| Summary: | Alaska has two polar bear populations: the Southern Beaufort Sea population, shared with Canada, and the Chukchi/Bering Seas population, shared with Russia. Currently a reliable population estimate for the Chukchi/Bering Seas population does not exist. Land-based aerial and mark-recapture population surveys may not be possible in the Chukchi Sea because variable ice conditions, the limited range of helicopters, extremely large polar bear home ranges, and severe weather conditions may limit access to remote areas. Thus line-transect aerial surveys from icebreakers may be the best available tool to monitor this polar bear stock. In August 2000, a line-transect survey was conducted in the eastern Chukchi Sea and western Beaufort Sea from helicopters based on a U.S. Coast Guard icebreaker under the "Ship of Opportunity" program. The objectives of this pilot study were to estimate polar bear density in the eastern Chukchi and western Beaufort Seas and to assess the logistical feasibility of using ship-based aerial surveys to develop polar bear population estimates. Twenty-nine polar bears in 25 groups were sighted on 94 transects (8257 km). The density of bears was estimated as 1 bear per 147 km² (CV = 38%). Additional aerial surveys in late fall, using dedicated icebreakers, would be required to achieve the number of sightings, survey effort, coverage, and precision needed for more effective monitoring of population trends in the Chukchi Sea. L'Alaska a deux populations d'ours polaires : celle du sud de la mer de Beaufort, commune avec le Canada, et celle de la mer des Tchouktches / mer de Béring, commune avec la Russie. À l'heure actuelle, on ne possède pas d'estimation fiable de la population de la mer des Tchouktches / mer de Béring. En raison des conditions variables de la glace, de la portée limitée des hélicoptères, de la très grande étendue du domaine vital de l'ours polaire et des conditions météorologiques particulièrement mauvaises - facteurs qui limitent l'accès aux régions éloignées -, il n'est ...
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