02-2998. Small Takes of Marine Mammals Incidental to Specified Activities; Seismic Hazard Investigations in Washington State

AGENCY:

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

ACTION:

Notice of receipt of application and proposed authorization for a small take exemption; request for comments.

SUMMARY:

NMFS has received a request from the U.S. Geological Survey (USGS) for an authorization to take small numbers of marine mammals by harassment incidental to collecting marine seismic reflection data to investigate the earthquake hazard in the Straits of Georgia region of Washington State. Under the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to authorize the USGS to incidentally take, by harassment, small numbers of marine mammals in the above mentioned area during April and late May, 2002.

DATES:

Comments and information must be received no later than March 11, 2002.

ADDRESSES:

Comments on the application should be addressed to Donna Wieting, Chief, Marine Mammal Conservation Division, Office of Protected Resources, NMFS, 1315 East-West Highway, Silver Spring, MD 20910-3225. A copy of the application, which includes a list of references used in this document, and an Environmental Assessment (EA) may be obtained by writing to this address or by telephoning one of the contacts listed below.

FOR FURTHER INFORMATION CONTACT:

Kenneth R. Hollingshead, Office of Protected Resources, NMFS, [phone], or Brent Norberg, Northwest Regional Office, NMFS, [phone].

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 small numbers 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 if 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.”

Subsection 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. The MMPA defines “harassment” as:

* * * any act of pursuit, torment, or annoyance which (a) has the potential to injure a marine mammal or marine mammal stock in the wild; or (b) 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.

Subsection 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 small numbers 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

In April and May, 2002, the USGS, in cooperation with the Geological Survey of Canada and the University of Victoria, will collect marine seismic reflection data to investigate the earthquake hazards in the Straits of Georgia. For approximately 2 to 4 days this research will be in U.S. waters and about 17 to 19 days will be in Canadian waters. Geological features around the Straits of Georgia that might produce earthquakes lie obscured beneath water, urban areas, forest, and thick glacial deposits. As a result, investigators must use sound waves that are produced by either single airguns or more usually an array of airguns to indirectly view these features. Because seismic noise from the proposed survey's airguns could potentially affect marine mammals due to disturbance by sound (i.e., acoustic harassment), an incidental harassment authorization (IHA) under the MMPA is warranted.

Throughout western Washington state and southwest British Columbia (BC), geological faults that might produce earthquakes lie hidden beneath the dense forest and the waters of Puget Sound and the Strait of Georgia. Although some faults are known from limited exposures on land and from marine seismic surveys, such as the Lummi Island and Outer Islands faults (see Figure 1 in the USGS application), more may have eluded detection in this little-studied area. Furthermore, the amount of recent (<50,000 years) motion on these faults, if any, is unknown. Estimating the frequency and sizes of earthquakes on both the known and unknown faults is crucial to understanding the earthquake risk to the cities of Bellingham and Anacortes, WA to Vancouver and Victoria, BC and to the more rural parts of the region. For more detailed information on the geological faults in this area, please refer to the USGS application.

Seismic reflection data will be collected during the period of April and May by the Canadian research vessel J. P. Tully. Seismic profiling will be done by towing a 600-m (1,968.5-ft) long hydrophone streamer for sensing and recording pressure changes from the airgun echos. The streamer will be towed at a depth of 5 m (16.4 ft). Near the forward end of the streamer, an airgun will be towed about 10 m (32.8 ft) behind the ship at a depth of about 5 m (16.4 ft). The hydrophone streamer, which is connected to a computer recording system, will record echos coming from the strata beneath the sea bottom. These recordings will be computer-processed to create an image of the subsurface strata, including any faults that are crossed during the profiling. The seismic operation will operate 24 hours/day while in U.S. waters and will be traveling at a speed of 6 to 8 knots (6.9 to 9.2 miles/hr; 11.1 to 14.8 km/hr).

