Incidental Takes of Marine Mammals During Specified Activities; Marine Geophysical Surveys in the Eastern Tropical Pacific Ocean in 2008, 24223-24235 [E8-9717]
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Federal Register / Vol. 73, No. 86 / Friday, May 2, 2008 / Notices
conduct of Sunset Reviews.1 Please
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concerning antidumping and
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This notice of initiation is being
published in accordance with section
751(c) of the Act and 19 CFR 351.218(c).
Dated: April 25, 2008.
Stephen J. Claeys,
Deputy Assistant Secretary for Import
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[FR Doc. E8–9710 Filed 5–1–08; 8:45 am]
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Dated: April 28, 2008.
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[FR Doc. E8–9723 Filed 5–1–08; 8:45 am]
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric
Administration
RIN 0648–XH14
Incidental Takes of Marine Mammals
During Specified Activities; Marine
Geophysical Surveys in the Eastern
Tropical Pacific Ocean in 2008
National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Notice; issuance of an
incidental take authorization.
AGENCY:
In accordance with
regulations implementing the Marine
SUMMARY:
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SUPPLEMENTARY INFORMATION:
Background
BILLING CODE 3510–DR–S
1 In comments made on the interim final sunset
regulations, a number of parties stated that the
proposed five-day period for rebuttals to
substantive responses to a notice of initiation was
insufficient. This requirement was retained in the
final sunset regulations at 19 CFR 351.218(d)(4). As
provided in 19 CFR 351.302(b), however, the
Department will consider individual requests for
extension of that five-day deadline based upon a
showing of good cause.
17:17 May 01, 2008
Copies of the application,
IHA, the Environmental Assessment of
Two Marine Geophysical Surveys by the
R/V Marcus G. Langseth in the Eastern
Tropical Pacific, 2008, prepared for the
L-DEO and the National Science
Foundation (NSF) by the LGL Ltd., and/
or a list of references used in this
document may be obtained by writing to
P. Michael Payne, Chief, Permits,
Conservation and Education Division,
Office of Protected Resources, National
Marine Fisheries Service, 1315 EastWest Highway, Silver Spring, MD
20910–3225, or by telephoning one of
the contacts listed here (see FOR
FURTHER INFORMATION CONTACT).
FOR FURTHER INFORMATION CONTACT:
Shane Guan, Office of Protected
Resources, NMFS, (301) 713–2289, ext
137.
ADDRESSES:
BILLING CODE 3510–DR–S
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Mammal Protection Act (MMPA),
notification is hereby given that an
Incidental Harassment Authorization to
take marine mammals, by Level-B
harassment, incidental to conducting
two marine geophysical surveys by the
Lamont-Doherty Earth Observatory (LDEO) in the Eastern Tropical Pacific
Ocean (ETP), has been issued for a
period of one year.
DATES: The authorization is effective
from April 24, 2008, until April 23,
2009.
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Sections 101(a)(5)(A) and (D) of the
MMPA (16 U.S.C. 1361 et seq.) direct
the Secretary of Commerce to allow,
upon request, the incidental, but not
intentional, taking of marine mammals
by U.S. citizens who engage in a
specified activity (other than
commercial fishing) within a specified
geographical region if certain findings
are made and either regulations are
issued or, if the taking is limited to
harassment, a notice of a proposed
authorization is provided to the public
for review.
Authorization shall be granted if
NMFS finds that the taking will have a
negligible impact on the species or
stock(s), will not have an unmitigable
adverse impact on the availability of the
species or stock(s) for certain
subsistence uses, and if the permissible
methods of taking and requirements
pertaining to the mitigation, monitoring
and reporting of such takings are set
forth. NMFS has defined ‘‘negligible
impact’’ in 50 CFR 216.103 as ’’...an
impact resulting from the specified
activity that cannot be reasonably
expected to, and is not reasonably likely
to, adversely affect the species or stock
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24223
through effects on annual rates of
recruitment or survival.’’
Section 101(a)(5)(D) of the MMPA
established an expedited process by
which citizens of the United States can
apply for an authorization to
incidentally take small numbers of
marine mammals by harassment. Except
with respect to certain activities not
pertinent here, the MMPA defines
‘‘harassment’’ as:
any act of pursuit, torment, or annoyance
which (i) has the potential to injure a marine
mammal or marine mammal stock in the wild
[Level A harassment]; or (ii) has the potential
to disturb a marine mammal or marine
mammal stock in the wild by causing
disruption of behavioral patterns, including,
but not limited to, migration, breathing,
nursing, breeding, feeding, or sheltering
[Level B harassment].
Section 101(a)(5)(D) establishes a 45–
day time limit for NMFS review of an
application followed by a 30–day public
notice and comment period on any
proposed authorization for the
incidental harassment of marine
mammals. Within 45 days of the close
of the comment period, NMFS must
either issue or deny issuance of the
authorization.
Summary of Request
L-DEO submitted to NMFS an
application from L-DEO for the taking,
by Level B harassment, of several
species of marine mammals incidental
to conducting, with research funding
from the NSF, two marine seismic
surveys in the ETP. This project would
be conducted with L-DEO’s new seismic
vessel, the R/V Marcus G. Langseth
(Langseth), which would deploy
different configurations of airguns and a
different bottom-mapping sonar than
used previously by L-DEO. The first
survey was planned to be approximately
39 days between September and October
2007, and the second one approximately
6 days in between November and
December 2007. However, due to
scheduling issues with the vessel, the
39–day survey is rescheduled to June
and August 2008, and the 6–day survey
to April and May 2008.
Description of the Specified Activity
The April-May 6–day survey would
examine two important types of seismic
behavior of the Quebrada, Discovery,
and Gofar fault systems (QDG) to
understand better the behavior of
earthquakes and faults in general.
The June-August 39–day survey
would obtain seismic reflection imaging
of the internal structure of the
magmatic-hydrothermal system at the
fast-spreading mid-ocean ridge of the
East Pacific Rise (EPR).
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within which the seismic survey will
occur is located between 8.3° and 10.2°
N, and between 104.1° and 104.5° W.
The survey would take place in water
more than 2,000 m (6,562 ft) deep.
In addition to the operations of the
airgun array, a multi-beam bathymetric
sonar would be operated from the
source vessel continuously throughout
the entire cruise, and a lower-energy
sub-bottom profiler will also be
operated during most of the survey.
Detailed descriptions of these
activities were published in the Federal
Register on March 5, 2008 (72 FR
11876). No changes have been made to
these proposed marine geophysical
surveys.
The Langseth would also serve as the
platform from which vessel-based visual
marine mammal observers will watch
for marine mammals before and during
airgun operations. The characteristics of
the Ewing that make it suitable for
visual monitoring are described under
Monitoring, later in this document.
Airguns
The airgun array to be used will
consist of 36 airguns, with maximum
total discharge volume of approximately
6,600 in3. The airguns will comprise a
mixture of Bolt 1500LL and Bolt
1900LLX airguns. The array will consist
of four identical linear arrays or
‘‘strings.’’ Each string would have ten
airguns; the first and last airguns in the
strings are spaced 16 m (52.5 ft) apart.
Nine airguns would be fired
simultaneously, while the tenth is kept
in reserve as a spare, to be turned on in
case of failure of another airgun. Two of
the four strings would be fired during
the EPR survey (18 airguns), and three
strings would be fired during the QDG
survey (27 airguns). The airgun strings
would be distributed across an
approximate area of 24 x 16 m (78.7 x
52.5 ft) behind the Langseth and would
be towed approximately 50 - 100 m (164
- 328 ft) behind the vessel. The firing
pressure of the array is 2,000 psi. During
firing, a brief (∼0.1 s) pulse of sound is
emitted. During the EPR survey, the
shots would be emitted at intervals of
∼15 s, corresponding to a shot interval
of ∼37.5 m (∼123 ft). During the QDG
survey, the shots would be emitted at
intervals of ∼60 s, corresponding to a
shot interval of ∼150 m (492 ft). The
airguns would be towed at a depth of 7
m (23 ft) during both the QDG and the
EPR surveys. The depth at which the
source is towed affects the maximum
near-field output and the shape of its
frequency spectrum. In deeper water,
the effective source level for sound
propagating in near-horizontal
directions is higher than in shallow
water; however, the nominal source
levels of the array at various tow depths
are nearly identical.
Because the actual source is a
distributed sound source (up to 27
airguns in these surveys) rather than a
single point source, the highest sound
levels measurable at any location in the
water would be less than the nominal
source level. In addition, the effective
source level for sound propagating in
near-horizontal directions would be
substantially lower than the nominal
source level applicable to downward
propagation because of the directional
nature of the sound from the airgun
array.
The specifications of each source
planned for use are described in Table
1.
18-Airgun Array (2 Strings)
The seismic surveys will involve one
vessel. The source vessel Langseth
would deploy a 36–airgun array as an
energy source. However, for the EPR
study, two identical two-string sources
will be firing alternately, so that no
more than 18 airguns will be firing at
any time, with a maximum discharge
volume of 3,300 in3. The Langseth
would also tow the receiving system,
which consists of four 6–km (3.73–mi)
hydrophone streamers. For the QDG
study, no more than 27 airguns would
be fired at any time, with a maximum
discharge volume of 4,950 in3. The
Langseth would also tow the receiving
system, a single 8–km (4.97–mi)
streamer, and would also deploy 40
long-term Ocean Bottom Seismometers
(OBSs) that would be recovered 1 year
after deployment, and another 8–10
short-term OBSs on each line that will
be retrieved after the seismic surveys are
completed.
The EPR and QDG programs would
consist of a maximum of approximately
7,992 km (4,967 mi) and 654 km (406
mi) of surveys, respectively.
The QDG seismic survey would also
occur in international waters of the ETP,
approximately 2,265 km (1,408 mi) off
the coast of Ecuador and approximately
1,300 km (808 mi) west of the Galapagos
Islands. The overall area within which
the seismic survey would occur is
located between 3° and 5° S, and
between 103° and 106° W. Water depths
in the survey area are more than 3,000
m (9,843 ft) deep. The EPR seismic
survey would take place in international
waters of the ETP, offshore from Mexico
and Central America at the East Pacific
Rise. The closest land mass to this
survey is Mexico, located approximately
890 km (553 mi) away. The overall area
27-Airgun Array (3 Strings)
Acoustic Source Specifications
Energy Source
18, 2,000 psi Bolt airguns of 40-360 in3
27, 2,000 psi Bolt airguns of 40-360 in3
Source output (downward)
0-pk: 252 dB re 1 microPa-m;pk-pk: 259 dB
re 1 microPa-m
0-pk: 256 dB re 1 microPa-m;pk-pk: 262 dB
re 1 microPa-m
Air discharge volume
Approximately 3,300 in3
Approximately 4,950 in3
Towing depth of energy source
7 m (23 ft)
7 m (23 ft)
Dominant frequency components
0 - 188 Hz
0 - 188 Hz
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Table 1. L-DEO airgun configuration and specification of each source planned for use in the proposed projects.
A detailed discussion of the
characteristics of airgun pulses has been
provided in L-DEO’s application, and in
previous Federal Register notices (see
69 FR 31792 (June 7, 2004) or 69 FR
34996 (June 23, 2004)). Reviewers are
referred to those documents for
additional information.
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17:17 May 01, 2008
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Received sound levels have been
predicted by L-DEO in relation to
distance and direction from the airguns
for the 36–airgun array with 18 and 27
airguns firing and for a single 1900LL
40–in3 airgun, which would be used
during power downs.
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The predicted sound contours are
shown as sound exposure levels (SEL)
in decibels (dB) re 1 microPa2-s. SEL is
a measure of the received energy in the
pulse and represents the sound pressure
level (SPL) that would be measured if
the pulse energy were spread evenly
across a 1–s period. Because actual
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seismic pulses are less than 1 s in
duration, this means that the SEL value
for a given pulse is lower than the SPL
calculated for the actual duration of the
pulse. The advantage of working with
SEL is that the SEL measure accounts
for the total received energy in the
pulse, and biological effects of pulsed
sounds probably depend mainly on
pulse energy. SPL for a given pulse
depends greatly on pulse duration. A
pulse with a given SEL can be long or
short depending on the extent to which
propagation effects have ‘‘stretched’’ the
pulse duration. The SPL will be low if
the duration is long and higher if the
duration is short, even though the pulse
energy (and presumably the biological
effects) is the same.
Although SEL may be a better
measure than SPL when dealing with
biological effects of pulsed sound, SPL
is the measure that has been most
commonly used in studies of marine
mammal reactions to airgun sounds and
in NMFS practice concerning levels
above which ‘‘taking’’ might occur. SPL
is often referred to as rms or ‘‘root mean
square’’ pressure, averaged over the
pulse duration. As noted above, the rms
received levels that are used as impact
criteria for marine mammals are not
directly comparable to pulse energy
(SEL). The SPL (i.e., rms sound
pressure) for a given pulse is typically
10 - 15 dB higher than the SEL value for
the same pulse as measured at the same
location (Greene et al., 1997; McCauley
et al., 1998; 2000). For this project, L-
DEO assumes that rms pressure levels of
received seismic pulses would be 10 dB
higher than the SEL values predicted by
L-DEO’s model. Thus, the L-DEO
assumes that 170 dB SEL can be viewed
as 180 dB rms. NMFS considers that this
assumption is valid.
It should be noted that neither the
SEL nor the SPL (rms) measure is
directly comparable to the peak or peakto-peak pressure levels normally used
by geophysicists to characterize source
levels of airguns. Peak and peak-to-peak
pressure levels for airgun pulses are
always higher than the rms dB referred
to in much of the biological literature
(Greene et al., 1997; McCauley et al.,
1998; 2000). For example, a measured
received level of 160 dB rms in the far
field would typically correspond to a
peak measurement of 170 - 172 dB re 1
microPa, and to a peak-to-peak
measurement of 176 - 178 dB, as
measured for the same pulse received at
the same location (Greene et al., 1997;
McCauley et al., 1998; 2000). The
precise 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. However, the rms level is
always lower than the peak or peak-topeak level, and higher than the SEL
value, for an airgun-type source.
