Invasive Mussel News

CDFW News | CDFW Confirms Northernmost Detection of Golden Mussel in Port of West Sacramento

The California Department of Fish and Wildlife (CDFW) is notifying the public and officials with the city of West Sacramento and Yolo and Sacramento counties that invasive golden mussels have been found in and around the Port of West Sacramento. 

This is the northernmost detection of golden mussel since the species was discovered in the Port of Stockton in the Sacramento-San Joaquin Delta in 2024. 

CDFW staff monitoring for golden mussel presence collected one mussel between the Jefferson Boulevard overpass and the west lock, and a second near the intersection of Boathouse Road and Stone Boulevard. The mussels were sent to CDFW’s genetics lab that confirmed on June 25 the specimens were golden mussel. Additional surveys around the docks in Washington Lake found additional mussels.  

It is believed the golden mussels found in the Port of West Sacramento are from a source population within the vicinity. Golden mussels are harmful to aquatic ecosystems, water conveyance systems and water infrastructure. 

Anyone boating or recreating on waterways around the Sacramento area, and throughout the Delta, should take precautions to stop the spread of golden mussel further upstream and overland on watercraft and equipment used in mussel-infested waters. Golden mussels attach to almost any underwater surface, including but not limited to boats, ropes, buoys and aquatic plants that entangle on anchors and trailers. 

Clean, Drain, Dry — inspect your watercraft, kayak, life vests, paddles and anything that touched the water every time it is removed from a water body. Remove all debris, animals, and plants, and dispose of them in the trash. Drain all water from ballasts, bilges and live wells. Lastly, allow everything to dry until moisture is no longer present. 

Through the continued efforts by boaters and others recreating on California’s waters, golden mussel can be prevented from spreading to waters not connected to the Delta. 

Help CDFW monitor the state’s waters for golden mussel by reporting organisms suspected to be golden mussel to CDFW’s Invasive Species Program. Include the specific location of the observation, at least one clear close-up photograph of the organism and your contact information. 

Submit reports via one of the following options: 

• Online at Report Golden Mussel
• Via email to invasives@wildlife.ca.gov
• Via telephone to (866) 440-9530

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Media Contact:  
Krysten Kellum, CDFW Communications, (916) 825-7120 

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.

Golden Mussel Detections in California

Delta-Mendota Canal at Bass Avenue Bridge

September 17, 2025 – adult mussels were discovered in the Delta-Mendota Canal at the Bass Avenue Bridge in Mendota, Fresno County. The mussels were genetically identified as golden mussels using qPCR analysis.

San Luis Reservoir/Pacheco Pumping Plant

September 9, 2025 – golden mussel veligers were detected by cross-polarized light microscopy (CPLM) in a plankton sample collected at the Pacheco Pumping Plant, Merced County. The veligers were genetically identified via polymerase chain reaction (PCR) analysis and were negative for quagga/zebra mussels. Pacheco Pumping Plant draws water from San Luis Reservoir, Merced County. San Luis Reservoir receives water from O’Neill Forebay which is infested with golden mussel. For more information, read the October 3, 2025 news release.

For a list and map of all confirmed detections of invasive mussels visit:

• Golden mussel map
• Quagga/zebra mussel map

Golden Mussel Detections in California

Sacramento-San Joaquin Delta

Rio Vista: July 1, 2025 – golden mussel veligers were detected by cross-polarized light microscopy (CPLM) in a plankton sample collected in the Sacramento River near Rio Vista, Solano County. The veligers were genetically identified via polymerase chain reaction (PCR) analysis. On September 4, 2025, one adult golden mussel was detected at the same location and genetically identified via PCR analysis.

New Bridge Marina: July 29, 2025 – three adult mussels were discovered on the underside of the slips at New Bridge Marina by the Highway 160 Bridge in Antioch, Contra Costa County. The mussels were genetically identified as golden mussel using PCR analysis and DNA sequencing.

Pittsburgh Yacht Club: July 29, 2025 – one mussel was discovered on the underside of a slip at Pittsburgh Yacht Club in Pittsburgh, Contra Costa County. The mussels were genetically identified as golden mussel using PCR analysis and DNA sequencing.

South Delta: September 3, 2025 – adult mussels were discovered in Grant Line Canal and at two sites in the Upper Old River. All 3 sites are in San Joaquin County. The adult mussels were morphologically identified.

