Watershed Invasive Watch - The Chinese Mystery Snail

Post date: Jan 4, 2011 11:05:45 PM

Originally posted November 9, 2009

Finding new and interesting creatures in the watershed is most often a positive and exciting experience. Sometimes however, the creatures we find turn out to be unwelcome visitors. Invasive species are any organism that is found in an area where it has not occupied historically. Most often these organisms are from far away, and arrive here as a result of human activity. The introduction of an invasive species can prove to be devastating to local food webs and ecosystems. One example of an invasive species that can be found in the Bonnechere River Watershed is the Chinese Mystery Snail (CMS).

The Chinese Mystery Snail, Cipangopaludina chinensis, is also known as the Chinese vivipara, tanisha, rice snail, Chinese apple snail, or the Asian apple snail. These gastropods are easily identified as an invader to our watershed by their size. An adult can reach the length of 65mm (about the size of a walnut or larger), with a shell with 6 or 7 whorls, much larger than any snails native to our area. Their solid colour ranges from light to dark olive green. Their main source of food is algae, but they have also been known to eat plankton and zooplankton in the Great Lakes.

As their name suggests, these giant snails are native to Southeast Asia. Presence of this species has been documented as early as 1965 in the Great Lakes, and the early 1900s on the Atlantic coast. The question then arises, if these snails are naturally found over 9000km away, how is it that they are living on the shores of our lakes and water bodies in parts of North America? There are several ways this species may have been introduced into our waters. It is possible that they hitched a ride on boats, in ballast water or in bait buckets. It is also suspected that some intentional release has occurred in some regions in the past to establish a local supply of snails for the Asian food market. This species of snail is also quite popular in aquariums as they help to keep them clean. The live release of aquarium pets (via live dumping or flushing) is another likely way that this invasive makes its way into our watershed.

If you’re thinking “so what’s the big deal? How much harm could a snail really do?”, I’m going to give you a few good reasons why the Chinese Mystery Snail is an unwelcome visitor. Firstly, these large snails compete with our much smaller native aquatic snails for food and habitat. Since these snails can multiply quite aggressively, our native species can be quickly outnumbered. Secondly, the CMS has been known to be a host to various parasites. One in particular, <em>Echinostoma cinetorchis</em>, has been known to infect humans who have handled these snails. Lastly, in areas where the Chinese Mystery Snail has overpopulated, they can clog water intake pipes, inhibiting the flow of water.

There is no specified method of control for the Chinese Mystery Snail. The measures that have been used to control snail populations in the past are biological control (using species of fish or turtles that feed on snails to control their population) and chemical control (snail-i-cides). Biological control is risky because the predator species may feed on native species, or begin to overpopulate themselves. Chemical control is almost impossible to monitor in natural aquatic environments, and are often toxic enough to harm non-target native species. By far the best method of control for this invasive is prevention. Please DO NOT release aquarium pets into the natural environment. What may seem like a humane or kind act can actually cause a multitude of environmental issues. If you have decided that you no longer wish to keep aquarium pets, be sure to euthanize the animals prior to dumping or flushing them. It’s the ecologically responsible thing to do.

For more information on the Chinese Mystery Snail, see the following websites:



For information on other invasive species, check out the Ontario Federation of Anglers and Hunters (O.F.A.H) Invading Species Awareness Program website: http://www.invadingspecies.com/indexen.cfm