The sound source will be either a single, 120 inch³ airgun or, more likely, a small array of airguns consisting of two 40-in³ and two 20-in³ guns being fired within several milliseconds (1/1000 second) of each other. The source will be chosen after tests at the beginning of the cruise. Either way, this sound source, as measured by the volume of the chamber, is only 2 percent of the size of the airgun array used in the USGS survey conducted in 1998 in Puget Sound (see 63 FR 2213, January 14, 1998). Both of the USGS' potential sources will produce similar levels of sound pressure, which is estimated to be about 225 dB. An array of small airguns increases the frequency of the sound over that from a single gun, and an array better directs the sound downward. This array has been used previously in the inland waters of Canada (Reidel et al., 1999), and the characteristics of this sound source have been measured (see Figure 3 in the USGS application).

The airgun does not emit a prolonged sound source; rather, it emits an impulsive noise burst (<10 milliseconds) with a peak-to-peak (P-P) sound pressure level (SPL) estimated to be 220 to 230 dB. The USGS' best estimate is that the source will have an SPL of about 225 dB. This compares to an estimated 240 dB SPL for the 6730 inch ³ airgun array used in the 1998 Puget Sound seismic survey project (Fisher, 1997). This also compares with the continuous noise from freighters and other ship traffic in the area, which is estimated to be 150 to 205 dB (Natural Resources Defense Council, 1998). The airgun will be fired almost continuously 3 to 6 times per minute.

The frequency spectrum of the sound emission was measured when the array was used in a previous study (Reidel et al., 1999). The airgun's energy is concentrated below 200 Hz, with a rapid decrease in amplitude with increasing frequency between 200 and 400 Hz. Frequencies above 400 Hz have amplitudes that are less than 10 percent of the lower frequencies. For purposes of later discussion, frequencies below 1,000 Hz (1 kHz) are considered low frequency (LF).

Description of Habitat and Marine Mammals Affected by the Activity

A description of the affected habitat and its associated marine mammals can be found in the USGS application and in several documents issued previously for acoustic research in Washington State waters (NMFS, 1996, 1997).

Marine Mammals

The species of marine mammals that are likely to be present in the region of the Straits of Georgia include the harbor porpoise (Phocoena phocoena), killer whale (Orcinus orca), Dall's porpoise (Phocoenoides dalli), harbor seal (Phoca vitulina) California sea lion (Zalophus californianus) and elephant seal (Mirounga angustirostris) (Calambokidis and Baird, 1995). Additional species that are rare or only occasionally seen in the area at the time of the survey include: Pacific white-sided dolphin (Lagenorhynchus obliquidens), northern sea lion (Eumetopias jubatus), minke whale (Balaenoptera acutorostrata) humpback whale (Megaptera novaengliae) and gray whale (Eschrichtius robustus). However, because of the short duration of this project in waters under the jurisdiction of the United States, it is very unlikely that these latter species would be harassed, or injured as a result of conducting seismic surveys. These species include: Pacific white-sided dolphin, northern sea lion, minke whale, humpback whale, and gray whale.

General information on the marine mammal species can be found in the USGS application and the previously mentioned documents prepared under the National Environmental Policy Act (NEPA). Information on marine mammal species in this area can also be found in Forney et al. (2000). The NEPA documents are available upon request (see ADDRESSES); Forney et al. (2000) is available at the following URL: http://www.nmfs.noaa.gov/​prot_​res/​PR2/​Stock_​Assessment_​Program/​sars.html. Please refer to these documents for specific information on marine mammal species.

Potential Effects of Seismic Surveys on Marine Mammals

Discussion

Disturbance by seismic noise is the principal means of taking incidental to this activity. Vessel noise may provide a secondary source. Also, the physical presence of vessel(s) could also lead to some non-acoustic effects involving visual or other cues.