Pirates Lair Marina: September 4, 2025 – adult mussels were discovered at Pirate Lair Marina, Sacramento County, attached to docks. The adult mussels were morphologically identified.

San Joaquin River: September 4, 2025 – 100+ juvenile mussels were detected in San Joaquin River downstream of Mossdale Crossing, San Joaquin County, attached to flow monitoring equipment. The mussels were morphologically identified.

Patterson Pass Water Treatment Plant

August 14, 2025 – a single adult golden mussel was discovered in a strainer on a raw water sample line during routine cleaning at the Patterson Pass Water Treatment Plant in Livermore, Alameda County. The veligers were genetically identified via PCR analysis and DNA sequencing.

Chrisman Wind Gap Pumping Plant

August 22, 2025 – 25 adult golden mussels were discovered on the man doors of pump units at Chrisman Wind Gap Pumping Plant (just south of Wheeler Ridge Pumping Plant on the California Aqueduct), Kern County. The adult mussels were morphologically identified.

Silverwood Lake

August 26, 2025 – a golden mussel veliger was detected by CPLM in a plankton sample collected at the Silverwood Lake outlet. The veligers were genetically identified via PCR analysis and negative for quagga/zebra mussels.

Pyramid Lake

August 28, 2025 – adult golden mussels were discovered in Pyramid Lake, Los Angeles County, attached to settlement plates located at the William E. Warne Powerplant. Quagga mussels were also attached to the settlement plates. The mussels were genetically identified as golden mussel using PCR analysis. Sequencing results are pending. Quagga mussels were first detected in Pyramid Lake in 2016.

For a map of all confirmed detections of invasive mussels visit:

• Golden mussel map
• Quagga/zebra mussel map (PDF)

On July 15, 2025, CDFW’s Invasive Species Program (ISP) laboratory staff detected a total of three suspected golden mussel (Limnoperna fortunei) veligers in plankton tow samples collected at Dock 25 in Lake Palmdale on June 26, 2025 and July 10, 2025. The veligers were confirmed by cross-polarized light microscopy (CPLM), polymerase chain reaction (PCR), and DNA sequencing for species confirmation.

Lake Palmdale, also known as Harold Reservoir, is a freshwater storage reservoir located near the City of Palmdale in the Antelope Valley in Los Angeles County, CA, and is owned and operated by the Palmdale Water District (PWD). The lake’s two water sources include the East Branch of the California Aqueduct (State Water Project) and Littlerock Reservoir. Water is stored in Lake Palmdale and eventually treated at PWD’s Leslie O. Carter Water Treatment Plant for distribution to the public, serving residents and businesses of the City of Palmdale and unincorporated areas of Los Angeles County.

Lake Palmdale receives water from the State Water Project’s East Branch and is the first detection of golden mussel on the East Branch. Multiple detections of golden mussel have been observed upstream of Lake Palmdale in the California Aqueduct.

For specific questions about Palmdale Water District’s response, please contact Scott Rogers, Assistant General Manager, at (661) 456-1020. For questions regarding CDFW’s response, please contact CDFW’s hotline at (866) 440-9530.

On July 7, 2025, Department of Water Resources staff found a single golden mussel attached to an intake stop log at John R Teerink Wheeler Ridge Pumping Plant. This pumping plant is located on the California Aqueduct near Mettler and it is the southernmost detection to date of an adult golden mussel in California. Water from the California Aqueduct flows south of here and splits into the East and West Branches of the Aqueduct. Water in the Western Branch of the Aqueduct flows into Quail Lake, where golden mussel veligers were detected in May and June 2025. Water from Quail Lake is released via the Lower Quail Canal, passes through the Warne Powerplant, and flows to Pyramid Lake. Water from Pyramid Lake flows into Elderberry Forebay, and Castaic Lake, which is the terminus of the West Branch. Water from Castaic Lake flows into Castaic Lagoon, Castaic Creek, and the Santa Clara River. Pyramid Lake also releases water to Middle Piru Creek which flows to Lake Piru, Lower Piru Creek, and Santa Clara River. Quagga mussels have been detected in Pyramid Lake and downstream waters.

Water in the East Branch of the Aqueduct flows into Silverwood Lake and Lake Perris. Lake Perris is the terminus of the East Branch.

In response to the detection of golden mussel in California waterways, the state of California has developed a comprehensive Golden Mussel Response Framework (PDF) to address this invasive species threat. 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.

