A new invader threatens California water supplies. Can the state stop its spread?
One of the state’s best investigators was on the hunt for golden mussels — a dangerous new invader in California’s waters, with a reputation for destruction.
Wearing a collar and a tongue-lolling grin, Allee, a Belgian Malinois, sniffed along the glittering hull of a bass boat at an inspection station in Butte County.
The dog’s handler, California Department of Fish and Wildlife Warden Mark Rose, pointed at the outboard motor and the dog delicately nosed the propellers. She stretched up on her hind legs to get a good whiff of the port side before Rose led her away. She yawned. Nothing here.
The dog was searching for any hint of the thimble-sized mussels hidden in the nooks and crannies of boats headed to Lake Oroville, the state’s second-largest reservoir, or two smaller reservoirs nearby. Her human counterparts at the Department of Water Resources’ inspection station combed the boat’s interior for standing water that could harbor larvae.
Mandatory boat inspections are among the few weapons in California’s arsenal for protecting its thousands of lakes and reservoirs from the invasion. The mussels’ prolific growth and voracious appetites can upend entire ecosystems, encrust underwater surfaces, choke off water supplies and damage dams and power plants.
“We have been on high alert,” said Tanya Veldhuizen, special projects section manager in the California Department of Water Resources’ environmental assessment branch, which operates the state’s water delivery system. “It’s not just on our doorstep, it’s in our house.”
State water managers made the alarming discovery last October that golden mussels, which are native to China and Southeast Asia, had invaded the Sacramento-San Joaquin River Delta — the core of California’s massive water delivery systems. It marked the first detection in North America.
The mussels, first discovered encrusting a float near the Port of Stockton, have already infiltrated California’s two major state and federal water systems, which export water from the Delta to supply 30 million people and millions of acres of farmland. Their larvae are spreading through the network of pumps, pipes and canals.
“To everyone’s horror, it was in many, many more places than we expected,” said Ted Grosholz, a professor emeritus with the UC Davis Coastal and Marine Sciences Institute. “The further they looked, the further they found them.”
Now the mussels are here to stay. They cannot be eradicated. Water suppliers bracing for the onslaught have instead turned their efforts to shoring up pipes, pumps and treatment plants against the infestation.
Golden mussels, a destructive species from Asia, are concentrated in the Sacramento-San Jaoquin River Delta, according to California Department of Fish and Wildlife surveys.
The state’s most immediate priority is protecting the small pipes at upstream pumping facilities that keep water deliveries flowing, then they’ll move their efforts downstream, Veldhuizen said.
“It is a huge undertaking,” Veldhuizen said. “We’re not looking at removing mussels from all the water, because it’s just not feasible.”
The race is on to keep the mussels and their microscopic larvae from infesting untainted lakes by stowing away on hulls or inside damp, internal cavities of boats.
But resources are stretched precariously thin. There is no funding dedicated to fighting invasive golden mussels in the state’s budget. And each new infestation means one more place from which they can spread.
Boaters statewide are warned to “clean, drain and dry” anything that touches water before moving it to another lake or river. Microscopic larvae can survive in tiny amounts of trapped water. Adult mussels may survive for around a week or longer with no water at all.
Water managers in some lakes and reservoirs now require inspections, quarantine periods and decontamination with hot water before boats can enter. Others have closed or limited access to boating. But a patchwork of oversight leaves many lakes with no protection at all.
‘Oh, look what we found’ — the hunt for mussels
Allee, with her sensitive snout and devotion to Rose, is one of the state’s more finely-honed weapons against this invasion. But she is one of only 14 dogs with the wildlife agency trained to detect invasive mussels, Rose said. And she is also tasked with sniffing out the guns, ammunition and kills of wildlife poachers farther north in Tehama County, where Rose is the only game warden for nearly 3,000 square miles.
