Can a river-reservoir interface serve as nursery habitat for riverine fishes?
Acre, Matthew Ross
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Anthropogenic modifications to riverine systems have reduced access to important off-channel nursery habitats, but the river-reservoir interface (RRI) may offer surrogate nursery habitat. I sampled ichthyoplankton assemblages in off-channel and main channel habitats of the Lake Livingston RRI and middle Trinity River to: 1) compare species composition and abundance in these different habitat types, and 2) evaluate the influence of abiotic characteristics on ichthyoplankton assemblages in these habitats. Ichthyoplankton was sampled using light traps and paired push nets deployed off jet-propelled kayaks during March—July in 2013 and February—June in 2014. A total of 44,029 larval fishes were collected, representing 27 taxa. A few taxa were dominant at all sites, such as Threadfin Shad Dorosoma petenense and Inland Silverside Menidia beryllina; however, less common taxa such as moronids, sciaenids, and centrarchids were captured more frequently in RRI habitats. Sites with frequent connectivity to the main channel, in particular the RRI backwater habitats, had higher taxonomic richness, diversity, and overall abundance than similar habitats lacking this connectivity. Canonical correspondence analysis suggests that there are major divisions between mesohabitats in the Trinity River being driven by physicochemical components and species assemblage structure related to connectivity to the main channel of the river. These differences suggest RRI habitat may act as a surrogate nursery for some species when access to other off-channel habitat is limited.