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Research Document - 2009/053

The 2008 assessment of snow crab, Chionoecetes opilio, stocks in the southern Gulf of St. Lawrence (Areas 12, 19, E and F)

By M. Hébert, E. Wade, M. Biron, P. DeGrâce, R. Sonier and M. Moriyasu

Abstract

The 2008 assessment of the southern Gulf of St. Lawrence snow crab, Chionoecetes opilio, stock (Areas 12, 19, E and F) was based on data from the commercial fishery (fishermen’s logbooks, at-sea observer measurements and quota monitoring reports) and trawl surveys. The 2008 landings in Area 12 were 20,911 t (quota of 20,900 t) with an average catch per unit of effort (CPUE) of 56.4 kg/trap haul (kg/th) and a total fishing effort of 370,762 trap hauls. The CPUE decreased from 2007 (65.7 kg/th) but has remained high since 2003. Some indicators (e.g., CPUE, mean size of commercial-sized adult males and incidence of soft-shelled crabs) show that the fishery performance was good in 2008. The 2008 landings in Area 19 were 2,929 t (quota of 3,002 t). The CPUE was 76.3 kg/th and was within the range of values from previous years. In Area E, the 2008 landings were 187 t, 47% of the 400 t quota. The CPUE decreased in 2008 (20.3 kg/th) to the lowest value of the time series (1995-2008). The 2008 landings in Area F were 431 t, representing 74% of the 585 t quota. The CPUE decreased in 2008 (27.8 kg/th) to the second lowest value of the time series (1995-2008).

Snow crab in management Areas12, 19, E and F comprise a single biological population and the southern Gulf of St. Lawrence stock is considered as one unit for assessment purposes. The 2008 survey biomass of commercial-sized crabs in the southern Gulf of St. Lawrence was 48,000 t (43,800 t – 52,400 t), a decrease of 16% compared to the 2007 estimate of 56,800 t (52,000 t – 61,800 t). Fifty six percent (56%) of the 2008 survey biomass, available for the 2009 fishery, is composed of new recruitment estimated at 27,100 t (24,100 t – 30,300 t). The recruitment to the fishery decreased by 13% relative to 2007.  The 2008 residual biomass estimated at 20,700 t (17,900 t - 23,800 t) decreased by 20% compared to 2007 (25,900 t) but it has been maintained at 20,000 t to 26,000 t since 2003. The recruitment to the fishery is expected to remain low into 2010. An increase in the abundance of prerecruits (R-4) of size between 56 and 69 mm of carapace width (CW) was observed in the 2008 trawl survey, which may indicate a potential upward phase in recruitment starting in 2011. The abundance of males smaller than 56 mm CW observed in the trawl surveys from 2002 to 2008 has increased but is lower than the previous recruitment waves observed from 1993 to 1998. The abundance of mature females has declined since 1990 and reached the lowest observed from 2006 to 2008. The 2008 exploitation rate in the southern Gulf of St. Lawrence, corrected for non-directed fishing losses, was 50%. Exploitation rates varied between 41% and 62% from 2000 to 2008 compared to 17% and 33% from 1990 to 1999. A risk analysis of consequences to biomass indicators relative to catch options for the 2009 fishery is provided. The choice of biomass indicator to use and the risk level (probability of the event happening) to apply are the decision of management and the stakeholders.

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