A Survey of Floodplain Habitat Use by Missouri River Fishes

Regular flooding is a natural phenomenon in unaltered lotic systems.  Fish and other aquatic organisms in large rivers evolved under conditions which allowed annual or semi annual access to floodplain habitats.  Drastic alterations in the Middle Missouri River’s flow regime and an advanced network of levees have made main channel-floodplain interaction far less frequent than historical conditions.  During winter and spring 2011, above normal snow pack and rainfall in the Upper Missouri River watershed led to a prolonged flood of greater magnitude and duration than had occurred in over 50 years.  This led to overbank flows and floodplain inundation for nearly the entire summer and fall.  We investigated large river fish use of floodplain habitats at five sites along the Missouri River, Nebraska.   Sampling took place between 27 June and 30 September, 2011 using 15 Hz and 60 Hz electrofishing to collect fish in four meso and four micro habitat types. In total, 584 electrofishing runs collected 5,598 fish.  Electrofishing runs using 60 Hz had highest catch rates in permanent backwaters (mean = 319.01 fish/hr), while 15 Hz runs caught more fish in bankline habitats (mean = 155.95 fish/hr).  Species-specific catch rates were also compared among habitats for eight commonly sampled species. Discussion will include implications of fish habitat use in floodplain ecosystems.