Research Document - 2005/017

An estimate of the Western Hudson Bay beluga population size in 2004

By Richard, P.R.

Abstract

Aerial surveys of belugas were flown in western and southern Hudson Bay between 29 July and 6 August 2004. A combination of aerial visual line-transect surveys and photographic surveys were used to estimate the numbers of belugas present in that region. These estimates were corrected for availability bias based on a correction factor obtained from target experiment and beluga surfacing observations conducted in the similarly-silted waters of the St. Lawrence. These aerial surveys have allowed us to produce a most conservative estimate for this population, represented by the sum of the estimates of the Churchill-Seal and Nelson areas, and rounded to the nearest hundred, of 57,300 (95% C.L.: 37,700-87,100). There were belugas seen in an adjacent stratum but it is unclear if they moved into those areas between surveys. The uncorrected estimate of belugas (i.e.: seen near the surface) in the Churchill-Seal and Nelson areas (27,200) is very similar to the number (25,100) estimated in 1987. We conclude that the population has not experienced a detectable change in numbers since 1987. More than 7,000 belugas were also estimated to occur along the Ontario coast of Hudson Bay but it is difficult to assign them all to a single beluga stock due to a lack of stock identity information. It is also possible that some moved out of the Nelson stratum into that Ontario coast stratum between survey days.

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