Ecosystem and Fisheries Impacts of Asian Carps on Lake Michigan - the Atlantis Ecosystem Model Approach

Bighead (Hypophthalmichthys nobilis) and silver (H. molitrix) carps ('AC', Asian carps) threaten to invade the Great La­­­­kes and may disrupt food webs and fisheries through the consumption of lower trophic levels. However, these potential impacts vary amongst habitats (i.e., offshore, nearshore, drown river mouths and tributaries). To account for habitat heterogeneity, we are using the Atlantis model that incorporates spatially explicit 3-D information on biological (food web), geochemical, and physical processes and simulates potential impacts on food webs resulting from stressors (e.g., AC invasion). The model was forced by nutrient inputs, and daily flow fields and water temperatures from a 3-D hydrodynamic model, and calibrated (without AC) with available abundance/biomass time series of modeled groups. AC were then added to the food web to forecast impacts for a range of scenarios: three AC biomass levels (none, low and high), with/without climate change, and high/low nutrient loading. By comparing the differences amongst forecasts, we assessed the likely impacts of AC on food webs, and production, recruitment and harvest of key prey and predator fish species among Lake Michigan habitats.