Restoring to zero
©; 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) .
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.
"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.
Parks staff helps recovery
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 .
Since 1915, nearly 40 million non-native fish and eggs have been released into Banff National Park's watersheds. In 2002, a team of Aquatic Specialists began removing non-native Brook trout from Banff's Devon Lakes.