[Federal Register Volume 72, Number 242 (Tuesday, December 18, 2007)]
[Notices]
[Pages 71625-71644]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-24508]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RIN 0648-XE34]


Small Takes of Marine Mammals Incidental to Specified Activities; 
Marine Geophysical Survey off Central America, February-April 2008

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

ACTION: Notice; proposed incidental take authorization; request for 
comments.

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SUMMARY: NMFS has received an application from Lamont-Doherty Earth 
Observatory (L-DEO), a part of Columbia University, for an Incidental 
Harassment Authorization (IHA) to take marine mammals incidental to 
conducting a marine seismic survey off Central America during February-
April 2008. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS 
is requesting comments on its proposal to issue an IHA to L-DEO to 
incidentally take, by Level B harassment only, small numbers of several 
species of marine mammals during the aforementioned activity.

[[Page 71626]]


DATES: Comments and information must be received no later than January 
17, 2008.

ADDRESSES: Comments on the application should be addressed to P. 
Michael Payne, Chief, Permits, Conservation and Education Division, 
Office of Protected Resources, National Marine Fisheries Service, 1315 
East-West Highway, Silver Spring, MD 20910-3225. The mailbox address 
for providing e-mail comments is [email protected]. 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, 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 United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
Except with respect to certain activities not pertinent here, the MMPA 
defines ``harassment'' as:

any act of pursuit, torment, or annoyance which (i) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild [Level A harassment]; or (ii) has the potential to disturb a 
marine mammal or marine mammal stock in the wild by causing 
disruption of behavioral patterns, including, but not limited to, 
migration, breathing, nursing, breeding, feeding, or sheltering 
[Level B harassment].

    Section 101(a)(5)(D) establishes a 45-day time limit for NMFS 
review of an application followed by a 30-day public notice and comment 
period on any proposed authorizations for the incidental harassment of 
marine mammals. Within 45 days of the close of the comment period, NMFS 
must either approve or deny the authorization.

Summary of Request

    On August 24, 2007, NMFS received an application from L-DEO for the 
taking, by Level B harassment only, of small numbers of 26 species of 
marine mammals incidental to conducting, under a cooperative agreement 
with the National Science Foundation (NSF), a seismic survey in the 
Pacific Ocean and Caribbean Sea off Central America as part of the 
Subduction Factory (SubFac) initiative of NSF's MARGINS program from 
January-March, 2008. (The dates of the cruise were subsequently moved 
to the February-April 2008 timeframe.) The MARGINS program was 
developed to facilitate the study of continental margins. The SubFac 
initiative will determine the inputs, outputs, and controlling 
processes of subduction zone systems by obtaining seismic measurements 
of magma flux, arc composition, and lower-plate serpentinization at the 
Central American Focus Site.

Description of the Activity

    The seismic survey will involve one source vessel, the R/V Marcus 
G. Langseth (Langseth), which will operate in two regions during the 
proposed survey: the Caribbean Sea and the Pacific Ocean. The Langseth 
will deploy an array of 36 airguns (6,600 in\3\ ) as an energy source 
and, at times, a receiving system consisting of a 6-km (3.7-mi) towed 
hydrophone streamer. The streamer will be towed at a depth of 5-8 m 
(16-26 ft). As the airgun array is towed along the survey lines, the 
hydrophone streamer will receive the returning acoustic signals and 
transfer the data to the on-board processing system. In the Caribbean 
region, the Langseth will also deploy Ocean Bottom Seismometers (OBSs) 
to receive the returning acoustic signals. In the Pacific Ocean, a 
second vessel, the R/V New Horizon, will deploy and retrieve the OBSs.
    For the first part of the cruise, the Langseth is expected to 
depart Puerto Limon, Costa Rica, on approximately February 3, 2008 for 
the study area in the Caribbean Sea (see Figure 1 in the application). 
The seismic survey will commence following the transit and deployment 
of the streamer and airgun array. Following approximately 25 days of 
surveying in the Caribbean Sea, all equipment will be recovered, and 
the vessel will return to Puerto Limon on approximately March 5, 2008. 
The vessel will then transit through the Panama Canal, likely taking on 
fuel in Panama. The second part of the survey will commence in the 
Pacific Ocean on approximately March 11, 2008 from Puerto Caldera, 
Costa Rica. The Pacific survey is estimated to last approximately 25 
days. Currently, the vessel is scheduled to arrive at an unspecified 
port (likely in Panama) on April 6, 2008. The order of the two surveys 
may be reversed due to logistics, if necessary. The exact dates of the 
activities depend upon logistics, as well as weather conditions and/or 
the need to repeat some lines if data quality is substandard.
    The Central American SubFac survey will encompass the area from 
9.6[deg]-14[deg] N., 82[deg]-83.8[deg] W. in the Caribbean Sea and the 
area 8[deg]-11.5[deg] N., 83.6[deg]-88[deg] W. in the Pacific Ocean 
(see Figure 1 in the application). Water depths in the survey area 
range from less than 100 m (328 ft) to greater than 2,500 m (8,202 ft). 
The seismic survey will take place in the Exclusive Economic Zones 
(EEZ) of Costa Rica and Nicaragua.
    The marine seismic survey will consist of approximately 2,149 km 
(1,335 mi) of unique survey lines: 753 km (468 mi) in the Caribbean and 
1,396 km (867 mi) in the Pacific (see Table 1 in the application). With 
the exception of two lines (D and E) located in shallow to 
intermediate-depth water, all lines will be shot twice, once at 
approximately a 50 m (164 ft; 20-s) shot spacing for multichannel 
seismic data and once at approximately a 200 m (656 ft; 80-s) shot 
spacing for OBS refraction data, for a total of approximately 3,980 km 
(2,473 mi) of survey lines (see Table 1 in the application). The 
approximate numbers of line kilometers expected to

[[Page 71627]]

be surveyed in the Pacific and Caribbean in three different water depth 
categories are shown in Table 2 of the application. There will be 
additional operations associated with equipment testing, startup, line 
changes, and repeat coverage of any areas where initial data quality is 
substandard. There may also be an additional 77 km (48 mi) of survey 
effort in the Pacific Ocean around Culebra off Nicoya Peninsula not 
reflected in Table 1 of L-DEO's application. These additional six 
transect lines will occur in water greater than 100 m (328 ft) deep and 
are not expected to increase the number of takes by harassment (see 
below).
    The New Horizon will be the dedicated OBS vessel during the Pacific 
part of the survey and will deploy and retrieve the OBSs. A combination 
of 85 OBSs (150 total deployments) will be used during the project. A 
total of 60 OBS deployments will take place in the Caribbean (from the 
Langseth), and 90 deployments will take place in the Pacific from the 
New Horizon.
    In addition to the operations of the airgun array, a 12-kHz Simrad 
EM120 multibeam echosounder (MBES) will be operated from the Langseth 
continuously throughout the cruise. Also, a 3.5-kHz sub-bottom profiler 
(SBP) will be operated by the Langseth during most of the survey and 
during normal operations by the New Horizon.

Vessel Specifications

    The Langseth has a length of 71.5 m (234.6 ft), a beam of 17 m 
(55.8 ft), and a maximum draft of 5.9 m (19.4 ft). The ship was 
designed as a seismic research vessel, with a propulsion system 
designed to be as quiet as possible to avoid interference with the 
seismic signals. The ship is powered by two Bergen BRG-6 diesel 
engines, each producing 3,550 hp, that drive the two propellers 
directly. Each propeller has four blades, and the shaft typically 
rotates at 750 rpm. The vessel also has an 800-hp bowthruster. The 
operation speed during seismic acquisition is typically 7.4-9.3 km/h 
(4-5 kt). When not towing seismic survey gear, the Langseth can cruise 
at 20-24 km/h (11-13 kt). The Langseth has a range of 25,000 km (15,534 
mi).
    The New Horizon will be the dedicated OBS vessel during the Pacific 
part of the survey and will deploy and retrieve the OBSs. The ship has 
a length of 51.8 m (170 ft), a beam of 11 m (36 ft), and a maximum 
draft of 3.7 m (12 ft). The ship is powered by two 850 hp D398 
Caterpillar engines. The typical cruising speed is 18.5 km/h (10 kt) 
with a maximum speed of 22.8 km/h (12.3 kt). The New Horizon has a 
range of 18,000 km (11,185 mi).

Acoustic Source Specifications

Seismic Airguns

    During the survey, the airgun array to be used will consist of 36 
airguns, with a total volume of approximately 6,600 in3. The 
airguns will comprise a mixture of Bolt 1500LL and 1900LL airguns. The 
array will consist of four identical linear arrays or ``strings'' (see 
Figure 2 in L-DEO's application). Each string will have ten airguns; 
the first and last airguns in each string are spaced 16 m (52.5 ft) 
apart. Nine airguns in each string will be fired simultaneously, while 
the tenth is kept in reserve as a spare, to be turned on in case of 
failure of another airgun. The four airgun strings will be distributed 
across an approximate area of 24 x 16 m (78.7 x 52.5 ft) behind the 
Langseth and will be towed approximately 50-100 m (164-328 ft) behind 
the vessel. The firing pressure of the array is 2,000 psi. The airgun 
array will fire in two modes: every 50 m (164 ft; 20 s) or every 200 m 
(656 ft; 80 s). During firing, a brief (approximately 0.1 s) pulse of 
sound is emitted. The airguns will be silent during the intervening 
periods. The airguns will be towed at a depth of 9 or 12 m (29.5 or 39 
ft). The dominant frequency components are 0-188 Hz.
    Received sound levels have been predicted by L-DEO for the 36-
airgun array operating in deep water and for a single 1900LL 40 
in3 airgun to be used during power-downs (see below). The 
predicted received levels depend upon distance and direction from the 
airguns. This source, which is directed downward, was found to have an 
output (0-peak) of 258 dB re 1 [mu]Pa m. The maximum relevant depth 
(2,000 m; 6,562 ft) represents the maximum anticipated dive depth of 
marine mammals and is relevant for predicting safety or exclusion zones 
(EZs; see below). A detailed description of L-DEO's modeling effort is 
provided in Appendix A of the application.
    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, 2000a). 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.

