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Zebra Mussels Found in Eastern Iowa Lake

July 25, 2006

The Iowa Department of Natural Resources (DNR) has confirmed the presence of zebra mussels in Lake Delhi, an on stream impoundment of the Maquoketa River, in Delaware County. Local residents recently contacted the DNR after discovering zebra mussels attached to concrete block they removed from the lake. Further investigation revealed additional mussels on rocks above and below the dam.

"The number and various sizes of zebra mussels that were found appear to indicate that there is a reproducing population in the lake," said Kim Bogenschutz, the DNR's aquatic nuisance species program coordinator.

Zebra mussels look like small, fingernail-sized clams. The D-shaped shells have alternating light and dark bands, and most are less than one inch long. Zebra mussels are filter feeders that can form dense clusters as they attach to hard underwater surfaces. In the case of large infestations, they may interfere with aquatic food chains, kill native mussels, clog water intakes, increase algae blooms, and cover beaches with dead shells. There is no getting rid of zebra mussels once they are in a lake or river.

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. There were no reports of zebra mussels in interior waters until 2005 when two adults were found in Clear Lake and in 2006 when juvenile zebra mussels were reported from the same area in Clear Lake.

DNR biologists plan to continue monitoring Lake Delhi to determine the distribution of zebra mussels in the lake and in the Maquoketa River below the dam.

One thing is certain, the sighting of zebra mussels in Lake Delhi highlights the spread of invasive species in Iowa water, she said.

"The zebra mussels in Lake Delhi probably arrived on or in a boat that had picked up the mussels in an infested water body," said Bogenschutz.

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. If boaters come from an infested water body, 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 emphasized that anglers and boaters can help prevent the spread of aquatic invasive species by following the steps outlined below.

* 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, live well, bilge, transom, and motor before leaving a water access.

* Dispose of unwanted live bait and worms in the trash. Never release plants, fish, or animals into a water body unless they came out of that water body.

* 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 will work with local units of government and the lake association to increase public awareness efforts to control the further spread of zebra mussels. The DNR is also requesting the help of anglers, boaters, and homeowners in the search for zebra mussels in Lake Delhi. If you see a zebra mussel, please note its location and contact Bryan Hayes, the local fisheries management biologist, at 563-927-3276.


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