Utilization of the intertidal zone of a salt marsh by the blue crab Callinectes sapidus: density, return frequency, and feeding habits

Abstract

In the salt marshes of Sapelo Island, Georgia, blue crabs were absent or had an extremely low density within an intertidal marsh impoundment during winter, when water temperature was <15°C. Juveniles ≤80 mm carapace width started moving into the intertidal zone in March or April, but the intertidal density of blue crabs was dominated by larger juveniles and adults (>80 mm) throughout the summers of the 2.5 yr study. Densities were not large, peaking at 40-50 crabs ha-1 during September. A non-impounded site had similar total densities to those of the impoundment, but had significantly more juveniles ≤80 mm. All sizes of crabs (≥35 mm) moved into the intertidal zone of the marsh during the summer in approximate proportion to their abundance within the source (subtidal) population. The principal prey consumed by relatively large (mostly >100 mm) blue crabs within the study zone were natant fishes (38%) and resident non-portunid crabs (43%). Shrimp and similar crustaceans formed 12% of the diet. Returns of individual blue crabs to the same intertidal marsh zone primarily occurred within 10 d of their initial capture, after which they apparently emigrated from the local area. -from Authors