Chinese Mystery Snails

By Susan Gallo

Chinese Mystery Snails (Cipangopaludina chinensis) were brought to North America in the late 1800s for Asian food markets and for the aquarium trade. In the time since, they have spread across much of the U.S. and Canada, with strongholds in the Great Lakes and the northeast. They were first discovered in Maine’s lakes in the mid ‘60s, probably spread by recreational boaters and/or released from aquariums . They are relatively easy to identify as adults, since at 2-3 inches they are about twice as big as any of our native snails. They are typically olive green to dark brown, with thick shells. Like other invasive species, they can outcompete natives and multiply and spread rapidly.

My first experience with Chinese Mystery Snails was when my kids were little and we were visiting family friends on Raymond Pond. There was an effort underway to collect the snails to try to reduce their impact on the ecosystem. It was a perfect task for a bunch of kids who wanted to be in the water all day anyway, and the volume of snails collected was impressive.

What wasn’t impressive was what happened after collection. Chinese Mystery Snails have some uncanny habits, including the ability to seal themselves up and survive for three weeks or more out of water. They are also hearty and able to travel overland quite a distance to get back to water. We learned the hard way that dead snails also have a terrible (and I do mean TERRIBLE) smell. Not a good thing when you’re in close proximity to your neighbors.

I now know that sealing Chinese Mystery Snails in Ziploc bags and putting them in the freezer for 24-48 hours is a much better way to dispose of these invasive species. Because they are able to seal their shell and go into a cold sort of hibernation, they can survive shorter periods in the freezer. Leaving them in the bags for disposal is also a good way to reduce the smell and stay on good terms with your neighbors.

Several lake associations have organized teams of snail removers, including: the Square Pond Association Snail Snatchers and the Mousam Lake Association Dive Team. The Washington Lakes Watershed Association has even had snail derbies and found a composter to accept the snails they collect.

While teams like these are unlikely to eradicate established populations, they can be effective at reducing local densities, preventing booms in populations, and keeping impacts to other species and lake systems at bay. Collection programs also provide a valuable service in educating the public, which helps increase the likelihood that new populations in nearby lakes or expansions of populations in infested lakes will be detected earlier.

If you want to learn more, you can read about the ecology and spread of the Chinese Mystery Snail here.