Clean, drain, dry and tag: State and county officials are relying on boaters to prevent the spread of an invasive golden mussel that has infested much of the San Francisco estuary. On Monday, new rules that aim to curb the spread of the species go into effect for all reservoirs open to recreational boating within Santa Clara County.

The first North American detection of golden mussel was in California in 2024, according to the state Department of Fish and Wildlife. The inch-long golden mussels live in both fresh and brackish waters, and county officials say they can hitch rides on boats and trailers, allowing them to spread rapidly between waterways.

Water agencies have reported infestations at facilities connected to California’s vast water delivery system, clustering onto pumps, pipes and fish screens, potentially threatening drinking water supplies, agriculture and hydropower operations.

Battle of the bands

The new rules in Santa Clara include placing color-coded zip-ties after a vessel has passed inspection. The bands are specific to water bodies. If a boat passes inspection for Coyote Lake, it will only be good for Coyote Lake, the county said in an announcement. Only vessels registered in Santa Clara County will be allowed to launch after inspections. Vessels registered to other counties or ones that have visited other counties, need to undergo a 30-day quarantine period before launching in Santa Clara County.

A golden mussel is measured with a calipers at the John E. Skinner Delta Fish Protective Facility in Discovery Bay on Thursday, June 19, 2025. (Nick Shockey/California Department of Water Resources via Bay City News)

Nonpowered vessels remain exempt from quarantine requirements but must still undergo inspections.

Vessels registered in these central and Southern California counties or outside California will not be allowed to launch at any Santa Clara County boating reservoir: Imperial, Kern, Los Angeles, Orange, Riverside, San Bernardino, San Diego, San Luis Obispo, Santa Barbara and Ventura.

Lawmakers and water managers have responded with a variety of measures. Several reservoirs, including Lake Tahoe and Lake Berryessa, maintain strict boat inspection programs aimed at preventing new infestations. Federal lawmakers are also seeking a broader response. U.S. Sens. Alex Padilla and Adam Schiff recently introduced the Golden Mussel Eradication and Control Act of 2026, legislation that would establish research, monitoring and rapid-response programs while providing grants to state and local agencies working to contain the species.

Ruth Dusseault is an investigative reporter and multimedia journalist focused on environment and energy. Her position is supported by the California local news fellowship, a statewide initiative spearheaded by UC Berkeley aimed at supporting local news platforms. While a student at UC Berkeley’s Graduate School of Journalism (c’23), Ruth developed stories about the social and environmental circumstances of contaminated watersheds around the Great Lakes, Mississippi River and Florida’s Lake Okeechobee. Her thesis explored rights of nature laws in small rural communities. She is a former assistant professor and artist in residence at Georgia Tech’s School of Architecture, and uses photography, film and digital storytelling to report on the engineered systems that undergird modern life.