Abundance and Potential Biological Removal (PBR) Estimates for Canada’s High Arctic Atlantic Walrus Management Stocks, Summer 2022

Abstract

The High Arctic Atlantic walrus (Odobenus rosmarus rosmarus) population in the eastern Canadian Arctic comprises three management stocks: Penny Strait-Lancaster Sound (PS-LS), West Jones Sound (WJS), and Baffin Bay (BB). Photographic aerial surveys of haulout sites and adjoining coastline were flown during August 2022 to update stock abundances last estimated in 2009. The areas that were surveyed included most of the known distributions of the PS-LS and WJS stocks and focused on the summer core-use area of the BB stock. Two surveys of both the PS-LS (August 13-16 and 24-27) and WJS (August 17-18 and August 22) stocks were completed, while the summer core-use area of the BB stock was surveyed three times (August 7, 16, and 26). Abundance estimates from the first survey replicates of each stock were used as the basis for scientific advice due to uncertainty regarding walrus movements between subsequent surveys. Abundance estimates accounted for animals at sea during the survey using the average proportion of time hauled-out (P = 0.3) and correlated walrus haulout behaviour. First survey abundance estimates were 887 (95% confidence interval [CI] = 475–1,653) for the PS-LS stock; 1,157 (95% CI = 618–2,166) for the WJS stock, and 847 (95% CI = 254* – 3,286) for the BB stock. Potential Biological Removal (PBR) estimates based on the first surveys of each stock are 6.8 walruses for the PS-LS stock, 8.8 for the WJS stock, and 4.7 for the BB stock. PBR estimates were calculated using a recovery factor (RF) of 0.25. PBR estimates are heavily dependent on the selected RF value and updated PBR estimates may differ from previous estimates largely due to this term in the calculation. Reported Canadian hunts from each of the three High Arctic management stocks are generally lower than PBR estimates. However, the winter hunt of walruses in Greenland exceeds the PBR estimate for the shared BB stock.