Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Marine Seismic Survey in the Beaufort and Chukchi Seas, Alaska
Notice; Proposed Incidental Harassment Authorization; Request For Comments.
NMFS received an application from ION Geophysical (ION) for an Incidental Harassment Authorization (IHA) to take marine mammals, by harassment only, incidental to a proposed marine seismic survey in the Beaufort and Chukchi Seas, Alaska, between October and December 2012. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an IHA to ION to take, by harassment, nine species of marine mammals during the specified activity.
Table of Contents Back to Top
- FOR FURTHER INFORMATION CONTACT:
- SUPPLEMENTARY INFORMATION:
- Summary of Request
- Description of the Specified Activity
- Acoustic Sources
- (1) Seismic Airgun Array
- (2) Echo Sounders
- Dates, Duration, and Region of Activity
- Description of Marine Mammals in the Area of the Specified Activity
- Potential Effects of the Specified Activity on Marine Mammals
- Potential Effects of Airgun Sounds on Marine Mammals
- (1) Behavioral Disturbance
- (2) Masking
- (3) Hearing Impairment
- (4) Non-Auditory Physical Effects
- (5) Stranding and Mortality
- Potential Effects From Echo Sounders on Marine Mammals
- Potential Effects From Icebreaking on Marine Mammals
- (1) Noise Source Levels From Icebreaking
- (2) Impacts of Icebreaking Noise on Marine Mammals
- Vessel Sounds
- Anticipated Effects on Habitat
- Potential Impacts on Prey Species
- Potential Impacts on Physical Environment
- Potential Impacts on Availability of Affected Species or Stock for Taking for Subsistence Uses
- Relevant Subsistence Uses
- (1) Bowhead Whales
- (2) Beluga Whales
- (3) Ice Seals
- Potential Impacts to Subsistence Uses
- Proposed Mitigation
- Mitigation Measures Proposed in ION's IHA Application
- (1) Exclusion Zones
- (2) Speed or Course Alteration
- (3) Ramp Ups
- (4) Power Down Procedures
- (5) Shutdown Procedures
- Additional Mitigation Measures Proposed by NMFS
- Mitigation Measures for Subsistence Activities
- (1) Subsistence Mitigation Measures
- (2) Plan of Cooperation (POC)
- Mitigation Conclusions
- Proposed Monitoring and Reporting
- Proposed Monitoring Measures
- (1) Protected Species Observers
- A. Number of Observers
- B. Observer Qualifications and Training
- C. PSO Handbook
- (2) Monitoring Methodology
- A. General Monitoring Methodology
- B. Monitoring At Night and In Poor Visibility
- B. (1) FLIR and NVD Monitoring
- B. (2) FLIR Search Methods
- B. (3) NVD Methods
- C. Field Data-Recording, Verification, Handling, and Security
- D. Effort and Sightings Data Collection Methods
- (3) Acoustic Monitoring Plan
- A. Sound Source Measurements
- B. Seismic Hydrophone Streamer Recordings of Vessel Sounds
- C. Over-winter Acoustic Recorders
- Monitoring Plan Peer Review
- Recommendations for Inclusion in the 2012 4MP and IHA
- Recommendations for Inclusion in Future Monitoring Plans
- Other Recommendations in the Report
- Reporting Measures
- (1) SSV Report
- (2) Field Reports
- (3) Technical Reports
- (4) Notification of Injured or Dead Marine Mammals
- Estimated Take by Incidental Harassment
- Basis for Estimating “Take by Harassment”
- Marine Mammal Density Estimates
- (1) Cetaceans
- (2) Pinnipeds
- Potential Number of Takes by Level B Behavioral Harassment
- (1) Potential Number of Takes by Seismic Airguns at Received Levels ≥160 dB
- (2) Potential Number of Takes by Icebreaking at Received Levels ≥120 dB
- Potential Number of Takes by Level B TTS and Level A Harassment
- Estimated Take Conclusions
- Negligible Impact and Small Numbers Analysis and Preliminary Determination
- Level B Behavioral Harassment
- Hearing Impairment (TTS, Level B Harassment, or PTS, Level A Harassment)
- Effects on Marine Mammal Habitat
- Unmitigable Adverse Impact Analysis and Preliminary Determination
- Proposed Incidental Harassment Authorization
- 5. Prohibitions
- 6. Mitigation
- (a) Exclusion Zones
- (b) Speed or Course Alteration
- (b) At Night and Poor Visibility Visual Monitoring
- (iii) FLIR and NVD Monitoring Protocols
- (iv) FLIR and NVD Search Methods
- (c) Field Data-Recording, Verification, Handling, and Security
- (d) Acoustic Monitoring
- (i) Sound Source Verification
- (iii) Over-Winter Acoustic Recorders
- Technical Reports
- 9. Notification of Injured or Dead Marine Mammals
- Endangered Species Act (ESA)
- National Environmental Policy Act (NEPA)
- Proposed Authorization
Tables Back to Top
- Table 1—Marine Mammal Exclusion Zones From the 26 Airgun, 4,450-in3Array, for Specific Categories Based on the Water Depth
- Table 2—Expected densities of cetaceans in the Arctic Ocean in October-December by water depth and survey area
- Table 3—Expected Densities (#/km2) of Pinnipeds in the East Survey Area of the U.S. Beaufort Sea in October
- Table 4—Expected Densities (#/km2) of Pinnipeds in the Beaufort West and Chukchi Survey Areas of the Arctic Ocean in November-December
- Table 5—Estimates of the Possible Numbers of Marine Mammals Exposed to ≥160 dB re 1 μPa (rms) During ION's Proposed Seismic Program in the Beaufort and Chukchi Seas, October-December 2012
- Table 6—Estimates of the Possible Numbers of Marine Mammals Exposed to ≥120 dB re 1 μPa (rms) During Icebreaking Activities Associated With the Preferred Alternative for Refueling During ION's Proposed Seismic Program in the Beaufort Sea, October-December 2012
- Table 7—Estimates of the Possible Numbers of Marine Mammals Exposed to ≥120 dB re 1 μPa (rms) During Icebreaking Activities Associated With the Secondary Alternative for Refueling During ION's Proposed Seismic Program in the Beaufort and Chukchi Seas, October-December 2012
- Table 1—Marine Mammal Exclusion Zones for Specific Categories Based on the Water Depth
DATES: Back to Top
Comments and information must be received no later than September 17, 2012.
ADDRESSES: Back to Top
Comments on the application should be addressed to Michael Payne, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910. The mailbox address for providing email comments is email@example.com. NMFS is not responsible for email comments sent to addresses other than the one provided here. Comments sent via email, including all attachments, must not exceed a 25-megabyte file size.
Instructions: All comments received are a part of the public record and will generally be posted to http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications without change. All Personal Identifying Information (for example, name, address, etc.) voluntarily submitted by the commenter may be publicly accessible. Do not submit Confidential Business Information or otherwise sensitive or protected information.
An electronic copy of the application used in this document may be obtained by writing to the address specified above, telephoning the contact listed below (see FOR FURTHER INFORMATION CONTACT), or visiting the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications. The following associated document is also available at the same internet address: Draft Plan of Cooperation. Documents cited in this notice may also be viewed, by appointment, during regular business hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Back to Top
Shane Guan, Office of Protected Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION: Back to Top
Background Back to Top
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.
An authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of such takings are set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 as “* * * an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.”
Section 101(a)(5)(D) of the MMPA established an expedited process by which citizens of the U.S. can apply for a one-year authorization to incidentally take small numbers of marine mammals by harassment, provided that there is no potential for serious injury or mortality to result from the activity. 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 the authorization.
Except with respect to certain activities not pertinent here, the MMPA defines “harassment” as: Any act of pursuit, torment, or annoyance which (i) has the potential to injure a marine mammal or marine mammal stock in the wild [“Level A harassment”]; or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering [“Level B harassment”].
Summary of Request Back to Top
NMFS received an application on March 1, 2012, from ION for the taking, by harassment, of marine mammals incidental to a marine seismic survey in ice in the Beaufort and Chukchi Seas, Alaska, during October through December 2012. After addressing comments from NMFS, ION modified its application and submitted a revised application on June 11, 2012. The June 11, 2012, application is the one available for public comment (see ADDRESSES) and considered by NMFS for this proposed IHA. ION also submitted IHA applications for essentially the same in-ice seismic survey activity in 2010 and 2011. However, in both years ION withdrew its applications due to logistical issues in carrying out such activities before NMFS published a notice of proposed IHA and request for public comments. Take by Level B harassment only of nine species of marine mammals is anticipated to result from the specified activity. ION has also requested authorization for Level A harassment of a few individuals of bowhead whale, beluga whale, and ringed seal.
Description of the Specified Activity Back to Top
ION's proposed activities consist of a geophysical in-ice (seismic reflection/refraction) survey and related vessel operations to be conducted primarily in the Alaskan Beaufort and Chukchi seas from October to December 2012. The primary survey area extends from the U.S.-Canadian border in the east to Point Barrow in the west. Two survey lines extend west of Point Barrow into the northern Chukchi Sea, and three short tie lines are proposed near the U.S.-Russian border (see Figure 1 of ION's IHA application). The bathymetry of the proposed survey area ranges from shallow (<20 m [66 ft]) to relatively deep (>3,500 m [11,483 ft]) water over the continental shelf, the continental slope, and the abyssal plain.
The survey would be conducted from the seismic vessel Geo Arctic escorted by the Polar Prince, a medium class (100A) icebreaker. The survey grid consists of ∼7,175 km (4,458 mi) of transect line, not including transits when the airguns are not operating. There may be small amounts of additional seismic operations associated with airgun testing, start up, and repeat coverage of any areas where initial data quality is sub-standard. The seismic source towed by the Geo Arctic would be an airgun array consisting of 26 active Sercel G-gun airguns with a total volume of 4,450 in  . A single hydrophone streamer 4.5-9 km (2.8-5.6 mi) in length, depending on ice conditions, would be towed by the Geo Arctic to record the returning seismic signals.
The survey vessels would access the survey area from Canadian waters in late September to begin data collection on or after October 1, 2012. After completion of the survey, or when ice and weather conditions dictate, the vessels would exit to the south, transiting through the Chukchi and Bering Seas. The Polar Prince may be used to perform an at-sea refueling (bunkering) operation to supply as much as 500 metric tons of Arctic diesel to the Geo Arctic. The Polar Prince would carry that fuel onboard at the start of the operation, and it would be transferred to the Geo Arctic if/when necessary. Depending on its own fuel consumption, the Polar Prince may then transit to Tuktoyuktuk, Canada to take on additional fuel for itself. Once the Polar Prince returns to the Geo Arctic the survey would continue. The entire refueling operation would therefore involve one fuel transfer and potentially one transit to and from Tuktoyuktuk. The refueling operation would likely take place in late October, at which time the Geo Arctic would likely be in the eastern or east-central Alaskan Beaufort Sea.
ION's geophysical survey has been designed and scheduled to minimize potential effects to marine mammals, bowhead whales in particular, and subsistence users. For mitigation and operational reasons, the survey area has been bisected by a line that runs from 70.5° N. 150.5° W. to 73° N. 148° W. (see Figure 1 of ION's IHA application). Weather and ice permitting, ION plans to begin survey operations east of the line described above (eastern survey area) and in offshore waters (>1,000 m [3,281 ft]) where bowheads are expected to be least abundant in early October. This operational plan is based on the fact that only ∼2% of bowhead whales observed by Bureau of Ocean Energy Management's (BOEM) aerial surveys from 1979-2007 occurred in areas of water depth >1,000 m (3,281 ft) (MMS, 2010), and on average ∼97% of bowheads have passed through the eastern U.S. Beaufort Sea by October 15 (Miller et al., 2002). The survey would then progress to shallower waters in the eastern survey area before moving to the western survey area in late October or early November 2012.
Ice conditions are expected to range from open water to 10/10 ice cover. However, the survey cannot take place in thick multi-year ice as both the icebreaker and seismic vessel must make continuous forward progress at 3-4 kts. In order for the survey to proceed, areas of high ice concentration can only consist of mostly newly forming juvenile first year ice or young first year ice less than 0.5 m (1.6 ft) thick. Sounds generated by the icebreaker and seismic vessel moving through these relatively light ice conditions are expected to be far below the high sound levels often attributed to icebreaking. These high sound levels (>200 dB re 1 µPa [rms]) have been recorded from icebreakers during backing and ramming operations in very heavy ice conditions and are created by cavitation of the propellers as the vessel is slowed by the ice or reverses direction (Erbe and Farmer, 1998; Roth and Schmidt, 2010).
(1) Seismic Airgun Array
The seismic source used during the project would be an airgun array consisting of 28 Sercel G-gun airguns, of which 26 would be active and have a total discharge volume of 4,450 in  . The 28 airguns would be distributed in two sub-arrays with 14 airguns per sub-array. Individual airgun sizes range from 70 to 380 in  . Airguns would be operated at 2,000 psi. The seismic array and a single hydrophone streamer 4.5-9 km (2.8-5.6 mi) in length would be towed behind the Geo Arctic. Additional specifications of the airgun array are provided in Appendix B of ION's IHA application.
(2) Echo Sounders
Both vessels would operate industry standard echo sounder/fathometer instruments for continuous measurements of water depth while underway. These instruments are used by all large vessels to provide routine water depth information to the vessel crew. Navigation echo sounders send a single, narrowly focused, high frequency acoustic signal directly downward to the sea floor. The sound energy reflected off the sea floor returns to the vessel where it is detected by the instrument, and the depth is calculated and displayed to the user. Source levels of navigational echo sounders of this type are typically in the 180-200 dB re 1 µPA-m (Richardson et al., 1995a).
The Geo Arctic would use one navigational echo sounder during the project. The downward facing single-beam Simrad EA600 operates at frequencies ranging from 38 to 200 kHz with an output power of 100-2000 Watts. Pulse durations are between 0.064 and 4.096 milliseconds, and the pulse repetition frequency (PRF or ping rate) depends on the depth range. The highest PRF at shallow depths is about 40 pings per second. It can be used for water depths up to 4,000 m (13,123 ft) and provides up to 1 cm (0.4 in) resolution.
The Polar Prince would use one echo sounder, an ELAC LAZ-72. The LAZ-72 has an operating frequency of 30 kHz. The ping rate depends on the water depth and the fastest rate, which occurs in shallow depths, is about 5 pings per second.
Dates, Duration, and Region of Activity
The proposed geophysical survey would be conducted for ∼76 days from approximately October 1 to December 15, 2012. Both the Geo Arctic and the Polar Prince would leave from Tuktoyaktuk, Canada, during late September and enter the Alaskan Beaufort Sea from Canadian waters. The survey area would be bounded approximately by 138° to 169° W. longitude and 70° to 73° N. latitude in water depths ranging from <20 to >3,500 m (66 to 11,483 ft) (see Figure 1 of ION's IHA application). For mitigation and operational reasons the survey area has been bisected by a line that runs from 70.5° N, 150.5° W to 73° N, 148° W. Weather and ice permitting, ION plans to begin survey operations east of the line (eastern survey area) in offshore waters (>1,000 m [3,281 ft]) where bowheads are expected to be least abundant in early October. The survey would then progress to shallower waters in the eastern survey area before moving to the west survey area in late October or early November. The vessels would depart the region to the south via the Chukchi and Bering Seas and arrive in Dutch Harbor in mid- to late December.
Description of Marine Mammals in the Area of the Specified Activity Back to Top
The marine mammal species under NMFS jurisdiction most likely to occur in the seismic survey area include two cetacean species, beluga (Delphinapterus leucas) and bowhead whales (Balaena mysticetus), and two pinniped species, ringed (Phoca hispida) and bearded (Erignathus barbatus) seals. It is possible that some bowhead whales may be encountered as they migrate out of the area, particularly in the portion of the survey area where water depths are <200 m (656 ft). Beluga whales are most likely to be encountered farther offshore than bowheads.
The ringed seal is the most abundant marine mammal in the proposed survey area. Although bearded seals typically migrate south in the fall, it is possible that small numbers of them may be present in the survey area. Most other marine mammal species have typically migrated south into the Chukchi and Bering Seas by the time this survey will take place. The polar bear is managed by the U.S. Fish and Wildlife Service (USFWS) and is not considered further in this proposed IHA notice.
Seven additional cetacean species have known occurrences within the proposed project area and some may occur in the area during the time of the proposed in-ice seismic survey: harbor porpoise (Phocoena phocoena); gray whale (Eschrichtius robustus); humpback whale (Megaptera novaeangliae); fin whale (Balaenoptera physalus); minke whale (B. acutorostrata); killer whale (Orcinus orca); and narwhal (Monodon monoceros). The gray whale occurs regularly in continental shelf waters along the Chukchi Sea coast in summer and to a lesser extent along the Beaufort Sea coast. Recent evidence from monitoring activities in the Chukchi and Beaufort Seas during industry seismic surveys suggests that the harbor porpoise and minke whale, which have been considered uncommon or rare in the Chukchi and Beaufort Seas, may be increasing in numbers in these areas (Funk et al., 2010). Additional pinniped species under NMFS jurisdiction that could be encountered during the proposed geophysical in-ice survey include spotted (P. largha) and ribbon seals (Histriophoca fasciata). Spotted seals are more abundant in the Chukchi Sea and occur in small numbers in the Beaufort Sea. The ribbon seal is uncommon in the Chukchi Sea, and there are few reported sightings in the Beaufort Sea.
Small numbers of killer whales have also been recorded during recent industry surveys, along with a few sightings of fin and humpback whales. The narwhal occurs in Canadian waters and occasionally in the Beaufort Sea but is rare there and not expected to be encountered. Each of these species (killer, fin, and humpback whales and narwhal) is uncommon or rare in the Beaufort Sea, particularly during early winter, and relatively few if any encounters with these species are expected during the time period of the proposed seismic program.
The bowhead, humpback, and fin whales are listed as “endangered” under the Endangered Species Act (ESA) and as depleted under the MMPA. Certain stocks or populations of gray and beluga whales and spotted seals are listed as endangered or proposed for listing under the ESA; however, none of those stocks or populations occur in the proposed activity area. Additionally, the ribbon seal is considered a “species of concern”, meaning that NMFS has some concerns regarding status and threats of this species, but for which insufficient information is available to indicate a need to list the species under the ESA. On December 10, 2010, NMFS published a notice of proposed threatened status for subspecies of the ringed seal (75 FR 77476) and a notice of proposed threatened and not warranted status for subspecies and distinct population segments of the bearded seal (75 FR 77496) in the Federal Register. Neither of these two ice seal species is considered depleted under the MMPA.
Based on the occurrence of marine mammal species in the proposed project area and the time of year in which the survey is proposed to be conducted, NMFS is proposing to authorize take by harassment for the following species: Beluga, bowhead, gray, and minke whales; harbor porpoise; and ringed, bearded, spotted, and ribbon seals.
ION's application contains information on the status, distribution, seasonal distribution, and abundance of each of the species under NMFS jurisdiction mentioned in this document. Please refer to the application for that information (see ADDRESSES). Additional information can also be found in the NMFS Stock Assessment Reports (SAR). The Alaska 2011 SAR is available at: http://www.nmfs.noaa.gov/pr/pdfs/sars/ak2011.pdf.
