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Another threat to the Great Lakes

Zebra mussels have become a household name because of the environmental and economic damage they have done to the Great Lakes region. Now, scientific findings show that another aquatic invasive species may have entered southern Lake Michigan, threatening native fish and wildlife populations with disaster.

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 Chicago Area Waterway System (CAWS) means that if ruffe are present, they not only pose enormous risks to the Great Lakes region, but to the Mississippi basin as well.

The CAWS consists of more than 100 miles of canals and waterways, including the Chicago River and the Calumet Rivers. The system moves storm water and sewage away from the city’s water supply and creates an artificial connection between the Mississippi River and Lake Michigan. This artificial connection is what has become a source of growing concern for environmentalists, non-government organizations, industries, business leaders, and public officials alike. A high-risk area for the movement of aquatic invasive species in both directions, the CAWS has already allowed zebra mussels and round goby to invade the Mississippi basin, and more are on the way. Currently there are 10 invasive species in the Mississippi River that could use the CAWS to invade the Great Lakes and 29 species in the Great Lakes that could enter the Mississippi basin — one of which is Eurasian ruffe.

Eurasian ruffe were introduced into Lake Superior from ship’s ballast water in the mid-80s, and have slowly spread into northern Lake Michigan and 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.

The introduction of Eurasian ruffe to the Mississippi basin would spell disaster not only for native fish and wildlife, but to local economies as well. A 2012 report by Anderson Economic Group commissioned by The Nature Conservancy revealed that it costs hundreds of millions of dollars to control aquatic invasive species annually. Industries like sport and commercial fishing, water treatment, power generation and tourism are all affected by this threat.

There are preventative measures in place, but we need to do more. The electric barriers currently used to keep Asian carp from entering Lake Michigan only work one way; they won’t stop Lake Michigan species from moving into the Mississippi River. Furthermore, these barriers will not prevent the passage of invertebrates or aquatic plants that can be just as harmful as invasive fish.

While we need additional testing to confirm the presence of Eurasian ruffe in southern Lake Michigan, we cannot afford to wait to take action. The introduction of new organisms poses enormous economic risks to Illinois, the Great Lakes, and downstream Mississippi basin states. This is a shared problem that requires a shared solution. Understanding the magnitude of this threat, continuing stakeholder dialogue, and collaborating on an interim solution that will prevent the two-way movement of invasive species are the first steps towards a long-term solution.

You can learn more about the Conservancy’s work to fight invasive species on

Michelle S. Carr is state director of The Nature Conservancy in Illinois.

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