The Feeding Habits and Relative Abundances of Bowfin, Spotted Gar, and Largemouth Bass: Can Native Piscivores Control Invasive Common Carp?

The Illinois River is a very productive, floodplain river system, but its natural biological productivity has changed through floodplain disconnection, elevated nutrient inputs, and invasive fish species introductions. For example, Common Carp Cyprinus carpio directly and indirectly degrade aquatic ecosystems through benthic foraging behaviors. Currently, floodplain restoration efforts are intended to benefit and improve the natural health of the Illinois River and other rivers worldwide. Thompson and Flag lakes at The Nature Conservancy’s (TNC) Emiquon Preserve serve as one example and have experienced increased Common Carp relative abundances since restoration. Management of Common Carp is critical for maintaining healthy aquatic ecosystems and rotenone is not 100% effective. Biomanipulation of Largemouth Bass Micropterus salmoides at TNC’s Emiquon Preserve has also been tested and results suggested that they do not select Common Carp as a prey type. I hypothesized that hypoxia-tolerant native fishes such as Bowfin Amia calva and Gars Lepisosteus can control Common Carp through direct predation. During 2010-2012, I conducted a comparative diet study to test my hypothesis and whether specific fish community characteristics were correlated with Common Carp relative abundances. The information gained from this research will continually serve useful for the Emiquon Preserve and future floodplain restoration projects.