THE RISK IS QUITE STAGGERING’: INVASIVE MUSSEL THREAT SPURS STATES TO CREATE NEAR-TERM ACTION PLAN

JUNE 14, 2025

Columbia Basin Bulletin

Washington and Oregon are expanding efforts to prevent invasive mussels from entering the two states and the Columbia River basin. If they get a foothold in the basin, invasive zebra, quagga and golden mussels would cause considerable economic and environmental damage that could slow recovery of the basin’s federally listed salmon and steelhead runs, according to each state’s invasive species manager speaking at the May Northwest Power and Conservation Council meeting.

After Idaho detected quagga mussels in a section of the Snake River near Twin Falls in the fall of 2023, and after Marimo moss balls were discovered at an aquatic supply store in August 2024, and, now, with the threat of the golden mussel, a third species discovered in October 2024 and working its way up from California, the two states are joining forces on an action plan to combat what has been termed “the greatest known threat in the Columbia River Basin from aquatic invasive species.”

It was Council’s 2014 Columbia River Basin Fish and Wildlife Program that first called the introduction of zebra and quagga mussels the greatest threat to the basin. They have a history “of global invasion and successful establishment outside their native range,” a May 6 Council Memorandum says(https://www.nwcouncil.org/calendar/council-meeting-2025-05-13/).

30/06/2025, 09:12 ‘The Risk Is Quite Staggering’: Invasive Mussel Threat Spurs States To Create Near-Term Action Plan – Columbia Basin Bulletin https://columbiabasinbulletin.org/the-risk-is-quite-staggering-invasive-mussel-threat-spurs-states-to-create-near-term-action-plan/ 1/8

Economically, the “risk is quite staggering,” said Justin Bush, Aquatic Invasive Species Division Manager, Washington Department of Fish and Wildlife.

Just in Washington alone, the cost to the hydroelectric system would be $100 million a year for mitigation and maintenance and would have similar impacts on Columbia basin hatcheries, irrigation systems, fish passage structures, navigational locks and drinking and waste water systems, he said.

A mussel invasion would impact three drivers of the Northwest economy:

• Columbia River shipping worth $31.2 billion each year;
• Irrigated agriculture worth $9.6 billion;
• Outdoor recreation and fisheries worth $20.5 billion,

“If impacted, we would lose those resources,” Bush said.

There are also environmental risks, according to Keith DeHart, Invasive Species and Wildlife Integrity Supervisor, Oregon Department of Fish and Wildlife, including reductions in aquatic habitat, a reduction in water quality and an increase in pollution, and all of this would impact salmon and steelhead populations, as well as Southern resident killer whales.

Human health would suffer, as well. For example, there would be an increase of harmful cyanobacteria and harmful algal blooms, and on the cultural side, treaty resources would be impacted and our sense of place would be impacted.

Washington’s legislature in 2025 set aside $1.8 billion with federal matching funds for prevention, nitoring and preparedness, Bush said. He said short-term actions with this money will:

• Develop and deploy a long-term leadership, planning, and command structure that includes internal and external partners including tribal, federal, regional, state, and local governments.
• Fully staff Southeast Region mandatory watercraft inspection and decontamination stations in Clarkston and Pasco.
• Procure and deploy one additional invasive mussel detection canine to support Southeast Region check stations and early detection monitoring.
• Perform intensive Snake River and Middle Columbia River early detection and monitoring to detect downstream quagga mussel establishment.
• Strengthen prevention of quagga mussel importation from both recreational and commercial pathways by addressing pet trade, food fish aquaculture, and recreational transportation of live fish.
• Expand state preparedness for containment and rapid response treatment for quagga mussels through procurement of equipment and training.
• Understand risk to infrastructure such as irrigation systems and fish hatcheries to develop strategies to prevent and mitigate quagga mussel establishment and impacts.
• 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 Snake and Columbia River basins.

Still, routine early detection is key to keeping mussels out of Northwest waterways and both states are continuing those efforts at seasonal watercraft inspection stations at each state’s borders. Washington has six permanent inspections stations, mostly at its borders.
Bush said Washington inspected 54,790 watercraft in 2024, finding and decontaminating 13 watercraft fouled with mussels, and through April 30 this year have inspected 5,943 watercraft, finding and decontaminating 6 watercraft. Previous years were similar with 58,618 inspections and 25 fouled watercraft in 2023, 51,942 inspections with 25 fouled watercraft in 2022 and 55,812 inspections with 39 fouled watercraft in 2021.

The inspections stations also search for and decontaminate for invasive weeds, which pushed total decontaminations in 2024 to 2,130, and so far this year 130 decontaminations.

