Small Takes of Marine Mammals Incidental to Specified Activities; Low-Energy Marine Seismic Survey in the Northeast Pacific Ocean, September 2007

Note: EPA no longer updates this information, but it may be useful as a reference or resource.


[Federal Register: August 1, 2007 (Volume 72, Number 147)]
[Notices]
[Page 42045-42058]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr01au07-44]

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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XB70

Small Takes of Marine Mammals Incidental to Specified Activities;
Low-Energy Marine Seismic Survey in the Northeast Pacific Ocean,
September 2007

AGENCY:  National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION:  Notice; proposed incidental take authorization; request for
comments.

-----------------------------------------------------------------------

SUMMARY:  NMFS has received an application from Scripps Institute of
Oceanography (SIO) for an Incidental Harassment Authorization (IHA) to
take marine mammals incidental to conducting a low-energy marine
seismic survey in the northeastern Pacific Ocean during September,
2007. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is
requesting comments on its proposal to issue an IHA to SIO to
incidentally take, by Level B harassment only, several species of
marine mammals during the aforementioned activity.

DATES:  Comments and information must be received no later than August
31, 2007.

ADDRESSES:  Comments on the application should be addressed to P.
Michael Payne, Chief, Permits, Conservation and Education Division,
Office of Protected Resources, National Marine Fisheries Service, 1315
East-West Highway, Silver Spring, MD 20910-3225. The mailbox address
for providing email comments is PR1.0648XB70@noaa.gov. NMFS is not
responsible for e-mail comments sent to addresses other than the one
provided here. Comments sent via e-mail, including all attachments,
must not exceed a 10-megabyte file size.
    A copy of the application containing a list of the references used
in this document may be obtained by writing to the address specified
above, telephoning the contact listed below (see FOR FURTHER
INFORMATION CONTACT), or visiting the internet at: 
http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
    Documents cited in this notice may be viewed, by appointment,
during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Candace Nachman or Jolie Harrison,
Office of Protected Resources, NMFS, (301) 713-2289.

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.)
direct the Secretary of Commerce to allow, upon request, the
incidental, but not intentional, taking of marine mammals by U.S.
citizens who engage in a specified activity (other than commercial
fishing) within a specified geographical region if certain findings are
made and either regulations are issued or, if the taking is limited to
harassment, a notice of a proposed authorization is provided to the
public for review.
    Authorization shall be granted if NMFS finds that the taking will
have a negligible impact on the species or stock(s), will not have an
unmitigable adverse impact on the availability of the species or
stock(s) for subsistence uses (where relevant), and if the permissible
methods of taking and requirements pertaining to the mitigation,
monitoring, and reporting of such takings are set forth. NMFS has
defined ``negligible impact'' in 50 CFR 216.103 as ''...an impact
resulting from the specified activity that cannot be reasonably
expected to, and is not reasonably likely to, adversely affect the species
or stock through effects on annual rates of recruitment or survival.
    Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the U.S. can apply for an authorization to
incidentally take small numbers of marine mammals by harassment. Except
with respect to certain activities not pertinent here, the MMPA defines
``harassment'' as:
    any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
    Section 101(a)(5)(D) establishes a 45-day time limit for NMFS
review of an application followed by a 30-day public notice and comment
period on any proposed authorizations for the incidental harassment of
marine mammals. Within 45 days of the close of the comment period, NMFS
must either approve or deny the authorization.

Summary of Request

    On May 4, 2007, NMFS received an application from SIO for the
taking, by Level B harassment only, of 32 species of marine mammals
incidental to conducting, with research funding from the National
Science Foundation (NSF), an ocean-bottom seismograph (OBS) deployment
and a magnetic, bathymetric, and seismic survey program off the Oregon
coast in the northeastern Pacific Ocean during September, 2007. The
purpose of the research program is to record microearthquakes in the
forearc to determine whether seismicity on the plate boundary is
characteristic of a locked or a freely slipping fault plane. OBSs will
be deployed and left in place for a year, and a seismic survey will be
used to locate the instruments accurately and precisely on the seafloor
and to characterize the shallow sediment structure around the
instrument. Seismometers measure movement in the Earth's crust. About
90 percent of all natural earthquakes occur under water, where great
pressure and cold make measurements difficult. The OBS was developed
for this task. Scientists use seismometer data to calculate the energy
released by earthquakes. Also included in the research is the use of a
magnetometer and sub-bottom profiler.

Description of the Activity

    The seismic surveys will involve one vessel, the R/V Wecoma (Wecoma),

[[Page 42046]]

which is scheduled to depart from Newport, Oregon on September 5, 2007
and return on September 11, 2007. The exact dates of the activities may
vary by a few days because of weather conditions, repositioning, OBS
and streamer operations and adjustments, GI-gun deployment, or the need
to repeat some lines if data quality is substandard. The seismic
surveys will take place off the Oregon coast in the northeastern
Pacific Ocean. The overall area within which the seismic surveys will
occur is located between approximately 44[deg]
and 45[deg] N. and
124.5[deg]
and 126[deg] W. (Figure 1 in the application). The surveys
will occur approximately 25-110 km (15.5-68.4 mi) offshore from Oregon
in water depths between approximately 110 and 3,050 m (361 and 10,007
ft), entirely within the Exclusive Economic Zone of the U.S.
    The Wecoma will deploy a single low-energy Generator-Injector (GI)
airgun as an energy source (with a discharge volume of 45 in\3\), 16
OBSs that will remain in place for a year, and a 300 m-long (984 ft-
long), 16-channel, towed hydrophone streamer. The program will consist
of approximately 21 km (13 mi) of surveys over each of the 16 OBSs. The
GI gun will be operated on a small grid for approximately 2 hours at
each of 16 OBS sites over an approximately 7-day period during
September, 2007. There will be additional seismic operations associated
with equipment testing, start-up, and repeat coverage of any areas
where initial data quality is sub-standard. The OBSs are acoustically
passive and do not emit any sounds into the ocean.
    In addition to the operations of the GI gun, a 3.5-kHz sub-bottom
profiler, a Knudsen 320BR sub-bottom profiler, and a magnetometer may
be run on the transit between OBS locations.

Vessel Specifications

    The Wecoma has a length of 56.4 m (185 ft), a beam of 10.1 m (33.1
ft), and a maximum draft of 5.6 m (18.4 ft). The ship is powered by a
single 3,000-hp EMD diesel engine driving a single, controllable-pitch
propeller through a clutch and reduction gear, and an electric, 350-hp
azimuthing bow thruster. An operation speed of 11.1 km/h (6 knots) is
used during seismic acquisition. When not towing seismic survey gear,
the Wecoma cruises at 22.2 km/h (12 knots) and has a maximum speed of
26 km/h (14 knots). It has a normal operating range of approximately
13,300 km (8,264 mi).

Acoustic Source Specifications

Seismic Airguns
    The vessel Wecoma will tow a GI gun and an 300 m-long (984-ft)
streamer containing hydrophones along predetermined lines. Seismic
pulses will be emitted at intervals of 10 s, which corresponds to a
shot interval of approximately 31 m (102 ft) at a speed of 6 knots
(11.1 km/h). The generator chamber of the GI gun, the one responsible
for introducing the sound pulse into the ocean, is 45 in\3\. The larger
(105 in\3\) injector chamber injects air into the previously-generated
bubble to maintain its shape and does not introduce more sound into the
water. The 45 in\3\ GI gun will be towed 21 m (69 ft) behind the
Wecoma, at a depth of 4 m (13 ft). The dominant frequency components
are 0-188 Hz.
    The sound pressure field of the GI gun variation at a tow depth of
2.5 m (8.2 ft) has been modeled by the Lamont-Doherty Earth Observatory
(L-DEO) in relation to distance and direction from the airgun. This
source, which is directed downward, was found to have an output (0-
peak) of 225.3 dB re 1 microPa m.
    The rms (root mean square) received levels that are used as impact
criteria for marine mammals are not directly comparable to the peak or
peak to peak values normally used to characterize source levels of
airgun arrays. The measurement units used to describe airgun sources,
peak or peak-to-peak decibels, are always higher than the rms decibels
referred to in biological literature. A measured received level of 160
dB rms in the far field would typically correspond to a peak
measurement of approximately 170 to 172 dB, and to a peak-to-peak
measurement of approximately 176 to 178 dB, 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 peak-to-
peak 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 peak-to-peak level for an airgun-type source.
Sub-bottom Profiler
    The Wecoma will utilize the Knudsen Engineering Model 320BR sub-
bottom profiler, which is a dual-frequency transceiver designed to
operate at 3.5 and/or 12 kHz. It is used to provide data about the
sedimentary features that occur below the sea floor. The energy from
the sub-bottom profiler is directed downward (in an 80-degree cone) via
a 12-kHz transducer (EDO 323B) or a 3.5-kHz array of 16 ORE 137D
transducers in a 4 x 4 arrangement. The maximum power output of the
320BR is 10 kilowatts for the 3.5-kHz section and 2 kilowatts for the
12-kHz section.
    The pulse length for the 3.5 kHz section of the 320BR is 0.8-24 ms,
controlled by the system operator in regards to water depth and
reflectivity of the bottom sediments, and will usually be 12 or 24 ms
in this survey. The system produces one sound pulse and then waits for
its return before transmitting again. Thus, the pulse interval is
directly dependent upon water depth, and in this survey is 4.5-8 sec.
Using the Sonar Equations and assuming 100 percent efficiency in the
system (impractical in real world applications), the source level for
the 320BR is calculated to be 211 dB re 1 mPa-m. In practice, the
system is rarely operated above 80 percent power level.

