[Federal Register Volume 76, Number 146 (Friday, July 29, 2011)]
[Notices]
[Pages 45518-45540]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-19244]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XA507
Takes of Marine Mammals Incidental to Specified Activities; Low-
Energy Marine Geophysical Survey in the Western Tropical Pacific Ocean,
November to December, 2011
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed Incidental Harassment Authorization; request
for comments.
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SUMMARY: NMFS has received an application from the Scripps Institution
of Oceanography (SIO) for an Incidental Harassment Authorization (IHA)
to take marine mammals, by harassment, incidental to conducting a low-
energy marine geophysical (i.e., seismic) survey in the western
tropical Pacific Ocean, November to December, 2011. Pursuant to the
Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its
proposal to issue an IHA to SIO to incidentally harass, by Level B
harassment only, 19 species of marine mammals during the specified
activity.
DATES: Comments and information must be received no later than August
29, 2011.
ADDRESSES: Comments on the application should be addressed to P.
Michael Payne, Chief, Permits, Conservation and Education Division,
Office of Protected Resources, National Marine Fisheries Service, 1315
East-West Highway, Silver Spring, MD 20910. The mailbox address for
providing e-mail comments is [email protected]. NMFS is not
responsible for e-mail comments sent to addresses other than the one
provided here. Comments sent via e-mail, including all attachments,
must not exceed a 10-megabyte file size.
All comments received are a part of the public record and will
generally be posted to http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications without change. All Personal Identifying
Information (for example, name, address, etc.) voluntarily submitted by
the commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.
A copy of the application containing a list of the references used
in this document may be obtained by writing to the above address,
telephoning the contact listed here (see FOR FURTHER INFORMATION
CONTACT) or visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
The National Science Foundation (NSF) has prepared a draft
``Environmental Assessment of a Marine Geophysical Survey by the R/V
Thompson in the western tropical Pacific Ocean November-December 2011
(EA).'' The draft EA incorporates an ``Environmental Assessment of a
Low-Energy Marine Geophysical Survey by the R/V Thompson in the Western
Tropical Pacific Ocean, November-December 2011,'' prepared by LGL Ltd.,
Environmental Research Associates (LGL), on behalf of NSF and SIO,
which is also available at the same Internet address. Documents cited
in this notice may be viewed, by appointment, during regular business
hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Howard Goldstein or Jolie Harrison,
Office of Protected Resources, NMFS, 301-427-8401.
SUPPLEMENTARY INFORMATION:
Background
Section 101(a)(5)(D) of the MMPA (16 U.S.C. 1371 (a)(5)(D)) directs
the Secretary of Commerce (Secretary) to authorize, upon request, the
incidental, but not intentional, taking of small numbers of marine
mammals of a species or population stock, by United States citizens who
engage in a specified activity (other than commercial fishing) within a
specified geographical region if certain findings are made and, if the
taking is limited to harassment, a notice of a proposed authorization
is provided to the public for review.
Authorization for the incidental taking of small numbers of marine
mammals shall be granted if NMFS finds that the taking will have a
negligible impact on the species or stock(s), and will not have an
unmitigable adverse impact on the availability of the species or
stock(s) for subsistence uses (where relevant). The authorization must
set forth the permissible methods of taking, other means of effecting
the least practicable adverse impact on the species or stock and its
habitat, and requirements pertaining to the mitigation, monitoring and
reporting of such takings. NMFS has defined ``negligible impact'' in 50
CFR 216.103 as ``* * * an impact resulting from the specified activity
that cannot be reasonably expected to, and is not reasonably likely to,
adversely affect the species or stock through effects on annual rates
of recruitment or survival.''
Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the United States can apply for an authorization
to incidentally take small numbers of marine mammals by harassment.
Section 101(a)(5)(D) of the MMPA establishes a 45-day time limit for
NMFS' review of an application followed by a 30-day public notice and
comment period on any proposed authorizations for the incidental
harassment of small numbers of marine mammals. Within 45 days of the
close of the public comment period, NMFS must either issue or deny the
authorization.
[[Page 45519]]
Except with respect to certain activities not pertinent here, the
MMPA defines ``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
Summary of Request
NMFS received an application on June 14, 2011, from SIO for the
taking by harassment, of marine mammals, incidental to conducting a
low-energy marine seismic survey in the western tropical Pacific Ocean.
SIO, a part of the University of California, in collaboration with
University of Washington (UW), Woods Hole Oceanographic Institution
(WHOI), Texas A&M University (TAMU), and Kutztown University, plans to
conduct a magnetic and seismic study of the Hawaiian Jurassic crust
onboard an oceanographic research vessel in the western tropical
Pacific Ocean north of the Marshall Islands for approximately 32 days.
The survey will use a pair of Generator Injector (GI) airguns each with
a discharge volume of 105 cubic inches (in\3\). SIO plans to conduct
the proposed survey from approximately November 5 to December 17, 2011.
The proposed seismic survey will be conducted partly in international
waters and partly in the Exclusive Economic Zone (EEZ) of Wake Island
(U.S.), and possibly in the EEZ of the Republic of the Marshall
Islands.
SIO plans to use one source vessel, the R/V Thomas G. Thompson
(Thompson) and a seismic airgun array to collect seismic reflection and
refraction profiles from the Hawaiian Jurassic crust in the western
tropical Pacific Ocean. In addition to the proposed operations of the
seismic airgun array, SIO intends to operate a multibeam echosounder
(MBES) and a sub-bottom profiler (SBP) continuously throughout the
survey.
Acoustic stimuli (i.e., increased underwater sound) generated
during the operation of the seismic airgun array may have the potential
to cause a short-term behavioral disturbance for marine mammals in the
survey area. This is the principal means of marine mammal taking
associated with these activities and SIO has requested an authorization
to take 19 species of marine mammals by Level B harassment. Take is not
expected to result from the use of the MBES or SBP, for reasons
discussed in this notice; nor is take expected to result from collision
with the vessel because it is a single vessel moving at a relatively
slow speed during seismic acquisition within the survey, for a
relatively short period of time (approximately 39 days). It is likely
that any marine mammal would be able to avoid the vessel.
Description of the Proposed Specified Activity
SIO's proposed seismic survey in the western tropical Pacific
Ocean, as part of an integrated magnetic and seismic study of the
Hawaiian Jurassic crust, will take place for approximately 32 days in
November to December, 2011 (see Figure 1 of the IHA application). The
proposed seismic survey will take place in water depths ranging from
approximately 2,000 to 6,000 meters (m) (6,561.7 to 19,685 feet [ft])
and consist of approximately 1,600 kilometers (km) (863.9 nautical
miles [nmi]) of transect lines in the study area. The survey will take
place in the area 13[deg] to 23[deg] North, 158[deg] to 172[deg] East,
just north of the Marshall Islands. The project is scheduled to occur
from approximately November 5 to December 17, 2011. Some minor
deviation from these dates is possible, depending on logistics and
weather.
The goal of the proposed research is to define the global nature
and significance of variations in intensity and direction of the
Earth's magnetic field during the Jurassic time period (approximately
145 to 180 million years ago), which appears to have been a period of
sustained low intensity and rapid directional changes or polarity
reversals compared to other periods in Earth's magnetic field history.
Access to Jurassic-aged crust with good magnetic signals is very
limited, with the best continuous records in ocean crust, but only one
area of the ocean floor has been measured to date: the western Pacific
Japanese magnetic lineations. To properly assess the global
significance of the variations and to eliminate local crustal and
tectonic complications, it is necessary to measure Jurassic magnetic
signals in a different area of the world. The proposed study will
attempt to verify the unusual behavior of the Jurassic geomagnetic
field and test whether it was behaving in a globally coherent way by
conducting a near-bottom marine magnetic field survey of Pacific
Hawaiian Jurassic crust located between Hawaii and Guam.
Widespread, younger, Cretaceous-aged (65 to 140 million years ago)
volcanism overprinted much of the western Pacific, so it is important
to know the extent of Cretaceous-aged volcanic crust. This will be
assessed by carrying out a seismic reflection and refraction survey of
the Hawaiian Jurassic crust. First, the autonomous underwater vehicle
(AUV) Sentry and a simultaneously deployed deep-towed magnetometer
system will acquire two parallel profiles of the near-bottom crustal
magnetic field 10 km (5.4 nmi) apart and approximately 800 km (432 nmi)
long. More information on the AUV Sentry is available at http://www.whoi.edu/page.do?pid=38098. Second, the seismic survey will be
conducted using airguns, a hydrophone streamer, and sonobuoys directly
over the same profile as the AUV magnetic survey.
The survey will involve one source vessel, the Thompson. For the
seismic component of the research program, the Thompson will deploy an
array of two low-energy Sercel Generator Injector (GI) airguns as an
energy source (each with a discharge volume of 105 in\3\) at a tow
depth of 3 m (9.8 ft). The acoustic receiving system will consist of an
800 m (2,624.7 ft), 48 channel hydrophone streamer and directional,
passive sonobuoys. Over the course of the seismic operations, 50 Ultra
Electronics AN/SSQ-53D(3) directional, passive sonobuoys will be
deployed from the vessel. The sonobuoys consist of a hydrophone,
electronics, and a radio transmitter. As the airgun is towed along the
survey lines, the hydrophone streamer and sonobuoys will receive the
returning acoustic signals and transfer the data to the on-board
processing system. The seismic signal is measured by the sonobuoy's
hydrophone and transmitted by radio back to the source vessel. The
sonobuoys are expendable, and after a pre-determined time (usually
eight hours), they self-scuttle and sink to the ocean bottom.
The survey lines will be within the area enclosed by red lines in
Figure 1 of the IHA application, but the exact locations of the survey
lines will be determined during transit after observing the location of
the appropriate magnetic lineation by surface-towed magnetometer.
Magnetic and seismic data acquisition will alternate on a daily basis;
seismic surveys will take place while the AUV used to collect magnetic
data is on deck to recharge its batteries. In addition to the
operations of the airgun array, a Kongsberg EM300 MBES and ODEC Bathy-
2000 SBP will also be operated from the Thompson continuously
throughout the cruise. There will be additional seismic operations
associated with equipment testing, start-up, and possible line changes
or repeat coverage of any areas where initial data quality is sub-
standard. In SIO's calculations, 25% has
[[Page 45520]]
been added for those contingency operations.
All planned geophysical data acquisition activities will be
conducted by technicians provided by SIO, with on-board assistance by
the scientists who have proposed the study. The Principal Investigators
are Drs. Masako Tominaga, Maurice A. Tivey, Daniel Lizarralde of WHOI,
William W. Sager of TAMU, and Adrienne Oakley of Kutztown University.
The vessel will be self-contained, and the crew will live aboard the
vessel for the entire cruise.
Vessel Specifications
The Thompson is operated by the University of Washington under a
charter agreement with the U.S. Office of Naval Research. The title of
the vessel is held by the U.S. Navy. The Thompson will tow the two GI
airgun array, as well as the hydrophone streamer, along predetermined
lines.
The vessel has a length of 83.5 m (274 ft); a beam of 16 m (52.5
ft), and a full load draft of 5.8 m (19 ft). It is equipped with twin
360[deg] azimuth stern thrusters each powered by a 3,000 horsepower
(hp) DC motor and a water-jet bow thruster powered by a 1,600 hp DC
motor. The motors are driven by up to three 1,500 kiloWatt (kW) and
three 715 kW generators; normal operations use two 1,500 kW and one 750
kW generator, but this changes with ship speed, sea state, and other
variables. An operations speed of 7.4 km/hour (hr) (4 knots [kt]) will
be used during seismic acquisition. When not towing seismic survey
gear, the Thompson cruises at 22 km/hr (12 kt) and has a maximum speed
of 26.9 km/hr (14.5 kt). The Thompson has a range of 24,400 km (13,175
nmi) (the distance the vessel can travel without refueling).
The vessel will also serve as a platform for which vessel-based
Protected Species Observers (PSOs) will watch for marine mammals before
and during the proposed airgun operations.
Acoustic Source Specifications
Seismic Airguns
The Thompson will deploy and tow an array consisting of a pair of
45 to 105 in\3\ Sercel GI airgun and a streamer containing hydrophones
along predetermined lines. Seismic pulses will be emitted at intervals
of five or ten seconds (s). At speeds of approximately 7.4 km/hr, the
five to ten s spacing corresponds to shot intervals of approximately 10
to 20 m (32.8 to 65.6 ft).
The generator chamber of each GI airgun, the one responsible for
introducing the sound pulse into the ocean, is either 45 in\3\ or 105
in\3\, depending on how it is configured. The injector chamber injects
air into the previously-generated bubble to maintain its shape, and
does not introduce more sound into the water. The two GI airguns will
be towed 8 m (26.2 ft) apart side-by-side, 21 m (68.9 ft) behind the
Thompson, at a depth of 3 m (9.8 ft). Depending on the configuration,
the total effective volume will be 90 in\3\ or 210 in\3\. As a
precautionary measure, SIO assumes that the larger volume will be used.
