DIETARY OVERLAP BETWEEN BIGHEAD AND SILVER CARP WITH THREE NATIVE FILTER FEEDING 
FISHES OF THE ILLINOIS AND MISSOURI RIVERS

Schuyler J. Sampson1, John H. Chick2, and Mark A. Pegg3
1Illinois Natural History Survey, Center for Aquatic Ecology, 607 East Peabody 
Drive, Champaign, IL 61821, 2Great Rivers Field Station, 8450 Montclair Ave., 
Brighton, IL 62012, 3Illinois River Biological Station, 704 N. Schrader, Havana, 
IL 62644.

During the 1980’s bighead carp (Hypophthalmichthys nobilis) and silver carp 
(Hypophthalmichthys molitrix) were introduced into the Mississippi River via 
accidental escape from aquaculture facilities. Since their introduction, 
populations of these non-native fishes have dramatically increased and expanded 
their range within the Mississippi River drainage. The result has been a rising 
concern about the potential negative effects on native fishes. Both species are 
considered filter-feeders, consuming zooplankton and algae; therefore, bighead 
carp and silver carp may directly compete for food resources with three 
economically and ecologically important native filter-feeders: bigmouth buffalo 
(Ictiobus cyprinellus), gizzard shad (Dorosoma cepedianum) and paddlefish 
(Polyodon spathula).  Our objectives for this investigation were to: 1) assess 
zooplankton abundance and composition to allow for the evaluation of feeding 
electivity and influence of bighead carp and silver carp on the zooplankton 
community, and 2) evaluate dietary overlap between bighead and silver carp with 
these three native filter-feeders. Our preliminary data suggest the diet of 
bighead carp and silver carp primarily consists of rotifers and other 
zooplankton less than 200 mm, and the diets of bighead carp and silver carp are 
more similar to gizzard shad and bigmouth buffalo diets than with paddlefish 
diet.

Keywords: Asian carp, diet overlap, native fish, Mississippi River, zooplankton, 
Illinois River