For hundreds of years koi fish, a variety of carp, have been a domestic fish. Bred for their colour koi fish are a popular choice for introducing to an ornamental backyard pond because koi seemingly glow beneath the water and are often considered a relatively pretty fish.
The situation becomes ugly, however, when koi are either released or make their way to the wild due possibly to floods.
Koi, are an intrusive fish, which can drastically alter ecosystems. Koi being a type of carp are a cold water fish that stir the floor of the lakes they find themselves in which muddies the water and can destroy aquatic vegetation, which degrades the water they are in forcing other species to struggle in what had been their natural environment.
Locally, just south of Estevan, at Boundary Dam, Landon Polk and Chelsea Greening, happened upon what they thought were carp as the two species do look similar except for the koi’s unique colourings. The couple were out bow fishing and upon seeing the large fish took aim.
“While at Boundary Dam near the hot water return we spotted a few large fish that we thought were carp,” Chelsea explained to The Observer. “We got the bow, which is equipped for shooting fish, and were able to shoot one, to our surprise it was not a carp. We had a conservation officer send the picture of the fish away to Saskatchewan Fisheries and it was confirmed as a koi fish.”
After looking into this Chelsea and Landon discovered that koi pose a threat to the ecosystem.
“They stir up the bottom making the water murky which also increases nutrient levels and algae concentrations, which also contributes to erosion. They also feed on and remove aquatic plants, they prey on invertebrates, native fish and their eggs, causing a competition for the native species.”
It is essential for Conservation Officers to remove these fish from the lake before great destruction is done to Saskatchewan native species. Thus, if anyone catches one they are not to return it to the water.
“Landon… has now shot two of the Koi out [of] the lake which both weighed around 25-30lbs,” Chelsea explained.
“As far as we know we are the first ones to have [gotten] one of these fish from out of the water, although we know many have spotted them, since they hang out near the hot water return, come close to shore, and kind of look as if they are glowing in the water.”
Invasive species found at Boundary Dam
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