Bull trout
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[Photo] Bull trout Salvelinus confluentus

The bull trout (Salvelinus confluentus) is a char of the family Salmonidae. It is most commonly found in the high mountains of western North America, ranging from the Yukon to northern Nevada. A population of bull trout exists east of the Continental Divide in Alberta, where the bull trout is the provincial fish. S. Confluentus has also been known by the name "Dolly Varden trout."

It has been recorded at up to 103 cm in length and weighing 14.5 kg. Its head and mouth are unusually large for salmonids, giving it its name.

The bull trout favors the deep pools of the larger cold lakes and rivers, where it feeds on zooplankton and zoobenthos, especially chironomids. As they grow larger, they begin to feed heavily upon other fish. Indeed, the fish was once maligned out of fear that they threatened populations of other native species more prized by anglers. In coastal Washington, some of the southernmost populations of bull trout feed heavily on salmon eggs and fry, as well as fish.

Confusingly, a different species (Salvelinus malma malma), today commonly called the Dolly Varden trout, is also known as "bull trout" in Canada; there has been historic confusion between the two species, likely due to an over-lapping range, similar appearance, and an over-lapping variation in appearance among members of the two species.

Historical Naming
The first recorded use of the name "Dolly Varden" for a fish species was applied to members of S. confluentus caught in the McCloud River in northern California in the early 1870s.

In his book, Inland Fishes of California, Peter Moyle recounts a letter sent to him on March 24, 1974 from Mrs. Valerie Masson Gomez: "My grandmother's family operated a summer resort at Upper Soda Springs on the Sacramento River just north of the present town of Dunsmuir, California. She lived there all her life and related to us in her later years her story about the naming of the Dolly Varden trout. She said that some fishermen were standing on the lawn at Upper Soda Springs looking at a catch of the large trout from the McCloud River that were called 'calico trout' because of their spotted, colorful markings. They were saying that the trout should have a better name. My grandmother, then a young girl of 15 or 16, had been reading Charles Dickens' Barnaby Rudge in which there appears a character named Dolly Varden; also the vogue in fashion for women at that time (middle 1870s) was called 'Dolly Varden,' a dress of sheer figured muslin worn over a bright-colored petticoat. My grandmother had just gotten a new dress in that style and the red-spotted trout reminded her of her printed dress. She suggested to the men looking down at the trout, 'Why not call them "Dolly Varden"?' They thought it a very appropriate name and the guests that summer returned to their homes (many in the San Francisco Bay area) calling the trout by this new name. David Starr Jordan, while at Stanford University, included an account of this naming of the Dolly Varden Trout in one of his books."

In 1874, Livingston Stone, a naturalist working for the U.S. government wrote of this fish: "Also called at (Upper) Soda Springs the 'Varden' trout. … The handsomest trout, and, on the whole, having the most perfect form of all the trout we saw on the McCloud. Also, the only fish that had colored spots. This one was profusely spotted over most of the body with redish golden spots. ... The local name at (Upper) Soda Springs is the Dolly Varden". Quoted from: VI. Report of Operations During 1872 at the United States Salmon-Hatching Establishment on the M’Cloud River, and on the California Salmonidae generally; with a list of Specimens Collected. By Livingstone Stone. In: United States Commission of Fish and Fisheries. Part II. Report of the Commissioner for 1872 and 1873. A- Inquiry into the Decrease of the Food Fishes. B- The Propagation of Food-Fishes in the Waters of the United States. With Supplementary Papers. Washington: Government Printing Office, 1874 at pp. 203 - 207.

It is currently unknown whether the name "Dolly Varden" was later applied to a different subspecies (S. malma malma) because of the similar appearance of the two fish (the two may have been believed to be the same species), or whether the name "Dolly Varden" was given to S. m. malma independent of the McCloud River fish.

Ironically, it appears that the "original" Dolly Varden trout (i.e., S. confluentus) likely became locally extinct in the McCloud River in the 1970s (although reports continue of its being caught in the McCloud River). Other fish species (typically introduced trout) will out-compete the Dolly Varden/Bull trout, and will actually interbreed with the Dolly Varden/Bull trout, producing sterile hybrids. As a result, an attempt to re-introduce the Dolly Varden/Bull trout to the river where it received its name (the McCloud River), was unsuccessful, and no additional attempts are expected.

The "Dolly Varden" name is also applied to a third subspecies (S. m. miyabei) - which is a subspecies found on the island of Hokkaido in Japan.

The name has also been applied to still a third species (S. alpinus), today more commonly known as Arctic char.

http://en.wikipedia.org/wiki/Bull_trout

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