Boaters are banned from the secure zone, which extends one-half mile from the Selfridge coast and spans the area of Anchor Bay from Hall Road (Rosso Highway) south to Mac & Ray's marina.

The Coast Guard boosted patrols in the area Sept. 11, hours after the terrorist attacks on New York and the Pentagon. But the security zone was announced Wednesday in advance of Saturday's opening of duck hunting season. The waters near Selfridge have been a popular spot for duck hunters in the past.

"We're just trying to be diligent and protect any areas that are considered important for national security or the health and well-being of the public," said Coast Guard Lt. Commander Brian Hall.

Those who breach the security zone could face federal prosecution and penalties of up to 10 years in prison and a $10,000 fine.

The zone is being patrolled by the Coast Guard, Macomb County Sheriff's Department and Selfridge security patrols.

Alice Errington, spokeswoman for the base, said the Selfridge waterfront is not entirely secured with fencing. What's more, the prospect of hunters shooting guns nearby when the military base is on heightened alert could be unnerving.

"If nothing else, it might alarm some people," Errington said.

The round-the-clock patrols will continue indefinitely, according to the Coast Guard. They were ordered by Commander Pat Gerrity of the Coast Guard's Detroit district office.

Hall would not say how many Coast Guard boats are patrolling the area, but the operation is being assisted by Coast Guard reservists who have been called up since Sept. 11.

The Coast Guard has activated 2,727 reservists nationwide to protect the U.S. coastline. Some 270 have been called to active duty in the Great Lakes region, including seven in southeast Michigan.

Hall said the security zone will not block access to and from Mac & Ray's marina, which is located adjacent to the base and at the southern edge of the zone. The lieutenant commander said boaters can secure authorization to enter the zone under "unusual circumstances" if they receive approval in advance.