US Fish & Wildlife Service
Date of this Version
Bull trout are members of the char subgroup of the salmon family (salmonids), which also includes the Dolly Varden, lake trout and Arctic char. Bull trout living in streams grow to about 4 pounds while those in lake or large river environments can weigh more than 20 pounds.
Biologists distinguish char from other salmonids such as trout and salmon by
the absence of teeth in the roof of the mouth, the presence of light-colored spots on a dark background (trout and salmon have dark spots on a lighter background), the absence of spots on the dorsal fin, their smaller scales, and differences in skeletal structure. Char species such as bull trout live farther north than any other group of freshwater fish except Alaskan blackfish and are well adapted for life in very cold water.
Bull trout and Dolly Varden look very similar and once were considered the
same species. However, taxonomic research has identified them as different
species. Both have small pale yellow to crimson spots on a darker background, which ranges from olive green to brown above, fading to white on the belly. Spawning adults develop varying amounts of red on the belly. Both species also exhibit differences in size, body characteristics, coloration, and behavior across their range.
Published by the U.S. Fish and Wildlife Service, 1-2, (2003)