A new fishery for grooved Tanner crab (Chionoecetes tanneri) off the coast of British Columbia, Canada

A new fishery for grooved Tanner crab (Chionoecetes tanneri) off the coast of British Columbia, Canada

G.D. Workman, A.C. Phillips, F.E. Scurrah, and J.A. Boutillier

A new fishery for grooved Tanner crab (Chionoecetes tanneri) off the coast of British Columbia, CanadaThis is part of Crabs in Cold Water Regions: Biology, Management, and Economics
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A process for controlled, stepwise development of a new fishery for the deepwater grooved Tanner crab, Chionoecetes tanneri, off British Columbia, Canada, is described. This is the first new fishery on the Pacific coast of Canada to which this process has been rigorously applied. The "Phased Approach" is designed to ensure that sufficient biological information is gathered throughout development of the fishery to minimize risk to the target species and/or any other fish stock or marine community impacted by the new fishery, while working toward an eventual viable and sustainable managed fishery. We describe trawl and trap surveys undertaken to assess the abundance and distribution of C. tanneri off Canada's west coast and the methods used to produce biomass estimates for surveyed areas. The Canadian Department of Fisheries and Oceans (DFO) conducted a trawl survey off the west coast of Vancouver Island between July 21 and August 3, 1999, during which 34 trawl sets were completed covering an area of 600 km2 (60 km ¥ 10 km). Tanner crabs were present in all but four sets with an average catch rate of 13.08 kg per hour. The survey trawl retained Tanner crabs ranging in size from 10 to 176 mm carapace width (CW). The population was partitioned by depth with mature hard-shell male Tanner crabs (>110 mm CW) found at the shallowest depths (~550-650 m), and mature ovigerous females and soft-shelled males occurring deeper (~650-750 m). Subadult (40-100 mm CW) crabs were found at the greatest depths (~900-1,000 m) while juveniles (<40 mm CW) were found in all depths. Size at 50% morphometric maturity was determined to be 112 mm CW for males and 88 mm CW for females. The fishery proponents conducted a distributional trap survey between December 16, 1999 and March 31, 2000 off the west coast of Vancouver Island covering an area of approximately 5,500 km2 (500 km ¥ 11 km) with 231 sets of survey gear totaling 7,600 individual trap hauls. Catch rates for large male crabs (>112 mm CW) ranged from 0 to 18 per trap with an average of 2. The biomass of large males (>112 mm CW) was estimated to be 672 t for surveyed areas off the west coast of Vancouver Island. A summary of biological findings to date, estimates of Tanner crab biomass by area, and an assessment of Tanner crab mortality in other existing fisheries are also presented. Finally, we propose a rationale and design for an experimental harvest in the form of a depletion experiment and an evaluation of the "Phased Approach" as a fisheries development process.

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