Growing number of 'invasive' goldfish in Kitchener pond sparks concern from locals, advocates

CBC

30-05-2025

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A rainy and gloomy Thursday afternoon didn't stop Aiden Roth from patiently waiting for some goldfish to bite in a Kitchener pond.
"I just want to see if there's a chance I could get one," Roth told CBC News.
Earlier that morning, Jim Penny, Roth's grandfather, read in a newspaper article that "a whole lot of [gold] fish" were sighted at a pond off of Spurline Trail in Kitchener.
"[Aiden] wasn't feeling well this morning… [but] I know he's got a big interest in fishing," Penny said. "I showed him the article, and after lunch he said he was feeling a little better… so we thought we'd come over and see."
Roth could not catch a single goldfish at the pond off of Spurline Trail. But he said he's noticed goldfish growing in numbers at a pond in the Lakeside Park, which is closer to his home.
"Sometimes you'll find these holes in the ice in the shallower areas of a pond… there's like 20 goldfish in one hole two years ago," he said. "This year, just in the past winter, there [were] at least 100 per hole."
While exciting for the young fisherman, the growth of goldfish populations in these local ponds is a sign of a growing environmental concern according to Terre Chartrand, a land-based educator from the Red Osier Guild in Waterloo region. She was at the Lakeside Park pond for World Turtle Day when she noticed that goldfish populations at the pond were getting out of hand.
"Goldfish don't occur naturally in North America, but they've been released in [North American] waters since the 1600s," she said. "This is 100 per cent someone releasing a pet that they no longer wanted, or can't take care of, into the water."
Chartrand, along with other experts, say goldfish are causing some issues in ponds like this one.
The goldfish problem
Jessica Kellerman, the manager of stormwater operations and construction at the City of Waterloo, says it's not uncommon to see goldfish in stormwater management ponds.
"The size of the facility, the location of the facility, the proximity to houses or things like that would sort of dictate how many [goldfish] you might find in there," she explained.
Goldfish are mainly acquired as pets. Chartrand says when pet owners think they can no longer care for these foreign species, they tend to believe that releasing these animals in the wild is the most humane course of action.
"Some people think [releasing their pets into ponds] is the more merciful thing to do with their pets," she said. "It's certainly more merciful than… just disposing of them in a way that kills them."
But the problem with goldfish – along with other invasive species – is that they bring a host of problems to their new habitat.
Kevin McCann, a professor at the University of Guelph's department of integrative biology and the director for the Centre for Ecosystem Management, says goldfish are a "free willy" invasive species.
"Goldfish are what we call high r species, and so they can be formidable competitors with native species as such," he said.
A food web ecologist, McCann says such "runaway growth" could have impacts on a local pond's food webs and overall biodiversity.
Goldfish also "increases water turbidity," which Chartrand describes as the "murkiness" of the water.
"In their own water systems, [goldfish] would have different types of critters that would deal with that turbidity… but here we don't have those things," she said. "It creates a condition that becomes harder and harder for our own aquatic species to live in."
When water has high turbidity, sunlight has a hard time penetrating the surface, which affects the pond's biodiversity as a whole.
There's also the issue of diseases, which Chartrand says the local fish have "no ability to defend itself from." Goldfish can harbour "diseases, parasites, viruses, or bacteria," which can do harm to the native species in any one area.
What could be done
CBC News reached out to the City of Kitchener for comments on the goldfish situation at the pond off of Spurline Trail. They did not provide a response by deadline.
As for Waterloo, Kellerman says the city hasn't had to "actively manage goldfish," but that they are "likely to implement a program to remove them" if the fish population goes out of control.
Chartrand says when it comes to proper disposal of goldfish and other aquatic pets, the best thing to do is to reach out to organizations that have the capability to take in these animals.
"Donate them to a school, or contact the place where you've got the goldfish from and see if you can relinquish it back," she said. "The last thing one should do other than just outright killing that pet is putting it in the waterways."
Although he's only been fishing for a year, Roth shares the same opinion.
"You could sell it somewhere… If you have a pond somewhere or know somebody with a pond, give it to them," he said.