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Grass carp have arrived in Great Lakes, study concludes

Grass carp are considered the greatest invasive species threat to the Great Lakes because they "aggressively outcompete" native fish for food and are capable of overtaking an ecosystem, according to Fisheries and Oceans Canada.

Fish have been found in Lake Michigan, Erie and Ontario

A grass carp similar to the one shown found here was caught in Lake Erie just west of Point Pelee. (Toronto and Region Conservation) (Toronto and Region Conservation)

Grass carp are living in the Great Lakes, according to a new international study.

The fish, one of four Asian carp species, are believed to have found their way into lakes Michigan, Erie and Ontario.

"Unfortunately, the news is not good," said Robert Hecky, vice-chair of the Great Lakes Fishery Commission. "The assessment suggests grass carp pose substantial risk to the Great Lakes."

Grass carp are considered the greatest invasive species threat to the Great Lakes because they "aggressively outcompete" native fish for food and are capable of overtaking an ecosystem, according to a media release from Fisheries and Oceans Canada.

The report, titled Binational Ecological Risk Assessment of Grass Carp for the Great Lakes Basin, was a combined effort by Canadian and American experts including Fisheries and Oceans Canada, the U.S. Fish and Wildlife Services and the Great Lakes Fisheries Commission.

Between 2013 and 2016, 23 Grass Carp were caught and analyzed. Nine of the fish who were caught were fertile and all of them were born outside of the Great Lakes then made their way into Canada.

Tommy Goszewski, a technician with the U.S. Geological Survey, holds a grass carp taken from a pond at an agency lab in Columbia, Mo., in spring 2013. (AP Photo/U.S. Geological Survey)

"Grass carp have been in the Great Lakes for ... probably 30 years or even more but they've been sterile," said Mark Gaden, with the Great Lakes Fishery Commission. "Lately ... we've been seeing recurring incidents of fertile grass carp in the Great Lakes. They're not supposed to be fertile."

The fish probably made their way through the Chicago-area waterway system, an artificial canal that connects the Mississippi River to the Great Lakes, he added.

"Grass carp are abundant in the Mississippi River system," Gaden explained.

In response to the study, Dominic LeBlanc, Canada's minister of fisheries and oceans, said the government is committed to protecting the Great Lakes.

"This study will inform our management and policy decisions with an objective of preventing the survival, establishment and spread of grass carp in the Great Lakes basin on both sides of the border," he said.