mammals at distances more than a few kilometers
from operating seismic vessels often show no apparent response
(tolerance) (see Appendix A of NSF's EA). That is often true even in
cases when the pulsed sounds must be readily audible to the animals
based on measured received levels and the hearing sensitivity of 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 usually seem to be
more tolerant of exposure to airgun pulses than cetaceans, with the
relative responsiveness of baleen and toothed whales being variable.
Masking
Introduced underwater sound may, through masking, reduce the
effective communication distance of a marine mammal species if the
frequency of the source is close to that used as a signal
[[Page 50767]]
by the marine mammal, and if the anthropogenic sound is present for a
significant fraction of the time (Richardson et al., 1995).
Masking effects of pulsed sounds (even from large arrays of
airguns) on marine mammal calls and other natural sounds are expected
to be limited, although there are very few specific data on this.
Because of the intermittent nature (one pulse every 105 or 210 seconds)
and low duty cycle of seismic pulses, animals can emit and receive
sounds in the relatively quiet intervals between pulses. However, in
exceptional situations, reverberation occurs for much or all of the
interval between pulses (e.g., Simard et al., 2005; Clark and Gagnon,
2006) which could mask calls. Some baleen and toothed whales are known
to continue calling in the presence of seismic pulses, and their calls
can usually be heard between the seismic pulses (e.g., Richardson et
al., 1986; McDonald et al., 1995; Greene et al., 1999; Nieukirk et al.,
2004; Smultea et al., 2004; Holst et al., 2005a,b, 2006). In the
northeastern Pacific Ocean, blue whale calls have been recorded during
a seismic survey off Oregon (McDonald et al., 1995). Among odontocetes,
there has been one report that sperm whales ceased calling when exposed
to pulses from a very distant seismic ship (Bowles et al., 1994), but
more recent studies found that they continued calling in the presence
of seismic pulses (Madsen et al., 2002c; Tyack et al., 2003; Smultea et
al., 2004; Holst et al., 2006; Jochens et al., 2006). Dolphins and
porpoises commonly are heard calling while airguns are operating (e.g.,
Gordon et al., 2004; Smultea et al., 2004; Holst et al., 2005a,b;
Potter et al., 2007). The sounds important to small odontocetes are
predominantly at much higher frequencies than are the dominant
components of airgun sounds, thus limiting the potential for masking.
In general, masking effects of seismic pulses are expected to be minor,
given the normally intermittent nature of seismic pulses and the
Melville being the only seismic vessel operating in the area for a
limited time. Masking effects on marine mammals are discussed further
in Appendix A of NSF's EA.
Disturbance Reactions
Disturbance includes a variety of effects, including subtle to
conspicuous changes in behavior, movement, and displacement. Based on
NMFS (2001, p. 9293), NRC (2005), and Southall et al. (2007), it is
assumed that simple exposure to sound, or brief reactions that do not
disrupt behavioral patterns in a potentially significant manner, do not
constitute harassment or ``taking,'' with ``potentially significant''
meaning ``in a manner that might have deleterious effects to the well-
being of individual marine mammals or their populations''.
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 does react briefly to an underwater
sound by changing its behavior or moving a small distance, the impacts
of the change are unlikely to be significant to the individual, let
alone the stock or population. However, if a sound source displaces
marine mammals from an important feeding or breeding area for a
prolonged period, impacts on individuals and populations could be
significant. Given the many uncertainties in predicting the quantity
and types of impacts of noise on marine mammals, it is common practice
to estimate how many mammals would be present within a particular
distance of industrial activities and exposed to a particular level of
industrial sound. In most cases, this approach likely overestimates the
numbers of marine mammals that would be affected in some biologically-
important manner.
The sound criteria used to estimate how many marine mammals might
be disturbed to some biologically-important degree by a seismic program
are based primarily on behavioral observations of a few species.
Detailed studies have been done on humpback, gray, bowhead (Balaena
mysticetus), and sperm whales, and on ringed seals (Pusa hispida). Less
detailed data are available for some other species of baleen whales,
small toothed whales, and sea otters, but for many species there are no
data on responses to marine seismic surveys.
Baleen Whales
Baleen whales generally tend to avoid operating airguns, but
avoidance radii are quite variable. Whales are often reported to show
no overt reactions to pulses from large arrays of airguns at distances
beyond a few kilometers, even though the airgun pulses remain well
above ambient noise levels out to much longer distances. However, as
reviewed in SIO's application and Appendix A of NSF's EA, baleen whales
exposed to strong noise pulses from airguns often react by deviating
from their normal migration route and/or interrupting their feeding and
moving away. In the cases of migrating gray and bowhead whales, the
observed changes in behavior appeared to be of little or no biological
consequence to the animals. They simply avoided the sound source by
displacing their migration route to varying degrees, but within the
natural boundaries of the migration corridors.
Studies of gray, bowhead, and humpback whales have shown that
seismic pulses with received levels of 160-170 dB re 1 [mu]Pa (rms)
seem to cause obvious avoidance behavior in a substantial fraction of
the animals exposed (Richardson et al., 1995). In many areas, seismic
pulses from large arrays of airguns diminish to those levels at
distances ranging from 4-15 km (2.5-9.3 mi) from the source. A
substantial proportion of the baleen whales within those distances may
show avoidance or other strong behavioral reactions to the airgun
array. Subtle behavioral changes sometimes become evident at somewhat
lower received levels, and studies, summarized in Appendix A(5) of
SIO's EA, have shown that some species of baleen whales, notably
bowhead and humpback whales, at times show strong avoidance at received
levels lower than 160-170 dB re 1 [mu]Pa (rms).
Responses of humpback whales to seismic surveys have been studied
during migration, on summer feeding grounds, and on Angolan winter
breeding grounds; there has also been discussion of effects on the
Brazilian wintering grounds. McCauley et al. (1998, 2000a) studied the
responses of humpback whales off Western Australia to a full-scale
seismic survey with a 16-airgun, 2678-in\3\ array, and to a single 20-
in\3\ airgun with source level 227 dB re 1 [mu]Pa [middot] m (peak to
peak). McCauley et al. (1998) documented that avoidance reactions began
at 5-8 km (3-5 mi) from the array, and that those reactions kept most
pods approximately 3-4 km (1.8-2.5 mi) from the operating seismic boat.
McCauley et al. (2000a) 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
more sensitive resting pods of cow-calf pairs. Avoidance distances with
respect to the single airgun were smaller but consistent with the
results from the full array in terms of the received sound levels. The
mean received level for initial avoidance of an approaching airgun was
140 dB re 1 [mu]Pa (rms) for humpback pods containing females, and at
the mean closest point of approach distance the received level was 143
dB re 1 [mu]Pa (rms). The initial avoidance response generally occurred
at distances of 5-8 km (3.1-4.9 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
[[Page 50768]]
m (328-1312 ft), where the maximum received level was 179 dB re 1
[mu]Pa (rms).
Humpback whales on their summer feeding grounds in southeast Alaska
did not exhibit persistent avoidance when exposed to seismic pulses
from a 1.64-L (100-in\3\) airgun (Malme et al., 1985). Malme et al.
reported that some of the humpbacks seemed startled at received levels
of 150-169 dB re 1 [mu]Pa and concluded that there was no clear
evidence of avoidance, despite the possibility of subtle effects, at
received levels up to 172 re 1 [mu]Pa on an approximate rms basis. It
has been suggested that South Atlantic humpback whales wintering off
Brazil may be displaced or even strand upon exposure to seismic surveys
(Engel et al., 2004). The evidence for this was circumstantial and
subject to alternative explanations (IAGC, 2004). Also, the evidence
was not consistent with subsequent results from the same area of Brazil
(Parente et al., 2006), or with direct studies of humpbacks exposed to
seismic surveys in other areas and seasons. After allowance for data
from subsequent years, there was ``no observable direct correlation''
between strandings and seismic surveys (IWC, 2007:236).
