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Great Lakes

Eurasian Ruffe DNA Found in Lake Michigan

Eurasian Ruffe Threatens Lake Michigan

Illinois State Director Michelle Carr sits with Fox32 News in Chicago to explain the threat of Eurasian ruffe. 


Two environmental DNA (eDNA) samples collected by The Nature Conservancy and its partners on July 8, 2013, from the Calumet Harbor, at the mouth of the Chicago Area Waterway System (CAWS) in Lake Michigan, tested positive for Eurasian ruffe DNA. eDNA is a surveillance tool used to monitor for the genetic presence of an aquatic species. 

Eurasian ruffe are a small perch species native to Central and Western Europe. They were introduced into Lake Superior in the mid-80s, and have slowly spread along the southern shore of Lake Superior gaining a foothold in northern Lakes Michigan and Huron. The concern is that if ruffe establish in the southern lakes they may compete with native species like walleye and perch because their diet and habitats potentially overlap. 

These Eurasian ruffe detections do not represent a pattern of repeated detection, and while we cannot rule out the DNA coming from a ballast water discharge of ships arriving from an invaded northern Great Lakes port, we think it is just as possible that these detections indicate the presence of Eurasian ruffe in Calumet Harbor. Further monitoring is required to determine whether or not they are present in Calumet Harbor.

Even if live Eurasian ruffe exist in Calumet Harbor, it’s not too late to control the population and prevent establishment. Genetic detection methods such as eDNA has made it possible to detect new invasions early when the invasive species are vulnerable, so that they can be controlled or eradicated if possible. It is important that state and government agencies take advantage of these results and make it a priority to prevent both establishment of Eurasian ruffe in southern Lake Michigan and the spread of other invasives through the CAWS into the Mississippi River.

Eurasian ruffe were identified by the US Army Corps of Engineers as one of the 29 species with the potential to transfer between the Great Lakes and the Mississippi River basins. Ruffe are at home in large rivers, and the Conservancy is worried about the threat that this fish poses to the Mississippi River basin, because its tributaries have nearly twice the number of native fish as the Great Lakes basin, and are considered the world center of freshwater mussel diversity.

Aquatic invasive species are a shared problem and require a shared solution. These results highlight the importance of establishing a two-way barrier to the movement of aquatic invasive species through the CAWS and the need for interim prevention measures that can be implemented sooner rather than later to protect both the Great Lakes and Mississippi from the impacts of aquatic invasive species.


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