Impact of Irrigation Canal Operations on the Fish Communities and Biomass of a Connected Stream

The influence of canal operations on the available habitat and fish communities in conjoined Great Plains streams is not well understood. Three-pass backpack electrofishing was used twice within a three-week period in fall 2018 to identify changes in Turkey Creek (near Kearney, NE) before and after the Kearney Canal was dewatered. Diversity was greater while the canal was operational (t = 398.14, p < 0.001), but community composition remained similar following canal dewatering (J = 62.9%). Species-specific differences between the two time periods were most often observed among cyprinids and centrarchids, and non-native species were more abundant (z = 6.0, p < 0.001) and comprised a greater percentage of the available biomass (z = 75.7, p < 0.001) when the canal was operational. The wetted width (t = 2.27, p = 0.04) and depth of Turkey Creek (t = 1.90, p = 0.06) significantly decreased after the canal ceased operation. Findings from this case study can be used to further the understanding of fish community responses within streams conjoined with canals and may provide regional water and fish managers important information to improve future management of these systems to support native fishes while simultaneously meeting other water uses for agriculture and recreation.