At least two specimens of grass carp were spotted near the Saint-Ours dam in the Richelieu River in Montérégie last week. This is only the third occasion where this invasive fish species has been observed in the natural environment in Quebec since 2016.
It was at the observation window of the Vianney-Legendre pass – adjacent to the dam – that the two grass carp were seen on June 18, the Ministry of the Environment, the Fight against Changes reported on Tuesday. Climate Change, Wildlife and Parks (MELCCFP) by means of a press release.
As it has a fast growth, a voracious appetite and a diet based on aquatic vegetation, this fish is considered an invasive species. It can “significantly damage fish habitat, disrupt the functioning of aquatic ecosystems and affect 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.
Ministry of the Environment, the Fight Against Climate Change, Wildlife and Parks
Along with Parks Canada, the MELCCFP claims to have “realized a status report and put in place an intervention strategy” to capture the two specimens, in order to determine their provenance.
Grass carp is a brown colored fish usually measuring 50 to 90 centimeters, but can grow up to 1.3 m. It can weigh up to nearly 50 kg, according to the Government of Quebec.
Imported to the United States along with three other species of carp in 1963 for aquaculture purposes, it has naturally dispersed throughout the Mississippi and Missouri River watershed. It has since been used as a eutrophication (nutrient buildup) control agent in waterways in some US states.
“The most likely hypothesis of their presence in Quebec is that individuals arrive from other infested bodies of water that are connected to the St. Lawrence River and the Richelieu River,” notes the ministry.
In Quebec, the first individual was seen by a commercial fisherman in the Contrecœur sector in May 2016. The second was captured in July 2020 by a sport fisherman in the Chambly basin. The three events therefore all took place in Montérégie.
The MELCCFP recalls that the release of invasive carp, including grass carp, is prohibited anywhere in the province. If a person believes they have caught one, they are invited to contact the ministry by email or by calling 1 877 346-6763.