ACCESS NUMBER: MMS-1.00

STUDY TITLE: MMS Bowhead Whale Aerial Survey Project.

REPORT TITLE: Aerial Surveys of Endangered Whales in the Beaufort Sea, Fall 2002-2004.

CONTRACT N UMBER(S): MMS-1 (in-house study).

SPONSORING OCS REGION: Alaska.

APPLICABLE PLANNING AREA(S): Beaufort Sea, Chukchi Sea.

FISCAL YEAR(S) OF PROJECT FUNDING: 1987-present.

COMPLETION DATE OF REPORT: Published July 2004.

COST(S): average annual costs:$375,000.

PROJECT MANAGER(S): Charles Monnett.

AFFILIATION: Minerals Management Service.

ADDRESS: 3801 Centerpoint Drive, Suite 500, Anchorage, AK 99503.

PRINCIPAL INVESTIGATOR(S): Charles Monnett.

KEY WORDS: Beaufort Sea, Chukchi Sea, Alaska, Arctic, endangered species, whales, bowhead whale,

beluga whale, ringed seal, bearded seal, polar bear, Balaena mysticetus, aerial survey, monitoring,

behavior, relative abundance, distribution, density, migration, habitat, feeding, bathymetry, ice, oil and gas

industry.

BACKGROUND: Monitoring endangered bowhead whales by the Environmental Studies Section, Alaska

Outer Continental Shelf (OCS) Region, Minerals Management Service (MMS), has become an important

component in mitigation of potential effects of offshore exploration, especially in determining the time and

occurrence of the bowhead migration in arctic waters. The MMS (or, previously, the Bureau of Land

Management) has funded whale surveys in the Beaufort and Chukchi Seas each year since 1978. Since

1987, Alaska OCS Regional staff have conducted aerial surveys of the fall bowhead whale migration in the

Beaufort Sea.

OBJECTIVES: The present goals of the ongoing program for monitoring endangered whales are to: (1) Define

the annual fall migration of bowhead whales, significant inter-year differences, and long-term trends in the

distance from shore and water depth at which whales migrate; (2) Monitor temporal and spatial trends in the

distribution, relative abundance, habitat, and behaviors (especially feeding) of endangered whales in arctic

waters; (3) Provide real-time data to MMS and NMFS on the general progress of the fall migration of bowhead

whales across the Alaskan Beaufort Sea, for use in protection of this Endangered Species; (4) Provide an

objective wide-area context for management interpretation of the overall fall migration of bowhead whales and

site-specific study results; (5) Record and map beluga whale distribution and incidental sightings of other

marine mammals; and (6) Determine seasonal distribution of endangered whales in other planning areas of

interest to MMS.

DESCRIPTION: This report describes field activities and data analyses for aerial surveys of bowhead whales

conducted during Fall 2002-2004 in the Beaufort Sea, primarily between 140°W. and 157°W. longitudes south

of 72°N. latitude. This area is divided into survey blocks suitable for conducting random-transect surveys.

Dedicated aerial surveys were flown to assess the status of the fall bowhead migration and to investigate

bowhead whale distribution, migration corridors, and migration timing in the Beaufort Sea. These broad-area

surveys provide information on bowhead whale migration patterns upstream, in the vicinity, and downstream of

gas and oil drilling and seismic exploration activities. They provide data on the axis of the bowhead whale

migration from year to year for analyses of any significant or cumulative displacement of the migration corridor

potentially due to industrial and/or environmental factors. Two basic types of aerial surveys--random-transect

surveys and search surveys--are used to accomplish the listed objectives: (1) Random-transect surveys are

flown in survey blocks to determine bowhead whale distribution patterns, to estimate relative abundance and

density, and to determine the location of the migration axis. Whales are recorded, regardless of distance from
ACCESS NUMBER: MMS-1.00

a transect line, and are used in determining the median and mean water depths at bowhead sightings. Only

whales sighted within one kilometer of a random-transect line are included in density calculations. (2) Search

surveys are flown to locate whales and observe their behavior en route to transect blocks or when transiting to

a new base of operations. Search surveys do not follow a preset flight pattern, but data from nonrandom

surveys are considered combinable with random-transect data to obtain distribution patterns, relative

abundance, and behavior of whales and other marine mammals.

SIGNIFICANT CONCLUSIONS: The axis of the annual fall migration by bowhead whales in the Eastern and

Western Alaska Beaufort Sea (2002-2004) was compared with similar data from the 20 years between 1982-

2001. It was found that the axis of migration tended to lie relatively closer to shore in 5 of the 6 comparisons,

and significantly so in the East Region in 2002 and 2004, and in the West Region in 2004. This tendency is

consistent with the fact that 2002, 2003, and 2004 were all mild ice years and bowheads tend to be found in

waters nearer the shoreline in such years. Observations indicated that bowheads showed considerable

tendency to feed or mill in groups near shore during 2002 and 2004, but not in 2003. The axis of fall migration

for both the Eastern and Western Regions in all 3 years was within the respective 25th 75th quartile ranges

derived for all years (1982-2001).

STUDY RESULTS: This report describes field activities and data analyses for aerial surveys of bowhead

whales conducted during Fall 2002 (22 August - 7 October), Fall 2003 (1 September - 19 October), and Fall

2004 (1 September - 18 October) in the Beaufort Sea, between 1 40°W. and 1 5°W. longitudes south of 72°N.

latitude.

During Fall 2002, general ice cover during September and October was the 5th-mildest open-water season

(1953-2002). A total of 27 survey flights were attempted. There were 74 sightings for a total of 83 bowhead

whales counted during Fall 2002. Additionally, 645 beluga whales, 97 bearded seals, 618 ringed seals, and 11

polar bears were observed during 98.6 hours of survey effort that included 60.0 hours on randomized

transects.

During Fall 2003, general ice cover during September and October was relatively light. A total of 28 survey

flights were attempted. There were 146 sightings for a total of 245 bowhead whales counted. Additionally,

444 beluga whales, 26 bearded seals, 301 ringed seals, and 45 polar bears were observed during 76.3 hours

of survey effort that included 40.0 hours on randomized transects.

During Fall 2004, general ice cover during September and October was very light. A total of 29 survey flights

were attempted. There were 238 sightings for a total of 496 bowhead whales counted. Additionally, 447

beluga whales, 93 bearded seals, 2896 ringed seals, and 55 polar bears were observed during 115.9 hours of

survey effort that included 66.0 hours on randomized transects.

In 2002, 2003 and 2004 the respective axes of bowhead whale sightings were: East Region 21.9 km, 31.8 km,

and 26.2 km; and West Region 41.9 km, 34.4 km and 26.0 km. Means were compared with combined data

for other years and comparisons indicated that bowhead whales were closer to shore in the East Region in

2002 and 2004, and in the West Region in 2004 than in previous years. Mean values for both Regions in all 3

years were within the respective 25th - 75th quartile ranges for all years (1982-2001).

STUDY PRODUCT(S): Monnett, C. and S. D. Treacy. 2005. Aerial Surveys of Endangered Whales in the

Beaufort Sea, Fall 2002 - 2004. OCS Study MMS 2005-037. Anchorage, AK: USD01, MMS, Alaska OCS

Region, 153 pp.
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ACCESS NUMBER: MMS-1.00

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