ENDANGERED SPECIES ACT - SECTION 7 CONSULTATION

BIOLOGICAL OPINION

AGENCY: Minerals Management Service

National Marine Fisheries Service

ACTIVITY: Oil and Gas Leasing and Exploration Activities in the U.S. Beaufort and Chukchi

Seas, Alaska; and Authorization of Small Takes Under the Marine Mammal Protection Act

CONSULTATION CONDUCTED BY: National Marine Fisheries Service

APPROVED BY:

DATE ISSUED:
Biological Opinion 

The U.S. Minerals Management Service (MMS) and NOAA Fisheries, Office of Protected 

Resources, have formally consulted National Marine Fisheries Service, Alaska Region, on the 

potential effects of oil and gas leasing and exploration in the U. S. Beaufort Sea and Chukchi 

Seas, and authorization of “small take” permits under section 101 (a)(5) of the Marine Mammal 

Protection Act, as amended. This opinion considers the effects of these actions on threatened 

and endangered species under the jurisdiction of NOAA Fisheries. In formulating this 

Biological Opinion, NOAA Fisheries used information presented in the MMS’s 2008 

Supplement to the 2006 Biological Evaluation of the Potential Effects of Oiland Gas Leasing 

and Exploration in the Alaska OCS Beaufort Sea and Chukchi Sea Planning Areas on 

Endangered Bowhead Whales (Balaena mysticetus), Fin Whales (Balaenoptera physalus), and 

Humpback Whales (Megaptera novaeangliae), NMFS’s 2006 Draft Recovery Plan for Fin 

Whales, NMFS’s 1991 Recovery Plan for Humpback Whales, NMFS’s 2008 Marine Mammal 

Stock Assessment Reports, reports from the International Whaling Commission along with other 

research relating to bowhead whales and information provided by NOAA=s National Marine 

Mammal Laboratory, the North Slope Borough, the Alaska Eskimo Whaling Commission, and 

the traditional knowledge of the Alaskan Eskimo community. 

Consultation History 

Pursuant to requirements under the Endangered Species Act of 1973, as amended (ESA), 

Minerals Management Service (MMS) has previously consulted with the National Marine 

Fisheries Service (NMFS) on the potential effects of oil and gas leasing and exploration in the 

Arctic, including activities in the Beaufort Sea and Chukchi Sea Planning Areas. Between 1980 

and 1987, inclusive, MMS and NMFS repeatedly consulted on lease sales in the Beaufort Sea, 

Chukchi Sea, and Hope Basin Planning Areas. Between 1982 and 1987, inclusive, NMFS 

issued seven Biological Opinions related to Outer Continental Shelf (OCS) lease sales. In 

November 1988, NMFS concluded an incremental step consultation; the Arctic Regional 

Biological Opinion (ARBO), which concerned leasing and exploration activities in the Arctic 

Region (Beaufort Sea, Chukchi Sea, and Hope Basin OCS Planning Areas). Because of the 

removal of the gray whale from the list of threatened and endangered species, the availability of 

new information on the potential impacts of oil and gas-related noise on bowhead whales, the 

use of new seismic survey technology in the Arctic, and trends in OCS activities in the Arctic 

Region, this consultation was re-initiated in 1999. Due to lack of industry interest in the 

Chukchi Sea and Hope Basin Planning Areas at that time this consultation concerned leasing 

and exploration activities only in the Beaufort Sea Planning Area. A revised Biological Opinion 

for Oil and Gas Leasing and Exploration Activities in the Beaufort Sea was issued May 25, 

2001. The action area for that opinion was defined as the Alaskan Beaufort Sea Planning Area, 

extending from the Canadian border to the Barrow area. The 2001 Biological Opinion 

concluded that oil and gas leasing and exploration in the Beaufort Sea was not likely to 

jeopardize the continued existence of bowhead whales. 

Due to industry response to MMS’ recent Beaufort Sea lease sales and call for information and 

nominations in the Chukchi Sea, and based on discussions with industry, MMS requested reinitiation of consultation in 2006 so that the area of coverage would included OCS planning 

areas in both the Beaufort and Chukchi Seas. A revised opinion was issued in March 2006. 

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Recently, monitoring by industry has indicated the presence of humpback and, possibly, fin 

whales in the action area. Responding to this new information, MMS requested re-initiation of 

consultation on May 8, 2008, and provided a Biological Evaluation of the potential 

consequences of their actions to these species. 

 

I. DESCRIPTION OF THE PROPOSED ACTION 

This opinion will address oil and gas leasing and exploration by the U.S. Department of the 

Interior, MMS, on the Outer Continental Shelf (OCS) waters of the Chukchi and Beaufort Seas. 

Its purpose is to provide an assessment of those actions on the continued existence of the 

bowhead whale, humpback whale, and fin whale, as well as to provide measures to conserve the 

species and mitigate impact. Federal oil and gas leasing consists of several stages, or 

increments; 1) leasing and exploration, 2) development, production, and transportation, and 3) 

abandonment. The MMS offers leases on the OCS through periodic sales. Exploration 

activities may occur prior to or after such sales, while later phases of leasing would all be postlease actions. Various actions may be associated with each phase of the leasing process. 

Leasing and Exploration 

* Seismic geophysical surveys 

* High-resolution and shallow hazard surveys 

* Exploratory drilling using various platforms 

* Boat and aircraft activity 

Development, production, and transportation 

* Drilling from artificial islands, drilling platforms, or drill ships 

* Pipelines 

* Tankering 

Abandonment 

* Rig demobilization 

* Platform removal 

* Site restoration 

This consultation as it relates to the MMS actions will address the first of these incremental 

steps: leasing and exploration. Subsequent phases of OCS development (production, 

transportation, and abandonment) will require additional consultation. This is due in part to 

uncertainty at this time and the many variables associated with individual tract development. 

There is, in fact, considerable chance that economic quantities of recoverable oil may not be 

discovered, and no subsequent phases would occur. However, some information on the later 

phases is presented and assessed in this opinion in order to provide an adequate evaluation 

regarding the reasonable likelihood of the entire action violating section 7(a)(2) of the 

Endangered Species Act, as amended. Should commercially producible quantities of oil be 

discovered and development and production be proposed, MMS would initiate new formal 

consultation. Further consultation would also occur if additional species were listed or critical 

habitat designated, if the proposed action were substantially modified, or if significant new 

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effects-related information were developed. This Biological Opinion incorporates much of the 

information presented within the Biological Evaluation (BE) prepared by MMS, as well as 

pertinent research on bowhead, humpback, and fin whales and matters related to oil exploration. 

Traditional knowledge and the observations of Inupiat hunters are presented, along with 

information gained through scientific research. This knowledge contributes, along with 

scientific information, to a more complete understanding of these issues. A reasonable 

assessment of potential effects can only be made by considering both these systems of 

knowledge. 

This opinion will also address authorization of the incidental and unintentional taking of fin, 

humpback, and bowhead whales due to certain oil and gas exploration activities by NMFS. 

Section 101 (a)(5) of the Marine Mammal Protection Act (MMPA), directs the Secretary of 

Commerce to allow, upon request by U.S. citizens engaged in a specific activity (other than 

commercial fishing) in a specified geographical region, the incidental but not intentional taking 

of small numbers of marine mammals if certain findings are made. Such authorization may be 

accomplished through regulations and issuance of letters of authorization under those 

regulations, or through issuance of an incidental harassment authorization (IHA). These 

authorizations may be granted only if an activity would have no more than a negligible effect on 

the species (or stock) in question, would not have an unmitigable adverse impact on the 

availability of the marine mammal for subsistence uses, and that the permissible method of 

taking and requirements pertaining to the monitoring and reporting of such taking are set forth to 

ensure the activity will have the least practicable adverse effect on the species or stock and its 

habitat. These authorizations are often requested for oil and gas activities which produce 

underwater noise capable of harassing or harming marine mammals. Harassment is a form of 

taking otherwise prohibited by the MMPA and ESA. While MMS permits issued under the 

Outer Continental Shelf Lands Act are necessarily confined to Federal waters of the U.S. Outer 

Continental Shelf, MMPA authorizations may be issued for work within State of Alaska waters 

of the Chukchi and Beaufort Seas. 

The actions, consequence, and environmental effects of these MMPA authorizations are the 

same as those described here for the oil and gas leasing and exploration activities (i.e., the 

activities for which an MMPA authorization would be issued). However, the actual 

consequence of these incidental take authorizations are likely to be less overall than that 

associated with leasing and exploration, because 1) not all actions may be authorized, 2) these 

authorizations only apply to unintentional and incidental takes, 3) illegal activity such as an oil 

spill cannot be authorized under this program, and 4) the level of authorized take may not result 

in more than a negligible impact to marine mammals, including these endangered whales. 

Term of this Opinion 

This opinion will be valid upon issuance and remain in force until re-initiation may become 

necessary. Consultation will be re-initiated if there are significant changes in the type of 

exploratory activities occurring, if new information indicates these actions are impacting the 

bowhead stock or other listed species/critical habitats to a degree or in a manner not previously 

considered, or if new species are listed or critical habitat are designated or revised become under 

the Act. 

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Action Area 

The action area for purposes of this Biological Opinion is defined as the Alaskan Beaufort and 

Chukchi Seas. The direct and indirect effects of this action on the endangered fin, humpback, 

and bowhead whale are expected to be confined to the action area. 

Leasing and Exploration Activities 

The opinion provides an exploration scenario based on a composite of feasible options that 

could be developed. The options are the result of discussions within MMS, the State of Alaska, 

other government agencies, and with industry. The locations of existing infrastructure, sites 

with potential as support facilities, area-resource estimates, and scenarios developed for previous 

OCS sales in these waters were all considered in developing this scenario. A summary of the 

major exploration assumptions follows: 

 Exploration Activities in the Beaufort Sea

A detailed description of all exploratory activity associated with this action cannot be made at 

this time, as it will depend on the interests of the oil and gas industry, oil prices and other 

economic considerations, and other factors. However, for purposes of analyses MMS assumes 

that a maximum of two drilling rigs would operate at any time, with a total of six exploration 

and six delineation wells expected to be drilled over the 8-year exploration period. 

Exploration activity (seismic surveys and drilling) will begin with seismic surveying in summer 

of 2006 and continue through 2013, with delineation wells drilled through 2014. The type of 

units that might be used in exploration drilling would depend on water depth, sea-ice conditions, 

ice-resistance of the units, and availability of drilling units. Artificial ice islands grounded on 

the seabed have been used as drilling platforms in shallow water (less than 10 meters [m]), and 

nearshore operations would be supported by ice roads over the landfast ice. Gravel islands are 

not likely to be constructed for exploration drilling in OCS waters (generally deeper than 10 m), 

although older artificial islands or natural shoals could be used as a base for temporary gravel or 

ice islands. Movable platforms resting on the seafloor likely would be used for exploration 

drilling. These platforms are designed to withstand winter ice forces, and drilling could be 

conducted year-round. Bottom-founded platforms (set on the seafloor) could be used to drill 

prospects in water depths of 10-20 m, and drillships or other types of floating platforms would 

be used in deeper water. These floating systems can operate only in open-water and broken-ice 

conditions and not in midwinter pack-ice conditions. Because mobile ice conditions in deeper 

water make ice roads unfeasible, deeper water (Far Zone) operations would take place during the 

summer open-water season and would be supported by icebreakers and supply boats. They 

would be stored in protected inshore areas when not in use. 

Based on geologic studies, MMS assumes that exploration and delineation wells generally 

would test prospects from 3,000-15,000 feet (ft) (914-4,572 m), and a representative 

exploration-well depth of 7,000 ft (2,133 m). At this depth, each exploratory or delineation well 

would require 425 short tons of drilling muds (dry weight) and produce approximately 525 short 

tons of dry rock cuttings. MMS assumes that 80% of the drilling muds would be recycled, 

leaving 85 tons of “spent mud” to be discharged along with all the drill cuttings at each 

exploration site or disposed of onshore. MMS estimates that 935-1,040 short tons (dry weight) 

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of drilling muds and 5,775-6,300 short tons (dry weight) of bore cuttings would need to be 

disposed of for the exploration and delineation activities for each sale. These materials would be 

disposed of primarily at the drill site under conditions prescribed by the Environmental 

Protection Agency’s National Pollution Discharge Elimination System (NPDES) (Clean Water 

Act of 1977, as amended (33 U.S.C. 1251 et seq.). 

High-resolution seismic survey is the preferred method used by the oil and gas industry to 

provide required information on shallow hazards, archaeological resources, and potential benthic 

communities in support of proposed exploration and development plans. Typical highresolution seismic survey operations are described in Section IV. 

MMS also estimates that no more than seven 2D/3D seismic surveys would occur in the 

Chukchi and Beaufort Sea planning areas each year. 

Offshore exploration-drilling operations in the Beaufort Sea may require onshore support 

facilities such as the following: 

• a staging area for construction equipment, drilling equipment, and supplies; 

• a transfer point for drilling and construction personnel; 

• a harbor to serve as a base for vessels required to support offshore operations; and 

• an airfield for fixed-wing aircraft and helicopters. 

Typically, a mobile drilling platform used for exploration drilling would enter its area of 

operation fully supplied for the drilling season. The level of support-boat traffic would vary by 

distance from shore and/or support base and whether or not the facility can be supported by 

vehicles using ice roads in the winter. 

Ice roads are assumed to be the principal route for transporting routine supplies and materials to 

ice islands and/or nearshore gravel islands. For drilling platforms farther offshore in the brokenice zone, material and supplies would be transported by support/supply boats (with icebreaking 

capacity, if necessary) during the open-water season and by helicopter at all other times. For 

both types of drilling structures, it is probable that most personnel would be transported by 

helicopters. The number of helicopter trips flown in support of exploration and delineation well 

drilling is assumed to range from about 90-270 each year, depending on the number of wells (1-

3) that are drilled. For each drilling operation, we assume there would be one flight per day of 

drilling. The time required to drill and test a well is about 90 days. 

Exploration Activities in the Chukchi Sea 

Approximately 100,000 line-miles of 2D seismic surveys have been collected to-date in the 

Chukchi Planning Area. Additional 3D surveys have occurred in 2006, 2007, and are planned 

for 2008. The number of high energy seismic surveys is expected to decrease over time as data 

is collected over most prospects. 3D seismic surveys can only be conducted during open water 

(approximately June to November). Seismic surveys in the Chukchi will probably be 

coordinated with surveys in the Beaufort Sea to employ the same vessels. An icebreaker may be 

used as a support boat and this would ensure that the large seismic vessel could exit the area at 

the end of the season. The rate of seismic survey may average 20-30 days (with downtime) to 

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cover a 200-mi2

 area. At normal vessel speeds, the airgun array would produce a sound signal 

every 10-15 seconds. One or more seismic surveys may be conducted (with down time) during 

the entire open water period as compatible with mitigation requirements. Each permit may 

authorize multiple surveys in a planning area. So, surveys in different parts of a planning area 

may overlap in time.

Based on mapping of the subsurface structures using 3D seismic data, several well locations will 

be proposed. Prior to drilling deep test wells, high-resolution site-clearance seismic surveys and 

geotechnical studies will examine the proposed exploration drilling locations for geologic 

hazards, archeological features, and biological populations. Site clearance and studies required 

for exploration will be conducted during the open water season before the drill rig is mobilized 

to the site. Such activities are expected to begin in 2008. 

Considering water depth and the remoteness of this area, drilling operations are likely to employ 

drillships with icebreaker support vessels. Water depths greater than 100 ft and possible packice incursions during the open water season will preclude the use of bottom-founded drilling 

platforms. Using drillships allows the operator to temporarily move off the drill site, if sea or 

ice conditions require it, and the suspended well is controlled by so-called blow-out-prevention 

equipment installed on wellheads on the seabed. Bottom-founded platforms that are more 

permanently installed are better choices for production platforms. Drilling operations are 

expected to range between 30 and 90 days at different well sites, depending on the depth to the 

target formation, difficulties during drilling, and logging/testing operations. Considering the 

relatively short open water season in the Chukchi (June-November), only 1-2 wells are expected 

per drilling season. MMS assumes that one well could be drilled, tested, and abandoned and 

another well could be started each summer season. Five exploration wells have been drilled todate on the Chukchi shelf and MMS assumes that 7-14 additional wells will be needed to 

discover and delineate the first commercial field. 

Seismic geophysical operations will occur during exploration phases of leasing for both the 

Chukchi and Beaufort Seas. The MMS anticipates a maximum of seven (7) 2D/3D marine 

streamer seismic operations to be conducted annually in the Chukchi and Beaufort Seas. 

In addition to high energy/low resolution seismic work (2D/3D), there will be need for highresolution seismic and other exploratory activities which look for shallow hazards, bottom depth 

and contours, or are otherwise necessary for site preparation work prior to drilling. These 

devices use lower energy and sound than 2D/3D seismic and sound would be less likely to travel 

as far. 

II. STATUS OF THE SPECIES (RANGEWIDE) 

NMFS has determined that the described actions may affect the following species provided 

protection under the Endangered Species Act of 1973 (16 U.S.C. 1531 et seq.; ESA): 

Marine Mammals 

Fin whale (Balaenoptera physalus) Endangered 

Bowhead whale (Balaena mysticetus) Endangered 

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Humpback whale (Megaptera novaeangliae) Endangered 

This opinion will consider the potential effects of these actions on these species. However, we 

believe the bowhead whale is most likely to be affected by oil and gas leasing and exploration, 

and that this species is likely more sensitive to noise and disturbance than are humpback and fin 

whales. Additionally, there now exists a considerable database on the Western Arctic bowhead 

stock and the potential and measured impacts to these whales due to oil exploration in the 

Arctic. Much of this information will be generally applicable to other large balenopterid whales, 

notably fin and humpback whales. Therefore, the bowhead whale often receives the most 

attention under this opinion. 

Bowhead Whale 

ESA Listing History and Status 

The bowhead whale was listed as a Federal endangered species on June 2, 1970 (35 FR 8495). 

While five stocks are recognized, the Western Arctic population of the bowhead whale is the 

only one known to occur in the action area. All further references to the bowhead whale in this 

document concern only the Western Arctic population. No critical habitat has been designated 

for the species. 

Population and Stock Structure 

The bowhead whale was historically found in all arctic waters of the northern hemisphere. Five 

populations are currently recognized by the IWC (1992). Three of these populations are found 

in the North Atlantic and two in the North Pacific, some or all of which may be reproductively 

isolated (Shelden and Rugh, 1995). The Spitsbergen population is found in the North Atlantic 

east of Greenland in the Greenland, Kara, and Barents Seas. Thought to have been the most 

numerous of bowhead populations, Woodby and Bodkin (1993) estimate the unexploited 

population at 24,000 animals. The Spitsbergen bowhead is now severely depleted, possibly in 

the tens of animals (Shelden and Rugh, 1995). 

The Davis Strait population is found in Davis Strait, Baffin Bay, and along the Canadian Arctic 

Archipelago. This population is separated from the Bering Sea population by the heavy ice 

found along the Northwest Passage (Moore and Reeves, 1993). The population was estimated to 

have originally numbered over 11,700 (Woodby and Botkin, 1993) but was significantly 

reduced by commercial whaling between 1719 and 1915. The population is today estimated at 

350 animals (Zeh et al., 1993) and recovery is described as “at best, exceedingly slow” (Davis 

and Koski, 1980). 

The Hudson Bay population, also found in Foxe Basin, is differentiated from the Davis Strait 

population by their summer distribution, rather than genetic or morphological differences 

(Reeves et al., 1983). No reliable estimate exists for this population; however, Mitchell (1977) 

places a conservative estimate at 100 or less. More recently, estimates of 256-284 whales have 

been presented for the number of whales within Foxe Basin (Cosens et al., 1997). There has 

been no appreciable recovery of this population. 

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The Okhotsk Sea population occurs in the North Pacific off the western coast of Siberia near the 

Kamchatka Peninsula. The pre-exploitation size of this population may have been 3,000 to 

6,500 animals (Shelden and Rugh, 1995), and may now number somewhere in the 300-400 

range, although reliable population estimates are not currently available. It is possible this 

population has mixed with the Bering Sea population, although the available evidence indicates 

the two populations are essentially separate (Moore and Reeves, 1993). 

Of the five stocks of bowheads whales currently recognizes by the IWC for management 

purposes (IWC, 1992), the Western Arctic stock is the largest, and the only stock to inhabit U.S. 

waters. All of the stocks except for the Western Arctic are “comprised of only a few tens to a 

few hundreds of individuals” (Angliss and Outlaw, 2008). Thus, the Western Arctic stock of 

bowheads is the most robust and viable of surviving bowhead populations. The viability of 

bowheads in the Western Arctic stock is critical to the long-term future of the biological species 

as a whole. 

The Scientific Committee of the IWC previously concluded that the Western Arctic stock of 

bowheads comprise a single stock (DeMaster et al., 2000). However, after an in-depth 

evaluation of available data, the Scientific Committee (IWC, 2004a) concluded that there is 

temporal and spatial heterogeneity among these bowheads, but analyses do not necessarily imply 

the existence of subpopulations with limited interbreeding; it was premature to draw conclusions 

about the relative plausibility of any hypotheses about stock structure or to reject any of them. 

Subsequently, NMFS and the North Slope Borough created a set of five stock-structure 

hypotheses, modified this set, and currently recommends testing of the following hypotheses: 

(1) a single stock; (2) spatial segregation; (3) temporal; (4) feeding; and (5) immigration. After 

more recent information provided to the IWC Subcommittee on bowhead, right and gray whales 

(IWC, 2005b), the subcommittee agree that what is termed the “Oslo Bump” (a significant 

increase in genetic difference between pairs of whales sampled approximately 1 week apart at 

Barrow during the fall migration) appears to be a real pattern within the data that are available. 

However, additional data are needed to determine if these data actually typify the bowhead 

population, and there is no single hypothesis adequate to explain the pattern. Stock structure is 

unclear at the time of this writing. The IWC will be conducting an Implementation Review 

focusing on the stock structure of the Western Arctic stock of bowhead with the goal of 

completing this at the 2007 annual meeting (IWC, 2005a). Two related intersessional 

workshops, one that occurred in 2005 and one that will occur in spring 2006, are focusing on 

this topic (IWC, 2005a,b). 

Taylor et al. (2007) examined the plausibility of multiple bowhead whale stocks in the Western 

Arctic population. They synthesised four lines of evidence that related to understanding stock 

structure: (1) movement and distribution, (2) basic biology, (3) history of commercial whaling, 

and (4) interpretation of genetic patterns. The paper reviewed 30 years of research plus 

contributions from traditional ecological knowledge. In terms of bowhead biology, bowhead 

whales have adapted to living in an arctic ecosystem where ice coverage and food resources vary 

through time. Taylor et al. (2007) concluded that this varying environment makes both the 

evolutionary reason for multiple breeding stocks within the Bering Sea and the biological 

feasibility of maintaining separation within a relatively small pelagic area unlikely. There is 

variability in the timing that individual bowhead whales migrate, in the timing of the peak of the 

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migration itself, and in the location of both summering and wintering grounds. The variation is 

a result of both changing environmental conditions and changes in the whales’ age and 

reproductive state. Furthermore, the available area for any potential segregation of feeding or 

breeding groups is well within the ability of individual whales to travel in a few days time. No 

evidence was found that a small discrete stock, like the Okhotsk Sea stock, is present and killed 

in any numbers during the spring or autumn migration of Western Arctic bowhead whales. No 

data were found to support risk to a separate feeding group. Other insights using genetic data 

were weak, but nearly all results were consistent with a single stock that is out of equilibrium 

following commercial depletion. Bowhead whales being out of genetic equilibrium was 

supported by differences found between age cohorts, both in empirical data and simulated data. 

The only significant genetic findings worth further consideration were differences involving St. 

Lawrence Island. However, the comparisons that were significant involved small sample sizes 

and could just as well result from genetic patterns found between different age cohorts. 

At the 2007 IWC meeting in Anchorage, Alaska, the IWC Scientific Committee Sub-committee 

on Bowhead, Right and Gray Whales concluded after a three year investigation of the stock 

structure of the Bering-Chukchi-Beaufort population of bowhead whales (as summarized in 

Taylor et al. (2007)) that the available evidence best supports a single-stock hypothesis for 

Western Arctic bowhead whales (IWC 2007). 

Woody and Botkin (1993) estimated that the historic population abundance of bowheads in the 

Western Arctic stock was between 10,400 and 23,000 whales in 1848 before the advent of 

commercial whaling, which severely depleted bowhead whales. They estimated that between 

1,000 and 3,000 animals remained in 1914 near the end of the commercial-whaling period. 

Based on both survey data and the incorporation of acoustic data, the abundance of the Western 

Arctic stock of bowhead whales was estimated between 7,200 and 9,400 individuals in 1993 

(Zeh, Raftery, and Schaffner, 1995), with 8,200 as the best population estimate. An alternative 

method produced an estimate of 7,800 individuals, with a 95% confidence interval of 6,800-

8,900 individuals. Data indicate that the Western Arctic stock increased at an estimated rate of 

about 3.1% (Raftery, Zeh, and Givens, 1995) to 3.2% (Zeh, Raftery, and Schaffner, 1995) per 

year from 1978-1993. The estimated increase in the population size most likely is due to a 

combination of improved data and better census techniques, along with an actual increase in the 

population. 

George et al. (2004) estimated abundance in 2001 to be 10,470 (SE = 1,351) with a 95% 

confidence interval of 8,100-13,500. This estimate indicates a substantial increase in population 

abundance since 1993 and suggests that population abundance may have reached the lower 

limits of the historical population estimate. Zeh and Punt (2004, cited in Angliss and Outlaw, 

2005) provided a slightly revised population estimate of 10,545 CV(N) =0.128 to the IWC in 

2004. This is the best estimate currently used by NMFS in the 2008 Stock Assessment Reports 

(Angliss and Outlaw 2008). George et al. (2004) estimated that the annual rate of increase 

(ROI) of the population from 1978-2001 was 3.4% (95% CI 1.7%-5%) and Brandon and Wade 

(2004) estimate an ROI of 3.5% (95% CI 2.2-4.9%). The number of calves (121) counted in 

2001 was the highest ever recorded for this population and this fact, when coupled with the 

estimated rate of increase, suggests a steady recovery of this population (George et al., 2004). 

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This steady recovery is likely due to low anthropogenic mortality, a relatively pristine habitat, 

and a well-managed subsistence hunt (George et al., 2004). 

Reproduction, Survival and Non-Human Sources of Mortality

Information gained from the various approaches at aging the Western Arctic stock of bowhead 

whales and estimating survival rates all suggest that bowheads are slow-growing, late-maturing, 

long-lived animals with survival rates that are currently high (Zeh et al., 1993; see below). 

Female bowheads probably become sexually mature at an age exceeding 15 years, from their 

late teens to mid-20’s (Koski et al., 1993) ( Schell and Saupe, 1993: about 20 years). Their size 

at sexual maturity is about 12.5-14.0 meters (m) long, probably at an age exceeding 15 years 

(17-29 years: Lubetkin et al., 2004 (cited in IWC, 2004b). Most males probably become 

sexually mature at about 17-27 years (Lubetkin et al., 2004 cited in IWC, 2004b). Schell and 

Saupe (1993) looked at baleen plates as a means to determine the age of bowhead whales and 

concluded that bowheads are slow-growing, taking about 20 years to reach breeding size. Based 

on population structure and dynamics, Zeh et al. (1993) also concluded that the bowhead is a 

late-maturing, long-lived animal (George et al., 1999) with fairly low mortality. Photographic 

recaptures by Koski et al. (1993) also suggested advanced age at sexual maturity of late teens to 

mid-twenties. 

Mating may start as early as January and February, when most of the population is in the Bering 

Sea but has also been reported as late as September and early October (Koski et al., 1993). 

Mating probably peaks in March-April (IWC, 2004b). Gestation has been estimated to range 

between 13 and 14 months (Nerini et al., 1984; Reese et al., 2001) and between 12 and 16 

months by Koski et al. (1993) (see also information and discussion in IWC, 2004b). Reese et al. 

(2001) developed a nonlinear model for fetal growth in bowhead whales to estimate the length 

of gestation, with the model indicating an average length of gestation of 13.9 months. Data 

indicate most calving occurs during the spring migration when whales are in the Chukchi Sea. 

Koski et al. (1993) reported that calving occurs from March to early August, with the peak 

probably occurring between early April and the end of May (Koski et al., 1993). The model by 

Reese et al. (2001) also indicated that conception likely occurs in early March to early April, 

suggesting that breeding occurs in the Bering Sea. The conception date and length of gestation 

suggests that calving is likely to occur in mid-May to mid-June, when whales are between the 

Bering Strait and Point Barrow (in the Chukchi Sea). Reese et al. (2001) said this is consistent 

with other observations in the region, including: (a) relatively few neonate-cow pairs reported 

by whalers at St. Lawrence Island; (b) many neonates seen during the whale census in late May; 

(c) relatively few term females taken at Barrow; (d) taken females with term pregnancies 

appeared close to parturition; and (e) most of the herd believed to have migrated past Barrow by 

late May. Females give birth to a single calf probably every 3-4 years. 

Discussion during the in-depth assessment by the IWC (2004b) also indicated that differences in 

lipid content between females of the same length and size are attributable to pregnant versus 

nonpregnant females. This may imply a high biological cost of reproduction, a fact noteworthy 

in considering the potential impact of excluding females from feeding areas. George et al. 

(2004) estimated pregnancy rates of 0.333/year and an estimated interbirth interval of 3.0 years 

using data from postmortem examinations of whales landed at Barrow and Kaktovik in the 

winter. 

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There is little information regarding causes of natural mortality for Western Arctic bowhead 

whales. Bowhead whales have no known predators except, perhaps, killer whales and 

subsistence whalers. The frequency of attacks by killer whales probably is low (George et al., 

1994). A relatively small number of whales likely die as a result of entrapment in ice (Philo et 

al., 1993). Little is known about the effects of microbial or viral agents on natural mortality. 

The discovery of traditional whaling tools recovered from five bowheads landed since 1981 

(George et al., 1995) and estimates of age using aspartic-acid racemization techniques (George 

et al., 1999) both suggest bowheads can live a very long time, in some instances more than 100 

years. The oldest harvested females whose ages were estimated using corpora albicans 

accumulation to estimate female age were more than 100 years old (George et al., 2004, cited in 

IWC, 2004b). Discussion in the IWC (2004b) indicated that neither lifespan nor age at sexual 

maturity is certain. Lifespan may be greater than the largest estimates. 

Using aerial photographs of naturally marked bowheads collected between 1981 and 1998, Zeh 

et al. (2002:832) estimated “the posterior mean for bowhead survival rate...is 0.984, and 95% of 

the posterior probability lies between 0.948 and 1.” They noted that a high estimated survival 

rate is consistent with other bowhead life-history data. 

Distribution and Habitat Use 

The Western Arctic stock of bowheads generally occur north of 60° N. and south of 75° N. 

(Angliss and Outlaw, 2005) in the Bering, Chukchi, and Beaufort seas. They have an affinity 

for ice and are associated with relatively heavy ice cover and shallow continental shelf waters 

for much of the year. Bowhead whales of the Western Arctic stock overwinter in the central and 

western Bering Sea. Most mating probably occurs in the Bering Sea. The amount of feeding in 

the Bering Sea in the winter is unknown as is the amount of feeding in the Bering Strait in the 

fall (Richardson and Thomson, 2002). In the Bering Sea, bowheads frequent the marginal ice 

zone, regardless of where the zone is, and polynyas. Important winter areas in the Bering Sea 

include polynyas along the northern Gulf of Anadyr, south of St. Matthew Island, and near St. 

Lawrence Island. Bowheads congregate in these polynyas before migrating (Moore and Reeves, 

1993). 

Observations by Mel’nikov, Zelensky, and Ainana (1997) from shore-based observations of 

waters adjacent to the Chukotka Peninsula in 1994-1995 indicate that bowheads winter in the 

Bering Sea along leads and polynyas adjacent to the Asian coastline. Mel’nikov, Zelensky, and 

Ainana (1997) summarized that in years when there is little winter ice, bowheads inhabit the 

Bering Strait and potentially inhabit southern portions of the Chukchi Sea. 

During their southward migration in the autumn, bowheads pass through the Bering Strait in late 

October through early November on their way to overwintering areas in the Bering Sea. Large 

numbers of bowheads were taken in June and July during commercial whaling over large 

portions of the northwestern and northcentral Bering Sea (Figure 1b in Dahlheim et al., 1980, 

from Townsend, 1935). 

11
Some, or nearly all of the bowheads that winter in the Bering Sea migrate northward through the 

Bering Strait to the Chukchi Sea and through the Alaskan Beaufort Sea to summer feeding 

grounds in the Canadian Beaufort Sea. The bowhead northward spring migration appears to 

coincide with ice breakup and probably begins most years in April (possibly late March 

depending on ice conditions) and early May. It is thought to occur after the peak of breeding, 

which is believed to occur in March-April (C. George, cited in IWC, 2004b). 

Bowheads congregate in the polynyas before migrating (Moore and Reeves, 1993; Mel’nikov, 

Zelensky, and Ainana, 1997). Large numbers of bowheads were taken in June and July during 

commercial whaling over large portions of the northwestern and northcentral Bering Sea (Figure 

1b in Dahlheim et al., 1980, from Townsend, 1935). Bowheads migrate up both the eastern and 

western sides of the Bering Strait in the spring (Mel’nikov, Zelensky, and Ainana, 1997; 

Mel’nikov et al., 2004). They pass through the Bering Strait and eastern Chukchi Sea from late 

March to mid-June through newly opened leads in the shear zone between the shorefast ice and 

the offshore pack ice. During spring aerial surveys in the late 1980’s, bowheads were 

documented to be migrating in shorefast leads and polynyas up the coast of northwestern Alaska 

(see Figures 4 and 5 in Mel’nikov, Zelensky, and Ainana, 1997). 

Based on shore-based surveys in 1999-2001, Mel’nikov et al. (2004) observed that the start of 

spring migration from the Gulf of Anadyr varies between cold and mild years by up to 30 days, 

but in both instances, continues at least until June 20. Mel’nikov et al. (2004) also reported that 

weather influenced migration, with migration seeming to stop when there were storms or high 

winds in the western Bering Strait or at the exit from the Gulf of Anadyr. 

The migration past Barrow takes place in pulses in some years (e.g., in 2004) but not in others 

(e.g., 2003) (Koski et al., 2004, cited in IWC, 2004b). At Barrow, the first migratory pulse is 

typically dominated by juveniles. This pattern gradually reverses and by the end of the 

migration, there are almost no juveniles. Currently, the whales are first seen at Barrow around 

April 9-10. In later May (May 15-June), large whales and cow/calf pairs are seen (H. Brower, in 

USDOC, NOAA and NSB, 2005; IWC, 2004b). Koski et al. (2004b) found that females and 

calves constituted 31-68% of the total number of whales seen during the last few days of the 

migration. Their rate of spring migration was slower and more circuitous than other bowheads. 

Calves had shorter dive duration, surface duration, and blow interval than their mothers. Calf 

blow rate was nearly 3 times that of their mothers. Most calving probably occurs in the Chukchi 

Sea. Some individuals or subset of the population may summer in the Chukchi Sea. 

Several studies of acoustical and visual comparisons of the bowhead’s spring migration off 

Barrow indicate that bowheads also may migrate under ice within several kilometers of the 

leads. Data from several observers indicate that bowheads migrate underneath ice and can break 

through ice 14-18 centimeters [cm] (5.5-7 inches [in]) thick to breathe (George et al., 1989; 

Clark, Ellison, and Beeman, 1986). Bowheads may use cues from ambient light and echoes 

from their calls to navigate under ice and to distinguish thin ice from multiyear floes (thick ice). 

After passing through Barrow from April through mid-June, they move easterly through or near 

offshore leads. East of Point Barrow, the lead systems divide into many branches that vary in 

location and extent from year to year. The spring-migration route is offshore of the barrier 

islands in the central Alaskan Beaufort Sea. 

12
Bowheads arrive on their summer feeding grounds near Banks Island from mid-May through 

June (July: IWC, 2005b) and remain in the Canadian Beaufort Sea and Amundsen Gulf until late 

August or early September (Moore and Reeves, 1993). Bowhead whales are seen also in the 

central Chukchi Sea and along the Chukotka coast in July and August. They may occupy the 

northeastern Chukchi Sea in late summer more regularly than commonly believed (Moore, 1992; 

USDOC, NOAA, and NSB, 2005), but it is unclear if these are “early-autumn” migrants or 

whales that have summered nearby (Moore et al., 1995) or elsewhere. Bowhead whales have 

been observed near Barrow in the mid-summer (e.g., Brower, as cited in USDOI, MMS, 1995). 

Eight bowheads were observed near Barrow on July 25, 1999, 2 at 71° 30’ N., 155° 40’W. to 

155° 54’ W. from a helicopter during a search, and six at 71° 26’ N., 156° 23’ W. from the 

bridge of the icebreaker Sir Wilfrid Laurier (Moore and DeMaster, 2000). Moore and DeMaster 

(2000:61) noted that these observations are consistent with Russian scientist suggestions that 

“...Barrow Canyon is a focal feeding area for bowheads and that they ‘move on’ from there only 

when zooplankton concentrations disperse (Mel’nikov et al. 1998)” and consistent with the time 

frame of earlier observations summarized by Moore (1992.) 

Some biologists conclude that almost the entire Bering Sea bowhead population migrates to the 

Beaufort Sea each spring and that few whales, if any, summer in the Chukchi Sea. Incidental 

sightings suggest that bowhead whales may occupy the Chukchi Sea in the summer more 

regularly than commonly believed. Moore (1992) summarized observations of bowheads in the 

northeastern Chukchi in late summer. Other scientists maintain that a few bowheads swim 

northwest along the Chukotka coast in late spring and summer in the Chukchi Sea. Observation 

by numerous Russian authors (cited in Mel’nikov, Zelensky, and Ainana [1997:8]) indicates that 

bowheads occur in waters of the Chukchi Sea off the coast of Chukotka in the summer. 

Harry Brower, Jr. observed whales in the Barrow area in the middle of the summer, when 

hunters were hunting bearded seals on the ice edge (Brower, as cited in USDOI, MMS, 1995). 

The monitoring program conducted while towing the single steel drilling caisson to the 

McCovey location in 2002 recorded five bowhead whales off Point Barrow on July 21. 

Recent systematic data about bowhead distribution and abundance in the Chukchi Sea OCS 

Planning Area are lacking. The MMS funded large-scale surveys in this area when there was oil 

and gas leasing and exploration, but while surveys in the Beaufort Sea have continued, the last 

surveys in the Chukchi Sea were about 15 years ago. 

Bowheads found in the Bering and Chukchi Seas in the summer may be part of the expanding 

Western Arctic stock (Rugh et al. 2004), as referenced in Angliss, DeMaster, and Lopez, 2001). 

Evidence indicates that the number of bowheads in the Western Arctic stock has increased 

substantially since the time of the surveys (Brandon and Wade, 2004, cited in IWC, 2004b). 

Temporal and spatial patterns of distribution also may be modified. Conversely, earlier 

information may have inferred less variability in distribution than actually existed. 

Those bowheads that have been summer feeding in the Canadian Beaufort Sea begin moving 

westward into Alaskan waters in August and September. While few bowheads generally are 

seen in Alaskan waters until the major portion of the migration takes place (typically mid13
September to mid-October), in some years bowheads are present in substantial numbers in early 

September (Greene and McLennan, 2001; Treacy, 1998). In 1997, Treacy (1998) reported 

sighting 170 bowheads, including 6 calves, between Cross Island and Kaktovik on September 3 

during the first flight of the survey that year. In 1997, Treacy (1998) observed large numbers of 

bowheads between Barrow and Cape Halkett in mid-September. Large numbers were still 

present between Dease Inlet and Barrow in early October (although they may not have been the 

same individuals). 

There is some indication that the fall migration, just as the spring migration, takes place in 

pulses or aggregations of whales (Moore and Reeves, 1993). Eskimo whalers report that smaller 

whales precede large adults and cow-calf pairs on the fall migration (Braham et al., 1984, as 

reported in Moore and Reeves, 1993). During the autumn migration Koski and Miller (2004, 

cited in IWC, 2004b) found decreasing proportions of small whales and increasing proportions 

of large whales as one moved offshore. “Mothers and calves tended to avoid water depths less 

than (<) 20 m.” (Koski and Miller, cited in IWC, 2004b:14). These authors also found that in 

the Central Beaufort Sea in late August, the vast majority of the whales were subadults and this 

percentage declined throughout the autumn to about 35% by early October. They reported that 

mother/calf pairs “arrived in September and were common until early October” (Koski and 

Miller, 2004, cited in IWC, 2004b). 

Inupiat whalers estimate that bowheads take about 2 days to travel from Kaktovik to Cross 

Island, reaching the Prudhoe Bay area in the central Beaufort Sea by late September, and 5 days 

to travel from Cross Island to Point Barrow (T. Napageak, 1996, as cited in NMFS, 1999). 

Individual movements and average speeds (approximately 1.1-5.8 kilometers per hour [km/h]) 

vary widely (Wartzog et al., 1990; Mate, Krutzikowsky, and Winsor, 2000). Much faster speeds 

(e.g., up to 9.8 + 4.0 km/h) were estimated for bowheads migrating out of the Gulf of Anadyr 

during the northward spring migration (Mel’nikov et al., 2004). 

Wartzog et al. (1989) placed radio tags on bowheads and tracked the tagged whales in 1988. 

One tagged whale was tracked for 915 km as it migrated west at an average speed of 2.9 km/h in 

ice-free waters. It traveled at an average speed of 3.7 km/h in relatively ice-free waters and at an 

average speed of 2.7 km/h through eight-tenths ice cover and greater. Another whale traveled 

1,291 km at an average speed of 5.13 km in ice-free waters but showed no directed migratory 

movement, staying within 81 km of the tagging site. Additional tagged whales in 1989 migrated 

954-1,347 km at average speeds of 1.5-2.5 km/h (Wartzog et al., 1990). Mate, Krutzikowsky, 

and Winsor (2000) tagged 12 juvenile bowhead whales with satellite-monitored radio tags in the 

Canadian Beaufort Sea. The whale with the longest record traveled about 3,886 km from 

Canada across the Alaskan Beaufort Sea to the Chukchi Sea off Russia and averaged 5.0 km/h. 

This whale’s speed was faster, though not significantly faster, in heavy ice than in open water. 

Oceanographic conditions can vary during the fall migration from open water to more than ninetenths ice coverage. The extent of ice cover may influence the timing or duration of the fall 

migration. Miller, Elliot, and Richardson (1996) observed that whales within the Northstar 

region (long. 147°-150° W.) migrate closer to shore in light and moderate ice years and farther 

offshore in heavy ice years, with median distances offshore of 30-40 km (19-25 miles [mi]) in 

14
both light and moderate ice years and 60-70 km (37-43 mi) in heavy ice years. Moore (2000) 

looked at bowhead distribution and habitat selection in heavy, moderate, and light ice conditions 

in data collected during the autumn from 1982-1991. This study concluded that bowhead 

whales select shallow inner-shelf waters during moderate and light ice conditions and deeper 

slope habitat in heavy ice conditions. During the summer, bowheads selected continental slope 

waters and moderate ice conditions (Moore, DeMaster, and Dayton, 2000). Interseasonal depth 

and ice-cover habitats were significantly different for bowhead whales. Ljungblad et al. (1987) 

observed during the years from 1979-1986 that the fall migration extended over a longer period, 

that higher whale densities were estimated, and that daily sighting rates were higher and peaked 

later in the season in light ice years as compared to heavy ice years. 

Fall aerial surveys of bowhead whales in the Alaskan Beaufort Sea have been conducted since 

1979 by the Bureau of Land Management and the MMS (Ljungblad et al., 1987; Treacy, 1988-

1998, 2000). Over a 19-year period (1982-2000), there were 15 years with some level of 

offshore seismic exploration and/or drilling activity and 4 years (1994, 1995, 1999, and 2000) in 

which neither offshore activity took place during September or October. The parametric Tukey 

HSD test was applied to MMS fall aerial-transect data (1982-2000) to compare the distances of 

bowhead whales north of a normalized coastline in two analysis regions of the Alaskan Beaufort 

Sea from 140-156° W. longitude (see USDOI, MMS, 2003). While the Tukey HSD indicates 

significant differences between individual years, it does not compare actual levels of human 

activity in those years nor does it test for potential effects of sea ice and other oceanographic 

conditions on bowhead migrations (Treacy, 2000). Treacy (2000) showed in a year-to-year 

comparison that the mean migration regionwide in fall 1998 was significantly closer to shore in 

both the East and West Regions than in 1999, a year with no offshore seismic or drilling activity 

during the fall season in the Alaskan Beaufort Sea. 

While other factors may have dominating effects on site-specific distributions, such as prey 

concentrations, seismic activities, and localized vessel traffic, broad-area fall distributions of 

bowhead whale sightings in the central Alaskan Beaufort Sea may be driven by overall sea-ice 

severity (Treacy, 2001). Treacy (2002) concluded that: 

Bowhead whales occur farther offshore in heavy-ice years during fall migrations across the 

Central Alaskan Beaufort Sea (142° W to 155° W longitudes). Bowheads generally occupy 

nearshore waters in years of light sea-ice severity, somewhat more offshore waters in moderate 

ice years, and are even farther offshore in heavy ice years. While other factors...may have 

localized effects on site-specific distributions, broad-area distributions of bowhead whale 

sightings in the central Alaskan Beaufort Sea are related to overall sea-ice severity.