Multibeam Echosounder

    The Simrad EM120 operates at 11.25-12.6 kHz and is hull-mounted on 
the Langseth. The beamwidth is 1[deg] fore-aft and 150[deg] 
athwartship. The maximum source level is 242 dB re 1 [mu]Pa (rms; 
Hammerstad, 2005). For deep-water operation, each ``ping'' consists of 
nine successive fan-shaped transmissions, each 15 ms in duration and 
each ensonifying a section that extends 1[deg] fore-aft. The nine 
successive transmissions span an overall cross-track angular extent of 
about 150[deg], with 16 ms gaps between the pulses for successive 
sectors. A receiver in the overlap area between the two sectors would 
receive two 15-ms pulses separated by a 16-ms gap. In shallower water, 
the pulse duration is reduced to 5 or 2 ms, and the number of transmit 
beams is also reduced. The ping interval varies with water depth, from 
approximately 5 s at 1,000 m (3,280 ft) to 20 s at 4,000 m (13,123 ft; 
Kongsberg Maritime, 2005).

Sub-Bottom Profiler

    The SBP is normally operated to provide information about the 
sedimentary features and the bottom topography that is simultaneously 
being mapped by the MBES. The energy from the SBP is directed downward 
by a 3.5 kHz transducer in the hull of the Langseth. The output varies 
with water depth from 50 watts in shallow water to 800 watts in deep 
water. The pulse interval is 1 s, but a common mode of operation is to 
broadcast five pulses at 1-s intervals followed by a 5-s pause.

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

[[Page 71628]]

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 [mu]Pa (rms). NMFS also assumes that cetaceans or pinnipeds 
exposed to levels exceeding 160 dB re 1[mu]Pa (rms) may experience 
Level B Harassment.
    The depth at which the source is towed impacts the maximum near-
field output and the shape of the frequency spectrum. If the source is 
towed at a relatively deep depth (e.g., approximately 12 m; 39 ft), the 
effective source level for sound propagating in near-horizontal 
directions is substantially greater than if the array is towed at 
shallower depths (e.g., approximately 9 m; 29.5 ft; see Figure 4 vs. 
Figure 3 in the application).
    Empirical data concerning 180 and 160 dB re 1 [mu]Pa distances in 
deep and/or shallow water were acquired for various airgun 
configurations during the acoustic calibration study of the R/V Maurice 
Ewing's (Ewing) 20-airgun 8,600 in3 array in 2003 (Tolstoy 
et al., 2004a, b). The results showed that radii around the airguns 
where the received level was 160 dB re 1 [mu]Pa varied with water 
depth. Similar depth-related variation is likely for the 180-dB re 1 
[mu]Pa safety criterion applicable to cetaceans and the 190-dB re 1 
[mu]Pa radius applicable to pinnipeds, although these were not 
measured. The L-DEO model does not allow for bottom interactions, and 
thus is most directly applicable to deep water and to relatively short 
ranges.
    The empirical data indicated that, for deep water (>1,000 m; 3,280 
ft), the L-DEO model overestimates the received sound levels at a given 
distance (Tolstoy et al., 2004a,b). However, to be conservative, the 
distances predicted by L-DEO's model will be applied to deep-water 
areas during the proposed study (see Table 3 in the application and 
Table 1 here). As very few, if any, mammals are expected to occur below 
2,000 m (6,562 ft), this depth was used as the maximum relevant depth.
    Empirical measurements indicated that in shallow water (<100 m; 328 
ft), the L-DEO model underestimates actual levels. In previous L-DEO 
projects done since the calibration results were obtained by Tolstoy et 
al. (2004a,b), the EZs in shallow water were typically adjusted upward 
from the values predicted by L-DEO's model by factors of 1.3x to 15x 
depending on the size of the airgun array and the sound level measured 
(Tolstoy et al., 2004b). During the proposed cruise, similar factors 
will be applied to the shallow-water radii (see Table 3 in the 
application and Table 1 here).
    Empirical measurements were not conducted for intermediate depths 
(100-1,000 m; 328-3,280 ft). On the expectation that results would be 
intermediate between those from shallow and deep water, a correction 
factor of 1.5x was applied during former L-DEO cruises to the estimates 
provided by the model for deep-water situations to obtain estimates for 
intermediate-depth sites. The correction factor was used during 
previous L-DEO surveys and will be used during the proposed study for 
intermediate depths (see Table 3 in the application and Table 1 here).
    Table 3 in the application and Table 1 here outline the distances 
to which sound levels of the various EZs might be received, considering 
both the 36-airgun array and a single airgun in three different water 
depths. In deep water, the maximum depth considered is 2,000 m (6,562 
ft). If marine mammals are detected within or about to enter the 
appropriate EZ, the airguns will be powered down (or shutdown if 
necessary) immediately.

   Table 1.--Predicted Distances to Which Sound Levels >=190, 180, and 160 dB re 1 [mu]Pa Might Be Received in
 Shallow (<100 m; 328 ft), Intermediate (100-1,000 m; 328-3,280 ft), and Deep (>1,000 m; 3,280 ft) Water During
                                       the Central American SubFac Survey
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                                                                                Predicted RMS distances (m)
          Source and volume            Tow depth         Water depth      --------------------------------------
                                          (m)                                 190 dB       180 dB       160 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun 40 in3...........            9  Deep..................           12           40          385
                                      ...........  Intermediate..........           18           60          578
                                      ...........  Shallow...............          150          296         1050
4 strings 36 airguns 6600 in3.......            9  Deep..................          300          950         6000
                                      ...........  Intermediate..........          450         1425         6667
                                      ...........  Shallow...............         2182         3694         8000
4 strings 36 airguns 6600 in3.......           12  Deep..................          340         1120         7400
                                      ...........  Intermediate..........          510         1680         8222
                                      ...........  Shallow...............         2473         4356         9867
----------------------------------------------------------------------------------------------------------------

    Because the predictions in Table 3 in the application and Table 1 
here are based in part on empirical correction factors derived from 
acoustic calibration of different airgun configurations than those to 
be used on the Langseth (cf. Tolstoy et al., 2004a,b), L-DEO is 
planning an acoustic calibration study of the Langseth's 36-airgun 
(6,600 in3) array, which is scheduled to go out in the Gulf 
of Mexico in January 2008. Distances where sound levels (e.g., 190, 
180, and 160 dB re 1 [mu]Pa) are received in deep, intermediate, and 
shallow water will be determined for various airgun configurations. The 
empirical data from the calibration study will be used to refine the 
EZs used during the Central American SubFac survey, if the data are 
appropriate and available at the time of the survey.

Description of Marine Mammals in the Activity Area

    A total of 34 marine mammal species are known to or may occur in 
the study area off Central America, including 25 odontocete (dolphins 
and small and large toothed whales) species, six mysticete (baleen 
whales) species, two pinniped species, and the West Indian manatee. Six 
of the species that may occur in the project area are listed under the 
U.S. Endangered Species Act (ESA) as Endangered: The sperm, humpback, 
sei, fin, and blue whale and the manatee. The West Indian manatee is 
under the jurisdiction of the U.S. Fish and Wildlife Service and 
therefore is not considered further in this analysis.

[[Page 71629]]

    The distribution and occurrence of marine mammal species are 
different on the Pacific and Caribbean coasts of Central America; 
therefore, these two areas are discussed separately here and in greater 
detail in L-DEO's application. Thirty-two species of marine mammals 
have been documented to occur in Costa Rican waters, most of which are 
cetaceans (Rodr[iacute]guez-Herrera et al., 2002). At least 10 of the 
32 species are known to occur on the Caribbean side, including the 
manatee (Rodr[iacute]guez-Fonseca, 2001 and pers. comm.; 
Rodr[iacute]guez-Herrera et al., 2002). Twenty-seven species are known 
to occur on the Pacific side of Costa Rica, including the California 
and Gal[aacute]pagos sea lions (see Wade and Gerrodette, 1993; Ferguson 
and Barlow, 2001; Rodr[iacute]guez-Fonseca, 2001; Rodr[iacute]guez-
Herrera et al., 2002; Rasmussen et al., 2004; Holst et al., 2005a; May-
Collado et al., 2005). In addition there are two other species that 
could potentially occur in the Pacific study area: the ginkgo-toothed 
(e.g., Rodr[iacute]guez-Fonseca, 2001) and Longman's beaked whales 
(e.g., Pitman et al., 1999; Ferguson and Barlow, 2001). Information on 
the occurrence, distribution, population size, and conservation status 
for each of the 34 marine mammal species that may occur in the proposed 
project area is presented in Table 5 of L-DEO's application.

Caribbean

    Studies of marine mammals inhabiting the Caribbean have been scarce 
(Jefferson and Lynn, 1994; Rodr[iacute]guez-Fonseca, 2001), and 
abundance in this area is mostly unknown (Roden and Mullin, 2000). At 
least one systematic ship-based study employing visual and passive-
acoustic survey methods has been undertaken in the eastern Caribbean 
(Swartz and Burks, 2000; Swartz et al., 2001, 2003). In addition, an 
extensive visual and acoustic survey was conducted in the SE Caribbean 
Sea off northern Venezuela from the Ewing and the R/V Seward Johnson II 
as part of a marine mammal monitoring program during an L-DEO marine 
seismic cruise in April-June 2004 (Smultea et al., 2004). Data on the 
western Caribbean is even more limited.
    One mysticete, eight odontocetes, and one sirenian are known to 
occur in the Caribbean study area (Rodr[iacute]guez-Fonseca, 2001 and 
pers. comm.; Rodr[iacute]guez-Herrera et al., 2002). These include the 
fin, sperm, short-finned pilot, and killer whale; the bottlenose, 
Atlantic spotted, and clymene dolphin; tucuxi, Gervais' beaked whale, 
and West Indian manatee. The last four of these species only occur in 
the Caribbean part of the study area (see Table 5 of the application). 
Based on other available information (Swartz and Burks, 2000; Romero et 
al., 2001; Swartz et al., 2001, 2003; Smultea et al., 2004), an 
additional five species may potentially occur in the study area: two 
mysticetes (humpback and Bryde's whale) and three delphinids 
(pantropical spotted, striped, and rough-toothed dolphin). Pinnipeds 
are unlikely to be seen in the Caribbean part of the study area. 
Vagrant hooded seals have been seen in the Caribbean (Rice, 1998; 
Mignucci-Giannoni and Odell, 2001; Reeves et al., 2002), but are not 
considered further here. The Caribbean monk seal (Monachus tropicalis) 
is considered extinct (Debrot, 2000; Mignucci-Giannoni and Odell, 
2001).

