Invasive golden mussels reach Southern California reservoirs, threatening water supply and prompting new Silverwood Lake boating protocols
Silverwood Lake, California (High Desert News Online) – Invasive golden mussels have been detected in Southern California’s Silverwood and Pyramid Lakes in 2025, marking the species’ southernmost spread and posing an irreversible threat to water supplies, infrastructure and native ecosystems; new boating protocols are in effect.
Key takeaways
- Golden mussels detected at Silverwood Lake (San Bernardino County) and Pyramid Lake (Los Angeles County) in 2025; agencies confirm rapid spread since first California detections in late 2024.
- New exit-only boating protocols at Silverwood focus on removing drain plugs and enforcing clean, drain, dry to prevent veligers from leaving.
- Major threat to infrastructure and ecosystems: mussels clog pipes and intake systems, alter water quality, and currently lack reliable eradication in open waters.
- Statewide coordination: DWR, CDFW and State Parks expanding testing, monitoring and outreach to slow spread and protect water delivery.
Background and detections
The invasive golden mussel (Limnoperna fortunei) was detected in 2025 at Silverwood Lake and Pyramid Lake. The discovery was confirmed by the California Department of Water Resources (DWR). State records show the invasion began with detections in October 2024 in the Sacramento‑San Joaquin Delta and O’Neill Forebay, as documented by the California Department of Fish and Wildlife (CDFW).
How the mussels were found
Routine testing by the DWR detected small specimens and alerted partners and the public through a release. Officials say mussels likely moved through interconnected water systems and by attaching to boats, trailers and equipment. The species also releases microscopic larvae called veligers that travel in water and can be carried in live wells and bilge water.
“They can cling to hulls, motors and trailer parts and travel as microscopic veligers in trapped water,” officials said in agency updates.
DWR confirmed the detections in its news release (California Department of Water Resources (DWR)).
Why golden mussels are a serious threat
Though small, golden mussels reproduce rapidly and filter large volumes of water. Their biology creates multi-faceted risks:
Infrastructure damage
Mussels encrust pipes, pumps and intake screens, leading to clogging that can reduce water flow to treatment plants, farms and cities. State officials warn damage could threaten delivery systems serving millions of people and hundreds of thousands of acres of farmland (DWR; KPBS).
Ecosystem impacts
As aggressive filter feeders, golden mussels change nutrient cycles and water clarity, potentially harming native fish and plants and contributing to harmful algal blooms (Keep Tahoe Blue; NAISMA).
Recreation and boat costs
Mussels stick to boats and gear, raising maintenance costs and increasing the risk of spreading to otherwise clean waters. Boaters are a primary transfer pathway, making preventive checks essential (DWR).
Irreversibility
Experts warn there are currently no proven ways to eradicate golden mussels from open reservoirs, which raises the stakes for early prevention and rapid response (DWR; Keep Tahoe Blue; KPBS).
Current actions at affected lakes
Silverwood Lake: Now listed as infested. Entry inspections have been suspended; instead DWR conducts strict exit checks to ensure boats leave drained. Boaters must remove drain plugs and follow clean, drain, dry rules.
Pyramid Lake: Managed and monitored with protocols similar to past invasive mussel responses (for example, quagga mussel plans), with ongoing monitoring and outreach.
Lake Perris and other at‑risk waters: Perris is not confirmed infested but is at heightened risk because of daily transfers from Silverwood; inspections continue and exit-only protocols could be implemented if mussels are found.
Statewide response and resources
The DWR, CDFW, and California State Parks are coordinating expanded testing, research and public outreach. Technical teams are evaluating mitigation options for pumps and intake systems, while outreach emphasizes prevention as the best defense.
Public guidance and boating rules
Officials advise boaters to:
- Clean all visible debris from boats, trailers and gear.
- Drain all water — live wells, bilges, motor cavities — and remove drain plugs before driving away.
- Dry boats and gear thoroughly before moving to another body of water.
Report any suspect mussel sightings to the California Department of Fish and Wildlife.
Implications for The High Desert, California
Economic impact: The High Desert relies on nearby reservoirs for recreation, tourism and local water deliveries. Spread to more local waters could increase repair and maintenance costs for agencies, often passed to residents via fees, taxes or higher water rates.
Political consequences: Local leaders will face pressure to secure state funding and prioritize inspections and infrastructure upgrades to protect water reliability.
Social effects: Exit-only boat checks and stricter protocols may slow access to recreation but community adherence to clean, drain, dry and reporting can help protect regional waters.
Cultural relevance: Local stewardship and outreach by marinas, civic leaders and community groups can be decisive in preventing further spread.
Practical applications: What High Desert residents should do now
- Follow all Silverwood Lake boating protocols when visiting or launching, including drain‑plug removal and exit checks (DWR release).
- Always clean, drain, dry boats and gear before moving between waters (CDFW guidance).
- Report suspected mussels to the California Department of Fish and Wildlife.
- Stay informed via official state channels and local water agencies for inspection rules and lake access updates (DWR; CDFW).
Costs and technical challenges
Eradicating mussels from pipes and pumps is expensive and technically difficult. Chemical, mechanical and thermal controls can work in closed systems but are impractical for open reservoirs, leaving prevention and rapid response as the most feasible strategies (NAISMA).
Ongoing monitoring and next steps
State agencies plan to expand monitoring, research and outreach. The Silverwood and Pyramid detections are part of an invasion that began in the Delta in 2024. Agencies emphasize prevention while technical teams study mitigation for critical infrastructure (DWR; KPBS; NAISMA).