Further evidence that bowhead whales migrate at varying distances from shore in different years 

also is provided by site-specific studies monitoring whale distribution relative to local seismic 

exploration in nearshore waters of the central Beaufort Sea (Miller et al., 1997; Miller, Elliot, 

and Richardson, 1998; Miller et al., 1999). In 1996, bowhead sightings were fairly broadly 

distributed between the 10-m and 50-m depth contours. In 1997, bowhead sightings were fairly 

broadly distributed between the 10-m and 40-m depth contours, unusually close to shore. In 

1998, the bowhead migration corridor generally was farther offshore than in either 1996 or 

1997, between the 10-m and 100-m depth contours and approximately 10-60 km from shore. 

15
Aerial surveys near the proposed Liberty development project in 1997 (BPXA, 1998) showed 

that the primary fall-migration route was offshore of the barrier islands, outside the proposed 

development area. However, a few bowheads were observed in lagoon entrances between the 

barrier islands and in the lagoons immediately inside the barrier islands, as shown in Figures 4-4 

and 4-5 of the Environmental Report submitted by BPXA for the Liberty development project 

(BPXA, 1998). Because survey coverage in the nearshore areas was more intensive than in 

offshore areas, maps and tabulations of raw sightings overestimate the importance of nearshore 

areas relative to offshore areas. Transects generally did not extend south of the middle of 

Stefansson Sound. Nevertheless, these data provide information on the presence of bowhead 

whales near the then-proposed Liberty development area during the fall migration. Probably 

only a small number of bowheads, if any, came within 10 km (6 mi) of the area. 

Some bowheads may swim inside the barrier islands during the fall migration. For example 

Frank Long, Jr. reported that whales are seen inside the barrier islands near Cross Island nearly 

every year and are sometimes seen between Seal Island and West Dock (U.S. Army Corps of 

Engineers, 1999). Crews from the commercial-whaling ships looked for the whales near the 

barrier islands in the Beaufort Sea and in the lagoons inside the barrier islands (Brower, 1980). 

Whales have been known to migrate south of Cross Island, Reindeer Island, and Argo Island 

during years when fall storms push ice against the barrier islands (Brower, 1980). Inupiat 

whaling crews from Nuiqsut also have noticed that the whale migration appears to be influenced 

by wind, with whales stopping when the winds are light and, when the wind starts blowing, the 

whales started moving through Captain Bay towards Cross Island (Tuckle, as cited in USDOI, 

MMS, 1986). Some bowhead whales have been observed swimming about 25 yards from the 

beach shoreline near Point Barrow during the fall migration (Rexford, as cited in USDOI, MMS, 

1996). A comment received from the Alaska Eskimo Whaling Commission on the Liberty draft 

EIS indicated that Inupiat workers at Endicott have, on occasion, sighted bowheads on the north 

side of Tern Island. No specific information was provided regarding the location of the whale. 

Data are limited on the bowhead fall migration through the Chukchi Sea before the whales move 

south into the Bering Sea. Bowhead whales commonly are seen from the coast to about 150 km 

(93 mi) offshore between Point Barrow and Icy Cape, suggesting that most bowheads disperse 

southwest after passing Point Barrow and cross the central Chukchi Sea near Herald Shoal to the 

northern coast of the Chukotka Peninsula. However, sightings north of 72° N. latitude suggest 

that at least some whales migrate across the Chukchi Sea farther to the north. Mel’nikov, 

Zelensky, and Ainana (1997) argued that data suggest that after rounding Point Barrow, some 

bowheads head for the northwestern coast of the Chukotka Peninsula and others proceed 

primarily in the direction of the Bering Strait and into the Bering Sea. Mel’nikov (in USDOC, 

NOAA, and NSB, 2005) reported that abundance increases along northern Chukotka in 

September as whales come from the north. More whales are seen along the Chukotka coast in 

October. J.C. George (cited in IWC, 2004b) noted that bowheads pass through the Bering Strait 

into the Bering Sea between October and November on their way to overwintering areas in the 

Bering Sea. 

The timing, duration, and location of the fall migration along the Chukotka Peninsula are highly 

variable and are linked to the timing of freezeup (Mel’nikov, Zelensky, and Ainana, 1997). 

16
Whales migrate in “one short pulse over a month” in years with early freezeup, but when ice 

formation is late, whales migrate over a period of 1.5-2 months in 2 pulses (Mel’nikov, 

Zelensky, and Ainana, 1997:13. 

Feeding 

Bowheads are filter feeders, filtering prey from the water through baleen fibers in their mouth. 

They apparently feed throughout the water column, including bottomfeeding as well as surface 

skim feeding (Würsig et al., 1989). Skim feeding can occur when animals are alone and 

conversely may occur in coordinated echelons of over a dozen animals (Würsig et al., 1989). 

Food items most commonly found in the stomachs of harvested bowheads include euphausiids, 

copepods, mysids, and amphipods. Euphausiids and copepods are thought to be their primary 

prey. Lowry, Sheffield, and George (2004) documented that other crustaceans and fish also 

were eaten but were minor components in samples consisting mostly of copepods or 

euphausiids. 

Available data indicate that bowhead whales feed in both the Chukchi and Beaufort Sea 

Planning Areas and that this use varies in degree among years, among individuals, and among 

areas. It is likely that bowheads continue to feed opportunistically where food is available as 

they move through or about the Alaskan Beaufort Sea, similar to what they are thought to do 

during the spring migration. Observations from the 1980’s documented that some feeding 

occurs in the spring in the northeastern Chukchi Sea, but this feeding was not consistently seen 

(e.g., Ljungblad et al., 1987; Carroll et al., 1987). Stomach contents from bowheads harvested 

between St. Lawrence Island and Point Barrow during April into June also indicated it is likely 

that some whales feed during the spring migration (Carroll et al., 1987; Shelden and Rugh, 1995, 

2002). Carroll et al. (1987) reported that the region west of Point Barrow seems to be of 

particular importance for feeding, at least in some years, but whales may feed opportunistically 

at other locations in the lead system where oceanographic conditions produce locally abundant 

food. Lowry (1993) reported that the stomachs of 13 out of 36 spring-migrating bowheads 

harvested near Point Barrow between 1979 through 1988 contained food. Lowry estimated total 

volumes of contents in stomachs ranged from less than 1 to 60 liters (L), with an average of 12.2 

L in eight specimens. Shelden and Rugh (1995) concluded that “In years when oceanographic 

conditions are favorable, the lead system near Barrow may serve as an important feeding ground 

in the spring (Carroll et al., 1997).” Richardson and Thomson (2002) concluded that some, 

probably limited, feeding occurs in the spring. 

It is known that bowhead whales feed in the Canadian Beaufort in the summer and early fall 

(e.g., Würsig et al, 1985), and in the Alaskan Beaufort in late summer/early fall (Lowry and 

Frost, 1984; Ljungblad et al., 1986; Schell and Saupe, 1993; Lowry, Sheffield, and George, 

2004; summarized in Richardson and Thomson, 2002). Available information indicates it is 

likely there is considerable inter-annual variability in the locations where feeding occurs during 

the summer and fall in the Alaska Beaufort Sea, in the length of time individuals spend feeding, 

and in the number of individuals feeding in various areas in the Beaufort Sea. 

In at least some years, some bowheads apparently take their time returning westward during the 

fall migration, sometimes barely moving at all, with some localities being used as staging areas 

due to abundant food resources or social reasons (Akootchook, 1995, as reported in NMFS, 1). 

17
The Inupiat believe that whales follow the ocean currents carrying food organisms (e.g., 

Napageak, 1996, as reported in NMFS, 2001). Bowheads have been observed feeding not more 

than 1,500 feet (ft) offshore in about 15-20 ft of water (Rexford, 1979, as reported in NMFS, 

2001). Nuiqsut Mayor Nukapigak testified at the Nuiqsut Public Hearing on March 19, 2001, 

that he and others saw a hundred or so bowhead whales and gray whales feeding near Northstar 

Island (USDOI, MMS, 2002). Some bowheads appear to feed east of Barter Island as they 

migrate westward (Thomson and Richardson, 1987). 

Interannual variability in the use of areas of the Beaufort Sea by bowheads for feeding also has 

been observed during aerial surveys by MMS and others. Ljungblad et al. (1986) reported that 

feeding bowheads comprised approximately 25% of the total bowheads observed during aerial 

surveys conducted in the Beaufort Sea from 1979 through 1985. Miller, Elliott, and Richardson 

(1998) reported observing many aggregations of feeding whales in nearshore waters near or just 

offshore of the 10-m depth contour during late summer/autumn 1997. In some years (e.g., 1997) 

(Miller, Elliot, and Richardson, 1998; Treacy, 2002), many aggregations have been seen feeding 

(e.g., between Point Barrow and Smith Bay), whereas in other years very little feeding was 

observed. Bowheads occasionally have been observed feeding north of Flaxman Island. 

Based on stomach content data supplemented by behavioral evidence, far more than 10% of the 

bowheads that passes through the eastern Alaskan Beaufort Sea during late summer and autumn 

feed there. Based on examination of the stomach contents of whales harvested in the autumn 

between 1969-2000, Lowry, Sheffield, and George (2004) found that there were no significant 

difference in the percentages of bowheads that had been feeding between those harvested near 

Kaktovik (83%), Barrow (75%), or between subadults (78%) versus adults (73%). Twenty-four 

out of 32 whales taken during the fall at Kaktovik from 1979-2000 and included in this analysis 

were considered to have been feeding (Lowry and Sheffield, 2002). 

Length-girth relationships show that subadult bowheads, and possibly adults, gain weight while 

in the Beaufort Sea in summer and lose weight while elsewhere. Lipid content of blubber, at 

least in subadults, is higher when they leave the Beaufort in fall than when they return in spring. 

This evidence suggests the importance of feeding in the Beaufort Sea during summer and early 

autumn. They do not show what fraction of the annual feeding occurs in the eastern and central 

Beaufort Sea. Lowry, Sheffield, and George (2004:221) concluded that: 

...Bowhead whales feed regularly in the nearshore waters of the eastern, central and western 

Alaskan Beaufort Sea during September and October...this entire region should be considered 

an integral part of the summer-autumn feeding range of bowhead whales. Results of stomach 

contents analysis, aerial observations, and traditional knowledge suggest that reference to the 

passage of bowhead whales through this region as a ‘westward autumn migration’ is 

misleading...it is a very incomplete description of their activities in the region. Second, feeding 

near Barrow during the spring migration is not just occasional, but rather a relatively common 

event...However, the amount of food in the stomachs tends to be lower in spring than in 

autumn.... 

However, examination of stomach contents only showed whether or not bowhead whales had 

fed and what prey were eaten, and it does not directly address the relative significance of feeding 

18
in various regions...This unresolved issue remains important in the evaluation of possible 

cumulative effects of oil and gas development on bowhead whales..... 

Richardson and Thomson (2002) pointed out that bowhead activity throughout the year needs to 

be considered when evaluating the importance of feeding in the eastern Alaskan Beaufort Sea in 

late summer and autumn. Although numerous observations have been made of bowheads 

feeding during both the spring migration north to the Beaufort Sea and the fall migration west 

across the Alaskan Beaufort Sea, quantitative data showing how food consumed in the Alaskan 

Beaufort Sea contributes to the bowhead whale population’s overall annual energy needs is 

fairly limited. A study by Richardson (1987) concluded that food consumed in the eastern 

Beaufort Sea contributed little to the bowhead whale population’s annual energy needs, although 

the area may be important to some individual whales. The study area for this 1985-1986 study 

extended from eastern Camden Bay to the Alaska/Canada border from shore to the 200-m depth 

contour for the intensive study area, and beyond this contour only for aerial survey data 

(Richardson and Thomson, 2002). The conclusion was controversial. The NSB’s Science 

Advisory Committee (1987) believed the study was too short in duration (two field seasons, one 

of which was limited by ice cover), suboptimal sampling designs, and difficulties in estimating 

food availability and consumption. The Committee did not accept the conclusion that the study 

area is unimportant as a feeding area for bowhead whales. 

Richardson and Thomson (2002) finalized the report from the MMS-funded feeding study 

entitled Bowhead Whale Feeding in the Eastern Alaskan Beaufort Sea: Update of Scientific and 

Traditional Information, which compiled and integrated existing traditional and scientific 

knowledge about the importance of the eastern Alaskan Beaufort Sea for feeding by bowhead 

whales. The project was an extension, with additional fieldwork (mainly in September of 1998, 

1999, and 2000), of the previous study conducted in 1985 and 1986. The primary study area for 

this study extended the westward boundary about 1° longitude from that of the 1985-1986 study. 

Thus the boundary for the latter study was near the middle of Camden Bay (145° W. longitude). 

With the concurrence of the NSB Scientific Review Board, efforts in deep offshore areas were 

de-emphasized in this latter study so as to concentrate efforts in shallow areas of particular 

concern to Kaktovik hunters and, potentially, to oil industry. Boat-based zooplankton sampling 

in 1998-2000 was limited to areas seaward of the 50-m contour. Aerial surveys extended to the 

200-m contour, and MMS surveys extended further. 

Baleen from bowhead whales provides a multiyear record of isotope ratios in prey species 

consumed during different seasons, including information about the occurrence of feeding in the 

Bering Sea and Chukchi Sea system. The isotopic composition of the whale is compared with 

the isotope ratios of its prey from various geographic locations to make estimates of the 

importance of the habitat as a feeding area. Carbon-isotope analysis of bowhead baleen has 

indicated that a significant amount of feeding may occur in wintering areas (Schell, Saupe, and 

Haubenstock, 1987). Carbon-isotope analysis of zooplankton, bowhead tissues, and bowhead 

baleen indicates that a significant amount of feeding may occur in areas west of the eastern 

Alaskan Beaufort Sea, at least by subadult whales (Schell, Saupe, and Haubenstock, 1987). 

19
Recently, Lee at al. (2005) published data from isotope ratio analyses of bowhead baleen from 

whales all except one of whom had been harvested in the autumn of 1997. Results of these 

samples were compared to data from baleen collected in past studies from both spring 

(predominantly) and autumn whales in 1986-1988 (see Table 1 in Lee et al., 2005:274). Lee et 

al. (2005:285) concluded that the new data continue to indicate that the “bowhead whale 

population acquires the bulk of its annual food intake from the Bering-Chukchi system.... Our 

data indicate that they acquire only a minority of their annual diet from the eastern and central 

Beaufort Sea...although subadult bowheads apparently feed there somewhat more often than do 

adults.” 

Thomson, Koski, and Richardson (2002) concluded that bowheads fed for an average of 47% of 

their time in the eastern Alaskan Beaufort Sea during late summer and autumn. A substantial 

portion of the feeding occurred during travel. Among traveling whales, feeding as well as travel 

was occurring during a substantial percentage of the time, on the order of 43%. 

The amount of feeding in the Chukchi Sea and Bering Strait in the fall is unknown, as is the 

amount of feeding in the Bering Sea in the winter (Richardson and Thomson, 2002). 

Vocalizations and hearing 

Bowhead whales are believed to be most sensitive to lower frequency sound. It may be 

reasonable that whales are most sensitive to noise at the frequencies at which they vocalize. 

Most bowhead calls are at 50-400 Hz, although components may reach as low as 35 Hz or as 

high as 5 kHz (Burns et al. 1993). Bowhead produce various types of vocalizations, described 

as frequency modulated tonal calls in the 50-300 Hz range, complex calls which include pulsed 

sounds, squeals, growl-type sounds with abundant harmonic content, and call sequences. 

Bowhead vocalizations and hearing remain poorly understood, although call duration, 

frequency, and type appear dependent on life history, age, sex, behavior, time of year, and 

outside stimuli such as industrial noise. No studies have directly measured the sound sensitivity 

of bowhead whales. In a study of the morphology of the mysticete auditory apparatus, Ketten 

(1997) hypothesized that large mysticetes have acute infrasonic hearing. 

Bowhead whales are also known to sing during spring migrations. Source levels for bowhead 

calls have been estimated as high as 180-189 dB (Wursig and Clark, 1993). In addition to 

functioning with regard to communicating with others, bowheads may utilize vocalizations to 

maintain cohesion in migrations or to locate ice in order to migrate through the spring leads in 

the Chukchi and Beaufort Seas. 

Fin whale 

ESA Listing History and Status 

The fin whale was listed as an endangered species on June 2, 1970 (35 FR 8495). No critical 

habitat has been designated for the species. 

Population and Stock Structure 

20
The fin whale is considered one of the more abundant large whale species, with a worldwide 

population estimate of 120,000. Three stocks are currently recognized in U.S. waters: 1) Alaska 

(North Pacific), 2) California/Washington/Oregon, and 3) Hawaii. Prior to exploitation by 

whaling vessels, the North Pacific population consisted of an estimated 42,000 to 45,000 fin 

whales (Ohsumi and Wada 1974). Between 1914 and 1975, over 26,040 fin whales were 

harvested throughout the North Pacific (in Perry and others 1999). Annual catches in the North 

Pacific and Bering Sea range between 1,000 and 1,500 fin whales during the 1950's and 1960's. 

However, not all Soviet catches were reported. No reliable current population estimate exists, 

but Angliss and Outlaw (2007) report a minimum estimate of 5,700 for the North Pacific stock 

based on incomplete surveys over a portion of their range. 

The distinctness of North Pacific and North Atlantic fin whales has been supported by recent 

genetic analysis and by differences in vocalizations (NMFS 2006). At present, there are two 

named subspecies, B. p. physalus (Linnaeus 1758) in the North Atlantic and B. p. quoyi (Fischer 

1829) in the southern oceans. Most experts consider the North Pacific fin whales a separate 

unnamed subspecies. On a global scale, populations in the North Atlantic, North Pacific, and 

Southern Ocean probably mix rarely (if at all), and there are geographical populations within 

these ocean basins. Hatch (2004) reported differences in fin whale vocalizations between the 

North Atlantic and North Pacific, as well as regional differences within the North Atlantic. In 

addition there are morphological distinctions between these three groups. Adults in the Antarctic 

can be more than 23 m long and weigh more than 70,000 kg. In general, fin whales in the 

Northern Hemisphere attain a smaller maximum body length (by up to 3 m) than Antarctic fin 

whales, and those in the North Atlantic are leaner than their Antarctic counterparts (Lockyer and 

Waters 1986). 

Reproduction, Survival and Non-Human Sources of Mortality 

The gestation period is probably somewhat less than a year, and fin whale calves are nursed for 6-7 

months (NMFS 2006). The average calving interval has been estimated at about two years, based on 

whaling data. Natural sources and rates of mortality are largely unknown, but Aguilar and 

Lockyer (1987) suggest annual natural mortality rates may range between 0.04 and 0.06 (based 

on studies of northeast Atlantic fin whales).

Little is known about the natural causes of mortality of fin whales. Ice entrapment is known to 

have injured or killed some fin whales in the North Atlantic, particularly in the Gulf of St. 

Lawrence (NMFS 2006), and killer whales may attack fin whales, as has been reported for gray 

whales Disease presumably plays a major role in natural mortality as well, and shark attacks on 

weak or young individuals are probably common, but have not been documented. Lambertsen 

(in NMFS 2006) contended that crassicaudiosis in the urinary tract, was the primary cause of 

natural mortality in North Atlantic fin whales. Rates of natural mortality in fin whales generally 

are thought to range between 0.04 and 0.06.

Distribution and Habitat Use 

The distribution of fin whales can be understood only in light of their feeding ecology (Mizroch 

et al. 2001). Fin whales are known to migrate between high latitude summer feeding grounds 

and lower-latitude wintering areas, although some individuals and even local populations do not. 

21
Rice (1974) reported that the summer distribution of fin whales included immediate offshore 

waters throughout the North Pacific from central Baja California to Japan, and as far north as the 

Chukchi Sea. They occurred in high densities in the northern Gulf of Alaska and southeastern 

Bering Sea from May to October, with some movement through the Aleutian passes into and out 

of the Bering Sea (NMFS 2006). Fin whales were observed and taken by Japanese and Soviet 

whalers off eastern Kamchatka and Cape Navarin, both north and south of the eastern Aleutians, 

and in the northern Bering and southern Chukchi Seas (NMFS 2006). They were also taken by 

whalers off central California throughout the year. 

NMFS (2006) reports that fin whales have been observed year-round off central and southern 

California, with peak numbers in summer and fall, in summer off Oregon, and in summer and 

fall in the Gulf of Alaska (including Shelikof Strait), and the southeastern Bering Sea. Their 

regular summer occurrence has also been noted in recent years around the Pribilof Islands in the 

northern Bering Sea. Data suggest that, as in the North Atlantic, the migratory behavior of fin 

whales in the eastern North Pacific is complex: whales can occur in any one season at many 

different latitudes, perhaps depending on their age or reproductive state as well as their stock 

affinity. Movements can be either inshore/offshore or north/south. Some individuals remain at 

high latitudes through the winter. Fin whale concentrations in the northern North Pacific and 

Bering Sea generally form along frontal boundaries, or mixing zones between coastal and 

oceanic waters, which themselves correspond roughly to the 200-m isobath (shelf edge) (NMFS 

2006). 

Fin whales may occur seasonally in the southwestern Chukchi Sea, north of the Bering Strait 

along the coast of the Russian Chukotka (also referenced as the Chukchi) Peninsula. Their 

known current summer feeding habitat includes the southern portion, especially the 

southwestern portion, of the Chukchi Sea along the Asian coast. This species’ current use of 

parts of its historic range probably is modified due to serious population reduction during 

commercial hunting. However, there is no indication that fin whales typically occur within the 

Chukchi Sea or Beaufort Sea Planning Areas or in areas directly adjacent. There have been only 

rare observations of fin whales into the eastern half of the Chukchi Sea. In the southeast 

Chukchi Sea on September 23, 2006, three adult fin whales were seen from a vessel by marine 

mammal observers (Patterson, et al., 2007). In 1981, three fin whales (two adults, one calf) 

were observed (Ljungblad, et al., 1982) in the extreme southern Chukchi Sea associated with the 

aerial surveys of endangered whales in the Beaufort Sea, Chukchi Sea, and northern Bering Sea. 

These represent the only confirmed observations since 1979 in or near the planning areas 

(neither of these occurrences occurred within the planning areas). No other sightings of fin 

whales were reported during aerial surveys of endangered whales in summer (July) and autumn 

(August, September, and October) of 1979-1987 in the northern Bering Sea (from north of St. 

Lawrence Island), the Chukchi Sea north of lat. 66o N. and east of the International Date Line, 

and the Alaskan Beaufort Sea from long. 157o01’ W. east to long. 140o W. and offshore to lat. 

72o N. (Ljungblad et al., 1988). Fin whales have not been observed during annual aerial surveys 

of the Beaufort Sea conducted in September and October from 1982-2007 (e.g., Monnett and 

Treacy, 2005; Moore et al., 2000; Treacy, 2002; Monnett, 2008, pers. commun.). During a 

research cruise in the Chukchi and Beaufort seas (from July 5-August 18, 2003), in which all 

marine mammals observed were recorded, no fin whales were observed (Bengtson and 

Cameron, 2003). 

22
Thus, for the purposes of our analyses, we assume that: 

• Fin whales are uncommon to the eastern Chukchi Sea and the Chukchi OCS Planning 

Area in which lease sales are held. 

• Fin whales do occur south and west of the Chukchi Sea Planning Areas, and may expand 

northward in the future. 

Continued arctic warming could result in changes in oceanographic conditions favorable to the 

distribution and abundance of fin whale prey species, and the extended distribution into waters 

of the Chukchi and possibly Beaufort Sea. 

Feeding 

Fin whales feed primarily on euphausiids, or “krill”, but also consume substantial quantities of 

fish. In the North Pacific overall, fin whales apparently prefer euphausiids (mainly Euphausia 

pacifica, Thysanoessa longipes, T. spinifera, and T. inermis) and large copepods (mainly 

Calanus cristatus), followed by schooling fish such as herring, walleye pollock (Theragra 

chalcogramma), and capelin (Nemoto 1970; Kawamura 1982). Fin whales killed off central 

California in the early twentieth century were described as having either plankton (assumed to 

have been mainly or entirely euphausiids) or sardines (assumed to have been anchovies, 

Engraulis mordax) in their stomachs (Clapham et al. 1997). A larger sample of fin whales taken 

off California in the 1950s and 1960s were feeding mainly on krill (Euphausia pacifica), with 

only about 10% of the individuals having anchovies in their stomachs. 

Mizroch et al. 2001 report Thyanoessa raschii is the only species of euphausiid taken by fin 

whales In the northern Bering Sea, while fishes consumed by fin whales in Arctic and Subarctic 

waters are mainly capelin, Alaska Pollock, herring, and saffron cod. Fish is the main food for 

fin whales north of 58 degreees in the Bering Sea, and consists mainly of capelin, Pollock, and 

herring. 

Foraging areas tend to occur along continental shelves with productive upwellings or thermal 

fronts. Fin whales tend to avoid tropical and pack ice waters (NMFS 2006) with the northern 

limit set by ice and the southern limit by warm water of approximately 15°C (60°F. 

Vocalizations and hearing 

Underwater sounds of the fin whale are one of the most studied of the Balaenopteras. Fin 

whales produce a variety of low-frequency sounds in the 10 to 200 Hz band (NMFS 2005). The 

most typical signals are long, patterned sequences of short duration (0.5 to 2 seconds) infrasonic 

pulses in the 18 to 35 Hz range (Patterson and Hamilton 1964). Estimated source levels are as 

high as 190 dB re 1 μPa (McDonald and others 1995a; Patterson and Hamilton 1964; Thompson 

and others 1992; Watkins and others 1987), but Charif and others (2002) estimated source levels 

at 159 to 184 dB re 1 μPa after correcting for the Lloyd Mirror effect. In temperate waters 

intense bouts of long patterned sounds are very common from fall through spring, but also occur 

to a lesser extent during the summer in high latitude feeding areas (Clark and Charif 1998). 

Short sequences of rapid pulses in the 20 to 70 Hz band are associated with animals in social 

groups (McDonald and others 1995a). Each pulse lasts on the order of one second and contains 

twenty cycles (Tyack 1999). 

23
Particularly in the breeding season, fin whales produce series of pulses in a regularly repeating 

pattern. These bouts of pulsing may last for longer than one day (Tyack 1999). The seasonality 

and stereotype of the bouts of patterned sounds suggest that these sounds are male reproductive 

displays (Watkins and others 1987), while the individual counter-calling data of McDonald and 

others (1995a) suggest that the more variable calls are contact calls. As with other mysticete 

sounds, the function of vocalizations produced by fin whales is unknown. As with blue whales, 

the low-frequency sounds produced by fin whales have the potential to travel over long 

distances, and it is possible that long-distance communication occurs (Edds-Walton 1997; Payne 

and Webb 1971). 

No studies have directly measured the sound sensitivity of fin whales. In a study of the 

morphology of the mysticete auditory apparatus, Ketten (1997) hypothesized that large 

mysticetes have acute infrasonic hearing. 

Humpback Whale 

ESA Listing History and Current Status 

The humpback whale was listed as an endangered species on June 2, 1970 (35 FR 8495). No 

critical habitat has been designated for the species. 

Distribution 

Humpback whales are found primarily in coastal and continental shelf waters, but are known to 

migrate through deep waters between tropical/sub-tropical breeding and calving habitats during 

the winter and temperate/polar feeding habitats during the summer. Known breeding areas in the 

Pacific Ocean include Japan, the Hawaiian Islands, coastal Central America and Mexico, and 

Revillagigedo Archipelago. Humpback whales summer throughout the central and western 

portions of the Gulf of Alaska, including Prince William Sound, around Kodiak Island 

(including Shelikof Strait and the Barren Islands), and along the southern coastline of the Alaska 

Peninsula, as well as the coast of California. It is believed that minimal feeding occurs in 

wintering grounds (Salden 1987). 

NMFS (1991a) (citing Nikulin, 1946 and Berzin and Rovnin, both in Russian), summarized that 

the northern Bering Sea, Bering Strait, and southern Chukchi Sea along the Chukchi Peninsula 

are the northern extreme of the range of the humpback. Figure 38 of the most recent (Angliss 

and Outlaw, 2008) stock assessment for the Western North Pacific Stock (WNPS) depicts the 

southwestern Chukchi Sea as part of the “approximate distribution” of humpback whales in the 

North Pacific. Other references indicate that both the historical and current summer feeding 

habitat of the humpback included, and at least sometimes includes, the southern portion, 

especially the southwestern portion, of the Chukchi Sea. Mizroch et al. (In prep.) cited 

Zenkovich, a Russian biologist who wrote that in the 1930’s (quote in Mizroch et al., In prep.): 

“The Polar Sea, in areas near Cape Dezhnev...is frequented by large schools (literally 

hundreds...) of fin whales, humpbacks, and grays.” Mel’nikov (2000) wrote: 

In the fall, humpback whales formed aggregations in the most southern part of the 

Chukchi Sea, in the Senyavin Strait, and in the northern part of the Gulf of Anadyr. The 

24
whales left the area of the survey prior to the start of ice formation. Both in the past and 

at present, these waters are the summer feeding ground of humpback whales. The 

regular character of the encounters with the humpback whales points to signs of the 

restoration in their numbers in the waters off Chukchi Peninsula. 

Until 2007, historic and recent information did not indicate humpback whales inhabit northern 

portions of the Chukchi Sea or enter the Beaufort Sea. No sightings of humpback whales were 

reported during aerial surveys of endangered whales in summer (July) and autumn (August, 

September, and October) of 1979-1987 in the Northern Bering Sea (from north of St. Lawrence 

Island), the Chukchi Sea north of lat. 66o N. and east of the International Date Line, and the 

Alaskan Beaufort Sea from long. 157o01’ W. east to long. 140o W. and offshore to lat. 72o N. 

(Ljungblad et al., 1988). They have not been observed during annual aerial surveys of the 

Beaufort Sea conducted in September and October from 1982-2007 (e.g., Monnett and Treacy, 

2005; Moore et al., 2000; Treacy, 2002; Monnett, 2008, pers. commun.). During a 2003 

research cruise in which all marine mammals observed were recorded from July 5 to August 18 

in the Chukchi and Beaufort seas, no humpback whales were observed (Bengtson and Cameron, 

2003). One observation of one humpback whale was recorded in 2006 by marine mammal 

observers aboard a vessel in the southern Chukchi Sea outside of the Chukchi Sea Planning Area 

(Patterson et al., 2007; unpublished MMS marine mammal-observer reports, 2006). During 

summer 2007 between August 1 and October 16, humpback whales were observed during seven 

observation sequence events in the western Alaska Beaufort Sea (1) and eastern and 

southeastern Chukchi Sea (6) (unpublished MMS marine mammal-observer reports, 2007) and 

one other observation in the southern Chukchi Sea in 2007 (Sekiguchi, In prep.). 

Thus, for the purposes of our analyses, we assume that: 

• Humpback whales recently have been observed in the western Alaskan Beaufort Sea 

(2007) and southern and eastern Chukchi Sea (2006, 2007). We assume these areas are a 

portion of the potentially expanding summer distribution or summer feeding grounds for 

this species. 

• We assume that the humpback whales recently encountered in the Chukchi and Beaufort 

seas most likely would belong to the WNPS, but individual photo-identification and 

genetic data are needed to confirm stock origin. 

• We assume it is unlikely that humpback whales from the Central North Pacific Stock 

(CNPS) would be present in the northernmost Bering Sea near Bering Strait or 

seasonally be present within the southwestern, southeastern, or eastern Chukchi Sea or 

the western Beaufort Sea. 

• Humpback whales do not tend to occur farther north but can and do occur within the 

Chukchi Sea and western Beaufort Sea Planning Areas, and may continue to do so in the 

future. 

• Continued arctic warming could result in changes in oceanographic conditions favorable 

to the distribution and abundance of humpback whale prey species, and the seasonal 

distribution and movements of humpback whales. 

Observations by Mel’nikov (2000) of humpback whales adjacent to the Chukotka Peninsula 

indicate that humpbacks whales are present and feeding in the most northerly portions of the 

northwestern Bering Sea in the summer and autumn prior to ice formation. Thus, for purposes 

25
of analyses, we assume that humpbacks do occur seasonally just south of the Bering Strait and 

that these whales are the source of those observed in the U. S. Beaufort and Chukchi Seas in 

2006-2007 and likely to be of the WNPS. In 2007 humpbacks did occur in the western Beaufort 

Sea (one documented sighting sequence) and, in 2006 and 2007, were observed in the southern 

and eastern Chukchi Sea (seven documented sighting sequences); they transit between the 

Chukchi and Bering seas through the Bering Strait in summer and autumn. 

Population status and trends 

Three management units (populations) of humpback whales currently are recognized in the 

North Pacific. The following units migrate between their respective summer/fall feeding areas 

to winter/spring calving and mating areas in the North Pacific (Calambokidis et al. 1997, Baker 

et al. 1998): 

1) the California/Oregon/Washington and Mexico population, which are found 

winter/spring in coastal Central America and Mexico and migrate to the coast of 

California to southern British Columbia in summer/fall (Calambokidis et al. 

1989, Steiger et al. 1991, Calambokidis et al. 1993); 

2) the Central North Pacific population, which are found winter/spring in the 

Hawaiian Islands and migrate to northern British Columbia/southeast Alaska 

(including Glacier Bay) and Prince William Sound west to Kodiak in summer/fall 

(Baker et al. 1990, Perry et al. 1990, Calambokidis et al. 1997); and 

3) the Western North Pacific population, which occurs in winter/spring off Japan 

and, based on Discovery Tag information, probably migrate to waters west of the 

Kodiak Archipelago (the Bering Sea and Aleutian Islands) in summer/fall (Berzin 

and Rovnin 1966, Nishiwaki 1966, Darling 1991). 

For the purposes of this Opinion, the effects of the proposed action on humpback whales will be 

assessed for two of these three management units based on the known and suspected ranges of 

these populations, which would place only the Central North Pacific population and the Western 

North Pacific population within this area. 

Western North Pacific Population 

The continental shelf of the Aleutian Islands and Alaska Peninsula were once considered the 

center of the North Pacific humpback whale population (Berzin and Rovnin 1966; Nishiwaki 

1966). The northern Bering Sea, Bering Strait, and the southern Chukchi Sea along the Chukchi 

Peninsula appear to form the northern extreme of the Western North Pacific population’s range 

(Nikulin 1946, Berzin and Rovnin 1966). However, sightings of humpback whales in the Bering 

Sea were most frequent south of Nunivak Island and east of the Pribilof Islands (Berzin and 

Rovnin 1966; Braham et al. 1977; Nemoto 1978; Braham et al. 1982; Leatherwood et al. 1983). 

Surveys in the central-eastern and southeastern Bering Sea in 1999 and 2000 resulted in new 

information about the distribution of humpback whales in these areas (Moore et al. 2002). The 

only sightings of humpback whales in the central-eastern Bering Sea were southwest of St. 

26
Lawrence Island; animals co-occurred with a group of killer whales and a large aggregation of 

Arctic cod. A few sightings occurred in the southeast Bering Sea, primarily outside Bristol Bay 

and north of the eastern Aleutian Islands (Moore et al. 2002). In a NMFS survey cruise in 2001 

and 2002 of the central and eastern Aleutian Islands, humpback whales were most common in 

the area between Samalga and Unimak Islands (Sinclair et al. 2005). Of the 259 individuals 

seen, only 3 were west of Samalga. These recent sightings clearly demonstrate that the Aleutian 

Islands and Bering Sea remain important feeding areas (NMFS 2006a). In addition, a NOAA 

survey conducted in 2005 found numerous humpback whales north of the central Aleutian 

Islands, reinforcing the idea that the Bering Sea is an important foraging habitat (Angliss and 

Outlaw 2008). 

New information from a variety of sources indicates that humpback whales from the western 

and central North Pacific stocks mix on summer feeding grounds in the central Gulf of Alaska 

and perhaps the Bering Sea. A major research effort, SPLASH (Structure of Populations, Levels 

of Abundance and Status of Humpback Whale Stocks), was initiated in 2002 in order to better 

delineate stock structure of humpback whales in the North Pacific using a variety of techniques, 

and it is expected that this effort will assist in resolving stock structure in the near future 

(Angliss and Outlaw 2008). 

Central North Pacific Population 

Humpback whales in the Central North Pacific population summer throughout southeast Alaska, 

the central and western portions of the GOA, including Prince William Sound, around Kodiak 

Island (including Shelikof Strait and the Barren Islands), and along the southern coastline of the 

Alaska Peninsula. In Prince William Sound, during recent years [i.e., prior to 1991], humpback 

whales have congregated near Naked Islands, in Perry Passage, near Chenega Island, in Jackpot, 

Icy and Whale Bays, in Port Bainbridge and north of Montague Islands between Green Island 

and the Needle (Hall 1979, 1982; von Ziegesar 1984; von Ziegesar and Matkin 1986). The few 

sightings of humpback whales in offshore waters of the central GOA are usually attributed to 

animals migrating into coastal waters (Morris et al. 1983), although use of offshore banks for 

feeding is also suggested. 

Humpback whales of the Central North Pacific population spend the winter months in the waters 

off Hawaii where they breed, give birth to and nurse their calves. The whales undertake the 

northward migration to Alaska waters in late winter and generally arrive on the feeding grounds 

in May, remaining into November before returning to the waters off Hawaii. Some animals, 

however, remain on the feeding grounds year-round. Humpback whales do not feed while on 

the wintering grounds off Hawaii. 

Impacts of human activities 

Humpback whale populations were severely depleted from commercial whaling (see Forney and 

others 2000). With the prohibition on whaling, incidental entanglements in fisheries gear and 

ship strikes are the primary threats to humpback whales. Angliss and Outlaw (2008) report 54 

incidents of human-related mortalities between 2001 and 2005, of which 40 involved 

commercial fishing gear. On the Pacific coast, a humpback whale is killed about every other 

year by ship strikes (Barlow et al. 997). On the Atlantic coast, six out of 20 humpback whales 

stranded along the mid- Atlantic coast showed signs of major ship strike injuries (Wiley et al. 

27
1995). Almost no information is available on the number of humpback whales killed or injured 

by entanglement in fishing gear or ship strikes outside of U.S. waters. 

Life history 

Humpback whale reproductive activities occur primarily in winter. The age distribution of the 

humpback whale population is unknown, but the proportion of calves in various populations has 

been estimated at 4 to 12% (Bauer 1986; Clapham and Mayo 1987; Whitehead 1982). 

Humpback whales exhibit a wide range of foraging behaviors, and feed on a range of prey types 

including small schooling fishes, euphausiids, and other large zooplankton. Fish prey in the 

North Pacific include herring, anchovy, capelin, pollock, Atka mackerel, eulachon, sand lance, 

pollock, Pacific cod, saffron cod, arctic cod, juvenile salmon, and rockfish. Invertebrate prey 

include euphausiids, mysids, amphipods, shrimps, and copepods. 

Diving and social behavior 

Maximum diving depths for humpbacks are approximately 150 m (492 ft) (but usually <60 m or 

197 ft), with a very deep dive (240 m or 787 ft) recorded off Bermuda (Hamilton and others 

1997). They may remain submerged for up to 21 min (Dolphin 1987). In southeast Alaska 

average dive times were 2.8 min for feeding whales, 3.0 min for non-feeding whales, and 4.3 

min for resting whales (Dolphin 1987). In the Gulf of California humpback whale dive times 

averaged 3.5 min (Strong 1990). Because most humpback prey is likely found in waters 

shallower than 300 m most humpback dives are probably relatively shallow. Clapham (1996) 

reviewed the social behavior of humpback whales. They form small unstable groups during the 

breeding season. During the feeding season they form small groups that occasionally aggregate 

on concentrations of food. Feeding groups are sometimes stable for long periods of times. There 

is good evidence of some territoriality on feeding grounds (Clapham 1994; 1996), and on 

wintering grounds (Tyack 1981). On the breeding grounds males sing long complex songs 

directed towards females, other males or both. 

Vocalizations and hearing 

Humpbacks produce a wide variety of sounds. During the breeding season males sing long, 

complex songs, with frequencies in the 25 to 5000 Hz range and intensities as high as 181 dB 

(Payne 1970; Thompson et al 1986). Source levels average 155 dB and range from 144 to 174 

dB (Thompson et al. 1979). The songs appear to have an effective range of approximately 10 to 

20 km (six to 12 mi). Animals in mating groups produce a variety of sounds (Silber 1986; Tyack 

1981; Tyack and Whitehead 1983). Sounds are produced less frequently on the summer feeding 

grounds. Feeding groups produce distinctive sounds ranging from 20 Hz to 2 kHz, with median 

durations of 0.2 to 0.8 sec and source levels of 175 to 192 dB (Thompson and others 1986). No 

studies have directly measured the sound sensitivity of humpback whales. In a study of the 

morphology of the mysticete auditory apparatus, Ketten (1997) hypothesized that large 

mysticetes have acute infrasonic hearing. 

III. ENVIRONMENTAL BASELINE 

For the purposes of interagency consultations under Section 7 of the ESA, the environmental 

baseline is defined to include the past and present impacts of all Federal, State, or private actions 

and other human activities in an action area, the anticipated impacts of all proposed Federal 

28
projects in an action area that have already undergone formal or early Section 7 consultation, 

and the impact of State or private actions that are contemporaneous with the consultation in 

process [50 CFR §402.02]. 

The following factors, other than the proposed action, have had or are having potential effects on 

all or some of these endangered species of whales: 

historic commercial whaling; 

subsistence hunting; 

oil- and gas-related activity; 

non-oil and gas industrial development within the range of these whales; 

research activities; 

marine vessel-traffic and commercial-fishing; 

pollution and contaminants baseline; and 

climate change. 

There are no data available that indicate that, other than historic commercial whaling, any 

previous human activity has had a significant population-level adverse impact on the current 

status of fin whales, the Western Arctic stock of bowheads, the Central North Pacific and 

Western North Pacific stocks of humpback whales, or the recovery of any of these species. 

Currently available information indicates that at the population level, bowheads using the 

Beaufort and Chukchi Sea Planning Areas are resilient at least to the level of human-caused 

mortality and disturbance that currently exists within their range, and has existed since the 

cessation of commercial whaling. Although data on such impacts to humpback and fin 

populations in the Beaufort and Chukchi Sea Planning Areas are currently lacking, it is 

reasonable to assume that effects may be similar and that these species are also resilient to the 

current level of human-caused mortality and disturbance in these areas. Given that these whales 

have not previously been detected in the action area, it is likely that only a small portion of the 

population is using this habitat and thus impacts would not rise to a population level effect. 

Data indicate that at least some bowheads are extremely long-lived (100+ years or more). Thus, 

many of the individuals in this population may already have been exposed to a high number of 

disturbance events in their lifetimes. The primary known current human-related cause of 

mortality is a regulated subsistence hunt by Alaska Natives, which occurs at different times of 

the year in many of the coastal portions of their range. No subsistence hunt occurs on either fin 

whales or humpback whales. 

The existence of the bowhead hunt has focused Native, local, state, federal, international, and 

industry research and monitoring attention on this stock and the development of mitigations 

intended to ensure its continued availability for subsistence take adequate to meet the needs of 

bowhead-hunting Native communities. Since the level of take is directly linked to the 

population abundance and status of this population, protection of the availability of whales for 

subsistence take is linked to protection needed to ensure the long-term viability of the 

population. Whether there are long-lasting behavioral effects from this activity is unknown, but 

overall habitat use appears to be relatively unaffected. 

Historical Commercial Whaling 

29
It is clear that commercial whaling between 1848 and 1915 was the human activity that had the 

greatest adverse effect on the bowhead whale population. Woody and Botkin (1993) estimated 

that the historic abundance of bowheads in this population was between 10,400 and 23,000 

whales in 1848, before the advent of commercial whaling. Woody and Botkin (1993) estimated 

between 1,000 and 3,000 animals remained in 1914, near the end of the commercial-whaling 

period. Commercial whaling also may have caused the extinction of some subpopulations and 

some temporary changes in distribution. Following protection from whaling, this population 

(but not some other bowhead populations) has shown marked progress toward recovery. As 

noted in the affected environment section, bowhead population estimates for 2001 range 

between 10,470 (SE = 1,351) with a 95% confidence interval of 8,100–13,500 (George et al., 

2004) and 10,545 CV(N) =0,128 (Zeh and Punt, 2004, cited in Angliss and Outlaw, 2005. Thus 

estimated bowhead population size is within the lower bounds of estimates of the historic 

population size. Recently, Shelden et al. (2001, 2003) concluded that this population should be 

removed from the list of species designated as endangered under the ESA. 

Significant commercial whaling harvest also reduced the size of the humpback whale 

population. At the time of its listing as endangered under the ESA in 1973, the population was 

considered to be in danger of extinction in all or a portion of its range. Historically, both 

aboriginal and early commercial harpoon whalers harvested an unknown number of humpback 

whales. Much greater harvest pressure occurred in the 20th century when these animals were 

subject to heavy commercial exploitation during modern whaling operations. Prior to 1905, 

there were an estimated 15,000 humpback whales in the entire North Pacific; by 1966, following 

commercial harvest, the population was estimated to be between 1,000 and 1,200 animals. 