There are no data on reactions of right whales to seismic surveys,
but results from the closely-related bowhead whale show that their
responsiveness can be quite variable depending on their activity
(migrating versus feeding). Bowhead whales migrating west across the
Alaskan Beaufort Sea in autumn, in particular, are unusually
responsive, with substantial avoidance occurring out to distances of
20-30 km from a medium-sized airgun source at received sound levels of
around 120-130 dB re 1 [mu]Pa (rms) (Miller et al., 1999; Richardson et
al., 1999). However, more recent research on bowhead whales (Miller et
al., 2005; Harris et al., 2007) corroborates earlier evidence that,
during the summer feeding season, bowheads are not as sensitive to
seismic sources. Nonetheless, subtle but statistically significant
changes in surfacing-respiration-dive cycles were evident upon
statistical analysis (Richardson et al., 1986). In summer, bowheads
typically begin to show avoidance reactions at received levels of about
152-178 dB re 1 [mu]Pa (rms) (Richardson et al., 1986, 1995; Ljungblad
et al., 1988; Miller et al., 2005).
Reactions of migrating and feeding (but not wintering) gray whales
to seismic surveys have been studied. Malme et al. (1986, 1988) studied
the responses of feeding eastern Pacific gray whales to pulses from a
single 100-in\3\ airgun off St. Lawrence Island in the northern Bering
Sea. They estimated, based on small sample sizes, that 50 percent of
feeding gray whales stopped feeding at an average received pressure
level of 173 dB re 1 [mu]Pa on an (approximate) rms basis, and that 10
percent of feeding whales interrupted feeding at received levels of 163
dB re 1 [mu]Pa (rms). Those findings were generally consistent with the
results of experiments conducted on larger numbers of gray whales that
were migrating along the California coast (Malme et al., 1984; Malme
and Miles, 1985), and western Pacific gray whales feeding off Sakhalin
Island, Russia (Wursig et al., 1999; Gailey et al., 2007; Johnson et
al., 2007; Yazvenko et al., 2007a, b), along with data on gray whales
off British Columbia (Bain and Williams, 2006).
Various species of Balaenoptera (blue, sei, fin, and minke whales)
have occasionally been reported in areas ensonified by airgun pulses
(Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006).
Sightings by observers on seismic vessels off the United Kingdom from
1997 to 2000 suggest that, during times of good sightability, sighting
rates for mysticetes (mainly fin and sei whales) were similar when
large arrays of airguns were shooting vs. silent (Stone, 2003; Stone
and Tasker, 2006). However, these whales tended to exhibit localized
avoidance, remaining significantly further (on average) from the airgun
array during seismic operations compared with non-seismic periods
(Stone and Tasker, 2006). In a study off Nova Scotia, Moulton and
Miller (2005) found little difference in sighting rates (after
accounting for water depth) and initial sighting distances of
balaenopterid whales when airguns were operating versus silent.
However, there were indications that these whales were more likely to
be moving away when seen during airgun operations. Similarly, ship-
based monitoring studies of blue, fin, sei and minke whales offshore of
Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more than
small differences in sighting rates and swim directions during seismic
vs. non-seismic periods Moulton et al., 2005, 2006a,b).
Data on short-term reactions by cetaceans to impulsive noises are
not necessarily indicative of long-term or biologically significant
effects. It is not known whether impulsive sounds affect reproductive
rate or distribution and habitat use in subsequent days or years.
However, gray whales have continued to migrate annually along the west
coast of North America with substantial increases in the population
over recent years, despite intermittent seismic exploration (and much
ship traffic) in that area for decades (Appendix A in Malme et al.,
1984; Richardson et al., 1995; Angliss and Outlaw, 2008). The western
Pacific gray whale population did not seem affected by a seismic survey
in its feeding ground during a previous year (Johnson et al., 2007).
Similarly, bowhead whales have continued to travel to the eastern
Beaufort Sea each summer, and their numbers have increased notably,
despite seismic exploration in their summer and autumn range for many
years (Richardson et al., 1987; Angliss and Outlaw, 2008).
Toothed Whales
Little systematic information is available about reactions of
toothed whales to noise pulses. Few studies similar to the more
extensive baleen whale/seismic pulse work summarized above and (in more
detail) in Appendix A of SIO's application have been reported for
toothed whales. However, there are recent systematic studies on sperm
whales (Jochens et al., 2006; Miller et al., 2006), and there is an
increasing amount of information about responses of various odontocetes
to seismic surveys based on monitoring studies (e.g., Stone, 2003;
Smultea et al., 2004; Moulton and Miller, 2005; Bain and Williams,
2006; Holst et al., 2006; Stone and Tasker, 2006; Potter et al., 2007;
Weir, 2008).
Seismic operators and marine mammal observers on seismic vessels
regularly see dolphins and other small toothed whales near operating
airgun arrays, but in general there is a tendency for most delphinids
to show some avoidance of operating seismic vessels (e.g., Goold,
1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and
Miller, 2005; Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008).
Some dolphins seem to be attracted to the seismic vessel and floats,
and some ride the bow wave of the seismic vessel even when large arrays
of airguns are firing (e.g., Moulton and Miller, 2005). Nonetheless,
small toothed whales more often tend to head away, or to maintain a
somewhat greater distance from the vessel, when a large array of
airguns is operating than when it is silent (e.g., Stone and Tasker,
2006; Weir, 2008). In most cases the avoidance radii for delphinids
appear to be small, on the order of 1 km less, and some individuals
show no apparent avoidance. The beluga (Delphinapterus leucas) is a
species that (at least at times) shows long-distance avoidance of
seismic
[[Page 50769]]
vessels. Aerial surveys conducted in the southeastern Beaufort Sea
during summer found that sighting rates of beluga whales were
significantly lower at distances 10-20 km (6.2-12.4 mi) compared with
20-30 km (12.4-18.6 mi) from an operating airgun array, and observers
on seismic boats in that area rarely see belugas (Miller et al., 2005;
Harris et al., 2007).
Captive bottlenose dolphins and beluga whales exhibited changes in
behavior when exposed to strong pulsed sounds similar in duration to
those typically used in seismic surveys (Finneran et al., 2000, 2002,
2005). However, the animals tolerated high received levels of sound
before exhibiting aversive behaviors.
Results for porpoises depend on species. The limited available data
suggest that harbor porpoises show stronger avoidance of seismic
operations than do Dall's porpoises (Stone, 2003; MacLean and Koski,
2005; Bain and Williams, 2006; Stone and Tasker, 2006). Dall's
porpoises seem relatively tolerant of airgun operations (MacLean and
Koski, 2005; Bain and Williams, 2006), although they too have been
observed to avoid large arrays of operating airguns (Calambokidis and
Osmek, 1998; Bain and Williams, 2006). This apparent difference in
responsiveness of these two porpoise species is consistent with their
relative responsiveness to boat traffic and some other acoustic sources
(Richardson et al., 1995; Southall et al., 2007).
Most studies of sperm whales exposed to airgun sounds indicate that
the sperm whale shows considerable tolerance of airgun pulses (e.g.,
Stone, 2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir,
2008). In most cases the whales do not show strong avoidance, and they
continue to call (see Appendix A of NSF's EA for review). However,
controlled exposure experiments in the Gulf of Mexico indicate that
foraging behavior was altered upon exposure to airgun sound (Jochens et
al., 2006).
There are almost no specific data on the behavioral reactions of
beaked whales to seismic surveys. However, northern bottlenose whales
(Hyperoodon ampullatus) continued to produce high-frequency clicks when
exposed to sound pulses from distant seismic surveys (Laurinolli and
Cochrane, 2005; Simard et al., 2005). Most beaked whales tend to avoid
approaching vessels of other types (e.g., Wursig et al., 1998). They
may also dive for an extended period when approached by a vessel (e.g.,
Kasuya, 1986). Thus, it is likely that beaked whales would also show
strong avoidance of an approaching seismic vessel, although this has
not been documented explicitly.
There are increasing indications that some beaked whales tend to
strand when naval exercises involving mid-frequency sonar operation are
ongoing nearby (e.g., Simmonds and Lopez-Jurado, 1991; Frantzis, 1998;
NOAA and USN, 2001; Jepson et al., 2003; Hildebrand, 2005; Barlow and
Gisiner, 2006; see also the ``Strandings and Mortality'' subsection,
later). These strandings are apparently at least in part a disturbance
response, although auditory or other injuries or other physiological
effects may also be a involved. Whether beaked whales would ever react
similarly to seismic surveys is unknown (see ``Strandings and
Mortality'', below). Seismic survey sounds are quite different from
those of the sonar in operation during the above-cited incidents.
