Potential Impacts of Asian Carps on the Food Web and Fisheries in a Lake Michigan Estuary

Bighead (Hypophthalmichthys nobilis) and silver (H. molitrix) carp (Asian carps) threaten to invade the Great Lakes and disrupt aquatic food webs and fisheries. Muskegon Lake (ML) is a shallow, productive, drowned river mouth lake that supports important recreational fisheries and provides nursery habitats for many ecologically or economically important fishes of Lake Michigan. ML is susceptible to Asian carp invasion given its eutrophic status, its close proximity to the sources of Asian carps, and the presence of suitable spawning habitat upstream in the Muskegon River. We used Ecopath with Ecosim (EwE) to evaluate the potential impact of Asian carps on food web structure, fish production and fisheries. The food web model included 1 detritus group, 1 algal group, 5 zooplankton groups, 15 fish groups with a couple of species broken down to 2-3 life stages, and 5 benthic groups. We used data collected from ML during 2000-2006 to balance the Ecopath model. Under current conditions of nutrient loading, fish stocking and harvest, we added Asian carps to the food web, and used Ecosim to forecast the potential impact of Asian carps on food web structure and fish production over a period of 50 years.