As the GI airguns are towed along the survey lines, the towed
hydrophone array in the streamer and the sonobuoys receive the
reflected 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 (much greater than 1 km [0.5
nmi]). Thus maneuverability of the vessel is not limited much during
operations.
Metrics Used in This Document
This section includes a brief explanation of the sound measurements
frequently used in the discussions of acoustic effects in this
document. Sound pressure is the sound force per unit area, and is
usually measured in micropascals ([mu]Pa), where 1 pascal (Pa) is the
pressure resulting from a force of one newton exerted over an area of
one square meter. Sound pressure level (SPL) is expressed as the ratio
of a measured sound pressure and a reference level. The commonly used
reference pressure level in underwater acoustics is 1 [mu]Pa, and the
units for SPLs are dB re: 1 [mu]Pa. SPL (in decibels [dB]) = 20 log
(pressure/reference pressure).
SPL is an instantaneous measurement and can be expressed as the
peak, the peak-peak (p-p), or the root mean square (rms). Root mean
square, which is the square root of the arithmetic average of the
squared instantaneous pressure values, is typically used in discussions
of the effects of sounds on vertebrates and all references to SPL in
this document refer to the root mean square unless otherwise noted. SPL
does not take the duration of a sound into account.
Characteristics of the Airgun Pulses
Airguns function by venting high-pressure air into the water which
creates an air bubble. The pressure signature of an individual airgun
consists of a sharp rise and then fall in pressure, followed by several
positive and negative pressure excursions caused by the oscillation of
the resulting air bubble. The oscillation of the air bubble transmits
sounds downward through the seafloor and the amount of sound
transmitted in the near horizontal directions is reduced. However, the
airgun array also emits sounds that travel horizontally toward non-
target areas.
The nominal downward-directed source levels of the airgun arrays
used by SIO on the Thompson do not represent actual sound levels that
can be measured at any location in the water. Rather they represent the
level that would be found 1 m (3.3 ft) from a hypothetical point source
emitting the same total amount of sound as is emitted by the combined
GI airguns. The actual received level at any location in the water near
the GI airguns will not exceed the source level of the strongest
individual source. In this case, that will be about 234.4 dB re 1
[mu]Pam peak, or 239.8 dB re 1 [mu]Pam peak-to-peak. However, the
difference between rms and peak or peak-to-peak values for a given
pulse depends on the frequency content and duration of the pulse, among
other factors.
Accordingly, Lamont-Doherty Earth Observatory of Columbia
University (L-DEO) has predicted the received sound levels in relation
to distance and direction from the two GI airgun array. A detailed
description of L-DEO's modeling for marine seismic source arrays for
species mitigation is provided in Appendix A of SIO's EA. These are the
nominal source levels applicable to downward propagation. The effective
source levels for horizontal propagation are lower than those for
downward propagation when the source consists of numerous airguns
spaced apart from one another.
Appendix A of SIO's EA discusses the characteristics of the airgun
pulses. NMFS refers the reviewers to the application and EA documents
for additional information.
Predicted Sound Levels for the Airguns
Received sound levels have been modeled by L-DEO for a number of
airgun configurations, including two 105 in\3\ GI airguns, in relation
to distance and direction from the airguns (see Figure 2 of the IHA
application). 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 airguns where sound
levels of 190, 180, and 160 dB re 1 [mu]Pa (rms) are predicted to be
received
[[Page 45521]]
in deep water are shown in Table 1 (see Table 1 of the IHA
application).
Empirical data concerning the 190, 180, and 160 dB (rms) distances
were acquired for various airgun arrays based on measurements during
the acoustic verification studies conducted by L-DEO in the northern
GOM in 2003 (Tolstoy et al., 2004) and 2007 to 2008 (Tolstoy et al.,
2009). Results of the 36 airgun array are not relevant for the two GI
airguns to be used in the proposed survey. The empirical data for the
6, 10, 12, and 20 airgun arrays indicate that, for deep water, the L-
DEO model tends to overestimate the received sound levels at a given
distance (Tolstoy et al., 2004). Measurements were not made for the two
GI airgun array in deep water, however, SIO proposes to use the EZ
predicted by L-DEO's model for the proposed GI airgun operations in
deep water, although they are likely conservative given the empirical
proposed GI airgun operations in deep water. Using the L-DEO model,
Table 1 (below) shows the distances at which three rms sound levels are
expected to be received from the two GI airgun array. The 180 and 190
dB re 1 [mu]Pa (rms) distances are the safety criteria for potential
Level A harassment as specified by NMFS (2000) and are applicable to
cetaceans and pinnipeds, respectively. If marine mammals are detected
within or about to enter the appropriate EZ, the airguns will be shut-
down immediately.
Table 1 summarizes the predicted distances at which sound levels
(160, 180, and 190 dB [rms]) are expected to be received from the two
GI airgun array operating in deep water depths.
Table 1--Distances to Which Sound Levels >= 190, 180, and 160 dB re 1 [mu]Pa (rms) Could be Received in Deep
Water During the Proposed Seismic Survey in the Western Tropical Pacific Ocean, November to December, 2011.
Distances Are Based on Model Results Provided by L-DEO.
----------------------------------------------------------------------------------------------------------------
Predicted RMS radii distances
Tow (m)
Source and volume depth Water depth (m) --------------------------------
(m) 190 dB 180 dB 160 dB
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Two GI airguns (105 in\3\)............... 3 Deep (> 1,000)............. 20 70 670
----------------------------------------------------------------------------------------------------------------
MBES
The Thompson will operate a Kongsberg EM 300 MBES concurrently
during airgun operations to map characteristics of the ocean floor. The
MBES has a hull-mounted transducer within a transducer pod that is
located amidships. The system's normal operating frequency is
approximately 30 kHz. The transmit fan-beam is split into either three
or nine narrower beam sectors with independent active steering to
correct for vessel yaw. Angular coverage is 36[deg] (in Extra Deep
Mode, for use in water depths 3,000 to 6,000 m [9,842.5 to 19,685 ft])
or 150[deg] (in shallower water). The total angular coverage of 36[deg]
to 150[deg] consists of the three or nine beams transmitted
sequentially at each ping. Except in very deep water where the total
beam is 36[deg] x 1[deg], the composite fan beam is 150[deg] x 1[deg],
150[deg] x 2[deg] or 150[deg] x 4[deg] depending on water depth. The
nine beams making up the composite fan will overlap slightly if the
vessel yaw is less than the fore-aft width of the beam (1, 2, or
4[deg], respectively). Achievable swath width on a flat bottom will
normally be approximately five times the water depth. The maximum
source level is 237 dB re 1 [mu]Pam (rms) (Hammerstad, 2005). In deep
water (500 to 3,000 m [1,640.4 to 9,842.5 ft]), a pulse length of 5
milliseconds (ms) is normally used, and the ping rate is mainly limited
by the round trip travel time in the water.
SBP
The Thompson will also operate an Ocean Data Equipment Corporation
Bathy-2000 SBP continuously throughout the cruise simultaneously with
the MBES to map and provide information about the sedimentary features
and bottom topography. The SBP has a maximum 7 kilowatt (kW) transmit
capacity into the underhull array. The energy from the SBP is directed
downward from a 3 kHz transducer in the transducer array mounted in the
hull of the vessel. Pulse duration ranges from 1.5 to 24 ms and the
interval between pulses is controlled automatically by the system or
manually by an operator depending on water depth and reflectivity of
the bottom sediments. The system produces one sound pulse and then
waits for its return before transmitting again. The swept (chirp)
frequency ranges from 6 to 35 kHz. The maximum source output downward
is 221 dB re 1 [mu]Pam (rms), but in practice, the system is rarely
operated above 80% power level.
NMFS expects that acoustic stimuli resulting from the proposed
operation of the two GI airgun array has the potential to harass marine
mammals, incidental to the conduct of the proposed seismic survey. NMFS
expects these disturbances to be temporary and result, at worst, in a
temporary modification in behavior and/or low-level physiological
effects (Level B harassment) of small numbers of certain species of
marine mammals. NMFS does not expect that the movement of the Thompson,
during the conduct of the seismic survey, has the potential to harass
marine mammals because of the relatively slow operation speed of the
vessel (7.4 km/hr or 4 kt) during seismic acquisition.
Description of the Proposed Dates, Duration, and Specified Geographic
Region
The Thompson is expected to depart Honolulu, Hawaii, on November 5,
2011 and spend approximately 7 days in transit to the proposed survey
area, 32 days alternating between acquiring magnetic and seismic data,
and approximately 3 days in transit, arriving at Apra Harbor, Guam, on
December 17, 2011. Seismic operations will be conducted for a total of
approximately 16 days. Some minor deviation from this schedule is
possible, depending on logistics and weather. The survey will encompass
the area approximately 13[deg] to 23[deg] North, approximately 158[deg]
to 172[deg] East, just north of the Marshall Islands (see Figure 1 of
the IHA application). Water depths in the survey area generally range
from approximately 2,000 to 6,000 m (6,561.7 to 19,685 ft); Wake Island
is included in the survey area. The seismic survey will be conducted
partly in international waters and partly in the EEZ of Wake Island
(U.S.), and possibly in the EEZ of the Republic of the Marshall
Islands.
Description of the Marine Mammals in the Area of the Proposed Specified
Activity
Twenty-six marine mammal species (19 odontocetes, 6 mysticetes, and
one pinniped) are known to or could occur in the Marshall Islands
Marine Eco-region (MIME) study area. Several of
[[Page 45522]]
these species are listed as endangered under the U.S. Endangered
Species Act of 1973 (ESA; 16 U.S.C. 1531 et seq.), including the
humpback (Megaptera novaeangliae), sei (Balaenoptera borealis), fin
(Balaenoptera physalus), blue (Balaenoptera musculus), and sperm
(Physeter macrocephalus) whales, as well as the Hawaiian monk seal
(Monachus schauinslandi). The North Pacific right whale (Eubalaena
japonica), listed as endangered under the ESA, was historically
distributed throughout the North Pacific Ocean north of 35[deg] North
and occasionally occurred as far south as 20[deg] North. Whaling
records indicate that the MIME was not part of its range (Townsend,
1935).
The dugong (Dugong dugon), also listed as endangered under the ESA,
is distributed in shallow coastal waters throughout most of the Indo-
Pacific region between approximately 27[deg] North and South of the
equator (Marsh, 2008). Its historical range extended to the Marshall
Islands (Nair et al., 1975). However, the dugong is declining or
extinct in at least one third of its range and no long occurs in the
MIME (Marsh, 2008). The dugong is managed by the U.S. Fish and Wildlife
Service (USFWS) and is not considered further in this analysis; all
others are managed by NMFS.
The marine mammals that occur in the proposed survey area belong to
three taxonomic groups: odontocetes (toothed cetaceans, such as
dolphins), mysticetes (baleen whales), and pinnipeds (seals, sea lions,
and walrus). Cetaceans are the subject of the IHA application to NMFS.
Table 2 (below) presents information on the abundance,
distribution, population status, conservation status, and density of
the marine mammals that may occur in the proposed survey area during
November to December, 2011.
BILLING CODE 3510-22-P
[[Page 45523]]
[GRAPHIC] [TIFF OMITTED] TN29JY11.003
[[Page 45524]]
[GRAPHIC] [TIFF OMITTED] TN29JY11.004
[[Page 45525]]
[GRAPHIC] [TIFF OMITTED] TN29JY11.005
BILLING CODE 3510-22-C
Refer to Section III and IV of SIO's application for detailed
information regarding the abundance and distribution, population
status, and life history and behavior of these species and their
occurrence in the proposed project area. The application also presents
how SIO calculated the estimated densities for the marine mammals in
the proposed survey area. NMFS has reviewed these data and determined
them to be the best available scientific information for the purposes
of the proposed IHA.
Potential Effects on Marine Mammals
Acoustic stimuli generated by the operation of the airguns, which
introduce sound into the marine environment, may have the potential to
cause Level B harassment of marine mammals in the proposed survey area.
The effects of sounds from airgun operations might include one 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).
Permanent hearing impairment, in the unlikely event that it
occurred, would constitute injury, but temporary threshold shift (TTS)
is not an injury (Southall et al., 2007). Although the possibility
cannot be entirely excluded, it is unlikely that the proposed project
would result in any cases of temporary or permanent hearing impairment,
or any significant non-auditory physical or physiological effects.
Based on the available data and studies described here, some behavioral
disturbance is expected, but NMFS expects the disturbance to be
localized and short-term.
Tolerance to Sound
Studies on marine mammals' tolerance to sound in the natural
environment are relatively rare. Richardson et al. (1995) defines
tolerance as the occurrence of marine mammals in areas where they are
exposed to human activities or man-made noise. In many cases, tolerance
develops by the animal habituating to the stimulus (i.e., the gradual
waning of responses to a repeated or ongoing stimulus) (Richardson, et
al., 1995; Thorpe, 1963), but because of ecological or physiological
requirements, many marine animals may need to remain in areas where
they are exposed to chronic stimuli (Richardson, et al., 1995).
