74906 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric 

Administration

[I.D. 031104B]

Small Takes of Marine Mammals 

Incidental to Specified Activities; 

Marine Seismic Survey on the Blanco 

Fracture Zone in the Northeastern 

Pacific Ocean

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce.

ACTION: Notice of issuance of an 

incidental harassment authorization.

SUMMARY: In accordance with provisions 

of the Marine Mammal Protection Act 

(MMPA) as amended, notification is 

hereby given that an Incidental 

Harassment Authorization (IHA) to take 

small numbers of marine mammals, by 

harassment, incidental to conducting 

oceanographic seismic surveys on the 

Blanco Fracture and Gorda Ridge zones 

in the Northeastern Pacific Ocean has 

been issued to Lamont-Doherty Earth 

Observatory (L-DEO).

DATES: Effective from October 20, 2004 

through October 19, 2005.

ADDRESSES: The application, IHA and a 

list of the references used in this 

document are available by writing 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. A copy of the 

application 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 

for certain categories of activities not 

pertinent here, the MMPA defines 

‘‘harassment’’ as:

any act of pursuit, torment, or annoyance 

which (i) has the potential to injure a marine 

mammal or marine mammal stock in the wild 

[Level A harassment]; or (ii) has the potential 

to disturb a marine mammal or marine 

mammal stock in the wild by causing 

disruption of behavioral patterns, including, 

but not limited to, migration, breathing, 

nursing, breeding, feeding, or sheltering 

[Level B harassment].

Section 101(a)(5)(D) establishes a 45–

day time limit for NMFS review of an 

application followed by a 30–day public 

notice and comment period on any 

proposed 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 March 8, 2004, NMFS received an 

application from L-DEO for the taking, 

by harassment, of several species of 

marine mammals incidental to 

conducting a seismic survey program. LDEO plans to conduct a marine seismic 

survey in the Northeastern Pacific 

Ocean (NPO), off Oregon, during the fall 

of 2004. Up to two seismic surveys are 

scheduled to take place in the NPO. The 

main survey is planned to occur near 

the intersection of the Blanco Transform 

and the Juan de Fuca Ridge. Time 

permitting, a second survey may be 

conducted at Gorda Ridge. The main 

seismic survey will take place between 

44°0 20′ and 44° 42′N and between 129°

50′ and 130° 30′W or at least 450 km 

(243 nm) offshore and outside the 

Exclusive Economic Zone (EEZ) of any 

nation. The Gorda Ridge survey is 

located between 42° 20′ and 43° N and 

between 126° 30′ and 127° W, at least 

84 nm (155.6 km) offshore, but within 

the EEZ of the United States.

The purpose of the seismic survey is 

to obtain information on the structure of 

the oceanic crust created at the Juan de 

Fuca Ridge. More specifically, the 

survey will obtain information on the 

geologic nature of boundaries of the 

earth’s crust created at the intermediatespreading Juan de Fuca Ridge. Past 

studies have mapped those boundaries 

using manned submersibles, but they 

have not provided a link between 

geologic and seismic structure. This 

study will provide the seismic data to 

assess the geologic nature of the 

previously mapped areas.

Description of the Activity

The proposed seismic survey will 

involve one vessel, the R/V Maurice 

Ewing (Ewing). The Ewing will deploy a 

10– or 12–airgun array as an energy 

source, with discharge volumes of 3050 

in3 and 3705 in3, respectively. The 

Ewing will also deploy and retrieve 12 

Ocean Bottom Seismometers (OBSs), 

plus tow a 6–km (3.2 nm) streamer 

containing hydrophones, to receive the 

returning acoustic signals. As the 

airguns are towed along the survey 

lines, these two systems will receive the 

returning acoustic signals.

A total of approximately 150 

kilometers (km) (81 nautical miles (nm)) 

of OBS surveys using a 12–gun array (24 

hours of operation) and approximately 

1017 km (549 nm) of Multi-Channel 

Seismic (MCS) profiles using a 10–gun 

array (6.5 days of operation) are planned 

to be conducted during the main survey. 

These line-kilometer figures include 

operations associated with start up, line 

changes of 10 km (5 nm) for the 12–gun 

array and 90 km (49 nm) for the 10–gun 

array, equipment testing, contingency 

profiles, and repeat coverage of any 

areas where initial data quality is substandard. In the unlikely event that 

there are no weather or equipment 

delays, additional MCS profiles may be 

acquired at the northern end of the 

Gorda Ridge where it intersects the 

Blanco Transform. The contingency 

survey would consist of 220 km (119 

nm) of survey lines using the 10–gun 

seismic array, plus 63 km (34 nm) for 

turns and connecting lines, for a total of 

283 km (153 nm). Water depths within 

the seismic survey areas are 1600 5000 

m (5250 16,405 ft).

During the airgun operations, the 

vessel will travel at 7.4–9.3 km/hr (4–5 

knots), and seismic pulses will be 

emitted at intervals of 60–90 sec for the 

OBS lines and approximately 20 sec for 

the Multi-Channel Seismic profiles 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74907

(MCS lines). The 20–sec spacing 

corresponds to a shot interval of about 

50 m (164 ft), while the 60–90 sec 

spacing corresponds to a distance of 150 

m (492 ft) to 220 m (722 ft), respectively. 

The 60–90 sec spacing along OBS lines 

is to minimize reverberation from 

previous shot noise during OBS data 

acquisition, and the exact spacing will 

depend on water depth.

For the 10- and 12–airgun arrays, the 

sound pressure fields have been 

modeled by L-DEO in relation to 

distance and direction from the airguns, 

and in relation to depth. Predicted 

sound levels are depicted in Figures 6 

and 7 in L-DEO’s application. Empirical 

data concerning those sound levels have 

been acquired 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. L-DEO’s analysis of the acoustic 

data from that study (Tolstoy et al. 2004) 

provides limited measurements in deep 

water, such as found at Blanco Fracture 

and Gorda Ridge. Those data indicate 

that, for deep water, L-DEO’s model 

tends to overestimate the received 

sound levels at a given distance. NMFS 

and L-DEO, therefore, propose that the 

180–dB and 190–dB (re 1 microPascal 

(root-mean-squared (rms)) sound 

pressure fields that will correspond to 

the safety radii (see Mitigation) will be 

the values predicted by L-DEO’s model 

during airgun operations in deep water, 

including these planned survey 

operations.

For the Blanco Fracture survey using 

10–gun and 12–gun arrays, the distances 

at which seismic pulses are expected to 

diminish to received levels of 190 dB, 

180 dB, 170 dB and 160 dB re 1 microPa 

rms are as follows:

TABLE 1. DISTANCES TO WHICH SOUND LEVELS MIGHT BE RECEIVED FROM THE AIRGUN ARRAYS PLANNED FOR USE IN THE

BLANCO FRACTURE ZONE. 

Airgun Array 

RMS Radii (m/ft) 

190 dB 180 dB 170 dB 160 dB

1 airgun ............................................................................................................ 13/43 36/118 110/361 350/1148

10 airguns ........................................................................................................ 200/656 550/1805 2000/6562 6500/21325

12 airguns ........................................................................................................ 250/820 600/1968 2200/1718 7250/23786

Additional information is contained 

in the L-DEO application, especially in 

Appendix A.

In addition to the operations of the 

airgun array, the ocean floor will be 

mapped continuously throughout the 

entire cruise with an Atlas Hydrosweep 

DS–2 Multibeam 15.5–kHz bathymetric 

sonar, and a 3.5–kHz sub-bottom 

profiler. Both of these sound sources are 

commonly operated simultaneously 

with the airgun array, but may, on 

occasion, be utilized independent of the 

seismic array.

The Atlas Hydrosweep 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 deep-water modes: 

an Omni mode 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 crosstrack 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 

(<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 1/5th of these values or 

2/5th 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.

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 sub-bottom 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 duration is 1, 2 or 4 

ms and the 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.

Sound levels have not been measured 

directly for the sub-bottom profiler used 

by the Ewing, but Burgess and Lawson 

(2000) measured sounds propagating 

more or less horizontally from a similar 

unit with similar source output (205 dB 

re 1 microPa m). The 160 and 180 dB 

re 1 microPa rms radii in the horizontal 

direction were estimated to be, 

respectively, near 20 m (66 ft) and 8 m 

(26 ft) from the source, as measured in 

13 m or 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), assuming spherical 

spreading.

The sub-bottom profiler on the Ewing

has a stated maximum source level of 

204 dB re 1 microPa. Thus the received 

level 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 

(30° beamwidth) and the measurements 

of Burgess and Lawson (2000).

Characteristics of Airgun Pulses

Discussion of the characteristics of 

airgun pulses was provided in the 

notice of proposed authorization to LDEO for this activity (69 FR 31792, June 

7, 2004) and is not repeated here. 

Reviewers are encouraged to read this 

earlier document for information on 

how airgun arrays function.

Comments and Responses

A notice of receipt and request for 

public comment on the application and 

proposed authorization was published 

on June 7, 2004 (69 FR 31792). During 

the 30–day public comment period, 

comments were received from the 

Center for Biological Diversity (CBD), 

the Natural Resources Defense Council 

(NRDC), the New York Whale and 

Dolphin Action League (NYWDAA), the 

Animal Welfare Institute (AWI), and one 

74908 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

individual member of the public. In 

addition, NMFS received approximately 

300 e-comments on this proposed 

action. These comments did not raise 

additional significant issues on the 

proposed authorization that are not also 

addressed by the commenters 

mentioned here.

Marine Mammal Concerns (MMC)

Comment MMC 1: The CBD states the 

notice and application do not have 

sufficient data to support the conclusion 

that only small numbers (of marine 

mammals) will be taken. For many 

species, NMFS is relying on incomplete, 

outdated, or no surveys whatsoever. For 

example, there is no information 

provided at all for Blainville’s, Hubb’s, 

and Stejneger’s beaked whales, 

California sea lion, Steller sea lion, or 

harbor seal. Surveys should be 

conducted prior to authorizing the IHA.

Response: NMFS does not agree that 

marine mammal assessment surveys are 

needed prior to issuing an IHA. When 

information is unavailable on a local 

marine mammal population size, NMFS 

uses either stock or species information 

on abundance. Therefore, additional 

surveys are unnecessary. Also, while 

information may be lacking for some 

species of beaked whales, information 

on pinniped abundance and trends is 

found in the application.

Comment MMC 2: The CBD believes 

that NMFS’ analyses of small numbers 

and negligible impact are flawed. First, 

NMFS uses ‘‘North Pacific Ocean’’ to 

define the geographical limits of the 

‘‘regional’’ populations that form the 

basis of its analyses instead of providing 

an analysis of impacts on stocks or more 

localized populations that overlap with 

the project area. The CBD believes that 

the appropriate geographic scale should 

be populations and stocks inhabiting the 

survey area and not the entire North 

Pacific. Similarly, the NRDC believes 

that L-DEO uses the population size for 

humpback whales for the entire North 

Pacific (6000 animals) rather than on the 

lower estimates produced for the U.S. 

West Coast or the defined feeding area 

off Oregon and Washington coasts 

(between 300 and 1400).

Response: NMFS agrees that impacts 

should be assessed on the population or 

stock unit whenever possible. L-DEO’s 

application (see especially Table 2 in 

the application) provides information 

on stock abundance in Oregon/

Washington (when available) and larger 

water bodies (such as the North Pacific 

Ocean). The data source for each stock 

estimate is provided. NMFS believes 

that these data are the best scientific 

information available for estimating 

impacts on marine mammal species and 

stocks. However, Congress recognized 

that information on marine mammal 

stock abundance may not always be 

satisfactory. When information is 

lacking to define a particular population 

or stock of marine mammals then 

impacts are to be assessed with respect 

to the species as a whole (54 FR 40338, 

September 29, 1989). Table 2 in this 

Federal Register document provides the 

percentage of the regional population of 

each species of marine mammal (when 

known) estimated to be exposed to SPLs 

at or greater than 160 dB (rms).

When estimating take levels for 

humpback whales, L-DEO calculated 

humpback whale density using the 1996 

and 2001 marine mammal ship survey 

data for waters off Washington and 

Oregon found in Barlow (2003). This 

estimate is based on nine humpback 

whale sightings during 7482 km (4044 

nm) of survey effort during both years. 

The final density estimate found in 

Table 3 in the L-DEO application of 

0.0005/sq km is the weighted average 

(based on effort in each year) of the 

densities reported in Barlow (2003) for 

the 1996 and 2001 surveys.

Comment MMC 3: The NRDC argues 

that the numbers used by L-DEO for 

killer whale abundance estimates fail to 

capture the distinctions made in the 

literature among the various resident 

and transient stocks in the Pacific 

Northwest. One citizen believes that the 

management unit for NMFS is the stock, 

not the species and that while the 

estimated impacts may be small relative 

to population size of the species, they 

may not be small relative to the affected 

stock. For example, one commenter 

states the proposed study site is used by 

the Eastern North Pacific (ENP) Resident 

Stock of killer whales. It numbers fewer 

than 85 individuals. It rarely travels in 

units of fewer than 20 individuals, so if 

present in the study area at all, at least 

25 percent of the population would be 

affected. Since the stock is already 

depleted, a lethal taking of this 

magnitude would be devastating. The 

potential is obscured by including 

members of other stocks in the 

population estimate for killer whales. 

