Science Advisory Report 2018/008

Harvest advice for eastern and western Hudson Bay Beluga (Delphinapterus leucas)

Summary

• Aerial surveys designed to estimate beluga abundance in Hudson, James and Ungava bays were conducted during August 2015. Surveys were completed of belugas in high concentration areas around the Nelson, Churchill and Seal River estuaries on the western side of Hudson Bay, in James Bay, and eastern Hudson Bay. Owing to inclement weather, surveys did not cover northwest Hudson Bay, the Ontario coast and Ungava Bay.
• Although UB was not surveyed, no belugas were detected during systematic surveys flown in 1985, 1993, 2001 and 2008. This indicates that there is a strong probability that the stock numbers less than 100 individuals.
• Aerial survey estimates of abundance, accounting for submerged animals, were 54,500, 10,600 and 3,800 (rounded to the nearest 100) for the western Hudson Bay, James Bay and eastern Hudson Bay respectively.
• Genetic analyses have shown that the proportion of Eastern Hudson Bay (EHB) beluga in the harvest of hunters from Nunavik and the Nunavut community of Sanikiluaq varies spatially and seasonally.
• After correcting for struck and loss, annual reported harvests of 88, 68 and 43 EHB type belugas will have a probability of the stock size increasing by 25%, 50% and 75%, respectively, over the next 10 years.
• A precautionary approach framework was developed that accounts for the amount of data available for a particular stock. Criteria were identified that could be used to evaluate which approach could be applied to different stocks. For stocks where there is considerable information (Data Rich), two approaches that identified management objectives and reference levels were identified. For these frameworks, the probability of different harvest levels attaining the management objectives can be expressed explicitly.
• For stocks where less information was available (Data Poor), the Potential Biological Removal (PBR) approach was applied. Criteria for identifying the recovery factor to be used in the PBR equation were also developed.
• Information on the EHB stock allows it to be managed using the Data Rich frameworks and was considered to lie in the Cautious zone.
• One PA framework is based on the DFO- Maximum Sustainable Yield (MSY) framework and sets the Precautionary and Limit Reference Levels at 48% and 24% of K, a proxy for the maximum stock size that the ecosystem is able to support. Harvests between 26 and 61 EHB belugas would allow the stock to increase to the Healthy zone (i.e. recover above 4000 EHB belugas), within two generations (50 years) with probabilities of 80% and 50% respectively.
• The second PA framework, based on the DFO-Atlantic Seal Management framework, sets the Precautionary and Limit Reference Levels at 70% and 30% of the largest stock size observed or estimated. Harvests of 17 and 50 EHB belugas would allow the stock to increase to the Healthy zone (i.e. recover above 4700 EHB belugas) within two generations (50 years) with probabilities of 80% and 50% respectively.
• WHB belugas are abundant, but are considered to be Data Poor and therefore, the Potential Biological Removal (PBR) approach should be used to estimate a Total Allowable Harvest (TAH).
• Using a Recovery Factor of 0.75, (based upon Recovery Factor criteria reviewed during the assessment), the PBR estimate for WHB belugas would be 753 animals. Current reported harvests of WHB animals are at 495 belugas from the Nunavut and Nunavik hunts. If a Struck and Loss rate of 1.18% was assumed, then total removals are on the order of 584 animals, which is below the PBR level.

This Science Advisory Report is from the October 17-21 2016 on Eastern and Western Hudson Bay Beluga - 2015 Aerial Survey Abundance Estimates and Sustainable Harvest Advice. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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