[Federal Register Volume 71, Number 193 (Thursday, October 5, 2006)]
[Notices]
[Pages 58790-58804]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-16412]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[I.D. 090706B]


Incidental Takes of Marine Mammals During Specified Activities; 
Seismic Testing and Calibration in the Northern Gulf of Mexico, Fall 
2006

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

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

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

SUMMARY: NMFS has received an application from the Lamont-Doherty Earth 
Observatory (L-DEO) for an Incidental Harassment Authorization (IHA) to 
take small numbers of marine mammals, by harassment, incidental to 
conducting an acoustic calibration and seismic testing program in the 
northern Gulf of Mexico in Fall, 2006. Under the Marine Mammal 
Protection Act (MMPA), NMFS is requesting comments on its proposed IHA 
for these activities.

DATES: Comments and information must be received no later than November 
6, 2006.

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

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

SUPPLEMENTARY INFORMATION:

Background

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

Summary of Request

    On June 2, 2006, NMFS received an application from L-DEO for the 
taking, by Level B harassment, of several species of marine mammals 
incidental to conducting, with research funding from the National 
Science Foundation (NSF), an acoustic calibration and seismic testing 
program in the northern Gulf of Mexico in Fall, 2006. This project will 
be conducted with L-DEO's new seismic vessel, the R/V Marcus G. 
Langseth (Langseth), which will deploy different configurations of 
airguns and a different bottom-mapping sonar than used previously by L-
DEO. L-DEO requests that it be issued an IHA allowing Level B 
Harassment takes of marine mammals incidental to the planned seismic 
surveys in the Gulf of Mexico.
    The primary purpose of the calibration program is to obtain 
measurement data to better understand the sound fields around various 
configurations of the 36-airgun array and the GI guns, during seismic 
operations in different water depths. The data will be used to verify 
and refine model-based estimates of ``safety radii'' for different 
configurations of the 36-airgun array and the GI guns that will be used 
during future seismic surveys to be conducted by L-DEO. Such data are 
important to better define the distances within which mitigation may be 
necessary in order to avoid exposing marine mammals to received sound 
levels above those believed to have adverse effects, as well as to 
develop a better general understanding of the impact of man-made 
acoustic sources on marine mammals.

Description of the Specified Activity

    The Langseth is expected to depart Mobile, AL in late October 2006 
(at the earliest) and will transit to the survey area in the northern 
Gulf of Mexico. The survey will encompass an area between 24oN. and 
31oN. and between 83[deg]W. and 96[deg]W., which is within the 
Exclusive Economic Zone (EEZ) of the U.S.A. The proposed study will 
consist of three phases: (1) an initial testing/

[[Page 58791]]

shakedown phase, (2) measurements of the sounds produced by various 
airgun arrays to be used by the Langseth (calibration), and (3) a 
three-dimensional (3D) seismic testing phase. The entire survey, 
calibration and testing included, will take approximately 25 days and 
include approximately 1420 km (174 hours) of airgun operation. 
Measurements will be made during seismic operations in three categories 
of water depth: shallow (<100 m or <328 ft), intermediate/slope (100-
1000 m or 328-3281 ft), and deep (>1000 m or >3281 ft). The vessel will 
transit to Miami after the study is completed. The exact dates of the 
activities will depend on logistics and weather conditions.

Vessel Specifications

    The Langseth is owned by NSF and operated by L-DEO. The Langseth 
will tow the airgun array and, at times, up to four 6-km (3.7-mi) 
streamers containing hydrophones along predetermined lines. The 
Langseth will also deploy a floating spar buoy and a bottom-moored 
hydrophone array.
    The Langseth has a length of 71.5 m (235 ft), a beam of 17.0 m (56 
ft), and a maximum draft of 5.9 m (19 ft). The gross tonnage is 2925 
and the Langseth can accommodate 55 people. The ship is powered by two 
Bergen BRG-6 engines each producing 3550 hp; 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 (13,500 nm).
    Given the presence of the airgun array (and at times streamer(s)) 
behind the vessel, the turning rate of the ship while the gear is 
deployed is limited to five degrees per minute. Thus, the 
maneuverability of the vessel is limited during operations.

Acoustic Source Specifications

Airguns
    The full airgun array on the Langseth consists of 36 airguns, with 
a total discharge volume of 6600 in\3\. The array is made up of four 
identical linear arrays or strings, with 10 airguns on each string. For 
each operating string, nine airguns 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 calibration phase will use the full 36-
airgun array and subsets thereof. The subsets will consist of either 1 
string (9 airguns, 1650 in\3\) or 2 strings (18 airguns, 3300 in\3\). 
In addition, sounds from a single 45 in\3\ GI gun and 2 GI guns (210 
in\3\) will be measured. During the seismic testing phase, the 2-string 
array will be used at most times, although the full 36-airgun array may 
also be used.
    The 36-airgun array will consist of a mixture of Bolt 1500LL and 
1900LLX airguns, ranging in size from 40 to 360 in\3\. The airguns will 
fire for a brief (0.1 s) pulse every 30 s and will be silent during the 
intervening periods. The airgun array will be towed approximately 50-
100 m (164-328 ft) behind the seismic vessel at a depth of 6-12 m (20-
39 ft). The dominant frequency component is 0-188 Hz.
    The specifications of each source planned for use are described in 
Table 1.

----------------------------------------------------------------------------------------------------------------
                                                                             9-Airgun    18-Airgun    36-Airgun
                                    1 GI Gun      2 GI Guns     1 Single     Array (1     Array (2     Array (4
                                                                 Airgun      String)      Strings)     Strings)
----------------------------------------------------------------------------------------------------------------
Airgun Specifications             ............  ............  ...........  ...........  ...........  ...........
----------------------------------------------------------------------------------------------------------------
  Energy Source                   One 45 in\3\  Two 105       One 2000     Nine 2000    Eighteen     Thirty-six
                                   GI Airgun     in\3\ GI      psi Bolt     psi Bolt     2000 psi     2000 psi
                                                 Airguns       Airgun       Airguns of   Bolt         Bolt
                                                                            40-360       Airguns of   Airguns of
                                                                            in\3\        40-360       40-360
                                                                                         in\3\        in\3\
----------------------------------------------------------------------------------------------------------------
  Air Discharge Volume (in\3\)    45 in3        210 in\3\     40 in\3\     1650 in\3\   3300 in\3\   6600 in\3\
----------------------------------------------------------------------------------------------------------------
  Towing Depth of Source          2.5m          3m            6 m          6m           6m           6m or 12m
----------------------------------------------------------------------------------------------------------------
  Source Output (dB re 1 miPa m)  225.3         237 (243)     ...........  246 (253)    252 (259)    259 (265)
   0-pk (pk.pk)*                   (230.7)
----------------------------------------------------------------------------------------------------------------
Proposed Approximate Airgun Use
                                 --------------                           -------------             ------------
 Calibration Phase                ............  ............  ...........  ...........  ...........  ...........
----------------------------------------------------------------------------------------------------------------
   Shallow Site (30-60m)          10km          10km          ...........  34km         34km         34km
----------------------------------------------------------------------------------------------------------------
   Intermediate/Slope Site        ............  ............  ...........  34km         34km>        34km
    (475m)
----------------------------------------------------------------------------------------------------------------
   Deep Site (1500m)              10km          10km          ...........  45km         45km         45km
----------------------------------------------------------------------------------------------------------------
Testing Phase                     ............  ............  ...........  ...........  ...........  ...........
----------------------------------------------------------------------------------------------------------------
   Shallow Site (<100m)           ............  ............  89km         24km         175km        58km
----------------------------------------------------------------------------------------------------------------
   Intermediate/Slope (100-1000   ............  ............  89km         24km         175km        58km
    m)
----------------------------------------------------------------------------------------------------------------
   Deep (>1000 m)                 ............  ............  89km         24km         175km        58km
 
----------------------------------------------------------------------------------------------------------------
Table 1. L-DEO airgun configurations and proposed approximate use for each configuration by depth and phase.
* The root mean square values (typically discussed in biological literature) for these sources will generally be
  about 10-15 dB lower than those reflected here


[[Page 58792]]

Multibeam Sonar
    The ocean floor will be mapped with the 12-kHz Simrad EM120 MBB 
sonar. This sonar will be operated from the Langseth simultaneous with 
the airgun array during the seismic testing program, but will likely be 
operated on its own during the acoustic calibration study. The Simrad 
EM120 operates at 11.25-12.6 kHz and will be 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 microPa. The pressure level is 
expected to drop to 180 dB at a distance of 1 km or 0.5 nm (this 
distance is the maximum estimate for on-axis and with no defocusing); 
pressure level does not vary with water depth. Each ``ping'' consists 
of nine successive fan-shaped transmissions, each ensonifying a sector 
that extends 1[deg] fore-aft and 16[deg] in the cross-track direction. 
The transmission length varies with water depth; each of the nine 
transmissions is approximately 2 ms in shallow water, 5 ms at 
intermediate water depths, and 15 ms in deep water. The nine successive 
transmissions span an overall cross-track angular extent of about 
150[deg], with 16 ms gaps between the pulses for successive sectors. A 
receiver in the overlap area between two sectors would receive two 
pulses separated by a 16-ms gap. The ``ping'' interval varies with 
water depth and ranges from 0.2 s in really shallow water, to 
approximately 5 s at 1000 m (3281 ft) and 20 s at 4000 m (13,124 ft).

