Several hundred mountain whitefish that were found dead along the shores of Calgary’s Bow River this week are believed to have died of natural causes.
Biologists with Alberta Environment and Parks began an investigation earlier this week after learning of the fish kill. Fish and Wildlife was also notified of this occurrence by a tip that came in to the Report-a-Poacher hotline.
On Wednesday, Global News captured pictures of several dead fish just west of the 10 Street Bridge. Alberta Environment and Parks estimates several hundred fish are dead.
A spokesperson with Alberta Environment and Parks said Thursday morning the department suspects the fish became isolated in a side channel of the Bow at some point in the fall or winter, and were unable to move back into the main channel of the river.
The fish either froze within the isolated channel or experienced what is known as winter kill, a natural event that is caused by decreased oxygen levels in the water. This can occur across Alberta at this time of year, according to Alberta Environment and Parks, generally because of ice and/or snow cover that reduces fresh oxygen in the water.
“Fish and aquatic vegetation continue to use oxygen from the water during the winter and this, combined with the reduction or elimination of fresh water input, can result in low concentrations of oxygen that can be lethal for fish species,” read a statement from the department.
“Evidence of winter kills are often observed at this time of year during ice melt, when fish can be readily observed. Winter kills are most common in shallow lakes or isolated pools, where the volume of water is lower.”
Fisheries management have conducted fish population assessments on the Bow River since the mid-2000s and Alberta Environment and Parks said recent surveys show mountain whitefish were the most abundant sport fish captured in the river.
Water samples have not been collected but Alberta Environment and Parks said the investigation is ongoing.
Comments