POST FALLS — Two years after forcing the closure of Falls Park Pond, invasive Chinese mystery snails remain a persistent problem.

"The snails are still there," said Post Falls parks director Dave Fair, describing an infestation that shuttered the popular fishing spot throughout the summer of 2023.

Despite years of manual removal efforts by Post Falls Parks and Recreation staff and Avista Utilities, the invasive shelled gastropods continue to repopulate the pond's banks and bed. 

City staff have removed thousands of the mollusks since first discovering them, but their rapid reproduction has complicated control efforts.

Officials believe aquarium owners likely introduced the species by dumping them into the pond, which violates Idaho Fish and Game regulations prohibiting the release of aquatic animals into local waters. 

The snails, prized in the aquarium trade for their algae-eating abilities, pose multiple threats to the ecosystem. As well as causing issues for local wildlife by competing with native snail species for resources, invasive species such as the mystery snails also cause issues for park facilities as they infiltrate their habitat.

They also potentially spread diseases and parasites to fish and wildlife and can also clog water intakes, according to IDFG.

The battle against invasive species at Falls Park Pond began in September 2021, when parks staff started addressing both the snails and Eurasian watermilfoil, an invasive aquatic plant. While the watermilfoil has been successfully controlled, the snails persist despite continuous culling efforts. 

In addition to curtailing the snails for the betterment of Falls Park Pond, disposing of the snails prevents the population to flow further upstream to cause further issues to the surrounding area.

The pond, which typically receives regular stockings of rainbow trout from April to September, remained operational throughout 2024. Idaho Fish and Game records show continued replenishment with hayspur triploid rainbow trout during that period.

    Post Falls Park Pond closed spring 2023 because of an infestation of a non-native species, the Chinese Mystery Snail, along the bank and bed of the pond. Post Falls Parks and Recreation Department and Avista have been working to remove the snails by hand.