Odontocete reactions to large arrays of airguns are variable and,
at least for delphinids and Dall's porpoises, seem to be confined to a
smaller radius than has been observed for the more responsive of the
mysticetes, belugas, and harbor porpoises (refer to Appendix A in NSF's
EA). NMFS has established a 160 dB re 1 [mu]Pa disturbance threshold.
Animals exposed to received sound levels at or above this threshold
(but below injurious threshold) shall be considered ``taken'' by
behavioral harassment (Level B).
Pinnipeds
Pinnipeds are not likely to show a strong avoidance reaction to the
airgun array. Visual monitoring from seismic vessels has shown only
slight (if any) avoidance of airguns by pinnipeds, and only slight (if
any) changes in behavior (Appendix A in NSF's EA). In the Beaufort Sea,
some ringed seals avoided an area of 100 m (328 ft) to (at most) a few
hundred meters around seismic vessels, but many seals remained within
100-200 m (328-656 ft) of the trackline as the operating airgun array
passed by (e.g., Harris et al., 2001; Moulton and Lawson, 2002; Miller
et al., 2005). Ringed seal sightings averaged somewhat farther away
from the seismic vessel when the airguns were operating than when they
were not, but the difference was small (Moulton and Lawson, 2002).
Similarly, in Puget Sound, sighting distances for harbor seals and
California sea lions tended to be larger when airguns were operating
(Calambokidis and Osmek, 1998). Previous telemetry work suggests that
avoidance and other behavioral reactions may be stronger than evident
to date from visual studies (Thompson et al., 1998). 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-term effects on pinniped individuals or populations. As
for cetaceans, the 160 dB or above disturbance threshold, but below
injurious levels (190 dB), is considered appropriate for pinnipeds.
Hearing Impairment and Other Physical Effects
Temporary or permanent hearing impairment is a possibility when
marine mammals are exposed to very strong sounds, and temporary
threshold shift (TTS) has been demonstrated and studied in certain
captive odontocetes and pinnipeds exposed to strong sounds (reviewed in
Southall et al., 2007). However, there has been no specific
documentation of TTS let alone permanent hearing damage, i.e.,
permanent threshold shift (PTS), in free-ranging marine mammals exposed
to sequences of airgun pulses during realistic field conditions.
Current NMFS policy regarding exposure of marine mammals to high-level
sounds is that cetaceans and pinnipeds should not be exposed to
impulsive sounds with received levels of 180 and 190 dB re 1
[mu]Parms or above, respectively, are considered to have
been taken incidentally taken by Level A harassment. (NMFS, 2000).
These levels are precautionary and were used in establishing the
exclusion (i.e., shut-down) zones planned for the proposed seismic
survey.
Several aspects of the planned monitoring and mitigation measures
for this project are designed to detect marine mammals occurring near
the airgun array, and to avoid exposing them to sound pulses that
might, at least in theory, cause hearing impairment. In addition, many
cetaceans and (to a limited degree) pinnipeds and sea turtles are
likely to show some avoidance or the area with high received levels of
airgun sound. 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 might also occur in marine mammals
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that might (in theory) occur
in mammals close to a strong sound source include stress, neurological
effects, bubble formation, and other types of organ or tissue damage.
It is possible that some
[[Page 50770]]
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 unlikely that any effects
of these types would occur during the proposed project given the brief
duration of exposure of any given mammal, the deep water in the survey
area, 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. At least in terrestrial mammals, TTS can last from minutes or
hours to (in cases of strong TTS) days. For sound exposures at or
somewhat above the TTS threshold, hearing sensitivity in both
terrestrial and marine mammals recovers rapidly after exposure to the
noise ends. Few data on sound levels and durations necessary to elicit
mild TTS have been obtained for marine mammals, and none of the
published data concern TTS elicited by exposure to multiple pulses of
sound. Available data on TTS in marine mammals are summarized in
Southall et al. (2007).
For toothed whales exposed to single short pulses, the TTS
threshold appears to be, to a first approximation, a function of the
energy content of the pulse (Finneran et al., 2002, 2005). Sound
exposure level (SEL), which takes into account the duration of the
sound, is the metric used to measure energy and uses the units dB re 1
[mu]Pa\2\ [middot] s, as opposed to sound pressure level (SPL), which
is the pressure metric used in the rest of this document (units--dB re
1 [mu]Pa). Given the available data, the received energy level of a
single seismic pulse (with no frequency weighting) might need to be
approximately 186 dB re 1 [mu]Pa2 [middot] s, (i.e., 186 dB SEL or
approximately 196-201 dB re 1 [mu]Parms) in order to produce
brief, mild TTS. Exposure to several strong seismic pulses that each
have received levels near 190 dB re 1 [mu]Parms might result
in cumulative exposure of approximately 186 dB SEL and thus slight TTS
in a small odontocete, assuming the TTS threshold is (to a first
approximation) a function of the total received pulse energy. The
distances from the Melville's single airgun at which the received
energy level (per pulse, flat-weighted) would be expected to be 190 dB
re 1 [mu]Parms or above, are shown in Table 2. Levels 190 dB
re 1 [mu]Parms or above are expected to be restricted to
radii no more than 12m (39 ft) (Table 2) from the airgun at full
chamber size (45 in\3\). Again, this is a conservative safety zone
since the applicant has indicated the airgun will likely be operated at
25-35 in\3\. For an odontocete closer to the surface, the maximum
radius with 190 dB re 1 [mu]Parms or above, would be
smaller.
The above TTS information for odontocetes is derived from studies
on the bottlenose dolphin and beluga. There is no published TTS
information for other types of cetaceans. However, preliminary evidence
from a harbor porpoise exposed to airgun sound suggests that its TTS
threshold may have been lower (Lucke et al., 2007).
For baleen whales, there are no data, direct or indirect, on levels
or properties of sound that are required to induce TTS. The frequencies
to which baleen whales are most sensitive are assumed to be lower than
those to which odontocetes are most sensitive, and natural background
noise levels at those low frequencies tend to be higher. As a result,
auditory thresholds of baleen whales within their frequency band of
best hearing are believed to be higher (less sensitive) than are those
of odontocetes at their best frequencies (Clark and Ellison, 2004).
From this, it is suspected that received levels causing TTS onset may
also be higher in baleen whales (Southall et al., 2007). In any event,
no cases of TTS are expected given three considerations: (1) The low
abundance of baleen whales in most parts of the planned study area; (2)
the strong likelihood that baleen whales would avoid the approaching
airgun (or vessel) before being exposed to levels high enough for TTS
to occur; and (3) the mitigation measures that are planned.
In pinnipeds, TTS thresholds associated with exposure to brief
pulses (single or multiple) of underwater sound have not been measured.
Initial evidence from more prolonged (non-pulse) exposures suggested
that some pinnipeds (harbor seals in particular) incur TTS at somewhat
lower received levels than do small odontocetes exposed for similar
durations (Kastak et al., 1999, 2005; Ketten et al., 2001). The
pinniped TTS threshold for pulsed sounds has been indirectly estimated
as being a SEL of approximately 171 dB re 1 [mu]Pa\2\ [middot] s,
(Southall et al., 2007), which would be equivalent to a single pulse
with received level of approximately 181-186 dB re 1
[mu]Parms, or a series of pulses for which the highest rms
values are a few dB lower.
Permanent Threshold Shift (PTS)
When PTS occurs, there is physical damage to the sound receptors in
the ear. In severe cases, there can be total or partial deafness, while
in other cases, the animal has an impaired ability to hear sounds in
specific frequency ranges (Kryter, 1985). There is no specific evidence
that exposure to pulses of airgun sound can cause PTS in any marine
mammal, even with large arrays of airguns. However, given the
possibility that mammals close to an airgun array might incur at least
mild TTS, there has been further speculation about the possibility that
some individuals occurring very close to airguns might incur PTS
(Richardson et al., 1995, p. 372ff). Single or occasional occurrences
of mild TTS are not indicative of permanent auditory damage.
