'Monster' goldfish threaten native species in Alberta ponds

CTV News Channel: 'Monster' fish problem St. Albert Director of Environment Leah Kongsrude says the Asian goldfish is not native to Canadian waters and grows at a very quick rate.

They’re bright orange with bulging eyes and might have a tricky time squeezing into a standard fishbowl.

That’s because these “Franken-fish” are not your average goldfish.

Thousands of giant, invasive Asian Goldfish have overrun at least two storm water ponds in St. Albert, Alta. since someone released their pet goldfish into the pond more than three years ago.

The fish started out the same size as typical pet goldfish and then grew exponentially when they were set free in a larger body of water, Leah Konsgrude, the city’s director of environment, told CTV Edmonton.

“As soon as you let it out into the natural environment they grow,” Konsgrude explained on Tuesday. “They become very competitive. I call it going from cute fish to monster fish.”

So competitive that crews have pulled out huge goldfish measuring 15 to 30 centimetres in length from the city’s Edgewater Pond and Ted Hole Pond.

“You compare that to a fish at a pet store, it’s one inch (2.5 centimetres), that’s pretty extraordinary in terms of growth,” Konsgrude said. “I call them ‘Franken-fish.’”

The invasive goldfish can “out-compete” the area’s native fish by preying on weaker species or eating all of the food, which poses a threat to the original fish’s survival, Konsgrude warned.

“They can live in more low-oxygen conditions, they can live in dirty water and they also reproduce extremely quickly,” she said. “They are much hardier, much stronger than our native fish.”

That’s why the city has been engaged in a three-year effort to eradicate the Asian Goldfish from the ponds.

In 2015, workers drained water from Edgewater Pond so it would freeze over in the winter, but alas, the resilient fish returned in the spring. The following year, city staff tried stunning the goldfish with an electric current and scooping them out, but again, the fish prevailed.

In order to prevent the Asian Goldfish from spreading to other bodies of water, such as the nearby Sturgeon River, the City of St. Albert treated the two affected ponds with an organic chemical called Rotenone on Tuesday. The chemical only impacts fish, according to Konsgrude. City officials are hoping the sprayed chemical will finally kill the thousands of hefty goldfish that have occupied the ponds.

City workers plan to revisit the ponds for a second chemical treatment to ensure this latest measure to cull the fish is successful. As of Wednesday morning, approximately 4,000 goldfish had been pulled out from Edgewater Pond, with the largest one measuring more than 22 centimetres in length.

The city is reminding the public to avoid releasing any fish into ponds or other bodies of water, including flushing them down a toilet.

Instead, Konsgrude suggested an alternative way to dispose of dead fish – by burying them in a biodegradable fish pod or “fish coffin.”

With a report from CTV Edmonton’s Nicole Weisberg