[Federal Register Volume 73, Number 44 (Wednesday, March 5, 2008)]
[Notices]
[Pages 11874-11886]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-4237]
-----------------------------------------------------------------------
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XF15
Incidental Takes of Marine Mammals During Specified Activities;
Marine Geophysical Surveys in the Eastern Tropical Pacific Ocean in
2007
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental take authorization; request for
comments.
-----------------------------------------------------------------------
SUMMARY: NMFS has received an application from the Lamont-Doherty Earth
Observatory (L-DEO) for an Incidental Harassment Authorization (IHA) to
take small numbers of marine mammals, by harassment, incidental to
conducting two marine seismic surveys in the Eastern Tropical Pacific
Ocean (ETP) during 2008. Under the Marine Mammal Protection Act (MMPA),
NMFS is requesting comments on its proposed IHA for these activities.
DATES: Comments and information must be received no later than April 4,
2008.
ADDRESSES: Comments on the application should be addressed to P.
Michael Payne, Chief, Permits, Conservation and Education Division,
Office of Protected Resources, National Marine Fisheries Service, 1315
East-West Highway, Silver Spring, MD 20910-3225. The mailbox address
for providing e-mail comments is [email protected]. NMFS is not
responsible for e-mail comments sent to addresses other than the one
provided here. Comments sent via e-mail, including all attachments,
must not exceed a 10-megabyte file size.
A copy of the application containing a list of the references used
in this document may be obtained by writing to the address specified
above, telephoning the contact listed below (see FOR FURTHER
INFORMATION CONTACT), or visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm.
Documents cited in this notice may be viewed, by appointment,
during regular business hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT: 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 authorizations 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 National Science
Foundation (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
[[Page 11875]]
understand better the behavior of earthquakes and faults in general.
The Discovery and Gofar faults generate more foreshocks in the 1,000 s
before large earthquakes than anywhere else in the world. Year-long
Ocean Bottom Seismometer (OBS) deployments during the survey are
designed to use those foreshock sequences to answer questions about how
large earthquakes nucleate. Despite accommodating the same amount of
plate motion (14 cm/year, or 5.5 in/year) and being composed of similar
oceanic crust, the Discovery and Quebrada faults differ in their
ability to generate large earthquakes: the Discovery fault routinely
generates earthquakes >5.5 in magnitude, whereas the Quebrada fault has
had only one such event in the last 25 years. Refraction images of the
material properties in both fault zones will show if some subtle
difference (e.g., in hydrothermal alteration of the rocks) is
responsible for the difference in seismogenic behavior.
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).
Much is already known about processes at the EPR, but the proposed
survey will provide an understanding of how the magmatic system, which
is known at large spatial scales (1-100 km, or 0.62-62 mi), is coupled
to volcanic/hydrothermal/biological systems, which are known at
comparatively small spatial scales (0.001-1 km, or 0.00062-0.62 mi).
The survey would also provide an understanding of the relationships
between the temporal variations in subsurface magma systems and highly
transient phenomena observed at the seafloor like faulting, volcanism,
and hydrothermal venting.
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 proposed QDG seismic survey would last for approximately 6
days, and the proposed EPR seismic survey would last for approximately
39 days. All activities would be conducted in the period between April
and August, 2008. The exact dates of the activities will be depend on
ship scheduling, weather conditions, repositioning, streamer operations
and adjustments, airgun deployment, or the need to repeat some lines if
data quality is substandard.
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 Gal[aacute]pagos 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.
Vessel Specifications
The Langseth would tow the airgun array and, at times, up to four
6-km (3.7-mi) streamers containing hydrophones along predetermined
lines. The operation speed during seismic acquisition is typically
7.4--9.3 km/h (4--5 kt). When not towing seismic survey gear, the
Langseth can cruise at 20--24 km/h (11--13 kt).
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.
