Monday, January 30th, 2023
Monday, January 30th, 2023

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Eurasian ruffe: another river fish causing worry

Chicago — Genetic evidence of Eurasian ruffe, an invasive species originating in the temperate regions of Europe and northern Asia, was found in Calumet Harbor in a recent survey of Lake Michigan conducted by a conservation group.

The findings raise concerns that the fish could jump over to the Mississippi River system via the Chicago Area Waterway System, a month before a government plan to separate the two systems is expected to be released by the U.S. Army Corps of Engineers.

“We are concerned about the Mississippi River,” said Kevin Irons, aquatic nuisance species program manager for Illinois DNR. “They do like rivers. We don’t want that to happen.”

Irons said it is not believed that there is an established population of Eurasian ruffe at the southern end of Lake Michigan.

Two eDNA samples collected in July were the only positives for the species, and do not necessarily mean that there are live fish present, Irons said.

The Nature Conservancy, which is part of a research team trying to determine the presence of invasive species throughout the Great Lakes, along with researchers from the University of Notre Dame and Central Michigan University, announced the positive results.

“These Eurasian ruffe detections do not represent a pattern of repeated detection, and while we cannot rule out the DNA coming from 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,” Lindsay Chadderton, aquatic invasive species director for The Nature Conservancy’s Great Lakes Project said in a statement.

The samples, which were collected at the mouth of the Chicago Area Waterway System, had initially tested negative for Eurasian ruffe, only to test positive on a second round of testing, Irons said.

Irons said there is a good chance that the genetic material was brought over on ballast tanks that had water from Lake Superior, where the species has been established since the 1980s. The fish have slowly spread along the south shore of Superior and are now established on the northern ends of Lake Michigan and Lake Huron.

“We have mild concern,” Irons said. “I think right now there is good traffic from Duluth-Superior to Chicago-Calumet.”

Initially, the fish are believed to have first invaded the Great Lakes via shipping traffic and ballast water between Europe and Lake Superior.

“Ultimately, that’s how these guys were transported,” Irons said. “They came over in ballast water from across the pond. Now there are regulations for those vessels.”

Irons said that if Eurasian ruffe, which are a small perch species, do establish themselves on the southern end of Lake Michigan, perch fishermen may be the first to come into contact with them.

“We have perch fishermen in that harbor,” said Irons. “If they are there in any numbers, people will start catching them.”

Chadderton wrote that there are concerns that they may compete with native species such as walleye and perch in Lake Michigan because their diets and habitats can overlap.

Even though most of the concern about invasive species jumping watersheds has centered around Asian carp in the Mississippi River gaining access to the Great Lakes via Chicago Area Waterway system, Eurasian ruffe were one of 29 identified by the Army Corps with the potential to transfer between the Great Lakes and the Mississippi River basins.

This summer, Illinois Gov. Pat Quinn broke with Illinois’ previous stance opposing separation on the Chicago Sanitary and Shipping Canal.

At a meeting of governors held in Michigan, Quinn called separation the “ultimate solution.”

The possibility of Eurasian ruffe reaching the Mississippi River has The Nature Conservancy worried about that possibility since the fish are most at home in large rivers, and the Mississippi’s tributaries have nearly twice the number of native fish as the Great Lakes basin, Chadderton wrote.

“These results highlight the importance of establishing a two-way barrier to the movement of aquatic invasive species through the Chicago Area Waterway System and the need for interim prevention measures that can be implemented sooner rather than later to protect both the Great Lakes and the Mississippi from the impacts of aquatic invasive species,” Chadderton said.

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