State and federal authorities should permanently close the Mississippi River lock at the Twin Cities Ford Dam to slow the spread of Asian carp, a coalition of Minnesota conservation groups said this week.

Their comments followed news that silver carp DNA has been found as far upriver as Coon Rapids and threw new weight behind one of the more controversial measures that has been proposed to stop the invasive species.

When the Mississippi's chain of lock and dams closes for the winter, on Dec. 5, the one at the Ford dam should stay closed after ice-out until state and federal authorities adopt some long-term carp prevention strategy, the advocates said this week.

The coalition will present its plan at Gov. Mark Dayton's next carp summit Dec. 20. It calls for short-term priorities to be enacted this winter, mid-term priorities to be completed over the next six to 18 months and long-term priorities for over 18 months.

The voracious carp species, which can disrupt aquatic food chains and displace more desirable fish, have been moving up the Mississippi from southern states for some years. Water samples taken by the state Department of Natural Resources have found Asian carp DNA in the St. Croix River below St. Croix Falls, Wis., and the Mississippi below Hastings -- then, recently, around and upriver from the Coon Rapids Dam. So far, no actual carp have been caught at those locations.