58396 Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 

proposed collection of information; (c) 

ways to enhance the quality, utility, and 

clarity of the information to be 

collected; and (d) ways to minimize the 

burden of the collection of information 

on respondents, including through the 

use of automated collection techniques 

or other forms of information 

technology.

Comments submitted in response to 

this notice will be summarized and/or 

included in the request for OMB 

approval of this information collection; 

they also will become a matter of public 

record.

Dated: September 22, 2004.

Gwellnar Banks,

Management Analyst, Office of the Chief 

Information Officer.

[FR Doc. 04–21971 Filed 9–29–04; 8:45 am]

BILLING CODE 3510–22–S

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric 

Administration

[I.D. 070104A]

Small Takes of Marine Mammals 

Incidental to Specified Activities; 

Marine Seismic Survey in the Eastern 

Tropical Pacific Ocean off Central 

America

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce.

ACTION: Notice of receipt of application 

and proposed incidental take 

authorization; request for comments.

SUMMARY: NMFS has received an 

application from the Lamont-Doherty 

Earth Observatory (L-DEO), a part of 

Columbia University, for an Incidental 

Harassment Authorization (IHA) to take 

small numbers of marine mammals, by 

harassment, incidental to conducting 

oceanographic seismic surveys in the 

eastern tropical Pacific Ocean (ETPO) 

off Central America. Under the Marine 

Mammal Protection Act (MMPA), NMFS 

is requesting comments on its proposal 

to issue an authorization to L-DEO to 

incidentally take, by harassment, small 

numbers of several species of cetaceans 

and pinnipeds for a limited period of 

time within the next year.

DATES: Comments and information must 

be received no later than November 1, 

2004.

ADDRESSES: Comments on the 

application should be addressed to 

Steve Leathery, Chief, Permits, 

Conservation and Education Division, 

Office of Protected Resources, National 

Marine Fisheries Service, 1315 EastWest Highway, Silver Spring, MD 

20910–3225, or by telephoning the 

contact listed here. The mailbox address 

for providing email comments is 

PR1.070104A@noaa.gov. Include in the 

subject line of the e-mail comment the 

following document identifier: 

070104A. NMFS is not responsible for email 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 this address or 

by telephoning the contact listed here 

and is also available at: http://www.

nmfs.noaa.gov/protlres/PR2/

SmalllTake/smalltakelinfo.

htm#applications.

FOR FURTHER INFORMATION CONTACT:

Kenneth Hollingshead, Office of 

Protected Resources, NMFS, (301) 713–

2322, ext 128.

SUPPLEMENTARY INFORMATION:

Background

Sections 101(a)(5)(A) and (D) of the 

MMPA (16 U.S.C. 1361 et seq.) direct 

the Secretary of Commerce to allow, 

upon request, the incidental, but not 

intentional, taking of marine mammals 

by U.S. citizens who engage in a 

specified activity (other than 

commercial fishing) within a specified 

geographical region if certain findings 

are made and either regulations are 

issued or, if the taking is limited to 

harassment, a notice of a proposed 

authorization is provided to the public 

for review.

Permission may be granted if NMFS 

finds that the taking will have a 

negligible impact on the species or 

stock(s) and will not have an 

unmitigable adverse impact on the 

availability of the species or stock(s) for 

subsistence uses and that the 

permissible methods of taking and 

requirements pertaining to the 

monitoring and reporting of such 

takings are set forth. NMFS has defined 

‘‘negligible impact’’ in 50 CFR 216.103 

as ’’...an impact resulting from the 

specified activity that cannot be 

reasonably expected to, and is not 

reasonably likely to, adversely affect the 

species or stock through effects on 

annual rates of recruitment or survival.’’

Section 101(a)(5)(D) of the MMPA 

established an expedited process by 

which citizens of the United States can 

apply for an authorization to 

incidentally take small numbers of 

marine mammals by harassment. 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 28, 2004, NMFS received an 

application from L-DEO for the taking, 

by harassment, of several species of 

marine mammals incidental to 

conducting a marine seismic survey 

program during a four-week period 

beginning in late November 2004 in the 

Exclusive Economic Zones of El 

Salvador, Honduras, Nicaragua, and 

Costa Rica. The purpose of the seismic 

survey is to investigate stratigraphic 

development in the presence of tectonic 

forcing in the Sandino basin off 

Nicaragua and Costa Rica. Because of 

the variations in subsidence/uplift 

histories within the Sandino Basin, and 

the inability to provide whole-basin 

coverage during a research cruise of 

reasonable length, data will be collected 

in two primary grids in the Sandino 

Basin and a third, smaller grid off 

Nicoya Peninsula. Grid descriptions are 

provided in L-DEO’s application.

Description of the Activity

The seismic survey will involve one 

vessel. The source vessel, the R/V 

Maurice Ewing, will deploy three lowenergy GI airguns as an energy source, 

with a total discharge volume of up to 

315 in3. As the airguns are towed along 

the survey lines, the towed hydrophone 

system will receive the returning 

acoustic signals.

The program will consist of a 

maximum of 6048 km (3266 nm) of 

surveys. Water depths within the survey 

area are up to 5000 m (16,400 ft); most 

of the survey will be conducted in water 

depths less than 2000 m (6560 ft). The 

area to be surveyed extends from 

approximately 4 to 150 km (2 to 80 nm) 

offshore. The airguns may also be 

operated closer to, and farther from, 

shore while the ship is maneuvering 

toward or between survey lines.

Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 58397

The proposed program will use 

conventional seismic methodology with 

a small towed array of three GI airguns 

as the energy source, and a towed 

hydrophone streamer as the receiver 

system. The energy to the airguns is 

compressed air supplied by compressors 

on board the source vessel. Seismic 

pulses will be emitted at intervals of 5 

seconds. The 5–sec spacing corresponds 

to a shot interval of approximately 12.5 

m (41 ft).

The generator chamber of each GI 

gun, the one responsible for introducing 

the sound pulse into the ocean, is 105 

in3. The injector chamber injects air into 

the previously generated bubble to 

maintain its shape, and does not 

introduce appreciably more sound into 

the water. The three 105–in3 GI guns 

will be towed behind the Ewing, at a 

depth of 2.5 m (8.2 ft). Operating 

pressure will be 2000 psi. The GI guns 

will be 7.8 m (25.6 ft) apart and will be 

towed 37 m (121.4 ft) behind the Ewing. 

The Ewing will also tow a hydrophone 

streamer that is up to 1500 m (4922 ft) 

long. As the airguns are operated along 

the survey lines, the hydrophone 

receiving system will receive and record 

the returning acoustic signals.

General-Injector Airguns

Three GI-airguns will be used from 

the Ewing during the proposed program. 

These 3 GI-airguns have a zero to peak 

(peak) source output of 240.7 dB re 1 

microPascal-m (10.8 bar-m) and a peakto-peak (pk-pk) level of 246 dB (21 barm). However, these downward-directed 

source levels do not represent actual 

sound levels that can be measured at 

any location in the water. Rather, they 

represent the level that would be found 

1 m (3.3 ft) from a hypothetical point 

source emitting the same total amount 

of sound as is emitted by the combined 

airguns in the airgun array. The actual 

received level at any location in the 

water near the airguns will not exceed 

the source level of the strongest 

individual source and actual levels 

experienced by any organism more than 

1 m (3.3 ft) from any GI gun will be 

significantly lower.

Further, the root mean square (rms) 

received levels that are used as impact 

criteria for marine mammals (see 

Richardson et al., 1995) are not directly 

comparable to these peak or pk-pk 

values that are normally used to 

characterize source levels of airgun 

arrays. The measurement units used to 

describe airgun sources, peak or pk-pk 

decibels, are always higher than the rms 

decibels referred to in biological 

literature. For example, a measured 

received level of 160 decibels rms in the 

far field would typically correspond to 

a peak measurement of about 170 to 172 

dB, and to a pk-pk measurement of 

about 176 to 178 decibels, as measured 

for the same pulse received at the same 

location (Greene, 1997; McCauley et al. 

1998, 2000). The precise difference 

between rms and peak or pk-pk values 

depends on the frequency content and 

duration of the pulse, among other 

factors. However, the rms level is 

always lower than the peak or pk-pk 

level for an airgun-type source.

The depth at which the sources are 

towed has a major impact on the 

maximum near-field output, because the 

energy output is constrained by ambient 

pressure. The normal tow depth of the 

sources to be used in this project is 2.5 

m (6.7 ft), where the ambient pressure 

is approximately 3 decibars. This also 

limits output, as the 3 decibars of 

confining pressure cannot fully 

constrain the source output, with the 

result that there is loss of energy at the 

sea surface. Additional discussion of the 

characteristics of airgun pulses is 

provided later in this document (see 

Characteristics of Airgun Pulses).

For the GI-airguns, the sound pressure 

field has been modeled by L-DEO in 

relation to distance and direction from 

the airguns, and in relation to depth. 

Table 1 shows the maximum distances 

from the airguns where sound levels of 

190-, 180-, 170- and 160–dB re 1 

microPa (rms) are predicted to be 

received.

Some empirical data concerning the 

180, 170 and 160 dB distances have 

been acquired for several airgun 

configurations, including two GI-guns, 

based on measurements during an 

acoustic verification study conducted by 

L-DEO in the northern Gulf of Mexico 

from 27 May to 3 June 2003 (see Tolstoy 

et al., 2004). Although the results are 

limited and do not include 

measurements for three GI-guns, the 

data for other airgun configurations 

showed that water depth affected the 

radii around the airguns where the 

received level would be 180 dB re 1 

microPa (rms), NMFS’ current injury 

threshold safety criterion applicable to 

cetaceans (NMFS, 2000). Similar depthrelated variation is likely in the 190–dB 

distances applicable to pinnipeds. 

Water depths within the survey area are 

up to 5000 m (16400 ft), but most of the 

survey will be conducted in water 

depths less than 2000 m (6560 ft), as 

shown in Table 1, column 3.

58398 Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 

The empirical data indicate that, for 

deep water (greater than 1000 m (3281 

ft)), the L-DEO model for the airguns 

tends to overestimate the received 

sound levels at a given distance (Tolstoy 

et al., 2004). However, to be 

precautionary pending acquisition of 

additional empirical data, L-DEO and 

NMFS propose that the mitigation safety 

radii during airgun operations in deep 

water will be the values predicted by LDEO’s model (see Table 1).

The 180- and 190–dB radii were not 

measured for three GI- guns operating in 

shallow water (less than 100 m (328 ft)). 

However, the measured 180–dB radius 

for the 6–airgun array operating in 

shallow water was 6.8x that predicted 

by L-DEO’s model for operation of the 

six-airgun array in deep water. The 

conservative correction factor is applied 

to the model estimates to predict the 

radii for the three GI-guns in shallow 

water, as shown in Table 1.

Empirical measurements were not 

conducted for intermediate depths 

(100–1000 m (328–3281 ft)). On the 

expectation that results will be 

intermediate between those from 

shallow and deep water, a 1.5x 

correction factor is applied to the 

estimates provided by the model for 

deep water situations, as shown in 

Table 1. This is the same factor that was 

applied to the model estimates during LDEO cruises in 2003.

Bathymetric Sonar and Sub-bottom 

Profiler

In addition to the 3 GI-airguns, a 

multibeam bathymetric sonar and a lowenergy 3.5–kHz sub-bottom profiler will 

be used during the seismic profiling and 

continuously when underway.

