[Federal Register Volume 69, Number 120 (Wednesday, June 23, 2004)]
[Notices]
[Pages 34996-35011]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-14242]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[I.D. 051704A]


Small Takes of Marine Mammals Incidental to Specified Activities; 
Marine Seismic Survey in the Gulf of Alaska, Northeastern Pacific Ocean

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Notice of receipt of application and proposed incidental take 
authorization; request for comments.

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SUMMARY: NMFS has received an application from the Lamont-Doherty Earth 
Observatory (L-DEO), a part of Columbia University, for an Incidental 
Harassment Authorization (IHA) to take small numbers of marine mammals, 
by harassment, incidental to conducting oceanographic seismic surveys 
in the Gulf of Alaska (GOA). Under the Marine Mammal Protection Act 
(MMPA), NMFS is requesting comments on its proposal to issue an 
authorization to L-DEO to incidentally take, by harassment, small 
numbers of several species of cetaceans and pinnipeds for a limited 
period of time within the next year.

DATES: Comments and information must be received no later than July 23, 
2004.

ADDRESSES: Comments on the application should be addressed to P.

[[Page 34997]]

Michael Payne, Chief, Marine Mammal Conservation Division, Office of 
Protected Resources, National Marine Fisheries Service, 1315 East-West 
Highway, Silver Spring, MD 20910-3225, or by telephoning the contact 
listed here. The mailbox address for providing email comments is 
[email protected]. Include in the subject line of the e-mail comment 
the following document identifier: 051704A. 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 this address or by 
telephoning the contact listed here and is also available at: http://www.nmfs.noaa.gov/prot_res/PR2/Small_Take/smalltake_info.htm#applications

FOR FURTHER INFORMATION CONTACT: Kenneth Hollingshead, Office of 
Protected Resources, NMFS, (301) 713-2322, ext 128.

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.
    Permission may be granted if NMFS finds that the taking will have a 
negligible impact on the species or stock(s) and will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses and that the permissible methods of 
taking and requirements pertaining to the 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. 
Under section 3(18)(A), 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

    On April 19, 2004, NMFS received an application from L-DEO for the 
taking, by harassment, of several species of marine mammals incidental 
to conducting a seismic survey program during a four-week period within 
a general time window from late July to October 2004. The purpose of 
the seismic survey is to locate sedimentary records of environmental 
change in the GOA, including Holocene climate variability, 
anthropogenic warming and glacier melting of the past century, and 
dynamics of erosion and deposition associated with glaciation. This 
research has important implications for understanding long-term 
variability of North Pacific ecosystems, with relevance towards 
managing fisheries, marine mammals and other species. Geophysical site 
survey and safety information will be used to optimally locate coring 
sites and to understand regional sedimentation patterns. The marine 
paleoclimatic record in this region has received relatively little 
study because very few suitable sediment cores have been taken. 
Nevertheless, enough basic knowledge of fjord sedimentation processes 
exists to support a strategy of targeting deep-silled basins of fjords 
with adequate connections to the open ocean, as well as shelf and slope 
sediments in the open ocean. Fjord basins likely contain a rich array 
of biogenic and sedimentologic evidence for regional climate change. 
Regions of turbidite sedimentation (i.e., coarse sediments transported 
down-slope in turbidity currents) will be documented using shipboard 
geophysical sensing and sedimentological proxies in recovered sediments 
and will be avoided during coring. However, if some isolated turbidites 
are present, this may present an opportunity to examine seismically 
triggered events that provide useful synchronous stratigraphic markers.

Description of the Activity

    The proposed seismic survey will involve one vessel, the R/V 
Maurice Ewing (Ewing). The Ewing will deploy a pair of low-energy 
Generator-Injector (GI) airguns as an energy source (each with a 
discharge volume of 105 in3). The energy to the airguns will be 
compressed air supplied by compressors on board the source vessel. 
Seismic pulses will be emitted at intervals of 6-10 seconds. This 
spacing corresponds to a shot interval of approximately 16-26 m (52-85 
ft). The Ewing will also tow a hydrophone streamer that is up to 1500 m 
(4922 ft) long. As the airguns are operated along the survey lines, the 
hydrophone receiving system will receive and record the returning 
acoustic signals. In constrained fjord settings, only part of the 
streamer may be deployed, or a shorter streamer may be used, to 
increase the maneuverability of the ship.
    The program will consist of approximately 1779 km (960 nm) of 
surveys, not including transits. Water depths within the seismic survey 
area are approximately 30 3000 m (98 9843 ft). There will be additional 
operations associated with airgun testing, start-up, line changes, and 
repeat coverage of any areas where initial data quality is sub-
standard.
    The GOA research will consist of four different stages of seismic 
surveys interspersed with coring operations in 4 general areas. The 4 
different stages are outlined here in the order that they are currently 
planned to take place. Transit time between areas and between lines is 
not included in the estimates of survey time below, because the seismic 
source will generally not be operating during transits.
    Stage 1-Prince of Wales Island. During this stage, 4 short seismic 
surveys will be completed in conjunction with 4 coring sites that will 
be sampled. Each of the 4 surveys, including seismic lines and coring, 
will take 9-14 hr and cover 17.7- 45.3 nm (32.9-83.8 km), for a total 
of 229 km (124 nm). All lines will be conducted in water depths less 
than 100 m (328 ft). A total of 13 lines will be shot around the 4 
coring stations. Stage 1 will take approximately 50 hr of survey time 
over approximately 3 days to complete.
    Stage 2-Baranof Island. During this stage, five short seismic 
surveys will be completed in conjunction with 6 coring sites that will 
be sampled. Each of the 5 surveys, including seismic lines and coring, 
will take approximately 6-17 hr

[[Page 34998]]

and cover 4.1-54.5 nm (7.6-101.0 km), for a total of 109 km (59 nm) of 
which 25 km (13.5 nm) will be conducted in waters less than 100 m (328 
ft) deep and 84 km (45 nm) will be in waters from 100 to 1000 m (328-
3281 ft) deep. Stage 2 will take approximately 45 hr of survey time 
over approximately 4.5 days to complete.
    Stage 3-Juneau (Southeast Alaska Inland Waters). During Stage 3, 3 
short seismic surveys will be completed in conjunction with four coring 
sites that will be sampled. Each survey, including seismic lines and 
coring, will take approximately 8-21 hr and will cover 15.1-104.1 nm 
(27.7-192.9 km), for a total of 249 km (134 nm) conducted in water 100 
m (328 ft) to 1000 m (3281 ft) deep. Stage 3 will take approximately 38 
hr of survey time over 2.5 days to complete.
    Stage 4-Glacier Bay, Yakutat Bay, Icy Bay, Prince William Sound, 
and Gulf of Alaska. During Stage 4, 14 seismic surveys will be 
conducted in conjunction with 16 coring sites that will be sampled. 
Surveys during Stage 4, including seismic lines and coring, will range 
in length from 5.3 - 111.2 nm (9.8-205.9 km),km), for a total of 1192 
km (644 nm) of which 382 km (206 nm) will be conducted in waters less 
than 100 m (328 ft) deep, 453 km (245 nm) will be in waters from 100 to 
1000 m (328 -3281 ft) deep and 357 km (187 nm) will be in waters deeper 
than 1000 m (3281 ft). Stage 4 will take approximately 72 h or survey 
time over approximately 13 days to complete.
    In the event that one or more of the planned sites are unavailable 
due to poor weather conditions, ice conditions, unsuitable geology 
(shallow sediments), or other reasons, contingency sites (alternative 
seismic survey and coring locations) will be substituted. Alternative 
research sites (see Fig. 6 in the L-DEO application) will only be 
undertaken by L-DEO as replacements for the planned sites, and their 
use will not substantially change the total length or duration of the 
proposed seismic surveys. Seismic survey lines have not been selected 
or plotted by L-DEO for some contingency core sites. However, L-DEO 
anticipates that each contingency core site would require approximately 
40 km (22 nm) of seismic surveying to locate optimal coring locations. 
It is highly unlikely that all contingency sites will be used. To the 
extent that contingency sites are used, a similar number of ``primary'' 
sites will be dropped from the project.

General-Injector Airguns

    Two GI-airguns will be used from the Ewing during the proposed 
program. These 2 GI-airguns have a zero to peak (peak) source output of 
237 dB re 1 microPascal-m (7.2 bar-m) and a peak-to-peak (pk-pk) level 
of 243 dB (14.0 bar-m). However, these downward-directed source levels 
do not represent actual sound levels that can be measured at any 
location in the water. Rather, they represent the level that would be 
found 1 m (3.3 ft) from a hypothetical point source emitting the same 
total amount of sound as is emitted by the combined airguns in the 
airgun array. The actual received level at any location in the water 
near the airguns will not exceed the source level of the strongest 
individual source. In this case, that will be about 231 dB re 1 
microPa-m peak, or 237 dB re 1 microPa-m pk-pk. Actual levels 
experienced by any organism more than 1 m (3.3 ft) from either GI gun 
will be significantly lower.
    Further, the root mean square (rms) received levels that are used 
as impact criteria for marine mammals (see Richardson et al., 1995) are 
not directly comparable to these peak or pk-pk values that are normally 
used to characterize source levels of airgun arrays. The measurement 
units used to describe airgun sources, peak or pk-pk decibels, are 
always higher than the rms decibels referred to in biological 
literature. For example, a measured received level of 160 decibels rms 
in the far field would typically correspond to a peak measurement of 
about 170 to 172 dB, and to a pk-pk measurement of about 176 to 178 
decibels, as measured for the same pulse received at the same location 
(Greene, 1997; McCauley et al. 1998, 2000). The precise difference 
between rms and peak or pk-pk values depends on the frequency content 
and duration of the pulse, among other factors. However, the rms level 
is always lower than the peak or pk-pk level for an airgun-type source.
    The depth at which the sources are towed has a major impact on the 
maximum near-field output, because the energy output is constrained by 
ambient pressure. The normal tow depth of the sources to be used in 
this project is 3 m (9.8 ft), where the ambient pressure is 3 decibars. 
This also limits output, as the 3 decibars of confining pressure cannot 
fully constrain the source output, with the result that there is loss 
of energy at the sea surface. Additional discussion of the 
characteristics of airgun pulses is provided later in this document.
    For the 2 GI-airguns, the sound pressure field has been modeled by 
L-DEO in relation to distance and direction from the airguns, and in 
relation to depth. Table 1 shows the maximum distances from the airguns 
where sound levels of 190-, 180-, 170- and 160-dB re 1 microPa (rms) 
are predicted to be received. Empirical data concerning the 180, 170 
and 160 dB distances have been acquired based on measurements during an 
acoustic verification study conducted by L-DEO in the northern Gulf of 
Mexico from 27 May to 3 June 2003 (Tolstoy et al., 2004). Although the 
results are limited, the data showed that radii around the airguns 
where the received level would be 180 dB re 1 microPa (rms), NMFS' 
current injury threshold safety criterion applicable to cetaceans 
(NMFS, 2000), varies with water depth. Similar depth-related variation 
is likely in the 190-dB distances applicable to pinnipeds. The proposed 
L-DEO study area will occur in water approximately 30 3000 m (98 9843 
ft).

