Estimating Relative Abundance of the Female Blue Crab Spawning Stock in North Carolina

Abstract

Accurate assessment of the spawning stock should be important in informing fisheries management decisions. The life history and behav ior of blue crabs (Callinectes sapidus) makes assessment of the spawning stock complex. In North Carolina, female blue crabs undergo their terminal molt and mate from March through November. After a variable amount of time, their ovaries mature and they extrude their first clutch of eggs. Crabs that mature in the upper estuary move from low salinity ( 22 ppt) to release their first clutch of eggs. Crabs in good habitat then forage and produce subsequent clutches of eggs, continuing to move seaward with each subsequent clutch. Thus, at any particular location, different spawning crabs will be seen each month and will build up in high salinity areas in the sounds and in the coastal ocean. The spawning population peaks in number in August/ September with some crabs releasing their first clutch and others releas ing their second or higher clutch. Using blue crab bycatch data from Division of Marine Fisheries monthly gill net surveys may be helpful in estimating blue crab spawning stock. Gill net data show the monthly pattern of spawning stock movement from low to high salinity and the