Juvenile Asian Carp As Forage for Native Predators in the Lagrange Reach, Illinois River

Increasing numbers of silver carp (Hypopthalmichthys molotrix) and bighead carp (Hypopthalmichthys nobilis) in the Illinois River has led to concerns about the impact their invasion has on native food web dynamics. Asian carp have high fecundities and rapid growth and in the absence of predator controls, they can quickly achieve high densities. A large Asian carp spawning event on the Illinois River was observed in the summer of 2014 providing us an opportunity to determine how native piscivorous fish (n-1527) respond to high juvenile Asian carp densities. White bass (Morone chrysops), black crappie (Pomoxis nigromaculatus), white crappie (P. annularis), largemouth bass (Micropterus salmoides), and shortnose gar (Lepisosteus platostomus) were collected as predators from the LaGrange Reach (August 3-October 31) using pulsed-DC boat electrofishing and ¾ in. fyke nets. Fish were immediately anesthetized and put on ice following collection. Stomachs were dissected and preserved in 95% EtOH and the contents of each stomach were quantified visually. Diet analysis reveals that all 5 species fed heavily on juvenile Asian carp over a discrete juvenile size range. The duration of the sampling period also allowed us to determine the vulnerability to predation by native predators with changing densities of juveniles in the environment.