[[Page 34999]]

[GRAPHIC] [TIFF OMITTED] TN23JN04.006

Bathymetric Sonar, Sub-bottom Profiler, and Pinger

    In addition to the 2 GI-airguns, a multibeam bathymetric sonar and 
a low-energy 3.5-kHz sub-bottom profiler will be used during the 
seismic profiling and continuously when underway. While on station for 
coring, a 12-kHz pinger will be used to monitor the depth of coring 
devices relative to the sea floor.
    Bathymetric Sonar-Atlas Hydrosweep- The 15.5-kHz Atlas Hydrosweep 
sonar is mounted on the hull of the Maurice Ewing, and it operates in 
three modes, depending on the water depth. There is one shallow water 
mode and two deep-water modes: an Omni mode (similar to the shallow-
water mode but with a source output of 220 dB (rms)) and a Rotational 
Directional Transmission (RDT) mode. The RDT mode is normally used 
during deep-water operation and has a 237-dB rms source output. In the 
RDT mode, each ``ping'' consists of five successive transmissions, each 
ensonifying a beam that extends 2.67 degrees fore-aft and approximately 
30 degrees in the cross-track direction. The five successive 
transmissions (segments) sweep from port to starboard with minor 
overlap, spanning an overall cross-track angular extent of about 140 
degrees, with small (much less than 1 millisec) gaps between the pulses 
for successive 30-degree segments. The total duration of the ``ping'' 
including all five successive segments, varies with water depth, but is 
1 millisec in water depths less than 500 m and 10 millisec in the 
deepest water. For each segment, ping duration is 1/5 of these values 
or 2/5 for a receiver in the overlap area ensonified by two beam 
segments. The ``ping'' interval during RDT operations depends on water 
depth and varies from once per second in less than 500 m (1640.5 ft) 
water depth to once per 15 seconds in the deepest water. During the 
proposed project, the Atlas Hydrosweep will generally be used in waters 
greater than 800 m (2624.7 ft), but whenever water depths are less than 
400 m (1312 ft) the source output is 210 dB re 1 microPa-m (rms) and a 
single 1-ms pulse or ``ping'' per second is transmitted.
    Bathymetric Sonar-EM1002 Portable Sonar - The EM1002 is a compact 
high-resolution multibeam echo sounder that operates at a frequency of 
92 to 98 kHz in water depths from 10 to 800 m (33 2625 ft). The EM1002 
will be used instead of the Atlas Hydrosweep in waters <800 m deep. The 
EM1002 will be pole mounted on the Ewing, either over the side or 
through a well. The system operates with one of three different 
pulselengths: 0.2, 0.7 and 2 ms. Pulselength increases with increased 
water depth. Overall angular coverage of the transmitted beam is 3 
degrees along the fore-aft axis and 150 degrees (7.4 times the water 
depth) along the cross-track axis when operating in the shallowest 
mode. Maximum ping rate is 10/sec (in shallow water) with the ping rate 
decreasing with increasing water depth. Maximum output using long 
pulses in 800 m (2624.7 ft) water depth is 226 dB re 1 microPa, 
although operations in shallower depths, including most of the work in 
these surveys, will use significantly lower output levels.
    Sub-bottom Profilers - 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 Hydrosweep. The 
energy from the EDO Corporation's (EDO) sub-bottom profiler is directed 
downward by a 3.5-kHz transducer mounted in the hull of the Ewing. The 
output varies with water depth from 50 watts in shallow water to 800 
watts in deep water. Pulse interval is 1 second (s) but a common mode 
of operation is to broadcast five pulses at 1-s intervals followed by a 
5-s pause. The beamwidth is approximately 30o and is directed downward. 
Maximum source output is 204 dB re 1 microPa (800 watts) while nominal 
source output is 200 dB re 1 microPa (500 watts). Pulse duration will 
be 4, 2, or 1 ms, and the bandwith of pulses will be 1.0 kHz, 0.5 kHz, 
or 0.25 kHz, respectively.
    An ODEC Bathy 2000P ``chirp'' sonar may be used instead of the EDO 
sub-bottom profiler. This sonar transmits a 50-ms pulse during which 
the frequency is swept from 4 to 7 kHz. The transmission rate is 
variable from 1 to 10 seconds, and the maximum output power is 2 kW. 
This sonar uses a transducer array very similar to that used by the 3.5 
kHz sub-bottom profiler.
    The EDO sub-bottom profiler on the Ewing has a stated maximum 
source level of 204 dB re 1 microPa and a nominal source level of 200 
dB. Although the sound levels have not been measured directly for the 
sub-bottom profilers used by the Ewing, Burgess and Lawson (2000) 
measured sounds propagating more or less horizontally from a sub-bottom 
profiler similar to the EDO unit with similar source output (i.e., 205 
dB re 1 microPa m). For that profiler, the 160 and 180 dB re 1 microPa 
(rms) radii in the horizontal direction were estimated to be, 
respectively, near 20 m (66 ft) and 8 m (26 ft) from the source, as 
measured in 13 m or 43 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. Thus the received level for the EDO sub-bottom 
profiler would be expected to decrease to 160 and 180 dB about 160 m 
(525 ft) and 16 m (52 ft) below the transducer, respectively, assuming 
spherical

[[Page 35000]]

spreading. Corresponding distances in the horizontal plane would be 
lower, given the directionality of this source (300 beamwidth) and the 
measurements of Burgess and Lawson (2000).
    12 kHz Pinger - A 12-kHz pinger will be used only during coring 
operations, to monitor the depth of the coring apparatus relative to 
the sea floor. The pinger is a battery-powered acoustic beacon that is 
attached to a wire just above the corehead. The pinger produces an 
omnidirectional 12 kHz signal with a source output of 193 dB re 1 
microPa-m. The pinger produces a 2 ms pulse every second.

Characteristics of Airgun Pulses

    Airguns function by venting high-pressure air into the water. The 
pressure signature of an individual airgun consists of a sharp rise and 
then fall in pressure, followed by several positive and negative 
pressure excursions caused by oscillation of the resulting air bubble. 
The resulting downward-directed pulse has a duration of only 10 to 20 
ms, with only one strong positive and one strong negative peak pressure 
(Caldwell and Dragoset, 2000). Most energy emitted from airguns is at 
relatively low frequencies. For example, typical high-energy airgun 
arrays emit most energy at 10-120 Hz. However, the pulses contain some 
energy up to 500-1000 Hz and above (Goold and Fish, 1998).
    The pulsed sounds associated with seismic exploration have higher 
peak levels than other industrial sounds to which whales and other 
marine mammals are routinely exposed. As mentioned previously, the pk-
pk source levels of the 2 GI-gun array that will be used for the GOA 
project is 231 dB re 1 microPa (peak) and 237 dB re 1 microPa (pk-pk). 
However, the effective source level for horizontal propagation will be 
lower and actual levels experienced by any marine mammal more than 1 m 
(3.3 ft) from either GI-gun will be significantly lower.
    Several important factors need are considered when assessing airgun 
impacts on the marine environment: (1) Airgun arrays produce 
intermittent sounds, involving emission of a strong sound pulse for a 
small fraction of a second followed by several seconds of near silence. 
In contrast, some other acoustic sources produce sounds with lower peak 
levels, but their sounds are continuous or discontinuous but continuing 
for much longer durations than seismic pulses. (2) Airgun arrays are 
designed to transmit strong sounds downward through the seafloor, and 
the amount of sound transmitted in near-horizontal directions is 
considerably reduced. Nonetheless, they also emit sounds that travel 
horizontally toward non-target areas. (3) An airgun array is a 
distributed source, not a point source. The nominal source level is an 
estimate of the sound that would be measured from a theoretical point 
source emitting the same total energy as the airgun array. That figure 
is useful in calculating the expected received levels in the far field 
(i.e., at moderate and long distances). Because the airgun array is not 
a single point source, there is no one location within the near field 
(or anywhere else) where the received level is as high as the nominal 
source level.
    The strengths of airgun pulses can be measured in different ways, 
and it is important to know which method is being used when 
interpreting quoted source or received levels. Geophysicists usually 
quote pk-pk levels, in bar-meters or dB re 1 microPa-m. The peak level 
for the same pulse is typically about 6 dB less. In the biological 
literature, levels of received airgun pulses are often described based 
on the ``average'' or ``root-mean-square'' (rms) level over the 
duration of the pulse. The rms value for a given pulse is typically 
about 10 dB lower than the peak level, and 16 dB lower than the Pk-pk 
value (Greene, 1997; McCauley et al., 1998; 2000). A fourth measure 
that is being used more frequently is the energy level, in dB re 1 
microPa\2.\s. Because the pulses are less than 1 sec in duration, the 
numerical value of the energy is lower than the rms pressure level, but 
the units are different. Because the level of a given pulse will differ 
substantially depending on which of these measures is being applied, it 
is important to be aware which measure is in use when interpreting any 
quoted pulse level. NMFS commonly references the rms levels when 
discussing levels of pulsed sounds that might harass marine mammals.
    Seismic sound received at any given point will arrive via a direct 
path, indirect paths that include reflection from the sea surface and 
bottom, and often indirect paths including segments through the bottom 
sediments. Sounds propagating via indirect paths travel longer 
distances and often arrive later than sounds arriving via a direct 
path. These variations in travel time have the effect of lengthening 
the duration of the received pulse. At the source, seismic pulses are 
about 10 to 20 ms in duration. In comparison, the pulse duration as 
received at long horizontal distances can be much greater.
    Another important aspect of sound propagation is that received 
levels of low-frequency underwater sounds diminish close to the surface 
because of pressure-release and interference phenomena that occur at 
and near the surface (Urick, 1983, Richardson et al., 1995). Paired 
measurements of received airgun sounds at depths of 3 m (9.8 ft) vs. 9 
or 18 m (29.5 or 59 ft) have shown that received levels are typically 
several decibels lower at 3 m (9.8. ft)(Greene and Richardson, 1988). 
For a mammal whose auditory organs are within 0.5 or 1 m (1.6 or 3.3 
ft) of the surface, the received level of the predominant low-frequency 
components of the airgun pulses would be further reduced.
    Pulses of underwater sound from open-water seismic exploration are 
often detected 50 to 100 km (30 to 54 nm) from the source location 
(Greene and Richardson, 1988; Burgess and Greene, 1999). At those 
distances, the received levels on an approximate rms basis are low 
(below 120 dB re 1 microPa). However, faint seismic pulses are 
sometimes detectable at even greater ranges (e.g., Bowles et al., 1994; 
Fox et al., 2002). Considerably higher levels can occur at distances 
out to several kilometers from an operating airgun array. Additional 
information is contained in the L-DEO application, especially in 
Appendix A.

