Fish community response to habitat variables in two restored side channels of the lower Platte River, Nebraska

Abstract

Anthropogenic alterations to large rivers ranging from impoundments to channelization and levees have caused many rivers to no longer access the floodplain in a meaningful capacity. Floodplain habitats are important to many riverine fishes to complete their life‐history strategies. The fish community and species of fish that inhabit floodplain habitats are often dictated by the type of habitat and the conditions within that habitat (e.g., temperature, water velocity, depth, and discharge). As mitigation and restoration projects are undertaken, it is imperative that managers understand how various habitat components will affect the fish community in floodplain habitats. We collected fish and habitat data from two restored side channels with different structural designs on the lower Platte River, Nebraska, to determine how habitat variables predicted species diversity and individual species presence. We found a decrease in discharge in the main‐stem river resulted in increased diversity in one of the side channels, with the greatest diversity values occurring during summer. No habitat variables performed well for predicting fish species diversity for an adjacent side channel with more uniform depth and velocity and no groundwater inputs. However, several native riverine fish species in this side channel were shown to be associated with high temperature, dissolved oxygen, main‐stem discharge, and discharge variability. These results highlight the importance of considering the physical design of restored floodplain habitats when attempting to enhance fish communities.

A study of the hydraulic parameters and ecological significance of braided rivers under flow variations

“…When restoring fish habitats, it is possible to restore fish communities cost‐effectively by studying the needs of the fishes with regard to the natural geomorphological and hydrological conditions (Rabeni & Jacobson, 1993). For example, in continuously dry or flooded rivers, the topographic conditions and flow processes combine to create specific fish avoidance and spawning behaviors (Marshall et al, 2016; Uerling, Hamel, & Pegg, 2019). Some rivers are also characterized by large hydrological variations, but these flow variations may have a smaller effect on the average flow velocity and water depth of the downstream HB sections than on the LB sections, suggesting that the potential impact of daily regulating power plants on downstream spawning grounds may be less harmful.…”