Empirical data concerning 190, 180,
170, and 160 dB (rms) isopleths in deep
and shallow water were acquired for
various airgun configurations during the
acoustic calibration study of the Ewing’s
20–airgun, 8,600–in3 array in 2003
(Tolstoy et al., 2004a; 2004b). The
results showed that radii around the
airguns where the received level was
180 dB re 1 microPa (rms), the onset
point for estimating temporary hearing
threshold shift (TTS) in cetaceans
(NMFS, 2000), varied with water depth.
Similar depth-related variation is likely
for 190–dB, the onset point used for
estimating TTS in pinnipeds, although
these were not measured. The empirical
data indicated that, for deep water
(>1,000 m, or 3,280 ft), the L-DEO model
overestimates the received sound levels
at a given distance (Tolstoy et al., 2004a;
2004b). However, to be conservative, the
Ewing’s modeled distances would be
applied to deep-water areas during the
proposed study. As very few, if any,
mammals are expected to occur below
2,000 m (6,562 ft), this depth was used
as the maximum relevant depth.
For the proposed programs in the
ETP, the modeled distances are used to
estimate deep-water mitigation safety
zones; no correction factors are
necessary because all activities will take
place in deep (>2,000 m, or 6,562 ft)
water. The 180 and 190 dB re 1 microPa
(rms) distances define the safety criteria,
used for mitigation for cetaceans and
pinnipeds, respectively.
The predicted distances to which
sound levels higher than 190, 180, and
160 dB re 1 microPa (rms) could be
received, based on the model
calculation, are shown in Table 2.
Predicted RMS Radii (m)
Source and Volume
Min. Water Depth
190 dB
160 dB
180 dB
Single Bolt airgun (40 in3)
3000 m
12
40
385
36-airgun array: 3 strings
(4950 in3)
3000 m
200
650
4400
36-airgun array: 2 strings
(3300 in3)
2000 m
140
450
3800
Table 2. Predicted distances to which sound levels higher than 190, 180, and 160 dB re 1 microPa (rms) could be received from the airgun
array and single airgun planned for use during the surveys in the ETP.
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Bathymetric Sonar and Sub-bottom
Profiler
Along with the airgun operations, two
additional acoustical data acquisition
systems would be operated during parts
of the Langseth’s cruises. The ocean
floor would be mapped with the 12–kHz
Kongsberg Simrad EM 120 MBB sonar,
and a 2.5 - 7 kHz sub-bottom profiler
would also be operated along with the
MBB sonar. These sound sources would
be operated from the Langseth, at times
simultaneously with the airgun array.
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The Kongsberg Simrad EM 120
operates at 11.25 - 12.6 kHz and would
be mounted in a sonar pod hung below
the hull of the Langseth. The beamwidth
is 1o fore-aft and 150° athwartship. The
maximum source level is 242 dB re 1
microPa at 1 m (rms). For deep-water
operation, each ‘‘ping’’ consists of nine
successive fan-shaped transmissions,
each 15 ms in duration and each
ensonifying a sector that extends 1° foreaft. The nine successive transmissions
span an overall cross-track angular
extent of about 150°, with 16 ms gaps
between the pulses for successive
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sectors. A receiver in the overlap area
between two sectors would receive two
15–ms pulses separated by a 16–ms gap.
In shallower water, the pulse duration is
reduced to 2 ms, and the number of
transmit beams is also reduced. The
ping interval varies with water depth,
from ∼5 s at 1,000 m (3,280 ft) to 20 s
at 4,000 m (13,123 ft).
The sub-bottom profiler is normally
operated to provide information about
the sedimentary features and the bottom
topography that is simultaneously being
mapped by the MBB sonar. The energy
from the sub-bottom profiler is directed
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Description of Marine Mammals in the
Activity Area
downward by a 3.5–kHz transducer in
the hull of the Langseth. The output
varies with water depth from 50 watts
in shallow water to 800 watts in deep
water. Pulse interval is 1 second but a
common mode of operation is to
broadcast five pulses at 1-s intervals
followed by a 5-s pause.
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Comments and Responses
A notice of receipt and request for
public comment on the application and
proposed authorization was published
on March 5, 2008 (73 FR 11874). During
the 30–day public comment period,
NMFS received the following comments
from the Marine Mammal Commission
(Commission).
Comment 1: The Commission
recommends to extend to one hour the
monitoring period imposed prior to the
initiation of seismic activities and
resumption of airgun activities after a
power-down.
Response: NMFS acknowledges that
several species of deep-diving cetaceans
are capable of remaining underwater for
more than 30 minutes. However, for the
following reasons, NMFS believes that
30 minutes is an adequate duration for
the monitoring period prior to the startup of airguns: (1) because the Langseth
is required to ramp-up, the time of
monitoring prior to start-up of any but
the smallest array is effectively longer
than 30 minutes (i.e., ramp-up will
begin with the smallest gun in the array
and airguns will be added in a sequence
such that the source level of the array
will increase in steps not exceeding
approximately 6 dB per 5–min period
over a total duration of 20–40 min); (2)
L-DEO decides to conduct marine
mammal monitoring during transient
even though the airguns are not in
operation, so that all safety redii will be
under monitoring prior to the 30–min
observation period anyway; and (3) the
majority of the species that may be
exposed do not stay underwater more
than 30 minutes.
Comment 2: The Commission
recommends that NMFS require marine
mammal monitoring be made during all
ramp-up procedures to gather data
regarding the effectiveness of ramp-up
as a mitigation tool.
Response: NMFS concurs with the
Commission’s recommendation that all
ramp-up procedures will be visually
monitored when visibility permits. For
ramp-up during low-light hours, visual
monitoring is ineffective, nonetheless,
passive acoustic monitoring will be
implemented during all ramp-up
procedures.
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A total of 34 cetacean species and 6
species of pinnipeds are known to or
may occur in the ETP. Of the 34
cetacean species, 27 are likely to occur
in the proposed survey area.
Five of those 27 cetacean species are
listed under the U.S. Endangered
Species Act (ESA) as endangered: sperm
whale (Physeter macrocephalus),
humpback whale (Megaptera
novaeangliae), blue whale
(Balaenoptera musculus), fin whale (B.
physalus), and sei whale (B. borealis).
The other 22 species that are likely to
occur in the proposed survey areas are:
Minke whale (B. acutorostrata), Bryde’s
whale (B. edeni), Pygmy sperm whale
(Kogia breviceps), Dwarf sperm whale
(K. simus), Cuvier’s beaked whale
(Ziphius cavirostris), Longman’s beaked
whale (Indopacetus pacificus), Pygmy
beaked whale (Mesoplodon peruvianus),
Ginkgo-toothed beaked whale (M.
ginkgodens), Blainville’s beaked whale
(M. densirostris), Rough-toothed
dolphin (Steno bredanensis), Bottlenose
dolphin (Tursiops truncatus),
Pantropical spotted dolphin (Stenella
attenuata), Spinner dolphin (S.
longirostris), Striped dolphin (S.
coeruleoalba), Fraser’s dolphin
(Lagenodelphis hosei), Short-beaked
common dolphin (Delphinus delphis),
Risso’s dolphin (Grampus griseus),
Melon-headed whale (Peponocephala
electra), Pygmy killer whale (Feresa
attenuata), False killer whale
(Pseudorca crassidens), Killer whale
(Orcinus orca), and Short-finned pilot
whale (Globicephala macrorhynchus).
A detailed description of the biology,
population estimates, and distribution
and abundance of these species is
provided in the L-DEO’s IHA
application and in the March 5, 2008
Federal Register notice (73 FR 11874).
Therefore, it is not repeated here.
Additional information regarding the
stock assessment of these species are be
found in NMFS Pacific Marine Mammal
Stock Assessment Report (Carretta et al.,
2007), and can also be accessed via the
following URL link: https://
www.nmfs.noaa.gov/pr/pdfs/sars/
po2006.pdf.
Summary of Potential Effects of Airgun
Sounds on Marine Mammals
The effects of sounds from airguns
might include one or more of the
following: tolerance, masking of natural
sounds, behavioral disturbance, and at
least in theory, temporary or permanent
hearing impairment, or non-auditory
physical or physiological effects
(Richardson et al., 1995). These effects
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are discussed below, but also in further
detail in Appendix B of L-DEO’s
application.
The potential effects of airguns
discussed below are presented without
consideration of the required mitigation
measures described below. When these
measures are taken into account, it is
unlikely that this project would result in
temporary, or especially, permanent
hearing impairment or any non-auditory
physical or physiological effects.
Tolerance
Numerous studies have shown that
pulsed sounds from airguns are often
readily detectable in the water at
distances of many kilometers. A
summary of the characteristics of airgun
pulses is provided in Appendix B of LDEO’s application. Studies have also
shown that marine mammals at
distances more than a few kilometers
from operating seismic vessels often
show no apparent response (tolerance)
(Appendix B (e)). That is often true even
in cases when the pulsed sounds must
be readily audible to the animals based
on measured received levels and the
hearing sensitivity of that mammal
group. Although various baleen whales,
toothed whales, and (less frequently)
pinnipeds have been shown to react
behaviorally to airgun pulses under
some conditions, at other times
mammals of all three types have shown
no overt reactions. In general, pinnipeds
and small odontocetes seem to be more
tolerant of exposure to airgun pulses
than are baleen whales.
Masking
Masking effects of pulsed sounds
(even from large arrays of airguns) on
marine mammal calls and other natural
sounds are expected to be limited,
although there are very few specific data
of relevance. Some whales are known to
continue calling in the presence of
seismic pulses. Their calls can be heard
between the seismic pulses (e.g.,
Richardson et al., 1986; McDonald et al.,
1995; Greene et al., 1999; Nieukirk et
al., 2004). Although there has been one
report that sperm whales ceased calling
when exposed to pulses from a very
distant seismic ship (Bowles et al.,
1994), a more recent study reports that
sperm whales off northern Norway
continued calling in the presence of
seismic pulses (Madsen et al., 2002).
That has also been shown during recent
work in the Gulf of Mexico (Tyack et al.,
2003; Smultea et al., 2004). Masking
effects of seismic pulses are expected to
be negligible in the case of the smaller
odontocete cetaceans, given the
intermittent nature of seismic pulses.
Dolphins and porpoises commonly are
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heard calling while airguns are
operating (e.g., Gordon et al., 2004;
Smultea et al., 2004; Holst et al., 2005a;
2005b). Also, the sounds important to
small odontocetes are predominantly at
much higher frequencies than are airgun
sounds. Masking effects, in general, are
discussed further in LDEO’s application
Appendix B (d).
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Disturbance Reactions
Disturbance includes a variety of
effects, including subtle changes in
behavior, more conspicuous changes in
activities, and displacement.
Reactions to sound, if any, depend on
species, state of maturity, experience,
current activity, reproductive state, time
of day, and many other factors. If a
marine mammal does react briefly to an
underwater sound by slightly 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 the species as a
whole. However, if a sound source
displaces a marine mammal(s) from an
important feeding or breeding area for a
prolonged period, impacts on the
animal(s) could be significant.
There are many uncertainties in
predicting the quantity and types of
impacts of noise on marine mammals.
NMFS uses exposures to 180 and 190
dB re 1 microPa rms to estimate the
number of animals that may be harassed
by a particular sound source in a given
area (and also uses those SPLs for use
in the development of shutdown zones
for mitigation). These estimates are
based on behavioral observations during
studies of several species. However,
information is lacking for many species.
Detailed studies have been done on
humpback, gray, and bowhead whales,
and on ringed seals. Less detailed data
are available for some other species of
baleen whales, sperm whales, and small
toothed whales.
Hearing Impairment and Other Physical
Effects
Temporary or permanent hearing
impairment is a possibility when marine
mammals are exposed to very strong
sounds, but there has been no specific
documentation of this for marine
mammals exposed to sequences of
airgun pulses. NMFS’ incidental take
authorizations generally protect against
exposure to impulsive sounds greater
than 180 and 190 dB re 1 microPa (rms),
for cetaceans and pinnipeds,
respectively (NMFS, 2000). Those
criteria have been used in defining the
safety (shut down) radii planned for the
proposed seismic surveys.
Several aspects of the monitoring and
mitigation measures required for this
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project are designed to detect marine
mammals occurring near the airguns to
avoid exposing them to sound pulses
that might, at least in theory, cause
hearing impairment (see Mitigation and
Monitoring section below). In addition,
many cetaceans are likely to show some
avoidance of the area with high received
levels of airgun sound. In those cases,
the avoidance responses of the animals
themselves will reduce or (most likely)
avoid any possibility of hearing
impairment.
Non-auditory physical effects may
also occur in marine mammals exposed
to strong underwater pulsed sound.
Possible types of non-auditory
physiological effects or injuries that
theoretically might occur in mammals
close to a strong sound source include
stress, neurological effects, bubble
formation, and other types of organ or
tissue damage. It is possible that some
marine mammal species (e.g., beaked
whales) may be especially susceptible to
injury and/or stranding when exposed
to strong pulsed sounds. However, there
is no definitive evidence that any of
these effects occur even for marine
mammals in close proximity to large
arrays of airguns. It is unlikely that any
effects of these types would occur
during the proposed project given the
brief duration of exposure of any given
mammal, and the planned monitoring
and mitigation measures (see below).
Strandings and Mortality
Marine mammals close to underwater
detonations of high explosive can be
killed or severely injured, and the
auditory organs are especially
susceptible to injury (Ketten et al., 1993;
Ketten, 1995). Airgun pulses are less
energetic and have slower rise times,
and there is no proof that they can cause
serious injury, death, or stranding even
in the case of large airgun arrays.
However, the association of mass
strandings of beaked whales with naval
exercises involving mid-frequency sonar
and, in one case, an L-DEO seismic
survey, has raised the possibility that
beaked whales exposed to strong pulsed
sounds may be especially susceptible to
injury and/or behavioral reactions that
can lead to stranding.