Bush said the state discovered its largest ever haul of invasive mussels in January this year when two 30-foot trailered tugboats were inspected at an inspection station near Spokane, WA. The tugs had been hauled from Lake Michigan. One of the boats was infested and state staff removed 21 gallons of invasive mussels (the largest haul in seven years) and some may have been alive, Bush said. It took the staff some 20 hours to complete the task.

Washington and Oregon also monitor water bodies for signs of invasive mussels, either looking for live mussels, larvae or eDNA. In 2024, WDFW staff inspected 173 water bodies (lakes and streams) at 392 sites and took 7,519 samples.

The states of Oregon and Washington face an imminent threat from invasive mussels. Zebra, quagga, and golden mussels have a history of global invasion and successful establishment outside their native range. Routine early detection is key, with recent threats emanating from pathways like the detection of quagga mussels in Idaho in the Fall of 2023, the introduction of invasive mussels through contaminated Marimo moss balls in August of 2024, and an emerging threat from golden mussels, detected for the first time in California in October 2024.

Oregon, with one of the smallest invasive species programs of the four Northwest states, according to DeHart, has 5.5 permanent positions and 14 seasonal positions; it has two permanent inspections stations, one at the Idaho border on I-84 and one at the state’s southern border on I-5. It also has three
seasonal check stations and a roving inspection crew. Oregon Department of Environmental Quality has 1.5 full time positions dedicated to ballast water inspections at Oregon ports.

Since 2010 and through last year, Oregon has inspected 226,524 watercraft, finding 173 watercraft fouled with mussels and a total of 3,636 watercraft fouled with either mussels or invasive weeds. All were decontaminated.

The growing threat of invasive mussels is spurring the two states to work together to fashion a near-term action plan to prevent and prepare for invasive mussels in the shared waters of the Columbia River (see May 6 Council Memorandum at https://www.nwcouncil.org/fs/19400/2025_05_5.pdf).

At a March 19, 2024, joint state meeting WDFW and ODFW, along with more than a dozen state, federal and other organization partners, arrived at this statement of purpose for their joint near-term action working group:

“The State of Oregon and Washington Departments of Fish and Wildlife requested participation from organizations to join a joint state working group tasked to identify near-term actions and to assist with the development of findings and recommendations to prevent and prepare for invasive quagga and zebra mussels in the shared waters of the Columbia River Basin between Washington and Oregon. It was the intention of this working group to complete this task prior to December 2024, including the development of a finding and recommendations report.”

The final working group meeting was in December 2024 at which the group unveiled their product that included their findings and near term action plan.

The plan is at https://wdfw.wa.gov/sites/default/files/2025-01/oregon-washington-invasive-mussel-findings-and-near-term-action-recommendations.pdf.

Near term action goals include:

1. Enhance prevention efforts
2. Coordinated public awareness
3. Ensure rapid response preparedness
4. Build partnerships and facilitate coordination
5. Invest in Research

Examples of what to do, Bush said, include:

The states of Oregon and Washington should expand early detection monitoring efforts to identify new infestations of invasive mussels as early as possible for the purpose of initiating response actions.

The states should develop a communications plan identifying key stakeholders, partners, policy makers and audiences; objectives and measurements for success; challenges; themes and messaging; and products and deliverables.

The states should work with State Legislatures and Governor’s Offices to develop a mutually agreeable process for declaring emergencies in shared waters of Washington and Oregon, that include decision support tools with criteria that need to be met for an invasive species emergency to be declared.

The states should reaffirm a regional commitment to addressing invasive mussels through participation in updating of the 100th Meridian Initiative Columbia River Basin Interagency Invasive Species Response Plan: Dreissenid Mussels, signed by state governors in 2008, updated in 2018.

The states should develop a model funding pathway, such as a grant program, to cost-share funding for installation and management of mitigation systems for consideration by state legislatures and federal funding agencies.

Long-term action goals are:

1. Enhance regulatory effort
2. Ensure rapid response readiness
3. Support long-term management
4. Invest in research

Examples of what to do are:

The states should increase law enforcement action at mandatory watercraft inspection stations, improving compliance with state laws and creating new partnerships with state and local law enforcement agencies as force multipliers.

The states should emphasize the need for and hold regular response exercises, of region, state, and site specfic response plans, in addition to holding training workshops and drills for functions and roles, such as Multi-Agency Coordination (MAC) Groups, containment systems, or mock treatments

The states should continue to support and/or develop new local funding programs to build and maintain capacity of key response partners, including tribal nations, local governments, or industry. An economic study would help emphasize the impacts of invasive mussels on shipping, recreation, agricultural production, food security, irrigation, navigational locks, fish passage, fish hatcheries and salmon recovery investments in the Columbia River. It would also help to understand the long-term costs of mitigation systems and ongoing maintenance and operations costs.

