Historical Effects of Streamflow Alteration on Fish Assemblages in Northwestern Kansas

Many authors have suggested that the impoundment of streams affect fishes both directly and indirectly. Direct effects include blocking of dispersal routes, modifications in timing and intensity of streamflow, and loss of habitat, but the indirect effects may be just as harmful. These include the introduction of non-native fishes and reduction in water quality. Fish assemblage data were obtained from museum collection records for northwestern Kansas streams. Cluster analysis and principal coordinates analysis were used to examine the changes in fish assemblages before and after the construction of impoundments in four drainages in northwestern Kansas. Results indicate that changes in fish assemblages have occurred in drainages with impoundments. Assemblages near impoundments have changed from those with characteristically variable flowers, diverse habitats, and lotic habitats to those with stable flows, monotonous and lentic habitats. Assemblages not impacted by impoundments show a greater similarity than those impacted by impoundments. I conclude that the changes in fish assemblages in this region are primarily the result of habitat alterations caused by the construction and operation of stream impoundments