The Relationships Between Flow Alteration and Fish-Trait Combinations in a Large Great Plains River

Changes to rivers are multifaceted with flow modifications a driver of changing channel and habitat conditions. The flow regime of the Canadian River, located in the US Great Plains, has been altered by the construction of major reservoirs. This fragmentation has resulted in modification of the river continuum and the fish assemblage. We used a physics-based spatially distributed hydrologic model (Vflo^®) to simulate river discharge at all sampling locations. The simulated streamflow was used to calculate ecologically-relevant flow indices that captured the major components of streamflow (e.g., duration, magnitude). Correlation and stepwise variance inflation factor analyses were used to reduce flow indices from 178 to a final subset of 8 indices. These flow indices were related to a subset of fish groups derived using morphological and ecological traits. Reproductive and morphological groups showed significant responses to flow variability and timing of maximum and minimum flows. Understanding the link between the flow regime and fish assemblages in the Canadian River will allow management agencies to better predict outcomes of climate change and future flow alteration and protect species of special concern.