Signs of the times: Isotopic signature changes in several fish species following invasion of Lake Constance by quagga mussels

Since the arrival of invasive quagga mussels Dreissena rostriformis bugensis in Lake Constance, significant changes zooplankton and benthic invertebrate community were observed. Five years later mussel has become dominating species community. Its effects on other components food web, especially those at higher trophic levels such as fish, remain unclear around world. To evaluate actual impact quaggas local web stable isotope compositions pelagic whitefish different fish from before after invasion compared. A increase δ13C was detected one year establishment lake. This change most likely consequence an benthic-derived nearshore primary production a shift towards more littoral feeding, than dietary composition. Stomach content analysis contemporary samples revealed that (Coregonus wartmanni) still feed exclusively zooplankton. In contrast, macrophthalmus), roach (Rutilus rutilus) tench (Tinca tinca) show today high consumption. However, this behaviour alone could not explain observed differences δ15N periods invasion. The results suggest energy sources pathways have changed considerably for both dwelling Constance following quaggas.