Research Document - 2011/126

Information on abundance and harvest of Ungava Bay beluga

By T. Doniol-Valcroze and M.O. Hammill

Abstract

Beluga whales (Delphinapterus leucas) were historically abundant in Ungava Bay (Nunavik, Quebec), where they are considered to form a distinct summer stock based on their disjoint summer distribution and their fidelity to certain areas. This stock has been depleted by commercial whaling and its recovery has been limited by excessive subsistence hunting. Its current population size is unknown. It is important to determine the maximum harvest that can take place in Ungava Bay in the context of managing both this stock and the Eastern Hudson Bay stock (EHB).

Systematic aerial surveys were flown in 1985, 1993, 2001, and 2008, but no whales were seen within the strip-width of the transects. Based on the 1993 survey, an imprecise upper 90% confidence limit of 150 individuals was proposed. This number, however, was not corrected for availability and does not include the results of previous and subsequent surveys. To provide probabilistic statements about the impact of different harvest levels, we used a Bayesian approach which allowed us to make use of all four surveys with zero-counts. Using the mean group size observed during surveys and the correction factors for animals underwater, the mean estimate of the current population size was 32 individuals (95% CI 0–94). With this estimate, the Potential Biological Removal was equal to 0.16 individuals. Assuming an annual growth rate of 2.7%, the harvest levels for which there is a 5%, 50% and 75% probability of stock increase were 0.95, 0.63, and 0.32 respectively.

The proportions of EHB beluga in harvest samples from the five communities of Ungava Bay as well as Quaqtaq have been estimated at 2% ± 7% in spring, 4% ± 9% in summer, and 28% ± 9% in the fall. These numbers suggest that EHB beluga do not pass by Ungava Bay in great numbers during the spring migration. The high proportion of EHB beluga in the fall is difficult to interpret because samples from Quaqtaq have been pooled with those of communities from inside Ungava Bay. However, satellite telemetry has confirmed that EHB beluga migrate through Ungava Bay during their fall migration. Estimating the proportion of UB beluga at different times of the year is not possible without a dedicated genetic analysis and might be limited by small sample size.

Our results indicate that any harvest from the UB stock poses a threat to its recovery. There is currently a Total Allowable Take of 10 beluga per year in Ungava Bay in the three-year management plan (2011−2013), but 17 beluga were taken there in 2011. The hunt is open from June 24 to August 31, to minimize the amount of EHB beluga killed. However, hunting in Ungava Bay in the summer probably increases the probability of taking UB beluga. A detailed genetic analysis that focuses on Ungava Bay is necessary to better understand the contribution of each stock to the harvest.

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