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
Malme et al., (1985) studied the responses of humpback whales on their
summer feeding grounds in southeast Alaska to seismic pulses from a
airgun with a total volume of 100 in \3\. They noted that the whales
did not exhibit persistent avoidance when exposed to the airgun and
concluded that there was no clear evidence of avoidance, despite the
possibility of subtle effects, at received levels up to 172 dB re 1
[mu]Pa.
Weir (2008) observed marine mammal responses to seismic pulses from
a 24 airgun array firing a total volume of either 5,085 in \3\ or 3,147
in \3\ in Angolan waters between August 2004 and May 2005. She recorded
a total of 207 sightings of humpback whales (n = 66), sperm whales (n =
124), and Atlantic spotted dolphins (n = 17) and reported that there
were no significant differences in encounter rates (sightings/hr) for
humpback and sperm whales according to the airgun array's operational
status (i.e., active versus silent).
Masking of Natural Sounds
The term masking refers to the inability of a subject to recognize
the occurrence of an acoustic stimulus as a result of the interference
of another acoustic stimulus (Clark et al., 2009). Introduced
underwater sound may, through masking, reduce the effective
communication distance of a marine mammal species if the frequency of
the source is close to that used as a signal by the marine mammal, and
if the anthropogenic sound is present for a significant fraction of the
time (Richardson et al., 1995).
Masking effects of pulsed sounds (even from large arrays of
airguns) on marine mammal calls and other natural sounds are expected
to be limited. Because of the intermittent nature and low duty cycle of
seismic airgun pulses, animals can emit and receive sounds in
[[Page 45526]]
the relatively quiet intervals between pulses. However, in some
situations, reverberation occurs for much or the entire interval
between pulses (e.g., Simard et al., 2005; Clark and Gagnon, 2006)
which could mask calls. Some baleen and toothed whales are known to
continue calling in the presence of seismic pulses, and their calls can
usually be heard between the seismic pulses (e.g., Richardson et al.,
1986; McDonald et al., 1995; Greene et al., 1999; Nieukirk et al.,
2004; Smultea et al., 2004; Holst et al., 2005a, b, 2006; and Dunn and
Hernandez, 2009). However, Clark and Gagnon (2006) reported that fin
whales in the northeast Pacific Ocean went silent for an extended
period starting soon after the onset of a seismic survey in the area.
Similarly, there has been one report that sperm whales ceased calling
when exposed to pulses from a very distant seismic ship (Bowles et al.,
1994). However, more recent studies found that they continued calling
in the presence of seismic pulses (Madsen et al., 2002; Tyack et al.,
2003; Smultea et al., 2004; Holst et al., 2006; and Jochens et al.,
2008). Dolphins and porpoises commonly are heard calling while airguns
are operating (e.g., Gordon et al., 2004; Smultea et al., 2004; Holst
et al., 2005a, b; and Potter et al., 2007). The sounds important to
small odontocetes are predominantly at much higher frequencies than are
the dominant components of airgun sounds, thus limiting the potential
for masking.
In general, NMFS expects the masking effects of seismic pulses to
be minor, given the normally intermittent nature of seismic pulses.
Refer to Appendix A(4) of SIO's EA for a more detailed discussion of
masking effects on marine mammals.
Behavioral Disturbance
Disturbance includes a variety of effects, including subtle to
conspicuous changes in behavior, movement, and displacement. Reactions
to sound, if any, depend on species, state of maturity, experience,
current activity, reproductive state, time of day, and many other
factors (Richardson et al., 1995; Wartzok et al., 2004; Southall et
al., 2007; Weilgart, 2007). If a marine mammal does react briefly to an
underwater sound by changing its behavior or moving a small distance,
the impacts of the change are unlikely to be significant to the
individual, let alone the stock or population. However, if a sound
source displaces marine mammals from an important feeding or breeding
area for a prolonged period, impacts on individuals and populations
could be significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007).
Given the many uncertainties in predicting the quantity and types of
impacts of noise on marine mammals, it is common practice to estimate
how many mammals would be present within a particular distance of
industrial activities and/or exposed to a particular level of
industrial sound. In most cases, this approach likely overestimates the
numbers of marine mammals that would be affected in some biologically-
important manner.
The sound criteria used to estimate how many marine mammals might
be disturbed to some biologically-important degree by a seismic program
are based primarily on behavioral observations of a few species.
Scientists have conducted detailed studies on humpback, gray, bowhead
(Balaena mysticetus), and sperm whales, and on ringed seals (Phoca
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 (reviewed in Richardson
et al., 1995). Whales are often reported to show no overt reactions to
pulses from large arrays of airguns at distances beyond a few kms, even
though the airgun pulses remain well above ambient noise levels out to
much longer distances. However, as reviewed in Appendix A (5) of SIO'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 (Richardson,
et al., 1995). They simply avoided the sound source by displacing their
migration route to varying degrees, but within the natural boundaries
of the migration corridors.
Studies of gray, bowhead, and humpback whales have shown that
seismic pulses with received levels of 160 to 170 dB re 1 [mu]Pa (rms)
seem to cause obvious avoidance behavior in a substantial fraction of
the animals exposed (Malme et al., 1986, 1988; Richardson et al.,
1995). In many areas, seismic pulses from large arrays of airguns
diminish to those levels at distances ranging from 4.5 to 14.5 km (2.4
to 7.8 nmi) 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 to 170 dB re 1
[mu]Pa (rms).
McCauley et al. (1998, 2000a) studied the responses of humpback
whales off western Australia to a full-scale seismic survey with a 16
airgun array (2,678 in \3\) and to a single airgun (20 in\3\) with
source level of 227 dB re 1 [micro]Pa (p-p). In the 1998 study, they
documented that avoidance reactions began at five to eight km (2.7 to
4.3 nmi) from the array, and that those reactions kept most pods
approximately three to four km from the operating seismic boat. In the
2000 study, they noted localized displacement during migration of four
to five km by traveling pods and seven to 12 km (6.5 nmi) 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 five to eight km from the airgun array and two km from
the single airgun. However, some individual humpback whales, especially
males, approached within distances of 100 to 400 m (328 to 1,312 ft),
where the maximum received level was 179 dB re 1 [mu]Pa (rms).
Data collected by observers during several seismic surveys in the
Northwest Atlantic showed that sighting rates of humpback whales were
significantly greater during non-seismic periods compared with periods
when a full array was operating (Moulton and Holst, 2010). In addition,
humpback whales were more likely to swim away and less likely to swim
towards a vessel during seismic vs. non-seismic periods (Moulton and
Holst, 2010).
Humpback whales on their summer feeding grounds in southeast Alaska
did not exhibit persistent avoidance when exposed to seismic pulses
from a 1.64-L (100 in \3\) airgun (Malme et al., 1985). Some humpbacks
seemed ``startled'' at received levels of 150 to 169 dB re 1 [mu]Pa.
Malme et al. (1985) concluded that there was no clear evidence of
avoidance, despite the possibility of subtle effects, at received
levels up to
[[Page 45527]]
172 dB re 1 [mu]Pa (rms). However, Moulton and Holst (2010) reported
that humpback whales monitored during seismic surveys in the Northwest
Atlantic had lower sighting rates and were most often seen swimming
away from the vessel during seismic periods compared with periods when
airguns were silent.
Studies have suggested that south Atlantic humpback whales
wintering off Brazil may be displaced or even strand upon exposure to
seismic surveys (Engel et al., 2004). The evidence for this was
circumstantial and subject to alternative explanations (IAGC, 2004).
Also, the evidence was not consistent with subsequent results from the
same area of Brazil (Parente et al., 2006), or with direct studies of
humpbacks exposed to seismic surveys in other areas and seasons. After
allowance for data from subsequent years, there was no observable
direct correlation between strandings and seismic surveys (IWC,
2007:236).
There are no data on reactions of right whales to seismic surveys,
but results from the closely-related bowhead whale show that their
responsiveness can be quite variable depending on their activity
(migrating versus feeding). Bowhead whales migrating west across the
Alaskan Beaufort Sea in autumn, in particular, are unusually
responsive, with substantial avoidance occurring out to distances of 20
to 30 km (10.8 to 16.2 nmi) from a medium-sized airgun source at
received sound levels of around 120 to 130 dB re 1 [mu]Pa (Miller et
al., 1999; Richardson et al., 1999; see Appendix A (5) of SIO's EA).
However, more recent research on bowhead whales (Miller et al., 2005;
Harris et al., 2007) corroborates earlier evidence that, during the
summer feeding season, bowheads are not as sensitive to seismic
sources. Nonetheless, subtle but statistically significant changes in
surfacing-respiration-dive cycles were evident upon statistical
analysis (Richardson et al., 1986). In the summer, bowheads typically
begin to show avoidance reactions at received levels of about 152 to
178 dB re 1 [mu]Pa (Richardson et al., 1986, 1995; Ljungblad et al.,
1988; Miller et al., 2005).
Reactions of migrating and feeding (but not wintering) gray whales
to seismic surveys have been studied. Malme et al. (1986, 1988) studied
the responses of feeding eastern Pacific gray whales to pulses from a
single 100 in \3\ airgun off St. Lawrence Island in the northern Bering
Sea. They estimated, based on small sample sizes, that 50 percent of
feeding gray whales stopped feeding at an average received pressure
level of 173 dB re 1 [mu]Pa on an (approximate) rms basis, and that 10
percent of feeding whales interrupted feeding at received levels of 163
dB re 1 [mu]Pa (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 seen in areas ensonified by airgun pulses
(Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006), and
calls from blue and fin whales have been localized in areas with airgun
operations (e.g., McDonald et al., 1995; Dunn and Hernandez, 2009;
Castellote et al., 2010). 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). Castellote et al. (2010)
reported that singing fin whales in the Mediterranean moved away from
an operating airgun array.
Ship-based monitoring studies of baleen whales (including blue,
fin, sei, minke, and humpback whales) in the Northwest Atlantic found
that overall, this group had lower sighting rates during seismic vs.
non-seismic periods (Moulton and Holst, 2010). Baleen whales as a group
were also seen significantly farther from the vessel during seismic
compared with non-seismic periods, and they were more often seen to be
swimming away from the operating seismic vessel (Moulton and Holst,
2010). Blue and minke whales were initially sighted significantly
farther from the vessel during seismic operations compared to non-
seismic periods; the same trend was observed for fin whales (Moulton
and Holst, 2010). Minke whales were most often observed to be swimming
away from the vessel when seismic operations were underway (Moulton and
Holst, 2010).
Data on short-term reactions by cetaceans to impulsive noises are
not necessarily indicative of long-term or biologically significant
effects. It is not known whether impulsive sounds affect reproductive
rate or distribution and habitat use in subsequent days or years.
However, gray whales have continued to migrate annually along the west
coast of North America with substantial increases in the population
over recent years, despite intermittent seismic exploration (and much
ship traffic) in that area for decades (Appendix A in Malme et al.,
1984; Richardson et al., 1995; Allen and Angliss, 2010). The western
Pacific gray whale population did not seem affected by a seismic survey
in its feeding ground during a previous year (Johnson et al., 2007).
Similarly, bowhead whales have continued to travel to the eastern
Beaufort Sea each summer, and their numbers have increased notably,
despite seismic exploration in their summer and autumn range for many
years (Richardson et al., 1987; Allen and Angliss, 2010).
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 EA have been reported for toothed
whales. However, there are recent systematic studies on sperm whales
(e.g., Gordon et al., 2006; Madsen et al., 2006; Winsor and Mate, 2006;
Jochens et al., 2008; Miller et al., 2009). There is an increasing
amount of information about responses of various odontocetes to seismic
surveys based on monitoring studies (e.g., Stone, 2003; Smultea et al.,
2004; Moulton and Miller, 2005; Bain and Williams, 2006; Holst et al.,
2006; Stone and Tasker, 2006; Potter et al., 2007; Hauser et al., 2008;
Holst and Smultea, 2008; Weir, 2008; Barkaszi et al., 2009; Richardson
et al., 2009; Moulton and Holst, 2010).
Seismic operators and marine mammal observers on seismic vessels
regularly see dolphins and other small toothed whales near operating
airgun arrays, but in general there is a tendency for most delphinids
to show some avoidance of operating seismic vessels (e.g., Goold,
1996a, b, c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and
Miller, 2005; Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008;
Richardson et al., 2009; Barkaszi et al., 2009; Moulton and Holst,
2010). 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).
[[Page 45528]]
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; Barry et al., 2010; Moulton and Holst, 2010).
In most cases, the avoidance radii for delphinids appear to be small,
on the order of one km or less, and some individuals show no apparent
avoidance. The beluga whale (Delphinapterus leucas) is a species that
(at least at times) shows long-distance avoidance of seismic vessels.
Aerial surveys conducted in the southeastern Beaufort Sea during summer
found that sighting rates of beluga whales were significantly lower at
distances 10 to 20 km compared with 20 to 30 km from an operating
airgun array, and observers on seismic boats in that area rarely see
belugas (Miller et al., 2005; Harris et al., 2007).
