Do River-Reservoir Interfaces Serve As Surrogate Nurseries for Floodplain-Dependent Riverine Fishes?

Anthropogenic modification to riverine systems has reduced access to important off-channel nursery habitats. Some species utilize these floodplain habitats during early life history. The river-reservoir interface (RRI), a transitional zone between lentic and lotic habitats, may provide surrogate nursery habitats for these species. We sampled ichthyoplankton assemblages in riverine and RRI off-channel and main channel habitats in the Trinity River system of east Texas to compare species composition and abundance in these different habitat types and evaluate the influence of abiotic and physicochemical characteristics on ichthyoplankton assemblages. Ichthyoplankton was sampled using light traps and paired push nets deployed off jet-powered kayaks during February-July 2013 and 2014. Over 50,000 larval fishes were collected, representing 11 taxa. A few taxa were dominant at all sites, however, less common ichthyofauna such as moronids, centrarchids, and Freshwater Drum were captured more frequently in RRI habitats. In general, larval fish abundance, species richness, and species diversity, were greater in the RRI off-channel habitats than other habitat types. The duration and size of connection to the main channel best explained species richness, diversity, and overall abundance in RRI off-channel habitats. Our results suggest RRI habitat may serve as a surrogate nursery for some species.