Science Advisory Report 2005/036

Recovery Potential Assessment of Cumberland sound, Ungava Bay, Eastern Hudson Bay and St. Lawrence beluga populations (Delphinapterus leucas)

Summary

Cumberland Sound Beluga

• In Cumberland Sound, reconstruction of the historical population using the available catch information provides an estimated historical (pre-commercial whaling) population size of 8,465 (Standard Error (S.E.) = 426). A Bayesian model estimated the 2002 population size to number 2,018 (95% C.L.: 1,553-2,623), or 24% of its estimated historical population size. The population is estimated to be on an increasing trend even with the quotaregulated local subsistence hunt.
• A recovery target at 70% of historical population size would correspond to 5,926 individuals. This target could be reached in 40, 55 and 90 years for harvest scenarios of 0, 20 and 41 (actual quota), respectively. The population would likely decline under a harvest scenario of 60.
• Subsistence hunting might be considered as a threat to the Cumberland Sound beluga population. Nevertheless, the actual carefully managed subsistence hunt, that inflicts a low mortality rate, does not seem to be an impediment to recovery over the long term.

Eastern Hudson Bay Beluga

• Estimates of the historical (pre-commercial whaling) Eastern Hudson Bay (EHB) beluga population size using catch data and a population model suggest a minimum population of 12,500 belugas in 1854. Modelling of current population size indicates that the population has declined from 4,200 (SE=300) whales in 1985 to 3,100 (SE=800) in 2004, and would be at 25% of its historical size. The population would likely stabilize at current harvest levels (60 belugas).
• A recovery target at 70% of the historical estimate would represent 8,750 belugas based on current information. This target could be reached by 2046 with a complete closure of harvesting, by 2081 with a reduction in reported harvests to 25 animals, and by more than 150 years from now with a reported harvest of 40 animals.
• Subsistence hunting continues to be a cause for concern. There is uncertainty associated with total numbers of animals actually harvested by Inuit from Nunavut (Sanikiluaq), Nunavik and along the Labrador coast, as well as the stock identity of the animals taken by these hunters.

Ungava Bay Beluga

• In Ungava Bay, reconstruction of the historical population using the available catch information provides an estimated historical (pre-commercial whaling) population size of 1,900 animals in the late 1800s. There are no current estimates of abundance for this population, but modeling suggests that numbers are less than 200 animals. Small numbers of beluga continue to be seen in the Mucalic River, in southern Ungava Bay during the summer. This population may be extirpated and the few beluga observed in Ungava Bay may be from neighboring stocks.
• A recovered population of 70% of the historical estimate would number 1,330 animals. There is no scope for human induced mortality with this population. Any harvesting on this population poses a threat to recovery.

St. Lawrence Beluga

• Historical (pre-commercial whaling) abundance of beluga in the St. Lawrence River Estuary was likely in the order of 10,100 animals during the 1800s. High harvests led to a decline in the population. Although protected from harvesting since 1979, little sign of recovery has been observed. Fitting a population model to aerial survey data collected between 1988 and 2003 suggests that the population has increased only slightly from 900 (SE=70) animals in 1988 to 1100 (SE=200) animals in 2003.
• Since there is currently no harvesting of this population, it is unclear whether the failure of this population to increase more rapidly results from high mortality rates, a reduction in recruitment or a combination of the two. If the factors limiting growth of this population could be identified and rectified, then the population would be expected to reach the recovery population level of 7,070 by 2049. If current conditions continue, then recovery would not be expected before 2101.

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