Potential Effects of the Specified Activity on Marine Mammals Back to Top
Operating active acoustic sources such as an airgun array, echo sounders, and icebreaking activities could potentially affect marine mammals.
Potential Effects of Airgun Sounds on Marine Mammals
The effects of sounds from airgun pulses might include one or more of the following: tolerance, masking of natural sounds, behavioral disturbance, and, at least in theory, temporary or permanent hearing impairment or non-auditory effects (Richardson et al., 1995). As outlined in previous NMFS documents, the effects of noise on marine mammals are highly variable, and can be categorized as follows (based on Richardson et al., 1995):
(1) Behavioral Disturbance
Marine mammals may behaviorally react when exposed to anthropogenic sound. These behavioral reactions are often shown as: changing durations of surfacing and dives; changing number of blows per surfacing; moving direction and/or speed; reduced/increased vocal activities; changing/cessation of certain behavioral activities (such as socializing or feeding); visible startle response or aggressive behavior (such as tail/fluke slapping or jaw clapping); avoidance of areas where noise sources are located; and/or flight responses (e.g., pinnipeds flushing into water from haulouts or rookeries).
The biological significance of many behavioral disturbances is difficult to predict, especially if the detected disturbances appear minor. While many behavioral responses would not be expected to likely affect the fitness of an individual, other more severe behavioral modifications, especially in certain circumstances, could potentially have adverse affects on growth, survival, and/or reproduction. Some more potentially significant behavioral modifications include: drastic change in diving/surfacing patterns (such as those thought to be potentially associated with beaked whale stranding due to exposure to military mid-frequency tactical sonar) or longer-term habitat abandonment.
For example, at the Guerreo Negro Lagoon in Baja California, Mexico, which is one of the important breeding grounds for Pacific gray whales, shipping and dredging associated with a salt works may have induced gray whales to abandon the area through most of the 1960s (Bryant et al., 1984). After these activities stopped, the lagoon was reoccupied, first by single whales and later by cow-calf pairs.
The onset of behavioral disturbance from anthropogenic sound, which is difficult to predict, depends on both external factors (e.g., characteristics of sound sources and their paths) and the receiving animals (hearing, motivation, experience, demography) (Southall et al. 2007).
Currently NMFS uses 160 dB re 1 μPa (rms) received level for impulse noises (such as airgun pulses) as the threshold for the onset of Level B (behavioral) harassment.
In addition, behavioral disturbance is also expressed as the change in vocal activities of animals. For example, there is one recent summary report indicating that calling fin whales distributed in one part of the North Atlantic went silent for an extended period starting soon after the onset of a seismic survey in the area (Clark and Gagnon, 2006). It is not clear from that preliminary paper whether the whales ceased calling because of masking, or whether this was a behavioral response not directly involving masking (i.e., important biological signals for marine mammals being “masked” by anthropogenic sound; see below). Also, bowhead whales in the Beaufort Sea may decrease their call rates in response to seismic operations, although movement out of the area might also have contributed to the lower call detection rate (Blackwell et al., 2009a; 2009b). Some of the changes in marine mammal vocal communication are thought to be used to compensate for acoustic masking resulting from increased anthropogenic noise (see below). For example, blue whales are found to increase call rates when exposed to seismic survey noise in the St. Lawrence Estuary (Di Iorio and Clark, 2009). Researchers have noted North Atlantic right whales (Eubalaena glacialis) exposed to high shipping noise increase call frequency (Parks et al., 2007) and intensity (Parks et al., 2010), while some humpback whales respond to low-frequency active sonar playbacks by increasing song length (Miller el al., 2000). These behavioral responses could also have adverse effects on marine mammals.
Mysticete: Baleen whales generally tend to avoid operating airguns, but avoidance radii are quite variable. Whales are often reported to show no overt reactions to airgun pulses at distances beyond a few kilometers, even though the airgun pulses remain well above ambient noise levels out to much longer distances (reviewed in Richardson et al., 1995; Gordon et al., 2004). However, studies done since the late 1990s of migrating humpback and migrating bowhead whales show reactions, including avoidance, that sometimes extend to greater distances than documented earlier. Therefore, it appears that behavioral disturbance can vary greatly depending on context and not just received levels alone. Avoidance distances often exceed the distances at which boat-based observers can see whales, so observations from the source vessel can be biased. Observations over broader areas may be needed to determine the range of potential effects of some large-source seismic surveys where effects on cetaceans may extend to considerable distances (Richardson et al., 1999; Moore and Angliss, 2006). Longer-range observations, when required, can sometimes be obtained via systematic aerial surveys or aircraft-based observations of behavior (e.g., Richardson et al., 1986, 1999; Miller et al., 1999, 2005; Yazvenko et al., 2007a, 2007b) or by use of observers on one or more support vessels operating in coordination with the seismic vessel (e.g., Smultea et al., 2004; Johnson et al., 2007). However, the presence of other vessels near the source vessel can, at least at times, reduce sightability of cetaceans from the source vessel (Beland et al., 2009), thus complicating interpretation of sighting data.
Some baleen whales show considerable tolerance of seismic pulses. However, when the pulses are strong enough, avoidance or other behavioral changes become evident. Because the responses become less obvious with diminishing received sound level, it has been difficult to determine the maximum distance (or minimum received sound level) at which reactions to seismic activity become evident and, hence, how many whales are affected.
Studies of gray, bowhead, and humpback whales have determined that received levels of pulses in the 160-170 dB re 1 μPa (rms) range seem to cause obvious avoidance behavior in a substantial fraction of the animals exposed (McCauley et al., 1998, 1999, 2000). In many areas, seismic pulses diminish to these levels at distances ranging from 4-15 km (2.5-9.3 mi) from the source. A substantial proportion of the baleen whales within such distances may show avoidance or other strong disturbance reactions to the operating airgun array. Some extreme examples include migrating bowhead whales avoiding considerably larger distances (20-30 km [12.4-18.6 mi]) at lower received sound levels (120-130 dB re 1 μPa (rms)) when exposed to airguns from seismic surveys. Also, even in cases where there is no conspicuous avoidance or change in activity upon exposure to sound pulses from distant seismic operations, there are sometimes subtle changes in behavior (e.g., surfacing-respiration-dive cycles) that are only evident through detailed statistical analysis (e.g., Richardson et al., 1986; Gailey et al., 2007).
Data on short-term reactions by cetaceans to impulsive noises are not necessarily indicative of long-term or biologically significant effects. It is not known whether impulsive sounds affect reproductive rates or distribution and habitat use in subsequent days or years. However, gray whales have continued to migrate annually along the west coast of North America despite intermittent seismic exploration (and much ship traffic) in that area for decades (Appendix A in Malme et al., 1984; Richardson et al., 1995), and there has been a substantial increase in the population over recent decades (Allen and Angliss, 2010). The western Pacific gray whale population did not seem affected by a seismic survey in its feeding ground during a prior year (Johnson et al., 2007). Similarly, bowhead whales have continued to travel to the eastern Beaufort Sea each summer despite seismic exploration in their summer and autumn range for many years (Richardson et al., 1987), and their numbers have increased notably during that same time period (Allen and Angliss, 2010). Bowheads also have been observed over periods of days or weeks in areas ensonified repeatedly by seismic pulses (Richardson et al., 1987; Harris et al., 2007). However, it is generally not known whether the same individual bowheads were involved in these repeated observations (within and between years) in strongly ensonified areas.
Odontocete: Little systematic information is available about reactions of toothed whales to airgun pulses. Few studies similar to the more extensive baleen whale/seismic pulse work summarized above have been reported for toothed whales. However, there are recent systematic data on sperm whales (e.g., Gordon et al., 2006; Madsen et al., 2006; Winsor and Mate, 2006; Jochens et al., 2008; Miller et al., 2009). There is also an increasing amount of information about responses of various odontocetes to seismic surveys based on monitoring studies (e.g., Stone, 2003; Smultea et al., 2004; Moulton and Miller, 2005; Holst et al., 2006; Stone and Tasker, 2006; Potter et al., 2007; Hauser et al., 2008; Holst and Smultea, 2008; Weir, 2008; Barkaszi et al., 2009; Richardson et al., 2009).
Dolphins and porpoises are often seen by observers on active seismic vessels, occasionally at close distances (e.g., bow riding). Marine mammal monitoring data during seismic surveys often show that animal detection rates drop during the firing of seismic airguns, indicating that animals may be avoiding the vicinity of the seismic area (Smultea et al., 2004; Holst et al., 2006; Hauser et al., 2008; Holst and Smultea, 2008; Richardson et al., 2009). Also, belugas summering in the Canadian Beaufort Sea showed larger-scale avoidance, tending to avoid waters out to 10-20 km (6.2-12.4 mi) from operating seismic vessels. In contrast, recent studies show little evidence of conspicuous reactions by sperm whales to airgun pulses, contrary to earlier indications (e.g., Gordon et al., 2006; Stone and Tasker, 2006; Winsor and Mate, 2006; Jochens et al., 2008), except the lower buzz (echolocation signals) rates that were detected during exposure of airgun pulses (Miller et al., 2009).
There are almost no specific data on responses of beaked whales to seismic surveys, but it is likely that most if not all species show strong avoidance. There is increasing evidence that some beaked whales may strand after exposure to strong noise from tactical military mid-frequency sonars. Whether they ever do so in response to seismic survey noise is unknown. Northern bottlenose whales seem to continue to call when exposed to pulses from distant seismic vessels.
For delphinids, and possibly the Dall's porpoise, available data suggest that individuals may not react until sounds are ≥170 dB re 1 μPa (rms). With a medium-to-large airgun array, received levels typically diminish to 170 dB within 1-4 km (0.62-2.5 mi), whereas levels typically remain above 160 dB out to 4-15 km (e.g., Tolstoy et al., 2009). Reaction distances for delphinids are more consistent at the typical 170 dB re 1 μPa (rms) distances. Stone (2003) and Stone and Tasker (2006) reported that all small odontocetes (including killer whales) observed during seismic surveys in UK waters remained significantly further from the source during periods of shooting on surveys with large volume airgun arrays than during periods without airgun shooting.
Due to their relatively higher frequency hearing ranges when compared to mysticetes, odontocetes may have stronger responses to mid- and high-frequency sources such as sub-bottom profilers, side scan sonar, and echo sounders than mysticetes (Richardson et al., 1995; Southall et al., 2007).
Pinnipeds: Few studies of the reactions of pinnipeds to noise from open-water seismic exploration have been published (for review of the early literature, see Richardson et al., 1995). However, pinnipeds have been observed during a number of seismic monitoring studies. Monitoring in the Beaufort Sea during 1996-2002 provided a substantial amount of information on avoidance responses (or lack thereof) and associated behavior. Additional monitoring of that type has been done in the Beaufort and Chukchi Seas in 2006-2009. Pinnipeds exposed to seismic surveys have also been observed during seismic surveys along the U.S. west coast. Also, there are data on the reactions of pinnipeds to various other related types of impulsive sounds.
Early observations provided considerable evidence that pinnipeds are often quite tolerant of strong pulsed sounds. During seismic exploration off Nova Scotia, gray seals exposed to noise from airguns and linear explosive charges reportedly did not react strongly (J. Parsons in Greene et al., 1985). An airgun caused an initial startle reaction among South African fur seals but was ineffective in scaring them away from fishing gear. Pinnipeds in both water and air sometimes tolerate strong noise pulses from non-explosive and explosive scaring devices, especially if attracted to the area for feeding or reproduction (Mate and Harvey, 1987; Reeves et al., 1996). Thus, pinnipeds are expected to be tolerant of, or to habituate to, repeated underwater sounds from distant seismic sources, at least when the animals are strongly attracted to the area.
In summary, visual monitoring from seismic vessels has shown only slight (if any) avoidance of airguns by pinnipeds, and only slight (if any) changes in behavior. These studies show that many pinnipeds do not avoid the area within a few hundred meters of an operating airgun array. However, based on the studies with large sample size, or observations from a separate monitoring vessel, or radio telemetry, it is apparent that some phocid seals do show localized avoidance of operating airguns. The limited nature of this tendency for avoidance is a concern. It suggests that pinnipeds may not move away, or move very far away, before received levels of sound from an approaching seismic survey vessel approach those that may cause hearing impairment.
Masking is the obscuring of sounds of interest by other sounds, often at similar frequencies. Chronic exposure to excessive, though not high-intensity, noise could cause masking at particular frequencies for marine mammals that utilize sound for vital biological functions. Masking can interfere with detection of acoustic signals such as communication calls, echolocation sounds, and environmental sounds important to marine mammals. Since marine mammals depend on acoustic cues for vital biological functions, such as orientation, communication, finding prey, and avoiding predators, marine mammals that experience severe (intensity and duration) acoustic masking could potentially suffer some adverse effects.
Masking occurs when noise and signals (that animal utilizes) overlap at both spectral and temporal scales. For the airgun noise generated from the proposed in-ice marine seismic survey, these are low frequency (under 1 kHz) pulses with extremely short durations (in the scale of milliseconds). Lower frequency man-made noises are more likely to affect detection of communication calls and other potentially important natural sounds such as surf and prey noise. There is little concern regarding masking due to the brief duration of these pulses and relatively longer silence between airgun shots (9-12 seconds) near the sound source. However, at long distances (over tens of kilometers away) in deep water, due to multipath propagation and reverberation, the durations of airgun pulses can be “stretched” to seconds with long decays (Madsen et al., 2006; Clark and Gagnon, 2006). Therefore it could affect communication signals used by low frequency mysticetes (e.g., bowhead and gray whales) when they occur near the noise band and thus reduce the communication space of animals (e.g., Clark et al., 2009a, 2009b) and affect their vocal behavior (e.g., Foote et al., 2004; Holt et al., 2009). Further, in areas of shallow water, multipath propagation of airgun pulses could be more profound, thus affecting communication signals from marine mammals even at close distances. Average ambient noise in areas where received seismic noises are heard can be elevated. At long distances, however, the intensity of the noise is greatly reduced. Nevertheless, partial informational and energetic masking of different degrees could affect signal receiving in some marine mammals within the ensonified areas. Additional research is needed to further address these effects.
Although masking effects of pulsed sounds on marine mammal calls and other natural sounds are expected to be limited, there are few specific studies on this. Some whales continue calling in the presence of seismic pulses, and whale calls often can be heard between the seismic pulses (e.g., Richardson et al., 1986; McDonald et al., 1995; Greene et al., 1999a, 1999b; Nieukirk et al., 2004; Smultea et al., 2004; Holst et al., 2005a, 2005b, 2006; Dunn and Hernandez, 2009).
Among the odontocetes, there has been one report that sperm whales ceased calling when exposed to pulses from a very distant seismic ship (Bowles et al., 1994). However, more recent studies of sperm whales found that they continued calling in the presence of seismic pulses (Madsen et al., 2002; Tyack et al., 2003; Smultea et al., 2004; Holst et al., 2006; Jochens et al., 2008). Madsen et al. (2006) noted that airgun sounds would not be expected to mask sperm whale calls given the intermittent nature of airgun pulses. Dolphins and porpoises are also commonly heard calling while airguns are operating (Gordon et al., 2004; Smultea et al., 2004; Holst et al., 2005a, 2005b; Potter et al., 2007). Masking effects of seismic pulses are expected to be inconsequential in the case of the smaller odontocetes, given the intermittent nature of seismic pulses plus the fact that sounds important to them are predominantly at much higher frequencies than are the dominant components of airgun sounds.
Pinnipeds have best hearing sensitivity and/or produce most of their sounds at frequencies higher than the dominant components of airgun sound, but there is some overlap in the frequencies of the airgun pulses and the calls. However, the intermittent nature of airgun pulses presumably reduces the potential for masking.
Marine mammals are thought to be able to compensate for masking by adjusting their acoustic behavior, such as shifting call frequencies and increasing call volume and vocalization rates, as discussed earlier (e.g., Miller et al., 2000; Parks et al., 2007; Di Iorio and Clark, 2009; Parks et al., 2010); the biological significance of these modifications is still unknown and would certainly depend on the duration of the masking event, the behavioral state of the animal, and the overall context of the exposure.
(3) Hearing Impairment
Marine mammals exposed to high intensity sound repeatedly or for prolonged periods can experience hearing threshold shift (TS), which is the loss of hearing sensitivity at certain frequency ranges (Kastak et al., 1999; Schlundt et al., 2000; Finneran et al., 2002; 2005). TS can be permanent (PTS), in which case the loss of hearing sensitivity is unrecoverable, or temporary (TTS), in which case the animal's hearing threshold will recover over time (Southall et al., 2007). Marine mammals that experience TTS or PTS will have reduced sensitivity at the frequency band of the TS, which may affect their capability of communication, orientation, or prey detection. The degree of TS depends on the intensity of the received levels the animal is exposed to, and the frequency at which TS occurs depends on the frequency of the received sound. It has been shown that in most cases, TS occurs at the frequencies approximately one-octave above that of the received sound. Repeated sound exposure that leads to TTS could cause PTS. For transient sounds, the sound level necessary to cause TTS is inversely related to the duration of the sound.
TTS is the mildest form of hearing impairment that can occur during exposure to a strong sound (Kryter, 1985). While experiencing TTS, the hearing threshold rises, and a sound must be stronger in order to be heard. It is a temporary phenomenon, and (especially when mild) is not considered to represent physical damage or “injury” (Southall et al., 2007). Rather, the onset of TTS is an indicator that, if the animal is exposed to higher levels of that sound, physical damage is ultimately a possibility.
The magnitude of TTS depends on the level and duration of noise exposure, and to some degree on frequency, among other considerations (Kryter, 1985; Richardson et al., 1995; Southall et al., 2007). For sound exposures at or somewhat above the TTS threshold, hearing sensitivity recovers rapidly after exposure to the noise ends. In terrestrial mammals, TTS can last from minutes or hours to (in cases of strong TTS) days. Only a few data have been obtained on sound levels and durations necessary to elicit mild TTS in marine mammals (none in mysticetes), and none of the published data concern TTS elicited by exposure to multiple pulses of sound during operational seismic surveys (Southall et al., 2007).
For toothed whales, experiments on a bottlenose dolphin (Tursiops truncatus) and beluga whale showed that exposure to a single watergun impulse at a received level of 207 kPa (or 30 psi) peak-to-peak (p-p), which is equivalent to 228 dB re 1 μPa (p-p), resulted in a 7 and 6 dB TTS in the beluga whale at 0.4 and 30 kHz, respectively. Thresholds returned to within 2 dB of the pre-exposure level within 4 minutes of the exposure (Finneran et al., 2002). No TTS was observed in the bottlenose dolphin.
Finneran et al. (2005) further examined the effects of tone duration on TTS in bottlenose dolphins. Bottlenose dolphins were exposed to 3 kHz tones (non-impulsive) for periods of 1, 2, 4 or 8 seconds (s), with hearing tested at 4.5 kHz. For 1-s exposures, TTS occurred with sound exposure levels (SELs) of 197 dB, and for exposures >1 s, SEL >195 dB resulted in TTS (SEL is equivalent to energy flux, in dB re 1 μPa  -s). At an SEL of 195 dB, the mean TTS (4 min after exposure) was 2.8 dB. Finneran et al. (2005) suggested that an SEL of 195 dB is the likely threshold for the onset of TTS in dolphins and belugas exposed to tones of durations 1-8 s (i.e., TTS onset occurs at a near-constant SEL, independent of exposure duration). That implies that, at least for non-impulsive tones, a doubling of exposure time results in a 3 dB lower TTS threshold.
