August 30, 2005

BOONE - The Iowa Department of Natural Resources (DNR) has confirmed that two zebra mussels were recently found in Clear Lake near Methodist Camp. Further investigation of the area revealed no additional mussels.

"This sighting of zebra mussels is certainly cause for concern," said Kim Bogenschutz, the DNR's aquatic nuisance species program coordinator. "But it is too early to tell if there is a reproducing population in the lake or if this is an isolated incidence of a couple individuals that were released into the lake."

Zebra mussels look like fingernail-sized clams. The D-shaped shells have alternating light and dark bands, and most are less than one inch long.

Zebra mussels are native to the Caspian Sea region of Asia and were introduced into the Great Lakes in the 1980s from ballast water of oceangoing ships. They spread from the Great Lakes to the Mississippi River and were first documented in the Mississippi River in Iowa in 1992. Clear Lake is the state's first inland report of zebra mussels.

Zebra mussels are filter feeders that attach to hard underwater surfaces using fibers called byssal threads. In the case of large infestations, they may interfere with aquatic food chains, kill native mussels and clog water intakes. "There's no getting rid of zebra mussels once they are in a lake or river," Bogenschutz said.

DNR biologists will continue monitoring Clear Lake to determine whether there are more zebra mussels. Divers will search underwater surfaces, and docks and hoists will be inspected for zebra mussels as they are removed from the lake for the winter.

One thing is certain, Bogenschutz said, the sighting of zebra mussels in an interior lake highlights the spread of invasive species in Iowa waters. "The zebra mussels in Clear Lake probably arrived on or in a boat that had picked up the mussels in an infested waterbody," she said.

Young zebra mussels are microscopic and can be unintentionally transported with water in live wells or bait buckets. Adult zebra mussels can attach to boats, trailers and aquatic vegetation.

"People from all over Iowa and the Midwest visit Clear Lake. If they come from an infested waterbody, they can unintentionally transport zebra mussels, Eurasian watermilfoil, or other aquatic invasive species if they do not take the proper precautions to prevent their spread," Bogenschutz said.

Anglers and boaters can help prevent the spread of aquatic invasive species.

Inspect your boat, trailer, and equipment and remove visible aquatic plants, zebra mussels, other animals, and mud before leaving a water access.

Drain water from bait buckets, livewell, bilge, transom, and motor before leaving a water access.

Dispose of unwanted live bait and worms in the trash.

Spray/wash your boat, trailer, and equipment with high pressure or hot water before going to other waters, OR

Dry everything for at least five days before going to other waters.

The DNR is requesting the help of anglers, boaters, and homeowners in the search for zebra mussels in Clear Lake. If you see a zebra mussel, please note its location and contact Jim Wahl, fisheries management biologist, at 641-357-3517.