Small Takes of Marine Mammals Incidental to Specified Activities; Marine Geophysical Survey Across the Arctic Ocean, 47792-47809 [05-16116]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 70, Number 156 (Monday, August 15, 2005)]
[Notices]
[Pages 47792-47809]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-16116]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[I.D. 040505A]


Small Takes of Marine Mammals Incidental to Specified Activities; 
Marine Geophysical Survey Across the Arctic Ocean

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

[[Page 47793]]


ACTION: Notice; issuance of incidental harassment authorization.

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SUMMARY: In accordance with the provisions of the Marine Mammal 
Protection Act (MMPA) as amended, notification is hereby given that 
NMFS has issued an Incidental Harassment Authorization (IHA) to the 
University of Alaska, Fairbanks (UAF) to take marine mammals by Level B 
harassment incidental to conducting a marine seismic survey across the 
Arctic Ocean from northern Alaska to Svalbard.

DATES: Effective from August 5, 2005, through August 4, 2006

ADDRESSES: A copy of the IHA and the application are available by 
writing to Steve Leathery, Chief, Permits, Conservation, and Education 
Division, Office of Protected Resources, National Marine Fisheries 
Service, 1315 East-West Highway, Silver Spring, MD 20910-3225, or by 
telephoning the contact listed here. A copy of the application 
containing a list of references used in this document may be obtained 
by writing to this address, by telephoning the contact listed here (see 
FOR FURTHER INFORMATION CONTACT) or online at: https://
www.nmfs.noaa.gov/prot_res/PR2/Small_Take/smalltake_
info.htmapplications. Documents cited in this notice may be viewed, by 
appointment, during regular business hours, at the aforementioned 
address.

FOR FURTHER INFORMATION CONTACT: Jolie Harrison, Office of Protected 
Resources, NMFS, (301) 713-2289, ext 166.

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 small numbers 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, notice of a proposed authorization is 
provided to the public for review.
    Authorization for incidental takings may be granted if NMFS finds 
that the taking will have no more than 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, and that 
the permissible methods of taking and requirements pertaining to the 
monitoring and reporting of such taking 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.
    Subsection 101(a)(5)(D) of the MMPA established an expedited 
process by which citizens of the United States can apply for an 
authorization to incidentally take small numbers of marine mammals by 
harassment. Except for certain categories of activities not pertinent 
here, the MMPA defines ``harassment'' as:
    any act of pursuit, torment, or annoyance which (i) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild [``Level A harassment'']; or (ii) has the potential to disturb 
a marine mammal or marine mammal stock in the wild by causing 
disruption of behavioral patterns, including, but not limited to, 
migration, breathing, nursing, breeding, feeding, or sheltering 
[``Level B harassment''].
    Section 101(a)(5)(D) establishes a 45-day time limit for NMFS 
review of an application followed by a 30-day public notice and comment 
period on any proposed authorization for the incidental harassment of 
small numbers of marine mammals. Within 45 days of the close of the 
comment period, NMFS must either issue or deny issuance of the 
authorization.

Summary of Request

    On March 30, 2005, NMFS received an application from UAF for the 
taking, by harassment, of several species of marine mammals incidental 
to conducting, with research funding from the National Science 
Foundation (NSF) and the Norwegian Petroleum Directorate (NPD), a 
marine seismic survey across the Arctic Ocean from northern Alaska to 
Svalbard during the period 5 August to 30 September 2005. The purpose 
of the proposed seismic study is to collect seismic reflection and 
refraction data that reveal the structure and stratigraphy of the upper 
crust of the Arctic Ocean. These data will assist in the determination 
of the history of ridges and plateaus that subdivide the Amerasian 
basin in the Arctic Ocean. Past studies have mapped the bottom of the 
Arctic Ocean, but data are needed to describe the boundaries and 
connections between the ridges and plateaus in the Amerasian basin and 
to study the stratigraphy of the smaller basins. This information will 
assist in preparing for future scientific drilling that is crucial to 
reconstructing the tectonic, magmatic, and paleoclimatic history of the 
Amerasian basin.
    Subsequent to the Federal Register notice announcing NMFS' receipt 
of UAF's application (70 FR 24539, May 10, 2005), minor changes were 
made to the proposed action. These changes are documented in detail in 
the NMFS administrative record, are included in the Specified 
Activities below, and are summarized here: (1) the seismic survey will 
commence more than 125 mi (201 km) northwest of the coast of Barrow, 
instead of approximately 25 mi (40 km) off the coast of Barrow, AK, 
which means that none of the survey will be conducted in waters less 
than 100-meters deep, and (2) UAF has added a passive acoustic 
monitoring component to the project (to gather additional information, 
not as part of mitigation implementation), wherein marine mammal 
observers (MMOs) will be able to listen to, and visually analyze, 
marine mammal signals received by sonobuoys deployed every four hours. 
As a result of the seismic survey track amendments, adverse impacts to 
all species addressed in the EA will be equal to or less than those 
predicted in the original EA, with the possible exception of walruses. 
In summer, potential walrus numbers along the new track are very 
difficult to predict because they are distributed patchily, depending 
on the ice pack distribution, which is very unpredictable. Regardless 
of numbers, though, if the ship encounters walruses, it will implement 
the same mitigation measures to avoid take as for other marine mammals 
and suspend seismic operations until the vessel has traveled well past 
the animals.

Description of the Activity

    The geophysical survey will involve the United States Coast Guard 
(USCG) cutter Healy. The Healy will rendezvous with the Swedish 
icebreaker Oden near Alpha Ridge. The Oden will be working on a 
separate project, conducting an oceanographic section across the Arctic 
Ocean basin and will coordinate its timing to meet the Healy. The Oden 
will cut a path through the ice as necessary, leading the Healy for the 
remainder of the trans-ocean track past the North Pole and then on 
towards Svalbard. The two icebreakers working in tandem will optimize 
seismic data collection and safety through the heaviest multi-year ice.
    The source vessel, the USCG icebreaker Healy, will use a portable 
Multi-Channel Seismic (MCS) system from the University of Bergen to 
conduct the seismic survey. The Healy will tow two different airgun 
configurations. The primary energy source will be two Generator guns 
(G. guns), each with a discharge volume of 250 in\3\ for a total volume 
of 500 in\3\. The secondary energy source will be a

