Post Falls closes pond with invasive snail

An invasive snail has infested the pond at Falls Park in Post Falls. The pond will be closed until further notice.

Snails and empty shells litter the muddy bed of the emptied manmade pond.

The city’s parks and recreation director Dave Fair has been dealing with the infestation of Chinese mystery snails for three years. The snails, native to East Asia, can grow up to two or three inches.

Fair has tried many things, including mechanical methods of physically removing the snails and cleaning the pond.

Staff has harvested thousands of snails, but the population continues to grow out of control.

“Unfortunately, no one has a perfect solution,” Fair said. “They’re very tough.”

The parks department is collaborating with Idaho State Department of Agriculture, Idaho Department of Fish and Game, experts from University of Idaho and with Avista Utilities, which owns a hydroelectric dam next to the park on the Spokane River.

The pond was drained last year in an effort to dry out the snails, but they simply hibernated in the mud.

Staff will try more control methods this year, including possible chemical treatments.

It is important to eradicate the snails, Fair said, so they don’t spread to the river system or upstream to Lake Coeur d’Alene.

The snails are believed to have been introduced from people emptying their aquariums into the pond, which is illegal. Aquarium owners use the snails to clean algae.

“We see a lot of aquatic animals dumped into the pond, like goldfish and turtles,” Fair said.

Abandoning pets and plants, including the mystery snails, into ponds harms native species, he added.

The parks department also recently eradicated invasive milfoil weed from the pond.

“The theory at one point was that was what they ate, which turned out not to be totally true,” Fair said.

The pond is a popular and accessible fishing hole. Fish and Game will not stock the pond with rainbow trout this year while the parks department works to remove the pests.

Although the pond is closed, Falls Park remains open to the public.