Captive bottlenose dolphins (Tursiops truncatus) and beluga whales
exhibited changes in behavior when exposed to strong pulsed sounds
similar in duration to those typically used in seismic surveys
(Finneran et al., 2000, 2002, 2005). However, the animals tolerated
high received levels of sound before exhibiting aversive behaviors.
Results for porpoises depend on species. The limited available data
suggest that harbor porpoises 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 SIO's EA for review). However,
controlled exposure experiments in the GOM indicate that foraging
behavior was altered upon exposure to airgun sound (Jochens et al.,
2008; Miller et al., 2009; Tyack, 2009).
There are almost no specific data on the behavioral reactions of
beaked whales to seismic surveys. However, some northern bottlenose
whales (Hyperoodon ampullatus) remained in the general area and
continued to produce high-frequency clicks when exposed to sound pulses
from distant seismic surveys (Gosselin and Lawson, 2004; Laurinolli and
Cochrane, 2005; Simard et al., 2005). Most beaked whales tend to avoid
approaching vessels of other types (e.g., Wursig et al., 1998). They
may also dive for an extended period when approached by a vessel (e.g.,
Kasuya, 1986), although it is uncertain how much longer such dives may
be as compared to dives by undisturbed beaked whales, which also are
often quite long (Baird et al., 2006; Tyack et al., 2006). Based on a
single observation, Aguilar-Soto et al. (2006) suggested that foraging
efficiency of Cuvier's beaked whales may be reduced by close approach
of vessels. In any event, it is likely that most beaked whales would
also show strong avoidance of an approaching seismic vessel, although
this has not been documented explicitly. In fact, Moulton and Holst
(2010) reported 15 sightings of beaked whales during seismic studies in
the Northwest Atlantic; seven of those sightings were made at times
when at least one airgun was operating. There was little evidence to
indicate that beaked whale behavior was affected by airgun operations;
sighting rates and distances were similar during seismic and non-
seismic periods (Moulton and Holst, 2010).
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 Stranding and Mortality section in this
notice). These strandings are apparently a disturbance response,
although auditory or other injuries or other physiological effects may
also be involved. Whether beaked whales would ever react similarly to
seismic surveys is unknown. Seismic survey sounds are quite different
from those of the sonar in operation during the above-cited incidents.
Odontocete reactions to large arrays of airguns are variable and,
at least for delphinids and Dall's porpoises, seem to be confined to a
smaller radius than has been observed for the more responsive of the
mysticetes, belugas, and harbor porpoises (Appendix A of SIO's EA).
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, see Appendix A(5) of SIO's
EA. In the Beaufort Sea, some ringed seals avoided an area of 100 m to
(at most) a few hundred meters around seismic vessels, but many seals
remained within 100 to 200 m (328 to 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).
Hearing Impairment and Other Physical Effects
Exposure to high intensity sound for a sufficient duration may
result in auditory effects such as a noise-induced threshold shift--an
increase in the auditory threshold after exposure to noise (Finneran,
Carder, Schlundt, and Ridgway, 2005). Factors that influence the amount
of threshold shift include the amplitude, duration, frequency content,
temporal pattern, and energy distribution of noise exposure. The
magnitude of hearing threshold shift normally decreases over time
following cessation of the noise exposure. The amount of threshold
shift just after exposure is called the initial threshold shift. If the
threshold shift eventually returns to zero (i.e., the threshold returns
to the pre-exposure value), it is called temporary threshold shift
(TTS) (Southall et al., 2007).
Researchers have studied TTS in certain captive odontocetes and
pinnipeds exposed to strong sounds (reviewed in Southall et al., 2007).
However, there has been no specific documentation of TTS let alone
permanent hearing damage, i.e., permanent threshold shift (PTS), in
free-ranging marine mammals exposed to sequences of airgun pulses
during realistic field conditions.
Temporary Threshold Shift--TTS is the mildest form of hearing
impairment that can occur during exposure to a strong sound (Kryter,
1985). While experiencing TTS, the hearing threshold rises and a sound
must be stronger in order to be heard. At least in terrestrial mammals,
TTS can last from minutes or
[[Page 45529]]
hours to (in cases of strong TTS) days. For sound exposures at or
somewhat above the TTS threshold, hearing sensitivity in both
terrestrial and marine mammals recovers rapidly after exposure to the
noise ends. Few data on sound levels and durations necessary to elicit
mild TTS have been obtained for marine mammals, and none of the
published data concern TTS elicited by exposure to multiple pulses of
sound. Available data on TTS in marine mammals are summarized in
Southall et al. (2007). Table 1 (above) presents the distances from the
Thompson's airguns at which the received energy level (per pulse, flat-
weighted) would be expected to be greater than or equal to 190 dB re 1
[mu]Pa (rms).
Researchers have derived TTS information for odontocetes from
studies on the bottlenose dolphin and beluga. For the one harbor
porpoise tested, the received level of airgun sound that elicited onset
of TTS was lower (Lucke et al., 2009). If these results from a single
animal are representative, it is inappropriate to assume that onset of
TTS occurs at similar received levels in all odontocetes (cf. Southall
et al., 2007). Some cetaceans apparently can incur TTS at considerably
lower sound exposures than are necessary to elicit TTS in the beluga or
bottlenose dolphin.
For baleen whales, there are no data, direct or indirect, on levels
or properties of sound that are required to induce TTS. The frequencies
to which baleen whales are most sensitive are assumed to be lower than
those to which odontocetes are most sensitive, and natural background
noise levels at those low frequencies tend to be higher. As a result,
auditory thresholds of baleen whales within their frequency band of
best hearing are believed to be higher (less sensitive) than are those
of odontocetes at their best frequencies (Clark and Ellison, 2004).
From this, it is suspected that received levels causing TTS onset may
also be higher in baleen whales (Southall et al., 2007). For this
proposed study, SIO expects no cases of TTS given the low abundance of
baleen whales in the proposed survey area at the time of the proposed
survey, and the strong likelihood that baleen whales would avoid the
approaching airguns (or vessel) before being exposed to levels high
enough for TTS to occur.
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 TTS
threshold for pulsed sounds has been indirectly estimated as being an
SEL of approximately 171 dB re 1 [micro]Pa\2\[middot]s (Southall et
al., 2007) which would be equivalent to a single pulse with a received
level of approximately 181 to 186 dB re 1 [micro]Pa (rms), or a series
of pulses for which the highest rms values are a few dB lower.
Corresponding values for California sea lions and northern elephant
seals are likely to be higher (Kastak et al., 2005).
To avoid the potential for injury, NMFS (1995, 2000) concluded that
cetaceans should not be exposed to pulsed underwater noise at received
levels exceeding 180 dB re 1 [mu]Pa (rms) and pinnipeds should not be
exposed to pulsed underwater noise at received levels exceeding 190 dB
re 1 [mu]Pa (rms). NMFS believes that to avoid the potential for
permanent physiological damage (Level A harassment), cetaceans should
not be exposed to pulsed underwater noise at received levels exceeding
180 dB re 1 [mu]Pa (rms) and pinnipeds should not be exposed to pulsed
underwater noise at received levels exceeding 190 dB re 1 [mu]Pa (rms).
The 180 dB and 190 dB levels are the shutdown criterion applicable to
cetaceans and pinnipeds, respectively, as specified by NMFS (2000);
these levels were used to establish the EZs. NMFS also assumes that
marine mammals exposed to levels exceeding 160 dB re 1 [mu]Pa (rms) may
experience Level B harassment.
Permanent Threshold Shift--When PTS occurs, there is physical
damage to the sound receptors in the ear. In severe cases, there can be
total or partial deafness, whereas in other cases, the animal has an
impaired ability to hear sounds in specific frequency ranges (Kryter,
1985). There is no specific evidence that exposure to pulses of airgun
sound can cause PTS in any marine mammal, even with large arrays of
airguns. However, given the possibility that mammals close to an airgun
array might incur at least mild TTS, there has been further speculation
about the possibility that some individuals occurring very close to
airguns might incur PTS (e.g., Richardson et al., 1995, p. 372ff;
Gedamke et al., 2008). Single or occasional occurrences of mild TTS are
not indicative of permanent auditory damage, but repeated or (in some
cases) single exposures to a level well above that causing TTS onset
might elicit PTS.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals, but are assumed to be similar to those in humans and
other terrestrial mammals. PTS might occur at a received sound level at
least several dBs above that inducing mild TTS if the animal were
exposed to strong sound pulses with rapid rise time--see Appendix A (6)
of SIO'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
six dB (Southall et al., 2007).
Given the higher level of sound necessary to cause PTS as compared
with TTS, it is considerably less likely that PTS would occur. Baleen
whales generally avoid the immediate area around operating seismic
vessels, as do some other marine mammals.
Stranding and Mortality--Marine mammals close to underwater
detonations of high explosives can be killed or severely injured, and
the auditory organs are especially susceptible to injury (Ketten et
al., 1993; Ketten, 1995). However, explosives are no longer used for
marine waters for commercial seismic surveys or (with rare exceptions)
for seismic research; they have been replaced entirely by airguns or
related non-explosive pulse generators. Airgun pulses are less
energetic and have slower rise times, and there is no specific evidence
that they can cause serious injury, death, or stranding even in the
case of large airgun arrays. However, the association of strandings of
beaked whales with naval exercises involving mid-frequency active sonar
and, in one case, an L-DEO seismic survey (Malakoff, 2002; Cox et al.,
2006), has raised the possibility that beaked whales exposed to strong
``pulsed'' sounds may be especially susceptible to injury and/or
behavioral reactions that can lead to stranding (e.g., Hildebrand,
2005; Southall et al., 2007). Appendix A (6) of SIO's EA provides
additional details.
Specific sound-related processes that lead to strandings and
mortality are not well documented, but may include:
(1) Swimming in avoidance of a sound into shallow water;
(2) A change in behavior (such as a change in diving behavior) that
might contribute to tissue damage, gas bubble formation, hypoxia,
cardiac arrhythmia, hypertensive hemorrhage or other forms of trauma;
(3) A physiological change such as a vestibular response leading to
a behavioral change or stress-induced hemorrhagic diathesis, leading in
turn to tissue damage; and
[[Page 45530]]
(4) Tissue damage directly from sound exposure, such as through
acoustically-mediated bubble formation and growth or acoustic resonance
of tissues. Some of these mechanisms are unlikely to apply in the case
of impulse sounds. However, there are indications that gas-bubble
disease (analogous to ``the bends''), induced in supersaturated tissue
by a behavioral response to acoustic exposure, could be a pathologic
mechanism for the strandings and mortality of some deep-diving
cetaceans exposed to sonar. However, the evidence for this remains
circumstantial and associated with exposure to naval mid-frequency
sonar, not seismic surveys (Cox et al., 2006; Southall et al., 2007).
Seismic pulses and mid-frequency sonar signals are quite different,
and some mechanisms by which sonar sounds have been hypothesized to
affect beaked whales are unlikely to apply to airgun pulses. Sounds
produced by airgun arrays are broadband impulses with most of the
energy below one kHz. Typical military mid-frequency sonar emits non-
impulse sounds at frequencies of two to 10 kHz, generally with a
relatively narrow bandwidth at any one time. A further difference
between seismic surveys and naval exercises is that naval exercises can
involve sound sources on more than one vessel. Thus, it is not
appropriate to assume that there is a direct connection between the
effects of military sonar and seismic surveys on marine mammals.
However, evidence that sonar signals can, in special circumstances,
lead (at least indirectly) to physical damage and mortality (e.g.,
Balcomb and Claridge, 2001; NOAA and USN, 2001; Jepson et al., 2003;
Fern[aacute]ndez et al., 2004, 2005; Hildebrand 2005; Cox et al., 2006)
suggests that caution is warranted when dealing with exposure of marine
mammals to any high-intensity ``pulsed'' sound.
There is no conclusive evidence of cetacean strandings or deaths at
sea as a result of exposure to seismic surveys, but a few cases of
strandings in the general area where a seismic survey was ongoing have
led to speculation concerning a possible link between seismic surveys
and strandings. Suggestions that there was a link between seismic
surveys and strandings of humpback whales in Brazil (Engel et al.,
2004) were not well founded (IAGC, 2004; IWC, 2007). In September 2002,
there was a stranding of two Cuvier's beaked whales (Ziphius
cavirostris) in the Gulf of California, Mexico, when the L-DEO vessel
R/V Maurice Ewing was operating a 20 airgun (8,490 in\3\) 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 high likelihood that any beaked whales nearby would avoid
the approaching vessel before being exposed to high sound levels, and
(2) Differences between the sound sources operated by SIO and those
involved in the naval exercises associated with strandings.
Non-auditory Physiological Effects--Non-auditory physiological
effects or injuries that theoretically might occur in marine mammals
exposed to strong underwater sound include stress, neurological
effects, bubble formation, resonance, and other types of organ or
tissue damage (Cox et al., 2006; Southall et al., 2007). Studies
examining such effects are limited. However, resonance effects (Gentry,
2002) and direct noise-induced bubble formations (Crum et al., 2005)
are implausible in the case of exposure to an impulsive broadband
source like an airgun array. If seismic surveys disrupt diving patterns
of deep-diving species, this might perhaps result in bubble formation
and a form of the bends, as speculated to occur in beaked whales
exposed to sonar. However, there is no specific evidence of this upon
exposure to airgun pulses.
