Invasive quagga mussels detected in Idaho; monitoring and prevention efforts ramp up in Washington

Preliminary results from 2023 detected no presence in Washington. In response to the Idaho detection, WDFW is redirecting staff from statewide monitoring to the Snake River.

Invasive quagga mussels covering hydro dam equipment. Photo by Washington Invasive Species Council.

On Sept. 19, the Idaho State Department of Agriculture (ISDA) announced the presence of quagga mussel larvae detected in the Snake River in the south-central area of that state near Twin Falls.

ISDA is initiating a rapid response plan that includes notifying impacted entities, implementing containment measures, conducting delimiting surveys, and evaluating potential treatment options. They have established a webpage for their incident response.

A regional effort is underway to ensure invasive mussels stay contained to Idaho, including activating the Columbia River Basin Interagency Invasive Species Response Plan: Dreissenid Species. More information is available at:

Quagga and zebra mussels, collectively called dreissenid mussels, are non-native, freshwater mollusks. They were first discovered in the U.S. in the Great Lakes in the 1980s after apparently hitching a ride in ballast water in ships from the Caspian and Black Seas in Eurasia. Since then, they have invaded fresh waterbodies and estuaries across North America as far west as eastern Montana and Lake Mead in Arizona.

These small but sturdy invasive mussels can clog pipes and mechanical systems of industrial plants, utilities, locks, dams, and hatcheries, as well as cause serious environmental damage to native aquatic species and habitats.

If invasive mussels take hold in Washington, officials estimate it would cost more than $100 million each year to keep Washington’s power and water infrastructure running, in addition to causing ecological damage.

WDFW Aquatic Invasive Species (AIS) unit field staff sampling for mussels and other invasive species on the Columbia River in 2022. WDFW monitored 306 sites at 124 waterbodies last year. 2022 sampling found no invasive quagga or zebra mussels in Washington’s waters including in the Snake River.

Invasive mussel prevention efforts in Washington

The Washington Department of Fish and Wildlife (WDFW) is the lead state agency for prevention and management of aquatic invasive species including quagga mussels. We stand ready to assist Idaho’s incident management team if assistance is requested.

Washington currently has a robust multi-agency effort monitoring for invasive quagga and zebra mussels in our state’s waters, coordinated by WDFW, Washington Invasive Species Council (WISC), and other state and federal agencies, tribes, and partners.

The WDFW Fish Program Aquatic Invasive Species (AIS) unit conducts widespread monitoring annually each spring through fall. In 2022, WDFW monitored 306 sites at 124 waterbodies. 2022 sampling found no invasive quagga or zebra mussels in Washington’s waters including in the Snake River. Preliminary results from 2023 confirm no presence. In response to the Idaho detection, WDFW is redirecting staff from statewide monitoring to the Snake River for additional monitoring.

If detected, we have the needed expertise, equipment, and have recently practiced a first-of-its-kind on-the-ground quagga and zebra mussel response exercise. While there is reason for concern for potential spread into our state’s waters, WDFW and Washington are well positioned to take quick action if needed.

Detailed information is available in the Washington Dreissenid Mussel Rapid Response Plan.

State, federal, and tribal governments came together at Lake Roosevelt National Recreation Area in 2019 for the first on-the-ground exercise in the Columbia River basin to prepare for an infestation of quagga and zebra mussels.

WDFW Police operate watercraft inspection stations in Spokane, Clarkston, Pasco, and Cle Elum under the direction of Capt. Eric Anderson, including a trained detection dog, Fin, and enforcement of AIS permits for watercraft registered outside our state.

Statewide, in 2022, WDFW inspected 51,877 watercraft and intercepted 19 invasive mussel-fouled watercraft. The Clarkston inspection station is positioned to support protection for Washington’s portion of the Snake River. Already in 2023, 1,265 watercraft have been inspected at this southeast Washington station including 1 vessel fouled with invasive mussels. With the Idaho quagga mussel detection, WDFW is ramping up roving watercraft inspection stations in the area.

We have also worked with WISC, U.S. Department of the Interior, public utility districts, and other partners to install Clean, Drain, Dry, Dispose (CD3) units at boat launches and marinas around the Columbia Basin, created a new mobile AIS outreach trailer and program, and disseminated regular communications on these topics.

In March 2021, several states reported the presence of both live and dead zebra mussels at pet store retailers nationwide. WDFW and other agencies quickly worked with retailers to pull the product from shelves and place them in quarantine.

Invasive species detection dog Fin and his handler Nicholas Knauss with WDFW Police conduct a watercraft inspection at our check station near Spokane.

Help prevent the spread of invasive zebra and quagga mussels

Aquatic invasive species (AIS) represent a huge threat to the state’s native ecosystems, but there are several ways the hazard to Washington’s waters can be fought.

Zebra mussels are relatively small (typically the size of an adult fingernail) with thin shells of variable coloring, often with stripes or zig-zag patterns. They are triangular in shape, and sit flat on ventral side. Quagga mussels are usually light tan to almost white, with narrow stripes, fan shaped, and rounded, and typically larger than the zebra mussel.

Zebra and quagga mussels with scale. Photo by Wen Baldwin / OSU.
Boat propeller encrusted with invasive mussels. Zebra and quagga mussels are easily transported on recreational boats and can live out of water for up to a month. Photo by U.S. Fish and Wildlife Service

Boaters, kayakers and anglers should contact WDFW’s Aquatic Invasive Species hotline if they suspect their boats or gear have been used in waters of states infested with zebra or quagga mussels (see map).

Aquatic Invasive Species hotline: 1–888-WDFW-AIS (1–888–933–9247)

Anyone who recreates or works in Washington’s waters should take measures to prevent the spread of aquatic invasive species. There are two methods recommended: the basic “Clean/Drain/Dry” and the more rigorous “decontamination” protocol for known or suspected infested waters.

How to Clean, Drain, Dry, Dispose (CD3)

  • Clean equipment that has come into contact with Washington waters by removing all visible native and non-native plants, algae or mud from shoes, waders, life vests, boat hulls and engines, trailers and other gear. Use a stiff-bristled brush to clean equipment.
  • Drain any accumulated water from boats or gear — including water used in cleaning — back into the lake, stream, or other waterbody from which it came.
  • Rinse all surfaces with potable water.
  • Let boats or gear fully dry before using again.

More detailed information is available at:

To learn more or reserve a mobile CD3 unit, please visit this webpage. Or get tips and learn more at!

One of our mobile Clean, Drain, Dry units. This unit is available for fishing derbies and boating events!

Penalties for introducing aquatic invasive species

It is against the law to release non-native species into Washingtin state waters through intentional or unintentional means. This includes animals and plants hitchhiking on boats or field gear; aquarium or terrarium pets or plants; animals or plants used in research or education; unused live fishing bait; or live seafood purchased from a store.

It is illegal to transport aquatic invasive species from one waterbody to another in the state of Washington. Violators face a maximum penalty of one year in jail and $5,000 in fines.

More information on invasive quagga and zebra mussels is also available from Washington Invasive Species Council and Washington State University.

Signage at one of WDFW’s watercraft inspection stations.



The Washington Department of Fish and Wildlife

The Washington Department of Fish and Wildlife is dedicated to preserving, protecting and perpetuating the state’s fish and wildlife resources.