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.
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 suing they 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 one 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.
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 velgers 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.
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.
