Covariation Among Plains Stream Fish Assemblages, Flow Regimes, and Patterns of Water Use
Christopher M. Taylor
Abstract.—Riverine fish assemblages on the North American plains continue to change as native species’ distributions shrink and become increasingly fragmented due to impoundment, changes in the quantity and quality of water, and negative interactions of introduced species. To identify important changes to fish assemblages and their environment, long-term data are needed. I used fish assemblage and discharge data from 22 plains river localities across nearly 20 years to identify potential covariation between fish assemblages and the flow regime. I also obtained data on water use at the watershed scale to determine its potential effects on flow regimes and fish assemblages. A modified time series analysis indicated that directional change was occurring for many of the fish assemblages, though the strength of this change was highly variable among localities. Directional change was strongly and positively associated with change in flow regime, and change in flow regime was positively associated with human modification of the landscape, including number of wastewater facilities and returns. These results illustrate how demands on our water resources can ultimately influence riverine fish assemblages, largely by disrupting natural flow regimes. As population growth continues, the integrity of plains fish assemblages and their riverine environment will likely continue to decline, further exacerbating the fragmentation and reduction of species’ geographic ranges.