[[Page 47794]]

single Bolt airgun of 1200 in\3\ that will be used for deeper 
penetration over three ridges (the Alpha, Mendeleev, and Gakkel 
ridges).
    The Healy will also tow a hydrophone streamer 100-150 m (328-492 
ft) behind the ship, depending on ice conditions. The hydrophone 
streamer will be up to 300 m (984 ft) long. As the airguns are towed 
along the survey lines, the receiving system will receive the returning 
acoustic signals. In addition to the airguns, a multi-beam sonar and 
sub-bottom profiler will be used during the seismic profiling and 
continuously when underway.
    The program will consist of a total of approximately 4131 km (2230 
nautical miles (nm)) of surveys, not including transits when the 
airguns are not operating, plus scientific coring at nine locations. 
The seismic survey will commence <200 km (108 nm) off the northwest 
coast of Barrow, AK, and the seismic activities will be completed 
northwest of Svalbard, in Norwegian territorial waters. Water depths 
within the study area are 170 4000 m (66-13123 ft). Approximately 9 
percent of the survey will be conducted in water 100 1000-m (328-3280-
ft) deep, and most (91 percent) of the survey (approximately 3759 km 
(1976 nm)) will occur in water <1000-m (3280-ft) deep. Additional 
seismic operations will be associated with airgun testing, start up, 
and repeat coverage of any areas where initial data quality is sub-
standard.
    Along with the airgun operations, additional acoustical systems 
will be operated during much of, or the entire, cruise. The ocean floor 
will be mapped with a multi-beam sonar, and a sub-bottom profiler will 
be used. These two systems are commonly operated simultaneously with an 
airgun system. An acoustic Doppler current profiler will also be used 
through the course of the project. A 12-kHz pinger will be used during 
the sea-bottom coring operations to monitor the depth of the corer 
relative to the ocean floor. A detailed description of the acoustic 
sources proposed for use during this survey can be found in the UAF 
application, which is available at: https://www.nmfs.noaa.gov/prot_res/
PR1/Small_Take/smalltake_info.htm#applications.
    The coring operations constitute a separate project, which will be 
conducted in conjunction with the seismic study from the Healy. Seismic 
operations will be suspended while the USCG Healy is on site for coring 
at each of nine locations. Depending on water depth and the number of 
cores to be collected, the Healy may be at each site for between 8 and 
36 hours.

Vessel Specifications

    The Healy has a length of 128 m (420 ft), a beam of 25 m (82 ft), 
and a full load draft of 8.9 m (29.2 ft). The Healy is a USCG 
icebreaker, capable of traveling at 5.6 km/h (3 knots) through 1.4 m 
(4.6 ft) of ice. A ``Central Power Plant'', four Sultzer 12Z AU40S 
diesel generators, provides electric power for propulsion and ship's 
services through a 60 Hz, 3-phase common bus distribution system. 
Propulsion power is provided by two electric AC Synchronous, 11.2 MW 
drive motors, fed from the common bus through a Cycloconverter system, 
that turn two fixed-pitch, four-bladed propellers. The operation speed 
during seismic acquisition is expected to be approximately 6.5 km/h 
(3.5 knots). When not towing seismic survey gear or breaking ice, the 
Healy cruises at 22 km/h (12 knots) and has a maximum speed of 31.5 km/
h (17 knots). She has a normal operating range of about 29,650 km 
(16,000 nm) at 23.2 km/hr (12.5 knots).
    The Healy will also serve as the platform from which vessel-based 
marine mammal observers will watch for marine mammals before and during 
airgun operations. The characteristics of the Healy that make it 
suitable for visual monitoring are described in the monitoring section.

Airgun Description and Safety Radii

    The University of Bergen's portable MCS system will be installed on 
the Healy for this cruise. The Healy will tow either two Sodera 250-
in\3\ G. guns (for a total discharge volume of 500 in\3\) or a single 
1200-in3 Bolt airgun, along with a streamer containing hydrophones, 
along predetermined lines. Seismic pulses will be emitted at intervals 
of 20 seconds (s) and recorded at a 2 millisecond (ms) sampling rate. 
The 20 s spacing corresponds to a shot interval of approximately 36 m 
(118 ft) at the typical cruise speed.
    The two-G. gun-cluster configuration will be towed below a 
depressor bird at a depth between 7 and 20 m (23 and 66 ft), as close 
to the Healy's stern as possible to minimize ice interference 
(preferred depth is 8 to 10 m (26 to 29 ft)). The two airguns will be 
towed 1 m (3.3 ft) apart, separated by a spreader bar. The G. guns have 
a zero to peak (peak) source output of 236 dB re 1 microPascal-m (6.5 
bar-m) and a peak-to-peak (pk-pk) level of 241 dB (11.7 bar-m). The 
dominant frequency components of these airguns are in the range of 0-
150 Hz. For a one-gun source, the nominal source level represents the 
actual level that would be found about 1 m (3.3 ft) from the airgun. 
Actual levels experienced by any marine organism more than 1 m (3.3 ft) 
from the airguns will be significantly lower.
    The single Bolt airgun will be towed below a depressor bird at a 
depth of 10 m (29 ft). This airgun has peak source output of 234 dB re 
1 microPascal-m (5 bar-m) and a pk-pk level of 241 dB (11.7 bar-m). The 
dominant frequency components of these airguns are in the range of 8-40 
Hz. Indicated source outputs are for sources at 5 m (16 ft) and for a 
filter bandwidth of approximately 0-250 Hz.
    Received sound levels were modeled by Lamont Doherty Earth 
Observatory (L-DEO) for single 1200-in\3\ Bolt airguns and for the one 
and two 250-in\3\ G. guns in relation to distance and direction from 
the gun. This publically available model does not allow for bottom 
interactions, and, thus, is most directly applicable to deep water. For 
deep water, where most of the present project is to occur, the L-DEO 
model has been shown to be precautionary, i.e., it tends to 
overestimate radii for 190, 180, etc., dB re 1 microPa rms (Tolstoy et 
al., 2004a,b). Based on the models, table 1 shows the distances from 
the planned sources where sound levels of 190, 180, and 160 dB re 1 
microPa root-mean squared (rms) are predicted to be received. The rms 
pressure is an average over the pulse duration. This is the measure 
commonly used in studies of marine mammal reactions to airgun sounds, 
and in NMFS guidelines concerning levels above which ``taking'' might 
occur. The rms level of a seismic pulse is typically about 10 dB less 
than its peak level (Greene 1997; McCauley et al., 1998, 2000a).

