Abundance estimate of Northwest Atlantic harp seals, Pagophilus groenlandicus, and harvest advice for 2025-2029

Abstract

The Northwest Atlantic (NWA) harp seal population is harvested for commercial and subsistence purposes in Canada and Greenland, and is caught incidentally in commercial fisheries. A new pup production survey in 2022 estimated total pup production at 614,100, the lowest estimate since 1994. Stock status is estimated using a Bayesian Integrated Population Model (IPM) which incorporates periodic estimates of pup production along with updated data on age composition, age-specific reproductive rates, total removals, and environmental conditions. Based on the IPM, NWA harp seal abundance increased rapidly from the 1970s through the 1990s, peaking at an estimated abundance of 7.5 million seals (95% Credible Interval, CrI: 6.75-8.42) in 1998. The population declined from 1998-2024 with the exception of a period of relative stability between 2009-2019. The estimated 2024 total abundance was 4.4 million seals (95% CrI: 3.65-5.35). This represents a decline in abundance from 2019 (5.6 million, 95% CrI: 4.78-6.63) at a rate of 4.7% (95% CrI: 2.14-7.45%) per year. Harp seals are managed under the Atlantic Seal Management Strategy (ASMS). Under the current ASMS, Nₘₐₓ (largest population observed or estimated) was estimated to be 7.5 million seals (95% CrI: 6.81-8.35).This results in a Precautionary Reference Point (PRP, 70% of Nₘₐₓ) of 5.3 million seals and a Limit Reference Point, (LRP, 30% of Nₘₐₓ) of 2.2 million seals. The estimated 2024 total abundance has a 96% probability of being below this PRP and is, therefore, in the Cautious Zone. Under the current ASMS, there is no harvest level that would have an 80% probability of the population increasing above the PRP in 10 years. Under the proposed Revised ASMS (R-ASMS), the environmental carrying capacity (K) was estimated to be 6.9 million seals (95% CrI: 5.27-8.48). This results in a PRP (70% of K) of 4.8 million seals and a LRP (30% of K) of 2.1 million seals. The estimated 2024 total abundance has a 80% probability of being below this PRP and is, therefore, in the Cautious Zone. Under the proposed R-ASMS, we estimated the sustainable harvest levels for the next five years (2025-2029) that would have an 80% probability of the population increasing above the PRP in 1.5 generations (30 years). The annual Atlantic Canadia sustainable harvest levels which meet this criteria are 253,000, 222,000, and 113,000 seals assuming harvest age compositions of 95%, 90%, and 50% young of the year, respectively. These harvest projections assume that ice conditions and environmental variables will remain similar to recently observed conditions. Harvest levels compatible with the harvest control rule would be less assuming future ice conditions were to deteriorate further as projected due to climate change.