Two fishermen in Quebec's Lanaudière region have caught an invasive grass carp, raising concerns about the presence of the invasive fish in the St. Lawrence River.

Pierre Thériault and Gerald Boucher, commercial fisherman from Lanoraie, northeast of Montreal, reeled in the 29-kilogram specimen on May 27.

"We really weren't sure what it was. It looked like a carp … It had the same colour, but it was huge! We could see it was different from the others," said Thériault.

asian carp st. lawrence river

This grass carp caught on May 27 is the first reported discovery in the St. Lawrence River. (Dominic Brassard/Radio-Canada)

Not long after contacting biologists from Quebec's Forests, Wildlife and Parks Ministry, it was confirmed that the fishermen's catch was a one-metre-long female grass carp, one of four Asian carp species.

"For biologists, it's been a big surprise. It's as if they didn't want to see it here," said Boucher.

The fish is native to east Asia and has been used in North America for consumption and management of aquatic vegetation.

Some varieties of Asian carp, such as the silver and bighead, reproduce quickly and can eat up to 20 per cent of their body weight in plankton each day. 

The grass carp, by comparison, eats primarily aquatic vegetation, often uprooting large areas of vegetation which can deplete other native populations. Some biologists believe they are less of a threat to the ecosystem compared to other types.

This specimen was probably between 15 and 30 years old, according to biologist Michel LegaultAccording to preliminary analysis, the fish's belly was full of sterile eggs.

"We actually thought the Asian carp was confined," said Legault. "But we know that in recent years the grass carp has been found in a small section of Lake Erie. And last summer, nine grass carp were caught in the Toronto area."

"This is not good news, in principle."

The discovery has forced Quebec's Forests, Wildlife and Parks Ministry to immediately roll out its plan to fight the invasive species, which will be headed by Legault.

The ministry will spend $1.7 million over three years to try and detect the Asian carp in the river and educate commercial fishermen.

Clarifications

  • A previous version of this story featured an Associated Press photo of a different variety of Asian carp, not a grass carp.
    Jun 06, 2016 3:14 PM ET
With files from Dominic Brassard/Radio-Canada