Wednesday, June 19, 2024

Mystery snails turn up in Flathead Lake

Daily Inter Lake | May 24, 2024 12:00 AM

Dumping aquarium pets into local waters can negatively affect the ecosystem — and the consequences don’t always come at a snail’s pace.

Flathead Lake is now home to mystery snails, a common house pet and invasive species, according to Montana Fish, Wildlife and Parks. It is the first detection in Montana, but they are common in other states, thanks to aquarium dumping.

“Statewide and nationally, this is something we are trying to get the public to realize: It's never OK to dump a pet. In this case, you dumped a species that is not desirable, that we may never get rid of,” said Tom Woolf, aquatic invasive species bureau chief at Montana Fish, Wildlife and Parks. 

One snail shell was found — empty — in the Finley Point area of Flathead Lake two years ago, according to Woolf. But several dozen snails were found this spring, some alive. 

The snails, which can grow to the size of a golf ball, are called mystery snails due to their unique life and reproductive cycles. Females of the species give birth to hundreds of young, fully developed snails that suddenly, and randomly, appear. 

You buy one snail and you end up with hundreds — that’s the mystery of them, Woolf joked. 

But the quick reproductive ability allows the snails to take over an ecosystem, he warned. 

“It's great when they stay in the aquarium but when it’s released into the environment it can cause significant problems,” Woolf said. 

Montana Fish, Wildlife and Parks personnel intend to go back to Flathead Lake when it is at full pool to dive and look for shells. They encourage others to report any sightings and findings to the state agency as well. The more people looking for invasive species, the better chance the state has to catch them, Woolf said.

“If we beat their population back, hopefully we can stop them from spreading,” said Woolf. “... But it would be difficult to eradicate something like this.”

In northern Idaho, mystery snails have been found in Priest Lake, a lake similar in water quality to Flathead Lake. The Priest Lake snails have kept to just one bay of the lake. That gives Woolf hope that the mystery snails might not spread to all corners of Flathead Lake.

The state wildlife agency also alerted the public to another invasive aquarium pet found near Bozeman, a Dojo loach. Slender and eel-like, Dojo loach are native to East Asia and are a popular aquarium pet in the United States.  

For more information on how releasing pets into the wild can negatively affect a habitat, visit To learn more about aquatic invasive species and how to report a sighting, visit 

Reporter Kate Heston can be reached at or 758-4459.