Importance of Season and Size of Release to Stocking Success for the Blue Crab in Chesapeake Bay

Abstract

A critical step toward optimizing the success of stock enhancement is to identify release strategies that maximize survival and enhance growth of released hatchery-reared individuals. A key, but often overlooked, consideration for optimizing release strategies is the interaction of factors (e.g., release season, release size, stocking density, release habitat, etc.). Here, we summarize seasonal and size-dependent patterns of survival and growth for juvenile blue crabs using long-term field tethering and experimental releases of hatchery-reared cohorts within the Rhode and South Rivers, Maryland, USA, and review the direct and interactive effects of these factors. Survival of both tethered and free-ranging hatchery-reared juvenile crabs was high in early spring and fall and lowest in summer. Survival was largely independent of size during spring and fall, but increased with size in summer, indicating that optimal size at release varies seasonally. Hatchery-reared juveniles from spring releases grew rapidly, matured during their first season, and migrated to the spawning sanctuary in the fall of their first year. While release season and size each had direct effects on enhancement success, the results also highlight the important interaction between release season and size on enhancement success using the blue crab in Chesapeake Bay as a model.

Keywords:

• stock enhancement
• release strategies
• blue crab
• Callinectes sapidus
• survival

ACKNOWLEDGEMENTS

We thank many undergraduate students and technicians for assistance in field and laboratory experiments. We also thank the many researchers and technicians at COMB for rearing the hatchery crabs used in this study. We are particularly grateful to U.S. Senator Barabara Mikulski, whose strong support made this research possible. Funding for this research was provided by the NOAA Chesapeake Bay Program; Phillips Seafood, Inc.; Maryland Watermen's Association; and the Fellowship program of the Smithsonian Environmental Research Center.