Forecasting the Responses of Bighead and Silver Carp Populations to Commercial Harvest in the Illinois River

Invasive Asian carp are threatening to enter the Great Lakes through Chicago-area canals and rivers, with potentially serious consequence for the aquatic food web.  To minimize propagule pressure on the electric barriers separating Lake Michigan from the Illinois River, the Illinois Department of Natural Resources initiated an Asian carp eradication plan aimed at reducing population densities through intensive commercial exploitation.  However, a prerequisite for the development of an effective eradication program is an understanding of the population dynamics of Asian carp and potential population responses to a range of fishing scenarios.  Using all available data, we assessed the population dynamics of Asian carp in the Illinois River and Middle Mississippi River and developed a population model that could inform decisions regarding the level of effort required to achieve suppression targets for the Illinois River.  Based on our estimates of the life history parameters of silver and bighead carp populations from the Illinois and middle Mississippi Rivers, size-selective harvesting that targets large (> 500 mm) Asian carp is unlikely to reduce these populations to less than 10% of the equilibrium unfished biomass.   Our results highlight the need for baseline life history data to develop an effective control program for the invasive Asian carp species.