Pacific

    Of the 36 marine mammal species known to occur in the eastern 
tropical Pacific (ETP), 29 may occur in the proposed survey area off 
the west coast of Costa Rica and Nicaragua (see Table 5 of the 
application). Seven species that are present in the wider ETP but not 
in the proposed survey area are excluded from Table 5. They include: 
Pacific white-sided dolphin (Lagenorhynchus obliquidens) and Baird's 
beaked whale (Berardius bairdii), which are seen very occasionally (6 
and 2 sightings, respectively, in several years of surveys) in the 
northernmost portions of the ETP (Ferguson and Barlow, 2001); Long-
beaked common dolphin (Delphinus capensis), which is known to occur in 
the northernmost areas of the ETP off Baja California, Mexico, and off 
the coast of Peru (Heyning and Perrin, 1994); Dusky dolphin 
(Lagenorhynchus obscurus), southern right whale dolphin (Lissodelphis 
peronii), Burmeister's porpoise (Phocoena spinipinnis), and long-finned 
pilot whale (Globicephala melas) occur near the Peruvian coast but are 
unlikely to occur in the present study area (Leatherwood et al., 1991; 
Van Waerebeek et al., 1991; Brownell and Clapham, 1999; Olson and 
Reilly, 2002).
    Although unlikely, two of the six species of pinnipeds known to 
occur in the ETP could potentially occur in the proposed project area 
on rare occasions. These include the California and Gal[aacute]pagos 
sea lions, which have been documented off western Costa Rica (Acevedo-
Gutierrez, 1994; Cubero-Parado and Rodr[iacute]guez, 1999; 
Rodr[iacute]guez-Herrera et al., 2002; May-Collado, 2006, in press). 
The remaining four pinniped species known from the ETP, the Guadalupe 
fur seal (Arctocephalus townsendi), South American fur seal (A. 
australis), southern sea lion (Otaria flavescens), and Gal[aacute]pagos 
fur seal, are not expected to occur in the survey area because their 
known ranges are substantially farther north or south of the proposed 
seismic survey area (Reeves et al., 2002).
    Most cetacean research off the west coast of Central America has 
involved three of the most common, coastal resident species: The 
bottlenose and coastal pantropical spotted dolphin and humpback whale 
(May-Collado et al., 2005). The remaining marine mammal populations in 
the region have not been studied in much detail. The most extensive 
regional distribution and abundance data that encompass the entire 
study area come primarily from multi-year vessel surveys conducted in 
the wider ETP by the NMFS Southwest Fisheries Science Center.
    Table 5 of L-DEO's application summarizes the abundance, habitat, 
and conservation status of all marine mammal species considered likely 
to occur in the proposed survey area in the Pacific. Based on a 
compilation of data from 1979 to 2001, many cetaceans within the 
Pacific EEZ of Costa Rica occur in both oceanic and coastal waters. 
However, beaked, sperm, dwarf/pygmy sperm, and baleen whales (except 
for the humpback) occur predominantly in oceanic waters (May-Collado et 
al., 2005). Bottlenose and pantropical spotted dolphins, as well as the 
humpback whale, tend to be coastal.
    The proposed survey area in the Pacific is part of the ``Central 
American Bight'', which extends from Guatemala to Ecuador. Costa Rican 
waters in particular are one of the most biologically productive 
regions of the world (Philbrick et al., 2001; Rodr[iacute]guez-Herrera 
et al., 2002; May-Collado et al., 2005; Ferguson et al., 2006a). The 
characteristics that likely make this region so productive are linked 
to the thermal structure of the water column, including a shallow 
thermocline (see Fielder and Talley, 2006). Two regions within the ETP 
that are considered to be important to certain species of cetaceans 
include the Costa Rica Dome (CRD) and the countercurrent thermocline 
ridge at approximately 10[deg] N. (see Au and Perryman, 1985; Reilly, 
1990; Reilly and Thayer, 1990; Fielder, 2002; Ballance et al., 2006).
    At least five marine areas are considered ecologically important 
for different marine mammals off western Costa Rica, including areas 
near the proposed transect lines (Acevedo and Burkhart, 1998; 
Rodr[iacute]guez-Fonseca, 2001; May-Collado et al., 2005; Ferguson et 
al., 2006a). From north to south, the five areas are as follows: Gulf 
of Papagayo; Punta Guiones to Cabo

[[Page 71630]]

Blanco, southern Nicoya Peninsula; CRD; Quepos-Manuel Antonio National 
Park region; and Isla del Ca[ntilde]o, Golfo Dulce, and Osa Peninsula. 
Marine mammal species inhabiting these five areas, as well as their 
seasonal use of the habitats, are described in the species accounts in 
L-DEO's application.
    Table 2 below outlines the species, their habitat and abundance in 
the proposed project area, and the requested take levels. 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 L-DEO's application.

Table 2.--The Habitat, Abundance, and Requested Take Levels of Marine Mammals That May Be Encountered During the
                      Proposed Central American SubFac Seismic Survey Off Central America.
----------------------------------------------------------------------------------------------------------------
                                                   Abun. in NW                     Rqstd take in   Rqstd take in
           Species                  Habitat       Atlantic \1\   Abun. in ETP\2\    Carib. Sea          ETP
----------------------------------------------------------------------------------------------------------------
Odontocetes:
    Sperm whale (C,P)          Pelagic.........       \a\13,190  26,053 \b\.....               5             239
     (Physeter macrocephalus).                            4,804
    Pygmy sperm whale (C*,P)   Deeper water off         \c\ 395  N.A............               0               0
     (Kogia breviceps).         shelf.
    Dwarf sperm whale (C*,P)   Deeper waters            \c\ 395  11,200 \d\.....               0             856
     (Kogia sima).              off shelf.
    Cuvier's beaked whale      Pelagic.........       \e\ 3,513  20,000.........               0             302
     (C*,P) (Ziphius                                             90,725 \bb\....
     cavirostris).
    Longman's beaked whale     Pelagic.........            N.A.  291 \bb\.......               0               9
     (P?) (Indopacetus
     pacificus).
    Pygmy beaked whale (P)     Pelagic.........            N.A.  25,300 \f\.....               0               0
     (Mesoplodon peruvianus).                                    32,678\cc\.....
    Gingko-toothed beaked      Pelagic.........            N.A.  25,300 \f\.....               0               0
     whale (P?) (Mesoplodon                                      32,678\cc\.....
     ginkgodens).
    Gervais' beaked whale      Pelagic.........            N.A.  N.A............               4               0
     (C?) (Mesoplodon
     europaeus).
    Blainville's beaked whale  Pelagic.........            N.A.  25,300 \f\.....               0              29
     (C*,P) (Mesoplodon                                          32,678\cc\.....
     densirostris).
    Rough-toothed dolphin      Mainly pelagic..       \g\ 2,223  145,900........               9             954
     (C?,P) (Steno
     bredanensis).
    Tucuxi (C) (Sotalia        Freshwater and            \h\ 49  N.A............               0               0
     fluviatilis).              coastal waters.          \i\705
    Bottlenose dolphin (C,P)   Coastal, shelf         \j\43,951  243,500........             389           2,380
     (Tursiops truncatus).      and pelagic.         \k\ 81,588
    Pantropical spotted        Coastal and                4,439  2,059,100......              37           7,560
     dolphin (C?,P) (Stenella   pelagic.
     attenuata).
    Atlantic spotted dolphin   Coastal and               50,978  N.A............             440               0
     (C) (Stenella frontalis).  shelf.
    Spinner dolphin (C*,P)     Coastal and            \g\11,971  1,651,100......               0           7,856
     (Stenella longirostris).   pelagic.
    Costa Rican spinner        Coastal.........            N.A.  N.A............               0           3,358
     dolphin (P) (Stenella l.
     centroamericana).
    Clymene dolphin (C?)       Pelagic.........           6,086  N.A............              29               0
     (Stenella clymene).
    Striped dolphin (C*,P)     Coastal and               94,462  1,918,000......              31           8,110
     (Stenella coeruleoalba).   pelagic.
    Short-beaked common        Shelf and                   N.A.  3,093,300......               0          14,045
     dolphin (P) (Delphinus     pelagic.
     delphis).
    Fraser's dolphin (C*,P)    Pelagic.........         \g\ 726  289,300........               0             144
     (Lagenodelphis hosei).
    Risso's dolphin (C*,P)     Shelf and                 20,479  175,800........               0             651
     (Grampus griseus).         pelagic.
    Melon-headed whale (C*,P)  Pelagic.........       \g\ 3,451  45,400.........               0           1,315
     (Peponocephala electra).
    Pygmy killer whale (C*,P)  Pelagic.........           \l\ 6  38,900.........               0             231
     (Feresa attenuata).                                \g\ 408
    False killer whale (C*,P)  Pelagic.........       \g\ 1,038  39,800.........               0             479
     (Pseudorca crassidens).
    Killer whale (C,P)         Coastal.........         \g\ 133  8,500..........              10              17
     (Orcinus orca).                                   \m\6,600
    Short-finned pilot whale   Pelagic.........      \n\ 31,139  160,200 \n\....              36           3,717
     (C,P) (Globicephala
     macrorhynchus).
Mysticetes:
    Humpback whale (C?,P)      Mainly nearshore      \o\ 10,400  NE Pacific                    3             101
     (Megaptera novaeangliae).  waters and            \p\11,570   1,391\q\;.
                                banks.                           SE Pacific
                                                                  2,900\r\.
    Minke whale (C*,P)         Coastal.........       \s\ 3,618  N.A............               0               0
     (Balaenoptera                                   \t\174,000
     acutorostrata).
    Bryde's whale (C?,P)       Coastal and               \g\ 35  13,000 \u\.....               3              68
     (Balaenoptera edeni).      pelagic.
    Sei whale (C*,P)           Pelagic.........             12-  N.A............               0               0
     (Balaenoptera borealis).                        \v\ 13,000