The CBD believes that the appropriate 

geographical scale is particularly critical 

for the killer whale, such as the ENP 

Transient, ENP Offshore, and the 

Northern and Southern Resident stocks. 

NMFS does not even mention the 

impacts of the proposed authorization 

on these stocks of killer whales in the 

proposed authorization, rendering the 

analysis wholly useless. The take of 

even one killer whale from these stocks 

will have more than a negligible impact 

on the stock and the species.

Response: Information on the killer 

whale stocks can be found in Angliss 

and Lodge (2003), particularly on the 

ENP Northern Resident and Transient 

stocks, and in Caretta et al. (2003), 

particularly on the ENP Offshore and 

Southern Resident stocks. Information 

was provided in L-DEO’s application 

and in NMFS’ proposed authorization 

notice (see text and Table 2).

Based on summer/fall shipboard linetransect surveys in 1996 (Barlow, 1997) 

and 2001 (Barlow, 2003) the total 

number of killer whales within 300 nm 

(556 km) of the coasts of California, 

Oregon and Washington has been 

estimated to be 1340 (CV=0.31). Caretta 

et al. (2003) note the while there is 

currently no way to reliably distinguish 

the different stocks of killer whales from 

sightings at sea they estimate that, by 

prorating (as explained in Caretta et al., 

2003) there are 466 offshore killer 

whales along the U.S. West Coast with 

a Pmin of 361 animals. Because of the 

location of the Blanco Fracture survey, 

NMFS believes that Level B harassment 

would be limited to the ENP Offshore 

stock of killer whales.

Since this species is unlikely to be in 

the vicinity of the Ewing at the time 

seismic is operating (L-DEO, 2004), and 

would be highly visible to observers if 

it was present, no killer whales will be 

injured or killed (i.e., no removals from 

the species or stock) as a result of the 

Ewing’s seismic operations. Therefore, 

the only potential taking might be by 

Level B harassment. As indicated in 

Table 2 in this document, L-DEO 

estimates that approximately 12 killer 

whales might be within the 160–dB 

(rms) isopleth and, therefore, presumed 

to be harassed. This is less than 0.1 

percent of the regional killer whale 

population and less than 0.3 percent of 

the regional offshore population.

Moreover, since the killer whale’s 

optimum hearing range is not in the low 

frequency used by seismic sources, this 

number should not be interpreted as the 

number being ‘‘taken’’ by Level B 

harassment, only the number that might 

be exposed to that level of noise. 

Therefore, it is highly unlikely that the 

taking by Level B harassment will be 

more than negligible on the offshore 

killer whale stock.

Comment MMC 4: The NRDC states 

that L-DEO appears to be relying on 

survey data that are quite limited and, 

for some species, may be misleading. 

For Cuvier’s beaked whales, a species 

now thought to be extremely vulnerable 

to intense noise, the abundance estimate 

provided by L-DEO and adopted by 

NMFS is zero, based presumably on a 

lack of sightings of these animals during 

the 1996 and 2001 surveys by the 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74909

Southwest Fisheries Science Center. It 

has recently been observed, however, 

that the likelihood of sighting beaked 

whales in anything heavier than a light 

breeze is minimal. If the 1996 and 2001 

surveys were mainly conducted in 

rougher weather, then the density of 

these animals at the Blanco and Gorda 

sites may be higher than supposed.

Response: Caretta et al. (2004) 

determined that a multi-year average 

abundance estimate for Cuvier’s beaked 

whales along the coasts of California, 

Oregon and Washington is the most 

appropriate estimate for management 

purposes on the U.S. West Coast 

because this species probably spends 

time outside the U.S. EEZ. The 1996–

2001 weighted average abundance 

estimate is 1884 (CV=0.68) and the 

minimum population size is 1121 

animals. No marine mammal assessment 

surveys have been conducted off Oregon 

and Washington so there is not a 

population estimate for these states 

separate from California. That was the 

reason for Table 2 in L-DEO’s 

application indicating zero Cuvier’s 

beaked whales off Oregon and 

Washington. The population estimate of 

1884, as shown in Table 2 of L-DEO’s 

application, has been accepted by 

NMFS as the best scientific information 

available for the stock size for Cuvier’s 

beaked whale along the Pacific coast of 

the United States.

There is a scientific methodology to 

estimate the probability of detecting 

marine mammals during vessel 

assessment surveys, as explained in 

detail in Buckland et al. (1993). NMFS 

marine mammal ship survey procedures 

are detailed in Barlow (1995). 

Methodology includes several 

components, including the probability 

that the mammal will be at the surface 

and potentially sightable while within 

visual range of the observers, the 

probability that an animal at the surface 

will in fact be detected, and the 

relationship between sighting 

probability and lateral distance from the 

ship’s trackline. All of these factors are 

taken into account when making density 

and population abundance estimates. 

Finally, Barlow (1995) notes that 

because small whales and ‘‘cryptic’’

marine mammal species were seldom 

seen in rough conditions, the abundance 

estimate for these species were made 

using only data from calm conditions 

(see also Barlow, 2003).

Comment MMC 5: The AWI states that 

combining the ramifications of studies 

and statements cited in its letter(Jepsen, 

2003; Taylor et al., 2004; Mead, 2000; 

Simmonds and Lopez-Jurado, 1991; 

Martin-Martel, 2003; and Frantzis, 

1998), a highly plausible new 

mechanism for injury emerges that must 

be considered by NMFS in all 

applications requesting permission to 

take marine mammals incidental to 

emission of intense sounds into the 

ocean, especially, but not exclusively 

when beaked whales are known to live 

in the area. This mechanism appears to 

be an acute behavioral response to 

relatively low (100–160 dB) levels of 

sound, which may lead to death.

Response: A review of the 

Smithsonian stranding database by 

Mead (2000) shows that there had been 

seven instances of multiple beaked 

whale strandings up to that date. One of 

these instances involved ordnance, two 

were not associated with military 

activities, and four were concurrent 

with military maneuvers. (Taylor et al.

(2004) recently updated this list.) It is 

not known whether sonar was involved 

with these naval exercises (NOAA, 

2002). Simmonds and Lopez-Jurado 

(1991) state that between 1982 and 1989 

there were 22 strandings of cetaceans in 

the Canary Islands, with three being 

related to military activity. The 

Simmonds and Lopez-Jurado (1991) and 

Frantzis (1998) articles were published 

scientific correspondences based solely 

on observations. The Jepsen et al. (2003) 

paper, which discussed the September, 

2002 multi-species stranding in the 

Canary Islands, is analyzed in a later 

response.

Prior to the 2000 Bahamas stranding 

(see DON and NOAA, 2001), no tissues 

were collected, and the type of military 

maneuvers and time and distance 

separating them from the animals’

original location are not known. 

Without this information NMFS cannot 

conclude whether sonar did or did not 

cause these deaths. Therefore, the data 

do not necessarily suggest a high 

correlation between naval activities and 

beaked whale strandings, nor do they 

provide evidence of causation. It should 

also be noted that the implicated sonar 

in the 2000 Bahamas stranding incident 

was a mid-frequency sonar (2.6 and 3.3 

kHz), not the low frequency (0–188 Hz) 

seismic airguns found on the Ewing. In 

addition, as for reasons noted in 

response to comment MMC 8, the other 

acoustic equipment onboard the Ewing

(the Atlas Hydrosweep DS–2 Multibeam 

15.5–kHz bathymetric sonar and the 

3.5–kHz sub-bottom profiler) are not 

likely to be capable of causing marine 

mammal strandings because of their 

brief pings.

After the 2000 Bahamas beaked whale 

stranding, two hypotheses were 

identified on a possible mechanism for 

the stranding event. The most widely 

discussed hypothesis was that the 

stranding may have resulted from air 

cavity resonance caused by exposure to 

mid-frequency active sonar, or to a 

source with similar operating 

characteristics. It was concluded that 

acoustic resonance in air-filled 

structures was not likely to have played 

a primary role in the Bahamas stranding 

(but could play a secondary 

role)(Gentry, R. 2002, available at http:/

/www.nmfs.noaa.gov/protlres/

readingrm/MMSURTASS/

ReslWkshplRptlFin.PDF).

A second hypothesis developed at the 

workshop considered as a possible 

cause of beaked whale strandings was 

the acoustic activation of nitrogen 

bubble nuclei in tissues that are 

supersaturated with nitrogen from 

respiratory gases after diving. Factors 

that support this hypothesis include: (1) 

Beaked whales are deep divers with 

slow descent and ascent rates that 

promote high degrees of supersaturation 

which, in theory, should increase their 

susceptibility to bubble growth, and (2) 

some trauma in the Bahamas animals 

was similar to that experienced by 

terrestrial animals subjected to rapid 

decompression. Factors that refute the 

hypothesis include: (1) the resonant 

frequency of microbubbles is much 

higher than either low- or midfrequency sonars, and (2) deep-diving 

mammals that produce intense 

vocalizations would be expected to have 

evolved some bubble suppression 

mechanisms over time. The Gentry 

report states that less is known about 

acoustically mediated bubble activation 

than about any other hypothesized 

mechanisms for the strandings. 

Especially important is (1) determining 

whether marine mammals have bubbles 

at all when they dive, (2) the lowest SPL 

that can trigger bubble activation if it 

occurs, (3) modeling bubble onset 

(nucleation) and stabilization, and (4) 

modeling the role of acoustic waves in 

bubble growth under realistic levels of 

nitrogen supersaturation.

NMFS concluded that the scientific 

community needs more information 

before it can satisfactorily explain: (1) 

why most sonar operations apparently 

do not cause strandings, but some do, 

depending upon factors present, (2) 

which taxa are most, and which are 

least, susceptible to these sounds, (3) 

whether the differences between these 

groups suggest a plausible mechanism 

of effect, (4) whether there is some as 

yet unknown physiological effect of 

exposure much lower than those that 

cause trauma in laboratory animals, (5) 

whether animals respond behaviorally 

to sonar in ways that may increase their 

exposure, and (6) whether midfrequency sonars affect populations of 

animals in ways they do not affect 

74910 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

individuals (i.e. through socially 

facilitated panic). At the present time, 

NMFS believes that beaked whales are 

sometimes affected by mid-frequency 

sonar, but does not know the 

mechanism for that effect.

Only two papers, Taylor et al. (2004) 

and Engel et al. (2004) reference seismic 

signals as a possible cause for a marine 

mammal stranding. Taylor et al. (2004) 

noted two beaked whale stranding 

incidents related to the Ewing. Both of 

those stranding incidents were 

discussed in L-DEO’s application. 

Additional discussion can be found in 

response to comment MMC7. However, 

in recognition of a possibility that 

seismic operations may be having this 

possible effect, NMFS is requiring 

additional mitigation measures as 

discussed later in this document (see 

Mitigation).

Engel et al. (2004), a recent paper 

presented to the International Whaling 

Commission (IWC) in 2004 (SC/56/E28), 

mentioned a possible link between oil 

and gas seismic activities and the 

stranding of 8 humpback whales (7 off 

the Bahia or Espirito Santo States and 1 

off Rio de Janeiro, Brazil). Additional 

concerns about the relationship between 

this stranding event and seismic activity 

were raised by the International 

Association of Geophysical Contractors 

(IAGC). The IAGC (2004) argues that not 

enough evidence is presented in Engel 

et al. (2004) to assess whether or not the 

relatively high proportion of adult 

strandings in 2002 is anomalous. The 

IAGC contends that the data do not 

establish a clear record of what might be 

a ‘‘natural’’ adult stranding rate, nor is 

any attempt made to characterize other 

natural factors that may influence 

strandings. NMFS is concerned that the 

Engel et al. (2004) article appears to 

compare stranding rates made by 

opportunistic sightings in the past with 

organized aerial surveys beginning in 

2001. If so, then the data are suspect.

Comment MMC 6: The AWI quotes 

portions of the Jepsen et al. (2003) paper 

that ‘‘these lesions (found in the 14 

beaked whales that stranded in the 

Canary Islands in 2002) are consistent 

with acute trauma due to in vivo bubble 

formation resulting from rapid 

decompression (as occurs in 

decompression sickness (DCS)). Bubble 

formation in response to sonar exposure 

might result from behavioral changes to 

normal dive profiles (such as 

accelerated ascent rate), causing 

excessive nitrogen supersaturation in 

the tissues (as occurs in decompression 

sickness); alternatively, bubble 

formation might result from a physical 

effect of sonar on in vivo bubble 

precursors (gas nuclei) in nitrogensupersaturated tissues.’’

Response: The hypothesis proposed 

by Jepsen et al. (2003) is considered by 

NMFS scientists and others to be 

speculative at this time. Piantadosi and 

Thalman (2004) consider the hypothesis 

to contain two flaws. First, whales do 

not develop sufficient gas 

supersaturation in the tissues on ascent 

to cause extensive bubble formation in 

the liver (i.e., Jepsen et al. (2003) found 

the livers of these animals to be the 

most consistently affected organ). 

