Science Advisory Report 2021/021

Assessment of snow crab (Chionoecetes opilio) in the southern Gulf of St. Lawrence (Areas 12, 12E, 12F and 19) to 2020 and advice for the 2021 fishery

Summary

• Snow crab in the southern Gulf of St. Lawrence (sGSL) is considered to be a single stock unit for assessment purposes and comprises snow crab fishing areas 12, 12E, 12F, and 19.
• The landings of snow crab from the sGSL in 2020 were 28,270 tonnes (t) from a revised quota of 31,152 t. Catch per unit of effort have decreased in all fishing areas in 2020 from 2019.
• Concerns of biomass overestimation were raised during the 2019 assessment and persisted in 2020. Indicators of survey biases were presented with supporting data and hypotheses were discussed.
• The exploitation rate of the 2020 fishery was estimated at 35.6% based on the 2019 survey commercial biomass estimate. However, overestimation of the commercial biomass would imply that the exploitation rate during the 2020 fishing season was higher than estimated.
• The 2020 commercial biomass was estimated at 77,748 t and composed of 75% recruitment and 25% of residual biomass.
• Overestimation biases ranged from 30 to 40% among mature females and sub-legal males. Overestimation bias estimates among commercial crab were estimated at 14%, though this value was deemed less reliable because of complex fishery-related dynamics.
• Recurrent overestimations of the commercial biomass would result in exploitation rates exceeding the agreed upon level in the Precautionary Approach harvest decision rules.
• The risks of biomass indicators falling under the limit and upper stock reference points assuming different levels of overestimation biases were presented. However, no consensus on the level of overestimation bias was reached.
• Despite overestimation in the abundance indices, the stock continues to show signs of sustained recruitment and productivity. Overall, the stock is expected to remain in the healthy zone of the Precautionary Approach.
• A plan will be developed to address bias and catchability issues for the upcoming surveys and consistency in the indicators used in the stock assessment.
• There is continued evidence of warming conditions in the sGSL and the extent to which it could impact snow crab population dynamics and distribution is not well understood.

This Science Advisory Report is from the February 10-11, 2021 regional advisory meeting on the stock status in 2020 and fishery advice for 2021 for Snow Crab from the Southern Gulf of St. Lawrence. 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 2021/021 (PDF, 1,580 KB)

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