Description of Habitat and Marine Mammals Affected by the Activity

    A detailed description of the GOA area and its associated marine 
mammals can be found in the L-DEO application and a number of documents 
referenced in the L-DEO application, and is not repeated here. A total 
of 18 cetacean species, 3 species of pinnipeds, and the sea otter are 
known to or may occur in SE Alaska (Rice, 1998; Angliss and Lodge, 
2002). The marine mammals that occur in the proposed survey area belong 
to four taxonomic groups: odontocetes (sperm whales (Physeter 
macrocephalus), beaked whales (Cuvier's (Ziphius cavirostris), Baird's 
(Berardius bairdii), and Stejneger's (Mesoplodon stejnegeri)), beluga 
(Delphinapterus leucas), Pacific white-sided dolphin (Lagenorhynchus 
obliquidens), Risso's dolphin (Grampus griseus), killer whale (Orcinus 
orca), short-finned pilot whale (Globicephala macrorhynchus), harbor 
porpoise* (Phocoena phocoena), and Dall's porpopise (Phocoenoides 
dalli)), mysticetes (North Pacific right whales (Eubalaena japonica), 
gray whales (Eschrichtius robustus), humpback whales (Megaptera 
novaeangliae), minke whales (Balaenoptera acutorostrata), sei whales 
(Balaenoptera borealis), fin whales (Balaenoptera physalus), and blue 
whales ((Balaenoptera musculus)), pinnipeds (Steller sea lion 
(Eumetopias jubatus), harbor seal (Phoca vitulina) and

[[Page 35001]]

northern fur seal (Callorhinus ursinus)), and fissipeds (sea otter 
(Enhydra lutris)). Of the 18 cetacean species in the area, nine are 
commonly found in the activity area (see Table 2) and may be affected 
by the proposed acitivty. Of the three species of pinnipeds that could 
potentially occur in SE Alaska, only the Steller sea lion and harbor 
seal are likely to be present. The northern fur seal inhabits the 
Bering Sea during the summer and is generally found in SE Alaska in low 
numbers during the winter, and during the northward migration in 
spring. Sea otters generally inhabit coastal waters within the 40-m 
(131-ft) depth contour (Riedman and Estes, 1990) and may be encountered 
in coastal areas of the study area. More detailed information on these 
species is contained in the L-DEO application and additional 
information is contained in Angliss and Lodge, 2002 which are available 
at: http://www.nmfs.noaa.gov/prot_res/PR2/Small_Take/smalltake_info.htm#applications, and http://www.nmfs.noaa.gov/prot_res/PR2/Stock_Assessment_Program/sars.html, respectively.

Potential Effects on Marine Mammals

    As outlined in several previous NMFS documents, the effects of 
noise on marine mammals are highly variable, and can be categorized as 
follows (based on Richardson et al., 1995):
    (1) The noise may be too weak to be heard at the location of the 
animal (i.e., lower than the prevailing ambient noise level, the 
hearing threshold of the animal at relevant frequencies, or both);
    (2) The noise may be audible but not strong enough to elicit any 
overt behavioral response;
    (3) The noise may elicit reactions of variable conspicuousness and 
variable relevance to the well being of the marine mammal; these can 
range from temporary alert responses to active avoidance reactions such 
as vacating an area at least until the noise event ceases;
    (4) Upon repeated exposure, a marine mammal may exhibit diminishing 
responsiveness (habituation), or disturbance effects may persist; the 
latter is most likely with sounds that are highly variable in 
characteristics, infrequent and unpredictable in occurrence, and 
associated with situations that a marine mammal perceives as a threat;
    (5) Any anthropogenic noise that is strong enough to be heard has 
the potential to reduce (mask) the ability of a marine mammal to hear 
natural sounds at similar frequencies, including calls from 
conspecifics, and underwater environmental sounds such as surf noise;
    (6) If mammals remain in an area because it is important for 
feeding, breeding or some other biologically important purpose even 
though there is chronic exposure to noise, it is possible that there 
could be noise-induced physiological stress; this might in turn have 
negative effects on the well-being or reproduction of the animals 
involved; and
    (7) Very strong sounds have the potential to cause temporary or 
permanent reduction in hearing sensitivity. In terrestrial mammals, and 
presumably marine mammals, received sound levels must far exceed the 
animal's hearing threshold for there to be any temporary threshold 
shift (TTS) in its hearing ability. For transient sounds, the sound 
level necessary to cause TTS is inversely related to the duration of 
the sound. Received sound levels must be even higher for there to be 
risk of permanent hearing impairment. In addition, intense acoustic or 
explosive events may cause trauma to tissues associated with organs 
vital for hearing, sound production, respiration and other functions. 
This trauma may include minor to severe hemorrhage.

Effects of Seismic Surveys on Marine Mammals

    The L-DEO application provides the following information on what is 
known about the effects on marine mammals of the types of seismic 
operations planned by L-DEO. The types of effects considered here are 
(1) masking, (2) disturbance, and (3) potential hearing impairment and 
other physical effects. Additional discussion on species specific 
effects can be found in the L-DEO application.

Masking

    Masking effects of pulsed sounds on marine mammal calls and other 
natural sounds are expected to be limited, although there are very few 
specific data on this. Seismic sounds are short pulses generally 
occurring for less than 1 sec every 20 or 60-90 sec during this 
project. Sounds from the multibeam sonar are very short pulses, 
occurring for 1-10 msec once every 1 to 15 sec, depending on water 
depth. (During operations in deep water, the duration of each pulse 
from the multibeam sonar as received at any one location would actually 
be only 1/5 or at most 2/5 of 1-10 msec, given the segmented nature of 
the pulses.) Some whales are known to continue calling in the presence 
of seismic pulses. Their calls can be heard between the seismic pulses 
(Richardson et al., 1986; McDonald et al., 1995, Greene et al., 1999). 
Although there has been one report that sperm whales cease calling when 
exposed to pulses from a very distant seismic ship (Bowles et al., 
1994), a recent study reports that sperm whales continued calling in 
the presence of seismic pulses (Madsen et al., 2002). Given the small 
source planned for use during this survey, there is even less potential 
for masking of sperm whale calls during the present study than in most 
seismic surveys. Masking effects of seismic pulses are expected to be 
negligible in the case of the smaller odontocete cetaceans, given the 
intermittent nature of seismic pulses and the relatively low source 
level of the airguns to be used in the GOA. Also, the sounds important 
to small odontocetes are predominantly at much higher frequencies than 
are airgun sounds.
    Most of the energy in the sound pulses emitted by airgun arrays is 
at low frequencies, with strongest spectrum levels below 200 Hz and 
considerably lower spectrum levels above 1000 Hz. These frequencies are 
mainly used by mysticetes, but not by odontocetes or pinnipeds. An 
industrial sound source will reduce the effective communication or 
echolocation distance only if its frequency is close to that of the 
cetacean signal. If little or no overlap occurs between the industrial 
noise and the frequencies used, as in the case of many marine mammals 
vs. airgun sounds, communication and echolocation are not expected to 
be disrupted. Furthermore, the discontinuous nature of seismic pulses 
makes significant masking effects unlikely even for mysticetes.
    A few cetaceans are known to increase the source levels of their 
calls in the presence of elevated sound levels, or possibly to shift 
their peak frequencies in response to strong sound signals (Dahlheim, 
1987; Au, 1993; Lesage et al., 1999; Terhune, 1999; as reviewed in 
Richardson et al., 1995). These studies involved exposure to other 
types of anthropogenic sounds, not seismic pulses, and it is not known 
whether these types of responses ever occur upon exposure to seismic 
sounds. If so, these adaptations, along with directional hearing, pre-
adaptation to tolerate some masking by natural sounds (Richardson et 
al., 1995) and the relatively low-power acoustic sources being used in 
this survey, would all reduce the importance of masking marine mammal 
vocalizations.

Disturbance by Seismic Surveys

    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous dramatic changes in activities, and 
displacement.

[[Page 35002]]

 However, there are difficulties in defining which marine mammals 
should be counted as ``taken by harassment''. For many species and 
situations, scientists do not have detailed information about their 
reactions to noise, including reactions to seismic (and sonar) pulses. 
Behavioral reactions of marine mammals to sound are difficult to 
predict. 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 to an 
underwater sound by changing its behavior or moving a small distance, 
the impacts of the change may not rise to the level of a disruption of 
a behavioral pattern. However, if a sound source would displace marine 
mammals from an important feeding or breeding area for a prolonged 
period, such a disturbance would constitute Level B harassment. Given 
the many uncertainties in predicting the quantity and types of impacts 
of noise on marine mammals, scientists often resort to estimating how 
many mammals may be present within a particular distance of industrial 
activities or exposed to a particular level of industrial sound. This 
likely overestimates the numbers of marine mammals that are affected in 
some biologically important manner.
    The sound criteria used to estimate how many marine mammals might 
be harassed behaviorally by the seismic survey are based on behavioral 
observations during studies of several species. However, information is 
lacking for many species. More detailed information on potential 
disturbance effects on baleen whales, toothed whales, and pinnipeds can 
be found on pages 36-38 and Appendix A in L-DEO's application.