Seismic pulses and mid-frequency
sonar pulses are quite different. Sounds
produced by airgun arrays are
broadband with most of the energy
below 1 kHz. Typical military midfrequency sonars operate at frequencies
of 2–10 kHz, generally with a relatively
narrow bandwidth at any one time.
Thus, it is not appropriate to assume
that there is a direct connection between
the effects of military sonar and seismic
surveys on marine mammals. However,
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evidence that sonar pulses can, in
special circumstances, lead to physical
damage and mortality (NOAA and USN,
2001; Jepson et al., 2003; Fernandez et
al., 2005a), even if only indirectly,
suggests that caution is warranted when
dealing with exposure of marine
mammals to any high-intensity pulsed
sound.
In September, 2002, there was a
stranding of two Cuvier’s beaked whales
in the Gulf of California, Mexico, when
the L-DEO vessel Maurice Ewing was
operating a 20 airgun, 8,490 in3 airgun
array in the general area. The link
between the stranding and the seismic
surveys was inconclusive and not based
on any physical evidence (Hogarth,
2002; Yoder, 2002). Nonetheless, that
together with the incidents involving
beaked whale strandings near naval
exercises suggests a need for caution in
conducting seismic surveys in areas
occupied by beaked whales. No injuries
of beaked whales are anticipated during
the proposed study, due to the required
monitoring and mitigation measures.
Possible Effects of Multibeam
Bathymetric (MBB) Sonar Signals
The Kongsberg Simrad EM 120 12–
kHz sonar will be operated from the
source vessel at some times during the
planned study. As discussed above,
sounds from the MBB sonar are very
short pulses, occurring for 15 ms once
every 5 - 20 s, depending on water
depth. Most of the energy in the sound
pulses emitted by this MBB sonar is at
frequencies centered at 12 kHz. The
beam is narrow (1°) in fore-aft extent
and wide (150°) in the cross-track
extent. Each ping consists of nine
successive fan-shaped transmissions
(segments) at different cross-track
angles. Any given mammal at depth
near the trackline would be in the main
beam for only one or two of the nine
segments. Also, marine mammals that
encounter the Kongsberg Simrad EM
120 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 15 ms pulse (or two pulses if in the
overlap area). Similarly, Kremser et al.
(2005) noted that the probability of a
cetacean swimming through the area of
exposure when an MBB sonar 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 be subjected to sound
levels that could cause TTS.
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Navy sonars that have been linked to
avoidance reactions and stranding of
cetaceans (1) generally have a longer
pulse duration than the Kongsberg
Simrad EM 120, and (2) are often
directed close to horizontally vs.
downward for the Kongsberg Simrad
EM 120. The area of possible influence
of the EM 120 is much smaller-a narrow
band below the source vessel. The
duration of exposure for a given marine
mammal can be much longer for a Navy
sonar. Possible effects of sonar on
marine mammals are outlined below.
Possible Effects of Sub-bottom Profiler
Signals
A sub-bottom profiler would be
operated from the source vessel during
the planned study. As discussed before,
sounds from the sub-bottom profiler are
very short pulses, occurring for 1, 2, or
4 ms once every second. Most of the
energy in the sound pulses emitted by
this sub-bottom profiler is at mid
frequencies, centered at 3.5 kHz. The
beam width is approximately 30° and is
directed downward.
Sound levels have not been measured
directly for the sub-bottom profiler used
by the Langseth, but Burgess and
Lawson (2000) measured sounds
propagating more or less horizontally
from a similar unit with similar source
output (205 dB re 1 microPa at 1 m).
The 160 and 180 dB re 1 microPa (rms)
radii, in the horizontal direction, were
estimated to be, respectively, near 20 m
(65.6 ft) and 8 m (26.2 ft) from the
source, as measured in 13 m (42.7 ft)
water depth. The corresponding
distances for an animal in the beam
below the transducer would be greater,
on the order of 180 m (591 ft) and 18
m (59 ft), respectively, assuming
spherical spreading.
The sub-bottom profiler on the
Langseth has a stated maximum source
level of 204 dB re 1 microPa at 1 m.
Thus, the received level would be
expected to decrease to 160 and 180 dB
about 160 m (525 ft) and 16 m (53 ft)
below the transducer, respectively,
again assuming spherical spreading.
Corresponding distances in the
horizontal plane would be lower, given
the directionality of this source (30°
beam width) and the measurements of
Burgess and Lawson (2000).
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Numbers of Marine Mammals
Estimated to be Taken
All anticipated takes would be takes
by Level B harassment, involving
temporary changes in behavior. The
required mitigation measures will
prevent the possibility of injurious
takes. The basis for the take estimates
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from the airgun array is described in
this section.
The anticipated radii of influence of
the MBB sonar are less than those for
the airgun array. It is assumed that,
during simultaneous operations of the
airgun array and sonar, any marine
mammals close enough to be affected by
the sonar would already be affected by
the airguns. However, whether or not
the airguns are operating
simultaneously with the sonar, marine
mammals are not expected to be ‘‘taken’’
by the sonar given its characteristics
(e.g., narrow downward-directed beam)
and other considerations described
above. Therefore, no additional
allowance is included for animals that
might be affected by sound sources
other than airguns.
Basis for Take Estimates
As discussed above, several extensive
marine mammal surveys have been
conducted in the ETP over numerous
years. The most comprehensive data
available for the regions encompassing
the proposed survey areas are the
Ferguson and Barlow (2001) data
collected from late July to early
December 1986–1996.
Because the proposed QDG survey is
planned for April-May 2008, data
collected by Ferguson and Barlow
(2001) in July - December may not be as
representative for the QDG survey.
Again, however, it is the best available
information. For some species, the
densities derived from past surveys may
not be representative of the densities
that would be encountered during the
actual proposed seismic studies. For
example, the density of cetaceans
sighted during L-DEO’s 2003 Hess Deep
survey was considerably lower (only
one sighting) than the densities
anticipated to occur there based on the
Ferguson and Barlow (2001) data. The
Hess Deep survey occurred in mid-July,
and was apparently not well
represented by the Ferguson and Barlow
(2001) data collected during the fall,
beginning just after the Hess Deep
survey.
Despite the above caveats, the
Ferguson and Barlow (2001) data still
represent the best available data for
estimating numbers of animals
potentially exposed to the proposed
seismic sounds. Average and maximum
densities for marine mammals from
Ferguson and Barlow (2001) were
calculated for each of the project areas
based on encompassing and adjacent
survey blocks. Maximum densities were
either the highest estimated density in
any of the blocks or, if that number was
zero, the average group size for that
species. The densities reported in
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Ferguson and Barlow (2001) were
corrected for both detectability [f(0)] and
availability [g(0)] biases, and therefore,
are relatively unbiased.
Estimated Number of Takes by
Harassment
The number of individuals that may
be exposed to airgun sounds with
received levels higher than 160 dB re 1
microPa (rms) on one or more occasions
can be estimated by considering the
total marine area that would be within
the 160–dB radius around the operating
airgun array on at least one occasion. In
the QDG survey, the proposed seismic
lines do not run parallel to each other
in close proximity, and only one
transect line might be surveyed a second
time, which minimizes the number of
times an individual mammal may be
exposed during the survey. In the EPR
survey, the seismic lines are parallel
and in close proximity, and the entire
grid may be surveyed more than twice,
which may result in individuals being
exposed on two or more occasions. It is
not known how much time will pass
between the first and the second transit
along each line, so it is also possible
that different marine mammals could
occur in the area during the second
pass. Thus, the best estimates in this
section are based on a single pass of all
survey lines (including turns), and
maximum estimates are based on
maximum densities, i.e., the highest
single-block density among all of the
blocks used in the calculations. Tables
3 and 4 show the best and maximum
estimates of the number of marine
mammals that could potentially be
affected during the EPR and QDG
seismic surveys, respectively.
The number of individuals potentially
exposed to 160 dB re 1 microPa (rms)
or higher in each area was calculated by
multiplying
• The expected species density, either
‘‘mean’’ (i.e., best estimate) or
‘‘maximum’’ (maximum estimate) times
by
• The anticipated minimum area to
be ensonified to that level during airgun
operations.
The area expected to be ensonified
was determined by entering the planned
survey lines into a MapInfo Geographic
Information System (GIS), using the GIS
to identify the relevant areas by
‘‘drawing’’ the applicable 160–dB buffer
around each seismic line and then
calculating the total area within the
buffers. Areas where overlap occurred
(because of intersecting lines) were
included only once to determine the
minimum area expected to be
ensonified to higher than 160 dB re 1
microPa at least once.
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Number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
Best estimate
Percent of regional population based
on best estimate
Maximum estimate
Humpback whale
0
0.00
2
Minke whale
0
NA
1
Bryde’s whale
3
0.02
7
Sei whale
0
NA
2
Fin whale
0
0.00
2
Blue whale
0
0.03
1
Sperm whale
2
0.01
4
Pygmy sperm whale
0
NA
1
Dwarf sperm whale
66
0.59
87
Cuvier’s beaked whale
16
0.08
30
Longman’s beaked whale
0
0.00
4
Pygmy beaked whale
0
NA
4
Blainville’s beaked whale
0
NA
4
Mesoplodon sp.
8
0.03
Rough-toothed dolphin
27
0.02
109
Bottlenose dolphin
18
0.01
38
Spotted dolphin
697
0.03
1327
Spinner dolphin
342
0.02
695
Striped dolphin
303
0.02
792
Fraser’s dolphin
5
0.00
47
Short-beaked common dolphin
7
0.00
835
Risso’s dolphin
18
0.01
53
Melon-headed whale
5
0.01
30
Pygmy killer whale
9
0.02
46
False killer whale
3
0.01
8
Killer whale
1
0.01
3
Short-finned pilot whale
20
0.01
41
Species
Table 3. Estimates of the numbers of different individual marine mammals that might be exposed to sound levels > 160 dB re 1 microPa (rms)
during L-DEO’s proposed EPR seismic program in the ETP. The proposed sound source is an 18-airgun array with a total volume of 3,300 in3.
″NA″ indicates that no percentage of population data were available due to the lack of population estimate.
Number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
Best estimate
Percent of regional population based
on best estimate
Maximum estimate
Humpback whale
0
0.00
2
Minke whale
0
NA
1
Bryde’s whale
3
0.02
7
Sei whale
0
NA
2
Fin whale
0
0.00
2
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Species
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Number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
Best estimate
Percent of regional population based
on best estimate
Maximum estimate
Blue whale
0
0.03
1
Sperm whale
4
0.01
13
Pygmy sperm whale
0
NA
1
Dwarf sperm whale
0
0.00
2
Cuvier’s beaked whale
48
0.24
81
Longman’s beaked whale
0
0.00
3
Pygmy beaked whale
0
NA
3
Blainville’s beaked whale
0
NA
3
Mesoplodon sp.
7
0.03
Rough-toothed dolphin
24
0.02
166
Bottlenose dolphin
17
0.01
48
Spotted dolphin
468
0.02
1236
Spinner dolphin
226
0.01
431
Striped dolphin
482
0.03
599
Fraser’s dolphin
43
0.01
151
Short-beaked common dolphin
30
0.00
2089
Risso’s dolphin
16
0.01
68
Melon-headed whale
7
0.01
38
Pygmy killer whale
3
0.01
16
False killer whale
11
0.03
47
Killer whale
1
0.01
2
Short-finned pilot whale
35
0.02
105
Species
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Table 4. Estimates of the numbers of different individual marine mammals that might be exposed to sound levels > 160 dB re 1 microPa (rms)
during L-DEO’s proposed QDG seismic program in the ETP. The proposed sound source is an 27-airgun array with a total volume of 4,950 in3.
″NA″ indicates that no percentage of population data were available due to the lack of population estimate.
Applying the approach described
above, 2,492 km2 (923 mi2) would be
within the 160–dB isopleth on one or
more occasions during the EPR survey,
and 2,911 km2 (1,224 mi2) would be
ensonified on one or more occasions
during the QDG survey. This approach
does not allow for turnover in the
marine mammal populations in the
study areas during the course of the
studies. That might underestimate
actual numbers of individuals exposed,
although the conservative distances
used to calculate the area may offset
this. In addition, the approach assumes
that no cetaceans would move away or
toward the trackline as the Langseth
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
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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 160
dB re 1 microPa (rms) or higher.
The ‘‘best estimate’’ of the number of
individual marine mammals that might
be exposed to seismic sounds with
received levels of 160 dB re 1 microPa
(rms) or higher during the EPR survey
includes 2 endangered whales (both
sperm whales), 24 beaked whales, and
3 Bryde’s whales. Pantropical spotted,
spinner, and striped dolphins are
estimated to be the most common
species exposed; the best estimates for
those species are 697, 342, and 303,
respectively. Estimates for other species
are lower (Table 3).
The ‘‘best estimate’’ of the number of
individual marine mammals that might
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be exposed to seismic sounds with
received levels of 160 dB re 1 microPa
(rms) or higher during the QDG survey
includes 5 endangered whales (4 sperm
whales and 1 blue whale), 55 beaked
whales, and 6 Bryde’s whales. Striped,
spotted, and spinner dolphins are
estimated to be the most common
species exposed; the best estimates for
those species are 482, 468, and 226,
respectively. Estimates for other species
are lower (Table 4).
The ‘‘best estimate’’ of the total
number of individual marine mammals
that might be exposed to seismic sounds
with received levels of 160 dB re 1
microPa (rms) or higher for both
surveys, along with the percentage of
regional population, is listed in Table 5.
It includes two ESA-listed species (6
sperm whales and 1 blue whale), 79
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beaked whales, and 9 Bryde’s whales.
Striped, spotted, and spinner dolphins
are estimated to be the most common
species exposed; the best estimates for
those species are 785, 1,165, and 568,
respectively. Estimates for other species
are lower (Table 5).
