Assessing the potential for stock enhancement in the case of the Chesapeake Bay blue crab (Callinectes sapidus)

Abstract

In certain cases of severely depleted fishery stocks, combining stock enhancement with traditional management techniques may be a useful way of returning stocks to an exploitable size. The Chesapeake Bay stock of blue crabs (Callinectes sapidus) has declined over the past decade and appears to be recruitment-limited, making it an appropriate candidate for enhancement efforts. This study serves as a first step in determining whether large-scale enhancement of blue crab stocks is feasible. Four hatchery-raised cohorts of 4000 – 10 000 (25 000 in total) juvenile (6–30 mm carapace width, 58–70 days old) crabs were released in upper Chesapeake Bay coves. Sixty days after release, these crabs constituted 22%–79% of all crabs in the hatchery-crab size range (corresponding to an enhancement level of 28%–366%). Crabs released earlier in the summer reached maturity at the age of 6 months, younger than their wild counterparts. Estimated survivorship to maturity was 16%–20% for early-released crabs and 5–15% for late-released crabs. Late-released crabs, like wild crabs, had to overwinter before becoming mature. Our study suggests ways to improve success of hatchery-raised individuals that can be broadly applied across taxa. The results also contribute specifically to determining whether large-scale stock enhancement is possible in the case of the Chesapeake Bay blue crab.