There was an increase in species richness of streams with an increase in watershed area, stream length, and average annual discharge. Figure 13 .
Lines represent the simple regression models provided.
Species characterization of reaches Occurrence of stream fish species varied between 46 stream reaches in the Red River basin. The length of arrows represents the degree to which each is correlated with CCA axes. Figure 14 . In terms of predicting fish assemblage compostion, important environmental variables have longer arrows than less important ones. The environmental variables most important in explaining fish distributions were determined by examining correlations with axes.