Abstract
The presence of relatively rare species in estuarine fish communities can influence niche differentiation among species, functional redundancy, and ecosystem stability when faced with environmental disturbance. In southeastern Florida, at least four species of snook (Centropomidae) occur in coastal river systems, but only one species occurs elsewhere in the state. To better understand how these species can co-occur, we analyzed data from electrofishing and diet studies conducted during 2007–2010 to investigate niche partitioning between two species: Common Snook Centropomus undecimalis and Smallscale Fat Snook Centropomus parallelus (common and fat snook hereafter). Although the diets of the two species collected from coastal rivers were barely distinguishable, there was separation of habitat use. Adult fat snook had affinities for low salinity portions of rivers, while common snook were distributed more widely. Use of nursery habitat by fat snook occurred during early spring, confirming winter spawning, which contrasts with the protracted spawning of common snook that occurs spring through fall. While in riverine nurseries, juvenile fat snook occupied shallow to moderate depths with cover (e.g., woody debris, docks); common snook had greater affinity for shallow natural shorelines (e.g., mangroves, aquatic macrophytes). Overall, fat snook appeared to occupy niches left open by the generalist common snook. Considering that centropomids are likely to expand their range northward in Florida with climate change, understanding habitat use and niche partitioning among the species may help predict which species is likely to expand first and what habitat types will be occupied.