[[Page 71631]]

 
    Fin whale (C,P)            Pelagic.........           2,814  1,851\q\.......               2               0
     (Balaenoptera physalus).                        \t\ 30,000
    Blue whale (C*,P)          Coastal, shelf,          \w\ 320  1,400..........               0              15
     (Balaenoptera musculus).   and pelagic.
Sirenian:
    West Indian manatee (C)    Freshwater and            \x\ 86  N.A............               0               0
     (Trichechus manatus        coastal waters.         \y\ 340
     manatus).
Pinnipeds:
    California sea lion (P)    Coastal.........            N.A.  237,000-.......               0               0
     (Zalophus californianus).                                   244,000 \z\....
    Gal[aacute]pagos sea lion  Coastal.........            N.A.  30,000 \aa\....               0              0
     (P?) (Zalophus
     wollebaeki).
----------------------------------------------------------------------------------------------------------------
Note: Abun. = abundance, NWA = Northwest Alantic Ocean, P = may occur off Pacific coast of proposed project
  area, C = may occur off Caribbean coast of proposed project area, * = very unlikely to occur in proposed
  project area, ? = potentially possible but somewhat unlikely to occur in proposed project area, N.A. = Not
  available or not applicable.
\1\ For cetaceans, abundance estimates are given for U.S. Western North Atlantic stocks (Waring et al. 2006)
  unless otherwise noted.
\2\ Abundance estimates for the ETP from Wade and Gerrodette (1993) unless otherwise indicated.
\a\ g(o) corrected total estimate for the Northeast Atlantic, Faroes-Iceland, and the U.S. east coast (Whitehead
  2002).
\b\ Whitehead 2002.
\c\ This estimate is for Kogia sp.
\d\ This abundance estimate is mostly for K. sima but may also include some K. breviceps.
\e\ This estimate is for Mesoplodon and Ziphius spp.
\f\ This estimate includes all species of the genus Mesoplodon from Wade and Gerrodette (1993).
\g\ This estimate is for the northern Gulf of Mexico.
\h\ Estimate from a portion of Cayos Miskito Reserve, Nicaragua (Edwards and Schnell 2001).
\i\ Estimate from the Canan[eacute]ia estuarine region of Brazil (Geise et al. 1999).
\j\ Estimate for the Western North Atlantic coastal stocks (North Carolina (summer), South Carolina, Georgia,
  Northern Florida, and Central Florida).
\k\ Estimate for the for the Western North Atlantic offshore stock.
\l\ Based on a single sighting.
\m\ Estimate for Icelandic and Faroese waters (Reyes 1991).
\n\ This estimate is for G. macrorhynchus and G. melas.
\o\ Estimate for the entire North Atlantic (Smith et al. 1999).
\p\ This estimate is for the entire North Atlantic (Stevick et al. 2001, 2003).
\q\ Carretta et al. 2007.
\r\ Felix et al. 2005.
\s\ This estimate is for the Canadian East Coast stock.
\t\ Estimate is for the North Atlantic (IWC 2007a).
\u\ This estimate is mainly for Balaenoptera edeni but may include some B. borealis.
\v\ Abundance estimate for the North Atlantic (Cattanach et al. 1993).
\w\ Minimum abundance estimate (Sears et al. 1990).
\x\ Antillean Stock in Puerto Rico only.
\y\ Antillean Stock in Belize (Reeves et al. 2002).
\z\ Estimate for the U.S. stock (Carretta et al. 2007).
\aa\ Reeves et al. 2002.
\bb\ Ferguson and Barlow 2001 in Barlow et al. 2006.
\cc\ This estimate includes all species of the genus Mesoplodon (Ferguson and Barlow 2001 in Barlow et al.
  2006).

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 
disturbances, and at least in theory, temporary or permanent hearing 
impairment, or non-auditory physical or physiological effects 
(Richardson et al., 1995; Gordon et al., 2004; Nowacek et al., 2007). 
However, it is 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 Appendices A 
and C (c) of L-DEO's application. Several studies have shown that 
marine mammals at distances more than a few kilometers from operating 
seismic vessels often show no apparent response--see Appendix C (e) of 
the application. 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 the mammal group. 
Although various baleen whales, toothed whales, and (less frequently) 
pinnipeds have been shown to react behaviorally to airgun pulses under 
some conditions, at other times, mammals of all three types have shown 
no overt reactions. In general, pinnipeds and small odontocetes seem to 
be more tolerant of exposure to airgun pulses than are baleen whales.

Masking

    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 few 
specific data of relevance. Some whales are known to continue calling 
in the presence of seismic pulses. The airgun sounds are pulsed, with 
quiet periods between the pulses,

[[Page 71632]]

and whale calls often can be heard between the seismic pulses 
(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 more recent study 
reports that sperm whales off northern Norway continued calling in the 
presence of seismic pulses (Madsen et al., 2002). That has also been 
shown during recent work in the Gulf of Mexico and Caribbean Sea 
(Smultea et al., 2004; Tyack et al., 2006). Masking effects of seismic 
pulses are expected to be negligible in the case of the small 
odontocetes given the intermittent nature of seismic pulses. Dolphins 
and porpoises commonly are 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 the airgun sounds. Masking effects, in 
general, are discussed further in Appendix C (d) of L-DEO'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.
    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 C (e) of L-DEO'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 [mu]Pa 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 C (e) of L-DEO'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 [mu]Pa rms.
    Responses of humpback whales to seismic surveys have been studied 
during migration and on the summer feeding grounds, and there has also 
been discussion of effects on the Brazilian wintering grounds. 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 [mu]Pa 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 [mu]Pa (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 [mu]Pa 
(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 [mu]Pa (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 [mu]Pa 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 [mu]Pa (approximately rms).
    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 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 [mu]Pa (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 [mu]Pa (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 
C (e) of L-DEO's

[[Page 71633]]

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 [mu]Pa 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 United Kingdom 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 (see Appendix A in Malme et al., 
1984). The western Pacific gray whale population did not seem affected 
by a seismic survey in its feeding ground during a prior year (Johnson 
et al., 2007). 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, brief exposures to sound pulses from the proposed 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. Controlled exposure experiments on 
sperm whales took place in the Gulf of Mexico in 2002 and 2003 (see 
Miller et al., 2006; Tyack 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; 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 airgun arrays 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, 1996a,b,c; Calambokidis and Osmek, 1998; Stone, 
2003; Stone and Tasker, 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). No other odontocete is known to show avoidance at such 
distances.
    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). The animals tolerated high received 
levels of sound (pk-pk level >200 dB re 1 [mu]Pa) before exhibiting 
aversive behaviors. For pooled data at 3, 10, and 20 kHz, sound 
exposure levels during sessions with 25, 50, and 75 percent altered 
behavior were 180, 190, and 199 dB re 1 [mu]Pa\2\, respectively 
(Finneran and Schlundt, 2004).
    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).
    Sperm whales show considerable tolerance of airgun pulses. In most 
cases, the whales do not show strong avoidance and continue to call 
(see Appendix C of L-DEO's application). However, controlled exposure 
experiments in the Gulf of Mexico indicate that foraging effort is 
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 (Miller et al. 2006; Tyack et al., 2006).
    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 (W[uuml]rsig 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 (Appendix C of L-
DEO's application).
    Pinnipeds--Pinnipeds are not likely to show a strong avoidance 
reaction to the airgun sources 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 C (e) of L-DEO'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;

[[Page 71634]]

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. It should be noted that pinnipeds are not 
likely to be encountered often, if at all, during the present study.
    Additional details on the behavioral reactions (or the lack 
thereof) by all types of marine mammals to seismic vessels can be found 
in Appendix C (e) of L-DEO's application.

Hearing Impairment and Other Physical Effects

    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds, but there has been no 
specific documentation of this for marine mammals exposed to 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 [mu]Pa (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 C (f) 
of L-DEO'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) 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.
    Several aspects of the planned monitoring and mitigation measures 
for this project (see below) are designed to detect marine mammals 
occurring near the airguns to avoid exposing them to sound pulses that 
might, at least in theory, cause hearing impairment. 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 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 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. At least in terrestrial mammals, 
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 in both terrestrial and marine mammals 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 
[mu]Pa\2\[middot]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 Langseth's airguns at which the received energy 
level (per pulse) would be expected to be >=175-180 dB SEL are the 
distances shown in the 190 dB re 1 [mu]Pa (rms) column in Table 3 of L-
DEO's application and Table 1 above (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 >=175-180 dB SEL (190 dB re 
1 [mu]Pa (rms)) are expected to be restricted to radii no more than 
140-200 m (459-656 ft) around the airguns. The specific radius depends 
on the number of airguns, the depth of the water, and the tow depth of 
the airgun array. For an odontocete closer to the surface, the maximum 
radius with >=175-180 dB SEL or >=190 dB re 1 [mu]Pa (rms) would be 
smaller.
    For baleen whales, direct or indirect data do not exist on levels 
or properties of sound that are 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 relatively 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 
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, on the order of 171 dB SEL 
(Kastak et al., 1999, 2005; Ketten et al., 2001). However, pinnipeds 
are not expected to occur in or near the planned study areas.
    A marine mammal within a radius of less than 100 m (328 ft) around 
a typical

