Golden mussels are an invasive aquatic species that disrupt ecosystems, filter away nutrients and damage shorelines – and they were recently spotted on a boat trying to enter Lake Tahoe. 

WHAT IS A GOLDEN MUSSEL?

The golden mussel, a shellfish growing up to two inches in size, looks a lot like a mussel you might order at a restaurant. While they are native to Southeast Asia, the yellow-tinted water-dwellers are considered ecosystem engineers based on how heavily they can alter – or destroy – a non-native habitat. The mussel found on a boat visiting Lake Tahoe threatens not only the boater but Tahoe’s entire ecosystem.

The first golden mussel spotting in North America was identified in October 2024 in California. Most likely carried across the globe on a cargo ship, golden mussels first colonized in Brazil before docking in California and spreading to the Sacramento-San Joaquin Delta. Their lack of predators allowed for a quick spread wherever they were introduced. 

This season, boating in California’s Folsom Lake State Recreation Area requires a mandatory 30-day quarantine or decontamination, while other water bodies like Shasta Lake do not require any pre-launch inspection. No matter the protocol, the spread of the golden mussel has raised alarm among scientists and advocates, and its spotting in the Tahoe basin is no small scare.

“They’re very prolific,” said Kevin Netcher, aquatic invasive species specialist for the Nevada Department of Wildlife. “They spread rapidly and they form really heavy, dense mats, so there’ll be thousands of mussels on a single rock.” 

Unlike New Zealand mudsnail, a smaller species that invaded Lake Tahoe in 2023, Netcher noted how larger golden mussels need less calcium to grow their shells and reproduce. The faster they can multiply, the faster they can alter the lake. 

“They’re filter feeders,” Netcher highlighted,” so they’re constantly filtering water, which takes nutrients that would be available to other native species out of the water. They have the potential to disrupt the food web within Lake Tahoe.” 

For those of us living above the water, the sharp edges of the golden mussel’s shell could disrupt recreation for locals and tourists alike. The sandy shores of Tahoe could all but disappear, requiring water shoes to walk the beach or splash in the waves. 

For a day on the water, “you don’t want people cutting their feet on the rocks,” Netcher warned.

HOW TO PREVENT THE INVASION

Since 2008, the Tahoe Regional Planning Agency has conducted watercraft inspections for all boats entering Lake Tahoe. It is because of this program that the golden mussel was found in late May on a boat instead of in the water. 

Historically, boats visiting Lake Tahoe could enter without a decontamination process as long as inspectors found them to be clean, drained and dry for at least seven days prior. Starting this year, however, every motorized boat coming from an outside water source will need to be decontaminated (the process takes roughly an hour and pricing varies depending on the complexity of the boat’s internal systems). Boats that prove they were last launched in Lake Tahoe can forgo the decontamination. 

Jeff Cowen, public information officer of the Tahoe Regional Planning Agency, shared how Tahoe has one of the most comprehensive watercraft inspection programs in the United States. 

“We have all of the equipment and sophisticated kinds of methods for pushing very hot water through any part of a vessel that is sealed and runs water,” Cowen voiced. “We have high-powered and high-temperature pressure washers and an amazing training program for our inspectors.” 

Of the roughly 15,000 boats launched on the lake each year and roughly 4,000 annual inspections, 59 vessels were intercepted in 2024 with existing invasives like the New Zealand mudsnail and quagga mussel. 

In the past, some marinas shut down completely after the discovery of a new invasive species – this happened in Lake Mead after the 2007 introduction of zebra mussels. Because Tahoe is so intertwined with outdoor recreation, though, enhanced enforcements need to be thoughtfully crafted. 

“Boating has a very long and storied history, and there’s a boating history and culture in the Tahoe Basin that’s always been here,” Cowen understood. “It isn’t necessarily that we want to support any type of use, but it’s rather how we can accommodate what’s already happening in the Tahoe Basin in a way that still protects what everybody’s here to enjoy.”

RESEARCHERS ARE LEARNING MORE

Unlike existing Lake Tahoe invasives, little is known about the golden mussel due to its recent introduction to North America. Sudeep Chandra, professor of limnology at the University of Nevada, Reno and co-coordinator of the Tahoe Environmental Observatory Network, said now is the time to learn more. 

“The University of Nevada, Reno has been meeting with agency partners that are both local, whether it’s TRPA, or with federal and state partners in California and Nevada to try to understand what this mussel invasion could mean for fresh waters.” 

Research in other countries includes studies on the golden mussel’s wide tolerance for environmental conditions compared to other mussels. This includes its unique ability to live in freshwater as well as brackish, or saltier, water. And because of how golden mussels filter feed, Chandra wants to prevent Lake Tahoe from losing its crystal-clear waters.

“[Golden mussels] are changing all of the energy and nutrients going to the bottom of the river. That means that we might see more mucky green bottoms, for example, of rivers and lakes.” 

While boats and vessels are the main culprits for invasive species like golden mussels, Chandra said that other factors determine the fate of Lake Tahoe, such as kayaks, paddleboards and fishing gear. 

“For me, the larger concern now isn’t just around having motorized watercraft inspections but ensuring that the public knows that they need to decontaminate their gear and their equipment when they’re moving from one lake to another as they recreate this summer season.”

If you need a Tahoe mantra as you head to the lake, Chandra suggests acting like an inspector and “don’t move a mussel.” 

Ali Dickson (she/her) is a science reporter and graduate journalism student at the University of Nevada, Reno. She has lived in the Reno area since 2020 and enjoys covering stories on climate change, natural resources, and local food systems. When she isn’t writing, you can find Ali running, knitting and playing in her garden.