No. Bull trout (
Salvelinus confluentus) and dolly varden (
Salvelinus malma) are two different species.
The ones that we encounter in the Fraser River and tributaries are bull trout.
I've written about this many times, so I'll just copy and paste a summary that I did recently regarding the differences.
The differences between the two species are pretty inconspicuous that most people (myself included) are unable to identify them correctly after a couple of glances. Lately I've simply been referring all of them as coastal char (when fishing in coastal rivers) whenever people ask what they are.
Even trained individuals make lots of errors in differentiation the two. Take a look at this
PDF file.
There are three differences. They differ in total number of branchiostegal rays, total number of anal fin rays and jaw length. They also differ in maximum size but that's not a good identification key, since an old dolly varden can be the same size as a young bull trout.
Page two of this PDF file summarizes the distribution of the two species. Bull trout are more widely distributed and have four different types of life histories. Stream resident (reside and spawn in small streams), fluvial (reside in large rivers, spawn in small streams), lacustrine-adfluvial (reside in lakes, spawn in tributaries), anadromous (migrate into ocean, spawn in streams). The first three life histories are mainly found in Interior BC, where dolly varden do not exist so you can safely assume that they are bull trout when you catch them away from the coast.
The anadromous/coastal populations of bull trout overlap with populations of dolly varden. The relationship between the two has only been studied and more understood in the past couple of decades. Even though there is an overlap in distribution and the two only differ slightly physically, those little differences determine the different types of waters where they inhabit. Bull trout tend to take over deep large runs while dolly varden tend to utilize headwaters/small streams. The two come in contact during their spawning phases and hybridization has been well documented by genetic studies in most drainages (Columbia, Skagit, Fraser, Skeena, Peace, Nass, Stikine, etc) since the late 90s.
Knowing how to tell the differences between the two is not so important for anglers in areas where retention of both species does not exist, we just have to look and appreciate them before releasing. On the other hand, the differences and extent of hybridization become important in management and protection of headwaters.