Harvest as Control of Asian Carp

Bighead and silver carp (hereafter Asian carp) became abundant in the upper Mississippi River over a decade ago and now are threatening to invade the Great Lakes via the Illinois River.  We conducted split-beam echosounding and acoustic telemetry to determine the standing biomass and potential immigration of these species into the Illinois River during 2011.  These estimates provide insight into the potential for control efforts such as commercial harvest to reduce the populations and prevent individuals from moving upstream toward the Great Lakes. Greater than 3,000 kilometers of echosounding transects revealed that Asian carp comprise 60% of fish biomass in the main channel; standing biomass of carp in the river was about 1.5 million kilograms.  Movement of 380 tagged Asian carp into the Illinois River from the Mississippi River revealed a 30% immigration rate.  Asian carp moved as far as 240 km upstream.   Given that annual mortality of Asian carp was 70%, production plus immigration may yield greater than 5 million kilograms per year in the Illinois River.  To prevent this mass of individuals from moving upstream, harvest and other control efforts will need to be sufficiently efficient to suppress standing biomass plus individuals moving in from other river reaches.