In October 1999, the presence in Québec of the tench was confirmed by the identification of a first specimen brought to us by a commercial fisherman of the Upper Richelieu. Finding its origin in Europe and Asia, this cyprinid (family of the carps and minnows) comes from a stock imported directly from Germany. Specimens raised in a private pond escaped toward the Richelieu River at the start of 1990’s. In November of 1999, an inquiry conducted with three commercial fishermen of this sector revealed that the first tench captures go back to 1994. The number of captures increased year after year to reach a maximum last fall. Around sixty adult specimens measuring up to 45 cm (18 inches) and 1,3 kg (almost 3 pounds) have since been examined.

Because of its fertility, its capacity to adapt to all kinds of environmental conditions, even severe ones, its leaning to scounge the bottom and its feeding habits for aquatic invertebrates, the tench could become a nuisance to our indigenous species. Its ability to support our aquatic winter conditions could also lead to another threat, that is, its migration into the St. Lawrence River and the Lake Champlain basins. Furthermore, the Richelieu River being an important fishing site for baitfish could lead to involuntary transfers within lakes and rivers of other watersheds.