[[Page 11876]]
Table 1.--L-DEO Airgun Configuration and Specification of Each Source
Planned for Use in the Proposed Projects
------------------------------------------------------------------------
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.
------------------------------------------------------------------------
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 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.
[[Page 11877]]
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
----------------------------------------------------------------------------------------------------------------
Predicted RMS radii (m)
Source and volume Min. water --------------------------------------
depth (m) 190 dB 180 dB 160 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun (40 in\3\)............................... 3000 12 40 385
36-airgun array: 3 strings (4950 in\3\)..................... 3000 200 650 4400
36-airgun array: 2 strings (3300 in\3\)..................... 2000 140 450 3800
----------------------------------------------------------------------------------------------------------------
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 1[deg] 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 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.
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 are provided in the L-DEO's
IHA application. 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: http://www.nmfs.noaa.gov/pr/pdfs/sars/po2006.pdf.
The most extensive regional distribution and abundance data that
encompass the entire study area come primarily from multi-year vessel
surveys conducted in the wider ETP by the NMFS Southwest Fisheries
Science Center. Information on the distribution of cetaceans inhabiting
the ETP has been summarized in several studies (e.g., Polacheck, 1987;
Wade and Gerrodette, 1993; Ferguson and Barlow, 2001), and is also
described in detail in the L-DEO's IHA application.
Seven species, although present in the wider ETP, likely would not
be found in the proposed seismic survey areas. These species are:
Pacific white-sided dolphins (Lagenorhynchus obliquidens), Baird's
beaked whales (Berardius bairdii), Long-beaked common dolphins
(Delphinus capensis), Dusky dolphins (L. obscurus), southern right
whale dolphins (Lissodelphis peronii), Burmeister's porpoises (Phocoena
spinipinnis), and long-finned pilot whales (Globicephala melas)
(Leatherwood et al., 1991; Van Waerebeek et al., 1991; Heyning and
Perrin, 1994; Brownell and Clapham, 1999; Ferguson and Barlow, 2001;
Olson and Reilly, 2002). Accordingly, those species are not considered
any further.
Six species of pinnipeds are known to occur in the ETP: The
Guadalupe fur seal (Arctocephalus townsendi), California sea lion
(Zalophus californianus), Gal[aacute]pagos sea lion (Z. wollebaeki),
Gal[aacute]pagos fur seal (A. galapagoensis), southern sea lion (Otaria
flavescens), and South American fur seal (A. australis). However,
pinnipeds likely would not be encountered during the proposed seismic
surveys. Therefore, they are not considered further here.
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 proposed
[[Page 11878]]
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 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's 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 proposed
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,
[[Page 11879]]
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 proposed 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.
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[deg] 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 proposed mitigation
measures will prevent the possibility of injurious takes. The estimates
of take are based on consideration of the number of marine mammals that
might be disturbed by approximately 654 km (406 mi) of seismic surveys
at the QDG study site and approximately 7,992 km (4,967 mi) of seismic
surveys at the EPR study site in the ETP.
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.
There is some uncertainty about how representative the data are for
the QDG survey because of the time of year and the validity of the
assumptions used below to estimate the potential take by harassment.
The data derived from marine mammals surveys that were conducted from
the time of year that is different from the proposed QDG seismic
surveys. However, the approach used here is based on the best available
data. To provide some allowance for those uncertainties, ``best
estimates'' and ``maximum estimates'' of the numbers potentially
affected have been derived based on the average and maximum estimates
of densities reported by Ferguson and Barlow (2001) for the survey
blocks encompassing each project study area as presented in Tables 3
and 4 of L-DEO's application.
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
[[Page 11880]]
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.