Relationships between TTS and PTS thresholds have not been studied in
marine mammals, but are assumed to be similar to those in humans and
other terrestrial mammals. PTS might occur at a received sound level at
least several decibels above that inducing mild TTS if the animal were
exposed to strong sound pulses with rapid rise time--see Appendix A of
NSF's EA. Based on data from terrestrial mammals, a precautionary
assumption is that the PTS threshold for impulse sounds (such as airgun
pulses as received close to the source) is at least 6 dB higher than
the TTS threshold on a peak-pressure basis, and probably greater than 6
dB (Southall et al., 2007). On an SEL basis, Southall et al. (2007:441-
4) estimated that received levels would need to exceed the TTS
threshold by at least 15 dB for there to be risk of PTS. Thus, for
cetaceans, they estimate that the PTS threshold might be an mammal-
weighted (M-weighted) SEL (for the sequence of received pulses) of
approximately 198 dB re 1 [mu]Pa\2\ [middot] s, (15 dB higher than the
TTS threshold for an impulse), where the SEL value is accumulated over
the sequence of pulses. Additional assumptions had to be made to derive
a corresponding estimate for pinnipeds, as the only available data on
TTS-thresholds in pinnipeds pertain to non-impulse sound. Southall et
al. (2007) estimate that the PTS threshold could be a cumulative
Mpw-weighted SEL of approximately 186 dB re 1 [mu]Pa\2\
[middot] s, in the harbor seal exposed to impulse sound. The PTS
threshold for the California sea lion and northern elephant seal, the
PTS threshold would
[[Page 50771]]
probably be higher, given the higher TTS thresholds in those species.
Southall et al. (2007) also note that, regardless of the SEL, there
is concern about the possibility of PTS if a cetacean or pinniped
received one or more pulses with peak pressure exceeding 230 or 218 dB
re 1[mu]Pa (peak), respectively. A peak pressure of 230 dB re 1[mu]Pa
(3.2 bar [middot] m, 0-peak) would only be found within a few meters of
the largest (360 in\3\) airgun in the planned airgun array (Caldwell
and Dragoset, 2000). A peak pressure of 218 dB re 1 [mu]Pa could be
received somewhat farther away; to estimate that specific distance, one
would need to apply a model that accurately calculates peak pressures
in the nearfield around an array of airguns.
Given the higher level of sound necessary to cause PTS as compared
with TTS, it is considerably less likely that PTS would occur. 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, PAM,
power downs, and shut downs of the airguns when mammals are seen within
or approaching the exclusion zones, will further reduce the probability
of exposure of marine mammals to sounds strong enough to induce PTS.
Non-Auditory Physiological Effects
Non-auditory physiological effects or injuries that theoretically
might occur in marine mammals exposed to strong underwater sound
include stress, neurological effects, bubble formation, resonance, and
other types of organ or tissue damage (Cox et al., 2006; Southall et
al., 2007). Studies examining such effects are limited. However,
resonance (Gentry, 2002) and direct noise-induced bubble formation
(Crum et al., 2005) are not expected in the case of an impulsive source
like an airgun array. If seismic surveys disrupt diving patterns of
deep-diving species, this might perhaps result in bubble formation and
a form of the bends, as speculated to occur in beaked whales exposed to
sonar. However, there is no specific evidence of this upon exposure to
airgun pulses.
In general, very little is known about the potential for seismic
survey sounds (or other types of strong underwater sounds) to cause
non-auditory physical effects in marine mammals. Such effects, if they
occur at all, would presumably be limited to short distances and to
activities that extend over a prolonged period. The available data do
not allow identification of a specific exposure level above which non-
auditory effects can be expected (Southall et al., 2007), or any
meaningful quantitative predictions of the numbers (if any) of marine
mammals that might be affected in those ways. Marine mammals that show
behavioral avoidance of seismic vessels, including most baleen whales,
some odontocetes, and some pinnipeds, are especially unlikely to incur
non-auditory physical effects. Also, the planned mitigation measures,
including shut downs of the airguns, will reduce any such effects that
might otherwise occur.
Strandings and Mortality
Marine mammals close to underwater detonations of high explosives
can be killed or severely injured, and the auditory organs are
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995).
However, explosives are no longer used for marine seismic research or
commercial seismic surveys, and have been replaced entirely by airguns
or related non-explosive pulse generators. Airgun pulses are less
energetic and have slower rise times, and there is no specific evidence
that they can cause serious injury, death, or stranding even in the
case of large airgun arrays. However, the association of mass
strandings of beaked whales with naval exercises and, in one case, an
L-DEO seismic survey (Malakoff, 2002; Cox et al., 2006), has raised the
possibility that beaked whales exposed to strong pulsed sounds may be
especially susceptible to injury and/or behavioral reactions that can
lead to stranding (e.g., Hildebrand, 2005; Southall et al., 2007).
Specific sound-related processes that lead to strandings and
mortality are not well documented, but may include: (1) Swimming in
avoidance of a sound into shallow water; (2) a change in behavior (such
as a change in diving behavior) that might contribute to tissue damage,
gas bubble formation, hypoxia, cardiac arrhythmia, hypertensive
hemorrhage or other forms of trauma; (3) a physiological change such as
a vestibular response leading to a behavioral change or stress-induced
hemorrhagic diathesis, leading in turn to tissue damage; and (4) tissue
damage directly from sound exposure, such as through acoustically
mediated bubble formation and growth or acoustic resonance of tissues.
There are increasing indications that gas-bubble disease (analogous to
the bends), induced in supersaturated tissue by a behavioral response
to acoustic exposure, could be a pathologic mechanism for the
strandings and mortality of some deep-diving cetaceans exposed to
sonar. However, the evidence for this remains circumstantial and
associated with exposure to naval mid-frequency sonar, not seismic
surveys (Cox et al., 2006; Southall et al., 2007).
Seismic pulses and mid-frequency sonar signals are quite different,
and some mechanisms by which sonar sounds have been hypothesized to
affect beaked whales are unlikely to apply to airgun pulses. Sounds
produced by airgun arrays are broadband impulses with most of the
energy below 1 kHz. Typical military mid-frequency sonars emit non-
impulse sounds at frequencies of 2-10 kHz, generally with a relatively
narrow bandwidth at any one time. A further difference between seismic
surveys and naval exercises is that naval exercises can involve sound
sources on more than one vessel. Thus, it is not appropriate to assume
that there is a direct connection between the effects of military sonar
and seismic surveys on marine mammals. However, evidence that sonar
signals can, in special circumstances, lead (at least indirectly) to
physical damage and mortality (e.g., Balcomb and Claridge, 2001; NOAA
and USN, 2001; Jepson et al., 2003; Fernandez et al., 2004, 2005;
Hildebrand, 2005; Cox et al., 2006) suggests that caution is warranted
when dealing with exposure of marine mammals to any high-intensity
pulsed sound.
There is no conclusive evidence of cetacean strandings or deaths at
sea as a result of exposure to seismic surveys, but a few cases of
strandings in the general area where a seismic survey was ongoing have
led to speculation concerning a possible link between seismic surveys
and strandings. Suggestions that there was a link between seismic
surveys and strandings of humpback whales in Brazil (Engel et al.,
2004) were not well founded (IAGC, 2004; IWC, 2007). In September 2002,
there was a stranding of two Cuvier's beaked whales (Ziphius
cavirostris ) in the Gulf of California, Mexico, when the L-DEO vessel
R/V Maurice Ewing was operating a 20-airgun, 8490-in\3\ airgun array in
the general area. The link between the stranding and the seismic
surveys was inconclusive and not based on any physical evidence
(Hogarth, 2002; Yoder, 2002). Nonetheless, the Gulf of California
incident plus the beaked whale strandings near naval exercises
involving use of mid-frequency sonar suggests a need for caution in
conducting seismic surveys in areas occupied by beaked whales until
more is known about effects of seismic surveys on those species
(Hildebrand, 2005). No injuries of beaked whales are anticipated during
the proposed study because of: (1) The
[[Page 50772]]
high likelihood that any beaked whales nearby would avoid the
approaching vessel before being exposed to high sound levels; (2) the
proposed monitoring and mitigation measures; (3) the use of a single,
low-energy airgun; and (4) differences between the sound sources
operated by SIO and those involved in the naval exercises associated
with strandings.
