New invasive species found in Lake Tahoe

In an announcement that will come as a disappointment to conservationists, a Tahoe environmental organization announced on Thursday that invasive New Zealand mudsnails, or NZMS, were recently found in the weeds along Lake Tahoe’s shoreline. 

While studying one of the lake’s other invasive species, divers found tiny New Zealand mudsnails clinging to underwater plants. Now, government and local organizations are putting into effect a “rapid response protocol” to determine the extent of the infestation and create an interagency plan for managing their spread. According to Jesse Patterson, chief strategy officer for the League to Save Lake Tahoe, finding a new invasive species in the lake is “very uncommon.” There hasn’t been a new invasive species detected in at least 15 years, he says, which suggests holes in Tahoe’s current boat inspection program. 

According to Dennis Zabaglo, aquatic invasive species program manager at the Tahoe Regional Planning Agency, it’s too soon to tell what impact the invasive mudsnails will have on Tahoe, though he says they’re likely to affect both lake health and recreation opportunities. “NZMS can outcompete native invertebrates for space and food, which can decrease native invertebrates — a prime food source for fish,” which can lead to impacts on recreational fishing, he told SFGATE.

“New Zealand mudsnails threaten Lake Tahoe’s delicate ecology, which can impact water clarity,” agreed Patterson. “They outcompete native species, affect nutrient cycling and impact algal growth, which can turn Lake Tahoe’s blue water green.”

The snails likely made their way to Tahoe’s shores on the bottom of non-motorized boats. “We don’t know specifically, but they were all but certainly introduced by people, probably as stowaways on someone’s recreational gear,” said Patterson. “It could have been a kayak, canoe, waders, fishing equipment or even a float toy.” Though Tahoe began a robust program for inspecting motorized watercraft like jet skis and pontoon boats in 2008, non-motorized vessels are not required to undergo inspection before getting on the water (though free inspections are available at three area watercraft inspection stations). 

Because the snails can live for up to 24 hours out of water, or up to 50 days with minimal moisture, keeping them out of recreational bodies of water is a tough challenge. “Enforcing rules for every angler, paddler and swimmer would be nearly impossible,” said League to Save Lake Tahoe CEO Darcie Goodman Collins in a statement following the official release, “so every person who enjoys the lake has to take personal responsibility to clean, drain and dry their gear.” 

New Zealand mudsnails are a tiny species in the U.S., growing no more than 4 to 6 millimeters long, roughly the size of a grain of rice. First discovered in North America in Idaho’s Snake River in 1987, they’ve since spread to many waterways in the US, including the Lower Truckee River near Reno, Nev., where they were first identified in 2013. 

The New Zealand mudsnails aren’t the first potentially destructive invasive animal species to be found in the lake. In 2011, researchers confirmed the presence of smallmouth bass (likely introduced in the 1970s), describing them at the time as “a much more ferocious predator than other species known to have invaded the lake.” Efforts to remove the fish have been underway with limited success, and scientists think their presence, along with other invasive species like brown bullhead catfish, is one of many contributing factors to Tahoe’s decreasing water clarity. 

Lake Tahoe organizations have been trying to prevent the introduction of NZMS through the lake’s Prevention Program. Along with quagga mussels and zebra mussels, the mudsnails are listed as one of the biggest potential environmental threats to the lake by the Tahoe Resource Conservation District, an organization that works to protect natural resources around the Tahoe basin. 

“We’re lucky we’re dealing with mudsnails and not quagga or zebra mussels,” he says, “which we know would be the worst invasive species to have in Tahoe. Once a new species gets in, it’s almost impossible to get them out.”