However, the assumption that, in marine mammals, the occurrence and magnitude of TTS is a function of cumulative acoustic energy (SEL) is probably an oversimplification. Kastak et al. (2005) reported preliminary evidence from pinnipeds that, for prolonged non-impulse noise, higher SELs were required to elicit a given TTS if exposure duration was short than if it was longer, i.e., the results were not fully consistent with an equal-energy model to predict TTS onset. Mooney et al. (2009a) showed this in a bottlenose dolphin exposed to octave-band non-impulse noise ranging from 4 to 8 kHz at SPLs of 130 to 178 dB re 1 μPa for periods of 1.88 to 30 minutes (min). Higher SELs were required to induce a given TTS if exposure duration was short than if it was longer. Exposure of the aforementioned bottlenose dolphin to a sequence of brief sonar signals showed that, with those brief (but non-impulse) sounds, the received energy (SEL) necessary to elicit TTS was higher than was the case with exposure to the more prolonged octave-band noise (Mooney et al., 2009b). Those authors concluded that, when using (non-impulse) acoustic signals of duration ∼0.5 s, SEL must be at least 210-214 dB re 1 μPa  -s to induce TTS in the bottlenose dolphin. The most recent studies conducted by Finneran et al. (2010a, 2010b) also support the notion that exposure duration has a more significant influence compared to sound pressure level (SPL) as the duration increases, and that TTS growth data are better represented as functions of SPL and duration rather than SEL alone (Finneran et al., 2010a, 2010b). In addition, Finneran et al. (2010b) conclude that when animals are exposed to intermittent noises, there is recovery of hearing during the quiet intervals between exposures through the accumulation of TTS across multiple exposures. Such findings suggest that when exposed to multiple seismic pulses, partial hearing recovery also occurs during the seismic pulse intervals.
For baleen whales, there are no data, direct or indirect, on levels or properties of sound that are required to induce TTS. The frequencies to which baleen whales are most sensitive are lower than those to which odontocetes are most sensitive, and natural ambient noise levels at those low frequencies tend to be higher (Urick, 1983). As a result, auditory thresholds of baleen whales within their frequency band of best hearing are believed to be higher (less sensitive) than are those of odontocetes at their best frequencies (Clark and Ellison, 2004). From this, it is suspected that received levels causing TTS onset may also be higher in baleen whales. However, no cases of TTS are expected given the size of the airguns proposed to be used and the strong likelihood that baleen whales (especially migrating bowheads) would avoid the approaching airguns (or vessel) before being exposed to levels high enough for there to be any possibility of TTS.
In pinnipeds, TTS thresholds associated with exposure to brief pulses (single or multiple) of underwater sound have not been measured. Initial evidence from prolonged exposures suggested that some pinnipeds may incur TTS at somewhat lower received levels than do small odontocetes exposed for similar durations (Kastak et al., 1999; 2005). However, more recent indications are that TTS onset in the most sensitive pinniped species studied (harbor seal, which is closely related to the ringed seal) may occur at a similar SEL as in odontocetes (Kastak et al., 2004).
Most cetaceans show some degree of avoidance of seismic vessels operating an airgun array (see above). It is unlikely that these cetaceans would be exposed to airgun pulses at a sufficiently high enough level for a sufficiently long enough period to cause more than mild TTS, given the relative movement of the vessel and the marine mammal. TTS would be more likely in any odontocetes that bow- or wake-ride or otherwise linger near the airguns. However, while bow- or wake-riding, odontocetes would be at the surface and thus not exposed to strong sound pulses given the pressure release and Lloyd Mirror effects at the surface. But if bow- or wake-riding animals were to dive intermittently near airguns, they could be exposed to strong sound pulses, possibly repeatedly.
If some cetaceans did incur mild or moderate TTS (a Level B harassment) through exposure to airgun sounds in this manner, this would very likely be a temporary and reversible phenomenon. However, even a temporary reduction in hearing sensitivity could be deleterious in the event that, during that period of reduced sensitivity, a marine mammal needed its full hearing sensitivity to detect approaching predators, or for some other reason.
Some pinnipeds show avoidance reactions to airguns, but their avoidance reactions are generally not as strong or consistent as those of cetaceans. Pinnipeds occasionally seem to be attracted to operating seismic vessels. There are no specific data on TTS thresholds of pinnipeds exposed to single or multiple low-frequency pulses. However, given the indirect indications of a lower TTS threshold for the harbor seal than for odontocetes exposed to impulse sound (see above), it is possible that some pinnipeds close to a large airgun array could incur TTS.
NMFS typically includes mitigation requirements to ensure that cetaceans and pinnipeds are not exposed to pulsed underwater noise at received levels exceeding, respectively, 180 and 190 dB re 1 μPa (rms). The 180/190 dB acoustic criteria were taken from recommendations by an expert panel of the High Energy Seismic Survey (HESS) Team that performed an assessment on noise impacts by seismic airguns to marine mammals in 1997, although the HESS Team recommended a 180-dB limit for pinnipeds in California (HESS, 1999). The 180 and 190 dB re 1 μPa (rms) levels have not been considered to be the levels above which TTS might occur. Rather, they were the received levels above which, in the view of a panel of bioacoustics specialists convened by NMFS 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 summarized above, data that are now available imply that TTS is unlikely to occur in various odontocetes (and probably mysticetes as well) unless they are exposed to a sequence of several airgun pulses stronger than 180 dB re 1 μPa (rms). On the other hand, for the harbor seal, harbor porpoise, and perhaps some other species, TTS may occur upon exposure to one or more airgun pulses whose received level equals the NMFS “do not exceed” value of 180 dB re 1 μPa (rms). That criterion corresponds to a single-pulse SEL of 175-180 dB re 1 μPa  -s in typical conditions, whereas TTS is suspected to be possible in harbor seals and harbor porpoises with a cumulative SEL of ∼171 and ∼164 dB re 1 μPa  -s, respectively.
It has been shown that most large whales and many smaller odontocetes (especially the harbor porpoise) show at least localized avoidance of ships and/or seismic operations. Even when avoidance is limited to the area within a few hundred meters of an airgun array, that should usually be sufficient to avoid TTS based on what is currently known about thresholds for TTS onset in cetaceans. In addition, ramping up airgun arrays, which is standard operational protocol for many seismic operators, may allow cetaceans near the airguns at the time of startup (if the sounds are aversive) to move away from the seismic source and to avoid being exposed to the full acoustic output of the airgun array. Thus, most baleen whales likely will not be exposed to high levels of airgun sounds provided the ramp-up procedure is applied. Likewise, many odontocetes close to the trackline are likely to move away before the sounds from an approaching seismic vessel become sufficiently strong for there to be any potential for TTS or other hearing impairment. Hence, there is little potential for baleen whales or odontocetes that show avoidance of ships or airguns to be close enough to an airgun array to experience TTS. Nevertheless, even if marine mammals were to experience TTS, the magnitude of the TTS is expected to be mild and brief, only in a few decibels for minutes.
When PTS occurs, there is physical damage to the sound receptors in the ear. In some cases, there can be total or partial deafness, whereas in other cases, the animal has an impaired ability to hear sounds in specific frequency ranges (Kryter, 1985). 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. (Rise time is the interval required for sound pressure to increase from the baseline pressure to peak pressure.)
There is no specific evidence that exposure to pulses of airgun sound can cause PTS in any marine mammal, even with large arrays of airguns. However, given the likelihood that some mammals close to an airgun array might incur at least mild TTS (see above), there has been further speculation about the possibility that some individuals occurring very close to airguns might incur PTS (e.g., Richardson et al., 1995; Gedamke et al., 2008). Single or occasional occurrences of mild TTS are not indicative of permanent auditory damage, but repeated or (in some cases) single exposures to a level well above that causing TTS onset might elicit PTS.
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 (Southall et al., 2007). Based on data from terrestrial mammals, a precautionary assumption is that the PTS threshold for impulse sounds (such as airgun pulses as received close to the source) is at least 6 dB higher than the TTS threshold on a peak-pressure basis and probably >6 dB higher (Southall et al., 2007). The low-to-moderate levels of TTS that have been induced in captive odontocetes and pinnipeds during 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; 2005; Nachtigall et al., 2003; 2004). 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). 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; Southall et al., 2007). However, there is special concern about strong sounds whose pulses have very rapid rise times. In terrestrial mammals, there are situations when pulses with rapid rise times (e.g., from explosions) can result in PTS even though their peak levels are only a few dB higher than the level causing slight TTS. The rise time of airgun pulses is fast but not as fast as that of an explosion.
Some factors that contribute to onset of PTS, at least in terrestrial mammals, are as follows:
- Exposure to a single very intense sound,
- Fast rise time from baseline to peak pressure,
- Repetitive exposure to intense sounds that individually cause TTS but not PTS, and
- Recurrent ear infections or (in captive animals) exposure to certain drugs.
Cavanagh (2000) reviewed the thresholds used to define TTS and PTS. Based on this review and SACLANT (1998), it is reasonable to assume that PTS might occur at a received sound level 20 dB or more above that inducing mild TTS. However, for PTS to occur at a received level only 20 dB above the TTS threshold, the animal probably would have to be exposed to a strong sound for an extended period or to a strong sound with a rather rapid rise time.
More recently, Southall et al. (2007) estimated that received levels would need to exceed the TTS threshold by at least 15 dB, on an SEL basis, for there to be risk of PTS. Thus, for cetaceans exposed to a sequence of sound pulses, they estimate that the PTS threshold might be an M-weighted SEL (for the sequence of received pulses) of ∼198 dB re 1 μPa  -s. Additional assumptions had to be made to derive a corresponding estimate for pinnipeds, as the only available data on TTS-thresholds in pinnipeds pertained to non-impulse sound (see above). Southall et al. (2007) estimated that the PTS threshold could be a cumulative SEL of ∼186 dB re 1 μPa  -s in the case of a harbor seal exposed to impulse sound. The PTS threshold for the California sea lion and northern elephant seal would probably be higher given the higher TTS thresholds in those species. Southall et al. (2007) also note that, regardless of the SEL, there is concern about the possibility of PTS if a cetacean or pinniped received one or more pulses with peak pressure exceeding 230 or 218 dB re 1 μPa, respectively. Thus, PTS might be expected upon exposure of cetaceans to either SEL ≥198 dB re 1 μPa  -s or peak pressure ≥230 dB re 1 μPa. Corresponding proposed dual criteria for pinnipeds (at least harbor seals) are ≥186 dB SEL and ≥ 218 dB peak pressure (Southall et al., 2007). These estimates are all first approximations, given the limited underlying data, assumptions, species differences, and evidence that the “equal energy” model may not be entirely correct.
Sound impulse duration, peak amplitude, rise time, number of pulses, and inter-pulse interval are the main factors thought to determine the onset and extent of PTS. Ketten (1994) has noted that the criteria for differentiating the sound pressure levels that result in PTS (or TTS) are location and species specific. PTS effects may also be influenced strongly by the health of the receiver's ear.
As described above for TTS, in estimating the amount of sound energy required to elicit the onset of TTS (and PTS), it is assumed that the auditory effect of a given cumulative SEL from a series of pulses is the same as if that amount of sound energy were received as a single strong sound. There are no data from marine mammals concerning the occurrence or magnitude of a potential partial recovery effect between pulses. In deriving the estimates of PTS (and TTS) thresholds quoted here, Southall et al. (2007) made the precautionary assumption that no recovery would occur between pulses.
It is unlikely that an odontocete would remain close enough to a large airgun array for a sufficiently long enough period to incur PTS. There is some concern about bow-riding odontocetes, but for animals at or near the surface, auditory effects are reduced by Lloyd's mirror and surface release effects. The presence of the vessel between the airgun array and bow-riding odontocetes could also, in some but probably not all cases, reduce the levels received by bow-riding animals (e.g., Gabriele and Kipple, 2009). The TTS (and thus PTS) thresholds of baleen whales are unknown but, as an interim measure, assumed to be no lower than those of odontocetes. Also, 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. The TTS (and thus PTS) thresholds of some pinnipeds (e.g., harbor seal) as well as the harbor porpoise may be lower (Kastak et al., 2005; Southall et al., 2007; Lucke et al., 2009). If so, TTS and potentially PTS may extend to a somewhat greater distance for those animals. Again, Lloyd's mirror and surface release effects will ameliorate the effects for animals at or near the surface. NMFS considers PTS to be a Level A harassment.
(4) Non-Auditory Physical Effects
Non-auditory physical effects might 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 neurological effects, bubble formation, and other types of organ or tissue damage. Some marine mammal species (i.e., beaked whales) may be especially susceptible to injury and/or stranding when exposed to intense sounds. However, there is no definitive evidence that any of these effects occur even for marine mammals in close proximity to large arrays of airguns, and beaked whales do not occur in the proposed project area. In addition, marine mammals that show behavioral avoidance of seismic vessels, including most baleen whales, some odontocetes (including belugas), and some pinnipeds, are especially unlikely to incur non-auditory impairment or other physical effects.
Therefore, it is unlikely that such effects would occur during ION's proposed in-ice seismic surveys given the brief duration of exposure and the planned monitoring and mitigation measures described later in this document.
Additional non-auditory effects include elevated levels of stress response (Wright et al., 2007; Wright and Highfill, 2007). Although not many studies have been done on noise-induced stress in marine mammals, extrapolation of information regarding stress responses in other species seems applicable because the responses are highly consistent among all species in which they have been examined to date (Wright et al., 2007). Therefore, it is reasonable to conclude that noise acts as a stressor to marine mammals. Furthermore, given that marine mammals will likely respond in a manner consistent with other species studied, repeated and prolonged exposures to stressors (including or induced by noise) could potentially be problematic for marine mammals of all ages. Wright et al. (2007) state that a range of issues may arise from an extended stress response including, but not limited to, suppression of reproduction (physiologically and behaviorally), accelerated aging and sickness-like symptoms. However, as mentioned above, ION's proposed activity is not expected to result in these severe effects due to the nature of the potential sound exposure.
(5) Stranding and Mortality
Marine mammals close to underwater detonations 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 their peak amplitudes have slower rise times, while stranding and mortality events would include other energy sources (acoustical or shock wave) far beyond just seismic airguns. To date, there is no evidence that serious injury, death, or stranding by marine mammals can occur from exposure to airgun pulses, even in the case of large airgun arrays.
However, in past IHA notices for seismic surveys, commenters have referenced two stranding events allegedly associated with seismic activities, one off Baja California and a second off Brazil. NMFS has addressed this concern several times, and, without new information, does not deem the issue to warrant further discussion. For information relevant to strandings of marine mammals, readers are encouraged to review NMFS' response to comments on this matter found in 69 FR 74906 (December 14, 2004), 71 FR 43112 (July 31, 2006), 71 FR 50027 (August 24, 2006), and 71 FR 49418 (August 23, 2006).
It should be noted that strandings related to sound exposure have not been recorded for marine mammal species in the Beaufort Sea. NMFS notes that in the Beaufort Sea, aerial surveys have been conducted by the Minerals Management Service (now BOEM) and industry during periods of industrial activity (and by BOEM during times with no activity). No strandings or marine mammals in distress have been observed during these surveys, and none have been reported by North Slope Borough inhabitants. In addition, there are very few instances that seismic surveys in general have been linked to marine mammal strandings, other than those mentioned above. As a result, NMFS does not expect any marine mammals will incur serious injury or mortality in the Arctic Ocean or strand as a result of the proposed seismic survey.
Potential Effects From Echo Sounders on Marine Mammals
Three types of echo sounders have been proposed for ION's 2012 in-ice seismic survey in the Beaufort and Chukchi Seas. In general, the potential effects of this equipment on marine mammals can be expected to be similar to those from the airgun, except that the sounds from these sources are at much higher frequencies than those from airguns, and thus may have more potential to affect mid- and high-frequency hearing odontocetes and pinnipeds than mysticetes, who are thought to be more sensitive to low-frequency sounds. Therefore, it is possible that the onset of hearing impairment to odontocetes and pinnipeds that are exposed to mid- or high-frequency sources could be lower, or the growth of TTS and/or PTS could be faster than the earlier empirical measurements using the watergun source (Finneran et al., 2002) or 3 kHz tones (Finneran et al., 2005). However, the magnitude of the impacts is expected to be less due to the lower intensity of the sound from echo sounders when compared to seismic airguns. Because of the higher frequencies of the echo sounder signals, the propagation ranges of acoustic signals are also much shorter than those from the airgun array. Since these echo sounders will be operating during the seismic survey, no additional takes of marine mammals would be considered as take estimates would be calculated from ensonified zones from seismic airguns. In addition, due to the fact that the operating frequencies of some of this equipment (e.g., Skipper GDS102 that operates at frequencies above 200 kHz) are above the hearing ranges of marine mammals, use of the equipment is not expected to cause any take of marine mammals. Furthermore, the beam patterns of the echo sounders are directed downward and are narrow, so any marine mammals that encounter the echo sounders at close range are unlikely to be subjected to repeated pulses.
Potential Effects From Icebreaking on Marine Mammals
(1) Noise Source Levels From Icebreaking
Most sounds generated by icebreaking activities are caused by cavitation of the propellers. Propeller cavitation and resulting sounds tend to be greatest when a vessel is moving astern or when its forward progress has been stopped by heavy ice during ramming. When making continuous forward progress through ice, more power is required than when traveling through open water. The greater the resistance, the greater the propeller cavitation and resulting sounds, although they are typically less strong during continuous forward progress than during backing and ramming in heavy ice.
Measurements of the Robert Lemur pushing and breaking ice in the Beaufort Sea in 1986 resulted in an estimated broadband source level of 193 dB re 1 μPa @ 1 m (Richardson et al., 1995). Ice conditions were not described in detail, but at that time of year (in September), ice is not typically forming, so the ice pans that were encountered were likely composed of second year ice or multi-year ice.
The broadband source levels of three different vessels pushing on or breaking ice during drilling activities in the U.S. Beaufort Sea in 1993 were 181-183, 184, and 174 dB re 1 μPa @ 1 m (Hall et al., 1994). Similar to the above, ice conditions in mid-August when these recordings were made were likely to have been thick first year (sea ice does not reach “second year” status until September 1), second year, or multi-year ice.
The strongest sounds produced by an icebreaker backing and ramming an ice ridge were measured at 203 dB re 1 μPa @ 1 m at the point when the propellers were still turning at full speed ahead, but the vessel had come to a stop when it failed to break the ice ridge (Erbe and Farmer, 1998). A similar maximum source level (200 dB re 1 μPa @ 1m) was reported during backing and ramming activities by the U.S. Coast Guard Cutter Healy as measured by a sonobuoy deployed from that vessel in 2009 (Roth and Schmidt, 2010).
Roth and Schmidt (2010) describe three very recent “case studies” of Healy breaking ice in the high Arctic. Ice type is not described, but given the date, location, and pictures provided the ice is clearly not first year ice and instead likely second year or multi-year ice. The first case study provides an example of the Healy traveling through 7-9/10ths ice and then entering open-water. Average source levels in ice were estimated to be ∼185 dB while average source levels in open-water were estimated between 175-180 dB. The second case study is an example of backing and ramming in 8/10ths ice. Maximum source levels reached 191-195 dB. The third case study is another example of backing and ramming, this time in 9/10ths ice, where maximum source levels reached 200 dB.