Potential Effects of Other Acoustic Devices
Multibeam Echosounder (MBES) Signals
The Simrad EM120 12-kHz MBES will be operated from the source
vessel at some times during the planned study. Sounds from the MBES are
very short pulses, occurring for 2-15 ms once every 5-20 s, depending
on water depth. Most of the energy in the sound pulses emitted by this
MBES is at frequencies near 12 kHz, and the maximum source level is 242
dB re 1 [mu]Parms. The beam is very narrow (1 degree) in
fore-aft extent and wide (150 degrees) in the cross-track extent. Each
ping consists of nine successive fan-shaped transmissions (segments) at
different cross-track angles. Any given mammal at depth near the
trackline would be in the main beam for only one or two of the nine
segments. Also, marine mammals that encounter the Simrad EM120 are
unlikely to be subjected to repeated pulses because of the narrow fore-
aft width of the beam and will receive only limited amounts of pulse
energy because of the short pulses. Animals close to the ship (where
the beam is narrowest) are especially unlikely to be ensonified for
more than one 2-15 ms pulse (or two pulses if in the overlap area).
Similarly, Kremser et al. (2005) noted that the probability of a
cetacean swimming through the area of exposure when an MBES emits a
pulse is small. The animal would have to pass the transducer at close
range and be swimming at speeds similar to the vessel in order to
receive the multiple pulses that might result in sufficient exposure to
cause TTS.
Navy sonars that have been linked to avoidance reactions and
stranding of cetaceans (1) generally have a longer pulse duration than
the Simrad EM120, and (2) are often directed close to omnidirectionally
versus more downward for the Simrad EM120. 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 naval sonar. During SIO's operations, the individual pulses
will be very short, and a given mammal would not receive many of the
downward-directed pulses as the vessel passes by. Possible effects of
an MBES on marine mammals are outlined below.
Masking
Marine mammal communications will not be masked appreciably by the
MBES signals given the low duty cycle of the echosounder and the brief
period when an individual mammal is likely to be within its beam.
Furthermore, in the case of baleen whales, the MBES signals (12 kHz) do
not overlap with the predominant frequencies in the calls, which would
avoid any significant masking.
Behavioral Responses
Behavioral reactions of free-ranging marine mammals to sonar,
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 sonar with a source level of 215 dB re 1[mu]Pa, gray whales
reacted by orienting slightly away from the source and being deflected
from their course by approximately 200 m (Frankel, 2005). When a 38-kHz
echosounder and a 150-kHz acoustic Doppler current profiler were
transmitting during studies in the Eastern Tropical Pacific, baleen
whales showed no significant responses, while spotted and spinner
dolphins were detected slightly more often and beaked whales less often
during visual surveys (Gerrodette and Pettis, 2005).
Captive bottlenose dolphins and a white whale exhibited changes in
behavior when exposed to 1-s tonal signals at frequencies similar to
those that will be emitted by the MBES used by SIO, and to shorter
broadband pulsed signals. Behavioral changes typically involved what
appeared to be deliberate attempts to avoid the sound exposure
(Schlundt et al., 2000; Finneran et al., 2002; Finneran and Schlundt
2004). The relevance of those data to free-ranging odontocetes is
uncertain, and in any case, the test sounds were quite different in
duration as compared with those from an MBES.
Very few data are available on the reactions of pinnipeds to sonar
sounds at frequencies similar to those used during seismic operations.
Hastie and Janik (2007) conducted a series of behavioral response tests
on two captive gray seals to determine their reactions to underwater
operation of a 375-kHz multibeam imaging sonar that included
significant signal components down to 6 kHz. Results indicated that the
two seals reacted to the sonar signal by significantly increasing their
dive durations. Because of the likely brevity of exposure to the MBES
sounds, pinniped reactions are expected to be limited to startle or
otherwise brief responses of no lasting consequence to the animals.
Hearing Impairments and Other Physical Effects
Given recent stranding events that have been associated with the
operation of naval sonar, there is concern that mid-frequency sonar
sounds can cause serious impacts to marine mammals (see above).
However, the MBES proposed for use by SIO is quite different than sonar
used for navy operations. Pulse duration of the MBES is very short
relative to the naval sonar. Also, at any given location, an individual
marine mammal would be in the beam of the MBES for much less time given
the generally downward orientation of the beam and its narrow fore-aft
beamwidth; navy 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 sonar used by the navy.
Given the maximum source level of 242 dB re 1 [mu]Parms
(see Sec. I), the received level for an animal within the MBES beam
100 m below the ship would be approximately 202 dB re 1
[mu]Parms, assuming 40 dB of spreading loss over 100 m
(circular spreading). Given the narrow beam, only one pulse is likely
to be received by a given animal as the ship passes overhead. The
received energy level from a single pulse of duration 15 ms would be
about 184 dB re 1 [mu]Pa\2\ [middot] s, i.e., 202 dB + 10 log (0.015
s). That is below the TTS threshold for a cetacean receiving a single
non-impulse sound (195 dB re 1 [mu]Pa\2\ [middot] s) and even further
below the anticipated PTS threshold (215 dB re 1 [mu]Pa\2\ [middot] s)
(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., 204 dB re 1 [mu]Pa\2\ [middot] 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 cetaceans. As noted by Burkhardt et al. (2007, 2008),
cetaceans are very unlikely to incur PTS from operation of scientific
sonars on a ship that is underway.
In the harbor seal, the TTS threshold for non-impulse sounds is
about 183 dB re 1 [mu]Pa\2\ [middot] s, as compared with ~195 dB re 1
[mu]Pa\2\ [middot] s in odontocetes (Kastak et
[[Page 50773]]
al., 2005; Southall et al., 2007). TTS onset occurs at higher received
energy levels in the California sea lion and northern elephant seal
than in the harbor seal. A harbor seal as much as 100 m below the
Melville could receive a single MBES pulse with received energy level
of >=184 dB re 1 [mu]Pa\2\ [middot] s (as calculated in the toothed
whale subsection above) and thus could incur slight TTS. Species of
pinnipeds with higher TTS thresholds would not incur TTS unless they
were closer to the transducers when a sonar ping was emitted. However,
the SEL threshold for PTS in pinnipeds (203 dB re 1 [mu]Pa\2\ [middot]
s) might be exceeded for a ping received within a few meters of the
transducers, although the risk of PTS is higher for certain species
(e.g., harbor seal). Given the intermittent nature of the signals and
the narrow MBES beam, only a small fraction of the pinnipeds below (and
close to) the ship would receive a pulse as the ship passed overhead.
Sub-Bottom Profiler Signals
An SBP may be operated from the source vessel at times during the
planned study. Sounds from the sub-bottom profiler are very short
pulses, occurring for 1-4 ms once every second. Most of the energy in
the sound pulses emitted by the SBP is at 3.5 kHz, and the beam is
directed downward in a narrow beam with a spacing of up to 15 degrees
and a fan width up to 30 degrees. The Edgetech 512i Chirp and Knudsen
320BR sub-bottom profilers on the Melville have a maximum source level
of 198 and 211 dB re 1 [mu]Pa [middot] m, respectively. Kremser et al.
(2005) noted that the probability of a cetacean swimming through the
area of exposure when a bottom profiler emits a pulse is small--even
for an SBP more powerful than that on the Melville 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.
Masking
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 baleen whales, the SBP signals do not
overlap with the predominant frequencies in the calls, which would
avoid significant masking.
Behavioral Reactions
Marine mammal behavioral reactions to other pulsed sound sources
are discussed above, and responses to the SBP are likely to be similar
to those for other pulsed sources if received at the same levels.
However, the pulsed signals from the SBP are considerably weaker than
those from the MBES. Therefore, behavioral responses would not be
expected unless marine mammals were to approach very close to the
source.
Hearing Impairment and Other Physical Effects
It is unlikely that the SBP produces pulse levels strong enough to
cause hearing impairment or other physical injuries even in an animal
that is (briefly) in a position near the source. The SBP is usually
operated simultaneously with other higher-power acoustic sources. Many
marine mammals will move away in response to the approaching higher-
power sources or the vessel itself before the mammals would be close
enough for there to be any possibility of effects from the less intense
sounds from the SBP. In the case of mammals that do not avoid the
approaching vessel and its various sound sources, mitigation measures
that would be applied to minimize effects of other sources would
further reduce or eliminate any minor effects of the SBP.
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.) The sections below describe methods to estimate
``take by harassment'', and present estimates of the numbers of marine
mammals that might be affected during the proposed SBC seismic program.
The estimates of ``take by harassment'' are based on consideration of
the number of marine mammals that might be disturbed appreciably by
approximately 600 km of trackline, including turns, using the airgun
and approximately 500 km of trackline using the sparker or boomer. The
main sources of distributional and numerical data used in deriving the
estimates are described below.