Second, large gas-filled cavities in the 

liver are inconsistent with the pathology 

of DCS in humans and other mammals 

in which the bones, joints, lungs and 

central nervous system are primarily 

affected. They conclude that identifying 

the cetacean gas disease with DCS is, 

therefore, premature because its 

pathology not only differs from that 

underlying the syndrome in other 

mammals, but it also cannot be 

explained by any physiological 

mechanism related to diving. Fernandez 

et al. (2004) reply that even if naturally 

occurring levels of nitrogen 

supersaturation in the tissues of diving 

cetaceans are normally insufficient to 

initiate bubble growth, a theoretical 

possibility remains that cetaceans with 

supersaturated tissues could experience 

bubble growth or formation as a result 

of intense acoustic exposure. However, 

Fernndez et al. (2004) conclude that 

these uncertainties argue for caution in 

interpreting the limited studies 

available. Finally, all authors concur 

that further investigation is needed, 

including an analysis of the 

composition of the gas in the bubbles.

Comment MMC 7: The AWI states 

that, in light of the Taylor et al. (2004) 

paper, NMFS needs to reassess its 

statement that ‘‘the evidence with 

respect to seismic surveys and beaked 

whale strandings is inconclusive and 

NMFS has not established a link 

between the Gulf of California stranding 

and the seismic activities.’’ The AWI 

believes the authors document firsthand experience of beaked whale 

strandings that coincided exactly with a 

seismic survey being conducted by the 

Ewing.

Response: Taylor et al. (2004) does 

not refute NMFS’ statement made in the 

proposed IHA notice. The statement in 

Taylor et al. (2004) was that the Ewing

was firing its airguns at 1300 hrs on 

September 24 and that between 1400 

and 1600 hrs, local fishermen found 

live-stranded beaked whales some 22 

km (12 nm) from the ship’s location. 

Review of the Ewing’s trackline 

indicates that the closest approach of 

the Ewing and the beaked whales 

stranding location was 18 nm (33 km) at 

1430 hrs. At 1300 hrs, the Ewing was 

located 25 nm (46 km) from the 

stranding location. What is unknown is 

the location of the beaked whales prior 

to the stranding in relation to the Ewing, 

but the close timing of events indicates 

that the distance was not less than 18 

nm (33 km). No physical evidence for a 

link between the seismic event and the 

stranding was obtained. In addition, 

Taylor et al. (2004) indicates that the 

Ewing was operating 500 km (270 nm) 

from the 2000 Galapagos Island 

stranding site. Whether the Ewing 

seismic survey caused to beaked whales 

to strand is a matter of considerable 

debate (Cox et al., in review). NMFS 

believes that scientifically, these events 

do not constitute evidence that seismic 

surveys have an effect similar to that of 

mid-frequency sonar. However, these 

incidents do point to the need to look 

for such effects during future surveys. 

Follow-up surveys by the Ewing and 

other vessels are now required 

whenever time and tracklines permit 

doing so. To date, follow-up 

observations have not indicated any 

beaked whale stranding incidents (a 

marine mammal does not need to be on 

the beach in order for it to be considered 

a stranding).

Comment MMC 8: The AWI argues 

that given recent events, subsequent 

research, and expert discussion that 

support the contention that beaked 

whales may startle when ensonified by 

specific anthropogenic noises from 

seismic survey experiments and midrange sonars, rise suddenly without 

adequate decompression time, and 

suffer injuries and/or die from 

symptoms similar to decompression 

sickness in humans, the premise that a 

ship can avoid causing severe injury or 

death because they can visually identify 

whales within the safety zone that 

extends to the perimeter of 180 dB, is 

false for two reasons: because the onset 

of injury appears to come from much 

lower sound levels and because the 

whales can’t be seen. If the safety 

perimeter is to include levels of sound 

that might cause physical injury, 

injuries that come from an acute 

behavioral response must be included. 

Judging from the evidence from 

strandings of beaked whales in Greece, 

the Bahamas, Canary Islands, Baja 

California, and the Azores, and 

considering the likely received levels of 

sound from the location of the ships and 

the location of the strandings, it cannot 

be proven that this startle response by 

whales who died was not provoked by 

received levels of sound well below 160 

dB.

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74911

Response: As discussed previously, 

the hypothesis proposed by Jepsen et al.

(2003) that beaked whales suffer from 

DCS is considered speculative at this 

time. In addition, reports by Simmonds 

and Lopez-Jurado (1991), Martin-Martel 

(2003), and Frantzis (1998) on the 

association of beaked whale strandings 

concerns high intensity, mid-frequency 

military sonars, not low-frequency 

seismic activity. NMFS believes that 

scientifically, the stranding events in 

the Gulf of California and the Galapagos 

Islands do not constitute evidence that 

seismic surveys have an effect similar to 

that of mid-frequency sonar. The 

question on whether the Ewing seismic 

survey caused beaked whales to strand 

is a matter of considerable debate. 

Finally, not knowing the location of 

beaked whales in relation to an acoustic 

source does not allow one to assume 

that a certain sound pressure level is 

unsafe.

Comment MMC 9: The CBD states that 

there is insufficient disclosure of the 

compounded impact of the array’s 

seismic output along with the other 

acoustical data acquisition systems, the 

multi-beam sonar and sub-bottom 

profiler. Despite the fact that the sonar 

and pinger will be operating 

continuously during the voyage, NMFS 

assumes there will be no additional take 

from these instruments individually or 

from all sources collectively. NMFS 

must address instances when all sources 

may not be operating simultaneously 

and provide a substantiated explanation 

why it assumes there is no enhanced 

impact of multiple acoustic sources 

operating together.

Response: This information is 

provided in detail in the L-DEO 

application and NSF EA. Although not 

stated in these document, additive 

effects from these sources will not occur 

because they are not operating in the 

same frequency, are not in phase with 

each other and do not have the same 

sound pressure levels. The multibeam 

sonar and sub-bottom profiler have 

anticipated radii of influence 

significantly less than that for the airgun 

array. NMFS has stated previously that 

marine mammals close enough to be 

affected by the multibeam sonar or subbottom profiler would already be 

affected by the airguns when they are 

both working. Since NMFS considers all 

marine mammals to be affected equally 

by underwater sound and does not 

determine which species are lowfrequency hearing specialists and 

therefore more affected by seismic (a 

low-frequency source) and which 

species are mid- or high-frequency 

specialists and therefore more likely to 

be affected by these sonars, NMFS does 

not consider it necessary to conduct an 

analysis on the enhancement of effects 

for animals that might be affected by 

these sonars. In other words, the 

acoustic source with the largest zone of 

influence is used to determine 

incidental take levels.

Also, estimates of incidental take by 

harassment for times when the 

multibeam sonar and/or sub-bottom 

profiler are operated without airguns are 

not necessary because the 160–dB and 

180–dB isopleths of the sub-bottom 

profiler and multibeam are either too 

small or the acoustic beams are very 

narrow, making the duration of the 

exposure and the potential for taking 

marine mammals by harassment small 

to non-existent. As provided in the LDEO application, the 160–dB and 180–

dB radii in the horizontal direction for 

the sub-bottom profiler are estimated to 

be near 20 m (66 ft) and 8 m (26 ft), 

respectively. In the vertical direction, 

the 160–dB and 180–dB radii are 160 m 

(525 ft) and 16 m (52 ft) directly below 

the hull-mounted transducer. With the 

Ewing’s beam at 14.1 m (46.25 ft) little 

noise is, therefore, likely to exist at the 

water surface beyond the immediate 

vicinity of the Ewing from this hullmounted sonar. As a result, it is 

unlikely that marine mammals would be 

affected by sub-bottom profiler signals 

whether operating alone or in 

conjunction with other acoustic devices 

since the animals would need to be 

swimming immediately adjacent to the 

vessel or directly under the vessel. This 

is unlikely to occur during the Ewing

cruise since the vessel is likely to be in 

transit mode, when not towing seismic, 

and will therefore be traveling at about 

10–11 knots (18.5–20.4 km/hr) at the 

time.

For the Hydrosweep multi-beam sonar 

there is minimal horizontal propagation 

as these signals project downward and 

obliquely to the side at angles up to 

approximately 70 degrees from the 

vertical, but not horizontally. For the 

deep-water mode, directly under the 

Ewing the 160- and 180–dB zones are 

estimated to extend to 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 moving vessel, 

meaning that a marine mammal diving 

(not on the surface) could receive at 

most 1 to 2 signals from the 

Hydrosweep. Also, because NMFS treats 

behavioral harassment or injury from 

pulsed sound as a function of total 

energy received, the actual harassment 

or injury threshold for Hydrosweep 

signals (approximately 10 millisec in 

duration) would be at a much higher dB 

level than that for longer duration 

pulses such as seismic or military sonar 

signals. As a result, NMFS believes that 

marine mammals are unlikely to be 

harassed or injured from the multibeam 

sonar or the Hydrosweep sonar due to 

the short duration and only 1 to 2 pulses 

received.

MMPA Concerns (MMPAC)

Comment MMPAC 1: The AWI states 

that L-DEO has applied for the wrong 

type of ‘‘small take authorization’’

asserting that the proposed project poses 

a lethal threat to the marine mammals 

and, therefore, does not qualify for an 

IHA, which is only allowed where there 

is no possibility whatsoever of causing 

a severe injury or death. By law, all 

possibility of any severe injury or deaths 

must be eliminated by mitigation, or not 

exist.

Response: While an authorization for 

taking marine mammals by mortality 

cannot be authorized under section 

101(a)(5)(D) of the MMPA, those 

paragraphs do authorize taking by Level 

A harassment. Level A harassment 

means any act of pursuit, torment, or 

annoyance which has the potential to 

injure a marine mammal or a marine 

mammal stock in the wild. While it is 

true that an injury can be so severe that 

it later may result in mortality, the 

MMPA does not preclude issuance of an 

authorization under section 101(a)(5)(D) 

of the MMPA for activities that have the 

potential to cause injury. However, as 

NMFS shows in this document 

mortality and serious injury are not 

expected to occur during this seismic 

survey cruise due to implementation of 

mitigation measures (e.g., ramp-up, 

passive acoustic and visual monitoring, 

and quiet acoustic periods). Nor is take 

by mortality authorized. Therefore, 

issuance of an IHA is appropriate. 

Mitigation measures are discussed later 

in this document.

Comment MMPAC 2: The CBD 

believes NMFS has not demonstrated 

that the LDEO project will take only 

small numbers of marine mammals.

Response: NMFS believes that the 

small numbers requirement has been 

satisfied. The U.S. District Court for the 

Northern District of California held in 

NRDC v. Evans that NMFS’ regulatory 

definition of ‘‘small numbers’’

improperly conflates it with the 

‘‘negligible impact’’ definition. Even if 

that is the case, in the proposed IHA 

notice and in this document, NMFS has 

made a separate determination that the 

takes of the affected marine mammal 

species will be small. The species most 

likely to be harassed during seismic 

surveys in the Blanco Fracture area is 

the Dall’s porpoise, with a ‘‘best 

estimate’’ of 551 animals being exposed 

74912 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

to sound levels of 160 dB or greater. It 

should be understood that this does not 

mean that this is the number of Dall’s 

porpoises that will be taken by Level B 

harassment, only the best estimate of the 

number of animals that potentially 

could have a behavioral modification 

due to the noise (ignoring for example 

that Dall’s porpoise have best hearing at 

high frequencies, not the low 

frequencies used by seismic, and may 

not even hear seismic sounds). If in fact 

Dall’s porpoise cannot hear the lowfrequency seismic sounds, then no 

taking of this species will occur. 

Although it might be argued that the 

absolute number of Dall’s porpoise 

behavioral harassment numbers may not 

be small, the number is relatively small, 

representing less than 1 percent of the 

regional population of that species. It 

should be noted that during this project, 

no more than 1 percent of any marine 

mammal stock will be potentially 

subject to Level B harassment.

In addition, the mitigation measures 

set forth by this IHA ensure that there 

will be negligible impacts on the marine 

mammals. Cetaceans are expected, at 

most, to show an avoidance response to 

the seismic pulses. Mitigation measures 

such as controlled speed, course 

alteration, visual and passive acoustic 

marine mammal monitoring, and shutdowns when marine mammals are 

detected within the defined ranges 

should further reduce short-term 

reactions to disturbance, and minimize 

any effects on hearing sensitivity. Due to 

these mitigation measures, the impacts 

will be negligible.

Mitigation Concerns (MIC)

Comment MIC 1: The AWI questions 

whether the downward directional 

nature of seismic airguns would be a 

mitigation measure as stated by L-DEO 

and NMFS. The AWI believes that deep 

diving whales, such as the beaked 

whale, could be hit by SPLs of at least 

168 dB many kilometers from the 

Ewing, and no observer would ever 

know. Supersaturated whales might be 

startled to the surface very quickly, 

perhaps, triggering a DCS event. The 

applicant must disprove this potential 

for a wide horizontal impact zone from 

airgun array signals.

Response: Discussion of the potential 

impacts on marine mammals, including 

beaked whales, was provided previously 

in this document. Implementation of 

ramp-up is presumed to allow marine 

mammals, including beaked whales, to 

become aware of the approaching vessel 

and move away from the noise, if they 

find the noise annoying. This is 

discussed in more detail later in this 

section. However, the downward 

directionality of the seismic signal 

provides for lower SPLs for marine 

mammals, sea turtles and other marine 

life that spend most of their time in 

surface waters. As indicated in Figure 7 

in L-DEO’s application, a safety zone 

has been established at 600 m (1968 ft) 

for the 12–gun array (which will be used 

for only 24 hrs of seismic) where the 

180 dB isopleth is at its maximum 

distance from the sound source at a 

water depth of 500 m (1640 ft). 

