The role of freshwater discharges on Common Snook movements and distribution in a south Florida estuary

ABSTRACT Objective Estuarine ecosystems are dynamic habitats where the convergence of marine water and freshwater results in constant fluxes in abiotic environmental conditions. Organisms must face these fluctuating conditions within their optimal range to minimize physiological costs, often by moving from unsuitable to more suitable areas. Anthropogenic hydrologic discharges further alter environmental conditions and may cause population-wide movement responses of mobile organisms. Organismal responses to anthropogenic and natural fluctuations can differ based on time of year, life history stage, or individual characteristics. Methods We used acoustic telemetry to track the movements of Common Snook Centropomus undecimalis, a euryhaline sport fish, before, during, and after high-discharge events in a managed waterway. Result We did not find large-scale, synchronous movement. Common Snook were more likely to move during a high-discharge event and with increased changes in salinity. Although size and sex did not influence movement on a larger scale within the estuary, small to intermediate size-classes (602–786 mm TL) occupied adjacent slower flow habitats that mimicked natural conditions during high discharge, likely due to decreased energy expenditure. Individual identity played a role in determining the probability of movement, which may reflect behavioral contingencies that exhibit differences in habitat preference and movements. Conclusions This sport fish population may be more resilient to this type of disturbance than previously hypothesized. Understanding the relationships between the movement of fish and abiotic and anthropogenic factors can guide the management of waterways and provide insight into how changes will affect their distribution in estuarine environments.