ST. PAUL — Conservation groups are pressing the U.S. Army Corps of Engineers to help block invasive carp species by ending operations at two Twin Cities-area locks in the Mississippi River.

The corps has proposed reducing hours by nearly half. The congressionally mandated closure of the river’s uppermost lock by June 2015 is expected to eliminate shipping traffic at the next two locks in the metro area.

River tour operators oppose more lock restrictions, which would also limit recreational boating.

The Stop Carp Coalition of 10 environmental and conservation groups wants one of the locks to be open to commercial vessels by appointment only. They said the changes would block carp from migrating north and will protect boaters from being hit by the jumping fish.