Bathymetric Sonar-Atlas HydrosweepThe 15.5–kHz Atlas Hydrosweep sonar 

is mounted on the hull of the Maurice 

Ewing, and it operates in three modes, 

depending on the water depth. There is 

one shallow water mode and two deepwater modes: an Omni mode (similar to 

the shallow-water mode but with a 

source output of 220 dB (rms)) and a 

Rotational Directional Transmission 

(RDT) mode. The RDT mode is normally 

used during deep-water operation and 

has a 237–dB rms source output. In the 

RDT mode, each ‘‘ping’’ consists of five 

successive transmissions, each 

ensonifying a beam that extends 2.67 

degrees fore-aft and approximately 30 

degrees in the cross-track direction. The 

five successive transmissions (segments) 

sweep from port to starboard with minor 

overlap, spanning an overall cross-track 

angular extent of about 140 degrees, 

with small (much less than 1 millisec) 

gaps between the pulses for successive 

30–degree segments. The total duration 

of the ‘‘ping,’’ including all five 

successive segments, varies with water 

depth, but is 1 millisec in water depths 

less than 500 m and 10 millisec in the 

deepest water. For each segment, ping 

duration is 1/5 of these values or 2/5 for 

a receiver in the overlap area ensonified 

by two beam segments. The ‘‘ping’’

interval during RDT operations depends 

on water depth and varies from once per 

second in less than 500 m (1640.5 ft) 

water depth to once per 15 seconds in 

the deepest water. During the proposed 

project, the Atlas Hydrosweep will 

generally be used in waters greater than 

800 m (2624.7 ft), but whenever water 

depths are less than 400 m (1312 ft) the 

source output is 210 dB re 1 microPam (rms) and a single 1–ms pulse or 

‘‘ping’’ per second is transmitted.

Sub-bottom Profiler-The sub-bottom 

profiler is normally operated to provide 

information about the sedimentary 

features and the bottom topography that 

is simultaneously being mapped by the 

Hydrosweep. The energy from the subbottom profiler is directed downward by 

a 3.5–kHz transducer mounted in the 

hull of the Ewing. The output varies 

with water depth from 50 watts in 

shallow water to 800 watts in deep 

water. Pulse interval is 1 second (s) but 

a common mode of operation is to 

broadcast five pulses at 1–s intervals 

followed by a 5–s pause. The 

beamwidth is approximately 30° and is 

directed downward. Maximum source 

output is 204 dB re 1 microPa (800 

watts) while nominal source output is 

200 dB re 1 microPa (500 watts). Pulse 

duration will be 4, 2, or 1 ms, and the 

bandwith of pulses will be 1.0 kHz, 0.5 

kHz, or 0.25 kHz, respectively.

Although the sound levels have not 

been measured directly for the subbottom profilers used by the Ewing, 

Burgess and Lawson (2000) measured 

sounds propagating more or less 

horizontally from a sub-bottom profiler 

similar to the L-DEO unit with similar 

source output (i.e., 205 dB re 1 microPa 

m). For that profiler, the 160 and 180 dB 

re 1 microPa (rms) radii in the 

horizontal direction were estimated to 


EN30SE04.200</GPH>
Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 58399

be, respectively, near 20 m (66 ft) and 

8 m (26 ft) from the source, as measured 

in 13 m (43 ft) water depth. The 

corresponding distances for an animal 

in the beam below the transducer would 

be greater, on the order of 180 m (591 

ft) and 18 m (59 ft) respectively, 

assuming spherical spreading. Thus the 

received level for the L-DEO sub-bottom 

profiler would be expected to decrease 

to 160 and 180 dB about 160 m (525 ft) 

and 16 m (52 ft) below the transducer, 

respectively, assuming spherical 

spreading. Corresponding distances in 

the horizontal plane would be lower, 

given the directionality of this source 

(300 beamwidth) and the measurements 

of Burgess and Lawson (2000).

Characteristics of Airgun Pulses

Airguns function by venting highpressure air into the water. The pressure 

signature of an individual airgun 

consists of a sharp rise and then fall in 

pressure, followed by several positive 

and negative pressure excursions caused 

by oscillation of the resulting air bubble. 

The resulting downward-directed pulse 

has a duration of only 10 to 20 ms, with 

only one strong positive and one strong 

negative peak pressure (Caldwell and 

Dragoset, 2000). Most energy emitted 

from airguns is at relatively low 

frequencies. For example, typical highenergy airgun arrays emit most energy at 

10–120 Hz. However, the pulses contain 

some energy up to 500–1000 Hz and 

above (Goold and Fish, 1998).

The pulsed sounds associated with 

seismic exploration have higher peak 

levels than other industrial sounds to 

which whales and other marine 

mammals are routinely exposed. As 

mentioned previously, the pk-pk source 

levels of the 2 GI-gun array that will be 

used for the ETPO project are 231 dB re 

1 microPa (peak) and 237 dB re 1 

microPa (pk-pk). However, the effective 

source level for horizontal propagation 

will be lower and actual levels 

experienced by any marine mammal 

more than 1 m (3.3 ft) from either GIgun will be significantly lower.

Several important factors need to be 

considered when assessing airgun 

impacts on the marine environment. (1) 

Airgun arrays produce intermittent 

sounds, involving emission of a strong 

sound pulse for a small fraction of a 

second followed by several seconds of 

near silence. In contrast, some other 

acoustic sources produce sounds with 

lower peak levels, but their sounds are 

continuous or discontinuous but 

continuing for much longer durations 

than seismic pulses. (2) Airgun arrays 

are designed to transmit strong sounds 

downward through the seafloor, and the 

amount of sound transmitted in nearhorizontal directions is considerably 

reduced. Nonetheless, they also emit 

sounds that travel horizontally toward 

non-target areas. (3) An airgun array is 

a distributed source, not a point source. 

The nominal source level is an estimate 

of the sound that would be measured 

from a theoretical point source emitting 

the same total energy as the airgun 

array. That figure is useful in calculating 

the expected received levels in the far 

field (i.e., at moderate and long 

distances). Because the airgun array is 

not a single point source, there is no one 

location within the near field (or 

anywhere else) where the received level 

is as high as the nominal source level.

The strengths of airgun pulses can be 

measured in different ways, and it is 

important to know which method is 

being used when interpreting quoted 

source or received levels. Geophysicists 

usually quote pk-pk levels, in barmeters or dB re 1 microPa-m. The peak 

level for the same pulse is typically 

about 6 dB less. In the biological 

literature, levels of received airgun 

pulses are often described based on the 

‘‘average’’ or ‘‘root-mean-square’’ (rms) 

level over the duration of the pulse. The 

rms value for a given pulse is typically 

about 10 dB lower than the peak level, 

and 16 dB lower than the Pk-pk value 

(Greene, 1997; McCauley et al., 1998; 

2000). A fourth measure that is being 

used more frequently is the energy level, 

in dB re 1 microPa2.s. Because the 

pulses are less than 1 sec in duration, 

the numerical value of the energy is 

lower than the rms pressure level, but 

the units are different. Because the level 

of a given pulse will differ substantially 

depending on which of these measures 

is being applied, it is important to be 

aware which measure is in use when 

interpreting any quoted pulse level. 

NMFS commonly references the rms 

levels when discussing levels of pulsed 

sounds that might harass marine 

mammals.

Seismic sound received at any given 

point will arrive via a direct path, 

indirect paths that include reflection 

from the sea surface and bottom, and 

often indirect paths including segments 

through the bottom sediments. Sounds 

propagating via indirect paths travel 

longer distances and often arrive later 

than sounds arriving via a direct path. 

These variations in travel time have the 

effect of lengthening the duration of the 

received pulse. At the source, seismic 

pulses are about 10 to 20 ms in 

duration. In comparison, the pulse as 

received at long horizontal distances 

can have a much longer duration.

Another important aspect of sound 

propagation is that received levels of 

low-frequency underwater sounds 

diminish close to the surface because of 

pressure-release and interference 

phenomena that occur at and near the 

surface (Urick, 1983, Richardson et al., 

1995). Paired measurements of received 

airgun sounds at depths of 3 m (9.8 ft) 

vs. 9 or 18 m (29.5 or 59 ft) have shown 

that received levels are typically several 

decibels lower at 3 m (9.8. ft)(Greene 

and Richardson, 1988). For a mammal 

whose auditory organs are within 0.5 or 

1 m (1.6 or 3.3 ft) of the surface, the 

received level of the predominant lowfrequency components of the airgun 

pulses would be further reduced.

Pulses of underwater sound from 

open-water seismic exploration are 

often detected 50 to 100 km (30 to 54 

nm) from the source location (Greene 

and Richardson, 1988; Burgess and 

Greene, 1999). At those distances, the 

received levels on an approximate rms 

basis are low (below 120 dB re 1 

microPa). However, faint seismic pulses 

are sometimes detectable at even greater 

ranges (e.g., Bowles et al., 1994; Fox et 

al., 2002). Considerably higher levels 

can occur at distances out to several 

kilometers from an operating airgun 

array. Additional information is 

contained in the L-DEO application, 

especially in Appendix A (see 

ADDRESSES).

Description of Habitat and Marine 

Mammals Affected by the Activity

A detailed description of the ETPO 

area and its associated marine mammals 

can be found in the L-DEO application 

and a number of documents referenced 

in the L-DEO application, and is not 

repeated here. Thirty-four species of 

cetaceans are known to occur in the 

ETPO, belonging to two taxonomic 

groups: odontocetes (sperm whale 

(Physeter macrocephalus), dwarf sperm 

whale (Kogia sima), pygmy sperm whale 

(K. breviceps), Cuvier’s beaked whale 

(Ziphius cavirostris), Longman’s beaked 

whale (Indopacetus pacificus), pygmy 

beaked whale (Mesoplodon peruvianus), 

gingko-toothed beaked whale (M. 

ginkgodens), Blainville’s beaked whale 

(M. densirostris), rough-toothed dolphin 

(Steno bredanensis), bottlenose dolphin 

(Tursiops truncatus), pantropical 

spotted dolphin (Stenella attenuata), 

spinner dolphin (S. longirostris), striped 

dolphin (S. coeruleoalba), short-beaked 

common dolphin (Delphinus delphis), 

Fraser’s dolphin (Lagenodelphis hosei), 

Risso’s dolphin (Grampus griseus), 

melon-headed whale (Peponocephala 

electra), pygmy killer whale (Feresa 

attenuata), false killer whale (Pseudorca 

crassidens), killer whale (Orcinus orca), 

and short-finned pilot whale 

(Globicephala macrorhynchus)); and 

mysticetes humpback whale (Megaptera 

58400 Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 

novaeangliae), minke whale 

(Balaenoptera acutorostrata), sei whale 

(B. borealis), fin whale (B. physalus), 

Bryde’s whale (B. edeni), and blue 

whale (B. musculus). Of these 34 

species, L-DEO states that 27 cetacean 

species are likely to occur in the 

proposed survey area. These 27 species 

are shown in Table 2 of this document 

and are described in L-DEO (2004)).

Seven cetacean species (Pacific whitesided dolphin (Lagenorhynchus 

obliquidens), Baird’s beaked whale 

(Berardius bairdii), long-beaked 

common dolphin (Delphinus capensis), 

dusky dolphin (Lagenorhynchus 

obscurus), southern right whale dolphin 

(Lissodelphis peronii), Burmeister’s 

porpoise (Phocoena spinipinnis), and 

long-finned pilot whale (Globicephala 

melas)) although present in the wider 

ETPO, are unlikely to be found in LDEO’s proposed survey area (L-DEO, 

2004). These species are mentioned 

briefly in L-DEO’s application, but are 

unlikely to be taken by incidental 

harassment and therefore are not 

analyzed further in this document.