[[Page 47795]]



  Table 1. Estimated distances to which sound levels [gteqt]190, 180, and 160 dB re 1 microPa (rms) might be received from the 250-in\3\ G. gun(s) and
   1200-in\3\ Bolt airgun that will be used during the seismic survey across the Arctic Ocean during 2005. The sound radii used during the survey will
 depend on water depth (see text). Due to revision in survey start point, no surveys will be conducted in < 100 m. Distances are based on model results
                                        provided by the Lamont-Doherty Earth Observatory of Columbia University.
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                                                                                      Estimated Distances at Received Levels (m)
                                                            --------------------------------------------------------------------------------------------
    Seismic Source Volume              Water depth            190 dB (safety criterion for   180 dB (safety criterion for     160 dB (assumed onset of
                                                                       pinnipeds)                     cetaceans)               behavioral harassment)
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                  250 in\3\                        >1000 m                             17                             52                            500
                   G. gun                       100-1000 m                             26                             78                            750
                                                   <:100 m                            213                            385                           1364
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                  500 in\3\                        >1000 m                            100                            325                           3300
                   2 G. guns                    100-1000 m                            150                            500                           5000
                                                    <100 m                           1500                           2400                           9700
--------------------------------------------------------------------------------------------------------------------------------------------------------
                  1200 in\3\                       >1000 m                             25                             50                            560
                   Bolt                         100-1000 m                             38                             75                            840
                   airgun                           <100 m                            313                            370                           1527
--------------------------------------------------------------------------------------------------------------------------------------------------------

    For the two-G. gun source, the highest sound level measurable at 
any location in the water would be slightly less than the nominal 
source level because the actual source is a distributed source rather 
than a point source. However, the two guns would be only 1 m (3.3 ft) 
apart, so the non-point-source effect would be slight. For the single 
Bolt airgun, the source level represents the actual level that would be 
found about 1 m from the energy source. Actual levels experienced by 
any organism more than 1 m (3.3 ft) from either of the sources will be 
significantly lower.
    The rms received levels that are used by NMFS 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 airguns. The 
measurement units used to describe airgun sources, i.e., peak or pk-pk 
decibels, are always higher than the rms decibels referred to in much 
of the biological literature. A measured received level of 160 decibels 
rms in the far field would typically correspond to a peak measurement 
of about 170 to 172 dB, and to a peak-to-peak measurement of about 176 
to 178 decibels, as measured for the same pulse received at the same 
location (Greene 1997; McCauley et al. 1998, 2000a). The precise 
difference between rms and peak or pk-pk values for a given pulse 
depends on the frequency content and duration of the pulse, among other 
factors. However, the rms level is always lower than the peak or pk-pk 
level for an airgun-type source.
    The depth at which the sound source is towed has a major impact on 
the maximum near-field output, and on the shape of its frequency 
spectrum. In this case, the source is expected to be towed at 
relatively deep depths of 7 to 20 m (23 to 66 ft).
    Empirical data concerning the 190-, 180-, and 160-dB (rms) 
isopleths in deep and shallow water have been acquired for various 
airgun configurations 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., 2004a, b). Those data 
demonstrated that L-DEO's model tends to overestimate the isopleth 
distances applied in deep water. During that study, empirical data were 
not obtained for either the 1200-in\3\ Bolt airgun or the G. guns that 
will be used during this survey. Although the results were limited, the 
calibration-study results showed that radii around the airguns where 
the received level would be 180 dB re 1 microPa (rms), the safety zone 
radius NMFS uses for cetaceans, (NMFS 2000), vary with water depth. 
Similar depth-related variation is likely in the 190 dB distances used 
for pinnipeds. Although sea turtle sightings are highly unlikely, the 
180-dB distance will also be used as the safety radius for sea turtles, 
as required by NMFS in another recent seismic project (Smultea et al., 
2005). The safety zones are used to trigger mitigation measures, which 
are described below.
    The L-DEO model does not allow for bottom interactions, and thus is 
most directly applicable to deep water and to relatively short ranges. 
In intermediate-depth water a precautionary 1.5x factor will be applied 
to the values predicted by L-DEO's model. Due to UAF's revision of the 
survey start In shallow water, larger precautionary factors derived 
from the empirical shallow-water measurements would be applied, 
however, no seismic will be conducted in shallow water. The proposed 
study area will occur mainly in water 1000 to 4000 m (3280 to 13123 ft) 
deep, with approximately 9 percent of the survey lines in intermediate 
water depths <100 1000 m (328-3280 ft)), and with no seismic survey 
lines in shallow (<100 m (328 ft)) water, since the application was 
revised to start the survey >200 km (108 nm) off the coast of Barrow, 
AK.
    The empirical data indicate that, for deep water (>1000 m (3280 
ft)), the L-DEO model tends to overestimate the received sound levels 
at a given distance (Tolstoy et al., 2004a,b). However, to be 
precautionary pending acquisition of additional empirical data, UAF has 
proposed using safety radii during airgun operations in deep water that 
correspond to the values predicted by L-DEO's model for deep water 
(Table 1). In deep water, the estimated 190 and 180 dB radii for two 
250-in\3\G. guns are 100 and 325 m (328 and 1067 ft), respectively. 
Those for one 1200-in\3\ Bolt airgun are 25 and 50 m (82 and 164 ft), 
respectively.

[[Page 47796]]

