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Experts ponder looming ‘carpification’ of Great Lakes

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Troy Shantz

Twenty-eight grass carp have been caught in the Great Lakes since 2013, isolated outliers of what officials fear will become a full-scale invasion.

In an open forum last week, researchers, anglers and conservation experts met with the public to discuss the threat Asian carp pose to the Great Lakes, and what they’re doing to stop it.

The term Asian carp refers to four species native to China and Russia: grass, bighead, black and silver carp. Though not yet established in Canada, all four species have escaped into the wild in the U.S. and established populations in lakes and rivers, including the Mississippi.

The fish are a perfect invader, able to adapt their diet and breeding habits to local ecosystems, said Maude Tremblay, a biologist with Fisheries and Oceans Canada and one of several experts at the Point Edward Yacht Club event.

Scientists estimate bighead and silver carp now make up 80% of the fish biomass in parts of the Mississippi. Each fish consumes 20% to 40% of its bodyweight daily in food, and their sporadic breeding overwhelms native fish stocks, Tremblay said.

Silver and bighead carp are the most aggressive threat to the Great Lakes because of their potential to degrade water quality and devastate commercial and recreational fishing, she said.

The images many have seen of large fish leaping out of the water after feeling boat motor vibrations are silver carp.

“I’ve been on the Illinois River when all the fish are jumping, and it’s incredible that they come from all directions,” said environmental journalist, Andrew Reeves, whose new book Overrun documents the ‘carpification’ of U.S. waters.

One unlucky boater he interviewed suffered a cracked jaw and broken teeth when he was struck by a leaping carp near St. Louis.

Some have suggested the best way to fight back is for humans to start eating Asian carp.

But Tim Purdy of Purdy Fisheries, whose crews caught two of the 28 grass carp, doubts that’s a viable option because the flesh is too boney.

Though some U.S. operations are turning Asian carp into fertilizer, preparing it as food is so labour intensive customers would have to pay $60 a plate for it to be profitable, Reeves noted.

Unfortunately, warm and shallow Lake Erie is an ideal habitat for grass carp, Tremblay said. It could take just 10 males and 10 females to establish a viable population in one year, which could then spread to the rest of the Great Lakes in less than a decade, she added.

None of the experts on hand could predict what will happen if Asian carp become established in Canada.

“The best bang for your buck is to prevent them,” Tremblay said.

A series of electric fences in U.S. waters has so far kept bighead and silver carp from reaching the Great Lakes in large numbers.

Any angler that catches an Asian carp is urged to contact authorities immediately by calling Ontario’s Invading Species Awareness Program at 1-800-563-7711, said David Marson, with Fisheries and Oceans Canada.

Provincial and federal officials will respond quickly, he said.

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