Airgun Operations

Acoustic Calibration Study
    Location of Sites - L-DEO will work together with Texas A&M 
University to choose the exact study sites at the three depths, 
however, the approximate locations are indicated in Figure 1 of L-DEO's 
application. Site locations will depend on currents, surface ducts, and 
concentrations of marine mammals. Sites will be chosen to avoid high 
currents with large vertical shear, as were encountered during the 2003 
study. Conductivity/Temperature/Depth (CTDs) and Expendable 
Bathythermograph (XBTs) measurements will be taken at each site to 
confirm local water column properties. Near-surface ducts may play a 
significant role in the propagation of sound, so a deep site with and 
without a surface duct will be surveyed if practical. Areas with 
concentrations of marine mammals will be avoided.
    L-DEO proposes to start with the shallow site, where the instrument 
redundancy will allow some flexibility in gain settings to ensure that 
signals will not be clipped. This information will be used to optimize 
gain settings at the slope and deep sites. The water depths at the 
three different depth sites are expected to be 30-60 m (98-197 ft) at 
the shallow site, approximately 475 m (1,558 ft) at the intermediate/
slope site, and approximately1500 m (4922 ft) at the deep site. This 
phase of the study will take approximately 14 days.
    Acoustic Measurements - The 2006 program is designed to document 
the received levels of the airgun sounds, relative to distance, during 
operation of the Langseth's 36-airgun 4-string array and subsets 
thereof, and up to 2 GI guns. During the calibration study, three 
configurations (1, 2, and 4 strings in equal amounts) of the 36-airgun 
array will be measured in three different water depths (deep, 
intermediate/slope, and shallow). A single and two GI guns will be 
measured in deep and shallow water only. Measurements will be made at 
varying distances from the guns using suitable electronics installed in 
the spar buoy and a bottom-moored hydrophone array. In addition, one 6-
km (3.7-mi) long hydrophone streamer will be used at times for 
calibrations of shallow-water safety radii. The hydrophones will be 
deployed and retrieved by the Langseth.
    At each of the three sites, the Langseth, towing various 
configurations of the 36-airgun array at a depth of 6 m (20 ft), will 
travel toward the spar buoy and/or moored hydrophone array from a 
distance of approximately10-15 km (5.4-8.1 nm) away and will pass over 
the receiving system. The Langseth will then continue out to a distance 
of approximately 10-15 km beyond the hydrophones. The approximate 15 km 
distance will be used at the shallow and slope sites (total line length 
of 30 km or 16 nm), and the approximate 10 km distance will be used at 
the deep-water site (total line length of 20 km or 11 nm). Longer lines 
are planned at the shallow and slope sites than at the deep site 
because in 2003, received sound levels diminished below 160 dB re 1 
microPa (rms) well within 10 km at the deep site, but not at the 
shallow site (Tolstoy et al., 2004a,b). After completing the straight 
line, the airgun array will then be towed in a spiral fashion towards 
the hydrophones in order to measure received levels as a function of 
distance when the receiving hydrophones are to the side of the 
trackline. The spirals are designed such that the radius will decrease 
linearly with time.
    At each site, the Langseth will make one straight line pass over 
the receiving hydrophones with the 36-airgun array, followed by the 
spiral pattern towards the hydrophones. At the deep site, two 
additional 20-km (11-nm) straight lines will be shot, for a total of 
three 20-km straight lines at that site: (a) with the airgun array at 6 
m (20 ft) tow depth, (b) with the array at a tow depth of 12 m (39 ft), 
and (c) in waters with/without a surface duct [whichever was not the 
case in (a) and (b)]. In addition, two 10-km (5.4-nm) straight line 
passes will be made at the deep as well as the shallow-water sites; one 
pass at each site will be made with a single GI gun, and one pass will 
be made using 2 GI guns.
    The total number of kilometers and hours of airgun shooting during 
the calibration phase of the project are indicated in Table 1. However, 
operations at each site will require approximately 36 hours, allowing 
for the time needed to deploy and recover the hydrophones as well as 
the time to shoot the survey. Although the lines will be longer for the 
slope and shallow sites, the deep site is likely to take the longest, 
because of the increased drop and surfacing time for the instruments 
plus the plans to shoot three 20 km (11 nm) lines.
    Airguns will fire every 30 s, and operations are proposed to occur 
24 hours per day to maximize effective and economic use of the limited 
ship time and to maximize the amount of calibration data collected. 
Operating airguns over 24-hour periods will also reduce the overall 
duration of airgun operations at each site, thus reducing the span of 
time when marine mammals in those areas will be exposed to airgun 
sounds.
Systematic Testing Phase
    The exact site of the seismic testing phase has not yet been 
chosen, but is planned to range from shallow (approximately 30 m or 98 
ft) to deep (>1000 m or 3281 ft) water and will fall within the general 
area described earlier. During the testing phase, the Langseth will 
deploy the 2-string 18-airgun array (and at times the 36-airgun array) 
as an energy source; a single 40 in3 airgun will be fired during turns. 
The Langseth will also deploy a receiving system consisting of up to 
four 6-km (3.7-mi) towed hydrophone streamers. There will be 200 m (656 
ft) separation between adjacent pairs of the four streamers. As the 
airgun array is towed along the survey lines, the receiving system will 
receive the returning acoustic signals and transfer the data to the on-
board processing system. The airgun array will be towed at a depth of 9 
m (30 ft).
    The testing phase will consist of a series of tracklines in a 
racetrack-type configuration. This racetrack will consist of 17 loops, 
with a total of 35

[[Page 58793]]

tracklines. Each trackline will be approximately 20 km (10.8 nm) long, 
for a total of approximately 700 km (378 nm) of shooting along 
tracklines. The spacing between adjacent tracklines will be 400 m (1312 
ft). An additional 10 km (5.4 nm) of seismic will be shot during each 
turn between lines and during the ensuing run-in (the distance from the 
end of the turn to the start of the line during which the airgun array 
will be ramped up). In total, this will account for an additional 340 
km (183 nm). Of this 340 km, approximately 73 km (39.4 nm) will consist 
of ramp ups, and 267 km (144.2 nm) will be shot with a 40 in\3\ airgun 
during turns. These numbers are also presented in Table 1.
    In total, 1040 km (562 nm) of seismic will be shot. The seismic 
testing program will take approximately 4 to 7 days.

Characteristics of Airgun Pulses

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

Safety Radii

    To aid in determining at what point during exposure to seismic 
airguns (and other acoustic sources) marine mammals are harassed, 
pursuant to the MMPA, and in developing effective mitigation measures, 
NMFS applies certain acoustic thresholds. The distance from the sound 
source at which an animal would be exposed to these different received 
sound levels may be estimated and is typically referred to as a safety 
radii. These safety radii are specifically used to help NMFS estimate 
the number of marine mammals likely to be harassed by the proposed 
activity and in deciding how close a marine mammal may approach an 
operating sound source before the applicant will be required to power-
down or shut down the sound source.
    L-DEO has estimated the safety radii around their proposed 
operations using a model, but also by adjusting the model results based 
on empirical data gathered in the Gulf of Mexico in 2003. Additional 
information regarding how the safety radii were calculated and how the 
empirical measurements were used to correct the modeled numbers may be 
found in Section I and Appendix A of L-DEO's application. Using the 
modeled distances and various correction factors, Table 2 shows the 
distances at which three rms sound levels (190 dB, 180 dB, and 160 dB) 
are expected to be received from the various airgun configurations in 
shallow, intermediate, and deep water depths.

----------------------------------------------------------------------------------------------------------------
                                                                               Predicted RMS Radii (m)
         Source and Volume           Tow Depth (m)    Water Depth  ---------------------------------------------
                                                                        190 dB          180 dB         160 dB
----------------------------------------------------------------------------------------------------------------
                                    ..............  Deep            9               25             236
 
Single GI gun                       2.5             Intermediate/   13.5            38             354
                                                     Slope
 
45 in\3\                            ..............  Shallow         113             185            645
----------------------------------------------------------------------------------------------------------------
                                    ..............  Deep            20              69             670
 
2 GI guns                           3               Intermediate/   30              104            1005
                                                     Slope
 
210 in\3\                           ..............  Shallow         294             511            1970
----------------------------------------------------------------------------------------------------------------
                                    ..............  Deep            12              36             360
 
Single Bolt                         6               Intermediate/   18              54             540
                                                     Slope
 
40 in\3\                            ..............  Shallow         150             267            983
----------------------------------------------------------------------------------------------------------------
1 string                            ..............  Deep            200             650            6200
 
9 airguns                           6               Intermediate/   300             975            7880
                                                     Slope
 
1650 in\3\                          ..............  Shallow         1450            2360           8590
----------------------------------------------------------------------------------------------------------------
2 strings/ENT>                      ..............  Deep            250             820            6700
 
18 airguns                          6               Intermediate/   375             1230           7370
                                                     Slope
 
3300 in\3\                          ..............  Shallow         1820            3190           8930
----------------------------------------------------------------------------------------------------------------
4 strings                           ..............  Deep            410             1320           8000
 
36 airguns                          6               Intermediate/   615             1980           8800
                                                     Slope
 
6600 in\3\                          ..............  Shallow         2980            5130           10670
----------------------------------------------------------------------------------------------------------------
4 strings                           ..............  Deep            620             1980           12000
 
36 airguns                          12              Intermediate/   930             2970           13200
                                                     Slope
 
6600 in\3\                          ..............  Shallow         4500            7700           16000
 
----------------------------------------------------------------------------------------------------------------
Table 2. Modeled distances towhich sound levels 190,180, and 160 dB re 1uPa (rms) might be received in shallow
  (>100 m), intermediate/slope (100-1000 m), and deep (<1000 m) water from the various sources planned for use
  during the Gulf of Mexico study, fall 2006.


