Juvenile Asian Carp Predation on the La Grange Reach, Illinois River

In 2014, a large Asian carp spawning event in the La Grange reach, Illinois River produced an abundance of juvenile silver carp in 2015. This provided the opportunity to investigate their use as forage for native piscivorous fishes and the size structure of fish utilizing this resource. We collected fishes from contiguous backwaters and tributaries on the La Grange Reach, Illinois River using pulsed DC- electrofishing from June through November, 2015. Diets were removed for analysis from all native piscivorous fishes during runs when young Asian carp were detected. Diet components were identified, enumerated, and weighed by taxa. The presence of silver carp pharyngeal teeth in the diets were used to confirm identification and allowed us to estimate silver carp length. Silver carp were predominantly found in the diets of largemouth bass (25/262, 9%), white bass (6/67, 9%), and shortnose gar (6/30, 20%). We estimated silver carp lengths found in the predators diets, and determined that there was a significant relationship between the size of largemouth bass and the size of silver carp they consumed (p=0.0001). Identifying species and size of native predators able to utilize this resource provides insight into natural biological management of this invasive species.