In general, very little is known about the potential for seismic
survey sounds (or other types of strong underwater sounds) to cause
non-auditory physical effects in marine mammals. Such effects, if they
occur at all, would presumably be limited to short distances and to
activities that extend over a prolonged period. The available data do
not allow identification of a specific exposure level above which non-
auditory effects can be expected (Southall et al., 2007), or any
meaningful quantitative predictions of the numbers (if any) of marine
mammals that might be affected in those ways. Marine mammals that show
behavioral avoidance of seismic vessels, including most baleen whales
and some odontocetes, are especially unlikely to incur non-auditory
physical effects.
Potential Effects of Other Acoustic Devices
MBES
SIO will operate the Kongsberg EM 300 MBES from the source vessel
during the planned study. Sounds from the MBES are very short pulses,
occurring for five ms once every five to 20 s, depending on water
depth. Most of the energy in the sound pulses emitted by this MBES is
at frequencies near 30 kHz, and the maximum source level is 237 dB re 1
[mu]Pa (rms). The beam is narrow (1[deg]) in fore-aft extent and wide
(36[deg]) in the cross-track extent. Each ping consists of nine (in
water greater than 1,000 m deep) or three (in water less than 1,000 m
deep) successive fan-shaped transmissions (segments) at different
cross-track angles. Any given mammal at depth near the trackline would
be in the main beam for only one or two of the nine segments. Also,
marine mammals that encounter the Kongsberg EM 300 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
five ms pulse (or two pings 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 longer pulse duration than
the Kongsberg EM 300; and (2) are often directed close to horizontally
versus more downward for the MBES. The area of possible influence of
the MBES is much smaller--a narrow band below the source vessel. Also,
the duration of exposure for a given marine mammal can be much longer
for naval sonar. During 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
[[Page 45531]]
whales, the MBES signals (12 kHz) do not overlap with the predominant
frequencies in the calls, which would avoid any significant masking.
Behavioral Responses--Behavioral reactions of free-ranging marine
mammals to sonars, echosounders, and other sound sources appear to vary
by species and circumstance. Observed reactions have included silencing
and dispersal by sperm whales (Watkins et al., 1985), increased
vocalizations and no dispersal by pilot whales (Globicephala melas)
(Rendell and Gordon, 1999), and the previously-mentioned beachings by
beaked whales. During exposure to a 21 to 25 kHz ``whale-finding''
sonar with a source level of 215 dB re 1 [micro]Pa, gray whales reacted
by orienting slightly away from the source and being deflected from
their course by approximately 200 m (Frankel, 2005). When a 38 kHz
echosounder and a 150 kHz acoustic Doppler current profiler were
transmitting during studies in the Eastern Tropical Pacific, baleen
whales showed no significant responses, while spotted and spinner
dolphins were detected slightly more often and beaked whales less often
during visual surveys (Gerrodette and Pettis, 2005).
Captive bottlenose dolphins and a beluga whale exhibited changes in
behavior when exposed to 1 s tonal signals at frequencies similar to
those that will be emitted by the MBES used by 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
echosounder sounds at frequencies similar to those used during seismic
operations. Hastie and Janik (2007) conducted a series of behavioral
response tests on two captive gray seals to determine their reactions
to underwater operation of a 375 kHz multibeam imaging echosounder that
included significant signal components down to 6 kHz. Results indicated
that the two seals reacted to the 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 consequences to the animals.
Hearing Impairment and Other Physical Effects--Given recent
stranding events that have been associated with the operation of naval
sonar, there is concern that mid-frequency sonar sounds can cause
serious impacts to marine mammals (see above). However, the MBES
proposed for use by 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 sonar often uses near-horizontally-directed sound. Those factors
would all reduce the sound energy received from the MBES rather
drastically relative to that from naval sonar.
NMFS believes that the brief exposure of marine mammals to one
pulse, or small numbers of signals, from the MBES is not likely to
result in the harassment of marine mammals.
SBP
SIO will also operate a SBP from the source vessel during the
proposed survey. Sounds from the SBP are very short pulses, occurring
for up to 25 ms once every three to eight s. Most of the energy in the
sound pulses emitted by the SBP is at three to six kHz, and the beam is
directed downward. The SBP on the Thompson has a maximum source level
of 211 dB re 1 [mu]Pa (rms).
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
Thompson--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 SBP signals given the directionality of the signal
and the brief period when an individual mammal is likely to be within
its beam. Furthermore, in the case of most baleen whales, the SBP
signals do not overlap with the predominant frequencies in the calls,
which would avoid significant masking.
Behavioral Responses--Marine mammal behavioral reactions to other
pulsed sound sources are discussed above, and responses to the SBP are
likely to be similar to those for other pulsed sources if received at
the same levels. However, the pulsed signals from the SBP are
considerably weaker than those from the MBES. Therefore, behavioral
responses are not expected unless marine mammals are very close to the
source.
Hearing Impairment and Other Physical Effects--It is unlikely that
the SBP produces pulse levels strong enough to cause hearing impairment
or other physical injuries even in an animal that is (briefly) in a
position near the source. The SBP is usually operated simultaneously
with other higher-power acoustic sources, including airguns. Many
marine mammals will move away in response to the approaching higher-
power sources or the vessel itself before the mammals would be close
enough for there to be any possibility of effects from the less intense
sounds from the SBP.
The potential effects to marine mammals described in this section
of the document do not take into consideration the proposed monitoring
and mitigation measures described later in this document (see the
``Proposed Mitigation'' and ``Proposed Monitoring and Reporting''
sections) which, as noted are designed to effect the least practicable
adverse impact on affected marine mammal species and stocks.
Anticipated Effects on Marine Mammal Habitat
The proposed seismic survey will not result in any permanent impact
on habitats used by the marine mammals in the proposed survey area,
including the food sources they use (i.e. fish and invertebrates), and
there will be no physical damage to any habitat. While it is
anticipated that the specified activity may result in marine mammals
avoiding certain areas due to temporary ensonification, this impact to
habitat is temporary and reversible and was considered in further
detail earlier in this document, as behavioral modification. The main
impact associated with the proposed activity will be temporarily
elevated noise levels and the associated direct effects on marine
mammals, previously discussed in this notice.
Anticipated Effects on Fish
One reason for the adoption of airguns as the standard energy
source for marine seismic surveys is that, unlike explosives, they have
not been associated with large-scale fish kills. However, existing
information on the impacts of seismic surveys on marine fish
populations is limited (see Appendix C of SIO'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
[[Page 45532]]
involve temporary and permanent primary and secondary stress responses,
such as changes in levels of enzymes and proteins. Behavioral effects
refer to temporary and (if they occur) permanent changes in exhibited
behavior (e.g., startle and avoidance behavior). The three categories
are interrelated in complex ways. For example, it is possible that
certain physiological and behavioral changes could potentially lead to
an ultimate pathological effect on individuals (i.e., mortality).
The specific received sound levels at which permanent adverse
effects to fish potentially could occur are little studied and largely
unknown. Furthermore, the available information on the impacts of
seismic surveys on marine fish is from studies of individuals or
portions of a population; there have been no studies at the population
scale. The studies of individual fish have often been on caged fish
that were exposed to airgun pulses in situations not representative of
an actual seismic survey. Thus, available information provides limited
insight on possible real-world effects at the ocean or population
scale. 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.
Hastings and Popper (2005), Popper (2009), and Popper and Hastings
(2009a,b) provided recent critical reviews of the known effects of
sound on fish. The following sections provide a general synopsis of the
available information on the effects of exposure to seismic and other
anthropogenic sound as relevant to fish. The information comprises
results from scientific studies of varying degrees of rigor plus some
anecdotal information. Some of the data sources may have serious
shortcomings in methods, analysis, interpretation, and reproducibility
that must be considered when interpreting their results (see Hastings
and Popper, 2005). Potential adverse effects of the program's sound
sources on marine fish are noted.
Pathological Effects--The potential for pathological damage to
hearing structures in fish depends on the energy level of the received
sound and the physiology and hearing capability of the species in
question (see Appendix C of SIO's EA). For a given sound to result in
hearing loss, the sound must exceed, by some substantial amount, the
hearing threshold of the fish for that sound (Popper, 2005). The
consequences of temporary or permanent hearing loss in individual fish
on a fish population are unknown; however, they likely depend on the
number of individuals affected and whether critical behaviors involving
sound (e.g., predator avoidance, prey capture, orientation and
navigation, reproduction, etc.) are adversely affected.
Little is known about the mechanisms and characteristics of damage
to fish that may be inflicted by exposure to seismic survey sounds. Few
data have been presented in the peer-reviewed scientific literature. As
far as SIO and NMFS know, there are only two papers with proper
experimental methods, controls, and careful pathological investigation
implicating sounds produced by actual seismic survey airguns in causing
adverse anatomical effects. One such study indicated anatomical damage,
and the second indicated TTS in fish hearing. The anatomical case is
McCauley et al. (2003), who found that exposure to airgun sound caused
observable anatomical damage to the auditory maculae of pink snapper
(Pagrus auratus). This damage in the ears had not been repaired in fish
sacrificed and examined almost two months after exposure. On the other
hand, Popper et al. (2005) documented only TTS (as determined by
auditory brainstem response) in two of three fish species from the
Mackenzie River Delta. This study found that broad whitefish (Coregonus
nasus) exposed to five airgun shots were not significantly different
from those of controls. During both studies, the repetitive exposure to
sound was greater than would have occurred during a typical seismic
survey. However, the substantial low-frequency energy produced by the
airguns [less than 400 Hz in the study by McCauley et al. (2003) and
less than approximately 200 Hz in Popper et al. (2005)] likely did not
propagate to the fish because the water in the study areas was very
shallow (approximately nine m in the former case and less than two m in
the latter). Water depth sets a lower limit on the lowest sound
frequency that will propagate (the ``cutoff frequency'') at about one-
quarter wavelength (Urick, 1983; Rogers and Cox, 1988).
Wardle et al. (2001) suggested that in water, acute injury and
death of organisms exposed to seismic energy depends primarily on two
features of the sound source: (1) The received peak pressure and (2)
the time required for the pressure to rise and decay. Generally, as
received pressure increases, the period for the pressure to rise and
decay decreases, and the chance of acute pathological effects
increases. According to Buchanan et al. (2004), for the types of
seismic airguns and arrays involved with the proposed program, the
pathological (mortality) zone for fish would be expected to be within a
few meters of the seismic source. Numerous other studies provide
examples of no fish mortality upon exposure to seismic sources (Falk
and Lawrence, 1973; Holliday et al., 1987; La Bella et al., 1996;
Santulli et al., 1999; McCauley et al., 2000a,b, 2003; Bjarti, 2002;
Thomsen, 2002; Hassel et al., 2003; Popper et al., 2005; Boeger et al.,
2006).
Some studies have reported, some equivocally, that mortality of
fish, fish eggs, or larvae can occur close to seismic sources
(Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman et al., 1996;
Dalen et al., 1996). Some of the reports claimed seismic effects from
treatments quite different from actual seismic survey sounds or even
reasonable surrogates. However, Payne et al. (2009) reported no
statistical differences in mortality/morbidity between control and
exposed groups of capelin eggs or monkfish larvae. Saetre and Ona
(1996) applied a `worst-case scenario' mathematical model to
investigate the effects of seismic energy on fish eggs and larvae. They
concluded that mortality rates caused by exposure to seismic surveys
are so low, as compared to natural mortality rates, that the impact of
seismic surveying on recruitment to a fish stock must be regarded as
insignificant.
Physiological Effects--Physiological effects refer to cellular and/
or biochemical responses of fish to acoustic stress. Such stress
potentially could affect fish populations by increasing mortality or
reducing reproductive success. Primary and secondary stress responses
of fish after exposure to seismic survey sound appear to be temporary
in all studies done to date (Sverdrup et al., 1994; Santulli et al.,
1999; McCauley et al., 2000a,b). The periods necessary for the
biochemical changes to return to normal are variable and depend on
numerous aspects of the biology of the species and of the sound
stimulus (see Appendix C of SIO's EA).
Behavioral Effects--Behavioral effects include changes in the
distribution, migration, mating, and catchability of fish populations.
Studies investigating the possible effects of sound (including seismic
survey sound) on fish behavior have been conducted on both uncaged and
caged individuals (e.g., 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
[[Page 45533]]
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 founded by other sources of disturbance (Dalen and Raknes,
1985; Dalen and Knutsen, 1986; Lokkeborg, 1991; Skalski et al., 1992;
Engas et al., 1996). In other airgun experiments, there was no change
in catch per unit effort of fish when airgun pulses were emitted,
particularly in the immediate vicinity of the seismic survey (Pickett
et al., 1994; La Bella et al., 1996). For some species, reductions in
catch may have resulted from a change in behavior of the fish, e.g., a
change in vertical or horizontal distribution, as reported in Slotte et
al. (2004).
