Canadian national parks workers are attempting to remove invasive Eastern Brook trout, (Salvelinus fontinalis) from Hidden Lake and a stream that flows from it in Banff National Park, Alberta.
The alien species is responsible for the extinction of the native Westslope Cutthroat trout (Oncorhynchus clarkii lewisi), pictured above, which disappeared from the lake only seven years after the first Eastern Brook trout were recorded.
Although the park authority had stocked the invader in other lakes in the past at the request of anglers, no record exists for their introduction to Hidden Lake.
The lake is being fished with five gill nets to remove the Brook trout. At the same time electro-fishing is being used to try and rescue a remnant population of Cutthroats being pushed out of a small creek separated from the lake and its outlet streams by waterfalls.
When Cutthroats are captured they are injected with transponders and have a sample of their DNA taken for testing.
The unfortunate Brook trout will be killed and donated to a local centre that helps injured birds of prey.
Once the test results are ready, those fish with undiluted Cutthroat DNA will be recaptured and returned to Hidden Lake by helicopter but not before the lake is clear of the introduced species which is expected to take up to three years to achieve.
The waterfall should prevent any Brook trout left in adjoining streams regaining access to the lake once it has been cleared.
Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.