The effects of underwater noise on marine mammals are highly variable, and can be categorized as follows (based on Richardson et al., 1995): (1) The noise may be too weak to be heard at the location of the animal (i.e. lower than the prevailing ambient noise level, the hearing threshold of the animal at relevant frequencies, or both); (2) the noise may be audible but not strong enough to elicit any overt behavioral response; (3) the noise may elicit behavioral reactions of variable conspicuousness and variable relevance to the well being of the animal; these can range from subtle effects on respiration or other behaviors (detectable only by statistical analysis) to active avoidance reactions; (4) upon repeated exposure, animals may exhibit diminishing responsiveness (habituation), or disturbance effects may persist (the latter is most likely with sounds that are highly variable in characteristics, unpredictable in occurrence, and associated with situations that the animal perceives as a threat); (5) any noise that is strong enough to be heard has the potential to reduce (mask) the ability of marine mammals to hear natural sounds at similar frequencies, including calls from conspecifics and/or echolocation sounds, and environmental sounds such as storms and surf noise; and (6) very strong sounds have the potential to cause either a temporary or a permanent reduction in hearing sensitivity (i.e., temporary threshold shift (TTS) or permanent threshold shift (PTS), respectively). In addition, intense acoustic or explosive events may cause trauma to tissues associated with organs vital for hearing, sound production, respiration and other functions. This trauma may include minor to severe hemorrhage.

Few data on the effects of non-explosive sounds on hearing thresholds of marine mammals have been obtained. However, in terrestrial mammals (and presumably in marine mammals), received sound levels must far exceed the animal's hearing threshold for there to be any TTS and must be even higher for there to be risk of PTS (Richardson et al., 1995).

Depending upon ambient conditions and the sensitivity of the receptor, underwater sounds produced by open-water seismic operations may be detectable some substantial distance away from the activity. Any sound that is detectable is (at least in theory) capable of eliciting a disturbance reaction by a marine mammal or masking a signal of comparable frequency. An incidental harassment take is presumed to occur when marine mammals in the vicinity of the seismic source (or vessel) show a significant behavioral response to the generated sounds or visual cues.

High-intensity LF seismic pulses are known to cause some species of whales, including gray and bowhead whales, to behaviorally respond within a distance of several kilometers (Richardson et al. 1995). Although some limited masking of low-frequency sounds is a possibility for those species of whales using low frequencies for communication, the intermittent nature of seismic source pulses will limit the extent of masking. Bowhead whales, for example, are known to continue calling in the presence of seismic survey sounds, and their calls can be heard between seismic pulses (Richardson et al. 1986).

When the received levels of noise exceed some behavioral reaction threshold, cetaceans will show disturbance reactions. The levels, frequencies, and types of noise that will elicit a response vary between and within species, individuals, locations and season. Behavioral changes may be subtle alterations in surface-dive-respiration cycles. More conspicuous responses include changes in activity or aerial displays, movement away from the sound source, or complete avoidance of the area. The reaction threshold and degree of response are related to the activity of the animal at the time of the disturbance. Whales engaged in active behaviors such as feeding, socializing or mating are less likely than resting animals to show overt behavioral reactions, unless the disturbance is directly threatening.

Hearing damage is not expected to occur during the project. While it is not known whether a marine mammal very close to an airgun array would be at risk of temporary or permanent hearing impairment, TTS is a theoretical possibility for animals within a few hundred meters (Richardson et al. 1995), if the SPL of an acoustic source is of sufficient intensity. However, planned monitoring and mitigation measures (described later in this document) are designed to detect marine mammals occurring near the seismic array and to avoid, to the greatest extent practicable, exposing them to sound pulses that have any possibility of causing hearing damage.

Two factors determine the effect of the airgun array on marine mammals: (1) The intensity of the sound, and (2) the frequency range of the sound. There is about a 16-dB difference between measuring the P-P sound pressure and the more commonly used root-mean-square (RMS) measurement of sound pressure on marine mammals (6 dB converts P-P to peak-to-zero values, and an additional 10 dB converts peak-to-zero to RMS values). These conversions mean that the USGS airgun array will be approximately equivalent to a source with a RMS sound pressure of about 204 to 214 dB (relative to 1 micron Pa-m), with a best estimate being about 209 dB (RMS).

The airgun sound spreads laterally in the water as the radius of the sound wave increases, resulting in a decrease in amplitude with distance of 20Log(R) or greater (R=distance in meters). Given this estimate of decay, a 230 dB (P-P) sound pressure decays to 180 dB (P-P) at a distance of about 300 m (984.3 ft) (see Figure 4 in the USGS application) and to 180 dB (RMS) at about 50 m (164 ft) from the source. Thus, the maximum range at which the USGS sound source could theoretically result in TTS is 50 m (164 ft).

