Science Advisory Report 2020/014

Assessment of snow crab (Chionoecetes opilio) in the southern Gulf of St. Lawrence (Areas 12, 19, 12E and 12F) to 2019 and advice for the 2020 fishery

Summary

• Snow crab in the southern Gulf of St. Lawrence (sGSL) is considered as a single stock unit for assessment purposes. This stock unit comprises snow crab fishing areas 12, 19, 12E, and 12F.
• The landings of snow crab from the sGSL in 2019 were 31,707 tonnes (t) from a revised quota of 32,215 t.
• The exploitation rate of the 2019 fishery in the sGSL was estimated at 39.3%.
• The catchability for commercial-sized adult male snow crab in the snow crab bottom trawl survey is assumed to be constant over the time series and equal to one. The catchability for commercial-sized adult male snow crab in the snow crab bottom trawl survey is assumed to be constant over the time series and equal to one. The snow crab indices from the 2019 trawl survey are likely overestimated due to an unplanned change in trawl hauling procedures in 2019. This resulted in the trawl fishing and catching snow crab over a larger area than estimated using the standardization procedures in this assessment.
• The 2019 post-fishery survey biomass of commercial-sized adult male crabs (carapace width (CW) >= 95mm) was estimated at 79,066 t (95% confidence interval of 69,072 to 90,091 t), which is similar to 2018. The estimated biomass for the 2020 fishery, derived from the 2019 survey, is within the healthy zone of the Precautionary Approach (PA) framework.
• Total commercial biomass in the 2019 survey was composed 75% of new recruitment (58,995 t) and 25% of residual biomass (20,291 t).
• Based on the agreed harvest decision rule, the point estimate of the biomass in the 2019 survey of 79,066 t corresponds to an exploitation rate of 40.6% and a Total Allowable Catch (TAC) of 32,101 t for the 2020 fishery. At this harvest level, there is zero chance of residual biomass post-fishery in 2020 being in the critical zone.
• A risk assessment to attainment of PA objectives given potential positive biases in the 2019 commercial biomass estimate is provided.
• Despite the possible overestimation concerns of the 2019 assessment, the biomass of commercial-sized adult males is considered to be at a high level and in the healthy zone of the PA. There is a broad distribution of snow crab in the sGSL and continued positive signs of sustained recruitment and high female abundances.

This Science Advisory Report is from the February 5-6, 2020 regional advisory meeting on the Stock assessment of the southern Gulf of St. Lawrence snow crab stock to 2019 and catch advice for the 2020 fishery. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2020/014 (PDF, 1,911 KB)

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