Adaptive significance of habitat selection by molting adult blue crabs Callinectes sapidus (Rathbun) within a subestuary of central Chesapeake Bay

Abstract

In the Rhode River subestuary, higher proportions of molting male blue crabs occupy a tidal creek, while molting and mating pubertal females are more common in the adjacent river basin. Predation pressure, mate availability, and physiological costs or benefits (competency to molt, survive ecdysis, and postmolt size increment) were estimated for these two habitats using a combination of caging and tethering techniques. Predation on molting crabs was less in the tidal creek, however, cannibalism may not explain these site-specific predation differences. There were no site-specific differences in survival, postmolt size increment, or competency for premolt crabs to molt when protected from predators. The results suggest that by molting in the creek males avoid higher predation in the river. Habitat selection by pubertal females may depend more on mate availability. Females may actively select the river or simply molt in the habitat in which they encounter a mate. Further experiments are needed to resolve the selection pressures eliciting the observed distribution of pubertal females.