bull trout
FWS Focus

Overview

Bull trout (Salvelinus confluentus) are members of the family Salmonidae and are char native Washington, Oregon, Idaho, Nevada, Montana and western Canada. Compared to other salmonids, bull trout have more specific habitat requirements that appear to influence their distribution and abundance. They need cold water to survive, so they are seldom found in waters where temperatures exceed 59 to 64 degrees (F). They also require stable stream channels, clean spawning and rearing gravel, complex and diverse cover, and unblocked migratory corridors. Bull trout may be distinguished from brook trout (Salvelinus fontinalis) by several characteristics: spots never appear on the dorsal (back) fin, and the spots that rest on the fish's olive green to bronze back are pale yellow, orange or salmon-colored. The bull trout's tail is not deeply forked as is the case with lake trout (Salvelinus namaycush).

Bull trout exhibit two forms: resident and migratory. Resident bull trout spend their entire lives in the same stream/creek. Migratory bull trout move to larger bodies of water to overwinter and then migrate back to smaller waters to reproduce. An anadromous form of bull trout also exists in the Coastal-Puget Sound population, which spawns in rivers and streams but rears young in the ocean. Resident and juvenile bull trout prey on invertebrates and small fish. Adult migratory bull trout primarily eat fish. Resident bull trout range up to 10 inches long and migratory forms may range up to 35 inches and up to 32 pounds. Bull trout are currently listed coterminously as a threatened species.

Scientific Name

Salvelinus confluentus
Common Name
bull trout
FWS Category
Fishes
Kingdom

Location in Taxonomic Tree

Identification Numbers

TSN:

Characteristics

Characteristic category

Geography

Characteristics

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 are usually found in mountain or coastal streams.

Characteristic category

Physical Characteristics

Characteristics

Size & Shape

Common length for the bull trout is 25 inches with the maximum reported length being 40.5 inches. 

Weight

The maximum reported weight of a bull trout is at 31 pounds and 15 ounces. 

Color & Pattern

Adult bull Trout are olive or drab in overall color with pale orange, round spots along their sides

Physical Characteristics

Migration Behavior 

Bull trout are a migratory species. Some bull trout spend their entire lifetime in the same stream, but the majority move to larger bodies of water to overwinter and forage. During the spawning migration, these bull trout move into the smaller streams to build redds and reproduce. Some bull trout are born in fresh water and then migrate to the ocean for their adult lives, then return to fresh water to reproduce. 

Characteristic category

Lifecycle

Characteristics

Reproduction

Bull trout are a char native to the Pacific Northwest, Alaska, 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. Typically spawning for bull trout occurs between August and November, but sometimes as late as December. Redds (egg nests) are dug into clean gravel and laid during spawning: females lay an average of 5,000 eggs.

Eggs remain in the gravel for up to 210 days, when bull trout fry emerge. Upon emergence, juvenile bull trout may rear one to four years in their natal (or birth) stream before migrating either to river, lake/river, or nearshore marine areas to mature.

Characteristic category

Habitat

Characteristics

Habitat

Bull trout have specific habitat requirements; cold, clean, complex, and connected habitats. They are native to Canada and the United States.

A variety of activities impact bull trout survival and population recovery. These impacts occur from development or land use that degrades habitat and water quality, barriers to migration such as dams or weirs, and introduction of non-native species that compete for food or eat bull trout.

River or Stream
Lake
Characteristic category

Overview

Characteristics

Overview

Bull trout have specific habitat requirements that are called the Four Cs; cold, clean, complex, and connected habitats. They 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.

Geography

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