Six species of pinnipeds are known to 

occur in the ETPO: Guadalupe fur seal 

(Arctocephalus townsendi), California 

sea lion (Zalophus californianus), 

Galapagos sea lion (Z. wollebaeki), 

Galapagos fur seal (A. galapagoensis), 

southern sea lion (Otaria flavescens), 

and South American fur seal (A. 

australis). The last four species could 

potentially occur within the proposed 

seismic survey area, but they are 

expected to be, at most, uncommon. 

Ranges of the first two species are 

substantially north of the proposed 

seismic survey area and, therefore, 

unlikely to be taken by incidental 

harassment.

More detailed information on these 

species is contained in the L-DEO 

application, which is available at: http:/

/www.nmfs.noaa.gov/protlres/PR2/

SmalllTake/

smalltakelinfo.htm#applications.

Potential Effects on Marine Mammals

As outlined in several previous NMFS 

documents, the effects of noise on 

marine mammals are highly variable, 

and can be categorized as follows (based 

on Richardson et al., 1995):

(1) The noise may be too weak to be 

heard at the location of the animal (i.e., 

lower than the prevailing ambient noise 

level, the hearing threshold of the 

animal at relevant frequencies, or both);

(2) The noise may be audible but not 

strong enough to elicit any overt 

behavioral response;

(3) The noise may elicit reactions of 

variable conspicuousness and variable 

relevance to the well being of the 

marine mammal; these can range from 

temporary alert responses to active 

avoidance reactions such as vacating an 

area at least until the noise event ceases;

(4) Upon repeated exposure, a marine 

mammal may exhibit diminishing 

responsiveness (habituation), or 

disturbance effects may persist; the 

latter is most likely with sounds that are 

highly variable in characteristics, 

infrequent and unpredictable in 

occurrence, and associated with 

situations that a marine mammal 

perceives as a threat;

(5) Any anthropogenic noise that is 

strong enough to be heard has the 

potential to reduce (mask) the ability of 

a marine mammal to hear natural 

sounds at similar frequencies, including 

calls from conspecifics, and underwater 

environmental sounds such as surf 

noise;

(6) If mammals remain in an area 

because it is important for feeding, 

breeding or some other biologically 

important purpose even though there is 

chronic exposure to noise, it is possible 

that there could be noise-induced 

physiological stress; this might in turn 

have negative effects on the well-being 

or reproduction of the animals involved; 

and

(7) Very strong sounds have the 

potential to cause temporary or 

permanent reduction in hearing 

sensitivity. In terrestrial mammals, and 

presumably marine mammals, received 

sound levels must far exceed the 

animal’s hearing threshold for there to 

be any temporary threshold shift (TTS) 

in its hearing ability. For transient 

sounds, the sound level necessary to 

cause TTS is inversely related to the 

duration of the sound. Received sound 

levels must be even higher for there to 

be risk of permanent hearing 

impairment. In addition, intense 

acoustic or explosive events may cause 

trauma to tissues associated with organs 

vital for hearing, sound production, 

respiration and other functions. This 

trauma may include minor to severe 

hemorrhage.

Effects of Seismic Surveys on Marine 

Mammals

The L-DEO application provides the 

following information on what is known 

about the effects on marine mammals of 

the types of seismic operations planned 

by L-DEO. The types of effects 

considered here are (1) tolerance, (2) 

masking of natural sounds, (2) 

behavioral disturbance, and (3) potential 

hearing impairment and other nonauditory physical effects (Richardson et 

al., 1995). Given the relatively small size 

of the airguns planned for the present 

project, its effects are anticipated to be 

considerably less than would be the 

case with a large array of airguns. L-DEO 

and NMFS believe it is very unlikely 

that there would be any cases of 

temporary or especially permanent 

hearing impairment, or non-auditory 

physical effects. Also, behavioral 

disturbance is expected to be limited to 

distances less than 823 m (2700 ft) in 

deep water and 2469 m (8100 ft) in 

shallow water, the zones calculated for 

160 dB or the onset of Level B 

harassment. Additional discussion on 

species specific effects can be found in 

the L-DEO application.

Tolerance

Numerous studies (referenced in LDEO, 2004) have shown that pulsed 

sounds from airguns are often readily 

detectable in the water at distances of 

many kilometers, but that marine 

mammals at distances more than a few 

kilometers from operating seismic 

vessels often show no apparent 

response. That is often true even in 

cases when the pulsed sounds must be 

readily audible to the animals based on 

measured received levels and the 

hearing sensitivity of that mammal 

group. However, most measurements of 

airgun sounds that have been reported 

concerned sounds from larger arrays of 

airguns, whose sounds would be 

detectable farther away than that 

planned for use in the proposed survey. 

Although various baleen whales, 

toothed whales, and pinnipeds have 

been shown to react behaviorally to 

airgun pulses under some conditions, at 

other times mammals of all three types 

have shown no overt reactions. In 

general, pinnipeds and small 

odontocetes seem to be more tolerant of 

exposure to airgun pulses than are 

baleen whales. Given the relatively 

small and low-energy airgun source 

planned for use in this project, 

mammals are expected to tolerate being 

closer to this source than would be the 

case for a larger airgun source typical of 

most seismic surveys.

Masking

Masking effects of pulsed sounds on 

marine mammal calls and other natural 

sounds are expected to be limited (due 

in part to the small size of the GI 

airguns), although there are very few 

specific data on this. Given the small 

source planned for use in the ETPO, 

there is even less potential for masking 

of baleen or sperm whale calls during 

the present research than in most 

seismic surveys (L-DEO, 2004). Seismic 

sounds are short pulses generally 

occurring for less than 1 sec every 5 

seconds or so. The 5–sec spacing 

corresponds to a shot interval of 

Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 58401

approximately 12.5 m (41 ft). Sounds 

from the multibeam sonar are very short 

pulses, occurring for 1–10 msec once 

every 1 to 15 sec, depending on water 

depth. (During operations in deep water, 

the duration of each pulse from the 

multibeam sonar as received at any one 

location would actually be only 1⁄5 or at 

most 2⁄5 of 1–10 msec, given the 

segmented nature of the pulses.)

Some whales are known to continue 

calling in the presence of seismic 

pulses. Their calls can be heard between 

the seismic pulses (Richardson et al., 

1986; McDonald et al., 1995, Greene et 

al., 1999). Although there has been one 

report that sperm whales cease calling 

when exposed to pulses from a very 

distant seismic ship (Bowles et al., 

1994), a recent study reports that sperm 

whales continued calling in the 

presence of seismic pulses (Madsen et 

al., 2002). Given the relatively small 

source planned for use during this 

survey, there is even less potential for 

masking of sperm whale calls during the 

present study than in most seismic 

surveys. Masking effects of seismic 

pulses are expected to be negligible in 

the case of the smaller odontocete 

cetaceans, given the intermittent nature 

of seismic pulses and the relatively low 

source level of the airguns to be used in 

the ETPO. Also, the sounds important to 

small odontocetes are predominantly at 

much higher frequencies than are airgun 

sounds.

Most of the energy in the sound 

pulses emitted by airgun arrays is at low 

frequencies, with strongest spectrum 

levels below 200 Hz and considerably 

lower spectrum levels above 1000 Hz. 

These low frequencies are mainly used 

by mysticetes, but generally not by 

odontocetes or pinnipeds. An industrial 

sound source will reduce the effective 

communication or echolocation 

distance only if its frequency is close to 

that of the marine mammal signal. If 

little or no overlap occurs between the 

industrial noise and the frequencies 

used, as in the case of many marine 

mammals relative to airgun sounds, 

communication and echolocation are 

not expected to be disrupted. 

Furthermore, the discontinuous nature 

of seismic pulses makes significant 

masking effects unlikely even for 

mysticetes.

A few cetaceans are known to 

increase the source levels of their calls 

in the presence of elevated sound levels, 

or possibly to shift their peak 

frequencies in response to strong sound 

signals (Dahlheim, 1987; Au, 1993; 

Lesage et al., 1999; Terhune, 1999; as 

reviewed in Richardson et al., 1995). 

These studies involved exposure to 

other types of anthropogenic sounds, 

not seismic pulses, and it is not known 

whether these types of responses ever 

occur upon exposure to seismic sounds. 

If so, these adaptations, along with 

directional hearing, pre-adaptation to 

tolerate some masking by natural 

sounds (Richardson et al., 1995) and the 

relatively low-power acoustic sources 

being used in this survey, would all 

reduce the importance of masking 

marine mammal vocalizations.

Disturbance by Seismic Surveys

Disturbance includes a variety of 

effects, including subtle changes in 

behavior, more conspicuous dramatic 

changes in activities, and displacement. 

However, there are difficulties in 

defining which marine mammals should 

be counted as ‘‘taken by harassment’’. 

For many species and situations, 

scientists do not have detailed 

information about their reactions to 

noise, including reactions to seismic 

(and sonar) pulses. Behavioral reactions 

of marine mammals to sound are 

difficult to predict. Reactions to sound, 

if any, depend on species, state of 

maturity, experience, current activity, 

reproductive state, time of day, and 

many other factors. If a marine mammal 

does react to an underwater sound by 

changing its behavior or moving a small 

distance, the impacts of the change may 

not rise to the level of a disruption of 

a behavioral pattern. However, if a 

sound source would displace marine 

mammals from an important feeding or 

breeding area, such a disturbance would 

constitute Level B harassment under the 

MMPA. Given the many uncertainties in 

predicting the quantity and types of 

impacts of noise on marine mammals, 

scientists often resort to estimating how 

many mammals may be present within 

a particular distance of industrial 

activities or exposed to a particular level 

of industrial sound. With the possible 

exception of beaked whales, NMFS 

believes that this is a conservative 

approach and likely overestimates the 

numbers of marine mammals that are 

affected in some biologically important 

manner.

The sound exposure criteria used to 

estimate how many marine mammals 

might be harassed behaviorally by the 

seismic survey are based on behavioral 

observations during studies of several 

species. However, information is lacking 

for many species. Detailed information 

on potential disturbance effects on 

baleen whales, toothed whales, and 

pinnipeds can be found on pages 35–37 

and Appendix A in L-DEO’s ETPO 

application.

Hearing Impairment and Other Physical 

Effects

Temporary or permanent hearing 

impairment is a possibility when marine 

mammals are exposed to very strong 

sounds, but there has been no specific 

documentation of this for marine 

mammals exposed to airgun pulses. 

Current NMFS policy precautionarily 

sets impulsive sounds equal to or 

greater than 180 and 190 dB re 1 

microPa (rms) as the exposure 

thresholds for onset of Level A 

harassment for cetaceans and pinnipeds, 

respectively (NMFS, 2000). Those 

criteria have been used in defining the 

safety (shut-down) radii for seismic 

surveys. However, those criteria were 

established before there were any data 

on the minimum received levels of 

sounds necessary to cause auditory 

impairment in marine mammals. As 

discussed in the L-DEO application and 

summarized here,

1. The 180 dB criterion for cetaceans 

is probably quite precautionary, i.e., 

lower than necessary to avoid TTS let 

alone permanent auditory injury, at 

least for delphinids.

2. The minimum sound level 

necessary to cause permanent hearing 

impairment is higher, by a variable and 

generally unknown amount, than the 

level that induces barely-detectable 

TTS.

3. The level associated with the onset 

of TTS is often considered to be a level 

below which there is no danger of 

permanent damage.

Because of the small size of the 3 105 

in3 GI-airguns, along with the planned 

monitoring and mitigation measures, 

there is little likelihood that any marine 

mammals will be exposed to sounds 

sufficiently strong to cause even the 

mildest (and reversible) form of hearing 

impairment. Several aspects of the 

planned monitoring and mitigation 

measures for this project are designed to 

detect marine mammals occurring near 

the 3 GI-airguns (and multibeam 

bathymetric sonar), and to avoid 

exposing them to sound pulses that 

might (at least in theory) cause hearing 

impairment. In addition, research and 

monitoring studies on gray whales, 

bowhead whales and other cetacean 

species indicate that many cetaceans are 

likely to show some avoidance of the 

area with ongoing seismic operations. In 

these cases, the avoidance responses of 

the animals themselves will reduce or 

avoid the possibility of hearing 

impairment.

Non-auditory physical effects may 

also occur in marine mammals exposed 

to strong underwater pulsed sound. 

Possible types of non-auditory 

58402 Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 

physiological effects or injuries that 

theoretically might occur in mammals 

close to a strong sound source include 

stress, neurological effects, bubble 

formation, resonance effects, and other 

types of organ or tissue damage. It is 

possible that some marine mammal 

species (i.e., beaked whales) may be 

especially susceptible to injury and/or 

stranding when exposed to strong 

pulsed sounds. However, L-DEO and 

NMFS believe that it is especially 

unlikely that any of these non-auditory 

effects would occur during the proposed 

survey given the small size of the 

sources, the brief duration of exposure 

of any given mammal, and the planned 

mitigation and monitoring measures. 

The following paragraphs discuss the 

possibility of TTS, permanent threshold 

shift (PTS), and non-auditory physical 

effects.

TTS

TTS is the mildest form of hearing 

impairment that can occur during 

exposure to a strong sound (Kryter, 

1985). When an animal experiences 

TTS, its hearing threshold rises and a 

sound must be stronger in order to be 

heard. TTS can last from minutes or 

hours to (in cases of strong TTS) days. 

Richardson et al. (1995) note that the 

magnitude of TTS depends on the level 

and duration of noise exposure, among 

other considerations. For sound 

exposures at or somewhat above the 

TTS threshold, hearing sensitivity 

recovers rapidly after exposure to the 

noise ends. Little data on sound levels 

and durations necessary to elicit mild 

TTS have been obtained for marine 

mammals.

For toothed whales exposed to single 

short pulses, the TTS threshold appears 

to be, to a first approximation, a 

function of the energy content of the 

pulse (Finneran et al., 2002). Given the 

available data, the received level of a 

single seismic pulse might need to be on 

the order of 210 dB re 1 microPa rms 

(approx. 221 226 dB pk pk) in order to 

produce brief, mild TTS. Exposure to 

several seismic pulses at received levels 

near 200 205 dB (rms) might result in 

slight TTS in a small odontocete, 

assuming the TTS threshold is (to a first 

approximation) a function of the total 

received pulse energy (Finneran et al., 

2002). Seismic pulses with received 

levels of 200 205 dB or more are usually 

restricted to a zone of no more than 100 

m (328 ft) around a seismic vessel 

operating a large array of airguns. Such 

sound levels would be limited to 

distances within a few meters of the 

small airguns planned for use during 

this project.

There are no data, direct or indirect, 

on levels or properties of sound that are 

required to induce TTS in any baleen 

whale. However, TTS is not expected to 

occur during this survey given the small 

size of the source, and the strong 

likelihood that baleen whales would 

avoid the approaching airguns (or 

vessel) before being exposed to levels 

high enough for there to be any 

possibility of TTS.

TTS thresholds for pinnipeds exposed 

to brief pulses (single or multiple) have 

not been measured, although exposures 

up to 183 dB re 1 microPa (rms) have 

been shown to be insufficient to induce 

TTS in California sea lions (Finneran et 

al., 2003). However, prolonged 

exposures show that some pinnipeds 

may incur TTS at somewhat lower 

received levels than do small 

odontocetes exposed for similar 

durations (Kastak et al., 1999; Ketten et 

al., 2001; Au et al., 2000).

A marine mammal within a zone of 

less than 100 m (328 ft) around a typical 

large array of operating airguns might be 

exposed to a few seismic pulses with 

levels of ≥205 dB, and possibly more 

pulses if the mammal moved with the 

seismic vessel. Also, around smaller 

arrays, such as the 3 GI-airgun array 

proposed for use during this survey, a 

marine mammal would need to be even 

closer to the source to be exposed to 

levels greater than or equal to 205 dB, 

at least in waters greater than 100 m 

(328 ft) deep. However, as noted 

previously, most cetacean species tend 

to avoid operating airguns, although not 

all individuals do so. In addition, 

ramping up airgun arrays, which is now 

standard operational protocol for L-DEO 

and other seismic operators, should 

allow cetaceans to move away from the 

seismic source and to avoid being 

exposed to the full acoustic output of 

the airgun array. It is unlikely that these 

cetaceans would be exposed to airgun 

pulses at a sufficiently high level for a 

sufficiently long period to cause more 

than mild TTS, given the relative 

movement of the vessel and the marine 

mammal. However, TTS would be more 

likely in any odontocetes that bow-ride 

or otherwise linger near the airguns. 

While bow-riding, odontocetes would 

be at or above the surface, and thus not 

exposed to strong sound pulses given 

the pressure-release effect at the surface. 

However, bow-riding animals generally 

dive below the surface intermittently. If 

they did so while bow-riding near 

airguns, they would be exposed to 

strong sound pulses, possibly 

repeatedly. During this project, the bow 

of the Ewing will be 107 m (351 ft) 

ahead of the airguns and the 205–dB 

zone would be less than 100 m (328 ft). 

Thus, TTS would not be expected in the 

case of odontocetes bow riding during 

airgun operations and if some cetaceans 

did incur TTS through exposure to 

airgun sounds, it would very likely be 

a temporary and reversible 

phenomenon.

Currently, NMFS believes that, to 

avoid Level A harassment, cetaceans 

should not be exposed to pulsed 

underwater noise at received levels 

exceeding 180 dB re 1 microPa (rms). 

The corresponding limit for pinnipeds 

has been set at 190 dB. The predicted 

180- and 190–dB distances for the 

airgun arrays operated by L-DEO during 

this activity are summarized in Table 1 

in this document. These sound levels 

are not considered to be the levels at or 

above which TTS might occur. Rather, 

they are the received levels above 

which, in the view of a panel of 

bioacoustics specialists convened by 

NMFS (at a time before TTS 

measurements for marine mammals 

started to become available), one could 

not be certain that there would be no 

injurious effects, auditory or otherwise, 

to marine mammals. As noted here, TTS 

data that are now available imply that, 

at least for dolphins, TTS is unlikely to 

occur unless the dolphins are exposed 

to airgun pulses substantially stronger 

than 180 dB re 1 microPa (rms).

It has also been shown that most 

whales tend to avoid ships and 

associated seismic operations. Thus, 

whales will likely not be exposed to 

such high levels of airgun sounds. 

Because of the slow ship speed, any 

whales close to the trackline could 

move away before the sounds become 

sufficiently strong for there to be any 

potential for hearing impairment. 

Therefore, there is little potential for 

whales being close enough to an array 

to experience TTS. In addition, as 

mentioned previously, ramping up the 

airgun array, which has become 

standard operational protocol for many 

seismic operators including L-DEO, 

should allow cetaceans to move away 

from the seismic source and to avoid 

being exposed to the full acoustic 

output of the GI airguns.

Permanent Threshold Shift (PTS)

When PTS occurs there is physical 

damage to the sound receptors in the 

ear. In some cases there can be total or 

partial deafness, while in other cases the 

animal has an impaired ability to hear 

sounds in specific frequency ranges. 

Although there is no specific evidence 

that exposure to pulses of airgun sounds 

can cause PTS in any marine mammals, 

even with the largest airgun arrays, 

physical damage to a mammal’s hearing 

apparatus can potentially occur if it is 

Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 58403

exposed to sound impulses that have 

very high peak pressures, especially if 

they have very short rise times (time 

required for sound pulse to reach peak 

pressure from the baseline pressure). 

Such damage can result in a permanent 

decrease in functional sensitivity of the 

hearing system at some or all 

frequencies.

Single or occasional occurrences of 

mild TTS are not indicative of 

permanent auditory damage in 

terrestrial mammals. However, very 

prolonged exposure to sound strong 

enough to elicit TTS, or shorter-term 

exposure to sound levels well above the 

TTS threshold, can cause PTS, at least 

in terrestrial mammals (Kryter, 1985). 

Relationships between TTS and PTS 

thresholds have not been studied in 

marine mammals but are assumed to be 

similar to those in humans and other 

terrestrial mammals. The low-tomoderate levels of TTS that have been 

induced in captive odontocetes and 

pinnipeds during recent controlled 

studies of TTS have been confirmed to 

be temporary, with no measurable 

residual PTS (Kastak et al., 1999; 

Schlundt et al., 2000; Finneran et al., 

2002; Nachtigall et al., 2003). In 

terrestrial mammals, the received sound 

level from a single non-impulsive sound 

exposure must be far above the TTS 

threshold for any risk of permanent 

hearing damage (Kryter, 1994; 

Richardson et al., 1995). For impulse 

sounds with very rapid rise times (e.g., 

those associated with explosions or 

gunfire), a received level not greatly in 

excess of the TTS threshold may start to 

elicit PTS. Rise times for airgun pulses 

are rapid, but less rapid than for 

explosions.

Some factors that contribute to onset 

of PTS are as follows: (1) exposure to 

single very intense noises, (2) repetitive 

exposure to intense sounds that 

individually cause TTS but not PTS, 

and (3) recurrent ear infections or (in 

captive animals) exposure to certain 

drugs.

Cavanagh (2000) has reviewed the 

thresholds used to define TTS and PTS. 

Based on his review and SACLANT 

(1998), it is reasonable to assume that 

PTS might occur at a received sound 

level 20 dB or more above that which 

induces mild TTS. However, for PTS to 

occur at a received level only 20 dB 

above the TTS threshold, it is probable 

that the animal would have to be 

exposed to the strong sound for an 

extended period.

Sound impulse duration, peak 

amplitude, rise time, and number of 

pulses are the main factors thought to 

determine the onset and extent of PTS. 

Based on existing data, Ketten (1994) 

has noted that the criteria for 

differentiating the sound pressure levels 

that result in PTS (or TTS) are location 

and species-specific. PTS effects may 

also be influenced strongly by the health 

of the receiver’s ear.

Given that marine mammals are 

unlikely to be exposed to received levels 

of seismic pulses that could cause TTS, 

it is highly unlikely that they would 

sustain permanent hearing impairment. 

