Northern Beaufort Sea (NB)

The population is thought to be stable, and estimated using mark-recapture at approximately 980 (95% CI: 825-1135) animals in 2006.

Status table outtake

Size Sea ice metrics Human-caused removals 2010–2014
Estimate /
95% CI
Year Method Change in spring ice retreat / Change in fall ice advance (days per decade) Change in summer sea ice area (percent change per decade) 5-yr mean Last year
Potential Actual Potential Actual
980
825-1135
2006Physical capture-recapture-5.8/3.3-5.9142.2 (SB+NB)83 (SB+NB)133 (SB+NB)57 (SB+NB)
See also the complete table (all subpopulations)

Comments, vulnerabilities and concerns

Potential and actual removals merged for NB and SB due to unresolved boundary.

Status and delineation

Northern Beaufort Sea subpopulation mapThe Northern Beaufort Sea area. See also the complete map (all subpopulations).

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, 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 most northerly areas of the northwestern coast of Banks Island and M’Clure Strait were not permitted to be completely surveyed because of concern about disruption to guided polar bear sport hunters at the same time. The most northerly region of the NB subpopulation were later surveyed in 1990–92; the densities encountered were low, few subadult bears were seen, and the ratio of marked to unmarked polar bears was similar to that in the southern portion of the subpopulation. A mark-recapture survey, completed in 2006 suggested that the size of the NB subpopulation to be 980 ± 155, and that it has remained stable over the previous three decades, probably because ice conditions have remained stable and the harvest has been maintained within sustainable limits (Stirling et al. 2011). The amount of ice remaining over the continental shelf in NB in late summer fluctuates. Analyses using data from satellite tracking of female polar bears and spatial modeling techniques suggest that the boundary between NB and SB may need to be moved somewhat to the west of its current eastern limit at Pearce Point, in response to changing patterns of breakup and freeze-up resulting from climate warming (Amstrup et al. 2004, Amstrup et al. 2005). In 2014, the boundary (for management purposes within the Inuvialuit Settlement Area) between NB and SB was moved to the vicinity of Tuktoyaktuk on the basis of TEK (citation) and older satellite telemetry data (Amstrup et al. 2004). For the purposes of this assessment, we (IUCN/SSC/PBSG) will adopt interim use of the revised boundary between SB and NB used by management authorities in the Northwest Territories and Yukon Territory.

References

Amstrup, S.C. and Durner, G.M. 1995. Survival rates of radio-collared female polar bears and their dependent young. Can. J. Zoology 73:1312-1322.

Amstrup, S.C., McDonald, T.L. and Durner, G.M. 2004. Using satellite radiotelemetry data to delineate and manage wildlife populations. Wildl. Soc. Bull. 32:661-679.

Amstrup, S.C., Durner, G.M., Stirling, I. and McDonald, T.L. 2005. Allocating harvests among polar bear stocks in the Beaufort Sea. Arctic 58:247-259.

Bethke, R., Taylor, M., Amstrup, S. and Messier, F. 1996. Population delineation of polar bears using satellite collar data. Ecol. Appl. 6:311-317.

DeMaster, D.P., Kingsley, M.C.S. and Stirling, I. 1980. A multiple mark and recapture estimate applied to polar bears. Can. J. Zool. 58:633-638.

Lunn, N.J., Stirling, I. and Andriashek, D. 1995. Movements and distribution of polar bears in the northeastern Beaufort Sea and M'Clure Strait. Final Report to the Inuvialuit Wildlife Management Advisory Committee, Inuvik, Northwest Territories. Canadian Wildlife Service, Edmonton, Alberta, Canada. 65 pp.

Stirling, I., Andriashek, D., Latour, P.B. and Calvert, W. 1975. The distribution and abundance of polar bears in the eastern Beaufort Sea. Final Report to the Beaufort Sea Project. Fisheries and Marine Service, Department of Environment, Victoria, British Columbia, Canada. 59 pp.

Stirling, I., Kingsley, M.C.S. and Calvert, W. 1982. The distribution and abundance of seals in the eastern Beaufort Sea, 1974-79. Canadian Wildlife Service Occasional Paper 47. Edmonton, Alberta, Canada. 23 pp.

Stirling, I., Andriashek, D., Spencer, C. and Derocher, A.E. 1988. Assessment of the polar bear population in the eastern Beaufort Sea. Final Report to the Northern Oil and Gas Assessment Program. Canadian Wildlife Service, Edmonton, Alberta, Canada. 81 pp.

Stirling, I., McDonald, T.L., Richardson, E.S., Regehr, E.V., and Amstrup, S.C. 2011. Polar bear population status in the Northern Beaufort Sea, Canada, 1971–2006. Ecol. Appl. 21:859–876.

Taylor, M.K. and Lee J. 1995. Distribution and abundance of Canadian polar bear populations - a management perspective. Arctic 48:147-154.