Midwest Fish & Wildlife Conference 2016

AUTHORS: Eli Lampo*, Department of Biological Sciences, Western Illinois University; James T. Lamer, Department of Biological Sciences, Western Illinois University; James H. Larson, Upper Midwest Environmental Sciences Center, United States Geological Survey; Brent Knights, Upper Midwest Environmental Sciences Center, United States Geological Survey; John Vallazza, Upper Midwest Environmental Sciences Center, United States Geological Survey; Levi Solomon, Illinois River Biological Station, Illinois Natural History Survey; Rich Pendleton, Illinois River Biological Station, Illinois Natural History Survey; Andrew Casper, Illinois River Biological Station, Illinois Natural History Survey

ABSTRACT: In 2014, a large Asian carp spawning event in the La Grange reach of the Illinois River produced an abundance of age-one 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 of the Illinois River using pulse 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. Asian carp ≤250 mm were collected to validate age and build a length vs. pharyngeal teeth regression. 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 (25/222, 11%), white bass (6/56, 10%), and shortnose gar (6/30, 20%). Silver carp lengths are being estimated to determine the size relationship between silver carp and their predators. Identifying species and size of native predators able to utilize this resource provides insight into natural biological management of this invasive species.