The days are numbered for goldfish that have taken over ponds in St. Albert.
Officials believe the invasive Asian goldfish were dumped into a stormwater pond by pet owners who didn’t want the fish anymore.
“These fish are not native in Alberta, so it’s likely from someone taking it from their fish tank and placing it here or deciding they didn’t want it in their backyard fish pond and placing it in here,” said Leah Kongsrude, director of environment for the City of St. Albert. “Anytime you have a species that could potentially affect your native species, by law, we’re supposed to control or eradicate them.”
The goldfish have been dubbed “frankenfish” by St. Albert Environment because of how big they’ve gotten and how hard they are to get rid of.
Residents first noticed fish in the Edgewater Pond two summers ago, when city crews tried to scoop the fish out but couldn’t catch them all. In fall 2015, the pond was partially drained with hopes the remaining water would freeze to the bottom during the winter and the fish would die.
In 2016, crews tried electrofishing, which uses an electrical current in the water.
“Most fish will be stunned and they’d be able to scoop them out very easily,” Kongsrude said.
It didn’t work.
“The electrical current didn’t do anything to them,” she said.
The fish have also been found in the nearby Ted Hole Stormwater Facilities.
Kongsrude said the invasive species pose a threat to the operation of the stormwater facilities, the natural aquatic ecosystems and other species in the Sturgeon River.
“The risk is they could outcompete and our native fish species could be gone,” Kongsrude said.
The city is taking more aggressive action to kill off the unwanted invaders. Starting on Tuesday and continuing until Oct. 20, the ponds will be chemically treated to kill the fish.
St. Albert staff, in collaboration with Alberta Environment and Parks, will treat the stormwater ponds using rotenone, a naturally occurring compound derived from the roots of a tropical plant and commonly used to eradicate invasive fish.
The city said rotenone is not harmful to humans, pets, wildlife, or vegetation, and breaks down naturally after the application.
At a media event on Tuesday, staff also found another unusual resident: a crayfish.
While the crustaceans are found in some northern Alberta rivers, they are not native to the Edmonton area. They have also been found in some rivers near Calgary.
The city reminds people who no longer want their pet fish to dispose of them properly, by either returning them to the pet store or killing and burying them.