[[Page 71635]]

large array of operating airguns might be exposed to a few seismic 
pulses with levels of greater than or equal to 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.) In addition, ramping up airgun arrays, 
which is standard operational protocol for large airgun arrays, should 
allow cetaceans to move away form the seismic source and to avoid being 
exposed to the full acoustic output of the airgun array. Even with a 
large airgun array, it is unlikely that the 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. The potential for TTS is much lower in 
this project. With a large array of airguns, TTS would be most likely 
in any odontocetes that bow-ride or otherwise linger near the airguns. 
While bow-riding, odontocetes would be at or above the surface, and 
thus not exposed to strong pulses given the pressure-release effect at 
the surface. However, bow-riding animals generally dive below the 
surface intermittently. If they did so while bow-riding near airguns, 
they would be exposed to strong sound pulses, possibly repeatedly. If 
some cetaceans did incur TTS through exposure to airgun sounds, this 
would very likely be mild, temporary, and reversible.
    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 [mu]Pa (rms). 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 stronger than 180 dB re 1 [mu]Pa (rms).
    Permanent Threshold Shift--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 C (f) 
of L-DEO'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.
    Given the higher level of sound necessary to cause PTS as compared 
with TTS, it is even less likely that PTS could occur. In fact, even 
the levels immediately adjacent to the airguns may not be sufficient to 
induce PTS, especially because a mammal would not be exposed to more 
than one strong pulse unless it swam immediately alongside the airgun 
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, passive acoustic monitoring 
(PAM), power downs, and shut downs of the airguns when mammals are seen 
within the EZ 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. Fern[aacute]ndez et al. (2005a) showed 
those beaked whales did indeed have gas bubble-associated lesions, as 
well as fat embolisms. Fern[aacute]ndez 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; M[eacute]ndez 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; Fern[aacute]ndez 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. 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. It is not known whether aversive behavioral 
responses to airgun pulses by deep-diving species could lead to 
indirect physiological problems as apparently can occur upon exposure 
of some beaked whales to mid-frequency sonar (Cox et al., 2006). Also, 
the planned mitigation measures, including shut downs of the airguns, 
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;

[[Page 71636]]

Ketten 1995). Airgun pulses are less energetic and have slower rise 
times, and there is no proof that they can cause serious injury, death, 
or stranding even in the case of large airgun arrays. However, the 
association of mass strandings of beaked whales with naval exercises 
(see Appendix C of L-DEO's application) and, in one case, an L-DEO 
seismic survey, has raised the possibility that beaked whales exposed 
to strong pulsed sounds may be especially susceptible to injury and/or 
behavioral reactions that can lead to stranding.
    Seismic pulses and mid-frequency sonar pulses are quite different. 
Sounds produced by airgun arrays are broadband with most of the energy 
below 1 kHz. Typical military mid-frequency sonars operate at 
frequencies of 2-10 kHz, generally with a relatively narrow bandwidth 
at any one time. Thus, it is not appropriate to assume that there is a 
direct connection between the effects of military sonar and seismic 
surveys on marine mammals. However, evidence that sonar pulses can, in 
special circumstances, lead to physical damage and mortality (Balcomb 
and Claridge, 2001; NOAA and USN, 2001; Jepson et al., 2003; 
Fern[aacute]ndez 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 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). Yet, 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 mitigating 
measures.

Potential Effects of Other Acoustic Devices

Multibeam Echosounder Signals

    The Kongsberg Simrad EM 120 12-kHz MBES will be operated from the 
source vessel at some times during the planned study. Sounds from the 
MBES are very short pulses, occurring for 15 ms once every 5-20 s, 
depending on water depth. Most of the energy in the sound pulses 
emitted by the MBES is at frequencies centered at 12 kHz. The beam is 
narrow (1[deg]) in fore-aft extent and wide (150[deg]) in the cross-
track extent. Each ping consists of nine successive fan-shaped 
transmissions (segments) at different cross-track angles. Any given 
mammal at depth near the trackline would be in the main beam for only 
one or two of the nine segments. Also, marine mammals that encounter 
the MBES are unlikely to be subjected to repeated pulses because of the 
narrow fore-aft width of the beam and will receive only limited amounts 
of pulse energy because of the short pulses. Animals close to the ship 
(where the beam is narrowest) are especially unlikely to be ensonified 
for more than one 15 ms pulse (or two pulses if in the overlap area). 
Similarly, Kremser et al. (2005) noted that the probability of a 
cetacean swimming through the area of exposure when an MBES emits a 
pulse is small. The animal would have to pass the transducer at close 
range and be swimming at speeds similar to the vessel in order to be 
subjected to sound levels that could cause TTS.
    Marine mammal communications will not be masked appreciably by the 
MBES signals given its low duty cycle and the brief period when an 
individual mammal is likely to be within its beam. Furthermore, in the 
case of baleen whales, the signals (12 kHz) do not overlap with the 
predominant frequencies in the calls, which would avoid significant 
masking.
    Behavioral reactions of free-ranging marine mammals to sonars and 
other sound sources appear to vary by species and circumstance. 
Observed reactions have included silencing and dispersal by sperm 
whales (Watkins et al., 1985), increased vocalizations and no dispersal 
by pilot whales (Rendell and Gordon, 1999), and the previously-
mentioned beachings by beaked whales. During exposure to a 21-25 kHz 
whale-finding sonar with a source level of 215 dB re 1 [mu]Pa, gray 
whales showed slight avoidance (approximately 200 m; 656 ft) behavior 
(Frankel, 2005). However, all of those observations are of limited 
relevance to the present situation. Pulse durations from those sonars 
were much longer than those of the MBES, and a given mammal would have 
received many pulses from the naval sonars. During L-DEO's operations, 
the individual pulses will be very short, and a given mammal would not 
receive many of the downward-directed pulses as the vessel passes by.
    Captive bottlenose dolphins and a white whale exhibited changes in 
behavior when exposed to 1 s pulsed sounds at frequencies similar to 
those that will be emitted by the MBES used by L-DEO and to shorter 
broadband pulsed signals. Behavioral changes typically involved what 
appeared to be deliberate attempts to avoid the sound exposure 
(Schlundt et al., 2000; Finneran et al., 2002; Finneran and Schlundt, 
2004). The relevance of those data to free-ranging odontocetes is 
uncertain, and in any case, the test sounds were quite different in 
either duration or bandwidth as compared with those from an MBES.
    We are not aware of any data on the reactions of pinnipeds to sonar 
or echosounder sounds at frequencies similar to the 12 kHz frequency of 
the Langseth's MBES. Based on observed pinniped responses to other 
types of pulsed sounds, and the likely brevity of exposure to the MBES 
sounds, pinniped reactions are expected to be limited to startle or 
otherwise brief responses of no lasting consequence to the animals. 
Also, few if any pinnipeds will be encountered during this project.
    NMFS believes that the brief exposure of marine mammals to one 
pulse, or small numbers of signals, from the MBES are not likely to 
result in the harassment of marine mammals.

Sub-Bottom Profiler Signals

    An SBP will be operated from the source vessel during the planned 
study. Sounds from the SBP are very short pulses, occurring for 1, 2, 
or 4 ms once every second. Most of the energy in the sound pulses 
emitted by the SBP is at mid frequencies, centered at 3.5 kHz. The 
beamwidth is approximately 30[deg] and is directed downward.
    Sound levels have not been measured directly for the SBP used by 
the Langseth, but Burgess and Lawson (2000) measured sounds propagating 
more or less horizontally from a similar unit with similar source 
output (205 dB re 1 [mu]Pa at 1 m). The 160 and 180 dB re 1 [mu]Pa 
(rms) radii, in the horizontal direction, were estimated to be, 
respectively, near 20 m (66 ft) and 8 m (26 ft) from the source, as 
measured in 13 m (42.7 ft) water depth. The corresponding distances for 
an animal in the beam below the transducer would be greater, on the 
order of 180 m (590.6

[[Page 71637]]

ft) and 18 m (59 ft), assuming spherical spreading.
    The SBP on the Langseth has a stated maximum source level of 204 dB 
re 1 [mu]Pa at 1 m. Thus, the received level would be expected to 
decrease to 160 and 180 dB about 160 m (525 ft) and 16 m (52.5 ft) 
below the transducer, respectively, again assuming spherical spreading. 
Corresponding distances in the horizontal plane would be lower, given 
the directionality of this source (30[deg] beam width) and the 
measurements of Burgess and Lawson (2000).
    Kremser et al. (2005) noted that the probability of a cetacean 
swimming through the area of exposure when the SBP 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 
SBP 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 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 SBP are likely to be similar 
to those for other pulsed sources if received at the same levels. The 
pulsed signals from the SBP are somewhat weaker than those from the 
MBES. Therefore, behavioral responses are not expected unless marine 
mammals are very close to the source (e.g., about 160 m, 525 ft, below 
the vessel or a lesser distance to the side).
    Source levels of the SBP are much lower than those of the airguns 
and the MBES, which are discussed above. Sounds from the SBP are 
estimated to decrease to 180 dB re 1 [mu]Pa (rms) at 8 m (26 ft) 
horizontally from the source (Burgess and Lawson, 2000) and at 
approximately 18 m (59 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 SBP 
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 SBP 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 SBP. 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 other sources would further reduce or eliminate any minor effects of 
the SBP.

