External Influences On Nekton Abundance Within a Southwest Florida River and Its Associated Estuarine System; Can Trends in Annual Abundance be Used to Refine Relationships Between Nekton and Freshwater Inflow?

In order to establish the minimum amount of water flow necessary to preserve habitat values for several tidal rivers in southwest Florida, water managers have used the relationships between freshwater inflow and nekton abundance and distribution. In previous analyses of fisheries data from the Alafia River, which discharges into the Tampa Bay estuary, inflow relationships have been identified, but many are relatively weak (<25% variability explained).  Estuarine-dependent species that reproduce outside of a tidal river experience many population-level influences prior to recruitment into the river system that may influence success and that are unrelated to inflow. Using a long-term (12 year) fisheries-independent monitoring dataset, fourteen species that reproduce outside of the Alafia River but recruit into the river and Tampa Bay were assessed for annual abundance trends.  Annual trends were compared using regression to determine if species-specific abundances were concordant between the river and estuarine systems. Differences in annual abundance were investigated to determine if river influences, such as freshwater inflow, explain the variability in annual trends. The resulting relationships may dictate potential sampling design changes, such as adjusting the number of samples or re-stratification within habitats, to improve response relationships between inflow and nekton abundance and distribution.