Measures to protect the humpback whales in the North Atlantic were first taken in 1946 with the 

establishment of the regulatory International Whaling Commission (IWC), and a ban on nonsubsistence hunting followed in 1955. In 1965, the IWC banned the commercial hunting of 

humpback whales in the Pacific Ocean. Soviet whalers, however, continued to harvest 

humpback whales until 1980 (Perry et al.1999). Currently, some illegal whaling continues 

although actual harvest levels are unknown. 

Fin whales were hunted occasionally by the sailing-vessel whalers of the 19th century (e.g., see 

Scammon 1874; Mitchell and Reeves 1983). The introduction of steam power in the second half 

of that century made it possible for boats to overtake the large, fast-swimming rorquals, 

including fin whales, and the use of harpoon-gun technology resulted in a high loss rate (Schmitt 

et al. 1980; Reeves and Barto 1985). The eventual introduction of deck-mounted harpoon 

cannons made it possible to kill and secure blue, fin, and sei whales on an industrial scale 

(Tønnessen and Johnsen 1982). Fin whales were hunted, often intensively, in all the world's 

oceans for the first three-quarters of the twentieth century. The total reported catch of fin whales 

in the Southern Hemisphere from 1904 through 1979 was close to three-quarters of a million, 

making them numerically dominant, by far, among the commercially exploited baleen whales 

(see IWC 1995:129B30). 

Under the 1946 International Convention for the Regulation of Whaling, a minimum size limit 

of 55 ft (16.8 m) was in effect for fin whales taken by commercial whaling in the North Pacific, 

and two fin whales were calculated as equivalent to one Ablue whale unit@ under the initial 

production quota scheme (Allen 1980). The International Whaling Commission (IWC) did not 

begin managing commercial whaling for fin whales on a species basis until 1969 in the North 

Pacific (Allen 1980) and 1976 in the North Atlantic (Sigurjónsson 1988). The fin whale was 

given full protection from commercial whaling in the Antarctic beginning in the 1976/77 

whaling season, the North Pacific in the 1976 season, and the North Atlantic in the 1987 season. 

30
Since 1987, the only area in the Northern Hemisphere where fin whales have been hunted 

legally is Greenland. There, a take of about 20 fin whales per year has been authorized under the 

IWC=s aboriginal subsistence whaling scheme (Gambell 1993; Caulfield 1993). 

Subsistence Hunting 

Indigenous peoples of the arctic and subarctic of what is now Alaska have been hunting 

bowhead whales for at least 2,000 years (Stoker and Krupnik, 1993). Thus, subsistence hunting 

is not a new contributor to cumulative effects on this population. There is no indication that, 

prior to commercial whaling, subsistence whaling caused significant adverse effects at the 

population level. However, modern technology has changed the potential for any lethal hunting 

of this whale to cause population-level adverse effects if unregulated. Under the authority of the 

IWC, the subsistence take from this population has been regulated by a quota system since 1977. 

Federal authority for cooperative management of the Eskimo subsistence hunt is shared with the 

Alaska Eskimo Whaling Commission (AEWC) through a cooperative agreement between the 

AEWC and the United States Department of Commerce, National Oceanic and Atmospheric 

Administration (NOAA). 

The sustainable take of bowhead whales by indigenous hunters represents the largest known 

human-related cause of mortality in this population at the present time. Available information 

suggests that it is likely to remain so for the foreseeable future. While other potential effectors 

primarily have the potential to cause, or to be related to, behavioral or sublethal adverse effects 

to this population, or to cause the deaths of a small number of individuals, little or no evidence 

exists of other common human-related causes of mortality. Subsistence take, which all available 

evidence indicates is sustainable, monitored, managed, and regulated, helps to determine the 

resilience of the population to other impacts that could potentially cause lethal takes. 

Currently, Alaskan Native hunters from 10 villages harvest bowheads for subsistence and 

cultural purposes under a quota authorized by the IWC. Chukotkan Native whalers from Russia 

also are authorized to harvest bowhead whales under the same authorized quota. The status of 

the population is closely monitored, and these activities are closely regulated. Strike limits are 

established by the IWC and set at a 5-year quota of 280 landings. The sustained growth of the 

Western Arctic bowhead population indicates that the level of subsistence take has been 

sustainable. Because the quota for the hunt is tied to the population size and population 

parameters, it is unlikely this source of mortality will contribute to a significant adverse effect 

on the recovery and long-term viability of this population. 

There are adverse impacts of the hunting to bowhead whales in addition to the death of animals 

that are successfully hunted and the serious injury of animals that are struck but not immediately 

killed. Available evidence indicates that subsistence hunting causes disturbance to the other 

whales, changes in their behavior, and sometimes temporary effects on habitat use, including 

migration paths. Modern subsistence hunting represents a source of noise and disturbance to the 

whales. Whales in the vicinity of a struck whale could be disturbed by the sound of the 

explosive used in the hunt, the boat motors, and any sounds made by the injured whale. NMFS 

(2003a) pointed out that whales that are not struck or killed may be disturbed by noise 

associated with the approaching hunters, their vessels, and the sound of bombs detonating: 

“...the sound of one or more bombs detonations during a strike is audible for some distance. 

Acousticians, listening to bowhead whale calls as part of the census, report that calling rates 

drop after such a strike ...” (NMFS, 2003). We are not aware of data indicating how far 

31
hunting-related sounds (for example, the sounds of vessels and/or bombs) can propagate in areas 

where hunting typically occurs, but this is likely to vary with environmental conditions. It is not 

known if whales issue an “alarm call” or a “distress call” after they, or another whale, are struck. 

NMFS (2003) reported that: 

...whales may act skittish” and wary after a bomb detonates, or may be displaced further 

offshore (E. Brower, pers. com.). However, disturbances to migration as a result of a strike are 

temporary (J. George, 1996), as evidenced when several whales may be landed at Barrow in a 

single day. There is some potential that migrating whales, particularly calves, could be forced 

into thicker offshore ice as they avoid these noise sources. The experience of Native hunters 

suggests that the whales would be more likely to temporarily halt their migrations, turn 180 

degrees away...(i.e., move back through the lead systems), or become highly sensitized as they 

continue moving (E. Brower, pers. com.). 

Because evidence indicates that bowhead whales are long-lived, some bowhead whales may 

have been in the vicinity where hunting was occurring on multiple, perhaps dozens or more, 

occasions. Thus, some whales may have cumulative exposure to hunting activities. This form 

of noise and disturbance adds to noise and disturbance from other sources, such as shipping and 

oil and gas-related activities. To the extent such activities occur in the same habitats during the 

period of whale migration, even if the activities (e.g., hunting and shipping) themselves do not 

occur simultaneously, cumulative effects from all noise and disturbance could affect whale 

habitat use. However, we are not aware of information indicating long-term habitat avoidance 

has occurred with present levels of activity. Additionally, if whales become more “skittish” and 

more highly sensitized following a hunt, it may be that their subsequent reactions, over the 

short-term, to other forms of noise and disturbance are heightened by such activity. Data are not 

available that permit evaluation of this possible, speculative interaction. 

There is currently no subsistence hunt for humpback whales or fin whales in U.S. waters. Fin 

whales, however, are presently hunted legally in the Northern Hemisphere in Greenland under 

the IWC’s procedure for aboriginal subsistence whaling.

Commercial-Fishing, Marine Vessel-Traffic, and Research Activities 

Bowhead Whales 

Based on available data, previous incidental take of bowhead whales apparently has occurred 

only rarely. The bowhead’s association with sea ice limits the amount of fisheries activity 

occurring in bowhead habitat. However, the frequency of such interactions in the future would 

be expected to increase if commercial-fishing activities expand northward. There is some 

uncertainty about whether such expansion will occur. Increases in spatial overlap alone could 

result in increased interactions between bowheads and derelict fishing gear. In a discussion of 

population climate warming impacts on bowheads at the meeting of the Subcommittee on 

Bowheads, Right Whales and Gray Whales at the IWC’s annual meeting, P. Wade (referred to in 

IWC, 2005b) reported that that the commercial crab fishery extended further north the previous 

winter (winter 2004-2005) than in previous years. 

Between 1989 and 1994, logbook data on incidental take of bowheads are available, but after 

that time, the requirement is for fishers to self report. Angliss and Lodge (2002) reported that 

32
“the records are considered incomplete and estimates of mortality based on them represent 

minimums.” There are no observer program records of bowhead whale mortality incidental to 

commercial fisheries in Alaska (Angliss and Lodge, 2002). New information on entanglements 

of bowhead whales indicates that bowheads do have interactions with crab-pot gear. There have 

been two confirmed occurrences of entanglement in crab-pot gear, one in 1993 and one in 1999 

(Angliss and Lodge, 2008). Table 41 in Angliss and Lodge (2008) details reports of scarring of 

bowhead whales attributed to entanglement in ropes. Citing a personal communication from 

Craig George of the NSB, Department of Wildlife Management, Angliss and Lodge (2008 report 

a preliminary result from reexamination of bowhead harvest records suggest that there may be 

more than 20 cases indicating entanglements or scarring attributable to ropes in the bowhead 

harvest records. Angliss and Lodge (2008) reported that the annual rate of bowhead 

entanglement in marine debris/gear for the period 2003-2008 is 0.4. 

Potential effects on bowhead whales from commercial-fishing activities include incidental take 

in the fisheries and/or entanglement in derelict fishing gear resulting in death, injury, or effects 

on the behavior of individual whales; disturbance resulting in temporary avoidance of areas; and 

whales being struck and injured or killed by vessels. Bowheads have been entangled in ropes 

from crab pots, harpoon lines, or fishing nets; however, the frequency of occurrence is not 

known. 

Marine vessel traffic, in general, can pose a threat to bowheads because of the risk of ship 

strikes. Shipping and vessel traffic is expected to increase in the arctic if warming continues. 

Additionally, noise associated with ships or other boats potentially could cause bowheads to 

alter their movement patterns or make other changes in habitat use. Pollution from marine 

vessel traffic, especially from large vessels such as large cruise ships, also could cause 

degradation of the marine environment and increase the risk of the whales’ exposure to 

contaminants and disease vectors. The frequency of observations of vessel-inflicted injuries 

suggests that the incidence of ship collisions with bowhead whales is low but may be increasing. 

Between 1976 and 1992, only three ship-strike injuries were documented out of a total of 236 

bowhead whales examined from the Alaskan subsistence harvest (George et al. 1994). The low 

number of observations of ship-strike injuries suggests that bowheads either do not often 

encounter vessels, or they avoid interactions with vessels, or that interactions usually result in 

the animals’ death. 

Increased use of vessels for ice management associated with oil and gas exploration may present 

concerns for bowhead whales. During icebreaking, extremely variable increases in broad-band 

(10-10,000 Hz) noise levels of 5-10 dB are caused by propeller cavitation. Richardson et al. 

(1995a) reported estimated source levels for icebreakers to range from 177-191 db re 1 μPa-m. 

Based on previous studies of bowhead response to noise, such sound could result in temporary 

avoidance of animals from the areas where the icebreakers were operating and potentially cause 

temporary deflection of the migration corridor, depending of the location of the icebreakers. 

Richardson et al. (1995) concluded that: “Ships and larger boats routinely use fathometers, and 

powerful side-looking sonars are common on many military, fishing, and bottom-survey 

vessels.... Sounds from these sources must often be audible to marine mammals and apparently 

cause disturbances in some situations.” 

33
Active sonars were used in commercial whaling after World War II, and whaling boats 

sometimes tracked whales underwater using active sonar. Ash (1962), cited in Richardson et al., 

1995a) reported that this often caused strong avoidance by baleen whales. Reeves (1992) 

reported that ultrasonic pulses were used to scare baleen whales to the surface. Maybaum (1990, 

1993) reported that humpback whales on the wintering grounds moved away from 3.3 kHz sonar 

pulses and increased their swimming speed and swim-track linearity in response to 3.1- to 3.6-

kHz sonar sweeps. We have no information that active sonar is currently an issue within the 

action area. 

Large research ships that are active in the range of the bowheads during periods when they are 

present have the potential to cause noise and disturbance to the whales, potentially altering their 

movement patterns or other behavior. However, available evidence does not indicate such 

disturbance will have a significant effect on this population over the approximate life of the 

project, even when added to the effects of other effectors. The Western Arctic bowhead has 

been the focus of research activities that could, in some instances, cause minor temporary 

disturbance of the whales. During research on the whales themselves, the reactions of the 

whales generally are closely monitored to minimize potential adverse effects. Additionally, 

research conducted primarily for reasons other than the study of the bowhead has also occurred 

within the range of the bowhead. In some cases, such research has the potential to adversely 

affect the whales through the introduction of additional noise, disturbance, and low levels of 

pollution into their environment. 

Some of the research projects discussed here are continuing in the future, but have already been 

initiated. Previous research on bowheads has included aerial surveys, ship-based observations, 

acoustic studies, shore-based censuses, studies involving samples and examination of carcasses 

of animals killed in the subsistence hunt, and satellite tracking. NMFS recently initiated photoidentification studies. MMS will be procuring a large study aimed at better understanding the 

importance of feeding areas in the western Alaskan Beaufort Sea. In these future activities, as in 

the past, the primary result of ship-based activities could be temporary disturbance of individual 

whales from a highly localized area. Whales might slightly and temporarily alter their habitat 

use to avoid large vessels. Whales also could be temporarily harassed or disturbed by lowflying airplanes during photo-identification work. These effects would be as described for lowflying aircraft. All such effects are expected to be of short duration. Aerial surveys generally 

are flown at a height such that they do not cause harassment. 

Submarines are highly valued platforms for a variety of oceanic research in part because they are 

relatively quiet, enabling the use of active and passive acoustic technologies for a variety of 

studies. U.S. Navy submarines are likely to continue to be used as platforms in the future. In 

recent years, there also have been scientific field operations in the Arctic Ocean that have used 

U.S. Navy submarines as platforms. Other ships have made numerous research trips into the 

range of the bowhead. For example, in 1995, the NRC reported that the Alpha Helix had 

performed numerous research cruises in the North Pacific, Bering Sea, Chukchi Sea, and 

Alaskan coastal waters over the past 15 years (NRC, 1995). Operation of this vessel is primarily 

limited to open water. The R/V Alpha Helix has modest ice-strengthening characteristics but no 

icebreaking capability. 

34
Humpback Whales 

Humpback whales are killed incidentally in federal groundfish and longline fisheries and state 

managed-commercial salmon fisheries. The primary source for data on incidental mortalities of 

humpback whales in commercial fisheries is from the North Pacific Groundfish Observer 

Program database (NMFS GOP) and Alaska Marine Mammal Observer Program. Data on 

entanglements and other interactions with fishing gear is also reported through NMFS’ Alaska 

Marine Mammal Stranding Network. 

Until 2004, there were four different federally-regulated commercial fisheries in Alaska that 

occurred within the range of the Central North Pacific humpback whale stock that were 

monitored for incidental mortality by fishery observers: BSAI groundfish trawl, GOA 

groundfish trawl, longline, and pot fisheries. Average annual mortality from the observed 

fisheries was 1.5 (CV = 0.47) humpback whales from this population. As of 2004, changes in 

fishery definitions in the List of Fisheries have resulted in separating these four fisheries into 17 

fisheries (69 FR 70094, 2 December 2004). This change does not represent a change in fishing 

effort, but provides managers with better information on the component of each fishery that is 

responsible for the incidental serious injury or mortality of marine mammal stocks in Alaska. 

Between 2001 and 2005, there were incidental serious injuries and mortalities of Central North 

Pacific humpback whales in the Bering Sea/Aleutian Islands sablefish pot fishery. Estimates of 

marine mammal serious injury/mortality in observed fisheries can be found in Perez (2006). 

Within the range of the Western North Pacific humpback whale population, there were six 

different federally-regulated commercial fisheries in Alaska that were monitored for incidental 

mortality by fishery observers until 2004. At that time, changes in fishery definitions in the List 

of Fisheries have resulted in separating these six fisheries into 22 fisheries (69 FR 70094, 2 

December 2004). Between 2000 and 2004, there were incidental serious injuries and mortalities 

of Western North Pacific humpback whales in the Bering Sea/Aleutian Islands sablefish pot 

fishery. Average annual mortality from observed fisheries was 0.20 humpbacks from this stock. 

Note, however, that the stock identification is uncertain and the mortality may have involved a 

whale from the Central North Pacific stock of humpback whales. Thus, this mortality is 

assigned to both the Central and Western stocks. 

No strandings or sightings of entangled humpback whales from the Western North Pacific 

population were reported between 1999 and 2003; however, observing effort in western Alaska 

is low (Angliss and Outlaw 2006). The western population of humpback whales may be 

impacted by takes in other countries’ fisheries. Brownell et al. (2000) compiled records of 

bycatch of humpback whales in Japanese and Korean commercial fisheries between 1993 and 

2000 and found that, during 1995-99, six humpback whales were taken as bycatch. In addition, 

two strandings were reported by the Japanese or Korean during this period. Analysis of four 

samples from meat found in Japanese markets indicated that humpback whales are being sold 

(Angliss and Outlaw 2006). Where these animals are taken, however, and whether they are 

taken intentionally or as bycatch, is unknown (NMFS 2006a). 

In recent years, an increasing number of entangled humpback whales have been reported to 

NMFS Alaska Region stranding program. Ninety-seven humpback whales were reported 

entangled in Alaska from 1997-2007; the majority of these involved southeast Alaska 

35
humpbacks (NMFS Alaska Region stranding data). For some of these reports, it remains 

unclear whether they represent distinct events or re-sights of the same entangled animal. For 

many of these reports, it is not possible to identify the gear involved in the entanglement to a 

specific fishery. This is based on a general lack of data in reports received, the difficulty in 

accurately describing gear at a distance, and the fact that most entanglements are not re-sighted 

for follow-up analysis. The majority of gear reported in Alaska humpback whale entanglements 

involves crab, shrimp, and unidentified pot gear. 

Ship strikes are also a human-caused source of injury and mortality for humpback whales. A 

compilation of available vessel collision records to large whales from 1975 to 2002 indicated 

that humpback whales are one of the most frequently hit species worldwide (Jensen and Silber 

2003). Of the database containing 292 records, humpback whales (44 records) were the second 

most commonly hit species after fin whales (75 records). In Alaska, numerous incidents of 

vessel collisions have been documented, although there is no official reporting system for ship 

strikes. Fifty-four reports from 1986 to 2007 representing confirmed, unconfirmed and 

suspected ship strikes with humpback whales exist in the NMFS stranding database. This is a 

minimum estimate, as not all whales struck are reported and not all whales struck are identified 

to species or cause of mortality. The fate of struck animals is also not always determined unless 

the whale dies immediately upon impact or is discovered as a carcass on the bow of a ship and it 

can be determined that the strike was the cause of death. 

Records of vessel collisions with large whales in Alaska indicate that strikes have involved 

cruise ships, recreational cruisers, whale watching catamarans, fishing vessels, and skiffs. 

Vessel lengths associated with these records ranged from approximately 20 feet to over 250 feet, 

indicating that all types and sizes of watercraft pose a threat of collision for whales (Jensen and 

Silber 2003). This includes large commercial vessels such as cruise ships, large tug and barge 

transport vessels, and oil transport tankers. Cruise ships are of particular concern, as they 

operate at considerably high speeds and frequent the inside waters of southeast Alaska with 

routes passing through areas of humpback whale abundance such as Glacier Bay National Park 

and Preserve, Point Adolphus and Lynn Canal. Oil transport tankers are generally operating 

farther offshore where there are presumably fewer concentrations of humpback whales, except 

for transit through Prince William Sound. In addition to large ships, which are most likely to 

cause significant injury or death to humpback whales, smaller tour, charter and private vessels 

also significantly overlap with inshore humpback whale distribution in Alaska waters and also 

have the potential to cause disturbance, serious injury, and possibly mortality. Collisions in 

Alaska can occur throughout the region, peaking during the summer season. 

No humpback whale stranding, entanglement or ship strike reports exist on file with NMFS for 

the action area of the Chukchi and Beaufort Seas. At the time of this opinion, the number of 

entanglements in other parts of the state that might result in serious injury or mortality for 

humpback whales is not known to be at a level to have population level effects for the species. 

Although fishing effort in the Chukchi and Beaufort is currently minimal, with melting sea ice 

the industry may gradually move northward. Likewise, if warming continues, vessel traffic and 

shipping are expected to increase in the Arctic which may pose a greater threat of ship strike for 

humpback whales. In addition, the range of humpback whales in the North Pacific may expand 

as conditions shift, resulting in a greater probability of interaction. Noise and pollution from 

36
vessels could also cause humpback whales to alter their movement patterns or make other 

changes in habitat use. 

Fin Whales 

Fin whales are killed and injured at least occasionally by inshore fishing gear (e.g., gillnets and 

lobster lines) off eastern Canada and the United States (Read 1994; Lien 1994; Waring et al. 

1997). Although the mortality from entanglement is thought to be much less for fin whales in 

proportion to population abundance than it is for many other species of baleen whales, more 

information is needed to evaluate this supposition. Prior to 1999, there were no observed or 

reported mortalities of fin whales incidental to commercial fishing operations within their North 

Pacific range. However, in 1999, one fin whale was killed incidental to the Gulf of Alaska 

pollock trawl fishery (Angliss and Outlaw 2008). There have been no records of fin whale 

fishery interactions or entanglements within the action area of the Chukchi and Beaufort Seas. 

Ship strikes have injured or killed fin whales off both the U.S. east coast (Waring et al. 1997) 

and west coast. At least one, and probably more, fin whales were killed by collisions with ships 

off California in the early 1990s (Barlow et al. 1997). In a report by Jensen and Silber (2003) 

compiling large whale ship strikes world-wide, fin whales were the species most often reported 

as victims of ship strike out of the eleven species evaluated. Seventy-five reports were compiled 

for fin whales, from locations along the U.S. east coast and Canada, Washington and California. 

Internationally, a number of ship strikes with fin whales have been reported from the 

Mediterranean Sea, France and England (Jensen and Silber 2003). 

According to Schevill et al. (1964), fin whales Aseems somewhat to avoid ships.@ In Cape Cod 

waters, fin whales were notably wary of vessels before the mid-1970s, but since then they have 

become much less responsive to vessels (Watkins 1986). Edds and Macfarlane (1987) 

documented that a fin whale observed from an elevated site on the north shore of the St. 

Lawrence River significantly reduced its mean dive time while it was being pursued by a ferry 

carrying whale watchers. Also in the St. Lawrence, Michaud and Giard (1998) documented 

short-term changes in dive behavior of fin whales approached by vessels. Fin whales observed 

from a lighthouse in Maine responded to the presence of vessels by decreasing dive times, 

surface times, and number of blows per surfacing (Stone et al. 1992). 

Fourteen stranding records exist for fin whales in Alaska between 1981-2006 in the Alaska 

Region marine mammal stranding database. For most of these cases, the cause of death could 

not be determined. However, two records of fin whale ship strike exist; one in Uyak Bay in 

Kodiak in 2000, and one in Resurrection Bay near Seward in 2006. 

Fin whales may also be subject to disturbance from human activities. The species attracts many 

whale-watching enterprises in eastern Canada and the northeastern United States (Hoyt 1984; 

Beach and Weinrich 1989). As a result, they are regularly subjected to close and persistent 

following by vessels in these areas. However, given that fin whales are much less often subject 

to whale watching in the North Pacific than in the North Atlantic, disturbance in the Pacific is 

more likely to come from the abundant industrial, military, and fishing vessel traffic off the 

Mexican, U.S., and Canadian coasts than from the deliberate approaches of whale-watching 

vessels. The low-frequency sounds used by fin whales for communication and (possibly) in 

courtship displays (Watkins 1981) could be masked or interrupted by loud noise from ships, 

seismic testing, explosives, and other sources. In a study off Oregon, however, fin whales 

continued to produce their normal sounds despite the presence of seismic air gun pulses 

(McDonald et al. 1993). 

37
No evidence is available to indicate that military activities have had an impact on fin whale 

populations. However, concern about the potential for injury or disturbance to cetaceans 

influenced the siting and timing of ship-shock trials on the Scotian Shelf in November 1994 (see 

Reeves and Brown 1994), and off the California coast in June 1994. Recent military activities 

are not known to have had impacts on fin whales in the North Pacific. However, the large scale 

and diverse nature of military activities in this ocean basin mean that there is always potential 

for disturbing, injuring, or killing these and other whales (NMFS 2000). 

No fin whale stranding, entanglement or ship strike reports exist on file with NMFS for the 

action area of the Chukchi and Beaufort Seas. Currently, human impacts that might result in 

serious injury or mortality for fin whales in Alaska is not known to be at a level to have 

population level effects for the species. Although fishing effort in the Chukchi and Beaufort is 

currently minimal, with melting sea ice the industry may gradually move northward. Likewise, 

if warming continues, vessel traffic and shipping are expected to increase in the Arctic which 

may pose a greater threat of ship strike for fin whales. In addition, the range of fin whales in the 

North Pacific may expand as conditions shift, resulting in a greater probability of interaction. 

Noise and pollution from vessels could also cause fin whales to alter their movement patterns or 

make other changes in habitat use. 

Pollution and Contaminants 

Initial studies of bowhead tissues collected from whales landed at Barrow in 1992 (Becker et al., 

1995) indicate that bowhead whales have very low levels of mercury, PCB’s, and chlorinated 

hydrocarbons, but they have fairly high concentrations of cadmium in their liver and kidneys. 

The study concluded that the high concentration of cadmium in the liver and kidney tissues of 

bowheads warrants further investigation. Becker (2000) noted that concentration levels of 

chlorinated hydrocarbons in bowhead whale blubber generally are an order of magnitude less 

than what has been reported for beluga whales in the arctic. This probably reflects the 

difference in the trophic levels of these two species; the bowhead being a baleen whale feeding 

on copepods and euphausiids, while the beluga whale being a toothed whale feeding at a level 

higher in the food web. The concentration of total mercury in the liver also is much higher in 

beluga whales than in bowhead whales. 

Bratton et al. (1993) measured organic arsenic in the liver tissue of one bowhead whale and 

found that about 98% of the total arsenic was arsenobetaine. Bratton et al. (1997) looked at 

eight metals (arsenic, cadmium, copper, iron, mercury, lead, selenium, and zinc) in the kidneys, 

liver, muscle, blubber, and visceral fat from bowheads harvested from 1983-1990. They 

observed considerable variation in tissue metal concentration among the whales tested. Metal 

concentrations evaluated did not appear to increase over time between 1983 and 1990. Based on 

metal levels reported in the literature for other baleen whales, the metal levels observed in all 

tissues of the bowhead are similar to levels in other baleen whales. The bowhead whale has 

little metal contamination as compared to other arctic marine mammals, except for cadmium, 

which requires further investigation as to its role in human and bowhead whale health. The 

study recommended limiting the consumption of kidney from large bowhead whales pending 

further evaluation. 

Cooper et al. (2000) analyzed anthropogenic radioisotopes in the epidermis, blubber, muscle, 

kidney, and liver of marine mammals harvested for subsistence food in northern Alaska and in 

38
the Resolute, Canada region. The majority of samples analyzed had detectable levels of 137Cs. 

Among tissues of all species of marine mammals analyzed, 137Cs was almost always 

undetectable in the blubber and significantly higher in epidermis and muscle tissue than in the 

liver and kidney tissue. The levels of anthropogenic radioisotopes measured were orders of 

magnitude below levels that would merit public health concern. The study noted there were no 

obvious geographical differences in 137Cs levels between marine mammals harvested in 

Resolute, Canada and those from Alaska. However, the 137Cs levels in marine mammals were 

two to three orders of magnitude lower than the levels reported in caribou in northern Canada 

and Alaska. 

Based on the use of autometallography (AMG) to localize inorganic mercury in kidney and liver 

tissues for five bowhead whales, Woshner et al. (2002) reported that “AMG granules were not 

evident in bowhead tissues, confirming nominal mercury (Hg) concentrations.” Detected 

concentrations ranged from 0.011-0.038 micrograms per gram (μg/g) wet weight for total 

mercury. Mössner and Ballschmiter (1997) reported that total levels of 310 nanograms per gram 

(ng/g) polychlorinated biphenyls and chlorinated pesticides in bowhead blubber from the North 

Pacific/Arctic Ocean, an overall level many times lower than that of other species from the 

North Pacific or Arctic Ocean (beluga whales [2,226 ng/g]; northern fur seals [4,730 ng/g]) and 

than that of species from the North Atlantic (pilot whale [6,997 ng/g]; common dolphin [39,131 

ng/g]; and harbor seal [70,380 ng/g]). However, while total levels were low, the combined level 

of 3 isomers of the hexachlorocyclohexanes was higher in the bowhead blubber (160 ng/g) 

tested than in either the pilot whale (47 ng/g), the common dolphin (130 ng/g), and the harbor 

seal (140 ng/g). These results confirmed results expected due to the lower trophic level of the 

bowhead relative to the other marine mammals tested. 

In the Beaufort Sea multiple-sale EIS in 2003, MMS concluded that the levels of metals and 

other contaminants measured in bowhead whales appear to be relatively low, with the exception 

of cadmium. Since the finalization of the multiple-sale EIS, additional information (included in 

the review presented above) on contaminants in Western Arctic bowheads has become available. 

This information supports this same general conclusion. 

In contrast to the available data on contaminants in bowhead tissues, little information is 

available on contaminant levels for humpback and fin whales. Because these are not species 

which are subsistence hunted for consumption, fresh tissue samples are far less readily available 

and must be collected through necropsies performed by the stranding network. Although little 

data is available to form conclusions about contaminant levels in the tissues of these species, it is 

reasonable to assume that fin and humpback whales, as large mammals at a high trophic level, 

are susceptible to the bioaccumulation of organochlorine and metal contaminants through their 

regular diet of fish and euphausiids. 

Offshore Oil- and Gas-Related Activities and other Industrial Activities 

Offshore petroleum exploration, development, and production activities have been conducted in 

Alaska State waters or on the Alaska OCS in the Beaufort and Chukchi seas as a result of 

previous lease sales since 1979. Extensive 2D seismic surveying has occurred in both program 

areas. The MMS-permitted seismic surveys have been conducted in the Chukchi and Beaufort 

seas since the late 1960’s and early 1970’s. Much more seismic activity has occurred in the 

39
Beaufort Sea OCS than in the Chukchi Sea OCS. The 2D marine seismic surveys in the 

Beaufort Sea began with two exploration geophysical permits issued in 1968 and 4 in 1969. 

Both over-ice (29 permits) and marine 2D (43 permits) seismic surveys were conducted in the 

1970’s. With one exception, all 80 marine and 43 over-ice surveys permitted in the Beaufort 

Sea OCS by MMS in the 1980’s were 2D. In the Beaufort Sea, 23 MMS G&G permits were 

issued in 1982 (11 marine and 12 over-ice 2D surveys) and 24 MMS G&G permits were issued 

in 1983 (1, 3D over-ice survey; 14, 2-D over-ice surveys; and, 9, 2D marine surveys). The first 

3-D on-ice survey occurred in the Beaufort Sea OCS in 1983. In the 1990’s, both 2D (2 on-ice 

and 21 marine) and 3D (11 over-ice and 7 marine OBC) seismic surveys were conducted in the 

Beaufort Sea. The first marine 3D seismic survey in the Beaufort Sea OCS occurred in 1996. 

Thirty exploratory wells have been drilled in the Federal Beaufort over a 20+ year period 

between 1981 and 2002. This drilling occurred from a variety of drilling platforms (e.g., gravel 

islands, SSDC, drillships, etc.) and, during different seasons of the year, including the open 

water period. The last exploration well drilled in the Beaufort Sea OCS was drilled in the winter 

of 2002 at the McCovey prospect. 

Compared to the North Slope/Beaufort Sea, there has been little oil- and gas-related activity in 

the Chukchi Sea. There is no existing OCS offshore development or production in the Chukchi 

Sea. Outer Continental Shelf Lease Sale 193 (Chukchi Sea OCS planning area) was held on 

February 6, 2008. Sale 193 offered approximately 12 million acres for leasing, and bids were 

received for over 1,100,000 acres. Five exploratory wells have been drilled in the Chukchi Sea 

from past lease sales, all using drillships. These wells were drilled between 1989 and 1991, 

inclusive. The last Chukchi Sea well was drilled in 1991 at the Diamond Prospect. Recently 

several companies have conducted 2D/3D seismic work in the Chukchi, leading to Sale 193. 

Seismic work is expected to continue post-lease as prospects are explored. 

Many offshore activities also require ice management (icebreaking), helicopter traffic, fixed 

wing monitoring, other support vessels, and, in some cases stand-by barges. 

Available information does not indicate that oil- and gas-related activity (or any recent activity) 

has had detectable long-term adverse population-level effects on the overall health, current 

status, or recovery of the Western Arctic bowhead whale population. Data indicate that the 

Western Arctic population has continued to increase over the timeframe that oil and gas 

activities have occurred. There is no evidence of long-term displacement from habitat. 

However, there are no long-term oil and gas developments in the offshore within bowhead high 

use areas. Northstar is at the southern end of the migratory corridor and Endicott is within the 

barrier islands. Past behavioral (primarily, but not exclusively, avoidance) effects on bowhead 

whales from oil and gas activity have been documented in many studies. Inupiat whalers have 

stated that noise from seismic surveys and some other activities at least temporarily displaces 

whales farther offshore, especially if the operations are conducted in the main migration 

corridor. As noted in the section on effects, recent monitoring studies indicated that most fall 

migrating whales avoid an area with a radius about 20-30 km around a seismic vessel operating 

in nearshore waters. We are not aware of data that indicate that such avoidance is long-lasting 

after cessation of the activity. 

40
Likewise, available information does not indicate that oil- and gas-related activity (or any recent 

activity) in the Chukchi and Beaufort has had detectable long-term adverse population-level 

effects on the overall health, current status, or recovery of humpback and fin whales. At this 

time, we would expect little overlap of these activities with fin and humpback whale 

populations, given that the distribution of these species is limited in the Arctic and individuals 

have only been rarely sighted in this region. However, any reactions to noise by these species 

would be expected to be similar to that of bowheads, given their common low frequency hearing 

range as baleen whales. 

The MMS study 2002-071 titled GIS Geospatial Data Base of Oil-Industry and Other Human 

Activity (1979-1999) in the Alaskan Beaufort Sea provided a compilation of available data on 

the location, timing, and nature of oil- and gas-related activities from 1979-1999. It was 

intended to provide a “...database to address concerns expressed by subsistence hunters and 

others living within ...villages of the Beaufort Sea about the possible effects that oil and gas 

activity, particularly seismic activity, drilling, and oil and gas support vessel activities may have 

on the behavior of...especially the bowhead whale.” However, “(S)uch an analysis requires an 

adequate level of detail...”, “...there are significant gaps in the data for the period 1979-1989” 

(Wainwright, 2002) and “(V)ery limited information was obtained on ice management” 

(Wainwright, 2002). For all but 2 years, 1985-1986, during the period 1979-1989, inclusive, 

Wainwright (2002) assessed the availability of information about 2D/3D seismic surveys 

conducted under OCS permit as a 0 out of a possible 3. This score of 0 indicates: “Significant 

data sets are missing. These data are not suited for statistical analysis.” During this same 

period, they also provide a rank of 0 out of 3 to categorize the completeness and adequacy of 

information on seismic surveys under state MLUP permit. For the entire period of study (1979-

1998), they rate the completeness and adequacy of information on seismic and acoustic surveys 

in State waters without permits, ice management, and other vessel activity all as 0. Thus, while 

data on the bowhead status are adequate to determine that the Western Arctic population 

apparently continued to recover during the periods when past and current levels of oil and gas 

activities were occurring, we cannot adequately assess potential effects on patterns or durations 

of bowhead habitat use. Wainwright (2002) summarized that “...it was not possible to compile 

adequate data on seismic activity prior to 1990.” Because of the inadequacy of the data on 

activities, and because of the limitations inherent in studying large baleen whales, we also 

cannot assess whether there were any adverse health effects to individuals during the period of 

relatively intensive seismic survey activity in the 1980’s. 

Data for the 1990s are better, and the levels of activity are more comparable to those anticipated 

in the near future. There were no geohazard (high-resolution seismic) surveys during the fall 

migration period in the 1990s (Wainwright 2002). Table 4 of Wainwright (2002) gives 

information about the kinds and levels of seismic and acoustic activity in the 1990s. Except in 

1990 and 1998, seismic surveying activity was completed by September 30th and most of the 

activity was between September 1-15. During 3 of the years, there was no seismic surveying 

activity during the fall migration period. 

Data on past drilling in both federal and state waters is relatively complete, especially since 

1990. Data on other activities, such as hunting activity, barge traffic, and shipping noise are 

incomplete. Thus, while it is clear there have been multiple noise and disturbance sources in the 

41
Beaufort Sea over the past 30 years, because of the incompleteness of data, even for the 1990s, 

for many types of activities, we cannot evaluate the totality of past effects on fin, humpback, or 

bowhead whales resulting from multiple noise and disturbance sources (e.g., 2D seismic in state 

and federal waters, drilling, ice-management, high-resolution acoustic surveys, vessel traffic, 

construction, geotechnical bore-hole drilling, aircraft surveys, and hunting). Because data are 

also incomplete for the Chukchi Sea, we reach the same general conclusions. 

 

Climate Change 

There is now widespread consensus within the scientific community that atmospheric 

temperatures on earth are increasing (warming) and that this will continue for at least the next 

several decades. There is also consensus within the scientific community that this warming 

trend will alter current weather patterns. The strongest warming is expected in the north, 

exceeding the estimate for mean global warming by a factor or 3, due in part to the “ice-albedo 

feedback”, whereby as the reflective areas of arctic ice and snow retreat, the earth absorbs more 

heat, accentuating the warming (NRC 2003). The proximate effects of climate change in the 

arctic are being expressed as increased average winter and spring temperatures and changes in 

precipitation amount, timing, and type (Serreze et al. 2000). These changes in turn result in 

physical changes such as reduced sea ice, increased coastal erosion, changes in hydrology, depth 

to permafrost, and carbon availability (ACIA 2005). 

The IPCC (2001b) also highlights uncertainty and inconsistencies in local and regional model 

projections and the ability to predict quantitative changes at these scales due to the capabilities 

of regional scale models (especially regarding precipitation). 

The IPCC (2001b) concluded that: 

Human activities have increased the atmospheric concentrations of greenhouse gases and 

aerosols since the preindustrial era. 

An increasing body of observations gives a collective picture of a warming world and 

other changes in the climate system. 

On a global basis, it is very likely that 1998 was the warmest year and the 1990’s was the 

warmest decade in instrumented history (1861-2000) (IPCC, 2001a,b). 

There is new and stronger evidence that most of the warming observed over the last 50 

years is attributable to human activities.... The best agreement between model 

simulations and observations over the last 140 years has been found when 

all...anthropogenic and natural forcing factors are combined” (see Figure SPM-2 of 

IPCC, 2001b). 

Changes in sea level, snow cover, ice extent, and precipitation are consistent with a warming 

climate near the Earth’s surface. The IPCC (2001b) noted “Examples include...increases in sea 

level and ocean-heat content, and decreases in snow cover and sea-ice extent and thickness” and 

consider their statement that “rise in sea level during the 21st century that will continue for 

further centuries” to also be a “robust finding.” However, they highlight the uncertainty of 

understanding the probability distribution associated with both temperature and sea-level 

projections. 

42
The 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC 2007) 

reports that warming will be greatest over land and at most high northern latitudes. They also 

predict the continuation of recent observed trends such as contraction of snow cover area, 

increases in thaw depth over most permafrost regions, and decrease in sea ice extent. Projected 

surface temperature changes along the North Slope of Alaska may increase by 6.0-6.5 degrees C 

for the late 21st century (2090-2099), relative to the period 1980-1999 (IPCC 2007) 

The IPCC’s projections using the Special Reports on Emissions Scenarios (SRES) emissions 

scenarios in a range of climate models result in an increase in globally averaged surface 

temperature of 1.4-5.8 oC over the period 1990-2100. This is about 2-10 times larger than the 

central value of observed warming over the 20th century, and the projected rate of warming is 

very likely to be without precedent during at least the last 10,000 years, based on paleoclimate 

data. For the periods 1990-2025 and 1990-2050, the projected increases are 0.4-1.1 oC and 0.8-

2.6 oC, respectively (IPCC, 2001b). 

At the request of the White House, the NRC (NRC, 2001) identified areas in the science of 

climate change where there are the greatest certainties and uncertainties. In answer to the 

question of whether climate change is occurring and, if so, how, the NRC (2001) wrote that: 

Weather station records and ship-based observations indicate that global mean surface air 

temperature warmed between about 0.4 and 0.8 C...during the 20th century...the 

warming trend is spatially widespread and is consistent with an array of other 

evidence...in this report. The ocean....has warmed by about 0.05 C...averaged over the 

layer extending from the surface down to 10,000 feet, since the 1950s. 

The NRC concluded: 

The IPCC’s conclusion that most of the observed warming of the last 50 years is likely to 

have been due to the increase in greenhouse gas concentrations accurately reflects the 

current thinking of the scientific community on this issue. The stated degree of 

confidence in the IPCC assessment is higher today than it was 10, or even 5 years ago, 

but uncertainty remains.... 

The NRC (2001) also concluded that: “The predicted warming is larger over higher latitudes 

than over low latitudes, especially during winter and spring, and larger over land than over sea.” 

A general summary of the changes attributed to the current trends of arctic warming indicate sea 

ice in the Arctic is undergoing rapid changes. There are reported changes in sea-ice extent, 

thickness, distribution, age, and melt duration. In general, the sea-ice extent is becoming much 

less in the arctic summer and slightly less in winter. The thickness of arctic ice is decreasing. 

The distribution of ice is changing, and its age is decreasing. The melt duration is increasing. 

These factors lead to a decreasing perennial arctic ice pack. It is generally thought that the 

Arctic will become ice free in summer, but at this time there is considerable uncertainty about 

when that will happen. 

43
Predictions of future sea-ice extent, using several climate models and taking the mean of all the 

models, estimate that the Arctic will be ice free during summer in the latter part of the 21st

century (IPCC, 2007). There is considerable uncertainty in the estimates of summer sea ice in 

these climate models, with some predicting 40-60% summer ice loss by the middle of the 21st

century (Holland, 2006). Using a suite of models, a 40% loss is estimated for the Beaufort and 

Chukchi seas (Overland and Wang, 2007). Some investigators, citing the current rate of decline 

of the summer sea-ice extent believe it may be sooner than predicted by the models, and may be 

as soon as 2013 (Stroeve et al., 2007). Other investigators suggest that variability at the local 

and regional level is very important for making estimates of future changes. 

The sea ice was gone; there’s no main ice pack anymore. All of its just floating ice. 

There are just small pieces of ice. When I first went out whaling, I saw big icebergs, but 

not now. The ice is too far out to see it. In the 1970s and 1980s the ice was close. You 

didn’t have to go far to see it. Now you don’t see any glacier ice at all.” (Footnote 8, 

personal interview, October 5, 2004, as cited by McBeath and Shepro, 2007). 

The extent of winter sea ice, generally measured at the maximum in March, began changing in 

the late 1990’s and has declined through 2006 (Comiso, 2006; Stroeve et al., 2007; Francis and 

Hunter, 2007). Comiso (2006) attributed the changes to corresponding changes in increasing 

surface temperature and wind-driven ice motion. The factors causing the reduction in the winter 

sea-ice extent are different from those in the summer. The reduction of the winter sea-ice extent 

in the Bering Sea preconditions the environment during the melt season for the Chukchi Sea. 

The end-of-winter perennial sea-ice extent was the smallest on record in March 2007 (Nghiem et 

al., 2007). The arctic sea ice reached its maximum on March 10, 2008. Although the maximum 

in 2008 was greater than in 2007, it was below average and was thinner than normal (Martin and 

Comiso, 2008; University of Colorado, NSDIC, 2008). 

While changes in the reduction of summer sea-ice extent are apparent, the cause(s) of change are 

not fully established. The evidence suggests that it may be a combination of oceanic and 

atmospheric conditions that are causing the change. Incremental solar heating and ocean heat 

flux, longwave radiation fluxes, changes in surface circulation, and less multiyear sea ice all 

may play a role. 

These changes are resulting, or are expected to result, in changes to the biological environment, 

causing shifts, expansion, or retraction of home range, changes in behavior, and changes in 

population parameters of plant and animal species. Much research in recent years has focused on 

the effects of naturally-occurring or man-induced global climate regime shifts and the potential 

for these shifts to cause changes in habitat structure over large areas. Although many of the 

forces driving global climate regime shifts may originate outside the Arctic, the impacts of 

global climate change are exacerbated in the Arctic (ACIA 2005). Temperatures in the Arctic 

have risen faster than in other areas of the world as evidenced by glacial retreat and melting of 

sea ice. Threats posed by the direct and indirect effects of global climatic change are or will be 

common to Northern species. These threats will be most pronounced for ice-obligate species 

such as the polar bear, walrus, and ringed seal. 

44
However, not all arctic species are likely to be adversely influenced by global climate change. 

Conceptual models by Moore and Laidre (2006) suggested that, overall, reductions in sea ice 

cover should increase the Bering-Chukchi-Beaufort Sea stock of bowhead whale prey 

availability. 

This theory may be substantiated by the steady increase in the BCBS population during the 

nearly 20 years of sea ice reductions (Walsh 2008). Moore and Huntington (2008) anticipate that 

bowhead whales will alter migration routes and occupy new feeding areas in response to climate 

related environmental change. Sheldon et al. (2003) notes that there is a high probability that 

bowhead abundance will increase under a warming global climate. 