[[Page 58794]]

Description of Marine Mammals in the Activity Area

    In the Gulf of Mexico, 28 cetacean species and one species of 
manatee are known to occur (Jefferson and Schiro, 1997; Wursig et al., 
2000; Table 3). In the U.S., manatees are managed by the U.S. Fish & 
Wildlife Service (USFWS), are unlikely to be encountered in or near the 
open waters of the Gulf of Mexico where seismic operations will occur, 
and are, therefore, not addressed further in this document. Most of 
these species of cetaceans occur in oceanic waters (>200 m or 656 ft 
deep) of the Gulf, whereas the continental shelf waters (<200 m) are 
primarily inhabited by bottlenose dolphins and Atlantic spotted 
dolphins (Mullin and Fulling 2004).

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                    BEST                                  MAXIMUM
                                                                                         Abundance in GOM and/or  ------------------------------------------------------------------------------
             Species                           Habitat               Occurrence in GOM        North Atlantic            Estimated         Approx. % of       Est. Exposures       Approx. % of
                                                                                                                        Exposures          Population          Prop. IHA**         Population
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Odontocetes
----------------------------------                                 --------------------                           --------------------                    --------------------------------------
Sperm whale                        Usually pelagic and deep seas    Common              1349/13190 (add)           22                  0.2                 27                  0.2
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Pygmy sperm whale                  Deeper waters off the shelf      Common              742/695 (add)              56                  3.9                 ..................  4.1
---------------------------------------------------------------------------------------
Dwarf sperm whale                  Deeper waters off the shelf      Common              .........................  ..................  ..................  ..................  .................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Cuvier's beaked whale              Pelagic                          Rare                159/3196 (add)             10                  0.3                 21                  0.7
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Sowerby's beaked whale             Pelagic                          Extralimital        .........................  5                   0.8                 8                   1.2
---------------------------------------------------------------------------------------                           ------------------------------------------------------------------------------
Gervais' beaked whale              Pelagic                          Uncommon            106/541 (add)              5                   0.8                 8                   1.2
---------------------------------------------------------------------------------------                           ------------------------------------------------------------------------------
Blainville's beaked whale          Pelagic                          Rare                .........................  5                   0.8                 8                   1.2
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Rough-toothed dolphin              Mostly pelagic                   Common              2223/274 (add)             58                  2.3                 92                  3.7
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Bottlenose dolphin                 Cont. shelf, coastal and         Common              25,320/2239/29774 (add)    773                 1.3                 1713                5.0
                                    offshore
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Pantropical spotted dolphin        Mainly pelagic                   Common              91,321/13117 (add)         1282                1.2                 1587                1.5
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Atlantic spotted dolphin           Mainly coastal waters            Common              30,947/52279 (add)         876                 1.1                 1755                0.2
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Spinner dolphin                    Pelagic in Gulf of Mexico        Common              11,971                     168                 1.4                 921                 7.7
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Clymene dolphin                    Pelagic                          Common              17,355/6086 (add)          244                 1.0                 311                 1.3
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Stripped dolphin                   Off the continental shelf        Common              6505/61546 (add)           91                  0.1                 134                 0.2
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Short-beaked common dolphin        Cont. shelf and pelagic waters   Possible            30,768                     0                   0.0                 0(5)**              <0.1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Long-beaked common dolphin         Coastal                          Possible            N.A.                       0                   0.0                 0(5)**              0.0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Praser's dolphin                   Water>l000m                      Common              726                        10                  1.4                 60                  8.3
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Risso's dolphin                    Waters 400-1000 m                Common              2169/29110 (add)           54                  0.2                 81                  0.3
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Mellon-headed whale                Oceanic                          Common              3451                       49                  1.4                 142                 4.1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Pygmy killer whale                 Oceanic                          Uncommon            408                        10                  2.6                 21                  5.1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
False killer whale                 Pelagic                          Uncommon            1038                       14                  1.4                 28                  2.7
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Killer whale                       Widely distributed               Uncommon            133/6600 (add)             3                   <0.1                5                   0.1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Short-finned pilot whale           Mostly pelagic                   Common              2388/780000/14524          34                  <0.1                98                  <0.1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Long-finned pilot whale            Mostly pelagic                   Possible            N.A.                       0                   ..................  0(5)**              .................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 58795]]

 
Mysticetes
----------------------------------                                 --------------------                           --------------------                    --------------------------------------
North Atlantic right whale*        Coastal and shelf waters         Extralimital        291                        0                   ..................  0                   .................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale*                    Mainly near-shore waters/banks   Rare                11,570/10400               0                   ..................  0                   .................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Minke whale                        Coastal waters                   Rare                149,000                    0                   ..................  0                   .................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Bryde's whale                      Pelagic and coastal              Uncommon            40/90000                   1                   2.5                 2                   5.0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Sei whale*                         Primarily offshore, pelagic      Rare                12-13,000                  0                   ..................  0                   .................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Fin whale*                         Cont. slope, mostly pelagic      Rare                2814/47300                 0                   ..................  0                   .................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Blue whale*                        Coastal, shelf, and oceanic      Extralimital        308                        0                   ..................  0                   .................
                                    waters
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Pinnipeds
----------------------------------                                 --------------------                           --------------------                    --------------------------------------
Hooded seal                        Coastal                          Vagrant             400,000\z\                 0                   ..................  0(2)**              <0.1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                      Total                                                        3770                ..................  7096                .................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Table 3. Abundance, preferred habitat, and commonness of the marine mammal species found in the survey area. The far right columns indicate the estimated number each species that will be
  exposed to 160 dB based on best and maximum density estimates. NMFS believes that, when mitigation measures are taken into consideration, the activity is likely to result in take of numbers
  of animals less than those indicated by the best column, however, L-DEO has asked for authorization of the maximum.
*Federally listed endangered,
** Parenthetical number indicates take authorization, though exposure estimate is 0

    Seven species that may occur in the Gulf of Mexico are listed as 
endangered under provisions of the U.S. Endangered Species Act (ESA), 
including the sperm, North Atlantic right, humpback, sei, fin, and blue 
whale, as well as the West Indian manatee. However, of those species, 
only sperm whales are likely to be encountered. In addition to the 28 
species known to occur in the Gulf of Mexico, another three species of 
cetaceans could potentially occur there: the long-finned pilot whale, 
the long-beaked common dolphin, and the short-beaked common dolphin 
(Table 3). Though any pinnipeds sighted in the study area would be 
extralimital, hooded seals have been reported in Florida and L-DEO has 
requested authorization for the take of 2 animals.
    During the 2003 acoustical calibration study in the Gulf of Mexico 
from 28 May to 2 June, a total of seven visual sightings of marine 
mammals were documented from the Maurice Ewing; these included a total 
of approximately 38-40 individuals (LGL Ltd. 2003). In addition, three 
sea turtles were sighted. These totals include times when airguns were 
not operating as well as times when airguns were firing. Visual 
monitoring effort consisted of 60.9 hours of observations (all in 
daylight) along 891.5 km of vessel trackline on seven days, and passive 
acoustic monitoring (PAM) occurred for approximately 32 hours. Most of 
the monitoring effort (visual as well as acoustic) occurred when 
airguns were not operating, since airgun operations were limited during 
the 2003 study. No marine mammals were detected during acoustic 
monitoring. Marine mammal and sea turtle sightings and locations during 
the 2003 calibration study are summarized in Appendix C of L-DEOs 
application.
    Detailed information regarding the status and distribution of these 
marine mammals may be found in sections III and IV of L-DEOs 
application.

Potential Effects of the Proposed Activity on Marine Mammals

Summary of Potential Effects of Airgun Sounds on Marine Mammals

    The effects of sounds from airguns might include one or more of the 
following: tolerance, masking of natural sounds, behavioral 
disturbance, and at least in theory, temporary or permanent hearing 
impairment, or non-auditory physical or physiological effects 
(Richardson et al., 1995). These effects are discussed below, but also 
in further detail in Appendix B of L-DEO's application.
    The potential effects of airguns discussed below are presented 
without consideration of the mitigation measures that L-DEO has 
presented and that will be required by NMFS. When these measures are 
taken into account, it is unlikely that this project would result in 
temporary, or especially, permanent hearing impairment or any 
significant non-auditory physical or physiological effects.

