City of Lethbridge lowers lake to prepare for goldfish mitigation

The City of Lethbridge is lowering Chinook Lake to prepare for a goldfish mitigation in September. (Photo: X@LethbridgeCity)

A portion of Ermineglen Road was closed Wednesday in order to lower the water at Chinook Lake.

There will be no through traffic between 122 and 163 Emineglen Road, which is the intersection leaving Ermineglen Road through to Kodiak Boulevard, until September 15.

The closure is because the city is preparing to mitigate the goldfish population, which is an invasive species that has been introduced into Alberta lakes, ponds and waterways.

Goldfish and Koi are both aquatic invasive species, which the city says have high potential to cause "disastrous" harm to the environment, economy and human health.

The city said invasive species have the potential to increase pressure on native species for resources, including food, reproductive habitat and oxygen; have the potential to introduce new parasites and diseases; and alter habitats so significantly that they become uninhabitable for native populations.

There are no natural predators or parasites for goldfish or koi in North America, meaning their population can quickly grow out of control without human intervention. All the ponds and lakes in Lethbridge overflow or drain into the storm water system, which releases into the Oldman River.

Goldfish and koi are invasive species that have been introduced to a number of Lethbridge ponds. (Photo: City of Lethbridge)

The city will be using a chemical called rotenone to eradicate the invasive fish population. It says on the City of Lethbridge website that rotenone is a "naturally-derived compound with a short half-life, meaning it will not remain in the water system for long and does not pose threat to anything other than fish."

The city has identified goldfish in three ponds in Lethbridge, including Firelight Pond, Chinook Lake and Elma Groves Pond.

Goldfish were already eradicated from Firelight Pond in 2022, and are scheduled to be eradicated from Chinook Lake and Elma Groves Pond in 2023.

While it's being prepared for eradication, the pond's water level will be decreased, and access to the shoreline will be fenced off, with signs installed.

The pond will be isolated from the storm system during treatment and for up to four weeks after, so in the event of rain or snow, the pond won't release water and rotenone to the Oldman River.

The city asks residents not to release aquarium species or water into any bodies of water around Lethbridge, including storm water retention ponds. Unwanted aquarium pets can be returned to pet stores, or call the Alberta government t 1-855-336-BOAT (2628) so they can help.

Releasing fish or other aquatic species is illegal in Alberta, and can result in fines or jail time.