An Update on Prussian Carp in Evanston
Over the past couple of weeks, information has been circulating online about a stormwater pond in Evanston that appears to be full of Prussian carp. For residents, that has raised real concern, and for good reasons. When Prussian carp show up in a storm pond, it can be a sign that this highly invasive species is persisting through Calgary’s stormwater system, where it can spread through drainage routes, survive in tough conditions, and create long-term challenges for local waterways and native species. This article will give you more information on the issue, and how we are moving forward as a City, and a community.
What we know about the situation in Evanston
The infected storm pond that has been reported, is at Evanston’s southern tip, near the intersection of Beddington Trail NW and Stoney Trail NW. Storm ponds are not decorative water features. They are part of Calgary’s infrastructure, designed to hold runoff, reduce flooding, and improve water quality before water moves back into the Bow River system. When invasive fish take hold in a pond like this, they can complicate that job and create a risk of further spread into nearby waterways.
Prussian carp are especially concerning because they are not native to Alberta and can reproduce asexually, meaning a single fish can quickly establish a population. Built to survive in tough conditions, they tolerate poor water quality, compete effectively for food and habitat, and breed rapidly. Females may spawn up to three times a year, according to provincial material. Once established, they are difficult to remove and can spread if conditions allow, which is why the Evanston sighting is being treated as more than a one-time cleanup issue. While Prussian Carp have been found in many of the main river watersheds of Alberta including the bow, when found in our storm water system, the main priority is to ensure the population does not spread into these riverways.
According to the government of Alberta: “Some isolated stocked ponds are reported to have Prussian carp, which indicates the illegal movement of these invasive fish.” Prussian carp are often introduced when people illegally release aquarium pets or other unwanted fish into storm ponds and waterways. What may begin as a mistaken purchase or a well-intentioned release can quickly become a serious ecological problem, because once released, these fish can survive, reproduce, and spread beyond the original site.
What the City is doing
Recent reports have triggered a city-wide approach to managing invasive fish in Calgary’s storm ponds. While some ponds in the city have been managed through measures such as winter drainage, fish removal, and ongoing monitoring, the response to Prussian carp is not site-specific to Evanston at this time. Instead, Calgary is developing a five-year fish management and control plan to guide how the City responds across multiple locations, including the Evanston site. The full details of that plan are expected to be released in Q4 2026, once the strategy report is complete.
While every pond and waterway is different, and the right response depends on the site, the level of infestation, and the risk of spread; prevention remains the best defense.
What residents should know
The key message is simple: never release fish into storm ponds, rivers, lakes, or wetlands. Releasing fish into a storm pond is illegal and can result in a $3,000 fine under Calgary’s stormwater rules. If someone has an unwanted aquarium fish, it should be returned to a pet store, rehomed responsibly, or disposed of properly.
Residents who see fish in a storm pond can report the issue through 311 so City staff can investigate and decide whether monitoring or intervention is needed. In a case like Evanston, those reports help the City act faster and track where invasive species are appearing. That kind of community awareness is one of the most effective ways to protect local waterways.
Evanston is not facing this alone. I will keep you updated as the City releases their 5 year plan for invasive species in our water ways later this year.
Related resources
Categories: Evanston, Invasive Species, Prussian Carp