City drains 2 northwest Calgary ponds due to dumped goldfish

The city drained a pond in the northwest because invasive fish were dumped into it – something a spokesman says is a widespread problem affecting most of Calgary’s ponds.

A metal fence now surrounds a canyon in Edgemont that formerly contained a wetland storm pond. Edgemont resident Dario Rossi said it showed up around Christmas with a sign saying the city is draining and freezing the pond to try to get rid of invasive goldfish and Prussian carp.

“Apparently it’s quite common for people to have a goldfish and then it’s not fun anymore and they think they’re doing the goldfish a favor by putting it in the pond. But then they breed like crazy,” Rossi said.

According to Corey Colbran, the city’s manager of sewage and stormwater collection, there are more than 200 ponds in Calgary’s stormwater collection system, and most of these ponds are home to invasive fish.

“It’s a lot of them. Probably almost all of them, but I couldn’t give an exact number,” Colbran said.

He said many people are unaware that dumping the fish could wipe out native fish populations in the Bow River – and he said it was a widespread problem across the province.

“We have some world-class anglers on the Bow, and we definitely don’t want it to compete with the native species that live in the Bow River habitat,” said Colbran.

He added that some people don’t fully understand the impact the invasive fish can have if released into the wild.

“They could thrive in the pond, and they certainly do, which is part of the problem, because ultimately what happens when they make it to the Bow River, they can start to outperform the native species.”

Draining part of the new initiative

Colbran said the Edgemont pond drain is part of a pilot project to see if the city can reduce the number of invasive fish entering the Bow River.

The city also drains a pond in the northwestern municipality of Tuscany.

While the fish are killed in the drainage process, native species not found in the ponds are not affected. The rainwater flows to the bow but not back into the rainwater system.

Colbran said Prussian carp burrow into the pond’s sediment, so by removing the water, the city is attempting to freeze the bottom of the pond, including any potential eggs that might be down there.

But he says it won’t be easy because these fish are hardy and the city won’t know if they’ve succeeded until the snow melts and the ponds fill up again in the spring.