Potential Impacts to Subsistence
Harvest of Marine Mammals
The proposed activities will not have
any impact on the availability of the
species or stocks for subsistence use
described in section 101(a)(5)(D)(i)(II).
Total number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
Best estimate
Percent of regional population based on best estimate
Humpback whale
0
0.00
Minke whale
0
NA
Bryde’s whale
9
0.07
Sei whale
0
NA
Fin whale
0
0.00
Blue whale
1
0.04
Sperm whale
6
0.02
Pygmy sperm whale
0
NA
Dwarf sperm whale
66
0.59
Cuvier’s beaked whale
64
0.32
Longman’s beaked whale
0
0.00
Pygmy beaked whale
0
NA
Blainville’s beaked whale
0
NA
Mesoplodon sp.
15
0.06
Rough-toothed dolphin
51
0.04
Bottlenose dolphin
35
0.02
Spotted dolphin
1,165
0.05
Spinner dolphin
568
0.03
Striped dolphin
785
0.05
Fraser’s dolphin
48
0.01
Short-beaked common dolphin
37
0.00
Risso’s dolphin
34
0.02
Melon-headed whale
12
0.02
Pygmy killer whale
12
0.03
False killer whale
14
0.04
Killer whale
2
0.02
Short-finned pilot whale
55
0.03
Species
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Table 5. Estimates of the numbers of different individual marine mammals that might be exposed to sound levels > 160 dB re 1 microPa (rms)
during L-DEO’s two proposed seismic program in the ETP. ″NA″ indicates that no percentage of population data were available due to the lack
of population estimate.
Potential Impacts on Habitat and Prey
The proposed seismic survey would
not result in any permanent or
significant impact on habitats used by
marine mammals, or to the food sources
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they use. The main impact issue
associated with the proposed activity
would be temporarily elevated noise
levels and the associated direct effects
on marine mammals, as discussed
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above. The following sections briefly
review effects of airguns on fish and
invertebrates (both marine mammal
prey sources), and more details are
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included in Appendices C and D of the
L-DEO’s IHA application, respectively.
Effects on Fish
There are three types of potential
effects of exposure to seismic surveys:
(1) pathological, (2) physiological, and
(3) behavioral. Pathological effects
involve lethal and temporary or
permanent sub-lethal injury.
Physiological effects involve temporary
and permanent primary and secondary
stress responses, such as changes in
levels of enzymes and proteins.
Behavioral effects refer to temporary
and (if they occur) permanent changes
in exhibited behavior (e.g., startle and
avoidance behavior). The three
categories are interrelated in complex
ways. For example, it is possible that
certain physiological and behavioral
changes could potentially lead to an
ultimate pathological effect on
individuals (i.e., mortality).
The 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. For
a given sound to result in hearing loss,
the sound must exceed, by some
specific amount, the hearing threshold
of the fish for that sound (Popper, 2005).
The consequences of temporary or
permanent hearing loss in individual
fish on a fish population is unknown;
however, it likely depends on the
number of individuals affected and
whether critical behaviors involving
sound (e.g. predator avoidance, prey
capture, orientation and navigation,
reproduction, etc.) are adversely
affected. McCauley et al. (2003) found
that exposure to airgun sound caused
observable anatomical damage to the
auditory maculae of ‘‘pink snapper’’
(Pagrus auratus). This damage in the
ears had not been repaired in fish
sacrificed and examined almost two
months after exposure. On the other
hand, Popper et al. (2005) found that
received sound exposure levels of 177
dB re 1 microPa2–s caused no hearing
loss in broad whitefish (Coreogonus
nasus). During both studies, the
repetitive exposure to sound was greater
than would have occurred during a
typical seismic survey. However, the
substantial low-frequency energy
produced by the airgun arrays (less than
400 Hz in the study by McCauley et al.
(2003) and less than 200 Hz in Popper
et al. (2005)) likely did not propagate to
the fish because the water in the study
areas was very shallow (approximately
9 m (29.5 ft) in the former case and less
than 2 m (6.6 ft) in the latter). Water
depth sets a lower limit on the lowest
sound frequency that will propagate at
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about one-quarter wavelength (Urick,
1983; Rogers and Cox, 1988).
Except for these two studies, at least
with airgun-generated sound treatments,
most contributions rely on rather
subjective assays such as fish ‘‘alarm’’ or
‘‘startle response’’ or changes in catch
rates by fishers. These observations are
important in that they attempt to use the
levels of exposures that are likely to be
encountered by most free-ranging fish in
actual survey areas. However, the
associated sound stimuli are often
poorly described, and the biological
assays are varied (Hastings and Popper,
2005). 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; 2000b;
2003; Bjarti, 2002; Hassel et al., 2003;
Popper et al., 2005).
Some studies have reported, some
equivocally, that mortality of fish, fish
eggs, or larvae can occur close to
seismic sources (Kostyuchenko, 1973;
Dalen and Knutsen, 1986; Booman et
al., 1996; Dalen et al., 1996). Some of
the reports claimed seismic effects from
treatments quite different from actual
seismic survey sounds or even
reasonable surrogates. Saetre and Ona
(1996) applied a ‘‘worst-case scenario’’
mathematical model to investigate the
effects of seismic energy on fish eggs
and larvae. They concluded that
mortality rates caused by exposure to
seismic surveys are so low, as compared
to natural mortality rates, that the
impact of seismic surveying on
recruitment to a fish stock must be
regarded as insignificant.
Physiological effects refer to cellular
and/or biochemical responses of fish to
acoustic stress. Such stress potentially
could affect fish populations by
increasing mortality or reducing
reproductive success. Primary and
secondary stress responses of fish after
exposure to seismic survey sound
appear to be temporary in all studies
done to date (Sverdrup et al., 1994;
McCauley et al., 2000a; 2000b). The
periods necessary for the biochemical
changes to return to normal are variable,
and depend on numerous aspects of the
biology of the species and of the sound
stimulus.
Behavioral effects include changes in
the distribution, migration, mating, and
catchability of fish populations. Studies
investigating the possible effects of
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sound (including seismic survey sound)
on fish behavior have been conducted
on both uncaged and caged individuals
(Chapman and Hawkins, 1969; Pearson
et al., 1992; Santulli et al., 1999, Wardle
et al., 2001, Hassel et al., 2003).
Typically, in these studies fish
exhibited a sharp ‘‘startle’’ response at
the onset of a sound followed by
habituation and a return to normal
behavior after the sound ceased.
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. 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).
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. 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; 2000b) exposed to seismic survey
sound have not resulted in any
significant pathological impacts on the
animals. It has been suggested that
exposure to commercial seismic survey
activities has injured giant squid
(Guerra et al., 2004), but there is no
evidence to support such claims.
Physiological effects refer mainly to
biochemical responses by marine
invertebrates to acoustic stress. Such
stress potentially could affect
invertebrate populations by increasing
mortality or reducing reproductive
success. Any primary and secondary
stress responses (i.e., changes in
haemolymph levels of enzymes,
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proteins, etc.) of crustaceans after
exposure to seismic survey sounds
appear to be temporary (hours to days)
in studies done to date. 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.
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 prey availability to marine
mammals. 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; 2000b). In other
cases, no behavioral impacts were noted
(e.g., crustaceans in Christian et al.,
2003; 2004; DFO, 2004).
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Effects on Marine Mammal Habitat
The effects of the planned activity on
marine mammal habitats and food
resources are expected to be negligible,
as described above. A small minority of
the marine mammals that are present
near the proposed activity may be
temporarily displaced as much as a few
kilometers by the planned activity.
During the proposed survey, most
marine mammals will be dispersed
throughout the study area. However,
concentrations of marine mammals and/
or marine mammal prey species have
been reported to occur in and near the
proposed study area at the time of year
when the seismic programs are planned.
The countercurrent thermocline ridge at
approximately 10°N (in the EPR study
area) has been reported to be an
important area to cetacean species, as
has the Costa Rica Dome, located several
hundreds of kilometer to the east of the
study area. Although these areas are
thought to be important feeding grounds
for some marine mammal species, they
are not considered critical feeding areas
for any of the species that are found
there at that time of year.
The proposed activity is not expected
to have any habitat-related effects that
could cause significant or long-term
consequences for individual marine
mammals or their populations, since
operations at the various sites will be
limited in duration.
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Monitoring and Mitigation Measures
Monitoring
For the issuance of the IHA, NMFS
requires that L-DEO sponsor marine
mammal monitoring during the present
project.
(1) Safety Zones
Received sound levels have been
predicted by L-DEO in relation to
distance and direction from the airguns
for the 36–airgun array with 18 and 27
airguns firing and for a single 1900LL 40
in3 airgun, which will be used during
power downs. Those corresponding
radii were described above under
Acoustic Source Specifications and are
set out in Table 2 above. A detailed
description of the modeling effort is
provided in Appendix A of the L-DEO’s
IHA application.
If marine mammals are detected
within or about to enter the relevant
safety zone (180 dB for cetaceans, 190
dB for pinnipeds), the airguns will be
powered down (or shut down if
necessary) immediately.
(2) Vessel-based Visual Monitoring
A minimum of two (2) vessel-based
marine mammal observers (MMOs) will
be on board the seismic source vessel,
and they will watch for marine
mammals near the vessel during
daytime airgun operations and during
ramp-ups of airguns at night from
power-down only. MMOs will also
watch for marine mammals near the
seismic vessel for at least 30 minutes
prior to the start of airgun operations
after an extended shutdown (a
shutdown lasting more than 30
minutes). When feasible, MMOs will
also make observations during daytime
periods when the seismic systems are
not operating for comparison of animal
abundance and behavior. Based on
MMO observations, airguns will be
powered down (see below) or, if
necessary, shut down completely, when
marine mammals are observed within or
about to enter the relevant safety zone
(see below).
MMOs will be appointed by L-DEO,
with NMFS approval. At least one MMO
will monitor the safety zone during
daytime airgun operations and any
nighttime ramp-ups. MMOs will work
in shifts of 4 hour duration or less. The
vessel crew will also be instructed to
assist in detecting marine mammals.
The Langseth is a suitable platform for
marine mammal observations. When
stationed on the observation platform,
the eye level will be approximately 17.8
m (58.4 ft) above sea level, and the
observer will have a good view around
the entire vessel. During daytime, the
MMO will scan the area around the
vessel systematically with reticule
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24233
binoculars (e.g., 7 50 Fujinon), Big-eye
binoculars (25 150), and with the naked
eye. Night vision devices will be
available for use (ITT F500 Series
Generation 3 binocular-image intensifier
or equivalent), although they are
considered of limited effectiveness in
detecting marine mammals. Laser
rangefinding binoculars (Leica LRF 1200
laser rangefinder or equivalent) will be
available to assist in distance
estimation.
(3) Passive Acoustic Monitoring (PAM)
Passive acoustic monitoring (PAM)
will take place to complement the visual
monitoring program. PAM will involve
towing hydrophones that detect
frequencies produced by vocalizing
marine mammals. Two or more
hydrophones are used to allow some
localization of the bearing (direction) of
the animal from the vessel. PAM can be
effective at detecting some animals
before they are detected visually
(Smultea and Holst, 2003; Smultea et
al., 2004). Visual monitoring typically is
not effective during periods of bad
weather or at night, and even with good
visibility, is unable to detect marine
mammals when they are below the
surface or beyond visual range.
Therefore, acoustic monitoring can
improve detection, identification,
localization, and tracking of marine
mammals in these circumstances.
PAM’s value is limited, however, by
bottom configuration (water depth) and
other environmental factors, and in
some cases towing the PAM equipment
is not practicable. PAM would be
operated or overseen by personnel with
acoustic expertise.
The PAM system consists of hardware
(i.e., hydrophones) and software. The
‘‘wet end’’ of the hydrophone array
system consists of a low-noise, towed
hydrophone array that is connected to
the vessel by a cable. The array will be
deployed from a winch located on the
back deck. A deck cable will connect
from the winch to the main computer
lab where the acoustic station and signal
conditioning and processing system will
be located.
Proper steps should be taken to
ensure appropriate protection from
electric, electronic, and electro magnetic
interferences (power supply, radar
pulses, GPS etc.) that could introduce
noises into the PAM system. An airgun
shoots blanking mechanism should be
incorporated into the PAM system so
that adequate signal gain for PAM can
be achieved to detect vocalizing marine
mammals in the vicinity.
The acoustical array will be
monitored 24 h per day while at the
survey area during airgun operations.
One MMO will monitor the acoustic
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mstockstill on PROD1PC66 with NOTICES
detection system at any one time, by
listening to the signals from two
channels via headphones and/or
speakers and watching the real-time
spectrographic display for vocalizations
produced by cetaceans. MMOs
monitoring the acoustical data will be
on shift for 1 - 6 h. When a vocalization
is detected, the acoustic MMO will
contact the visual MMO immediately, to
alert him/her to the presence of
cetaceans (if they have not already been
seen). The information regarding the
call will be entered into a database. The
data to be entered include whether the
detection is linked with a visual
sighting, date, time when first and last
heard, if possible, and whenever any
additional information was recorded,
position and water depth when first
detected, bearing if determinable,
species or species group, types and
nature of sounds heard, and any other
notable information. The acoustic
detection can also be recorded for
further analysis.
Mitigation
Mitigation measures include (1) vessel
speed or course alteration, provided that
doing so will not compromise
operational safety requirements, (2)
airgun array power down, (3) airgun
array shut down, and (4) airgun array
ramp up.
(1) Speed or Course Alteration
If a marine mammal is detected
outside the safety zone but is likely to
enter it based on relative movement of
the vessel and the animal, then if safety
and scientific objectives allow, the
vessel speed and/or course will be
adjusted to minimize the likelihood of
the animal entering the safety zone.
NMFS acknowledges that major course
and speed adjustments are often
impractical when towing long seismic
streamers and large source arrays, thus
for surveys involving large sources.
Therefore the other mitigation measures
often will be required.
