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Bowhead whale

The bowhead whale (Balaena mysticetus) is found only in Arctic and sub-Arctic waters [1] and is the only baleen whale that spends its entire life near sea ice without migrating to temperate or tropical waters to calve [2]. For management purposes, five stocks of bowhead whales are recognized [3]. Four small stocks (comprised of only a few tens to a few hundred individuals) occur in 1) the Sea of Okhotsk, 2) Davis Strait, 3) Hudson Bay, and 4) the offshore waters of Spitsbergen [3]. The largest population, and the only stock that is found within U. S. waters, is the Western Arctic stock, also know as the Bering-Chukchi-Beaufort stock or Bering Sea stock [3]. The majority of this stock migrates annually from wintering areas in the northern Bering Sea, through the Chukchi Sea in the spring, to the Beaufort Sea where they spend much of the summer before returning again to the Bering Sea in the fall to overwinter [3]. This stock represents over 90% of the remaining world population [4] and appears to be making significant progress towards recovery [5].

All stocks of bowhead whales were severely depleted during intense commercial whaling prior to the 20th century [3]. In the Bering Sea, commercial whaling for bowheads occurred primarily from 1898-1919 [3]. Bowheads received complete protection from commercial whaling in 1946 [1]. It is estimated that whaling killed a total of 18,684 bowhead whales in the Bering Sea and a population, thought to have once numbered between 10,400-23,000, dropped to fewer than 3,000 before whaling stopped [3]. It has been suggested that whaling may have eliminated a stock (possibly non-migratory) of bowheads from the Bering Sea and left only the component of the population that migrated to the Beaufort Sea [5].

The remaining western arctic bowhead whales have been recovering slowly over the past 80 years [5]. As bowhead whales from the Western Arctic stock travel past Point Barrow, Alaska during migration, they are somewhat funneled between shore and the polar pack ice, providing a good location to study them [3]. Since 1978, systematic counts of bowhead whales during spring migration have been conducted in this area [3]. In 1978, after correcting for whales missed due to viewing conditions, it was estimated that the stock numbered 5,189 [3]. By 1993 this estimate had increased to 8,200 (95% C.I. 7,200-9,400), and as of 2001 the stock was estimated to number around 9,860 (95% C.I. 7,700-12,600) [3]. The rate of population increase from 1978-1993 was estimated at 3.1% (95% C.I. 1.4-4.7%) [3]. Adding 2001 data increases the rate to 3.3% (95% C.I. 2-4.7%) [3]. During 2001 surveys, 121 calves were observed -the highest number yet recorded [3]. Based on body condition and calf production, the recent retreat of ice may have benefited this population [6] which is thought to be healthy and nearing pre-exploitation numbers [3].

Current threats to bowheads include pollution and increased ship traffic associated with increasing oil and gas development in the arctic [3]. Bowheads are also sensitive to noise from offshore drilling rigs and seismic survey operations [3] and there is currently pressure for increased offshore development [6]. The effects of global warming on arctic ice and waters could also possibly affect the bowhead [6]. Ice entrapment and predation by killer whales, Orcinus orca, can also cause mortality [5]. In addition, native subsistence hunts are allowed in Alaska. Since 1977 subsistence takes have been regulated by the International Whaling Commission [3]. The number of kills per year has ranged from 14-72 [3]. The recent harvest rate has been 40 whales per year with another 10 or more stuck and lost [6].

[1] American Cetacean Society. 2004. Bowhead Whale (Balaena mysticetus) Fact Sheet. Available at <http://www.acsonline.org/factpack/bowhead.htm> Revised 3/2004.
[2] Caroll, G. 1994. Bowhead Whale. Alaska Department of Fish and Game. Website <http://www.adfg.state.ak.us/pubs/notebook/marine/bowhead.php> accessed March, 2006.
[3] NOAA Fisheries. 2003. Stock Assessment Report. Bowhead Whale (Balaena mysticetus): Western Arctic stock. National Oceanic and Atmospheric Administration, Washington, DC.
[4] National Audubon Society. 1992. Bowhead Whales in Beringia Natural History Notebook Series. Anchorage, AK. Available at <http://www.nps.gov/bela/html/bowhead.htm>.
[5] Shelden, K. E. W. and D. J. Rugh, 1995. The Bowhead Whale, Balaena mysticetus: Its Historic and Current Status. Marine Fisheries Review 57(3-4):1-20.
[6] George, C. 2006. Personal communication with Craig George, North Slope Borough Department of Wildlife Management. April, 2006.

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