Calgary: A stormwater pond in Calgary appears to be filled with Prussian carp; the invasive fish can produce all-female cloned offspring and spread through drainage ditches
A stormwater pond in Calgary appears to be filled with Prussian carp; the invasive fish can produce clone-like, all-female offspring and spread through drainage routes.Residents living in the northwest Calgary community of Evanston noticed that a local stormwater pond appeared to be filled with Prussian carp, raising serious concerns about the spread of the invasive species through the city’s drainage system. According to Rural Roots Canada, the discovery shows how easily unwanted aquarium pets can become established in local waterways.While no one knows for sure how the fish first entered Alberta, experts believe the problem started with the release of the goldfish. This happens when people illegally dump unwanted pet fish into stormwater ponds, local channels or rivers.Alberta was the first place in North America where the Prussian carp was found. Since first appearing, these fish have entered Saskatchewan via connected rivers and have appeared in several river systems in Alberta.
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Affected areas include the Bow River, South Saskatchewan, North Saskatchewan, Oldman River, Red Deer River and Rosebud River, according to Rural Roots Canada.
Why Prussian carp threaten local waters
The nature of the Prussian carp makes it difficult to get rid of them once they arrive. Native to central Europe and Asia, these fish can live in dirty water, survive harsh conditions, reproduce quickly, and steal food and living space from native fish.Of greatest concern is their ability to reproduce without mating, a process by which a single fish can produce all-female, clone-like babies. This means that a lone fish can start a completely new colony without the need for a male to fertilize the eggs.These invasive fish in local waters directly threaten urban infrastructure. In Calgary, stormwater ponds are built to capture rainwater, reduce flood risk and purify the water before it flows into the Bow River. If invasive fish take over these ponds, solving the problem will cost additional public funds and make it more difficult to protect the local environment.Invasive species crowd out native fish and disrupt local food chains, making it more difficult to keep natural water systems healthy over time.
Citywide action plan underway
Local leaders know the discovery in Evanston is not an isolated case and are moving toward a larger citywide plan. Calgary Ward 2 councilor Jennifer Wyness said the city is working on a comprehensive plan to track and manage the fish.“Evanston is not alone in facing this problem,” Wyness said. “Later this year, the city will release a five-year plan for invasive species in our waterways and I will keep you updated.”Once Prussian carp fall into a pond or river, it is very difficult to remove them, which makes stopping them as early as possible a primary goal. In Calgary, it is illegal to dump any live fish into a city stormwater pond and is punishable by a fine of up to $3,000 under city stormwater rules.City officials are asking anyone who sees fish in a storm pond to call 311 immediately so city staff can take a look.
Parallel wildlife conflicts: Elk pose alarming risk to Canadian parks
While water systems face fish invasion, wildlife workers in Canada’s national parks face a very different problem on land.Elk have more dangerous encounters with humans than grizzly bears in a Parks Canada tourist area, a finding that challenges the assumptions of many visitors to the Rocky Mountain West about which large animals pose the greater threat.The problem appears to be exacerbated in places where humans and wildlife often share space.Researchers looked at records from Parks Canada from 2010 to 2023 and found that elk were involved in 62 per cent of aggressive conflicts with humans, more than grizzly bears, black bears, coyotes and black-tailed deer, Cowboy State Daily reported.The research was published in Frontiers in Conservation Science.
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David Gummer, a wildlife management specialist with Parks Canada who helped collect the study data, said the animal’s size illustrates why these conflicts can be so dangerous.“Elk are large and have tough hooves. Their stomping and kicking can cause serious damage,” Gummer told Cowboy State Daily.Common injuries include broken bones, deep cuts and concussions, he said. However, not every aggressive confrontation involves direct physical contact.As Gummer said, “This could be evidence of animals expressing frustration [with people]. The elk may stomp their feet or knock something nearby with their antlers. “Most problems start when people get too close. Built-up space within parks can lead to more conflicts because elk prefer open spaces and green grass around park towns, buildings and golf courses.At the same time, large crowds of visitors can scare away predators and make elk feel safer in crowds.“They prefer open habitats where they can observe threats,” Gummer said. “Also, crowds may prevent natural predators from entering,” he added.Seasonal changes also play an important role in animal behavior. In the spring, “cattle elk are protective of their calves,” Gummer said, while in the fall, mating season can make male elk particularly angry.Two children in Estes Park, Colorado, were injured in several incidents in the spring of 2024 because female elk believed they posed a threat to their calves.Ron Dean of Etna, Wyoming, a retired Wyoming Game and Fish Department employee who spent 33 years running an elk feeding program, told Cowboy State Daily that elk located away from large tourist centers are generally more fearful of humans.Dean puts it more simply: “Especially those bull elk, when they’re in rut, they’re mean.”
Safe distance and management methods
Park staff’s main concern is keeping people and wildlife at a safe distance from each other.Visitors to Canada are told to stay at least 98 feet (30 meters) away from elk, deer and moose (about three bus lengths) and 328 feet (100 meters) away from wolves and bears. These rules are consistent with safety guidelines used in major U.S. parks such as Yellowstone and Grand Teton.When safety signs aren’t enough, park staff may build fences in busy areas or keep elk away from people. Crews may drive a truck toward them or walk up to “make themselves look bigger” to scare away the animals, Gummer said.In some cases, wildlife staff used paintball guns loaded with chalk pellets to remove elk from crowded areas.Visitors should keep their distance, never step between mother elk and calves, and take extra care in the spring and fall. If an elk begins to stomp, pant, or bang its antlers against a nearby object, park staff recommends that you back away slowly and calmly.