(2) Power-down Procedures
A power down involves reducing the
number of airguns operating to a single
airgun in order to reduce the size of the
safety zone. The continued operation of
one airgun is intended to alert marine
mammals to the presence of the seismic
vessel nearby.
If a marine mammal is detected
within, or is likely to enter, the safety
zone of the array in use, and if vessel
course and/or speed changes are
impractical or will not be effective to
prevent the animal from entering the
safety zone, then the array will be
powered down to ensure that the animal
remains outside the smaller safety zone
of the single 40–in3 airgun. If the size of
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17:17 May 01, 2008
Jkt 214001
the safety zone for the single airgun will
not prevent the animal from entering it,
then a shutdown will be required, as
described below.
Following a power down, airgun
activity will not resume until the marine
mammal is outside the safety zone for
the full array. The animal will be
considered to have cleared the safety
zone if it (1) is visually observed to have
left the relevant safety zone; or (2) has
not been seen within the safety zone for
15 min in the case of small odontocetes;
or has not been seen within the safety
zone for 30 min in the case of mysticetes
and large odontocetes, including sperm,
pygmy sperm, dwarf sperm, and beaked
whales.
Following a power down and
subsequent animal departure as above,
the airgun array may resume operations
following ramp-up procedures
described below.
(3) Shut-down Procedures
If a marine mammal is within or about
to enter the safety zone for the single
airgun, all airguns will be shut down
immediately. Airgun activity will not
resume until the animal has cleared the
safety zone, as described above.
(4) Ramp-up Procedures
A ramp-up procedure will be
followed when an airgun array begins
operating after a specified period
without operations or at single airgun
operation. For the present cruise, this
period would be 4–5 min. This period
is based on the largest modeled 180–dB
radius for the airgun array to be used in
relation to the planned speed of the
Langseth while shooting.
Ramp up will begin with the smallest
gun in the array (40 in3). Airguns will
be added in a sequence such that the
source level of the array will increase in
steps not exceeding 6 dB per 5–min
period. During ramp-up, the MMOs will
monitor the safety zone, and if marine
mammals are sighted, decisions about
course/speed changes, power down and
shutdown will be implemented as
though the full array were operational.
Initiation of ramp-up procedures from
shutdown requires that the full safety
zone must be visible by the MMOs. This
requirement will preclude starts at night
or in thick fog. Ramp-up is allowed from
a power down under reduced visibility
conditions, but only if at least one
airgun has operated continuously with a
source level of at least 180 dB re
microPa (rms) throughout the survey
interruption. It is assumed that the
single airgun will alert marine mammals
to the approaching seismic vessel,
allowing them to move away if they
choose. Ramp-up procedures will not be
initiated if a marine mammal is
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observed within the safety zone of the
airgun array to be operated.
Data Collection and Reporting
MMOs will record data to estimate the
numbers of marine mammals exposed to
various received sound levels and to
document apparent disturbance
reactions or lack thereof. Data will be
used to estimate numbers of animals
potentially ‘‘taken’’ by harassment. They
will also provide information needed to
order a power down or shutdown of
airguns when marine mammals are
within or near the safety zone.
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, and behavioral pace.
(2) Time, location, heading, speed,
activity of the vessel (including whether
and the level at which airguns are
operating), 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 airgun power
down and shutdown, will be recorded
in a standardized format. Data accuracy
will be verified by the MMOs 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. MMO observations
will provide the following information:
(1) The basis for decisions about
powering down or shutting down airgun
arrays.
(2) Information needed to estimate the
number of marine mammals potentially
taken by harassment as described above.
(3) Data on the occurrence,
distribution, and activities of marine
mammals in the area where the seismic
study is conducted.
(4) Data on the behavior and
movement patterns of marine mammals
seen at times with and without seismic
activity.
A final report will be submitted to
NMFS within 90 days after the end of
the cruise. The report will describe the
operations that were conducted and
sightings of marine mammals near the
operations. The report will also provide
full documentation of methods, results,
and interpretation pertaining to all
monitoring. The report will summarize
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the dates and locations of seismic
operations, and all marine mammal
sightings (dates, times, locations,
activities, associated seismic survey
activities), and the amount and nature of
potential take of marine mammals by
harassment or in other ways.
Endangered Species Act
On March 5, 2007, NMFS concluded
consultation with NSF under section 7
of the ESA on the proposed marine
geophysical surveys in the ETP and
issued a biological opinion on April 22,
2008. The finding of that consultation
was that the marine geophysical surveys
in the ETP may adversely affect, but is
not likely to jeopardize, the continued
existence of blue and sperm whales, and
leatherback, green, olive ridley,
hawksbill, and loggerhead turtles. The
proposed marine geophysical surveys
are not likely to adversely affect sei or
fin whales. NMFS’ IHA will not have
impacts beyond what was analyzed in
the biological opinion. Therefore,
additional consultation is not required.
mstockstill on PROD1PC66 with NOTICES
National Environmental Policy Act
(NEPA)
In April 2007, LGL Ltd. (LGL)
prepared a draft Environmental
Assessment of Two Marine Geophysical
Surveys by the R/V Marcus G. Langseth
in the Eastern Tropical Pacific, 2007
(EA) for L-DEO and NSF. NMFS has
reviewed this EA and has adopted it.
Therefore, the preparation of another
EIS or EA is not warranted. NMFS
issued a Finding of No Significant
Impact Statement on April 23, 2008.
Determination
Based on the preceding information,
and provided that the aforementioned
mitigation and monitoring measures are
incorporated, NMFS has determined
that the impact of conducting the
marine seismic survey in the ETP may
result, at worst, in a temporary
modification in behavior of small
numbers of certain species of marine
mammals. While behavioral and
avoidance reactions may be made by
these species in response to the
resultant noise from the airguns, these
behavioral changes are expected to have
a negligible impact on the affected
species and stocks of marine mammals.
While the number of potential
incidental harassment takes will depend
on the distribution and abundance of
marine mammals in the area of seismic
operations, the number of potential
harassment takings is estimated to be
relatively small in light of the
population sizes (see Tables 3, 4, and 5).
NMFS anticipates the actual take of
individuals to be even lower than the
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17:17 May 01, 2008
Jkt 214001
numbers depicted in the tables, because
those numbers do not reflect either the
implementation of the mitigation
numbers or the fact that some animals
likely will avoid the sound at levels
lower than those expected to result in
harassment.
In addition, no take by death and/or
injury is anticipated, and the potential
for temporary or permanent hearing
impairment will be avoided through the
incorporation of the mitigation
measures described in this document.
Authorization
NMFS has issued an IHA to L-DEO for
the potential Level B harassment of
small numbers of cetaceans incidental
to conducting marine geophysical
surveys in the ETP, provided the
previously mentioned mitigation,
monitoring, and reporting requirements
are incorporated.
Dated: April 23, 2008.
James H. Lecky,
Director, Office of Protected Resources,
National Marine Fisheries Service.
[FR Doc. E8–9717 Filed 5–1–08; 8:45 am]
BILLING CODE 3510–22–S
24235
England Fishery Management Council;
telephone: (978) 465–0492.
SUPPLEMENTARY INFORMATION: The
committee’s agenda for the meeting is as
follows:
1. Monday, May 19, 2008; The
committee will review final reports
generated through cooperative research
partnerships. Reports to be reviewed
address groundfish, monkfish, sea
scallops, herring and related topics.
2. Tuesday, May 20, 2008; The
committee will review habitat-related
final research reports that have been
funded through organizations that
support cooperative research in the New
England region. The committee may
consider other topics at their discretion.
Although non-emergency issues not
contained in this agenda may come
before this group for discussion, those
issues may not be the subject of formal
action during this meeting. Action will
be restricted to those issues specifically
listed in this notice and any issues
arising after publication of this notice
that require emergency action under
section 305(c) of the Magnuson-Stevens
Act, provided the public has been
notified of the Council’s intent to take
final action to address the emergency.
DEPARTMENT OF COMMERCE
Special Accommodations
National Oceanic and Atmospheric
Administration
This meeting is physically accessible
to people with disabilities. Requests for
sign language interpretation or other
auxiliary aids should be directed to Paul
J. Howard, Executive Director, at (978)
465–0492, at least 5 days prior to the
meeting date.
RIN: 0648–XH60
New England Fishery Management
Council; Public Meeting
National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Notice of a public meeting.
AGENCY:
SUMMARY: The New England Fishery
Management Council (Council) is
scheduling a public meeting of its
Research Steering Committee in May,
2008 to consider actions affecting New
England fisheries in the exclusive
economic zone (EEZ).
Recommendations from this group will
be brought to the full Council for formal
consideration and action, if appropriate.
DATES: This meeting will be held on
Monday, May 19, 2008 at 10 a.m. and
Tuesday, May 20, 2008 at 8:30 a.m.
ADDRESSES: This meeting will be held at
the Hilton Hotel, 25 Allied Drive,
Dedham, MA 02026; telephone: (781)
329–7900; fax: (781) 329–5552.
Council address: New England
Fishery Management Council, 50 Water
Street, Mill 2, Newburyport, MA 01950.
FOR FURTHER INFORMATION CONTACT: Paul
J. Howard, Executive Director, New
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Authority: 16 U.S.C. 1801 et seq.
Dated: April 29, 2008.
Tracey L. Thompson,
Acting Director, Office of Sustainable
Fisheries, National Marine Fisheries Service.
[FR Doc. E8–9655 Filed 5–1–08; 8:45 am]
BILLING CODE 3510–22–S
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric
Administration
RIN: 0648–XH59
North Pacific Fishery Management
Council; Public Meeting
National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Notice of a public meeting.
AGENCY:
SUMMARY: The North Pacific Fishery
Management Council’s (Council) Pacific
Northwest Crab Industry Advisory
Committee (PNCIAC) will meet in
E:\FR\FM\02MYN1.SGM
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]]>Agencies
[Federal Register Volume 73, Number 86 (Friday, May 2, 2008)]
[Notices]
[Pages 24223-24235]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-9717]
-----------------------------------------------------------------------
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XH14
Incidental Takes of Marine Mammals During Specified Activities;
Marine Geophysical Surveys in the Eastern Tropical Pacific Ocean in
2008
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; issuance of an incidental take authorization.
-----------------------------------------------------------------------
SUMMARY: In accordance with regulations implementing the Marine Mammal
Protection Act (MMPA), notification is hereby given that an Incidental
Harassment Authorization to take marine mammals, by Level-B harassment,
incidental to conducting two marine geophysical surveys by the Lamont-
Doherty Earth Observatory (L-DEO) in the Eastern Tropical Pacific Ocean
(ETP), has been issued for a period of one year.
DATES: The authorization is effective from April 24, 2008, until April
23, 2009.
ADDRESSES: Copies of the application, IHA, the Environmental
Assessment of Two Marine Geophysical Surveys by the R/V Marcus G.
Langseth in the Eastern Tropical Pacific, 2008, prepared for the L-DEO
and the National Science Foundation (NSF) by the LGL Ltd., and/or a
list of references used in this document may be obtained by writing to
P. Michael Payne, Chief, Permits, Conservation and Education Division,
Office of Protected Resources, National Marine Fisheries Service, 1315
East-West Highway, Silver Spring, MD 20910-3225, or by telephoning one
of the contacts listed here (see FOR FURTHER INFORMATION CONTACT).
FOR FURTHER INFORMATION CONTACT: Shane Guan, Office of Protected
Resources, NMFS, (301) 713-2289, ext 137.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.)
direct the Secretary of Commerce to allow, upon request, the
incidental, but not intentional, taking of marine mammals by U.S.
citizens who engage in a specified activity (other than commercial
fishing) within a specified geographical region if certain findings are
made and either regulations are issued or, if the taking is limited to
harassment, a notice of a proposed authorization is provided to the
public for review.
Authorization shall be granted if NMFS finds that the taking will
have a negligible impact on the species or stock(s), will not have an
unmitigable adverse impact on the availability of the species or
stock(s) for certain subsistence uses, and if the permissible methods
of taking and requirements pertaining to the mitigation, monitoring and
reporting of such takings are set forth. NMFS has defined ``negligible
impact'' in 50 CFR 216.103 as ''...an impact resulting from the
specified activity that cannot be reasonably expected to, and is not
reasonably likely to, adversely affect the species or stock through
effects on annual rates of recruitment or survival.''
Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the United States can apply for an authorization
to incidentally take small numbers of marine mammals by harassment.
Except with respect to certain activities not pertinent here, the MMPA
defines ``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS
review of an application followed by a 30-day public notice and comment
period on any proposed authorization for the incidental harassment of
marine mammals. Within 45 days of the close of the comment period, NMFS
must either issue or deny issuance of the authorization.
Summary of Request
L-DEO submitted to NMFS an application from L-DEO for the taking,
by Level B harassment, of several species of marine mammals incidental
to conducting, with research funding from the NSF, two marine seismic
surveys in the ETP. This project would be conducted with L-DEO's new
seismic vessel, the R/V Marcus G. Langseth (Langseth), which would
deploy different configurations of airguns and a different bottom-
mapping sonar than used previously by L-DEO. The first survey was
planned to be approximately 39 days between September and October 2007,
and the second one approximately 6 days in between November and
December 2007. However, due to scheduling issues with the vessel, the
39-day survey is rescheduled to June and August 2008, and the 6-day
survey to April and May 2008.
Description of the Specified Activity
The April-May 6-day survey would examine two important types of
seismic behavior of the Quebrada, Discovery, and Gofar fault systems
(QDG) to understand better the behavior of earthquakes and faults in
general.
The June-August 39-day survey would obtain seismic reflection
imaging of the internal structure of the magmatic-hydrothermal system
at the fast-spreading mid-ocean ridge of the East Pacific Rise (EPR).