In general, any adverse effects on fish behavior or fisheries
attributable to seismic testing may depend on the species in question
and the nature of the fishery (season, duration, fishing method). They
may also depend on the age of the fish, its motivational state, its
size, and numerous other factors that are difficult, if not impossible,
to quantify at this point, given such limited data on effects of
airguns on fish, particularly under realistic at-sea conditions.
Anticipated Effects on Invertebrates
The existing body of information on the impacts of seismic survey
sound on marine invertebrates is very limited. However, there is some
unpublished and very limited evidence of the potential for adverse
effects on invertebrates, thereby justifying further discussion and
analysis of this issue. The three types of potential effects of
exposure to seismic surveys on marine invertebrates are pathological,
physiological, and behavioral. Based on the physical structure of their
sensory organs, marine invertebrates appear to be specialized to
respond to particle displacement components of an impinging sound field
and not to the pressure component (Popper et al., 2001; see also
Appendix D of SIO's EA).
The only information available on the impacts of seismic surveys on
marine invertebrates involves studies of individuals; there have been
no studies at the population scale. Thus, available information
provides limited insight on possible real-world effects at the regional
or ocean scale. The most important aspect of potential impacts concerns
how exposure to seismic survey sound ultimately affects invertebrate
populations and their viability, including availability to fisheries.
Literature reviews of the effects of seismic and other underwater
sound on invertebrates were provided by Moriyasu et al. (2004) and
Payne et al. (2008). The following sections provide a synopsis of
available information on the effects of exposure to seismic survey
sound on species of decapod crustaceans and cephalopods, the two
taxonomic groups of invertebrates on which most such studies have been
conducted. The available information is from studies with variable
degrees of scientific soundness and from anecdotal information. A more
detailed review of the literature on the effects of seismic survey
sound on invertebrates is provided in Appendix D of SIO's EA.
Pathological Effects--In water, lethal and sub-lethal injury to
organisms exposed to seismic survey sound appears to depend on at least
two features of the sound source: (1) The received peak pressure; and
(2) the time required for the pressure to rise and decay. Generally, as
received pressure increases, the period for the pressure to rise and
decay decreases, and the chance of acute pathological effects
increases. For the type of airgun array planned for the proposed
program, the pathological (mortality) zone for crustaceans and
cephalopods is expected to be within a few meters of the seismic
source, at most; however, very few specific data are available on
levels of seismic signals that might damage these animals. This premise
is based on the peak pressure and rise/decay time characteristics of
seismic airgun arrays currently in use around the world.
Some studies have suggested that seismic survey sound has a limited
pathological impact on early developmental stages of crustaceans
(Pearson et al., 1994; Christian et al., 2003; DFO, 2004). However, the
impacts appear to be either temporary or insignificant compared to what
occurs under natural conditions. Controlled field experiments on adult
crustaceans (Christian et al., 2003, 2004; DFO, 2004) and adult
cephalopods (McCauley et al., 2000a,b) exposed to seismic survey sound
have not resulted in any significant pathological impacts on the
animals. It has been suggested that exposure to commercial seismic
survey activities has injured giant squid (Guerra et al., 2004), but
the article provides little evidence to support this claim. Recent work
by Andre et al. (2011) purports to present the first morphological and
ultrastructural evidence of massive acoustic trauma (i.e., permanent
and substantial alterations of statocyst sensory hair cells) in four
cephalopod species subjected to low-frequency sound. The cephalopods,
primarily cuttlefish, were exposed to continuous 50 to 400 Hz
sinusoidal wave sweeps (100% duty cycle and 1 s sweep period) for two
hours while captive in relatively small tanks (one 2,000 liter [L,
2m\3\] and one 200 L [0.2 m\3\] tank), and reported morphological and
ultrastructural evidence of massive acoustic trauma (i.e., permanent
and substantial alterations of statocyst sensory hair cells). The
received SPL was reported as 1575 dB re 1 [micro]Pa, with
peak levels at 175 dB re 1 [micro]Pa. As in the McCauley et al. (2003)
paper on sensory hair cell damage in pink snapper as a result of
exposure to seismic sound, the cephalopods were subjected to higher
sound levels than they would be under natural conditions, and they were
unable to swim away from the sound source.
Physiological Effects--Physiological effects refer mainly to
biochemical responses by marine invertebrates to acoustic stress. Such
stress potentially could affect invertebrate populations by increasing
mortality or reducing reproductive success. Primary and secondary
stress responses (i.e., changes in haemolymph levels of enzymes,
proteins, etc.) of crustaceans have been noted several days or months
after exposure to seismic survey sounds (Payne et al., 2007). The
periods necessary for these biochemical changes to return to normal are
variable and depend on numerous aspects of the biology of the species
and of the sound stimulus.
Behavioral Effects--There is increasing interest in assessing the
possible direct and indirect effects of seismic and other sounds on
invertebrate behavior, particularly in relation to the consequences for
fisheries. Changes in behavior could potentially affect such aspects as
reproductive success, distribution, susceptibility to predation, and
catchability by fisheries. Studies investigating the possible
behavioral effects of exposure to seismic survey sound on crustaceans
and cephalopods have been conducted on both uncaged and caged animals.
In some cases, invertebrates exhibited startle responses (e.g., squid
in McCauley et al., 2000a,b). In other cases, no behavioral impacts
were noted (e.g., crustaceans in Christian et al., 2003, 2004; DFO
2004). There have been anecdotal reports of reduced catch rates of
shrimp shortly after exposure to seismic surveys; however, other
studies have not observed any significant changes in shrimp catch rate
(Andriguetto-Filho et al., 2005). Similarly, Parry and Gason
[[Page 45534]]
(2006) did not find any evidence that lobster catch rates were affected
by seismic surveys. Any adverse effects on crustacean and cephalopod
behavior or fisheries attributable to seismic survey sound depend on
the species in question and the nature of the fishery (season,
duration, fishing method).
Proposed Mitigation
In order to issue an Incidental Take Authorization (ITA) under
section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible
methods of taking pursuant to such activity, and other means of
effecting the least practicable adverse impact on such species or stock
and its habitat, paying particular attention to rookeries, mating
grounds, and areas of similar significance, and the availability of
such species or stock for taking for certain subsistence uses.
SIO has based the mitigation measures described herein, to be
implemented for the proposed seismic survey, on the following:
(1) Protocols used during previous SIO seismic research cruises as
approved by NMFS;
(2) Previous IHA applications and IHAs approved and authorized by
NMFS; and
(3) Recommended best practices in Richardson et al. (1995), Pierson
et al. (1998), and Weir and Dolman, (2007).
To reduce the potential for disturbance from acoustic stimuli
associated with the activities, SIO and/or its designees has proposed
to implement the following mitigation measures for marine mammals:
(1) Proposed exclusion zones;
(2) Speed or course alteration;
(3) Shut-down procedures; and
(4) Ramp-up procedures.
Proposed Exclusion Zones--Received sound levels have been modeled
by L-DEO for a number of airgun configurations, including two 105 in\3\
GI airguns, in relation to distance and direction from the airguns (see
Figure 2 of the IHA application). 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 source where
sound levels are predicted to be 190, 180, and 160 dB re 1 [mu]Pa (rms)
in deep water were determined (see Table 1 above).
Empirical data concerning the 190, 180, and 160 dB (rms) distances
were acquired for various airgun arrays based on measurements during
the acoustic verification studies conducted by L-DEO in the northern
GOM in 2003 (Tolstoy et al., 2004) and 2007 to 2008 (Tolstoy et al.,
2009). Results of the 36 airgun array are not relevant for the two GI
airguns to be used in the proposed survey. The empirical data for the
6, 10, 12, and 20 airgun arrays indicate that, for deep water, the L-
DEO model tends to overestimate the received sound levels at a given
distance (Tolstoy et al., 2004). Measurements were not made for the two
GI airgun array in deep water, however, SIO proposes to use the EZ
predicted by L-DEO's model for the proposed GI airgun operations in
deep water, although they are likely conservative give the empirical
results for the other arrays.
The 180 and 190 dB radii are shut-down criteria applicable to
cetaceans and pinnipeds, respectively, as specified by NMFS (2000);
these levels were used to establish the EZs. If the PSO detects marine
mammal(s) within or about to enter the appropriate EZ, the airguns will
be shut-down, immediately.
Speed or Course Alteration--If a marine mammal is detected outside
the EZ an, based on its position and the relative motion, is likely to
enter the EZ, the vessel's speed and/or direct course could be changed.
This would be done if operationally practicable while minimizing the
effect on the planned science objectives. The activities and movements
of the marine mammal (relative to the seismic vessel) will then be
closely monitored to determine whether the animal is approaching the
applicable EZ. If the animal appears likely to enter the EZ, further
mitigative actions will be taken, i.e., either further course
alterations or a shut-down of the seismic source. Typically, during
seismic operations, the source vessel is unable to change speed or
course and one or more alternative mitigation measures will need to be
implemented.
Shut-down Procedures--SIO will shut down the operating airgun(s) if
a marine mammal is seen outside the EZ for the airgun(s), and if the
vessel's speed and/or course cannot be changed to avoid having the
animal enter the EZ, the seismic source will be shut-down before the
animal is within the EZ. If a marine mammal is already within the EZ
when first detected, the seismic source will be shut-down immediately.
Following a shut-down, SIO will not resume airgun activity until
the marine mammal has cleared the EZ. SIO will consider the animal to
have cleared the EZ if:
A PSO has visually observed the animal leave the EZ, or
A PSO has not sighted the animal within the EZ for 15 min
for species with shorter dive durations (i.e., small odontocetes or
pinnipeds), or 30 min for species with longer dive durations (i.e.,
mysticetes and large odontocetes, including sperm, killer, and beaked
whales).
Ramp-up Procedures--SIO will follow a ramp-up procedure when the
airgun array begins operating after a specified period without airgun
operations or when a shut-down has exceeded that period. SIO proposes
that, for the present cruise, this period would be approximately 15
min. SIO has used similar periods (approximately 15 min) during
previous SIO surveys.
Ramp-up will begin with a single GI airgun (105 in\3\). The second
GI airgun (105 in\3\) will be added after five min. During ramp-up, the
Protected Species Observers (PSOs) will monitor the EZ, and if marine
mammals are sighted, SIO will implement a shut-down as though both GI
airguns were operational.
If the complete EZ has not been visible for at least 30 min prior
to the start of operations in either daylight or nighttime, SIO will
not commence the ramp-up. If one airgun has operated, ramp-up to full
power will be permissible at night or in poor visibility, on the
assumption that marine mammals will be alerted to the approaching
seismic vessel by the sounds from the single airgun and could move away
if they choose. A ramp-up from a shut-down may occur at night, but only
where the EZ is small enough to be visible. SIO will not initiate a
ramp-up of the airguns if a marine mammal is sighted within or near the
applicable EZs during the day or close to the vessel at night.
NMFS has carefully evaluated the applicant's proposed mitigation
measures and has considered a range of other measures in the context of
ensuring that NMFS prescribes the means of effecting the least
practicable adverse impact on the affected marine mammal species and
stocks and their habitat. NMFS's evaluation of potential measures
included consideration of the following factors in relation to one
another:
(1) The manner in which, and the degree to which, the successful
implementation of the measure is expected to minimize adverse impacts
to marine mammals;
(2) The proven or likely efficacy of the specific measure to
minimize adverse impacts as planned; and
(3) The practicability of the measure for applicant implementation.
Based on NMFS's evaluation of the applicant's proposed measures, as
well as other measures considered by NMFS or recommended by the public,
NMFS has preliminarily determined that the proposed mitigation measures
provide the means of effecting the least practicable adverse impacts on
marine
[[Page 45535]]
mammal species or stocks and their habitat, paying particular attention
to rookeries, mating grounds, and areas of similar significance.
Proposed Monitoring and Reporting
In order to issue an ITA for an activity, section 101(a)(5)(D) of
the MMPA states that NMFS must set forth ``requirements pertaining to
the monitoring and reporting of such taking.'' The MMPA implementing
regulations at 50 CFR 216.104 (a)(13) indicate that requests for IHAs
must include the suggested means of accomplishing the necessary
monitoring and reporting that will result in increased knowledge of the
species and of the level of taking or impacts on populations of marine
mammals that are expected to be present in the action area.
Monitoring
SIO proposes to sponsor marine mammal monitoring during the
proposed project, in order to implement the proposed mitigation
measures that require real-time monitoring, and to satisfy the
anticipated monitoring requirements of the IHA. SIO's proposed
Monitoring Plan is described below this section. SIO understands that
this monitoring plan will be subject to review by NMFS, and that
refinements may be required. The monitoring work described here has
been planned as a self-contained project independent of any other
related monitoring projects that may be occurring simultaneously in the
same regions. SIO is prepared to discuss coordination of its monitoring
program with any related work that might be done by other groups
insofar as this is practical and desirable.
