An evaluation of the current minimum legal size limit for the Dungeness crab (Cancer magister Dana) fishery near Tofino, British Columbia

The Dungeness crab (Cancer magister Dana) trap fishery in British Columbia has been regulated by a minimum legal size limit of 165 mm spine-to-spine carapace width (CW, 154 mm notch-to-notch CW) since early this century. Evaluation of the size limit by yield- and eggs-per-recruit analyses has been precluded by a lack of information on basic population variables such as growth, mortality, movement and mating behavior. Information on these variables was obtained in an intensive two year study of the Dungeness crab fishery near Tofino, B.C. from April 1985 until March 1987. A cohort of pre-recruit males and females was followed as the males entered the fishery and were subsequently exploited, yielding information on moult increments-at-size , length of intermoult periods, size-at-maturity, size of mating pairs, mortality, movement, commercial fishing success and exploitation rates. Male C .magister entered the fishery during their fourth year after settlement. Size frequency analysis revealed that nearly all legal-sized (>154 mm notch-to-notch CW) males are within the 155.0±11.2 mm instar (≈50% of this instar). Sublegal-sized males in this instar have a high annual natural mortality rate (M=2.8-4.5), hence a low probability (