[[Page 24224]]
The seismic surveys will involve one vessel. The source vessel
Langseth would deploy a 36-airgun array as an energy source. However,
for the EPR study, two identical two-string sources will be firing
alternately, so that no more than 18 airguns will be firing at any
time, with a maximum discharge volume of 3,300 in\3\. The Langseth
would also tow the receiving system, which consists of four 6-km (3.73-
mi) hydrophone streamers. For the QDG study, no more than 27 airguns
would be fired at any time, with a maximum discharge volume of 4,950
in\3\. The Langseth would also tow the receiving system, a single 8-km
(4.97-mi) streamer, and would also deploy 40 long-term Ocean Bottom
Seismometers (OBSs) that would be recovered 1 year after deployment,
and another 8-10 short-term OBSs on each line that will be retrieved
after the seismic surveys are completed.
The EPR and QDG programs would consist of a maximum of
approximately 7,992 km (4,967 mi) and 654 km (406 mi) of surveys,
respectively.
The QDG seismic survey would also occur in international waters of
the ETP, approximately 2,265 km (1,408 mi) off the coast of Ecuador and
approximately 1,300 km (808 mi) west of the Galapagos Islands. The
overall area within which the seismic survey would occur is located
between 3[deg] and 5[deg] S, and between 103[deg] and 106[deg] W. Water
depths in the survey area are more than 3,000 m (9,843 ft) deep. The
EPR seismic survey would take place in international waters of the ETP,
offshore from Mexico and Central America at the East Pacific Rise. The
closest land mass to this survey is Mexico, located approximately 890
km (553 mi) away. The overall area within which the seismic survey will
occur is located between 8.3[deg] and 10.2[deg] N, and between
104.1[deg] and 104.5[deg] W. The survey would take place in water more
than 2,000 m (6,562 ft) deep.
In addition to the operations of the airgun array, a multi-beam
bathymetric sonar would be operated from the source vessel continuously
throughout the entire cruise, and a lower-energy sub-bottom profiler
will also be operated during most of the survey.
Detailed descriptions of these activities were published in the
Federal Register on March 5, 2008 (72 FR 11876). No changes have been
made to these proposed marine geophysical surveys.
The Langseth would also serve as the platform from which vessel-
based visual marine mammal observers will watch for marine mammals
before and during airgun operations. The characteristics of the Ewing
that make it suitable for visual monitoring are described under
Monitoring, later in this document.
Acoustic Source Specifications
Airguns
The airgun array to be used will consist of 36 airguns, with
maximum total discharge volume of approximately 6,600 in\3\. The
airguns will comprise a mixture of Bolt 1500LL and Bolt 1900LLX
airguns. The array will consist of four identical linear arrays or
``strings.'' Each string would have ten airguns; the first and last
airguns in the strings are spaced 16 m (52.5 ft) apart. Nine airguns
would be fired simultaneously, while the tenth is kept in reserve as a
spare, to be turned on in case of failure of another airgun. Two of the
four strings would be fired during the EPR survey (18 airguns), and
three strings would be fired during the QDG survey (27 airguns). The
airgun strings would be distributed across an approximate area of 24 x
16 m (78.7 x 52.5 ft) behind the Langseth and would be towed
approximately 50 - 100 m (164 - 328 ft) behind the vessel. The firing
pressure of the array is 2,000 psi. During firing, a brief (~0.1 s)
pulse of sound is emitted. During the EPR survey, the shots would be
emitted at intervals of ~15 s, corresponding to a shot interval of
~37.5 m (~123 ft). During the QDG survey, the shots would be emitted at
intervals of ~60 s, corresponding to a shot interval of ~150 m (492
ft). The airguns would be towed at a depth of 7 m (23 ft) during both
the QDG and the EPR surveys. The depth at which the source is towed
affects the maximum near-field output and the shape of its frequency
spectrum. In deeper water, the effective source level for sound
propagating in near-horizontal directions is higher than in shallow
water; however, the nominal source levels of the array at various tow
depths are nearly identical.
Because the actual source is a distributed sound source (up to 27
airguns in these surveys) rather than a single point source, the
highest sound levels measurable at any location in the water would be
less than the nominal source level. In addition, the effective source
level for sound propagating in near-horizontal directions would be
substantially lower than the nominal source level applicable to
downward propagation because of the directional nature of the sound
from the airgun array.
The specifications of each source planned for use are described in
Table 1.
------------------------------------------------------------------------
18-Airgun Array (2 27-Airgun Array (3
Strings) Strings)
------------------------------------------------------------------------
Energy Source 18, 2,000 psi Bolt 27, 2,000 psi Bolt
airguns of 40-360 airguns of 40-360
in\3\ in\3\
------------------------------------------------------------------------
Source output (downward) 0-pk: 252 dB re 1 0-pk: 256 dB re 1
microPa-m;pk-pk: microPa-m;pk-pk:
259 dB re 1 microPa- 262 dB re 1 microPa-
m m
------------------------------------------------------------------------
Air discharge volume Approximately 3,300 Approximately 4,950
in\3\ in\3\
------------------------------------------------------------------------
Towing depth of energy 7 m (23 ft) 7 m (23 ft)
source
------------------------------------------------------------------------
Dominant frequency 0 - 188 Hz 0 - 188 Hz
components
------------------------------------------------------------------------
Table 1. L-DEO airgun configuration and specification of each source
planned for use in the proposed projects.
A detailed discussion of the characteristics of airgun pulses has
been provided in L-DEO's application, and in previous Federal Register
notices (see 69 FR 31792 (June 7, 2004) or 69 FR 34996 (June 23,
2004)). Reviewers are referred to those documents for additional
information.
Received sound levels have been predicted by L-DEO in relation to
distance and direction from the airguns for the 36-airgun array with 18
and 27 airguns firing and for a single 1900LL 40-in\3\ airgun, which
would be used during power downs.
The predicted sound contours are shown as sound exposure levels
(SEL) in decibels (dB) re 1 microPa\2\-s. SEL is a measure of the
received energy in the pulse and represents the sound pressure level
(SPL) that would be measured if the pulse energy were spread evenly
across a 1-s period. Because actual
[[Page 24225]]
seismic pulses are less than 1 s in duration, this means that the SEL
value for a given pulse is lower than the SPL calculated for the actual
duration of the pulse. The advantage of working with SEL is that the
SEL measure accounts for the total received energy in the pulse, and
biological effects of pulsed sounds probably depend mainly on pulse
energy. SPL for a given pulse depends greatly on pulse duration. A
pulse with a given SEL can be long or short depending on the extent to
which propagation effects have ``stretched'' the pulse duration. The
SPL will be low if the duration is long and higher if the duration is
short, even though the pulse energy (and presumably the biological
effects) is the same.
Although SEL may be a better measure than SPL when dealing with
biological effects of pulsed sound, SPL is the measure that has been
most commonly used in studies of marine mammal reactions to airgun
sounds and in NMFS practice concerning levels above which ``taking''
might occur. SPL is often referred to as rms or ``root mean square''
pressure, averaged over the pulse duration. As noted above, the rms
received levels that are used as impact criteria for marine mammals are
not directly comparable to pulse energy (SEL). The SPL (i.e., rms sound
pressure) for a given pulse is typically 10 - 15 dB higher than the SEL
value for the same pulse as measured at the same location (Greene et
al., 1997; McCauley et al., 1998; 2000). For this project, L-DEO
assumes that rms pressure levels of received seismic pulses would be 10
dB higher than the SEL values predicted by L-DEO's model. Thus, the L-
DEO assumes that 170 dB SEL can be viewed as 180 dB rms. NMFS considers
that this assumption is valid.
It should be noted that neither the SEL nor the SPL (rms) measure
is directly comparable to the peak or peak-to-peak pressure levels
normally used by geophysicists to characterize source levels of
airguns. Peak and peak-to-peak pressure levels for airgun pulses are
always higher than the rms dB referred to in much of the biological
literature (Greene et al., 1997; McCauley et al., 1998; 2000). For
example, a measured received level of 160 dB rms in the far field would
typically correspond to a peak measurement of 170 - 172 dB re 1
microPa, and to a peak-to-peak measurement of 176 - 178 dB, as measured
for the same pulse received at the same location (Greene et al., 1997;
McCauley et al., 1998; 2000). The precise 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. However, the
rms level is always lower than the peak or peak-to-peak level, and
higher than the SEL value, for an airgun-type source.
Empirical data concerning 190, 180, 170, and 160 dB (rms) isopleths
in deep and shallow water were acquired for various airgun
configurations during the acoustic calibration study of the Ewing's 20-
airgun, 8,600-in\3\ array in 2003 (Tolstoy et al., 2004a; 2004b). The
results showed that radii around the airguns where the received level
was 180 dB re 1 microPa (rms), the onset point for estimating temporary
hearing threshold shift (TTS) in cetaceans (NMFS, 2000), varied with
water depth. Similar depth-related variation is likely for 190-dB, the
onset point used for estimating TTS in pinnipeds, although these were
not measured. The empirical data indicated that, for deep water (>1,000
m, or 3,280 ft), the L-DEO model overestimates the received sound
levels at a given distance (Tolstoy et al., 2004a; 2004b). However, to
be conservative, the Ewing's modeled distances would be applied to
deep-water areas during the proposed study. As very few, if any,
mammals are expected to occur below 2,000 m (6,562 ft), this depth was
used as the maximum relevant depth.
For the proposed programs in the ETP, the modeled distances are
used to estimate deep-water mitigation safety zones; no correction
factors are necessary because all activities will take place in deep
(>2,000 m, or 6,562 ft) water. The 180 and 190 dB re 1 microPa (rms)
distances define the safety criteria, used for mitigation for cetaceans
and pinnipeds, respectively.
The predicted distances to which sound levels higher than 190, 180,
and 160 dB re 1 microPa (rms) could be received, based on the model
calculation, are shown in Table 2.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Predicted RMS Radii (m)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source and Volume Min. Water Depth 190 dB 160 dB 180 dB
--------------------------------------------------------------------------------------------------------------------------------------------------------
Single Bolt airgun (40 in\3\) 3000 m 12 40 385
--------------------------------------------------------------------------------------------------------------------------------------------------------
36-airgun array: 3 strings (4950 3000 m 200 650 4400
in\3\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
36-airgun array: 2 strings (3300 2000 m 140 450 3800
in\3\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 2. Predicted distances to which sound levels higher than 190, 180, and 160 dB re 1 microPa (rms) could be received from the airgun array and
single airgun planned for use during the surveys in the ETP.
Bathymetric Sonar and Sub-bottom Profiler
Along with the airgun operations, two additional acoustical data
acquisition systems would be operated during parts of the Langseth's
cruises. The ocean floor would be mapped with the 12-kHz Kongsberg
Simrad EM 120 MBB sonar, and a 2.5 - 7 kHz sub-bottom profiler would
also be operated along with the MBB sonar. These sound sources would be
operated from the Langseth, at times simultaneously with the airgun
array.
The Kongsberg Simrad EM 120 operates at 11.25 - 12.6 kHz and would
be mounted in a sonar pod hung below the hull of the Langseth. The
beamwidth is 1o fore-aft and 150[deg] athwartship. The maximum source
level is 242 dB re 1 microPa at 1 m (rms). For deep-water operation,
each ``ping'' consists of nine successive fan-shaped transmissions,
each 15 ms in duration and each ensonifying a sector that extends
1[deg] fore-aft. The nine successive transmissions span an overall
cross-track angular extent of about 150[deg], with 16 ms gaps between
the pulses for successive sectors. A receiver in the overlap area
between two sectors would receive two 15-ms pulses separated by a 16-ms
gap. In shallower water, the pulse duration is reduced to 2 ms, and the
number of transmit beams is also reduced. The ping interval varies with
water depth, from ~5 s at 1,000 m (3,280 ft) to 20 s at 4,000 m (13,123
ft).
The sub-bottom profiler is normally operated to provide information
about the sedimentary features and the bottom topography that is
simultaneously being mapped by the MBB sonar. The energy from the sub-
bottom profiler is directed
[[Page 24226]]
downward by a 3.5-kHz transducer in the hull of the Langseth. The
output varies with water depth from 50 watts in shallow water to 800
watts in deep water. Pulse interval is 1 second but a common mode of
operation is to broadcast five pulses at 1-s intervals followed by a 5-
s pause.
Comments and Responses
A notice of receipt and request for public comment on the
application and proposed authorization was published on March 5, 2008
(73 FR 11874). During the 30-day public comment period, NMFS received
the following comments from the Marine Mammal Commission (Commission).
Comment 1: The Commission recommends to extend to one hour the
monitoring period imposed prior to the initiation of seismic activities
and resumption of airgun activities after a power-down.
Response: NMFS acknowledges that several species of deep-diving
cetaceans are capable of remaining underwater for more than 30 minutes.
However, for the following reasons, NMFS believes that 30 minutes is an
adequate duration for the monitoring period prior to the start-up of
airguns: (1) because the Langseth is required to ramp-up, the time of
monitoring prior to start-up of any but the smallest array is
effectively longer than 30 minutes (i.e., ramp-up will begin with the
smallest gun in the array and airguns will be added in a sequence such
that the source level of the array will increase in steps not exceeding
approximately 6 dB per 5-min period over a total duration of 20-40
min); (2) L-DEO decides to conduct marine mammal monitoring during
transient even though the airguns are not in operation, so that all
safety redii will be under monitoring prior to the 30-min observation
period anyway; and (3) the majority of the species that may be exposed
do not stay underwater more than 30 minutes.
Comment 2: The Commission recommends that NMFS require marine
mammal monitoring be made during all ramp-up procedures to gather data
regarding the effectiveness of ramp-up as a mitigation tool.
Response: NMFS concurs with the Commission's recommendation that
all ramp-up procedures will be visually monitored when visibility
permits. For ramp-up during low-light hours, visual monitoring is
ineffective, nonetheless, passive acoustic monitoring will be
implemented during all ramp-up procedures.
Description of Marine Mammals in the Activity Area
A total of 34 cetacean species and 6 species of pinnipeds are known
to or may occur in the ETP. Of the 34 cetacean species, 27 are likely
to occur in the proposed survey area.