The anticipated radii of influence of the MBES and the SBP are less
than those for the airgun array. It is assumed that, during
simultaneous operations of the airgun array and echosounders, marine
mammals close enough to be affected by the echosounders would already
be affected by the airguns. However, whether or not the airguns 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 above. NMFS
believes that such reactions are not considered to constitute
``taking.'' Therefore, no additional allowance is included for animals
that might be affected by sound sources other than airguns, boomer, and
sparker.
Extensive systematic aircraft- and ship-based surveys have been
conducted for marine mammals off the U.S. west coast; the most
comprehensive and recent density data available for cetacean species in
shelf, slope, and offshore waters of California are from the 1991,
1993, 1996, 2001, and 2005 NMFS/SWFSC shipboard surveys as synthesized
by Barlow and Forney (2007). The surveys were conducted up to
approximately 550 km offshore from June or July to November or
December. Densities are available for all of California in each of the
five years, and for southern California (south of the latitude of Point
Conception) for all years combined (Barlow and Forney, 2007), but not
for southern California in each year except 2005 (Forney, 2007).
Another set of surveys that included southern California was conducted
by NMFS in the ETP during summer and fall 1986-1996, as summarized by
Ferguson and Barlow (2001). Densities were calculated for 5[deg] x
5[deg] blocks; the partial block that includes the waters off southern
California (Block 58) has its northern boundary at 35[deg]N, just north
of Point Conception. It extends off the coast as a wedge with a maximum
distance of ~375 km offshore, and included 2925 km of survey effort in
Beaufort sea states 0-5 and 600 km of survey effort in Beaufort sea
states 0-2. We decided to use those density estimates because a smaller
proportion of the waters surveyed were offshore. For two species
expected to be common in the SBC but for which there were no sightings
in Ferguson and Barlow (2001)--humpback whales and Dall's porpoise--the
applicant estimated take using the 2005 densities for southern
California in Forney (2007).
Systematic at-sea survey data for pinnipeds are more limited. The
only densities to our knowledge are for California sea lions, and are
based on ~31,000 km of aerial surveys of the SCB during 1975-1978, as
summarized by Bonnell and Ford (1987). There are no density data, to
our knowledge, for sea otters in the study area.
[[Page 50774]]
Oceanographic conditions, including occasional El Nino and La Nina
events, influence the distribution and numbers of marine mammals
present in the NEPO, including California, 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; Becker 2007).
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.
The estimated numbers of individuals potentially exposed are
presented below based on the 160-dB re 1 [mu]Parms threshold
for all cetaceans and pinnipeds. It is assumed that marine mammals
exposed to seismic sounds this strong might change their behavior
sufficiently to be considered ``taken by harassment''. It should be
noted that the following estimates of exposures to various sound levels
assume that the surveys will be fully completed; in fact, the planned
number of line-kilometers has been increased by 25% to accommodate
lines that may need to be repeated, equipment testing, etc. As is
typical during ship surveys, inclement weather and equipment
malfunctions are likely to cause delays and may limit the number of
useful line-kilometers of seismic operations that can be undertaken.
Furthermore, any marine mammal sightings within or near the designated
exclusion zone will result in the shutdown of seismic operations as a
mitigation measure. Thus, the following estimates of the numbers of
marine mammals potentially expose to 160 dB re 1 [mu]Parms
sounds are precautionary, and probably overestimate the actual numbers
of marine mammals that might be involved. These estimates assume that
there will be no weather, equipment, or mitigation delays, which is
highly unlikely.
The number of different individuals that could be exposed to GI-gun
or boomer sounds with received levels 160 dB re 1 [mu]Parms
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
seismic sources on at least one occasion along with the expected
density of animals in the area. The proposed seismic lines run parallel
to each other in close proximity; thus, an individual mammal may be
exposed numerous times during the survey. The number of possible
exposures to GI-gun and boomer sounds with received levels >=160 dB re
1 [mu]Parms (including repeated exposures of the same
individuals) can be estimated by considering the total marine area that
would be within the 160-dB radius around the operating seismic sources,
including areas of overlap. However, it is unlikely that a particular
animal would stay in the area during the entire survey. The number of
potential exposures and the number of different individuals potentially
exposed to >=160 dB re 1 [mu]Parms were calculated by
multiplying: (1) The expected species density, either ``mean'' (i.e.,
best estimate) or ``maximum'', times; (2) the anticipated area to be
ensonified to that level during seismic operations including overlap
(exposures), or; (3) the anticipated area to be ensonified to that
level during seismic operations excluding overlap (individuals).
The area expected to be ensonified was determined by entering the
planned survey lines into a MapInfo Geographic Information System
(GIS), using the GIS to identify the relevant areas by ``drawing'' the
applicable 160-dB buffer around each seismic line, and then calculating
the total area within the buffers. Areas where overlap occurred
(because of closely-spaced lines) were included when estimating the
number of exposures, whereas the areas of overlap were included only
once when estimating the number of individuals exposed.
Applying the approach described above, approximately 289 km\2\
would be within the 160-dB isopleth on one or more occasions during the
survey, whereas approximately 690 km\2\ is the area ensonified to >=160
dB when overlap is included. Thus, it is possible that an average
individual marine mammal could be exposed up to two or three times
during the survey. Because this approach does not allow for turnover in
the mammal populations in the study area during the course of the
survey, the actual number of individuals exposed may be underestimated,
although the conservative (i.e., probably overestimated) line-kilometer
distances used to calculate the area may offset this. Also, the
approach assumes that no cetaceans will move away or toward the
trackline as the Melville approaches in response to increasing sound
levels prior to the time the levels reach 160 dB.
The best estimate of the number of individual marine mammals that
could be exposed to seismic sounds with received levels >=160 dB re 1
[mu]Parms (but below Level A harassment thresholds) during
the survey is 508 (Table 4). These estimates were derived from the best
density estimates calculated for these species in the area (see Table 4
of SIO's application). However, SIO is requesting takes of marine
mammals based on the maximum density estimates (see Table 4 in SIO's
application) given that density data is not always precise, hence best
and maximum estimates, and that these animals may be in the area.
Requested number of marine mammals taken is listed in Table 4 below. In
addition, the number of exposures those animals could be subjected to
is also outlined. These numbers are based on trackline length,
harassment isopleth distances, and density of animals. More information
on how number of individuals and number of exposures were calculated
can be found in SIO's application. Because the single 45 in\3\ airgun
will likely be operated at a reduced chamber size but exposures are
based on maximum chamber size, NMFS believes that the ``best'' estimate
of exposures is the most appropriate number to use. The best estimate
of the total number of exposures of marine mammals to seismic sounds
with received levels >=160 dB re 1 [mu]Parms during the
survey is 1212, including four blue whale exposures, and one Cuvier's
beaked whale exposure. The short-beaked common dolphin is estimated to
be exposed most frequently, with a best estimate of 942 exposures.
Two of the six pinniped species listed in Table 4, the Guadalupe
fur seal (Arctocephalus townsendi) and the Steller sea lion (Eumetopias
jubatus), are rare in the SBC, and another two, the northern fur seal
(Callorhinus ursinus) and northern elephant seal (Mirounga
angustirostris), are not expected to occur there at the time of the
proposed survey (November) because they are feeding offshore at that
time. Densities are available for the California sea lion, the most
abundant pinniped in the Channel Islands, but not for the harbor seal,
which could be encountered during the survey. Therefore, allowances
have been made in Table 4 for the exposure of a small number (20) of
harbor seals to received sound levels >=160 dB re 1
[mu]Parms.
Potential Effects on Marine Mammal 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 described above. The following sections briefly
review effects of airguns on fish and invertebrates, and more details
are
[[Page 50775]]
included in Appendices C and D, respectively, of NSF's EA,
respectively.
One reason for the adoption of airguns as the standard energy
source for marine seismic surveys is that, unlike explosives, they have
not been associated with large-scale fish kills. However, existing
information on the impacts of seismic surveys on marine fish
populations is very limited (see Appendix C of NSF's EA). There are
three types of potential effects of exposure to seismic surveys: (1)
Pathological, (2) physiological, and (3) behavioral. Pathological
effects involve lethal and temporary or permanent sub-lethal injury.
