Science Advisory Report 2023/030
*This advice was developed in a peer review meeting in 2020 and should be interpreted within the context of the situation at that time.
Estimates of abundance and total allowable removals for Hudson Bay-Davis Strait Atlantic Walrus (Odobenus rosmarus rosmarus) stock
Summary
- Aerial surveys of terrestrial haul out sites and adjoining coastline were flown during September 2017 to determine abundance of Walruses belonging to the Hudson Bay Davis Strait (HBDS) stock.
- The survey covered northern Hudson Bay, southern Foxe Basin, Hudson Strait, and southeastern Baffin Island.
- Uncorrected counts of hauled out Walruses in the surveyed area totaled 13,400.
- These counts were adjusted to account for animals at sea during the survey. The adjusted aerial survey estimate for the HBDS stock is 44,600 (95% CI = 19,500–102,000; rounded to the nearest 100).
- A survey of the northern Hudson Bay Hudson Strait component of the HBDS stock flown in 2014 produced an adjusted abundance estimate of 7,100 (95% CI = 2,500–20,400). In 2017, there were an estimated 38,500 (95% CI = 15,100–98,300) Walruses for the same area.
- The difference between the two estimates is greater than what would be expected from population growth alone. The higher 2017 count may have resulted from a greater proportion of animals hauled out than assumed, particularly at Walrus Island in northern Hudson Bay. Another possibility is movement of Walrus from other areas (e.g., Foxe Basin) into northern Hudson Bay, or a combination of the two factors. However, there were no reports of unusual Walrus movements in 2017.
- A population model fitted to the survey data and Canadian harvest data estimated a total abundance of 8,200 (95% CI = 5,800–19,700) for the northern Hudson Bay Hudson Strait component of the HBDS stock. Adding in the estimated abundance for Walruses along the east coast of Baffin Island (3,900; 95% CI = 2,200–7,200) results in a total abundance of 12,100 (95% CI = 7,000– 20,800) for the HBDS stock.
- The Potential Biological Removal estimate for the HBDS stock is 360, assuming a Recovery Factor of 1.
- Reported harvest levels by Canadian communities harvesting from this stock have declined from a high of 604 in 1954 to an annual estimated average of 95 animals over the last five years. Assuming a combined struck and loss (S&L) and non-reporting rate of 44% derived from a population model results in an estimated total annual removal of 137.
This Science Advisory Report is from the 17–22 February 2020 National peer review meeting on Hudson Bay Davis Strait Atlantic Walrus abundance estimate. 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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