Lake Oroville Just Dropped Its Mandatory Boat Inspection Requirement for Invasive Mussels

Boaters heading to Lake Oroville just got some welcome news. The mandatory invasive mussel inspection program is over.

The California Department of Water Resources announced on April 29 that watercraft inspections, decontamination services and the blue Oroville seal requirement have all been eliminated at Lake Oroville, the Thermalito Forebay and the Thermalito Afterbay. Inspectors will no longer be stationed at launch ramps, and launching is once again available 24 hours a day.

The inspection program was put in place in May 2025 after golden mussels were discovered at Folsom Lake, raising concerns about the species spreading to other reservoirs across the state. But after a year of study, DWR says the risk at Oroville is significantly lower than originally feared.

The key factor is water temperature. Golden mussels need sustained temperatures above 61.7 degrees for about 150 days to mature and reproduce, and water near 70 degrees for roughly 70 days for larvae to develop into hard-shell mussels. At Lake Oroville, those temperature thresholds only exist in the top 60 feet of the reservoir. The deep, cold water below and the continuous cold releases from Oroville Dam to support salmon habitat make it very difficult for mussels to establish a lasting population.

DWR also evaluated the Upper Feather River lakes, the Feather River Fish Hatchery and the Oroville-Thermalito Complex and determined that extended cold water conditions at all of those sites limit the potential for mussel colonization.

No golden mussels have been detected at any of DWR’s Oroville facilities.

Boaters should still clean, drain and dry their watercraft every time they leave the water to prevent spreading invasive species to other lakes and reservoirs.