None of these examples apply very well to ice conditions likely to be encountered during ION's proposed October-December survey. The ice regimes to be encountered along the Alaskan Coast in the proposed survey area during the proposed survey period will vary considerably from predominantly or entirely open water in early October to being predominantly new, first year ice in November. The survey work will take advantage of such variations to complete the more difficult lines when the ice conditions are favorable for that work.
This project will involve two ships working as one when in or near sea ice. In this mode, the icebreaker (Polar Prince) would escort the geophysical survey ship (Geo Arctic). As both ships must move continuously at near survey speed throughout this escort, it is essential that this work is carried out in ice conditions where the icebreaker is not obliged to undertake ramming operations.
ION used the Arctic Ice Regime Shipping System (AIRSS) to aid in their determination concerning suitable conditions for the survey. This system allows the Arctic Mariner/Ice Master to calculate the “toughness” of a particular ice regime. As a “rule of thumb,” seismic is normally considered achievable in ice where the calculation indicates navigation can safely be undertaken by the ice strengthened (Ice Class A1A, type A) geophysical ship, operating independently. ION states that it will take a conservative approach by using a heavy escort icebreaker. This means the icebreaker is normally working well below maximum power but does have a huge propulsive power capacity held in reserve in case ridges or other such ice features are encountered. Thus the icebreaker is breaking ice at a fraction of its maximum or rated capacity.
Compared to the aggressive icebreaking involved in the examples above, the icebreaking for in-ice seismic surveys is of a much different and considerably lower order. In most ice regimes expected to be encountered during ION's proposed survey, the Polar Prince will have about 5,123 HP available for propulsion, which is far less than the power of the heavy icebreaker Healy reported in Roth and Schmidt (2010). There would still be a direct correlation between icebreaking effort and icebreaking noise, although there are likely also many other variables such as thermal gradient, stage of ice development, speed of impact, propulsion system characteristics, hull and bow form, etc., that may differentiate the sounds produced during the proposed survey. In the examples provided in Roth and Schmidt (2010), the Healy appears to be backing and ramming in heavy multiyear ice (based on our interpretation of the pictures). Such conditions are beyond the allowable operational conditions of this project, and, if such conditions were encountered, the Type A geophysical ship could not follow such an ice-encumbered track of multiyear ice.
It should also be noted that the Healy was operating at maximum capacity during the measurements reported in Roth and Schmidt (2010), while during ice-seismic the escorting icebreaker rarely operates in excess of 50% capacity. Thus, accounting for the disparity in the horsepower ratings of the Polar Prince vs. the Healy, the Polar Prince is rendering an output, in terms of horsepower expended, of <25% each of that of the Healy during the reported measurements.
Based on available information regarding sounds produced by icebreaking in various ice regimes and the expected ice conditions during the proposed survey, NMFS determined that vessel sounds generated during ice breaking are likely to have source levels between 175 and 185 dB re 1 µPa-m.
(2) Impacts of Icebreaking Noise on Marine Mammals
Limited information is available about the effects of icebreaking ships on most species of marine mammals. Concerns have arisen in the past due to proposals (which were never realized) to conduct shipping of oil and gas in the Arctic via large icebreakers (Peterson, 1981). In the past, smaller icebreaking ships were used by the oil and gas industry in the Beaufort and Chukchi Seas to extend the offshore drilling period in support of offshore drilling, and several icebreakers or strengthened cargo ships have been used in the Russian northern sea route, as well as elsewhere in the Arctic and Antarctic (Armstrong, 1984; Barr and Wilson, 1985; Brigham, 1985).
The primary concern regarding icebreaking activities involves the production of intense underwater sound (Richardson et al., 1995). Estimated source levels of the ice-breaking cargo vessel MV Arctic may be detectable by seals under fast ice at distances up to 20-35 km (12.4-21.8 mi) (Davis and Malme, 1997). However, icebreaking activities may also have non-acoustic effects, such as the potential for causing injury, ice entrapment of animals that follow the ship, and disruption of ice habitat (reviewed in Richardson et al., 1989), though, as described below, these impacts are not anticipated during this action. The species of marine mammals that may be present and the nature of icebreaker activities are strongly influenced by ice type. Some species are more common in loose ice near the margins of heavy pack ice while others appear to prefer heavy pack ice. Propeller cavitation noise of icebreaking ships in loose ice is expected to be much lower than in areas of heavier pack ice or thick landfast ice where ship speed will be reduced, power levels will be higher, and there will be greater propeller cavitation and back-ramming (Richardson et al., 1995).
Beluga Whales—Erbe and Farmer (1998) measured masked hearing thresholds of a captive beluga whale. They reported that the recording of a Canadian Coast Guard ship, Henry Larsen, ramming ice in the Beaufort Sea, masked recordings of beluga vocalizations at a noise-to-signal pressure ratio of 18 dB. That occurred when the noise pressure level was eight times as high as the call. In linear units, the ramming noise was 8 times as strong as the call (Erbe and Farmer, 1998). A similar study using a software model to estimate the zones of impact around icebreakers affecting beluga whales in the Beaufort Sea predicted that masking of beluga communication signals by ramming noise from an icebreaker could occur within 40-71 km (25-44 mi), depending on the location. However, Arctic beluga whales have shown avoidance of icebreakers when first detected (Erbe and Farmer, 2000), so individuals are unlikely to get close enough for effects such as masking to occur. In addition, vocal behavior of beluga whales in the St. Lawrence River in the presence of a ferry and a small motorboat have shown that belugas can change the types of calls they use, as well as shift the mean call frequency up during noise exposure (Lesage et al., 1999). Therefore, it is possible that beluga whales in the Beaufort and Chukchi Seas may also have some mechanism that would allow them to adapt to ambient noise due to icebreaking activities.
In 1991 and 1994 in the Alaskan Beaufort Sea, Richardson et al. (1995b) recorded reactions of beluga and bowhead whales to playbacks of underwater propeller cavitation noise from the icebreaker Robert Lemeur operating in heavy ice. Migrating belugas were observed close to the playback projectors on three dates, but interpretable data were only collected on 17 groups for two of these occasions. A minimum of six groups apparently altered their path in response to the playback, but whales approached within a few hundred (and occasionally tens of) meters before exhibiting a response. Icebreaker sounds were estimated at 78-84 dB re 1μPa in the 1/3-octave band centered at 5,000 Hz, or 8-14 dB above ambient sound levels in that band, for the six groups that reacted. The authors estimated that reactions at this level would be estimated to occur at distances of approximately 10 km (6.2 mi) from an operating icebreaker.
Beluga whales are expected to avoid icebreaking vessels at distances of approximately 10 km (6.2 mi). The impacts of icebreaking associated with the seismic program on the behavior of belugas are expected to be temporary, lasting only as long as the activity is on-going, and would have a negligible impact on the species or stock.
Bowhead Whales—In 1991 and 1994 in the Alaskan Beaufort Sea, Richardson et al. (1995b) recorded reactions of beluga and bowhead whales to playbacks of underwater propeller cavitation noise from the icebreaker Robert Lemeur operating in heavy ice. Bowhead whales migrating in the nearshore appeared to tolerate exposure to projected icebreaker sounds at received levels up to 20 dB or more above ambient noise levels. However, some bowheads appeared to divert their paths to remain further away from the projected sounds, particularly when exposed to levels >20 dB above ambient. Turning frequency, surface duration, number of blows per surfacing, and two multivariate indices of behavior were significantly correlated with the signal-to-noise ratio >20 dB (and as low as 10 dB for turning frequency). The authors suggested that bowheads may commonly react to icebreakers at distances up to 10-50 km (6.2-31 mi), but note that reactions were highly dependent on several variables not controlled in the study.
There are few other studies on the reactions of baleen whales to icebreaking activities. During fall 1992, migrating bowhead whales apparently avoided (by at least 25 km [15.5 mi]) a drill site that was supported almost daily by intensive icebreaking activity in the Alaskan Beaufort Sea (Brewer et al., 1993). However, bowheads also avoided a nearby drill site in the fall of another year that had little icebreaking support (LGL and Greenridge, 1987). Thus, level of contribution from icebreaking, ice concentration, and drilling noise resulting in bowhead responses is unknown.
Bowhead whales are expected to avoid vessels that are underway, including icebreakers. The impacts of icebreaking on the behavior of bowheads are likely to occur only if bowheads are still in the western portion of the proposed study area, although most bowheads will likely have passed through the survey area prior to the start of survey activities. The effects of icebreaking activities on bowhead whales are expected to be minor and short-term.
Pinnipeds— Reactions of walruses to icebreakers are described more thoroughly in the available literature than are reactions by other pinnipeds. When comparing the reaction distances of walrus to icebreaking ships vs. other ships traveling in open water, Fay et al. (1984) found that walrus reacted at longer distances to icebreakers. They were aware of the icebreaker when it was >2 km (1.2 mi) away, and females with pups entered the water and swam away when the ship was ∼1 km (0.62 mi) away while adult males did so at distances of 0.1 to 0.3 km (0.1 to 0.2 mi). However, it was also noted that some walruses, ringed seals, and bearded seals also scrambled onto ice when an icebreaker was oriented toward them.
In another study of 202 walrus groups observed on ice floes during icebreaking activities, 32% dove into the water, and 6% became alert while on the ice (Brueggeman et al., 1990, 1991, 1992). Concurrent aerial surveys indicated that walruses hauling out on ice floes may have avoided icebreaking activities within 10—15 km (6.2—9.3 mi) (Brueggeman et al., 1990).
Ringed and bearded seals on pack ice approached by an icebreaker typically dove into the water within 0.93 km (0.58 mi) of the vessel but tended to be less responsive when the same ship was underway in open water (Brueggeman et al., 1992). In another study, ringed and harp seals remained on the ice when an icebreaker was 1-2 km (0.62—1.2 mi) away, but seals often dove into the water when closer to the icebreaker (Kanik et al., 1980 in Richardson et al., 1995a). Ringed seals have also been seen feeding among overturned ice floes in the wake of icebreakers (Brewer et al., 1993).
Seals swimming are likely to avoid approaching vessels by a few meters to a few tens of meters, while some “curious” seals are likely to swim toward vessels. Seals hauled out on ice also show mixed reaction to approaching vessels/icebreakers. Seals are likely to dive into the water if the icebreaker comes within 1 km (0.62 mi). The impact of vessel traffic on seals is expected to be negligible.
One potential impact from icebreaking activities is ice entrapment of pinnipeds that are following the vessels. However, NMFS does not consider this likely because ice formation at the time of the proposed survey consists mostly of loose annual ice floes that will not freeze into extensive pack ice. In addition, the time chosen for the icebreaking seismic survey would occur before ringed seals start constructing lairs in ice around early March.
Finally, the breaking of heavy pack ice or thick landfast ice could also indirectly increase the level of ambient noise due to broken ice floes cracking against each other, and effectively change the area's soundscape.
In addition to the noise generated from seismic airguns and active sonar systems, various types of vessels will be used in the operations, including source vessels and support vessels. Sounds from boats and vessels have been reported extensively (Greene and Moore, 1995; Blackwell and Greene, 2002; 2005; 2006). Numerous measurements of underwater vessel sound have been performed in support of recent industry activity in the Chukchi and Beaufort Seas. Results of these measurements have been reported in various 90-day and comprehensive reports since 2007 (e.g., Aerts et al., 2008; Hauser et al., 2008; Brueggeman, 2009; Ireland et al., 2009). For example, Garner and Hannay (2009) estimated sound pressure levels of 100 dB at distances ranging from approximately 2.4 to 3.7 km (1.5 to 2.3 mi) from various types of barges. MacDonald et al. (2008) estimated higher underwater SPLs from the seismic vessel Gilavar of 120 dB at approximately 21 km (13 mi) from the source, although the sound level was only 150 dB at 26 m (85 ft) from the vessel. Compared to airgun pulses, underwater sound from vessels is generally at relatively low levels.
The primary sources of sounds from all vessel classes are propeller cavitation, propeller singing, and propulsion or other machinery. Propeller cavitation is usually the dominant noise source for vessels (Ross, 1976). Propeller cavitation and singing are produced outside the hull, whereas propulsion or other machinery noise originates inside the hull. There are additional sounds produced by vessel activity, such as pumps, generators, flow noise from water passing over the hull, and bubbles breaking in the wake. Icebreakers contribute greater sound levels during ice-breaking activities than ships of similar size during normal operation in open water (Richardson et al., 1995). This higher sound production results from the greater amount of power and propeller cavitation required when operating in thick ice. Source levels from various vessels would be empirically measured before the start of marine surveys.
For this project, the majority of any vessel noise would occur concurrently with sounds generated by seismic airguns or icebreaking and any potential impacts would be expected to be subsumed by the impacts of those louder sources.
Anticipated Effects on Habitat Back to Top
The primary potential impacts to marine mammals and other marine species are associated with elevated sound levels produced by airguns and other active acoustic sources, noise generated from icebreaking, and breaking of ice during the seismic survey. However, other potential impacts to the surrounding habitat from physical disturbance are also possible.
Potential Impacts on Prey Species
With regard to fish as a prey source for cetaceans and pinnipeds, fish are known to hear and react to sounds and to use sound to communicate (Tavolga et al., 1981) and possibly avoid predators (Wilson and Dill, 2002). Experiments have shown that fish can sense both the strength and direction of sound (Hawkins, 1981). Primary factors determining whether a fish can sense a sound signal, and potentially react to it, are the frequency of the signal and the strength of the signal in relation to the natural background noise level.
The level of sound at which a fish will react or alter its behavior is usually well above the detection level. Fish have been found to react to sounds when the sound level increased to about 20 dB above the detection level of 120 dB (Ona, 1988); however, the response threshold can depend on the time of year and the fish's physiological condition (Engas et al., 1993). In general, fish react more strongly to pulses of sound rather than a continuous signal (such as noise from a vessel or icebreaking) (Blaxter et al., 1981), and a quicker alarm response is elicited when the sound signal intensity rises rapidly compared to sound rising more slowly to the same level.
Investigations of fish behavior in relation to vessel noise (Olsen et al., 1983; Ona, 1988; Ona and Godo, 1990) have shown that fish react when the sound from the engines and propeller exceeds a certain level. Avoidance reactions have been observed in fish, such as cod and herring, when vessels approached close enough that received sound levels are 110 dB to 130 dB (Nakken, 1992; Olsen, 1979; Ona and Godo, 1990; Ona and Toresen, 1988). However, other researchers have found that fish such as polar cod, herring, and capeline are often attracted to vessels (apparently by the noise) and swim toward the vessel (Rostad et al., 2006). Typical sound source levels of vessel noise in the audible range for fish are 150 dB to 170 dB (Richardson et al., 1995).
Further, during the proposed in-ice seismic survey, only a small fraction of the available habitat would be ensonified at any given time. Disturbance to fish species would be short-term, and fish would return to their pre-disturbance behavior once the seismic activity ceases (McCauley et al., 2000a, 2000b; Santulli et al., 1999; Pearson et al., 1992). Thus, the proposed survey would have little, if any, impact on the abilities of marine mammals to feed in the area where seismic work is planned.
Some mysticetes, including bowhead whales, feed on concentrations of zooplankton. Some feeding bowhead whales may occur in the Alaskan Beaufort Sea in July and August, and others feed intermittently during their westward migration in September and October (Richardson and Thomson [eds.] 2002; Lowry et al., 2004). However, by the time most bowhead whales reach the Chukchi Sea (October), they will likely no longer be feeding, or if feeding occurs it will be very limited. A reaction by zooplankton to a seismic impulse would only be relevant to whales if it caused concentrations of zooplankton to scatter. Pressure changes of sufficient magnitude to cause that type of reaction would probably occur only very close to the source. Impacts on zooplankton behavior are predicted to be inconsequential, and that would translate into negligible impacts on feeding mysticetes. Because ION will not start operations until early October, a substantial portion of the bowhead population that feeds in the Beaufort Sea during the fall westward migration will have already completed feeding and migrated out of the area before the proposed survey begins. Thus, the proposed activity is not expected to have any habitat-related effects on prey species or feeding marine mammals that could cause significant or long-term consequences for individual marine mammals or their populations.
Potential Impacts on Physical Environment
The proposed airgun operations will not result in any permanent impact on habitats used by marine mammals or to their food sources. The main impact issue associated with the proposed activities would be temporarily elevated noise levels and their associated direct effects on marine mammals, as discussed above, as well as the potential effects of icebreaking. The potential effects of icebreaking include locally altered ice conditions and the potential for the destruction of ringed seal lairs. However, ringed seals are not expected to enter these structures until later in the season, after the completion of ION's activities. Ice conditions at this time of year are typically quite variable with new leads opening and pressure ridges forming as wind and waves move the newly forming ice. This dynamic environment may be responsible for the mean date of permanent den entry on sea ice in the Beaufort Sea being later than on land (Amstrup and Gardner, 1994). The icebreaker and seismic vessel transit is not expected to significantly alter the formation of sea ice during this period.
Icebreaking would open leads in the sea ice along the vessel tracklines and could potentially destroy ringed seal lairs. However, ringed seals will not need lairs for pupping until the late winter or spring (after ION completes operations), so the impacts are not expected to impact pup survival. Ringed seals excavate lairs in snow that accumulates on sea ice near their breathing holes, and an individual seal maintains several breathing holes (Smith and Stirling, 1975). Ringed seal lairs are found in snow depths of 20-150 cm (8-59 in) (Smith and Stirling, 1975), and seals are not expected to enter lairs before the proposed seismic survey takes place. Damage to lairs caused by survey activities is not expected to exceed that which occurs naturally, and lair destruction in the early winter would likely not impact ringed seal survival. Lanugal pups born in the spring can become hypothermic if wetted, but by early winter they are robust to submersion having spent the entire summer at sea (Smith et al., 1991). The highest density of ringed seals reported from aerial surveys conducted during spring when seals were emerging from lairs was in areas with water depth ranging from 5-35 m (16.4-115 ft) (Frost et al., 2004). A relatively small proportion (5%; 364 km [226 mi]) of the proposed survey trackline is planned in that area.
During the seismic survey only a small fraction of the available habitat would be ensonified at any given time. Disturbance to fish species would be short-term, and fish are expected to return to their pre-disturbance behavior once the seismic activity ceases (McCauley et al., 2000a, b; Santulli et al., 1999; Pearson et al., 1992). Thus, the proposed survey would have little, if any, impact on the abilities of marine mammals to feed in the area where seismic work is planned.
Refueling at sea has the potential to impact the marine environment if a spill were to occur. However, there are multiple procedures and safeguards in place to avoid such an accident. Prior to conducting a fuel transfer, the area around the vessels would be checked for the presence of marine mammals and operations delayed until the area is clear. A leak during refueling would be detected and the system shut down within a maximum of 30 seconds. The diesel oil transfer pump is rated at 50 IGPM @ 60 ft pressure head. Therefore, the maximum amount of oil that could be spilled during a transfer is 25 imperial gallons. This risk is reduced further with the standard use of `dry-break' fittings for fuel transfers.