Five of those 27 cetacean species are listed under the U.S.
Endangered Species Act (ESA) as endangered: sperm whale (Physeter
macrocephalus), humpback whale (Megaptera novaeangliae), blue whale
(Balaenoptera musculus), fin whale (B. physalus), and sei whale (B.
borealis).
The other 22 species that are likely to occur in the proposed
survey areas are: Minke whale (B. acutorostrata), Bryde's whale (B.
edeni), Pygmy sperm whale (Kogia breviceps), Dwarf sperm whale (K.
simus), Cuvier's beaked whale (Ziphius cavirostris), Longman's beaked
whale (Indopacetus pacificus), Pygmy beaked whale (Mesoplodon
peruvianus), Ginkgo-toothed beaked whale (M. ginkgodens), Blainville's
beaked whale (M. densirostris), Rough-toothed dolphin (Steno
bredanensis), Bottlenose dolphin (Tursiops truncatus), Pantropical
spotted dolphin (Stenella attenuata), Spinner dolphin (S.
longirostris), Striped dolphin (S. coeruleoalba), Fraser's dolphin
(Lagenodelphis hosei), Short-beaked common dolphin (Delphinus delphis),
Risso's dolphin (Grampus griseus), Melon-headed whale (Peponocephala
electra), Pygmy killer whale (Feresa attenuata), False killer whale
(Pseudorca crassidens), Killer whale (Orcinus orca), and Short-finned
pilot whale (Globicephala macrorhynchus).
A detailed description of the biology, population estimates, and
distribution and abundance of these species is provided in the L-DEO's
IHA application and in the March 5, 2008 Federal Register notice (73 FR
11874). Therefore, it is not repeated here. Additional information
regarding the stock assessment of these species are be found in NMFS
Pacific Marine Mammal Stock Assessment Report (Carretta et al., 2007),
and can also be accessed via the following URL link: https://
www.nmfs.noaa.gov/pr/pdfs/sars/po2006.pdf.
Summary of Potential Effects of Airgun Sounds on Marine Mammals
The effects of sounds from airguns might include one or more of the
following: tolerance, masking of natural sounds, behavioral
disturbance, and at least in theory, temporary or permanent hearing
impairment, or non-auditory physical or physiological effects
(Richardson et al., 1995). These effects are discussed below, but also
in further detail in Appendix B of L-DEO's application.
The potential effects of airguns discussed below are presented
without consideration of the required mitigation measures described
below. When these measures are taken into account, it is unlikely that
this project would result in temporary, or especially, permanent
hearing impairment or any non-auditory physical or physiological
effects.
Tolerance
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
A summary of the characteristics of airgun pulses is provided in
Appendix B of L-DEO's application. Studies have also shown that marine
mammals at distances more than a few kilometers from operating seismic
vessels often show no apparent response (tolerance) (Appendix B (e)).
That is often true even in cases when the pulsed sounds must be readily
audible to the animals based on measured received levels and the
hearing sensitivity of that mammal group. Although various baleen
whales, toothed whales, and (less frequently) pinnipeds have been shown
to react behaviorally to airgun pulses under some conditions, at other
times mammals of all three types have shown no overt reactions. In
general, pinnipeds and small odontocetes seem to be more tolerant of
exposure to airgun pulses than are baleen whales.
Masking
Masking effects of pulsed sounds (even from large arrays of
airguns) on marine mammal calls and other natural sounds are expected
to be limited, although there are very few specific data of relevance.
Some whales are known to continue calling in the presence of seismic
pulses. Their calls can be heard between the seismic pulses (e.g.,
Richardson et al., 1986; McDonald et al., 1995; Greene et al., 1999;
Nieukirk et al., 2004). Although there has been one report that sperm
whales ceased calling when exposed to pulses from a very distant
seismic ship (Bowles et al., 1994), a more recent study reports that
sperm whales off northern Norway continued calling in the presence of
seismic pulses (Madsen et al., 2002). That has also been shown during
recent work in the Gulf of Mexico (Tyack et al., 2003; Smultea et al.,
2004). Masking effects of seismic pulses are expected to be negligible
in the case of the smaller odontocete cetaceans, given the intermittent
nature of seismic pulses. Dolphins and porpoises commonly are
[[Page 24227]]
heard calling while airguns are operating (e.g., Gordon et al., 2004;
Smultea et al., 2004; Holst et al., 2005a; 2005b). Also, the sounds
important to small odontocetes are predominantly at much higher
frequencies than are airgun sounds. Masking effects, in general, are
discussed further in LDEO's application Appendix B (d).
Disturbance Reactions
Disturbance includes a variety of effects, including subtle changes
in behavior, more conspicuous changes in activities, and displacement.
Reactions to sound, if any, depend on species, state of maturity,
experience, current activity, reproductive state, time of day, and many
other factors. If a marine mammal does react briefly to an underwater
sound by slightly 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 the species as a whole. However, if a sound
source displaces a marine mammal(s) from an important feeding or
breeding area for a prolonged period, impacts on the animal(s) could be
significant.
There are many uncertainties in predicting the quantity and types
of impacts of noise on marine mammals. NMFS uses exposures to 180 and
190 dB re 1 microPa rms to estimate the number of animals that may be
harassed by a particular sound source in a given area (and also uses
those SPLs for use in the development of shutdown zones for
mitigation). These estimates are based on behavioral observations
during studies of several species. However, information is lacking for
many species. Detailed studies have been done on humpback, gray, and
bowhead whales, and on ringed seals. Less detailed data are available
for some other species of baleen whales, sperm whales, and small
toothed whales.
Hearing Impairment and Other Physical Effects
Temporary or permanent hearing impairment is a possibility when
marine mammals are exposed to very strong sounds, but there has been no
specific documentation of this for marine mammals exposed to sequences
of airgun pulses. NMFS' incidental take authorizations generally
protect against exposure to impulsive sounds greater than 180 and 190
dB re 1 microPa (rms), for cetaceans and pinnipeds, respectively (NMFS,
2000). Those criteria have been used in defining the safety (shut down)
radii planned for the proposed seismic surveys.
Several aspects of the monitoring and mitigation measures required
for this project are designed to detect marine mammals occurring near
the airguns to avoid exposing them to sound pulses that might, at least
in theory, cause hearing impairment (see Mitigation and Monitoring
section below). In addition, many cetaceans are likely to show some
avoidance of the area with high received levels of airgun sound. In
those cases, the avoidance responses of the animals themselves will
reduce or (most likely) avoid any possibility of hearing impairment.
Non-auditory physical effects may also occur in marine mammals
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that theoretically might
occur in mammals close to a strong sound source include stress,
neurological effects, bubble formation, and other types of organ or
tissue damage. It is possible that some marine mammal species (e.g.,
beaked whales) may be especially susceptible to injury and/or stranding
when exposed to strong pulsed sounds. However, there is no definitive
evidence that any of these effects occur even for marine mammals in
close proximity to large arrays of airguns. It is unlikely that any
effects of these types would occur during the proposed project given
the brief duration of exposure of any given mammal, and the planned
monitoring and mitigation measures (see below).
Strandings and Mortality
Marine mammals close to underwater detonations of high explosive
can be killed or severely injured, and the auditory organs are
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995).
Airgun pulses are less energetic and have slower rise times, and there
is no proof that they can cause serious injury, death, or stranding
even in the case of large airgun arrays. However, the association of
mass strandings of beaked whales with naval exercises involving mid-
frequency sonar and, in one case, an L-DEO seismic survey, has raised
the possibility that beaked whales exposed to strong pulsed sounds may
be especially susceptible to injury and/or behavioral reactions that
can lead to stranding.
Seismic pulses and mid-frequency sonar pulses are quite different.
Sounds produced by airgun arrays are broadband with most of the energy
below 1 kHz. Typical military mid-frequency sonars operate at
frequencies of 2-10 kHz, generally with a relatively narrow bandwidth
at any one time. Thus, it is not appropriate to assume that there is a
direct connection between the effects of military sonar and seismic
surveys on marine mammals. However, evidence that sonar pulses can, in
special circumstances, lead to physical damage and mortality (NOAA and
USN, 2001; Jepson et al., 2003; Fernandez et al., 2005a), even if only
indirectly, suggests that caution is warranted when dealing with
exposure of marine mammals to any high-intensity pulsed sound.
In September, 2002, there was a stranding of two Cuvier's beaked
whales in the Gulf of California, Mexico, when the L-DEO vessel Maurice
Ewing was operating a 20 airgun, 8,490 in\3\ airgun array in the
general area. The link between the stranding and the seismic surveys
was inconclusive and not based on any physical evidence (Hogarth, 2002;
Yoder, 2002). Nonetheless, that together with the incidents involving
beaked whale strandings near naval exercises suggests a need for
caution in conducting seismic surveys in areas occupied by beaked
whales. No injuries of beaked whales are anticipated during the
proposed study, due to the required monitoring and mitigation measures.
Possible Effects of Multibeam Bathymetric (MBB) Sonar Signals
The Kongsberg Simrad EM 120 12-kHz sonar will be operated from the
source vessel at some times during the planned study. As discussed
above, sounds from the MBB sonar are very short pulses, occurring for
15 ms once every 5 - 20 s, depending on water depth. Most of the energy
in the sound pulses emitted by this MBB sonar is at frequencies
centered at 12 kHz. The beam is narrow (1[deg]) in fore-aft extent and
wide (150[deg]) in the cross-track extent. Each ping consists of nine
successive fan-shaped transmissions (segments) at different cross-track
angles. Any given mammal at depth near the trackline would be in the
main beam for only one or two of the nine segments. Also, marine
mammals that encounter the Kongsberg Simrad EM 120 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
15 ms pulse (or two pulses if in the overlap area). Similarly, Kremser
et al. (2005) noted that the probability of a cetacean swimming through
the area of exposure when an MBB sonar 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 be subjected to sound
levels that could cause TTS.
[[Page 24228]]
Navy sonars that have been linked to avoidance reactions and
stranding of cetaceans (1) generally have a longer pulse duration than
the Kongsberg Simrad EM 120, and (2) are often directed close to
horizontally vs. downward for the Kongsberg Simrad EM 120. The area of
possible influence of the EM 120 is much smaller-a narrow band below
the source vessel. The duration of exposure for a given marine mammal
can be much longer for a Navy sonar. Possible effects of sonar on
marine mammals are outlined below.
Possible Effects of Sub-bottom Profiler Signals
A sub-bottom profiler would be operated from the source vessel
during the planned study. As discussed before, sounds from the sub-
bottom profiler are very short pulses, occurring for 1, 2, or 4 ms once
every second. Most of the energy in the sound pulses emitted by this
sub-bottom profiler is at mid frequencies, centered at 3.5 kHz. The
beam width is approximately 30[deg] and is directed downward.
Sound levels have not been measured directly for the sub-bottom
profiler used by the Langseth, but Burgess and Lawson (2000) measured
sounds propagating more or less horizontally from a similar unit with
similar source output (205 dB re 1 microPa at 1 m). The 160 and 180 dB
re 1 microPa (rms) radii, in the horizontal direction, were estimated
to be, respectively, near 20 m (65.6 ft) and 8 m (26.2 ft) from the
source, as measured in 13 m (42.7 ft) water depth. The corresponding
distances for an animal in the beam below the transducer would be
greater, on the order of 180 m (591 ft) and 18 m (59 ft), respectively,
assuming spherical spreading.
The sub-bottom profiler on the Langseth has a stated maximum source
level of 204 dB re 1 microPa at 1 m. Thus, the received level would be
expected to decrease to 160 and 180 dB about 160 m (525 ft) and 16 m
(53 ft) below the transducer, respectively, again assuming spherical
spreading. Corresponding distances in the horizontal plane would be
lower, given the directionality of this source (30[deg] beam width) and
the measurements of Burgess and Lawson (2000).
Numbers of Marine Mammals Estimated to be Taken
All anticipated takes would be takes by Level B harassment,
involving temporary changes in behavior. The required mitigation
measures will prevent the possibility of injurious takes. The basis for
the take estimates from the airgun array is described in this section.
The anticipated radii of influence of the MBB sonar are less than
those for the airgun array. It is assumed that, during simultaneous
operations of the airgun array and sonar, any marine mammals close
enough to be affected by the sonar would already be affected by the
airguns. However, whether or not the airguns are operating
simultaneously with the sonar, marine mammals are not expected to be
``taken'' by the sonar given its characteristics (e.g., narrow
downward-directed beam) and other considerations described above.
Therefore, no additional allowance is included for animals that might
be affected by sound sources other than airguns.
Basis for Take Estimates
As discussed above, several extensive marine mammal surveys have
been conducted in the ETP over numerous years. The most comprehensive
data available for the regions encompassing the proposed survey areas
are the Ferguson and Barlow (2001) data collected from late July to
early December 1986-1996.
Because the proposed QDG survey is planned for April-May 2008, data
collected by Ferguson and Barlow (2001) in July - December may not be
as representative for the QDG survey. Again, however, it is the best
available information. For some species, the densities derived from
past surveys may not be representative of the densities that would be
encountered during the actual proposed seismic studies. For example,
the density of cetaceans sighted during L-DEO's 2003 Hess Deep survey
was considerably lower (only one sighting) than the densities
anticipated to occur there based on the Ferguson and Barlow (2001)
data. The Hess Deep survey occurred in mid-July, and was apparently not
well represented by the Ferguson and Barlow (2001) data collected
during the fall, beginning just after the Hess Deep survey.
Despite the above caveats, the Ferguson and Barlow (2001) data
still represent the best available data for estimating numbers of
animals potentially exposed to the proposed seismic sounds. Average and
maximum densities for marine mammals from Ferguson and Barlow (2001)
were calculated for each of the project areas based on encompassing and
adjacent survey blocks. Maximum densities were either the highest
estimated density in any of the blocks or, if that number was zero, the
average group size for that species. The densities reported in Ferguson
and Barlow (2001) were corrected for both detectability [f(0)] and
availability [g(0)] biases, and therefore, are relatively unbiased.
