A stormwater pond in Calgary appears to be filled with Prussian carp; Invasive fishes can produce completely female clone-like offspring and spread through drainage channels.Residents living in the northwest Calgary community of Evanston noticed that a local stormwater pond appears to be filled with Prussian carp, raising serious concerns over the spread of the invasive species through the city’s drainage systems. According to Rural Roots Canada, the discovery shows how easily unwanted aquarium pets can take root in local waterways.Although no one knows how the fish first came to Alberta, experts believe the problem began with the introduction of goldfish. This happens when people illegally dump unwanted pet fish into storm ponds, local channels or rivers.Alberta was the first place in North America to see the Prussian carp. Since they first appeared, the fish have traveled through connected rivers to Saskatchewan and have appeared in many Alberta river systems.
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According to Rural Routes Canada, affected areas include the Bow, South Saskatchewan, North Saskatchewan, Oldman, Red Deer and Rosebud rivers.
Why do Prussian carp threaten local waters?
Prussian carp have natural properties that make them difficult to get rid of once they arrive. Native to central Europe and Asia, these fish can live in dirty waters, survive in harsh conditions, reproduce rapidly, and steal food and living space from native fish.Of most concern is their ability to reproduce without a partner through a process where a fish can produce completely female, clone-like babies. This means that a single fish can start a new group without needing a male fish to fertilize the eggs.The presence of these invasive fish in local waters directly threatens the city’s infrastructure. In Calgary, storm ponds are built to capture rainwater, reduce the risk of flooding, and clean the water before it flows into the Bow River. If invasive fish take over these ponds, it will cost additional public money to fix the problem and make it harder to protect the local environment.Invasive species deplete native fish and disrupt local food chains, making it harder to keep natural water systems healthy over time.
Citywide action plan underway
Knowing that Evanston’s discovery is not an isolated case, local leaders are switching to a larger city-wide plan. City of Calgary Ward 2 councilor Jennifer Wynes said the city is working on a comprehensive plan to track and manage the fish.“Evanston is not facing this alone,” Wyness said. “I will keep you updated as the city releases its 5-year plan for invasive species in our waterways later this year.”Once Prussian carp settle in a pond or river, they are extremely difficult to remove, making their early containment the main goal. In Calgary it is illegal to put any live fish into a city stormwater pond and carries a fine of up to $3,000 under the city’s stormwater regulations.City officials ask anyone who sees a fish in the storm pond to call the 311 line immediately so city staff can investigate.
Parallel wildlife conflicts: Elk pose surprising threat to Canada’s parks
While water systems face fish invasions, wildlife workers in Canadian national parks face a very different problem on land.In Canadian park tourist areas, elk were linked to far more dangerous encounters with people than grizzly bears, a finding that challenges the perception that many visitors to the Rocky Mountain West make about which larger animal poses the greater threat.This problem becomes worse in places where people and wild animals often share the same space.According to Cowboy State Daily, looking at Canadian parks records from 2010 to 2023, researchers found that elk were involved in 62% of reported aggressive encounters with people, more than grizzlies, black bears, coyotes and mule deer.The study was published in Frontiers in Conservation Science.
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Understanding the threat of large herbivores
Parks Canada wildlife management specialist David Gummer, who helped collect data for the study, said the animal’s size shows why these run-ins can be so dangerous.“Elk are very large and have tough hooves. They can do serious damage with those kicks and kicks,” Gummer told Cowboy State Daily.Common injuries include broken bones, deep lacerations and concussions, he said. However, not every aggressive run-in involves direct physical contact.As Gummer said, “This may be evidence of the animal expressing its frustration (with people). The elk may be stomping its feet or banging its antlers on nearby objects.”Most problems start when people get too close. Constructed spaces inside parks may lead to more such conflicts, as elk prefer the open spaces and green grass found around park towns, buildings, and golf courses.Also, large groups of tourists can scare off natural predators, making elk feel safer around human crowds.“They like open habitats where they can keep an eye out for threats,” Gummer said. Additionally, “crowds can deter natural predators from coming in.”Changing seasons also play a big role in animal behavior. In the spring, “cow elk protect their young,” Gummer said, and in the fall, mating season can quickly anger a male elk.Two fawns were injured in separate incidents in the spring of 2024 in Estes Park, Colorado, after mother elk thought they were a threat to her calves.Etna’s Ron Dean, a retired Wyoming Game and Fish Department worker who spent 33 years running an elk feeding program, told Cowboy State Daily that elk that live away from big tourist centers are generally more afraid of people.Dean put it even more simply: “Especially those bull elk, during the rut, they were mean.”
Safety distances and management methods
Park staff are mostly focused on keeping people and wildlife at a safe distance from each other.Visitors in Canada are asked to stay at least 98 feet (30 m) away from elk, deer and moose (about the length of three buses) and 328 feet (100 m) away from wolves and bears. These rules match the safety guidance used at major US parks such as Yellowstone and Grand Teton.When safety signs are not sufficient, park staff may erect fences in busy areas or herd elk away from crowds. Gummer said employees may drive trucks toward animals to scare them off or walk over to “make themselves look bigger.”In some cases, wildlife staff use paintball guns loaded with chalk rounds to push elk out of crowded areas.Visitors should maintain distance, never step between a mother elk and her calf, and take extra care during the spring and fall. If an elk begins to stomp, lunge, or hit nearby objects with its antlers, park staff gently and calmly ask to step back.