Therefore, in the surface waters, SPLs 

are more likely to be in the range of 

160–170 dB and 180 dB would not be 

found unless in the immediate vicinity 

of the Ewing.

NMFS recognizes that deep-diving 

marine mammals, such as sperm whales 

and beaked whales, might receive 

higher SPLs at depth than they would 

at the surface. That is why the safety 

zone is established at the maximum 

distance at depth and not at the 180 dB 

isopleth at the surface. This provides 

greater protection for marine mammals 

in surface waters than would otherwise 

be warranted.

Comment MIC 2: The AWI contends 

that L-DEO does not have the capability 

to determine the actual acoustical 

environment (water depth, currents, 

mixing, lenses, channels, wave action, 

biologics, etc.) prior to or during an 

experiment, or to predict zones of 

potential impact on beaked whales and 

other marine animals. There is no 

empirical evidence to substantiate LDEOs implied claim that there will be 

no injurious behavioral responses or 

direct injury, because they also lack the 

technology and data to determine risk 

thresholds within the zones. It is also 

inappropriate for L-DEO to assume that 

conditions on one day will be similar to 

the next day.

Response: The issue of potential 

impacts to beaked whales and other 

marine mammal species is addressed 

elsewhere in this document. In regard to 

the significance of applying empirical 

measurements, this can be done either 

on-site at the time of the acoustic work 

or by modeling site-specific existing 

data beforehand. If neither is 

practicable, L-DEO proposed and NMFS 

has implemented conservative distances 

for safety zones in the IHA.

It should be noted however, that the 

deep sound channel (SOFAR channel) is 

usually found in the 750–1200 m (2461–

3937 ft) depth range at this latitude. For 

this channel to become a duct for 

seismic sounds from the surface, the 

most likely scenario would be for the 

seismic survey to be taking place in an 

area where this channel would 

encounter a slope which would redirect 

the sound into the SOFAR channel. 

Both seismic surveys planned for this 

cruise will be conducted in areas that 

are well below this water depth and 

thus increased sound propagation 

within the deep sound channel is not 

likely. Shallow water ducts are 

associated with continental shelves with 

depths less than 200 m (656 ft) in 

winter-time. Again this would not apply 

to the Blanco Fracture cruise. In regard 

to surface duct effects, increased sound 

propagation within the mixed water 

layer between the sea surface and the 

sonic layer depth could be associated 

with the seismic sound sources. 

However, it is unlikely that this effect 

would be significant because the 

downward directivity of the sound 

source will direct most of the energy ray 

path at an angle greater than the 1.76 

degrees (from the surface) within which 

the sound will enter this duct. It should 

be noted that strong surface ducts are 

most common in nearshore areas where 

there is significant freshwater inflow. 

That is not a factor in the offshore 

environment of the Blanco Fracture 

Zone. Finally, the deep scattering layer 

and daily fluctuations in temperature, 

salinity and wave motion are considered 

inconsequential for calculating sound 

propagation for estimating safety zones.

While L-DEO has not proposed 

making empirical measurements of the 

actual acoustical environment prior to 

or during a survey, the Ewing has that 

capability if additional equipment were 

onboard and time was available. 

Calibration is principally conducted 

using a specially adapted spar buoy 

with two hydrophones suspended at 

depth beneath the buoy. A second 

system is the U.S. Navy/University of 

New Orleans Environmental Recording 

System (EARS), a bottom-moored 

recording system. For the Blanco 

Fracture cruise, neither ship time nor 

the equipment is available. It should 

also be recognized that undertaking 

measurements during a survey would 

likely result in a smaller observer 

complement being onboard due to 

berthing space. Also, because the 

marine mammal safety zones are 

conservatively established, based on the 

2003 Gulf of Mexico calibration study, 

use of empirical measurements may 

result in smaller safety zones rather than 

larger safety zones.

Comment MIC 3: The AWI questions 

the validity of the L-DEO statement that 

the smaller size of the airgun array being 

deployed (10 and 12–airguns) is a 

mitigation measure. The AWI states that 

these airguns would produce 255 (peakpeak (pk-pk) and 257 dB (pk-pk), 

respectively, both levels among the 

highest anthropogenic sounds ever 

made.

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74913

Response: The source levels provided 

here are estimated from a far-field 

measurement that is extrapolted back to 

a hypothetical point 1 m (3.3 ft) from 

the center of a seismic array that is, in 

this case, 30 m (98 ft) across. Therefore, 

this number does not closely resemble 

what a marine mammal might actually 

experience. NMFS encourages, and 

works with, applicants for IHAs and 

Letters of Authorization to design their 

activity to ensure the lowest levels of 

sound possible going into the marine 

environment without compromising the 

success of the work planned. For the 

Blanco Fracture study, L-DEO has 

proposed using the Ewing’s 10–gun (255 

dB pk-pk or 241.0 dB rms) and 12–gun 

(257 db pk-pk, 242.7 dB rms) arrays, 

instead of its 20–gun (262 dB pk-pk, 

244.4 dB rms) array. The larger 12–gun 

array will be used a total of 24 hours 

and the smaller 10–gun array will be 

used for 6.5 days at the Blanco Fracture 

area. The difference between the 160 dB 

(rms) isopleths for these two arrays is 

750 m (2461 ft). If L-DEO had designed 

the Blanco Fracture study using the 

Ewing’s standard 20–gun array, the 160 

dB isopleth would have been at 9000 m 

(29529 ft), or 2500 m (8202 ft) larger 

than the 160 dB isopleth around the 10–

gun array. Because of the water depth at 

the site and the need to determine the 

structure of the oceanic crust, the 10- 

and 12–gun arrays were determined by 

L-DEO to be the smallest sources 

possible for use at this site. Since L-DEO 

chose not to use the 20–gun array, this 

is considered by NMFS to be a valid 

measure to reduce impacts on marine 

mammals to the lowest level 

practicable.

Safety Zones

Comment MIC 4: The CBD believes 

that NMFS’ discussion of measures to 

ensure the least practicable impact is 

lacking. For example, NMFS provides 

no analysis of why larger safety radii 

were not practicable or why the 

additional correction factors provided in 

previous authorizations were not 

provided.

Response: Safety zones were 

established and are monitored closely to 

ensure, to the greatest extent 

practicable, that no marine mammals 

would be injured by the proposed 

activity. While extending safety zones to 

reduce Level B behavioral harassment 

would, in theory, result in reducing 

‘‘takes’’ further, monitoring larger safety 

zones results in lower effort directed to 

the area of greatest concern, the area for 

potential injury. This lower effort might 

result in missed animals. This is not 

acceptable to NMFS and, for that reason, 

NMFS has determined that safety and 

monitoring zones should be established 

at 180 dB for cetaceans and 190 dB 

(rms) for pinnipeds.

Additional correction factors for 

calculating safety zones are necessary 

based on attenuation due to water 

depth, not because of distance from 

shore (although in most cases the two 

are related). Underwater seismic sounds 

are subject to spherical spreading to a 

distance approximately 1.5 times water 

depth. This is essentially what occurred 

in the Gulf of Mexico seismic 

calibration study. These additional 

correction factors are applied for L-DEO 

seismic activities taking place in water 

depths less than 1000 m (3281 ft), which 

do not apply for the Blanco Fracture 

study area.

Ramp-Up

Comment MIC 5: The AWI notes that 

ramp-up assumes that all vulnerable 

animals will be motivated to move away 

from the sound source to avoid 

receiving levels that may result in 

deleterious impacts. This assumption 

apparently comes exclusively from 

citations from Richardson concerning 

avoidance of bowhead and beluga 

whales in the path of approaching 

icebreakers and gray whale avoidance 

by Tyack during the Navy’s low 

frequency sonar scientific research. Both 

of these references involved millions of 

times less intense levels of sound with 

a greatly diminished reach.

Response: In addition to providing 

this information in L-DEO’s application, 

observations of behavioral changes in 

marine mammals in response to seismic 

surveys were summarized in Gordon et 

al. (2004). Those authors summarized 

avoidance response levels to seismic 

noise for a number of species with 

bowhead whales apparently the most 

sensitive (120 dB rms and above), other 

balaenopterid whales less sensitive 

(blue whales 143 dB pk-pk, humpback 

whales 157–160 dB pk-pk, and gray 

whales 164–180 dB (rms)) and dolphins 

and seals the least sensitive.

Comment MIC 6: The AWI notes that 

considerable evidence instead 

documents numerous behaviors such as 

approaching operating sources, or 

bowriding on vessels towing operating 

arrays. It is logical to expect different 

responses from experienced and naive 

individuals.

Response: As noted in greater detail 

in L-DEO’s application and especially in 

Appendix A(e), there may be several 

reasons why marine mammals may not 

react to anthropogenic sounds: (1) The 

source is not within the frequency range 

for best hearing of the species; (2) the 

sounds at a distance from the source is 

not within the best hearing frequencies 

of the species; (3) the individual animal 

has a hearing impairment, and (4) the 

mammal(s) hear the sound but ignore 

the sound due to other, more important, 

biological concerns. If ramp-up was 

considered to be 100 percent effective, 

then observers would not be needed to 

monitor safety zones and could 

concentrate on monitoring and 

recording behavioral reactions to 

seismic sounds.

Anecdotal information obtained from 

observing bow-riding dolphins and 

dolphins rubbing on the hydophone 

streamer cables may indicate that 

bottlenose dolphins, whose best hearing 

frequencies are considerably higher than 

seismic signals, are either not affected or 

are tolerant of seismic signals that are 

not within their range of best hearing. 

Also, although preliminary, Smultea et 

al.(2004) found that marine mammal 

densities were 35 percent and 55 

percent lower during periods of seismic 

activity than periods without seismic 

activity in water depths of 100–1000 m 

(328–3281 ft) and greater than 1000 m 

(3281 ft), respectively. The authors 

hypothesize that some cetaceans 

probably either moved away from the 

approaching seismic vessel, beyond the 

detection range of the observers (i.e. 

reacted to the seismic sounds), or 

changed their behavior in a way that 

made them less conspicuous to the 

observers. The differences could be a 

combination of these hypothesized 

effects. However, Smultea et al. (2004) 

also note the observed differences 

(especially in intermediate depths) are 

well within the normal range of 

variation that might be expected for the 

study area. As one cannot be certain 

from this single uncontrolled study 

what fraction of the apparent 

displacement effect is attributable to 

avoidance or behavioral responses, as 

opposed to natural variation, NMFS 

recommends priority be given to 

conducting a controlled exposure 

experiment to determine if ramping-up 

seismic signals provides for marine 

mammals protection through avoidance 

behavior on the part of the mammals.

Comment MIC 7: The AWI states that 

ramp-up cannot guarantee a response 

sufficient to negate any possibility of 

severe injury or death.

Response: As discussed in detail 

elsewhere in this document, NMFS 

believes that ramp-up of the seismic 

airgun array in combination with the 

slow vessel speed, use of trained 

observers, passive acoustics, shut-down 

procedures, and the behavioral response 

of marine mammals to avoid areas of 

high anthropogenic noise all provide 

protection to marine mammals from 

serious injury or mortality.

74914 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

Comment MIC 8: One commenter 

stated that the ramp-up procedure is 

flawed. Many marine mammals travel 

extended distances at speeds ranging 

from 4–8 km/hr (2.1–4.3 knots). The 

proposal calls for the 160 dB contour to 

reach 7 km (3.8 nm) within 20 minutes, 

requiring travel at speeds up to 21 km/

hr to remain outside it. While not 

explicitly stated, the 140–dB contour, at 

which strong behavioral responses 

could be expected, would reach roughly 

70 km (37.8 nm) in 20 minutes, 

requiring travel at speeds in excess of 

200 km/hr (108 knots) to remain outside 

it. This is a biologically unrealistic 

expectation.

Response: NMFS requires ramp-up in 

order to allow marine mammals to 

vacate the area that the HESS Workshop 

(HESS, 1999) and the NMFS Workshop 

believed to be a level above which 

injury could occur. Ramp-up is not 

intended to prevent marine mammals 

from Level B behavioral harassment. 

Ramp-up begins with the smallest 

airgun in the array (80 in3). Airguns are 

added in a sequence such that the 

source level of the array would increase 

in steps not exceeding 6 dB per 5–

minute period. As shown in Table 1 in 

this document, while the 160–dB 

isopleth is expected to reach 6.5 km (3.5 

nm) for the 10–airgun array and 7.25 km 

(3.9 nm) for the 12–airgun array, the 

180–dB isopleth for cetaceans would be 

only 550 m (1804 ft) and 600 m (1968 

ft) from the Ewing for the 10–gun and 

12–gun arrays, respectively. Using the 

commenter’s statement that many 

marine mammals travel for extended 

periods of time at 4–8 km/hr (2.1–4.3 

knots), there would not be a problem for 

even slower marine mammals to move 

out of the 180–dB safety zone within the 

20 minutes required for the 12–airgun 

array to reach full power (Smultea et al.

(2004).