For background, see: — CBB, June 6, 2025, OREGON BOAT INSPECTION STATIONS OPEN TO PROTECT WATERS FROM AQUATIC INVASIVE SPECIES, GOLDEN MUSSELS NEW THREAT, HTTPS://COLUMBIABASINBULLETIN.ORG/OREGON-BOAT-INSPECTION-STATIONS-OPEN-TO-PROTECT-WATERS-FROM-AQUATIC-INVASIVE-SPECIES-GOLDEN-MUSSELS-NEW-THREAT/ — CBB, February 7, 2025, WASHINGTON

INTERCEPTS TUGBOAT AT WATERCRAFT INSPECTION STATION CARRYING 21 GALLONS OF INVASIVE MUSSELS, LARGEST VOLUME FROM ONE BOAT IN 7 YEARS, HTTPS://COLUMBIABASINBULLETIN.ORG/WASHINGTON-INTERCEPTS-TUGBOAT-AT-WATERCRAFT-INSPECTION-STATION-CARRYING-21-GALLONS-OF-INVASIVE-MUSSELS-LARGEST-VOLUME-FROM-ONE-BOAT-IN-7-YEARS/ — CBB, OCTOBER 8, 2024, ODFW SAYS UNCERTIFIED MOSS BALLS HAVE BEEN SHIPPED TO OREGON, RAISING CONCERNS ABOUT ZEBRA MUSSEL INFESTATION, HTTPS://COLUMBIABASINBULLETIN.ORG/ODFW-SAYS-UNCERTIFIED-MOSS-BALLS-HAVE-BEEN-SHIPPED-TO-OREGON-RAISING-CONCERNS-ABOUT-ZEBRA-MUSSEL-INFESTATION/ — CBB, AUGUST 18, 2024, ONCE AGAIN INVASIVE ZEBRA MUSSELS FOUND IN AQUARIUM MOSS BALLS IN WASHINGTON, PROMPTS RAPID RESPONSE, HTTPS://COLUMBIABASINBULLETIN.ORG/ONCE-AGAIN-INVASIVE-ZEBRA-MUSSELS-FOUND-IN-AQUARIUM-MOSS-BALLS-IN-WASHINGTON-PROMPTS-RAPID-RESPONSE/ — CBB, SEPTEMBER 27, 2024, MORE INVASIVE QUAGGA MUSSELS FOUND AGAIN IN SNAKE RIVER, IDAHO TO RESPOND WITH CHEMICAL TREATMENT PLAN, HTTPS://COLUMBIABASINBULLETIN.ORG/MORE-INVASIVE-QUAGGA-MUSSELS-FOUND-AGAIN-IN-SNAKE-RIVER-IDAHO-TO-RESPOND-WITH-CHEMICAL-TREATMENT-PLAN/ — CBB, Nov. 16, 2023, Idaho Details Successful Eradication Treatment Of Invasive, Destructive Quagga Mussels In Snake River, First Sighting In Columbia River Basin https://columbiabasinbulletin.org/idaho-details-successful-eradication-treatment-of-invasive-destructive-quagga-mussels-in-snake-river-first-siting-in-columbia-river-basin/ — CBB, September 26, 2023, IDAHO INITIATES RAPID RESPONSE PLAN AFTER QUAGGA MUSSEL LARVAE DETECTED IN SNAKE RIVER NEAR TWIN FALLS; WDFW INCREASES MONITORING, https://columbiabasinbulletin.org/idaho-initiates-rapid-response-plan-after-quagga-mussel-larvae-detected-in-snake-river-near-twin-falls-wdfw-increases-monitoring/ — CBB, February 17, 2023, COLUMBIA RIVER BASIN STILL ONLY MAJOR BASIN IN U.S. FREE OF DESTRUCTIVE ZEBRA/QUAGGA
MUSSELS; FLUCTUATING RESERVOIRS MAY PROVIDE SOME PROTECTION, https://columbiabasinbulletin.org/columbia-river-basin-still-only-major-basin-in-u-s-free-of-destructive-zebra-quagga-mussels-fluctuating-reservoirs-may-provide-some-protection/ — CBB, March 24, 2017, “Study: Basin Efforts To Detect Non-Native Mussels Must Increase, Improve To Prevent Costly Invasion” https://www.www.www.columbiabasinbulletin.org/438583.aspx