Abstract
To measure the effect of salinity on estuarine communities, spatial and temporal variations in population distribution were investigated in the flatback mud crab Eurypanopeus depressus (Smith, 1869), a dominant species on oyster reefs in southwest Florida. Eurypanopeus depressus were collected using lift nets (1 m2 ) deployed at three morphologically homologous stations along a salinity gradient in each of three estuaries. They were sampled monthly during three seasonally wet and three seasonally dry months. An analysis of abundance showed that although this species can survive extreme salinities, it is most common in moderate environments. Biomass is also highest at moderate salinities, though mean size is larger at low salinities. Few significant differences in these metrics between seasons were observed. These results suggest that although E. depressus is little affected by normal seasonal changes in salinity, salinity does play a role in its distribution. In light of these findings, changes in the freshwater flow regime of Southwest Florida estuaries as a result of land use changes resulting from human development have the potential to alter oyster-reef community structure.