Golden mussel (Limnoperna fortunei) veligers have been detected in Quail Lake, Los Angeles County, following testing of plankton samples collected by California Department of Water Resources (DWR) and California Department of Fish and Wildlife (CDFW).

On June 9, DWR detected golden mussel veligers in plankton tow samples that were collected at the Quail Lake outlet location on June 3 and analyzed with cross-polarized light microscopy (CPLM). The veligers were confirmed by polymerase chain reaction (PCR) analysis as golden mussel.

On June 16, CDFW’s Invasive Species Program (ISP) detected 12 veligers using CPLM in plankton tow samples collected at the inlet and outlet of Quail Lake on May 8 and May 29. The veligers were confirmed by PCR analysis and DNA sequencing as golden mussels.

Quail Lake, part of the State Water Project’s West Branch, only allows shoreline fishing and no boating. The lake is located downstream of Check 24, previously the southern-most sighting of golden mussel.

Water from Quail Lake is released via the Lower Quail Canal, passes through the Warne Powerplant, and flows to Pyramid Lake. Water from Pyramid Lake flows into Elderberry Forebay, and Castaic Lake, which is the terminus of the West Branch. Water from Castaic Lake flows into Castaic Lagoon, Castaic Creek, and the Santa Clara River. Pyramid Lake also releases water to Middle Piru Creek which flows to Lake Piru, Lower Piru Creek, and Santa Clara River. Quagga mussels have been detected in Pyramid Lake and downstream waters.

In response to the detection of golden mussel in California waterways, the state of California has developed a comprehensive Golden Mussel Response Framework (PDF) to address this invasive species threat. 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, contact Maggie Macias, DWR Information Officer, at (916) 902-7405. For questions regarding CDFW’s response, contact CDFW’s hotline at (866) 440-9530.

This message is being forwarded on behalf of the US Fish and Wildlife Service:

The Funding Opportunity for the U.S. Fish and Wildlife QZAP FY2025 has officially been posted. The total funding amount for projects $1.75 M. There has been significant change in the application process over the past three years, resulting from our transition to GrantSolutions.gov. This opportunity will be open for application through September 5, 2025.

Applications will need to be submitted through grantsolutions.gov, and you will need to create a login and password to access the system. There are recipient tutorials online linked below. Below are the steps you will need to take to access and locate the funding announcement. The funding announcement number is F25AS00313 and the full title is "F25AS00313 FY2025 Implementation of the Quagga and Zebra Mussel Action Plan (QZAP) in the Western United States"

Please disseminate this opportunity to all interested parties. Feel free to reach out to barak_shemai@fws.gov. The opportunity can also be found at grants.gov, but applications may NOT be submitted through grants.gov. The grants.gov announcement: 2025 QZAP Grant Announcement.

Please follow these instructions after creating a GrantSolutions.gov username and password.

• Sign into grantsolutions.gov
• Go to the Funding Opportunities page
• Once there use CTRL + F to search the name of the opportunity "name in full" or "QZAP"
• You should see the QZAP opportunity - Select Apply on the far right

Recipient training videos:

• https://www.doi.gov/grants/grantsolutions
• GS Recipient Training Videos

General information:

• FWS GrantSolutions

Do NOT submit applications through Grants.gov.

Golden Mussel Detections in California, October 2024-June 2025

October 17, 2024 – Golden mussel (Limnoperna fortunei), an invasive, non-native freshwater bivalve, was discovered in the Sacramento-San Joaquin Delta (Delta). This is the first known detection of golden mussel in North America. Waters that are downstream of the Delta are presumed to be exposed to golden mussel.

The mussels were found attached to a float near the Port of Stockton by the California Department of Water Resources (DWR) and immediately reported to the California Department of Fish and Wildlife (CDFW). No mussels had been observed on the float in the prior months’ inspection. The mussels were sent to the UC Davis Genomic Variation Laboratory and the California Department of Food and Agriculture’s (CDFA) laboratory for identification. On October 23 and 24 UC Davis and CDFA independently returned genetic analysis results consistent with golden mussel.

Following the initial discovery of golden mussels in the Port of Stockton, observations of additional mussels were made at numerous locations throughout the Delta on water quality monitoring equipment and artificial substrates (deployed for the purpose of detecting invasive mussels.) Historical statewide quagga/zebra mussel and golden mussel early-detection monitoring is ongoing, and would be effective for detecting golden mussel.

