Bull Trout Facts

(Salvelinus confluentus)

What is a bull trout?

Bull trout are members of the salmon family known as char. Char are distributed farther north than any other group of freshwater fish except Alaskan Blackfish and are well adapted for life in very cold water. Bull trout, Dolly Varden and lake trout are species of char native to the northwest. Bull trout, like other char, exhibit differences in body characteristics and life history behavior across their range. They can grow to more than 20 pounds in lake environments.

How are char different from other salmonids?

Char (genus Salvelinus) are distinguished from trout and salmon by the absence of teeth in the roof of the mouth, presence of light colored spots on a dark background, absence of spots on the dorsal fin, small scales and differences in the structure of their skeleton.

Are they the same as Dolly Varden?

Bull trout and Dolly Varden were once considered the same species. Taxonomic work, published in 1978, identified bull trout as distinct from Dolly Varden. This designation was accepted by the American Fisheries Society in 1980. Of the two species, bull trout are larger and primarily an inland species, while Dolly Varden are generally smaller and distributed primarily in coastal areas. In Washington, both species are present in the Puget Sound area.

What was the historic range of bull trout?

Bull trout are native throughout the Pacific Northwest and historically occurred throughout the Columbia River Basin, east to western Montana, south to the Jarbidge River in northern Nevada, the Klamath Basin in Oregon, the McCloud River in California and north to Alberta, British Columbia and possibly southeastern Alaska. Although the species was once abundant and widespread, bull trout now exist primarily in upper tributary streams and several lake and reservoir systems. The main populations remaining in the lower 48 states are in Montana, Idaho, Oregon and Washington with a small population in northern Nevada. Bull trout have been extirpated from California.

What do bull trout eat?

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.

What is the life cycle of a bull trout?

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 degrees Fahrenheit, 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 bed for up to three weeks before emerging. Juvenile fish retain their fondness for the stream bottom and are often found at or near it.

Do bull trout migrate?

Bull trout may live near areas where they were spawned or migrate from small streams to larger streams and rivers or from streams to lakes, reservoirs or salt water. 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 km to spawn. Migration is important to maintaining healthy bull trout populations.

Why are they in trouble?

Bull trout are vulnerable to many of the same threats that have reduced salmon populations in the Snake River Basin. Due to their range of preferred cold water habitat conditions and life history requirements, bull trout are also 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, brown trout and lake trout, overfishing, poaching, and man-made structures that block migration.

What are the biggest threats to bull trout?

In many areas, continued bull trout survival 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 stream areas 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 many 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 also 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 effect bull trout by blocking migration routes, altering water temperatures and causing loss of fish as they pass through and over dams or are trapped in irrigation and other diversion structures.

What is being done to protect bull trout?

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. Several states have also drafted or have adopted conservation plans to help bull trout populations recover.

What more can be done to help bull trout?

Changes in land management practices, some already underway to help restore salmon stocks, will also help bull trout in many areas. But a strong commitment by private citizens, industry, state, Federal and tribal groups to change, reduce or eliminate activities that degrade streams and rivers will be necessary to truly recover many species of native fish. Much bull trout habitat in mainstream rivers and streams is privately owned, making conservation activities on private lands a key element to restoring aquatic habitat and recovering native fish populations. In some areas, reducing the potential for hybridization of bull trout with non-native fish species would enhance bull trout survival and recovery.

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