Ballast water stow-aways
Zebra mussels and a related species, quagga mussels, are fingernail-sized, black-and-white striped bivalve mollusks native to the Caspian Sea region of Asia.
They came to North American waters in international shipping ballast water and were discovered in Lake St. Clair near Detroit in 1988. Since then, zebra mussels have spread rapidly throughout the Great Lakes and connected waterways of the Mississippi River, including the Arkansas, Illinois, Ohio and Tennessee rivers.
Zebra mussels were first reported in Missouri in 1991 in the Mississippi River. For eight years, they were not found west of the Mississippi in our state. In spring 1999, however, zebra mussels were reported in the Missouri River near Sioux City, Iowa. In August 1999, zebra mussels were found in the lower Meramec River, a Mississippi River tributary south of St. Louis.
It's suspected that commercial barges originating from the Mississippi River, transported attached adult zebra mussels upstream to these previously un-infested areas. During the next several decades, zebra mussels could spread to other freshwater locations in Missouri and throughout North America.
Rapid reproducers coat surfaces, clog pipes and smother native species
Female zebra mussels can produce as many as 1 million eggs per year. These develop into microscopic free-swimming larvae (veligers) that quickly begin to form shells. At about three weeks, the sand-grain-sized larvae start to settle, and by using their byssal threads, attach to any firm surface. They clump together and cover rock, metal, rubber, wood, docks, boat hulls, native mussels, crayfish and even aquatic plants.
Zebra mussels filter plankton from the surrounding water. Each mussel can filter about 1 quart of water per day. However, not all of what they remove is eaten.
What they don't eat is combined with mucus as "pseudo-feces" and discharged onto the lake bottom where it accumulates. This material, which may benefit bottom feeders, also may reduce the plankton food chain for upper water species. Diving ducks, the freshwater drum and other fish eat zebra mussels, but will not control them.
Economic impact expected to be in the billions
Zebra mussels can clog power plants, industrial and public drinking water intakes, foul boat hulls, decimate populations of native freshwater mussels, impact fisheries and disrupt aquatic ecosystems. Economic impacts of zebra mussels in North America during the next decade are expected to be in the billions of dollars.
Overland transport on boats, motors, trailers and aquatic plants poses one of the greatest risk for spreading zebra mussels. Larger adult zebra mussels can live several days out of water in moist, shaded areas.
Boats that have been moored or stored for more than just a day or two in zebra mussel-infested waters may carry "hitchhiking" mussels attached to their hulls, engine drive units and anchor chains. Boats that have been in infested waters for only a day or two are less likely to transport adult zebra mussels.
Microscopic zebra mussel veligers can survive in boat bilge water, livewells, bait buckets and engine-cooling water systems, regardless of how long the boat has been in infested waters.
However, they will die very quickly when their hiding places are warmed in the sun or when they "blow dry" on the highway on the trip home.
You can help prevent their spread
If you are a water recreationist (boater, angler, water-skier, scuba-diver, sailor or canoeist) there are some important things you can do to prevent the transport of zebra mussels and other harmful exotic species from one lake or river to another. In some states and provinces it is illegal to transport harmful exotic species.
Zebra mussel prevention tips
To prevent the spread of zebra mussels throughout Missouri and North America--and to keep your own equipment from being fouled--please observe the following "clean boating" suggestions when transporting your boat from waterway to waterway.
Thoroughly inspect your boat's hull, drive unit, trim plates, trolling plates, prop guards, transducers, centerboards, rollers, axles, anchor, anchor rope and trailer. Scrape off and trash any suspected mussels, however small. Remove all water weeds hanging from the boat or trailer before leaving any water body.
Drain water from the motor, livewell, bilge and transom wells and any other water from your boat and equipment while on land before leaving any water body.
Trash leftover bait on land, away from water, before leaving any water body. Leftover live aquatic bait that has contacted infested waters should not be taken to uninfested waters.
When you get home--before launching your boat into uninfested waters--thoroughly rinse and dry the hull, drive unit, livewells (and livewell 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 (140 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.
Boats, motors and trailers should be allowed to 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).
On boats which remain in the water, zebra mussels can attach to drive units, cover or enter water intakes, and clog, overheat and destroy the engine.
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.
Identify the Enemy
Learn what these organisms look like (at least those you can see). If you suspect a new infestation of an exotic plant or animal, report it to your natural resource agency.
Consult the agency for recommendations and permits before you try to control or eradicate an exotic "pest."
Remember, exotic "pest" species thrive on disturbance. Do-it-yourself control treatments often make matters worse and can harm native species.
Where to look for zebra mussels
- Bait bucket
- Recreational watercraft
For more information or to report a zebra mussel sighting, contact your local MDC office or write:
Missouri Department of Conservation
PO Box 180
Jefferson City, MO 65102-0180
Several Missouri Stream Teams already are helping by monitoring streams for zebra mussels. If you would like to join the effort, call (800) 781-1989 or visit the Stream Team website at www.mostreamteam.org.