Safety Radii

    NMFS has determined that for acoustic effects, using acoustic
thresholds in combination with corresponding safety radii is the most
effective way to consistently apply measures to avoid or minimize the
impacts of an action, and to quantitatively estimate the effects of an
action. Thresholds are used in two ways: (1) to establish a mitigation
shut-down or power down zone, i.e., if an animal enters an area
calculated to be ensonified above the level of an established
threshold, a sound source is powered down or shut down; and (2) to
calculate take, in that a model may be used to calculate the area
around the sound source that will be ensonified to that level or above,
then, based on the estimated density of animals and the distance that
the sound source moves, NMFS can estimate the number of marine mammals
that may be ``taken''. NMFS believes that to avoid permanent
physiological damage (Level A Harassment), cetaceans and pinnipeds
should not be exposed to pulsed underwater noise at received levels
exceeding, respectively, 180 and 190 dB re 1 microPa (rms). NMFS also
assumes that cetaceans or pinnipeds exposed to levels exceeding 160 dB
re 1 microPa (rms) may experience Level B Harassment.
    Received sound levels have been modeled by L-DEO for a number of
airgun configurations, including one 45-in\3\ GI gun, in relation to
distance and direction from the airgun(s). The model does not allow for
bottom interactions and is most directly applicable to deep water.
Based on the modeling, estimates of the maximum distances from the GI
gun where sound levels of 190, 180, and 160 dB re 1 microPa

[[Page 42047]]

(rms) are predicted to be received in deep (>1000-m, 3280-ft) water are
8, 23, and 220 m (26.2, 75.5, and 721.8 ft), respectively and 12, 35,
and 330 m (39.4, 115, and 1,082.7 ft), respectively for intermediate
water depths (100-1000m, 328-3,280 ft). Because the model results are
for a 2.5-m (8.2-ft) tow depth, the above distances slightly underestimate
the distances for the 45-in\3\ GI gun towed at 4-m (13-ft) depth.
    Empirical data concerning the 180- and 160- dB distances 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 (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 mPa (rms) vary with water depth. Similar depth-related
variation is likely in the 190-dB distances applicable to pinnipeds.
Correction factors were developed for water depths 100-1,000 m (328-
3,280 ft) and < 100 m (328 ft). The proposed survey will occur in depths
110-3,050 m (361-10,007 ft), so the correction factors for the latter
are not relevant here.
    The empirical data indicate that, for deep water (>1,000 m, 3,280
ft), the L-DEO model tends to overestimate the received sound levels at
a given distance (Tolstoy et al., 2004). However, to be precautionary
pending acquisition of additional empirical data, it is proposed that
safety radii during airgun operations in deep water will be the values
predicted by L-DEO's model (above). Therefore, the assumed 180- and
190-dB radii are 23 m and 8 m (75.5 and 26.2 ft), respectively.
    Empirical measurements were not conducted for intermediate depths
(100-1,000 m, 328-3,280 ft). On the expectation that results will be
intermediate between those from shallow and deep water, a 1.5x
correction factor is applied to the estimates provided by the model for
deep water situations. This is the same factor that was applied to the
model estimates during L-DEO cruises in 2003. The assumed 180- and 190-
dB radii in intermediate-depth water are 35 m and 12 m (115 and 39.4
ft), respectively.
    The airgun will be shut down immediately when cetaceans or
pinnipeds are detected within or about to enter the appropriate 180-dB
(rms) or 190-dB (rms) radius, respectively.

Description of Marine Mammals in the Activity Area

    Thirty-two marine mammal species, including 19 odontocete (dolphins
and small and large toothed whales) species, seven mysticete (baleen
whales) species, five pinniped species, and the sea otter, may occur or
have been documented to occur in the marine waters off Oregon and
Washington, excluding extralimital sightings or strandings (Table 1
here). Six of the species that may occur in the project area are listed
under the U.S. Endangered Species Act (ESA) as Endangered, including
sperm, humpback, blue, fin, sei, and North Pacific right whales. One
other species listed as Threatened may occur in the project area: the
Steller sea lion.
    Gray whales and sea otters (which is under the jurisdiction of the
U.S. Fish and Wildlife Service) are not expected in the project area
because their occurrence off Oregon is limited to very shallow, coastal
waters. The California sea lion, Steller sea lion, and harbor seal are
also mainly coastal and would be rare at most at the OBS locations.
Information on habitat and abundance of the species that may occur in
the study area are given in Table 1 below. Vagrant ringed seals, hooded
seals, and ribbon seals have been sighted or stranded on the coast of
California (see Mead, 1981; Reeves et al., 2002) and presumably passed
through Oregon waters. A vagrant beluga was seen off the coast of
Washington (Reeves et al., 2002).
    The six species of marine mammals expected to be most common in the
deep pelagic or slope waters of the project area, where most of the
survey sites are located, include the Pacific white-sided dolphin,
northern right whale dolphin, Risso's dolphin, short-beaked common
dolphin, Dall's porpoise, and northern fur seal (Green et al., 1992,
1993; Buchanan et al., 2001; Barlow, 2003; Carretta et al., 2006).
    The sperm, pygmy sperm, mesoplodont species, Baird's beaked, and
Cuvier's beaked whales and the northern elephant seal are considered
pelagic species but are generally uncommon in the waters near the
survey area.
    Additional information regarding the distribution of these species
expected to be found in the project area and how the estimated
densities were calculated may be found in SIO's application.

------------------------------------------------------------------------
                                                                   Rqstd
           Species                   Habitat         Abundance\1\   Take
------------------------------------------------------------------------
Mysticetes
------------------------------                                    ------
North Pacific right whale      Inshore,             N.A.\2\        0
 (Eubalaena japonica) *         occasionally
                                offshore
------------------------------------------------------------------------
Humpback whale (Megaptera      Mainly nearshore     1391           0
 novaeangliae) *                waters and banks
------------------------------------------------------------------------
Minke whale (Balaenoptera      Pelagic and coastal  1015           0
 acutorostrata)
------------------------------------------------------------------------
Sei whale (Balaenoptera        Primarily offshore,  56             0
 borealis) *                    pelagic
------------------------------------------------------------------------
Fin whale (Balaenoptera        Continental slope,   3279           0
 physalus) *                    mostly pelagic
------------------------------------------------------------------------
Blue whale (Balaenoptera       Pelagic and coastal  1744           0
 musculus) *
------------------------------------------------------------------------
Odontocetes
------------------------------                                    ------
Sperm whale (Physeter          Usually pelagic and  1233           0
 macrocephalus) *               deep seas
------------------------------------------------------------------------
Pygmy sperm whale (Kogia       Deep waters off the  247            1
 breviceps)                     shelf
------------------------------------------------------------------------
Dwarf sperm whale (Kogia       Deep waters off the  N.A.           0
 sima)                          shelf
------------------------------------------------------------------------
Cuvier's beaked whale          Pelagic              1884           0
 (Ziphius cavirostris)
------------------------------------------------------------------------
Baird's beaked whale           Pelagic              228            0
 (Berardius bairdii)
------------------------------------------------------------------------

[[Page 42048]]

Blainville's beaked whale      Slope, offshore      1247\3\        0
 (Mesoplodon densirostris)
------------------------------------------------------------------------
Hubb's beaked whale            Slope, offshore      1247\3\        0
 (Mesoplodon carlhubbsi)
------------------------------------------------------------------------
Stejneger's beaked whale       Slope, offshore      1247\3\        0
 (Mesoplodon stejnegeri)
------------------------------------------------------------------------
Offshore bottlenose dolphin    Offshore, slope      5,065          0
 (Tursiops truncatus)
------------------------------------------------------------------------
Striped dolphin (Stenella      Off continental      13,934         0
 coeruleoalba)                  shelf
------------------------------------------------------------------------
Short-beaked common dolphin    Shelf and pelagic,   449,846        4
 (Delphinus delphis)            seamounts
------------------------------------------------------------------------
Pacific white-sided dolphin    Offshore, slope      59,274         6
 (Lagenorhynchus obliquidens)
------------------------------------------------------------------------
Northern right whale dolphin   Slope, offshore      20,362         5
 (Lissodelphis borealis)        waters
------------------------------------------------------------------------
Risso's dolphin (Grampus       Shelf, slope,        16,066         3
 griseus)                       seamounts
------------------------------------------------------------------------
False killer whale (Pseudorca  Pelagic,             N.A.           0
 crassidens)                    occasionally
                                inshore
------------------------------------------------------------------------
Killer whale (Orcinus orca)    Widely distributed   466            0
                                                     (Offshore)
------------------------------------------------------------------------
Short-finned pilot whale       Mostly pelagic,      304            0
 (Globicephala macrorhynchus)   high-relief
                                topography
------------------------------------------------------------------------
Harbor porpoise (Phocoena      Coastal and inland   39,586 (OR/    0
 phocoena)                      waters               WA)
------------------------------------------------------------------------
Dall's porpoise (Phocoenoides  Shelf, slope,        99,517         39
 dalli)                         offshore
------------------------------------------------------------------------
Pinnipeds
------------------------------                                    ------
Northern fur seal              Pelagic, offshore    688,028\2\     3
 (Callorhinus ursinus)
------------------------------------------------------------------------
California sea lion (Zalophus  Coastal, shelf       237,000-       0
 californianus californianus)                        244,000
------------------------------------------------------------------------
Steller sea lion (Eumetopias   Coastal, shelf       44,996\2\      0
 jubatus) *                                          Eastern U.S.
------------------------------------------------------------------------
Harbor seal (Phoca vitulina    Coastal              24,732 (OR/    1
 richardsi)                                          WA)
------------------------------------------------------------------------
Northern elephant seal         Coastal, pelagic     101,000 (CA)   0
 (Mirounga angustirostris)      when migrating
------------------------------------------------------------------------
Table 1. Species expected to be encountered (and potentially harassed)
  during SIO's Pacific Ocean cruise.
N.A. - Data not available or species status was not assessed.
* Species are listed as threatened or endangered under the Endangered
  Species Act.

