Schools of goldfish are still swimming in Okotoks storm ponds one year after they were discovered.
Last spring, at least 200 koi and goldfish between six to 10 inches long were discovered in the Crystal Ridge and Drake Landing ponds.
“We expect someone released their goldfish into the pond intentionally, who didn’t want to care for them anymore, or didn’t want to overwinter their pond fish,” said Christa Michailuck, Okotoks parks manager.
She said the Town is assessing the situation to get a sense of how many of the fish survived the winter. Crews will also look at other ponds through town to ensure more fish haven’t been released in other areas, she said.
“The issue is our ponds do have outflows that go to the Sheep River,” said Michailuck. “These fish could become a problem in the river, where they may interfere with the natural fisheries in the Sheep River.”
Over the past year, the Town has worked with the provincial government to develop a plan to get rid of the non-native, invasive species before they have a chance to reach the Sheep River, she said.
According to Michailuck, the Town will drain the water to fairly low levels, leaving enough to allow the filtration system at the bottom of the ponds to continue to function properly. Then the fish will be taken out of the ponds. It is expected to cost about $20,000, and the Town has received a grant for $10,000 toward the goldfish eradication project.
“We need to filter while we’re draining so we’re not releasing fish in the process,” said Michailuck. “We’ll reduce the water level and then we can harvest the fish.”
The harvested fish will be donated to a Calgary-based wildlife organization as feed for animals, she said.
It’s impossible to remove 100 per cent of the fish and their eggs, she said, so the draining process will be followed up with the application of rotenone, an aquatic pesticide. The low water level means requiring less of the pesticide, she said.
Water levels will be kept low through the winter, said Michailuck, which may also help eliminate any remaining fish. Similar efforts in other communities have shown goldfish and koi are fairly hardy though, she said.
“St. Albert lowered their water levels hoping it would freeze solid and kill the fish, but their efforts have been unsuccessful,” said Michailuck.
While the solution sounds simple enough, Michailuck said a number of potential complications could arise.
“There could be unanticipated rain levels, there could be issues draining the ponds,” she said.
Work is tentatively planned to begin in the fall, when reasonably dry stretches of weather can be expected, she said.
In the meantime, the Town is putting the contract out to tender and exploring the possibility of training employees or contractors in rotenone application.
“At this time, only one person in the province is certified in the application of the pesticide,” said Michailcuk. “He works for the provincial government, so he can’t contract out.”
The project should be underway by September to ensure the goldfish are under control before another winter sets in, she said.