Based on the information provided in this section, the proposed activity is not expected to have any habitat-related effects that could cause significant or long-term consequences for individual marine mammals or their populations.
Potential Impacts on Availability of Affected Species or Stock for Taking for Subsistence Uses Back to Top
Relevant Subsistence Uses
Subsistence hunting and fishing continue to be prominent in the household economies and social welfare of some Alaskan residents, particularly among those living in small, rural villages (Wolfe and Walker, 1987). The disturbance and potential displacement of marine mammals by sounds from the proposed marine surveys are the principal concerns related to subsistence use of the area. Subsistence remains the basis for Alaska Native culture and community. Marine mammals are legally hunted in Alaskan waters by coastal Alaska Natives. In rural Alaska, subsistence activities are often central to many aspects of human existence, including patterns of family life, artistic expression, and community religious and celebratory activities. Additionally, the animals taken for subsistence provide a significant portion of the food that will last the community throughout the year. The main species that are hunted include bowhead and beluga whales, ringed, spotted, and bearded seals, walruses, and polar bears. (Both the walrus and the polar bear are under the USFWS' jurisdiction.) The importance of each of these species varies among the communities and is largely based on availability.
(1) Bowhead Whales
Bowhead whale hunting is a key activity in the subsistence economies of Barrow and other Native communities along the Beaufort Sea and Chukchi Sea coast. The whale harvests have a great influence on social relations by strengthening the sense of Inupiat culture and heritage in addition to reinforcing family and community ties.
An overall quota system for the hunting of bowhead whales was established by the International Whaling Commission in 1977. The quota is now regulated through an agreement between NMFS and the Alaska Eskimo Whaling Commission (AEWC). The AEWC allots the number of bowhead whales that each whaling community may harvest annually during five-year periods (USDI/BLM, 2005). NMFS proposed continuation of the bowhead hunt for the five-year period 2008-2012 (NMFS, 2008b), and in June 2012, NMFS released a Draft Environmental Impact Statement proposing to continue the bowhead hunt for the period 2013-2017/2018 (NMFS, 2012).
The community of Barrow hunts bowhead whales in both the spring and fall during the whales' seasonal migrations along the coast. Often the bulk of the Barrow bowhead harvest is taken during the spring hunt. However, with larger quotas in recent years, it is common for a substantial fraction of the annual Barrow quota to remain available for the fall hunt. The communities of Nuiqsut and Kaktovik participate only in the fall bowhead harvest. The fall migration of bowhead whales that summer in the eastern Beaufort Sea typically begins in late August or September. Fall migration into Alaskan waters is primarily during September and October. However, in recent years a small number of bowheads have been seen or heard offshore from the Prudhoe Bay region during the last week of August (Treacy, 1993; LGL and Greeneridge, 1996; Greene, 1997; Greene et al., 1999; Blackwell et al., 2004).
In autumn, westward-migrating bowhead whales typically reach the Kaktovik and Cross Island (Nuiqsut hunters) areas by early September, at which points the hunts begin (Kaleak, 1996; Long, 1996; Galginaitis and Koski, 2002; Galginaitis and Funk, 2004, 2005; Koski et al., 2005). Around late August, the hunters from Nuiqsut establish camps on Cross Island from where they undertake the fall bowhead whale hunt. The hunting period starts normally in early September and may last as late as mid-October, depending mainly on ice and weather conditions and the success of the hunt. Most of the hunt occurs offshore in waters east, north, and northwest of Cross Island where bowheads migrate and not inside the barrier islands (Galginaitis, 2007). Hunters prefer to take bowheads close to shore to avoid a long tow during which the meat can spoil, but Braund and Moorehead (1995) report that crews may (rarely) pursue whales as far as 80 km (50 mi) offshore. Whaling crews use Kaktovik as their home base, leaving the village and returning on a daily basis. The core whaling area is within 19.3 km (12 mi) of the village with a periphery ranging about 13 km (8 mi) farther, if necessary. The extreme limits of the Kaktovik whaling limit would be the middle of Camden Bay to the west. The timing of the Kaktovik bowhead whale hunt roughly parallels the Cross Island whale hunt (Impact Assessment Inc, 1990b; SRB&A, 2009:Map 64). In recent years, the hunts at Kaktovik and Cross Island have usually ended by mid- to late September (prior to the proposed start date for ION's seismic survey).
The spring hunts at Wainwright and Barrow occur after leads open due to the deterioration of pack ice; the spring hunt typically occurs from early April until the first week of June. The location of the fall subsistence hunt depends on ice conditions and (in some years) industrial activities that influence the bowheads as they move west (Brower, 1996). In the fall, subsistence hunters use aluminum or fiberglass boats with outboards. At Barrow the fall hunt usually begins in mid-September, and mainly occurs in the waters east and northeast of Point Barrow. In 2007 however, all bowheads taken in fall at Barrow were harvested west of Pt. Barrow in the Chukchi Sea (Suydam et al., 2008). The whales have usually left the Beaufort Sea by late October (Treacy, 2002a; 2002b).
The scheduling of this seismic survey was introduced to representatives of those concerned with the subsistence bowhead hunt including the AEWC and the North Slope Borough (NSB) Department of Wildlife Management during a meeting in Barrow on December 15, 2009. Additional meetings occurred in 2010, 2011, and 2012 with more planned later in 2012 to share information regarding the survey with other members of the subsistence hunting community. The timing of the proposed geophysical survey in October-December will not affect the spring bowhead hunt. The fall bowhead hunt may be occurring near Barrow during October, and operations will be coordinated with the AEWC. ION will operate at the eastern end of the survey area until fall whaling in the Beaufort Sea near Barrow is finished. Fall bowhead whale hunts by members of the communities of Kaktovik and Nuiqsut will likely be completed prior to October.
Whaling communities of the Bering Strait area, such as Gambell and Savoonga on St. Lawrence Island, hunt bowheads in the late fall (typically around Thanksgiving). Because ION intends to conduct operations in the Beaufort and Chukchi Seas until early to mid-December, ION's vessel transits through the Bering Strait should not interfere with these late fall hunts.
(2) Beluga Whales
Beluga whales are available to subsistence hunters at Barrow in the spring when pack-ice conditions deteriorate and leads open up. Belugas may remain in the area through June and some-times into July and August in ice-free waters. Hunters usually wait until after the spring bowhead whale hunt is finished before turning their attention to hunting belugas. The average annual harvest of beluga whales taken by Barrow for 1962-1982 was five (MMS, 1996). The Alaska Beluga Whale Committee recorded that 23 beluga whales had been harvested by Barrow hunters from 1987 to 2002, ranging from 0 in 1987, 1988 and 1995 to the high of 8 in 1997 (Fuller and George, 1999; Alaska Beluga Whale Committee, 2002 in USDI/BLM, 2005). The timing of the proposed survey will not overlap with the beluga harvest.
(3) Ice Seals
Ringed seals are hunted mainly from October through June. Hunting for these smaller mammals is concentrated during winter because bowhead whales, bearded seals and caribou are available through other seasons. In winter, leads and cracks in the ice off points of land and along the barrier islands are used for hunting ringed seals. The seismic survey would be largely in offshore waters where the activities would not influence ringed seals in the nearshore areas where they are hunted.
The spotted seal subsistence hunt peaks in July and August, at least in 1987 to 1990, but involves few animals. Spotted seals typically migrate south by October to overwinter in the Bering Sea, and therefore the proposed October-December survey will not affect hunting of this species. Admiralty Bay, less than 60 km (37 mi) to the east of Barrow, is a location where spotted seals are harvested. Spotted seals are also occasionally hunted in the area off Point Barrow and along the barrier islands of Elson Lagoon to the east (USDI/BLM, 2005). The average annual spotted seal harvest by the community of Barrow from 1987-1990 was one (Braund et al., 1993)
Bearded seals, although not favored for their meat, are important to subsistence activities in Barrow because of their skins. Six to nine bearded seal hides are used by whalers to cover each of the skin-covered boats traditionally used for spring whaling. Because of their valuable hides and large size, bearded seals are specifically sought. Bearded seals are harvested during the summer months in the Beaufort Sea (USDI/BLM, 2005). The animals inhabit the environment around the ice floes in the drifting ice pack, so hunting usually occurs from boats in the drift ice. Braund et al. (1993) mapped the majority of bearded seal harvest sites from 1987 to 1990 as being within ∼24 km (∼15 mi) of Point Barrow. The average annual take of bearded seals by the Barrow community from 1987 to 1990 was 174. Because bearded seal hunting typically occurs during the summer months, the proposed October-December survey is not expected to affect bearded seal harvests.
Potential Impacts to Subsistence Uses
NMFS has defined “unmitigable adverse impact” in 50 CFR 216.103 as: “* * * an impact resulting from the specified activity: (1) That is likely to reduce the availability of the species to a level insufficient for a harvest to meet subsistence needs by: (i) Causing the marine mammals to abandon or avoid hunting areas; (ii) Directly displacing subsistence users; or (iii) Placing physical barriers between the marine mammals and the subsistence hunters; and (2) That cannot be sufficiently mitigated by other measures to increase the availability of marine mammals to allow subsistence needs to be met.”
Seismic surveys and associated icebreaking operations have the potential to impact marine mammals hunted by Native Alaskans. In the case of cetaceans, the most common reaction to anthropogenic sounds (as noted previously in this document) is avoidance of the ensonified area. In the case of bowhead whales, this often means that the animals could divert from their normal migratory path by up to several kilometers. Additionally, general vessel presence in the vicinity of traditional hunting areas could negatively impact a hunt.
In the case of subsistence hunts for bowhead whales in the Beaufort and Chukchi Seas, there could be an adverse impact on the hunt if the whales were deflected seaward (further from shore) in traditional hunting areas. The impact would be that whaling crews would have to travel greater distances to intercept westward migrating whales, thereby creating a safety hazard for whaling crews and/or limiting chances of successfully striking and landing bowheads. Native knowledge indicates that bowhead whales become increasingly “skittish” in the presence of seismic noise. Whales are more wary around the hunters and tend to expose a much smaller portion of their back when surfacing (which makes harvesting more difficult). Additionally, natives report that bowheads exhibit angry behaviors in the presence of seismic, such as tail-slapping, which translate to danger for nearby subsistence harvesters.
However, due to its proposed time and location, ION's proposed in-ice seismic survey in the Beaufort and Chukchi Seas would be unlikely to result in the aforementioned impacts. As discussed earlier in detail, the only potential impacts on subsistence use of marine mammals from ION's proposed icebreaking seismic survey during October-December period are the fall bowhead hunt and ringed seal harvest. Nevertheless, the proposed seismic survey is expected to occur in waters far offshore from the regular seal hunting areas, and ION indicates it would elect to operate at the eastern end of the survey area until fall whaling in the Beaufort Sea near Barrow is finished, thus reducing the likelihood of interfering with subsistence use of marine mammals in the vicinity of the project area.
Proposed Mitigation Back to Top
In order to issue an incidental take authorization (ITA) under Section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible methods of taking pursuant to such activity, and other means of effecting the least practicable impact on such species or stock and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of such species or stock for taking for certain subsistence uses.
For the proposed ION in-ice seismic survey in the Beaufort and Chukchi Seas, ION worked with NMFS and proposed the following mitigation measures to minimize the potential impacts to marine mammals in the project vicinity as a result of the marine seismic survey activities.
As part of the application, ION submitted to NMFS a Marine Mammal Monitoring and Mitigation Program (4MP) for its in-ice seismic survey in the Beaufort and Chukchi Seas during the 2012 fall season. The objectives of the 4MP are:
- To ensure that disturbance to marine mammals and subsistence hunts is minimized and all permit stipulations are followed,
- To document the effects of the proposed survey activities on marine mammals, and
- To collect baseline data on the occurrence and distribution of marine mammals in the study area.
The 4MP may be modified or supplemented based on comments or new information received from the public during the public comment period or from the peer review panel (see the “Monitoring Plan Peer Review” section later in this document).
Mitigation Measures Proposed in ION's IHA Application
ION listed the following protocols to be implemented during its marine seismic survey in the Beaufort and Chukchi Seas.
(1) Exclusion Zones
Under current NMFS guidelines, “exclusion zones” for marine mammals around industrial sound sources are customarily defined as the distances within which received sound levels are ≥180 dB re 1 μPa (rms) for cetaceans and ≥190 dB re 1 μPa (rms) for pinnipeds. These criteria are based on an assumption that sound energy at lower received levels will not injure these animals or impair their hearing abilities but that higher received levels might have some such effects. Disturbance or behavioral effects to marine mammals from underwater sound may occur after exposure to sound at distances greater than the exclusion zone (Richardson et al., 1995; see above).
Received sound levels were modeled for the full 26 airgun, 4,450 in  array in relation to distance and direction from the source (Zykov et al., 2010). Based on the model results, Table 1 in this document shows the distances from the airguns where ION predicts that received sound levels will drop below 190, 180, and 160 dB re 1 μPa (rms). A single 70-in  airgun would be used during turns or if a power down of the full array (see below) is necessary due to the presence of a marine mammal within or about to enter the applicable exclusion zone of the full airgun array. To model the source level of the 70-in  airgun, ION used the measurements of a 30-in  airgun. Underwater sound propagation of a 30-in  airgun was measured in <100 m (328 ft) of water near Harrison Bay in 2007, and results were reported in Funk et al. (2008). The constant term of the resulting equation was increased by 2.45 dB based on the difference between the volume of the two airguns [2.45 = 20Log(70/30)⁁(1/3)]. The 190 and 180 dB (rms) distances for the 70-in  airgun from the adjusted equation, 19 m (62 ft) and 86 m (282 ft) respectively, would be used as the exclusion zones around the single 70 in  airgun in all water depths until results from field measurements are available.
An acoustics contractor would perform the direct measurements of the received levels of underwater sound versus distance and direction from the energy source arrays using calibrated hydrophones (see below “Sound Source Verification” in the “Proposed Monitoring” section). The acoustic data would be analyzed as quickly as reasonably practicable in the field and used to verify (and if necessary adjust) the size of the exclusion zones. The field report will be made available to NMFS and the Protected Species Observers (PSOs) within 120 hrs of completing the measurements. The mitigation measures to be implemented at the 190 and 180 dB (rms) sound levels would include power downs and shut downs as described below.
|rms (dB re. 1 μPa)||Exclusion and disturbance zones (meters)|
|less than 100 m||100 m-1,000 m||more than 1,000 m|
(2) Speed or Course Alteration
If a marine mammal (in water) is detected outside the exclusion zone and, based on its position and the relative motion, is likely to enter the exclusion zone, the vessel's speed and/or direct course shall be changed in a manner that also minimizes the effect on the planned objectives when such a maneuver is safe.
Another measure proposes to avoid concentrations or groups of whales by all vessels in transit under the direction of ION. Operators of vessels should, at all times, conduct their activities at the maximum distance possible from such concentrations of whales.
All vessels during transit shall be operated at speeds necessary to ensure no physical contact with whales occurs. If any barge or transit vessel approaches within 1.6 km (1 mi) of observed bowhead whales, the vessel operator shall take reasonable precautions to avoid potential interaction with the bowhead whales by taking one or more of the following actions, as appropriate:
(A) Reducing vessel speed to less than 5 knots within 300 yards (900 feet or 274 m) of the whale(s);
(B) Steering around the whale(s) if possible;
(C) Operating the vessel(s) in such a way as to avoid separating members of a group of whales from other members of the group;
(D) Operating the vessel(s) to avoid causing a whale to make multiple changes in direction; and
(E) Checking the waters immediately adjacent to the vessel(s) to ensure that no whales will be injured when the propellers are engaged.
When weather conditions require, such as when visibility drops, adjust vessel speed accordingly to avoid the likelihood of injury to whales.
In the event that any aircraft (such as helicopters) are used to support the planned survey, the proposed mitigation measures below would apply:
(A) Under no circumstances, other than an emergency, shall aircraft be operated at an altitude lower than 1,000 feet above sea level (ASL) when within 0.3 mile (0.5 km) of groups of whales.
(B) Helicopters shall not hover or circle above or within 0.3 mile (0.5 km) of groups of whales.
(3) Ramp Ups
A ramp up of an airgun array provides a gradual increase in sound levels and involves a step-wise increase in the number and total volume of airguns firing until the full volume is achieved. The purpose of a ramp up is to “warn” marine mammals in the vicinity of the airguns and to provide the time for them to leave the area and thus avoid any potential injury or impairment of their hearing abilities.
During the proposed seismic survey program, the seismic operator will ramp up the airgun arrays slowly. Full ramp ups (i.e., from a cold start after a shut down or when no airguns have been firing) will begin by firing a single airgun in the array. A full ramp up, following a cold start, can be applied if the exclusion zone has been free of marine mammals for a consecutive 30-minute period. The entire exclusion zone must have been visible during these 30 minutes. If the entire exclusion zone is not visible, then ramp up from a cold start cannot begin.
Ramp up procedures from a cold start shall be delayed if a marine mammal is sighted within the exclusion zone during the 30-minute period prior to the ramp up. The delay shall last until the marine mammal(s) has been observed to leave the exclusion zone or until the animal(s) is not sighted for at least 15 or 30 minutes. The 15 minutes applies to small odontocetes and pinnipeds, while a 30 minute observation period applies to baleen whales and large toothed whales.
A ramp up, following a shutdown, can be applied if the marine mammal(s) for which the shutdown occurred has been observed to leave the exclusion zone or until the animal(s) is not sighted for at least 15 minutes (small odontocetes and pinnipeds) or 30 minutes (baleen whales and large toothed whales).
If, for any reason, electrical power to the airgun array has been discontinued for a period of 10 minutes or more, ramp-up procedures shall be implemented. Only if the PSO watch has been suspended, a 30-minute clearance of the exclusion zone is required prior to commencing ramp-up. Discontinuation of airgun activity for less than 10 minutes does not require a ramp-up.
The seismic operator and PSOs shall maintain records of the times when ramp-ups start and when the airgun arrays reach full power.
During turns and transit between seismic transects, the 70 in  mitigation gun will remain operational. The ramp up procedure will still be followed when increasing the source levels from one airgun to the full array. PSOs will be on duty whenever the airguns are firing during daylight and during the 30 minute periods prior to full ramp ups. Daylight will occur for ∼11 hours/day at the start of the survey in early October diminishing to ∼3 hours/day in mid-November.
(4) Power Down Procedures
A power down involves decreasing the number of airguns in use such that the radii of the 190 and 180 dB re 1 μPa (rms) zones are decreased to the extent that observed marine mammals are not in the applicable exclusion zone. A power down may also occur when the vessel is moving from one seismic line to another. During a power down, only one airgun is operated. The continued operation of one airgun is intended to (a) alert marine mammals to the presence of the seismic vessel in the area, and (b) retain the option of initiating a ramp up to full array under poor visibility conditions. In contrast, a shutdown is when all airgun activity is suspended (see next section).