Potential Effects on Marine Mammals

Potential Effects of Airguns

    The effects of sounds from airguns might include one or more of the
following: tolerance, masking of natural sounds, behavioral
disturbance, and temporary or permanent hearing impairment or non-
auditory physical or physiological effects (Richardson et al., 1995;
Gordon et al., 2004). Given the small size of the GI gun planned for
the present project, effects are anticipated to be considerably less
than would be the case with a large array of airguns. It is very
unlikely that there would be any cases of temporary or, especially,
permanent hearing impairment or any significant non-auditory physical
or physiological effects. Also, behavioral disturbance is expected to
be limited to relatively short distances.
Tolerance
    Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
For a summary of the characteristics of airgun pulses, see Appendix A
of SIO's application. However, it should be noted that most of the
measurements of airgun sounds that have been reported concerned sounds
from larger arrays of airguns, whose sounds would be detectable
considerably farther away than the GI gun planned for use in the
present project.
    Numerous other studies have shown that marine mammals at distances
more than a few kilometers from operating seismic vessels often show no
apparent response (see Appendix A (e) of SIO's application). That is
often true even in cases when the pulsed sounds appear to be readily
audible to the animals based on measured received levels and the
hearing sensitivity of that mammal group. Although various baleen
whales, toothed whales, and (less frequently) pinnipeds have been shown
to react behaviorally to airgun pulses under some conditions, at other
times mammals of all three types have shown no overt reactions. In
general, pinnipeds and small odontocetes seem to be more tolerant of
exposure to airgun pulses than are baleen whales. Given the relatively
small and low-energy airgun source planned for use in this project,
NMFS expects mammals (and sea turtles) to tolerate being closer to this
source than for a larger airgun source typical of most seismic surveys.
Masking
    Obscuring of sounds of interest by interfering sounds, generally at
similar frequencies, is known as masking. Masking effects of pulsed
sounds (even from large arrays of airguns) on marine mammal calls and
other natural sounds are expected to be limited, although there are
very few specific data on this matter. Some whales are known to
continue calling in the presence of

[[Page 42049]]

seismic pulses. Their calls can be heard between the seismic pulses
(e.g., Richardson et al., 1986; McDonald et al., 1995; Greene et al.,
1999; Nieukirk et al., 2004; Smultea et al., 2004). 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 off northern Norway continued calling in the
presence of seismic pulses (Madsen et al., 2002c). Similar reactions
have also been shown during recent work in the Gulf of Mexico (Tyack et
al., 2003; Smultea et al., 2004). Given the small source planned for
use here, there is even less potential for masking of baleen or 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 airgun to
be used here. Dolphins and porpoises are commonly heard calling while
airguns are operating (Gordon et al., 2004; Smultea et al., 2004; Holst
et al., 2005a,b). Also, the sounds important to small odontocetes are
predominantly at much higher frequencies than are airgun sounds.
Masking effects, in general, are discussed further in Appendix A (d) of
SIO's application.
Disturbance Reactions
    Disturbance includes a variety of effects, including subtle changes
in behavior, more conspicuous changes in activities, and displacement.
Reactions to sound, if any, depend on species, state of maturity,
experience, current activity, reproductive state, time of day, and many
other factors. If a marine mammal responds to an underwater sound by
changing its behavior or moving a small distance, the response may or
may not rise to the level of harassment, let alone affect the stock or
the species as a whole. Alternatively, if a sound source displaces
marine mammals from an important feeding or breeding area, effects on
the stock or species could potentially be more than negligible. Given
the many uncertainties in predicting the quantity and types of impacts
of noise on marine mammals, it is common practice to estimate how many
mammals are likely to be present within a particular distance of
industrial activities, or exposed to a particular level of industrial
sound. This practice potentially 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 disturbed to some biologically-important degree by a seismic program
are based on behavioral observations during studies of several species.
However, information is lacking for many species. Detailed studies have
been done on humpback, gray, and bowhead whales and ringed seals. Less
detailed data are available for some other species of baleen whales,
sperm whales, small toothed whales, and sea otters. Most of those
studies have focused on the impacts resulting from the use of much
larger airgun sources than those planned for use in the present
project. Thus, effects are expected to be limited to considerably
smaller distances and shorter periods of exposure in the present
project than in most of the previous work concerning marine mammal
reactions to airguns.
    Baleen Whales - Baleen whales generally tend to avoid operating
airguns, but avoidance radii are quite variable. Whales are often
reported to show no overt reactions to pulses from large arrays of
airguns at distances beyond a few kilometers, even though the airgun
pulses remain well above ambient noise levels out to much longer
distances. However, as reviewed in Appendix A (e) of SIO's application,
baleen whales exposed to strong noise pulses from airguns often react
by deviating from their normal migration route and/or interrupting
their feeding activities and moving away from the sound source. In the
case of the migrating gray and bowhead whales, the observed changes in
behavior appeared to be of little or no biological consequence to the
animals. They simply avoided the sound source by displacing their
migration route to varying degrees, but within the natural boundaries
of the migration corridors.
    Studies of gray, bowhead, and humpback whales have determined that
received levels of pulses in the 160-170 dB re 1 microPa rms range seem
to cause obvious avoidance behavior in a substantial fraction of the
animals exposed. In many areas, seismic pulses from large arrays of
airguns diminish to those levels at distances ranging from 4.5-14.5 km
(2.8-9 mi) from the source. A substantial proportion of the baleen
whales within those distances may show avoidance or other strong
disturbance reactions to the airgun array. Subtle behavioral changes
sometimes become evident at somewhat lower received levels, and recent
studies, reviewed in Appendix A (e) of SIO's application, have shown
that some species of baleen whales, notably bowheads and humpbacks, at
times show strong avoidance at received levels lower than 160-170 dB re
1 microPa rms. Reaction distances would be considerably smaller during
the present project, in which the 160-dB radius is predicted to be
approximately 0.22 or 0.33 km (0.14 or 0.21 mi), as compared with
several kilometers when a large array of airguns is operating.
    McCauley et al. (1998, 2000) studied the responses of humpback
whales off Western Australia to a full-scale seismic survey with a 16-
airgun, 2,678-in\3\ array, and to a single 20-in\3\ airgun with a
source level of 227 dB re 1 microPa m. McCauley et al. (1998)
documented that avoidance reactions began at 5-8 km (3.1-5 mi) from the
array, and that those reactions kept most pods approximately 3-4 km
(1.9-2.5 mi) from the operating seismic boat. McCauley et al. (2000)
noted localized displacement during migration of 4-5 km (2.5-3.1 mi) by
traveling pods and 7-12 km (4.3-7.5 mi) by cow-calf pairs. Avoidance
distances with respect to the single airgun were smaller but consistent
with the results from the full array in terms of received sound levels.
Mean avoidance distance from the airgun corresponded to a received
sound level of 140 dB re 1 microPa (rms); that was the level at which
humpbacks started to show avoidance reactions to an approaching airgun.
The standoff range, i.e., the closest point of approach of the whales
to the airgun, corresponded to a received level of 143 dB re 1 microPa
(rms). The initial avoidance response generally occurred at distances
of 5-8 km (3.1-5 mi) from the airgun array and 2 km (1.2 mi) from the
single airgun. However, some individual humpback whales, especially
males, approached within distances of 100-400 m (328-1,312 ft), where
the maximum received level was 179 dB re 1 microPa (rms).
    Humpback whales summering in southeast Alaska did not exhibit
persistent avoidance when exposed to seismic pulses from a 1.64-L (100
in\3\) airgun (Malme et al., 1985). Some humpbacks seemed ``startled''
at received levels of 150-169 dB re 1 microPa on an approximate rms
basis. Malme et al. (1985) concluded that there was no clear evidence
of avoidance, despite the possibility of subtle effects, at received
levels up to 172 re 1 microPa (approximately rms). Additional effects
from seismic surveys to wintering humpback whales off Brazil can be
found in Appendix A (e) of SIO's application.
    Results from bowhead whales show that responsiveness of baleen
whales to seismic surveys can be quite variable depending on the
activity (migrating vs. feeding) of the whales. Bowhead whales
migrating west across the Alaskan Beaufort Sea in autumn, in
particular, are unusually responsive, with

[[Page 42050]]

