Early Spring Distribution of Bowhead Whales in the Bering Sea

Abstract

Helicopter surveys were conducted of the pack ice in the northwestern Bering Sea during early spring 1979 to determine bowhead whale (Balaena mysticetus) distribution. One hundred and nine bowheads were observed in the approximately 15,000 km2 surveyed. Whale use of the pack ice was disproportionately highest in the 3-4 okta ice concentration category and lowest in the 7-8 okta category; the 1-2 and 5-6 okta categories were used in proportion to their availability. The association of whales with these ice concentration categories appeared to suggest the possible location of a spring migration corridor. No calves were observed during the study. J. WILDL. MANAGE. 46(4):1036-1044 The geographic range of the western Arctic bowhead whale population includes the Bering, Chukchi, and Beaufort seas. Seasonal distribution of the bowhead in the Chukchi and Beaufort seas has been reasonably well documented by Maher and Wilimovsky (1963), Foote (1964), Mansfield (1971), Sergeant and Hoek (1974), Braham and Krogman (1977), Braham et al. (1979), Durham (1979), and Fraker and Bockstoce (1980), but is less well known in the Bering Sea. Evidence of its occurrence in the Bering Sea derives from whaling records (Townsend 1935), whalers' accounts (Scammon 1874, Aldrich 1889, Cook 1926), and Eskimo observations (Durham 1979). This evidence indicates that bowheads have historically overwintered in the area from St. Lawrence Island south and west to the ice edge. Although whales have occurred as far south as Cape Kronotsky (USSR) (Zenkovich 1954), most of those reported by whalers have been north of Cape Olyutroskiy (USSR). Bowheads have seldom been seen in the eastern Bering Sea. The objective of this study was to determine the distribution of bowhead whales in the Bering Sea during the period when pack ice is usually at its maximum southern extent confining the distribution of the animals. Concurrent studies were conducted to characterize the ice and identify those ice conditions associated with bowhead occurrence. I thank L. Consiglieri, M. Dahlheim, B. Kelly, D. Rugh, J. Taggart, and D. Wencker for their participation in the data collection and tabulation. M. Dahlheim was instrumental in organizing the project. Logistic support was supplied by the staff of the U.S. Coast Guard icebreaker, Polar Sea. H. Braham provided guidance and encouragement during the study. Advice on data analysis was generously given by A. York. J. Bums, D. Rice, M. Tillman, and the Northwest and Alaska Fisheries Center (National Marine Fishery Service) editorial staff reviewed the manuscript and made useful suggestions for its improvement. STUDY AREA AND METHODS The study area, in the pack ice of the northwestern Bering Sea, encompasses approximately 47,380 km2 (Fig. 1). Within this area, aerial and shipboard surveys were conducted from an icebreaker between 2 March and 13 April 1979. Military restrictions limited surveys to 46 km from the USSR coast. 1 Present address: Envirosphere Co., 400 112th Ave., Bellevue, WA 98004. 1036 J. Wildl. Manage. 46(4):1982 This content downloaded from 157.55.39.243 on Thu, 06 Oct 2016 04:45:09 UTC All use subject to http://about.jstor.org/terms SPRING DISTRIBUTION OF BOWHEAD WHALES* Brueggeman 1037 1800 VV 175 W 170 W