If a marine mammal is detected outside the exclusion zone but is likely to enter the exclusion zone, and if the vessel's speed and/or course cannot be changed to avoid having the mammal enter the exclusion zone, the airguns may (as an alternative to a complete shutdown) be powered down before the mammal is within the exclusion zone. Likewise, if a mammal is already within the exclusion zone when first detected, the airguns will be powered down immediately if this is a reasonable alternative to a complete shutdown. During a power down of the array, the number of guns operating will be reduced to a single 70 in  airgun. The pre-season estimates of the 190 dB re 1 μPa (rms) and 180 dB re 1 μPa (rms) exclusion zones around the power down source are 19 m (62 ft) and 86 m (282 ft), respectively. The 70 in  airgun power down source will be measured during acoustic sound source measurements conducted at the start of seismic operations. If a marine mammal is detected within or near the applicable exclusion zone around the single 70 in  airgun, it too will be deactivated, resulting in a complete shutdown (see next subsection).
Marine mammals hauled out on ice may enter the water when approached closely by a vessel. If a marine mammal on ice is detected by PSOs within the exclusion zones, it will be watched carefully in case it enters the water. In the event the animal does enter the water and is within an applicable exclusion zone of the airguns during seismic operations, a power down or other necessary mitigation measures will immediately be implemented. If the animal does not enter the water, it will not be exposed to sounds at received levels for which mitigation is required; therefore, no mitigation measures will be taken.
Following a power down, operation of the full airgun array will not resume until the marine mammal has cleared the exclusion zone. The animal will be considered to have cleared the exclusion zone if it:
- Is visually observed to have left the exclusion zone, or
- Has not been seen within the zone for 15 min in the case of pinnipeds (excluding walruses) or small odontocetes, or
- Has not been seen within the zone for 30 min in the case of mysticetes or large odontocetes.
(5) Shutdown Procedures
The operating airgun(s) will be shut down completely if a marine mammal approaches or enters the then-applicable exclusion zone and a power down is not practical or adequate to reduce exposure to less than 190 or 180 dB re 1 μPa (rms). The operating airgun(s) will also be shut down completely if a marine mammal approaches or enters the estimated exclusion zone around the reduced source (one 70 in  airgun) that will be used during a power down.
Airgun activity will not resume until the marine mammal has cleared the exclusion zone. The animal will be considered to have cleared the exclusion zone if it is visually observed to have left the exclusion zone, or if it has not been seen within the zone for 15 min (pinnipeds and small odontocetes) or 30 min (mysticetes and large odontocetes). Ramp up procedures will be followed during resumption of full seismic operations after a shutdown of the airgun array.
Additional Mitigation Measures Proposed by NMFS
In addition to ION's proposed mitigation measures discussed above, NMFS proposes the following additional measures during the long periods of darkness when the seismic survey is proposed. Specifically in this case, With the exception of turns when starting a new trackline, or short transits or maintenance with a duration of less than one hour, NMFS does not recommend keeping one airgun (also referred to as the “mitigation gun” in past IHAs) firing for long periods of time during darkness or other periods of poor visibility, as it would only introduce more noise into the water with no potential near-term avoidance benefits for marine mammals.
Furthermore, NMFS proposes that the airgun array be shut down if a pinniped is sighted hauled out on ice within the underwater exclusion zone (received level 190 dB re 1 μPa (rms)). Even though the pinniped may not be exposed to in-air noise levels that could be considered a take, the presence of the seismic vessel could prompt the animal to slip into the water, and thus be exposed to a high intensity sound field as a result.
Mitigation Measures for Subsistence Activities
(1) Subsistence Mitigation Measures
Since ION's proposed October-December in-ice seismic survey in the Beaufort and Chukchi Seas is not expected to affect subsistence use of marine mammals by Alaskan Natives due to its proposed time and location, no specific mitigation measures are proposed other than those general mitigation measures discussed above.
(2) Plan of Cooperation (POC)
Regulations at 50 CFR 216.104(a)(12) require IHA applicants for activities that take place in Arctic waters to provide a POC or information that identifies what measures have been taken and/or will be taken to minimize adverse effects on the availability of marine mammals for subsistence purposes.
ION has developed a “Plan of Cooperation” (POC) for the proposed 2012 seismic survey in the Beaufort and Chukchi Seas in consultation with representatives of Barrow, Nuiqsut, Kaktovik, and Wainwright and subsistence users within these communities. NMFS received a final draft of the POC on May 22, 2012. The final draft POC is posted on NMFS Web site at http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
ION will continue to engage with the communities of Barrow, Nuiqsut, Kaktovik, and Wainwright to identify and avoid areas of potential conflict. The meetings with stakeholders that took place in 2010 and 2011 are listed in Table 16 and Table 17, respectively, of ION's IHA application. The meetings that have taken place in 2012, as well as additional proposed meetings, are listed in Table 18 of ION's IHA application. Members of marine mammal co-management groups and groups that address subsistence activities were specifically notified of the public meetings so that they could provide input. A record of all consultation with subsistence users will be included in the 2012 Final POC document.
NMFS has carefully evaluated the applicant's proposed mitigation measures and considered a range of other measures in the context of ensuring that NMFS prescribes the means of effecting the least practicable impact on the affected marine mammal species and stocks and their habitat. Our evaluation of potential measures included consideration of the following factors in relation to one another:
- The manner in which, and the degree to which, the successful implementation of the measure is expected to minimize adverse impacts to marine mammals;
- The proven or likely efficacy of the specific measure to minimize adverse impacts as planned; and
- The practicability of the measure for applicant implementation.
Based on our evaluation of the applicant's proposed measures, as well as other measures considered by NMFS, NMFS has preliminarily determined that the proposed mitigation measures provide the means of effecting the least practicable impact on marine mammal species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance.
Proposed Monitoring and Reporting Back to Top
In order to issue an ITA for an activity, Section 101(a)(5)(D) of the MMPA states that NMFS must set forth “requirements pertaining to the monitoring and reporting of such taking”. The MMPA implementing regulations at 50 CFR 216.104(a)(13) indicate that requests for ITAs must include the suggested means of accomplishing the necessary monitoring and reporting that will result in increased knowledge of the species and of the level of taking or impacts on populations of marine mammals that are expected to be present in the proposed action area.
Proposed Monitoring Measures
The monitoring plan proposed by ION can be found in the 4MP. The plan may be modified or supplemented based on comments or new information received from the public during the public comment period. A summary of the primary components of the plan follows.
(1) Protected Species Observers
Vessel-based monitoring for marine mammals will be performed by trained PSOs throughout the period of survey activities, supplemented by the officers on duty, to comply with expected provisions in the IHA (if issued). The observers will monitor the occurrence and behavior of marine mammals near the survey vessels during all daylight periods. PSO duties will include watching for and identifying marine mammals; recording their numbers, distances, and reactions to the survey operations; and documenting “take by harassment” as defined by NMFS.
A. Number of Observers
A sufficient number of PSOs will be required onboard the survey vessel to meet the following criteria:
- 100% monitoring coverage during all periods of survey operations in daylight;
- Maximum of 4 consecutive hours on watch per PSO; and
- Maximum of ∼12 hours of watch time per day per PSO.
An experienced field crew leader will supervise the PSO team onboard the survey vessels. ION's proposed survey will occur in October-December when the number of hours of daylight is significantly reduced, and thus will require fewer PSOs to be aboard the survey vessel than required for surveys conducted during the open water season with nearly 24 hrs of daylight. PSOs aboard the icebreaker operating 0.5-1 km (0.31-0.62 mi) ahead of the survey vessel will provide early detection of marine mammals along the survey track. Three PSOs will be stationed aboard the icebreaker Polar Prince to take advantage of this forward operating platform and provide advance notice of marine mammals to the PSO on the survey vessel. Three PSOs will be stationed aboard the survey vessel Geo Arctic to monitor the exclusion zones centered on the airguns and to request mitigation actions when necessary.
B. Observer Qualifications and Training
Crew leaders and most other biologists serving as observers will be individuals with recent experience as observers during one or more seismic monitoring projects in Alaska, the Canadian Beaufort Sea, or other offshore areas.
Biologist-observers will have previous marine mammal observation experience, and field crew leaders will be highly experienced with previous vessel-based marine mammal monitoring and mitigation projects. Résumés for all individuals will be provided to NMFS for review and acceptance of their qualifications. Inupiat observers will be experienced in the region, familiar with the marine mammals of the area, and complete an approved observer training course designed to familiarize individuals with monitoring and data collection procedures. A PSO handbook, adapted for the specifics of the planned survey program, will be prepared and distributed beforehand to all PSOs (see summary below).
Biologist-observers and Inupiat observers will also complete a two or three-day training and refresher session together on marine mammal monitoring, to be conducted shortly before the anticipated start of the seismic survey. When possible, experienced observers will be paired with inexperienced observers. The training session(s) will be conducted by qualified marine mammalogists with extensive crew-leader experience during previous vessel-based seismic monitoring programs.
Primary objectives of the training include:
- Review of the marine mammal monitoring plan for this project, including any amendments specified by NMFS in the IHA (if issued);
- Review of marine mammal sighting, identification, and distance estimation methods using visual aids;
- Review of operation of specialized equipment (reticle binoculars, night vision devices (NVDs), and GPS system);
- Review of, and classroom practice with, data recording and data entry systems, including procedures for recording data on marine mammal sightings, monitoring operations, environmental conditions, and entry error control. These procedures will be implemented through use of a customized computer database and laptop computers;
- Review of the specific tasks of the Inupiat Communicator; and
- Exam to ensure all observers can correctly identify marine mammals and record sightings.
C. PSO Handbook
A PSOs' Handbook will be prepared for ION's monitoring program. Handbooks contain maps, illustrations, and photographs, as well as text, and are intended to provide guidance and reference information to trained individuals who will participate as PSOs. The following topics will be covered in the PSO Handbook for the ION project:
- Summary overview descriptions of the project, marine mammals and underwater noise, the marine mammal monitoring program (vessel-based, aerial, acoustic measurements), the NMFS' IHA (if issued) and other regulations/permits/agencies, the Marine Mammal Protection Act;
- Monitoring and mitigation objectives and procedures, initial exclusion zones;
- Responsibilities of staff and crew regarding the marine mammal monitoring plan;
- Instructions for ship crew regarding the marine mammal monitoring plan;
- Data recording procedures: codes and coding instructions, common coding mistakes, electronic database; navigational, marine physical, field data sheet;
- List of species that might be encountered: identification cues, natural history information;
- Use of specialized field equipment (reticle binoculars, NVDs, forward-looking infrared (FLIR) system);
- Reticle binocular distance scale;
- Table of wind speed, Beaufort wind force, and sea state codes;
- Data storage and backup procedures;
- Safety precautions while onboard;
- Crew and/or personnel discord; conflict resolution among PSOs and crew;
- Drug and alcohol policy and testing;
- Scheduling of cruises and watches;
- Communication availability and procedures;
- List of field gear that will be provided;
- Suggested list of personal items to pack;
- Suggested literature, or literature cited; and
- Copies of the NMFS IHA and USFWS LOA when available.
(2) Monitoring Methodology
A. General Monitoring Methodology
The observer(s) will watch for marine mammals from the best available vantage point on the survey vessels, typically the bridge. The observer(s) will scan systematically with the unaided eye and 7×50 reticle binoculars, supplemented during good visibility conditions with 20×60 image-stabilized Zeiss Binoculars or Fujinon 25×150 “Big-eye” binoculars, a thermal imaging (FLIR) camera, and night-vision equipment when needed (see below). Personnel on the bridge will assist the marine mammal observer(s) in watching for marine mammals.
Information to be recorded by observers will include the same types of information that were recorded during recent monitoring programs associated with Industry activity in the Arctic (e.g., Ireland et al., 2009). When a mammal sighting is made, the following information about the sighting will be recorded:
- Species, group size, age/size/sex categories (if determinable), behavior when first sighted and after initial sighting, heading (if determinable), bearing and distance from observer, apparent reaction to activities (e.g., none, avoidance, approach, etc.), closest point of approach, and pace;
- Additional details for any unidentified marine mammal or unknown observed;
- Time, location, speed, and activity of the vessel, sea state, ice cover, visibility, and sun glare; and
- The positions of other vessel(s) in the vicinity of the observer location.
The ship's position, speed of the vessel, water depth, sea state, ice cover, visibility, airgun status (ramp up, mitigation gun, or full array), and sun glare will also be recorded at the start and end of each observation watch, every 30 minutes during a watch, and whenever there is a change in any of those variables.
Distances to nearby marine mammals will be estimated with binoculars containing a reticle to measure the vertical angle of the line of sight to the animal relative to the horizon. Observers may use a laser rangefinder to test and improve their abilities for visually estimating distances to objects in the water. However, previous experience has shown that a Class 1 eye-safe device was not able to measure distances to seals more than about 70 m (230 ft) away. The device was very useful in improving the distance estimation abilities of the observers at distances up to about 600 m (1,968 ft), the maximum range at which the device could measure distances to highly reflective objects such as other vessels. Humans observing objects of more-or-less known size via a standard observation protocol, in this case from a standard height above water, quickly become able to estimate distances within about ±20% when given immediate feedback about actual distances during training.
When a marine mammal is seen within the exclusion zone applicable to that species, the geophysical crew will be notified immediately so that mitigation measures required by the IHA (if issued) can be implemented. It is expected that the airgun array will be shut down within several seconds, often before the next shot would be fired, and almost always before more than one additional shot is fired. The protected species observer will then maintain a watch to determine when the mammal(s) appear to be outside the exclusion zone such that airgun operations can resume.
ION will provide or arrange for the following specialized field equipment for use by the onboard PSOs: 7 × 50 reticle binoculars, Big-eye binoculars or high power image-stabilized binoculars, GPS unit, laptop computers, night vision binoculars, digital still and possibly digital video cameras in addition to the above mentioned FLIR camera system (see below).
B. Monitoring At Night and In Poor Visibility
Night-vision equipment (Generation 3 binocular image intensifiers, or equivalent units) will be available for use when/if needed. Past experience with NVDs in the Beaufort Sea and elsewhere has indicated that NVDs are not nearly as effective as visual observation during daylight hours (e.g., Harris et al., 1997, 1998; Moulton and Lawson, 2002). A FLIR camera system mounted on a high point near the bow of the icebreaker will also be available to assist with detecting the presence of seals and polar bears on ice and, perhaps also in the water, ahead of the airgun array. The FLIR system detects thermal contrasts and its ability to sense these differences is not dependent on daylight.
Additional details regarding the monitoring protocol during NVD and FLIR system use has been developed in order to collect data in a standardized manner such that the effectiveness of the two devices can be analyzed and compared.
B. (1) FLIR and NVD Monitoring
The infrared system is able to detect differences in the surface temperature of objects making it potentially useful during both daylight and darkness periods. NVDs, or light intensifiers, amplify low levels of ambient light from moonlight or sky glow light in order to provide an image to the user. Both technologies have the potential to improve monitoring and mitigation efforts in darkness. However, they remain relatively unproven in regards to their effectiveness under the conditions and it the manner of use planned for this survey. The protocols for FLIR and NVD use and data collection described below are intended to collect the necessary data in order to evaluate the ability of these technologies to aid in the detection of marine mammals from a vessel.
- All PSOs will monitor for marine mammals according to the procedures outlined in the PSO handbook.
- One PSO will be responsible for monitoring the FLIR system (IR-PSO) during most darkness and twilight periods. The on-duty IR-PSO will monitor the IR display and alternate between the two search methods described below. If a second PSO is on watch, they will scan the same area as the FLIR using the NVDs for comparison. The two PSOs will coordinate what area is currently being scanned.
- The IR-PSO should rotate between the search methods (see below) every 30 minutes in the suggested routine (see below):
○ 00:00-00:30: Method I
○ 00:30-01:00: Method II, Port side
○ 01:00-01:30: Method I
○ 01:30-02:00: Method II, Starboard side
B. (2) FLIR Search Methods
The FLIR system consists of a camera that will be mounted on high point in front of the vessel. The camera is connected to a joystick control unit (JCU) and a display monitor that will be located on the bridge of the vessel. The IR-PSO will manually control the view that is displayed by adjusting the pan (360° continuous pan) and tilt (+/−90° tilt) settings using the JCU. The FLIR manufacturer has indicated that they have tested the FLIR unit (model M626L) to −25 °C (−13 °F), but expect that it will operate at colder temperatures. During the time of the proposed seismic survey, the average minimum temperatures at Prudhoe Bay in October and November are +10 °F and −10 °F, respectively. Colder temperatures are certainly likely at times, but overall the temperatures should generally be within the operational range of the equipment.
As noted above, two different search methods will be implemented for FLIR monitoring and results from the two will be compared. The first method involves a back-and-forth panning motion and the second utilizes the FLIR unit focused on a fixed swath ahead and to one side of the vessel track:
Method I: Set the horizontal tilt of the camera to an angle that provides an adequate view out in front of the vessel and also provides good resolution to potential targets (this will likely mean that the lower portion of the view displayed on the monitor is of an area relatively close to the vessel (<100 m [328 ft]) while the middle and upper portions of the view are at greater distances (500-2,000 m [1,640-6,562 ft]). Pan back and forth across the forward 180° of the vessels heading at a slow-scanning rate of approximately 1-2°/sec, as one would with binoculars. This method is intended to replicate the type of observations conducted using binoculars and cover a relatively wider swatch compared to Method II. It should produce sightings data that can be analyzed using line-transect methodologies to estimate marine mammal densities in the survey area.
Method II: Set the horizontal tilt of the camera to an angle that provides an adequate view out in front of the vessel (similar or identical to the above), and then set the camera at a fixed position that creates a swath of view off the bow and to one side of the vessel (see Figure 1 of ION's monitoring plan). This method essentially establishes a fixed-strip width that is intended to produce sightings data that can be analyzed using strip-transect methodologies to estimate marine mammal densities.
B. (3) NVD Methods
The NVDs are goggles worn by the observer and are to be used in a similar fashion as binoculars. When observing in conjunction with the FLIR system, the objective will be to replicate the monitoring methodology being employed by the FLIR system. Method I requires a full 180° scan (or as large of a range as possible from the observer's location) with the NVDs, and Method II requires a focused scan of the ∼60° swath being monitored by the FLIR system.
C. Field Data-Recording, Verification, Handling, and Security
The observers will record their observations onto datasheets or directly into handheld computers. During periods between watches and periods when operations are suspended, those data will be entered into a laptop computer running a custom computer database. The accuracy of the data entry will be verified in the field by computerized validity checks as the data are entered, and by subsequent manual checking of the database printouts. These procedures will allow initial summaries of data to be prepared during and shortly after the field season, and will facilitate transfer of the data to statistical, graphical or other programs for further processing. Quality control of the data will be facilitated by (1) the start-of-season training session, (2) subsequent supervision by the onboard field crew leader, and (3) ongoing data checks during the field season.
The data will be backed up regularly onto CDs and/or USB disks, and stored at separate locations on the vessel. If possible, data sheets will be photocopied daily during the field season. Data will be secured further by having data sheets and backup data CDs carried back to the Anchorage office during crew rotations.
In addition to routine PSO duties, observers will use Traditional Knowledge and Natural History datasheets to record observations that are not captured by the sighting or effort data. Copies of these records will be available to observers for reference if they wish to prepare a statement about their observations. If prepared, this statement would be included in the 90-day and final reports documenting the monitoring work.
D. Effort and Sightings Data Collection Methods
Observation effort data will be designed to capture the amount of PSO effort itself, environmental conditions that impact an observer's ability to detect marine mammals, and the equipment and method of monitoring being employed. These data will be collected every 30 minutes or when an effort variable changes (e.g., change in the equipment or method being used to monitor, on/off-signing PSO, etc.), and will be linked to sightings data. Effort and sightings data forms are the same forms used during other marine mammal monitoring in the open water season, but additional fields have been included to capture information specific to monitoring in darkness and to more accurately describe the observation conditions. The additional fields include the following.
