Invasive clones are clogging up western Canada’s waterways. Although it may sound like sci-fi, the Prussian carp — a Eurasian freshwater fish that steals other species’ sperm in order to replicate itself — is invading Albertan and Saskatchewan lakes and rivers. First documented in Alberta in 2000, the Prussian carp — often misidentified as an enlarged goldfish — is believed to have been introduced into North American waters by an unwitting pet owner.
Why Prussian carp are a threat
According to a study published by researchers at the University of Alberta, Prussian carp “aggressively colonize new habitats and become the most dominant species.” This is accomplished through their ability to reproduce asexually, the females stealing sperm from similar species in order to fertilize their eggs. It is only the female’s genetic material that gets imprinted on the offspring, ostensibly making them carbon copies.
Their sperm snatching also lowers native species’ chances of reproducing while increasing the frequency of their own reproduction. Jesse Shirton, a research technician in the University of Alberta’s department of renewable resources, says the Prussian carp are notorious for outcompeting other species for resources, and digging in sediment for food, disturbing the area’s water quality. Like many invasive species, the Prussian carp is able to survive in extreme environmental conditions, such as low oxygen levels or high amounts of algae, and have few natural predators.
What to do if you catch one
By law, you are required to kill an invasive species if you catch one, Shirton says. But killing a living creature can be a stomach-churning task, one you want to perform as humanely as possible.
Scott Gardner, an editor at Outdoor Canada magazine, wrote in an email that for smaller fish (10 to 20 centimetres) “the easiest way is to break its neck by firmly holding the body and bending the head up.” For a larger fish, Gardner suggests “placing [the fish] on its side on a hard surface and hitting it sharply on the side of the head with something sturdy and blunt, like a mallet or the butt of a hatchet.” Although both sound macabre, remember, you’re helping save an ecosystem.