Spatial and temporal patterns of estuarine fish communities relative to habitat structure and freshwater inflow

Distribution maps of species are often used to prioritize areas for conservation and management. However, variability in freshwater inflow may cause temporal changes in the distribution of estuarine fishes, and thus hinder our ability to identify general spatial distribution patterns of these species. In this analysis, we used relationships between estuarine landscape structure, defined as the amount and spatial arrangement of habitat types (salt marshes, mangroves, and seagrass beds), and the fish community to describe the distribution of juveniles of fishery species and associated ecologically important fish species in shallow areas of Charlotte Harbor, Florida (USA). Through cluster analysis, we identified three broad-scale spatial zones with relatively similar community compositions across the riverine-estuarine landscape. We then compared temporal variability in the abundance of fish species in the three zones during two time periods: two years with lower-than-average monthly freshwater inflow and two years with average to higher-than-average monthly inflow. We found that densities of most species were higher during the years with higher freshwater inflow than they were during lower inflow years. In addition, we found that the center of most species' abundances did not generally move from one zone to another based on changes in freshwater inflow patterns.