This text is taken from our April 26, 2022 “Le Courrier de la Planète” newsletter. To subscribe, click here.
The presence of Asian carp in Quebec waterways has been a source of serious concern for several years now, due to the devastation caused by this invasive species in several regions of the United States. But it seems that this fish from Asia is not increasing, according to information obtained by The duty with the Ministry of Forests, Wildlife and Parks (MFFP).
Since 2015, the Quebec government has been funding a program to monitor the presence of Asian carp, which actually includes four species: grass carp, silver carp, bighead carp and black carp.
So far, only grass carp — which can reach a length of 1.25 meters and weigh more than 100 pounds — has been detected by MFFP experts, primarily through “environmental DNA” (eDNA). This technique actually makes it possible to isolate DNA sequences of a species by collecting samples from the environment, for example from a stream.
It was thus possible to observe the presence of grass carp in the St. Lawrence, mainly between Montreal and Lake Saint-Pierre, but also in the Richelieu River. Two carp were also accidentally caught by fishermen, including a fertile 64-pound female in the Contrecœur sector in 2016.
This arrival in Quebec was all the more worrying since this voracious herbivore can eliminate a good part of the aquatic plants on which several other species depend, such as the copper redhorse. Carp are also likely to find suitable habitat here similar to the Asian rivers where they naturally live.
No increase
For five years, however, the MFFP has not observed an increase in the species, contrary to what some experts feared. “No invasive carp were caught during the 2021 season and no suspicious observations were made by the ministry, citizens or its various partners”, confirms the MFFP by email.
As part of the work of the team from the “Québec Invasive Species Control Program”, three samples, out of a total of 593, made it possible to detect the presence of grass carp. They were collected from sites south of the Sorel Islands (2) and in the Contrecœur sector (1).
This result is comparable [à ceux] previous years, although it is among the weakest results obtained since 2017. According to the interpretation of the Ministère des Forêts, de la Faune et des Parcs, the eDNA signals for grass carp remain weak and without a tendency to the increase”, concludes the ministry. The work will nevertheless continue during the summer of 2022.
Big lakes
It must be said that grass carp is already present in the Great Lakes, which are connected to the St. Lawrence. Last year alone, 183 grass carp were caught by wildlife management agencies in Ohio. Furthermore, breeding of the species has been confirmed in two rivers that flow into Lake Erie.
On this side of the border, experts therefore fear the American scenario. Asian carp were imported into the United States in the 1970s for aquaculture purposes. Thanks to floods, they were able to reach the Mississippi River, then invade the waterways attached 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 river. No steps taken to try to eliminate it or control its presence have worked in the United States.
According to a report by Fisheries and Oceans Canada published in 2019, if grass carp settle in the Great Lakes, connected to the St. Lawrence, they “could become the dominant species to the detriment of native species”, “virtually eliminate aquatic plants” and even be “harmful” to the habitat of bird species.