    Empirical measurements were not conducted for intermediate depths 
(100 1000 m (328-3280 ft)). On the expectation that results would be 
somewhere between those from shallow and deep water, UAF has applied a 
1.5x correction factor to the estimates provided by the model for deep 
water situations. This is the same factor that has been applied to the 
model estimates during L-DEO operations in intermediate-depth water 
from 2003 through early 2005. The estimated 190- and 180-dB radii in 
intermediate-depth water are 150 m (490 ft) and 500 m (1640 ft), 
respectively, for the two G. gun system and 38 and 75 m (125 and 246 
ft), respectively, for the single Bolt airgun (Table 1).
    Though no seismic exercises will be conducted in shallow water, the 
explanation for the safety ranges in shallow water is included below 
because it is cross-referenced elsewhere. Empirical measurements were 
not made for the sources that will be employed during the proposed 
survey operating in shallow water (<100 m (328 ft)). The empirical data 
on operations of two 105 in\3\ GI guns in shallow water showed that 
modeled values underestimated actual levels in shallow water at 
corresponding distances of 0.5 to 1.5 km (0.3 to 0.5 nm) by a factor of 
approximately 3x (Tolstoy et al., 2004b). Sound level measurements for 
the 2 GI guns were not available for distances <0.5 km (0.3 nm) from 
the source. The radii estimated here for two G. guns operating in 
shallow water are derived from L-DEO's deep water estimates, with the 
same adjustments for depth-related differences in sound propagation 
used for 2 GI guns in earlier applications (and approximately the same 
factors as used for L-DEO's 10-airgun array). Similarly, the factors 
for the single airguns are the same as those for a single GI gun in 
earlier applications. Thus, the estimated 190- and 180-dB radii in 
shallow water are 1500 and 2400 m (4921 and 7874 ft), respectively, for 
the two G. guns (Table 1). The corresponding radii for the single G. 
gun in shallow water are estimated to be 213 and 385 m (699 and 1263 
ft), respectively. The sound radii for the single Bolt airgun in 
shallow water are estimated to be 313 m (1027 ft) for 190 dB and 370 m 
(1214 ft) for 180 dB.

Characteristics of Airgun Pulses

    Discussion of the characteristics of airgun pulses has been 
provided in the application and in previous Federal Register notices 
(see 69 FR 31792 (June 7, 2004) or 69 FR 34996 (June 23, 2004)). 
Reviewers are referred to those documents for additional information.

Comments and Responses

    A notice of receipt of the UAF application and proposed IHA was 
published in the Federal Register on May 10, 2005 (70 FR 24539). The 
Federal Register notice also invited comments on UAF's associated draft 
Environmental Assessment (EA), which was posted on the NMFS website. 
During the comment period, NMFS received comments only from the Marine 
Mammal Commission (Commission) and one individual.
    Comment 1: The Commission notes that the May, 2005 Federal Register 
notice states that monitoring would be conducted by at least one 
observer and, when practical, two observers, but does not indicate what 
factors will be used to determine when monitoring by two observers will 
be considered ``practical.'' The Commisssion recommends that NMFS seek 
clarification of this point.
    Response: There will always be two observers watching for at least 
30 minutes before seismic operations begin. Observation coverage during 
this time period is especially important in order to avoid surprising a 
marine mammal. Once seismic operations have begun, it is more likely a 
marine mammal will move to avoid the area within the safety radii. Once 
operations have begun, the time that two observers are on watch will be 
maximized within the constraints of four observers, working watches no 
longer than 4 hours, with 8-hr breaks in each 24-hr period, and needing 
time to work the data.
    Comment 2: In light of the fact that marine mammal detection is 
especially difficult in the dark, the Commission recommends that NMFS 
more explicitly define what constitutes daytime and nighttime for 
purposes of the proposed mitigation measures.
    Response: NMFS appreciates the Commissions concerns regarding the 
detection of marine mammals in the dark. However, whether it is night-
time or a foggy day, the Healy's start-up procedures require that 
seismic operation ramp-up may not begin unless the entire safety radius 
has been completely visible for at least 30 minutes prior to start-up.
    Comment 3: The Commission notes that the use of passive acoustic 
detection techniques to locate whales and ice seals by their 
vocalizations prior to start-up of the airguns might increase the 
efficacy of the monitoring effort and may be a useful additional 
mitigation measure that should be implemented. They further suggest 
that NMFS consult with the applicant about the possibility of 
establishing a one-half hour listening period prior to start-up of the 
airguns for this purpose.
    Response: In response to a request and subsequent discussion at the 
Anchorage MMPA Peer-review meeting in May, 2005, UAF has added a 
passive acoustic monitoring component (described in the Monitoring 
section below), which will utilize data collected by the sonobuoys that 
are deployed from the Healy every 4 hours. The plan is for one MMO to 
listen to the sound being received by the closest sonobuoy for 10 
minutes out of every 30 they are monitoring, which will include time 
prior to ramp up of seismic operations. The added passive acoustic 
monitoring with sonobuoys, though it will allow marine mammal observers 
(MMOs) to identify the presence of marine mammals in a region in which 
visual observations are restricted by ice and poor visibility, will not 
be used directly to implement mitigation measures (i.e. to necessitate 
a shut-down) because the direction and exact distance from which the 
signals are coming cannot be determined. However, any information 
gathered could help to fill a data gap about the habitats marine 
mammals occupy in the very high Arctic latitudes.
    Comment 4: The Commission states concerns about whether the 
proposed monitoring effort will be sufficient to determine that no 
marine mammal, especially species that may be difficult to detect, are 
within the safety zones (190 dB for pinnipeds, 180 dB for cetaceans) at 
start up or will be an effective means of detecting when marine mammals 
enter the safety zones during operations.
    Response: For this activity, the safety radii range from 17 to 78 m 
(56 to 256 ft) in deep water (91 percent of survey), to 100 to 500 m 
(328 to1640 ft) in intermediate depth water (9 percent of survey). 
Considering the small size of the conservative shutdown zones, the 
speed of the vessel when towing the airgun (6.5 km/h (3.5 knots)), and 
the marine mammal avoidance measures that are implemented on the vessel 
for animals on the vessel's track, it is very unlikely that any marine 
mammals would enter the safety zone undetected. If a marine mammal 
enters the small safety zone, operational shutdown will be implemented 
until the animal leaves the safety zone.

Description of Habitat and Marine Mammals Affected by the Activity

    A detailed description of the Healy's revised track from northwest 
of Barrow, through the Arctic ocean to northwest of

[[Page 47797]]