A state and federal mussels task force released recommendations in April, including mandatory decontamination of boats in infested areas for longer than five days and prevention programs at all accessible, uninfested waters. But these are monumental tasks, especially amid federal staff cuts and the state’s $12 billion budget deficit. California’s fish and wildlife agency, for instance, is severely understaffed, with only 33% of the resources needed to fulfill its law enforcement duties and 26% needed for habitat and species conservation, according to a 2021 analysis mandated by the Legislature. Even so, Gov. Gavin Newsom proposed cutting 164 vacant positions at the department this year, including wardens and other enforcement positions, according to HD Palmer with the Department of Finance. Lawmakers rejected the cuts for now, but the finance department said the budget does not provide funding to fight golden mussels. “Everybody’s under fire,” UC Davis’ Grosholz said. “It’s not a great time for resource agencies to suddenly have a brand new threat.”
At the Department of Water Resources’ Oroville inspection station last month, trucks hauling expensive fishing boats and beat-up skiffs rolled over the dusty parking lot at the Thermalito Forebay, a smaller, downstream reservoir. The boats that passed Allee’s smell test and neon-vested inspectors were recorded and tagged, then sent to the open ramps. Boats that failed because they were still wet — even wet cupholders and life jackets can trigger a failure — were sent to a decontamination station, where they were sprayed and flushed with steaming water. Inspection stations set up by multiple agencies have already intercepted boats contaminated with golden mussels bound for lakes Tahoe, Folsom, Berryessa and Oroville. Leaning against his sailboat at an Oroville boat ramp, boater Dean Dyrr said inspectors spotted mussels on the boat right next to his when his sailboat was checked at the Thermalito Forebay in May. “They were like, ‘Oh, look what we found!’ and it was a handful of mussels,” Dyrr said as his wife loaded up their boat with supplies and water. Lake Oroville glinted against the dry, oak-studded foothills, and dozens of boats bobbed on its surface.
When mussels are found, the boat is pressure-washed and flushed with hot water, then confirmed free of mussels before it can be launched at the lake.
“The program’s actually working. They’re actually doing some good to keep the mussels out of the water” at Oroville, Dyrr said. “Don’t know what they’re doing with all the other thousands of lakes around that they’re not monitoring, though.”
Various authorities — federal, state, local and private — manage access to California’s lakes and reservoirs. Of particular concern are the lakes and waterways that are not fed by Delta water, because they have the best chance of being spared infestations. Around thirty lakes and reservoirs have inspection programs and quarantine requirements of up to 60 days, and a handful have limited or barred access to boats, according to the state’s Division of Boating and Waterways’ analysis of a list they maintain. The division warns, however, that the list is not comprehensive and is kept as a courtesy with the limited staff that they have; boaters are advised to contact lakes and reservoirs to confirm. Among the biggest gaps in oversight are federally-managed Whiskeytown and Shasta lakes. Shasta Lake is the biggest reservoir in the state, and both are popular with boaters. Neither have mandatory inspection programs. “If golden mussels are detected in Shasta Lake, we will reassess the current approach and consider additional measures,” a spokesperson with the U.S. Forest Service said in an email. The agency asks boaters to voluntarily dry their boats for five days between visits to local North State lakes like Shasta and Whiskeytown, and 30 days if entering the lakes from outside the area. Laura Shaskey, division lead of resource management and interpretation with the Whiskeytown National Recreation Area, said voluntary inspections are offered during peak visiting periods. The inspection programs that do exist are costly and labor intensive. Lake Tahoe’s has been in place since 2008, after invasive quagga mussels breached California’s borders. But golden mussels are more ecologically nimble than previous invaders, and can survive in a much bigger range of waters. So the threat that they pose to Lake Tahoe is even greater, said Jeff Cowen, a spokesperson for the Tahoe Regional Planning Agency.