Tolerance

    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
A summary of the characteristics of airgun pulses is provided in 
Appendix B of L-DEO's application. Studies have also shown that marine 
mammals at distances more than a few kilometers from operating seismic 
vessels often show no apparent response (tolerance) (Appendix B (e)). 
That is often true even in cases when the pulsed sounds must be readily 
audible to the animals based on measured received levels and the 
hearing sensitivity of that mammal group. Although various baleen 
whales, toothed whales, and (less frequently)

[[Page 58796]]

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, small odontocetes, and sea 
otters seem to be more tolerant of exposure to airgun pulses than are 
baleen whales. Pinnipeds and sea otters are not found in the Gulf of 
Mexico; small odontocetes of numerous species are the predominant 
marine mammals in the area.

Masking

    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal calls and other natural sounds are expected 
to be limited, although there are very few specific data of relevance. 
Some whales are known to continue calling in the presence of seismic 
pulses. Their calls can be heard between the seismic pulses (e.g., 
Richardson et al., 1986; McDonald et al., 1995; Greene et al., 1999; 
Nieukirk et al., 2004). Although there has been one report that sperm 
whales 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 (Tyack et al., 2003). Masking effects of 
seismic pulses are expected to be negligible in the case of the smaller 
odontocete cetaceans, given the intermittent nature of seismic pulses. 
Also, the sounds important to small odontocetes are predominantly at 
much higher frequencies than are airgun sounds. Masking effects, in 
general, are discussed further in Appendix B (d).

Disturbance Reactions

    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous changes in activities, and displacement. 
Simple exposure to sound, or brief reactions that do not disrupt 
behavioral patterns in a potentially significant manner, do not 
constitute harassment or ``taking''. By potentially significant, we 
mean ``in a manner that might have deleterious effects to the well-
being of individual marine mammals or their populations''. Reactions to 
sound, if any, depend on species, state of maturity, experience, 
current activity, reproductive state, time of day, and many other 
factors. If a marine mammal does react briefly to an underwater sound 
by minorly changing its behavior or moving a small distance, the 
impacts of the change are unlikely to be significant to the individual, 
let alone the stock or the species as a whole. However, if a sound 
source displaces marine mammals from an important feeding or breeding 
area for a prolonged period, impacts on the animals could be 
significant.
    There are many uncertainties in predicting the quantity and types 
of impacts of noise on marine mammals. As mentioned earlier in this 
document, NMFS applies acoustic criteria developed to help estimate the 
number of animals likely to be harassed by a particular sound source in 
a given area and for use in the development of shutdown zones for 
mitigation. 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 on 
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. There is no specific information 
about reactions of Bryde's whales-the baleen whales most likely to be 
encountered in the Gulf of Mexico-to seismic pulses. 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, baleen whales exposed to strong noise pulses from 
airguns often react by deviating from their normal migration route and/
or interrupting their feeding and moving away. In the case of the 
migrating gray and bowhead whales, the observed changes in behavior 
appeared to be of little or no biological consequence to the animals. 
They simply avoided the sound source by displacing their migration 
route to varying degrees, but within the natural boundaries of the 
migration corridors.
    Studies of gray, bowhead, and humpback whales have determined that 
received levels of pulses in the 160-170 dB re 1 microPa rms range seem 
to cause obvious avoidance behavior in a substantial fraction of the 
animals exposed. In many areas, seismic pulses from large arrays of 
airguns diminish to those levels at distances ranging from 4.5 to 14.5 
km (2.4-7.8 nm) 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 have shown that some species of baleen whales, notably bowhead 
and humpback whales, at times show strong avoidance at received levels 
lower than 160-170 dB re 1 microPa rms. Bowhead whales migrating west 
across the Alaskan Beaufort Sea in autumn, in particular, are unusually 
responsive. Substantial avoidance occurred out to distances of 20-30 km 
(11-16 nm) from a medium-sized airgun source, where received sound 
levels were on the order of 130 dB re 1 microPa rms (Miller et al., 
1999; Richardson et al., 1999; see Appendix B (e)). More recent 
research on bowhead whales (Miller et al., 2005), however, suggests 
that during the summer feeding season, bowheads are not nearly as 
sensitive to seismic sources, with onset of avoidance at the more 
typical level of 160-170 dB re 1 microPa rms.
    Malme et al., (1986, 1988) studied the responses of feeding eastern 
gray whales to pulses from a single 100 in3 airgun off St. Lawrence 
Island in the northern Bering Sea. They estimated, based on small 
sample sizes, that 50 percent of feeding gray whales ceased feeding at 
an average received pressure level of 173 dB re 1 microPa on an 
(approximate) rms basis, and that 10 percent of feeding whales 
interrupted feeding at received levels of 163 dB. Those findings were 
generally consistent with the results of experiments conducted on 
larger numbers of gray whales that were migrating along the California 
coast.
    Blue, sei, fin, and minke whales have occasionally been reported in 
areas ensonified by airgun pulses. Sightings by observers on seismic 
vessels off the U.K. from 1997 to 2000 suggest that, at times of good 
sightability, numbers of rorquals seen are similar when airguns are 
shooting and not shooting (Stone 2003). Although individual species did 
not show any significant displacement in relation to seismic activity, 
all baleen whales combined were found to remain significantly further 
from the airguns during shooting compared with periods without shooting 
(Stone 2003).
    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

[[Page 58797]]

traffic in that area for decades (Appendix A in Malme et al., 1984). 
Bowhead whales continued to travel to the eastern Beaufort Sea each 
summer despite seismic exploration in their summer and autumn range for 
many years (Richardson et al., 1987). Populations of both gray and 
bowhead whales grew substantially during this time. In any event, the 
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 and in 
Appendix B have been reported for toothed whales. However, systematic 
work on sperm whales is underway (Tyack et al., 2003), and there is an 
increasing amount of information about responses of various odontocetes 
to seismic surveys based on monitoring studies (e.g., Stone, 2003; 
Haley and Koski, 2004; Smultea et al., 2004; Holst et al., 2005a,b; 
MacLean and Koski, 2005).
    Seismic operators sometimes see dolphins and other small toothed 
whales near operating airgun arrays, but in general there seems to be a 
tendency for most delphinids to show some limited avoidance of seismic 
vessels operating large airgun systems. However, some dolphins seem to 
be attracted to the seismic vessel and floats, and some ride the bow 
wave of the seismic vessel even when large arrays of airguns are 
firing. Nonetheless, there have been indications that small toothed 
whales sometimes move away, or maintain a somewhat greater distance 
from the vessel, when a large array of airguns is operating than when 
it is silent (e.g., Goold, 1996a,b,c; Calambokidis and Osmek, 1998; 
Stone, 2003). In most cases the avoidance radii for delphinids appear 
to be small, on the order of 1 km (0.5 nm) or less. However, aerial 
surveys during seismic operations in the southeastern Beaufort Sea 
recorded much lower sighting rates of beluga whales within 10-20 km (5-
11 nm) 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 (Miller et al., 2005).
    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; 
Finneran and Schlundt 2004). The animals tolerated high received levels 
of sound 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 microPa\2\ . 
s, respectively (Finneran and Schlundt, 2004).
Pinnipeds
    No pinnipeds are expected to be encountered in the Gulf of Mexico, 
and thus it is most likely that none will be affected by the proposed 
activity. At most, up to two extralimital hooded seals might be 
encountered and potentially be behaviorally disturbed or have a low-
level physiological response to the seismic exposure.

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 exposed to 
impulsive sounds of 180 and 190 dB re 1 microPa (rms) or above, 
respectively, are considered to have been incidentally taken by Level A 
Harassment. These levels are precautionary.
    Several aspects of the planned monitoring and mitigation measures 
for this project are designed to detect marine mammals occurring near 
the airguns, and to avoid exposing them to sound pulses that could 
potentially cause hearing impairment. In addition, many cetaceans are 
likely to show some avoidance of the area with high received levels of 
airgun sound. In those cases, the avoidance responses of the animals 
themselves will reduce or (most likely) avoid any possibility of 
hearing impairment.
    Non-auditory physical effects might also occur in marine mammals 
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that theoretically might 
occur in mammals close to a strong sound source include stress, 
neurological effects, bubble formation, 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 
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, permanent threshold shift (PTS), and non-auditory physical 
effects.
Temporary Threshold Shift (TTS)
    TTS is the mildest form of hearing impairment that can occur during 
exposure to a strong sound (Kryter, 1985). While experiencing TTS, the 
hearing threshold rises and a sound must be stronger in order to be 
heard. TTS can last from minutes or hours to (in cases of strong TTS) 
days. For sound exposures at or somewhat above the TTS threshold, 
hearing sensitivity recovers rapidly after exposure to the noise ends. 
Few data on sound levels and durations necessary to elicit mild TTS 
have been obtained for marine mammals, and none of the published data 
concern TTS elicited by exposure to multiple pulses of sound.
    For toothed whales exposed to single short pulses, the TTS 
threshold appears to be, to a first approximation, a function of the 
energy content of the pulse (Finneran et al., 2002, 2005). Sound 
exposure level (SEL), which takes into account the duration of the 
sound, is the metric used to measure energy and uses the units dB re 1 
microPa2 . s, as opposed to sound pressure level (SPL), which is the 
pressure metric used in the rest of this document (units - dB re 1 
microPa). Given the available data, the received energy level of a 
single seismic pulse might need to be approximately 186 dB re 1 
microPa\2\ . s (i.e., 186 dB SEL or approximately 221-226 dB pk-pk) in 
order to produce brief, mild TTS. Exposure to several strong seismic 
pulses at 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 
distances from the Langseth's airguns at which the received energy 
level would be expected to be 175 dB SEL are the distances shown in the 
190 dB rms column in Table 2 (given that the rms level is approximately 
15 dB higher than the SEL value for the same pulse). In deep water, 
where L DEO's model is directly applicable, seismic pulses with 
received energy levels 175 dB SEL (190 dB rms) are expected to be 
restricted to radii no more than 200-620 m (656-2034 ft)

