Over the last two centuries, bull trout populations have declined across North America. The bull trout, Salvelinus confluentus, once thrived in the Columbia River Basin and coastal rivers of Washington and Oregon, extending north into British Columbia and Alberta.

Bull trout are members of the genus Salvelinus, which also includes Arctic char, brook trout, and lake trout. Like its relatives, male bull trout exhibit brilliant colors during the spawning season. Bull trout migrate during summer, traveling up to 150 miles from lakes and rivers upstream to their natal headwaters to spawn.

A variety of factors have been cited in the decline of bull trout. Habitat degradation and fragmentation, migratory fish passage obstacles, poor water quality, the effects of climate change, bounty fishing, and the introduction of non-native fish species.

Currently, American bull trout populations are scattered across portions of Oregon, Washington, Idaho, Montana, and Nevada. They populate several river systems including the Klamath,Columbia and Snake River Basins. In 1998, bull trout were listed as a threatened species under the Endangered Species Act.

In 2011, bull trout were re-introduced into the Clackamas River after a nearly 50-year absence. The reintroduction team included representatives from the U.S. Fish and Wildlife Service, Oregon Department of Fish and Wildlife, U.S.Geological Survey, and Mt. Hood National Forest. The project was one of several bull trout restoration programs that are ongoing in western river systems.

bull trout      (photo credit: USFWS)

As part of an overall recovery strategy for bull trout, the U.S. Fish and Wildlife Service and the Oregon Department of Fish and Wildlife will reintroduce the species to the Clackamas River, a major tributary of the Willamette River.

Beginning in the summer of 2011, bull trout of different life stages will be reintroduced into historic bull trout habitat in the upper Clackamas River, within the Mt. Hood National Forest.

The project is expected to include additional fish transfers annually for at least seven and possibly up to 15 years.  The goal is to reestablish a self-sustaining population of 300-500 spawning adult bull trout within 20 years.

Bull trout are primarily threatened by habitat degradation and fragmentation, blockage of migratory corridors from hydroelectric and diversion dams, poor water quality, the effects of climate change, and past fisheries management practices, including targeted eradication through bounty fishing and the introduction of non-native species such as brown, lake, and brook trout.

Bull trout have been extirpated from four sub-basins in the Willamette River Basin, including the Clackamas River. Once widely distributed in the Clackamas River, the last known bull trout was documented there in 1963.  The species is highly unlikely to re-colonize the area naturally due to the geographic distance to existing bull trout populations.

Once plentiful throughout the coldwater rivers and lakes of the Northwest, bull trout populations in the U.S. are now scattered and patchy in portions of Oregon, Washington, Idaho, Montana, and Nevada.

Bull trout occur in the Columbia and Snake River Basins, extending east to headwater streams in Montana and Idaho and north into Canada, and south into the Klamath River Basin in south-central Oregon.  Though still wide-ranging, many of the remaining populations are small and isolated from each other.

Some bull trout populations are migratory, spending portions of their life cycle in larger rivers or lakes before returning to smaller streams to spawn, while others complete their entire life cycle in the same stream. Some bull trout in the Coastal-Puget Sound population migrate between fresh- and saltwater.

Bull trout require extremely cold, clean water and specific habitat features, as well as connectivity from river, lake, and ocean habitats to headwater streams for annual spawning and feeding migrations.

source: U.S. Fish and Wildlife Service