In order to gauge the influence of freshwater inflow on the habitat value of oyster reefs, spatial and seasonal patterns of the presence of reef-resident fishes and decapods were assessed in the Caloosahatchee, Estero, and Faka-Union estuaries of Southwest Florida. Lift nets (1 m2) containing 5 liters of oyster clusters were deployed on intertidal reefs at three sites along the salinity gradient of each estuary. Nets were deployed during three seasonally dry and three seasonally wet months for a period of 30 d. Oyster densities were estimated at each site and a number of community metrics were calculated as a measure of habitat value (e.g., abundance, biomass, presence of oyster-dependent organisms, diversity, dominance, richness).

Several metrics trended downstream in one or more systems (e.g., abundance and biomass increased downstream in all three systems, and measures of biodiversity were higher downstream in the Caloosahatchee) and appeared to be unrelated to the density of living oysters present. Although abundance was higher during the wet season for all three systems, biomass was lower during this season in the Caloosahatchee. In both the Caloosahatchee and the Estero, measures of biodiversity were higher during the dry season. A number of metrics were positively correlated with salinity in one or more systems: biomass, biodiversity, and the presence of oyster-dependent species. Additional data collected in the Caloosahatchee demonstrated that some metrics were also related to freshwater inflow; for example, biomass and biodiversity varied inversely with inflow recorded during the sampling period as well as with inflow recorded at time lags of up to 3-4 months. These results suggest that regulated freshwater releases can be a useful tool for managing Southwest Florida oyster reefs, but that resource managers should consider the habitat requirements of oyster-reef organisms in addition to those of the oysters themselves when establishing release guidelines.