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

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.