Flathead Catfish artificial nest structure utilization within the Illinois Rock River system

Flathead Catfish (Pylodictis olivaris) are large-bodied piscivores that are growing in popularity among anglers in the Midwest. Flathead Catfish nest in cavities or protective crevices in the bank, woody debris, and riprap near the shore in June and July in the upper Midwest. In 2009, 14 train tanker cars derailed and spilled approximately 60,000 gallons of 95% ethanol into the Rock River system southeast of Rockford, IL. The ethanol degradation caused low oxygen levels that contributed to the hypoxia-induced kill of an estimated 75,000 fish, including many Flathead Catfish. Restoration efforts to reestablish the fish community downstream of the spill site included the placement of 20 artificial nesting structures at three locations between Dixon and Sterling/Rock Falls IL in 2015. Despite the installation of the artificial nesting structures, it is still unknown whether they promote their intended goal of increasing Flathead Catfish reproduction. Mature Flathead Catfish (n=225) were tagged with radio-transmitters in October 2020 to evaluate artificial nesting structure use. Intensive tracking efforts in the Dixon Reach and around the nesting structures will occur from Mid-May to Mid-August. Stationary receivers will also be deployed upstream and downstream of the study reach to understand potential fish movement out of the study reach. The usage of active remote sensing techniques such as side scanning sonar and real-time Panoptix scanning sonar will help to verify artificial nest structure use. Habitat use outside of the artificial nesting structures will also be examined to identify other nesting areas within the study reach.