Hearing Impairment and Other Physical Effects

    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds, but there has been no 
specific documentation of this for marine mammals exposed to airgun 
pulses. Current NMFS policy regarding exposure of marine mammals to 
high-level sounds is that cetaceans and pinnipeds should not be exposed 
to impulsive sounds [gteqt]180 and 190 dB re 1 microPa (rms), 
respectively (NMFS, 2000). Those criteria have been used in defining 
the safety (shut down) radii for seismic surveys. However, those 
criteria were established before there were any data on the minimum 
received levels of sounds necessary to cause auditory impairment in 
marine mammals. As discussed in the L-DEO application and summarized 
here,
    1. The 180 dB criterion for cetaceans is probably quite 
precautionary, i.e., lower than necessary to avoid TTS let alone 
permanent auditory injury, at least for delphinids.
    2. The minimum sound level necessary to cause permanent hearing 
impairment is higher, by a variable and generally unknown amount, than 
the level that induces barely-detectable TTS.
    3. The level associated with the onset of TTS is often considered 
to be a level below which there is no danger of permanent damage.
    Because of the small size of the GI airguns, along with the planned 
monitoring and mitigation measures, there is little likelihood that any 
marine mammals will be exposed to sounds sufficiently strong to cause 
even the mildest (and reversible) form of hearing impairment. Several 
aspects of the planned monitoring and mitigation measures for this 
project are designed to detect marine mammals occurring near the 2 GI-
airguns (and multibeam bathymetric sonar), and to avoid exposing them 
to sound pulses that might cause hearing impairment. In addition, many 
cetaceans are likely to show some avoidance of the area with ongoing 
seismic operations. In these cases, the avoidance responses of the 
animals themselves will reduce or avoid the possibility of hearing 
impairment.
    Non-auditory physical effects may also occur in marine mammals 
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that theoretically might 
occur in mammals close to a strong sound source include stress, 
neurological effects, bubble formation, resonance effects, and other 
types of organ or tissue damage. It is possible that some marine mammal 
species (i.e., beaked whales) may be especially susceptible to injury 
and/or stranding when exposed to strong pulsed sounds. However, L-DEO 
believes that it is especially unlikely that any of these non-auditory 
effects would occur during the proposed survey given the small size of 
the sources, the brief duration of exposure of any given mammal, and 
the planned mitigation and monitoring measures. The following 
paragraphs discuss the possibility of TTS, permanent threshold shift 
(PTS), and non-auditory physical effects.

TTS

    TTS is the mildest form of hearing impairment that can occur during 
exposure to a strong sound (Kryter, 1985). When an animal experiences 
TTS, its hearing threshold rises and a sound must be stronger in order 
to be heard. TTS can last from minutes or hours to (in cases of strong 
TTS) days. Richardson et al. (1995) notes that the magnitude of TTS 
depends on the level and duration of noise exposure, among other 
considerations. For sound exposures at or somewhat above the TTS 
threshold, hearing sensitivity recovers rapidly after exposure to the 
noise ends. Little data on sound levels and durations necessary to 
elicit mild TTS have been obtained for marine mammals.
    For toothed whales exposed to single short pulses, the TTS 
threshold appears to be, to a first approximation, a function of the 
energy content of the pulse (Finneran et al., 2002). Given the 
available data, the received level of a single seismic pulse might need 
to be on the order of 210 dB re 1 microPa rms (approx. 221 226 dB pk 
pk) in order to produce brief, mild TTS. Exposure to several seismic 
pulses at received levels near 200 205 dB (rms) might result in slight 
TTS in a small odontocete, assuming the TTS threshold is (to a first 
approximation) a function of the total received pulse energy (Finneran 
et al., 2002). Seismic pulses with received levels of 200 205 dB or 
more are usually restricted to a zone of no more than 100 m (328 ft) 
around a seismic vessel operating a large array of airguns. Such sound 
levels would be limited to distances within a few meters of the small 
airgun source to be used during this project.
    There are no data, direct or indirect, on levels or properties of 
sound that are required to induce TTS in any baleen whale. However, TTS 
is not expected to occur during this survey given the small size of the 
source, and the strong likelihood that baleen whales would avoid the 
approaching airguns (or vessel) before being exposed to levels high 
enough for there to be any possibility of TTS.
    TTS thresholds for pinnipeds exposed to brief pulses (single or 
multiple) have not been measured, although exposures up to 183 db re 1 
microPa (rms) have been shown to be insufficient to induce TTS in 
California sea lions (Finneran et al. (2003). However, prolonged 
exposures show that some pinnipeds may incur TTS at somewhat lower 
received levels than do small odontocetes exposed for similar durations 
(Kastak et al., 1999; Ketten et al., 2001; Au et al., 2000).
    A marine mammal within a zone of <=100 m (<= 328 ft) around a 
typical large array of operating airguns might be exposed to a few 
seismic pulses with

[[Page 35003]]

levels of [gteqt]205 dB, and possibly more pulses if the mammal moved 
with the seismic vessel. Also, around smaller arrays, such as the 2 GI-
airgun proposed for use during this survey, a marine mammal would need 
to be even closer to the source to be exposed to levels >205 dB, at 
least in waters greater than 100 m (328 ft) deep. However, as noted 
previously, most cetacean species tend to avoid operating airguns, 
although not all individuals do so. In addition, ramping up airgun 
arrays, which is standard operational protocol for L-DEO and other 
seismic operators, should allow cetaceans to move away from the seismic 
source and to avoid being exposed to the full acoustic output of the 
airgun array. It is unlikely that these cetaceans would be exposed to 
airgun pulses at a sufficiently high level for a sufficiently long 
period to cause more than mild TTS, given the relative movement of the 
vessel and the marine mammal. However, TTS would be more likely in any 
odontocetes that bow-ride or otherwise linger near the airguns. While 
bow-riding, odontocetes would be at or above the surface, and thus not 
exposed to strong sound pulses given the pressure-release effect at the 
surface. However, bow-riding animals generally dive below the surface 
intermittently. If they did so while bow-riding near airguns, they 
would be exposed to strong sound pulses, possibly repeatedly. If some 
cetaceans did incur TTS through exposure to airgun sounds, this would 
very likely be a temporary and reversible phenomenon.
    Currently, NMFS believes that, whenever possible to avoid Level A 
harassment, cetaceans should not be exposed to pulsed underwater noise 
at received levels exceeding 180 dB re 1 microPa (rms). The 
corresponding limit for pinnipeds has been set at 190 dB. The predicted 
180- and 190-dB distances for the airgun arrays operated by L-DEO 
during this activity are summarized elsewhere in this document. These 
sound levels are not considered to be the levels at or above which TTS 
might occur. Rather, they are the received levels above which, in the 
view of a panel of bioacoustics specialists convened by NMFS (at a time 
before TTS measurements for marine mammals started to become 
available), one could not be certain that there would be no injurious 
effects, auditory or otherwise, to marine mammals. As noted here, TTS 
data that are now available imply that, at least for dolphins, TTS is 
unlikely to occur unless the dolphins are exposed to airgun pulses 
substantially stronger that 180 dB re 1 microPa (rms).
    It has also been shown that most whales tend to avoid ships and 
associated seismic operations. Thus, whales will likely not be exposed 
to such high levels of airgun sounds. Because of the slow ship speed, 
any whales close to the trackline could move away before the sounds 
become sufficiently strong for there to be any potential for hearing 
impairment. Therefore, there is little potential for whales being close 
enough to an array to experience TTS. In addition, as mentioned 
previously, ramping up the 2 GI-airgun array, which has become standard 
operational protocol for many seismic operators including L-DEO, should 
allow cetaceans to move away from the seismic source and to avoid being 
exposed to the full acoustic output of the GI airguns.

Permanent Threshold Shift (PTS)

    When PTS occurs, there is physical damage to the sound receptors in 
the ear. In some cases, there can be total or partial deafness, while 
in other cases, the animal has an impaired ability to hear sounds in 
specific frequency ranges. Physical damage to a mammal's hearing 
apparatus can occur if it is exposed to sound impulses that have very 
high peak pressures, especially if they have very short rise times 
(time required for sound pulse to reach peak pressure from the baseline 
pressure). Such damage can result in a permanent decrease in functional 
sensitivity of the hearing system at some or all frequencies.
    Single or occasional occurrences of mild TTS are not indicative of 
permanent auditory damage in terrestrial mammals. However, very 
prolonged exposure to sound strong enough to elicit TTS, or shorter-
term exposure to sound levels well above the TTS threshold, can cause 
PTS, at least in terrestrial mammals (Kryter, 1985). Relationships 
between TTS and PTS thresholds have not been studied in marine mammals 
but are assumed to be similar to those in humans and other terrestrial 
mammals. The low-to-moderate levels of TTS that have been induced in 
captive odontocetes and pinnipeds during recent controlled studies of 
TTS have been confirmed to be temporary, with no measurable residual 
PTS (Kastak et al., 1999; Schlundt et al., 2000; Finneran et al., 2002; 
Nachtigall et al., 2003). In terrestrial mammals, the received sound 
level from a single non-impulsive sound exposure must be far above the 
TTS threshold for any risk of permanent hearing damage (Kryter, 1994; 
Richardson et al., 1995). For impulse sounds with very rapid rise times 
(e.g., those associated with explosions or gunfire), a received level 
not greatly in excess of the TTS threshold may start to elicit PTS. 
Rise times for airgun pulses are rapid, but less rapid than for 
explosions.
    Some factors that contribute to onset of PTS are as follows: (1) 
exposure to single very intense noises, (2) repetitive exposure to 
intense sounds that individually cause TTS but not PTS, and (3) 
recurrent ear infections or (in captive animals) exposure to certain 
drugs.
    Cavanagh (2000) has reviewed the thresholds used to define TTS and 
PTS. Based on his review and SACLANT (1998), it is reasonable to assume 
that PTS might occur at a received sound level 20 dB or more above that 
which induces mild TTS. However, for PTS to occur at a received level 
only 20 dB above the TTS threshold, it is probable that the animal 
would have to be exposed to the strong sound for an extended period.
    Sound impulse duration, peak amplitude, rise time, and number of 
pulses are the main factors thought to determine the onset and extent 
of PTS. Based on existing data, Ketten (1994) has noted that the 
criteria for differentiating the sound pressure levels that result in 
PTS (or TTS) are location and species-specific. PTS effects may also be 
influenced strongly by the health of the receiver's ear.
    Given that marine mammals are unlikely to be exposed to received 
levels of seismic pulses that could cause TTS, it is highly unlikely 
that they would sustain permanent hearing impairment. If we assume that 
the TTS threshold for exposure to a series of seismic pulses may be on 
the order of 220 dB re 1 microPa (pk-pk) in odontocetes, then the PTS 
threshold might be about 240 dB re 1 microPa (pk-pk). In the units used 
by geophysicists, this is 10 bar-m. Such levels are found only in the 
immediate vicinity of the largest airguns (Richardson et al., 1995; 
Caldwell and Dragoset, 2000). However, it is very unlikely that an 
odontocete would remain within a few meters of a large airgun for 
sufficiently long to incur PTS. The TTS (and thus PTS) thresholds of 
baleen whales and pinnipeds may be lower, and thus may extend to a 
somewhat greater distance. However, baleen whales generally avoid the 
immediate area around operating seismic vessels, so it is unlikely that 
a baleen whale could incur PTS from exposure to airgun pulses. Some 
pinnipeds do not show strong avoidance of operating airguns. In 
summary, it is highly unlikely that marine mammals could receive sounds 
strong enough

[[Page 35004]]

(and over a sufficient period of time) to cause permanent hearing 
impairment during this project. In the proposed project, marine mammals 
are unlikely to be exposed to received levels of seismic pulses strong 
enough to cause TTS and because of the higher level of sound necessary 
to cause PTS, it is even less likely that PTS could occur. This is due 
to the fact that even levels immediately adjacent to the 2 GI-airguns 
may not be sufficient to induce PTS because the mammal would not be 
exposed to more than one strong pulse unless it swam alongside an 
airgun for a period of time.