substantial avoidance occurring out to distances of 20 30 km (12.4-18.6
mi) from a medium-sized airgun source, where received sound levels were
on the order of 130 dB re 1 microPa (rms) (Miller et al., 1999;
Richardson et al., 1999). However, more recent research on bowhead
whales (Miller et al., 2005a) corroborates earlier evidence that,
during the summer feeding season, bowheads are not as sensitive to
seismic sources. In summer, bowheads typically begin to show avoidance
reactions at a received level of about 160 170 dB re 1 microPa (rms)
(Richardson et al., 1986; Ljungblad et al., 1988; Miller et al., 1999).
There are not data on reactions of wintering bowhead whales to seismic
surveys. See Appendix A (e) of SIO's application for more information
regarding bowhead whale reactions to airguns.
    Malme et al. (1986, 1988) studied the responses of feeding Eastern
Pacific gray whales to pulses from a single 100 in\3\ airgun off St.
Lawrence Island in the northern Bering Sea. Malme et al. (1986, 1988)
estimated, based on small sample sizes, that 50 percent of feeding gray
whales ceased feeding at an average received pressure level of 173 dB
re 1 microPa on an (approximate) rms basis, and that 10 percent of
feeding whales interrupted feeding at received levels of 163 dB. Those
findings were generally consistent with the results of experiments
conducted on larger numbers of gray whales that were migrating along
the California coast and on observations of Western Pacific gray whales
feeding off Sakhalin Island, Russia (Johnson, 2002).
    We are not aware of any information on reactions of Bryde's whales
to seismic surveys. However, other species of Balaenoptera (blue, sei,
fin, and minke whales) have occasionally been reported in areas
ensonified by airgun pulses. Sightings by observers on seismic vessels
off the U.K. from 1997 to 2000 suggest that, at times of good
sightability, numbers of rorquals seen are similar when airguns are
shooting and not shooting (Stone, 2003). Although individual species
did not show any significant displacement in relation to seismic
activity, all baleen whales combined were found to remain significantly
further from the airguns during shooting compared with periods without
shooting (Stone, 2003; Stone and Tasker, 2006). In a study off Nova
Scotia, Moulton and Miller (in press) found only a little or no
difference in sighting rates and initial sighting distances of
balaenopterid whales when airguns were operating vs. silent. However,
there were indications that these whales were more likely to be moving
away when seen during airgun operations.
    Data on short-term reactions (or lack of reactions) of cetaceans to
impulsive noises do not necessarily provide information about long-term
effects. It is not known whether impulsive noises affect reproductive
rate or distribution and habitat use in subsequent days or years.
However, gray whales continued to migrate annually along the west coast
of North America despite intermittent seismic exploration and much ship
traffic in that area for decades (Appendix A in Malme et al., 1984).
Bowhead whales continued to travel to the eastern Beaufort Sea each
summer despite seismic exploration in their summer and autumn range for
many years (Richardson et al., 1987). In any event, the brief exposures
to sound pulses from the present small airgun source are highly
unlikely to result in prolonged effects.
    Toothed Whales - Little systematic information is available about
reactions of toothed whales to noise pulses. Few studies similar to the
more extensive baleen whale/seismic pulse work summarized above have
been reported for toothed whales. However, a systematic study on sperm
whales has been done (Jochens and Biggs, 2003; Tyack et al., 2003;
Miller et al., 2006), and there is an increasing amount of information
about responses of various odontocetes to seismic surveys based on
monitoring studies (Stone, 2003; Smultea et al., 2004; Bain and
Williams, 2006; Holst et al., 2006; Stone and Tasker, 2006; Moulton and
Miller, in press).
    Seismic operators sometimes see dolphins and other small toothed
whales near operating airgun arrays, but in general there seems to be a
tendency for most delphinids to show some limited avoidance of seismic
vessels operating large airgun systems. However, some dolphins seem to
be attracted to the seismic vessel and floats, and some ride the bow
wave of the seismic vessel even when large arrays of airguns are
firing. Nonetheless, there have been indications that small toothed
whales sometimes tend to head away, or to maintain a somewhat greater
distance from the vessel, when a large array of airguns is operating
than when it is silent (Goold, 1996; Calambokidis and Osmek, 1998;
Stone, 2003). In most cases, the avoidance radii for delphinids appear
to be small, on the order of 1 km (0.62 mi) or less.
    The beluga may be a species that (at least at times) shows long-
distance avoidance of seismic vessels. Aerial surveys during seismic
operations in the southeastern Beaufort Sea recorded much lower
sighting rates of beluga whales within 10-20 km (6.2-12.4 mi) of an
active seismic vessel. These results were consistent with the low
number of beluga sightings reported by observers aboard the seismic
vessel, suggesting that some belugas might be avoiding the seismic
operations at distances of 10-20 km (6.2-12.4 mi) (Miller et al.,
2005a). Similarly, captive bottlenose dolphins and beluga whales
exhibit changes in behavior when exposed to strong pulsed sounds
similar in duration to those typically used in seismic surveys
(Finneran et al., 2000, 2002, 2005; Finneran and Schlundt, 2004).
However, the animals tolerated high received levels of sound (pk-pk
level >200 dB re 1 microPa) before exhibiting aversive behaviors.
    Results for porpoises depend on species. Dall's porpoises seem
relatively tolerant of airgun operations (MacLean and Koski, 2005; Bain
and Williams, 2006), whereas the limited available data suggest that
harbor porpoises show stronger avoidance (Stone, 2003; Bain and
Williams, 2006). This apparent difference in responsiveness of these
two porpoise species is consistent with their relative responsiveness
to boat traffic in general (Richardson et al., 1995).
    Most studies of sperm whales exposed to airgun sounds indicate that
this species shows considerable tolerance of airgun pulses. In most
cases, the whales do not show strong avoidance, and they continue to
call (see Appendix A (e) of SIO's application for review). However,
controlled exposure experiments in the Gulf of Mexico indicate that
foraging effort is apparently somewhat reduced upon exposure to airgun
pulses from a seismic vessel operating in the area, and there may be a
delay in diving to foraging depth.
    There are no specific data on the behavioral reactions of beaked
whales to seismic surveys. Most beaked whales tend to avoid approaching
vessels of other types (Wursig et al., 1998). They may also dive for an
extended period when approached by a vessel (Kasuya, 1986). It is
likely that these beaked whales would normally show strong avoidance of
an approaching seismic vessel, but this has not been documented
explicitly.Odontocete reactions to large arrays of airguns are variable
and, at least for delphinids and some porpoises, seem to be confined to
a smaller radius than has been observed for mysticetes (see Appendix A
of SIO's application for more information). Behavioral reactions of
odontocetes to the small GI-gun source to be used here are expected to
be very localized, probably to distances < 0.4 km (0.25 mi).

[[Page 42051]]

    Pinnipeds - Pinnipeds are not likely to show a strong avoidance
reaction to the GI gun that will be used. Visual monitoring from
seismic vessels, usually employing larger sources, has shown only
slight (if any) avoidance of airguns by pinnipeds, and only slight (if
any) changes in behavior (see Appendix A (e) of SIO's application).
Ringed seals frequently do not avoid the area within a few hundred
meters of operating airgun arrays (Harris et al., 2001; Moulton and
Lawson, 2002; Miller et al., 2005a). However, initial telemetry work
suggests that avoidance and other behavioral reactions by two other
species of seals to small airgun sources may at times be stronger than
evident to date from visual studies of pinniped reactions to airguns
(Thompson et al., 1998). Even if reactions of any pinnipeds that might
be encountered in the present study area are as strong as those evident
in the telemetry study, reactions are expected to be confined to
relatively small distances and durations, with no long-term effects on
pinniped individuals or populations.
    Additional details on the behavioral reactions (or the lack
thereof) by all types of marine mammals to seismic vessels can be found
in Appendix A (e) of SIO'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 sequences
of 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 of 180 and 190 dB re 1 microPa (rms),
respectively. Those criteria have been used in defining the safety
(shut-down) radii planned for the proposed seismic survey. The
precautionary nature of these criteria is discussed in Appendix A (f)
of SIO's application, including the fact that 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 temporary threshold shift (TTS) (which NMFS' criteria
are based on) and the level associated with the onset of TTS is often
considered to be a level below which there is no danger of permanent
damage. NMFS is presently developing new noise exposure criteria for
marine mammals that take account of the now-available scientific data
on TTS, the expected offset between the TTS and permanent threshold
shift (PTS) thresholds, differences in the acoustic frequencies to which
different marine mammal groups are sensitive, and other relevant factors.
    Because of the small size of the airgun source in this project (one
45-in3 GI gun), alongwith the planned monitoring and mitigation
measures, there is little likelihood that any marine mammals will be
exposed to sounds sufficiently strong to cause hearing impairment.
Several aspects of the planned monitoring and mitigation measures for
this project are designed to detect marine mammals occurring near the
GI gun (and sub-bottom profiler), and to avoid exposing them to sound
pulses that might, at least in theory, cause hearing impairment. In
addition, many cetaceans are likely to show some avoidance of the area
with high received levels of airgun sound (see above). In those cases,
the avoidance responses of the animals themselves will reduce or (most
likely) avoid any possibility of hearing impairment.
    Non-auditory physical effects may also occur in marine mammals
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that theoretically might
occur in mammals close to a strong sound source include stress,
neurological effects, bubble formation, 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, as
discussed below, there is no definitive evidence that any of these
effects occur even for marine mammals in close proximity to large
arrays of airguns. It is especially unlikely that any effects of these
types would occur during the present project given the small size of
the source, the brief duration of exposure of any given mammal, and the
planned monitoring and mitigation measures (see below). The following
subsections discuss in somewhat more detail the possibilities of TTS,
PTS, and non-auditory physical effects.
    Temporary Threshold Shift (TTS) - TTS is the mildest form of
hearing impairment that can occur during exposure to a strong sound
(Kryter 1985). While experiencing TTS, the hearing threshold rises and
a sound must be stronger in order to be heard. TTS can last from
minutes or hours to (in cases of strong TTS) days. For sound exposures
at or somewhat above the TTS threshold, hearing sensitivity recovers
rapidly after exposure to the noise ends. Few data on sound levels and
durations necessary to elicit mild TTS have been obtained for marine
mammals, and none of the published data concern TTS elicited by
exposure to multiple pulses of sound.
    For toothed whales exposed to single short pulses, the TTS
threshold appears to be, to a first approximation, a function of the
energy content of the pulse (Finneran et al., 2002, 2005). Given the
available data, the received level of a single seismic pulse (with no
frequency weighting) might need to be approximately 186 dB re 1
microPa\2\.s (i.e., 186 dB SEL or approximately 221-226 dB pk-pk) in
order to produce brief, mild TTS. Exposure to several strong seismic
pulses that each have received levels near 175-180 dB SEL 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.
The distance from the Wecoma's GI gun at which the received energy
level (per pulse) would be expected to be [gteqt]175-180 dB SEL are the
distances shown in the 190 dB re 1 microPa (rms) column in Table 1 of
SIO's application (given that the rms level is approximately 10-15 dB
higher than the SEL value for the same pulse). Seismic pulses with
received energy levels [gteqt]175-180 dB SEL (190 dB re 1 microPa
(rms)) are expected to be restricted to radii no more than 23-35 m
(75.5-115 ft) around the GI gun. The specific radius depends on the
depth of the water. For an odontocete closer to the surface, the
maximum radius with [gteqt]175-180 dB SEL or [gteqt]190 dB re 1 microPa
(rms) would be smaller. Such levels would be limited to distances
within a few meters of the small GI gun source to be used in this project.
    For baleen whales, direct or indirect data do not exist on levels
or properties of sound thatare required to induce TTS. The frequencies
to which baleen whales are most sensitive are lower than those to which
odontocetes are most sensitive, and natural background noise levels at
those low frequencies tend to be higher. As a result, auditory
thresholds of baleen whales within their frequency band of best hearing
are believed to be higher (less sensitive) than are those of
odontocetes at their best frequencies (Clark and Ellison, 2004). From
this, it is suspected that received levels causing TTS onset may also
be higher in baleen whales. In any event, no cases of TTS are expected
given three considerations: (1) the low abundance of baleen whales
expected in the planned study areas; (2) 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