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 Maximum estimate
on best 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
----------------------------------------------------------------------------------------------------------------
[[Page 11881]]
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
a 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]
----------------------------------------------------------------------------------------------------------------
Number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
-----------------------------------------------------------------------------------------------------------------
Percent of
regional
Species Best estimate population based Maximum estimate
on best estimate
----------------------------------------------------------------------------------------------------------------
Humpback whale......................................... 0 0.00 1
Minke whale............................................ 0 NA 1
Bryde's whale.......................................... 6 0.05 24
Sei whale.............................................. 0 NA 2
Fin whale.............................................. 0 0.00 2
Blue whale............................................. 1 0.04 3
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
----------------------------------------------------------------------------------------------------------------
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.
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 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).
[[Page 11882]]
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]
------------------------------------------------------------------------
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
------------------------------------------------------------------------
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).
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,
and more details are 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
microPa\2\-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 about one-quarter wavelength (Urick,
1983; Rogers and Cox, 1988).
[[Page 11883]]
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 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, thereby justifying further discussion and
analysis of this issue. The three types of potential effects of
exposure to seismic surveys on marine invertebrates are pathological,
physiological, and behavioral. Based on the physical structure of their
sensory organs, marine invertebrates appear to be specialized to
respond to particle displacement components of an impinging sound field
and not to the pressure component (Popper et al., 2001).
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, 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).
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[deg] 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.
[[Page 11884]]
Proposed Monitoring and Mitigation Measures
Monitoring
L-DEO proposes to sponsor marine mammal monitoring during the
present project, in order to implement NMFS's proposed mitigation and
monitoring measures.
(1) Proposed 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 in\3\ 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
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 start-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 startups. 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 binoculars
(e.g., 7 x 50 Fujinon), Big-eye binoculars (25 x 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.
SEAMAP (Houston, TX) will be used as the primary acoustic
monitoring system. This system was also used during previous L-DEO
seismic cruises (e.g., Smultea et al., 2004, 2005; Holst et al., 2005a;
2005b). The PAM system consists of hardware (i.e., hydrophones) and
software. The ``wet end'' of the SEAMAP system consists of a low-noise,
towed hydrophone array that is connected to the vessel by a ``hairy''
faired 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. The lead-in from the hydrophone
array is approximately 400 m (1,312 ft) long, and the active part of
the hydrophone array is approximately 56 m (184 ft) long. The
hydrophone array is typically towed at depths about 30 m (98 ft).
Dedicated or clean power supply and grounding should be used to
operate both hydrophone system and sound acquisition computer(s).
Proper steps should be taken to ensure appropriate shielding from any
electronic noise and electro magnetic interferences (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 and when the Langseth is underway
while the airguns are not operating. One MMO will monitor the acoustic
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. All MMOs are
expected to rotate through the PAM position, although the most
experienced with acoustics will be on PAM duty more frequently.
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 an
acoustic encounter identification number, whether it was linked with a
visual sighting, date, time when first and last heard 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
Proposed 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
[[Page 11885]]
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-in\3\ airgun. If the size of 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. It is proposed that, 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 in\3\).
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 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, 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
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
Under section 7 of the ESA, the NSF has begun consultation on this
proposed seismic survey. NMFS will also consult on the issuance of an
IHA under section 101(a)(5)(D) of the MMPA for this activity.
Consultation will be concluded prior to a determination on the issuance
of an IHA.
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 will review this EA and will either adopt it or prepare its own
NEPA document before making a determination on the issuance of the IHA.
Preliminary Determination
Based on the preceding information, and provided that the proposed
mitigation and monitoring are incorporated, NMFS has preliminarily
determined that the impact of conducting the marine seismic survey in
the ETP may result, at worst, in a temporary modification in behavior
of
[[Page 11886]]
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 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.
Proposed Authorization
NMFS proposes to issue an IHA to L-DEO for a marine seismic survey
project in the ETP in April-August 2008, provided the previously
mentioned mitigation, monitoring, and reporting requirements are
incorporated.
Dated: February 28, 2008.
Helen Golde,
Deputy Director, Office of Protected Resources, National Marine
Fisheries Service.
[FR Doc. E8-4237 Filed 3-4-08; 8:45 am]
BILLING CODE 3510-22-P