Research Document - 2016/089

Trends in the biomass, distribution, size composition and model-based estimates of commercial abundance of snow crab (Chionoecetes opilio) based on the multi-species bottom trawl survey of the southern Gulf of St. Lawrence, 1980-2015

By Benoît, H.P., and Cadigan, N.

Abstract

The research vessel bottom-trawl survey of the southern Gulf of St. Lawrence undertaken each September (RV survey) provides reliable standardized indices of biomass, spatial distribution and habitat use of commercial-sized male snow crab (Chionoecetes opilio) for 2001 to the present and of all snow crab (aggregated index) for 1980 to the present. Furthermore, results from that survey have successfully been combined with data from a dedicated snow crab survey as part of model-based estimation of the abundance of commercial male snow crab. This document provides an update for biomass indices, spatial distribution, and size composition based on the results of the 2015 RV survey and an update of the model-based estimates of commercial crab abundance. This information was provided in support of the regional snow crab assessment process that took place in Moncton, NB on January 27-28, 2016. Of particular note, the RV survey confirmed a slight decline in the biomass of commercial-sized adult male snow crab from a recent high level, as was also estimated by the dedicated snow crab survey. Model-based estimates of commercial crab abundance in 2015 were above, yet close to, the long-term average. As in recent years, the 2015 RV survey captured an unusually high number of small crabs (≤15 mm) in several areas of the southern Gulf of St. Lawrence. This is seemingly part of a general increase in small crab abundance since the early 2000s.

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