Svalbard and the associated marine mammals can be found in the UAF 
application (including revisions) and a number of documents referenced 
in the UAF application. A total of 17 cetacean species and 10 pinniped 
species may occur in the proposed study area. The marine mammals that 
occur in the proposed survey area belong to four taxonomic groups: 
odontocetes (toothed cetaceans, such as dolphins and sperm whales), 
mysticetes (baleen whales), pinnipeds (seals, sea lions, and walrus), 
and fissipeds (polar bear).
    Odontocete whales include the sperm whale, northern bottlenose 
whale, beluga whale, narwhal, Atlantic white-beaked dolphin, Atlantic 
white-sided dolphin, killer whale, long-finned pilot whale, and harbor 
porpoise.
    Mysticete whales include the North Atlantic right whale, bowhead 
whale, gray whale, humpback whale, minke whale, sei whale, fin whale, 
and blue whale.
    Pinnipeds include the walrus, bearded seal, harbor seal, spotted 
seal, ringed seal, hooded seal, and harp seal.
    The marine mammal species most likely to be encountered include 
four cetacean species (beluga whale, narwhal, gray whale, bowhead 
whale), five pinniped species (walrus, bearded seal, ringed seal, 
hooded seal, harp seal), and the polar bear. However, most of these 
will occur in low numbers and are most likely to be encountered within 
100 km (54 nm) of shore. The most abundant marine mammal likely to be 
encountered throughout the cruise is the ringed seal. The most widely 
distributed marine mammals are expected to be the beluga, ringed seal, 
and polar bear.
    About 13 additional cetacean species could occur in the project 
area, but are unlikely to be encountered along the proposed trackline. 
If encountered at all, those species would be found only near one end 
of the track, either near Svalbard or near Alaska. The following 12 
species, if encountered at all, would be found close to Svalbard: sperm 
whale, northern bottlenose whale, long-finned pilot whale, Atlantic 
white-sided dolphin, Atlantic white-beaked dolphin, harbor porpoise, 
killer whale, North Atlantic right whale, humpback whale, minke whale, 
sei whale, fin whale, and blue whale. Two additional pinniped species, 
the harbor seal and spotted seal, are also unlikely to be encountered.
    Although information on the walrus and polar bear are included 
here, they are managed by the U.S. Fish & Wildlife Service (USFWS) and 
are not the subject of this authorization. UAF will coordinate with the 
USFWS regarding the effects of project operations on walruses and polar 
bears.
    More detailed information on these species is contained in the UAF 
application (see ADDRESSES).

Potential Effects of Activities on Marine Mammals

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

Effects of Seismic Surveys on Marine Mammals

    The UAF application provides the following information on what is 
known about the effects on marine mammals of the types of seismic 
operations planned by UAF. The types of effects considered in here are 
(1) tolerance, (2) masking of natural sounds, (3) behavioral 
disturbance, and (4) potential hearing impairment and other non-
auditory physical effects (Richardson et al., 1995). Because the airgun 
sources planned for use during the present project involve only one or 
two airguns, the effects are anticipated to be considerably less than 
would be the case with a large array. UAF and NMFS believe it is very 
unlikely that there would be any cases of temporary or permanent 
hearing impairment, or non-auditory physical effects. Also, behavioral 
disturbance is expected to be limited to animals that are near the 
vessel at distances less than 3300 m (10827 ft) in deep water (91 
percent of survey) and less than 5000 m (16404 ft) in intermediate 
water depths, where the received sound levels greater than160 dB are 
expected to be. This corresponds to the value NMFS uses for onset of 
Level B harassment due to impulse sounds. Additional discussion on 
effects on marine mammal species can be found in the UAF application.
Tolerance
    Numerous studies (referenced in L-DEO, 2004) have shown that pulsed 
sounds from airguns are often readily detectable in the water at 
distances of many kilometers, but that marine mammals at distances more 
than a few kilometers from operating seismic vessels often show no 
apparent response. That is often true even in cases when the pulsed 
sounds must be readily audible to the animals based on measured 
received levels and the hearing sensitivity of that mammal group. 
However, most measurements of airgun sounds that have been reported 
concerned sounds from larger arrays of airguns, whose sounds would be 
detectable farther away than the ones that are planned to be used in 
the proposed survey. Although various baleen whales, toothed whales, 
and pinnipeds have been shown to react behaviorally to airgun pulses 
under some conditions, at other times all three types of mammals have 
shown no overt reactions. In general, pinnipeds and

[[Page 47798]]

small odontocetes seem to be more tolerant of exposure to airgun pulses 
than are baleen whales. Given the low-energy airgun sources planned for 
use in this proposed project, marine mammals would be expected to 
tolerate being closer to these sources than would be the case for a 
larger airgun source typical of most seismic surveys.
Masking
    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal vocalizations and other natural sounds are 
expected to be limited, although there are very few specific data of 
relevance. Some whales are known to continue calling in the presence of 
seismic pulses. Their calls can be heard between the seismic pulses 
(e.g., Richardson et al., 1986; McDonald et al., 1995; Greene et al., 
1999; Nieukirk et al., 2004). Although there has been one report that 
sperm whales cease calling when exposed to pulses from a very distant 
seismic ship (Bowles et al., 1994), a more recent study reports that 
sperm whales off northern Norway continued calling in the presence of 
seismic pulses (Madsen et al., 2002). That behavior has also been shown 
during recent work in the Gulf of Mexico (Tyack et al., 2003). Given 
that the airgun sources planned for use here involve only 1 or 2 
airguns, 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 odontocete cetaceans, given the intermittent nature of 
seismic pulses and the relatively low source level of the airgun 
configurations to be used here. Also, the sounds important to 
odontocetes are predominantly at much higher frequencies than are 
airgun sounds and would not be masked by the airguns.
    Most of the energy in the sound pulses emitted by airguns is at low 
frequencies, with strongest spectrum levels below 200 Hz and 
considerably lower spectrum levels above 1000 Hz. These low frequencies 
are mainly used by mysticetes, but generally not by odontocetes or 
pinnipeds. An industrial sound source will reduce the effective 
communication or echolocation distance only if its frequency is close 
to that of the marine mammal's signal. If little or no overlap occurs 
between the frequencies of the industrial noise and the marine mammals, 
as in the case of many marine mammals relative to airgun sounds, 
communication and echolocation are not expected to be disrupted. 
Furthermore, the discontinuous nature of seismic pulses makes 
significant masking effects unlikely even for mysticetes.
    A few cetaceans are known to increase the source levels of their 
calls in the presence of elevated sound levels, or possibly to shift 
their peak frequencies in response to strong sound signals (Dahlheim, 
1987; Au, 1993; Lesage et al., 1999; Terhune, 1999; as reviewed in 
Richardson et al., 1995). These studies involved exposure to other 
types of anthropogenic sounds, not seismic pulses, and it is not known 
whether these types of responses ever occur upon exposure to seismic 
sounds. If so, these adaptations, along with directional hearing, pre-
adaptation to tolerate some masking by natural sounds (Richardson et 
al., 1995) and the relatively low-power acoustic sources being used in 
this survey, would all reduce the possible adverse impacts of masking 
marine mammal vocalizations.
Behavioral Disturbance by Seismic Surveys
    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous changes in activities, and displacement. 
Not all behavioral disturbances rise to the level of Level B 
Harassment, which requires a disruption of behavioral patterns of 
biological importance. Exposure to sound alone may not constitute 
harassment or ``taking'' (NMFS 2001, p. 9293). Behavioral reactions of 
marine mammals to sound are difficult to predict. Reactions to sound, 
if any, depend on species, individual variation, state of maturity, 
experience, current activity, reproductive state, time of day, season, 
and many other factors. If a marine mammal does react to an underwater 
sound by changing its behavior or moving a small distance, the impacts 
of the change may not rise to the level of a disruption of a behavioral 
pattern. However, if a sound source would displace a marine mammal from 
an important feeding or breeding area, such a disturbance may 
constitute Level B harassment under the MMPA. In addition, effects that 
might not constitute Level B harassment may still result in spatial 
displacement of sensitive species, such as bowhead whales, thereby 
affecting subsistence needs. Given the many uncertainties in predicting 
the quantity and types of impacts of noise on marine mammals, NMFS 
estimates the number of marine mammals that may be present within a 
particular distance of industrial activities or exposed to a particular 
level of industrial sound and uses these numbers as a proxy. With the 
possible exception of beaked whales, NMFS believes that this is a 
conservative approach and likely overestimates the numbers of marine 
mammals that may experience a disruption of a behavioral pattern.
    The sound exposure criteria used to estimate how many marine 
mammals might be harassed behaviorally by the seismic survey are based 
on behavioral observations during studies of several species. However, 
information is lacking for many other species. Detailed studies have 
been conducted on humpback, gray, and bowhead whales, and on 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 been on behavioral reactions to much larger 
airgun sources than the airgun configurations 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. Detailed information on potential 
disturbance effects on baleen whales, toothed whales, and pinnipeds can 
be found in the UAF application.
Hearing Impairment and Other Physical Effects
    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds, but there has been no 
specific documentation of this for marine mammals exposed to airgun 
pulses. Based on current information, NMFS precautionarily sets 
impulsive sounds equal to or greater than 180 and 190 dB re 1 microPa 
(rms) as the exposure thresholds for onset of Level A harassment 
(injury) for cetaceans and pinnipeds, respectively (NMFS, 2000). Those 
criteria have been used for several years in setting the safety (shut-
down) radii for seismic surveys. As discussed in the UAF application 
and summarized here,
    1. The 180-dB criterion for cetaceans is probably quite 
precautionary, i.e., lower than necessary to avoid TTS let alone 
permanent auditory injury, at least for delphinids.
    2. The minimum sound level necessary to cause permanent hearing 
impairment is higher, by a variable and generally unknown amount, than 
the level that induces barely-detectable TTS.
    3. The level associated with the onset of TTS is often considered 
to be lower than levels that may cause permanent hearing damage.
    Because the airgun sources planned for use during this project 
involve only

