Time for Nature

Helping Native Fish Come Back

August 16, 2004

Banff National Park of Canada

Aerial view of Upper, middle and lower Devon Lakes
© C. Pacas, Parks Canada

When thousands of brook trout ( Salvalinus fontinalis ) were stocked into Banff National Park ’s Devon Lakes in the 1960s, the hope was to lure anglers with the new stock. Who could foresee that the brook trout would begin to change the ecosystem at its most basic level and migrate into the surrounding rivers, crowding out native species such as the bull trout ( Salvelinus confluentus ) . Following several years of park staff efforts to remove brook trout and restore the region’s ecological integrity , bull trout will eventually win back its habitat from its invading cousin.

Tough competition

“ Brook trout operate differently from bull trout,” says Charlie Pacas, aquatic specialist with the Banff field unit. “They mature at a younger age, so that when they move into the system, they’re producing a lot more progeny in the time it takes the bull trout to get to the same stage.” That raises concerns about what’s called hybridization, or the potential loss of native bull trout genes when the two species interbreed. The bull trout has been listed as a species of special concern in Alberta.

Brook trout have changed the lakes by feeding on certain invertebrate species that were not eaten by other predators. As they began to move out of the lakes, located in the northwest corner of the park, they also began out-competing native species for food and habitat.

Parks staff helps recovery

Electrofishing in Clearwater River
© C. Pacas, Parks Canada

For several years, Banff staff have been working to ease the threat posed to the bull trout and its habitat by removing brook trout from the Devon Lakes and, ultimately, the Upper Clearwater River . In 2003, staff removed more than 2000 brook trout from the two lakes where their population was highest.

The brook trout are culled, then weighed, measured and tested for things such as pollutants. “If we can remove them out of the lake system, we can restore the lake to the way it was,” says Pacas. “Ideally we’re looking at doing that in another two years.”

Help for the bull trout

Private citizens can make a contribution too. Fishing enthusiasts need to be able to recognize a bull trout so that they can release any that are caught by mistake. Bull trout have no black markings -- so, if there’s “no black, put it back.” They can also learn about the bait restrictions that will help bull trout survive being caught and released. Avoiding spawning bull trout and helping to keep their waters clean will help this native fish make a comeback.

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