Polar Bear Aerial Survey in the Eastern Chukchi Sea: A Pilot Study

Abstract

ABSTRACT. 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 shipbased 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 km 2 (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.

Barents Sea polar bears (Ursus maritimus): population biology and anthropogenic threats

“…The density of bears on land-fast ice and pack ice in the Russian areas to the east was much higher ( !2 bears/ 100 km 2 ) than in the Norwegian territory (0.4Á1 bears/ 100 km 2 ). The mean density of polar bears across the whole region was, however, close to the densities described elsewhere in the Arctic (Taylor & Lee 1995;Evans et al 2003). Polar bear spatial patterns are known to vary with both season and year.…”

Investigating the potential use of aerial line transect surveys for estimating polar bear abundance in sea ice habitats: A case study for the Chukchi Sea

“…Polar bear group sizes detected by Evans et al (2003) were not correlated with distance from the transect line ( r =−0.12; 95% confidence interval from −0.49 to 0.25), so probability of detection was considered independent of group size in this investigation.…”

“… Study area, flight lines, and polar bear observations in the eastern Chukchi Sea and western Beaufort Sea off northern Alaska during August 2000 (pilot study; fig. 1 in Evans et al 2003). …”

“…We simulated a DS survey for polar bears in sea ice habitats using two or more helicopters with two observers each, assuming observers would sit on each side of the aircraft in the rear seats. We also assumed that future surveys would follow survey protocol described by Evans et al (2003).…”

A circumpolar monitoring framework for polar bears

“…Counts of polar bears from systematic aerial transects may provide indications of distribution change in portions of subpopulation (Schliebe et al 2008), and therefore alert resource managers of possible environmental changes. Similar to M-R studies, aerial surveys are typically constrained to short periods when weather conditions are suitable for aircraft and sometimes to portions of the potential subpopulation range (Evans et al 2003). Identification of optimal sea ice habitat may be a useful proxy of distribution when other monitoring data, such as radiotelemetry or aerial surveys, are not possible.…”