Effects of structural complexity and water depth on the juvenile blue crab Callinectes sapidus in a simulated salt marsh mesocosm

The blue crab (Callinectes sapidus) is ecologically and economically important in Chesapeake Bay. Nursery habitats, which disproportionately contribute individuals to the adult segment of populations, are essential to blue crab population dynamics. Spartina alterniflora salt marshes are productive but fragmented intertidal nursery habitats which may serve as a refuge from predation for juvenile blue crabs. However, the effects of various characteristics of salt marshes on nursery metrics, such as survival, have not been quantified. Using mesocosm experiments, we examined the effects of shoot density and water depth on juvenile blue crab survival using adult blue crabs as predators. Survival increased significantly with shoot density, whereas water depth did not affect survival. Thus, in contrast to several previous studies, water depth did not influence survival of juvenile blue crabs, possibly due to different environmental conditions from prior studies. These findings indicate that salt marsh structural complexity enhances juvenile survival, and that the beneficial effect of shallow water on juvenile survival differs by environmental conditions.