St. Lawrence River Institute of Environmental Sciences raising awareness about latest alien invader, the ‘tench’

CORNWALL — An alien invader threatens Great Lakes system, and the St. Lawrence River Institute of Environmental Sciences is raising awareness about the anticipated arrival of the ‘tench’ in Ontario waters.

Native to Europe and Asia, the green-coloured fish is “a threat to local waterways,” says the Institute in a recent Facebook post. The tench species may not be used as bait, and if you happen to see one, the Institute advises reporting it to the tench hotline: 1-800-563-7711.

An app to report sightings is also available for download at

Tench are not yet known to be in Ontario, according to the website above. However, recent reports say the fish been found in the St. Lawrence River at Montreal, and there are fears it could now head upstream. Although well established in the United States, the tench’s Canadian presence was previously limited to the Columbia watershed in British Columbia as well as the Richelieu River in Quebec, where the species escaped from an illegal fish farm in the 1980s.



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