{"id":360247,"date":"2026-06-14T10:43:08","date_gmt":"2026-06-14T10:43:08","guid":{"rendered":"https:\/\/www.newsbeep.com\/us-ca\/360247\/"},"modified":"2026-06-14T10:43:08","modified_gmt":"2026-06-14T10:43:08","slug":"california-cuts-lake-oroville-golden-mussel-safeguards","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/us-ca\/360247\/","title":{"rendered":"California cuts Lake Oroville golden mussel safeguards"},"content":{"rendered":"\n

The state of California is walking back protections meant to keep destructive golden mussels out of Lake Oroville, one of the largest and most important<\/a> reservoirs in the state. <\/p>\n

The move follows a new state-funded risk assessment that the invasive species poses a lower risk to the lake, which water managers say changes the state\u2019s calculus on costly and difficult measures aimed at keeping the invaders at bay. <\/p>\n

No state agencies or scientists have found mussels in Oroville yet. But invasive species experts say the revised policy by the Department of Water Resources increases the likelihood that golden mussels will invade Lake Oroville and hitch a ride on boats to other lakes. They disagree, though, about whether preventing such an incursion is even possible. <\/p>\n

\u201cCalifornia is under an epidemic of golden mussels,\u201d said Anthony Ricciardi<\/a>, a professor of biology and the director of the Bieler School of Environment at McGill University in Montreal. \u201cLike in any epidemic, you got to control the key hubs \u2014 or else the war is lost.\u201d<\/p>\n

Reopening Lake Oroville
California water managers first discovered<\/a> golden mussels invading California\u2019s Sacramento-San Joaquin River Delta in October 2024 \u2014 marking their first detection in North America. <\/p>\n

The voracious and rapidly spreading mussels can encrust surfaces so thoroughly that they choke off water supplies and damage dams and power plants. <\/p>\n

They are now invading critical infrastructure in the Delta. And the very pumps, canals and aqueducts that keep water flowing to much of the state are funneling the larvae<\/a> to irrigation districts and water suppliers downstream.<\/p>\n

San Joaquin<\/a> and Kern Counties<\/a> have declared states of emergency, and officials are updating key facilities along the state\u2019s nature-defying water delivery system to reduce mussel damage. <\/p>\n

With summer weather heating up, state water managers said that they are ending<\/a> a program to prevent mussels and their larvae from stowing away on boats and invading Lake Oroville, one of California\u2019s largest reservoirs. <\/p>\n

The department now no longer requires inspections and decontamination<\/a> for boats launching at Lake Oroville and nearby reservoirs \u2014 the Thermalito Forebay and the Thermalito Afterbay. <\/p>\n

The Department of Water Resources says lakes and launches upstream in the Feather River watershed didn\u2019t take similar precautions, raising the risk that golden mussel larvae would wash into the reservoir on river flows regardless of the boat inspections.<\/p>\n

The cost of the inspection program for the lake was also around $7.5 million to start it up, and $6.5 million per year to continue it. Installing UV treatment to prevent mussels from settling in the pipes at powerplants downstream from Oroville, by contrast, would cost an estimated $1 million. <\/p>\n

\u201cWe severely impacted recreation at that lake,\u201d said Tanya Veldhuizen, special projects section manager in the California Department of Water Resources\u2019 environmental assessment branch. \u201cWe also evaluated the risk to our infrastructure and what it would take to mitigate mussels \u2014 and that was much lower than expected.\u201d <\/p>\n

Cold water, fewer mussels?<\/p>\n

The decision reflects the findings from a new risk analysis the department commissioned for these reservoirs and related hydropower and fishery hatchery facilities, as well as for the Upper Feather River Lakes<\/a>. <\/p>\n

Conducted by a Canada-based consulting firm<\/a> specializing in aquatic invasive species, the assessment reports that, while surface temperatures are warm enough for the mussels to survive in shallower water at Lake Oroville, they\u2019re too cold farther down for the mussels to reproduce at depths greater than 60 feet below the surface. <\/p>\n

