Science Advisory Report  2013/003

Advice on size and trend of the Cumberland Sound beluga whale population, 1990 to 2009

Summary

• Results of an aerial survey in 2009 indicate that the number of belugas in surveyed areas was lower than those estimated 1999.
• Present population within the survey area on 2 August 2009 was estimated at 788 belugas (2.5-97.5 bootstrap percentiles = 310-1,679).
• Comparison of the population indices for the three years of surveys suggests they do not reflect the underlying population dynamics because they imply unrealistic rates of increase or total mortality. Consequently, there must be sampling error which is unaccounted for by the survey results. 
• There are several possible sources of bias:
1. differences in the proportion of the population that was sampled each survey year (i.e., some belugas were outside of the surveyed areas);
2. inter-annual variation in the proportion of time that belugas spent at or near the surface during surveys;
3. unmeasured differences in survey efficiency at detecting belugas (e.g., observer error, visibility conditions) between survey years;
4. some aggregations of belugas were missed within the survey area.
• In view of these potential sources of uncertainty, it is recommended that Bayesian population dynamic modeling be conducted to see if unaccounted sources of error can be estimated from the model and to obtain a model estimate of the present population status of the Cumberland Sound population and the sustainable harvest.
• A new survey should be completed soon to better inform the trend analysis.

This Science Advisory Report is from the November 22-26, 2010 National Marine Mammal Peer Review Committee Meeting (NMMPRC). Additional publications from this process will be posted as they become available on the Fisheries and Oceans Canada Science Advisory Schedule.

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Inuktitut Atuinnaummijuq (PDF, 212 KB)

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