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

Summary of Status Report

Prior to commercial whaling, the Bering-Chukchi-Beaufort population is estimated to have numbered 10 400-23 000 (reduced to fewer than 3 000 at the end of commercial whaling). In 2001, that population was estimated to contain 10 470 (95% CI 8 100-13 500) whales, increasing at an annual rate of 3.4% (95% CI 1.74-5.0%).

The Hudson Bay population (excluding the Foxe Basin segment) was estimated to number 440-470 whales, and the Davis Strait-Baffin Bay population was estimated to number 12 000 whales prior to the onset of commercial whaling. In 1994 the Foxe Basin segment of the northern Foxe Basin summering aggregation was estimated to number 270 bowheads (95% CI 210 to 331), and in 1995 the Hudson Bay segment was estimated to number 75 bowheads (95% CI 17 to 133), with no correction in either case for submerged animals that would have been missed by the observers, e.g., due to submergence. In 2003, the best partial estimate for the Hudson Bay-Foxe Basin population (corrected for animals underwater) was 1026 individuals (95% CI = 338-3124) (DFO 2005, Cosens et al. 2005). However, there is considerable uncertainty in the estimates (given the wide confidence limits) and there is an error in calculating the probability of detecting bowheads in 2003 that is believed to have positively biased the estimate by some unknown amount.

The Davis Strait-Baffin Bay population was estimated in the early 1990s to number at least 375 (95% CI 315 to 435; uncorrected estimates), but more extensive surveys in 2002-2004 resulted in a partial estimate (corrected for submerged animals) of between 1539 (95% CI = 631- 3770) and 1944 individuals (95% CI = 797 – 4762) (Cosens et al. 2005, DFO 2005). 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 population and Hudson Bay-Foxe Basin population combined) (DFO 2005, Cosens et al. 2005). However, estimates have extremely wide confidence limits, the correction factor applied to estimate total abundance is overly optimistic, and quantitative data are insufficient to assess trends for either population.

The bowhead has great cultural and, potentially, economic significance to Inuit in parts of the Canadian Arctic. NWMB (2000) documented knowledge of interactions between killer whales and bowheads, including predation and the effect of killer whales on bowhead behaviour, distribution, and migration. In addition to predation, climatic factors that influence ice conditions may affect the survival and distribution of bowhead whales. An additional concern is the increased interest in offshore oil and gas development in the Beaufort Sea and the eastern Arctic. Bowhead whales respond to man-made sources of underwater noise. They avoid seismic vessels, with avoidance responses observed at distances of up to 20 km from the sound source. Such disturbance would be significant if the seismic vessel was operating in a prime feeding area at a time when bowheads are present.