[[Page 47799]]

1 or 2 guns, and with the planned monitoring and mitigation measures, 
there is little likelihood that any marine mammals will be exposed to 
sounds sufficiently strong to cause even the mildest (and reversible) 
form of hearing impairment. Several aspects of the planned monitoring 
and mitigation measures for this project are designed to detect marine 
mammals occurring near the airgun(s), and multi-beam sonar, 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 small area with high received levels of 
airgun sound (see above). In those cases, the avoidance responses of 
the animals themselves will likely reduce or prevent any possibility of 
hearing impairment.
    Non-auditory physical effects might 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 in marine mammals that are in close proximity to 
large arrays of airguns. UAF and NMFS believe that it is highly 
unlikely that any of these non-auditory effects would occur during the 
proposed survey given the small size of the source, the brief duration 
of exposure of any given mammal, and the planned mitigation and 
monitoring measures. The following paragraphs discuss the possibility 
of TTS, permanent threshold shift (PTS), and non-auditory physical 
effects.
TTS
    TTS is the mildest form of hearing impairment that can occur during 
exposure to a strong sound (Kryter, 1985). When an animal experiences 
TTS, its hearing threshold rises and a sound must be stronger in order 
to be heard. TTS can last from minutes or hours to (in cases of strong 
TTS) days. Richardson et al. (1995) note that the magnitude of TTS 
depends on the level and duration of noise exposure, among other 
considerations. For sound exposures at or somewhat above the TTS 
threshold, hearing sensitivity recovers rapidly after exposure to the 
noise ends. Little data on pulsed 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, at a first approximation, a function of the 
energy content of the pulse (Finneran et al., 2002). Given the 
available data, the received level of a single seismic pulse might need 
to be approximately 210 dB re 1 microPa rms (approx. 221 226 dB pk pk) 
in order to produce brief, mild TTS. Exposure to several seismic pulses 
at received levels near 200 205 dB (rms) might result in slight TTS in 
a small odontocete, assuming the TTS threshold is at a function of the 
total received pulse energy (Finneran et al., 2002). Seismic pulses 
with received levels of 200 205 dB or more are usually restricted to a 
zone of no more than 100 m (328 ft) around a seismic vessel operating a 
large array of airguns. Such sound levels would be limited to distances 
within a few meters of the single airgun planned for use during this 
project.
    There are no data, direct or indirect, on levels or properties of 
sound that are required to induce TTS in any baleen whale. However, TTS 
is not expected to occur during this survey given that the airgun 
sources involve only 1 or 2 airguns, and the strong likelihood that 
baleen whales would avoid the approaching airgun(s), or vessel, before 
being exposed to levels high enough for there to be any possibility of 
TTS.
    TTS thresholds for pinnipeds exposed to brief pulses (single or 
multiple) have not been measured, although exposures up to 183 dB re 1 
microPa (rms) have been shown to be insufficient to induce TTS in 
captive California sea lions (Finneran et al., 2003). However, studies 
for prolonged exposures show that some pinnipeds may incur TTS at 
somewhat lower received levels for prolonged exposures than do small 
odontocetes exposed for similar durations (Kastak et al., 1999; Ketten 
et al., 2001; Au et al., 2000). 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).
    A marine mammal within 100 m ( <=328 ft) of a typical large array 
of operating airguns might be exposed to a few seismic pulses with 
levels of [gteqt] 205 dB, and possibly more pulses if the mammal moved 
with the seismic vessel. (As noted above, most cetacean species tend to 
avoid operating airguns, although not all individuals do so.) However, 
several of the considerations that are relevant in assessing the impact 
of typical seismic surveys with arrays of airguns are not directly 
applicable here:(1) The planned airgun sources involve only 1 or 2 
airguns, with correspondingly smaller radii within which received sound 
levels could exceed any particular level of concern.
    (2) ``Ramping up'' (soft start) is standard operational protocol 
during startup of large airgun arrays in many jurisdictions. Ramping up 
involves starting the airguns in sequence, usually commencing with a 
single airgun and gradually adding additional airguns. This practice 
will be employed when the 2 G. guns are operated.
    (3) Even with a large airgun array, it is unlikely that cetaceans 
would be exposed to airgun pulses at a sufficiently high level for a 
sufficiently long period to cause more than mild TTS, given the 
relative movement of the vessel and the marine mammal. In this project, 
the airgun sources are much less strong, so the area of influence and 
duration of exposure to strong pulses is much smaller, especially in 
deep and intermediate-depth water.
    (4) With a large array of airguns, TTS would be most likely to 
occur in any odontocetes that bow-ride or otherwise linger near the 
airguns. In the present project, the anticipated 180 dB distances in 
deep and intermediate-depth water are 325 and 500 m (1066 and 1640 ft), 
respectively, for the 2 G. gun system, and 50 and 75 m (164 and 246 
ft), respectively, for the single Bolt airgun (Table 2). The waterline 
at the bow of the Healy will be approximately 123 m (403 ft) ahead of 
the airgun.
    NMFS believes that, to avoid Level A harassment, cetaceans should 
not be exposed to pulsed underwater noise at received levels exceeding 
180 dB re 1 microPa (rms). The corresponding limit for pinnipeds is 190 
dB. The predicted 180- and 190-dB distances for the airgun arrays 
operated by UAF during this activity are summarized in Table 1 in this 
document.
    It has also been shown that most whales tend to avoid ships and 
associated seismic operations. Thus, whales will likely not be exposed 
to such high levels of airgun sounds. Because of the slow ship speed, 
any whales close to the trackline could move away before the sounds 
become sufficiently strong for there to be any potential for hearing 
impairment. Therefore, there is little potential for whales being close 
enough to an array to experience TTS. In addition, ramping up multiple 
airguns in arrays has become standard operational protocol for many 
seismic operators and will occur when the 2 G. guns are operated.

