Spatial Variation in the Fish Assemblage of a Large Great Plains River

Changes to riverine systems are multifaceted with flow modifications being a driver of changing channel and habitat conditions. The flow regime of the Canadian River, located in the US Great Plains, has been fragmented by major reservoirs constructed for human and agricultural uses. This fragmentation has altered the river continuum; however, our knowledge of flow conditions is limited to gage locations. This study used a spatially-distributed hydrologic model, Vflo^®, to simulate river discharge at ungaged locations. Vflo^® incorporates high-resolution rainfall radar data to account for the range of precipitation events that drive the variable hydrologic regime of the Canadian River. The simulated streamflow was used to calculate ecologically-relevant flow metrics that captured the magnitude, frequency, duration, timing, and rate of change of the Canadian River flow regime. These flow metrics were related to structural components of the fish assemblage at sites throughout the Canadian River. The fish assemblage showed notable changes in structure with a perceived shift in reproductive traits of the constituent members. Understanding the link between the flow regime and fish communities in the Canadian River will allow management agencies to better predict outcomes of climate change and future flow alteration, and to protect species of special concern.