Aquatic Invasive Species

Quagga on Pipe
Quagga cloged pipe on display through the US Fish and Wildlife Service.

US Fish and Wildlife Service.

What are aquatic invasive species (AIS)?

Aquatic invasive species are non-native organisms that can cause significant harm to an ecosystem when introduced. Aquatic invasive species like quagga mussels and zebra mussels are small organisms that could have huge impacts for Montana and Wyoming waters, boaters, and anglers. They can ruin fisheries, clog cooling systems in motorboats, foul hulls, and ruin equipment.

What is a quagga or zebra mussel?

Both are closely related, freshwater mollusk species. Other types of mollusks include snails, clams, oysters, and scallops.

quagga in hand
Quagga mussels (Dreissena bugensis) in hand for size comparison.

What do quagga and zebra mussels look like?

Quagga and zebra mussels are commonly called ‘bivalves,’ meaning they have two shells (or valves). Shell color and patterns vary from a dark striped pattern, to a light tan shell with zig-zag stripes, to completely brown or light colored with little striping. These mussels have byssal threads, which allow them to attach to hard surfaces such as boats. Quagga and zebra mussel larvae are microscopic, while adults may be up to two inches long. They are usually found in clusters and may live 4 to 5 years.

Where do quagga and zebra mussels come from?

These species came to North America from the Black and Caspian Sea drainages in Eurasia.

How did quagga and zebra mussels get to North America?

These mussels were first discovered in Lake St. Clair, Michigan, in 1988. It is believed they were transported to North America in ballast water of large vessels from Europe. Since becoming established in the Great Lakes, they have primarily been transported downstream through water currents and transported overland on trailered boats.

Are quagga and zebra mussels in Montana or Wyoming?

These organisms have not been documented in Montana or Wyoming yet, but are present in several bordering states like Utah, Nebraska, and Colorado. You can help protect Montana and Wyoming waters by making sure you "Drain, Clean and Dry," and by supporting efforts to prevent their introduction into Wyoming and Montana.

Why are they called "quagga" and "zebra" mussels?

Both species are sometimes referred to as zebra mussels because they both have light and dark alternating stripes. Quagga mussels are actually a distinct, but similar, species named after an extinct animal related to zebras. Although these species differ slightly in appearance, the concerns with both of these species are the same.

What are the potential impacts if quagga and zebra mussels become introduced into Montana and Wyoming?

If you use water or electricity, you do not want invasive mussels introduced into your state’s waters. These species can have widespread impacts on power plants, municipalities, irrigation systems, and other water users. They impede water delivery and increase maintenance costs by clogging pipes, pumps, turbines, and filtration systems--costs that are all passed on to the consumer.

Fisheries are destroyed by the presence of these invasive filter-feeding mussels. Quagga and zebra mussels remove plankton from the water. Plankton are the primary food source for forage fish and forage fish are the food of sport fishes. For example, the lake trout population in Lake Ontario has declined by 95 percent in the past 10 years due to a crash in the food chain caused by invasive mussels.

What can I do to prevent the introduction of quagga and zebra mussels into Montana and Wyoming?

Boaters should follow these three simple steps before launching or leaving a body of water:

  • DRAIN all water from your watercraft including the ballast, bilge, live-well and motor.
  • CLEAN all plants, mud and debris from equipment and watercraft.Flush all interior compartments and inboard motors.
  • DRY your watercraft and equipment before launching in a new body of water. Dry your watercraft for 5 days in the summer, 18 days in the spring or fall, or 3 days at freezing temperatures.

I don't have a boat, why should I care?

You may not have a boat, but like many in the Bighorn Basin and areas north of Yellowtail Dam, you depend on power and irrigation from Buffalo Bill Dam, Boysen Dam, and Yellowtail Dam. You also enjoy scenic waterways and fishing opportunities along waterways created by these facilities.

Zebra or quagga mussels have widespread impacts on power plants, irrigation systems, and other water users. They clog pipes, pumps, turbines and filtration systems. Costs for repairs and maintenance are then passed to you. These exotic mussels remove plankton from the water, a primary food source for forage fish. Forage fish are the food of sport fisheries.

What would this do to the fisheries of the Bighorn and Shoshone Rivers? The lake trout population in Lake Ontario has declined by 95% in the past 10 years due to a crash in the food chain caused by exotic mussels. Keep Wyoming and Montana waters free of these aquatic hitchikers. Help spread the message!

For more information:

Last updated: February 16, 2020

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Bighorn Canyon National Recreation Area South District Visitor Center
20 US Hwy 14A

Lovell, WY 82431


307 548-5406
(307) 548-5406 is the South District in Lovell, WY. (406) 666-9961 is the North District in Fort Smith, MT.

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