Non-native aquatic snails offer reminder on invasive species
By Jenn Watt
Several years ago, Minden Hills resident Paul Prentice started noticing that there were aquatic snails in the lake bigger than the ones you’d usually find and they seemed to be proliferating.
Together with Debbie Balika, a science advisor for the Coalition of Haliburton Property Owners’ Associations, and students from Fleming College, they’ve been studying the snails to find out more about their numbers.
The Chinese mystery snails prefer lakes with silty bottoms, reproduce quickly and have few predators. Plus, Prentice said during a presentation at the CHA annual general meeting on June 8, they have a trapdoor on their shells that can be closed to keep water in and predators out.
“The big thing that makes them extremely difficult to deal with is the operculum [shell closure]. What takes place is if the snail is in a situation where it’s being attacked or irritated it closes right up, crawls back into its shell, closes the operculum down and as a result of that, it can live a long time,” he said.
Prentice said the snails are more of an irritant than anything else.
The Invading Species Awareness Program, run by the Ontario Federation of Anglers and Hunters, has confirmed 68 reports of the snail in Ontario since 2014, said Alison Morris, assistant co-ordinator of the program.
Chinese mystery snails are found in southern Ontario mostly, in a few of the Great Lakes, as far north as Manitoulin Island and as far east as Ottawa.
“We usually receive a handful of calls each year as well as inquiries related to disposing of dead snail shells that have washed ashore,” Morris wrote in an email.
Morris said the snails can be a problem in several ways: “Chinese mystery snails, like other invasive snails, have the ability to reproduce quickly, they reduce plankton levels and will feed on fish eggs, they can outcompete our native snails for food and habitat, and they can be a vector for transmitting diseases, some of which may infect humans.”
Balika said the snails are one of 180 invasive species in the province and people should be diligent about not inadvertently introducing new species as they travel.
“It’s all carried through us, through humans. It’s carried on our boats, on our fishing gear, on our kayaks, on our canoes,” Balika said. The snails, which likely were initially introduced to North America as a food source long ago, also could be deposited in lakes by those who have them in aquariums and decide there’s no harm in dumping the aquarium’s contents in the lake.
“We have people that are boating more, travelling more, touring more and it’s possible that they’re bringing in things they don’t even see,” she said.
Once in a waterbody, the snails can move to connected waterways. Balika said this was how many invasive aquatic species spread.
“I look at the Trent Severn Waterway, my cottage is up on one of the reservoir lakes and really we’re all attached going downstream. There’s no physical barrier to stop those invasive species,” she said.
Balika said issues with non-native plants and animals is not isolated to one lake or region – it’s a provincial problem. She said funding had recently been cut to the OFAH for their citizen science invasive species watch and that CHA would be doing some of that work this summer. She said more invasive species need to be monitored especially as climate change alters the environment, potentially creating more comfortable conditions for non-native species.
Morris said if you see a snail that seems like it could be an invasive species, call the hotline at 1-800-563-7711 or go online to www.eddmaps.org/ontario or www.iNaturalist.org.
“If they want to remove the snails, I would advise that you wear gloves prior to picking up the Chinese mystery snail. Using a bucket or other apparatus, collect the snails and dispose of them on land but away from a common area,” she said. “Since these snails are aquatic in nature, they cannot survive on land. Options for disposal can include burying the snails or even bagging them and putting them out with the trash. If you’re looking to dispatch a snail quickly and humanely, it is recommended that they be bagged and put in a freezer before being disposed.”
You can prevent introducing the snail by always cleaning, draining and drying your boat each time you leave a waterbody. Do a visual inspection and remove suspicious material, drain standing water, and dry the boat, Morris advises.
Balika recommends that lakefront property owners contact the Federation of Cottagers Associations for a free invasive species poster to install at public boat launches if there isn’t one there already. Lake associations might also consider purchasing a boat wash station.