- Observation Method: FLIR, NVD, spotlight, eye (naked eye or regular binoculars), or multiple methods. This data is collected every 30 minutes with the Observer Effort form and with every sighting.
- Cloud Cover: Percentage. This can impact lighting conditions and reflectivity.
- Precipitation Type: Fog, rain, snow, or none.
- Precipitation Reduced Visibility: Confirms whether or not visibility is reduced due to precipitation. This will be compared to the visibility distance (# km) to determine when visibility is reduced due to lighting conditions versus precipitation.
- Daylight Amount: Daylight, twilight, dark. The addition of the twilight field has been included to record observation periods where the sun has set and observation distances may be reduced due to lack of light.
- Light Intensity: Recorded in footcandles (fc) using an incident light meter. This procedure was added to quantify the available light during twilight and darkness periods and may allow for light-intensity bins to be used during analysis.
Analysis of the sightings data will include comparisons of nighttime (FLIR and NVD) sighting rates to daylight sighting rates. FLIR and NVD analysis will be independent of each other and according to method (I or II) used. Comparison of NVD and FLIR sighting rates will allow for a comparison of marine mammal detection ability of the two methods. However, results and analyses could be limited if relatively few sightings are recorded during the survey.
(3) Acoustic Monitoring Plan
A. Sound Source Measurements
As described above, received sound levels were modeled for the full 26 airgun, 4,450 in  array in relation to distance and direction from the source (Zykov et al., 2010). These modeled distances will be used as temporary exclusion zones until measurements of the airgun sound source are conducted. The measurements will be made at the beginning of the field season, and the measured radii will be used for the remainder of the survey period. An acoustics contractor with experience in the Arctic conducting similar measurements in recent years will use their equipment to record and analyze the underwater sounds and write the summary reports as described below.
The objectives of the sound source measurements planned for 2012 in the Beaufort Sea will be (1) to measure the distances in potentially ice covered waters in the broadside and endfire directions at which broadband received levels reach 190, 180, 170, 160, and 120 dB re 1 μPa (rms) for the energy source array combinations that may be used during the survey activities, and (2) measure the sounds produced by the icebreaker and seismic vessel as they travel through sea ice. Conducting the sound source and vessel measurements in ice-covered waters using bottom founded recorders creates a risk of not being able to retrieve the recorders and analyze the data until the following year. If the acoustic recorders are not deployed or are unable to be recovered because of too much sea ice, ION will use measurements of the same airgun source taken in the Canadian Beaufort Sea in 2010, along with sound velocity measurements taken in the Alaskan Beaufort Sea at the start of the 2012 survey to update the propagation model and estimate new exclusion zones. These modeled results will then be used for mitigation purposes during the remainder of the survey.
The airgun configurations measured will include at least the full 26 airgun array and the single 70 in  mitigation airgun that will be used during power downs. The measurements of airgun array sounds will be made by an acoustics contractor at the beginning of the survey and the distances to the various radii will be reported as soon as possible after recovery of the equipment. The primary area of concern will be the 190 and 180 dB re 1 μPa (rms) exclusion zones for pinnipeds and cetaceans, respectively, and the 160 dB re 1 μPa Level B harassment (for impulsive sources) radii. In addition to reporting the radii of specific regulatory concern, nominal distances to other sound isopleths down to 120 dB re 1 μPa (rms) will be reported in increments of 10 dB.
Data will be previewed in the field immediately after download from the hydrophone instruments. An initial sound source analysis will be supplied to NMFS and the airgun operators within 120 hours of completion of the measurements. The report will indicate the distances to sound levels based on fits of empirical transmission loss formulae to data in the endfire and broadside directions. A more detailed report will be issued to NMFS as part of the 90-day report following completion of the acoustic program.
B. Seismic Hydrophone Streamer Recordings of Vessel Sounds
Although some measurements of icebreaking sounds have previously been reported, acoustic data on vessels traveling through relatively light ice conditions, as will be the case during the proposed survey, are not available. In order to gather additional information on the sounds produced by this type of icebreaking, ION proposes to use the hydrophones in the seismic streamer on a routine basis throughout the survey. Once every hour the airguns would not be fired at 2 consecutive intervals (one seismic pulse interval is typically ∼18 seconds, so there will be ∼54 seconds between seismic pulses at this time) and instead a period of background sounds would be recorded, including the sounds generated by the vessels. Over the course of the survey this should generate as many as 750 records of vessel sounds traveling through various ice conditions (from open water to 100% cover juvenile first year ice or lighter multi-year ice). The acoustic data during each sampling period from each hydrophone along the 9 km (5.6 mi) streamer would be analyzed and used to estimate the propagation loss of the vessel sounds. The acoustic data received from the hydrophone streamer would be recorded at an effective bandwidth of 0-400 Hz. In order to estimate sound energy over a larger range of frequencies (broadband), results from previous measurements of icebreakers could be generalized and added to the data collected during this project.
C. Over-winter Acoustic Recorders
In order to collect additional data on the propagation of sounds produced by icebreaking and seismic airguns in ice-covered waters, as well as on vocalizing marine mammals, ION intends to collaborate with other Industry operators to deploy acoustic recorders in the Alaskan Beaufort Sea in fall 2012, to be retrieved during the 2013 open-water season.
During winter 2011-2012, AURAL acoustic recorders were deployed at or near each of the 5 acoustic array sites established by Shell for monitoring the fall bowhead whale migration through the Beaufort Sea, as well as one site near the shelf break in the central Alaskan Beaufort Sea. These recorders will be retrieved in July 2012, when Shell deploys Directional Autonomous Seafloor Acoustic Recorders (DASARs) at 5 array locations. When the DASAR arrays are retrieved in early October, ION intends to coordinate with Shell to re-deploy the 6 AURAL recorders to the same locations used during the 2011-2012 winter. Redeploying the recorders in the same locations will provide comparable data from a year with little to no offshore industrial activity (2011) to a year with more offshore industrial activity (2012). Acoustic data from the over-winter recorders will be analyzed to address the following objectives:
- Characterize the sounds and propagation distances produced by ION's source vessel, icebreaker, and airguns on and to the edge of the U.S. Beaufort Sea shelf,
- Characterize ambient sounds and marine mammal calls during October and November to assess the relative effect of ION's seismic survey on the background conditions, and to characterize marine mammal calling behavior, and
- Characterize ambient sound and enumerate marine mammal calls through acoustic sampling of the environment form December 2012 through July 2013, when little or no anthropogenic sounds are expected.
Monitoring Plan Peer Review
The MMPA requires that monitoring plans be independently peer reviewed “where the proposed activity may affect the availability of a species or stock for taking for subsistence uses” (16 U.S.C. 1371(a)(5)(D)(ii)(III)). Regarding this requirement, NMFS' implementing regulations state, “Upon receipt of a complete monitoring plan, and at its discretion, [NMFS] will either submit the plan to members of a peer review panel for review or within 60 days of receipt of the proposed monitoring plan, schedule a workshop to review the plan” (50 CFR 216.108(d)).
NMFS convened independent peer review panels to review ION's mitigation and monitoring plan in its IHA applications submitted in 2010 and 2011 for taking marine mammals incidental to the proposed seismic survey in the Beaufort and Chukchi Seas, during 2010 and 2011. The panels met on March 25 and 26, 2010, and on March 9, 2011, and provided their final report to NMFS on April 22, 2010 and on April 27, 2011, respectively. The full panel reports can be viewed at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
ION's proposed 2012 action is essentially the same as described in its 2010 and 2011 IHA applications. NMFS worked with ION in 2010 and 2011 to address the peer review panels' recommendations on its 2010 and 2011 4MPs. Since ION's 2012 4MP addressed all issues raised during the 2010 and 2011 peer reviews and incorporated all of NMFS' requested changes, no peer-review of ION's 2012 4MP was conducted.
In 2010, NMFS provided the panel with ION's 4MP and asked the panel to address the following questions and issues for ION's plan:
(1) The monitoring program should document the effects (including acoustic) on marine mammals and document or estimate the actual level of take as a result of the activity. Does the monitoring plan meet this goal?
(2) Ensure that the monitoring activities and methods described in the plan will enable the applicant to meet the requirements listed in (1) above;
(3) Are the applicant's objectives achievable based on the methods described in the plan?
(4) Are the applicant's objectives the most useful for understanding impacts on marine mammals?
(5) Should the applicant consider additional monitoring methods or modifications of proposed monitoring methods for the proposed activity? and
(6) What is the best way for an applicant to report their data and results to NMFS?
In 2011, NMFS revised its guidance to the peer review panel and asked the panel to focus on more specific questions:
(1) Are the applicant's stated objectives the most useful for understanding impacts on marine mammals and otherwise accomplishing the goals stated in the paragraph above?
(2) Are the applicant's stated objectives able to be achieved based on the methods described in the plan?
(3) Are there techniques not proposed by the applicant, or modifications to the techniques proposed by the applicant, that should be considered for inclusion in the applicant's monitoring program to better accomplish the goals stated above?
(4) What is the best way for an applicant to present their data and results (formatting, metrics, graphics, etc.) in the required reports that are to be submitted to NMFS?
In 2010, the panel members provided general recommendations that were applicable to all monitoring plans from all seismic activities during that year in section 3 of the report and recommendations that were specific to ION's in-ice seismic survey 4MP in section 4.1.
In 2011, the panel members provided general recommendations that were applicable to all monitoring plans from all seismic activities during that year in section 4 of the report and recommendations that were specific to ION's in-ice seismic survey 4MP in section 5.2.
NMFS reviewed the reports and evaluated all recommendations made by the panel. NMFS determined that there were several measures that ION could incorporate into its 2012 in-ice seismic survey monitoring plan. Additionally, there were other recommendations that NMFS has determined would also result in better data collection, and could potentially be implemented by oil and gas industry applicants, but which likely could not be implemented for the 2012 in-ice season due to technical issues (see below). While it may not be possible to implement those changes this year, NMFS believes that they are worthwhile and appropriate suggestions that may require additional technology advancement for them to be implemented, and ION should consider incorporating them into future monitoring plans should ION decide to apply for IHAs in the future.
The following subsections lay out measures from the panel reports that NMFS recommended for implementation as part of the 2012 in-ice seismic survey by ION and those that are recommended for future programs.
Recommendations for Inclusion in the 2012 4MP and IHA
Section 3.3 of the 2010 panel report contains several recommendations regarding PSOs, which were also included in a general list in the 2011 panel report. NMFS agreed that ION should incorporate these measures:
- Observers should be trained using visual aids (e.g., videos, photos), to help them identify the species that they are likely to encounter in the conditions under which the animals will likely be seen.
- Observers should understand the importance of classifying marine mammals as “unknown” or “unidentified” if they cannot identify the animals to species with confidence. In those cases, they should note any information that might aid in the identification of the marine mammal sighted. For example, for an unidentified mysticete whale, the observers should record whether the animal had a dorsal fin.
- Observers should attempt to maximize the time spent looking at the water and guarding the exclusion zones. They should avoid the tendency to spend too much time evaluating animal behavior or entering data on forms, both of which detract from their primary purpose of monitoring the exclusion zone.
- `Big eye' binoculars (e.g., 25 x 150 power) should be used from high perches on large, stable platforms. They are most useful for monitoring impact zones that extend beyond the effective line of sight. With two or three observers on watch, the use of big eyes should be paired with searching by naked eye, the latter allowing visual coverage of nearby areas to detect marine mammals. When a single observer is on duty, the observer should follow a regular schedule of shifting between searching by naked-eye, low-power binoculars, and big-eye binoculars based on the activity, the environmental conditions, and the marine mammals of concern.
- Observers should use the best possible positions for observing (e.g., outside and as high on the vessel as possible), taking into account weather and other working conditions.
- Whenever possible, new observers should be paired with experienced observers to avoid situations where lack of experience impairs the quality of observations. If there are Alaska Native MMOs, the MMO training that is conducted prior to the start of the survey activities should be conducted with both Alaska Native MMOs and biologist MMOs being trained at the same time in the same room. There should not be separate training courses for the different MMOs.
In Section 3.4 of the 2010 panel report, panelists recommend collecting some additional data to help verify the utility of the “ramp-up” requirement commonly contained in IHAs. To help evaluate the utility of ramp-up procedures, NMFS recommends that observers be required to record, analyze, and report their observations during any ramp-up period. NMFS also supports the inclusion of specific studies using multiple types of monitoring (visual, acoustic, tagging) to evaluate how marine mammals respond to increasing received sound levels. Such information should provide useful evidence as to whether ramp-up procedures are an effective form of mitigation.
In the same section of the 2010 report, panelists recommend collecting data to evaluate the efficacy of using FLIR vs. night-vision binoculars. The panelists note that while both of these devices may increase detection capabilities by PSOs of marine mammals, the reliability of these technologies should be tested under appropriate conditions and their efficacy evaluated. NMFS recommends that ION design a study using both FLIR and night-vision binoculars and collect data on levels of detection of marine mammals using each type of device.
Among other things, Section 3.5 of the 2010 panel report recommends recording visibility data because of the concern that the line-of-sight distance for observing marine mammals is reduced under certain conditions. PSOs should “carefully document visibility during observation periods so that total estimates of take can be corrected accordingly”.
Section 4.1 of the 2010 panel report contained recommendations specific to ION's 2010 2D marine seismic survey monitoring plan, which were also relevant to ION's 2012 4MP. NMFS worked with ION and decided that some of the measures presented in this section of the report, such as supporting overwintering buoy studies and coordinating in conducting tagging studies using satellite linked telemetry, were not ready for ION's to implement for its 2010 season operations, but are feasible for its 2012 season as ION has worked to make the necessary preparations over the past two years. In addition, the following recommendations will also be implemented for the 2012 season:
- Conduct sound source verification measurements to verify calculated exclusion zones to account for possible sound channels in deeper water.
- Summarize observation effort and conditions, the number of animals seen by species, the location and time of each sighting, position relative to the survey vessel, the company's activity at the time, each animal's response, and any adjustments made to operating procedures. Provide all spatial data on charts (always including vessel location).
- Make all data available in the report or (preferably) electronically for integration with data from other companies.
- Accommodate specific requests for raw data, including tracks of all vessels and aircraft associated with the operation and activity logs documenting when and what types of sounds are introduced into the environment by the operation.
NMFS spoke with ION about the inclusion of these recommendations into the 2012 4MP and IHA. ION indicated to NMFS that they will incorporate these recommendations into the 4MP, and NMFS will make several of these recommendations requirements in any issued IHA.
Section 4.3 of the 2011 report contains several recommendations regarding PSOs. NMFS agreed that the following measures should be incorporated into the 2012 4MP.
- PSOs record additional details about unidentified marine mammal sightings, such as “blow only”, mysticete with (or without) a dorsal fin, “seal splash”, etc. That information should also be included in 90-day and final reports.
In Section 4.7 of the 2011 panel report, panelists included a section regarding the need for a more robust and comprehensive means of assessing the collective or cumulative impact of many of the varied human activities that contribute noise into the Arctic environment. Specifically, for data analysis and integration, the panelists recommended, and NMFS agrees, that the following recommendations be incorporated into the 2012 program:
- To better assess impacts to marine mammals, data analysis should be separated into periods when a seismic airgun array (or a single mitigation airgun) is operating and when it is not. Final and comprehensive reports to NMFS should summarize and plot:
○ Data for periods when a seismic array is active and when it is not; and
○ The respective predicted received sound conditions over fairly large areas (tens of km) around operations.
- To help evaluate the effectiveness of PSOs and more effectively estimate take, reports should include sightability curves (detection functions) for distance-based analyses.
- To better understand the potential effects of oil and gas activities on marine mammals and to facilitate integration among companies and other researchers, the following data should be obtained and provided electronically in the final and comprehensive reports:
○ The location and time of each aerial or vessel-based sighting or acoustic detection;
○ Position of the sighting or acoustic detection relative to ongoing operations (i.e., distance from sightings to seismic operation, drilling ship, support ship, etc.), if known;
○ The nature of activities at the time (e.g., seismic on/off);
○ Any identifiable marine mammal behavioral response (sighting data should be collected in a manner that will not detract from the PSO's ability to detect marine mammals); and
○ Any adjustments made to operating procedures.
In Section 4.9 of the 2011 panel report, the panelists discussed improving take estimates and statistical inference into effects of the activities. NMFS agreed that the following measures should be incorporated into the 2012 4MP:
- Reported results from all hypothesis tests should include estimates of the associated statistical power.
- Estimate and report uncertainty in all take estimates. Uncertainty could be expressed by the presentation of confidence limits, a minimum-maximum, posterior probability distribution, etc.; the exact approach would be selected based on the sampling method and data available.
Section 5.2 of the 2011 report contained recommendations specific to ION's 2011 2D seismic survey monitoring plan. Of the recommendations presented in this section, NMFS determined that the following should be implemented for the 2012 season:
- ION should test thermal imaging technologies during the proposed activities.
- Airguns should be turned off for two shots (i.e., 60 seconds) to provide sufficient time to record the background noise associated with the vessels.
- ION should deploy overwintering acoustic recorders within their survey area during their eastward transit across the Alaskan Beaufort to the Canadian Beaufort Sea early in the summer. The recorders would monitor sounds during the summer, the seismic shoot, and over the winter. ION should contract someone to return in 2012 (2013 in the case that the seismic survey is delayed to 2012) to retrieve the instruments and analyze the data. These acoustic data would provide some true baseline information to compare the occurrence, distribution, and behavior of marine mammals at times when ION's activities are occurring and when they are absent. To accomplish this, ION should present a plan for an acoustic monitoring program to a NMFS-approved expert for review. The plan should consider the best placement of the instruments relative to ION's proposed activities, the expected distribution and gradients in marine mammal distribution, and other existing overwintering recorders. There are relatively few data on the distribution and relative abundance of marine mammals in the Beaufort Sea during ION's planned seismic survey.
- The report should clearly compare authorized takes to the level of actual estimated takes.
- Sightability curves (detection functions) for PSOs should be provided.
In addition, the panelists included a list of general recommendations from the 2010 Peer-review Panel Report to be implemented by operators in their 2011 open-water season activities. NMFS agreed that the following recommendations should be implemented in ION's 2012 monitoring plan (only those not mentioned previously in this document are noted here):
- Sightings should be entered and archived in a way that enables immediate geospatial depiction to facilitate operational awareness and analysis of risks to marine mammals. Real-time monitoring is especially important in areas of seasonal migration or influx of marine mammals. Various software packages for real-time data entry, mapping, and analysis are available for this purpose.
- Whenever possible, new observers should be paired with experienced observers to avoid situations where lack of experience impairs the quality of observations.
Recommendations for Inclusion in Future Monitoring Plans
Section 3.5 of the 2010 report recommends methods for conducting comprehensive monitoring of a large-scale seismic operation. One method for conducting this monitoring recommended by panel members is the use of passive acoustic devices. Additionally, Section 3.2 of the 2010 report encourages the use of such systems if aerial surveys will not be used for real-time mitigation monitoring. NMFS acknowledges that there are challenges involved in using this technology in conjunction with seismic airguns in this environment, especially in real time. However, NMFS recommends that ION work to help develop and improve this type of technology for use in the Arctic (and use it once it is available and effective), as it could be valuable both for real-time mitigation implementation, as well as for archival data collection.
