Contrasting river migrations of Common Snook between two Florida rivers using acoustic telemetry

Abstract

The widespread use of electronic tags allows us to ask new questions regarding how and why animal movements vary across ecosystems. Common Snook (Centropomus undecimalis) is a tropical estuarine sportfish that have been well studied throughout the state of Florida, including multiple acoustic telemetry studies. Here, we ask; do the spawning behaviors of Common Snook vary across two Florida coastal rivers that differ considerably along a gradient of anthropogenic change? We tracked Common Snook migrations toward and away from spawning sites using acoustic telemetry in the Shark River (U.S.), and compared those migrations with results from a previously published Common Snook tracking study in the Caloosahatchee River. We found that the proportions of fish that did not migrate out of rivers during the spawning season and presumably skip spawned were similar between the two systems. However, in the Shark River, there was more year-to-year variability in this behavior, likely tied to freshwater flow and floodplain inundation. Second, we found that the length of time individuals spent outside of rivers during the spawning season (i.e. proxy for time spent spawning) was less in the Shark River than in the Caloosahatchee. Last, the proportion of Snook at emigrated and did not return in the Shark River was higher than in the Caloosahatchee. These latter finding could reflect higher straying rates or higher mortality at spawning grounds. Future work should evaluate whether these spatial differences in river migrations are meaningful enough to affect management. This study illustrates that cross-site comparisons can improve confidence in our understanding of life history metrics while also highlighting differences between sites that are worth exploring to gain a better understanding of a species plasticity in adapting to their environment.