Plan to remove all fish from Banff lake to stop deadly whirling disease reaches environmental assessment phase

A plan to try to stop the spread of a deadly fish disease by removing all the fish from a lake has reached the environmental assessment stage in Banff National Park.

Whirling disease affects trout and salmon and can cause infected fish to swim in a whirling pattern and die prematurely. 

It was first detected in Canada when it was found in Johnson Lake in Banff in August 2016, but has since been detected in the entire Bow River watershed. 

Now, officials are considering removing fish from Johnson Lake in an effort to stop whirling disease from spreading to the nearby Two Jack Lake and Lake Minnewanka.

Lake Minnewanka and Two Jack Lake are part of the Upper Cascade area and testing has shown the disease has not spread to those waters.

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"The Minnewanka system is connected, it's fed by the Upper Cascade, and that's one of the areas in Banff that has two or three of our critical habitat areas for westslope cutthroat trout," said Bill Hunt, resource conservation manager for Banff National Park.

"We're very concerned about preventing whirling disease from getting into Minnewanka and the Upper Cascade. We have Sawback Lake, Sawback Creek, Cuthead Creek — are all critical habitat for westslope cutthroat trout."

Hunt said officials are working on a plan to remove the fish from Johnson Lake, which is currently in the environmental assessment stage.

The plan will see the lake closed in the spring and nets used to remove as many fish as possible.

"We would then open the lake for recreation from the July long weekend to the September long weekend and allow people to swim and enjoy the lake," he said.

"There will be no fishing or boating to reduce the likelihood of moving fish or mud out of the lake, and then in the fall, after the Labour Day long weekend, we would close the lake again and proceed with netting and perhaps even look at lowering the water levels a bit."

The strategy is a slightly novel one, said Hunt, as this will be the first time it is attempted in Canada.

"We have eradicated fish from lakes before, at Devon Lakes and at Rainbow Lake, using netting and electrofishing techniques we're proposing," he said.

"We've never done it on this timeline, it's usually taken two or three years ... But because we can adjust the water levels in Johnson hoping we can do it in a single season."

The disease is caused by the microscopic parasite Myxobolus cerebralis.

In order of potential risk, from highest to lowest, the movement of fish, mud or sediment and water can spread whirling disease.

It can be transmitted through equipment used for swimming, paddling, boating, water pumping and fishing, or through infected fish and fish parts.

The province is therefore urging anglers, boaters and recreational water users to thoroughly clean all of their equipment and remove any water, mud, or plant material from their property before and after each use. 

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