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.) The sections below describe methods to estimate 
``take by harassment'', and present estimates of the numbers of marine 
mammals that might be affected during the proposed Central American 
SubFac seismic program. The estimates of ``take by harassment'' are 
based on consideration of the number of marine mammals that might be 
disturbed appreciably by approximately 1,328 km of seismic surveys in 
the western Caribbean and 2,652 km in the eastern Pacific. The main 
sources of distributional and numerical data used in deriving the 
estimates are described below.
    The anticipated radii of influence of the MBES and the SBP are less 
than those for the airgun array. It is assumed that, during 
simultaneous operations of the airgun array and echosounders, marine 
mammals close enough to be affected by the echosounders would already 
be affected by the airguns. However, whether or not the airguns are 
operating simultaneously with the echosounders, marine mammals are 
expected to exhibit no more than short-term and inconsequential 
responses to the echosounders given their characteristics (e.g., narrow 
downward-directed beam) and other considerations described above. NMFS 
believes that such reactions are not considered to constitute 
``taking.'' Therefore, no additional allowance is included for animals 
that might be affected by sound sources other than airguns.
    Extensive marine mammal surveys have been conducted in the ETP over 
numerous years (e.g., Polacheck, 1987; Wade and Gerrodette, 1993; 
Kinsey et al., 1999, 2000, 2001; Ferguson and Barlow, 2001; Smultea and 
Holst, 2003; Jackson et al., 2004; Holst et al., 2005a; May-Collado et 
al., 2005). Therefore, for the Pacific portion of the proposed seismic 
survey, marine mammal density data were readily available. The most 
comprehensive data available for the region encompassing the proposed 
survey area are from Ferguson and Barlow (2001) and Holst et al. 
(2005a). The Ferguson and Barlow (2001) surveys took place from late 
July to early December across a large area of the ETP. For density 
estimates in this project, L-DEO only used data from areas in or 
adjacent to the proposed study location. These areas included ten 
5[deg] x 5[deg] survey blocks from the Ferguson and Barlow (2001) 
surveys: 118, 119, 137, 138, 139, 140, 158, 159, 160, and 161. These 
blocks included survey effort in all water depths, but primarily deeper 
than 100 m (328 ft). Similarly, survey data from all water depths were 
included from Holst et al. (2005a), although most effort (more than 93 
percent) occurred in water more than 100 m (328 ft) deep. Survey data 
collected by Holst et al. (2005a) were the result of a marine mammal 
monitoring and mitigation program during L-DEO's seismic survey off 
Costa Rica and Nicaragua in November-December, 2004. Only data 
collected during non-seismic periods were combined with data from 
Ferguson and Barlow (2001) to calculate mean densities for the proposed 
study area. However, data collected by Holst et al. (2005a) during 
seismic and non-seismic periods were used to estimate allowances for 
sightings identified to species.
    The proposed survey off the Pacific coast of Central America is 
presently scheduled to occur in the February-April period. Therefore, 
the representativeness of the data collected by Holst et al. (2005a) in 
November-December and especially by Ferguson and Barlow (2001) in July-
December is uncertain. For some species, the densities derived from 
past surveys may not be representative of the densities that will be 
encountered during the proposed seismic study. As an example of 
potential uncertainty of the data, the number of cetaceans sighted 
during L-DEO's 2003 Hess Deep seismic operations (see Smultea and 
Holst, 2003) was considerably lower (only one sighting) than expected 
based on the Ferguson and Barlow (2001) data. The Hess Deep Survey 
occurred in mid-July and was apparently not well represented by the 
Ferguson and Barlow (2001) data collected largely during the autumn in 
other years. Similarly, the densities calculated by Holst et al. 
(2005a) were generally lower for dolphins and greater for humpbacks

[[Page 71638]]

compared with those determined by Ferguson and Barlow (2001).
    Despite the above caveats, the Ferguson and Barlow (2001) and Holst 
et al. (2005a) data still represent the best available data for 
estimating numbers of marine mammals potentially exposed to the 
proposed seismic sounds. Table 6 of L-DEO's application shows the 
densities that were derived from Ferguson and Barlow (2001) and Holst 
et al. (2005a), which were used to estimate numbers of marine mammals 
potentially exposed. The densities reported by Ferguson and Barlow 
(2001) and Holst et al. (2005a) were corrected for both detectability 
[f(0)] and availability [g(0)] biases, and therefore, are relatively 
unbiased. To provide some allowances for uncertainties in these data, 
``best estimates'' and ``maximum estimates'' of the numbers potentially 
affected have been derived (see Table 7 in the application).
    For the Caribbean portion of the Central American SubFac program, 
we were unable to find published data on marine mammal densities in or 
immediately adjacent to the proposed seismic survey area. The closest 
quantitative surveys were conducted in the southeast Caribbean (Swartz 
and Burks, 2000; Swartz et al., 2001; Smultea et al., 2004). Most of 
the survey effort by Swartz and Burks (2000) and Swartz et al. (2001) 
took place during March and April near the islands on the east side of 
the Caribbean Sea and near the north and northeast coasts of Venezuela 
in water depths <1,000 m. Survey data from Smultea et al. (2004) were 
collected north of Venezuela during April-June in association with a 
previous L-DEO seismic survey. The proposed survey is scheduled to 
occur sometime in February to early April in the western Caribbean Sea, 
a location and time of year in which the species densities are likely 
different from those during the above-mentioned surveys in the 
southeast Caribbean. Therefore, the representativeness of the data is 
uncertain, but they are the best available at this time.
    The data from Smultea et al. (2004) were deemed to be more 
representative of the proposed study area than those from Swartz and 
Burks (2000) and Swartz et al. (2001) because Smultea et al. (2004) 
reported separate densities for different water depth categories, 
whereas the other surveys did not.
    However, there was no shallow-water effort during surveys by 
Smultea et al. (2004). Densities from a survey off Yucat[aacute]n, 
Mexico (Holst et al., 2005b), were used for shallow water, as those 
data were deemed more appropriate than densities for deeper waters from 
the southeast Caribbean surveys. Therefore, for the Central American 
SubFac survey, mean densities for intermediate and deep water are those 
for non-seismic periods from Smultea et al. (2004), and for shallow 
water, densities for non-seismic periods from Holst et al. (2005b) were 
used (see Table 8 in L-DEO's application). Densities were available for 
striped, Atlantic spotted, and bottlenose dolphins, as well as for 
short-finned pilot whales, and were corrected for detectability [f(0)] 
and availability [g(0)] biases and for unidentified sightings by the 
original authors. To allow for the possibility of encountering small 
numbers of individuals of other species in the survey area, even though 
they were not recorded during previous surveys, L-DEO adjusted the 
`maximum estimates' based on mean group size, if available (e.g., 
Swartz and Burks, 2000).
    The number of different individuals that may be exposed to airgun 
sounds with received levels >=160 dB re 1 [mu]Pa (rms) on one or more 
occasions can be estimated by considering the total marine area that 
would be within the 160-dB radius around the operating airgun array on 
at least one occasion. Most of the proposed lines (9 of 11) will be 
surveyed twice, although it is unknown how much time will pass between 
the first and second transit along each line. Therefore, some of the 
same individuals may be approached by the operating airguns and come 
within the 160-dB distance on two occasions. However, this also means 
that some different marine mammals could occur in the area during the 
second pass. Thus, the best estimates in this section are based on a 
single pass of all survey lines (including a 15 percent contingency for 
airgun operations during turns), and maximum estimates are based on 
maximum estimates (i.e., for the Pacific) or on at least two times the 
best estimate. Table 8 in L-DEO's application shows the best and 
maximum estimates of the number of marine mammals that could 
potentially be affected during the Caribbean portion of the seismic 
survey.
    The potential number of different individuals that might be exposed 
to received levels >=160 dB re 1 [mu]Pa (rms) was calculated separately 
for the Pacific and Caribbean study areas. For the Caribbean portion of 
the Central American SubFac survey, the number of potentially-affected 
individuals was calculated for each of three water depth categories 
(shallow, <100 m or <328 ft; intermediate-depth, 100-1,000 m or 328-
3,280 ft; and deep, >1,000 m or 3,280 ft). However, for the Pacific 
area, no distinction was made between different water depth categories 
for several reasons: (1) Less than five percent of the proposed survey 
in the Pacific will take place in water <100 m (328 ft) deep; (2) most 
of the effort (>93 percent) during surveys by Holst et al. (2005a) took 
place in waters deeper than 100 m (328 ft); and (3) Ferguson and Barlow 
(2001) did not present depth-specific densities.
    The number of different individuals potentially exposed to received 
levels *160 dB re 1 [mu]Pa (rms) was calculated by multiplying:
    The expected species density, either ``mean'' (i.e., best estimate) 
or ``maximum'', for a particular water depth, times
    The anticipated minimum area to be ensonified to that level during 
airgun operations in each water depth category. The 160-dB re 1 [mu]Pa 
(rms) distances were as predicted by L-DEO's model, with adjustments 
based on Tolstoy et al. (2004a,b) for shallow and intermediate-depth 
water.
    The area expected to be ensonified was determined by entering the 
planned survey lines into a MapInfo Geographic Information System 
(GIS), using the GIS to identify the relevant areas by ``drawing'' the 
applicable 160-dB buffer around each seismic line (depending on water 
and tow depth) and then calculating the total area within the buffers. 
Areas where overlap occurred were included only once to determine the 
minimum area expected to be ensonified to >=160 dB at least once.
    Applying the approach described above, approximately 19,193 km\2\ 
would be within the 160-dB isopleth on one or more occasions during the 
Pacific portion of the survey, and 12,643 km\2\ would be ensonified on 
one or more occasions during the Caribbean portion of the survey. 
However, this approach does not allow for turnover in the mammal 
populations in the study area during the course of the studies. This 
might somewhat underestimate actual numbers of individuals exposed, 
although the conservative distances used to calculate the area may 
offset the underestimate. In addition, the approach assumes that no 
cetaceans will move away or toward the trackline as the Langseth 
approaches in response to increasing sound levels prior to the time the 
levels reach 160 dB re 1 [mu]Pa (rms). Another way of interpreting the 
estimates that follow is that they represent the number of individuals 
that are expected (in the absence of a seismic program) to occur in the 
waters that will be exposed to *160 dB re 1 [mu]Pa (rms).
    The `best estimate' of the number of individual marine mammals that 
might be exposed to seismic sounds with

