The Canadian government has confirmed that, for the first time, a fertile grass carp has been caught in the Canadian waters of western Lake Erie.
Grass carp are considered less of a threat than bighead and silver carp (but grass carp can eat a lot of aquatic plants) and for a long time, people thought the grass carp in the lakes were sterile. But lately, fertile grass carp have been turning up.
A commercial fisherman caught the fish off Point Pelee.
Becky Cudmore is the manager of the Asian Carp Program with Fisheries and Oceans Canada.
“It’s the first diploid – fertile – grass carp in Canadian waters, so I wasn’t happy about it. I wouldn’t say I was surprised because we do know there has been some reproduction in the American waters of Lake Erie,” she says.
Earlier this summer, scientists found grass carp eggs in the Sandusky River, which flows into Lake Erie.
Cudmore says grass carp have been stocked for decades in the U.S. to control aquatic plants, so it’s possible some of the fish have escaped from ponds.
“They are supposed to be sterile if they’re stocked now, but it doesn’t mean they weren’t a few decades ago and these fish are a long lived species,” says Cudmore.
But she says they don’t know yet where this particular fish came from.
Patrick Kocovsky is running tests on the carp carcass now. He’s a grass carp expert and a research fishery biologist with the U.S. Geological Survey.
"The first one in Canadian waters is perhaps a bit surprising or maybe even shocking to some in Canada. But to those of us on the U.S. side of the border, it has become unfortunately a little more common than we might like," he says. "There have been a handful of reproductively capable fish captured in Lake Erie."
He says they'll be testing various parts of the fish to estimate its age, and small bones in the fish's head called otoliths to use a "CSI approach" to try to figure out where the fish has been in the lake.
You can listen above to hear more about grass carp from Patrick Kocovsky.