Invasive goldfish in Terwillegar Towne pond to be ‘eradicated,’ officials say

Invasive goldfish found in a stormwater pond in southwest Edmonton will need to be eradicated before they spread to the North Saskatchewan River, officials say.

The Terwillegar Towne pond was fenced off ahead of treatment, which is scheduled to take place at some point between Aug. 19 and Sept. 16.

“The facility will require two treatments as rotenone is not effective on fish eggs and treatments must be staged to capture the entire population,” EPCOR, which manages Edmonton’s drainage system, wrote in a notice.

EPCOR described rotenone as an organic chemical compound derived from plants that’s not harmful to humans, pets, other wildlife or vegetation, as it only affects animals with gills.

“Wildlife that drink the water in the facility or eat the dead fish will not be harmed as their digestive enzymes will neutralize the rotenone,” the EPCOR notice reads.

A sign at the fenced-off Terwillegar Towne pond did however recommend “all pets and people” to keep their distance during treatment.

Officials warned of a possible partial closure of the trail system around the facility during treatment and 48 hours afterwards. “Increased odours” may also be present during treatment, they say.

An EPCOR spokesperson told CityNews the work is dependent on weather conditions, and it was not scheduled to begin Monday.

“This work is weather sensitive and cannot be completed during rainfall as the additional water will dilute the compound and reduce its effectiveness,” the notice specified.

Female goldfish can release thousands of eggs at a time, three times a summer. The goldfish compete with native species for food and space, and they carry parasites and diseases that can spread to other fish, experts say.

EPCOR says it is required by Alberta Environment and Protected Areas (AEPA), through legislation, to eradicate the invasive fish from stormwater management facilities before they spread to the North Saskatchewan River.

“Or they could overwhelm native species and destroy other ecosystems,” the utility company warned.

Terwillegar Towne is just the latest Edmonton pond being treated for invasive fish species. EPCOR says it has treated four stormwater management facilities, successfully eradicating the fish each time.