Invasive Species

Invasive Species Over 6,500 non-native invasive species have been documented on park lands. Invasive species are plants, animals and pathogens that are non-native to an ecosystem. They are likely to cause harm to the ecosystems they invade. Two aquatic species that threaten the water and ecosystems of the Missouri National Recreational River are the zebra mussel and the Asian carp.

The National Park Service is working to protect and manage both endangered and invasive species respectively on park lands through partnerships with both national and local programs. One of the strategies is to conduct “boat checks” to help visitors make sure their boats are free of zebra mussels prior to entering the park. Many endangered species are relocated to a national park unit in order to stop their decline and to help them recover.

Cluster of Zebra Mussels with D-shaped shells with alternating black bands.
Zebra Mussels


Don't Move a Mussel!

What are they?

Zebra mussels are small, two-shelled clams, typically 3/8 to 3/4 inches long, that can grow up to two inches (5 cm) in length. Light and dark bands give the D-shaped shell a zebra-striped appearance. They produce a tuft of fiber known as byssal threads that allow the adults to attach to hard surfaces. Adults often attach to vessels in large clusters, like branches. Immature zebra mussels, called veligers, are microscopic larvae that float in the water with the current.


Where do they come from?

Zebra mussels are native to southern Russia. Ships transported them in their ballast water from Europe to the Great Lakes where they spread rapidly. First found in 1988, in Lake St. Clair near Detroit, zebra mussels have spread throughout the Great Lakes and Mississippi River drainages by commercial and recreational boats. The size and growth of infestation in the U.S. and Canada is much greater and more severe than in Europe. The predators and diseases that control zebra mussels in southern Russia are not found in any numbers in North America.

Mussels on outboard motor.
Zebra Mussels on outboard motor

Why are they an invasive species?

The zebra mussel is well adapted for explosive population growth and concentrates in large numbers. Their presence can starve or smother native mussels. Nationwide, native mussels are the most imperiled group of animals, and are declining at an alarming rate. Zebra mussels are accelerating this decline. They consume significant amounts of plankton, altering the available food on which fish and wildlife depend, including the paddlefish native to the Missouri River. Zebra mussels can damage boat engines, docks, and breakwaters. They can also clog water intake systems of industries, power facilities, and engine outdrives, causing expensive shutdowns, repairs and replacement of treatment systems. They have interrupted the flow of drinking water to entire communities.

Stop Aquatic Hitchikers graphic of boat on a boat ramp in red and white hexagon.

What are we doing?

Zebra mussel adults and veligers cannot move upstream against the current without human assistance. Public and private interests at the federal, state, and local levels formed a consortium in 2004 whose purpose is to attempt to forestall the spread of zebra mussels along the Missouri River. Park staffs monitor the river for these aquatic hitchhikers and educate the public about the importance of preventing zebra mussel infestations.

The future?

At this time there are no methods for eliminating zebra mussels once they establish a reproducing population. Some native species, such as ducks and fish, eat the mussels, but not in enough quantities to limit the spread. Scientists are looking for ways to reduce or eliminate zebra mussel populations.

Diagram of vehicle, trailer, rollers, anchor, dock lines, hull, axle, live wells blige and motor where Zebra mussels can attach.
Places to check for Zebra mussel attachments

California Dep't of Fish & Game

What You Can Do to Help

Visual Inspection and Removal
Look for zebra mussels attached to your trim tabs, swim platform, motor mounts, hull, and equipment. The young are too small to see with the naked eye, but newly settled ones feel like fine sandpaper on smooth boat hulls. Treat zebra mussels like litter and dispose of them in a trash can. Remember to remove all plan material you find while looking for zebra mussels, because they can attach to plants, including milfoil. Put plants in trash if possible.

Decontaminate Your Boat
Thoroughly hose down the hull surface, transom, keels, boat drive units, wet walls, bilages, trailer, bait buckets, etc. with hot water (120 to 140 degrees F). Zebra mussels are intolerant of heat and a good soaking will kill both young larvae and adults. As an alternative to hosing down your boat. Let it and equipment dry completely for five days before you use it in uninfested waters. Add a day to the number of drying days for each day of rain. Using both hot water treatment and drying adds additional protection.

Be on the Lookout!

If you find zebra mussels in the Missouri River or if you would like more information, please call Missouri National recreational river at 605-665-0209.


Asian Carp

Silver and Bighead (Asian) Carp, AKA silverfin - These plankton feeders were imported to clear the water in aquaculture and settling ponds. Escaped, they have flourished and spread, taking resources form native species. They have become popular targets for bowfishing and, as an entirely different species from the common grass carp, are excellent eating.

See Bowfishing or Preparing and Cooking Silverfin for more information.

Live bait: Please use caution when using live bait. Follow all existing regulations. Due to the presence of asian carp, South Dakota prohibits seining of bait from the rivers below Gavins Point Dam. Empty all bait buckets in the water they were filled from or on land.

Last updated: September 10, 2021

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Contact Info

Mailing Address:

508 East 2nd Street
Yankton, SD 57078


605-665-0209 x21

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