Contrary to their name, bull trout are not really trout at all. They are members of the char family, which also includes brook trout, lake trout, Dolly Varden and Arctic char. Once common throughout the Pacific Northwest from Northern California to Alaska, bull trout are now extinct in roughly half their historical range. Northern Idaho's Lake Pend Orielle and Montana's Flathead Basin are the two most important remaining strongholds for bull trout in the entire Columbia River Basin. Because bull trout have experienced sharp declines throughout their range and are now listed under the federal Endangered Species Act.
Bull trout require the cleanest, coldest water of any stream-dwelling fish in North America.
For this reason, their last remaining strongholds are mostly in federally-designated wilderness areas. Sedimentation and elevated water temperatures pose the two greatest threats to bull trout in Idaho. Major sediment sources include poorly constructed forest roads, clearcut mountain-sides, and overgrazed stream banks. Stream temperatures can reach lethal levels if too much shade-giving vegetation is removed by logging and grazing in riparian corridors. Because bull trout are sensitive to even the smallest changes in water quality, they make an excellent indicator species for the mountain streams in which they live.