[[Page 58798]]

around the airguns. The specific radius would depend on number of 
operating airguns (9-36) and their operating depth (6 vs. 12 m). The 
depth associated with the above radii ranges from about 125 m (410 ft) 
for a 9-airgun array to =500 m (=1640 ft) for the 36-airgun array. For 
an odontocete closer to the surface, the maximum radius with 175 dB SEL 
or 190 dB rms would be smaller. In intermediate-depth and shallow 
water, the 175 dB SEL or 190 dB rms radius would be larger.
    For baleen whales, there are no data, direct or indirect, on levels 
or properties of sound that are required to induce TTS. However, no 
cases of TTS are expected given two considerations: (1) the low 
abundance of baleen whales in the planned study area, and (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.
    In pinnipeds, TTS thresholds associated with exposure to brief 
pulses (single or multiple) of underwater sound have not been measured. 
Initial evidence from prolonged exposures suggested that some pinnipeds 
may incur TTS at somewhat lower received levels than do small 
odontocetes exposed for similar durations (Kastak et al., 1999; Ketten 
et al., 2001; cf. Au et al., 2000). However, pinnipeds are not expected 
to occur in or near the planned study area.
Permanent Threshold Shift (PTS)
    When PTS occurs, there is physical damage to the sound receptors in 
the ear. In some cases, there can be total or partial deafness, whereas 
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.
    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. 
The planned monitoring and mitigation measures, including visual 
monitoring, PAM, power-downs, and shut downs of the airguns when 
mammals are seen within the ``safety radii'', will minimize the 
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, and other types 
of organ or tissue damage. However, studies examining such effects are 
very limited. If any such effects do occur, they probably would 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 sufficiently long 
that significant physiological stress would develop.
    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, the 
opinions were inconclusive. Jepson et al. (2003) first suggested a 
possible link between mid-frequency sonar activity and acute and 
chronic tissue damage that results from the formation in vivo of gas 
bubbles, based on the beaked whale stranding in the Canary Islands in 
2002 during naval exercises. Fernandez et al. (2005a) showed those 
beaked whales did indeed have gas bubble-associated lesions as well as 
fat embolisms. Fernandez et al. (2005b) also found evidence of fat 
embolism in three beaked whales that stranded 100 km (54 nm) north of 
the Canaries in 2004 during naval exercises. Examinations of several 
other stranded species have also revealed evidence of gas and fat 
embolisms (e.g., Arbelo et al., 2005; Jepson et al., 2005a; Mendez et 
al., 2005). Most of the afflicted species were deep divers. There is 
speculation that gas and fat embolisms may occur if cetaceans ascend 
unusually quickly when exposed to aversive sounds, or if sound in the 
environment causes the destabilization of existing bubble nuclei 
(Potter, 2004; Arbelo et al., 2005; Fernandez et al., 2005a; Jepson et 
al., 2005b). Even if gas and fat embolisms can occur during exposure to 
mid-frequency sonar, there is no evidence that that type of effect 
occurs in response to airgun sounds.
    In general, little is known about the potential for seismic survey 
sounds to cause auditory impairment or other physical effects in marine 
mammals. Available data suggest that such effects, if they occur at 
all, would be limited to short distances and probably to projects 
involving large arrays of airguns. However, the available data do not 
allow for meaningful quantitative predictions of the numbers (if any) 
of marine mammals that might be affected in those ways. Marine mammals 
that show behavioral avoidance of seismic vessels, including most 
baleen whales and some odontocetes, are especially unlikely to incur 
auditory impairment or other physical effects. Also, the planned 
monitoring and mitigation measures include shut downs of the airguns, 
which will reduce any such effects that might otherwise occur.

Strandings and Mortality

    Marine mammals close to underwater detonations of high explosive 
can be killed or severely injured, and the auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). 
Airgun pulses are less energetic and have slower rise times, and there 
is no proof that they can cause serious injury, death, or stranding 
even in the case of large airgun arrays. However, the association of 
mass strandings of beaked whales with naval exercises 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

[[Page 58799]]

surveys on marine mammals. However, evidence that sonar pulses can, in 
special circumstances, lead to physical damage and mortality (NOAA and 
USN 2001; Jepson et al., 2003; Fernandez et al., 2005a), even if only 
indirectly, suggests that caution is warranted when dealing with 
exposure of marine mammals to any high-intensity pulsed sound.
    In May 1996, 12 Cuvier's beaked whales stranded along the coasts of 
Kyparissiakos Gulf in the Mediterranean Sea. That stranding was 
subsequently linked to the use of low- and medium-frequency active 
sonar by a North Atlantic Treaty Organization (NATO) research vessel in 
the region (Frantzis 1998). In March 2000, a population of Cuvier's 
beaked whales being studied in the Bahamas disappeared after a U.S. 
Navy task force using mid-frequency tactical sonars passed through the 
area; some beaked whales stranded (Balcomb and Claridge, 2001; NOAA and 
USN 2001). In September 2002, a total of 14 beaked whales of various 
species stranded coincident with naval exercises in the Canary Islands 
(Martel n.d.; Jepson et al., 2003; Fernandez et al., 2004). Some 
additional related incidents have also been reported, e.g., Southall et 
al. (2006).
    Also in Sept. 2002, there was a stranding of two Cuvier's beaked 
whales in the Gulf of California, Mexico, when the L-DEO vessel Maurice 
Ewing was operating a 20 airgun, 8490 in3 airgun array in the general 
area. The link between the stranding and the seismic surveys was 
inconclusive and not based on any physical evidence (Hogarth, 2002; 
Yoder, 2002). Nonetheless, that 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, 
due to the proposed monitoring and mitigation measures.

Possible Effects of Multibeam Bathymetric (MBB) Sonar Signals

    The Simrad EM120 12-kHz sonar will be operated from the source 
vessel at some times during the planned study. Sounds from the MBB 
sonar are very short pulses, occurring for 15 ms once every 5 to 20 s, 
depending on water depth. Most of the energy in the sound pulses 
emitted by this MBB sonar is at frequencies centered at 12 kHz. The 
beam is narrow (1[deg]) in fore-aft extent and wide (150[deg]) in the 
cross-track extent. Each ping consists of nine successive fan-shaped 
transmissions (segments) at different cross-track angles. Any given 
mammal at depth near the trackline would be in the main beam for only 
one or two of the nine segments. Also, marine mammals that encounter 
the Simrad EM120 are unlikely to be subjected to repeated pulses 
because of the narrow fore-aft width of the beam and will receive only 
limited amounts of pulse energy because of the short pulses. Animals 
close to the ship (where the beam is narrowest) are especially unlikely 
to be ensonified for more than one 15 ms pulse (or two pulses if in the 
overlap area). Similarly, Kremser et al. (2005) noted that the 
probability of a cetacean swimming through the area of exposure when an 
MBB sonar emits a pulse is small. The animal would have to pass the 
transducer at close range and be swimming at speeds similar to the 
vessel in order to be subjected to sound levels that could cause TTS.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans (1) generally have a longer pulse duration than 
the Simrad EM120, and (2) are often directed close to horizontally vs. 
downward for the Simrad EM120. The area of possible influence of the 
Simrad EM120 is much smaller-a narrow band below the source vessel. The 
duration of exposure for a given marine mammal can be much longer for a 
Navy sonar.
    Because of the unlikelihood of an animal being exposed to more than 
one or two pulses and the low energy the animal would most likely be 
exposed to due to the short pulses, NMFS does not expect the operation 
of the MBB sonar to result in the harassment of any marine mammals.

