'Mind-blowing:' Up to 1,000 feral goldfish overrun Ottawa pond
"The fact that we’ve had approximately 6,000 fish in this pond, in this year, is mind-blowing."
Ottawa officials will have to euthanize up to 1,000 feral goldfish in a stormwater pond in the city’s Central Park neighbourhood, The CBC reports.
Staff removed 5,000 dead goldfish from the same pond in Celebration Park back in March.
The new population is a recent discovery. The exact number is unclear, but it is estimated to be between 500 and 1,000 fish.
"The fact that we’ve had approximately 6,000 fish in this pond, in this year, is mind-blowing,” Coun. Riley Brockington, who represents the area, told the CBC.
"It’s just a number that’s difficult for me to wrap my head around."
Goldfish can breed quickly, especially in an environment where there are no natural predators. The average female can have up to 6,000 young a year. Cooke says because of this, the actual goldfish population could be far greater than current estimates, potentially numbering in the millions.
A not-so-small problem
Goldfish are a popular aquarium pet native to China, Hong Kong, Japan, and the Republic of Korea.
In many parts of North America, they have no known predators and can quickly overwhelm an ecosystem.
When well-meaning people discard unwanted goldfish into Canadian waterways, they mulitply quickly and outcompete native species.
In some places, Like Lake Erie, they have been known to grow to the size of a football or larger.
They tend to do most of their growing (and cause the most damage) during the summer months. But they're hardy enough to survive the winter and outcompete native species year-round.
According to Ontario's Invading Awareness Program, the fish stir up mud and debris when they feed, resulting in cloudiness that can negatively impact aquatic plants.
"If you can’t keep your fish, rehome it," U.S. Fish & Wildlife Services said in a February 2025 Facebook post.
"Just don’t let it loose."
With files from CBC News.Header image: File photo for illustration purposes only, via Canva Pro.