October 25, 2024 – State Parks reported adult mussels on an artificial substrate deployed for monitoring for the presence of quagga/zebra mussels in O’Neill Forebay. Specimens collected from O’Neill Forebay were later confirmed to be golden mussel by genetic analysis conducted by UC Davis and CDFA labs.

October 31, 2024 – A multi-agency press release was published.

November 22, 2024 – DWR found an adult golden mussel on the louvers of the Skinner Fish Facility, just downstream of Clifton Court Forebay. The mussel was visually identified as a golden mussel by DWR. The Skinner Fish Facility is located at the entrance to the California Aqueduct. The facility works to divert fish away from the pumps that lift water into the California Aqueduct.

December 18, 2024 – US Bureau of Reclamation (USBR) discovered upwards of 20 adult mussels on the Tracy Fish Facility louvers, downstream of Clifton Court Forebay. The mussels were visually identified as golden mussel by USBR. The facility is located at the entrance to the Delta Mendota Canal, and it intercepts fish and diverts them away from the pumps that lift water into the canal.

December 30, 2024 – DWR reported adult mussels on an artificial substrate deployed in Bethany Reservoir. No mussels had been observed in the prior months’ inspection. DWR staff visually identified the species as golden mussel.

February 12, 2025 – DWR detected 3 adult golden mussels in a drained discharge pipe at the Las Perillas Pumping Plant. Subsequently, DWR inspected the pipe and found and removed several hundred mussels ranging in size from 0.7 to 2.2 cm. The Las Perillas Pumping Plant is a facility of the State Water Project (SWP) that is part of the Coastal Branch Aqueduct and located about one mile from the California Aqueduct near Avenal in Kings County. It lifts water from the aqueduct for delivery through the first 15 miles of the Coastal Branch. Water undergoes a conventional water treatment process at the Polonio Pass Water Treatment Plant (PPWTP). This conventional water treatment process includes flocculation, sedimentation, filtration, and disinfection with chlorine. This process is an effective built-in control to remove golden mussel veligers from source water and prevent passage further downstream. However, there is a water diversion upstream of the treatment plant that delivers untreated water from the Coastal Branch to Lake Evans and Lake Woollomes in Kern County.

February 26, 2025 – DWR detected an adult mussel in the backflush debris filter at Dos Amigos Pumping Plant. DWR visually identified the species as golden mussel. The Dos Amigos Pumping Plant is a facility of the State Water Project (SWP) that is part of the California Aqueduct. It is located about 15 miles downstream from Check 13, the outlet of O’Neill Forebay.

March 20, 2025 – DWR detected multiple adult golden mussels at Check 24 of the California Aqueduct. DWR visually identified the species as golden mussel. Check 24 is located near the junction of Highway 46 and Interstate 5. This is the southern-most sighting of golden mussels in the SWP to-date. The California Aqueduct delivers water to reservoirs throughout Southern California.

April 11, 2025 – Three adult mussels were discovered in the discharge pipeline at Pleasant Valley Pumping Plant. The mussels were sent to CDFW and were genetically identified as golden mussel. Pleasant Valley Pumping Plant draws water from a canal that is connected to the California Aqueduct. It is located about a mile and a half from the California Aqueduct.

April 30, 2025 – Westlands Water District reported more than 100 adult mussels on a pump at a pumping plant on the San Luis Canal. The mussels were sent to CDFW and were genetically identified as golden mussel. The San Luis Canal is a segment of the California Aqueduct that extends from south of O’Neill Forebay to Kettleman City in Kings County.

New confirmed golden mussel detections within the bounds of Highway 160, Highway 12, Interstate 5, and Interstate 205 will added to the map; however notifications will not be distributed via the Invasive Mussel News. To receive notices for significant detections beyond these bounds, subscribe to the Invasive Mussel News.

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For a list and map of all confirmed detections of invasive mussels visit:
Golden mussel map
Quagga/zebra mussel map

Report invasive mussel detections to CDFW’s online at Invasive Species Program, email invasives@wildlife.ca.gov, or call (866) 440-9530. Please include the specific location of the observation, and at least one clear close-up photograph of the organism, and your contact information.

Hello Water Managers,

This is a friendly reminder that Division of Boating and Waterways' Quagga and Zebra Mussel Infestation Prevention grant period close tomorrow, April 18, 2025 at 5 p.m. If you submitted your grants early, we encourage you to review your submission for completeness.

Thank you!