An autopsy of the silver carp found this past June, nine miles from Lake Michigan in the Little Calumet River of the Chicago Area Waterway System, has found that the fish came from the Illinois/Middle Mississippi watershed.

Analysis shows the 4-year-old male silver carp spent a quarter of its life in the Des Plaines River watershed before being caught and removed from the Little Calumet River above the U.S. Army Corps of Engineers’ electric dispersal barriers. Though it is not known how the fish was able to get above the barrier defense system, analysis shows that the fish spent no more than a few weeks to a few months in the stretch of river where it was found.

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The autopsy and analysis of the silver carp was completed by Southern Illinois University, the U.S. Fish and Wildlife Service and the U.S. Geological Survey.

“While we were disappointed to find an Asian carp close to Lake Michigan, we are pleased that we had a successful plan in place that found and removed it so quickly,” said Kevin Irons, Illinois Department of Natural Resources Aquatic Nuisance Species program manager. “We will continue to work with our partners to ensure we have the resources we need to maintain the effectiveness of our monitoring plan.”

The live capture of the silver carp on June 22 in the Little Calumet River just below the T.J. O’Brien Lock and Dam triggered two additional weeks of intense sampling in the area, as outlined in the Asian Carp Regional Coordinating Committee’s Contingency Response Plan. The multi-agency response included electrofishing and contract netting across more than 13 miles of the Calumet River, Little Calumet River and Calumet Harbor. More than 20,000 fish were captured, but no additional bighead or silver carps were caught or seen.

“Our work with federal, provincial and state partners to prevent the establishment of Asian carp in the Great Lakes continues to be coordinated and proactive,” said Charlie Wooley, U.S. Fish and Wildlife Service Midwest Deputy Regional Director. “After more than eight years working in the Illinois Waterway, we’re not backing down. We are going to continue to hold the line against these aquatic invaders.”

Future work stretches into the fall and includes intensive fish removal in the Illinois Waterway by contracted commercial fishers, coordinated fish sampling around the electric dispersal barriers and heightened detection work in the Lockport and Brandon Road Pools of the waterway.