Research Document - 2015/084

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, 1980-2014

By H.P. Benoît and N. Cadigan

Abstract

The research vessel bottom-trawl survey of the southern Gulf of St. Lawrence undertaken each September (RV survey) has been shown to provide reliable standardized indices of biomass, spatial distribution and habitat use of commercial-sized male snow crab (Chionoecetes opilio) for 2001-present and of all snow crab (aggregated index) for 1980-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 2014 RV survey. Furthermore, the document provides an update of the model-based estimates of commercial crab abundance, as well as a presentation and discussion of a few changes that were made for that estimation since 2014. This information was provided in support of the regional snow crab assessment process that took place in Moncton, NB on January 27-29, 2015. Of particular note, the RV survey confirmed continued high biomasses of commercial-sized adult male snow crab since 2011 which were also estimated by the dedicated snow crab survey. Model-based estimates of commercial crab abundance in 2013 and 2014 were above the long-term average. The 2014 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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