Approximately 882 goldfish were culled from an Anders storm retention pond this spring.
To call this non-native species a good breeder would be an understatement: “They are very prolific,” said Tim Ainscough, the City of Red Deer’s environmental services manager.
Last month, the city wrapped up a $250,000 project to remove goldfish that had either been released into the Anders pond by pet owners, or ended up there after being dumped down stormwater drains.
Ainscough said Alberta Environment had asked the city to get rid of these fish, which are closely related to the aggressive Prussian carp, because they can make their way into the Red Deer River and out-compete native species and threaten the aquatic ecosystem.
Ainscough knows a lot of carp already exist in the Red Deer River.
The Asiatic fish regularly turn up in a shallow channel through which treated water is released into the river from the city’s water treatment plant.
“The water is warmer there … they seem to like it,” said Ainscough.
When carp numbers in the channel build up, the city gets a biologist to electroshock the fish and remove them from this channel.
Goldfish (or Prussian carp, a form of wild goldfish) have no natural predators and can grow very large. They out-compete native species for food and habitat and can introduce diseases and parasites, reducing biodiversity.
They also stir up sediment, clouding the water and causing more algae and plant growth.
Ainscough said a type of organic product was used in the Anders storm pond that kills these fish without harming frogs or other native aquatic life.
The city will now be monitoring the Anders pond “to determine our success.”
Next year, Ainscough said city workers will sample other ponds in the city — including one at West Park that reportedly contains goldfish.
The City of Red Deer urges residents not to release non-native species into ponds, or dump fish down drains.