[[Page 71639]]

received levels >=160 dB re 1 [mu]Pa (rms) during the Pacific portion 
of the proposed survey is 15,572 (Table 7 in L-DEO's application). That 
total includes 79 endangered whales (71 sperm, 4 humpback, and 4 blue 
whales), 156 beaked whales, and 21 Bryde's whale (Table 7 in the 
application). Striped, short-beaked common, and pantropical spotted 
dolphins are expected to be the most common species in the Pacific part 
of the study area. The best estimates for those species are 4,005, 
3,931, and 2,952, respectively (Table 7). Estimates for other species 
are lower (Table 7). The `maximum estimate' for the Pacific is 52,438 
individual marine mammals. Most of these would be dolphins (Table 7). 
The maximum estimate of 101 humpback whales is likely a more realistic 
estimate of the number of individuals that might be exposed to seismic 
sound levels >=160 dB re 1 [mu]Pa (rms) during the Pacific survey, as 
these estimates are based on density data from July-December and not 
from the peak breeding/calving period in January-March. The numbers for 
which take authorization is requested, given in the far right column in 
Table 7 of L-DEO's application and Table 2 here, are the maximum 
estimates. Since the take estimates proposed in this document fall 
largely within 3 percent (all but dwarf sperm (7.64 percent) and 
humpback (7.26 percent) whales) of the numbers estimated to be present 
during a localized survey in the Pacific Ocean off the coasts of Costa 
Rica and Nicaragua, and the species range far beyond the Pacific Ocean 
(i.e., the abundance of the species is notably larger), NMFS believes 
that the estimated take numbers for these species are small relative 
both to the worldwide abundance of these species and to numbers taken 
in other activities that have been authorized for incidental take of 
these species.
    The `best estimate' of the number of individual marine mammals that 
might be exposed to seismic sounds with received levels >=160 dB re 1 
[mu]Pa (rms) during the Caribbean portion of the proposed survey is 461 
(Table 8 in L-DEO's application). That total includes five endangered 
whales (three sperm, one humpback, and one fin whale), two beaked 
whales, and two Bryde's whale (Table 8 in the application). Atlantic 
spotted and bottlenose dolphins are expected to be the most common 
species in the Caribbean part of the study area; the best estimates for 
those species are 220 and 194, respectively (Table 8). Estimates for 
other species are lower (Table 8). The maximum estimate for the 
Caribbean is 998 individual marine mammals. The numbers for which take 
authorization is requested, given in the far right column in Table 8 of 
L-DEO's application and Table 2 here, are the maximum estimates. Since 
the take estimates proposed in this document are less than 1 percent 
(all but killer (7.52 percent) and Bryde's (8.57 percent) whales) of 
the numbers estimated to be present during a localized survey in the 
Caribbean Sea off the coasts of Costa Rica and Nicaragua, and the 
species range far beyond the Caribbean (i.e., the abundance of the 
species is notably larger), NMFS believes that the estimated take 
numbers for these species are small relative both to the worldwide 
abundance of these species and to numbers taken in other activities 
that have been authorized for incidental take of these species.
    No pinnipeds are expected to be encountered in the Caribbean, and 
the likelihood of encountering sea lions or other pinnipeds in the 
Pacific study area is also very low. No take of any pinniped species is 
requested.

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. The following sections briefly 
review effects of airguns on fish and invertebrates, and more details 
are included in Appendices D and E, respectively, in L-DEO's 
application.
    One of the reasons for the adoption of airguns as the standard 
energy source for marine seismic surveys was that, unlike explosives, 
they have not been associated with large-scale fish kills. However, the 
existing body of information relating to the impacts of seismic surveys 
on marine fish (see Appendix D of L-DEO's application) and invertebrate 
species (Appendix E of the application) 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 is from studies of individuals or portions of a 
population; there have been no studies conducted at the population 
level. Thus, available information provides limited insight on possible 
real-world effects at the ocean or population scale. This makes drawing 
conclusions about impacts on fish and invertebrates problematic because 
ultimately, the most important aspect of potential impacts relates to 
how exposure to seismic survey sound affects marine fish and 
invertebrate populations and their viability, including their 
availability to fisheries.
    The following sections provide an overview of the information that 
exists on the effects of exposure to seismic and other anthropogenic 
sounds on fish and invertebrates. The information comprises results 
from scientific studies of varying degrees of soundness and some 
anecdotal information.
    Pathological Effects--Wardle et al. (2001) suggested that 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. 
Generally, as received pressure increases, the period for the pressure 
to rise and decay decreases, and the chance of acute pathological 
effects increases. According to Buchanan et al. (2004), for the types 
of seismic airguns and arrays involved with the proposed program, the 
pathological (mortality) zone for fish and invertebrates would be 
expected to be within a few meters of the seismic source. Numerous 
other studies provide examples of no fish mortality upon exposure to 
seismic sources (Falk and Lawrence, 1973; Holliday et al., 1987; La 
Bella et al., 1996; Santulli et al., 1999; McCauley et al., 2000a,b, 
2003; Bjarti, 2002; Hassel et al., 2003; Popper et al., 2005).
    The potential for pathological damage to hearing structures in fish 
depends on the energy level of the received sound and the physiology 
and hearing capability of the species in question (see Appendix D of L-
DEO's application). For a given sound to result in hearing loss, the 
sound must exceed, by some specific amount, the hearing threshold of 
the fish for that sound (Popper et al., 2005). The consequences of 
temporary or permanent hearing loss in individual fish on a fish 
population is unknown; however, it likely depends on the number of 
individuals affected and whether critical behaviors involving

[[Page 71640]]

sound (e.g., predator avoidance, prey capture, orientation and 
navigation, reproduction, etc.) are adversely affected.
    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 
[mu]Pa\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) 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, as compared to natural mortality rates, that the impact of seismic 
surveying on recruitment to a fish stock must be regarded as 
insignificant.
    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--Physiological effects refer to cellular and/
or biochemical responses of fish and invertebrates to acoustic stress. 
Such stress potentially could affect fish and invertebrate populations 
by increasing mortality or reducing reproductive success. Primary and 
secondary stress responses (i.e., changes in haemolymph levels of 
enzymes, proteins, etc.) of crustaceans or fish after exposure to 
seismic survey sounds appear to be temporary (hours to days) in studies 
done to date (see Payne et al., 2007 for invertebrates; see Sverdrup et 
al., 1994; McCauley et al., 2000a,b for fish). The periods necessary 
for these biochemical changes to return to normal are variable and 
depend on numerous aspects of the biology of the species and of the 
sound stimulus.
    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. 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 2008 is predicted to have 
negligible to low physical effects on the various life stages of fish 
and invertebrates for its short duration (approximately 25 days each in 
the Pacific Ocean and Caribbean Sea) and approximately 2,149-km of 
unique survey lines extent. Therefore, physical effects of the proposed 
program on fish and invertebrates would not be significant.
    Behavioral Effects--Because of the apparent lack of serious 
pathological and physiological effects of seismic energy on marine fish 
and invertebrates, the highest level of 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; L[phis]okkeborg, 1991; Skalski et al., 1992; Enges et al., 1996). 
In other airgun experiments, there was no change in catch per unit 
effort (CPUE) 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,

[[Page 71641]]

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). Parry 
and Gason (2006) reported no changes in rock lobster CPUE during or 
after seismic surveys off western Victoria, Australia, from 1978-2004. 
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 E (c) of L-DEO's application.
    Summary of Behavioral Effects--is the case with pathological and 
physiological effects of seismic on fish and invertebrates, available 
information is relatively scant and often 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 relatively short duration and extent.
    Because of the reasons noted above and the nature of the proposed 
activities, 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 Visual Monitoring

    Vessel-based marine mammal visual observers (MMVOs) will be based 
aboard the seismic source vessel and will watch for marine mammals near 
the vessel during daytime airgun operations and during start-ups of 
airguns at night. MMVOs will also watch for marine mammals near the 
seismic vessel for at least 30 minutes prior to the start of airgun 
operations after an extended shutdown of the airguns. 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, airguns will be powered down, or 
if necessary, shut down completely (see below), when marine mammals are 
detected within or about to enter a designated EZ (safety radius). The 
MMVOs will continue to maintain watch to determine when the animal(s) 
are outside the EZ, and airgun operations will not resume until the 
animal has left that zone. The EZ is a region in which a possibility 
exists of adverse effects on animal hearing or other physical effects.
    During seismic operations off Central America, at least three 
observers will be based aboard the Langseth. MMVOs will be appointed by 
L-DEO with NMFS concurrence. At least one MMVO, and when practical two, 
will monitor the EZ for marine mammals during daytime operations and 
nighttime startups of the airguns. MMVO(s) will be on duty in shifts of 
duration no longer than 4 hours. The crew will also be instructed to 
assist in detecting marine mammals and implementing mitigation 
requirements (if practical).
    The Langseth is a suitable platform for marine mammal observations. 
When stationed on the observation platform, the eye level will be 
approximately 17.8 m (58.4 ft) above sea level, and the observer will 
have a good view around the entire vessel. During daytime, the MMVO(s) 
will scan the area around the vessel systematically with reticle 
binoculars (e.g., 7x50 Fujinon), Big-eye binoculars (25x150), and with 
the naked eye. During darkness, night vision devices will be available 
(ITT F500 Series Generation 3 binocular-image intensifier or 
equivalent). Laser rangefinding binoculars (Leica LRF 1200 laser 
rangefinder or equivalent) will be available to assist with distance 
estimation.

