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Concerns raised about possibility of invasive fish disease in B.C. waters

Whirling disease has decreased fish populations by 90 per cent in certain regions
Rainbow trout infected with whirling disease which damages the backbone of the fish causing them to swim in a “whirling” pattern. (Photo: Sascha Hallett,

As spring transitions into summer and the lakes thaw across British Columbia, boaters and anglers prepare for another season on the water.

However, as watercraft travel across the province this year, there is a risk of accidentally introducing of an invasive species decimating fish populations across North America known as whirling disease.

According to Sue Davies, outreach and aquatic coordinator at the Columbia Shuswap Invasive Species Society, it’s up to people in B.C. to keep the disease from ravaging fish in local lakes and rivers.

Whirling disease is caused by an invasive microscopic parasite known as known as myxobolus cerebralis. Victims of the disease are young salmonids, a family of fish including whitefish, trout and salmon, keystone species which are vital to the ecosystems in B.C. waters according to Davies.

Once the spores enter a fish, they feast on cartilage and multiply rapidly. The weakened cartilage in the backbone causes the fish to become deformed and crooked, and as the name suggests, infected fish are often found swimming in an abnormal whirling pattern. The fish excretes parasitic spores through its gills and feces, further spreading the disease.

The disease makes it difficult for young fish to swim and avoid predators, and causes them to die prematurely.

Whirling disease has devastated fish populations in North America since the 1950s. In certain regions, including Montana and Colorado, the disease has caused a 90 per cent population decrease of salmonid species. There are currently no known occurrences of whirling disease in B.C., however the Bow River, which runs through Banff and Lake Louise just across the divide to Alberta, is infected. It was first detected in Canada at Banff National Park in 2016.

“We as fisher people, as boaters, we can prevent the spread of this disease,” said Davies. “We don’t want it to damage our lakes, our fish, our recreation opportunities.”

According to Davies, locals need to be vigilant and ensure that they don’t transmit whirling disease into local watersheds through the mud and debris on their boats and equipment. Once the disease reaches local waters, there’s no way to stop it from spreading downstream, and once infected, it’s impossible to remove. If a portion of the Columbia River were to be infected, all bodies of water downstream would also be devastated.

Anglers and recreational boaters must take steps to stop transmission by cleaning, draining, and fully drying anything that’s been in the water, including boats, boots, waders, and anything that might touch mud. Fishing bait should never be used in more than one place, and fish should never be taken across a watershed boundary for cleaning or gutting.

Davies added that infectious molecules can bypass water treatment plants and continue downstream into a body of water, so fish waste should be placed in the garbage and not down the drain.

Most of the species affected are regularly caught both for game and commercially.

“As a human being, we like to go fishing and eat fish, so we want to protect the game population,” said Davies. “We wanna make sure there’s actually fish out there to catch.”

Additionally, these species are vital to the environment. The loss of a keystone species would have major ramifications on the rest of the ecosystem according to Davies.

Members of the public are encouraged to report any suspected invasive species using the provincial Report Invasives BC smartphone application or, if invasive mussels are suspected, to call the Report All Poachers and Polluters hotline at 1-877-952-7277.

READ MORE: B.C. conservation group moves thousands of salmon that will produce millions of eggs

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