The discovery of juvenile zebra mussels below two Missouri River dams in South Dakota has water officials worried about a possible infestation by this harmful species.

They’re asking visiting boaters for the Lewis and Clark Bicentennial to be vigilant about keeping their boats clean.

The zebra mussel is an exotic nuisance species native to the Caspian region of western Russia. It was most likely brought to the United States in the late 1980s in the ballast water of a foreign vessel.

The zebra mussel damages ecosystems, native fish, and shellfish and has caused millions of dollars in damage to water intakes and pipes in 20 states in the East and Midwest.

Until the discovery of juvenile zebra mussels in El Dorado Reservoir in Kansas and parts of South Dakota last year, the zebra mussel had not spread to western waters.

The discovery is of particular concern because these mussels may have been transported into the Missouri River by recreational watercraft.

The zebra mussel moves to new locations by sticking to boat hulls, fittings, plants, and other surfaces. Recreational boaters who don’t carefully clean their boats may unknowingly transport the zebra mussel from infested lakes and streams to uninfested waters.

This species can live outside of the water for at least five days.

Millions of dollars are at stake because of the damage zebra mussels can cause.

The species is non-native has few natural predators and reproduces very quickly.