[Federal Register Volume 69, Number 239 (Tuesday, December 14, 2004)]
[Notices]
[Pages 74906-74928]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-27267]



[[Page 74905]]

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Part VI





Department of Commerce





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National Oceanic and Atmospheric Administration



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Small Takes of Marine Mammals Incidental to Specified Activities; 
Marine Seismic Survey on the Blanco Fracture Zone in the Northeastern 
Pacific Ocean; Notice

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

[[Page 74906]]


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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.

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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 East-West 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/prot_res/PR2/Small_Take/smalltake_info.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. L-DEO 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[deg]0 20' and 44[deg] 42'N 
and between 129[deg] 50' and 130[deg] 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[deg] 20' and 43[deg] N and 
between 126[deg] 30' and 127[deg] 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 intermediate-
spreading 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 in\3\ and 3705 
in\3\, 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 sub-standard. 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

[[Page 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.
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                                                                         RMS Radii (m/ft)
                  Airgun Array                   ---------------------------------------------------------------
                                                      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 cross-track direction. The five 
successive transmissions (segments) sweep from port to starboard with 
minor overlap, spanning an overall cross-track angular extent of about 
140 degrees, with small (<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 2/5\th\ 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[deg] 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[deg] 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 L-DEO 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

[[Page 74908]]

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 line-transect 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

[[Page 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/prot_res/readingrm/MMSURTASS/Res_Wkshp_Rpt_Fin.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 mid-frequency 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 mid-frequency sonars affect populations of animals in ways they 
do not affect

[[Page 74910]]

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 nitrogen-
supersaturated 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 first-hand 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 mid-range 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.

[[Page 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 
sub-bottom 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 low-frequency 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 L-DEO 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 hull-mounted 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

[[Page 74912]]

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 low-frequency 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 
shut-downs 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 L-DEOs 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 (peak-peak (pk-pk) and 257 dB (pk-pk), 
respectively, both levels among the highest anthropogenic sounds ever 
made.

[[Page 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.

[[Page 74914]]

    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 
in\3\). 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

[[Page 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 L-DEO 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

[[Page 74916]]

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 [gteqt] 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 [gteqt] 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 microPa (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

[[Page 74917]]

the L-DEO application, and is not repeated here. This document is 
available online at: http://www.nmfs.noaa.gov/prot_res/PR2/Small_Take/smalltake_info.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 
white-sided 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/prot_res/PR2/Small_Take/smalltake_info.htm#applications, and http://www.nmfs.noaa.gov/prot_res/PR2/Stock_Assessment_Program/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 L-DEO 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 1/5\th\ or at most 2/5\th\ 
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

[[Page 74918]]

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 
high-level 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 [gteqt]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 bow-riding near airguns, they would be exposed to 
strong sound pulses, possibly repeatedly. If some cetaceans did incur 
TTS through exposure to airgun sounds, 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

[[Page 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-to-moderate levels of TTS that have been induced in 
captive odontocetes and pinnipeds during recent controlled studies of 
TTS have been confirmed to be temporary, with no measurable residual 
PTS (Kastak et al. 1999, Schlundt et al. 2000, Finneran et al. 2002, 
Nachtigall et al. 2003). In terrestrial mammals, the received sound 
level from a single non-impulsive sound exposure must be far above the 
TTS threshold for any risk of permanent hearing damage (Kryter 1994, 
Richardson et al. 1995). For impulse sounds with very rapid rise times 
(e.g., those associated with explosions or gunfire), a received level 
not greatly in excess of the TTS threshold may start to elicit PTS. 
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, mid-frequency 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

[[Page 74920]]

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 microPa, 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 noise-induced injuries to the ears or other organs. 
Another stranding of beaked whales (15 whales) happened on 24-25 
September 2002 in the Canary Islands, where naval maneuvers were taking 
place 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 mid-frequency sonars 
operate at frequencies of 2 to 10 kHz, generally with a relatively 
narrow bandwidth at any one time (though the center frequency may 
change over time). Because seismic and sonar sounds have considerably 
different characteristics and duty cycles, it is not appropriate to 
assume that there is a direct connection between the effects of 
military sonar and seismic surveys on marine mammals. However, evidence 
that sonar pulses can in special circumstances lead to hearing damage 
and, indirectly, 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-in\3\ 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 
multi-beam 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 multi-beam 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 air-filled 
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,

[[Page 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 
microtransducer, 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 sub-bottom 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 sub-bottom 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 bow-mounted 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 
downward-directed pulses as the vessel passes by.
    Captive bottlenose dolphins and a white whale exhibited changes in 
behavior when exposed to 1-sec pulsed sounds at frequencies similar to 
those that will be emitted by the multi-beam sonar used by L-DEO and to 
shorter broadband pulsed signals. Behavioral changes typically involved 
what appeared to be deliberate attempts to avoid the sound exposure 
(Schlundt et al. 2000, Finneran et al. 2002). The relevance of these 
data to free-ranging odontocetes is uncertain and in any case the test 
sounds were quite different 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 sub-bottom 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 L-DEO 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 multi-beam 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

[[Page 74922]]

higher-power acoustic sources. Many marine mammals will move away in 
response to the approaching higher-power sources or the vessel itself 
before the mammals would be close enough for there to be any 
possibility of effects from the less intense sounds from the 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 multi-beam 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).
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    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 [gteqt]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 [gteqt]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 
[gteqt]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 [gteqt]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

[[Page 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 [gteqt]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 short-
term 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 
microPa (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 in\3\ and 3705 in\3\, 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 
microPa (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 microPa (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 L-DEO (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/prot--res/PR2/

[[Page 74926]]

Small--Take/smalltake--info.htmapplications, L-DEO'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 then-
operating source, typically a single gun of 80 in\3\. 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 in\3\ 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 in\3\). 
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 ramp-up 
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 
shut-down 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 ramp-up 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

[[Page 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 
night-time 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 
night-time 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.

[[Page 74928]]

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