Using Geomorphology to Better Define Habitat Associations of a Large-Bodied Fish, Common Snook Centropomus undecimalis, in Coastal Rivers of Florida

Abstract

To adequately protect habitat for economically important fishes, the habitats used must first be identified and described. Coastal geomorphology is often overlooked as an influential parameter of fish habitat use in favor of readily available data taken at the time of sampling. We hypothesized that river dynamics (e.g., length, watershed, floodplain connectivity) and mesohabitat categories based on geomorphology (e.g., backwater, river bend) were at least as important as fine-scale microhabitat (e.g., depth, shore type) for describing the distribution and habitat affinities of Common Snook Centropomus undecimalis (hereafter referred to as snook) in coastal rivers of the Atlantic coast and Tampa Bay, Florida. Contrary to previously studied rivers where adult snook abundance increased during a seasonal prey pulse, adult snook abundance in the study rivers differed little between seasons and the rivers were used as nurseries by juveniles. Mesohabitat categories were important for describing snook distribution. For example, the smallest snook (≤ 250 mm total length, TL) strongly selected for backwater habitats while the largest (≥ 851 mm TL) selected river bends. Detailed microhabitat data collected at individual capture locations were helpful in describing the habitat associations of the smallest size group of snook (shallow depths and aquatic macrophytes with various shore types) and for characterizing river bends (high flow, deep water, and lower salinities) but were not strongly associated with other snook sizes or mesohabitat categories. Thus, broader scale habitat features were found to be equally as important as detailed microhabitat and should be considered when informing conservation efforts.