grass carp
Photo by Vladimir Wrangel/

Discovery of grass carp in St. Lawrence River alarms experts

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Just a few short months ago, experts reported that no new invasive species have been found in the Great Lakes in decades. But all that could soon change.

Last month, two fisherman reeled in a grass carp from the St. Lawrence. The 29-kilogram fish, which is native to east Asia, was pulled in around Quebec’s Lanaudière region.

According to reports, if the species manages to reproduce in the St. Lawrence or Great Lakes, it could pose a major threat to native fish and vegetation.

“A grass carp is one of the four or five species of Asian carp that we do not want to see in the Great Lakes or the St. Lawrence,” Anthony Ricciardi, an invasive species biologist at McGill University, told CBC.

That’s why the government is now fast-tracking its plan to fight the invasive species, spending $1.7 million over the next three years to both detect the carp and educate commercial fisherman.

Invasive species like these are known to reproduce quickly, degrading natural habitats, out-competing native species, and effectively altering food chains. They can also be difficult, if not impossible, to eradicate once they establish a population.

When compared to other species of Asian carp, which reproduce quickly and can eat up to 20 percent of their body weight in plankton each day, the grass carp isn’t as big of an environmental threat. But, as with any invasive species, there’s still cause for concern.

Grass carp eat aquatic vegetation, and were once brought to the United States on purpose to try to control weedy lakes. But because they often uproot large areas of vegetation, it poses a problem for smaller fish that use these plants to dodge predators.

“If such a thing were to become established in the river or anywhere in the Great Lakes, it would be a threat—if it was in a dense population—to wetlands and all the things that depend on wetlands,” Ricciardi said.

Although researchers are still trying to determine exactly where the fish came from, they do know that it was likely between 15 and 30 years old. Based on its belly full of sterile eggs, they also believe it was able to reproduce in the past.

Michael Legault, a biologist for the government of Quebec, told CBC that it’s too early at this point to say whether or not there are more grass carp in the St. Lawrence, but that the chance of it being the only one is “unlikely.”

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