Dead Bow River fish chose the wrong winter hangout, says biologist

A local biologist says Calgarians need not fret over a large deposit of dead, rotting, stinky fish on the banks of the Bow River.

The downtown riverside has become the final resting place for about 100 mountain whitefish that have washed up over the past few days.

The decaying fish can be attributed to “winter kill,” typically observed at the end of the season as snow and ice melt, according to Jennifer Earle, a fisheries biologist with Alberta Environment and Parks based in Cochrane.

And while it’s more common to see this type of winter kill in more stagnant bodies of water like ponds and lakes, Earle says the fish likely got caught in a side channel.

The decaying fish can be attributed to ‘winter kill,’ typically observed at the end of the season as snow and ice melt. (Mike Symington/CBC)

“These fish were just unfortunate … it seemed like a good place maybe to them in the fall when they decided to hang out there and spend the winter but then as the water levels receded they just got isolated and trapped, couldn’t get out anymore, used up the oxygen that was there and unfortunately perished in that spot.”

Mountain whitefish are closely related to trout and are the most abundant species in that area of the Bow River.

Aside from the slower seasonal melt, Earle says the dead fish so far don’t seem to be too unusual. 

“It’s probably natural causes but we sure appreciate if people let us know,” said Earle. 

Earle and her colleagues rely on the public — often anglers — to report incidents like this one so they can dispatch experts to investigate.

“We really do appreciate and rely on people to report.”