To add some info to this great thread:
"Bull trout (scientific name: Salvelinus confluentus), like their cousins, the lake trout and brook trout, are not considered trout at all. Along with the Dolly Varden (and of course Arctic char), they are members of the char family. For years people believed that the bull trout was just a localized version of Dolly Varden, but it is now accepted that they are two different species."