Strandings and Mortality

    Marine mammals close to underwater detonations of high explosives 
can be killed or severely injured, and the auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). 
Airgun pulses are less energetic and have slower rise times. While 
there is no documented evidence that airgun arrays can cause serious 
injury, death, or stranding, the association of mass strandings of 
beaked whales with naval exercises and, recently, an L-DEO seismic 
survey have raised the possibility that beaked whales may be especially 
susceptible to injury and/or stranding when exposed to strong pulsed 
sounds.
    In March 2000, several beaked whales that had been exposed to 
repeated pulses from high intensity, mid-frequency military sonars 
stranded and died in the Providence Channels of the Bahamas Islands, 
and were subsequently found to have incurred cranial and ear damage 
(NOAA and USN, 2001). Based on post-mortem analyses, it was concluded 
that an acoustic event caused hemorrhages in and near the auditory 
region of some beaked whales. These hemorrhages occurred before death. 
They would not necessarily have caused death or permanent hearing 
damage, but could have compromised hearing and navigational ability 
(NOAA and USN, 2001). The researchers concluded that acoustic exposure 
caused this damage and triggered stranding, which resulted in 
overheating, cardiovascular collapse, and physiological shock that 
ultimately led to the death of the stranded beaked whales. During the 
event, five naval vessels used their AN/SQS-53C or -56 hull-mounted 
active sonars for a period of 16 hours. The sonars produced narrow 
(<100 Hz) bandwidth signals at center frequencies of 2.6 and 3.3 kHz (-
53C), and 6.8 to 8.2 kHz (-56). The respective source levels were 
usually 235 and 223 dB re 1 micro Pa, but the -53C briefly operated at 
an unstated but substantially higher source level. The unusual 
bathymetry and constricted channel where the strandings occurred were 
conducive to channeling sound. This, and the extended operations by 
multiple sonars, apparently prevented escape of the animals to the open 
sea. In addition to the strandings, there are reports that beaked 
whales were no longer present in the Providence Channel region after 
the event, suggesting that other beaked whales either abandoned the 
area or perhaps died at sea (Balcomb and Claridge, 2001).
    Other strandings of beaked whales associated with operation of 
military sonars have also been reported (e.g., Simmonds and Lopez-
Jurado, 1991; Frantzis, 1998). In these cases, it was not determined 
whether there were noise-induced injuries to the ears or other organs. 
Another stranding of beaked whales (15 whales) happened on 24-25 
September 2002 in the Canary Islands, where naval maneuvers were taking 
place. Jepson et al. (2003) concluded that cetaceans might be subject 
to decompression injury in some situations. If so, this might occur if 
the mammals ascend unusually quickly when exposed to aversive sounds. 
Previously, it was widely assumed that diving marine mammals are not 
subject to the bends or air embolism.
    It is important to note that seismic pulses and mid-frequency sonar 
pulses are quite different. Sounds produced by the types of airgun 
arrays used to profile sub-sea geological structures are broadband with 
most of the energy below 1 kHz. Typical military mid-frequency sonars 
operate at frequencies of 2 to 10 kHz, generally with a relatively 
narrow bandwidth at any one time (though the center frequency may 
change over time). Because seismic and sonar sounds have considerably 
different characteristics and duty cycles, 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 hearing damage 
and, indirectly, mortality suggests that caution is warranted when 
dealing with exposure of marine mammals to any high-intensity pulsed 
sound.
    In addition to the sonar-related strandings, there was a September, 
2002 stranding of two Cuvier's beaked whales in the Gulf of California 
(Mexico) when a seismic survey by the Ewing was underway in the general 
area (Malakoff, 2002). The airgun array in use during that project was 
the Ewing's 20-gun 8490-in\3\ array. This might be a first indication 
that seismic surveys can have effects, at least on beaked whales, 
similar to the suspected effects of naval sonars. However, the evidence 
linking the Gulf of California strandings to the seismic surveys is 
inconclusive, and to date is not based on any physical evidence 
(Hogarth, 2002; Yoder, 2002). The ship was also operating its multi-
beam bathymetric sonar at the same time but this sonar had much less 
potential than these naval sonars to affect beaked whales. Although the 
link between the Gulf of California strandings and the seismic (plus 
multi-beam sonar) survey is inconclusive, this plus the various 
incidents involving beaked whale strandings associated with naval 
exercises suggests a need for caution in conducting seismic surveys in 
areas occupied by beaked whales.

Non-auditory Physiological Effects

    Possible types of non-auditory physiological effects or injuries 
that might theoretically occur in marine mammals exposed to strong 
underwater sound might include stress, neurological effects, bubble 
formation, resonance effects, and other types of organ or tissue 
damage. There is no evidence that any of these effects occur in marine 
mammals exposed to sound from airgun arrays. However, there have been 
no direct studies of the potential for airgun pulses to elicit any of 
these effects. If any such effects do occur, they would probably be 
limited to unusual situations when animals might be exposed at close 
range for unusually long periods.
    Long-term exposure to anthropogenic noise may have the potential to 
cause physiological stress that could affect the health of individual 
animals or their reproductive potential, which could theoretically 
cause effects at the population level (Gisner (ed.), 1999). However, 
there is essentially no information about the occurrence of noise-
induced stress in marine mammals. Also, it is doubtful that any single 
marine mammal would be exposed to strong seismic sounds for 
sufficiently long that significant physiological stress would develop. 
This is particularly so in the case of broad-scale seismic surveys 
where the tracklines are generally not as closely spaced as in many 
industry seismic surveys.
    Gas-filled structures in marine animals have an inherent 
fundamental resonance frequency. If stimulated at this frequency, the 
ensuing resonance could cause damage to the animal. There may also be a 
possibility that high sound levels could cause bubble formation in the 
blood of diving mammals that in turn could cause an air

[[Page 35005]]

embolism, tissue separation, and high, localized pressure in nervous 
tissue (Gisner (ed), 1999; Houser et al., 2001). In 2002, NMFS held a 
workshop (Gentry (ed.) 2002) to discuss whether the stranding of beaked 
whales in the Bahamas in 2000 might have been related to air cavity 
resonance or bubble formation in tissues caused by exposure to noise 
from naval sonar. A panel of experts concluded that resonance in air-
filled structures was not likely to have caused this stranding. Among 
other reasons, the air spaces in marine mammals are too large to be 
susceptible to resonant frequencies emitted by mid- or low-frequency 
sonar; lung tissue damage has not been observed in any mass, multi-
species stranding of beaked whales; and the duration of sonar pings is 
likely too short to induce vibrations that could damage tissues (Gentry 
(ed.), 2002). Opinions were less conclusive about the possible role of 
gas (nitrogen) bubble formation/growth in the Bahamas stranding of 
beaked whales. Workshop participants did not rule out the possibility 
that bubble formation/growth played a role in the stranding and 
participants acknowledged that more research is needed in this area. 
The only available information on acoustically-mediated bubble growth 
in marine mammals is modeling that assumes prolonged exposure to sound.
    In summary, little is known about the potential for seismic survey 
sounds to cause either auditory impairment or other non-auditory 
physical effects in marine mammals. Available data suggest that such 
effects, if they occur at all, would be limited to short distances from 
the sound source. However, the available data do not allow for 
meaningful quantitative predictions of the numbers (if any) of marine 
mammals that might be affected in these ways. Marine mammals that show 
behavioral avoidance of seismic vessels, including most baleen whales, 
some odontocetes, and some pinnipeds, are unlikely to incur auditory 
impairment or other physical effects.

Possible Effects of Mid-frequency Sonar Signals

    A multi-beam bathymetric sonar (Atlas Hydrosweep DS-2 (15.5-kHz) or 
Simrad EM1002 (95 kHz)) and a sub-bottom profiler will be operated from 
the source vessel essentially continuously during the planned survey. 
Details about these sonars were provided previously in this document.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans generally (1) are more powerful than the Atlas 
Hydrosweep or EM1002 sonars, (2) have a longer pulse duration, and (3) 
are directed close to horizontally (vs. downward for the Atlas 
Hydrosweep and EM1002). The area of possible influence for the Ewing's 
sonars is much smaller - a narrow band below the source vessel. For the 
Hydrosweep there is no horizontal propagation as these signals project 
at an angle of approximately 45 degrees from the ship. For the deep-
water mode, under the ship the 160- and 180-dB zones are estimated to 
be 3200 m (10500 ft) and 610 m (2000 ft), respectively. However, the 
beam width of the Hydrosweep signal is only 2.67 degrees fore and aft 
of the vessel, meaning that a marine mammal diving could receive at 
most 1-2 signals from the Hydrosweep and a marine mammal on the surface 
would be unaffected. Marine mammals that do encounter the bathymetric 
sonars at close range 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 and vessel 
speed. Therefore, as harassment or injury from pulsed sound is a 
function of total energy received, the actual harassment or injury 
threshold for the bathymetric sonar signals (approximately 10 ms) such 
sounds would be at a much higher dB level than that for longer duration 
pulses such as seismic signals. As a result, NMFS believes that marine 
mammals are unlikely to be harassed or injured from the multibeam 
sonar.

Masking by Mid-frequency Sonar Signals

    Marine mammal communications will not be masked appreciably by the 
multibeam sonar signals or the sub-bottom profiler given the low duty 
cycle and directionality of the sonars and the brief period when an 
individual mammal is likely to be within its beam. Furthermore, in the 
case of baleen whales, the sonar signals from the Hydrosweep sonar do 
not overlap with the predominant frequencies in the calls, which would 
avoid significant masking. The 95-kHz pulses from the EM1002 sonar will 
be inaudible to baleen whales and pinnipeds.
    For the sub-bottom profiler and 12-kHz pinger, marine mammal 
communications will not be masked appreciably because of their 
relatively low power output, low duty cycle, directionality (for the 
profiler), and the brief period when an individual mammal may be within 
the sonar's beam. In the case of most odonotocetes, the sonar signals 
from the profiler do not overlap with the predominant frequencies in 
their calls. In the case of mysticetes, the pulses from the pinger do 
not overlap with their predominant frequencies.

