A calf index for monitoring reproductive success in the BeringChukchi-Beaufort Seas bowhead whale (Balaena mysticetus) population

The percentage of calves in a whale population can provide information on whether is increasing, stable or decreasing and an input to models. In this paper method for estimating the Bering-Chukchi-Beaufort Seas (B-CB) bowhead any given year by obtaining passing Point Barrow, Alaska, during last three weeks spring migration presented. incorporates timing with detected calf index surveys conducted weekly periods from 14 May early June. Historic data different proportions low, medium high years. adjusted allow before that are born after their mothers pass Barrow. was calculated eight years using aerial photographic near Barrow 1985 2004 mean sampled 6.1%. Power analyses indicate nine required following decline detect 60% reduction index. Additional prior would increase power decline. This robust estimate each modest survey effort at be valuable evaluating calving rates within range tested purpose reviewing B-C-B Strike Limit Algorithm.