Goldfish that found their way into the storm water retention pond in Anders have successfully been culled.
Late last summer, city workers started treating the popular pond to eliminate the goldfish, which are a non-native invasive species and pose a threat to natural aquatic ecosystems.
“Our storm pond system is tied to the creeks, and tied to the river, and if those fish get into the river, they have a negative impact on the natural species,” said Tim Ainscough, the city’s environmental services manager.
Goldfish — or Prussian carp, a form of wild goldfish — compete with native species for food and habitat and can introduce diseases and parasites, all of which can reduce biodiversity.
They also stir up sediments and nutrients, clouding the water and causing more algae and plant growth.
Alberta Environment alerted the city to the problem. Facing no natural predators in the province, goldfish can grow very large.
Ainscough said two rounds of treatments to kill the fish were completed last fall.
“Now, we’ll monitor it. Hopefully, if nobody re-introduces the fish species into the pond, then we shouldn’t have anymore.”
The fish were either dumped directly into the pond, or put down stormwater drains, said Ainscough.
He said when the pond was drained in the winter, a valve froze and could not be fully closed. So when spring runoff came, the pond failed to fill up.
While the water level was low, children were spotted crossing the pond where the ground was exposed. After the valve was shut, and the rain came last Thursday, the pond filled to its normal level and eliminated the path through the pond.
People should always be careful around water features and keep an eye on small children and pets, so they don’t get too close to the water, Ainscough said.
“Whether the pond is partially or completely full, small children playing around it is always a concern.”
Pumps for fountains in the pond were temporarily removed so they could be rebuilt.