DNA seen as key to restoring genetic purity of westslope cutthroat trout

·3 min read
This is a westslope cutthroat trout, known for its freckle-like spots and orange hue. (Stephen Glendinning/Submitted by Brian Keating - image credit)
This is a westslope cutthroat trout, known for its freckle-like spots and orange hue. (Stephen Glendinning/Submitted by Brian Keating - image credit)

Picture it. Banff National Park. Late 1940s.

Park officials wanted to make recreational fishing more attractive by introducing non-native species to lure anglers.

At the time, freshwater species like westslope cutthroat trout, bull trout, lake trout and Rocky Mountain whitefish had the rivers pretty much to themselves.

So those crafty park officials started their own hatchery and added Yellowstone cutthroat trout and rainbow trout to the mix.

And they got along beautifully, if you know what we mean. But that's the problem.

Stephen Glendinning/Submitted by Brian Keating
Stephen Glendinning/Submitted by Brian Keating

"The program of fish introductions worked very well," naturalist Brian Keating told The Homestretch.

"But now we need to turn our thinking around to put back the original genetics."

And recently while in the park, Keating stumbled across a research team that is trying to do just that.

"We were just putting our boots back on when a fisherman appeared out of the woods. He turned out to be a National Parks research student," Keating said.

"After a short discussion, he pulled out a little vial filled with preservative solution and a tiny little clipping of the caudal fin of a trout he had caught and released."

Parks Canada/Submitted by Brian Keating
Parks Canada/Submitted by Brian Keating

That student is doing a second DNA analysis, with the last one completed in 2007. The technology has improved over the years. A lot.

"The technology of today allows for an extremely detailed genetic analysis, so it was decided to re-analyze the creek's fish. Pure stocks of westslope cutthroat have a protected species designation, and if their genetics are, indeed, found to be pure, the creek will remain closed, not only to preserve the population of westslope cutthroat, but also the native bull trout," he explained.

But why is genetic purity so important?

"Crossbreeding of different species can weaken the genetic stock, making them more susceptible to any kind of environmental changes, including parasites, diseases or even water temperature change," Keating said.

Cutthroat hybrids also reproduce less, which puts them at risk of being overtaken by other invasive species.

The research team has projects running in five lakes within Banff National Park. It involves killing off the unwanted fish with a chemical called rotenone, which paves the way for reintroduction of the desired native species.

Researchers say the chemical — which comes from the roots of a specific family of beans that grow in tropical climates — does not make the fish inedible.

Parks Canada/Submitted by Brian Keating
Parks Canada/Submitted by Brian Keating

Progress has been excellent

"Once the lake is cleared of its fish populations, fisheries biologists can start the introductions of the right (and original) species of fish," Keating said.

"Only a small number of donor fish are required to make all this work, too."

Semen is drawn from male fish. The fluid, called milt, is combined with the eggs of a female.

They are nurtured in a lab for about three weeks, then transferred to incubators in the lake to grow stronger for another week or two until they are released.

Progress has been excellent, Keating said.

"If people would like to know more, Hidden Creek, which flows out of Hidden Lake, is where a lot of the action is happening at Lake Louise."

Park staff even offer guided interpretive walks in the area.

For more fascinating stories about Alberta's wildlife from naturalist Brian Keating, visit his website and check out these stories:

With files from The Homestretch.

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