Golden Mussel Detections in California
Martinez Reservoir
September 8, 2025 – juvenile mussels were discovered on a settlement plate in Martinez Reservoir, Contra Costa County. The reservoir is the terminal reservoir of the Contra Costa Canal and receives water from the Delta. The mussels were genetically confirmed as golden mussel by polymerase chain reaction (PCR) analysis and DNA sequencing.
Santa Ana Valley Pipeline
September 29, 2025 – golden mussel veligers were detected by cross-polarized light microscopy (CPLM) in plankton samples collected at two routine sampling locations on the Santa Ana Valley Pipeline located downstream of Silverwood Lake and the Devil Canyon Powerplant, San Bernardino County. The samples were collected on September 23rd and 29th. The veligers were genetically confirmed by PCR analysis and DNA sequencing.
DWR, in coordination with partner agencies, has implemented regular inspections and maintenance at State Water Project facilities to minimize the effects of golden mussels. The discovery of golden mussels poses no imminent impacts to water quality or DWR’s ability to deliver water to 27 million Californians. DWR continues to work diligently to implement protective measures to minimize the spread of this invasive species, prevent the fouling of equipment and maintain operational capacity. For specific questions about DWR’s response, please contact Maggie Macias, DWR Information Officer at (916) 902-7405. For questions regarding CDFW’s response, please contact CDFW’s hotline at (866) 440-9530.
Contra Loma Reservoir
October 7, 2025 – juvenile mussels were discovered on a settlement plate in Contra Loma Reservoir, Contra Costa County. The reservoir is part of the Central Valley Project and receives water from the Delta. The mussels were genetically confirmed as golden mussel by PCR analysis and DNA sequencing.