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Grass Carp Overstaying Their Welcome in Illinois

PHOTO: Grass Carp have been found in unintended areas of the Great Lakes, leaving researchers concerned about their potentially destructive habits. Photo credit: US Geological Survey.
PHOTO: Grass Carp have been found in unintended areas of the Great Lakes, leaving researchers concerned about their potentially destructive habits. Photo credit: US Geological Survey.
March 12, 2014

CHICAGO - Fish introduced into the Great Lakes to help manage weeds could be overstaying their welcome. Grass carp feed on aquatic plants and new research finds they've been captured in places where they were not originally intended to be used.

Marion Wittmann is a post-doctoral researcher at the University of Notre Dame and the lead author of the study.

"Grass carp, if they establish, and it's not clear whether they've established yet, could come in and impact those wetland areas or some of the native plants," Wittmann said. "Which in turn would have effect on other species."

Wittmann said wetland plants provide spawning grounds and habitat for young fish, and some species would not do well in places infested with grass carp.

According to the research, 45 grass carp are known to have been caught in the Great Lakes Basin from 2007 to 2012, which is enough to be of some concern.

The paper was published online by the Canadian Journal of Fisheries and Aquatic Sciences.

According to Wittmann, the Great Lakes states have a wide variety of regulations about grass carp. They are prohibited in Michigan and Minnesota. In Wisconsin they are only allowed for research purposes. By contrast, Illinois, Indiana and Ohio allow the use of grass carp, but only those that have first been sterilized.

"They don't reproduce, but we'd still get the benefit of using them as a weed control, said Wittmann. "So, all these different states have different permissions or different kinds of policies or regulations that make it hard to manage across the Great Lakes watershed."

Wittmann added that the fish do have some beneficial qualities and she doesn't think they should be banned entirely.

"Grass carp are a non-chemical alternative for treating aquatic weeds," she said. "So, by using grass carp, we don't have to put pesticides in to remove weeds."

She said she believes the Great Lakes states should work to better coordinate their efforts and develop policies that can allow for the safe use of grass carp.

Read the research grass carp study at the Canadian Journal of Fisheries and Aquatic Sciences

Mary Kuhlman, Public News Service - IL