The recent observations of humpback and fin whales in the Beaufort and Chukchi seas may be 

indicative of seasonal habitat expansion in response to receding sea ice or increases in prey 

availability which these whales now exploit. Range expansions in response to habitat change 

are not uncommon among cetaceans. Gray whales in Alaska have shown pronounced change 

over the last several decades; overwintering at higher latitudes and occupying previously lesserused feeding areas in the Beaufort Sea. Concentrations of the rare North Pacific right whale 

were first observed in the southeast Bering Sea in 1996 and have continued until recently, 

possibly reflecting changes in zooplankton distribution due to large-scale oceanographic change 

within the Bering Sea. Since humpback and fin whales are not ice-obligate or ice-associated 

species, it is unknown how long this habitat will remain viable for the species. However, it is 

logical to assume these whales will continue to utilize these waters as long as the availability of 

prey remains. 

IV. EFFECTS OF THE ACTION 

One of the greatest concerns associated with the impacts of oil and gas exploration on marine 

mammals has to do with potential impacts of noise. During OCS oil and gas exploration, 

human-caused noise is transmitted through the air and through marine waters from a variety of 

sources including, but not limited to: 2D/3D seismic surveys; pipeline, platform, and related 

shore-based construction; drilling; icebreakers and other ships, barge transit; high-resolution 

seismic surveys; and helicopter and fixed-winged aircraft traffic. Because of the importance of 

this issue, we provide two background sections. The first provides very general information 

relevant to understanding the fate of noise in the marine environment. The second provides 

general background about potential types of effects of noise on marine mammals. 

Background on Noise in the Marine Environment 

Properties of sound that influence how far that sound is transmitted, what species hear it, and 

what physical and behavioral effects it can have include the following: its intensity, frequency, 

amplitude, wavelength, and duration; distance between the sound source and the animal; 

whether the sound source is moving or stationary; the level and type of background noise; and 

the auditory and behavioral sensitivity of the species (Richardson et al., 1995a). The frequency 

of the sound is usually measured in hertz (Hz), pressure level in micropascals (μP) (Gausland, 

1998), and intensity levels in decibels (dB) (Richardson et al., 1995a; McCauley et al., 2000). 

McCauley et al. (2000) and others (see references in McCauley et al., 2000) express this in terms 

of its equivalent energy decibels re 1 μPa2

. The perceived loudness of any given sound is 

influenced by many factors including both the frequency and pressure of the sound (Gausland, 

45
1998), the hearing ability of the listener, the level of background noise, and the physical 

environment through which the sound traveled before reaching the animal. Based on summaries 

in key references (e.g., Richardson et al, 1995a; Gausland, 1998; and Ketten, 1998), and other 

references as noted, the following information about sound transmission is relevant to 

understanding potential impacts of sound on marine mammals: 

1. Sound travels faster and with less attenuation in water than it does in air. 

2. The fate of sound in water can vary greatly, depending on characteristics of the sound itself, 

characteristics of the location where it is released, characteristics of the environment through 

which it travels (Richardson et al., 1995a; McCauley et al., 2000), and the characteristics (for 

example, depth, orientation) of the receiver (Richardson et al., 1995a; Gausland, 1998). 

3. Sound propagation can vary seasonally in the same environment. 

4. Extrapolation about the likely impacts of a given type of sound source in a given location 

within the Chukchi Sea or Beaufort Sea OCS Planning Areas on a particular marine mammal, 

based on published studies conducted elsewhere, are somewhat speculative because 

characteristics of the marine environment such as bathymetry, sound-source depth, and seabed 

properties greatly impact the propagation of sound horizontally from the source (McCauley et 

al., 2000; see also Chapter 4 in Richardson et al., 1995a and references provided therein). 

Richardson et al. (1995a:425) summarized that: “...a site-specific model of sound propagation 

is needed to predict received sound levels in relation to distance from a noise source.” 

Especially within the Chukchi Sea Planning Area, differences in site characteristics in different 

parts of the planning area make predictions about sound propagation relatively difficult. 

5. There is a great deal of naturally occurring noise in the ocean from volcanic, earthquake, 

wind, ice, and biotic sources (see Richardson et al., 1995). Ambient noise levels affect whether 

a given sound can be detectable by a receiver, including a living receiver, such as a whale. 

Ambient noise levels can change greatly throughout the course of a season at a particular site, 

and vary from site to site. 

6. Because the air-water interface acts as a good reflector, sound generated underwater generally 

will not pass to the air (Gausland, 1998). 

General Background on Potential Effects of Noise and Disturbance on Cetaceans 

In this section, we provide background about potential effects of impacts of OCS oil- and gasrelated noise and disturbance. This section should not be interpreted as indicating effects that 

are likely to occur due to the proposed actions on the bowhead whale, humpback or fin whale. 

Hearing (auditory) systems and perception are species specific and habitat dependent. As noted 

in the previous section, and elsewhere in this evaluation, the fate of sound after it is produced is 

also site (especially in the arctic), season, and weather specific. Because of these fundamental 

facts, the potential for a given sound to cause adverse effects to an animal also is species specific 

and habitat dependent. Because of differences in bathymetry and seabed characteristics of sites 

throughout the Chukchi Sea and Beaufort Sea Planning Areas, the distances that sounds of 

46
various frequencies, intensities, and pressures will propagate, and the resulting effects such 

sounds could have, also are expected to differ greatly among specific sites (for example, among 

specific leasing blocks that differ in seabed properties, bathymetry, and the amount of wave 

action). Thus, the exact location of any sound source will determine the fate of sound released 

at that site and, therefore, will affect the possibility of impact on threatened and endangered 

species in or near the area. The time of year such sound is released will determine whether there 

is potential for individuals of a species to be exposed to that sound. 

Many marine mammals rely primarily on hearing for orientation and communication (e.g., Erbe 

and Farmer, 1998; NRC, 2003, 2005). The scientific community generally agrees that hearing is 

an important sense used by cetaceans (for example see Richardson et al., 1995; NRC, 2003, 

2005; National Resources Defense Council (NRDC), 1999, 2005; Marine Mammal Commission 

Sound Advisory Panel Minutes from meetings, MMC website). Marine mammals rely on sound 

to communicate, to find mates, to navigate, to orient (Erbe et al. 1999), to detect predators, and 

to gain other information about their environment. Because of their reliance on hearing, there is 

an increasing concern about the impacts of proliferation of anthropogenic noise on marine 

mammals, especially cetaceans. NMFS (Carretta et al. 2001) summarized that a habitat concern 

for all whales, and especially for baleen whales, is the increasing level of human-caused noise in 

the world’s oceans. Increased noise levels could interfere with communication among whales, 

mask important natural sound, cause physiological damage, or alter normal behavior, such as 

causing avoidance behavior that keeps animals from an important area or displace a migration 

route farther from shore. Noise from various sources has been shown to affect many marine 

mammals (e.g. Richardson et al. 1995; Kraus et al. 1997; NRC 2003; 2005) in ways ranging 

from subtle behavioral and physiological impacts to fatal effects. 

Several important documents that summarize information on this topic include: Richardson et al. 

(1995a); Hoffman (2002); Tasker et al. (1998); NRC (2003, 2005); National Resources Defense 

Council (NRDC) (1999, 2005); IWC (2004a). Two particularly relevant summaries by the NRC 

have occurred within the last few years: Ocean Noise and Marine Mammals (NRC, 2003) and 

Marine Mammal Populations and Ocean Noise, Determining when Noise Causes Biologically 

Significant Effects (NRC 2005). The IWC (2004) Scientific Committee Standing Working 

Group on Environmental Concerns held a mini symposium on acoustics with a section of the 

report dealing with seismic surveying. Lastly, the Marine Mammal Commission (MMC) 

convened an Advisory Committee on Acoustic Impacts on Marine Mammals which is producing 

summaries of areas of agreement and disagreement concerning the impacts of noise on marine 

mammals as well as a summary from a subcommittee on mitigation and management of 

anthropogenic noise. 

Results from several experimental studies have been published regarding sound exposure 

metrics incorporating sound pressure level and exposure duration. Recently, several 

investigators have examined noise-induced temporary threshold shift (TTS) in hearing in some 

odontocetes and pinnipeds exposed to moderate levels of underwater noise of various 

bandwidths and durations. Kastak et al. (2005) summarized that “Because exposure to...noise in 

the marine environment is sporadic and interrupted, it is necessary to examine variables 

associated with varying noise sound pressure levels, intermittence of exposure, and total 

acoustic energy of exposure, in order to accurately predict the effects of noise on marine 

47
mammal hearing.” However, while there is scientific acknowledgement of this statement, there 

are few instances where data are sufficient to evaluate the total energy exposure of a marine 

mammal from a given source. We acknowledge that evaluation of total energy could change our 

analyses. However, at present, we do not have the data necessary to make such a determination. 

Despite the increasing concern and attention noted above, there is still uncertainty about the 

potential impacts of sound on marine mammals, on the factors that determine response and 

effects, and especially, on the long-term cumulative consequences of increasing noise in the 

world’s oceans from multiple sources (e.g., NRC, 2003, 2005). The NRC (2005) Committee on 

Characterizing Biologically Significant Marine Mammal Behavior concluded that it is unknown 

how or in what cases responses of marine mammals to anthropogenic sound rise to the levels of 

biologically significant effects. This group also developed an approach of injury and behavioral 

“Take equivalents”. These take equivalents use a Severity Index that estimates the fraction of a 

take experienced by an individual animal. This severity index is higher if the activity could be 

causing harassment at a critical location or during a critical time (e.g., calving habitat). Because 

we have uncertainty about exactly where and how much activity will occur in a given year, we 

incorporate recommendations from the NRC (2005) qualitatively. Available evidence indicates 

that reaction to sound, even within a species, may depend on the listener’s sex and reproductive 

status, possibly age and/or accumulated hearing damage, type of activity engaged in at the time 

or, in some cases, group size. For example, reaction to sound may vary depending on whether 

females have calves accompanying them, or whether individuals are feeding or migrating. It 

may depend on whether, how often, and in what context, the individual animal has heard the 

sound before. All of this specificity greatly complicates our ability, in a given situation, to 

predict the impacts of sound on a species or on classes of individuals within a species. Because 

of this, and following recommendations in McCauley et al. (2000), we attempt to take a 

conservative approach in our analyses and base conclusions about potential impacts on potential 

effects on the most sensitive members of a population. In addition, we make assumptions that 

sound will travel the maximums observed elsewhere, rather than minimums. While there is some 

general information available, evaluation of the impacts of noise on marine mammal species, 

particularly on cetaceans, is greatly hampered by a considerable uncertainty about their hearing 

capabilities and the range of sounds used by the whales for different functions (Richardson et al., 

1995a; Gordon et al., 1998; NRC, 2003, 2005). This is particularly true for baleen whales. Very 

little is known about the actual hearing capabilities of the large whales or the impacts of sound 

on them, especially physical effects. While research in this area is increasing, it is likely that we 

will continue to have great uncertainty about physiological effects on baleen whales because of 

the difficulties in studying them. Baleen whale hearing has not been studied directly. There are 

no specific data on sensitivity, frequency or intensity discrimination, or localization (Richardson 

et al., 1995a). Thus, predictions about probable impact on baleen whales generally are based on 

assumptions about their hearing rather than actual studies of their hearing (Richardson et al., 

1995a; Gordon et al., 1998; Ketten, 1998). Ketten (1998) summarized that the vocalizations of 

most animals are tightly linked to their peak hearing sensitivity. Hence, it is generally assumed 

that baleen whales hear in the same range as their typical vocalizations, even though there are no 

direct data from hearing tests on any baleen whale. Most baleen whale sounds are concentrated 

at frequencies less than 1 kHz, but the frequency range in bowhead songs can approach 4,000 

Hz (Richardson et al., 1995a). Most calls emitted by bowheads are in the frequency range of 50-

400 Hz, with a few extending to 1,200 Hz. Based on indirect evidence, at least some baleen 

48
whales are quite sensitive to frequencies below 1 kHz but can hear sounds up to a considerably 

higher but unknown frequency. Most of the manmade sounds that elicited reactions by baleen 

whales were at frequencies below 1 kHz (Richardson et al., 1995a). Some or all baleen whales 

may hear infrasounds, sounds at frequencies well below those detectable by humans. Functional 

models indicate that the functional hearing of baleen whales extends to 20 Hz, with an upper 

range of 30 Hz. Even if the range of sensitive hearing does not extend below 20-50 Hz, whales 

may hear strong infrasounds at considerably lower frequencies. Based on work with other 

marine mammals, if hearing sensitivity is good at 50 Hz, strong infrasounds at 5 Hz might be 

detected (Richardson et al., 1995a). Bowhead whales, as well as blue and fin whales, are 

predicted to hear at frequencies as low as 10-15 Hertz. McDonald, Hildebrand, and Webb 

(1995) summarize that many baleen whales produce loud low-frequency sounds underwater a 

significant part of the time. Thus, species that are likely to be impacted by low-frequency sound 

include baleen whales such as fin, humpback, and bowhead whales. 

Most species also have the ability to hear beyond their peak range. This broader range of 

hearing probably is related to their need to detect other important environmental phenomena, 

such as the locations of predators or prey. Ketten (1998:2) summarized that, “The consensus of 

the data is that virtually all marine mammal species are potentially impacted by sound sources 

with a frequency of 500 Hertz or higher. This statement refers solely to the probable potential 

for marine mammal species to hear sounds of various frequencies. If a species cannot hear a 

sound, or hears it poorly, then the sound is unlikely to have a significant effect. Other factors, 

such as sound intensity, will determine whether the specific sound reaches the ears of any given 

marine mammal.” Considerable variation exists among marine mammals in hearing sensitivity 

and absolute hearing range (Richardson et al., 1995; Ketten, 1998). Because of suspected 

differences in hearing sensitivity, it is likely that baleen whales and pinnipeds are more likely to 

be harmed by direct acoustic impact from low- to mid-sonic range devices than odontocetes. 

Conversely, odontocetes are more likely to be harmed by high-frequency sounds. 

Little data are available about how most marine mammal species, especially large cetaceans, 

respond either behaviorally or physically to intense sound and to long-term increases in ambient 

noise levels, especially over the long term. Large cetaceans cannot be easily examined after 

exposure to a particular sound source. 

Whales often continue a certain activity (for example, feeding) even in the presence of airgun, 

drilling, or vessel sounds. Such continuation of activity does not confirm that the sound is not 

harmful to the cetacean. In many or all cases, this may be true: it may not be harmful. 

However, this type of interpretation is speculative. Whales, other marine mammals, and even 

humans, sometimes continue with important behaviors even in the presence of noise or other 

potentially harmful factors. Whales often fast for long lengths of time during the winter. The 

need to feed or to transit to feeding areas, for example, is possibly so great that they continue 

with the activity despite being harmed or bothered by the noise. For example, Native hunters 

reported to Huntington (2000) that beluga whales often ignore the approach of hunters when 

feeding, but at other times will attempt to avoid boats of hunters. 

Potential damage to hearing 

Ketten (1998) reported that hearing loss can be caused by exposure to sound that exceeds an 

ear’s tolerance (i.e., exhaustion or overextension of one or more ear components). Hearing loss 

49
to a marine mammal could result in an inability to communicate effectively with other members 

of its species, detect approaching predators or vessels, or echolocate (in the case of the toothed 

whales). Hearing loss resulting from exposure to sound often is referred to as a threshold shift. 

Some studies have shown that following exposure to a sufficiently intense sound, marine 

mammals may exhibit an increased hearing threshold, a threshold shift, after the sound has 

ceased (for example, Nachtigall et al., 2004; Kastak et al., 1999; Schlundt et al., 2000; Finneran 

et al., 2002). Thus, a threshold shift indicates that the sound exposure resulted in hearing loss 

causing decreased sensitivity. This type of hearing loss is called a temporary threshold shift if 

the individual recovers its pre-exposure sensitivity of hearing over time, or a permanent 

threshold shift if it does not. 

Ketten (1998) reported that whether or not a temporary threshold shift or a permanent threshold 

shift occurs will be determined primarily based on the extent of inner ear damage the received 

sound and the received sound level causes. In general, whether a given species will tend to be 

damaged by a given sound depends on the frequency sensitivity of the species. Long-lasting 

increases in hearing thresholds, which also can be described as long-lasting impairment of 

hearing ability, could impair the ability of the affected marine mammal to hear important 

communication signals or to interpret auditory signals. Most experiments have looked at the 

characteristics (for example, intensity, frequency) of sounds at which temporary threshold shift 

and permanent threshold shift occurred. However, while research on this issue is occurring, it is 

still uncertain what the impacts may be of repeated exposure to such sounds and whether the 

marine mammals would avoid such sounds after exposure even if the exposure was causing 

temporary or permanent hearing damage if they were sufficiently motivated to remain in the 

area (for example, because of a concentrated food resource). There are not data on which to 

determine the kinds or intensities of sound that could cause a TTS in a baleen whale. 

Permanent threshold shifts are less species dependent and more dependent on the length of time 

the peak pressure lasts and the signal rise time. Usually if exposure time is short, hearing 

sensitivity is recoverable. If exposure to the sound is long, or if the sound is broadband in 

higher frequencies and has intense sudden onset, loss might be permanent. Repeated long 

exposures to intense sound or sudden onset of intense sounds generally characterize sounds that 

cause permanent threshold shift in humans. Ketten (1998) stated that age-related hearing loss in 

humans is related to the accumulation of permanent-threshold-shift and temporary-thresholdshift damage to the ear. The NRC (2005) concluded that: “...there is evidence of age-related 

hearing loss” in marine mammals. A very powerful sound at close range can cause death due to 

rupture and hemorrhage of tissues in lungs, ears, or other parts of the body. At greater distance, 

that same sound can cause temporary or permanent hearing loss. Noise can cause modification 

of an animal s behavior (for example, approach or avoidance behavior, or startle). 

Long-term impacts of OCS seismic survey noise on the hearing abilities of individual marine 

mammals are unknown. Information about the hearing capabilities of large baleen whales is 

mostly lacking. As noted previously, the assumption is made that the area of greatest hearing 

sensitivity are at frequencies known to be used for intraspecific communication. However, 

because real knowledge of sound sensitivity is lacking, we assume in our analyses that 

sensitivities shown by one species of baleen whale also could apply to another. This assumption 

is conservative, especially when using studies on a species such as the humpback, which uses a 

50
large sound repertoire in intraspecific communication, to infer possible impacts on other species 

such as the fin whale. 

Masking

When noise interferes with sounds used by the marine mammals (for example, interferes with 

their communication or echolocation), it is said to “mask” the sound (for example, a call to 

another whale might be masked by an icebreaker operating at a certain distance away). Noises 

can cause the masking of sounds that marine mammals need to hear to function (Erbe et al. 

1999). That is, the presence of the masking noise can make it so that the animal cannot discern 

sounds of a given frequency and at a given level that it would be able to do in the absence of the 

masking noise. If sounds used by the marine mammals are masked to the point where they 

cannot provide the individual with needed information, harm can result (Erbe and Farmer, 

1998). In the presence of the masking sounds, the sounds the animal needs to hear must be of 

greater intensity for it to be able to detect and to discern the information in the sound. 

Erbe and Farmer (1998) summarize that in “...the human and dolphin ear, low frequencies are 

more effective at masking high frequencies than vice versa; masking is maximum if the 

characteristic frequencies of the masker are similar to those of the signal...” They proposed that 

the factor most important for determining the masking effect of the noises was their temporal 

structure. The noise that was the most continuous with respect to frequency and time masked 

the beluga vocalization most effectively, whereas sounds (for example, natural icebreaking 

noise) that occurred in sharp pulses left quiet bands in between and left gaps through which the 

beluga could detect pieces of the call. In a given environment, then, the impact of a noise on 

cetacean detection of signals likely would be influenced by both the frequency and the temporal 

characteristics of the noise, its signal-to-noise ratio, and by the same characteristics of other 

sounds occurring in the same vicinity (for example, a sound could be intermittent but contribute 

to masking if many intermittent noises were occurring). It is not known whether (or which) 

marine mammals can (Erbe and Farmer, 1998) and do adapt their vocalizations to background 

noise. 

Behavioral Reactions 

Available evidence also indicates that behavioral reaction to sound, even within a species, may 

depend on the listener’s sex and reproductive status, possibly age and/or accumulated hearing 

damage, type of activity engaged in at the time or, in some cases, on group size. For example, 

reaction to sound may vary depending on whether females have calves accompanying them, 

whether individuals are feeding or migrating. Response may be influenced by whether, how 

often, and in what context, the individual animal has heard the sound before. All of this 

specificity greatly complicates our ability, in a given situation, to predict the behavioral response 

of a species, or on classes of individuals within a species, to a given sound. Because of this, and 

following recommendations in McCauley et al. (2000) (discussed above), we attempt to take a 

conservative approach in our analyses and base conclusions about potential impacts on potential 

effects on the most sensitive members of a population. In addition, we evaluate the potential for 

effects on fin, humpback, and bowhead whales by making the implicit assumptions that sound 

may travel the maximums observed, rather than minimums and that whales engaged in a 

particular activity may respond at the maximum, not the minimum, distances observed in studies 

to date. These assumptions overestimate potential effect in many cases. However, since at least 

51
some of the airgun arrays being used in the Chukchi and Beaufort Seas have greater total output 

than many of those in previous studies, we may also underestimate impact in some cases. 

Potential Exposure of Whales to Seismic Survey Activities 

Bowhead whales have documented use of portions of both the Chukchi Sea and Beaufort Sea 

evaluation areas for: spring and fall migration; feeding; calving; resting; and limited breeding. 

Most of the calving for this population probably occurs between the Bering Strait and Point 

Barrow. Bowhead whales have a demonstrated sensitivity to some noise and disturbance, 

including noise and disturbance from seismic surveys. It is clear that if 2D/3D seismic surveys 

impacted areas of the spring lead and polynya system during the spring migration, impacts could 

be potentially biologically significant. We note that the general location of the spring lead 

system in the Chukchi and Beaufort seas is based on relatively limited survey data and is not 

well defined. Noise-producing activities, such as seismic surveys, in the spring lead system 

during the spring bowhead migration have a fairly high potential of affecting the whales, 

including females with newborn calves. Fin whale distribution in the action area appears very 

limited, and restricted to the Chukchi Sea during summer months. Humpback whales are also 

likely to occur only seasonally, predominately within the Chukchi Sea, although humpback 

whales were observed in the western Beaufort Sea in 2007. Thus, both fin and humpback 

whales may occur in waters subject to seismic survey. 

Sources of Noise and Disturbance from Seismic Surveys 

During OCS oil and gas 2D/3D seismic exploration, human-caused noise can be transmitted 

through the air and through marine waters from a variety of sources including, but not limited to: 

the seismic noise sources themselves that purposely release noise into the water; icebreakers, 

other ships, and boats; high-resolution seismic surveys; and helicopter and fixed-winged aircraft 

traffic. Endangered cetaceans conceivably could be disturbed or struck by ships or boats during 

seismic surveys. Small fuel spills could occur. Any or all of these factors potentially could 

adversely affect bowhead whales in and/or near the Chukchi Sea or Beaufort Sea Planning Areas 

during OCS oil and gas seismic exploration activities. 

Sound from seismic exploration is a potential source of noise disturbance to bowhead, fin and 

humpback whales in and near areas where the surveys may occur. Marine seismic operations 

use high-energy airguns to produce a burst of underwater sound from the release of compressed 

air, which forms a bubble that rapidly expands and then contracts. Typically, seismic sources 

used in such surveys involve the rapid release of compressed air to produce an impulsive signal 

that is directed downward through the seabed. Thus, the source for the sound is called an 

airgun. 

Seismic airguns are meant to produce low-frequency noise, generally below 200 Hz. However, 

the impulsive nature of the collapse of the air bubbles inevitably results in broadband sound 

characteristics. Goold (1996, cited in Stone, 2001) reported that high-frequency noise is also 

produced. Goold also found significant levels of energy from airguns across the bandwidth up 

to 22 kilohertz. Seismic surveys using airguns, especially 2D and 3D seismic surveys, produce 

at the source, underwater sound levels exceeding those of other activities discussed in this 

section. This means animals sensitive to either low-frequency or high-frequency sounds may be 

affected. Bowhead whales emit tonal frequency modulated sounds at 50-400 Hz. A few calls 

52
have energy extending to 1,200 Hz. Bowheads also emit impulsive sounds in the frequency 

range of 25-3,500 Hz, as well as songs of about 20-500 Hz (Richardson et al. 1995a). Airgun 

arrays are designed to focus the sound energy downward. Despite this, sound pulses also are 

projected horizontally, with the distance traveled depending on many factors, such as those 

discussed by Richardson et al. (1995a) and McCauley et al. (2000). Airgun arrays produce 

short-duration (transient) noise pulses with very high peak levels. The high peak level and 

impulsive nature of airguns have caused concern in the scientific and environmental 

communities. 

McCauley et al. (2000) concluded that the most consistent measure of a received airgun signal 

was a measure of its energy, as was suggested by Richardson et al. (1995) for pulsed sounds. 

In Alaska, 2D/3D seismic surveying, during which large areas are surveyed to obtain 

information on the subsurface, are generally undertaken before a proposed lease sale. The 

2D/3D seismic surveys are also undertaken after lease sales or between one lease sale and the 

next. On-lease high-resolution seismic profiling usually is undertaken for engineering purposes 

to determine the suitability of locations for emplacement of seafloor-founded structures (drilling 

rigs, platforms, pipelines). The energy level in these types of surveys is much lower than that 

used in the 2D/3D seismic surveys; thus, the radius of noise exposure is many times smaller. 

Seismic surveys often employ other activities that may result in an increase in noise and 

disturbance to whales (see below). Seismic ships have navigational equipment that produces 

noise, and the ships themselves introduce noise, cause disturbance and may strike cetaceans. 

Marine vessel traffic and aircraft traffic, in support of the surveys and used in marine mammal 

monitoring, all introduce noise and disturbance into the marine environment, with potential 

adverse impacts on the whales. 

McCauley et al. (2000) stated that a precise definition of the seabed to at least 50-100 m is 

required to accurately predict horizontal propagation along a travel path. Based on experimental 

measurement of signals from a single airgun, McCauley et al. (2000) found signal differences of 

airgun broadband levels of up to 10 dB at a 1-km range. They concluded that such large 

differences in levels, measured for the same source at a given range within the same bay, 

demonstrated the importance of localized properties of seabeds in determining sound 

propagation. Other factors that also can significantly affect sound propagation include the 

orientation of the receivers (the orientation of living animals could similarly affect reception), 

alignments and depths of array components and of functioning guns within the array, and airgun 

source depth. The depth at which the firing airgun is placed plays a crucial role in the potential 

for propagation. Increasing source depth consistently increased the received signal at any 

specified receiver depth (for example, the depth of the animal) and horizontal range. If the 

animal is in a shallow-water area and on the bottom, and the airgun is in much deeper water and 

downslope from the animal, attenuation will greatly affect the sound the animal will receive. 

Based on all of the aforementioned, McCauley et al. (2000) concluded that predicting sound 

propagation from any specified airgun array needs to be done on a case-by-case basis.

Bain (2002) found that approximately one-third of sound levels measured during seismic 

surveys varied by 6 dB from expected values. Shadow zones caused sound levels lower than 

expected, and land was an effective barrier to direct sound propagation. Cases of levels higher 

than expected probably were due to upslope enhancement of sound. Long-range propagation 

through the Strait of Juan de Fuca was better than expected, resulting in airgun noise being 

53
clearly audible at ranges of 60-70 km. This was the longest distance at which signal 

measurement was attempted, and it is possible that the sound was audible at even greater 

distances. Bain (2002) reports that high frequencies attenuated faster with distance, and low 

frequencies were filtered out by propagation through shallow water. 

Tolstoy et al. (2004) compared measured versus modeled noise level radii associated with 

different seismic arrays in shallow and very deep water in the Gulf of Mexico and concluded 

that models may have been underestimating noise level radii in shallow water and 

overestimating those in very deep waters. Richardson et al. (1995a:290-291) summarized: 

“Underwater sound pulses from airgun arrays and similar sources are often audible many tens of 

kilometers away.” Transient noise from such a survey has been recorded on land seismometer 

arrays 6,100 km away after traveling the deep sound channel (Okal and Talandier 1986). 

However, McDonald, Hildebrand, and Webb (1995) suggest that these same sounds may not 

have been detectable by a whale near the surface in the mid-Pacific because of entrapment in the 

deep sound channel. During monitoring using passive acoustics in the mid-Atlantic Ocean, 

Nieukirk et al. (2004) frequently recorded sounds from seismic airguns from locations more than 

3,000 km from their array of autonomous hydrophones moored near the mid-Atlantic Ridge. 

Trends in the patterns of detection were similar in the two years of monitoring with airguns 

being detected every 10-20 seconds. Nieukirk et al. (2004) reported that “Although airgun 

sounds tended to dominate recordings during the summer months, loud whale vocalizations 

could still be detected during intense airgun activity...The high received level of these impulses 

on multiple hydrophones made it possible to estimate the location of the ships conducting the 

airgun surveys.” 

Timing of Potential Exposure to Noise and Disturbance from Active Seismic Surveys 

In the proposed actions under consideration, we assume that 2D/3D seismic surveys could occur 

during the entire open water period in the Chukchi Sea and Beaufort Sea, except as restricted by 

mitigations. Further, ice conditions within the Chukchi would be likely to prevent seismic 

earlier than July 1 of any year. 

Open-water 2D/3D seismic surveys in the Beaufort Sea Planning Area likely would be feasible 

only in the months of August, September, and October. Depending on the restrictions usually 

agreed to in past conflict avoidance agreements for bowhead whales, it is likely that 2D/3D 

seismic surveys will not occur after the bowhead westward migration has occurred, except in 

areas outside of hunting areas or after hunting for a given Beaufort Sea village has ceased. We 

assume that steps will be taken to avoid an unmitigable adverse effect on the availability of 

bowhead whales for take for subsistence, or that steps will be taken to avoid unreasonable 

conflict with such activities. Timing to avoid effects on subsistence takes may amplify 

disturbance on the whales, since it may concentrate seismic activity in between hunting activity, 

both spatially and temporally. 

In the Chukchi Sea, depending on ice conditions and conflict avoidance requirements, seismic 

surveys could not begin until July 1 (unless authorized by NMFS) and end in November. Thus, 

the total period of seismic surveys is likely to be considerably longer in the Chukchi Sea than in 

the Beaufort Sea. No subsistence take of fin or humpback whales occurs. 

54
High-Resolution Seismic Surveys 

High-resolution seismic surveys generally are conducted on lease following a lease sale to 

evaluate potential shallow hazards and identify seafloor features and resources (e.g., shipwrecks, 

potential archaeological sites). Vessels used for high-resolution seismic are typically smaller 

(about 37 to 47 m) than those used for 2D/3D seismic surveys. Some high-resolution seismic 

surveys, such as those using airguns, emit loud sounds; but the sounds would not be as loud as 

sounds from 2D/3D seismic surveys. The sound also would not be likely to propagate as great a 

distance as sounds from 2D/3D seismic surveys. 

A “typical” high-resolution survey involves a ship towing an airgun about 25 m behind the ship 

and a 600-m streamer cable with a tail buoy. The ship travels at 3-3.5 kn (5.6-6.5 km/h), and the 

airgun is fired every 7- 8 seconds (or about every 12.5 m). Typical surveys cover one lease 

block, which is 4.8 km on a side. 

Potential Effects of High-Resolution Seismic 

Because high-resolution seismic surveys use relatively lower energy and sound would be less 

likely to travel as far as sound from 2D/3D seismic surveys, these activities are less likely to 

have significant effects on endangered bowhead, fin, and humpback whales. Bowheads appear 

to continue normal behavior at closer distances to high-resolution seismic surveys than to 2D/3D 

deep penetration seismic surveys. In the study by Richardson, Wells, and Wursig (1985), four 

controlled tests were conducted by firing a single 40 cubic inch (in3

) (0.66-metric liter) airgun at 

a distance of 2-5 kilometers (km) (1.2-3.1 mi) from the whales. Bowheads sometimes continued 

normal activities (skim feeding, surfacing, diving, and travel) when the airgun began firing 3-5 

km (1.86-3.1 mi) away (received noise levels at least 118-133 dB re 1 μPa) root-mean-square 

(rms). Some bowheads oriented away during an experiment at a range of 2-4.5 km (1.2-2.8 mi) 

and another experiment at a range of 0.2-1.2 km (0.12-0.75 mi) (received noise levels at least 

124-131 and 124-134 dB, respectively). Frequencies of turns, predive flexes, and fluke-out 

dives were similar with and without airgun noise; and surfacing and respiration variables and 

call rates did not change significantly during the experiments. 

Responses of fin and humpback whales to high-resolution surveys are uncertain and data 

specific to these species is lacking. Because the site-clearance activities are of shorter duration 

and have a smaller zone of influence than 2D/3D deep penetration seismic surveys, we believe it 

unlikely they would result in a biologically significant effect on fin and humpback whales, and 

responses would be similar to that of bowhead whales. Our primary concern with respect to 

high-resolution surveys is the potential for these activities to add to the noise and disturbance 

footprint of concurrent 2D/3D seismic survey(s) and/or drilling activities, and to cause local 

effects within a specific area, if large numbers of whales are present. We are specifically 

concerned about potential effects that could occur if high-resolution seismic survey activity were 

inshore of 2D/3D seismic survey activities or drilling operations. A concentration of noise- and 

disturbance-producing factors may keep humpback and fin whales from high-value areas. 

Humpback and fin whale data for the planning areas currently are not sufficient to identify highvalue areas. 

55
2D/3D Seismic Surveys. 

Description and Discussion of the Activity

Offshore geophysical exploration seismic surveys conducted in the summer, and on-ice seismic 

surveys conducted in the winter, are other sources of noise in the arctic marine environment. 

Airgun arrays are the most common source of seismic survey noise. A typical full-scale array 

produces a source level of 248-255 dB re 1 μPa -m, zero to peak (Barger and Hamblen 1980; 

Johnston and Cain 1981). These surveys emit loud sounds, which are pulsed rather than 

continuous, and can propagate long distances (in some habitats, very long distances) from their 

source. However, most energy is directed downward, and the short duration of each pulse limits 

the total energy. Received levels within a few kilometers typically exceed 160 dB re 1 μPa 

(Richardson et al. 1995a), depending on water depth, bottom type, ice cover, etc. 

While the seismic airgun pulses are directed towards the ocean bottom, sound propagates 

horizontally for several kilometers (Greene and Richardson 1988; Hall et al. 1994). In waters 

25-50 m deep, sound produced by airguns can be detected 50-75 km away, and these detection 

ranges can exceed 100 km in deeper water (Richardson et al. 1995a). Sounds produced by 

seismic pulses can be detected by mysticetes and odontocetes that are from 10-100 km from the 

source (Greene and Richardson 1988; Bowles et al. 1994; Richardson et al. 1995a) or potentially 

further under some conditions. 

Recent 3D seismic surveys in the Chukchi Sea, using a 24 gun array consisting of 3147 c.i., 

produced sounds up to 160 dB out to a distance of over 8km, while the 120 dB isopleths often 

extended over 70 km from the source vessel(Funk et al. 2008). 

In the Biological Evaluation prepared for Beaufort OCS Lease Sale 195 in 2003, MMS 

concluded that, “Geophysical surveys conducted in conjunction with proposed Lease Sale 195 

are likely to cover much smaller areas to fill in gaps from earlier seismic surveys. Also, some of 

the seismic work that may be needed may be conducted when whales are not present in the 

area.” However, recent interest in 2D/3D seismic exploration by oil and gas companies in the 

Beaufort and Chukchi Seas indicate this assumption is no longer true. We now expect regular 

2D/3D, as well as high-resolution seismic survey activity in Federal waters of the Beaufort Sea 

over the next 5 years. We expect this level of activity to be greater than that during the period of 

the previous 5 years (2000-2005). New seismic survey activity is expected to be mostly 3D 

seismic. We still expect that some of the seismic survey work will be conducted when whales 

are not present. However, at present, much of the proposed seismic survey work in both the 

Beaufort Sea and Chukchi Sea Planning Areas is expected to be open water 2D or 3D seismic 

surveys using streamers. 

Potential Effects of 2D/3D Seismic Surveys on Whales 

Baleen whales generally tend to avoid operating airguns, but avoidance radii are quite variable. 

Whales are often reported to show no overt reactions to pulses from large arrays of airguns at 

distances beyond a few kilometers, even though the airgun pulses remain well above ambient 

noise levels out to much longer distances. However, baleen whales exposed to strong noise 

pulses from airguns often react by deviating from their normal migration route and/or 

56
interrupting their feeding and moving away. 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. In many 

areas, seismic pulses from large arrays of airguns diminish to those levels at distances of 4.5 to 

14.5 km (2.4 to 7.8 n.mi.) from the source. A substantial proportion of the baleen whales within 

those distances may show avoidance or other strong disturbance reactions to the airgun array. 

Subtle behavioral changes sometimes become evident at somewhat lower received levels, and 

recent studies have shown that some species of baleen whales, notably bowhead and humpback 

whales, at times show strong avoidance at received levels lower than 160–170 dB re 1 μPa rms. 

Numerous studies have been conducted on the effects of noise from seismic surveys on bowhead 

whales, but few have been conducted on either humpback or fin whales. The results from the 

studies on bowhead whales have varied, in some cases considerably. Among some of these 

studies important variables were different. These included the type of seismic survey (2D versus 

3D), the location of the study, and the year in which the study was conducted. Ice (and other 

weather-related factors) also varies among years as does the use of total available habitat by 

bowhead whales. Some of the studies employed different methodologies, some of which have 

been criticized by peer reviewers and others of which are more widely adopted. Because of the 

importance of the issue of potential noise disturbance of bowhead whales, we provide 

considerable detail on these studies below. However, we preface this section with an 

observation: In numerous reports regarding whale response to sound, it has been shown that 

multiple factors may be important in the whale’s response (e.g., McCauley et al., 2000). In 

some studies, these factors have been shown to include (but may not be limited to): the physical 

characteristics of the location into which the sound is released and the physical characteristics of 

the location where the whale is located at the time the sound is released; the whale’s sex and 

reproductive condition (e.g., groups with or without calves); the behavior of the whale (e.g., 

migrating or feeding); specific characteristics of the sound (e.g., frequency, duration, whether 

impulsive or not, etc.), and prior exposure to the sound. Thus, the fact that results from different 

studies of bowhead response to oil and gas-related sound have varied is not surprising. The 

studies involving the response of bowheads to 3D marine streamer seismic surveys are most 

relevant to evaluating the potential effects of the proposed action. 

During the 1980’s, the behavior of bowhead whales exposed to noise pulses from seismic 

surveys was observed during the summer in the Canadian Beaufort Sea and during the fall 

migration across the Alaskan Beaufort Sea. In general, many of the seismic surveys conducted 

during the 1980’s were 2D seismic surveys that covered fairly large areas in deeper waters. 

Additional studies on seismic surveys were conducted in the central Alaskan Beaufort Sea 

during the fall migration in 1996-1998. These surveys were 3D ocean bottom cable (OBC) 

seismic surveys that covered fairly small areas in relatively shallow water fairly close to shore. 

Reeves, Ljungblad, and Clarke (1983) conducted aerial surveys to observe bowhead whale 

behavior in the presence of active seismic vessels. Whales were observed as close as 3 km (1.86 

mi) and as far away as 135 km (83.9 mi) from active seismic vessels. A pair of whales observed 

at a distance of 3 km (1.83 mi) were not moving while at the surface although the two whales’ 

heads were in contact. This pair of whales was closer to a shooting seismic vessel than any 

other whales observed during the study. No obvious response was apparent, but the observation 

time was brief. (The received level of low-frequency underwater sound from an underwater 

57
source, generally is lower by 1-7 dB near the surface (depth of 3 m) than at deeper (greater than 

9 m) depths (Richardson et al., 1995a). It is possible these whales may have been at the surface 

to avoid the louder noise in deeper water. For the group of 20 whales at a distance of 

approximately 135 km (83.9 mi), the blow frequency per surfacing and time at the surface were 

greater during the period immediately after the seismic vessel began shooting than before it 

began shooting. The authors stated that no major changes in whale behavior (such as flight 

reactions) were observed that could unequivocally be interpreted as responses to seismic noise. 

They noted a possible exception of “huddling behavior”, which they thought may have been 

caused by the onset of seismic sounds. The authors concluded that although their results suggest 

some changes in behavior related to seismic sounds, the possibility that unquantified factors 

could be correlative dictates caution in attempting to establish causative explanations from the 

preliminary findings. 

Ljungblad et al. (1985) also reported findings from early tests of bowhead reactions to active 

seismic vessels in the Beaufort Sea. However, methodological problems with this early study 

preclude us from drawing conclusions about probable bowhead reactions based on its findings. 

A subcommittee of the Scientific Committee of the IWC previously reviewed the data from this 

study and some members were critical of the methodology and analysis of the results. 

Comments included reference to: the small sample size; inconsistencies between the data and the 

conclusions; lack of documentation of calibration of sound monitoring; and possible interference 

from other active seismic vessels in the vicinity. The subcommittee acknowledged the difficulty 

of performing experiments of this kind, particularly in the absence of a control environment free 

of industrial noise. The subcommittee recommended that additional research taking into account 

the concerns expressed above be undertaken, and that the 1984 experimental results be subjected 

to rigorous reanalysis, before it could be used to draw any conclusions about the effects of 

seismic activity on this species (IWC 1987). 

In the May 25, 2001 Biological Opinion for Federal Oil and Gas Leasing and Exploration by the 

MMS within the Alaskan Beaufort Sea and its effects on the endangered bowhead whale, NMFS 

(2001:20) noted that early tests of bowhead reactions to active seismic vessels by Ljungblad et 

al. (1985): 

...were not conducted under controlled conditions (i.e., other noise sources were operating at the 

time), and approaches at greater ranges were not conducted, so results cannot be used to 

determine the range at which the whales first begin to respond to seismic activity. 

In Fraker et al. (1985), an active seismic vessel traveled toward a group of bowheads from a 

distance of 19 km (11.8 mi) to a distance of 13 km (8.18 mi). The whales did not appear to alter 

their general activities. Most whales surfaced and dove repeatedly and appeared to be feeding in 

the water column. During their repeated surfacing and dives, they moved slowly to the 

southeast (in the same direction as seismic-vessel travel) and then to the northwest (in the 

opposite direction of seismic-vessel travel). The study first stated that a weak avoidance 

reaction may have occurred but then stated there is no proof that the whales were avoiding the 

vessel. The net movement was about 3 km (1.86 mi). The study found no evidence of 

differences in behavior in the presence and absence of seismic noise, but noted that observations 

were limited. 

58
In another study (Richardson, Wells, and Wursig 1985) involving a full-scale seismic vessel 

with a 47-L airgun array (estimated source level 245-252 dB re 1 μPa), bowheads began to 

orient away from the approaching ship when its airguns began to fire from 7.5 km (4.7 mi) 

away. This airgun array had about 30 airguns, each with a volume of 80-125 in3

. The Mariner

had been shooting seismic about 10 km to the west of a group of six whales. Prior to the start of 

the experimental seismic period, the whales were surfacing and diving and moving at slow to 

medium speed while at the surface. The vessel ceased shooting and moved within 7.5 km of the 

whales and began firing the airgun array while approaching the whales. The study reported no 

conspicuous change in behavior when the Mariner resumed shooting at 7.5 km away. The 

bowheads continued to surface and dive, moving at slow to medium speeds. The received level 

was estimated at 134-138 dB at 7 km (4.35 mi). Some near-bottom feeding (evidenced by mud 

being brought to the surface) continued until the vessel was 3 km (1.86 mi) away. The closest 

point of approach to any whale was approximately 1.5 km (0.93 mi), with the received level 

probably well over 160 dB. When the seismic vessel was within 1.5 km of whales at the 

original location, at least two of the whales were observed to have moved about 2 km to the 

south of the original location. The movements of the whales, at least while they were at the 

surface, were at the usual slow to moderate speeds. The study reported no conspicuous changes 

in behavior when the Mariner ceased shooting at 6 km beyond the whales. The bowheads were 

still surfacing and diving and moving at slow to medium speed. The most notable change in 

behavior apparently involved the cessation of feeding when the vessel was 3 km away. The 

whales began feeding again about 40 minutes after the seismic noise ceased. 

While conducting a monitoring program around a drilling operation, Koski and Johnson (1987) 

noted that the call rate of a single observed bowhead whale increased after a seismic operation 

had ceased. During the 6.8 hours of observation, the whale was within 23-27 km (14.3-16.8 mi) 

from the drillship. A seismic vessel was reported to be from 120-135 km (74.58-83.9 mi) from 

the sonobuoy; the two loudest calls received were determined to be approximately 7 km (4.35 

mi) and 9 km (5.6 mi) from the sonobuoy, with received levels of 119 and 118 dB, respectively. 

