Michigan asked the U.S. Supreme Court on Monday to sever a century-old connection between the Great Lakes and the Mississippi River system to prevent Asian carp from invading the lakes and endangering their $7 billion fishery.

State Attorney General Mike Cox filed a lawsuit with the nation's highest court against Illinois, the U.S. Army Corps of Engineers and the Metropolitan Water Reclamation District of Greater Chicago. They operate canals and other waterways that open into Lake Michigan.

Bighead and silver carp from Asia have been detected in those waterways after migrating north in the Mississippi and Illinois rivers for decades.

Officials poisoned a section of the Chicago Sanitary and Ship Canal this month to prevent the carp from getting closer to Lake Michigan while an electrical barrier was taken down for maintenance.

But scientists say DNA found north of the barrier suggest at least some of the carp have gotten through and may be within 6 miles of Lake Michigan. If so, the only other obstacle between them and the lake are shipping locks and gates, which open frequently to grant passage for cargo vessels.

The lawsuit asks for the locks and waterways to be closed immediately as a stopgap measure, echoing a call by 50 members of Congress and environmental groups last week. But the suit goes further, also requesting a permanent separation between the carp-infested waters and the lakes.