Fish and Wildlife Tech, Resort Municipality of Whistler
Recent genetic tests in the Whistler area reveal that the fish in our streams we have been calling Dolly Varden are actually bull trout.
Dolly Varden and bull trout are two species of fish that are often mistaken. In fact, they are so similar in their appearance and habitat characteristics that up until 15 to 20 years ago they were believed to be the same species.
Since then, genetic testing has shown that Dolly Varden are actually a closer relative to the Arctic char, while bull trout are genetically more similar to the white spotted char.
It is often difficult to tell the two species apart, even for trained biologists! Both fish have olive-green to brown bodies with orange, yellow or red spots on their sides and backs. Subtle differences in their appearance include:
- The number of rays (tiny supportive bones in the fins and other membranes) in their anal fins and below their gill covers (operculum)
- The curve of the upper jaw
- The length of the upper jaw in relation to the body, and
- The size and spacing of their spots.
In terms of habitat, both species of fish spawn in cold waters during the fall in small, steep tributary streams that most other species of trout and char are unable to access. Although most populations of Dolly Varden are like salmon, traveling to the ocean as adults before returning to spawn, many are land-locked. Like bull trout, they can spend their entire lives in small streams; live in rivers and migrate to smaller streams to spawn, or live as adults in lakes but spawn in streams.
Bull trout and Dolly Varden are ranked under two lists: the B.C. red (endangered) and blue (threatened) list, and a global ranking list which looks at the threats of a species to extirpation/extinction over its entire range.
In B.C., Dolly Varden and bull trout are both blue-listed species, meaning that they are a sensitive species vulnerable to human and natural disturbances. The small tributary streams these species use for spawning and rearing are subject to sedimentation and riparian degradation, resulting in increases in water temperature. Although globally Dolly Varden are listed as abundant and secure, likely due to a more widespread distribution than bull trout, bull trout have a fairly restricted range and are listed globally as vulnerable to extirpation and extinction. Disturbance to habitat from human activities such as logging, mining, agriculture, urban development, and historic overfishing has caused bull trout numbers to decline over their entire range.
So knowing that Whistler is home to bull trout and not Dolly Varden may not change how we manage the species, but be aware that we are blessed to have this rarer species in our area, and please be respectful of their habitat. Bull trout can be found in Fitzsimmons Creek, Green Lake, and occasionally Alta Lake. There are past reports of these fish in Alta Creek, Lost Lake and below Rainbow Falls in 21-Mile Creek.