Increasing the Selectivity of the Stone Crab Menippe mercenaria Trap by the Addition of a Cull Ring

The fishery for stone crab Menippe mercenaria in Florida is dominated by plastic traps that do not require a cull ring or device that limits retention of prerecruits and bycatch. An experiment was conducted to determine what size of cull ring would reduce the catch of prerecruit stone crabs and bycatch while maintaining legal catch. Catch compositions of crabs from unmodified plastic commercial stone crab traps and traps fitted with a 54.0-, 55.6-, or 57.2-mm cull ring were compared in the stone crab fishery across Florida's west coast. Traps outfitted with cull rings retained bigger crabs, less bycatch, and fewer prerecruit stone crabs and, for most cull ring sizes tested, yielded the same number of legal-size claws. Retention of prerecruit crabs in traps with cull rings varied among regions because of the sexual dimorphism in carapace length (males, 58.2mm; females, 64.6mm) observed when an original crusher claw has reached legal size (>70mm). We recommend that a minimum size cull ring of 55.6-mm (2(3)/(16)in) be used in stone crab traps fished in state and federal waters off Florida.