If we assume that the TTS threshold for 

odontocetes for exposure to a series of 

seismic pulses may be on the order of 

220 dB re 1 microPa (pk-pk) 

(approximately 204 dB re 1 microPa 

rms), then the PTS threshold might be 

about 240 dB re 1 microPa (pk-pk). In 

the units used by geophysicists, this is 

10 bar-m. Such levels are found only in 

the immediate vicinity of the largest 

airguns (Richardson et al., 1995; 

Caldwell and Dragoset, 2000). However, 

it is very unlikely that an odontocete 

would remain within a few meters of a 

large airgun for sufficiently long to incur 

PTS. The TTS (and thus PTS) thresholds 

of baleen whales and pinnipeds may be 

lower, and thus may extend to a 

somewhat greater distance from the 

source. However, baleen whales 

generally avoid the immediate area 

around operating seismic vessels, so it 

is unlikely that a baleen whale could 

incur PTS from exposure to airgun 

pulses. Some pinnipeds do not show 

strong avoidance of operating airguns. 

In summary, it is highly unlikely that 

marine mammals could receive sounds 

strong enough (and over a sufficient 

period of time) to cause permanent 

hearing impairment during this project. 

In the proposed project marine 

mammals are unlikely to be exposed to 

received levels of seismic pulses strong 

enough to cause TTS, and because of the 

higher level of sound necessary to cause 

PTS, it is even less likely that PTS could 

occur. This is due to the fact that even 

levels immediately adjacent to the 3 GIairguns may not be sufficient to induce 

PTS because the mammal would not be 

exposed to more than one strong pulse 

unless it swam alongside an airgun for 

a period of time.

Strandings and Mortality

Marine mammals close to underwater 

detonations of high explosives can be 

killed or severely injured, and the 

auditory organs are especially 

susceptible to injury (Ketten et al., 1993; 

Ketten, 1995). Airgun pulses are less 

energetic and have slower rise times. 

While there is no documented evidence 

that airgun arrays can cause serious 

injury, death, or stranding, the 

association of mass strandings of beaked 

whales with naval exercises and, 

recently, an L-DEO seismic survey have 

raised the possibility that beaked whales 

may be especially susceptible to injury 

and/or stranding when exposed to 

strong pulsed sounds.

In March 2000, several beaked whales 

that had been exposed to repeated 

pulses from high intensity, midfrequency military sonars stranded and 

died in the Providence Channels of the 

Bahamas Islands, and were 

subsequently found to have incurred 

cranial and ear damage (NOAA and 

USN, 2001). Based on post-mortem 

analyses, it was concluded that an 

acoustic event caused hemorrhages in 

and near the auditory region of some 

beaked whales. These hemorrhages 

occurred before death. They would not 

necessarily have caused death or 

permanent hearing damage, but could 

have compromised hearing and 

navigational ability (NOAA and USN, 

2001). The researchers concluded that 

acoustic exposure caused this damage 

and triggered stranding, which resulted 

in overheating, cardiovascular collapse, 

and physiological shock that ultimately 

led to the death of the stranded beaked 

whales. During the event, five naval 

vessels used their AN/SQS–53C or -56 

hull-mounted active sonars for a period 

of 16 hours. The sonars produced 

narrow (<100 Hz) bandwidth signals at 

center frequencies of 2.6 and 3.3 kHz (-

53C), and 6.8 to 8.2 kHz (-56). The 

respective source levels were usually 

235 and 223 dB re 1 μ Pa, but the -53C 

briefly operated at an unstated but 

substantially higher source level. The 

unusual bathymetry and constricted 

channel where the strandings occurred 

were conducive to channeling sound. 

This, and the extended operations by 

multiple sonars, apparently prevented 

escape of the animals to the open sea. 

In addition to the strandings, there are 

reports that beaked whales were no 

longer present in the Providence 

Channel region after the event, 

suggesting that other beaked whales 

either abandoned the area or perhaps 

died at sea (Balcomb and Claridge, 

2001).

Other strandings of beaked whales 

associated with operation of military 

sonars have also been reported (e.g., 

Simmonds and Lopez-Jurado, 1991; 

Frantzis, 1998). In these cases, it was 

not determined whether there were 

noise-induced injuries to the ears or 

other organs. Another stranding of 

beaked whales (15 whales) happened on 

24–25 September 2002 in the Canary 

Islands, where naval maneuvers were 

taking place. Jepson et al. (2003) 

concluded that cetaceans might be 

subject to decompression injury (the 

bends or air embolism) in some 

58404 Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 

situations. If so, this might occur if the 

mammals ascend unusually quickly 

when exposed to aversive sounds. 

Previously, it was widely assumed that 

diving marine mammals are not subject 

to decompression injury.

It is important to note that seismic 

pulses and mid-frequency sonar pulses 

are quite different. Sounds produced by 

the types of airgun arrays used to profile 

sub-sea geological structures are 

broadband with most of the energy 

below 1 kHz. Typical military midfrequency sonars operate at frequencies 

of 2 to 10 kHz, generally with a 

relatively narrow bandwidth at any one 

time (though the center frequency may 

change over time). Because seismic and 

sonar sounds have considerably 

different characteristics and duty cycles, 

it is not appropriate to assume that there 

is a direct connection between the 

effects of military sonar and seismic 

surveys on marine mammals. However, 

evidence that sonar pulses can, in 

special circumstances, lead to hearing 

damage and, indirectly, mortality 

suggests that caution is warranted when 

dealing with exposure of marine 

mammals to any high-intensity pulsed 

sound.

In addition to the sonar-related 

strandings, there was a September, 2002 

stranding of two Cuvier’s beaked whales 

in the Gulf of California (Mexico) when 

a seismic survey by the Ewing was 

underway in the general area (Malakoff, 

2002). The airgun array in use during 

that project was the Ewing’s 20–gun 

8490–in3 array. This might be a first 

indication that seismic surveys can have 

effects, at least on beaked whales, 

similar to the suspected effects of naval 

sonars. However, the evidence linking 

the Gulf of California strandings to the 

seismic surveys is inconclusive, and to 

date is not based on any physical 

evidence (Hogarth, 2002; Yoder, 2002). 

The ship was also operating its multibeam bathymetric sonar at the same 

time but this sonar had much less 

potential than these naval sonars to 

affect beaked whales. Although the link 

between the Gulf of California 

strandings and the seismic (plus multibeam sonar) survey is inconclusive, this 

plus the various incidents involving 

beaked whale strandings associated 

with naval exercises suggests a need for 

caution in conducting seismic surveys 

in areas occupied by beaked whales.

Non-auditory Physiological Effects

Possible types of non-auditory 

physiological effects or injuries that 

might theoretically occur in marine 

mammals exposed to strong underwater 

sound might include stress, neurological 

effects, bubble formation, resonance 

effects, and other types of organ or 

tissue damage. There is no evidence that 

any of these effects occur in marine 

mammals exposed to sound from airgun 

arrays. However, there have been no 

direct studies of the potential for airgun 

pulses to elicit any of these effects. If 

any such effects do occur, they would 

probably be limited to unusual 

situations when animals might be 

exposed at close range for unusually 

long periods.

Long-term exposure to anthropogenic 

noise may have the potential to cause 

physiological stress that could affect the 

health of individual animals or their 

reproductive potential, which could 

theoretically cause effects at the 

population level (Gisner (ed.), 1999). 

However, there is essentially no 

information about the occurrence of 

noise-induced stress in marine 

mammals. Also, it is doubtful that any 

single marine mammal would be 

exposed to strong seismic sounds for 

sufficiently long that significant 

physiological stress would develop. 

This is particularly so in the case of the 

proposed L-DEO project where the 

airguns are small.

Gas-filled structures in marine 

animals have an inherent fundamental 

resonance frequency. If stimulated at 

this frequency, the ensuing resonance 

could cause damage to the animal. 

There may also be a possibility that high 

sound levels could cause bubble 

formation in the blood of diving 

mammals that in turn could cause an air 

embolism, tissue separation, and high, 

localized pressure in nervous tissue 

(Gisner (ed), 1999; Houser et al., 2001). 

In 2002, NMFS held a workshop (Gentry 

(ed.) 2002) to discuss whether the 

stranding of beaked whales in the 

Bahamas in 2000 might have been 

related to air cavity resonance or bubble 

formation in tissues caused by exposure 

to noise from naval sonar. A panel of 

experts concluded that resonance in airfilled structures was not likely to have 

caused this stranding. Among other 

reasons, the air spaces in marine 

mammals are too large to be susceptible 

to resonant frequencies emitted by midor low-frequency sonar; lung tissue 

damage has not been observed in any 

mass, multi-species stranding of beaked 

whales; and the duration of sonar pings 

is likely too short to induce vibrations 

that could damage tissues (Gentry (ed.), 

2002). Opinions were less conclusive 

about the possible role of gas (nitrogen) 

bubble formation/growth in the 

Bahamas stranding of beaked whales. 

Workshop participants did not rule out 

the possibility that bubble formation/

growth played a role in the stranding 

and participants acknowledged that 

more research is needed in this area. 

The only available information on 

acoustically-mediated bubble growth in 

marine mammals is modeling that 

assumes prolonged exposure to sound.

Until recently, it was assumed that 

diving marine mammals are not subject 

to the bends or air embolism. However, 

a paper concerning beaked whales 

stranded in the Canary Islands in 2002 

suggests that cetaceans might be subject 

to decompression injury in some 

situations (Jepson et al., 2003). If so, that 

might occur if they ascend unusually 

quickly when exposed to aversive 

sounds. However, the interpretation that 

the effect was related to decompression 

injury is unproven (Piantadosi and 

Thalmann, 2004; Fernandez et al., 

2004). Even if that effect can occur 

during exposure to mid-frequency 

sonar, there is no evidence that this type 

of effect occurs in response to lowfrequency airgun sounds. It is especially 

unlikely in the case of the proposed LDEO survey which involves only three 

GI-guns.

In summary, little is known about the 

potential for seismic survey sounds to 

cause either auditory impairment or 

other non-auditory physical effects in 

marine mammals. Available data 

suggest that such effects, if they occur 

at all, would be limited to short 

distances from the sound source. 

However, the available data do not 

allow for meaningful quantitative 

predictions of the numbers (if any) of 

marine mammals that might be affected 

in these ways. Marine mammals that 

show behavioral avoidance of seismic 

vessels, including most baleen whales, 

some odontocetes, and some pinnipeds, 

are unlikely to incur auditory 

impairment or other physical effects. 

Also, the planned mitigation and 

monitoring measures are expected to 

minimize any possibility of serious 

injury, mortality or strandings.

Possible Effects of Mid-frequency Sonar 

Signals

A multi-beam bathymetric sonar 

(Atlas Hydrosweep DS–2 (15.5–kHz) 

and a sub-bottom profiler will be 

operated from the source vessel 

essentially continuously during the 

planned survey. Details about these 

sonars were provided previously in this 

document.

Navy sonars that have been linked to 

avoidance reactions and stranding of 

cetaceans generally (1) are more 

powerful than the Atlas Hydrosweep 

sonars, (2) have a longer pulse duration, 

and (3) are directed close to horizontally 

(vs. downward for the Atlas 

Hydrosweep). The area of possible 

influence for the Ewing’s sonars is much 

Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 58405

smaller - a narrow band below the 

source vessel. For the Hydrosweep there 

is no horizontal propagation as these 

signals project at an angle of 

approximately 45 degrees from the ship. 

