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Invasive parasite that could pose a big threat to wild salmon is now in B.C.

Whirling disease has arrived in B.C. The tiny parasite kills about 90 per cent of young fish that it infects, such as commercially important salmon and trout species. 

Fish showing symptoms of whirling disease were found in Emerald Lake, located in Eastern B.C.’s Yoho National Park. The parasite has the potential to spread far and wide – unless everyone helps to contain the threat. 

There’s no cure – so prevention is key to preventing the invasive parasite from killing fish, and the jobs and food security they support, throughout B.C.

The tiny invasive parasite, Myxobolus cerebralis, while lethal to fish and fishing industries, does not directly harm people or other creatures. It was first identified in Germany in 1893, and spread around the world, likely through exports of fish and fish products. Once in waterways, it reproduces by contact between finfish and a common freshwater worm. Infected fish swim in a whirling pattern, become deformed, and can have dark or black tails.

Governments take the disease so seriously that all the fish in the first Canadian waterway where the disease was found – in Banff National Park in 2016 – were killed to prevent the parasite from spreading. Killing all fish will likely be necessary in B.C.’s Emerald Lake, fisheries researcher Juan José Alava told CBC news.

Everyone can help, starting with keeping out of closed zones, reporting sightings of infected fish to the Canadian Food Inspection Agency, calling 1-877-855-3222, or emailing [email protected]Never move fish, mud, or water between bodies of water, advises the Habitat Conservation Trust Foundation, which led research and planning on the parasite in B.C.  It notes that the parasite’s spores attach to sports gear and industrial equipment, pets, dead or live fish, and fish parts. Anything that’s been in contact with infected water, from boats to trailers, or hip waders to life jackets, and even pets, needs cleaning. 

– Bathe pets before letting them into a new body of water.

– Remove mud, sand and plant materials from all gear before leaving the shore. 

– Rinse, scrub or pressure wash gear, preferably water that’s hotter than 90 degrees Celsius, away from storm drains, ditches, or waterways.

– Let gear dry off between trips, for a minimum of 24 hours before entering new waters.

On Sept. 22 Parks Canada prohibited most activities in all water bodies around Emerald Lake, about 10 km northwest of the town of Field, in Yoho National Park. Parks Canada said it is investigating a suspected detection of the disease, and moved to prevent its spread. Ignoring that closure could be very pricey: violators charged under the Canada National Parks Act could be fined up to $25,000, according to a recent Parks Canada bulletin.

The loss of recreational opportunities in the area hurts, but the invasive parasite has the potential to do much worse. This introduction poses a threat to many communities in B.C., where wild salmon and trout provide both food on the table and help fuel local economies. 



Habitat Conservation Trust:


Parks Canada bulletin, Sept 22, 2023:


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  • Meghan Rooney
    published this page in Stories 2023-10-03 10:23:03 -0700