4 golden mussels found on a boat bound for Tahoe. It could have been a disaster.

Four golden mussels were tucked tightly beneath the bolt of a screw, hiding behind metal plates and a small flap on the back of the boat. The stowaways latched onto the boat in the Sacramento-San Joaquin Delta, securing themselves with byssal threads as thin as hair but strong enough for a journey more than 150 miles long, all the way to the Lake Tahoe Basin.

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Each was as small as a sunflower seed, but don’t be fooled: Golden mussels are like an aquatic invasive species on steroids, officials say, with power to destroy ecosystems, decimate local fish populations, overwhelm water infrastructure, litter beaches with shells and fuel algae growth. They could turn Tahoe’s blues into greens. 

Tahoe’s boat inspectors saved the day, once again. They crawled under the boat on their hands and knees, using flashlights to see in the dark shadows and mirrors to look farther back and behind the boat’s components. Finding the four mussels, the inspectors intercepted the infested boat before it hit Tahoe’s waters — a close call, but further proof that Tahoe’s defenses against aquatic invasive species are working.

Golden mussels have never been found in Lake Tahoe, and officials hope they’ll never be here. But they are nonetheless one of the biggest existential threats facing the region. Lake Tahoe started its watercraft inspection program in 2008, and the program has largely been a huge success protecting the lake from new aquatic invasive species. Last year, after golden mussels were discovered in the Port of Stockton, Tahoe doubled down on its defenses, requiring every single motorized vessel to not only be inspected but also go through a decontamination process. The decision essentially doubled the workload for the two dozen inspectors who work at three stations in the basin, at Alpine Meadows, Meyers and Spooner Summit. 

That was the easy part. Now, as Tahoe enters its second summer with the threat of golden mussels looming, the region is facing up to a much bigger and harder-to-control battlefront: the beaches. The mollusks have no preference when it comes to watercraft. They’ll just as easily latch on to kayaks, canoes, stand-up paddleboards, inflatable rafts and tubes, fishing waders or even electric hydrofoils. It’s impossible to enforce an inspection on every single floatie that goes into the water, so the responsibility lies on the beach-going public to make sure golden mussels stay out of Lake Tahoe.

“Clean, drain, dry” is the new mantra in Lake Tahoe, the water-based version of “Leave no trace.” Those three words are both a set of instructions and Tahoe’s biggest hope for a golden mussel-free future. The catchphrase is displayed loudly on billboards and sign posts at beaches around the lake. They will be spoken repeatedly by dozens of volunteers who are being dispatched this summer to talk to boaters, paddlers, anglers and swimmers. 

“We have the ability to stop [golden mussels] from going into Lake Tahoe, because that is all human impact, right? That’s all human transport,” said McKenzie Koch, the aquatic invasive species outreach and education specialist for the Tahoe Regional Planning Agency. 

Koch was speaking at an Eyes on the Lake training, hosted by Keep Tahoe Blue, held last week at Tahoe’s historic Valhalla estate. It was part crash-course on aquatic invasive species and part motivational boot camp for volunteers who are passionate about joining the cause to protect Lake Tahoe.

“Clean, drain, dry. Tell your friends. Tell your friends from the Bay: We are trying to stop this,” Koch said.

Stowaways hiding in the nooks and crannies

When a boat arrives in the Lake Tahoe Basin, the first question asked is where it is coming from. 

“That clues us into what we might find,” said Tom Boos, the aquatic invasive species coordinator for the Tahoe Regional Planning Agency. He oversees the boat inspection stations, working closely with the Tahoe Resource Conservation District that hires the staff and operates them.

Say a boat is traveling from the Delta. That information puts inspectors on high alert to search for the tiny mollusks. Boat inspectors go through three days of intensive training. A typical inspection takes between 10 and 15 minutes. The job requires getting up close and examining every “nook and cranny of a boat,” Boos said. 

“Mussels like to hide in tight little places,” he added.

After the inspection, workers blast streams of hot water to decontaminate every surface of the boat, inside and out: “Anchor, locker, ski locker, the bilge, any pump that pumps raw water from the lake,” Boos said. 