Passive Acoustic Monitoring

    PAM will take place to complement the visual monitoring program. 
Visual monitoring typically is not effective during periods of bad 
weather or at night, and even with good visibility, is unable to detect 
marine mammals when they are below the surface or beyond visual range. 
Acoustic monitoring can be used in addition to visual observations to 
improve detection, identification, localization, and tracking of 
cetaceans. It is only useful when marine mammals call, but it can be 
effective either by day or by night and does not depend on good 
visibility. The acoustic monitoring will serve to alert visual 
observers (if on duty) when vocalizing cetaceans are detected. It will 
be monitored in real time so visual observers can be advised when 
cetaceans are detected. When bearings (primary and mirror-image) to 
calling cetacean(s) are determined, the bearings will be relayed to the 
visual observer to help him/her sight the calling animal(s).
    SEAMAP (Houston, Texas) will be used as the primary acoustic 
monitoring system. This system was also used during several previous L-
DEO seismic cruises (e.g., Smultea et al., 2004, 2005; Holst et al., 
2005a,b). The PAM system consists of hardware (i.e., hydrophones) and 
software. The ``wet end'' of the SEAMAP system consists of a low-noise, 
towed hydrophone array that is connected to the vessel by a ``hairy'' 
faired cable. The array will be deployed from a winch located on the 
back deck. A deck cable will connect form the winch to the main 
computer lab where the acoustic station and signal conditioning and 
processing system will be located. The lead-in from the hydrophone 
array is approximately 400

[[Page 71642]]

m (1,312 ft) long, and the active part of the hydrophone array is 
approximately 56 m (184 ft) long. The hydrophone array is typically 
towed at depths less than 20 m (66 ft).
    While the Langseth is in the seismic survey area, the towed 
hydrophone array will be monitored 24 hours per day while at the survey 
area during airgun operations and also during most periods when the 
Langseth is underway with the airguns not operating. One marine mammal 
observer (MMO) will monitor the acoustic detection system at any one 
time, by listening to the signals from two channels via headphones and/
or speakers and watching the real time spectrographic display for 
frequency ranges produced by cetaceans. MMOs monitoring the acoustical 
data will be on shift for 1-6 hours. All MMOs are expected to rotate 
through the PAM position, although the most experienced with acoustics 
will be on PAM duty more frequently.
    When a cetacean vocalization is detected, the acoustic MMO will, if 
visual observations are in progress, contact the MMVO immediately to 
alert him/her to the presence of the cetacean(s), if they have not 
already been seen and to allow power down or shutdown to be initiated, 
if required. The information regarding the call will be entered into a 
database. The data to be entered include an acoustic encounter 
identification number, whether it was linked with a visual sighting, 
date, time when first and last heard and whenever any additional 
information was recorded, position and water depth when first detected, 
bearing if determinable, species or species group (e.g., unidentified 
dolphin, sperm whale), types and nature of sounds heard (e.g., clicks, 
continuous, sporadic, whistles, creaks, burst pulses, strength of 
signal, etc.), and any other notable information. The acoustic 
detection can also be recorded for further analysis.

MMVO Data and Documentation

    MMVOs will record data to estimate the numbers of marine mammals 
exposed to various received sound levels and to document any apparent 
disturbance reactions or lack thereof. Data will be used to estimate 
the numbers of mammals potentially ``taken'' by harassment. They will 
also provide information needed to order a power down or shutdown of 
airguns when marine mammals are within or near the EZ. When a sighting 
is made, the following information about the sighting will be recorded:
    (1) Species, group size, age/size/sex categories (if determinable), 
behavior when first sighted and after initial sighting, heading (if 
consistent), bearing and distance from seismic vessel, sighting cue, 
apparent reaction to the airguns or vessel (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, as well as information regarding airgun 
power down and shutdown, 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 powering down or shutting down 
airgun arrays.
    (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 L-DEO seismic studies and associated environmental assessments 
(EAs), IHA applications, and IHAs. The mitigation and monitoring 
measures described herein represent a combination of the procedures 
required by past IHAs for other similar projects and on recommended 
best practices in Richardson et al. (1995), Pierson et al. (1998), and 
Weir and Dolman (2007). 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 and 
worldwide population sizes. With the proposed monitoring and mitigation 
provisions, 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 include: (1) Speed or 
course alteration, provided that doing so will not compromise 
operational safety requirements; (2) power-down procedures; (3) 
shutdown procedures; (4) ramp-up procedures; and (5) minimizing 
approaches to slopes and submarine canyons, if possible, because of 
sensitivity of beaked whales.
    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 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, thus for surveys involving large sources, 
alternative mitigation measures are required.
    Power-down Procedures--A power-down involves reducing the number of 
operating airguns, typically to a single airgun (e.g., 40 
in3), to minimize the EZ, so that marine mammals are no 
longer in or about to enter this zone. A power-down of the airgun array 
to a reduced number of operating airguns may also occur when the vessel 
is moving from one seismic line to another. The continued operation of 
at least one airgun is intended to alert marine mammals to the presence 
of the seismic vessel in the area.
    If a marine mammal is detected outside the EZ but is likely to 
enter it, and if the vessel's speed and/or course cannot be changed, 
the airguns will be powered down to a single airgun before the animal 
is within the EZ. Likewise, if a mammal is already within the EZ when 
first detected, the airguns will be powered down immediately. If a 
marine mammal is detected within or near the smaller EZ around that 
single airgun (see Table 1 of L-DEO's application and Table 1 above), 
all airguns will be shutdown (see next subsection).
    Following a power down, airgun 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) Is visually observed to have left the EZ; or
    (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.

[[Page 71643]]

    Following a power-down and subsequent animal departure as above, 
the airgun array will resume operations following ramp-up procedures 
described below.
    Shutdown Procedures--The operating airgun(s) will be shutdown if a 
marine mammal is detected within the EZ of a single 40 in3 
airgun while the airgun array is at full volume or during a power down. 
Airgun activity will not resume until the marine mammal has cleared the 
EZ or until the MMVO is confident that the animal has left the vicinity 
of the vessel. Criteria for judging that the animal has cleared the EZ 
will be as describing in the preceding subsection.
    Ramp-up Procedures--A ramp-up procedure will be followed when the 
airgun array begins operating after a specified-duration period without 
airgun operations or when a power down has exceeded that period. It is 
proposed that, for the present cruise, this period would be 
approximately 8 minutes. This period is based on the modeled 180-dB 
radius for the 36-airgun array (see Table 3 of L-DEO's application and 
Table 1 here) in relation to the planned speed of the Langseth while 
shooting in deep water. Similar periods (approximately 8-10 minutes) 
were used during previous L-DEO surveys.
    Ramp-up will begin with the smallest airgun in the array (40 
in3). Airguns will be added in a sequence such that the 
source level of the array will increase in steps not exceeding 6 dB per 
5-minute period over a total duration of approximately 20-25 minutes. 
During ramp-up, the MMVOs will monitor the EZ, and if marine mammals 
are sighted, a course/speed change, power down, or shutdown will be 
implemented as though the full array were operational.
    Initiation of ramp-up procedures from shutdown requires that the 
full EZ must be visible by the MMVOs, whether conducted in daytime or 
nighttime. This requirement likely will preclude start ups at night or 
in thick fog because the outer part of the EZ for that array will not 
be visible during those conditions. Ramp-up is allowed from a power 
down under reduced visibility conditions only if at least one airgun 
(e.g., 40 in3 or similar) has operated continuously 
throughout the survey without interruption, on the assumption that 
marine mammals will be alerted to the approaching seismic vessel by the 
sounds from the single airgun and could move away if they choose. Ramp-
up of the airguns will not be initiated if a marine mammal is sighted 
within or near the applicable EZ during the day or close to the vessel 
at night.
    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 (e.g., mid-frequency sonar). Beaked 
whales tend to concentrate in continental slope areas and in areas 
where there are submarine canyons. There are no submarine canyons 
within or near the study area. Three of the transect lines are on the 
continental slope, which accounts for only a small portion of the 
proposed study area (207 km; 128.6 mi) and a minimal amount of time (30 
hours).

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 sightings of marine mammals 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.

Endangered Species Act (ESA)

    Under section 7 of the ESA, NSF has begun consultation with the 
NMFS, Office of Protected Resources, Endangered Species Division on 
this proposed seismic survey. NMFS will also consult on the issuance of 
an IHA under section 101(a)(5)(D) of the MMPA for this activity. 
Consultation will be concluded prior to a determination on the issuance 
of the IHA.

National Environmental Policy Act (NEPA)

    NSF prepared an Environmental Assessment of a Marine Geophysical 
Survey by the R/V Marcus G. Langseth off Central America, January-March 
2008. NMFS will either adopt NSF's EA or conduct a separate NEPA 
analysis, as necessary, prior to making a determination of the issuance 
of the IHA.

Preliminary Determinations

    NMFS has preliminarily determined that the impact of conducting the 
seismic survey in the Pacific Ocean and Caribbean Sea off Central 
America may result, at worst, in a temporary modification in behavior 
(Level B Harassment) of small numbers of 26 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 40 m (131 ft) in deep water, 60 m (197 ft) at 
intermediate depths, or 296 m (971 ft) in shallow water when a single 
airgun is in use from the vessel to be exposed to levels of sound (180 
dB) believed to have even a minimal chance of causing TTS; (3) the fact 
that marine mammals would have to be closer than 950 m (0.6 mi) in deep 
water, 1,425 m (0.9 mi) at intermediate depths, and 3,694 m (2.3 mi) in 
shallow water when the full array is in use at a 9 m (29.5 ft) tow 
depth from the vessel to be exposed to levels of sound (180 dB) 
believed to have even a minimal chance of causing TTS; (4) the fact 
that marine mammals would have to be closer than 1,120 m (0.7 mi) in 
deep water, 1,680 m (1 mi) at intermediate depths, and 4,356 (2.7 mi) 
in shallow water when the full array is in use at a 12 m (39 ft) tow 
depth from the vessel to be exposed to levels of sound (180 dB) 
believed to have even a minimal chance of causing TTS; and (5) 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 L-DEO for conducting a marine geophysical survey in the 
Pacific

[[Page 71644]]

Ocean and Caribbean Sea off Central America from February-April, 2008, 
provided the previously mentioned mitigation, monitoring, and reporting 
requirements are incorporated.

    Dated: December 12, 2007.
Helen Golde,
Deputy Director, Office of Protected Resources, National Marine 
Fisheries Service.
 [FR Doc. E7-24508 Filed 12-17-07; 8:45 am]
BILLING CODE 3510-22-P