Vessel-Based Visual Monitoring
PSOs will be based aboard the seismic source vessel and will watch
for marine mammals near the vessel during daytime airgun operations and
during any ramp-ups at night. PSOs will also watch for marine mammals
near the seismic vessel for at least 30 min prior to the ramp-up of
airgun operations after an extended shut-down (i.e., greater than
approximately 15 min for this proposed cruise). When feasible, PSOs
will conduct observations during daytime periods when the seismic
system is not operating for comparison of sighting rates and behavior
with and without airgun operations and between acquisition periods.
Based on PSO observations, the airguns will be shut-down when marine
mammals are observed within or about to enter a designated EZ. The EZ
is a region in which a possibility exists of adverse effects on animal
hearing or other physical effects.
During seismic operations in the western tropical Pacific Ocean, at
least three PSOs will be based aboard the Thompson. SIO will appoint
the PSOs with NMFS's concurrence. At least one PSO will monitor the EZs
during seismic operations. Observations will take place during ongoing
daytime operations and nighttime ramp-ups of the airguns. PSO(s) will
be on duty in shifts of duration no longer than 4 hr. The vessel crew
will also be instructed to assist in detecting marine mammals.
The Thompson is a suitable platform for marine mammal observations.
Two locations are likely as observation stations onboard the Thompson.
At one station on the bridge, the eye level will be approximately 13.8
m (45.3 ft) above sea level and the location will give the PSO a good
view around the entire vessel (i.e., 310[deg] for one PSO and a full
360[deg] when two PSOs are stationed at different vantage points). A
second observation site is the 03 deck where the PSOs eye level will be
10.8 m (35.4 ft) above sea level. The 03 deck offers a view of 330[deg]
for the two PSOs.
During daytime, the PSVOs will scan the area around the vessel
systematically with reticle binoculars (e.g., 7 x 50 Fujinon), Big-eye
binoculars (25 x 150), optical range finders and with the naked eye.
During darkness, night vision devices (NVDs) will be available, when
required. The PSOs will be in wireless communication with the vessel'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. When marine mammals are detected
within or about to enter the designated EZ, the airguns will
immediately be shut-down if necessary. The PSO(s) will continue to
maintain watch to determine when the animal(s) are outside the EZ by
visual confirmation. Airgun operations will not resume until the animal
is confirmed to have left the EZ, or if not observed after 15 min for
species with shorter dive durations (small odontocetes and pinnipeds)
or 30 min for species with longer dive durations (mysticetes and large
odontocetes, including sperm, killer, and beaked whales).
PSO Data and Documentation
PSOs will record data to estimate the numbers of marine mammals
exposed to various received sound levels and to document apparent
disturbance reactions or lack thereof. Data will be used to estimate
numbers of animals potentially `taken' by harassment (as defined in the
MMPA). They will also provide information needed to order a shut-down
of the airguns when a marine mammal is within or near the EZ.
Observations will also be made during daytime periods when the Thompson
is underway without seismic operations (i.e., transits to, from, and
through the study area) to collect baseline biological data.
When a sighting is made, the following information about the
sighting will be recorded:
1. Species, group size, age/size/sex categories (if determinable),
behavior when first sighted and after initial sighting, heading (if
consistent), bearing and distance from seismic vessel, sighting cue,
apparent reaction to the airguns or vessel (e.g., none, avoidance,
approach, paralleling, etc.), and behavioral pace.
2. Time, location, heading, speed, activity of the vessel, Beaufort
sea state, visibility, and sun glare.
The data listed under (2) will also be recorded at the start and
end of each observation watch, and during a watch whenever there is a
change in one or more of the variables.
All observations as well as information regarding shut-downs of the
seismic source, will be recorded in a standardized format. The data
accuracy will be verified by the PSOs 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.
Vessel-based observations by the PSO will provide:
1. The basis for real-time mitigation (airgun shut-down).
2. Information needed to estimate the number of marine mammals
potentially taken by harassment, which must be reported to NMFS.
3. Data on the occurrence, distribution, and activities of marine
mammals in the area where the seismic study is conducted.
4. Information to compare the distance and distribution of marine
mammals relative to the source vessel at times with and without seismic
activity.
5. Data on the behavior and movement patterns of marine mammals
seen at times with and without seismic activity.
SIO will submit a report to NMFS and NSF within 90 days after the
end of the cruise. The report will describe the operations that were
conducted and sightings of marine mammals near the operations. The
report will provide full documentation of methods, results, and
interpretation pertaining to all monitoring. The 90-day report will
[[Page 45536]]
summarize the dates and locations of seismic operations, and all marine
mammal sightings (dates, times, locations, activities, associated
seismic survey activities). The report will also include estimates of
the number and nature of exposures that could result in potential
``takes'' of marine mammals by harassment or in other ways.
In the unanticipated event that the specified activity clearly
causes the take of a marine mammal in a manner prohibited by this IHA,
such as an injury (Level A harassment), serious injury or mortality
(e.g., ship-strike, gear interaction, and/or entanglement), SIO will
immediately cease the specified activities and immediately report the
incident to the Chief of the Permits, Conservation, and Education
Division, Office of Protected Resources, NMFS at 301-427-8401 and/or by
e-mail to [email protected] and [email protected], and the
NMFS Pacific Islands Regional Office Stranding Coordinator at 808-944-
2269 ([email protected]). The report must include the following
information:
Time, date, and location (latitude/longitude) of the
incident;
Name and type of vessel involved;
Vessel's speed during and leading up to the incident;
Description of the incident;
Status of all sound source use in the 24 hours preceding
the incident;
Water depth;
Environmental conditions (e.g., wind speed and direction,
Beaufort sea state, cloud cover, and visibility);
Description of all marine mammal observations in the 24
hours preceding the incident;
Species identification or description of the animal(s)
involved;
Fate of the animal(s); and
Photographs or video footage of the animal(s) (if
equipment is available).
Activities shall not resume until NMFS is able to review the
circumstances of the prohibited take. NMFS shall work with SIO to
determine what is necessary to minimize the likelihood of further
prohibited take and ensure MMPA compliance. SIO may not resume their
activities until notified by NMFS via letter or e-mail, or telephone.
In the event that SIO discovers an injured or dead marine mammal,
and the lead PSO determines that the cause of the injury or death is
unknown and the death is relatively recent (i.e., in less than a
moderate state of decomposition as described in the next paragraph),
SIO will immediately report the incident to the Chief of the Permits,
Conservation, and Education Division, Office of Protected Resources,
NMFS, at 301-427-8401, and/or by e-mail to [email protected] and
[email protected], and the NMFS Pacific Islands Regional Office
(808-944-2269) and/or by e-mail to the Pacific Islands Regional
Stranding Coordinator ([email protected]). The report must
include the same information identified in the paragraph above.
Activities may continue while NMFS reviews the circumstances of the
incident. NMFS will work with SIO to determine whether modifications in
the activities are appropriate.
In the event that SIO discovers an injured or dead marine mammal,
and the lead PSO determines that the injury or death is not associated
with or related to the activities authorized in the IHA (e.g.,
previously wounded animal, carcass with moderate to advanced
decomposition, or scavenger damage), SIO will report the incident to
the Chief of the Permits, Conservation, and Education Division, Office
of Protected Resources, NMFS, at 301-427-8401, and/or by e-mail to
[email protected] and [email protected], and the NMFS
Pacific Islands Regional Office (808-944-2269), and/or by e-mail to the
Pacific Islands Regional Stranding Coordinator
([email protected]), within 24 hours of discovery. SIO will
provide photographs or video footage (if available) or other
documentation of the stranded animal sighting to NMFS and the Marine
Mammal Stranding Network.
Estimated Take by Incidental Harassment
Except with respect to certain activities not pertinent here, the
MMPA defines ``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
Only take by Level B harassment is anticipated and proposed to be
authorized as a result of the proposed marine geophysical survey in the
western tropical Pacific Ocean. Acoustic stimuli (i.e., increased
underwater sound) generated during the operation of the seismic airgun
array may have the potential to cause marine mammals in the survey area
to be exposed to sounds at or greater than 160 dB or cause temporary,
short-term changes in behavior. There is no evidence that the planned
activities could result in injury, serious injury, or mortality within
the specified geographic area for which SIO seeks the IHA. The required
mitigation and monitoring measures will minimize any potential risk for
injury, serious injury, or mortality.
The following sections describe SIO's methods to estimate take by
incidental harassment and present the applicant's estimates of the
numbers of marine mammals that could be affected during the proposed
seismic program. The estimates are based on a consideration of the
number of marine mammals that could be disturbed appreciably by
operations with the two GI airgun array to be used during approximately
1,600 km of survey lines in the western tropical Pacific Ocean.
SIO assumes that, during simultaneous operations of the airgun
array and the other sources, any marine mammals close enough to be
affected by the MBES and SBP would already be affected by the airguns.
However, whether or not the airguns are operating simultaneously with
the other sources, marine mammals are expected to exhibit no more than
short-term and inconsequential responses to the MBES and SBP given
their characteristics (e.g., narrow, downward-directed beam) and other
considerations described previously. Such reactions are not considered
to constitute ``taking'' (NMFS, 2001). Therefore, SIO provides no
additional allowance for animals that could be affected by sound
sources other than airguns.
Extensive systematic ship-based surveys have been conducted by NMFS
Southwest Fisheries Science Center (SWFSC) for marine mammals in the
eastern, but not the western tropical Pacific Ocean. A systematic
vessel-based marine mammal survey was conducted approximately 2,500 km
(1,349.9 nmi) west of the proposed survey area in the Commonwealth of
the Northern Mariana Islands (CNMI) for the U.S. Navy during January to
April, 2007 (SRS-Parsons et al., 2007; Fulling et al., in press). The
cruise area was defined by the boundaries 10[deg] to 18[deg] North,
142[deg] to 148[deg] East, encompassing an area approximately 585,000
km\2\ (170,558.7 nmi\2\) including the islands of Guam and the southern
CNMI. The survey was conducted using standard line-transect protocols
developed by NMFS SWFSC. Observers visually surveyed 11,033 km (5,957.3
nmi) of trackline, mostly in high sea states (88% of the time in
Beaufort Sea states four to six). Another survey was conducted by SWFSC
approximately 3,500 km (1,889.8 nmi) east of the proposed survey area
in the EEZ around Hawaii during August to November, 2002;
[[Page 45537]]
survey effort was 3,550 km (1,916.8 nmi) in the ``Main Island
stratum,'' which had a surface area of 2,240,024 km\2\ (653086.5
nmi\2\) (Barlow, 2006).
SIO used densities that were the effort-weighted means for the CNMI
(Fulling et al., in press) and the outer EEZ stratum of Hawaii (Barlow,
2006). The densities had been corrected, by the original authors, for
trackline detection probability bias, and for data from Hawaii, for
availability bias. Trackline detection probability bias is associated
with diminishing sightability with increasing lateral distance from the
trackline, and is measured by [fnof](0). Availability bias refers to
the fact that there is less-than-100% probability of sighting an animal
that is present along the survey trackline [fnof](0), and it is
measured by g(0). Fulling et al. (in press) did not correct the CNMI
densities for availability bias (i.e., it was assumed that g(0)=1),
which resulted in underestimates of density. The densities are given in
Table 3 of SIO's IHA application.
There is some uncertainty about the representativeness of the data
and the assumptions used in the calculations, for example:
(1) The timing of most of the surveys was different, the CNMI
survey was from January to April, the Hawaii survey was from August to
November, and the proposed SIO survey is from November to December;
(2) Locations were also different, with the proposed survey area
approximately 2,500 km east of the CNMI and approximately 3,500 km west
of Hawaii; and
(3) Most of the Marianas survey was in high sea states that would
have prevented detection of many marine mammals, especially cryptic
species such as beaked whales and Kogia spp.
However, the approach used here is believed to be the best
available approach.
SIO's estimates of exposures to various sound levels assume that
the proposed surveys will be fully completed; in fact, the ensonified
areas calculated using the planned number of line-km have been
increased by 25% to accommodate turns, lines that may need to be
repeated, equipment testing, etc. As is typical during offshore ship
surveys, inclement weather and equipment malfunctions are likely to
cause delays and may limit the number of useful line-kilometers of
seismic operations that can be undertaken. Furthermore, any marine
mammal sightings within or near the designated EZs will result in the
shut-down of seismic operations as a mitigation measure. Thus, the
following estimates of the numbers of marine mammals potentially
exposed to sound levels of 160 dB re 1 [mu]Pa (rms) are precautionary
and probably overestimate the actual numbers of marine mammals that
might be involved. These estimates also assume that there will be no
weather, equipment, or mitigation delays, which is highly unlikely.
SIO estimated the number of different individuals that may be
exposed to airgun sounds with received levels greater than or equal to
160 dB re 1 [mu]Pa (rms) on one or more occasions by considering the
total marine area that would be within the 160 dB radius around the
operating airgun array on at least one occasion, along with the
expected density of marine mammals in the area. The proposed seismic
lines do not run parallel to each other in close proximity and the
ensonified areas do not overlap, thus an individual mammal that was
stationary would be exposed once during the proposed survey.
