The U.S. state of Washington is taking emergency action to reclassify golden mussels as a Prohibited Level 1 invasive species following the discovery of the species in Oregon earlier in the month.
Originally from China and Southeast Asia, golden mussels are an invasive species in the U.S. that are known to cause damage to infrastructure and reduce water quality, harming local fishing operations. The species was first detected in California in 2024, but a second instance was detected in Oregon in April 2026. According to the Oregon Department of Fish and Wildlife (ODFW), a watercraft was intercepted at the Ashland Boat Inspection Station carrying golden mussels.
“This interception confirms an active pathway for invasive mussels to spread northward through movement of contaminated recreational boating and aquatic equipment,” the Washington Department of Fish and Wildlife (WDFW) said in a release.
WDFW has undertaken emergency rulemaking procedures to list the species as Prohibited Level 1, which would bar live golden mussels from being possessed, retained, transported, or introduced into a water body. The department estimates that golden mussels could cause USD 100 million (EUR 85.3 million) in annual damage if they become established in the state.
“While not currently known to be established in Washington, federal and state risk assessments, including a 2025 ecological risk screening summary by the U.S. Fish and Wildlife Service and the United States Geological Survey Nonindigenous Aquatic Species resource system, identify golden mussels as a high-risk invasive species. WDFW’s risk assessment similarly identified severe risks to native species, water-dependent industries, and cultural resources,” the department said.
