Bull trout, a species of char, are native throughout the Pacific Northwest and were an important food source for Columbia River Basin tribes, particularly those that did not have access to anadromous salmon and steelhead.
Char is a group of fish within the same family as salmon, steelhead, and trout, but distinct from those other species. According to the U.S. Fish and Wildlife Service (USFWS), other North American char species include Dolly Varden, lake trout, brook trout, and arctic char. Char are distinguished from trout and salmon by small scales, a lack of black spots on the body, and being highly adapted to life in very cold water.
Bull trout are native throughout the Pacific Northwest. Historically they were found in the Willamette River Basin west of the Cascades in Oregon, and in the Columbia and Snake river basins inland. Currently, most bull trout populations are confined to headwater areas of tributaries to the Columbia, Snake, and Klamath rivers.
Bull trout are vulnerable to many of the same threats that have reduced salmon populations. Due to their need for very cold water and the long incubation period for their eggs, bull trout are more sensitive to increased water temperatures, poor water quality, and degraded stream habitat than other salmonids. Further threats to bull trout include hybridization and competition with non-native brook trout, predation by and competition with non-native brown trout and lake trout, poaching, and human-made structures that block migration and divert water from stream channels.
In many basins, continued survival of the species is threatened by a combination of factors rather than a single major threat, the USFWS reports. Past and continuing land management activities have degraded stream habitat, especially along larger rivers and streams located in valley bottoms. As a result, water temperature, stream flow and other water quality metrics fall below the range of conditions that bull trout can tolerate. Dams and other in-stream structures impact bull trout by blocking migration routes, altering water temperatures, and killing or trapping fish. Degraded conditions, along with barriers to migration, have severely reduced or eliminated the migratory life history. In many watersheds, remaining populations of bull trout are small, resident fish isolated in headwater streams. Nonnative brook trout, also in the char family of fishes, were introduced throughout much of the range of bull trout. In the cold, headwater streams, brook trout compete for food and space, and hybridize with bull trout.
Bull trout migrate from spawning grounds to rearing habitat in lakes and rivers. They can spawn multiple times, unlike salmon. Adult bull trout typically are small, but given an abundant prey base migratory bull trout can grow to 36 inches in length and weigh up to 32 pounds.
To address the threat of non-native brook trout, management agencies are researching new methods of eradication and planning for small scale suppression and control projects. In basins where bull trout were historically present, the feasibility of their re-introduction is under consideration.
In addition, the State of Oregon implements fishing regulations appropriate to the conservation of all bull trout populations throughout the state.
References and Links
- U.S. Fish and Wildlife Service. 1998. Determination of threatened status for the Klamath River and Columbia River Distinct Population Segments of bull trout. Federal Register (63):31647-31674.
- U.S. Fish and Wildlife Service. 1999. Determination of threatened status for bull trout in the coterminous United States. Federal Register (64):58910-58933.
- U.S. Fish and Wildlife Service. 2005. Designation of Critical Habitat for the Bull Trout. Federal Register (70): 56211-56311.
- U.S. Fish and Wildlife Service. 2010. Revised Designation of Critical Habitat for Bull Trout in the Coterminous United States. Federal Register (75): 63897-64070.
- U.S. Fish and Wildlife Service. 2015. Recovery Plan for the conterminous United States populations of bull trout (Salvelinus confluentus). Federal Register (80): 58767-58768.