[[Page 42052]]

possibility of TTS; and (3) the mitigation measures that are planned.
    In pinnipeds, TTS thresholds associated with exposure to brief
pulses (single or multiple) of underwater sound have not been measured.
Initial evidence from prolonged exposures suggested that some pinnipeds
may incur TTS at somewhat lower received levels than do small
odontocetes exposed for similar durations (Kastak et al., 1999, 2005;
Ketten et al., 2001; cf. Au et al., 2000). However, more recent
indications are that TTS onset in the most sensitive pinniped species
studied (harbor seal) may occur at a similar sound exposure level as in
odontocetes (Kastak et al., 2004).
    To avoid injury, NMFS has determined that cetaceans and pinnipeds
should not be exposed to pulsed underwater noise at received levels
exceeding, respectively, 180 and 190 dB re 1 microPa (rms). Those sound
levels were not considered to be the levels above which TTS might
occur. Rather, they were the received levels above which, in the view
of a panel of bioacoustics specialists convened by NMFS 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 summarized above, data that are now
available imply that TTS is unlikely to occur unless odontocetes (and
probably mysticetes as well) are exposed to airgun pulses strong than
180 dB re 1 microPa (rms).
    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.
    There is no specific evidence that exposure to pulses of airgun
sound can cause PTS in any marine mammal, even with large arrays of
airguns. However, given the possibility that mammals close to an airgun
array might incur TTS, there has been further speculation about the
possibility that some individuals occurring very close to airguns might
incur PTS. Single or occasional occurrences of mild TTS are not
indicative of permanent auditory damage in terrestrial mammals.
Relationships between TTS and PTS thresholds have not been studied in
marine mammals, but are assumed to be similar to those in humans and
other terrestrial mammals. PTS might occur at a received sound level at
least several decibels above that inducing mild TTS if the animal were
exposed to strong sound pulses with rapid rise time (see Appendix A (f)
of SIO's application). The specific difference between the PTS and TTS
thresholds has not been measured for marine mammals exposed to any
sound type. However, based on data from terrestrial mammals, a
precautionary assumption is that the PTS threshold for impulse sounds
(such as airgun pulses as received close to the source) is at least 6
dB higher than the TTS threshold on a peak-pressure basis and probably
more than 6 dB.
    In the present project employing a single 45-in\3\ GI gun, marine
mammals are highly unlikely to be exposed to received levels of seismic
pulses strong enough to cause TTS, as they would probably need to be
within a few meters of the GI gun for that to occur. Given the higher
level of sound necessary to cause PTS, it is even less likely that PTS
could occur. In fact, even the levels immediately adjacent to the GI
gun may not be sufficient to induce PTS, especially since a mammal
would not be exposed to more than one strong pulse unless it swam
immediately alongside the GI gun for a period longer than the inter-
pulse interval. Baleen whales generally avoid the immediate area around
operating seismic vessels, as do some other marine mammals. The planned
monitoring and mitigation measures, including visual monitoring and
shut downs of the GI gun when mammals are seen within the ``safety
radii'', will minimize the already-minimal probability of exposure of
marine mammals to sounds strong enough to induce PTS.
    Non-auditory Physiological Effects - Non-auditory physiological
effects or injuries that theoretically might occur in marine mammals
exposed to strong underwater sound include stress, neurological
effects, bubble formation, resonance effects, and other types of organ
or tissue damage. However, studies examining such effects are limited.
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. It is doubtful that any single marine mammal would be
exposed to strong seismic sounds for time periods long enough to induce
physiological stress.
    Until recently, it was assumed that diving marine mammals are not
subject to the bends or air embolism. This possibility was first
explored at a workshop (Gentry [ed.], 2002) held to discuss whether the
stranding of beaked whales in the Bahamas in 2000 (Balcomb and
Claridge, 2001; NOAA and USN, 2001) might have been related to bubble
formation in tissues caused by exposure to noise from naval sonar.
However, this link could not be confirmed. Jepson et al. (2003) first
suggested a possible link between mid-frequency sonar activity and
acute chronic tissue damage that results from the formation in vivo of
gas bubbles, based on the beaked whale stranding in the Canary Islands
in 2002 during naval exercises. Fernandez et al. (2005a) showed those
beaked whales did indeed have gas bubble-associated lesions, as well as
fat embolisms. Fernandez et al. (2005b) also found evidence of fat
embolism in three beaked whales that stranded 100 km (62 mi) north of
the Canaries in 2004 during naval exercises. Examinations of several
other stranded species have also revealed evidence of gas and fat
embolisms (Arbelo et al., 2005; Jepson et al., 2005a; Mendez et al.,
2005). Most of the afflicted species were deep divers. There is
speculation that gas and fat embolisms may occur if cetaceans ascend
unusually quickly when exposed to aversive sounds, or if sound in the
environment causes the destablization of existing bubble nuclei
(Potter, 2004; Arbelo et al., 2005; Fernandez et al. 2005a; Jepson et
al., 2005b; Cox et al., 2006). Even if gas and fat embolisms can occur
during exposure to mid-frequency sonar, there is no evidence that that
type of effect occurs in response to airgun sounds.
    In general, little is known about the potential for seismic survey
sounds to cause auditory impairment or other physical effects in marine
mammals. Available data suggest that such effects, if they occur at
all, would be limited to short distances and probably to projects
involving large arrays of airguns. However, the available data do not
allow for meaningful quantitative predictions of the numbers (if any)
of marine mammals that might be affected in those ways. Marine mammals
that show behavioral avoidance of seismic vessels, including most
baleen whales, some odontocetes, and some pinnipeds, are especially
unlikely to incur auditory impairment or other physical effects. Also,
the planned mitigation measures, including shut downs of the GI gun,
will reduce any such effects that might otherwise occur.
Strandings and Mortality
    Marine mammals close to underwater detonations of high explosives
can be killed or severely injured, and their auditory organs are
especially susceptible to injury (Ketten et al., 1993; Ketten 1995).
Airgun pulses are less energetic and have slower rise times, and there
is no proof that they can cause serious injury, death, or stranding
even in the case of large airgun arrays.

[[Page 42053]]

However, the association of mass strandings of beaked whales with naval
exercises and, in one case, an L-DEO seismic survey, has raised the
possibility that beaked whales exposed to strong pulsed sounds may be
especially susceptible to injury and/or behavioral reactions that can
lead to stranding. Appendix A (g) of SIO's application provides
additional details.
    Seismic pulses and mid-frequency sonar pulses are quite different.
Sounds produced by airgun arrays are broadband with most of the energy
below 1 kHz. Typical military mid-frequency sonars operate at
frequencies of 2-10 kHz, generally with a relatively narrow bandwidth
at any one time. Thus, it is not appropriate to assume that there is a
direct connection between the effects of military sonar and seismic
surveys on marine mammals. However, evidence that sonar pulses can, in
special circumstances, lead to physical damage and mortality (Balcomb
and Claridge, 2001; NOAA and USN, 2001; Jepson et al., 2003; Fernandez
et al., 2004, 2005a; Cox et al., 2006), even if only indirectly,
suggests that caution is warranted when dealing with exposure of marine
mammals to any high-intensity pulsed sound.
    There is no conclusive evidence of cetacean strandings as a result
of exposure to seismic surveys. Speculation concerning a possible link
between seismic surveys and strandings of humpback whales in Brazil
(Engel et al., 2004) was not well founded based on available data
(IAGC, 2004; IWC, 2006). In September 2002, there was a stranding of
two Cuvier's beaked whales in the Gulf of California, Mexico, when the
L-DEO vessel Maurice Ewing was operating a 20-gun, 8,490-in\3\ array in
the general area. The link between the stranding and the seismic survey
was inconclusive and not based on any physical evidence (Hogarth, 2002;
Yoder, 2002). Nonetheless, the preceding example plus the incidents
involving beaked whale strandings near naval exercises suggests a need
for caution in conducting seismic surveys in areas occupied by beaked
whales. No injuries of beaked whales are anticipated during the
proposed study because of the proposed monitoring and mitigation measures.
    The present project will involve a much smaller sound source than
used in typical seismic surveys. That, along with the monitoring and
mitigation measures that are planned, are expected to minimize any
possibility for strandings and mortality.

Potential Effects of Other Acoustic Devices

Sub-bottom Profiler Signals
    A sub-bottom profiler will be operated from the source vessel at
all times during the planned study. Sounds from the sub-bottom profiler
are very short pulses, occurring for 12 or 24 ms once every 4.5-8
seconds. Most of the energy in the sound pulses emitted by this sub-
bottom profiler is at mid frequencies, centered at 3.5 kHz. The beam
width is approximately 80o (cone-shaped) and is directed downward.
    The sub-bottom profiler on the Wecoma has a stated maximum source
level of 211 dB re 1 microPa m (see section II of SIO's application).
Thus, the received level would be expected to decrease to 180 dB and
160 dB approximately 35 m (115 ft) and 350 m (1,148.3 ft) below the
transducer, respectively, assuming spherical spreading. Corresponding
distances in the horizontal plane would be substantially lower, given
the directionality of this source. Kremser et al. (2005) noted that the
probability of a cetacean swimming through the area of exposure when a
bottom profiler emits a pulse is small, and if the animal was in the
area, it would have to pass the transducer at close range in order to
be subjected to sound levels that could cause TTS.
    Marine mammal communications will not be masked appreciably by the
sub-bottom profiler signals given their directionality and the brief
period when an individual mammal is likely to be within its beam.
Furthermore, in the case of most odontocetes, the sonar signals do not
overlap with the predominant frequencies in the calls, which would
avoid significant masking.
    Marine mammal behavioral reactions to other pulsed sound sources
are discussed above, and responses to the sub-bottom profiler are
likely to be similar to those for other pulsed sources if received at
the same levels. Behavioral responses are not expected unless marine
mammals are very close to the source.
    Source levels of the sub-bottom profiler are much lower than those
of the airguns and the multi-beam sonar, which are discussed above.
Sounds from the sub-bottom profiler are estimated to decrease to 180 dB
re 1 microPa (rms) at approximately 35 m (115 ft) 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). 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.

