Dispersal and recruitment of fiddler crab larvae in the Delaware River estuary

In spite of a semi-terrestnal adult habitat, fiddler crabs of the Middle Atlantic Bight show no adaptahon for retaining larvae in hdal marsh creeks Abundant data show that newly hatched zoeae are rapidly carned Into pnmary estuanes The present inveshgahon shows that there is some retenhon of all zoeal stages w t h i n the estuary but that substantial numbers of zoeae are carned to the adjacent continental shelf Later zoeal stages are common deep in the water colun~n at stahons as far as 35 km from the bay mouth Collechons over 6 consecutive tidal cycles in a secondary estuary indicate that megalopae u t h z e flood hdal cuirents to augment their upstream migration to adult habitat A conceptual model based on both fleld and laboratory data predicts that sahnity is a gross filter separating populatlons of Uca mjnax and Uca pugnax but that final selection of adult habitat is controlled by other factors