Five species of fish are known to exist in Idlewild Lake. Native Westslope cutthroat trout, Rocky Mountain whitefish and Bull trout swim along with Rainbow trout and non-native Eastern Brook char.

The Westslope cutthroat trout (Oncorhynchus clarkii lewisi) is one of two sub-species of cutthroat trout native to B.C. Like other cutthroat trout sub-species, older fish can be distinguished by characteristic orange-red slashes on each side of the lower jaw and an arc of irregular dark from the dorsal in toward the tail.

Most populations of the Westslope cutthroat have been in steep decline throughout its habitat due to factors such as habitat loss, being out competed by non-native species, and hybridization with non-native rainbow trout. Idlewild Lake is stocked exclusively with Westslope cutthroat from Connor Lakes, located in the Height of the Rockies Provincial Park, the sole source of wild westslope cutthroat broodstock for hatchery production.

Westslope cutthroat are typically small compared to other trout, occasionally reaching upwards of 50 centimetres. What these trout lack in size, they make up for in tenacity when hooked. They are opportunistic feeders, aggressively pursuing whatever is seasonably abundant. They will feed on most invertebrates underwater, as well as flying or terrestrial insects that land on the water’s surface. Please consult the provincial government fishing regulations for Idlewild Lake.