Comment MIC 9: In response to our 

requirement for night-vision devices 

(NVDs) to be onboard the Ewing, one 

commenter stated that Generation III 

light enhancement gear requires 

significant ambient light to be effective 

for marine mammal viewing. It is 

unlikely that sufficient light will be 

available far from shore.

Response: Earlier this year, L-DEO 

completed two tests of the effectiveness 

of monitoring using NVDs (Smultea and 

Holst 2003, Appendix C; Holst 2004, 

Appendix B). Results of those tests 

indicated that the Night Quest NQ220 

NVD is effective at least to 150 to 200 

m (492 to 656 ft) away under certain 

conditions. That type of NVD is not 

effective at the much larger 180–dB 

radii applicable when a large array of 

airguns is in use. However, it is the 

smaller zone where the received level is 

well above 180 dB where detection of 

any marine mammals that are present 

would be of particular importance. For 

reasons explained elsewhere in this 

document, the 205–dB zone, within 

which TTS might occur, is likely to be 

about 50 m (164 ft) in radius. That is 

sufficiently within the range of the 

NVDs to allow some chance of detecting 

marine mammals visually within the 

area of potential TTS during ramp-up. 

Furthermore, a substantial proportion of 

the marine mammals that might be 

within that distance would be expected 

to move away either during ramp-up or, 

if the airguns were already operating, as 

the vessel approaches.

Comment MIC 10: The same 

commenter notes that his personal 

observation is that thermal infrared 

technology would be more appropriate. 

Not only is it usable in total darkness, 

warm blows of the larger marine 

mammals remain visible after they have 

submerged, and the disturbance of the 

surface layer also can remain visible for 

several seconds in a calm sea. However, 

in practice, even this technology has 

limited effectiveness. When 

magnification is sufficiently high to 

ensure marine mammals can be seen, 

the field of view is so small that it is 

difficult to point the devices in the right 

direction at the right time. When the 

field of view is increased, marine 

mammals may not be sufficiently large 

and warm to create ‘‘warm’’ pixels that 

will stand out above the noise.

Response: For the reasons pointed out 

by this marine mammal scientist, NMFS 

has determined that use of thermal 

infrared technology is not currently 

practicable for use in detecting marine 

mammals at night.

Comment MIC 11: The CBD states that 

NMFS’ analysis of mitigation measures 

to ensure least practicable impact is 

flawed because the notice fails to 

require dedicated observers at night.

Response: Trained marine mammal 

observers using NVDs will be on watch 

during periods prior to and during 

ramp-up from a power-down situation 

at night. They will also be on watch at 

other periods during the night, 

particularly if marine mammals are 

sighted in the seismic survey area 

during the day or passive acoustics 

indicates marine mammal presence. 

Also, similar to several previous IHA 

actions, NMFS is requiring that, if 

marine mammals are detected during 

daylight hours, the passive acoustic 

monitoring will need to continue to be 

operated throughout the succeeding 

night (if seismic operations are 

underway). At other times during the 

night observers will be available, but it 

is not necessary or very effective for 

them to be on watch constantly. The use 

of passive acoustic monitoring will 

improve the detection of marine 

mammals by indicating to the visuals 

observers when an animal is potentially 

near and prompting a shut-down when 

necessary.

Comment MIC 12: The CBD states that 

there is no discussion or consideration 

of additional monitoring or mitigation 

measures, such as aerial surveys during 

operations to search for animals that 

may be affected, as well as to search 

nearby remote beaches for possible 

stranded animals. Without requiring 

such additional measures, or at a 

minimum discussing why they are not 

practical, NMFS cannot lawfully issue 

the requested authorization.

Response: Prior to issuing this IHA, 

NMFS thoroughly investigated all 

measures that might reduce the 

incidental taking of marine mammals to 

the lowest level practicable. Mitigation 

measures are discussed later in this 

document (see Mitigation). Mitigation 

measures, such as aerial overflights or 

support vessels to look for marine 

mammals prior to an animal entering a 

safety zone, may be given consideration 

if the safety zone cannot be adequately 

monitored from the source vessel. 

Consideration also must be given to 

aircraft/vessel availability, access to 

nearby airfields, distance from an 

airfield to the survey area, and the 

aircraft’s flight duration. There are 

serious safety issues regarding aircraft 

flights over water that must be 

considered prior to requiring aerial 

overflights. Additional consideration 

must be given to the potential for 

aircraft to also result in Level B 

harassment since a plane or helicopter 

would need to fly at low altitudes to be 

effective. Because the safety zones for 

this proposed activity are relatively 

small (≤ 600 m (1968 ft)) and can be 

monitored from the Ewing, use of 

aircraft or a second vessel for mitigation 

purposes is not warranted.

Even if aircraft or a second vessel are 

not necessary or feasible to monitor a 

safety zone, they might be appropriateto 

monitor shorelines (presumably for 

strandings related to the activity). NMFS 

has weighed this suggestion carefully 

and has determined that for this survey, 

neither aircraft, vessel or a land-based 

team is warranted due to the great 

distances between the survey site and 

the nearest land, and the prevailing 

currents that would tend to move a dead 

marine mammal lateral to the shore 

instead of immediately ashore, meaning 

the animal might land many miles from 

the nearest shoreside location. However, 

NMFS has notified the NMFS Stranding 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74915

Network regarding the calendar dates 

that the Ewing will be operating sonar 

off the coast of Oregon.

For this survey, the most appropriate 

monitoring is for the biological 

observers onboard the Ewing to also 

monitor the previously run transect 

lines as the Ewing returns along a 

parallel transect track. Survey lines for 

this survey are from 0.5 km (0.3 nm) to 

2 km (1.1 nm) apart in a concentrated 

area. Additionally, observers will 

continue to monitor for marine 

mammals while the Ewing repositions to 

run another seismic line. Zamboni-style 

seismic surveys provide extensive 

opportunities for the biological 

observers to look for distressed, injured 

or dead marine mammals (although no 

injuries or mortalities are expected 

during this research cruise). The IHA 

requires immediate suspension of 

seismic activity and immediate 

notification to NMFS is an observation 

is made of a distressed or recently 

deceased marine mammal. Also, a final 

post-survey transect will be conducted 

by the Ewing as it retrieves the 

hydrophone array and as it transits from 

the survey location to San Diego, CA.

Endangered Species Act (ESA) Concerns 

(ESAC)

Comment ESAC 1: The CBD states 

that L-DEO’s proposed project may 

affect 7 species listed as endangered 

under the ESA. As a result, consultation 

under section 7 of the ESA must occur 

prior to authorization of the project. 

NMFS has not yet complied with its 

(ESA) duties, and thus may not issue a 

small take authorization for the LDEO 

project.

Response: NMFS has completed 

consultation under section 7 of the ESA. 

The biological opinion resulting from 

that consultation concluded that this 

action is not likely to jeopardize the 

continued existence of listed species or 

result in the destruction or adverse 

modification of critical habitat.

National Environmental Policy Act 

(NEPA) Concerns (NEPAC)

Comment NEPAC 1: The CBD states 

that NSF and NMFS have never 

prepared a comprehensive 

Environmental Impact Statement (EIS) 

that fully analyzes the environmental 

impacts of its seismic surveys, either 

individually or collectively, as well as 

provide the public with the critical 

opportunity to participate in the 

decision making process as required by 

NEPA for actions of this magnitude. The 

CBD believes that NMFS must prepare 

an EIS prior to approving this project.

Response: NMFS disagrees that an EIS 

is required for this action. An EA was 

prepared by NSF for this action. NMFS 

fully reviewed the EA and announced 

its availability to allow for public 

review and comment (69 FR 31792, June 

7, 2004). Thereafter, NMFS adopted the 

NSF EA and made a Finding of No 

Significant Impact (FONSI), determining 

that an EIS was not required.

NMFS also does not agree that its 

issuance of multiple IHAs for seismic 

surveys requires an EIS. Each seismic 

survey and corresponding IHA is 

geographically and/or temporally 

spaced and unrelated to others for 

purposes of evaluating environmental 

impacts.

Comment NEPA 2: Prior to approving 

this project, NMFS must prepare an EIS. 

An EIS is required if ‘‘substantial 

questions are raised as to whether a 

project...may cause significant 

degradation of some human 

environmental factor.’’ (Idaho Sporting 

Congress v. Thomas, 137 F.3d 1146, 

1149–50 (9th Circ. 1998) citing 

Greenpeace Action v. Franklin, 14 F.3d 

1146, 1149–1150 (9th Cir. 1998). In this 

case, CBD asserts an EIS is required 

because substantial questions have been 

raised as to the significance factors 

found in 40 CFR 1508.27(b). First, CBD 

states there are ‘‘uncertain impacts or 

unknown risks’’ associated with this 

project and other similar seismic 

surveys and geophysical activities 

undertaken by L-DEO and NSF and 

authorized by NMFS. There exist large 

data gaps regarding the impacts of 

acoustics on marine life. Given the 

many stranding events that have been 

linked to underwater acoustics, 

including the melon-headed whale 

stranding near Hanalei Bay, Hawaii, a 

more detailed analysis in the form of a 

full EIS is more than warranted. CBD 

also asserts there is significant 

controversy over the impacts of 

underwater seismic activity on the 

environment. In support, CBD states 

that there are extremely divergent views 

on how substantial a change in behavior 

or activity is required before an animal 

should be deemed to be harassed or 

impacted, what received levels can be 

considered ‘‘safe,’’ what mitigation 

measures are effective, and, in general, 

how to proceed in the face of existing 

scientific uncertainty on these and other 

issues.

Response: While NMFS agrees that 

there are some unknown risks and 

uncertain impacts associated with this 

project, the major outstanding issue is in 

regard to the biological mechanism that 

caused some sound-related strandings to 

occur. It is important to note that those 

strandings occurred in the absence of 

standard mitigation and monitoring 

measures employed by seismic vessels 

that are designed to prevent serious 

impacts. Also, it is recognized by many 

scientists that data gaps exist because of 

the difficulty of obtaining data in a 

humane manner on many of the species. 

NMFS is in the process of developing 

more species-specific guidelines, but 

that information is not yet available for 

use. In the interim, surrogate species are 

used and conservative mitigation 

measures taken to ensure that injury or 

mortality to these animals does not 

occur. NMFS’ FONSI takes into account 

the considerable mitigation and 

monitoring efforts required by the IHA 

to counter the uncertainty of impacts 

and risks. NMFS also would like to 

clarify that the melon-headed whale 

stranding near Hanalei Bay, as with 

other strandings that coincided with 

underwater anthropogenic acoustic 

events, was not caused by seismic 

survey work.

NMFS does not agree that there is a 

substantial dispute about the impacts of 

this action (including all required 

mitigation and monitoring). 

Calculations for Level B harassment for 

this action were based upon 

conservative assumptions of distance 

from the source for impact in that LDEO did not make a judgement as to 

whether the anticipated impacts would 

be biologically significant. The actual 

impacts of the action were analyzed 

based on the best available science. 

There was no information suggesting 

that the mitigation measures are not 

effective, and, in fact, empirical 

information from previous surveys 

suggest they are effective. Moreover, 

NMFS is charged with basing its 

decisions on the best available scientific 

information. Also, while there is 

currently some debate regarding how 

effective mitigation measures are, the 

estimates of take (mortality, injury, or 

harassment) were made without taking 

mitigation into account.

Comment NEPAC 3: The CBD states 

that L-DEO, NSF, and numerous private 

seismic vessels, may have as yet 

unanalyzed cumulatively significant 

effects on the environment. Cumulative 

impacts is the ‘‘impact on the 

environment which results from the 

incremental impact of the action when 

added to other past, present, and 

reasonably foreseeable future actions. 

The EA generally describes fishing, 

shipping and other vessel noise, but 

provides no discussion of actual or 

potential impacts on the marine 

environment, either individually or 

cumulatively. Instead, the EA 

summarily concludes that actual or 

potential impacts ‘‘are expected to be no 

more than a very minor (and short-term) 

within the study area, even when 

74916 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

viewed in light of other human 

activities occurring in the area.’’ The 

CBD claims that this explanation turns 

the cumulative impacts requirement on 

its head.

Response: The NSF EA adequately 

addresses the cumulative impacts of a 

short-term, low-intensity seismic airgun 

survey in relation to long-term noise 

and taking events, such as shipping, 

fishing, and marine tourism. These 

other activities are long-term activities 

which are unaffected by NMFS’ action 

here. Nor does this action, when 

considered in light of the other 

activities, becomes significant.

Comment NEPA 4: Because the 

proposed survey has the potential to 

expose single individuals to repeated 

sound exposures, the CBD also believes 

that the analysis is insufficient as the 

EA fails to analyze what the cumulative 

behavioral or other impacts to L-DEO’s 

proposal may be on these individuals.

