Spatial Variability in the Fish Assemblage of a Large River–Reservoir Ecosystem.

This article focuses on the spatial variability of fish assemblages within the Trinity River–Lake Livingston river–reservoir ecosystem (RRE) in Texas, USA, to evaluate its suitability as a management scale integrating conservation and recreational fishery objectives. The study identified eight unique fish assemblages distributed along longitudinal (river, river–reservoir interface [RRI], reservoir) and lateral (backwaters, main channels) habitat gradients, with species richness highest in the river and RRI segments and fish abundance greatest in the RRI. Notably, some species of conservation concern and important sport fishes were unevenly distributed across segments, highlighting the ecological significance of the transitional RRI zone and backwaters. The findings suggest that managing at the RRE scale can better capture habitat diversity and connectivity, supporting both native rheophilic species and recreational fisheries, and may improve integrated management outcomes in regulated river systems.