[[Page 47800]]

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. Although there is no specific evidence that 
exposure to pulses of airgun sounds can cause PTS in any marine 
mammals, even with the largest airgun arrays, physical damage to a 
mammal's hearing apparatus can potentially occur if it is exposed to 
sound impulses that have very high peak pressures, especially if they 
have very short rise times (time required for sound pulse to reach peak 
pressure from the baseline pressure). Such damage can result in a 
permanent decrease in functional sensitivity of the hearing system at 
some or all frequencies.
    Single or occasional occurrences of mild TTS are not indicative of 
permanent auditory damage in terrestrial mammals. However, very 
prolonged exposure to sound strong enough to elicit TTS, or shorter-
term exposure to sound levels well above the TTS threshold, can cause 
PTS, at least in terrestrial mammals (Kryter, 1985). Relationships 
between TTS and PTS thresholds have not been studied in marine mammals 
but are assumed to be similar to those in humans and other terrestrial 
mammals, based on their similar anatomy and inner ear structures. The 
low-to-moderate levels of TTS that have been induced in captive 
odontocetes and pinnipeds during recent controlled studies of TTS have 
been confirmed to be temporary, with no measurable residual PTS (Kastak 
et al., 1999; Schlundt et al., 2000; Finneran et al., 2002; Nachtigall 
et al., 2003). In terrestrial mammals, the received sound level from a 
single non-impulsive sound exposure must be far above the TTS threshold 
for any risk of permanent hearing damage (Kryter, 1994; Richardson et 
al., 1995). For impulse sounds with very rapid rise times (e.g., those 
associated with explosions or gunfire), a received level not greatly in 
excess of the TTS threshold may start to elicit PTS. The rise times for 
airgun pulses are rapid, but less rapid than for explosions.
    Some factors that contribute to onset of PTS are as follows: (1) 
exposure to single very intense noises, (2) repetitive exposure to 
intense sounds that individually cause TTS but not PTS, and (3) 
recurrent ear infections or (in captive animals) exposure to certain 
drugs.
    Cavanagh (2000) has reviewed the thresholds used to define TTS and 
PTS. Based on his review and SACLANT (1998), it is reasonable to assume 
that PTS might occur at a received sound level 20 dB or more above that 
which induces mild TTS. However, for PTS to occur at a received level 
only 20 dB above the TTS threshold, it is probable that the animal 
would have to be exposed to the strong sound for an extended period.
    Sound impulse duration, peak amplitude, rise time, and number of 
pulses are the main factors thought to determine the onset and extent 
of PTS. Based on existing data, Ketten (1994) has noted that the 
criteria for differentiating the sound pressure levels that result in 
PTS (or TTS) are location and species-specific. PTS effects may also be 
influenced strongly by the health of the receiver's ear.
    Given that marine mammals are unlikely to be exposed to received 
levels of seismic pulses that could cause TTS, it is highly unlikely 
that they would sustain permanent hearing impairment. If we assume that 
the TTS threshold for odontocetes for exposure to a series of seismic 
pulses may be on the order of 220 dB re 1 microPa (pk-pk) 
(approximately 204 dB re 1 microPa rms), then the PTS threshold might 
be about 240 dB re 1 microPa (pk-pk). In the units used by 
geophysicists, this is 10 bar-m. Such levels are found only in the 
immediate vicinity of the largest airguns (Richardson et al., 1995; 
Caldwell and Dragoset, 2000). However, as noted previously in this 
document, it is very unlikely that an odontocete would remain within a 
few meters of a large airgun for sufficiently long to incur PTS. The 
TTS (and thus PTS) thresholds of baleen whales and pinnipeds may be 
lower, and thus may extend to a somewhat greater distance from the 
source. However, baleen whales generally avoid the immediate area 
around operating seismic vessels, so it is unlikely that a baleen whale 
could incur PTS from exposure to airgun pulses. Some pinnipeds do not 
show strong avoidance of operating airguns.
    In summary, during this project, it is highly unlikely that marine 
mammals could receive sounds strong enough and over a sufficient period 
of time to cause permanent hearing impairment. In the proposed project 
marine mammals are unlikely to be exposed to received levels of seismic 
pulses strong enough to cause TTS, and because of the higher level of 
sound necessary to cause PTS, it is even less likely that PTS could 
occur. This is due to the fact that even levels immediately adjacent to 
the single G. gun may not be sufficient to induce PTS because the 
mammal would not be exposed to more than one strong pulse unless it 
swam alongside an airgun for a period of time.
Strandings and Mortality
    Marine mammals close to underwater detonations of high explosives 
can be killed or severely injured, and the auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). 
Airgun pulses are less energetic and have slower rise times than 
underwater detonations. While there is no documented evidence that 
airgun arrays can cause serious injury, death, or stranding, the 
association of mass strandings of beaked whales with naval exercises 
and, in one case, an L-DEO seismic survey have raised the possibility 
that beaked whales may be especially susceptible to injury and/or 
behavioral reactions that can lead to stranding when exposed to strong 
pulsed sounds.
    It is important to note that seismic pulses and mid-frequency 
military sonar pulses are quite different. Sounds produced by the types 
of airgun arrays used to profile sub-sea geological structures are 
broadband with most of the energy below 1 kHz. Typical military mid-
frequency sonars operate at frequencies of 2 to 10 kHz, generally with 
a relatively narrow bandwidth at any one time (though the center 
frequency may change over time). Because seismic and sonar sounds have 
considerably different characteristics and duty cycles, it is not 
appropriate to assume that there is a direct connection between the 
effects of military sonar and seismic surveys on marine mammals. 
However, evidence that sonar pulses can, in special circumstances, lead 
to hearing damage and, indirectly, mortality suggests that caution is 
warranted when dealing with exposure of marine mammals to any high-
intensity pulsed sound.
    In addition to mid-frequency sonar-related strandings (see 69 FR 
74906 (December 14, 2004) for additional discussion), there was a 
September, 2002 stranding of two Cuvier's beaked whales in the Gulf of 
California (Mexico) when a seismic survey by the R/V Maurice Ewing was 
underway in the general area (Malakoff, 2002). The airgun array in use 
during that project was the Ewing's 20-gun 8490-in\3\ array. This might 
be a first indication that seismic surveys can have effects, at least 
on beaked whales, similar to the suspected effects of naval sonars. 
However, the evidence linking the Gulf of California strandings to the 
seismic surveys is inconclusive, and is not based on any physical 
evidence (Hogarth, 2002; Yoder, 2002). The ship was also operating its 
multi-beam