Proposed Monitoring and Mitigation Measures

Monitoring

    L-DEO proposes to sponsor marine mammal monitoring of its seismic 
program, in order to implement the planned mitigation measures and to 
satisfy the requirements of the IHA. The monitoring work described here 
has been planned as a self-contained project independent of any other 
related monitoring projects that may be occurring simultaneously in the 
same regions. L-DEO is prepared to discuss coordination of its 
monitoring program with any related work that might be done by other 
groups insofar as this is practical and desirable.
Vessel Based Monitoring
    Vessel-based marine mammal observers (MMOs) will watch for marine 
mammals and turtles near the seismic source vessel during all daytime 
airgun operations and during any start ups of the airguns at night. 
Airgun operations will be suspended when marine mammals or turtles are 
observed within, or about to enter, designated safety radii where there 
is concern about effects on hearing or other physical effects. MMOs 
also will watch for marine mammals and turtles near the seismic vessel 
for at least 30 min prior to the planned start of airgun operations 
after an extended shut down of the airguns. When feasible, observations 
will also be made during daytime periods without seismic operations 
(e.g., during transits).
    During seismic operations in the Gulf of Mexico, five observers 
will be based aboard the vessel. MMOs will be appointed by L-DEO with 
NMFS concurrence. At least one MMO, and when practical two MMOs, will 
watch for marine mammals and turtles near the seismic vessel during 
ongoing daytime operations and nighttime start ups of the airguns. Use 
of two simultaneous observers will increase the proportion of the 
animals present near the source vessel that are detected. MMO(s) will 
be on duty in shifts of duration no longer than 4 h. The crew will also 
be instructed to assist in detecting marine mammals and turtles and 
implementing mitigation requirements (if practical). Before the start 
of the seismic survey the crew will be given additional instruction in 
how to do so.
    The Langseth is a suitable platform for marine mammal and turtle 
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. However, 
neither the actual bow of the vessel nor the stern will be visible from 
the observation platform, although it will be possible to see the 
airguns. To monitor the areas immediately at the bow and stern of the 
vessel, two video cameras will be installed at the bow (one on the 
starboard and one on the port side), and a wide-angle camera will be 
installed at the stern. Real-time footage from these cameras will be 
played on the observation platform, so that the MMO(s) are able to 
monitor those areas. In addition a high-power video camera will be 
mounted on the observation platform to assist with species 
identification.
    During daytime, the MMO(s) will scan the area around the vessel 
systematically with reticle binoculars (e.g., 7 50 Fujinon), Big-eye 
binoculars (25 150), and with the naked eye. At night, Night Vision 
Devices (NVDs) will be available (ITT F500 Series Generation 3 
binocular-image intensifier or equivalent), when required. Laser

[[Page 58800]]

rangefinding binoculars (Leica LRF 1200 laser rangefinder or 
equivalent) will be available to assist with distance estimation. Those 
are useful in training observers to estimate distances visually, but 
are generally not useful in measuring distances to animals directly. 
MMOs will not be on duty during ongoing seismic operations at night. At 
night, bridge personnel will watch for marine mammals and turtles 
(insofar as practical at night) and will call for the airguns to be 
shut down if marine mammals or turtles are observed in or about to 
enter the safety radii. If the airguns are started up at night, two 
MMOs will watch for marine mammals and turtles near the source vessel 
for 30 min prior to start up of the airguns using NVDs, if the proper 
conditions for nighttime start up exist (see Mitigation below).
    The vessel-based monitoring will provide data to estimate the 
numbers of marine mammals exposed to various received sound levels, to 
document any apparent disturbance reactions or lack thereof, and thus 
to estimate the numbers of mammals potentially ``taken'' by harassment. 
It will also provide the information needed in order to power down or 
shut down the airguns at times when mammals and turtles are present in 
or near the safety radii. 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, sea 
state, visibility, and sun glare.
    The data listed under (2) will also be recorded at the start and 
end of each observation watch, and during a watch whenever there is a 
change in one or more of the variables.
    All observations and power-downs or shut downs will be recorded in 
a standardized format. Data will be entered into a custom database 
using a notebook computer. The accuracy of the data entry will be 
verified by computerized validity data checks as the data are entered 
and by subsequent manual checking of the database. These procedures 
will allow initial summaries of data to be prepared during and shortly 
after the field program, and will facilitate transfer of the data to 
statistical, graphical, or other programs for further processing and 
archiving.
    Results from the vessel-based observations will provide:
    1. The basis for real-time mitigation (airgun power-down or shut 
down).
    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 and turtles in the area where the seismic study is conducted.
    4. Information to compare the distance and distribution of marine 
mammals and turtles relative to the source vessel at times with and 
without seismic activity.
    5. Data on the behavior and movement patterns of marine mammals and 
turtles seen at times with and without seismic activity.
Passive Acoustic Monitoring
    Passive acoustic monitoring will take place to complement the 
visual monitoring program. Visual monitoring typically is less 
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. Acoustical monitoring can be used in 
addition to visual observations to improve detection, identification, 
localization, and tracking of cetaceans. The acoustic monitoring will 
serve to alert visual observers when vocalizing cetaceans are detected. 
It will be monitored in real time so that the visual observers can be 
advised when cetaceans are detected.
    SEAMAP (Houston, TX) will be used as the primary acoustic 
monitoring system. This system was also used during previous L-DEO 
seismic cruises (e.g., Smultea et al., 2004, 2005; Holst et al., 
2004a,b). The PAM system consists of hardware (i.e., the hydrophone) 
and software. The ``wet end'' of the SEAMAP system consists of a low-
noise, towed hydrophone array that is connected to the vessel by a 
``hairy'' faired cable. The array will be deployed from a winch located 
on the back deck. A deck cable will connect from the winch to the main 
computer lab where the acoustic station and signal conditioning and 
processing system will be located. The lead-in from the hydrophone 
array is approximately 400 m (1312 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 of less than 20 m or 66 ft.
    The acoustical array will be monitored 24 hour per day while at the 
seismic survey area during airgun operations and during most periods 
when airguns are not operating. One MMO will monitor the acoustic 
detection system at any one time, by listening to the signals from two 
channels via headphones and/or speakers and watching the real-time 
spectrographic display for frequency ranges produced by cetaceans. MMOs 
monitoring the acoustical data will be on shift from 1-6 h. All MMOs 
are expected to rotate through the PAM position, although the most 
experienced with acoustics will be on PAM duty more frequently.
    When a vocalization is detected, the acoustic MMO will contact the 
visual MMO immediately (so a power-down or shut down can be initiated, 
if required), and 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, 
GMT date, GMT time when first and last heard and whenever any 
additional information was recorded, GPS position and water depth when 
first detected, 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 onto the hard-drive for further 
analysis.

Mitigation

    For the proposed study in the northern Gulf of Mexico, L-DEO will 
deploy an energy source of up to 36 airguns (6600 in\3\). The airguns 
comprising the array will be spread out horizontally, so that the 
energy will be directed mostly downward. The directional nature of the 
array to be used in this project is an important mitigating factor. 
This directionality will result in reduced sound levels at any given 
horizontal distance than would be expected at that distance if the 
source were omnidirectional with the stated nominal source level.
    Localized and temporally-variable areas of concentrated feeding or 
of special significance for marine mammals may occur within or near the 
planned area of operations during the season of operations. However, L-
DEO will avoid conducting the proposed activities near important 
concentrations of marine mammals insofar as these can be identified in 
advance from other sources of information, or during the cruise.
Safety Radii
    As noted earlier (Table 2), received sound levels were modeled by 
L-DEO

[[Page 58801]]

