Fish and Aquatic Conservation

illustration of a Bull trout

Bull Trout

Salvelinus confluentus, (Suckley, 1859)

Cool Facts

The maximum reported weight for a bull trout is 14.5 kg (31 lbs. 15 oz.) Bull trout may live 12 years or longer The specific habitat requirements of the bull trout are often described as the “Four C’s”: Cold, Clean, Complex and Connected Habitat.

SIZE: Common length for the bull trout is 62.5 cm (24.6 in) with the maximum reported length being 103 cm (40.5 in).

RANGE: The Bull trout is native to Canada and the United States. The geographic range of the bull trout is confined to northwestern North America from Alaska to northern California. These fish inhabit Artic waters, Pacific waters and the Missouri River drainages in mountain and coastal streams.

HABITAT: Bull trout are most common in high mountainous areas where snowfields and glaciers are present. They mainly occur in deep pools of large, cold, rivers and lakes.

DIET: Juvenile bull trout, during their first year of life, feed primarily on small aquatic invertebrates. As the bull trout grows larger their diet begins to consist of other fish species. This piscivorous behavior increases as the fish continues to grow. Bull trout, depending on what part of their native range they inhabit or what life form strategy they are exhibiting, have been known to feed on the following fish such as whitefish, sculpins, darters, trout and salmon.

Natural History

Bull trout are a char native to the Pacific Northwest and Canada. Bull trout exhibit one of the most complex life history strategies of the Pacific salmonids. This species exhibits four different life history strategies. These strategies include a non-migratory or resident bull trout form, a riverine or fluvial bull trout form, a lacustrine or adfluvial bull trout form and a rare marine or amphidromous/anadromous form.

Bull trout usually mature between four to seven years of age. An individual may spawn annually or every other year. Bull trout typically spawn from late July through December, with peak spawning in September for most interior forms and late October for most coastal forms.

The period of egg incubation to emergence for bull trout fry may take up to 210 days. Upon emergence, juvenile Bull trout fry may rear one to four years in their natal stream before migrating either to river, lake/river, or nearshore marine areas to mature.


All populations of the bull trout were listed as Endangered in 1998 and reclassified as Threatened under the Endangered Species Act in 1999. A critical habitat designation for the bull trout was completed in 2010.

Bull trout have been negatively impacted by the combined effects of a variety of factors including habitat degradation and fragmentation, blockage of migration corridors, poor water quality, past fishery management practices, and the introduction of non-native species.

Migration Behavior

Bull trout are a migratory species. Some of these fish might spend their entire lifetime in the same stream or they may move to larger bodies of water to overwinter and then migrate to smaller streams to reproduce. On the other hand, some bulltrout are born in fresh water and then migrate to the ocean for their adult lives and return to fresh water to reproduce.