The panelists also recommend adding a tagging component to monitoring plans. “Tagging of animals expected to be in the area where the survey is planned also may provide valuable information on the location of potentially affected animals and their behavioral responses to industrial activities. Although the panel recognized that such comprehensive monitoring might be difficult and expensive, such an effort (or set of efforts) reflects the complex nature of the challenge of conducting reliable, comprehensive monitoring for seismic or other relatively-intense industrial operations that ensonify large areas of ocean.” While this particular recommendation is not feasible for implementation in 2012, NMFS recommends that ION consider adding a tagging component to future seismic survey monitoring plans should ION decide to conduct such activities in future years.
To the extent possible, NMFS recommends implementing the recommendation contained in Section 4.1.6 of the 2010 report: “Integrate all observer data with information from tagging and acoustic studies to provide a more comprehensive description of the acoustic environment during its survey.” However, NMFS recognizes that this integration process may take time to implement. Therefore, ION should begin considering methods for the integration of the observer data now if ION intends to apply for IHAs in the future.
In Section 4.7 of the 2011 report, the panelists stated that advances in integrating data from multiple platforms through the use of standardized data formats are needed to increase the statistical power to assess potential effects. Therefore, the panelists recommended that industry examine this issue and jointly propose one or several data integration methods to NMFS at the Open Water Meeting in 2012 (in this case, at the Open Water Meeting in 2013, since ION cancelled its proposed 2011 operation). NMFS concurs with the recommendation and encourages ION to collaborate with other companies to discuss data integration methods to achieve these efforts and to present the results of those discussions at the 2013 Open Water Meeting.
Other Recommendations in the Report
The panel also made several recommendations in 2010, which were not discussed in the two preceding subsections. NMFS determined that many of the recommendations were made beyond the bounds of what the panel members were tasked to do. For example, the panel recommended that NMFS begin a transition away from using a single metric of acoustic exposure to estimate the potential effects of anthropogenic sound on marine living resources. This is not a recommendation about monitoring but rather addresses a NMFS policy issue. NMFS is currently in the process of revising its acoustic guidelines on a national scale. Section 3.7 of the 2010 report contains several recommendations regarding comprehensive ecosystem assessments and cumulative impacts. These are good, broad recommendations, however, the implementation of these recommendations would not be the responsibility solely of oil and gas industry applicants. The recommendations require the cooperation and input of several groups, including Federal, state, and local government agencies, members of other industries, and members of the scientific research community. NMFS will encourage the industry and others to build the relationships and infrastructure necessary to pursue these goals, and incorporate these recommendations into future MMPA authorizations, as appropriate. Section 3.8 of the 2010 report makes a recommendation regarding data sharing and reducing the duplication of seismic survey effort. While this is a valid recommendation, it does not relate to monitoring or address any of the six questions which the panel members were tasked to answer.
For some of the recommendations, NMFS determined that additional clarification was required by the panel members before NMFS could determine whether or not applicants should incorporate them into the monitoring plans. NMFS asked for additional clarification on some of the recommendations regarding data collection and take estimate calculations. In addition, NMFS asked the panel members for clarification on the recommendation contained in Section 3.6 of the 2010 report regarding baseline studies.
Reporting Measures Back to Top
(1) SSV Report
A report on the preliminary results of the acoustic verification measurements, including as a minimum the measured 190-, 180-, 160-, and 120-dB re 1 μPa (rms) radii of the airgun arrays will be submitted within 120 hr after collection and analysis of those measurements at the start of the field season. This report will specify the distances of the exclusion zones that were adopted for the marine survey activities.
(2) Field Reports
Throughout the survey program, the observers will prepare a report each day or at such other intervals as the IHA may specify (if issued), or ION may require summarizing the recent results of the monitoring program. The field reports will summarize the species and numbers of marine mammals sighted. These reports will be provided to NMFS and to the survey operators.
(3) Technical Reports
The results of the vessel-based monitoring, including estimates of “take by harassment”, will be presented in the 90-day and final technical reports. Reporting will address the requirements established by NMFS in the IHA (if issued). The technical report will include:
(a) Summaries of monitoring effort: total hours, total distances, and distribution of marine mammals through the study period accounting for sea state and other factors affecting visibility and detectability of marine mammals;
(b) Methods, results, and interpretation pertaining to all acoustic characterization work and vessel-based monitoring;
(c) Analyses of the effects of various factors influencing detectability of marine mammals including sea state, number of observers, and fog/glare;
(d) Species composition, occurrence, and distribution of marine mammal sightings including date, water depth, numbers, age/size/gender categories, group sizes, and ice cover; and
(e) Analyses of the effects of survey operations:
- Sighting rates of marine mammals during periods with and without airgun activities (and other variables that could affect detectability);
- Initial sighting distances versus airgun activity state;
- Closest point of approach versus airgun activity state;
- Observed behaviors and types of movements versus airgun activity state;
- Numbers of sightings/individuals seen versus airgun activity state;
- Distribution around the survey vessel versus airgun activity state; and
- Estimates of “take by harassment”.
(4) Notification of Injured or Dead Marine Mammals
In addition to the reporting measures proposed by ION, NMFS will require that ION notify NMFS' Office of Protected Resources and NMFS' Stranding Network of sighting an injured or dead marine mammal in the vicinity of marine survey operations. Depending on the circumstance of the incident, ION shall take one of the following reporting protocols when an injured or dead marine mammal is discovered in the vicinity of the action area.
(a) In the unanticipated event that survey operations clearly cause the take of a marine mammal in a manner prohibited by this Authorization, such as an injury, serious injury or mortality (e.g., ship-strike, gear interaction, and/or entanglement), ION shall immediately cease survey operations and immediately report the incident to the Supervisor of Incidental Take Program, Permits and Conservation Division, Office of Protected Resources, NMFS, and the Alaska Regional Stranding Coordinators. The report must include the following information:
(i) Time, date, and location (latitude/longitude) of the incident;
(ii) The name and type of vessel involved;
(iii) The vessel's speed during and leading up to the incident;
(iv) Description of the incident;
(v) Status of all sound source use in the 24 hours preceding the incident;
(vi) Water depth;
(vii) Environmental conditions (e.g., wind speed and direction, Beaufort sea state, cloud cover, and visibility);
(viii) Description of marine mammal observations in the 24 hours preceding the incident;
(ix) Species identification or description of the animal(s) involved;
(x) The fate of the animal(s); and
(xi) Photographs or video footage of the animal (if equipment is available).
Activities shall not resume until NMFS is able to review the circumstances of the prohibited take. NMFS shall work with ION to determine what is necessary to minimize the likelihood of further prohibited take and ensure MMPA compliance. ION may not resume their activities until notified by NMFS via letter, email, or telephone.
(b) In the event that ION discovers an injured or dead marine mammal, and the lead PSO determines that the cause of the injury or death is unknown and the death is relatively recent (i.e., in less than a moderate state of decomposition as described in the next paragraph), ION will immediately report the incident to the Supervisor of the Incidental Take Program, Permits and Conservation Division, Office of Protected Resources, NMFS, and the Alaska Regional Stranding Coordinators. The report must include the same information identified above. Activities may continue while NMFS reviews the circumstances of the incident. NMFS will work with ION to determine whether modifications in the activities are appropriate.
(c) In the event that ION discovers an injured or dead marine mammal, and the lead PSO determines that the injury or death is not associated with or related to the activities authorized in the IHA (if issued) (e.g., previously wounded animal, carcass with moderate to advanced decomposition, or scavenger damage), ION shall report the incident to the Supervisor of the Incidental Take Program, Permits and Conservation Division, Office of Protected Resources, NMFS, and the Alaska Regional Stranding Coordinators, within 24 hours of the discovery. ION shall provide photographs or video footage (if available) or other documentation of the stranded animal sighting to NMFS and the Marine Mammal Stranding Network. ION can continue its operations under such a case.
Estimated Take by Incidental Harassment Back to Top
Except with respect to certain activities not pertinent here (military readiness activities), 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]. For the most part, only take by Level B behavioral harassment is anticipated as a result of the proposed marine seismic survey. However, due to the limited effectiveness of marine mammal monitoring during ice cover and in darkness, NMFS has preliminarily determined that Level A takes of a few individuals of marine mammals could occur if the animals remain undetected within the exclusion zones for a prolonged period of time. Although NMFS believes this is not very likely, NMFS is proposing to authorize limited takes from Level A harassment in order to address the uncertainty regarding the effectiveness of the proposed monitoring measures in these conditions. Anticipated impacts to marine mammals are associated with noise propagation from the seismic airgun(s) and the icebreaking used during the seismic survey.
The full suite of potential impacts to marine mammals was described in detail in the “Potential Effects of the Specified Activity on Marine Mammals” section found earlier in this document. The potential effects of sound from the proposed marine survey programs might include one or more of the following: tolerance; masking of natural sounds; behavioral disturbance; non-auditory physical effects; and, at least in theory, temporary or permanent hearing impairment (Richardson et al. 1995). As discussed earlier in this document, the most common impact will likely be from behavioral disturbance, including avoidance of the ensonified area or changes in speed, direction, and/or diving profile of the animal.
NMFS uses the 160 dB and 120 dB re 1 μPa (rms) isopleths to indicate the onset of Level B harassment by seismic airgun impulses and by icebreaking noises, respectively. ION provided calculations for the 160-dB and 120-dB isopleths produced by these active acoustic sources and then used those isopleths to estimate takes by harassment. NMFS used the calculations to make preliminary findings under the MMPA. ION provided a full description of the methodology used to estimate takes by harassment in its IHA application (see ADDRESSES), which is also described in the following sections.
ION has requested an authorization to take ten marine mammal species by Level B harassment. These ten marine mammal species are: beluga whale, harbor porpoise, bowhead whale, gray whale, humpback whale, minke whale, bearded seal, ringed seal, spotted seal, and ribbon seal. However, NMFS does not anticipate that humpback whales are likely to be encountered during the season of ION's icebreaking seismic survey. Therefore, NMFS determined that only nine of the species could be affected and potentially taken by harassment. In addition, although unlikely, NMFS determined that Level A takes of beluga whales, bowhead whales, and ringed seals could also occur, as the proposed monitoring and mitigation measures may not be 100% effective due to ice coverage and long periods of darkness.
Basis for Estimating “Take by Harassment”
As stated previously, it is current NMFS practice to estimate take by Level A harassment for received levels above 180 dB re 1μPa (rms) for cetaceans and 190 dB re 1μPa (rms) for pinnipeds, and take by Level B harassment for all marine mammals under NMFS jurisdiction by impulse sounds at a received level above 160 dB re 1μPa (rms) and by non-impulse sounds at a received level above 120 dB re 1μPa (rms). However, not all animals are equally affected by the same received noise levels and, as described earlier, in most cases marine mammals are not likely to be taken by Level A harassment (injury) when exposed to received levels higher than 180 dB for a brief period of time.
For behavioral harassment, marine mammals will likely not show strong reactions (and in some cases any reaction) until sounds are much stronger than 160 or 120 dB (for impulse and continuous sounds, respectively). Southall et al. (2007) provide a severity scale for ranking observed behavioral responses of both free-ranging marine mammals and laboratory subjects to various types of anthropogenic sound (see Table 4 in Southall et al. (2007)). Tables 7, 9, and 11 in Southall et al. (2007) outline the numbers of low-frequency cetaceans, mid-frequency cetaceans, and pinnipeds in water, respectively, reported as having behavioral responses to multi-pulses in 10-dB received level increments. These tables illustrate that the more severe reactions did not occur until sounds were much higher than 160 dB re 1μPa (rms).
Anticipated takes would include “takes by harassment” involving temporary changes in behavior (Level B harassment) and TTS (Level B harassment). NMFS does not consider injury (Level A harassment) to be likely, however, due to the limited effectiveness of monitoring and mitigation measures for animals undetected under the ice and/or during the long periods of darkness, a small amount of Level A harassment takes are also proposed to be authorized. The sections below describe methods used to estimate “take by harassment” and present estimates of the numbers of marine mammals that might be affected during the proposed seismic survey in the U.S. Beaufort Sea. The estimates are based on data obtained during marine mammal surveys in the Beaufort Sea and on estimates of the sizes of the areas where effects could potentially occur. In some cases, these estimates were made from data collected from regions and habitats that differed from the proposed project area. Adjustments to reported population or density estimates were made on a case by case basis to account for differences between the source data and the available information on the distribution and abundance of the species in the project area. This section provides estimates of the number of potential “exposures” to impulsive sound levels ≥160 dB re 1 μPa (rms), non-pulse sound levels ≥120 dB (rms) from icebreaking, and also includes estimates of exposures to ≥180 dB (rms) for cetaceans and ≥190 dB (rms) for seals.
Although several systematic surveys of marine mammals have been conducted in the southern Beaufort Sea during spring and summer, few data (systematic or otherwise) are available on the distribution and numbers of marine mammals during the early winter period of this survey, particularly in the northern Beaufort Sea. The main sources of distributional and numerical data used in deriving the estimates are described in the next subsection. There is some uncertainty about how representative those data are and the assumptions used below to estimate the potential “take by harassment”. However, the approach used here is accepted by NMFS as the best available at this time. The following estimates are based on a consideration of the number of marine mammals that might be disturbed appreciably by ∼7,250 line kilometers (4,505 line miles) of seismic surveys across the Beaufort Sea and, to a lesser extent, the northern Chukchi Sea.
Marine Mammal Density Estimates
This section describes the estimated densities of marine mammals that may occur in the survey area. The area of water that may be ensonified to various levels is described below in the section Potential Number of “Takes by Harassment.” Although a marine mammal may be exposed to icebreaking sounds > 120 dB (rms) or airgun sounds > 160 dB (rms), this does not mean that it will actually exhibit a disruption of behavioral patterns in response to the sound source. Rather, the estimates provided here are simply the best estimates of the number of animals that potentially could have a behavioral modification due to the noise. However, not all animals react to sounds at this low level, and many will not show strong reactions (and in some cases any reaction) until sounds are much stronger. There are several variables that determine whether or not an individual animal will exhibit a response to the sound, such as the age of the animal, previous exposure to this type of anthropogenic sound, habituation, etc.
The survey has been designed to minimize interactions with marine mammals by planning to conduct the work at times and in areas where the relative density of marine mammals is expected to be quite low. The survey will begin in offshore waters (>1,000 m [3,281 ft] deep) of the eastern U.S. Beaufort Sea (east survey area) in early October. Weather and ice permitting, the waters <1,000 m (3,281 ft) deep will not be surveyed until mid-October and thereafter, in order to avoid migrating bowhead whales. The western U.S. Beaufort Sea and north-eastern Chukchi Sea (west survey area) is not expected to be surveyed until late October through December.
Separate densities were calculated for habitats specific to cetaceans and pinnipeds. For cetaceans, densities were estimated for areas of water depth <200 m (656 ft), 200-1,000 m (656-3,281 ft), and >1,000 m (3,281 ft), which approximately correspond to the continental shelf, the continental slope, and the abyssal plain, respectively. Separate densities of both cetacean and pinnipeds were also estimated for the east and west survey areas within each water depth category. However, pinniped densities in the west survey area and <200 m (656 ft) water depth category were further sub-divided into <35 m (115 ft) and 35-200 m (115-656 ft) depth categories. This was done because the west survey area is not expected to be surveyed until November-December, and based on historic sea ice data (NOAA National Ice Center, available online at www.natice.noaa.gov), it is expected that substantial amounts of sea ice, including shorefast ice, will be present in the west survey area at that time. Past studies have found that seal densities in ice-covered areas of the Beaufort Sea are different where water depths are <35 m (115 ft) and >35 m (Moulton et al., 2002; Frost et al., 2004); therefore, densities were calculated separately for these water depths. The north-eastern Chukchi Sea is composed of mostly continental shelf waters between 30 m (98 ft) and 200 m (656 ft) in depth, so only a single density estimate for each marine mammal species was used in that area. Since most marine mammals will be continuing their southerly migration in November and early December, the same density estimates for continental shelf waters in the west survey area of the Beaufort Sea were used in the Chukchi Sea. When the seismic survey area is on the edge of the range of a species at this time of year, it is assumed that the average density along the seismic trackline will be 10% (0.10×) the density determined from available survey data within the main range. Density estimates for the Chukchi Sea during the period of November-December were taken from the west survey density estimates at the appropriate depth.
Detectability bias, quantified in part by f(0), is associated with diminishing sightability with increasing lateral distance from the survey trackline. Availability bias, g(0), refers to the fact that there is <100% probability of sighting an animal that is present along the survey trackline. Some sources used below took account of one or both of these correction factors in reporting densities. When these factors had not been accounted for, the best available correction factors from similar studies and/or species were applied to reported results. Details regarding the application of correction factors are provided below for each species.
Beluga Whales: Beluga density estimates were calculated based on aerial survey data collected in October in the eastern Alaskan Beaufort Sea by the NMML (as part of the Bowhead Whale Aerial Survey Project (BWASP) program funded by BOEM) in 2007-2010. They reported 31 sightings of 66 individual whales during 1,597 km (992 mi) of on-transect effort over waters 200-2,000 m (656-6,562 ft) deep. An f(0) value of 2.326 was applied and it was calculated using beluga whale sightings data collected in the Canadian Beaufort Sea (Innes et al. 2002). A g(0) value of 0.419 was used that represents a combination of ga(0) = 0.55 (Innes et al., 2002) and gd(0) = 0.762 (Harwood et al., 1996). The resulting density estimate (0.1169 individuals/km  ; Table 2 in this document) was applied to areas of 200-1,000 m (656 -3,281 ft). There were 3 sightings of 4 individual beluga whales during 7,482 km (4,649 mi) of on-transect effort over waters 0-200 m (0-656 ft) deep during this same time period. Using the same f(0) and g(0) values from above, the resulting density estimate for continental shelf waters (0-200 m deep) is 0.0015 individuals/km  (Table 2 in this document). The density estimate for waters >1000 m (3,281 ft) deep was estimated as 40% of the 200-1,000 m (656-3,281 ft) density based on the relative number of sightings in the two water depth categories. For all water depth and survey area categories, the maximum beluga density estimates represent the mean estimates multiplied by four to allow for chance encounters with unexpected large groups of animals or overall higher densities than expected.
Beluga density estimates for the west survey area, which is planned to be surveyed beginning in November, represent the east survey area estimates multiplied by 0.1 because the Beaufort Sea and north-eastern Chukchi Sea is believed to be at the edge of the species' range in November-December. Belugas typically migrate into the Bering Sea for the winter (Allen and Angliss, 2011) and are not expected to be present in the study area in high numbers in November-December. Satellite tagging data support this and indicate belugas migrate out of the Beaufort Sea in the October-November period (Suydam et al., 2005).
Bowhead Whales: Bowhead whale density estimates were calculated based on aerial survey data collected in the Beaufort Sea as part of the BWASP program funded by BOEM. The average density estimate was based on surveys in October 2007-2010 and the maximum density estimate was based on surveys conducted in October 1997-2004. The earlier data were used to calculate the maximum estimate becaus