Approximate signal-to-noise ratios were 24 and 22 dB, respectively. No information is provided 

regarding the exact distance the whale was from the operating seismic vessel. The increase in 

call rate was noted within 25 minutes after seismic noise ceased. It also needs to be noted that 

there were few, if any, calls heard during the 2 hours prior to the start of seismic operations, so it 

is unclear whether the increase in call rate relates to cessation of seismic noise, the presence of 

the operating drillship, the combination of both activities, or some other factor that occurred in 

the late afternoon. During this same study a subgroup of four to seven whales within a larger 

group (15-20 whales) was noted moving rapidly away from an approaching seismic vessel at a 

distance of 22-24 km (13.7-14.9 mi). The received level of seismic pulses was 137 dB at 19 km 

(11.8 mi) from the sonobuoy and 22 km from the whales. The surfacing and diving were 

unusually brief, and there were unusually few blows per surfacing. No information was 

available regarding the time required for these whales to return to normal behavior. 

The North Slope Borough (NSB) believes that many studies were different from the real-world 

situation, and various limitations have been pointed out. Most studies did not involve actively 

migrating whales; and those whales were being approached by the seismic ships whereas in the 

real world, the fall migrating whales are actively moving to the west and they are approaching a 

distant seismic boat that is firing. The MMS has noted that many studies were observational and 

59
involved opportunistic sightings of whales in the vicinity of seismic operations. The studies 

were not designed to show whether more subtle reactions are occurring that can displace the 

migration corridor, so no definitive conclusions can be drawn from them on whether or not the 

overall fall migration is displaced by seismic activity. 

Based on early data, Richardson and Malme (1993) concluded that collectively, scientific 

studies have shown that most bowheads usually show strong avoidance response when an 

operating seismic vessel approaches within 6-8 km (3.8-5.0 mi). Strong avoidance occurs when 

received levels of seismic noise are 150-180 dB re 1 μPa (Richardson and Malme, 1993). 

Strong pulses of seismic noise often are detectable 25-50 km (15.5-31 mi) from seismic vessels, 

but in early studies, bowheads exposed to seismic sounds from vessels more than about 7.5 km 

(4.7 mi) away rarely showed avoidance. Seismic pulses can be detectable 100 km (62.2 mi) or 

more away. Bowheads also may show specific behavioral changes, such as reduced surfacing; 

reduced dive durations; changes in respiration rates, including fewer blows per surfacing, and 

longer intervals between successive blows; and they may temporarily change their individual 

swimming paths. The authors noted that surfacing, respiration, and dive cycles may be altered 

in the same manner as those of whales closer to the vessels. Bowhead surface-respiration-dive 

characteristics appeared to recover to pre-exposure levels within 30-60 minutes following the 

cessation of the seismic activity. 

Inupiat whalers suggested that the fall bowhead migration tended to be farther offshore when 

there was abundant seismic work off northern Alaska. Aerial surveys have been conducted 

since 1979 to determine the distribution and abundance of bowhead whales in the Beaufort Sea 

during their fall migration. These surveys have been used for comparing the axis of the 

bowhead whale migration between years. Survey data from 1982-1987 were examined to 

determine whether industrial activity was resulting in displacement of bowhead whales farther 

offshore (Ljungblad et al. 1988). It was determined that a good indicator of annual shifts in 

bowhead distribution could be obtained by analyzing the distance of random bowhead sightings 

from shore (Zeh, as cited in Ljungblad et al. 1988). An analysis of the distance of random 

bowhead sightings from shore (a total of 60 bowhead sightings) was conducted, but no 

significant differences were detected in the bowhead migratory route between years. The axis of 

the bowhead migratory route near Barrow was found to fall between 18 and 30 km (7.76 and 

18.6 mi) from shore. Although the analysis involved a relatively small sample size, these 

observations provide some insight into migration patterns during these years. The NSB, in a 

letter dated July 25, 1997, questioned the sample size and the precision of the Ljungblad et al. 

(1988) report to determine whether or not a displacement of fall migrating whales had occurred 

and how big a displacement would have to be before it could be detected. Using larger sample 

sizes (for which confidence intervals were calculated) obtained over a larger study area, the 

aerial survey project found many between-year (1982-1996) differences in the median water 

depth at whale sightings that were highly significant (P less than 0.05) (Treacy 1997). Median 

depths ranged between 18 m (59 ft) in 1989 and 347 m (1,138 ft) in 1983, with an overall 

cumulative depth of 37 m (121 ft, confidence interval = 37-38 m). The aerial survey project has 

reported a potential association between water depth of the bowhead migration and general ice 

severity, especially in 1983, when severe ice cover may have forced the axis of the migration 

into waters 347 m (1,138 ft) deep. To address short-term bowhead whale displacement within a 

given year from site-specific industrial noise, MMS and NMFS require industry to conduct site60
specific monitoring programs when industrial activity occurs in the Beaufort Sea Planning Area 

during fall bowhead migrations. 

Since 1996, many of the open water seismic surveys in State of Alaska waters and adjacent 

nearshore Federal waters of the central Alaskan Beaufort Sea were ocean-bottom cable surveys. 

These surveys were 3D seismic programs. The area to be surveyed is divided into patches, each 

patch being approximately 5.9 by 4.0 km in size. Within each patch, several receiving cables 

are laid parallel to each other on the seafloor. Seismic data are acquired by towing the airguns 

along a series of source lines oriented perpendicular to the receiving cables. While seismic-data 

acquisition is ongoing on one patch, vessels are deploying cable on the next patch to be surveyed 

and/or retrieving cables from a patch where seismic surveys have been completed. Airgun 

arrays have varied in size each year from 1996-1998 with the smallest, a 560 in3

 array with 8 

airguns, and the largest, a 1,500 in3 array with 16 airguns. A marine mammal and acoustical 

monitoring program was conducted in conjunction with the seismic program each year in 

accordance with provisions of the NMFS Incidental Harassment Authorization. Based on 1996-

1998 data, there was little or no evidence that bowhead headings, general activities, or 

swimming speeds were affected by seismic exploration. Bowheads approaching from the 

northeast and east showed similar headings at times with and without seismic operations. Miller 

et al. (1999) stated that the lack of any statistically significant differences in headings should be 

interpreted cautiously. Changes in headings must have occurred given the avoidance by most 

bowheads of the area within 20 or even 30 km of active seismic operations. Miller et al. (1999) 

noted that the distance at which deflection began cannot be determined precisely, but they stated 

that considering times with operations on offshore patches, deflection may have begun about 35 

km to the east. However, some bowheads approached within 19-21 km of the airguns when they 

were operating on the offshore patches. It appears that in 1998, the offshore deflection might 

have persisted for at least 40-50 km west of the area of seismic operations. In contrast, during 

1996-1997, there were several sightings in areas 25-40 km west of the most recent shotpoint, 

indicating the deflection in 1996-1997, may not have persisted as far to the west. 

LGL Ltd.; Environmental Research Assocs., Inc.; and Greeneridge Sciences Inc. conducted a 

marine mammal monitoring program for a seismic survey near the Northstar Development 

Project in 1996 (Miller et al., 1997). The marine mammal monitoring program was continued 

for subsequent seismic surveys in nearshore waters of the Beaufort Sea in 1997 and 1998 

(Miller, Elliot, and Richardson, 1998; Miller et al., 1999). Details of these studies are provided 

in the Beaufort Sea multiple-sale final EIS. These studies indicated that the bowhead whalemigration corridor in the central Alaskan Beaufort Sea during 1998 was similar to the corridor in 

many prior years, although not 1997. In 1997, nearly all bowheads sighted were in relatively 

nearshore waters. The results of the 1996-1998 studies indicated a tendency for the general 

bowhead whale-migration corridor to be farther offshore on days with seismic airguns operating 

compared to days without seismic airguns operating, although the distances of bowheads from 

shore during airgun operations overlapped with those in the absence of airgun operations. 

Aerial-survey results indicated that bowheads tended to avoid the area around the operating 

source, perhaps to a radius of about 20-30 km. Sighting rates within a radius of 20 km of 

seismic operations were significantly lower during seismic operations than when no seismic 

operations were happening. Within 12-24 hours after seismic operations ended, the sighting rate 

within 20 km was similar to the sighting rate beyond 20 km. There was little or no evidence of 

61
differences in headings, general activities, and swimming speeds of bowheads with and without 

seismic operations. Overall, the 1996-1998 results show that most bowheads avoided the area 

within about 20-30 km of the operating airguns. Within 12-24 hours after seismic operations 

ended, the sighting rate within 20 km was similar to the sighting rate beyond 20 km. 

The observed 20-30 km area of avoidance is a larger avoidance radius than documented by 

previous scientific studies in the 1980s and smaller than the 30 mi suggested by subsistence 

whalers, based on their experience with the types of seismic operations that occurred in the 

Beaufort Sea before 1996 (Richardson 2000). The seismic activities in the 1980s were 2D in 

deeper water. Recent seismic activities were 3D OBC concentrated in shallow water. 

Based on recordings of bowhead whale calls made during these same studies, Greene et al. 

(1999), summarized that results for the 3 years of study indicated that: (1) bowhead whales call 

frequently during the autumn migration through the study area; (2) calling continued at times 

when whales were exposed to airgun pulses; and (3) call-detection rates at some locations 

differed significantly when airguns were detectable versus not detectable. However, there was 

no significant tendency for the call-detection rate to change in a consistent way at times when 

airguns started or stopped. 

Richardson provided a brief comparison between observations from seismic studies conducted 

in the 1980s and the 1996 seismic survey at the Arctic Seismic Synthesis Workshop in Barrow 

(USDOI, MMS 1997). Observations from earlier seismic studies during the summer and early 

autumn show that most bowhead whales interrupt their previous activities and swim strongly 

away when a seismic ship approaches within about 7.5-8 km. At the distances where this strong 

avoidance occurs, received levels of seismic pulses typically are high, about 150-180 dB re 1 

μPa. The surfacing, respiration, and dive cycles of bowheads engaged in strong avoidance also 

change in a consistent pattern involving unusually short surfacing and diving and unusually few 

blows per surfacing. These avoidance and behavioral effects among bowheads close to seismic 

vessels are strong, reasonably consistent, and relatively easy to document. Less consistent and 

weaker disturbance effects probably extend to longer distances and lower received sound levels 

at least some of the time. Bowheads often tolerate much seismic noise and, at least in summer, 

continue to use areas where seismic exploration is common. However, at least one case of 

strong avoidance has been reported as far as 24 km from an approaching seismic boat (Koski 

and Johnson 1987) and, as noted above, the aerial survey data (Miller et al. 1999) indicated that 

bowheads tended to avoid the area around the operating source, perhaps to a radius of about 20-

30 km. Richardson noted that many of the observations involved bowheads that were not 

actively migrating. Actively migrating bowheads may react somewhat differently than 

bowheads engaged in feeding or socializing. Migrating bowheads, for instance, may react by 

deflecting their migration corridor away from the seismic vessel. Monitoring of the bowhead 

migration past a nearshore seismic operation in September 1996 provided evidence consistent 

with the possibility that the closest whales may have been displaced several miles seaward 

during periods with seismic activity. 

With respect to these studies conducted in the Beaufort Sea from 1996-1998, the peer-review 

group at the Arctic Open-Water Noise Peer Review Workshop in Seattle from June 5-6, 2001, 

prepared a summary statement supporting the methods and results reported in Richardson (1999) 

concerning avoidance of seismic sounds by bowhead whales: 

62
Monitoring studies of 3-D seismic exploration (8-16 airguns totaling 560-1,500 in3

) in the 

nearshore Beaufort Sea during 1996-1998 have demonstrated that nearly all bowhead whales 

will avoid an area within 20 km of an active seismic source, while deflection may begin at 

distances up to 35 km. Sound levels received by bowhead whales at 20 km ranged from 117-

135 dB re 1 μPa rms and 107-126 dB re 1 μPa rms at 30 km. The received sound levels at 20-30 

km are considerably lower levels than have previously been shown to elicit avoidance in 

bowhead or other baleen whales exposed to seismic pulses. 

A recent study in Canada provides recent information on the behavioral response of bowhead 

whales in feeding areas to seismic surveys (Miller and Davis, 2002). During the late summer 

and autumn of 2001, Anderson Resources Ltd. conducted an open-water seismic exploration 

program offshore of the Mackenzie Delta in the Canadian Beaufort Sea. The program consisted 

of streamer seismic surveys and associated bathymetric surveys conducted off the Mackenzie 

Delta. The bathymetric surveys were conducted by two medium-sized vessels equipped with 

side-scan sonar and single-beam echo sounders. The seismic vessel was the Geco Snapper. The 

acoustic sources used in the seismic operations were two 2,250 in3

 arrays of 24 sleeve-type 

airguns. Each 2,250 in3 airgun array was comprised of 24 airguns with volumes ranging from 

40-150 in3

. The two airgun arrays fired alternately every 8 seconds along the survey lines. The 

airgun arrays were operated at a depth of 5 m below the water surface. Water depths within the 

surveyed areas ranged from 6-31 m and averaged 13 m (Miller, 2002). Because marine seismic 

projects using airgun arrays emit strong sounds into the water and have the potential to affect 

marine mammals, there was concern about the acoustic disturbance of marine mammals and the 

potential effects on the accessibility of marine mammals to subsistence hunters. Although there 

are no prescribed marine mammal and acoustic monitoring requirements for marine seismic 

programs in the Canadian Beaufort Sea, it was decided that monitoring and mitigation measures 

in the Canadian Beaufort Sea should be as rigorous as those designed and implemented for 

marine seismic programs conducted in the Alaskan Beaufort Sea in recent years. The 

monitoring program consisted of three primary components: acoustic measurements, vesselbased observations, and aerial surveys. The NMFS-recommended criterion that exposure of 

whales to impulse sound not exceed 180 dB re 1 Pa rms (65 FR 16374) was adopted as a 

mitigation standard for this monitoring program. Estimates of sound-propagation loss from the 

airgun array were used to determine the designated 1,000-m safety radius for whales (the 

estimated zone within which received levels of seismic noise were 180 dB re 1μPa rms or 

higher). 

Aerial and vessel-based surveys confirmed the presence of substantial numbers of bowheads 

offshore of the Mackenzie Delta from late August until mid-September. The distribution of 

bowheads in the study area was typical of patterns observed in other years and suggests that 

there were good feeding opportunities for bowheads in these waters during that period. A total 

of 262 bowheads were observed from the seismic vessel Geco Snapper (Moulton, Miller, and 

Serrano, 2002). Sighting rates during daylight hours were higher when no airguns were 

operating than during periods with airguns operating. During the period when bowheads were 

most abundant in the study area (August 23-September 19), the bowhead sighting rate during 

periods with no seismic (0.85 bowheads/hour) was about twice as high as that recorded during 

periods with seismic (0.40 bowheads/h) or all seismic operations combined (0.44 bowheads/h). 

Average sighting distances from the vessel were significantly (P <0.001) lower during no 

63
airguns (a mean radial distance of 1,368 m) versus line-seismic periods (a mean radial distance 

of 1,957 m). The observed difference in sighting rates and the significant difference in sighting 

distances suggest that bowheads did avoid close approach to the area of seismic operations. 

However, the still substantial number of sightings during seismic periods and the relatively short 

(600 m) but significant difference in sighting distances suggests that the avoidance may have 

been localized and relatively small in nature. At a minimum, the distance by which bowheads 

avoided seismic operations was on the order of 600 m greater than the average distance by 

which they avoided general vessel operations. The lower sighting rates recorded during seismic 

operations suggest that some bowheads avoided the seismic operations by larger distances and, 

thereby, stayed out of visual range of the marine mammal observers on the Geco Snapper. 

In this study, a total of 275 bowhead whale sightings were recorded during aerial transects with 

good lighting conditions (Holst et al. 2002). Bowheads were sighted at similar rates with and 

without seismic, although the no feeding-seismic sample was too small for meaningful 

comparisons. Bowheads were seen regularly within 20 km of the operations area at times 

influenced by airgun pulses. Of 169 transect sightings in good conditions, 30 sightings were 

seen within 20 km of the airgun operations at distances of 5.3-19.9 km. The aerial surveys were 

unable to document bowhead avoidance of the seismic operations area. The area of avoidance 

around the seismic operations area was apparently too small to be evident from the broadscale 

aerial surveys that were flown, especially considering the small amount of surveying done when 

seismic was not being conducted. General activities of bowheads during times when seismic 

operations were conducted were similar to times without seismic. 

The bowheads that surfaced closest to the vessel (323-614 m) would have been exposed to 

sound levels of about 180 dB re 1 μPa rms before the immediate shutdown of the array (Miller 

et al. 2002). There were seven shutdowns of the airgun array in response to sightings of 

bowheads within 1 km of the seismic vessel. Bowheads at the average vessel-based sighting 

distance (1,957 m) during line seismic would have been exposed to sound levels of about 170 

dB re 1 μPa rms. The many aerial sightings of bowheads at distances from the vessel ranging 

from 5.3-19.9 km would have been exposed to sound levels ranging from approximately 150-

130 dB re 1 μPa rms, respectively. 

The results from the study in summer 2001 are markedly different from those obtained during 

similar studies during the autumn migration of bowheads through the Alaskan Beaufort Sea 

(Miller et al. 2002). For example, during the Alaskan studies only 1 bowhead whale was 

observed from the seismic vessel(s) during six seasons (1996-2001) of vessel-based observations 

compared with 262 seen from the Geco Snapper in 2001. The zone of avoidance for bowhead 

whales around the airgun operations in 2001 was clearly much smaller (~2 km) than that 

observed for migrating bowhead whales in recent autumn studies in Alaskan waters (up to 20-30 

km). Davis (1987) concluded that migrating bowheads during the fall migration may be more 

sensitive to industrial disturbance than bowheads on their summering grounds, where they may 

be engaged in feeding activities. 

Inupiat subsistence whalers have stated that industrial noise, especially noise due to seismic 

exploration, has displaced the fall bowhead migration seaward and, thereby, is interfering with 

the subsistence hunt at Barrow (Ahmaogak 1989). Whalers have reported reaction distances, 

64
where whales begin to divert from their migratory path, on the order of 10 mi (T. Albert cited in 

USDOI, MMS 1995) to 35 mi (F. Kanayurak in USDOI, MMS 1997. Kanayurak stated that the 

bowheads “...are displaced from their normal migratory path by as much as 30 miles.” Also at 

the March 1997 workshop, Mr. Roxy Oyagak, Jr., a Nuiqsut whaling captain, stated in written 

testimony: 

“Based on the industrial activity, there is an unmitigable adverse impact on the village of 

Nuiqsut on subsistence whaling. i.e., 1) by causing the whales to abandon the hunting area 

...and 3) placing physical barriers between the subsistence whalers and marine mammals, 

including altering the normal bowhead whale migration route.”

Data available from MMS’ BWASP surveys over about a 27 year period indicate that, at least 

during the primary open water period during the autumn (when open water seismic activities are 

most likely to occur), there are areas where bowheads are much more likely to be encountered 

and where aggregations, including feeding aggregations and/or aggregations with large numbers 

of females and calves, are more likely to occur in the Beaufort . Such areas include the areas 

north of Dease Inlet to Smith Bay, northeast of Smith Bay, and Northeast of Cape Halkett, as 

well as areas near Brownlow Point. Such aggregations have been observed in multiple years 

during BWASP surveys. However, in some years no large aggregations of bowheads were seen 

anywhere within the study area. In their Biological Evaluation, the MMS voiced particular 

concern for the potential for seismic to impact significant life history stages of bowhead whales. 

If 2D/3D seismic surveys occurred in these areas when large aggregations were present, and 

particularly if multiple 2D/3D seismic surveys occurred concurrently in these areas, MMS 

concluded either hundreds of whales could be excluded (through avoidance) from a large area 

for a relatively long portion of the season, or many more individuals would likely avoid the area 

as they sequentially came in to use the area. 

We are aware that the extent of avoidance will vary both due to the actual noise level radii 

around each seismic vessel, the context in which it is heard, and the motivation of the animal to 

stay within the area. It also may vary depending on the age, and most likely, the sex and 

reproductive status of the whale. It may be related to whether subsistence hunting has begun 

and/or is ongoing. Because the areas where large aggregations of whales have been observed 

during the autumn also are areas used, at least in some years, for feeding, it may be that the 

whales would show avoidance more similar to that observed in studies of whales on their 

summer feeding grounds. However, as noted above, it is not clear that reduced avoidance 

should be interpreted as a reduction in impact. It may be that bowheads are so highly motivated 

to stay on a feeding ground that they remain at noise levels that could, with long term exposure, 

cause adverse effects. 

Seismic activity should have little effect on zooplankton. Bowheads feed on concentrations of 

zooplankton. Zooplanktons that are very close to the seismic source may react to the shock 

wave, but little or no mortality is expected (LGL Ltd. 2001). A reaction by zooplankton to a 

seismic impulse would be relevant only if it caused a concentration of zooplankton to scatter. 

Pressure changes of sufficient magnitude to cause zooplankton to scatter probably would occur 

only if they were very close to the source. Impacts on zooplankton behavior are predicted to be 

negligible and would have negligible effects on feeding bowheads (LGL Ltd. 2001). 

65
Fin and humpback whales feed on euphausiids (krill) and small schooling fish. Fish prey 

species in the North Pacific include Pacific herring (Clupea harengus pallasi), capelin (Mallotus 

villosus), juvenile walleye pollock (Theragra chalcogramma), and sand lance (Ammodytes 

hexapterus). Humpback whales are also known to feed on eulachon, Atka mackerel, Pacific 

cod, saffron cod, arctic cod, juvenile salmon, and rockfish (NMFS 2005). 

Fish species may react to seismic activity. Fish are able to detect and respond to a wide variety 

of sounds. Species differ in the range of frequencies, or bandwidth, and in the threshold sound 

pressure levels they are able to detect. Many behavioral and physiological investigations of fish 

hearing show that a number of species, and perhaps all, have the same basic acoustic capabilities 

as other vertebrates, including mammals (Popper et al. 2003, Ladich and Popper 2004). Herring 

are hearing specialists, their greater hearing capability is due to specialized extensions of the 

swim bladder that enters the cranial capsule and lies close to the inner ear (Moyle and Cech 

1988). This adaptation allows herring to detect and respond to signals up to 4000 Hz with 

thresholds that are 20dB lower than fish with general hearing capability and is thought important 

for schooling behavior and detecting predators and other hazards (Whitehead 1985). This 

sensitive hearing capability also makes herring more vulnerable to interference from 

anthropogenic noise sources due to its increased dependence on sound detection as a means of 

avoiding predation (NMFS 2005). In this case, it is reasonable that impacts to prey would be 

negligible unless prey were very close to the source of the seismic activity. Impacts on feeding 

humpbacks or fin whales would also be expected to be minimal given their limited distribution 

in the Arctic environment. 

Various vessels are necessary to support seismic work, and may impact bowhead, humpback, 

and fin whales. Bowheads react to the approach of vessels at greater distances than they react to 

most other industrial activities. According to Richardson and Malme (1993), most bowheads 

begin to swim rapidly away when vessels approach rapidly and directly. This avoidance may be 

related to the fact that bowheads have been commercially hunted within the lifetimes of some 

individuals within the population and they continue to be hunted for subsistence throughout 

many parts of their range. Avoidance usually begins when a rapidly approaching vessel is 1-4 

km (0.62-2.5 mi) away. A few whales may react at distances from 5-7 km (3-4 mi), and a few 

whales may not react until the vessel is less than 1 km (less than 0.62 mi) away. Received noise 

levels as low as 84 dB re 1 μPa (rms) or 6 dB above ambient may elicit strong avoidance of an 

approaching vessel at a distance of 4 km (2.5 mi) (Richardson and Malme, 1993). 

In the Canadian Beaufort Sea, bowheads observed in vessel-disturbance experiments began to 

orient away from an oncoming vessel at a range of 2-4 km (1.2-2.5 mi) and to move away at 

increased speeds when approached closer than 2 km (1.2 mi) (Richardson and Malme 1993). 

Vessel disturbance during these experimental conditions temporarily disrupted activities and 

sometimes disrupted social groups, when groups of whales scattered as a vessel approached. 

Reactions to slow-moving vessels, especially if they do not approach directly, are much less 

dramatic. Bowheads often are more tolerant of vessels moving slowly or in directions other than 

toward the whales. Fleeing from a vessel generally stopped within minutes after the vessel 

passed, but scattering may persist for a longer period. After some disturbance incidents, at least 

some bowheads returned to their original locations (Richardson and Malme 1993). Some 

whales may exhibit subtle changes in their surfacing and blow cycles, while others appear to be 

66
unaffected. Bowheads actively engaged in social interactions or mating may be less responsive 

to vessels. 

Seismic vessel support activities may also impact humpback and fin whales. Research has 

suggested that noise may cause humpback whales to avoid or leave feeding or nursery areas 

(Jurasz and Jurasz 1979). Other research has suggested that humpback whales may become 

habituated to vessel traffic and its associated noise. Still other researchers suggest that 

humpback whales may become more vulnerable to vessel strikes once they habituate to vessel 

traffic (Swingle et al. 1993, Wiley et al. 1995). While measurable startle responses might 

diminish with time, this does not necessarily indicate that a negative impact has not occurred. 

Vessels could still cause physiological stress impacts or could disrupt prey aggregations forcing 

whales to spend a greater amount of time and energy foraging. 

Baker and Herman (1989) conducted controlled studies on the impact of vessel traffic on 

humpback whales in southeast Alaska. They examined responses to obtrusive, unobtrusive, and 

“passby” conditions created by different vessel classes. In that study, respiratory behaviors 

were the most sensitive indicators of response to a vessel. The obtrusive condition resulted in a 

striking increase in the frequency of blows when the whale was near the surface and an increase 

in the longest submergence observed. The effects declined as the activity of the vessel 

moderated during the unobtrusive and “passby” conditions. Within the 400 m range of 

influence, vessel operations accounted for 27.5% of the variance in the blow intervals of whales. 

The study also noted the tendency of humpback whales to orient in the direction of a vessel as it 

approached, and then to turn away at a perpendicular as the vessel reached its closest point of 

approach. The percentage of whale movement devoted to avoidance behavior increased from 

15% at a distance from the vessel of 4000 m to 27% at a distance from the vessel of 1000 m. 

Other studies on humpback whales in their wintering grounds indicate some changes in behavior 

in response to vessels. Corkeron (1995) showed that animals dove more often in the presence of 

vessels when the vessels were within 300 m of the animal. Mother-calf pairs almost never dove 

when vessels were absent yet did so when vessels were present, spending significantly more 

time submerged or traveling and potentially incurring energetic costs. For non-calf pods, the 

rates at which certain behaviors (e.g., roll, lunge, fluke and flipper activity, and breaching) 

occurred were significantly different when vessels were present than when vessels were absent. 

Bauer et al. (1993) found that smaller humpback whale pods with calves were more affected by 

vessel activity than were larger pods without calves. 

Although it is difficult to quantify the behavioral effect of vessel noise impacts on humpback 

whales, based on existing information we can assume that individual humpback whales may 

alter their behavior in the presence of the vessels. Whales may leave the action area if 

sufficiently disturbed. It is more likely they will leave an area if not actively involved in feeding 

at the time of the disturbance. Displacement may adversely affect individual animals by 

requiring additional energy investment to forage elsewhere, and thus may translate into the 

reduced fitness of an individual. However, given that a relatively small number of humpback 

whales appear to use the Arctic environment at present, the effects of alterations in behavior, 

temporary disruption, or displacement are not expected to impact a significant portion of the 

population such that the recovery or survival of the species would be compromised. One can 

67
infer similar behavioral reactions for fin whales, as baleen whales closely related to humpbacks. 

Likewise, the effects of vessel noise and approach are likely to be minimal on the fin whale 

population given the limited number of animals thought to be regularly present in the action 

area. 

Bowhead, fin and humpback whales could encounter noise and disturbance from multiple 

seismic vessels and multiple support vessels as they migrate and feed in the Beaufort and 

Chukchi Seas. The likelihood of encounter for fin and humpback whales is considered to be 

low; however, if an encounter were to occur, the impacts may be expected to be similar to those 

involving bowheads. The significance of such encounters is expected to depend on the area in 

which the vessels are transiting, the total number of vessels in the area, the presence of other 

vessels (see cumulative effects section), and variables already identified regarding the number, 

behavior, age, sex and reproductive condition of the whales. Depending on ice conditions, it is 

likely that vessels actively involved in ice management or moving from one site to another 

would be more disturbing to whales than vessels idling or maintaining their position. In either 

case, bowheads, fins and humpbacks probably would adjust their individual swimming paths to 

avoid approaching within several kilometers of vessels attending a drilling unit and probably 

would move away from vessels that approached within a few kilometers. Vessel activities 

associated with exploration are not expected to disrupt the bowhead migration. Small 

deflections in individual bowhead-swimming paths and a reduction in use of possible bowheadfeeding areas near exploration units may result in adverse effects on the species. During their 

spring migration (April through June), bowheads likely would encounter few, if any, vessels 

along their migration route, because ice at this time of year typically would be too thick for 

seismic-survey ships and supply vessels to operate in. Because MMS is not allowing seismic 

shooting in the spring lead system until July 1 unless authorized by NMFS, we do not expect 

seismic survey vessel interaction to be an important source of disturbance during the northward 

migration. Given that fin and humpback whales, to our knowledge, do not migrate through any 

of these areas and are most likely infrequent visitors, we do not expect seismic survey vessel 

interaction to be a source of disturbance for these two species. 

In addition to acting as a source of noise and disturbance, marine vessels could potentially strike 

whales, causing injury or death. As noted in the baseline section of this evaluation, available 

information indicates that current rates of vessel strikes of fin, humpback, and bowhead whales 

in these waters are low. At present, available data do not indicate that strikes by oil and gasrelated vessels will become an important source of injury or mortality in the Chukchi or 

Beaufort Sea Planning Areas. Risk of strikes would increase as vessel traffic in whale habitat 

increases. 

If seismic survey vessels are attended by icebreakers involving active ice management, 

additional disturbance and noise will be introduced by the noise of the icebreaker. There are no 

observations of bowhead, fin or humpback reactions to icebreakers breaking ice. Response 

distances would vary, depending on icebreaker activities and sound-propagation conditions. 

Based on models, bowhead whales likely would respond to the sound of the attending 

icebreakers at distances of 2-25 km (1.24-15.53 mi) from the icebreakers (Miles, Malme, and 

Richardson 1987). Zones of responsiveness for intermittent sounds, such as an icebreaker 

pushing ice have not been studied. The study noted above predicts that roughly half of the 

68
bowhead whales show avoidance response to an icebreaker underway in open water at a range of 

2-12 km (1.25-7.46 mi) when the sound-to-noise ratio is 30 dB. The study also predicts that 

roughly half of the bowhead whales would show avoidance response to an icebreaker pushing 

ice at a range of 4.6-20 km (2.86-12.4 mi) when the sound-to-noise ratio is 30 dB. Richardson 

et al. (1995b) found that bowheads migrating in the nearshore lead often tolerated exposure to 

projected icebreaker sounds at received levels up to 20 dB or more above the natural ambient 

noise levels at corresponding frequencies. The source level of an actual icebreaker is much 

higher than that of the projectors (projecting recorded sound) used in this study (median 

difference 34 dB over the frequency range 40-6,300 Hz). Over the two-season period (1991 and 

1994) when icebreaker playbacks were attempted, an estimated 93 bowheads (80 groups) were 

seen near the ice camp when the projectors were transmitting icebreaker sounds into the water, 

and approximately 158 bowheads (116 groups) were seen near there during quiet periods. Some 

bowheads diverted from their course when exposed to levels of projected icebreaker sound 

greater than 20 dB above the natural ambient noise level in the one-third octave band of the 

strongest icebreaker noise. However, not all bowheads diverted at that sound-to-noise ratio, and 

a minority of whales apparently diverted at a lower sound-to-noise ratio. The study concluded 

that exposure to a single playback of variable icebreaker sounds can cause statistically but 

probably not biologically significant effects on movements and behavior of migrating whales in 

the lead system during the spring migration east of Point Barrow. The study indicated the 

predicted response distances for bowheads around an actual icebreaker would be highly 

variable; however, for typical traveling bowheads, detectable effects on movements and 

behavior are predicted to extend commonly out to radii of 10-30 km (6.2-18.6 mi). It should be 

noted that these predictions were based on reactions of whales to playbacks of icebreaker sounds 

in a lead system during the spring migration and are subject to a number of qualifications. The 

predicted typical radius of responsiveness around an icebreaker like the Robert Lemeur is quite 

variable, because propagation conditions and ambient noise vary with time and with location. In 

addition, icebreakers vary widely in engine power and noise output, with the Robert Lemeur

being a relatively low-powered icebreaker. Furthermore, the reaction thresholds of individual 

whales vary by at least 10 dB around the typical threshold, with commensurate variability in 

predicted reaction radius. 

While conducting aerial surveys over the Kuvlum drilling location, Brewer et al. (1993) showed 

that bowhead whales were observed within about 30 km (18.6 mi) north of the drilling location. 

The closest observed position for a bowhead whale detected during the aerial surveys was 

approximately 23 km (14.3 mi) from the project icebreakers. The drilling rig was not operating 

on that day, but all three icebreakers had been actively managing ice periodically during the day. 

The study did not indicate what the whale’s behavior was, but it did not appear to be avoiding 

the icebreakers. Three whales were sighted that day, and all three appeared to be moving to the 

northwest along the normal migration route at speeds of 2.4-3.4 km/h (1.5-2.1 mi/h). Bowhead 

whale call rates peaked when whales were about 32 km (19.9 mi) from the industrial activity. 

There was moderate to heavy ice conditions throughout the monitoring area, with heavy, 

grounded icefloes to the west, north, and east of the drilling site. Brewer et al. (1993) were 

unable to determine if either ice or industrial activity by themselves caused the whales to 

migrate to the north of the drilling location, but they concluded that ice alone probably did not 

determine the observed distribution of whales. 

69
Humpback whales summering in southeast Alaska did not exhibit persistent avoidance when 

exposed to seismic pulses from a 1.64-L (100 in3) airgun (Malme and Miles 1985). Some 

humpbacks seemed “startled” at received levels of 150–169 dB re 1 μPa on an approximate rms 

basis. McCauley et al. (1998, 2000) studied the responses of humpback whales off Western 

Australia to a full-scale seismic survey with a 16-airgun 2678-in3 array, and to a single 20 in3 

airgun with source level 227 dB re 1 μPa·m (p-p). They found that the overall distribution of 

humpbacks migrating through their study area was unaffected by the full-scale seismic program. 

McCauley et al. (1998) did, however, document localized avoidance of the array and of the 

single gun. Avoidance reactions began at 5–8 km (2.7–4.3 n.mi.) from the array and those 

reactions kept most pods about 3–4 km (1.6–2.2 n.mi.) from the operating seismic boat. 

Observations were made from the seismic vessel, from which the maximum viewing distance 

was listed as 14 km (7.6 n.mi.). Avoidance distances with respect to the single airgun were 

smaller but consistent with the results from the full array in terms of the received sound levels. 

Mean avoidance distance from the airgun corresponded to a received sound level of 140 dB re 1 

μPa rms; this was the level at which humpbacks started to show avoidance reactions to an 55 

approaching airgun. The standoff range, i.e., the closest point of approach of the airgun to the 

whales, corresponded to a received level of 143 dB rms. The initial avoidance response 

generally occurred at distances of 5–8 km (2.7–4.3 n.mi.) from the airgun array and 2 km (1.1 

n.mi.) from the single gun. However, some individual humpback whales, especially males, 

approached within distances 100–400 m (328–1312 ft), where the maximum received level was 

179 dB re 1 μPa rms. 

Data on short-term reactions (or lack of reactions) of cetaceans to impulsive noises do not 

necessarily provide information about long-term effects. It is not known whether impulsive 

noises affect reproductive rate or distribution and habitat use in subsequent days or years. 

However, gray whales continued to migrate annually along the west coast of North America 

despite intermittent seismic exploration and much ship traffic in that area for decades. Bowhead 

whales 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). Populations of both 

gray whales and bowhead whales grew substantially during this time. Humpback and fin whales 

which occur seasonally in the action areas are likely feeding or migrating. The observations 

summarized above indicate that any fin or humpback whale that is exposed to seismic pulses at 

particular levels may alter their behaviors. The responses of these whales are likely dependent 

on the received level and duration of the airgun pulses, but they may exhibit avoidance, suspend 

feeding, or shift their migration pathway. Avoidance responses or other behavioral disruptions 

could be expected to last during the exposure. Whales that are migrating may be diverted from 

their path or feeding whales may be interrupted, but these disruptions would be temporary. 

Although we do not have evidence to support this assumption for all baleen whales, gray whales 

have been observed to migrate annually along the west coast of North America despite 

intermittent seismic exploration (and much ship traffic) and bowhead whales continue to travel 

to the eastern Beaufort Sea each summer despite seismic exploration in the summer and autumn 

range for many years. Also, humpback whales exposed to LFA sonar changed song length but 

then returned to “normal” duration after exposure (Miller et al 2000). Fin and humpback whales 

are expected to resume their behavior after the seismic vessel has moved out of their immediate 

area without impairment of feeding, migration, or other behaviors. 

70
Effects from Aircraft Traffic 

Most offshore aircraft traffic in support of the oil industry involves turbine helicopters flying 

along straight lines. Underwater sounds from aircraft are transient. According to Richardson et 

al. (1995a), the angle at which a line from the aircraft to the receiver intersects the water’s 

surface is important. At angles greater than 13 degrees from the vertical, much of the incident 

sound is reflected and does not penetrate into the water. Therefore, strong underwater sounds 

are detectable while the aircraft is within a 26-degree cone above the receiver. An aircraft 

usually can be heard in the air well before and after the brief period while it passes overhead and 

is heard underwater. 

Data on reactions of bowheads, and especially fin and humpback whales, to helicopters are 

limited. Most bowheads are unlikely to react significantly to occasional single passes by lowflying helicopters ferrying personnel and equipment to offshore operations. Observations of 

bowhead whales exposed to helicopter overflights indicate that most bowheads exhibited no 

obvious response to helicopter overflights at altitudes above 150 m (500 ft). At altitudes below 

150 m (500 ft), some bowheads probably would dive quickly in response to the aircraft noise 

(Richardson and Malme 1993). This noise generally is audible for only a brief time (tens of 

seconds) if the aircraft remains on a direct course, and the whales should resume their normal 

activities within minutes. Patenaude et al. (1997) found that most reactions by bowheads to a 

Bell 212 helicopter occurred when the helicopter was at altitudes of 150 m or less and lateral 

distances of 250 m or less. The most common reactions were abrupt dives and shortened surface 

time and most, if not all, reactions seemed brief. However, the majority of bowheads showed no 

obvious reaction to single passes, even at those distances. The helicopter sounds measured 

underwater at depths of 3 and 18 m showed that sound consisted mainly of main-rotor tones 

ahead of the aircraft and tail-rotor sounds behind the aircraft; more sound pressure was received 

at 3 m than at 18 m; and peak sound levels received underwater diminished with increasing 

aircraft altitude. Sound levels received underwater at 3 m from a Bell 212 flying overhead at 

150 m ranged from 117-120 dB re 1 μPa in the 10-500-Hz band. Underwater sound levels at 18 

m from a Bell 212 flying overhead at 150 m ranged from 112-116 dB re 1 μPa in the 10-500-Hz 

band. 

Fixed-wing aircraft flying at low altitude often cause hasty dives. Reactions to circling aircraft 

are sometimes conspicuous if the aircraft is below 300 m (1,000 ft), uncommon at 460 m (1,500 

ft), and generally undetectable at 600 m (2,000 ft). Repeated low-altitude overflights at 150 m 

(500 ft) during aerial photogrammetry studies of feeding bowheads sometimes caused abrupt 

turns and hasty dives (Richardson and Malme 1993). Aircraft on a direct course usually produce 

audible noise for only tens of seconds, and the whales are likely to resume their normal activities 

within minutes (Richardson and Malme 1993). Patenaude et al. (1997) found that few bowheads 

(2.2%) during the spring migration were observed to react to Twin Otter overflights at altitudes 

of 60-460 m. Reaction frequency diminished with increasing lateral distance and with 

increasing altitude. Most observed reactions by bowheads occurred when the Twin Otter was at 

altitudes of 182 m or less and lateral distances of 250 m or less. There was little, if any, reaction 

by bowheads when the aircraft circled at an altitude of 460 m and a radius of 1 km. The effects 

from an encounter with aircraft are brief, and the whales should resume their normal activities 

within minutes. 

71
While the obvious behavioral reaction of a bowhead to a single low-flying helicopter or fixedwinged aircraft flying overhead is probably temporary (Richardson et al. 1995a), most “fleeing” 

reactions in mammals are accompanied by endocrine changes, which, depending on other 

stressors to which the individual is exposed, could contribute to a potentially adverse effect on 

health. 

Humpback and fin whales could be also be disturbed by aircraft noise associated with oil and 

gas leasing and exploration. Shallenberger (1978) reported some humpbacks were disturbed by 

overflights at 1,000 ft (305 m), whereas others showed no response at 500 ft (152 m). As with 

response to airgun noise, pods varied in their response. Humpbacks in large groups showed 

little or no response, but some adult-only groups exhibited avoidance (Herman et al. 1980). 

Information is lacking regarding the potential effects of aircraft noise on fin or humpback 

whales. It is likely the discussion of these effects on bowhead whales (above) is generally 

applicable to fin and humpback whales. 

On-Ice 2D/3D Seismic Surveys 

The 2D/3D seismic surveying in shallow water could also be conducted during the winter over 

the ice and we anticipate that some on-ice surveys could occur. Seismic profiling on shore-fast 

ice using vibroseis is another source of introduction of noise into the arctic environment. 

Richardson et al. (1995a) summarized that typical signals associated with this kind of seismic 

activity sweep from 10-70 Hz but harmonics extend to about 1.5 kHz (Richardson et al. 1995a). 

In this activity, hydraulically driven pads mounted beneath a line of trucks are used to vibrate, 

and thereby energize the ice. Noise incidental to the activity is introduced by the vehicles 

associated with this activity. 

These on-ice surveys often extend into the period in April when bowhead whales begin to be 

observed at Barrow and are present in the Chukchi and Beaufort Sea in the spring lead system. 

However, during that period in the Beaufort Sea, the whales are far offshore in the spring leads 

and distant from shallow water areas where such surveys could occur. On-ice surveys are not 

expected in the Chukchi Sea. These surveys have occurred regularly in nearshore areas of the 

Alaska Beaufort Sea over the past 30 years. If bowhead whales detect these sounds, there is no 

indication of any adverse effect on their migration or population recovery. For these reasons, we 

believe that on-ice surveys are not likely to have detectable adverse effects on bowhead whales. 

We do not believe these surveys will affect humpback or fin whales because these whales are 

not present during the periods in which on-ice surveys may occur. 

Potential Effects from Exploratory Drilling Operations 

Exploration drilling units and other drilling units are sources of noise and disturbance to 

bowhead whales. Exploration drilling in the Beaufort Sea can be conducted from manmade 

gravel islands, ice islands, caisson-retained islands, bottom-founded drilling platforms such as 

the concrete island drilling system or single steel drilling caisson, or from drillships in deeper 

water supported by icebreakers. The type of drilling platform used depends on water depth, 

oceanography, ice cover, and other factors. Stationary sources of offshore noise (such as drilling 

units) appear less disruptive to bowhead whales than moving sound sources (such as vessels). 

72
Drilling operations from many of these structures except drillships are likely to be conducted 

during the winter months. Drilling from ice islands would occur only during the winter when 

bowheads are not present, and noise from these activities would not affect bowhead whales. 

Therefore, this type of drilling activity is not discussed here. 

MMS anticipates that gravel islands are not likely to be constructed for exploratory drilling in 

OCS waters, but that old artificial islands might be used temporarily. In the near future MMS 

expects that exploratory drilling in the Beaufort Sea will also be conducted from other platforms 

and during the open water period depending on water depth, sea ice conditions, availability of 

drilling units, and the ice-resistance of units. MMS said moveable platforms resting on the 

seafloor could be used to drill in water depths of 10-20 m, but that drillships or other floating 

units would be used in deeper water. Drilling from these units will be in open water. Such 

drilling would be supported by icebreakers and supply boats. 

In the Beaufort Sea, MMS assumes a maximum of two drilling rigs would operate at any one 

time with a total of six exploration wells and six delineation wells drilled over an eight year 

period, beginning in 2007. Exploration drilling in the Chukchi Sea evaluation area could begin 

as early as 2008. Drilling operations in the Chukchi Sea are likely to employ drillships with icebreaker support vessels and to operate at a given well site between 30 and 90 days. MMS 

assumes one to two exploration wells per season drilled between June-November. No 

exploration drilling from Sale 193 would occur in the polynya. Thus, based on the 

aforementioned scenario, fin, humpback, or bowhead whales could potentially encounter a total 

of 3 exploration drilling units within evaluation areas, with icebreaker support possible in the 

Chukchi Sea and likely in the Beaufort Sea. Beginning in 2012, production and injection wells 

may also be drilled. 

Noise-producing activities, such as drilling operations, in the spring lead and polynya system 

during the spring bowhead migration have a fairly high potential of affecting the whales. MMS 

has decided not to allow seismic survey activity in the spring lead system through late June, or 

as prescribed by NMFS to protect bowhead whales. No exploration activities would occur in the 

spring lead system from Sale 193. Exploration drilling from future OCS sales would not occur 

before 2011. At this time, it is unknown whether future Chukchi Sea Sales will include or 

exclude the spring lead system. The general location of the spring lead system is based on 

relatively limited survey data and is not well defined. 

