Biologists are testing fish in the Bow River and other bodies of water near Banff National Park's Johnson Lake to see if Canada's first case of whirling disease has spread.
Whirling disease — discovered earlier this month in Johnson Lake — affects trout and salmon, and can cause infected fish to swim in a whirling pattern and die prematurely.
As a precaution, senior fisheries biologist Paul Christensen from Alberta Environment and Parks says biologists from his department and Parks Canada have collected hundreds of fish from water bodies near the lake, which is just east of the Banff townsite.
"These are flowing systems so we are looking in various reaches of the Bow River and some of the tributaries that feed into the Bow River," he said.
"It can actually have a pretty profound impact on the fish population itself.… Various life stages of this parasite are pretty persistent in the environment. There's a mix of spore stage that can last 30 years in the environment. Once it's in a system it's difficult, if not impossible, to get rid of it."