The Bow River likely won’t be able to support its “world-renowned” recreational fishery in future as the river’s rainbow trout population is in drastic decline, according to a new study.

Thousands of anglers flock to Calgary each year — some from around the globe — bringing in an estimated $24.5 million to the local economy, said PhD student Chris Cahill, the lead author on the study.

The main factors of the decline:

The first is flooding. Major floods in 2005 and 2013 likely displaced fish downstream and modified habitats enough to impact populations.

Another factor is whirling disease — a parasite that infects trout and makes them swim in circles. It’s usually fatal.

One factor that might surprise people is the increased mortality rate from practicing catch and release.

For more info this this CBC article.