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
--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
--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
--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
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 email@example.com.
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
For more information about zebra mussels, contact Canaday at (573)
751-4115, ext. 3371, or go to
To report a potential zebra mussel sighting, contact the nearest
Missouri Conservation Department office or go to: