Alberta city guts ponds of invasive 'monster' goldfish
Three-year battle against goldfish hits invasive species with freezing, electro-fishing and chemicals
By Zoe Todd, CBC News Posted: Sep 26, 2017 4:18 PM MT Last Updated: Sep 27, 2017 6:13 AM MT
Lurking in the depths of a quiet St. Albert stormwater pond are schools of goldfish, threatening to out-compete native species if they spread.
Someone set free a pair of pet fish about four years ago. Now, the infested water glimmers gold with thousands of Asian goldfish.
For the past three years, the City of St. Albert has tried to eradicate the invasive species at Edgewater Pond on the city's northern edge.
In 2015, staff drained water so the pond would freeze completely over winter. The fish survived.
In 2016, they electro-shocked the water and then scooped the stunned fish out of the pond. Again, the fish survived.
This year, after goldfish were spotted at Ted Hole Pond downstream, the city decided to pump chemicals designed to kill fish into both ponds.
"The battle goes on," said Leah Kongsrude, St. Albert's director of environment. "I think of zombie movies when I think about [how] we froze the storm pond right to the bottom and they survived through that, when we tried to electro-fish 'em it didn't do anything.
"They're very resilient, very tough and our native fish species wouldn't have a chance if they got out there."
Kongsrude inspected Edgewater Pond on Tuesday morning as staff circled the shoreline in hazmat suits.
The province donated the chemicals, which target animals with gills. Goldfish are the only gilled species in the pond, Kongsrude said.
Before spraying the water, staff blocked all entries and exits...MOREhttp://www.cbc.ca/news/canada/edmonton/goldfish-invasive-species-pond-environment-stalbert-infest-1.4308288