Biologists test Bow River fish for whirling disease

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.

Parasite has not been found outside Johnson Lake so far

Whirling disease has been observed in the United States since the 1950s, but the discovery of the disease in Johnson Lake this month is a Canadian first. (Mike Lawrence/The Gleaner/Associated Press)

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.

Difficult to 'get rid of'

"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."

The disease is caused by the microscopic parasite myxobolus cerebralis, which can be transmitted to other water bodies through gear and equipment used for swimming, paddling, boating and fishing. It poses no risk to humans, but Parks Canada has banned fishing, swimming and other activities in Johnson Lake.

So far, the parasite hasn't been found outside of Johnson Lake.

The parasite affects young fish of the "salmonids" family, which includes char, trout and whitefish in Alberta. 

Parks Canada closed Johnson Lake and some surrounding marsh and waterways after discovering whirling disease in the lake's fish. (Parks Canada)