Seasonal Variability in Morphology of Blue Crab, Callinectes sapidus, Megalopae and Early Juvenile Stage Crabs, and Distinguishing Characteristics Among Co-Occurring Portunidae

Abstract

Abstract Declines in abundance of the commercially important blue crab Callinectes sapidus have led fishery managers to search for new management strategies. Assessing year-class strength at megalopal or early juvenile stages may contribute to this effort, but separation from co-occurring species is difficult in many areas because morphological characteristics vary with season and published descriptions do not adequately distinguish C. sapidus from C. similis and other related species. Callinectes sapidus and C. similis megalopae were collected monthly and cultured in the laboratory to a size at which positive identification could be made. Measurements on intact megalopae and early crab exuviae of both species revealed seasonal differences, with spring megalopae having larger carapaces, longer rostral spines and antennae and more setae on some mouth parts than fall megalopae. This seasonal pattern of morphological variability was verified through examination of samples collected from MS (1976–1979) and NC...