Invasive Golden Mussels Detected in California

Angela De Palma-Dow, Invasive Species Coordinator from the Lake County Department of Water Resources, shared in a board meeting on December 10, 2024, that the Golden Mussel is a freshwater bivalve that has been found in several locations in the Port of Stockton and in the Sacramento-San Joaquin Delta region. The species had not been previously detected in North America, in contrast to South America where it quickly spread. Golden Mussels were likely introduced to California by a ship travelling from an international port. Lake County Water Managers are concerned Golden Mussels may mobilize from the Delta to Lake County on a visiting boat.

De Palma-Dow underscored that studies from Golden Mussel-infested waters in South America have shown that these mussels are “resistant to disease and industry treatments, and can withstand brackish/saltier water, making them tougher than other nonnative mussels. They have been known to survive in fish guts and they do not have natural enemies in their native areas. Golden Mussels have some enemies in introduced areas, such as some fish and crabs. Particularly concerning is that if they find their way to Lake County, they could proliferate in Clear Lake and other Lake County Water Bodies.” To view the presentation, click here.

Golden Mussels pose a significant threat to Lake County’s ecosystems, water quality and infrastructure. Water Resource managers warn that these invasive mussels, which resemble Zebra and Quagga Mussels but are more dangerous, could outcompete sport fisheries like bass, crappie and catfish for algae, impacting native species such as the Clear Lake Hitch and Western Grebes. Unlike other mussels, Golden Mussel juveniles are free-swimming, and adults have been observed to be more mobile than Quagga or Zebra Mussels, allowing them to rapidly spread. Their ability to filter feed and disrupt aquatic plant populations could severely alter the ecological balance if they arrive in Lake County’s water bodies.

As the County of Lake Water Resources Department informational video, “Invasive Mussel Prevention” explains, “for the drinking water systems on the lake, [invasive mussels are] especially concerning as Clear Lake provides 66% of the population’s drinking water. The added costs to remove mussels would make drinking water treatment even more difficult and more expensive. If [Golden] Mussels are introduced into Clear Lake, their devastating impacts will forever change Clear Lake as we know it.” As of now, thanks to the diligent and dutiful efforts of our ramp monitors, no Golden Mussels have been detected in our county.

The County of Lake Water Resources Department reminds all residents and visiting boaters to have their vessels screened by trained and certified inspectors through the Lake County Invasive Mussel Prevention Program when returning from the Delta region or other water bodies. Remember to check in with a participating screener when returning from any out-of-county trips with your boat, as required by law. Some vessels may be required to undergo further extensive inspection and decontamination. Our staff, certified screeners and vendors thank all boaters for your patience and understanding so we can protect our beloved Clear Lake and other Lake County Water Bodies.