For the deep-water mode, under the 

ship the 160- and 180–dB zones are 

estimated to be 3200 m (10500 ft) and 

610 m (2000 ft), respectively. However, 

the beam width of the Hydrosweep 

signal is only 2.67 degrees fore and aft 

of the vessel, meaning that a marine 

mammal diving could receive at most 1–

2 signals from the Hydrosweep and a 

marine mammal on the surface would 

be unaffected. Marine mammals that do 

encounter the bathymetric sonars at 

close range are unlikely to be subjected 

to repeated pulses because of the narrow 

fore-aft width of the beam, and will 

receive only limited amounts of pulse 

energy because of the short pulses and 

vessel speed. Therefore, as harassment 

or injury from pulsed sound is a 

function of total energy received, the 

actual harassment or injury threshold 

for the bathymetric sonar signals 

(approximately 10 ms) would be at a 

much higher dB level than that for 

longer duration pulses such as seismic 

signals. As a result, NMFS believes that 

marine mammals are unlikely to be 

harassed or injured from the multibeam 

sonar.

Masking by Mid-frequency Sonar 

Signals

Marine mammal communications will 

not be masked appreciably by the 

multibeam sonar signals or the subbottom profiler given the low duty cycle 

and directionality of the sonars and the 

brief period when an individual 

mammal is likely to be within its beam. 

Furthermore, in the case of baleen 

whales, the sonar signals from the 

Hydrosweep sonar do not overlap with 

the predominant frequencies of the 

calls, which would avoid significant 

masking.

For the sub-bottom profiler, marine 

mammal communications will not be 

masked appreciably because of their 

relatively low power output, low duty 

cycle, directionality (for the profiler), 

and the brief period when an individual 

mammal may be within the sonar’s 

beam. In the case of most odonotocetes, 

the sonar signals from the profiler do 

not overlap with the predominant 

frequencies in their calls. In the case of 

mysticetes, the pulses from the pinger 

do not overlap with their predominant 

frequencies.

Behavioral Responses Resulting from 

Mid-Frequency Sonar Signals

Behavioral reactions of free-ranging 

marine mammals to military and other 

sonars appear to vary by species and 

circumstance. Observed reactions have 

included silencing and dispersal by 

sperm whales (Watkins et al., 1985), 

increased vocalizations and no dispersal 

by pilot whales (Rendell and Gordon, 

1999), and the previously-mentioned 

strandings by beaked whales. Also, 

Navy personnel have described 

observations of dolphins bow-riding 

adjacent to bow-mounted mid-frequency 

sonars during sonar transmissions. 

However, all of these observations are of 

limited relevance to the present 

situation. Pulse durations from these 

sonars were much longer than those of 

the L-DEO multibeam sonar, and a given 

mammal would have received many 

pulses from the naval sonars. During LDEO’s operations, the individual pulses 

will be very short, and a given mammal 

would not receive many of the 

downward-directed pulses as the vessel 

passes by.

Captive bottlenose dolphins and a 

white whale exhibited changes in 

behavior when exposed to 1–sec pulsed 

sounds at frequencies similar to those 

that will be emitted by the multi-beam 

sonar used by L-DEO and to shorter 

broadband pulsed signals. Behavioral 

changes typically involved what 

appeared to be deliberate attempts to 

avoid the sound exposure (Schlundt et 

al., 2000; Finneran et al., 2002). The 

relevance of these data to free-ranging 

odontocetes is uncertain and in any case 

the test sounds were quite different in 

either duration or bandwidth as 

compared to those from a bathymetric 

sonar.

L-DEO and NMFS are not aware of 

any data on the reactions of pinnipeds 

to sonar sounds at frequencies similar to 

those of the 15.5 kHz frequency of the 

Ewing’s multibeam sonar. Based on 

observed pinniped responses to other 

types of pulsed sounds, and the likely 

brevity of exposure to the bathymetric 

sonar sounds, pinniped reactions are 

expected to be limited to startle or 

otherwise brief responses of no lasting 

consequences to the individual animals. 

The pulsed signals from the sub-bottom 

profiler are much weaker than those 

from the airgun array and the multibeam 

sonar. Therefore, significant behavioral 

responses are not expected.

Hearing Impairment and Other Physical 

Effects

Given recent stranding events that 

have been associated with the operation 

of naval sonar, there is much concern 

that sonar noise can cause serious 

impacts to marine mammals (for 

discussion see Effects of Seismic 

Surveys on Marine Mammals). 

However, the multi-beam sonars 

proposed for use by L-DEO are quite 

different than sonars used for navy 

operations. Pulse duration of the 

bathymetric sonars is very short relative 

to the naval sonars. Also, at any given 

location, an individual marine mammal 

would be in the beam of the multi-beam 

sonar for much less time given the 

generally downward orientation of the 

beam and its narrow fore-aft beamwidth. (Navy sonars often use nearhorizontally-directed sound.) These 

factors would all reduce the sound 

energy received from the multi-beam 

sonar rather drastically relative to that 

from the sonars used by the Navy. 

Therefore, hearing impairment by multibeam bathymetric sonar is unlikely.

Source levels of the sub-bottom 

profiler are much lower than those of 

the airguns and the multi-beam sonar. 

Sound levels from a sub-bottom profiler 

similar to the one on the Ewing were 

estimated to decrease to 180 dB re 1 

microPa (rms) at 8 m (26 ft) horizontally 

from the source (Burgess and Lawson, 

2000), and at approximately 18 m 

downward from the source. 

Furthermore, received levels of pulsed 

sounds that are necessary to cause 

temporary or especially permanent 

hearing impairment in marine mammals 

appear to be higher than 180 dB (see 

earlier discussion). Thus, it is unlikely 

that the sub-bottom profiler produces 

pulse levels strong enough to cause 

hearing impairment or other physical 

injuries even in an animal that is 

(briefly) in a position near the source.

The sub-bottom profiler is usually 

operated simultaneously with other 

higher-power acoustic sources. Many 

marine mammals will move away in 

response to the approaching higherpower sources or the vessel itself before 

the mammals would be close enough for 

there to be any possibility of effects 

from the less intense sounds from the 

sub-bottom profiler. In the case of 

mammals that do not avoid the 

approaching vessel and its various 

sound sources, mitigation measures that 

would be applied to minimize effects of 

the higher-power sources would further 

reduce or eliminate any minor effects of 

the sub-bottom profiler.

Estimates of Take by Harassment for 

the ETPO Seismic Survey

Although information contained in 

this document indicates that injury to 

marine mammals from seismic sounds 

potentially occurs at sound pressure 

levels significantly higher than 180 and 

190 dB, NMFS’ current criteria for onset 

of Level A harassment of cetaceans and 

pinnipeds from impulse sound are, 

respectively, 180 and 190 re 1 microPa 

rms. The rms level of a seismic pulse is 

58406 Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 

typically about 10 dB less than its peak 

level and about 16 dB less than its pkpk level (Greene, 1997; McCauley et al., 

1998; 2000a). The criterion for Level B 

harassment onset is 160 dB.

Given the proposed mitigation (see 

Mitigation later in this document), all 

anticipated takes involve a temporary 

change in behavior that may constitute 

Level B harassment. The proposed 

mitigation measures will minimize or 

eliminate the possibility of Level A 

harassment or mortality. L-DEO has 

calculated the ‘‘best estimates’’ for the 

numbers of animals that could be taken 

by level B harassment during the 

proposed ETPO seismic survey using 

data on marine mammal density and 

abundance from marine mammal 

surveys in the region, and estimates of 

the size of the affected area, as shown 

in the predicted RMS radii table (see 

Table 1).

These estimates are based on a 

consideration of the number of marine 

mammals that might be exposed to 

sound levels greater than 160 dB, the 

criterion for the onset of Level B 

harassment, by operations with the 3 GIgun array planned to be used for this 

project. The anticipated zone of 

influence of the multi-beam sonar is less 

than that for the airguns, so it is 

assumed that any marine mammals 

close enough to be affected by the multibeam sonar would already be affected 

by the airguns. Therefore, no additional 

incidental takings are included for 

animals that might be affected by the 

multi-beam sonar.

Table 2 explains the corrected density 

estimates as well as the best estimate of 

the numbers of each species that would 

be exposed to seismic sounds greater 

than 160 dB. A detailed description on 

the methodology used by L-DEO to 

arrive at the estimates of Level B 

harassment takes that are provided in 

Table 2 can be found in L-DEO’s IHA 

application for the ETPO survey.

BILLING CODE 3510–22–S

Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 58407


EN30se04.201</GPH>
58408 Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 

BILLING CODE 3510–22–C 

Conclusions

Effects on Cetaceans

Strong avoidance reactions by several 

species of mysticetes to seismic vessels 

have been observed at ranges up to 6–

8 km (3.2–4.3 nm) and occasionally as 

far as 20–30 km (10.8–16.2 nm) from the 

source vessel. However, reactions at the 

longer distances appear to be atypical of 

most species and situations, particularly 

when feeding whales are involved. Few 

mysticetes are expected to be 

encountered during the proposed survey 

in the ETPO (Table 2) and disturbance 

effects would be confined to shorter 

distances given the low-energy acoustic 

source to be used during this project. In 

addition, the estimated numbers 

presented in Table 2 are considered 

overestimates of actual numbers that 

may be harassed.

Odontocete reactions to seismic 

pulses, or at least the reactions of 

dolphins, are expected to extend to 

lesser distances than are those of 

mysticetes. Odontocete low-frequency 

hearing is less sensitive than that of 

mysticetes, and dolphins are often seen 

from seismic vessels. In fact, there are 

documented instances of dolphins 

approaching active seismic vessels. 

However, dolphins as well as some 

other types of odontocetes sometimes 

show avoidance responses and/or other 

changes in behavior when near 

operating seismic vessels.

Taking into account the small size 

and the relatively low sound output of 

the 3 GI-guns to be used, and the 

mitigation measures that are planned, 

effects on cetaceans are generally 

expected to be limited to avoidance of 

a small area around the seismic 

operation and short-term changes in 

behavior, falling within the MMPA 

definition of Level B harassment. 

Furthermore, the estimated numbers of 

animals potentially exposed to sound 

levels sufficient to cause appreciable 

disturbance are very low percentages of 

the affected populations.

Based on the 160–dB criterion, the 

best estimates of the numbers of 

individual cetaceans that may be 

exposed to sounds ≥ 160 dB re 1 

microPa (rms) represent 0 to 

approximately 0.4 percent (except for 

approximately 2.4 percent for dwarf 

sperm whales) of the regional ETPO 

species populations (Table 2). L-DEO 

also estimates that approximately 0.1 

percent of the estimated (corrected) 

regional ETPO population of 

approximately 26,053 sperm whales 

(Table 2) would be exposed to sounds 

≥ 160 dB re 1 microPa (rms). In the case 

of endangered balaenopterids, it is most 

likely that no humpback, sei, or fin 

whales will be exposed to seismic 

sounds ≥ 160 dB re 1 microPa (rms), 

based on the reported (corrected) 

densities of those species in the survey 

region. However, L-DEO has requested 

an authorization to expose up to 2 

individuals of each of those species to 

seismic sounds of ≥ 160 dB during the 

proposed survey given the possibility of 

encountering one or more groups. Best 

estimates of blue whales are 3 

individuals that might be potentially 

exposed to seismic pulses with received 

levels ≥ 160 dB re 1 microPa (rms), 

representing approximately 0.2 percent 

of the estimated regional ETP 

population of approximately 1400 blue 

whales (Table 2).

Larger numbers of delphinids may be 

affected by the proposed seismic 

surveys, but the population sizes of 

species likely to occur in the survey area 

are large, and the numbers potentially 

affected are small relative to population 

sizes (Table 2). The best estimates of the 

numbers of individual delphinids that 

will potentially be exposed to sounds ≥

160 dB re 1 microPa (rms) represent less 

than 0.1 percent of the approximately 

10,000,000 dolphins estimated to occur 

in the ETPO, and less than 0.3 percent 

of the bottlenose dolphin population 

occurring there (Table 2).

