POPULATION-DYNAMICS AND LIFE-HISTORY CHARACTERISTICS OF THE BLUE CRABS CALLINECTES-SIMILIS AND C-SAPIDUS IN BAY ENVIRONMENTS OF THE NORTHERN GULF-OF-MEXICO

The population dynamics and life history characteristics of Callinecte s similis and C. sapidus in the Mobile Bay-Mississippi Sound estuarine system of the northern Gulf of Mexico were studied. We report that C. similis is numerically dominant in open-bays, while C. sapidus is mor e abundant in shallow salt marshes. Juvenile C. similis recruit into b oth open-bays and salt marshes, but juvenile C. sapidus primarily recr uit into shallow salt marshes. Sex ratios of C. similis and C. sapidus were generally skewed towards higher proportions of males than female s. Callinectes similis appears to have a life cycle similar to that of C. sapidus. Egg-carrying C. similis migrate to higher salinity waters and presumably release larvae to nearshore shelf waters; following de velopment, the larvae re-invade estuaries as megalopae. Juvenile C. si milis grow more slowly than C. sapidus. This may be attributable to re duced feeding rates. Marked differences in fecundity and reproductive effort were found between these species. Callinectes similis and C. sa pidus, respectively, produced 2.4-5.5 x 10(5) and 2.1-3.2 x 10(6) eggs and invested 24-49 and 171-372 kJ per brood. Rhizocephalan barnacle i nfestation by Loxothylacus texanus was encountered in C. sapidus, whil e sympatric C. similis were free of this rhizocephalan parasite.