The U.S. Supreme Court decided Monday not to get involved in a dispute over how to prevent invasive Asian carp from making their way into the Great Lakes.

The justices turned down a new request from Michigan to consider ordering closure of Chicago-area shipping locks to prevent the fish from threatening the Great Lakes. The locks could provide a pathway to Lake Michigan for the unwanted carp.

The court had previously declined twice to order the locks closed on an emergency basis while it considered whether to hear the case. This time, the court rejected a proposal by Michigan and six other states to use a long-standing case involving water diversion from Lake Michigan as a vehicle for seeking to permanently sever a man-made linkage between the Great Lakes and the Mississippi River basin.

Michigan has led the legal fight to close the locks, arguing that the ravenous carp, weighing up to 100 pounds, could decimate the lakes' $7 billion fishing industry by starving out competitors such as salmon and walleye.