Research Document 2021/010

The 2019 assessment of the snow crab (Chionoecetes opilio) stock in the southern Gulf of St. Lawrence (Areas 12, 19, 12E and 12F)

By Hébert, M., Surette T., Wade, E., Landry J.-F., and Moriyasu, M.

Abstract

The 2019 assessment of the southern Gulf of St. Lawrence (sGSL) snow crab, Chionoecetes opilio, stock (Areas 12, 19, 12E and 12F) is presented. Snow crab in the sGSL is considered as a single stock unit for assessment purposes. The 2019 assessment was conducted as per the recommendations of the Snow Crab Assessment Methods Framework Science Review held in November 2011. 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 positively biased, resulting from a change in vessel and trawl fishing procedures in 2019. The trawl may have been fishing and catching snow crab over a larger area than estimated using the standardization procedures in this assessment. For the purpose of the assessment, the estimates of the commercial biomass and all abundances of males and females presented here have not been corrected according to this bias. The exploitation rate of the 2019 fishery in the sGSL was 39.3 %. The 2019 post-fishery survey biomass of commercial-sized adult male crabs was estimated at 79,066 t (95 % confidence intervals 69,072 to 90,091 t), which is similar to 2018 (80,746 t). The available biomass for the 2020 fishery, derived from the 2019 survey, is within the healthy zone of the Precautionary Approach (PA) Framework. The residual biomass from the 2019 survey was estimated at 20,291 t, a decrease of 5.3 % compared to the 2018 survey estimate (21,432 t). Seventy-five percent (75 %) of the 2019 survey biomass, available for the 2020 fishery, is composed of new recruitment (58,995 t). The recruitment to the commercial biomass from the 2019 survey is similar to 2018 (59,609 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 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 of 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.

Research Document 2021/010 (PDF, 10,899 KB)

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