However, the frequency range of the airguns lies primarily outside the hearing range of most marine mammals. Data on hearing thresholds for odontocetes and pinnipeds show that the most sensitive hearing is in the 1,000- to 100,000-Hz frequency range (see Figure 5 of the USGS application; Richardson et al., 1995; Kastack and Schusterman, 1995). The USGS airgun source rapidly decreases in strength above 200 Hz, resulting in the source strength above 400 Hz being less than 10 percent of the amplitude at lower frequencies. The USGS has estimated the SPL of its airgun source as a function of frequency. The P-P sound pressure is created by the sum of waves of all the frequencies emitted by the airguns, with each frequency contributing only a portion of the total sound. If the maximum P-P SPL is divided by the frequency spectrum of the airgun array, the amplitude of the individual frequency components can be estimated at several distances, as shown in Figure 5 of the USGS application. The results indicate that the noise from any specific frequency emitted from the airgun array lies below the TTS of marine mammals at all distances (see Figure 5 of the USGS application).

The latter estimate of the strength of the individual frequency components is an underestimate, however, because it assumes that all the frequencies are exactly in phase to produce the sound pulse. In reality, the system is not perfectly efficient as implied in this calculation, and the individual frequency components are somewhat larger than shown in Figure 4 of the USGS application. If it is assumed that the USGS source is about 70 percent efficient, the individual frequency components would be about 1.43 times what the USGS estimates assuming perfect efficiency. By this calculation, the sound levels from the airgun lie below the temporary hearing shift of most marine mammals at any distance greater than 50 m (164 ft)(USGS, 2001).

The USGS proposes that the best estimate of the strength of the airgun source is the 209 dB (RMS) measure of sound pressure. Using this RMS measure, the “annoyance” or behavioral-response threshold is reached at a distance of 300 m (984.3 ft) from the airguns. This implies that animals 300 m (984.3 ft) from the USGS airguns will become annoyed and presumably will move away, but TTS would potentially not occur unless the USGS airguns were within 50 m (164 ft) of a marine mammal.

Mitigation

Several mitigation measures to reduce the potential for marine mammal harassment will be implemented by USGS as part of their proposed activity. These include:

(1) Scheduling the survey for the period of April and May, when marine mammal abundance in the Straits of Georgia is low;

(2) Having the vessel's speed between 6 and 8 knots to permit marine mammals that hear the ship and airgun noise to be able to move out of the area of the ship's track if they find the approaching vessel and accompanying noise annoying.

(3) A safety zone of 100 m (328 ft) around the seismic aigruns will be established and the USGS will shut down the airgun operation if any marine mammal except seals enters the safety zone. The 100-m (328-ft) distance is double the 50-m (164-ft) estimate of the distance for TTS. This safety zone radius compares with a 100-m or 200-m (328- or 656-ft) safety radius for marine mammals that was used successfully in the 1998 Puget Sound seismic experiment using much larger airguns (Fisher, 1997; Calambokidis and Osmek, 1998; Bain, 1998). The 1998 experiment had a 500-m (1,640-ft) safety radius for gray, humpback and minke whales, which are not expected to be in the area during the short period of time (2-4 days) for surveys in U.S. waters. Given that the current USGS airgun source is only 2 percent of the size of the 1998 source as measured in chamber volume (120 inch ³ versus 6730 inch ³, the USGS believes that a 100-m (328-ft) safety radius is ample to ensure that no injury is caused to a marine mammal.

(4) For pinnipeds (seals and sea lions), if the seismic vessel approaches a pinniped, a safety radius of 100 m (328 ft) will be maintained from the animal(s). However, if a pinniped approaches the towed airgun array during airgun transmissions, the USGS will not be required to shutdown the airguns. Experience indicates that pinnipeds will come from great distances to scrutinize seismic operations. Seals have been observed swimming within airgun bubbles, 10 m (33 ft) away from active arrays and, more recently, Canadian scientists, who were using a high-frequency seismic system that produced sound closer to pinniped hearing than will the USGS airgun array, describe how seals frequently approached close to the seismic source, presumably out of curiosity. Therefore, the above-mentioned mitigation plan has been proposed. In addition, the USGS will gather information on how often pinnipeds approach the airgun array on their own volition, and what effect the airguns appear to have on them.

