The state of California has ended a costly boat inspection and decontamination program at Lake Oroville, one of its largest and most critical reservoirs, a move that has alarmed invasive species experts. The decision, announced by the California Department of Water Resources (DWR), follows a state-funded risk assessment suggesting the golden mussel poses a lower threat to the lake than previously thought.
No golden mussels have been detected in Lake Oroville to date, but the species was first discovered in California's Sacramento-San Joaquin River Delta in October 2024, marking its first appearance in North America. Since then, the voracious mollusks have infested critical water infrastructure in the Delta, prompting states of emergency in San Joaquin and Kern Counties.
The DWR's new policy eliminates mandatory inspections and decontamination for boats launching at Lake Oroville and the adjacent Thermalito Forebay and Afterbay. The program cost approximately $7.5 million to establish and $6.5 million annually to operate.
Tanya Veldhuizen, special projects section manager at DWR, stated that the program severely impacted recreation and that the risk to infrastructure was lower than expected. The risk assessment, conducted by a Canadian consulting firm, concluded that while surface waters are warm enough for mussel survival, the deeper waters below 60 feet are too cold for reproduction.
Additionally, the lake's low nutrient levels and fluctuating water levels are expected to limit mussel growth. However, experts like Anthony Ricciardi, a biology professor at McGill University, warn that the shoreline, boats, and docks remain vulnerable.
Boats can transport mussels to other lakes, potentially spreading the infestation. Demetrio Boltovskoy, a retired researcher, noted that adult mussels can survive in very cold water and that preventing range expansion may be impossible.
The DWR now relies on boaters to voluntarily clean, drain, and dry their vessels, especially when leaving infested waters like the Delta. If mussels are detected, inspections will be implemented for boats leaving the lake.
Managers of other Northern California lakes, including Folsom, Tahoe, and Berryessa, have stated they will continue their inspection programs. Drew Gantner, manager of water resources at Solano County Water Agency, expressed concern that an infested Lake Oroville would increase the risk for all water bodies, as boats traveling from Oroville would pose a threat similar to those from the Delta.
The decision has divided invasive species experts, with some arguing that delaying invasions saves money and protects the environment, while others believe that stopping the spread is ultimately futile. The stakes extend beyond Oroville, as the mussels could hitch a ride on boats to other lakes and reservoirs across the state.