Utilization of Marsh and Seagrass Habitats by Early Stages of Callinectes Sapidus: A Latitudinal Perspective

Seagrass beds and marshes have been identified as important nurseries for the blue crab, Callinectes sapidus. This nursery paradigm is based on blue crab abundance data from trawl, seine and drop-net sampling that has revealed greater abundances in these habitats than in adjacent unvegetated areas. Recently, more quantitative and intensive sampling in seagrass beds and marshes over broad latitudinal scales, combined with manipulative experiments, indicate that the same habitat may vary in utilization on regional scales. Mechanisms accounting for enhanced abundances in these nursery habitats have not been elucidated from a latitudinal perspective. Regional comparisons of blue crab catch data regressed on habitat area were not significant whereas similar comparisons within the Gulf region showed a significant positive relationship of crab harvest with total vegetated area. Thus, the quantity of habitat may be important over small latitudinal scales but other factors could affect population abundances across broad latitudinal distances. Latitudinal differences in habitat use may result from alternate modes of settlement via megalopae or recruitment by juveniles, active or passive habitat selection, post-settlement mortality and food quality and quantity. Tidal regimes and coastal morphology in relation to physical processes may influence the accessibility of important habitats by settling or recruiting individuals and thus be equally important. These factors are reviewed in an attempt to understand regional differences in the patterns of C. sapidus abundance.