New invasive species poses threat to Lake Tahoe

Another invasive species is encroaching on Lake Tahoe Basin waters.

Three New Zealand mudsnails were found in the Truckee River near Reno earlier this spring, increasing the chances the invasive species could migrate to the basin.

“It’s certainly bad news,” said Tahoe Regional Planning Agency Senior Wildlife and Fisheries Biologist Patrick Stone. “Any time the proximity of an infestation moves closer, the risk of that animal making its way into the region increases.”

The tiny mudsnails compete directly with other wildlife in the ecosystem, threatening fisheries by depleting the nutrients the fish depend on to survive. They reproduce quickly — Stone said he’s seen 1,000 snails crammed into one square foot — and there’s no natural predator in the region to keep the population in check.

The snails typically prefer muddy, turbid waters and they could thrive farther upstream in the Truckee or in one of the 63 tributaries that flow into Lake Tahoe, said Tahoe Resource Conservation District Assistant District Manager Kim Boyd.

“Boater use patterns would indicate we have some pressures, but it’s all about habitat suitability. They’re not typically associated with lakes,” Boyd said.

While the snails can’t move upstream on their own, they can catch a ride with unsuspecting humans or wildlife, Stone said. Since the snails stick to shoe soles and can become wedged under boot laces or in caked mud, Stone said anglers in particular have to be careful when transporting equipment from one location to another.

For South Shore-based Blue Ribbon Fishing Charters Operator Gene St. Denis, the snails threaten a way of life.

“It’s a huge thing. I’m very concerned. They compete directly with all the other insects, the other animals in the ecosystem,” St. Denis said. “Anybody who knows anything about freshwater ecology knows this is a big deal.”

This spring, the Nevada Division of Environmental Protection officials found a single mudsnail in a water sample collected last summer from near the East McCarran Bridge. After conducting additional surveys, the Nevada Department of Wildlife discovered two additional snails about a mile upstream near Rock Park, said NDOW spokesman Chris Healy. The department will continue surveys this summer to determine the animal’s range.

“Right now we know we have a few mudsnails. What we don’t know is the extent of the population,” Healy said. “But once you know you have them, you have them.”

The TRPA included the mudsnail in its annual monitoring three years ago after watercraft inspection staff discovered the invasive species on a boat at an off-ramp station in Meyers. The discovery of the animals in the Truckee doesn’t change the preventive measures TRPA already uses to keep the snails from entering Tahoe, Stone said, it just heightens concern.

“I believe it’s very significant for the Tahoe/Truckee watershed as a whole. For Lake Tahoe preventative programs, it means very little,” Stone said. “We certainly need the public’s help in resisting the significantly increased threat.”

For more information on Tahoe’s self-inspection training for watercraft and equipment, visit tahoekeepers.org.