Scale Dependent Movements and Protection of the Female Blue Crab, Callinectes sapidus

Abstract

Little is known about the migration of female crabs (Callinectes sapidus) to spawning grounds or how effectively they are protected by North Carolina 'spawning sanctuaries'. To quantify migration, 300 mature female crabs were tagged and released the fall'01, summer'02, and fall'02, at each of three locations: Neuse River, Pamlico River, and Albemarle Sound. Tag returns indicate that females begin migration during Oct/Nov and that they probably do not complete their spawning migration until spring of the following year. To assess site fidelity and protection of females by spawning sanctuaries, 400 tagged adult females were released in/near Ocracoke and Hatteras spawning sanctuaries. They tended to be caught near their release site, suggesting that mobility declines once females reach euhaline waters, that animals move over scales larger than sanctuaries, and that they derive only temporary protection by entering sanctuaries. Ovigerous females fitted with ultrasonic pingers were tracked after release inside the boundary of Ocracoke spawning sanctuary. Crabs with orange (new) egg masses meandered over small areas with no directed movement, but those with eggs approaching hatching showed directed movement seaward.