Estimated Take by Incidental Harassment

    All anticipated takes would be ``takes by harassment'', involving
temporary changes in behavior. The proposed mitigation measures are
expected to minimize the possibility of injurious takes. (However, as
noted earlier, there is no specific information demonstrating that
injurious ``takes'' would occur even in the absence of the planned
mitigation measures.) In the sections below, we describe methods to
estimate ``take by harassment'', and present estimates of the numbers
of marine mammals that might be affected during the proposed seismic
survey in the northeast Pacific Ocean. The estimates are based on data
concerning marine mammal densities (numbers per unit area) obtained
during surveys off Oregon and Washington during 1996 and 2001 by NMFS
Southwest Fisheries Science Center (SWFSC) and estimates of the size of
the area where effects potentially could occur.
    The following estimates are based on a consideration of the number
of marine mammals that might be disturbed appreciably by operations
with the GI gun to be used during approximately 340 line-km of surveys
at 16 sites off the coast of Oregon in the northeastern Pacific Ocean.
The anticipated radii of influence of the sub-bottom profiler are less
than those for the GI gun. It is assumed that, during simultaneous
operations of the GI gun and sub-bottom profiler, any marine mammals
close enough to be affected by the sub-bottom profiler would already be
affected by the airgun. No animals are expected to exhibit more than
short-term and inconsequential responses to the sub-bottom profiler,
given its characteristics (e.g., narrow downward-directed beam)

[[Page 42054]]

and other considerations described previously. Therefore, no additional
allowance is included for animals that might be affected by this source.
    Extensive systematic aircraft- and ship-based surveys have been
conducted for marine mammals offshore of Oregon and Washington (Bonnell
et al., 1992; Green et al., 1992, 1993; Barlow, 1997, 2003; Barlow and
Taylor, 2001; Calambokidis and Barlow, 2004). The most comprehensive
and recent density data available for cetacean species off slope and
offshore waters of Oregon are from the 1996 and 2001 NMFS SWFSC
``ORCAWALE'' ship surveys as synthesized by Barlow (2003). The surveys
were conducted from late July to early November (1996) or early
December (2001). They were conducted up to approximately 556 km (1,824
ft) offshore from Oregon and Washington.Systematic, offshore, at-sea
survey data for pinnipeds are more limited. The most comprehensive such
studies are reported by Bonnell et al. (1992) and Green et al. (1993)
based on systematic aerial surveys conducted in 1989 1990 and 1992,
primarily from coastal to slope waters with some offshore effort as well.
    Oceanographic conditions, including occasional El Nino and La Nina
events, influence the distribution and numbers of marine mammals
present in the northeastern Pacific Ocean, including Oregon, resulting
in considerable year-to-year variation in the distribution and
abundance of many marine mammal species (Forney and Barlow, 1998;
Buchanan et al., 2001; Escorza-Trevino, 2002; Ferrero et al., 2002;
Philbrick et al., 2003). Thus, for some species the densities derived
from recent surveys may not be representative of the densities that
will be encountered during the proposed seismic survey.
    Table 3 in SIO's application gives the average and maximum
densities for each species or species group of marine mammals reported
off Oregon and Washington (and used to calculate the take estimates in
Table 1 here), corrected for effort, based on the densities reported
for the 1996 and 2001 ORCAWALE surveys (Barlow, 2003). The densities
from these studies had been corrected, by the original author, for both
detectability bias and availability bias. Detectability bias is
associated with diminishing sightability with increasing lateral
distance from the trackline [f(0)]. Availability bias refers to the
fact that there is less-than-100 percent probability of sighting an animal
that is present along the survey trackline, and it is measured by g(0).
    It should be noted that the following estimates of ``takes by
harassment'' assume that the seismic surveys will be undertaken and
completed; in fact, the planned number of line-kms has been increased
by 25 percent to accommodate lines that may need to be repeated,
equipment testing, etc. As is typical on offshore ship surveys,
inclement weather, and equipment malfunctions may cause delays and may
limit the number of useful line-kms of seismic operations that can be
undertaken. Furthermore, any marine mammal sightings within or near the
designated safety zones will result in the shut down of seismic
operations as a mitigation measure. Thus, the following estimates of
the numbers of marine mammals potentially exposed to 160-dB sounds are
precautionary, and probably overestimate the actual numbers of marine
mammals that might be involved. These estimates assume that there will
be no weather, equipment, or mitigation delays, which is unlikely.
    There is some uncertainty about the representativeness of the data
and the assumptions used in the take calculations. However, the
approach used here is believed to be the best available approach. Also,
to provide some allowance for the uncertainties, ``maximum estimates''
as well as ``best estimates'' of the numbers potentially affected have
been derived. Best and maximum estimates are based on the average and
maximum estimates of densities reported by Barlow (2003) described
above. SIO has requested authorization for the take of the maximum
estimates and NMFS has analyzed the maximum estimate for it's effect on
the species or stock.
    The number of different individuals that may be exposed to GI-gun
sounds with received levels [gteqt]160 dB re 1 microPa (rms) on one or
more occasions can be estimated by considering the total marine area
that would be within the 160-dB radius around the operating GI gun on
at least one occasion. The proposed seismic lines do not run parallel
to each other in close proximity, which minimizes the number of times
an individual mammal may be exposed during the survey. The best
estimates in this section are based on the average of the densities
from the 1996 and 2001 NMFS surveys, and maximum estimates are based on
the higher estimate. Table 4 in SIO's application (and used to
calculate the take estimates in Table 1 here) shows the best and
maximum estimates of the number of marine mammals that could
potentially be affected during the seismic survey.
    The number of different individuals potentially exposed to received
levels [gteqt]160 dB re 1 microPa (rms) was calculated by multiplying:
    • The expected species density, either ``average'' (i.e.,
best) or ``maximum'', times
    • The anticipated minimum area to be ensonified to that
level during GI gun operations.
    The area expected to be ensonified was determined by entering the
planned survey lines into a MapInfo Geographic Information System
(GIS), using the GIS to identify the relevant areas by ``drawing'' the
applicable 160-dB around each seismic line and then calculating the
total area within the buffers. Areas where overlap occurred (because of
intersecting lines) were included only once to determine the minimum
area expected to be ensonified.
    Applying the approach described above, approximately 206 km\2\
would be within the 160-dB isopleth on one or more occasions. This
approach does not allow for turnover in the mammal populations in the
study area during the course of the studies. That might underestimate
actual numbers of individuals exposed, although the conservative
distances used to calculate the area may offset this. In addition, the
approach assumes that no cetaceans will move away or toward the
trackline as the Wecoma approaches in response to increasing sound
levels prior to the time the levels reach 160 dB. Another way of
interpreting the estimates that follow is that they represent the
number of individuals that are expected (in the absence of a seismic
program) to occur in the waters that will be exposed to [gteqt]160 dB
re 1 microPa (rms).
    The `best estimate' of the number of individual cetaceans that
might be exposed to seismic sounds with received levels [gteqt]160 dB
re 1 microPa (rms) during the surveys is 57 (Table 4 in SIO's
application). The total does not include any endangered or beaked
whales. Dall's porpoise and Pacific white-sided and northern right
whale dolphins are estimated to be the most common species exposed; the
best estimates for those species are 39, 6, and 5, respectively.
Estimates for the two other dolphin species that could be exposed are
lower (Table 4 in SIO's application).
    The `maximum estimate' column in Table 4 of SIO's application shows
an estimated total of 109 cetaceans that might be exposed to seismic
sounds [gteqt]160 dB during the surveys. In most cases, those estimates
are based on survey data, as described above. For endangered species,
the `maximum estimate' is the mean group size (from Barlow and Forney,
in prep) in cases where the calculated maximum number of individuals
exposed was between

[[Page 42055]]

0.05 and the mean group size (humpback, fin, blue, and sperm whales).
The numbers for which take authorization is requested, given in the far
right column of Table 4 in SIO's application and Table 1 here, are the
best estimates. Based on the abundance numbers given in Table 2 of
SIO's application and Table 1 here for non-listed cetacean species,
NMFS believes that the estimated take numbers are small relative to the
stock sizes for these species (i.e., no more than 0.4 percent of any
species).
    Only two of the five pinniped species discussed in Section III of
SIO's application the northern fur seal and the northern elephant seal
are likely to occur in the offshore and slope waters (where 12 of the
16 OBSs are located) in numbers greater than a few stray individuals.
The other three species of pinnipeds known to occur regularly off
Oregon and Washington the California sea lion, Steller sea lion, and
harbor seal likely would not be found at the OBS locations, or could be
found only at the inshore locations, because they are coastal, usually
staying within approximately 20 km (12.4 mi) of the coast (see Section
III of SIO's application). A best estimate of three northern fur seals,
one harbor seal, and one Steller sea lion could be exposed to airgun
sounds with received levels [gteqt]160 dB re 1 microPa (rms). Numbers
of sightings of the other two species that could occur in the study
area were too low to warrant density estimates. The numbers for which
``take authorization'' is requested, given in the far right column of
Table 4 of SIO's application and Table 1 here, are for the average or
(for the northern fur seal) the maximum estimate. The estimated numbers
of pinnipeds that may be exposed to received levels [gteqt]160 dB are
probably overestimates of the actual numbers that will be affected
significantly. Less than 0.01 percent of northern fur seals and harbor
seals are expected to be affected.

