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COSEWIC Assessment and Update Status Report on the Bowhead Whale in Canada

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COSEWIC
Executive Summary

Bowhead Whale
Balaena Mysticetus

Species Information

Bowhead whales (Balaena mysticetus) (Linnaeus 1758) are large baleen whales of the family Balaenidae. The body is predominantly black with white (nonpigmented) regions on the chin, eyelids, flipper insertions, ano-genital area, tail stock, and flukes.

Distribution

Bowheads have a nearly circumpolar distribution in the northern hemisphere. There are 3 recognized populations in Canada. The Bering-Chukchi-Beaufort population summers in the eastern Beaufort Sea and Amundsen Gulf, and winters in the Bering Sea. The Hudson Bay-Foxe Basin population summers mainly in northwestern Hudson Bay and northern Foxe Basin, and may winter in northern Hudson Bay and Hudson Strait. The Davis Strait-Baffin Bay population summers in the Lancaster Sound region and western Baffin Bay and winters in Davis Strait.

Habitat

Bowheads occur in marine waters and in conditions ranging from open water to thick, extensive (but unconsolidated) pack ice.

Biology

Bowhead whales become sexually mature at around 25 years of age, and give birth to a single calf about every 3 years. Longevity may exceed 100 years. Growth is rapid during the first year (1.5 cm/day) and appears to slow after weaning to less than 1 m/yr. The Bering-Chukchi-Beaufort population consists of about 5% calves (<6 m), 54% juveniles (6-13 m) and 41% adults (>13 m), with an even sex ratio. Age-class segregation has been documented in all three populations. The spring and autumn migrations along northern Alaska are age-structured. In the eastern Canadian Arctic, juveniles and mothers with calves tend to remain apart from the rest of the adults during summer. Bowheads eat zooplankton, particularly euphausiids and copepods. Adaptations include great longevity, massive energy storage capability, a fairly sophisticated acoustic sense for ice navigation and long-range communication, and a peaked head profile with a “crown” for pushing up through ice to breathe.

Population Sizes and Trends

All populations were severely depleted during intense commercial whaling prior to the 20th century. In 2001, the Bering-Chukchi-Beaufort population consisted of approximately 10 470 whales (95% CI 8 100-13 500), with an estimated annual rate of increase of 3.4% (95% CI 1.7-5.0%).

The Hudson Bay- Foxe Basin population numbered at least 345 individuals in the mid-1990s. This estimate was not adjusted for submerged animals that would have been missed during the aerial surveys, and is the sum of 270 whales estimated in northern Foxe Basin (95% CI 210-331) and 75 in northwestern Hudson Bay (95% CI 17‑133). In 2003, the best partial estimate for the Hudson Bay-Foxe Basin population (corrected for animals underwater) was 1026 individuals (95% CI = 338-3124, using a correction factor of 3.8).

The Davis Strait-Baffin Bay population numbered at least 11 000 whales prior to commercial whaling. At least 375 whales were present in the early 1990s (95% CI 315 to 435; uncorrected estimates), but more extensive surveys in 2003 resulted in a partial estimate (corrected for submerged animals) of between 1539 (95% CI = 63-3770) and 1944 individuals (95% CI = 797- 4762).

The best partial estimate for the combined 2002 eastern Canadian arctic bowhead populations was 5016 (95% CI = 2611-9633) (i.e., Davis Strait-Baffin Bay and Hudson Bay-Foxe Basin populations combined).

No quantitative data are available for trend analyses of either of the two eastern arctic populations.

Limiting Factors and Threats

The bowhead is a large, long-lived species with low fecundity and small population sizes. It has a fairly narrow niche in high northern latitudes and can be affected by a range of human activities (underwater noise and illegal hunting) and by climate change that reduces ice coverage and refuge from predation by killer whales.

Special Significance of the Species

Bowheads are hunted by Alaska Natives for subsistence and cultural purposes. A much smaller hunt by Inuit takes place in the Canadian Arctic.

Existing Protection or Other Status Designations

All bowhead populations in Canadian waters were designated as Endangered in 1980. The population in the Beaufort Sea was last reviewed in 1986. The species is legally protected in Canada under the Cetacean Protection Regulations of 1982, with hunting allowed only by permit. Bowhead whales are currently listed as Endangered under the US Endangered Species Act of 1973 and as Depleted under the US Marine Mammal Protection Act of 1972.