Discovery of Zebra Mussels in Lewis and Clark Lake a Major Disappointment


The report yesterday that a reproducing population of zebra mussels is in Lewis and Clark Lake was tough to hear. The lake, located on the South Dakota-Nebraska border, is a reservoir on the Missouri River. Last November, a single zebra mussel was found by South Dakota Game, Fish and Parks Department staff on a dock removed from Lewis and Clark Lake. At the time, we all hoped that this lone zebra mussel was a one-time appearance. Unfortunately, the recent discovery of zebra mussels in other locations around the lake has proven otherwise.

The fact that zebra mussels are noHigginsEyeWithZebraMusselsByUSFWSw established in Lewis and Clark is especially disappointing because this area has been the hub of our annual Missouri River Clean Boat Event. Every year, the League and other groups talk with boaters and anglers about preventing the spread of invasive species. All it takes is three steps: Clean, drain, and dry boats and equipment.

These steps are even more critical today to contain the zebra mussel invasion to this one lake. The Game, Fish, and Parks Department has implemented more strict invasive species regulations and now requires all watercraft to pull drain plugs prior to leaving boat ramp areas.

What’s the fuss about a mussel the size of a quarter? Zebra mussels arrived in the U.S. from Europe in the 1980s through ballast water from ships entering the Great Lakes. They can spread quickly. Females produce up to 1 million eggs per year. Veligers, the larval stage of zebra mussels, are nearly impossible to detect due to their small size and can be easily transported in a small amount of water remaining in a boat, watercraft, or bait bucket. Once grown, zebra mussels cause costly problems.

pipe with zebra mussels_water power magazineFor example, zebra mussels clog water intake pipes for power plants and municipal water systems, decreasing water flow and in some cases causing plants to shut down. Removing the mussels and preventing future clogs is expensive – a cost passed along to ratepayers. (The University of Wisconsin Sea Grant estimates the annual cost in the Great Lakes just to control zebra mussels in water intake pipes at $250 million.)

Zebra mussels also wreak havoc on fish populations by depleting plankton – the food that larval and juvenile fish need to survive. This could have a major impact on fishing in Lewis and Clark Lake. Zebra mussels also attach themselves to native mussels, making natives more vulnerable to other stressors.

It’s critical to keep these invaders from spreading to other waters along the Missouri River. Zebra mussels can be killed by washing equipment with 140 degree water and letting it completely dry it before launching in another waterway. (You can find more details on our Clean Boats Web page.)

It’s up to each of us. Spread the word – not invasive species!

For more details on the recent zebra mussel discovery, visit the South Dakota Game, Fish and Parks Department Web site. For information on invasives in South Dakota, visit South Dakota's Least Wanted.