The numbers of different individuals potentially exposed to greater
than or equal to 160 dB (rms) were calculated by multiplying the
expected species density times the anticipated area to be ensonified.
The area was determined by entering the planned survey lines into a
MapInfo GIS, using the GIS to identify the relevant areas by
``drawing'' the applicable 160 dB buffer (see Table 1 of the IHA
application) around each seismic line, and then calculating the total
area within the buffers. For this survey, there were no areas of
overlap because of crossing lines.
Applying the approach described above, approximately 2,144 km\2\
(625.1 nmi\2\) (approximately 2,680 km\2\ [781.4 nmi\2\] including the
25% contingency) would be within the 160 dB isopleth on one or more
occasions during the proposed survey. Because this approach does not
allow for turnover in the marine mammal populations in the study area
during the course of the survey, the actual number of individuals
exposed could 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 from or toward the trackline as the Thompson approaches in
response to increasing sound levels prior to the time the levels reach
160 dB. Another way of interpreting the estimates that follow is that
they represent the number of individuals that are expected (in the
absence of a seismic program) to occur in the waters that will be
exposed to greater than or equal to 160 dB re 1 [micro]Pa (rms).
Table 3 (Table 4 of the IHA application) shows the estimates of the
number of different individual marine mammals that potentially could be
exposed to greater than or equal to 160 dB re 1 [mu]Pa (rms) during the
seismic survey if no animals moved away from the survey vessel. The
requested take authorization is given in Table 3 (below; the far right
column of Table 4 of the IHA application). For ESA listed species, the
requested take authorization has been increased to the mean group size
in the CNMI (Fulling et al., in press) for the particular species in
cases where the calculated number of individuals exposed was between
0.05 and the mean group size (i.e., for the sei whale). For species not
listed under the ESA that could occur in the study area, the requested
take authorization has been increased to the mean group size in the
CNMI (Fulling et al., in press) or, for species not sighted in the CNMI
survey, Hawaii (Barlow, 2006) for the particular species in cases where
the calculated number of individuals exposed was between 1 and the mean
group size.
The estimate of the number of individual cetaceans that could be
exposed to seismic sounds with received levels greater than or equal to
160 dB re 1 [mu]Pa (rms) during the proposed survey is 118 (see Table 4
of the IHA application). That total includes 1 Bryde's whale, 6 sperm
whales, 5 pygmy sperm whales, 12 dwarf sperm whales, 10 Cuvier's beaked
whales, 1 Longman's beaked whale, 2 Blainville's beaked whales, 5
rough-toothed dolphins, 2 bottlenose dolphins, 30 pantropical spotted
dolphins, 5 spinner dolphins, 16 striped dolphins, 7 Fraser's dolphins,
1 Risso's dolphin, 7 melon-headed whales, 2 false killer whales, and 6
short-finned pilot whales which would represent less than 0.01%, 0.02%,
NA, less than 0.01%, 0.05%, NA, less than 0.01%, less than 0.01%, less
than 0.01%, less than 0.01%, less than 0.01%, less than 0.01%, less
than 0.01%, less than 0.01%, 0.02%, less than 0.01%, and less than
0.01% of the regional populations, respectively. Most (68.6%) of the
cetaceans potentially exposed are delphinids; pantropical spotted,
striped, and Fraser's dolphins are estimated to be the most common
species in the proposed study area.
BILLING CODE 3510-22-P
[[Page 45538]]
[GRAPHIC] [TIFF OMITTED] TN29JY11.006
BILLING CODE 3510-22-C
Encouraging and Coordinating Research
SIO and NSF will coordinate the planned marine mammal monitoring
program associated with the seismic survey in the western tropical
Pacific Ocean with any parties that may have or express an interest in
the proposed seismic survey. UW will work with the U.S. Department of
State to obtain the necessary approvals for operating in the foreign
EEZ of the Republic of the Marshall Islands.
Negligible Impact and Small Numbers Analysis and Determination
NMFS has defined ``negligible impact'' in 50 CFR 216.103 as ``* * *
an impact resulting from the specified activity that cannot be
reasonably expected to, and is not reasonably likely to, adversely
affect the species or stock through effects on annual rates of
recruitment or survival.'' In making a negligible impact determination,
NMFS evaluated factors such as:
(1) The number of anticipated injuries, serious injuries, or
mortalities;
(2) The number, nature, and intensity, and duration of Level B
harassment (all relatively limited);
[[Page 45539]]
(3) The context in which the takes occur (i.e., impacts to areas of
significance, impacts to local populations, and cumulative impacts when
taking into account successive/contemporaneous actions when added to
baseline data);
(4) The status of stock or species of marine mammals (i.e.,
depleted, not depleted, decreasing, increasing, stable, and impact
relative to the size of the population);
(5) Impacts on habitat affecting rates of recruitment/survival; and
(6) The effectiveness of monitoring and mitigation measures (i.e.,
the manner and degree in which the measure is likely to reduce adverse
impacts to marine mammals, the likely effectiveness of the measures,
and the practicability of implementation).
For reasons stated previously in this document, the specified
activities associated with the marine seismic survey are not likely to
cause PTS, or other non-auditory injury, serious injury, or death
because:
(1) The likelihood that, given sufficient notice through relatively
slow ship speed, marine mammals are expected to move away from a noise
source that is annoying prior to its becoming potentially injurious;
(2) The potential for temporary or permanent hearing impairment is
relatively low and would likely be avoided through the incorporation of
the required monitoring and mitigation measures (described above);
(3) The fact that pinnipeds would have to be closer than 20 m (65.6
ft) in deep water when the two GI airgun array is in use at 3 m (9.8
ft) tow depth from the vessel to be exposed to levels of sound believed
to have even a minimal chance of causing PTS;
(4) The fact that cetaceans would have to be closer than 70 m
(229.7 ft) in deep water when the two GI airgun array is in 3 m tow
depth from the vessel to be exposed to levels of sound believed to have
even a minimal chance of causing PTS; and
(5) The likelihood that marine mammal detection ability by trained
PSOs is high at close proximity to the vessel.
No injuries, serious injuries, or mortalities are anticipated to
occur as a result of SIO's planned marine seismic survey, and none are
authorized by NMFS. Only short-term, behavioral disturbance is
anticipated to occur due to the brief and sporadic duration of the
survey activities. Table 3 in this document outlines the number of
Level B harassment takes that are anticipated as a result of the
activities. Due to the nature, degree, and context of Level B
(behavioral) harassment anticipated and described (see Potential
Effects on Marine Mammals section above) in this notice, the activity
is not expected to impact rates of recruitment or survival for any
affected species or stock.
Many animals perform vital functions, such as feeding, resting,
traveling, and socializing, on a diel cycle (i.e., 24 hr cycle).
Behavioral reactions to noise exposure (such as disruption of critical
life functions, displacement, or avoidance of important habitat) are
more likely to be significant if they last more than one diel cycle or
recur on subsequent days (Southall et al., 2007). While seismic
operations are anticipated to occur on consecutive days, the entire
duration of the survey is not expected to last more than 32 days and
the Thompson will be continuously moving along planned tracklines.
Therefore, the seismic survey will be increasing sound levels in the
marine environment surrounding the vessel for several weeks in the
study area. Of the 26 marine mammal species under NMFS jurisdiction
that are known to or likely to occur in the study area, six are listed
as threatened or endangered under the ESA: humpback, sei, fin, blue,
sperm, and Hawaiian monk seals. These species are also considered
depleted under the MMPA. The Hawaiian monk seal population has
generally been decreasing (the main Hawaiian islands population appears
to be increasing). There is generally insufficient data to determine
population trends for the other depleted species in the study area. To
protect these animals (and other marine mammals in the study area), SIO
must cease or reduce airgun operations if animals enter designated
zones. No injury, serious injury, or mortality is expected to occur and
due to the nature, degree, and context of the Level B harassment
anticipated, the activity is not expected to impact rates of
recruitment or survival.
As mentioned previously, NMFS estimates that 19 species of marine
mammals under its jurisdiction could be potentially affected by Level B
harassment over the course of the proposed IHA. For each species, these
numbers are small (each less than one percent) relative to the regional
population size. The population estimates for the marine mammal species
that may be taken by harassment were provided in Table 2 of this
document.
NMFS's practice has been to apply the 160 dB re 1 [micro]Pa (rms)
received level threshold for underwater impulse sound levels to
determine whether take by Level B harassment occurs. Southall et al.
(2007) provide a severity scale for ranking observed behavioral
responses of both free-ranging marine mammals and laboratory subjects
to various types of anthropogenic sound (see Table 4 in Southall et al.
[2007]).
NMFS has preliminarily determined, provided that the aforementioned
mitigation and monitoring measures are implemented, that the impact of
conducting a marine geophysical survey in the western tropical Pacific
Ocean, November to December, 2011, may result, at worst, in a temporary
modification in behavior and/or low-level physiological effects (Level
B harassment) of small numbers of certain species of marine mammals.
See Table 3 (above) for the requested authorized take numbers of
cetaceans.
While behavioral modifications, including temporarily vacating the
area during the operation of the airgun(s), may be made by these
species to avoid the resultant acoustic disturbance, the availability
of alternate areas within these areas and the short and sporadic
duration of the research activities, have led NMFS to preliminary
determine that this action will have a negligible impact on the species
in the specified geographic region.
Based on the analysis contained herein of the likely effects of the
specified activity on marine mammals and their habitat, and taking into
consideration the implementation of the mitigation and monitoring
measures, NMFS preliminarily finds that SIO's planned research
activities, will result in the incidental take of small numbers of
marine mammals, by Level B harassment only, and that the total taking
from the marine seismic survey will have a negligible impact on the
affected species or stocks of marine mammals; and that impacts to
affected species or stocks of marine mammals have been mitigated to the
lowest level practicable.
Impact on Availability of Affected Species or Stock for Taking for
Subsistence Uses
Section 101(a)(5)(D) also requires NMFS to determine that the
authorization will not have an unmitigable adverse effect on the
availability of marine mammal species or stocks for subsistence use.
There are no relevant subsistence uses of marine mammals in the study
area (offshore waters of the western tropical Pacific Ocean) that
implicate MMPA section 101(a)(5)(D).
Endangered Species Act
Of the species of marine mammals that may occur in the proposed
survey
[[Page 45540]]
area, several are listed as endangered under the ESA, including the
humpback, sei, fin, blue, and sperm whales, as well as the Hawaiian
monk seal. Under section 7 of the ESA, NSF has initiated formal
consultation with the NMFS, Office of Protected Resources, Endangered
Species Division, on this proposed seismic survey. NMFS's Office of
Protected Resources, Permits, Conservation and Education Division, has
initiated formal consultation under Section 7 of the ESA with NMFS's
Office of Protected Resources, Endangered Species Division, to obtain a
Biological Opinion evaluating the effects of issuing the IHA on
threatened and endangered marine mammals and, if appropriate,
authorizing incidental take. NMFS will conclude formal section 7
consultation prior to making a determination on whether or not to issue
the IHA. If the IHA is issued, NSF and SIO, in addition to the
mitigation and monitoring requirements included in the IHA, will be
required to comply with the Terms and Conditions of the Incidental Take
Statement corresponding to NMFS's Biological Opinion issued to both NSF
and NMFS's Office of Protected Resources.
National Environmental Policy Act (NEPA)
With its complete application, NSF and SIO provided NMFS a draft EA
analyzing the direct, indirect, and cumulative environmental impacts of
the proposed specified activities on marine mammals including those
listed as threatened or endangered under the ESA. The draft EA,
prepared by NSF incorporates a document prepared by LGL on behalf of
NSF and SIO. It is entitled ``Environmental Assessment of a Low-Energy
Marine Geophysical Survey by the R/V Thompson in the Western Tropical
Pacific Ocean, November-December 2011.'' Prior to making a final
decision on the SIO application, NMFS will either prepare an
independent EA, or, after review and evaluation of the SIO EA for
consistency with the regulations published by the Council of
Environmental Quality (CEQ) and NOAA Administrative Order 216-6,
Environmental Review Procedures for Implementing the National
Environmental Policy Act, adopt the NSF EA and make a decision of
whether or not to issue a Finding of No Significant Impact (FONSI).
Proposed Authorization
NMFS proposes to issue an IHA to SIO for conducting a marine
geophysical survey in the western tropical Pacific Ocean, provided the
previously mentioned mitigation, monitoring, and reporting requirements
are incorporated. The duration of the IHA would not exceed one year
from the date of its issuance.
Information Solicited
NMFS requests interested persons to submit comments and information
concerning this proposed project and NMFS's preliminary determination
of issuing an IHA (see ADDRESSES). Concurrent with the publication of
this notice in the Federal Register, NMFS is forwarding copies of this
application to the Marine Mammal Commission and its Committee of
Scientific Advisors.
Dated: July 25, 2011.
Helen M. Golde,
Deputy Director, Office of Protected Resources, National Marine
Fisheries Service.
[FR Doc. 2011-19244 Filed 7-28-11; 8:45 am]
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