Response: The issue of repeated 

exposures is discussed in the NSF EA 

and in the L-DEO application. This 

information was summarized in Table 4 

of the application and in Table 2 in both 

the proposed IHA notice and this 

document. As those documents note, 

the difference between the number of 

exposures calculated versus the number 

of individuals that may be exposed to 

SPLs ≥ 160 dB is important for this 

survey because the proposed survey 

plan calls for repeated airgun operations 

through the same or adjacent waters. If 

many marine mammals are present near 

any of the survey transit lines, then 

many of the same individuals are likely 

to be approached by the operating 

airguns more than once during the 7–

day survey operation. However, any 

animals that react to distant seismic 

sounds by moving away from the area 

are not likely to be present and affected 

during any subsequent transit lines that 

are run. Estimates of the number of 

exposures are, therefore, considered 

precautionary overestimates of the 

actual numbers of different individuals 

potentially exposed to seismic sounds, 

because in all likelihood, exposures 

represent repeated exposures of some of 

the same individuals and not all 

animals will react to the sound 

exposure, as described in L-DEO’s 

application. For this survey, therefore, 

both the numbers of individuals in each 

species/stock potentially exposed to 

SPLs ≥ 160 dB and the number of 

potential exposures that a marine 

mammal may experience are small in 

number and not likely to have more 

than a negligible impact on marine 

mammal populations.

Comment NEPAC 5: The CBD states 

that the proposed project and other 

activities in the area have the potential 

to impact species listed under the ESA, 

including sperm, humpback, sei, fin, 

blue, and North Pacific right whales, the 

Steller sea lion, and the leatherback sea 

turtles. The EA does not adequately 

discuss this impact and instead 

concludes that the ‘‘brief exposure’’ of 

these listed species equates to an 

insignificant impact. Mere conclusions 

in an EA do not satisfy NEPA. The 

presence of these and other significance 

factors clearly triggers the need for an 

EIS.

Response: NMFS believes that the 

impacts on marine species listed under 

the ESA have been adequately 

addressed in NSF’s EA. In addition, 

impacts on marine species listed under 

the ESA have been addressed in NMFS’

Biological Opinion on this action. The 

finding of that biological opinion is that 

this action is not likely to jeopardize the 

continued existence of listed species or 

result in the destruction or adverse 

modification of critical habitat. No 

listed species are expected to be killed 

or seriously injured, and all impacts 

will be short-term resulting in no more 

than minor behavioral harassment. No 

critical habitat will be affected. A copy 

of the Biological Opinion has been 

forwarded to the CBD as requested.

Comment NEPAC 6: The CBD states 

that the EA lacks the required 

environmental baseline data and 

adequate analysis of impacts and 

mitigation measures for marine 

mammals, sea turtles, fish, and other 

marine life as discussed previously.

Response: NMFS disagrees. The NSF 

EA provides a level of detail not usually 

found in many EAs. The EA provides a 

step-by-step analysis on how impacts 

were assessed, starting with (and citing) 

the best scientific information available 

on marine mammal and sea turtle 

distribution and abundance and using 

those data to make conservative 

estimates on levels of take by 

harassment and reasonable assumptions 

on why no marine mammals are likely 

to be injured or killed by this survey. A 

discussion on addressing the mitigation 

measures as alternatives to the proposed 

action is provided in the next response.

Comment NEPAC 7: The CBD states 

that the EA does not evaluate a 

reasonable range of alternatives to the 

proposed action. The EA does not 

analyze any alternative that incorporates 

more mitigation or otherwise lessens the 

impacts of the seismic operations on the 

marine environment. Impacts on 

protected marine species from airgun 

surveys are not just temporary or 

transient but have the significant 

potential to result in lethal impacts. 

Such impacts clearly require better 

analsysis in the EA and the preparation 

of a full EIS.

Response: Discussion on the potential 

for marine mammal mortality by seismic 

sounds has been discussed previously 

in this document. NMFS reviewed the 

range of alternatives addressed in NSF’s 

EA and agrees with CBD that the 

alternatives can be expanded by 

providing an additional analysis of the 

mitigation measures that have been 

identified for use during seismic 

surveys (but not necessarily practicable 

for each and every survey). For reader 

convenience that discussion has been 

provided in this document. It is also 

found in NMFS’ FONSI statement (see 

NEPA later in this document).

Comment NEPA 8: The CBD states 

that the EA is also grossly deficient in 

its discussion of potential impacts to 

fish species. While the EA briefly 

analyses the impacts of fishing on 

marine mammals and secondary 

impacts to fish as food for marine 

mammals, the EA fails to analyze 

impacts to fish stocks themselves.

Response: In the EA, NSF notes that 

‘‘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. 

Finally, exposure to seismic sound is 

considered unlikely to result in direct, 

or even cryptic, fish mortality 

(Department of Fisheries, 2004). 

Although not tested independently, 

post-seismic monitoring has not 

indicated fish kills (IBID, 2004). NMFS 

therefore believes that while significant 

changes in behavior would mean that 

these fish might be unavailable for 

fisheries, there would not be a long-term 

impact on fish stocks themselves. NMFS 

is confident that the EA has provided 

the level of information necessary to 

determine that the Ewing survey in the 

Northeast Pacific Ocean will not have a 

significant effect on fish stocks, because, 

as stated in the EA, it will not have 

more than a short-term behavioral 

response on the part of the fish 

themselves.

Description of Habitat and Marine 

Mammals Affected by the Activity

A detailed description of the NPO in 

the Blanco Fracture/Gorda Ridge area 

and its associated marine mammals can 

be found in the L-DEO application and 

a number of documents referenced in 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74917

the L-DEO application, and is not 

repeated here. This document is 

available online at: http://

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

SmalllTake/

smalltakelinfo.htm#applications.

The main Blanco Transform survey 

site, and the Gorda Ridge contingency 

survey site, are located approximately 

450 and 150 km (243 and 81 nm) 

offshore from Oregon, respectively, over 

water depths of 1600 to 5000 m (5250 

to 16405 ft). Based on their preference 

for offshore (>2000 m (6560 ft) depth) 

and/or slope (200–2000 m or 656–6560 

ft) waters, 19 of the 39 marine mammal 

species known to occur in Oregon and 

Washington waters are considered likely 

to occur near the survey areas. An 

additional 14 species could occur, but 

are unlikely to occur in the project area 

because they are rare or uncommon in 

slope and offshore waters or they 

generally do not occur off Oregon or 

Washington. While these 14 species are 

addressed in the L-DEO application it is 

unlikely that they will occur in the 

survey area. An additional six species 

are not expected in the project area 

because their occurrence off Oregon is 

limited to coastal/shallow waters (gray 

whale and sea otter) or they are 

considered extralimital (beluga whale, 

ringed seals, ribbon seal, and hooded 

seal). As it is unlikely that these rare, 

vagrant mammals would occur during 

the short time period of this seismic 

survey, these latter six species are not 

addressed further as they are unlikely to 

be impacted by seismic signals from this 

research operation.

The six species of marine mammals 

expected to be most common in the 

deep pelagic or slope waters of the 

project area include the Pacific whitesided dolphin, northern right whale 

dolphin, Risso’s dolphin, short-beaked 

common dolphin, Dall’s porpoise , and 

northern fur seal (Green et al. 1992, 

1993; Buchanan et al. 2001; Carretta et 

al. 2002; Barlow 2003). The sperm 

whale , pygmy sperm whale, 

mesoplodont species (Blainville’s 

beaked whale, Stejneger’s beaked whale, 

and Hubb’s beaked whale), Baird’s 

beaked whale, Cuvier’s beaked whale, 

and northern elephant seals are 

considered pelagic species but are 

generally uncommon in the waters near 

the survey area.

Of the five species of pinnipeds 

known to occur regularly in waters off 

Oregon, Washington, or northern 

California, only the northern fur seal 

and northern elephant seal are likely to 

be present in the pelagic waters of the 

proposed project area, located 

approximately 150–450 km (243–481 

nm) offshore. The Steller sea lion may 

also occur there in small numbers. The 

California sea lion and harbor seal occur 

in shallow coastal or shelf waters off 

Oregon and Washington (Bonnell et al. 

1992, Green et al. 1993, Buchanan et al.

2001), and are not expected to be seen 

in the proposed study area. Sea otters 

were translocated to shallow coastal 

waters off the Olympic Peninsula of 

Washington, but are not found in the 

pelagic waters of the project area off 

Oregon. More detailed information on 

these species is contained in the L-DEO 

application and additional information 

is contained in Caretta et al. (2002) 

which are available at: http://

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

SmalllTake/

smalltakelinfo.htm#applications, and 

http://www.nmfs.noaa.gov/protlres/

PR2/StocklAssessmentlProgram/

sars.html, respectively.

Potential Effects on Marine Mammals

The effects of sounds from airgun 

arrays might include one or more of the 

following: tolerance, masking of natural 

sounds, behavioral disturbance and 

perhaps temporary or permanent 

hearing impairment (Richardson et al.

1995). In addition, intense acoustic 

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) masking, (2) 

disturbance, and (3) potential hearing 

impairment and other physical effects. 

Additional discussion on species 

specific effects can be found in the LDEO application.

Masking

Masking effects of pulsed sounds on 

marine mammal calls and other natural 

sounds are expected to be limited, 

although there are very few specific data 

on this. Seismic sounds are short pulses 

occurring for less than 1 sec every 20 or 

60–90 sec in this project. 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 1/5th or 

at most 2/5th 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). 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 that sounds 

important to these species 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 frequencies are mainly used by 

mysticetes, but 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 cetacean 

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 and preadaptation to 

tolerate some masking by natural 

sounds (Richardson et al. 1995), would 

all reduce the importance of masking.

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 

74918 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

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 disruption of a 

behavioral pattern. However, if a sound 

source would displace marine mammals 

from an important feeding or breeding 

area for a prolonged period, such a 

disturbance would constitute Level B 

harassment. 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. This 

likely overestimates the numbers of 

marine mammals whose behavioral 

patterns may be disrupted. 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.

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 regarding 

exposure of marine mammals to highlevel sounds is that cetaceans and 

pinnipeds should not be exposed to 

impulsive sounds ≤180 and 190 dB re 1 

microPa (rms), 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 onset 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.

Several aspects of the planned 

monitoring and mitigation measures for 

this project are designed to detect 

marine mammals occurring near the 

airgun array (and multibeam sonar), and 

to avoid exposing them to sound pulses 

that might cause hearing impairment. In 

addition, 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 

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. 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 radius of no more than 

100 m (328 ft) around a seismic vessel.

There are no data, direct or indirect, 

on levels or properties of sound that are 

required to induce TTS in any baleen 

whale. TTS thresholds for pinnipeds 

exposed to brief pulses (single or 

multiple) have not been measured, 

although exposures to pulses 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 radius of 

≤100 m (≤ 328 ft) around a typical 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. 

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 

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. Odontocetes would be at or 

above the surface while bow-riding, 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 bowriding near airguns, they would be 

exposed to strong sound pulses, 

possibly repeatedly. If some cetaceans 

did incur TTS through exposure to 

airgun sounds, it would very likely be 

a temporary and reversible 

phenomenon.

NMFS currently believes that, 

whenever possible 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 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74919

for pinnipeds has been set at 190 dB. 

The predicted 180- and 190–dB received 

level distances for the airgun arrays 

operated by L-DEO during this activity 

are summarized elsewhere 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 and belugas, 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 ramping 

up airgun arrays, 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 airgun array.

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. 

Physical damage to a mammal’s hearing 

apparatus can occur if it is exposed to 

sound impulses that have very high 

peak pressures, especially if they have 

very short rise times (time required for 

sound pulse to reach peak pressure from 

the baseline pressure). Such damage can 

result in a permanent decrease in 

functional sensitivity of the hearing 

system at some or all frequencies.

Single or occasional occurrences of 

mild TTS are not indicative of 

permanent auditory damage in 

terrestrial mammals. However, very 

prolonged exposure to sound strong 

enough to elicit TTS, or shorter-term 

exposure to sound levels well above the 

TTS threshold, can cause PTS, at least 

in terrestrial mammals (Kryter 1985). 

Relationships between TTS and PTS 

thresholds have not been studied in 

marine mammals but are assumed to be 

similar to those in humans and other 

terrestrial mammals. 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, (3) 

recurrent ear infections or (in captive 

animals) exposure to certain drugs, and 

(4) normal aging process.

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 receiving animal’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 

exposure to a series of seismic pulses in 

odontocetes may be on the order of 220 

dB re 1 microPa (pk-pk), 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). It is very unlikely that 

an odontocete would remain within a 

few meters of a large airgun for 

sufficiently long to incur PTS. 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. However, pinnipeds are 

expected to be (at most) uncommon in 

the Blanco Fracture survey area. 

However, although it is unlikely that the 

planned seismic surveys could cause 

PTS in any marine mammals, caution is 

warranted given the limited knowledge 

about noise-induced hearing damage in 

marine mammals, particularly baleen 

whales.

Strandings and Mortality

Marine mammals close to underwater 

detonations of high explosives can be 

killed or severely injured, and the 

auditory organs are especially 

susceptible to injury (Ketten et al. 1993, 

Ketten 1995). Airgun pulses are less 

energetic and have slower rise times 

than underwater detonations, and, 

while there is no documented evidence 

that airgun arrays can cause serious 

injury, death, or stranding, the temporal 

association of strandings of beaked 

whales with naval exercises and, more 

recently, an L-DEO seismic survey has 

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 

74920 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

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 μPa, 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 

into surface waters. 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 noiseinduced 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 in the area. Jepson et al. (2003) 

concluded that cetaceans might be 

subject to decompression injury (i.e., the 

bends or air embolism) in some 

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 and currently 

there are no data to question that 

assumption.

