Canada: Authorities in Ottawa are preparing to remove thousands of feral goldfish from a stormwater pond in Celebration Park, as the city struggles with a fast-spreading invasive species that has taken hold across the region.
City staff have already pulled 5,000 goldfish from the pond this year, yet officials estimate another 1,000 remain. The real number could be far higher, with countless juveniles still too small to detect.
Councillor Riley Brockington, who represents the area, said the scale of the infestation has shocked residents and city officials alike. He noted that having nearly 6,000 goldfish in a single pond within a year is mind-blowing and highlights how quickly the species can multiply.
Goldfish, typically kept in household aquariums, can lay more than 100,000 eggs per mature female. In the wild, with warm waters and few predators, they reproduce rapidly, grow to large sizes, and outcompete native species by disturbing sediment and harming aquatic vegetation.
Carleton University biology professor Steven Cooke suggested the actual population could reach into the millions once young fish are counted, warning that small ponds and urban waterways offer ideal breeding grounds.
The problem is not limited to Ottawa. Rising water temperatures linked to climate change have created more favourable environments for goldfish across Canada and the United States. The species has been found in rivers, lakes, and stormwater systems, eventually spreading into larger ecosystems such as the Great Lakes.
Officials on both sides of the border have repeatedly urged aquarium owners not to release unwanted fish into natural waterways. In Minnesota, authorities removed nearly 50,000 goldfish from local waters and warned that pets released at just a few inches long can grow to more than a foot.
Shelby Riskin, an ecologist at the University of Toronto, said stormwater ponds have become hotspots for goldfish populations and pose significant challenges to restoring local ecosystems. She noted that even small water bodies in Toronto’s Don Valley can become overrun.
Goldfish are highly adaptable and survive in low-oxygen, murky water, often outperforming native species. Their ability to thrive in degraded environments has left ecologists drawing comparisons to the endurance theme from Jurassic Park- life, it seems, always finds a way.
Ottawa officials plan to continue removals in the coming weeks as they work to curb the spread and protect the region’s fragile aquatic ecosystems.