Behavioral Responses Resulting from Mid-Frequency Sonar Signals

    Behavioral reactions of free-ranging marine mammals to military and 
other sonars appear to vary by species and circumstance. Observed 
reactions have included silencing and dispersal by sperm whales 
(Watkins et al., 1985), increased vocalizations and no dispersal by 
pilot whales (Rendell and Gordon, 1999), and the previously-mentioned 
beachings by beaked whales. Also, Navy personnel have described 
observations of dolphins bow-riding adjacent to bow-mounted mid-
frequency sonars during sonar transmissions. However, all of these 
observations are of limited relevance to the present situation. Pulse 
durations from these sonars were much longer than those of the L-DEO 
multibeam sonar, and a given mammal would have received many pulses 
from the naval sonars. During L-DEO's operations, the individual pulses 
will be very short, and a given mammal would not receive many of the 
downward-directed pulses as the vessel passes by.
    Captive bottlenose dolphins and a white whale exhibited changes in 
behavior when exposed to 1-sec pulsed sounds at frequencies similar to 
those that will be emitted by the multi-beam sonar used by L-DEO and to 
shorter broadband pulsed signals. Behavioral changes typically involved 
what appeared to be deliberate attempts to avoid the sound exposure 
(Schlundt et al., 2000; Finneran et al., 2002). The relevance of these 
data to free-ranging odontocetes is uncertain and in any case the test 
sounds were quite different in either duration or bandwidth as compared 
to those from a bathymetric sonar.
    L-DEO and NMFS are not aware of any data on the reactions of 
pinnipeds to sonar sounds at frequencies similar to those of the 15.5 
kHz frequency of the Ewing's multibeam sonar. Based on observed 
pinniped responses to other types of pulsed sounds, and the likely 
brevity of exposure to the bathymetric sonar sounds, pinniped reactions 
are expected to be limited to startle or otherwise brief responses of 
no lasting consequences to the individual animals. As mentioned, the 
95-kHz sounds from the EM1002 will be inaudible to pinnipeds and to 
baleen whales, so it will have no disturbance effects on those groups 
of mammals. The pulsed signals from the sub-bottom profiler and pinger 
are much weaker than those from the airgun array and the multibeam 
sonar. Therefore, significant behavioral responses are not expected.

[[Page 35006]]

Hearing Impairment and Other Physical Effects

    Given recent stranding events that have been associated with the 
operation of naval sonar, there is much concern that sonar noise can 
cause serious impacts to marine mammals (for discussion see Effects of 
Seismic Surveys). However, the multi-beam sonars proposed for use by L-
DEO are quite different than sonars used for navy operations. Pulse 
duration of the bathymetric sonars is very short relative to the naval 
sonars. Also, at any given location, an individual marine mammal would 
be in the beam of the multi-beam sonar for much less time given the 
generally downward orientation of the beam and its narrow fore-aft 
beam-width. (Navy sonars often use near-horizontally-directed sound.) 
These factors would all reduce the sound energy received from the 
multi-beam sonar rather drastically relative to that from the sonars 
used by the Navy. Therefore, hearing impairment by multi-beam 
bathymetric sonar is unlikely.
    Source levels of the sub-bottom profiler are much lower than those 
of the airguns and the multi-beam sonar. Sound levels from a sub-bottom 
profiler similar to the one on the Ewing were estimated to decrease to 
180 dB re 1 microPa (rms) at 8 m (26 ft) horizontally from the source 
(Burgess and Lawson, 2000), and at approximately 18 m downward from the 
source. Furthermore, received levels of pulsed sounds that are 
necessary to cause temporary or especially permanent hearing impairment 
in marine mammals appear to be higher than 180 dB (see earlier 
discussion). Thus, it is unlikely that the sub-bottom profiler produces 
pulse levels strong enough to cause hearing impairment or other 
physical injuries even in an animal that is (briefly) in a position 
near the source.
    The sub-bottom profiler is usually operated simultaneously with 
other higher-power acoustic sources. Many marine mammals will move away 
in response to the approaching higher-power sources or the vessel 
itself before the mammals would be close enough for there to be any 
possibility of effects from the less intense sounds from the sub-bottom 
profiler. In the case of mammals that do not avoid the approaching 
vessel and its various sound sources, mitigation measures that would be 
applied to minimize effects of the higher-power sources would further 
reduce or eliminate any minor effects of the sub-bottom profiler.
    The 12-kHz pinger is unlikely to cause hearing impairment or 
physical injuries even in an animal that is in a position near the 
source because is does not produce strong pulse levels.

Estimates of Take by Harassment for the Gulf of Alaska Seismic Survey

    Although information contained in this document indicates that 
injury to marine mammals from seismic sounds potentially occurs at 
sound pressure levels significantly higher than 180 and 190 dB, NMFS' 
current criteria for onset of Level A harassment of cetaceans and 
pinnipeds from impulse sound are, respectively, 180 and 190 re 1 
microPa rms. The rms level of a seismic pulse is typically about 10 dB 
less than its peak level and about 16 dB less than its pk-pk level 
(Greene, 1997; McCauley et al., 1998; 2000a). The criterion for Level B 
harassment onset is 160 dB.
    Given the proposed mitigation (see Mitigation later in this 
document), all anticipated takes involve a temporary change in behavior 
that may constitute Level B harassment. The proposed mitigation 
measures will minimize or eliminate the possibility of Level A 
harassment or mortality. L-DEO has calculated the ``best estimates'' 
for the numbers of animals that could be taken by level B harassment 
during the proposed GOA seismic survey using data on marine mammal 
density and abundance from marine mammal surveys in the region, and 
estimates of the size of the affected area, as shown in the predicted 
RMS radii table (see Table 1).
    These estimates are based on a consideration of the number of 
marine mammals that might be exposed to sound levels greater than 160 
dB, the criterion for the onset of Level B harassment, by operations 
with the 2 GI-gun array planned to be used for this project. The 
anticipated zone of influence of the multi-beam sonar is less than that 
for the airguns, so it is assumed that any marine mammals close enough 
to be affected by the multi-beam sonar would already be affected by the 
airguns. Therefore, no additional incidental takings are included for 
animals that might be affected by the multi-beam sonar.
    Table 2 explains the corrected density estimates as well as the 
best estimate of the numbers of each species that would be exposed to 
seismic sounds greater than 160 dB. A detailed description on the 
methodology used by L-DEO to arrive at the estimates of Level B 
harassment takes that are provided in Table 2 can be found in L-DEO's 
IHA application for the GOA survey.
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Conclusions

Effects on Cetaceans
    Strong avoidance reactions by several species of mysticetes to 
seismic vessels have been observed at ranges up to 6-8 km (3.2-4.3 nm) 
and occasionally as far as 20-30 km (10.8-16.2 nm) from the source 
vessel. However, reactions at the longer distances appear to be 
atypical of most species and situations, particular when feeding whales 
are involved. Many of the mysticetes that will be encountered in SE 
Alaska at the time of the proposed seismic survey will be feeding. In 
addition, the estimated numbers presented in Table 2 are considered 
overestimates of actual numbers that may be harassed. The estimated 
160-dB radii used here are probably overestimates of the actual 160-dB 
radii at water depths [gteqt]100 m ( ft) based on the few calibration 
data obtained in deep water (Tolstoy et al., 2004).
    Odontocete reactions to seismic pulses, or at least the reactions 
of dolphins, are expected to extend to lesser distances than are those 
of mysticetes. Odontocete low-frequency hearing is less sensitive than 
that of mysticetes, and dolphins are often seen from seismic vessels. 
In fact, there are documented instances of dolphins approaching active 
seismic vessels. However, dolphins as well as some other types of 
odontocetes sometimes show avoidance responses and/or other changes in 
behavior when near operating seismic vessels.
    Taking into account the small size and the relatively low sound 
output of the 2 GI-guns to be used, and the mitigation measures that 
are planned, effects on cetaceans are generally expected to be limited 
to avoidance of a small area around the seismic operation and short-
term changes in behavior, falling within the MMPA definition of Level B 
harassment. Furthermore, the estimated numbers of animals potentially 
exposed to sound levels sufficient to cause appreciable disturbance are 
very low percentages of the affected populations.
    Based on the 160-dB criterion, the best estimates of the numbers of 
individual cetaceans that may be exposed to sounds >160 dB re 1 microPa 
(rms) represent 0 to 1.1 percent of the populations of each species in 
the North Pacific Ocean (Table 2). For species listed as endangered 
under the Endangered Species Act (ESA), this includes no North Pacific 
right whales or blue whales; <=0.01 percent of the Northeast Pacific 
population of sperm whales; 1.1 percent of the humpback whale 
population; and 0.8 percent of the whale population (Table 2). In the 
cases of belugas, beaked whales, and sperm whales, these potential 
reactions are expected to involve no more than very small numbers (0 to 
11) of individual cetaceans. Humpback and whales are the endangered 
species that are most likely to be exposed and their Northeast Pacific 
populations are approximately 6000 (Caretta et al., 2002) and 10970 
(Ohsumi and Wada, 1974), respectively.
    It is highly unlikely that any North Pacific right whales will be 
exposed to seismic sounds [gteqt]160 dB re 1 microPa (rms). This 
conclusion is based on the rarity of this species in SE Alaska and in 
the Northeast Pacific (less than 100, Carretta et al., 2002), and that 
the remnant population of this species apparently migrates to more 
northerly areas during the summer. However, L-DEO has requested an 
authorization to expose up to two North Pacific right whales to 
[gteqt]160 dB, given the possibility (however unlikely) of encountering 
one or more of this endangered species. If a right whale is sighted by 
the vessel-based observers, the 2 GI-airguns will be shut down (not 
just powered down) regardless of the distance of the whale from the 
airguns.
    Substantial numbers of phocoenids and delphinids may be exposed to 
airgun sounds during the proposed seismic studies, but the population 
sizes of species likely to occur in the operating area are large, and 
the numbers potentially affected are small relative to the population 
sizes (Table 2). The best estimates of the numbers of individual Dall's 
and harbor porpoises that might be exposed to [gteqt]160 dB represent 
0.8 percent and 0.4 percent of their Northeast Pacific populations. The 
best estimates of the numbers of individual delphinids that might be 
exposed to sounds [gteqt]170 dB re 1 microPa (rms) represents much less 
than 0.01 percent of the approximately 600,000 dolphins estimated to 
occur in the Northeast Pacific, and 0 to 0.2 percent of the populations 
of each species occurring there (Table 2).
    Varying estimates of the numbers of marine mammals that might be 
exposed to sounds from the 2 GI-airguns during the 2004 seismic surveys 
off SW Alaska have been presented, depending on the specific exposure 
criteria, calculation procedures (exposures vs. individuals), and 
density criteria used (best vs. maximum). The requested ``take 
authorization'' for each species is based on the estimated maximum 
number of exposures to >160 dB re 1 microPa (rms). That figure likely 
overestimates (in most cases by a large margin) the actual number of 
animals that will be exposed to these sounds; the reasons for this have 
been discussed previously and in L-DEO's application. Even so, the 
estimates for the proposed surveys are quite low percentages of the 
population sizes. Also, these relatively short-term exposures are 
unlikely to result in any long-term negative consequences for the 
individuals or their populations.
    Mitigation measures such as controlled speed, course alteration, 
observers, ramp ups, and shut downs when marine mammals are seen within 
deed ranges (see Mitigation) should further reduce short-term 
reactions, and minimize any effects on hearing sensitivity. In all 
cases, the effects are expected to be short-term, with no lasting 
biological consequence. In light of the type of take expected and the 
small percentages of affected stocks, the action is expected to have no 
more than a negligible impact on the affected species or stocks of 
marine mammals.

