St. Albert to destroy koi that pose threat to native fish species

Your pet fish might not seem like a menace, but the little creatures are causing big conservation concerns in St. Albert.

Fish will be eradicated Wednesday as pond is treated with chemical called rotenone

City of St. Albert staff will remove invasive koi fish from a local pond on Wednesday. (Anna McMillan/CBC)

Your pet fish might not seem like a menace, but the little creatures are causing big conservation concerns in St. Albert.

Koi fish have taken over Lacombe Lake in the west end, leaving city staff with the task of killing them off.

Melissa Logan, an environmental coordinator with the city, said the fish will be eradicated Wednesday morning, as crews treat the pond with a
Melissa Logan says people can give unwanted fish to pet stores. (Scott Neufeld/CBC)
chemical called rotenone. It interferes with fish respiration, she said, but doesn't harm mammals.

Killing the koi will prevent people or birds from transferring them to nearby stormwater management facilities connected to the Sturgeon River. There, they could outcompete native species.

"They stir up the sediments and make the water very murky. It makes it difficult for the other fish to see and it affects the success of their eggs," Logan said.

"And they just eat everything in sight. So they're a very vigorous competitor."

Some of those hungry competitors are huge, like a 30-inch koi caught in Lacombe Lake on Aug. 29.

Logan expects to see other monsters float to the top of the pond Wednesday morning, about 30 minutes after the chemical treatment is sprayed into the water.

This 16-pound koi was caught in Lacombe Lake on Aug. 29. (Sam Martin/CBC)

Fishy situation

The booming koi population is likely the result of people illegally dumping unwanted pet fish, which then breed multiple times a year, Logan said.

"They think the humane thing to do is to put them in a stormwater facility or a lake," she said. "But there is the option of returning it to a pet store or finding another owner that would be happy to take it."

Fish dumping is a problem across Alberta, she said, noting invasive carp have also been a problem in Red Deer, Grande Prairie and Fort Saskatchewan.

"It's a widespread issue that the province is hoping to get under control before our native waterways are affected," she said, highlighting Alberta Environment's Don't Let it Loose campaign, which discourages people from abandoning fish in local water bodies.

Portions of trails around Lacombe Lake will be closed during treatment. (Scott Neufeld/CBC)

Invasive goldfish have been an ongoing problem in St. Albert. Last year, about two tons of goldfish were removed from the Edgewater and Ted Hole stormwater facilities. Crews continue to monitor those sites, along with other local water bodies.

Lacombe Lake will be treated again on Sept. 19 to ensure the koi are gone for good.

The man-made pond won't be fish-free for long — it will be stocked with rainbow trout in the spring.