Northern Beaufort Sea (NB)

Status table outtake

Table comment: Population estimate is from on-going analysis of a new mark-recapture inventory.Boundary with SB is being re-considered, which will affect vital rates and population estimate.

Studies of movements and abundance estimates of polar bears in the eastern Beaufort Sea have been conducted using telemetry and mark-recapture at intervals since the early 1970’s (Stirling et al. 1975, Demaster et al. 1980, Stirling et al. 1988, 1997, Lunn et al. 1995). As a result, it was recognized that there were separate populations in the North and South Beaufort Sea areas (NB and SB) and not a single population as was suspected initially (Stirling et al. 1988, Amstrup et al. 1995, Taylor and Lee 1995, Bethke et al. 1996). The density of polar bears using the multi-year ice of the northernmost area was lower than it was further south. The subpopulation estimate of 1,200 (Stirling et al. 1988) for NB was believed to be relatively unbiased at the time but the northwestern coast of Banks Island was not completely surveyed in the 1980s because of perceived conflicts with guided sport hunters in the area. The northern region of the NB subpopulation was surveyed in 1990 – 92, but the densities encountered were low and the marked to unmarked ratio was the same as for the southern portion of the subpopulation. There was no indication that the subpopulation estimate of 1,200 should be increased. A recently completed mark-recapture survey suggested that the size of the NB subpopulation has remained stable at approximately 1,200 bears, probably because ice conditions have remained stable and the harvest has been maintained at sustainable levels (Stirling et al. 2007). Although there are fluctuations in the amount of ice remaining in NB by late summer, to date there is no significant trend though it appears the total area of sea ice may be beginning to show a decline Analyses using data from satellite tracking of female polar bears and spatial modeling techniques indicate the boundary between NB and SB may need to be adjusted, probably expanding the area occupied by bears from NB and retracting that of SB (Amstrup et al. 2004a, Amstrup et al. 2005). See summary of the southern Beaufort Sea subpopulation for more details regarding the NB-SB boundary.