Potential Effects on Habitat

    The proposed seismic surveys will not result in any permanent
impact on habitats used by marine mammals or to the food sources they
use. The main impact issue associated with the proposed activity will
be temporarily elevated noise levels and the associated direct effects
on marine mammals, as discussed above.
    One of the reasons for the adoption of airguns as the standard
energy source for marine seismic surveys was that, unlike explosives,
they do not result in any appreciable fish kill. However, the existing
body of information relating to the impacts of seismic surveys on
marine fish (see Appendix B of SIO's application) and invertebrate
species is very limited. The various types of potential effects of
exposure to seismic on fish and invertebrates can be considered in
three categories: (1) pathological, (2) physiological, and (3)
behavioral. Pathological effects include lethal and sub-lethal damage
to the animals, physiological effects include temporary primary and
secondary stress responses, and behavioral effects refer to changes in
exhibited behavior of the fish and invertebrates. The three categories
are interrelated in complex ways. For example, it is possible that
certain physiological and behavioral changes could potentially lead to
the ultimate pathological effect on individual animals (i.e., mortality).
    Available information on the impacts of seismic surveys on marine
fish and invertebrates provides limited insight on the effects only at
the individual level. Ultimately, the most important knowledge in this
area relates to how significantly seismic affects animal populations.
    The following sections provide an overview of the information that
exists on the effects of seismic surveys on fish and invertebrates. The
information comprises results from scientific studies of varying
degrees of soundness and some anecdotal information.
    Pathological Effects - In water, acute injury and death of
organisms exposed to seismic energy depends primarily on two features
of the sound source: (1) the received peak pressure, and (2) the time
required for the pressure to rise and decay (Hubbs and Rechnitzer, 1952
in Wardle et al., 2001). Generally, the higher the received pressure
and the less time it takes for the pressure to rise and decay, the
greater the chance of acute pathological effects. Considering the peak
pressure and rise/decay time characteristics of seismic airgun arrays
used today, the pathological zone for fish and invertebrates would be
expected to be within a few meters of the seismic source (Buchanan et
al., 2004). For the proposed survey, any injurious effects on fish
would be limited to very short distances, especially considering the
small source planned for use in this project (one 45-in3 GI gun).
Numerous other studies provide examples of no fish mortality upon
exposure to seismic sources (Falk and Lawrence, 1973; Holliday et al.,
1987; La Bella et al., 1996; Santulli et al., 1999; McCauley et al., 2000a,
2000b, 2003; Bjarti, 2002; Hassel et al., 2003; Popper et al., 2005).
    Little is known about the mechanisms and characteristics of damage
to fish that may be inflicted by exposure to seismic survey sounds. Few
data have been presented in the peer-reviewed scientific literature.
There are two valid papers with proper experimental methods, controls,
and careful pathological investigation implicating sounds produced by
actual seismic survey airguns with adverse anatomical effects. One such
study indicated anatomical damage and the second indicated TTS in fish
hearing. McCauley et al. (2003) found that exposure to airgun sound
caused observable anatomical damage to the auditory maculae of ``pink
snapper'' (Pagrus auratus). This damage in the ears had not been
repaired in fish sacrificed and examined almost two months after
exposure. On the other hand, Popper et al. (2005) documented only TTS
(as determined by auditory brainstem response) in two of three fishes
from the Mackenzie River Delta. This study found that broad whitefish
(Coreogonus nasus) that received a sound exposure level of 177 dB re 1
microPa\2\.s showed no hearing loss. During both studies, the
repetitive exposure to sound was greater than would have occurred
during a typical seismic survey. However, the substantial low-frequency
energy produced by the airgun arrays [less than approximately 400 Hz in
the study by McCauley et al. (2003) and less than approximately 200 Hz
in Popper et al. (2005)]
likely did not propagate to the fish because
the water in the study areas was very shallow (approximately 9 m, 29.5
ft, in the former case and < 2 m, 6.6 ft, in the latter). Water depth
sets a lower limit on the lowest sound frequency that will propagate
(the ``cutoff frequency'') at about one-quarter wavelength (Urick,
1983; Rogers and Cox, 1988).
    Except for these two studies, at least with airgun-generated sound
treatments, most contributions rely on rather subjective assays such as
fish ``alarm'' or ``startle response'' or changes in catch rates by
fishers. These observations are important in that they attempt to use
the levels of exposures that are likely to be encountered by most free-
ranging fish in actual survey areas. However, the associated sound
stimuli are often poorly described, and the biological assays are
varied (Hastings and Popper, 2005).
    Some studies have reported that mortality of fish, fish eggs, or
larvae can occur close to seismic sources (Kostyuchenko, 1973; Dalen
and Knutsen, 1986; Booman et al., 1996; Dalen et al., 1996). Some of
the reports claimed seismic effects from treatments quite different
from actual seismic survey sounds or even reasonable surrogates. Saetre
and Ona (1996)

[[Page 42056]]

applied a `worst-case scenario' mathematical model to investigate the
effects of seismic energy on fish eggs and larvae and concluded that
mortality rates caused by exposure to seismic are so low compared to
natural mortality that the impact of seismic surveying on recruitment
to a fish stock must be regarded as insignificant.
    For the single GI gun planned for the proposed program, the
pathological (mortality) zone for crustaceans and cephalopods is
expected to be within a few meters of the seismic source; however, very
few specific data are available on levels of seismic signals that might
damage these animals. This premise is based on the peak pressure and
rise/decay time characteristics of seismic airgun arrays currently in
use around the world.
    Some studies have suggested that seismic survey sound has a limited
pathological impact on early developmental stages of crustaceans
(Pearson et al., 1994; Christian et al., 2003; DFO, 2004). However, the
impacts appear to be either temporary or insignificant compared to what
occurs under natural conditions. Controlled field experiments on adult
crustaceans (Christian et al., 2003, 2004; DFO, 2004) and adult
cephalopods (McCauley et al., 2000a,b) exposed to seismic survey sound
have not resulted in any significant pathological impacts on the
animals. It has been suggested that exposure to commercial seismic
survey activities has injured giant squid (Guerra et al., 2004), but
there is no evidence to support such claims.
    Physiological Effects - Biochemical responses by marine fish and
invertebrates to acoustic stress have also been studied, although in a
limited way. Studying the variations in the biochemical parameters
influenced by acoustic stress might give some indication of the extent
of the stress and perhaps forecast eventual detrimental effects. Such
stress could potentially affect animal populations by reducing
reproductive capacity and adult abundance and increasing mortality.
    Stress indicators in the haemolymph of adult male snow crabs were
monitored after exposure of the animals to seismic energy (Christian et
al., 2003, 2004) and at various intervals after exposure. No
significant acute or chronic differences between exposed and unexposed
animals were found in the stress indicators (e.g., proteins, enzymes,
cell type count).
    Primary and secondary stress responses of fish after exposure to
seismic energy all appear to be temporary in any studies done to date
(Sverdrup et al., 1994; McCauley et al., 2000a,b). The periods
necessary for these biochemical changes to return to normal are
variable depending on numerous aspects of the biology of the species
and of the sound stimulus. See Appendix B of SIO's application for more
information on the effects of airgun sounds on marine fish.
    Summary of Physical (Pathological and Physiological) Effects - As
indicated in the preceding general discussion, there is a relative lack
of knowledge about the potential physical (pathological and
physiological) effects of seismic energy on marine fish and
invertebrates. Available data suggest that there may be physical
impacts on egg, larval, juvenile, and adult stages at very close range.
Considering typical source levels associated with commercial seismic
arrays, close proximity to the source would result in exposure to very
high energy levels. Again, this study will employ a sound source that
will generate low energy levels. Whereas egg and larval stages are not
able to escape such exposures, juveniles and adults most likely would
avoid it. In the case of eggs and larvae, it is likely that the numbers
adversely affected by such exposure would not be that different from
those succumbing to natural mortality. Limited data regarding
physiological impacts on fish and invertebrates indicate that these
impacts are short term and are most apparent after exposure at close range.
    The proposed seismic program for 2007 is predicted to have
negligible to low physical effects on the various life stages of fish
and invertebrates for its short duration (approximately 2 hours at each
of 16 sites off the coast of Oregon) and approximately 21-km (13-mi)
extent. Therefore, physical effects of the proposed program on the fish
and invertebrates would be not significant.
    Behavioral Effects - Because of the apparent lack of serious
pathological and physiological effects of seismic energy on marine fish
and invertebrates, most concern now centers on the possible effects of
exposure to seismic surveys on the distribution, migration patterns,
mating, and catchability of fish. There is a need for more information
on exactly what effects such sound sources might have on the detailed
behavior patterns of fish and invertebrates at different ranges.
    Studies investigating the possible effects of seismic energy on
fish and invertebrate behavior have been conducted on both uncaged and
caged animals (Chapman and Hawkins, 1969; Pearson et al., 1992;
Santulli et al., 1999; Wardle et al., 2001; Hassel et al., 2003).
Typically, in these studies fish exhibited a sharp ``startle'' response
at the onset of a sound followed by habituation and a return to normal
behavior after the sound ceased.
    There is general concern about potential adverse effects of seismic
operations on fisheries, namely a potential reduction in the
``catchability'' of fish involved in fisheries. Although reduced catch
rates have been observed in some marine fisheries during seismic
testing, in a number of cases the findings are confounded by other
sources of disturbance (Dalen and Raknes, 1985; Dalen and Knutsen,
1986; Lokkeborg, 1991; Skalski et al., 1992; Engas et al., 1996). In
other airgun experiments, there was no change in catch per unit effort
of fish when airgun pulses were emitted, particularly in the immediate
vicinity of the seismic survey (Pickett et al., 1994; La Bella et al.,
1996). For some species, reductions in catch may have resulted from a
change in behavior of the fish (e.g., a change in vertical or
horizontal distribution) as reported in Slotte et al. (2004).
    In general, any adverse effects on fish behavior or fisheries
attributable to seismic testing may depend on the species in question
and the nature of the fishery (season, duration, fishing method). They
may also depend on the age of the fish, its motivational state, its
size, and numerous other factors that are difficult, if not impossible,
to quantify at this point, given such limited data on effects of
airguns on fish, particularly under realistic at-sea conditions.
    For marine invertebrates, behavioral changes could potentially
affect such aspects as reproductive success, distribution,
susceptibility to predation, and catchability by fisheries. Studies of
squid indicated startle responses (McCauley et al., 2000a,b). In other
cases, no behavioral impacts were noted (e.g., crustaceans in Christian
et al., 2003, 2004; DFO, 2004). There have been anecdotal reports of
reduced catch rates of shrimp shortly after exposure to seismic
surveys; however, other studies have not observed any significant
changes in shrimp catch rate (Andriguetto-Filho et al., 2005). Any
adverse effects on crustacean and cephalopod behavior or fisheries
attributable to seismic survey sound depend on the species in question
and the nature of the fishery (season, duration, fishing method).
Additional information regarding the behavioral effects of seismic on
invertebrates is contained in Appendix C of SIO's application.
    Summary of Behavioral Effects - As is the case with pathological
and physiological effects of seismic on fish and invertebrates,
available information is relatively scant and often

[[Page 42057]]

contradictory. There have been well-documented observations of fish and
invertebrates exhibiting behaviors that appeared to be responses to
exposure to seismic energy (i.e., startle response, change in swimming
direction and speed, and change in vertical distribution), but the
ultimate importance of those behaviors is unclear. Some studies
indicate that such behavioral changes are very temporary, whereas
others imply that fish might not resume pre-seismic behaviors or
distributions for a number of days. There appears to be a great deal of
inter- and intra-specific variability. In the case of finfish, three
general types of behavioral responses have been identified: startle,
alarm, and avoidance. The type of behavioral reaction appears to depend
on many factors, including the type of behavior being exhibited before
exposure, and proximity and energy level of sound source.
    During the proposed study, only a small fraction of the available
habitat would be ensonified at any given time, and fish species would
return to their pre-disturbance behavior once the seismic activity
ceased. The proposed seismic program is predicted to have negligible to
low behavioral effects on the various life stages of the fish and
invertebrates during its short duration (approximately 2 hours at each
of 16 sites off the coast of Oregon) and 21-km (31-mi) extent.Because
of the reasons noted above and the nature of the proposed activities
(small airgun and limited duration), the proposed operations are not
expected to have any habitat-related effects that could cause
significant or long-term consequences for individual marine mammals or
their populations or stocks. Similarly, any effects to food sources are
expected to be negligible.

