Invasive Mussel News

The deadline to submit a proposal for CDFW’s Boating Access Grant Program is Friday, November 7, 2025, at 4:00 p.m. PST.

For more information, see the 2026-27 Boating Access Proposal Solicitation Notice (PDF) and CDFW's Boating Access page. All proposals must be submitted via the CDFW WebGrants portal.

Contact BoatingAccess@wildlife.ca.gov with any questions.

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

SACRAMENTO, California – The California Department of Water Resources (DWR), in coordination with California Department of Fish and Wildlife (CDFW) and California State Parks, is highlighting new measures to protect California’s water infrastructure and slow the spread of invasive golden mussels following a recent discovery of the species at San Luis Reservoir in Merced County.

San Luis Reservoir, the largest off-stream reservoir in the nation, is part of the San Luis Joint-Use Complex that serves the State Water Project (SWP) and federal Central Valley Project. The invasive species was recently discovered at the facility during a routine water test conducted by DWR. In response, mandatory watercraft inspections of all vessels leaving San Luis Reservoir are now in place and will help prevent the spread of mussel to other lakes and reservoirs.

Golden mussels, an invasive species detected in North America in October 2024, pose a threat to infrastructure and the ecological health of all state waterways. While the mussels pose no immediate threat to water quality or supplies, if left unchecked, they can compromise water delivery systems by clogging pipelines, screens, and filters.

To help reduce the risk of mussel colonization, DWR has implemented routine inspections of SWP facilities and expanded its efforts by applying new strategies to protect pumping plants, hydroelectric plants, and water supply deliveries.

The department will be installing medium-pressure ultraviolet light disinfection systems at several facilities to prevent mussel settlement in small-diameter piping of cooling water and fire protection water systems. DWR staff are also researching the use of low-dose chlorine, copper, and hot water to control mussel settlement in pipelines and on fish screens.

To date, golden mussels have not been detected at the SWP’s Oroville or Upper Feather River Lakes facilities. A new mapping tool developed by CDFW is now available online that shows the latest golden mussels detections in California.

Boaters and recreationists can also do their part in combating the spread of invasive mussels by following mandatory watercraft inspections of all vessels leaving SWP reservoirs, and remembering to “clean, drain, and dry” their watercraft before entering and leaving waterways. DWR’s new video series provides information about golden mussels, tips on how boaters can stop the spread, and what to expect during a mussel inspection.

State Parks’ Division of Boating and Waterways (DBW) maintains a list of its reservoir contacts, and the public is urged to visit State Parks DBW website to check current information on inspections or restrictions before heading out to recreate on the water. DBW also provides boaters and water body managers with up-to-date information through its invasive mussels page.

To report suspected golden mussel sightings or learn more about invasive species prevention, visit CDFW’s golden mussel page, call (866) 440-9530 or email invasives@wildlife.ca.gov. More information about the state’s coordinated efforts to combat golden mussels can be found in California’s comprehensive Golden Mussel Response Framework (PDF).

Additional Resources:

• Golden Mussels Fact Sheet (PDF)
• Golden Mussel SWP Detections Map (PDF)
• Golden Mussel Photos
• Golden Mussels Video Series
• DWR's Invasive Mussel Mitigation website

For more information, follow us on X or Facebook and read our news releases and DWR updates.

Today the California Department of Fish and Wildlife (CDFW) announced the award of $2.5 million in grants for five projects to support public recreational boating access to state waterways. These projects will help prevent the spread of invasive golden mussels, improve public access to California’s waterways, expand recreational boating opportunities, and promote stewardship of aquatic resources.

”Supporting safe and reliable access for all boaters and anglers means investing in boating facilities as well as protecting our waterways from invasive species,” said CDFW Director Charlton H. Bonham. “A portion of this grant funding will directly support California’s response to limiting the spread of golden mussels as part of a larger ongoing coordinated effort.”

Looking ahead, CDFW also announced today that the Boating Access Grant Program is now accepting proposals for the Fiscal Year 2026/2027 Boating Access Proposal Solicitation Notice (PDF) and has approximately $2 million to award. Proposals are due by 4 p.m. on Nov. 7, 2025, through the CDFW WebGrants Portal. Contact BoatingAccess@wildlife.ca.gov with any questions.

