Agencies warn of growing mussel threat; new inspection station planned to close I-5 gap

State agencies told the Washington Invasive Species Council on July 16 that invasive freshwater mussels present a growing, imminent threat and that several prevention steps are underway.

Justin Bush of the Washington Department of Fish and Wildlife reported that in late June Oregon intercepted a watercraft carrying live golden mussels—an interception that represents the species moving beyond California in overland or conveyance pathways. WDFW also reported a single dead quagga mussel found on the shoreline of Prineville Reservoir; surveys continue and federal partners have assisted with dive teams.

"This underscores that golden mussels are no longer a distant threat," Bush said. He said WDFW has undertaken emergency rulemaking to prohibit golden mussels statewide and will begin permanent rulemaking soon. The department has also received a $350,000 U.S. Bureau of Reclamation award intended to close the inspection gap on Interstate 5 at Ridgefield; WDFW is negotiating site plans with the Washington State Patrol to establish a new mandatory watercraft inspection station.

Bush urged continued coordination on surveys and inspections and noted that WDFW has offered technical assistance—underwater drones, trained canine teams, shoreline inspection procedures—to Oregon partners and local jurisdictions. He described interceptions of quagga and zebra mussels on conveyances in 2025 as evidence the threat remains active.

Agency representatives said monitoring, emergency rulemaking and inspection-station planning are ongoing; they asked the council and partner agencies to remain engaged on prevention, screening and local readiness.