Identification of Bighead Carp and Silver Carp Natal Environments and Detection of Lock and Dam 19 Passage in the Upper Mississippi River: Insights from Otolith Chemistry

Knowledge of the principal natal environments and movement patterns of Bighead carp (Hypopthalmichthys nobilis) and Silver carp (H. molitrix) in the upper Mississippi River (UMR) would be valuable for informing potential control measures to limit further population expansion and impacts of these species.  A high-head dam (Lock and Dam 19) on the UMR delineates downriver areas where Asian carp are well-established from upriver pools where these species are less abundant and evidence of reproduction and recruitment are limited.  However, the principal natal environments of Bighead and Silver carp in the UMR and the relative contributions of local recruitment and immigrants from downriver to emerging populations upstream of Lock and Dam 19 are unknown.  The objectives of this study were to identify natal environment of Asian carps collected in the Upper Mississippi River using otolith stable isotope and trace element compositions and to use natal environment assignments and capture location to detect individuals that passed through the lock chamber at Lock and Dam 19.  Our results indicate that multiple sources (including tributaries) contribute to Bighead and Silver carp in the UMR and that fish passage through Lock 19 may be more common than previously thought.