Bowhead and White Whale Migration, Distribution, and 



Abundance in the Bering, Chukchi, and 



Beaufort Seas, 1975-78 



HOWARD W. BRAHAM, BRUCE D. KROGMAN, and GEOFFREY M. CARROLL' 



ABSTRACT 



From September 1975 (o September 1977 we conducted field research on bowhead, Balaena mysticetus, and 

 while, Delphinapterus leucas, whales in (he U.S. Bering, Chukchi, and Beaufort Seas. The objectives were to de- 

 termine the general distribution and migration of these whales in spring and autumn and to estimate abundance. 

 We also surveyed the literature beginning in June 1975 through March 1978 to augment our empirical results. 



Bowhead and white whales spend the winter months among the pack ice and open water of the central and 

 western Bering Sea. They migrate into the eastern Chukchi Sea and across the southern and central Beaufort Sea 

 from April through June. Their route takes them along the west side of the northern Bering Sea through Bering 

 Strait, along the northwest coast of Alaska between Point Hope to Point Barrow , generally within 50 km of shore 

 (closer to Point Barrow than off Point Hope and Cape Lisburne), and offshore in the Beaufort Sea generally to 

 within 60 km of the coast. Exceptions exist, and these are pointed out in the text. 



It appears that virtually the entire bowhead migration follows this pattern; however, white whales may be 

 divided into groups (or stocks) of varying sizes, some occurring in Bristol Ba>, Norton Sound, KoUebue Sound, 

 and along the northwest coast of Alaska during summer. The largest component of the white whale population 

 migrates into the Canadian Beaufort Sea in spring at roughly the same time as the bowheads. Autumn migration 

 results were not obtained, generall), for either species. 



The 1978 minimum estimate of the size of the bowhead population was 1,800 to 2,900 individuals, and for 

 the white whales occurring in Alaskan waters between 9,000 and 16,000 individuals. 



INTRODUCTION 



In 1975 the Outer Continental Shelf Environmental Assess- 

 ment Program (OCSEAP) Office awarded a contract to the 

 Marine Mammal Division (now the National Marine Mammal 

 Laboratory) of the Northwest and Alaska Fisheries Center, 

 NMFS, to study the bowhead whale, Balaena mysticetus, and 

 white whale, Delphinapterus leucas, in the Bering, Chukchi, 

 and Beaufort Seas. The objectives were to summarize the 

 current state of knowledge on each population, define migra- 

 tion routes and timing, and make an estimate of population 

 size from original field research and a review of the literature. 

 Field research was funded from September 1975 to September 

 1977. 



This report is the final of two reports written under OCSEAP 

 contract number R7120807, research unit 69/70. Braham and 

 Krogman (1977) 2 covered our first full year's research, 1976. 

 All significant research findings, including those already re- 

 ported on in our other OCSEAP reports, are incorporated 

 into this report. This document is an update of the final re- 

 port submitted to OCSEAP in September 1979. 



During the course of our field research, information was 

 acquired on spring movements of whales from St. Lawrence 

 Island to Point Barrow. Research on bowhead and white 

 whale distribution south of St. Lawrence Island was not ex- 



tensive, nor was much information found in the literature. 

 Also, our understanding of distribution in the Beaufort Sea 

 was fragmentary, coming from scant data from our research, 

 from Eskimo informants, and from early commercial whaling 

 accounts. At the time this contract was active, specific oil 

 lease sites were not known. Therefore, our research was 

 directed only at a general understanding of these species. 



In 1978, the National Marine Fisheries Service expanded its 

 research on bowhead whales, with the principal objectives of 

 determining population size and obtaining information on 

 life history parameters. Data acquired during the 1978 and 

 1979 field seasons are reported in Braham et al. (1979, 1980c, 

 d, e). Further analyses, and reports, are continuing. Where 

 applicable, information from these papers is presented here. 



The bowhead whale is the most depleted marine mammal 

 occurring in Arctic and sub-Arctic waters of the Northern 

 Hemisphere. Under the Endangered Species Act of 1973, no 

 human activities of any kind can take place which are likely 

 to jeopardize the continuing existence of a species or popula- 

 tion. Proposed OCS development for oil and gas in the Beau- 

 fort, Chukchi, and Bering Seas includes habitat essential for 

 the survival of this population. 



Results presented in this report represent the first research 

 funded by a U.S. Federal agency to provide baseline infor- 

 mation on the endangered bowhead whale in relation to pro- 

 posed OCS development. 



'National Marine Mammal Laboratory, National Marine Fisheries Service, 

 NOAA, 7600 Sand Point Way NE., Bldg. 32, Seattle, WA 981 15. 



J Braham, H. W., and B. D. Krogman. 1977. Population biology of the bow- 

 head (Balaena mysticetus) and beluga (Delphinapterus leucas) whales in the 

 Bering, Chukchi and Beaufort Seas. Processed rep., 29 p. Natl. Mar. Mammal 

 Lab., Northwest and Alaska Fish. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 

 Sand Point Way NE., Bldg. 32, Seattle, WA 981 15. 



STUDY AREA AND DATA SOURCES 



Study Area 



The study area included the eastern Bering Sea, the Chuk- 

 chi Sea east of the USA-USSR 1867 Convention Line, and 



