Cooperative Fish and Wildlife Research Units Program: Mississippi
Education, Research and Technical Assistance for Managing Our Natural Resources

The Tennessee River basin and its cascade of reservoirs are home to some of the most diverse fish assemblages in the world. This unique system is threatened by the ongoing invasion of Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis, hereafter bigheaded carps. Bigheaded carps may directly compete for food resources with native clupeid species such as Gizzard Shad Dorosoma cepedianum, and this potential interaction could have damaging ecological and economic consequences. High relative abundances of Gizzard Shad are crucial to the Tennessee River food web and associated fisheries because of their role as a forage base for piscivorous species. We analyzed an extensive dataset of annual gillnetting and electrofishing data extending from 1990 to 2017, to test whether Gizzard Shad relative abundances have changed in Tennessee River reservoirs since the invasion of bigheaded carps. Our analyses indicate that Gizzard Shad abundances have been declining and were already declining prior to the discovery of bigheaded carps in the Tennessee River. The Tennessee River system needs to be continually monitored for any signs of possible interactions between bigheaded carps and Gizzard Shad.