Seasonal and Diel Habitat Shifts by Juvenile Ictalurids in a Flow-regulated Prairie River

Abstract

Currently, no flow regulations exist for the protection of riverine fishes in Missouri. Prerequisites for establishing flow guidelines are understanding what habitats are used by fishes at different times of the year and how much of that habitat will be available to each species under different discharge scenarios. We quantified microhabitat associations and selection for juvenile channel catfish Ictalurus punctatus, flathead catfish Pylodictis olivaris and stonecat Noturus flavus in a flow-regulated prairie river during summer (diurnal and nocturnal periods) and autumn (diurnal period) and then presented two-dimensional hydraulic modeling results from a previous study to determine how diel and seasonal microhabitat shifts might impact the availability of selected habitats at different flows. All ictalurid species exhibited seasonal and diel shifts in microhabitat selection. Selected habitat available would generally be maximized for each species between 10 m3/s and 30 m3/s which is greater than the current median discharge. Stonecats are most susceptible to dewatering during the diurnal summer period; however, the availability of selected habitat becomes flow limited (<10 m3/s) for all species during summer nocturnal and autumn periods because of changes in microhabitat selection during these periods. Channel catfish could be substantially impacted by extremely low flows during the summer nocturnal and autumn periods with no selected habitat available below 1 m3/s. Quantifying the amount of selected habitat that may be available under different discharge scenarios will aid managers in determining appropriate minimum flows for maintaining habitats for these species under a flow regime that continues to be partitioned to different stakeholder groups.