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Deadly fish disease continues to spread in Alberta

Whirling disease was first found here in 2016 and has now spread to a fourth watershed

The Canadian Food Inspection Agency has declared the North Saskatchewan River watershed infected with whirling disease.

The declaration covers all streams, creeks, lakes, and rivers feeding into the North Saskatchewan River and ends at the Saskatchewan border. Earlier declarations of infection have been made for the Bow, Oldman and Red Deer River watersheds.

Whirling disease, which has no impact on human health, is caused by a microscopic parasite of salmonid fish, including trout, salmon and whitefish. Rainbow, westslope cutthroat, and brook trout, as well as mountain whitefish, are particularly susceptible to whirling disease, though its impact differs among salmonid fish species and in different waterbodies.

The severity of whirling disease depends largely on the age and size of the salmonid host. Young fish are most vulnerable, with mortality rates reaching up to 90 per cent. Infected fish often display a ‘whirling’ swimming behaviour as well as skeletal deformities and changes in colour such as a dark or black tail.

The province has ramped up its response to whirling disease over the past year, including opening a whirling disease laboratory in Vegreville last summer and hiring additional staff for education and mitigation efforts. Researchers at the University of Alberta are working to develop non-lethal testing methods for the whirling disease parasite.

Anglers and boaters should adhere to Clean, Drain, Dry Your Gear protocols.

Whirling disease was first observed in the U.S. in the 1950s, and in the 1990s made a resurgence in states such as Utah, Idaho, Colorado and Montana. It has since been detected in 25 states and is particularly prevalent in western and northeastern areas of the U.S. It was found in Johnson Lake in Banff National Park in 2016, and in the Bow, Oldman and Red Deer River watersheds last year.

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