Zebra mussels have become a household name because of the significant environmental and economic damage they have caused across the Great Lakes region. Now, recent scientific findings show that another aquatic invasive species may have entered southern Lake Michigan.
On July 8, water samples collected from the Calumet Harbor by researchers from The Nature Conservancy, University of Notre Dame, and Central Michigan University tested positive for Eurasian ruffe DNA. The fact that these samples were found at the mouth of the Chicago Area Waterway System means that if ruffe are present, they not only pose enormous risks to the southern Great Lakes, but to the Mississippi River basin as well.
The Waterway System consists of more than 100 miles of canals and waterways, including the Chicago River and the Calumet River. The system moves storm water and sewage away from Chicago’s water supply and creates an artificial connection between the Mississippi River and Lake Michigan. This artificial connection is a high-risk area for the movement of aquatic invasive species in both directions. Zebra mussels and round goby easily moved through the Waterway System to invade the Mississippi basin, and more are on the way. Another 29 aquatic invasive species in the Great Lakes could swim or float through the Waterway System and enter the Mississippi basin — one of which is Eurasian ruffe.
Eurasian ruffe were introduced into Lake Superior from ships’ ballast water in the mid-80s, and have slowly spread into northern Lake Michigan and Lake Huron. If ruffe establish in the southern lakes, they may compete with native species like walleye and perch. Additionally, this fish potentially poses a grave threat to the Mississippi River basin, as its tributaries have nearly twice the number of native fish as the Great Lakes and are considered the world center of freshwater mussel diversity.