The agency has budgeted $1.1 million this fiscal year for its mandatory inspection program, which now also requires decontamination for boats entering on trailers. Boaters launching for the first time in Tahoe will need to pay a $115 registration fee for the year, plus $30 to $60 decontamination fees each time the boat returns from another lake. Kayaks, paddleboards and other hand-launched boats can skip the line and be decontaminated for free. At Folsom Lake and Lake Clementine, the U.S. Bureau of Reclamation and California State Parks require boaters to quarantine their boats for 30 days after inspection before they can enter the water, or pay a company for decontamination. By mid-June, staff braving sometimes sweltering weather had inspected more than 7,000 boats in just two months. But for all the expense and effort, there are still too many ways for boats to leave the Delta with invasive stowaways, and too few resources to stop them. There are also traces of DNA that suggest golden mussels had already invaded the Delta more than a year before they were first spotted near the Port of Stockton, Veldhuizen said. “There is the real potential that watercraft have moved golden mussels out of the Delta, and my fear is that we will begin to see detections outside of that interconnected water,” Martha Volkoff, environmental program manager for the California Department of Fish and Wildlife’s Invasive Species Program, said at a recent webinar. Still, Volkoff told CalMatters, it is worth trying to slow the spread as much as possible. California has done it before: Quagga mussels are thought to have spread to only two unconnected bodies of water since they were first discovered in Southern California’s Colorado River Aqueduct in 2007. “There’s so much to protect yet,” Volkoff said. “Yes, it’s a lot of work, but the long-term savings — to the environment and to all the other ways that it costs us — is investment well spent, even if we just delay new introductions.” Rose, in his K-9 unit vest, led Allee toward a pickup hauling an aluminum fishing boat when the driver rattled away, kicking up dust. The boat had not been inspected; the lake he was heading to — Collins Lake, in Yuba County — doesn’t require them. “There’s just too many boats and too many people out there to not miss them. It’s physically impossible,” Rose said. Another boat pulled up, and Allee happily trotted over.
Boaters upset about long dry-outs
About 25 miles away in the Sierra foothills, Collins Lake brimmed with campers on a Friday afternoon in June. People lounged on the sandy beach and paddled on kayaks and floats. A handful of fishing boats bobbed in the deeper water.
A sign at the lake’s boat ramp warned “DON’T MOVE A MUSSEL. CLEAN. DRAIN. DRY.” It was a precaution against the older threats of quagga and zebra mussels, and hadn’t been updated yet to include the state’s newest invader.
There was no one checking boats at the ramp, though — which had drawn Mark Mezzanares and his friend Sonny Steuart to the lake. The retirees from Colfax were put off by the 30-day dry-out periods required at Folsom Lake in Sacramento County and Rollins Lake in Nevada County, though boaters who want to fast-track entry can pay for disinfection.
“I’m not gonna go sit over there and have my boat sit in the freaking driveway for 30 days and then go fishing once,” Mezzanares said. Rollins’ quarantine is an even more stringent 60 days for boats with bilges, ballasts and live water tanks that could carry stowaways.
“You don’t buy and spend $45,000 on a boat to go to one lake,” he said. They wished the state offered a pass that allowed boats cleared for one lake to visit others.
It’s a common refrain among boaters who chafe at the new restrictions. Maggie Macias, a spokesperson for the Department of Water Resources, said in an email they are discussing a pass program from Lake Oroville with other lake managers, but will need to ensure that any potential partners have rigorous inspections — and don’t already have mussels in the water themselves.
Those whose livelihoods depend on keeping lakes open for visitors are facing a difficult new reality. Jacob Young, the general manager of Collins Lake recreation area, is leaving it up to the boaters to ensure their boats are clean, drained and dry — at least for now.
“You can just sense a lot of that frustration that they’re feeling, like, ‘This is ridiculous,’” Young said. “And the same token, you get some people who might say, ‘Man, you’re not doing any golden mussel inspections? How could you not be doing that and making sure you’re staying safe?’”
At the boat ramp, water poured from the motor of a cherry-red bass boat that visitor Dan Jacobs had just hauled off the lake. Jacobs said he wished California had a network of courtesy decontamination stations like the ones offered in Minnesota to combat the spread of invasive zebra mussels, instead of lengthy quarantines.
“One of the rare times our tax dollars were spent wisely,” he said.
For him, the risk to Collins Lake feels personal; he and his wife camped there decades ago, when he was stationed at Beale Air Force Base, and now their children and grandchildren return for family camping trips.
“As bad as the mussels are, it makes you kind of nervous,” he said. “All it takes is one person to screw it up for everyone.”
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Natasha Uzcátegui-Liggett contributed reporting.
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This story was originally published by CalMatters and distributed through a partnership with The Associated Press.
By RACHEL BECKER/CalMatters
CalMatters