(5) To ensure no marine mammals are inadvertently harmed when data collection first begins or resumes after operations have ceased, the airguns will be turned on sequentially, so that peak power is achieved gradually to give marine mammals a chance to move away from the source.

(6) Upon notification by a local stranding network that a marine mammal has been found dead within the waters of the Straits of Georgia or nearby U.S. waters when the array is operating within that body of water, NMFS will investigate the stranding to determine whether a reasonable chance exists that the USGS seismic survey project caused the animal's death. If NMFS determines, based upon a necropsy of the animal(s), that the death was likely due to the seismic source, the survey must cease U.S. operations until procedures are altered to eliminate the potential for future deaths.

Monitoring

To monitor the 100 m (328 ft) safety zone when in U.S. waters, the USGS proposes to have two observers, one on each side of the ship, specifically watching for marine mammals at all times that the airguns are operating. Members of the crew, specifically the ship's pilot, will also be instructed to immediately notify the observers if any marine mammals are sited. Observations will begin at least 10 minutes before airguns are turned on. The observers will be equipped with binoculars during the day and night-vision equipment during the night, both of which are believed adequate to monitor the 100-m (328-ft) safety zone while standing on the ship. The observers will order the airgun operations to cease if the vessel approaches within 100 m (328 ft) of a marine mammal.

The objectives of the proposed monitoring program will be: To mitigate potential harassment of marine mammals, to document the number of animals of each species present in the vicinity of the sound transmissions, and to evaluate the reactions of marine mammals to these transmissions.

It should be recognized that, at this time, the monitoring program may not be adequately funded to meet the requirements of the MMPA and therefore may need to be modified. In order for an IHA to be issued, monitoring will need to be conducted at a level which ensures that the activity will have no more than a negligible impact on marine mammal species or stocks.

Reporting

The USGS will provide an initial report to NMFS within 120 days of the completion of the Straits of Georgia marine seismic survey project. This report will provide dates and locations of seismic operations, details of marine mammal sightings, and estimates of the amount and nature of all takes by harassment. A final technical report will be provided by USGS within 1 year of completion of the project. The final technical report will contain a description of the methods, results, and interpretation of all monitoring tasks.

NEPA

In conjunction with a seismic survey project in Puget Sound in 1998, NMFS completed an EA that addressed the impacts on the human environment from issuance of an authorization and the alternatives to that action. NMFS' analysis resulted in a Finding of No Significant Impact. This proposed seismic survey will operate in the same geographic area as the 1998 survey and as the seismic airgun sources used in this proposed action are significantly less intense. Accordingly, this proposed action qualifies for a categorical exclusion under NEPA. Therefore, a new EA will not be prepared. A copy of the 1997 EA is available upon request (see ADDRESSES).

Preliminary Conclusions

NMFS has preliminarily determined that the short-term impact of conducting a marine seismic survey in the Straits of Georgia will result, at worst, in a temporary modification in behavior by certain species of pinnipeds, and possibly some individual cetaceans. While behavioral modifications may occur in certain species of marine mammals to avoid the resultant noise from airgun arrays, this behavioral change is expected to result in the harassment of only small numbers of each of several species of marine mammals and would have no more than a negligible impact on the affected species or stocks of marine mammals.

In addition, no take by injury and/or death is anticipated and takes by harassment will be at the lowest level practicable due to incorporation of the mitigation measures mentioned previously. No known rookeries, mating grounds, areas of concentrated feeding, or other areas of special significance for marine mammals occur within or near the planned area of operations during the season of operations.

As a result, NMFS proposes to issue an IHA to the USGS for the possible harassment of small numbers of several species of marine mammals incidental to collecting marine seismic data in Straits of Georgia region of Washington State, provided the above-mentioned mitigation, monitoring, and reporting requirements are incorporated.

Information Solicited

NMFS requests interested persons to submit comments, information, and suggestions concerning this request (see ADDRESSES).

Dated: January 31, 2002.

David Cottingham,

Deputy Director, Office of Protected Resources, National Marine Fisheries Service.