Science Advisory Report 2022/024
Harvest advice for eastern Hudson Bay and James Bay beluga (Delphinapterus leucas)
- A genetic re-analysis of nearly 3000 beluga samples from the Hudson Bay-Strait complex reaffirmed the existence of four populations (WHB, EHB, JAM, Cumberland Sound), and distinguished a new population in the Belcher Islands (BEL).
- The BEL and EHB populations overlap genetically and in summer distribution, making it impossible to distinguish animals belonging to these two populations either in the harvest or during the aerial abundance surveys. Therefore, these two populations were combined for the purposes of stock assessment to form a BEL-EHB stock.
- Total harvest in Nunavik averaged 344 beluga/year during 2016-2021. Three hundred and sixty-six beluga were harvested in 2021-2022.
- The new genetic analysis was used to adjust the harvest time series which increased the proportion of the newly defined BEL-EHB stock in the total harvest. The greatest changes in proportions were observed in the Hudson Strait Fall, Northeastern Hudson Bay Fall and Sanikiluaq (Belcher Island, Nunavut) harvests.
- In Hudson Strait, the proportion of BEL-EHB beluga in the harvest is higher in Fall, than during Spring. In October and early November, the proportion of BEL-EHB beluga in the harvest is approximately 50%, but this proportion declined to approximately 10% by the 3rd week of November.
- Using the new proportions and the newly defined BEL-EHB stock, an average of 95 beluga were removed annually from the BEL-EHB stock between 2016-2021 by Nunavik hunters. An estimated 139 BEL-EHB beluga were harvested in 2020-21.
- In Sanikiluaq, using these new proportions and the newly defined BEL-EHB stock, an average of 24 animals were removed annually from the BEL-EHB stock between 2016-2021. An estimated 19 BEL-EHB beluga were harvested in 2020-21.
- As in the past, visual line-transect surveys were flown in July-August 2021 to estimate beluga abundance in eastern Hudson and James Bays. Ungava Bay was not surveyed.
- New survey-specific correction factors were developed for availability and perception bias and applied to the time series.
- Survey corrected abundance estimates were 16,300 (95% CI=9,800-27,200) for James Bay and 2,300 (95% CI=1,300-4,200) (rounded to the nearest 100) for the BEL-EHB stock.
- The 2021 BEL-EHB abundance estimate is the lowest in the time series and has the smallest confidence interval.
- A population model was fitted to the aerial survey estimates, considering reported harvests and the proportion of BEL-EHB stock animals in the harvests, to provide information on abundance trends and sustainable harvest levels.
- For the BEL-EHB stock, the model estimated a 2015 abundance of 3,500 animals declining to 2,700 (95% CI=1,500-3,700) beluga in 2021 for an average rate of decline of 4%/year.
- An alternative BEL-EHB model run assumed a 2021 survey coefficient of variation of 48%. This run provided an abundance estimate of 3,900 in 2015, declining to 3,200 (95% CI=1,600-4,600) beluga in 2021 for an average rate of decline of 3% per year.
- The decline is associated with a combination of the Total Allowable Take (TAT) being exceeded and an under-estimate of the proportion of BEL-EHB stock animals in the harvest.
- In James Bay, the model estimated a 2021 abundance of 19,200 (95% CI=12,500-25,100) in 2021. The population has levelled off since the last assessment. The Potential Biological Removal for this population would be 335 beluga per year.
- For the BEL-EHB stock, the management objective is to ensure a 50% probability that the stock will be at or above the 2015 abundance estimate of 3,400 animals after 5 years and 10 years. The model estimates that harvest levels of 0 and 20 beluga respectively would respect this objective. In the alternative model run, assuming a 2021 survey coefficient of variation of 48%, harvests of 48 and 65 beluga would respect the management objective after 5 and 10 years respectively.
- However, since the last assessment, new availability and perception bias corrections have been applied and there is a new survey estimate of abundance. Together these changes result in different estimates of abundance in 2015 of 3,500 or 3,900 animals depending on model scenario. To respect the new benchmarks (3,500 or 3,900), harvest levels need to be reduced to 0-65 BEL-EHB beluga depending on the model scenario, and time frame. The Potential Biological Removal is 5 animals/year assuming a Recovery factor of 0.1.
This Science Advisory Report is from the February 14-18, 2022 Annual Meeting of the National Marine Mammal Peer Review Committee (NMMPRC) on Population status assessment for beluga stocks in Nunavik (northern Quebec). 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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