Effects on Pinnipeds

    Two pinniped species, the Steller sea lion and the harbor seal, are 
likely to be encountered in the study area. In addition, it is possible 
(although unlikely) that a small number of northern fur seals may be 
encountered. An estimated 1498 harbor seals and 195 Steller sea lions 
(or 1 percent of the Northeast Pacific population) may be exposed to 
airgun sounds during the seismic survey. It is unknown how many of 
these would actually be disturbed, but most likely it would only be a 
small percentage of that population. Similar to cetaceans, the short-
term exposures to airgun and sonar sounds are not expected to result in 
any long-term negative consequences for the individuals or their 
populations.

Potential Effects on Fissipeds

    As indicated in Table 2, L-DEO estimates that 68 sea otters that 
could potentially be encountered during airgun operations with a 
maximum estimate of 123 sea otters. L-DEO believes these estimates are 
likely an overestimate of the number of otters affected, as there is 
little evidence that sea otters are disturbed by sounds from either a 
small airgun source or from a large array of airguns (Riedman 1983, 
1984). However, sea otters are under the jurisdiction of the U.S. Fish 
and Wildlife Service (USFWS). L-DEO is consulting with the USFWS 
regarding whether sea otters will be affected by the 2 GI-airguns being 
employed in the GOA project.

Potential Effects on Habitat

    The proposed seismic survey will not result in any permanent impact 
on habitats used by marine mammals, or to

[[Page 35009]]

the food sources they utilize. The main impact issue associated with 
the proposed activity will be temporarily elevated noise levels and the 
associated direct effects on marine mammals. The actual area that will 
be affected by coring operations will be a very small fraction of the 
marine mammal habitat and the habitat of their food species in the 
area; thus, any effects are expected to be highly localized and 
insignificant. Coring operations would result in no more than a 
negligible and highly localized short-term disturbance to sediments and 
benthic organisms. The area that might be disturbed is a very small 
fraction of the overall area occupied by a fish or marine mammal 
species.
    One of the reasons for the adoption of airguns as the standard 
energy source for marine seismic surveys was that they (unlike the 
explosives used in the distant past) do not result in any appreciable 
fish kill. Various experimental studies showed that airgun discharges 
cause little or no fish kill, and that any injurious effects were 
generally limited to the water within a meter or so of an airgun. 
However, it has recently been found that injurious effects on captive 
fish, especially on fish hearing, may occur to somewhat greater 
distances than previously thought (McCauley et al., 2000a,b, 2002; 
2003). Even so, any injurious effects on fish would be limited to short 
distances. Also, many of the fish that might otherwise be within the 
injury-zone are likely to be displaced from this region prior to the 
approach of the airguns through avoidance reactions to the passing 
seismic vessel or to the airgun sounds as received at distances beyond 
the injury radius.
    Fish often react to sounds, especially strong and/or intermittent 
sounds of low frequency. Sound pulses at received levels of 160 dB re 1 
microPa (peak) may cause subtle changes in behavior. Pulses at levels 
of 180 dB (peak) may cause noticeable changes in behavior (Chapman and 
Hawkins, 1969; Pearson et al., 1992; Skalski et al., 1992). It also 
appears that fish often habituate to repeated strong sounds rather 
rapidly, on time scales of minutes to an hour. However, the habituation 
does not endure, and resumption of the disturbing activity may again 
elicit disturbance responses from the same fish. Fish near the airguns 
are likely to dive or exhibit some other kind of behavioral response. 
This might have short-term impacts on the ability of cetaceans to feed 
near the survey area. However, only a small fraction of the available 
habitat would be ensonified at any given time, and fish species would 
return to their pre-disturbance behavior once the seismic activity 
ceased. Thus, the proposed surveys would have little impact on the 
abilities of marine mammals to feed in the area where seismic work is 
planned. Some of the fish that do not avoid the approaching airguns 
(probably a small number) may be subject to auditory or other injuries.
    Zooplankters that are very close to the source may react to the 
airgun's impulse. These animals have an exoskeleton and no air sacs; 
therefore, little or no mortality is expected. Many crustaceans can 
make sounds and some crustacea and other invertebrates have some type 
of sound receptor. However, the reactions of zooplankters to sound are 
not known. Some mysticetes feed on concentrations of zooplankton. A 
reaction by zooplankton to a seismic impulse would only be relevant to 
whales if it caused a concentration of zooplankton to scatter. Pressure 
changes of sufficient magnitude to cause this type of reaction would 
probably occur only very close to the source, so few zooplankton 
concentrations would be affected. Impacts on zooplankton behavior are 
predicted to be negligible, and this would translate into negligible 
impacts on feeding mysticetes.

Potential Effects on Subsistence Use of Marine Mammals

    The proposed seismic project could potentially impact the 
availability of marine mammals for subsistence harvests in a very small 
area immediately around the Ewing, and for a very short time period 
while conducting seismic activities. However, considering the limited 
time and locations for the planned surveys, the proposed survey is not 
expected to have an unmitigable adverse impact on the availability of 
Steller sea lions, harbor seals or northern sea otters for subsistence 
harvests. Nevertheless, L-DEO plans to coordinate its activities with 
local subsistence communities so that seismic activities will be 
conducted outside subsistence hunting areas and times, if possible.

Mitigation

    For the proposed seismic survey in the GOA, L-DEO will deploy 2 GI-
airguns as an energy source, with a total discharge volume of 210 in3. 
The energy from the airguns will be directed mostly downward. The 
directional nature of the airguns to be used in this project is an 
important mitigating factor. This directionality will result in reduced 
sound levels at any given horizontal distance as compared with the 
levels expected at that distance if the source were omnidirectional 
with the stated nominal source level. Also, the small size of these 
airguns is an inherent and important mitigation measure that will 
reduce the potential for effects relative to those that might occur 
with large airgun arrays. This measure is in conformance with NMFS 
encouraging seismic operators to use the lowest intensity airguns 
practical to accomplish research objectives.

Proposed Safety Radii

    Received sound levels have been modeled by L-DEO for the 2 GI-
airguns, in relation to distance and direction from the airguns. The 
model does not allow for bottom interactions, and is most directly 
applicable to deep water. Based on the model, the distances from the 2 
G-airguns where sound levels of 190 dB, 180 dB, 170 dB, and 160 dB re 1 
microPa (rms) are predicted to be received are shown in the >1000 m 
(3281 ft) line of Table 1.
    Empirical data concerning these safety radii have been acquired 
based on measurements during the acoustic verification study conducted 
by L-DEO in the northern Gulf of Mexico from 27 May to 3 June 2003 (see 
68 FR 32460, May 30, 2003). Although the results are limited, L-DEO's 
analysis of the acoustic data from that study (Tolstoy et al., 2004) 
indicate that the radii around the airguns where the received level 
would be 180 dB re 1 microPa (rms), the safety zone applicable to 
cetaceans, vary with water depth.
    The proposed study area will occur in water approximately 30-3000 m 
(98-9843 ft) deep. In deep water (>1000 m (3281 ft)), the safety radii 
during airgun operations will be the values predicted by L-DEO's model 
(Table 1). Therefore, the assumed 180- and 190-dB radii are 54 m (177 
ft) and 17 m (56 ft), respectively. For operations in shallow (<100 m 
(328 ft)) water, conservative correction factors were applied to the 
predicted radii for the 2 GI-airgun array. The 180- and 190-dB radii in 
shallow water are assumed to be 400 m (1312 ft) and 250 m (820 ft), 
respectively. In intermediate depths (100-1000 m (328-3281 ft)), a 1.5x 
correction factor was applied to the estimates provided by the model 
for deep water situations. The assumed 180- and 190-dB radii in 
intermediate-depth water are 81 m (266 ft) and 26 m (85 ft), 
respectively. The 2 GI-airguns will be immediately shutdown when 
cetaceans or pinnipeds are detected within or about to enter the 
appropriate 180- or 190-dB zone.

Additional Mitigation Measures

    The following mitigation measures, as well as marine mammal visual 
monitoring (discussed later in this

[[Page 35010]]

document), are proposed for the subject seismic surveys: (1) Speed and 
course alteration (provided that they do not compromise operational 
safety requirements); (2) shut-down procedures; and (3) avoid 
encroaching upon critical habitat around Steller sea lion rookeries and 
haulouts. As discussed elsewhere in this document, special mitigation 
measures will be implemented for the North Pacific right whale.
    Although a ``power-down'' procedure is often applied by L-DEO 
during seismic surveys with larger arrays of airguns, L-DEO does not 
propose powering down to a single gun during this proposed project. 
Powering down from two guns to one gun would make only a small 
difference in the 180- or 190-dB zone, which is probably not enough 
distance to allow one-gun to continue operations if a mammal came 
within the safety zone for two guns.
    At night, vessel lights and/or night-vision devices (NVDs) could be 
useful in sighting some marine mammals at the surface within a short 
distance from the ship (within the safety radii for the 2-GI guns in 
deep and intermediate waters). Thus, start up of the airguns may be 
possible at night in deep and intermediate waters, in situations when 
the entire safety zone is visible with vessel lights and NVDs. However, 
lights and NVDs will probably not be very effective for monitoring the 
larger safety radii around the 2 GI-airguns operating in shallow water. 
In shallow water, therefore, nighttime start ups of the airguns are not 
proposed to be authorized.

