Assemblage and Trophodynamic Structure of Three Prairie Rivers during the Initial Invasion of Bighead Carp Hypophthalmichthys Nobilis and Silver Carp H. Molitrix

Invasive species effect global change by altering community composition and the interactions and processes that occur within recipient ecosystems. Knowledge of impacts on community structure and food webs is essential to recognize invasion effects. The northern Great Plains, represents the northwestern North American front of two global invaders, Bighead Carp Hypophthalmichthys nobilis and Silver Carp, H. molitrix. Post-invasion research in invaded areas suggests that their expansion could have wide ranging ecological and economic consequences through middle out and cascading effects on native fishes and plankton. This study examined assemblage structure and food web consequences of Asian carps invasion at the onset in three Great Plains tributaries. We quantified invasive species-driven ecological changes in assemblage structure and tested whether these changes corresponded to changes in fish trophic position and river food web structure using stable isotope and diet analysis. We showed that silver carp used numerous food resources. Isotope analysis and diet analysis revealed trophic overlap between Asian carps and native planktivores, particularly Gizzard shad and Silver Carp and Bighead Carp and Bigmouth Buffalo. Results indicated negative impacts may already be occurring between Silver Carp and Emerald Shiner, and there is potential for trophic competition between Silver Carp and Gizzard Shad.