Physiological effects involve temporary and permanent primary and
secondary stress responses, such as changes in levels of enzymes and
proteins. Behavioral effects refer to temporary and (if they occur)
permanent changes in exhibited behavior (e.g., startle and avoidance
behavior). The three categories are interrelated in complex ways. For
example, it is possible that certain physiological and behavioral
changes potentially could lead to an ultimate pathological effect on
individuals (i.e., mortality).
The specific received sound levels at which permanent adverse
effects to fish potentially could occur are little studied and largely
unknown. Furthermore, the available information on the impacts of
seismic surveys on marine fish is from studies of individuals or
portions of a population; there have been no studies at the population
scale. Thus, available information provides limited insight on possible
real-world effects at the ocean or population scale. This makes drawing
conclusions about impacts on fish problematic because ultimately, the
most important aspect of potential impacts relates to how exposure to
seismic survey sound affects marine fish populations and their
viability, including their availability to fisheries.
The following sections provide a general synopsis of available
information on the effects of exposure to seismic and other
anthropogenic sound as relevant to fish. The information comprises
results from scientific studies of varying degrees of rigor plus some
anecdotal information. Some of the data sources may have serious
shortcomings in methods, analysis, interpretation, and reproducibility
that must be considered when interpreting their results (see Hastings
and Popper, 2005). Potential adverse effects of the program's sound
sources on marine fish are then noted.
Pathological Effects--Wardle et al. (2001) suggested that in water,
acute injury and death of organisms exposed to seismic energy depends
primarily on two features of the sound source: (1) The received peak
pressure and (2) the time required for the pressure to rise and decay.
Generally, as received pressure increases, the period for the pressure
to rise and decay decreases, and the chance of acute pathological
effects increases. According to Buchanan et al. (2004), for the types
of seismic airguns and arrays involved with the proposed program, the
pathological (mortality) zone for fish and invertebrates would be
expected to be within a few meters of the seismic source. Numerous
other studies provide examples of no fish mortality upon exposure to
seismic sources (Falk and Lawrence, 1973; Holliday et al., 1987; La
Bella et al., 1996; Santulli et al., 1999; McCauley et al., 2000a,b,
2003; Bjarti, 2002; Hassel et al., 2003; Popper et al., 2005).
The potential for pathological damage to hearing structures in fish
depends on the energy level of the received sound and the physiology
and hearing capability of the species in question (see Appendix C of
NSF's EA). For a given sound to result in hearing loss, the sound must
exceed, by some specific amount, the hearing threshold of the fish for
that sound (Popper 2005). The consequences of temporary or permanent
hearing loss in individual fish on a fish population is unknown;
however, it likely depends on the number of individuals affected and
whether critical behaviors involving sound (e.g., predator avoidance,
prey capture, orientation and navigation, reproduction, etc.) are
adversely affected.
Little is known about the mechanisms and characteristics of damage
to fish that may be inflicted by exposure to seismic survey sounds. Few
data have been presented in the peer-reviewed scientific literature. As
far as we know, there are only two valid papers with proper
experimental methods, controls, and careful pathological investigation
implicating sounds produced by actual seismic survey airguns with
adverse anatomical effects. One such study indicated anatomical damage
and the second indicated TTS in fish hearing. The anatomical case is
McCauley et al. (2003), who found that exposure to airgun sound caused
observable anatomical damage to the auditory maculae of ``pink
snapper'' (Pagrus auratus). This damage in the ears had not been
repaired in fish sacrificed and examined almost two months after
exposure. On the other hand, Popper et al. (2005) documented only TTS
(as determined by auditory brainstem response) in two of three 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
[mu]Pa\2\ [middot] s showed no hearing loss. During both studies, the
repetitive exposure to sound was greater than would have occurred
during a typical seismic survey. However, the substantial low-frequency
energy produced by the airgun arrays [less than approximately 400 Hz in
the study by McCauley et al. (2003) and less than approximately 200 Hz
in Popper et al. (2005)] likely did not propagate to the fish because
the water in the study areas was very shallow (approximately 9 m in the
former case and <2 m in the latter). Water depth sets a lower limit on
the lowest sound frequency that will propagate (the ``cutoff
frequency'') at about one-quarter wavelength (Urick, 1983; Rogers and
Cox, 1988). 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, some equivocally, that mortality of
fish, fish eggs, or larvae can occur close to seismic sources
(Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman et al., 1996;
Dalen et al., 1996). Some of the reports claimed seismic effects from
treatments quite different from actual seismic survey sounds or even
reasonable surrogates. Saetre and Ona (1996) applied a ``worst-case
scenario'' mathematical model to investigate the effects of seismic
energy on fish eggs and larvae. They concluded that mortality rates
caused by exposure to seismic surveys are so low, as compared to
natural mortality rates, that the impact of seismic surveying on
recruitment to a fish stock must be regarded as insignificant.
Physiological Effects--Physiological effects refer to cellular and/
or biochemical responses of fish to acoustic stress. Such stress
potentially could affect fish populations by increasing mortality or
reducing reproductive success. Primary and secondary stress responses
of fish after exposure to seismic survey sound appear to be temporary
in all studies done to date (Sverdrup et al., 1994; McCauley et al.,
2000a, 2000b). The periods necessary for the biochemical changes to
return to normal are variable, and depend on numerous aspects of the
[[Page 50776]]
biology of the species and of the sound stimulus (see Appendix C of
NSF's EA).
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. 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 SIO's proposed seismic survey is predicted to have negligible
to low physical effects on the various life stages of fish and
invertebrates for its short duration (approximately 25 days each in the
Pacific Ocean and Caribbean Sea) and approximately 2,149-km of unique
survey lines extent. Therefore, physical effects of the proposed
program on fish and invertebrates would not be significant.
Behavioral Effects--Behavioral effects include changes in the
distribution, migration, mating, and catchability of fish populations.
Studies investigating the possible effects of sound (including seismic
survey sound) on fish behavior have been conducted on both uncaged and
caged individuals (Chapman and Hawkins, 1969; Pearson et al., 1992;
Santulli et al., 1999; Wardle et al., 2001; Hassel et al., 2003).
Typically, in these studies fish exhibited a sharp ``startle'' response
at the onset of a sound followed by habituation and a return to normal
behavior after the sound ceased.
There is general concern about potential adverse effects of seismic
operations on fisheries, namely a potential reduction in the
``catchability'' of fish involved in fisheries. Although reduced catch
rates have been observed in some marine fisheries during seismic
testing, in a number of cases the findings are confounded by other
sources of disturbance (Dalen and Raknes, 1985; Dalen and Knutsen,
1986; L[oslash]kkeborg, 1991; Skalski et al., 1992; Eng[aring]s et al.,
1996). In other airgun experiments, there was no change in catch per
unit effort (CPUE) of fish when airgun pulses were emitted,
particularly in the immediate vicinity of the seismic survey (Pickett
et al., 1994; La Bella et al., 1996). For some species, reductions in
catch may have resulted from a change in behavior of the fish, e.g., a
change in vertical or horizontal distribution, as reported in Slotte et
al., (2004).
In general, any adverse effects on fish behavior or fisheries
attributable to seismic testing may depend on the species in question
and the nature of the fishery (season, duration, fishing method). They
may also depend on the age of the fish, its motivational state, its
size, and numerous other factors that are difficult, if not impossible,
to quantify at this point, given such limited data on effects of
airguns on fish, particularly under realistic at-sea conditions.
For marine invertebrates, behavioral changes could potentially
affect such aspects as reproductive success, distribution,
susceptibility to predation, and catchability by fisheries. Studies of
squid indicated startle responses (McCauley et al., 2000a,b). In other
cases, no behavioral impacts were noted (e.g., crustaceans in Christian
et al., 2003, 2004; DFO, 2004). There have been anecdotal reports of
reduced catch rates of shrimp shortly after exposure to seismic
surveys; however, other studies have not observed any significant
changes in shrimp catch rate (Andriguetto-Filho et al., 2005). Parry
and Gason (2006) reported no changes in rock lobster CPUE during or
after seismic surveys off western Victoria, Australia, from 1978-2004.
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).
Additional information regarding the behavioral effects of seismic on
invertebrates is contained in Appendix D in NSF's EA.
Summary of Behavioral Effects--As is the case with pathological and
physiological effects of seismic on fish and invertebrates, available
information is relatively scant and often contradictory. There have
been well-documented observations of fish and invertebrates exhibiting
behaviors that appeared to be responses to exposure to seismic energy
(i.e., startle response, change in swimming direction and speed, and
change in vertical distribution), but the ultimate importance of those
behaviors is unclear. Some studies indicate that such behavioral
changes are very temporary, whereas others imply that fish might not
resume pre-seismic behaviors or distributions for a number of days.