Monitoring

    Vessel-based marine mammal visual observers (MMVOs) will be based
aboard the seismic source vessel and will watch for marine mammals and
turtles near the vessel during all daytime GI gun operations and during
start-ups of the gun at night. MMVOs will also watch for marine mammals
and turtles near the seismic vessel for at least 30 minutes prior to
the start of GI gun operations. When feasible, MMVOs will also make
observations during daytime periods when the seismic system is not
operating for comparison of animal abundance and behavior. Based on
MMVO observations, the airgun will be shut down when marine mammals are
observed within or about to enter a designated exclusion zone (EZ;
safety radius). The EZ is a region in which a possibility exists of
adverse effects on animal hearing or other physical effects.
    MMVOs will be appointed by the academic institution conducting the
research cruise, with NMFS Office of Protected Resources concurrence.
At least one MMVO will monitor the EZ during daytime GI gun operations
and any nighttime startups. MMVOs will normally work in shifts of 4
hours duration or less. The vessel crew will also be instructed to
assist in detecting marine mammals and turtles.
    The Wecoma is a suitable platform for marine mammal observations.
Observing stations will be on the bridge wings, with observers' eyes
approximately 6.5 m (21.3 ft) above the water line and a 180[deg]
view
outboard from either side, on the whaleback deck in front of the
bridge, with observers' eyes approximately 7.5 m (24.6 ft) above the
waterline and an approximate 200[deg]
view forward, and on the aft
control station, with observers' eyes approximately 5.5 m (18 ft) above
the waterline and an approximate 180[deg]
view aft that includes the
40-m (131-ft; 180-dB) radius area around the GI gun. The eyes of the
bridge watch will be at a height of approximately 6.5 m (21.3 ft).
MMVOs will repair to the enclosed bridge during any inclement weather.
    Standard equipment for MMVOs will be 7 x 50 reticule binoculars and
optical range finders. At night, night-vision equipment will be
available. Observers will be in wireless communication with ship
officers on the bridge and scientists in the ship's operations
laboratory, so they can advise promptly of the need for avoidance
maneuvers or GI gun shut down.
    MMVOs will record data to estimate the numbers of marine mammals
exposed to various received sound levels and to document any apparent
disturbance reactions. Data will be used to estimate the numbers of
mammals potentially ``taken'' by harassment. It will also provide the
information needed to order a shutdown of the GI gun when a marine
mammal is within or near the EZ. When a mammal sighting is made, the
following information about the sighting will be recorded:
    (1) Species, group size, age/size/sex categories (if determinable),
behavior when first sighted and after initial sighting, heading (if
consistent), bearing and distance from seismic vessel, sighting cue,
apparent reaction to the GI gun or seismic vessel (e.g., none,
avoidance, approach, paralleling, etc.), and behavioral pace.
    (2) Time, location, heading, speed, activity of the vessel
(shooting or not), sea state, visibility, cloud cover, and sun glare.
    The data listed under (2) will also be recorded at the start and
end of each observation watch and during a watch, whenever there is a
change in one or more of the variables.
    All mammal observations and airgun shutdowns will be recorded in a
standardized format. Data accuracy will be verified by the MMVOs at
sea, and preliminary reports will be prepared during the field program
and summaries forwarded to the operating institution's shore facility
and to NSF weekly or more frequently. MMVO observations will provide
the following information:
    (1) The basis for decisions about shutting down the GI gun.
    (2) Information needed to estimate the number of marine mammals
potentially ``taken'' by harassment, which must be reported to NMFS.
    (3) Data on the occurrence, distribution, and activities of marine
mammals in the area where the seismic study is conducted.
    (4) Data on the behavior and movement patterns of marine mammals
seen at times with and without seismic activity.

Mitigation

    Mitigation and monitoring measures proposed to be implemented for
the proposed seismic survey have been developed and refined during
previous SIO and L-DEO seismic studies and associated EAs, IHA
applications, and IHAs. The mitigation and monitoring measures
described herein represent a combination of the procedures required by
past IHAs for other SIO and L-DEO projects. The measures are described
in detail below.
    The number of individual animals expected to be approached closely
during the proposed activity will be small in relation to regional
population sizes. With the proposed monitoring and shut-down provisions
(see below), any effects on individuals are expected to be limited to
behavioral disturbance and will have only negligible impacts on the
species and stocks.
    Mitigation measures that will be adopted will include (1) vessel
speed or course alteration, provided that doing so will not compromise
operational safety requirements, (2) GI gun shut down, and (3)
minimizing approach to slopes and submarine canyons, if possible,
because of sensitivity of beaked whales. Two other standard mitigation
measures airgun array power down and airgun array ramp up are not
possible because only one, low-volume GI gun will be used for the surveys.

[[Page 42058]]

    Speed or Course Alteration - If a marine mammal is detected outside
the EZ but is likely to enter it based on relative movement of the
vessel and the animal, then if safety and scientific objectives allow,
the vessel speed and/or direct course will be adjusted to minimize the
likelihood of the animal entering the EZ. Major course and speed
adjustments are often impractical when towing long seismic streamers
and large source arrays, but are possible in this case because only one
GI gun and a short (300-m, 984-ft) streamer will be used. If the animal
appears likely to enter the EZ, further mitigative actions will be
taken, i.e. either further course alterations or shut down of the airgun.
    Shut-down Procedures - If a marine mammal is within or about to
enter the EZ for the single GI gun, it will be shut down immediately.
Following a shut down, GI gun activity will not resume until the marine
mammal is outside the EZ for the full array. The animal will be
considered to have cleared the EZ if it: (1) visually observed to have
left the EZ; (2) has not been seen within the EZ for 15 minutes in the
case of small odontocetes and pinnipeds; or (3) has not been seen
within the EZ for 30 minutes in the case of mysticetes and large
odontocetes, including sperm, pygmy sperm, dwarf sperm, and beaked whales.
    Minimize Approach to Slopes and Submarine Canyons - Although
sensitivity of beaked whales to airguns is not known, they appear to be
sensitive to other sound sources (mid-frequency sonar; see section IV
of SIO's application). Beaked whales tend to concentrate in continental
slope areas and in areas where there are submarine canyons. Avoidance
of airgun operations over or near submarine canyons has become a
standard mitigation measure, but there are none within or near the
study area. Four of the 16 OBS locations are on the continental slope,
but the GI gun is low volume (45 in\3\), and it will operate only a
short time (approximately 2 hours) at each location.

Reporting

    A report will be submitted to NMFS within 90 days after the end of
the cruise. The report will describe the operations that were conducted
and the marine mammals that were detected near the operations. The
report will be submitted to NMFS, providing full documentation of
methods, results, and interpretation pertaining to all monitoring. The
90-day report will summarize the dates and locations of seismic
operations, all 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 NSF has begun informal consultation
on this proposed seismic survey. NMFS will also consult informally on
the issuance of an IHA under section 101(a)(5)(D) of the MMPA for this
activity. Consultation will be concluded prior to a determination on
the issuance of the IHA.

National Environmental Policy Act (NEPA)

    NSF prepared an Environmental Assessment of a Planned Low-Energy
Marine Seismic Survey by the Scripps Institution of Oceanography in the
Northeast Pacific Ocean, September 2007. NMFS will either adopt NSF's
EA or conduct a separate NEPA analysis, as necessary, prior to making a
determination on the issuance of the IHA.

Preliminary Determinations

    NMFS has preliminarily determined that the impact of conducting the
seismic survey in the northeast Pacific Ocean may result, at worst, in
a temporary modification in behavior (Level B Harassment) of small
numbers of eight species of marine mammals. Further, this activity is
expected to result in a negligible impact on the affected species or
stocks. The provision requiring that the activity not have an
unmitigable adverse impact on the availability of the affected species
or stock for subsistence uses does not apply for this proposed action.
     For reasons stated previously in this document, this determination
is supported by: (1) the likelihood that, given sufficient notice
through relatively slow ship speed, marine mammals are expected to move
away from a noise source that is annoying prior to its becoming
potentially injurious; (2) the fact that marine mammals would have to
be closer than either 35 m (115 ft) in intermediate depths or 23 m
(75.5 ft) in deep water from the vessel to be exposed to levels of
sound (180 dB) believed to have even a minimal chance of causing TTS;
and (3) the likelihood that marine mammal detection ability by trained
observers is high at that short distance from the vessel. As a result,
no take by injury or death is anticipated and the potential for
temporary or permanent hearing impairment is very low and will be
avoided through the incorporation of the proposed mitigation measures.
    While the number of 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, less than a few percent of any of the
estimated population sizes, and has been mitigated to the lowest level
practicable through incorporation of the measures mentioned previously
in this document.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to
issue an IHA to SIO for conducting a low-energy seismic survey in the
Pacific Ocean during September, 2007, provided the previously mentioned
mitigation, monitoring, and reporting requirements are incorporated.

    Dated: July 26, 2007.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries Service.
[FR Doc. E7-14883 Filed 7-31-07; 8:45 am]
BILLING CODE 3510-22-S
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Small Takes of Marine Mammals Incidental to Specified Activities; Low-Energy Marine Seismic Survey in the Northeast Pacific Ocean, September 2007

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