Year after year, for almost 10 years, Quebec government experts have detected the presence of Asian carp in the province. But until now, monitoring of this formidable invasive species has still not made it possible to confirm whether it reproduces in Quebec waters, even if the recurrence of detections in the Richelieu River raises concerns for this fragile ecosystem.
The Ministry of the Environment, the Fight against Climate Change, Wildlife and Parks (MELCCFP) confirms that monitoring of Asian carp will continue this year, after a year in 2023 which once again confirmed that Grass carp, one of the four species of Asian carp, is indeed present in Quebec.
According to records provided to Duty by the ministry, 313 environmental DNA (eDNA) samples were analyzed last year. In total, “three samples collected in the Richelieu River, one near the Chambly basin and two in the downstream portion of the Saint-Ours dam, were positive. No capture of carp was made during the ministry’s inventory or via commercial fishermen,” specifies the MELCCFP.
Live carp
However, at least two grass carp were observed in the window of the Vianney-Legendre fishway, located on the edge of the Richelieu River. The ministry therefore attempted to capture individuals of this invasive species from the United States. “No grass carp was captured during the search operation and all the eggs and larvae collected belonged to species other than grass carp,” the ministry said by email.
“There is currently no evidence of reproduction of grass carp in Quebec,” we add. Nevertheless, “the recurrent positive signals of grass carp eDNA as well as the observations and captures allow us to conclude that this species is indeed present in Quebec”. The ministry declined our interview request.
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.
The 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. This species can exceed one meter in length and weigh more than 50 kilos as an adult.
“Very worrying”
For the director of the Richelieu River Basin Consultation and Development Committee, Sylvain Lapointe, the presence of this fish raises serious concerns. “It’s very worrying, because if their population grows, it would be the hooligans of the Richelieu River. They tear up everything like a bunch of hungry people,” he explains in an interview.
He points out that grass carp, as adults, feed mainly on aquatic plants. However, these plants, in the Richelieu River, constitute a crucial element of the habitat of the copper redhorse, an endangered species which only exists in Quebec.
What’s more, Mr. Lapointe believes that this river constitutes a very suitable habitat for the reproduction of grass carp. In this context, he welcomes the monitoring efforts of the MELCCFP. “We absolutely must slow down the spread of this invasive species if it were to reproduce in the river, especially since we observe it year after year. »
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.
Grass carp, one of four species of Asian carp, is already present in the Great Lakes, which are connected to the St. Lawrence River. Furthermore, reproduction of the species has been confirmed in two rivers draining into Lake Erie.
According to Fisheries and Oceans Canada, if the species settles 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. It also risks costing the Canadian economy billions of dollars over the coming decades.