Speed and Course Alteration

    If a marine mammal is detected outside the safety zone and, based 
on its position and the relative motion, is likely to enter the safety 
zone, the vessel's speed and/or direct course may, when practical and 
safe, be changed in a manner that also minimizes the effect to the 
planned science objectives. The marine mammal activities and movements 
relative to the seismic vessel will be closely monitored to ensure that 
the marine mammal does not approach within the safety zone. If the 
mammal appears likely to enter the safety zone, further mitigative 
actions will be taken (i.e., either further course alterations or shut 
down of the airguns). In the closely constrained waters of Lynn Canal, 
Muir Inlet, and Frederick Sound, it is unlikely that significant 
alterations to the vessel's speed or course could be made. In these 
circumstances, shut-down procedures would be implemented rather than 
speed or course changes.

Shut-down Procedures

    If a marine mammal is detected outside the safety zone but is 
likely to enter the safety zone, and if the vessel's speed and/or 
course cannot be changed to avoid having the mammal enter the safety 
zone, the airguns will be shut down before the mammal is within the 
safety zone. Likewise, if a mammal is already within the safety zone 
when first detected, the airguns will be shut down immediately. The 
airguns will be shut down if a North Pacific right whale is sighted 
from the vessel, even if it is located outside the safety zone.
    Following a shut down, airgun activity will not resume until the 
marine mammal has cleared the safety zone. The animal will be 
considered to have cleared the safety zone if it (1) is visually 
observed to have left the safety zone, or (2) has not been seen within 
the zone for 15 min in the case of small odontocetes and pinnipeds, or 
(3) has not been seen within the zone for 30 min in the case of 
mysticetes and large odontocetes, including sperm, pygmy sperm, dwarf 
sperm, and beaked whales.
    If the complete safety zone has not been visible for at least 30 
min prior to the start of operations in either daylight or nighttime, 
airgun operations will not commence. However, if the airgun array has 
been operational before nightfall, it can remain operational throughout 
the night, even though the entire safety radius may not be visible. If 
the entire safety zone is visible at night, using vessel lights and 
NVDs (as may be the case in deep and intermediate waters), then start 
up of the airguns may occur at night.

Ramp-up

    When airgun operations commence after a certain period without 
airgun operations, the number of guns firing will be increased 
gradually, or ``ramped up'' (also described as a ``soft start''). 
Usually, operations begin with the smallest gun in the array and guns 
are added in sequence such that the source level of the array will 
increase in steps not exceeding 6 dB per 5-min period. However, during 
this survey, with only 2 GI-guns, ramp-up will be implemented by 
turning on one airgun, followed 5 minutes later by the second airgun. 
Throughout the ramp-up procedure, the safety zone will be maintained.
    Comments on past IHAs raised the issue of prohibiting nighttime 
operations as a practical mitigation measure. However, this is not 
practicable due to cost considerations. The daily cost to the federal 
government to operate vessels such as Ewing is approximately $33,000 to 
$35,000/day (Ljunngren, pers. comm. May 28, 2003). If the vessels were 
prohibited from operating during nighttime, it is possible that each 
trip would require an additional three to five days, or up to $175,000 
more, depending on average daylight at the time of work.
    If a seismic survey vessel is limited to daylight seismic 
operations, efficiency would be much reduced. Without commenting 
specifically on how that would affect the present project, for seismic 
operators in general, a daylight-only requirement would be expected to 
result in one or more of the following outcomes: cancellation of 
potentially valuable seismic surveys; reduction in the total number of 
seismic cruises annually due to longer cruise durations; a need for 
additional vessels to conduct the seismic operations; or work conducted 
by non-U.S. operators or non-U.S. vessels when in waters not subject to 
U.S. law.
    Taking into consideration the additional costs of prohibiting 
nighttime operations and the likely impact of the activity (including 
all mitigation and monitoring), NMFS has preliminarily determined that 
the proposed mitigation and monitoring ensures that the activity will 
have the least practicable impact on the affected species or stocks. 
Marine mammals will have sufficient notice of a vessel approaching with 
operating seismic airguns, thereby giving them an opportunity to avoid 
the approaching array; if ramp-up is required, two marine mammal 
observers will be required to monitor the safety radii using shipboard 
lighting or NVDs for at least 30 minutes before ramp-up begins and 
verify that no marine mammals are in or approaching the safety radii; 
ramp-up may not begin unless the entire safety radii are visible. 
Therefore it is likely that the 2 GI-airgun array will not be ramped-up 
from a shut-down at night when in waters shallower than 100 m (328 ft).

Marine Mammal Monitoring

    L-DEO must have at least three visual observers on board the Ewing, 
and at least two must be an experienced marine mammal observer that 
NMFS has approved in advance of the start of the GOA cruise. These 
observers will be on duty in shifts of no longer than 4 hours.
    The visual observers will monitor marine mammals and sea turtles 
near the seismic source vessel during all daytime airgun operations, 
during any nighttime start-ups of the airguns and at night, whenever 
daytime monitoring resulted in one or more shut-down

[[Page 35011]]

situations due to marine mammal presence. During daylight, vessel-based 
observers will watch for marine mammals and sea turtles near the 
seismic vessel during periods with shooting (including ramp-ups), and 
for 30 minutes prior to the planned start of airgun operations after a 
shut-down.
    Use of multiple observers will increase the likelihood that marine 
mammals near the source vessel are detected. L-DEO bridge personnel 
will also assist in detecting marine mammals and implementing 
mitigation requirements whenever possible (they will be given 
instruction on how to do so), especially during ongoing operations at 
night when the designated observers are on stand-by and not required to 
be on watch at all times.
    The observer(s) will watch for marine mammals from the highest 
practical vantage point on the vessel, which is either the bridge or 
the flying bridge. On the bridge of the Ewing, the observer's eye level 
will be 11 m (36 ft) above sea level, allowing for good visibility 
within a 210[deg] arc. If observers are stationed on the flying bridge, 
the eye level will be 14.4 m (47.2 ft) above sea level. The observer(s) 
will systematically scan the area around the vessel with Big Eyes 
binoculars, reticle binoculars (e.g., 7 X 50 Fujinon) and with the 
naked eye during the daytime. Laser range-ding binoculars (Leica L.F. 
1200 laser rangefinder or equivalent) will be available to assist with 
distance estimation. The observers will be used to determine when a 
marine mammal or sea turtle is in or near the safety radii so that the 
required mitigation measures, such as course alteration and power-down 
or shut-down, can be implemented. If the airguns are shut down, 
observers will maintain watch to determine when the animal is outside 
the safety radius.
    Observers will not be on duty during ongoing seismic operations at 
night; bridge personnel will watch for marine mammals during this time 
and will call for the airguns to be shut-down if marine mammals are 
observed in or about to enter the safety radii. However, a biological 
observer must be on standby at night and available to assist the bridge 
watch if marine mammals are detected. If the airguns are ramped-up at 
night, two marine mammal observers will monitor for marine mammals for 
30 minutes prior to ramp-up and during the ramp-up using either deck 
lighting or night vision equipment that will be available (ITT F500 
Series Generation 3 binocular image intensifier or equivalent).

Passive Acoustic Monitoring (PAM)

    Although PAM has been used in previous seismic surveys, L-DEO does 
not propose to use the PAM system during this research cruise. First, 
the 180-dB zones are significantly smaller than those found for the 
larger L-DEO arrays making the PAM unnecessary for locating marine 
mammals. Secondly, the effectiveness of the PAM in shallow water is not 
high and third, because of the coring operations, additional berthing 
is unavailable for the PAM operators.

Reporting

    L-DEO will submit a report to NMFS within 90 days after the end of 
the cruise, which is currently predicted to occur during August, 2004. 
The report will describe the operations that were conducted and the 
marine mammals that were detected. The report must provide full 
documentation of methods, results, and interpretation pertaining to all 
monitoring tasks. The report will summarize the dates and locations of 
seismic operations, marine mammal sightings (dates, times, locations, 
activities, associated seismic survey activities), and estimates of the 
amount and nature of potential take of marine mammals by harassment or 
in other ways.

ESA

    Under section 7 of the ESA, the National Science Foundation (NSF), 
the agency funding L-DEO, has begun consultation on the 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)

    The NSF has prepared an EA for the GOA oceanographic surveys. NMFS 
is reviewing this EA and will either adopt it or prepare its own NEPA 
document before making a determination on the issuance of an IHA. A 
copy of the NSF EA for this activity is available upon request (see 
ADDRESSES).

Preliminary Conclusions

    NMFS has preliminarily determined that the impact of conducting the 
seismic survey in the GOA in the northeastern Pacific Ocean will 
result, at worst, in a temporary modification in behavior by certain 
species of marine mammals. This activity is expected to result in no 
more than a negligible impact on the affected species or stocks.
    For reasons stated previously in this document, this preliminary 
determination is supported by (1) the likelihood that, given sufficient 
notice through slow ship speed and ramp-up, marine mammals are expected 
to move away from a noise source that it ds annoying prior to its 
becoming potentially injurious; (2) recent research that indicates that 
TTS is unlikely (at least in delphinids) until levels closer to 200-205 
dB re 1 microPa are reached rather than 180 dB re 1 microPa; (3) the 
fact that 200-205 dB isopleths would be within 100 m (328 ft) of the 
vessel even in shallow water; and (4) the likelihood that marine mammal 
detection ability by trained observers is close to 100 percent during 
daytime and remains high at night to that distance from the seismic 
vessel. As a result, no take by injury and/or death is anticipated, and 
the potential for temporary or permanent hearing impairment is very low 
and will be avoided through the incorporation of the mitigation 
measures mentioned in this document.
    While the number of potential incidental harassment takes will 
depend on the distribution and abundance of marine mammals in the 
vicinity of the survey activity, the number of potential harassment 
takings is estimated to be small. In addition, the proposed seismic 
program is not expected to interfere with any subsistence hunts, since 
seismic operations will not take place in subsistence whaling and 
sealing areas and will not affect marine mammals used for subsistence 
purposes.

Proposed Authorization

    NMFS proposes to issue an IHA to L-DEO for conducting a 
oceanographic seismic survey in the GOA, northeastern Pacific Ocean, 
provided the previously mentioned mitigation, monitoring, and reporting 
requirements are incorporated. NMFS has preliminarily determined that 
the proposed activity would result in the harassment of small numbers 
of marine mammals; would have no more than a negligible impact on the 
affected marine mammal stocks; and would not have an unmitigable 
adverse impact on the availability of species or stocks for subsistence 
uses.

Information Solicited

    NMFS requests interested persons to submit comments and information 
concerning this request (see ADDRESSES).

    Dated: June 17, 2004.
Laurie K. Allen,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 04-14242 Filed 6-22-04; 8:45 am]
BILLING CODE 3510-22-S