Testing the flood pulse concept: The importance of floodplain inundation on fish and invertebrates of a Great Plains river

The flood-pulse of large rivers is considered a principle driving force of nutrient flow and food web composition for biota in large river ecosystems. We sampled zooplankton, invertebrates, and fishes in inundated habitats, adjacent main channel, and downstream reaches of the Kansas River before, during, and after a flood to quantify how floodplain inundation impacts river biota. Drifting invertebrate densities were highest during flooding (mean=0.04 individuals/L) and lowest post-flooding (mean=0.003 individuals/L) (p<0.01). During the flood, invertebrate density was higher in inundated habitat than at all other sites (p<0.01). Overall fish abundance at adjacent main channel and downstream sites did not differ among sampling periods (p=0.13). Similarly, fish abundance did not differ among sites during the flood (p=0.17). However, the abundance of fishes >200mm was higher in inundated habitats during the flood (p=0.02) indicating that large-bodied fishes are moving into inundated habitats during periods of high flow. The results of this study indicate that fishes utilized flooded habitats when available, and that the inundation of terrestrial habitats during the flood pulse provides invertebrates to the main channel that may be consumed by main channel fishes.