By Steve Hubrecht

All shorelines and waterbodies in Kootenay National Park are closed until March in an effort to stop the spread of a parasite that is deadly to fish.

The parasite — myxobolus cerebralis — causes whirling disease in salmon, trout and mountain whitefish. 

Similar waterbody and shoreline closures are also in effect in Yoho National Park. The closures were announced last week, about a month after Parks Canada found the first suspected case of whirling disease in Emerald Lake in Yoho.

Parks Canada conducted tests after that first case and found more suspected cases of the disease in the Kicking Horse River, Wapta Lake, Finn Creek, Monarch Creek, and at the confluence of the Kootenay and Emerald Rivers, all in Yoho. These are the first reported suspected cases of whirling disease anywhere in B.C.

Parks Canada Lake Louise, Yoho and Kootenay field unit superintendent Francois Masse told media the closures are necessary because the mortality rate among fish that get the parasite is very high (up to 90 per cent), and because Yoho and Kootenay contain at-risk fish species that are vulnerable to whirling disease, such as the iconic Kokanee salmon and westslope cutthroat trout.

Parks Canada officials outlined that the parasite causing whirling disease is very difficult, if not impossible, to eradicate once it is present in an ecosystem.

Whirling disease typically affects younger fish, making them “whirl” in corkscrewing circles when they try to swim (which is what gives the ailment its name). This makes it difficult for the fish to get food and to avoid getting eaten themselves.

Visitors not only need to stay out of waterbodies, they need to stay well back from them – no closer than three metres. This means no hiking or walking along shorelines, and obviously no fishing, swimming, wading and or use of boats, paddleboards or other watercraft.

The only exceptions are: crossing a waterbody on a bridge or other part of an official trail, or fording a stream or river as part of an official trail; collecting treatable water for drinking; crossing a frozen waterbody or shoreline; and using the rental canoes at Emerald Lake in Yoho.

Whirling disease is spread through an ecosystem mainly by fish moving upstream or downstream, but can also easily be spread by humans, especially those recreating. In fact, Parks Canada officials suspect that recreational activities are likely what brought the parasite into B.C. They warned the public that transporting items such as fishing gear, paddleboards and kayaks from an area with whirling disease to one without comes with risk of introducing the disease.

The parasite can live in most forms of water and even in mud. It has been present in Alberta, including in the Bow Valley, which borders both Yoho National Park and Kootenay National Park, for several years.

(Getty Images)