Estimated Number of Takes by Harassment
The number of individuals that may be exposed to airgun sounds with
received levels higher than 160 dB re 1 microPa (rms) on one or more
occasions can be estimated by considering the total marine area that
would be within the 160-dB radius around the operating airgun array on
at least one occasion. In the QDG survey, the proposed seismic lines do
not run parallel to each other in close proximity, and only one
transect line might be surveyed a second time, which minimizes the
number of times an individual mammal may be exposed during the survey.
In the EPR survey, the seismic lines are parallel and in close
proximity, and the entire grid may be surveyed more than twice, which
may result in individuals being exposed on two or more occasions. It is
not known how much time will pass between the first and the second
transit along each line, so it is also possible that different marine
mammals could occur in the area during the second pass. Thus, the best
estimates in this section are based on a single pass of all survey
lines (including turns), and maximum estimates are based on maximum
densities, i.e., the highest single-block density among all of the
blocks used in the calculations. Tables 3 and 4 show the best and
maximum estimates of the number of marine mammals that could
potentially be affected during the EPR and QDG seismic surveys,
respectively.
The number of individuals potentially exposed to 160 dB re 1
microPa (rms) or higher in each area was calculated by multiplying
The expected species density, either ``mean'' (i.e., best
estimate) or ``maximum'' (maximum estimate) times by
The anticipated minimum area to be ensonified to that
level during airgun operations.
The area expected to be ensonified was determined by entering the
planned survey lines into a MapInfo Geographic Information System
(GIS), using the GIS to identify the relevant areas by ``drawing'' the
applicable 160-dB buffer around each seismic line and then calculating
the total area within the buffers. Areas where overlap occurred
(because of intersecting lines) were included only once to determine
the minimum area expected to be ensonified to higher than 160 dB re 1
microPa at least once.
[[Page 24229]]
----------------------------------------------------------------------------------------------------------------
Number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
-----------------------------------------------------------------------------------------------------------------
Percent of regional
Species Best estimate population based on best Maximum estimate
estimate
----------------------------------------------------------------------------------------------------------------
Humpback whale 0 0.00 2
----------------------------------------------------------------------------------------------------------------
Minke whale 0 NA 1
----------------------------------------------------------------------------------------------------------------
Bryde's whale 3 0.02 7
----------------------------------------------------------------------------------------------------------------
Sei whale 0 NA 2
----------------------------------------------------------------------------------------------------------------
Fin whale 0 0.00 2
----------------------------------------------------------------------------------------------------------------
Blue whale 0 0.03 1
----------------------------------------------------------------------------------------------------------------
Sperm whale 2 0.01 4
----------------------------------------------------------------------------------------------------------------
Pygmy sperm whale 0 NA 1
----------------------------------------------------------------------------------------------------------------
Dwarf sperm whale 66 0.59 87
----------------------------------------------------------------------------------------------------------------
Cuvier's beaked whale 16 0.08 30
----------------------------------------------------------------------------------------------------------------
Longman's beaked whale 0 0.00 4
----------------------------------------------------------------------------------------------------------------
Pygmy beaked whale 0 NA 4
----------------------------------------------------------------------------------------------------------------
Blainville's beaked whale 0 NA 4
----------------------------------------------------------------------------------------------------------------
Mesoplodon sp. 8 0.03 .......................
----------------------------------------------------------------------------------------------------------------
Rough-toothed dolphin 27 0.02 109
----------------------------------------------------------------------------------------------------------------
Bottlenose dolphin 18 0.01 38
----------------------------------------------------------------------------------------------------------------
Spotted dolphin 697 0.03 1327
----------------------------------------------------------------------------------------------------------------
Spinner dolphin 342 0.02 695
----------------------------------------------------------------------------------------------------------------
Striped dolphin 303 0.02 792
----------------------------------------------------------------------------------------------------------------
Fraser's dolphin 5 0.00 47
----------------------------------------------------------------------------------------------------------------
Short-beaked common dolphin 7 0.00 835
----------------------------------------------------------------------------------------------------------------
Risso's dolphin 18 0.01 53
----------------------------------------------------------------------------------------------------------------
Melon-headed whale 5 0.01 30
----------------------------------------------------------------------------------------------------------------
Pygmy killer whale 9 0.02 46
----------------------------------------------------------------------------------------------------------------
False killer whale 3 0.01 8
----------------------------------------------------------------------------------------------------------------
Killer whale 1 0.01 3
----------------------------------------------------------------------------------------------------------------
Short-finned pilot whale 20 0.01 41
----------------------------------------------------------------------------------------------------------------
Table 3. Estimates of the numbers of different individual marine mammals that might be exposed to sound levels >
160 dB re 1 microPa (rms) during L-DEO's proposed EPR seismic program in the ETP. The proposed sound source is
an 18-airgun array with a total volume of 3,300 in\3\. ''NA'' indicates that no percentage of population data
were available due to the lack of population estimate.
----------------------------------------------------------------------------------------------------------------
Number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
-----------------------------------------------------------------------------------------------------------------
Percent of regional
Species Best estimate population based on best Maximum estimate
estimate
----------------------------------------------------------------------------------------------------------------
Humpback whale 0 0.00 2
----------------------------------------------------------------------------------------------------------------
Minke whale 0 NA 1
----------------------------------------------------------------------------------------------------------------
Bryde's whale 3 0.02 7
----------------------------------------------------------------------------------------------------------------
Sei whale 0 NA 2
----------------------------------------------------------------------------------------------------------------
Fin whale 0 0.00 2
----------------------------------------------------------------------------------------------------------------
[[Page 24230]]
Blue whale 0 0.03 1
----------------------------------------------------------------------------------------------------------------
Sperm whale 4 0.01 13
----------------------------------------------------------------------------------------------------------------
Pygmy sperm whale 0 NA 1
----------------------------------------------------------------------------------------------------------------
Dwarf sperm whale 0 0.00 2
----------------------------------------------------------------------------------------------------------------
Cuvier's beaked whale 48 0.24 81
----------------------------------------------------------------------------------------------------------------
Longman's beaked whale 0 0.00 3
----------------------------------------------------------------------------------------------------------------
Pygmy beaked whale 0 NA 3
----------------------------------------------------------------------------------------------------------------
Blainville's beaked whale 0 NA 3
----------------------------------------------------------------------------------------------------------------
Mesoplodon sp. 7 0.03 .......................
----------------------------------------------------------------------------------------------------------------
Rough-toothed dolphin 24 0.02 166
----------------------------------------------------------------------------------------------------------------
Bottlenose dolphin 17 0.01 48
----------------------------------------------------------------------------------------------------------------
Spotted dolphin 468 0.02 1236
----------------------------------------------------------------------------------------------------------------
Spinner dolphin 226 0.01 431
----------------------------------------------------------------------------------------------------------------
Striped dolphin 482 0.03 599
----------------------------------------------------------------------------------------------------------------
Fraser's dolphin 43 0.01 151
----------------------------------------------------------------------------------------------------------------
Short-beaked common dolphin 30 0.00 2089
----------------------------------------------------------------------------------------------------------------
Risso's dolphin 16 0.01 68
----------------------------------------------------------------------------------------------------------------
Melon-headed whale 7 0.01 38
----------------------------------------------------------------------------------------------------------------
Pygmy killer whale 3 0.01 16
----------------------------------------------------------------------------------------------------------------
False killer whale 11 0.03 47
----------------------------------------------------------------------------------------------------------------
Killer whale 1 0.01 2
----------------------------------------------------------------------------------------------------------------
Short-finned pilot whale 35 0.02 105
----------------------------------------------------------------------------------------------------------------
Table 4. Estimates of the numbers of different individual marine mammals that might be exposed to sound levels >
160 dB re 1 microPa (rms) during L-DEO's proposed QDG seismic program in the ETP. The proposed sound source is
an 27-airgun array with a total volume of 4,950 in\3\. ''NA'' indicates that no percentage of population data
were available due to the lack of population estimate.
Applying the approach described above, 2,492 km\2\ (923 mi\2\)
would be within the 160-dB isopleth on one or more occasions during the
EPR survey, and 2,911 km\2\ (1,224 mi\2\) would be ensonified on one or
more occasions during the QDG survey. This approach does not allow for
turnover in the marine mammal populations in the study areas during the
course of the studies. That might underestimate actual numbers of
individuals exposed, although the conservative distances used to
calculate the area may offset this. In addition, the approach assumes
that no cetaceans would move away or toward the trackline as the
Langseth 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 160 dB re 1 microPa (rms) or higher.
The ``best estimate'' of the number of individual marine mammals
that might be exposed to seismic sounds with received levels of 160 dB
re 1 microPa (rms) or higher during the EPR survey includes 2
endangered whales (both sperm whales), 24 beaked whales, and 3 Bryde's
whales. Pantropical spotted, spinner, and striped dolphins are
estimated to be the most common species exposed; the best estimates for
those species are 697, 342, and 303, respectively. Estimates for other
species are lower (Table 3).
The ``best estimate'' of the number of individual marine mammals
that might be exposed to seismic sounds with received levels of 160 dB
re 1 microPa (rms) or higher during the QDG survey includes 5
endangered whales (4 sperm whales and 1 blue whale), 55 beaked whales,
and 6 Bryde's whales. Striped, spotted, and spinner dolphins are
estimated to be the most common species exposed; the best estimates for
those species are 482, 468, and 226, respectively. Estimates for other
species are lower (Table 4).
The ``best estimate'' of the total number of individual marine
mammals that might be exposed to seismic sounds with received levels of
160 dB re 1 microPa (rms) or higher for both surveys, along with the
percentage of regional population, is listed in Table 5. It includes
two ESA-listed species (6 sperm whales and 1 blue whale), 79
[[Page 24231]]
beaked whales, and 9 Bryde's whales. Striped, spotted, and spinner
dolphins are estimated to be the most common species exposed; the best
estimates for those species are 785, 1,165, and 568, respectively.
Estimates for other species are lower (Table 5).
Potential Impacts to Subsistence Harvest of Marine Mammals
The proposed activities will not have any impact on the
availability of the species or stocks for subsistence use described in
section 101(a)(5)(D)(i)(II).
------------------------------------------------------------------------
Total number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
-------------------------------------------------------------------------
Percent of regional
Species Best estimate population based on
best estimate
------------------------------------------------------------------------
Humpback whale 0 0.00
------------------------------------------------------------------------
Minke whale 0 NA
------------------------------------------------------------------------
Bryde's whale 9 0.07
------------------------------------------------------------------------
Sei whale 0 NA
------------------------------------------------------------------------
Fin whale 0 0.00
------------------------------------------------------------------------
Blue whale 1 0.04
------------------------------------------------------------------------
Sperm whale 6 0.02
------------------------------------------------------------------------
Pygmy sperm whale 0 NA
------------------------------------------------------------------------
Dwarf sperm whale 66 0.59
------------------------------------------------------------------------
Cuvier's beaked whale 64 0.32
------------------------------------------------------------------------
Longman's beaked whale 0 0.00
------------------------------------------------------------------------
Pygmy beaked whale 0 NA
------------------------------------------------------------------------
Blainville's beaked whale 0 NA
------------------------------------------------------------------------
Mesoplodon sp. 15 0.06
------------------------------------------------------------------------
Rough-toothed dolphin 51 0.04
------------------------------------------------------------------------
Bottlenose dolphin 35 0.02
------------------------------------------------------------------------
Spotted dolphin 1,165 0.05
------------------------------------------------------------------------
Spinner dolphin 568 0.03
------------------------------------------------------------------------
Striped dolphin 785 0.05
------------------------------------------------------------------------
Fraser's dolphin 48 0.01
------------------------------------------------------------------------
Short-beaked common dolphin 37 0.00
------------------------------------------------------------------------
Risso's dolphin 34 0.02
------------------------------------------------------------------------
Melon-headed whale 12 0.02
------------------------------------------------------------------------
Pygmy killer whale 12 0.03
------------------------------------------------------------------------
False killer whale 14 0.04
------------------------------------------------------------------------
Killer whale 2 0.02
------------------------------------------------------------------------
Short-finned pilot whale 55 0.03
------------------------------------------------------------------------
Table 5. Estimates of the numbers of different individual marine mammals
that might be exposed to sound levels > 160 dB re 1 microPa (rms)
during L-DEO's two proposed seismic program in the ETP. ''NA''
indicates that no percentage of population data were available due to
the lack of population estimate.
Potential Impacts on Habitat and Prey
The proposed seismic survey would not result in any permanent or
significant impact on habitats used by marine mammals, or to the food
sources they use. The main impact issue associated with the proposed
activity would be temporarily elevated noise levels and the associated
direct effects on marine mammals, as discussed above. The following
sections briefly review effects of airguns on fish and invertebrates
(both marine mammal prey sources), and more details are
[[Page 24232]]
included in Appendices C and D of the L-DEO's IHA application,
respectively.
Effects on Fish
There are three types of potential effects of exposure to seismic
surveys: (1) pathological, (2) physiological, and (3) behavioral.
Pathological effects involve lethal and temporary or permanent sub-
lethal injury. Physiological effects involve temporary and permanent
primary and secondary stress responses, such as changes in levels of
enzymes and proteins. Behavioral effects refer to temporary and (if
they occur) permanent changes in exhibited behavior (e.g., startle and
avoidance behavior). The three categories are interrelated in complex
ways. For example, it is possible that certain physiological and
behavioral changes could potentially lead to an ultimate pathological
effect on individuals (i.e., mortality).
The 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. For a given sound to
result in hearing loss, the sound must exceed, by some specific amount,
the hearing threshold of the fish for that sound (Popper, 2005). The
consequences of temporary or permanent hearing loss in individual fish
on a fish population is unknown; however, it likely depends on the
number of individuals affected and whether critical behaviors involving
sound (e.g. predator avoidance, prey capture, orientation and
navigation, reproduction, etc.) are adversely affected. McCauley et al.
(2003)
