Attorneys for and against closing Chicago-area shipping locks to stop the spread of Asian carp are making their final pitches to a federal judge.
Oral arguments Monday are the last step before Judge Robert Dow decides the issue.
Michigan, Minnesota, Ohio, Pennsylvania and Wisconsin say the action would ensure the invasive fish won't overrun the Great Lakes and devastate a $7 billion-a-year fishing industry.
But the city of Chicago, barge companies and others counter that closing the locks would undermine flood-control measures and cost businesses billions of dollars.
Dow heard witness testimony in September. The states say carp could enter Lake Michigan from Chicago waterways at any time, so Dow could rule soon after oral arguments.