Variability in the length of the megalopal stage and its consequence to dispersal and recruitment in the portunid crab Callinectes sapidus Rathbun

The degree of dispersion of larvae may be influenced both by transport processes and by the length of larval life. The present study examines variability in duration of the megalopa of the crab Callinectes sapidus. Exposure of day 1 megalopae to reduced temperature and higher salinity typical of deep continental shelf water reduces survival and delays development to the crab stage. Maintenance of megalopae at temperatures and salinities typical of surface conditions for 10 days prior to exposure to deep water conditions results in reduced mortality and faster development than if megalopae are exposed to conditions of depth on day 1. Nevertheless, development still is prolonged sufficiently to account for recruitment via on-shore residual drift of bottom water. Because larvae are unable to control their location on the shelf in a manner to assure exploitation of favorable circulation, increased dispersion of larvae due to variability in both zoeal and megalopal duration may increase the probability that some members of a brood will be transported from the ocean to the estuarine adult habitat.