Trophic Analysis of Asian Carps in Newly Invaded Prairie Streams

South Dakota prairie streams are on the northwestern front of the bighead and silver carp invasion.  Predicting long-term effects of Asian carps are difficult, but there is potential for altered food web structure and competition with native planktivores.  We used stable isotope and diet analysis to estimate Asian carp trophic position in the food web and to identify diet overlap with native species.  Standardized sampling at ten sites occurred seasonally from 2009-2012.  Isotope analysis revealed that native planktivores and Asian carps were feeding at the same trophic level with means ranging from 13.70 (SE=0.15) to 15.63 (SE=0.20) δ15N.   Asian carps were 5% more depleted in δ¹³C than native planktivores indicating that Asian carps were acquiring more energy from open water resources than native planktivores which were more benthic. Based on δ¹⁵N and δ¹³C, there was trophic overlap between bighead carp and gizzard shad, indicating the potential for food resources competition. Stomach contents of Asian carps were diverse consisting of rotifers, diatoms, detritus, and inorganic matter.  This study represents a unique opportunity to study the beginning of an invasion and follow the potential changes in the food web as the population of Asian carps increase.