A large concentration of Prussian carp in a northwest Calgary stormwater pond is drawing concern. Because the invasive fish can reproduce quickly and push native wildlife aside, their presence could create wider problems for the city's waterways and the people who depend on them.
What's happening?
According to Rural Roots Canada, residents of Calgary's Evanston community say a local stormwater pond seems filled with Prussian carp. That has prompted worries that the introduced species may be established in Calgary's stormwater system and able to spread beyond the pond.
Officials still have not determined how the fish first reached Alberta.
As Rural Roots Canada reported, Prussian carp are native to central Europe and Asia. They are thought to have arrived through a "goldfish" release, in which aquarium pets or other unwanted fish are illegally released — intentionally or accidentally — into waterways, storm ponds, and similar channels.
Alberta was the first North American jurisdiction to identify the species, and it has since moved into Saskatchewan through connected waterways.
Prussian carp has now been detected in multiple Alberta watersheds, including the Bow and South Saskatchewan systems, as well as the North Saskatchewan, Oldman, Red Deer, and Rosebud watersheds, Rural Roots Canada reported.
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Why does it matter?
Prussian carp are especially concerning because they are highly adaptable. They can survive in poor water quality, reproduce quickly, compete aggressively for food and habitat, and even reproduce asexually, meaning a single fish can potentially establish an entire population, Rural Roots Canada reported.
Invasive species can displace native fish and disrupt food webs, making it harder to sustain local ecosystems and waterways.
In Calgary, stormwater ponds serve as city infrastructure. They are designed to capture runoff, reduce flood risk, and improve water quality before it flows back into the Bow River system.
If invasive fish take hold in those ponds, managing them could require additional public resources and make it harder for the city to preserve the environmental benefits those systems are intended to provide.
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What's being done?
The City of Calgary is taking a broader approach rather than treating the Evanston pond as an isolated case.
Rural Roots Canada reported that Ward 2 Councillor Jennifer Wyness said the city is working on a plan to manage and control fish, with a five-year invasive species plan for local waterways expected later this year.
Once Prussian carp become established, they are extremely difficult to remove. Preventing new introductions may be just as important as dealing with the fish already in the system.
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