The lakes and rivers of the Canadian Rockies hold a variety of fish, most of which belong to the trout and salmon family and are classed as coldwater species—that is, they inhabit waters where the temperature ranges 4–18°C (39–64°F). The predominant species, the rainbow trout, is not native to the mountains; it was introduced from more northern Canadian watersheds as a sport fish and is now common throughout lower elevation lakes and rivers. It has an olive green back and a red strip running along the center of its body.

Only three species of trout are native to the mountains. One of these, the bull trout, is Alberta’s provincial fish. Throughout the mid-1900s, this truly native Canadian trout was perceived as a predator of more favored introduced species and was mostly removed. Today, what was once the most widespread trout east of the Continental Divide is confined to the headwaters of Canadian Rockies’ river systems and is classed as a threatened species. While the bull trout has adapted to the harsh conditions of its reduced habitat, its continuing struggle for survival can be attributed to many factors, including a scarcity of food and a slow reproductive cycle. Bull trout grow to 70 centimeters (27 inches) in length and weigh up to 10 kilograms (22 pounds).

The lake trout, which grows to 20 kilograms (44 pounds), is native to large, deep lakes throughout the mountains. Identified by a silvery gray body and irregular white splotches along its back, this species grows slowly, taking up to eight years to reach maturity and living up to 25 years. Named for a bright red dash of color that runs from below the mouth almost to the gills, the cutthroat trout is native to southern Alberta’s mountain streams, but it has been introduced to high-elevation lakes and streams on both sides of the Canadian Rockies.

The brown trout, introduced from Europe in 1924, is found in the Bow and Red Deer Rivers and some slower streams in the eastern zones of Kananaskis Country. Its body is a golden brown color, and it is the only trout with both black and red spots. The brook trout is a colorful fish identified by a dark green back with pale-colored splotches and purple-sheened sides. It is native to eastern Canada but was introduced to the mountains as early as 1903 and is now widespread throughout lakes and streams on the Alberta side of the Continental Divide. Golden trout were introduced to a few mountain lakes around 1960 as a sport fish. They are a smallish fish, similar in color to rainbow trout.

The mountain whitefish (commonly but incorrectly called arctic grayling by Albertan anglers) is a light gray fish native to most lower-elevation lakes and rivers of the Canadian Rockies. Also inhabiting the region’s waters are arctic grayling and Dolly Varden (named for a colorful character in a Charles Dickens story).