for various configurations of the 36-airgun array in relation to 
distance and direction from the airguns, and for a single and 2 GI 
guns. Correction factors based on empirical measurements were applied 
to estimate safety radii in shallow and intermediate-depth water. The 
distances from the airguns where sound levels of 190, 180, and 160 dB 
re 1 microPa (rms) are estimated to be received are shown Table 2. 
Also, the safety radii for a single (40 in3) airgun are given, as that 
source will be in operation when the 36-airgun array is powered down. 
Airguns will be powered down (or shut down if necessary) immediately 
when marine mammals or turtles are detected within or about to enter 
the appropriate radius: 180 dB (rms) for cetaceans and turtles, and 190 
dB (rms) for pinnipeds, in the very unlikely event that pinnipeds are 
encountered.
Mitigation During Operations
    Mitigation measures that will be required will include (1) speed or 
course alteration, provided that doing so will not compromise 
operational safety requirements, (2) power-down procedures, (3) shut-
down procedures, (4) special shut-down procedures for any endangered 
baleen whales, (5) ramp-up procedures, (6) avoidance of areas with 
concentrations of marine mammal, and (7) shut down and notification of 
NMFS if an injured or dead marine mammal is found and is judged likely 
to have resulted from the operation of the airguns.
    Speed or Course Alteration - If a marine mammal or sea turtle is 
detected outside the safety radius and, based on its position and the 
relative motion, is likely to enter the safety radius, the vessel's 
speed and/or direct course may be changed. This would be done if 
practicable while minimizing the effect to the planned science 
objectives. The activities and movements of the marine mammal or sea 
turtle (relative to the seismic vessel) will be closely monitored to 
determine whether the animal is approaching the applicable safety 
radius. If the animal appears likely to enter the safety radius, 
further mitigative actions will be taken, i.e., either further course 
alterations or a power-down or shut down of the airguns.
    Power-down Procedures - A power-down involves decreasing the number 
of airguns in use such that the radius of the 180-dB (or 190-dB) zone 
is decreased to the extent that marine mammals or turtles are no longer 
in or about to enter the safety zone. A power-down may also occur when 
the vessel is moving from one seismic line to another (i.e., during a 
turn). During a power-down, one airgun will be operated. The continued 
operation of one airgun is intended to alert marine mammals and turtles 
to the presence of the seismic vessel in the area. In contrast, a shut 
down occurs when all airgun activity is suspended.
    If a marine mammal or turtle is detected outside the safety zone 
but is likely to enter the safety radius, and if the vessel's speed 
and/or course cannot be changed to avoid having the animal enter the 
safety radius, the airguns will be powered down before the animal is 
within the safety radius. Likewise, if a mammal or turtle is already 
within the safety zone when first detected, the airguns will be powered 
down immediately. During a power-down of the airgun array, at least one 
airgun (e.g., 40 in\3\) will be operated. If a marine mammal or turtle 
is detected within or near the smaller safety radius around that single 
airgun (Table 2), all airguns will be shut down (see next subsection).
    Following a power-down, airgun activity will not resume until the 
marine mammal or turtle has cleared the safety zone. The animal will be 
considered to have cleared the safety zone if it: (1) is visually 
observed to have left the safety zone; or, (2) has not been seen within 
the zone for 15 min in the case of small odontocetes and pinnipeds; or, 
(3) has not been seen within the zone for 30 min in the case of 
mysticetes and large odontocetes, including sperm, pygmy sperm, dwarf 
sperm, and beaked whales; or, (4) the vessel has moved outside the 
safety zone for turtles.
    During airgun operations following a power-down whose duration has 
exceeded specified limits, the airgun array will be ramped up 
gradually. Ramp-up procedures are described below.
    Shut-down Procedures - During a power-down, the operating airgun 
will be shut down if a marine mammal or turtle approaches within the 
modeled safety radius for the then-operating source, typically a single 
40 in\3\ gun or a GI gun (Table 2). If a marine mammal or turtle is 
detected within or about to enter the appropriate safety radius around 
the small source in use during a power-down, airgun operations will be 
entirely shut down.
    Airgun activity will not resume until the animal has cleared the 
safety zone, or until the MMO is confident that the marine mammal or 
turtle has left the vicinity of the vessel. Criteria for judging that 
the animal has cleared the safety zone will be as described in the 
preceding subsection.
    Special Shut-down Provision for Highly Endangered Mysticetes - The 
airguns will be shut down (not just powered down) if an endangered 
mysticete is sighted anywhere near the vessel, even if the whale is 
located outside the safety radius. In this cruise, this provision would 
apply in the unlikely event of sighting any of the following whales: 
the North Atlantic right whale; the humpback whale; the sei whale; the 
fin whale; or the blue whale. This measure is planned because of the 
assumed greater effects of seismic surveys on mysticetes in general (as 
compared with other marine mammals).
    Ramp-up Procedures - A ramp-up procedure will be followed when the 
airgun array begins operating after a specified-duration without airgun 
operations. It is proposed that, for the present cruise, this period 
would be approximately 10 min. This duration is based on provisions 
during previous L-DEO surveys and on the approximately 180-dB radius 
for the 4-string array in deep water in relation to the planned speed 
of the Langseth while shooting. Ramp up will begin with the smallest 
gun in the array. Airguns will be added in a sequence such that the 
source level of the array will increase in steps not exceeding 
approximately 6 dB per 5-min period over a total duration of 20-30 min. 
During ramp up, the safety zone for the full airgun array to be used 
will be maintained.
    If the complete safety radius has not been visible for at least 30 
min prior to the start of operations in either daylight or nighttime, 
ramp up will not commence unless at least one airgun has been operating 
during the interruption of seismic survey operations. That airgun will 
have a source level of more than 180 dB re 1 microPa . m (rms). It is 
likely that the airgun array will not be ramped up from a complete shut 
down at night or in thick fog (the array will definitely not be ramped 
up from a complete shut down at night in shallow water), because the 
outer part of the safety zone for the array will not be visible during 
those conditions. If one airgun has operated during a power-down 
period, ramp up to full power will be permissible at night or in poor 
visibility, 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 sea turtle or marine mammal is sighted within or near 
the applicable safety radii during the day or close to the vessel at 
night.
    Avoidance of Areas with Concentrations of Marine Mammals - Beaked 
whales may be highly sensitive to sounds produced by airguns, based 
mainly on what is known about their

[[Page 58802]]

responses to other sound sources. Beaked whales tend to concentrate in 
continental slope areas, and especially in areas where there are 
submarine canyons on the slope. Therefore, L DEO will, if possible, 
avoid airgun operations over or near submarine canyons within the 
present study area. Also, if concentrations of beaked whales are 
observed at the slope site just prior to or during the airgun 
operations there, those operations will be moved to another location 
along the slope based on recommendations by the lead MMO aboard the 
Langseth. Furthermore, any areas where concentrations of sperm whales 
are known to be present will be avoided if possible.
    Shutdown if Injured or Dead Whale is Found - In the unanticipated 
event that any cases of marine mammal injury or mortality are found and 
are judged likely to have resulted from these activities, L-DEO will 
cease operating seismic airguns and report the incident to the Office 
of Protected Resources, NMFS immediately.

Reporting

    L-DEO will provide brief field reports on the progress of the 
project on a weekly basis.
    A report will be submitted to NMFS within 90 days after the end of 
the cruise. The report will describe the operations that were conducted 
and the marine mammals and turtles that were detected near the 
operations. The report will be submitted to NMFS, providing full 
documentation of methods, results, and interpretation pertaining to all 
monitoring. The 90-day report will summarize the dates and locations of 
seismic operations, and all marine mammal and turtle sightings (dates, 
times, locations, activities, associated seismic survey activities). 
The report will also include estimates of the amount and nature of 
potential ``take'' of marine mammals by harassment or in other ways.

Estimated Take by Incidental Harassment

    Because of the mitigation measures that will be required and the 
likelihood that some cetaceans will avoid the area around the operating 
airguns of their own accord, NMFS does not expect any marine mammals to 
approach the sound source close enough to be injured (Level A 
harassment). All anticipated takes would be ``takes by Level B 
harassment'', as described previously, involving temporary behavioral 
modifications or low level physiological effects.
    Estimates of the numbers of marine mammals that might be affected 
during the proposed seismic program in the northern Gulf of Mexico are 
based on consideration of the number of marine mammals that might be 
disturbed appreciably by approximately 1420 km (767 nm) of seismic 
surveys during the Gulf of Mexico program. The numbers of animals 
estimated below do not take into consideration the implementation of 
mitigation measures and, therefore, probably overestimate the take to 
some degree. These estimates are calculated using density estimates of 
marine mammals and the total area around the source vessel that is 
ensonified to 160 dB or more (based on the calculated safety radii, 
discussed previously), the received sound level at which NMFS estimates 
marine mammals are behaviorally disturbed to an extent that rises to 
Level B Harassment. The basis for estimating the densities of marine 
mammals in the proposed study area is discussed in section VII of L-
DEO's application and the estimates are listed in Table 3, in the same 
section.
    The potential number of different individuals that might be exposed 
to received levels 160 dB re 1 microPa (rms) was calculated for each of 
the three water depth categories (<100 m or <328 ft, 100-1000 m or 328-
3281 ft, and >1000 m or >3281 ft) 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 during operations with each airgun array to be used in each 
water depth category.
    The area expected to be ensonified was determined by entering the 
planned survey lines (including turns) 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 the water depth and array to be used), and then 
calculating the total area within the buffers. Areas where overlap 
occurred (due to closely spaced survey lines or repeat passes) were 
included only once to determine the minimum area expected to be 
ensonified.
    Due to the spiral pattern of the calibration survey, and the fact 
that shots from each of the three subsets (1-string, 2-string, and 4-
string) of the 36-airgun array will be fired in sequence 30 s apart, 
the 4-string array was used for area calculations during the 
calibration phase; the GI guns were considered separately. For the 
seismic testing survey, the three different airgun configurations that 
will operate (single 40 in\3\ airgun; 2-string and 4-string array) were 
used to determine the area ensonified. The area for both of those 
phases was then summed, and a contingency factor of 15 percent was 
added, because of the initial seismic testing/shakedown phase, for 
which line-km effort is unknown at this time.
    For the maximum estimates for oceanic species, the reported maximum 
densities were assumed to occur in intermediate and deep waters, and a 
density of zero was assumed for shallow waters. For species occurring 
in shallow water (as shown in Table 3), the maximum reported densities 
were used for intermediate and deep waters, whereas 2x the mean density 
was used for shallow water.
    Applying the approach described above, approximately 9045 km\2\ 
would be within the 160 dB isopleth on one or more occasions. However, 
this approach does not allow for turnover in the mammal populations in 
the study area during the course of the study. This might somewhat 
underestimate actual numbers of individuals exposed, although the 
conservative distances used to calculate the area may offset this. In 
addition, the approach assumes that no cetaceans move away or toward in 
response to increasing sound levels prior to the time the levels reach 
160 dB. Another way of interpreting the estimates that follow is that 
they represent the number of individuals that are expected (in the 
absence of a seismic program) to occur in the waters that will be 
exposed to 160 dB re 1 microPa (rms).
    To determine the mean number of times an individual might be 
exposed during the survey, the maximum area ensonified by sounds 160 dB 
during the survey was used. This area was determined by GIS, as 
described above, but instead of including all overlapping areas only 
once, the overlapping segments and areas with repeat coverage were 
added together. This maximum area was then multiplied by the 
appropriate species densities to determine the total number of 
exposures during the survey. The total number of exposures to sound 
levels 160 dB was then divided by the total number of individuals for 
each species. The mean number of times an individual may be exposed to 
levels 160 dB during the survey range from 3x (for two shallow-water 
species) to 4x.
    The ``best estimate'' of the number of individual marine mammals 
that might be exposed, absent any mitigation measures, to seismic 
sounds with received levels 160 dB re 1 microPa (rms) is 3770 (Table 
3). That total includes 22 endangered sperm whales, 25 beaked whales, 
and one Bryde's whale (Table 3). Pantropical spotted dolphins, Atlantic 
spotted dolphins, and bottlenose dolphins are expected to be