Previously, MMS concluded that exploratory drilling operations using floating platforms within 

the portion of the Beaufort Sea spring lead system during the bowhead migration are unlikely, 

because the ice at this time of year would be too thick for floating drilling platforms to get to the 

location and conduct drilling operations, even with icebreaker support. Thus, in the Beaufort 

Sea multiple-sale EIS, MMS concluded that spring-migrating bowheads are not likely to be 

exposed to drilling noise from activities on leases from Sales 186, 195, or 202. MMS concluded 

that areas in or near the spring lead system in the Beaufort Sea could be leased during these 

sales, but any exploratory drilling operations likely would be conducted during the open-water 

season (August-October) using floating drilling platforms. 

73
Future lease sale decisions will determine whether the polynya area will be offered for lease in 

the future. No exploratory drilling in the Chukchi Sea portion of the lead system could begin 

unless tracts within the polynya area are offered and leased. Open water in this polynya area 

typically begins in June and continues through November. 

Some bowheads in the vicinity of drilling operations would be expected to respond to noise from 

drilling units by slightly changing their migration speed and swimming direction to avoid 

closely approaching these noise sources. Miles, Malme, and Richardson (1987) predicted the 

zone of responsiveness to continuous noise sources. They predicted that roughly half of the 

bowheads likely would respond at a distance of 0.02-0.2 km (0.12-1.12 mi) to drilling from an 

artificial island when the signal-to-noise ratio is 30 dB. By comparison, they predicted that 

roughly half of the bowheads likely would respond at a distance of 1-4 km (0.62-2.5 mi) from a 

drillship drilling when the signal-to-noise ratio is 30 dB. A smaller proportion would react when 

the signal-to-noise ratio is about 20 dB (at a greater distance from the source), and a few may 

react at a signal-to-noise ratio even lower or at a greater distance from the source. 

Drilling for oil and gas generally produces low-frequency sounds with strong tonal components. 

There are few data on the noise from conventional drilling platforms. Recorded noise from an 

early study of one drilling platform and three combined drilling production platforms found that 

noise was so weak, it was almost not detectable alongside the platform at sea states of 3 or 

above. The strongest tones were at very low frequencies near 5 Hz, and received levels of these 

tones at near-field locations were 119-127 dB re 1 μPa (Richardson et al. 1995a). 

Although underwater sounds from drilling on some artificial islands and caissons have been 

measured, little information is available about reactions of bowheads to drilling from these 

structures. Underwater noise levels from drilling operations on natural barrier islands or 

artificial islands are low and are not audible beyond a few kilometers (Richardson et al. 1995a). 

Noise is transmitted very poorly from the drill-rig machinery through land into the water. Even 

under open-water conditions, drilling sounds are not detectable very far from the structure. 

Drilling noise from caisson-retained islands is much stronger. At least during open-water 

conditions, noise is conducted more directly into the water than from island drill sites. Noise 

associated with drilling activities at both sites varies considerably with ongoing operations. The 

highest documented levels were transient pulses from hammering to install conductor pipe. 

NMFS (2001) concluded that: 

...bowhead whale responses to noise from drilling and exploration activities are expected to 

depend on the type of activity and its location relative to the whales’ normal migration 

corridors...Thus, a drill ship operating offshore and closer to the center of the migration is 

expected to have a greater biological impact than a drilling operation from an artificial island 

situated in very shallow water along the nearshore edge of the migration. 

Artificial Gravel Islands 

Shallow nearshore waters of the Beaufort Sea are suitable for development of artificial gravel 

islands to support oil production. Costs are prohibitive for use of this technology for exploratory 

activities. Compared to caissons emplaced on the ocean bottom, platforms standing on legs, or 

drilling vessels, offshore drilling from natural or man-made islands generally produces 

74
underwater sounds that are weak and do not propagate beyond a few kilometers (Richardson et 

al. 1995). The following is a brief discussion of several studies on the measurement of 

underwater noise and the effects of noise from drilling operations on gravel islands on bowhead 

whales. Although we are uncertain of the impacts to fin and humpback whales, similar 

conclusions for these two baleen species may be reasonable to assume. 

Seal Island: Noise measurements were made during the open-water season near Seal Island, a 

manmade gravel island off Prudhoe Bay in water 12 m deep. Seal Island is the approximate 

location for the Northstar Project. Davis, Greene, and McLaren (1985) measured underwater 

noise from Seal Island during the open-water season while well logging was occurring but not 

drilling operations. Underwater sound levels recorded from bottom hydrophones 1.65-2.4 km 

from Seal Island were strongly affected by wind speed and active barge or tug traffic at the 

island. The strongest tone measured was 486 Hz from turbochargers on the generators used for 

well-logging operations. This tone was measured by a hydrophone on a boat at distances of up 

to 5 km from Seal Island. Noise associated with barge or tug movement at the island readily 

could be detected at 2.4 km from the island, even during high winds. Noise levels in the 20-

1,000-Hz band from barge traffic were about 118 dB re 1 μPa at 1.6 km and had decreased to 

108-110 dB re 1 μPa at 2.4 km. At that rate of sound attenuation, the noise level from barges 

was estimated to be about 92 dB at 6 km. Underwater sounds from Seal Island were not 

detectable 2.3 km away while people were on the island and power generators were operating, 

but no logging or drilling operations were ongoing. 

Aerial surveys for bowhead whales near Seal Island in 1982 (during island construction) and 

1984 found that most whales were in water deeper than 18 m, which is consistent with data from 

previous studies (Davis, Greene, and McLaren 1985). In 1982, one whale was sighted in 12 m 

of water about 11 km northwest of Seal Island. In 1984, there were two sightings of single 

whales in 12-15 m of water. Whales migrating in water deeper than 18 m would have been too 

far away to detect noise from Seal Island, because industrial noise was not audible in the water 

more than a few kilometers away. Acoustic data collected in 1982 and 1984 suggest that some 

bowheads were closer to Seal Island in 1984 than in 1982. Localizations made by the 

hydrophone array on three occasions indicated the whales were present between 2.5 and 6 km 

from Seal Island. Bowhead calls recorded on hydrophones were thought to be from whales that 

were in water at least 18 m deep. The study concluded that there was no evidence to suggest 

that bowheads avoided Seal Island in 1984 compared to 1982. 

Sandpiper Island: Johnson et al. (1986) measured underwater noise from Sandpiper Island, a 

manmade gravel island in water 15 m deep. Sound was measured using a bottom-hydrophone 

system at 0.5 km from the island and sonobuoys at greater distances from the island. The 

median sound levels observed at a fixed location 0.5 km from Sandpiper Island were relatively 

low. Median noise levels in the 20-1,000-Hz band were 93 and 95 dB re 1 μPa during two 

periods without drilling and 100 dB re 1 μPa during one period with drilling. In the absence of 

shipping or other industrial sounds, the expected level of noise in the 20-1,000-Hz band is about 

100 dB re 1 μPa for Beaufort Sea State 2 conditions (wind speeds at 7-10 kn and wave heights 

up to 0.5 m). The most obvious components were tones at 20 and 40 Hz, which were attributed 

to power generation on the island. 

75
The low-frequency industrial sounds from Sandpiper Island attenuated rapidly with increasing 

range, at least partially due to the shallow water. The low-frequency sounds were evident when 

ambient noise levels were low but were largely masked during periods when ambient noise was 

above average. Sound levels received at a sonobuoy 3.7 km from Sandpiper Island (76 dB re 1 

μPa in both the 20- and 40-Hz bands) were 24-30 dB lower than the levels received at the 

bottom hydrophone 0.5 km from the island. The bottom hydrophone measured drilling sounds 

of 100 dB re 1 μPa in the 20-Hz-frequency band at 0.5 km from Sandpiper Island. The sounds 

were severely attenuated at 3.7 km and not detectable at 9.3 km. The effective source level of 

the 40-Hz tone was estimated at 145 dB re 1 μPa at 1 m. 

Impulsive hammering sounds associated with installation of a conductor pipe were as high as 

131-135 dB re 1 μPa at 1 km, when pipe depth was about 20 m below the island. In contrast, 

broadband drilling noise at this distance was about 100-106 dB. During hammering, the 

transient signals had the strongest components at 30-40 Hz and about 100 Hz. Moore et al. 

(1984, as cited in Richardson et al. 1995b) reported that received levels for transient piledriving 

sounds recorded at 1 km from a manmade island near Prudhoe Bay were 25-35 dB above 

ambient levels in the 50- to 200-Hz band. They estimated that the sounds might be received 

underwater as far as 10-15 km from the source, farther than drilling sounds. Aerial surveys for 

bowhead whales in 1985 indicated that no bowheads were seen closer than 30 km from 

Sandpiper Island (Johnson et al. 1986). Almost all of the migrating bowheads traveled in water 

deeper than 18 m, as was found in the surveys for Seal Island. Sandpiper and Northstar islands 

are both about 6 km south of the 18-m-depth contour. Industrial noise from Sandpiper Island, 

with or without drilling, was not audible in the water more than a few kilometers away. Because 

the migration route of almost all bowheads is north of the 18-m contour, few individual whales 

moved into the zone where industrial noise potentially was detectable. 

The authors concluded that the number of whales that passed along the southern edge of the 

migration route and approached the artificial islands, both Seal and Sandpiper, must have been a 

very low fraction of the total population given the absence of sightings close to the islands. 

Tern Island: Studies at Tern Island were conducted to determine sound levels that could be 

expected from the Liberty development project. The studies provide information on distances 

that sound travels as a result of activities on gravel islands. 

Greene (1997) measured underwater sounds under the ice at the Liberty Island location from 

drilling operations on Tern Island in Foggy Island Bay in February 1997. Sounds from the drill 

rig generally were masked by ambient noise at distances near 2 km. The strongest tones were at 

frequencies below 170 Hz, but the received levels diminished rapidly with increasing distance 

and dropped below the ambient noise level at ranges of about 2 km. Drilling sounds were not 

detected at frequencies above 400 Hz, even at 200 m from the drill rig. 

Northstar Island: Formerly known as Seal Island, British Petroleum expanded this island for 

oil production in 2000, with production beginning in October 2001. Two pipelines connect the 

island to shore-based infrastructure and the Trans-Alaska Pipeline. An extensive acoustic 

monitoring program was implemented for the Northstar project. That work found that in-water 

drilling sounds from the island reached background levels at distances of 2-4km (Richardson 

76
2006). Noise from the island was higher during construction. During production, researchers 

were unable to detect any differences in broadband sound pressure levels with and without 

drilling. The most important contributor to noise from the Northstar project was associated with 

vessels (crew boats, tugs, and self-propelled barges). 

Oooguruk and Nikaitchuq Islands 

Two offshore production pads (islands) are currently being developed in Harrison Bay near 

Oliktok Point. Produced oil from these facilities will be delivered by sub-sea pipelines which 

utilize pipe-in-pipe technology to reduce the risk of failure and spills. These will be in very 

shallow water; depths are less than 3 meters. Large whales would not occur at these sites, 

however in-water noise could extend out to deeper waters where whales (mainly bowhead 

whales) may be found. In-water noise was measured during construction of the Oooguruk 

Island facility in 2006 (Zykov, Hannay, and Link 2007). Noise levels at 1 mile were measured 

at 92 dB re 1 μPa, and not detectable at 4 miles. Tug and barge noise had higher detections, as 

expected. 

Bottom-Founded Structures 

Two types of drilling platforms have been used for offshore drilling in the Alaska Beaufort Sea: 

the concrete island drilling system, which is a floating concrete rig that is floated into place, 

ballasted with seawater, and sits on the seafloor; and the single steel drilling caisson, which is a 

section of a ship with a drill rig mounted on it and also is floated into place, ballasted with 

seawater, and sits on the seafloor. Drilling from these platforms generally begins after the 

bowhead whale migration is done and continues through the winter season. 

In the absence of drilling operations, radiated levels of underwater sound from the concrete 

island drilling system were low, at least at frequencies above 30 Hz. The overall received level 

was 109 dB re 1 μPa at 278 m, excluding any infrasonic components. When the concrete island 

drilling system was operating in early winter, radiated sound levels above 30 Hz again were 

relatively low (89 dB at 1.4 km). However, when infrasonic components were included, the 

received level was 112 dB at 1.4 km. More than 99% of the sound energy received was below 

20 Hz. Received levels of sound at 222-259 m ranged from 121-124 dB. The maximum 

detection distance for infrasonic sounds was not determined. Such tones likely would attenuate 

rapidly in water shallow enough for a bottom-founded structure. Overall, the estimated source 

levels were low for the concrete island drilling system, even when the infrasonic tones were 

included (Richardson et al. 1995a). 

Sounds from the steel drilling caisson were measured during drilling operations in water 15 m 

deep with 100% ice cover. The strongest underwater tone was at 5 Hz (119 dB re μPa) at a 

distance of 115 m. The 5-Hz tone apparently was not detectable at 715 m, but weak tones were 

present at 150-600 Hz. The broadband (20-1,000 Hz) received level at 215-315 m was 116-117 

dB re μPa, higher than the 109 dB reported for the concrete island drilling system at 278 m. 

Inupiat whalers believe that noise from drilling activities displace whales farther offshore, away 

from their traditional hunting areas. These concerns were expressed primarily for drilling 

activities from drillships with icebreaker support that were operating offshore in the main 

migration corridor. Concerns also have been expressed about noise generated from the single 

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steel drilling caisson, the drilling platform used to drill two wells on the Cabot Prospect east of 

Barrow in October 1990 and November 1991. Mr. Jacob Adams, Mr. Burton Rexford, Mr. Fred 

Kanayurak, and Mr. Van Edwardson, all with the Barrow Whaling Captain’s Association, stated 

in written testimony at the Arctic Seismic Synthesis and Mitigating Measures Workshop on 

March 5-6, 1997, in Barrow: “We are firmly convinced that noise from the Cabot drilling 

platform displaced whales from our traditional hunting area. This resulted in us having to go 

further offshore to find whales” (USDOI, MMS 1997). 

No data were found to describe possible reaction of humpback or fin whales to these structures. 

However, we would expect these whales would show similar response as bowhead whales. We 

expect bottom-founded structures would be used primarily in the more shallow waters of the 

eastern Beaufort Seas, beyond the present range of fin and humpback whales. 

Drillships and other Floating Platforms 

Bowhead reaction to drillships is variable. Bowhead whales whose behavior appeared normal 

have been observed on several occasions within 10-20 km (6.2-12.4 mi) of drillships in the 

eastern Beaufort Sea, and there have been a number of reports of sightings within 0.2-5 km 

(0.12-3 mi) from drillships (Richardson et al. 1985a; Richardson and Malme 1993). On several 

occasions, whales were well within the zone where drillship noise should be clearly detectable 

by them. In other cases, bowheads may avoid drillships and their support vessels at 20-30 km 

(see below and NMFS, 2003a). The factors associated with the variability are not fully 

identified or understood. 

Richardson and Malme (1993) point out that the data, although limited, suggest that stationary 

industrial activities producing continuous noise, such as stationary drillships, result in less 

dramatic reactions by bowheads than do moving sources, particularly ships. It also appears that 

bowhead avoidance is less around an unattended structure than one attended by support vessels. 

Most observations of bowheads tolerating noise from stationary operations are based on 

opportunistic sightings of whales near ongoing oil-industry operations, and it is not known 

whether more whales would have been present in the absence of those operations. Because 

other cetaceans seem to habituate somewhat to continuous or repeated noise exposure when the 

noise is not associated with a harmful event, this suggests that bowheads will habituate to certain 

noises that they learn are nonthreatening. Additionally, it is not known what components of the 

population were observed around the drillship (e.g., adult or juvenile males, adult females, etc.). 

In Canada, bowhead use of the main area of oil-industry operations within the bowhead range 

was low after the first few years of intensive offshore oil exploration in 1976 (Richardson, 

Wells, and Wursig 1985), suggesting perhaps cumulative effects from repeated disturbance may 

have caused the whales to leave the area. In the absence of systematic data on bowhead summer 

distribution until several years after intensive industry operations began, it is arguable whether 

the changes in distribution in the early 1980’s were greater than natural annual variations in 

distribution, such as responding to changes in the location of food sources. Ward and Pessah 

(1988) concluded that the available information from 1976-1985 and the historical whaling 

information do not support the suggestion of a trend for decreasing use of the industrial zone by 

bowheads as a result of oil and gas exploration activities. They concluded that the exclusion 

hypothesis is likely invalid. 

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The distance at which bowheads may react to drillships is difficult to gauge, because some 

bowheads would be expected to respond to noise from drilling units by changing their migration 

speed and swimming direction to avoid closely approaching these noise sources. For example, 

in the study by Koski and Johnson (1987), one whale appeared to adjust its course to maintain a 

distance of 23-27 km (14.3-16.8 mi) from the center of the drilling operation. Migrating whales 

apparently avoided the area within 10 km (6.2 mi) of the drillship, passing both to the north and 

to the south of the drillship. The study detected no bowheads within 9.5 km (5.9 mi) of the 

drillship, and few were observed within 15 km (9.3 mi). The principal finding of this study was 

that migrating bowheads appeared to avoid the offshore drilling operation in fall 1986. Thus, 

some bowheads may avoid noise from drillships at 20 km (12.4 mi) or more. 

In other studies, Richardson, Wells, and Wursig (1985) observed three bowheads 4 km (2.48 mi) 

from operating drillships, well within the zones ensonified by drillship noise. The whales were 

not heading away from the drillship but were socializing, even though exposed to strong 

drillship noise. Eleven additional whales on three other occasions were observed at distances of 

10-20 km (6.2-12.4 mi) from operating drillships. On two of the occasions, drillship noise was 

not detectable by researchers at distances from 10-12 km (6.2-7.4 mi) and 18-19 km (11.2-11.8 

mi), respectively. In none of the occasions were whales heading away from the drillship. Ward 

and Pessah (1988, as cited in Richardson and Malme 1993) reported observations of bowheads 

within 0.2-5 km (0.12-3 mi) from drillships. 

The ice-strengthened Kulluk, a specialized floating platform designed for arctic waters, was 

used for drilling operations at the Kuvlum drilling site in western Camden Bay in 1992 and 

1993. Data from the Kulluk indicated broadband source levels (10-10,000 Hz) during drilling 

and tripping were estimated to be 191 and 179 dB re μPa at 1 m, respectively, based on 

measurements at a water depth of 20 m in water about 30 m deep (Richardson et al. 1995a). 

Hall et al. (1994) conducted a site-specific monitoring program around the Kuvlum drilling site 

in the western portion of Camden Bay during the 1993 fall bowhead whale migration. Results 

of their analysis indicated that bowheads were moving through Camden Bay in a significantly 

nonrandom pattern but became more randomly distributed as they left Camden Bay and moved 

to the west. The results also indicated that whales were distributed farther offshore in the 

proximal survey grid (near the drill site) than in the distant survey grid (an area east of the drill 

site), which is similar to results from previous studies in this general area. The authors noted 

that information from previous studies indicated that bowheads routinely were present nearshore 

to the east of Barter Island and were less evident close to shore from Camden Bay to Harrison 

Bay (Moore and Reeves, as cited in Hall et al., 1994). The authors believed that industrial 

variables such as received level were insufficient as a single predictor variable to explain the 

1993 offshore distribution of bowhead whales, and they suggested that water depth was the only 

variable that accounted for a significant portion of the variance in the model. They concluded 

that for 1993, water depth, received level, and longitude accounted for 85% of the variance in 

the offshore distribution of the whales. Based on their analyses, the authors concluded that the 

1993 bowhead whale distribution fell within the parameters of previously recorded fallmigration distributions. 

79
Davies (1997) used the data from the Hall et al. study in a Geographic Information System 

model to analyze the distribution of fall-migrating bowheads in relation to an active drilling 

operation. He also concluded that the whales were not randomly distributed in the study area, 

and that they avoided the region surrounding the drill site at a range of approximately 20 km 

(12.4 mi). He noted that the whales were located significantly farther offshore and in 

significantly deeper water in the area of the drilling rig. As noted by Hall et al. (1994), the 

distribution of whales observed in the Camden Bay area is consistent with previous studies 

(Moore and Reeves 1993), where whales were observed farther offshore in this portion of the 

Beaufort Sea than they were to the east of Barter Island. Davies concluded, as did Hall et al., 

that it was difficult to separate the effect of the drilling operation from other independent 

variables. The model identified distance from the drill rig and water depth as the two 

environmental factors that were most strongly associated with the observed distribution of 

bowheads in the study area. The Davies analysis, however, did not note that surface observers 

(Hall et al. 1994) observed whales much closer to the drilling unit and support vessels than did 

aerial observers. In one instance, a whale was observed approximately 400 m (436 yd) from the 

drill rig. Hall et al. suggest that bowheads, on several occasions, were closer to industrial 

activity than would be suggested by an examination of only aerial-survey data. 

Schick and Urban (2000) also analyzed data from the Hall et al. study and tested the correlation 

between bowhead whale distribution and variables such as water depth, distance to shore, and 

distance to the drilling rig. The distribution of bowhead whales around the active drilling rig in 

1993 was analyzed and the results indicated that whales were distributed farther from the 

drilling rig than they would be under a random scenario. The area of avoidance was localized 

and temporary (Schick and Urban 2000); Schick and Urban stated they could not conclude that 

noise from the drilling rig caused the low density near the rig, because they had no data on 

actual noise levels. They also noted that ice, an important variable, is missing from their model 

and that 1992 was a particularly heavy ice year. Because ice may be an important patterning 

variable for bowheads, Schick and Urban said they were precluded from drawing strong 

inference from the 1992 results with reference to the interaction between whales and the drilling 

rig. Moore and DeMaster (1998, as cited in Schick and Urban 2002) proposed that migrating 

bowheads are often found farther offshore in heavy ice years because of an apparent lack of 

feeding opportunities. Schick and Urban (2002) stated that ultimately, the pattern in the 1992 

data may be explained by the presence of ice rather than by the presence of the drilling rig. 

In playback experiments, some bowheads showed a weak tendency to move away from the 

sound source at a level of drillship noise comparable to what would be present several 

kilometers from an actual drillship (Richardson and Malme 1993). In one study, sounds 

recorded 130 m (426 ft) from the actual Karluk drill rig were used as the stimulus during 

disturbance test playbacks (Richardson et al., 1991). For the overall 20- to 1,000-Hz band, the 

average source level was 166 dB re 1 μPa in 1990 and 165 dB re 1 μPa in 1989. Bowheads 

continued to pass the projector while normal Karluk drilling sounds were projected. During the 

playback tests, the source level of sound was 166 dB re 1 μPa. One whale came within 110 m 

(360 ft) of the projector. Many whales came within 160-195 m (525-640 ft), where the received 

broadband (20-1,000 Hz) sound levels were about 135 dB re 1 μPa. That level was about 46 dB 

above the background ambient level in the 20- to 1,000-Hz band on that day. Bowhead 

movement patterns were strongly affected when they approached the operating projector. When 

80
bowheads still were several hundred meters away, most began to move to the far side of the lead 

from the projector, which did not happen during control periods while the projector was silent. 

In a subsequent phase of this continuing study, Richardson et al. (1995b) concluded: 

...migrating bowheads tolerated exposure to high levels of continuous drilling noise if it was 

necessary to continue their migration. Bowhead migration was not blocked by projected drilling 

sounds, and there was no evidence that bowheads avoided the projector by distances exceeding 1 

kilometer (0.54 nautical mile). However, local movement patterns and various aspects of the 

behavior of these whales were affected by the noise exposure, sometimes at distances 

considerably exceeding the closest points of approach of bowheads to the operating projector. 

Richardson et al. (1995b) reported that bowhead whale avoidance behavior has been observed in 

half of the animals when exposed to 115 dB re 1 μPa rms broadband drillship noises. However, 

reactions vary depending on the whale activity, noise characteristics, and the physical situation 

(Richardson and Greene, 1993). 

Some migrating bowheads diverted their course enough to remain a few hundred meters to the 

side of the projector. Surfacing and respiration behavior, and the occurrence of turns during 

surfacings, were strongly affected out to 1 km (0.62 mi). Turns were unusually frequent out to 2 

km (1.25 mi), and there was evidence of subtle behavioral effects at distances up to 2-4 km 

(1.25-2.5 mi). The study concluded that the demonstrated effects were localized and temporary 

and that playback effects of drilling noise on distribution, movements, and behavior were not 

biologically significant. 

The authors stated that one of the main limitations of this study (during all 4 years) was the 

inability of a practical sound projector to reproduce the low-frequency components of recorded 

industrial sounds. Both the Karluk rig and the icebreaker Robert Lemeur emitted strong sounds 

down to ~10-20 Hz, and quite likely at even lower frequencies. It is not known whether the 

under-representation of low-frequency components (less than 45 Hz) during icebreaker 

playbacks had significant effects on the responses by bowheads. Bowheads presumably can 

hear sounds extending well below 45 Hz. It is suspected but not confirmed that their hearing 

extends into the infrasonic range below 20 Hz. The authors believed the projector adequately 

reproduced the overall 20- to 1,000-Hz level at distances beyond 100 m (109 yd), even though 

components below 80 Hz were under-represented. If bowheads are no more responsive to sound 

components at 20-80 Hz than to those above 80 Hz, then the playbacks provided a reasonable 

test of the responsiveness to components of Karluk sound above 20 Hz. 

The authors also stated that the study was not designed to test the potential reactions of whales 

to nonacoustic stimuli detected via sight, olfaction, etc. At least in summer/autumn, responses 

of bowheads to actual dredges and drillships seem consistent with reactions to playbacks of 

recorded sounds from those same sites. Additional limitations of the playbacks identified by the 

authors included low sample sizes and the fact that responses were only evident if they could be 

seen or inferred based on surface observations. The numbers of bowhead whales observed 

during both playback and control conditions were low percentages of the total Beaufort Sea 

population. Also, differences between whale activities and behavior during playback versus 

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control periods represent the incremental reactions when playbacks are added to a background of 

other activities associated with the research. Thus, playback results may somewhat understate 

the differences between truly undisturbed whales versus those exposed to playbacks. 

Few data were found to describe possible reaction of humpback or fin whales to drillships and 

other floating platforms. Malme (in Richardson et al. 1995) observed reactions among 

humpback whales exposed to drillship, semi-submersible, drilling platform, and production 

platform noises and found no clear responses at broadband received levels up to 116 dB. Again, 

we would expect fin and humpback whales generally would show similar response as bowhead 

whales, reacting more at higher received levels or to start-up or transient signals. The data 

suggest that stationary industrial activities producing continuous noise result in less dramatic 

reactions by cetaceans than do moving sound sources, particularly ships (Richardson et al. 

1995). However, bowhead whales may be especially sensitive to such noise. 

Icebreakers 

If drillships are attended by icebreakers, as typically is the case during the fall in the U.S. 

Beaufort Sea, and we expect to be the case in the Chukchi Sea, the drillship noise frequently 

may be masked by icebreaker noise, which often is louder. Response distances would vary, 

depending on icebreaker activities and sound-propagation conditions. Based on models, 

bowhead whales likely would respond to the sound of the attending icebreakers at distances of 

2-25 km (1.24-15.53 mi) from the icebreakers (Miles, Malme, and Richardson 1987). Zones of 

responsiveness for intermittent sounds, such as an icebreaker pushing ice have not been studied. 

This study predicts that roughly half of the bowhead whales show avoidance response to an 

icebreaker underway in open water at a range of 2-12 km (1.25-7.46 mi) when the sound-tonoise ratio is 30 dB. The study also predicts that roughly half of the bowhead whales would 

show avoidance response to an icebreaker pushing ice at a range of 4.6-20 km (2.86-12.4 mi) 

when the sound-to-noise ratio is 30 dB. 

Richardson et al. (1995b) found that bowheads migrating in the nearshore lead often tolerated 

exposure to projected icebreaker sounds at received levels up to 20 dB or more above the natural 

ambient noise levels at corresponding frequencies. The source level of an actual icebreaker is 

much higher than that of the projectors (projecting recorded sound) used in this study (median 

difference 34 dB over the frequency range 40-6,300 Hz). Over the two-season period (1991 and 

1994) when icebreaker playbacks were attempted, an estimated 93 bowheads (80 groups) were 

seen near the ice camp when the projectors were transmitting icebreaker sounds into the water, 

and approximately 158 bowheads (116 groups) were seen near there during quiet periods. Some 

bowheads diverted from their course when exposed to levels of projected icebreaker sound 

greater than 20 dB above the natural ambient noise level in the one-third octave band of the 

strongest icebreaker noise. However, not all bowheads diverted at that sound-to-noise ratio, and 

a minority of whales apparently diverted at a lower sound-to-noise ratio. The study concluded 

that exposure to a single playback of variable icebreaker sounds can cause statistically but 

probably not biologically significant effects on movements and behavior of migrating whales in 

the lead system during the spring migration east of Point Barrow. The study indicated the 

predicted response distances for bowheads around an actual icebreaker would be highly 

variable; however, for typical traveling bowheads, detectable effects on movements and 

behavior are predicted to extend commonly out to radii of 10-30 km (6.2-18.6 mi). 

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It should be noted that these predictions were based on reactions of whales to playbacks of 

icebreaker sounds in a lead system during the spring migration and are subject to a number of 

qualifications. The predicted “typical” radius of responsiveness around an icebreaker like the 

Robert Lemeur is quite variable, because propagation conditions and ambient noise vary with 

time and with location. In addition, icebreakers vary widely in engine power and thus noise 

output, with the Robert Lemeur being a relatively low-powered icebreaker. Furthermore, the 

reaction thresholds of individual whales vary by at least 10 dB around the “typical” threshold, 

with commensurate variability in predicted reaction radius. 

Richardson et al. (1995a) reported that broadband (20-1,000 Hz) received levels at 0.37 km for 

the icebreaking supply vessel the Canmar Supplier underway in open water were 130 dB and 

144 dB when it was breaking ice. The increase in noise during icebreaking is apparently due to 

propeller cavitation. Richardson et al. (1995a) summarized that icebreaking sound from the 

Robert Lemeur pushing on ice were detectable >50 km away. We anticipate that an icebreaker 

would attend a drillship in the Chukchi Sea. Brewer et al. (1993) reported that in the autumn of 

1992, migrating bowhead whales avoided an icebreaker-accompanied drillship by 25+ km. This 

ship was icebreaking almost daily. However, Richardson et al. (1995a) noted that in 1987, 

bowheads also avoided another drillsite with little icebreaking. 

No data were found to describe possible reaction of humpback or fin whales to icebreakers. We 

would not expect icebreaking to be an issue for these species for the proposed actions, as their 

distribution is primarily within the Chukchi and western Beaufort Seas where ice management is 

less likely to be needed to support exploratory activity. 

Vessel Traffic 

Bowheads react to the approach of vessels at greater distances than they react to most other 

industrial activities. According to Richardson and Malme (1993), most bowheads begin to swim 

rapidly away when vessels approach rapidly and directly. This avoidance may be related to the 

fact that bowheads have been commercially hunted within the lifetimes of some individuals 

within the population and they continue to be hunted for subsistence throughout many parts of 

their range. Avoidance usually begins when a rapidly approaching vessel is 1-4 km (0.62-2.5 

mi) away. A few whales may react at distances from 5-7 km (3-4 mi), and a few whales may 

not react until the vessel is less than 1 km (less than 0.62 mi) away. Received noise levels as 

low as 84 dB re 1 μPa or 6 dB above ambient may elicit strong avoidance of an approaching 

vessel at a distance of 4 km (2.5 mi) (Richardson and Malme 1993).

In the Canadian Beaufort Sea, bowheads observed in vessel-disturbance experiments began to 

orient away from an oncoming vessel at a range of 2-4 km (1.2-2.5 mi) and to move away at 

increased speeds when approached closer than 2 km (1.2 mi) (Richardson and Malme 1993). 

Vessel disturbance during these experimental conditions temporarily disrupted activities and 

sometimes disrupted social groups, when groups of whales scattered as a vessel approached. 

Reactions to slow-moving vessels, especially if they do not approach directly, are much less 

dramatic. Bowheads often are more tolerant of vessels moving slowly or in directions other than 

toward the whales. Fleeing from a vessel generally stopped within minutes after the vessel 

passed, but scattering may persist for a longer period. After some disturbance incidents, at least 

83
some bowheads returned to their original locations (Richardson and Malme 1993). Some 

whales may exhibit subtle changes in their surfacing and blow cycles, while others appear to be 

unaffected. Bowheads actively engaged in social interactions or mating may be less responsive 

to vessels. Data are not sufficient to determine sex, age, or reproductive characteristics of 

response to vessels. We are not aware of data that would allow us to determine whether females 

with calves tend to show avoidance and scattering at a greater, lesser, or at the same distances as 

other segments of the population. 

The encounter rate of bowhead whales with vessels associated with exploration would be 

determined by which areas were being explored. Bowhead whales probably would encounter 

relatively few vessels associated with exploration activities during their fall migration through 

the Alaskan Beaufort Sea. Vessel traffic generally would be limited to routes between the 

exploratory-drilling units and the shore base. Each floating drilling unit probably would have 

one vessel remaining nearby for emergency use. Depending on ice conditions, floating drilling 

units may have two or more icebreaking vessels standing by to perform ice-management tasks. 

It is likely that vessels actively involved in ice management or moving from one site to another 

would be more disturbing to whales than vessels idling or maintaining their position. In either 

case, bowheads probably would adjust their individual swimming paths to avoid approaching 

within several kilometers of vessels attending a drilling unit and probably would move away 

from vessels that approached within a few kilometers. Vessel activities associated with 

exploration are not expected to disrupt the bowhead migration, and small deflections in 

individual bowhead-swimming paths and a reduction in use of possible bowhead-feeding areas 

near exploration units should not result in significant adverse effects on the species. During 

their spring migration (April through June), bowheads likely would encounter few, if any, 

vessels along their migration route, because ice at this time of year typically would be too thick 

for seismic-survey ships, drillships, and supply vessels to operate in. 

In 2003, there was concern by Alaskan Native whalers that barge traffic associated with oil and 

gas activities might have caused bowhead whales to move farther offshore and, thus, to be less 

accessible to subsistence hunters. In addition to acting as a source of noise and disturbance, 

marine vessels could potentially strike bowhead whales, causing injury or death. As noted in the 

baseline section of this evaluation, available information indicates that current rates of vessel 

strikes of bowheads are low. At present, available data do not indicate that strikes of bowheads 

by oil and gas-related vessels will become an important source of injury or mortality in the 

Beaufort Sea Planning Area. Risk of strikes would increase as vessel traffic in bowhead habitat 

increases. 

Information is sparse regarding fin whale response to vessels, while considerable work exists 

regarding humpback whale response. Richardson et al (1995) presents a discussion of pertinent 

research here, finding that humpbacks overall attempted to avoid vessels and displayed such 

behavioral responses as aggressiveness, increased surfacing, or changes in dive patterns. In 

research in southeast Alaska, humpback whales moved away from large cruise boats when 

approached within a few kilometers (Richardson et al. 1995). Similar to bowhead whales, 

humpback whales seem less likely to react to vessel noise when actively feeding than when 

resting or engaged in other activities (Richardson et al. 1995). The most extensive data set on 

this issue exists for the Atlantic seaboard at summering grounds off Cape Cod. There, 

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humpback whales are regularly found and continue to return each year despite exposure to many 

ships, fishing vessels, and whale watching boats (Richardson et al. 1995). 

The Chukchi Sea Planning Area experiences relatively low volumes of marine traffic associated 

with fishing, recreation, and commercial-shipping traffic at this time, as transit activities 

normally occur closer to shore than the boundary of the Planning Area. Traffic presently is 

limited to research vessel cruises, some of which engage in a variety of seismic-survey 

operations, and energy-related seismic-survey support activity. Increases in support-vessel 

traffic in habitats occupied by humpback whales would increase the risk of collision. Risk of 

collision to humpbacks of the WNPS is very low in U.S. waters and is not an important source 

of injury or mortality. Seismic-survey vessels and accompanying support vessels could 

adversely affect fin and humpback whales by inducing avoidance responses. The incremental 

additional marine traffic noise by transiting seismic vessels would remain short term, and total 

traffic volume would remain low. In the western Beaufort OCS, seismic-survey vessel-transit 

noise would add incrementally to the volume of marine traffic noise experienced in that area, but 

it would not add substantially to the current levels of volume of traffic or noise. Currently all 

vessels (including seismic-survey support vessels) are required to comply with law that forbids a 

person subject to the jurisdiction of the U.S. to approach, by any means, within 100 yd (91.4 m) 

of a humpback whale in any waters within 200 nmi of Alaska (FR 66, No. 105, May 31, 2001). 

Vessels (with some exceptions) transiting near humpbacks also are required to adhere to a 

“slow, safe speed” requirement to prevent disturbance that could adversely affect humpbacks. 

Vessel interaction and approaches with fin whales and other listed marine mammals are subject 

to guidelines to meet the requirements of the ESA rather than species-specific regulation in 

Alaskan waters. 

Other Construction Activities 

Island-construction activities could cause noise and disturbance to bowhead whales. Placement 

of fill material for island construction generally occurs during the winter, when bowhead whales 

are not present. Completion of island construction and placement of slope-protection materials 

may take place during the open-water season, but these activities generally are completed before 

the bowhead whale fall migration. Placement of sheetpile, if used, would generate noise during 

the open-water period for one construction season but also should be completed in early to midAugust, before the whales migrate. Noise is not likely to propagate far due to the shallow water 

and the presence of barrier islands that, in many cases, may lie between the drilling location and 

the migration corridor used by bowhead whales, depending on the island location. Even during 

the migration, noise from these activities would be minor and would not affect bowhead whales. 

If such construction were to occur in an area where large numbers of whales were attempting to 

feed (such as has been observed in a few years (but not in many other years) in the Dease 

Inlet/Smith Bay area, the whales might be displaced from a small portion of the feeding range 

for that year. 

Preliminary analysis of noise measurements during the open-water construction season at 

Northstar Island by Blackwell and Greene (2001) indicated that the presence of self-propelled 

barges had the largest impact on the level of sound coming from Northstar Island. Selfpropelled barges remained at Northstar for days or weeks and always had their engines running, 

85
because they maintained their position by “pushing” against the island. Sound measurements on 

a day when there were no self-propelled barges showed that sounds were inaudible to the field 

acoustician listening to the hydrophone signal beyond 1.85 km, even on a relatively calm day. 

By comparison, the sounds produced by self-propelled barges, while limited in their frequency 

range, were detectable underwater as far as 28 km north of the island. Other vessels, such as the 

crew boat and tugs, produced qualitatively the same types of sounds, but they were present 

intermittently, and their effect on the sound environment was lower. 

Summary of Potential Effects of Noise and Disturbance Sources 

Available information indicates that baleen whales, and bowhead whales in particular, are 

responsive (in some cases highly responsive) to anthropogenic noise in their environment. At 

present, the primary response that has been documented is avoidance, sometimes at considerable 

distance. Response is variable, even to a particular noise source and the reasons for this 

variability are not fully understood. 

Oil and gas exploration could result in considerable increase in noise and disturbance in the 

spring, summer, and autumn range of the Western Arctic bowhead whales, and to summering fin 

and humpback whales. This noise may result from various activities, including seismic, vessel 

traffic and icebreaker operation, drilling, and construction, and support activities. Depending on 

their timing, location, and number, these activities potentially could produce sufficient noise and 

disturbance that whales might avoid an area of high value to them and suffer consequences of 

biological significance. These consequences would be of particular concern if such areas 

included those used for feeding or resting by large numbers of individuals or by females and 

calves. In other species of mammals, including cetaceans, females with young are more 

responsive to noise and human disturbance than other segments of the population. 

If seismic operations overlap in time, the zone of seismic exclusion or influence could 

potentially be quite large, depending on the number, and the relative proximity of the surveys. 

NMFS is concerned these simultaneous seismic activities could result in effects that are 

biologically significant, if they cause avoidance of feeding, resting, or calving areas by large 

numbers of females with calves over a period of many weeks. The impact to individuals would 

likely be related to the importance of the food source or resting area to the component of the 

population that would have utilized it, had not the disturbance caused them to avoid the area. 

This is likely to remain unknown. Potential impacts to the population would be related to the 

numbers and types of individuals that were affected (e.g., juvenile males versus females with 

calves). Activities that cause active avoidance over large distances may reduce the availability 

of any rest areas. Such areas may provide important energetic needs for bowheads during their 

autumn migration and other use of the Beaufort Sea. Less is currently known of the habitat use 

and value of the action area for fin and humpback whales. 

The observed response of bowhead whales to seismic noise has varied among studies. The 

factors associated with variability are not entirely clear. However, data indicate that fall 

migrating bowheads show greater avoidance of active seismic vessels than do feeding 

bowheads. Recent monitoring studies (1996-1998) and traditional knowledge indicate that 

during the fall migration, most bowhead whales avoid an area around a seismic vessel operating 

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in nearshore waters by a radius of about 20 km and may begin avoidance at greater distances. 

Received sound levels at 20 km ranged from 117-135 dB re 1 μPa rms and 107-126 dB re 1μ Pa 

rms at 30 km. This is a larger avoidance radius than was observed from scientific studies 

conducted in the 1980’s. Avoidance did not persist beyond 12-24 hours after the end of seismic 

operations. In some early studies, bowheads also exhibited tendencies for reduced surfacing and 

dive duration, fewer blows per surfacing, and longer intervals between successive blows. 

Available data indicate that behavioral changes are temporary. Baleen whales respond to 

drilling noise at different distances depending on the types of platform from which the drilling is 

occurring. Data indicate that many whales can be expected to avoid an active drillship at 10-20 

km or possibly more. The response of whales to construction in high use areas is unknown and 

is expected to vary with the site and the type of facility being constructed. Similarly, the longterm response of whales to production facilities other than gravel islands located at the southern 

end of the bowhead migration corridor is unknown. 

Exploration will result in an increase in marine vessel activity, and depending on location and 

season, may include icebreakers, barges, tugs, supply and crew boats, and other vessels. Whales 

respond strongly to vessels directly approaching them. Avoidance of vessels usually begins 

when a rapidly approaching vessel is 1-4 km away, with a few whales possibly reacting at 

distances from 5-7 km. Received noise levels as low as 84 dB re 1 μPa or 6 dB above ambient 

may elicit strong avoidance of an approaching vessel at a distance of 4 km. Fleeing from a 

vessel generally stopped within minutes after the vessel passed, but scattering may persist for a 

longer period. 

Icebreaker response distances vary. Predictions from models indicate that bowhead whales 

likely would respond to the sound of the attending icebreakers at distances of 2-25 km, with 

roughly half of the bowhead whales showing avoidance response to an icebreaker underway in 

open water at a range of 2-12 km when the sound-to-noise ratio is 30 dB and roughly half of the 

bowhead whales showing avoidance response to an icebreaker pushing ice at a range of 4.6-20 

km when the sound-to-noise ratio is 30 dB. Whales appear to exhibit less avoidance behavior 

with stationary sources of relatively constant noise than with moving sound sources. 

Exploration also results in increased aircraft traffic, including possible whale monitoring flights. 

Most bowheads exhibit no obvious response to helicopter overflights at altitudes above 150 m 

(500 ft). At altitudes below 150 m (500 ft), some whales probably would dive quickly in 

response to the aircraft noise. Bowheads are relatively unaffected by aircraft overflights at 

altitudes above 300 m (984 ft). Below this altitude, some changes in whale behavior may occur, 

depending on the type of plane and the responsiveness of the whales present in the vicinity of 

the aircraft. Fixed-wing aircraft flying at low altitude often cause hasty dives. Reactions to 

circling aircraft are sometimes conspicuous if the aircraft is below 300 m (1,000 ft), uncommon 

at 460 m (1,500 ft), and generally undetectable at 600 m (2,000 ft). The effects from such an 

encounter with either fixed-wing aircraft or helicopters generally are brief, and the whales 

should resume their normal activities within minutes. If numerous flights for exploration or 

development and production occur (depending on the location) fin, humpback, and bowhead 

whales may be repeatedly exposed to helicopter noise in areas between shorebases and/or 

airports and the production facilities. Depending on where shorebases for activities are located, 

87
effects could be mitigated by ensuring that flight paths avoided whale aggregations or that 

flights were high enough to avoid disturbance. 

We anticipate that gravel islands are not likely to be constructed for exploratory drilling in most 

OCS waters, but that old artificial islands might be used temporarily. In the near future we 

expect that exploratory drilling in the Chukchi and Beaufort Sea will also be conducted from 

other platforms and during the open water period depending on water depth, sea ice conditions, 

availability of drilling units, and the ice-resistance of units. Moveable platforms resting on the 

seafloor could be used to drill in water depths of 10-20 m, but drillships or other floating units 

would be used in deeper waster. Drilling from these units will be in open water. Such drilling 

would be supported by icebreakers and supply boats. This is expected to be the norm in the 

Chukchi Sea. 

If gravel islands were used for exploration drilling, noise produced probably would not have 

large effects on bowhead or other whales, because gravel islands are constructed in fairly 

shallow water shoreward of the main migration route, and noise from operations on gravel 

islands generally is not audible beyond a few kilometers. In the Beaufort Sea, islandconstruction activities likely would be conducted during the winter and generally are in 

nearshore shallow waters shoreward of the main bowhead whale migration route. However, as 

evidenced by Northstar, such construction was supported by numerous trips by barges and other 

vessels providing materials. 

As development moves farther offshore, we anticipate much greater aircraft and vessel support. 

