Invasive New Zealand mudsnails found in Lake Tahoe

SOUTH LAKE TAHOE — A minuscule but “highly problematic” invasive aquatic species is threatening Lake Tahoe, according to the California Department of Fish and Wildlife.

Divers tasked with monitoring the body of water for invasive species recently discovered New Zealand mudsnails in it for the first time, the CDFW said in a statement Thursday. While the creatures typically reach no more than half a dozen millimeters in length, dense populations can displace and out-compete native species.

The snails have been linked to reduced populations of aquatic insects, including mayflies and stoneflies, which salmon and trout depend upon, according to the CDFW.

“This is a significant detection and one we’re treating with the utmost seriousness and urgency to determine the extent of the infestation and prevent any further spread within the Lake Tahoe watershed,” said Colin Purdy, environmental program manager for CDFW’s North Central Region, which encompasses the California portion of Lake Tahoe and the surrounding areas of Placer and El Dorado counties.

“We greatly appreciate the communication, collaboration and rapid response coordinated so far by the Tahoe Regional Planning Agency and the Tahoe Resource Conservation District,” he said. “It will take a coordinated commitment by all the entities that serve the Tahoe Basin as well as the public to prevent the further spread of these invasives in a lake and a watershed that’s cherished around the world.”

Once New Zealand mudsnails are established in a new habitat, they are impossible to eradicate without damaging other parts of the ecosystem, according to the CDFW.

So what can be done? Anglers, boaters, visitors and residents should “clean, drain and dry” all recreational and fishing gear, the CDFW said. Best practices include freezing waders for at least six hours; leaving all water, debris and organic plant matter at the body of water; removing any snails with a stiff brush; and never transporting any live fish or other aquatic plants or animals from one body of water to another.

The CDFW said its scientists are developing and implementing plans for sampling bodies of water around the Tahoe Basin to better define the geographic range of the snails. While no snails have been found in surrounding bodies of water, they have been found in lakes and rivers throughout California and in neighboring states.

The snails were first discovered in North America in Idaho’s Snake River in 1987 and in California’s Owens River in 2000, according to the CDFW. It is believed they were introduced via shipments of live fish and spread through recreational activities.