Ontario's top 5 invasive species of summer 2023
Oak wilt, grass carp and asexual crayfish on the list
From a carp that can reach 45 kilograms to a female crayfish that reproduces without a male, the summer of 2023 saw new invasive species spottings in Ontario.
With the climate crisis expected to accelerate their introduction and spread, CBC London asked an expert to share his list of the province's top invaders.
#1 Oak Wilt
"That's the primary concern of mine," said Brook Schryer, assistant coordinator with the invading species awareness program for Ontario Federation of Anglers and Hunters.
The vascular disease showed up in the city of Niagara Falls in June, making it the first confirmed detection in Canada. It's since been found in the Township of Springwater in Simcoe County, and the town of Niagara-on-the-Lake.
"This is an invasive pathogen that is known to occur in the United States, particularly in places like Minnesota, but it has jumped over the border," said Schryer.
Oak wilt impacts what Schryer calls the "pipeline" of the tree, making it hard to send water and nutrients up and down. "The tree is not able to provide its canopy with water and nutrients," he said, adding that some species with oak wilt can die within two weeks.
The Canadian Food Inspection Agency has restrictions on the movement of firewood to try to prevent the spread of oak wilt to the rest of the province.
#2 Grass Carp
"The grass carp is the most imminent threat to the Great Lakes today," said Schryer, adding that it's been found in Lake Ontario, Erie and Huron.
He said three grass carp were counted this year in Ontario. The first one was on the Grand River, which feeds into Lake Erie, and was found by the Department of Fisheries and Oceans.
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Other reports of grass carp have been in Fort Erie, a town on the Niagara River. The other was on the Bay of Quinte, on Lake Ontario's north shore, he said.
This invader is known for a few things: growing so quickly in its first year of life that it outgrows the mouth size of possible predators, consuming large amounts of aquatic vegetation, and the potential for females to lay up to a million eggs in a single spawning.
Grass carp is unable to fully digest the plants, so they expel a nutrient-rich waste that can contribute to algal blooms, Schryer said.
#3 Marbled Crayfish
A crayfish that can reproduce asexually has been spotted in Burlington.
"This crayfish in particular is a prohibited species in Ontario," said Schryer. Of even more concern: female marbled crayfish can reproduce without a male mate.
"We do not want it spreading," said Schryer.
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"It's not the biggest crayfish, it's not the most aggressive, but it would still be competing for resources and space against our native crayfish species."
It's against the law in Ontario to move crayfish over land for any reason, alive or dead, he said.
#4 White River Crayfish
This crayfish can contribute to shoreline erosion when it burrows.
"When you have hundreds of those dug into an embankment every year, you're going to see shoreline erosion," said Schryer, who described this crayfish's burrows as "massive."
The white river crayfish is native to the U.S., but popped up in the Six Mile Lake area, in the Township of Georgian Bay, Muskoka, and also on Pelee Island in Lake Erie.
Schryer believes the crayfish was introduced by a human who possibly used it as bait. "I just want to reiterate to all anglers that you should never dump your bait," he said. "And, in this case, they shouldn't have been transporting crayfish in the first place."
Compared to the marbled crayfish, the white river variety has larger claws and seems to be more aggressive.
#5 Spotted Lanternfly
Unlike the other species, the spotted lanternfly is a news maker for not showing up this summer.
"I think it's one of the good stories from this year," Schryer said. "It's now spread to various locations in the U.S., and it's close to the border."
He's asking people to stay on the lookout. As a fruit-feeding species, the fly could have serious environmental and economic impacts, for industries like grapes and wines.
Spotted an invasive species? Try to capture a photo and note your location. You can report it two ways:
▪ call the toll-free hotline at 1-800-563-7711
▪ report it online or with your mobile device here.
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