Research Document - 2005/059
Criteria and Proposition for the Definition of Snow Crab (Chionoecetes opilio) Production Units in the Estuary and Northern Gulf of St. Lawrence
By Sainte-Marie, B., R. Dufour, L. Bourassa, D. Chabot, M. Dionne, D. Gilbert, A. Rondeau, and J.-M. Sévigny
Abstract
The current borders of snow crab management areas in the Department of Fisheries and Oceans (DFO) Québec region are not based on biological or oceanographical criteria and some times enclose territories with very different characteristics. As noted by the FRCC (2005), there is a need to define biological production units to better monitor the status and ensure conservation of populations. Toward that goal, we conducted a literature review and used trawl data from the Gulf of Saint Lawrence to identify the biological and physical factors that constrain the distribution and dispersal of snow crab. This information allows us to characterize snow crab habitat, which can be defined as a territory with bottoms of soft sediments, bathed by waters with a salinity > 26 ‰, part of which is at a temperature of 0-2°C and the remainder at a temperature varying from about –1.5 to 4 °C. The surface waters above this territory must generally have a salinity > 26 ‰ and warm up to 5–15 °C for several weeks for larvae to survive and grow. Snow crab larvae can disperse themselves over long distances and this may explain the weak genetic differentiation of populations within the Gulf. However, the various benthic stages generally have a much smaller dispersal capability. We describe the criteria used to define biological production units and on that basis we propose to divide the territory under the responsibility of DFO-Québec into seven units.
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