There appears to be a great deal of inter- and intra-specific
variability. In the case of finfish, three general types of behavioral
responses have been identified: Startle, alarm, and avoidance. The type
of behavioral reaction appears to depend on many factors, including the
type of behavior being exhibited before exposure, and proximity and
energy level of sound source.
During the proposed study, only a small fraction of the available
habitat would be ensonified at any given time, and fish species would
return to their pre-disturbance behavior once the seismic activity
ceased. The proposed seismic program is predicted to have negligible to
low behavioral effects on the various life stages of the fish and
invertebrates during its relatively short duration and extent.
Because of the reasons noted above and the nature of the proposed
activities, the proposed operations are not expected to have any
habitat-related effects that could cause significant or long-term
consequences for individual marine mammals or their populations or
stocks. Similarly, any effects to food sources are expected to be
negligible.
Proposed Monitoring
SIO proposes to sponsor marine mammal monitoring during the present
project, in order to implement the proposed mitigation measures that
require real-time monitoring, and to satisfy the anticipated monitoring
requirements of the Incidental Harassment Authorization. Vessel-based
marine mammal visual observers (MMVOs) will be based on board the
seismic source vessel, and they will watch for marine mammals and
turtles near the vessel during seismic operations. MMVOs will also
watch for marine mammals and turtles near the seismic vessel for at
least 30 minutes prior to the start of seismic operations after an
extended shutdown. When feasible, MMVOs will also make observations
during daytime periods when the seismic system is not operating for
comparison of animal abundance and behavior. Based on MMVO
observations, the seismic source will be shut down when marine mammals
are observed within or about to enter a designated exclusion zone (EZ).
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.
At least one MMVO will monitor the EZ
[[Page 50777]]
during seismic operations. MMVOs will normally work in shifts of 4-hour
duration or less. The vessel crew will also be instructed to assist in
detecting marine mammals and turtles.
Standard equipment for marine mammal observers will be 7 x 50
reticule binoculars and optical range finders. At night, night-vision
equipment will be available, although seismic activity will be
restricted to daylight hours. 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 seismic source shut down.
Proposed Mitigation During Operations
Mitigation measures that will be adopted will include (1) Vessel
speed or course alteration, provided that doing so will not compromise
operational safety requirements, (2) GI-gun or boomer shut down within
calculated exclusion zones, and (3) shut down at any range in the
unlikely event that a North Pacific right whale or a concentration of
sea otters is sighted. Two other standard mitigation measures--airgun
array power down and airgun array ramp up--are not possible because
only one, low-volume GI airgun, boomer, or sparker will be used for the
surveys. In addition, avoidance of airgun operations over or near steep
slopes or submarine canyons has become a standard mitigation measure,
as these are places where beaked whales tend to concentrate. However,
no such bathymetric features exist in the study area; therefore, this
mitigation measure is not applicable to these surveys.
Speed or Course Alteration
If a marine mammal or turtle is detected outside the EZ but is
likely to enter it based on relative movement of the vessel and the
animal, then if safety and scientific objectives allow, the vessel
speed and/or 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 one small source and a short
(450-m) streamer will be used.
Shut-Down Requirements and Procedures
If a marine mammal is detected outside the exclusion zones but is
likely to enter the exclusion zone, and if the vessel's speed and/or
course cannot be changed to avoid having the animal enter the exclusion
zone, the seismic source will be shut down before the animal is within
the exclusion zone. Likewise, if a mammal is already within the safety
zone when first detected, the seismic source will be shut down
immediately.
Following a shut down, seismic activity will not resume until the
marine mammal or turtle has cleared the exclusion zone. The animal will
be considered to have cleared the exclusion zone if it is visually
observed to have left the exclusion zone; has not been seen within the
zone for 10 min in the case of small odontocetes and pinnipeds; or has
not been seen within the zone for 15 min in the case of mysticetes and
large odontocetes, including sperm, pygmy sperm, dwarf sperm, and
beaked whales.
In the unanticipated event that any cases of marine mammal injury
or mortality are judged to result from these activities, SIO will cease
operating seismic airgun operation and report the incident to the
Office of Protected Resources, NMFS, and the Southwest Regional
Administrator, NMFS, immediately.
Proposed Reporting
MMVOs will record data to estimate the numbers of marine mammals
and turtles exposed to various received sound levels and to document
apparent disturbance reactions or lack thereof. Data will be used to
estimate numbers of animals potentially ``taken'' by harassment (as
defined in the MMPA). They will also provide information needed to
order a shutdown of the seismic source when a marine mammal or sea
turtles is within or near the EZ.
When a sighting is made, the following information about the
sighting will be recorded: Species, group size, and age/size/sex
categories (if determinable); behavior when first sighted and after
initial sighting; heading (if consistent), bearing, and distance from
seismic vessel; sighting cue; apparent reaction to the seismic source
or vessel (e.g., none, avoidance, approach, paralleling, etc.); and
behavioral pace. In addition, time, location, heading, speed, activity
of the vessel, sea state, visibility, and sun glare will also be
recorded. This data (time, location, etc.) will also be recorded at the
start and end of each observation watch, and during a watch whenever
there is a change in one or more of the variables.
All observations, as well as information regarding seismic source
shutdown, 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 seismic source.
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 or regulations.
3. Data on the occurrence, distribution, and activities of marine
mammals and turtles in the area where the seismic study is conducted.
4. Data on the behavior and movement patterns of marine mammals and
turtles seen at times with and without seismic activity.
A report will be submitted to NMFS within 90 days after the end of
the cruise. The report will describe the operations that were conducted
and sightings of marine mammals and turtles near the operations. The
report will be submitted to NMFS, providing full documentation of
methods, results, and interpretation pertaining to all monitoring. The
90-day report will summarize the dates and locations of seismic
operations, and all marine mammal 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.
All injured or dead marine mammals (regardless of cause) must be
reported to NMFS as soon as practicable. Report should include species
or description of animal, condition of animal, location, time first
found, observed behaviors (if alive) and photo or video, if available.
Endangered Species Act (ESA)
Under section 7 of the ESA, NSF has begun consultation with the
NMFS, Office of Protected Resources, Endangered Species Division on
this proposed seismic survey. NMFS will also consult on the issuance of
an IHA under section 101(a)(5)(D) of the MMPA for this activity.
Consultation will be concluded prior to a determination on the issuance
of the IHA.
National Environmental Policy Act (NEPA)
NSF prepared an Environmental Assessment (EA) of a Marine
Geophysical Survey by the R/V Melville in the Santa Barbara Channel,
November 2008. NMFS will either adopt NSF's EA or conduct a separate
NEPA analysis, as necessary, prior to making a
[[Page 50778]]
determination of the issuance of the IHA.
Preliminary Determinations
NMFS has preliminarily determined that the impact of conducting the
seismic survey in the SBC may result, at worst, in a temporary
modification in behavior (Level B Harassment) of small numbers of 26
species of marine mammals. This activity is expected to result in a
negligible impact on the affected species or stocks. There are no
subsistence uses of affected marine mammals in this area.
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 35 m (114 ft) in water less than 1,000 m to be exposed
to levels of sound which could result in Level A harassment (injury);
(3) the 35 m distance is conservative as it is for the airgun opening
at full chamber size (45 in\3\) and the airgun will likely be operating
at reduced chamber size; and (4) the marine mammal detection ability by
trained observers is high at that very 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 marine mammals potentially harassed will depend
on the distribution and abundance of marine mammals in the vicinity of
the survey activity, the number of potential harassment takings is
estimated to be small, less than a few percent of any of the estimated
population sizes, and has been mitigated to the lowest level
practicable through incorporation of the measures mentioned previously
in this document.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
issue an IHA to SIO for conducting a marine geophysical survey in the
Santa Barbara Channel, November 2008, provided the previously mentioned
mitigation, monitoring, and reporting requirements are incorporated.
Dated: August 22, 2008.
Helen M. Golde,
Deputy Director, Office of Protected Resources, National Marine
Fisheries Service.
[FR Doc. E8-20014 Filed 8-27-08; 8:45 am]
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