[[Page 58803]]

the most common species in the study area; the best estimates for those 
species, absent any mitigation, are 1282, 876, and 773, respectively 
(Table 3). Estimates for other species are lower.
    The ``Maximum Estimate'' column in Table 3 shows estimates totaling 
7082 individual marine mammals based on maximum densities, and taking 
into account an adjustment for small numbers of other species that 
might be encountered in the survey area, even though there were not 
recorded during previous surveys. These are the numbers for which 
``take authorization'' is requested. NMFS does not expect the total 
number of marine mammal takes to be this high, however, it is 
appropriate to err on the cautious side to ensure that L-DEO is covered 
in the event that an unexpectedly large number of any particular 
species were exposed to >160 dB during the survey and, further, to 
ensure that this exposure would result in a negligible impact to the 
species or stock.
    Based on numbers of animals encountered during L-DEO's 2003 cruise 
in the Gulf of Mexico, the likelihood of the successful implementation 
of the required mitigation measure, and the likelihood that some 
animals will avoid the area around the operating airguns, NMFS believes 
that L-DEOs airgun calibration and seismic testing program may result 
in the Level B harassment of some lower number of individual marine 
mammals than is indicated by the ``best estimates'' in Table 3. These 
best estimates compose no more than 3.9 percent of any given species 
population in the northern Gulf of Mexico, and NMFS has preliminarily 
determined that these numbers are small relative to the population 
sizes in the specified geographic area (Table 3). L-DEO has asked for 
authorization for take of their ``maximum estimate'' of numbers for 
each species, which includes the take of two hooded seals. Though NMFS 
believes that take of the maximum numbers is unlikely, we still find 
these numbers small (up to 8.3 percent of the Fraser's dolphin 
population and 7.7 percent of the spinner dolphin population, but less 
than 5 percent the others) relative to the population sizes.

Potential Effects on Habitat

    The proposed airgun operations will not result in any permanent 
impact on habitats used by marine mammals or to the food sources they 
utilize. The main impact issue associated with the proposed activity 
will be temporarily elevated noise levels and the associated direct 
effects on marine mammals.
    The actual area contacted temporarily by the bottom-moored 
hydrophone array will be an insignificant and very small fraction of 
the marine mammal habitat and the habitat of their food species in the 
area. The use of this equipment would result in no more than a 
negligible and highly localized short-term disturbance to sediments and 
benthic organisms. The area that might be disturbed is a very small 
fraction of the overall area.
    One of the reasons for the adoption of airguns as the standard 
energy source for marine seismic surveys was that, unlike explosives, 
they do not result in any appreciable fish kill. However, the existing 
body of information relating to the impacts of seismic on marine fish 
and invertebrate species is very limited. The 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).
    The available information on the impacts of seismic surveys on 
marine fish and invertebrates provides limited insight on the effects 
only at the individual level. Ultimately, the most important knowledge 
in this area relates to how significantly seismic affects animal 
populations. However, the few available data suggest that there may be 
physical impacts on eggs and on larval, juvenile, and adult stages at 
very close range. Considering typical source levels associated with 
airgun arrays, close proximity to the source would result in exposure 
to high energy levels. Whereas egg and larval stages are not able to 
escape such exposures, juveniles and adults most likely would avoid 
them. In the cases of eggs and larvae, it is likely that the numbers 
adversely affected by such exposure would be small in relation to 
natural mortality. The 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.
    Exposure to seismic surveys may else cause changes in the 
distribution, migration patterns, and catchability of fish. 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 the sound source. There is a need for more information 
on exactly what effects seismic sounds might have on the detailed 
behavior patterns of fish and invertebrates at different ranges.
    During the proposed study, only a small fraction of the available 
habitat would be ensonified at any given time, and fish and 
invertebrate species would be expected to return to their pre-
disturbance behavior once the seismic activity ceased. The proposed 
seismic survey is predicted to have negligible to low physical and 
behavioral effects on the various life stages of fish and 
invertebrates, because of its short duration and 1420 km (767 nm) 
extent. More detailed information on studies of potential impacts of 
sounds on fish and invertebrates is provided in Appendix D of L-DEO's 
application.
    The effects of the planned activity on marine mammal habitats and 
food resources are expected to be negligible, as described above. A 
small minority of the marine mammals that are present near the proposed 
activity may be temporarily displaced as much as a few kilometers by 
the planned activity. Areas with concentrations of marine mammals will 
be avoided when specific study sites are selected immediately before 
the start of acoustic measurement activities in deep, intermediate, and 
shallow regions. In this manner, any major feeding area that might 
occur in the general vicinity of the project will be avoided. 
Therefore, the proposed activity is not expected to have any habitat-
related effects that could cause significant or long-term consequences 
for individual marine mammals or their populations.

Negligible Impact Determination

    NMFS has preliminarily determined, provided that the aforementioned 
mitigation and monitoring measures are

[[Page 58804]]

implemented, that the impact of conducting an acoustic calibration and 
seismic testing program in the Gulf of Mexico may result, at worst, in 
a temporary modification in behavior and/or low-level physiological 
effects (Level B Harassment) of small numbers of certain species of 
marine mammals. While behavioral and avoidance reactions may be made by 
these species in response to the resultant noise from the airguns, 
these behavioral changes are expected to have a negligible impact on 
the affected species and stocks of marine mammals.
    While the number of potential incidental harassment takes will 
depend on the distribution and abundance of marine mammals in the area 
of seismic operations, the number of potential harassment takings is 
estimated to be relatively small in light of the population size (see 
Table 3). NMFS anticipates the actual take of individuals to be lower 
than the numbers depicted in the table, because those numbers do not 
reflect either the implementation of the mitigation numbers or the fact 
that some animals will avoid the sound at levels lower than those 
expected to result in harassment. Additionally, mitigation measures 
requires that the Langseth avoid any areas where marine mammals are 
concentrated.
    In addition, no take by death and/or serious injury is anticipated, 
and the potential for temporary or permanent hearing impairment will be 
avoided through the incorporation of the required mitigation measures 
described in this document. This determination is supported by (1) the 
likelihood that, given sufficient notice through slow ship speed and 
ramp-up of the seismic array, marine mammals are expected to move away 
from a noise source that it is annoying prior to its becoming 
potentially injurious; (2) TTS is unlikely to occur, especially in 
odontocetes, until levels above 180 dB re 1 microPa are reached; (3) 
the fact that injurious levels of sound are only likely very close to 
the vessel; and (4) the likelihood that marine mammal detection ability 
by trained observers is close to 100 percent during daytime (in good 
weather) and remains high at night close to the vessel.

Endangered Species Act

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

National Environmental Policy Act (NEPA)

    In 2003, NSF prepared an Environmental Assessment (EA) for a marine 
seismic survey by the R/V Maurice Ewing in the Northern Gulf of Mexico. 
This EA addressed the potential effects of a different combination of 
airgun arrays, but with a higher total output (20 airguns, total volume 
8580 in3) being operated in the same part of the ocean as is proposed 
for the Langseth in this application. NMFS will either adopt NSF's EA 
or prepare its own supplemental NEPA document before making a 
determination on the issuance of an IHA. NSF's EA has been posted on 
NMFS' website.

Preliminary Conclusions

    Based on the preceding information, and provided that the proposed 
mitigation and monitoring are incorporated, NMFS has preliminarily 
concluded that the proposed activity will incidentally take, by Level B 
harassment only, small numbers of marine mammals. NMFS has further 
preliminarily determined that the proposed activity will have a 
negligible impact on the affected species or stocks of marine mammals.

Proposed Authorization

    NMFS proposes to issue an IHA to L-DEO for an acoustic calibration 
and seismic testing program in the northern Gulf of Mexico in Fall, 
2006 provided the previously mentioned mitigation, monitoring, and 
reporting requirements are incorporated.

    Dated: September 27, 2006.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. E6-16412 Filed 10-4-06; 8:45 am]
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