Foot-Long Giant Goldfish Are Causing Chaos In A Canadian Waterway


Tom Hale


Tom Hale

Senior Journalist

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

Senior Journalist

An image from Alberta's "Don't Let it Loose" campaign in 2015. Rebecca Baldwin/Alberta Environment and Parks

Giant goldfish are causing havoc in the Canadian city of St Albert. Not quite in the Godzilla-esque giant monster wrecking skyscrapers kind of way, but these freakishly large fish have become a persistent problem that wildlife officials are struggling to control.

The rogue goldfish were originally pets that had been released by their owners into public water, either intentionally or accidentally. The fish have since grown to huge proportions, occasionally growing up to 30 centimeters (12 inches) in length. Without the threat of natural predators, they have also bred like crazy and can be found in their thousands in St Albert's Edgewater Pond, according to CBC News.


These plate-sized pets are dramatically out-competing the area’s native wildlife, earning themselves a reputation as an invasive species. Officials are now fearing they could work their way into water systems and lakes where more vulnerable fish species live.

"Because the species that's here now is extremely competitive with any native species, if it got into our Sturgeon River there's a risk that the native fish that are in there would not live," Leah Kongsrude, St Albert's director of environment, told CBC News.

"These fish would out-compete them and we would have lower biodiversity and our natural ecosystem would be permanently affected."


The winter of 2015 brought some particularly harsh weather, so the city drained the lake just enough to ensure it froze solid. Unfortunately, when spring came, the water thawed and the fish were completely fine. The following year, electric pulses were sent through the water to shock the fish. This didn’t work either.


Over the past few weeks, the city has been using chemicals designed specifically to kill the goldfish.

"I think of zombie movies when I think about [how] we froze the storm pond right to the bottom and they survived through that, when we tried to electro-fish 'em it didn't do anything,” added Kongsrude.

The problem has become so severe that the Alberta local government even started a "Don't Let it Loose" campaign in 2015 to ensure pet owners and live food market customers don't release unwanted species of plants, animals, and invertebrates into Alberta's waterways. In fact, releasing fish into public waters in Alberta can land you with a $100,000 fine and a year in prison. The authorities are even warning people not to flush their deceased pets down the toilet, as this runs the risk of introducing pathogens into the water system.


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  • giant animal,

  • ponds