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, to 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 may possibly 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 

this 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 

event 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 includes 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. It should be noted that seismic 

has been used far more extensively than 

tactical sonar, but currently information 

on strandings associated with seismic is 

not as clear as it is with sonar. 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 during 

a seismic survey for a sufficiently long 

period of time that significant 

physiological stress would develop. For 

the Blanco Fracture study, the survey 

area is only 70 km2 and the survey will 

last less than one week.

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 have resonant 

frequencies equal to frequencies emitted 

by mid- or low-frequency sonar; lung 

tissue damage has not been observed in 

any mass, multi-species stranding of 

beaked whales; and the duration of 

sonar pings is likely too short to induce 

vibrations that could damage tissues 

(Gentry (ed.) 2002). Opinions were less 

conclusive about the possible role of gas 

(nitrogen) bubble formation/growth in 

the Bahamas stranding of beaked 

whales. Workshop participants did not 

rule out the possibility that bubble 

formation/growth caused by static 

diffusion 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.

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, 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74921

are unlikely to incur auditory 

impairment or other physical effects.

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 during 

much of 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 

and sub-bottom profiler, (2) have a 

longer pulse duration than these two 

instruments, and (3) are directed close 

to horizontally (vs. downward for the 

Hydrosweep and sub-bottom profiler). 

Also, the area of possible influence of 

the Hydrosweep and sub-bottom profiler 

is much 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 Hydrosweep 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.

Sounds from the sub-bottom profiler 

are very short pulses, occurring for 1, 2 

or 4 ms once every second with a stated 

maximum source level of 204 dB re 1 

Pa-m. Most of the energy in the sound 

pulses emitted by this sub-bottom 

profiler is at mid frequencies, centered 

at 3.5 kHz. The beamwidth is 

approximately 30 and is directed 

downward. Thus the received level 

would be expected to decrease to 160 

and 180 dB about 160 m (525 ft) and 16 

m (52 ft) below the μtransducer, 

respectively, assuming spherical 

spreading. Corresponding distances in 

the horizontal plane would be lower, 

given the directionality of this source 

(30 beamwidth) and the measurements 

of Burgess and Lawson (2000).

Therefore, as harassment or injury 

from pulsed sound is a function of total 

energy received, the actual harassment 

or injury threshold for Hydrosweep 

signals (approximately 10 ms) and subbottom profiler signals (approximately 

1–4 ms) would be at a much higher dB 

level than that for longer duration 

pulses such as sonar signals. As a result, 

NMFS believes that marine mammals 

are unlikely to be harassed or injured 

from either the multibeam sonar or the 

sub-bottom profiler.

Masking by Mid-Frequency Sonar 

Signals

Marine mammal communications will 

be not 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 do not overlap 

with the predominant frequencies of the 

calls, which would avoid significant 

masking.

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 

beachings by beaked whales. Also, Navy 

personnel have described observations 

of dolphins bow-riding adjacent to bowmounted mid-frequency sonars during 

sonar transmissions. However, all of 

these observations are of limited 

relevance to the present situation. Pulse 

durations from those 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 L-DEO’s 

operations, the individual pulses will be 

very short, and a given mammal would 

not receive many of the downwarddirected 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 from 

a bathymetric sonar in either duration or 

bandwidth.

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. 

Finally, the pulsed signals from the subbottom profiler are much weaker than 

those from the airgun array and the 

multibeam sonar. Therefore, 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). It is worth noting that the 

multi-beam sonar proposed for use by LDEO is quite different than sonars used 

for navy operations. Pulse duration of 

the multi-beam sonar 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 a very limited time 

given the generally downward 

orientation of the beam and its narrow 

fore-aft beamwidth. (Navy sonars often 

use near-horizontally-directed sound.) 

These factors would all reduce the 

sound energy received from the multibeam sonar rather drastically relative to 

that from the sonars used by the Navy. 

Therefore, hearing impairment by the 

multi-beam 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 

74922 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

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 Blanco Fracture Zone Survey

Although information contained in 

this document indicates that injury to 

marine mammals from seismic sounds 

potentially occurs at sound pressure 

levels 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 

typically about 10 dB less than its peak 

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 would be limited to 

Level B harassment. The proposed 

mitigation measures will minimize or 

eliminate the possibility of Level A 

harassment. L-DEO has calculated the 

‘‘best estimates’’ for the numbers of 

animals that could be taken by level B 

harassment during the proposed Blanco 

Fracture 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 (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 10- 

and 12–gun array planned to be used for 

this project. The anticipated radius of 

influence of the multi-beam sonar is less 

than that for the airgun array, 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.

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. 

Furthermore, if they are encountered, 

the numbers of mysticetes estimated to 

occur within the 160–dB isopleth at the 

Blanco Fracture and Gorda Ridge survey 

sites are expected to be low. In addition, 

the estimated numbers presented in 

Table 2 are considered overestimates of 

actual numbers for two primary reasons. 

First, the number of line kilometers 

used to estimate the number of 

exposures and individuals exposed 

assumes that both the main and 

contingency surveys will be completed; 

this is highly unlikely given the 

likelihood that some inclement weather, 

equipment malfunction, and/or 

implementation of mitigative shut 

downs or power downs will occur. 

Secondly, the estimated 160–dB radii 

used here are probably overestimates of 

the actual 160–dB radii at deep water 

sites such as the Blanco Fracture and 

Gorda Ridge sites (Tolstoy et al. 2004).

BILLING CODE 3510–22–S

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74923


EN14DE04.154</GPH>
74924 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

BILLING CODE 3510–22–C 

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 mitigation 

measures that are required to be 

undertaken, effects on cetaceans are 

generally expected to be limited to 

avoidance of the 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 small 

percentages of the population sizes in 

the NPO generally.

The best estimates of the numbers of 

individual cetaceans that may be 

exposed to sounds ≥160 dB re 1 microPa 

(rms)(the current criterion for level B 

harassment) represent 0 to 0.7 percent of 

the populations of each species in the 

NPO. For species listed as endangered 

under the ESA, this includes no North 

Pacific right whales or sei whales; less 

than 0.02 percent of the NPO 

populations of sperm, humpback and 

blue whales; and 0.1 percent of the fin 

whale population (Table 2). In the cases 

of mysticetes, beaked whales, and sperm 

whales, these exposure levels are 

expected to involve no more than very 

small numbers (0 to 7) of individual 

cetaceans. Sperm and fin whales are the 

endangered species that are most likely 

to be exposed, and their NPO 

populations are approximately 26,053 

and 8520, respectively (Ohsumi and 

Wada 1974, Carretta et al. 2002).

It is highly unlikely that any right 

whales will be exposed to seismic 

sounds ≥160 dB re 1 microPa (rms). This 

conclusion is based on the rarity of this 

species off Oregon/Washington and in 

the NPO generally (less than 100, 

Carretta et al. 2002), and information 

that the remnant population of this 

species apparently migrates to more 

northerly areas during the summer. 

However, L-DEO has requested an 

authorization to expose up to two North 

Pacific right whales to ≥160 dB, given 

the possibility (however unlikely) of 

encountering one or more of this 

endangered species. If a right whale is 

sighted by the vessel-based observers, 

the airguns will be shut down (not just 

powered down) regardless of the 

distance of the whale from the airgun 

array.

Larger numbers of delphinids may be 

affected by the proposed main and 

contingency seismic studies, but the 

population sizes of species likely to 

occur in the operating area are large, 

and the numbers potentially affected are 

small relative to the population sizes. 

As indicated in Table 2, the best 

estimate of number of individual 

delphinids that might be exposed to 

sounds greater than or equal to 160 dB 

re 1 microPa (rms) represents a small 

percentage of the populations of each 

species occurring there.

Varying estimates of the numbers of 

marine mammals that might be exposed 

to airgun sounds during the October 

2004 seismic surveys off Oregon have 

been presented, depending on the 

specific exposure criteria, calculation 

procedures (exposures vs. individuals), 

and density criteria used (best vs. 

maximum). The requested ‘‘take 

authorization’’ for each species is based 

on the estimated maximum number of 

exposures to ≥160 dB re 1 microPa 

(rms). That figure likely overestimates 

(in most cases by a large margin) the 

actual number of animals that will be 

exposed to these sounds; the reasons for 

this have been outlined previously. 

Even so, the combined estimates for the 

main and contingency surveys are quite 

low percentages of the population sizes. 

Furthermore, mitigation measures such 

as controlled speed, course alternation, 

look outs, non-pursuit, ramp ups, and 

power downs or shut downs when 

marine mammals are seen within 

defined ranges should further reduce 

any short-term reactions, and minimize 

any effects on hearing sensitivity. In all 

cases, these relatively short-term 

exposures are unlikely to result in any 

long-term negative consequences for the 

individuals or their populations.

In light of the type of take expected 

and the small numbers of affected 

stocks, the action is expected to have no 

more than a negligible impact on the 

affected species or stocks of marine 

mammals. In addition, mitigation 

measures such as controlled vessel 

speed, course alteration, look-outs, 

ramp-ups, and power-downs when 

marine mammals are seen within 

defined ranges (see Mitigation) should 

further reduce short-term reactions to 

disturbance, and minimize any effects 

on hearing sensitivity.

Conclusions- Effects on Pinnipeds

Two pinniped species, the northern 

fur seal and the northern elephant seal, 

are likely to be encountered at the 

survey sites, as they are associated with 

pelagic slope and offshore waters off 


EN14DE04.155</GPH>
Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74925

Oregon. In addition, it is possible 

(although unlikely) that a small number 

of Steller sea lions, California sea lions, 

and/or harbor seals may also be 

encountered, most likely at the Gorda 

Ridge survey area located closer to shore 

in continental slope water; these three 

species tend to inhabit primarily coastal 

and shelf waters. An estimated 79 

individual fur seals and 15 individual 

elephant seals may be exposed to airgun 

sounds with received levels ≥160 dB re 

1 microPa (rms). It is most likely that no 

California sea lions, Steller sea lions, or 

harbor seals will be exposed to such 

sounds. Similar to cetaceans, the 

estimated numbers of pinnipeds that 

may be exposed to received levels ≤160 

dB are probably overestimates of the 

actual numbers that will be significantly 

affected. This action would therefore 

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. The 

actual area that will be affected by the 

OBSs will be a very small fraction of the 

marine mammal habitat and the habitat 

of their food species in the area; thus, 

any effects are expected to be highly 

localized and insignificant. The use of 

OBSs would result in no more than a 

negligible and highly localized shortterm disturbance to sediments and 

benthic organisms. The area that might 

be disturbed is a very small fraction of 

the overall area occupied by fish or 

marine mammal species.

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 to 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 zone 

within the injury zone 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 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 

impulse. 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 subsistence hunting for 

those marine mammal stocks potentially 

affected by the Blanco Fracture seismic 

survey, so the proposed activity will not 

have any impact on the availability of 

the species or stocks for subsistence 

users.

Mitigation

For the proposed Blanco Fracture 

seismic survey, L-DEO will deploy a 10- 

or 12–airgun array as an energy source, 

with discharge volumes of 3050 in3 and 

3705 in3, respectively. The airguns in 

the arrays will be spread out 

horizontally so the energy from the 

array will be directed mostly 

downward. The directional nature of the 

arrays 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. Because the actual 

seismic source is a distributed sound 

source (10–12 airguns) rather than a 

single point source, the highest sound 

levels measurable at any location in the 

water will be less than the nominal 

source level. Also, the size of the airgun 

arrays (which are smaller than the 20–

gun array used for some other surveys) 

is another important mitigation measure 

that will reduce the potential for effects 

relative to those that might occur with 

a larger array of airguns. This is in 

conformance with NMFS’ encouraging 

seismic operators to use the lowest 

intensity airguns practical to 

accomplish research objectives.

Safety Radii

Received sound levels have been 

modeled by L-DEO in relation to 

distance and direction from the two 

arrays. The radii around the 10–airgun 

array where the received levels would 

be 180 dB and 190 dB re 1 μPa (rms) 

were estimated as 550 m (1805 ft) and 

200 m (656 ft), respectively. For the 12–

airgun array, the radii around the array 

where the received levels would be 180 

dB and 190 dB re 1 μPa (rms) were 

estimated as 600 m (1969 ft) and 250 m 

(820 ft), respectively. The 180 and 190 

dB shutdown criteria, applicable to 

cetaceans and pinnipeds, respectively, 

are specified by NMFS (2000) and, as 

mentioned previously in this document, 

are considered conservative for 

protecting marine mammals from 

potential injury.

Empirical data concerning these 

safety radii have been acquired based on 

measurements during the acoustic 

verification study conducted in the 

northern Gulf of Mexico from 27 May to 

3 June 2003 under an IHA issued to LDEO (see 68 FR 32460, May 30, 200). A 

copy of that report (Tolstoy et al., 2004) 

is available on-line at: http://

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

74926 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

SmalllTake/

smalltakelinfo.htm#applications, LDEO’s analysis of the acoustic data from 

that study provides limited 

measurements in deep water, the 

situation relevant here. Those data 

indicate that, for deep water, the model 

tends to overestimate the received 

sound levels at a given distance. Until 

additional data become available, it is 

proposed that safety radii during airgun 

operations in deep water, including the 

planned operations off Oregon, will be 

the values predicted by L-DEO’s model. 

