| opulation dynamics, life history, salinity tolerance, congeneric interactions, and diets of the blue crabs Callinectes similis and C. sapidus were compared in the Mobile Bay-Mississippi Sound estuarine systems of the northern Gulf of Mexico. Crabs were collected monthly from May 1989 to June 1990 by otter trawl or seine from four sampling sites that represented open-bay and salt marsh habitats. Callinectes similis and C. sapidus co-occured at all four sampling sites. However, with few exceptions, C. similis numerically dominated in open-bays, while C. sapidus was more abundant in salt marshes. It appeared that C. sapidus was forced to migrate from shallow waters into open-bays during periods of high freshwater influx. Population size structures of both blue crab populations in open-bays and salt marshes indicate that juvenile C. similis recruited into both salt marsh and open-bay habitats, whereas juvenile C. sapidus recruited primarily into salt marshes. Callinectes similis and C. sapidus appeared to have similar life cycles. Adult female crabs migrated to either coastal or offshore high-salinity waters to spawn and release crab larvae, which then re-invaded estuaries as megalopae. Juvenile C. similis consumed less food per day and grew slower than C. sapidus under laboratory conditions. In addition, C. similis attained a smaller maximum body size than C. sapidus (125 vs 190 mm CW). Female C. similis and C. sapidus became sexually mature at body sizes of 60 and 100 mm CW, respectively. Consequently, fecundity and reproductive output of C. similis were less (2.4-5.5... |