Mitigation measures such as 

controlled speed, course alteration, 

observers, use of the PAM system, nonpursuit, ramp ups, and power downs or 

shut downs when marine mammals are 

seen within defined ranges should 

further reduce short-term reactions, and 

minimize any effects on hearing. In all 

cases, the effects are expected to be 

short-term, with no lasting biological 

consequence. In light of the type of take 

expected and the small percentages of 

affected stocks of cetaceans, the action 

is expected to have no more than a 

negligible impact on the affected species 

or stocks of cetaceans.

Effects on Pinnipeds

It is unlikely that any pinnipeds will 

be encountered during the proposed 

survey. However, to ensure that the LDEO project remains in compliance 

with the MMPA in the event that a few 

pinnipeds are encountered, L-DEO has 

requested an authorization to expose up 

to 10 individuals of each of four 

pinniped species to seismic sounds with 

rms levels ≥ 160 dB re 1 μPa. If 

pinnipeds are encountered, they will be 

stray individuals outside of their normal 

range. The proposed survey would have, 

at most, a short-term effect on their 

behavior and no long-term impacts on 

individual pinnipeds or their 

populations. Responses of pinnipeds to 

acoustic disturbance are variable, but 

usually quite limited. Effects are 

expected to be limited to short-term and 

localized behavioral changes falling 

within the MMPA definition of Level B 

harassment. As is the case for cetaceans, 

the short-term exposures to sounds from 

the three GI-guns are not expected to 

result in any long-term consequences for 

the individuals or their populations and 

the activity is expected to have no more 

than a negligible impact on the affected 

species or stocks of pinnipeds.

Potential Effects on Habitat

The proposed seismic survey 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.

One of the reasons for the adoption of 

airguns as the standard energy source 

for marine seismic surveys was that they 

(unlike the explosives used in the 

distant past) do not result in any 

appreciable fish kill. Various 

experimental studies showed that 

airgun discharges cause little or no fish 

kill, and that any injurious effects were 

generally limited to the water within a 

meter or so of an airgun. However, it has 

recently been found that injurious 

effects on captive fish, especially on fish 

hearing, may occur at somewhat greater 

distances than previously thought 

(McCauley et al., 2000a,b, 2002; 2003). 

Even so, any injurious effects on fish 

would be limited to short distances from 

the source. Also, many of the fish that 

might otherwise be within the injuryzone are likely to be displaced from this 

region prior to the approach of the 

airguns through avoidance reactions to 

the passing seismic vessel or to the 

airgun sounds as received at distances 

beyond the injury radius.

Fish often react to sounds, especially 

strong and/or intermittent sounds of low 

frequency. Sound pulses at received 

levels of 160 dB re 1 μPa (peak) may 

cause subtle changes in behavior. Pulses 

at levels of 180 dB (peak) may cause 

noticeable changes in behavior 

(Chapman and Hawkins, 1969; Pearson 

et al., 1992; Skalski et al., 1992). It also 

appears that fish often habituate to 

repeated strong sounds rather rapidly, 

on time scales of minutes to an hour. 

However, the habituation does not 

endure, and resumption of the 

disturbing activity may again elicit 

disturbance responses from the same 

fish.

Fish near the airguns are likely to dive 

or exhibit some other kind of behavioral 

response. This might have short-term 

Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 58409

impacts on the ability of cetaceans to 

feed near the survey area. However, 

only a small fraction of the available 

habitat would be ensonified at any given 

time, and fish species would return to 

their pre-disturbance behavior once the 

seismic activity ceased. Thus, the 

proposed surveys would have little 

impact on the abilities of marine 

mammals to feed in the area where 

seismic work is planned. Some of the 

fish that do not avoid the approaching 

airguns (probably a small number) may 

be subject to auditory or other injuries.

Zooplankton that are very close to the 

source may react to the airgun’s shock 

wave. These animals have an 

exoskeleton and no air sacs; therefore, 

little or no mortality is expected. Many 

crustaceans can make sounds and some 

crustacea and other invertebrates have 

some type of sound receptor. However, 

the reactions of zooplankton to sound 

are not known. Some mysticetes feed on 

concentrations of zooplankton. A 

reaction by zooplankton to a seismic 

impulse would only be relevant to 

whales if it caused a concentration of 

zooplankton to scatter. Pressure changes 

of sufficient magnitude to cause this 

type of reaction would probably occur 

only very close to the source, so few 

zooplankton concentrations would be 

affected. Impacts on zooplankton 

behavior are predicted to be negligible, 

and this would translate into negligible 

impacts on feeding mysticetes.

Potential Effects on Subsistence Use of 

Marine Mammals

There is no legal subsistence hunting 

for marine mammals in the ETPO off 

Central America, so the proposed L-DEO 

activities will not have any impact on 

the availability of these species or stocks 

for subsistence users.

Mitigation

For the proposed seismic survey in 

the ETPO off Central America, L-DEO 

will deploy 3 GI-airguns as an energy 

source, with a total discharge volume of 

315 in3. The energy from the airguns 

will be directed mostly downward. The 

directional nature of the airguns to be 

used in this project is an important 

mitigating factor. This directionality 

will result in reduced sound levels at 

any given horizontal distance as 

compared with the levels expected at 

that distance if the source were 

omnidirectional with the stated nominal 

source level. Also, the small size of 

these airguns is an inherent and 

important mitigation measure that will 

reduce the potential for effects relative 

to those that might occur with large 

airgun arrays. This measure is in 

conformance with NMFS encouraging 

seismic operators to use the lowest 

intensity airguns practical to 

accomplish research objectives.

The following mitigation measures, as 

well as marine mammal visual 

monitoring (discussed later in this 

document), will be implemented for the 

subject seismic surveys: (1) Speed and 

course alteration (provided that they do 

not compromise operational safety 

requirements); (2) power-down and 

shut-down procedures; (3) ramp-up 

procedures, and (4) use of passive 

acoustics to detect vocalizing marine 

mammals.

Speed and Course Alteration

If a marine mammal is detected 

outside its respective safety zone (180 

dB for cetaceans, 190 dB for pinnipeds) 

and, based on its position and the 

relative motion, is likely to enter the 

safety zone, the vessel’s speed and/or 

direct course may, when practical and 

safe, be changed in a manner that also 

minimizes the effect to the planned 

science objectives. The marine mammal 

activities and movements relative to the 

seismic vessel will be closely monitored 

to ensure that the marine mammal does 

not approach within the safety zone. If 

the mammal appears likely to enter the 

safety zone, further mitigative actions 

will be taken (i.e., either further course 

alterations or shut down of the airguns).

Power-down and Shut-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 are not in the safety 

zone. During a power down, one GIairgun will continue to be operated. The 

continued operation of one airgun is 

intended to alert marine mammals 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 is detected 

outside the safety radius but is likely to 

enter the safety radius, and if the 

vessel’s speed and/or course cannot be 

changed to avoid having the mammal 

enter the safety radius, the GI-guns will 

be powered down before the mammal is 

within the safety radius. Likewise, if a 

mammal is already within the safety 

zone when first detected, the airguns 

will be powered down immediately. 

During a power down, one GI-airgun 

(i.e., 105 in3) will be operated. If a 

marine mammal is detected within or 

near the smaller safety radius around 

that single GI-gun (Table 1), all guns 

will be shut down.

Following a power down, airgun 

activity will not resume until the marine 

mammal has cleared the safety zone. 

The animal will be considered to have 

cleared the safety zone if it (1) is 

visually observed to have left the safety 

zone, or (2) has not been seen within the 

zone for 15 min in the case of small 

odontocetes and pinnipeds, or (3) has 

not been seen within the zone for 30 

min in the case of mysticetes and large 

odontocetes, including sperm, pygmy 

sperm, dwarf sperm, and beaked 

whales.

During airgun operations following a 

power-down whose duration has 

exceeded these specified limits, the 

airgun array will be ramped-up 

gradually. Ramp-up is described later in 

this document.

During a power down, the operating 

GI-airgun will be shut down if a marine 

mammal approaches and is about to 

enter the modeled safety radius for the 

operating single GI gun. For a 105 in3 GI 

gun, the predicted 180–dB distances 

applicable to cetaceans are 27–189 m 

(89–620 ft), depending on water depth, 

and the corresponding 190–dB radii 

applicable to pinnipeds are 10–150 m 

(33–492 ft), depending on depth (Table 

1). Airgun activity will not resume until 

the marine mammal has cleared the 

safety radius, as described for powerdown situations.

Ramp-up Procedure

When airgun operations commence 

after a specified period without airgun 

operations, the number of guns firing 

will be increased gradually, or ‘‘ramped 

up’’ (also described as a ‘‘soft start’’). 

The specified period of time for the GIairguns varies depending on the speed 

of the source vessel. Under normal 

operational conditions (vessel speed 4.9 

knots or 9 km/h), the Ewing would 

travel 574 m (1476 ft) in about 4 

minutes. The 574–m distance is the 

calculated 180–dB safety radius for the 

three GI-gun array operating in shallow 

water. Thus, a ramp up would be 

required after a power down or shut 

down period lasting about 4 minutes or 

longer if the Ewing was traveling at 4.9 

knots and was towing the three GIairgun array. Ramp up will begin with 

one of the 105–in3 GI guns. The other 

two GI-guns will be added at 5 min 

intervals. During ramp up, the safety 

radius for the full gun array will be 

maintained.

During the day, ramp-up cannot begin 

from a shut-down unless the entire 180–

dB safety radius has been visible for at 

least 30 minutes prior to the ramp up 

(i.e., no ramp-up can begin in heavy fog 

or high sea states). However, ramp up 

may occur from a power down in heavy 

fog or high sea states, as long as at least 

one GI gun has been maintained during 

the interruption of seismic activity.

58410 Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 

During nighttime operations, if the 

entire safety radius is visible using 

vessel lights and night-vision devices 

(NVDs) (as may be the case in deep and 

intermediate waters), then start up of 

the airguns from a shut down may 

occur. However, lights and NVDs will 

probably not be very effective as a basis 

for monitoring the larger safety radii 

around the three GI-guns operating in 

shallow water. It is proposed that, in 

shallow water, nighttime start ups of the 

airguns will not be authorized. 

However, ramp-up may occur from a 

power-down at night, as long as at least 

one GI-gun has been maintained during 

the interruption of the seismic signal. 

Also, if the airgun array has been 

operational before nightfall, it can 

remain operational throughout the 

night, even though the entire safety 

radius may not be visible.

Comments on past IHAs raised the 

issue of prohibiting nighttime 

operations as a practical mitigation 

measure. However, this is not 

practicable due to cost considerations 

and ship time schedules. The daily cost 

to the federal government to operate 

vessels such as Ewing is approximately 

$33,000-$35,000 /day (Ljunngren, pers. 

comm. May 28, 2003). If the vessels 

were prohibited from operating during 

nighttime, each trip could require an 

additional three to five days to 

complete, or up to $175,000 more, 

depending on average daylight at the 

time of work.

If a seismic survey vessel is limited to 

daylight seismic operations, efficiency 

would also be much reduced. Without 

commenting specifically on how that 

would affect the present project, for 

seismic operators in general, a daylightonly requirement would be expected to 

result in one or more of the following 

outcomes: cancellation of potentially 

valuable seismic surveys; reduction in 

the total number of seismic cruises 

annually due to longer cruise durations; 

a need for additional vessels to conduct 

the seismic operations; or work 

conducted by non-U.S. operators or 

non-U.S. vessels when in waters not 

subject to U.S. law.