Previously, more conservative (larger) 

safety radii that are 1.5 times the 

modeled radii have been used for these 

surveys. However, given that these 

modeled radii are already conservative 

(i.e., overestimates) for deep water 

situations, even without the X 1.5 factor, 

these larger radii will not be used 

during this seismic survey.

Mitigation Measures

The following mitigation measures, as 

well as marine mammal visual 

monitoring (discussed later in this 

document), are required to be carried 

out for the subject seismic surveys, 

provided that they do not compromise 

operational safety requirements of the 

Ewing: (1) Speed and course alteration; 

(2) power-down and shut-down 

procedures; (3) ramp-up procedures; (4) 

use of passive acoustics to detect 

vocalizing marine mammals; and (5) 

incorporation of non-seismic/sonar 

periods to allow marine mammals to 

surface from deep dives if acoustic 

sounds are disrupting dive patterns. 

Some of these mitigation measures will 

also be implemented to protect sea 

turtles. In addition, stricter mitigation 

measures will be implemented for the 

North Pacific right whale.

Speed and Course Alteration

If a marine mammal is detected 

outside the appropriate safety radius 

and, based on its position and the 

relative motion, is likely to enter the 

safety radius, the vessel’s speed and/or 

direct course will be changed if this is 

practical while minimizing the effects 

on planned science objectives. Given 

the presence of the streamer and airgun 

array behind the vessel, the turning rate 

of the vessel with trailing streamer and 

array is no more than five degrees per 

minute, limiting the maneuverability of 

the vessel during operations. 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 radius. If the mammal 

appears likely to enter the safety radius, 

further mitigative actions will be taken, 

(i.e., either further course alterations or 

shutdown 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. A power down may also occur 

when the vessel is moving from one 

seismic line to another, unless the full 

airgun array is scheduled to be operated 

during line changes. During a power 

down, one 80 in3 airgun 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 airguns 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, at least one 

airgun (e.g., 80 in3) will be operated. If 

a marine mammal is detected within or 

near the smaller safety radius around 

that single airgun (Table 1), all airguns 

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 a power down, the operating 

airgun will be shut down if a marine 

mammal approaches within the 

modeled safety radius for the thenoperating source, typically a single gun 

of 80 in3. Because no calibration 

measurements have been done to 

confirm the modeled safety radii for the 

single gun, conservative radii may be 

used (1.5 times the modeled safety 

radius). For an 80 in3 airgun, the 

predicted 180–dB distance applicable to 

cetaceans is 36 m (118 ft) and the x1.5 

conservative radius is 54 m (177 ft). The 

corresponding 190–dB radius applicable 

to pinnipeds is 13 m (43 ft), with the 

x1.5 conservative radius being 20 m (66 

ft). If a marine mammal is detected 

within or about to enter the appropriate 

safety radius around the small source in 

use during a power down, airgun 

operations will be entirely shut down. 

In addition, the airguns will be shut 

down if a North Pacific right whale is 

sighted anywhere near the vessel, even 

if it is located outside the safety radius, 

because of the rarity and sensitive status 

of this species. Resumption of airgun 

activity will follow procedures 

described for power-down operations.

Ramp-up Procedure

When airgun operations commence 

after a certain period without airgun 

operations, the number of guns firing 

will be increased gradually, or ‘‘ramped 

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

Operations will begin with the smallest 

gun in the array (80 in3). Guns will be 

added in sequence such that the source 

level of the array will increase in steps 

not exceeding 6 dB per 5–min period 

over a total duration of approximately 

18–20 minutes. Throughout the rampup procedure, the safety zone for the 

full 10- or 12–gun array will be 

maintained.

The ‘‘ramp-up’’ procedure will be 

required under the following 

circumstances. Under normal 

operational conditions (vessel speed 4 

knots (7.4 km/hr)), a ramp-up would be 

required after a power-down or shutdown period lasting more than 4 

minutes if the Ewing was towing the 10–

or 12–gun array. At 4 knots, the Ewing

would travel 600 m (1969 ft) during a 

5–minute period. The 600–m (1969 ft) 

distance is the calculated 180–dB safety 

radius.

If the towing speed is reduced to 3 

knots (5.6 km/hr) or less, as sometimes 

required when maneuvering in shallow 

water (not a factor here), it is proposed 

that a ramp-up would be required after 

a ‘‘no shooting’’ period lasting greater 

than 7 minutes. At towing speeds not 

exceeding 3 knots (5.6 km/hr), the 

source vessel would travel no more than 

600 m (1969 ft) in about 7 minutes. 

Based on the same calculation, a rampup procedure would be required after a 

4–minute period if the speed of the 

source vessel was 5 knots (9.3 km/hr).

Ramp-up will not occur if the safety 

radius has not been visible for at least 

30 minutes prior to the start of ramp-up 

operations in either daylight or 

nighttime. If the safety radius has not 

been visible for that 30–minute period 

(e.g., during darkness or fog), ramp-up 

will not commence unless at least one 

airgun has been firing continuously 

during the interruption of seismic 

activity. That airgun will have a source 

level of at least 180 dB re 1 microPa m 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 74927

(rms). It is likely that the airgun arrays 

will not be ramped up from a complete 

shut down at night or in thick fog, 

because the outer part of the safety zone 

for those arrays will not be visible 

during those conditions. If one airgun 

has operated during a power down 

period, ramp up to full power will be 

permissible at night or in poor visibility, 

on the assumption that marine 

mammals will be alerted to the 

approaching seismic vessel by the 

sounds from the single airgun and could 

move away. Ramp up of the airguns will 

not be initiated if a marine mammal is 

sighted within or near the applicable 

safety radii during the day or close to 

the vessel at night.

Non-seismic/sonar Periods

To address the current hypothesis that 

seismic and/or sonar sounds are 

preventing normal dive patterns by 

beaked whales, NMFS and L-DEO will 

implement an acoustic flushing method 

to allow marine mammals (principally 

beaked whales) to vacate an area prior 

to the use of more intense acoustic 

sounds. Although NMFS believes that 

beaked whales will generally avoid 

vessels and vessel noise and, in this 

instance are unconstrained by 

topography from moving away from the 

acoustic source in either their horizontal 

or vertical movements in the ways that 

are suspected to have contributed to 

recent beaked whale strandings. 

However, in order to address new 

hypotheses (discussed previously in this 

document), NMFS and L-DEO will 

implement the following mitigation 

measures:

OBS Deployments

L-DEO will secure the multibeam and 

sub-bottom sonars until approximately 

10 minutes prior to deployment of the 

OBS. At this time these two sonars will 

commence operation to ensure that the 

depths and bottom topography are in 

accordance with the planned OBS 

location. Immediately after the OBS has 

been deployed and the Ewing is 

underway to the next site, these sonars 

will be secured until 10 minutes from 

the OBS deployment site.

Shooting Periods During Turns

The volume of the airgun array will be 

reduced during vessel turns while 

running seismic lines. L-DEO will 

develop a protocol that will address the 

operation’s capability to reduce sound 

in the water column with a reasonable 

ramp up period following the period of 

volume reduction. The multi-beam and 

3.5 kHz bottom profiler will be secured 

during turns (unless there is a safety 

issue).

Night-time Seismic

Comments on past proposed IHAs 

raised the issue of prohibiting nighttime operations as mitigation. However, 

this is not practicable due to cost 

considerations. The daily cost to the 

Federal Government to operate vessels 

such as Ewing is approximately $33,000 

to $35,000/day (Ljunngren, pers. comm. 

May 28, 2003). If the vessels were 

prohibited from operating during 

nighttime, it is possible that each trip 

would require an additional 3 to 5 days, 

or up to $175,000 more, depending on 

average daylight at the time of work.

Taking into consideration the 

additional costs of prohibiting nighttime operations and the likely impact of 

the activity (including all mitigation and 

monitoring), NMFS has determined that 

the mitigation and monitoring required 

to be undertaken during this research 

cruise, including the new requirements 

to secure the mid-frequency sonars 

between OBS deployments and during 

seismic turns, ensures that the activity 

will have the least practicable impact on 

the affected species or stocks. Marine 

mammals will have sufficient notice of 

a vessel approaching with operating 

seismic airguns (at least 1 hour in 

advance), thereby giving them an 

opportunity to avoid the approaching 

array; if ramp-up is required after an 

extended power-down, two marine 

mammal observers will be required to 

monitor the safety radii using night 

vision devices for 30 minutes before 

ramp-up begins and verify that no 

marine mammals are in or approaching 

the safety radii; ramp-up may not begin 

unless the entire safety radii are visible; 

and ramp-up may occur at night only if 

one airgun with a sound pressure level 

of at least 180 dB has been maintained 

during interruption of seismic activity. 

Therefore it is likely that the 10–12–

airgun array will not be ramped-up from 

a shut-down at night.

Marine Mammal Monitoring

L-DEO must have at least three visual 

observers and two passive acoustic 

system biological monitors on board the 

vessels, and at least two must be 

experienced marine mammal observers 

that NMFS approves. 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 power-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 an extended 

power-down or 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 and sea turtles from the 

highest practical vantage point on the 

vessel, which is either the bridge or the 

flying bridge. On the bridge of the 

Maurice 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 airguns are powered 

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 if 

marine mammals or sea turtles are 

observed in or about to enter the safety 

radii. However, an 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 from a power-down situation, at 

least two marine mammal observers will 

monitor for marine mammals for 30 

minutes prior to ramp-up and during 

the ramp-up using night vision 

equipment that must be available (ITT 

F500 Series Generation 3 binocular 

image intensifier or equivalent). All 

observer activity will be assisted by 

passive acoustic monitoring.

74928 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Notices 

Passive (Acoustic) Monitoring (PAM)

L-DEO will use the PAM system 

during the OBS deployment (1) to assess 

pre-disturbance vocalization behavior, 

(2) during all seismic operations; and (3) 

while the Ewing is retrieving the 

hydrophone array and OBSs after 

completion of the survey. The primary 

purpose of the acoustic monitoring is to 

aid visual observers in detecting 

vocalizing marine mammals, 

particularly during periods with poor 

observation conditions, including high 

sea states, fog, or darkness, when visual 

monitoring is largely or totally 

ineffective (Smultea et al., 2004). 

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 L-DEO’s SE Caribbean 

study (69 FR 24571, May 4, 2004). 

Smultea et al. (2004) provides 

additional information on testing and 

evaluating the PAM system during this 

cruise.

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 to 3 

additional biologists 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. 

Perhaps with continued studies 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.

Reporting

L-DEO will submit a report to NMFS 

within 90 days after the end of the 

cruise in late October, 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. This report will be considered the 

final report unless NMFS provides 

comments to L-DEO on the 90–day 

report within 30 days of receipt.

Endangered Species Act (ESA)

NMFS has issued a biological opinion 

regarding the effects of this action on 

ESA-listed species and critical habitat 

under the jurisdiction of NMFS. That 

biological opinion concluded that this 

action is not likely to jeopardize the 

continued existence of listed species or 

result in the destruction or adverse 

modification of critical habitat. A copy 

of the Biological Opinion is available 

upon request (see ADDRESSES).

National Environmental Policy Act 

(NEPA)

The NSF made a FONSI 

determination on February 6, 2004, 

based on information contained within 

its EA, that implementation of the 

subject action is not a major Federal 

action having significant effects on the 

environment within the meaning of 

NEPA. NSF determined, therefore, that 

an environmental impact statement 

would not be prepared. On June 7, 2004 

(69 FR 31792), NMFS noted that the 

NSF had prepared an EA for the Blanco 

Fracture Zone surveys and made this EA 

available upon request. In accordance 

with NOAA Administrative Order 216–

6 (Environmental Review Procedures for 

Implementing the National 

Environmental Policy Act, May 20, 

1999), NMFS has reviewed the 

information contained in NSF’s EA and 

determined that the NSF EA accurately 

and completely describes the proposed 

action alternative, and the potential 

impacts on marine mammals, 

endangered species, and other marine 

life that could be impacted by the 

preferred alternative and the other 

alternatives. Accordingly, NMFS 

adopted the NSF EA under 40 CFR 

1506.3 and made its own FONSI. The 

NMFS FONSI also takes into 

consideration additional mitigation 

measures required by the IHA that are 

not in NSF’s EA. Therefore, it is not 

necessary to issue a new EA, 

supplemental EA or an environmental 

impact statement for the issuance of an 

IHA to L-DEO for this activity. A copy 

of the NSF EA and the NMFS FONSI for 

this activity is available upon request 

(see ADDRESSES).

Conclusions

Based on the information summarized 

in this document, NMFS has 

determined that the impact of 

conducting the seismic survey on the 

Blanco Fracture Zone in the NPO. will 

result, at worst, in a temporary 

modification in behavior, constituting 

level B harassment, 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.

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 is not expected to interfere 

with any 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.

Authorization

NMFS has issued an IHA to L-DEO to 

take marine mammals, by harassment, 

incidental to conducting seismic 

surveys in the Blanco Fracture Zone, 

North Pacific Ocean for a 1–year period, 

provided the mitigation, monitoring, 

and reporting requirements are 

undertaken.

Dated: December 7, 2004.

Stephen L. Leathery,

Acting Director, Office of Protected Resources, 

National Marine Fisheries Service.

[FR Doc. 04–27267 Filed 12–13–04; 8:45 am]

BILLING CODE 3510–22–S