Invasive freshwater mussel monitoring ramping up in Washington waters

Beginning July 1, $3.62 million in additional funding from the Washington State Legislature and federal partners will allow WDFW to increase monitoring for harmful quagga and zebra mussels in the Snake and Columbia rivers, and across our state.

Cluster of invasive quagga mussels on a pipe used as an educational display.

If invasive freshwater mussels take hold in Washington, state and federal officials estimate it would cost more than $100 million each year to keep our power and water infrastructure running, in addition to causing extensive ecological damage such as impeding salmon recovery and fish passage.

Quagga and zebra mussels are considered the most economically damaging aquatic organisms to invade the United States. Collectively called dreissenid mussels, these are non-native, freshwater mollusks classified as prohibited aquatic invasive species (AIS) in Washington. They were first discovered in the U.S. in the Great Lakes in the 1980s in ships’ ballast water. Recently, these harmful invaders have been getting closer to our state, with quagga mussels confirmed in the Snake River in south-central Idaho in September 2023.

These mussel populations can reach astonishing densities of up to tens of thousands of individuals per square meter, clogging pipes and mechanical systems of hydropower and drinking water utilities, aqueducts, locks, fish ladders, and hatcheries.

Invasive mussels also filter enormous amounts of algae, disrupting the food chain, and impacting water quality. They can cause serious environmental damage to native species and aquatic habitats through intense filter feeding as well as their dense clusters of sharp-edged shells, which can harm fish and wildlife.

WDFW Aquatic Invasive Species (AIS) Unit staff monitoring for invasive mussels.

Increased funding to meet a growing threat

The eye-popping price tag of managing invasive mussels once they become established, as well as their potential to cause major harm to the ecosystem and communities of the Columbia Basin and beyond, are why the Washington Department of Fish and Wildlife (WDFW) received additional dedicated funding for mussel monitoring and readiness from the State Legislature during the 2024 supplemental session. This funding will increase our AIS unit’s monitoring, watercraft inspection program, and other prevention and rapid response efforts.

With strong support from the state legislature, including sponsorship by Representative Mary Dye, we are grateful that $1.81 million was appropriated from the General Fund for invasive mussel prevention efforts in fiscal year 2025, which begins July 1, 2024. The additional state funding will leverage $1.81 million in federal funds from a United States Army Corps of Engineers cost-share program administered by the Pacific States Marine Fisheries Commission (PSMFC).

These additional funds will support coordination with state partners including the Washington Invasive Species Council, as well as tribal, federal, regional, and local entities, increase watercraft inspections and decontamination work, equipment and training, monitoring of potential residential and commercial pathways, and public outreach.

Among other partners, the PSMFC AIS Prevention Program also supports invasive mussel monitoring and outreach.

Monitoring for invasive mussels takes many forms, from high-tech eDNA sampling to more traditional field work such as “plankton tows” and “ponar grabs”. You can learn all about the eight zebra and quagga mussel sampling methods WDFW AIS unit staff and partners use in our new video series on YouTube.

Our 2023 monitoring efforts confirmed no presence of invasive mussels in Washington waters. In response to the Idaho detection, WDFW redirected staff from statewide monitoring to the Snake River for additional monitoring there, and so far, they have not detected quagga mussels in our state’s portion of this large watershed. However, it is critical that all government agencies, commercial industries, and recreational boaters, anglers, and paddlers remain vigilant for these small but damaging invaders.

More information on Clean, Drain, Dry methods to help prevent the spread of invasive mussels is available on this WDFW webpage or from the Washington Invasive Species Council, and in the below infographic.

You can also get tips and learn more at!

Rapid response and long-term planning

WDFW is the lead state agency for prevention and management of aquatic invasive species in Washington.

In addition to the field teams conducting monitoring for invasive mussels and other AIS in rivers and lakes across Washington — with special emphasis on the Snake and Columbia Rivers — we also work with WDFW Police to ensure watercraft entering Washington or moving across our state visit mandatory watercraft inspection stations and meet Clean, Drain, Dry requirements. Clean, Drain, Dry isn’t just a best practice, it is also the law. It is illegal to transport aquatic invasive species from one waterbody to another in Washington state. Violators face a maximum penalty of one year in jail and $5,000 in fines.

The additional funding for fiscal year 2025 will allow us to increase staffing at WDFW’s Eastern Region mandatory watercraft inspection and decontamination stations in Spokane, Clarkston, and Pasco. We also plan to procure and deploy one additional invasive mussel detection canine to support check stations and early detection monitoring. This popular program uses the power of a dog’s nose to sniff out invasive mussels, and in recent years has detected hundreds of invasive mussels hiding in watercraft.

In 2024, more than 58,000 watercraft were inspected by WDFW, which led to interception of 25 invasive mussel-fouled watercraft that were cleaned and decontaminated.

Invasive mussel sniffing dog Fin and his handler checking a watercraft at the Spokane check station.

We will also be working to strengthen prevention of quagga mussel importation from both recreational and commercial pathways by addressing risks from the pet trade (a known potential vector for spreading this species), food fish aquaculture, and transportation of live fish, which requires a permit from WDFW.

And we will be working to better understand the risk to infrastructure such as irrigation systems, drinking water systems, or fish hatcheries, and develop strategies to prevent and mitigate quagga mussel establishment and infrastructure impacts, with emphasis on the Columbia Basin.

If quagga or zebra mussels are detected in Washington, we have the needed expertise, equipment, and have recently practiced a first-of-its-kind on-the-ground quagga and zebra mussel response exercise. Detailed information is available in the Washington Dreissenid Mussel Rapid Response Plan. An improved and expanded response plan is in process and will be available in August of 2024.

Thanks to the additional funding, we will be working with partners to update and deploy a long-term leadership, planning, and command structure that includes internal and external partners including tribal, federal, regional, state, and local governments. As funding and capacity allows, this plan will also increase communications and outreach capacity focused on invasive mussel prevention, response, and enforcement to grow awareness and support among decisionmakers, media, communities, and the public in the Columbia River Basin and beyond.

Invasive mussels and other AIS don’t respect jurisdictional boundaries. To control them and limit spread and harm requires all organizations and the public working together.

WDFW is appreciative of the increased support we are receiving from the Washington State Legislature, federal partners, and the residents of Washington. We are committed to doing everything we can with these resources to detect invasive mussels as soon as they arrive in our state, and to respond rapidly to initiate control actions and management plans.

Outboard engine and propeller covered in invasive quagga mussels. Photo by the National Park Service.



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.