Evaluation of Multi-Decadal Changes in the Nekton Community of the Lower Brazos River: Potential Influence of Freshwater Inflow

Estuaries and their numerous subsystems provide countless vital services to human beings including support for major fisheries, water quality enhancement, storm protection and flood mitigation. The impact of modified flow regimes from artificial impoundments on various water quality and nekton community parameters have been studied; however, not on a northwestern Gulf of Mexico “riverine” estuary. Research was needed to determine if nekton communities have changed since last being sampled nearly 40 years earlier and how nekton utilization of the lower Brazos River changes with variable flow and water quality parameters. An extensive nekton sampling effort was conducted once a month for 6 months at four previously studied sites on the lower Brazos River and two controls on the Trinity River. Preliminary results suggest that (1) nekton assemblages have changed since last being studied; (2) nekton are regulated by freshwater inflow; (3) diversity and evenness have increased under oligohaline conditions; and (4) several spatial mechanisms are also responsible for regulating nekton communities. This data is critically needed by resource managers to understand the impact that has been made on the riverine, estuarine and near shore marine ecosystem due to changes in freshwater inflow and water quality management.