CDFW will hold an online Public Workshop (PDF) on Oct. 2, 2025, at 10 a.m., to provide an overview of the Boating Access Program, including eligible activities, program requirements, and granting process. Workshop attendance is not a requirement for submitting a proposal.

Below is a list of awarded projects which will soon begin work supported by CDFW Boating Access Grant Program funds. The Boating Access projects are supported with federal funding from the Sport Fish Restoration Grant Program, administered by the U.S. Fish and Wildlife Service, which provides funds to state fish and wildlife agencies for fishery projects, boating access, and aquatic education.

Invasive Golden Mussel Program

($1.3 million to CDFW)

After the discovery of the invasive golden mussel (Limnoperna fortunei) in the Sacramento-San Joaquin Delta in Oct. 2024, CDFW responded with approximately $1.3 million in Sport Fish Restoration/Boating Access grant funding to support the program and projects that prevent the spread of invasive mussels in California waters. Funds will support the purchase of decontamination units, high-pressure wash stations, improvements to boat ramps and wash stations, and hands-on training for facility staff in boat inspection and decontamination procedures. More information can be found on CDFW’s golden mussel page.

Other Boating Access Project Highlights

Alviso Marina County Park Boat Ramp Replacement

($226,000 to county of Santa Clara, Parks and Recreation Department)

“The County of Santa Clara deeply values its long-term partnership with CDFW,” said Todd Lofgren, Director of Santa Clara County Parks Department. “Alviso Marina County Park is well-loved by boaters, as it provides one of the few clear routes through the salt marshes out to the open waters of San Francisco Bay, and the repair and replacement of the launch and dock is a community need that the Department is excited to deliver on with CDFW’s support.” The project will repair the boat launch ramp, the replacement of existing wooden planks on three public access boardwalks, and improvements to the facility parking lot.

Copco Valley Public Access and Recreational Boating Facility for a Renewed Klamath River

($582,915 to Klamath River Renewal Corporation)

As the Klamath River recovers and flows change following the dam removal in 2024, there are new recreational opportunities and increased public interest in the area. To meet capacity and safety needs, the construction of the Copco Valley recreation site will be a critical access point on the Klamath River for boating, fishing, and other uses. The project will not only support recreation and public interest opportunities but further allow the public to see first-hand the positive impacts of dam removal on conservation, wildlife, and the local communities and economies.

Arena Cove Boating Access Project

($224,000 to City of Point Arena)

This project will enhance boating access from Arena Cove, which is a major point of entry for many residents of Mendocino and Sonoma counties. Project activities will include the replacement of the aging boat launch hoist, boarding float and gangway, all of which are essential components of boating access from Arena Cove. The urgent facility repairs address site safety, negative environmental impacts of old equipment and ensure continued boating access in the future.

Santa Ana Launch Ramp Slurry/Crack-fill FY25/26

($223,000 to Casitas Municipal Water District)

This project will support vital maintenance of the Lake Casitas Santa Ana Boat Launch Facility in Ventura County and encourage public use of the lake for boating and recreation. Refurbishment of the existing parking lot will allow continued public use of the boat launch facility, which is currently largely unused due to deferred maintenance.

Background

In late 2023 CDFW announced availability of funding for the Boating Access Grant Program. The Sport Fish Restoration Act (SFRA) created the Sport Fish Restoration Grant Program, administered by the U.S. Fish and Wildlife Service. The Program provides funds to state fish and wildlife agencies for fishery projects, boating access, and aquatic education. The funding for this grant program comes through revenue from manufacturers’ excise taxes on sport fishing equipment, import duties on fishing tackle and pleasure boats, and a portion of gasoline fuel tax attributable to small engines and motorboats. The Boating Access sub-program of the Sport Fish Restoration Grant program provides federal funds for facilities that create or add to public access for recreational boating and improvements to waterways that increase access to recreational boating opportunities. 

Media Contacts:
Matt Wells, CDFW Watershed Restoration Grant Branch, (916) 216-7848
Steve Gonzalez, CDFW Communications, (916) 804-1714