Experts from the Quebec Ministry of the Environment recently captured three imposing Asian carp measuring more than a meter in length in Lac des Deux Montagnes. These were the first catches of this formidable invasive species in this watercourse.
According to data provided by the ministry, the largest of these grass carp was a female of almost 1.3 meters, weighing more than 50 pounds. Two other males exceeded a meter in length, weighing more than 30 pounds.
Biologist at the Quebec Ministry of the Environment and head of the risk prevention division, Annick Drouin adds that experts noted the presence of other grass carp as part of their capture operation in Vaudreuil Bay in Lake of the Two Mountains.
“These are very important catches for our work,” she explains in an interview, specifying that the fish have been analyzed. They showed no signs of reproduction, which is good news in itself, but further analyzes are underway. They could help determine whether these adult-sized fish come from Quebec or whether they may have traveled from the Great Lakes, where the presence of grass carp is well known.
Could these captures mean that this species of Asian carp is colonizing Quebec’s waterways? “It’s too early to tell, because we need more captures and data. We already had some for the Contrecoeur sector and the Richelieu River, but we have just opened a new chapter with captures in Lac des Deux Montagnes. We must analyze this new information,” argues Ms. Drouin.
The ministry is also continuing work to monitor the presence of grass carp in the St. Lawrence, but also in certain rivers in the south of the province. The Richelieu River and the St. Lawrence River, from Lake Saint-François to Lake Saint-Pierre, are sectors “visited” by grass carp, according to detections by ministry experts since the start of monitoring in 2015.
Before the captures in Lac des Deux Montagnes, two fish observed in the Richelieu River in 2023 were the third and fourth grass carp recorded alive in Quebec since 2016. That year, a fisherman caught one weighing 27 kilos in Contrecoeur . A second grass carp was caught in July 2020 by a sport fisherman in the Chambly basin.
Invasive species
The experts’ concern is therefore very real. “Given its rapid growth, voracious appetite and diet of aquatic vegetation, grass carp can significantly damage fish habitat, disrupt the functioning of aquatic ecosystems and harm water quality,” explains the ministry.
“Even without forming a viable long-term population, grass carp can cause significant damage to aquatic grass beds on which many native fish species depend for food or reproduction,” it adds.
Asian carp were imported to the United States in the 1970s for aquaculture purposes. Thanks to floods, they were able to reach the Mississippi River, then go up the mythical river and invade the waterways linked to it over a distance of more than 1,500 kilometers. In the Illinois River, a few dozen kilometers from the Great Lakes, carp represent in some places more than 90% of the animal biomass of the watercourse. No measures taken to try to eliminate it or control its presence have worked in the United States.
The grass carp, one of the four species of Asian carp, is already well present in Canada. Furthermore, reproduction of the species has been confirmed in two rivers draining into Lake Erie. According to Fisheries and Oceans Canada, if the species establishes itself in the Great Lakes, it “could become the dominant species to the detriment of native species, almost completely eliminate aquatic plants” and even be “harmful” to the habitat of bird species.