New Zealand’s Mud Snails Feared To Threaten Lake Tahoe’s Ecosystem, Experts Say

Lake Tahoe has been invaded by the invasive New Zealand mudsnail, and experts have expressed concern.

Divers recently discovered the mudsnail on Tahoe's south shore, according to the Tahoe Regional Planning Agency.

This is the first time the possibly harmful mud snail has been discovered in the lake.

The spread of the snail

New Zealand mudsnails are often smaller than a grain of rice (2 to 6 mm).

Without natural predators or controls, they can outcompete native species and disrupt ecological functioning.

It's unclear how the species ended up in the Sierra Nevada's azure-blue waters.

However, officials claimed that the mud snails "are able to colonize new waters quickly" and are "difficult to detect" due to their small size.

Scientists and divers are now being deployed to survey the scope of the infestation.

Scientists with the California Department of Fish and Wildlife are creating and implementing plans to sample bodies of water throughout the Tahoe Basin in order to better characterize the invasive species' geographic spread.

High-traffic sites, boat launches, access points, coves, inlets and outflows, and side channels will all be sampled. The snails had not been identified in any of the neighboring waterbodies as of Thursday, but they have been spotted in multiple lake and river systems throughout California and virtually the whole western United States.

"It is critical that everyone remain vigilant and adhere to the mantra of Clean, Drain and Dry," said Julie Regan, executive director of the Regional Planning Agency. "Every boater, paddler and angler shares the responsibility to protect Lake Tahoe's native species and the waters we enjoy."

Disrupt ecosystem

The New Zealand mud snail was most likely spread into new places by fishermen who did not adequately clean their waders, wading boots, nets, and other gear.

Unfortunately, once the New Zealand mud snails have established themselves in a new location, they are impossible to eradicate without causing harm to other ecosystem components.

They have been connected to decreased populations of aquatic insects on which the lake's trout and salmon rely as they feed on plant and animal waste, algae, and diatoms.

Invasive populations reproduce in an unexpected way. Asexual reproduction is possible in New Zealand mud snails, as female snails are born with growing embryos inside them.

"It will take a coordinated commitment by all the entities that serve the Tahoe Basin as well as the public to prevent further spread of these invasives in a lake and watershed that's cherished around the world," said Colin Purdy, Environmental Program Manager for CDFW's North Central region, which includes the California portion of Lake Tahoe and most of Placer and El Dorado counties.

New Zealand mud snails were first discovered in Idaho in 1987 and are now prevalent in 22 states, including California and Nevada.

The largest population of New Zealand mud snails ever recorded was in Lake Zurich, Switzerland, where the species colonized the entire lake in seven years, colonizing the entire lake to a density of 800,000 per square meter.

Surprisingly, these vast populations did not last, and a population fall occurred owing to unexplained causes.