Last year, more than 4,700 boats were decontaminated, a 60% increase from the year before, officials reported. Inspectors found 73 vessels that were harboring aquatic invasive species. 

“They do an incredibly thorough job,” said Laura Patten, natural resource director for Keep Tahoe Blue. “They’re trained really well. We’re really considered the premier inspection program.”

Aquatic invasive species are an economic danger as much as an environmental one. Damage from aquatic invasive species on Tahoe’s recreation and tourism industries, property values, water supply and infrastructure could cost as much as $22 million a year, . That’s in 2008 prices and a decade before golden mussels arrived in the United States. Since golden mussels were discovered in 2024 in the Port of Stockton, they’ve traveled along the California State Water Project, all the way to San Diego.

Tahoe is a leader in how seriously it takes aquatic invasive species, and how many resources it has to devote to the cause. It’s also increasingly alone in this fight. Even as golden mussels spread across California, the state recently dropped the requirement to inspect and decontaminate boats in Lake Oroville. 

That’s a concern, Patten said, and shifts the burden to other lakes, including those that don’t have the same level of resources or experience with invasives as Tahoe. 

“There’s not even inspection requirements at all major water bodies, and so we’re concerned that this could really perpetuate the spread of golden mussels,” Patten said. “We might have a really robust program up here in Tahoe, but a lake that might have a smaller inspection program or doesn’t have the same decontamination protocol might be at risk from some of those water bodies that have nothing at all.”

Patten wants to see lawmakers implement policies that would protect not only Lake Tahoe but all of California’s water supply from golden mussels.

For nearly 20 years, boat inspectors have successfully protected Lake Tahoe from mollusk invaders. Already this year, inspectors have caught three vessels with zebra mussels, which have been spreading in the United States for two decades. 

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Golden mussels could hitch a ride to Lake Tahoe on your floatie

Saturday was another idyllic day at Lake Tahoe’s Meeks Bay: A motorboat zipped across the horizon, leaving a white wake in its trail. Kayakers dipped their paddles in the water and headed around the bend, while stand-up paddlers kept their balance in the shallow bay. People relaxed on inflatable inner tubes. A group of wetsuit-clad scuba divers emerged from the water. Children filled up their buckets with sand and water. It was a hot afternoon, and the shoreline was crowded with beachgoers who’d come to enjoy Tahoe’s clear, cool water. 

That scene, however, is increasingly terrifying in light of golden mussels. 

Someone paddleboarding in the Delta a few days before could have easily rolled up their deflated gear while it was still wet, put it in the trunk of their car and driven up to Tahoe, not knowing that golden mussels had sneaked in for the ride. That’s all it would take to destroy Lake Tahoe. Keep Tahoe Blue doesn’t mince words about what an infestation would look like: “They’re small, fast-spreading, and nearly impossible to remove once established. They encrust any hard surface: dock pilings, water intake pipes, boat hulls, and even beach rocks. Their colonies are dense, sharp, and destructive.”

Once they’re in Lake Tahoe, it will be too late. The mussels will trigger algae growth and turn the water green. Harmful algal blooms will make it unsafe to swim. They will “encrust every surface in sharp, slimy shells, from boats to beaches,” Keep Tahoe Blue writes. Hence, the urgency to prevent them from getting to Tahoe in the first place.

This summer, Tahoe is homing in on the beaches that surround the basin, with layers of outreach to educate visitors and locals alike about this huge problem and also recruit people to become part of the solution.

There’s no way to police every single floatie or blow-up paddleboard in Tahoe. Still, officials are urgently asking beachgoers to take action: Non-motorized recreation equipment can skip the line at the boat inspection stations and get a free wash and decontamination. Four solar-powered cleaning stations are set up at some of Tahoe’s most popular beaches, with more on the way.

In 2023, Tahoe officials were devastated to find an invader had sneaked in: the New Zealand mud snail. They’re so tiny, just 4-6 millimeters long, they look like black dots. There’s no way to know for sure how they came to Lake Tahoe, but by their nature, mud snails like to hide in the dirt and debris, so it’s highly likely the snails caught a ride in someone’s fishing gear — skipping the boat inspections altogether.  