[[Page 47801]]

bathymetric sonar at the same time but this sonar had much less 
potential to affect beaked whales than either the airguns in use or 
these naval sonars. Although the link between the Gulf of California 
strandings and the seismic (plus multi-beam sonar) survey is 
inconclusive, this event, in addition to the various incidents 
involving beaked whale strandings associated with naval exercises, 
suggests a need for caution in conducting seismic surveys in areas 
occupied by beaked whales.
    The present project will involve lower-energy sound sources than 
used in typical seismic surveys. That, along with the monitoring and 
mitigation measures that are planned, and the infrequent occurrence of 
beaked whales in the project area, will minimize any possibility for 
strandings and mortality.
Non-auditory Physiological Effects
    Possible types of non-auditory physiological effects or injuries 
that might theoretically occur in marine mammals exposed to strong 
underwater sound include stress, neurological effects, bubble 
formation, resonance effects, and other types of organ or tissue 
damage. There is no evidence that any of these effects occur in marine 
mammals exposed to sound from airgun arrays. However, there have been 
no direct studies of the potential for airgun pulses to elicit any of 
these effects. If any such effects do occur, they would probably be 
limited to unusual situations when animals might be exposed at close 
range for unusually long periods.
    Long-term exposure to anthropogenic noise may have the potential to 
cause physiological stress that could affect the health of individual 
animals or their reproductive potential, which could theoretically 
cause effects at the population level (Gisner (ed.), 1999). However, 
there is essentially no information about the occurrence of noise-
induced stress in marine mammals. Also, it is doubtful that any single 
marine mammal would be exposed to strong seismic sounds for 
sufficiently long that significant physiological stress would develop. 
That is especially so in the case of the present project which will 
deploy only 1 or 2 airguns, the ship is moving 3 4 knots, and for the 
most part the tracklines will not ``double back'' through the same 
area.
    Gas-filled structures in marine animals have an inherent 
fundamental resonance frequency. If stimulated at this frequency, the 
ensuing resonance could cause damage to the animal. There may also be a 
possibility that high sound levels could cause bubble formation in the 
blood of diving mammals that in turn could cause an air embolism, 
tissue separation, and high, localized pressure in nervous tissue 
(Gisner (ed), 1999; Houser et al., 2001). In 2002, NMFS held a workshop 
(Gentry (ed.), 2002) to discuss whether the stranding of beaked whales 
in the Bahamas in 2000 might have been related to air cavity resonance 
or bubble formation in tissues caused by exposure to noise from naval 
sonar. A panel of experts concluded that resonance in air-filled 
structures was not likely to have caused this stranding. Among other 
reasons, the air spaces in marine mammals are too large to be 
susceptible to resonant frequencies emitted by mid- or low-frequency 
sonar; lung tissue damage has not been observed in any mass, multi-
species stranding of beaked whales; and the duration of sonar pings is 
likely too short to induce vibrations that could damage tissues (Gentry 
(ed.), 2002).
    Opinions were less conclusive about the possible role of gas 
(nitrogen) bubble formation/growth in the Bahamas stranding of beaked 
whales. Workshop participants did not rule out the possibility that 
bubble formation/growth played a role in the stranding and participants 
acknowledged that more research is needed in this area. The only 
available information on acoustically-mediated bubble growth in marine 
mammals is modeling that assumes prolonged exposure to sound.
    A short paper concerning beaked whales stranded in the Canary 
Islands in 2002 suggests that cetaceans might be subject to 
decompression injury in some situations (Jepson et al., 2003). If so, 
that might occur if they ascend unusually quickly when exposed to 
aversive sounds. However, the interpretation that the effect was 
related to decompression injury is unproven (Piantadosi and Thalmann, 
2004; Fernandez et al., 2004). Even if that effect can occur during 
exposure to mid-frequency sonar, there is no evidence that this type of 
effect occurs in response to low-frequency airgun sounds. It is 
especially unlikely in the case of the proposed survey, involving only 
1 or 2 airguns that will operate in any one location only briefly.
    In summary, little is known about the potential for seismic