Aquatic Invasive Species Background - Frequently Asked Questions

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.

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.

Last updated: June 8, 2015

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