New Zealand mud snails were a wake-up call, spotlighting a huge loophole in Tahoe’s defense against aquatic species: “New Zealand mud snails were really a call to action to pivot and focus on non-motorized and not just build up the motorized program,” Patten said. 

That laid the groundwork for a boots-on-the-ground approach. Now, trained watercraft inspectors rove from beach to beach across the Lake Tahoe Basin. Their job is to talk to people about aquatic invasive species, especially golden mussels, and how to clean and take care of their equipment. When they meet someone who has just arrived from an infested body of water, they steer those people to the inspection station, to get their gear decontaminated. 

Where their counterparts at the inspection station are on hands and knees, the rovers at the beach are deep in conversation with people visiting Lake Tahoe from all over the world. Last year, three roving inspectors talked to 17,000 people and sent about 100 non-motorized vessels to the boat inspection stations. This year, a fourth person will be added to the team.

Keep Tahoe Blue has also dispatched mobile, solar-powered cleaning stations — called CD3 stations — to some of the most popular beaches and launch points for rafting and floating. Each is equipped with a blower, a brush and a vacuum so people can clean their kayaks or paddleboards and remove all plant debris. The CD3 stations are currently parked at Fallen Leaf Lake, Sand Harbor, Meeks Bay and the Tahoe Keys Marina. 

Paid staff can’t be everywhere in Lake Tahoe, all the time, however. That’s where volunteers come in. At the Eyes on the Lake training last week, Lake Tahoe sparkled beyond the soaring pines on the Valhalla grounds. Inside the historic estate, longtime locals and second-home owners alike gathered to listen to presentations from Keep Tahoe Blue, the Lahontan Regional Water Quality Control Board and the Tahoe Regional Planning Agency about the array of aquatic invasive species and toxic cyanobacteria, or blue-green algae, that threaten Lake Tahoe. 

Some invasives are already in the lake, such as Eurasian watermilfoil and curlyleaf pondweed. For those, the goal is to contain the spread and report new infestations quickly so they can be eradicated. Larvae for zebra, quagga or golden mussels can float in the standing water in your canoe: “Over 50 veligers can be held in one cup of water,” Koch said. If that water reaches Lake Tahoe, the mollusks will be impossible to eradicate. 

Aquatic invasive species can also stay alive for days without water. “New Zealand mud snails, in a perfectly dry desert condition, can survive for seven days out of water,” Koch said. 

After the presentations, the Eyes on the Lake volunteers huddled around a table to inspect specimens of the different plants and mollusks that threaten Lake Tahoe, learning how to identify the ripple on curlyleaf pondweed, which looks like a crinkle-cut french fry, and the specific crop of the fan that marks Eurasian watermilfoil. Anyone can report an aquatic weed they’ve spotted to Eyes on the Lake, and a trained professional will follow up.

The Tahoe Keepers program is yet another way that people are being recruited to a community of environmental stewards. More than 8,400 people have completed an online course that goes over aquatic invasive species and how to responsibly recreate on the water. 

Some volunteers are going a step further, signing up for shifts on weekend mornings at Tahoe’s popular beaches, to share what they’ve learned with paddlers and swimmers. Linda Kenney and Ron Kline live part time in Tahoe and part time in the Bay Area. They’ve long participated in the annual clean-up after the Fourth of July, picking up trash on Nevada Beach, and this summer, they’ll also be walking the beach and talking about aquatic invasive species. 

Kline said he’s seen the difference awareness makes: Over the years, Tahoe’s Fourth of July litter problem has incrementally improved. Now, he wants to help protect the lake from aquatic invasive species.

“It’s really trying to prevent the lake from being overrun by invasive species. We’re doing our part. Can you help us?” Kline said. 

The pitch is an easy sell, especially when they’re standing on a beach with clear water lapping nearby. For the most part, people are receptive and want to be a part of the solution, Patten said.

“People come to Tahoe because it’s beautiful and pristine, and they want to keep it that way,” Patten said.

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