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Bull Trout

Bull Trout

Scientific Name: Salvelinus confluentus

Status: Threatened

Critical Habitat: Designated

Listing Activity:  Bull trout were listed as threatened throughout Washington in November 1999 and critical habitat was designated in 2005. In January 2010, the USFWS proposed a revision of critical habitat. On September 3, 2014, the USFWS announced a Revised Draft Recovery Plan, updating the recovery criteria proposed in the 2002 and 2004 draft recovery plans.

  • Background

    Bull trout are members of the salmonid family known as char. Bull trout, Dolly Varden and lake trout are all species of char native to parts of the northwest. Char are distributed farther north than any other group of freshwater fish except the Alaskan blackfish and are well adapted for life in very cold water.

    Historical Status and Current Trends

    Bull trout are native throughout the Pacific Northwest. In Washington, bull trout were historically found in major tributaries to the Columbia River on the eastside of the Cascades; major westside tributaries on the westside of the Cascades flowing into Puget Sound; and major tributaries  to the Olympic Mountains flowing into Hood Canal, Strait of Juan de Fuca, and the Pacific Ocean. Anadromous bull trout can occasionally be found in smaller streams flowing into saltwater to search for food and overwinter.

    Bull trout are vulnerable to many of the same threats that have reduced salmon populations. Due to their need for very cold waters and a long incubation time, bull trout are more sensitive to increased water temperatures, poor water quality and degraded stream habitat than many other salmonids. Further threats to bull trout include hybridization and competition with non-native brook trout (another species of char), non-native brown trout and introduced lake trout, overfishing, poaching, and man-made structures that block migration.

    In many areas, continued survival of the species is threatened by a combination of factors rather than one major problem. For example, past and continuing land management activities have degraded stream habitat, especially along larger river systems and streams located in valley bottoms. Degraded conditions have severely reduced or eliminated migratory bull trout as water temperature, stream flow and other water quality parameters fall below the range of conditions which these fish can tolerate. In some watersheds, remaining bull trout are smaller, resident fish, isolated in headwater streams. Brook trout, introduced throughout much of the range of bull trout, easily hybridize with them, producing sterile offspring. Brook trout reproduce earlier and at a higher rate than bull trout so bull trout populations are often supplanted by these non-natives. Dams and other in-stream structures also affect bull trout by blocking migration routes, altering water temperatures and killing fish as they pass through and over dams or are trapped in irrigation and other diversion structures.

    Habitat

    Bull trout are seldom found in waters where temperatures are warmer than 59º to 64º F. Besides very cold water, bull trout require stable stream channels, clean spawning gravel, complex and diverse cover, and unblocked migration routes.

    Life History

    Small bull trout eat terrestrial and aquatic insects but shift to preying on other fish as they grow larger. Large bull trout are primarily fish predators. Bull trout evolved with whitefish, sculpins and other trout and use all of them as food sources. In western Washington, small saltwater fish (surf smelt, herring, and sandlance) are an important food source for the anadromous form of bull trout that is unique to this area. Like salmon and steelhead, the anadromous form of bull trout enters saltwater for part of its life history, returning to freshwater to spawn. Adult bull trout are usually small, but can grow to as much as 36 inches in length and weigh up to 32 pounds. Bull trout reach sexual maturity at between four and seven years of age and are known to live as long as 12 years. They spawn in the fall after temperatures drop below 48 º F, in streams with abundant cold, unpolluted water, clean gravel and cobble substrate, and gentle stream slopes. Many spawning areas are associated with cold water springs or areas where stream flow is influenced by groundwater. Bull trout eggs require a long incubation period compared to other salmon and trout, hatching in late winter or early spring. Fry may remain in the stream gravels for up to three weeks before emerging.

    Bull trout may be either resident or migratory. Resident fish live for their entire life near areas where they were spawned. Migratory fish are usually spawned in small headwater streams, and then migrate to larger streams, rivers, lakes, reservoirs or saltwater where they grow to maturity. Smaller resident fish remain near the areas where they were spawned while larger, migratory, fish will move considerable distances to spawn when habitat conditions allow. For instance, bull trout in Montana's Flathead Lake have been known to migrate up to 250 kilometers (150 miles) to spawn.

    Conservation Measures

    Many of the same management actions that are being done to protect other declining salmonids may also help bull trout. Stream and habitat protection and restoration, reduction of siltation from roads and other erosion sites and modification of land use practices to improve water quality and temperature are all important. Several state agencies have also enacted regulations reducing or prohibiting bull trout harvest. States have also adopted conservation plans to help bull trout populations recover.

    References and Links

    U.S. Fish and Wildlife Service. 1999. Determination of threatened status for bull trout in the coterminous United States. Federal Register (64):58910-58933.

    All Region 1 bull trout related info: U.S. Fish and Wildlife Service Region 1

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