LAKE TAHOE, Calif./Nev. – Divers monitoring Lake Tahoe have discovered invasive New Zealand mudsnails in areas off the South Shore, the Tahoe Regional Planning Agency and Tahoe Resource Conservation District announced today. This is the first time the species has been detected in the Tahoe Basin.

The Lake Tahoe Aquatic Invasive Species Program includes comprehensive monitoring of Lake Tahoe for aquatic invaders. Contract divers with Marine Taxonomic Services, Ltd. surveying invasive weeds on the South Shore discovered tiny snails on the bottom of the lake nearly a half mile offshore from the mouth of the Upper Truckee River.

Consultation with experts and a DNA lab analysis confirmed the species is New Zealand mudsnail, an aquatic invasive species (AIS) that has been detected in nearby waterways including the Lower Truckee River downstream from Lake Tahoe near Reno, Nevada. No other AIS, such as the destructive quagga and zebra mussel, have been detected, according to the agencies.

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Following rapid response protocols under the federally approved Lake Tahoe Aquatic Invasive Species Management Plan, TRPA convened an incident team comprised of staff from TRPA and Tahoe RCD and partner experts. The team is rapidly deploying scientists, beginning with lake-wide dive surveys to determine the extent of the infestation and sharing all available information with state and federal wildlife managers through the Lake Tahoe Aquatic Invasive Species Coordinating Committee.

“Lake Tahoe is one of the most protected waterbodies in the United States and our aquatic invasive species monitoring program is credited as the reason for this concerning discovery,” TRPA Executive Director Julie Regan said. “It is critical that everyone remain vigilant and adhere to the mantra of Clean, Drain, and Dry. Every boater, paddler, and angler shares the responsibility to protect Lake Tahoe’s native species and the waters we enjoy.”

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As climate change continues to affect Lake Tahoe’s native ecosystem, the threat of new invasive species taking hold in the region is increasing. Under the Lake Tahoe Environmental Improvement Program, the AIS Program is helping protect water quality and native species and is a key program to improve the climate resilience of the region, according to TRPA.

Invasive species can be carried on boats, fishing gear, paddle craft, life vests, and beach toys, according to the national Stop Aquatic Hitchhikers! campaign. The most effective way to prevent their spread is to Clean, Drain, and Dry boats and gear before entering a new waterbody.

“The recent discovery of New Zealand mudsnails in our Lake is disheartening, but not unexpected. Tahoe’s program to manage aquatic invasive species leads the nation, but it does have gaps and room for improvement – in the need for more frequent lakewide surveys and stronger inspection requirements for recreational equipment. This discovery shines a light on them,” said League to Save Lake Tahoe CEO Dr. Darcie Goodman Collins in a statement regarding the discovery.

“Lakewide surveys for aquatic invasive species should be more thorough and frequent, but they are resource- and time-intensive. The League has worked to fill these gaps through our Eyes on the Lake program, where we train the public, marina staff and others to identify and report aquatic invasive species as a crowdsourced solution for monitoring,” Collins continued.

The League said there is no standard for checking non-motorized watercrafts such as kayaks and paddleboards or scuba and fishing equipment.

“Enforcing rules for every angler, paddler and swimmer would be nearly impossible, so every person who enjoys the Lake has to take personal responsibility to Clean, Drain and Dry their gear. The League has made that easier by funding and recently rolling out a mobile, free-to-use cleaning station for non-motorized watercraft – the CD3 – which can help prevent new invasives from getting in the water. Donations from our supporters make this work possible,” Collins said.

TRPA offers free sanitizing for those items at their boat inspection stations.

“Watercraft inspection managers have taken steps to intercept and educate non-motorized users. The Tahoe Keepers program is an online certification class that invites paddlers to become invasive species ambassadors and keep their craft Clean, Drain, and Dry. Nearly 7,000 paddlers have become Tahoe Keepers to date. The program also includes screenings at popular launch locations where at-risk vessels are directed by staff to an inspection station if warranted,” TRPA Aquatic Invasives Species Program Manager and incident team co-lead Dennis Zabaglo said.

Since 2008, the Lake Tahoe AIS Program has served as the national model and maintained one of the lowest risk profiles in the nation for introduction of new invasive species.

“Lake Tahoe’s robust watercraft inspection program, and commitment from the public, shows that preventing the spread of aquatic invasive species is possible,” said Lisa Heki, Lahontan National Fish Hatchery Complex Project Leader, U.S. Fish and Wildlife Service. “Now more than ever, we have to support and strengthen our work with anglers, boaters, paddlers, and everyone who interacts with the waters of Lake Tahoe and its 63 tributaries.”

Periodic monitoring for invasive species in the basin is an integral part of the Lake Tahoe AIS Management Plan. Early detection and rapid response also helps agencies control the spread of aquatic invasive weeds that were introduced before the inspection program, such as the ongoing weed removal project in Emerald Bay.

“We clearly all need to double our efforts to prevent other invasive species, like quagga and zebra mussels, from getting into Lake Tahoe and turning its blue water green. The League will keep working to make sure the agencies charged with prevention, control, surveillance, and monitoring aquatic invasive species fulfill their responsibility – but they can’t do it alone, nor should they,” Collins said.

The weeds in Emerald Bay were first discovered during a MTS site assessment in 2021, during which they removed less than 100 rooted plants. A California State Parks Dive Team assessment saw a small patch of the plants again in June 2021.

“In October 2022, MTS surveyed again and the infestation was half an acre of patchy dense Eurasian watermilfoil,” said Victoria Ortiz, Community Engagement Manager, TRPA. “The plants can grow very quickly with the right conditions.”

Work to remove those weeds should be complete this week.

“As Lake Tahoe’s popularity grows, and the effects of climate change make the ecosystem more vulnerable, everyone who enjoys Tahoe must do their part to protect it. That starts with cleaning, draining and drying every piece of equipment that touches the Lake, from your sandals and life vests, to your kayak and ski boat, including your waders and all fishing gear,” Collins said.

“Lake Tahoe has a well-established network of regional and national partnerships that are all working together to reduce the threat of AIS,” Zabaglo said. “The incident team and our partners are dedicated to protecting Lake Tahoe and will be working together to evaluate options for responding to this new finding.”

TRPA advocated for federal funds to be set aside for early detection and rapid response actions throughout the nation. Tahoe agencies are using critical federal funds to address the New Zealand mudsnail introduction.

“We can keep this from happening again. It’s up to all of us to Keep Tahoe Blue. Please do your part,” Collins added.