Marine Mammal Monitoring

L-DEO must have at least three visual 

observers on board the Ewing, and at 

least two must be an experienced 

marine mammal observer that NMFS 

has approved in advance of the start of 

the ETPO cruise. These observers will 

be on duty in shifts of no longer than 

4 hours.

The visual observers will monitor 

marine mammals and sea turtles near 

the seismic source vessel during all 

daytime airgun operations, during any 

nighttime start-ups of the airguns and at 

night, whenever daytime monitoring 

resulted in one or more shut-down 

situations due to marine mammal 

presence. During daylight, vessel-based 

observers will watch for marine 

mammals and sea turtles near the 

seismic vessel during periods with 

shooting (including ramp-ups), and for 

30 minutes prior to the planned start of 

airgun operations after a shut-down.

Use of multiple observers will 

increase the likelihood that marine 

mammals near the source vessel are 

detected. L-DEO bridge personnel will 

also assist in detecting marine mammals 

and implementing mitigation 

requirements whenever possible (they 

will be given instruction on how to do 

so), especially during ongoing 

operations at night when the designated 

observers are on stand-by and not 

required to be on watch at all times.

The observer(s) will watch for marine 

mammals from the highest practical 

vantage point on the vessel, which is 

either the bridge or the flying bridge. On 

the bridge of the Ewing, the observer’s 

eye level will be 11 m (36 ft) above sea 

level, allowing for good visibility within 

a 210 arc. If observers are stationed on 

the flying bridge, the eye level will be 

14.4 m (47.2 ft) above sea level. The 

observer(s) will systematically scan the 

area around the vessel with Big Eyes 

binoculars, reticle binoculars (e.g., 7 X 

50 Fujinon) and with the naked eye 

during the daytime. Laser range-finding 

binoculars (Leica L.F. 1200 laser 

rangefinder or equivalent) will be 

available to assist with distance 

estimation. The observers will be used 

to determine when a marine mammal or 

sea turtle is in or near the safety radii 

so that the required mitigation 

measures, such as course alteration and 

power-down or shut-down, can be 

implemented. If the GI-airguns are 

powered-down or shut down, observers 

will maintain watch to determine when 

the animal is outside the safety radius.

Observers will not be on duty during 

ongoing seismic operations at night; 

bridge personnel will watch for marine 

mammals during this time and will call 

for the airguns to be powered-down or 

shut-down if marine mammals are 

observed in or about to enter the safety 

radii. However, a biological observer 

must be on standby at night and 

available to assist the bridge watch if 

marine mammals are detected. If the 

airguns are ramped-up at night (see 

previous section), two marine mammal 

observers will monitor for marine 

mammals for 30 minutes prior to rampup and during the ramp-up using either 

deck lighting or NVDs that will be 

available (ITT F500 Series Generation 3 

binocular image intensifier or 

equivalent).

Post-Survey Monitoring

In addition, the biological observers 

will be able to conduct monitoring of 

most recently-run transect lines as the 

Ewing returns along a parallel transect 

track. A final post-survey transect will 

be conducted by the Ewing as it 

retrieves the hydrophone array. This 

will provide the biological observers 

with opportunities to look for injured or 

dead marine mammals (although no 

injuries or mortalities are expected 

during this research cruise).

Passive Acoustic Monitoring (PAM)

L-DEO has agreed to use the PAM 

system whenever the Ewing is operating 

in waters deep enough for the PAM 

hydrophone array to be towed. Passive 

acoustic equipment was first used on 

the Ewing during the 2003 Sperm Whale 

Seismic Study conducted in the Gulf of 

Mexico and subsequently was evaluated 

by L-DEO to determine whether it was 

practical to incorporate it into future 

seismic research cruises. The SEAMAP 

system has been used successfully in LDEO’s SE Caribbean study (69 FR 24571, 

May 4, 2004). The SEAMAP PAM 

system has four hydrophones, which 

allow the SEAMAP system to derive the 

bearing toward the a vocalizing marine 

mammal. In order to operate the 

SEAMAP system, the marine mammal 

monitoring contingent onboard the 

Ewing will be increased by 2 additional 

biologists/acousticians who will 

monitor the SEAMAP system. 

Verification of acoustic contacts will 

then be attempted through visual 

observation by the marine mammal 

observers. However, the PAM system by 

itself usually does not determine the 

distance that the vocalizing mammal 

might be from the seismic vessel. It can 

be used as a cue by the visual observers 

as to the presence of an animal and to 

its approximate bearing (with some 

ambiguity). At this time, however, it is 

doubtful if PAM can be used as a trigger 

to initiate power-down of the array. 

NMFS encourages L-DEO to continue to 

study the relationship between a signal 

on a passive acoustic array and distance 

from the array can be determined with 

sufficient accuracy to be used for this 

purpose without complementary visual 

observations.

Taking into consideration the 

additional costs of prohibiting nighttime 

operations and the likely impact of the 

activity (including all mitigation and 

monitoring), NMFS has preliminarily 

determined that the proposed mitigation 

and monitoring ensures that the activity 

will have the least practicable impact on 

Federal Register / Vol. 69, No. 189 / Thursday, September 30, 2004 / Notices 58411

the affected species or stocks. Marine 

mammals will have sufficient notice of 

a vessel approaching with operating 

seismic airguns, thereby giving them an 

opportunity to avoid the approaching 

array; if ramp-up is required, two 

marine mammal observers will be 

required to monitor the safety radii 

using shipboard lighting or NVDs for at 

least 30 minutes before ramp-up begins 

and verify that no marine mammals are 

in or approaching the safety radii; rampup may not begin unless the entire 

safety radii are visible. Therefore as 

mentioned earlier, it is likely that the 3 

GI-airgun array will not be ramped-up 

from a shut-down at night when in 

waters shallower than 100 m (328 ft).

Reporting

L-DEO will submit a report to NMFS 

within 90 days after the end of the 

cruise, which is currently predicted to 

occur during November and December, 

2004. The report will describe the 

operations that were conducted and the 

marine mammals that were detected. 

The report must provide full 

documentation of methods, results, and 

interpretation pertaining to all 

monitoring tasks. The report will 

summarize the dates and locations of 

seismic operations, marine mammal 

sightings (dates, times, locations, 

activities, associated seismic survey 

activities), and estimates of the amount 

and nature of potential take of marine 

mammals by harassment or in other 

ways.

Endangered Species Act (ESA)

Under section 7 of the ESA, the 

National Science Foundation (NSF), the 

agency funding L-DEO, has begun 

consultation on the proposed seismic 

survey. NMFS will also consult on the 

issuance of an IHA under section 

101(a)(5)(D) of the MMPA for this 

activity. Consultation will be concluded 

prior to a determination on the issuance 

of an IHA.

National Environmental Policy Act 

(NEPA)

The NSF has prepared an EA for the 

ETPO oceanographic surveys. NMFS is 

reviewing this EA and will either adopt 

it or prepare its own NEPA document 

before making a determination on the 

issuance of an IHA. A copy of the NSF 

EA for this activity is available upon 

request (see ADDRESSES).

Preliminary Conclusions

NMFS has preliminarily determined 

that the impact of conducting the 

seismic survey in the ETPO off Central 

America may result, at worst, in a 

temporary modification in behavior by 

certain species of marine mammals. 

This activity is expected to result in no 

more than a negligible impact on the 

affected species or stocks.

For reasons stated previously in this 

document, this preliminary 

determination is supported by (1) the 

likelihood that, given sufficient notice 

through slow ship speed and ramp-up, 

marine mammals are expected to move 

away from a noise source that it is 

annoying prior to its becoming 

potentially injurious; (2) recent research 

that indicates that TTS is unlikely (at 

least in delphinids) until levels closer to 

200–205 dB re 1 microPa are reached 

rather than 180 dB re 1 microPa; (3) the 

fact that 200–205 dB isopleths would be 

well within 100 m (328 ft) of the vessel 

even in shallow water; and (4) the 

likelihood that marine mammal 

detection ability by trained observers is 

close to 100 percent during daytime and 

remains high at night to that distance 

from the seismic vessel. As a result, no 

take by injury or death is anticipated, 

and the potential for temporary or 

permanent hearing impairment is very 

low and will be avoided through the 

incorporation of the proposed 

mitigation measures mentioned in this 

document.

While the number of potential 

incidental harassment takes will depend 

on the distribution and abundance of 

marine mammals in the vicinity of the 

survey activity, the number of potential 

harassment takings is estimated to be 

small. In addition, the proposed seismic 

program will not interfere with any legal 

subsistence hunts, since seismic 

operations will not take place in 

subsistence whaling and sealing areas 

and will not affect marine mammals 

used for subsistence purposes.

Proposed Authorization

NMFS proposes to issue an IHA to LDEO for conducting a oceanographic 

seismic survey in the ETPO off Central 

America, provided the previously 

mentioned mitigation, monitoring, and 

reporting requirements are incorporated. 

NMFS has preliminarily determined 

that the proposed activity would result 

in the harassment of small numbers of 

marine mammals; would have no more 

than a negligible impact on the affected 

marine mammal stocks; and would not 

have an unmitigable adverse impact on 

the availability of species or stocks for 

subsistence uses.

Information Solicited

NMFS requests interested persons to 

submit comments and information 

concerning this request (see ADDRESSES).

Dated: September 24, 2004.

Laurie K. Allen,

Director, Office of Protected Resources, 

National Marine Fisheries Service.

[FR Doc. 04–21973 Filed 9–29–04; 8:45 am]

BILLING CODE 3510–22–S

COMMITTEE FOR THE 

IMPLEMENTATION OF TEXTILE 

AGREEMENTS

Adjustment of an Import Sublimit for 

Certain Man-Made Fiber Textile 

Products Produced or Manufactured in 

Belarus

September 28, 2004.

AGENCY: Committee for the 

Implementation of Textile Agreements 

(CITA).

ACTION: Issuing a directive to the 

Commissioner, Bureau of Customs and 

Border Protection adjusting a sublimit.

EFFECTIVE DATE: September 30, 2004.

FOR FURTHER INFORMATION CONTACT:

Naomi Freeman, International Trade 

Specialist, Office of Textiles and 

Apparel, U.S. Department of Commerce, 

(202) 482–4212. For information on the 

quota status of this sublimit, refer to the 

Quota Status Reports posted on the 

bulletin boards of each Customs port, 

call (202) 927–5850, or refer to the 

Bureau of Customs and Border 

Protection website at http://

www.cbp.gov. For information on 

embargoes and quota re-openings, refer 

to the Office of Textiles and Apparel 

website at http://otexa.ita.doc.gov.

SUPPLEMENTARY INFORMATION:

Authority: Section 204 of the Agricultural 

Act of 1956, as amended (7 U.S.C. 1854); 

Executive Order 11651 of March 3, 1972, as 

amended.

The current sublimit for Category 622-

N is being adjusted for carryforward. 

The limit and sublimit for 622 and 622-

L remain unchanged.

A description of the textile and 

apparel categories in terms of HTS 

numbers is available in the 

CORRELATION: Textile and Apparel 

Categories with the Harmonized Tariff 

Schedule of the United States (see 

Federal Register notice 69 FR 4926, 

published on February 2, 2004). Also 

see 68 FR 70494, published on