Observations on gray whale (Eschrichtius robustus) utilization patterns in the northeastern Chukchi Sea, July–October 1982–1987

Abstract

A total of 821 gray whales were seen during aerial surveys in the northeastern Chukchi Sea from July through October 1982–1987. Gray whale distribution extended from south of Point Hope to northeast of Point Barrow, Alaska, between 0.5 and 166 km offshore. Monthly abundance estimates (number of whales/survey hour) were highest in July (6.81) and lowest in October (0.40). Gray whales were usually in open water (82%, n = 670) or in light ice (16%, n = 134) and were seldom associated with heavy ice (2%, n = 17). Most whales were feeding (63%, n = 514), with the majority of the others swimming and diving (24%, n = 193) or forming part of a cow–calf association (9%, n = 72). One group of three whales was involved in sexual activity. Feeding whales were seen most often within 40 km of the shore, but also occurred offshore. Thirty-six gray whale calves were seen. Calf abundance (number of calves/survey hour) was significantly higher (p < 0.001) in July, when 92% (n = 33) of all calves were seen, than in any other month. Most cow–calf pairs were seen nearshore between Point Hope and Point Barrow. Monthly calf ratios (number of calves/number of whales) ranged from 0.09 in July to 0.00 in October, with an overall rate of 0.04.