For example, MMS estimates that marine transport requirements during construction in the Far 

Zone would range between 150-250 vessel trips including numerous barges during the open 

water period. Bowheads may exhibit temporary avoidance behavior if approached by vessels at 

a distance of 1-4 km (0.62-2.5 mi). Humpback whales are reported to avoid vessels at distances 

of 2-4 km. Marine-vessel traffic also may include seagoing barges transporting equipment and 

supplies from Southcentral Alaska to drilling locations, most likely between mid-August and 

mid- to late September. Some fin, humpback, or bowheads may be disturbed by barge traffic. 

Fleeing behavior from vessel traffic generally stops within minutes after the vessel passed, but 

scattering may persist for a longer period. Given results from Northstar regarding noise from 

barges, and the reaction of bowheads to moving vessels, the level of barge and vessel activity 

that would occur if development and production proceeds as envisioned in the scenario could 

potentially cause bowhead whales to avoid the area between the production platform and 

docking facilities during the period of activity. The significance of such a potential effect would 

depend on where the production facility was located. 

Overall, fin, humpback, or bowhead whales exposed to noise-producing activities such as vessel 

and aircraft traffic, drilling operations, and seismic surveys most likely would experience 

temporary, nonlethal effects. Whale response to certain noise sources varies. Some of the 

variability appears to be context specific (i.e., feeding versus migrating whales) and also may be 

related to reproductive status and/or sex or age. As time goes on, many of these activities can 

and probably will occur in both program areas in the same season and, in some cases, in closely 

adjacent areas. In 2008, 2D and 3D seismic surveys, icebreaker activity for transit, high 

resolution surveys, and other support vessel traffic are expected in the Beaufort Sea. Aerial 

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surveys also may be conducted. In 2008, 2D and 3D seismic surveying, and high-resolution 

seismic surveys are anticipated in the Beaufort Sea and 2D and 3D seismic are anticipated in the 

Chukchi Sea. If these activities are coincident in space and time, especially during migrations or 

in areas of aggregations, whales may be adversely affected, including large numbers of 

bowheads. 

Data are sufficient to conclude that all response to future noise and disturbance is likely to vary 

with time of year; sex and reproductive status of individuals exposed; site (because of 

differences in noise propagation and use by bowheads); activity and the exact characteristics of 

that activity (e.g., drilling versus seismic, airgun array and configuration, etc.); the animal’s 

motivation to be in an area; and options for alternative routes, places to feed, etc. While 

habituation is seen in some species, and behavioral studies have suggested that bowheads 

habituate to noise from distant, ongoing drilling or seismic operations, localized avoidance still 

occurred. Bowheads may be less likely to habituate to at least certain types of noise than fin or 

humpback whales because they are hunted annually, and thus, many individuals may have a 

strong negative association with human noise. 

The potential total adverse effects of long-term added noise, disturbance, and related avoidance 

of feeding and resting habitat in an extremely long-lived species such as the bowhead whale are 

unknown. Available information does not indicate any long-term adverse effects on the Western 

Arctic stock from the high level of seismic surveys and exploration drilling during the 1980’s in 

the Beaufort and Chukchi seas. However, sub-lethal impacts on health (such as reduced hearing 

or increased stress) could not be detected in this population. The rate of this population’s 

increase in abundance does not indicate any sub-lethal effects (if they occurred) resulted in an 

effect on this population’s recovery. There has been no documented evidence that noise from 

previous OCS operations has served as a barrier to migration. Because whales respond 

behaviorally to loud noise, they are less likely to suffer hearing loss from increased noise. 

However, whales appear to be more tolerant of noise when feeding, and future work is needed to 

determine potential effects on hearing due to long periods over many years of exposure to loud 

noise at distances tolerated in feeding areas. Similarly, concern needs to be given to other 

potential physiological effects of loud noise, including the potential for increased noise to cause 

physiological stress responses. 

We are not certain about the effects of multiple seismic surveys and other noise and disturbance 

sources over many years within areas which may be frequently used for feeding or resting by 

large numbers of whales. Concentrations of loud noise and disturbance activities during the 

open water period have the potential to cause large numbers of these whales to avoid using areas 

for resting and feeding for long periods of time (days to months) while the noise producing 

activities continue. Because recent data are not sufficient to evaluate current habitat use by 

season or area in the Chukchi Sea by bowhead, humpback, or fin whales, we cannot fully 

estimate the consequence of industrial noise on these species. 

Effects from Discharges 

Exploration drilling activity and other OCS exploratory actions would require the discharge of 

certain pollutants into the receiving waters of the Chukchi and Beaufort Seas. The EPA must 

permit such discharges under their National Pollutant Discharge Elimination System (NPDES) 

89
program. The NPDES discharges are not part of this action, and EPA must consult with NMFS 

and USFWS on the effects of that program on listed species and critical habitat. However, the 

following discussion is presented to provide general information on these discharges and their 

potential affects.

There could be alterations in fin, humpback, or bowhead habitat as a result of exploration, 

including localized pollution and habitat destruction. Any potential adverse effects on these 

whales from discharges are directly related to whether or not any potentially harmful substances 

are released, if they are released to the marine environment, what their fate in that environment 

likely is (for example, different hypothetical fates could include rapid dilution or 

biomagnification through the food chain), and thus, whether they are bioavailable to the species 

of interest. 

Disposal of drilling muds and cuttings would be as specified under conditions prescribed by the 

EPA. Discharge of drilling muds and cuttings during exploration activities is not expected to 

cause population-level effects, either directly through contact or indirectly by affecting prey 

species. Any effects would be localized primarily around the drill rig because of the rapid 

dilution/deposition of these materials. Exploration drilling muds and cuttings may cover 

portions of the seafloor and cause localized pollution. However, the effects likely would be 

negligible, because the areas of sea bottom that are impacted would be inconsequential in 

relation to the available habitat. 

Bottom-founded drilling units and/or gravel islands may cover areas of benthic habitat that 

support epibenthic invertebrates used for food by bowhead whales. Muds and cuttings from 

development drilling from platforms are expected to be treated and disposed of in disposal wells, 

Muds and cuttings from satellite development wells are expected to be barged either to the host 

platform for downhole disposal or to shore for disposal. Produced waters are expected to be reinjected. 

Gravel-island-construction activities, including placement of fill material, or installation of 

sheetpile or gravel bags for slope protection could cause loss of habitat, depending on the 

location of the gravel island. This construction would cause temporary sediment suspension or 

turbidity in the water as well as noise and disturbance (see noise and disturbance section). 

 

Potential Effects of Oil Spills from Exploration Activity 

The MMS estimates the chance of a large (>1,000 bbl) oil spill from exploratory activities to be 

very low. On the Beaufort and Chukchi Federal OCS, the oil industry drilled 35 exploratory 

wells. During the time of this drilling, industry has had 35 small spills totaling 1,120 gallons 

(gal) or 26.7 bbl. Of the 26.7 bbl spilled, approximately 24 bbl were recovered or cleaned up. 

Small (1,000 gal or less) operational spills of diesel, refined fuel, or crude oil may occur. The 

MMS estimates this to be the typical scenario during exploratory drilling in the Beaufort and 

Chukchi seas. These small spills often are onto containment and gravel islands or ice and can be 

cleaned up. No exploratory drilling blowouts have occurred on the Arctic or the Alaskan OCS. 

Since 1971, industry has drilled approximately 172 exploration wells in the Pacific, 51 in the 

Atlantic, 10,524 in the Gulf of Mexico, and 97 in Alaska, for a total of 10,844 wells (Brajas, 

Howard, and Monkelein 1999). From 1971-1999, there were 53 blowouts during exploration 

drilling. With the exception of three spills, 200, 100, and 11 bbl, respectively, no additional oil 

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spills have occurred. Therefore, more than 13,000 wells have been drilled, and three spills 

resulted in crude reaching the environment during exploration. 

Small spills are unlikely to have significant effects on fin, humpback, or bowheads because of 

their reduced volumes and areas of impact and because it is anticipated that these whales will 

generally avoid exploration activities and, hence, not be in the immediate vicinity at the time of 

a spill. Fuel spills associated with the vessels used during exploration activities could occur, 

especially during fuel transfer. There could be localized short-term alterations in habitat and 

habitat use as a result of such a spill. Whales exposed to a small fuel spill likely would 

experience temporary, nonlethal effects. It is difficult to accurately predict the effects of oil on 

these whale species (or any cetacean) because of a lack of data on the metabolism of this species 

and because of inconclusive results of examinations of baleen whales found dead after major oil 

releases. 

Although there is no conclusive evidence that large baleen whales would be killed as a result of 

contact with spilled oil, it is well documented that exposure of at least some mammals to 

petroleum hydrocarbons through surface contact, ingestion, and especially inhalation can be 

harmful. Surface contact with petroleum hydrocarbons, particularly the low-molecular-weight 

fractions, can cause temporary or permanent damage of the mucous membranes and eyes (Davis, 

Schafer, and Bell, 1960) or epidermis (Hansbrough et al. 1985; St. Aubin 1988; Walsh et al., 

1974). Contact with crude oil can damage eyes (Davis, Schafer, and Bell 1960). Ingestion of 

petroleum hydrocarbons can lead to subtle and progressive organ damage or to rapid death. 

Inhalation of volatile hydrocarbon fractions of fresh crude oil can damage the respiratory system 

(Hansen, 1985; Neff, 1990), cause neurological disorders or liver damage (Geraci and St. Aubin 

1982), have anesthetic effects (Neff 1990) and, if accompanied by excessive adrenalin release, 

cause sudden death (Geraci 1988). 

Climate Change 

Climate change could potentially affect fin, humpback, or bowhead whales in several ways 

including: 

* Increased noise and disturbance related to increased shipping, and possibly related to increased 

development, within their range; 

* Increased interactions with commercial fisheries, including increased noise and disturbance, 

incidental take, and gear entanglement; 

* Decreases in ice cover with the potential for resultant changes in prey species concentrations 

and distribution; 

* Related changes in whale distributions; 

* Changes in bowhead whale subsistence-hunting practices that could result in smaller, younger 

whales being taken and, possibly, in fewer whales being taken; 

* More frequent climatic anomalies, such as El Niños and La Niñas, with potential resultant 

changes in prey concentrations; and 

* A northern expansion of other whale species, with the possibility of increased overlap in the 

northern Bering and/or the Chukchi seas. 

The potential effects of climate change on fin, humpback, and bowhead whales are uncertain. 

There is no current evidence of negative effects on the whales. There is no evidence suggesting 

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that many of the changes that could occur, such as changes in timing of migrations and shifts in 

distribution, would be associated with overall adverse effects on these whales. Conceptual 

models by Moore and Laidre (2006) suggested that reductions in sea ice cover should increase 

the Bering-Chukchi-Beaufort Sea stock of bowhead whale prey availability. In Shelden et al.’s 

(2003) response to Taylor’s statements regarding the expectation of future downward trends in 

abundance based on what he termed “available evidence” regarding climate change, they point 

out that Taylor did not provide citations supporting this claim. Shelden et al. (2003) state that: 

Although available data do indicate that the Bering Sea environment is changing (e.g., Angel & 

Smith 2002), we are aware of no evidence that environmental changes will be detrimental to the 

population in the foreseeable future. In fact, our review...on this issue suggests that climate 

change may actually result in more favorable conditions for Western Arctic bowheads. 

This theory may be substantiated by the steady increase in the BCBS population during the 

nearly 20 years of sea ice reductions (Walsh 2008). Moore and Huntington (2008) anticipate that 

bowhead whales will alter migration routes and occupy new feeding areas in response to climate 

related environmental change. Sheldon et al. (2003) notes that there is a high probability that 

bowhead abundance will increase under a warming global climate. Bluhm and Gradinger (2008) 

state new pelagic feeding grounds may open up to Arctic marine mammals and subarctic marine 

mammals in high Arctic basins, while nearshore areas may provide less abundant food in the 

future due to increased precipitation, river run-off, lowered salinities, and increasing turbidity. 

The recent observations of humpback whales in the Beaufort and Chukchi seas may be 

indicative of seasonal habitat expansion in response to receding sea ice or increases in prey 

availability which these whales now exploit. Range expansions in response to habitat change 

are not uncommon among cetaceans. Gray whales in Alaska have shown pronounced change 

over the last several decades; overwintering at higher latitudes and occupying previously lesserused feeding areas in the Beaufort Sea. Concentrations of the rare North Pacific right whale 

were first observed in 1996 and have continued until recently, possible reflecting changes in 

zooplankton distribution due to large-scale oceanographic change within the Bering Sea. 

New information regarding humpback whale occurrence in the Chukchi Sea and Beaufort Sea 

Planning Areas are limited to data from marine mammal monitoring in 2006 and 2007 whale. 

This limited and low intensity sampling is insufficient to make reliable predictions about the 

effect of arctic climate change on humpback whales. We cannot rule out that recent changes in 

humpback distribution may be due in part to climate change phenomena. Since humpback and 

fin whales are not ice-obligate or ice-associated species, it is unknown how long this habitat will 

remain viable for these species. However, it is logical to assume these whales will continue to 

utilize these waters as long as the availability of prey remains. 

We emphasize that there is uncertainty associated with many of the predictions about potential 

climate changes, especially at a regional level, and associated environmental changes that could 

occur. However, if this change occurs, it is likely that shipping would increase throughout the 

range of fin, humpback and bowhead whales, especially in the Chukchi and southern portions of 

the Beaufort Sea. If commercial fisheries were to expand into the Chukchi or Beaufort Sea, fin, 

bowhead, or humpback whale death and or injury due to interactions with fishing gear, possibly 

injury and/or death due to incidental take in commercial fisheries, and temporary effects on 

92
behavior potentially could occur. There are, however, few data that would permit us to 

quantitatively predict such types of effects. The North Slope Borough Department of Wildlife 

has examined harvested bowhead whales and found 0% to 33% of those displayed line wounds 

indicative of fishing gear interaction. Humpbacks in southeastern Alaska interact with various 

fishing gear, notably set gill nets and pot gear in nearshore areas. 

Tynan and DeMaster (1997) note an earlier IPCC report that concluded that an increase in 

human activity is likely to accompany the opening of the Northwest Passage and the Russian 

Northern Sea Route. They identify a potential for increased environmental pollution, an 

increased incidence of epizootics, exploration, increased ship traffic, increased fisheries, and 

increased industrial activities, and the synergistic effects of these factors with ecosystem 

changes due to climate change as potential concerns for marine mammals populations. Perhaps 

the greatest potential adverse effect associated with global warming could occur if predictions 

that the Northwest Passage may become ice free for significant lengths of time prove accurate, 

opening sea routes across the Beaufort Sea and a Northern Sea Route along the Russian north 

coast and increasing shipping in parts of the range of the WNPS of humpback, fin and bowhead 

whales. 

The Office of Naval Research (2001) reported that climate warming in the Arctic is likely to 

result in the northward migration of subarctic species of marine mammals and an increase in 

commercial-fishing activities into the Chukchi and Beaufort seas, where operations have been 

minimal in the past. If substantial increases in shipping were to occur that placed more ships in 

waters inhabited by humpback whales, increases in adverse effect to them also might occur due 

to shipping-related noise and disturbance, vessel strikes, and pollution. Quantification of such 

potential changes are not possible at this time due to the level of uncertainty about changes that 

might occur over the course of the proposed project and the shipping industry’s response to 

greater cross-Beaufort transiting opportunities, when they do occur. 

We conclude that the potential effects of climate change on humpback whales, fin whales, or 

bowhead stock in Alaska are uncertain. The NMFS’ National Marine Mammal Laboratory has 

stated there are insufficient data to make reliable predictions of the effects of Arctic climate 

change on bowhead whales (Angliss and Outlaw 2008). There is no current evidence of adverse 

effects on these whales due to climate change. There is no documented evidence suggesting that 

many of the changes that could occur, such as changes in timing of migrations, shifts in 

distribution, shifts in migration routes, and shifts in abundance and distribution of prey would be 

associated with overall adverse or positive effects on these whales. The occurrence of fin and 

humpbacks in the Chukchi and Beaufort seas in 2006 and 2007 may be initial indications that 

habitat conditions may be changing that favor humpback whales pioneering new summer 

ranges; however, the short duration of observations is insufficient to conclude whether the recent 

observations indicate an anomaly or a trend. We remain concerned that increasing shipping and 

industrial activity associated with arctic warming will occur. This increase in noise and 

disturbance will be in addition to the levels of noise from current industrial activity, subsistence 

harvest activities, local/regional shipping, research, recreational, military, aircraft, and other 

vessel traffic. 

V. CUMULATIVE EFFECTS 

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Cumulative effects are defined in 50 CFR 402.02 (Interagency Cooperation on the ESA of 1973, 

as amended): “...those effects of future State or private activities not involving Federal 

activities that are reasonably certain to occur within the action area of the Federal action subject 

to consultation.” Reasonable foreseeable future federal actions and potential future Federal 

actions that are unrelated to the proposed action are not considered in the analysis of cumulative 

effects because they would require separate consultation pursuant to section 7 of the ESA. 

Cumulative effects are usually viewed as those effects that impact the existing environment and 

remain to become part of the environment. These effects differ from those that may be attributed 

to past and ongoing actions within the area since they are considered part of the environmental 

baseline. Additionally, most structures and major activities within the Chukchi and Beaufort 

Sea OCS require Federal authorizations from one or more agencies, such as the MMS, Army 

Corps of Engineers, and the Environmental Protection Agency. Such projects must consult 

under the ESA on their effects to the bowhead whale, and are therefore not addressed here as 

cumulative impacts. 

 

The State of Alaska is currently leasing State-owned portions of the Beaufort Sea for oil and gas 

exploration and production. No sales have occurred nor are planned for the Chukchi Sea by the 

State. The current State of Alaska Five-Year Oil and Gas Leasing Program published in January 

2006 lists Beaufort Sea area wide sales continuing in October 2006-2010. The State is 

currently conducting a “best interest finding” in anticipation of leasing over the period 2009-

2019. The proposed sales consist of all unleased tide and submerged lands between the 

Canadian Border and Point Barrow as well as some upland acreage. If any of the scheduled 

sales occur, additional effects similar to those described for OCS lease sales could occur. All 

producing fields on the North Slope are onshore and on State leases, with the exception of the 

Duck Island Unit (which contains the Endicott field). Endicott is on State leases and was the 

first offshore production facility developed in the Beaufort Sea. Endicott has been producing oil 

since 1987. Endicott is located on a manmade gravel structure inside the barrier islands in 

relatively shallow water. Support traffic is over a gravel causeway that also contains the 

pipeline to shore. New production islands in State waters now include Northstar Island near 

Prudhoe Bay, and Oooguruk and Nikaitchuq Islands off Harrison Bay. 

Oil and gas development is also underway in the Eastern Beaufort Sea off the Canadian 

Mackenzie Delta. This includes seismic surveys, drilling, and infrastructure and support 

facilities as described for the US OCS. Seismic programs have recently been conducted off the 

Mackenzie Delta. 

Bowhead whales may be disturbed during the summer in the Canadian Beaufort Sea, if offshore 

oil and gas exploration and development and production activities occur there in the future. The 

main area of industry interest to date has centered around the Mackenzie River Delta and 

offshore of the Tuktoyaktuk Peninsula. There has been little industry activity in this area in 

recent years, and we are not aware of any proposed activities. This area comprises a minor 

portion of the bowhead’s summer range. Possible disturbance to bowhead whales from 

helicopters, vessels, seismic surveys, and drilling would be as previously described. 

Since offshore oil and gas activities in State waters are generally well shoreward of the 

bowheads’ main migration route, and some of the activities occur inside the barrier islands, the 

94
overall effects on bowheads from activities on State leases is likely to be minimal. These 

impacts could be magnified, however, if construction activity associated with additional 

development projects were to occur simultaneously, rather than consecutively. For example, 

construction and drilling noise from multiple drilling sites could result in a long-term, offshore 

shift in bowhead migration routes. The extra distance and heavier ice encountered could result 

in slower migration or physiological stress that may noticeably affect the whales. However, the 

majority of bowhead, fin and humpback whales are generally found offshore of State waters. 

Some effects on bowhead, fin and humpback whales may occur because of activities from lease 

sales within State waters (within 3 miles of shore). Generally, bowhead whales remain far 

enough offshore to be found mainly in Federal waters, but they may occur in State waters in 

some areas, such as the Beaufort Sea southeast and north of Kaktovik and near Point Barrow. 

Presumably, fin whales in these areas also remain far enough offshore to be found mainly in 

Federal waters. Humpback whales, however, are largely nearshore feeders and are most often 

found in State waters throughout southeast and southcentral Alaska, as well as the Aleutian 

Islands. Given the minimal sighting data for humpback whales in the Arctic, it is difficult to 

predict whether the species would be found primarily in Federal or State waters in this region. 

If exploration and development and production activities occur on leases from previous or 

proposed State sales, noise effects on whales may occur as described previously. These effects 

could include behavioral responses, including local avoidance to noise from aircraft and vessel 

traffic; seismic surveys; exploratory drilling; construction activities, including dredging; and 

development drilling and production operations that occur within several miles of the whales. 

Future exploration and development within the Canadian Beaufort would present concerns 

beyond those associated with leasing in the Alaskan Beaufort Sea. The main area of industry 

interest has been the Mackenzie Delta and offshore of the Tuktoyaktuk Peninsula (MMS 1995). 

The large estuarine front associated with the Mackenzie Delta and upwellings near the 

Tuktoyaktuk Peninsula provide conditions which concentrate zooplankton (Moore and Reeves 

1993). These areas are important feeding habitat to the Bering Sea bowhead stock. There are no 

reported plans for oil and gas exploration or production within the Canadian Beaufort Sea at this 

time, however, and this activity would not be considered reasonably expected to occur. 

Current State leases with production, such as Endicott, Oooguruk, and Nikaitchuq, are well 

removed from the normal fall migration route of the bowhead whale. Bowhead whales are not 

likely to be affected by noise from the these projects due to their distance from the bowhead’s 

fall migration route and the limited distance into the marine environment that noise travels from 

gravel structures. 

Each of the projects described would require some equipment and supplies to be transported to 

the site by barge or sealift should development and production plans proceed. The process 

modules and permanent living quarters and other equipment and supplies likely would be 

transported to these sites on seagoing barges during the open-water season. Barge traffic around 

Point Barrow is likely to be limited to a short period from mid-August through mid-to-late 

September and should be completed before the bowhead whale migration reaches this area 

unless it encounters severe ice conditions. Barge traffic continuing into September is likely to 

95
disturb some bowheads during their migration. Whales may react briefly by diving in response 

to low-flying helicopters and they would seek to avoid close approach by vessels. Oil spill 

probabilities associated with exploration are extremely low. In the event an oil spill occurred on 

State leases during the fall bowhead migration, or during the presence of fin and humpback 

whales, the effects of an oil spill on these whales would be as have been described earlier in this 

document. These effects include inhalation of hydrocarbon vapors, a loss of prey organisms, 

ingestion of spilled oil or oil-contaminated prey, baleen fouling with a reduction in feeding 

efficiency, and skin and/or sensory organ damage. These effects would be most pronounced 

whenever whales were confined to an area of freshly spilled oil. Of course, if the spill occurred 

over a prolonged period of time, more individuals could be contacted. Some individuals could 

be killed as a result of prolonged contact with freshly spilled oil, particularly if spills were to 

occur within ice-lead systems. 

Activities that are not oil and gas related also affect bowhead, fin and humpback whales. 

Between 1976 and 1992, only three ship-strike injuries were documented out of a total of 236 

bowhead whales examined from the Alaskan subsistence harvest (George et al., 1994). The low 

number of observed ship-strike injuries suggests that bowheads either do not often encounter 

vessels or they avoid interactions with vessels, or that interactions usually result in the death of 

the animals. However, there is recent evidence that interaction of bowhead whales with ships 

and fishing gear may be increasing. Evidence also exists for ship strikes of fin and humpback 

whales by both small and large tonnage vessels in Southeast and Southcentral Alaska. As the 

population of humpback whales continues to recover, the species’ growing abundance will likely 

result in a greater probability of interactions with ships and fisheries. 

Subsistence harvest by Alaska Natives is another non-OCS activity that affects the bowhead 

whale, although not the fin or humpback whale as neither of these species is taken for 

subsistence use. Bowheads are taken in the northern Bering Sea and in the Chukchi Sea on 

their spring migration and in the Beaufort Sea on their fall migration. Barrow whalers harvest 

whales during both the spring and the fall migrations. Requests to harvest bowheads also have 

been made by Canadian and Russian Natives. The Canadian Government granted permission in 

1991 to kill one bowhead, and a bowhead was harvested in Mackenzie Bay in the fall of 1991. 

Additional permits were granted in 1993 and 1994, but no bowheads were harvested in either 

year. There has been a renewed interest by villages along the Russian Chukchi Sea coast to hunt 

bowhead whales. At the 1997 IWC, the Commission approved a combined quota allowing an 

average of 56 bowheads to be landed each year to meet the needs of Eskimos in Alaska and 

Chukotka Natives of the Russian Far East. The annual number of bowheads landed by Alaskan 

Natives has ranged from 8 in 1982 to 55 in 2005 (USDOC 2008). Struck-but-lost figures have 

been between 5 in 1999 to 82 in 1977. 

There currently is a 5-year block quota of 280 bowhead whales landed, authorized by the IWC 

for 2008-2012. The number of bowheads struck in each year may not exceed 67, except that any 

unused portion of a strike quota from any year may be carried forward. No more than 15 strikes 

may be added to the strike quota for any one year. This level of harvest was approved by the 

IWC under the supposition that it still would allow for continued growth in the bowhead 

population. It is likely the bowhead whale population will continue to be monitored and that 

harvest quota will be set accordingly to maintain a healthy bowhead population level. 

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The cumulative effects of noise on bowheads, fins, and humpbacks from offshore oil and gas 

activities would be similar to that described and summarized for OCS leasing and exploration. 

The effects from an encounter with aircraft generally are brief, and the whales should resume 

their normal activities within minutes. Bowheads and humpbacks may exhibit temporary 

avoidance behavior to vessels at a distance of 1-4 kilometers. Fleeing from a vessel generally 

stopped within minutes after the vessel passed, but scattering may persist for a longer period. 

Bowheads also exhibited tendencies for reduced surfacing and dive duration, fewer blows per 

surfacing, and longer intervals between successive blows. Bowheads appear to recover from 

these behavioral changes within 30-60 minutes following the end of seismic activity. However, 

recent monitoring studies indicate that bowhead whales during the fall migration avoid an area 

around a seismic vessel operating in nearshore waters by a radius of about 20 kilometers. 

Avoidance did not persist beyond 12 hours after the end of seismic operations. This work also 

stated that bowhead whales may begin to deflect around a seismic source at distances up to 35 

km. 

Bowheads have been sighted within 0.2-5 kilometers from drill ships, although bowheads 

change their migration speed and swimming direction to avoid close approach to most noiseproducing activities. Bowheads may avoid drilling noise at 20-30 kilometers. There are no 

observations of bowhead reactions to icebreakers breaking ice, but it has been predicted that 

roughly half of the bowheads would respond at a distance of 4.6-20 kilometers when the S:N is 

30 dB. Overall, bowhead whales exposed to noise-producing activities most likely would 

experience temporary, nonlethal effects. Some avoidance behavior could persist up to 12 hours. 

Some whales could be exposed to spilled oil, resulting in temporary, nonlethal effects, although 

some mortality might result if there were a prolonged exposure to freshly spilled oil. Overall, 

whales exposed to noise-producing activities and oil spills associated with the proposal and 

other future and existing projects within the Arctic region—combined with the other activities 

within the range of these whales—most likely would experience temporary, nonlethal effects. 

However, exposure to oil spills could result in lethal effects. 

Vessel traffic and, perhaps, aircraft activity may be expected to occur in the future in both the 

Chukchi and Beaufort Seas. The effects of these actions would be the same as that presented for 

traffic associated with oil and gas actions. NMFS is aware of speculation that warmer ocean 

temperatures associated with climate change may allow for increased commercial fishing in the 

Chukchi Sea. However, we have no further information which would substantiate or quantify 

such development. 

VI. CONCLUSIONS 

This Biological Opinion has considered the effects of the oil and gas leasing and exploration on 

the Outer Continental Shelf portion of the U.S. Chukchi and Beaufort Seas on the fin, humpback 

and bowhead whale. These actions are likely to adversely affect these whales due to vessel 

operations, marine geophysical (seismic) exploration, aircraft traffic, and drilling noises from 

various structures. The probability of a large oil spill is remote during exploration, but spill 

probabilities may be significant during latter phases. 

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Elevated noise levels in the marine environment could alter the hearing ability of whales, 

causing temporary or permanent threshold shifts. However, information suggests most 

continuous and impulsive underwater noise levels would be at levels or durations below those 

expected to injure hearing mechanisms. Nonetheless, marine seismic activities may present 

concerns with respect to hearing, and should be closely conditioned and monitored to avoid 

these effects. Noise has also been shown to cause avoidance in migrating gray and bowhead 

whales. Seismic geophysical surveys and the possible use of ice breakers to support OCS 

activities present the highest probability for avoidance of any of the activities associated with oil 

exploration. Studies have shown noise from ice breakers may be detected at distances exceeding 

50 km. It is reasonable to assume that bowheads could also detect this noise at this distance, 

however the distance at which bowheads may react to such noise is poorly described. 

Available data do not indicate that noise and disturbance from oil and gas exploration and 

development activities since the mid-1970s had a lasting population-level adverse effect on 

bowhead whales. Data indicate that bowhead whales are robust, increasing in abundance, and 

have been approaching (or have reached) the lower limit of their historic population size at the 

same time that oil and gas exploration activities have been occurring in the Beaufort Sea and, to 

a lesser extent, the Chukchi Sea. 

Although reliable estimates for the North Pacific fin whale population are currently not 

available, Zerbini et al. (2006) estimated rates of increase of fin whales in coastal waters south 

of the Alaska Peninsula and found a rate of increase of 4.8% (95% CI: 41.-5.4%) for the period 

1987-2003 (Angliss and Outlaw 2008). This estimate is consistent with the population growth 

rate of other large whales. A recent annual abundance estimate for the entire North Pacific 

population of humpback whales (Central, Eastern, and Western) was 6,010 animals 

(Calambokidis et al. 1997), with the best available estimate of the current rate of increase for the 

Central North Pacific population acknowledged as 7% per year (Angliss and Outlaw 2008). 

However, new data revealed by the SPLASH research effort (Structure of Populations, Levels of 

Abundance and Status of Humpback Whale Stocks), initiated in 2002 and involving more than 

400 researchers from 10 nations, indicates that current population levels for North Pacific 

humpback whales have rebounded to 18,000-20,000 individuals (NMFS 2008). Given these 

data, there is no indication that noise and disturbance from oil and gas exploration and 

development activities since the mid-1970s had a lasting population-level adverse effect on 

either fin or humpback whales. 

Research on the effects of offshore seismic exploration in the Beaufort Sea, supported by the 

testimony of Inupiat hunters based on their own experience, has shown bowhead whales avoid 

these operations when within 20 km of the source and may begin to deflect at distances up to 35 

km (Richardson, 1999a). Davies (1997) concludes bowheads avoided an active drilling rig at a 

distance of 20 km. While such deflections during migration may not be injurious to individual 

animals, concern is warranted for cumulative noise and multiple disturbance; the consequences 

of which might include long-term shifts in migrational paths or displacement from nearshore 

feeding habitats. However, it is unlikely that even these impacts would prevent the survival and 

recovery of this species, as the primary feeding habitat is considered to be in the Canadian 

Beaufort and, perhaps, the Bering Sea (Shell, 1998.). It can be assumed that these impacts 

98
would also have an insignificant impact on the survival and recovery of both fin and humpback 

whales, as their current primary distribution and feeding habitat remains farther south. To date, 

concentrations of humpback and fin whales have not been observed in the Beaufort or Chukchi 

Seas. 

The Alaskan Beaufort Sea certainly provides feeding habitat for bowhead whales, however the 

importance of this habitat is not fully studied at this time. Similarly, current data do not fully 

identify the importance of the Chukchi Sea to fin, humpback, or bowhead whales (it is known to 

be important as a migrational corridor for bowheads). Concern is warranted over the distribution 

in time and space of several noise-producing activities. The most potentially disruptive of these 

would be seismic operations, with the potential to deflect whales at a distance of 30 km. It may 

be prudent, then, to avoid creating an acoustic gauntlet caused by multiple operations in a 

common area by requiring minimum separations between operations. We offer a Conservation 

Recommendation regarding this concern. Such effect is at least partially mitigated by the 

activity itself; all but very small operations would have to avoid other seismic signals by 15 

miles (24.1 km) to eliminate interference from that signal. Additional mitigative measures are 

offered (see Conservation Recommendations). Because of the potential for noise disturbance to 

displace whales from important feeding areas, special scrutiny should be given to seismic and 

drilling operations which may impact these areas. While many feeding areas are dynamic and 

may change location from year to year, Native hunters have reported the Kaktovik area as a 

traditional feeding area for bowheads. 

Consideration of the potential impacts of oil spills to the fin, humpback, or bowhead whale must 

assess 1) the probabilities for a spill to occur and to make contact with the whales and/or their 

habitat, 2) the effects of oil spills and spill responses on these whales, and 3) the ability of 

industry to prevent, control, and recover spilled oil. Should a spill occur, its effects to these 

whales would depend on factors such as the time and location of the spill, the nature of the 

product spilled, its persistence and toxicity, and the effectiveness of any response measures. 

The estimated physical and behavioral effects of an oil spill on fin, humpback, or bowhead 

whales have been described. While it is clear additional research is needed to assess these 

effects and that no consensus has been reached regarding the degree to which oiling might 

impact the whales, we believe that whales contacting oil, particularly freshly-spilled oil, could 

be harmed and possibly killed. Additionally, an oil spill reaching into the spring lead system has 

the potential to impact a significant number of bowheads. Several coincidental events would be 

necessary for this scenario; the spill would have to occur, the spill would have to coincide with 

the seasonal occurrence of whales in these waters, the spill would have to be transported to the 

area the whales occupy (e.g. the migrational corridor or spring lead system), and clean-up or 

response efforts would have to have been at least partially unsuccessful. The impact of such an 

event would be significant, yet the probability for the coincident occurrence of these events 

would be low. It must also be recognized that the spring lead system is not static, as leads open 

and close and whales navigate not only through the leads but surrounding ice (Clark and Ellison, 

1988). Because of this it is often difficult to assess the potential effects of exploration within the 

spring lead system. 

The ability to prevent, identify, locate, contain, and remove spilled oil is a significant concern. 

NMFS believes that, while spills represent low-probability events, their biological impacts are 

99
significant and that the operator should make every reasonable effort to meet these challenges. 

We are especially concerned with the ability to contain and remove or recover spilled oil under 

broken or newly-forming ice conditions. Spill response drills have failed to demonstrate 

industry can adequately respond under these conditions in the Beaufort Sea (ADEC, 2000). 

Similarly, spill response protocols, technologies, plans, or infrastructure to respond to spills in 

the Chukchi Sea are not fully developed or untested. While oil spills are not expected during 

exploration, we believe MMS must recognize this failing, and take actions prior to later phases 

of development which task industry to develop effective response capabilities during all possible 

conditions and spill scenarios, and that each operator is held to strict standards to further reduce 

any likelihood of oil spills. 

Because the Western Arctic bowhead whale population is approaching its pre-exploitation 

population size and has been documented to be increasing at a roughly constant rate for over 20 

years, the impacts of oil and gas industry on individual survival and reproduction in the past 

have likely been minor (Angliss and Outlaw 2008). These activities are unlikely to have any 

effect on the other four stocks of bowhead whales. Similarly, only the western North Pacific 

stock of humpback whales and the Northeast Pacific stock of fin whales would be potentially 

affected by oil and gas leasing and exploration activities in the Chukchi and Beaufort Seas. The 

described work would have no effect on the remaining worldwide stocks of humpback or fin 

whales. No lethal takes are anticipated because of these activities, nor are population-level 

consequence to the stocks expected. Most impact would be due to harassment of whales, which 

may lead to behavioral reactions from which recovery is fairly rapid. Mitigative measures will 

be recommended to reduce harassment and the possibility of harm or lethal takes. 

After reviewing the current status of the fin, humpback, and bowhead whale, the environmental 

baseline for the action area, the biological and physical impacts of oil leasing and exploration, 

and cumulative effects, and in consideration that the described actions are expected to impact 

only a single stock of each of these endangered whales, and not the species as a whole, it is 

NMFS’s biological opinion that oil and gas leasing and exploration in the Chukchi and Beaufort 

Seas, and authorization of small takes under the MMPA, are not likely to jeopardize the 

continued existence of the endangered fin, humpback, or bowhead whale. No critical habitat has 

been designated for these species; therefore none will be affected. 

VII. INCREMENTAL STEP CONULTATION 

This opinion addresses the incremental step of MMS leasing and exploration actions in the U.S. 

Chukchi and Beaufort Seas. For the MMS to proceed with the incremental step, there must be a 

reasonable likelihood the entire action will not violate section 7 (a)(2) of the ESA (50 CFR 

402.14(k)). Therefore, NMFS is providing its views on the subsequent phases of development 

and production, should commercially-viable discoveries of oil occur. 

Development and Production Scenario 

 

If commercial quantities of oil are discovered and development and production proceed, gravel 

island construction/platform installation and pipeline construction activities would occur. 

Activities during development and production, like those occurring during exploration, will 

100
result in noise, altered habitat, and adverse effects on behavior, distribution, and abundance of 

individuals or populations occurring in or adjacent to the sale area. In addition, cleanup 

activities associated with any oil spill may result in disturbance. 

Oil or other petroleum products released during development or production may cause adverse 

effects on individuals either through direct contact or indirectly as a result of effects on prey 

populations or important habitats. Contaminants, other than crude oil, such as drilling muds and 

cuttings, are not expected to cause significant effects, because they are likely to become rapidly 

diluted near the point of release. Moreover, the Environmental Protection Agency’s discharge 

permits may require re-injection of muds and cuttings whenever possible, eliminating these 

discharges. The Northstar project has been so designed. 

Noise effects associated with development and production activities on endangered whales 

would be similar to those described earlier. Whales would exhibit avoidance behavior from 

noise associated with aircraft traffic, supply vessels, barge traffic, icebreakers, drilling 

operations or seismic-survey vessels. Whales may temporarily interrupt their activities and 

swim away from the vessel’s path. In most cases such behavioral changes last from minutes to 

as much as an hour. Avoidance movements around a stationary noise source such as a 

production platform could require several hours. Recent studies on the effects of seismic 

operations on bowheads indicate the avoidance behavior may persist for as much as 12-24 hours. 

As stated earlier, underwater industrial noise, including drilling noise, measured from artificial 

gravel islands, has not been audible in the water more than a few kilometers away. Because the 

bowhead whale’s main migration corridor is 10 kilometers or more seaward of the barrier 

islands (and future humpback and fin whale presence is largely unknown for this area), drilling 

and production noise from inside the barrier islands may not reach many migrating whales. It 

also likely would not affect the few whales that may be in lagoon entrances or inside the barrier 

islands because of the rapid attenuation of industrial sounds in a shallow-water environment. 

Marine-vessel traffic outside the barrier islands probably would include only seagoing barges 

transporting equipment and supplies from Southcentral Alaska, most likely between mid-August 

and mid-to-late September. Barge traffic continuing into September is likely to disturb some 

bowheads during their migration. Whales would avoid being within 1-4 kilometers of barges. 

Fleeing behavior usually stops within minutes after a vessel has passed but may last longer. 

Vessels and aircraft inside the barrier islands should not affect bowhead, fin or humpback 

whales. 

Offshore production within the normal fall migration route of the bowhead whale is likely to 

disturb some bowhead whales on their fall migration. Marine-vessel traffic probably would 

include, but not be limited to, seagoing barges transporting equipment and supplies from 

Southcentral Alaska to the location, most likely between mid-August and mid- to late 

September. Barge traffic continuing into September is likely to disturb some bowheads during 

their migration. Whales would try to avoid close approach by vessels. Aircraft traffic, such as 

helicopters from Deadhorse, would cause bowheads to dive if they pass low overhead. We do 

not have enough evidence to know whether or not industrial activity for several years would 

keep bowheads, fins or humpbacks from using an area, although abandonment of feeding habitat 

is a significant concern. 

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There would be additional noise-producing activities such as dredging (trenching) for pipeline 

construction. Dredging or trenching may be used in constructing the gathering pipeline from the 

production platform to shore. Bowhead reactions to dredge noise have been observed to be 

similar to their reactions to drilling noise, including avoidance of the near vicinity of the activity. 

In one instance, as many as 12 bowheads were observed within 5 kilometers (3 miles) from 

active dredging operations on their summer-feeding grounds. However, some bowheads were 

detected within 800 meters (2,625 feet) of the site (Richardson and Malme 1993). Dredge 

sounds were well above ambient levels up to several kilometers away (22 dB above average 

ambient level at 1.2 kilometers [0.75 miles] from the dredge). In other instances, bowheads 

were observed at distances where they were well within the ensonified area of dredging 

operations. However, in playback experiments, some whales responded to the onset of similar 

levels of dredge noise by exhibiting weak avoidance. Bowheads seen in the vicinity of actual 

dredging operations may have habituated to the activity, or there may be variation among 

bowheads in the degree of sensitivity toward noise disturbance, so that bowheads seen in the 

vicinity of dredging operations may have been the more tolerant individuals. Noise from these 

activities may cause whales to avoid the immediate vicinity of the pipeline construction and 

platforms. It is likely that the area of avoidance would be relatively small, because whales 

appear to exhibit less avoidance behavior with stationary sources of relatively constant noise 

than with moving sound sources. Dredging activities may occur during the winter through the 

ice and therefore, would not affect bowheads, fins or humpbacks. 

Cleanup activities associated with an oil spill, other than during winter, are likely to result in 

disturbance to whales. If an oil spill does occur, it is likely that large numbers of personnel, 

vessels, and aircraft will be present and conducting cleanup operations in the Chukchi or 

Beaufort Sea. If spilled oil is present during the bowhead whale migration, it could result in 

disturbance and possible displacement of whales from their normal migration route. Response 

actions may also cause fin, humpback, and bowhead whales to abandon feeding areas. 

Disturbance effects are expected to persist for the duration of cleanup operations if the 

operations are conducted during the summer or fall period. The effects of oil spills on fin, 

humpback, and bowhead whales have been discussed previously in this document. 

Development within the spring lead system may be limited by current technology. However, 

any such activity within this area of the Chukchi and Beaufort Sea presents several unique and 

unanswered concerns with respect to these whales. Operation in relatively deep waters subject 

to heavy ice is likely to require ice management. The drilling structure alone may cause springmigrating bowheads to deflect around the source, possibly into the pack ice if other leads are not 

available. While Eskimo hunters have often observed that bowhead whales can travel through 

ice, breaking ice up to a foot or more in thickness, other smaller whales and calves may be 

unable to do so. Additionally, any oil spills within the spring lead system would be detrimental 

to the migrating bowheads, and would present the potential to impact a significant percentage of 

the stock. 

We are not, and we cannot be, certain of the level of effects on endangered whales should a large 

or very large oil spill occur. Should development and production occur in the Chukchi Sea 

OCS, the estimated chance of spills >1,000 bbl occurring in the Chukchi Sea OCS is estimated 

to be about 40%. The estimated chance of one or more 1,000-bbl spills occurring in the 

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Beaufort Sea OCS is about 10-11%. Oil spilled in the Beaufort Sea OCS could contact 

resources in the Chukchi Sea OCS and vice versa. Thus, humpback, fin and bowhead whales 

could conceivably be exposed to oil and oil spill response from spills in either planning areas. 

The estimated chance of one or more large spills occurring, based on lease sales in both areas, is 

47%. 

Adult whales exposed to spilled oil likely would experience temporary, or perhaps permanent, 

nonlethal effects, although prolonged exposure to freshly spilled oil could kill whales. This 

conclusion is supported by the best available information. There are no available data that 

definitely link a large oil spill with a significant population-level effect on a species of large 

cetacean. 

• However, while data from previous spills in other locations worldwide are broadly 

informative, we acknowledge uncertainty about the potential for population level effects 

or other potential outcomes should a large or very large spill occur in instances where 

whales are aggregated and/or constrained in their option for alternative routes (for 

example, in the spring lead and polynya system due to ice conditions) or are aggregated 

in a feeding area, especially if aggregations contained large numbers of females and 

calves. The potential for a population level effect may exist if large numbers of females 

and calves, especially newborn or very young calves, were to be contacted by large 

amounts of freshly spilled oil. 

Well Abandonment 

On completion of production, wells would be abandoned and sites rehabilitated as may be 

required by the MMS. Noise, disturbance, and possible injury to threatened and endangered 

species during OCS oil and gas exploration are activities associated with abandonment of 

exploration and delineation wells. The casings for wells can be cut mechanically or with 

explosives during the process of well abandonment. The use of explosives could result in injury 

or even death to whales that are in the area at the time of the explosions, although the threshold 

levels for injury or death are not well established (for example, Ketten, Lien and Todd, 1993; 

Richardson et al., 1995). With respect to well abandonment, the MMS (USDOI, MMS, Pacific 

OCS Region, 2001) previously summarized that: 

...the use of explosives for delineation well abandonment would involve the detonation of a 

relatively small, 16- to 20-kilogram charge in the well casing 5 meters below the sea floor. This 

positioning of the charge would dampen the explosion and restrict shock and acoustic effects 

primarily to the area of water immediately above the well head. However, a marine mammal 

close to the detonation site potentially could be injured or killed, or suffer permanent or 

temporary hearing damage. Some disturbance of marine mammals present in the vicinity of the 

detonation area could also occur, but these would be expected to be minor and 

temporary...Overall, impacts from this source are expected to be low. 