Unlike the Delta, the waters at Lake Oroville are also low in nutrients, Veldhuizen said. Between the scarce food, cold temperatures and water levels that drop enough to dry out mussels on the shoreline, Veldhuizen said she doesn\u2019t expect the mussels to reach nuisance levels. <\/p>\n

The department also expects that cold water released from the reservoir will slow the growth of any larvae that reach the Feather River Fish Hatchery and the Oroville-Thermalito Complex power plants downstream.<\/p>\n

But Oroville\u2019s shoreline, boats and docks remain at risk \u2014 and those are what worries Ricciardi. <\/p>\n

\u201cThat\u2019s where the action is. The boats will be moving them,\u201d Ricciardi said \u2014 because boats and aquatic weeds clinging to vessels and their trailers can ferry mussels from one lake to another. <\/p>\n

\"A <\/p>\n

Fish and Game Warden Mark Rose and Allee, a Belgian Malinois trained to sniff golden mussels at Thermalito Forebay, in Oroville on June 20, 2025. The dog sniffs watercrafts in an attempt at detecting the golden mussel and preventing its spread into California lakes. <\/p>\n

(Miguel Gutierrez Jr. \/ CalMatters)<\/p>\n

And adult mussels can actually survive even in extremely cold water, says Demetrio Boltovskoy, a retired researcher formerly at Argentina\u2019s National Scientific and Technical Research Council. One study in China found that they can live for weeks<\/a> at near-freezing temperatures. <\/p>\n

Still, Boltovskoy said that while he isn\u2019t specifically familiar with Lake Oroville, reducing precautions may be reasonable. <\/p>\n

\u201cNo matter what precautionary measures you take, sooner or later it will spread,\u201d he said. \u201cI don\u2019t think that stopping their range expansion is actually feasible at all.\u201d<\/p>\n

But invasive species experts are sharply divided on the subject. That\u2019s true especially in California. <\/p>\n

Last year, the California Department of Fish and Wildlife told CalMatters<\/a> that invasions delayed translated to money saved. This year, the wildlife department directed inquiries about the new Oroville strategy to the Department of Water Resources. <\/p>\n

\u201cThere\u2019s so much to protect yet,\u201d Martha Volkoff, environmental program manager for the California Department of Fish and Wildlife\u2019s invasive species program, said last summer.<\/a> \u201cYes, it\u2019s a lot of work, but the long-term savings \u2014 to the environment and to all the other ways that it costs us \u2014 is investment well spent, even if we just delay new introductions.\u201d <\/p>\n

Relying on boaters: Clean, drain, dry<\/p>\n

The responsibility now rests more heavily with boaters to ensure their boats are clean, drained and dry \u2014 especially when leaving an infested body of water such as the Delta. <\/p>\n

If state water managers detect mussels at Lake Oroville, Volkoff said, the department will begin inspecting boats as they leave the lake. <\/p>\n

It\u2019s a strategy already in use at other infested lakes, including Castaic<\/a> and Pyramid<\/a>. Managers of other Northern California lakes told CalMatters they will continue their inspection programs, including at lakes Folsom<\/a>, Tahoe<\/a> and Berryessa<\/a>. <\/p>\n

Drew Gantner, manager of water resources at Solano County Water Agency, which oversees the mussel program at Lake Berryessa, called the Oroville decision concerning.<\/p>\n

\u201cIf Lake Oroville does surrender its program and becomes infested with golden mussels it creates an increased risk for all waterbodies,\u201d Gantner said. \u201cAt that point, any watercraft traveling to Berryessa (or anywhere else) from Lake Oroville would essentially be no different than watercraft coming from the Delta.\u201d <\/p>\n

Ricciardi agreed that the stakes extend well past Oroville\u2019s dam and downstream facilities. <\/p>\n

\u201cThere is another thing about invasions. They often surprise you,\u201d Ricciardi said. \u201cSometimes invaders don\u2019t act the way they\u2019re supposed to act.\u201d<\/p>\n

Becker<\/a> writes for CalMatters.<\/p>\n