As boating season kicks off, help protect our waters from golden mussels

May 27, 2026

Close-up of the invasive golden mussel. Photo by Marcela Uliano da Silva

By Nai Hsueh, Director, Valley Water

Memorial Day weekend marks the traditional start of boating and fishing season across the Bay Area. It's a time to honor service, enjoy the outdoors, and this year especially, to take personal responsibility for safeguarding our waterways. The recent detection of golden mussels in California is an urgent reminder: a single uncleaned boat, anchor, or fishing line can transport invasive species from one waterbody to another. Your actions at the ramp can make a real difference to our reservoirs, infrastructure, and environment.

Golden mussels were first found in the Sacramento–San Joaquin Delta in late 2024, the first detection in North America. They spread easily on boats, trailers, anchors, and gear, and once they take hold, they can clog pipes and pumps, damage water infrastructure, and disrupt ecosystems.

Golden mussels were recently detected at the Penitencia and Santa Teresa water treatment plants, which receive water from imported water sources, the San Luis Reservoir and the South Bay Aqueduct, where golden mussels are already present. Valley Water’s existing treatment processes are effective in removing mussels and there is no impact on the quality of drinking water delivered to our customers, which continues to meet all safety and regulatory standards.

Golden mussels can be smaller than a fingernail and hide in places boaters often overlook, such as the underside of engines, inside intakes, or on anchor ropes. That's why your role is essential. Recreational boats are one of the most common ways invasive mussels move from one waterbody to another.

The most important thing you can do is clean, drain, and dry your vessel and fishing gear after every outing and avoid using live wet bait, which can carry invasive species between waterbodies. Before you head to the lake, take a moment to check the inspection rules for your destination, especially if you plan to visit more than one reservoir this summer. If you ever notice something unusual clinging to your hull, anchor, or fishing line, report it right away.

As of today, all Valley Water reservoirs in Santa Clara County are free of any golden mussels, and that's excellent news. But detections in neighboring counties are a reminder of how quickly the situation can change. A single contaminated boat could introduce golden mussels into a clean reservoir, where they can multiply rapidly and become challenging to remove. Preventing the first introduction is far more effective and far less costly than trying to control an established population.

This holiday weekend, enjoy our lakes but help safeguard them too. For more information about golden mussels, what to look for, and what Valley Water is doing to protect our reservoirs, visit valleywater.org/goldenmussels.

Valley Water manages an integrated water resources system that includes the supply of clean, safe water, flood protection and stewardship of streams on behalf of Santa Clara County's 2 million residents. Valley Water effectively manages 10 dams and surface water reservoirs, three water treatment plants, an advanced recycled water purification center, a state-of-the-art water quality laboratory, nearly 285 acres of groundwater recharge ponds and 333 miles of waterways. We provide wholesale water and groundwater management services to local municipalities and private water retailers who deliver drinking water directly to homes and businesses in Santa Clara County.