Impacts to whales from well-abandonment activities could be avoided if these activities were 

implemented only when fin, humpback, and bowheads were absent or if sufficient monitoring 

(e.g., aerial surveys and passive acoustic monitoring) for bowheads occurred prior to the use of 

any explosives and protocols were implemented to ensure that such explosives were not used if 

such species were in areas where there was a potential for them to be adversely impacted by the 

explosives. 

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Analyses of Potential Effects of an Oil Spill on Fin, Humpback, and Bowhead Whales. 

Following a large or very large oil spill, baleen whales could suffer adverse effects due to:

• inhalation of toxic components of crude oil; 

• ingesting oil and/or contaminated prey; 

• fouling of their baleen; 

• oiling of skin; 

• reduced food source; and 

• displacement from feeding areas. 

Effects of Inhalation of Toxic Components of Crude Oil 

The greatest threat to large cetaceans probably is from inhalation of volatile compounds present 

in fresh crude oil. Based on literature on other mammals indicating severe adverse effects of 

inhalation of the toxic aromatic components of fresh oil, mortality of whales could occur if they 

surfaced in large quantities of fresh oil. Inhalation of volatile hydrocarbon fractions of fresh 

crude oil can damage the respiratory system (Hansen 1985; Neff 1990), cause neurological 

disorders or liver damage (Geraci and St. Aubin 1982), have anesthetic effects (Neff 1990) and, 

if accompanied by excessive adrenalin release, cause sudden death (Geraci 1988). 

Based on evidence of observation of individuals from the AB pod of killer whales in heavy oil, 

and large disappearances of whales from the AB pod in the 2 years following that exposure 

(Dahlheim and Matkin 1994; Harvey and Dahlheim 1994), one could conclude that whales are 

vulnerable, probably due to inhalation, if they are present within a large spill. However, this 

link is circumstantial, and there is not agreement in the scientific community as to whether or 

not there likely was an oil-spill impact on killer whales after the EVOS. Similarly, gray whales 

with apparently abnormal behavior were observed in oil after the EVOS in an area where fumes 

from the spill were apparently very strong (J. Lentfer, cited in Harvey and Dahlheim 1994). 

Subsequently large numbers of gray whale carcasses were discovered. One of three of these 

whales had elevated levels of polycyclic aromatic hydrocarbons in its blubber. Loughlin (1994) 

concluded it was unclear what caused the death of the gray whales. During the oil spill off Santa 

Barbara in 1969, an estimated 80,000 bbl of oil may have entered the marine environment. Gray 

whales were beginning their annual migration north during the spill. Whales were observed 

migrating northward through the slick. Several dead whales were observed and carcasses 

recovered, including six gray whales, one sperm whale, one pilot whale, five common dolphins, 

one Pacific white-sided dolphin, and two unidentified dolphins. Brownell (1971, as reported by 

Geraci 1990) acknowledged that these whales totaled more than the usual number of gray 

whales and dolphins stranding annually on California shores, and concluded that increased 

survey efforts had led to the higher counts. Several of the whales examined were thought to 

have died from natural causes, and one may have been harpooned. No evidence of oil 

contamination was found on any of the whales examined. The Batelle Memorial Institute 

concluded the whales were either able to avoid the oil, or were unaffected when in contact with 

it. 

Based on all available information, if individual, small groups or, less likely, large groups of 

whales were exposed to large amounts of fresh oil, especially through inhalation of highly toxic 

104
aromatic fractions, they might be seriously injured or die from such exposure. Although there is 

very little definitive evidence linking cetacean death or serious injury to oil exposure, 

disappearances (and probable deaths) of killer whales and the deaths of large number of gray 

whales both coincided with the EVOS and with observations of members of both species in oil. 

However, in these two cases, even if one assumed the disappearances of the killer whales and 

the high number of gray whale carcasses both were the result of the coinciding oil spill, and one 

assumed impacts on bowhead whales of the same magnitude, it is unlikely that there would be a 

significant population-level adverse effect in the event of a large oil spill. 

As noted above, we know of no fin, humpback, or bowhead whale deaths resulting from an oil 

spill. For the reasons discussed in the previous paragraph, it is difficult to predict the impact of 

a large or very large spill on these whales. Based on literature on other mammals indicating 

severe adverse effects of inhalation of the toxic aromatic components of fresh oil, mortality of 

cetaceans could occur if they surfaced in large quantities of fresh oil. We believe this is most 

likely if bowhead calves were exposed to fumes from a large spill. Calves take more breaths 

than do their mothers and spend more time at the surface. Thus, it is likely they would be most 

likely to succumb to inhalation of toxic aromatic compounds. 

The potential for there to be long-term sublethal (for example, reduced body condition, poorer 

health, reduced immune function, reduced reproduction or longer dependency periods) effects 

on large cetaceans from a large oil spill is essentially unknown. There are no data on large 

cetaceans adequate to evaluate the probability of sublethal effects. 

Geraci and St. Aubin (1982) calculated the concentrations of hydrocarbons associated with a 

theoretical spill of a typical light crude oil. They calculated the concentrations of the more 

volatile fractions of crude oil in air. The results showed that vapor concentrations could reach 

critical levels for the first few hours after a spill. If a whale or dolphin were unable to leave the 

immediate area of a spill during that time, it would inhale some vapors, perhaps enough to cause 

damage. Fraker (1984) stated that a whale surfacing in an oil spill will inhale vapors of the 

lighter petroleum fractions, and many of these can be harmful in high concentrations. Animals 

that are away from the immediate area or that are exposed to weathered oils would not be 

expected to suffer serious consequences from inhalation, regardless of their condition. The most 

serious situation would occur if oil spilled into a lead that whales could not escape. In this case, 

Bratton et al. (1993) theorized the whales could inhale oil vapor that would irritate their mucous 

membranes or respiratory tract. They also could absorb volatile hydrocarbons into the 

bloodstream. Within hours after the spill, toxic vapors from oil in a lead could harm the whales’ 

lungs and even kill them. The number of whales affected would depend on how large the spill 

was, its behavior after being spilled, and how many whales were present in areas contacted in 

the first several days following the spill. 

Effects of Direct Contact of Skin and other Surfaces with Spilled Oil

Oil first would contact a whale’s skin as it surfaces to breathe. The effects of oil contacting skin 

are largely speculative. We do not know how long spilled oil will adhere to the skin of a freeranging whale. Oil might wash off the skin and body surface shortly after the whales vacated 

oiled areas, if they left shortly after being oiled. However, oil might adhere to the skin and other 

surface features (such as callosities on humpbacks or sensory hairs on bowheads) longer, if 

whales remained in these areas or after leaving the oiled area. 

105
Bowhead whale eyes may be vulnerable to damage from oil on the water due to their unusual 

anatomical structure. It is documented that crude oil can damage eyes (Davis, Schafer, and Bell 

1960). Corneal ulcers and abrasions, conjunctivitis, and swollen nictitating membranes were 

observed in captive ringed seals placed in crude oil-covered water (Geraci and Smith 1976), and 

in seals in the Antarctic after an oil spill (Lillie, 1954). Corneal ulcers and scarring were 

observed in otters captured in oiled areas (Monnett and Rotterman 1989) and in oiled otters 

brought into oil-spill treatment centers (Wilson et al. 1990) after the EVOS. 

In a study on nonbaleen whales and other cetaceans, Harvey and Dahlheim (1994) observed 80 

Dall’s porpoises, 18 killer whales, and 2 harbor porpoises in oil on the water’s surface from the 

EVOS. They observed groups of Dall’s porpoises on 21 occasions in areas with light sheen, 

several occasions in areas with moderate-to-heavy surface oil, once in no oil, and once when 

they did not record the amount of oil. Thirteen of the animals were close enough to determine if 

oil was present on their skin. They confirmed that 12 animals in light sheen or moderate-toheavy oil did not have oil on their skin. One Dall’s porpoise had oil on the dorsal half of its 

body. It appeared stressed because of its labored breathing pattern. The authors gave no other 

information on effects. The 18 killer whales and 2 harbor porpoises were in oil but had none on 

their skin. None of the cetaceans appeared to alter their behaviors when in areas where oil was 

present. The authors concluded their observations were consistent with other reports of 

cetaceans behaving normally when oil is present. However, as noted above in the review of 

observations following other spills, observations of cetaceans behaving is a lethargic fashion or 

having labored breathing has been documented in more than one species, including one in which 

large numbers of individuals were subsequently found dead. 

Histological data and ultrastructural studies by Geraci and St. Aubin (1990) showed that 

exposures of skin to crude oil for up to 45 minutes in four species of toothed whales had no 

effect. They switched to gasoline and applied the sponge up to 75 minutes. This produced 

transient damage to epidermal cells in whales. Subtle changes were evident only at the cell 

level. In each case, the skin damage healed within a week. They concluded that a cetacean’s 

skin is an effective barrier to the noxious substances in petroleum. These substances normally 

damage skin by getting between cells and dissolving protective lipids. In cetacean skin, 

however, tight intercellular bridges, vital surface cells, and the extraordinary thickness of the 

epidermis impeded the damage. The authors could not detect a change in lipid concentration 

between and within cells after exposing skin from a white-sided dolphin to gasoline for 16 hours 

in vitro. 

Geraci and St. Aubin also investigated how oil might affect healing of superficial wounds in a 

bottlenose dolphin’s skin. They found that following a cut, newly exposed epidermal cells 

degenerate to form a zone of dead tissue that shields the underlying cells from seawater during 

healing. They massaged the superficial wounds with crude oil or tar for 30 minutes, but the 

substances did not affect healing. Lead-free gasoline applied in the same manner caused strong 

inflammation, but it subsided within 24 hours and was indistinguishable from control cuts. The 

authors concluded that the dead tissue had protected underlying tissues from gasoline in the 

same way it repels osmotic attack by seawater. The authors further concluded that in real life, 

contact with oil would be less harmful to cetaceans than they and others had proposed. 

While petroleum can damage mammalian skin, Geraci and St. Aubin (1985) reported little 

effects with exposures of 75 minutes. We noted that after a real spill, oil could be in contact 

with skin for much longer periods. Lipid composition was not modified, and epidermal cell 

106
proliferation was not significantly reduced. However, as pointed out by Harvey and Dahlheim 

(1994), the significance of these results is uncertain because of small sample sizes and the 

uncertainty of their applicability to natural situations. It is not clear why some cetaceans that are 

observed in oil do not become oiled while at least a few apparently do. It is not clear how long 

crude oil would remain on a free-ranging cetacean’s skin once it was oiled. Bratton et al. (1993) 

synthesized studies on the potential effects of contaminants on bowhead whales. They 

concluded that no published data proved oil fouling of the skin of any free-living whales, and 

conclude that bowhead whales contacting fresh or weathered petroleum are unlikely to suffer 

harm. 

Although oil is unlikely to adhere to smooth skin, it may stick to rough areas on the surface 

(Henk and Mullan, 1997). Haldiman et al. (1985) found the epidermal layer to be as much as 

seven to eight times thicker than that found on most whales. They also found that little or no 

crude oil adhered to preserved bowhead skin that was dipped into oil up to three times, as long 

as a water film stayed on the skin’s surface. Oil adhered in small patches to the surface and 

vibrissae (stiff, hairlike structures), once it made enough contact with the skin. The amount of 

oil sticking to the surrounding skin and epidermal depression appeared to be in proportion to the 

number of exposures and the roughness of the skin’s surface. 

Albert (1981) suggested that oil would adhere to the skin’s rough surfaces (eroded areas on the 

skin’s surface, tactile hairs, and depressions around the tactile hairs). He theorized that oil could 

irritate the skin, especially the eroded areas, and interfere with information the animal receives 

through the tactile hairs. Because we do not know how these hairs work, we cannot assess how 

any damage to them might affect bowheads. Albert (1981) noted that eroded skin may provide a 

point of entry into the bloodstream for pathogenic bacteria, if the skin becomes more damaged. 

Evidence from Shotts et al. (1990) suggests that the lesions are active sites of necrosis. The 

authors noted that 38% of the microorganisms in lesions contained enzymes necessary for 

hemolytic activity of blood cells (breaking down of red blood cells and the release of 

hemoglobin) compared to 28% of the microorganisms on normal skin. Many of these species of 

bacteria and yeast were determined to be potential pathogens of mammalian hosts. 

The potential effect of crude oil on the function of the cetacean blowhole is unknown. As noted, 

a Dall’s porpoise was observed after the EVOS with crude oil covering its skin and blowhole. 

This individual was described as having labored breathing. Other porpoise swimming in the 

same area in oil did not appear to be oiled or to have abnormal behavior (Harvey and Dahlheim, 

1994). 

Effects of Ingestion of Spilled Oil

It is documented that, with respect to mammals in general, ingestion of petroleum hydrocarbons 

can lead to subtle and progressive organ damage or to rapid death. Also as noted above, many 

polycyclic aromatic hydrocarbons are teratogenic and embryotoxic in at least some mammals 

(Khan et al., 1987). Maternal exposure to crude oil during pregnancy may negatively impact 

birth weight and health of young in at least some mammals (Khan et al., 1987; Currie et al., 

1970). In at least some marine mammals, digestion and behavior is affected with decrease food 

assimilation of prey eaten (for example, St. Aubin, 1988), increased gastrointestinal motility, 

increased vocalization, and decreased sleep (Geraci and Smith, 1976; Engelhardt, 1985, 1987) 

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(see discussion above for more detail). Oil ingestion can decrease food assimilation of prey 

eaten (for example, St. Aubin, 1988). 

Bowheads sometimes skim the water surface while feeding, filtering a lot of water for extended 

periods. If oil were present, they could swallow it. Albert (1981) suggested that whales could 

take in tarballs or large “blobs” of oil with prey. He also said that swallowed baleen “hairs” mix 

with the oil and mat together into small balls. These balls could block the stomach at the 

connecting channel, which is a very narrow tube connecting the stomach’s fundic and pyloric 

chambers (the second and fourth chambers of the stomach) (Tarpley et al., 1987). Humback and 

fin whales might also encounter oil as they feed by filtering large quantities of water. Hansen 

(1985; 1992) suggests that cetaceans can metabolize ingested oil, because they have cytochrome 

p-450 in their livers (Hansen, 1992). The presence of cytochrome p-450 (a protein involved in 

the enzyme system associated with the metabolism and detoxification of a wide variety of 

foreign compounds, including components of crude oil) suggests that cetaceans should be able 

to detoxify oil (Geraci and St. Aubin, 1982, as cited in Hansen, 1992). He also suggests that 

digestion may break down any oil that adheres to baleen filaments and causes clumping 

(Hansen, 1985). Observations and stranding records do not reveal whether cetaceans would feed 

around a fresh oil spill long enough to accumulate a critical dose of oil. There is great 

uncertainty about the potential effects of ingestion of spilled oil on bowheads, especially on 

bowhead calves. Decreased food assimilation could be particularly important in very young 

animals, those that seasonally feed, and those that need to put on high levels of fat to survive 

their environment. 

Fin, humpback, and bowheads may swallow some oil-contaminated prey, but it likely would be 

only a small part of their food. It is not known if whales would leave a feeding area where prey 

was abundant following a spill. Some zooplankton eaten by bowheads consume oil particles and 

bioaccumulation can result (see section on Potential Effects on Food Source below). Tissue 

studies by Geraci and St. Aubin (1990) revealed low levels of naphthalene in the livers and 

blubber of baleen whales. This result suggests that prey have low concentrations in their tissues, 

or that baleen whales may be able to metabolize and excrete certain petroleum hydrocarbons. 

Potential Effects of Baleen Fouling 

If a baleen whale encountered spilled oil, baleen hairs might be fouled, which would reduce a 

whale’s filtration efficiency during feeding. In a recent peer-reviewed paper in the Journal of 

Mammalogy, Lambertsen et al. (2005:349) concluded that because previous “(E)xperimental 

assessment of the effects of baleen function...thus far has considered exclusively the role of 

hydraulic pressure in powering baleen function...” but “...our present results indicate that more 

subtle hydrodynamic pressure may play a critical role in the function of the baleen in 

the...balaenids...the current state of knowledge of how oil would affect the function of the mouth 

of right whales and bowheads can be considered poor, despite considerable past research on the 

effects of oil on cetaceans.” 

Lambertsen et al. (2005) contended that oil could be efficiently ingested if globules of oil 

behave like prey inside the mouth. They point out that if oil is of low viscosity and does not 

behave like prey, only small amounts would be ingested. Lambertsen et al. (2005:350) 

characterize these two conditions as being of “questionable validity” and note that if, on the 

other hand, the resistance of the baleen is significantly increased by oil fouling, as experimental 

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evidence on the baleen of other mysticetes indicates it may be, the most likely adverse effect 

“...would be a substantial reduction in capture of larger, more actively mobile species, that is 

euphausiids, with possible reductions in capture of copepods and other prey” (Lambertsen et al., 

2005:350). They concluded that their results highlight the uncertainty about how rapidly oil 

would depurate at the near zero temperatures of arctic waters and whether baleen function would 

be restored after oiling. 

Earlier studies on baleen fouling were summarized by Geraci (1990) who, with colleagues, had 

also undertaken studies of the effects of oil on baleen function. Geraci (1990:184) noted that 

while there was “A great deal of interest...in the possibility that residues of oil may adhere to 

baleen plates so as to block the flow of water and interfere with feeding. The concerns are 

largely speculative.” He also noted that “Such an effect may be imperceptible, though leading to 

subtle, long-term consequences to the affected animal.” Geraci (1990:184) concluded that “A 

safe assumption is that any substance in seawater which alters the characteristics of the plates, 

the integrity of the hairs, or the porosity of the sieve may jeopardize the nutritional well-being of 

the animal.” 

Braithwaite (1983, as cited in Bratton et al., 1993) used a simple system to show a 5-10% 

decrease in filtration efficiency of bowhead baleen after fouling, which lasted for up to 30 days. 

Geraci (1990:186) stated that the “Details of the experimental protocol” used in that study “...are 

not entirely clear.” 

Geraci (1990) summarized studies by Geraci and St. Aubin (1982, 1985) where the effects of 

contamination by different kinds of oil on humpback, sei, fin, and gray whale baleen were tested 

in saltwater ranging from 0 to 20 o

C. In these studies, resistance to flow of some humpback 

baleen was increased more than 100%, less than 75% in gray and sei whale baleen, and gray 

whale samples were “relatively unaffected” (Geraci, 1990). Resistance to water flow through 

baleen was increased the greatest with contamination by Bunker C oil at the coldest 

temperatures. He summarized that oil of medium weight had little effect on resistance to water 

flow at any temperature. Fraker (1984) noted that there was a reduction in filtering efficiency in 

all cases, but only when the baleen was fouled with 10 millimeters of oil was the change 

statistically different. 

In the study in which baleen from fin, sei, humpback, and gray whales was oiled, Geraci and St. 

Aubin (1985) found that 70% of the oil adhering to baleen plates was lost within 30 minutes 

(Geraci, 1990) and in 8 of 11 trials, more than 95% of the oil was cleared after 24 hours. The 

study could not detect any change in resistance to water flowing through baleen after 24 hours. 

The baleen from these whales is shorter and coarser than that of bowhead whales, whose longer 

baleen has many hairlike filaments. Geraci (1990) concluded that: 

Combined evidence...suggests that a spill of heavy oil, or residual patches of weathered 

oil, could interfere with the feeding efficiency of the fouled plates for several days at 

least. Effects would likely be cumulative in an animal feeding in a region so blanketed 

by weathered oil that the rate of cleansing is outpaced by fouling. That condition could 

describe the heart of a spill, or a contaminated bay or lead. 

Lighter oil should result in less interference with feeding efficiency. Lambertsen et al. (2005) 

concluded that results of their studies indicate that Geraci’s analysis of physiologic effects of 

oiling on mysticete baleen “considered baleen function to be powered solely by hydraulic 

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pressure,” a perspective they characterized as a “gross oversimplification of the relevant 

physiology.” 

A reduction in food caught in the baleen could have an adverse affect on the body condition and 

health of affected whales. If such an effect lasted for 30 days, as suggested by the experiments 

of Braithwaite (1983), this could potentially be an effect that lasted a substantial proportion of 

the period that fin, humpback, and bowheads spend on their summer feeding grounds. Repeated 

baleen fouling over a long time, however, might also reduce food intake and blubber deposition, 

which could harm the bowheads. As pointed out by Geraci (1990), the greatest potential for 

adverse effects to bowheads would be if a spill occurred in the spring lead system. 

Potential Effects on Food Source 

Data from a recent study (Duesterloh, Short, and Barron, 2002) indicated that aqueous 

polyaromatic compounds (PAC) dissolved from weathered Alaska North Slope crude oil are 

phototoxic to subarctic marine copepods at PAC concentrations that would likely result from an 

oil spill and at UV levels that are encountered in nature. Calanus marshallae exposed to UV in 

natural sunlight and low doses (~2μg of total PAC per liter (PAC/L) of the water soluble 

fraction of weathered North Slope crude oil for 24 hours) showed an 80-100% morbidity and 

mortality as compared to less than 10% with exposure to the oil-only or sun-light only 

treatments. At 100% mortality occurred in Metridia okhotensis with the oil and UV treatment, 

while only 5% mortality occurred with the oil treatment alone. Duesterloh, Short, and Barron 

(2002) reported that phototoxic concentrations to some copepod species were lower by a factor 

of 23 to >4,000 than the lethal concentrations of total PAC alone (0.05-9.4 mg/L). 

This research also indicated that copepods may passively accumulate PACs from water and 

could thereby serve as a conduit for the transfer of PAC to higher trophic level consumers. 

Bioaccumulation factors were ~2,000 for M. okhotensis and about ~8,000 for C. marshallae. 

Calanus and Neocalanus copepods have relatively higher bioaccumulation than many other 

species of copepods because of their characteristically high lipid content. The authors 

concluded that phototoxic effects on copepods could conceivably cause ecosystem disruptions 

that have not been accounted for in traditional oil spill damage assessments. Particularly in 

nearshore habitats where vertical migration of copepods is inhibited due to shallow depths and 

geographical enclosure, phototoxicity could cause mass mortality in the local plankton 

population. (Duesterloh, Short, and Barron, 2002:3959). 

An oil spill probably would not permanently affect zooplankton populations, the bowhead’s 

major food source, and major effects are most likely to occur nearshore (Richardson et al., 1987, 

as cited in Bratton et al., 1993). The amount of zooplankton lost, even in a large oil spill, would 

be very small compared to what is available on the whales’ summer-feeding grounds (Bratton et 

al., 1993). 

The potential effects to bowheads of exposure to PACs through their food are unknown. 

Because of their extreme longevity, bowheads are vulnerable to incremental long-term 

accumulation of pollutants. With increasing development within their range and long-distance 

transport of other pollutants, individual bowheads may experience multiple large and small 

polluting events within their lifetime. 

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Fin and humpback whales feed primarily on small fish such as herring, capelin, and sandlance. 

These fish occupy the water column and do not have contact with the surface In the event of a 

large crude or diesel-fuel spill, effects on arctic fishes primarily would depend on the season and 

location of the spill; the lifestage of the fishes (adult, juvenile, larval, or egg); and the duration 

of the oil contact. Because of their low numbers in the spill area, no immediate effects are likely 

on fishes during winter. Effects more likely would occur from an offshore oil spill during 

summer or spring melt out, moving into nearshore waters, where fishes concentrate to feed, 

migrate, and spawn or rear. If an offshore spill did occur and contact the nearshore area, some 

marine and migratory fish likely would be harmed or killed. MMS has stated that for some of 

the more abundant fish species (e.g., capelin, herring), spawning aggregations in some coastal 

reaches could be lost but could be replaced within less than three generations from the larger 

population (MMS 2008). Thus, there is potential for local depletion of prey resources for fin and 

humpback whales. 

Effects of Displacement from Feeding Areas 

We have no observations of the response of bowhead whales following a large oil spill to 

determine whether they may be temporarily displaced from an area because of an oil spill or 

cleanup operations. However, Thomas Brower, Sr. (1980) described the effects on bowhead 

whales of a 25,000-gallon (595-bbl) oil spill at Elson Lagoon (Plover Islands) in 1944. It took 

approximately 4 years for the oil to disappear. For four years after the oil spill, Brower observed 

that bowhead whales made a wide detour out to sea when passing near Elson Lagoon/Plover 

Islands during fall migration. Bowhead whales normally moved close to these islands during the 

fall migration. These observations indicate that some displacement of whales may occur in the 

event of a large oil spill, and that the displacement may last for several years. Based on these 

observations, it also appears that bowhead whales may have some ability to detect an oil spill 

and avoid surfacing in the oil by detouring around the area of the spill. 

Several other investigators have observed various cetaceans in spilled oil, including fin whales, 

humpback whales, gray whales, dolphins, and pilot whales. Typically, the whales did not avoid 

slicks but swam through them, apparently showing no reaction to the oil. During the spill of 

Bunker C and No. 2 fuel oil from the Regal Sword, researchers saw humpback and fin whales, 

and a whale tentatively identified as a right whale, surfacing and even feeding in or near an oil 

slick off Cape Cod, Massachusetts (Geraci and St. Aubin, 1990). Whales and a large number of 

white-sided dolphins swam, played, and fed in and near the slicks. The study reported no 

difference in behavior between cetaceans within the slick and those beyond it. None of the 

observations prove whether cetaceans can detect oil and avoid it. None of these observations is 

sufficient to determine the long-term impacts of such exposure. Some researchers have 

concluded that baleen whales have such good surface vision that they rely on visual clues for 

orientation in various activities. In particular, bowhead whales have been seen “playing” with 

floating logs and sheens of fluorescent dye on the sea surface of the sea (Wursig et al., 1985, as 

cited in Bratton et al., 1993). These observations suggest that if oil is present on the sea surface 

and is of such quality or in such quantity that it is readily optically recognizable, bowhead 

whales may be able to recognize and avoid it (Bratton et al., 1993). However, the observation of 

their playing with dye may also indicate that they would play with it. 

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After the EVOS, researchers studied the potential effects of an oil spill on cetaceans. Dahlheim 

and Loughlin (1990) documented no effects on the humpback whale. Von Ziegesar, Miller, and 

Dahlheim (1994) found no indication of a change in abundance, calving rates, seasonal 

residency time of female-calf pairs, or mortality in humpback whales as a result of that spill, 

although they did see temporary displacement from some areas of Prince William Sound. It was 

difficult to determine whether the spill changed the number of humpback whales occurring in 

Prince William Sound. This study could not have detected long-term physiological effects to 

whales or to the humpback’s prey. 

Cleanup operations following a large or very large spill would be expected to involve multiple 

marine vessels operating in the spill area for extended periods of time, perhaps over multiple 

years. Based on information provided in the above section on vessel traffic, bowheads react to 

the approach of vessels at greater distances than they react to most other industrial activities. 

According to Richardson and Malme (1993), most bowheads begin to swim rapidly away when 

vessels approach rapidly and directly. Avoidance usually begins when a rapidly approaching 

vessel is 1-4 km (0.62-2.5 mi) away. A few whales may react at distances from 5-7 km (3-4 mi). 

After a large or very large spill, there are typically overflights using helicopters and fixedwinged aircraft to track the spill and to determine distributions of wildlife that may be at risk 

from the spill. We summarize the response of bowheads to aircraft here. Most bowheads are 

unlikely to react significantly to occasional single passes by helicopters flying at altitudes above 

150 m (500 ft). At altitudes below 150 m (500 ft), some bowheads probably would dive quickly 

in response to the aircraft noise (Richardson and Malme, 1993; Patenaude et al., 1997) and may 

have shortened surface time (Patenaude et al., 1997). Bowhead reactions to a single helicopter 

flying overhead probably are temporary (Richardson et al., 1995a). Whales should resume their 

normal activities within minutes. Fixed-wing aircraft flying at low altitude often cause hasty 

dives. Reactions to circling aircraft are sometimes conspicuous if the aircraft is below 300 m 

(1,000 ft), uncommon at 460 m (1,500 ft), and generally undetectable at 600 m (2,000 ft). 

Repeated low-altitude overflights at 150 m (500 ft) sometimes caused abrupt turns and hasty 

dives (Richardson and Malme, 1993). The effects from an encounter with aircraft are brief, and 

the whales should resume their normal activities within minutes. 

Based on all of the above information, we conclude that there could potentially be displacement 

of fin, humpback, and bowhead whales from a feeding area following a large or very large spill 

and this displacement could last as long as there is a large amount of oil and related clean-up 

vessels present. 

Conclusions of Potential Oil-Spill Effects 

The effects of a large oil spill and subsequent exposure of fin, humpback, or bowhead whale 

populations to fresh crude oil are uncertain, speculative, and controversial. The effects would 

depend on how many whales contacted oil; the ages and reproductive condition of the whales 

contacted; the duration of contact, the amount of oil spilled, and the age/degree of weathering of 

the spilled oil at the time of contact. The number of whales contacting spilled oil would depend 

on the size, timing, and duration of the spill; how many whales were near the spill; and the 

whales’ ability or inclination to avoid contact. If oil got into leads or ice-free areas frequented 

by migrating bowheads, a large portion of the population could be exposed to spilled oil. If a 

very large slick of fresh oil contacted a large aggregation or aggregations of feeding whales, 

112
especially with a high percent of calves, the effect might be expected to be greater than under 

more typical circumstances. There is great uncertainty about the effects of fresh crude oil on 

cetacean calves. Prolonged exposure to freshly spilled oil could kill some adult whales, but, 

based on available information, the number likely would be small if the spill contacted whales in 

open water. However, Engelhardt (1987) theorized that bowhead whales would be particularly 

vulnerable to effects from oil spills during their spring migration into arctic waters because of 

their use of ice edges and leads, where spilled oil tends to accumulate. Several other researchers 

(Geraci and St. Aubin, 1982; St. Aubin, Stinson, and Geraci, 1984) concluded that exposure to 

spilled oil is unlikely to have serious direct effects on baleen whales. There is some uncertainty 

and disagreement within the scientific community on the results of studies on the impacts of the 

EVOS on large cetaceans (for example, Loughlin, 1994, Dahlheim and Matkin, 1994, Dahlheim 

and Loughlin, 1990). Bowheads, fins and humpbacks may also have heightened vulnerability to 

spilled oil because of the functional morphology of their baleen. If baleen in fouled, and if crude 

oil s ingested, there could be adverse effects on the feeding efficiency and food assimilation of 

these whales. Such effects are expected to be of most importance to calves, pregnant females, 

and lactating females. However, loss of feeding efficiency could potentially reduce the chance 

of survival of any whale and could affect the amount of energy female whales have to invest in 

reproduction. 

Assuming that development and production occurs, large oil spills are less likely to occur in the 

Beaufort Sea than in the Chukchi Sea. MMS estimates about a 40% chance of a spill of 1,000 

bbl in the Chukchi Sea Planning Area should production occur. 

Despite the fact that there is no definitive mortality of a large cetacean due to an oil spill, based 

on the fact that certain components of crude oil are highly toxic to other mammals, such 

mortality could potentially occur. Ingestion, surface contact with, and especially inhalation of 

fresh crude oil has been shown to cause serious damage and even death in many species of 

mammals. This does not mean that such effect would occur. Such an assumption, if it provides 

an overestimate of potential effects, is more protective of the population than erring on the side 

of assuming that such impacts could not occur because they previously have not been 

documented. Relatedly, because of unique ecological characteristics of the bowhead whale in 

particular, they may be more vulnerable than other cetaceans to large and very large oil spills 

within their range (see below). 

In conclusion, we reiterate that there is uncertainty about effects on fin, humpback, or bowheads 

in the unlikely event of a very large spill. There are, in some years and in some locations, 

relatively large aggregations of feeding bowhead whales within the Beaufort Sea. If a large 

amount of fresh oil contacted a significant portion of such an aggregation, effects potentially 

could be greater than typically would be assumed. Additionally, highly significant effects could 

occur if a large number of females and newborn or very young calves were contacted by a large 

amount of fresh crude oil. Available information indicates it is unlikely that fin, humpback, or 

bowhead whales would be likely to suffer significant population-level adverse affects from a 

large spill originating in the Chukchi or Beaufort Sea. However, individuals or small groups 

could be injured or potentially even killed in a large spill. Oil spill response activities (including 

active attempts to move whales away from oiled areas) could cause short-term changes in local 

distribution and abundance. 

CONCLUSION 

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The effects of noise on fin, humpback, and bowheads from various OCS production activities 

have been described. The effects from an encounter with aircraft generally are brief, and the 

whales should resume their normal activities within minutes. Whales may exhibit temporary 

avoidance behavior to vessels at a distance of 1-4 kilometers. Many earlier studies indicate that 

most bowheads exhibit avoidance behavior when exposed to sounds from seismic activity. 

Bowheads also exhibited tendencies for reduced surfacing and dive duration, fewer blows per 

surfacing, and longer intervals between successive blows. Bowheads appeared to recover from 

these behavioral changes within 30-60 minutes following the end of seismic activity. 

Monitoring has shown bowheads avoid areas exposed to seismic sounds, with near total 

avoidance of the area within 20 km or 11 n. mi. (12 st. mi.) of the source vessel at times 

influenced by airgun operations. Data from monitoring seismic operations from 1996-98 

suggested that the offshore displacement may have begun roughly 35 km (19 n. mi. or 22 st. mi.) 

east of the activity, and may have persisted >30km to the west (Richardson, 1999a). 

Bowheads have been sighted within 0.2-5 kilometers from drill ships, although bowheads 

change their migration speed and swimming direction to avoid close approach to noiseproducing activities. Bowheads may avoid drilling noise at 20-30 kilometers. There are no 

observations of fin, humpback, or bowhead reactions to icebreakers breaking ice, but it has been 

predicted that roughly half of exposed bowheads would respond at a distance of 4.6-20 

kilometers when the S:N is 30 dB. Overall, we believe fin, humpback, or bowhead whales 

exposed to noise-producing activities most likely would experience temporary, nonlethal effects. 

Some avoidance behavior could persist up to 12-24 hours. 

MMS investigated the probability of spilled oil contacting bowhead whales (MMS 2000). 

Specific offshore areas (Ice/Sea Segments or ISS) were identified and modeled for probability of 

contact. Certain of these ISS’s overlay the migratory corridor of the bowhead. Using data from 

the MMS oil spill analysis for Sale 170, and assuming an oil spill of 1,000 barrels or more 

occurred at any of several offshore release areas (launch boxes) during the summer season, the 

chance of that oil contacting these ISS’s within 30 days during the summer season ranged from 

5-82%. The reader should note that the MMS model includes ISS’s that are within the launch 

box. That is, some of the offshore habitats being assessed for probability of contact lay within 

the area of the theoretical spill release. Despite the statistical probabilities presented, which 

depend on a spill contacting a discrete area, NMFS believes there are many scenarios for which 

the conditional probability of spilled oil reaching areas utilized by bowhead whales is 100%. 

Most whales exposed to spilled oil are expected to experience temporary, nonlethal effects from 

skin contact with oil, inhalation of hydrocarbon vapors, ingestion of oil-contaminated prey 

items, baleen fouling, reduction in food resources, or temporary displacement from some 

feeding areas. A few individuals may be killed as a result of exposure to freshly spilled oil. 

However, the combined probabilities of a spill occurring and also contacting bowhead habitat 

during periods when whales are present is considered as low, and the percentage of the Beaufort 

Sea stock so-affected is expected to be very small. 

The probability of an oil spill increases as more oil fields become active. Few empirical data 

exist on the effects of oil and these whales. No measurable impact on humpback whales in 

Prince William Sound was observed in 1989 as a result of the Exxon Valdez oil spill (von 

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Ziegesar et al., 1994:188), but a coincident decline in numbers of killer whales following this 

spill suggests that whales may be severely impacted by an oil spill (Matkin et al. 1994). Without 

conclusive data, it is assumed that bowhead, fin and humpback whales would be susceptible to 

an oil spill during feeding and migration, particularly if they came in contact with oil in the lead 

system during spring migration. A number of small oil spills have occurred during oil and gas 

exploration in the Alaskan Beaufort Sea in past years. Only five spills have been greater than 

one barrel, and the total spill volume from drilling 52 exploration wells (1982 through 1991) 

was 45 barrels (USDOI, MMS, 1996). Based on historical data, most oil spills would be less 

than one barrel, but a larger oil spill could also occur. Considering the number of days each year 

that fin, humpback, or bowhead whales may be present in or migrating through the Chukchi or 

Beaufort Seas, the probability that a spill would occur, the probability for a spill to occur or 

persist during periods when whales are present, and the probability that oil would move into the 

migration corridor of the whales or waters in which whales occur, it is unlikely that fin, 

humpback, or bowhead whales would be impacted by oil. Significant adverse affects would 

only be expected if all of the low probability events occurred at the same time. 

Taking these factors into consideration, NMFS concludes that, at this time, there is a reasonable 

likelihood that oil and gas development and production in the Alaskan Beaufort and Chukchi 

Seas, as described, would not violate section 7(a)(2) of the ESA. 

After reviewing the current status of the endangered bowhead whale, the environmental baseline 

for the action area, the proposed action, and the cumulative effects, it is NMFS’ biological 

opinion that individual bowhead whales within the action area may be adversely affected, but 

that the proposed action is not likely to jeopardize the continued existence of Western Arctic 

bowhead whales. No critical habitat has been designated for this species, therefore, none will be 

affected. 

After reviewing the current status of the endangered fin whale, the environmental baseline for 

the action area, the proposed action, and the cumulative effects, it is NMFS’ biological opinion 

that individual fin whales within the action area may be adversely affected, but that the proposed 

action is not likely to jeopardize the continued existence of North Pacific fin whales. No critical 

habitat has been designated for this species, therefore, none will be affected. 

After reviewing the current status of the endangered humpback whale, the environmental 

baseline for the action area, the proposed action, and the cumulative effects, it is NMFS’ 

biological opinion that individual humpback whales within the action area may be adversely 

affected, but that the proposed action is not likely to jeopardize the continued existence of 

humpback whales. No critical habitat has been designated for this species; therefore, none will 

be affected. 

VIII. CONSERVATION RECOMMENDATIONS

Section 7(a)(1) of the ESA directs Federal agencies to utilize their authorities to further the 

purposes of the Act by carrying out conservation programs for the benefit of endangered and 

115
threatened species. Conservation recommendations are discretionary agency activities to 

minimize or avoid adverse effects of a proposed action on listed species or critical habitat, to 

help implement recovery plans, or to develop information. 

The National Marine Fisheries Service and the Minerals Management Service should implement 

the following measures for these purposes: 

 

1. MMS and NMFS should continue research to update environmental inventories for the 

Chukchi Sea. Marine mammal surveys should be continued. MMS should consider a 

comprehensive program for this purpose which employs aerial and ship-based efforts as well as 

the use of passive acoustics. In particular, the current BWASP program should be expanded to 

include Block 13. MMS should particularly engage in research to describe bowhead whale 

behavior, movements and distribution, and important habitats in these waters. Efforts should be 

made to acquire photographs of humpback whales within the action area for photoidentification. NMFS and MMS shall encourage industry to photographs humpback whales they 

encounter. 

2. Vessel operations in the Beaufort Sea, including seismic geophysical exploration, should be 

scheduled to minimize operations in order to reduce potential harassment of whales. These 

activities should, to the extent practicable, avoid bowhead migratory periods in the spring and 

fall. Vessel operators should maintain separation with the bowhead whale migrational corridor 

by remaining 35 miles offshore whenever possible. 

 3. The MMS should continue research to describe the impact of exploration activities on the 

migrational movements and feeding behavior of the bowhead whale. Specific plans should be 

developed and implemented to monitor the cumulative effects of exploration, development, and 

production on the bowhead whale. These research designs and results should be reviewed 

annually to ensure that the information collected is addressing the concerns of NMFS and the 

affected Native communities. 

4. The MMS should continue to provide Information to Lessees and Lease Stipulations intended 

to reduce impacts to the bowhead whale, including stipulations on protection of biological 

resources, industry site-specific bowhead whale monitoring program, and conflict avoidance 

mechanisms to protect subsistence whaling and other subsistence activities. It may be 

appropriate to develop similar language to address humpback whales. 

5. To minimize potential harassment of fin, humpback, and bowhead whales, operators should 

be advised that aircraft (other than monitoring flights) should observe a minimum altitude of 

1500 feet (approximately 500 meters), weather and safety factors permitting. 

6. Major oil spills are not anticipated during exploration activities. However, to avoid adverse 

effects should a major oil spill occur, NMFS and MMS should cooperate with the USCG to 

ensure that areas occupied by bowhead, fin or humpback whales are clear of spilled oil. Special 

precautions should be taken to ensure that spilled oil does not reach or persist in areas in or near 

the spring lead system (SLS) used by bowhead whales during their spring migration (April 

116
through June), the fall migrational corridor, or whale feeding areas. The NMFS and MMS 

should investigate the possible use of airguns as a deterrent for whales near an oil spill. 

Research has shown most whales avoid these noise sources by at least 20 km, and an airgun 

system may be an effective tool in any North Slope offshore response arsenal for the intentional 

hazing of bowhead whales. 

7. Upon learning of any unauthorized take of bowhead, fin or humpback whales which occurs as 

a result of OCS exploratory activity, NMFS or MMS should immediately notify the assistant 

Regional Administrator for Protected Resources at (907) 586-7235 of this taking to determine 

the appropriate and necessary course of action. 

8. MMS and NMFS should use their authorities to avoid multiple seismic work operating in 

such manner as to significantly impair the bowhead migration. Multiple seismic operations 

should be prohibited from operating offshore of one another (i.e., to the north or south) when 

they might cause a delay in the migratory movements of bowhead whales. This measure does 

not include high-resolution seismic operations, or seismic work nearshore or in shallow waters 

which have less potential to harass or harm bowhead whales. 

9. The MMS and NMFS should continue to coordinate research associated with OCS actions 

and the fin, humpback, and bowhead whale, with emphasis on cumulative impacts of OCS 

activities. These agencies are encouraged to cooperatively approach this issue. 

10. The MMS should continue to investigate the use of the Chukchi and Beaufort Seas by 

feeding bowhead whales, and assess the importance of this feeding to the health and well being 

of these animals. 

11. The NMFS and MMS should consider the traditional observations of Eskimo hunters of the 

importance of the nearshore waters of the Chukchi and Beaufort Seas in their decision making. 

The MMS should take measures to protect and conserve these values, including consideration of 

deferral areas, to protect important habitat areas. 

12. The MMS should investigate methods to acquire necessary geophysical data using 

alternative methods for airguns, or to develop improved software or other technologies which 

would effectively reduce the level of noise from airguns used for geophysical research. 

13. The MMS should defer from leasing those tracts within the SLS of the Chukchi and 

Beaufort Seas. Additionally, seismic geophysical surveys should not occur within these areas 

prior to open-water conditions, and MMS should consider means to minimize any activities 

which may cross or occupy the SLS, such as pipelines. 

14. NMFS and MMS should advocate that all oil and gas-related exploration activities which 

may result in the taking of endangered marine mammals be authorized under the Marine 

Mammal Protection Act. NMFS shall condition these authorizations as necessary to minimize 

adverse effects and ensure each action would have no more than a negligible level of impact to 

the stock(s) of endangered marine mammal. Mitigative measures shall be included which are 

intended to prevent mortality or serious injury. 

117
IX. REINITIATION OF CONSULTATION

This concludes formal consultation on this action. As provided in 50 CFR §402.16, reinitiation 

of formal consultation is required where discretionary Federal agency involvement or control 

over the action has been retained (or is authorized by law) and if: (1) the amount or extent of 

incidental take is exceeded; (2) new information reveals effects of the agency action that may 

affect listed species or critical habitat in a manner or to an extent not considered in this 

Biological Opinion; (3) the agency action is subsequently modified in a manner that causes an 

effect to the listed species or critical habitat not considered in this Biological Opinion; or (4) a 

new species is listed or critical habitat designated that may be affected by this action. In 

circumstances where the amount or extent of incidental take is exceeded, any operations causing 

such take must cease pending reinitiation. 

Also, leasing and exploration activities within the area of the Chukchi and Beaufort Sea which 

includes the spring lead/polynya system are not expected to occur during the spring bowhead 

whale migration (April through June). If new technology, procedures, etc. are developed which 

allow for these activities during this period, additional and separate consultation under section 7 

(a)(2) of the ESA will be necessary. 

X. INCIDENTAL TAKE STATEMENT 

Section 9 of the ESA and Federal regulations pursuant to section 4(d) of the ESA prohibit the 

take of endangered and threatened species, respectively, without special exemption. Take is 

defined as to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture or collect, or to attempt 

to engage in any such conduct. Incidental take is defined as take that is incidental to, and not the 

purpose of, the carrying out of an otherwise lawful activity. Under the terms of section 7(b)(4) 

and section 7(o)(2), taking that is incidental to and not intended as part of the agency action is 

not considered to be prohibited taking under the ESA provided that such taking is in compliance 

with the terms and conditions of this incidental take statement. 

This opinion does not include an incidental take statement at this time. Upon issuance of 

regulations or authorizations under Section 101(a)(5) of the Marine Mammal Protection Act 

and/or its 1994 Amendments, NMFS will amend this opinion to include an incidental take 

statement(s) for the described work. 

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