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Boaters', Anglers' Help Critical To Slowing Spread Of Zebra Mussels

July 20, 2006

Jefferson City, Missouri - The recent discovery of zebra mussels at Lake of the Ozarks caught some by surprise, but officials with the Missouri Department of Conservation say this is just the latest chapter in a long and continuing saga. Agency officials say this latest development is a reminder of the important role citizens play in efforts to slow the spread of the troublesome mollusk and other potentially damaging exotic species.

The zebra mussel (Dreissena polymorpha) is native to the Caspian Sea region. Adults are dime- to quarter-sized. They attach to solid objects and gather food by filtering tiny plants and animals from the surrounding water. Females produce up to a million offspring a year. They can form dense colonies several layers thick, encrusting objects with their shells.

In some waters, zebra mussels thrive and produce heavy infestations. They can clog the water intakes of boat motors and power plants. They compete with native animals for food, and they can smother native mussels, many of which already are endangered.

An alert citizen noticed the fingernail-sized zebra mussels June 15 on submerged objects beneath a private boat dock at Lake of the Ozarks. An inspection of nearby docks turned up a total of about 50 of the mussels.

State and federal officials are working to determine the extent of the infestation. They say it is too early to tell whether the exotic mussels will thrive in Lake of the Ozarks, but they say the fact that zebra mussels have reached Lake of the Ozarks is not surprising, considering the species' history in North America:
--1985-1986 - Zebra mussels enter the St. Lawrence Seaway, probably in ballast water from ocean-going ships.
--1988 - Zebra mussels found in Lake St. Clair.
--1989 - First live zebra mussels found in Lake Michigan.
--1991 - First zebra mussels discovered in the upper Mississippi River.
--1992 - Zebra mussels spread along the Arkansas River between the Mississippi River and Oklahoma.
--1993 - Zebra mussels found in inland lakes in Michigan and in the Mississippi River in southern Louisiana.
--1999 - A single adult zebra mussel found attached to a native mussel shell in the Meramec River near the I-55 Bridge.
--2000 - A marina employee spots thousands of zebra mussels on a 32-foot cabin cruiser brought to Lake of the Ozarks from out of state.
--2001 - A small number of zebra mussel shells turn up in a filter screen at a power plant on the Missouri River in the Kansas City area.
--2003 - Zebra mussels found in a lake in Kansas.
--2005 - Zebra mussels found in a lake in Oklahoma.

Brian Canaday, who oversees the Conservation Department's efforts to keep invasive plants and animals out of Missouri, says the fact that it took this long for zebra mussels to invade interior waters of the Show-Me State is a strong indication that Missourians take zebra mussel control seriously.

"The zebra mussel is easy to spread," said Canaday. "It could have been here much sooner if anglers and pleasure boaters were not taking care to avoid spreading it."

Immature zebra mussels, called veligers, are tiny and float free in infested waters. They can hitch a ride to new locations in even small amounts of water left in bait buckets, live wells, boat bilges or in the cooling systems of marine motors. Adults attached to the hulls of boats are capable of surviving out of water for several days.

If you are a boater, angler, water-skier, scuba-diver, sailor or canoeist, you can help prevent the spread of zebra mussels by taking the following precautions.

IDENTIFY - Learn how to identify zebra mussels. For information, write to MDC, "Zebra Mussel Watch Card" and "Zebra Mussel: Missouri's Most Unwanted," P.O. Box 180, Jefferson City, MO 65102. Or E-mail a request for these publications to pubstaff@mdc.mo.gov. If you suspect a new infestation, report it to the nearest Conservation Department office.

INSPECT - Thoroughly inspect your boat and trailer and other items that come in contact with the water. Scrape off and trash any suspected mussels, however small. Remove all weeds hanging from the boat or trailer before leaving any water body.

DRAIN - Drain water from the motor, live well, bilge and transom wells and any other water from your boat and equipment while on land before leaving any water body.

DUMP - Trash leftover bait away from water before leaving any water body. Leftover live bait that has contacted infested waters should not be taken to uninfested waters.

RINSE - When you get home - before launching your boat into uninfested waters - thoroughly rinse and dry the hull, drive unit, live wells, live well pumping system, bilge, trailer, bait buckets, engine cooling system and other boat parts that got wet while in infested waters; use a hard spray from a garden hose.

If your boat was in infested waters for a long period of time, or if you find any attached adult mussels, use hot (104 F) water instead of cold, or tow the boat through a do-it-yourself carwash and use the high pressure hot water to "de-mussel" your boat. Do not use chlorine bleach or other environmentally unsound washing solutions.

DRY - Let boats, motors and trailers dry thoroughly in the sun for at least five days before boating again.

IN THE SLIP - In infested waters, the best way to keep a hull mussel-free is to run the boat frequently. Small juvenile mussels are quite soft and are scoured off the hull at high speeds.

If possible, leave outboards or outdrives in the up position. Periodically inspect hulls and drive units, and scrape free of mussels. Pump hot water through your engine's intake on a regular basis to prevent mussel growth inside the engine's cooling system.

Consult the Conservation Department before trying to control or eradicate zebra mussels or any other exotic pest. Pest species often thrive on disturbance. Do-it-yourself control treatments can make matters worse and can harm native species.

Several Missouri Stream Teams are monitoring lakes and streams for zebra mussels. If you would like to join the effort, call (800) 781-989 or visit the Stream Team web-site at www.mostreamteam.org.

For more information about zebra mussels, contact Canaday at (573) 751-4115, ext. 3371, or go to www.protectyourwaters.net.

To report a potential zebra mussel sighting, contact the nearest Missouri Conservation Department office or go to: www.missouriconservation.org/nathis/exotic/zebra/.

-Jim Low-


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