Comparison of the relationship between nutrient loads and fish production in Lakes Michigan and Erie

Session: Cross-lake Comparisons: Frameworks for Understanding Ecosystem Change

Hongyan Zhang, Eureka Aquatic Research, LLC., [email protected]
Ed Rutherford, NOAA Great Lakes Environmental Research Laboratory, [email protected]
Doran Mason, NOAA Great Lakes Environmental Research Lab, [email protected]
Tonyisha Harris, 1997, [email protected]
Eric Weimer, Ohio Department of Natural Resources, [email protected]
Ali Shakoor, Wayne State University, [email protected]

Abstract

The Great Lakes are under polarizing changes related to nutrient management and food web disruption from invasive species. Nearshore waters have become more eutrophic, while offshore waters are more oligotrophic. While nutrient management aims to control eutrophication in the nearshore, oligotrophication affects management of offshore fish production and fisheries. Moreover, Dreissena mussels have fundamentally changed the nutrient cycling processes in the Great Lakes.  We used Ecopath with Ecosim models to investigate the relationships between nutrient loads and fish production under conditions of with and without dreissenid mussels for western Lake Erie and Lake Michigan. Western Lake Erie represents the nearshore food web, and Lake Michigan model simulates the offshore food web. In both lake simulations, biomass of most fish groups increased with increasing nutrient loads. However, in western Lake Erie, the increases in most fish biomass slowed down after nutrient loads passed the current load target.  Details about fish biomass changes in responding to nutrient loads, with and without dreissenid mussels and between the two lakes will be presented.