San Joaquin County lawmakers are urging state and federal officials to expand research and prevention efforts to combat invasive golden mussels threatening the Sacramento-San Joaquin Delta and the region’s waterways.
During a discussion Monday at Hilton Stockton with water managers and other stakeholders, Assemblymember Rhodesia Ransom, D-Tracy, and U.S. Rep. Josh Harder, D-Tracy, discussed state and federal legislation aimed at addressing the infestation and the need to identify effective solutions.
Golden mussels were first detected in North America in October 2024, when California Department of Water Resources staff discovered them attached to a float near the Port of Stockton.
According to the California Department of Fish and Wildlife, the invasive species poses environmental, recreational and economic risks. The mussels compete with native and game fish for food and can contribute to harmful algal blooms that kill fish.
Their presence also can disrupt recreation through waterway closures, mandatory inspections and increased boat launch or entry fees. The mussels can clog water infrastructure, damage boats and hydroelectric facilities, and reduce water flow, potentially affecting agricultural production, water deliveries to homes and flood control.
Soon after taking office in December 2024, Ransom said she began seeking resources and contacting lawmakers in other regions to learn how they were addressing the spread of golden mussels.
In October 2025, Ransom helped secure $20 million in state funding through Assembly Bill 149, the Public Resources Trailer Bill, to combat the spread of invasive species and support local prevention efforts.
In July, she helped secure an additional $6 million in the 2026-27 state budget for Delta decontamination sites to help prevent golden mussels from spreading to other California waterways.
Ransom said the state should help fund efforts to combat the infestation, but water managers and other officials dealing with the problem firsthand must ensure the money is spent effectively.
“We want to make sure that we’re spending the money not only to contain it but to make people’s lives easier,” she said.
Ransom also authored Assembly Bill 2032, the Golden Mussel Response Act, which Gov. Gavin Newsom signed into law in September. The law allows water agencies that have submitted golden mussel control plans to perform necessary maintenance, including removing the mussels from pipes, screens and other infrastructure, without waiting for additional permits.
She said the legislation gives agencies greater flexibility to test potential solutions rather than spend months waiting for approvals while the species continues to spread.
Harder has introduced federal legislation that has yet to become law.
The Golden Mussel Eradication and Control Act would establish a rapid-response program to monitor and contain the infestation and pursue eradication. It would also invest in new technology and inspection stations and improve coordination among state, local and federal agencies through a report on best practices and new guidance on prevention.
The legislation received a congressional hearing in September but must still be approved by Congress before it can become law.
Harder said he wants the federal government to “supercharge” local efforts.
“We’re seeing so much great leadership by other agencies that are already putting their own money into this because they see it’s a problem,” Harder said. “We need to be able to scale that up and to make sure that there’s one successful idea that’s been proven in one specific district that doesn’t stop there, and we’re able to export that all across the state.”
The Delta is a shared resource that is not owned by the state or federal government, he said.
“It belongs to all of us,” Harder said, emphasizing the need for cooperation among local, state and federal agencies, as well as the private sector.
He also called for more federal investment in surveillance, research and decontamination. Although some containment strategies have shown promise, Harder said more work is needed to determine whether eradication is possible.
“This is a problem that we might be living with for generations, and I don’t think that’s an acceptable answer given how much damage that we’ve already seen them make,” he said.
The economic stakes extend beyond the Delta, Harder said, pointing to California’s agricultural industry, which generates more than $50 billion a year and depends on the Central Valley, particularly the Delta and regional waterways. Delaying action could make the infestation more costly to address, he said.
“The challenge is most folks have never heard of a golden mussel,” Harder said. “They don’t really understand why it’s actually a problem or what’s actually at stake with them. The sooner we get people through that first step of education, the better.”
Research, outreach key to response
Both lawmakers emphasized the need to share findings from research into potential solutions.
Harder said a centralized system for collecting research findings could help agencies avoid duplicating work and identify effective strategies. He said developing a coordinated research plan involving UC Davis is a priority for his proposed federal legislation.
“We’re in touch with UC Davis and agree that making a big research plan there is a complete priority for our legislation,” Harder said. “We see so much great effort happening in so many different water districts. People are doing this job. We have to make sure that it’s systematized, and that it comes together, and it’s not actually reinventing the wheel.”
Ransom said she supports expanding research partnerships, including potential efforts involving UC Davis, to identify solutions that can be tested in different environments.
The lawmakers also stressed the importance of educating the public about the threat. Ransom encouraged local officials to tailor outreach to residents’ concerns, whether those involve boating, recreation or flood protection.
“Everyone has a different reason why it matters to them,” she said. “I think we all need to make sure that we meet people where they are about what matters to them.”
Harder said raising awareness beyond the Delta region is important because the problem could affect communities across the country.
“The more advocacy that we can do to show that this isn’t just a regional, Central Valley or California problem — this is something that the entire country is going to be dealing with — it makes my job a lot easier,” he said.
Lawmakers outline goals for containment
Asked what progress would look like a year from now, both lawmakers outlined goals for California’s response to the infestation.
“I think we’ve been on defense for a long time and I don’t think we’re winning,” Harder said.
He said he hopes to prevent new infestations and develop more effective strategies for controlling the mussels.
Ransom said she wants to see fewer new infestations, more research underway and control plans in place across affected water districts.
“We want to see results and impact,” she said.
Both lawmakers acknowledged that complete eradication may be difficult but said officials should continue pursuing solutions rather than accept the infestation as permanent.